JPH0869185A - Electrophotographic carrier, two-component developer and image forming method - Google Patents

Abstract

PURPOSE: To obtain an electrophotographic carrier for a two-component devel oper in which the characteristic balance in resistance, saturation oxidation and electrification can be maintained in a proper range and the initial performances such as picture quality and charge amt. can be maintained for a long period without decreasing even for a repeated use. CONSTITUTION: This electrophotographic carrier consists of a magnetic ferrite component expressed by formula (Fe2 O3 )x (Mn0)y (A)z . In formula, A is Na2 O, K2 O, CaO, SrO or mixture of them, x, y, z are molar ratios satisfying 0.3<x<0.8, 0.01<y<0.5, 0<z<0.69, and x+y+z<=1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier which constitutes a two-component developer used for developing an electric latent image or a magnetic latent image in electrophotography or electrostatic printing, and the carrier. Regarding the used two-component developer, in particular, a carrier constituting the two-component developer having significantly improved durability, image quality and environmental characteristics, a two-component developer using the carrier and the two-component developer are used. The image forming method described above.

[0002]

2. Description of the Related Art There are many electrophotographic developing methods such as a cascade developing method and a magnetic brush developing method. The developers used in these various developing methods include a one-component developer and a two-component developer. There is a developer.

Carriers constituting the two-component type developer are roughly classified into conductive carriers and insulating carriers, and oxidized or unoxidized iron powder is usually used as the conductive carrier.
In the two-component type developer containing the iron powder carrier as a component, the triboelectrification property with respect to the toner is unstable, so that there is a problem in that a visible image is easily fogged. That is, since the toner particles adhere to and accumulate on the surface of the iron powder carrier particles (spent toner) with the use of the two-component developer, the electric resistance of the iron powder carrier particles increases and the bias current decreases. In addition, the triboelectrification becomes unstable, and as a result, the image density of the visible image formed is reduced and fog increases. Therefore, if a two-component developer containing an iron powder carrier is continuously used for copying with an electronic copying machine, the two-component developer will deteriorate with a small number of copies. It will need to be replaced, which will result in high costs.

For this reason, in recent years, it has been proposed to use ferrite particles as a carrier in order to solve the drawbacks of the iron powder carrier (Japanese Patent Laid-Open No. 52-565).
36, JP-A-58-202456, etc.).

However, although the ferrite carrier which has been practically used in the past exhibits excellent characteristics not possessed by the iron powder carrier when used in a specific toner and electrophotographic equipment, considering the above-mentioned required characteristics, There are still issues to be improved and the complete one is not known so far. For example, the desired magnetic characteristics cannot be obtained even if a carrier with an appropriate resistance is obtained by changing the ferrite composition or firing temperature, or the charge amount cannot be well controlled even if the resistance and magnetic characteristics are kept within an appropriate range. There was an inconvenience.

A typical example of the insulating carrier is a carrier obtained by uniformly coating the surface of a carrier core material made of a ferromagnetic material such as iron, nickel or ferrite with an insulating resin. In the two-component type developer using the insulating carrier, the toner particles are not significantly fused to the carrier surface as compared with the case of the conductive carrier, and at the same time, the triboelectric charging property between the toner and the carrier can be controlled. It is easy, has excellent durability, and has a long service life, which is an advantage that it is particularly suitable for high-speed electrophotographic copying machines.

There are various characteristics required for the insulating carrier, but as particularly important characteristics, appropriate chargeability, impact resistance, abrasion resistance, good adhesion between the core and the coating material, charge distribution Uniformity and the like can be mentioned.

Further, in recent years, demands for high definition and high image quality of copying machines have been increasing in the market, and in this technical field, an attempt has been made to achieve high image quality color by reducing the particle size of toner. However, as the particle size becomes smaller, the surface area per unit weight increases, the electrification amount of the toner increases, and the charging speed tends to slow, which results in deterioration of durability such as low image density, fog, and toner scattering. Is a concern.

That is, in the development of the electrostatic latent image held on the electrostatic latent image holding member, the toner is mixed with a carrier which is a relatively large particle and used as a two-component developer for electrophotography. The composition of both the toner and the carrier is chosen such that due to contact friction between them, for example, the toner will assume the opposite polarity of the charge on the photoconductive layer. As a result of the contact friction between the two, the carrier electrostatically attaches the toner to the surface, conveys it as a developer in the developing device, and supplies the toner onto the photoconductive layer of the electrostatic latent image carrier.

However, when a large number of sheets are continuously copied by an electronic copying machine using such a two-component developer, an image with clear and good image quality is obtained in the initial stage, but after copying tens of thousands of sheets, The image has a lot of fog and a remarkable edge effect, and is poor in gradation and sharpness.

In color copying using chromatic color toner, continuous gradation is an important factor affecting image quality, and an edge effect in which only the peripheral portion of the image is emphasized after copying a large number of sheets causes the image The gradation is greatly impaired. Copying reproducibility including color reproducibility in color copying is reduced by forming a pseudo contour by the edge effect in the vicinity of the actual contour.

Further, the image area used in the conventional black-and-white copy is 10% or less, and the image is almost a line image portion as in letters, documents, and reports, whereas it is a color copy image. The image area is at least 20
%, And solid images having gradation such as photographs, catalogs, maps, and paintings occupy a considerable frequency or area.

When continuous copying is performed using such an original having a large image area, a copy having a high image density is usually obtained in the initial stage, but the toner supply to the two-component developer cannot be completed in time. When the density decreases or the charging is insufficient, the replenishment toner and the carrier are mixed with each other, which may cause fog, and the partial toner density (showing the mixing ratio of the toner and the carrier) on the developing sleeve. There is a tendency that an increase or decrease occurs and image blurring and image density uniformity cannot be obtained. This tendency is more remarkable when the toner diameter is reduced.

This is because the amount of toner included in the two-component developer (that is, the toner concentration) is too low, or the rapid rise of triboelectric charging between the replenishment toner and the carrier in the two-component developer is poor. It is considered that these insufficient development and fog occur due to the fact that the toner having an insufficiently controllable charge amount is involved in the development.

As a color developer, the ability to always output a good quality image by continuously copying a document having a large image area is essential. Conventionally, in order to deal with a document having a large image area and a large amount of toner consumption, much has been dealt with by improving the developing device rather than improving the developer itself. That is, in order to increase the chance of contact of the developing sleeve with the electrostatic latent image, the peripheral speed of the developing sleeve is increased, and the size of the developing sleeve is increased.

Although these measures improve the developing ability, contamination of the inside of the machine due to toner scattering from the developing device,
Due to an overload on the driving of the developing device, the life of the device may be significantly limited. Furthermore, in order to make up for the lack of developing ability of the developer, it may be possible to deal with it by introducing a large amount of developer into the developing device, but these also increase the weight of the entire device and increase the cost by increasing the size of the device. However, as in the case described above, it may result in an overload on the driving of the developing device, which is not preferable.

Therefore, improvement studies from both the toner and carrier have been reported for the purpose of maintaining high image quality for a long period of time.

Up to now, several developers have been proposed for the purpose of improving the image quality. For example, in JP-A-51-3244, the particle size distribution is regulated,
Non-magnetic toner intended to improve image quality has been proposed.
Among the toners, the toner having a particle size of 8 to 12 μm is mainly used, and it is relatively coarse. According to the study of the present inventors, it is difficult for the toner to have a uniform “paste” on the latent image. And, 5 μm or less is 30% by number or less, and 20 μ
From the characteristic that m is 5% by number or less, the particle size distribution is broad, which also tends to reduce the uniformity. In order to form a clear image using a toner having such a coarse toner particle and a broad particle size distribution, the toner particles are superposed in a thick manner to fill the gaps between the toner particles to form an apparent image. There is also a problem that it is necessary to increase the image density, and the amount of toner consumption required to obtain a predetermined image density increases.

Japanese Unexamined Patent Publication (Kokai) No. 54-72054 proposes a non-magnetic toner having a sharper distribution than the former, but the size of particles having an intermediate weight is 8.5 to 11.0.
There is still room for improvement as a high-resolution toner having a roughness of about μm.

Japanese Unexamined Patent Publication (Kokai) No. 58-129437 proposes a non-magnetic toner having an average particle size of 6 to 10 μm and a maximum number of particles of 5 to 8 μm, but particles of 5 μm or less are 15% by number or less. There is a tendency that an image lacking sharpness is formed.

According to the studies made by the present inventors, it has been found that toner particles of 5 μm or less clearly reproduce the outline of the latent image and have a main function of fine toner paste to the entire latent image. Was done. In particular, in the electrostatic latent image on the photoconductor, the electric field lines are concentrated in the electrostatic charge latent image, so the electric field strength is higher at the edge portion that is the contour than inside, and the quality of the toner particles gathering at this portion causes
The sharpness of the image quality is decided. According to the study by the present inventors, 5 μ
It has been found that the amount of particles of m or less is effective for solving the problem of sharpness of image quality.

Therefore, the inventors of the present invention disclosed in Japanese Patent Laid-Open No. 222222
No. 966, the toner particles of 5 μm or less are
Although a toner containing several% has been proposed, a considerable improvement in image quality has been achieved, but further improved image quality is also desired.

Japanese Patent Application Laid-Open No. 2-877 proposes a toner containing 17 to 60% by number of toner particles having a particle size of 5 μm or less, which certainly stabilizes the image quality and the image density. It has also been found that it is difficult to always obtain a constant image when printing an original that consumes a large amount continuously, because the particle size distribution of the toner changes only by taking measures as a toner.

On the other hand, as an indication of the average particle size and particle size distribution of the carrier, JP-A-51-3238, JP-A-58-144839, and JP-A-61-20464 have been proposed.
There is No. 6 publication. JP-A-51-3238 refers to a rough particle size distribution. However, it does not specifically disclose the magnetic characteristics that are closely related to the developability of the developer and the transportability within the developing device. Further, regarding the particle size of the carrier, all the carriers in the examples are 250.
There is about 80% by weight or more of mesh and the average particle size is 6
It is 0 μm or more.

Japanese Unexamined Patent Publication (Kokai) No. 58-144839 discloses only the average particle size of the carrier, and the amount of fine powder that affects the adhesion of the carrier to the photoreceptor and the coarse powder that affects the sharpness of the image. The amount is not mentioned, and the distribution is not described in detail in consideration of the characteristics of color reproduction.

Japanese Patent Application Laid-Open No. 61-204646 discloses a combination of a copying machine and a suitable developer as the essence of the invention, and does not specifically describe the particle size distribution or magnetic characteristics of the carrier. Moreover, it does not even disclose why the developer is so effective in the copying machine.

Japanese Unexamined Patent Publication No. 49-70630 describes the magnetic force of a carrier. This is for iron powder having a larger specific gravity than ferrite as a carrier material, and has a high saturation magnetism. is there. Iron powder carriers have been widely used in the past, but due to their large specific gravity, the weight of the copying machine and the overload of the driving torque are apt to occur, and the environmental dependence is large.

The ferrite carrier described in Japanese Patent Application Laid-Open No. 58-23032 is for a porous material having many pores, and such a carrier is liable to have an edge effect and poor in durability. Therefore, it has been found to be unsuitable as a color carrier.

Up to now, there has been a demand for a developer capable of continuously copying an image having a large image area with a small amount of the developer and satisfying the characteristic peculiar to color copying in which the edge effect does not occur even after the endurance. ing. Although developers and carriers have been studied, most of them have been proposed in consideration of black-and-white copying, and very few have been proposed as applicable to full-color copying. Furthermore, a carrier having the ability to continue copying an image having an image area of 20% or more, which is almost similar to a solid image, the reduction of edge effect, and the ability to maintain the uniformity of image density in one copy are Long-awaited.

In view of this, Japanese Patent Application Laid-Open No. 2-281280 proposes a carrier having a narrow particle size distribution in which the amount of fine powder and the amount of coarse powder are controlled to achieve a carrier having improved developing characteristics.

However, as described above, there is an increasing demand in the market for high-definition and high-quality copying machines, and in this technical field, the particle size of toner should be reduced to achieve high-quality color. However, when the particle diameter of the toner becomes finer, the surface area per unit weight increases, and the amount of electrification of the toner tends to increase, so that the image density is low and the durability is deteriorated.

As described above, attempts have been made to further reduce the diameter of the carrier for the purpose of reducing the image density and preventing the deterioration of durability by reducing the toner particle diameter, or improving the developing efficiency. However, in such a carrier,
In the actual situation, it is difficult to achieve all of high image density, high image quality, good fog prevention and carrier adhesion prevention because the quality is not sufficient to deal with the change in charge amount due to the environment or durability of the toner. is there.

[0033]

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

An object of the present invention is to provide a carrier having an appropriate charge imparting ability without impairing desired carrier resistance and magnetic properties.

A further object is to provide a two-component developer in which the image quality, charging characteristics and durability thereof are greatly improved by using the carrier, and an image forming method using the two-component developer. To provide.

A further object is to obtain a high-quality image with little fog and toner scattering by increasing the charging speed and uniformly charging when combined with a toner having a small particle size. A possible carrier,
A two-component developer having the toner and the carrier, and an image forming method using the two-component developer.

[0037]

MEANS FOR SOLVING THE PROBLEMS The present invention is based on the following formula (I) (Fe ₂ O ₃ ) _x (MnO) _y (A) _z formula (I) [wherein A is Na ₂ O, K ₂ O, CaO, SrO or a mixture thereof show a, x, y and z represents the mole fraction, and the following conditions 0.3 <x <0.8,0.01 <y < 0.5, It satisfies 0 <z <0.69 and x + y + z ≦ 1. ] The present invention provides a carrier for electrophotography, which is formed of a magnetic ferrite component represented by

The present invention also provides a two-component developer having a toner and a carrier, the toner having toner particles, and the carrier having the formula (I) (Fe ₂ O ₃ ) _x (MnO) _y (A) _z formula (I) [wherein A represents Na ₂ O, K ₂ O, CaO, SrO or a mixture thereof, x, y and z represent mole fractions, and It satisfies 0.3 <x <0.8, 0.01 <y <0.5, 0 <z <0.69, and x + y + z ≦ 1. ] A two-component developer having a magnetic ferrite component represented by

Further, according to the present invention, a two-component developer having a toner and a carrier is circulated and conveyed by a developer carrier to develop the electrostatic latent image held on the electrostatic latent image carrier in the developing area. In the image forming method of developing with the toner of the two-component developer carried on the agent carrier, the toner contains toner particles, and the carrier is represented by the following formula (I) (Fe ₂ O ₃ ) _x (MnO) _y (A) _z Formula (I) [wherein A represents Na ₂ O, K ₂ O, CaO, SrO or a mixture thereof, and x, y and z represent mole fractions. Also, the following conditions 0.3 <x <0.8, 0.01 <y <0.5, 0 <z <0.69, and x + y + z ≦ 1 are satisfied. ] The present invention provides an image forming method characterized by being formed of a magnetic ferrite component represented by

The feature of the electrophotographic carrier in the present invention is that the magnetic ferrite component constituting the carrier is Fe ₂ O ₃
And MnO, Na ₂ O, K ₂ O, CaO,
It is to make one or more components selected from SrO and a mixture thereof an essential component.

Fe ₂ O ₃ is a component necessary for obtaining proper magnetic properties, and particularly in the magnetic brush developing method, good image quality can be obtained.

The inclusion of an oxide of an alkali metal or an alkaline earth metal is effective in controlling the charge amount while maintaining the carrier resistance within an appropriate range.
Especially when used in combination with MnO, the effect is dramatically increased.

However, according to the detailed study by the present inventors,
It has been clarified that not all alkali metals or alkaline earth metals are effective, but only metal atoms having physical property values within a specific range are effective.

That is, in order for the respective composition components to form a solid solution with each other to form a crystal lattice and control the electric resistance and the charge amount, an appropriate ionic radius range is required in the contained metal. As a result of diligent studies by the present inventors, the ion radius of Li ⁺ , Be ²⁺ and Mg ²⁺ is smaller than the proper range, and the ion radius of Rb ⁺ and Cs ⁺ is larger than the proper range. In either case, the carrier resistance was lower than the desired range, and it was unsuitable for use as a carrier for electrophotography. Further, in order to control the charge amount, it is necessary that the ionization potential of the metal is low and that a high valence state exists, and
It has also been clarified that even if a metal having a higher valence such as ²⁺ is not contained, a high charge amount cannot be obtained.

When MnO coexists as described above,
Although the reason why a particularly high effect is obtained is not clear, since Mn oxide and Fe ₂ O ₃ can form a solid solution with each other to form a spinel structure, the resistance can be controlled to some extent, and the ionization potential is It is considered that one of the causes is that it has a relatively high charging ability because it has a low valence state and a high valence state. That is, MnO
By coexisting with and alkali metal or alkaline earth metal, the lattice structure or the metal valence state perturbs each other, and it is considered that the respective effects are synergistically improved.

Ferrite carriers containing MnO and MgO as essential components are disclosed in JP-A-58-123552, JP-A-59-111159, and JP-B-6-23866. Have been proposed, JP-A-58-215664, JP-A-59-111926, and JP-A-62-2.
Japanese Patent No. 97857 proposes a ferrite carrier containing MnO and Li ₂ O as essential components. However, according to the study by the present inventors, MgO or Li ₂
Even if O coexisted with MnO, the effect was insufficient in terms of resistance adjustment. As described above, this is Li ⁺ or M
This is probably because g ^{2+ and the} like deviate from the range of the proper ionic radius required to form a stable and uniform crystal lattice.

In Japanese Patent Publication No. 6-23866,
In addition to MnO and MgO in the ferrite composition, C
It has been proposed that metals such as u, Zn and Co may coexist. However, studies by the present inventors have revealed that it is not easy to enhance the charge imparting ability of the carrier even if such a metal is contained.

This is because there is generally a correlation between the ionization potential of the metal contained in the carrier and the charging ability of the carrier, and the larger the ionization potential is, the more difficult it is to be positively charged.

Comparison of the ionization potentials of the metal contained in the ferrite composition described in JP-B-6-23866 and the metal contained in the magnetic ferrite component in the oxide state in the present invention shows the following relationship. The order is as shown by Cu, Zn, Co> Na, K, Ca, Sr (large ← ionization potential → small), and the negative ionization potentials of Na, K, Ca, and Sr are smaller than those of Cu, Zn, and Co. When contained in the carrier, it acts so as to be more positively charged.

The magnetic ferrite component used in the present invention is represented by the following formula (I) (Fe ₂ O ₃ ) _x (MnO) _y (A) _z formula (I) [A is Na ₂ O, K ₂ O, CaO]. , SrO or a mixture thereof, x, y and z are mole fractions, and the following conditions 0.3 <x <0.8, 0.01 <y <0.5, 0 <z <0. 69, x + y + z ≦ 1 is satisfied. ] Is shown.

In the above formula (I), more preferably
x, y and z are the following conditions 0.3 <x <0.8, 0.01 <y <0.5, x + y <
Satisfying 1, z = 1-xy is preferable from the viewpoint of improving the charging ability of the carrier, but in the present invention, within the range of 3% by weight or less, which does not prevent the effect of the magnetic ferrite component. Other metal elements for the purpose of adjusting the crystal grain size of the magnetic carrier core material particle surface, for the purpose of preventing coalescence during firing, or as a particle size distribution adjusting agent, hydroxide, oxide in the magnetic ferrite component, It may be contained in the form of a sulfide or a fatty acid compound.

In the above formula (I), x is 0.3 mol%
In the following, the resistance becomes very high, making it difficult to control the resistance value. In the case where x is 0.8 mol% or more, the magnetic properties deteriorate, and it is difficult to obtain a good image quality when used in the magnetic brush developing method. When y is 0.01 mol% or less, it is difficult to control both carrier resistance and magnetic properties within appropriate ranges,
If y is 0.5 mol% or more, the magnetic properties deteriorate.
When z is 0 mol%, that is, when (A) is not included, especially when combined with a fine particle size toner, the charging ability is lowered and it becomes difficult to maintain durability.

When z is 0.69 mol% or more, the charge holding ability is lowered particularly in high humidity, and toner scattering easily occurs.

In the above formula (I), x, y and z are
It is more preferable to satisfy the following conditions. 0.4 <x <0.8, 0.02 <y <0.3, 0 <z <
0.3, x + y + z ≦ 1 In the present invention, it is possible to control the carrier resistance to a desired value in a wider range by adding a predetermined amount of Bi ₂ O ₃ to the ferrite component. This Bi ₂ O ₃
If the content of is within the range of 0.01 to 3 mol% with respect to the above-mentioned ferrite component, it becomes possible to adjust the carrier resistance while maintaining the magnetic characteristics and charging ability of the carrier. When the content of Bi ₂ O ₃ is less than 0.01 mol%, it is difficult to adjust the carrier resistance, and when it exceeds 3 mol%, the magnetic characteristics of the carrier are likely to change.

As one of the further characteristics of the present invention, when the weight average particle diameter of the carrier is 50 μm or less, the above-mentioned effect of controlling the carrier characteristics is more remarkably exhibited, and the performance as a two-component developer is further improved. There are things to do.

The reason for this is not clear, but as the carrier surface area increases, the contact area between the carriers also increases, and the ferrite composition dependence of the resistance as the carrier particle aggregates becomes gradual. It seems that it is possible to adjust the resistance.

According to the studies made by the present inventors, a more preferable weight average particle diameter of the carrier is 10 to 45 μm, and more preferably 15 to 40 μm. When the weight average particle diameter of the carrier exceeds 50 μm, it becomes somewhat difficult to adjust the resistance from the material composition, and when the durability test is performed, the charge amount tends to be slightly decreased. When the weight average particle diameter of the carrier is too small, scattering of the carrier from the magnetic roll becomes conspicuous, and white spots are easily generated on the image.

As one of the further features of the present invention, by coating the surface of the carrier particles with a resin coating layer, it is possible to further finely adjust the carrier resistance while maintaining the magnetic properties and prevent toner spent, thereby improving durability. There are significant improvements.

The coating amount of the coating agent for forming the resin coating layer is 0.05% by weight to 10% by weight, preferably 0.1% by weight to 5% by weight, based on the carrier core particles. If it is less than 0.05% by weight, the effect of coating the carrier core particles with the resin coating layer is not sufficient, and a coating amount of more than 10% by weight is meaningless, and an excess resin alone exists from the viewpoint of production. In some cases, it is not preferable.

As the resin used as the resin coating layer of the carrier of the present invention, the following resins can be used.

Polymers or copolymers of vinyl compounds, polyester resins, epoxy resins, melamine resins,
Examples thereof include silicone resins and resins containing fluorine or halogen. These can be used alone or in combination of two or more.

The method of coating the carrier may be any method as long as it can form a coating layer such as a dry method or a wet method.

In the present invention, the carrier is 10 ⁶ to 10
It is preferable to have an electric resistance of ¹⁵ Ω · cm. When the electric resistance of the carrier exceeds 10 ¹⁵ Ω · cm, especially when an original document with a high image area ratio is continuously copied,
The rising of the charge of the replenishment toner is lowered and the fog is apt to occur. On the other hand, when it is less than 10 ⁶ , the amount of charge is greatly reduced particularly under high humidity, and toner scattering occurs.

The magnetic characteristics of the carrier are influenced by the magnet roller incorporated in the developing sleeve, and greatly affect the developing characteristics and the transportability of the two-component developer.

In the present invention, a two-component developer having a carrier composed of magnetic particles and an insulating color toner is prepared by rotating the developing sleeve alone with the magnet roller fixed on the developing sleeve having a built-in magnet roller. When the electrostatic latent image held on the surface of the electrostatic latent image holding member is developed by being circulated and conveyed on the developing sleeve, which is a developing carrier, the magnet roller has a repulsive pole. When the magnetic flux density in the developing region is 500 to 1200 gauss and the saturation magnetization of the carrier is 20 to 70 Am ² / kg, the uniformity and gradation reproducibility of an image in color copying are excellent and suitable.

The saturation magnetization of the carrier is 70 Am ² / kg
If it exceeds (for an applied magnetic field of 3000 oersteds), the brush-like spikes formed by the carrier and toner on the developing sleeve facing the electrostatic latent image on the photoconductor during development are tightly tightened. And the reproduction of gradation and halftone deteriorates, and when it is less than 20 Am ² / kg, it becomes difficult to satisfactorily hold the toner and carrier on the developing sleeve, and carrier adhesion and toner scattering easily occur. .

When the carrier of the present invention is mixed with a toner to be used as a two-component developer for forming a magnetic brush,
As the toner, any toner which is obtained by dispersing a colorant in a binder resin and which is usually used in an electrophotographic method can be used and is not particularly limited. More preferably from an average particle size of 1 to 9 μm,
It was found that the effect is great when a toner having a weight average particle diameter of 2 to 8 μm is used.

Generally, the finer the toner particle size, the finer the electrophotographic image obtained, but the charging speed of the toner becomes slower, and it becomes difficult to uniformly charge all the toner particles. Therefore, the image density is lowered and the fog is deteriorated.

However, in the carrier of the present invention, by adjusting the composition of the ferrite component to regulate the carrier resistance to an appropriate value, it is possible to improve the charging speed and to uniformly charge individual toner particles with high charging ability.
When combined with a miniaturized toner, it is possible to obtain a very high quality image while maintaining the image density and the fog level.

When a two-component type developer is prepared by mixing the carrier according to the present invention with a toner, the mixing ratio is 1.0% by weight to 15% by weight, preferably 3% by weight as the toner concentration in the developer. Good results are obtained when the amount is up to 12% by weight. If the toner concentration is less than 1.0% by weight, the image density will be low, and if it exceeds 15% by weight, fog and scattering in the machine will be increased and the useful life of the developer will be shortened.

The preferred form of the toner used in the two-component developer will be described below.

As described above, the toner used in the present invention preferably has a weight average particle diameter of 1 to 9 μm, and more preferably has a weight average particle diameter of 2 to 8 μm to improve the definition of an image. Is good.

When the weight smoothness of the toner is less than 1 μm, the mixing property with the carrier is deteriorated, and defects such as toner scattering and fog occur. When it exceeds 9 μm, the reproducibility of a minute dot latent image is reproduced. , Or scattering at the time of transfer occurs, which hinders high image quality.

Further, in the toner, the binder resin has a polyester resin as a main component, and the toner is 1 to 20 KO.
It preferably has an acid value of Hmg / g.

That is, the above 1 to 20 KOHmg / g
By using a toner having an acid value of 1, especially the charging stability with the carrier having the above-mentioned specific magnetic ferrite component is improved, quick charging becomes possible, and even when the original with a high image ratio is used, Thus, a two-component developer free from fog and toner scattering is achieved.

Here, when the acid value is less than 1 KOHmg / g, the rise of charging is lowered, and as a result, fog is apt to be deteriorated. When the acid value is more than 20 KOHmg / g, the charging property under high humidity is obtained. Fogging and toner scattering occur as a result.

In the toner used in the present invention, in order to control the acid value of the toner to 1 to 20 KOHmg / g and to improve the low temperature fixability and durability of the toner,
As the acid component of the binder resin, a trivalent or higher polyvalent carboxylic acid is more preferably 0.1 to 20 mol%, more preferably 0.1 to 10 m
It is preferable to contain ol%. Further, preferably,
The glass transition temperature (Tg) of the toner containing the binder resin having the polyester resin is in the range of 45 to 70 ° C., and the temperature (Tm) exhibiting an apparent viscosity of 10 ⁵ poise is in the range of 8 to 120 ° C. preferable.

Particularly preferably, the following formula (II)

[0079]

Embedded image (In the formula, R is an ethylene or propylene group, and x, y
Are each an integer of 1 or more, and the average value of x + y is 2 to 10. ) A bisphenol derivative or an etherified bisphenol such as a substituted product represented by the formula (1) as a diol component, and a carboxylic acid component consisting of a carboxylic acid having a valence of 2 or more or an acid anhydride thereof or a lower alkyl ester thereof (eg fumaric acid, maleic acid A polyester resin obtained by copolycondensation of maleic anhydride, phthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.) is more preferable because it has sharp melting characteristics.

As the binder resin used in the toner of the present invention, various material resins may be used in combination with the above-mentioned polyester resin.

For example, polystyrene, styrene copolymers such as styrene-butadiene copolymer, styrene-acrylic copolymer, etc., ethylene series such as polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer. Examples thereof include copolymers, phenolic resins, epoxy resins, acrylic phthalate resins, polyamide resins, and maleic acid resins. The manufacturing method of any resin is not particularly limited.

The toner used in the present invention is preferably composed of toner particles having at least a binder resin and a colorant and an external additive containing an inorganic fine powder.
Examples of the inorganic fine powder used as an external additive for the toner include alumina, titanium oxide and silica. Among them, alumina or titanium oxide fine particles are particularly preferable because they further stabilize the charging of the toner.

Further, it is preferable that the inorganic fine powder is subjected to a hydrophobic treatment in order to reduce environmental dependence such as temperature and humidity of the charge amount of the toner and to prevent liberation from the toner surface. Examples of the hydrophobizing agent include silane coupling agents, titanium coupling agents, coupling agents such as aluminum coupling agents, oils such as silicone oils, fluorine-based oils, and various modified oils. Of the above-mentioned hydrophobic treatment agents, the coupling agent is particularly preferable from the viewpoint of stabilizing the charge of the toner and imparting fluidity.

Therefore, as the external additive used in the present invention,
Particularly preferably, fine particles of alumina or titanium oxide that have been surface-treated while hydrolyzing the coupling agent are extremely effective in terms of stabilizing charging and imparting fluidity.

The hydrophobically treated inorganic fine powder is preferably 20 to 80%, more preferably 40 to 8%.
It is preferable to have a hydrophobicity of 0%.

If the degree of hydrophobicity of the inorganic fine powder is less than 20%, the amount of charge is greatly reduced by leaving it in a high humidity for a long period of time, and a mechanism for accelerating the charge on the hardware side is required, which complicates the apparatus and makes it hydrophobic. If the degree of conversion exceeds 80%, it becomes difficult to control the charge of the inorganic fine powder itself, and as a result, the toner is likely to be charged up under low humidity.

The above-mentioned hydrophobized inorganic fine powder should have a number average particle diameter of 0.05 μm to 0.2 μm in a state of being dispersed on the toner in order to improve the fluidity of the toner and the surface of the toner particle at the time of durability. Is preferable in terms of preventing the release of the inorganic fine powder.

When the number average particle diameter is less than 0.005 μm, the inorganic fine powder is apt to be embedded on the surface of the toner particles, the toner is deteriorated, and the durability is apt to be deteriorated.
When it exceeds 2 μm, it is difficult to obtain sufficient fluidity of the toner, the toner is liable to be unevenly charged, and as a result, toner scattering and fog are likely to occur.

The above-mentioned hydrophobized inorganic fine powder is 4
The light transmittance at a light length of 00 nm is preferably 40% or more.

That is, even if the inorganic fine powder used in the present invention has a small primary particle diameter, when it is actually contained in the toner, it is not necessarily dispersed in the state of primary particles. It may be present as secondary particles. Therefore, no matter how small the primary particle diameter is, the effect of the present invention will be reduced if the effective diameter acting as the secondary particles is large. However, the higher the light transmittance at 400 nm, which is the lower limit wavelength in the visible region, the smaller the secondary particle size, the better the fluidity imparting ability, and the better the sharpness of the OHP projection image in the case of color toner. Can be expected. The reason for selecting 400 nm is the boundary region between ultraviolet and visible, and it is said that particles with a particle size of 1/2 or less of the light wavelength are transmitted, so the transmittance for wavelengths longer than that is naturally large, It is meaningless.

As the colorant contained in the toner used in the present invention, known dyes and pigments such as phthalocyanine blue, induslen blue, peacock blue, permanent red, lake red, rhodamine lake, hansa yellow, permanent yellow, Benzidine yellow can be used. Its content is OH
In order to sensitively reflect the transparency of the P film, the amount is preferably 12 parts by weight or less, more preferably 0.5 to 9 parts by weight, based on 100 parts by weight of the binder resin.

If necessary, the toner used in the present invention may be mixed with additives within a range not impairing the characteristics of the toner. Examples of such additives include Teflon, zinc stearate, and polyvinylidene fluoride. And a fixing aid (for example, low molecular weight polyethylene, low molecular weight polypropylene, etc.), organic resin particles and the like.

In the production of the toner used in the present invention, after the constituent materials are well kneaded by a heat kneader such as a heat roll, a kneader or an extruder, a method of obtaining by mechanical pulverization and classification, in a binder resin solution, A method in which a toner raw material such as a colorant is dispersed and then spray-dried, or a polymerizable monomer capable of forming a binder resin is mixed with a predetermined material, and then the emulsion suspension is polymerized. A polymerized toner manufacturing method for obtaining a toner can be applied.

Next, the image forming method of the present invention using the above two-component developer will be described.

In the image forming method of the present invention, a two-component developer having a toner and a carrier is circulated and conveyed on a developer carrier to hold a latent image on the latent image carrier and the development area of the developer carrier opposite thereto. The latent image held on the body is developed with the toner of the two-component developer on the developer carrier.

The magnetic characteristics of the carrier are affected by the magnet roller incorporated in the developing sleeve, and greatly affect the developing characteristics and the transportability of the developer.

In the image forming method of the present invention, of the developing sleeve (developer carrying member) and the magnet roller incorporated therein, for example, the magnet roller is fixed and the developing sleeve is rotated by itself to be composed of magnetic particles. A two-component developer composed of a carrier and an insulating color toner is circulated and conveyed on a developing sleeve, and the two-component developer develops the electrostatic latent image held on the surface of the electrostatic latent image carrier. is there.

In the image forming method of the present invention, the magnet roller has a five-pole structure having a repelling pole as described above, and the magnetic flux density in the developing region is 500 to 1200.
Gaussian, saturation magnetization of carrier is 20-70 Am
^{In the} case of ² / kg, the uniformity and gradation reproducibility of the image in color copying are excellent and suitable.

In the image forming method of the present invention, it is preferable to apply a developing bias in the developing area to develop the electrostatic latent image with the toner of the two-component developer.

A particularly preferable developing bias will be described in detail below.

In the image forming method of the present invention, the first voltage for directing the toner from the latent image carrier to the developing carrier in the developing region and the second voltage for directing the toner from the developer carrier to the latent image carrier. And a third voltage between the first voltage and the second voltage.
By applying a voltage to the developer carrier to form a developing electric field between the latent image carrier and the developer carrier, the latent image carried on the latent image carrier is converted into a two-component latent image on the developer carrier. It is preferable to develop with a toner of a system developer.

Further, the first voltage for directing the toner from the latent image carrier to the developer carrier and the second voltage for directing the toner from the developer carrier to the latent image carrier are applied to the developer carrier. The time (T ₂ ) for applying the third voltage between the first voltage and the second voltage to the developer carrying member is longer than the total time (T ₁ ) for the latent image holding member. It is particularly preferable for the purpose of rearranging the toner and reproducing the latent image faithfully.

Specifically, in the developing area, between the latent image holding member and the developer carrying member, the electric field in which toner is directed from the latent image holding member to the developer holding member and from the developer holding member to the latent image holding member. After the electric field directed by the toner is formed at least once, the toner moves from the developer carrying member to the latent image holding member in the image portion of the latent image holding member, and the toner moves to the latent image holding member in the non-image portion of the latent image holding member. To develop the latent image held on the latent image holding member by the toner of the two-component developer carried on the developer holding member by forming an electric field from the developer holding member to the developer holding member for a predetermined time, From the total time (T ₁ ) for forming the electric field in which the toner goes from the latent image carrier to the developer carrying member and the electric field in which the toner goes from the developer carrying member to the latent image carrying member, the toner is From the developer carrier to the latent image carrier, the latent image carrier In the non-image portion, the time for forming an electric field in which the toner is directed from the latent image bearing member to the developer carrying member (T ₂₎
It is preferable to make the length longer.

In the developing method in which the above-mentioned specific developing electric field, that is, an alternating electric field is formed to develop, it is more difficult for carrier adhesion to occur when the developing is carried out by using the developing electric field for periodically turning off the alternating electric field. is there. The reason for this is not clear yet, but it can be considered as follows.

That is, in the conventional continuous sine wave or rectangular wave, when the electric field strength is increased in order to achieve high image density, the toner and the carrier are integrated into a space between the latent image carrier and the developer carrier. As a result, the carrier strongly rubs against the latent image carrier, and carrier adhesion occurs. This tendency becomes more remarkable as the amount of fine powder carrier increases.

However, when a specific AC electric field is applied as in the present invention, the toner or the carrier makes a reciprocating motion which does not reciprocate between the developer carrying member and the latent image holding member in one pulse, so that the latent image holding thereafter is carried out. When the potential difference V _cont between the surface potential of the body and the DC component of the developing bias is V _cont <0,
Although the direct current component acts to fly the carrier from the developer carrying member, carrier adhesion can be prevented by controlling the magnetic characteristics of the carrier and the magnetic flux density in the developing area of the magnet roller, and when V _cont > 0. Is
The force of the magnetic field and the direct current component work to attract the carrier to the developer carrying member side, and carrier adhesion does not occur.

A preferred form of the electrostatic latent image carrier which can be used in the image forming method of the present invention will be described with reference to FIG.

The electrostatic latent image holder 1 has a photosensitive layer 43 and a protective layer 44 provided on a conductive support 41, and at least the protective layer 44 reduces the friction resistance of the surface of the electrostatic latent image holder 1. To this end, the protective layer 44 is mechanically polished so that it contains fluorine atom-containing resin particles, and the average surface roughness of the protective layer 44 is preferably 10-point average surface roughness defined in JIS B061. The roughness R _z (hereinafter, simply referred to as average surface roughness) is preferably 0.01 to 1.5 μm.

If the average surface roughness is within the above range, the friction between the cleaning blade 50 and the surface of the electrostatic latent image carrier 1 is sufficiently small, and no image defect appears even after repeated use. In addition, the highlight reproduction will be very good.

In the protective layer 44, the content of the fluorine atom-containing resin fine particles capable of effectively lowering the friction coefficient of the surface of the electrostatic latent image carrier 1 is 5 to 5 based on the total weight of the protective layer 44.
40% by weight, preferably 10 to 40% by weight is good. The thickness of the protective layer 44 is preferably 0.05 μm to 80 μm
Range, and more preferably 0.1 μm to 6.0 μm
The range of m is preferable.

In the present invention, when the photosensitive layer 43 portion also contains fluorine atom-containing resin fine particles, the photosensitive layer 43 is thicker than the thin protective layer 44, so that the content of the fine particles is limited. Specifically, the content rate in the photosensitive layer 43 is
Preferably 10% by weight based on the total weight of the photosensitive layer 43
It is below, more preferably below 7% by weight.

Even if the amount of fluorine atom-containing resin fine particles in the photosensitive layer 43 is limited, if the total thickness of the photosensitive layer 43 is large,
When photocarriers are generated mainly on the support side of the photosensitive layer 43, sensitivity deterioration due to light scattering and deterioration of image uniformity are remarkable. If the photosensitive layer 43 is too thin, it may cause a decrease in sensitivity and a decrease in charging ability due to an increase in the electric capacity of the photosensitive layer 43. Further, even when the photosensitive layer 43 does not contain the fine particles, it is not preferable to make the photosensitive layer 43 extremely thick. The reason is that the protective layer 44 containing the fine particles is
Is laminated on the photosensitive layer 43, the protective layer 44 becomes a light-scattering layer, and particularly when the photo or carrier is mainly generated on the support side of the warm layer, the generation part of the photocarrier is far from the light-scattering layer. That is, the thicker the photosensitive layer 43, the longer the optical path length of light after scattering, and the greater the influence of light scattering.

Therefore, the total thickness of the photosensitive layer 43 and the protective layer 44 is preferably 10 to 35 μm, more preferably 1
It is 5 to 30 μm. The fine particles contained in the photosensitive layer 43 are preferably as small as possible, so that the average content of the fine particles in the total film thickness of the photosensitive layer 43 and the protective layer 44 is the same as that of the photosensitive layer 43 and the protective layer 44. 1 based on weight
It is preferably 7.5% by weight or less.

In the present invention, the fluorine atom-containing resin fine particles used for the electrostatic latent image carrier are polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polydichlorodifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether. One or more selected from a copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, a tetrafluoroethylene-ethylene copolymer, and a tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer. It is composed of It is possible to use commercially available fluorine atom-containing resin fine particles as they are. Those having a molecular weight of 30,000 to 5,000,000 can be used, and 0.01 to 10μ
It is possible to use particles having a particle size of m, preferably 0.05 to 2.0 μm.

In the present invention, the photosensitive layer 43 of the electrostatic latent image carrier contains at least a charge generating material and a charge transporting material as an organic photoconductive substance.

Examples of the charge generating material include phthalocyanine pigments, polycyclic quinone pigments, trisazo pigments, disazo pigments, azo pigments, perylene pigments, indigo pigments, quinacridone pigments, azurenium salt dyes, squalium dyes, cyanine dyes, pyrylium dyes, Examples thereof include thiopyrylium dye, xanthene dye, quinoneimine dye, triphenylmethane dye, styryl dye, selenium, selenium-tellurium alloy, amorphous silicon, and cadmium sulfide.

Examples of the charge transport material include pyrene compounds, N-alkylcarbazole compounds, hydrazone compounds, N, N-dialkylaniline compounds, diphenylamine compounds, triphenylamine compounds, triphenylmethane compounds, pyrazoline compounds, styryl compounds, Examples include stilbene compounds, polynitro compounds, polycyano compounds, and pendant polymers in which these compounds are fixed on a polymer.

In many cases, each of the above-mentioned fluorine atom-containing resin fine particles, charge generating material and charge transporting material is dispersed and contained in a binder resin having film forming properties to form each protective layer and photosensitive layer. As such a binder resin, polyester, polyurethane, polyacrylate, polyethylene,
Polystyrene, polycarbonate, polyamide, polypropylene, polyimide, phenol resin, acrylic resin, silicone resin, epoxy resin, urea resin, allyl resin, alkyd resin, polyamide-imide, nylon, polysulfone, polyallyl ether, polyacetal, butyral resin. .

Next, the layer structure of the electrostatic latent image carrier will be described.
The conductive support 41 is made of iron, copper, gold, silver, aluminum,
Metals and alloys such as zinc, titanium, lead, nickel, tin, antimony and indium, oxides of the above metals, carbon and conductive polymers can be used. The shape includes a drum shape such as a cylindrical shape and a cylindrical shape, a belt shape, and a sheet shape. The conductive material may be molded and processed as it is, used as a paint, vapor-deposited, or processed by etching or plasma treatment. In the case of paint, not only the above-mentioned metals and alloys but also paper and plastic are used as the support.

The photosensitive layer 43 in the electrostatic latent image carrier 1 is
It may have a single-layer structure or a laminated structure. In the case of the laminated structure, it is composed of at least the charge generation layer 43a and the charge transport layer 43b. However, the case where the charge generation layer 43a is provided on the conductive support 41 side and the charge transport layer 43b.
The charging polarity and the polarity of the toner to be used are different from those in the case where is provided. The thickness of the charge generation layer 43a is preferably 0.001 to 6 μm, more preferably 0.01.
~ 2 μm. The content ratio of the charge generating material contained in the charge generating layer 43a is 1 based on the total weight of the charge generating layer.
The amount is preferably 0 to 100% by weight, more preferably 50 to 100% by weight. The thickness of the charge transport layer is the thickness of the photosensitive layer 43 minus the thickness of the charge generation layer 43a. The content of the charge transporting material contained in the charge transporting layer 43b is preferably 20 to 80% by weight, more preferably 30 to 80% by weight based on the total weight of the charge generating layer.
It is 70% by weight.

An undercoat layer 42 may be provided between the conductive support 41 and the photosensitive layer 43. The undercoat layer 42 functions as charge injection control at the interface and as an adhesive layer. Subbing layer 42
Is mainly composed of a binder resin, but may contain the above-mentioned metals or alloys, or their oxides, salts, surfactants and the like. As the binder resin for forming the undercoat layer 42, those mentioned as the binder resin for the photosensitive layer 43 can be used, and the film thickness of the undercoat layer is preferably 0.05 to 7 μm, more preferably 0. It is 1 to 2 μm.

The protective layer is provided on the photosensitive layer as described above, and is preferably composed of resin fine particles containing at least a high concentration of fluorine atoms and a binder resin.

A vapor deposition or coating method is used as a method for manufacturing the electrostatic latent image carrier. The coating method can form a wide range of films from thin films to thick films, and can form films of various compositions. Specifically, coating is carried out using a coating method such as bar coater, knife coater, dip coating, spray coating, beam coating, electrostatic coating, roll coater, attritor or powder coating.

The paint used for applying the protective layer is
It is obtained by dispersing the fluorine atom-containing resin fine particles in a binder resin and a solvent. As a dispersion method, a method such as a ball mill, ultrasonic wave, Peyton shaker, red devil, or sand mill is used. The same dispersion method can be used when the conductive fine powder, the pigment, and the charge generation material are pigments.

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

In FIG. 1, the image forming apparatus has a photosensitive drum 1 as an electrostatic latent image holder, and a developing device 4
The inside of the developing container 16 is separated by a partition wall 17 into the developing chamber (first
Room) R ₁ and agitation room (second room) R _2
A toner storage chamber R ₃ is formed above _{2 with} a partition wall 17 therebetween. A developer 19 is contained in the developing chamber R ₁ and the stirring chamber R ₂ , and a replenishment toner (non-magnetic toner) 18 is contained in the toner storage chamber R ₃ . A replenishment port 20 is provided in the toner storage chamber R _3, and a replenishment toner 18 in an amount commensurate with the toner consumed through the replenishment port 20 is dropped and replenished into the stirring chamber R ₂ .

[0127] A conveying screw 13 in the developing chamber R ₁ is formed, the developer 19 in the developing chamber R ₁ by the driving rotation of the conveying screw 13 is conveyed toward the longitudinal direction of the developing sleeve 11 . Similarly, the conveying screw 14 is provided in the storage chamber R ₂ , and the conveying screw 14
The toner dropped from the replenishing port 20 into the stirring chamber R ₂ is conveyed along the longitudinal direction of the developing sleeve 11.

The developer 19 is a two-component developer containing a non-magnetic toner and a magnetic carrier.

An opening is provided in a portion of the developing container 16 near the photosensitive drum 1, and the developing sleeve 1 is opened from the opening.
1 protrudes to the outside, and a gap is provided between the developing sleeve 11 and the photosensitive drum 1. Bias applying means 30 for applying a bias is disposed on the developing sleeve 11 formed of a non-magnetic material.

As described above, the magnet roller fixed to the developing sleeve 11 as the magnetic field generating means, that is, the magnet 12, has the developing magnetic pole S ₂ and the magnetic pole N ₂ located downstream thereof.
And magnetic poles N ₃ , S ₁ and N ₁ for carrying the developer 19. The magnet 12 is arranged in the developing sleeve 11 so that the developing magnetic pole S ₂ faces the photosensitive drum 1.
The developing magnetic pole S ₂ forms a magnetic field in the vicinity of the developing section between the developing sleeve 11 and the photosensitive drum 1, and the magnetic field forms a magnetic brush.

The regulating blade 15 arranged above the developing sleeve 11 and regulating the layer thickness of the developer 19 on the developing sleeve 11 is an end portion of the nonmagnetic blade 15 made of a nonmagnetic material such as aluminum or SUS316. And the surface of the developing sleeve 11 is 300 to 1000 μm, preferably 400 to 900 μm. If this distance is less than 300 μm, the magnetic carrier is clogged between them and unevenness is likely to occur in the developer layer, and the developer necessary for good development cannot be applied, resulting in a thin developed image with a large unevenness. There is a problem that you can only get it. In order to prevent uneven coating (so-called blade clogging) due to unnecessary particles mixed in the developer, 400 μm or more is preferable. If it is larger than 1000 μm, the amount of the developer coated on the developing sleeve 11 increases, and the predetermined developer layer thickness cannot be regulated, so that the magnetic carrier particles adhere to the photosensitive drum 1 more and the developer circulates or does not flow. There is a problem that the regulation of development by the magnetic blade 15 is weakened, toner tribo is insufficient, and fogging easily occurs.

The angle θ1 is -5 ° to 35 °, preferably 0.
The angle is 25 °. When θ1 <−5 °, the thin developer layer formed by the magnetic force, mirroring force, cohesive force, etc. acting on the developer becomes sparse and uneven, and when θ> 35 °, a non-magnetic blade is used. The amount of developer applied increases, and it is difficult to obtain a predetermined amount of developer.

This magnetic carrier particle layer is used for the sleeve 11
Even if is driven to rotate in the direction of the arrow, the movement becomes slower as it moves away from the sleeve surface due to the balance between the restraining force based on the magnetic force and gravity and the conveying force in the moving direction of the sleeve 11.
Of course, some fall under the influence of gravity.

Therefore, by appropriately arranging the positions of the magnetic poles N ₁ and N ₂ and the fluidity and magnetic characteristics of the magnetic carrier particles, the magnetic carrier particle layer is conveyed in the direction of the magnetic pole N _{1 as} it is closer to the sleeve to form a moving layer. To do. Due to the movement of the magnetic carrier particles, the developer is conveyed to the developing area with the rotation of the developing sleeve 11 and provided for development. Reference numeral 21 denotes an upstream side toner scattering suppressing section, 22 denotes a downstream side toner scattering suppressing section, and the upstream side toner scattering suppressing section 21 and the downstream side toner scattering suppressing section 22 suppress the occurrence of toner scattering.

Another example of the image forming apparatus capable of carrying out the image forming method of the present invention will be described with reference to FIG.

The developing device shown in FIG. 7 has a non-magnetic developing sleeve (developer carrying member) inside the developing chamber 145 of the developing container 102, which faces the electrostatic latent image holding member 101 rotated in the direction of arrow a. A developer carrying member) 121, and a magnetic roller 12 as a magnetic field generating means in the developing sleeve 121.
2 is left unmoved, and the magnetic (magnet) roller 122 is moved in the direction of arrow b from the position of the top to the position S.
It is magnetized to ₁ , N ₁ , S ₂ , N ₂ , and N ₃ .

The developing chamber 145 contains a two-component developer 141 in which the toner 140 and the magnetic carrier 143 are mixed.

When the developer 141 is sent into the stirring chamber 142 of the developing container 102 through one opening (not shown) of the partition wall 148 at the upper end at one end of the developing chamber 145, the inside of the stirring chamber 142 is discharged from the toner chamber 147. Toner 14 supplied to
0 is replenished and mixed by the first developer agitating / conveying means 150 in the agitating chamber 142 and conveyed to the other end of the agitating chamber 142. The developer 141 conveyed to the other end of the stirring chamber 142 is returned to the inside of the developing chamber 145 through the other opening (not shown) of the partition wall 148, where the second developer inside the developing chamber 145 is discharged.
The developer agitating / conveying means 151 and the third developer agitating / conveying means that conveys the developer in the upper direction inside the developing chamber 145 in the direction opposite to the conveying direction of the conveying means 151 are supplied to the developing sleeve 121 while being agitated / conveyed. To be done.

Developer 1 supplied to developing sleeve 121
41 is magnetically restrained by the action of the magnetic force of the magnet roller 122, is carried on the developing sleeve 121, and is regulated by a developer regulating member blade 123 provided substantially on the top of the developing sleeve 121. While being formed as a thin layer of the developer 141 on the developing sleeve 1
21 is rotated in the direction of the arrow b, the electrostatic latent image holding member 101.
The electrostatic latent image is conveyed to a developing unit 110 opposed to the electrostatic latent image holding member 101 and developed there. The remaining two-component developer 141 which has not been consumed for the development is collected in the developing container 102 by the rotation of the developing sleeve 121. Reference numeral 103 denotes an upstream side toner scattering suppressing section, and 104 denotes a downstream side toner scattering suppressing section. The upstream side toner scattering suppressing section 103 and the downstream side toner scattering suppressing section 104 suppress the occurrence of toner scattering.

In the developing container 102, the residual undeveloped two-component developer 141 magnetically restrained on the developing sleeve 121 by the repulsive magnetic field between N ₂ and N ₃ having the same polarity is peeled off. Has become. In order to prevent the toner from scattering when the two-component developer 141 stands up along the lines of magnetic force due to the magnetic pole N ₂ , an elastic seal member 131 contacts one end of the developer 141 to the lower part of the developer container 102. It is fixed and installed in this way.

Further, as a result of diligent studies on the image density, highlight reproducibility, and fine line reproducibility of the color image forming method, the present inventors have confirmed that the toner having a specific particle size distribution described later is applied to the specific development described above. They have found that when used in an image forming method using a developing method in which an electric field is formed, high image density excellent in high image density, highlight reproduction, and fine line reproduction can be achieved.

That is, the toner used in the present invention is
The toner contains at least toner particles and an external additive, and the toner has a weight average particle diameter of 3 to 7 μm.
more than 40% by number of toner particles having a particle size of m or less, 10-70% by number of toner particles having a particle size of 4 μm or less, and 2-20 toner particles having a particle size of 8 μm or more.
It is preferable that the toner contains 10% by volume of the toner and 0 to 6% by volume of the toner having a particle diameter of 10.08 μm or more.

The toner having the above-mentioned particle size distribution can faithfully reproduce the latent image formed on the photosensitive member, and is excellent in the reproducibility of a dot and a minute dot latent image such as a digital image. In particular, it gives an image excellent in gradation and resolution in the highlight part. Furthermore, even when copying or printing out is continued, high image quality is maintained, and even in the case of a high density image, good development can be performed with a toner consumption amount smaller than that of the conventional non-magnetic toner. And the miniaturization of the copying machine or printer body.

However, even if the toner is originally excellent in latent image reproducibility, in the conventional continuous sine wave or rectangular wave, an electric field is not generated in a latent image having a small development contrast such as a highlight latent image. Since the intensity is not sufficient, the proportion of toner that does not reach the latent image carrier increases with continuous pulses. That is, under the bias under the above conditions, the toner makes an oscillating motion such that the toner does not reach the latent image carrier from the developer carrier.

However, according to the present invention, since a specific developing electric field as described later is formed in the developing area, it is possible to obtain a good highlight image without roughness. That is, in one pulse, the toner vibrates so as not to reciprocate between the developer carrying member and the electrostatic latent image holding member, but thereafter, the surface potential of the electrostatic latent image holding member and the direct current of the developing bias are changed. When the potential difference V _{cont of the} components is V _cont <0, the direct current component works to attract the toner to the developer carrying member side,
When the toner is biased toward the developer carrying member side and conversely, V _cont > 0, the DC component acts to attract the toner to the electrostatic latent image holding member side according to the latent image potential, and the latent image potential matches. The amount of toner is biased toward the electrostatic latent image carrier. Further, when the toner is developed under such conditions, the toner reaching the latent image carrier repeats vibration there and concentrates on the latent image portion.
For this reason, the dot shapes are made uniform, and a good image without unevenness can be obtained.

From the above, when the latent image is visualized with the developing bias under the above conditions, dot loss does not occur even in the case of a highlight latent image. further,
By repeating the vibration on the latent image carrier, the toner is concentrated on the latent image portion, and each dot is faithfully reproduced. In the two-component developer, there is no unevenness due to the contact state of the magnetic brush. A halftone image can be output.

The measuring method in the present invention will be described below.

(1) Measurement of Magnetic Properties of Carrier As a device, a BHU-60 type magnetization measuring device (manufactured by Riken measurement) is used. About 1.0 g of the measurement sample is weighed and packed in a cell having an inner diameter of 7 mmφ and a height of 10 mm and set in the above-mentioned device. In the measurement, the applied magnetic field is gradually added and changed up to 3,000 oersted. Next, the applied magnetic field is reduced to finally obtain the hysteresis curve of the sample on the recording paper. From this, the saturation magnetization, remanent magnetization, and coercive force are obtained.

(2) Measurement of particle size distribution of carrier The SRA type of Microtrac particle size analyzer (Nikkiso Co., Ltd.) was used as the device and the range was set to 0.7 to 125 μm.

(3) Method of Measuring Electric Resistance of Carrier Particles The resistance value of the carrier particles was measured using the cell shown in FIG. That is, the cell A is filled with carrier particles, and the electrodes 81 and 8 are placed in contact with the filled carrier particles.
2 was arranged, a sinusoidal alternating voltage of 2 kHz was applied between the electrodes, and the alternating current flowing at that time was measured to obtain the value. The measurement conditions are as follows: Contact area of the filled carrier particles with the cell S = 2 cm ² , thickness d = 3 mm, upper electrode load 1
5 kg and applied voltage Vpp = 100V. In addition, 83 is an insulator, 84 is an ampere meter, 85 is a voltmeter, 86 is a voltage stabilizer, 87 is a carrier particle, and 88 is a guide ring.

(4) Particle size distribution of toner (weight average particle size)
The average particle size and particle size distribution of the toner can be measured using a Coulter Counter TA-II type or Coulter Multisizer (manufactured by Coulter Co.), but in the present invention, Coulter Multisizer (manufactured by Coulter Co.) is used. An interface (manufactured by Nikkaki Co., Ltd.) that outputs a number distribution and a volume distribution and a PC9801 personal computer (manufactured by NEC) are connected, and a 1% NaCl aqueous solution is prepared using primary sodium chloride as an electrolytic solution. For example, I
SOTON R-II (manufactured by Coulter Scientific Japan) can be used. As a measuring method, a surfactant, preferably an alkylbenzene sulfonate, as a dispersant was added to 100 to 150 ml of the electrolytic aqueous solution in an amount of 0.1%.
Add 1 to 5 ml, and further add 2 to 20 mg of the measurement sample.
The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the Coulter Multisizer was used to make an aperture of 100 μm as an aperture.
The volume distribution and the number distribution were calculated by measuring the volume and the number of the toner having a particle size of μm or more. Then, based on the volume-based volume average particle diameter (D _v : the median value of each channel is a representative value of the channels) and the weight average particle diameter (D ₄ ) obtained from the volume distribution according to the present invention, from the number distribution The number-based length average particle diameter (D ₁ ) obtained, the volume-based particle ratio obtained from the volume distribution (8.00 μm or more and 3.17 μm or less), and the number-based particle ratio obtained from the number distribution ( 5μ
m or less and 3.17 μm or less).

(5) Measurement of number average particle diameter of external additive (inorganic fine powder) The number average particle diameter on the toner particles was observed at 50,000 times using a scanning electron microscope, and 100 particles in the visual field were observed. The particles are qualitatively analyzed by an X-ray microanalyzer (XMA), and the particle diameter is measured to determine the number average particle diameter.

(6) Measurement of Hydrophobicity of Inorganic Fine Powder The methanol measurement test is an experimental test for confirming the hydrophobicity of inorganic fine powder having a hydrophobized surface.

The "methanol titration test" defined in this specification for evaluating the hydrophobicity of the treated inorganic fine powder is performed as follows.

The inorganic fine powder 0.2 g to be tested has a capacity of 250 ml.
Add to 50 ml water in Erlenmeyer flask. Methanol is titrated from the burette until the total amount of inorganic fines is wet. At this time, the solution in the flask is constantly stirred with a magnetic stirrer. The end point is observed by suspending the total amount of the inorganic fine powder in the liquid, and the degree of hydrophobization is expressed as the percentage of methanol in the liquid mixture of methanol and water when the end point is reached.

(7) Measurement of light transmittance Sample 0.10 g Alkyd resin 13.20 g (Dainippon Ink & Co. Beccosol 1323-60-EL) Melamine resin 3.30 g (Dainippon Ink Super Beckamine J-820-6)
0) Thinner 3.50g (Karasai Paint Aramic Thinner) Glass media 50.00g

The above formulation was sampled in a 150 cc glass bottle,
Disperse for 1 hour with a paint conditioner manufactured by Red Devil.

After the dispersion is completed, the distance between the surface of the PET film and the doctor blade is set to 2 mm, and the dispersion liquid is applied to the PET film.

[0159] is heated at 120 ° C for 10 minutes to perform baking.

The sheet of U-BEST manufactured by JASCO
The light transmittance was measured at 50 in the range of 320 to 800 nm.

(8) Measurement of Specific Surface Area This is carried out by the following procedure using a Shimadzu powder specific surface area measuring device (SS-100 type). 1) To fill the sample iron powder, turn on the power of the autoslider of the powder tester and adjust it to 100V. 2) Adjust the timer to 1 minute by tapping the changeover switch on the passender tester (50 times ± 1 time / 1 minute). 3) Put a sieve plate in a plastic sample tube, lay a piece of filter paper on it, and put the sample on it up to 1/3 of the sample tube. 4) Set the sample tube on the tap stand of the powder tester and insert the start button (tap for 1 minute). 5) The sample cylinder is tapped further and the sample is ⅔ of the sample cylinder.
Put in. 6) Perform the same work as in 4 above. 7) Insert a supplemental cylinder (plastic) on top of the sample cylinder and place the sample on top of it. 8) Perform the same work as the above 4 and 6. 9) Take out the tapped sample tube from the tap mount, remove the supplementary tube, and cut the extra sample with a spatula. 10) Fill the water up to the S scale of the specific surface area measuring tube. 11) Connect the sample tube to the measuring tube (after filling the sample, apply grease to the mating surface). 12) Open the cock at the lower outlet and let the water level of the measuring tube be zero.
Start the stopwatch as it passes the scale (lower runoff received in beaker). 13) Measure the time for the water surface to drop to the 20 scale (unit: cc). 14) Remove the sample tube and measure the weight of the sample. 15) Calculation of specific surface area

The specific surface area is calculated by the following formula.

[0163]

[Equation 1]

SW: Specific surface area of powder cm ² / g e: Porosity of sample packed layer ρ: Density of powder g / cm ³ η: Viscosity coefficient of fluid g / cm · sec L: Thickness of sample layer cm Q: sample layer permeation fluid amount cc ΔP: pressure difference between both ends of sample layer g / cm ² A: cross sectional area of sample layer cm ² t: time required for Qcc fluid (air) to permeate sample layer sec W : Sample weight g

(9) Acid value measuring method 2 to 10 g of the sample is weighed in a 200 to 300 ml Erlenmeyer flask, and about 50 ml of a mixed solvent of methanol: toluene = 30: 70 is added to dissolve the resin. A small amount of acetone may be added if the solubility is poor. 0.1%
Using a mixed indicator of bromthymol blue and phenol red, the titration was performed with a previously standardized N / 10 potassium-alcohol solution, and the acid value was calculated from the consumption of the alcohol potassium solution by the following calculation.

Acid value = KOH (number of ml) × N × 56.1 / Sample weight (where N is a factor of N / 10 KOH)

(10) Measurement of glass transition temperature Tg In the present invention, measurement is carried out using a differential thermal analysis measuring device (DSC measuring device), DSC-7 (manufactured by Perkin Elmer Co.).

A measurement sample is 5 to 20 mg, preferably 10
Precisely weigh mg.

This was placed in an aluminum pan, and an empty aluminum pan was used as a reference, and the measurement temperature range was 30 ° C to 2 ° C.
The measurement is performed at a temperature rising rate of 10 ° C./min between 00 ° C. and normal temperature and normal humidity.

During this temperature rising process, the endothermic peak of the main peak in the temperature range of 40 to 100 ° C. is obtained.

The intersection point between the line at the midpoint of the baseline and the differential heat curve before and after the endothermic peak appears at this time is the glass transition temperature Tg in the present invention.

(11) Softening point temperature (Tm) A flow tester CFT-500 type (manufactured by Shimadzu Corporation) is used. A sample weighs about 1.0 g of a 60 mesh pass product. Using a molding machine, this is pressed for 1 minute with a load of 100 kg / cm ² .

This pressurized sample is subjected to flow tester measurement under the following conditions at room temperature and normal humidity (temperature of about 20 to 30 ° C., humidity of 30 to 70% RH) to obtain a temperature-apparent viscosity curve. From the obtained smooth curve, the temperature (= T _1/2 ) when the sample flows out by 50% by volume is obtained, and this is defined as the softening point temperature (Tm).

RATE TEMP 6.0 D / M (° C. 1 minute) SET TEMP 50.0 DEG (° C.) MAX TEMP 180.0 DEG INTERVAL 3.0 DEG PREHEAT 300.0 SEC (sec) LOAD 20.0 KGF ( kg) DIE (DIA) 1.0 MM (mm) DIE (LENG) 1.0 MM (mm) PLUNGER 1.0 CM ² (cm ² )

[0175]

EXAMPLES In the following examples, "parts" and "%" indicate "parts by weight" and "% by weight" unless otherwise specified.

(Manufacturing Example 1 of Carrier) Fe ₂ O ₃ , MnO and Na ₂ O as additives were weighed so as to have the respective mole fractions of ferrite components shown in Table 1 and mixed by a ball mill. The obtained mixed powder was calcined at about 900 ° C., then crushed, and the particle size of the crushed particles after crushing was measured by an air permeation method. As a result, the average particle size was about 2.0 μm. Then, an aqueous solution of PVA (polyvinyl alcohol) as a binder was added to the pulverized particles (the amount of PVA was 0.
5 to 5.0% by weight) was added and the mixture was granulated with a spray dryer.

The obtained granulated powder was added at 1,100 to 1,300
After calcination at ℃, pulverized, and classified to obtain carrier particles having a desired particle size.

In order to coat the surface of the obtained carrier particles with a resin coating layer, the curable silicone resin material forming the coating layer is dissolved in xylene to form a 10% solid content solution, and this coating solution is applied by an applicator (Okada Seiko). Coated carrier 1 was obtained by coating the carrier particles with a Spira coater (manufactured by the company), removing the solvent by drying, and heating.

Table 1 shows various characteristics of the carrier 1 thus obtained.

(Carrier Production Examples 2 to 14) Coated carriers 2 to 12 having the physical properties shown in Table 1 were prepared in the same manner as in Carrier Production Example 1 with the composition, mole fraction and resin coating layer of the ferrite component shown in Table 1. did.

When the resin material of the resin coating layer for coating the surface of the carrier particles is a silicone resin, xylene is used as the solvent and polytetrafluoroethylene / polyvinylidene fluoride (PTEF / PVDF = 5/5) is used. In some cases, methyl ethyl ketone was used as the solvent.

Various properties of the obtained carriers 2 to 14 are shown in Table 1.
Described in.

[0183]

[Table 1]

(Toner Production Example 1) Polyester resin obtained by condensation of propoxylated bisphenol and fumaric acid 100 parts Phthalocyanine pigment 4 parts Di-tert-butylsalicylic acid chromium complex 4 parts

The above raw materials were sufficiently premixed with a Henschel mixer, melt-kneaded with a twin-screw extruder,
After cooling, it was roughly pulverized to about 1 to 2 mm using a hammer mill, and then finely pulverized by an air jet type fine pulverizer. Further, the obtained finely pulverized product was classified to obtain a negative triboelectrically chargeable cyan powder having a weight average particle diameter of 8.5 μm. To 100 parts of the colored powder, 1.0 part of titanium oxide fine powder was added and mixed by a Henschel mixer,
Cyan toner 1 was obtained.

(Toner Production Example 2) Polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts Phthalocyanine pigment 4 parts Di-tert-butylsalicylic acid chromium complex 4 parts

The above raw materials were sufficiently premixed by a Henschel mixer, and melt-kneaded by a twin-screw extruder kneader,
After cooling, it was roughly pulverized to about 1 to 2 mm using a hammer mill, and then finely pulverized by an air jet type fine pulverizer. Further, the obtained finely pulverized product was classified to obtain a negative triboelectrically chargeable cyan powder having a weight average particle diameter of 6.2 μm. To 100 parts of the colored powder, 1.3 parts of titanium oxide fine powder was added and mixed by a Henschel mixer,
Cyan toner 2 was obtained.

Example 1 Cyan Toner 1 and Carrier 1 Obtained in Toner Production Example 1
Were mixed to have a toner concentration of 8% to prepare a two-component developer, and the alternating electric field shown in FIG. 3 was applied to the image forming apparatus shown in FIG. Table 2 shows the results of printing an image of 50,000 sheets at a temperature of 26 ° C. and a humidity of 60% using a color copying machine CLC-500 (manufactured by Canon) and an original document having an image area ratio of 5.0%. It was It can be seen from Table 2 that the above-mentioned two-component type developer is very good in that variations in charge amount, image quality and fog in the printing endurance test are small, and that the inside of the machine is not stained after 50,000 sheets.

The following Comparative Examples and Examples are also shown in Table 2.

Example 2 The same experiment as in Example 1 was carried out except that toner 1 and carrier 2 were used and the toner concentration was set to 5%, but the image quality after 50,000 sheets was slightly deteriorated, but it was practically used. As shown in Table 2, good results were obtained without any problems.

Example 2 The same experiment as in Example 1 was conducted using Toner 1 and Carrier 3, but the image quality after 50,000 sheets was slightly deteriorated, but there was no problem in practical use and the results are shown in Table 2. So good results have been obtained.

Example 3 The same experiment as in Example 1 was carried out except that toner 2 and carrier 4 were used and the toner density was 6%, and a very high-definition image was high from the initial stage to after 50,000 sheets. Obtained at image density. There was no problem with fog and dirt inside the machine.

Examples 5 and 6 Toner 1 was combined with Carriers 4 and 5, respectively, and the same experiment as in Example 1 was conducted. As a result, good results were obtained as shown in Table 2.

Examples 7 and 9 Toner 2 was combined with Carriers 5 to 7 and the same experiment as in Example 4 was carried out. As a result, good results were obtained as shown in Table 2.

Comparative Example 1 The same experiment as in Example 1 was carried out using Toner 1 and Carrier 8, and the image quality was at a slightly low level from the initial stage and after 50,000 sheets. This is probably because the magnetic properties are not proper and the shape and density of the magnetic brush are not preferable. Although the charge amount and the fog were not problematic at the initial stage, the charge amount decreased after 50,000 sheets, and the fog was deteriorated and the inside of the machine was stained with the toner. This is because the resistance and charge amount of the carrier core material used are not appropriate,
Although the initial properties were improved by the coating material, it is considered that the resistance and charge amount of the carrier decreased as the coating layer deteriorated due to durability.

Comparative Examples 2 to 7 An experiment similar to that of Example 1 was carried out using toner 1 and carriers 9 to 14 in combination, respectively. In all cases, the initial characteristics were not a problem, but the charge amount was increased along with the number of durable sheets. And the fog worsened. In addition, dirt inside the aircraft was also seen.
It is considered that all of the carriers had a poor balance of the resistance, charge amount and magnetic characteristics of the carrier core material, and the characteristics of the carrier deteriorated as the coating material deteriorated.

[0197]

[Table 2]

Example 11 Using the two-component type developer in which the toner 1 and the carrier 1 used in Example 1 are combined, the developing sleeve has a developing main pole of 960 gauss by using the image forming apparatus shown in FIG. A magnet roller having a 5-pole structure is built in, the alternating electric field shown in FIG. 4 is superimposed, and the developing conditions are V _cont = 250 V and V _back = −130.
The image formation test was performed under the temperature / humidity of 26 ° C./60% RH by setting V.

As a result, a higher definition image was obtained as compared with Example 1, and there was no problem in durability.

Example 12 An image drawing test was conducted in the same manner as in Example 11 except that the alternating electric field shown in FIG. 5 was used instead of the alternating electric field used in Example 11. As a result, although the reproducibility of the photograph was slightly lowered as compared with Example 11, better results than Example 11 were obtained.

Polyester Resin Synthesis Example 1 Polyoxypropylene (2.2) -2,2bis 45 mol% (4-hydroxyphenyl) propane Polyoxyethylene (2) -2,2-bis 6 mol% (4-hydroxy) Phenyl) propane fumaric acid 47 mol% trimellitic anhydride 2 mol%

Dibutyltin oxide was added as a catalyst to the above raw materials, polycondensation reaction was carried out at 200 ° C. under a nitrogen stream, and when the softening point 92 ° C. according to ASTM E28-51T was reached, the reaction was terminated. Resin (I)
I got

The acid value of the resin was 9.5 KOHmg / g and the glass transition temperature was 57.2 ° C.

Polyester Resin Synthesis Example 2 Polyoxypropylene (2.2) -2,2bis 45 mol% (4-hydroxyphenyl) propane Polyoxyethylene (2) -2,2-bis 4 mol% (4-hydroxy) Phenyl) propane fumaric acid 40 mol% terephthalic acid 10 mol% trimellitic anhydride 1 mol%

Dibutyltin oxide was added to the above raw materials as a catalyst to carry out a polycondensation reaction at 200 ° C. in a nitrogen stream, and when the softening point 91 ° C. according to ASTM E28-51T was reached, the reaction was terminated. Resin (I
I) was obtained.

The acid value of the resin is 22.0 KOHmg / g,
The glass transition temperature was 55.3 ° C.

Polyester Resin Synthesis Example 3 Polyoxypropylene (2.2) -2,2bis 45 mol% (4-hydroxyphenyl) propane Polyoxyethylene (2) -2,2-bis 10 mol% (4-hydroxy) Phenyl) propane fumaric acid 43 mol% 1,2,5-hexanetricarboxylic acid 2 mol%

Dibutyltin oxide was added as a catalyst to the above raw materials, the polycondensation reaction was carried out at 200 ° C. under a nitrogen stream, and the reaction was terminated when the softening point of 95 ° C. according to ASTM E28-51T was reached. Resin (II
I) was obtained.

The acid value of the resin was 0.8 KOHmg / g and the glass transition temperature was 58.1 ° C.

(Polyester Resin Synthesis Example 4) Polyoxypropylene (2.2) -2,2bis 49 mol% (4-hydroxyphenyl) propane terephthalic acid 49 mol% 2,5,7-naphthalenetricarboxylic acid 2 mol%

Dibutyltin oxide was added to the above raw materials as a catalyst to carry out polycondensation reaction at 200 ° C. under a nitrogen stream, and when the softening point of 92 ° C. according to ASTM E28-51T was reached, the reaction was terminated. Resin (I
V) was obtained.

The acid value of the resin is 17.1 KOHmg / g,
The glass transition temperature was 57 ° C.

(Polyester Resin Synthesis Example 5) Polyoxypropylene (2.2) -2,2bis 53 mol% (4-hydroxyphenyl) propane fumaric acid 45 mol% 1,2,7,8-octanetetracarboxylic acid 2 mol%

Dibutyltin oxide was added as a catalyst to the above raw materials, and the polycondensation reaction was carried out at 200 ° C. under a nitrogen stream. When the softening point of 95 ° C. according to ASTM E28-51T was reached, the reaction was terminated. Resin (V)
I got

The acid value of the resin was 2.2 KOHmg / g and the glass transition temperature was 59 ° C.

Polyester Resin Synthesis Example 6 Polyoxypropylene (2.2) -2,2bis 50 mol% (4-hydroxyphenyl) propane terephthalic acid 49.5 mol% trimellitic anhydride 0.5 mol%

Dibutyltin oxide was added as a catalyst to the above raw materials, and a polycondensation reaction was carried out at 200 ° C. under a nitrogen stream to give a softening point of 103 ° C. according to ASTM E28-51T.
The reaction is terminated when the temperature reaches
I) was obtained.

The acid value of the resin was 8.7 KOHmg / g and the glass transition temperature was 61 ° C.

(Production Example 3 of Toner) Propoxylated bisphenol and fumaric acid and trimellitic acid 100 parts Polyester resin (I) obtained by condensing trimellitic acid (I) Phthalocyanine pigment 4 parts Metal complex of di-tert-butylsalicylic acid 4 copies

The above was sufficiently premixed with a Henschel mixer, melt-kneaded with a twin-screw extruder, cooled, and roughly crushed to about 1 to 2 mm with a hammer mill.
Then, it was pulverized by an air jet pulverizer. Further, the obtained finely pulverized product was classified to obtain a blue powder having a weight average particle diameter of 5.8 μm.

20 parts of iso-C ₄ H ₉ —Si— (OCH ₃ ) ₃ was added to 100 parts of the above colored powder and water / butanol mixed medium.
Alumina fine powder having an average particle diameter of 0.02 μm and a hydrophobicity of 65% and 1.5 parts were mixed by a Henschel mixer to obtain a cyan toner 3.

The acid value of this toner is 9.5 KOHmg /
g, Tm was 90 ° C and Tg was 55 ° C.

(Production Example 4 of toner) In Production Example 3 of toner, instead of alumina, n-C ₄ H ₉ was used in an aqueous medium.
Cyan Toner 4 was prepared in the same manner as in Toner Production Example 3 except that titanium oxide fine powder (average particle size 0.03 μm, hydrophobicity 60%) treated with 25 parts of —Si— (OCH ₃ ) ₃ was used. Obtained.

The acid value, Tm and Tg of this toner were the same as those of Toner 3.

(Toner Production Examples 5 to 9) Table 3 is similarly shown except that polyester resins (II) to (VI) were used in place of the polyester resin (I) used in Toner Production Example 3. Toners 5-9 were obtained.

Table 3 shows the constitutions and physical properties of the toners 3 to 9 obtained above.

[0227]

[Table 3]

Examples 13 and 14 The above-mentioned cyan toners 3 and 4 and the carrier 1 were mixed at a toner concentration of 7% to prepare a two-component type developer, and the color copying machine CLC700 (manufactured by Canon Inc.) was used. An electrostatic latent image carrier (I) containing 30% by weight of fluorine atom-containing resin particles in the protective layer of the latent image carrier, and a discontinuous electric field shown in FIG. Table 4 shows the results of printing 10,000 images at 30 ° C./80% RH and 20 ° C./10% RH using an original document having an image area ratio of 25%.

Examples 15 to 18 Example 1 is repeated except that cyan toners 5 to 8 are used instead of the cyan toners 3 and 4 used in Examples 13 and 14.
Table 4 shows the results of image formation in the same manner as 3 and 14. In Examples 15 and 16 using the toner 5 having a high acid value and the toner 6 having a low acid value, the toner scattering was slightly worse than the toners of Examples 13 and 14, but there was no problem in practical use.

Example 19 The procedure of Examples 13 and 14 was repeated except that Toner 9 was used instead of Toners 3 and 4 used in Examples 13 and 14, and the image gloss was lowered and the image density was slightly increased. Although it was lowered, good results were obtained as shown in Table 4.

Examples 20 to 23 Images were produced in the same manner as in Examples 13 and 14 except that Carriers 2, 3, 4 and 5 were used instead of Carrier 1 used in Examples 13 and 14. Good results were obtained as shown in Table 4.

Example 24 Images were produced in the same manner as in Examples 13 and 14 except that the carrier 6 was used instead of the carrier 1 used in Examples 13 and 14, and the coating material was a silicone resin. Therefore, the durability was slightly lowered, but good results were obtained as shown in Table 4.

Example 25 Images were produced in the same manner as in Examples 13 and 14 except that the carrier 7 was used in place of the carrier 1 used in Examples 13 and 14, and the results were good as shown in Table 4. The results were obtained.

Examples 26 to 28 In place of the electrostatic latent image carrier (I) used in Examples 13 and 14, the content of the fluorine atom-containing resin particles in the protective layer of the electrostatic latent image carrier was 20 respectively. Table 4 shows the results obtained in the same manner as in Examples 13 and 14 except that the electrostatic latent image carriers (II) to (IV) changed to 6%, 6% and 0% were used. As the content of the fluorine atom-containing resin particles decreased, the solid uniformity slightly deteriorated, but there was no problem in practical use.

Examples 29 and 30 Examples 29 and 30 were carried out in the same manner as Examples 13 and 14 except that the alternating electric fields shown in FIGS. 5 and 4 were used instead of the alternating electric fields used in Examples 13 and 14, respectively. As shown in 4, good results were obtained.

Example 31 The same procedure as in Examples 13 and 14 was repeated except that the continuous electric field shown in FIG. 3 was used as the alternating electric field instead of the alternating electric field used in Examples 13 and 14, and the image density was increased. Was slightly decreased and the solid uniformity was slightly deteriorated, but as shown in Table 4, it was at a level where there was no practical problem.

[0237]

[Table 4]

In the above examples, the charge amount, image quality, fog and toner scattering were evaluated by the following evaluation methods.

The [charge amount] measuring method will be described in detail with reference to the drawings.

FIG. 9 is an explanatory view of an apparatus for measuring the triboelectric charge amount of toner. First, about 0.5 to 0.9 g of a mixture of toner and carrier (developer) whose triboelectric charge is to be measured is placed in a metal measuring container 92 having a 500 mesh screen 93 at the bottom, and a metal lid 94 is placed therein. do. At this time, the total weight of the measuring container 92 is weighed and set as W ₁ (kg). Next, in the suction device 91 (at least the portion in contact with the measurement container 92 is an insulator), suction is performed from the suction port 97 to adjust the air volume control valve 96 to adjust the pressure of the vacuum gauge 95 to 250 mmA.
Let q. In this state, the toner is suctioned sufficiently, preferably for about 2 minutes to remove the toner by suction. The potential of the electrometer 99 at this time is V (volt). Here, 98 is a capacitor, and the capacity is C (mF). The weight of the entire measuring container after suction is weighed and is W ₂ (g). The triboelectric charge amount (mC / kg) of this toner is calculated by the following formula.

Toner triboelectric charge amount (mC / kg) = (C
_{× V) / (W 1 -W} 2)

[Image quality] CLC SK paper (Canon sales)
After being left for 3 days, images are printed and the Macbeth density is reduced to 0.
The halftone uniformity of 6 (especially transfer unevenness) was evaluated.

◎: Very good (no problem at all) ○: Good ○ △: Somewhat bad level but no problem △: Some problem

[Fog] REFLECTOMETER MODELTC-6D manufactured by Tokyo Denshoku Co., Ltd.
S is used to measure, and for cyan toner images, it is amber
It was calculated from the following formula using a filter. The smaller the number, the less fog.

Fog (reflectance) (%) = reflectance of standard paper (%)-reflectance of non-image part of sample (%)

[Toner Scattering] Toner scattering is determined according to the following evaluation criteria by observing the dirt on the outer surface of the upstream side toner scattering suppressing section and the downstream side toner scattering suppressing section of the developing container with the toner and the toner outside the developing container. Based on the evaluation.

◎ Not observed at all.

A small amount of dirt is found on the outer surface of the upstream toner scattering suppressing portion of the developing container, but no dirt is found on the outer surface of the downstream toner scattering suppressing portion.

Δ: Contamination is observed on the outer surface of the upstream toner scattering suppressing portion and the outer surface of the downstream toner scattering preventing portion of the developing container, but no stain is observed on parts other than the developing container.

× Stain is observed even in areas other than the developing container.

[0251]

According to the present invention, since the carrier is composed of magnetic carrier particles formed of a specific ferrite component, the characteristic balance of resistance, saturation magnetization and charge amount can be maintained within an appropriate range. It is possible to maintain the initial performance such as the amount for a long period of time without impairing durability, and especially when combined with a toner having a small particle diameter, there is little fog and high image quality from the beginning to the end of durability. An image with high density and very high definition can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of an image forming apparatus used in an image forming method of the present invention.

FIG. 2 is a diagram showing an alternating electric field used in Examples 13 to 28.

FIG. 3 is a diagram showing an alternating electric field used in Examples 1 to 10 and 31.

FIG. 4 is a diagram showing an alternating electric field used in Examples 11 and 30.

FIG. 5 is a diagram showing an alternating electric field used in Examples 12 and 29.

FIG. 6 is a diagram showing a preferred form of an electrostatic latent image carrier that can be used in the image forming method of the present invention.

FIG. 7 is a diagram showing another example of an image forming apparatus used in the image forming method of the present invention.

FIG. 8 is an explanatory diagram of an apparatus for measuring electric resistance of carrier particles.

FIG. 9 is an explanatory diagram of an apparatus for measuring a triboelectric charge amount of toner.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location G03G 9/107 9/113 G03G 9/08 371 374 9/10 321 351

Claims (17)

[Claims] 1. The following formula (I) (Fe ₂ O ₃ ) _x (MnO) _y (A) _z formula (I) [wherein A is Na ₂ O, K ₂ O, CaO, SrO or their Shows a mixture, x, y and z represent mole fractions, and the following conditions 0.3 <x <0.8, 0.01 <y <0.5, 0 <z <0.69, x + y + z ≦ Satisfy 1. ] A carrier for electrophotography, which is formed of a magnetic ferrite component represented by: 2. The values of x, y and z in the formula (I) are as follows: 0.3 <x <0.8, 0.01 <y <0.5, x + y <
The electrophotographic carrier according to claim 1, wherein 1, z = 1-xy is satisfied. 3. The carrier core material particles contain Bi ₂ O ₃ of 0.
The electrophotographic carrier according to claim 1, wherein the carrier is contained in an amount of 01 to 3 mol%. 4. The electrophotographic carrier according to claim 1, wherein the carrier has a weight average particle diameter of 50 μm or less. 5. The electrophotographic carrier according to claim 1, wherein the carrier has carrier particles and a resin coating layer that coats the surfaces of the carrier particles. 6. A two-component developer having a toner and a carrier, wherein the toner has toner particles, and the carrier has the following formula (I) (Fe ₂ O ₃ ) _x (MnO) _y (A). _z Formula (I) [wherein A represents Na ₂ O, K ₂ O, CaO, SrO or a mixture thereof, x, y and z represent a mole fraction, and the following condition 0.3 < x <0.8, 0.01 <y <0.5, 0 <z <0.69, and x + y + z ≦ 1 are satisfied. ] A two-component developer having a magnetic ferrite component represented by: 7. In the formula (I), x, y and z are as follows: 0.3 <x <0.8, 0.01 <y <0.5, x + y <
The two-component developer according to claim 6, which satisfies 1, z = 1-xy. 8. The carrier core material particles contain Bi ₂ O ₃ of 0.
The two-component developer according to claim 6 or 7, wherein the two-component developer is contained in an amount of 01 to 3 mol%. 9. The two-component developer according to claim 6, wherein the carrier has a weight average particle diameter of 50 μm or less. 10. The two-component developer according to claim 6, wherein the carrier has carrier particles and a resin coating layer that coats the surface of the carrier particles. 11. The toner has a weight average particle diameter of 1 to 9 μm.
The two-component developer according to any one of claims 6 to 10, further comprising: 12. The toner has a weight average particle diameter of 2 to 8 μm.
The two-component developer according to any one of claims 6 to 10, further comprising: 13. The toner contains the toner particles and an external additive, and the external additive is 0.00-hydrophobized.
The two-component developer according to any one of claims 6 to 12, which has an inorganic fine powder of 5 µm to 0.2 µm. 14. The two-component toner according to claim 6, wherein the toner particles contain a binder resin and a colorant, and the binder resin contains a polyester resin. System developer. 15. The toner particles have an acid value of 1 to 20 KOH.
The two-component developer according to claim 14, which has a mg / g content. 16. A two-component developer having a toner and a carrier is circulated and conveyed by a developer carrying member, and the electrostatic latent image held on the electrostatic latent image carrying member in the developing area is transferred to the developer carrying member. In the image forming method of developing with the toner of the carried two-component developer, the toner contains toner particles, and the carrier has the following formula (I) (Fe ₂ O ₃ ) _x (MnO) _y (A) _z formula (I) [wherein A represents Na ₂ O, K ₂ O, CaO, SrO or a mixture thereof, x, y and z represent mole fractions, and It satisfies 0.3 <x <0.8, 0.01 <y <0.5, 0 <z <0.69, and x + y + z ≦ 1. ] An image forming method characterized by being formed of a magnetic ferrite component represented by 17. The two-component developer according to any one of claims 7 to 1.
17. The image forming method according to claim 16, wherein the image forming method is any one of two-component type developers selected from 5.