JP3397543B2 - Two-component developer, developing method and image forming method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developer for developing an electrostatic latent image in electrophotography, electrostatic recording, etc., a developing method and an image forming method.

[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. 42-23910 and Japanese Patent Publication No. 43-24748. In all of these methods, an electrostatic latent image is formed by irradiating the photoconductive layer with an optical image corresponding to the original, and then a coloring called a toner having a polarity opposite to that of the electrostatic latent image is formed on the electrostatic latent image. The electrostatic latent image is developed by adhering fine powder, the toner image is transferred to a transfer material such as paper, if necessary, and then fixed by heat, pressure, heating, pressurization or solvent vapor to obtain a copy. I will get it.

In the step of developing the electrostatic latent image, the charged toner particles are used to form a toner image by utilizing the electrostatic interaction of the electrostatic latent image. Of the methods for developing such an electrostatic latent image with toner, generally, a two-component developer in which toner is mixed with a carrier is preferably used for a full-color copying machine or a printer which requires particularly high image quality.

Further, in recent years, with the development of computers and high-definition televisions, there has been a demand for means for outputting higher-definition full-color images. For this purpose, efforts are being made to further improve the quality of full-color copied images to high image quality, high definition, and image quality of silver halide photography. In response to these requirements, studies have been added from the viewpoint of processes and materials.

For example, regarding the developer, a representative method is to reduce the particle diameters of the toner and the carrier. However, reducing the particle size of the toner increases the difficulty in handling the powder, and it is difficult to optimize the electrophotographic characteristics other than development such as transfer and fixing accompanying the reduction in the particle size of the toner. However, there is a limit in terms of improving the image quality of the toner by itself because the property is increased.

On the other hand, in the study of the electrophotographic process, there is a possibility that high image quality can be achieved by making the magnetic brush on the developer carrier (for example, the developing sleeve) dense. From the process side, a method of developing between the magnetic poles of the magnetic poles of the developing sleeve and a method of reducing the strength of the magnetic poles of the developing sleeve can be considered for making the magnetic brush denser. While these methods are less susceptible to the influence of the magnetic brush, it is difficult to simply use them in terms of scattering due to insufficient binding force of the developer and transportability. Further, the magnetic brush can be densified by reducing the particle size of the magnetic carrier particles used in the developer or reducing the magnetic force.

For example, JP-A-59-104663 discloses a method of using a magnetic carrier having a small saturation magnetization. However, the reproducibility of fine lines is improved by simply using a magnetic carrier having a small saturation magnetization, but on the other hand, the binding force of the magnetic carrier particles on the developing sleeve is reduced, so that the magnetic carrier moves to the photosensitive drum. The carrier adhesion phenomenon that easily causes image defects is likely to occur.

Further, it is known that the carrier adhesion phenomenon easily occurs even when a magnetic carrier having a small particle size is used. Specifically, for example, Japanese Patent Publication No. 5-8424
The publication describes a method of developing in a non-contact system under an oscillating electric field using a magnetic carrier and a toner which are made into fine particles. The publication describes that increasing the resistance of the magnetic carrier is effective in improving the carrier adhesion in the developing process in which an oscillating electric field is applied. However, in order to improve the generated carrier adhesion, the magnetic carrier Even if the specific resistance is increased, if the specific resistance of the carrier core is low and exposed to the surface even a little, it may be insufficient to sufficiently improve carrier adhesion and achieve high image quality. Also,
According to this method, when the magnetic strength of the magnetic carrier at the developing pole is high because of non-contact, the image density is moderate, and an image without carrier adhesion can be obtained. When the value becomes smaller, there arises a problem that the image density becomes particularly low.

By the way, in general, the bulk resistance of a magnetic resin carrier is higher than that of an iron powder core or a metal oxide (for example, ferrite or magnetite) core. However, even in these cases, for example, JP-A-5-10
As described in Japanese Patent No. 0494, by incorporating magnetic substances having different particle diameter ratios into a resin to increase the amount of magnetic substance in the resin, the magnetic substance added internally has a specific resistance. In the case of containing a magnetic material having a low magnetic field, the binding force of the magnetic carrier becomes high, but when such a magnetic carrier is used in a developing method using an alternating electric field, carrier adhesion cannot be sufficiently improved. was there.

As described above, various methods have been attempted in order to achieve high image quality while preventing carrier adhesion, but in particular, a two-component developer and a developing method in which the above-mentioned problems are improved. And, an image forming method is desired.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a two-component developer which solves the above problems, a developing method using the two-component developer, and an image forming method.

An object of the present invention is to provide a two-component developer capable of forming a high-quality toner image in which no carrier is attached and fogging is prevented or suppressed, and a development method using the two-component developer. An object is to provide an image forming method.

An object of the present invention is to provide a two-component developer capable of forming a high-definition color toner image with a high image density, a developing method and an image forming method using the two-component developer. .

An object of the present invention is to provide a two-component developer having excellent durability on a large number of sheets.

An object of the present invention is to provide a two-component type developer which does not cause image deterioration even when a large number of images are printed.

An object of the present invention is to provide an image forming method capable of forming a full color image having high definition and high image quality.

An object of the present invention is to provide an image forming method capable of forming a full-color image having a good halftone color.

[0018]

The present invention provides a two-component developer having at least a toner and a magnetic coated carrier, wherein the magnetic coated carrier has a number average particle diameter of 1 to 100.
.mu.m, the cumulative distribution value of ½ times the number average particle diameter or less is 20 number% or less, and the specific resistance of the magnetic coated carrier is 1 × 10 ¹² Ωcm or more, which constitutes the magnetic coated carrier. The specific resistance of the core is 7.7 × 10 ¹⁰ Ωcm or more, and the magnetic strength of the magnetic coated carrier at 1 kilo-oersted is 30 to 150 emu / cm ³ ,
The toner has a weight average particle diameter of 1 to 10 μm, a cumulative distribution value of ½ times the number average particle diameter (D1) or less and 20 number% or less, and a double diameter of the weight average particle diameter (D4). The present invention relates to a two-component developer having a cumulative distribution value of 10% by volume or less.

Further, according to the present invention, the number average particle diameter is 1 to 1.
The number of particles is 00 μm, the cumulative distribution value of ½ times the number average particle diameter or less is 20 number% or less, and the specific resistance of the magnetic coated carrier is 1 × 10 ¹² Ωcm or more, which constitutes the magnetic coated carrier. Specific resistance of core is 7.7 × 10 ¹⁰ Ωcm
The above is the magnetic coated carrier having a magnetic strength of 30 to 150 emu / cm ³ at 1 kilo Oersted of the magnetic coated carrier, and a weight average particle diameter of 1 to 10 μm.
And the cumulative distribution value of diameters equal to or less than 1/2 times the number average particle diameter (D1) is 20 number% or less, and the weight average particle diameter (D4).
A two-component developer containing a toner having a distribution cumulative value equal to or more than twice the diameter of 10% by volume or less is carried on a developer carrier containing a magnetic field generating means, and the toner is carried on the developer carrier. A magnetic brush of a two-component developer is formed on, the magnetic brush is brought into contact with the latent image carrier, and the electrostatic image of the latent image carrier is developed while applying an alternating electric field to the developer carrier to form a toner image. The present invention relates to a developing method characterized by forming.

Further, in the present invention, the number average particle size is 1 to 1.
The number of particles is 00 μm, the cumulative distribution value of ½ times the number average particle diameter or less is 20 number% or less, and the specific resistance of the magnetic coated carrier is 1 × 10 ¹² Ωcm or more, which constitutes the magnetic coated carrier. Specific resistance of core is 7.7 × 10 ¹⁰ Ωcm
The above is the magnetic carrier having a magnetic strength of 30 to 150 emu / cm ³ at 1 kilo Oersted of the magnetic coated carrier, and a weight average particle diameter of 1 to 10 μm, which is 1 / of the number average particle diameter (D1). The cumulative distribution value of the double diameter or less is 20 number% or less, and the weight average particle diameter (D4) is 2
A two-component developer containing a magenta toner having a cumulative distribution value of double diameter or more of 10 volume% or less is carried on a developer carrier containing a magnetic field generating means, and the magenta toner is carried on the developer carrier. A two-component developer magnetic brush is formed, the magnetic brush is brought into contact with the latent image carrier, and an electrostatic field on the latent image carrier is developed while applying an alternating electric field to the developer carrier to form a magenta toner image. Formed to have a number average particle size of 1 to 100 μm,
The cumulative distribution value of the number average particle diameter of 1/2 times or less is 20 number% or less, and the specific resistance of the magnetic coated carrier is 1 × 1.
0 ¹² Ωcm or more, the specific resistance of the core constituting the magnetic coated carrier is 7.7 × 10 ¹⁰ Ωcm or more, and the magnetic carrier has a magnetization strength of 3 at 1 kOe.
A magnetic coated carrier of 0 to 150 emu / cm ³ , a weight average particle diameter of 1 to 10 μm, and a cumulative distribution value of ½ times or less of the number average particle diameter (D1) of 20 number% or less, A two-component developer containing a cyan toner having a distribution cumulative value equal to or larger than twice the weight average particle diameter (D4) of 10% by volume or less is provided on a developer carrier containing a magnetic field generating means. Carry and form a magnetic brush of a two-component developer on the developer carrier, bring the magnetic brush into contact with the latent image carrier, and apply an alternating electric field to the developer carrier to electrostatically charge the latent image carrier. The image is developed to form a cyan toner image, and the number average particle diameter is 1 to 100 μm.
The cumulative distribution value of the double diameter or less is 20% by number or less, the specific resistance of the magnetic coated carrier is 1 × 10 ¹² Ωcm or more, and the specific resistance of the core constituting the magnetic coated carrier is 7.
7 × 10 ¹⁰ Ωcm or more, and the magnetic carrier has a magnetization strength of 30 to 150 emu / km at 1 kilo Oersted.
a magnetic carrier of cm ³ and a weight average particle size of 1 to 10
.mu.m, and the cumulative distribution value of ½ times the number average particle diameter (D1) or less is 20 number% or less, and the weight average particle diameter (D
4) A two-component developer containing a yellow toner having a distribution cumulative value of at least 2 times the diameter of 10% by volume or less is carried on a developer carrier containing magnetic field generating means, A two-component developer magnetic brush is formed on the carrier, the magnetic brush is brought into contact with the latent image carrier, and an electrostatic charge image of the latent image carrier is developed while applying an alternating electric field to the developer carrier. Forming a yellow toner image, the formed magenta toner image,
The present invention relates to an image forming method characterized by forming a full-color image using at least a cyan toner image and a yellow toner image.

[0021]

DETAILED DESCRIPTION OF THE INVENTION As a result of a detailed study by the present inventors, regarding the magnetic coated carrier, the strength of magnetization of the magnetic carrier at the developing pole (the magnetic pole strength is about 1000 oersted) is 30 to 150 emu / in cm ^3, the carrier particle size becomes dense density of the magnetic brush in a developing pole used 1~100μm magnetic coated carrier, it was found that a good image dot reproducibility can be obtained.

However, there is a tendency for carrier adhesion to increase, contrary to the improvement in image quality. Therefore, in the developer of the present invention, the number average particle diameter is 1 to 100 μm,
The particle size distribution of the magnetic carrier is sharpened so that the cumulative distribution value of the number average particle diameter of ½ times or less is 20 number% or less, and the specific resistance of the magnetic coated carrier is 1 ×.
The magnetic coat carrier having a specific resistance of 10 ¹² Ωcm or more and a core constituting the magnetic coat carrier having a specific resistance of 7.7 × 10 ¹⁰ Ωcm or more is made to have a high resistance, and the magnetization of the magnetic coat carrier at 1 kilo Oersted is increased. Strength is 30
A magnetic coated carrier having a density of 150 emu / cm ³ is used. This can improve the image quality while preventing carrier adhesion.

This is considered to be because the driving force of carrier adhesion is a dominant factor in the contact development method of the magnetic brush under the application of the alternating electric field, in which the charge injection from the developing sleeve to the magnetic coat carrier is applied when the developing bias is applied. To be

It has also been found that the other cause of carrier adhesion is related to the charging of the magnetic carrier in the frictional charging between the toner and the magnetic carrier. If the charged magnetic coat carrier has a large particle size, it is less likely to adhere to the photoconductor due to magnetic force and its own weight, but fine powder of the magnetic coat carrier may fly onto the photoconductor.

The above-mentioned carrier adhesion by charge injection to the magnetic coated carrier is a core having a core specific resistance of 9 × 10 ⁸ Ωcm or less, such as a metallic iron core, a magnetite core or a ferrite core, even if it is a magnetic coated carrier. If the core is used, even if the core is partially exposed on the surface of the magnetic coated carrier particles, charge injection occurs and carrier adhesion easily occurs. It was also found that even with a magnetic resin carrier in which a magnetic material is dispersed, charge injection occurs when a carrier having a specific resistance of less than 9 × 10 ⁹ Ωcm is used.

Further, regarding the particle size of the magnetic coated carrier, it was found that the particle size distribution is broad, and particularly the magnetic coated carrier having a large amount of fine powder also increases the carrier adhesion amount.

Therefore, in order to prevent carrier adhesion, if a magnetic coated carrier with a high specific resistance of the core particles is used, the bulk resistance of the core increases and charge injection can be prevented, and by using a magnetic carrier obtained by cutting fine powder, carrier adhesion becomes possible. Can be effectively prevented.

However, when a magnetic resin carrier capable of preventing carrier adhesion due to charge injection is used without a surface coating, the charge amount control for various toners may not be successful. In addition, when the amount of the magnetic material contained is small, the application of triboelectric charge to the toner may be unstable, although the reason is not clear.

In the magnetic coated carrier used in the present invention, a resin coating is applied to a high resistance core for preventing charge injection to prevent the carrier from adhering and at the same time give a good charge amount to the toner.

In particular, as a constitution of the magnetic coated carrier which can satisfactorily satisfy the charging property and the prevention of carrier adhesion, in order to increase the resistance of the core while containing a large amount of metal oxide,
By replacing a part of the magnetic fine particles with a metal oxide having a higher resistance and a larger particle size, the ratio of the metal oxide / binder near the surface of the magnetic coated carrier particles can be apparently reduced, and as a result, The bulk resistance of the carrier can be increased, which can improve the image quality and prevent the carrier from adhering well. Further, in particular, in the case of producing a magnetic carrier core by directly polymerizing a monomer in the presence of a metal oxide,
It was found that many large metal oxides were present on the surface. Also, the larger the particle size ratio, the easier the large particles are to reach the surface. Therefore, it is considered that the bulk electric resistance of the carrier core can be further increased by introducing a high resistance metal oxide having a particle size larger than that of the ferromagnetic material. Further, when the thermosetting resin is used as the binder, various coating resins can be well coated on the surface of the core particle because the coating method is not limited to a wet or dry coating method, and a good charge can be imparted to the toner.

Further, by using the above-mentioned magnetic coated carrier, reproducibility of dots forming an electrostatic charge image is further improved. The cause of dot deterioration is that the electrostatic charge image on the photoconductor drum leaks due to the rubbing of the magnetic coat carrier, so the dot-shaped digital electrostatic charge latent image near the leak is uneven. It is estimated that it will be in a shape. It is presumed that the magnetic coated carrier used in the present invention does not disturb the digital latent image because the core resistance is increased.

Therefore, in the two-component type developer of the present invention, the magnetic force of the magnetic coated carrier is set to 30 to 150 emu / cm ³ to make the density of the magnetic brush in the developing pole dense. Furthermore, by increasing the bulk resistance of the core and cutting fine particles of the carrier, charge injection can be prevented, development can be performed without disturbing the latent image, and a higher quality image can be obtained.

However, it is difficult to prevent fog and improve the reproducibility of the dots forming the electrostatic latent image only by improving the magnetic carrier. It is also necessary to improve the toner because the charge imparted to the toner and the interaction between the toner and the magnetic coated carrier affect the image quality of the final image.

That is, the toner used in the present invention has a weight average particle diameter of 1 to 10 μm and a number average particle diameter of 1
A sharp toner with a particle size distribution having a cumulative distribution value of less than or equal to 2 times the diameter is 20 number% or less, and a cumulative distribution value of the diameter of at least twice the weight average particle diameter is not more than 10% by volume, and fine particles of the carrier are cut. By using the magnetic coated carrier having a sharp particle size distribution described above, an image having good dot reproducibility without fog can be obtained. This is because when the toner and the magnetic coated carrier are triboelectrically charged, the tribo distribution of the toner is sharpened by sharpening the particle size distribution of the toner and the particle size of the magnetic coated carrier for imparting charge is uniform. / By making the contact opportunities of the carrier uniform, more uniform charging can be performed, the tribo distribution of the toner becomes sharp, and the toner of the reversal component having the same triboelectric charge as the triboelectric charge of the carrier particles is obtained. It is considered that the existence is extremely small.

The reason why the deterioration of the developer can be prevented and the initial high quality image can be maintained in the present invention is considered to be as follows.

That is, the developer is deteriorated when the developer is used for a long period of time, and the magnetic share or the share due to the weight acting between the toner and the carrier in the developing device or between the magnetic coat carriers is the toner and the magnetic coat carrier. It is thought that the main cause is damage to. In particular, in both the toner and the magnetic coated carrier, the particles on the fine powder side are more seriously spent and deteriorated. Further, since the toner is consumed but the magnetic coated carrier is repeatedly used without being consumed, the damage received on the surface thereof is accumulated.

Therefore, when a magnetic coated carrier having a low magnetic force and a sharp particle size distribution and a toner having a sharp particle size distribution are used, the magnetic share acting between the toner and the carrier or between the carriers becomes small, and the surface of the carrier particle is reduced. It is thought that the damage received by is reduced.

The present invention will be described in more detail below.

The particle size of the magnetic coated carrier is preferably as small as possible from the viewpoint of high image quality, but carrier adhesion occurs due to the relationship between the magnetic force and the particle size. From this point of view, the magnetic coated carrier used in the present invention may have a number average particle size in the range of 1 to 100 μm, and the magnetic coated carrier has a magnetization strength of 100 to 150 emu / cm ^3. In this case, it is more preferable that the number average particle diameter is in the range of 5 to 35 μm from the viewpoint of high image quality and prevention of carrier adhesion. On the other hand, the magnetic strength of the magnetic coated carrier is 30 to 100 emu / c.
When it is m ^3, the number average particle diameter is preferably in the range of 35 to 80 μm from the viewpoint of high image quality, prevention of carrier adhesion, and prevention of developer deterioration due to durability. If the number average particle size of the carrier exceeds 100 μm, sweeping is likely to occur when the magnetic brush rubs the surface of the photoreceptor, which is not preferable from the viewpoint of high image quality. Further, if the number average particle diameter of the carrier is smaller than 1 μm, the magnetic force of one magnetic coated carrier particle is small, so that carrier adhesion is likely to occur.

Further, what is important in the present invention is to have a particle size distribution such that the cumulative distribution value of the diameters of 1/2 times the number average particle diameter of the magnetic coated carrier is 20 number% or less. If the cumulative distribution value of ½ diameter or less exceeds 20% by number, carrier adhesion increases as described above,
It is not preferable in that charging to the toner becomes poor. The method for measuring the particle size of the magnetic coated carrier powder used in the present invention will be described later.

As the magnetic characteristics of the magnetic coated carrier used in the present invention, it is important to use one having a magnetization intensity of 30 to 150 emu / cm ³ at 1 kilo Oersted, and more preferably 40 to 50 emu / cm ^3. 130 emu / cm ³
It is preferable to use a magnetic coated carrier having a low magnetic force such that As described above, the strength of magnetization of the magnetic coated carrier is appropriately selected according to the carrier particle size. When the magnetization intensity exceeds 150 emu / cm ³ , it is related to the carrier particle size, but the density of the magnetic brush formed on the developing sleeve at the developing pole decreases, the brush length becomes longer, and the brush becomes rigid. As a result, uneven sweeping is generated on the toner image, and image deterioration such as halftone shading and solid image unevenness is likely to occur due to deterioration in durability of the developer caused by copying a large number of sheets. On the other hand, if it is less than ³⁰ emu / cm ³ , the magnetic force of the magnetic coated carrier will be insufficient, carrier adhesion will occur, and the toner transportability will deteriorate.

The measurement of magnetic characteristics in the present invention is
Riken Denshi Co., Ltd. oscillating magnetic field type automatic recording device for magnetic characteristics B
It was carried out using HV-30. A specific example of the measurement condition will be described later.

The specific resistance of the magnetic coated carrier used in the present invention is 1 × 10 at an electric field strength of 5 × 10 ⁴ V / m.
It is important to have a resistance of ¹² Ωcm or more. 1 x 1
If the specific resistance is less than 0 ¹² Ωcm, as described above, the carrier is attached and the image quality of the image is lowered in the process of visualizing the latent image, and the objects of the present invention such as high image quality and high definition cannot be achieved. The method for measuring the resistance of the magnetic coated carrier powder used in the present invention will be described later.

The resistivity of the carrier core is 5 × 10 ⁴
It is important to have a resistance of 7.7 × 10 ¹⁰ Ωcm or more at an electric field strength of V / m. If the specific resistance is less than 1 × 10 ¹⁰ Ωcm, charge injection occurs or the latent image leaks when the core is exposed even in a part of the coated carrier, which easily causes carrier adhesion and deterioration of dot reproducibility.

[0045] As the core material of the magnetic coated carrier, magnetite represented by the general formula MO · Fe ₂ O ₃ or MFe ₂ O ₄ exhibiting magnetism, can be preferably used ferrite. Here, M is a divalent or monovalent metal ion (Mn, Fe, Ni, Co, Cu, Mg, Zn, Cd,
Li or the like), and M may be a single metal or a plurality of metals. For example, magnetite, gamma iron oxide,
Mn-Zn based ferrite, Ni-Zn based ferrite, M
n-Mg type ferrite, Li type ferrite, Cu-Zn
An iron oxide such as a ferrite can be used.
Among them, inexpensive magnetite can be more preferably used.

As other metal oxides, Mg, Al,
Si, Ca, Sc, Ti, V, Cr, Mn, Fe, C
o, Ni, Cu, Zn, Sr, Y, Zr, Nb, Mo,
A non-magnetic metal oxide containing a single metal or a plurality of metals such as Cd, Sn, Ba and Pb and a metal oxide exhibiting the above-mentioned magnetism can be used. For example, as a non-magnetic metal oxide, Al
₂ O ₃ , SiO ₂ , CaO, TiO ₂ , V ₂ O ₅ , CrO ₂ ,
MnO ₂ , Fe ₂ O ₃ , CoO, NiO, CuO, Zn
O, it can be used _{SrO, Y 2 O 3, ZrO} 2 system or the like.

The above-mentioned metal oxide can be used alone as a carrier core, but in that case, the core specific resistance is 1 × 10 ¹⁰ by performing treatment such as intense oxidation of the core surface.
It is necessary to use Ωcm or more. Further, as a particularly preferable carrier form, it is possible to disperse the above metal oxide in a resin and use it as a carrier core. In this case, one kind of metal oxide may be dispersed in the resin for use, but it is particularly preferable to use at least two kinds of metal oxides in a mixed state. In that case, it is more preferable to use particles having a similar specific gravity and shape in order to improve the adhesiveness with the binder and the carrier strength. For example, magnetite and hematite, magnetite and γ-Fe ₂ O ₃ , magnetite and SiO ₂ , magnetite and Al ₂ O ₃ , magnetite and TiO ₂ , and magnetite and Cu-Zn-based ferrite can be preferably used. Above all, a combination of magnetite and hematite can be preferably used in terms of price and carrier strength.

When the above metal oxide is dispersed in a resin to form core particles, the number average particle diameter of the metal oxide exhibiting magnetism varies depending on the carrier particle diameter, but 0.02 to 2 μm is preferably used. be able to. When two or more kinds of metal oxides are dispersed and used, the number average particle diameter of the metal oxide exhibiting magnetism may be 0.02 to 2 μm, and the number average particle of the other metal oxide may be used. The diameter is 0.
Those having a thickness of 05 to 5 μm can be preferably used. in this case,
Particle size ratio rb / ra of the other metal oxide to the magnetic particles
Preferably exceeds 1.0. When the ratio is 1.0 times or less, metal oxide particles having high specific resistance are hard to appear on the surface, it is difficult to sufficiently increase the resistance of the carrier core, and it becomes difficult to obtain the effect of preventing carrier adhesion.
On the other hand, if it exceeds 5.0 times, the incorporation of the metal oxide particles into the resin becomes unsuccessful, the strength of the magnetic carrier is lowered, and the carrier is easily broken. The method for measuring the particle size of the metal oxide used in the present invention will be described later.

The specific resistance of the metal oxide dispersed and used in the resin is preferably such that the magnetic particles have a specific resistance of 1 × 10 ³ Ω · cm or more. In particular, when two or more kinds of metal oxides are mixed and used, magnetic particles are 1 × 10 ³ Ω · c.
m or more, and the other non-magnetic particles preferably have a higher specific resistance than the magnetic particles. More preferably, the specific resistance of the non-magnetic metal oxide is 1 × 10 ⁸ Ω · c.
Those of m or more are preferably used. If the specific resistance of the magnetic particles is less than 1 × 10 ³ Ω · cm, it is difficult to obtain the desired carrier specific resistance even if the content of the dispersed metal oxide is reduced, which may lead to charge injection and deteriorate the image quality. Easy to cause adhesion. Further, when two or more kinds of metal oxides are dispersed, the specific resistance of the metal oxide having a large particle size is 1 × 10 ⁸
When it is less than Ω · cm, the specific resistance of the carrier core cannot be sufficiently increased, and the effect of the present invention is difficult to be obtained.
The method for measuring the specific resistance of the metal oxide used in the present invention will be described later.

The content of the metal oxide in the metal oxide-dispersed resin core used in the present invention is preferably 50% by weight to 99% by weight. If the amount of the metal oxide is less than 50% by weight, the chargeability tends to be unstable, and the magnetic coat carrier is charged, especially in a low temperature and low humidity environment, and the residual charge thereof tends to remain. The agent or the like easily adheres to the surface of the magnetic coated carrier particles. On the other hand, if it exceeds 99% by weight, the strength of the carrier particles decreases, and the problem of carrier particle cracking due to durability tends to occur.

Further, as a preferred embodiment of the present invention, 2
In the metal oxide-dispersed resin core in which one or more metal oxides are dispersed, the content of magnetic metal oxides in the entire metal oxides contained is preferably 30% by weight to 95% by weight. If it is less than 30% by weight, the core can have a high resistance, but the magnetic force as a carrier becomes small, which may cause carrier adhesion. Also 95% by weight
If it exceeds, it is difficult to increase the resistance of the core though it depends on the specific resistance of the magnetic metal oxide.

The binder resin used in the metal oxide dispersed core used in the present invention includes vinyl resin; polyester resin, epoxy resin, phenol resin, urea resin, polyurethane resin, polyimide resin, cellulose resin and polyether resin. A non-vinyl condensation resin; or a mixture of these with the vinyl resin can be used.

Examples of vinyl monomers for forming vinyl resins include styrene; o-methylstyrene,
m-methylstyrene, p-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, p- n-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-chlorostyrene, 3,4-dichlorostyrene, m-nitrostyrene, o -Nitrostyrene, p-
Styrene derivatives such as nitrostyrene; ethylene and unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; unsaturated diolefins such as butadiene and isoprene; vinyl chloride, vinylidene chloride,
Vinyl halides such as vinyl bromide and vinyl fluoride;
Vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate; methacrylic acid; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate. Α-methylene aliphatic monocarboxylic acid esters such as 2-ethylhexyl methacrylate, stearyl methacrylate and phenyl methacrylate; acrylic acid; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, acrylic Propyl acid, acrylic acid n-
Acrylic esters such as octyl, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; maleic acid, maleic acid half ester; vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl Vinyl ethers such as ethers; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidone; vinyl Naphthalene; acrylic acid or methacrylic acid derivative such as acrylonitrile, methacrylonitrile, acrylamide;
Examples include acrolein. A vinyl resin polymerized by using one or more of these is used.

As a method for producing the magnetic metal oxide-dispersed core particles, a vinyl-based or non-vinyl-based thermoplastic resin,
Magnetic metal oxides and other additives such as curing agents are thoroughly mixed by a mixer, and then melted and kneaded by using a kneader such as a heating roll, a kneader and an extruder, cooled, crushed and classified. It is possible to obtain carrier core particles. At this time, it is preferable that the obtained magnetic metal oxide-containing resin particles are thermally or mechanically spheroidized to be used as a core.

As another method for producing the metal oxide-dispersed core particles, in addition to the method of melt-kneading the above-mentioned resin and the above-mentioned magnetic metal oxide and pulverizing to obtain carrier core particles,
There is also a method of mixing a monomer and a metal oxide and polymerizing the monomer to obtain carrier core particles. At this time, in addition to the vinyl-based monomers described above, bisphenols and epichlorohydrin for forming an epoxy resin; phenols and aldehydes for forming a phenol resin; and a urea resin for forming a phenol resin Urea and aldehydes, melamine and aldehydes are used. For example, as a method for producing a carrier core using a curable phenol resin, phenols and aldehydes are added in the presence of a basic catalyst to a metal oxide and a dispersion stabilizer in the presence of a basic catalyst, and suspension polymerization is performed. Obtain core particles.

Particularly preferred methods for producing carrier core particles include increasing the strength of the carrier core,
In order to coat the coat resin better, it is preferable to use the binder resin in a crosslinked state. For example, a method of adding a crosslinking component at the time of melt-kneading and crosslinking at the time of kneading; a method of using a monomer for forming a curable resin and polymerizing the monomer in the presence of a metal oxide to obtain a core; A method of polymerizing the charged monomer composition in the presence of a metal oxide can be mentioned.

In the magnetic coated carrier used in the present invention, it is important to coat the surface of the carrier core particles with an appropriate resin according to the charge amount of the toner used in the present invention.
The coating amount of the coating resin used in the present invention is preferably in the range of 0.5% by weight to 10% by weight (carrier basis),
Most preferably, it is in the range of 0.6% by weight to 5% by weight. In the metal oxide-dispersed resin carrier, within this range, the exposure density of the metal oxide on the surface of the coated carrier is preferably 5 pieces / μm ² or less in order to favorably prevent carrier adhesion. More preferably 3 pieces / μ
m ² or less.

When the resin coating amount is less than 0.5% by weight, it becomes difficult to sufficiently coat the carrier core particles, and it is particularly difficult to control sufficient charge imparting to the toner after endurance. If it exceeds 10% by weight, the amount of resin coating is too large so that the specific resistance can be set in a desired range, but the fluidity is deteriorated and the durable image characteristics due to the copying of a large number of sheets are easily deteriorated, which is not preferable. A method for calculating the exposure density of the metal oxide on the surface of the resin-coated carrier will be described later.

The coating resin usable in the present invention includes
An insulating resin can be preferably used. The insulating resin may be a thermoplastic resin or a thermosetting resin. As the thermoplastic resin, polystyrene; acrylic resin such as polymethylmethacrylate, styrene-acrylic acid copolymer; styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, vinyl chloride, vinyl acetate,
Polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, solvent-soluble perfluorocarbon resin polyvinyl alcohol, polyvinyl acetal, polyvinyl pyrrolidone, petroleum resin, cellulose; cellulose acetate, cellulose nitrate, methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc. Aromatic polyester resin, polyamide resin, polyacetal resin, polycarbonate resin, polyether sulfone resin, polysulfone resin, such as cellulose derivative, novolac resin, low molecular weight polyethylene, saturated alkyl polyester resin, polyethylene terephthalate, polybutylene terephthalate, and polyarylate. Polyphenylene sulfide resin, polyether Mention may be made of a ton resin.

Examples of the curable resin include phenol resin, modified phenol resin, malein resin, alkyd resin, epoxy resin, acrylic resin, unsaturated polyester obtained by polycondensation of maleic anhydride, terephthalic acid and polyhydric alcohol. , Urea resin, melamine resin, urea-melamine resin, xylene resin, toluene resin, guanamine resin, melamine-guanamine resin, acetoguanamine resin, glyptal resin, furan resin, silicone resin, polyimide resin, polyamideimide resin, polyetherimide resin , Polyurethane resin and the like. The above-mentioned resins may be used alone, or may be used by mixing them. Further, a thermoplastic resin may be mixed with a curing agent and cured to be used.

Preferred methods for producing the magnetic coated carrier include a method of spraying a coating resin solution while floating and flowing carrier core particles to form a coating film on the surface of the core particles, and a spray drying method. The above coating method is particularly suitable for coating the metal oxide-dispersed resin core particles using a thermoplastic resin.

As another coating method, the magnetic resin-coated carrier can be produced by a coating method in which the solvent is gradually volatilized while applying shear stress.
As such a method, specifically, a method of crushing the magnetic carrier particles fixed after solvent volatilization at the glass transition point of the coating resin or higher, and a method of curing and crushing the film while applying shear stress can also be produced. it can.

The bulk density of the magnetic coated carrier used in the present invention is preferably 3.0 g / cm ³ or less. 3.0 g /
When it exceeds cm ³ , the share in the developer becomes large, and the toner is liable to be spent or the coating resin is easily peeled off. The bulk density of the carrier is measured by JI
It is carried out according to the method described in SK5101.

The shape of the magnetic coated carrier is appropriately selected so as to be convenient for a predetermined system. However, the sphericity of the magnetic coated carrier used in the present invention is
It is preferably 2 or less. The magnetic coated carrier has a sphericity of 2
If it exceeds, the fluidity as a developer becomes poor,
It becomes difficult to obtain a high-quality image because the ability of imparting triboelectric charge to the toner is reduced and the shape of the magnetic brush becomes uneven at the developing pole. In addition, the sphericity of the carrier is measured by randomly extracting 300 or more carriers by a field emission scanning electron microscope S-800 manufactured by Hitachi, Ltd., and an image processing analyzer Luzex3 manufactured by Nireco.
Is calculated by calculating the sphericity derived by the following equation.

[0065]

[Outer 1] [In the formula, MX LNG represents the maximum diameter of the carrier, and AR
EA indicates the projected area of the carrier. ]

Here, SF1 means that the closer it is to 1, the more spherical it is.

In the magnetic coated carrier used in the present invention, the carrier particle size and the magnetic force are important parameters for improving the image quality of the toner image as described above. As an index of image quality improvement of the present invention, the carrier image quality improvement parameter KP can be defined by the following formula from the above-mentioned carrier particle size and magnetic force. KP = I × D (where I is the magnetic force of the carrier emu / cm ³ unit,
D is the carrier particle size in cm. The carrier image quality improvement parameter of the magnetic carrier used in the present invention is preferably in the range of 0.08 <KP <1.0 emu / cm ² in order to achieve the object of the present invention, and more preferably 0. The range of 1 <KP <0.8 emu / cm ² is more preferable.

The carrier image quality improvement parameter KP is 0.
May restraining force from the sleeve against becomes smaller when the magnetic brush than 08emu / cm ² is possible to prevent the carrier adhesion better for smaller becomes difficult and becomes greater than 1.0emu / cm ^2, Since the density of the magnetic brush becomes low and the magnetic brush becomes rigid, high image quality may not be achieved in some cases.

The toner used in the present invention preferably has a weight average particle size of 1 to 10 μm, preferably 3 to 8 μm. Further, the distribution cumulative value of ½ times the number average particle diameter or less is 20 number% or less, and the distribution cumulative value of 2 times or more the weight average particle diameter is 10% by volume or less. It is important for satisfying good charge imparting, reproducibility of latent image dots, and the like. Further, in order to improve the triboelectric chargeability of the toner and enhance the dot reproducibility, the cumulative distribution value of ½ times the number average particle diameter or less is 15 number% or less, and the distribution average value of the weight average particle diameter is 2 times or more. Distribution cumulative value is 5% by volume
The following is more preferable. Furthermore, the cumulative distribution value of ½ times the number average particle diameter or less is 10 number% or less, and the cumulative distribution value of the weight average particle diameter twice or more is 2% by volume.
The following is more preferable.

The weight average particle diameter (D4) of the toner is 10 μm.
If the magnetic force of the magnetic coated carrier is decreased, the toner particles for developing the electrostatic latent image become large, and therefore, the toner image cannot be faithfully developed even if the magnetic force of the magnetic coated carrier is decreased. Will become more scattered. Further, a toner having a weight average particle diameter of 1 μm or less causes a problem in handling property as a powder.

Further, if the cumulative distribution value of the particles having a number average particle size of 1/2 times or less exceeds 20% by number, the toner charging cannot be satisfactorily applied to the fine toner particles, and the tribo distribution of the toner becomes wide, and the charging becomes large. Due to defects (reverse component generation) and uneven distribution of the particle size of the developed toner, the problem of particle size change due to durability tends to occur. Further, if the cumulative distribution value of particles having a diameter of at least twice the weight average particle diameter exceeds 10% by volume, frictional charging with the magnetic coated carrier cannot be performed well, and it becomes difficult to faithfully reproduce the latent image. The toner particle size distribution can be measured by, for example, a method using a Coulter counter.

The particle size of the toner used in the present invention is closely related to the particle size of the magnetic coated carrier. When the number average particle diameter of the magnetic carrier is 35 to 80 μm, it is necessary for the toner to have a weight average diameter of 3 to 8 μm in order to improve the charging property and to improve the image quality. On the other hand, when the number average particle diameter of the magnetic coated carrier is 5 to 35 μm, the toner has a weight average particle diameter of 1 to 6 μm in order to prevent the deterioration of the developer and to improve the image quality at the initial stage and especially after the durability test.
It is preferably m.

As the binder resin of the toner used in the present invention, styrene-based polymers obtained from styrene and its derivatives such as polystyrene, poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymerization Coal, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene- Acrylonitrile copolymer, styrene-vinyl ethyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, polyvinyl chloride, phenol resin, modified phenol resin, maleic resin ,acrylic resin Methacrylic resins, polyvinyl acetate,
Silicone resin, aliphatic polyhydric alcohol, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, aromatic dialcohol,
Polyester resins having monomers selected from diphenols as structural units, polyurethane resins, polyamide resins, polyvinyl butyral, terpene resins, coumarone indene resins, petroleum resins, crosslinked styrene resins and crosslinked polyester resins, etc. Can be mentioned.

Specific examples of the monomer capable of being polymerized with styrene used in the styrene-acrylic copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, and acrylic acid. Octyl acid, 2-ethylhexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate,
Acrylic esters having an ethylenic double bond such as butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile and acrylamide; maleic acid; half esters or diesters of maleic acid such as butyl maleate; vinyl acetate, chloride vinyl,
Examples thereof include vinyl esters such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether and vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl hexyl ketone.

As the cross-linking agent, unsaturated bonds are mainly used.
The compound which has more than one can be mentioned. For example, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene, carboxylic acid esters having two unsaturated bonds such as ethylene glycol diacrylate and ethylene glycol dimethacrylate, divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide and divinyl sulfone. , And compounds having three or more unsaturated bonds. These can be used alone or in combination. The cross-linking agent is 0.01 to 10% by weight, preferably 0.0
Preference is given to using from 5 to 5% by weight.

When the pressure fixing method is used, a binder resin for pressure fixing toner is used. For example polyethylene,
Polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, paraffin and other waxes. Can be mentioned.

In the toner used in the present invention, a charge control agent may be blended with the toner for use. By adding the charge control agent, the charge amount can be optimized according to the developing system. Nigrosine as a positive charge control agent,
And quaternary ammonium salts such as fatty acid metal salt derivatives, tributylbenzylammonium-1-hydroxy-4naphthosulfonate, tetrabutylammonium tetrafluoroborate; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyldioxide; Examples thereof include dibutyl tin borate, dioctyl tin borate, and dicyclohexyl tin borate. These can be used alone or in combination of two or more. Of the above-mentioned charge control agents, charge control agents such as nigrosine compounds and quaternary ammonium salts are particularly preferable.

Examples of the negative charge control agent include organic metal complexes and chelate compounds. Acetylacetone metal complexes (including monoalkyl-substituted products and dialkyl-substituted products), salicylic acid-based metal complexes (including monoalkyl-substituted products and dialkyl-substituted products), or salts thereof are preferred, and salicylic acid-based metal salts are particularly preferred. It is suitable. For example, aluminum acetylacetonate, iron (II) acetylacetonate, 3,5-ditertiary butyl salicylic acid metal salt or metal complex can be mentioned. When added to the toner, the charge control agent is 0.1 to 20 parts by weight, more preferably 0.2 to 100 parts by weight of the binder resin.
It is preferred to use from 10 to 10 parts by weight. Particularly when used for color image formation, it is preferable to use a colorless or light-colored charge control agent.

As the colorant which can be added to the toner used in the present invention, conventionally known dyes and pigments can be used. For example carbon black,
Phthalocyanine blue, peacock blue, permanent red, lake red, rhodamine lake, Hansa yellow, permanent yellow, benzidine yellow and the like can be used. The amount of addition at that time is 0.1 to 20 parts by weight, preferably 0.5 to 20 parts by weight, based on 100 parts by weight of the binder resin. Further, in consideration of the suitable transparency of the toner image to the OHP film fixed image, the colorant is preferably used in the range of 12 parts by weight or less, and most preferably 0.5 to 9 parts by weight.

Wax components such as polyethylene, polypropylene, microcrystalline wax, carnauba wax, sazol wax, and paraffin wax may be added to the toner for the purpose of improving releasability at the time of heat roll fixing.

For the toner used in the present invention, inorganic fine particles such as silica, alumina and titanium oxide; fine powder such as organic fine particles such as polytetrafluoroethylene, polyvinylidene fluoride, polymethylmethacrylate, polystyrene and silicone are used. It is preferable that it is added.
By externally adding the above-mentioned fine powder to the toner, the fine powder is present between the toner and the carrier or between the toner particles, the fluidity of the developer is improved, and the life of the developer is also improved. improves. The above-mentioned fine powder preferably has an average particle diameter of 0.2 μm or less. If the average particle size exceeds 0.2 μm, the effect of improving the fluidity is reduced, and the image quality may be deteriorated due to defects during development or transfer. The measurement of the average particle size of these fine powders will be described later.

As for the surface area of these fine powders, the specific surface area by nitrogen adsorption by the BET method is 30 m ² / g or more,
Particularly, those in the range of 50 to 400 m ² / g are good.
The amount of fine powder added is 0.1 with respect to 100 parts by weight of the toner.
It is preferred to use ˜20 parts by weight.

The method of producing the toner used in the present invention is as follows. A vinyl or non-vinyl type thermoplastic resin, a colorant, a charge control agent, and other additives are sufficiently mixed by a mixer and then heated by a heating roll or a kneader. , Melt-knead with a kneader such as an extruder to thoroughly mix the resins, and disperse the colorant and the like therein. After cooling this, it can be pulverized and classified to obtain toner particles. As the toner classification method in the present invention, preferably, a multi-division classification device utilizing inertial force is used. By using this apparatus, the toner having the particle size distribution of the present invention can be efficiently manufactured.

Further, the toner particles can be used as they are, but if necessary, fine powder is externally added.

The toner and the fine powder can be mixed with each other by using a mixer such as a Henschel mixer. A toner having an external additive is mixed with a magnetic coated carrier to prepare a two-component developer. When forming a two-component developer, the proportion of the toner in the developer is typically 1 to 20% by weight, more preferably 1 to 1 depending on the development process.
It is preferably in the range of 0% by weight. The triboelectric charge amount of the toner in the two-component developer is 5 to 100 μC / g
It is preferable that it is in the range of 5 to 6, most preferably 5 to 6.
It is 0 μC / g. The conditions for measuring the triboelectric charge amount used in the present invention will be described later.

As the developing method of the present invention, for example, the developing means as shown in FIG. 1 can be used for the development. Specifically, it is preferable to perform development in a state where the magnetic brush is in contact with the latent image carrier, for example, the photosensitive drum 3, while applying an alternating electric field. Developer carrier (development sleeve)
1 and the photosensitive drum 3 distance (S-D distance) B is 100
It is good for preventing carrier adhesion and improving dot reproducibility to be about 1000 μm. If it is narrower than 100 μm, the supply of the developer tends to be insufficient and the image density becomes low, and if it exceeds 1000 μm, the magnetic lines of force from the developer S1 spread and the density of the magnetic brush becomes low, resulting in poor dot reproducibility and magnetic coating. The force for restraining the carrier is weakened, and the carrier is easily attached.

The voltage between the peaks of the alternating electric field is 500 to 50.
00V is preferable, the frequency is 500 to 10000 Hz,
The frequency is preferably 500 to 3000 Hz, and can be appropriately selected and used depending on the process. In this case, the waveform is triangular wave, rectangular wave, sine wave, or D
Various types of waveforms with different duty ratios can be selected and used. If the applied voltage is lower than 500 V, it may be difficult to obtain a sufficient image density, and the fog toner in the non-image area may not be collected well. On the other hand, when the voltage exceeds 5000 V, the latent image may be disturbed via the magnetic brush, and the image quality may be deteriorated.

By using a two-component type developer having a well-charged toner, the fogging removal voltage (Vback)
Can be lowered, and the primary charging of the photoconductor can be reduced, so that the life of the photoconductor can be extended. Vbac
The value k depends on the developing system, but is preferably 150 V or less, more preferably 100 V or less.

The contrast potential is preferably 200 V to 500 V so that a sufficient image density can be obtained.

When the frequency is lower than 500 Hz, although it is related to the process speed, charge injection into carriers may occur, which may deteriorate the image quality by adhering carriers or disturbing the latent image. If the frequency exceeds 10000 Hz, the toner cannot follow the electric field and the image quality is likely to deteriorate.

What is important in the developing method of the present invention is that the photosensitive drum 3 of the magnetic brush on the developing sleeve 1 is provided in order to achieve sufficient image density, excellent dot reproducibility, and development without carrier adhesion. The contact width (developing nip C) of is preferably 3 to 8 mm. Development nip C is 3
If it is less than 8 mm, it is difficult to satisfactorily satisfy the sufficient image density and dot reproducibility. If it is more than 8 mm, packing of the developer occurs and operation of the machine is stopped, and carrier adhesion is sufficiently suppressed. It becomes difficult to keep up. As a method of adjusting the developing nip, the nip width is appropriately adjusted by adjusting the distance A between the developer regulating member 2 and the developing sleeve 1 or the distance B between the developing sleeve 1 and the photosensitive drum 3.

In the image forming method of the present invention, three or more developing devices for magenta, cyan and yellow are used to output a full-color image particularly emphasizing halftone, and the developer of the present invention is used. And development method,
In particular, by combining with a developing system that forms a digital latent image, there is no influence of the magnetic brush, and since the latent image is not disturbed, the dot latent image can be faithfully developed. Also in the transfer step, a high transfer rate can be achieved by using a toner having a fine particle cut and a sharp particle size distribution, and therefore high image quality can be achieved in both the halftone portion and the solid portion.

Further, in addition to the improvement of the initial image quality, by using the two-component developer of the present invention, the share of the developer in the developing device is small, and the image quality does not deteriorate even when copying a large number of sheets. The effect of can be fully exerted.

In order to obtain a tighter image, it is preferable to have a developing unit for magenta, cyan, yellow, and black, and to give a tighter image by the last development of black. it can.

An image forming apparatus capable of favorably carrying out the full-color image forming method of the present invention will be described with reference to FIG.

The color electrophotographic apparatus shown in FIG. 3 includes a transfer material conveying system I provided from the right side of the apparatus main body 1 (right side of FIG. 1) to the substantially central portion of the apparatus main body, and the apparatus main body 1
A latent image forming section II provided in the approximate center of the image forming section II in the vicinity of the transfer drum 315 forming the transfer material conveying system I.
And a developing means (that is, a rotary developing device) III arranged in proximity to the latent image forming section II.

The transfer material carrying system I has the following structure. An opening is formed in the right wall (right side in FIG. 3) of the apparatus main body 1, and transfer material supply trays 302 and 303 that are detachable are arranged in the opening so as to partially project outside the machine. Paper feed rollers 304 and 305 are arranged substantially directly above the trays 302 and 303, and these paper feed rollers 304 and 305 and a transfer drum 305 disposed on the left side and rotatable in the direction of arrow A are arranged. To work together,
A paper feed roller 306 and paper feed guides 307 and 308 are provided. In the vicinity of the outer peripheral surface of the transfer drum 315, a contact roller 309, a gripper 310, a transfer material separating charger 311 from the upstream side to the downstream side in the rotation direction,
Separation claws 312 are sequentially arranged.

A transfer charger 313 and a transfer material separating charger 314 are provided on the inner peripheral side of the transfer drum 315. A transfer sheet (not shown) made of a polymer such as polyvinylidene fluoride is attached to a portion of the transfer drum 315 around which the transfer material is wound, and the transfer material is electrostatically attached on the transfer sheet. It is attached closely to. On the upper right side of the transfer drum 315, a conveyor belt means 316 is arranged in the vicinity of the separation claw 312, and a fixing device 318 is arranged at the end (right end) of the conveyor belt means 316 in the transfer material conveying direction. There is. A discharge tray 317 that extends to the outside of the apparatus main body 301 and is detachable from the apparatus main body 301 is disposed further downstream than the fixing device 318 in the transport direction.

Next, the structure of the latent image forming section II will be described. A photosensitive drum (for example, an OPC photosensitive drum) 319 which is a latent image carrier rotatably in the direction of the arrow in FIG. 3 is arranged with its outer peripheral surface in contact with the outer peripheral surface of the transfer drum 315. Above the photosensitive drum 319, in the vicinity of the outer peripheral surface thereof, a charger 320 for removing electricity and a cleaning unit 321 from the upstream side to the downstream side in the rotation direction of the photosensitive drum 319.
And a primary charger 323 are sequentially arranged, and an image exposure unit 324 such as a laser beam scanner for forming an electrostatic latent image on the outer peripheral surface of the photosensitive drum 319, and an image exposure reflection unit 325 such as a mirror. It is arranged.

The structure of the rotary developing device III is as follows. A rotatable housing (hereinafter referred to as “rotating body”) 3 is provided at a position facing the outer peripheral surface of the photosensitive drum 319.
26, four types of developing devices are mounted at four positions in the circumferential direction in the rotating body 326.
The electrostatic latent image formed on the outer peripheral surface of is visualized (that is, developed). The above four types of developing devices
Each has a yellow developing device 327Y, a magenta developing device 327M, a cyan developing device 327C, and a black developing device 327BK.

The sequence of the entire image forming apparatus having the above configuration will be described by taking the case of the full color mode as an example. When the photosensitive drum 319 described above rotates in the direction of the arrow in FIG. 3, the photosensitive member on the photosensitive drum 319 is charged by the primary charger 323. In the apparatus of FIG. 3, the peripheral speed of the photosensitive drum (hereinafter, referred to as process speed) is 100 mm / sec or more (for example, 130 to 25).
0 mm / sec). When the photosensitive drum 319 is charged by the primary charger 323, image exposure is performed by the laser light E modulated by the yellow image signal of the original 328, an electrostatic latent image is formed on the photosensitive drum 319, and rotation is performed. By the rotation of the body 326, the electrostatic latent image is developed by the yellow developing device 327Y which is fixed at the developing position in advance, and a yellow toner image is formed.

Paper feed guide 307, paper feed roller 306,
The transfer material conveyed through the paper feed guide 308 is
It is held by the gripper 310 at a predetermined timing,
It is electrostatically wound around the transfer drum 315 by the contact roller 309 and the electrode facing the contact roller 309. The transfer drum 315 is the photosensitive drum 319.
The yellow toner image formed by the yellow developing device 327Y rotates in the direction of the arrow in FIG.
The outer peripheral surface of the photosensitive drum 319 and the transfer drum 315
The image is transferred onto the transfer material by the transfer charger 313 at the portion in contact with the outer peripheral surface of. The transfer drum 315 continues to rotate and the next color (magenta in FIG. 3)
Prepare for the transfer.

The photosensitive drum 319 is the charger 3 for static elimination.
After the charge is removed by 20 and the cleaning means 321 by the cleaning blade cleans it, it is charged again by the primary charger 323, and image exposure is performed by the next magenta image signal to form an electrostatic latent image. The rotary developing device rotates while an electrostatic latent image is formed on the photosensitive drum 319 by imagewise exposure with a magenta image signal to position the magenta developing device 327M at the above-described predetermined developing position and to perform a predetermined operation. Develop with magenta toner. Subsequently, the above-described processes are performed for cyan and black, respectively, and when the transfer of the four color toner images is completed, the four color developed images formed on the transfer material are charged by the chargers 322 and 314, respectively. The gripping of the transfer material by the gripper 310 is released, the transfer material is separated from the transfer drum 315 by the separating claw 312, and the transfer belt 316 fixes the fixing material to the fixing device 3.
Then, it is sent to 18 and fixed by heat and pressure to complete a series of full-color printing sequence, and a required full-color printing image is formed on one surface of the transfer material.

At this time, the fixing operation speed of the fixing device 318 is the peripheral speed of the photosensitive drum (for example, 160 mm / sec).
It is performed at a slower speed (for example, 90 mm / sec). This is because when the unfixed image in which two to four layers of toner are laminated is melt-mixed, it is necessary to give a sufficient heating amount to the toner. The amount is increasing.

The methods for measuring each physical property are described below.

The method of measuring the carrier particle size will be described.

Regarding the particle size of the magnetic coated carrier of the present invention, 300 or more carrier particles having a particle size of 0.1 μm or more are randomly extracted by an optical microscope (100 to 5000 times), and image processing analysis by Nireco Co., Ltd. is conducted. Using the device Luzex3, measure the horizontal ferret diameter as the carrier particle diameter,
Calculate the number average particle size. From the number-based particle size distribution measured under these conditions, the cumulative proportion of the number average particle diameter of 1/2 times the diameter cumulative distribution or less is obtained, and the cumulative value of the 1/2 times diameter cumulative distribution or less is calculated.

The magnetic characteristics of the magnetic coated carrier are the oscillating magnetic field type automatic recording apparatus BHV-3 manufactured by Riken Denshi Co., Ltd.
Measure with 0. For the magnetic characteristic value of the magnetic coated carrier powder, an external magnetic field of 1 kilo Oersted is generated, and the strength of magnetization at that time is obtained. The magnetic coated carrier is prepared in a state in which it is packed in a cylindrical plastic container having a volume of about 0.07 cm ³ so as to be sufficiently dense. In this state, the magnetization moment is measured, the actual volume when the sample is put in is measured, and the strength of the magnetization per unit volume is obtained from this.

The specific resistance of the magnetic coated carrier or carrier core is measured using the measuring device shown in FIG. Cell E
, A magnetic coated carrier or core is filled, electrodes 21 and 22 are arranged so as to be in contact with the filled magnetic coated carrier or core, a voltage is applied between the electrodes, and the current flowing at that time is measured to obtain a ratio. Ask for resistance. In the above measuring method, since the magnetic coated carrier or the core is a powder, the filling rate may change, and accordingly the specific resistance may change, which requires caution. The specific resistance measurement conditions are: contact area S between the filled magnetic coated carrier or core and the electrode S = about 2.3 cm ² , thickness d = about 2 mm, upper electrode 22 load 180 g, and applied voltage 100 V.

The method for measuring the particle size of the metal oxide is described below. The number average particle size of the metal oxide is 5,000 to 2,000 with a transmission electron microscope H-800 manufactured by Hitachi, Ltd.
Using a photographic image magnified 0 times, the particle size is randomly set to 0.0
300 or more particles having a size of 1 μm or more are extracted, and the horizontal Feret diameter is measured as a metal oxide particle diameter by an image processing analyzer Luzex3 manufactured by Nireco Corporation, and the number average particle diameter is calculated by averaging. .

The measurement of the specific resistance of the metal oxide is based on the method of the carrier specific resistance. The cell E of FIG. 2 is filled with a metal oxide, the electrodes 21 and 22 are arranged so as to be in contact with the filled metal oxide, a voltage is applied between the electrodes, and the current flowing at that time is measured. Calculate the specific resistance. When filling the metal oxide, the upper electrode 21 is rotated left and right so that the electrode uniformly contacts the sample. In the above measurement method, the specific resistance is measured under the following conditions: contact area S between filled metal oxide and electrode S = about 2.3 cm ² , thickness d = about 2
mm, load of upper electrode 22 180 g, applied voltage 100 V
And

The metal oxide exposure density on the carrier surface of the magnetic coated carrier particles was determined by using a photographic image (accelerating voltage 1 kV) by a scanning electron microscope S-800 (manufactured by Hitachi Ltd.) magnified 5000 to 10000 times. To measure. Magnetically coated carrier particles are observed with a scanning microscope, and the number of exposed metal oxides per unit area (that is, the number of metal oxide particles protruding from the surface) is counted and calculated for the carrier particle surface hemisphere. To do.
In this operation, 300 or more magnetic coated carrier particles are randomly extracted and an averaging process is performed. Particle size 0.01 μm
The above protrusions are targeted.

A specific example of measuring the toner particle size will be described below.

0.1 to 5 ml of a surfactant (alkylbenzene sulfonate) is added to 100 to 150 ml of the electrolyte solution.
2 to 20 mg of the measurement sample is added thereto. The electrolytic solution in which the sample was suspended was subjected to dispersion treatment for 1 to 3 minutes by an ultrasonic disperser, and the above-mentioned Coulter counter multisizer was used to adjust the volume to a value of 0. Three
The particle size distribution and the like of -40 μm shall be measured. The number average particle diameter and the weight average particle diameter measured under these conditions are obtained by computer processing, and the cumulative ratio equal to or less than ½ times the number average particle diameter cumulative distribution is calculated from the number-based particle diameter distribution. Calculate the cumulative value below the double diameter cumulative distribution. Similarly, the cumulative ratio of the double diameter cumulative distribution or more of the weight average particle diameter is calculated from the volume-based particle size distribution, and the cumulative value of the double diameter cumulative distribution or more is obtained.

A method for measuring the triboelectric charge amount will be described.

The toner and the magnetic coated carrier are mixed so that the weight of the toner is 5% by weight, and the mixture is mixed with a turbula mixer.
Mix for 0 seconds. This mixed powder (developer) is applied to the bottom of 500
It is put in a metal container equipped with a mesh conductive screen, sucked by a suction device, and the triboelectric charge amount is obtained from the difference in weight before and after suction and the potential accumulated in the condenser connected to the container. At this time, the suction pressure is 250 mmHg. By this method, the triboelectric charge amount is calculated using the following formula.

Q (μC / g) = (C × V) × (W ₁ −W ₂ ) ⁻¹ (where W ₁ is the weight before suction, W ₂ is the weight after suction, and C is The capacity of the capacitor and V are the potentials stored in the capacitor.)

The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples.

[0119]

【Example】

Example 1 Phenol 10 parts by weight Formaldehyde 6 parts by weight (formaldehyde about 40% by weight, methanol about 10% by weight, balance water) 31 parts by weight magnetite (particle size 0.24 μm, specific resistance 5 × 10 ⁵ Ωcm) α -Fe ₂ O ₃ 53 parts by weight (particle size 0.60 μm, specific resistance 8 × 10 ⁹ Ωcm)

The above materials and 4 parts by weight of 28% by weight ammonia water as a basic catalyst and 15 parts by weight of water were placed in a flask, and the temperature was raised to 85 ° C. in 40 minutes while stirring and mixing.
It was held and reacted and cured for 3 hours. Then, after cooling to 30 ° C. and adding 100 parts by weight of water, the supernatant was removed, and the precipitate was washed with water and air dried. Next, this was dried under reduced pressure (5 mmHg or less) at 50 to 60 ° C., and magnetite and hematite were bound with a phenol resin as a binder to obtain a spherical magnetic carrier core. This was classified using a multi-division classifier [Elbow Jet Lab EJ-L-3 (manufactured by Nittetsu Mining Co., Ltd.)] to cut fine powder.
The obtained magnetic carrier core has a number average particle size of 40 μm,
The cumulative distribution value of 20 μm (1/2 diameter) or less was 5.7% by number. The resistance of the obtained magnetic carrier core was 7.3 × 10 ¹² Ω · cm.

The surface of the obtained magnetic carrier core particles was coated with a thermosetting silicone resin by the following method. A 10 wt% carrier coat solution was prepared using toluene as a solvent so that the amount of coat resin was 1.2 wt%. Shear stress was continuously applied to this coating solution to volatilize the solvent to coat the carrier core. The magnetic coated carrier particles were cured at 250 ° C. for 1 hour, crushed, and then classified with a 100 mesh screen to obtain magnetic coated carrier particles. The number average particle size and particle size distribution of the obtained magnetic coated carrier particles were substantially the same as those of the core. Also,
The sphericity (SF-1) of the magnetic coated carrier was measured and found to be 1.04.

The metal oxide exposure density of the obtained magnetic coated carrier particles was measured by an electron microscope and an image processing device. As a result, the average metal oxide exposure density on the surface of the carrier particles was 2.2 particles / μm ² . .

The specific resistance of the magnetic coated carrier was measured and found to be 9.2 × 10 ¹³ Ω · cm. Moreover, as a result of measuring the magnetic characteristics of the magnetic coated carrier, the magnetic characteristics at that time were the magnetization intensity (σ ₁₀₀₀ ) at 1 kilo Oersted = 57 emu / cm ³ (the packing density of the sample was 2.10 g / cm ³ ).

Table 1 shows the physical properties of the magnetic coated carrier.

On the other hand, a toner was prepared as follows.

Yellow toner 100 parts by weight of a polyester resin obtained by condensing propoxylated bisphenol and fumaric acid. I. Pigment Yellow 15 (colorant) 4.5 parts by weight Chromium complex salt of di-tert-butylsalicylic acid (negative charge control agent, light color) 4 parts by weight

These were sufficiently premixed, melt-kneaded, cooled, and coarsely pulverized to a particle size of about 1 to 2 mm using a hammer mill. Then, it was pulverized by an air jet pulverizer. Further, the obtained finely pulverized product was classified using an elbow jet classifier to obtain a negatively chargeable yellow powder (nonmagnetic yellow toner). The weight-average particle diameter (D4) is 6.9 μm, the number-average particle diameter (D1) is 5.1 μm, and the cumulative distribution value of ½ times the number-average particle diameter or less is 7.3% by number. The cumulative distribution value of the particles having a diameter twice the weight average particle diameter or more was 0% by volume.

100 parts by weight of the above yellow toner and hydrophobized titanium oxide fine powder (average particle diameter 0.02 μm)
1.0 parts by weight are mixed with a Henschel mixer,
A yellow toner having titanium oxide fine powder externally added was prepared. The average particle size and particle size distribution of this yellow toner were substantially the same as those before external addition. The tribo with the magnetic coated carrier was −36.5 μc / g.

Magenta toner Polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts by weight of C.I. I. Pigment Red 122 4 parts by weight C.I. I. Basic Red 12 1 part by weight Di-tert-butylsalicylic acid chromium complex salt 4 parts by weight

In the same manner as the yellow toner, a negatively chargeable magenta powder (non-magnetic magenta toner) was obtained. The weight average particle diameter (D4) is 6.4 μm, the number average particle diameter (D1) is 4.9 μm, and the cumulative distribution value of ½ times the number average particle diameter or less is 6.7% by number. The cumulative distribution value of the particles having a diameter twice the weight average particle diameter or more was 0% by volume.

100 parts by weight of the above magenta toner and hydrophobized titanium oxide fine powder (average particle diameter 0.02 μm)
1.0 parts by weight are mixed with a Henschel mixer,
A magenta toner to which titanium oxide fine powder was externally added was prepared. The average particle size and particle size distribution of this toner were substantially the same as those before external addition. The tribo with the magnetic coated carrier was −34.9 μc / g.

Cyan toner Polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts by weight Copper phthalocyanine pigment 5 parts by weight Chromium complex salt of di-tert-butylsalicylic acid 4 parts by weight

Negatively chargeable cyan powder (non-magnetic cyan toner) was obtained in the same manner as the yellow toner. The weight average particle diameter (D4) is 6.6 μm, and the number average particle diameter (D
1) is 5.0 μm, the cumulative distribution value of 1/2 times or less of the number average particle diameter is 8.2 number%, and the cumulative distribution value of 2 times or more of the weight average particle diameter is 0% by volume. Met.

100 parts by weight of the above cyan toner and hydrophobized titanium oxide fine powder (average particle diameter 0.02 μm)
1.0 parts by weight are mixed with a Henschel mixer,
A cyan toner to which titanium oxide fine powder was externally added was prepared. The average particle size and particle size distribution of this toner were substantially the same as those before external addition. The tribo with the magnetic coated carrier was −37.7 μc / g.

Black toner Polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts by weight Carbon black (primary particle diameter 60 nm) 5 parts by weight Chromium complex salt of di-tert-butylsalicylic acid 4 parts by weight

Negatively chargeable black powder (non-magnetic black toner) was obtained in the same manner as the yellow toner. The weight average particle diameter (D4) is 6.4 μm, the number average particle diameter (D1) is 4.7 μm, and the cumulative distribution value of ½ times the number average particle diameter or less is 9.9% by number. The cumulative distribution value of the particles having a diameter twice the weight average particle diameter or more was 0% by volume.

100 parts by weight of the above black toner and hydrophobized titanium oxide fine powder (average particle diameter 0.02 μm)
1.0 parts by weight are mixed with a Henschel mixer,
A black toner to which titanium oxide fine powder was externally added was prepared. The average particle size and particle size distribution of this toner were substantially the same as those before external addition. The tribo with the magnetic coated carrier was −33.3 μc / g.

The magnetic coated carrier and the toner for each color were mixed so as to have a toner concentration of 6.5% by weight to obtain a two-component developer. Images of the two-component developer were printed using a full-color laser copying machine CLC-500 modified by Canon. A schematic diagram of the periphery of the developing unit is shown in FIG. 1 and will be described below. The distance A between the developer bearing member (developing sleeve) 1 and the developer regulating member (magnetic blade) 2 of the developing device is 600 μm, and the distance B between the developing sleeve 1 and the electrostatic latent image bearing member (photosensitive drum) 3 is 500 μm. And The developing nip at this time was 5 mm. The peripheral speed ratio between the developing sleeve 1 and the photosensitive drum 3 is 2.0: 1, the magnetic field of the developing pole S1 of the developing sleeve 1 is 1 kilo Oersted, and the developing conditions are an alternating electric field of 2000 V (peak-to-peak voltage) and a frequency. The square wave was 2200 Hz, and the developing bias was set to -470V. Further, the toner development contrast (Vcont) was 350V and the fog removal voltage (Vback) was 80V. The primary charging of the photosensitive drum was −560V. Under these development conditions, the digital latent image (spot diameter 64 μm) on the photoconductor was developed by the reversal development method.

As a result, the density of the solid image of the cyan toner was as high as 1.75, the dots were not rough, and the reproducibility of the halftone portion was good. Further, the image discoloration and toner fog in the image area and non-image area due to carrier adhesion were not observed.

Further, a durability test of a large number of 30,000 sheets was performed. After this, images were printed in the same manner as in the initial image printing test. As a result, the density of the solid image of cyan toner was as high as 1.73, and the reproducibility of the halftone portion was also good. Further, neither fogging nor carrier adhesion was observed. When the SEM image of the cyan developer was observed, the coating material did not peel off, and the surface state was similar to the initial magnetic coated carrier surface.

The results are listed in Table 2.

Example 2 Phenol 10 parts by weight Formaldehyde 6 parts by weight (formaldehyde about 40%, methanol about 10%, balance water) 44 parts by weight magnetite (particle size 0.24 μm, specific resistance 5 × 10 ⁵ Ωcm) 44 parts by weight of α-Fe ₂ O ₃ (particle size 0.40 μm, specific resistance 8 × 10 ⁹ Ωcm)

Example 1 except that the amount of basic catalyst and the amount of water were changed.
Polymerization was carried out in the same manner as in. The polymer particles obtained were classified using an elbow jet to cut fine powder. The obtained carrier core had a number average particle size of 55 μm, and the cumulative distribution value of ½ times or less of the number distribution was 7.1% by number. The obtained core resistance is 5.3 × 10 ¹² Ω.
It was cm.

The surface of the obtained core particles was coated in the same manner except that the coating amount used in Example 1 was 0.8%.

The particle size and particle size distribution of the obtained coated carrier particles were substantially the same as those before coating. The sphericity of the carrier was measured and found to be 1.06.

The metal oxide exposure density of the obtained carrier particles was measured by an electron microscope and an image processing device. As a result, the average metal oxide density in the vicinity of the carrier surface was 2.0 particles / μm ² .

The specific resistance of the carrier particles was measured and found to be 8.0 × 10 ¹³ Ω · cm. Also, the strength of magnetization at 1 kilo Oersted (σ ₁₀₀₀ ) = 70 em
u / cm ³ (packing density of sample: 2.11 g
/ Cm ³ ).

A two-component type developer (toner concentration 6%) was prepared in the same manner as in Example 1 by using the obtained magnetic coated carrier together with the toner used in Example 1, and the mixture was put in a copying machine to perform an image formation test. I went. On the other hand, when the tribo of the toner at the toner concentration of 5% was measured, the yellow toner was -36.
2 μc / g, magenta toner: −34.7 μc / g, cyan toner: −37.9 μc / g, black toner: −
It was 32.8 μc / g. Further, the setting of the developing device and the developing method was the same as in the first embodiment. As a result, Example 1
Similarly to the above, the initial image quality, especially the dot reproducibility, was excellent and a high resolution image was obtained. In addition, good results were obtained without fogging or carrier adhesion. In addition, 3000 in full color
The image quality after the 0-copy test was almost the same as the initial image. At this time, no carrier adhesion was observed even in durability. Observation of the carrier surface after the endurance was similar to the initial surface state and was good.

(Example 3) Phenol 10 parts by weight Formaldehyde 6 parts by weight (formaldehyde about 40% by weight, methanol about 10% by weight, balance water) 75 parts by weight magnetite (particle size 0.24 μm, specific resistance 5 × 10 ^5). Ωcm) 9 parts by weight of α-Fe ₂ O ₃ (particle size 0.60 μm, specific resistance 8 × 10 ⁹ Ωcm)

Polymerization was carried out in the same manner as in Example 1 except that the amounts of basic catalyst and water were changed. The polymer particles obtained were classified to obtain a magnetic substance-dispersed resin carrier core. This was classified using an elbow jet to cut fine powder. The obtained carrier core has a number average particle size of 3
At 2 μm, the cumulative distribution value of 1/2 diameter or less is 9.2% by number.
Met. The resistance of the obtained core is 2.4 × 10.
It was ¹² Ω · cm.

The surface of the obtained core particles was coated in the same manner except that the coating amount used in Example 1 was changed to 1.8%.

The particle size and particle size distribution of the obtained coated carrier particles were substantially the same as those before coating. The sphericity of the carrier was measured and found to be 1.08.

The metal oxide exposure density of the obtained carrier particles was measured by an electron microscope and an image processing device. As a result, the average metal oxide exposure density in the vicinity of the carrier surface was 2.
The number was 0 / μm ² .

The specific resistance of the carrier particles was measured and found to be 2.1 × 10 ¹³ Ω · cm. Also, the strength of magnetization at 1 kilo Oersted (σ ₁₀₀₀ ) = 127e
was mu / cm ³ (packing density of the sample was 2.11)
g / cm ³ ).

On the other hand, as the toner, the same colorant was used for each color as in Example 1, and the prescription amount was 6 parts by weight for each yellow,
Magenta 5 parts by weight or magenta 1 part by weight, cyan 6.5
It was produced by changing the weight part and the black 6.5 part by weight, and changing the crushing condition and the classification condition. The average particle size and particle size distribution of each toner are as follows:
Weight average particle diameter 5.0 μm, number average particle diameter 3.6 μm, distribution cumulative value of 1/2 times or less of number average particle diameter is 12.2% by number, distribution cumulative value of 2 times or more of weight average particle diameter Value is 0% by volume, magenta toner: weight average particle diameter 5.0 μm, number average particle diameter 3.7 μm, distribution cumulative value of 1/2 times or less of number average particle diameter is 10.1 number%, weight average particle 0% by volume of distribution cumulative value equal to or more than twice the diameter, cyan toner: weight average particle diameter 5.2 μm, number average particle diameter 3.7 μm, distribution cumulative value equal to or less than 1/2 times the number average particle diameter. 10.6% by number, cumulative distribution value of diameters equal to or more than twice the weight average particle diameter is 0% by volume, black toner: weight average particle diameter 4.9 μm, number average particle diameter 3.6
The cumulative distribution value of μm, which is ½ the diameter of the number average particle diameter or less, was 9.8% by number, and the cumulative distribution value of the particle diameter of 2 times or more the weight average particle diameter was 0% by volume. The titanium oxide used in Example 1 was externally added to each of these toners by 2.0%. A developer (toner concentration 7%) was prepared from the obtained carrier in the same manner as in Example 1 using the toner used in Example 1, and the resulting carrier was put in a copying machine to conduct an image development test. When toner tribo was measured, yellow toner: -39.1 μc / g, magenta toner: -37.3 μc / g, cyan toner: -41.
7 [mu] c / g, black toner: -37.0 [mu] c / g. Further, the setting of the developing device and the developing method was the same as in the first embodiment. As a result, an image having excellent dot reproducibility, uniform halftone and high resolution was obtained as in Example 1. In addition, good results were obtained without fogging and carrier adhesion. Further, the image quality after performing the copying test of 30,000 sheets in full color was almost the same as the initial image. At this time, no carrier adhesion was observed even in durability.

Example 4 Phenol 6.5 parts by weight Formaldehyde 3.5 parts by weight (formaldehyde about 40%, methanol about 10%, balance water) 81 parts by weight magnetite (particle size 0.24 μm, specific resistance 5 ×) 10 ⁵ Ωcm) 9 parts by weight of Al ₂ O ₃ (particle size 0.63 μm, specific resistance 5 × 10 ¹³ Ωcm)

Polymerization was carried out in the same manner as in Example 1 except that the above materials were used. This was classified using an elbow jet to cut fine powder. The obtained carrier core had a number average particle diameter of 28 μm, and the cumulative distribution value of ½ or less diameter was 12.4 number%. The resistance of the obtained core was 4.2 × 10 ¹¹ Ω · cm.

On the surface of the obtained core particles, the coating resin was changed to the following styrenic copolymer so that the coating amount was 2.2%,
Coated Further, it was dried at 150 ° C. for 1 hour.

Styrene-2-ethylhexyl methacrylate copolymer (copolymerization ratio: 50/50)

The particle size and particle size distribution of the obtained coated carrier particles were substantially the same as those before coating. The sphericity of the carrier was measured and found to be 1.09.

The metal oxide exposure density of the obtained carrier particles was measured by an electron microscope and an image processing device. As a result, the metal oxide exposure density in the vicinity of the carrier surface was 3.0 particles / μm ² .

The specific resistance of the carrier particles was measured and found to be 5.2 × 10 ¹³ Ω · cm. The strength of magnetization at 1 kilo Oersted (σ ₁₀₀₀ ) = 140e
was mu / cm ³ (the packing density of the sample was 2.41).
g / cm ³ ).

Using the toner used in Example 3, a developer (toner concentration 9%) was prepared in the same manner as in Example 3.
The toner tribo is yellow toner: −37.5.
μc / g, magenta toner: −35.3 μc / g, cyan toner: −39.1 μc / g, black toner: −3
It was 5.8 μc / g. Further, the developer carrying member (developing sleeve) 1 of the developing device and the developer regulating member (magnetic blade)
The setting of the developing method was the same as in Example 1 except that the distance A from 2 was set to 750 μm. As a result, an image with excellent dot reproducibility and high resolution was obtained. In addition, good results were obtained without fogging or carrier adhesion. Further, the image quality after performing the copying test of 30,000 sheets in full color was almost the same as the initial image. At this time, no carrier adhesion was observed even in durability.

(Example 5) Melamine 25 parts by weight Formaldehyde 15 parts by weight (formaldehyde about 40%, methanol about 10%, balance water) Magnetite 60 parts by weight (particle size 0.24 μm, specific resistance 5 × 10 ⁵ Ωcm)

According to Example 1, PVA1 was used as a dispersion stabilizer.
Polymerization was carried out in the same manner except that parts by weight were used as the dispersion stabilizer and the above materials were used. This was classified using an elbow jet to cut fine powder. The obtained carrier core had a number average particle diameter of 48 μm and a cumulative distribution value of ½ times or less the diameter was 6.6% by number. The resistance of the obtained core was 7.7 × 10 ¹⁰ Ω · cm.

The surface of the obtained core particles was coated in the same manner except that the coating amount used in Example 1 was changed to 1.0 part by weight.

The particle size and particle size distribution of the obtained coated carrier particles were substantially the same as those before coating. The sphericity of the carrier was measured and found to be 1.15.

The metal oxide exposure density of the obtained carrier particles was measured by an electron microscope and an image processing device.
Metal oxide exposure density near the carrier surface is 1.4 / μ
It was m ² .

The specific resistance of the carrier particles was measured and found to be 1.5 × 10 ¹³ Ω · cm. Also, the strength of magnetization at 1 kilo-ested (σ ₁₀₀₀ ) = 49 emu
/ Cm ³ (packing density of the sample 1.32 g /
cm ³ ).

The toner obtained by using the obtained carrier in Example 1 was used as a two-component type developer (toner concentration: 6.
5%) was prepared and put in a copying machine to conduct an image formation test. When the toner tribo was measured, the yellow toner:
-33.4 μc / g, magenta toner: -34.7 μc
/ G, cyan toner: -30.4 μc / g, black toner: -28.6 μc / g. The setting of the developing device and the developing method was the same as in the first embodiment. As a result, in the same manner as in Example 1, the initial image quality, especially the dot reproducibility is excellent,
A high-resolution image was obtained. In addition, good results were obtained without fogging or carrier adhesion. In addition, 3 in full color
The image quality after the copying test of 0000 sheets was almost the same as the initial image. At this time, neither fog nor carrier adhesion was observed in durability. Observation of the carrier surface after the endurance revealed the same as the initial surface condition.

Example 6 Phenol 6.5 parts by weight Formaldehyde 3.5 parts by weight (formaldehyde about 40%, methanol about 10%, balance water) 54 parts by weight magnetite (particle size 0.24 μm, specific resistance 5 ×) 10 ⁵ Ωcm) CuO _0.17 ZnO _0.23 Fe ₂ O _{3 0.60} 36 parts by weight (particle size 0.78 μm, specific resistance 8 × 10 ⁸ Ωcm)

Polymerization was carried out in the same manner as in Example 1. This was classified using an elbow jet to cut fine powder. The obtained carrier core has a number average particle diameter of 34 μm.
The cumulative distribution value of ½ diameter or less was 4.4% by number. The resistance of the obtained core is 6.7 × 10 ¹² Ω.
It was cm.

Fluorine resin was coated on the surface of the obtained core particles. A carrier coating solution of 5% by weight was prepared using toluene as a solvent so that the amount of resin was 1.0% by weight.
The coating was performed in the same manner as the coating method used in 1.

The average particle size and particle size distribution of the obtained coated carrier particles were the same before and after coating. The sphericity of the carrier was measured and found to be 1.09.

The metal oxide exposure density of the obtained carrier particles was measured by an electron microscope and an image processing device. As a result, the average metal oxide exposure density in the vicinity of the carrier surface was 2.
The number was 0 / μm ² .

The resistivity of the carrier particles was measured and found to be 7.2 × 10 ¹³ Ω · cm. Also, the strength of magnetization at 1 kilo Oersted (σ ₁₀₀₀ ) = 120e
was mu / cm ³ (packing density of the sample was 2.44
g / cm ³ ).

The carrier thus obtained was mixed with the toner used in Example 3 to prepare a developer (toner concentration: 7%), which was put in a copying machine and an image forming test was conducted. When the toner tribo was measured, the yellow toner was -34.4 μc /
g, magenta toner: -31.2 μc / g, cyan toner: -38.8 μc / g, black toner: -34.5
It was μc / g. The setting of the developing device and the developing method was the same as in the first embodiment. As a result, as in Example 1, the initial image quality and the image quality after 30,000 sheets were as good as in Example 1. In particular, halftone roughness was very good in displaying images before and after running.
It is considered that this is because the surface energy of the fluororesin was low and the release of the agent was performed well. The surface of the carrier after the endurance was the same as the initial surface state and was good.

Example 7 Melamine 10 parts by weight Formaldehyde 6 parts by weight (formaldehyde about 40%, methanol about 10%, balance water) CuO _0.25 ZnO _0.25 Fe ₂ O _{3 0.50} 59 parts by weight (particle size 0.25 μm, Specific resistance 7 × 10 ⁸ Ωcm) Al ₂ O ₃ 25 parts by weight (particle size 0.63 μm, specific resistance 5 × 10 ¹³ Ωcm)

Polymerization was carried out in a basic solvent in the same manner as in Example 1. This was classified using an elbow jet to cut fine powder. The obtained carrier core had a number average particle diameter of 48 μm and a cumulative distribution value of ½ or less diameter was 4.5 number%. In addition, the resistance of the obtained core is
It was 5.4 × 10 ¹³ Ω · cm.

The coating resin used in Example 6 was similarly coated on the surface of the obtained core particles.

The average particle size and particle size distribution of the obtained coated carrier particles were substantially the same as those before coating. The sphericity of the carrier was measured and found to be 1.08.

The exposed metal oxide density of the obtained particles was measured by an electron microscope and an image processing device.
The average metal oxide exposure density in the vicinity of the carrier surface was 2.0 pieces / μm ² .

The specific resistance of the carrier particles was measured and found to be 1.1 × 10 ¹⁴ Ω · cm. Also, the strength of magnetization at 1 kilo-ested (σ ₁₀₀₀ ) = 87 emu
/ Cm ³ (packing density of sample: 2.35 g /
cm ³ ).

The carrier thus obtained was mixed with the toner used in Example 1 to prepare a developer (toner concentration: 6%), which was put in a copying machine and an image forming test was conducted. When the toner tribo was measured, the yellow toner was −27.3 μc /
g, magenta toner: −25.5 μc / g, cyan toner: −26.6 μc / g, black toner: −25.9
It was μc / g. The setting of the developing device and the developing method was the same as in the first embodiment. As a result, as in Example 1, the initial image quality and the image quality after durability were as good as in Example 1. Fog and carrier adhesion were good before and after durability. Further, the surface of the carrier after the durability was the same as the initial surface state.

(Example 8) Styrene-isobutyl acrylate copolymer (copolymerization weight ratio 85/15) 20 parts by weight magnetite 70 parts by weight (particle size 0.24 μm, specific resistance 5 × 10 ⁵ Ωcm) γ-Fe ₂ O ₃ 10 parts by weight (particle size 0.80 μm, specific resistance 2 × 10 ⁸ Ωcm)

The above materials were sufficiently premixed with a Henschel mixer, melt-kneaded with a three-roll mill twice, and after cooling, coarsely pulverized with a hammer mill to a particle size of about 2 mm. Then, it was pulverized to a particle size of about 33 μm by an air jet pulverizer. Further, the obtained finely pulverized product was put into MechanoMill MM-10 (manufactured by Okada Seiko) and mechanically spheroidized.

The finely pulverized particles that had been made spherical were further classified to obtain a magnetic material-dispersed resin carrier core. The obtained carrier core had a number average particle size of 34 μm and a cumulative distribution value of ½ times or less of the diameter was 12.2% by number. Further, the specific resistance of the obtained core was 2.7 × 10 ¹² Ω · cm. Using a fluidized bed coater, this was coated with the resin used in Example 4 by adjusting the concentration of the coating liquid to 5% so that the coating amount was 2.0%, and at 1 ° C at 60 ° C. Dried for hours.

The average particle size and particle size distribution of the obtained carrier particles were substantially the same before and after coating. The sphericity of the carrier was measured and found to be 1.19.

The metal oxide exposure density of the obtained carrier particles was measured by an electron microscope and an image processing device, and as a result, the metal oxide exposure density in the vicinity of the carrier surface was 2.2 particles / μm ² .

When the specific resistance of the carrier particles was measured,
It was 5.1 × 10 ¹³ Ω · cm. Also, the strength of magnetization at 1 kilo-ested (σ ₁₀₀₀ ) = 80 emu / cm
³ (packing density of sample 1.90 g / cm
³ ).

The carrier thus obtained was mixed with the toner used in Example 3 to prepare a developer (toner concentration: 7%), which was put in a copying machine and an image forming test was conducted. When the toner tribo at this time was measured, the yellow toner was -38.
8 μc / g, magenta toner: −37.1 μc / g, cyan toner: −40.2 μc / g, black toner: −
It was 37.3 μc / g. The setting of the developing device and the developing method was the same as in the first embodiment. As a result, similar to Example 1, the initial image quality, carrier adhesion, fog, and image quality after endurance were as good as Example 1. Further, the surface of the carrier after the endurance was similar to the initial surface state and was good.

Comparative Example 1 Magnetite particles having a number average particle diameter of 49 μm were mixed in air in 8
It heated at 00 degreeC for 2 hours. The specific resistance of the obtained particles is 2.
It was 0 × 10 ¹⁰ Ω · cm. This was coated in the same manner as in Example 1.

The obtained carrier particles were classified using an elbow jet classifier to cut fine powder. The obtained carrier had a number average particle diameter of 48 μm, and the cumulative distribution value of ½ times the diameter or less was 11.5 number%. The specific resistance was 6.7 × 10 ¹² Ω · cm. The sphericity of the carrier was measured and found to be 1.20. Also,
Magnetization strength at 1 kilo Oersted (σ ₁₀₀₀ ) = 1
It was 09 emu / cm ³ (packing density of the sample was 3.30 g / cm ³ ).

The carrier thus obtained was mixed with the toner used in Example 1 to prepare a developer (toner concentration: 6%), which was put in a copying machine and an image forming test was conducted. When the toner tribo was measured, the yellow toner was −27.2 μc /
g, magenta toner: −25.1 μc / g, cyan toner: −27.9 μc / g, black toner: −25.5
It was μc / g. The setting of the developing device and the developing method was the same as in the first embodiment. As a result, good results were obtained in both the initial image quality and the image quality after endurance.

(Comparative Example 2 ) The molar ratios of Fe ₂ O ₃ = 50 mol%, CuO = 27 mol% and ZnO = 23 mol% were weighed and mixed using a ball mill. After calcining this at a temperature of 1000 ° C., the burnable material was pulverized by a ball mill. 100 parts by weight of the obtained powder, 0.5 parts by weight of sodium polymethacrylate and water were put into a wet ball mill and mixed,
A slurry was obtained. The obtained slurry was granulated with a spray dryer. This was sintered at a temperature of 1200 ° C. to obtain a core particle. When the resistance of the obtained carrier core particles was measured, it was 4.0 × 10 ⁸ Ω · cm.

The carrier core was coated with the same resin as in Example 1 to obtain coated carrier particles. The number average particle diameter of the obtained carrier particles was 47 μm, and the cumulative distribution value of ½ or less diameter was 23.1 number%. The specific resistance was 1.1 × 10 ¹⁰ Ω · cm. The sphericity of the carrier was measured and found to be 1.24. Also,
Magnetization strength at 1 kilo Oersted (σ ₁₀₀₀ ) = 2
It was 06 emu / cm ³ (packing density of the sample was 3.46 g / cm ³ ).

The carrier thus obtained was mixed with the toner used in Example 1 to prepare a developer, which was put in a copying machine and an image forming test was conducted. When the toner tribo at this time was measured, the yellow toner was −25.5 μc / g, the magenta toner was −23.7 μc / g, and the cyan toner was −26.
1 μc / g, black toner: −24.3 μc / g. Further, a developer carrying member (developing sleeve) 1 of the developing device 1
The distance A between the developer regulating member (magnetic blade) 2 and 85
The setting of the developing method was the same as in Example 1 except that the thickness was 0 μm. As a result, the density of the solid image was high, but the dots were rough and the reproducibility of the halftone portion was poor. further,
Roughness of the non-image area due to carrier adhesion was observed.
When this was observed, it was a fine powder of 20 μm or less of the carrier. In addition, toner fog was recognized. Further, as in Example 1, when 30,000 sheets of the carrier after the durability test were observed, toner spent was generated. In the image display after the endurance, the halftone part was further deteriorated in the roughness and the fog was also deteriorated.

Comparative Example 3 Styrene-isobutyl acrylate copolymer (90/10) 40 parts by weight magnetite 60 parts by weight (particle size 0.24 μm, specific resistance 5 × 10 ⁵ Ωcm)

The above materials were kneaded, pulverized, and mixed in the same manner as in Example 7.
Spheroidizing treatment was performed to obtain a magnetic material-dispersed resin carrier core. No classification operation was performed. This was used as a carrier without coating. The specific resistance of the carrier is 9.3 × 10.
It was ¹² Ω · cm. The number average particle diameter of carrier particles was 53 μm, and the cumulative distribution value of ½ times or less diameter was 22.0 number%. The sphericity of the carrier was measured and found to be 1.16.

The metal oxide exposure density of the obtained carrier particles was measured by an electron microscope and an image processing device. As a result, the average metal oxide exposure density in the vicinity of the carrier surface was 1.
It was 9 pieces / μm ² .

The strength of magnetization at 1 kilo-oersted (σ ₁₀₀₀ ) was 50 emu / cm ³ (packing density of the sample was 1.32 g / cm ³ ).

The obtained carrier was used as a developer with the toner used in Example 1 (toner concentration: 6%) and put in a copying machine to conduct an image forming test. When the toner tribo at this time was measured, the yellow toner was −29.7 μc / g, the magenta toner was −25.7 μc / g, and the cyan toner was −.
28.7 μc / g, black toner: −26.8 μc / g
It was g. Further, the setting of the developing device and the developing method was the same as in the first embodiment. As a result, the initial halftone roughness was slightly inferior and carrier adhesion was observed.

(Comparative Example 4 ) Phenol 6.5 parts by weight Formaldehyde 3.5 parts by weight (formaldehyde about 40%, methanol about 10%, balance water) 45 parts by weight magnetite (particle size 0.24 μm, specific resistance 5 ×) 10 ⁵ [Omega] cm) magnetite 45 parts by weight (particle size 0.66 .mu.m, specific resistance ⁵ × 10 5 Ωcm)

Polymeric particles were obtained from the above materials in the same manner as in Example 1, and then classified to obtain a magnetic material-dispersed resin calicore. The obtained carrier core has a number average particle size of 4
At 5 μm, the cumulative distribution value of 1/2 diameter or less is 6.8% by number.
Met. Moreover, the resistance of the obtained core is 3.5 × 10.
It was ⁸ Ω · cm.

The surface of the obtained core particles was coated in the same manner except that the coating amount used in Example 1 was changed to 1.0 part by weight.

The particle size and particle size distribution of the obtained coated carrier particles were substantially the same as those before coating. The sphericity of the carrier was measured and found to be 1.06.

The metal oxide exposure density of the obtained carrier particles was measured by an electron microscope and an image processing device. As a result, the metal oxide exposure density in the vicinity of the carrier surface was 1.4 particles / μm ² .

The resistivity of the carrier particles was measured and found to be 2.2 × 10 ¹⁰ Ω · cm. Also, the strength of magnetization at 1 kilo-ested (σ ₁₀₀₀ ) = 166 em
u / cm ³ (packing density of sample 2.43 g
/ Cm ³ ).

The carrier thus obtained is mixed with the toner used in Example 1 to prepare a developer (toner concentration 6.5%) in the same manner as in Example 1, and the mixture is put in a copying machine and an image formation test is conducted. I went. When the toner tribo was measured, the yellow toner was -35.8 μc / g, and the magenta toner was -33.4.
μc / g, cyan toner: −34.9 μc / g, black toner: −32.1 μc / g. The setting of the developing device and the developing method was the same as in the first embodiment. As a result, carrier adhesion was good. The dot shape in the halftone part was slightly uneven, and rustling was observed.

(Comparative Example 5 ) The coated carrier used in Example 1 was used as the carrier, and a toner having the same formulation as in Example 1 was pulverized and prepared by changing the classification conditions. The average particle size and particle size distribution of each toner are as follows: Yellow toner: weight average particle size 6.7μ
m, number average particle diameter 4.3 μm, distribution cumulative value of 1/2 times diameter of number average particle diameter or less is 25.5 number%, distribution cumulative value of weight average particle diameter of 2 times or more is 0.1 volume. %, Magenta toner: weight average particle diameter 6.5 μm, number average particle diameter 4.2 μ
m, the cumulative value of distribution of 1/2 times the number average particle diameter or less is 2
1.5% by number, the cumulative distribution value of the particles having a diameter twice or more the weight average particle diameter is 0% by volume, cyan toner: weight average particle diameter 6.8 μm,
The number-average particle size is 4.5 μm, the distribution cumulative value of the number-average particle size of 1/2 times or less is 23.6 number%, and the distribution cumulative value of the weight-average particle size is two times or more is 0.1% by volume. Black toner:
Weight average particle size of 6.7 μm, number average particle size of 4.3 μm, distribution cumulative value of 1/2 times or less of number average particle size is 23.8% by number, distribution cumulative value of 2 times or more of weight average particle size is cumulative. Value is 0.1
It was% by volume. The same titanium oxide as in Example 1 was externally added thereto in an amount of 0.8% by weight. The above carrier and toner were mixed to prepare a developer (toner concentration 6.5%). Tribo with the carrier is yellow toner: -38.8
μc / g, magenta toner: −37.5 μc / g, cyan toner: −39.1 μc / g, black toner: −3
It was 8.8 μc / g. The setting of the developing device and the developing method was the same as in the first embodiment. As a result, the dot reproduction in the halftone portion was poor, the halftone portion was rugged, and the non-image portion was fogged. In addition, the particle size distribution of the toner after running was changed, and the density of the image was increased, but the halftone portion was harsh and the fog was also observed.

[0211]

[Table 1]

[0212]

[Table 2]

(1) Image Density: The image density is the Macbeth Densitometer RD918 type (Macbeth Densittom, manufactured by Macbeth Co., Ltd., equipped with an SPI filter).
ether RD918manufactured by
Macbeth Co. ) Was used to measure the relative density of images formed on plain paper.

(2) Degree of roughness in the halftone part:
Visual evaluation was performed with reference to the original image and the standard sample.

(3) Adhesion of carrier: A solid white image is formed, and a portion of the photosensitive drum between the developing portion and the cleaner portion is sampled by bringing a transparent adhesive tape into close contact and sampling.
The number of magnetic carrier particles adhering to the photosensitive drum in × 5 cm is counted, and the number of adhering carrier particles per cm ² is calculated. Excellent: Less than 10 / cm ² Good: 10 to less than 20 / cm ² Acceptable: 20 to less than 50 / cm ² Slightly worse: 50 to less than 100 / cm ² Poor: 100 or more

(4) The average reflectance Dr (%) of the plain paper before the fogging image is output is measured by a reflectometer (“REFLECTOME” manufactured by Tokyo Denshoku Co., Ltd.).
TER ODEL TC-6DS "). On the other hand, a solid white image was printed on plain paper, and then the reflectance Ds (%) of the solid white image was measured. Fog (%)
Is calculated from the following formula Fog (%) = Dr (%) − Ds (%). Excellent: Less than 1.0 (%) Good: 1.0 to less than 1.5 (%) Possible: Less than 1.5 to 2.0 (%) Slightly worse: Less than 2.0 to 3.0 (%) Poor : 3 (%) or more

[0217]

EFFECT OF THE INVENTION The developer of the present invention is used for controlling the particle size distribution of the toner and controlling the particle size distribution of the toner, as well as controlling the particle size distribution of the carrier, lowering the magnetic force, increasing the core resistance, and performing surface coating. The use of a carrier improves the image quality, especially high image density, and the halftone part with a good image quality, and provides a good image without carrier adhesion or fog. Furthermore, the deterioration of the developer is eliminated even when copying a large number of sheets. The effect of preventing image quality deterioration after endurance is provided.

[Brief description of drawings]

FIG. 1 is a schematic view showing a specific example of an apparatus for carrying out the developing method of the present invention.

FIG. 2 is a schematic diagram of an apparatus for measuring the specific resistance of a magnetic carrier, a carrier core and a metal oxide.

FIG. 3 is a schematic view showing a specific example of an apparatus for carrying out the image forming method of the present invention.

[Explanation of symbols]

1 Development sleeve 2 Developer regulating member 3 photosensitive drum 4 magnets 5 stirrer 6 stirrer 7 developer container 11 toner 12 Developer A Distance between developing sleeve and developer control member B Distance between developing sleeve and photosensitive drum C development nip 21 Lower electrode 22 Upper electrode 23 Insulator 24 ammeter 25 constant voltage device 27 careers 28 Guide ring d Sample thickness E Resistance measuring cell

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI G03G 15/01 G03G 9/10 331 15/08 507 9/08 361 15/09 15/08 507X 21/10 21/00 316 ( 58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 9/10

Claims (30)

(57) [Claims] 1. In a two-component developer having at least a toner and a magnetic coated carrier, the magnetic coated carrier has a number average particle diameter of 1 to 100 μm, and a cumulative distribution of particles having a number average particle diameter of 1/2 times or less. The value is 20% by number or less, the specific resistance of the magnetic coated carrier is 1 × 10 ¹² Ωcm or more, and the specific resistance of the core constituting the magnetic coated carrier is 7.7 × 10 ¹⁰ Ωcm or more. Has a magnetization intensity of 30 to 1 at 1 kilo Oersted
50 emu / cm ³ , the toner has a weight average particle diameter of 1 to 10 μm, a cumulative distribution value of ½ times the number average particle diameter (D1) or less, and 20 weight% or less. A two-component developer having a cumulative distribution value of at least twice the diameter of (D4) of 10% by volume or less. 2. The magnetic coated carrier is a magnetic coated carrier in which a core particle having a binder resin and a metal oxide is coated with a resin, and the amount of the metal oxide in the core particle is 50 to 99% by weight. the average exposure density of the metal oxide on the surface of five / [mu] m ² hereinafter
Two-component developer according to claim 1, characterized in that. Wherein said binder resin of the magnetic coated carrier has a heat-curable resin, the core particles, the metal oxide
Particles obtained by polymerizing monomers in the presence
The two-component developer according to claim 2, wherein 4. The magnetic coated carrier is (a) a magnetic coated carrier having at least two kinds of metal oxides and a binder resin, and (b) a ratio of the total amount of metal oxides to the binder resin is 50 to 50. 99% by weight, (c) at least one of the metal oxides is a ferromagnetic substance, and the other is a metal oxide having a higher resistance than the ferromagnetic substance,
In addition, the ratio rb / ra of the number average particle diameter rb of the high resistance metal oxide to the number average particle diameter ra of the ferromagnetic material exceeds 1.0, and (d) is strong with respect to the total amount of the metal oxide. The ratio of magnetic material is 30
The two-component developer according to any one of claims 1 to 3, wherein the content of the two-component developer is about 95% by weight. 5. A magnetic coated carrier, a number number average particle size of 5 to 35 m, intensity of magnetization at 1 kOe is 100~150emu / cm ^3, the toner has a weight average diameter (D4) is The two-component developer according to claim 1, having a thickness of 1 to 6 μm. 6. The magnetic coated carrier is a number average number particle size 35～80Myuemu, intensity of magnetization at 1 kOe is 30~100emu / cm ^3, the toner has a weight-average particle diameter (D4) of Is 3 to 8 μm.
The two-component developer according to any one of 1 to 4. 7. The two-component developer according to claim 4, wherein the ferromagnetic material is magnetite and at least one of the high resistance metal oxides is hematite. 8. The following inorganic fine average particle size 0.2μm addition
Two-component developer according to any of claims 1 to 7 of the following organic fine particles an average particle diameter 0.2μm is contained as an external additive. 9. The number average particle diameter is 1 to 100 μm,
The cumulative distribution value of the number average particle diameter of 1/2 times or less is 20 number% or less, and the specific resistance of the magnetic coated carrier is 1 × 1.
0 ¹² Ωcm or more, the specific resistance of the core constituting the magnetic coated carrier is 7.7 × 10 ¹⁰ Ωcm or more, and the magnetic coating carrier has a magnetization intensity of 30 to 150 emu / cm ³ at 1 kilo-oersted. The magnetically-coated carrier has a weight average particle diameter of 1 to 10 μm and a number average particle diameter (D
A toner having a distribution cumulative value of ½ times or less of 1) of 20 number% or less, and a distribution cumulative value of 2 times or more of the weight average particle diameter (D4) of 10% by volume or less. A two-component developer is carried on a developer carrier containing magnetic field generating means, a magnetic brush of the two-component developer is formed on the developer carrier, and the magnetic brush is brought into contact with the latent image carrier. Then, the electrostatic charge image on the latent image carrier is developed while applying an alternating electric field to the developer carrier to form a toner image. 10. The magnetic coated carrier is a magnetic coated carrier in which a core particle having a binder resin and a metal oxide is coated with a resin, and the amount of the metal oxide in the core particle is 50 to 99% by weight. The average exposure density of the metal oxide on the surface of is 5 or less / μm ²
The developing method according to claim 9, wherein the developing method is below . 11. The binder resin of the magnetic coated carrier is a resin of thermosetting, the core particles, metal oxides
Granules obtained by polymerizing monomers in the presence of
The developing method according to claim 10, which is a child . 12. The magnetic coated carrier is (a) a magnetic coated carrier having at least two kinds of metal oxides and a binder resin, and (b) the ratio of the total amount of the metal oxide to the binder resin is 50 to 50. 99% by weight, (c) at least one of the metal oxides is a ferromagnetic substance, and the other is a metal oxide having a higher resistance than the ferromagnetic substance,
In addition, the ratio rb / ra of the number average particle diameter rb of the high resistance metal oxide to the number average particle diameter ra of the ferromagnetic material exceeds 1.0, and (d) is strong with respect to the total amount of the metal oxide. The ratio of magnetic material is 30
The developing method according to any one of claims 9 to 11, which is about 95% by weight. 13. The magnetic coated carrier is the number the number average particle size of 5 to 35 m, intensity of magnetization at 1 kOe is 100~150emu / cm ^3, the toner has a weight average diameter (D4) is It is 1 to 6 μm.
13. The developing method according to any one of 1 to 12. 14. The magnetic coated carrier is a number average number particle size 35～80Myuemu, intensity of magnetization at 1 kOe is 30~100emu / cm ^3, the toner has a weight-average particle diameter (D4) of Is 3 to 8 μm, and the developing method according to claim 9. 15. The developing method according to claim 12, wherein the ferromagnetic material is magnetite, and at least one of the high resistance metal oxides is hematite. 16. Inorganic fine particles having an average particle size of 0.2 μm or less
Or developing method according average particle size 0.2μm or less of the organic fine particles are in any of claims 9 to 15 is contained as an external additive. 17. The developing method according to claim 9, wherein the electrostatic latent image is a digital latent image. 18. The developing method according to claim 9, wherein the electrostatic latent image is developed by a reversal developing method. 19. The developing method according to claim 9, wherein the magnetic brush is in contact with the latent image carrier at a developing nip of 3 to 8 mm. 20. The number average particle diameter is 1 to 100 μm, and the cumulative distribution value of the particles having a diameter of ½ times the number average particle diameter or less is 2.
0% by number or less, and the specific resistance of the magnetic coated carrier is 1
× 10 ¹² Ωcm or more, the specific resistance of the core constituting the magnetic coated carrier is 7.7 × 10 ¹⁰ Ωcm or more,
A magnetic carrier having a magnetic strength of 30 to 150 emu / cm ³ at 1 kilo-oersted of the magnetic coated carrier, and a weight average particle diameter of 1 to 10 μm and not more than 1/2 times the number average particle diameter (D1). The cumulative value of distribution is 20%
A developer containing a two-component developer containing a magenta toner having a distribution cumulative value equal to or more than twice the weight average particle diameter (D4) of 10 volume% or less in a magnetic field generating means. Carry on the carrier, form a magnetic brush of two-component developer on the developer carrier, bring the magnetic brush into contact with the latent image carrier, and carry an latent image while applying an alternating electric field to the developer carrier. The electrostatic charge image of the body is developed to form a magenta toner image, and the number average particle diameter is 1 to 100 μm, and the cumulative distribution value of ½ times the number average particle diameter or less is 20 number% or less. The specific resistance of the magnetic coated carrier is 1 × 10 ¹² Ωcm or more, and the specific resistance of the core constituting the magnetic coated carrier is 7.7 × 10 ¹⁰ Ωcm or more,
The strength of the magnetization in kilo-oersted is 30 to 150e
a magnetic coated carrier having a mu / cm ³ of 1 to 10 μm in weight average particle diameter and 1 / of the number average particle diameter (D1)
A two-component system development containing a cyan toner having a cumulative distribution value of 2 times or less diameter is 20 number% or less and a cumulative distribution value of 2 times diameter or more of weight average particle diameter (D4) is 10 vol% or less. The developer is carried on a developer carrier containing magnetic field generating means, a magnetic brush of a two-component developer is formed on the developer carrier, the magnetic brush is brought into contact with the latent image carrier, and an alternating electric field is applied. Is applied to the developer carrying member to develop the electrostatic charge image on the latent image carrying member to form a cyan toner image, and the number average particle size is 1 to 100 μm, and the diameter is 1/2 times the number average particle size. The following distribution cumulative value is 20% by number or less, the specific resistance of the magnetic coated carrier is 1 × 10 ¹² Ωcm or more, and the specific resistance of the core constituting the magnetic coated carrier is 7.7 × 10 ¹⁰ Ωcm or more. , One of the magnetic carriers
The strength of the magnetization in kilo-oersted is 30 to 150e
Magnetic carrier with mu / cm ³ and weight average particle size of 1
-10 μm, the cumulative distribution value of the number average particle diameter (D1) of 1/2 times or less is 20 number% or less, and the cumulative distribution value of the weight average particle diameter (D4) of 2 times or more is 10 volume. % Of yellow toner is carried on a developer carrier containing a magnetic field generating means to form a magnetic brush of the two-component developer on the developer carrier. Then, the magnetic brush is brought into contact with the latent image carrier, and while applying an alternating electric field to the developer carrier, the electrostatic charge image on the latent image carrier is developed to form a yellow toner image, and the formed magenta toner image, An image forming method comprising forming a full-color image using at least a cyan toner image and a yellow toner image. 21. The magnetic coated carrier is a magnetic coated carrier in which a core particle having a binder resin and a metal oxide is coated with a resin, and the amount of the metal oxide in the core particle is 50 to 99% by weight. The average exposure density of the metal oxide on the surface of is 5 or less / μm ²
21. The image forming method according to claim 20, which is below . 22. The binder resin of the magnetic coated carrier is a resin of thermosetting, the core particles, metal oxides
Granules obtained by polymerizing monomers in the presence of
The image forming method according to claim 20, wherein the image forming apparatus is a child . 23. The magnetic coated carrier is (a) a magnetic coated carrier having at least two kinds of metal oxides and a binder resin, and (b) the ratio of the total amount of metal oxides to the binder resin is 50 to 50. 99% by weight, (c) at least one of the metal oxides is a ferromagnetic substance, and the other is a metal oxide having a higher resistance than the ferromagnetic substance,
In addition, the ratio rb / ra of the number average particle diameter rb of the high resistance metal oxide to the number average particle diameter ra of the ferromagnetic material exceeds 1.0, and (d) is strong with respect to the total amount of the metal oxide. The ratio of magnetic material is 30
The image forming method according to any one of claims 20 to 22, wherein the content is about 95% by weight. 24. The magnetic coated carrier is the number the number average particle size of 5 to 35 m, intensity of magnetization at 1 kOe is 100~150emu / cm ^3, the toner has a weight average diameter (D4) is It is 1 to 6 μm.
The image forming method according to any one of 0 to 23. 25. The magnetic coated carrier is a number average number particle size 35～80Myuemu, intensity of magnetization at 1 kOe is 30~100emu / cm ^3, the toner has a weight-average particle diameter (D4) of The image forming method according to any one of claims 20 to 23, wherein is 3 to 8 µm. 26. The image forming method according to claim 23, wherein the ferromagnetic material is magnetite, and at least one of the high resistance metal oxides is hematite. 27. Inorganic fine particles having an average particle size of 0.2 μm or less
Or the image forming method according to any one of claims 20 to 26 is contained an average particle size of 0.2μm or less of the organic fine particles as the external additive. 28. The image forming method according to claim 20, wherein the electrostatic latent image is a digital latent image. 29. The image forming method according to claim 20, wherein the electrostatic latent image is developed by a reversal development method. 30. The image forming method according to claim 20, wherein the magnetic brush is in contact with the latent image carrier at a developing nip of 3 to 8 mm.