JP2736978B2 - Magnetic toner for developing electrostatic images - 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.

[Prior Art] In a toner for electrostatic charge development, a constant chargeability cannot be obtained by a binder resin used alone, and therefore, in order to control the toner to a desired frictional chargeability, a charge of a dye, a pigment or the like is required. Addition of control substances has been performed.

At present, in the art, practical applications or studies have been made on the use of a nigrosine dye or JP-B-57-3940, JP-B-58-9415, or JP-B-58-9415 when imparting or controlling a positive charge to a toner. JP-A-54-84732,
JP-A-56-46248, JP-A-56-54446, JP-A-60-107654, JP-A-61-124955 and triphenylmethane dyes and laked pigments thereof Or JP-A-62-192755 and JP-A-62-87
No. 974, Japanese Unexamined Patent Publication No. Sho 62-53944, and many other quaternary ammonium salts disclosed in
There are condensed polymers having an amino group disclosed in JP-A-284 and the like.

On the other hand, in recent years, the desire for image quality of copied images has increased,
There has been a demand for a toner capable of providing an image with higher resolution and fine line reproducibility than ever before. For this reason, the particle size of the toner shifts to a finer direction.

However, when the particle size of a conventional toner using a nigrosine dye having a high charge-imparting ability is reduced, the charge amount is increased more than necessary due to the reduced particle size, and the image density is liable to decrease. Another problem is that the selection of other materials is restricted due to sleeve contamination or the like.

In addition, quaternary ammonium salts and polyamines have insufficient charging ability, and when they are used in magnetic toners, further improvement of other materials is required.

On the other hand, it is disclosed that triphenylmethane dyes show good results when used in a two-component developer, but when used in magnetic toner, fog or image density is comparable to that of nigrosine. Was not obtained.

Therefore, in order to apply a triphenylmethane dye to a magnetic toner, it is necessary to improve the magnetic toner.

[Problems to be Solved by the Invention] An object of the present invention is to provide a magnetic toner which has solved the above-mentioned problems.

Still another object is to provide a toner that provides an image with high resolution and fine line reproducibility.

Still another object is to provide a toner having a volume average particle diameter of 4 to 10 μm which does not unnecessarily increase the triboelectric charge amount (so-called charge-up phenomenon) and causes less contamination of a toner carrier such as a sleeve.

Still another object is to provide a toner which always has a high density and gives an image without fogging.

Another object of the present invention is to provide a toner which is excellent in durability and always gives a stable image even when used continuously for a long period of time.

A further object of the present invention is to provide a magnetic toner capable of obtaining 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.

[Means for Solving the Problems] The present invention relates to a magnetic toner for developing electrostatic images having at least a binder resin and a magnetic powder, comprising a dye represented by the following general formula (1) or a pigment obtained by raked the dye. 12 to 60% by number of magnetic toner particles having a particle diameter of 5 μm or less, 1 to 33% by number of magnetic toner particles having a particle diameter of 8 to 12.7 μm, and having a particle diameter of 16 μm or more The magnetic toner particles are 2.0% by volume or less, the volume average particle size of the magnetic toner is 4 to 10 μm, and the number% (N) and the volume% (V) of the magnetic toner particles having a particle size of 5 μm or less are as follows: /V=−0.04N+k [where k is a positive number from 4.5 to 6.5. ] It is related with the magnetic toner for electrostatic image development characterized by satisfying the following.

[In the formula, ^one of X ¹ and X ² represents an amino group, and the other represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, a halogen atom, or an alkoxy group. . R ¹ and R ² represent a hydrogen atom or a substituted or unsubstituted alkyl group which may be the same or different. R ³ , R ⁴ and R ⁵ represent a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group which may be the same or different. The present inventors have conducted intensive studies on a magnetic toner having the above-mentioned particle size distribution as a toner for providing an image having excellent high resolution and high fine line reproducibility. As a result, the dye represented by the above formula (1) or It has been found that a magnetic toner having excellent electrophotographic properties can be obtained by using a pigment obtained by raked this, and the present invention has been achieved.

As a method for incorporating the compound used in the present invention into a toner, there are a method of adding the compound to the inside of the toner and a method of externally adding the compound. The amount of these compounds used depends on the type of binder resin,
The presence or absence of the additives used as necessary, which is determined by the toner manufacturing method including the dispersion method, is not specifically limited, but is preferably 0.1 to 100 parts by weight of the binder resin. To 10 parts by weight, more preferably 0.1 to 5 parts by weight. When adding externally, use resin 10
It is preferably 0.01 to 10 parts by weight based on 0 part by weight, and particularly preferably mechanochemically fixed to the surface of the toner particles.

Further, the compound used in the present invention can be used in combination with a conventionally known charge control agent.

The dyes used in the present invention are exemplified below, but they are not intended to limit the present invention.

The laking of the dye is carried out in a known manner. For example, an aqueous solution of a lake agent is added to an aqueous solution of acetic acid of a dye to precipitate a lake pigment. Alternatively, the extender pigment is suspended in an aqueous acetic acid solution of a dye, and then an aqueous solution of a laker is added to precipitate the lake pigment on the surface of the extender pigment. The lake pigment is filtered, washed with water and dried. Examples of the laker include water-soluble salts of phosphotungsten molybdic acid, phosphotungstic acid, phosphomolybdic acid, and water-soluble salts containing complex anions such as ferrocyan and ferricyan. Organic acid salts can also be used as the laker, but, for example, gallic acid lakes do not have very good charging characteristics. This is considered to be due to the fact that the compatibility between the resin and the lake is good in the organic acid lake, so that the properties of the resin having poor charging characteristics appear remarkably.

Further, according to the present invention, there is provided a magnetic toner having at least a binder resin and a magnetic powder, wherein the magnetic toner contains the above dye or pigment, and contains 12 to 60% by number of magnetic toner particles having a particle size of 5 μm or less. 1 to 33% by number of magnetic toner particles having a particle diameter of about 12.7 μm, 2.0% by volume or less of magnetic toner particles having a particle diameter of 16 μm or more, and a volume average particle diameter of the magnetic toner of 4 to 10 μm And
The number% (N) and the volume% (V) of the magnetic toner particles having a particle diameter of 5 μm or less are as follows: N / V = −0.04N + k [where k represents a positive number of 4.5 to 6.5. ] Is satisfied.

The magnetic toner of the present invention having the above-described particle size distribution can faithfully reproduce even a fine line of a latent image formed on a photoreceptor, and can reproduce a halftone dot and a dot latent image such as a digital image. And provides an image with excellent 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, 5 μm
For the following magnetic toner particles, it was difficult to control the charge amount and the charge was likely to be excessive. For this reason, the toner particles having a size of 5 μm or less have a strong reflection force on the developing sleeve and the like, and adhere to the sleeve surface, hinder the triboelectric charging of other particles, generate poorly charged toner particles, reduce roughness, and reduce density. In some cases, it was thought that aggressive reduction was necessary.

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 Hoftone, and further, a very small amount of toner The latent image with the surface potential changed on the photoreceptor was developed to a small development potential contrast where only the particles were developed, the developed toner particles on the photoreceptor were collected, and the toner particle size distribution was measured. It was found that there were many 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.

The magnetic toner containing the charge control agent of the present invention has a thickness of 8 μm
Hereinafter, in particular, the charging of the magnetic toner particles having a size of 5 μm or less is appropriately controlled, and the above-described effects are effectively exhibited.

Further, in the magnetic toner of the present invention, 8 to 12.7 μm
One feature is that the particles in the range of 1 to 33% by number. This is related to the need for the presence of magnetic toner particles having a particle size of 5 μm or less, as described above. The magnetic toner particles having a particle size of 5 μm or less strictly cover the latent image and have an ability to faithfully reproduce the latent image. However, in the latent image itself, the electric field intensity at the peripheral edge portion is higher than that at the central portion, so that the toner particles may be thinner inside the latent image than at 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 solved this problem and found that the toner particles can be further sharpened by containing 1% to 33% by number of toner particles in the range of 8 to 12.7 μm. That is, it is considered that the toner particles having a particle size in the range of 8 to 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 inside with low intensity, the small amount of toner particles on the inside with respect to the edge part is compensated, and a uniform developed image is formed. As a result, sharpness with high density and excellent resolution and gradation is obtained. The image is provided.

Further, for particles having a particle size of 5 μm or less, between the number% (N) and the volume% (V), N / V = −0.04N + k [where k represents a positive number of 4.5 to 6.5. It is also preferred that the magnetic toner of the present invention satisfies the following relationship. The magnetic toner of the present invention having a particle size distribution satisfying this range can achieve more 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.

 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 tend to aggregate with each other, resulting in a toner mass larger than the original particle size, resulting in rough image quality, reduced resolution, or an edge portion of the latent image. The density difference between the image 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 contours 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, a large amount of fine powder must be cut by classification or the like to satisfy the condition of k <4.5, which is disadvantageous in terms of yield and toner cost.
When k> 6.5, the presence of more fine powder than necessary
During repeated copying, the balance of the particle size distribution may be lost, the degree of aggregation of the toner may be increased, or frictional charging may not be performed effectively, resulting in poor cleaning or fogging.

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 charge control agent of the present invention cannot sufficiently control the charge of the magnetic toner particles having a size of 16 μm or more, resulting in poor charging and fogging of the background portion and the reversal portion.

The volume average diameter of the magnetic toner is 4 to 10 μm, preferably 4 to 10 μm.
９9 μm, which 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. When the volume average particle diameter is larger than 10 μm, the resolution is not good, and the image quality is liable to be deteriorated if the use is continued at best at the beginning of copying.

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

In other words, the Coulter Counter TA is used as a measuring device.
Using Type II (manufactured by Coulter), connected to an interface (manufactured by Nikkaki) for outputting the number distribution and volume distribution and a CX-1 personal computer (manufactured by Canon), the electrolyte was 1% using primary grade sodium chloride. Prepare an aqueous NaCl solution. As a measuring method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the aqueous electrolytic solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample was suspended was treated with an ultrasonic
After 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.

As described above, the toner having the above-described particle size distribution can provide a very excellent image if the triboelectric charge amount is controlled to an appropriate value. However, when a toner having the above-mentioned particle size distribution is obtained with a conventionally known composition of a magnetic toner, the triboelectric charge increases more than necessary. Therefore, particularly under low humidity, it causes white dropouts and rough rust.

On the other hand, when a charge control agent having a weak charge-providing ability such as a quaternary ammonium salt is used, a good image can be obtained under low humidity, but the charge amount decreases under high humidity, so that the image becomes rough and the density decreases. Occurs.

As described above, to fully utilize the characteristics of the toner having the above particle size distribution, it is necessary to develop a charge control agent.
As a result of intensive studies, the present inventors have found that the use of the dye represented by the above formula (1) or a pigment obtained by raked the same allows good charge control of the magnetic toner having the particle size distribution of the present invention. That is, the present invention has been completed.

The feature of the charge control agent of the present invention is that the charge control ability is lower than that of a conventionally known charge control agent such as nigrosine, while it is higher than a quaternary ammonium salt.
It is considered that this charge imparting property can impart an optimal amount of charge to the magnetic toner having the particle size distribution of the present invention.

Therefore, the use of the charge control agent of the present invention does not greatly restrict the selection of other materials, and greatly facilitates toner design.

In addition, the charge control agent used in the present invention is characterized in that it is improved in moisture absorption properties by lake formation. Therefore, the toner of the present invention is a good magnetic toner with little image quality fluctuation due to temperature and humidity changes.

As the binder resin used in the present invention, all resins generally used as binder resins for toner can be used.

For example, polystyrene, poly-p-chlorostyrene,
Styrenes such as polyvinyltoluene and their substituted homopolymers; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylate copolymer, styrene -Methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl methone Styrene-based copolymers such as copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers; polyvinyl chloride, phenolic resins, naturally-modified phenolic resins, and natural-resin-modified malees Acid resin, Acrylic Resins, methacrylic resins, polyvinyl acetate, silicone resins, polyester resins, polyurethane, polyamide resins, furan resins, epoxy resins, xylene resins, polyvinyl butyral, terpene resin, coumarone-indene resins, and petroleum resins.

Further, a crosslinked styrene copolymer is also a preferable binder resin.

Examples of the comonomer for the styrene monomer of the styrene copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, and methacrylic. Acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, a monocarboxylic acid having a double bond such as acrylamide or a substituted product thereof; for example, maleic acid, butyl maleate, Dicarboxylic acids having a double bond such as methyl maleate, dimethyl maleate and the like and their substituted products; 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 isobutyl ether and the like; alone or two or more vinyl monomers are used.

Here, as the cross-linking agent, a compound having two or more polymerizable double bonds is mainly used, for example, an aromatic divinyl compound such as divinylbenzene, divinylnaphthalene, or the like; for example, ethylene glycol diacrylate, ethylene glycol diacrylate, or the like. Double bonds such as methacrylate, 1,3-butanediol dimethacrylate
Carboxylic acid esters having two or more compounds; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide and divinyl sulfone; and compounds having three or more vinyl groups are used alone or as a mixture.

When a pressure fixing method is used, a binder resin for a pressure fixing toner can be used. For example, polyethylene, polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer can be used. Coalescent, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, paraffin and the like.

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, 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 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 Also, in this production process, for example, by using another metal halide such as aluminum chloride or titanium chloride together with a silicon halide, a fine composite powder of silica and another metal oxide is obtained. It is also possible to obtain and include them.

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

Silica such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, zinc silicate, etc. can be applied to the silica fine powder here, in addition to anhydrous silicon dioxide (silica).

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

When used in the magnetic toner of the present invention, the positively charged silica fine powder is used rather than negatively charged as the silica fine powder added to prevent wear of the toner and contamination of the sleeve surface. It is more preferable to do so without impairing the charging stability.

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

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

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 based on 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.

In addition, the silica fine powder used in the present invention may be, if necessary, a known silane coupling agent containing no nitrogen atom, a known silicon oil containing no nitrogen atom for the purpose of hydrophobicity, a treating agent such as an organosilicon compound. Alternatively, it may be treated in combination with various treating agents, and treated with the treating agent which reacts or physically adsorbs with the silica fine powder.

The magnetic toner of the present invention may optionally contain additives. Other additives include, for example, a lubricant such as zinc stearate, an abrasive such as cerium oxide and silicon carbide, a fluidity imparting agent such as aluminum oxide, an anti-caking agent, and a conductive agent such as carbon black and tin oxide. There is a property imparting agent.

Further, a fluorine-containing polymer fine powder such as polyvinylidene fluoride fine powder is also a preferable additive from the viewpoint of fluidity, abrasiveness, charge stability and the like.

Further, in order to improve the releasability at the time of hot roll fixing, a wax-like substance such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, sasol wax, paraffin wax, etc.
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 contains a magnetic material which may also serve as a colorant. Examples of the magnetic material contained in the magnetic toner of the present invention include iron oxides such as magnetite, γ-iron oxide, ferrite, and iron-rich ferrite;
Metals such as cobalt, nickel or these metals with metals such as aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium Alloys and mixtures thereof.

These ferromagnetic substances preferably have an average particle diameter of 0.1 to 1 μm, preferably about 0.1 to 0.5 μm, and the amount contained in the magnetic toner is 40 to 1 part by weight per 100 parts by weight of the resin component.
50 to 100 parts by weight, preferably 100 to 100 parts by weight of the resin component.
Parts by weight.

In order to obtain good development characteristics, the magnetic toner of the present invention has a residual magnetization σ _r of 0.5 to 6 emu / g, preferably 1 to 5 emu / g.
u / g, the saturation magnetization _s is 10 to 40 emu / g, and the coercive force
H _c is preferably satisfies the magnetic properties of 20 to 100 Esuteddo _(e) (both measured magnetic field is 1K _e.).

In producing the magnetic toner according to the present invention, the above-described magnetic toner constituting materials are sufficiently mixed by a ball mill or other mixer, then kneaded well using a hot roll kneader, a heat kneader of an extruder, and cooled. A method of obtaining a magnetic toner by mechanical pulverization and classification after solidification is preferable. Alternatively, a method of dispersing a constituent material in a binder resin solution and then spray-drying to obtain a magnetic toner; In a so-called microcapsule toner comprising a core material and a shell material, a polymerization method in which a predetermined material is mixed with a monomer to be formed into an emulsified suspension and then polymerized to obtain a magnetic toner;
A method of including a predetermined material in the core material or the shell material, or both of them, can be applied. Further, if necessary, the desired additives are sufficiently mixed with a mixer such as a Henschel mixer to produce the magnetic toner according to the present invention.

The magnetic toner of the present invention can be used by a conventionally known means for one-component development for visualizing an electrostatic image in electrophotography, electrostatic recording, electrostatic printing and the like.

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 building a latent image on the photoconductor, it is preferable to fly magnetic toner having triboelectric charge from the sleeve to the photoconductor while applying an alternating electric field between the photoconductor 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. That is, an image obtained by copying an original original of a fine line accurately having a width of 100 μm under appropriate copying conditions is used as a measurement sample, and using a Luzex 450 particle analyzer as a measuring device, a line width is determined by an indicator from an enlarged monitor image. Measurement. At this time, since the line width measurement position has irregularities in the width direction of the thin line image of the toner, the average line width of the irregularities is used as the measurement point. Thereby, 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 the same interval, and 2.8, 3.2, 3.6, 4.0, 4.5,
Create an original image drawn as if there were 5.0, 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.

[Examples] 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. After cooling the obtained mixture and coarsely pulverizing it with a cutter mill, it is finely pulverized using a fine pulverizer using a jet stream, and the obtained finely pulverized powder is classified by a fixed wall type air classifier and classified. The powder was purified.

Furthermore, the obtained classified powder is strictly classified and removed at the same time by a multi-division classifier using a Coanda effect (an elbow jet classifier manufactured by Nittetsu Mining Co., Ltd.) to remove black and black having a volume average particle size of 7.2 μm. A fine powder (magnetic toner) was obtained.

0.5 part of positively charged hydrophobic dry silica (BET specific surface area 200 m ^{2 /} g) was added to 100 parts of the magnetic toner of the obtained black fine powder,
The mixture was mixed with a Henschel mixer to obtain a positively chargeable one-component magnetic toner.

The obtained magnetic toner was used in a commercially available electrophotographic copying machine NP-35.
Table 2 shows the results of 5000 copy tests performed on 25 (manufactured by Canon Inc.).

As is clear from Table 2, the magnetic toner of the present invention has excellent image density in both the line portion and the solid black portion, and the fine line reproducibility and the resolution are excellent. Image quality was maintained. Also, the per copy cost was small and the economy was excellent.

Example 2 Instead of the compound (1) used in Example 1, the compound (2) was replaced with a phosphotungsten molybdate lake pigment.
A classified powder was obtained in the same manner as in Example 1 except that parts were used. Table 1 shows the particle size distribution. The following materials were added to 100 parts of the classified powder and mixed with a Henschel mixer to obtain a one-component magnetic toner.

Table 2 shows the result of a copy test performed on this magnetic toner in the same manner as in Example 1.

As is clear from Table 2, the image density and the image quality were excellent in stability, an image without fog was obtained, and the consumption was small.

Example 3 A classified powder was obtained in the same manner as in Example 1, except that 4 parts of the ferrocyan lake pigment of the compound (3) was used instead of the compound (1) used in the example 1. Table 1 shows the particle size distribution.

To 100 parts of the classified powder, 0.4 parts of hydrophobic silica (BET300m ² / g) was added and mixed with a Henschel mixer to obtain a one-component magnetic toner.

Table 2 shows the result of a copy test performed on this magnetic toner in the same manner as in Example 1. Good images were obtained as shown in Table 2.

Example 4 A classified powder was obtained in the same manner as in Example 1 except that 4 parts of the compound (4) was used instead of the compound (1) used in the example 1. Table 1 shows the particle size distribution.

The following materials were added to 100 parts of the classified powder, and mixed with a Henschel mixer to obtain a one-component magnetic toner.

Table 2 shows the results of a copy test performed on this magnetic toner in the same manner as in Example 1. As a result, a good image without fog was obtained.

Comparative Example 1 The material used in Example 1 was used, and the volume average particle diameter was 11.7 μm.
m was obtained (the particle size distribution is shown in Table 1), and the same external addition as in Example 1 was performed to obtain a magnetic toner.

Table 2 shows the result of a copy test performed on this magnetic toner in the same manner as in Example 1.

The image of this magnetic toner had a slightly low image density and fogging was somewhat noticeable. In addition, fine line reproducibility and resolution were poor, and consumption was large.

Comparative Example 2 A one-component magnetic toner was obtained in the same manner as in Example 1, except that 3 parts of benzylmethylhexadecyl ammonium chloride was used instead of the compound (1) used in Example 1.

Table 2 shows the result of a copy test performed on this magnetic toner in the same manner as in Example 1.

The image obtained in this copying test was noticeably rough. Further, the image density gradually decreased.

[Effects of the Invention] The present invention uses a compound represented by the above formula (1) as a charge control agent for a magnetic toner having a specific particle size distribution, and is therefore a toner excellent in resolution and fine line reproducibility.

Further, it is excellent in durability and can obtain high image density with small consumption.

Claims (1)

(57) [Claims] 1. A magnetic toner for developing an electrostatic image comprising at least a binder resin and a magnetic powder, comprising a dye represented by the following general formula (1) or a pigment obtained by raked the dye, and having a particle size of 5 μm or less. 12 to 60% by number of magnetic toner particles having a particle diameter of 1 to 33% by number, and 1 to 33% by number of magnetic toner particles having a particle diameter of 8 to 12.7 μm, and 2.0% by volume or less of magnetic toner particles having a particle diameter of 16 μm or more. Where the volume average particle diameter of the magnetic toner is 4 to 10 μm, and the number% (N) and the volume% (V) of the magnetic toner particles having a particle diameter of 5 μm or less satisfy the following condition: N / V = −0.04N + k In the formula, k represents a positive number of 4.5 to 6.5. ] A magnetic toner for developing an electrostatic image, characterized by satisfying the following. [In the formula, ^one of X ¹ and X ² represents an amino group, and the other represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, a halogen atom, or an alkoxy group. . R ¹ and R ² represent a hydrogen atom or a substituted or unsubstituted alkyl group which may be the same or different. R ³ , R ⁴ and R ⁵ represent a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group which may be the same or different. ]