JPH0862884A - Treatment of toner particles - Google Patents

Abstract

PURPOSE: To obtain toner particles almost free from voids in the particles. CONSTITUTION: Toner particles having voids in the particles and contg. a colorant (A) and a resin (B) convertible into a resin self-dispersible in water by neutralization or a resin (C) self-dispersible in water as essential component are treated by adding a hydrophobic org. solvent (D) having <=1wt.% solubility to water at 20 deg.C and not dissolving the resin B or C so that the resin B or C is swollen and the voids are filled. The objective toner particles almost free from voids in the particles are obtd. and toner powder excellent in mechanical strength is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating toner for electrostatic printing.

[0002]

2. Description of the Related Art Nowadays, in electrostatic printing, a higher resolution is required for an image, and therefore a reduction in particle size of toner is an issue. With respect to this problem, the inventors have used an encapsulation technique (Japanese Patent Laid-Open No. 5-66600)
Provided are a capsule-type toner in which a colorant is uniformly encapsulated in particles without using a dispersion stabilizer, and a method for preparing the toner by an extremely simple process.

This manufacturing method is an epoch-making manufacturing method which not only easily achieves a reduction in particle size but also solves the problems of the polymerization method, and the toner obtained by this is stable. It develops charging characteristics and images (high resolution) and is practically usable as a toner for electrostatic printing. In addition, due to its characteristics, the manufacturing method is very easy to form a composite structure such as having a multi-layer structure or having crosslinkability, and thus various functions such as storage stability and fixability can be easily and surely imparted. It has excellent characteristics.

[0004]

By the way, particles having many voids in the particles have low mechanical strength. When some of the toner particles having remarkable voids are generated, the toner may be crushed in the process of being stirred in a printing machine such as a printer, and fine powder may be generated.

[0005] Such fine powder causes adverse effects on stable image supply such as deterioration of powder fluidity, change of chargeability due to change of charge distribution, stains inside machine, fogging, etc.
Very unfavorable.

It has been found that in the conventional manufacturing method, voids may be generated in the toner particles due to water entrainment or the like due to various conditions such as stirring during phase inversion emulsification.

[0007]

DISCLOSURE OF THE INVENTION The present invention proposes a method for eliminating voids in particles to eliminate voids in the particles and obtain a toner having uniform mechanical strength.

That is, according to the present invention, a toner having voids in particles, which comprises, as essential components, a colorant (A) and a resin (B) or a self-water-dispersible resin (C) which can be self-water dispersible by neutralization. A hydrophobic organic solvent (D) which has a solubility in water of 1% by weight or less at 20 ° C. and does not dissolve the resin (B) or the self-water-dispersible resin (C) is added to the particles to swell the resin. Disclosed is a method for treating toner particles, characterized in that voids in the particles are eliminated.

In the treatment step, the resin (B) or the resin (C) portion of the toner particles is swollen with a specific hydrophobic organic solvent (D), so that the particles retain their particulate form. Again, the inside has fluidity and the voids inside the particles can be reduced.

The processing steps of the present invention will be sequentially described. In the present invention, the colorant (A) and the resin (B) or resin (C) which can be self-water dispersible by neutralization are essential components.
A hydrophobic organic solvent (D) which does not dissolve the resin (B) or the resin (C) constituting the toner particles and having a solubility in water of 1% by weight or less at 20 ° C. is added to the toner particles having voids in the particles. Then, the resin (B) or (C) is swollen to eliminate voids in the particles.

A known and commonly used colorant (A) can be used in the toner particles of the present invention. Specifically, for example, carbon black, magnetic powder, nigrosine dye, aniline blue, calcyl blue, chrome yellow. , Ultramarine Blue, DuPont Oil Red, Quinoline Yellow, Methylene Blue Chloride, Phthalocyanine Blue,
Malachite Green Oxalate, Lamp Black, Rose Bengal, C.I. I. Pigment Red 122, C.I.
I. Pigment Yellow 97, C.I. I. Pigment Blue 15, ferrosoferric oxide, ferric oxide, iron powder, zinc oxide, selenium, etc. can be used, and they can be used alone or in combination of two or more.

Next, the resin (B) and the self-water dispersible resin (C) which can be self-water-dispersible by neutralization in the toner particles used in the present invention will be described. In the present invention, the resin (B) capable of becoming self-water dispersible by neutralization is stable under the action of an aqueous medium due to the action of a functional group in the molecule capable of becoming a hydrophilic group by neutralization without using an emulsifier. Is a resin having the ability to form a water dispersion.

On the other hand, the self-water-dispersible resin (C) is a resin in which a functional group which can be a hydrophilic group by neutralizing the resin (B) is neutralized with a neutralizing agent.

The resin (B) is, for example, an acid group or a third group.
A resin (C) has a functional group such as a primary amino group that can be converted into a hydrophilic group by neutralization in the resin, and the functional group is neutralized to form a salt structure. This salt structure participates in stable dispersion in an aqueous medium. Even if such a salt structure is obtained by neutralizing the functional group in the resin with a neutralizing agent as described above, the effect is the same whether it is already present in the resin as a salt structure.

Of course, in carrying out the present invention, when it is necessary to convert a part or all of the resin (B) forming the toner particles into the resin (C), it is included in the resin (B). It is sufficient to neutralize a part or all of functional groups that can become hydrophilic groups by neutralization with a neutralizing agent having an opposite polarity. On the other hand, as described below, when it is necessary to convert a part or all of the resin (C) into the resin (B), a part or all of the hydrophilic group contained in the resin (C) is latently changed. It is sufficient to neutralize with a neutralizing agent having the same polarity as the functional group capable of becoming a hydrophilic group by neutralizing.

That is, in an aqueous medium, the self-water-dispersible resin (C) takes a form such that it exposes hydrophilic groups on the particle surface (O / W interface) and wraps around the hydrophobic site to form stable particles. Of. The so-called self-water dispersible resin (C) has such characteristics.

Examples of the functional group which the resin (B) can have as a hydrophilic group by neutralizing an acid group or a tertiary amino group contained in the resin include a carboxyl group, a phosphoric acid group, a sulfone group or a sulfuric acid group. The tertiary amino group is, for example, a dimethylamino group or a diethylamino group. The amount of these functional groups capable of becoming hydrophilic groups is 10 to 500 mg equivalent based on 100 g of the resin (B) solid content,
Preferably 20 to 400 mg equivalent, more preferably 30
~ 300 mg equivalent.

Further, the amount (neutralization amount, neutralization rate) of functional groups such as neutralized acid groups or tertiary amino groups necessary for exhibiting the self-water-dispersing function is determined by the composition, molecular weight, Since the hydrophilicity of the resin itself varies depending on the structure and the like, the neutralization rate varies depending on the resin, but is 10 to 400 mg equivalent per 100 g of the resin (C) solid content, preferably 100 resin solids.
It is in the range of 20 to 250 mg equivalent per g, more preferably 30 to 200 mg equivalent per 100 g of resin solids.

As the neutralizing agent for neutralizing the acid group or the tertiary amino group in the resin (B), when the resin has a carboxylic acid (anionic), a tertiary agent such as triethylamine is used. Examples include inorganic amines, inorganic bases such as sodium hydroxide and potassium hydroxide, ammonia, etc. When the resin has a tertiary amino group (cationic), organic acids such as acetic acid, hydrochloric acid, etc. Inorganic acids are mentioned, and these are neutralized in appropriate amounts.

The hydrophilicity of the resin (B) is controlled by the amount of functional groups capable of becoming hydrophilic groups by neutralization, that is, the neutralization amount (neutralization ratio), as described above. Further, the hydrophilicity determines the size of particles when dispersed. That is, it is possible to easily obtain an arbitrary particle size by controlling the neutralization rate.

As the resin (B) which can be self-dispersible in water by the neutralization, a polymerizable vinyl monomer containing an acid group or a tertiary amino group as described above and the acid group or the tertiary group are used. Those obtained by radically polymerizing a polymerizable vinyl monomer other than the polymerizable vinyl monomers containing a primary amino group in the presence of a radical initiator can be used. As such a resin (B), typically, an acrylic resin having a carboxyl group and a styrene resin having a carboxyl group are preferably used.

Examples of the polymerizable vinyl monomers having an acid group or a tertiary amino group include acrylic acid, methacrylic acid, α-chloroacrylic acid, α-bromoacrylic acid, α-acylamidoacrylic acid, α-benzamide acrylic acid, α-phenylacetamide acrylic acid, α-
(Meth) acrylic acids such as ethyl acrylic acid, and tertiary amino (meth) acrylates such as diethylamino methacrylate and dimethylamino acrylate may be mentioned.

As the polymerizable vinyl monomer other than the polymerizable vinyl monomers containing an acid group or a tertiary amino group,
Specifically, for example, styrenes such as styrene, α-methylstyrene, chlorostyrene and vinylstyrene, monoolefins such as ethylene, propylene, butylene and isobutylene, diolefins such as butadiene and isoprene, vinyl acetate and propion vinyl. , Vinyl butyrate, vinyl benzoate and other vinyl esters, methyl acrylate,
Α-methylene aliphatic monocarboxylic acid esters such as ethyl acrylate, butyl acrylate, octyl acrylate, phenyl dodecyl acrylate, methyl methacrylate, ethyl methacrylate butyl methacrylate, dodecyl methacrylate, vinyl methyl ether, Vinyl ethers such as vinyl ethyl ether and vinyl butyl ether, vinyl methyl ketone, vinyl hexyl ketone,
Examples thereof include vinyl ketones such as vinyl propenyl ketone.

The resin (B) may be obtained by polymerizing the above polymerizable vinyl monomer and a polymerizable unsaturated group-containing oligomer. As the polymerizable unsaturated group-containing oligomer, for example, vinyl-modified polyester, vinyl-modified urethane, vinyl-modified epoxy compound and the like are particularly representative. In addition to the above resins,
Either a polyester resin, a urethane resin or an epoxy resin may be used.

Of course, the monomer is not limited to the above-mentioned one, and any polymerizable vinyl monomer or a polymerizable unsaturated group-containing oligomer that is commonly used can be used.

The above contents will be further explained by showing more specific examples. A polymerizable acrylic monomer containing an acid group or a tertiary amino group, which corresponds to the above-mentioned amount range, and styrene. Alternatively, an acrylic resin or a styrene resin having self-water dispersibility can be obtained by radical polymerization with another polymerizable acrylic monomer and neutralizing the hydrophilic group of such a resin within the above-mentioned appropriate range.

The molecular weight of the resin (B) which can be self-dispersible in water by the neutralization is not particularly limited, but within the range of 3,000 to 100,000 as the weight average molecular weight,
By neutralization, a sufficiently stable self-water-dispersing function is exhibited, and in the range of 5000 to 70,000, very good particles having a narrow particle size distribution can be obtained, which is preferable.

The toner particles used in the present invention may contain a charge control agent. Specific examples of the charge control agent include copper phthalocyanine, perylene, quinacridone, azo pigments, azo metal-containing dyes, and azochrome complexes.

Further, the toner particles used in the present invention may contain various auxiliaries as required, and examples of such auxiliaries include waxes such as polyethylene wax, polypropylene wax, paraffin wax, and metals. Examples thereof include a lubricant such as soap and zinc stearate, and an abrasive such as cerium oxide and silicon carbide.

As described above, the resin component of the void-containing toner particles of the present invention may be a resin that can be self-water dispersible by neutralization, or may be a self-water dispersible resin itself. Good.

The former toner particles having voids include, for example, a colorant (A), a resin (B) capable of becoming self-water dispersible by neutralization, a neutralizing agent and, if necessary, a charge control agent and various auxiliaries. , A first step of uniformly mixing the resin (B) in the presence of an organic solvent to prepare an organic solvent solution of a self-water-dispersible resin in which the colorant (A) is dispersed, and the mixture in an aqueous medium. And a second step of forming a toner particle by phase inversion emulsification. Of course, contrary to the second step, a product obtained by adding an aqueous medium to the mixture to perform phase inversion emulsification to form toner particles may be used.

The neutralizing agent may not be used in the first step, but the neutralizing agent may be contained in the aqueous medium of the second step.
The self-water-dispersible resin (C) can be used in the first step, and in this case, the neutralizing agent is not particularly required in the first step or the second step.

The organic solvent used in the first step is different from the hydrophobic organic solvent (D) described below, and is the resin (B).
Alternatively, the solubility of the resin (C) at 20 ° C. exceeds 1% by weight. The organic solvent that dissolves the resin (B) or the resin (C) is preferably one in which the solubility of the resin (B) or the resin (C) is 70% by weight or more.

As the organic solvent that dissolves the resin (B) or the resin (C) used in the first step, a solvent that dissolves the resin (B) or the resin (C) is appropriately selected from known and commonly used organic solvents. Although it can be used, when the resin (B) or the resin (C) is a styrene resin or an acrylic resin having a weight average molecular weight of about tens of thousands, for example, isopropyl alcohol, n-butanol, methyl ethyl ketone, methyl isobutyl ketone, etc. Is mentioned.

By this phase inversion emulsification operation, the colorant (A)
The toner particles composed of the self-water-dispersible resin (C) in which are encapsulated can be emulsified and dispersed in the aqueous medium phase. The organic solvent in which the resin (C) had been dissolved by the phase inversion emulsification was partially extracted to the water side, but since the toner particle surface was predominantly in contact with a large amount of water, it was once formed. The resin portion of the toner particles is not easily dissolved. Therefore, even if the resin (B) or the organic solvent capable of dissolving the resin (C) is contained after the phase inversion emulsification, the organic solvent capable of dissolving the resin (B) or the resin (C) is in the aqueous medium phase of the toner particles. It does not dissolve the resin part of.

The toner particles containing the organic solvent capable of dissolving the resin (B) or the resin (C) obtained by the above-mentioned operation and dispersed in an aqueous medium are usually subjected to the treatment of the present invention as they are. Although the work process is short and the void elimination effect is large, for example, from there, resin (B) or resin (C)
Is removed, or the organic solvent that dissolves the resin (B) or the resin (C) and the aqueous medium are removed to leave only the toner particle aqueous medium dispersion liquid or toner particles and then the treatment of the present invention is performed. May be.

Then, for example, obtained as described above,
The hydrophobic organic solvent (D) is added to toner particles having voids in the particles, which contains the colorant (A) and the resin (B) or the resin (C) as essential components to swell the resin in the particles. Voids in the particles disappear.

The hydrophobic organic solvent (D) used in the treatment method has a solubility in water of 1% by weight or less at 20 ° C. and is used for swelling the resin (B) or the resin (C). Stay and resin (B) or (C)
The particle shape should not be impaired, for example, the particles are fused together or completely dissolved by the dissolution of the solvent, that is, the solvent (D) completely dissolves the resin (B) or (C). Not, or resin (B) or resin (C)
Has a solubility of 1% by weight or less at 20 ° C., and has extremely low solubility. In this respect, the organic solvent that dissolves the resin (B) or the resin (C) used in the first step and the solvent (D) are clearly distinguished.

In the case of the organic solvent (D) which becomes strong, the affinity for the colorant (A) constituting the particles is much higher than the hydrophilicity, so that the particles can be efficiently formed without damaging the shape of the particles. It can be permeated and swollen, and the effect of eliminating voids can be sufficiently exhibited.

As the solvent (D), a solvent selected from publicly known and commonly used organic solvents depending on the kind of the resin (B) or the resin (C) used can be used. When the resin (B) or the resin (C) is a styrene resin or an acrylic resin having a weight average molecular weight of about tens of thousands, for example, hexane, toluene,
Examples include octane.

In the present invention, the toner particles having voids in the particles to be treated, as described above, may be in the form of powder or wet, or in the state of the aqueous medium dispersion alone. After the phase inversion emulsification, it may be in a state of containing an organic solvent capable of dissolving the resin (B) or the resin (C), but in the case of and, since the toner particles are wet, The hydrophobic organic solvent (D) can swell the toner particles in a much shorter time than that of the form, and can eliminate more voids in a shorter time. In carrying out the present invention in any toner form, it is preferable to perform stirring in order to improve the contact efficiency between the toner particles and the organic solvent (D).

In this state, the hydrophobic organic solvent (C) is added to the dry powder or wet toner particles of the toner particles so as to have an appropriate fluidity so as to facilitate stirring.
Should be added in a large excess.

When the hydrophobic organic solvent (D) is added to the toner particles and swelled, they may be heated to some extent within a range where the particles are not fused. In addition, in such processing steps,
In order to improve the contact efficiency of the particles with the organic solvent (D) and prevent the particles from being fused to each other, it is preferable to carry out the whole system while stirring.

In the case of the above, the amount of the hydrophobic organic solvent (D) used is 10% or more based on the aqueous medium alone or the total of the aqueous medium and the organic solvent, and based on the resin solid content. In the range of 10 to 300% by weight, the effect can be sufficiently exhibited.

The thus obtained toner particles containing the resin (C) and having voids disappeared, the resin (B) is self-water-dispersed in the first step or the second step in which the toner particles having voids are obtained. Toner particles having no voids containing the resin (B), which does not have self-water dispersibility by itself, by adding thereto a neutralizing agent having a polarity opposite to that of the neutralizing agent used for the property Can be

In the present invention, the hydrophobic organic solvent (D) may or may not be removed from the toner particles from which voids have disappeared, but it is usually removed. Examples of the method for removing the hydrophobic organic solvent (D) include a method in which toner particles are separated by filtration and dried.

Of course, when the present invention is carried out in a system containing not only an organic solvent but also an aqueous medium, it is preferable to remove not only the organic solvent but also the aqueous medium after the treatment of the present invention. In any case, the wet toner particles can be made into toner particle powder by drying.

Regarding the presence or absence of voids inside the toner particles, after adding the hydrophobic organic solvent (D), sampling is carried out at each elapsed time, and it is dried to obtain powder toner particles obtained, for example, with a transmission type. By observing with an electron microscope, the presence or absence and the degree of the void can be confirmed. By performing such an operation in advance and grasping the relationship between the elapsed time from the addition of the hydrophobic organic solvent (D) and the porosity,
Porosity can be estimated by time.

[0049]

EXAMPLES Next, the present invention will be described more specifically with reference examples and examples. In the following, all parts and% are based on weight unless otherwise specified.

Production Example 1 Preparation of Resin (I) Which Can Be Self-Water Dispersible by Neutralization 400 parts of methyl ethyl ketone (ME
K) was heated to 80 ° C. and refluxed, and the mixture in the proportions shown below was added dropwise over 2 hours.

Methacrylic acid 90 parts 2-Ethylhexyl acrylate 66 parts Methyl methacrylate 90 parts Styrene 354 parts Perbutyl O (manufactured by NOF Corporation) 6 parts

1 hour and 2 from the end of dropping the above mixture
After a lapse of time and thereafter every 4 hours, 0.5 part of perbutyl O was added to the reaction solution, and aging was carried out for 22 hours.
The reaction temperature was kept at 80 degrees. MEK was added at the end of the reaction to adjust the nonvolatile content to 40%. A resin (I) having a weight average molecular weight of 40,000, which can be self-dispersible in water, was obtained.

Preparation Example 2 Preparation of Resin (II) Which Can Be Self-Water Dispersible by Neutralization 300 parts of methyl ethyl ketone (ME
K) was heated to 80 ° C. and refluxed, and the mixture in the following ratio was added dropwise over 2 hours.

Dimethylaminoethyl acrylate 10 parts 2-Ethylhexyl acrylate 12 parts Styrene 78 parts Perbutyl O (manufactured by NOF Corporation) 3 parts

1 hour and 2 from the end of dropping the above mixture
After the lapse of time and thereafter every 4 hours, 0.5 part of perbutyl O was added to the reaction solution and aging was carried out for 22 hours. The reaction temperature was kept at 80 degrees. MEK was added at the end of the reaction to adjust the nonvolatile content to 40%. A resin (II) which can be self-dispersible in water was obtained by neutralization with a weight average molecular weight of 40,000.

Example 1 Preparation and Treatment of Toner Particles 675 g of Resin (I) obtained in Production Example 1 (nonvolatile matter 4
0%) and 30 g of "ELFTEX 8" (carbon black manufactured by Cabot, USA)
Was mixed for 20 minutes at 3500 RPM with a homomixer, and then mixed for 1 hour with "Eiger Motor Mill M-250" (manufactured by Eiger), and the resulting mixture had a nonvolatile content of 40% by weight with MEK. Was adjusted so that [mixture (a)].

2.73 g of triethylamine (TEA) and 25 g of isopropyl alcohol (IPA) were added to 175 g of the mixture (a), and the mixture was stirred until it became uniform.
While stirring at 350 RPM, 500 g of water was slowly added dropwise to cause phase inversion emulsification, and an aqueous dispersion of resin particles (II)
I got

70 g of toluene was added to the dispersion liquid (II),
The mixture was stirred at 150 RPM for 2 hours while maintaining the temperature at 30 ° C.
After that, the particles are filtered off from the treatment liquid, and this is again treated with water 500
g, the aqueous medium was adjusted to pH 2 with a 0.5 N aqueous hydrochloric acid solution, and stirred for 30 minutes to convert the resin in the toner particles into a resin that can be self-water dispersible by neutralization. The obtained particles were separated by filtration and washed with water, and then the obtained toner cake was dried by freeze-drying to be pulverized.

The obtained particles were spherical particles having an average particle size of 8.5 microns and having few voids, as measured by Coulter Multisizer II (manufactured by Nikkaki Co., Ltd.).
The presence or absence of voids in the particles was confirmed with an optical microscope and a transmission electron microscope (TEM). It was confirmed with an optical microscope that disappearance of the transmitted part upon irradiation with transmitted light was observed, and with TEM, observation of particle sections confirmed that voids were significantly reduced.

Next, the result of observation with an optical microscope showed the presence or absence of a transparent portion of the particles upon irradiation with transmitted light. Further, the porosity was obtained from the area of the voids in the image of the transmission electron microscope.

Further, the toner particles thus obtained were mixed with a ferrite carrier to prepare a developer, and a forced crushability test by a developing machine was conducted to examine the crushability. The average particle size of the toner after the test was measured, and the variation rate between the average particle size before the test and the particle size after the test was determined by the formula (1).

1- (Average particle size after test / Average particle size before test) (1) Formula (1) When there is an increase in fine powder due to crushing of toner particles after the test, the fluctuation rate is shown as a large value. Be done. The results are shown in Table 1.

Example 2 The organic solvent was removed from the dispersion (II) obtained in Example 1 above by vacuum distillation, and the aqueous medium and the particles were filtered off.
The obtained particles were treated in 210 g of toluene at 150 RPM with stirring at room temperature for 2 hours.

After that, the particles are separated from the treatment liquid by filtration, dispersed again in 500 g of water, the pH of this aqueous medium is adjusted to 2 with a 0.5 N hydrochloric acid aqueous solution, and the mixture is stirred for 30 minutes to obtain the toner particles. The resin was converted to a resin that could become self-water dispersible by neutralization. After the particles were separated by filtration and washed with water, the obtained toner cake was dried by the freeze-drying method and pulverized.

The obtained particles were spherical particles having an average particle size of 8.5 microns and having few voids, as measured by Coulter Multisizer II. The presence or absence of voids in the particles was confirmed with an optical microscope and a transmission electron microscope (TEM). It was confirmed with an optical microscope that disappearance of the transmitted part upon irradiation with transmitted light was observed, and with TEM, observation of particle sections confirmed that voids were significantly reduced. The porosity is shown in Table 1.

Further, the toner thus obtained was mixed with a ferrite carrier to prepare a developer, and a forced crushability test by a developing machine was conducted. Table 1 shows the results of the variation rate measurement.

Example 3 675 g of resin (II) (40% non-volatile content) capable of becoming self-water dispersible by neutralization obtained in Production Example 2 and "ELFTEX 8" (manufactured by Cabot Corp., USA) 30 g of carbon black) was mixed with a homomixer for 20 minutes at 3500 RPM, and then mixed with "Eiger Motor Mill M-250" (manufactured by Eiger) for 1 hour.

Then, with respect to the tertiary amino group in the resin, 0.13 mol of acetic acid and 50% by weight with respect to the solid content.
After adding acetone, 1500 g of water was slowly added dropwise while stirring at 350 RPM using a three-one motor to cause phase inversion emulsification, and the resin particle aqueous medium dispersion (I
V) was obtained.

To the dispersion (IV), 270 g of toluene was added, and the mixture was stirred at 150 RPM for 2 hours while maintaining the temperature at 30 ° C. After that, the particles are separated from the treatment liquid by filtration, and this is again washed with water 1
Dispersion in 000 g, the pH of this aqueous medium was adjusted to 2 with a 0.5N aqueous hydrochloric acid solution, and the mixture was stirred for 30 minutes to convert the resin in the toner particles into a resin that can be self-water dispersible by neutralization. After the particles were separated by filtration and washed with water, the obtained toner cake was dried by the freeze-drying method and pulverized.

The obtained particles were spherical particles having an average particle size of 8.5 microns and having few voids, as measured by Coulter Multisizer II. The presence or absence of voids in the particles was confirmed with an optical microscope and a transmission electron microscope (TEM). It was confirmed with an optical microscope that disappearance of the transmitted part upon irradiation with transmitted light was observed, and with TEM, observation of particle sections confirmed that voids were significantly reduced. The porosity is shown in Table 1.

Further, the toner thus obtained and a ferrite carrier were mixed to prepare a developer, and a forced crushability test was carried out by a developing machine. Table 1 shows the results of the variation rate measurement.

Comparative Example 1 The organic solvent was removed from the aqueous dispersion (II) of resin particles obtained in Example 1 by evaporation, the particles were filtered off, and this was again dispersed in 500 g of water. This aqueous medium was adjusted to pH 2 with a 0.5N hydrochloric acid aqueous solution and stirred for 30 minutes. After washing the particles with water, the aqueous medium was filtered off, and the resulting toner cake was dried by freeze-drying to give particles.

The obtained particles were spherical particles having an average particle size of 8.5 microns as measured by Coulter Multisizer II. The presence or absence of voids in the particles was confirmed with an optical microscope and a transmission electron microscope (TEM). Example 1
The porosity of the toner particles and the friability (variability) as a developer were measured in the same manner as in Nos. 3 to 3. The results are shown in Table 1.

[0074]

[Table 1]

Comparing Example 1 with Comparative Example 1, the toner particles treated according to the present invention have a very small void ratio in the particles and a particle size variation rate of 1 when used as a two-component developer. Since it is extremely close to, it is understood that toner particles having good durability and uniform mechanical strength are obtained.

[0076]

In the present invention, the resin constituting the toner particles is swelled by adding a hydrophobic organic solvent which has a solubility in water of 1% by weight or less at 20 ° C. and does not dissolve the resin, The voids of toner particles having voids in the particles can be significantly reduced. As a result, the toner particle strength is increased, and the particle specific gravity and the particle charging property are equalized, so that it is possible to provide a toner exhibiting higher characteristics than conventional toners.

Claims (6)

[Claims] 1. A toner particle having voids in the particle, which comprises a colorant (A) and a resin (B) or a self-water dispersible resin (C) which can be self-water dispersible by neutralization as essential components, Within the particles, a hydrophobic organic solvent (D) having a solubility in water of 1% by weight or less at 20 ° C. and not dissolving the resin (B) or the self-water-dispersible resin (C) is added to swell the resin. A method for treating toner particles, characterized by eliminating the voids. 2. The treatment method according to claim 1, further comprising removing the hydrophobic organic solvent (D). 3. The amount of the hydrophobic organic solvent (D) used is
The processing method according to claim 1, wherein the resin solid content is in the range of 10 to 300% by weight. 4. The resin (B) is a resin having an acid group or a tertiary amino group in an amount of 10 to 500 mg equivalent per 100 g of resin solid content, or the resin (C) is a neutralized acid group or a neutralized group. The processing method according to claim 1, which is a resin having 10 to 400 mg equivalent of the obtained tertiary amino group per 100 g of resin solid content. 5. A toner particle comprising, as essential components, a colorant (A) and a resin (B) or a self-water dispersible resin (C) capable of becoming self-water dispersible by neutralization, wherein voids are present in the particles. A hydrophobic organic solvent (D) having a solubility in water of 1% by weight or less at 20 ° C. and not dissolving the resin (B) or the self-water-dispersible resin (C) is added to an aqueous medium dispersion of toner particles having And swelling the resin to eliminate voids in the particles. 6. The treatment method according to claim 1, further comprising removing the hydrophobic organic solvent (D) and water.