JP2603286B2 - Magnetic toner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic toner for visualizing an electrostatic latent image in an image forming method such as electrophotography and electrostatic recording.

(Background technology)

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

Various development methods for visualizing an electrostatic latent image using toner are also known. For example, a magnetic brush method described in U.S. Pat.No. 2,874,063, a cascade development method described in U.S. Pat.No. 2,815,552 and a powder cloud method, a fur brush development method described in U.S. Pat. Many development methods such as a liquid development method and the like are known. Among these developing methods, a magnetic brush method, a cascade method, a liquid developing method and the like using a developer mainly composed of a toner and a carrier have been widely put to practical use. Each of these methods is an excellent method of obtaining a good image relatively stably, but has the common problems of the two-component developer such as deterioration of the carrier and fluctuation of the mixing ratio of the toner and the carrier.

In order to solve such a problem, 1
Various development methods using a component-based developer have been proposed, and among them, many of the methods using a developer composed of magnetic toner particles are excellent.

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

As a developing method using a high-resistance magnetic toner capable of electrostatically transferring, there is a developing method using dielectric polarization of toner particles. However, such a method has a problem that the developing speed is essentially low and a sufficient density of a developed image cannot be obtained, and is practically difficult.

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

However, Japanese Patent Application Laid-Open No. 55-18656 and the like have proposed a new developing method which eliminates the above-mentioned problems. This involves applying a very thin coating of magnetic toner on a sleeve, triboelectrically charging it, and then developing it very close to the electrostatic image. This method increases the chance of contact between the sleeve and the toner by applying a very thin magnetic toner on the sleeve, enables sufficient triboelectric charging, supports the toner by magnetic force, and keeps the magnet and toner relatively By moving the toner particles to each other, the cohesion between the toner particles is eliminated, and the toner particles are sufficiently rubbed with the sleeve.The toner image is supported by magnetic force, and the toner is developed without facing the electrostatic image to develop an excellent image. It is obtained.

2. Description of the Related Art In recent years, as image forming apparatuses such as electrophotographic copiers have become widespread, their uses have been diversified, and requirements for image quality have become strict. 2. Description of the Related Art In copying images such as ordinary documents and books, it is required to reproduce very finely and faithfully without crushing or breaking even fine characters. In particular, when the latent image on the photoreceptor of the image forming apparatus is a line image of 100 μm or less, thin line reproducibility is generally poor, and the line image is not yet sufficiently sharp. Recently, in an image forming apparatus such as an electrophotographic printer using a digital image signal, a line image is formed by collecting dots of a constant potential, and a solid portion,
The halftone portion and the light portion are expressed by changing the dot density. However, when the toner particles do not adhere to the dots and the toner particles protrude from the dots, the gradation of the toner image corresponding to the dot density ratio of the black part and the white part of the digital line image cannot be obtained. There is a problem. Furthermore, when the resolution is improved by reducing the dot size in order to improve the image quality, the reproducibility of a latent image formed from minute dots becomes more difficult, and the resolution and gradation are poor, and the sharpness is low. Image tends to be lacking.

Although the image quality is good in the early stage, the image quality may deteriorate while copying or printing out. It is considered that this development is caused by the fact that only toner particles which are easily developed are consumed first while copying or printing is continued, and the toner particles having poor developability accumulate and remain in the developing machine.

Heretofore, some developers have been proposed for the purpose of improving image quality. JP-A-51-3244 proposes a non-magnetic toner intended to improve image quality by regulating the particle size distribution. In the toner, 8
The main component is a toner having a particle size of about 12 μm, which is relatively coarse. According to the study of the present inventors, it is difficult to make a “glue” to a latent image densely, and the particle size is 5 μm or less. 30
From the characteristic that the particle size distribution is not more than 5% by number when the particle size is 20% or more, the particle size distribution is also broad, which tends to lower the uniformity. In order to form a clear image using toner having such coarse toner particles and a broad particle size powder cloth, it is necessary to fill the gaps between the toner particles by thickly overlapping the toner particles. It is necessary to increase the image density, and the amount of toner consumption required to obtain a predetermined image density also increases.

Also, Japanese Patent Application Laid-Open No. 54-72054 proposes a non-magnetic toner having a sharper distribution than the former,
The size of particles having an intermediate weight is as coarse as 8.5 to 11.0 μm, and there is still room for improvement as a high-resolution toner.

In Japanese Patent Application Laid-Open No. 58-1229437, the average particle size is 6 to 10 μm.
Non-magnetic toners having the largest number of particles of 5 to 8 μm have been proposed, but the number of particles of 5 μm or less is as small as 15% by number or less, and an image lacking sharpness tends to be formed.

According to the study of the present inventors, it has been found that toner particles having a size of 5 μm or less clearly reproduce the outline of the latent image and have a main function of dense toner adhesion to the entire latent image. In particular, in the electrostatic latent image on the photoreceptor, due to the concentration of lines of electric force, the contoured edge portion has a higher electric field intensity than the inside, and the sharpness of the image quality is determined by the quality of the toner particles collected in this portion. According to the study of 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. Pat.No. 4,299,900, 20-35 μm
A jumping development method using a developer having 10 to 50% by weight of a magnetic toner has been proposed. In other words, the toner particle size suitable for frictionally charging the magnetic toner, uniformly and thinly applying the toner layer on the sleeve, and further improving the environmental resistance of the developer has been devised. However, considering stricter requirements such as reproducibility of fine lines and resolution, it is not sufficient, and further improvements are required. The present inventors have found that in such circumstances, the magnetic toner having the particle size distribution according to the present invention satisfies the above strict requirements.

However, the magnetic toner having the particle size distribution proposed in the present invention contains more magnetic toner particles having a particle size of 5 μm or less than many conventional magnetic toners, and has a particle size of 5 μm or less. Since the magnetic toner particles greatly contribute to the developability of the magnetic toner and determine the sharpness of the image quality, it is important to disperse the magnetic toner composition more homogeneously than before, and this is also a difficult task.

In the magnetic toner having the particle size distribution of the present invention, when the magnetic toner composition is not uniformly dispersed, the uneven amount of charge of the developer causes background fog development, which causes a great problem on an image. Become. In recent years, the functions of copiers have diversified, and some of the images have been erased by exposure, etc.
Then, in a function such as making multiple copies to insert another image in that part or removing the frame around the transfer paper, the fact that fogging has occurred in the part of the image that should be widely removed, This is very problematic in terms of color tone and image quality.

That is, when a potential opposite to the latent image potential with respect to the development reference potential is given by strong light such as an LED or a fuse lamp to erase an image, fogging occurs at that portion. further,
When performing multiple copies with multiple colors, color mixing occurs,
It also impairs the sharpness of the image.

In particular, when the charge control agent is contained in the toner, if the charge control agent is not sufficiently dispersed, the distribution of the triboelectric charge amount tends to be broad and non-uniform, and the triboelectric charge varies depending on environmental conditions such as temperature and humidity. The amount is more likely to be unstable.

In order to improve the dispersibility of the charge control agent, the present inventor studied the type, amount, particle size, treatment, and matching of the charge control agent with the binder resin to improve the dispersibility of the charge control agent.
In a positively charged positive magnetic toner, a nigrosine powder having a number average particle diameter of 2 μm or less is used as a charge control agent, and a copolymer of a hydrocarbon-based monomer having a conjugated diene bond is contained in a binder resin. The present inventors have found that environmental stability and uniform dispersion of the charge control agent can be obtained, and have reached the present invention.

[Object of the invention]

An object of the present invention is to provide a magnetic toner which has solved the above-mentioned problems.

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

It is a further object of the present invention to provide a magnetic toner which does not change its performance over a long period of use.

Further, an object of the present invention is to provide a magnetic toner whose performance does not change with environmental changes.

It is a further object of the present invention to resist magnetic toner having excellent transferability.

Another object of the present invention is to provide a magnetic toner capable of changing a high image density with a small consumption.

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

It is a further object of the present invention to provide a magnetic toner with less fog and reverse fog.

An object of the present invention is that the amount of triboelectric charge between toner particles, between a toner and a toner carrier such as a sleeve is stable,
It is another object of the present invention to provide a magnetic toner which has a uniform and triboelectric charge distribution and can be controlled to a charge amount suitable for a developing system to be used.

[Summary of the Invention]

More specifically, the present invention relates to a magnetic toner having at least a binder resin and magnetic powder, wherein 12 to 60 magnetic toner particles having a particle size of 5 μm or less are contained, and 8 to 12.7
1 to 33% by number of magnetic toner particles having a particle size of 0.1 μm, and 2.0% or more of magnetic toner particles having a particle size of 16 μm or more.
% By volume and the volume average particle diameter of the magnetic toner is 4%.
The magnetic toner particles having a particle size of 5 μm or less are represented by the following formula: [Wherein, N represents the number% of magnetic toner particles having a particle size of 5 μm or less, V represents the volume% of magnetic toner particles having a particle size of 5 μm or less, and k represents a positive number of 4.5 to 6.5. . Here, N indicates a positive number of 12 to 60. Wherein the charge control agent is a nigrosine powder having a number average particle diameter of 2 μm or less, and the binder resin contains a copolymer of a hydrocarbon monomer having a conjugated diene bond. The invention relates to a magnetic toner characterized by the following.

The magnetic toner of the present invention having the above particle size distribution can faithfully reproduce even a fine line of a latent image formed on a photoreceptor, and can reproduce dot and digital dot latent images. To provide an image which is excellent in gradation and resolution. Furthermore, high image quality can be maintained even when copying or printing out is continued, and even in the case of high-density images, good development can be performed with less toner consumption than conventional magnetic toners. and,
It also has an advantage in reducing the size of the copying machine or the printer body.

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

That is, one feature of the magnetic toner of the present invention is that 12 to 60% by number of magnetic toner particles having a particle diameter of 5 μm or less. Conventionally, magnetic toner particles having a particle size of 5 μm or less have difficulty in controlling the charge amount, impair the fluidity of the magnetic toner, and cause fogging of the image as a component that scatters the toner and soils the machine. It was thought that it was necessary to aggressively reduce it as a component.

However, studies by the present inventors have revealed that magnetic toner particles having a size of 5 μm or less are essential components for forming high-quality images.

For example, using a magnetic toner having a particle size distribution ranging from 0.5 μm to 30 μm, the surface potential on the photoreceptor is changed, and from a large development potential contrast in which a large number of toner particles are easily developed, to a halftone, and further, a very small amount. A latent image with a changed surface potential on the photoreceptor was developed to a small development potential contrast where only toner particles were developed, and the developed toner particles on the photoreceptor were collected. The toner particle size distribution was measured. It has been found that there are many magnetic toner particles, especially magnetic toner particles of 5 μm or less. In other words, when magnetic toner particles having a particle size of 5 μm or less, which are most suitable for development, are smoothly supplied to the development of the latent image on the photoreceptor, the toner is faithful to the latent image and does not protrude from the latent image, and is truly reproducible And excellent images can be obtained.

One feature of the magnetic toner of the present invention is that the number of particles in the range of 8 to 12.7 μm is 1 to 33% by number. This is related to the necessity of magnetic toner particles having a particle size of 5 μm or less as described above. Magnetic toner particles having a particle size of 5 μm or less strictly cover a latent image and have an ability to faithfully reproduce the latent image. However, in the latent image itself, the electric field strength of the edge portion around the latent image is higher than that of the central portion, so that the toner particles may be thinner inside the latent image than in the edge portion, and the image density may appear to be light. In particular, magnetic toner particles of 5 μm or less have a strong tendency. However, the present inventors have found that toner particles having a size of 8 to 12.7 μm
It has been found that this problem can be solved and further clarified by containing up to 33% by number. That is, 8
It is considered that the toner particles having a particle size in the range of 12.7 μm have a moderately controlled charge amount with respect to the magnetic toner particles having a particle size of 5 μm or less. Supplied to the small inner side, a uniform developed image is formed by compensating for the small amount of toner particles on the inner side of the edge portion, and as a result, a high-density sharp image with excellent resolution and gradation is obtained. Is provided.

Further, for particles having a particle diameter of 5 μm or less, between the number% (N) and the volume% (V), N / V = −0.04N + k (4.5 ≦ k ≦ 6.5; 12 ≦ N ≦ 60) One of the features is that the magnetic toner of the present invention satisfies the following relationship. FIG. 2 shows this range, and together with other features, the magnetic toner of the present invention having a particle size distribution satisfying this range can achieve excellent developability.

The present inventors have studied the state of the particle size distribution of 5 μm or less and found that there is a state of existence of the fine powder most suitable for achieving the object as shown by the above formula. In other words, for a given value of N, a large N / V means that 5 μm
It indicates that the following particles are widely contained, and N / V
Is small, it is understood that the abundance of particles around 5 μm is high, and that particles having a particle size smaller than 5 μm are small, and the value of N / V is in the range of 2.1 to 5.82; and N is
When the ratio is in the range of 12 to 60 and the above relational expression is further satisfied, good fine line reproducibility and high resolution are achieved.

Further, for magnetic toner particles having a particle size of 16 μm or more, the content is preferably set to 2.0% by volume or less, and as small as possible.

A coarse charge control agent having a number average particle diameter of about 3 to 8 μm and a broad particle size distribution, which has been widely used, has a volume average particle diameter of 4 to 10 μm, and magnetic toner particles having a particle diameter of 5 μm or less have a particle diameter of 12 to 10 μm. In the magnetic toner having the particle size distribution of the present invention containing 60% by number, the particle diameter of the charge control agent is relatively smaller than the particle diameter of the magnetic toner particles because the particle diameter is smaller than that of the magnetic toners that have been widely used. Since it becomes large, its dispersibility is questioned. At the same time, the use of a charge control agent having a larger particle size than the magnetic toner particle size makes the charge control agent prominently protrude from the surface of the magnetic toner particles, and this is released by stirring in the developing device. This results in non-uniform tribocharging. This phenomenon is caused by the fact that in the magnetic toner having the particle size distribution of the present invention, the particle size of the charge control agent is relatively large with respect to the particle size of the magnetic toner particles, and further, the particle size of the magnetic toner particles is small. This becomes more remarkable as the surface area per unit weight of the magnetic toner particles increases. For this reason, in the magnetic toner having the particle size distribution of the present invention, uniform dispersion of the charge control agent becomes a more important problem than ever.

In particular, when the magnetic toner having the particle size distribution of the present invention is used as a positive charge, many resins conventionally used exhibit a negative charge, and the charge control agent imparts a positive charge to the magnetic toner particles. Therefore, sufficient and stable charge control ability and even better dispersion of the charge control agent in the magnetic toner are required.

The present inventors have solved the above problem by using a nigrosine powder having a number average particle size of 2 μm or less as a charge control agent.

If the number average particle diameter of the nigrosine powder exceeds 2 μm, the dispersion of the nigrosine in the magnetic toner is insufficient, and the expected stable triboelectric charging is not obtained, and fog and reversal fog are generated. This can hinder maximizing the high image quality obtained by the distribution of magnetic toner.

Incidentally, the nigrosine powder used in the present invention,
It is important that substantially no particles having a particle size exceeding 20 μm are contained and that the volume average particle size (dv) / number average particle size (dn) is 2.5 or less. As a result, a fine and sharp particle distribution is obtained, and the effect becomes more remarkable.

If these conditions are not satisfied, the coarse particles in the nigrosine powder exhibit an unstable dispersion state in the magnetic toner and are easily released from the magnetic toner particles. The released nigrosine shows uneven triboelectric charging, which not only causes fogging and reversal fog, but also adheres to the sleeve, hinders triboelectric charging of the toner and the developing sleeve, and substantially reduces the developability of the magnetic toner. Becomes

In the present invention, the particle size of the nigrosine powder is determined by a Coulter Counter TA-II (described below).
It is measured using a 24 μm aperture.

However, there is still a problem even when the particle size of the nigrosine powder is reduced to sufficiently disperse the nigrosine in the magnetic toner.

As a problem of the nigrosine dye itself, the so-called sleeve contamination, in which the nigrosine or the resin component containing the nigrosine migrates to and adheres to the surface of the developing sleeve, may be caused. Even if contamination occurs, it is necessary to select a resin having excellent developability that does not cause inconvenience such as a decrease in image density.

Further, even after the toner is left in a high-temperature and high-humidity environment, it is desired that the triboelectric charge rises more quickly and a high image density can be obtained from the beginning.

The present inventors have solved these problems by adding a copolymer of a hydrocarbon monomer having a conjugated diene bond to a binder resin.

The copolymer of a hydrocarbon monomer having a conjugated diene bond is excellent in developability, and by giving a higher image density, the high resolution and excellent process realized by the magnetic toner having the particle size distribution of the present invention can be achieved. In addition to making the tone reproducibility even more prominent, even after being left in a high-temperature, high-humidity environment for a long time, triboelectric charging starts more quickly, and a high resolution density can be obtained from the beginning.

As described above, the magnetic toner of the present invention solves the conventional problems, and can withstand recent severe demands for high image quality.

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

Magnetic toner particles having a particle size of 5 μm or less have a total particle number of 12 to
It is preferably 60% by number, more preferably 25 to 50% by number, and even more preferably 30 to 50% by number. When the number of magnetic toner particles having a particle size of 5 μm or less is less than 12% by number, the amount of magnetic toner particles effective for high image quality is small. In particular, as the toner is used by continuing copying or printing out, the effective magnetic toner particles are effective. Ingredients decrease,
As shown in the present invention, the balance of the particle size distribution of the magnetic toner deteriorates, and the image quality gradually decreases. On the other hand, if it is more than 60% by number, the magnetic toner particles are likely to aggregate with each other, resulting in a toner mass larger than the original particle size, resulting in rough image quality, reduced resolution, or latent image edge. The density difference between the part and the inside becomes large, and the image tends to be slightly hollow.

The particle size in the range of 8 to 12.7 μm is preferably 1 to 33% by number, and more preferably 8 to 20% by number. If the content is more than 33% by number, the image quality is deteriorated, and the development is performed more than necessary, that is, the toner is excessively applied, which leads to an increase in toner consumption. On the other hand, if it is less than 1% by number, it becomes difficult to obtain a high image density. Further, there is a relationship of N / V = −0.04N + k between the number% (N%) and the volume% (V%) of the magnetic toner particle group having a particle diameter of 5 μm or less, and 4.5 ≦ k ≦ 6.5.
Indicates a positive number in the range. Preferably, 4.5 ≦ k ≦ 6.0, more preferably 4.5 ≦ k ≦ 5.5. As indicated earlier, 12
≦ N ≦ 60, preferably 25 ≦ N ≦ 50, more preferably 30
≦ N ≦ 50.

When k <4.5, the number of magnetic toner particles having a particle diameter smaller than 5.0 μm is small, and the image density, resolution, and sharpness are poor. The appropriate presence of fine magnetic toner particles, which was conventionally considered unnecessary, contributes to the closest packing of the toner in development and contributes to the formation of a uniform image without roughness. In particular, by uniformly filling the fine lines and the outline of the image, the sharpness is further enhanced visually.
That is, when k <4.5, these properties are inferior due to the lack of the particle size distribution component.

From another aspect, in production, it is necessary to cut a large amount of fine powder by classification or the like to satisfy the condition of k <4.5, which is disadvantageous in terms of yield and toner cost. If k> 6.5, the image density tends to decrease during repeated copying due to the presence of unnecessarily fine powder. Such a phenomenon occurs when excessive fine powdered magnetic toner particles having an unnecessary charge are charged and adhered to the developing sleeve shape, thereby hindering normal magnetic toner from being carried on the developing sleeve and applying charge. Conceivable.

The content of the magnetic toner particles having a particle diameter of 16 μm or more is preferably 2.0% by volume or less, more preferably 1.0% by volume.
Or less, more preferably 0.5% by volume or less.
When the content is more than 2.0% by volume, not only does it hinder the reproduction of fine lines, but also in the transfer, coarse toner particles of 16 μm or more protrude from the thin layer surface of the toner particles developed on the photoreceptor. The delicate state of contact between the photoreceptor and the transfer paper via the layer is made irregular, causing fluctuations in the transfer conditions and causing poor transfer images. Further, the volume average diameter of the magnetic toner is 4 to 10 μm, preferably 4 to 8 μm, and this value cannot be considered separately from the above-mentioned components. When the volume average particle diameter is less than 4 μm, in applications having a high image area ratio such as a graphic image, there is a problem that the amount of applied toner on transfer paper is small and the image density is low. This is considered to be due to the same reason as described above for lowering the density inside the edge portion of the latent image. If the volume average particle diameter exceeds 10 μm, the resolution is not good, and if the use is continued at the beginning of copying at the best, the image quality tends to deteriorate.

As the nigrosine powder used as a charge control agent in the present invention, a well-known nigrosine-based dye can be used if adjusted by pulverization and / or classification so as to have a particle size specified in the present invention, and these are acid or acid. It may be one treated with a base or modified with a resin.

In the present invention, by setting the number average particle size of the nigrosine powder to 2 μm or less, the dispersibility in the magnetic toner is improved, the exposure of the nigrosine is uniformly distributed on the surface of the magnetic toner, and the magnetic properties of the nigrosine powder are improved. Unstable dispersion such as protrusion from the toner surface was eliminated.

When the exposed portions of nigrosine are not uniformly distributed on the surface of the magnetic toner, the frictional charging in the magnetic toner is made nonuniform, and a broad charge amount distribution is provided. In some cases, charges are locally accumulated in the magnetic toner.

In an unstable dispersion state where the nigrosine powder protrudes and is exposed from the surface of the magnetic toner, the nigrosine powder in the unstable dispersion state may be agitated in a developing device or the like. , And not only causes non-uniform triboelectric charging, but also adheres to the developing sleeve and causes so-called sleeve contamination which hinders triboelectric charging between the developing sleeve and the magnetic toner.

By solving these problems, the magnetic toner of the present invention makes it possible to obtain a sharp image free from fog and reversal fog, and exhibits extremely excellent environmental stability.

In the present invention, the amount of nigrosine powder added to the magnetic toner is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the binder resin. If the amount is less than 0.1 part by weight, sufficient charge control is not exhibited. If the amount exceeds 10 parts by weight, sleeve contamination by nigrosine tends to occur.

In the present invention, the copolymer of the hydrocarbon monomer having a conjugated diene bond contained in the binder resin, the portion composed of the hydrocarbon monomer having a conjugated diene bond is a part of the binder resin.
It is good to be 40% by weight or less, preferably 30% by weight or less. If the amount exceeds 40% by weight, the elasticity of the toner increases and the adhesiveness to the transfer paper decreases, so that the fixability becomes insufficient.
Further, there is a problem that the pulverizability is poor in the toner production process.

As the copolymer of a hydrocarbon monomer having a conjugated diene bond contained in the binder resin used in the present invention, a copolymer having a melt index (MI) value of 0.05 to 20 is used. When the MI value is 0.05 or less, the fixing point becomes high, and when the MI value is 20 or more, the offset resistance becomes insufficient. The glass transition point (Tg) is preferably from 40 to 75 ° C. Preferably, the temperature is 50 to 70 ° C.
When the temperature is lower than 40 ° C., blocking is easy, and when the temperature is higher than 75 ° C., the fixability is not sufficient. The molecular weight distribution is n at 5,
It is preferable that 000 to 50,000 and w be adjusted to about 100,000 to 1,000,000. Further, when a magnetic toner is produced by containing a copolymer of a hydrocarbon monomer having a conjugated diene bond used in the present invention, the gel content of the toner is 0 to 80% by weight based on the binder resin. Is preferred. If it exceeds 80% by weight, the fixing property is reduced.

By containing a copolymer of a hydrocarbon monomer having a conjugated diene bond that satisfies these in the binder resin,
The reason why the toner using Nigrosine powder as a charge control agent suppresses inconveniences such as image density reduction due to sleeve contamination and obtains even better environmental stability is as follows.
Although not clearly known, the present inventors presume as follows.

As described above, the magnetic toner having the particle size distribution of the present invention contains more particles having finer particles than many conventional magnetic toners, so that the particle size of the nigrosine powder is reduced on the surface of the magnetic toner. However, even if the dispersibility is greatly improved, the protrusion of the nigrosine powder tends to be more remarkable than many toners containing the conventional nigrosine powder, whereby the nigrosine powder or the nigrosine powder is reduced. Sleeve contamination by the contained resin component tends to be remarkable.

It is considered that the copolymer of the hydrocarbon monomer having a conjugated diene bond has a high affinity with the nigrosine powder on the surface of the magnetic toner, and has an effect of reducing the falling off of the nigrosine powder from the toner surface. It is considered that the effect of preventing the nigrosine powder from falling off from the surface of the magnetic toner in this manner makes sleeve contamination extremely unlikely to occur and maintains high developability. This effect is considered to be particularly remarkable when the particle size of the nigrosine powder is sufficiently small and coarse particles of the nigrosine powder are not contained.

In addition, if a binder resin contains a copolymer of a hydrocarbon monomer having a conjugated diene bond, charging is performed promptly, and the rise of image density is accelerated. As described above, this is a characteristic of the excellent developing characteristics of the copolymer comprising a hydrocarbon monomer having a conjugated diene bond.

As the conjugated diene-based monomer used in the present invention, butadiene, isoprene, chloroprene, and the like, and derivatives thereof can be used, and butadiene is particularly preferable.

Monomers other than the conjugated diene monomer applicable to the present invention include styrene such as styrene, α-methylstyrene, and p-chlorostyrene, and their substituted products; acrylic acid,
Methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, dimeraminoethyl methacrylate, acrylonitrile Carboxylic acid having a double bond such as methacrylonitrile, acrylamide or the like; a dicarboxylic acid having a double bond such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate and the like; Substitutes thereof; vinyl esters such as vinyl chloride, vinyl acetate and vinyl benzoate; vinyl ketones such as vinyl methyl ketone and vinyl ethyl ketone; vinyl methyl ether and vinyl Chirueteru, vinyl monomers such as vinyl ethers such as vinyl isobutyl ether is used two or more. In particular, a combination of a styrene monomer and a butadiene monomer is preferred because the rise in image density is fast and environmental stability (particularly under a high-temperature high-quality environment) is excellent. In particular, the effect is remarkable in the case of a positively chargeable toner. The copolymerization weight ratio of the styrene monomer and the butadiene monomer is preferably 50:50 to 95: 5, particularly 70:30 to 9
5: 5 is preferred from the viewpoint of the heat fixing property of the toner and the pulverizability at the time of manufacturing the toner.

In the polymerization, the polymerization may be carried out in the presence of the following crosslinking monomer. Divinylbenzene, divinylnaphthalene, divinylether, divinylsulfone, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol dimethacrylate , 1,6-Hexane glycol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2'-bis (4-methacryloxydiethoxyphenyl) propane, 2,2 ' -Screw (4
-Acryloxydiethoxyphenyl) propane, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, dibromoneopentyl glycol dimethacrylate, allyl phthalate, 1,2-propylene glycol, 1,3 -A general crosslinking agent such as butanediol can be appropriately used.

The copolymer of the conjugated diene-based monomer contained in the binder resin of the present invention may be prepared by an emulsion polymerization method, a solution polymerization method, a suspension polymerization method,
It is synthesized by a well-known method such as a bulk polymerization method.

In the magnetic toner of the present invention, the resin contained in the binder resin other than the copolymer of the hydrocarbon monomer having a conjugated diene bond includes, for example, styrene such as polystyrene, poly p-chlorostyrene, and polyvinyl toluene, and a substituted product thereof. A styrene-p-chlorostyrene copolymer, a styrene-propylene copolymer, a styrene-vinyltoluene copolymer, a styrene-vinylnaphthalene copolymer, a styrene-methyl acrylate copolymer,
Styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer Polymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene Styrene copolymers such as acrylonitrile-indene copolymers; silicone resins, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane,
Polyamide, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. can be used alone or in combination. .

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

The particle size distribution of the toner and nigrosine powder can be measured by various methods. In the present invention, the measurement was performed using a Coulter counter.

In other words, the Coulter Counter TA is used as a measuring device.
-Interface (Nikkaki) and CX-1 that output number distribution and volume distribution using Type II (Coulter)
A personal computer (manufactured by Canon Inc.) is connected, and a 1% aqueous NaCl solution is prepared using primary grade sodium chloride as an electrolytic solution. As a measuring method, a surfactant as a dispersant, preferably 0.1 to 5 ml of an alkylbenzene sulfonate is added to the electrolytic aqueous solution of 100 to 150 ml, and a measurement sample is 2 to 20 mg.
Add. The electrolyte in which the sample is suspended is about ~ 3 with an ultrasonic disperser.
After a dispersion treatment for minutes, the Coulter Counter TA-II
According to the mold, the particle size distribution of particles of 2 to 40 μ was measured on the basis of the number, using a 100 μ aperture as the aperture, and then the value according to the present invention was determined.

In the present invention, THF-insoluble matter or gel content is defined by a value measured as follows. That is, the binder resin is weighed as a fixed weight (W _{1 g} ) sample, and components soluble in hot tetrahydrofuran (THF) in the binder resin are removed using an extraction means such as a Soxhletley extractor, and further extracted. The remaining sample is weighed after drying (W _{2 g} ). Gerukontento is calculated as _{W 2 / W 1 × 100 (} %).

Further, in the present invention, the melt index (MI) value is determined by the flow test method for thermoplastic plastics of Japanese Industrial Standards.
Orifice inner diameter 2.0955 ± 0.0051mm, length 8.000 ± 0.025mm at 125 ℃, load 2160g using the equipment described in JIS K7210
The measurements were made by

Further, it is preferable to add fine silica powder to the magnetic toner of the present invention. A magnetic toner having a particle size distribution as a feature of the present invention has a larger specific surface area than conventional toners. When magnetic toner particles are brought into contact with the surface of a cylindrical conductive sleeve having a magnetic field generating means inside due to triboelectric charging, the number of times of contact between the surface of the toner particles and the sleeve increases compared to conventional magnetic toner, and the toner Particle wear and contamination of the sleeve surface are likely to occur. When the magnetic toner according to the present invention is combined with silica fine powder, wear is significantly reduced because the silica fine powder is interposed between the toner particles and the sleeve surface. As a result, the life of the magnetic toner and the sleeve can be prolonged, and a stable chargeability can be maintained, and a developer having a magnetic toner that is more excellent for long-term use can be obtained. Furthermore, the magnetic toner particles having a particle diameter of 5 μm or less, which play a major role in the present invention, exhibit more effects in the presence of the silica fine powder, and can stably provide high-quality images.

As the silica fine powder, any of a 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 obtained by a dry method.

The dry method referred to here is a method for producing silica fine powder generated by vapor phase oxidation of a silicon halide. For example, in a method utilizing the thermal decomposition oxidation reaction of silicon tetrachloride gas in oxygen-hydrogen, the basic reaction formula is as follows.

SiCl ₄ + 2H ₂ + O ₂ → SiO ₂ + 4HCl In this production process, for example, another metal halide such as aluminum chloride or titanium chloride is used together with a silicon halide to produce a composite fine powder of silica and another metal oxide. It is also possible to obtain and include them.

Examples of commercially available fine silica powder produced by vapor phase oxidation of a silicon halide used in the present invention include, for example, those commercially available under the following trade names.

AEROSIL 130 200 300 380 OX50 TT600 MOX80 MOX170 COK84 Ca-O-SiL (CABOTO Co.) M-5 MS-7 MS-75 HS-5 EH-5 Wacker HDK N20 (WACKER-CHEMIE GMBH) V15 N20E T30 T40 DC Fine Silica (Dow Corning Co.) Fransol (Fransil) On the other hand, as the method for producing the silica fine powder used in the present invention by a wet method, various conventionally known methods are applied. it can.
For example, the decomposition of sodium silicate with an acid is represented by the following general reaction formula.

Na ₂ O ・ XSiO ₂ + HCl + H ₂ O → SiO ₂・ nH ₂ O + NaCl In addition, decomposition of sodium silicate with ammonium salts or alkali salts, formation of alkaline earth metal silicate from sodium silicate, and decomposition with acid Silicate, a method in which a sodium silicate solution is converted into silicate using an ion exchange resin, a method in which natural silicate or silicate is used, and the like.

As the fine silica powder here, anhydrous silicon dioxide (silica), and other silicic acid complex salts such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate and zinc silicate can be used.

Commercially available fine silica powder synthesized by a wet method is, for example, commercially available under the following trade names.

Carprex Shionogi Pharmaceutical Niepsil Nippon Silica Tokushir, Hine Seal Tokuyama Soda Vitaseal Takihito Shilton, Shirunetusu Mizusawa Chemical Starsill Kamijima Chemical Himezil Ehime Pharmaceuticals Syloid Fuji Davison Chemical Hi-Si Pittsburgh Plate Glass.Co (Pittsburgh Plate Glass) Ultorasil Fiulstoff-Gesellschaft Marquart Manosil Hardman and Holden Hoesch Hoesch Chemische Fabrik Hoesch K-G Silent Stoner Rubber Stoner Rubber Co. (Stonener Rubber) Nalco (Narco) Nalco Chem. Co. (Narco Chemical) Quso (Kuso) Phladelphia Quartz Co. (Fila Rufia Quartz) Imsil (Imsil) Illinois Minerals Co. (Illinois Minerals) Calcium Silikat (Calcium Zilicat) Chemische Fabrik Hoesch. ) Imperial Chemical Industries.Ltd. (Imperial Chemical Industries) Microcal (Microcal) Joseph Crosfiels & Sons.Ltd. -G. (Farubenh Faburi Ken Baya) Tufknit (Tafnit) Durham Chemicals. Ltd. (Dulham Chemicals) Silmos Shiraishi Kogyo Starrex Kamijima Chemical Of glycosyl multi wood fertilizer the silica fine powder, those specific surface area by nitrogen adsorption measured by BET method in the range of 30 m ² / g or more (especially 50 to 400 m ² / g) gives good results. 0.01 to 8 parts by weight of silica fine powder, preferably 100 parts by weight of magnetic toner, preferably
It is preferable to use 0.1 to 5 parts by weight.

Further, in the magnetic toner of the present invention, the positively charged silica fine powder is more stable to charge than the negatively charged silica fine powder added as a silica fine powder to prevent abrasion of the toner and contamination of the sleeve surface. It is preferable without impairing the properties.

As a method for obtaining a positively chargeable silica fine powder, the above-described untreated silica fine powder is prepared by adding at least one nitrogen atom to a side chain.
There is a method of treating with a silicon oil having one or more organo groups, a method of treating with a nitrogen-containing silane coupling agent, or a method of treating with both.

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

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

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

The asphyxiated silane coupling agent used in the present invention generally has a structure represented by the following formula.

R _m -Si-Y _n (R represents an alkoxy group or a halogen, Y represents an organo group having at least one amino group or a nitrogen atom, m and n is an integer of 1 to 3 m + n
= 4. Examples of the organo group having at least one nitrogen atom include an amino group having an organic group as a substituent, a nitrogen-containing heterocyclic group, or a group having a nitrogen-containing heterocyclic group. As the nitrogen-containing heterocyclic group, there is an unsaturated heterocyclic group or a saturated heterocyclic group, and known ones can be applied. Examples of the unsaturated heterocyclic group include the following.

Examples of the saturated heterocyclic group include the following.

The heterocyclic group used in the present invention is preferably a 5- or 6-membered ring in consideration of stability.

Examples of such treating agents include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, Butylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-
γ-propylphenylamine, trimethoxysilyl-γ
-Propylbenzylamine and the like, and the nitrogen-containing heterocycle may have the above-mentioned structure. Examples of such compounds include trimethoxysilyl-γ-propylpiperidine and trimethoxysilyl-γ-propylmorpholine. And trimethoxysilyl-γ-propylimidazole.

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

Further, the silica fine powder used in the present invention may be treated with a silane coupling agent, if necessary, with a treating agent such as silicon oil or an organosilicon compound for the purpose of hydrophobization. It is treated with the treatment agent that physically adsorbs. Such treatment agents include
For example, hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, arylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α -Chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane , Hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane Examples include siloxanes and dimethylpolysiloxanes having from 2 to 12 siloxane units per molecule, with each terminal unit containing one hydroxyl group bonded to Si. One or two of these
Used in mixtures of more than one species.

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

In particular, in the magnetic toner in which the silica fine powder and the above fine powder are combined, the reason is not clear, but stabilizes the state of silica attached to the toner, for example, the attached silica is released from the toner, The effect on abrasion and sleeve fouling is not reduced, and the charging stability can be further increased.

The magnetic toner of the present invention may optionally contain additives. Dyes conventionally known as colorants,
Pigments can be used, and usually 0.5 to 20 parts by weight per 100 parts by weight of the binder resin may be used. As other additives, for example, a lubricant such as zinc stearate, or an abrasive such as cerium oxide or silicon carbide or a fluidity imparting agent such as colloidal silica or aluminum oxide;
There are anti-caking agents and conductivity-imparting agents such as carbon black and tin oxide.

In addition, wax-like substances such as low-molecular-weight polyethylene, low-molecular-weight polypropylene, microcrystalline wax, carnauba wax, sasol wax, and paraffin wax are used for the purpose of improving the releasability at the time of hot roll fixing.
Addition of about 5 wt% to the magnetic toner is also a preferred embodiment of the present invention.

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

These ferromagnetic materials preferably have an average particle size of 0.1 to 1 μm, preferably about 0.1 to 0.5 μm, and the amount contained in the magnetic toner is 60 to 1 part by weight per 100 parts by weight of the resin component.
10 parts by weight, preferably 65 to 100 parts by weight of the resin component
Parts by weight.

To prepare a magnetic toner for electrostatic charge development according to the present invention, a magnetic powder and a vinyl-based, non-vinyl-based thermoplastic resin, a pigment or dye as a colorant as needed, a charge control agent,
The other additives and the like were sufficiently mixed by a mixer such as a ball mill, and then melted, kneaded and kneaded using a hot kneader such as a heating roll, kneader, or extruder to make the resins compatible with each other. A magnetic toner according to the present invention can be obtained by dispersing or melting pigments or dyes, cooling and solidifying, and then performing pulverization and strict classification.

The magnetic toner of the present invention is preferably applied to an image forming method of developing a latent image while flying toner from a toner carrier such as a cylindrical sleeve to a latent image carrier such as a photoconductor. That is, the magnetic toner is provided with a triboelectric charge mainly by contact with the sleeve surface, and is applied in a thin layer on the sleeve surface. The thickness of the thin layer of the magnetic toner is formed to be smaller than the gap between the photosensitive member and the sleeve in the developing area. In developing the photoreceptor-like latent image, it is preferable to fly the magnetic toner having triboelectric charge from the sleeve to the photoreceptor while applying an alternating electric field between the photoreceptor and the sleeve.

Examples of the alternating electric field include a pulsed electric field, an AC bias, and a combination of an AC and a DC bias.

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

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

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

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

Example 1 After the above materials were mixed well in a blender, they were kneaded with a biaxial kneading extruder set at 150 ° C. The obtained kneaded material was cooled, coarsely pulverized by a cutter mill, and then finely pulverized by using a fine pulverizer using a jet stream, and the obtained finely pulverized powder was classified by a fixed wall type air classifier to classify. A powder was produced. In addition, the obtained classified powder is subjected to strict classification and removal of ultrafine powder and coarse powder at the same time by multi-division classification using the Coanda effect (Elbojet classifier manufactured by Nippon Steel Mining Co., Ltd.).
A fine black powder (magnetic toner) of 7 μm was obtained. The resulting black fine powder had a value of +9 μc / g as measured by triboelectric charge after being mixed with iron powder Chiaria.

0.5 part by weight of positively charged hydrophobic dry silica (BET specific surface area: 200 m ² / g) was added to 100 parts by weight of the obtained black fine powder magnetic toner, and the mixture was mixed with a Hensiel mixer. A component magnetic developer was used.

The particle size distribution and various characteristics of this magnetic toner are as shown in Table 1.

A commercially available copying machine NP-55 using this positively chargeable magnetic toner
The test was performed for 10,000 images by applying to 40. Move the copier to a high-temperature and high-humidity environment (temperature 30 ° C, humidity 90%)
I made 1,000 images. As a result, as shown in Table 2, it was possible to stably obtain an image having no fog, high image density, and excellent fine line reproducibility.

After a 10,000-sheet image test, the copier was moved to a high-temperature and high-humidity environment (temperature: 30 ° C, humidity: 90%), and after 1,000 sheets of image were printed, the developer and toner hopper containing magnetic toner Was removed from the copier and left outside the copier in a high-temperature, high-humidity environment. One week later, the developing machine and the toner hopper were set in the copying machine again, and an image output test was continuously performed on 300 sheets. During this period, the high-temperature and high-humidity stability of the toner was evaluated from the change in image density. FIG. 1 shows this image density transition graph.

Example 2 Instead of the toner used in Example 1, only nigrosine was changed to one having dn = 1.3 μm, dn / dv = 1.4, a particle diameter of 20 or more, and 0.0% by volume, in the same manner as in Example 1. A positively chargeable magnetic toner having various characteristics as shown in Table 1 was obtained.

The magnetic toner was evaluated using a commercially available digital copying machine NP-9330 (manufactured by Canon Inc.) in the same manner as in Example 1. As shown in Table 2 and FIG. An image of high quality was obtained, and excellent high-temperature and high-humidity resistance was exhibited due to rapid triboelectric charging.

Example 3 The above-mentioned materials were mixed, kneaded and pulverized in the same manner as in Example 1, and then air-classified, followed by 0.4 parts by weight of positively charged hydrophobic dry silica and 0.2 parts by weight of polyvinylidene fluoride fine powder per 100 parts by weight of the obtained black fine powder. Parts were added and mixed with a Hexiel mixer to obtain a positively chargeable magnetic toner having various properties as shown in Table 1.

The magnetic toner was evaluated in the same manner as in Example 1. As shown in Table 2 and FIG. 1, the magnetic toner was free from fog, was stable in image density and image quality, and was excellent in high-temperature, high-humidity resistance. It was proved.

Example 4 Using the above materials, a positively chargeable magnetic toner having various properties as shown in Table 1 was obtained in the same manner as in Example 1.

When this magnetic toner was evaluated in the same manner as in Example 1, as shown in Table 2, a stable, clear, high-quality image without fog could be obtained. In addition, even when left in a high-temperature and high-humidity environment, a rapid rise in image density was obtained as shown in FIG.

Comparative Example 1 A positively chargeable magnetic toner was prepared in the same manner as in Example 1 except that styrene / butadiene / divinylbenzene copolymer was not used and 100 parts by weight of styrene / butyl acrylate / divinylbenzene copolymer was used. As a result, the magnetic toner exhibited various properties as shown in Table 1.

When evaluated in the same manner as in Example 1, there was no fog at the initial stage and the reproducibility of fine lines was good, but the solid density was slightly low.

In particular, after standing in a high-temperature and high-humidity environment, the image was noticeably rough and the image density was slow to rise.

Comparative Example 2 Using the same material as in Example 1, a positively chargeable magnetic toner having only a particle size distribution different from that of Example 1 was adjusted by adjusting the powder and powder conditions and air classification, and the characteristics shown in Table 1 were obtained. The magnetic toner shown was obtained.

Although the image density is not inferior, the line image tends to be crushed, the reproducibility of the fine line is poor, and the fogging is gradually seen by repeated copying.

Comparative Example 3 Commercially available nigrosine (dn = 9.2 μm, particle size 20 μm or more, 2.6
%, Dv / dn = 2.8), and the first embodiment
When a positively chargeable magnetic toner was prepared in the same manner as in Example 1, various properties as shown in Table 1 were exhibited. When this magnetic toner was evaluated in the same manner as in Example 1, the fogging was large, and the image density gradually decreased due to repeated copying.
Further, as shown in FIG. 1, the rise of the image density after being left in a high-temperature, high-humidity environment was slow.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the number of copies and the image density in the toners of Examples and Comparative Examples, and FIG. 2 is the number% (N) of particles having a particle size of 5 μm or less in the toner. FIG. 3 is a graph showing a plot of the value of /% by volume (V).

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirohide Tanikawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-54-72054 (JP, A) JP-A-58 JP 129437 (JP, A) JP-A-61-189560 (JP, A)

Claims (1)

(57) [Claims] 1. A magnetic toner having at least a binder resin, a magnetic powder and a charge control agent, containing 12 to 60% by number of magnetic toner particles having a particle size of 5 μm or less, and 8 to 12.7%.
1 to 33% by number of magnetic toner particles having a particle size of 0.1 μm, and 2.0% or more of magnetic toner particles having a particle size of 16 μm or more.
% By volume and the volume average particle diameter of the magnetic toner is 4%.
The magnetic toner particles having a particle size of 5 μm or less are represented by the following formula: [Wherein, N represents the number% of magnetic toner particles having a particle size of 5 μm or less, V represents the volume% of magnetic toner particles having a particle size of 5 μm or less, and k represents a positive number of 4.5 to 6.5. . Here, N indicates a positive number of 12 to 60. Wherein the charge control agent is a nigrosine powder having a number average particle diameter of 2 μm or less, and the binder resin has a conjugated diene bond.