JPH1010773A - Negative charge toner and negative charge developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a negative charge toner excellent in environmental stability and flowability, not causing the sticking of a toner component to a photoreceptor, voids in a solid image and fog after printing even at the time of repetitive use and giving a superior image. SOLUTION: Negative charge toner particles are mixed with at least three kinds of additives to obtain the objective negative charge toner. The additives are 1st inorg. fine particles having 10-30nm number average particle diameter, 2nd inorg. fine particles having 10-90nm number average particle diameter and 3rd inorg. fine particles having 100-1,000nm number average particle diameter. The quantity of electric charges of the 1st inorg. fine particles by blow-off charge is -2,000 to -500μC/g, that of the 2nd inorg. fine particles is -300 to +50μC/g and that of the 3rd inorg. fine particles is -10 to +100μC/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negatively chargeable toner for developing an electrostatic latent image formed on an electrostatic latent image carrier, a negatively chargeable developer, and a method of manufacturing the negatively chargeable toner. .

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image formed on an electrostatic latent image carrier such as a photosensitive member is developed using toner, and the toner image is transferred onto a recording member such as recording paper. The forming method is widely used in copiers, printers, facsimile machines, and the like, and is also employed in a full-color image forming apparatus that reproduces a multicolor image by overlapping a plurality of color toners. Among these image forming apparatuses, a regular development type image forming apparatus using a positively chargeable and highly durable amorphous silicon photoreceptor as an electrostatic latent image carrier, and an organic photosensitive element having a negatively chargeable and high performance and low cost. In a reversal developing type image forming apparatus using a body, a negatively charged toner having excellent characteristics is required. In particular, the image forming apparatus of the reversal development method is employed in a digital image forming apparatus that forms an electrostatic latent image in dot units,
An excellent negatively chargeable toner is desired as such a digital toner.

As described above, the negatively chargeable toner used in various image forming apparatuses is required to have various characteristics. One of such requirements is high fluidity. For example, in a digital image forming apparatus,
The area gradation method and the laser intensity modulation method are adopted as the multi-gradation image reproduction method, but high fluidity is required for the toner in any method in order to perform excellent gradation image reproduction. In particular, in the laser intensity modulation method, a higher fluidity is required because gradation reproduction is performed by a change in toner adhesion amount corresponding to a change in the amount of charge of the latent image due to laser intensity modulation.

Further, a full-color toner needs to have a light-transmitting property, so that a binder resin used for toner particles needs to have a sharp melt property. However, toner having such characteristics tends to cause toner agglomeration due to stress in the developing device during printing, and the likelihood of white spots due to the agglomerates in solid images. There is.

[0005] Further, such a toner has a small fluctuation range of the toner charge amount with respect to environmental changes such as temperature and humidity, does not cause the toner component to adhere to the photoreceptor (BS), and has a printing durability. Are required to have characteristics such as no background fogging due to developer deterioration.

However, there are various technical problems to satisfy the above-mentioned characteristics. For example, in order to improve the fluidity, it is effective to externally add a fluidizing agent such as silica fine particles or titania fine particles to the toner to increase the amount thereof, but the amount of the external additive added to the toner increases. To do
The amount of external additive that passes through the cleaning blade and adheres to the surface of the photoreceptor also increases, and this external additive becomes a nucleus, and other toner components adhere to the edge of the photoconductor during cleaning to remove the skirt. The problem of sticking to the body (BS) becomes significant. When the amount of the external additive is reduced so that BS does not occur, not only does the fluidity become insufficient, but also toner agglomeration occurs due to stress in the developing device during printing,
The problem of white spots in a solid image occurs. Further, in a high-fluidity toner having a large amount of silica fine particles added thereto, the silica fine particles and the like are easily fixed (spent) to the carrier by printing, so that the chargeability of the carrier to the toner is reduced and the problem of background fog is remarkable. Become.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a negatively charged toner and a negatively charged developer which solve the above-mentioned problems. That is, the present invention provides a negatively chargeable toner and a negatively chargeable developer which are excellent in environmental stability, have a small fluctuation range of the toner charge amount due to a change in humidity or temperature, and have solved the problems such as white spots on an image. Aim. Another object of the present invention is to provide a negatively chargeable toner and a negatively chargeable developer which are excellent in fluidity and solve the problem of adhesion of a toner component to a photoreceptor. Also, the present invention
An object of the present invention is to provide a negatively charged toner and a negatively charged developer which solve the problem of background fog due to printing. Another object of the present invention is to provide a negatively charged toner and a negatively charged developer suitable for full-color image formation.

[0008]

According to the present invention, there is provided a negatively charged toner obtained by mixing and adding at least three types of external additives to negatively charged toner particles.
0-30 nm first inorganic fine particles, and a number average particle size of 10
-90 nm second inorganic fine particles, and a number average particle size of 100
And third inorganic fine particles having a blow-off charge of -2000 to -50 nm.
0 μC / g, the blow-off charge amount of the second inorganic fine particles is −3
The present invention relates to a negatively chargeable toner having a blow-off charge amount of -10 to +100 µC / g of the third inorganic fine particles.

The present invention also provides a negatively charged developer comprising negatively charged toner particles, at least three types of external additives mixed and added to the toner particles, and magnetic carrier particles, wherein the external additive is used. A first inorganic fine particle having a number average particle size of 10 to 30 nm, a second inorganic fine particle having a number average particle size of 10 to 90 nm, and a third inorganic fine particle having a number average particle size of 100 to 1000 nm.
Wherein the first inorganic fine particles have a blow-off charge of -2000 to -500 µC / g, and the second inorganic fine particles have a blow-off charge of -300 to +50 µC / g.
g, the blow-off charge amount of the third inorganic fine particles is -10 to +1
It relates to a negatively charged developer which is 00 μC / g. The present invention also relates to a negatively charged toner and a negatively charged developer used in a full-color image forming apparatus that reproduces a multicolor image using magenta, cyan, yellow, and black toners.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention solves the above-mentioned problems by using inorganic fine particles having a specific number average particle diameter and a specific charge as externally added and mixed with negatively charged toner particles. It is. In the present invention, the number average particle diameter of the primary particles as the first inorganic fine particles is 10 to 30 n.
m, preferably an inorganic fine particle having a particle diameter of 10 to 25 nm, and a charge amount of iron powder by a blow-off method of -2000 to -50.
0 μC / g, preferably −1500 to −800 μC / g
Use those. By adding such first inorganic fine particles, the fluidity and negative charge of the toner can be improved, and the lubricating property of the cleaning blade to the photoconductor can be imparted. If the average particle size is larger than 30 nm, the effect of improving the fluidity of the toner and the effect of improving the lubricity of the cleaning blade become insufficient. On the other hand, when the average particle size is smaller than 10 nm, embedding in toner particles is apt to occur, and the change in powder characteristics at the time of printing endurance becomes large, and environmental stability is lowered.

As the first inorganic fine particles, fine particles of silica, titania, alumina, barium titanate, magnesium titanate, calcium titanate, strontium titanate, chromium oxide, cerium oxide, magnesium oxide, zirconium oxide, or the like can be used alone or in combination. Two or more kinds can be used in combination. Silica fine particles are preferred from the viewpoint of improving fluidity and imparting negative charge to toner particles.

The amount of the first inorganic fine particles added to the toner particles is 0.1 to 3.0% by weight, preferably 0.3 to 2.0% by weight.
0% by weight. If the amount is less than 0.1% by weight, the effect of the above-mentioned addition is insufficient. If the amount is more than 3% by weight, BS is generated or fog is liable to occur during printing.

The second inorganic fine particles have a number average particle diameter of primary particles of 10 to 90 nm, preferably 30 to 80 nm.
And the charge amount of the iron powder by the blow-off method is -300.
To +50 μC / g, preferably -200 to −30 μC / g
g. By using such second inorganic fine particles, the problem of image density reduction due to charge-up in a low-temperature and low-humidity environment due to the first inorganic fine particles is eliminated, the problem of white spots is prevented, and the heat-resistant storage stability is improved. Can be improved. If the average particle size is larger than 90 nm, the coverage of the toner will be reduced, and the environmental stability, heat storage stability and white spot prevention effect will be reduced. If it is smaller than 10 nm, the stirring stress in the developing device during printing use will be reduced. As a cause, the particles are easily embedded in the toner particles, and as a result, the effect of suppressing the aggregation of the developer is reduced, and white spots are easily generated in the solid image.

As such second inorganic fine particles, particles having a number average particle size of 10 to 30 nm and a number average particle size of 30 to 30 nm are used.
Particles of 90 nm, preferably 35 to 80 nm may be used in combination.

As the second inorganic fine particles, fine particles of silica, titania, alumina, barium titanate, magnesium titanate, calcium titanate, strontium titanate, chromium oxide, cerium oxide, magnesium oxide, zirconium oxide, or the like can be used alone or in combination. Although two or more kinds can be used in combination, it is preferable to use titania fine particles from the viewpoint of improving environmental stability. As the titania fine particles, anatase titania, rutile titania, amorphous titania and the like can be used, and anatase titania is preferable.

The amount of the second inorganic fine particles to be added to the toner particles is 0.1 to 3.0% by weight, preferably 0.3 to 2.0% by weight.
0% by weight. If the amount is less than 0.1% by weight, the effect of the above-mentioned addition is insufficient, and if it is more than 3% by weight, BS is likely to be generated. Further, it is preferable to use the first inorganic fine particles and the second inorganic fine particles so that the total added amount is 1.0 to 3.0% by weight, from the viewpoint of improving fluidity and preventing white spots.

The first inorganic fine particles and the second inorganic fine particles are preferably surface-treated with a hydrophobizing agent.
In particular, it is desirable to use those having a hydrophobicity of 50 or more. By using the inorganic fine particles thus hydrophobized, it is possible to prevent the toner charge amount from lowering even at high temperature and high humidity.

The degree of hydrophobicity in the present invention is measured by a methanol wettability method. First, methanol is dropped into water in which a sample is dispersed, and the weight of methanol required to wet the entire sample is measured. The percentage of the weight of methanol in water and methanol at this time was defined as the degree of hydrophobicity.

As the hydrophobizing agent for treating the surface of the inorganic fine particles, a silane coupling agent, a titanate coupling agent, silicone oil, silicone varnish and the like can be used. Examples of the silane coupling agent include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane, methyltrimethoxysilane, methyltriethoxysilane, and isobutyl Trimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n
-Butyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltrimethoxysilane,
Vinyl trimethoxy silane, vinyl triethoxy silane, γ-methacryloxypropyl trimethoxy silane, vinyl triacetoxy silane, etc. can be used,
As the silicone oil, for example, dimethylpolysiloxane, methylhydrogenpolysiloxane, methylphenylpolysiloxane and the like can be used.

In order to surface-treat the inorganic fine particles with the above-mentioned hydrophobizing agent, for example, the hydrophobizing agent is diluted with a solvent, the above-mentioned diluent is added to the inorganic fine particles and mixed, and the mixture is heated, dried and crushed. A dry method, a wet method of dispersing inorganic fine particles in an aqueous system to form a slurry, adding and mixing a hydrophobizing agent, heating and drying, and then disintegrating the resulting mixture can be used. In particular, when titania is used as the inorganic fine particles, it is preferable to perform the hydrophobizing treatment in an aqueous system from the viewpoints of uniformity of the surface treatment of the hydrophobizing agent, prevention of aggregation of the titania particles, and the like.

In the toner of the present invention, in addition to the first and second inorganic fine particles, a third inorganic fine particle has a number average particle diameter of 100 to 1,000 nm, preferably 100 to 1000 nm.
８００800 nm, the charge amount of the iron powder by the blow-off method is -10 to +100 μC / g, preferably +5 to +8
Use 0 μC / g. By using such third inorganic fine particles in combination, it is possible to solve the problem of BS and the problem of fog at the time of printing durability caused by the addition of the first and second inorganic fine particles. It is considered that the problem of the BS can be solved because the third inorganic fine particles have a function of reducing the amounts of the first and second inorganic fine particles that pass through the blade during blade cleaning. Also,
The problem of fogging during printing can be solved because the above-mentioned third inorganic fine particles having the specific chargeability adhere to the toner surface, so that even when the external additive is spent on the carrier, Since the third inorganic fine particles have a charge property of negatively charging the toner particles, it is considered that fog based on a decrease in the toner charge amount is eliminated. From such a viewpoint, it is preferable that the third inorganic fine particles have chargeability on the positive side of the carrier particles. In the present invention, the reason why the third inorganic fine particles adhere to the toner particle surface even though they are large-diameter fine particles is that the first inorganic fine particles have a strong negative charge This is considered to be because the fine particles have the opposite polarity of the chargeability to the first inorganic fine particles in the chargeability based on the toner particles. Therefore, it is preferable that the third inorganic fine particles are mixed after the first inorganic fine particles are mixed with the toner particles. Further, the second inorganic fine particles may be used together with the first inorganic fine particles or the third inorganic fine particles.
What is necessary is just to carry out the mixing treatment with the inorganic fine particles, and after mixing the first inorganic fine particles, mixing the second inorganic fine particles,
Thereafter, the third inorganic fine particles may be mixed.

If the average particle size of the third inorganic fine particles is smaller than 100 nm, the effect of preventing BS becomes insufficient, and
When m is larger than m, the amount of toner particles coated and the adhesion are reduced, and the above-mentioned effects become insufficient.If image formation is repeatedly performed, the transfer drum is used during blade cleaning or in a full-color image forming apparatus. At the time of pressure transfer, the photosensitive member is easily damaged.

Examples of the third inorganic fine particles include fine particles of silica, titania, alumina, barium titanate, magnesium titanate, calcium titanate, strontium titanate, chromium oxide, cerium oxide, magnesium oxide, zirconium oxide, and the like. They can be used alone or in combination of two or more. Since the third inorganic fine particles have a number average particle diameter of 100 to 1000 nm and are somewhat large, they exist as primary particles and have an average particle diameter in the above range. Agglomerates) whose average particle size is in the above range,
Alternatively, primary particles and aggregates of the primary particles may be mixed and the average particle size may be in the above range. In particular, fine particles containing sintered aggregates of primary particles and having the above-described chargeability are preferable from the above viewpoint, and strontium titanate fine particles are preferable as such fine particles. As for other fine particles, those whose surface is treated with, for example, an aminosilane coupling agent or aminosilicone oil to adjust the chargeability can be suitably used.

The third inorganic fine particles are added in an amount of 0.3 to 5.0% by weight, preferably 0.5 to 3.0% by weight, based on the colored resin particles. If the amount is less than 0.3% by weight, the effect of preventing BS and toner scattering and fogging will be insufficient. If the amount is more than 5% by weight, damage to the photoreceptor and the effect on the chargeability of the toner will be large. Is not preferred.

As the binder resin used in the toner of the present invention, known resins can be used, for example, styrene resins, acrylic resins such as alkyl acrylates and alkyl methacrylates, styrene-acrylic copolymer resins, and polyester resins. Resins, epoxy resins, silicon resins, olefin resins, amide resins and the like can be mentioned, and these can be used alone or in combination.

In the present invention, the binder resin used for full-color toners such as cyan toner, magenta toner, yellow toner and black toner has a number average molecular weight (Mn) of 3,000 to 6,000, preferably 35 to 6,000.
00 to 5500, the ratio Mw / Mn of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 2 to 6, preferably 2.5
~ 5.5, glass transition point 50 ~ 70 ° C, preferably 5
It is preferable to use a polyester resin or an epoxy resin having a temperature of 5 to 65 ° C and a softening point of 90 to 110 ° C, preferably 90 to 105 ° C.

The number average molecular weight of the binder resin is 3000
If it is smaller than that, the image portion is peeled off when a full-color solid image is bent, causing image defects (bending fixability is deteriorated). If it is larger than 6000, the heat melting property at the time of fixing is reduced and the fixing strength is reduced. I do. If Mw / Mn is less than 2, high-temperature offset is likely to occur, and if it is greater than 6, sharp melt characteristics at the time of fixing deteriorate, and the light transmittance of the toner and the color mixing at the time of full-color image formation decrease. I will. On the other hand, if the glass transition point is lower than 50 ° C., the heat resistance of the toner becomes insufficient, and the toner tends to aggregate during storage. If the glass transition point is higher than 75 ° C., the fixability decreases and the color mixture during full-color image formation. Is reduced. If the softening point is lower than 90 ° C., high-temperature offset is likely to occur, and 1
If the temperature is higher than 10 ° C., the fixing strength, the light transmittance, the color mixing, and the gloss of a full-color image are reduced. As the polyester resin, those containing etherified diphenols as an alcohol component and aromatic dicarboxylic acids as an acid component can be used.

As the above etherified diphenols,
For example, polyoxypropylene (2,2) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2) -2,2-bis (4-hydroxyphenyl) propane and the like can be mentioned.

Further, together with the above etherified diphenols, diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, etc. Kind,
Sorbitol, 1,2,3,6-hexanetetrol,
1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,2
4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2
-Methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene and the like may be used.

As the aromatic dicarboxylic acids, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, acid anhydrides thereof and lower alkyl esters thereof can be used.

Further, aliphatic dicarboxylic acids such as fumaric acid, maleic acid, succinic acid, alkyl or alkenyl succinic acids having 4 to 18 carbon atoms, and aliphatic dicarboxylic acids such as acid anhydrides or lower alkyl esters thereof are used. You may.

Further, 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid,
2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanenetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, Polyvalent carboxylic acids such as 4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, anhydrides thereof and lower alkyl esters are used as acid values of polyester resins. Adjustment of,
For the purpose of improving the resin strength, a small amount may be used as long as the translucency is not impaired. When used for a black toner, it is not necessary to particularly consider the translucency.

As the colorant used in the toner of the present invention,
Known ones can be used and are not particularly limited.

It is preferable that the colorant used in the color toner has improved dispersibility of the colorant by a master batch process or a flushing process. The content of the colorant is preferably 2 to 15 parts by weight based on 100 parts by weight of the binder resin.

The toner of the present invention may contain desired additives such as a charge control agent, a magnetic powder, and a wax, in addition to the colorant.

Known charge control agents can be used, and are not particularly limited. The charge control agent used for the color toner is the color tone of the color toner,
A colorless, white or light-colored charge control agent which does not adversely affect light transmittance can be used. It is preferable to use a charge control agent such as a system compound. The salicylic acid metal complex is described in, for example,
JP-A-127726, JP-A-62-145255 and the like; calixarene-based compounds described in, for example, JP-A-2-201378 and the like; -221
No. 967 and the like, and fluorine-containing quaternary ammonium salt-based compounds are described, for example, in JP-A-3-1162.
Publications described in Japanese Patent Application Laid-Open No. H10-260, etc. can be used.

When such a charge control agent is added,
It is preferable to use 0.1 to 10 parts by weight, preferably 0.5 to 5.0 parts by weight, based on 100 parts by weight of the binder resin.

The volume average particle diameter of the toner according to the present invention is preferably adjusted to 5 to 10 μm, more preferably 6 to 9 μm, from the viewpoint of high definition reproducibility of an image.

The toner of the present invention can be used as a two-component developer toner used by mixing with a carrier, or as a one-component developer toner not using a carrier.

As the carrier used in combination with the toner of the present invention, those conventionally known as carriers for two-component developers can be used. For example, carriers made of magnetic particles such as iron and ferrite can be used. A resin-coated carrier obtained by coating such magnetic particles with a resin,
Alternatively, a binder-type carrier formed by dispersing a magnetic fine powder in a binder resin or the like can be used. Among these carriers, a silicone resin as a coating resin,
Use of a resin-coated carrier using a copolymer resin (graft resin) of an organopolysiloxane and a vinyl monomer or a polyester-based resin, or a binder-type carrier using a polyester-based resin as a binder resin is a toner spent. Carriers coated with a resin obtained by reacting an isocyanate with a copolymer resin of an organopolysiloxane and a vinyl monomer are preferred from the viewpoint of durability, environmental stability and spent resistance. Is preferred. As the vinyl monomer, it is necessary to use a monomer having a substituent such as a hydroxyl group reactive with isocyanate. Further, it is preferable to use a carrier having a volume average particle diameter of 20 to 100 μm, preferably 30 to 80 μm, from the viewpoint of securing high image quality and preventing carrier fogging.

[0041]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited thereto.

(Production of Polyester Resin) A 2-liter four-necked flask was equipped with a reflux condenser, a water separator, a nitrogen gas inlet tube, a thermometer, and a stirrer. , 2) -2,2
-Bis (4-hydroxyphenyl) propane (PO),
Polyoxyethylene (2,0) -2,2-bis (4-hydroxyphenyl) propane (EO), fumaric acid (F
A) and terephthalic acid (TPA) in a molar ratio of 5:
The reaction mixture was charged so that the ratio became 5: 5: 4, and the reaction was carried out by heating and stirring while introducing nitrogen into the flask. The progress of the reaction was monitored while measuring the acid value. When the acid value reached a predetermined value, the reaction was terminated, and the number average molecular weight Mn was 4,800, and the ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn was calculated. 4.
0, a polyester resin having a glass transition point of 58 ° C and a softening point of 100 ° C was obtained.

The number-average molecular weight and weight-average molecular weight were determined by gel permeation chromatography (807-I
(T type: manufactured by JASCO Corporation), the column was kept at 40 ° C., tetrahydrofuran was flowed at 1 kg / cm ³ as a carrier solvent, and 30 mg of a sample to be measured was dissolved in 20 ml of tetrahydrofuran. 5m
g was introduced together with the above-mentioned carrier solvent, and determined in terms of polystyrene.

The glass transition point was measured using a differential scanning calorimeter (DSC-200: manufactured by Seiko Instruments Inc.).
About 0 mg, the measurement was performed at a heating rate of 10 ° C./min using alumina as a reference, and the shoulder value of the main absorption peak was defined as the glass transition point.

For the softening point, use a flow tester (CF
T-500: manufactured by Shimadzu Corporation) for 1.0 g of a sample, using a die having a pore diameter of 1.0 mm and a pore length of 1.0 mm, a temperature rising rate of 3.0 ° C./min, and a preheating time of 18
The measurement was performed under the conditions of 0 seconds, a load of 30 kg, and a measurement temperature range of 60 to 140 ° C., and the temperature at which the sample flowed out by １ ／ was defined as the softening point.

(Production of Toner Particle A) The above polyester resin and magenta pigment (CI Pigment Red 18)
4) was charged and kneaded in a pressure kneader so that the weight ratio of resin: pigment was 7: 3. The obtained kneaded material was cooled and pulverized by a feather mill to obtain a pigment master batch.

93 parts by weight of the polyester resin, 10 parts by weight of the pigment masterbatch, and 2 parts by weight of a charge control agent (zinc salicylate complex: E-84: manufactured by Orient Chemical Industries) were mixed using a Henschel mixer. The mixture was kneaded with a screw extruder. The resulting kneaded product was cooled, coarsely pulverized by a feather mill, finely pulverized by a jet mill, and classified to obtain toner particles A having a volume average particle size of 8.5 μm. The blow-off charge of the toner particles with respect to the iron powder was -53 [mu] C / g. Further, the amount of blow-off charge was measured at -20 μC / g when the iron powder was replaced with a carrier obtained in a carrier production example described later.

The measurement of the blow-off charge amount is based on the blow-off method and is based on a standard iron powder carrier (Z150 / 250).
25g (made by Powder Tech) and 50mg of sample 25c
After placing in a polybin of c and mixing with a turbuler mixer for 1 minute, 0.1 g of the sample was placed in a measuring container having a 400 mesh stainless screen, and a nitrogen gas flow rate of 1.0 kgf / cm ² and an inflow time of 60 seconds were used. And blow-off charge meter (TB-200: manufactured by Toshiba Chemical Corporation)
Was measured.

(Production of Toner Particles B) 100 parts by weight of the above polyester resin, 3 parts by weight of carbon black (Mogal L: manufactured by Cabot), and a charge control agent (zinc salicylate complex: E-84: manufactured by Orient Chemical Industries) 2 After mixing parts by weight with a Henschel mixer, the mixture was kneaded with a twin-screw extruder. After cooling the obtained kneaded material, it is roughly pulverized by a feather mill, finely pulverized by a jet mill, and classified to obtain toner particles B having a volume average particle diameter of 8.5 μm.
I got The blow-off charge of the toner particles with respect to the iron powder was -48 [mu] C / g. Further, when the amount of blow-off charge was measured by replacing the iron powder with the carrier obtained in a carrier production example described later, it was -18 μC / g.

(Adjustment of Toner) The toner particles obtained above were mixed with an external additive shown in Table 1 in an amount shown in Table 2 using a Henschel mixer.
The toners of Examples and Comparative Examples were obtained through a 00 mesh circular vibrating screen. The mixing was performed by mixing the first inorganic fine particles with the toner particles using a Henschel mixer, and then adding and mixing the second inorganic fine particles and the third inorganic fine particles. In the comparative example in which the first inorganic fine particles were not added, all the inorganic fine particles were collectively mixed with the toner particles. The charge amount in Table 1 is the blow-off charge amount of each inorganic fine particle measured by the method described above.

[0051]

[Table 1]

[0052]

[Table 2]

(Example of Carrier Production) Capacity 500 equipped with a stirrer, condenser, thermometer, nitrogen inlet tube and dropping device
100 parts by weight of methyl ethyl ketone was charged into a ml flask. Separately, methyl methacrylate at 80 ° C under nitrogen atmosphere
36.7 parts by weight, 5.1 parts by weight of 2-hydroxyethyl methacrylate, 58.2 parts by weight of 3-methacryloxypropyltris (trimethylsiloxy) silane and 1,1'-azobis (cyclohexane- A solution obtained by dissolving 1 part by weight of 1-carbonitrile in 100 parts by weight of methyl ethyl ketone was dropped into a reaction vessel over 2 hours and aged for 5 hours.

To the obtained resin, isophorone diisocyanate / trimethylolpropane adduct (IPDI / TMP system: NCO% = 6.1%) was added as a crosslinking agent to O.
After adjusting the H / NCO molar ratio to be 1/1, it was diluted with methyl ethyl ketone to prepare a coat resin solution having a solid ratio of 3% by weight.

Fired ferrite powder F-300 as core material
(Volume average particle size: 50 μm, manufactured by Powder-Tech Co.), and the above coating resin solution was applied with a spira coater (manufactured by Okada Seiko Co., Ltd.) so that the coating resin amount to the core material was 1.5% by weight.・ Dried. The obtained carrier was calcined at 160 ° C. for 1 hour in a hot-air circulation oven. After cooling, the ferrite powder bulk was
The mixture was crushed using a sieve shaker equipped with a 5 μm screen mesh to obtain a resin-coated carrier.

(Aggregation noise (white spots)) Each toner was mixed with the carrier obtained in the above-mentioned production example at a toner mixing ratio of 7% by weight.
To prepare a developer. This developer was used under a N / N environment (25 ° C., 50%) using a digital full-color copying machine CF900 (manufactured by Minolta).
/ W15% images were printed on 5000 sheets. After printing, three full-size solid images (ID = 1.2) are printed on A3 paper.
Evaluation was performed according to the following criteria, and the average value of the three sheets was used as the evaluation result. The evaluation criterion is x when the image unevenness (white spot) having an ID of 1/2 or less of the solid image ID of 2 mm ² or more in the solid image occurs, and the white spot does not occur. Are observed in the image where nuclei of aggregates of about 0.3 μm are observed and the surrounding image density is slightly reduced at three or more places in the image. Those that did not occur at all were marked with ◎. Table 3 shows the results.

(Environmental Stability) The developer prepared in the same manner as above was used under CF / L900 under L / L environment (1
(0 ° C., 15%), an image of B / W 15% was formed. The image density (ID) of the obtained image is determined by a Macbeth reflection densitometer R
Measured by D-900, the image density is 1.2 or more,
1.0 or more and less than 1.2 were evaluated as Δ, and less than 1.0 was evaluated as x. In addition, under the H / H environment (30
(85 ° C., 85%), 5000 images of B / W 15% were formed. The white part of the obtained image was evaluated by visual observation, and the result was evaluated as follows: ○: no fogging occurred in the image; Δ: slight fogging but no practical problem; Is indicated by x. Table 3 shows the results.

(Fixing of Toner Component on Photoconductor (BS))
For the developer adjusted in the same manner as above, CF900
5,000 images of B / W 15% under N / N environment using
Printed. Evaluation was performed by visual observation on the photoreceptor at the beginning and after printing and evaluation by electron microscope observation, and evaluation by visual observation of a solid image at the beginning and after printing was performed. The external additives were not fixed on the photoreceptor by electron microscope observation. ◎ The external additives were fixed on the photoreceptor by electron microscope observation, but the external additive was fixed by visual observation. O: No image noise was observed and no image noise was generated. O: External additives and toner components were fixed on the photoreceptor by visual observation. When the external additive and toner component were fixed on the top, and this was recognized as noise on the image, it was evaluated as x. Table 3 shows the results.

(Evaluation of fog after printing) With respect to the developer prepared in the same manner as above, 10,000 images of B / W 15% images were printed under N / N environment using CF900. The image obtained after printing was evaluated as ○ when there was no fog on a white background portion, evaluated as 若干 when slightly fogged but had no practical problem, and evaluated as x when fogged and had a practical problem. . Table 3 shows the results.

[0060]

[Table 3]

[0061]

According to the present invention, a negatively charged toner and a negatively charged developer which are excellent in environmental stability, have a small fluctuation range of the toner charge amount due to humidity and temperature changes, and solve the problem such as white spots on an image. Can be provided. Further, according to the present invention, it is possible to provide a negatively chargeable toner and a negatively chargeable developer which are excellent in fluidity and solve the problem of adhesion of a toner component to a photoreceptor. Further, according to the present invention, it is possible to provide a negatively charged toner and a negatively charged developer which solve the problem of fog after printing. Further, according to the present invention, a negatively charged toner and a negatively charged developer suitable for full-color image formation can be provided.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Fukuda 2-3-113 Azuchicho, Chuo-ku, Osaka-shi Osaka International Building Minolta Co., Ltd.

Claims (6)

[Claims] 1. A negatively charged toner obtained by mixing and adding at least three types of external additives to negatively charged toner particles.
This external additive is composed of first inorganic fine particles having a number average particle diameter of 10 to 30 nm, second inorganic fine particles having a number average particle diameter of 10 to 90 nm, and third inorganic fine particles having a number average particle diameter of 100 to 1000 nm. The first inorganic fine particles have a blow-off charge of -2000 to -500 [mu] C / g, the second inorganic fine particles have a blow-off charge of -300 to +50 [mu] C / g, and the third inorganic fine particles have a blow-off charge of -10 to +100 [mu] C.
C / g is a negatively chargeable toner. 2. The negatively chargeable toner according to claim 1, wherein the first inorganic fine particles and the second inorganic fine particles are surface-treated with a hydrophobizing agent, and each has a degree of hydrophobicity of 50 or more. . 3. The first inorganic fine particles have a blow-off charge of -1500 to -800 .mu.C / g, the second inorganic fine particles have a blow-off charge of -200 to -10 .mu.C / g, and the third inorganic fine particles have a blow-off charge of +10. Up to +100 μC / g
2. The negatively chargeable toner according to claim 1, wherein: 4. The developer according to claim 1, wherein the developer is used in a full-color image forming apparatus that reproduces a multicolor image using magenta toner, cyan toner, yellow toner, and black toner. The negatively-charged toner as described in the above. 5. A negatively charged developer comprising negatively charged toner particles, at least three kinds of external additives mixed and added to the toner particles, and magnetic carrier particles, wherein the external additive is a number average particle. A first inorganic fine particle having a diameter of 10 to 30 nm, a second inorganic fine particle having a number average particle diameter of 10 to 90 nm, and a third inorganic fine particle having a number average particle diameter of 100 to 1000 nm; The blow-off charge is -2000 to -500 µC / g, the blow-off charge of the second inorganic fine particles is -300 to +50 µC / g, and the blow-off charge of the third inorganic fine particles is -10 to +100 µC / g.
g of a negatively charged developer. 6. The negatively chargeable developer according to claim 5, wherein the third inorganic fine particles have a more positive charge than the magnetic carrier.