JPH0962036A - Electrophotographic toner and its production - Google Patents

Abstract

(57) [Abstract] (Correction) [Problem] Originally, the environmental stability of the chargeability of the toner itself is obtained by using spherical toner particles having an acid group exposed on the surface, which adversely affects the environmental stability of the chargeability. Has been improved,
In addition, a positively chargeable electrophotographic toner effectively provided with a chargeability control effect is also provided. SOLUTION: Toner particles composed of a binder resin containing a colorant and having an acid group exposed on the particle surface and a nigrosine compound are essential components, and the acid group exposed on the particle surface of the binder resin is A positively chargeable electrophotographic toner comprising spherical particles, which is ion-bonded to a nitrogen atom of a nigrosine compound to form a salt structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner for developing an electrostatic latent image in electrophotography, electrostatic recording, electrostatic printing and the like, and a method for producing the same.

[0002]

2. Description of the Related Art In electrophotography, dry developers are roughly classified into one-component developers using a toner itself in which a colorant is dispersed in a binder resin and two-component developers in which the toner and a carrier are mixed. can do.

In any case, when copying, the electrostatic latent image formed on the photoconductor is developed with these developers, and the toner powder imaged on the photoconductor is transferred to a transfer material such as paper or sheet. The image is fixed using heat, pressure, etc. to obtain a permanent image. At that time, in order to obtain a permanent image with sufficient image density and high resolution, it is necessary to adhere a predetermined amount of toner powder to the electrostatic latent image formed on the photoconductor faithfully to the latent image. .

Normally, the polarity of the electrostatic latent image formed on the photoconductor is positive or negative depending on the type of the photoconductor or the difference in the developing system. It is required to have a charging property with a negative or positive polarity opposite to the electrostatic latent image on the photoconductor.

In recent years, a wet-process toner has attracted attention as a toner whose amount used as an image forming material for a copying machine, a laser printer and the like is increasing.

In the conventional toner manufacturing method, a mixture of a binder resin and a coloring agent is kneaded while being melted by a heating mixer, cooled, and then mechanically pulverized and finely pulverized by a pulverizer such as a jet mill. A method is generally used in which toner particles are classified and mechanically mixed with an external additive or the like, if necessary, and the shape of the particles is an angular polyhedral shape like crushed ice. I was trying.

On the other hand, Japanese Patent Laid-Open No. 5-66600 discloses a method for producing a toner by a wet method, which is completely different from the conventional mechanical pulverization method, in the presence of a colorant and the like in an aqueous medium. A wet process is described in which the colorant-encapsulated toner particles are obtained by phase inversion emulsification of the polymer to be obtained, whereby the toner particles are produced in one step.

A major feature of this wet process is that the toner shape can be made substantially spherical and that a uniform particle toner having a sharp particle size distribution can be easily produced. Such a spherical toner offers the advantage of being able to design a small particle size toner having excellent powder flowability, and is expected to develop into a high-performance toner that matches the market demand for high image quality and high resolution. There is.

[0009]

However, an electrophotographic toner comprising spherical toner particles containing the above-mentioned colorant and containing a binder resin having acid groups exposed on the surface of the particles is
There is a problem in that the charging property is limited to the negative polarity, and the exposure of the acid group causes insufficient environmental stability during development.

[0010] Further, toner particles containing the above-mentioned colorant and comprising a binder resin in which acid groups are exposed on the surface of the particles, inorganic basic compounds such as alkali metal hydroxide and ammonia, and tertiary amines and the like. And an organic basic compound as an essential component, and the acid groups exposed on the particle surface of the binder resin are spherical particles characterized by forming an ion bond with the basic compound to form a salt structure. The electrophotographic toner is improved in environmental stability at the time of development, but still has a problem that it cannot be used in a developing method that requires a positively chargeable toner.

Conventionally, in the pulverizing method, a charge control agent has been used for the purpose of controlling the charging characteristics of the toner, and by appropriately selecting the type of the charge control agent added at the time of kneading, the steps before and after that are changed. Without doing so, the negatively chargeable toner or the positively chargeable toner could be manufactured relatively easily.

On the other hand, in the phase inversion emulsification method, in order to granulate the toner particles in an aqueous medium, when the kind of the charge control agent is changed, the dispersibility of each component in the aqueous medium is different. However, there was a problem that the pH during granulation was changed, and uniform colorant-dispersed particles could not be granulated, and the charge control agent could not be freely selected. .

Although the conventional pulverization method can be diverted to allow the spherical toner to contain a nigrosine charge control agent, the nigrosine charge control agent is generally composed of a nigrosine compound and a higher fatty acid. Therefore, even if the acid group is included in the toner particles made of the binder resin exposed on the surface of the particle, the nigrosine compound does not localize on the surface of the toner particle, and the charging property is higher than expected even if added. There was also a problem that the control effect could not be obtained.

In view of the above-mentioned circumstances, the present invention uses spherical toner particles having an acidic group exposed on the surface, which has a negative effect on the environmental stability of the charging property, so that the toner itself has the environmental stability of the charging property. It provides a positively chargeable toner for electrophotography with improved chargeability control effect, and can efficiently respond to product type change in multi-product production such as positive chargeability and negative chargeability. The present invention provides a method for producing a phase inversion emulsification method toner, more specifically, negatively charged toner particles obtained by the phase inversion emulsification method can be prepared by a simple operation of chemical surface modification. An object of the present invention is to provide a positively chargeable toner and a method for producing the same.

[0015]

As a result of intensive studies, the present inventors have found that spherical negatively-charged toner particles having an acidic group exposed on the surface have a negative effect on the environmental stability of the charging property. Even by adding a nigrosine compound containing no higher fatty acid, it is selectively localized in the acid group on the toner particle surface due to the cationic nature of the nigrosine compound itself, and it is found that the acid group is ionically bonded, The nigrosine compound and the higher fatty acid are not simply and uniformly dispersed in the toner particles as in the case of using a nigrosine type charge control agent containing a higher fatty acid, and even a smaller amount of the nigrosine compound is obtained by the localization effect. The charge control effect can be effectively brought out, the environmental stability of the charging property can be improved more than that in the state of being an acid group, and the toner particles can be positively charged. This has led to the completion of the present invention found that the can.

That is, in order to solve the above-mentioned problems, the present invention comprises, as an essential component, toner particles comprising a binder resin containing a colorant and having an acid group exposed on the particle surface, and a nigrosine compound. The acid group exposed on the particle surface of the binder resin is a positively chargeable electrophotographic toner (hereinafter, referred to as a toner having a spherical shape, which is characterized by forming a salt structure by ionic bond with the nitrogen atom of the nigrosine compound). 1 invention).

The positively chargeable electrophotographic toner according to the first aspect of the present invention has been conventionally contained in a nigrosine type charge control agent.
It is characterized by not containing a counter ion (counter anion) such as a higher fatty acid corresponding to the anion component, whereby the above-mentioned effects of the present invention are exhibited.

The positively chargeable electrophotographic toner according to the first aspect of the present invention includes, for example, a case of phase inversion emulsification using an emulsifier and / or a dispersion stabilizer and an acid group capable of self-water dispersion by neutralization with a basic compound. The following 6 in the case of phase inversion emulsification using a resin having a base and a basic compound, or using a self-water-dispersible resin
There are two typical production methods.

There are the following four production methods using the emulsifier or dispersion stabilizer. (1) A synthetic resin having an acid group, an emulsifier and / or a dispersion stabilizer, an organic solvent, and a colorant are added to an aqueous medium for phase inversion emulsification. By adding an aqueous medium to the mixed composition for phase inversion emulsification,
The first step of generating and dispersing the toner particles of the resin in which the colorant is encapsulated in the aqueous medium, the aqueous dispersion of the toner particles obtained in the above step and the nigrosine compound are mixed, and A method for producing an electrophotographic toner, comprising a second step of neutralizing the acid group of the resin with a nigrosine compound, and a third step of removing the aqueous medium from the aqueous dispersion of the toner particles obtained in the above step and drying.

(2) A mixed composition containing a synthetic resin having an acid group, an organic solvent, and a colorant as essential components is added to an aqueous medium containing an emulsifier and / or a dispersion stabilizer for phase inversion emulsification. Alternatively, by adding an aqueous medium containing an emulsifier and / or a dispersion stabilizer to the mixed composition and subjecting it to phase inversion emulsification, the toner particles of the resin in which the colorant is encapsulated are generated and dispersed in the aqueous medium. Step, the second step obtained by mixing the aqueous dispersion of toner particles obtained in the above step and a nigrosine compound, and neutralizing the acid groups of the resin in the dispersed toner particles with the nigrosine compound Third, removing the aqueous medium from the toner particle aqueous medium dispersion and drying
A method for producing an electrophotographic toner, which comprises the steps of:

(3) A synthetic resin having an acid group neutralized with a nigrosine compound, an emulsifier and / or a dispersion stabilizer,
An organic solvent and a mixed composition containing a colorant as an essential component,
Phase-inversion emulsification by adding in an aqueous medium or phase-inversion emulsification by adding an aqueous medium to the mixed composition, to produce and disperse the toner particles of the resin in which the colorant is encapsulated in the aqueous medium. A method for producing an electrophotographic toner, comprising one step, and a second step of removing the aqueous medium from the aqueous dispersion of the toner particles obtained in the above step and drying.

(4) A mixed composition containing, as essential components, a synthetic resin having an acid group neutralized with a nigrosine compound, an organic solvent, and a colorant in an aqueous medium containing an emulsifier and / or a dispersion stabilizer. In addition to phase inversion emulsification, or by adding an aqueous medium containing an emulsifier and / or a dispersion stabilizer to the mixed composition to perform phase inversion emulsification, a toner of the resin in which a colorant is included in the aqueous medium. A method for producing an electrophotographic toner, comprising a first step of generating and dispersing particles, and a second step of removing an aqueous medium from the aqueous dispersion of toner particles obtained in the above step and drying.

The following two methods are available for the combined use of a basic compound and a resin having an acid group capable of self-water dispersion by neutralization with a basic compound, or for phase inversion emulsification using a self-water-dispersible resin. Can be mentioned.

(5) A mixed composition containing an anionic self-water-dispersible resin having an acid group and an acid group neutralized with a basic compound, an organic solvent, and a colorant as essential components in an aqueous medium. In addition to phase inversion emulsification, or by adding an aqueous medium to the mixed composition to perform phase inversion emulsification, in the aqueous medium, a first step of generating and dispersing toner particles of the resin in which the colorant is encapsulated, Second step of mixing the aqueous dispersion of toner particles obtained in the above step and a nigrosine compound, and neutralizing the acid groups of the resin in the dispersed toner particles with the nigrosine compound, the toner particles obtained in the above step A method for producing an electrophotographic toner, comprising a third step of removing an aqueous medium from an aqueous medium dispersion and drying.

(6) A mixed composition containing a synthetic resin having an unneutralized acid group, which is self-dispersible in water by neutralization, an organic solvent, and a colorant as essential components, Phase inversion emulsification by adding it to an aqueous medium containing a basic compound necessary for neutralizing a part of the acid groups of the sum, or by adding an aqueous medium containing the compound to the mixed composition. Thereby, in the aqueous medium, the first step of forming and dispersing the toner particles of the anionic self-water-dispersible resin having the colorant encapsulated therein and having the acid group neutralized with the basic compound, the step The second step obtained by mixing the aqueous dispersion of the toner particles obtained in 1 above with a nigrosine compound and neutralizing the unneutralized acidic groups on the surface of the dispersed toner particles with the organic basic compound, obtained in the above step Remove the aqueous medium from the toner particle aqueous medium dispersion and dry. Third step, the manufacturing method of an electrophotographic toner comprising a that.

The toner particles that can be used in the present invention are spherical particles containing a colorant and a synthetic resin as essential components, and the resin containing the colorant contains an acid group and contains the acid group. It is a toner particle having a predetermined average particle diameter in which a group is exposed on the surface of the particle. The synthetic resin acts as a binder resin. The acid group forms an ionic bond with the nitrogen atom of the nigrosine compound to form a salt structure, which contributes to selectively improving the electrical characteristics of the toner particle surface.

As the binder resin having an acid group exposed on the surface, for example, a synthetic resin having an unneutralized acid group in the molecule can be used, and the resin is used so that the acid group is exposed on the surface. To be Of course, it may have a functional group other than the acid group. Examples of such resin include epoxy resin, urethane resin, polyamide resin, acrylic resin, alkyd resin, polyester resin and the like. These may be used alone or in combination of two or more. Among them, an acrylic resin that is relatively easy to obtain a balance of powder fluidity, fixability, etc. as a toner,
A styrene / acrylate copolymer resin is especially preferable.

The above-mentioned resin has a molecular weight of a level required to develop sufficient mechanical strength, usually has a weight average molecular weight of 3,000 to 200,000, and, in the case of an acrylic resin, has 5,000 to 150,000, and D
In SC measurement, glass transition temperature (Tg) is 50 to 1
The temperature is preferably 00 ° C, and for heat roll fixing, the temperature is preferably about 60 to 80 ° C.

Taking an acrylic resin as an example of the resin, a polymer resin obtained by polymerizing a monomer such as (meth) acrylic acid ester can be given as a typical example. Specifically, for example, styrene. , Α
-Styrenes such as methylstyrene, chlorostyrene, vinylstyrene, monoolefins such as ethylene, propylene, butylene, isobutylene, diolefins such as butadiene and isoprene, vinyl acetate, propion vinyl, vinyl butyrate, vinyl benzoate, etc. Α of vinyl esters, methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, phenyl dodecyl acrylate, methyl methacrylate, ethyl methacrylate butyl methacrylate, dodecyl methacrylate, etc.
-Acrylic monomers such as vinyl ethers such as methylene aliphatic monocarboxylic acid esters, vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl propenyl ketone, acrylic acid and methacrylic acid Acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, monobutyl itaconic acid, monobutyl maleate,
Acid phosphooxyethyl methacrylate, acid phosphooxypropyl methacrylate, 3-chloro-2
-Acrylamido-2-methylpropanesulfonic acid, 2
-The resin can be obtained by copolymerizing at least one kind of monomer selected from acid group-containing monomers such as sulfoethyl methacrylate.

Further, in detail of such an acrylic resin, a polymer unsaturated group-containing oligomer having an acid group can also be used as a copolymerization component, such as maleic anhydride, fumaric acid, tetrahydrophthalic anhydride and endo. Vinyl-modified polyesters obtained by polycondensation or addition condensation of methylenetetrahydromaleic anhydride, α-terpinene maleic anhydride adduct and the like with monoallyl ether of triol, pentaerythrite diallyl ether or allyl glycidyl ether, dimethylolpropion Vinyl modified urethanes obtained by addition polymerization of diisocyanate with acid, glycerin monoallyl ether, 1,2 butadiene polyol, etc., vinyl modified by adding glycidyl group containing monomer to carboxyl group containing vinyl copolymer Epoxy, and the like can be mentioned.

As the polymerization initiator used to obtain such a resin, of course, a usual one can be used.
Various peroxides such as benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, t-butyl peroxide or 2-ethylhexanoate; or azobisisobutyronitrile or azobisisovaleronitrile As mentioned above, various azo compounds and the like can be mentioned.

The resin itself may be obtained by solution polymerization in an organic solvent, suspension polymerization, emulsion polymerization, or bulk polymerization.

The polyester resin as the resin is
It can be obtained by condensation of a polyol and a polybasic acid, and an acid group can be easily introduced into an ordinary polyester resin by using an excessive amount of a dibasic acid such as phthalic acid.

As the colorant in the toner particles used in the present invention, known and commonly used colorants can be used. Specifically, for example, carbon black, magnetic powder, aniline blue, calcoil 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.

In the present invention, the obtained toner may be magnetic toner particles in which magnetic fine particles are dispersed in a binder resin. As the magnetic substance fine particles, any ferromagnetic substance that is normally used can be used.

Specific examples of the magnetic substance include magnetic metals such as iron, cobalt and nickel, alloys thereof, metal oxides such as cobalt-added iron oxide and chromium oxide, Mn / Zn ferrite, Ni / Zn ferrite and the like. Various kinds of ferrite,
In addition to magnetite, hematite, etc., the surface of these, silane coupling agent, aluminum coupling agent,
Powders such as those treated with a surface treatment agent such as a titanium coupling agent or those coated with a polymer can be used.

The weight ratio of the colorant and the resin is not particularly limited, but when the total weight thereof is 100, it is preferable that the colorant is 3 to 30% by weight.

Toner particles composed of a binder resin containing a colorant, which is obtained from the colorant and the binder resin, must have acid groups exposed on the particle surface. There are various methods for that purpose. In the conventional method of melt-kneading a colorant and a binder resin and pulverizing them to obtain toner particles, the acid group of the binder resin is the toner particles. It is unsuitable because it is randomly oriented inside and most of them are present inside the particles. Therefore, in order to selectively orient the acid groups on the surface of the toner particles with a high probability, a granulation method called phase inversion emulsification, which will be described in detail later, is suitable.

The method for obtaining an aqueous dispersion of toner particles having an acid group on the surface of the particles in the present invention is not particularly limited, but if explained step by step, for example, the following method is used. Is mentioned.

First, a mixed composition, which is a solution of the resin in an organic solvent in which the colorant is dispersed, is prepared.

Examples of the organic solvent which can be used in preparing the organic solvent solution include various aromatic hydrocarbons such as toluene, xylene or benzene; various alcohols such as methanol, ethanol, propanol or butanol; cellosolve. Or various ether alcohols such as carbitol; various ketones such as acetone, methyl ethyl ketone or methyl isobutyl ketone; various esters such as ethyl acetate or butyl acetate; or various ether esters such as butyl cellosolve acetate And the like.

At this time, the nonvolatile content of the organic solvent solution is not particularly limited, but usually 10 to 70% by weight is suitable.

Then, a mixed composition comprising the binder resin in an organic solvent, in which the colorant obtained above is dispersed, is phase-inverted and emulsified in an aqueous medium to form toner particles in the aqueous medium. Granulation is performed to prepare an aqueous medium dispersion of the toner particles.

In this case, of course, an aqueous medium may be added to the organic solvent solution for phase inversion emulsification, or the organic solvent solution may be added to the aqueous medium for phase inversion emulsification.
The former is preferable because toner particles having a narrower particle size distribution can be obtained. As a method of adding, dropping is generally used.

In order to smoothly carry out this phase inversion emulsification granulation, an emulsifier and / or a dispersion stabilizer may be contained in the organic solvent solution and / or the aqueous medium.

As the dispersion stabilizer, a water-soluble polymer compound is generally used, and examples thereof include polyvinyl alcohol, polyvinylpyrrolidone, hydroxyethyl cellulose, carboxymethyl cellulose and cellulose gum.

Examples of the emulsifier include sodium dodecylbenzene sulfonate, sodium lauryl sulfate,
Anionic surfactants such as sodium dodecyldiphenyl oxide disulfonate, and non-ionic surfactants such as polyoxyethylene lauryl ether and polyoxyethylene ninyphenol ether can be used in combination. Of course, the dispersion stabilizer and the emulsifier can be used together.

According to the phase inversion emulsification method using an emulsifier and / or a dispersion stabilizer, as in the production methods (1) and (2), a binder resin having an unneutralized acid group is used. It is also possible to obtain an aqueous dispersion of toner particles using a binder resin, mix this with a nigrosine compound, and neutralize at least a part of the acid groups with the nigrosine compound to form an ion bond to form a salt structure. Separately from the above, as in the production methods of (3) and (4), a binder resin having a salt structure is prepared by previously neutralizing at least a part of the acid groups with a nigrosine compound to form an ionic bond. A method of performing phase inversion emulsification can also be adopted.

However, in the production methods (1) to (4) above, as a method of exposing a larger number of acid groups neutralized with a nigrosine compound on the surface of the particles to further bring out the effect of the present invention, The manufacturing methods 1) and 2) are more preferable than the manufacturing methods 3) and 4).

Here, as the binder resin, an anionic self-water-dispersible resin having an acid group neutralized with a basic compound, which may contain an acid group, or an anionic self-dispersible resin by neutralization. A water-dispersible synthetic resin having an unneutralized acid group and a basic compound necessary for neutralizing at least a part of the unneutralized acid group to make the resin anionic self-water dispersible If they are used in combination with and, phase inversion emulsion granulation can be performed without using a dispersion stabilizer or an emulsifier.

In the present invention, the self-water-dispersible resin is a synthetic resin containing in its molecule a functional group capable of becoming a hydrophilic group by neutralization, and some or all of the acid groups capable of becoming hydrophilic are basic compounds. A resin having the ability to form a stable aqueous dispersion without the use of an emulsifier or a dispersion stabilizer when neutralized by.

Examples of the acid group which can become a hydrophilic group by neutralization in this resin include a carboxyl group, a phosphoric acid group,
Examples include so-called acid groups such as sulfonic acid groups, and when the carboxy group-containing anionic resin is taken as an example, the content of the carboxyl group that can become an anionic hydrophilic group by neutralization is particularly limited. Acid value 4
About 0 or more is preferable because particles can be easily formed by the phase inversion emulsification method. Particularly preferably, the acid value is 50 to 150.

The basic compound used in the self-water-dispersible resin is not limited to the kind as long as the resin exhibits hydrophilicity to the extent that it can be self-water-dispersed in an aqueous medium. A basic compound that easily forms a cation ion in water can be used.

Specific examples of effective basic compounds include:
Other than ammonia, for example, sodium silicate, potassium silicate, sodium hydroxide, potassium hydroxide, lithium hydroxide, dibasic sodium phosphate, tribasic sodium phosphate,
Inorganic metal basic compounds such as dibasic ammonium phosphate, tribasic ammonium phosphate, sodium metasilicate, sodium carbonate, and ammonia, mono-, di-, or trimethylamine, mono-, di-, or triethylamine, mono-, or diisopropylamine, n- Organic amine compounds such as butylamine, mono-, di-, or triethanolamine, mono-, di-, or triisopropanolamine, ethyleneimine, ethylenediimine can be mentioned.

At this time, by carrying out phase inversion emulsification using the above-mentioned basic compound as a neutralizing agent, capsule fine particles can be produced in any case, but the particle size distribution of the produced particles is made sharp, that is, In order to obtain a toner having a uniform particle size, it is preferable to use an inorganic metal basic compound.

The phase-inversion emulsification granulation using the self-water-dispersible resin as a binder resin is described above in a solution of a colorant-dispersed resin which can be self-water-dispersed by neutralization in an organic solvent. A basic compound sufficient to make the resin self-dispersible in water is added and dispersed, and an organic solvent solution of an anionic self-water-dispersible resin is mixed, and then phase-inversion emulsified by mixing with an aqueous medium, or a colorant is added. The dispersed organic solvent solution of a resin having an acid group and capable of self-water dispersion by neutralization, and an aqueous medium containing a basic compound sufficient to make the resin self-water dispersible are mixed for phase inversion. By emulsifying, it is possible to obtain an aqueous dispersion of toner particles, which are spherical particles of a binder resin in which a colorant is encapsulated and which are dispersed in an aqueous medium containing an acidic group on the particle surface.

The toner particles obtained by the above-mentioned phase inversion emulsification granulation method and having acid groups exposed on the surface of the particles themselves exhibit a good negative chargeability and can be used as a negatively chargeable toner.

The electrophotographic toner of the present invention can be obtained, for example, by the above-mentioned production method, by ionically bonding a nigrosine compound to the surface of the toner particles exposing the acid groups.

The nigrosine compound used in the present invention is not particularly limited structurally, and a compound having a cation structure containing no counter anion component is preferable. Specifically, the one represented by the following equation can be used. When a conventional nigrosine charge control agent containing a counter anion such as a higher fatty acid as described above is used, it does not show reactivity with an acid group exposed on the particle surface, or an anion exchange reaction occurs, and the counter anion component is It is difficult to obtain the desired effect due to elution.

[0060]

Embedded image

[However, Ar in the formula is an aryl group. ]

Examples of the nigrosine compound include nitrobenzene, nitrophenol, nitrocresol, aniline,
It can be obtained by heating and melting and condensing aniline hydrochloride or the like as a raw material in the presence of a catalyst. When an anionic component such as higher fatty acid is contained in the production process, it is used after removing it.

Specific examples of the nigrosine compound in the present invention include those represented by the following structural formulas. As commercially available products, for example, Bontron N-01, Bontron N-07, Bontron EX [all manufactured by Orient Chemical Industry Co., Ltd.] and the like can be used.

In the case of the above-mentioned production methods (5) and (6) which do not require the use of an emulsifier and / or a dispersion stabilizer,
To attach the nigrosine compound to the acid groups on the surface of the toner particles by ionic bond, the nigrosine compound is added to the toner particle aqueous medium dispersion liquid dispersed in an aqueous medium, mixed and dispersed, and then the aqueous medium is removed and dried. It is easily achieved by using a dry toner.

In the production methods (5) and (6) relating to the phase inversion emulsion granulation method using a basic compound,
If necessary, an acid is added to the toner particle aqueous medium dispersion liquid to carry out reverse neutralization treatment to remove at least a part of the basic compound adhering to the surface of the toner particles so as to contain unneutralized acid groups. After that, a nigrosine compound can be attached by ionic bond. At this time, an acid is added to carry out reverse neutralization, followed by filtration and washing, and at least a part or all of the neutralized acid groups are returned to the unneutralized acid groups, and the toner particles are reconstituted in water. After the dispersion, the dispersion and the nigrosine compound may be mixed.

Any known and commonly used acid can be used for the reverse neutralization. As the acid, for example, inorganic acids such as oxalic acid, hydrochloric acid, sulfuric acid and phosphoric acid and organic acids such as formic acid and acetic acid can be used. When the inorganic metal basic compound is used as the basic compound, it is neutralized with hydrochloric acid. Is preferred.

The nigrosine compound used in the present invention is added in an amount of 0.3 to 100 mol% based on the acid groups on the toner particle surface.
A considerable amount can be used, but more preferably 10 to
Addition of an amount equivalent to 85 mol% gives good results. Within this range, the sufficient effects of the present invention can be obtained, and the characteristics of the toner particles themselves are not impaired.

The amount of acid groups on the surface of the toner particles can be determined by, for example, a titration method. For example, the concentration can be calculated by the following method.

To the toner particle aqueous dispersion containing the granulated acid groups, an excess of 1N sodium hydroxide aqueous solution is added and thoroughly stirred and mixed to add sodium ions to the acid groups on the surface of the toner particles. After that, the aqueous dispersion of the toner particles in the aqueous medium is filtered and washed to remove excess sodium hydroxide other than those ionically bonded to the acid groups on the surface of the particles. Next, the toner particles are redispersed in water, and a 1N hydrochloric acid aqueous solution is added dropwise while stirring until the pH of the aqueous medium dispersion becomes 3. From the dropped amount of this 1N hydrochloric acid, the amount of sodium ions on the surface of the toner particles, that is, the amount of acid groups can be calculated.

Of the above-mentioned production methods exemplified for producing the toner particles containing the acid groups exposed on the surface, a separate step such as a water washing step for separately removing the dispersion stabilizer and the emulsifier is unnecessary. The self-water-dispersible resin is a binder resin based on the above-mentioned production methods (5) and (6), which does not substantially use an emulsifier and / or a dispersion stabilizer in terms of excellent productivity. It is preferable to use a certain toner particle aqueous medium dispersion as the toner particle aqueous medium dispersion of the present invention.

The phase inversion emulsification method utilizing a self-water-dispersible resin without using an emulsifier or a dispersion stabilizer is compared with other phase inversion emulsification method toners in the final toner powder of the emulsifier or the dispersion stabilizer. Since it does not remain in the toner, a spherical dry toner having more stable charging characteristics can be obtained.

In obtaining the electrophotographic toner of the present invention, waxes and other auxiliary agents such as a charge control agent may be incorporated, if desired, in any step of its production.

Examples of the auxiliaries include waxes such as polyethylene wax, polypropylene wax and paraffin wax, metal soaps, lubricants such as zinc stearate, and the like.
Alternatively, an abrasive such as cerium oxide or silicon carbide can be used.

Dry toner powder can be obtained by removing the aqueous medium from the aqueous dispersion of the toner particles in which the nigrosine compound is ion-bound and drying. In removing the aqueous medium from the dispersion, any effective method such as decantation or filtration can be adopted.

In removing the aqueous medium from the aqueous dispersion of the toner particles in which the nitrogen atom of the nigrosine compound and the acid groups on the surface of the toner particles are ionically bonded, the above-mentioned production methods (1) to (6) of the present invention are carried out. In any of the above, the organic solvent and water may be removed at the same time, or the organic solvent may be removed and then the water may be removed. The method of removing the organic solvent from the aqueous dispersion of the toner particles in the aqueous solution and then removing the water is preferable because the toner particles obtained are less likely to aggregate in the dispersion.

When the nigrosine compound is ionically bonded to the toner particles having the acid groups exposed on the surface, the toner particles are tonically bonded as described in the production methods (1), (2), (5) and (6). To the toner particles of the aqueous medium containing the organic solvent used to granulate the particles, the nigrosine compound can also be mixed and dispersed and adhered, but the nigrosine compound is removed after removing the organic solvent from the toner particle aqueous medium dispersion in advance. It is preferable to mix and disperse and to adhere, since a more uniform ionic bond structure can be formed.

For the drying, any known and commonly used method can be adopted. For example, hot air drying may be performed at a temperature at which the toner particles are not thermally fused or agglomerated, or freeze drying may be used. There is also a method of simultaneously separating and drying toner particles from an aqueous medium using a spray dryer or the like.

As the particle size of the toner powder of the present invention, any size can be selected within a practical level as a toner. The volume average particle diameter is 3 to 30 μm, preferably 4 to 12 in view of the matching property with the current machine.
The range of μm is preferable.

The electrophotographic toner of the present invention can be used as a non-magnetic one-component toner or a magnetic one-component toner, or as a two-component developer when combined with a carrier, and is particularly excellent as a two-component developer. The characteristics can be obtained.

As the carrier, any of the known and commonly used carriers can be used. For example, iron, nickel, copper, zinc,
Powders of metals such as cobalt, manganese, chromium, rare earths and alloys or oxides thereof, surface-treated glass, silica and the like can be used. Of course, resin-coated carriers such as acrylic resin-coated carriers, fluororesin-coated carriers, and silicone resin-coated carriers can also be used. As the carrier, for example, a carrier of about 20 to 200 microns is used.

When a two-component electrostatic image developer is obtained from the toner obtained in the present invention and a carrier, the toner is mixed, for example, at a ratio of 1 to 15 parts by weight of toner per 100 parts by weight of carrier. You can use it.

[0082]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an optimum embodiment of the present invention will be described. First, styrene, (meth) acrylic acid ester, and (meth) acrylic acid are polymerized in a hydrophobic organic solvent as essential components to obtain a glass transition temperature of 60 to 80 ° C. and an acid value of 60 to
120, nonvolatile content of styrene-acrylic copolymer having a weight average molecular weight of 20000 to 100000, 30 to 60% by weight
To prepare a hydrophobic organic solvent solution, and add a hydrophilic organic solvent thereto, and add 5 to 100 parts by weight of the non-volatile content of the copolymer.
Add 15 parts by weight of colorant and mix well, and add to it an aqueous solution of an inorganic metal basic compound in a weight necessary for the copolymer to be self-dispersible in water without an emulsifier and / or a dispersion stabilizer. A mixed solvent solution of a hydrophobic organic solvent and a hydrophilic organic solvent of an anion-type self-water-dispersible resin having a neutralized carboxyl group, which may contain an unneutralized acid group is obtained.

Then, to this mixed solvent solution, an aqueous medium consisting of only water is added dropwise to carry out phase inversion emulsification to obtain an aqueous dispersion of toner particles having a particle diameter of 4 to 12 μm. Remove the organic solvent by distillation,
An inorganic monobasic acid aqueous solution sufficient to expose the neutralized carboxyl group is added, filtered and washed, and only the toner particles are redispersed in water to obtain a dispersion liquid in which only the water of the toner particles is used as an aqueous medium.

A nigrosine compound containing no counter anion was added to this dispersion in an amount of 10 to 85 mol% based on the exposed carboxyl groups on the surface of the toner particles, and the mixture was sufficiently stirred to convert the carboxyl groups into nigrosine compounds. Ionic bond with nitrogen atom. Next, the dispersion liquid thus obtained is filtered, and only the toner is taken out and dried to obtain toner particle powder having a particle diameter of 4 to 12 μm.

The positively chargeable toner thus obtained is
An electron having a negatively charged electrostatic latent image electrophotographic photoreceptor is prepared by mixing 1 to 10 parts by weight per 100 parts by weight of a resin-coated magnetic carrier having an average particle diameter of 50 to 150 μm. If developed with a photocopier, the electrostatic latent image can be visualized.

[0086]

The present invention will be described more specifically below with reference to examples of the present invention. However, the invention is not limited to these examples.

(Example 1) 200 g of methyl ethyl ketone
Was placed in a reactor and heated to 80 ° C. Then, the mixture in the proportions shown below was added dropwise over about 2 hours. Meanwhile, the reaction was carried out in a nitrogen stream.

Methacrylic acid 45 g Styrene 207 g 2-Ethylhexyl acrylate 33 g Methyl methacrylate 15 g Perbutyl O [manufactured by Nippon Shokubai Co., Ltd.] 3 g Methyl ethyl ketone 12 g

One hour after the completion of the dropping of the above mixture, 0.25 g of perbutyl O was additionally added, and 0.25 g was added after 2 hours, and the reaction was continued for 24 hours. After completion of the reaction, a styrene-acrylic copolymer resin solution having a nonvolatile content of 54% by weight and capable of becoming self-dispersible in water was obtained. This resin had an acid value of 100 and a weight average molecular weight of 40,000.

200 g of this copolymer solution, 35 g of isopropyl alcohol, and 12.0 g of "MA-100" (carbon black manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) were kneaded with "Eiger M-250VSE-EXJ" (manufactured by Eiger USA). After mixing for 1 hour with a kneading machine), 11.5 g of a 1N-caustic soda aqueous solution was added, and water was added dropwise while stirring at 350 rpm using a three-one motor to perform phase inversion emulsification, and a colorant was included. An aqueous dispersion of toner particles comprising a self-water-dispersible resin was obtained. When the toner particles were measured with a Coulter counter, they were toner particles having an average particle diameter of 8 microns. Further, it was confirmed by observation with an electron microscope that the toner particles were truly spherical.

Next, the organic solvent was removed by vacuum distillation so that the temperature became lower than the softening point of the toner particles, and the pH was adjusted to 6
A 0.01N aqueous hydrochloric acid solution was added to the mixture until filtration and filtered and washed, and then the toner particles were returned to water to obtain an aqueous dispersion of toner particles. "Bontron N-07" as a nigrosine compound (manufactured by Orient Chemical Industry Co., Ltd.) was added to this aqueous dispersion of toner particles. Nigrosine type charge control agent containing no counter anion. 2.39 g was added, and the mixture was sufficiently stirred to attach the nigrosine compound to 18% of the carboxyl groups on the surface. Although Bontron N-07 was a powder, it could be uniformly dispersed and dissolved in the toner dispersion aqueous solution.

Then, it was filtered and treated with a freeze dryer for 3 days to obtain a dry toner. This toner had excellent fluidity, and no aggregation of particles was observed. The average particle size was also 8 microns, and no change in particle size due to treatment was observed.

The dry toner thus obtained has an average particle diameter of 100.
The developer was prepared by mixing and stirring 4 parts by weight with respect to 100 parts by weight of the micron coated magnetite carrier, and the charge amount of the toner was measured by the blow-off method. As a result, a value of +18.7 μC / g was shown, and the positive polarity was shown. It was confirmed to be a charged toner. When a copying test was carried out using a commercially available electronic copying machine using this developer, a clear image faithful to 20,000 or more originals having a uniform image density was obtained.

Comparative Example 1 A dry toner was prepared without adding the Nigrosine compound “Bontron N-07” used in Example 1. That is, a toner was prepared in which the nigrosine compound was not ionically added to the carboxyl groups on the surface of the toner particles. Similar to the toner obtained in Example 1, this toner had excellent fluidity, and no aggregation of particles was observed. This dry toner was mixed and stirred at a ratio of 5 parts by weight to 100 parts by weight of a ferrite carrier having an average particle diameter of 100 microns to prepare a developer, which was -62.5 μC.
The charging amount was / g, and the charging amount was sufficient for practical use as a negatively charged toner. However, when the developer was prepared by mixing and stirring at a ratio of 4 parts by weight to 100 parts by weight of the coated magnetite carrier having an average particle diameter of 100 microns as in Example 1, the toner charge amount by the blow-off method was It showed a value of -7.1 μC / g, and it was still negatively charged and could not be used as a positively charged toner.

Comparative Example 2 200 g of the copolymer solution prepared in Example 1, 35 g of isopropyl alcohol, and “MA
-100 "[Carbon Black manufactured by Mitsubishi Kasei Co., Ltd.]
12.0 g, and "Bontron N-04" [a nigrosine type charge control agent manufactured by Orient Chemical Industry Co., Ltd.]. Contains counter anions. ] 5.0 g of kneading machine "Eiger M-
250 VSE-EXJ "(kneader manufactured by Eiger, USA) for 1 hour, and then 1N-caustic soda aqueous solution 11.
Add 5g, and use three-one motor, 350rp
Water was added dropwise with stirring at m to perform phase inversion emulsification to obtain an aqueous dispersion of toner particles including a colorant and comprising a self-water-dispersible resin. When the toner particles were measured with a Coulter counter, they were toner particles having an average particle diameter of 8 microns. Further, it was confirmed by observation with an electron microscope that the toner particles were truly spherical.

The average particle size was 1 as in Example 1.
00 micron coated magnetite carrier 10
When a developer was prepared by mixing and stirring at a ratio of 4 parts by weight to 0 parts by weight, the toner charge amount by the blow-off method showed a negative chargeability, and it could not be used as a positive charge toner. .

[0097]

The electrophotographic toner according to the first aspect of the invention is
Since the nigrosine compound is chemically bonded to the surface of the toner particles and exposed, the toner particles are originally negatively charged, and even if the toner particles have an acid group with poor environmental stability, stable positive chargeability can be obtained. It has a particularly remarkable effect of being excellent in environmental stability.

Since the inventions of claims 2 to 7 employ the phase inversion emulsification granulation method, the positively chargeable toner of claim 1 can be easily obtained. That is, a positively charged toner having a nitrogen atom of a nigrosine compound ionically attached to the acid group at a predetermined point in the process of manufacturing a toner particle that has an acid group exposed on the surface and is originally negatively charged. Therefore, according to the same granulation process as that of the conventional negatively chargeable toner, the positively chargeable toner can be easily produced, which is a remarkable effect.

Claims (9)

[Claims] 1. A toner particle comprising a binder resin containing a colorant and having an acid group exposed on the particle surface, and a nigrosine compound as essential components, and an acid exposed on the particle surface of the binder resin. A positively chargeable electrophotographic toner comprising spherical particles, the group of which has a salt structure by ionic bonding to the nitrogen atom of the nigrosine compound. 2. A mixed composition comprising a synthetic resin having an acid group, an emulsifier and / or a dispersion stabilizer, an organic solvent and a colorant as essential components is added to an aqueous medium for phase inversion emulsification. ,
By adding an aqueous medium to the mixed composition and subjecting it to phase inversion emulsification, the first step of generating and dispersing the toner particles of the resin containing the colorant in the aqueous medium, the toner particle aqueous solution obtained in the step A second step of mixing the medium dispersion and a nigrosine compound and neutralizing the acid groups of the resin in the dispersed toner particles with the nigrosine compound, an aqueous medium from the toner particle aqueous medium dispersion obtained in the step A method for producing an electrophotographic toner, which comprises the third step of removing and drying. 3. A method of phase inversion emulsification by adding a mixed composition comprising a synthetic resin having an acid group, an organic solvent and a colorant as essential components to an aqueous medium containing an emulsifier and / or a dispersion stabilizer. A first step of generating and dispersing toner particles of the resin containing a colorant in an aqueous medium by adding an aqueous medium containing an emulsifier and / or a dispersion stabilizer to the mixed composition and performing phase inversion emulsification A second step of mixing the aqueous dispersion of toner particles obtained in the above step with a nigrosine compound and neutralizing the acid groups of the resin in the dispersed toner particles with the nigrosine compound, the toner obtained in the above step A method for producing an electrophotographic toner, comprising a third step of removing an aqueous medium from a particle aqueous medium dispersion and drying the same. 4. A mixed composition comprising a synthetic resin having an acid group neutralized with a nigrosine compound, an emulsifier and / or a dispersion stabilizer, an organic solvent and a colorant as essential components in an aqueous medium. In addition, phase inversion emulsification, or by adding an aqueous medium to the mixed composition to perform phase inversion emulsification, in the aqueous medium, the first step of generating and dispersing the toner particles of the resin in which the colorant is encapsulated, A method for producing an electrophotographic toner, comprising a second step of removing an aqueous medium from the aqueous dispersion of the toner particles obtained in the step and drying the aqueous medium. 5. A mixed composition containing a synthetic resin having an acid group neutralized with a nigrosine compound, an organic solvent, and a colorant as essential components in an aqueous medium containing an emulsifier and / or a dispersion stabilizer. In addition, phase inversion emulsification is performed, or an aqueous medium containing an emulsifier and / or a dispersion stabilizer is added to the mixed composition to perform phase inversion emulsification, and toner particles of the resin in which a colorant is encapsulated in the aqueous medium. And a second step of removing the aqueous medium from the aqueous dispersion of the toner particles obtained in the above step and drying it. 6. A mixed composition containing an anionic self-water-dispersible resin having an acid group and an acid group neutralized with a basic compound, an organic solvent, and a colorant as essential components in an aqueous medium. In addition, phase inversion emulsification, or by adding an aqueous medium to the mixed composition to perform phase inversion emulsification, in the aqueous medium, the first step of generating and dispersing the toner particles of the resin in which the colorant is encapsulated, A second step of mixing the aqueous dispersion of toner particles obtained in the step and a nigrosine compound, and neutralizing the acid groups of the resin in the dispersed toner particles with the nigrosine compound,
A method for producing an electrophotographic toner, comprising a third step of removing an aqueous medium from the aqueous dispersion of toner particles obtained in the above step and drying the same. 7. A non-neutralized resin composition containing a synthetic resin having an unneutralized acid group capable of self-dispersing in water by neutralization, an organic solvent, and a colorant as essential components. Phase-inversion emulsification by adding it to an aqueous medium containing a basic compound necessary for neutralizing a part of the acid groups of, or by adding an aqueous medium containing the compound to the mixed composition. According to the first step, in which the colorant-encapsulated toner particles of the anionic self-water-dispersible resin having the acid group and the acid group neutralized with the basic compound are dispersed in the aqueous medium, Second step of mixing the obtained toner particle aqueous medium dispersion and a nigrosine compound and neutralizing the unneutralized acidic groups on the dispersed toner particle surface with the organic basic compound, the toner obtained in the above step Removing the aqueous medium from the particle aqueous medium dispersion and drying. Method of manufacturing an electrophotographic toner comprising a. 8. An anionic self-water-dispersible resin having an acid group partially neutralized with a basic compound in toner particles dispersed in an aqueous medium dispersion of toner particles obtained in the first step. In order that the acid group neutralized with the basic compound becomes the original non-neutralized acid group, an acid is added to the toner particle aqueous medium dispersion to reverse neutralize and filter and wash. , The second
The manufacturing method according to claim 6 or 7, wherein steps are performed. 9. The second step is carried out after removing the organic solvent contained therein from the aqueous dispersion of the toner particles in the aqueous medium obtained in the first step. The manufacturing method described.