JPH08286423A - Magnetic developer - Google Patents

Abstract

PURPOSE: To obtain a toner almost free from defectively charged toner particles and having sharp particle size distribution and satisfactory flowability by emulsifying and dispersing a dispersion liq. contg. a resin binder, magnetic powder and an org. solvent and removing the org. solvent from the resultant oil-in-water type emulsion while heating and stirring the emulsion. CONSTITUTION: A resin binder, magnetic powder and an org. solvent are dissolved or dispersed in a water-insoluble org. solvent and the resultant dispersion liq. is emulsified and dispersed in an aq. dispersive liq. to form an oil-in-water type emulsion. The org. solvents are then removed from the emulsion while heating and stirring the emulsion to obtain the objective magnetic developer. An arom. solvent such as toluene or xylene or a halogenated hydrocarbon solvent such as methylene chloride, carbon tetrachloride, 1,2-dichloro-ethane or chloroform is preferably used as the water-insoluble org. solvent. At the time of forming the emulsion, a dispersion stabilizer or an auxiliary dispersion stabilizer is preferably added.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to electrophotography, electrostatic recording,
The present invention relates to a magnetic developer in electrostatic printing or the like, specifically a magnetic carrier or a magnetic toner.

[0002]

2. Description of the Related Art Magnetic toners and magnetic carriers are known as magnetic developers used in electrophotography and the like.

As a method for producing these magnetic developers,
After kneading magnetic powder and the like in a binder resin, pulverizing method to pulverize into fine particles, method to mix particles into magnetic particles when polymerizing particles by suspension polymerization of monomers, or binder into organic solvent A spray method and the like are known in which a resin is dissolved and magnetic powder is dispersed in the resin to be granulated in a hot air stream.

However, in the pulverization method, it is difficult to make the dispersed state of the magnetic powder uniform and the magnetic properties become unstable. Alternatively, the magnetic powder is liable to be exposed on the surface of the particles, and the fluidity is inferior in terms of powder characteristics. Further, in the polymerization method, the magnetic powder influences the polymerization reaction, and it is difficult to make the dispersed state of the magnetic powder uniform, and the magnetic force characteristics are likely to become unstable.
Alternatively, in order to suppress the influence on the polymerization reaction, the amount of magnetic powder to be filled in the magnetic particles has to be small, and when using the magnetic particles as a magnetic toner that does not require much magnetic force, there is not much problem. This is not the case, but this is a great disadvantage when manufacturing a magnetic carrier that requires a large magnetic force. Furthermore, the spray method is convenient for obtaining coated magnetic particles (for example, coated carrier) obtained by coating the surface of magnetic powder with a resin, but dispersed magnetic particles obtained by dispersing magnetic powder inside a resin are used. It is difficult to obtain particles, and even if the amount of magnetic powder added is increased and the coating system is configured as a dispersion system, the magnetic properties are not uniform because the dispersed state of the magnetic powder is not uniform, and the particle diameter Will become larger.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in the fine particles in which the magnetic powder is dispersed in the binder resin, the magnetic fine particles have a uniform dispersion state of the magnetic powder and stable magnetic characteristics. Aim to get.

Another object of the present invention is to obtain magnetic fine particles having excellent fluidity, which were difficult to produce by the conventional pulverization method.

Another object of the present invention is to obtain magnetic fine particles containing a high concentration of magnetic powder, which was difficult to produce by the conventional polymerization method.

Another object of the present invention is to obtain magnetic fine particles in which a uniform dispersion state is maintained, which was difficult to produce by the conventional spraying method.

[0009]

According to the present invention for solving the above-mentioned various objects, a dispersion containing a binder resin, a magnetic powder and an organic solvent is formed, and the dispersion is emulsified and dispersed in an aqueous medium to obtain O / W. It is a magnetic developer obtained by obtaining a type emulsion (oil-in-water type emulsion) and then removing the organic solvent in the emulsion while heating and stirring.

[0010]

In the past, an emulsion dispersion granulation method has been proposed in JP-A-3-15078 as a method for producing fine particles.
In this method, a polymer solution prepared by dissolving a polymer in a water-insoluble organic solvent is emulsified and dispersed in an aqueous dispersion to form an O / W type emulsion, and heat is applied to the O / W type emulsion while agitating the organic solution. It is carried out by evaporating the solvent and precipitating polymer particles.

The outline of the method for producing a magnetic developer according to the present invention is basically the same as this. That is, first, the magnetic powder and the resin are dispersed in an organic solvent, and if necessary, an additive such as a charge control agent is dissolved to form a dispersion liquid, and the obtained dispersion liquid is emulsified and dispersed in an aqueous medium. Droplets are formed as / W emulsion.

Next, stirring is continued until the droplets have a desired particle size distribution, and then the temperature is increased to remove the organic solvent. Then, the dispersant is filtered to remove the dispersant by washing with water and then dried to produce the magnetic powder-containing resin particles.

When the emulsification dispersion granulation method as described above is applied to the production of magnetic particles in the present invention, the dispersion state of the magnetic powder is other particle production method (crushing method, polymerization method, spray method, etc.). It was made as a result of the first discovery by the present inventor that it is significantly improved as compared with.

Hereinafter, the present invention will be described in more detail based on embodiments. The solvent used in producing the magnetic developer of the present invention may be any solvent that is insoluble or hardly soluble in water and dissolves the binder resin as described below, for example, toluene, xylene, benzene, etc. Aromatic solvents, carbon tetrachloride, methylene chloride,
Halogenated hydrocarbons such as 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene and dichloroethylidene, acetic acid esters such as methyl acetate and ethyl acetate, ketones such as methyl ethyl ketone and isobutyl ketone Etc., and various organic solvents may be used alone or in combination of two or more, and among these, aromatic solvents such as toluene and xylene and halogenated methylene chloride, 1,2-dichloroethane, chloroform, carbon tetrachloride and the like. Hydrocarbons are particularly preferably used.

Among these solvents, in order to improve the dispersion state of the magnetic powder, it is necessary to select a solvent which has a good compatibility with the magnetic powder and also forms uniform droplets in the solvent. preferable. Specifically, since the specific gravity of the magnetic powder is high, the dispersibility of the magnetic powder is better as the specific gravity of the solvent is higher, and a solvent having a specific gravity of 1 or more is selected.

As the aqueous dispersion used to form the O / W type emulsion, water can be basically used, but it may contain a water-soluble organic solvent to such an extent that the emulsion is not destroyed. . For example, water, water / methanol mixed liquid (weight ratio 50/50 to 100/0), water / ethanol mixed liquid (weight ratio 50/50 to 100 /), water / acetone mixed liquid (weight ratio 50/50 to 100/0) , Water / methyl ethyl ketone mixture (weight ratio 70/30 to 100/0)
Etc. can be used.

Further, when forming such an O / W emulsion, it is possible to add a dispersion stabilizer or a dispersion stabilizing auxiliary, if necessary. The dispersion stabilizer is one having a hydrophilic colloid in the aqueous dispersion, and particularly gelatin, gum arabic, agar, a cellulose derivative (for example,
Hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc.), synthetic polymers (polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyacrylic acid salts, polymethacrylic acid salts, etc.), calcium phosphate salts and the like. A surfactant is usually used as a dispersion stabilizer, and a natural surfactant such as saponin, a nonionic surfactant such as alkylene oxide, glycerin, and glycidol, a carboxylic acid, a sulfonic acid, a phosphoric acid, and a sulfuric acid ester. Base,
Examples thereof include anionic surfactants containing an acidic group such as a phosphate ester group. In particular, a combination of the dispersion stabilizer and the dispersion stabilizer auxiliary is preferably calcium phosphate and an anionic surfactant (sodium dodecylbenzenesulfonate).

When the pH of the aqueous dispersion containing the calcium phosphate salt used here is adjusted to preferably 5 to 14, more preferably 6 to 12, the dispersion stability is good and the particle size distribution becomes sharp. In order to adjust to a suitable pH, for example, alkali such as calcium hydroxide or sodium hydroxide may be used, or acid such as hydrochloric acid or phosphoric acid may be used.

When the magnetic powder is contained as in the present invention, the emulsifying power is required more than the usual emulsifying dispersion. Therefore,
A sparingly soluble inorganic salt having a higher emulsifying power than the polymer dispersion stabilizer, such as calcium phosphate, is particularly preferable.

The magnetic developer according to the present invention contains the above components, that is, the binder resin, the magnetic powder (and the coloring agent, the charge control agent, the offset preventing agent, etc. added in the case of the magnetic toner) as described above. It is dissolved or dispersed in a non-water-soluble organic solvent as described above, and the obtained dispersion is emulsified and dispersed in an aqueous dispersion to form an O / W type emulsion, and then the non-water-soluble emulsion is removed from the droplets of the emulsion. It is produced by removing the water-soluble organic solvent.

To dissolve and disperse the magnetic powder and the resin in the non-water-soluble organic solvent, a ball mill, a sand grinder,
A general kneading / stirring device such as an ultrasonic homogenizer or a medium bead mill can be used.

The solid content concentration in this magnetic powder-containing dispersion is such that the water-insoluble organic solvent is removed from the droplets by heating an O / W type emulsion obtained by emulsifying and dispersing this resin solution in an aqueous dispersion. At this time, it is necessary to set so that the liquid droplets can be easily solidified into fine particles. Particularly, the concentration of the binder resin component in this resin solution is 5 to 50% by weight, more preferably about 10 to 40% by weight. To be done.

The ratio of the volume (V _p ) of the dispersion containing magnetic powder to the volume (V _w ) of the aqueous dispersion when preparing the O / W type emulsion is V _p / V _w ≦ 1 Preferably, it is desirable that 0.3 ≦ V _p / V _w ≦ 0.7. That is, if V _p / V _w > 1, then stable O
This is because there is a high possibility that a / W-type emulsion cannot be formed, a phase transition occurs in the middle, or a W / O-type emulsion is formed.

After forming the O / W type emulsion as described above, the temperature of the entire system is gradually raised to completely remove the non-water-soluble organic solvent in the droplets to form magnetic particles. Alternatively, it is also possible to spray the O / W type emulsion in a dry atmosphere, completely remove the water-insoluble organic solvent in the droplets to form magnetic particles, and evaporate and remove the aqueous dispersion. . A dry atmosphere in which the O / W emulsion is sprayed includes air, nitrogen, carbon dioxide gas, combustion gas, etc. at 20 ° C.
A gas heated to about 250 ° C. to about 250 ° C., in particular, various air streams heated to a temperature above the boiling point of the highest boiling solvent used are generally used.

After forming the magnetic particles in this way, if necessary, further steps such as washing, drying and classification are carried out to obtain a sharp particle size distribution of the electrostatic charge image developing carrier and the magnetic toner according to the present invention. Can be obtained.

Hereinafter, preferred embodiments in the case where the magnetic developer according to the present invention is a magnetic toner used in electrophotography and a preferred embodiment in the case of a magnetic carrier will be described.

When the magnetic developer according to the present invention is a magnetic toner for electrostatic image development, the average particle size is 2 to 40 μm.
And more preferably about 4 to 20 μm.

The binder resin contained in the magnetic developer according to the present invention is not particularly limited as long as it is soluble in the water-insoluble organic solvent used and is unnecessary or hardly soluble in water. Conventionally used styrene resin, (meth) acrylic resin, styrene- (meth) acrylic copolymer resin, olefin resin, polyester resin, amide resin, polycarbonate resin, polyether resin , Polyvinyl acetate resin, polysulfone resin, epoxy resin,
Resins such as polyurethane resins and urea resins can be used alone or in combination of two or more kinds.

Among these binder resins, in order to improve the dispersion state of the magnetic powder, a resin having not only good compatibility with the magnetic powder but also forming uniform droplets in the solvent should be selected. Is preferred. Specifically, it is a polyester resin, a styrene-acrylic copolymer resin, or an epoxy resin. Other resins have no problem in a production method such as a kneading pulverization method, but it becomes difficult to achieve both dispersibility of forming uniform droplets in a solvent and compatibility with magnetic powder, that is, a state of emulsion dispersion. This is because there is a risk that it will deteriorate.

The binder resin has a glass transition point (T
g) is about 50 to 70 ° C., and its number average molecular weight (Mn) is 1,000 to 50,000, preferably 300.
It is desirable that the molecular weight distribution (Mw / Mn) represented by the ratio of 0 to 20,000 and Mn and the weight average molecular weight (Mw) is 2 to 60. However, from the viewpoint of compatibility with magnetic powder, it is preferable that the molecular weight is relatively high, and those having a weight average molecular weight of 9000 to 20000 are suitable for granulation. Tg
Is less than 50 ° C., the heat resistance of the obtained toner is lowered, while if it exceeds 70 ° C., the fixing property of the obtained toner is lowered. If Mn is less than 1000, high-temperature offset is likely to occur in the obtained toner, while if it exceeds 50,000, low-temperature offset is likely to occur. Further, if Mw / Mn is less than 2, the non-offset region may be narrow in the obtained toner, while if it exceeds 60, low temperature offset is likely to occur.

It is more preferable that Mw / Mn is 2 to 5 when the toner is an oil coating and fixing toner, and Mw is Mn when the oilless fixing toner is a toner.
/ MN is more preferably 20 to 50.

As the magnetic powder contained in the magnetic developer of the present invention, various conventionally known materials such as magnetite, γ-hematite and various ferrites can be used.
It is particularly desirable that the magnetic powder has a particle size of 0.05 to 1 μm, more preferably 0.1 to 0.5 μm. The content of such magnetic powder is 10 with respect to the total weight of the toner.
It is desirable that the content is ˜50% by weight, more preferably 10 to 40% by weight.

The colorant that can be contained in the magnetic toner for developing an electrostatic charge image according to the present invention can be an organic or inorganic pigment or dye as shown below, but the magnetic powder itself is colored ( (Black), it is not essential to obtain a normal black toner. That is, as the black pigment, carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, non-magnetic ferrite,
Magnetic ferrite, magnetite, etc. are used. As other colorants, known dyes such as acidic or basic dyes, metal complex dyes, acidic or basic mordant dyes, or pigments of various colors such as white pigments such as titanium white and zinc white may be used. .

These colorants may be used alone or in combination of two or more, but usually 1 to 20 parts by weight, more preferably 2 to 15 parts by weight are used per 100 parts by weight of the binder resin component. Preferably. That is, if the amount is more than 20 parts by weight, the fixing property of the toner is deteriorated,
On the other hand, if the amount is less than 1 part by weight, the desired image density may not be obtained.

The toner particles according to the present invention may contain a charge control agent, if necessary, in addition to the above-mentioned magnetic powder and binder resin. Generally, charge control agents (CC
As A), various substances are known as substances capable of giving a positive or negative charge by triboelectric charging, and examples of the positive charge control agent include nigrosine base EX (manufactured by Orient Chemical Industry Co., Ltd.) and the like. Dyes, quaternary ammonium salts P-51 (manufactured by Orient Chemical Industry Co., Ltd.), quaternary ammonium salts such as Copy Charge PXVP435 (manufactured by Hoechst KK), alkoxylated amines, alkylamides, molybdic acid chelate pigments, and PLZ10.
01 (manufactured by Shikoku Kasei Kogyo Co., Ltd.) and the like, and examples of the negative charge control agent include Bontron S-22 (manufactured by Orient Chemical Industry) and Bontron S-34 (manufactured by Orient Chemical Industry). ), Bontron E-81 (manufactured by Orient Chemical Industry Co., Ltd.), Bontron E-
84 (manufactured by Orient Chemical Industry), Spiron Black T
Metal complexes such as RH (Hodogaya Chemical Co., Ltd.), thioindigo pigments, quaternary ammonium salts such as Copy Charge NX VP434 (manufactured by Orient Chemical Co., Ltd.), Bontron E-89 (manufactured by Orient Chemical Co., Ltd.), etc. Examples thereof include calixarene compounds, fluorine compounds such as magnesium fluoride, carbon fluoride, and the like, but of course the invention is not limited thereto. In addition, as the metal complex serving as the negative charge control agent, other than those shown above, an oxycarboxylic acid metal complex, a dicarboxylic acid metal complex, an amino acid metal complex, a diketone metal complex, a diamine metal complex, an azo group-containing benzene-benzene can be used. Those having various structures such as a derivative skeleton metal complex and an azo group-containing benzene-naphthalene derivative skeleton metal complex are included.

These are preferably contained in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the binder resin contained in the toner. That is, if the content of CCA is less than 0.1 parts by weight, sufficient charging performance may not be obtained, while if the content of any of the CCA exceeds 5 parts by weight, the spent may not be printed. This is because there is a possibility that the charge may be generated and the charge amount may be reduced.

If necessary, an offset preventing material may be added to the magnetic toner for developing an electrostatic image according to the present invention. As the material for preventing offset, polyolefin wax, carnauba wax, chandelier wax, higher fatty acid wax, higher fatty acid ester wax and the like can be used alone or in combination of two or more, and particularly low molecular weight polypropylene, polyethylene, or Polyolefin waxes such as oxidized polypropylene and oxidized polyethylene are preferable from the viewpoint of compatibility with magnetic powder.

The magnetic toner for developing an electrostatic image according to the present invention may be further added (typically, externally added) with a fluidizing agent and a cleaning aid. Further, as a fluidizing agent, silicon oxide (silica), nitric oxide (titania),
Aluminum oxide (alumina), zinc oxide or the like is used. The fluidizing agent may be hydrophobized with a coupling agent, a surfactant, or the like. As a cleaning aid,
Polystyrene fine particles and polymethylmethacrylate fine particles are used. The addition amount of these fluidizing agents and cleaning aids is 0.1 with respect to 100 parts by weight of the toner mother particles.
About 20 parts by weight is suitable.

On the other hand, when the magnetic developer of the present invention is manufactured as a carrier, its average particle size is 20 to 100 μm.
The magnetic toner can be manufactured without changing the basic structure of the magnetic toner as described above except that the thickness is about 40 to 80 μm.

When manufactured as a carrier,
The binder resin preferably has Tg of 50 to 75 ° C., preferably 63 to 72 ° C., Mn of 3000 to 5000, preferably 3500 to 4000, and Mw / Mn of 2 to 3. If the Tg is less than 50 ° C, the heat resistance of the obtained carrier is lowered, while if it exceeds 75 ° C, the particle size distribution of the obtained carrier becomes large and the yield is lowered. If Mn is less than 3,000, the stress resistance of the carrier obtained is insufficient, whereas if it exceeds 5,000, the yield may be reduced. Further Mw / Mn
If the value exceeds 3, there is a fear that the particle size distribution is large. It should be noted that a low Mw / Mn does not cause any particular problem in the characteristics of the carrier to be obtained, but a resin having a Mw / Mn of less than 2 is generally difficult to obtain, and therefore it is preferable to set it within the above range.

[0041]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. Example 1: Production of magnetic carrier (1) 100 g of a styrene-acrylic copolymer resin (Hymer 73, manufactured by Sanyo Kasei Co., Ltd.) was dissolved in 400 g of methylene chloride,
After adding and mixing 4 g of carbon black and 200 g of magnetic powder (RB-BL, manufactured by Titanium Industry Co., Ltd.), the mixture was placed in a wet bead mill and mixed for 3 hours to disperse to obtain a uniform mixed dispersion liquid.
The obtained dispersion was mixed as a dispersion stabilizer into a dispersion prepared by dissolving 0.1 g of sodium lauryl sulfate (manufactured by Wako Pure Chemical Industries, Ltd.) in 1000 g of a 4% solution of calcium hydroxide phosphate having a pH of 10, and mixing the TK auto homomixer (special The number of revolutions was adjusted so that the above-mentioned uniform dispersion liquid would form droplets having an average of 40 to 60 μm, and the product was suspended in water. Then, 60-65 ℃, 140mmHg-70mm
After removing methylene chloride under Hg condition, dissolving calcium hydroxide phosphate with concentrated hydrochloric acid, and repeating filtration / washing with water, a slurry dryer (disper coat,
The particles were dried by Nisshin Engineering Co., Ltd. to obtain magnetic particles having an average particle size of 50 μm, which were used as a magnetic carrier (1).

As a result of the roasting test, the internal addition rate of the magnetic powder in the obtained magnetic particles was 95% or more based on the charged amount. As a result of observing the particle cross section with a transmission electron microscope (TEM), the particle diameter of the magnetic powder internally added is
It was 0.1 to 0.3 μm.

Example 2 Production of Magnetic Carrier (2) 100 g of a styrene-acrylic copolymer resin (Hymer 73, manufactured by Sanyo Chemical Co., Ltd.) was dissolved in 400 g of methylene chloride,
Carbon black 4g, Methylenediphenyl-4,4 '
-Diisocyanate 10 g and magnetic powder (RB-BL, manufactured by Titanium Industry Co., Ltd.) 200 g were added and mixed, and then placed in a wet bead mill and mixed for 3 hours to disperse to obtain a uniform mixed dispersion. The obtained dispersion was used as a dispersion stabilizer in 1000 g of a 4% solution of polyvinyl alcohol (PVA PA-18, manufactured by Shin-Etsu Chemical Co., Ltd.) in sodium lauryl sulfate (manufactured by Wako Pure Chemical Industries, Ltd.).
Mix 0.1 g of the solution in a dispersion, and use TK Auto Homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to adjust the rotation speed so that the uniform dispersion forms droplets of 40 to 60 μm on average. And suspended in water. Then, after adding 10 g of ethylenediamine and stirring at room temperature (20 ° C. ± 2 ° C.) for 2 to 3 hours, 60 to 65 ° C. and 140 mmHg to 70 m
After removing methylene chloride under mHg conditions and repeating filtration / washing with water, the slurry was dried using a slurry dryer (Dispercoat, manufactured by Nisshin Engineering Co., Ltd.) to obtain magnetic particles having an average particle size of 50 μm. The magnetic carrier (2) was used.

As a result of the roasting test, the internal addition rate of the magnetic powder in the obtained magnetic particles was 95% or more based on the charged amount. As a result of observing the particle cross section by TEM, the particle diameter of the internally added magnetic powder was 0.1 to 0.3 μm.

Example 3: Production of magnetic toner (1) 100 g of polyester resin (NE-382, manufactured by Kao Corporation)
Dissolved in 400 g of methylene chloride, carbon black 5
g, magnetite KBC-100L (manufactured by Kanto Denka Co., Ltd.) 2
0 g and 2 g of a zinc metal complex (E-84, manufactured by Orient Chemical Industry Co., Ltd.) as a charge control agent were added and mixed, and then placed in a wet bead mill and mixed and dispersed for 3 hours to obtain a uniform mixed dispersion liquid. The obtained dispersion was used as a dispersion stabilizer in 1000 g of a 1.5% calcium hydroxide calcium phosphate solution having a pH of 9 and sodium dodecylbenzenesulfonate (manufactured by Wako Pure Chemical Industries, Ltd.).
1 g was mixed in the dissolved dispersion, and the number of revolutions was adjusted using TK Auto Homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) so that the uniform dispersion forms droplets having an average of 3 to 12 μm. Suspended in water. Thereafter, 500 g of a 5% tricalcium phosphate solution having a pH of 9 was added, methylene chloride was removed under the conditions of 35 to 40 ° C. and atmospheric pressure (760 mmHg ± 5 mmHg), and calcium hydroxide phosphate was dissolved with concentrated hydrochloric acid, followed by filtration. / After repeated washing with water, the particles were dried with a slurry dryer (Dispercoat, manufactured by Nisshin Engineering Co., Ltd.) to obtain magnetic particles having an average particle size of 7 μm. Then, the magnetic particles 10 thus obtained
0.3 part by weight of hydrophobic silica (H-2000, manufactured by Wacker) and hydrophobic titanium oxide (T-8) per 0 part by weight.
05, manufactured by Nippon Aerosil Co., Ltd.) 0.5 part by weight, and 1000 by a Henschel mixer (manufactured by Mitsui Miike Kakoki Co., Ltd.)
Magnetic toner (1) by processing at rpm for 1 minute
I got

As a result of the roasting test, the internal addition rate of the magnetic powder in the obtained magnetic particles was 95% or more based on the charged amount. As a result of observing the particle cross section by TEM, the particle diameter of the internally added magnetic powder was 0.1 to 0.3 μm.

Example 4: Production of magnetic toner (2) Styrene-butylmethacrylate resin (softening point 121
C., Tg 65.degree. C., Mn = 2300, Mw / Mn = 8.
5) 100 g was dissolved in 400 g of methylene chloride, 5 g of carbon black, 20 g of magnetite KBC-100L (manufactured by Kanto Denka Co., Ltd.) and 5 g of terpene diphenol as a charge control agent were added and mixed, and then placed in a wet bead mill 3
The mixture was mixed and dispersed for a time to obtain a uniform mixed dispersion liquid. The obtained dispersion liquid was added as a dispersion stabilizer to a dispersion liquid in which 0.1 g of sodium dodecylbenzenesulfonate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 1000 g of 4% solution of PVA PA-18 (manufactured by Shin-Etsu Chemical Co., Ltd.). , TK Auto Homo Mixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), and the above uniform dispersion has an average of 3 to 12 μm.
The number of rotations was adjusted so as to form the liquid droplets of and was suspended in water. Then, 60-65 ℃, 140mmHg-70m
After removing methylene chloride under mHg conditions and repeating filtration / washing with water, the particles were dried by a slurry dryer (Dispercoat, manufactured by Nisshin Engineering Co., Ltd.) to obtain magnetic particles having an average particle size of 7 μm. . Then, in the same manner as in Example 1, the hydrophobic silica and the hydrophobic titanium oxide were added to the magnetic particles thus obtained, and the mixture was treated with a Henschel mixer to obtain a magnetic toner (2).

As a result of the roasting test, the internal addition rate of the magnetic powder in the obtained magnetic particles was 95% or more based on the charged amount. As a result of observing the particle cross section by TEM, the particle diameter of the internally added magnetic powder was 0.1 to 0.3 μm.

Comparative Example 1 Production of Magnetic Carrier (3) by Grinding Method 100 g of styrene-acrylic copolymer resin (Hymer 73, Sanyo Kasei Co.) and 200 g of magnetic powder (RB-BL, Titanium Industry Co., Ltd.), 4 g of carbon black was mixed in a ball mill for 20 hours, thoroughly mixed in a three-roll mill, allowed to cool, coarsely crushed to a size of 5 mm or less in a feather mill, and then classified to give a binder having an average particle size of 37 μm. A type magnetic carrier (3) was obtained.

As a result of observing the cross section of the magnetic carrier particles obtained by TEM, the particle diameter of the internally added magnetic powder was 0.5 to 1.0 μm.

Comparative Example 2: Magnetic toner (3) obtained by a pulverization method
Styrene-butyl methacrylate resin (softening point 121
° C, Tg65 ° C, Mn = 2300, Mw / Mn = 8.
5) 100 parts by weight of carbon black (MA #
8, Mitsubishi Kasei Co., Ltd.) 8 parts by weight, zinc metal complex (E-8
4, Orient Chemical Industry Co., Ltd.) 5 parts by weight and magnetite KBC-100L (Kanto Denka Co., Ltd.) 20 parts by weight, and after thoroughly mixing with a ball mill, 140 ° C.
The kneaded material, which had been kneaded on a three-roll heated to 1, was left to cool, coarsely pulverized with a feather mill, and then finely pulverized with a jet mill. Then, air classification was performed to obtain magnetic particles having an average particle size of 8 μm. Then, with respect to 100 parts by weight of the magnetic particles thus obtained, hydrophobic silica (H-2000,
0.3 parts by weight of Wacker Co., Ltd. and 0.5 parts by weight of hydrophobic titanium oxide (T-805, manufactured by Nippon Aerosil Co., Ltd.) were added and treated with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) at 1000 rpm for 1 minute. By doing so, magnetic toner (3) was obtained.

As a result of observing the cross section of the magnetic particles obtained by TEM, the particle diameter of the internally added magnetic powder was found to be
It was 0.5 to 1.0 μm.

Reference Example 1: Production of non-magnetic toner (4) 100 g of polyester resin (NE-382, manufactured by Kao Corporation)
Was dissolved in 400 g of methylene chloride, 6 g of a phthalocyanine pigment and 2 g of a zinc metal complex (E-84, manufactured by Orient Chemical Industry Co., Ltd.) were added, and the mixture was placed in a ball mill and mixed for 3 hours to disperse to obtain a uniform mixed dispersion. Using the obtained dispersion as a dispersion stabilizer, calcium hydroxide phosphate 4 having a pH of 10
% Sodium lauryl sulfate (manufactured by Wako Pure Chemical Industries, Ltd.) 0.1 g was dissolved in 1000 g of the solution, and TK Auto Homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) was used in the dispersion, and the uniform dispersion had an average of 3 to 12 μm. The rotation speed was adjusted so as to form droplets, and the suspension was suspended in water. Then, 60-65 ℃, 14
After removing methylene chloride under the condition of 0 mmHg to 70 mmHg, dissolving calcium hydroxide phosphate with concentrated hydrochloric acid, and repeating filtration / washing with water, a slurry drying device (Dispercoat, manufactured by Nisshin Engineering Co., Ltd.) It was dried to obtain colored particles having an average particle size of 6 μm.
Next, with respect to 100 parts by weight of the colored particles thus obtained, hydrophobic silica (H-2000, manufactured by Wacker)
By adding 0.3 parts by weight and 0.5 parts by weight of hydrophobic titanium oxide (T-805, manufactured by Nippon Aerosil Co., Ltd.), and treating with a Henschel mixer (manufactured by Mitsui Miike Kakoki Co., Ltd.) at 1000 rpm for 1 minute, A non-magnetic toner (4) was obtained.

Evaluation of Carrier The toner 4 obtained in Reference Example 1 above and the carriers (1) to (3) obtained in Examples 1 and 2 and Comparative Example 1 have a toner mixing ratio of 5.0% by weight. Thus mixed to obtain a developer. The obtained developer was evaluated for the charge amount, the poorly charged toner amount, and the scattering amount in the following manner. The results obtained are shown in Table 1.

Charge amount: 30 g of the developer was put in a 50 ml polyethylene bottle and rotated at 1200 rpm for 10 minutes, and the charge amount was measured.

Amount of poorly charged toner: Adjusted in the same manner as in the above measurement of the amount of charge, 3 g of the stirred developer is set on a magnet roll having a diameter of 310 mm, and precisely weighed.
Set the counter electrode. A bias voltage of 1 kV is applied to the polarity opposite to the toner polarity, and the magnet roll is rotated at 1000 rpm.
And rotate for 1 minute. After the operation was completed, the counter electrode was precisely weighed, the difference from the initial value was calculated to determine the amount of separated toner (non-charged toner) adhering to the counter electrode, and this non-charged toner amount was calculated as a ratio to the total toner amount.

Amount of scattering: A digital dust meter (P5H2 type, manufactured by Shibata Chemical Co., Ltd.) was used to set the dust meter 10 cm away from the magnet roll, and 2 g of the developer was set on this magnet roll, 2000r magnet
Particles of the toner that generate dust when rotated at pm are read by the dust meter and the count number (cpm) per minute is measured. The amount of scattering obtained here was evaluated according to the following criteria. ◯: The amount of scattering is less than 300 cpm. Δ: The amount of scattering is 300 to 500 cpm. X: The amount of scattering exceeds 500 cpm and cannot be used. The toner and carrier thus obtained were mixed at a toner / carrier mixing ratio of 5% by weight to serve as an initial developer, and a commercially available color copying machine (CF-80, manufactured by Minolta Co., Ltd.) was used to carry out a copy test on 5,000 sheets. The amount was also measured.

[0058]

[Table 1]

As is clear from the results shown in Table 1, the toners of Examples 1 and 2 according to the present invention exhibited a sufficient amount of charge, the occurrence of poorly charged toner was extremely small, and the amount of scattered toner was small and good. there were. On the other hand, in Comparative Example 1, a large amount of poorly charged toner was generated and the amount of scattering was large, so that it was not practically usable.

Evaluation of Toners Toners (1) to (1) obtained in Examples 3 and 4 and Comparative Example 2
(3) and the carrier (3) obtained in Comparative Example 1 were mixed at a toner mixing ratio of 5.0% by weight to obtain a developer. The developer thus obtained was evaluated for the amount of charge, the amount of poorly charged toner, and the amount of scattering in the same manner as in the evaluation of the above toner. The obtained results are shown in Table 2. The toner and carrier thus obtained were mixed at a toner / carrier mixing ratio of 5% by weight to serve as an initial developer, and a commercially available color copying machine (CF-80, manufactured by Minolta Co., Ltd.) was used to carry out a copying test on 5000 sheets, and then charging was performed. The amount was also measured.

[0061]

[Table 2]

As is clear from the results shown in Table 2, the toners of Examples 3 and 4 according to the present invention exhibited a sufficient amount of charge, the occurrence of poorly charged toner was extremely small, and the amount of scattered toner was small and good. there were. On the other hand, in Comparative Example 2, a large amount of poorly charged toner was generated, and the amount of scattering was large, so that it was practically unusable.

Evaluation of Particle Characteristics of Carrier and Toner Carriers (1) to (1) obtained in Examples 1 and 2 and Comparative Example 1
The particle size distribution and fluidity of (3) and the toners (1) to (3) obtained in Examples 3 and 4 and Comparative Example 2 were evaluated.

Particle size distribution The average particle size is measured by Coulter Counter TA-II type (manufactured by Coulter Counter).
Was used to measure the relative weight distribution by particle size using a 500 μm aperture tube. The obtained results are shown in Tables 3 and 4.

[0065]

[Table 3]

[0066]

[Table 4]

As is clear from Tables 3 and 4, in the present invention, magnetic carriers and magnetic toners having a relatively sharp particle size distribution were obtained.

Fluidity The fluidity was evaluated by using a powder tester manufactured by Hosokawa Micron Co., Ltd. to measure the loose apparent specific gravity. The results are shown in Table 5.

[0069]

[Table 5]

As is clear from Table 5, in the present invention, magnetic carriers and toners having good fluidity were obtained.

[0071]

As described above, when the magnetic developer according to the present invention is used as a toner and a carrier, a sufficient charge amount can be secured with a small particle diameter, and charging defects such as scattered toner and reversely charged toner can be prevented. It is possible to provide a toner having a small amount of toner, a sharp particle size distribution, and good fluidity, and a carrier having good chargeability and good fluidity. The magnetic particles obtained by the emulsification dispersion granulation method have such an effect because of their excellent dispersibility of the magnetic particles.

[0072]

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G03G 9/10 331

Claims (3)

[Claims] 1. A dispersion containing a binder resin, magnetic powder and an organic solvent is formed, and the dispersion is emulsified and dispersed in an aqueous medium to obtain an O / W type emulsion, which is then heated and stirred in the emulsion. A magnetic developer obtained by removing the organic solvent of. 2. The magnetic developer according to claim 1, wherein the organic solvent has a specific gravity of 1 or more. 3. The magnetic developer according to claim 1, wherein the binder resin is any one selected from the group consisting of polyester resins, styrene-acrylic copolymer resins and epoxy resins. .