JPH08314187A - Magnetic toner and image forming method - Google Patents

Abstract

PURPOSE: To provide magnetic toner and an image forming method by which toner consumption is made lower than heretofore, image density is made high, a sharp image obtained by developing a small spot latent image with fidelity and the clear image without fogging in substance can be obtained, and toner welding does not occur on a latent image carrier. CONSTITUTION: Voltage for restoring toner from the latent image carrier 100 to a toner carrier, and voltage for making the toner fly from the toner carrier to the latent image carrier 100 are impressed at least once for T1 hours on the toner carrier, then voltage in a direction where the toner is made to fly is impressed with respect to an image part and voltage in a direction where the toner is restored is impressed with respect to a non-image part for T2 hours. The magnetic toner used in a developing process in which T2/T1 is >=0.1 is the magnetic toner which is obtained by externally adding and mixing magnetic toner particles and organically processed non-organic fine powder and where volume average particle size Dv(μm) is 3<=Dv<6, weight average particle size D4(μm) is 3.5<=D4<6.5, and the existence rate Nm of the particles whose size is <=5μm on number particle size distribution is 60<Nm<=90.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a number of electrophotographic methods are known, but generally, a photoconductive material is used to form an electric latent image on a photoconductor by various means, and then the electrophotographic image is formed. The latent image is developed with toner to make it a visible image, and if necessary, the toner image is transferred to a transfer material such as paper, and then the toner image is fixed on the transfer material by heat, pressure, etc. to make a copy. I will get it. In recent years, a large number of devices using the above-mentioned electrophotographic method have become printers, facsimiles, etc. in addition to conventional copying machines. Particularly in printers and facsimiles, a developing device using a one-component toner is often used because it is necessary to reduce the size of the copying device. The one-component developing method does not require carrier particles such as glass beads and iron powder as in the two-component method, and thus has an advantage that the developing device itself can be made smaller and lighter. Further, in the two-component developing method, it is necessary to keep the toner concentration in the developer constant, so that a device for detecting the toner concentration and supplying a required amount of toner is required, which also makes the developing device large and heavy. However, the one-component developing system does not require such a device, and therefore the device can be made smaller and lighter.

As for the printer device, LED and LBP printers have recently become the mainstream of the market, and the direction of technology is higher resolution, that is, 240, 300 dp in the past.
What was i is now 400, 600, 800 dpi. Therefore, the developing system is also required to have higher definition. Copiers are also becoming more sophisticated, and as a result, they are moving toward digitalization. In this direction, the method of forming an electrostatic charge image with a laser is the main method, so it is also advancing toward the direction of high resolution, and here again, similarly to the printer, a high resolution and high definition developing method is required. There is. For this reason, the toner is becoming finer in particle size, and is disclosed in JP-A-1-112253, JP-A-1-191156, JP-A-2-214156, JP-A-2-284158, and JP-A-3-2843. 18
Japanese Patent Laid-Open No. 1952 and Japanese Patent Laid-Open No. 4-162048 propose a toner having a specific particle size distribution and a small particle size.

Further, in copying machines, there is always a demand for higher speed and stabilization, but especially in medium speed machines and high speed machines, the two-component developing system is predominant. This is because, in such a large machine, stability for long-term use at high speed becomes the most important point due to the problem of size and weight of the developing device. Generally, a toner for a two-component developer is colored with carbon black or the like, and the rest is made of a polymer. For this reason, the toner particles are light and have no force other than the electrostatic force to adhere to the carrier particles, which causes scattering of the developer particularly in high-speed development. This may cause stains and the like, impairing image stability.
Therefore, by including a magnetic substance in the toner,
A developer has been put into practical use in which the toner is prevented from being scattered by making the toner heavy and at the same time capable of adhering to the magnetic carrier particles by magnetic force in addition to electrostatic force.
As described above, the importance of the magnetic toner containing the magnetic substance is increasing at present.

By the way, in the one-component magnetic development method, since the toner is developed in a chain (generally called "brush") at the time of development, the resolution in the horizontal direction of the image is worse than that in the vertical direction. In addition, the toner tends to be overloaded on the line and the toner consumption amount tends to increase as compared with a solid black image. As a result, for example, in the non-image portion in the latter half of the developed image, the trailing phenomenon due to the protrusion of the ears is likely to occur, and a rough image tends to be produced as compared with the two-component developing method. Also 400 μm
In some cases, the amount of toner on a line having a width reaches almost twice the amount of toner on a solid black image. Therefore, as a method of further improving the image reproducibility and reducing the consumption amount, it is conceivable to make the ears of the magnetic toner shorter and denser.

The relationship between the magnetic strength of the magnetic toner and the shape of the spikes is also qualitatively understood as follows. That is, when the magnetic toner has a large magnetization intensity, a strong attractive force along the magnetic field direction and a strong repulsive force in the direction perpendicular to the magnetic field are generated between the magnetic toner particles. Therefore, when the intensity of magnetization is high, the ears formed by the magnetic toner are long, the ears on the toner carrier have a low density, and the individual ears are thin. On the contrary, if the magnetic toner has a small magnetization, the ears are short and the ears on the toner carrier become denser, but the individual magnetic toners cannot be uncoupled from each other. The ears are thick and short, and are in an aggregated state. In this case, the magnetic toner present inside the ears is less likely to come into contact with the surface of the toner carrier, resulting in poor charging. Such a poorly charged magnetic toner appears as a fog on the image and deteriorates the image quality. That is, if the content of the magnetic material is the same, the finer the toner, the shorter and the denser the ears are.
Furthermore, as the toner particle size decreases, the amount of fine powder with high charge increases, and it is expected that the line consumption will be reduced in that the latent image electric field can be easily filled with a small amount of toner. The toner containing a large amount of toner particularly has excellent reproducibility of one minute dot of a digital latent image, but tends to be inferior in image quality due to insufficient image density or fogging.

Further, in recent years, from the viewpoint of environmental protection, the primary charging / transferring process using a photoconductor contact member is becoming mainstream from the conventionally used primary charging / transferring process using corona discharge. For example, JP-A-63-
It is proposed in Japanese Laid-Open Patent Publication No. 149669 and Japanese Laid-Open Patent Publication No. 2-123385. These are related to the contact charging method and the contact transfer method, but a conductive elastic roller is brought into contact with the electrostatic latent image bearing member, and the electrostatic latent image bearing member is removed while applying a voltage to the conductive roller. After charging in the same manner and then obtaining a toner image by the exposure and development steps, while pushing another conductive roller to which a voltage has been applied to the electrostatic latent image carrier, the material to be transferred is passed between the rollers. After the toner image on the electrostatic latent image carrier is transferred to the transfer material, a fixing image is obtained to obtain a copied image. However, in such a roller charging method that does not use corona discharge, the corona charging method is the physical / chemical action of the surface of the electrostatic latent image bearing member due to the discharge generated between the charging roller and the electrostatic latent image bearing member. However, in the case of an organic photoconductor (OPC), toner fusion on the photoconductor surface is likely to occur. Furthermore, in recent years, with the increasing awareness of resource saving, it has been demanded to further reduce the toner consumption amount (the amount of toner used for forming one image).
Satisfaction of all of these problems is still insufficient in the above-mentioned proposal regarding the fine particle diameter toner.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic toner and an image forming method which solve the above problems of the prior art. That is, it is an object of the present invention to provide a magnetic toner and an image forming method that consume less toner than in the past. A further object of the present invention is to provide a magnetic toner having a high image density and capable of faithfully developing a small spot latent image to obtain a sharp high-quality image, and a method for forming an image. A further object of the present invention is to provide a magnetic toner and an image forming method capable of obtaining a clear image with substantially no fog. Further, the object of the present invention is to
To provide a magnetic toner and an image forming method in which toner fusion does not occur on an electrostatic latent image carrier.

[0009]

The above objects can be achieved by the present invention described below. That is, the present invention is a developing area composed of a latent image carrier and a toner carrier facing the latent image carrier,
A voltage for returning the toner from the latent image carrier to the toner carrier between the latent image carrier and the toner carrier and a voltage for causing the toner to fly from the toner carrier to the latent image carrier are set to T1.
After the voltage is applied at least once for a time, a voltage is applied to the toner carrier for a time of T2 for a time in which the toner is ejected to the image portion and the toner is returned to the non-image portion, and
A toner used in an image forming method having a developing step in which a ratio T2 / T1 of 1 hour and T2 time is 0.1 or more is a magnetic toner particle including at least a binder resin and a magnetic material, and an organically treated inorganic fine powder. Are externally added and mixed, and the magnetic toner has a volume average particle diameter Dv (μ
m) is 3 μm ≦ Dv <6, and the weight average particle diameter D4 (μ
m) is 3.5 ≦ D4 <6.5, and the abundance ratio Nm (% by number) of particles of 5 μm or less in the number particle size distribution is 6
A magnetic toner characterized by 0 <Nm ≦ 90, and an image forming method using the toner.

[0010]

The reason why the developing bias voltage according to the present invention can prevent the toner fusion on the photoconductor is considered to be as follows. Due to the force of the developing electric field applied to the developing area, the toner flies from the toner carrier to the photoconductor, which is the latent image carrier, and collides with the photoconductor surface. At this time, an impact is applied from the toner to the surface of the photoconductor, and in some cases, the surface of the photoconductor is scratched. Since the toner of the present invention contains inorganic fine powder particles having a relatively large particle size and a relatively high hardness, the surface of the photoconductor is easily scratched. In particular, scratches are likely to occur on the surface of the organic photoreceptor having a relatively low hardness. When toner is embedded in the scratches by the charging roller, toner fusion on the surface of the photoconductor is likely to occur.

The impact force of the toner on the surface of the photosensitive member depends on the magnitude of the developing electric field applied to the developing region, which is the magnitude of the voltage (peak to peak) of the AC component of the bias applied to the toner carrier. Is almost decided by. However,
The voltage of this AC component needs to have a certain magnitude in order to obtain a sufficient image density, and it cannot be made smaller to some extent even for the purpose of preventing toner fusion on the surface of the photoconductor. However, the non-continuous AC component of the developing electric field used in the present invention reduces the number of times the toner collides with the surface of the photoconductor per unit time, as compared with the continuous AC component generally used conventionally. Further, since the time for which the toner is pressed against the surface of the photoconductor by the strong electric field is shortened, it is possible to prevent the occurrence of scratches on the surface of the photoconductor due to the collision of the toner, and effectively prevent the fusion of the toner to the surface of the photoconductor. I believe.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to preferred embodiments. First, the magnetic toner of the present invention will be described. The magnetic toner of the present invention is obtained by externally mixing at least a binder resin, magnetic toner particles made of a magnetic material, and organically treated inorganic fine powder, and the volume average particle diameter Dv (μm) of the magnetic toner is 3 μm ≦ Dv. <6, the weight average particle diameter D4 (μm) is 3.5 ≦ D4 <6.5, and the existence ratio Nm (number%) of particles of 5 μm or less in the number particle size distribution is 60 <Nm ≦ 90. It is characterized by being.

The magnetic toner of the present invention is obtained by externally adding at least organically treated inorganic fine powder to magnetic toner particles, but in addition, organic particles having an average particle size smaller than the average particle size of the toner particles are used. Fine powder, resin fine powder, untreated inorganic fine powder, or the like may be added. The magnetic toner of the present invention has a volume average particle diameter Dv (μm) of 3 μm ≦ Dv <6,
It is necessary that the weight average particle diameter D4 (μm) is 3.5 ≦ D4 <6.5, and the abundance ratio Nm (number%) of particles of 5 μm or less in the number particle size distribution is 60 <Nm ≦ 90. It is more preferable that the magnetic toner particles constituting the magnetic toner of the present invention also have the above particle size distribution. That is, when the number of particles of 5 μm or less is 60% by number or less, the effect of reducing the consumption is not sufficient, and when the number of particles of 5 μm or less is more than 90% by number, the image density becomes insufficient, which is not preferable. In the present invention, the existence ratio Nm (number%) of particles of 5 μm or less is 62 number% <N
m ≦ 88 number%, further 64 number% <Nm ≦ 86 number%
It is preferred to have a particle size distribution of

Further, in the magnetic toner of the present invention, when the volume average particle diameter Dv (μm) is 6 μm and the weight average particle diameter D4 (μm) is 6.5 μm or more, the resolution of isolated dots of small spots is sufficient. Is no longer desirable. At this time, if it is attempted to forcefully resolve the image under developing conditions or the like, line thickening and toner scattering occur, which is not preferable. Further, if the volume average particle diameter Dv (μm) is 6 μm and the weight average particle diameter D4 (μm) is 6.5 μm or more, the effect of reducing the toner consumption becomes insufficient, which is not preferable. Regarding the average particle diameter of the magnetic toner, in order to further improve the resolution, the volume average particle diameter Dv is in the range of 3.2 μm ≦ Dv ≦ 5.8 μm, and the weight average particle diameter D4 is in the range of 3.6 μm ≦ D4 ≦ 6.3 μm. Is more preferable.

In the magnetic toner of the present invention, the number% of particles having a particle size of 3.17 μm or less is
Between (Nf) and volume% (Vf), 2 ≦ Nf / Vf ≦
It is also one of the preferable embodiments to satisfy the relationship of 8 and 5 ≦ Nf ≦ 40. A magnetic toner satisfying the particle size distribution in this range is preferable because it can give particularly excellent resolution to a digital latent image formed from minute spots. That is, if the value of Nf / Vf is less than 2, fog is likely to occur,
If it exceeds 8, the resolution of minute isolated dots of about 50 μm tends to deteriorate, which is not preferable. The value of Nf / Vf is more preferably 3 to 7. If the value of Nf is less than 5, the toner production efficiency tends to be deteriorated.
If it exceeds, the image density tends to decrease, which is not preferable. A more preferable range of Nf is 7 to 35.

That is, when the Nf / Vf value is in the range of 2 to 8 and the Nf value is in the range of 5 to 40, the fine spot latent image has good isolated dot resolution and good toner consumption. Amount improvement, sufficient image density, and high durability are simultaneously achieved. The fact that Nf / Vf is large with respect to a certain value of Nf means that from particles exceeding 3.17 μm to 3.17 μm.
It shows that it contains a wide range of particles up to m.
The fact that Nf / Vf is small indicates that the abundance of particles in the vicinity of 3.17 μm is high. Nf / Vf value is 2
In the range of 8 to 8 and Nf in the range of 5 to 40, good isolated dot resolution of fine spot latent image, good toner consumption improvement, sufficient image density, and high durability are obtained. To be achieved. Further, in the present invention, it is preferable to set the volume ratio Vg (volume%) of particles of 8 μm or more in the volume particle size distribution of the magnetic toner to 10 or less because scattering of the toner can be reduced.

The magnetic toner of the present invention achieves a higher image quality due to its small particle size, and further has a low toner consumption amount by increasing the number of particles having a high charge amount per unit weight of 5 μm or less. It is a thing. Generally, the reason why a larger amount of toner is developed in the line image area than in the solid image area is considered as follows. That is, in the electrostatic latent image of the line image portion on the photoconductor, unlike the solid image portion, the lines of electric force are densely wrapping around the line latent image from the outside of the line latent image. This is because a large amount of toner is attracted to and pressed against the latent image surface of the photoconductor, and more toner is easily developed on the line latent image surface.

On the other hand, the magnetic toner of the present invention has a smaller amount of toner on the line image portion than the conventional toner, and the reason why the toner consumption can be reduced is considered as follows. . That is, in the one-component developing method in which the magnetic toner is used, the toner is developed on the surface of the photoconductor in a state where the toner particles are aggregated to some extent, but the toner of the present invention contains many particles having a high charge amount of 5 μm or less. In addition, since the magnetic force per toner is small and the latent image potential is easily filled, more than necessary toner particles once developed in the line image portion on the photoconductor are latent image electric force lines. It is believed that this is because the toner can return to the sleeve against the force caused by the wraparound, and only an appropriate amount of toner remains in the line image portion. Since particles of 5 μm or less have a high charge amount per unit weight, they reach the latent image on the photoconductor faster and weaken the developing electric field as compared with particles having a large particle size. I think that is because other particles are hard to receive. Further, even in a solid black image, by reducing the particle size, the image density can be increased with a smaller amount of toner, and it is expected that the toner consumption amount can be reduced.

The constituent materials constituting the magnetic toner of the present invention will be described below. Examples of the magnetic material used in the magnetic toner of the present invention include metal oxides containing elements such as iron, cobalt, nickel, copper, magnesium, manganese, aluminum and silicon. Among them, ferric oxide, γ
-Iron oxide or the like having iron oxide as a main component is preferable.
From the viewpoint of controlling the toner chargeability, the content of silicon element in the magnetic material is 0.5 to 4% by mass based on the iron element.
From the viewpoint of toner fluidity, it is more preferable that the surface contains a silicon atom. Specific examples of the magnetic substance containing silicon atoms on the surface include, for example, the amount of silicon atoms present when the dissolution rate of iron element in the magnetic substance is up to 20%, and the amount of silicon element when 100% is dissolved. Is preferably 44 to 84%.
The silicon atom may be added in the form of a water-soluble silicon compound at the time of forming the magnetic substance, or may be added in the form of a silicic acid compound after forming the magnetic substance, filtration and drying, and fixed on the surface with a mix muller or the like. Good. These magnetic particles are BET produced by the nitrogen adsorption method.
The specific surface area is preferably ² to 30 m ² / g, more preferably 3 to 28 m ² / g, and the Mohs hardness is 5 to
It is preferable to use about 7 magnetic particles.

As the shape of the magnetic material, octahedron, hexahedron, sphere, needle, scale, etc. are known.
Those having a small anisotropy such as a tetrahedron, a hexahedron, a sphere, or an indeterminate type are preferable, and further, a magnetic body having a sphericity Ψ of 0.8 or more is preferable for increasing the image density. The average particle size of the magnetic material is preferably about 0.05 to 1.0 μm, more preferably 0.1 to 0.6 μm.
Further, it is preferably in the range of 0.1 to 0.4 μm.
Further, the content of the above-mentioned magnetic material constituting the magnetic toner of the present invention is 30 to 200 with respect to 100 parts by mass of the binder resin.
The amount is preferably 60 to 200 parts by mass, more preferably 70 to 150 parts by mass. If the amount is less than 60 parts by mass, the transportability is insufficient, the developer layer on the developer carrying member becomes uneven, and the image tends to become uneven, and further, the image density decreases due to the increase in the developer tribo. It tends to occur. On the other hand, if the amount exceeds 200 parts by mass, a problem tends to occur in the fixability.

Next, the binder resin used in the magnetic toner of the present invention will be described. Examples of the binder resin used in the present invention include homopolymers of styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene, and substitution products thereof; styrene-p-chlorostyrene copolymer, styrene. -Vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer Coalesced, styrene-
Styrene such as vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer -Based copolymer; polyvinyl chloride, phenol resin, natural resin modified phenol resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy Resins, xylene resins, polyvinyl butyral, terpene resins, coumarone indene resins, petroleum-based resins and the like can be used. Further, a crosslinked styrene resin can also be used as a preferable binder resin.

Examples of the comonomer for the styrene monomer of the styrene type copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate,
Dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, etc. A monocarboxylic acid having a heavy bond, or a substitution product thereof;
For example, a dicarboxylic acid having a double bond such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate and the like; and substituted products thereof; for example, vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate and the like. , For example, ethylene-based olefins such as ethylene, propylene, butylene, etc .; for example, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, etc .; for example, vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc. Vinyl monomers such as vinyl ethers can be used, and these can be used alone or in combination. As the cross-linking agent used at this time, a compound having two or more polymerizable double bonds is mainly used. For example, an aromatic divinyl compound such as divinylbenzene, divinylnaphthalene; Carboxylic acid ester having two double bonds such as diacrylate, ethylene glycol dimethacrylate, and 1,3-butanediol dimethacrylate; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone; and 3 The above compounds having a vinyl group; can be used alone or as a mixture.

Examples of the binder resin used for pressure fixing constituting the magnetic toner of the present invention include low molecular weight polyethylene, low molecular weight polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer. Examples thereof include polymers, higher fatty acids, polyamide resins and polyester resins. These are preferably used alone or in combination. In the present invention, it is also preferable to include the following waxes in the toner from the viewpoint of improving the releasability from the fixing member during fixing and the fixing property. Examples thereof include paraffin wax and its derivatives, microcrystalline wax and its derivatives, Fischer-Tropsch wax and its derivatives, polyolefin wax and its derivatives, carnauba wax and its derivatives, and the like. The derivatives include oxides, block copolymers with vinyl monomers, and graft modified products. In addition, alcohols, fatty acids, acid amides, esters, ketones, hydrogenated castor oil and its derivatives, plant waxes, animal waxes, mineral waxes, petrolactam and the like can be used.

In the magnetic toner of the present invention, a charge control agent can be mixed with the toner particles (internal addition) or mixed with the toner particles (external addition). By adding the charge control agent, it becomes possible to control the optimum charge amount according to the developing system, and particularly in the present invention, it is possible to further stabilize the balance between the particle size distribution and the charge amount, preferable. As the negative charge control agent for controlling the magnetic toner of the present invention to have negative charge, there are the following substances. For example, organic metal complexes and chelate compounds are effective, and specific examples thereof include monoazo metal complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acids, and aromatic dicarboxylic acid metal complexes. Other examples include aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids, and their metal salts, anhydrides, esters, and phenol derivatives such as bisphenol.

Further, examples of the positive charge control agent for controlling the positive charge property include the following substances. Modified products of nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate, and onium such as phosphonium salts which are analogs thereof. Salts and lake pigments thereof, triphenylmethane dyes and lake pigments thereof, (as a laking agent, phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide, Ferrocyanide, etc.) Metal salts of higher fatty acids; Diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; Dibutyltin borate, dioctyltin borate, dicyclohexyltin volley Diorgano tin borate such like; may be used in combination singly or two or more kinds. The charge control agents described above are preferably used in the form of fine particles, and in this case, the number average particle diameter of these charge control agents is preferably 4 μm or less, more preferably 3 μm or less. When these charge control agents are internally added to the toner, 0.1 to 20 parts by mass, particularly preferably 0.2 to 100 parts by mass of the binder resin are used.
Use 10 to 10 parts by mass. Examples of the coloring material that can be further added to the toner of the present invention include conventionally known carbon black and copper-phthalocyanine.

Further, the magnetic toner of the present invention contains an inorganic fine powder which has been organically treated in order to improve environmental stability, charge stability, developability, fluidity and storage stability. The inorganic fine powder is added to the magnetic toner of the present invention by stirring and mixing with a mixer such as a Henschel mixer. Examples of the inorganic fine powder used in the present invention include silicic acid fine powder, titanium oxide (titania), aluminum oxide, and the like. Among them, silicic acid fine powder is particularly preferably used. As the silicic acid fine powder, any of so-called wet silica produced by vapor-phase oxidation of silicon halide, so-called dry method or dry silica called fumed silica, or so-called wet silica produced by water glass or the like is used. However, it is more preferable to use dry silica having less silanol groups on the surface and inside the silica fine powder and less production residues such as Na ₂ O and SO ₃ ²⁻ . Further, in the case of dry silica, it is also possible to obtain a composite fine powder of silica and another metal oxide by using another metal halogen compound such as aluminum chloride and titanium chloride together with the silicon halogen compound in the manufacturing process. And they are also included.

The present invention is characterized in that the inorganic fine powder as described above is subjected to an organic treatment to be used as a magnetic toner. As an organic treatment method, a silane coupling agent that reacts with or physically adsorbs to the inorganic fine powder is used. , A method of treating with an organometallic compound such as a titanium coupling agent, a method of treating with a silane coupling agent, or a method of treating with a silane coupling agent and simultaneously treating with an organic silicon compound such as silicone oil. Examples of the silane coupling agent used in the organic treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane. , Benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, Dimethyldiethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-
Divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and 2-1 per molecule
Examples thereof include dimethylpolysiloxane having two siloxane units and having a hydroxyl group bonded to a silicon atom directed to each one at the terminal unit.

Further, aminopropyltrimethoxysilane having a nitrogen atom, aminopropyltriethoxysilane,
Dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, monobutylaminopropyltrimethoxysilane, dioctylaminopropyldimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylamino Propyl monomethoxysilane, dimethylaminophenyl triethoxysilane, trimethoxysilyl-
γ-propylphenylamine, trimethoxysilyl-γ
A silane coupling agent such as propylbenzylamine may also be used alone or in combination. A preferred silane coupling agent is hexamethyldisilazane (H
MDS).

As the organic silicon compound, silicone oil can be mentioned. A preferred silicone oil having a viscosity at 25 ° C. of 50 to 100 centistokes is used, and examples thereof include dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, and fluorine modified silicone oil. And the like are particularly preferably used. As the method for treating silicone oil, for example, silica fine powder treated with a silane coupling agent and silicone oil may be directly mixed using a mixer such as a Henschel mixer, or silica fine powder to be a base may be added. A method of spraying silicone oil may be used. Alternatively, a method may be used in which after dissolving or dispersing silicone oil in an appropriate solvent, silica fine powder is added and mixed to remove the solvent.

The inorganic fine powder organically treated by the above method used in the present invention has a specific surface area of 30 m ² / g or more, particularly 50 to 400, as measured by the BET method by nitrogen adsorption.
Those in the m ² / g range give good results. The organically treated inorganic fine powder used in the present invention is preferably used in the range of 0.01 to 8 parts by mass, preferably 0.1 to 5 parts by mass, relative to 100 parts of the toner particles. It is particularly preferable that the amount is in the range of 0.2 to 3 parts by mass.
If it is less than 0.01 parts by mass, the effect of improving toner aggregation will be poor, and if it exceeds 8 parts by mass, problems such as toner scattering between fine lines, contamination inside the machine, scratches and abrasion of the photoconductor tend to occur. is there.

In the magnetic toner of the present invention, other additives may be added within a range that does not substantially affect, for example, lubricant powder such as Teflon powder, zinc stearate powder, polyvinylidene fluoride powder, or cerium oxide powder. Abrasives such as silicon carbide powder and strontium titanate powder, or
For example, titanium oxide powder, fluidity imparting agent such as aluminum oxide powder, anti-caking agent, or conductivity imparting agent such as carbon black powder, zinc oxide powder, tin oxide powder, or organic fine particles of opposite polarity, A small amount of inorganic fine particles can be used as a developability improver.

The method for producing the magnetic toner of the present invention includes:
For example, a binder resin, a wax, a metal salt or a metal complex, a pigment as a coloring agent, or a raw material such as a dye, a magnetic material, a charge control agent, and other additives, if necessary, is mixed with a Henschel mixer, a ball mill, or the like. After sufficiently mixing with a container, a heating roll, a kneader, a heat kneader such as an extruder is used to melt-knead the resins to make them compatible with each other, and the metal compound, the pigment, the dye, and the magnetic material are dispersed or After being melted and solidified by cooling, pulverization and classification are performed to form a magnetic toner. Of course, the present invention is not limited to this.

The magnetic toner of the present invention composed of the constituent materials as described above has a specific average particle size and particle size distribution. The average particle size and particle size distribution of the developer (toner) can be measured by various methods, but in the present invention, it is measured by the following method using Coulter Multisizer-II type (manufactured by Coulter Co.). Was done. The electrolyte used at this time is a 1% NaCl aqueous solution prepared using first-grade sodium chloride. For example, ISOTONf-II (manufactured by Coulter Scientific Japan Co.) can be used. As the measuring method, the electrolytic aqueous solution 100 to 150 is used.
A surfactant, preferably an alkylbenzene sulfonate, as a dispersant is added in an amount of 0.1 to 5 ml, and a measurement sample is added in an amount of 2 to 20 mg. The electrolytic solution in which this sample was suspended was subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and then, as an aperture, 10
The volume and number of toner were measured using a 0 μm aperture to calculate the volume distribution and number distribution. After that, the weight-based weight average particle diameter (D
4: The median value of each channel is used as a representative value for each channel), and the volume-based volume average particle size obtained from the volume distribution (Dv: The median value of each channel is used as a representative value of the channel) and the number distribution The number-based length average particle diameter (D1) determined, the mass-based particle ratio (Vf / Vg) determined from the volume distribution, and the number-based particle ratio (Nm / Nf) determined from the number distribution were determined.

The BET specific surface area of the magnetic material used in the present invention was determined by the BET multipoint method using a specific surface area measuring device Autosorb 1 (manufactured by Yuasa Ionics) by nitrogen adsorption. As a pretreatment of the sample, 1 at 50 ° C
Time was degassed. The sphericity Ψ of the magnetic material used in the present invention was calculated as follows. Sphericality ψ = minimum length (μm) of magnetic substance / maximum length (μm) of magnetic substance That is, the sphericity ψ used in the present invention is processed into a collodion film copper mesh with a transmission electron microscope (Hitachi H-700H). Applied voltage of 100k using sample of magnetic particles
Photographed with V at 10,000 times, with a printing magnification of 3 times, a final magnification of 30,000 times was taken randomly from 10 times.
This is a method in which 0 magnetic particles were selected, the maximum length and the minimum length were measured, and then the average value was calculated. Further, the average particle diameter is obtained by averaging the maximum lengths of the respective particles by the same method. The magnetic properties of the magnetic material according to the present invention are values measured using a vibration type magnetometer VSM-3S-15 (manufactured by Toei Industry Co., Ltd.). In order to obtain a high image quality, the magnetic toner of the present invention as described above is preferably magnetic with a layer thickness smaller than the closest distance (between S and D) between the toner carrier and the latent image carrier on the toner carrier. Toner is applied and developed by an image forming method including a developing step of applying an alternating electric field as described below to perform development.

In the image forming method of the present invention, the toner is transferred from the latent image carrier to the toner between the latent image carrier and the toner carrier in the developing area consisting of the latent image carrier and the toner carrier opposite thereto. The voltage for returning to the carrier and the voltage for flying from the toner carrier to the latent image carrier are set to at least 1 for T1 time.
After the toner is applied to the toner carrier once, a voltage is applied to the toner carrier for a time period of T2 for causing the toner to fly to the image portion and to pull back the toner to the non-image portion.
It is characterized by having a developing step in which / T1 is 0.1 or more. That is, in the image forming method of the present invention, the above-described magnetic toner of the present invention is used, and in the developing step, (1) voltage for drawing the toner back from the latent image carrier to the toner carrier (2) toner carrying the toner Voltage to fly from the body to the latent image carrier (3) Toner is applied to the image area, and voltage is applied to the toner carrier to the non-image area in the order of returning the toner. When
The voltages of (1) and (2) are applied at least once for T1 time, and the voltage of (3) is applied for T2 time.
By applying a voltage so that the ratio T2 / T1 of 2 hours is 0.1 or more, it is possible to maintain the obtained image density and reduce the occurrence of fog.

In the present invention, the value of T2 / T1 is 0.
It may be 1 or more, but preferably 0.3 to
5, and more preferably 0.5 to 3.
That is, if it is less than 0.3, the effect of preventing fogging is not sufficient, and if the value of T2 / T1 is more than 5, the reproducibility of isolated dots tends to be poor, which is not preferable.

Further, according to the developing bias voltage according to the present invention as described above, it is possible to effectively prevent the toner fusion on the photosensitive member. The reason for this is considered to be as follows. In a developing area composed of a latent image carrier and a toner carrier facing the latent image carrier, the toner flies from the toner carrier toward the photoconductor, which is the latent image carrier, by the force of the developing electric field applied to the developing area, Collide with the surface of the photoconductor. At this time, the toner impacts the surface of the photoconductor, and in some cases scratches the surface of the photoconductor. In particular, since the magnetic toner of the present invention having the above-described structure contains inorganic fine powder particles having a relatively large particle diameter and a relatively high hardness, the surface of the photoreceptor is likely to be scratched.
Furthermore, when an organic photoreceptor having a relatively low hardness is used as the latent image carrier, scratches are likely to occur on the surface thereof. The scratches generated on the surface of the latent image carrier are apt to be filled with the toner by the charging roller, so that the toner is easily fused to the surface of the photoreceptor.

The impact force of the toner on the surface of the photosensitive member depends on the magnitude of the developing electric field applied to the developing region, which is the magnitude of the voltage (peak to peak) of the AC component of the bias applied to the toner carrier. Is almost decided by. However, the voltage of this AC component needs to have a certain level in order to obtain a sufficient image density, and it cannot be made smaller than a certain level even to prevent toner fusion on the surface of the photoconductor. . On the other hand, the discontinuous AC component of the developing electric field used in the present invention described above is less likely to cause the toner to collide with the surface of the photoconductor per unit time, as compared with the continuous AC component generally used conventionally. In addition, since the time for which the toner is pressed against the surface of the photoconductor by the strong electric field is shortened, the damage on the surface of the photoconductor due to the collision of the toner can be prevented, and the fusion of the toner on the surface of the photoconductor can be effectively prevented. it is conceivable that.

Further, the surface roughness of the toner carrier used in the image forming method of the present invention is in the range of 0.2 to 3.5 μm in terms of JIS center line average roughness (Ra), and more preferably Ra. Is preferably in the range of 0.5 to 3.0 μm. If the Ra value is less than 0.2 μm, the amount of charge on the toner carrier becomes high, and the developability becomes insufficient, which is not preferable. If Ra exceeds 3.5 μm,
This is not preferable because unevenness occurs in the toner coat layer on the toner carrier, resulting in uneven density on the image. Further, since the magnetic toner of the present invention has a high charging ability, it is desirable to control the total toner charge amount during development. Therefore, the surface of the toner carrier used in the image forming method of the present invention is preferably covered with a resin layer in which conductive fine particles and / or a lubricant are dispersed.

As the conductive fine particles contained in the resin layer coating the surface of the toner carrier at this time, conductive metal oxides such as carbon black, graphite and conductive zinc oxide, and metal double oxides are used alone. Alternatively, two or more are used in combination. Further, as the resin in which such conductive fine particles are dispersed, phenol resin, epoxy resin, polyamide resin, polyester resin, polycarbonate resin, polyolefin resin, silicone resin, fluorine resin, styrene resin Known resins such as resins and acrylic resins are used. In particular, a thermosetting or photocurable resin is preferably used. Furthermore, a resin layer in which conductive particles and / or a lubricant as described above are dispersed on the surface of the toner carrier is blast-treated with regular particles or irregular particles having a diameter (or major axis) of 20 to 250 μm. Is preferable in order to keep Ra of the surface layer through durability.

Further, in the image forming method of the present invention, the ratio Vt between the peripheral speed Vt of the toner carrier and the peripheral speed V of the latent image carrier.
/ V should be 1.1 ≦ Vt / V ≦ 3,
It is preferable from the viewpoint of achieving high image density and reducing fog. More preferably, the ratio of Vt / V is 1.2 ≦ Vt / V ≦
It is preferably 2.5.

Further, in the image forming method of the present invention, the member for regulating the magnetic toner carried on the toner carrier as described above is an elastic member which is in contact with the toner carrier via the toner. The regulation is particularly preferable from the viewpoint of uniformly charging the magnetic toner. or,
At this time, it is preferable in terms of environmental protection that the charging member and the transfer member are in contact with the photoconductor so that ozone is not generated.

Next, the image forming method of the present invention will be described.
This will be specifically described. An example of the image forming apparatus to which the image forming method of the present invention is applied is the apparatus shown in FIG. Hereinafter, a specific description will be given with reference to the drawings. FIG.
In the above, 100 is a photosensitive drum, and a primary charging roller 117, a developing device 140, a transfer charging roller 114, a cleaner 116, a register roller 124 and the like are provided around the photosensitive drum. Then, the photosensitive drum 100 is charged to −800V by the primary charging roller 117. Then, the laser light 123 is generated by the laser generator 121.
Is exposed to the photosensitive drum 100. The electrostatic latent image on the photosensitive drum 100 is developed with one-component magnetic toner by the developing device 140, and the transfer roller 114
Is transferred onto the transfer material by the applied DC voltage of 2 k
V). The transfer material on which the toner image is placed is the conveyor belt 125.
It is conveyed to the fixing device 126 and fixed on the material to be transferred. In addition, the toner partially left on the photosensitive drum 100 is
It is cleaned by the cleaning means 116.

FIG. 2 shows a partial enlargement of the developing device 140. The developing device 140, as shown in FIG.
A cylindrical toner carrier 102 (hereinafter referred to as a developing sleeve) made of a non-magnetic metal such as aluminum or stainless steel is disposed in the vicinity of 0, and the gap between the photosensitive drum 100 and the developing sleeve 102 is It is maintained at about 300 μm by a sleeve / drum gap holding member (not shown). Further, a stirring rod 141 is provided in the developing device 140,
Inside the developing sleeve 102, a magnet roller 104 having a plurality of magnetic poles is fixed and arranged concentrically with the developing sleeve 102. However, the developing sleeve 102 is configured to be rotatable. The magnet roller 104 is provided with a plurality of magnetic poles as shown in the drawing. S1 influences development, N1 regulates toner amount, S2 influences toner intake / conveyance, and N2 influences toner blowout prevention.

The contact blade 1 serves as a member for controlling the amount of magnetic toner attached to the developing sleeve 102 and conveyed.
03 is provided, and the amount of toner conveyed to the developing area is controlled by the contact pressure of the contact blade 103 with respect to the developing sleeve 102. In the developing area, a developing bias is applied between the photosensitive drum 100 and the developing sleeve 102,
The toner on the developing sleeve corresponds to the electrostatic latent image on the photosensitive drum 1.
It flies over 00 and becomes a visible image. FIG. 3 and FIG. 5 illustrate an example of a voltage application state used in the present invention. Vdc indicates a DC power supply voltage when AC is applied.
Further, Vd represents a dark portion potential on the photosensitive drum, and VL represents a light portion potential. FIG. 4 is a diagram for explaining a conventional voltage application state.

[0046]

EXAMPLES The present invention will be specifically described below with reference to production examples and examples, but the present invention is not limited thereto. All parts in the following formulations are parts by mass unless otherwise specified.

[Toner Production Example 1] Magnetic material (saturation magnetization σ _s = 63 emu / g at 1 kOe, silicon element content rate 1.7%, average particle size 0.22 μm, BET specific surface area 22 m ² / g, sphericity Ψ = 0.90) 100 parts by mass Styrene-butyl acrylate-butyl maleic acid half ester copolymer 100 parts by mass Iron complex of monoazo dye (negative charge control agent) 2 parts by mass Low molecular weight polyolefin (mold release) Agent) 2 parts by mass

The above materials were mixed in a blender to obtain 130
Melted and kneaded in a twin-screw extruder heated to ℃, chilled kneaded material is roughly crushed with a hammer mill, coarsely crushed material is finely crushed with a jet mill, and the obtained finely pulverized material is subjected to multi-division classification using Coanda effect Strictly classifying with a machine, magnetic toner particles were obtained. To the obtained magnetic toner particles, 1.5% by mass of dry silica (BET specific surface area of 200 m ^{2 /} g) treated with silicone oil and hexamethyldisilazane was added and mixed with a Henschel mixer to obtain the toner of the present invention. Magnetic toner A was obtained. The obtained magnetic toner has a weight average particle diameter (D
4) = 5.5 μm, volume average particle diameter (Dv) = 4.8 μm
m, Nm = 68 number%, Vg = 2.1 volume%, Nf / V
f = 5.5. Table 1 shows the physical properties of Toner A thus obtained.

[Toner Production Example 2 and Production Example 3] The coarsely pulverized product obtained in Toner Production Example 1 was used to control the pulverization and classification steps to obtain black fine powder having various particle sizes and particle size distributions. Obtained. To the obtained black fine powder, 1.3% by mass of organically treated dry silica similar to that used in Toner Production Example 1 was added and mixed with a mixer to prepare magnetic toners B and C of the present invention. Got Table 1 shows the physical properties of the obtained magnetic toners B and C.

[Toner Production Example 4] As an inorganic fine powder, silica (BET) organically treated with hexamethyldisilazane was used.
A magnetic toner D of the present invention was obtained in the same manner as in Toner Production Example 1 except that 2.0% by mass of the specific surface area of 380 m ² / g) was used. Table 1 shows the physical properties of the obtained magnetic toner D.

[Toner Production Example 5] Silica organically treated with silicone oil and dimethyldichlorosilane (BET
A magnetic toner E of the present invention was obtained in the same manner as in Toner Production Example 1 except that the addition amount of the specific surface area of 130 m ² / g) was 1.2% by mass. Table 1 shows the physical properties of the obtained magnetic toner E.

[Toner Production Example 6] The same as Toner Production Example 1 except that titania (BET specific surface area 50 m ² / g) treated with silicone oil was used as the inorganic fine powder in Example 1 in an amount of 1.0% by mass. Then, a magnetic toner F of the present invention was obtained. Table 1 shows the physical properties of the obtained magnetic toner F.

[Toner Production Example 7] In Example 1, 0.3% by mass of alumina (BET specific surface area 100 m ^{2 /} g) treated with silicone oil as the inorganic fine powder,
Dry silica treated with silicone oil and hexamethyldisilazane (BET specific surface area 200 m ² / g) 1.
Toner Production Example 1 except that 2% by mass is mixed and used
Magnetic toner G of the present invention was obtained in the same manner as in. Table 1 shows the physical properties of the resulting magnetic toner G.

[Toner Production Example 8] Saturation magnetization at 1 kOe σs = 65 emu / g, silicon element content rate 0.3
%, Average particle size 0.19 μm, BET specific surface area 8 m ² /
A magnetic toner H of the present invention was obtained in the same manner as in Toner Production Example 1 except that a magnetic substance having g and sphericity ψ = 0.78 was used. Table 1 shows the physical properties of the resulting magnetic toner H.

[Toner Production Example 9] Magnetic substance (saturation magnetization at 1 kOe σ _s = 60 emu / g, silicon element content rate 3.1%, average particle size 0.24 μm, BET specific surface area 26 m ² / g, sphericity Ψ = 0.87) 90 parts by mass Polyester resin 100 parts by mass Chromium complex of monoazo dye (negative charge control agent) 2 parts by mass Low molecular weight polyolefin (release agent) 2 parts by mass Toner except for using the above materials In the same manner as in Production Example 1,
The magnetic toner I of the present invention was obtained. The physical properties of the obtained magnetic toner I are shown in Table 1.

[Toner Comparative Production Examples 1 to 3] The coarsely pulverized product obtained in Toner Production Example 1 was used, and the coarsely pulverized product was pulverized and classified to control black having various particle sizes and particle size distributions. A fine powder was obtained. Dry silica treated with 1.3% by mass of hexamethyldisilazane was added to the obtained black fine powder and mixed by a mixer to obtain magnetic toners J, K and L for comparison. Table 1 shows the physical properties of the obtained magnetic toners J, K and L.

Table 1

(Example 1) A rubber roller (diameter 12 mm, contact pressure 50 g / cm) in which conductive carbon coated with nylon resin is dispersed is used as a primary charging roller, and a diameter 24 mm is used as an electrostatic latent image carrier. Laser exposure (600 dpi, laser spot diameter 50 μm) was used to set the dark portion potential VD = −700 V and the light portion potential VL = −200 V. As a toner carrier, a layer thickness of about 7 μm and a JIS center line average roughness (R
a) The surface of the 2.2 μm resin layer is blasted and the diameter is 1
A developing sleeve was manufactured by forming the developing sleeve on a 2φ stainless steel cylinder. -Phenolic resin 100 parts-Graphite (particle size about 7 μm) 90 parts-Carbon black 10 parts

Next, the gap between the photosensitive drum and the developing sleeve (between S and D) was set to 300 μm, the developing magnetic pole was 800 gauss, and the toner regulating member was a urethane rubber blade having a thickness of 1.0 mm and a free length of 10 mm of 15 g / cm. It was made to contact by the linear pressure. As the developing bias, the bias of the waveform of FIG. 3 is set in the order of (1) to (3) below, and T1 = 0.
25 msec. , T2 / T1 = 1.0, and repeated application was performed. Incidentally, T1 is a time for applying a voltage for returning the toner from the latent image carrier to the toner carrier and a voltage for causing the toner to fly to the latent image carrier to the toner carrier, and T2 is an image of It is the time for which the voltage is applied to the toner carrier for causing the toner to fly to some areas and pulling the toner back to the non-image areas. (1) Voltage for returning the toner from the latent image carrier to the toner carrier: 300V (2) Voltage for causing the toner to fly from the toner carrier to the latent image carrier: -1300V (3) Flying toner to the image area For the non-image portion, the voltage Vdc in the direction to pull back the toner is Vdc: -500
V

Further, as a photoconductor cleaning blade,
A urethane rubber blade having a thickness of 2.0 mm and a free length of 8 mm was brought into contact with the linear pressure of 25 g / cm. The process speed is 48 mm / sec, and the peripheral speed of the developing sleeve is Vt.
The ratio Vt / V of the peripheral speed V of the photosensitive member was set to 1.5, and the photosensitive member was rotated in the forward direction. As the magnetic toner, the magnetic toner A of the invention of Toner Production Example 1 was used, and the room temperature was 15 ° C. and the humidity was 10% RH.
The image drawing test was conducted under the following environment. As a result, as shown in Table 2, a good image having substantially no fog and no scattering on the image and high resolution was obtained. Also, the transfer rate was high and a sufficient image density was obtained. When the toner consumption amount was calculated, it was 0.032 g / sheet. Further, when the 10-dot line width was measured, it was confirmed that the line width was 430 μm, the line was reproduced with high density and clearly, and the low consumption was achieved while maintaining the latent image reproducibility. Further, in the environment of 23 ° C. and 65% RH, images were continuously printed on 5,000 sheets, but no abnormality such as toner fusion occurred on the surface of the photoconductor (OPC).

The image evaluation method will be described below.
Scattering Evaluation of scatter in the present invention is scatter evaluation in fine fine lines related to image quality of a graphical image, and scatter is easier than scatter in character lines 1
It is the scattering evaluation in the 00 μm line.

[0062] fogging fogging of the transfer paper of the image is reflection densitometer (Toky
O DENSHOKU CO. , LTD, REF
LECTOMETER ODEL TC-6DS). The worst value of the reflection density of the white background after printing is D
s, and Ds-Dr is the fogging amount, where Dr is the average reflection density of the paper before printing. As a result, when the fog amount was 2% or less, a good image with substantially no fog was obtained, but when the fog amount exceeded 5%, the fog was not clearly visible.

Resolving power The resolving power was evaluated by the reproducibility of small-diameter isolated dots (laser spot diameter 50 μm) as shown in FIG.

Toner consumption amount At a room temperature of 23 ° C. and a humidity of 65% RH, an A4 size paper (basis weight: 75 g / m ² ) is continuously printed with 500 sheets of a character pattern of 4% printing from the initial stage, and the toner in the developing device is printed. The change in the amount was measured and the toner consumption amount was obtained.

Laser exposure on a 10-dot line width electrostatic latent image bearing member by laser exposure at 600 dots, a 10-dot horizontal line pattern latent image (latent image line width of about 420 μm).
m) write it at 1 cm intervals, develop it, and use PET made O
Transferred and fixed on HP. The obtained horizontal line pattern image was obtained by using a surface roughness meter Surfcorder SE-30H (manufactured by Kosaka Laboratory Ltd.) as a profile of the surface roughness of the horizontal line toner, and the profile width was used to determine the line width. I asked. Toner fusing In an environment of 23 [deg.] C. and 65% RH, images were continuously printed on 5,000 sheets, and toner fusing on the surface of the photoreceptor (OPC) was visually observed.

(Comparative Example 1) The toner J of Toner Comparative Production Example 1 was used as a toner, and an image forming test was conducted under the same apparatus and conditions as in Example 1. The results are shown in Table 2.
As is clear from Table 2, the toner consumption amount was large, the scattering amount was a little large, and the resolution was a little inferior to that of Example 1. Furthermore, it is continuously 5,0 in an environment of 23 ° C and 65% RH.
When 00 images were printed, toner fusion was recognized on the surface of the photoreceptor (OPC).

(Comparative Example 2) In Comparative Example 1, the developing bias is set to a voltage (DC (direct current)) in the direction of causing the toner to fly to the image portion and pulling the toner back to the non-image portion as shown in FIG. Bias component) Vdc = -500V, voltage for causing toner to fly from the toner carrier to the latent image carrier = -13
00V, voltage for returning toner from the latent image carrier to the toner carrier = 300V, T1 = 0.5 msec. , T2 / T
The same procedure as in Comparative Example 1 was carried out except that the waveform was set to 1 = 0. As a result, an image having a large amount of toner consumption, a little scattering, and a slightly poor resolution was obtained. Also, 23 ℃ 6
When continuous printing of 5,000 sheets was performed in an environment of 5% RH, many white spots appeared on a solid black image, and when the surface of the photoconductor was observed, many toners were found on the surface of the photoconductor (OPC). Fusion was observed. The results are shown in Table 2.

Comparative Example 3 An image output test was conducted in the same manner as in Comparative Example 2 except that the toner L of Toner Comparative Production Example 3 was used as the toner in Comparative Example 2.
The results shown in Table 2 were obtained, and the image was unclear with many fog. Furthermore, under the environment of 23 ° C and 65% RH, continuous 5,
When 000 sheets were printed, a large number of white spots were generated on the image, and a large amount of toner fusion was observed on the surface of the photoreceptor (OPC).

(Comparative Example 4) As a toner carrier, JIS
Toner K of Toner Comparative Production Example 2 was used as a magnetic toner by using an aluminum cylinder having a diameter of 12φ having a center line average roughness (Ra) of 1.0 μm blasted as a developing sleeve.
Image formation was performed using the same apparatus and conditions as in Comparative Example 2 except that was used. As a result, as shown in Table 2, the obtained image was a poor image with many fogs, thin lines, and scattered. Further, when images were continuously printed on 5000 sheets in an environment of 23 ° C. and 65% RH, many white spots were generated on the image, and many toner fusions were observed on the surface of the photoconductor (OPC). It was

(Comparative Example 5) In Comparative Example 2, the ratio Vt / V of the peripheral speed Vt of the developing sleeve to the peripheral speed V of the photosensitive member is 1.0.
Then, the toner was rotated in the forward direction, and image formation was performed under the same apparatus and conditions as in Comparative Example 2 except that the toner L of Toner Comparative Production Example 3 was used as the magnetic toner. As a result, as shown in Table 2, the obtained image was an unclear image with a lot of fog. Further, when images were continuously printed on 5000 sheets in an environment of 23 ° C. and 65% RH, many white spots were generated on the image, and many toner fusions were observed on the surface of the photoconductor (OPC). It was

(Example 2) Image formation was performed using the same apparatus and conditions as in Example 1 except that Toner B of Toner Production Example 2 was used as the toner, and good images and consumption were obtained. It was Table 2 shows the results.

(Example 3) Image formation was performed using the same apparatus and conditions as in Example 1 except that Toner C of Toner Production Example 3 was used as the toner, and a good image and consumption amount were obtained. It was Table 2 shows the results.

(Embodiment 4) In Embodiment 1, as a developing bias, as shown in FIG. 5, a voltage (DC bias) in the direction of causing toner to fly to the image portion and pulling back toner to the non-image portion. Component) Vdc = -500V, voltage for flying toner from toner carrier to latent image carrier = -1
300 V, voltage for returning toner from latent image carrier to toner carrier = 300 V, T1 = 0.18 msec. , T2
When the same procedure as in Example 1 was carried out except that /T1=2.0, good images and good consumption were obtained. Table 2 shows the results.

(Embodiment 5) In Embodiment 1, as a developing bias, a voltage Vdc = − in the direction of causing toner to fly to the image portion and pulling back toner to the non-image portion.
500V, voltage for causing toner to fly from toner carrier to latent image carrier = -1300V, voltage for pulling toner back from latent image carrier to toner carrier = 300V, T1 = 0.42
msec. , T2 / T1 = 0.3, the same procedure as in Example 1 was carried out. As a result, slight toner fusion on the drum was observed, but a good image with no practical problems and a good consumption amount were obtained. Was obtained. Table 2 shows the results.

(Embodiment 6) In Embodiment 1, as the developing bias, the voltage Vdc = − in the direction in which the toner is ejected to the image portion and the toner is returned to the non-image portion.
500V, voltage for causing toner to fly from toner carrier to latent image carrier = -1300V, voltage for pulling back toner from latent image carrier to toner carrier = 300V, T1 = 0.15
msec. , T2 / T1 = 3.0, the same procedure as in Example 1 was carried out. As a result, good images and good consumption were obtained. Table 2 shows the results.

(Embodiment 7) In Embodiment 1, as the developing bias, the voltage Vdc = − in the direction of causing the toner to fly to the image portion and pulling the toner back to the non-image portion.
500V, voltage for causing toner to fly from toner carrier to latent image carrier = -1300V, voltage for pulling toner back from latent image carrier to toner carrier = 300V, T1 = 0.12
msec. , T2 / T1 = 4.0 Example 1
As a result, the toner consumption was good although the resolution was slightly lowered. Table 2 shows the results.

(Examples 8 and 9) As the magnetic toner, the magnetic toners D and E of Toner Production Examples 3 and 4 were used.
As the developing bias, in the order of (1) to (3) below,
T1 = 0.35 msec. , T2 / T1 = 0.5, and repeatedly applied. (1) Voltage for returning the toner from the latent image carrier to the toner carrier: 300V (2) Voltage for causing the toner to fly from the toner carrier to the latent image carrier: -1300V (3) Flying toner to the image area For the non-image portion, the voltage Vdc in the direction to pull back the toner is Vdc: -500
V Also, the ratio of the peripheral speed Vt of the developing sleeve to the peripheral speed V of the photosensitive member Vt /
Example 1 except that V is set to 2.0 and rotation is performed in the forward direction.
Images were printed using the same equipment and conditions. Magnetic toner E
In the case of using, a good image was obtained although the toner consumption was a little large. Table 2 shows the results.

(Example 10) Image formation was carried out using the same apparatus and conditions as in Example 1 except that Toner F of Toner Production Example 6 was used as the toner, and a good image was obtained. Table 2 shows the results.

(Example 11) Image formation was carried out using the same apparatus and conditions as in Example 1 except that Toner G of Toner Production Example 7 was used as the toner, and a good image was obtained. Table 2 shows the results.

(Examples 12 and 13) As the toner, the magnetic toner H of the toner manufacturing examples 5 and 6 was used as the toner.
Using I, and rotating in the forward direction with the ratio Vt / V of the peripheral speed Vt of the developing sleeve to the peripheral speed V of the photosensitive member set to 1.1, image formation is performed under the same apparatus and conditions as in Example 1. When carried out, a good image was obtained although the image density was slightly low. Table 2 shows the results.

Table 2 Evaluation results

The evaluation criteria for scattering in the table are as follows. ◯: Very good Δ: Good x: Scattering is noticeable The evaluation criteria of resolution in the table are as follows. ◯: Very good Δ: Good ×: Insufficient resolution The evaluation criteria for toner fusion in the table are as follows. ◯: Very good Δ: Good (toner fusion is seen on the photoconductor, but there is no problem on the image) ×: Toner fusion is conspicuous (white spots occur on the image)

[0083]

As described above, according to the present invention, while keeping high image density and latent image reproducibility, excessive toner is prevented from being carried on the line image, and the toner consumption amount is lower than that of the conventional one. It is possible to further reduce the amount, and further, the fusion of the toner on the photosensitive member is prevented, and a high-quality and sharp image can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an image forming apparatus to which an image forming method of the present invention is applied.

FIG. 2 is a partially enlarged view of the developing device 140 in FIG.

FIG. 3 is a developing bias used in Example 1.

FIG. 4 is a developing bias of a conventional example.

5 is a developing bias used in Example 4. FIG.

FIG. 6 is an explanatory diagram of small-diameter isolated dots for evaluating the resolution of an image.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location G03G 9/08 374 375 (72) Inventor Yuki Nishio 3-30-2 Shimomaruko, Ota-ku, Tokyo Kiya Non-Incorporated (72) Inventor Motoki Hisaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (15)

[Claims] 1. A voltage for drawing back toner from the latent image carrier to the toner carrier between the latent image carrier and the toner carrier in a developing region composed of the latent image carrier and a toner carrier opposite thereto. A voltage for causing the latent image carrier to fly from the toner carrier is applied to the toner carrier at least once for T1 time. T is applied to the toner carrier
It is applied for 2 hours, and the ratio of the above T1 time and T2 time is T2 /
A toner used in an image forming method having a developing step in which T1 is 0.1 or more is a magnetic toner obtained by externally mixing at least a binder resin, magnetic toner particles made of a magnetic material, and organically treated inorganic fine powder. In the magnetic toner, the volume average particle diameter Dv (μm) is 3 μm ≦ Dv <6, and the weight average particle diameter D4 (μm) is 3.5 ≦ D4 <6.5.
The magnetic toner is characterized in that the abundance ratio Nm (number%) of particles of 5 μm or less in the number particle size distribution is 60 <Nm ≦ 90. 2. The number% of magnetic toner of 3.17 μm or less
Is Nf, and the volume% of the magnetic toner of 3.17 μm or less is Vf
, 2 ≦ Nf / Vf ≦ 8 and 5 ≦ N
The magnetic toner according to claim 1, wherein f ≦ 40. 3. The magnetic toner according to claim 1, wherein the existence ratio Vg (volume%) of particles of 8 μm or more in the volume particle size distribution is 10 or less. 4. The inorganic fine powder is selected from titania, alumina, silica, or a double oxide thereof.
The magnetic toner according to claim 3. 5. The magnetic toner according to claim 1, wherein the inorganic fine powder is treated with at least silicone oil. 6. The magnetic material has a sphericity Ψ of 0.8 or more and a silicon element content of 0.5 based on the iron element.
It is -4 mass%, The magnetic toner in any one of Claims 1-4. 7. A voltage for drawing toner back from the latent image carrier to the toner carrier between the latent image carrier and the toner carrier in a developing area composed of the latent image carrier and the toner carrier opposite thereto. A voltage for causing the latent image carrier to fly from the toner carrier is applied to the toner carrier at least once for T1 time. T is applied to the toner carrier
It is applied for 2 hours, and the ratio of the above T1 time and T2 time is T2 /
In the image forming method having a developing step in which T1 is 0.1 or more, the toner is a magnetic toner obtained by externally mixing at least a binder resin, magnetic toner particles made of a magnetic material, and organically treated inorganic fine powder. The magnetic toner has a volume average particle diameter Dv (μm) of 3 μm ≦ Dv <6 and a weight average particle diameter D4 (μm) of 3.5 ≦ D4 <6.5.
The image forming method is characterized in that the abundance ratio Nm (number%) of particles of 5 μm or less in the number particle size distribution is 60 <Nm ≦ 90. 8. The number% of magnetic toner of 3.17 μm or less
Is Nf, and the volume% of the magnetic toner of 3.17 μm or less is Vf
And 2 ≦ Nf / Vf ≦ 8, and 5 ≦ N
The image forming method according to claim 7, wherein f ≦ 40. 9. The image forming method according to claim 7, wherein the existence ratio Vg (volume%) of particles of 8 μm or more in the volume particle size distribution is 10 or less. 10. The inorganic fine powder is titania, alumina,
8. Silica or a complex oxide thereof is selected from the group consisting of:
The image forming method according to claim 9. 11. The image forming method according to claim 7, wherein the inorganic fine powder is treated with at least silicone oil. 12. The magnetic material has a sphericity Ψ of 0.8 or more and a silicon element content of 0.5 based on the iron element.
It is 4 mass%, The image forming method in any one of Claims 7-11. 13. The image forming method according to claim 7, wherein a ratio Vt / V between the peripheral speed Vt of the toner carrier and the peripheral speed V of the latent image carrier has the following relationship. . 1.
1 ≦ Vt / V ≦ 3 14. The image forming method according to claim 7, wherein the electrostatic latent image carrier is an organic photoconductor. 15. The charging member for charging the electrostatic latent image carrier is in contact with the electrostatic latent image carrier.
5. The image forming method according to any one of 4 above.