JP2000112174A - Electrostatic charge image developing toner and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrostatic charge image developing toner excellent in solidifying property and fixability by forming core particles by suspension polymerization, coating a certain proportion or more of the surfaces of the core particles with emulsified fine particles and carrying out heating under specified conditions. SOLUTION: An aqueous dispersion of fine particles prepared by emulsion polymerization is added to polymer particles formed by suspension polymerization and they are heated at the glass transition temperature of the polymer particles or above to coat >=95% of the surfaces of the polymer particles with the fine particles. The objective toner whose surface is substantially free from projections is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic image developing toner used in an electrophotographic machine or the like.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for a toner which can be fixed at a low temperature from the viewpoint of energy saving and high copy speed. In order to realize a low-temperature fixing toner, it is conceivable to lower the softening point of the toner binder. However, if the softening point is lowered, the toner solidifies and the storability deteriorates.
To break this relationship, capsule toner has been proposed. That is, by using a binder polymer having a low softening point as a core particle and using a polymer having a high glass transition point as a shell material, both properties are compatible. However, with the conventionally known encapsulation method, it was not possible to sufficiently achieve both of the above performances.

[0003] In the published patent publication, Sho 57-45558,
A method is described for coating particles formed by polymerization with microparticles formed by emulsion polymerization. As a method of forming the coating layer, a method of adding an inorganic salt and a method of changing the pH are described, but heating during and after the formation of the coating layer is not described. Without heat treatment, the adhered particles easily fall off, resulting in poor mechanical strength and lack of stability in actual photography.

[0004] Published Japanese Patent Application No. 63-501040 and Japanese Patent Application Laid-Open No. 1-500621 disclose 10 to 91% and 1 to 10% of the surface of particles obtained by suspension polymerization, respectively.
A method for coating the particles with fine particles is described. The purpose is to use toner particles with a rough surface to suppress adsorption to the photographic drum and to facilitate removal of toner after the transfer process. Was not intended to be compatible. Therefore, the purpose of removing the toner cannot be achieved by attaching more than 91% of the fine particles. Published patent publication Hei 10-268
42 and Published Patent Application No. 10-123748,
A method of heating by attaching fine particles to the surface of a core particle obtained by aggregating or associating polymer particles is described,
The surface of the aggregated or associated particles was not smooth, and the fine particles did not uniformly adhere to the surface. Heating the aggregated or associated particles to smooth the surface and then attaching the fine particles increases the number of steps, and it is not preferable because the smoothing takes time. There was also a problem in mechanical strength. Agglomeration,
In the method of forming core particles by association, it is difficult to lower the softening point of the core particles from the viewpoint of manufacturing, and it is suitable for a toner characterized by lowering the softening point of the core particles and coating it with shell particles having a high Tg. I didn't.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a toner having both the solidifying property (preservability) and the low-temperature fixing property of the toner. Another object is to produce a toner having no bumps on its surface, which is smooth and has sufficient mechanical strength.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the core particles are not subjected to the pulverization method, the aggregation and aggregation method of the emulsified particles, but to the suspension polymerization method. Then, after coating the surface of the core particles with emulsified fine particles at a certain ratio or more, by heating under specific conditions, a smooth toner having substantially no bump on the surface is obtained. I found something to be done.

That is, according to the present invention, by adding an aqueous dispersion of fine particles obtained by emulsion polymerization or soap-free emulsion polymerization to polymer particles obtained by suspension polymerization, 95% or more of the surface of the polymer particles is reduced. After being coated with the fine particles, there is a method for producing a toner for electrostatic image development characterized by heating to a glass transition temperature or more of the polymer particles,
Further, the present invention resides in a toner characterized in that 95% or more of the surface of polymer particles is coated with fine particles and the surface is substantially free of protrusions.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
As the polymer particles obtained by the suspension polymerization, those already known as a polymerized toner are used. Examples of the vinyl monomer as a raw material include a vinyl aromatic monomer, a (meth) acryl ester monomer, a (meth) acrylic acid monomer, and a vinyl ether monomer.
Specific examples include, for example, styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene, o, m, p
-Chlorostyrene, p-ethylstyrene, divinylbenzene, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, 2 -Hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, acrylic acid, methacrylic acid, maleic anhydride, vinyl-n-butyl ether, Vinyl phenyl ether, vinyl cyclohexyl ether, etc. It is below.

These monomers may be used alone, or two or more of them may be copolymerized. Of these monomers, it is preferable to use a styrene monomer or a (meth) acrylic ester monomer. The amount (copolymerization ratio) of these monomers used during polymerization is determined so that the following glass transition point (Tg) becomes an appropriate temperature. Particularly preferably, styrene is copolymerized in an amount of 50% by weight or more. It is also preferable to copolymerize (meth) acrylic acid, maleic anhydride, dialkylaminoalkyl (meth) acrylate, or the like in an amount of 10% by weight or less for the purpose of controlling the zeta potential.

The glass transition point (Tg) of the polymer particles
Is preferably 60 ° C. or lower, more preferably 55 ° C.
Or less, particularly preferably 50 ° C. or less and 20 ° C. or more. The softening point is preferably at most 120 ° C, more preferably at most 110 ° C, particularly preferably at most 100 ° C,
0 ° C. or higher. The glass transition point (Tg) and softening point are determined by the high Tg styrene monomer and low Tg (meth)
It can be adjusted by the copolymerization ratio of the acrylate. If the softening point and the glass transition point (Tg) are too high, the fixability will be poor, and if it is too low, the production of particles will be difficult or the fixing strength will be poor, which is not preferable. Suspension polymerization is particularly suitable for forming polymer particles under the above conditions, and core particles obtained by aggregating or associating emulsion polymerized particles preferably have a low softening point and a low glass transition point. It is not preferable because it is difficult to obtain core particles having a smooth surface.

The molecular weight distribution is not particularly limited, but preferably has a component having a molecular weight of 100,000 or more and a molecular weight peak of 500
It is 0 or more and 70,000 or less. It has a gel component and may have an insoluble component in tetrahydrofuran. Particularly in the case of black toner, a gel component is useful for preventing hot offset with respect to the fixing roller. Preferably, it is a polymer containing 5 to 60% by weight of a gel component. The weight average molecular weight is preferably from 10,000 to 100,000, and particularly preferably from 15,000 to 50,000. The molecular weight can be adjusted by the polymerization temperature, the amount of the polymerization initiator, the amount of the chain transfer agent, and the like.

The average particle size of the polymer particles is preferably 2
10 to 10 μm, particularly preferably 3 to 6 μm. The method of obtaining the core particles by the pulverization and classification method is not preferable because the classification is performed in a dry manner and then dispersed again in water to adhere the fine particles, so that the number of steps is increased. In addition, the surface cannot be encapsulated sufficiently due to the bumps.

[0013] A radical polymerization initiator is dissolved in the vinyl-based monomer, a colorant is further added, if necessary, an additive is added, and the mixture is dispersed in water using a high-speed rotary disperser.
Predetermined polymer particles are obtained by heating. At this time, it is desirable to add a water-soluble monomer such as polyvinyl alcohol or a dispersion stabilizer such as calcium phosphate to the water.

The colorant to be contained in the toner can be selected from a wide range including known ones. For example, carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue, phthalocyanine green, and high yellow are available. , Chrome yellow,
Rose bengal, triarylmethane dyes, monoazo or disazo dyes and the like can be mentioned. Further, a magnetic substance powder can be used as a coloring agent.

These colorants may be incorporated into blue, red, yellow and other color toners used in full-color development. In this case, a colorant composed of a dye or pigment having a corresponding color tone is used. The content of the colorant is usually 1 polymerizable monomer.
The amount is preferably 3 to 50 parts by weight with respect to 00 parts.

In addition to the above polymerizable monomers and colorants, the polymerizable composition of the present invention may further comprise, as additives, for example, a crosslinking agent for improving the physical properties of the polymer, a reactive prepolymer, and a low molecular weight. A release agent for preventing offset in fixing with a heating roller, such as a polyolefin or an ester wax, and a fixability improving agent can be added. In addition, a charge control agent and the like can be added as needed.

As a method of dispersing these additives such as a coloring agent in a polymerizable monomer, the above-described high-speed rotary disperser can be used. Further, a known ball mill, sand grinder mill or the like may be used. Further, as the dispersion stabilizer, an amide amine salt of a polyester, a polyamine having a polyester in a side chain, or the like may be used.

In the present invention, as a polymerization initiator for the polymerization of the above-mentioned monomer, a usual one is used within a usual temperature range. Specific examples thereof include 2,2'-azobisisobutyronitrile, 2,2'-azobis- (2,4-dimethylvaleronitrile), and dimethyl-2,2'-azobisisobutyrate. be able to. Fine particles obtained by emulsion polymerization or soap-free emulsion polymerization are adhered in water to the polymer particles (core particles) obtained by the above suspension polymerization.

The emulsifier used in the emulsion polymerization method includes:
Conventional emulsifiers may be used. As a polymerization initiator used in the emulsion polymerization or the soap-free emulsion polymerization method, a conventional water-soluble initiator, for example, a persulfate, hydrogen peroxide, hydroperoxide or the like is used. Further, a redox initiator obtained by combining a peroxide and a reducing substance may be used. Further, a polymerization accelerator such as copper sulfate may be used together.

The fine particles preferably have an average particle size of 0.0
1 μm to 1.0 μm, particularly preferably 0.03 μm
m to 0.3 μm. If the average particle diameter is too small, the effect of improving toner solidification (preservability) cannot be expected, and if it is too large, it is difficult to improve the smoothness of the toner surface, and the quality is undesirably deteriorated. The glass transition point (Tg) of the fine particles is preferably 60 ° C or higher, more preferably 60 ° C or higher and 90 ° C or lower,
Particularly preferably, it is 65 ° C. or more and 80 ° C. or less. If the glass transition point is too low, the solidification property (preservability) of the toner is poor, which is not preferable. If it is too high, the fixability is poor.

The vinyl compound that can be suitably used for the production of the fine particles is not particularly limited, and examples thereof include a vinyl aromatic monomer, a (meth) acrylic ester monomer, a (meth) acrylic acid monomer, and a vinyl ether monomer. Is raised. Specific examples include, for example, styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene, o, m, p-chlorostyrene, p-ethylstyrene, divinylbenzene, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl Acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate,
-Hydroxyethyl methacrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, acrylic acid, methacrylic acid, maleic anhydride, vinyl-n-butyl ether, vinyl phenyl ether, vinyl cyclohexyl ether and the like.

These monomers may be used alone, or two or more of them may be copolymerized. Of these monomers, it is preferable to use a styrene monomer or a (meth) acrylic ester monomer. The copolymerization ratio of these monomers is determined so that the glass transition point (Tg) falls within the above preferred range. Particularly preferably, 50% by weight or more of styrene or methyl methacrylate is copolymerized. For the purpose of controlling zeta potential, (meth) acrylic acid, maleic anhydride, dialkylaminoalkyl (meth) acrylate, etc.
It is also suitable to copolymerize in an amount of 0% by weight or less.

It is preferable that the fine particles forming the shell material contain a charge controlling agent. As the charge control agent,
Examples thereof include an amide compound, a fluorine atom-containing compound, a phenol compound, a boron-containing compound, and a metal-containing salt or complex, and those which dissolve in the vinyl compound at a polymerization temperature, particularly preferably at room temperature (25 ° C.). Is raised.

The addition amount of the charge control agent to the vinyl compound forming the fine particles for the shell material is preferably 0.5 to 20 parts by weight, more preferably 100 parts by weight of the vinyl compound.
It is 1 to 10 parts by weight. If the content of the charge control agent is too small, the effect of improving the chargeability cannot be expected. If the content is too large, the monomer will precipitate out of the system during the polymerization, and the quality of the toner will be deteriorated.

In order to adhere the fine particles obtained by emulsion polymerization or soap-free emulsion polymerization to the polymer particles obtained by suspension polymerization, the pH of water as a medium is adjusted or the stirring conditions are adjusted. However, the present invention is further characterized in that the system is heated to a temperature equal to or higher than the Tg of the polymer particles (core particles) after the attachment of the fine particles. The heating temperature is preferably 2 ° C. or more, particularly 5 ° C., higher than the Tg of the polymer particles (core particles).
More preferably, it is higher. Further, it is preferable that the softening point is lower than the softening point of the fine particles as the shell material.

Specifically, it is preferably 40 to 95 ° C., more preferably 45 to 90 ° C., and particularly preferably 50 to 90 ° C.
８０80 ° C. If not heated, the fine particles attached to the surface are easily removed during the production, and it is difficult to coat uniformly. Furthermore, the mechanical strength is poor even during toner copying, and fine particles are easily removed. Japanese Patent Application Laid-Open Publication No. Hei 10-2682 describes a method of fusing adhered fine particles by heating them at a temperature equal to or higher than Tg and lower than the decomposition point (generally, Tg to 180 ° C.).
However, heating above the softening point of the attached fine particles is not preferred because fusion of toner particles occurs.
When heated above the glass transition temperature of the polymer particles (core particles), the surface becomes sufficiently smooth and the above-mentioned problems do not occur. When heated below the softening point of the fine particles, there is also a problem of fusion due to excessive heating. Does not happen.

It is necessary that at least 95% of the surface area of the polymer particles (core particles) is covered with fine particles. It is preferably at least 99%, particularly preferably 100%. If the coverage is low, polymer particles (core particles) having a low softening point appear on the toner surface, so that the solidification property is poor and a smooth toner surface cannot be obtained, which is not preferable. The weight of the attached fine particles with respect to the weight of the polymer particles (core particles) is not particularly limited as long as the above coverage is obtained, but is preferably 0.03 times or more, more preferably 0.05 times or more, and particularly preferably. Is not less than 0.08 times and not more than 0.3 times. It is not always necessary to cover the surface with one layer, but it is not preferable to attach more than necessary because the fixability deteriorates.

It is necessary to heat above the glass transition point of the polymer particles to provide a substantially bumpless surface.
A surface substantially free of bumps is defined by a scanning electron microscope.
When the surface of the toner particles is viewed at a magnification of 00, irregularities caused by the fine particles are not seen. Published Patent Gazette Showa 63
Although -50040 describes a toner having a bump on the surface with a coverage of 91% or less, the purpose is to remove the toner from the photographic drum. In fact, the strength of the bumped surface is poor, In addition, it cannot be used because of poor fluidity. The toner of the present invention is useful for a black toner or a color toner. It is also useful for non-magnetic one-component toner, magnetic one-component toner, and two-component toner. It is also useful for both negatively charged toner and positively charged toner.

[0029]

EXAMPLES The present invention will be described in more detail with reference to Synthesis Examples and Examples, which should not be construed as limiting the scope of the invention. still,
In the examples, “parts” means “parts by weight”.

Synthesis Example 1 Preparation of Fine Particles Into 2.67 parts of ethyl methacrylate, 4,4'-methylenebis [2- [N- (4-chlorophenyl) amide] -3-hydroxynaphthalene] was added as a charge controlling agent in a concentration of 0.2%. 133 parts dissolved and 150 parts of water 300 m
1 glass flask (provided with a cooling tube, a stirrer, and a N ₂ gas introduction tube). The mixture is stirred for 7 min.
Warmed to 0 ° C. Under N ₂ atmosphere, 0.20 part of potassium persulfate, 0.19 part of sodium thiosulfate and 0.012 part of copper sulfate were added thereto. When the reaction was continued at 70 ° C. for 5 hours, a particulate polymer having an average particle size of 0.095 μm was obtained.

Synthesis Example 2 Preparation of Fine Particles 4 parts of styrene were charged with the charge control agent 0.4 used in Example 1.
Partially dissolved and sodium dodecyl sulfate 0.2
Parts and 35 parts of water were introduced into the same glass flask as in Synthesis Example 1. The mixture was warmed to 80 ° C. under stirring and brought to a N ₂ atmosphere. 0.04 parts of potassium persulfate was added thereto. After continuing the reaction at 80 ° C. for 5 hours, 0.3 part of sodium dodecyl sulfate, 0.1 part of divinylbenzene, 4 parts of styrene and 35 parts of water were added, and potassium persulfate was added to 0.04 part.
Then, the reaction was continued at 80 ° C. for 5 hours to obtain a fine particle polymer having an average particle size of 0.17 μm.

Synthesis Example 3 Production of Fine Particles Instead of using ethyl methacrylate, methyl methacrylate was used, and 0.1 part of divinylbenzene was added.
When the reaction was carried out in the same manner as in Synthesis Example 1, the average particle size was 0.0
A 7 μm fine particle polymer was obtained.

Synthesis Example 4 Preparation of polymer particles (core particles) 29.2 parts of styrene, 10.8 parts of 2-ethylhexyl acrylate, disparone (DA-703, manufactured by Kusumoto Chemicals)
-50 dry-up product) 0.6 parts, carbon black (MA-100 manufactured by Mitsubishi Chemical Corporation) 2.3 parts, styrene acrylic resin (Mw = 20,000) 6 parts are treated with a sand grinder mill for 10 hours, and carbon black is obtained. Was dispersed. 1.6 parts of azobisisobutyronitrile was dissolved therein. This mixed solution is mixed with water 20 containing 5% of tricalcium phosphate.
0 parts, and treated with a homomixer at 8000 rpm for 3 minutes.

The treatment liquid was introduced into a 500 ml glass flask (having a cooling tube, a stirrer, and a N ₂ gas introduction tube). The mixture was heated to 80 ° C. in an N ₂ atmosphere, and the reaction was continued for 9 hours. As a result, polymer particles (core particles) having an average particle size of 8.3 μm were obtained. The weight average molecular weight was 32,000, and the glass transition point (Tg) was 46 ° C.

Synthesis Example 5 Production of Polymer Particles (Core Particles) Polymer particles (core particles) were obtained in the same manner as in Synthesis Example 4 except that 32.0 parts of styrene and 8.0 parts of 2-ethylhexyl acrylate were used. The weight average molecular weight was 25,000 and the glass transition point (Tg) was 58 ° C. Synthesis Example 6 Production of polymer particles (core particles) 34 parts of styrene, 2-ethylhexyl acrylate
Polymer particles (core particles) were obtained in the same manner as in Synthesis Example 4 except that 4 parts were used. The weight average molecular weight was 25,000, and the glass transition point (Tg) was 65 ° C.

Synthesis Example 7 Preparation of polymer particles (core particles) 0.4 parts of dodecylbenzenesulfonic acid and 397.9 parts of deionized water (including the water in the wax emulsion) were added to 9 parts.
The temperature was raised to 0 ° C., and then the following monomers and initiator were added, and emulsion polymerization was carried out for 7 hours. Styrene 60 parts Butyl acrylate 40 parts Acrylic acid 3 parts Trichlorobromomethane 1 part 2% hydrogen peroxide aqueous solution 43.4 parts 2% ascorbic acid aqueous solution 43.4 parts

After the completion of the polymerization reaction, the mixture was cooled to obtain a milky white resin emulsion. The average particle diameter of the obtained emulsion was 100 nm, and the weight average molecular weight of the polymer was 53,000. The Tg of the obtained resin was 50 ° C. 120 parts of the above resin emulsion (manufactured by Orient Chemical Co.) (as solid content) 5 parts of charge control agent Bontron S-34 7 parts of carbon black MA-100 (manufactured by Mitsubishi Chemical Corporation) 7 parts The above mixture was dispersed and stirred with a disperser.
４０40 ° C. for 2 hours, and then with further stirring
The temperature was kept at 0 ° C. for 3 hours, and the temperature was raised to 95 ° C. and kept for 3 hours. Then, the polymer particles (core particles) were obtained by filtering, washing and drying.

Example 1 To 170 g of a slurry of the polymer particles (core particles) produced in Synthesis Example 4 (suspension polymerization), 150 parts of the polymer solution of the fine particles produced in Synthesis Example 1 was added, and hydrochloric acid was added to the system to adjust the pH of the system. Was added until it became 1.0, followed by stirring at 50 ° C. for 5 hours. After standing to cool, the mixture was filtered and washed, followed by vacuum drying. As a result, fine particles adhered to the surface, and the surface was smoothed by heating at 50 ° C. to obtain a toner. SEM (acceleration voltage 10k)
V, magnification 5000 times). A ferrite carrier (average particle size: 100 μm), in which 0.12 part of hydrophobic silica is added to 40 parts of the toner, and the surface is coated with acryl, 96
0 parts were mixed and stirred to prepare a developer. The charge amount of the toner at this time was measured by a blow-off method.
It was 9.5 μC / g. Consolidation and fluidity were both good. Next, when this developer was actually photographed by a copying machine using selenium as a photoreceptor, a clear copy was obtained. The mechanical strength during actual shooting was sufficient.

Examples 2 to 4 and Comparative Examples 1 to 4 In the same manner as in Example 1, an encapsulation operation was performed, and the toner performance was examined. The results are summarized in the following table. Solidification: Visual observation of solidification of toner after standing at 50 ° C. for 5 hours Good: No solidification Bad: Solidification Fixing: Judgment by lower limit of roller temperature at fixing when image is not strongly rubbed with finger Good: 130 ℃ or less Slightly defective: 130 to 150 ° C. Defective: 150 ° C. or more Surface smoothness: SEM (acceleration voltage 10 kV, magnification 5000)
Good): Fine particles are not visible at all Good: Fine particles are visible on the surface or polymer particles (core particles) are visible (there is a part that is not attached) Mechanical strength: Reciprocating shaker toner Particle size measurement after shaking at good: good particle size distribution inferior: increase in number of particles with average particle size of 5 μm or less or increase in average particle size

[0040]

[Table 1]

When the coverage is smaller than 95% (Comparative Example 1), when the heating temperature is lower than the Tg of the polymer particles (Comparative Example 2), or when the polymer particles (core particles) are aggregated particles (Comparative Example 4) In the case of ()), compatibility between caking property and fixing property could not be obtained. When the Tg of the polymer particles was 65 ° C. (Comparative Example 3), the fixability was slightly poor.

[0042]

As described above, the toner of the present invention has both performance of solidification and fixability, and has no problem in strength.

Claims (8)

[Claims] 1. A toner for developing an electrostatic charge image, wherein 95% or more of the surface of polymer particles is coated with fine particles and the surface is substantially free of protrusions. 2. The toner according to claim 1, wherein 99% or more of the surface of the polymer particles is coated with fine particles. 3. The toner according to claim 1, wherein the polymer particles are coated with fine particles at a solid content ratio of 0.05 or more. 4. The toner according to claim 1, wherein the glass transition point of the polymer particles is 60 ° C. or lower. 5. The toner according to claim 1, wherein the fine particles have a glass transition point of 60 ° C. or higher. 6. The toner according to claim 1, wherein the average particle diameter of the fine particles is 0.3 μm or less. 7. The toner according to claim 1, further comprising a charge control agent substantially dissolved in the fine particles. 8. An aqueous dispersion of fine particles obtained by emulsion polymerization or soap-free emulsion polymerization is added to the polymer particles obtained by suspension polymerization, whereby 95% or more of the surface of the polymer particles is coated with the fine particles. And heating the polymer particles to a temperature equal to or higher than the glass transition temperature of the polymer particles.