JP2003295498A - Toner and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide toner having good transfer ability even when printing is performed at high speed over a long term, and yielding an excellent image free from the lowering of printing density or the occurrence of fogging and having high resolution, and an image forming method using the toner. <P>SOLUTION: The toner is set so that its volume average particle size (dv) is 8.5 to 10.0 μm and its particle size distribution (dv/dp) is 1.0 to 1.3, and consists of coloring particles whose average sphericity (Sc/Sr) obtained by dividing the area (Sc) of a circle where the absolute maximum length of the particle is set as a diameter by the substantial projection area (Sr) of the particle is 1.0 to 1.3 and an additive. The angle of repose of the toner is 15 to 30° and the looseness apparent specific gravity thereof is 0.40 to 0.45 g/cc. Such toner and the image forming method using the toner are provided. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic latent image formed by an electrophotographic method, an electrostatic recording method or the like, and an image forming method using the toner.
In particular, the present invention relates to a toner that has good transferability even when performing durable printing at high speed for a long period of time, and does not cause a reduction in print density or fog, and an image forming method using this toner.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, an electrostatic latent image formed on a photoconductor is first developed with toner. Next, the formed toner image is transferred onto a transfer material such as paper, if necessary,
It is fixed by various methods such as heating, pressurizing or solvent vapor. Further, the toner remaining on the photosensitive member without being transferred is cleaned by a method such as blade cleaning or fur brush cleaning, and then the above-described image forming process is repeated.

In recent years, for such an image forming apparatus,
The demand for smaller size, lighter weight and higher speed is increasing.
In order to meet these demands for size reduction and weight reduction, a so-called cleanerless system has been proposed in which the device used in the cleaning method is omitted. In the cleanerless system, after passing through the charging step, the toner is attracted to the developing device by electrostatic force and collected due to the difference between the surface potential of the charged photoreceptor and the developing bias. Therefore, the collected toner can be used in the next image forming step,
Waste toner can be eliminated. In order to adopt this cleanerless method, it is necessary for the toner to have high fluidity. Further, in order to respond to the speeding up of the image forming apparatus, the fluidity of the toner is required so that the toner follows the developing roll and the photoconductor that rotate at a high speed.

It is known that it is effective to add inorganic fine particles such as hydrophobic silica fine particles as a fluidizing agent (hereinafter sometimes referred to as "external additive") in order to improve fluidity. ing. The angle of repose is used as an index showing this liquidity. It is said that the smaller the numerical value of the angle of repose, the better the fluidity. If the fluidity is too good, the transferability is improved, but other toner characteristics such as fog may be deteriorated. JP-A-8-15904 discloses a magnetic one-component toner having an average particle size of 8 to 14 μm, an angle of repose of 30 to 45 ° and a corrected bulk specific gravity of 0.25 to 0.40 g / cc. In Japanese Patent Laid-Open No. 2000-352840, there is disclosed a toner for developing an electrostatic latent image which satisfies specific conditions including an angle of repose of 28 to 38 ° and a volume average particle diameter of 3 to 10 μm. The toner for electrophotography has a volume average particle diameter of 6.0 μm or more and an angle of repose of 35 ° or less. These toners may be broken in an image forming apparatus when stress is applied in various states such as contact between toner particles, supply roll and developing roll, and developing roll and photoconductor,
As a result, there is a problem that the fluidity is lowered and the printing density is lowered.

In Japanese Unexamined Patent Publication No. 9-197713, a developing device for developing a latent image formed on an image bearing member in a non-contact manner with a one-component developer carried on a developer bearing member has a volume average particle diameter of 9 μm. , A spherical toner having an angle of repose of 42 ° and a change in angle of repose with time of 8 degrees or less. However, as a result of examination by the present inventor,
With the above toner, when an image is formed at high speed,
It was found that the print density was reduced and fogging occurred.

[0006]

The object of the present invention is to provide good transferability even when performing durable printing at high speed for a long period of time.
It is an object of the present invention to provide a toner that does not cause a reduction in print density and the occurrence of fog, and an image forming method using the toner.

[0007]

As a result of intensive studies aimed at achieving this object, the present inventor has found that the above object can be achieved by controlling some toner characteristics within a specific range. The present invention has been completed based on this finding. Thus, according to the present invention, the volume average particle size (dv) is 8.5 to 10.0 μm, and the particle size distribution (d
v / dp) is 1.0 to 1.3, and the average sphericity (Sc) obtained by dividing the area (Sc) of the circle whose diameter is the absolute maximum length of the particle by the substantial projected area (Sr) of the particle / Sr)
A toner having an angle of repose of 15 to 30 ° and a loose apparent specific gravity of 0.40 to 0.45 g / cc, which is composed of colored particles of 1.0 to 1.3 and an external additive, and An image forming method using a toner is provided.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The toner of the present invention contains colored particles and an external additive. The colored particles contain a binder resin, a colorant and a charge control agent as essential components, and may contain a release agent, a magnetic material and the like as required.

Specific examples of the binder resin include resins that have been widely used for toners such as polystyrene, styrene-butyl acrylate copolymer, polyester resin, and epoxy resin.

As the colorant, carbon black, titanium black, magnetic powder, oil black, titanium white, or any pigment and / or dye can be used. Black carbon black has a primary particle size of 20-
Those having a thickness of 40 nm are preferably used. When the particle diameter is within this range, carbon black can be uniformly dispersed in the toner and fog is reduced, which is preferable.

To obtain a full color toner, yellow colorants, magenta colorants and cyan colorants are usually used. As the yellow colorant, compounds such as azo pigments and condensed polycyclic pigments are used. Specifically, C.I. I. Pigment Yellow 3, 12, 13, 14, 15, 17,
62, 65, 73, 83, 90, 93, 97, 120,
138, 155, 180, 181, 185 and 186
Etc. As the magenta colorant, compounds such as azo pigments and condensed polycyclic pigments are used. Specifically, C.I. I. Pigment Red 48, 57, 58, 60,
63, 64, 68, 81, 83, 87, 88, 89, 9
0, 112, 114, 122, 123, 144, 14
6, 149, 163, 170, 184, 185, 18
7, 202, 206, 207, 209, 251, C.I.
I. Pigment Violet 19 and the like. As the cyan colorant, a copper phthalocyanine compound and its derivative, an anthraquinone compound, etc. can be used. Specifically, C.I. I. Pigment Blue 2, 3, 6, 15, 1
5: 1, 15: 2, 15: 3, 15: 4, 16, 17,
And 60 and the like. The amount of such a colorant is usually 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

As the charge control agent, the charge control agents conventionally used for toners can be used. For example, Bontron N-01 (manufactured by Orient Chemical Industry Co., Ltd.),
Nigrosine Base EX (manufactured by Orient Chemical Industry Co., Ltd.), Spiron Black TRH (manufactured by Hodogaya Chemical Industry Co., Ltd.), T-
77 (Hodogaya Chemical Co., Ltd.), Bontron S-34
(Orient Chemical Co., Ltd.), Bontron E-81 (Orient Chemical Co., Ltd.), Bontron E-84 (Orient Chemical Co., Ltd.), COPY CHARGE NX
(Made by Clariant), COPY CHARGE NE
Examples of charge control agents include G (manufactured by Clariant),
Also, JP-A-63-60458 and JP-A-3-17
Quaternary ammonium (salt) group-containing copolymers according to the description of JP-A-5456, JP-A-3-243954, JP-A-11-15192, and JP-A-1-2174.
It is also possible to synthesize a sulfonic acid (salt) group-containing copolymer according to the description in JP-A No. 64, JP-A-3-15858, etc. and use it as a charge control agent (hereinafter, referred to as "charge control resin"). it can.

Among these, it is preferable to use the charge control resin. The charge control resin is preferable because it has high compatibility with the binder resin, is colorless, and can provide a toner having stable chargeability even in continuous color printing at high speed. The glass transition temperature of the charge control resin is usually 40-80.
C, preferably 45 to 75 ° C., more preferably 45 to 75 ° C.
It is 70 ° C. When the glass transition temperature is within this range, the storage stability and fixing property of the toner can be improved in a well-balanced manner. The amount of the charge control agent is usually 0.01 to 20 parts by weight, preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the binder resin.

Examples of the releasing agent include polyolefin waxes such as low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polybutylene; plant-based natural waxes such as candelilla, carnauba, rice, wax, jojoba; paraffin, microcrystallin, Petroleum wax such as petrolactam and its modified wax;
Synthetic wax such as Fischer-Tropsch wax;
Polyfunctional ester compounds such as pentaerythritol tetramyristate, pentaerythritol tetrapalmitate, dipentaerythritol hexamyristate; and the like. These can be used alone or in combination of two or more.

Of these, synthetic waxes, terminal-modified polyolefin waxes, petroleum waxes, polyfunctional ester compounds and the like are preferable. Among the polyfunctional ester compounds, in the DSC curve measured by a differential scanning calorimeter, the endothermic peak temperature at the time of heating is 30 to 200 ° C, preferably 40 to 160 ° C, more preferably 50 to 120 ° C.
A polyfunctional ester compound such as a pentaerythritol ester in the range of ## STR3 ## or a dipentaerythritol ester having an endothermic peak temperature in the range of 50 to 80 ° C. is particularly preferable from the viewpoint of fixing-releasing property as a toner.
The pentaerythritol ester having an endothermic peak temperature in the range of 30 to 200 ° C. at the time of heating and the endothermic peak temperature of 5 are
Among polyfunctional ester compounds such as dipentaerythritol ester in the range of 0 to 80 ° C., the molecular weight is 10
00 or more, 25 ° C with respect to 100 parts by weight of styrene
5% by weight or more and an acid value of 10 mg / KOH or less are more preferable because they show a remarkable effect in lowering the fixing temperature. The endothermic peak temperature is the value measured by ASTM D3418-82. The amount of the release agent is usually 0.5 to 50 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the binder resin.

Examples of the magnetic material include iron oxides such as magnetite, γ-iron oxide, ferrite and iron-excessive ferrite; metals such as iron, cobalt and nickel; and metals such as aluminum, cobalt and copper; lead,
Magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium,
Examples thereof include alloys with metals such as titanium, tungsten and vanadium, and mixtures thereof.

The colored particles are so-called core-shell type (or also referred to as "capsule type") particles obtained by combining two different polymers inside (core layer) and outside (shell layer) of the particles. can do. In the core-shell type particles, by encapsulating the low softening point substance in the inside (core layer) with a substance having a higher softening point, it is possible to balance the lowering of the fixing temperature and the prevention of aggregation during storage. Therefore, it is preferable.

In the case of core-shell type particles, the volume average particle size of the core particles is 8.5 to 10.0 μm, preferably 9.0.
It is 10.0 μm. The particle size distribution (dv / dp), which is the ratio of the volume average particle size (dv) and the number average particle size (dp)
Is preferably 1.0 to 1.3, and more preferably 1.0 to 1.2.

The weight ratio of the core layer to the shell layer of the core-shell type particles is not particularly limited, but is usually 80/20 to 9
Used at 9.9 / 0.1. By setting the proportion of the shell layer to the above proportion, it is possible to have both the storage stability of the toner and the fixability at low temperature.

The average thickness of the shell layer of the core-shell type particles is usually 0.001 to 1.0 μm, preferably 0.00.
3 to 0.5 μm, more preferably 0.005 to 0.2 μm
considered to be m. If the thickness is large, the fixability may be lowered, and if it is small, the storage stability may be lowered. The core particles forming the core-shell type toner particles do not have to be entirely covered with the shell layer, and it is sufficient that a part of the surface of the core particles is covered with the shell layer. The core particle diameter of the core-shell type particles and the thickness of the shell layer are
If it can be observed with an electron microscope, it can be obtained by directly measuring the size and shell thickness of particles randomly selected from the observation photograph, and if it is difficult to observe the core and shell with an electron microscope, It can be calculated from the particle size of the core particles and the amount of the monomer forming the shell used during the toner production.

The colored particles used in the present invention have a volume average particle diameter (dv) of 8.5 to 10.0 μm, preferably 9.0 to 10.0 μm. If the particle size is small, the fluidity is lowered, the transferability is lowered, the blur is generated, and the printing density is lowered. On the contrary, if it is large, fog or toner scattering occurs, and the resolution of the image decreases. The particle size distribution (dv / dp), which is the ratio of the volume average particle size (dv) and the number average particle size (dp), is 1.0 to 1.3 and 1.0 to
More preferably, it is 1.2. If the particle size distribution is large, blurring occurs, and transferability, print density, and resolution decrease. The above volume average particle size and particle size distribution are
For example, the above range can be obtained by classifying. The volume average particle size and particle size distribution of the colored particles can be measured using, for example, Multisizer (manufactured by Beckman Coulter, Inc.).

The colored particles used in the present invention have an average sphericity (Sc / Sr) obtained by dividing the area (Sc) of a circle whose diameter is the absolute maximum length of the particle by the actual projected area (Sr) of the particle.
Is 1 to 1.3, more preferably 1.0 to 1.2, and even more preferably 1.0 to 1.15. If the average sphericity is larger than 1.3, the transferability may decrease. The average sphericity can be set within the above range by using, for example, a phase inversion emulsification method, a dissolution suspension method, a polymerization method, or the like. Here, the average sphericity is determined by taking an electron micrograph of the colored particles, and using the image processing analyzer Luzex IID (manufactured by Nireco Corporation) to measure the area ratio of the particles to the frame area up to 2% and the total number of processed particles. Is the value obtained by averaging the sphericity of 100 colored particles obtained by measuring 100 under the condition.

The colored particles that can be used in the present invention are not particularly limited by the manufacturing method. For example,
(1) In the thermoplastic resin which is the binder resin component, a colorant,
Colored particles obtained by melt-mixing a charge control agent, a release agent and the like to uniformly disperse the composition, then pulverizing and classifying the composition, and (2) a polymerizable resin as a binder resin raw material. A colorant, a charge control agent, a release agent, etc. are dissolved or suspended in a monomer, a polymerization initiator is added, and then dispersed in an aqueous dispersion medium containing a dispersion stabilizer, and heated to a predetermined temperature. Suspension polymerization is started, and after the polymerization is completed, colored particles obtained by filtration, washing, dehydration and drying, (3) primary particles of a binder resin containing a polar group obtained by emulsion polymerization are Colored particles obtained by adding a charge control agent to agglomerate them into secondary particles, and then stirring and associating the particles with stirring at a temperature higher than the glass transition temperature of the binder resin to obtain secondary particles. 63-186253), (4) hydrophilic group-containing resin And Chakujushi, after dissolving in an organic solvent by adding a coloring agent to it, phase inversion by neutralizing the resin,
Examples thereof include colored particles obtained by drying. Among these, substantially spherical colored particles obtained by the suspension polymerization method (2) are preferable from the viewpoint of obtaining a toner capable of responding to high-resolution image quality and high-speed printing.

The method for producing a toner by the suspension polymerization method will be described below. Examples of the polymerizable monomer for obtaining the binder resin include monovinyl monomer, crosslinkable monomer, macromonomer and the like. This polymerizable monomer is polymerized to form a binder resin component. Specific examples of the monovinyl monomer include aromatic vinyl monomers such as styrene, vinyltoluene, and α-methylstyrene; (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, ( Propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
Derivatives of (meth) acrylic acid such as cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and (meth) acrylamide; monoolefin monomers such as ethylene, propylene, and butylene; Etc. Monovinyl monomer is
They may be used alone or in combination of a plurality of monomers. Of these monovinyl monomers, an aromatic vinyl monomer alone, a combination of an aromatic vinyl monomer and a (meth) acrylic acid derivative, and the like are preferably used.

The hot offset is effectively improved by using the crosslinkable monomer and the polymer together with the monovinyl monomer. The crosslinkable monomer is a monomer having two or more vinyl groups. Specifically, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; diethylenically unsaturated carboxylic acid esters such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; N, N-divinylaniline, divinyl ether, etc. And a compound having three or more vinyl groups such as pentaerythritol triallyl ether and trimethylolpropane triacrylate. The crosslinkable polymer is a polymer having two or more vinyl groups in the polymer, and specifically, such as polyethylene, polypropylene, polyester and polyethylene glycol having two or more hydroxyl groups in the molecule. An ester obtained by subjecting a polymer and an unsaturated carboxylic acid monomer such as acrylic acid or methacrylic acid to a condensation reaction can be mentioned. These crosslinkable monomers and crosslinkable polymers may be used alone or in combination of two or more. The amount used is usually 10 per 100 parts by weight of the monovinyl monomer.
It is not more than 1 part by weight, preferably 0.1 to 2 parts by weight.

Further, it is preferable to use a macromonomer together with the monovinyl monomer because the storage stability and the fixability at low temperature are well balanced. The macromonomer has a polymerizable carbon-carbon unsaturated double bond at the end of the molecular chain and usually has a number average molecular weight of 1,000 to 30,
000 oligomers or polymers. When the number average molecular weight is within the above range, the fixability and the storage stability can be maintained without impairing the meltability of the macromonomer, which is preferable. Examples of the polymerizable carbon-carbon unsaturated double bond at the terminal of the macromonomer molecular chain include an acryloyl group and a methacryloyl group, and a methacryloyl group is preferable from the viewpoint of easy copolymerization.

The macromonomer preferably gives a polymer having a glass transition temperature higher than the glass transition temperature of the polymer obtained by polymerizing the monovinyl monomer. Specific examples of the macromonomer used in the present invention include:
Examples thereof include styrene, a styrene derivative, a methacrylic acid ester, an acrylic acid ester, acrylonitrile, and a polymer obtained by polymerizing two or more kinds of acrylonitrile, a macromonomer having a polysiloxane skeleton, and the like. Among them, hydrophilic polymers, particularly polymers obtained by polymerizing methacrylic acid esters or acrylic acid esters alone or in combination, are preferable. When a macromonomer is used, the amount thereof is usually 100 parts by weight of the monovinyl monomer.
0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight,
More preferably, it is 0.05 to 1 part by weight. When the amount of the macromonomer used is in the above range, the fixability is not deteriorated while maintaining the storage stability, which is preferable.

Examples of the dispersion stabilizer include sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate and magnesium carbonate; phosphates such as calcium phosphate; metal oxides such as aluminum oxide and titanium oxide. Compounds; metal compounds such as aluminum hydroxide, magnesium hydroxide, ferric hydroxide; water-soluble polymers such as polyvinyl alcohol, methyl cellulose, gelatin; anionic surfactants, nonionic surfactants Examples thereof include agents and amphoteric surfactants, which may be used alone or in combination of two or more kinds. Among these, a dispersion stabilizer containing a metal compound, particularly a colloid of a sparingly water-soluble metal hydroxide, can narrow the particle size distribution of polymer particles, and the dispersion stabilizer remains after washing. Is preferable and an image can be reproduced clearly, which is preferable.

In the particle size distribution of the poorly water-soluble metal hydroxide colloid, the cumulative number calculated from the small particle size side is 5
It is preferable that the particle size Dp50 of 0% is 0.5 μm or less and the particle size Dp90 of 90% is 1 μm or less.
If the particle size of the colloid becomes large, the stability of polymerization is impaired and the storage stability of the toner is deteriorated.

The dispersion stabilizer is usually used in a proportion of 0.1 to 20 parts by weight with respect to 100 parts by weight of the polymerizable monomer. When the ratio is within the above range, sufficient polymerization stability can be obtained, formation of polymer aggregates can be suppressed, and a toner having a desired particle size can be obtained, which is preferable.

As the polymerization initiator, persulfates such as potassium persulfate and ammonium persulfate; 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2-methyl-N- (2 -Hydroxyethyl) propionamide), 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile Azo compounds such as di-t-butyl peroxide, dicumyl peroxide, lauroyl peroxide,
Benzoyl peroxide, t-butylperoxy-2-
Ethyl hexanoate, t-hexyl peroxy-2-
Ethyl hexanoate, t-butyl peroxypivalate, di-isopropyl peroxydicarbonate, di-
t-butyl peroxyisophthalate, 1,1,3,3
Examples thereof include peroxides such as tetramethylbutylperoxy-2-ethylhexanoate and t-butylperoxyisobutyrate. Moreover, the redox initiator which combined these polymerization initiators and a reducing agent can be mentioned.

Among these, it is particularly preferable to select an oil-soluble polymerization initiator that is soluble in the polymerizable monomer used, and a water-soluble polymerization initiator can be used in combination therewith if necessary. . The polymerization initiator is a polymerizable monomer 10
0.1 to 20 parts by weight, preferably 0.3 to 15 parts by weight, and more preferably 0.5 to 10 parts by weight, relative to 0 parts by weight. The polymerization initiator can be added in advance to the polymerizable monomer composition, but in the case of suspension polymerization, the suspension after completion of the droplet formation step of the polymerizable monomer composition, emulsion polymerization In some cases, it may be added directly to the emulsion after the emulsification step.

Further, it is preferable to use a molecular weight modifier in the polymerization. As the molecular weight modifier, for example,
t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, 2,2,4,6,6-
Examples thereof include mercaptans such as pentamethylheptane-4-thiol; halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide; These molecular weight modifiers can be added before the start of the polymerization or during the polymerization. The molecular weight modifier is usually 0.01 to 10 parts by weight, preferably 0.1 to 100 parts by weight of the polymerizable monomer.
It is used in a proportion of up to 5 parts by weight.

Examples of the method for producing the core-shell type toner, which is a preferable toner described above, include a spray dry method, an interfacial reaction method, an in situ polymerization method and a phase separation method. Specifically, a toner obtained by a pulverization method, a polymerization method, an association method, or a phase inversion emulsification method is used as a core particle, and a shell layer is coated on the toner to obtain a core-shell type toner. In this manufacturing method,
The in situ polymerization method and the phase separation method are preferable from the viewpoint of production efficiency.

The method for producing the core-shell type toner by the in situ polymerization method will be described below. A core-shell type toner is obtained by adding a polymerizable monomer for forming a shell (polymerizable monomer for shell) and a polymerization initiator to an aqueous dispersion medium in which core particles are dispersed and polymerizing. be able to. As a specific method for forming the shell, a method of continuously adding a polymerizable monomer for a shell to a reaction system of a polymerization reaction carried out to obtain a core particle and continuously polymerizing it, or a method using another reaction system is used. Another method is to charge core particles, add a polymerizable monomer for shell to the core particles, and perform stepwise polymerization. The polymerizable monomer for shell may be added to the reaction system all at once, or may be added continuously or intermittently using a pump such as a plunger pump.

As the polymerizable monomer for the shell, styrene, acrylonitrile, methyl methacrylate and the like which form a polymer having a glass transition temperature of more than 80 ° C. may be used alone or in combination of two or more kinds. be able to.

When the polymerizable monomer for shell is added, it is preferable to add a water-soluble polymerization initiator because the core-shell type toner can be easily obtained. When a water-soluble polymerization initiator is added during the addition of the shell polymerizable monomer, the water-soluble polymerization initiator enters near the outer surface of the core particle to which the shell polymerizable monomer has migrated, and the core particle surface It is considered that the polymer (shell) is easily formed in the above.

As water-soluble polymerization initiators, persulfates such as potassium persulfate and ammonium persulfate; 2,2'-azobis (2-methyl-N- (2-hydroxyethyl) propionamide), 2,2 ' -Azobis- (2-methyl-
Examples thereof include azo initiators such as N- (1,1-bis (hydroxymethyl) ethyl) propionamide). The amount of the water-soluble polymerization initiator is 100 for the shell monomer.
It is usually 0.1 to 50 parts by weight, preferably 1 to 30 parts by weight, based on parts by weight.

The external additive has a volume average particle diameter of primary particles of 5 to 5.
It consists of silica fine particles (A) of 18 nm, preferably 7 to 16 nm. A preferable external additive has a volume average particle diameter of primary particles of 0.1 to 1 μm, preferably 0.2 to 0.8 μm.
As the fine particles (C) having m, organic fine particles (C-1) or inorganic fine particles (C-2) are further contained. Further, the external additive may contain silica fine particles (B) having a volume average particle diameter of primary particles of 20 to 60 nm, preferably 25 to 50 nm.

If the volume average particle diameter of the silica fine particles (A) is small, the photoreceptor is likely to cause filming, and conversely if the silica fine particles (A) are large, the fluidity is lowered and the particles are easily scraped. Silica fine particles (B)
When the volume average particle size is small, the photoreceptor is likely to cause filming, and conversely, when the volume average particle size is large, the fluidity is deteriorated and the image is easily scraped. When the volume average particle diameter of the fine particles (C) is small, the abrasivity is deteriorated, and when it is large, the fluidity may be deteriorated.

The silica fine particles (A) or the silica fine particles (B) are preferably subjected to a hydrophobic treatment. Hydrophobized silica fine particles are generally commercially available, but they can also be obtained by hydrophobizing with a silane coupling agent, a higher fatty acid metal salt, silicone oil or the like. As a method of hydrophobizing treatment, a method of dropping or spraying a treating agent such as silicone oil while stirring the fine particles at high speed, and adding and mixing the fine particles into an organic solvent in which the treating agent is dissolved and stirred , A method of heat treatment, and the like. In the former case, the treating agent may be diluted with an organic solvent or the like. The degree of hydrophobicity is such that the hydrophobicity measured by the methanol method is 20 to 90%, preferably 40 to 80%. If the degree of hydrophobicity is small, it tends to absorb moisture under high humidity, and if the degree of hydrophobicity is too high, sufficient polishing properties may not be obtained.

The organic fine particles (C-1) have a glass transition temperature or melting point of the compound constituting the fine particles of usually 80 to 250 from the viewpoint of suppressing blocking between particles.
C., preferably 90 to 200.degree. Examples of the compound that constitutes the organic fine particles include a methyl methacrylate polymer and a styrene-methyl methacrylate copolymer. Also, the area of a circle whose diameter is the absolute maximum length of the organic fine particles (S
The average sphericity (Sc / Sr) obtained by dividing (c) by the substantial projected area (Sr) of the particles is not particularly limited, but is usually 1 to 1.
3, preferably 1 to 1.2. If the average sphericity is large, the transferability may decrease.

As the inorganic fine particles (C-2), silica,
Examples thereof include calcium carbonate, titanium oxide, aluminum oxide, zinc oxide, tin oxide, barium titanate, strontium titanate, and those obtained by imparting electroconductivity to them by surface treatment with tin or antimony.

The amount of the silica fine particles (A) added is not particularly limited, but is usually 0.1 with respect to 100 parts by weight of the colored particles.
-3 parts by weight, preferably 0.2-2 parts by weight. If this amount is too small, the fluidity may be reduced to cause scraping, and conversely if the amount is too large, the fluidity may be increased and fogging may be likely to occur. The amount of the silica fine particles (B) added is not particularly limited, but is usually 0.1% with respect to 100 parts by weight of the colored particles.
It is 1 to 3 parts by weight, preferably 0.2 to 2 parts by weight. If this amount is too small, the polishing property may be deteriorated and filming may occur. On the contrary, if the amount is too large, the fluidity may be deteriorated and the film may be easily scraped. The amount of the fine particles (C) added is not particularly limited, but is usually 0.1% with respect to 100 parts by weight of the colored particles.
It is 1 to 2 parts by weight, preferably 0.2 to 1 part by weight.
If the amount is less than this amount, filming may occur, and conversely if the amount is greater, the fluidity may be lowered and the image may be easily scraped.

In the toner of the present invention, the above-mentioned colored particles and the external additive are put in a mixer such as a Henschel mixer and stirred to adhere or partially embed the external additive on the surface of the colored particles. To manufacture. By this, the chargeability,
It is possible to obtain a toner having excellent fluidity and storability.

The toner of the present invention has an angle of repose of 15 to 30.
And preferably 15 to 25 °. If the angle of repose is small, fogging or toner scattering occurs, and conversely, if the angle of repose is large, blurring occurs, and transferability and print density decrease. The apparent apparent specific gravity is 0.4 to 0.45 g / cc. When the apparent apparent specific gravity is small, the image is scraped, and the transferability and the print density are lowered. On the contrary, when the apparent specific gravity is large, the fog and the toner are scattered. The angle of repose and the apparent apparent specific gravity are measured using, for example, a powder measuring machine (trade name “Powder Tester” manufactured by Hosokawa Micron Co., Ltd.).

In the toner of the present invention, the volume average particle size, particle size distribution and average sphericity of the colored particles are set to the above ranges in order to adjust the repose angle and the apparent apparent specific gravity to the above ranges, and the external additive to be added is added. May be appropriately selected and controlled using the powder measuring machine as described above.

The image forming method of the present invention will be described in detail below with reference to the drawings. The image forming method of the present invention forms an electrostatic latent image on the surface of a uniformly charged photoreceptor, develops the electrostatic latent image into a toner image with toner, and transfers the obtained toner image to a transfer roll. The volume average particle diameter (dv) of the toner is fixed as a toner after being transferred to a transfer material by
Is 8.5-10.0 μm, and the particle size distribution (dv / d
p) is 1.0 to 1.3, and the area (Sc) of a circle whose diameter is the absolute maximum length of the particle is the substantial projected area (Sc) of the particle.
The average sphericity (Sc / Sr) obtained by dividing by r) is 1.
It is composed of colored particles of 0 to 1.3 and an external additive, has an angle of repose of 15 to 30 °, and a loose apparent specific gravity of 0.1.
Toner that is 4-0.45 g / cc is used.

FIG. 1 is a diagram showing an example of an image forming apparatus to which the image forming method of the present invention can be applied. Figure 1
As shown in FIG. 3, the image forming apparatus has a photosensitive drum 1 as a photosensitive member, which is mounted rotatably in the direction of arrow A. The photosensitive drum 1 has a photoconductive layer provided on a conductive support drum, and the photoconductive layer includes, for example, an organic photoconductor, a selenium photoconductor, a zinc oxide photoconductor, an amorphous silicon photoconductor, and the like. , Preferably composed of an organic photoreceptor. Examples of the resin that binds the photoconductive layer to the conductive support drum include polyester resin, acrylic resin, polycarbonate resin, phenol resin, epoxy resin, hydrogenated polystyrene resin, etc. Among them, the polycarbonate resin is abrasion resistant. It is preferable from the viewpoint of sex.

Around the photosensitive drum 1, a charging roll 3, a laser beam irradiation device 4 as an exposure device, a developing device 11, a transfer roll 5, and a cleaning device 2 are arranged along the circumferential direction. The charging is to charge the surface of the photosensitive drum 1 positively or negatively with a charging member. As the charging method with the charging member, in addition to the charging roll 3 shown in FIG. 1, there are a contact charging method of charging with a fur brush, a magnetic brush, a blade, etc., and a scorotron type non-contact charging method with corona discharge, It is also possible to replace them.

The exposure is to irradiate the charged photoconductor with light by an exposure device. For example, as an exposure device, a laser beam irradiation device 4 as shown in FIG.
The surface of the photosensitive drum can be irradiated with light corresponding to an image signal to form an electrostatic latent image on the surface of the charged drum. The laser light irradiation device 4 is composed of, for example, a laser irradiation device and an optical system lens. In addition to this, as an exposure device, there is an LED irradiation device.

The developing device 11 shown in FIG. 1 is a developing device used in the one-component contact developing system, and has a developing roll 7 and a supply roll 9 in a casing 12 in which a toner 10 is accommodated. The developing roll 7 is arranged so as to partially contact the photosensitive drum 1, and is rotated in the direction B opposite to the photosensitive drum 1. The supply roll 9 contacts the developing roll 7, rotates in the same direction C as the developing roll 7, and supplies the toner 10 to the outer periphery of the developing roll 7. As another developing method, there is a one-component non-contact developing method.

In the development, the toner is supplied to the developing roller 7 by the supplying roller 9, the toner layer thickness of the supplied toner is adjusted by the layer thickness regulating blade 8 described above, and the toner on the developing roller is applied to the photosensitive member. The toner corresponding to this is attached to the electrostatic latent image formed on.
At this time, a bias is applied between the developing roll 7 and the photosensitive drum 1 so that the toner can be attached only to the light irradiation portion in the reversal development and the toner can be attached only to the light non-irradiation portion in the regular development. A voltage is applied.

In the casing of the developing device, a supply roll may be rotatably arranged in the vicinity of the developing roll in order to favorably adhere the toner to the outer peripheral surface of the developing roll.
A bias voltage is preferably applied to the conductive shaft of the developing roll. In the case of reversal development, a voltage having the same polarity as that of the electrostatic latent image on the photoconductor is applied to the conductive shaft of the developing roll.

Transfer is to transfer the toner image formed on the surface of the photosensitive drum by the developing device 11 onto the transfer material 6 such as paper by applying a transfer voltage having a polarity opposite to that of the toner by the transfer roll 5. . At this time, the pressing force of the transfer roll on the photosensitive drum is 200 to 1000 g / cm ² , and preferably 300 to 800 g / cm ² . If the pressing force is small, the nip width becomes narrow and the transfer rate may decrease. On the contrary, if the pressing force is large, the developed toner may adhere and white spots may occur.

The fixing means fixing the toner image transferred to the transfer material 6 such as paper so as not to be separated from the transfer material. Usually, heat fixing is carried out by two rolls (heating roll 13 and pressure roll 14) as shown in FIG. 1, but another pressure roll is used instead of the heating roll 13. There are two types of pressure fixing, that is, fixing by pressure, flash fixing using a xenon lamp without using a roll at all, and solvent fixing using an organic solvent.

Although not necessary when cleaning is performed at the same time as development, a cleaning process for removing the toner remaining on the surface of the photosensitive drum by the cleaning device 2 may be provided between the transfer roll and the charging member. preferable. Normally, a cleaning blade is used for this cleaning device, but fur brush,
Cleaning with a magnetic brush, a cleaning roll, and static electricity has also been proposed.

In the image forming apparatus shown in FIG. 1, the surface of the photosensitive drum 1 is negatively charged uniformly by the charging roll 3 and then an electrostatic latent image is formed by the laser beam irradiating device 4. The developing device 11 develops the toner image. Subsequently, the toner image on the photosensitive drum 1 is transferred onto a transfer material 6 such as paper by the transfer roll 5, and is fixed on the transfer material by two fixing rolls (heating roll 13 and pressure roll 14). If necessary, the transfer residual toner remaining on the surface of the photosensitive drum is cleaned by the cleaning device 2, and then the next image forming cycle is started.

Although the image forming apparatus shown in FIG. 1 is for monochrome, the image forming method of the present invention can be applied to a color image forming apparatus such as a copying machine or a printer for forming a color image. As a color image forming apparatus, a multi-development method in which a multi-color toner image is developed on a photoconductor and is transferred to a transfer material at once is used. There is a multiple transfer system in which the transfer of the color toner is repeated for the number of colors of the color toner. In the multiple transfer method, a transfer material is wound around a transfer drum and transfer is performed for each color, and primary transfer is performed for each color on an intermediate transfer body, and a multicolor image is formed on the intermediate transfer body. After the formation, the intermediate transfer method in which the secondary transfer is performed at once, the developing devices are arranged in tandem around the photoconductor,
There is a tandem system in which a transfer material is sucked and conveyed by a transfer conveyor belt and each color is sequentially transferred to the transfer material. Among these, a tandem type image forming apparatus capable of performing image formation at high speed is preferable.

FIG. 2 is a schematic view showing an example of a tandem type color image forming apparatus to which the image forming method of the present invention can be applied. The tandem-type color image forming apparatus is provided with an image forming unit including a laser beam irradiating device 4, a photosensitive drum 1, a developing device 11, and a cleaning device 2 as many as the number of toner colors used. The image forming units are normally arranged in the order of yellow, magenta, cyan, and black along the conveyor belt 15, and the images formed by the image forming units are attracted to the conveyor belt and conveyed. The transfer roll 7 transfers the image onto the transfer material 7 so that the transfer material 7 is sequentially overlaid and fixed. As described above, the transfer material is generally conveyed by a conveyor belt, but it can also be adsorbed on the transfer drum and conveyed. in this case,
The image forming units are arranged in order along the transfer drum. In addition, Y of the alphabet shown in FIG.
M, C, and K respectively correspond to the colors of toner of the image forming units, namely yellow, magenta, cyan, and black.

Since the image forming method of the present invention can obtain an image in which cleaning failure does not occur on the photoconductor or the charging roll, when applied to the color image forming method, a clear image is obtained without toner color mixing. be able to.

[0062]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In addition, part and%
Is weight basis unless otherwise specified. In this example, the following methods were used for evaluation.

1. Colored particle characteristics (1) Average particle size of toner and particle size distribution Volume average particle size (dv) of colored particles and particle size distribution, that is, ratio of volume average particle size to number average particle size (dp) (dv / dp)
Was measured by Multisizer (manufactured by Beckman Coulter, Inc.). The measurement using this Multisizer was performed with an aperture diameter of 100 μm, a medium of Isoton II, and a concentration of 1.
The conditions were 0% and the number of measured particles: 100,000. (2) Average sphericity The average sphericity (Sc / Sr), which is the value obtained by dividing the area (Sc) of a circle whose diameter is the absolute maximum length of the particle by the actual projected area (Sr) of the particle, is Take an electron micrograph of the image of the image and analyze it with the image processing and analysis device Luzex IID
It is an average value of 100 particles measured and calculated under the conditions of (area ratio of particles to frame area: maximum 2%, total number of processed particles: 100) (manufactured by Nireco).

2. Toner characteristics (1) Using an angle of repose powder measuring machine (Hosokawa Micron, trade name "Powder Tester PT-E")
Put a sample funnel on it, and stack a standard sieve with a mesh size of 250 μm on it. After fixing, vibrate and pass through the sample funnel.
The toner was dropped on a circular table having a diameter of 8 cm to form a pile of toner. The angle between the ridgeline of the mountain and the horizon was taken as the angle of repose and measured with laser light. The amplitude of the vibration was adjusted so that the mountain of the toner would not collapse, and the falling speed of the toner was adjusted. (2) Loose apparent specific gravity Using the powder measuring instrument described above, place a sample chute on the stand of this device, stack a standard sieve with a mesh opening of 250 μm, and after fixing, vibrate and drop it, and drop it in a specified container (cup 100 ml). ) To receive. Adjust the falling speed so that the cup becomes piled up in 20 to 30 seconds, after finishing, flatten the pile with a cutter, measure the weight of the powder, convert the weight per volume and measure the apparent apparent specific gravity did.

3. Image quality evaluation (1) Fog and print density Copy paper was set in a commercially available non-magnetic one-component development type printer (manufactured by Oki Data Co., Ltd., trade name "Microline 24DX"), and a temperature of 10
After being left for one day under the environment of (L / L) at temperature of ℃ and humidity of 20% and in the environment of (H / H) at temperature of 35 ° C. and humidity of 80%, continuous printing is performed at 5% density every 1,000 sheets. Solid printing is performed, printing is stopped halfway, and the toner in the non-image area on the photoconductor after development is peeled off with an adhesive tape (Scotch Mending Tape 810-3-18 manufactured by Sumitomo 3M Ltd.), which is then peeled off. I put it on a new copy paper. The whiteness (B%) of the printing paper to which the adhesive tape was attached was measured with a whiteness meter (manufactured by Nippon Denshoku Co., Ltd.), and in the same manner, the whiteness (A) of the printing paper to which only the adhesive tape was attached (A %) Was measured. The difference ΔY between the whiteness (A%) and the whiteness (B%) was calculated, and the number of sheets in which this value exceeded 15% was counted, and at the same time, the print density was measured. For those in which continuous printing was performed up to 20,000 sheets and fog did not occur, printing was stopped after 20,000 sheets and the print density was measured. The print density was measured using a McBeth transmission type image density measuring device.

(2) Resolution Simultaneous black solid printing performed to evaluate the above-mentioned fog and print density, and at the same time, lines of 2 dots and 4 dots,
Two-dot and four-dot white lines were printed, and it was observed by an optical microscope whether the image quality of them was reproduced, and the following criteria were evaluated. ◯: A 2-dot line and a 2-dot white line are reproduced. Δ: A 2-dot line and a 2-dot white line are not reproduced, but a 4-dot line and a 4-dot white line are reproduced. X: Neither the 4-dot line nor the 4-dot white line is reproduced.

Example 1 80 parts of styrene, 20 parts of n-butyl acrylate, 0.6 part of divinylbenzene and polymethacrylic acid ester macromonomer (trade name "AA6" manufactured by Toagosei Kagaku Kogyo Co., Ltd., Tg = 94 ° C.) ) 0.25
Parts of core polymerizable monomer, carbon black (manufactured by Mitsubishi Chemical Co., trade name "# 25B") 7 parts, charge control resin (manufactured by Fujikura Kasei Co., trade name "FCA-626-NS"; weight average (Molecular weight 24,000, glass transition temperature 60 ° C) 2
Parts, t-dodecyl mercaptan 1 part, and dipentaerythritol hexamyristate 10 parts were dispersed by a bead mill at room temperature to obtain a polymerizable monomer composition for core.

On the other hand, 50 parts of ion-exchanged water was added to an aqueous solution of 9.9 parts of magnesium chloride dissolved in 250 parts of ion-exchanged water.
An aqueous solution having 6.0 parts of sodium hydroxide dissolved therein was gradually added with stirring to prepare a dispersion liquid of magnesium hydroxide colloid. The particle size distribution of the produced colloid is S
When measured with an ALD particle size distribution measuring device (manufactured by Shimadzu Corporation), the particle size Dp50 in which the cumulative number counted from the small particle size side is 50% is 0.36 μm, and the particle size Dp90 is 90%.
Was 0.68 μm. On the other hand, 2 parts of methyl methacrylate and 65 parts of water are finely dispersed by an ultrasonic emulsifier,
An aqueous dispersion of a polymerizable monomer for shell was obtained. Dp90 of the droplets of the polymerizable monomer for shell was 1.6 μm.

The polymerizable monomer composition for core was added to the magnesium hydroxide colloidal dispersion obtained above,
After stirring until the liquid droplets became stable, 5 parts of t-butylperoxy-2-ethylhexanoate (trade name “Perbutyl O” manufactured by NOF CORPORATION) was added thereto, and then 15,
An Ebara Milder (trade name "MDN303V", manufactured by EBARA CORPORATION) rotating at 000 rpm was passed for a total residence time of 3 seconds, and the passed dispersion was passed through the inner nozzle into the original stirring tank and the jet speed was 0. The liquid was recirculated at a rate of 0.5 m / s to form droplets of the monomer composition. The tip of the inner nozzle was adjusted so as to be located 50 mm below the surface of the dispersion liquid in the stirring tank, and droplets were formed by circulating 10 times. A cooling jacket was attached around the Ebara Milder, and cooling water of about 15 ° C was circulated.

1 part of sodium tetraborate decahydrate was added to the magnesium hydroxide colloidal dispersion liquid in which the core monomer composition was dispersed to form droplets, and the mixture was placed in a reactor equipped with a stirring blade. After the polymerization reaction was started at 85 ° C. and the polymerization conversion rate reached almost 100%, a water-soluble initiator (manufactured by Wako Pure Chemical Industries, trade name “Wako Pure Chemical Industries, Ltd.” was added to the aqueous dispersion of the polymerizable monomer for shell. VA-086 "= 2,2'-azobis (2-methyl-
N (2-hydroxyethyl) -propionamide))
0.2 parts was dissolved and it was added to the reactor. After continuing the polymerization for 4 hours, the reaction was stopped to obtain an aqueous dispersion of core-shell type colored particles. While stirring the aqueous dispersion of the colored particles obtained above, sulfuric acid was added to adjust the pH to 4 or less, acid washing was carried out, water was separated by filtration, and 500 parts of ion-exchanged water was newly added to reslurry. And washed with water.
After that, dehydration and water washing were repeated several times again, and the solid content was separated by filtration, followed by drying at 45 ° C. for 2 days and night, and the volume average particle diameter (dv) was 9.7 μm. Core-shell type colored particles having a distribution (dv / dp) of 1.10 and an average sphericity of 1.12 were obtained.

100 parts of the obtained core-shell type colored particles were used as an external additive with a hydrophobicity of 45% and a volume average particle diameter of 12 n.
m silica (product name “R10 manufactured by Nippon Aerosil Co., Ltd.
4 ") 0.7 part and 0.3 part of styrene-methyl methacrylate copolymer particles having a volume average particle size of 0.4 µm are added,
Rotation speed 1400 using Henschel mixer for 10 minutes
The toner was obtained by mixing at rpm. The obtained toner had an angle of repose of 16 ° and a loose apparent specific gravity of 0.43 g / cc. The image quality of the obtained toner was evaluated, and the results are shown in Table 1.

(Example 2) In Example 1, in producing the magnesium hydroxide colloid, the amount of magnesium chloride was 9.9 to 10.6 parts, and the amount of sodium hydroxide was 6.0 to 6.4 parts. Colored particles and toner were obtained in the same manner as in Example 1 except that the above was changed to. Table 1 shows the characteristics of the obtained colored particles and toner, and the results of image quality evaluation.

Comparative Example 1 100 parts of styrene acrylate copolymer (softening point 145 ° C., glass transition point 64 ° C.),
Carbon black (trade name "# 25" manufactured by Mitsubishi Chemical Corporation)
7 parts, 1 part of low molecular weight polypropylene (“Viscole 550P” manufactured by Sanyo Kasei Co., Ltd.) as a release agent, charge control agent (Hodogaya Chemical Co., Ltd., trade name “Spiron Black T”)
RH ") was mixed to prepare a colored particle raw material, which was kneaded by a melt extruder and extruded in a plate shape on a cooling belt to be cooled and solidified. Then, the cooled and solidified colored particle raw material is crushed by a hammer mill, roughly crushed to a weight average particle diameter of about 300 μm, crushed by an air jet crusher, and the crushed toner raw material is classified by a classifier. Then, colored particles having a volume average particle size of 9.3 μm, a particle size distribution (dv / dp) of 1.23, and an average sphericity of 1.38 were obtained.

To 100 parts of the obtained colored particles, 0.7 part of silica having a hydrophobicity of 45% and a volume average particle diameter of 12 nm (manufactured by Nippon Aerosil Co., Ltd., trade name "R104") as an external additive and a volume average particle diameter are used. 0.3 part of styrene-methyl methacrylate copolymer particles having a size of 0.4 μm was added and mixed using a Henschel mixer for 10 minutes at a rotation speed of 1400 rpm to obtain a toner. The toner obtained has an angle of repose of 41.
The apparent apparent specific gravity was 0.38 g / cc. Moreover, as a result of evaluating the image quality of the obtained toner, a large amount of fog was generated during continuous printing.
The printing was stopped and the print density and resolution were not evaluated.

(Comparative Example 2) In Example 1, when the magnesium hydroxide colloid was prepared, the amount of magnesium chloride was 9.9 to 12.9 parts and the amount of sodium hydroxide was 6.0 to 7.8 parts. Colored particles and toner were obtained in the same manner as in Example 1 except that the above was changed to. Table 1 shows the characteristics of the obtained colored particles and toner, and the results of image quality evaluation.

(Comparative Example 3) In Example 1, when the magnesium hydroxide colloid was prepared, the amount of magnesium chloride was changed from 9.9 to 7.9 parts and the amount of sodium hydroxide was changed to 6.
Colored particles and a toner were obtained in the same manner as in Example 1 except that the content was changed from 0 to 4.8 parts. Table 1 shows the characteristics of the obtained colored particles and toner, and the results of image quality evaluation.

(Comparative Example 4) 80 parts of styrene, 20 parts of n-butyl acrylate, 0.6 part of divinylbenzene and polymethacrylic acid ester macromonomer (trade name "AA6" manufactured by Toagosei Kagaku Kogyo KK, Tg = 94 ° C). ) 0.25
Part of a polymerizable monomer, carbon black (manufactured by Mitsubishi Chemical Corporation, trade name "# 25"), the charge control resin 6 described above.
Part, 1 part of t-dodecyl mercaptan, and 10 parts of dipentaerythritol hexamyristate were heated to 70 ° C. and dissolved and dispersed. Then, this was placed in a container equipped with a high shear mixing device (trade name "TK homomixer" manufactured by Tokushu Kika Kogyo Co., Ltd.)
After mixing for 5 minutes while heating at 60 ° C., 3 parts of azobisisobutyronitrile was dissolved. Separately, 2 parts of silica fine particles (manufactured by Nippon Aerosil Co., Ltd., trade name "# 200") as a dispersant was added to 500 parts of ion-exchanged water, heated to 60 ° C, and then stirred under the aforesaid TK homomixer. The polymerizable monomer composition was added, and the mixture was further stirred at 8000 rpm for 1 hour. Then, this mixed solution was put into a reactor equipped with a stirring blade and the polymerization was completed while stirring to obtain an aqueous dispersion of colored particles. A sodium hydroxide solution was added to the obtained aqueous dispersion to dissolve the dispersant, and filtration and washing were repeated, followed by drying to obtain a volume average particle diameter (dv) of 9.0.
Colored particles having a particle diameter distribution (dv / dp) of 1.48 and an average sphericity of 1.12.

To 100 parts of the obtained colored particles, 0.2 part of silica (manufactured by Nippon Aerosil Co., Ltd., trade name "R104") having a hydrophobicity of 45% and a volume average particle diameter of 12 nm was added as an external additive, and Henschel was added. Rotation speed 1 for 10 minutes using a mixer
The toner was obtained by mixing at 400 rpm. The obtained toner has a repose angle of 43 ° and a loose apparent specific gravity of 0.37 g /
It was cc. The image quality of the obtained toner was evaluated, and the results are shown in Table 1.

[0079]

[Table 1]

From the toner evaluation results in Table 1, the following can be seen. The toner of Comparative Example 1 in which the sphericity of the colored particles is larger than the range defined by the present invention, the repose angle of the toner is large, and the loose apparent specific gravity is small, the durable printing is performed in both the H / H environment and the L / L environment. A lot of fog occurred in the middle of. The toner of Comparative Example 2 in which the volume average particle diameter of the colored particles is smaller than the range specified in the present invention, the angle of repose is large, and the loose apparent specific gravity is small, the durable printing is performed in both the H / H environment and the L / L environment. The print density afterwards is low,
Fog is also likely to occur. The toner of Comparative Example 3 in which the volume average particle diameter of the colored particles is larger than the range defined by the present invention and the repose angle of the toner is small, fog occurs after durable printing in both the H / H environment and the L / L environment. Easy to do and poor resolution. The toner of Comparative Example 4, in which the particle size distribution of the colored particles is larger than the range specified in the present invention, the repose angle of the toner is large, and the apparent specific gravity is small, is durable printing in both the H / H environment and the L / L environment. The print density after that is low, and fog is likely to occur. On the other hand, Examples 1 to 1 of the present invention
The toner of No. 2 was used in both the H / H environment and the L / L environment even after performing the durable printing on 20,000 sheets.
It can be seen that the print density is high, fog hardly occurs, and the resolution of the obtained image quality is high.

[0081]

According to the present invention, even when durable printing is performed at high speed for a long period of time, an excellent image having high transferability, no decrease in print density and fog, and high resolution can be obtained. A toner that can be used and an image forming method using the toner are provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a tandem type color image forming apparatus according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Photosensitive drum 2..Cleaning device 3 ... Charging roll 4 ... Laser light irradiation device 5 ... Transfer roll 7 ... Development roll 8 ... Layer thickness control blade 9 ... Supply roll 10 ... Toner 11..Developing device 13 ... Heating roll 14 ... Pressure roll 15 ... Conveyor belt

Claims (4)

[Claims] 1. A volume average particle diameter (dv) of 8.5 to 10.
0 μm, and the particle size distribution (dv / dp) is 1.0 to 1.
3 and the average sphericity (Sc / Sr) obtained by dividing the area (Sc) of the circle having the diameter of the absolute maximum length of the particle by the substantial projected area (Sr) of the particle is 1.0 to 1.3. And the external additive, the angle of repose is 15 to 30 °, and the loose apparent specific gravity is 0.40 to 0.45 g /
Toner that is cc. 2. The toner according to claim 1, wherein the colored particles are core-shell type colored particles. 3. An external additive is silica fine particles (A) having a volume average particle diameter of primary particles of 5 to 18 nm, and 0.1 to 10.
3. The toner according to claim 1, further comprising fine particles (C) having a volume average particle diameter of 1.0 μm of primary particles. 4. An electrostatic latent image is formed on the surface of a uniformly charged photoconductor, the electrostatic latent image is developed into a toner image by toner, and the obtained toner image is transferred by a transfer roll. An image forming method of fixing after transfer to a toner, wherein the toner has a volume average particle diameter (dv) of 8.5 to 10.0 μm.
m, the particle size distribution (dv / dp) is 1.0 to 1.3, and the area (S) of the circle whose diameter is the absolute maximum length of the particle.
c) is divided by the substantial projected area (Sr) of the particles, the average sphericity (Sc / Sr) is 1.0 to 1.3, and the external additive is included. 30 ° and a loose apparent specific gravity of 0.40 to 0.45 g / c
An image forming method characterized by being c.