JP2675829B2 - Developer for developing electrostatic images - Google Patents

Description

The present invention relates to an electrostatic charge image developing developer containing a magnetic toner used in electrophotography, electrostatic recording, magnetic recording and the like.

Conventional electrophotographic methods are disclosed in U.S. Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910 (U.S. Pat. No. 3,666,363) and Japanese Patent Publication No. 43-24748 (U.S. Pat.
61)), a number of methods are known, but generally, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means. The latent image is developed with toner to form a visible image, and if necessary,
After a toner image is transferred to a transfer material such as paper, the toner image is fixed by heating, pressure, or the like to obtain a copy.

Various development methods for visualizing an electrostatic latent image using toner are also known. For example, the magnetic brush method described in U.S. Pat.No. 2,874,063, the cascade developing method described in U.S. Pat. No. 2,618,552 and 2,221,77
Numerous development methods are known, such as a powder cloud method, a fur brush development method, and a liquid development method described in the specification of Japanese Patent Application Laid-Open No. 6-204,086. Among these developing methods, a magnetic brush method, a cascade method, a liquid developing method and the like using a developer mainly composed of a toner and a carrier have been widely put to practical use. All of these methods are excellent methods in which a good image can be obtained relatively stably, but on the other hand, they have the common drawbacks associated with a two-component developer, such as deterioration of the carrier and variation in the mixing ratio of the toner and the carrier.

In order to avoid such a drawback, various developing methods using a one-component developer composed of only a toner have been proposed.
Among them, many are excellent in a method using a developer composed of toner particles having magnetism.

U.S. Pat. No. 3,909,258 proposes a method of developing using an electrically conductive magnetic toner. In this technique, a conductive magnetic toner is supported on a cylindrical conductive sleeve having magnetism therein, and is brought into contact with an electrostatic image for development. At this time, in the developing portion, a conductive path is formed by the toner particles between the surface of the recording material and the surface of the sleeve, and the electric charge is introduced from the sleeve to the toner particles through the conductive path, and the conductive path is formed between the electrostatic image and the image area. The Coulomb force causes the toner particles to adhere to the image area and be developed. The developing method using the conductive magnetic toner is an excellent method that avoids the problems associated with the conventional two-component developing method. However, since the toner is conductive, the developed image can be transferred from a recording medium to plain paper or the like. It has the disadvantage that it is difficult to transfer electrostatically to the final support member.

As a developing method using a high-resistance magnetic toner capable of electrostatic transfer, there is a developing method using dielectric polarization of toner particles. However, such a method is disadvantageous in that the development speed is essentially low and the density of a developed image cannot be sufficiently obtained, and is practically difficult.

As another developing method using a high-resistance magnetic toner, a method of frictionally charging toner particles due to friction between toner particles, friction between the toner particles and a sleeve or the like, and developing the toner particles by contacting the electrostatic image holding member is developed. It has been known. However, these methods have disadvantages in that the number of times of contact between the toner particles and the friction member is small and triboelectric charging is likely to be insufficient, and the charged toner particles are liable to agglomerate on the sleeve due to the strong Coulomb force between the sleeve and the sleeve. And it was practically difficult.

However, Japanese Patent Application Laid-Open No. Sho 55-18656 has proposed a new developing method which eliminates the above-mentioned disadvantages. This involves applying a very thin coating of magnetic toner on a sleeve, triboelectrically charging it, and then developing it very close to the electrostatic image. This method increases the chance of contact between the sleeve and the toner by applying the magnetic toner on the sleeve very thinly, enabling sufficient triboelectric charging,
The toner is supported by a magnetic force, and the toner and the toner are relatively moved to prevent the toner particles from aggregating with each other and to be sufficiently rubbed with the sleeve. An excellent image can be obtained by developing the films so that they face each other without coming into contact with each other.

However, as image forming apparatuses such as electrophotographic copying machines have become widespread in recent years, their applications have expanded to a wide variety and demands on their image quality are strict, and there are some problems while utilizing the advantages of conventional magnetic toners. I am being asked to settle.

In other words, even in general copying, it is required to faithfully reproduce the original manuscript, and to reproduce very finely even fine characters without being crushed, broken, or scattered, and further, a printer as a computer output. With high reliability, it is stable and clear even after continuous long-term use, and in the more precise graphic copy field, which has been performed by printing technology, large area high density copy, fine line reproducibility, and gradation Are required.

In particular, the latent image on the photoconductor of the image forming apparatus is 100 μm.
In the case of a line image of m or less, the reproducibility of fine lines is generally poor, and the sharpness of the line image is still insufficient. Recently, in an image forming apparatus such as an electrophotographic printer using digital image signals, a latent image is formed by collecting dots of a constant potential, and a solid portion, a halftone portion and a light portion have a dot density. It is expressed by changing.
However, if the toner particles do not adhere exactly to the dots and the toner particles protrude from the dots, the gradation of the toner image corresponding to the dot density ratio of the black portion and the white portion of the digital latent image cannot be obtained. There is a problem. Furthermore, when the resolution is improved by reducing the dot size in order to improve the image quality, the reproducibility of a latent image formed from minute dots becomes more difficult, and the resolution and gradation are poor, and the sharpness is low. Image tends to be lacking.

Some proposals have been made for these problems as magnetic toners.

U.S. Pat. No. 4,299,900 proposes a jumping development method using a developer having 10 to 50% by weight of a magnetic toner of 20 to 35 .mu.m. That is, the magnetic toner is triboelectrically charged, the toner layer is uniformly and thinly applied on the sleeve, and the toner particle size is devised so as to improve the image density and the environmental stability of the developer. However, it is not sufficient in view of more stringent requirements such as fine line reproducibility and resolution, and further improvement is required.

Further, in JP-A-56-21135, the number average molecular weight, the residual magnetic moment, and the saturation magnetic moment of a magnetic toner are specified, and the toner is transferred by a signal pulse from a special electrode facing the recording medium. With this toner and method, it is difficult to obtain fine resolving power and reproducibility because they are transferred to the recording material as a tower-shaped toner aggregate, and the number average particle diameter is 2 to 10 μm and the residual magnetic moment is 0.
Since it is as small as 1-2 emu / g, in the normal development method,
It does not solve the above problems.

Further, Japanese Patent Application Laid-Open No. 57-90640 defines the shape and magnetic characteristics of a magnetic material. Like the toner, it has a non-crushability of 1 to
Using a large agglomerated magnetite having a size of 10 μm tends to cause insufficient dispersion of magnetite in toner particles, causing fog and deterioration of image quality due to use.

Under these circumstances, the present inventors have found that the magnetic toner has insufficient image density, poor resolution, reproducibility of fine lines, and other instability in image quality such as blots and unevenness on the sleeve. In many cases, the magnetic toner has a small electrification power, the non-uniformity of the charge amount of each particle, and the ease with which the spikes are formed, the length of the spikes, and the shape of the toner. In particular, the present inventors have found that when the particle diameter of the toner and the remanent magnetization of the toner have a specific relationship, the preferable result is obtained, and the presence state of the magnetic powder is preferable for the specific binder resin. It is also found that it can be suppressed to an appropriate and uniform charge amount by containing a specific charge relaxation agent fine powder.
The present invention has been achieved by investigating this point.

[Object of the invention]

An object of the present invention is to provide a developer that solves the above problems.

Further, an object of the present invention is to provide a developer having high image density, fine line reproducibility, and gradation.

A further object of the present invention is to provide a developer whose performance does not change even after long-term use.

Further, an object of the present invention is to provide a developer which does not change its performance due to environmental changes and has excellent durability especially under low humidity conditions.

A further object of the present invention is to provide an excellent developer which does not impair the image quality during transfer and fixing.

Further, an object of the present invention is to provide a developer capable of obtaining a high image density with a small consumption amount.

Further, an object of the present invention is to provide a developer capable of forming a toner image excellent in resolution, gradation and fine line reproducibility even in an image forming apparatus using a digital image signal.

[Summary of the Invention]

The present invention relates to a magnetic toner having at least a binder resin and magnetic powder, wherein the binder resin is a vinyl polymer having a tetrahydrofuran insoluble content of 5 to 80% by weight, and the residual magnetization σ _r and volume of the magnetic toner are The average particle diameter d satisfies the following formula, 3.7-0.11d ≤ σ _r ≤ 6.5-0.23d [where σ _r is the remanent magnetization (emu / emu /
g). d is a volume average particle diameter (μm), and is 3 to 1
6 ] Melt index is 0.2 to 12g / 10 minutes (125 ℃, 10Kg load), and the amount of triboelectricity with iron powder is 50μc / g (absolute value)
The present invention relates to a developer for developing an electrostatic charge image, which comprises a carbon allotrope and a metal oxide as fine particles of a charge relaxation agent having a number average particle diameter of 0.5 μm or less.

The developer of the present invention as described above can faithfully reproduce even the fine lines of the latent image formed on the photoconductor, and reproduces dot latent images such as halftone dots and digital images. It also provides a high density image excellent in gradation and resolution and solves various objects of the present invention.

The reason why such effects are obtained in the developer of the present invention is not always clear, but it is presumed as follows.

In consideration of the above-mentioned problems, the inventors of the present invention have taken into account the blotches and unevenness on the developing sleeve as defects that extremely represent density thinness, image quality disturbance, and the like, and have clarified the development. Blotches and unevenness are spots or ripples on the developing sleeve that cause uneven coating of toner.In a solid black image, the development is defective. It will be developed as it is.

Observing such blots and unevenness causes adhered particles on the surface of the sleeve due to various causes.For this reason, insufficiently charged toner due to insufficient triboelectrification of the sleeve and insufficiently charged toner are disturbed on the upper surface of the toner. It was observed to form ears.

The adhered particles are usually the adhered toner particles adhered to the sleeve by electrostatic attraction, and are more likely to occur when the charge amount of the toner is increased to increase the image density.

This phenomenon may occur during continuous use under environmental conditions of ultra-low temperature and low humidity for a longer period of time than in ordinary repetitive copying.

This affects the coating uniformity of the toner in the upper portion of the developer layer and the easiness of development.Broching / unevenness is an extreme example, but poor image quality and low density also occur. Although it is different, it can be thought to be due to the same cause.

In other words, the disturbed ears and the ears that are too long cannot faithfully develop the latent image, the ears of the toner spill out from the latent image, scatter, and the latent image cannot be uniformly and densely developed, and the covering An image with low power and low density will be produced.

The present inventors consider that in order to achieve the object of the present invention, it is preferable that the charge amount of the developer is appropriately high and uniform.

That is, the reasonably high level ensures the flight of the developer from the developing sleeve to the electrostatic latent image on the photoconductor, enables high density and reproducibility, and has a uniform charge amount for each particle. , The ears of the magnetic toner are uniformly regulated, it is difficult to form disordered ears, and the bleeding from the latent image, popping, and uneven development are prevented, and stable image quality is maintained even after repeated use over a long period of time.

To this end, the inventors of the present invention, for example, use a developing sleeve having a smoother surface property, so that the chances of contact between the toner particles and the sleeve surface are increased, and a high charge amount and a more uniform charging are obtained. It was considered preferable to use a quantity distribution.

However, although it is effective to obtain a toner having a uniform charge amount distribution by such a method, when the charge amount is too high, as described above, the generation of the blots / unevenness on the sleeve and the deterioration of the image quality occur. The present inventors have investigated a charge relaxation agent fine powder that appropriately controls the charge amount while maintaining the charge uniformity.

Based on these results, the inventors of the present invention were suitable for development, against the electrification power of the toner that generates a mirroring force that causes the toner particles to adhere to and accumulate on the sleeve surface and a force that causes the toner particles to aggregate with each other. It has been found that it is effective to optimally control the magnetic action force of the toner for causing the spikes.

FIG. 1 shows one embodiment of a developing device which can use the magnetic toner of the present invention.

Here, when the magnetic toner passes through the gap between the sleeve and the magnetic blade, the magnetic toner receives a maximum magnetic field from the outside and tries to form a brush. However, inferring from the study by the present inventors, before and after this, in particular, the magnetic binding force passing through between the sleeve and the magnetic blade becomes small, and the force to attach and accumulate and aggregate to the sleeve again acts. Therefore, it is important to continue to hold the ears by the magnetic action force. Furthermore, since the length of the ears and the toner particle size have a relative relationship, the residual magnetization σ _r of the magnetic toner and the particle size d have problems. A characteristic relationship for solving the following, namely, 3.7−0.11d ≦ σ _r
≦ 6.5−0.23d, and further, in order to sufficiently exert this effect, the binder resin is a vinyl polymer having a tetrahydrofuran insoluble content of 5 to 80 wt%, and the MI of the magnetic toner is 0.2 to 12g / 10min is good, the amount of triboelectricity with iron powder is 50μc / g (absolute value) or less, and the number average particle size is 0.5.
It was concluded that the carbon allotrope and the metal oxide should be contained as the charge relaxation agent fine powder having a particle size of not more than μm.

 The configuration of the present invention will be described.

The residual magnetization σ _r and the volume average particle diameter d of the magnetic toner are 3.7−
0.11d ≤ σ _r ≤ 6.5-0.23d [where σ _r is the external magnetic field IK
Remanent magnetization at e (emu / g), d is volume average particle size (μ
It is 3 to 16 in m). ] Is good. The shaded area in FIG. 3 indicates this area.

When σ _r > 6.5-0.23d, the σ _{r of the} toner particles is too large relative to the magnetic toner particle size, the force for causing the toner particles to stand up from the developing sleeve is large, and blotting is less likely to occur, but conversely The ears become too long and exceed 100 μm, and even 150 μm, which is longer than the width of the fine line latent image, and sticks out or pops out of the latent image, resulting in poor image quality.

Furthermore, the toner ears are long, the toner coat thickness is large, and it becomes difficult for individual particles to be uniformly charged, resulting in density thinning, fog, and even repeated use.
Toner having a low charging ability remains in the developing machine, resulting in a long-term decrease in image density and image quality.

When σ _r <3.7−0.11d, the toner particle size is
The σ _{r of the} toner particles is too small, the density unevenness due to blotting unevenness on the sleeve or the disturbed tower-like toner ears,
The image quality deteriorates. In particular, when the volume average diameter of the toner is small, the surface area of the toner is large, frictional charging with the sleeve is large, and electrostatic adhesion to the sleeve is large, the above-mentioned problems are likely to occur.

However, as described above, the problem of the present invention may not be sufficiently solved even if the volume average particle diameter d and the residual magnetization σ _r of the magnetic toner are specified. It was found that there is a relation with the existence state of the binder resin of.

In the present invention, the binder resin is preferably a vinyl polymer having a tetrahydrofuran insoluble content of 5 to 80 wt%. Further, the tetrahydrofuran insoluble content is preferably 10 to 60 wt%.

When the tetrahydrofuran insoluble content is 5 to 80 wt%, the magnetic substance is extremely uniformly dispersed in the binder resin.

Considering that even if a small amount of inappropriate toner particles are included, it is likely to cause blots and unevenness, which is effective in that the magnetic properties of each particle can be made uniform. Is big.

From another aspect, if the kneading viscosity is simply increased and shear is applied, a similar result should be obtained by lowering the resin temperature at the time of kneading. Tetrahydrofuran insoluble matter in the binder resin,
Action to prevent the loss of magnetic material from the toner surface,
Further, it is considered that the coating of the magnetic substance or the charge control agent with the resin component reduces the tetrahydrofuran insoluble content and acts to increase the chargeability and stability on the toner surface, which makes the present invention more remarkable. be able to.
If the tetrahydrofuran insoluble content is less than 5 wt%, the above effect becomes small.

If the content of tetrahydrofuran insolubles is more than 80 wt%, the fixability will be poor and it will be difficult to pulverize the toner, resulting in a decrease in productivity. Further, in a usual kneading machine, insufficient melting or insufficient shearing force may occur, and on the contrary, the dispersion may not be sufficiently performed, and the problem may not be solved.

As the binder resin used in the magnetic toner of the present invention, the following vinyl polymers can be used.

For example, as a comonomer for the styrene monomer of the styrene copolymer, for example, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, acrylic acid-
A monocarboxylic acid having a double bond such as 2-ethylhexyl, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, or the like, or a substituted product thereof; For example, a dicarboxylic acid having a double bond such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate and the like; and substituted products thereof; vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate and the like; Ethylenic olefins such as ethylene, propylene, butylene, etc .; conjugated diene monomers such as butadiene, isoprene, chloroprene, and their derivatives; for example, vinyl methyl ketone,
Vinyl ketones such as vinyl hexyl ketone; and vinyl monomers such as vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc. may be used alone or in combination of two or more.

When a crosslinking agent is required here, a compound having two or more polymerizable double bonds is mainly used, for example,
Aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene and the like; for example, ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,3
A carboxylic acid ester having two double bonds such as butanediol dimethacrylate; a divinyl compound such as divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone; and a compound having three or more vinyl groups; Used alone or as a mixture.

Here, it is also possible to use a mixture of two or more of these vinyl polymers, and it is also possible to use a mixture of these vinyl polymers with other known binder resins for toner. is there.

Further, the binder resin of the present invention preferably has at least one peak of the molecular weight distribution between 2,000 and 10,000, and the peak component is preferably 3 to 60% by weight based on the binder resin. At this time, the toner composition is excellent in fixing property and toner crushing property, and has a more balanced toner structure.

The melt index of the magnetic toner of the present invention is related to the tetrahydrofuran insoluble content of various binder resins,
-12g / 10min (125 ° C, 10Kg charge) is preferred. More preferably, it is 0.5 to 8 g / 10 minutes. Melt index is 0.
If it is less than 2g / 10 minutes, it is difficult to fix the toner.Fixed toner may be electrified and adhered to the fixing roller, or unfixed toner may scatter due to the pressure of the fixing roller, resulting in deterioration of image quality. It is not what the invention wants.

Further, if the melt index is larger than 12 g / 10 min, the crushing due to fixing is large, which causes deterioration of resolution and fine line reproducibility, which is also not preferable.

Further, the magnetic toner of the present invention has a weight average molecular weight of 2,000.
~ 30,000 polyalkylene 0.1% based on resin component
It is good to contain about 10% by weight. Further, the content is preferably 0.5 to 8% by weight. Weight average molecular weight 2,000-30,
The addition of 000 polyalkylene has the effect of speeding the release from the fixing roller at the time of fixing and not deteriorating the image quality.However, as a lubricant, it has a great effect of reducing the core guillate between toner particles, which is important in the copying process. This also makes the flow of the toner in the developing machine uniform, stabilizes the charge, makes it difficult to form the aggregated toner, and has an effect on high image quality. Also in the toner manufacturing process, in the pulverization method, the high-pressure air from the nozzle and the coarsely crushed product are applied to the opposing collision plate to be finely pulverized, but at this time, adhesion to the collision plate and re-fusion between the pulverized particles are prevented. Desired performance
We have found that it is easy to produce shaped toner. In particular, the shape of the toner is greatly affected by the presence of magnetic powder on the surface.

A weight average molecular weight of 2,000 to 30,000 is preferable for obtaining the above effects. If the polyalkylene content is less than 0.5% by weight, the effect is small. When the polyalkylene content is more than 10% by weight, it is difficult to mix with the binder resin, free polyalkylene is likely to be generated, and image defects such as fog are likely to occur.

Examples of the polyalkylene used in the magnetic toner of the present invention include homopolymers such as ethylene, propylene, butene-1, hexene, and 4-methylpentene-1, and ethylene-propylene, ethylene-butene-1, and ethylene-propylene. Copolymers such as hexene, propylene-ethylene, propylene-butene, and propylene-hexene, and their thermally modified products can be used. In particular, polyethylene, polypropylene, a copolymer of propylene and ethylene, butene, and a heat modified product thereof are preferable.

The tetrahydrofuran (THF) insoluble matter in the present invention means
Indicates the weight ratio of the polymer component that became insoluble in the THF solvent in the resin composition in the toner, and the THF insoluble content is
It is defined by the values measured as follows.

That is, 0.5 to 1.0 g of a toner sample is weighed (W
₁ g), put in a thimble filter paper (for example, No.86R manufactured by Toyo Roshi Kaisha), extract through a Soxhletley extractor, using 100 to 200 ml of THF as a solvent for 6 hours, evaporate the soluble components extracted with the solvent, and evaporate 100 g. Vacuum dried at ℃ for several hours, THF
Weigh the amount of soluble resin component (W ₂ g). The weight of a component other than the resin component such as a magnetic substance or a pigment in the toner is expressed as (W
₃ g). The THF-insoluble content is obtained from the following formula.

Although the particle size distribution of the toner can be measured by various methods, in the present invention, the measurement was performed using a Coulter counter.

In other words, the Coulter Counter TA is used as a measuring device.
-Use type II (manufactured by Coulter), connect an interface (manufactured by Nikkaki) and a CX-1 personal computer (manufactured by Canon) that output the number distribution and volume distribution, and use primary sodium chloride as the electrolyte. Prepare 1% NaCl aqueous solution. As a measuring method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the aqueous electrolytic solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample was suspended was treated with an ultrasonic
After dispersing for 2 minutes, the Coulter Counter TA II
According to the mold, the particle size distribution of particles of 2 to 40 μ was measured on the basis of the number, using a 100 μ aperture as the aperture, and then the value according to the present invention was determined.

The melt index here is 125 ° C, a load of 10 kg, an inside diameter of an orifice of 2.095 using an apparatus described in JIS K 7210, a flow test method for thermoplastics of Japanese Industrial Standards.
The measurement was performed by 5 ± 0.0051 mm and length 8.000 ± 0.025 mm.

There are various methods for measuring the weight average molecular weight Mw, which causes some differences. Therefore, it is measured by the following measurement method.

That is, by gel permeation chromatography (GPC), temperature 40 ℃, solvent tetrahydrofuran,
A flow rate of 1.0 ml / min and a concentration of 0.1 wt% THF are injected at 300 μm. In measuring the molecular weight of the sample, a calibration curve created with a monodisperse polystyrene standard sample is used. The column is not limited to this, but for example, KF-80M, KF802, 803, 804, 805, etc. manufactured by SHIODEX. It is good to combine these columns for accurate measurement.

In the present invention, the magnetic characteristics of the magnetic toner are VSMP-1-
External magnetic field 1 Ke at room temperature using 10 (Toei Kogyo Co., Ltd.)
It was calculated from the result of measurement in.

Further, the magnetic toner of the present invention may also serve as a colorant, but contains a magnetic material. Examples of the magnetic material contained in the magnetic toner of the present invention include iron oxides such as magnetite, γ-iron oxide, ferrite, and iron-rich ferrite;
Metals such as iron, cobalt, nickel or these metals and aluminum, cobalt, copper, iron, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium. Examples thereof include alloys with various metals and mixtures thereof.

These ferromagnetic materials have an average particle size of 0.1 to 1 μm, preferably 0.1 to 0.5 μm, and the amount contained in the magnetic toner is 40 to 2 per 100 parts by weight of the resin component.
00 parts by weight, preferably 50 to 150 per 100 parts by weight of the resin component
Parts by weight.

The addition amount of these should be determined in relation to the residual magnetization of the toner and the particle size of the toner.

The developer of the present invention is based on the above findings and has a particle size distribution described above and a magnetic toner having a material composition and having a triboelectric charging property of 50 μc / g (absolute value) or less with iron powder, preferably 20 μc / g.
(Absolute value) or less, and a charge easing agent fine powder having a number average particle diameter of 0.5 μm or less or a mixture thereof is mixed with magnetic toner particles (internal addition) or mixed with magnetic toner particles (external addition). It is characterized by being used.

The content of the charge relaxation agent fine powder used in the present invention is 0.1 to 50 parts by weight, preferably 0.2 to 30 parts by weight with respect to 100 parts by weight of the binder resin in the case of internal addition, and magnetic in the case of external addition. Toner 1
It is 0.01 to 10 parts by weight, preferably 0.02 to 5 parts by weight, relative to 00 parts by weight.

Specific examples of the above charge easing agent include the following substances. Carbon black, graphite, etc., substances mainly consisting of carbon atoms, magnesium oxide, alumina, titanium oxide, iron oxide, nickel oxide, chromium oxide, copper oxide, zinc oxide, tin oxide, cerium oxide, cobalt oxide, zirconium oxide Examples thereof include metal oxides mainly composed of metal atoms (one or several) and oxygen atoms. It is considered that these substances are less likely to be charged, or are exposed to moisture in the air and easily release charges. In fact, the charge of these substances on iron powder is
It is 50 μc / g (absolute value) or less, preferably 20 μc / g (absolute value) or less.

By containing an appropriate amount of fine powders of these substances in the magnetic toner, excessive triboelectric charging can be suppressed, and excessively charged charges can be released.

That is, it is considered that these fine powders act as a charge easing agent that reduces the triboelectric charge amount of the magnetic toner to an appropriate size.

As a method of incorporating the charge relaxation agent fine powder into the developer of the present invention, there are an internal addition method and an external addition method. However, since the external addition method is more present on the surface of the magnetic toner, a small addition amount is required. Great effect can be expected. Further, when the effect is exerted in a very small amount or when the magnetic toner is easily desorbed from the surface of the magnetic toner, the addition amount can be increased in order to disperse well in the developer, or an internal addition method of fixing to the surface of the magnetic toner is also effective. .

When the fine powder in the developer of the present invention has magnetism, the internal addition method can be used as long as it is within the range of desired magnetic characteristics required for the magnetic toner. However, when the magnetic characteristics of the magnetic toner are greatly affected, the addition amount can be reduced by external addition to achieve the purpose.

When the triboelectrification property is 50 μc / g or more in absolute value, the relaxation of the charge may not be sufficient, and when the polarity is opposite to the polarity of the magnetic toner, fogging may be increased or the density may be reduced. May be given.

When the number average particle diameter exceeds 0.5 μm, the dispersibility in the developer becomes poor, the particles vary, the developability is adversely affected, and good images such as fogging increase can be provided. The effect may increase as the average particle diameter of the magnetic toner of the present invention decreases.

When the content is more than the predetermined content, the amount of decrease in the charge amount becomes large under high humidity and the like, and image defects such as low image density occur. On the other hand, when the content is less than the predetermined content, the effect of alleviating the electrostatic charge cannot be exerted well, and the electrostatic charge tends to be excessively charged, which may cause a decrease in density and unevenness of the sleeve coat.

Here, the method for measuring the charge amount of the developer and the charge relaxation agent fine powder in the present invention will be described in detail with reference to the drawings.

FIG. 5 is an illustration of an apparatus for measuring the amount of electric charge. First, in a metal measuring container 32 having a screen 33 of 400 mesh at the bottom, a weight ratio of the sample to be measured for the charge and the developer of the iron powder carrier (200 to 300 mesh) is 10: 9.
0, for the charge easing agent fine powder, about 1 g of a mixture having a weight ratio of 2:98 is put, and the metal lid 34 is placed. At this time, the weight of the entire measurement container 32 is weighed and set as W ₁ (g). Next, the suction device 31 (measurement container
At least the part in contact with 32) is the insulator
Suction from 37 and adjust the air volume control valve 36 to adjust the pressure of the vacuum gauge 35
250mmH ₂ O In this state, sufficient suction is performed to remove the sample by suction. At this time, the potential of the electrometer 39 is set to V (volt). Here, 38 is a capacitor whose capacity is C
(ΜF). Further, the weight of the whole measurement container after suction is weighed to be W ₂ (g). Electric charge of this sample (μc / g)
Is calculated as follows:

However, the measurement conditions are 23 ° C and 60% RH.

In addition, the carrier (iron powder) used for measurement is from 200 to 300 mesh, but in order to eliminate the error, the carrier was sufficiently sucked by the above suction device and the one that passed through the 400 mesh screen was removed before the sample. Mix.

In the magnetic toner of the present invention, it is preferable that a charge control agent is blended (internally added) to the toner particles or mixed (externally added) with the toner particles for use. The charge control agent makes it possible to control the optimum charge amount according to the developing system, and further stabilizes the effect of the charge easing agent. Examples of the positive charge control agent include modified products of nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate; dibutyltin oxide, dioctyltin oxide. , Diorganotin oxide such as dicyclohexyltin oxide; diorganotin borate such as dibutyltin borate, dioctyltin borate and dicyclohexyltin borate can be used alone or in combination of two or more kinds. Among these, charge control agents such as nigrosine and quaternary ammonium salts are particularly preferably used.

Also, the general formula R ₁ : H, CH ₃ R ₂ , R ₃ : a substituted or unsubstituted alkyl group (preferably C ₁
To C ₄ ): A homopolymer of a monomer represented by the following formula: or a copolymer with a polymerizable monomer such as styrene, an acrylate or a methacrylate as described above can be used as a positive charge control agent. In these cases, these charge control agents also have an action as (all or part of) the binder resin.

As the negative charge controlling agent that can be used in the present invention, for example, an organometallic complex and a chelate compound are effective, and examples thereof include aluminum acetylacetonate, iron (II) acetylacetonate, and 3,5-ditertiary. There are chromium butylsalicylate and the like, particularly preferred are acetylacetone metal complexes, salicylic acid-based metal complexes or salts,
Particularly, a salicylic acid-based metal complex or a salicylic acid-based metal salt is preferable.

When internally added to the toner, such a charge control agent is used in an amount of 0.1 to 20 parts by weight (more preferably, 0.2 to 10 parts by weight) based on 100 parts by weight of the binder resin.
Parts by weight).

Further, it is preferable to add fine silica powder to the magnetic toner of the present invention. It seems that this is due to the effect that the charge of the silica fine powder is appropriately leaked from the toner, but it is possible to maintain an appropriate amount of charge even in an environment of ultra-low temperature and low humidity, and the magnetic toner of the present invention is excellent. It can be.

As the silica fine powder, silica fine powder produced by a dry method or a wet method can be used, but it is preferable to use the silica fine powder by the dry method from the viewpoint of filming resistance and durability.

Among the above silica fine powders, those having a specific surface area of 30 m ² / g or more (particularly 50 to 400 m ² / g) measured by the BET method by nitrogen adsorption give good results. 0.01 to 8 parts by weight of silica fine powder, preferably 100 parts by weight of magnetic toner, preferably
It is preferable to use 0.1 to 5 parts by weight.

When the magnetic toner of the present invention is used as a positively chargeable magnetic toner, the silica fine powder added for preventing abrasion of the toner and preventing contamination of the sleeve surface is positively charged rather than negatively charged. It is preferable to use fine silica powder without damaging the charge stabilizer.

As a method for obtaining the positively chargeable silica fine powder, a method of treating the above-mentioned untreated silica fine powder with a silicon oil having an organo group having at least one nitrogen atom in a side chain, or a nitrogen-containing silane cap There is a method of treating with a ring agent or a method of treating with both.

In the present invention, the positively-charged silica refers to a silica having a positive tribocharge with respect to an iron powder carrier when measured by a blow-off method.

As the silicon oil having a nitrogen atom in a side chain used for treating the silica fine powder, a silicon oil having at least a partial structure represented by the following formula can be used.

(Wherein, R ₁ represents hydrogen, an alkyl group, an aryl group or an alkoxy group, R ₂ is an alkylene group or represents a phenylene group, R ₃ and R ₄ represents hydrogen, an alkyl group, or aryl group, R ₅ Represents a nitrogen-containing heterocyclic group) The alkyl group, aryl group, alkylene group, and phenylene group may have an organo group having a nitrogen atom, and may be substituted with halogen or the like as long as the chargeability is not impaired. It may have a group.

Further, the nitrogen-containing silane coupling agent used in the present invention,
It generally has a structure represented by the following formula.

R _m -Si-Y _n (R represents an alkoxy group or a halogen, Y represents an organo group having at least one amino group or a nitrogen atom, m and n is an integer of 1 to 3 m + n =
4. Examples of such treating agents are aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, Monobutylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-
γ-propylphenylamine, trimethoxysilyl-γ
-Propylbenzylamine and the like, and the nitrogen-containing heterocycle may have the above-mentioned structure. Examples of such compounds include trimethoxysilyl-γ-propylpiperidine and trimethoxysilyl-γ-propylmorpholine. And trimethoxysilyl-γ-propylimidazole.

The applied amount of these treated positively charged silica fine powders is 0.01 to 8 with respect to 100 parts by weight of the positively charged magnetic toner.
The effect is exhibited when the amount is by weight, and particularly preferably 0.1 to 5 parts by weight.
Positive chargeability with excellent stability when added in parts by weight. In a preferred embodiment, the addition form is such that 0.1 to 3 parts by weight of the treated silica fine powder is attached to the surface of the toner particles with respect to 100 parts by weight of the positively charged magnetic toner. The untreated silica fine powder described above can be used in the same application amount.

The silica fine powder used in the present invention may be treated with a silane coupling agent, if necessary, with a treating agent such as an organosilicon compound for the purpose of hydrophobization, and reacts or physically adsorbs with the silica fine powder. It is treated with the above treatment agent. Examples of such treating agents include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, and benzyldimethylchlorosilane. , Bromomethyldimethylchlorosilane,
α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxy. Silane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and 2 to 12 siloxane units per molecule, each of which is a terminally located unit. There is dimethylpolysiloxane containing a single Si-bonded hydroxyl group. These are used alone or in a mixture of two or more.

Further, in the present invention, a fine powder of a fluorine-containing polymer,
For example, it is preferable to add fine powder of polytetrafluoroethylene, polyvinylidene fluoride or the like and a tetrafluoroethylene-vinylidene fluoride copolymer. Particularly, fine powder of polyvinylidene fluoride is preferable in terms of fluidity and abrasivity. The amount added to the toner
0.01 to 2.0 wt%, particularly preferably 0.02 to 1.0 wt%.

In particular, in a magnetic toner in which silica fine powder and the above fine powder are combined, the reason is not clear, but stabilizes the presence state of silica attached to the toner, for example, the attached silica is released from the toner, and the effect Can be prevented, and the charging stability can be further increased.

The magnetic toner of the present invention may optionally contain additives. Dyes conventionally known as colorants,
Pigments can be used, and usually 0.5 to 20 parts by weight per 100 parts by weight of the binder resin may be used. Other additives include, for example, lubricants such as zinc stearate, abrasives such as silicon carbide, and anti-caking agents.

In producing the magnetic toner according to the present invention, the magnetic toner constituent materials as described above are thoroughly mixed by a ball mill or other mixing machine, and then thoroughly kneaded by using a heat kneader such as a heat roll kneader or an extruder, followed by cooling. A method of obtaining a magnetic toner by mechanical pulverization and classification after solidification is preferable; and a method of obtaining a magnetic toner by dispersing constituent materials in a binder resin solution and then spray-drying; or a binder resin. In a so-called microcapsule toner composed of a core material and a shell material, a polymerization method for producing a magnetic toner by mixing a predetermined material with a monomer to form an emulsified suspension, and then polymerizing the same.
A method of incorporating a predetermined material into the core material, the shell material, or both of them, and the like can be applied. Further, if desired, desired additives can be sufficiently mixed with a mixer such as a Henschel mixer to produce the developer for developing an electrostatic image according to the present invention.

In the present invention, a developing sleeve having a smooth surface property is preferable, but in particular, an electrostatic image holding member that holds an electrostatic image on the surface and a toner holding member that holds a magnetic toner on the surface are fixed in the developing unit. In a developing method, in which a magnetic toner is disposed with a gap, the magnetic toner is regulated to have a thickness smaller than the gap on the toner carrier, and the magnetic toner is conveyed to the developing unit, where the toner is developed while applying an alternating electric field to the toner, The carrier has a surface on which unevenness is formed by a plurality of spherical trace dents by blasting with shaped particles, and more preferably the surface of the toner carrier has a diameter of spherical trace dents R = 20 to
250 μm, irregular pitch P = 2 to 100 μ, surface roughness d = 0.
It is preferably 1 to 5 μ.

The sleeve in the present invention has a surface having irregularities formed by a plurality of spherical trace depressions. As a method for obtaining the surface state, a blasting method using shaped particles can be used. As the regular particles, for example, stainless steel, aluminum, steel, nickel, brass and other metals having a specific particle diameter, various rigid spheres such as ceramics, plastics and glass beads can be used. By blasting the sleeve surface with regular particles having a specific particle size, it is possible to form a plurality of spherical trace depressions having substantially the same diameter R.

In the present invention, the diameter R of the spherical dents on the surface of the sleeve is preferably 20 to 250 μm, and the diameter R is 20 μm.
If it is m or less, contamination by components in the magnetic toner increases, which is not preferable, and conversely, if the diameter R is 250 μm or more,
The toner coat on the sleeve is not uniform and is not preferable. Therefore, it is preferable that the regular particles used for the blast treatment of the sleeve surface have a diameter of 20 to 250 μm. Further, in the present invention, the irregularity pitch P and the surface roughness d of the sleeve surface are measured by using a fine surface roughness meter (sales agency, Taylor Hopson Co., Kosaka Laboratory, etc.) on the surface of the sleeve,
The surface roughness d is JIS 10-point average roughness (RZ) “JIS B 06
01 ”.

That is, as shown in FIG. 5, a straight line parallel to the average line of the portion obtained by extracting the reference length l from the sectional curve is 3 from the highest.
The distance between two straight lines, which passes through the top of the second peak and the bottom of the third valley from the deepest, is expressed in micrometers (μm), and the reference length l = 0.25 mm. Also pitch P
Is obtained as follows by counting the protrusions having a height of 0.1 μ or more with respect to the recesses on both sides as one ridge, and calculating the number of ridges within the reference length of 0.25 mm.

Number of peaks included in 250 (μ) / 250 (μ) (μ) In the present invention, the pitch P of the unevenness on the sleeve surface is 2
Is preferably 100 μm or less, and when P is 2 μm or less, contamination of the sleeve by the components in the magnetic toner increases, which is not preferable.
On the other hand, when P is 100 μ or more, the uniformity of the toner coat on the sleeve is deteriorated, which is not preferable. The surface roughness d of the irregularities on the sleeve surface is preferably 0.1 to 5 μm, and d is 5
When the thickness is more than μm, in the system in which an alternating voltage is applied between the sleeve and the latent image holding member to cause the magnetic toner to fly from the sleeve side to the latent image surface for development, the electric field is concentrated on the uneven portion. It is not preferable because it tends to cause disorder in the image,
On the other hand, if d is 0.1 μ or less, the uniformity of the toner coat on the sleeve is deteriorated, which is not preferable.

As a sleeve used in the present invention, the surface of a blasted glass sleeve having a diameter of 53 to 62 μm with a diameter of 53% to 62 μm having a stainless steel sleeve surface as a constant-diameter particle and a surface of the surface of which is 1000 times taken by a scanning electron microscope is shown in FIG. Show.

In the present invention, the amount of charge of the magnetic toner on the cylindrical sleeve was measured by the following method using the measuring device shown in FIG.

Put the magnetic toner to be measured in the measuring device set to the predetermined conditions, and rotate the cylindrical sleeve 12 at a peripheral speed of 150 mm / sec at 23 ° C. and 60% RH environment. The charge amount of the toner layer 13 per unit area was determined by using a so-called suction type Faraday gauge method. In this suction type Faraday gauge method, the outer cylinder is pressed against the sleeve 12 to suck all the toner on a certain area on the sleeve, and the toner is collected in the filter of the inner cylinder and from the weight increase of the filter,
The weight of the toner layer per unit area on the sleeve can be calculated. At the same time, by measuring the amount of electric charge accumulated in the inner cylinder that is electrostatically shielded from the outside, the amount of electric charge Q / S (μc / cm ² ) per unit area on the sleeve can be obtained. .

The conditions of the charge amount measuring device will be described with reference to FIG. The measuring device is similar to that of a developing machine, and is composed of a toner hopper 15, a cylindrical sleeve 12 and an opposing magnetic blade 11, and the cylindrical sleeve 12 is driven by a drive motor at a constant peripheral speed (150 mm / sec) in the direction of the arrow. Then, the toner is applied in a thin layer on the surface of the cylindrical sleeve 12 via the magnetic blade 11 and the charge amount is measured as described above over time, and the change of the toner on the sleeve 12 is observed. The gap between the blade 1 and the sleeve 12 is set to about 250 μm, the shape of the toner hopper is roughly the diameter of the sleeve, and the radius of the sleeve is larger than the radius of the sleeve. Make it smaller than the radius. The cylindrical sleeve 12 has a fixed magnet 14 inside.
And the magnetic pole strength is N ₁ about 800G (about 5 from the blade facing)
° Hopper side), S ₁ about 1000G, N ₂ about 750G, S ₂ about 550G. The sleeve 12 is made of stainless steel (SUS304) with a diameter of 20 mm, and the surface of the sleeve 12 is blasted with a blasting nozzle using regular glass bead particles having a diameter of 53 to 62 μm of 80% or more. 53-62 μm, uneven pitch P is about 33 μm, and surface roughness d is about 2 μm.

The pitch P of the irregularities on the sleeve surface and the surface roughness d were measured on the sleeve surface using a fine surface roughness meter (manufactured by Kosaka Laboratory).

In the present invention, the charge amount was measured by measuring methods specified below ^{Q / S (nc / cm 2} ) is good 3~12nc / cm ^2. More preferably 4 to 11 nc / cm ² , and even more preferably 5
~ 10nc / cm ² is good.

When Q / S> 12 (nc / cm ² ), the charge is excessive, the reflection power is too large, and the blotches and unevenness are likely to occur even in the measuring device.

If the remanent magnetization of the toner is further increased in order to counter this, the ears of the toner become long, and improvement in image quality cannot be expected.

When such a toner is used to continue copying, the toner adheres to the sleeve due to a strong mirroring force, which makes it difficult for the toner to fly to the photosensitive member, resulting in a decrease in density.

When Q / S <3 (nc / cm ² ), the charge amount is insufficient and the density becomes light. Especially in a high temperature and high humidity environment, the charge amount further decreases and the density becomes very low. If copying is continued, the toner having low developability remains due to the selective development, resulting in a decrease in density and a deterioration in image quality.

In the present invention, fine line reproducibility was measured by the following method. In other words, an image obtained by copying an original of a fine line accurately having a width of 100 μm under an appropriate copying condition is used as a measurement sample, and a Luzex 450 particle analyzer is used as a measuring device. Measurement. At this time, since the line width measurement position has irregularities in the width direction of the thin line image of the toner, the average line width of the irregularities is used as the measurement point. From this, the value (%) of the fine line reproducibility is calculated by the following equation.

In the present invention, the resolution was measured by the following method. That is, a pattern consisting of five fine lines with the same line width and spacing, and 2.8, 3.2, 3.6, 4.0, 4.5, 5.
Create an original image that is drawn as if there were 0, 5.6, 6.3, 7.1 or 8.0 lines. Observe an image obtained by copying the original manuscript with these 10 line images under appropriate copying conditions with a magnifying glass, and determine the resolution value with the number of images (lines / mm) in which fine lines are clearly separated. I do.

 The larger this number is, the higher the resolution is.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto. All parts in the following formulations are parts by weight.

Example 1 After thoroughly mixing the above ingredients with a Hensiel mixer,
It was kneaded with a kneading mixer set at 180 ° C.
After cooling the obtained kneaded material, coarsely pulverized by a cutter mill, finely pulverized using a fine pulverizer using a jet stream,
The finely pulverized powder obtained was classified by a fixed wall type air classifier to obtain a magnetic toner.

The volume average particle diameter of the obtained magnetic toner was 9.0 μm, the residual magnetization was 3.8 emu / g, and the melt index was 2.5 g / 10 minutes.

To 100 parts by weight of the obtained magnetic toner, 0.4 parts by weight of positively charged hydrophobic silica (BET specific surface area 130 m ² / g) and dry aluminum oxide fine particles (number average particle size 0.02 μm, charge amount +3.6
μc / g) 0.2 part by weight was added and mixed with a Henschel mixer to give a one-component magnetic developer.

In addition, the maximum Q / S value measured by the method defined in the present invention in a low temperature and low humidity environment (15 ° C, 10%) where broccles, unevenness, etc. are particularly likely to occur is 8.7 nc / cm ² No abnormality was found on the developing sleeve, and a uniform toner coat layer was always held.

In the developing area, the magnetic toner formed ears having a height of about 85 μm.

The above-mentioned one-component magnetic developer was applied to a high-speed copying machine having a developing device as shown in FIG. Cylindrical stainless steel sleeve 2 (SUS3
04) 80% or more diameter 53-62μ as regular particles on the surface
m glass beads, spray nozzle diameter 7φ, distance
Blasting treatment was performed under the conditions of 100 mm and an air pressure of 4 kg / cm ² for 2 minutes to form irregularities in which the diameter R of the plurality of spherical dents was 53 to 62 μm. The unevenness P on the surface of the sleeve was 33 μ, and the surface roughness d was 2.0. The one-component developer 10 is applied in a thin layer via a magnetic blade 1A on the surface of a stainless steel cylindrical sleeve 7 rotating at a peripheral speed of 390 mm / sec in the direction of the arrow, and the gap between the sleeve 2 and the blade 1A is approximately
It was set to 250 μm. The sleeve 2 has a fixed magnet 4 as a magnetic field generating means, and a magnetic field of 950 gauss is fixed in the vicinity of the sleeve surface in the developing area near the OPC photosensitive drum 9 having the organic photoconductive layer having a negatively charged latent image. Had formed. Rotate in the direction of the arrow at a peripheral speed of 260 mm / sec.
The closest distance between the OPC photosensitive drum 9 and the sleeve 2 is about 300 μm.
Set to. In addition, between the OPC photosensitive drum 9 and the sleeve 2, the AC bias and the DC bias are synergized to 2000 Hz / 135
A bias of 0 Vpp was applied.

Table 1 shows the results of the image-forming test performed 10,000 times under low-temperature and low-humidity conditions (15 ° C, 10% RH), which are particularly prone to causing blotches and unevenness. As is clear from Table 1, the image density was high, the fine line reproducibility and the resolution were excellent, and the initial good image quality was maintained even after outputting 10,000 sheets. In addition, there was no occurrence of blots or unevenness during image formation, and no problems related to fixing and offset occurred.

Example 2 Using the above materials, the volume average particle size is the same as in Example 1.
A black fine powder of 5.1 μm was obtained. Remanent magnetization is 4.8emu / g, M
I was 12.5 g / 10 minutes.

To 100 parts by weight of a magnetic toner of black fine powder, 0.5 parts by weight of hydrophobic dry silica was added and mixed with a Henschel mixer to prepare a one-component magnetic developer.

Using the same developing device as in Example 1, evaluation was performed in the same manner as in Example 1 under severe low humidity conditions of 15 ° C. and 10%. As is clear from Table 1, both the initial image and the image after the 10,000-sheet endurance have high image density, are free from fog, are clear, and have high image quality. Also, sleeve contamination and uneven toner coat of the sleeve are recognized. I couldn't do it.

The maximum Q / S value measured by the measurement method specified in the present invention is 7.8.
nc / cm ² , no abnormality was observed on the sleeve during the measurement for 2 hours, and a uniform toner coat layer was always held, and the height of the magnetic toner was about 65 μm.

Example 3 A magnetic toner was obtained in the same manner as in Example 1 using the above materials. The volume average particle size of the obtained magnetic toner was 13 μm, the residual magnetization was 2.6 emu / g, and the MI was 0.50 g / 10 minutes.

Fine powder of tin oxide (number average particle size)
0.1 μm, charge amount −6.6 μc / g) 0.2 part by weight is strongly mixed with a turbo mixer to strongly adhere, then 0.5 part by weight of positively charged hydrophobic silica is added and mixed with a Hensiel mixer, Used as a developer.

The maximum value of Q / S measured by the measurement method specified in the present invention is 7.0.
nc / cm ² , no abnormality was observed on the sleeve during the measurement for 2 hours, and a uniform toner coat layer was always held, and the height of the magnetic toner was about 110 μm. When evaluated in the same manner as in Example 1, a stable and clear high-quality image was obtained as shown in Table 1.

Comparative Example 1 The black fine powder of Example 1 was mixed with positively charged hydrophobic silica (BE
Only 0.4 parts by weight of T specific surface area of 130 m ² / g) was mixed with a Henschel mixer to prepare a developer, and the same high speed electrophotographic copying machine as in Example 1 was used for evaluation.

Under low temperature and low humidity conditions of 15 ℃, 10%, as the durability progresses,
The image density decreased to 1.31 from 1.40 to 10,000 sheets. In addition, the image quality was deteriorated due to fine lines and rustling due to the charge gap.

At this time, the toner charge amount Q / S on the sleeve is initially 12n
It was as high as 18 nc / cm ² after repeated copying at c / cm ² .

Comparative Example 2 A magnetic toner was obtained in the same manner as in Example 1 using the above materials. The volume average particle diameter of the obtained magnetic toner was 12 μm, and the residual magnetization was 2.1 emu / g. The melt index was 15 g / 10 minutes.

0.4 part by weight of hydrophobic silica fine powder was added to the obtained magnetic toner and mixed with a Henschel mixer to prepare a one-component magnetic developer.

The maximum value of Q / S measured by the measurement method specified in the present invention is 14.
It was as high as 5, and the blotting started to occur 2 minutes after the start of measurement. When the image formation was evaluated in the same manner as in Example 1, the height of the spikes on the sleeve was 140 μ, and the shapes were disordered and overlapped in a tower shape. The fine line reproducibility and resolution were poor, and when image formation was continued, the image density decreased, fine line reproducibility and resolution deteriorated, and sleeve unevenness that spreads in liquid form occurred.

Comparative Example 3 Using the above materials, in the same manner as in Example 1, hydrophobic silica and dry aluminum oxide fine powder were mixed to obtain a developer. The volume average particle diameter of the obtained developer was 7.5 μm, and the residual magnetization was 1.5 emu / g, which was smaller than that specified by the present invention. The melt index was 3.0 g / 10 minutes.

Using this developer, image formation was evaluated under the same severe conditions as in the examples. The image was relatively good at the initial stage, but when the image was continuously produced, the image quality was unclear, the density was lowered, and the image lacked sharpness, and spotted sleeve unevenness was generated. Further, when the toner was idly rotated by the measuring method defined in the present invention, the Q / S was 9.0, but after 10 minutes, a blot was generated. The problem is that σ _{r of} the toner is too small with respect to the particle size.

[Brief description of the drawings]

In the attached drawings, FIG. 1 shows a schematic cross-sectional view of a developing device used for image formation in Examples and Comparative Examples, and FIG. 2 shows a metallographic structure of a sleeve blasted with regular particles according to the present invention. The scanning electron micrograph of the surface is shown. FIG. 3 is a schematic diagram of the charge amount measuring device used in the present invention, FIG. 4 is a diagram showing the relationship between the volume average particle size of magnetic toner and residual magnetization, and FIG. 5 is the friction of fine powder. It is explanatory drawing of the apparatus which measures a charge amount. 1a Magnetic blade 2 Sleeve 3 Applied magnetic toner 4 Fixed magnetic roller 7 Developing container 9 Photosensitive drum 10 Magnetic toner 11 Magnetic blade 12 Cylindrical sleeve 13 Toner Coat layer 14 ... Fixed magnet 15 ... Toner hopper 16 ... Toner ... Gap between blade 11 and sleeve 12 ... Distance between sleeve upper surface and toner upper surface ... Distance from sleeve to hopper wall and ceiling 32 ... Measuring container 33 …… screen (400 mesh) 37 …… suction port 39 …… electrometer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Yoshida 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-55-147638 (JP, A) JP-A-62 -141568 (JP, A) JP 61-148457 (JP, A) JP 57-158658 (JP, A) JP 60-217368 (JP, A)

Claims (1)

(57) [Claims] 1. A magnetic toner having at least a binder resin and a magnetic powder, wherein the binder resin is a vinyl polymer having a tetrahydrofuran insoluble content of 5 to 80% by weight, and the residual magnetization σ _r of the magnetic toner is The volume average particle diameter d satisfies the following formula, 3.7-0.11d ≤ σ _r ≤ 6.5-0.23d [where σ _r is the residual magnetization (emu / emu /
g). d is a volume average particle diameter (μm), and is 3 to 1
6 ] Melt index is 0.2 to 12g / 10 minutes (125 ℃, 10Kg load), and the amount of triboelectricity with iron powder is 50μc / g (absolute value)
A developer for electrostatic charge image development, characterized in that it contains a carbon allotrope or a metal oxide as a charge relaxation agent fine powder having a number average particle diameter of 0.5 μm or less.