JP3122768B2 - Developer for developing electrostatic images - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to electrophotography, electrostatic recording,
The present invention relates to a developer for developing an electrostatic image in electrostatic printing or the like.

[0002]

2. Description of the Related Art It is well known in the art to form and develop an image on the surface of a photoconductive material by electrostatic means. That is, U.S. Pat. No. 2,297,691 and JP-B-42-239.
A number of methods are known, such as Japanese Patent Publication No. 10 and Japanese Patent Publication No. Sho 43-24748, but generally, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means.
Next, an extremely finely ground electro-sensitive material called a toner is attached on the latent image to form a toner image corresponding to an electrostatic latent image.

Then, if necessary, the toner is transferred onto the surface of an image support such as paper, and then fixed by heating, pressing or solvent vapor to obtain a copy. In the case where a step of transferring a toner image is provided, a step for removing the remaining toner is usually provided. A developing method for visualizing an electric latent image using toner is described in, for example, a powder cloud method described in US Pat. No. 2,221,776 and US Pat. No. 2,618,552. Cascade developing method, magnetic brush method described in Japanese Patent No. 2,874,063, and 3,909,2
A method using a conductive magnetic toner described in Japanese Patent No. 58-58 is known.

As a toner applied to these developing methods, a toner obtained by mixing and dispersing a colorant in a thermoplastic resin and then pulverizing the same is used. As the thermoplastic resin, a polystyrene resin is the most common, but a polyester resin, an epoxy resin, an acrylic resin, a urethane resin, or the like is also used. As a coloring agent, carbon black is most widely used, and in the case of a magnetic toner, iron oxide black magnetic powder is often used. In the case of a method using a so-called two-component developer, the toner is usually used by being mixed with carrier particles such as glass beads and iron powder.

[0005] The toner image on the final copy image forming member such as paper is permanently fixed on the support by heat, pressure or the like.
Conventionally, this fixing step has often been performed by heat. When a step of transferring a toner image is provided, a step for removing residual toner on the photoconductor is usually provided. In recent years, the development of mono-color copying to full-color copying in copying machines and the like is rapidly progressing.
The study and commercialization of color-color copying machines and full-color copying machines have been greatly promoted. For example, "Journal of the Society of Electrophotography" Vo
l 22, No. 1 (1983) and "Journal of the Society of Electrophotography"
Vol 25, No. 1, P52 (1986).

[0006] However, those who are not immediately compared with the real ones, such as televisions, photographs, and color prints, and who have seen color images processed more beautifully than the real ones, consider the full-color electronic currently in practical use. Photographic images are not always satisfactory. Furthermore, in recent years, the demand for high definition and high image quality of copying machines has been increasing in the market, and in this technical field, attempts have been made to achieve high image quality color by reducing the particle size of toner. When the particle diameter is small, the surface area per unit weight tends to increase, and the charge amount of the toner tends to increase.

That is, in the development of the electrostatic latent image, the toner is mixed with a carrier having relatively large particles and used as a developer for electrophotography. The composition of both the toner and the carrier is chosen such that the toner has a polarity opposite to the charge on the photoconductive layer due to mutual contact friction. As a result of the contact friction between the two, the carrier electrostatically attaches the toner to the surface, transports the toner as a developer in the developing device, and supplies the toner onto the photoconductive layer. However, when a large number of continuous copies are made with an electronic copying machine using such a two-component developer, an image with clear and good image quality can be obtained at the initial stage. The effect is remarkable, and an image having poor gradation and sharpness is obtained.

In color copying using a chromatic toner, continuous tone is an important factor affecting the image quality. An edge effect in which only a peripheral portion of an image is emphasized after copying a large number of sheets is caused by an image. Gradation is greatly impaired. For example, a pseudo contour by an edge effect is formed in the vicinity of the actual contour, thereby deteriorating copy reproducibility including color reproducibility in color copying. In addition, the image area used in the conventional black and white copy is 10% or less, and letters, documents,
In contrast to a line image portion such as a report, in the case of color copying, the image area is at least 20% or more, and the image is a solid image having gradation, such as a photograph, a catalog, a map, or a painting. Images occupy significant 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 gradually becomes insufficient, and The replenishment toner and the carrier are mixed with each other in a state of being reduced or insufficiently charged to cause fogging, or a partial toner concentration (indicating a mixing ratio of the toner and the carrier) on the developing sleeve. Increase or decrease,
There is a tendency that blurring of the image and uniformity of the density in the image cannot be obtained. This tendency is more remarkable when the diameter of the toner is reduced.

This is because the amount of toner included in the developer (that is,
(Toner concentration) is too low, or rapid rise of triboelectric charging between the replenishment toner and the carrier in the two-component developer is poor, and uncontrolled and insufficiently charged toner is involved in the development. It is thought that insufficient development and fogging will occur. As a color developer, the ability to always output a high-quality image by continuous copying of a document having a large image area is essential. Conventionally, in order to cope with a document having a large image area and an extremely large amount of toner consumption, the improvement of the developing device rather than the improvement of the developer itself has been dealt with more. That is, in order to increase the chance of the developing sleeve contacting the electrostatic latent image, the peripheral speed of the developing sleeve is increased, or the size of the developing sleeve is increased.

[0011] Although these measures increase the developing capacity, the inside of the apparatus is contaminated by toner scattering from the developing device,
An overload on the driving of the developing device may significantly limit the life of the device. Furthermore, in some cases, a large amount of developer is charged into the developing device to make up for the lack of developing ability of the developer, but these are also increased in cost due to an increase in the weight of the copying machine and an increase in the size of the device. As a result, as in the case described above, the overload of the driving of the developing device is caused, which is not so preferable. Thus, improvement studies from both toner and carrier have been reported for the purpose of maintaining high image quality for a long period of time.

That is, some developers have been proposed for the purpose of improving the image quality. For example, Japanese Patent Application Laid-Open No. 51-3244 proposes a non-magnetic toner intended to improve image quality by regulating the particle size distribution. The toner is mainly composed of a toner having a particle size of 8 to 12 μm, and is relatively coarse. According to the study of the present inventors, it is difficult for the toner to have a dense “glue” to a latent image, And 5 μm or less is 30% by number or less;
From the characteristic that 5 μm or more is 5% by number or less, the point that the particle size distribution is broad also tends to lower the uniformity.

In order to form a clear image using toner having such coarse toner particles and a broad particle size distribution, gaps between toner particles are filled by thickly overlapping toner particles. Therefore, it is necessary to increase the apparent image density, and there is also a problem that the amount of toner consumption required for obtaining a predetermined image density increases. Japanese Patent Application Laid-Open No. 54-72054 proposes a non-magnetic toner having a distribution which is sharper than the former, but the size of particles having an intermediate weight is as coarse as 8.5 to 11.0 μm, and high. The resolution toner still has room for improvement.

Japanese Unexamined Patent Publication (Kokai) No. 58-129439 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. However, images with low sharpness tend to be formed. According to the study of the present inventors, 5 μm
It has been found that the following toner particles clearly reproduce the outline of the latent image and have a major function of "glue" of the dense toner over the entire latent image. In particular, in the electrostatic latent image on the photoreceptor, due to concentration of lines of electric force, the contoured edge portion has a higher electric field strength than the inside, and the sharpness of the image quality is determined by the quality of the toner particles collected in this portion.

According to the study of the present inventors, it has been found that the amount of particles of 5 μm or less is effective in solving the problem of sharpness of image quality. Then, the present inventors disclosed in Japanese Patent Laid-Open No.
No. 2966 discloses that toner particles of 5 μm or less
Although a toner containing 0% by number has been proposed, a considerable improvement in image quality has been achieved by this, but a further improved image quality is also desired.

Further, in Japanese Patent Application Laid-Open No. 2-877, 5 μm
17 to 60% by number of the following toner particles.
Japanese Patent Publication No. 284151 proposes toners each containing 60% by number or more of toner particles of 5 μm or less. Although the image quality and the image density are surely stabilized by this, the original image which consumes a large amount of toner like a photographic original. When printing is continuously performed, the particle size distribution is inevitably changed, and a stable image cannot be obtained for a long period of time simply by limiting the amount of fine powder, and the existing amount of toner particles of 5 μm or less as in the past. However, it has not been possible to propose a toner that satisfies high image quality and high durability only by controlling the image quality.

On the other hand, carriers constituting a two-component developer are roughly classified into a conductive carrier represented by iron powder and a so-called insulating carrier in which the surface of iron powder, nickel, ferrite or the like is coated with an insulating resin. Is done. When an alternating electric field is applied to improve the image quality, if the resistance of the developer carrier is low, the carrier leaks the latent image potential and a good image cannot be obtained. When the carrier core is conductive, it is preferable to use the carrier core after coating, and ferrite having a relatively high resistance is preferably used as the core material.

Further, iron powder has a high magnetic force, and in a development area where the developer toner is developed, the developer brush becomes hard, so that nicks are formed. Cannot be obtained. Therefore, ferrite is also preferably used to reduce the magnetic force of the carrier to achieve high image quality. Japanese Patent Application Laid-Open
Japanese Patent Application Laid-Open No. 9-104663 discloses that the value of the saturation magnetization of the carrier is 5
It has been proposed that a good image without nicks can be obtained by setting the value to 0 emu / g or less, but the reproducibility of fine lines is improved by using a carrier whose saturation magnetization value is gradually reduced. On the other hand, development (carrier adhesion) in which the carrier adheres to the electrostatic image carrier, that is, a so-called photosensitive drum becomes more remarkable as the distance from the magnetic pole increases.

Japanese Patent Publication No. 4-3868 proposes using so-called hard ferrite having a coercive force of 300 gauss or more as a carrier. However, this is a system for using hard ferrite, which has high holding power, as a carrier, and it is inevitable that the size of the apparatus is increased. In order to realize a compact and high-quality color copier, it is preferable to use a developer carrier using a fixed magnetic core. In this case, a hard carrier having a high holding force has a There is a problem that the transportability is deteriorated.

Further, Japanese Patent Application Laid-Open No. 2-88429 proposes to use a hard ferrite composed of a spinel phase and a magnet plumbite phase containing a lanthanoid element as a carrier. In a system in which development is performed by using an alternating electric field for obtaining a higher quality image because of having conductivity, it is not preferable because charge leaks through carriers to disturb development. Therefore, in a system that performs development using an alternating electric field, the resistance of the carrier needs to be at least a certain level. As described above, sufficient developer carriers and developers that satisfy high image quality, in particular, reproducibility of highlight while preventing carrier adhesion have not yet been obtained.

[0021]

SUMMARY OF THE INVENTION An object of the present invention is to provide a developer for developing an electrostatic image having a carrier and a toner, which solves the above-mentioned problems. That is, an object of the present invention is to provide a developer for developing an electrostatic charge image having a carrier and a toner which does not cause a reduction in image density and does not cause blurring even when a color original having a large image area is continuously copied. A further object of the present invention is to provide a developer for developing an electrostatic charge image having a carrier and a toner which has clear image characteristics without fog and has excellent durability stability. Another object of the present invention is to provide a developer for developing an electrostatic charge image having a carrier and a toner capable of quickly raising a triboelectric charge between the toner and the carrier.

Another object of the present invention is to provide a developer for developing an electrostatic charge image having a carrier and a toner, which have less environmental dependency of triboelectric charging. Another object of the present invention is to provide a developer for developing an electrostatic image having a carrier and toner having good transportability in a developing device. Another object of the present invention is to provide a developer for developing an electrostatic charge image having a carrier and a toner which enables development faithful to a document while preventing carrier adhesion. The purpose of the present invention is
An object of the present invention is to provide a developer for developing an electrostatic charge image having a carrier and a toner for obtaining a high-quality image without carrier adhesion even in the development of an alternating electric field. SUMMARY OF THE INVENTION An object of the present invention is to provide a developer for electrostatic image development having a carrier and toner for a small developing device using a fixed magnetic developer carrier for obtaining a high quality image.

[0023]

The above objects are achieved by the present invention described below. That is, in the present invention, in a two-component color electrostatic image developing developer comprising at least a toner and a carrier, the toner is directly calculated from the weight average particle diameter of the toner calculated from the volume average distribution data of the Coulter counter. the specific surface area of the toner and S _a,
When the specific surface area of the toner was calculated from the number average distribution and a S _B, a S _B is ^{_{1.0 ≦ S B ≦ 1.8 (m}} 2 / g), and the ratio of S _A and S _B are the following _A color toner that satisfies the range of 1.20 ≦ S _B / S _A ≦ 1.70 and has a particle diameter of 4 μm or less by 10 to 70% by number, and the carrier has a particle diameter of 5 to 70%.
A carrier having a bulk density of 3.0 g / cm ³ or less and a magnetic intensity (σ _1,000 ) at 1,000 Oe after magnetic saturation of 30 to 150 μm.
emu / cm ³ , a magnetization intensity (residual magnetization: σr) in a magnetic field of 0 Oe is 25 emu / cm ³ or more, and a coercive force is less than 300 Oe, and the carrier satisfies the following expression at that time. And a developer for developing an electrostatic image. [Wherein σ _1,000 and σ ₃₀₀ indicate the magnetization intensity (emu / cm ³ ) at 1,000 and 300 Oe, respectively, after magnetic saturation. ]

[0024]

The present inventors have conducted intensive studies on the image density, highlight reproducibility and fine line reproducibility of the developer. As a result, by controlling the specific surface area and the spread of the particle size distribution of the toner, the high image density and highlight can be obtained. It has been found that high image quality with excellent reproducibility and fine line reproducibility can be achieved.
When a specific carrier is used as the carrier, good highlight reproducibility with little roughness is obtained, and when the specific carrier is used, the long-term durability is excellent. It has been found that a developer for developing a charge image can be provided.

The above specific surface area S _A and specific surface ratio S _B / S _A
Is capable of faithfully reproducing the latent image formed on the photoreceptor, and is excellent in reproducing minute dot latent images such as halftone dots and digital images. Provides an image with excellent reproducibility and resolution. Further S _B
The spread of the particle size distribution expressed by / S _A has a great effect on image deterioration in durability, toner scattering and fog, and by maintaining this, maintaining high image quality for a long period of time Was found to be possible. The reason why such an effect is obtained in the toner of the present invention is not necessarily clear, but is presumed as follows.

First, the first feature of the present invention is that the specific surface area S _B of the toner calculated from the number average distribution of the toner calculated by the Coulter counter is 1.0 ≦
S _B ≦ 1.8 (m ² / g).
Until now, the present inventors have shifted the average particle diameter of the toner finely in order to achieve higher image quality. The chance of contact is important not only for the rise of toner charge, but also for obtaining stable chargeability. To truly maintain and control image quality, the specific surface area of the toner is considered to be an important factor. was examined intensively Te, when there is S _B within the above range, in which it was found that good results are obtained. That is, S _B is 1.0 m
When it is smaller than ² / g, it means that the amount of fine particle toner which can contribute to the improvement of image quality is basically small, and it is easy to obtain a high image density.

Further, although there are merits such as excellent toner fluidity, it is difficult to adhere faithfully on a fine latent image on a drum, poor highlight reproducibility, and sufficient resolution. You won't get it. In addition, 1.0m is S _B
^{When the} ratio is less than ² / g, development more than necessary, that is, excessive toner transfer occurs, and the toner consumption tends to increase. Conversely, the specific surface area S _B of the toner is 1.8 m ²
If it is / g or more, it means that the charge amount per unit weight of the toner becomes extremely high, and the density is low, especially the image density is low under low temperature and low humidity. This is not suitable for applications having a high image area ratio such as graphic images.

Furthermore, in the S _B 1.8m ² / g or more, contact charging with the carrier is not performed smoothly, sufficiently charged toner not have increased, scattering of the non-image portion, that is noticeable fog Looks like To cope with this, it is conceivable to reduce the diameter of the carrier in order to increase the specific surface area of the carrier. However, when S _B is 1.8 m ² / g or more, self-aggregation of the toner is liable to occur, and uniform mixing with the carrier takes a short time. This is not achieved, and there is a tendency for fogging toner to occur in continuous toner replenishment durability. Therefore, in the present invention, the non-surface area S _{B of the} toner is 1.0 m ² / g.
Above, 1.8 m ² / g or less, preferably 1.05 m ² /
g or more and 1.7 m ² / g or less.

The second feature of the present invention, is made S _B / S _A of when the specific surface area of the toner where it is calculated directly from the weight average particle diameter (shown as normal D ₄₎ was S _A, Indicates the spread of the particle size distribution of the toner, which has a large effect on image deterioration during durability, toner scattering and fogging, and optimizing this is the key to maintaining high image quality over a long period of time Technology.

In the course of studying the state of the particle size distribution and the development characteristics, the present inventors found that the above-mentioned S _B / S _A was:
It was found that when the range was 20 ≦ S _B / S _A ≦ 1.70, the particle size distribution was most suitable for achieving the object of the present invention. That is, when S _B / S _A is smaller than 1.20, when the particle size distribution is adjusted by general air classification, a system in which extremely fine powder is cut off corresponds to this, and the toner has excellent toner fluidity. And a high image density is easily obtained. Furthermore, although there is a merit that there is little variation in the particle size due to durability and there is an advantage in long-term durability, since there is little fine powder which is an essential component for reproduction of the highlighted portion as described above, the gradation is inferior. However, the object of the present invention cannot be satisfied. In addition, an increase in the cost of the toner is inevitable, and the toner cannot be cost-effective.

Conversely, when S _B / S _A is greater than 1.70, the particle size distribution becomes broad, and a system in which there is a large amount of toner particularly on the fine powder side corresponds to this. With such a particle size distribution, an image with a lot of fog is generated as a whole, and a decrease in fluidity due to an increase in the amount of fine powder is unavoidable. As a result, a fine latent image on a drum cannot be faithfully developed with toner. Therefore, in the present invention, the particle size distribution of the toner is S _B / S _A
Is 1.20 or more and 1.70 or less, more preferably 1.20
When satisfying 1.60 or less, excellent fluidity and gradation, and excellent long-term durability stability can be obtained.

In the toner of the present invention, based on what has been described above, toner particles having a particle diameter of 4 μm or less are 10 to 70% by number, preferably 15 to 60% by number of the total number of particles. When the toner particles having a particle diameter of 4 μm or less are less than 10% by number, it means that there are few fine toner particles which are an essential component for high image quality. As the toner is continuously used, the effective toner particle component decreases, the balance of the toner particle size distribution shown in the present invention deteriorates, and the image quality tends to gradually decrease.

Further, toner particles having a particle size of 4 μm or less
When the content is more than 0% by number, toner particles are likely to aggregate with each other, and often behave as a toner mass having an original particle size or more. As a result, a coarse image is obtained or resolution is reduced. Or, the density difference between the edge portion and the inside of the latent image becomes large, and the image tends to be slightly hollow, which is not preferable.

The method of measuring the particle size distribution and calculating the specific surface area of the toner according to the present invention will be described below. As a measuring device, a Coulter counter TA-II type (manufactured by Coulter) was used, and an interface (manufactured by Nikkaki) for outputting a number average distribution and a volume average distribution and a CX-1 personal computer (manufactured by Canon) were connected to the electrolytic solution. Prepares a 1% NaCl aqueous solution using primary sodium chloride.

The measuring method is as follows.
In 150 ml, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant, and 0.5 to 50 mg of a measurement sample is further added. The electrolytic solution in which the sample was suspended was subjected to dispersion treatment for about 1 to 3 minutes using an ultrasonic disperser, and 2.00 using a 100 μm aperture as an aperture by the Coulter Counter TA-II.
The volume average distribution and the number average distribution are determined by measuring the particle size distribution of the particles having a size of ~ 50.80 µm. The number of fine powders (4.00 μm or less) according to the present invention was the number of fine powders calculated from the number average distribution.

[0036] In the calculation of the specific surface area S _B of the toner is divided particles 2.00~50.80μm to 14 channels, determine the number distribution for each channel, the specific gravity of the representative value and the toners of the respective channels The specific surface area when the toner was spherically approximated was determined, and the specific surface area of the toner was determined from the number ratio of each channel. In the present invention,
The logarithm of the upper and lower limits of each channel was used as the representative value of each channel, and the two-point average exponential value was used.

As an example, for example, 3.17 to 4.00
The typical value of the channel between μm is A representative value is similarly obtained for the other 13 channels, and a specific surface area of the toner is obtained for each channel.
It converted by number distribution described above with finally determine the specific surface area S _B of the toner. Incidentally, when the calculation of S _A, and a specific surface area by spherical approximation calculated directly by the weight-average particle diameter and the specific gravity of the toner.

Hereinafter, the carrier used in the present invention will be described in detail. The reason why the carrier used in the present invention can improve the drawbacks of the conventional carrier and prevent the adhesion of the carrier and can develop the image faithfully to the original document, that is, to the image faithfully to the latent image can be considered as follows. . In order to perform the development faithful to the latent image which is a feature of the present invention, the intensity of the carrier magnetization is set to 30 to 150 em in the magnetic field at the development pole.
u / cm ³ could be achieved. This is because the strength of the magnetic field at the developing pole is generally about 1,000 Oe, and the strength of the magnetization of the carrier at that time is weak, so that the magnetic brush of the developer becomes short and dense, and the brush becomes more dense. It is considered that development that was faithful to the latent image could be achieved by becoming soft. Since such a magnetic brush is short, dense, and soft, particularly in development in which an alternating electric field that vibrates the developer is applied,
It is considered that the development efficiency is increased and higher-fidelity development can be performed.

Another advantage of the present invention is that the use of such a low magnetic force carrier can prevent deterioration of image quality and maintain an initial high image quality.
When coating the developing sleeve with the developer, the magnetic coupling force of the carrier brush near the regulating member is weak, and the ears are soft, so the toner brush does not take up much share of the toner and maintains a high quality image for a long time. Is thought to be possible.
In particular, such an effect was more remarkable when the toner was reduced in size.

Further, detailed studies have revealed that carrier adhesion is apt to occur when the magnetic field strength is 0 to 300 Oe, and does not occur when the carrier magnetization strength at that time is high to some extent. Carrier adhesion also depends on the bias condition of development. Particularly in the case of development using an alternating electric field, the carrier is more likely to be developed if it has electric charges than a DC electric field. Is required. Therefore, in order to suppress carrier adhesion, it is considered that the intensity of magnetization in the magnetic field is required. Therefore, according to the present invention, as shown in the hysteresis curve of FIG. 1, the magnetization intensity σ _1,000 at 1,000 Oe is 30 to 150 emu / cm.
It is thought that by increasing the magnetization intensity at 0 to 300 Oe, although smaller than that of the conventional carrier of ³ , the carrier adhesion can be prevented while improving the image quality.

In general, a magnetic material having a large residual magnetization has a large coercive force. It is a magnetic material such as a hard ferrite like a so-called permanent magnet, and as described above, it causes poor mixing with the toner and poor developer transportability due to self-aggregation.
A large and special developing device is required in which the developer carrier is a rotary magnetic core applicator. Thus, the present invention does not use such a general hard magnetic material, but uses a carrier having a coercive force of less than 300 Oersteds, so that a small developing device using a fixed magnetic core-based developer carrier can be used. It is considered that a developer having good toner mixing properties and developer transportability can be achieved.

Next, the carrier used in the present invention will be described in more detail. Carrier used in the present invention,
It is necessary that the magnetic properties of the carrier particles are as follows. That is, the magnetization intensity (σ _1,000 ) at 1,000 Oe after magnetic saturation is 30 to 15
It must be 0 emu / cm ³ . In order to achieve higher image quality, preferably 30 to 120 emu / c
m is ^3. If it is larger than 150 emu / cm ^3, the density of the developer brush at the developing electrode is not so different from the conventional one, and it is difficult to obtain a high quality image as in the present invention.
If it is less than 30, the magnetic binding force at 0 to 300 Oe is also reduced, resulting in carrier adhesion.

The intensity of the remanent magnetization is 25 emu / cm ³
It is necessary to be above. If it is less than 25 emu / cm ³ , carrier adhesion is likely to occur particularly in a developing system using an alternating electric field having a large amplitude or high amplitude in order to achieve high image quality. However, a high quality image cannot be obtained due to transfer failure. Further, the holding force needs to be less than 300 Oersteds.
If it is more than 300 Oersteds, the carrier itself will self-agglomerate, resulting in poor mixing with the toner, and in particular, the carrier will not move easily in the developing sleeve containing the fixed magnet, and the transportability on the developing sleeve will be difficult. Gets worse,
A high-quality image cannot be obtained because the coating state of the developer deteriorates.

Furthermore, what is important in the present invention is that the magnetic field 0
Magnetization intensity in the vicinity of ~ 300 Oe.
Therefore, the following equation must be satisfied. [Wherein σ _1,000 and σ ₃₀₀ indicate the magnetization intensity (emu / cm ³ ) at 1,000 and 300 Oe, respectively, after magnetic saturation. ] Preferably, this value is 0.30 or less. Here, if it exceeds 0.40,
It is not possible to achieve both the effect of preventing carrier adhesion while achieving high image quality of the present invention.

In other words, if a value that satisfies σ _1,000 is taken, high image quality can be achieved, but carrier adhesion is likely to occur.
Also, taking a value such as to satisfy the sigma ₃₀₀ although the carrier adhesion can be prevented, it is impossible to obtain a high-quality image, such as in the present invention in that the value of sigma _1,000 increases.
Incidentally, the measurement of the magnetic characteristics in the present invention is performed by the following method.
Magnetization BH characteristics automatic recording apparatus BHH-50 manufactured by KK Corporation. Since the magnetic material is generally saturated by a magnetic field of 10 kOe, the saturation magnetization of the carrier is set to a value of 10 kOe in the present invention.
Therefore, the magnetic characteristic values were determined by a hysteresis curve at a magnetic field of ± 10 kOe.

In the present invention, the magnetic properties are measured by loosely placing the sample in a cylindrical plastic container, and then firmly packing and fixing the sample while applying a magnetic field of 10 kilograms, and measuring the magnetic properties in that state. did. This was used as the magnetic characteristic of the present invention. The volume of the sample holder at that time was 0.332 cm ³ , and the intensity of magnetization per unit volume was determined from this. The average particle size of the carrier particles of the present invention is preferably in the range of 5 to 100 μm, and more preferably 20 to 80 μm. If it is less than 5 μm, the carrier tends to adhere to the photoreceptor, and if it exceeds 100 μm, the magnetic brush at the developing pole becomes coarse and a high quality image cannot be obtained. In addition, the particle diameter of the carrier of the present invention was determined by randomly extracting 300 or more particles by an optical microscope, and measuring the horizontal particle diameter as a carrier particle diameter by an image processing / analyzing device Luzex3 manufactured by Nireco.

The carrier bulk density of the present invention is 3.0 g / c.
m ³ or less is preferable. If it exceeds 3.0 g / cm ³ , the rotation of the developing sleeve causes a large centrifugal force on one carrier as compared with the force of magnetically holding the carrier on the sleeve, so that carrier scattering easily occurs. The bulk density of the carrier of the present invention was measured according to the method described in JIS Z2504.

The sphericity of the carrier of the present invention is preferably 2 or less. When the sphericity of the carrier of the present invention exceeds 2, the fluidity as a developer becomes poor, and the shape of the magnetic brush at the developing pole becomes poor, so that a high-quality image cannot be obtained. The sphericity of the carrier of the present invention was measured by randomly extracting 300 or more carriers using a field emission scanning electron microscope S-800 manufactured by Toshiba Corporation, and an image processing analyzer Luzex3 manufactured by Nireco.
Was used to determine the shape factor derived by the following equation. MX LNG: maximum diameter of carrier AREA: projected area of carrier Here, SF1 is closer to 1 means closer to a sphere.

The specific resistance of the carrier of the present invention is 10 ⁸ to 10.
A range of ¹³ Ω · cm is appropriate. If it is less than 10 ⁸ Ω · cm, current leaks from the sleeve to the surface of the photoreceptor in the developing area in a developing method in which a bias voltage is applied, and a good image cannot be obtained. If it exceeds 10 ¹³ Ω · cm,
Causing a charge-up phenomenon under conditions such as low humidity,
It causes image deterioration such as low density, poor transfer, and fog.
In the present invention, the specific resistance was measured by a measuring method as shown in FIG. That is, the cell A is filled with a carrier,
Electrodes 1 and 2 were arranged so as to be in contact with the charged carrier, a voltage was applied between the electrodes, and a current flowing at that time was measured to obtain a specific resistance. In the above measurement method, since the carrier is a powder, a change occurs in the filling rate, and the specific resistance may change with the change. The conditions for measuring the specific resistance in the present invention are as follows: the contact area S between the filled carrier and the electrode is about 2.3 cm ² , the thickness d is about 1 mm, the load of the upper electrode 2 is 275 g, and the applied voltage is 100.
V.

In order to achieve the above-mentioned magnetic characteristics which are the most characteristic of the carrier of the present invention, a metal oxide magnetic material or an iron-based alloy such as carbon steel, chromium steel, cobalt-chromium steel, baicaloy, It is necessary to use an alnico alloy or the like. Preferably, the ferrite particles are made of ferrite, and the ferrite particles are in the periodic table IA, IIA, IIIA, IVA, VA, VI.
It is possible to use a carrier which contains at least one element selected from the group consisting of A, IB, IIB, IVB, VB, VIB, VIIB, and VIII, and has a content of other elements of less than 1% by weight. I can do it. Here, if another element is contained, it is difficult to obtain a carrier having the desired magnetic characteristics of the present invention, and furthermore, the resistance tends to decrease, which is not preferable.

The carrier of the present invention comprises: (i) a single phase of a magnet plumbite structure, or (ii) a spinel phase and a matrix.
The molar ratio with the gnet plumbite phase is 1: 1 to 10: 1
Of spinel structure and magnet plumbite structure
The phase is the preferred form. It is preferable that the magnetic particles having the spinel structure and the magnet plumbite structure do not react with each other. By adopting such a composition form, the magnetization intensity (σ _1,000 ) at 1,000 Oe after magnetic saturation is 30 to 1
50 emu / cm ³ and the residual magnetization σr is 25 emu
/ Cm ³ or more, and a carrier having magnetic properties with a coercive force of less than 300 Oe can be obtained. In the present invention, the measurement of the crystal constituting the carrier was performed by using the X-ray diffraction method and the fluorescent X-ray.

The carrier of the present invention can be manufactured by a manufacturing method such as a sintering method and an atomizing method. If necessary, the carrier of the present invention can be manufactured by mixing and sintering two or more kinds of fine crystal powders. Carriers having magnetic properties can also be manufactured. Further, by using the carrier of the present invention after being magnetically saturated, it is easy to achieve the characteristic magnetic characteristics of the present invention. As a method of magnetic saturation,
Exposing the carrier particles to a magnetic field of ± 10 kOe with a DC electromagnet is included.

Further, the carrier of the present invention can be used by coating the surface of the carrier particles with an optional resin, if necessary, in order to control the specific resistance and improve the durability. As the coating resin, a known appropriate resin can be used, and for example, an acrylic resin, a fluorine resin, a silicon resin, an epoxy resin, or the like can be used. In addition, a BHU-60 type magnetization measurement device (manufactured by Riken Keisoku Co., Ltd.) is used as a device for measuring the magnetic properties of the carrier. About 1.0 g of a measurement sample is weighed, packed in a cell having an inner mold of 7 mmφ and a height of 10 mm, and set in the above-mentioned apparatus.

In the measurement, an applied magnetic field was gradually applied, and a maximum of 3,0
Change to 00 Oersted. Next, the applied magnetic field is decreased, and finally a hysteresis curve of the sample is obtained on the recording paper. From this, the saturation magnetization, residual magnetization, and coercive force are obtained. The measurement of the particle size distribution of the carrier was carried out using an SRA type Microtrac particle size analyzer (manufactured by Nikkiso Co., Ltd.) in the range of 0.7 to 125 μm.

The toner and carrier used in the present invention will be described below. As the binder used in the colorant-containing resin particles of the present invention, various material resins conventionally known as electrophotographic toner binder resins are used.
For example, styrene-based copolymers such as polystyrene, styrene-butadiene copolymer, styrene-acrylic copolymer, and ethylene-based copolymers such as polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer , Phenolic resin, epoxy resin, acrylic phthalate resin, polyamide resin, polyester resin,
Maleic acid resin and the like. In addition, the production method of any resin is not particularly limited.

The effects of the present invention are remarkable when a polyester resin having a high negative chargeability is used among these resins. That is, the polyester resin has excellent fixability,
Although suitable for color toners, it has a strong negative charging ability and tends to be excessively charged. However, when a polyester resin is used in the composition of the present invention, the adverse effects are improved and an excellent toner can be obtained.

In particular, the following equation

Embedded image (Wherein R is an ethylene or propylene group, x and y
Is an integer of 1 or more, and the average value of x + y is 2 to 2.
It is 10. A) a carboxylic acid component comprising a divalent or higher carboxylic acid or an acid anhydride thereof or a lower alkyl ester thereof (for example, 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 properties.

In particular, in terms of light transmission with a trappen, 90%
Apparent viscosity at 5 ° C. is 5 × 10 ^{4 to} 5 × 10 ⁶ poise;
It is preferably 7.5 × 10 ^{4 to} 2 × 10 ⁶ poise, more preferably 10 ⁵ to 10 ⁶ poise, and the apparent viscosity at 100 ° C. is 10 ^{4 to} 5 × 10 ⁵ poise, preferably 1
0 ^{4 to} 3 × 10 ⁵ poise, more preferably 10 ⁴ to 2 ×
When it is 10 ⁵ poise, a color OHP having good light transmittance can be obtained, and good results can be obtained in a fixing property, a color mixing property and a high-temperature offset resistance as a full-color toner.
The absolute value of the difference between the apparent viscosity P _{1 at} 90 ° C. and the apparent viscosity P _{2 at} 100 ° C. is 2 × 10 ⁵ <| P ₁ −P ₂ |
It is particularly preferred to be in the range <4 × 10 ⁶ .

As the colorant used in the present invention, known dyes and pigments are used, and examples thereof include the following. As the color pigment for magenta, C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
11, 12, 13, 14, 15, 16, 17, 18, 1
9, 21, 22, 23, 30, 31, 32, 37, 3
8, 39, 40, 41, 48, 49, 50, 51, 5
2, 53, 54, 55, 57, 58, 60, 63, 6
4, 68, 81, 83, 87, 88, 89, 90, 11
2, 114, 122, 123, 163, 202, 20
6, 207, 209; I. Pigment Violet 19; I. Buttlets 1, 2, 10, 13, 1
5, 23, 29, 35 and the like.

Although the pigment alone may be used, it is more preferable to use the dye and the pigment together to improve the sharpness from the viewpoint of the image quality of a full-color image. Magenta dyes include C.I. I. Solvent Red 1, 3, 8, 23, 2
4, 25, 27, 30, 49, 81, 82, 83, 8
4, 100, 109, 121; I. Disperse Red 9; I. Solvent violet 8, 13, 1
4, 21, 27; I. Disperse Violet 1
Oil-soluble dyes such as C.I. I. Basic Red 1, 2, 9,
12, 13, 14, 15, 17, 18, 22, 23, 2,
4, 27, 29, 32, 34, 35, 36, 37, 3
8, 39, 40; I. Basic violet 1,
3, 7, 10, 14, 15, 21, 25, 26, 27,
And 28 basic dyes.

Examples of the pigment for cyan include C.I. I. Pigment Blue 2, 3, 15, 16, 17; I. Bat blue 6; I. Acid Blue 45 or a copper phthalocyanine pigment in which 1 to 5 phthalimidomethyl groups are substituted on a phthalocyanine skeleton having a structure represented by the formula (1).

Embedded image

As the yellow color pigment, C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 1
1, 12, 13, 14, 15, 16, 17, 23, 6
5, 73, 83; I. Bat Yellow 1, 3, 20
And the like. The amount of the colorant used is 0.1 to 60 parts by weight, preferably 0.5 to 5 parts by weight, per 100 parts by weight of the binder resin.
0 parts by weight.

Further, the toner in the present invention is not limited to the negative charge property or the positive charge property. However, in the case of producing a negative charge toner, a charge control agent is particularly used for the purpose of stabilizing the negative charge property. It is preferred to add. Examples of the negative charge control agent include an organometallic complex such as a metal complex of an alkyl-substituted salicylic acid (for example, a chromium complex or a zinc complex of di-tert-butylsalicylic acid).

When a positively chargeable toner is produced, nigrosine, a triphenylmethane compound, a rhodamine dye, polyvinyl pyridine or the like may be used as a charge control agent having a positive charge. In the case of producing a color toner, an aminocarboxylic acid ester such as dimethylaminomethyl methacrylate having positive chargeability is used as a monomer in an amount of 0.1 to 40 mol%, preferably 1 to 40 mol%.
It is desirable to use a binder resin containing about 30 mol% or a colorless or light-colored positive charge control agent that does not affect the color tone of the toner.

Further, in the toner of the present invention, a fluidity improver may be added for the purpose of improving the fluidity of the toner. As the fluidity improver used in the present invention, any one can be used as long as it can be added to the colorant-containing resin particles so that the fluidity can be increased as compared to before the addition.

For example, a fluorine-based resin powder such as vinylidene fluoride fine powder, polytetrafluoroethylene fine powder or the like, or a fatty acid metal salt such as zinc stearate, calcium stearate, or lead stearate, or a metal oxide such as oxidized Titanium powder, aluminum oxide powder, zinc oxide powder or the like, or fine powder silica, that is, wet-process silica,
There are dry-processed silica, silica treated with a silane coupling agent, a titanium coupling agent, silicon oil, and the like, and surface-treated with the silica.

In order to prepare the colorant-containing resin particles according to the present invention, a thermoplastic resin may be mixed, if necessary, with a pigment or dye as a colorant, a charge control agent, and other additives using a mixer such as a ball mill. After mixing well, using a hot kneader such as a heating roll, kneader or extruder, melt or knead and knead to disperse or disperse the pigment or dye in the resin and to solidify by cooling. After crushing and strict classification, the colorant-containing resin particles according to the present invention can be obtained. When a two-component developer is prepared by mixing with the toner according to the present invention, the mixing ratio is usually from 2% by weight to 15% by weight, preferably from 4% by weight to 13% by weight, as the toner concentration in the developer. Good results are obtained. If the toner concentration is less than 2% by weight, the image density is low and it becomes impractical. If the toner concentration is more than 15% by weight, fog and scattering inside the machine are increased, and the useful life of the developer is shortened.

[0068]

Next, the present invention will be described more specifically with reference to examples and comparative examples. In the following, "parts" and "%" are based on weight unless otherwise specified. Example 1 [Preparation of Toner] Polyester resin obtained by condensation of propoxylated bisphenol and fumaric acid 100 parts Phthalocyanine pigment 5 parts Chromium complex salt of di-tert-butylsalicylic acid 4 parts

The above components are sufficiently premixed by a Henschel mixer, melt-kneaded by a twin-screw extruder, cooled, coarsely pulverized to about 1 to 2 mm using a hammer mill, and then finely pulverized by an air jet method. And pulverized. Further, the obtained finely pulverized product was classified by a multi-segment classifier to obtain colorant-containing resin particles having a particle size distribution of the present invention. Next, a fine silica powder, Aerosil # 2, having a specific surface area of 200 m ² / g
After 100 parts of 00 (manufactured by Nippon Aerosil Co., Ltd.) are treated with 20 parts of hexamethyldisilazane (HMDS), 10 parts of dimethylsilicone oil KF-96 100cs (manufactured by Shin-Etsu Chemical Co., Ltd.) is diluted with a solvent. Do the processing,
After drying, a heat treatment was performed at about 250 ° C. to obtain hexamethyldisilazane, and then treated with dimethylsilicone oil to obtain fine silica powder. Cyan toner A is obtained by externally adding 1.0 part of the above-mentioned silicate fine powder and 0.5 part of aluminum oxide fine powder (BET 120 m ^{2 /} g) to 100 parts of the above-mentioned colorant-containing resin particles. Was.

[Preparation of Carrier] Fe ₂ O ₃
= 60 mol%, CuO = 20 mol%, ZnO = 20 mol%, while Fe ₂ O ₃ = 82 mol%,
It was weighed so that SrCO ₃ = 10 mol% and ZnO = 8 mol%, and each was mixed using a ball mill. After calcining each of them, pulverize them by a ball mill, mix the above formulations at a ratio of 2: 1 respectively, add a polyvinyl alcohol, an antifoaming agent and a dispersant to form a slurry, and granulate and dry using a spray drier. Then, sintering was performed. By further classification, carrier particles having an average particle size of 55 μm were obtained. The shape of the carrier obtained at that time was almost spherical.

Also, as a result of the X-ray diffraction and X-ray fluorescence analysis,
Spinel phase - the ratio of the (Cu-Z n ferrite) magnets plumbite phase and (Sr ferrite) is almost two-charged the same amount: had become 1. The bulk density is 2.32
g / cm ³ . When the resistance of the carrier particles was measured, it was 6.2 × 10 ⁹ Ω · cm. After saturating the carrier with a magnetic field of 10 kOe, a magnetic measurement was performed. As a result, the magnetic characteristic at that time was σ _1,000 =
142 emu / cm ³ , σr = 104 emu / cm ³ , σ
₃₀₀ = 122 emu / cm ³ and Hc = 260 Oersted. Then | σ _1,000 −σ ₃₀₀ | / σ _1,000 =
0.14.

Further, styrene-
2-ethylhexyl methacrylate (copolymerization ratio 45/5
5) The copolymer was coated by a fluidized bed coating method. The specific resistance of the carrier at that time is 9.5 × 10 ¹² Ω ·
cm. After the carrier was saturated and magnetized with a magnetic field of 10 kOe, the carrier and the toner were mixed to a toner concentration of 5% to obtain a developer. This was used to modify the Canon full color laser copying machine CLC-500 to produce an image.

The distance between the developing sleeve and the developer regulating member is 400 μm, the peripheral speed ratio between the developing sleeve and the photosensitive drum is 1.3: 1, and the developing conditions are as follows. 1,000 Oersted, alternating electric field 2,000 V
_PP , the frequency was 3,000 Hz, and the distance between the sleeve and the photosensitive drum was 500 μm. At this time, microscopic observation of the ears of the developing brush on the developing sleeve near the developing pole revealed that the ears were dense and the ear length was short.
As a result of image output, the density of the solid image was sufficient, there was no roughness, and particularly the reproducibility of the halftone portion and the reproducibility of the line image were very good. Further, no carrier adhesion was observed in both the image area and the non-image area. The developing device was idled at a speed of 200 rpm for 30 minutes. As a result, roughness in the halftone portion was slightly observed, but the others were good.

Example 2 Red resin particles were obtained in the same manner as in Example 1 except that a quinacridone pigment was used in place of the phthalocyanine pigment of Example 1. 0.8 parts of the silicic acid fine powder used in Example 1 and further 0.3 parts of aluminum oxide fine powder were externally added to 100 parts of the red resin particles to obtain a magenta toner B. Otherwise, when an image was formed in the same manner as in Example 1, good results were obtained.

Example 3 Yellow resin particles were obtained by replacing the phthalocyanine pigment of Example 1 with a disazo yellow pigment. Further, disazo yellow pigment 2 parts monoazo red pigment 2.8 parts copper phthalocyanine blue pigment 2 Black resin particles were obtained in the same manner as in Example 1 by using .4 parts of three kinds of pigments.

For 100 parts of each colored resin fine particle,
0.8 parts of the fine silica powder used in Example 1 and 0.5 parts of the fine aluminum oxide powder were externally added to obtain a yellow toner C and a black toner D. A developer was prepared in the same manner as in Example 1, and an image was formed using four colors of toner together with the cyan developer used in Example 1 and the magenta developer used in Example 2. As a result, a good image that faithfully reproduced the original image was obtained. In the durability test, high image quality was maintained and a full-color image excellent in gradation was obtained over a long period of time. The light transmittance of the OHP film was also very good. Further, at 23 ° C./5
When an image was similarly formed under the environment of% RH and 30 ° C./80%RH, good results were obtained without fogging or toner scattering.

Comparative Example 1 An image was produced in the same manner as in Example 1 by combining cyan toner E having the particle size distribution shown in Table 1 below with a carrier at a toner concentration of 6%, and the highlight reproducibility was reduced. I have. In this system, although the amount of the external additive, the toner concentration and the like were variously examined, improvement in highlight reproducibility could not be achieved.

Comparative Example 2 An image was produced in the same manner as in Example 1 by combining cyan toner F having a particle size distribution shown in Table 1 below with a carrier at a toner concentration of 6%, and a high image density was obtained. However, improvement in highlight reproducibility could not be achieved.

Comparative Example 3 Image formation was attempted using cyan toner G having the particle size distribution shown in Table 1 below. However, no matter how much the amount of the external additive was changed, the fluidity was not improved, and the image density was rough. Only images with low image quality were obtained.

Example 4 Weighed so that Fe ₂ O ₃ = 50 mol%, CuO = 20 mol% and ZnO = 30 mol% in molar ratio.
₂ O ₃ = 85 mol%, BaO = 12 mol%, ZnO = 3
It was weighed so that it might become mol%, and each was mixed using the ball mill. After calcining each of them, they are pulverized by a ball mill, and the above formulations are mixed at a ratio of 1.5: 1, and a polyvinyl alcohol, an antifoaming agent and a dispersing agent are added to form a slurry, which is formed using a spira coater. The particles were dried and sintered. By further classifying, carrier particles having an average particle size of 45 μm were obtained. The shape of the carrier obtained at that time was almost spherical.

As in Example 1, as a result of X-ray diffraction measurement and X-ray fluorescence measurement, the molar ratio of the spinel phase to the magnet planband phase was almost the same as the charged amount (1.6: 1). The bulk density was 2.30 g / cm ³ .
When the resistance of the carrier particles was measured, 9.2 × 1
Was 0 ⁹ Ω · cm. After saturating the carrier with a magnetic field of 10 kOe, a magnetic measurement was performed.
The magnetic properties at that time were σ _1,000 = 67 emu / cm ³ ,
σr = 36 emu / cm ³ , σ ₃₀₀ = 52 emu / cm
³ , Hc = 170 Oersted. Then | σ
_1,000− σ ₃₀₀ | / σ _1,000 = 0.22. The obtained carrier was surface-coated in the same manner as in Example 1.
The specific resistance of the carrier at this time is 1.3 × 10 ¹² Ω · cm.
Met.

Further, after the obtained carrier was magnetized in the same manner as the carrier of Example 1, the carrier and the toner used in Example 1 were mixed in the same manner as in Example 1 to obtain a developer. When an image forming test was performed using this developer in the same manner as in Example 1, the density of the magnetic brush on the developing sleeve was high, there was no roughness in the halftone portion, and the reproducibility of fine lines was very low. Was excellent. Further, despite the small value of σ _1,000, the carrier adhesion was good in both the image portion and the non-image portion. Further, the image after the idle rotation had a sufficient density of the solid black portion, no halftone portion and no roughness, and no carrier adhesion was observed.

Example 5 Fe = 61 mol%, Al = 9 mol%, Ni =
15 mol% and Co = 15 mol% were prepared, and carrier particles were obtained from the molten metal by a water atomizing method.
The obtained carrier was subjected to heat treatment and further classified by an air classifier to obtain carrier particles having an average particle size of 42 μm.
The shape of the carrier obtained at that time was almost spherical. The bulk density was 2.96 g / cm ³ . When the resistance of the carrier particles was measured, it was 2 × 10 ⁰ Ω · cm.
Met. As a result of the magnetic measurement of this carrier, the magnetic characteristics at that time were σ _1,000 = 89 emu / cm ³ , σr
= 37 emu / cm ³ , σ ₃₀₀ = 60 emu / cm ³ ,
Hc = 165 Oersted. Then | σ
_1,000− σ ₃₀₀ | / σ _1,000 = 0.33.

The obtained carrier was coated with the resin used in Example 1 in the same manner as in Example 1. The specific resistance of the carrier at this time was 2 × 10 ⁹ Ω · cm. After magnetizing this carrier in the same manner as the carrier of Example 1, the carrier and the toner used in Example 1 were mixed in the same manner as in Example 1 to obtain a developer. When an image forming test was performed using this developer in the same manner as in Example 1, the density of the magnetic brush on the developing sleeve was high, there was no roughness particularly at the halftone portion, and the reproducibility of fine lines was very low. Was excellent. or,
The carrier adhesion was good in both the image area and the non-image area, and a high-quality image could be output. In the idle rotation test, the roughness and image quality of the halftone portion were almost the same as those in the initial stage, and no carrier adhesion was observed.

Comparative Example 4 Fe ₂ O ₃ = 85 mol%, SrCO ₃ = 15
The mixture was weighed so as to be mol% and mixed using a ball mill. The mixed powder was calcined and then pulverized. The pulverized sample was made into a slurry, and the slurry was granulated with a spray drier, and the granulated powder was sintered.

The obtained sintered powder was classified by an air classifier to obtain carrier particles having an average particle size of 59 μm. The shape of the carrier obtained at that time was almost spherical. or,
The bulk density was 2.01 g / cm ³ . The specific resistance of the carrier particles was measured to be 9.5 × 10 ⁸ Ω · cm. As a result of performing a magnetic measurement on the carrier in a magnetic field of 10 kOe, the magnetic characteristic at that time was σ
_1,000 = 101 emu / cm ³ , σr = 76 emu / c
m ³ , σ ₃₀₀ = 87 emu / cm ³ , and Hc = 2040 Oersted. Then | σ _1,000 −σ ₃₀₀ | /
σ _1,000 = 0.12.

The obtained carrier was surface-coated in the same manner as in Example 1. The specific resistance of the carrier at this time is 3.5
× 10 ¹² Ω · cm. After the carrier was saturated and magnetized in the same manner as in Example 1, the carrier and the toner used in Example 1 were mixed in the same manner as in Example 1 to obtain a developer. When an image forming test was performed on this developer in the same manner as in Example 1, the flowability of the developer on the developing sleeve was poor due to the self-aggregation of the carrier, and the mixing of the toner and the transport of the developer were difficult. Couldn't do well.

Comparative Example 5 Spinel Phase (Cu-Zu Ferrite) Used in Example 1
A carrier was prepared in the same manner as in Example 1 except that the mixing ratio between the magnetic powder and the magnet plumbite phase (Sr ferrite) was changed to 1: 2, and carrier particles having an average particle diameter of 52 μm were obtained. The shape of the carrier obtained at that time was almost spherical.
As a result of X-ray diffraction and X-ray fluorescence analysis, the ratio between the spinel phase (Cu-Zu-ferrite) and the magnet plumbite phase (Sr ferrite) became 1: 2, which is almost the same as the charged amount. I have. The bulk density is 2.07 g / cm ³
Met. The measured resistance of the carrier particles was 5.1 × 10 ⁹ Ω · cm. 10 this carrier
After saturation with a magnetic field of kilo-Oersted, the magnetic properties were measured. As a result, the magnetic property at that time was σ _1,000 = 117 em
u / cm ³ , σr = 94 emu / cm ³ , σ ₃₀₀ = 10
6 emu / cm ³ and Hc = 1090 Oersted. At that time, | σ _1,000 −σ ₃₀₀ | / σ _1,000 = 0.0
Nine.

The obtained carrier was surface-coated in the same manner as in Example 1. The specific resistance of the carrier at this time is 7.5.
× 10 ¹² Ω · cm. After the carrier was subjected to saturation magnetization as in Example 1, the carrier and the toner used in Example 1 were mixed as in Example 1 to obtain a developer. An image forming test was performed on this developer in the same manner as in Example 1. As a result, similar to Comparative Example 1, the flowability of the developer on the developing sleeve was poor due to the self-aggregation of the carrier. The developer could not be transported favorably.

Comparative Example 6 Fe ₂ O ₃ = 62 mol%, ZnO = 16 mol%, and CuO = 22 mol% in a molar ratio were weighed and mixed using a ball mill. In the same manner as in Comparative Example 1, carrier particles having an average particle diameter of 50 μm were obtained. The shape of the carrier obtained at that time was almost spherical. The bulk density was 2.77 g / cm ³ . The resistance of the carrier particles was measured to be 4.0 × 10 ⁹ Ω · cm.
Magnetic properties of the carrier results of magnetic measurements in a magnetic field 10 kOe, then the sigma _1,000 =
214 emu / cm ³ , σr = 2 emu / cm ³ , σ
₃₀₀ = 113 emu / cm ³ and Hc = 10 Oe. Then | σ _1,000 −σ ₃₀₀ | / σ _1,000 =
0.47.

The obtained carrier was surface-coated in the same manner as in Example 1. The specific resistance of the carrier at this time is 3.2
× 10 ¹² Ω · cm. Further, the obtained carrier and the toner used in Example 1 were mixed in the same manner as in Example 1 to obtain a developer. An image forming test was performed on this developer in the same manner as in Example 1. As a result, the fluidity of the developer on the developing sleeve was good and the transportability was excellent. It was observed that the brush was coarse, and roughness was observed in the halftone portion on the image.
In addition, when an idling test was performed in the same manner as in Example 1, roughness was particularly observed in the halftone portion.

Comparative Example 7 Fe ₂ O ₃ = 60 mol%, SrCO ₃ = 3 mol%, ZnO = 21 mol%, CuO = 16 mol% were weighed so as to be in a molar ratio, and the mixture was mixed using a ball mill. went. In the same manner as in Comparative Example 1, carrier particles having an average particle size of 52 μm were obtained. The shape of the carrier obtained at that time was almost spherical. As a result of X-ray diffraction measurement and fluorescent X-ray measurement,
The molar ratio of the spinel phase (Cu-Zn ferrite) to the magnet plumbite phase (Sr ferrite) is approximately 1
5: 1. The bulk density was 2.32 g / cm ³ . When the resistance of the carrier particles was measured, it was 1 × 1
Was 0 ⁹ Ω · cm. As a result of the magnetic measurement of this carrier, the magnetic characteristic at that time was σ _1,000 = 58 emu /
cm ³ , σr = 6 emu / cm ³ , σ ₃₀₀ = 20 emu
/ Cm ³ , Hc = 60 Oersted. At that time, | σ _1,000 −σ ₃₀₀ | / σ _1,000 = 0.66.

The obtained carrier was surface-coated in the same manner as in Example 1. The specific resistance of the carrier at this time is 1.5
× 10 ¹² Ω · cm. Further, after the obtained carrier was subjected to saturation magnetization in the same manner as the carrier of Example 1, the carrier and the toner used in Example 1 were mixed in the same manner as in Example 1 to obtain a developer. When an image forming test was performed using this developer in the same manner as in Example 1, the density of the magnetic brush on the developing sleeve was high because the value of σ _1,000 was small, and the roughness in the halftone portion was also low. And excellent reproducibility of fine lines, but carrier adhesion was observed in the non-image area due to weak magnetization intensity at 0 to 300 Oe, and toner fog in the non-image area was observed. Was.

[0094]

[Table 1]

[0095]

[Table 2]

[0096]

According to the present invention, high definition, high image quality and high image density can be achieved over a long period of time by using a toner having a specific particle size distribution and a specific carrier.

[0097]

[Brief description of the drawings]

FIG. 1 is a diagram showing hysteresis curves in Examples and Comparative Examples of the present invention.

FIG. 2 illustrates a method for measuring a specific resistance.

[Explanation of symbols]

 C: Cell 1: Upper electrode 2: Lower electrode 3: Insulator 4: Ammeter 5: Voltmeter 6: Constant voltage device 7: Carrier 8: Guide ring

Claims (6)

(57) [Claims] 1. A two-component color electrostatic image developing developer comprising at least a toner and a carrier, wherein the toner is directly obtained from a weight average particle diameter of the toner calculated from volume average distribution data of a Coulter counter. When the calculated specific surface area of the toner is S _A and the specific surface area of the toner calculated from the number average distribution is S _B , S _B is 1.0 ≦
S _B ≦ 1.8 (m ² / g) and the ratio of S _A to S _B is within the following range: 1.20 ≦ S _B / S _A ≦ 1.70 and 4 μm or less A color toner containing 10 to 70% by number of a toner having a particle diameter of 5 to 100 μm and a bulk density of 3.0 g.
/ Cm ³ or less, the magnetization intensity (σ) at 1,000 Oe after magnetic saturation.
_1,000 ) is 30 to 150 emu / cm ³ , and the magnetization intensity (residual magnetization: σr) at a magnetic field of 0 Oe is 2
A developer for developing an electrostatic image, wherein the carrier has a coercive force of 5 emu / cm ³ or more and a coercive force of less than 300 Oersted, and the carrier satisfies the following formula at that time. 2. The developer according to claim 1, wherein the sphericity of the carrier is 2 or less . 3. The carrier according to claim 1, wherein the carrier is made of ferrite, and the ferrite particles are made of a periodic table IA, IIA, IIIA, IVA, V
A, VIA, IB, IIB, IVB, VB, VIB, VIIB
2. The developer according to claim 1, wherein the developer contains at least one element selected from the group consisting of VIII and VIII, and the content of other elements is less than 1% by weight. 4. The developer according to claim 1, wherein the carrier has a single phase of a magnet plumbite structure. 5. A carrier comprising a spinel phase and a magnet plate.
Spinel having a molar ratio of 1: 1 to 10: 1 with the rambite phase
Structure, a composite phase of magnet plumbite structure
The developer for developing an electrostatic image according to claim 1. 6. A carrier having a specific resistance of 10 ⁸ to 10 ¹³ Ω ·
2. The developer for developing an electrostatic image according to claim 1, wherein the developer is cm.