JPH07175262A - Magnetic, toner, process cartridge and image forming method - Google Patents

Abstract

PURPOSE:To obtain a magnetic toner excellent in electrostatic charge characteristics even at a high humidity and excellent in stability after it is allowed to stand over a long period of time, to obtain a process cartridge with the magnetic toner and to provide an image forming method using the magnetic toner. CONSTITUTION:This magnetic toner contains at least a bonding resin and magnetic iron oxide and has <=13.5mum weight average particle diameter. In the particle size distribution of this magnetic toner, the content of magnetic toner particles each having >=12.7mum particle diameter is <=50wt.%. The magnetic iron oxide contains 0.4-2.0wt.% elemental silicon basing on the amt. of elemental iron and the atomic ratio of Fe to Si in the outermost surface of the magnetic iron oxide is 1.2-4.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a magnetic toner for visualizing an electrostatic latent image in an image forming method such as electrophotography and electrostatic recording, a process cartridge having the magnetic toner, and the magnetic toner. Image forming method.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic method, U.S. Pat. No. 2,297,691 and JP-B-42-23910 are known.
Publication (US Pat. No. 3,666,363) and Japanese Patent Publication No. 43-24748 (US Pat. No. 4,074)
As described in Japanese Patent No. 1,361), many methods are known. Generally, a photoconductive substance is used to form an electrical latent image on a photoconductor by various means,
Then, the latent image is developed with toner to form a visible image, and if necessary, the toner image is transferred onto a transfer material such as paper, and then fixed by heating, pressure, heating and pressing, and a copy or print is made. Is what you get.

Various developing methods are known in which an electrostatic latent image is visualized using toner. For example, US Pat. No. 2,87
The magnetic brush method described in US Pat. No. 4,063, the cascade developing method described in US Pat. No. 2,618,552 and the US Pat. No. 2,221,776 US Pat. Many developing methods such as powder cloud method, fur brush developing method and liquid developing method are known. Among these developing methods, in particular, a magnetic brush method, a cascade method, a liquid developing method and the like using a developer mainly containing toner and carrier have been put into practical use. All of these methods are excellent methods in which a good image can be obtained relatively stably, but on the other hand, there are problems associated with the two-component developer, such as deterioration of the carrier and fluctuation of the mixing ratio of the toner and the carrier.

In order to solve such a problem, various developing methods using a one-component developer composed of only toner have been proposed. Among them, most of them are excellent in the method of using a developer composed of magnetic toner particles.

US Pat. No. 3,909,258 proposes a developing method using a magnetic toner having electrical conductivity. This is a method in which a conductive magnetic toner is supported on a cylindrical conductive sleeve having magnetism inside, and this is brought into contact with an electrostatic image carrier having an electrostatic image for development. At this time, in the developing section, a conductive path is formed by the toner particles between the surface of the recording material and the surface of the sleeve,
Electric charges are introduced from the sleeve to the magnetic toner particles through the conductive path, and the toner particles adhere to the image portion and are developed by the cloning force between the image portion of the electrostatic image and the magnetic toner particles. This developing method using a conductive magnetic toner is an excellent method that avoids the problems associated with the conventional two-component developing method, but on the other hand, since the toner is conductive, the electrostatic image bearing member having a toner image is transferred to a plain paper. However, there is a problem that it is difficult to electrostatically transfer to a final support member such as.

As a developing method using a high-resistance magnetic toner capable of being electrostatically transferred, there is a developing method utilizing dielectric polarization of toner particles. However, such a method inherently has a problem that the developing speed is slow and the density of the developed image is not sufficiently obtained.

As another developing method using a high-resistance insulating magnetic toner, the magnetic toner particles are triboelectrically charged by friction between the magnetic toner particles, friction between the magnetic toner particles and the sleeve, etc. A method of developing an electrostatic image with toner is known. However, these methods have a problem that the number of contacts between the magnetic toner particles and the friction member is small and triboelectric charging tends to be insufficient, and the charged magnetic toner particles tend to aggregate on the sleeve due to an increased cloning force between the magnetic toner particles and the sleeve. Have a point.

In Japanese Patent Laid-Open No. 55-18656 (corresponding US Pat. Nos. 4395476 and 4473627), a new jumping developing method which eliminates the above-mentioned problems is proposed. This involves applying a very thin coating of magnetic toner on a sleeve, tribocharging it, and then developing the magnetic toner layer on the sleeve close to the electrostatic image. This method increases the chance of contact between the sleeve and the magnetic toner by applying the magnetic toner very thinly on the sleeve, and enables sufficient triboelectrification of the magnetic toner. By relatively moving the magnetic toner and the magnetic toner, the magnetic toner particles are prevented from aggregating with each other and sufficiently rubbed with the sleeve, and so on, an excellent image can be obtained.

In the insulating toner used in the above-mentioned developing method, a considerable amount of fine powdery magnetic material is mixed and dispersed, and a part of the magnetic material is exposed on the surface of the toner particles. The type of the toner affects the fluidity and triboelectricity of the magnetic toner. As a result, it affects various characteristics required for the magnetic toner such as developing characteristics and durability of the magnetic toner.

More specifically, in the conventional jumping developing method using a magnetic toner containing a magnetic material, if a repeated developing process (for example, copying) is continued for a long period of time, the developer containing the magnetic toner is Liquidity decreases,
Sufficient triboelectrification cannot be obtained, charging is likely to be non-uniform, and fogging is likely to occur in a low temperature and low humidity environment, which is likely to cause a problem in image quality. When the adhesiveness between the binder resin forming the magnetic toner particles and the magnetic material is weak, the magnetic material is removed from the surface of the magnetic toner particles by the repeated development process, which may adversely affect the density of the toner image. Tend to give.

When the dispersion of the magnetic substance in the magnetic toner particles is not uniform, the magnetic toner particles containing a large amount of the magnetic substance and having a small particle size are accumulated on the sleeve, which is called image density reduction and sleeve ghost. Occurrence of uneven light and shade may be observed.

Conventionally, regarding magnetic iron oxide contained in a magnetic toner, JP-A-62-279352 (corresponding US Pat. No. 4820603) and JP-A-62-278131 are disclosed.
No. 4,975,214 (corresponding US Pat. No. 4,975,214) proposes a magnetic toner containing magnetic iron oxide particles containing a silicon element. Such magnetic iron oxide particles,
Although the elemental silicon is intentionally present inside the magnetic iron oxide particles, there is still a point to be improved in the fluidity of the magnetic toner containing the magnetic iron oxide particles.

Japanese Patent Publication No. 3-9045 (corresponding European Patent Application Publication EP-A187434) proposes to control the shape of magnetic iron oxide particles to be spherical by adding a silicate. Since the magnetic iron oxide particles obtained by this method use a silicate for controlling the particle size, a large amount of silicon element is distributed inside the magnetic iron oxide particles, and the amount of silicon element present on the surface of the magnetic iron oxide particles is large. Is less likely to improve the fluidity of the magnetic toner insufficiently.

JP-A-61-34070 proposes a method for producing ferric tetraoxide by adding a hydroxosilicate solution during the oxidation reaction to ferric tetraoxide. The ferrosoferric oxide particles produced by this method have Si
Although it has an element, it has a problem that the Si element exists as a layer near the surface of the ferrosoferric oxide particles, and the surface is weak against mechanical impact such as friction.

In order to solve the above problems, the inventors of the present invention disclosed in Japanese Patent Application Laid-Open No. 5-72801 (corresponding European Patent Application Publication EP-A533069) that an acidic iron oxide particle contains a silicon element, and , Near the surface of the magnetic particles,
A magnetic toner containing magnetic iron oxide particles having a total elemental silicon content of 44 to 84% was proposed.

However, in the magnetic toner containing the magnetic iron oxide particles, the toner fluidity and the adhesiveness between the binder resin and the magnetic iron oxide particles are improved, but the magnetic properties described in the production examples are improved. In the iron oxide particles, a large amount of silicic acid component is present on the outermost surface, and a pore structure is formed on the surface of the magnetic iron oxide particles, so that the BET specific surface area of the magnetic iron oxide particles is increased. The magnetic toner containing particles tended to have a considerably deteriorated triboelectrification property after being left in a high humidity environment for a long period of time.

Further, Japanese Patent Application Laid-Open No. 4-362954 (corresponding European Patent Application Publication EP-A468525) discloses that
Although magnetic iron oxide particles containing both silicon element and aluminum element are disclosed, further improvement of environmental characteristics is desired.

Further, JP-A-5-213620 discloses magnetic iron oxide particles containing a silicon component and having the silicon component exposed on the surface. Improvement is desired.

In recent years, the functions of image forming apparatuses using electrophotography, such as copying machines and laser beam printers, have been diversified, and there is a demand for higher definition and higher image quality of toner images obtained. There are various storage environments for toner and process cartridges filled with toner, and storage stability is indispensable as a toner characteristic.

[0020]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic toner which solves the above problems.

A further object of the present invention is that the image density is high,
It is to provide a magnetic toner having excellent image reproducibility.

A further object of the present invention is to provide a magnetic toner which is free from fog even when used for a long time and has stable charging performance.

A further object of the present invention is to provide a magnetic toner which has excellent charging characteristics even under high humidity and which has excellent long-term storage stability.

It is a further object of the present invention to provide a process cartridge containing the magnetic toner and an image forming method using the magnetic toner.

[0025]

The present invention provides a magnetic toner containing at least a binder resin and magnetic iron oxide, wherein the magnetic toner has a weight average particle diameter of 13.5 μm or less. Particle size in particle size distribution is 12.
The content of the magnetic toner particles of 7 μm or more is 50% by weight or less, and the magnetic iron oxide has a silicon element content of 0.4 to 2.0% by weight based on the iron element. And a Fe / Si atomic ratio on the outermost surface of the magnetic iron oxide is 1.2 to 4.0.

The present invention further relates to a magnetic toner characterized in that the magnetic iron oxide has a smoothness of 0.3 to 0.8.

Further, the present invention relates to a magnetic toner characterized in that the magnetic iron oxide has a bulk density of 0.8 g / cm ³ or more.

Further, the present invention relates to a magnetic toner characterized in that the specific surface area of the magnetic iron oxide is 15.0 m ² / g or less.

Furthermore, the present invention relates to a magnetic toner characterized in that the magnetic iron oxide is treated with 0.01 to 2.0% by weight of aluminum hydroxide in terms of aluminum element.

Furthermore, the present invention relates to a magnetic toner characterized in that the Fe / Al atomic ratio on the outermost surface of the magnetic iron oxide is 0.3 to 10.0.

Further, according to the present invention, in a process cartridge which can be attached to and detached from the main body of the image forming apparatus, an electrostatic charge image carrier and a developing process for developing the electrostatic charge image formed on the electrostatic charge image carrier using a developer. The developer has a magnetic toner containing at least a binder resin and magnetic iron oxide particles, and the magnetic toner has a weight average particle diameter of 13.5.
In the particle size distribution of the magnetic toner, the content of the magnetic toner particles having a particle size of 12.7 μm or more is 50% by weight or less, and the magnetic iron oxide particles contain the silicon element of the magnetic iron oxide particles. Content rate is 0.4 based on iron element
˜2.0 wt%, and the Fe / Si atomic ratio on the outermost surface of the magnetic iron oxide particles is 1.2 to 4.0.

Furthermore, the present invention provides an electrostatic charge image forming method for forming an electrostatic charge image on an electrostatic charge image carrier and developing the electrostatic charge image with a magnetic toner held in a developing means to form a toner image. The magnetic toner for developing a charge image contains at least a binder resin and magnetic iron oxide particles, and the magnetic toner has a weight average particle diameter of 13.5 μm or less,
In the particle size distribution of the magnetic toner, the content of magnetic toner particles having a particle size of 12.7 μm or more is 50% by weight or less,
The magnetic iron oxide particles have a silicon element content of 0.4 to 2.0% by weight based on the iron element, and Fe / S on the outermost surface of the magnetic iron oxide particles.
The present invention relates to an image forming method having an i atomic ratio of 1.2 to 4.0.

With the increase in the speed and the increase in the number of durable sheets in image forming apparatuses such as printers, it is required to improve the durability of toner.

The inventors of the present invention have controlled the average particle size and particle size distribution of the magnetic toner, the outermost surface of the magnetic iron oxide particles, the composition and the structure of the magnetic toner so that the magnetic toner containing the magnetic iron oxide particles has fluidity. Excellent, long-term storage stability, durability, uniform dispersion of the magnetic substance in the magnetic toner particles,
It has been found that a magnetic toner having excellent physical properties can be obtained.

In the magnetic toner of the present invention, the weight average particle diameter is 13.5 μm or less (preferably 3.5 to 13.5).
μm, more preferably 4.0-11.0 μm),
In the particle size distribution of the magnetic toner, the content of 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, more preferably 30% by weight or less). One of the characteristics is to use specific magnetic iron oxide particles containing an element.

The weight average particle diameter of the magnetic toner is 13.5 μm.
Or the content of the magnetic toner particles having a particle diameter of 12.7 μm or more exceeds 50% by weight, the resolution of the magnetic toner is lowered and fog is apt to occur.

Further, when the weight average particle diameter of the magnetic toner particles is smaller than 3.5 μm, the fluidity of the magnetic toner becomes low even if the special magnetic iron oxide particles used in the present invention are used, and charging failure is caused. Fog, light density, and further, the specific surface area of the toner increases, and problems such as a marked deterioration in storage stability are likely to occur. Therefore, the weight average particle diameter is 3.
It is preferably 5 μm or more.

In the magnetic toner of the present invention, the content of silicon element in the magnetic iron oxide particles is from 0.4 to 0.4 based on the iron element.
2.0 wt% (more preferably 0.5 to 0.9 wt%), and F on the outermost surface of the magnetic iron oxide particles
Magnetic iron oxide particles having an e / Si atomic ratio of 1.2 to 4.0 are used.

Fe / S on the outermost surface of magnetic iron oxide particles
The atomic ratio of i is measured by X-ray photoelectron spectroscopy (XPS).

When the content of the elemental silicon is less than 0.4% by weight or the Fe / Si atomic ratio exceeds 4.0, the effect of improving the magnetic toner, particularly the degree of improvement of the fluidity of the magnetic toner, is reduced. Low. When the content of the silicon element is more than 2.0% by weight or the Fe / Si atomic ratio is less than 1.2, the environmental characteristics, particularly the long-term storage under high humidity, deteriorates the charging property. Furthermore, the durability of the magnetic toner and the dispersibility of the magnetic iron oxide particles in the binder resin are also reduced.

The amount of silicon atoms on the outermost surface of the magnetic iron oxide particles has a correlation with the fluidity and water absorption of the magnetic iron oxide particles, and has a great influence on the physical properties of the magnetic toner containing the magnetic iron oxide particles.

Further, as a preferred system of the present invention, the magnetic iron oxide particles have a smoothness of 0.3 to 0.8, preferably 0.
It is to satisfy 45 to 0.7, and more preferably 0.5 to 0.7. The smoothness in the present invention is related to the amount of pores on the surface of the magnetic iron oxide particles, and when the smoothness is less than 0.3,
There are many pores on the surface of magnetic iron oxide, and water adsorption is promoted.

Further, one of the more preferable systems of the present invention is that the magnetic iron oxide particles have a bulk density of 0.8 g / cm ³ or more, preferably 1.0 g / cm ³ or more.

The magnetic iron oxide particles have a bulk density of 0.8 g / cm.
^{When it is} less than ³ , it adversely affects the physical mixing property with other toner materials at the time of toner production, and the dispersibility of the magnetic iron oxide particles decreases.

Further, as one of the more preferable systems of the present invention, the magnetic iron oxide particles have a BET specific surface area of 15.0 m.
² / g or less, preferably 12.0 m ² / g or less. BET specific surface area of magnetic iron oxide particles is 1
If it exceeds 5.0 m ² / g, the water adsorption property of the magnetic iron oxide particles increases, which adversely affects the hygroscopicity and the charging property of the magnetic toner containing the magnetic iron oxide particles.

As a result of intensive studies, the present inventors have found that the water adsorption properties of magnetic iron oxide particles are greatly related to the pores on the surface thereof, and it is most important to control the pore volume. I found it. The total pore volume of the magnetic iron oxide particles is 7.0 × 10 ^{−3 to} 15.0 × 10 ⁻³ ml /
g, more preferably 8.0 × 10 ^{−3 to} 12.0 × 10
It is preferably ⁻³ ml / g.

When the total pore volume is less than 7.0 × 10 ⁻³ ml / g, the adhesion to the binder resin is weak and the magnetic iron oxide particles are detached from the magnetic toner particles, resulting in the image. It is likely to have adverse effects such as a decrease in concentration. Further, the surface pores of the magnetic iron oxide particles are greatly involved in the adsorption of water, and have a great influence on the water adsorption property of the magnetic toner containing the magnetic iron oxide particles. The surface water content of the magnetic toner is greatly related to the charging characteristics of the toner.

The surface total pore volume of the magnetic iron oxide particles is 7.0.
When it is less than × 10 ^-3 ml / g, the water retention capacity of the magnetic iron oxide particles is significantly reduced. Therefore, in an environment of low humidity, the magnetic toner containing the magnetic iron oxide is likely to be charged up and the image density is likely to be lowered.

When the total pore volume exceeds 15.0 × 10 ^-3 ml / g, the water adsorption property of the magnetic iron oxide particles increases.
Therefore, in an environment of high humidity, the magnetic toner containing the magnetic iron oxide particles is liable to absorb moisture when left to stand, resulting in a decrease in charge amount, and as a result, a decrease in image density.

Further, in the magnetic iron oxide particles used in the present invention, in the surface pore distribution, the total specific surface area of pores (micropores) having a pore diameter of less than 20 Å is 20 Å or more (20 Å to 500 Å). It is preferable that the total specific surface area of the pores (mesopores) is less than or equal to the total specific surface area.

The surface pore size of the magnetic iron oxide particles has a great influence on the adsorption of water, and in the case of small pores, the adsorbed water is difficult to desorb. When the total specific surface area of the pores of the magnetic iron oxide particles having a pore diameter of less than 20 Å exceeds the total specific surface area of the pores having a pore diameter of 20 Å or more, there are more adsorption sites where adsorbed water is difficult to desorb. In the magnetic toner containing the magnetic iron oxide particles, especially when left for a long time under high humidity, the charging property is remarkably deteriorated, and it is difficult to recover the charging property.

Further, it is preferable that the magnetic iron oxide particles used in the present invention basically cause no hysteresis on the adsorption and desorption isotherms of nitrogen on the adsorption side and the desorption side. It is preferable that the adsorption gas desorption amount difference at any relative pressure on the isotherm is 4% or less.

Hysteresis (that is, a difference) is generated in the adsorption-desorption isotherm due to nitrogen, which has an ink bottle type pore in which the pore inlet is narrow and the internal pore is widened. Therefore, the adsorbed substance (water) is not easily desorbed, which adversely affects the charging characteristics of the toner containing the magnetic iron oxide particles, especially under high humidity.

Further, the magnetic iron oxide particles used in the present invention have a water content at a temperature of 23.5 ° C. and a humidity of 65% RH,
0.4-1.0 wt% (more preferably 0.45-
0.90% by weight) and a temperature of 32.5 ° C./humidity of 8
The water content at 5% RH is 0.6 to 1.5% by weight (more preferably 0.60 to 1.10% by weight), and the difference in water content between the environments is 0.6% by weight. It is preferably below (more preferably 0.3% by weight or less).

When the amount is below the above range, the magnetic toner is likely to be charged up especially under low humidity.
It tends to cause a decrease in the amount of charge. Furthermore, when the difference in water content between the environments exceeds 0.6% by weight, image characteristic differences due to the environment differences occur, which is not very preferable.

Furthermore, the magnetic iron oxide particles used in the present invention contain 0.01 to 2.0% by weight (more preferably 0.05 to 1.0% by weight) of aluminum hydroxide in terms of aluminum element. It is preferably treated with a product.

Although the reason is not clear, it was confirmed that it is possible to further stabilize the charging of the magnetic toner by treating the surface of the magnetic iron oxide particles with aluminum hydroxide. If it is less than 0.01% by weight in terms of aluminum element, its effect is small, and if it exceeds 2.0% by weight, the environmental characteristics of the magnetic toner, particularly the charging characteristics under high humidity, are likely to deteriorate.

Further, the Fe / Al atomic ratio on the outermost surface of the magnetic iron oxide particles used in the present invention is 0.3 to 1.
It is preferably 0.0 (more preferably 0.3 to 5.0, further preferably 0.3 to 2.0). When the Fe / Al atomic ratio on the outermost surface of the magnetic iron oxide particles is less than 0.3, the environmental characteristics of the toner, particularly the charging characteristics under high humidity, are easily deteriorated, and when it exceeds 10.0, the charge stabilization is performed. Cannot be obtained.

Further, the magnetic iron oxide particles used in the present invention have an average particle size of 0.1 to 0.4 μm, preferably 0.1.
It is preferable to have ~ 0.3 μm.

The method of measuring various physical property data in the present invention will be described in detail below.

(1) Particle size distribution of magnetic toner The particle size distribution of the magnetic toner can be measured by various methods. In the present invention, it is measured using a Coulter counter.

As a measuring device, Coulter Counter TA-II (manufactured by Coulter Co.) is used. 1 electrolyte
Prepare about 1% NaCl aqueous solution with grade sodium chloride. For example, ISOTON (R) -II (manufactured by Coulter Scientific Japan) can be used.
As a measuring method, the electrolytic aqueous solution is 100 to 150 ml.
As a dispersant, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the volume and number of toner particles are measured by the measuring device using a 100 μm aperture as an aperture to obtain a volume distribution. And the number distribution. Then, the weight-based weight average particle diameter (D4) obtained from the volume distribution according to the present invention (the median value of each channel is a representative value for each channel), and the number-based number average particle obtained from the number distribution The diameter (D1), the weight-based coarse powder amount (20.2 μm or more) determined from the volume distribution, and the number-based fine powder number (6.35 μm or less) determined from the number distribution are determined.

(2) Fe / Si atomic ratio, Fe / Al atomic ratio In the present invention, Fe on the outermost surface of the magnetic iron oxide particles is
The / Si atomic ratio and the Fe / Al atomic ratio are determined by XPS measurement.

The conditions are as follows: XPS measuring device; ESCALAB, 200-X manufactured by VG.
Type X-ray photoelectron spectrometer X-ray source; Mg Kα (300 W) analysis region; 2 × 3 mm.

(3) Bulk Density The bulk density of the magnetic iron oxide particles in the present invention is JIS-K.
It is measured according to the pigment test method of -5101.

(4) Smoothness In the present invention, the smoothness D of the magnetic iron oxide particles is determined as follows.

[0067]

[Outer 1]

(5) BET Specific Surface Area The BET specific surface area of the magnetic iron oxide particles is actually measured as follows.

BET specific surface area is manufactured by Yuasa Ionics Co., Ltd., fully automatic gas adsorption amount measuring device: Autosoap 1
Is used, nitrogen is used as an adsorption gas, and the BET multipoint method is used. As a pretreatment of the sample, deaeration is performed at 50 ° C. for 10 hours.

(6) Average Particle Size and Surface Area of Magnetic Iron Oxide Particles The average particle size and the surface area of magnetic iron oxide particles are calculated as follows.

A transmission electron microscope photograph of magnetic iron oxide particles was taken and magnified 40,000 times, and 250 pieces were arbitrarily selected. Then, the Martin diameter in the projected diameter (the projected area was divided into two equal parts in a fixed direction) was selected. The length of the line segment to be measured) is measured and expressed as a number average diameter.

For the calculation of the surface area, it is assumed that the magnetic iron oxide is spherical with the average particle diameter as the diameter, and the density of the magnetic iron oxide is measured by a usual method to obtain the surface area value.

[0073]

[Outside 2]

(7) Pore distribution The adsorption and desorption isotherms of the magnetic iron oxide particles in the present invention due to nitrogen gas, the total pore volume, the total specific surface area of pores with a pore diameter of less than 20Å, and the pores with a pore diameter of 20Å or more. The total specific surface area is obtained as follows.

As a measuring device, a fully automatic gas adsorption device:
Autosoap 1 (manufactured by Yuasa Ionics Co., Ltd.) was used, nitrogen was used as an adsorption gas, and 40 points of adsorption and 40 points of desorption were measured up to a relative pressure of 0 to 1.0.
e Boer's t-plot method, kelvin equation and B.E. J. The pore distribution is calculated by the H method, and each is obtained. As a pretreatment of the sample, deaeration is performed at 50 ° C. for 10 hours.

(8) Water Content The water content of the magnetic iron oxide particles in the present invention is determined as follows. The amount of water is 23.5 ° C. humidity 62% RH and the temperature is 32.5 ° C. humidity 85% RH, and the magnetic iron oxide particles are left for 3 days, and then a trace moisture measuring device AQ- manufactured by Hiranuma Sangyo Co., Ltd. A 6 type and an automatic moisture vaporizer SE-24 type are used, and a sample is heated to 130 ° C. while aeration of a nitrogen gas carrier of 0.2 liter / min is performed, and measurement is performed.

(9) Amount of Silicon Element The amount of silicon element in the magnetic iron oxide particles of the present invention is determined by fluorescent X-ray analyzer SYSTEM3080 (Rigaku Denki Kogyo KK).
Manufactured by K. Co., Ltd.) and fluorescent X-ray analysis is performed according to JIS K0119 “General rules for fluorescent X-ray analysis”.

The magnetic iron oxide particles used in the magnetic toner of the present invention are preferably used in an amount of 20 to 200 parts by weight with respect to 100 parts by weight of the binder resin. It is more preferable to use 30 to 150 parts by weight.

In some cases, the magnetic iron oxide particles used in the magnetic toner of the present invention may be treated with a silane coupling agent, a titanium coupling agent, a titanate, an aminosilane, an organosilicon compound or the like.

As the silane coupling agent used for the surface treatment of the magnetic iron oxide particles, hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane is used. , Allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilane mercaptan, trimethylsilylmercaptan, triorganosilylacrylate , Vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxa And 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane and the like.

As the titanium coupling agent, isopropoxy titanium triisostearate; isopropoxy titanium dimethacrylate isostearate; isopropoxy titanium tridodecylbenzene sulfonate;
Isopropoxy titanium / tris dioctyl phosphate; isopropoxy titanium tri N-ethylaminoethyl aminato; titanium bis dioctyl pyrophosphate oxyacetate; bis dioctyl phosphate ethylene dioctyl phosphite; di n-butoxy / bistriethanol aminato titanium and the like. To be

Examples of the organic silicon compound include silicone oil. As a preferable silicone oil, one having a viscosity of 30 to 1,000 centistokes at a temperature of 25 ° C. is used. For example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, fluorine modified silicone oil and the like are preferable.

As the binder resin used for the magnetic toner,
Polystyrene; homopolymer of styrene substitution product such as polyvinyltoluene; styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-acrylic acid Ethyl copolymer, styrene-
Butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methylmethacrylate copolymer, styrene-ethylmethacrylate copolymer, styrene-meth Butyl acrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer Styrene-based copolymers such as polymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, Polyvinyl Rahl, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin, rosin, modified rosin, tempel resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, paraffin wax, carnauba Wax etc. are mentioned. These can be used alone or as a mixture. In particular, styrene-based copolymers and polyester resins are preferable in terms of development characteristics, fixability and the like.

A hydrocarbon wax and an ethylene olefin polymer may be used as a fixing aid in the toner of the present invention together with a binder resin.

As the ethylene-based olefin homopolymer or ethylene-based olefin copolymer, polyethylene,
Examples include polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ionomer having a polyethylene skeleton. In the above copolymer, the olefin monomer unit is 50 mol% or more (more preferably 60 mol%).
The above is preferable.

As the coloring material which can be further added to the magnetic toner of the present invention, conventionally known pigments or dyes such as carbon black and copper phthalocyanine can be used.

The magnetic toner of the present invention may optionally contain a charge control agent. In the case of a negatively chargeable toner, a metal complex salt of a monoazo dye, salicylic acid, alkylsalicylic acid,
A negative charge control agent such as a metal complex salt of dialkyl salicylic acid or naphthoic acid is used.

In the case of a positively chargeable toner, a positive charge control agent such as a nigrosine compound or an organic quaternary ammonium salt is used.

Examples of the negative charge control agent include the following compounds.

[0090]

[Outside 3]

The following three types are more effective as the negative charge control agent to be combined with the magnetic iron oxide particles used in the present invention.

[0092]

[Outside 4] [Wherein, X ₁ and X ₂ represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, a nitro group or a halogen atom,
m and m'represent an integer of 1 to 3, Y ₁ and Y ₃ are hydrogen atoms, C _{1 to} C ₁₈ alkyl, C _{2 to} C ₁₈ alkenyl, sulfonamide, mesyl, sulfonic acid, carboxy ester, hydroxy , C ₁ -C ₁₈ acetylamino,
Benzoyl, an amino group or a halogen atom, n and n'represent an integer of 1 to 3, Y ₂ and Y _{4 each} represent a hydrogen atom or a nitro group, (the above X ₁ and X ₂ , m and m ' , Y ₁ and Y ₃ , n and n ′, Y ₂ and Y ₄ may be the same or different.)

[0093]

[Outside 5]

2) A compound of an aromatic hydroxycarboxylic acid, an aromatic diol or an aromatic dicarboxylic acid derivative represented by the following general formula and an iron atom.

[0095]

[Outside 6]

3) N, N'-bisarylurea derivative represented by the following general formula

[0097]

[Outside 7] [In the formula, Y ₁ and Y ₂ represent a phenyl group, a naphthyl group or an anthryl group, and R ¹ and R ² represent a halogen atom, a nitro group, a sulfonic acid group, a carboxyl group, a carboxylic acid ester group, a cyano group, a carbonyl group. And an alkyl group, an alkoxy group or an amino group, and R ³ and R ⁴ are a hydrogen atom, an alkyl group, an alkoxy group, a phenyl group which may have a substituent, an aralkyl group which may have a substituent or an amino group. represents a group, R ⁵ and R ₆ represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, k and j represents an integer of 0 to 3 (not 0 at the same time), m and n is 1 or 2 Indicates. (The above Y ₁ and Y ₂ , R ¹ and R ² , R ³ and R ⁴ ,
R ⁵ and R ⁶ , k and j, and m and n may be the same or different. )]

Although the details are not clear, it was confirmed that the image quality characteristics, particularly fog, tend to be improved by using the above three types of negative charge control agents and the magnetic iron oxide particles used in the present invention. Has been done.

Examples of the positive charge control agent include the following compounds.

[0100]

[Outside 8]

The magnetic toner of the present invention is preferably mixed with an inorganic fine powder or a hydrophobic inorganic fine powder.
For example, silica fine powder or titanium oxide fine powder is preferably used alone or in combination.

As the silica fine powder used in the present invention, both dry silica produced by vapor phase oxidation of a silicon halogen compound or dry silica called fumed silica and wet silica produced from water glass are used. It is possible, but there are few silanol groups on the surface and inside,
Preference is given to dry silica, which is free from production residues.

Further, the silica fine powder used in the present invention is preferably one which has been subjected to a hydrophobic treatment. The hydrophobic treatment is applied by treating with an organic silicon compound that reacts with or physically adsorbs the fine silica powder. As a preferred method, a method of treating dry silica fine powder produced by vapor phase oxidation of a silicon halogen compound with a silane coupling agent, or simultaneously treating with a silane coupling agent and an organosilicon compound such as silicone oil. Is mentioned.

Examples of the silane coupling agent used for the hydrophobizing treatment include hexamethyldisilazane, trimethylsilane, silitimerchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methylsilylchlorosilane, allyldimethylchlorosilane, Allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilane mercaptan, trimethylsilylmercaptan, triorganosilylacrylate, Vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-di Vinyl tetramethyldisiloxane,
1,3-diphenyltetramethyldisiloxane may be mentioned.

Examples of the organosilicon compound include silicone oil. As a preferable silicone oil, one having a viscosity of 30 to 1,000 centistokes at a temperature of 25 ° C. is used. For example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, fluorine modified silicone oil and the like are preferable.

As the method for treating silicone oil, for example, silica fine powder treated with a silane coupling agent and silicone oil may be directly mixed using a mixer such as a Henschel mixer, or silica silica as a base may be used. The method of injecting oil may also be used. Or after dissolving or dispersing silicone oil in a suitable solvent,
It may be produced by mixing the base fine silica powder and removing the solvent.

Further, as a preferable hydrophobic treatment of the silica fine powder used in the present invention, a method of preparing by treating with dimethyldichlorosilane, then with hexamethyldisilazane, and then with silicone oil can be mentioned.

As described above, it is preferable that the silica fine powder is treated with two or more kinds of silane coupling agents and then treated with an oil because the hydrophobicity can be effectively increased.

Those obtained by subjecting the above-mentioned silica fine powder to the hydrophobizing treatment and further the oil treatment to the titanium oxide fine powder can be used in the present invention, and are preferable like silica.

If necessary, external additives other than fine silica powder may be added to the magnetic toner of the present invention.

For example, a charging auxiliary agent, a conductivity-imparting agent, a fluidity-imparting agent, an anti-caking agent, a releasing agent at the time of heat roll fixing,
Resin fine particles or inorganic fine particles functioning as a lubricant or an abrasive may be externally added to the magnetic toner particles.

The resin fine particles have an average particle size of 0.
It is preferably from 03 to 1.0 μm. The polymerizable monomer that constitutes the resin includes styrene; o-methylstyrene; m-methylstyrene; p-methylstyrene; p-methoxystyrene; styrene-based monomers such as p-ethylstyrene; acrylic acid, Methacrylic acids such as methacrylic acid;
Methyl acrylate, ethyl acrylate, acrylic acid n-
Butyl, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate,
Acrylic esters such as 2-chloroethyl acrylate and phenyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate,
Methacrylic acid esters such as diethylaminoethyl methacrylate; acrylonitrile, methacrylonitrile, acrylamide and the like.

As the polymerization method, a suspension polymerization method, an emulsion polymerization method, a leap-free polymerization method and the like can be used, but more preferable is resin particles obtained by soap-free polymerization.

In particular, it has been confirmed that the resin fine particles having the above characteristics have a great effect on preventing drum fusion in a contact charging system such as a roller, a brush or a blade as a primary charging device.

Examples of the external additives include lubricants such as Teflon, zinc stearate and polyvinylidene fluoride (polyvinylidene fluoride is preferable); abrasives such as cerium oxide, silicon carbide and strontium titanate (titanic acid among others). Strontium is preferred); titanium oxide,
Examples thereof include fluidity imparting agents such as aluminum oxide (hydrophobicized ones are preferable); anti-caking agents; conductivity imparting agents such as carbon black, zinc oxide, antimony oxide, and tin oxide. Further, a small amount of white fine particles and black fine particles having a polarity opposite to that of the toner particles can be used as a developing property improver.

The inorganic fine powder or hydrophobic inorganic fine powder to be mixed with the magnetic toner is used in an amount of 0.1 to 5 parts by weight (preferably 0.1 to 3 parts by weight) per 100 parts by weight of the magnetic toner particles. Is good.

To prepare a magnetic toner, magnetic iron oxide particles, a thermoplastic resin, and if necessary, a pigment or dye as a colorant, a charge control agent, and other additives are sufficiently mixed with a mixer such as a ball mill. Then heating roll,
The magnetic iron oxide particles and pigments or dyes are dispersed or dissolved in the resin to make them compatible with each other by melting, kneading and kneading using a heat kneader such as a kneader or an extruder, and crushing after cooling and solidifying. Magnetic toner particles can be obtained by performing strict classification.

As another method for obtaining the magnetic toner,
It is possible to produce toner by the polymerization method. In this polymerization method, a polymerizable monomer, magnetic iron oxide particles, a polymerization initiator (and optionally a crosslinking agent, a charge control agent and other additives) are uniformly dissolved or dispersed to form a monomer composition. After that, this monomer composition, or one obtained by prepolymerizing this monomer composition is dispersed in a continuous phase containing a dispersion stabilizer (for example, water) using a suitable stirrer,
It is a method of causing a polymerization reaction to generate magnetic toner particles having a desired particle diameter. When the magnetic toner is produced by the polymerization method, it is preferable to previously make the magnetic iron oxide particles hydrophobic.

Next, the constitution and manufacturing method of the magnetic iron oxide particles used in the present invention will be explained. The silicon element in the magnetic iron oxide particles used in the present invention is basically present on the inner surface side of the magnetic iron oxide particles.

When the distribution of the internal silicon element in the magnetic iron oxide particles shown in the examples of the present invention was examined by an acid dissolution method, silicon element was present from the center of the magnetic iron oxide particles.
It was revealed that the surface was gradually increasing.

Further, when the magnetic iron oxide particles used in the present invention are treated with aluminum hydroxide, the aluminum element is basically present only on the surface and surface layer of the magnetic iron oxide particles.

The magnetic iron oxide containing elemental silicon according to the present invention is produced, for example, by the following method.

Aqueous ferrous salt solution and F in the aqueous ferrous salt solution
By aerating an oxygen-containing gas to a ferrous salt reaction aqueous solution containing a ferrous hydroxide colloid obtained by reacting 0.90 to 0.99 equivalent of an aqueous alkali hydroxide solution with respect to e ²⁺ In producing magnetite particles, a water-soluble silicate is previously contained in either the aqueous alkali hydroxide solution or the ferrous salt containing the ferrous hydroxide colloid in terms of silicon element with respect to the iron element, and the total content. (0.4
~ 2.0 wt%), and adding 50-99%, 85-10
While heating in the temperature range of 0 ° C., an oxygen-containing gas is passed through to carry out an oxidation reaction to generate magnetic iron oxide particles containing a silicon element from the ferrous hydroxide colloid. After that, Fe remaining in the suspension after the completion of the oxidation reaction
²⁺ and 1.00 equivalent or more of an alkali hydroxide aqueous solution and the remaining water-soluble silicate [total content (0.4 to 2.
0% by weight) of 1 to 50%], and further 85-1
While heating in the temperature range of 00 ° C., an oxidation reaction is performed to generate magnetic iron oxide particles containing elemental silicon.

Then, in the case of treatment with aluminum hydroxide, a water-soluble aluminum salt is converted to aluminum particles in terms of aluminum element in the alkaline suspension in which the magnetic iron oxide particles containing the silicon element are generated. After adding so as to be 0.01 to 2.0% by weight, the pH is adjusted to be in the range of 6 to 8 and aluminum hydroxide is deposited on the surface of the magnetic iron oxide particles. Next, the magnetic iron oxide particles according to the present invention are obtained by filtering, washing with water, drying and crushing. Further, as a method for adjusting the smoothness and the specific surface area within the preferable ranges, it is preferable to perform compression, shearing, and spatula using a mix muller or a ladle machine.

Examples of the silicic acid compound to be added to the magnetic iron oxide particles used in the present invention include commercially available silicates such as sodium silicate and silicic acid such as sol-like silicic acid produced by hydrolysis.

Examples of the water-soluble aluminum salt to be added include aluminum sulfate and the like.

As the ferrous salt, it is possible to use iron sulfate, which is a by-product of titanium production by the sulfuric acid method, and iron sulfate which is a by-product of cleaning the surface of a steel sheet. Further, iron chloride or the like can be used.

An example of the image forming method of the present invention will be described with reference to FIG.

The surface of the photosensitive drum 1 is negatively charged by the primary charger 702, a digital latent image is formed by image scanning by exposure 705 by laser light, and a developing sleeve 704 including a magnetic blade 711 and a magnet 714. The latent image is reversely developed with a one-component magnetic developer 710 having a developing device 709. In the developing section, the conductive substrate of the photosensitive drum 1 is grounded, and the developing sleeve 704 is applied with an alternate bias, a pulse bias and / or a DC bias by the bias applying means 712.
When the transfer paper P is conveyed and reaches the transfer portion, the roller transfer means 2 charges the transfer paper P from the back surface (the surface opposite to the photosensitive drum side) by the voltage applying means 8 to develop on the surface of the photosensitive drum 1. The image (toner image) is transferred onto the transfer paper P by the contact transfer means 2. The transfer paper P separated from the photosensitive drum 1 is fixed by a heating and pressure roller fixing device 707 to fix the toner image on the transfer paper P.

The one-component type developer remaining on the photosensitive drum 1 after the transfer step is removed by the cleaning means 708 having a cleaning blade. If the amount of the remaining one-component developer is small, the cleaning step can be omitted. Erase exposure 7 is applied to the photosensitive drum 1 after cleaning.
The voltage is gradually reduced by 06, and the process starting from the charging process by the primary charger 702 is repeated.

Photosensitive drum (that is, electrostatic charge image carrier)
Has a photosensitive layer and a conductive substrate, and moves in the direction of the arrow. The non-magnetic cylindrical developing sleeve 704, which is a toner carrier, rotates so as to move in the same direction as the surface of the photosensitive drum 1 in the developing section. Inside the developing sleeve 704, a multi-pole permanent magnet (magnet roll) which is a magnetic field generating means is arranged so as not to rotate. The one-component insulating magnetic developer 710 in the developing unit 709 is applied on the non-magnetic cylindrical surface, and due to the friction between the surface of the developing sleeve 704 and the magnetic toner particles, the magnetic toner particles have a negative triboelectric charge, for example. Given. Furthermore, iron magnetic doctor blade 7
11 close to the surface of the cylinder (spacing 50 μm to 500 μm
m), the developer layer is made thin (30 μm to 30 μm) by being arranged so as to face one magnetic pole position of the multi-pole permanent magnet.
(0 μm) and regulated uniformly to form a developer layer thinner than the gap between the photosensitive drum 1 and the developing sleeve 704 in the developing section. By adjusting the rotation speed of the developing sleeve 704, the surface speed of the sleeve is made substantially equal to or close to the surface speed of the photosensitive drum. Instead of iron as the magnetic doctor blade 711, a permanent magnet may be used to form the opposing magnetic poles. An AC bias or a pulse bias may be applied to the developing sleeve 704 in the developing section by the bias means 712. This AC bias has f of 200 to 4,000 Hz, Vpp
May be 500 to 3,000V.

When the magnetic toner particles are transferred in the developing section, the magnetic toner particles are transferred to the electrostatic image side by the action of the electrostatic force on the surface of the photosensitive drum and the AC bias or the pulse bias.

Instead of the magnetic doctor blade 711,
An elastic blade made of an elastic material such as silicone rubber may be used to regulate the layer thickness of the developer layer by pressing, and the developer may be applied onto the developing sleeve.

FIG. 2 shows an image forming apparatus having a contact charging means 712 and a corona transfer means 703 to which a voltage is applied from the bias applying means 743.

FIG. 3 shows an image forming apparatus having the contact charging means 742 and the contact charging means 2.

In FIG. 4, reference numeral 2 is a transfer roller, which has a basic core metal 2a and a conductive elastic layer 2b forming the outer periphery thereof as a basic structure. Transfer roller 2
Presses the transfer material against the surface of the photosensitive drum 1 with a pressing force to rotate the photosensitive drum 1 with a peripheral speed equal to or different from the peripheral speed of the photosensitive drum 1. The transfer material is conveyed between the photosensitive drum 1 and the transfer roller 2 through the guide 4, and a bias having a polarity opposite to that of the toner is applied to the transfer roller 2 from the transfer bias applying means 3 to form a toner image on the photosensitive drum 1. Is transferred to the surface side of the transfer material. Then, the transfer material is sent onto the guide 5.

The conductive elastic layer 2b is made of polyurethane or ethylene-propylene-diene terpolymer (EPDM) in which a conductive material such as carbon is dispersed and has a volume resistance of 10 ⁶ to 1 1.
It is made of an elastic body of about 0 ¹⁰ Ωcm.

Preferred transfer process conditions are as follows: the roller contact pressure is 5 to 500 g / cm, and the DC voltage is ±.
It is 0.2 to ± 10 kV.

In FIG. 5, reference numeral 1 denotes a rotary drum type electrostatic charge image carrier (hereinafter referred to as a photosensitive drum). The photosensitive drum 1 has a conductive base layer 1a such as aluminum and a photoconductive layer formed on the outer surface thereof. The layer 1b is a basic constituent layer and is rotated clockwise in the drawing at a predetermined peripheral speed (process speed).

Reference numeral 42 denotes a charging roller, which has a central core metal 4
2a, a conductive elastic layer 42b having its outer periphery formed, and a surface layer 42c have a basic configuration. Charging roller 4
2 is pressed against the surface of the photosensitive drum 1 with a pressing force,
It rotates following the rotation of the photosensitive drum 1. A voltage is applied to the charging roller 42 by the bias applying means E, and a bias is applied to the charging roller 42, so that the surface of the photosensitive drum 1 is charged to a predetermined polarity and potential. Then, an electrostatic charge image is formed by image exposure, and the electrostatic charge image is sequentially visualized as a toner image by the developing means.

A preferable process condition when the charging roller is used is that the contact pressure of the roller is 5 to 500 g / c.
In m, when a DC voltage superimposed with an AC voltage is used, AC voltage = 0.5 to 5 kVpp, AC frequency = 50
~ 5 kHz, DC voltage = ± 0.2 to ± 1.5 kV, and when using DC voltage, DC voltage = ± 0.2 to ±
It is 5 kV.

As a material for the charging roller and the charging blade, conductive rubber is preferable, and a releasing film may be provided on the surface thereof. As the releasable coating, nylon resin,
PVDF (polyvinylidene fluoride), PVDC (polyvinylidene chloride), etc. are applicable.

FIG. 7 shows a specific example of the process cartridge of the present invention. The process cartridge is a cartridge in which the developing device and the electrostatic image holder are at least integrally formed, and the process cartridge is formed so as to be attachable to and detachable from the image forming apparatus main body (for example, a copying machine, a laser beam printer, etc.).

In the present embodiment, the developing device 709, the drum-shaped electrostatic image carrier (photosensitive drum) 1, the cleaner 708 having the cleaning blade 708a, and the temporary charging device (charging roller) 742 are integrated into the process cartridge 750. Is exemplified.

In this embodiment, the developing means 709 has a magnetic blade 711 and a magnetic toner 710 in a toner container 760. The magnetic toner 710 is used, and at the time of development, it is developed with the photosensitive drum 1 by a bias from a bias applying means. The distance between the photosensitive drum 1 and the developing sleeve 704 is very important so that a predetermined electric field is formed between the sleeve 704 and the developing process.

The present invention will be described in detail below with reference to magnetic iron oxide production examples and toner examples. The parts or% given in the examples refer to parts by weight or% by weight.

Production Example 1 A ferrous sulfate solution was mixed with 0.95 equivalent of an aqueous sodium hydroxide solution with respect to Fe ²⁺ , and then Fe (OH) ₂ was added.
A ferrous salt aqueous solution containing was produced.

Then, sodium silicate was added to the iron element so as to be 1.0% by weight in terms of silicon element.
Next, the temperature of the ferrous salt aqueous solution containing Fe (OH) ₂ was adjusted to 90
The magnetic iron oxide particles containing elemental silicon were produced by aerating air at 0 ° C. and carrying out an oxidation reaction under the conditions of pH 6 to 7.5.

Further, to this suspension was added an aqueous sodium hydroxide solution in which 0.1 wt% of sodium silicate (calculated as silicon element for iron element) was dissolved in an amount of 1.05 equivalent to the residual Fe ²⁺ . , PH8 while heating at 90 ℃
The magnetic iron oxide particles containing elemental silicon were generated by the oxidation reaction under the condition of ˜11.5.

The produced magnetic iron oxide particles were washed by a conventional method and dried by filtration. Since the primary particles of the obtained magnetic iron oxide particles are aggregated to form an aggregate, a compressive force and a shearing force are applied to the aggregate of the magnetic iron oxide particles by using a mix muller, and the aggregate is formed. The aggregate was crushed to make the magnetic iron oxide particles into primary particles, and the surfaces of the magnetic iron oxide particles were smoothed to obtain magnetic iron oxide particles A having the characteristics shown in Tables 1 and 2. The average particle size of magnetic iron oxide particles is 0.2
It was 1 μm.

Manufacturing Examples 2 to 6 As in Manufacturing Example 1, magnetic iron oxide particles B to F of Manufacturing Examples 2 to 6 were obtained by changing the amount of silicon element.

Production Example 7 An aggregate of magnetic iron oxide particles obtained in the same manner as in Production Example 6 was
It was crushed into primary particles using a pin mill to obtain magnetic iron oxide particles G of Production Example 7. The magnetic iron oxide particles G had lower smoothness and a larger BET specific surface area than the magnetic iron oxide particles F.

Production Examples 8 to 12 Before the filtration step of the magnetic iron oxide particles obtained in Production Example 3, a predetermined amount of aluminum sulfate was added to the slurry liquid to adjust the pH to 6
The magnetic iron oxide particles H to L of Production Examples 8 to 12 were obtained by adjusting the surface area of the magnetic iron oxide particles as aluminum hydroxide by adjusting to the range of 8 to 8.

The magnetic iron oxides of Production Examples 8 to 12 are the same as those of Production Example 1
Similarly to the above, a consolidation crushing treatment was performed by a mix muller.

[0155] was charged with a predetermined total silicon content in the reaction of the first step of Production Example 13 and 14 prepared in Example 1, by changing the pH adjusted to 8-10, the magnetic iron oxide of Production Example 13 and Production Example 14 Particles M and N were obtained.

Comparative Production Examples 1 to 4 At the time of the reaction in the first step of Production Example 1, a predetermined total silicon content was added, and further the sodium hydroxide aqueous solution to be added was F.
Magnetic iron oxides Q to R of Comparative Production Examples 1 to 4 were obtained by changing the pH adjustment to an amount exceeding 1 equivalent to e ²⁺ .

Comparative Production Example 5 Sodium silicate was added to an aqueous ferrous sulfate solution so that the content ratio of silicon element to iron element was 1.8%, and then 1.0% to iron ion was added. An aqueous solution of ferrous salt containing Fe (OH) ₂ was produced by mixing ~ 1.1 equivalent of an aqueous solution of alkali hydroxide.

Next, while maintaining the pH of the aqueous solution at 9, air was blown at a temperature of 85 ° C. to carry out an oxidation reaction to produce magnetic iron oxide particles containing silicon element. Furthermore, after adding an aqueous solution of ferrous sulfate to the suspension so as to be 1.1 equivalents with respect to the initial alkali amount (sodium component of sodium silicate and sodium component of alkali hydroxide), the pH of the solution was adjusted. Was maintained at 8, the oxidation reaction was promoted while blowing air, and the pH was adjusted to the weak alkaline side at the end of the oxidation reaction to obtain magnetic iron oxide particles.

The produced magnetic iron oxide particles were washed, filtered and dried by a conventional method, and then the aggregated magnetic iron oxide particles were subjected to a usual crushing treatment to obtain magnetic iron oxide particles S.

[0160] compared to the spherical magnetic iron oxide particles of Production Example 6 BET specific surface area of 6.8 m ² / g, the silica fine powder of BET specific surface area of 400m ² / g 0.
8 wt% was mixed with a mix muller to obtain magnetic iron oxide particles T.

[0161]

[Table 1]

[0162]

[Table 2]

[0163]

EXAMPLE 1 Styrene-2-ethylhexyl acrylate copolymer 100 parts (copolymerization weight ratio = 88: 12, Mw = 240,000, Tg = 6
0 ° C) -Magnetic iron oxide particles A 100 parts-Low molecular weight ethylene-propylene copolymer 4 parts-Negatively charged control agent A 2 parts (monoazo iron complex represented by formula F)

[0164]

[Outside 9]

The above mixture was melt-kneaded with a twin-screw extruder heated to 140 ° C., the cooled kneaded product was roughly pulverized with a hammer mill, and the coarsely pulverized product was finely pulverized with a jet mill. Was classified with a fixed wall type air classifier to produce classified powder. Further, the weight-average particle size (D4) is obtained by strictly classifying the obtained classified powder at the same time strictly by using a multi-division classifier utilizing the Coanda effect (Elbow Jet classifier manufactured by Nittetsu Mining Co., Ltd.). A negatively chargeable insulating magnetic toner having a size of 6.7 μm was obtained. The content of the magnetic toner particles having a particle diameter of 12.7 μm or more was 0.2% by weight.

100 parts of this magnetic toner and 1.2 parts of hydrophobic silica fine powder (BET 300 m ² / g) which had been treated with dimethyldichlorosilane, then with hexamethyldisilazane, and then with dimethyl silicone oil,
A one-component magnetic developer was prepared by mixing 0.08 part of styrene-acrylic fine particles (average particle size: 0.05 μm) obtained by soap-free polymerization with a Henschel mixer.

The above one-component magnetic developer was modified from Canon laser beam printer LBP-8II (using an OPC photosensitive drum) from 8 sheets / minute to 16 sheets / minute, and further the transfer apparatus shown in FIG. 4 was incorporated. Images were evaluated using a machine.

As conditions for the transfer roller, the hardness of the conductive elastic layer of the transfer roller was 27 °, the transfer current was 1 μA, the transfer voltage was +2000 V, and the contact pressure was 50 [g / cm].
The conductive elastic layer of the transfer roller is made of EPDM in which conductive carbon is dispersed, and has a volume resistance of 10 ⁸ Ω · c.
had m.

In this example, the charging roller shown in FIG. 5 was used for the primary charging. The outer diameter of the charging roller 42 is 12 mm, and the conductive rubber layer 42b has EPDM,
A nylon resin having a thickness of 10 μm was used for the surface layer 42c. The hardness of the charging roller 42 is 54.5 ° (ASKE
R-C). E is a power source for applying a voltage to the charging roller 42, and supplies a predetermined voltage to the core metal 42a of the charging roller 42. In FIG. 5, E indicates a system in which an AC voltage is superimposed on a DC voltage.

The photosensitive drum is charged by the charging roller 42 so that the primary charge becomes −700 V, a gap is set in a non-contact manner between the photosensitive drum and the developer layer on the developing sleeve (including magnet), and an AC bias (f = 1,800Hz, Vpp =
1,600 V) and DC bias (V _DC = -500 V)
While applying and to the developing sleeve, _VL was set to -170 V, the electrostatic charge image was developed by reversal development to form a magnetic toner image on the OPC photosensitive member.

The formed magnetic toner image was transferred onto plain paper at the above-mentioned positive transfer potential, and the plain paper having the magnetic toner image was fixed on the plain paper through a heating and pressure roller fixing device.

While replenishing the magnetic developer successively, under normal temperature and normal humidity environment (23.5 ° C., 60% RH) up to 10,000 sheets, 1 sheet / 16 sec intermittent mode (that is, each sheet is printed in about 2 seconds. An image output test was performed in an intermittent mode in which the developing device was stopped for about 12 seconds after the output. Image density and reflectometer measured by Macbeth reflection densitometer (Tokyo Denshoku Co., Ltd.)
Table 3 shows the results of the fog calculated by comparing the whiteness of the transfer paper measured by Mfg. Co., Ltd.) with the whiteness of the transfer paper after printing the solid white.

Similarly, in a high temperature and high humidity environment (32.5
℃, 85% RH) and low temperature and low humidity environment (10 ℃, 15%
The image formation test was conducted in RH). The results are shown in Table 3.

In a high-temperature and high-humidity environment, after printing 4,000 sheets, it was left in the same environment for 3 days, and a test for printing 4,000 sheets was conducted. Regarding the fog, a paper that was passed through both sides was used for evaluation. An image drawing test of the pattern shown in FIG. 6 was performed to evaluate dot reproducibility in the latter half of the durability test under high temperature and high humidity.

Examples 2 to 14 Magnetic iron oxides B to N of Production Examples 2 to 14 were used instead of the magnetic iron oxides, and toners having substantially the same particle size distribution were obtained in the same manner as in Example 1.

Evaluation was carried out in the same manner as in Example 1. The results are shown in Table 3.

Example 15 Styrene-n-butyl acrylate copolymer 100
Part (copolymerization ratio = 83: 17, Mw = 280,000, Tg = 60
° C) ・ Magnetic iron oxide B 60 parts ・ Negative charge control agent A 1.5 parts ・ Low molecular weight ethylene-propylene copolymer 4 parts

The above mixture was melt-kneaded with a twin-screw extruder heated to 140 ° C., the cooled kneaded product was coarsely pulverized with a hammer mill, and the coarsely pulverized product was finely pulverized with a jet mill. The finely pulverized powder obtained is subjected to air classification to obtain a weight average particle diameter (D
4) A negatively chargeable magnetic toner having a particle size of 11.4 μm (content of magnetic toner particles having a particle size of 12.7 μm or more: 33% by weight) was obtained.

100 parts of the magnetic toner obtained and 0.6 part of hydrophobic colloidal silica treated with dimethyl silicone oil were mixed with a Henschel mixer to prepare a magnetic developer.

This magnetic developer was supplied to the process cartridge of the laser beam printer LBP-8II, and the image forming test was conducted in the same manner as in Example 1. The results are shown in Table 3.

Example 16 Evaluation was made in the same manner as in Example 15 except that the monoazo chromium complex (negative charge controlling agent B) in which the central metal of the negative charge controlling agent was changed from iron to chromium was used.

Example 17 Styrene-n-butyl acrylate 100 parts (copolymerization ratio = 83: 17, Mw = 300,000, Tg = 60)
° C) ・ Magnetic iron oxide C 120 parts ・ Negatively charged control agent A 3 parts ・ Low molecular weight ethylene-propylene copolymer 4 parts

Using the above materials, a magnetic toner having a weight average particle diameter (D4) of 5.4 μm (content of magnetic toner particles having a particle diameter of 12.7 μm or more of 0%) was obtained in the same manner as in Example 1.

100 parts of the magnetic toner obtained and Example 1
A magnetic developer was prepared by mixing 1.6 parts of the hydrophobic colloidal silica used in 1 above with 0.1 part of the resin fine particles used in Example 1 with a Henschel mixer.

For evaluation, a modified process cartridge similar to that in Example 1 was used, and an image formation test was performed in the same manner as in Example 1.

Example 18 Evaluation was carried out on the system obtained by removing the resin fine particles as the external additive from the toner obtained in Example 1.

As a result, the image density, fog, and dot reproducibility were almost the same, but in the endurance under high temperature and high humidity, some drum fusion occurred at the end of the endurance.

Example 19 A toner having the same particle size distribution as in Example 15 was obtained except that the content of the magnetic iron oxide was changed to 40 parts and 2 parts of carbon black was added.

The saturation magnetization of the magnetic toner particles in a magnetic field of 1 K Oersted was 20.0 emu / g. The magnetic characteristics of this magnetic toner are VSM P-1-10.
(Toei Kogyo Co., Ltd.) was used and the value was obtained from the result of measurement at 1 K Oersted at room temperature. Density is 1.42 g / cm ³
Met. DC bias component Vd is used as the developing bias.
c = -450V, superposed AC bias component Vpp =
1,200 V and f = 2,000 Hz were used. Other conditions were the same as in Example 15 except that images were drawn and evaluated. The results are shown in Table 3.

As compared with Example 15, the image was good without any scattering of the image. It was confirmed that the toner consumption was also small.

Comparative Examples 1 to 4 The magnetic iron oxides of Example 1 were changed to the magnetic iron oxides of Comparative Production Examples 1 to 4 to obtain toners having the same particle size distribution as in Example 1. Evaluation was performed in the same manner as in Example 1. The results are shown in Table 3.
Shown in.

Comparative Example 5 The magnetic iron oxide of Production Example 2 was used, and the weight average particle size was 11.8.
A magnetic toner having a particle size of μm (content of magnetic toner particles having a particle size of 12.7 μm or more: 54%) was obtained in the same manner as in Example 15.
The magnetic toner thus obtained was evaluated in the same manner as in Example 15.

Comparative Examples 6 and 7 Magnetic iron oxide particles S and T produced in Comparative Production Examples 5 and 6
Was used to prepare a magnetic toner in the same manner as in Example 1. The magnetic toner thus obtained was used and evaluated in the same manner as in Example 1. The results are shown in Table 3. As compared with the magnetic toner of Example 1, after left in a high temperature and high humidity environment for 3 days, the image density was lowered to 1.14 and 1.12.

[0194]

[Table 3] (Note) Evaluation of dot reproducibility ○: 2 defects or less / 100 defects ○ △: 3 to 5 defects / 100 defects Δ… 6 to 10 defects / 100 defects ×… 11 defects or more

[0195]

According to the present invention, magnetic iron oxide containing silicon element and having a Fe / Si atomic ratio on the outermost surface has a weight average particle diameter of 13.5 μm or less and a particle diameter of 1
The content of magnetic toner particles of 2.7 μm or more is 50% by weight.
By using it as a magnetic substance of a magnetic toner having a large number of magnetic toner particles having a small particle diameter, the environmental stability (especially high temperature and high humidity characteristics, leaving characteristics) and developing characteristics of the magnetic toner can be improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an image forming apparatus suitable for forming an image using the magnetic toner of the present invention.

FIG. 2 is a schematic diagram showing another example of a suitable image forming apparatus.

FIG. 3 is a schematic view showing another example of a suitable image forming apparatus.

FIG. 4 is a diagram showing an outline of a transfer device.

FIG. 5 is a diagram showing an outline of a charging roller.

FIG. 6 is an explanatory diagram of a checker pattern for testing the developing characteristics of magnetic toner.

FIG. 7 is an explanatory diagram showing an example of a process cartridge of the present invention.

[Explanation of symbols]

 1 Latent Image Carrier (Photoreceptor) 2 Transfer Roller 2a Core Bar 2b Conductive Elastic Layer 3 Constant Voltage Power Supply 42 Charging Roller 704 Development Sleeve (Toner Carrier) 705 Exposure 709 Developer 711 Magnetic Blade

Front page continuation (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location G03G 9/08 302 15/00 556 (72) Inventor Naofuni Kobori 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masaichiro Katada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Hiroyuki Suematsu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. Within

Claims (19)

[Claims] 1. A magnetic toner containing at least a binder resin and magnetic iron oxide, wherein the magnetic toner has a weight average particle size of 13.5 μm or less, and a particle size distribution of the magnetic toner is 12.7 μm or more. The content of the magnetic toner particles is 50% by weight or less, and the content of silicon element in the magnetic iron oxide is 0.4 to 2.0% by weight based on the iron element. A magnetic toner characterized in that the Fe / Si atomic ratio on the outermost surface of the magnetic iron oxide is 1.2 to 4.0. 2. The smoothness of the magnetic iron oxide is 0.3 to 0.8.
The magnetic toner according to claim 1, wherein 3. The bulk density of the magnetic iron oxide is 0.8 g / cm.
The magnetic toner according to claim 1, wherein the magnetic toner is ³ or more. 4. The specific surface area of the magnetic iron oxide is 15.0 m ^2.
4. The magnetic toner according to claim 1, wherein the magnetic toner is less than or equal to / g. 5. The method according to claim 1, wherein the magnetic iron oxide is treated with 0.01 to 2.0% by weight of aluminum hydroxide in terms of elemental aluminum. Magnetic toner. 6. Fe / A on the outermost surface of the magnetic iron oxide
6. The magnetic toner according to claim 1, wherein the atomic ratio of 1 is 0.3 to 10.0. 7. A process cartridge attachable to and detachable from a main body of an image forming apparatus, comprising: an electrostatic charge image carrier; and a developing means for developing an electrostatic charge image formed on the electrostatic charge image carrier using a developer. The developer has a magnetic toner containing at least a binder resin and magnetic iron oxide particles, and the magnetic toner has a weight average particle diameter of 13.5 μm or less. , Particle size 12.7μ
The content of the magnetic toner particles of m or more is 50 wt% or less, and the magnetic iron oxide particles have a silicon element content of 0.4 to 2.0 wt% based on the iron element. %, And Fe on the outermost surface of the magnetic iron oxide particles
/ Si atomic ratio is 1.2 to 4.0, a process cartridge. 8. The process cartridge according to claim 7, wherein the electrostatic image carrier is a photosensitive drum. 9. The smoothness of the magnetic iron oxide particles is 0.3 to.
9. The process cartridge according to claim 7, wherein the process cartridge is 0.8. 10. The bulk density of the magnetic iron oxide particles is 0.8 g.
The process cartridge according to any one of claims 7 to 9, characterized in that / cm ³ or more. 11. The specific surface area of the magnetic iron oxide particles is 15.
It is 0 m ² / g or less, characterized by the above-mentioned.
0. The process cartridge according to 0. 12. The magnetic iron oxide particle according to claim 7, wherein the magnetic iron oxide particle is treated with 0.01 to 2.0% by weight of aluminum hydroxide in terms of aluminum element. Process cartridge described. 13. Fe / at the outermost surface of the magnetic iron oxide
The process cartridge according to any one of claims 7 to 12, wherein the Al atomic ratio is 0.3 to 10.0. 14. An electrostatic charge image is formed on an electrostatic charge image carrier,
In an image forming method of developing an electrostatic charge image with a magnetic toner held in a developing means to form a toner image, the magnetic toner for developing the electrostatic charge image contains at least a binder resin and magnetic iron oxide particles. The weight average particle diameter of the magnetic toner is 13.5 μm or less, and the content of the magnetic toner particles having a particle diameter of 12.7 μm or more is 50% by weight or less in the particle size distribution of the magnetic toner. The magnetic iron oxide particles have a silicon element content of the magnetic iron oxide particles of 0.4 to 2.0 wt% based on the iron element,
An Fe / Si atomic ratio on the outermost surface of the magnetic iron oxide particles is 1.2 to 4.0. 15. The magnetic iron oxide particles have a smoothness of 0.3 to.
The image forming method according to claim 14, wherein the image forming method is 0.8. 16. The magnetic iron oxide particles have a bulk density of 0.8 g.
/ Cm ³ or more, the image forming method according to claim 14 or 15. 17. The specific surface area of the magnetic iron oxide particles is 15.
The image forming method according to any one of claims 14 to 16, wherein the image forming method is 0 m ² / g or less. 18. The method according to claim 14, wherein the magnetic iron oxide particles are treated with 0.01 to 2.0% by weight of aluminum hydroxide in terms of aluminum element. The image forming method described. 19. Fe / at the outermost surface of the magnetic iron oxide
19. The image forming method according to claim 14, wherein the Al atomic ratio is 0.3 to 10.0.