JP3091930B2 - Magnetic toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic toner used in electrophotography, electrostatic recording, and the like.

[0002]

2. Description of the Related Art Conventionally, many methods have been known as electrophotography. In general, 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, the toner image is transferred to a transfer material such as paper, and then heated,
It is fixed by pressure or the like to obtain a copy.

In recent years, devices using electrophotography have been increasing in number, such as printers and facsimile machines, in addition to conventional copying machines. Particularly in small printers and facsimile machines, it is necessary to reduce the size of the copying apparatus, so that a developing apparatus using one-component toner is often used. Unlike the two-component system, the one-component developing system does not use carrier particles such as glass and iron powder, so that the weight of the developer is light, and therefore the apparatus itself can be light.

Further, in the two-component system, since it is necessary to keep the toner concentration in the carrier of the two-component developer constant, a device for automatically detecting the concentration and replenishing a necessary amount of toner is required. Therefore, the developing device also becomes large and heavy here.
The one-component developing device does not require such a device, and thus can be made small and light.

[0005] Most of the one-component developers used in such a one-component developing system contain a large amount of a magnetic substance in a toner.

[0006] Further, in copiers, higher speed and more stable direction are always desired. In particular, the two-component developing system is mainly used for medium-speed machines and high-speed machines. This is because, in the case of a machine having a relatively large size, the stability for long-term use at high speed is more important than the problem of the size and weight of the developing device. Generally, the toner of a two-component developer is colored with carbon black or the like, and the other components are mostly made of a polymer. As a result, the toner particles are light and have no force to adhere to the carrier particles other than the electrostatic force, causing toner to scatter especially during high-speed development, causing the lens, document glass, and transport section to become dirty over a long period of use. May impair stability. Therefore, a developer has been put into practical use in which a magnetic substance is contained in the toner to increase the mass of the toner and, at the same time, allow the toner to adhere to the magnetic carrier particles not only by electrostatic force but also by magnetic force, thereby preventing toner scattering. ing. As described above, toners containing magnetic substances are becoming more and more important.

[0007] On the other hand, printers are mainly LED and LBP printers, and the technology is moving toward higher resolution. That is, the conventional 240, 300 dp
What became i can now be 400 and 600 dpi. Along with this, the developing system must be of a higher density and higher definition.

[0008] In addition, a medium-speed copying machine has become sophisticated,
Therefore, it is moving toward digitalization. This direction is
Since the main method is to form a latent image with a laser, the method is also moving toward higher resolution. Here, too, there is a strict requirement of high density and high definition for development.

Furthermore, a high-speed copier not only increases the speed and stabilizes, but also reproduces an image output from a high-quality printer as an original with high resolution and high fidelity. Has to be faithfully reproduced in high gradation.

As described above, a toner which is faithful to a signal and faithful to an original, that is, faithful to a latent image and is developed at a high density is required.

In addition, with the spread of these copiers and printers, there is also a demand that the copiers and printers have to have excellent environmental stability in order to be used in various environments.

However, it is difficult to satisfy the above-mentioned high demands by using a toner containing a magnetic substance.

In recent years, toners have been reduced in particle size for higher image quality.
Alternatively, it has been proposed to reduce the particle size.

Although this is an effective method for toner containing a magnetic substance, the toner is liable to scatter in such a direction, and the charge amount (q /
m) increases sharply in inverse proportion to the particle size, so that the electrostatic cohesive force increases, and image density and image quality often do not meet expectations. It is conceivable to externally add a conductive fine powder such as carbon black to adjust the charge amount. However, the environment dependency is increased, and particularly under a high temperature and high humidity environment, a decrease in image density and unevenness in density occur.

Further, when the particle size of the toner is reduced, the coloring power of one toner particle is considerably affected as compared with the related art. That is,
When one toner particle is placed on paper or the like, the paper is covered by the thickness of the toner, and the smaller the thickness, the lower the image density. To solve this problem, it is conceivable to increase the coloring power by mixing a large amount of a magnetic substance, but the magnetic cohesion of the toner is increased, so that the toner particles are easily aggregated and the image quality is reduced. In addition, the increase in the coloring power due to the internal addition of carbon black is a problem as in the case of the external addition, in which the image density is reduced in a high-temperature and high-humidity environment.

Further, when the particle diameter of the toner is reduced, the cohesive force between the toners is increased, and there is a possibility that the toner carrying property is deteriorated when the toner is carried on the toner carrier. Therefore, if a needle-shaped magnetic material is used for the purpose of lowering the cohesive force between toners, dispersing each toner one by one, and faithfully developing a latent image, the cohesive force of the toner is reduced, and the toner transportability is improved. On the other hand, in the case of ordinary needle-shaped magnetic materials, the cohesion of the magnetic materials themselves deteriorates the dispersibility with the binder resin, and eventually causes partial charging failure, which adversely affects the image. Tokunosho 5
In JP-A-9-7379, the residual magnetization of a toner using magnetic powder having an axial ratio of 1 to 5 which is made of cobalt-substituted iron tetroxide powder is 10 to 20 emu / g, and the coercive force is 150 to 4
A magnetic toner of 50 Oersted has been proposed. This means that the dispersibility of the magnetic substance in the binder resin is improved, and the toner transportability is also improved. However, since the residual magnetization of the toner is high, it is difficult to obtain a high quality image because the magnetic cohesion of the toner is large during development.

On the other hand, in order to improve the dispersibility of the magnetic substance in the binder resin, a method of treating the surface of the magnetic substance with various substances for the purpose of increasing the compatibility of the magnetic substance with an organic substance has also been proposed. Have been. For example, JP-A-53-137148
JP-A-53-811 discloses fatty acids and derivatives thereof.
No. 25 discloses a polymer material,
JP-A-55-280 discloses a silane coupling agent.
No. 19 discloses a method of treating with a titanium coupling agent. These are excellent in terms of improving compatibility, but in a conventional magnetic toner, when a magnetic material subjected to such treatment is used, the polarization of the magnetic material becomes large, and the release of electric charge is alienated. Since the appearance of the body on the toner surface is small, the toner is consequently excessively charged, may scatter on the image, and may have a rough feeling.
Further, there is a possibility that the reflection power on the developing sleeve is increased, causing a decrease in density, and unevenness in toner coating on the sleeve. This phenomenon is particularly noticeable in low-humidity and high-speed machines, and it is inevitable that image defects occur.
To solve this problem, it is conceivable to increase the amount of the magnetic substance on the toner surface by increasing the amount of the magnetic substance added, and to control the charge amount by lowering the volume resistance of the toner. And the faithful reproducibility of the latent image becomes difficult. Therefore, when such a magnetic material is used, the dispersibility is improved and the chargeability is stabilized, but in order to achieve further high-definition development, the magnetic force is further reduced to reduce the magnetic cohesion of the toner, It is preferable to reduce the height of the toner ears on the toner carrier.

As described above, in a toner containing a magnetic substance which is very effective for miniaturization, weight reduction, scattering, etc.,
Further, a sufficient amount of toner for developing a latent image faithfully to realize high resolution and high gradation in long-time operation has not yet been obtained.

[0019]

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

That is, it is an object of the present invention to provide a device which is faithful to a document, faithful to a signal,
That is, it is an object of the present invention to provide a magnetic toner which develops a latent image faithfully.

It is a further object of the present invention to provide a magnetic toner having high resolution and high fine line reproducibility.

It is a further object of the present invention to provide a magnetic toner having high gradation.

It is a further object of the present invention to provide a magnetic toner having a high image density.

It is a further object of the present invention to provide a magnetic toner which does not scatter.

It is a further object of the present invention to provide a magnetic toner having good production efficiency.

It is a further object of the present invention to provide a magnetic toner excellent in grandchild copyability.

It is a further object of the present invention to provide a magnetic toner having excellent durability.

[0028]

Means and Action for Solving the Problems The present inventors have
As a result of intensive studies on a magnetic toner containing a magnetic substance, the present invention described below has been completed, which can improve the dispersion of the magnetic substance in the toner and significantly improve the toner performance.

That is, in the present invention (1), the ratio of the major axis to the minor axis (axial ratio) is 2 to 4, and the specific surface area is 10 to 20 m ² /
g, a magnetic toner containing at least a needle-shaped magnetic material and a binder resin, the magnetic material is subjected to a treatment for increasing the bulk density, and the content of the magnetic material in the toner is reduced to Wt.
(Weight%), and when the weight average particle diameter of the toner is Dt (μm), the following condition is satisfied: 200 / (axial ratio × Dt) + 19 ≦ Wt ≦ 200 / (axial ratio × Dt) +31 Dt ≦ 9 Magnetic toner. Also,
The present invention (2) provides a magnetic toner containing at least a needle-like magnetic material having a major axis to minor axis ratio of 2 to 4 and a specific surface area of 10 to 20 m ² / g and a binder resin, A magnetic toner, wherein the surface of the magnetic material is subjected to a hydrophobic treatment.

The magnetic toner of the present invention is excellent in conveying toner on a toner carrier under any environment, and has high definition.
For high gradation, magnetic cohesion, electrostatic cohesion, small enough
Sufficient coloring power is exhibited in long-term use.

This is because, in the case of a toner containing a magnetic material, the environmental characteristics, transportability, and image performance of the toner depend on the properties of the magnetic material. This is because the shape, size, and density of the spikelets depend. That is, the magnetic toner of the present invention has an increased bulk density of a needle-shaped magnetic material having a ratio of the major axis to the minor axis (axial ratio) of 2 to 4 and a specific surface area of 10 to 20 m ² / g. The use of the magnetic material further enhances the dispersibility of the magnetic material in the toner, and at the same time, the needle-like magnetic material is appropriately present in the vicinity of the toner surface. Does not increase, the environmental stability is excellent, and the height of the toner ears on the toner carrier does not increase,
It is also considered that the size, shape, and density become uniform.

What is important in the present invention is that if the ratio between the major axis and the minor axis of the needle-shaped magnetic material is 2 to 4 and the axial ratio is less than 2,
The transportability on the toner carrier becomes a problem, and a uniform image cannot be obtained. On the other hand, if the axial ratio exceeds 4, the dispersibility with the binder resin becomes poor, the charge amount of the toner is partially reduced too much, and the coating of the toner on the toner carrier becomes non-uniform. I can't get it.

In the present invention, the specific surface area of the magnetic material which is closely related to the axial ratio of the magnetic material is 10 to 20 m ² / g.
Is preferred. If the specific surface area is less than 10 m ² / g, the particle size of the acicular magnetic material becomes coarse, the magnetic material near the toner surface is sparsely present, the charge amount increases, and only a rough image can be obtained. . On the other hand, the specific surface area is 20 m ²
/ G, on the contrary, the magnetic material near the toner surface increases too much, the charge amount decreases, the environment dependency increases, and
The toner coating on the toner carrier becomes non-uniform, and a uniform image cannot be obtained.

The maximum diameter of the needle-shaped magnetic material is 0.35 μm.
m or less, more preferably 0.30 μm or less. If the maximum diameter of the needle-shaped magnetic material exceeds 0.35 μm, the magnetic material near the toner surface will be sparse, the charge amount will be increased, a rough image will be easily obtained, and the coloring power will be reduced.

In the present invention, the maximum diameter and the axial ratio of the magnetic substance are determined by magnifying the photograph of the magnetic substance of 10,000 times obtained by the transmission electron microscope four times and making the photograph of 40,000 times, Then, 250 magnetic materials were selected, their diameters were measured, and the average maximum diameter and axial ratio were determined. The specific surface area is a value measured by the BET method.

In the present invention (1), the weight average particle diameter (D
For the magnetic toner having t) of 9 μm or less, the content Wt (% by weight) of the magnetic substance in the toner satisfies the following range.

200 / (axial ratio × Dt) + 19 ≦ Wt ≦ 2
00 / (axial ratio × Dt) +31 The magnetic toner is preferably 7 μm or less, and then 200 / (axial ratio × Dt) + 21 ≦ Wt ≦ 200 / (axial ratio × Dt) +29.

When the ratio is less than the above range, the coloring power of the toner,
Insufficient transportability results in low image density, uneven density, etc., and a uniform image cannot be obtained. On the other hand, if the ratio exceeds the above range, the residual magnetization of the toner becomes large, the magnetic aggregation of the toner is not loosened at the time of toner development, and a toner lump or the like is formed on the image, and a good image cannot be obtained. In the present invention, the residual magnetization (σr) of the toner is preferably less than 10 emu / g.

The coercive force (Hc) is also related to image quality. The range of Hc is preferably 50 to 350 Oe. Although the reason is not clear, when Hc is less than 50 Oersted, the background is easily stained. If Hc is greater than 350 Oersteds, the cohesiveness will be poor, and the coating will not be good, and the image quality will deteriorate, such as uneven image density. The magnetic properties of the magnetic material were measured with a measuring magnetic field of 1 kOe using Toei Kogyo Co., Ltd.

Another feature of the present invention (1) is to increase the bulk density of the magnetic material contained therein.

As a process for increasing the bulk density of the magnetic material, there is a process of crushing the magnetic material. Means used to crush the magnetic material include, for example, a mechanical crusher equipped with a high-speed rotor for crushing powder or a load roller for dispersing or crushing powder. And a pressure dispersing machine such as a fred mill equipped with

As the degree of the treatment for increasing the bulk density of the magnetic material, it is desirable to increase the bulk density of the magnetic material by 30% or more before and after the treatment. If the improvement in the bulk density is less than 30%, the effect of the present invention (1) cannot be sufficiently obtained. Further, the absolute value of the bulk density of the magnetic material after the above-mentioned treatment cannot be said unconditionally because it varies depending on the shape of the magnetic material, particularly the axial ratio, the length of the maximum diameter, etc., but is not less than 0.5 g / cm ³ It is preferred that If the bulk density of the magnetic material is less than 0.5 g / cm ³ , it is difficult to make the dispersion in the toner uniform, and the effect of the environment and the effect of making the toner ears uniform on the toner carrier will be reduced. Insufficiency is obtained, resulting in inconvenience such as loss of uniformity of image quality.

The bulk density of the magnetic material in the present invention (1) is a value measured according to JIS (Japanese Industrial Standard) K-5101.

As a measure of environmental characteristics, the charge amount of the toner was measured. Here, the method of measuring the triboelectric charge amount of the toner in the present invention will be described in detail with reference to FIG.

FIG. 1 is an explanatory view of a device for measuring the amount of triboelectric charge. A magnetic brush (toner and toner) on a developer carrier whose frictional charge is to be measured is measured in a metal measuring container 12 having a conductive screen 13 of 400 mesh (which can be appropriately changed to a size not allowing the passage of carrier particles) at the bottom. (Mixture of magnetic particles) and a metal lid 14 is placed. At this time, the weight of the entire measurement container 12 is weighed and set as W ₁ (g). Next, the suction device 11 (the part in contact with the measurement container 12 is at least an insulator)
In this case, the air is suctioned from the suction port 17 and the air volume control valve 16 is adjusted to adjust the pressure of the vacuum gauge 15 to 70 mmHg. In this state, suction is sufficiently performed (about one minute) to remove the toner by suction.
At this time, the potential of the electrometer 19 is set to V (volt). Here, reference numeral 18 denotes a capacitor having a capacity of C (μF). Further, the weight of the whole measurement container after suction is weighed to be W ₂ (g). The triboelectric charge amount Q (μc / g) is calculated according to the following equation.

Q (μc / g) = (C × V) / (W ₁ −W ₂ ) Exposure environment is low temperature and low humidity (15 ° C./10 RH%), normal temperature and normal humidity (23 ° C./60 RH%), high temperature and high humidity (32.5 ° C / 90
RH%), and the measurement was performed in a normal temperature and normal humidity environment. At this time, EFV200 / 300 (manufactured by Powder Tech) was used as a carrier, and the measurement was performed at a toner concentration of 2 wt%. The mixing time was about 2 minutes. The absolute value of the measured value at this time is 5
５０50 μc / g is good. If it is less than 5 μc / g, the sharpness of the image will be poor and the background will be stained. Further, in a high-temperature and high-humidity environment, a problem such as a decrease in image density becomes a problem. If it is larger than 50 μc / g, the electrostatic cohesive force is increased, the image quality is reduced, and the reproducibility of fine lines is insufficient. In particular, in a low-temperature and low-humidity environment, the mirror image with the toner carrier becomes unnecessarily large, and the image density is reduced.

The particle size of the toner of the present invention was measured by a TA-II type machine manufactured by Coulter Counter. An aperture having a diameter of 50 μm was used, and the particle size was expressed by a weight-based average diameter determined from the volume distribution.

The magnetic material in the present invention includes metal oxides containing elements such as iron, zinc, cobalt, nickel, copper, magnesium, manganese, aluminum and silicon.

The method for producing the magnetic material of the present invention may be a conventionally known method. An example of synthesizing a needle-shaped magnetic material having a small axial ratio from such magnetic materials will be described.

Synthesis Example 1 An ammonium carbonate solution was added to an aqueous solution of ferrous sulfate to which sodium citrate had been added.
Ferrous carbonate was produced at a temperature of 75 ° C., and oxygen was passed through the solution to obtain particles. The resulting particles were filtered, dried and pulverized. This was reduced to obtain a magnetic material having an axial ratio of 4.

The obtained magnetic material had a maximum particle size of 0.26 μm.
m, BET 18.7 m ² / g, σs (saturation magnetization)
3 emu / g, Hc 275 Oersted, σr 27.9
The emu / g and the bulk density were 0.22 g / cm ³ .

Synthesis Example 2 An ammonium carbonate solution was added to an aqueous solution of ferrous sulfate to which sodium citrate had been added.
Ferrous carbonate was produced at a temperature of 75 ° C., and oxygen was passed through the solution to obtain particles. The resulting particles were filtered, dried and pulverized. This was reduced to obtain a magnetic material having an axial ratio of 3.

The obtained magnetic material had a maximum particle size of 0.25 μm.
m, BET 14.6 m ^{2 /} g, σs 62.1 emu /
g, Hc257 Oersted, σr23.0 emu / g
Met.

The magnetic substance surface hydrophobizing agent which is a feature of the present invention (2) may be any commonly used coupling agent, but preferably includes a silane coupling agent and a titanium coupling agent. Examples of the hydrophobizing agent used in the present invention (2) are described below.

Examples of the silane coupling agent include the following compounds, but the present invention (2) is not limited thereto.

For example, methyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (2-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, N-β- (Aminoethyl)
-Γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, β- (3,4-epolycyclohexyl) ethyltrimethoxysilane, γ-
Glycidoxypropyltrimethoxysilane and the like.

The following compounds can be exemplified as the titanium-based coupling agent, but the present invention (2) is not limited thereto.

For example, isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, tetraisopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis (ditridecyl phosphite) titanate, isopropyl Trioctanoyl titanate, isopropyl dimethacryl isostearyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri (dioctyl phosphate) titanate, isopropyl tricyl phenyl titanate, isopropyl tri (N-aminoethyl-aminoethyl) titanate, dicumyl phenyl Oxyacetate titanate, diisostearo Le ethylene titanate, bis (dioctyl pyrophosphate) ethylene titanate,
Bis (dioctyl pyrophosphate) oxyacetate titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (di-tridecyl) phosphite titanate and the like can be mentioned.

As a method for hydrophobizing the magnetic substance used in the present invention (2), a conventionally known method is used.
As an example, a silane-based coupling agent or a titanium-based coupling agent is dissolved in a solvent such as toluene or xylene, and the magnetic substance is gradually added thereto, mixed and stirred, and then the solvent is removed by filtration or the like. By doing so, a hydrophobic treatment agent film is formed on the surface of the magnetic material. Further, a method of adsorbing on the surface of the magnetic material by mixing with a dry mixer or a method of mixing the magnetic material and the treating agent during toner production and adhering to the surface of the magnetic material by kneading may be used.

The treatment amount of the hydrophobizing agent with respect to the magnetic material is 0.01 to 10% by weight, preferably 0.1 to 10% by weight.
-8 wt%, more preferably 0.3-5 wt%.
It is.

As the binder resin of the magnetic toner used in the present invention, styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, styrene-p-chlorostyrene copolymer, styrene-vinyl-toluene copolymer, etc. Homopolymers and their copolymers; copolymers of styrene and acrylate such as styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-n-butyl acrylate copolymer, etc. Copolymers of styrene and methacrylate such as styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-n-butyl methacrylate copolymer; styrene and acrylate; Multi-component copolymer with methacrylic acid ester; Other styrene-acrylonitrile Polymers, styrene - vinyl methyl ether copolymer, styrene - butadiene copolymer,
Styrene-vinyl methyl ketone copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid ester copolymer and other styrene-based copolymers of styrene with other vinyl-based polymerizable monomers; polymethyl methacrylate , Polybutyl methacrylate, polyvinyl acetate,
Polyester, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid, phenol resin, aliphatic or alicyclic hydrocarbon resin, petroleum resin, chlorinated paraffin, and the like can be used alone or in combination.

In particular, low-molecular-weight polyethylene, low-molecular-weight polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, higher fatty acid, polyamide resin, A polyester resin or the like can be used alone or in combination.

The polymer, copolymer or polymer blend used as the above-mentioned binder resin is obtained by mixing a vinyl aromatic or acrylic monomer represented by styrene with 40%.
If the content is not less than wt%, more desirable results can be obtained.

Any suitable pigment or dye can be used as a colorant in the toner. For example, there are known dyes and pigments such as hydrophobicized carbon black, phthalocyanine blue, ultramarine, quinacridone, and benzidine yellow.

The method for producing the toner containing a magnetic substance used in the present invention may be a conventionally known method. That is,
Binder resin, charge control agent, coloring agent, magnetic substance, other additives are powder mixed in advance with a Henschel mixer, etc.
This is kneaded with a roll mill heated to about 150 ° C. for about 30 minutes to obtain a kneaded material, which is cooled, pulverized, and classified as necessary to obtain a toner composition.

At this time, if necessary, a fluidity-imparting agent, a lubricant, an abrasive, a cleaning aid, a resistance adjuster, a charge control agent and the like are added internally or externally.

When a two-component developer is used, conventionally known carrier particles can be used.

[0068]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which do not limit the present invention in any way. The percentages in the following formulations are all wt%.

Table 1 shows the magnetic materials used in the examples.

[0070]

[Table 1] Example 1 The magnetic material 1 was crushed by a fred mill to increase the bulk density from 0.22 g / cm ³ before the treatment to 0.54 g / cm ³ .・ Styrene-acrylic copolymer 61.0% ・ Negative charge control agent 0.5% ・ Magnetic substance 1 (treated above) 37.5% ・ Release agent 1.0% And set this to 140 ° C.
Heat kneading with this roll mill for about 30 minutes, after cooling, coarse pulverization,
It was pulverized (jet mill). Further, fine powder and coarse powder were cut by an elbow jet classifier to obtain a toner composition. The particle size of the obtained toner is 6.5.
μm. Here, 29.3 <Wt = 37.5 wt
% <41.2 satisfies the condition of the content of the magnetic material of the present invention (1).

When the magnetic properties of the toner were measured,
= 22.6 emu / g, σr = 10.5 emu / g, H
c = 267 Oersted.

The negatively chargeable colloidal silica was added to 0.8
% As a developer. The charge amount of this toner is -2
It was 2.4 μc / g. This was evaluated by modifying a laser beam printer LBP-SX manufactured by Canon Inc. under a developing condition of a developing bias of 1800 V _PP and a frequency of 2000 Hz, and using a machine for forming a fine latent image from 300 dpi to 800 dpi.

As a result, the spikes of the toner on the toner carrier were short, more uniform, and the transportability was good. Therefore, since the latent image was faithfully developed, it was found that the reproducibility of fine lines was very excellent. Further, the halftone dots were reproduced very well, and the gradation was very good. The solid black image had an image density of 1.4 or more, and was uniform without density unevenness.

Further, environmental characteristics were evaluated. Table 2 shows the results of the charge amount measurement from low temperature and low humidity to high temperature and high humidity. As shown in Table 2, the results did not depend much on the environment, and good results were obtained.

Comparative Example 1 A toner was produced in the same manner as in Example 1 except that the magnetic substance of Example 1 was used without performing the treatment for increasing the bulk density. The obtained toner had a weight average particle size of 6.2 μm. At this time, the condition of the content of the magnetic material of the present invention (1) 29.8 <W
t = 37.5 wt% <41.7 is satisfied.

When the magnetic properties of this toner were measured,
σs = 22.2 emu / g, σr = 10.1 emu / g
g, Hc = 266 Oersted. When the environmental dependency of the charge amount of the externally added toner was evaluated in the same manner as in Example 1, as shown in Table 2, the environmental dependency was inferior to that of Example 1.

Comparative Example 2 A toner was prepared in the same manner as in Example 1 except that the magnetic material 4 was used instead of the magnetic material 1 in Example 1. The bulk density of the magnetic material before and after treatment was 0.46 g / cm ³ and 0.95 g /
cm ³ . The particle size of the obtained toner was 6.7 μm in weight average particle size. At this time, Wt = 37.5 wt%, and the condition of the magnetic substance content of the present invention (1) 48.9 <W
t <60.9 was not satisfied. The magnetic properties of the toner are as follows: σs = 24.5 emu / g, σr = 1.5 e
mu / g, Hc = 49 Oersted. The charge amount of the toner externally added thereto as in Example 1 was -49.2.
μc / g.

This was evaluated in the same manner as in Example 1. As a result, toner coating failure occurred on the toner carrier, and the toner image was not faithful to the latent image. Table 2 shows the results of the charge measurement under each environment.

Comparative Example 3 A toner was produced in the same manner as in Example 1 except that the magnetic material 5 was used instead of the magnetic material 1 of Example 1. The bulk densities of the magnetic material before and after treatment were 0.19 g / cm ³ and 0.39 g / cm ³ , respectively.
cm ³ . The particle size of the obtained toner was 6.8 μm. At this time, Wt = 37.5 wt%, and the condition of the magnetic material content of the present invention (1) 23.6 ≦ W
It did not satisfy t ≦ 35.5. The magnetic properties of the toner are as follows: σs = 24.2 emu / g, σr = 12.8
emu / g, Hc = 312 Oersted. The charge amount of the toner externally added thereto in the same manner as in Example 1 was -5.
It was 9 μc / g.

This was evaluated in the same manner as in Example 1. As a result, the image was not faithful to the latent image, and the reproducibility of fine lines was poor.
Table 2 shows the results of the charge measurement under each environment.

Comparative Example 4 A toner was produced in the same manner as in Example 1 except that the magnetic material 6 was used instead of the magnetic material 1 of Example 1. The bulk densities of the magnetic material before and after the treatment were 0.28 g / cm ³ and 0.68 g / cm ³ , respectively.
cm ³ . The particle size of the obtained toner was 6.5 μm. At this time, the condition 34.4 <Wt = 37.5 wt% <46.3 of the magnetic material content of the present invention (1).
Meets. The magnetic properties of the toner are as follows: σs = 2
2.4 emu / g, σr = 7.7 emu / g, Hc = 2
It was 10 Oersted. The charge amount of the toner externally added in the same manner as in Example 1 was -45.5 μc / g.

This was evaluated in the same manner as in Example 1. As a result, the electrostatic cohesion was large, and in particular, the reproducibility of fine lines was insufficient. Table 2 shows the results of the charge measurement under each environment.

Comparative Example 5 -Styrene-acrylic copolymer 48.0%-Negative charge control agent 0.5%-Magnetic substance 1 (no crushing treatment) 50.5%-Release agent 1.0 % A toner was produced in the same manner as in Example 1 with the above-mentioned formulation amount. The particle size of the obtained toner was 6.6 μm in weight average particle size,
The pulverizability was excellent. At this time, Wt = 50.5 wt%
And the content condition of the magnetic substance of the present invention (1) 29.2 ≦
Wt ≦ 41.0 was not satisfied. Further, σs of the toner is 30.3 emu / g, and σr is 14.0 emu / g.
g, Hc = 272 Oersted.

In the same manner as in Example 1, the charge amount of the toner to which 0.8% of negatively chargeable colloidal silica was externally added was -7.7 μc.
/ G.

This was evaluated in the same manner as in Example 1. As a result, in particular, the reproducibility of the fine line was not as faithful to the latent image as in Example 1, and tailing was caused by the toner mass. Table 2 shows the results of the charge measurement under each environment.

Example 2 The magnetic material 2 was crushed by a fred mill to increase the bulk density from 0.25 g / cm ³ before processing to 0.56 g / cm ³ . -Styrene-acrylic copolymer 64.0%-Positive charge control agent 1.2%-Magnetic substance 2 (treated above) 33.3%-Release agent 1.5% Example 1 with the above formulation amount A toner was produced in the same manner as described above.
The particle size of the obtained toner was 5.2 μm. Here, 28.7 <Wt = 33.3 wt% <4
0.6 satisfies the condition of the content of the magnetic material of the present invention (1).

At this time, σs of the toner is 22.2 emu /
g, σr = 9.0 emu / g, and Hc = 265 Oersted. Further, 1.2% of positively chargeable colloidal silica was externally added as a fluidity imparting agent. The charge amount of this toner was +25.8 μc / g.

This is called a digital copier NP- manufactured by Canon.
9330 with developing bias of 1800 V _PP , frequency of 2000
The evaluation was performed with a machine that changed the resolution from 300 dpi to 600 dpi under the developing condition of Hz. As a result, the reproducibility of fine lines was particularly good, the gradation and the image density were good, and the image was very faithful to the latent image. The environmental characteristics were also good. Table 2 shows the results of the charge measurement under each environment.

Example 3 A magnetic material 3 was crushed by a fred mill to increase the bulk density from 0.36 g / cm ³ before treatment to 0.77 g / cm ³ . -53.1% of polyester-0.8% of negative charge control agent-44.4% of magnetic substance 3 (treated above)-1.7% of release agent 1.7% in the same formulation as in Example 1 with the above formulation amount . The pulverization efficiency was good when the toner was formed. The particle size of the obtained toner was 6.0 μm in weight average particle size. At this time, the condition of the content of the magnetic substance of the present invention (1) 35.7 <Wt = 44.
4 wt% <47.6 is satisfied. Σs of toner = 2
6.0 emu / g, σr = 8.0 emu / g, Hc = 2
00 Oersted. 0.9% of negatively chargeable colloidal silica was externally added thereto. The charge amount of this toner is −
It was 18.8 μc / g. In addition, it had excellent environmental characteristics.

This is called a Canon copier NP-8582.
At a developing bias of 1800 V _PP and a frequency of 2000
The evaluation was performed under the developing conditions of Hz and using a modified machine in which the peripheral speed ratio of the developing sleeve to the photosensitive drum was 1: 1.2. The obtained image was very good in fine line reproducibility and gradation, and was of high quality without scattering, image disorder, etc. despite the high-speed machine. Table 2 shows the results of the charge measurement under each environment.

[0091]

[Table 2] Example 4 First, a solution prepared by dissolving 1.5 g of methyltrimethoxysilane in 100 ml of toluene was added to 100 g of the magnetic substance 7, and the mixture was stirred for about 3 hours, filtered and dried, and subjected to a hydrophobic treatment with a silane coupling agent. A magnetic material was obtained.・ Styrene-acrylic copolymer 67.0% ・ Negative charge control agent 0.5% ・ Magnetic substance 7 (hydrophobicized) 31.5% ・ Release agent 1.0% The body was mixed and set at 140 ° C. 2
Heat kneading with this roll mill for about 30 minutes, after cooling, coarse pulverization,
It was pulverized (jet mill). Further, fine powder and coarse powder were cut by an elbow jet classifier to obtain a toner composition. The particle size of the obtained toner was 8.1.
μm. At this time, the condition of the content of the magnetic material of the present invention (1) 27.1 <31.5 wt% <39.2 is satisfied.

When the magnetic properties of the toner were measured, σs = 18.9 emu / g and σr = 6.8 emu / g
g, Hc = 249 Oersted.

The negatively chargeable colloidal silica was added to 0.8
% As a developer. The charge amount of this toner is -23
μc / g. This was evaluated using a modified laser beam printer LBPSX manufactured by Canon in the same manner as in Example 1.

As a result, the spikes of the toner on the toner carrier were short and uniform, and the transportability was good. Therefore, since the latent image was faithfully developed, it was found that the reproducibility of fine lines was very excellent. Further, the halftone dots were reproduced very well, and the gradation was very good. Further, the solid black image had an image density of 1.4 or more, and was uniform without density unevenness, and a good image was obtained even when copying a plurality of sheets.

Comparative Example 6 A toner was produced in the same manner as in Example 4 except that the magnetic material of Example 4 was used without surface treatment. The particle size of the obtained toner was 8.3 μm in weight average particle size. At this time, the condition of the content of the magnetic material of the present invention (1) was 27.0 <31.5 wt.
% <39.0. The magnetic properties of the toner are as follows: σs = 18.8 emu / g, σr = 6.8 emu / g
g, Hc = 247 Oersted. The charge amount of the toner externally added thereto in the same manner as in Example 4 was -18.0 μc
/ G.

This was evaluated in the same manner as in Example 4. As a result, the latent image fidelity was excellent and the gradation was good, but especially at low temperatures and low humidity, the image density was high at the beginning and showed good results. The concentration has dropped.

Example 5 In the same manner as in Example 4, the magnetic material 2 having increased bulk density used in Example 2 was subjected to a hydrophobic treatment.・ Styrene-acrylic copolymer 66.8% ・ Positive charge control agent 1.2% ・ Magnetic substance 2 (volume density increased and hydrophobized) 30.5% ・ Release agent 1.5% A toner was produced in the same manner as in Example 4 in the amount.
The particle size of the obtained toner was 6.8 μm in weight average particle size. At this time, condition 2 of the content of the magnetic material of the present invention (1)
6.4 <Wt = 30.5 wt% <38.3. Further, σs of the toner = 19.0 emu / g, σr =
8.0 emu / g, Hc = 265 Oersted. 1.0% of positively chargeable colloidal silica was externally added as a fluidity imparting agent. The charge amount of this toner is +1
It was 1.5 μc / g. This was carried out using a digital copying machine NP-9330 manufactured by Canon Inc. at a developing bias of 1800 V _PP and a frequency of 2000 Hz, from 300 dpi to 60 dpi.
The evaluation was performed using a machine at 0 dpi. As a result, the reproducibility of fine lines was particularly good, the gradation and the image density were good, and the image was very faithful to the latent image. Also, good images were obtained for a plurality of copies.

Example 6 In the same manner as in Example 4, the magnetic material 3 having increased bulk density in Example 3 was subjected to a hydrophobic treatment. -Polyester 62.5%-Negative charge control agent 0.8%-Magnetic substance 3 (hydrophobicized) 35.0%-Release agent 1.7% Toner in the same amount as in Example 4 with the above formulation amount Was prepared.
The pulverization efficiency was good when the toner was formed. The particle size of the obtained toner was 8.8 μm in weight average particle size. At this time, the condition of the content of the magnetic material of the present invention (1) 30.4 <W
t = 35 wt% <42.3 is satisfied. Σs = 20.1 emu / g, σr = 5.8 emu / g
g, Hc = 193 Oersted. 0.6% of negatively chargeable colloidal silica was externally added thereto. The charge amount of this toner was −18.6 μc / g.

This was evaluated in the same manner as in Example 3 using a modified copy machine NP-8582 manufactured by Canon. as a result,
It has very good fine line reproducibility and gradation, and it is of high quality without scattering or image disturbance despite high speed machine.
An image with excellent durability was obtained.

Example 7 A magnetic material 7 was subjected to a surface treatment in the same manner as in Example 4 except that the surface treating agent was changed to 2.5 g of isopropyl dimethacrylisostearoyl titanate.・ Styrene-acrylic copolymer 65.2% ・ Negative charge control agent 0.5% ・ Magnetic substance 7 (the above-mentioned surface treated) 33.3% ・ Release agent 1.0% In the same manner as in No. 4, a toner was produced. The particle size of the obtained toner is 8.2 μm in weight average particle size.
Met. At this time, the condition 27.0 <Wt = 33.3 wt% <39.1 of the content of the magnetic material of the present invention (1) is satisfied. Further, 0.8% of negatively chargeable colloidal silica was externally added as a fluidity imparting agent. The charge amount of this toner is −
It was 24 μc / g.

This was evaluated in the same manner as in Example 4. As a result, the reproducibility of fine lines, gradation, and image density were very good and very faithful to the latent image. In addition, good images were obtained in multiple copies.

Example 8 The surface treating agent was bis (dioctyl pyrophosphate)
The magnetic substance 2 used in Example 2 was replaced with 4.0 g of ethylene titanate and treated in the same manner as in Example 4.・ Low molecular weight polyester 67.0% ・ Negative charge controlling agent 4.0% ・ Magnetic substance 2 (surface treated) 29.0% The above formulation amount was mixed with powder and set to 100 ° C. 3
Heat kneading with this roll mill for about 30 minutes, after cooling, coarse pulverization,
It was pulverized (jet mill). Further, fine powder and coarse powder were cut by an elbow jet classifier to obtain a toner composition. The particle size of the obtained toner is 8.5.
μm. At this time, the condition of the content of the magnetic substance of the present invention (1) 24.9 <29.0 wt% <36.8 is satisfied. In addition, negatively chargeable colloidal silica was added to the mixture.
% Externally added, and further mixed with a ferrite-coated carrier by a turbuler mixer so that the toner concentration becomes 7% to obtain a developer. The charge amount of this toner is -21.8 μc / g
Met.

A digital color copier CLC-500 manufactured by Canon Inc. was developed with a developing bias of 1800 V _PP and a frequency of 2
The evaluation was performed in a remodeling machine with a developing condition of 000 Hz.
As a result, a very good image free of scattering and fogging and having no image unevenness was obtained even after long-time development. In particular, there was no roughening under low temperature and low humidity, and the reproducibility of the fine line of the character image was particularly good and sharp. Further, the solid black image was uniform and the image density was sufficient.

[0104]

As described above, in the magnetic toner of the present invention, since the magnetic substance is uniformly dispersed in the toner and is appropriately present near the toner surface, electrostatic aggregation is weakened, and The spikes of the toner on the carrier become uniform, and a stable image is obtained. Therefore, development faithful to the original and faithful to the signal, that is, development faithful to the latent image can be performed, and excellent in high resolution and high fine line reproducibility.

[Brief description of the drawings]

FIG. 1 is a schematic view schematically showing an apparatus for measuring the triboelectric charge amount of a toner according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Suction device 12 Measurement container 13 Conductive screen 14 Lid 15 Vacuum gauge 16 Air flow control valve 17 Suction port 18 Condenser 19 Electrometer

Claims (5)

(57) [Claims] 1. A magnetic toner containing at least a needle-like magnetic material having a ratio of a major axis to a minor axis (axial ratio) of 2 to 4 and a specific surface area of 10 to 20 m ² / g, and a binder resin. In the above, the magnetic material is subjected to a treatment for increasing the bulk density, and when the content of the magnetic material in the toner is Wt (% by weight) and the weight average particle diameter of the toner is Dt (μm), / (Axial ratio × Dt) + 19 ≦ Wt ≦ 200 / (axial ratio × Dt) +31 Dt ≦ 9. 2. The magnetic toner according to claim 1, wherein the bulk density of the magnetic material is processed to 0.5 g / cm ³ or more. 3. A magnetic toner containing at least a needle-like magnetic substance having a ratio of a major axis to a minor axis of 2 to 4 and a specific surface area of 10 to 20 m ² / g and a binder resin, A magnetic toner, wherein the surface of the body is subjected to a hydrophobic treatment. 4. The magnetic material according to claim 3, wherein the surface of the magnetic material is subjected to a hydrophobic treatment with a silane coupling agent.
The magnetic toner as described in the above. 5. The magnetic material according to claim 3, wherein the surface of the magnetic material is subjected to a hydrophobic treatment with a titanium-based coupling agent.
The magnetic toner as described in the above.