KR0135102B1 - Image forming apparatus - Google Patents

Abstract

The present invention includes an image forming apparatus comprising a latent image bearing member for carrying a latent image, and a developing apparatus for developing a latent image, wherein the developing apparatus includes a developer container accommodating a developer, and a latent image bearing portion from the developer container. An image forming apparatus having a developer carrying member for carrying and carrying a developer in a developing area facing the ash, wherein the developer contains a magnetic toner consisting of a binder resin and magnetic iron oxide, wherein the magnetic iron oxide comprises: When the silicon element content is 0.5 to 4% by weight based on the total iron element content, the total silicon element content of the magnetic iron oxide is assumed as (A), and the magnetic element dissolution rate of the magnetic iron oxide is dissolved to 20% by weight. When the silicon element content dissolved with iron oxide is assumed to be (B) and the silicon element content present on the surface is assumed to be (C), the relationship of (B / A) x100 = 44 to 84% is satisfied, ( C / A) x100 = The particle size distribution is satisfied so that the content of the magnetic toner particles having a weight average particle size of 13.5 µm or less and having a particle size of 12.7 µm or more and satisfying the relationship of 10 to 55% are 50% by weight or less. An image forming apparatus comprising: (FIG. 3)

Description

Image Forming Device

1 is a diagram showing a melting curve of magnetic iron oxide.

2 is a schematic diagram of magnetic iron oxide particles to illustrate silicon element distribution.

3 is a schematic diagram illustrating an embodiment of an image forming apparatus (with an elastic blade) according to the present invention.

4 is a schematic diagram illustrating an embodiment of an image type apparatus (with a magnetic doctor blade) according to the present invention.

5 is a schematic diagram of an example of one silencing of a process cartridge (apparatus unit) according to the present invention.

6 is a block diagram showing an embodiment of a facsimile apparatus according to the present invention.

FIG. 7 shows a checker pattern for testing the developing performance of magnetic toner. FIG.

Fig. 8 is a graph defining the qualitative range of toner particles having a particle size of 5 mu m or less which gives a preferred particle size distribution according to the present invention.

9 shows a mechanism for measuring triboelectric charge.

* Explanation of symbols for main parts of the drawings

1: developer device 2: developer container

3: photosensitive drum 4: electrostatic transfer means

5: laser light 6: developing sleeve

7: heating and pressing roller 8: cleaning blade

9: elastic blade 10: blade support member

11: primary charger 12: bias voltage application means

13: developer 14: cleaner

15: Magnet 16: Magnetic Doctor Blade.

The present invention relates to an image forming apparatus having a device unit (process cartridge) containing a magnetic toner or a magnetic developer for visualizing an electrostatic latent image in an image forming method such as an electrophotographic method and an electrostatic recording method.

Conventionally, as the transfer photographing method, many methods are known as well as those described in US Pat. Nos. 2,297,691, 3,666,363, 4,071,361, and the like, but these methods are generally photosensitive including photoconductive materials by various means. After developing the electrostatic latent image on the member, the resulting toner image is transferred to paper or the like as necessary, and then fixed by heating, pressure, heating pressure, or the like.

In addition, various developing methods for visualizing an electrostatic latent image with toner are known. For example, the magnetic brush method as disclosed in US Pat. No. 2,874,063, the cascade development method as disclosed in US Pat. No. 2,618,552, and the powder cloud method as disclosed in Japanese Patent No. 2,221,776. ), And the fur brush development method and the liquid development method. Among these developing methods, developing methods such as a magnetic toner method, a cascade method, and a liquid development method using a developer mainly composed of toner and a carrier are commercially available. These methods provide relatively stable and good images, but Common problems associated with the use of a two-component developer, such as deterioration and fluctuations in the mixing ratio of toner and carrier, are addressed.

In order to solve such a problem, various developing methods using a one-component developer composed only of toner have been proposed. Among these, there are many excellent developing methods using a developer composed of magnetic toner particles.

In the manifestation method using the electroconductive magnetic toner proposed in US Patent No. 3,909,258, the electrostatic latent image is brought into contact with a conductive magnetic toner on a cylindrical conductive sleeve provided with a magnet inside. In this method, as a developing area, a conductive passage is formed between the recording member surface and the sleeve surface by toner particles, and the toner particles are attached to the image portion by a Coulomb force acting from the image to form the shape. The method of using the conductive magnetic toner as described above is an excellent method of avoiding the problems related to the two-component developing method, but since the toner is conductive, it is difficult to transfer the shape image electrostatically from the recording member to the final supporting member such as plain paper. There is a problem.

As a shape method using a magnetic toner having high resistance to electrostatic transfer, a development method using dielectric polarization of toner particles is known, but this method has an important problem that the development speed is slow and a shape image of sufficient concentration cannot be obtained. have.

As another method of using a magnetic toner of high resistance, a method of contacting and developing an electrostatic charge image bearing member after frictionally charging the toner particles by friction between the toner particles or friction between the toner particles and the friction member such as the sleeve is known. These methods have a problem in that the frictional charge between the turner particles and the friction member is small, so that the charging of the friction becomes insufficient, and the coulomb force increases so that the toner particles charged on the sleeve tend to aggregate.

A developing method that eliminates the above problem has been proposed in U.S. Patent No. 4,395,476 (corresponding to Japanese Patent Application Laid-Open No. 55-18656), but in this method (the so-called jumping phenomenon method), a magnetic toner is applied to the slipper with a very thin thickness. After triboelectric charging, the image is subjected to extreme contact with an electrostatic latent image. More specifically, since the magnetic toner is applied very thinly on the ribs to increase the contact opportunity between the ribs and the toner, sufficient frictional charging can be obtained. The film is collapsed, the friction is sufficiently caused between the toner and the sleeve, and the development is performed by facing the toner layer without contacting the electrostatic latent image in the state where a magnetic field is formed, thereby obtaining an excellent image.

However, the method using the insulating toner includes an unstable element for the insulating toner used. That is, the insulating toner contains a considerable amount of fine powder magnetic material, and part of the fraudulent magnetic material is exposed to the surface of the toner particles, thus affecting the fluidity and frictional chargeability of the magnetic toner depending on the type of magnetic material. Therefore, regeneration or deterioration of dissimilar properties such as developing performance and subsequent image forming performance of low toner are caused.

More specifically, in the conventional jumping method using magnetic toner containing magnetic material, if the repeated development process is continued for a long time, that is, the radiation continues, the fluidity of the developer containing the magnetic toner deteriorates and the normal friction is caused. Since the charging cannot be provided, the charging becomes unstable, causing severe image defects such as blurring under low temperature and low humidity environment. In addition, when the adhesion between the magnetic material constituting the magnetic toner particles and the binder resin is weak, the magnetic material tends to fall off the surface of the magnetic toner when the developing process is repeated, so that the turner image concentration is adversely affected. Causes

In addition, when the magnetic material is unevenly dispersed in the magnetic toner particles, the magnetic toner fine particles containing a large amount of the magnetic material accumulate on the shape sleeve and cause an image density unevenness or a decrease in image density called a sleeve ghost. It may be.

Although various proposals have been made for the magnetic iron oxide contained in the magnetic tor, there is room for improvement.

For example, Japanese Patent Laid-Open No. 62-279352 discloses a magnetic toner containing magnetic iron oxide containing a silicon element. Since the magnetic iron oxide contains silicon element consciously placed inside the magnetic iron oxide particles, the magnetic toner containing the magnetic iron oxide has room for improvement in fluidity.

In addition, Japanese Patent Application Laid-Open No. 3-9045 proposes to control the shape of magnetic iron oxide particles into a spherical shape by adding silicate. In other words, since the magnetic iron iron particles obtained by this method contain a large amount of silicon elements therein and a small amount of silicon elements on the surface thereof, the fluidity improvement of the magnetic toner is insufficient, and the magnetic iron oxide has a surface flatness. Since it is high, the adhesiveness between the magnetic iron oxide and the binder resin constituting the magnetic toner tends to be insufficient.

Japanese Unexamined Patent Publication No. 61-34070 proposes a method of producing triiron tetraoxide, in which a hydrosulfate solution is added to triiron tetraoxide during oxidation. Since the ferric tetraoxide produced by this method contains a silicon element in the vicinity of the surface thereof, and the silicon element exists in the layered form on the surface of the triiron tetraoxide surface, the surface of the triiron tetraoxide is weak against the mechanical impact of rubbed. There is this.

In addition, with the recent use of image forming apparatuses such as an electrophotographic copying machine, their use is diversified and the demand for image quality is becoming more stringent. When copying images of plain paper or documents, even fine characters are required to be faithfully reproduced without resolution of images. In particular, when the electrostatic latent image on the winding-shaped member in the image forming apparatus is constituted by a line having a thickness of 100 μm or less, the conventional shaper is generally inadequate in reproducibility of thin lines, and the sharpness of the line image is insufficient. Also, in an image forming apparatus such as an electrophotographic printer using a digital image signal, when the latent image is composed of unit dots, the image density change from the sound portion, the halftone portion, and the light is expressed by changing the dot presence density. Is not faithfully disposed on the dots and only the dots are fixed, it is impossible to obtain the toner image gradation corresponding to the dot density ratio between black and white of the digital image. In addition, when the resolution is increased in order to improve the image quality using a small dot, it is difficult to reproduce the electrostatic latent image composed of fine dots, resulting in deterioration of the resolution and gradation of the image and lack of sharpness.

In some cases, a good image can be obtained in the initial stage, but the image quality deteriorates during continuous printing. This is presumably because toner particles suitable for development are preferentially consumed, and toner particles having inferior shapes are accumulated in the developing apparatus.

Background Art [0002] Conventionally, an isotropic shaped agent has been proposed. Japanese Patent Laid-Open No. 51-3244 proposes a nonmagnetic toner for the purpose of improved image quality by adjusting the particle size distribution. Since this toner is mainly composed of relatively coarse particles of 8 to 12 mu m, it is difficult to uniformly cover the latent image. In addition, since the toner contains 30% by number of particles of 5 µm or less, the uniformity decreases in a wide distribution containing 5% by mass or less of particles of 20 µm or more. Rather, in order to form a clear image using toner composed of coarse toe particles, it is necessary to overlap the toner particles thickly to fill the gaps between the toner particles, thereby increasing the apparent image density. Should be increased.

Japanese Unexamined Patent Application Publication No. 54-72054 proposes a nonmagnetic toner having a sharper particle size distribution than the above. However, since the intermediate weight of the particles is 8.5 to 11.0 mu m, there is room for improvement as a high-quality toner.

Japanese Unexamined Patent Publication No. 58-129437 proposes a non-transfer toner having an average particle size of 6 to 10 µm and a mode particle of 5 to 8 µm. It is easy to provide scarce images.

According to the researches of the present inventors, it has been found that, in principle, toner particles of 5 탆 or less clearly reproduce the latent image contour and form a whole latent image in a uniform and dense range. In particular, in the latent image on the photosensitive member, since the edge portion, that is, the contour portion has a higher electric field strength than the inside because the electric force lines are concentrated, the quality of the toner particles gathered in the contour portion determines the sharpness of the image. In addition, studies by the present inventors have found that the problem regarding the sharpness of an image can be efficiently solved by the amount of particles having a size of 5 µm or less.

U.S. Patent No. 4,299,900 proposes a jumping developing method using a developer containing 10 to 50% by weight of magnetic toner of 20 to 35 mu m. Toner particle size suitable for improving the environmental durability of the developer by frictionally charging porridge and magnetic toner and forming a thin layer of toner on the rib was considered. However, further improvements are needed to meet stringent requirements for thin line reproducibility, resolution and suitability for inversion.

In the method of using such a dry developer, finely divided silicate was added to the toner powder. Since the silicate powder is inherently hydrophilic, the developer obtained by adding the silicate powder is agglomerated by moisture in the air, and the fluidity of the developer is lowered. In severe cases, the charging of the developer is caused by moisture absorption by the silicate powder. Degrades. For this reason, for example, Japanese Unexamined Patent Application Publication Nos. 46-5782, 48-47345, and 48-47346 propose methods of using silica fine particles imparted with hydrophobicity. Specifically, the silicate powder is reacted with a silane coupling agent to substitute the silanol group of the surface sand of the silicate powder to other organic groups to provide hydrophobicity. As the silane coupling agent, dimethyldichlorosilane, trimethylalkoxysilane and the like are used.

In order to provide sufficient hydrophobicity, the hydrophobicity obtained by treating the fine silicate powder with a silane coupling agent and then treating with silicon oil of D / 25 ± D / 35 parts by weight (D: specific surface area of fine silicate powder) is 90%. It is proposed to use silicate powder having a percentage or more (for example, Japanese Patent Laid-Open Nos. 63-139367, 63-139369, etc.).

On the other hand, toners having finer particle sizes have been used in recent years to satisfy the functional diversification of the image forming apparatus by using electrophotographic techniques such as copiers and laser printers, and to increase the resolution and image quality. Therefore, it is desired to uniformly charge the toner than before, and it is desired to further increase the uniform charging property of the toner.

An object of the present invention is to improve the magnetic toner and the magnetic developer to solve the above problems.

A more specific object of the present invention is to provide a magnetic toner having excellent image reproducibility and high image density.

Another object of the present invention is to provide a magnetic developer having a stable charging performance without a cloudy state when used for a long time.

Still another object of the present invention is to provide a magnetic developer having no cloudy state and an eye fundus charging performance even when used for a long time.

Another object of the present invention is to provide a magnetic developer that is not easily affected by significant fluctuations in environmental conditions from low temperature to high temperature and high humidity.

Another object of the present invention is to provide a magnetic developer capable of faithfully developing digital high-definition images to obtain a clear high-concentration image.

It is another object of the present invention to provide a magnetic developer in which an image portion is densely coated with toner to obtain sharp images with high sharpness and sharp edges.

Another object of the present invention is to provide a magnetic developer capable of obtaining a high image density with low consumption.

Another object of the present invention is to provide a process cartridge, an image forming apparatus, and a facsimile apparatus using a magnetic developer having excellent body fluidity and high resolution.

According to the present invention, in a magnetic toner comprising a binder resin and magnetic iron oxide containing silicon, the magnetic iron oxide has a silicon element content of 0.5 to 4% by weight based on the total iron element content, and the total silicon of the magnetic iron oxide. When the content is assumed to be (A) and the iron element dissolution rate of the magnetic iron oxide is dissolved up to 20% by weight, the silicon element content dissolved together with the magnetic iron oxide is assumed to be (B), and the content of the silicon element present on the surface is represented by (C ), (B / A) x 100 = 44 to 84%, satisfies (C / A) x 100 = 10 to 55%, and the magnetic toner is 13.5 µm or less in weight average particles. A magnetic toner is provided, characterized by having a particle size distribution such that the content of the magnetic toner beads having a size and having a particle size of 12.7 µm or more is 50% by weight or less.

The present invention also provides a magnetic developer containing the magnetic toner, the inorganic fine powder, the hydrophobic minor powder or the resin fine particles.

The present invention also includes a latent image bearing member for supporting a latent image and a developing device for developing a latent image, wherein the developing device includes a shape container for accommodating a developer and a developer in the developer container. An image forming apparatus having a developer carrying member which is carried and carried in a developing area facing a counseling paper member, wherein the developer is provided with the magnetic toner.

In addition, the present invention is detachably mounted to the cast granules of the electrophotographic image forming apparatus, and includes a latent image bearing member for supporting a latent image and a developing apparatus for developing a latent image, wherein the developing apparatus includes a developer. A developer carrying member for accommodating the developer, a developer carrying member carrying the developer in the developing region facing the latent image bearing member, and a developer carried and conveyed by the developer carrying member. A process cartridge comprising a regulating blade for forming a thin layer of a developer on a developer carrying member by regulating to a predetermined thickness, wherein the developer provides a process cartridge comprising the magnetic toner.

In addition, the present invention is a facsimile apparatus having an electrophotographic apparatus and receiving means for receiving image data from a remote terminal, comprising: a latent image bearing member for supporting a latent image and a developing apparatus for developing the latent image; The developing apparatus includes a developer container for accommodating a developer, a shape bearing member for carrying and carrying the developer in the developer container in a developing area facing the latent image bearing member, and by the developer bearing member. Provided is a facsimile apparatus characterized by having a regulation blade for forming a thin layer of a developer on a developer carrying member by regulating the carried and transported developer to a predetermined thickness, the developer comprises the magnetic toner.

The above and other objects of the present invention, as well as the characteristics and advantages of the present invention will become more apparent from the following detailed description of the present invention with reference to the accompanying drawings.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The reason why excellent performance is obtained by the magnetic toner and the magnetic developer according to the present invention is not necessarily clear, but is estimated as follows.

The magnetic toner of the present invention is characterized in that the magnetic toner has a median average particle size of 13.5 µm or less (preferably 3.5 to 13.5 µm) and a content of magnetic toner particles having a particle size of 12.7 µm It has a particle size distribution so as to occupy less than 50% by weight, and has a particle size distribution containing a specific magnetic iron oxide containing silicon.

In the case of a magnetic toner containing a large amount of relatively coarse particles, such as a magnetic toner having a medium sized bacteria particle size exceeding 13.5 μm or a magnetic toner particle having a particle size of 12.7 μm or more, exceeding 50% by weight. In this case, even when the conventional magnetic iron oxide is used, the charging of the magnetic thinner can be stabilized.

In the case where the weight average particle diameter of the magnetic toner is less than 3.5 µm, even when the specific magnetic iron oxide according to the present invention is used, the flow order of the magnetic toner is lowered, so that problems such as cloudy conditions or inadequate concentrations due to insufficient charging are caused. Is generated. Therefore, the weight average particle size is preferably 3.5 µm or more.

The improvement in charging stability and fluidity of the magnetic toner has a remarkable effect compared to the conventional example, and has a median average particle size of 13.5 µm or less (preferably 3.5 to 13.5 µm, more preferably 5.0 to 13.0 µm), The content of magnetic toner particles on the magnetic toner particles having a particle size of 12.7 µm or more is 50% by weight or less, preferably 40% by weight or less.

Another characteristic of the magnetic toner according to the present invention is that the silicon (si) element content of the magnetic iron oxide is 0.5 to 4.0% by weight (preferably 0.8 to 3.0% by weight, more preferably based on the content of all iron elements). Is 0.9 to 3.0% of the center).

When the silicon element content is less than 0.5% by weight, the improvement effect (particularly on the flow book) for the magnetic toner is insufficient, and when the silicon element content exceeds 4.0% by weight, the silicic acid component remains on the magnetic iron oxide surface or It is easy to adversely affect self-specialization.

Further, another characteristic of the magnetic toner for the present invention is that the content (A) of the silicon element present in the magnetic oxide and the iron element dissolution rate of the magnetic iron oxide are dissolved together with the iron oxide oxide. The relationship between the silicon element content (B) and the silicon element content (C) present on the surface of the magnetic iron oxide is (B / A) x 100 = 44 to 84% (preferably 60 to 80%), and (C / A) x 100 = 10 to 55% (preferably 25 to 40%).

When the B / A ratio is less than 44%, the silicon element is excessively present in the center of the magnetic iron oxide, which tends to become magnetic iron oxide, in which the production efficiency is lowered and the magnetic characteristics are unstable.

In addition, when the B / A ratio exceeds 84%, a large amount of silicon elements are present in the layered portion of the magnetic iron oxide particles, and the surface of the magnetic iron oxide is weak against mechanical impact, which tends to adversely affect the magnetic toner. .

On the other hand, when the C / A ratio is less than 10%, silicon is less on the surface of the magnetic oxide blue, which makes it difficult to give magnetic iron oxide and magnetic toner good fluidity, and also lowers the charge amount and volume specific resistance of the magnetic iron oxide. It is easy to impair the charging and environmental stability of magnetic toner.

If the C / A ratio exceeds 55%, unevenness occurs on the surface of the magnetic oxidation target, and when the magnetic toner is manufactured, this uneven portion becomes debris and dispersed in the magnetic toner particles, which adversely affects the magnetic toner characteristics. give.

In order to obtain a good magnetic toner characteristic, as described above, it is preferable that the distribution of silicon elements present in the magnetic iron oxide particles increases continuously or stepwise from the center of the magnetic iron oxide particles toward the surface.

In the present invention, the charge amount of the magnetic iron oxide is preferably -40 to -60 mu c / g, and the volume specific resistance is 5 x 10 3 to 1 x 10 8 Pa.cm, and preferably 5 x 10 4 to 1 x 10 7 Pa.cm.

If the charge amount of the magnetic iron oxide is less than -25 µc / g, if the magnetic toner is repeatedly used for a long time, the charge amount required by the magnetic toner cannot be maintained, which causes problems such as a decrease in image density and generation of a cloudy state. On the other hand, when the charge amount of the magnetic iron oxide exceeds -70 mu c / g, the charge amount of the magnetic toner becomes too high, and the image concentration tends to decrease in a low temperature and low humidity environment.

When the volume specific resistance of the magnetic iron oxide is less than 5 x 10 < 3 > cm < cm >, the amount of charge required by the magnetic toner cannot be maintained and the image concentration is lowered. On the other hand, when the volume specific resistance of the magnetic iron oxide exceeds 1 x 108 Pa · cm, the charge amount is excessively high during repeated use in a low temperature and low humidity environment, and the image density tends to decrease.

In the present invention, the magnetic iron oxide has a degree of aggregation of 3 to 40%, particularly preferably 5 to 30%.

When the magnetic iron oxide has a cohesiveness of less than 3%, so-called flushing and blowing of the magnetic toner are likely to occur during the production of the magnetic toner, and thus, it is difficult to efficiently manufacture the magnetic toner.

On the other hand, when the degree of coagulation exceeds 40%, the magnetic iron oxide is not easily dispersed in the magnetic toner, which tends to adversely affect image density and blur. Further, in the present invention, since the fluidity of magnetic iron oxide is reflected in the fluidity of the magnetic toner, when magnetic iron oxide having a cohesiveness of more than 40% is used, it is difficult to obtain a magnetic toner having sufficient fluidity. It tends to adversely affect sex and cause blurring.

In the present invention, the smoothness D of the magnetic iron oxide is 0.2 to 0.6, and particularly preferably 0.3 to 0.5.

If the smoothness D is less than 0.2, the unevenness of the surface of the magnetic iron oxide becomes remarkable, and the uneven portion becomes fragmented and dispersed into the magnetic toner during the production of the magnetic toner, which adversely affects the toner properties.

On the other hand, when the smoothness exceeds 0.6, it is difficult to obtain sufficient adhesion between the binder resin constituting the magnetic toner and the magnetic iron oxide, and the magnetic iron oxide present on the surface of the magnetic toner gradually separates during repeated use, resulting in lowered image density. Cause adverse effects.

Moreover, in this invention, it is preferable that the sphericity degree (phi) of magnetic iron oxide is 0.8 or more. If the sphericity is less than 0.8, the magnetic iron oxide particles are in contact with each other, and the magnetic iron oxide particles having a small diameter of 0.1 to 1.0 μm cannot be easily separated even if mechanical shearing force is applied. Dispersion may not be performed sufficiently.

In addition, in the present invention, the average particle size of the magnetic iron oxide is 0.1 to 0.4 mu m, particularly preferably 0.1 to 0.3 mu m.

Various physical property variables in the present invention can be measured by the following method.

The particle size distribution of the toner may be measured by various methods, but in the present invention, it is measured by a Coulter counter.

As a measuring device, an interface (Nikkaki Co., Ltd.) and a personal computer (XI Canon Co., Ltd.) which outputs the number distribution and volume distribution using the Coulter Counter Model TA-II (manufactured by Coulter Electronics) Use to connect.

Especially as electrolyte solution, 1% NaCl aqueous solution is manufactured using sodium chloride reagent. 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added to 100 to 150 ml of the electrolyte as a dispersant, and 2 to 20 mg of the sample is added thereto. As a result, after the said electrolyte solution in which the sample was disperse | distributed by the ultrasonic disperser for about 1-3 minutes, the particle size distribution in 2-40 micrometers area | region was used by the said Coulter counter model TA-II using the 100 micrometer diameter. Measure to obtain volume distribution and coefficient distribution. From the results of the volume distribution and the number distribution, parameters representing the characteristics of the magnetic toner of the present invention can be obtained. In particular, the weight average particle size D4 can be obtained from the volume distribution while taking the median value of each channel as the representative value of each channel. Similarly, the weight percent of particles having a particle diameter of 12.7 µm is obtained from the volume distribution.

Silicon element content (C) of the surface of magnetic iron oxide can be measured by the following method. For example, about 3 L of deionized water is placed in a 5 L beaker and warmed to 50-60 ° C. in a water bath. About 25 g of magnetic iron oxide is dispersed into a slurry form with about 400 ml of deionized water, and the slurry is placed in a 5 l beaker with washing with about 300 ml of deionized water.

Thereafter, while maintaining the slurry containing magnetic iron oxide at a rate of about 5 g / l at a temperature of about 60 ° C. and a stirring speed of about 2000 rpm, a high-grade sodium hydroxide sample was added to prepare a sodium hydroxide solution of about 1 normal, and magnetic iron oxide particles. Dissolution of silicon on the surface is initiated in the form of a silicon compound such as silicic acid on the surface. After 30 minutes from the start of dissolution, 20 ml of sodium hydroxide solution was sampled and filtered through a 0.1 µm membrane filter, and then the content of silicon element was determined by plasma emission spectroscopy (ICP).

The silicon element content (C) on the surface is determined by dividing the silicon element concentration (mg / L) by the magnetic iron oxide concentration (about 5 g / L) in the sodium hydroxide aqueous solution.

The silicon element contents (A) and (B) corresponding to the total silicon element content (based on the total iron combustion content) and the iron (Fe) element dissolution rate and iron element dissolution rate can be obtained by the following method. For example, about 3 L of deionized water is placed in a 5 L beaker and warmed to 50-60 ° C. in a water bath. A slurry of about 25 g of magnetic iron oxide in about 400 ml of deionized water is added to a 5 l beaker, washing with about 300 ml of deionized water.

Thereafter, while maintaining the system at a temperature of about 50 DEG C and a stirring speed of about 200 rpm, dissolution is started by adding a special hydrochloric acid or a mixture of hydrochloric acid and hydrofluoric acid. At this time, when hydrochloric acid is added, for example, the magnetic iron oxide concentration is about 5 g / l, and the hydrochloric acid concentration is about 3 normals. About 20 ml of sample is taken every 10 minutes from the system until the solution is completely dissolved and becomes transparent. The filtrate is recovered by filtering with a 0.1 µm membrane filter. The filtrate is analyzed by ICP and the iron (Fe) element is analyzed. Content and silicon (Si) element content are determined.

The dissolution rate of iron element for each sample can be calculated as follows.

Dissolution rate of iron (Fe) element = [Iron element concentration (mg / l) / iron element concentration when completely dissolved (mg / l) in sample] × 100

The content of silicon element for each sample can be calculated as follows.

Content of silicon element = [silicon element concentration (mg / L) / iron element concentration (mg / L)] x 100

Content of all the silicon elements based on content of all iron elements can be calculated | required similarly to the sample after melt | dissolving completely.

The total silicon element content (A) per unit weight of magnetic iron oxide can be obtained by dividing the silicon element concentration (mg / L) in the sample after the complete dissolution by the magnetic iron oxide concentration (about 5 g / L) in the sample.

In addition, content (B) of a silicon element can be calculated | required by dividing the silicon element concentration (mg / L) in the sample with 20% of iron dissolution rate by the magnetic iron oxide concentration in a sample.

Said content (A), (B), (C) can be measured by the following different measuring methods, for example. In other words,

(1) A method of dividing a sample of magnetic iron oxide into two parts, one of which measures the total silicon element content, content (A) and (B), and the other of which measures the content (C).

(2) In order to measure content (C), the sample of magnetic iron oxide is used first, and the sample after measuring in this way measures content (B ') (= BC) and content (A') (= AC). The method of finally calculating content (A) and (B) after using it.

The charge amount (μc / g) of the magnetic iron oxide may be measured as follows.

About 2 g of magnetic iron oxide and about 198 g of carrier iron powder (TEFV 200-300 mesh), shaken by hand for about 10 seconds, shaken by hand in a V-type blender, and then blow-off The charge amount is measured with a) -type powder charge meter (manufactured by Toshiba Chemical Co., Ltd., Japan). At this time, 400 mesh stainless steel nets were set in a measuring yaw parage cage (Fara yaw Cage), and about 0.4 samples were taken and blown off for 30 seconds.

The lowest specific resistivity of magnetic iron oxide is measured as follows.

10 g of magnetic iron oxide is placed in a measuring cell and molded under a pressure of 600 kg / cm 2 by a hydraulic cylinder. After releasing the pressure, an ohmmeter (Yokogawa Denki Co., Ltd. product, YEW MODEL 2506A DIGITAL MULTIMETER) was set, and a pressure of 150 kg / cm 2 was again applied by a hydraulic cylinder. Start measurement and read resistance after 3 minutes. Then, the sample thickness is measured, and the volume specific resistance value is calculated from this measurement data.

Cohesion of the magnetic iron oxide can be measured as follows.

10 g of magnetic iron oxide is pulverized by a mixer, and a sample of 2 g is collected by passing through a 200 mesh sieve. In the powder tester (Hosoka Micron Co., Ltd.), three sieves were stacked in the order of 600 mesh, 100 mesh and 200 mesh, and 2 g of the sample was placed on the upper sieve and vibration of 1 mm in amplitude was performed. Add for seconds. Measure the remaining sample weight on each body, and calculate the degree of cohesion according to the following equation.

Cohesion (%) = {[(Sample weight remaining on 60 mesh bodies) × 1.0 + (Sample weight remaining on 100 mesh bodies) × 3/5 + (Sample weight remaining on 200 mesh bodies) × 1 / 5] / (Original weight of sample placed)} × 100

The smoothness D of the magnetic iron oxide can be obtained as follows.

Smoothness D = surface area of magnetic iron oxide (m 2 / g) / [measured BET surface area of magnetic iron oxide (m 2 / g)] calculated from average particle size

The BET surface area of magnetic iron oxide is determined by the BET multipoint method using nitrogen as the adsorption gas using a fully automatic gas adsorption measurement device (Autosorbl, manufactured by Yua Ionics Co., Ltd.). As a pretreatment of a sample, deaeration is performed at 50 degreeC for 1 hour.

The measurement of the average particle size and the calculation of the surface area of magnetic iron oxide can be performed as follows.

Using a magnetic iron oxide sample processed on a collodion film copper mesh with an electron microscope (H-700H), the product was photographed at 10,000 times at an acceleration voltage of 100KV and printed three times, resulting in a 30,000-fold magnification. Get About this photograph, particle size is observed, the maximum length (micrometer) of each particle is measured about 100 randomly selected particles, and the average length is calculated | required by averaging the maximum length.

The surface area is assumed that each particle is a sphere having an average particle size of magnetic iron oxide as the diameter, the surface area and volume of each sphere are obtained, the density of the magnetic iron oxide is measured by a conventional method, and the weight of each sphere is obtained from the volume and density. Based on the assumption that the surface area based on the average particle size is calculated from these values.

Spherical degree Φ of magnetic iron oxide is obtained as follows.

Spherical degree Φ = [minimum length of magnetic iron oxide particles (µm)] / [maximum length of magnetic iron oxide particles (µm)]

The sphericity Φ is calculated as an average based on 100 magnetic iron oxides randomly selected from the photograph to measure the average particle diameter.

Although the spherical degree Φ of the common cubic magnetic iron oxide is approximately 0.6 to 0.7, that is, 0.8 or less, the spherical degree Φ of the magnetic iron oxide used in the present invention is 0.8 or more, preferably 0.85 or more, more preferably 0.9 or more, and is angled. It has a shape close to a sphere with no end.

Magnetic iron oxide having a sphericity of less than 0.8 has poor dispersibility in the room kneader resin even when silicon is unevenly distributed on the surface of the magnetic iron oxide particles, for example, to cause magnetic toner having poor developing performance and poor dot reproducibility. do.

The magnetic toner according to the present invention preferably contains 20 to 200 parts by weight, more preferably 30 to 150 parts by weight of magnetic iron oxide with respect to 100 parts by weight of the binder resin.

Magnetic toner according to the present invention has a weight average particle size of magnetic toner of 6 to 8 µm, 17 to 60 number percent of toner particles of 5 µm or less, 5 to 50 number percent of toner particles of 6.35 to 10.08 µm, and 12.7 µm The above toner particles have a particle size distribution of 20.0% by volume, and the content of magnetic toner particles of 5 µm or less in number% (N%) and volume% (V%) is N / V = -0.05N + K (where It is preferable to satisfy the relationship of K as a positive number of 4.6-6.7, and N as a positive number of 17-60.

Conventionally, magnetic toner particles of 5 mu m or less show difficulty in charge control, impair the fluidity of the magnetic toner, and cause toner scattering to cause the device to become dirty and produce a cloudy state in the obtained image. Therefore, it is necessary to reduce the magnetic toner particles. Was considered to be.

However, the results of this study. Magnetic toner particles of 5 mu m or less proved to be essential components for forming a high quality image.

As a result of evaluating the developing characteristics of the magnetic toner, various surface potential contrasts ranging from the large development potential contrast where most toner particles are easily formed through the intermediate tone contrast, to the small development potential contrast where only a few toner particles are developed In order to develop a latent image on the photosensitive member having a magnetic toner having a particle distribution size of 0.5 ㎛ to 30 ㎛ was used. Next, when the toner particles used to develop the latent image were recovered from the photosensitive member and the particle size distribution was measured, it was found that the proportion of the magnetic toner particles of 8 µm or less, especially 5 µm or less increased. When the magnetic toner particles of 5 μm or less, which were most suitable for development, were smoothly supplied to the latent image on the photosensitive member, it was found that the latent image was faithfully developed with excellent reproducibility without enlargement. This phenomenon was also observed in the case of the reversal of the digital latent image.

Another characteristic of the magnetic toner used in the present invention is that the toner particles of 6.35 to 0.08 mu m are composed of 5 to 50 number%. This relates to the necessity of the above-mentioned magnetic toner particles of 5 mu m or less. Magnetic toner particles of less than 5㎛ are closely coated to faithfully reproduce the latent image, but since the latent body has a higher electric field strength at the peripheral edge than the middle or center portion, the toner particles adhere to the center portion thinner than the surrounding portion so that the concentration inside is thinner. Easy to be This tendency was especially observed by magnetic toner particles of 5 mu m or less. The present inventors solved this problem by providing 6.35-10.085 micrometer toner particles in the ratio of 5-50 number%, and were able to provide a clear image. This is considered to be because the magnetic toner particles of 6.35 to 10.08 mu m have an appropriately controlled charging amount for the magnetic toner particles of 5 mu m or less, but the magnetic toner particles of 6.35 to 10.08 mu m in the concentration lower than the edge of the latent image. This is due to the fact that the coverage of the toner particles is compensated for by providing a to provide a uniformly developed image. As a result, high density, excellent resolution and gradation characteristics, and a clear image can be obtained.

The toner particle content of 5 mu m or less expressed in N% and V% preferably satisfies the relationship of N / V = -0.05N + K (here, 4.6 ≦ K6.7, 17 ≦ N ≦ 60). 9 shows the range defined by this relationship, and in addition to other features of the present invention, a magnetic toner having a particle size distribution satisfying this relationship achieves better developing performance for very fine latent images.

In addition, the inventors found that while examining the state of the particle size distribution of 5 占 퐉 or less, there is a specific state of the presence of fine powder that satisfies the above formula and can achieve the intended performance. In other words, a large N / V for a specific N value indicates a wide range of particles up to 5 µm or less, and a small N / V / indicates a high abundance of particles around 5 µm. It is interpreted that this indicates that the ratio of the particle size below is small, and the fine wire reproducibility is good when the N / V value is in the range of 1.6 to 5.85, and N is in the range of 17 to 60, and the above formula is further satisfied. And high resolution is achieved.

Magnetic toner particles of 12.7 µm or more are suppressed to 2.0% by volume or less. As few as possible is preferable.

The magnetic developer according to the present invention solves the problems of the prior art and can satisfy the high quality which is strictly required in recent years.

The particle size distribution of the magnetic toner used in the present invention will be described below.

The magnetic toner particles of 5 µm or less are 17 to 60% by weight, preferably 25 to 60%, more preferably 30 to 60% by weight based on the total number of particles. When the content of magnetic toner particles of 5 µm or less is 17% or less, there are few magnetic toner particle portions effective to provide high quality, and in particular, the active ingredient is preferentially consumed as the toner is consumed during copying or printing. Uniformity of the particle size distribution of the magnetic toner deteriorates and image quality deteriorates gradually. In addition, when the content is 60% or more, the magnetic toner particles are easily coagulated, and a toner lump having a size larger than an appropriate size is generated, thereby exhibiting a high quality difference, a low resolution, a large density difference between the outline of the image and the inside. It causes the problem of forming a rather hollow hollow image.

The particle content of 6.35 µm to 10.08 µm is 5 to 50% by mass, more preferably 8 to 40%. If the content is 50% or more, the image quality deteriorates, the thin wire reproducibility decreases, and the coverage of the toner becomes excessive, resulting in excessive consumption of the toner. In addition, if it is 1% or less, it may be difficult to obtain a high image density. The content of the magnetic toner particles of 5 μm or less, expressed as the number% (N%) and the volume * V%), satisfies the relationship of N / V = −0.05N + K, where K is 4.6 ≦ K6 .7, preferably, a positive number satisfying 4.6≤K≤6.2, more preferably 4.6≤K≤5.7, and N is 17≤N≤60, preferably 25≤N≤60, more preferably 30 It is a number which satisfy | fills <= N <= 60.

In the case of K4.6, the magnetic toner particles of 5.0 µm or less are insufficient, resulting in deterioration of the image density, resolution and sharpness. If the fine toner particles of the magnetic toner, which have been considered unnecessary in the past, are present in an appropriate amount, they are effectively used for packing the toner to the maximum closeness during development, and are effective for uniformly forming the image without roughening it. In particular, these particles visually improve their sharpness by filling in the thin and outline portions of the image. Therefore, if K4.6 in the above formula, such a component becomes insufficient in the particle size distribution, and the above-mentioned characteristics are poor.

In addition, from the viewpoint of the manufacturing process, a large amount of fine particles should be removed by classification to satisfy the conditions of K4.6, but such a process is disadvantageous in view of the yield and the cost of the toner. On the other hand, with K6.7, an excessive amount of fine powder is present, which tends to lower the image density during continuous copying or printing. This decrease in image density is thought to prevent excessive magnetic powder toner particles having an unnecessarily high charge from adhering to the developing sleeve to prevent normal magnetic toner particles from being loaded onto the developing blister and to prevent charge from being applied. .

In the magnetic toner of the present invention, the magnetic toner particle amount having a particle size of 12.7 µm or more is 20% by volume or less, preferably 1.0% by volume or less, more preferably 0.5% by volume or less. If the amount is 2.0% by volume or more, these particles impair the reproducibility of thin wires.

The weight average particle size of the magnetic toner used in the present invention is 6 to 8 mu m, and this value can be considered independently of the above-mentioned factors. If the weight average particle size is less than 6 mu m, there is a problem that the amount of toner adhered on the transfer paper becomes insufficient for a digital latent image having a high image area ratio such as a graphic image. This is considered to arise for the same reason as the problem when the inside of the latent image is developed at a concentration lower than the contour. If the weight average particle size exceeds 8 mu m, good resolution cannot be obtained for fine points of 100 mu m or less, and they are scattered a lot in the non-image part. In addition, the image quality is satisfactory at the initial stage of copying, but the image quality is lowered if the copy continues.

The magnetic iron oxide used in the magnetic toner according to the present invention can be treated with a silane coupling agent, titanic acid coupling agent, aminosilane, or the like as necessary.

Examples of the binder resin constituting the toner according to the present invention include styrene homopolymers and derivatives thereof such as polystyrene and polyvinyl toluene; Styrene-propylene copolymer, Styrene-vinyl toluene copolymer, Styrene-vinyl naphthalene copolymer, Styrene-methyl acrylate copolymer-Styrene-ethyl acrylate copolymer, Styrene-butyl acrylate copolymer, Styrene-octyl acrylate Copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, Styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-methyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer and styrene maleic acid ester copolymer Styrene copolymers; Polymethyl methacrylate, polybutyl methacrylate, polyvinylacetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin, rosin, modified rosin, Terpene resins, phenol resins, aliphatic or aliphatic ring hydrocarbon resins, aromatic petroleum resins, paraffin waxes and carnauba waxes. These resins may be used alone or as a mixture, and styrene copolymers and polyester resins are particularly preferable in view of developability and fixability.

In the toner according to the present invention, a hydrocarbon wax or an ethylenic olefin polymer can also be used in combination with a binder resin as a fixing aid.

Examples of such ethylenic olefin homopolymers or copolymers include polyethylene, polypropylene, ethylene-propylene copolymers, ethylene vinyl acetate copolymers, ethylene ethyl acrylate copolymers and ionomers having polyethylene backbones. It is preferable to contain 50 mol% or more, preferably 60 mol% or more of the olefin monomer in the body weight.

The magnetic toner according to the present invention may contain a colorant containing a known pigment or dye such as carbon black and copper-phthalocyanine.

The magnetic toner according to the present invention may contain a charge control agent. For negatively charged toners, negative charge control agents such as metal complex salts of monoazo dyes, sillysilanes, alkyl salicylic acids, dialkyl salicylic acids or metal complex salts of naphthoic acid may be used. Can be.

As the positively charged toner, a positive charge control agent such as a nigrosine compound and an organic quaternary ammonium salt can be used.

It is preferable to mix the magnetic toner according to the present invention with an inorganic fine powder or a hydrophobic inorganic fine powder, for example, a silica fine powder.

The fine silica powder used in the present invention is so-called dry silica or steam silica obtained by oxidizing gaseous silicon halide or so-called wet silica produced from water glass or the like, and among them, the amount of silanol groups present on the particle surface or inside is different. Dry silica is preferred to wet silica in that it is small and free of residual products.

It is also preferable to hydrophobize the silica fine powder, and for the hydrophobic imparting treatment, the silica fine powder is chemically treated with an organosilicon compound which is physically adsorbed or reacted with, for example, the silica fine powder. As a preferable method, there is a method of treating dry silica fine powder generated by vapor phase oxidation of silicon halide with a silane coupling agent, and simultaneously or after that, fine silica powder with an organosilicon compound such as silicon oil.

Examples of the silane coupling agent used in the hydrophobic imparting treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethylchlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichloro Silane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilane mercaptan, trimethylsilyl mercaptan, trior Organosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysisilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane and 1,3-di Phenyl tetramethyl disiloxane is mentioned.

Examples of the organosilicon compounds include silicon oil, and the silicon oil preferably has a viscosity of about 30-1,000 centi-stokes at 25 ° C., for example, dimethyl methyl silicone, methylphenyl silicone oil, α- Methyl styrene-modified silicone oil, chlorophenyl silicone oil, and fluorinated silicone oil.

The treatment with silicon oil is, for example, directly mixing the silica fine powder treated with a silane coupling agent with the silicon oil with a mixer such as Henschel mixer, spraying the silicon oil on the fine silica powder, or silicon oil with a suitable solvent. Solution or fractions may be mixed with the fine silica powder to remove the solvent.

In the present invention, it is preferable to treat the inorganic fine powder forming the magnetic developer with silicon or silicone varnish in order to make the amount of carbon deposition 3 to 8% by weight.

Alternatively, in the present invention, it is preferable that the inorganic fine powder forming the magnetic developer is treated with silicon oil or silicone varnish to reduce the specific surface area of the inorganic fine powder to 0.4 to 0.6 times the value before the treatment.

By treatment with silicone oil or varnish, the fine powder surface is coated with oil or varnish to significantly improve moisture resistance.

In a preferred embodiment of the present invention, the fine powder is treated with a high negatively charged silicone oil or varnish to impart strong negative charge to the fine powder to produce a developer imparted with strong negative charge, which is easy to be supplied to an unstable stream. Effective for ingredient-based magnetic developer, especially when combined with magnetic toner that has been reduced in size to provide high image quality.

The fine powder includes inorganic materials, for example, fine powders of metal oxides of the third or fourth groups, such as silica or silicon materials, alumina, titanium oxide, and the like, and examples of preferred fine powders include gaseous halogen and silicon. The so-called wet silica which can be produced from the so-called dry silica, vapor phase silica, or water glass which can be obtained by oxidizing is mentioned. Among them, the amount of silanol groups present on the surface or inside of the particles is small and Na ₂ O, Dry silica is preferred over wet silica because there are no residual products such as these. Dry silica is a complex metal powder of silica and other metal oxides obtained using other metal halides such as aluminum chloride or titanium chloride together with silicon chloride. The average particle size of the silica powder is preferably 0.001 to 2 µm, particularly 0.002 to 0.2 µm.

The solid or dendritic content of silicone oil or silicone varnish can be represented by the following formula.

(Wherein, R is C ₁ ~C ₃ alkyl group, R 'is a silicone oil, a transformer, such as alkyl, halogen-modified alkyl, phenyl and modified phenyl group, R is a C ₁ ~C ₃ alkyl group or an alkoxy group)

Specific examples thereof include dimethyl silicone oil, alkyl modified silicone oil, α-methyl styrene modified silicone oil, chlorophenyl silicone oil, and fluoroplymatic silicone oil, and the viscosity of the silicone oil is about 50 to 1000enti- at 25 ° C. It is desirable to have stokes. If the molecular weight of the silicone oil is too small, volatiles are generated under heating, while if the molecular weight is too large, the viscosity is high, which makes handling difficult.

In order to treat the silica fine powder with silicon oil, a method of directly mixing the silica fine powder treated with a silane coupling agent with a silicon oil using a mixer such as Henschel mixer or spraying silicon oil on the silica as the base material can be used. . It is also preferable to use a method of dissolving or dispersing silicone oil in a suitable solvent and mixing the silica with the base silica and then removing the solvent to form hydrophobic silica.

Preferably, the silica fine powder is treated with a silicon oil or varnish so that the amount of carbon is 3 to 8% by weight based on the silica fine powder. Here, the carbon deposition amount can be measured by an elemental analyzer (CHN meter).

Alternatively, it is preferable to reduce the specific surface area of the silica fine powder to a degree of 0.4 to 0.6 times with respect to the value before the treatment by treatment with silicon oil or varnish. Here, the specific surface area of the silica fine powder can be measured by the BET method using N ₂ -adsorption. Such control of the processing degree is based on the following reasons. In other words, if the decrease in specific surface area is small, this is a case where the treatment with silicon oil or varnish is insufficient or nonuniform, and as a result, in the former case, sufficient moisture resistance is not obtained, and water absorption by the fine silica powder is absorbed. It becomes impossible to provide high quality under high humidity, and in the latter case, since the negative charge property is not uniformly imparted as a result of treatment with silicone oil or varnish, the uniform charging property of the developer is insufficient, and therefore, it is removed and recovered after transfer and is exposed to light. A problem arises in that the amount of toner remaining on the member cannot be particularly reduced when toner having a small particle size is used. On the other hand, when the specific surface area of the silica fine powder is reduced by treatment with silicon oil or varnish, the silica fine powder tends to aggregate and cannot provide a developer having improved fluidity.

The solid or resin content of the silicone oil or varnish used in the treatment is generally 3 to 50 parts by weight based on 100 parts by weight of the fine silica powder.

The fine silica powder is preferably treated with a silin coupling agent and then with silicone oil or silicone varnish.

When the inorganic fine powder is treated only with silicon oil or varnish, a large amount of silicon oil is required to cover the surface of the silica fine powder. Therefore, the silica fine powder aggregates to form a developer having poor fluidity. The process should be done carefully. If the silica fine powder is first treated with a silane coupler and then treated with a silicone oil, the fine powder may have good moisture resistance, while preventing the aggregation of the powder to sufficiently exhibit a treatment effect by the silicone oil or varnish.

The silane coupling agent used in the present invention is a general formula R _m SiY _n (where R is an alkoxy group or a chlorine atom, m is an integer of 1 to 3, Y is an alkyl group, vinyl group, glycidoxy group, methacryl group) Or other hydrocarbon group, n is an integer of 3 to 1) or hexamethyldisilazane. Specifically, for example, dimethyldichlorosilane, trimethylchlorosilane, allyldimethylchlorosilane, allylphenyldachlorosilane, benzyldimethylchlorosilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriace Methoxysilane, divinylchlorosilane, and dimethylvinylchlorosilane.

The treatment of the fine powder by the silane coupling agent is a dry method of reacting the vaporized or sprayed silane coupling agent in a solvent or a wet method in which a silane coupling agent is added dropwise to react with the fine powder. Stir to form a cloud shape.

The amount of the silica fine powder thus treated is 0.01 to 20 parts by weight, and preferably 0.1 to 3 parts by weight based on 100 parts by weight of the magnetic toner.

In the magnetic toner according to the present invention, external additives other than silica fine powder may be added if necessary. For example, it is preferable to add externally to the magnetic toner a resin fine particle having an average particle size of 0.03 to 2.0 탆 and having the same polarity as that of the magnetic toner.

The particle size of such resin fine particles can be measured by various methods, but the values shown here are measured by the following methods. In other words, such resin particles were photographed at an magnification of 10,00 to 20,000 using an electron microscope (S-800, manufactured by Hitachi Seisakusho Co., Ltd.), and 100 to 200 particles randomly selected from the photographed resin particles were calipers. The average particle size of the resin particles is obtained by averaging the measured diameters by measuring the diameters using.

The amount of frictional charge of such a fine resin powder can be measured by the following method. That is, a carrier iron powder (eg, Nippon Teppon Co., Ltd.), which is not coated with 0.2 g of a resin powder that is left overnight at 23.5 ° C. and a relative humidity of 60% RH and a resin having a mode particle size of 200 to 300 mesh; 9.8 g of EFV 200/300) are mixed thoroughly in a 500cc polyethylene stool with a lid in the same environment as mentioned above (mix the pot by shaking in a vertical direction for approximately 50 times with a hand, approximately 125 times).

Next, about 0.5 g of the mixed mixture is filled into the metal container 32 having the 400 mesh screen 33 installed on the bottom and covered with the metal lid 34, as shown in FIG. The total weight of the vessel 32 is measured and denoted by w ₁ (g), and then the intake air 31 made of at least an insulating material is operated for the portion in contact with the vessel 32, through the suction port 27. While suctioning sufficiently removes the silica in the container, by adjusting the intake control valve 36, the pressure is controlled to 250 mmHg by the vacuum gauge 35. At this time, the value of the potentiometer 39 connected to the container via a capacitor having a capacity C (μF) is expressed in V (volts), and the total weight of the container after intake is measured and displayed as w ₂ (g), The triboelectric charge (μc / g) of silica is calculated as follows. That is, C × V / (w ₁ -w ₂ ).

Resin fine particles used with the magnetic toner according to the present invention can be prepared by soap-free polymerization or emulsion polymerization. The resin fine particles produced by one or two or more types of monomers exhibit excellent effects, and preferred examples thereof include styrene, acrylic acid, methyl methacrylate, butyl acrylate and 2-ethyl hexyl acrylate.

The resin fine particles can be crosslinked with, for example, divinylbenzene and, as a preferred mode, can be surface treated with metals, metal oxides, pigments or dyes or surfactants.

In addition, other additives such as resin particles or inorganic particles functioning as a charge enhancer, an electrically conductive imparting agent, a fluidity imparting agent, a release agent added to a passion adhering agent, and a lubricant or abrasion agent to the magnetic toner according to the present invention. Can be added.

The amount of the inorganic fine powder or the hydrophobic inorganic fine powder mixed with the magnetic toner is 0.1 to 5 parts by weight, preferably 0.1 to 3 parts by weight based on 100 parts by weight of the magnetic toner.

The magnetic toner which develops the electrostatic charge image according to the present invention is a binder such as vinyl-based plastic resin or polyester resin and optionally a dye or pigment as a colorant, a charge control agent, other additives, etc., a mixer such as a ball mill. After sufficiently mixing with the magnetic iron oxide powder, the mixture is melt kneaded by heat kneading means such as a hot roller, a kneading machine and an extruder to disperse or dissolve the magnetic iron oxide powder or pigment or dye and any additives in the molten resin as necessary. It is prepared by cooling and pulverizing the mixture and precisely classifying the powder product to form the magnetic toner according to the present invention.

Hereinafter, a process cartridge, an image forming apparatus, and a facsimile apparatus using the magnetic toner or the magnetic developer according to the present invention will be described.

A preferred embodiment of the image forming apparatus will be described with reference to FIG.

The surface of the OPC photosensitive member 3 is negatively charged by the primary charger 11 and image-scanned by the laser beam 5 to form a digital latent image. The latent image obtained is installed in the counter direction and the elasticity of urethane rubber The development is reversed with the one-component developer 13 containing the magnetic toner of the developing apparatus 1 having the developing sleeve 6 in which the blade 9 and the magnet 15 are embedded. In the developing section, an alternating bias, pulse bias and / or DC bias is applied to the bias voltage applying means 12 between the conductive gas of the photosensitive drum 3 and the developing sleeve 6. When the transfer paper P is conveyed to the transfer unit, the electrostatic transfer means 4 is charged on the back surface (opposite side of the photosensitive drum axis) of the transfer paper, whereby the developing image (toner image) on the photosensitive drum is electrostatically discharged onto the transfer paper P. Is transferred. Then, by charging the photosensitive drum 3, the developing image (toner image) of the photosensitive drum pair is electrostatically transferred onto the transfer paper P. FIG. Next, the transfer paper P separated from the photosensitive drum 3 is fixed by a heat press roller fixing machine 7 for fixing the toner image on the transfer paper P. FIG.

The one-component developer remaining in the photosensitive drum after the transfer process is removed by the cleaner 14 having the cleaning blade 8. After cleaning, the photosensitive drum 3 is discharged by the erasure exposure 19, and then the first charging step 11 is repeated by the charging process.

The electrostatic image bearing member (photosensitive roller) includes a photosensitive layer and a conductive plate, and rotates in the direction of the arrow. The developing sleeve 6 of the nonmagnetic cylinder, the toner carrying member, rotates in the developing section in the same direction as the surface of the electrostatic image holding member. Inside the non-magnetic cylinder sleeve 6, the multipole permanent magnet 15 (magnetrol) is disposed so as not to rotate as a magnetic field generating means. The one-component insulating magnetic developer 13 in the developing apparatus is applied onto the nonmagnetic cylinder sleeve 6, and the toner particles are given, for example, negative frictional charges by friction between the surface of the sleeve 6 and the toner particles. do. In addition, by arranging the elastic blades 9, the thickness of the developer layer is regulated by a thin and uniform thickness (30 to 300 µ), so that the developer layer thinner than the gap between the photosensitive drum 3 and the developing sleeve 6 is subjected to the photosensitive drum ( 3) not to be in contact with This sleeve 6 adjusts the rotational speed so that the peripheral speed of the sleeve 6 is substantially equal to or close to the speed of the photosensitive drum surface. In the developing section, an AC bias or a pulse bias may be applied by the biasing means 12 between the sleeve 6 and the photosensitive drum 3. It is preferable that AC bias is f = 200-4000Hz, Vpp = 500-3000V.

In the developing section, the toner particles are transferred to the electrostatic image by the action of the electrostatic force and AC bias or pulse vias shown on the electrostatic image supporting surface of the photosensitive drum 3.

Another embodiment of the image forming apparatus according to the present invention will be described with reference to FIG.

The image forming apparatus shown in FIG. 4 differs from the image forming apparatus shown in FIG. 3 in that the magnetic doctor blade 16 restricts the thickness of the magnetic developer layer on the developing sleeve. In Figs. 3 and 4, the same reference numerals denote the same members.

As the magnetic doctor blade 16, for example, an iron doctor blade is disposed close to the cylinder surface (at an interval of 50 µm: 500 µm) so as to face the magnetic pole position of one of the multipolar permanent magnets, thereby developing a developer layer. The thickness of is controlled to a thin and uniform thickness (30 to 300 mu m) so that a developer layer thinner than the gap between the photosensitive drum 3 and the developing sleeve is formed so as not to come into contact with the photosensitive drum 3. By adjusting the rotational speed of the sleeve 6, the peripheral speed of the sleeve 6 is made to be substantially equal to or approximately equal to the speed of the photosensitive drum surface. As the magnetic doctor blade 16, instead of iron, permanent magnets may be used to form opposite magnetic poles.

In the transfer photographing apparatus, a plurality of members including an electrostatic image supporting member such as the above-described photosensitive drum, a developing apparatus, a cleaning means, or the like are integrally combined to form an apparatus unit (process cartridge), and thus the unit is The apparatus body can be detachably configured. For example, one of the charging means, the developing device, and the cleaning means is integrally combined with the photosensitive drum to form a single unit. Therefore, this single unit (process cartridge) is formed by a wife means such as a guide rail formed on the device body. Can be made detachable. In this case, the charging unit and / or the developing device can be integrated in the device unit (process cartridge).

5 shows an embodiment of the device unit according to the present invention. In FIG. 5, an electrophotographic apparatus having an image forming unit (process cartridge) including a developing device, a drum-shaped latent image bearing member (photosensitive drum) 3, a cleaner 14, and a primary charger 11 integrally. The image forming apparatus of the scheme is shown.

In the image forming apparatus, when the magnetic developer 13 in the image forming unit is exhausted, a new unit (process cartridge) is replaced.

In the present embodiment, the developing field 1 contains a one-component magnetic developer as the developer 13, and a predetermined electric field is formed between the photosensitive drum 3 and the developing sleeve 6. In order to perform the developing step appropriately, it is important to maintain a predetermined interval between the photosensitive drum 3 and the developing sleeve 6. Subsequently to this embodiment, this interval is centered on 300 µm and measured and adjusted so that the error is ± 30 µm.

The developing apparatus 1 according to the present invention shown in FIG. 5 carries the developer container 2 for accommodating the magnetic developer 13 and the magnetic developer 13 in the developer container 2 for development. The developing sleeve 6 conveyed from the brewing vessel 2 to the developing region facing the photosensitive drum 3, and the elasticity for regulating the self-developing agent to a predetermined thickness to form a thin developer layer on the developing sleeve 6. It consists of a blade (9).

The developing sleeve can have any structure, and is generally composed of a nonmagnetic developing sleeve 6 incorporating a magnet 15. As shown in the drawing, the developing sleeve 6 may be a cylindrical rotating body or a recirculation belt, and aluminum or stainless steel is preferable.

The elastic blade 9 is a rubber elastic body such as urethane rubber, silicone rubber, NBR; Metal elastic bodies such as phosphor bronze and stainless steel; It consists of an elastic plate formed from resin elastic bodies, such as polyethylene terephthalate and a high density polyethylene. The elastic blade 9 is brought into contact with the developing sleeve 6 by elasticity of the member itself, and is fixed to the developer container 2 by a blade supporting member 10 made of a rigid body such as iron. The elastic blade 9 is preferably in contact with the counter direction with respect to the rotation direction of the developing sleeve 6 at a linear pressure of 5 to 80 g / cm.

In the case where the chemical conversion device according to the present invention is used as a printer for facsimile, the laser light 5 (as shown in FIG. 3 or 4) becomes an exposure image for printing the reception data. 6 is a block diagram illustrating such an embodiment.

In FIG. 6, the controller 611 controls the image reading unit (or image reading unit) 610 and the printer 619. FIG. The entire controller 611 is controlled by the CPU 617. The data read out from the image reading unit 610 is transmitted to the printer 619 via the transmitting circuit 613.

The image memory 616 stores predetermined image data. The printer controller 618 controls the printer 619. The telephone 614 is connected to the receiving circuit 612 and the transmitting circuit 613.

More specifically, the image received from the line (or circuit) 615 (that is, the image data received from the remote terminal connected by the line) is demodulated by the receiving circuit 612, and then by the CPU 617. It is decoded and stored in the image memory 616 sequentially. When at least one page of image data is stored in the image memory 616, image recording or output is performed for the page. The CPU 617 reads one page of image data from the image memory 616 and sends the decoded one page data to the printer controller 618. When the printer controller 618 receives one page of image data from the CPU 617, the printer controller 618 controls the printer 619 to record image data of the page. While recording by the printer 619, the CPU 617 receives image data of the next page.

That is, the reception and recording of the image are executed through the apparatus shown in FIG. 6 in the above-mentioned manner.

The magnetic iron oxide containing silicon used in the present invention is produced by the following method, for example.

After the predetermined amount of the silicic acid compound is added to the ferrous salt solution, alkali, such as sodium hydroxide, at least the same as the iron component is added to prepare an aqueous solution containing ferrous hydroxide. While maintaining the pH of the prepared aqueous solution at pH 7 or more (preferably pH 8-10), air is blown to oxidize ferrous hydroxide while the aqueous solution is heated to 70 ° C or more to form a core of magnetic iron oxide particles. Seed crystals are fished first.

Next, an aqueous solution containing about 1 equivalent of burn ferrous iron based on the alkali added previously is added to the slurry liquid. The air is blown into the liquid while maintaining the pH of the liquid at 6 to 10, whereby ferrous hydroxide reaction with seed crystals is grown as a core while ferrous hydroxide is reacted. As the oxidation reaction proceeds, the pH of the liquid is shifted toward the acidic side, but the liquid is preferably not less than six. In the final stage of the oxidation reaction, the pH of the liquid is preferably adjusted to localize a predetermined amount of the silicic acid compound in the surface layer and the surface of the magnetic iron oxide particles.

As a silicic acid compound added to the said system, commercial silicate, such as sodium silicate, and silicic acid, such as a silicate sol formed by hydrolysis, can be used, for example. Other additives such as aluminum sulfate and alumina can be added as long as they do not adversely affect the present invention.

As the ferrous salt, ferrous sulfate produced as a by-product when producing tartan by the sulfuric acid method, ferrous sulfate and ferrous chloride produced as a by-product when washing the surface of the steel sheet can also be generally used.

In the method for producing magnetic iron oxide by the demand solution method, an iron concentration of 0.5 to 20 mol / l is generally used to avoid the increase in viscosity accompanying the reaction and in consideration of the solubility of ferrous sulfate. The lower the concentration of ferrous sulfate, the finer the particles generally produced. In addition, the larger the amount of air and the lower the reaction temperature, the easier it is to form particles.

When observed through a transmission electron microscope, particles of magnetic iron oxide containing silicon, which are mainly composed of spherical particles formed by curved surfaces excluding a plate-shaped surface and free of octahedral particles, are produced by the above production method, It is preferable to use the magnetic iron oxide particles for the production of the toner.

Hereinafter, the present invention will be described in more detail based on production examples and examples. The weight part means weight% here.

[Production Example 1]

An aqueous solution containing ferrous hydroxide by adding sodium silicate to the ferrous sulfate solution so that the silicon element content is 1.8% based on the iron content, and caustic soda solution 1.0-1.1 times the equivalent of iron ions. Was prepared.

While the aqueous solution was maintained at pH 7-10 (for example, Ph 9), air was stuck together to cause an oxidation reaction at 80 to 90 ° C to form a slurry containing seed crystals.

Next, an aqueous solution containing ferrous sulfate was added to this slurry so as to be 0.9 to 1.2 times the equivalent of the amount of alkali (sodium component of sodium silicate and sodium component of caustic soda) added in advance. In addition, while maintaining the slurry at pH 6-10 (for example, pH 8), air was stuck and oxidized to adjust the pH in the final step and localized the silicic acid component on the surface of the magnetic iron oxide particles. The produced magnetic iron oxide particles were washed by a conventional method, recovered by filtration, dried, and the aggregates were decomposed to obtain magnetic iron oxides having the characteristics shown in Table 2 below.

As a result of the gradual dissolution, the produced magnetic iron oxide was dissolved in iron and silicon contents measured at intervals of 10 minutes as shown in Table 1. The correlation between the dissolution rate of the iron (Fe) element and the dissolution rate of the silicon (Si) element is summarized in Table 1.

In the magnetic iron oxide produced as described above, the silicon content (C) on the surface (as illustrated in FIG. 2) is due to the silicate compound adhering to the surface (C) of the magnetic iron oxide particles and dissolved by the alkaline solution). 17.9 mg / l, silicon content (B) (due to the silicate compound contained in the surface layer (B) of the magnetic iron oxide particles as illustrated in FIG. 2 and dissolved in the iron dissolution rate to 20% by hydrochloric acid solution) Was 38.8 mg / l, and the total silicon content (A) was 59.7 mg / l.

[Production Example 2]

Magnetic iron oxide having the characteristics shown in Table 2 was prepared in the same manner as in Preparation Example 1, except that sodium silicate was added so that the silicon content based on the iron content was 2.9%.

[Manufacture example 3]

Magnetic iron oxide having the characteristics shown in Table 2 was prepared in the same manner as in Preparation Example 1, except that sodium silicate was added so that the silicon content based on the iron content was 0.9%.

[Production Example 4]

Magnetic iron oxide having the characteristics as shown in Table 2 was prepared in the same manner as in Preparation Example 1, except that sodium silicate was added so that the silicon content based on the iron content was 1.7%.

[Comparative Production Example 1]

Magnetic iron oxide having the characteristics as shown in Table 2 was prepared in the same manner as in Preparation Example 1, except that sodium silicate was not added.

[Comparative Production Example 2]

Remarks 1.5 parts by weight of sodium silicate were mixed with 100 parts by weight of the magnetic iron oxide obtained in Production Example 1 by a Henschel mixer to obtain a magnetic iron oxide having the characteristics shown in Table 1.

_{RP DC} ⁴

^{4 4}

⁴

⁴

_{RP DC} ⁴

⁴

⁴

1) N.T.-N.H. = normal temperature and humidity (23.5 ℃ -60% RH)

H.T.-H.H. = High temperature and humidity (32.5 ℃ -85% RH)

L.T.-L.H. = Low temperature low humidity (10 ℃ -15% RH)

2) Numbers in parentheses indicate the number of sheets of paper used for continuous image formation.

3) Evaluation criteria are shown in Table 3.

Example 11

100 parts by weight of styrene / 2-ethylhexyl acrylate / maleic acid n-butyl half ester

Copolymer (copolymer weight ratio = 7/2/1, weight average molecular weight (Mw) = 27 × 10 )

100 parts by weight of magnetic iron oxide of Preparation Example 1

0.8 parts by weight of negative charge control agent (mono-azo dye Cr complex)

3 parts by weight of low molecular weight polypropylene

The mixture of the above components is melt kneaded at 140 ° C. by a twin screw extruder, and after cooling the kneaded mixture, is roughly ground by a hammer mill, finely ground by a jet mill, classified by a fixed wind classifier, and classified. Powder was obtained. Ultrafine powder and coarse powder are 6.8 占 퐉 weight average particles by simultaneously and accurately removing the fine powder and coarse powder from the classified powder by a multi-segment classifier (Nittez Co., Ltd., Elbow Jet Classifier) using the Coanda effect. A negatively charged magnetic toner having a size (D4) was obtained.

The particle size distribution of the negatively charged magnetic toner thus produced was measured by a Coulter counter (Model TA-II manufactured by Coulter Electronics Co., Ltd.) having a diameter of 100 μm as described below. Table 6 shown below shows the data measured in this way. Table 7 shows the particle size distribution data characterizing the magnetic toner of the present invention and some data regarding the magnetic iron oxide used herein.

A magnetic developer was obtained by mixing 100 parts by weight of the magnetic toner and 1.2 parts by weight of hydrophobic silica fine powder treated with silicon oil after treatment with hexamethyldisilazane in a Henschel mixer.

Separately, a commercially available laser beam printer (Canon Co., Ltd., LBP-8II) was modified to provide a resolution of 600 dpi, and the developing device of the laser beam printer was modified as shown in Table 3. The developing sleeve made of aluminum was contacted with a contact pressure of 30 g / cm. Thereafter, the magnetic developer prepared as described above was imaged with a modified ray. As a result, as shown in Table 8, very good results were obtained.

In addition, the displayed image density represents the average value measured at 5 points by a Macbed reflectometer. Consumption represents the average amount of toner consumed per A4 size sheet when successively printing images having an image area ratio of 4% in 1000-1999 sheets and 4000-4999 sheets.

[Examples 12 to 14]

As shown in Table 7, a magnetic toner having a weight average particle size and a particle size distribution was prepared in the same manner as in Example 11 except for using the magnetic iron oxides of Preparation Examples 2, 3, and 4, respectively. .

A magnetic developer was prepared from these magnetic toners, and evaluated in the same manner as in Example 11 to obtain good results as shown in Table 8.

[Examples 15 and 16]

Magnetic notes were prepared in the same manner as in Example 11 except for their weight average particle size and particle size distribution as shown in Table 7. The magnetic developer was prepared from these magnetic toners and evaluated in the same manner as in Example 11, showing slightly inferior dot reproducibility, while showing good continuous printing characteristics as shown in Table 8.

[Comparative Examples 6 and 7]

As shown in Table 7, a magnetic toner having a weight average particle size and a particle size distribution was prepared in the same manner as in Example 11, except that Comparative Preparation Example 1 and 2 magnetic iron oxides were used, respectively. From these magnetic toners, by producing and evaluating the magnetic developer in the same manner as in Example 11, they exhibited clearly inferior continuous printing characteristics as shown in Table 8 as compared with those in Examples 11 to 16.

* Evaluation criteria of cloudy state and dot reproducibility are shown in Table 3.

Example 17

100 parts by weight of styrene / butyl acrylate / divinylbenzene copolymer

(Polymerization weight ratio = 80 / 19.5 / 0.5,

Weight average molecular weight (Mw) = 32 × 10 )

120 parts by weight of magnetic iron oxide of Preparation Example 1

2 parts by weight of mono azo dye-based Cr complex

4 parts by weight of low molecular weight polypropylene

The mixture of the above components is kneaded and kneaded at 140 ° C. by a twin screw compressor, the kneaded product is cooled, then roughly ground by a hammer mill, finely ground by a jet mill, and classified by a fixed wind classifier. Thus, classified powder was obtained. Ultrafine powder and coarse powder were simultaneously removed from the classified blade by a multi-classifier to obtain a negatively charged magnetic tolerant having a weight average particle size of 6.3 μm.

Separately, 100 parts by weight of silica fine powder (Aerosil # 300 manufactured by Nippon Aerosil Co., Ltd.) was treated with 30 parts by weight of dimethyldichlorosilane in order to provide a carbon deposition amount of 2.2% by weight, and dimethylsilicone oil diluted with solvent After mixing 15 parts by weight of Tsugagaku Kogyo KF-96 100cs), the mixture was heated to 190 ° C. under reduced pressure of a solvent and evaporated to remove it, thereby adding 6.5% by weight of carbon (for example, silicon oil treatment). Silica fine powder treated to have a carbon adhesion amount of 4.3% by weight).

Next, 100 parts by weight of the magnetic toner prepared as described above and 1.0 part by weight of the treated silica fine powder were mixed with a Henschel mixer to prepare a magnetic developer.

Separately, a commercially available laser beam printer (LBP-8II manufactured by Canon Inc.) was modified to provide an increased printing speed from 8 sheets / minute to 16 sheets / minute.

Next, the magnetic developer prepared as described above was placed in a modified laser beam printer and used for image formation in the same manner as in the previous example.

Therefore, continuous image formation was performed up to 8000 sheets at room temperature and humidity (23.5 ° C-60% RH).

As in the previous example, the image density measured by the Macbed reflectometer is compared with the whiteness of the new plain paper measured by the reflectometer (manufactured by Tokyo Denshoku Co., Ltd.) and the plain white paper with the solid white image printed thereon. The image is displayed with respect to the blurring state, dot reproducibility after image formation of the checker pattern shown in FIG. 7, and transfer bonding (defects inside the image, that is, hollow image defect) on the transparent film during transfer. Evaluated. The results are shown in Table 9 below.

Similarly, an image forming test was conducted in a high temperature-high humidity (32.5 ° C-85% RH) and low temperature-low humidity (10 ° C-15% RH) environment. The results are also shown in Table 9.

Example 18

100 parts by weight of styrene / butyl acrylate / divinylbenzene copolymer

(Weight ratio = 80 / 19.5 / 0.5, Mw = 32 * 10 )

120 parts by weight of magnetic iron oxide of Preparation Example 2

3 parts by weight of mono azo dye-based Cr complex salt

4 parts by weight of low molecular weight polypropylene

A magnetic toner having a weight average particle size of 5.4 mu m was prepared from the above components in the same manner as in Example 17.

Separately, 100 parts by weight of silica fine powder (Aerosil # 200 manufactured by Nippon Aerosil Co., Ltd.) was treated with 20 parts by weight of dimethyl diclosilane to provide a carbon deposition amount of 1.1% by weight, and dimethyl silicone oil (sil After mixing 15 parts by weight of KF-96 100cs) manufactured by Etsu Chemical Co., Ltd., the mixture is heated to 190 ° C. under reduced pressure of a solvent to be evaporated and removed. To give a treated silica fine powder having a carbon adhesion amount of 4.1% by weight. Then, 100 parts by weight of the magnetic toner prepared as described above and 1.6 parts by weight of the treated silica fine powder were mixed with a Henschel mixer to obtain a magnetic developer.

An image forming test was conducted in the same manner as in Example 17 using the magnetic developer. Moreover, the result is shown in Table 9.

Example 19

100 parts by weight of styrene / butyl acrylate / divinylbenzene copolymer

(Weight ratio = 80 / 19.5 / 0.5, Mw = 32 * 10 )

80 parts by weight of magnetic iron oxide of Preparation Example 3

0.8 parts by weight of mono azo dye-based Cr complex

3 parts by weight of low molecular weight polypropylene

A magnetic toner having a weight average particle size of 7.8 mu m was prepared from the above components in the same manner as in Example 17.

A magnetic developer was prepared by mixing 100 parts by weight of the magnetic toner and 1.0 part by weight of the fine silica powder treated in Example 18 with a Henschel mixer.

An image forming test was carried out in the same manner as in Example 17 using the magnetic developer, and the results are shown in Table 9.

Example 20

100 parts by weight of styrene / ethylhexyl acrylate / divinylbenzene copolymer

(Weight ratio = 80 / 19.5 / 0.5, Mw = 32 * 10 )

90 parts by weight of magnetic iron oxide of Preparation Example 4

1 part by weight of mono azo dye-based Cr complex

3 parts by weight of low molecular weight polypropylene

A magnetic toner having a weight average particle size of 6.9 mu m was prepared from the above components in the same manner as in Example 8.

Separately, 100 parts by weight of silica fine powder (manufactured by Nihon Aerosil Co., Ltd., Aerosil # 200) was treated with 30 parts by weight of trimethyldichlorosilane in order to provide 3.5% by weight of carbon, and dimethylsilicone oil diluted with solvent After mixing 10 parts by weight of Tsuka Chemical Co., Ltd. KF-96 100cs), the mixture was heated to 190 ° C. under reduced pressure of a solvent to be evaporated and removed, whereby a carbon content of 7.1 wt% (ie, 3.6% by silicon oil treatment) was removed. Treated silica fine powder having a weight percent carbon content).

Then, 100 parts by weight of the magnetic toner prepared as described above and 1.0 part by weight of the treated silica fine powder were mixed with a Henschel mixer to prepare a magnetic developer.

An image forming test was conducted in the same manner as in Example 17 using the magnetic developer, and the results are also shown in Table 9.

Example 21

100 parts by weight of silica fine powder (manufactured by Nippon Aerosil Co., Ltd., Aerosil # 200) was treated with 25 parts by weight of dimethyldichlorosilane, and diluted with solvents to provide 1.5% by weight of carbon deposition (Shin-Etsuka). KF-96 100cs) was mixed with 5 parts by weight, and then heated to 190 ° C. under reduced pressure of a solvent to be evaporated and removed, whereby a carbon deposition amount of 4.6% by weight (ie, 3.1% by silicon oil treatment) was applied. Silica fine powder treated to have a carbon content of (% by weight) was obtained.

Next, 1.0 parts by weight of the thus-treated silica fine powder and 100 parts by weight of the magnetic toner of Example 20 were mixed with a Henschel mixer to prepare a magnetic developer.

Using this magnetic developer, chemical formation tests were carried out in the same manner as in Example 17, and the results are also shown in Table 9.

Example 22

100 parts by weight of silica fine powder (manufactured by Nippon Aerosil Co., Ltd., Aerosil # 200) was treated with 20 parts by weight of dimethyldichlorosilane, and diluted with solvent to provide 1.1% by weight of carbon adhesion amount. After mixing 20 parts by weight of Tsuka Chemical Co., Ltd., KF-96 100cs), the mixture was heated to 190 ° C. under reduced pressure of a solvent to be evaporated and removed, thereby adding 7.3% by weight of carbon (ie carbon by silicon oil treatment). The fine silica powder was treated so that the adhesion amount was 6.2% by weight).

Thereafter, 1.0 parts by weight of the fine silica powder thus obtained and 100 parts by weight of the magnetic toner of Example 20 were mixed with a Henschel mixer to prepare a magnetic developer.

Using this magnetic developer, chemical formation tests were carried out in the same manner as in Example 17, and the results are shown in Table 9.

Example 23

100 parts by weight of silica fine powder (Nihon Aerosil Co., Ltd., Aerosil # 200) was treated with 20 parts by weight of dimethyldichlorosilane in order to provide a carbon content of 2.2% by weight, and dimethylsilicone oil diluted with solvent After mixing 15 parts by weight of Tsuka Chemical Co., Ltd., KF-410, the mixture was heated to 190 ° C. under reduced pressure of a solvent to be evaporated to remove it, thereby adding 6.1% by weight of carbon deposition (ie, carbon by silicon oil treatment). Treated silica fine powder having an adhesion amount of 3.9 wt%) was obtained.

Thereafter, 1.0 parts by weight of the fine silica powder thus obtained and 100 parts by weight of the magnetic toner of Example 20 were mixed with a Henschel mixer to prepare a magnetic developer.

Using this magnetic developer, chemical formation tests were carried out in the same manner as in Example 17, and the results are shown in Table 9.

Example 24

100 parts by weight of styrene / butyl acrylate / divinylbenzene copolymer

(Weight ratio = 80 / 19.5 / 0.5, Mw = 32 * 10 )

60 parts by weight of magnetic iron oxide of Preparation Example 2

1 part by weight of mono azo dye-based Cr complex

3 parts by weight of low molecular weight polypropylene

A magnetic toner having a weight average particle size of 11.6 mu m was prepared from the above components in the same manner as in Example 17.

A magnetic developer was prepared by mixing 100 parts by weight of the magnetic toner and 0.6 parts by weight of silica fine powder treated in Example 18 by a Henschel mixer.

The magnetic developer was put into a commercially available laser beam printer (LBP-A404, Canon Corp.), and the image forming test was conducted in the same manner as in Example 17. The results are shown in Table 9.

Comparative Example 8

A magnetic toner having a weight average particle size of 6.5 µm was manufactured in the same manner as in Example 17, except that the magnetic iron oxide of Comparative Preparation Example 1 was used.

A magnetic developer was obtained by mixing 100 parts by weight of the magnetic toner and 1.0 parts by weight of the treated silica fine powder (continuously treated with dimethyldichlorosilane and dimethylsilicone oil) used in Example 18 by a Henschel mixer.

An image forming test was conducted in the same manner as in Example 17 using the magnetic developer, and the results are also shown in Table 9.

Comparative Example 9

100 parts by weight of silica fine powder (Aerosil # 200) was treated with 20 parts by weight of dimethyldichlorosilane.

1.0 parts by weight of the fine silica powder thus obtained and 100 parts by weight of the magnetic toner of Comparative Example 8 were mixed with a Henschel mixer to obtain a magnetic developer.

An image forming test was conducted in the same manner as in Example 17 using the magnetic developer, and the results are also shown in Table 9.

Comparative Example 10

A magnetic toner having a weight average particle size of 6.4 μm was prepared in the same manner as in Example 17, except that the magnetic iron oxide of Comparative Preparation Example 2 was used.

A magnetic developer was prepared by mixing 100 parts by weight of the magnetic toner and 1.0 parts by weight of the treated silica fine powder (treated with dimethyldichlorosilane) used in Example 9 by a Henschel mixer.

An image forming test was conducted in the same manner as in Example 17 using the magnetic developer, and the results are shown in Table 9 below.

* 1) N.T.-N.H. = normal temperature and humidity (23.5 ℃ -60% RH)

H.T.-H.H. = High temperature and humidity (32.5 ℃ -85% RH)

L.T.-L.H. = Low temperature low humidity (10 ℃ -15% RH)

2) The evaluation criteria are shown in Table 3 except for the hollow image defects to be supplemented in the next page.

Hollow image defect

◎: highest amount

○: excellent

○ △: somewhat inferior but not a problem

△: somewhat inferior

×: defective

Example 25

100 parts by weight of styrene / butyl acrylate / divinylbenzene copolymer

(Copolymer weight ratio = 80 / 19.5 / 0.5, weight average molecular weight (Mw) = 32 x 10 )

90 parts by weight of magnetic iron oxide of Preparation Example 1

0.8 parts by weight of mono azo dye-based Cr complex

3 parts by weight of low molecular weight polypropylene

The mixture of the above components is melt kneaded at 140 ° C. by a twin screw extruder, the kneaded material is cooled, roughly ground by a hammer mill, finely ground by a jet mill, classified by a fixed wind classifier, and classified. Powder product was obtained. A negatively charged magnetic toner having a weight average particle size of 6.6 µm was obtained by simultaneously removing the ultra fine powder and the coarse powder from the powder classified by the multi-division classification apparatus.

Separately, 100 parts by weight of silica fine powder (Nihon Aerosil Co., Ltd., Aerosil # 200) was treated with 20 parts by weight of trimethylchlorosilane to form a specific surface area of 160 m 2 / g, and then diluted with dimethyl silicone oil. (Shin-Etsu Chemical Co., Ltd. product, KF-96 100cs) 10 parts by weight of the mixture was mixed, and then heated to 150 ° C. under reduced pressure of a solvent to be evaporated and removed, thereby obtaining a specific surface area of 90 m 2 / g (i.e., silicon). Treated silica fine powder having 0.56 times before treatment with oil) was prepared.

Next, 100 parts by weight of the magnetic toner prepared as described above and 1.0 part by weight of the treated silica fine powder were mixed with a Henschel mixer to obtain a magnetic developer.

Separately, a commercially available laser beam printer (manufactured by Canon Co., Ltd., LBP-8II) was prepared to provide an increased printing speed from 8 sheets / minute to 16 sheets / minute.

Next, the magnetic developer prepared as described above was placed in a modified laser beam printer and used for image formation in the same manner as in the previous example.

Therefore, 8000 series of continuous image formation were performed in a room temperature-humidity (23.5 degreeC-60% RH) environment.

As in the previous example, the image density measured by the Macbed reflectance densitometer and the whiteness of the new plain paper measured by the reflectometer (manufactured by Tokyo Denshoku Co., Ltd.) and the solid white image were calculated by comparing the whiteness of the printed plain paper. In a cloudy state, dot reproducibility after forming the checker pattern image shown in FIG. 7, and transfer defects on the transparent film during transfer (defects inside the image, for example, hollow image defects) The image was evaluated. The results are shown in Table 10 below.

Similarly, an image forming test was conducted in a high temperature-high humidity (32.5 ° C-85% RH) and low temperature-low humidity (10 ° C-15% RH) environment. Table 10 also shows the results.

Example 26

100 parts by weight of styrene / butyl acrylate / divinylbenzene copolymer

(Weight ratio = 80 / 19.5 / 0.5, Mw = 32 * 10 )

100 parts by weight of magnetic iron oxide of Preparation Example 2

1 part by weight of mono azo dye-based Cr complex

4 parts by weight of low molecular weight polypropylene

Except for the above components, a magnetic toner having a weight average particle size of 6.2 μm was prepared in the same manner as in Example 25.

Separately, 100 parts by weight of silica fine powder (manufactured by Nippon Aerosil Co., Ltd., Aerosil # 300) was treated with 30 parts by weight of dimethyldichlorosilane to form a specific surface area of 230 m 2 / g, followed by diluting with dimethylsilylcone diluted with a solvent. After mixing 15 parts by weight of oil (Shin-Etsu Chemical Co., Ltd. product, KF-96 100cs), the mixture was heated to 150 ° C. under reduced pressure of a solvent to be evaporated and removed, whereby a specific surface area of 120 m 2 / g (ie, Silica fine powder having 0.52 times before treatment with silicon oil) was prepared.

Next, 100 parts by weight of the magnetic toner prepared as described above and 1.0 part by weight of the treated silica fine powder were mixed with a Henschel mixer to obtain a magnetic developer.

An image forming test was conducted in the same manner as in Example 25 using the magnetic developer. Table 10 also shows the results.

Example 27

100 parts by weight of styrene / butyl acrylate / divinylbenzene copolymer

(Weight ratio = 80 / 19.5 / 0.5, Mw = 32 * 10 )

80 parts by weight of magnetic iron oxide of Preparation Example 3

1 part by weight of mono azo dye-based Cr complex

3 parts by weight of low molecular weight polypropylene

A magnetic toner having a weight average particle size of 7.5 μm was prepared from the above components in the same manner as in Example 25.

A magnetic developer was prepared by mixing 100 parts by weight of the magnetic toner and 1.0 part by weight of the finely divided silica powder of Example 26 with a Henschel mixer.

An image forming test was conducted in the same manner as in Example 25 using the magnetic developer.

Example 28

100 parts by weight of styrene / butyl acrylate / divinylbenzene copolymer

(Weight ratio = 80 / 19.5 / 0.5, Mw = 32 * 10 )

120 parts by weight of magnetic iron oxide of Preparation Example 4

4 parts by weight of monoazo dye-based Cr complex

4 parts by weight of low molecular weight polypropylene

A magnetic toner having a weight average particle size of 5.2 μm was prepared from the above components in the same manner as in Example 25.

Separately, 100 parts by weight of silica fine powder (Nihon Aerosil Co., Ltd., Aerosil # 200) was treated with 20 parts by weight of dimethyldichlorosilane to form a specific surface area of 180 m 2 / g, and then diluted with solvent 15 parts by weight of oil (Shin-Etsu Chemical Co., Ltd. product, KF-96 100cs) were mixed and then heated to 150 ° C. under reduced pressure of a solvent to be evaporated and removed, whereby a specific surface area of 100 m 2 / g (ie, silicone Treated silica fine powder having 0.56 times before treatment with oil) was prepared.

Next, 100 parts by weight of the magnetic toner prepared as described above and 1.6 parts by weight of the treated fine silica powder were mixed with a Henschel mixer to obtain a magnetic developer.

Using this magnetic developer, an image forming test was conducted in the same manner as in Example 25. Table 10 also shows the results.

Example 29

100 parts by weight of styrene / butyl acrylate / divinylbenzene copolymer

(Weight ratio = 80 / 19.5 / 0.5, Mw = 32 * 10 )

80 parts by weight of magnetic iron oxide of Preparation Example 1

1 part by weight of mono azo dye-based Cr complex

3 parts by weight of low molecular weight polypropylene

A magnetic toner having a weight average particle size of 7.2 mu m was prepared from the above components in the same manner as in Example 25.

Separately, 100 parts by weight of silica fine powder (manufactured by Nippon Aerosil Co., Ltd., Aerosil # 300) was treated with 30 parts by weight of dimethyldichlorosilane to form a specific surface area of 230 m 2 / g, followed by diluting with dimethylsilylcone diluted with a solvent. After mixing 20 parts by weight of oil (Shin-Etsu Chemical Co., Ltd., KF-96 100cs), the mixture is heated to 150 ° C. under reduced pressure of a solvent to be evaporated and removed, whereby a specific surface area of 100 m 2 / g (ie, The treated silica fine powder having 0.43 times before treatment with silicon oil) was prepared.

Next, 100 parts by weight of the magnetic toner prepared as described above and 0.8 parts by weight of the treated silica fine powder were mixed with a Henschel mixer to obtain a magnetic developer.

Using this magnetic developer, an image forming test was conducted in the same manner as in Example 25. Table 10 also shows the results.

Example 30

100 parts by weight of silica fine powder (Nihon Aerosil Co., Ltd., Aerosil # 300) was treated with 35 parts by weight of dimethyldichlorosilane to form a specific surface area of 210 m 2 / g, and then diluted with solvent It is mixed with 5 parts by weight of Shin-Etsu Chemical Co., Ltd., KF-96 100cs), heated to 150 ° C. under reduced pressure of a solvent and evaporated to remove it, thereby obtaining a specific surface area of 125 m 2 / g (ie, silicone oil). Treated silica fine powder having 0.59 times before treatment with).

Next, 0.8 parts by weight of the silica fine powder thus prepared and 100 parts by weight of the magnetic toner of Example 29 were mixed with a Henschel mixer to obtain a magnetic developer.

Using this magnetic developer, an image forming test was conducted in the same manner as in Example 25.

Table 10 also shows the results.

Example 31

100 parts by weight of silica fine powder (Nihon Aerosil Co., Ltd. product, Aerosil # 200) was treated with 20 parts by weight of trimethylchlorosilane to form a specific surface area of 160 m 2 / g, and then diluted with solvent, α-methylstyrene- It is mixed with 15 parts by weight of modified silicone oil (Shin-Etsu Chemical Co., Ltd., KF-410), heated to 150 ° C. under reduced pressure of a solvent, and evaporated to remove it. Thus, a specific surface area of 80 m 2 / g (ie, Treated silica fine powder having 0.5 times the pretreatment with silicon oil).

Next, 0.8 parts by weight of the silica fine powder thus obtained and 100 parts by weight of the magnetic toner of Example 29 were mixed with a Henschel mixer to obtain a magnetic developer.

Using this magnetic developer, an image forming test was conducted in the same manner as in Example 25. Table 10 also shows the results.

Example 32

100 parts by weight of styrene / butyl acrylate / divinylbenzene copolymer

(Weight ratio = 80 / 19.5 / 0.5, Mw = 32 * 10 )

60 parts by weight of magnetic iron oxide of Preparation Example 2

2 parts by weight of mono azo dye-based Cr complex

3 parts by weight of low molecular weight polypropylene

A magnetic toner having a weight average particle size of 11.8 μm was prepared from the above components in the same manner as in Example 25.

A magnetic developer was prepared by mixing 100 parts by weight of the magnetic toner and 0.6 parts by weight of the treated fine silica powder of Example 26 with a Henschel mixer.

This magnetic developer was placed in a commercially available laser beam printer (LBP-A404, manufactured by Canon Corporation), and an image forming test was conducted in the same manner as in Example 25. Table 10 shows the results.

Comparative Example 11

A magnetic toner having a weight average particle size of 6.8 μm was prepared in the same manner as in Example 25, except that the magnetic iron oxide of Comparative Preparation Example 1 was used.

100 parts by weight of the magnetic toner and 1.0 parts by weight of the treated fine silica powder (continuously treated with trimethylchlorosilane and dimethylsilicone oil) used in Example 25 were mixed with a Henschel mixer to obtain a magnetic developer.

Using this magnetic developer, an image forming test was conducted in the same manner as in Example 25. Table 10 also shows the results.

Comparative Example 12

100 parts by weight of silica fine powder (Aerosil # 200) was treated with 20 parts by weight of dimethyldichlorosilane.

1.0 parts by weight of the silica fine powder thus obtained and 100 parts by weight of the magnetic toner of Comparative Example 11 were mixed with a Henschel mixer to obtain a magnetic developer.

Using this magnetic developer, an image forming test was conducted in the same manner as in Example 25. Table 10 also shows the results.

Comparative Example 13

A magnetic toner having a weight average particle size of 6.7 μm was prepared in the same manner as in Example 25, except that the magnetic iron oxide of Comparative Preparation Example 2 was used.

A magnetic developer was obtained by mixing 100 parts by weight of the magnetic toner and 1.0 parts by weight of silica fine powder (treated with dimethyldichlorosilane) for use in Comparative Example 12 with a Henschel mixer.

Using this magnetic developer, an image forming test was conducted in the same manner as in Example 25. Table 10 also shows the results.

Claims (65)

The image forming apparatus includes a latent image bearing member supporting a latent image and a developing apparatus for developing a latent image, the developing apparatus comprising a developer container accommodating a developer and a latent image bearing member facing from the developer container. An image forming apparatus having a developer carrying member for carrying and carrying a developer in a developing area, wherein the developer contains a magnetic toner comprising a binder resin and magnetic iron oxide, wherein the magnetic iron oxide is a silicon element. When the content is 0.5 to 4% by weight based on the total iron element content, and the total silicon element content of the magnetic iron oxide is assumed to be (A), when the iron element dissolution rate of the magnetic iron oxide is dissolved to 20% by weight, Assuming that the silicon element content dissolved together is (B) and the silicon element content present on the surface is (C), the relationship of (B / A) × 100-44 to 84% is satisfied, and (C / A) × 100 = 10-55% The magnetic toner has a weight average particle size of 13.5 µm or less, and has a particle size distribution such that the content of magnetic toner particles having a particle size of 12.7 µm or more is 50% by weight or less. Image forming apparatus. The image forming apparatus according to claim 1, wherein the magnetic iron oxide contains 0.8 to 3.0% by weight of silicon element based on the total content of iron. The image forming apparatus according to claim 1, wherein the magnetic iron oxide contains 0.9 to 3.0% by weight of silicon element based on the total content of iron. An image forming apparatus according to claim 1, wherein the magnetic iron oxide satisfies a relationship of (B / A) x 100 = 60 to 80%. An image forming apparatus according to claim 1, wherein the magnetic iron oxide satisfies a relationship of (C / A) x 100 = 25 to 40%. The method according to claim 1, wherein the magnetic iron oxide contains 0.8 to 3.0% by weight of the silicon element based on the total content of iron, (B / A) x 100 = 60 to 80% of the relationship and (C / A) An image forming apparatus characterized by satisfying a relationship of x100 = 25 to 40%. 7. An image forming apparatus according to claim 6, wherein the magnetic iron oxide contains 0.9 to 3.0% by weight of silicon element based on the total content of iron. The image forming apparatus according to claim 1, wherein the magnetic iron oxide has an average particle size of 0.1 to 0.4 mu m. The image forming apparatus according to claim 1, wherein the magnetic iron oxide has an average particle size of 0.1 to 0.3 mu m. The image forming apparatus according to claim 1, wherein the magnetic iron oxide has a triboelectric charge characteristic of -25 to -70 mu c / g. The image forming apparatus of claim 1, wherein the magnetic iron oxide has a triboelectric charge characteristic of −40 to −60 μc / g. The image forming apparatus according to claim 1, wherein the magnetic iron oxide has a volume specific resistance value of 5 × 10 ^{3 to} 1 × 10 ⁸ Pa · cm. The image forming apparatus according to claim 1, wherein the magnetic iron oxide has a volume specific resistance value of 5 × 10 ^{4 to} 5 × 10 ⁷ Pa · cm. The image forming apparatus of claim 1, wherein the magnetic iron oxide has a degree of aggregation of 3 to 40%. The image forming apparatus of claim 1, wherein the magnetic iron oxide has a degree of aggregation of 5 to 30%. The image forming apparatus according to claim 1, wherein the magnetic iron oxide has a smoothness (D) of 0.2 to 0.6. The image forming apparatus according to claim 1, wherein the magnetic iron oxide has a smoothness (D) of 0.3 to 0.5. The image forming apparatus of claim 1, wherein the magnetic iron oxide has a spherical degree Φ of 0.8 or more. The image forming apparatus of claim 1, wherein the magnetic iron oxide has a spherical degree Φ of 0.85 or more. The image forming apparatus of claim 1, wherein the magnetic iron oxide has a spherical degree Φ of 0.9 or more. The image forming apparatus according to claim 1, wherein the magnetic toner has a weight average particle size of 3.5 to 13.5 mu m. The image forming apparatus according to claim 1, wherein the magnetic toner has a weight average particle size of 5.0 to 13.0 mu m. The image forming apparatus according to claim 1, wherein the magnetic toner has a weight average particle size of 3.5 to 13.5 mu m and contains 40 wt% or less of magnetic toner particles having a particle size of 12.7 mu m or more. The image forming apparatus according to claim 1, wherein the magnetic toner has a weight average particle size of 5.0 to 13.0 mu m and contains 40 wt% or less of magnetic toner particles having a particle size of 12.7 mu m or more. 2. The magnetic toner according to claim 1, wherein the magnetic toner has a weight average particle size of 6 to 8 mu m, contains 17 to 60 number% of toner particles having a particle size of 5 mu m or less, and has a particle size of 6.35 to 10.08 mu m. It has a particle size distribution so as to contain 5 to 50% by volume of toner particles and 2.0% by volume or more of toner particles having a particle size of 12.7 µm or more, and annular in number% (N%) and volume% (V%). So that the content of the toner particles of 5 mu m or less satisfies the relationship of N / V = 0.05 N + K, K is a positive number of 4.6 to 6.7, and N is a positive number of 17 to 60. The image forming apparatus according to claim 1, wherein the magnetic iron oxide is contained in an amount of 20 to 200 parts by weight based on 100 parts by weight of the binder resin. The image forming apparatus according to claim 1, wherein the magnetic iron oxide is contained in an amount of 30 to 150 parts by weight based on 100 parts by weight of the binder resin. The image forming apparatus of claim 1, wherein the binder resin is made of a styrene copolymer. The image forming apparatus according to claim 1, wherein the binder resin is made of a polyester resin. The image forming apparatus according to claim 1, wherein the magnetic toner is mixed with inorganic fine powder, hydrophobic inorganic fine powder or resin fine particles. 31. The image forming apparatus according to claim 30, wherein the hydrophobic inorganic fine powder is made of hydrophobic silica fine powder. 32. An image forming apparatus according to claim 31, wherein 0.1 to 5 parts by weight of hydrophobic silica fine powder is mixed with 100 parts by weight of the magnetic toner. 32. An image forming apparatus according to claim 31, wherein 0.1 to 3 parts by weight of hydrophobic silica powder is mixed with 100 parts by weight of the magnetic toner. 31. The image forming apparatus according to claim 30, wherein the resin fine particles have a chargeability of the same polarity as that of the magnetic toner. 35. An image forming apparatus according to claim 34, wherein the resin fine particles have an average particle size of 0.03 to 2.0 mu m. The image forming apparatus according to claim 30, wherein 0.1 to 5 parts by weight of the inorganic fine powder is mixed with 100 parts by weight of the magnetic toner. An image forming apparatus according to claim 30, wherein 0.1 to 3 parts by weight of the inorganic fine powder is mixed with 100 parts by weight of the magnetic toner. The image forming apparatus according to claim 30, wherein the magnetic iron oxide contains 0.8 to 3.0% by weight of silicon element based on the total content of iron. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic iron oxide contains 0.9 to 3.0% by weight of silicon element based on the total content of iron. An image forming apparatus according to claim 30, wherein said magnetic iron oxide satisfies a relationship of (B / A) x 100 = 60 to 80%. An image forming apparatus according to claim 30, wherein said magnetic iron oxide satisfies a relationship of (C / A) x 100 = 25 to 40%. 31. The magnetic iron oxide according to claim 30, wherein the magnetic iron oxide contains 0.8 to 3.0% by weight of a silicon element based on the total content of iron, and has a relationship of (B / A) x 100 = 60 to 80% and (C / A). An image forming apparatus characterized by satisfying a relationship of x100 = 25 to 40%. The image forming apparatus according to claim 42, wherein the magnetic iron oxide contains 0.9 to 3.0 wt% of silicon element based on the total content of iron. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic iron oxide has an average particle size of 0.1 to 0.4 mu m. 4. The image forming apparatus as claimed in claim 3, wherein the magnetic iron oxide has an average particle size of 0.1 to 0.3 mu m. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic iron oxide has a triboelectric charge characteristic of -25 to -70 mu c / g. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic iron oxide has a triboelectric charge characteristic of -40 to -60 mu c / g. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic iron oxide has a volume specific resistance value of 5x10 ^{3 to} 1x10 ⁸ Pa · cm. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic iron oxide has a volume specific resistance value of 5 x 10 ^{4 to} 5 x 10 ⁷ Pa · cm. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic iron oxide has a degree of aggregation of 3 to 40%. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic iron oxide has a degree of aggregation of 5 to 30%. 31. An image forming apparatus according to claim 30, wherein said magnetic iron oxide has a smoothness (D) of 0.2 to 0.6. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic iron oxide has a smoothness (D) of 0.3 to 0.5. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic iron oxide has a spherical degree Φ of 0.8 or more. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic iron oxide has a sphericity (Φ) of 0.85 or more. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic iron oxide has a spherical degree Φ of 0.9 or more. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic toner has a weight average particle size of 3.5 to 13.5 mu m. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic toner has a weight average particle size of 5.0 to 13.0 mu m. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic toner has a weight average particle size of 3.5 to 13.5 mu m and contains 40 wt% or less of magnetic toner having a particle size of 12.7 mu m or more. 31. The image forming apparatus as claimed in claim 30, wherein the magnetic toner has a weight average particle size of 5.0 to 13.0 mu m and contains 40 wt% or less of magnetic toner particles having a particle size of 12.7 mu m or more. 31. The magnetic toner according to claim 30, wherein the magnetic toner has a weight average particle size of 6 to 8 mu m, contains 17 to 60 number% of toner particles having a particle size of 5 mu m or less, and has a particle size of 6.35 to 10.08 mu m. It has a particle size distribution to contain 5 to 50% by volume of toner particles and 2.0% by volume or more of toner particles having a particle size of 12.7 µm or more, and converts into number% (N%) and volume% (V%). So that the content of the toner particles of 5 mu m or less satisfies the relationship of N / V = -0.05 N + K, K is a positive number of 4.6 to 6.7, and N is a positive number of 17 to 60. An image forming apparatus according to claim 30, wherein 20 to 200 parts by weight of magnetic iron oxide is contained with respect to 100 parts by weight of the binder resin. 31. An image forming apparatus according to claim 30, wherein the magnetic iron oxide is contained in an amount of 30 to 150 parts by weight based on 100 parts by weight of the binder resin. 31. The image forming apparatus as claimed in claim 30, wherein the binder resin is made of a styrene copolymer. 31. An image forming apparatus according to claim 30, wherein said binder resin is made of a polyester resin.