JPH02284161A - Negatively chargeable magnetic toner - Google Patents

Abstract

PURPOSE:To always stably form images high in quality without being affected by environments, such as temperature and humidity by incorporating at least 2 kinds of metal salts of fatty acids in a specified magnetic toner as an electric charge controller and specifying each triboelectrification amount with a charge controlling iron powder. CONSTITUTION:A combination of a complex salt and the metal salt of fatty acid in a specified proportion is incorporated as the charge controllers in the magnetic toner containing the magnetic toner particles of <= 5mum diameter having a particle diameter distribution satisfying expression I in which N is the number % of the toner particles of <= 5 mum diameter, V is the volume % of them, k is a positive number of 4.6 - 6.7, and N is that of 17 - 60. The triboelectrification amounts of the complex salt and the fatty acid metal salt with the iron powder are shown by expression II in which Ta is the triboelectrification amount of the toner containing only the metal complex salt of an azo type dye; Tb is that of the toner containing only the fatty acid metal salt; and Tc is that of the toner containing both of them, thus permitting high-quality images to be obtained even under environments of high temperature and high humidity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a negatively charged magnetic toner used as a developer for developing electrostatically charged images in electrophotography, electrostatic recording, electrostatic printing, etc.

More specifically, the present invention relates to a negatively charged magnetic toner that is uniformly strongly (negatively charged) and visualizes a negative electrostatic charge image by reversal development to provide a high quality image in a direct or indirect electrophotographic development method.

[Background technology]

2. Description of the Related Art In recent years, as image forming apparatuses such as electrophotographic copying machines have become widespread, their uses have expanded to a wide variety of uses, and demands on their image quality have become stricter.

When copying images such as general documents and books, it is required to reproduce extremely finely and faithfully, without being crushed or cut off, even down to the minute characters. especially,
When the latent image on the photoreceptor of an image forming apparatus is a line image of 10,071 m or less, fine line reproducibility is generally poor, and the sharpness of the line image is still not sufficient. In recent years, in image forming devices such as electrophotographic printers that use digital image signals, latent images are formed by dots with a constant potential, and solid areas, halftone areas, and light areas have a high dot density. It is expressed by changing. 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 the dot size 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.

In addition, the image quality may initially be good, but as you continue to copy or print out, the image quality may deteriorate. This is thought to occur because only toner particles that are easy to develop are consumed first, and toner particles with poor developability accumulate and remain in the developing machine.

Up to now, several developers have been proposed for the purpose of improving image quality. JP-A-51-3244
The publication proposes a non-magnetic toner intended to improve image quality by regulating particle size distribution. In the toner,
The toner mainly has a particle size of 8 to 12 μm, which is relatively coarse, and according to the studies of the present inventors, it is difficult to uniformly “glue” the latent image with this particle size, and toner with a particle size of 5 μm or less is 30% by number or less, and 20 μm or more is 5% by number or less, which means that the particle size distribution is broad, which also tends to reduce uniformity. In order to form clear images using such coarse toner particles and a toner with a broad particle size distribution, it is necessary to layer the toner particles thickly to fill the gaps between the toner particles and reduce the apparent appearance. There is also the problem that it is necessary to increase the image density, and the amount of toner consumption necessary to achieve a predetermined image density increases.

In addition, JP-A-54-72054 proposes a non-magnetic toner having a sharper distribution than both of them, but the particle size of intermediate weight particles is coarse, 8.5 to 11.0 μm, and There is still room for improvement as a toner in terms of resolution.

In JP-A-58-129437, the average particle size is 6.
A non-magnetic toner has been proposed in which the particle size is 10 μm or less and the maximum particle size is 5 to 8 μm. However, the number of particles of 5 μm or less is as small as 15% by number or less (and images lacking in sharpness tend to be formed).

According to studies conducted by the present inventors, it has been found that toner particles of 5 μm or less have the main function of clearly reproducing the outline of a latent image and densely applying the toner to the entire latent image.

In particular, in the electrostatic latent image on the photoreceptor, the electric field strength is higher at the edge part than the inside due to the concentration of electric lines of force.
The quality of the toner particles that collect in this area determines the sharpness of the image quality.

According to studies conducted by the present inventors, it has been found that the amount of particles of 5 μm or less is effective in solving the problem of sharpness of image quality.

Also, in U.S. Patent No. 4,299,900, 20
A jumping development method using a developer having ~50% by weight of ~35 μm 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 environmental resistance of the developer by adjusting the particle size of the toner. However, there is a need for improvements that can meet even stricter requirements such as fine line reproducibility and suitability for resolution reversal development systems.

Recently, electrophotographic systems have been used not only for obtaining copied images but also for printers used for computer output. In printer applications, a light emitter (such as a semiconductor laser) is turned on and off according to an image signal, and its light is projected onto a photoreceptor. In this case, usually the printing rate (ratio of printing area per page)
is less than 30%, and the method of exposing the text area (
Reversal development) is advantageous in terms of luminescent life.

In addition, reversal development is used in devices that output positive and negative images from the same document (for example, microfilm output devices), and regular development is used to develop two or more colors in the same device. It has come to be used in devices that combine reversal development and reversal development.

However, reversal development has the following problems. The transfer electric field in normal development (hereinafter referred to as "normal development") has the same polarity as the -order charge, and even if the transfer electric field is applied onto the photoreceptor after passing through the image carrier (hereinafter referred to as paper, etc.), its effect will not be affected by trace exposure. It is erased at (6 in FIG. 1).

On the other hand, the transfer electric field in reversal development has the opposite polarity to the negative charge, and even after the paper passes through, when the transfer electric field is applied, a charge of the opposite polarity occurs on the photoreceptor, which cannot be erased by erase exposure, and the image becomes dark and dark. It will come to you. This is a phenomenon called "paper trail."

As a countermeasure against paper traces, there are measures such as lowering the transfer current after the paper has passed, as shown in Japanese Patent Application Laid-Open No. 60-256173. This makes the device complicated and increases the cost of the device. Another possible method is to lower the transfer electric field to a range in which charging of opposite polarity does not occur on the photoreceptor. However, this method lowers the transfer efficiency, resulting in a reduction in image quality due to poor transfer. Another disadvantage of the reversal development method is that the photoconductor and paper are charged with opposite polarities, so when charged by a strong electric field, the photoconductor and paper, etc.
It is electrostatically adsorbed and does not separate even after the transfer process is completed, allowing for the next process (
(cleaning process, etc.), causing paper jams, etc. This is a phenomenon called "wrapping". As a countermeasure against wrapping, there is a means to prevent the photoreceptor from coming into close contact with paper, etc., as seen in Japanese Patent Laid-Open No. 56-60470.

However, this method is not necessarily effective in reversal development. That is, this is considered to be because the close contact during separation in the transfer process of reversal development is stronger than that of normal development. Another method is U.S. Patent 3,357,40
As seen in Specification No. 0, etc., as an auxiliary means of separation,
There are devices with separate charging or belt separation. Although this is effective against the wrapping phenomenon, it is not effective against the paper trail phenomenon. This is because the separation charge is smaller than the transfer charge and does not affect the potential on the photoreceptor.

Another method is to reduce the electrostatic adhesion force by lowering the transfer electric field, but as described above, this method is likely to cause deterioration in image quality due to poor transfer. In addition, lowering the transfer electric field results in a decrease in transfer efficiency, which is detrimental to the transfer of postcards and O.
Unable to meet diverse needs for HP films, etc. Furthermore, when the transfer electric field is lowered, "transfer voids", which are part of transfer defects, occur in areas where developer tends to concentrate (edge development areas), such as image outlines and line drawing areas. This is thought to be due to the fact that more developer is deposited in the edge development area than in the normal area, and developer aggregation occurs (and the response to the transfer electric field is lowered). The problem is that it is difficult to obtain.

In addition, in a method using dry toner, in order to form a visible image of good quality, the toner must have high fluidity.
In addition, it is necessary to have uniform chargeability, and for this purpose, toner has conventionally been incorporated with fine silica powder. However, since fine silica powder is hydrophilic as it is, toner containing fine silica powder may aggregate due to moisture in the air, reducing fluidity, and in extreme cases, the toner may become charged due to moisture absorption of fine silica powder. This will reduce performance.

Therefore, it is recommended to use silica fine powder subjected to hydrophobization treatment, as disclosed in JP-A-46-5782, JP-A-48-47345, JP-A-48-47346, and JP-A-55-120041.
This is known from Japanese Patent Laid-Open No. 59-34539 and other publications. Specifically, for example, fine silica powder is made by reacting fine silica powder with an organosilicon compound such as dimethyldichlorosilane, hexamethyldisilazane, or silicone oil, and replacing the silanol groups on the surface of the fine silica powder with organic groups to make it hydrophobic. It is used.

Among these, silicone oil treatment is preferable as a hydrophobic treatment that exhibits sufficient hydrophobicity and allows the toner to exhibit excellent transferability when contained in a toner, but since silicone oil is a polymeric substance, hydrophobic treatment During processing, fine silica powder aggregates, and some of it remains several tens of microns even after being dispersed in the toner.
Since the residual toner has the same negative chargeability as the remaining toner, it develops in the image area, resulting in white spots and deteriorating the image quality.

Generally, one-component magnetic toner used in dry electrophotography is a fine powder in which magnetite, a charge control agent, a lubricant, etc. are dispersed in a binder resin made of natural or synthetic resin.

As the negative charge control agent contained in such toners, for example, metal salts or metal complex salts of monoazo dyes, metal salts or metal complex salts of salicylic acid, naphthoic acid, and their derivatives are often used. These are usually added to a thermoplastic resin, heated and melted and dispersed, and then finely pulverized and adjusted to a suitable particle size as necessary before use.

However, these charge control agents are not susceptible to mechanical shock, friction,
A phenomenon in which charge controllability changes due to changes in temperature and humidity conditions is likely to occur, and this phenomenon is more likely to occur as the toner particle size becomes smaller.

Therefore, when a toner containing these as a charge control agent is used for development in a copying machine, the toner may deteriorate during durability as the number of copies increases.

For example, when metal complex salts of salicylic acid, naphthoic acid, and their derivatives are used, the amount of charge increases at low temperatures and low humidity.
It is easy to cause a decrease in concentration due to
No. 27229, No. 57-167033, etc. disclose methods using metal complex salts of monoazo dyes and their derivatives, but when these are used in magnetic toners, they may contaminate charge-imparting members such as developing sleeves. In addition, the concentration tends to decrease due to a decrease in the amount of charge under high temperature and high humidity conditions.

Also, special public service 1972-. Publication No. 3305, JP-A-56-1
No. 01150, Japanese Unexamined Patent Publication No. 59-137955, etc., propose a method of preventing contamination of sleeves, photoreceptors, etc. by toner by adding fatty acid derivatives inside the toner, and imparting uniform chargeability to the toner.

Although these methods are somewhat effective in preventing contamination, it is still difficult to optimize the amount of charge, which is particularly problematic when reducing the diameter of toner. As a result of intensive studies, the present inventors found that metal complex salts of azo dyes and their derivatives, which have been conventionally used as negative charge control agents, and specific fatty acids that have the opposite polarity and the same charge control properties as the metal complex salts. The inventors have discovered that the above-mentioned problems can be solved by using a metal salt as a negative charge control agent in a specific ratio, leading to the present invention.

[Problem to be solved by the invention]

An object of the present invention is to provide a magnetic toner that always provides high-quality and stable images without being affected by the environment such as temperature and humidity.

Another object of the present invention is to provide a magnetic toner that has good dispersion of magnetic materials, lubricants, etc. in resin, has excellent durability, and provides stable images without fogging or scattering even after long-term continuous use. It is about providing.

Another object of the present invention is to provide a magnetic toner that is always stably triboelectrified and maintains a high density without contaminating triboelectric charging members such as a developing sleeve.

Another object of the present invention is to provide a negatively charged toner that can produce high-quality images in an image forming method that requires transfer using a low transfer electric field, such as a reversal development method.

Another object of the present invention is to provide an image forming method in which phenomena such as "paper marks,""wrapping," and "transfer missing" do not occur or are controlled.

Another object of the present invention is to provide a toner and an image forming method that produce high quality images without fogging even when thick transfer paper is used.

Another object of the present invention is to provide a negatively chargeable toner and an image forming method suitable for developing digital latent images used in digital copying machines, laser beam printers, and the like.

Another object of the present invention is to provide a negatively charged toner and an image forming method that do not cause voiding even under a low transfer electric field as in a reversal developing device and have good durability.

Another object of the present invention is to provide a toner that has good fluidity and does not have white spots caused by silica aggregates on a solid black image.

[Summary of the invention]

More specifically, the present invention provides a magnetic toner having at least a binder resin and a magnetic powder, which contains 17 to 60 number % of magnetic toner particles having a particle size of 5 μm or less, and 6.
5 to 50% by number of magnetic toner particles having a particle size of 35 to 10.07 μm are contained, 2.0% by volume or less of magnetic toner having a particle size of 12.7 μm or more is contained, and the volume average particle size of the magnetic toner is The group of magnetic toner particles having a diameter of 6 to 8 μm and 5 μm or less is represented by the following formula % [In the formula, N represents the number % of magnetic toner particles having a particle size of 5 μm or less, and ■ indicates a particle size of 5 μm or less. k is a positive number from 4.6 to 6.7. However, N represents a positive number from 17 to 6o. ] A complex salt of chromium, iron or cobalt of an azo dye and its derivative and a fatty acid metal salt (metal content 2.0 to 4.5% by weight,
By using silica with a melting point of 110°C to 145°C at a specific ratio as a charge control agent, toner transfer voids can be prevented, and hydrophobized silica other than silicone oil treatment can provide sufficient transferred images and image density, resulting in a solid image. Black and white spots are also prevented. Furthermore, in the toner having the particle size distribution of the present invention, the charging property is stabilized, the magnetic material and lubricant are well dispersed in the resin, and the contamination of the charge imparting member is prevented, thereby improving environmental stability. A toner with excellent durability can be obtained.

In the magnetic toner of the present invention, the charge controllability of the chromium, iron, or cobalt complex salt of the azo dye and its derivative, and the fatty acid metal salt is determined by the amount of triboelectric charge against iron powder, l Tc l≧l T
a l≧1Tb (as a charge control agent), and the charge control property of the fatty acid metal salt is ■, which is the opposite polarity of the control property of the chromium or iron complex salt of the azo dye and its derivative used in combination, and its absolute value is approximately They are equivalent, and due to their synergistic effect, the controllability when used together is higher than when used alone.

When Tb>Tc and Ta>Tc, the combined effect is not so great (particularly when left at high temperatures, the concentration decreases).

Further, in the toner of the present invention, the content of the metal complex salt of the azo dye and the fatty acid metal salt in the toner is 0.3≦ωa+ωp≦3 and ωa≧0.3 and ωp≧0.
．． 10.1≦ωp/ωa≦1, and when ωa < 0.3, poor dispersion tends to occur, and when ωp < 0.1, transfer voids easily occur in reversal development. In addition, when ωa+ωp>3, it is easy to cause contamination of charge imparting members such as the developing sleeve, and ωp/
When ωa<0.1, the concentration tends to decrease under high temperature and high humidity.

Furthermore, when ωp/ωa>1, the fluidity deteriorates, resulting in an image with a lot of fog.

Further, the metal content of the resin acid metal salt used in the toner of the present invention is preferably 2.0% by weight to 4.5% by weight.

If it is less than 2.0% by weight, the concentration tends to decrease under high temperature and high humidity conditions (and the toner fluidity is also poor).If it is more than 465% by weight, the effect of the combination of the azo dye with the metal complex salt is not sufficient.

Further, the melting point of the fatty acid metal salt used in the toner of the present invention is preferably 110°C to 145°C. Below 110°C, the melt viscosity is too low when toner is mixed, resulting in poor dispersion (poor fluidity and toner), which also causes crosstalk and slippage, resulting in magnetic materials,
This also impairs the dispersion of the lubricant, resulting in images with a lot of fog. 145
If the temperature is above .degree. C., the toner will not melt sufficiently during kneading, and poor dispersion will likely occur.

The fatty acid metal salt that satisfies the above physical properties has 10 or more carbon atoms.
A combination of No. 20 fatty acid and a metal such as AI or Mg is preferred, and aluminum stearate is particularly preferred.

The magnetic toner of the present invention having the above particle size distribution 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 images with excellent gradation and resolution. Furthermore, it maintains high image quality even when copying or printing is continued, and even in the case of high-density images, it is possible to perform good development with less toner consumption than conventional magnetic toner, making it economical. It also has the advantage of making the main body of a copying machine or printer more compact.

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

That is, one of the characteristics of the magnetic toner of the present invention is that magnetic toner particles having a particle size of 5 μm or less account for 17 to 80% by number. Conventionally, in magnetic toner, 5μ
Magnetic toner particles with a size of less than m are difficult to control the amount of charge, impair the fluidity of the magnetic toner, and are actively used as components that cause toner scattering and stain machines, and as components that cause image fogging. It was considered necessary to reduce

However, according to studies conducted by the present inventors, it has been found that magnetic toner particles of 5 μm or less are an essential component for forming high-quality images.

For example, changing the surface potential on the photoreceptor using a magnetic toner having a particle size distribution ranging from 0.5 μm to 30 μm,
A latent image can be developed by changing the surface potential on the photoreceptor, from a large development potential contrast where many toner particles are easily developed, to a halftone, to a small development potential contrast where only a few toner particles are developed. ,
When the developed toner particles on the photoreceptor were collected and the toner particle size distribution was measured, it was found that there were many magnetic toner particles with a diameter of 8 μm or less, and particularly a large number of magnetic toner particles with a diameter of 5 μm or less. In other words, when magnetic toner particles with a particle size of 5 μm or less, which is the most suitable for development, are smoothly supplied to develop the latent image on the photoreceptor, the latent image is faithful to the latent image, does not protrude from the latent image, and true reproducibility is achieved. This is an excellent image changer.

This phenomenon was the same in the case of reversal development of digital latent images.

Further, in the magnetic toner according to the present invention, 6.35 to
One of the characteristics is that the number of particles in the range of 10.08 μm is 5 to 50%. As mentioned above, this is 5 μm
This is related to the need for the presence of magnetic toner particles with a particle size of 5 μm or less, which has the ability to strictly cover and faithfully reproduce the latent image, but in the latent image itself. The electric field strength at the surrounding edges is higher than at the center (therefore, the toner particles inside the latent image are thinner than at the edges), and the image density may appear thinner.

In particular, magnetic toner particles with a diameter of 5 μm or less have a strong tendency to do so. However, we found that 6.35-10.08
It has been found that this problem can be solved and further clarity can be achieved by containing 5% to 50% of toner particles in the μm range. That is, 6.35 to 10.08
This is thought to be due to the fact that toner particles in the particle size range of 5 μm have a suitably controlled amount of charge compared to magnetic toner particles with a particle size of 5 μm or less, but the inner side where the electric field strength is lower than the edge portion of the latent image A uniformly developed image is formed by supplementing the lack of adhesion of the inner toner particles to the edge areas, and as a result, a sharp image with high density and excellent resolution and gradation is provided. It is something that

Furthermore, for particles with a particle size of 5 μm or less, the number %
(N) and volume % (V), N/V=-0,05N
+k (However, 4.6≦S≦6.7; 17≦N≦6
Another feature of the magnetic toner of the present invention is that it satisfies the following relationship: 0). This range is shown in FIG. 4, and the magnetic developer containing the magnetic toner of the present invention having a particle size distribution that satisfies this range is excellent for digital latent images formed from fine spots. Achieves excellent developability.

While studying the state of particle size distribution of 5 μm or less, the present inventors found that there is a state of existence of fine powder most suitable for achieving the purpose as shown in the above formula. In other words, for a certain value of N, a large N/V means that 5 μm
It shows that it contains a wide range of particles, including N/
It is understood that a small v value indicates that the abundance of particles around 5 μm is high and that there are few particles with a particle size smaller than that, and the value of N/V is in the range of 1.6 to 5.85. When N is within the range of 17 to 60 and the above relational expression is further satisfied, good fine line reproducibility and high resolution can be achieved.

Further, it is preferable that the amount of magnetic toner particles having a particle size of 12.7 μm or more be 2.0% by volume or less, and as small as possible.

By adopting a completely different approach from the conventional viewpoint, the magnetic developer of the present invention solves the conventional problems and makes it possible to withstand the recent strict demands for high image quality.

The configuration of the present invention will be explained in more detail.

Magnetic toner particles with a particle size of 5 μm or less account for 17 to 17 of the total number of particles.
The content is preferably 60% by number, preferably 25 to 60% by number, and even more preferably 30 to 60% by number. If the number of magnetic toner particles with a particle size of 5 μm or less is less than 17%, there will be less effective magnetic toner particles for high image quality, and especially as the toner is used for continuous copying or printing, the effective magnetic toner particles will decrease. As the components decrease, the balance of the particle size distribution of the magnetic toner as shown in the present invention deteriorates, and the image quality gradually deteriorates.

If it exceeds 60% by number, magnetic toner particles tend to aggregate with each other, resulting in toner lumps larger than the original particle size, resulting in rough image quality, lowering resolution, or causing the edges of the latent image to The difference in density between the inner part and the inner part is large (the image tends to be hollow), and
It is good that the number of particles in the range of 8 μm is 5 to 50% (
, preferably 8 to 40% by number. If the amount is more than 50% by number, the image quality deteriorates and more development than necessary occurs, that is, too much toner is applied, resulting in a decrease in fine line reproducibility and an increase in toner consumption. On the other hand, if it is less than 5% by number, it is difficult to obtain a high image density.Also, the number% (N%) of magnetic toner particles with a particle size of 5 μm or less, the volume% (
7%), there is a relationship such that N-V=-0.05N+, which indicates a positive number in the range of 4.6≦ and ≦6.7. Preferably 4.6≦≦6.2, more preferably 4.6≦≦
It is 5.7. As shown above, 17≦N≦601, preferably 25≦N≦60. More preferably 3o≦N≦
It is 60.

When k<4.6 i, the number of magnetic toner particles having a particle size smaller than 5.0 μm is small, resulting in poor image density, resolution, and sharpness. The presence of an appropriate amount of fine magnetic toner particles, which were conventionally thought to be unnecessary, contributes to achieving close packing of toner during development and forming a uniform image without roughness. In particular, by uniformly filling in thin lines and image contours, visual sharpness is further enhanced.

That is, when k < 4.6, these properties are inferior due to the lack of this particle size distribution component.

Separately, in terms of production, it is necessary to cut a large amount of fine powder by classification or the like in order to satisfy the condition of k<4.6, which is disadvantageous in terms of yield and toner cost.

Furthermore, when k > 6.7, the image density tends to decrease as printouts are continued due to the presence of more fine powder than necessary.

This phenomenon occurs when excessive fine powder magnetic toner particles with more charge than necessary adhere to the developing sleeve and prevent the normal magnetic toner from being carried and charged on the developing sleeve. Conceivable.

In addition, magnetic toner particles having a particle size of 12.7 μm or more are 2.
It is preferably 0% by volume or less, and more preferably 1.
It is 0 volume % or less, more preferably 0.5 volume % or less. If it is more than 2.0% by volume, it will hinder fine line reproduction. In addition, the volume average diameter of the magnetic toner is 6 to 8 μm.
m, and this value cannot be considered separately from each component mentioned above. Volume average particle size 6μ
If it is less than m, in applications of digital latent images with a high image area ratio such as graphic images, the amount of toner on the transfer paper is small, which tends to cause the problem of low image density.

This is considered to be due to the same reason as the reason why the density inside the edge portion of the latent image decreases as described above.

When the volume average particle size exceeds 8 μm, the resolution of minute spots of 100 μm or less is not good (and there is a lot of scattering in non-image areas. Likely to happen.

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 a coal tar counter T.
Using the A-n type (manufactured by Coulter), an interface (manufactured by Nikkaki) and cx-
i Connect a personal computer (manufactured by Canon) and use 1% NaCj! electrolyte using primary sodium chloride. Prepare an aqueous solution. As a measurement method, the electrolytic aqueous solution 1100
=150 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, as a dispersant is added to Il, and 2 to 20 mg of the measurement sample is further added. The electrolytic solution in which the sample was suspended was dispersed for about 1 to 3 minutes using an ultrasonic disperser, and the particle size of the particles was 2 to 40 μ based on the number of particles, using a 100 μ aperture as an aperture using the Coulter Counter TAn type. The distribution was measured and the values according to the invention were determined therefrom.

The true density of the magnetic toner according to the present invention is l, 45 to 1.
8 g/crrf, preferably 1.
It is 55 to 1.75 g/c.

Within this range, the magnetic toner of the present invention having a specific particle size distribution can be most effective in terms of high image quality and durability stability. If the true density of the magnetic toner is less than 1.45, the weight of the magnetic toner particles themselves is too light, which tends to cause fogging during reversal development, crushing of fine lines due to too much toner particles, scattering, and deterioration of resolution. . In addition, if the true density of the magnetic toner is higher than 1.8, the image density will be low and the image will lack sharpness such as broken thin lines, and the magnetic force will also be relatively thick, so the toner spikes will also be long. In this case, when the digital latent image is developed, the image quality is likely to be disturbed, resulting in a rough image.

Although the true density of magnetic toner can be measured using several methods, in the present application, when measuring fine powder, the following method was adopted as an accurate and simple method.

A cylinder made of stainless steel with an inner diameter of 10 mm and a length of about 5 cm, and an outer diameter of about 10 m that can be inserted tightly into it.
m.

A disk (A) with a height of 5 mm and an outer diameter of about 10 mm.
, prepare a piston (B) with a length of about 8 cm. Place the disk (A) at the bottom of the cylinder, then add approximately 1 g of the sample to be measured.
and gently push in the piston (B). A force of 400 kg/crrf was applied to this using a hydraulic press, and the product was compressed for 5 minutes and taken out. The diameter (Dcm) and height (Lcm) of the compressed sample are measured using a weighing scale fIk (wg) L micrometer, and the true density is calculated using the following formula.

In order to obtain even better development characteristics, the magnetic toner of the present invention has a residual magnetization σ of 1 to 5 emu/g s.
It is preferably 2 to 4.5 emu/g, and the saturation magnetization σ,
is 20-40 emu/g, and the coercive force Hc
preferably satisfies a magnetic property of 40 to 100 nisted (Oc) (in both cases, the measured magnetic field is xKOe).

The transfer process used in the present invention includes an electrostatic transfer method using an electric field generated by a corona discharge charger, a contact roller charger, or the like. Transfer conditions are measured as follows. Referring to FIG. 1 of the accompanying drawings, the cleaning device 8, developing device 9, transfer charger 3, etc. are removed from the image forming apparatus, and the photosensitive member (photosensitive drum) l, which is an electrostatic image holder, is removed from the image forming apparatus. It is charged with charger 2. After the leakage light is substantially completely blocked and one revolution of the photoreceptor 1 is charged, the surface potential of the photoreceptor is measured with a surface electrometer. Let the value of the surface potential at this time be vpr[v]. Next, after wiping the surface of the photoconductor with a cloth impregnated with alcohol to remove static electricity from the surface of the photoconductor, the negative charger 2 is removed, and the transfer charger 3 is attached to charge one revolution of the photoconductor L. After that, the surface potential of the photoreceptor is measured. The value of the surface potential at this time is Vt
, [V]. In the present invention, Vtr/Vpr
The value of is negative, preferably Vtr/Vpr. If the absolute value is less than 0.5, the transfer electric field is too low and image deterioration is likely to occur during transfer (on the other hand, if the absolute value exceeds 1.6, the transfer electric field is too strong and the photoreceptor is It is easy to be positively charged (and the paper trail phenomenon and the wrapping phenomenon tend to occur. The more preferable range of the absolute value rr (1-1') is 0.9 to 1.4 and P
r Yes.

The present invention is effective for an image forming method (apparatus) using an organic photoreceptor (hereinafter referred to as an OPC photoreceptor), and the OPC photoreceptor is a multilayer OPC formed of a multilayer structure having at least a charge generation layer and a charge transport layer. This is particularly effective for image forming methods using reversal development methods. In an OPC photoreceptor, when the photosensitive layer is charged to the opposite polarity, the movement of charges is slow, and this tendency is particularly noticeable in multilayer OPCs.
The present invention is particularly effective because paper marks are likely to occur.

The value of Vpr used in the present invention is -300 to -1,
000[V] is preferable, especially -500 to -900[V]
] is preferred. If it is less than -300 [V], it is difficult to secure a potential difference during development, and the image tends to become unclear. On the other hand, if it exceeds -1,000 [V], dielectric breakdown of the photosensitive layer occurs due to the electric field, resulting in black Image quality deterioration such as spots is likely to occur. -500 to -900[V] due to durability etc.
is particularly preferred.

The image forming method of the present invention does not use mechanical separation means,
Elastic force of transfer material (paper, etc.), curvature of photoreceptor.

An image forming method in which the transfer material is separated from the photoreceptor using a static eliminating brush, etc. (This is particularly effective for equipment. The state of separation in equipment that does not have a mechanical separation mechanism depends on the transfer conditions. The present invention is particularly effective because the windings are prone to cracking.

In the present invention, the diameter of the photoreceptor l ("φ" in FIG. 1) is 500 mm.
Image forming method (apparatus) using a photoreceptor with a diameter of m or less
It is particularly effective. Devices that use photosensitive drums with a diameter of 50 mm or less are intended to be miniaturized, and the number of parts must be reduced. Usually, the separation process consists of separation using only the elastic force of paper and a static elimination brush 7, etc. (See Figure 2). At this time, the static electricity removal step only removes static electricity from the paper, etc., and usually does not affect the surface potential of the photoreceptor.

The image forming process will be explained with reference to FIG.

- A developing device comprising a magnetic blade 11 and a developing sleeve 4 that includes a magnetic blade 11 and a magnet, in which the surface of the photoreceptor is negatively charged with a charger 2, a latent image is formed by image scanning through exposure 5 using a light source or laser light; In a container 9, the latent image is reversely developed using a one-component magnetic developer 13. In the developing section, a bias is applied between the photosensitive drum 1 and the developing sleeve 4 by a bias applying means. When the transfer paper P is conveyed and reaches the transfer section, the transfer charger 3 positively charges the transfer paper P from the back side (the opposite side to the photosensitive drum 11 side), thereby charging the negatively charged toner on the surface of the photosensitive drum. The image is electrostatically transferred onto the transfer paper P. Immediately after passing through the transfer charger 3, the transfer paper P is separated from the photosensitive drum 1 by curvature separation while the charges on the back surface of the transfer paper are eliminated by the charge removal brush 1O. The toner image on the transfer paper P separated from the photosensitive drum 1 by curvature separation is fixed by the heating and pressure roller fixing device 7 .

Further, the one-component developer remaining on the photosensitive drum after the transfer process is removed by a cleaning device having a cleaning blade.
will be removed. After cleaning, the photosensitive drum 1 is neutralized by erase exposure 6, and the process starting from the charging process using the wide charger 2 is repeated again. Next, the negatively charged toner used in the present invention will be described.

Although there are many types of metal complex salts of azo dyes and their derivatives contained in the toner of the present invention, those having the following structure are particularly preferred.

(In the formula, Rl and R2 represent a nitro group, a halogen, an alkyl group, an alkoxy group, or a sulfonic acid group, and A is hydrogen,
Represents an alkali, alkaline group, ammonium or organic ammonium. M represents chromium, iron or cobalt. ) As the binder resin used in the toner of the present invention, the following binder resins for toners can be used when a heated pressure roller fixing device having an oil coating device is used.

For example, monopolymers of styrene and its substituted products such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers , styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-methyl chloromethacrylate copolymer, styrene-
Acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile- Styrenic copolymers such as indene copolymers; polyvinyl chloride, phenolic resin, naturally modified phenolic resin, natural resin-modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide Resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumaron indene resin, petroleum resin, etc. can be used.

In the heating and pressure roller fixing method, which does not apply much oil, important issues are so-called offset development, in which a part of the toner image on the toner image support member is transferred to the roller, and the adhesion of the toner to the toner image support member. be. Toners that are fixed with less thermal energy tend to be prone to blocking or caking during storage or in a developing device, so these problems must also be taken into consideration. The physical properties of the binder resin in the toner are most important (involved in these phenomena), but according to the research of the present inventors, reducing the content of magnetic material in the toner causes the toner image to deteriorate during fixing. Although the adhesion of the toner to the supporting member is improved, offset is more likely to occur, and blocking or caking is also more likely to occur. The selection of the binding resin is more important. Preferred binding materials include crosslinked styrenic copolymers or crosslinked polyesters.

Examples of comonomers for the styrene monomer of the styrene copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, and acrylic acid. Double bond-containing monocarboxylic acids such as phenyl, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, etc.; for example, maleic acid, Dicarboxylic acids with double bonds such as butyl maleate, methyl maleate, dimethyl maleate, etc. and substituted products thereof; for example, vinyl chloride, vinyl acetate,
Vinyl esters such as vinyl benzoate; ethylene olefins such as ethylene, propylene, butylene; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone; vinyl methyl ether, vinyl ethyl ether, Vinyl monomers such as vinyl ethers such as vinyl isobutyl ether may be used alone or in combination of two or more.

As the crosslinking agent, compounds having two or more polymerizable double bonds are mainly used, such as aromatic divinyl compounds such as divinylbenzene and divinylphthalene; for example, ethylene glycol diacrylate,
Carboxylic acid esters having two double bonds such as ethylene glycol dimethacrylate and 1,3-butanediol dimethacrylate; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide, and divinyl sulfone; and three or more vinyl Compounds having groups can be used alone or as a mixture.

Polyethylene, polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, paraffin, etc. be.

Further, it is preferable to add fine silica powder to the magnetic toner of the present invention. When the magnetic toner according to the present invention is combined with fine silica powder, wear is significantly reduced due to the presence of the fine silica powder between the toner particles and the sleeve surface. As a result, the life of the magnetic toner and the sleeve can be extended, and stable charging properties can also be maintained, making it possible to obtain a developer having a magnetic toner that is better for long-term use.

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.

The dry method referred to herein is a method for producing fine silica powder produced by vapor phase oxidation of a silicon/% rogen compound.

For example, this method utilizes the thermal decomposition oxidation reaction of silicon tetrachloride gas in oxygen and hydrogen, and the basic reaction formula is as follows.

5iCf4+2H2+02→SiO2+4HC1! or,
In this manufacturing process, for example, aluminum chloride or
It is also possible to obtain a composite fine powder of silica and other metal oxides by using other metal/) halogen compounds such as titanium chloride together with a silicon halide compound, and these are also included.

On the other hand, various conventionally known methods can be applied to produce the silica fine powder used in the present invention by a wet method.

For example, the general reaction formula for the decomposition of sodium silicate with an acid is shown below.

Na2O・XSiO2+HCI! +H2O−+5iO
z ・nH2+ NaCj7 Other methods include decomposition of sodium silicate with ammonia salts or alkali salts, a method of generating alkaline earth metal silicate from sodium silicate and then decomposing it with acid to form silicic acid, and a method of decomposing sodium silicate into silicic acid. There are two methods: one method uses ion exchange resin to produce silicic acid, and the other method uses natural silicic acid or silicate.

The silica fine powder referred to herein can be any of anhydrous silicon dioxide (silica) and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate.

Among the above silica fine powders, the specific surface area due to nitrogen adsorption measured by BET method is 30 rrr/g or more (especially 50 rrr/g or more).
400 rrr/g) gives good results. 0 parts of fine silica powder per 100 parts by weight of magnetic toner
．． 0.01 to 8 parts by weight, preferably 0.1 to 5 parts by weight.

Further, the silica fine particles used in the present invention are preferably hydrophobically treated. For the hydrophobization treatment, a conventionally known hydrophobization method is used, and it is imparted by chemical treatment with an organosilicon compound that reacts with or physically adsorbs the silica fine powder.

Such treatment agents include, for example, hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, l
-dimethylethoxysilane, dimethyldichlorosilane,
Methyltrichlorosilane, allyldimethylchlorosilane, allyl phenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-
Chlorethyltrichlorosilane, β-chloroethyltriclesilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyljethoxysilane,
Hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, l,3-diphenyltetramethyldisiloxane and siloxane units having 2 to 12 siloxane units per molecule, with one unit per molecule at each end. S
Examples include dimethylpolysiloxane containing a hydroxyl group, an alkyl group, or an alkoxy group bonded to i. These can be used alone or in a mixture of two or more.

Further, silicone oil is generally represented by the following formula.

Preferred silicone oils include those having a viscosity of approximately 5 to 5000 centistokes at 25°C, such as methyl silicone oil, dimethyl silicone oil, phenylmethyl silicone oil, chlorphenylmethyl silicone oil, alkyl-modified silicone oil, and fatty acid. Modified silicone oil, polyoxyalkylene-modified silicone oil, etc. are preferred. These may be used alone or in a mixture of two or more.

In the toner of the present invention, it is preferable to use dry silica treated with an organosilicon compound, and treatment with silicone oil is not preferable from the viewpoint of eliminating white spots in the image due to silica clumps.

The degree of water leakage of silica in the present invention is measured as follows. 200mj! Collect 0.1 g of sample into a separating funnel, and add 100 ml of ion-exchanged water using a graduated cylinder. This was shaken for 10 minutes at 9 rpm using a TAGRA shaker mixer model T2C.

20-30m from the bottom layer after leaving the separating funnel for 10 minutes.
j! After extraction, the sample is separated into a 10 mm cell, and the turbidity of the water layer is measured using a colorimeter using ion-exchanged water as a blank (wavelength: 500 nm). If the water wettability of the silica fine powder is 60% or less, image density fluctuations are likely to occur under high temperature and high humidity conditions.

The magnetic toner of the present invention may contain additives, if necessary. Other additives include abrasives such as cerium oxide and silicon carbide, flow agents such as aluminum oxide, anti-caking agents, and conductivity agents such as carbon black and tin oxide.

In addition, in order to improve mold releasability during hot roll fixing, waxy substances such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, Sasol wax, paraffin wax, etc.
It is also one of the preferred embodiments of the present invention to add about 5% by weight to the magnetic toner.

The magnetic materials contained in the magnetic toner of the present invention include iron oxides such as magnetite, magnetite, and ferrite, and iron oxides including other metal oxides; Fe;

Metals such as Co and Ni, or these metals and A
l, Co, Cu, Pb, Mg, Ni, Sn, Zn, S
b, Be, Bi, Cd.

Ca, Mn, Se, Ti, W
, alloys with metals such as V, and mixtures thereof.

These ferromagnetic materials have an average particle size of about 0.1 to 2 μm,
Magnetic properties with 10KOe applied is coercive force 20~1500e
It is desirable to have a saturation magnetization of 50 to 200 emu/g (preferably 50 to 100 emu/g) and a residual magnetization of 2 to 20 emu/g.

In the present invention, the amount of triboelectric charge is measured at a temperature/humidity of 23,
An iron powder carrier (Japan Iron Powder EFV2) with a particle size of 2,007,300 mesh was used to transfer the test substance in an environment of 5°C/60%.
00/300) and 2/98, accurately weighed 0.5 to 1.5 g of this mixture, and heated it to 25 cm H2O on a metal 400 mesh screen connected to an electrometer.
The amount of charge per unit weight is determined from the amount of the test substance sucked in at that time and the amount of charge.

Further, the order of charge amount in the present invention does not change even by conventionally known blow-off measurement methods.

Moreover, this order is more obvious in the black fine powder before silica is added and mixed.

In producing the toner of the present invention, the constituent materials are kneaded using a thermal kneading machine such as a hot roll, kneader, or extruder, and then obtained by mechanical crushing or classification, or the materials are mixed into a binder resin solution. A toner manufacturing method is a toner manufacturing method in which a toner is obtained by dispersing and spray-drying the binder resin, or a polymerization method in which a toner is obtained by mixing a specified material with a monomer to form a binder resin to form an emulsified suspension and then polymerizing the resulting toner. Each method can be applied.

The present invention will be specifically explained below using examples. All parts in the following formulations are parts by weight.

Example 1 The above materials were thoroughly mixed in a blender and then kneaded in a twin-screw kneading extruder set at 130°C.

At this time, if the set temperature is too high, the toner tends to fog. The obtained kneaded material was cooled and coarsely pulverized using a cutter mill, then finely pulverized using a pulverizer using a jet stream, and the obtained pulverized powder was classified using a fixed wall type wind classifier. A classified powder was produced. Furthermore, the obtained classified powder was strictly classified and removed at the same time to remove ultrafine powder and coarse powder using a multi-division classification device (elbow jet classifier manufactured by Shirazuki Mining Co., Ltd.) that utilizes the Coanda effect, resulting in a volume average particle size of 6.5 μm. A black fine powder (negatively charged insulating magnetic toner) (A) was obtained. The obtained black fine powder was negatively charged with respect to the iron powder carrier, and the particle size measured using the aforementioned Coulter counter TArI type is shown in Table 1.

For reference, the classification process using a multi-division classifier is shown in the third section.
This is schematically shown in the figure, and a cross-sectional perspective view (stereoscopic view) of the multi-division classifier is shown in FIG. 1.2 parts of hydrophobic silica (average diameter 8 μm, 1 BET specific surface area 300 rd/g dry silica, hydrophobized with hexamethyldisilazane, tribocharge fi-700 μc/g) per 100 parts of the negatively chargeable black fine powder.
(Water wetness: 95%) was added and mixed in a Henschel mixer to obtain a one-component negatively charged magnetic developer.

The surface treatment of silica in the present invention was carried out as follows.

l) Silica fine powder (BET specific surface area 300 i/g
100 parts of dry silica) are stirred in a mixing tank.

2) Dilute the above-mentioned treatment agent 4 times with xylene and spray it onto the silica in the mixing tank. (80 parts of diluted solution) 3) While stirring, the temperature inside the tank was raised to 100°C and maintained for 2 hrs.

4) Cool and take out.

The obtained developer was subjected to reversal development using a commercially available copying machine FC-5 (manufactured by Canon; OPC laminated type negatively charged photoreceptor, curvature separation type using a drum diameter of φ30, static elimination needle with a bias of -1, OkV applied). The transfer conditions shown in Figure 1 have been modified for use (
VL- = +700V), a gap was set so that the developer layer on the photosensitive drum and the developing drum (with magnet included) did not contact each other, and an AC bias (f = 1.800Hz, Vpp = 1.60) was applied.
Image formation was carried out while applying a voltage of 0 V) and a direct current (VDC=-500 V) to the developing drum.

The fixed toner image which was printed and fixed by a heating and pressure roller was evaluated as follows.The results are shown in Table 2.

a) Regular copying machine paper that maintains image density (75g/rrr
) Evaluation was made by maintaining image density when 1,000 sheets were passed.

○(Good): 1.35 or more, △(Acceptable): 1.0~
1.34, × (impossible) + 1.0 or less b) Transfer condition: Strict transfer conditions, t2og/rr
A thick paper of R was passed through the paper, and the transfer waves were evaluated based on the condition.

○: Good, Δ: Practical, ×: Not Practical C) Winding Condition: 1,000 sheets of 50 g/rrr thin paper were passed through and the occurrence of paper jams was evaluated.

○: Within 1 time / 1,000 sheets, △: 71,000 sheets 2 to 4 times, X: 5 on the same side / 1,000 sheets d) Paper trace: Output all solid images and evaluate based on their uniformity did.

O: concentration difference within 0.05, △: concentration difference 0.06 to 0.15,
X: 0.16 or more e) Image quality: Toner scattering, roughness, etc. were visually evaluated.

O: Good, Δ: Practical, ×: Not Practical f) Image White Spots: White spots due to silica clumps in the image area were visually evaluated.

O: Good, △: Practical, X: Not practical g) Fog: Fog in non-image areas was visually evaluated.

◯: Good, △: Practical, ×: Not suitable for practical use.The multi-segment classifier used in this example and the classification process using the classifier will be explained with reference to FIGS. 3 and 4. In FIGS. 3 and 4, the multi-divided classifier 101 has side walls 122. The lower wall has the shape shown at 124 and the side wall 123 has the shape shown at 125.
and the lower wall 125 are respectively provided with a knife-shaped classification edge 1.
17, 118, and this classification edge 117. 11
8, the classification zone is divided into three. side wall 122
A raw material supply nozzle 116 opening into the classification chamber is provided in the lower part, and a funder block 126 is provided which is bent downward in the direction of extension of the bottom tangent of the nozzle to draw an elongated arc. The upper wall 127 of the classification chamber is provided with a knife-shaped edge 119 toward the bottom of the classification chamber, and furthermore, the upper portion of the classification chamber is provided with tubes 114 and 115 that open into the classification chamber. Also, popular tube 114. 115 has a damper-like first
, second gas introduction adjustment means 120, 121 and static pressure gauge 1
28,129 are provided. At the bottom of the classification chamber are discharge pipes 111 each having a discharge port opening into the chamber corresponding to each fractionation area. 112. 113 is provided.

The classified powder is introduced into the classification area from the supply nozzle 116 under reduced pressure, and moves in a curved line 130 due to the Coanda effect of the Coanda block 126 and the action of the high-speed air flowing in at that time, and the coarse powder 111 , black fine powder magnetic toner having a predetermined volume average particle diameter and particle size distribution) 112 and ultrafine powder 113.

Example 2 Same as Example 1 except that the amount of magnetite was 80 parts by weight, the particle size of the negatively charged insulating magnetic toner was the particle size distribution of B in Table 1, and the amount of hydrophobic silica was 0.6 parts by weight. went. The results are shown in Table 2.

Example 3 Aluminum stearate with a melting point of 140°C and a metal content of 4
．． Good results were obtained in the same manner as in Example 1 except that aluminum stearate was used at 0% by weight.

The results are shown in Table 2.

Example 4 Good results were obtained in the same manner as in Example 1 except that the amount of aluminum stearate was 0.25 parts and the amount of metal complex salt of azo dye was 1.0 parts. The results are shown in Table 2.

Comparative Example 1 Same as Example 1 except that the amount of magnetite was 60 parts by weight, the particle size of the negatively charged magnetic toner was the particle size distribution of magnetic toner C in Table 1, and the amount of hydrophobic silica was 0.4 parts by weight. I did the same. The results are shown in Table 2.

Comparative Example 2 The same method as in Example 1 was carried out except that aluminum stearate was not used. The temperature was 32.5°C and 185%.
As images were printed repeatedly under this environment, the density decreased, and when the sleeve was cleaned with methyl ethyl ketone, the density was restored. The results are shown in Table 2.

Comparative Example 3 When the same method as in Example 1 was carried out without using the metal complex salt of the azo dye, only an image with extremely low image density was obtained.

Comparative Example 4 The same procedure as in Example 1 was carried out except that a chromium complex of salicylic acid was used instead of the metal complex salt of the azo dye. The amount of charge became too high and the concentration was low from the beginning. The results are shown in Table 2.

Comparative Example 5 Table 2 shows the results of the same procedure as in Example 1 except that the amount of magnetite was changed to 140 parts by weight and the particle size of the negatively charged insulating magnetic toner was changed to the particle size distribution of magnetic toner D in Table 1.
Shown below.

Comparative Example 6 In Example 1, the primary particle size was 12 μm as hydrophobic silica.
The same method was used except that dry silica having a BET specific surface area of 200 rrr/g and silica treated with silicone oil was used.

The silica had a triboelectric charge of -280 μc/g and a water wettability of 96%. The results are shown in Table 2.

Comparative Example 7 In Example 1, aluminum stearate had a melting point of 16
When the same procedure was performed except that the temperature was 0° C. and the metal content was 5°wt%, the dispersion of aluminum stearate was poor and black spot fog occurred.

The results are shown in Table 2.

Comparative Example 8 The same procedure as in Example 1 was carried out except that stearic acid was used instead of aluminum stearate, but the fluidity was extremely poor and the resulting image had a lot of fog. The results are shown in Table 2.

\・ / Table 3 shows the amount of triboelectric charge of the magnetic toner used in each example.

Table [Effects of the Invention] When an image is formed using the toner of the present invention as described above, a high quality image can be obtained even in a high temperature and high humidity environment.

[Brief explanation of drawings]

Among the accompanying drawings, Fig. 1 is a diagram schematically showing the image forming apparatus used in the embodiment of the present invention, and Fig. 2 is an enlarged view of the transfer portion where AC bias and DC bias are applied to the static elimination brush. This is a diagram showing the FIG. 3 shows an explanatory view of the classification process using the multi-segment classification means, FIG. 4 shows a schematic cross-sectional perspective view of the multi-segment classification means, and FIG. It is a figure showing the range of the content ratio of particles. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... - Blowing charger, 3... Transfer charger, 4... Developing sleeve, 5... Exposure, 6... Erase exposure, 7... Heating Pressure roller fixing device, 8... Blade cleaning device, 9... Developing device, lO... Static elimination brush, 11... Blade, 12... Bias application means, etc. -

Claims (1)

[Scope of Claims] (1) In a negatively charged magnetic toner having at least a binder resin and a magnetic powder, the number of magnetic toner particles having a particle size of 5 μm or less is 17 to 60 μm.
% by number, 5 to 50% by number of magnetic toner particles having a particle size of 6.35 to 10.07 μm, and 2.0% by volume or less of magnetic toner particles having a particle size of 12.7 μm or more. Volume average diameter is 6-8
μm, and the group of magnetic toner particles of 5 μm or less is represented by the following formula N/V=-0.05N+k [where N represents the number % of magnetic toner particles having a particle size of 5 μm or less, and V represents particles of 5 μm or less. represents the volume % of magnetic toner particles having a diameter, and k represents a positive number from 4.6 to 6.7. However, N represents a positive number from 17 to 60. A metal complex salt of an azo dye and a fatty acid metal salt having a metal content of 2.0 to 4.5% by weight and a melting point of 110°C to 145°C are used as a charge control agent in a magnetic toner that satisfies the following. A toner containing at least a small amount of seeds, each of which has charge controllability in terms of triboelectric charge against iron powder |Tc|≧|Ta|≧|Tb| (as a charge control agent) Ta: a toner containing only a metal complex salt of an azo dye Amount of charge (μc/g) Tb; Amount of charge of toner containing only fatty acid metal salt (μc/g)
c/g) Tc: Charge amount (μc/g) of a toner containing both a metal complex salt of an azo dye and a fatty acid metal salt. However, the values of Ta and Tc are ■, and the value of Tb is ■. A negatively charged magnetic toner characterized by: (2) The content of the metal complex salt of the azo dye and the fatty acid metal salt in the toner is 0.3≦ωa+ωp≦3 0.1≦ωp/ωa≦1 ωa; Content of the metal complex salt of the azo dye (wt%) ) ωp: Content of fatty acid metal salt (% by weight) The negatively charged magnetic toner according to claim (1).