JP3493466B2 - Electrophotographic toner - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a toner for electrophotography.

[0002]

2. Description of the Related Art Toners used for electronic copying have a small particle size in order to meet the recent demand for high definition images, and are generally obtained as fine particles having an average particle size of about 1 to 10 μm.

An emulsion dispersion method is known as one of the methods for producing such fine particles. In this method, a polymer solution obtained 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 stirring to produce an organic compound. It is carried out by evaporating the solvent and precipitating polymer particles.

According to this emulsification-dispersion method, the process is simplified and polymer fine particles can be obtained by a relatively simple operation, and production efficiency is improved and at the same time cost can be reduced. Further, compared with the pulverization method and suspension polymerization method, there are many kinds of resins that can be used, and the applications of the obtained polymer particles are expanded.

On the other hand, the shape of the polymer fine particles obtained by the emulsification dispersion method is spherical and the surface is smooth. Therefore, for example, when the polymer fine particles containing a colorant are used as a toner for developing an electrostatic latent image, It has problems such as poor cleaning property, charging property and transfer property.

[0006] Further, the polymer fine particles obtained by a wet production method such as an emulsion dispersion method have a high internal porosity and poor crack resistance. Therefore, when the fine particles are used as a toner, the toner particles are easily broken by mixing and stirring with a carrier, and fine powder is generated, which causes problems such as filming of the toner on the surface of the photoconductor, poor cleaning, and toner spent on the carrier.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and provides a polymer fine particle produced by a wet method which is excellent in crack resistance and uses the fine particle. It is an object of the present invention to provide a toner whose desired properties such as fluidity and cleaning property are adjusted.

The above object is achieved by adjusting the porosity of the toner manufactured by the wet manufacturing method within a certain range and controlling the shape of the toner particles.

[0009]

The present invention is obtained by a wet method.
The fine particles to be dispersed in a solvent that does not dissolve the fine particles.
From the glass transition point of the fine particle constituent resin minus 10 degrees
Stress the particles at low temperature to crush the particles
Obtained through a step of thermally restoring the crushed fine particles.
And an electrophotographic toner having an internal porosity of 5% or less. In the present invention, spherical fine particles obtained by a wet process are dispersed in a solvent that does not dissolve the fine particles, and the fine particles are deformed by applying stress to the fine particles constituting resin at a temperature higher than the glass transition point plus 10 degrees. The present invention relates to a spherical electrophotographic toner having an internal porosity of 5% or less, which is obtained through a process of thermal restoration.

With such a structure, it is possible to obtain a toner having excellent crack resistance even when using fine particles obtained by a wet manufacturing method.

The toner of the present invention uses fine polymer particles obtained by a wet method. In the present invention, the wet production method includes all methods such as suspension polymerization method, emulsion polymerization method, non-aqueous dispersion polymerization method, seed polymerization method, emulsion dispersion granulation method and spray drying method that can obtain substantially spherical polymer fine particles. It is a waste. In particular, the present invention is an emulsion dispersion granulation method, a suspension polymerization method and a spray method because of the large number of types of resins used, the homogeneity of resin dispersion, the ease of adjusting the molecular weight, the dispersibility of pigments or static-static agents, etc. It is suitable when applied to polymer fine particles obtained by a drying method.

When such polymer fine particles are used as toner particles, when the polymer fine particles are prepared by a suspension polymerization method, an emulsion polymerization method, a non-aqueous dispersion polymerization method or a seed polymerization method, a colorant is added from the time of polymerization. , The above method may be carried out with a desired additive such as a charge control agent added,
In the case of the emulsion dispersion granulation method or the spray drying method, the additive required for the toner may be added to the resin solution to carry out the method.

In the present invention, the internal porosity of the polymer fine particles obtained by the above-mentioned wet production method is adjusted to be 5% or less, preferably 2% or less. In the present invention, the internal porosity refers to a value obtained by observing the cross section of a toner with a microtome by SEM to obtain the ratio (%) of the area of the void portion to the toner cross-sectional area and expressing it as an average value of the number of data N = 1000.

In the polymer fine particles obtained by the wet manufacturing method, the solvent, the dispersion liquid and the like are easily mixed in the inside thereof, and after these are evaporated, the portions become bubbles. Further, in a system in which a polymerization initiator is added, gas generated from the polymerization initiator creates bubbles inside the fine particles. Therefore, the fine particles obtained by the wet process generally have a high internal porosity. In particular, the polymer fine particles obtained by the emulsion dispersion granulation method have a porosity of about 10 to 30%, and even the polymer fine particles obtained by the suspension polymerization method, the emulsion polymerization method, the non-aqueous dispersion polymerization method or the seed polymerization method. There are about 5 to 20% voids. When the toner is constituted by using such fine particles, the toner particles are easily cracked when the toner is mixed and stirred, so that fine particles are generated, cleaning failure, toner spent on the filming carrier of the toner on the surface of the photoconductor, and the like. The harmful effect becomes a problem. However, according to the present invention, when the toner is constituted by using the polymer fine particles having the internal porosity of 5% or less, the above-mentioned problems do not occur and a toner excellent in crack resistance can be obtained.

The fine polymer particles having a low internal porosity obtained by the wet method are obtained by dispersing the fine polymer particles obtained by the wet method in a solvent that does not dissolve the fine particles, and stressing the fine particles at a temperature near the glass transition point of the fine particle constituent resin. It is obtained by subjecting the fine particles to deformation.

A more specific description will be given. First, a dispersion solution is prepared by dispersing polymer particles obtained by the wet process in a solvent that does not dissolve the particles. Such a solvent may be appropriately selected depending on the polymer fine particle constituent resin, but water, from the viewpoint of easy handling and availability,
Methyl alcohol and ethyl alcohol are used, of which water is particularly preferable.

When water is used as the dispersion solvent, the polymer fine particles (10 to 20 parts by weight) obtained by the wet process are mixed with water (100 parts by weight) together with the dispersion stabilizer and the dispersion stabilizing aid (1 to 5 parts by weight). Is preferably dispersed in

As the dispersion stabilizer, those which become hydrophilic colloid in the aqueous dispersion are preferable, and particularly gelatin, gum arabic, agar, cellulose derivatives (for example, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc.), synthetic Polymers (for example, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylates, polymethacrylates, etc.) can be mentioned.

As the dispersion stabilizing aid, a surfactant is usually used, and a natural surfactant such as aponin, a nonionic surfactant such as alkylene oxide, glycerin or glycidol, carboxylic acid, sulfonic acid, phosphoric acid , An anionic surfactant containing an acidic group such as a sulfuric acid ester group and a phosphoric acid ester group.

Particularly preferred combination of the dispersion stabilizer and the dispersion stabilization aid is a cellulose derivative (methyl cellulose derivative) and an anionic surfactant (sodium dodecylbenzenesulfonate) or polyvinyl alcohol and an anionic surfactant. Is.

When the emulsification dispersion granulation method is used, the solvent for the dispersion solution may be used from the step of completely dissolving the resin forming the polymer fine particles in an appropriate solvent and dispersing the resin solution, and once the powder form It is not always necessary to take out the fine polymer particles.

When polymer fine particles are obtained by a suspension polymerization method, an emulsion polymerization method, a non-aqueous dispersion polymerization method or a seed polymerization method, the polymer fine particle dispersion solution is a dispersion solution in which a polymer is precipitated in these polymerization processes. You may use it as it is. Of course, the above dispersion solution may be prepared by using powdery polymer fine particles obtained by those polymerization methods.

Next, stress is applied to the dispersed polymer particles at a temperature near the glass transition point of the polymer particle constituent resin.

In order to apply stress, media such as glass beads, zirconia beads, resin particles, resin-coated ferrite particles, and the like are added to the dispersion solution of the polymer fine particles, and the volume of the dispersion solution and the volume thereof are mixed and stirred. Good.

When such a medium is used, the bead diameter (D) and the average particle diameter (d) of the polymer particles have the following relationship: 50 <D / d <500, preferably 100 <D / d <300. Is desirable. When the above relationship is not satisfied, that is, when D / d is 50 or less, sufficient stress cannot be applied to the polymer particles,
When D / d is 500 or more, it is difficult to apply uniform stress to the polymer particles. The specific gravity of the medium is preferably about 1.0 to 5.0.

The stirring and mixing is performed near the glass transition point of the resin constituting the polymer particles. In the present invention, the glass transition point refers to the temperature at which a single peak is observed when the glass transition point of the constituent resin is measured by a thermal analyzer (for example, DSC), and the peak is observed. It means the temperature at which the maximum peak is observed. When it has double peaks, it means the temperature between the peaks. Well
And the vicinity of the glass transition point within the range of the glass transition point ± 10 ° C., preferably in the range of ± 5 ℃ glass transition point, more preferably refers to the glass transition point.

By mixing and stirring the above glass beads in the vicinity of the glass transition point in this way, it is possible to deform the polymer fine particles to have irregularities on the surface without destroying them, and the internal porosity is increased. It is possible to obtain polymer particles of 5% or less.

When the toner is constituted by using the polymer fine particles thus obtained, it is possible to obtain a toner having excellent crack resistance and excellent cleaning characteristics. In particular, the unevenness formed has a rounded shape, and it is possible to obtain a toner having a significantly improved fluidity as compared with a toner having a corner shape obtained by a dry pulverization method.

Another embodiment will be described below.
When the mixing and stirring is carried out at a temperature lower than the glass transition point of the polymer fine particle constituting resin minus 10 degrees, the polymer particles are broken, and a spherical resin having irregularities on the surface as in the case where the polymer resin is prepared by kneading and pulverizing. Particles can be obtained. In this case, since it is destroyed from the internal voids, the internal porosity of the obtained polymer fine particles should be 5% or less.
It is easy to adjust the following. Even when the toner is constituted by using the polymer fine particles obtained in this way, it is possible to obtain a toner having excellent crack resistance and excellent cleaning characteristics.

When mixing and stirring are performed at a temperature higher than the glass transition point of the polymer fine particle constituent resin plus 10 degrees,
Immediately following the deformation of the polymer particles, thermal recovery occurs, and the deformation-recovery is repeated. In this case, from the above two examples, it is possible to obtain finer polymer particles that are more spherical and have an internal porosity of 5% or less. When the toner is constituted by using the polymer fine particles thus obtained, it is possible to prepare a toner having excellent crack resistance and fluidity.

A sand mill, an Eiger motor mill, or the like can be used as a specific device used for the mixing and stirring, but as a simple method, for example, a polymer fine particle dispersion liquid and a medium (glass beads) are placed in a closed container. , And roll with a ball stand, or mix and stir with a turbine blade.

[0032] If you want more precise control of the shape of the polymer is deformed into a shape having a temporarily uneven polymer particles at a temperature near the glass transition point of the constituent resin without stress the further the polymer particles, the polymer
It can be performed by applying a temperature in the vicinity of the glass transition point of the fine particle constituent resin to thermally restore the particle shape to a spherical shape. By controlling the degree of heat recovery, from the surface uneven shape before heat recovery to the shape close to a true sphere,
It is possible to prepare polymer fine particles having a shape at any stage, and it is possible to prepare such polymer fine particles in consideration of both properties of toner cleaning property and toner fluidity.

The temperature applied in the heat restoration is used in the same meaning as the temperature applied in applying the stress described above. Further, the same device can be used as a device that can be used for heat recovery such as mixing and stirring.

When the polymer fine particles obtained as described above are used as toner particles, a fluidizing agent such as silica, titanium oxide or alumina may be further added, if desired. Further, instead of internally adding additives such as a charge control agent, the additives may be externally attached and fixed to the surface of the obtained polymer fine particles to form toner particles.

[0035]

EXAMPLES The present invention will be specifically described below with reference to examples. In the following examples, "parts" means "parts by weight" unless otherwise specified.

Example 1 Low molecular weight polyester resin (Mw: 15000, Mn:
After completely dissolving 100 parts of 6000) in 20% by weight of methylene chloride, 6 parts of carbon black as a coloring agent and a charge control agent Bontron E84 (Orient) using an Eiger motor mill (manufactured by Eiger Japan). 4 parts (Chemical Industry Co., Ltd.) are dispersed in the resin solution.

The resin solution thus obtained was placed in an aqueous dispersion of 1% of Metrolose 65SH-50 (produced by Shin-Etsu Chemical Co., Ltd.) and 1% of sodium lauryl sulfate at room temperature using a homomixer (produced by Tokushu Kika Kogyo). 10 minutes, 38 per minute
It was emulsified and dispersed at 00 revolutions to obtain an O / W type emulsion. Next, replace with a 4-blade stirring blade, and
Methylene chloride was distilled off while stirring at ℃ for 3 hours to give a particle size of 1
An aqueous suspension (suspension) of 0 μm toner particles was obtained.

This aqueous suspension of 10 μm toner particles was mixed with glass beads of the same volume (diameter: 1.0 m).
m) together with vigorous mixing and stirring at a temperature of 25 ° C. (a temperature sufficiently lower than the glass transition point Tg of the resin for toner Tg = 68 ° C.), and 10 μm of toner particles are pulverized in a wet process.
An aqueous suspension of toner particles having a peak around μm was obtained. Next, after removing the glass beads with a 350 μm mesh, the pulverized aqueous suspension of toner particles was washed with 7
The toner particles were thermally restored by stirring with a stirring blade at 5 ° C. for 30 minutes.

The aqueous suspension of toner particles that has been thermally restored is decanted for 24 hours to remove the solid content that has accumulated below, and water / methanol (5/5 weight ratio), PH =
The washing operation was repeated twice with the washing liquid of 3 (using hydrochloric acid) to obtain a washed toner having an average particle size of 6 μm.

Example 2 Low molecular weight polyester resin (Mw: 15000, Mn:
100 parts of 6000) was completely dissolved in methylene chloride so as to be 20% by weight. Using an Eiger motor mill (manufactured by Eiger Japan), 6 parts of carbon black as a colorant and 4 parts of a charge control agent Bontron E84 (manufactured by Orient Chemical Industry Co., Ltd.) were dispersed in the resin solution.

The resin solution obtained as described above is
Using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) in an aqueous dispersion of 1% of METOLOSE 65SH-50 (manufactured by Shin-Etsu Chemical Co., Ltd.) and 1% of sodium lauryl sulfate, emulsion-disperse at 3800 rpm for 10 minutes at room temperature. , O / W emulsion was obtained. Next, replace with 4 stirring blades
Methylene chloride was distilled off while stirring at 5 ° C. for 3 hours to obtain an aqueous suspension (suspension) of polymer fine particles for toner having a particle size of 6 μm.

The obtained aqueous suspension of 6 μm fine particles for toner was mixed with glass beads (diameter: 1.
0 mm) and vigorously mixed and stirred at a temperature of 85 ° C. (glass transition point (Tg) of the polymer particles for toner: a temperature sufficiently lower than 68 ° C.) to repeatedly deform and restore 6 μm of the polymer particles for toner. While removing the internal cavity.

Then, the glass beads were removed with a 350 μm mesh, and the aqueous suspension was left for 24 hours. The obtained solution was decanted, and the solid content accumulated below was taken out. The solid matter taken out was washed twice with a washing liquid (water / methanol (5/5 weight ratio), pH: 3 (using hydrochloric acid)) to obtain a toner having an average particle diameter of 6 μm.

Example 3 (Experimental Example) Low molecular weight polyester resin (Mw: 15000, Mn:
100 parts of 6000) was completely dissolved in methylene chloride so as to be 20% by weight. Using an Eiger motor mill (manufactured by Eiger Japan), 6 parts of carbon black as a colorant and 4 parts of a charge control agent Bontron E84 (manufactured by Orient Chemical Industry Co., Ltd.) were dispersed in the resin solution.

The resin solution obtained as described above is
Using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) in an aqueous dispersion of 1% of METOLOSE 65SH-50 (manufactured by Shin-Etsu Chemical Co., Ltd.) and 1% of sodium lauryl sulfate, emulsion-disperse at 3800 rpm for 10 minutes at room temperature. , O / W emulsion was obtained. Next, replace with 4 stirring blades
Methylene chloride was distilled off while stirring at 5 ° C. for 3 hours to obtain an aqueous suspension (suspension) of polymer fine particles for toner having a particle size of 6 μm.

The obtained aqueous suspension of 6 μm fine particles for toner was mixed with glass beads (diameter: 1.
0 mm) and the mixture was vigorously mixed and stirred at a temperature of 65 ° C. (glass transition point (Tg) of polymer fine particles for toner: temperature near 68 ° C.) to deform 6 μm polymer fine particles for toner.

The obtained aqueous suspension of deformed polymer particles for toner was stirred with a stirring blade at 85 ° C. for 60 minutes to thermally restore the shape of the deformed polymer particles for toner.

The aqueous suspension of the polymer fine particles for toner that had been thermally restored was left standing for 24 hours, the solution was decanted, and the solid content accumulated below was taken out. The solid content taken out was washed with water (water / methanol (5/5 weight ratio), pH:
3 (using hydrochloric acid)) to obtain a toner having an average particle size of 6 μm.

Example 4 70 parts of styrene N-Butyl methacrylate 30 parts Low molecular weight polypropylene wax (Viscor 660P: manufactured by Sanyo Chemical Industries) 3 parts 8 parts of carbon black (MA-8: manufactured by Mitsubishi Kasei Co., Ltd.) 2,2'-Asobis- (2,4-dimethylvaleronitrile) 3 parts

The above substances were thoroughly mixed with a sand stirrer to prepare a polymerizable composition containing a polymerization initiator.
This polymerizable composition was added to a 1.25 wt% aqueous polyvinyl alcohol solution using "TK-auto homomixer" (manufactured by Tokushu Kika Kogyo Co., Ltd.) with stirring at a rotation speed of 3000 rpm, and then 3 sheets were added. 50 using turbine blades
Polymerization reaction was carried out at a temperature of 60 ° C. for 6 hours while stirring at 0 rpm, and after the completion of the polymerization reaction, the reaction system was cooled, hydrochloric acid was added, decantation, filtration, washing and drying were performed to obtain an average particle size of 1
4 μm toner mother particles were obtained.

An aqueous suspension of 14 μm toner particles was mixed with an equal volume of glass beads (1.0 m diameter).
m) with vigorous mixing and stirring at a temperature of 25 ° C. (a temperature sufficiently lower than the glass transition point Tg of the resin for toner Tg = 68 ° C.) to pulverize 14 μm toner particles in a wet type.
An aqueous suspension of toner particles having a peak around μm was obtained.

Next, after removing the glass beads with a mesh of 350 μm, the crushed aqueous suspension of toner particles was stirred with a stirring blade at 75 ° C. for 30 minutes to thermally restore the toner particles.

An aqueous suspension of toner particles that have been heat restored is
After decanting for 24 hours, the solid content collected below was taken out, and water / methanol (5/5 weight ratio), pH = 3.
The washing operation was repeated twice with the washing liquid (using hydrochloric acid) to obtain a washed toner having an average particle size of 6 μm.

Comparative Example 1 Low molecular weight polyester resin (Mw: 15000, Mn:
100 parts of 6000) was completely dissolved in methylene chloride so as to be 20% by weight. Using an Eiger motor mill (manufactured by Eiger Japan), 6 parts of carbon black as a colorant and 4 parts of a charge control agent Bontron E84 (manufactured by Orient Chemical Industry Co., Ltd.) were dispersed in the resin solution.

The resin solution obtained as described above was added to a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) in an aqueous dispersion of 1% Metroze 65SH-50 (manufactured by Shin-Etsu Chemical Co., Ltd.) and 1% sodium lauryl sulfate. Was emulsified and dispersed at 3,800 rpm for 10 minutes at room temperature to obtain an O / W type emulsion. Then replace with 4 blades of stirring blades
Methylene chloride was distilled off while stirring at ℃ for 3 hours to give a particle size of 6
An aqueous suspension (suspension) of fine polymer particles for toner having a size of μm was obtained.

2 parts of the obtained aqueous suspension of fine particles for toner are added.
After standing for 4 hours, the solution was decanted, and the solid content accumulated below was taken out. The solid matter taken out was washed twice with a washing liquid (water / methanol (5/5 weight ratio), pH: 3 (using hydrochloric acid)) to obtain a toner having an average particle diameter of 6 μm.

Comparative Example 2 70 parts of styrene N-Butyl methacrylate 30 parts Low molecular weight polypropylene wax (Viscor 660P: manufactured by Sanyo Chemical Industries) 3 parts 8 parts of carbon black (MA-8: manufactured by Mitsubishi Kasei Co., Ltd.) 2,2'-Asobis- (2,4-dimethylvaleronitrile) 3 parts

The above materials were thoroughly mixed with a sand stirrer to prepare a polymerizable composition containing a polymerization initiator.
This polymerizable composition was added to a 1.25 wt% aqueous polyvinyl alcohol solution using "TK-Auto Homomixer" (manufactured by Tokushu Kika Kogyo Co., Ltd.) with stirring at a rotation speed of 6000 rpm, and then 3 sheets were added. 50 using turbine blades
Polymerization reaction was carried out at a temperature of 60 ° C. for 6 hours while stirring at 0 rpm. After the completion of the polymerization reaction, the reaction system was cooled, hydrochloric acid was added, and decantation, filtration, washing and drying were performed to obtain an average particle size of 6
μm toner was obtained.

Evaluation (Production of Carrier) The materials shown in Table 1 below were thoroughly mixed and pulverized by a Henschel mixer. Next, melt kneading was carried out using an extrusion kneader set to a cylinder portion of 180 ° C. and a cylinder head portion of 170 ° C.

The kneaded product was left standing to cool, then roughly pulverized using a feather mill and then finely pulverized by a jet mill. The obtained pulverized product is classified using a classifier, and the average particle size is 60 μm.
Got a career.

[0061]

[Table 1]

Hydrophobic silica R-974 (manufactured by Nippon Aerosil Co., Ltd .; volume average particle size 6 mμm) was added to the toners obtained in Examples and Comparative Examples in a proportion of 0.2% by weight, and each minute was added using a Henschel mixer. The post-treatment was performed at 3000 rpm for 1 minute.

The toner and carrier obtained as described above were mixed in a toner mixing ratio of 5.0% by weight to obtain a developer.

With respect to each of the obtained developers, the fluidity, the cleaning property and the charge rising property, the internal porosity of each toner and the crack resistance were evaluated. The results are shown in Table 2 below.

[0065] flowability, bulk density meter (JIS standard Z2
504) was used to measure the bulk specific gravity of the developer. The ∘ mark in Table 2 indicates that the bulk specific gravity is 1.5 or more.

[0066] cleaning property; a copying machine (EP8600,
An image was printed on 10,000 sheets by Minolta Camera Co., Ltd. and the cleaning property on the photoconductor was evaluated. In Table 2, the mark ◯ indicates that there is no toner left unwiped on the photoconductor, or there is some toner left unwiped, but there is no problem in practical use because it does not affect the image.

Internal porosity : SEM observation of the toner cross section by a microtome was carried out, the ratio (%) of the area of the void portion to the toner cross sectional area was determined, and expressed as the average value of the number of data N = 1000.

50 g of the crack-resistant developer was put in a 100 ml poly bottle, and the paint conditioner (60 Hz, 3
After strong stirring under the condition of (0 minutes), the toner was separated by electric field separation and SEM observation was performed. The crack resistance was evaluated by the ratio (%) of the number of disintegrated toners to the total number of toners observed in this SEM observation (data number N = 1000).

[0069]

[Table 2]

[0070]

EFFECTS OF THE INVENTION Even polymer fine particles produced by a wet method are provided with excellent crack resistance, and a toner prepared by using the fine particles to have desired characteristics such as fluidity or cleaning property is provided. The toner can be provided and the toner can be controlled in any shape.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaaki Takama 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Osaka International Building Minolta Camera Co., Ltd. In-house (72) Inventor Junji Machida, Chuo-ku, Osaka-shi, Osaka 2-3-13 Azuchicho Osaka International Building Minolta Camera Co., Ltd. In-house (56) Reference JP-A-2-132461 (JP, A) JP-A-2-132460 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) G03G 9/087

Claims (2)

(57) [Claims] 1. The fine particles obtained by the wet process are dispersed in a solvent which does not dissolve the fine particles, and the fine particles are crushed by stressing the fine particles at a temperature lower than the glass transition point of the fine particle constituent resin minus 10 degrees. An electrophotographic toner having an internal porosity of 5% or less, which is obtained through a step of thermally restoring the crushed fine particles. 2. Spherical fine particles obtained by a wet process are dispersed in a solvent that does not dissolve the fine particles, and the fine particles are stressed at a temperature higher than the glass transition point of the fine particle constituent resin plus 10 degrees to deform the fine particles-heat. A spherical electrophotographic toner having an internal porosity of 5% or less, which is obtained through a restoration process.