JP2769814B2 - 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.

[Related Art] In recent years, as image forming apparatuses such as electrophotographic copying machines have become widespread, their uses have been expanded to a wide variety of uses, and requirements for image quality have become strict. 2. Description of the Related Art In copying images such as ordinary documents and books, it is required to reproduce very finely and faithfully without crushing or breaking even fine characters. In particular, when the latent image on the photoreceptor of the image forming apparatus is a line image of 100 μm or less, thin line reproducibility is generally poor, and the sharpness of the line image is still insufficient. Recently, in an image forming apparatus such as an electrophotographic printer using a digital image signal, a latent image is formed by collecting dots of a constant potential, and a solid portion, a halftone portion, and a light portion have a dot density. It is expressed by changing. However, in a state where the toner particles do not adhere to the dots and the toner particles protrude from the dots, it is not possible to obtain the gradation of the toner image corresponding to the dot density ratio of the black portion and the white portion of the digital latent image. There is a problem. Furthermore, when improving the resolution by reducing the dot size to improve the image quality,
The reproducibility of a latent image formed from minute dots becomes more difficult, and images tend to be poor in resolution and gradation and lack sharpness.

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

Heretofore, some developers have been proposed for the purpose of improving image quality. JP-A-51-3244 proposes a non-magnetic toner intended to improve image quality by regulating the particle size distribution. In the toner, 8 to
The main component is a toner having a particle size of 12 μm, which is relatively coarse. According to the study of the present inventors, it is difficult to achieve “density” on a latent image with a particle size of 30 μm.
From the characteristic that the particle size distribution is not more than 5% by number when the particle size is 20% or more, the particle size distribution is also broad, which tends to lower the uniformity.

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

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

Also, in U.S. Pat.No. 4,299,900, 20-35 μm
A jumping development method using a developer having 10 to 50% by weight of a magnetic toner has been proposed. In other words, the toner particle size suitable for frictionally charging the magnetic toner, uniformly and thinly applying the toner layer on the sleeve, and further improving the environmental resistance of the developer has been devised. However, considering stricter requirements such as fine line reproducibility and resolution, it is not sufficient, and further improvement is required.

According to the study of the present inventors, it has been found that toner particles having a size of 5 μm or less clearly reproduce the outline of the latent image and have a main function of dense toner adhesion to the entire latent image. In particular, in the electrostatic latent image on the photoreceptor, due to the concentration of lines of electric force, the contour edge portion has a higher electric field strength than the inside, and the sharpness of the image quality is determined by the quality of the toner particles collected in this portion. According to the study of the present inventors, it has been found that the amount of particles of 5 μm or less is effective in solving the problem of sharpness of image quality.

On the other hand, in electrophotography, first, charges are uniformly applied on a photoconductor layer, for example, which forms an electrostatic latent image, by utilizing the properties of a photoconductor such as cadmium sulfide, polyvinylcarbazole, selenium, and zinc oxide. To form an electrostatic latent image by performing image exposure, then developing with a toner powder charged to a polarity opposite to the charge of the electrostatic latent image, and further transferring and fixing to a transfer sheet as necessary. .

Of these, in the case of an apparatus having a transfer step, it is usual to remove the residual toner on the photoconductor that has not been transferred to the transfer sheet and use the photoconductor repeatedly.

As a method for removing the residual toner on the photoconductor, it is general to use a cleaning member in contact with the photoconductor, such as a blade cleaning method, a fur brush cleaning method, or a magnetic brush cleaning method.

However, the cleaning member is pressed against the photoreceptor with an appropriate pressure, and when a toner having a small toner particle size is used as described above, the unit surface area per unit weight of the toner particles becomes large. The above residual toner easily works as an abrasive. As a result, when a large number of copies are made, scratches on the surface of the photoreceptor and abrasion of the surface are remarkable, and the obtained image has problems such as a decrease in image quality and image density, and generation of black stripes and fog. is there.

[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.

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

It is still another object of the present invention to provide a magnetic toner that reduces the occurrence of wear and scratches on the surface of a photoreceptor due to residual toner on the photoreceptor and achieves a longer life of the photoreceptor.

It is a further object of the present invention to provide a magnetic toner whose performance does not change due to environmental changes.

Another object of the present invention is to provide a magnetic toner having excellent transferability.

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

[Means and Actions for Solving the Problems] Specifically, the present invention relates to a magnetic toner containing at least 60 to 120 parts by weight of a magnetic powder per 100 parts by weight of a binder resin, and having a particle diameter of 5 μm or less. The magnetic toner particles having
60% by number, 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. A magnetic material for developing an electrostatic image, wherein a fine particle of silica and a fine particle of fluorine-containing resin having a number average particle size of 0.01 to 1 μm are externally added to magnetic toner particles, having a particle size distribution of 4 to 9 μm. Related to toner.

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. To provide an image which is excellent in gradation and resolution. Furthermore, even when copying or printing out is continued, high image quality is maintained, and even in the case of a high-density image, good development can be performed with a smaller toner consumption than conventional magnetic toners. In addition, there is an advantage in downsizing 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
The following magnetic toner particles are difficult to control the charge amount, impair the fluidity of the magnetic toner, and actively decrease as a component that scatters the toner and stains the machine, as well as a component that causes image fogging. Was thought to be 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 halftone, and further, a very small amount. A latent image with a changed surface potential on the photoreceptor was developed to a small development potential contrast where only toner particles were developed, and the developed toner particles on the photoreceptor were collected. The toner particle size distribution was measured. It has been found that there are many magnetic toner particles, especially magnetic toner particles of 5 μm or less. That is, 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.

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 strength of the peripheral edge portion is higher than that of the central portion, and therefore, the inner portion of the latent image has less toner particles than the edge portion,
The image density may appear faint. 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, 8
It is considered that the toner particles having a particle size in the range of 12.7 μm have an appropriately controlled charge amount with respect to the magnetic toner particles having a particle size of 5 μm or less, but the electric field intensity is smaller than the edge portion of the latent image. The toner is supplied to the inside and compensates for the small amount of the toner particles on the inside with respect to the edge portion, so that a uniform developed image is formed. As a result, a sharp image with high resolution and excellent gradation is obtained at a high density. Provided.

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.

By a completely different idea from the conventional viewpoint, the magnetic toner of the present invention can solve the conventional problems and can withstand recent severe demands for high image quality.

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

Magnetic toner particles having a particle size of 5 μm or less have a total particle number of 12 to
It is preferably 60% by number, preferably 15 to 50% by number, and more preferably 20 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 copy or printout, the effective magnetic toner particles are effective. The amount of the component decreases, the balance of the particle size distribution of the magnetic toner as shown in the present invention deteriorates, and the image quality gradually decreases. In addition, 60 number%
When the particle size exceeds the threshold, the aggregation state of the magnetic toner particles easily occurs, and the toner mass becomes larger than the original particle size, resulting in rough image quality, lowering the resolution, or reducing the density difference between the edge portion and the inside of the latent image. The image becomes large and tends to become a hollow image.

The particle size in the range of 8 to 12.7 μm is preferably 1 to 33% by number, and more preferably 8 to 28% 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.

The content of the magnetic toner particles having a particle diameter of 16 μm or more is preferably 2.0% by volume or less, more preferably 1.0% by volume.
Or less, more preferably 0.5% by volume or less.
When the content is more than 2.0% by volume, not only does it hinder the reproduction of fine lines, but also in the transfer, coarse toner particles of 16 μm or more protrude from the thin layer surface of the toner particles developed on the photoreceptor. The delicate state of contact between the photoreceptor and the transfer paper via the layer is made irregular, causing fluctuations in the transfer conditions and causing poor transfer images. Further, the volume average diameter of the magnetic toner is 4 to 9 μm, and this value cannot be considered separately from the above-mentioned respective constituent elements. 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 toner on the 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. Volume average particle size is 10μm
Is exceeded, the resolution is not good, and at the beginning of copying, image quality is liable to be degraded if used at best.

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) that outputs 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 dispersing agent to 100 to 150 ml of the electric field aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is about 1 to 3 with an ultrasonic disperser.
After dispersing for 2 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.

According to the study of the present inventors, when a magnetic toner having a reduced toner particle size is applied for electrostatic charge image development, the occurrence of scratches on the surface of the photoreceptor and the abrasion of the surface are significantly increased. However, it has been found that it is very effective to include fluorine-containing resin fine particles in the magnetic toner in order to reduce or prevent these phenomena.

Examples of the fluorine-containing resin fine particles in the present invention include the following homopolymers of a fluorine-containing monomer;
Fine particles of a copolymer of at least one kind or a copolymer with another monomer can be given. As a fluorine-containing monomer,
For example, vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, 1-chloro-1,2-
Difluoroethylene, 1,2-dchloro-1,2-difluoroethylene, bromotrifluoroethylene, 3,3,3-trifluoropropene, 3-chloro-3,3-difluoro-1-propene, 3-fluoro -3,3-Dichloro-1-propene, 1
-Chloro-1-fluoroethylene, 1,1-difluoro-2
-Chloroethylene, 1,1-dichloro-2-fluoroethylene, 1-chloro-2,2-difluoroethylene, 1,1-dichloro-2,2-difluoroethylene, chlorotrifluoroethylene, 1-bromo -1-fluoroethylene, 1-chloro-
Fluorinated 2-fluoroethylene, acrylic acid and methacrylic acid, and derivatives thereof, and the like. Particularly preferably, tetrafluoroethylene, vinylidene fluoride, and tetrafluoroethylene - copolymer particles of vinylidene fluoride and the like, more preferably, wherein when measured in acetone by F ¹⁹ nuclear magnetic resonance [Wherein, Sa indicates the area of the absorption peak at about −23.5 ± 1 ppm, Sb indicates the area of the absorption peak at about −27.5 ± 1 ppm, Sc indicates the area of the absorption peak at about −45.8 ± 1 ppm, and Sd Indicates the area of the absorption peak at about −48.1 ± 1 ppm (however, 1,1,2-trichloro-14,
2,2-trifluoroethane))].

These F ¹⁹ NMR absorption spectra are, for example, J. Polymer
As shown on page 1305 (1963) of SeiAl, vinylidene fluoride polymer Is the absorption based on the chemical shift of

That is, the absorption at −23.5 ppm is absorption due to repeated regular head-to-tail bonding of the CF ₂ —CH ₂ unit. −2
7.5 ppm absorption As described above, in the chain, including the CH ₂ -CH ₂ bond Absorption. The −45.8 ppm absorption is As described above, in the chain, including a CF ₂ -CF ₂ bond Absorption.

The −48.1 ppm absorption is In the chain, including both CH ₂ -CH ₂ bond and CF ₂ -CF ₂ combined as Absorption.

The method of measurement by F ¹⁹ -nuclear magnetic resonance is as follows. A sample is extracted at a temperature from room temperature to 50 ° C., and the acetone solution or the heavy acetone solution is used for the measurement. The measurement was performed using an FX-90Q high-resolution NMR apparatus manufactured by JEOL Ltd. at an observation frequency of 84.25 MHz, an observation width of 9000 Hz, and an offset frequency of 55.33 KHz.

Chemical shifts are given relative to 1,1,2-trichloro-1,2,2-trifluoroethane. At this time, the four chemical shifts of CF ₂ are −23.5 ± 1 ppm, −27.5 ± 1 ppm,
It was −45.8 ± 1 ppm and −48.1 ± 1 ppm. At this time, when the toner extract and the vinylidene fluoride polymer were measured, the chemical shifts of the two were substantially the same, and there was no difference. From the integrated values of these peaks, Sa, S
b, Sc, and Sd were determined.

The number average particle diameter of the fluorine-containing resin fine particles in the present invention,
It is preferably from 0.05 to 1 μm, particularly preferably from 0.1 to 0.5 μm. Particle size 1.0
If it exceeds μm, the dispersion between the toner particles is not sufficient, the fluidity and lubricity cannot be imparted to the toner, and the effect is not exhibited. On the other hand, if the thickness is less than 0.05 μm, since the ultrafine particles cover the toner surface, the chargeability of the toner is deteriorated and the effect cannot be obtained. The shape is preferably a powder-like shape close to a spherical shape.

The fluorine-containing resin fine particles of the present invention are externally added and mixed in the magnetic toner of the present invention. When the fine particles are externally mixed, the amount added to the magnetic toner is 0.
01 to 2.0% by weight, particularly preferably 0.02 to 1.0% by weight.

Conventionally, these fluorine-containing resin fine particles have been known as a friction reducing substance that prevents the fusion or filming of the toner on the photoreceptor surface by being externally added to the toner particles. As a result of intensive studies, they have found an effect of reducing or preventing the abrasion of the surface of the photoreceptor and the increase in the occurrence of scratches on the surface, which are peculiar to the application of the magnetic toner having a reduced toner particle size. The reason for this effect is not clear, but when a magnetic toner having a reduced toner particle size is used, the unit surface area per unit weight of the toner particles becomes large, so that the residual toner and the photosensitive toner are not cleaned during cleaning after transfer on the photoconductor. The contact area with the body increases, and the surface of the photosensitive body is easily polished.However, since the fluorine-containing fine particles intervene on or near the surface of the magnetic toner, the contact area between the magnetic toner and the photosensitive body decreases. It is considered that the occurrence of surface wear and scratches can be reduced or prevented.

As the binder resin used for the magnetic toner in the present invention, when a heating / pressing roll fixing device having an apparatus for applying oil is used, the following binder resin for toner can be used.

For example, polystyrene, poly-p-chlorostyrene,
A homopolymer of styrene such as polyvinyl toluene and a substituted product thereof; a styrene-p-chlorostyrene copolymer, a styrene-vinyltoluene copolymer, a styrene-vinylnaphthalene copolymer, a styrene-acrylate copolymer, Styrene-methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl Styrene copolymers such as ketone copolymers, styrene-butadiene copolymers, ethylene-isoprene copolymers, styrene-acrylonitrile-indene copolymers; polyvinyl chloride, phenolic resins, naturally modified phenolic resins, and natural resin modified Maleic 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.

In a fixing method of a heating / pressing roller which hardly applies oil, a so-called offset phenomenon in which a part of a toner image on a toner image support member is transferred to the roller, and adhesion of the toner to the toner image support member are important issues. It is.
These problems must also be taken into account at the same time because toners that fix with less heat energy tend to block or cake during normal storage or development. The physical properties of the binder resin in the toner are most greatly involved in these phenomena. However, according to the study of the present inventors, when the content of the magnetic substance in the toner is reduced, the toner image supporting member is fixed at the time of fixing. Although the adhesiveness of the toner to the toner is improved, offset tends to occur, and blocking or caking tends to occur. Therefore, in the present invention, when using the heating / pressing roller fixing method in which almost no oil is applied, the selection of the binder resin is more important. Preferred binders include crosslinked styrenic copolymers or crosslinked polyesters.

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 methacryl. Acid, methyl methacrylate, ethyl methacrylate. Monocarboxylic acids having a double bond such as butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide or the like;
Dicarboxylic acids having a double bond such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate and the like and substituted products thereof; vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate, etc .; Olefins such as ethylene, propylene and butylene; vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; Monomers may be used alone or in combination of two or more.

Here, as the cross-linking agent, a compound having two or more polymerizable double bonds is mainly used, and examples thereof include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate and ethylene glycol dimethacrylate. Double bonds such as 1,3-butanediol dimethacrylate, etc.
Carboxylic acid esters; 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 the 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. Coal, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, paraffin and the like.

In the magnetic toner according to the present invention, a charge control agent is blended with toner particles (internal addition) or mixed with toner particles (external addition).
It is preferable to use them. The charge control agent makes it possible to control the amount of charge optimally according to the development system. In particular, in the present invention, the balance between the particle size distribution and the charge can be further stabilized.

Examples of positive charge control agents include denatured products such as nigrosine and fatty acid metal salts;
Quaternary amonium salts such as -hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide and dicyclohexyltin oxide; dibutyltin borate, dioctyltin borate and dicycle hexyl Diorganotin borates such as tin borates can be used alone or in combination of two or more. Among these, charge control agents such as nigrosine and quaternary ammonium salts are particularly preferably used.

Also, the general formula R ₁ ; H, CH ₃ R ₂ , R ₃ : a homopolymer of a monomer represented by a substituted or unsubstituted alkyl group (preferably C _{1 to} C ₄ ): or styrene, acrylate as described above, Copolymers with polymerizable monomers such as methacrylates can be used as positive charge control agents, in which case these charge control agents also act as (all or part of) the binder resin .

As the negative charge controlling agent that can be used in the present invention, for example, an organometallic complex or a chelate compound is effective, and examples thereof include aluminum acetylacetonate, iron (II) acetylacetonate, and 3,5-di-tert-. There are chromium butylsalicylate and the like, particularly preferably an acetylacetone metal complex, a salicylic acid-based metal complex or a salt, particularly preferably a salicylic acid-based metal complex or a salicylic acid-based metal salt.

The above-mentioned charge control agent (having no action as a binder resin) is preferably used in the form of fine particles. In this case, the number average particle size of the charge control agent is specifically preferably 4 μm or less (more preferably 3 μm or less).

When internally added to the toner, such a charge control agent is preferably used in an amount of 0.1 to 20 parts by weight (more preferably 0.2 to 10 parts by weight) based on 100 parts by weight of the binder resin.

Various additives may be added to the magnetic toner of the present invention internally or externally as necessary. As the colorant, conventionally known dyes and pigments can be used, and usually 0.5 to 20 parts by weight per 100 parts by weight of the binder resin may be used. Other additives include lubricants such as, for example, zinc stearate, abrasives such as cerium oxide and silicon carbide, or fluidity-imparting agents such as colloidal silica and aluminum oxide, anti-caking agents, or carbon black, tin oxide, for example. And the like.

Further, in order to improve the releasability at the time of fixing with a hot roll, a wax-like substance such as low-molecular-weight polyethylene, low-molecular-weight polypropylene, microcrystalline wax, carnauba wax, sazol wax, paraffin wax, etc. is used.
The addition of about 5% by weight to the magnetic toner is also a preferred embodiment of the present invention.

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

These ferromagnetic materials preferably have an average particle size of about 0.1 to 1 μm, preferably about 0.1 to 0.5 μm. The amount contained in the magnetic toner is 60 to 120 parts by weight per 100 parts by weight of the resin component.
It is 65 to 110 parts by weight, preferably 100 parts by weight of the resin component.

To prepare the magnetic toner for developing an electrostatic image according to the present invention, a magnetic powder and a vinyl-based or non-vinyl-based thermoplastic resin, a pigment or a dye as a colorant as needed, a charge control agent,
After the other additives and the like are sufficiently mixed by a mixer such as a ball mill, the resins are melted, kneaded, and kneaded using a hot kneader such as a heating roll, kneader, or extruder to make the resins compatible with each other. A magnetic toner according to the present invention can be obtained by dispersing or dissolving a pigment or dye in the mixture, and performing cooling and solidification followed by pulverization and strict classification.

Further, in the present invention, silica fine powder is externally added to the magnetic toner particles in addition to the fluorine-containing resin fine particles.
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 the magnetic toner particles for triboelectric charging are brought into contact with the surface of a cylindrical conductive sleeve having a magnetic field generating means inside,
The number of times of contact between the surface of the toner particles and the sleeve is increased as compared with the conventional magnetic toner, and the toner particles are more likely to be worn. 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 can be prolonged, and a stable chargeability can be maintained, and a developer having a magnetic toner that is more excellent and can withstand long-term use can be obtained.

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, a method utilizing the thermal decomposition oxidation reaction of silicon tetrachloride gas in the coexistence of oxygen and hydrogen, the basic reaction formula is as follows.

SiCl ₄ + 2H ₂ + O ₂ → SiO ₂ + 4HCl In this manufacturing 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.

Commercially available silica fine powder produced by vapor phase oxidation of a silicon halide compound used in the present invention includes:
For example, there is one that is marketed under the following trade names.

AEROSIL 130 (Nippon Aerosil) 200 300 380 OX50 TT600 MOX80 MOX170 COK84 Ca-O-SiL (Ca-O-Jill) M-5 (CABOTO Co.) MS-7 MS-75 HS- 5 EH-5 Wacker HDK H20 V15 (WACKER-CHEMIE GMBH) N20E T30 T40 DC Fine Silica (D-C Fine Silica) (Dow Corning Co.) Fransol (Franssil) 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 anhydrous silicon dioxide (silica) and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate and zinc silicate can be applied to the silica fine powder here.

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

Carplex Shionogi Yoshika Nipsil Nippon Silica Toksil, Fine Seal Soda Tokuyama Vitaseal Taki Fertilizer Shilton, Silnex Mizusawa Chemical Science Star Sil Kamishima Chemical Science Himezil Ehime Pharmaceutical Pharmaceutical Product Syloid Fuji Debison Chemical Hi-Sil (High Seal) Pittsburgh Plate Glass.Co. (Pittsburgh Plate Glass) Durosil (Duro Seal) Ultorasil (Ultra Seal) Fiillstoff-Gesells chaft Marquart (Fühlstoff-Gesellschaft Markquart) Manosil (Manoshir) Hardman and Holden Hoesch (Hesch) Chemische Fabrik Hoesch KG (Heemije Fabrik Heche) Sil-Stone (Seal Stone) Stoner Rubber Co. (Stonener Rubber) Nalco (Narco) Nalco Chem.Co. (Narco Chemical) Quso (Kuso) Phil adelphia Quartz Co. (Philadelphia Quartz) Imsil (Imsil) Illinois Minerals Co. (Illinois Mineral) Calcium Silikat (Calcium Zirikato) Chemische Fabrik Hoesch.KG (Gill) Gesellshaft Marc Ort Fortafil Imperial Chemical Industries. Ltd. (Imperial Chemical Industries) Microcal Joseph Crosfiels & Sons. Ltd. Kembaya) Tufknit Durham Chemicals. Ltd. (Doulham Chemicals) Silmos Shiroishi Kogyo Star Rex Kamishima Chemicals Among the powders, those having a specific surface area of 30 m ² / g or more (particularly 50 to 400 m ² / g) obtained by nitrogen adsorption measured by the BET method 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.

Further, when the magnetic toner in the present invention is used as a positively-chargeable magnetic toner, the silica fine powder to be added for the purpose of preventing abrasion of the toner may be a positively-charged silica fine powder rather than negatively-charged. It is preferable to use it without impairing the charging stability.

As a method for obtaining the positively chargeable silica fine powder, a method in which the untreated silica fine powder described above is treated with a silicon oil having an organo group having at least one suffocating 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.

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

(Wherein, R ₁ represents hydrogen, an alkyl group, an aryl group or an alkoxy group, R ₂ represents an alkylene group or a phenylene group, R ₃ and R ₄ represents hydrogen, an alkyl group or an aryl group,, R ₅ Represents a nitrogen-containing hetero environment.) The above alkyl group, aryl group, alkylene group, and phenylene group may have an organo group having a nitrogen atom, and substituents such as halogen may be used as long as chargeability is not impaired. May be provided.

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

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

Examples of the saturated heterocyclic group include the following.

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

Examples of such treating agents are aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutyl Aminopropyltrimethoxysilane, monobutylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ-propylphenylamine , Trimethoxysilyl-γ-propylbenzylamine, and the like, and the nitrogen-containing heterocycle has the structure described above. Examples of such compounds that can be used include trimethoxysilyl-γ-propylpiperidine, trimethoxysilyl-γ-propylmorpholine, trimethoxysilyl-γ-propylimidazole and the like.

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

The silica fine powder used in the present invention may be treated with a silane coupling agent or a treating agent such as an organosilicon compound for the purpose of hydrophobizing, if necessary, and react or physically adsorb with the silica fine powder. It is treated with the above treatment agent. Examples of such treating agents include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, Bromomethyldimethylchlorosilane,
α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane , Hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and 2 to 12 siloxane units per molecule, one for each terminal unit Si addressed to
And a dimethylpolysiloxane having a hydroxyl group bonded thereto. These are used alone or in a mixture of two or more.

Cadmium sulfide, selenium, zinc oxide, organic photoconductor (OP)
C), amorphous silicon (α-Si) and the like are used. In the present invention, an organic photoconductor (OPC) and amorphous silicon (α-Si) are used as an excellent combination of the developer and the photoreceptor of the present invention. Is preferred.

When the toner of the present invention is used, a blade cleaning method, a fur brush cleaning method, a magnetic brush cleaning method, or the like is used as a cleaning method. In consideration of the combination, the blade cleaning method is preferable. Further, a charge removing step or the like may be provided immediately before the cleaning step to facilitate toner cleaning as needed.

[Examples] Hereinafter, the method of the present invention will be specifically described based on examples. However, this does not limit the embodiment of the present invention at all. All parts in the examples are parts by weight.

Example 1 After the above materials were mixed well in a blender, they were kneaded with a biaxial kneading extruder set at 150 ° C. The obtained kneaded material was cooled, coarsely pulverized by a cutter mill, and then finely pulverized using a fine pulverizer using a jet stream, and the obtained finely pulverized powder was classified by a fixed wall type air classifier. A classified powder was produced. Further, the obtained classified powder is strictly classified and removed at the same time by a multi-division classifier utilizing a Coanda effect (an elbow jet classifier manufactured by Nittetsu Mining Co., Ltd.) to remove the ultrafine powder and the coarse powder at the same time.
0 μm black fine powder (magnetic toner) was obtained.

Table 1 below shows data obtained by measuring the magnetic toner as a positively-charged black fine powder using a Coulter Counter TA II having an aperture of 100 μ as described above.

100 parts by weight of the obtained black fine powder magnetic toner is added to positively charged hydrophobic dry silica fine powder (BET specific surface area 200 m ^{2 /} g) 0.5
A part by weight and 0.1 part by weight of a vinylidene fluoride polymer having a number average particle size of 0.30 μm and an average weight molecular weight of 300,000 were added, and mixed with a Henschel mixer to obtain magnetic toner A. The particle size distribution of the magnetic toner A was as shown in Table 2.

The magnetic toner A was added and mixed in (CD _{3) 2} CO, insoluble magnetite and other high resolution F ¹⁹ nuclear magnetic resonance was filtered off, measuring, -23.5, -27.5, -45.8, -48.1p
There are peaks due to four chemical shifts of pm, (Sb
+ Sc + Sd) / Sa value was 0.214.

Using a commercially available electrophotographic copying machine NP3525 (manufactured by Canon Inc.) equipped with an unused photoconductor using this magnetic toner,
The image formation test was continuously performed 5,000 times, and 5,000 toner images were generated. After that, the continuous image output test was continued, and after 100,000 times of durability, 100,000 sheets of toner images were checked for the presence of black stripes due to scratches on the surface of the photoreceptor, and the photoreceptor was removed and the surface of the photoreceptor was removed. Was measured using an overcurrent-type film thickness meter (released by Sanko Electronics Research Laboratory, Kett Science Laboratory, etc.).

 Table 3 shows the results.

As is apparent from Table 3, the magnetic toner of the present invention has excellent image density in both the line portion and the large area portion of characters and the like, and has excellent reproducibility and resolution of fine lines. , Maintaining the good image quality at the beginning. Also, the per copy cost was small and the economy was excellent.

Further, even after 100,000 sheets of images were formed, there was no occurrence of scratches on the photoreceptor surface which appeared as black streaks in the toner image, and the abrasion amount of the photoreceptor surface was 4.9 μm, which was within a practical range. Was.

Examples 2 to 7 In the same manner as in Example 1, magnetic toners B to G having various particle size distributions shown in Table 2 were prepared.

When the same evaluation as in Example 1 was performed using the magnetic toners B to G, as shown in Table 3, in each case, a stable and clear high-quality image was obtained for both the initial image and the 5,000-sheet durability image. I was able to. Further, even after 100,000 sheets of durability, the scratches and abrasion on the surface of the photoreceptor were good.

Comparative Example 1 In the same manner as in Example 1, a magnetic toner H having a particle size distribution shown in Table 2 was prepared. The magnetic toner H has a number% of magnetic toner particles having a particle diameter of 5 μm or less, a volume% of magnetic toner particles having a particle diameter of 16 μm or more, and 8 to 12.7.
The number and percentage of the magnetic toner particles having a particle diameter of μm and the volume average particle diameter of the magnetic toner are all larger than the range limited by the present invention, and do not satisfy the condition of the particle size distribution of the magnetic toner of the present invention. . Example 1 using this magnetic toner H
Table 3 shows the results of the evaluation performed in the same manner as described above.

In the obtained toner image, many toner particles protruded from the latent image formed on the photoreceptor, the reproducibility of fine lines was 135%, which was worse than that of Example 1, and the resolution was 4.5 lines. Furthermore, after 10,000 images were printed, a decrease in solid black density, a deterioration in fine line reproducibility, and resolution were observed. Also, the toner consumption was large.

Comparative Example 2 Evaluation was performed in the same manner as in Example 1 except that the toner I as shown in Table 2 was used instead of the magnetic toner A used in Example 1.

The thin line causes stains attributable to aggregates of toner particles in some places, the resolution is 4.5 lines / mm, and the density of solid black and the inside of the image is higher than the density of the line and image edges. It was low and seemed hollow. Spot-like fog stains also occurred. In addition, image quality was further deteriorated by repeating copying.

Comparative Example 3 Evaluation was performed in the same manner as in Example 1 except that the magnetic toner J shown in Table 2 was used instead of the magnetic toner used in Example 1.

In the development on the drum, there is some disturbance, but relatively
Although the image quality was good, the transfer was significantly disturbed, resulting in a transfer failure and a decrease in density. In particular, when the copy is repeated, defective toner particles remain and accumulate in the developing machine, so that the density reduction and the poor image quality are further exacerbated.

Comparative Example 4 Evaluation was performed in the same manner as in Example 1 except that the magnetic toner K shown in Table 2 was used instead of the magnetic toner used in Example 1.

Since the image density was low and the amount of toner on the image edge portion was poor, the outline was unclear and the image lacked sharpness. The resolution and gradation were poor.

In addition, the repetitive copying further deteriorates sharpness, fine line reproducibility, and resolution.

Comparative Example 5 Evaluation was performed in the same manner as in Example 1 except that the magnetic toner L shown in Table 2 was used instead of the magnetic toner used in Example 1.

As a result, image density, resolution, and fine line reproducibility were all poor. Observation of the toner spike on the sleeve, which is the toner carrier in the developing machine, is long and sparse. Even if it flies over the photoreceptor, the spike is too long, so that the tail of the toner protruding from the latent image The density was low due to the pulling state, the toner scattering state, and the coarseness of the toner particles.

Comparative Example 6 A magnetic toner 6 was prepared in the same manner as in Example 1, except that 0.1 parts by weight of polyvinylidene fluoride was omitted. When the same evaluation as in Example 1 was performed using the magnetic toner M, as shown in Table 3, after 100,000 sheets of images were formed, many scratches on the photoreceptor surface appeared as many black stripes on the toner image. The amount of abrasion on the surface of the photoreceptor was 10.7 μm, and obvious deterioration of the photoreceptor was observed.

Comparative Examples 7 and 8 Magnetic toners N and O were prepared in the same manner as in Example 7 and Comparative example 1, except that 0.1 parts by weight of polyvinylidene fluoride was omitted. The evaluation was performed in the same manner as in Example 1 using the magnetic toner N and the magnetic toner O. As shown in Table 3, in each case, after the endurance of 100,000 sheets, Black streaks occurred on the image due to the scratches, the amount of wear on the surface of the photoconductor was large, and deterioration of the surface of the photoconductor was observed.

[Effects of the Invention] As described above in detail, the use of the toner of the present invention makes it possible to obtain a clear image for a long period of time, and is very useful industrially.

Continuation of the front page (72) Inventor Satoshi Yoshida 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-62-245267 (JP, A) JP-A-58-117553 ( JP, A) JP-A-60-166957 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/08 G03G 9/083

Claims (3)

(57) [Claims] 1. A magnetic toner containing at least 60 to 120 parts by weight of a magnetic powder per 100 parts by weight of a binder resin.
12 to 60% by number of magnetic toner particles having the following particle size, 8
1 to 33% by number of magnetic toner particles having a particle diameter of 12.7 μm, 2.0% by volume or less of magnetic toner particles having a particle diameter of 16 μm or more, and the volume average particle diameter of the magnetic toner is 4 to 4%.
A magnetic toner for developing an electrostatic charge image, wherein a silica fine powder and a fluorine-containing resin fine particle having a number average particle diameter of 0.01 to 1 μm having a particle size distribution of 9 μm are externally added to magnetic toner particles. 2. The magnetic toner is a positively charged magnetic toner,
2. The magnetic toner according to claim 1, wherein the silica fine powder is a positively charged silica fine powder. 3. A positively charged silica fine powder is externally added to the positively charged magnetic toner in an amount of 0.01 to 8 parts by weight based on 100 parts by weight of the positively charged magnetic toner.
3. The magnetic toner for developing electrostatic images according to claim 2, which is externally added at 0% by weight.