JPH0264556A - Developer for electrostatic image development - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic image developer containing a magnetic toner used in electrophotography, electrostatic recording, magnetic recording, and the like.

As a conventional electrophotographic method, U.S. Patent No. 2,297,691
specification, Japanese Patent Publication No. 42-23910 (U.S. Patent No. 3,666.363) and Japanese Patent Publication No. 43-247
Publication No. 48 (U.S. Patent No. 4,071,361)
Although a number of methods are known, generally a photoconductive material is used to form an electrical latent image on a photoreceptor by various means, and then the latent image is The image is developed with toner to form a visible image, and if necessary, the toner image is transferred to a transfer material such as paper and then fixed by heating, pressure, etc. to obtain a copy.

Various developing methods are also known in which an electrostatic latent image is visualized using toner. For example, the magnetic brush method described in U.S. Pat. No. 2,874,063, U.S. Pat.
A large number of development methods are known, such as the cascade development method described in No. 2,221,776, the powder cloud method, the fur brush development method, and the liquid development method. ing. Among these developing methods, the magnetic brush method, cascade method, liquid developing method, etc., which use a developer mainly consisting of toner and carrier, are in particular widely put into practical use.

All of these methods are excellent methods in which good images can be obtained relatively stably, but on the other hand, they have common drawbacks associated with two-component developers, such as deterioration of the carrier and fluctuations in the mixing ratio of toner and carrier.

In order to avoid such drawbacks, various development methods have been proposed that use l-component developers made only of toner, but among these, many are superior to methods that use developers made of magnetic toner particles.

US Pat. No. 3,909,258 proposes a developing method using an electrically conductive magnetic toner. In this method, conductive magnetic toner is supported on a cylindrical conductive sleeve having magnetism inside, and is brought into contact with an electrostatic image to be developed. At this time, in the developing section, a conductive path is formed by the toner particles between the surface of the recording medium and the surface of the sleeve, and charges are guided from the sleeve to the toner particles through this conductive path, and between them and the image area of the electrostatic image. Toner particles adhere to the image area due to Coulomb force and are developed.

This developing method using conductive magnetic toner is an excellent method that avoids the problems associated with conventional two-component developing methods, but on the other hand, since the toner is conductive, the developed image
It has the disadvantage that it is difficult to electrostatically transfer it from a recording medium to a final support member such as plain paper.

As a developing method using a high-resistance magnetic toner that can be electrostatically transferred, there is a developing method that utilizes dielectric polarization of toner particles. However, such a method inherently has drawbacks such as slow development speed and insufficient density of the developed image, and is difficult in practice.

Other developing methods using high-resistance magnetic toner include
A known method is to triboelectrically charge toner particles by friction between toner particles or friction between toner particles and a sleeve or the like, and then develop the toner particles by bringing them into contact with an electrostatic image holding member. However, these methods have drawbacks such as the number of times the toner particles come into contact with the friction member is small (frictional charging tends to be insufficient), and the Coulomb force between the charged toner particles and the sleeve increases and they tend to aggregate on the sleeve. This makes it difficult to put it into practical use.

However, in JP-A-55-18656, etc.,
A new development method has been proposed which eliminates the above-mentioned drawbacks. This involves applying a very thin layer of magnetic toner onto the sleeve, triboelectrically charging it, and then developing it in close proximity to the electrostatic image. This method increases the chances of contact between the sleeve and the toner by applying an extremely thin layer of magnetic toner onto the sleeve, enabling sufficient frictional charging, supporting the toner with magnetic force, and moving the magnet and toner relative to each other. Excellent images can be produced by moving the toner particles to prevent mutual agglomeration and creating sufficient friction with the sleeve, supporting the toner by magnetic force, and developing it by facing the electrostatic image without touching it. That's what you get.

However, as image forming devices such as electrophotographic copying machines have become widespread in recent years, their uses have expanded to a wide variety of uses, and the demands on image quality have become stricter. There is a pressing need to resolve this issue.

In other words, even in general copying, it is faithful to the original manuscript, and even the smallest letters are not crushed, cut off, etc.
There is a need for extremely high-definition reproduction (without scattering), and printers that produce computer output must have high reliability to remain stable and clear even after continuous long-term use. Ta,
In the field of more precise graphic copying, large-area, high-density copying, fine line reproducibility, and gradation are required.

In particular, the latent image on the photoreceptor of the image forming device is 100 μm.
Thin line reproducibility is generally poor in the case of line images of less than A latent image is formed by a collection of dots with a constant potential, and solid areas, halftone areas, and light areas are expressed by changing the dot density.

However, if the toner particles do not adhere to the dots faithfully and the toner particles protrude from the dots, the gradation of the toner image that corresponds to the ratio of dot densities in the black and white areas of the digital latent image cannot be obtained. There is a problem. Furthermore, when improving resolution by reducing dot size in order to improve image quality, it becomes more difficult to reproduce latent images formed from minute dots, resulting in poor resolution, poor gradation, and poor sharpness. This tends to result in images lacking in detail.

Several proposals have been made for magnetic toners to address these problems.

In U.S. Pat. No. 4,299,900, 20 to 35
A jumping development method using a developer having 10 to 50% by weight of .mu.m magnetic toner has been proposed. That is, efforts have been made to triboelectrically charge the magnetic toner, to uniformly and thinly apply a toner layer on the sleeve, and to improve the image density and the environmental stability of the developer by determining the particle size of the toner. However, considering the stricter requirements such as fine line reproducibility and resolution, this is not sufficient (further improvements are required).

Further, in JP-A-56-21135, the number average molecular weight, residual magnetic moment, and saturation magnetic moment of a magnetic toner are defined, 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 resolution and reproducibility because it is transferred to the recording medium as a tower-shaped toner aggregate, and the number average particle size is 2 to 10 μm and the residual magnetic moment is 0.1. Since it is as small as ~2 emu/g, the above-mentioned problem cannot be solved in a normal development method.

Furthermore, Japanese Patent Laid-Open No. 57-90640 specifies the shape and magnetic properties of magnetic bodies. The use of non-friable large agglomerate magnetite of 1 to 10 μm as in the toner tends to cause poor dispersion of magnetite in the toner particles, resulting in fogging and deterioration of image quality due to use.

Against this background, the inventors of the present invention have found that magnetic toners have problems such as insufficient image density, poor image quality such as resolution and fine line reproducibility, and unstable image quality such as Bronner unevenness on the sleeve. Many of these factors are due to the small charging power of the magnetic toner on the surface, the non-uniformity of the amount of charge for each particle, the ease with which it stands up, the length and shape of the ears (the electrostatic properties of the toner, It is related to magnetic properties, and in particular, the present inventors have discovered that favorable results are produced when the particle size of the toner and the residual magnetization of the toner have a specific relationship, and that the preferred state of existence of the magnetic powder has a specific result. The inventors found that the amount of charge can be suppressed to an appropriate and uniform amount by using a binder resin or the like, and by containing a specific charge moderator fine powder, and after researching this point, they arrived at the present invention.

[Purpose of the invention]

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

A further object of the present invention is to provide a developer with high image density, excellent fine line reproducibility, and excellent gradation.

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

A further object of the present invention is to provide a developer that does not change in performance due to environmental changes and has excellent durability, particularly under low humidity conditions.

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

A further object of the present invention is to provide a developer that can provide high image density with low consumption.

A further object of the present invention is to provide a developer that can form toner images with excellent resolution, gradation, and fine line reproducibility even in image forming apparatuses using digital image signals.

[Summary of the invention]

The present invention provides a magnetic toner containing a binder resin and a small amount of magnetic powder, in which the molecular weight distribution of the binder resin is at least 2.
has two or more peaks and a peak molecular weight of 500 to 15,
000 and 100,000 to 3,500,000, and the residual magnetization σr and volume average particle diameter d of the magnetic toner satisfy the following formula, and 3.7-0.11d≦σr≦6.5.
−0.23d [where σr represents residual magnetization (em u / g) in an external magnetic field of 1 K■e. d indicates the volume average particle diameter (μm), and is 3 to 16. Comelt index is 0.2-12g710min (125
℃.

10Kg load), and the amount of frictional charge with iron powder is 50μC
/g (absolute value) or less, and the number average particle diameter is 0.5 μm
Carbon allotrope as a charge reliever fine powder, such as:
The present invention relates to a developer for electrostatic charge development characterized by containing a metal oxide.

The developer of the present invention shown above can faithfully reproduce down to the fine lines of the latent image formed on the photoreceptor, and can reproduce halftone dots and digital dot latent images. It provides a high-density image with excellent gradation and resolution, thereby solving various objects of the present invention.

The reason why such an effect is obtained in the developer of the present invention is not necessarily clear, but it is presumed as follows.

In examining the above-mentioned problems, the present inventors identified Bronner unevenness on the developing sleeve as a defect that extremely manifests as light density, disturbance in image quality, etc., and elucidated the problem in development. Bronner unevenness is an uneven coating of toner that occurs on the developing sleeve in the form of spots or ripples. In solid black images, it appears as a developing defect, resulting in a white spot in the Bronner shape, and in solid self-portraits, the Bronner shape remains as it is. It will be developed.

Observation of such Bronner unevenness shows that adhering particles are generated on the sleeve surface due to various causes, and as a result, the toner is insufficiently charged due to insufficient frictional charging with the sleeve.
It was observed that a disordered, bulky toner spike was formed on the top of the toner.

These adhesion particles are usually caused by charged toner particles adhering to the sleeve due to electrostatic attraction, and are more likely to occur when the amount of charge of the toner is increased in order to increase image density.

This phenomenon may occur during continuous use under extremely low temperature and low humidity environmental conditions for a longer period of time than in normal repeated copying.

This affects the coating uniformity of the toner in the upper layer of the developer layer and the ease with which it is developed. Bronner unevenness is an extreme example of this, but poor image quality and decreased density can also occur in other forms. Although different, it can be thought that the cause is similar.

In other words, disordered ears or ears that are too long will not allow the latent image to be developed faithfully, causing toner spikes to protrude from the latent image and scattering, and will also prevent uniform and dense development of the latent image, resulting in covering. This results in an image with low power and low density.

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

In other words, a moderately high density ensures that the developer can fly from the developing sleeve to the electrostatic latent image on the photoreceptor, resulting in high density,
This enables reproducibility, etc., and the uniform charge amount for each particle allows the magnetic toner spikes to be uniformly regulated, preventing irregular spikes (((), protruding from the latent image, sputtering, and uneven development. This prevents image damage and maintains stable image quality even after repeated use over a long period of time.

To this end, the present inventors have proposed, for example, that by using a developing sleeve with a smoother surface, the chances of contact between toner particles and the sleeve surface will increase, resulting in a higher amount of charge and a more uniform charge. We thought that it would be preferable to have a quantity distribution.

However, although it is effective to obtain a toner with a uniform charge amount distribution by this method, if the charge amount is too high, as mentioned above, the occurrence of unevenness on the sleeve and deterioration of image quality may occur. Therefore, the present inventors investigated a charge softening agent fine powder that can appropriately control the amount of charge while maintaining charge uniformity.

Based on these results, the present inventors have determined that the charging force of the toner, which causes the mirroring force that causes the toner particles to adhere to and accumulate on the sleeve surface, and the force that causes the toner particles to aggregate with each other, and the We have found that it is effective to optimally control the magnetic force of the toner to make it stand up.

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

Here, when the magnetic toner passes through the gap between the sleeve and the magnetic blade, it receives the maximum magnetic field from the outside and attempts to form ears. However, inferring from the studies conducted by the present inventors, before and after this, the magnetic binding force becomes weaker as it passes between the sleeve and the magnetic blade, and the force that tends to accumulate and aggregate on the sleeve acts again. Therefore, it is important to continue holding the ears using magnetic force, and furthermore, because there is a relative relationship between the length of the ears and the toner particle size,
There is a characteristic relationship between the residual magnetization σr and the particle size d of the magnetic toner to solve the problem, that is, 3.7-0. lid≦
We found that σr≦6.5-0.23d, and furthermore, in order for this effect to be fully exhibited, the molecular weight distribution of the binder resin must be small (both have two or more peaks and the peak molecular weight is 500 N15000). and 100,000 to 3.5 million vinyl polymers, and the MI of magnetic toner is 0.5 to 20 g.
/10 minutes is good (and the amount of frictional charge with iron powder is 50μc)
/g (absolute value) or less, and the number average particle diameter is 0.5 μm
Carbon allotrope as a charge reliever fine powder, such as:
It was concluded that it is better to include metal oxides.

The configuration of the present invention will be explained.

The residual magnetization σr and volume average particle diameter d of the magnetic toner are 3.7-
0.11d≦σr≦6.5−0.23d [where σr
is the residual magnetization (e m u /
g) and d are volume average particle diameters (μm) of 3 to 16. ] It is good. The shaded area in FIG. 3 indicates this area.

When σr>6.5-0.23d, the σr of the toner particles is too large relative to the magnetic toner particle diameter, and the force that causes the toner particles to stand up from the developing sleeve is large, making it difficult to generate blockers, but conversely, the toner particles The ears are long (too long, 100μ
Furthermore, m1 exceeds 150 μm, which is longer than the width of the thin line latent image, and the line protrudes or jumps out from the latent image, resulting in poor image quality.

Furthermore, the toner spikes become longer and the toner coat thickness becomes larger, making it difficult for individual particles to be uniformly charged, causing light density, fogging, and furthermore, with repeated use.
Toner with low charging ability remains in the developing machine, resulting in a long-term decrease in image density and image quality.

Moreover, σr<3.7-0. In the lid, the σr of the toner particles is too small compared to the toner particle size, resulting in unevenness on the sleeve, thin density due to disordered tower-shaped toner spikes, and deterioration of image quality. In particular, when the volume average diameter of the toner becomes smaller, the surface area of the toner increases, and the frictional electrification with the sleeve becomes thicker, and when the electrostatic adhesion force to the sleeve becomes larger, the above-mentioned problems are more likely to occur.

However, as mentioned above, the volume average particle diameter d of the magnetic toner
Even if the residual magnetization σr is defined as σr, the problems of the present invention may not be fully solved.When considering this point, it was found that it is related to the state of existence of the binder resin of the magnetic material contained. .

In the present invention, the molecular weight distribution of the binder resin is small (both have two or more peaks, and the peak molecular weight is 500-15
,000 and io to 3.5 million, preferably l,5
00 to 12,000 and 200,000 to 2.5 million, more preferably 2,000 to io, ooo and 200,000 to 15
00,000 is good.

Further, the composition ratio of the component (A) having a peak molecular weight of 500 to 15,000 and the component (B) having a peak molecular weight of 100,000 to 3,500,000 is preferably 10:90 to 90:10. Preferably 2
0:80 to 80:20 is good. More preferably, the ratio is 30:70 to 70:30.

When such a binder resin is used, the magnetic material is extremely uniformly dispersed. Considering that even a small amount of inappropriate toner particles is likely to cause Bronner unevenness, this method is effective in making the magnetic properties of each particle nearly uniform. big.

From another perspective, if you simply increase the cross-mixing viscosity and apply shear, you should be able to get the same result by lowering the resin temperature during kneading, but considering that the effect is greater than that, the binder resin The constituent components of the binder resin act to prevent the magnetic material from being removed from the toner surface, or the constituent components of the binder resin reduce the coating of the magnetic material and charge control agent with the resin component, thereby reducing the toner surface. It can be considered that this effect works to increase the chargeability and stability of the present invention, making the present invention even more remarkable.

When the component having a peak molecular weight of 100,000 to 3,500,000 in the binder resin is less than 10 wt% of the total binder resin, the above effect is small (both image quality and density are poor, and image quality is disturbed due to offset.

In addition, if the component having a peak molecular weight of 500 to 15,000 is less than 1.0 wt% of the total binder resin, the fixing properties will be poor, and the toner particles with poor fixing will form on the fixing roller surface. This is disturbed by the electric field generated by the charging with the transfer paper, causing image quality deterioration such as sputtering and trailing.

Furthermore, it becomes difficult to crush the toner, resulting in a decrease in productivity. Furthermore, with ordinary crosstalk machines, insufficient melting or insufficient shearing force may occur, and conversely, sufficient dispersion may not be achieved, making it impossible to solve the problem.

Furthermore, there are various methods for measuring the molecular weight distribution of the binder resin, and slight differences occur due to these methods. Therefore, it is measured by the following measurement method.

That is, gel permeation chromatography (
GPC), the temperature was 40°C, the solvent was tetrahydrofuran, and the measured flow rate was 1.0 mI! /min, concentration 0.1wt%T
300μ of HF! inject. When measuring the molecular weight of a sample, a calibration curve prepared using a monodisperse polystyrene standard sample is used. Columns are not limited to these, but examples include Shodex KF-80M and KF802.
, 803, 804, 805, etc.

For accurate measurements, it is best to combine these columns.

In the present invention, the method of determining the constituent component ratio from the molecular weight distribution is to separate the peaks in the molecular weight distribution at the lowest point valleys, and calculate the ratio from the integral value of each peak to the constituent component ratio. did.

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

For example, examples of comonomers for the styrene monomer in the styrene copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, and -2 acrylate.
- monocarboxylic acids with double bonds or substitutes thereof, such as ethylhexyl, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrinitrile, acrylamide, etc.; e.g. , dicarboxylic acids having a double bond, such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate, and substituted products thereof; vinyl esters, such as vinyl chloride, vinyl acetate, vinyl benzoate, etc.;
Ethylene-based olefins, such as ethylene, propylene, butylene, etc.; Conjugated diene-based monomers, such as butadiene, isoprene, chloroprene, etc. and their derivatives; Vinyl ketones, such as vinyl methyl ketone, vinyl hexyl ketone, etc.; For example, 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, a compound having two or more polymerizable double bonds is mainly used, such as aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate, Ethylene glycol dimethacrylate, 1,3
-Carboxylic acid esters having two double bonds such as butanediol dimethacrylate; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone; and compounds having three or more vinyl groups; singly or Used as a mixture.

Here, it is 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 toners. be.

Furthermore, it is also possible to cut the crosslinked component by applying a strong shearing force during the kneading process during toner production to obtain a binder resin having the molecular weight distribution of the present invention.

The melt index of the magnetic toner of the present invention is related to the tetrahydrofuran-insoluble content of various binder resins, but is 0.5
~15g/10min (125°C, 10Kg charging) is preferred. More preferably, it is 0.5 to 12 g/10 minutes. If the melt index is less than 0.5 g/10 minutes, it will not be fixed (<, the phenomenon that the poorly fixed toner is charged and adheres to the fixing roller, or the unfixed toner is easily scattered due to the pressure of the fixing roller, and as a result, This results in a decrease in image quality, which is not what the present invention desires.

Furthermore, if the melt index is greater than 15 g/10 minutes, the toner is undesirably crushed due to fixing (resulting in deterioration of resolution and thin line reproducibility).

Furthermore, the magnetic toner of the present invention has a weight average molecular weight of 2.00.
It is preferable to contain 0.1 to 10% by weight of polyalkylene having a molecular weight of 0 to 30,000 based on the resin component.

Furthermore, it is preferable to contain 0.5 to 8% by weight.

By adding polyalkylene with a weight average molecular weight of 2,000 to 30,000, it can be quickly released from the fixing roller during fixing and has the effect of not deteriorating image quality. It has a great reducing effect, and even in the copying process, it makes the flow of toner uniform in the developing machine, stabilizes charging, and reduces agglomerated toner (((()), which is effective in improving image quality.

In addition, in the toner manufacturing process, the crushing method uses high-pressure air from a nozzle to apply the crushed product to the opposing collision plate.
During this process, adhesion to the collision plate and re-fusion between the crushed particles are prevented, making it easier to produce toner with the desired performance and shape. There are also differences in the presence of magnetic powder on the surface, which has a large influence.

It is preferable that the weight average molecular weight is 2,000 to 30,000 in order to obtain the above-mentioned effects. Moreover, if the polyalkylene content is less than 0.5 wt%, the effect will be small.

If the polyalkylene content is greater than 10 wt%, it is difficult to mix with the binder resin, and free polyalkylene is likely to be generated, resulting in image defects such as fog.

Examples of the polyalkylene used in the magnetic toner of the present invention include monopolymers such as ethylene, propylene, butene-1, hexene, and 4-methylpentene-1, and ethylene-propylene, ethylene-butene-11, and ethylene-hexene. Copolymers such as propylene-ethylene, propylene-butene, propylene-hexene, and thermally modified products thereof can be used. Particularly preferred are polyethylene, polypropylene, copolymers of propylene, ethylene, butene, etc., and thermally modified products thereof.

The tetrahydrofuran (THF) insoluble matter in the present invention is
It indicates the weight percentage of the polymer component that has become insoluble in the THF solvent in the resin composition in the toner, and the THF-insoluble content is defined by the value measured as follows.

That is, weigh out 0.5 to 1.0 g of toner sample (Wtg), cylindrical filter paper (for example, Toyo Roshi Model No. 86R)
in a Soxhlet extractor with THF as a solvent.
After extracting for 6 hours using loo~200mj7 and evaporating the soluble components extracted by the solvent, 10
Vacuum dry at 0° C. for several hours and weigh the amount of THF-soluble resin component (Wzg). The weight of components other than resin components such as magnetic substances or pigments in the toner is assumed to be (Wsg). THF
The insoluble content is calculated from the following formula.

The particle size distribution of toner can be measured by various methods.
In the present invention, a Coulter counter was used.

In other words, the measuring device is Coulter counter TA.
- An interface (manufactured by Nikkaki) that outputs the number distribution and volume distribution using the n-type (manufactured by Coulter) and CX-1
A personal computer (manufactured by Canon) is connected, and the electrolyte is 1% NaCj! using primary sodium chloride. Prepare an aqueous solution. As a measurement method, the electrolytic aqueous solution 100-1
0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, as a dispersant is added to 50 ml, and 2 to 20 mg of the measurement sample is added. The electrolyte in which the sample was suspended was dispersed using an ultrasonic disperser for about 1 to 3 minutes.
The particle size distribution of particles having a size of 2 to 40 μm based on the number of particles was measured using the Coulter Counter Model TAII using a 100 μm aperture as the aperture, and the values according to the present invention were determined from the particle size distribution.

The melt index here was determined using the equipment described in JIS K 7210, a flow test method for thermoplastic plastics according to the Japanese Industrial Standards, at 125°C, load 10 kg, orifice inner diameter 2.0955 ± 0.0051 mm, length 8.0
Measurements were made by 00±0.025 mm.

In the present invention, the magnetic properties of the magnetic toner are VSMP-1-
10 (manufactured by Toei Kogyo Co., Ltd.) using an external magnetic field IK at room temperature.
It was determined from the results measured in Oe.

Furthermore, the magnetic toner of the present invention may also serve as a colorant, but it contains a magnetic material. The magnetic materials 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 cobalt, nickel or these metals with aluminum, cobalt, copper, iron, magnesium, tin,
Examples include alloys with metals such as zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, and vanadium, and mixtures thereof.

These ferromagnetic materials preferably have an average particle diameter of 0.1 to 1 μm, preferably 0.1 to 0.5 μm, and are contained in the magnetic toner in an amount of 40 to 200 parts by weight per 100 parts by weight of the resin component. parts, preferably 50-150 parts by weight per 100 parts by weight of the resin component.

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

Based on the above findings, the developer of the present invention has a magnetic toner having the particle size distribution and material composition described above, and has a triboelectric charging property with iron powder of 50 μc/g (absolute value) or less, preferably 20 μc/g (absolute value).
c/g (absolute value) or less, number average particle size 0.5μ
This method is characterized in that a fine charge moderating agent powder or a mixture thereof having a particle size of less than m is blended with magnetic toner particles (internal addition) or mixed with magnetic toner particles (external addition).

The content of the charge softening agent fine powder used in the invention is 0.1 to 50 parts by weight, preferably 0.2 to 30 parts by weight, per 100 parts by weight of the binder resin when added internally, and preferably 0.2 to 30 parts by weight when added externally. for,
0.01 to 10 parts by weight per 100 parts by weight of magnetic toner,
Preferably it is 0.02 to 5 parts by weight.

Specific examples of the above-mentioned charge moderating agent include the following substances. Substances mainly composed of carbon atoms such as carbon black, graphite, magnesium oxide, alumina, titanium oxide, iron oxide, nickel oxide, chromium oxide,
Examples include metal oxides mainly composed of metal atoms (one or more types) and oxygen atoms, such as copper oxide, zinc oxide, tin oxide, cerium oxide, cobalt oxide, and zirconium oxide. It is thought that these substances are difficult to charge or are likely to absorb moisture in the air and easily cause discharge of charge. In fact, the amount of charge of these substances on iron powder is 50
μc/g (absolute value) or less, preferably 20μc
/g (absolute value) or less.

By containing an appropriate amount of fine powder of these substances in a magnetic toner, excessive frictional electrification can be suppressed and excessively charged charges can be released.

In other words, these fine powders are considered to function as a charge moderating agent that reduces the amount of triboelectric charge of the magnetic toner to an appropriate level.

There are two ways to incorporate the fine powder of the charge softener into the developer of the present invention: an internal addition method and an external addition method. However, the external addition method is better because it is present in a larger amount on the surface of the magnetic toner. (If the effect is achieved with a small amount, or if the toner easily detaches from the surface of the magnetic toner, the amount added can be increased to ensure good dispersion in the developer, or the amount of toner that can be added to the surface of the magnetic toner can be increased.) The attached method is also effective.

Further, in the case where the fine powder in the developer of the present invention is magnetic, a method of internal addition can be used as long as the fine powder is within the range of desired magnetic properties required for a magnetic toner. However, in cases where the magnetic properties of the magnetic toner are significantly affected, the amount of addition can be reduced by external addition to achieve the objective.

When the triboelectric charging property is 50 μc/g or more in absolute value, the charging is not sufficiently relaxed (sometimes this occurs, and when the polarity is opposite to that of the magnetic toner, the developing property may be affected by increased fogging or decreased density). may have a negative impact.

If the number average particle size exceeds 0.5 μm, the dispersibility in the developer will be poor, and variations will occur between particles, which will adversely affect developability and increase fog, making it difficult to produce good images. However, the smaller the average particle size of the magnetic toner of the present invention, the greater the effect.

When the content exceeds a predetermined value, the amount of charge decreases greatly under conditions of high humidity, etc., resulting in image defects such as low image density. On the other hand, if the content is less than a predetermined value, the charging mitigation effect cannot be exerted, and excessive charging tends to occur, which may cause a decrease in density or uneven sleeve coating.

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

FIG. 5 is an explanatory diagram of an apparatus for measuring the amount of electric charge.

First, a metal measurement container 32 with a 400-mesh screen 33 at the bottom is placed in a sample whose charge amount is to be measured and a developer consisting of an iron powder carrier (200 to 300 meshes) at a weight ratio of 10:90, with a small amount of charge softening agent. For powder, 1 g of a mixture with a weight ratio of 2:98 is added and a metal lid 34 is placed. Weigh the entire weight of the measurement container 32 at this time, W+(g
). Next, in the suction device 31 (at least the part in contact with the measurement container 32 is an insulator), suction is performed from the suction port 37, and the air volume control valve 36 is adjusted to increase the pressure of the vacuum gauge 35 to 250.
Let it be mmH20. In this state, perform sufficient suction to remove the sample. The potential of the electrometer 39 at this time is assumed to be V (volt). Here, 38 is a capacitor, and the capacitance is C (μF). In addition, the weight of the entire measurement container after suction is measured and is defined as W2 (g). The amount of charge of this sample (μc
/g) is calculated as shown below.

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

In addition, the carrier (iron powder) used for measurement is 200 to 30
Although the carrier is 0 mesh, in order to eliminate errors, the carrier is sufficiently suctioned with the above-mentioned suction device, and the carrier that passes through the 400 mesh screen is removed before being mixed with the sample.

Further, in the magnetic toner of the present invention, it is preferable to use a charge control agent by blending it into the toner particles (internally adding it) or mixing it with the toner particles (externally adding it). The charge control agent makes it possible to control the amount of charge optimally depending on the development system.
To make the effect of a charge reducing agent more stable. Examples of positive charge control agents include modified products with nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate; dibutyltin oxide, dioctyltin diorganotin oxides such as oxide, dicyclohexyltin oxide; diorganotin borates such as dibutyltin borate, dioctyltin borate, and dicyclohexyltin borate can be used alone or in combination of two or more types. Among these, nigrosine,
Charge control agents such as quaternary ammonium salts are particularly preferably used.

Further, a monopolymer of a monomer represented by the general formula % R2, R3: substituted or unsubstituted alkyl group (preferably 01 to C4): or styrene, acrylic ester, methacrylic ester, etc. as described above. A copolymer with a polymerizable monomer can be used as a positive charge control agent, and in this case, these charge control agents also function as (all or part of) a binder resin.

Negative charge control agents that can be used in the present invention include:
For example, organometallic complexes and chelate compounds are effective; examples include aluminum acetylacetonate, iron (n)
Examples include acetylacetonate and chromium 3.5-ditertiary-butylsalicylate. Acetylacetone metal complexes and salicylic acid metal complexes or salts are particularly preferred, and salicylic acid metal complexes and salicylic acid metal salts are particularly preferred.

When internally added to the toner, such a charge control agent is added in an amount of 0.1 to 20 parts by weight (or even 0.1 to 20 parts by weight) per 100 parts by weight of the binder resin.
．． 2 to 10 parts by weight) is preferably used.

Further, it is preferable to add fine silica powder to the magnetic toner of the present invention. This seems to be due to the effect of leaking the electric charge of fine silica powder from the toner.
An appropriate amount of charge can be maintained even in an extremely low temperature and low humidity environment, and furthermore, the magnetic toner of the present invention can be made excellent.

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

Among the above silica fine powders, the specific surface area due to nitrogen adsorption measured by the BET method is 30 nf/g or more (especially 50 to 40 nf/g).
0rrf/g) gives good results.

0.01 part of silica fine powder per 100 parts by weight of magnetic toner
It is good to use 8 parts by weight, preferably 0.1 to 5 parts by weight.

In addition, when the magnetic toner of the present invention is used as a positively charged magnetic toner, the silica fine powder added to prevent wear of the toner and to prevent staining of the sleeve surface may be used as a positively charged magnetic toner rather than a negatively charged one. It is preferable to use fine silica powder because it does not impair charging stability.

As a method for obtaining positively chargeable silica fine powder, the above-mentioned untreated silica fine powder is mixed with fewer nitrogen atoms in the side chain (both 1 and 1).
There is a method of treatment with a silicone oil having more than one organo group, a method of treatment with a nitrogen-containing silane coupling agent, or a method of treatment with both.

In the present invention, positively charged silica refers to silica that has a positive tripo charge relative to the iron powder carrier when measured by a blow-off method.

As the silicone oil having a nitrogen atom in the side chain used in the treatment of silica fine powder, a silicone oil having a small amount (or a partial structure represented by the following formula) can be used.

(In the formula, R1 represents hydrogen, an alkyl group, an aryl group, or an alkoxy group, R2 represents an alkylene group or a phenylene group, R3' and R4 represent hydrogen, an alkyl group, or an aryl group, and R5 represents a nitrogen-containing hetero The above alkyl group, aryl group, alkylene group, and phenylene group (representing a cyclic group) may have an organo group having a nitrogen atom, or may have a substituent such as a halogen within a range that does not impair chargeability. You can leave it there.

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

Rm-3t-Yn (R represents an alkoxy group or a halogen, Y represents an amino group or an organo group having one or more nitrogen atoms, m and n are integers of 1 to 3, and m +
n = 4. ) Examples of such treatment agents include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, Monobutylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropyl monomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ
-Propylphenylamine, trimethoxysilyl-γ-
Propylbenzylamine, etc. Furthermore, as the nitrogen-containing heterocycle, those having the above-mentioned structure can be used. Examples of such compounds include trimethoxysilyl-γ-propylpiperidine, trimethoxysilyl-γ-propylmorpholine, Examples include trimethoxysilyl-γ-propylimidazole.

The application amount of these treated positively charged silica fine powders is
0.01 to 100 parts by weight of positively charged magnetic toner
The effect is exhibited when the amount is 8 parts by weight, particularly preferably 0.1
When added in an amount of up to 6 parts by weight, it exhibits positive chargeability with excellent stability. Regarding the form of addition, the preferred form is 0.1 to 100 parts by weight of positively charged magnetic toner.
It is preferable that 3 parts by weight of the treated silica fine powder be attached to the surface of the toner particles. Note that the untreated fine silica powder described above can also be used in the same amount.

In addition, the silica fine powder used in the present invention may be treated with a silane coupling agent or a treatment agent such as an organosilicon compound for the purpose of hydrophobization, if necessary. It is treated with the above-mentioned processing agent.

Examples of such treatment agents include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane,
Allyl phenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate , vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyljethoxysilane,
Hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and siloxane units having 2 to 12 siloxane units per molecule, one each for the terminally located unit. There are dimethylpolysiloxanes containing hydroxyl groups bonded to Si. These can be used alone or in a mixture of two or more.

Further, in the present invention, it is preferable to add fine powders of fluorine-containing polymers, such as polytetrafluoroethylene, polyvinylidene fluoride, etc., and fine powders of tetrafluoroethylene-vinylidene fluoride copolymers. Particularly preferred is polyvinylidene fluoride fine powder from the viewpoint of fluidity and polishability. Addition amount to toner is 0
．． 01 to 2.0 wt%, particularly 0.02 to 1.0 wt%.

In particular, in magnetic toners that combine fine silica powder with the above-mentioned fine powders, for reasons that are not clear, the state of existence of silica attached to the toner is stabilized, and for example, the attached silica is released from the toner, resulting in an effect. However, it is possible to further increase charging stability.

The magnetic toner of the present invention may contain additives, if necessary. As the colorant, conventionally known dyes and pigments can be used, and usually 0.5 to 20 parts by weight may be used per 100 parts by weight of the binder resin. 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 above-mentioned magnetic toner constituent materials are thoroughly mixed using a ball mill or other mixer, then thoroughly kneaded using a heat kneader such as a hot roll kneader or an extruder, and then cooled and solidified. After that, a method of obtaining a magnetic toner by mechanical crushing and classification is preferable.Other methods include: a method of obtaining a magnetic toner by dispersing the constituent materials in a binder resin solution and then spray drying;
Alternatively, a polymerization toner manufacturing method in which monomers to constitute the binder resin are mixed with a predetermined material to form an emulsified suspension and then polymerized to obtain a magnetic toner; In the capsule toner, methods such as a method of containing a predetermined material in the core material, the shell material, or both can be applied. Further, if necessary, desired additives may be sufficiently mixed using a mixer such as a Henschel mixer to produce the developer for developing electrostatic images according to the present invention.

In the present invention, a developing sleeve with a smooth surface is preferred, but in particular, an electrostatic image holder that holds an electrostatic image on its surface and a toner carrier that carries magnetic toner on its surface are used at a certain level in the developing section. In a developing method in which magnetic toner is arranged with a gap, the magnetic toner is regulated to a thickness thinner than the gap on a toner carrier, and the toner is conveyed to a developing section, and developed while applying an alternating electric field to the toner in the developing section. Preferably, the carrier has a surface on which a plurality of spherical trace depressions are formed by blasting with regular particles, and furthermore, the surface of the toner carrier has a diameter R of the spherical trace depressions of 20 to 20.
It is preferable that the surface roughness is 250 μm, the pitch P of the unevenness is 2 to 100 μm, and the surface roughness d is 0.1 to 5 μm.

The sleeve of the present invention has a surface with an uneven surface formed by a plurality of spherical trace depressions, and a blasting method using regular particles can be used to obtain this surface condition. Examples of fixed particles include metals such as stainless steel, aluminum, steel, nickel, and brass having a specific particle size;
Various rigid spheres such as ceramic, plastic, glass beads, etc. 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 with approximately the same diameter R.

In the present invention, the diameter R of the plurality of spherical trace depressions on the sleeve surface is preferably 20 to 250 μm;
If the diameter R is less than 0 μm, it is undesirable because it increases contamination by components in the magnetic toner, and on the other hand, if the diameter R is more than 250 μm, the uniformity of the toner coat on the sleeve decreases, which is undesirable. Therefore, it is preferable that the regular particles used during the blasting treatment of the sleeve surface have a diameter of 20 to 250 μm. In addition, in the present invention, the pitch P of unevenness on the sleeve surface and the surface roughness d are determined by measuring the surface of the sleeve using a microsurface roughness meter (
The surface roughness d is measured using JI3 10-point average roughness (
RZ) rJIS B 0601J.

In other words, as shown in Fig. 5, there are two straight lines parallel to the average line of the section cut out by the standard length l from the cross-sectional curve, one that passes through the third peak from the highest and one that passes through the bottom of the third valley from the deepest. , the distance between two straight lines is expressed in micrometers (μm), and the reference length is l-0.25 mm. In addition, the pitch P is determined as follows by counting the height of the convex part to the concave parts on both sides as 0.1μ or more as one mountain, and the number of peaks in the standard length of 0.25 mm. It is something that

250 (μ) / Number of mountains included in 250 (μ) (
μ) In the present invention, the pitch P of the unevenness on the sleeve surface is preferably 2 to 100 μ; if P is less than 2 μ, contamination of the sleeve by components in the magnetic toner increases, so it is not preferred (on the contrary, if P is 100 μ or more, If it is, the uniformity of the toner coat on the sleeve will deteriorate, which is undesirable. Also, the surface roughness d of the irregularities on the sleeve surface is preferably 0.1 to 5 μm, and if d is 5 μm or more, the difference between the sleeve and the latent image carrier will deteriorate. A method in which development is performed by applying an alternating voltage between the two and causing the magnetic toner to fly from the sleeve side to the latent image surface is undesirable because the electric field tends to concentrate on the uneven parts and cause image disturbance. On the other hand, if d is less than 0.1 μm, the uniformity of the toner coating on the sleeve will deteriorate, which is undesirable.

As the sleeve used in the present invention, the diameter of 80% or more is 53 to 62 μm using the stainless steel sleeve surface as constant diameter particles.
FIG. 2 shows a photograph taken with a scanning electron microscope at a magnification of 1000 times of the surface of the blast-treated glass beads.

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.

The magnetic toner to be measured was placed in a measuring device set to predetermined conditions, and was measured at 150 mm in an environment of 23°C and 60% RH.
The cylindrical sleeve 12 was rotated at a circumferential speed of 7 seconds, and the amount of charge on the toner layer 13 per unit area on the sleeve 12 was determined at regular intervals using a so-called suction type Faraday gauge method. This suction type Faraday gauge method presses the outer cylinder against the sleeve 12 to suck all the toner on a certain area on the sleeve, collects it in a filter in the inner cylinder, and calculates the amount of toner per unit area on the sleeve based on the increased weight of the filter. The weight of each toner layer can be calculated. At the same time, by measuring the amount of charge accumulated in the inner cylinder, which is electrostatically shielded from the outside, it is possible to determine the amount of charge Q/S (μc / crd) per unit area on the sleeve. .

The conditions of the charge amount measuring device will be explained with reference to FIG. The measuring device simulates the form of a developing machine, and consists of a toner hopper 15, a cylindrical sleeve 12, and an opposing magnetic blade 11. The cylindrical sleeve 12 is driven by a drive motor at a constant circumferential speed (150 mm/sec) in the direction of the arrow. The toner is applied in a thin layer onto the surface of the cylindrical sleeve 12 via the magnetic blade 11, and after a period of time, the amount of charge is measured and changes in the toner on the sleeve 12 are observed. .

The gap between the blade L and the sleeve 12 is set to about 250 μm, and the shape of the toner hopper is approximately ◎ is the diameter of the sleeve, ■ is thicker than the radius of the sleeve, and the amount of toner input is determined by ■ being the radius of the sleeve. greater than 1/2 of
The cylindrical sleeve 12 should be smaller than the radius.
It has a fixed magnet 14 inside, and the magnetic pole strength is N, about 800
G (approximately 5° hopper side from opposite blade), S1 approximately 1
000G, N2 about 750G, and S2 about 550G. The sleeve 12 has a diameter of 20 mm and is made of stainless steel (
Made of SUS304), more than 80% of its surface has a diameter of 53 mm.
Blast treatment was performed using regular glass beads particles having a diameter of ~62 μm using a blowing nozzle, and the diameter R of the depression was approximately 53 μm to 62 μm1, and the pitch P of the unevenness was approximately 33 μm1.
A plurality of spherical trace depressions with a surface roughness d of approximately 2 μm form irregularities.

The pitch P of the unevenness on the sleeve surface and the surface roughness d were measured on the sleeve surface using a micro surface roughness meter (manufactured by Koita Research Institute).

In the present invention, the amount of charge Q/5 (nc/crrf) measured by the measuring method specified below is 3 to 12 nc/c.
rrf is good. More preferably 4 to 1 lnc/crr
r is good, more preferably 5 to 10 nc/crrr.

When Q/S>12 (nc/crtr), the charge is excessive, the reflection force is too large, and Bronner unevenness is likely to occur in the measuring device.

In order to counter this, the residual magnetization of the toner is made thicker (then the toner spikes become longer and larger, and no improvement in image quality can be expected.

When copying is continued using such toner, the toner adheres to the sleeve due to strong mirroring force and flies to the photoreceptor ((), resulting in a decrease in density.

Further, when Q/S<3 (nc/crtr), the amount of charge is insufficient, resulting in a light concentration. Particularly in high temperature and high humidity environments, the amount of charge decreases further and the concentration becomes extremely low. If copying is continued, toner with low developability remains due to selective development, resulting in a decrease in density and deterioration in image quality.

In the present invention, fine line reproducibility was measured by the following method. In other words, an image of an original manuscript with thin lines exactly 100 μm in width was copied under appropriate copying conditions as a sample for measurement, and a Luzetx 450 Particle Analyzer was used as the measurement device to measure the line width using an indicator from the enlarged monitor image. Perform measurements. At this time, since the line width measurement position has irregularities in the width direction of the fine line image of the toner, the average line width of the irregularities is taken as the measurement point. From this, the value (%) of fine line reproducibility is calculated using the following formula.

In the present invention, resolution was measured by the following method. In other words, it is a pattern consisting of five thin lines with equal line width and spacing, and 2.8.3.2.3 between 1 mm.
．． 6.4.0.4.5.5.0.5.6.6.3゜7.
Create an original image that appears to have 1 or 8.0 lines. The original document with these 10 types of line images was copied under appropriate copying conditions, and the images were observed with a magnifying glass.
m m ) is taken as the value of resolution.

The larger this number, the higher the resolution.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but these are not intended to limit the present invention in any way. All parts in the following formulations are parts by weight.

Example 1 The above materials were thoroughly mixed in a Henschel mixer, and
The mixture was kneaded using a kneading mixer set at ℃. The obtained mixed material is cooled and coarsely pulverized using a cutter mill, then finely pulverized using a pulverizer using a jet stream, and the resulting pulverized powder is classified using a fixed wall type wind classifier. A magnetic toner was obtained.

The volume average particle size of the obtained magnetic toner was 8.2 μm, the residual magnetization was 3.6 emu/g, and the melt index was 1.
．． It was 8g/10 minutes. Furthermore, when the binder resin extracted from the magnetic toner was measured by GPC, the peak molecular weight was approximately 6,500 and approximately 750,000, and the component ratio was 50:
It was 50.

To 100 parts by weight of the obtained magnetic toner were added 0.4 parts by weight of positively charged hydrophobic silica (BET specific surface area 130 rd/g) and dry aluminum oxide fine particles (number average particle size 0.5 parts by weight).
0.02 pm, charge amount +3.6 μc7g) was added and mixed in a Henschel mixer to obtain a one-component magnetic developer. In addition, the method defined in the present invention can be used in low temperature, low humidity environments (15
The maximum value of Q/S measured at
crrr, no abnormalities were observed on the developing sleeve during the 2 hour measurement, and a uniform toner coat layer was always maintained.

In the development area, the magnetic toner formed spikes with a height of about 80 μm.

The above-described one-component magnetic developer was applied to a high-speed copying machine having a developing device as shown in FIG. 1 under conditions that facilitate offset without an oil coating device in the fixing machine. Cylindrical stainless steel sleeve 2 (SU
Glass beads having a diameter of 80% or more of 53 to 62 μm were used as regular particles on the surface of S304), the blowing nozzle diameter was 7φ, and the distance was 100 mm.

Blast treatment was performed under the conditions of air pressure 4Kg/crrf for 2 minutes, and the diameter R of the spherical trace groups was 53 to 6.
An unevenness of 2 μm was formed. The pitch P of the unevenness on the surface of this sleeve was 33μ, and the surface roughness d was 2.0. - The component developer 10 is 390 m in the direction of the arrow
m Stainless steel cylindrical sleeve 7 rotating at a circumferential speed of 7 seconds
A thin layer was applied onto the surface via a magnetic blade 1a, and the gap between the sleeve 2 and the blade 1a was set to about 250 μm. The sleeve 2 has a stationary magnet 4 as a magnetic field generating means and an OP comprising an organic photoconductive layer with a negatively charged latent image.
The fixed magnet formed a magnetic field of 950 Gauss near the sleeve surface in the developing area adjacent to the C photosensitive drum 9. 260 mm The closest distance between the sleeve 2 and the OPC photosensitive drum 9, which rotates in the direction of the arrow at a circumferential speed of 7 seconds, is approximately 30 mm.
It was set to 0 μm.

In addition, between the OPC photosensitive drum 9 and the sleeve 2, the frequency of 2000Hz/135, which is a combination of AC bias and DC bias, is
A bias of 0 Vpp was applied.

The image reproduction test was carried out under low temperature and low humidity conditions (15°C, 10% RH) where Bronze unevenness is likely to occur.
The results of the test are shown in Table 1. As is clear from Table 1, the image density was high, and the fine line reproducibility and resolution were also excellent, and the initial good image quality was maintained even after 10,000 images were printed. In addition, there was no occurrence of Bronner unevenness (or problems related to fixing or offset) during image output.

Example 2 A magnetic toner was obtained in the same manner as in Example 1 using the binder resin obtained by changing the polymerization conditions into two stages and the other materials described above. The volume average particle size of the obtained magnetic toner was 4.0μ
m, and the residual magnetization was 3.9 emu/g. Also,
The melt index was l1g/10min.

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

Using the same developing device as in Example 1, evaluation was conducted 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 10,000 sheets had high image density (no fog, clear, high quality images, no sleeve contamination, no toner coating unevenness on the sleeve). I was not able to admit.

The maximum value of Q/S measured by the measurement method specified in the present invention is 8
．． 5 nc/crrr, no abnormality was observed on the sleeve during the 2 hour measurement, a uniform toner coating layer was always maintained, and the height of the magnetic toner was about 65 μm.

Example 3 The above materials were thoroughly mixed using a Henschel mixer, and heated to 100°C using a Z-axis kneading extruder using a shallow groove type screw.
The mixture was kneaded under new conditions with high speed rotation and high concentration. A magnetic toner was obtained in the same manner as in Example 1.

The volume average particle size of the obtained magnetic toner was 12.5 μm, the residual magnetization was 3.4 emu/g, and the melt index was 1.1 g/10 min. Furthermore, the gel content of the binder resin obtained by removing the magnetic nigrosine from the magnetic toner is 0%, and when the binder resin extracted from the magnetic toner is measured by GPC, the peak molecular weight is approximately 700.
, 70,000, and 2.5 million, and the component ratio of each is 2.5 million.
:40:35 (the relative component ratio of peak molecular weights of 700 and 2.5 million was 42,758).

Tin oxide fine powder (number average particle size 0) was added to the obtained magnetic toner.
; 1 μm, charge amount -6.6 μc/g) 0.2 parts by weight were strongly mixed in a turbo mixer to make them adhere, and then 0.3 parts by weight of positively charged hydrophobic silica was added. The mixture was mixed with a Henshil mixer to prepare a developer.

The maximum value of Q/S measured by the measurement method specified in the present invention is 6
．． 0 nc/c%, no abnormality was observed on the sleeve during 2 hours of measurement, a uniform toner coating layer was always maintained, and the height of the magnetic toner was about 105 μm. When evaluation was carried out in the same manner as in Example 1, stable, clear, high-quality images could be obtained as shown in Table 1.

Comparative Example 1 Positively charged hydrophobic silica (BE
T specific surface area 130 rd/g> Only 0.4 parts by weight were mixed in a Henschel mixer to prepare a developer, and evaluated using the same high-speed electrophotographic copying machine as in Example 1.

Under low temperature and low humidity conditions of 150°C and 910%, as durability progresses, the image density decreases from 1.38 to 1.2 at 10,000 sheets.
It dropped to 9. Additionally, due to charge-up, there was a deterioration in image quality due to roughness and sputtering of fine lines.

At this time, the toner charge amount Q/S on the sleeve is initially 1.
If you keep copying repeatedly with 4nc/crrf, 19
．． It was as high as 5nc/crrr.

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 10.2 μm.
It has a residual magnetization of 2.1 emu/g and a melt index of 23g710min.

Only 0.3 parts by weight of hydrophobic silica fine powder was added to the obtained magnetic toner, mixed with a Henschel mixer, and used as a developer.

The maximum value of Q/S measured by the measurement method shown in the present invention is 1
It was 9.0 nc/cJ, and Bronna unevenness had occurred 2 minutes after the start of the measurement. The average height of the ears on the sleeve was 125 μm, and the height varied from 80 μm to 180 μm, and many were tower-shaped. Poor fine line reproducibility, resolution, image fog, and unevenness.
As the image output continued, the image quality deteriorated and speckled spots appeared.

The results are shown in Table 1.

Comparative Example 3 A magnetic toner was obtained in the same manner as in Example 1 except that the amount of magnetic material added was changed to 130 parts, and evaluation was performed in the same manner as in Example 1. The volume average particle size of the obtained magnetic toner was 7.2
In μm, the residual magnetization was 6.2 emu/g. Also,
Ml of the magnetic toner was 1.2 g/10 minutes.

Evaluation was performed using a developer obtained under the same conditions as in Example 1. The height of the magnetic toner spikes is approximately 175 μm (long), resulting in protrusion from minute latent images, fine line reproducibility with a lot of scattering, poor resolution, and fog due to non-uniform charging. In addition, a decrease in density and deterioration of image quality occurred due to continued image output.The maximum value of Q/S according to the measurement method defined by the present invention was 3.5 nc/crrr.

Comparative Example 4 Using the above materials, hydrophobic silica and dry aluminum oxide fine powder were mixed to obtain a developer in the same manner as in Example 1. The volume average particle diameter of the obtained developer was 7.6 μm, and the residual magnetization was 1.5 emu/g, which was smaller than the specification of the present invention. Also, the melt index is 18.
It was 0g/10 minutes.

Using this developer, image quality was evaluated under the same severe conditions as in the examples. Initially, the image was relatively good, but as the image output continued, the image quality became dull, the density decreased, the image lacked sharpness, and spotty sleeve unevenness occurred. Furthermore, when the toner was idle-rotated using the measurement method defined in the present invention, the Q/S was 8.5.
However, bloat appeared after 10 minutes. The problem is that the toner spread is too small relative to the particle size.

[Brief explanation of the drawing]

Among the accompanying drawings, Fig. 1 shows a schematic cross-sectional view of the developing device used for image formation in Examples and Comparative Examples, and Fig. 2 shows the metal structure of the sleeve blasted with regular particles according to the present invention. A scanning electron micrograph of the surface is shown. Figure 3 shows a schematic diagram of the electrostatic charge measuring device used in the present invention, Figure 4 shows the relationship between the volume average particle size and residual magnetization in magnetic toner, and Figure 5 shows the friction of fine powder. FIG. 2 is an explanatory diagram of a device that measures the amount of charge. a 1'2 Magnetic blade sleeve application Magnetic toner Fixed magnet roller Developing container Photosensitive drum Magnetic toner Magnetic blade Cylindrical sleeve Toner coating layer ■ ・・・・・・・・・・・・・・・ ■ ・・・・・・・・・・・・・・・◎、■ ・・・
...... Gap between fixed magnet toner hopper partner blade 11 and sleeve 12 Distance between upper surface of sleeve and upper surface of toner Distance from sleeve to hopper wall and ceiling Measuring container ......・・・・・・・・・Screen (400 mesh) Suction port electrometer

Claims (1)

[Scope of Claims] A magnetic toner having at least a binder resin and a magnetic powder, in which the molecular weight distribution of the binder resin has at least two or more peaks, and the peak molecular weights are 500 to 15,000 and 100,000 to 3.5 million. A certain vinyl polymer, the residual magnetization σ_r and the volume average particle diameter d of the magnetic toner satisfy the following formula, and 3.7-0.11d≦σ_r≦6.5-0.
23d [where σ_r represents residual magnetization (emu/g) in an external magnetic field of 1Ke. d is the volume average particle diameter (μm)
, and ranges from 3 to 16. ] Melt index is 0.5-20g/10min (125
℃, 10Kg load), and the amount of frictional charge with iron powder is 50
μc/g (absolute value) or less, and the number average particle diameter is 0.5
A magnetic toner characterized by containing a carbon allotrope or a metal oxide as a charge moderating fine powder having a particle size of .mu.m or less.