JP2654572B2 - Magnetic toner - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic toner for developing an electrostatic latent image formed in electrophotography, electrostatic printing, electrostatic recording, and the like.

[Prior art] Conventionally, as a developing method using a one-component magnetic toner,
The developing method using a conductive image magnetic toner disclosed in U.S. Pat. No. 3,909,258 and the like is known and widely used.

However, such a developing method requires that the toner is essentially conductive, and the conductive toner uses an electric field to transfer the toner image on the latent image holding member to the final image supporting member (for example, plain paper). It was difficult to perform transcription (although the cause has not been fully elucidated).

The present applicant has previously proposed a new developing method which solves such a problem of the conventional developing method using a one-component magnetic toner (for example, JP-A-55-18656 and JP-A-55-186).
No. 59). In this method, an insulating magnetic toner is uniformly applied on a cylindrical toner carrier having a magnet therein, and the applied toner is brought into contact with the latent image holding member without being brought into contact with the latent image holding member for development. As a method of forming a toner layer on a toner carrier, there is a method of using a coating blade at an outlet of a toner container. For example, the one shown in FIG.
A blade 1a made of a magnetic material is provided at a position opposite to one magnetic pole N1 of the fixed magnet 4 provided inside, and toner is raised along the line of magnetic force between the magnetic pole and the magnetic material blade. The thickness of the toner layer is regulated by utilizing the action of magnetic force by cutting at the edge (see, for example, JP-A-54-43037).

During development, a low-frequency alternating voltage is applied between the toner carrier and the base conductor of the latent image carrier, and the toner is reciprocated between the toner carrier and the latent image carrier to eliminate ground fog. In addition, it is excellent in reproduction of gradation and can perform favorable development without thinning of the image edge. In this developing method, electrostatic transfer is easy because the toner is an insulator.

In FIG. 1, reference numeral 7 denotes a developing device containing toner 10;
Denotes a latent image holding member (hereinafter referred to as a photosensitive member or a photosensitive drum) such as a photosensitive drum in electrophotography and an insulating drum in electrostatic recording.

In such a developing method, it is extremely important to have a problem: to uniformly coat the magnetic toner on the toner carrier, and to prevent or reduce contamination of the surface of the toner carrier by components in the magnetic toner. . However, the problem and the problem are in a mutually opposite relationship, and it is difficult to solve both at the same time.

That is, as a method of uniformly coating the magnetic toner on the toner carrier in the subject, the present applicant has developed a development method capable of stably forming a uniform toner coat layer on the toner carrier over a long period of practical use. An apparatus has been proposed (JP-A-57-66455). This is because, in FIG. 1, the surface of the toner carrier is made to have a rough surface with specific irregularities by sandblasting with irregular shaped particles, so that the surface of the toner carrier is uniformly and uniformly formed. It is an excellent developing device that can maintain a good toner coated state for a long time without unevenness. The intended surface is an embodiment in which the surface of the stainless steel cylindrical toner carrier is formed over the entire area with countless fine cuts or protrusions in random directions.

However, in a developing device using a toner carrier having such a specific surface state, depending on the magnetic toner to be applied, the toner or components in the toner are likely to adhere to the surface, so that the so-called contamination on the toner carrier surface is prevented. As a result, when the density of the initial image is lowered and the contamination is advanced due to the durability, the image is apt to be whitened in the rotation cycle of the toner carrier. This is because the components in the toner adhere to the slopes and the concave portions of the convex portions on the surface of the toner carrier, so that poor charging of the magnetic toner particles occurs and the charge amount of the toner layer decreases.

In general, components in a magnetic toner include a binder resin, a magnetic substance,
It is composed of materials such as a charge control agent and a release agent. Materials are designed to prevent contamination on the toner carrier surface,
Therefore, at present, the selection of materials is extremely restricted.

In the problem, as a method of preventing or reducing the contamination of the magnetic toner carrier, it can be easily guessed as the reverse tendency of the problem, but in fact, a method of making the surface of the toner carrier smoother is better. It was clear.
However, in such a method, the volume average particle diameter of the magnetic toner is
When the thickness is 12 μm or more, it has been found experimentally that the toner coat tends to be non-uniform and the visible image becomes uneven and a good image cannot be expected. When the phenomenon causing the toner coat unevenness was observed in detail by idling of the developing device, the following was found.

Although the cause is unknown at the beginning of idling, if the surface of the toner carrier is smooth, the toner coat layer becomes excessively thick, and when the toner thickness is gradually regulated by the blade 1a, the photosensitive member 9 of the blade 1a As shown in the enlarged cross-sectional view of FIG.
A toner pool 10a is generated in the portion. Then, when the toner pool reaches a certain limit, the toner is defeated by the conveying force of the sleeve 2 and is transferred onto the sleeve, causing application unevenness such as 3a.
If there is a toner lump such as 3a in the uniformly coated toner layer 3, this will appear unevenly on the image. The unevenness is unevenness of high density, uneven fog or the like. It was found that the shape of the toner application unevenness 3a had a rectangular spot pattern, a wavy spot pattern, a wavy pattern, and the like.

As described above, in the conventional developing method, it is extremely difficult to simultaneously solve both the problem and the problem.

Further, in a machine under a low humidity or a machine in which the peripheral speed of the toner carrier is increased, these tendencies become remarkable.

[Problems to be Solved by the Invention] An object of the present invention is to solve the problem of uniformly coating a magnetic toner on a toner carrier in a developing method as described above for a long period of time under any environment, even with a high-speed machine. It is another object of the present invention to provide an improved magnetic toner.

Another object of the present invention is to provide a high image density, fine line reproducibility,
It is an object of the present invention to provide a magnetic toner which is excellent in gradation and free of fog and which can provide a clear, high-quality image for a long time.

Means and Action for Solving the Problems The present invention relates to a magnetic toner having at least a binder resin and a magnetic powder, which has a volume average particle diameter in a range of 7 to 10 μm, and has a number distribution of magnetic toner particles and a triboelectric charge. The present invention relates to a magnetic toner whose amount satisfies the following general formula (1).

Q (μc / g) = 0.1 (μc / g) A + k (μc / g) (1) Conventionally, in the case of a magnetic carrier, when a surface of a toner carrier has a smooth or specific irregularity formed by a plurality of spherical trace depressions, it becomes difficult for toner components to adhere to the surface, and contamination over a long period of time. Since it is possible to prevent or reduce the charge, the magnetic toner can be always efficiently charged without a decrease in the charging ability of the toner carrier. However, the above-mentioned toner carrier has a capability of uniformly coating the toner carrier with the magnetic toner. The toner carrier has an uneven surface in which countless fine cuts or projections are formed in a random direction by sandblasting with irregular shaped particles. Slightly inferior to the body under certain conditions. For example, when a magnetic toner having a large charging ability is applied to a high-speed machine under low humidity, the charging ability of the toner carrying body is large, so that the amount of charge of the magnetic toner becomes large, and the reflection power on the toner carrying body is reduced. As the size increases, the cohesive force of the magnetic toner also increases, so that an aggregate of the magnetic toner is generated on the toner carrier, which causes unevenness in toner coating.

On the other hand, the magnetic toner of the present invention has a specific particle size distribution within the range of 7 to 10 μm in volume average particle diameter, and can be used with any toner carrier as long as it has an appropriate charge amount. Is prevented from being excessively thick, so that toner coating can be uniformly performed over a long period without causing toner coating unevenness.

As a result, a clear, high-quality image with high image density, excellent fine line reproducibility and gradation, and no fog can be obtained for a long period of time.

The present invention is specifically described above. The toner carrier is hereinafter referred to as a sleeve.

The sleeve carrying the magnetic toner in the present invention preferably has a surface having irregularities formed by a plurality of spherical trace depressions. As a method for obtaining the surface state, a blasting method using fixed particles can be used. As the fixed particles, for example, various hard spheres made of metal such as stainless steel, aluminum, steel, nickel, and brass having a specific particle size, or various hard spheres such as ceramic, plastic, and glass beads can be used. By blasting the sleeve surface using regular particles having a specific particle size, it is possible to form a plurality of spherical dents having substantially the same diameter R.

Also, the diameter R of the plurality of spherical trace depressions on the sleeve surface is
When the diameter R is less than 20 μm, the contamination due to the components in the magnetic toner tends to increase. Conversely, when the diameter R exceeds 250 μm, the uniformity of the toner coat on the sleeve decreases. Tend to. Therefore, it is preferable that the particles having a diameter of 20 to 250 μm are also used in the blasting of the sleeve surface. Further, in the present invention, the pitch P and the surface roughness d of the irregularities on the sleeve surface are:
The surface of the sleeve is measured using a micro-surface roughness meter (Taylor Hopson, Kosaka Laboratories, etc.), and the surface roughness d is based on JIS 10 point average roughness (RZ) "JIS B 0601". is there.

That is, as shown in FIG. 3, a straight line parallel to the average line of the portion extracted by the reference length 1 from the sectional curve is 3
The distance between the two straight lines, which passes through the top of the third valley and the bottom of the third valley from the deepest, is expressed in micrometers (μm), and the reference length 1 is 0.25 mm. The pitch P is obtained by using the number of peaks having a height of 0.1 μ or more with respect to the concave portions on both sides as one peak, and teaching them as one peak, and using the number of peaks within the standard length of 0.25 mm as follows. is there.

[250 (μ)] / [Number of peaks (μ) included in 250 (μ)] The pitch P of the unevenness on the sleeve surface is preferably 2 to 100 μ, and if P is less than 2 μ, the component in the magnetic toner When P exceeds 100 μ, the uniformity of the toner coat on the sleeve tends to decrease. The surface roughness d of the irregularities on the sleeve surface is preferably 0.1 to 5 μm. When d exceeds 5 μm, an alternating voltage is applied between the sleeve and the latent image holding member to transfer the magnetic toner from the sleeve side to the latent image surface. In the method of developing by flying, the electric field tends to be concentrated on the uneven portion and the image tends to be disturbed. Conversely, if d is less than 0.1 μ, the uniformity of the toner coat on the sleeve is reduced. It tends to decrease.

For example, as the most preferable sleeve used for the magnetic toner of the present invention, 80% or more of glass beads having a diameter of 53 to 62 μm are blasted using stainless steel sleeve surfaces as regular particles.

One feature of the magnetic toner according to the present invention is that the coefficient of variation of the number distribution is 25 to 45 (preferably 26 to 44) when the volume average particle diameter is in the range of 7 to 10 μm. As described above, the most preferable magnetic toner according to the present invention (hereinafter referred to as the present sleeve 2-1) has a specific uneven surface formed by a plurality of spherical trace depressions. As for the performance of coating uniformly on the surface, a slightly inferior experimental result was obtained under a specific environment as compared with a sleeve having an uneven surface by sandblasting with irregular shaped particles (hereinafter referred to as Comparative Sleeve 2-2).
That is, the temperature of a magnetic toner with a volume average particle size of 12 μm or more
Under a specific environment of 15 ° C. or less and a humidity of 10% or less, the toner layer per unit area on the sleeve is applied to the developing device having the present sleeve 2-1 and the comparative sleeve 2-2 and idling. The weight M / S of this sleeve 2-1 is 1.6 to 2.3 mg /
In cm ^2, a comparative sleeve 2-2 in 0.6~1.5mg / cm ^2, it is thick toner coat sleeve 2-1, continuing further prolonged idling, the sleeve 2-1, FIG. 2 It has been confirmed that toner coat unevenness may occur as shown in FIG.

However, according to the study of the present inventors, although the reason is not clear, a similar experiment was performed using the magnetic toner having the particle size distribution of the present invention.
Even in the case of 1, the M / S on the sleeve is 0.5 to 1.5 mg / cm ² ,
It was found that the toner coat thickness could be kept low, and as a result, idle rotation was continued for a long time, but sleeve coat unevenness did not occur, and reduction of the toner coat thickness was extremely effective for long-term uniformity of toner coat. I learned a certain fact.

However, even with a magnetic toner having a volume average diameter in the range of 7 to 10 μm and a coefficient of variation of the number distribution of 25 to 45, if the peripheral speed of the sleeve is increased (220 mm / sec or more) and the idle rotation time is increased under low humidity, It has been found that there is a toner that forms aggregates of the magnetic toner on the sleeve and causes unevenness of the sleeve coat. It has also been found that the higher the peripheral speed of the sleeve, the shorter the time until the magnetic toner aggregates are generated. The charge amount of the magnetic toner before the occurrence of the sleeve coat unevenness increased with the idling time, and became considerably larger than the magnetic toner in which the sleeve coat unevenness did not occur. When the magnetic toner was mixed with an iron powder carrier and the charge amount was measured, the former showed a larger value than the latter.

It has been found that when a magnetic toner having such a high triboelectric charge is applied to a high-speed machine, sleeve coat unevenness occurs under low humidity for the above-mentioned reason.

If the coefficient of variation of the number distribution is less than 25 within the range of the volume average particle diameter of 7 to 10 μm, although the reason is not clear, the M / S on the sleeve increases, and sleeve coat unevenness tends to occur. On the other hand, if it exceeds 45, the particle size distribution becomes wide, so that the chargeability of the toner particles becomes non-uniform, the density tends to decrease, and the state of the ears on the sleeve is disturbed, resulting in roughness and a decrease in resolution.

The coefficient of variation of the number distribution can be adjusted in the classification process, but 25 to 45
Within the range, if the charge amount of the magnetic toner with respect to the iron powder carrier is within the range of 4 ≦ k ≦ 12 in the general formula (1), sleeve coating can be performed uniformly and a good image can be obtained.

In the case of k> 12, that is, when the charge amount is large, the sleeve rotates at a high speed under the low humidity even on the sleeve (at the peripheral speed).
(220 mm / sec or more), the charging becomes excessive, and sleeve coat unevenness is likely to occur.

On the other hand, when k <4, that is, when the charge amount is small, sufficient developability cannot be obtained, the density is low, and a good image cannot be obtained. The charge amount can be controlled by selecting and using the charge control agent magnetic substance.

Further, the magnetic toner having a particle size distribution and a charge amount of the present invention,
The ears on the developing sleeve are thin and short without any disturbance,
Because it is in a uniform state, it provides excellent fine line reproducibility and resolution, and gives clear images without fog.

Further, the magnetic toner of the present invention is excellent in gradation because the method of applying to the transfer material is uniform, and can provide high image density while reducing consumption.

By the way, in the production of magnetic toner, if the powder is pulverized using a mechanical pulverizer using pins, disks, a rotor and a liner, or if the air pressure is reduced by a jet mill and gently pulverized, the magnetic toner tends to have a large charge amount. And the sleeve coat may be non-uniform. Therefore, when producing a magnetic toner, it is important to carry out jet mill pulverization at an appropriate air pressure. Also, the smooth developing sleeve used for the magnetic toner as described above has an excellent ability to impart frictional charge, so that the magnetic toner can effectively exert frictional charge, and the charge amount of the magnetic toner on the sleeve is stable. High image quality and high image quality can always be maintained.

Conventionally, after the electrostatic latent image shown in FIG. 4 is developed into a toner image, the transfer device 22 applies a charge of a polarity opposite to that of the toner to the back surface of the transfer material 24 adhered to the toner image by a separation method by electrostatic attraction. The toner image is transferred to the transfer material 24. Immediately after the transfer process is completed, an AC corona or the like is applied to the back surface of the transfer material 24 by the separation device 23 to remove the charge from the transfer material 24 and separate the toner from the image carrier 21 in the image forming method. In addition, the adhesion between the image carrier and the transfer material becomes strong, which is disadvantageous for retransfer in the separation step. However, the magnetism of the present invention is preferably used in the above-described image forming method since the charge amount of the toner is appropriately controlled in the developing step.

That is, when the charge amount of the magnetic toner is small, the toner is poorly adhered to the transfer material and re-transferred to the latent image carrier at the time of separation, causing defects such as whitening of the image. on the other hand,
When the charge amount is large, transfer unevenness or poor transfer to a transfer material may be caused, and retransfer may occur at the time of separation.

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.
-Type II (manufactured by Coulter, Inc.) was connected to an interface (manufactured by Nikkaki) for outputting the number distribution and volume distribution and a CX-1 personal computer (manufactured by Canon). Prepare a% NaCl aqueous solution. As a measuring method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the aqueous electrolytic solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample was suspended was treated with an ultrasonic
After a dispersion treatment for minutes, the Coulter Counter TA-II
According to the mold, the particle size distribution of particles of 2 to 40 μ was measured on the basis of the number, using a 100 μ aperture as the aperture, and then the value according to the present invention was determined.

As the binder resin used in the magnetic toner of the present invention,
In the case of using a heat and pressure roller fixing device having a device for applying oil, the following binder resin for toner can be used.

For example, polystyrene, poly-p-chlorostyrene,
Styrene such as polyvinyltoluene and its substituted homopolymers; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylate copolymer, styrene -Methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone Styrene-based copolymers such as copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers; polyvinyl chloride, phenolic resins, naturally-modified phenolic resins, and natural-resin-modified malees Acid resin, Le resin, methacrylic resin, polyvinyl acetate, silicone resins, polyester resins, polyurethane, polyamide resins, furan resins, epoxy resins,
Xylene resin, polyvinyl butyral, terpene resin,
Coumarone indene resin, petroleum resin and the like can be used.

In the heat and pressure roller fixing method in which almost no oil is applied, the so-called offset phenomenon in which a part of the toner image on the toner image support member is transferred to the roller and the adhesion of the toner to the toner image support member are important problems. is there.
Toners that fix with less heat energy tend to block or cake during storage or in a developing unit, and these problems must also be considered at the same time. The physical properties of the binder resin in the toner are most important in these developments. However, according to the study of the present inventors, when the magnetic material and the content in the toner are 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 methacrylic. Acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, a monocarboxylic acid having a double bond such as acrylamide or a substituted product thereof; for example, maleic acid, butyl maleate, Dicarboxylic acids having a double bond such as methyl maleate, dimethyl maleate and the like, and substituted products thereof; vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate, etc .; Vinyl olefins such as vinyl methyl ketone and vinyl hexyl ketone; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; A single monomer or two or more monomers are used.

Here, as the cross-linking agent, a compound having two or more polymerizable double bonds is mainly used, for example, an aromatic divinyl compound such as divinylbenzene, divinylnaphthalene and the like; for example, ethylene glycol diacrylate, 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 a pressure fixing method is used, a binder resin for a pressure fixing toner can be used. For example, polyethylene, polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer can be used. Coalescent, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, paraffin and the like.

In the magnetic toner of the present invention, a charge control agent is blended (internally added) to the toner particles in order to control the charge amount.
Alternatively, it is preferable to mix (externally add) the toner particles to use. 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 the positive charge control agent include denatured products such as nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate; dibutyltin oxide and dioctyltin Diorganotin oxides such as oxide and dicyclohexyltin oxide; diorganotin borates such as dibutyltin borate, dioctyltin borate and dicyclohexyltin borate 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 [Wherein, R ₁ represents H or CH ₃ , and R ₂ and R ₃ represent a substituted or unsubstituted alkyl group (preferably C ₁ -C ₄ ). ] Or a copolymer with a polymerizable monomer such as styrene, acrylate or methacrylate as described above can be used as a positive charge control agent. The charge control agent also functions as (all or part of) the binder resin.

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 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 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.
Parts by weight).

In the magnetic toner according to the present invention, various additives may be added 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 based on 100 parts by weight of the binder resin may be used. Other additives include, for example, a lubricant such as zinc stearate; an abrasive such as cerium oxide and silicon carbide;
For example, there are fluidity-imparting agents such as colloidal silica and aluminum oxide or anti-caking agents; and conductivity-imparting agents such as carbon black and tin oxide.

Further, for the purpose of improving the releasability at the time of heat roll fixing, a wax-like substance such as low-molecular-weight polyethylene, low-molecular-weight polypropylene, microcrystalline wax, carnauba wax, sasol wax, paraffin wax, etc. Addition to a magnetic toner of about 5 wt% is also a preferred embodiment of the present invention.

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

These ferromagnetic materials preferably have an average particle size of 0.1 to 1 μm, preferably 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 a magnetic toner for developing an electrostatic image according to the present invention, a magnetic powder and a vinyl-based, non-vinyl-based thermoplastic resin, a pigment or dye as a colorant, if necessary, 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, a kneader or an 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.

The magnetic toner according to the present invention may be internally or externally mixed with silica fine powder, but more preferably externally mixed.

The magnetic toner, which is a feature of the present invention, may have poor fluidity, and may not be able to sufficiently exhibit the triboelectric charging ability depending on the developing device.

By externally adding a silica fine powder to the magnetic toner according to the present invention, the fluidity is improved, the chance of contact with the frictional charging member is increased, and the frictional charging ability of more magnetic toner is effectively used, Good developability can be exhibited in any developing device.

Further, the magnetic toner having the particle size distribution as a feature of the present invention has a larger specific surface area than the conventional toner. When the magnetic toner particles are brought into contact with the sleeve surface and a cylindrical conductive member having a magnetic field generating means inside for friction charging, the number of times of contact between the toner particle surface and the sleeve is increased as compared with the conventional magnetic toner, Abrasion of toner particles is likely to occur. When the magnetic toner according to the present invention is combined with fine watermelon powder, abrasion is significantly reduced due to the presence of fine silica powder 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 the magnetic toner can be made more excellent by long-term use.

As the silica fine powder, any of a silica fine powder produced by a dry method and a wet method can be used, but from the viewpoint of filming resistance and durability, it is preferable to use a silica fine powder obtained by a dry method.

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

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

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

AEROSIL 130 200 300 380 OX50 TT600 MOX80 MOX170 COK84 Ca-O-SiL (CABOTO Co.) M-5 MS-7 MS-75 HS-5 EH-5 Wacker HDK N 20 (WACKER-CHEMIE GMBH) V15 N20E T30 T40 DC Fine Silica (Dow Corning Co.) Fransol (F
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 + 2HCl + nH ₂ O → xSiO ₂ .nH ₂ O + 2NaCl In addition, decomposition of sodium silicate with ammonium salts or alkali salts, formation of alkaline earth metal silicate from sodium silicate, and decomposition with acid Silicate, a method in which a sodium silicate solution is converted into silicate using an ion exchange resin, a method in which natural silicate or silicate is used, and the like.

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

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

Carplex Shionogi Pharmaceutical Neep Seal Nippon Silica Tokuseal, Fine Seal Tokuyama Soda Vita Seal Takihito Shilton, Shirunex Mizusawa Chemical Starsil Kamijima Chemical Himejir Ehime Pharmaceuticals Syroid Fuji Debison Chemical Hi-sil Pittsburgh Plate Glass.Co Durosil (Durosill) Ultorasil (Ultraseal) Fiillstoff-Gesellschaft Marquart (Fürstop Gesereshaft Marquart) Manosil (Manosir) Hardman and Holden (Headman and Holden) Hoesch (Hesh) Chemische Fabrik Hoesch KG (Hemische Fabrik Hesh) ) Sil-Stone Stoner Rubber Co. Nalco Nalco Chem. Co. Quso Philodelphia Quazts Co. Delphia Quartz) Imsil Illinois Minerals Co. Calcium Silikat Calcium Silikat Chemische Fabrik Hoesch. KG Calgir ) Fortafil Imperial Chemical Industries.Ltd.
Chemical Industries Microcal Joseph Crosfiels & Sons Ltd. (Joseph Crossfield and Sons) Vulkasil (Vulkasil) Fabenfabriken Bryer, A.-G. (Falben Fabry Ken Baya) Tufknit (Tuffnit) Durham Chemicals.Ltd. Durham Chemicals) Sirmos Shiraishi Kogyo Co., Ltd. Star Rex Kamishima Chemical Furicosyl Multi-wood fertilizer Of the above silica fine powders, the specific surface area by nitrogen adsorption measured by the BET method within the range of 30 m ² / g or more (particularly 50 to 400 m ² / g) 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.

In the case of the positively charged magnetic toner according to the present invention,
As the silica fine powder to be added for the purpose of preventing abrasion of the toner, it is preferable to use positively chargeable silica fine powder without impairing charging stability, rather than negatively chargeable.

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

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

As the silicone oil having a nitrogen atom in the side chain used for treating the silica fine powder, a silicone 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 heterocyclic group. The above alkyl group, aryl group, alkylene group and phenylene group may have an organo group having a nitrogen atom, and may be halogen or the like as long as the chargeability is not impaired. May have the following substituents.

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, or a group having a nitrogen-containing heterocyclic group. As the nitrogen-containing heterocyclic group, there is an unsaturated heterocyclic group or a saturated heterocyclic group, and known ones can be applied. Examples of the unsaturated heterocyclic group include the following.

Examples of the saturated heterocyclic group include the following.

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

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

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

Further, the silica fine powder used in the present invention may be treated with a silane coupling agent, if necessary, with a treating agent such as an organosilicon compound for the purpose of hydrophobicity, and reacts or physically adsorbs with the silica fine powder. It is treated with the above treatment agent. Examples of such a treating agent 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 And dimethylpolysiloxane containing a hydroxyl group bonded to Si. These are used alone or in a mixture of two or more.

In the magnetic toner according to the present invention, a fine powder of a fluorine-containing polymer may be added internally or externally. As the fluorine-containing polymer fine powder, for example, polytetrafluoroethylene, polyvinylidene fluoride and the like and tetrafluoroethylene-vinylidene fluoride copolymer fine powder and the like, and in particular, polyvinylidene fluoride fine powder flows It is preferable in terms of polishing properties and polishing properties. The amount added to the toner is 0.01 to 2.0 wt%, especially 0.02 to 1.0 wt%
% Is preferred.

In particular, in the magnetic toner mixed and externally added with the fine silica powder and the fine powder, the reason is not clear,
Stabilizes the presence of silica adhering to the toner. For example, the silica adhering to the toner is not separated from the toner and the effect on toner abrasion and sleeve fouling is not reduced, and the charging stability is further increased. It is possible to

FIG. 5 shows an example of a specific apparatus that can be used for performing the developing step in the present invention, but this does not limit the present invention in any way.

In the developing device of FIG. 5, for example, a stainless steel sleeve (SUS304) having a diameter of 50 m / m is used as the non-magnetic sleeve 2-1 as the toner carrier according to the present invention, and the magnetic pole N ₁ of the magnet 4 in the sleeve is 850 gauss. N ₂ = 500 gauss, S ₁ = 65
0 gauss, S ₂ = 500 gauss, iron as a magnetic material is used for the blade 1a, and the gap between the blade 1a and the sleeve 2-1 is 25.
0 μ, the toner 10 is a magnetic toner according to the present invention, and the bias power supply 11 is a bias power supply obtained by superimposing DC on AC, and V _pp = 120
An apparatus in which 0 V, f = 800 (Hz), and DC = + 100 W is exemplified.
In addition, the shortest distance between the sleeve 2 and the latent image holding member 9 may be set to 300 μm.

In the present invention, the charge amount of the toner layer per unit area on the carrier and the weight of the toner layer were determined by using a so-called suction Faraday cage method. In the suction type Faraday cage method, the outer cylinder is pressed against the toner carrier to suck all the toner on a certain area on the carrier, collected by a filter of the inner cylinder, and the toner carrier is increased from the weight increase of the filter. The weight of the toner layer per unit area above can be calculated. At the same time, the charge amount per unit area on the toner carrier can be determined by measuring the charge amount accumulated in the inner cylinder electrostatically shielded from the outside.

The method for measuring the charge amount of the magnetic toner in the present invention will be described in detail with reference to the drawings.

FIG. 6 is an explanatory view of an apparatus for measuring the charge amount of the magnetic toner. First, about 1 g of a mixture of magnetic toner and iron powder carrier (200 to 300 mesh) in a weight ratio of 1: 9 is put into a metal measuring container 32 having a 40-mesh screen 33 at the bottom, and the metal is charged. The lid 34 made of. At this time, the weight of the entire measurement container 32 is weighed and is defined as W ₁ (g). Next, the suction machine 31
In the part (at least the part in contact with the measurement container 32 which is an insulator), the pressure of the vacuum gauge is adjusted to 250 mmH ₂ O by adjusting the air volume control valve 36 by suctioning from the suction port 37. This state is enough (about 1 minute)
Suction is performed to remove toner by suction. At this time, electrometer 39
Is V (volt). Here, 38 is a capacitor, and the capacitance C is (μF). Further, the weight of the whole measurement container after suction is weighed to be W ₂ (g). The charge amount of the magnetic toner is calculated by the following equation.

However, the measurement conditions are 23 ° C and 60% RH. The carrier (iron powder) used for the measurement is 200 to 300 mesh, but in order to eliminate errors, the carrier is sufficiently sucked by the above suction device, and the carrier that passes through the 400 mesh screen is removed before removing the magnetic toner. Mix with.

 The mixing time is about 30 seconds.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples, which do not limit the present invention in any way. All parts in the following formulations are parts by weight.

Example 1 The surface of a cylindrical stainless steel sleeve (SUS304) having a magnet inside which can be installed in an electrophotographic copying machine NP-5540 (manufactured by Canon Inc., electrostatic separation method, sleeve peripheral speed: 325 mm / sec) is used as regular particles. 80% or more of glass beads with a diameter of 53-62 μm, blasting process under the condition of spray nozzle diameter 7θ distance 100 mm, air pressure 4 kg / cm ² , 2 minutes,
Irregularities in which a plurality of spherical trace depressions had a diameter R of 53 to 62 μm were formed. The pitch P of the irregularities on the sleeve surface is 33μ.
And the surface roughness d was 2.0 μm. The surface-treated sleeve was set in a copying machine NP-5540.

 On the other hand, the following were used as the magnetic toner.

After the above materials were mixed well in a blender, they were kneaded with a biaxial kneading extruder set at 150 ° C. The kneaded product obtained was cooled, it was coarsely crushed by a cutter mill, finely pulverized by air pressure of 6 kg / cm ² by using a pulverizer using a jet air stream, fixed wall-type milling powder obtained Classification was performed with an air classifier (DS-2 type air classifier manufactured by Nippon Pneumatic Co., Ltd.) to produce a classified powder having a volume average particle size of 8.36 μm. Further, the obtained classified powder is classified and removed simultaneously with a multi-segment classification device (Elbow Jet Classifier EJ-5 manufactured by Nippon Steel Mining Co., Ltd.) utilizing the Coanda effect to remove the ultrafine powder and the coarse powder at the same time to obtain a volume average particle diameter of 8.5 μm. Magnetic toner A was obtained. At that time, elbow jet classifier EJ
In the case of -5, the distance between the Coanda block and the first classification edge is set to 16 mm, the distance between the Coanda block and the second classification edge is set to 32 mm, and the distance between the Coanda block and the ultrafine powder discharge pipe is -20.
00mmH and vacuum suction with ₂ O, Chukonatai (i.e., the magnetic toner A) vacuum suction with a -1000mmH ₂ O from the exhaust pipe of a multi-division classifier at a reduced pressure suction at -1000mmH ₂ O from the exhaust pipe of the crude powder I did it. The volume average particle size of the ultrafine powder was 4.13 μm, and the volume average particle size of the coarse powder was 15.58 μm.

The variation coefficient of the number distribution of the magnetic toner A was 33.5. The coefficient of variation is a value indicating the degree of variation from the average value, and is a characteristic of the magnetic toner of the present invention. A magnetic toner having a particle size distribution was obtained. The coefficient of variation is a measure of variation,
Smaller means sharper and larger is broader, but it is a measure that also includes the degree of variation depending on the particle size. Therefore, it is not sufficient to simply classify and remove fine powder and coarse powder. Instead, the particle size distribution of the finely pulverized product is determined, and the peak value, the content of ultrafine powder to fine powder, and the content of peak value to coarse powder are referred to, and classification conditions ( The toner according to the present invention was obtained by adjusting the edge distance, differential pressure, etc. of the elbow jet, and carefully classifying the toner.

Table 1 shows the data of the particle size distribution of the obtained magnetic toner using a Coulter Counter Model TA-II having an aperture of 100 μm and the triboelectric charge amount against iron powder as described above. Further, the variation coefficient of the number distribution of the toner A and the value of the triboelectric charge amount are plotted in FIG. In the figure, the range surrounded by the solid line satisfies the general formula (1), and toners B to K described later are also blocked.

To 100 parts of the magnetic toner of the obtained black fine powder, 0.5 part of positively charged hydrophobic positive dry silica (BET specific surface area: 200 m ^{2 /} g) was added,
Mix with a Henschel mixer.

Electrophotographic copier NP-5540 equipped with the above-mentioned sleeve
The toner A was charged into the toner, and an image output test was performed in an environment of 15 ° C. and 10% RH. Table 2 shows the results of performing the image formation test continuously 5000 times. As is clear from Table 2, initially, the weight of the toner layer per unit area on the sleeve, M / S
Is 1.0 mg / cm ² , and the charge amount Q / S of the toner layer per unit area is
Together show a moderate value 7.8μc / cm ^2, 5000 sheets even in a post-durability and ^{M / S = 1.1mg / cm 2} , Q / S = 8.5μc / cm 2 is stable, the toner on the sleeve The coat was also very uniform. In addition, the surface of the sleeve after 5,000 sheets had been cleaned was air-cleaned and observed by a scanning electron microscope. As a result, no toner component was attached to the surface irregularities, and substantially no sleeve contamination occurred. Both the initial image and the 5,000-sheet endurance image have high image density, no fog, clear,
The image quality was high with excellent line reproducibility, halftone dot reproducibility, and gradation.

Similarly, good results were obtained in an endurance test in an environment of 32.5 ° C. and 85% RH.

Examples 2-3 Using the above materials, magnetic toners B and C having a particle size distribution as shown in Table 1 were prepared in the same manner as in Example 1. 100 parts of these magnetic toners are coated with positively charged hydrophobic dry silica (B
(ET150m ^{2 /} g) 0.6 part was added and mixed with a Henschel mixer, and the same evaluation as in Example 1 was performed. The result is the second
As shown in the table, both the initial image and the image after 5,000 sheets of durability were high in image density, free of fog, clear and of high image quality, and neither sleeve contamination nor toner coating unevenness on the sleeve was observed.

Example 4 Using the above materials, a magnetic toner D having a particle size distribution as shown in Table 1 was prepared in the same manner as in Example 1. To 100 parts of this magnetic toner, 0.5 parts of hydrophobic silica (BET200m ^{2 /} g) was added,
The mixture was mixed with a Henschel mixer, and the same evaluation as in Example 1 was performed.

The results were good as evident from Table 2.

Examples 5 to 6 Using the above materials, magnetic toners E and F having different particle size distributions as shown in Table 1 were prepared in the same manner as in Example 1.
100 parts of these magnetic toners have positively charged hydrophobic silica (BET
0.6 part of 200 m ^{2 /} g) was added, mixed with a Henschel mixer, and evaluated in the same manner as in Example 1.

The results are shown in Table 2. As is clear from this table, high quality images were obtained in good condition.

Example 7 The surface treatment of the sleeve was performed in the same manner as in Example 1 except that the glass beads used in Example 1 were replaced with carbon random particles of # 300, which were irregular particles. The same evaluation as in Example 1 was performed except that the above-mentioned sleeve was used instead of the sleeve used in Example 1. Table 2 shows the results.

As for the initial image, a clear image without fog was obtained,
A slight decrease in image density was observed in 5000 images. Further, after the endurance of the sleeve, the sleeve was air-cleaned and observed with a scanning electron microscope. As a result, it was found that the toner component adhered to the surface of the sleeve and the sleeve was contaminated.

Example 8 In Example 1, the surface of the sleeve was rubbed with fine powder of cerium oxide as an abrasive without blasting the surface of the sleeve with the regular particles to finish the surface into a smooth mirror surface. Evaluation was performed in the same manner as in Example 1 except that this sleeve was used instead of the sleeve used in Example 1. Table 2 shows the results.

The image was high in density and a clear image without fog was obtained, but was slightly inferior to Example 1 in terms of gradation.

Comparative Example 1 A magnetic toner G having a volume average particle diameter and a particle size distribution as shown in Table 1 was prepared in the same manner as in Example 1.

The same evaluation as in Example 1 was performed on the magnetic toner G with the same external addition as in Example 1. Table 2 shows the results.

When the toner G was used in this evaluation, the initial image was good. However, during the running, the toner coat on the sleeve showed partial unevenness, and the image portion corresponding to the portion had image defects and unevenness. Fog was observed.

Comparative Example 2 A magnetic toner H having a volume average particle diameter and a particle size distribution as shown in Table 1 was prepared in the same manner as in Example 2.

The same evaluation as in Example 1 was performed on the magnetic toner H with the same external addition as in Example 2. Table 2 shows the results.

When the toner H was used in this evaluation, the image density was low in both the initial image and after 5,000 sheets of durability, and fog was not conspicuous and was not satisfactory.

Comparative Example 3 The coarsely crushed product obtained in Example 2 was finely pulverized by a mechanical pulverizer using a rotor and a liner, and classified by the same method as in Example 1 to obtain a magnetic toner I as shown in Table 1. I got

Table 2 shows the results of the same evaluation test as in Example 1 with the same external addition as in Example 2. A good image was obtained at the beginning, but coat unevenness occurred on the sleeve during durability,
An image defect has occurred.

Comparative Example 4 The coarsely crushed material obtained in the same manner as in Example 1 using the above-mentioned materials was finely pulverized three times with a pulverizer using a jet stream at an air pressure of 3 kg / cm ² by a method similar to that of Example 1. After classification, magnetic toner J as shown in Table 1 was obtained.

Table 2 shows the results of the same evaluation tests as in Example 1 with the same external addition as in Example 1.

Although the image was good at the beginning, sleeve coat unevenness occurred during the running and image defects occurred.

Comparative Example 5 Using the above materials, magnetic toner K as shown in Table 1 was prepared in the same manner as in Example 1.

Table 2 shows the results of the same evaluations as in Example 1 except that this magnetic toner was externally added in the same manner as in Example 5.

As a result, the image density was low and the fog was somewhat high, but the resolution and fine line reproducibility were excellent.

[Effects of the Invention] Since the present invention is a magnetic toner having a specific particle size distribution and a triboelectric charge, it exhibits the following excellent effects.

(1) A magnetic toner capable of uniformly coating a sleeve under any environment and using any developing sleeve.

(2) Magnetic toner that uniformly coats the sleeve even when a developing sleeve that rotates at high speed is used.

(3) A magnetic toner which has a high image density, is excellent in fine line reproducibility, resolution and gradation, and gives clear images without fog for a long period of time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a developing device using a magnetic blade, FIG. 2 is a diagram illustrating a cause of toner coating unevenness, FIG. 3 is a diagram illustrating a definition of surface roughness and pitch, FIG. 4 is a schematic explanatory view of a transfer and separation device,
FIG. 5 is a schematic explanatory view of the developing device, and FIG.
FIG. 7 is a schematic explanatory view of a device for measuring the triboelectric charge amount of a magnetic toner, and FIG. 7 is a graph showing a plot of a coefficient of variation of a number distribution and a value of a triboelectric charge amount (μc / g) in the magnetic toner. 1a: magnetic blade, 2: sleeve, 3: coated magnetic toner, 4: fixed magnet roller, 7: developing container, 9: photosensitive drum, 10: magnetic toner, 11: alternating voltage power supply, 22 transfer device, 23 separation device, 24 transfer material, 32 measurement container, 33 screen, 39 electrometer.

Continuing from the front page (72) Inventor Masaji Fujiwara 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Kiichiro Sakashita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-1-295270 (JP, A) JP-A-1-223470 (JP, A) JP-A-57-24950 (JP, A)

Claims (1)

(57) [Claims] In a magnetic toner having at least a binder resin and a magnetic powder, the volume average particle diameter is in the range of 7 to 10 μm, and the number distribution of the magnetic toner particles and the triboelectric charge amount satisfy the following general formula (1). A magnetic toner characterized by satisfying. Q (μc / g) = 0.1 (μc / g) A + k (μc / g) (1)