JP2001005226A - Toner matrix particles, toner and developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a clear full-color image with satisfactory color reproducibility and color developing property. SOLUTION: A solution prepared by dissolving a pigment (A) in sulfuric acid is put in water to form a fine deposit and this deposit is washed and filtered to prepare an aqueous paste (B). A chelating agent (C) is added to the aqueous paste B, mixed, stirred, washed and filtered to obtain a treated pigment (D). The objective negative charge type toner matrix particles for developing an electrostatic charge image contain the treated pigment D. The objective toner and developer are obtained using the toner matrix particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negatively chargeable toner base particle for developing an electrostatic image used in developing an electrostatic latent image in electrophotography, electrostatic recording, electrostatic printing, and the like, and the toner base. The present invention relates to a toner and a developer formed using particles. More specifically, when an image is formed using magenta, cyan, yellow, and black toners together, a negatively chargeable toner for developing an electrostatic image capable of forming an image having excellent clarity, color reproducibility, and coloring. Particles and toners and developers.

[0002]

2. Description of the Related Art In recent years, development of full-color images in copying machines, printers, and the like has been rapidly progressing, and their practical use has been greatly increased. However, compared to photographs and printed matter, it is hard to say that a full-color electrophotographic image currently in practical use has reached a satisfactory image quality. In recent years, with the advancement and development of computers, high-definition televisions, and the like, there is a strong demand for a method of forming a higher-resolution full-color image. For this reason, there is a strong demand for further improving the quality of full-color electrophotographic images.

In electrophotography, an electrostatic latent image is generally developed using a developer. The methods are broadly classified into a method using a one-component developer without using a carrier, and a method using a two-component developer in which a small amount of a toner component is dispersed in a carrier. In the case of full-color electrophotography, a two-component developer is often used.

In color image formation by full-color electrophotography, all colors are reproduced by using three developers of three primary colors, magenta, cyan, and yellow, and preferably four colors of black for inking. Things. In this method, for example, light from a document is first subjected to analog or digital color separation and guided to a photoconductive layer of a photoreceptor to form an electrostatic latent image of the first color. Subsequently, through a development and transfer process, the developer is held on a recording medium such as paper. Further, for the second and subsequent colors, the above-described steps are sequentially performed a plurality of times, and a plurality of color developers are superimposed on the same transfer material, and a final full-color image is obtained by one-time fixing.

[0005] Today, full-color image formation on a transparent substrate such as a sheet for an overhead projector (hereinafter abbreviated as OHP) using a full-color copying machine or a full-color printer has been increasing. In the developer used for full-color image formation, various properties such as stable chargeability and good fluidity, sharpness, color, etc. Reproducibility, transparency, and the like are further required.

In recent years, photoreceptors for electrophotography have been developed using OPs using organic substances instead of toxic heavy metals such as selenium.
C (organic photoreceptor) is widely used. Recently, a method of digitally color-separating an image and using a laser beam to draw an electric latent image on the surface of the photoconductor has been widely adopted. In the case of digitally processing an image, the reversal development method makes it easier to obtain a high-definition image. OPC is inherently negatively charged, so the developer used for normal development is positively charged,
In recent years, reversal development has been adopted for the above reasons, and therefore, negatively chargeable developers are widely used. Therefore, in order to form a better image with a negatively chargeable developer, one having good chargeability is strongly demanded.

[0007]

In a conventional negatively chargeable developer, a small amount of free metal derived from unreacted raw materials or washing water at the time of pigment synthesis becomes ionized and becomes electrically positive. Had an adverse effect. For this reason, it has been difficult to obtain a clear image having high color reproducibility and coloring.

As a measure for improving transparency, it has been conventionally considered to increase the degree of dispersion of the pigment, that is, to reduce the particle size of the pigment in the developer. Generally, as the particle size of the pigment is reduced to increase the degree of dispersion, the transparency of the pigment dispersion is improved. However, ordinary dispersing machines such as a sand mill, a three-roll mill, a ball mill, and an extruder mainly break down secondary particles of the pigment (primary particles are weakly aggregated) into primary particles. It is actually difficult to reduce the particle size. Depending on the kind of the pigment, it is possible to make it fine by a high-speed sand mill or the like, but it requires a very large amount of energy and is inefficient.

A pigment and a water-soluble inorganic salt moistened with a small amount of a water-soluble solvent are kneaded strongly with a kneader or the like, and then the inorganic salt and the solvent are washed away with water to remove the pigment. Although there is a method of obtaining particles, there is a problem that strong secondary aggregation is likely to occur when dried.

As another method for making the pigment finer, there is a method in which the pigment and solid resin are heated and kneaded vigorously with a two-roll or Banbury mixer. However, since the pigment generally grows at high temperatures, The effectiveness of this method is the end point when the mechanical crushing force and the crystal growth are in an equilibrium state, and further refinement of the pigment is limited.

[0011]

Means for Solving the Problems A first invention of the present invention is:
A solution obtained by dissolving the pigment (A) in sulfuric acid is poured into water to form fine precipitates, and then the chelating agent (C) is added to the aqueous paste (B) obtained by washing and filtering, followed by mixing, stirring, and washing with water. And negatively chargeable toner base particles for developing an electrostatic image, characterized by containing a treated pigment (D) obtained by filtration.

In the second invention, the pigment (A) is preferably a quinacridone pigment, a phthalocyanine pigment, a benzimidazolone pigment, a diketopyrrolopyrrole pigment, a perinone pigment, an anthraquinone pigment, a dioxazine pigment, or a perylene pigment. The negatively chargeable toner base particles for electrostatic image development according to the first invention, wherein the mother particles are at least one member selected from the group consisting of pigments, isoindolinone pigments, and azo pigments.

According to a third aspect of the present invention, there is provided the electrostatic image developing apparatus according to the first or second aspect, wherein a solution obtained by dissolving the pigment (A) in sulfuric acid is thrown into continuously flowing water. These are negatively chargeable toner base particles.

According to a fourth aspect of the present invention, the treated pigment (D) is treated with 0.1 to 15 parts by weight of a chelating agent (C) based on 100 parts by weight of the pigment in the aqueous paste (B). The negatively chargeable toner base particles for electrostatic image development according to any one of the first to third aspects of the invention.

According to a fifth aspect of the present invention, there is provided an electrostatic charge obtained by mixing the negatively chargeable toner base particles for developing an electrostatic image according to any one of the first to fourth aspects with an external additive. This is a negatively chargeable toner for image development.

According to a sixth aspect of the present invention, there is provided a negatively chargeable developer comprising a mixture of the negatively chargeable toner for developing an electrostatic image described in the fifth aspect and a carrier.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The pigment (A) used in the present invention includes quinacridone pigments such as quinacridone red and quinacridone magenta; phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green; benzimidazolone pigments; and diketopyrrolopyrrole. Pigments, perinone pigments, anthraquinone pigments, dioxazine pigments, perylene pigments such as perylene red and perylene scarlet, isoindolinone pigments, azo pigments and the like are used, quinacridone pigments, phthalocyanine pigments,
Benzimidazolone-based pigments, diketopyrrolopyrrole-based pigments, perinone-based pigments, anthraquinone-based pigments, dioxazine-based pigments, perylene-based pigments, isoindolinone-based pigments, azo-based pigments, and the like. More than one combination is used. Further, a functional group may be added to the surface of these pigments.

After dissolving the pigment (A) in concentrated sulfuric acid, the solution is poured into water. At this time, since constant conditions are always maintained from the first stage to the last stage of the operation by pouring into continuously flowing water, not only stable precipitation of fine particles is generated but also A certain quality can be obtained (hereinafter, this step is referred to as acid paste). When the liquid in which the pigment is dissolved in concentrated sulfuric acid is put into water in which the liquid is retained, the temperature of the liquid sharply rises due to the heat of dissolution when the sulfuric acid is dissolved in the water, and the finely divided pigment crystals tend to grow. Therefore, it is preferable to pour into continuous flowing water.

In the present invention, the continuously flowing water is defined as
It means a tube having a water pressure of 0.5 to 4.5 kg / cm ² , or water flowing through the tube. The solution in which the pigment is dissolved in concentrated sulfuric acid can be introduced into the continuously flowing water quantitatively using a water aspirator, or the solution in which the pigment is dissolved in concentrated sulfuric acid can be used in an amount of 0.5 to 4. It is preferable to pressurize the water to 5 kg / cm ² and spray it into the water flowing continuously from the capillary.

The precipitate of pigment fine particles obtained by contacting a solution in which the pigment is dissolved in concentrated sulfuric acid with water that flows continuously is as follows:
After filtration and separation from water, washing and filtration are repeated with water, ion-exchanged water or an aqueous solution of a weak concentration such as caustic soda or caustic potassium, and the washing and filtration is repeated until the pH reaches a neutral range, and the aqueous paste (B) is obtained. The pigment concentration in the aqueous paste (B) is 10 to
40% by weight is preferred.

The preferred dispersed particle diameter and primary particle diameter of the pigment in the aqueous paste (B) are as follows: the average particle diameter is 1.0 μm as measured by laser scattering or electron microscope.
Hereinafter, it is more preferable that the thickness be 0.2 μm or less.

The chelating agent (C) used in the present invention comprises:
Reacts with metal ions derived from pigments, washing water, etc.
It is added to form and remove the ring. Ring formation is
It is caused by the formation of covalent bonds or coordination bonds or both. In a negatively chargeable developer, if a free metal is contained as an impurity in the pigment, the free metal is ionized and becomes positive, which adversely affects the chargeability of the developer. The chelating agent captures metal ions,
The content of free metal ions in the pigment is reduced to improve and improve the chargeability of the developer. In the usual pigment production process, it is quite difficult to completely remove the free metal ions mixed even by repeating filtration and washing with purified water. Then,
A free metal ion is trapped and removed using a chemical agent.

As specific examples of the chelating agent (C), ligands having two acidic groups include, for example, malonic acid, oxalic acid, phthalic acid, glycolic acid, salicylic acid and the like.
Examples of ligands having one acidic group and one non-acidic coordinating group include 8-quinolinol, acetylacetone, trifluoroacetone, dimethylglyoxime, dithizone, salicylaldehyde and the like. Ligands having two non-acidic coordination groups include ethylenediamine, 2,2′-bipyridine, 1,10-phenanthroline and the like. Examples of aminopolycarboxylic acids include ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, butylenediaminetetraacetic acid, pentylenediaminetetraacetic acid, and sodium or ammonium salts thereof.

The chelating agent is preferably used in an amount of 0.1 to 15 parts by weight, more preferably 1 to 10 parts by weight, particularly preferably 1 to 10 parts by weight, based on 100 parts by weight of the pigment in the aqueous paste (B).
-5 parts by weight. If the amount of the chelating agent is less than the lower limit, the effect of improving the chargeability is not seen, and if it is more than the upper limit, the risk of remaining in the developer increases, and it is difficult to obtain sharpness and transparency when an image is formed.

Since the purpose of the chelating agent treatment of the pigment is to capture a trace amount of metal ions mixed in the pigment, a chelating agent is added to the aqueous paste (B) of the pigment after the acid pasting step. Is most effective. The presence of water is essential for the treatment of the pigment with the chelating agent. The pigment concentration in the aqueous paste (B) is preferably from 0.1 to 20%. The chelating agent treatment is preferably performed after the sulfuric acid content is completely removed from the aqueous paste (B). To prevent aggregation of the pigment, the aqueous paste (B) is added with the chelating agent (C) without drying, mixed and stirred for 10 to 30 minutes, and then washed and filtered to remove the chelating agent capturing the metal. Then, dry and pulverized to obtain a treated pigment (D).

The method for producing the negatively chargeable toner base particles (hereinafter referred to as toner base particles) for developing an electrostatic image of the present invention can be any known one, and is not particularly limited. That is, a binder resin and, if necessary, a charge control agent and other additives are added to the above treated pigment (D), premixed by a Henschel mixer or the like, and then diluted and melt-kneaded by an extruder or the like. . Next, after cooling, it is coarsely pulverized by a hammer mill or the like and finely pulverized by a jet mill or the like. After that, it is classified with an air classifier or the like, and the average particle size is 5 to 2
A classified product having a particle size distribution of 0 μm was obtained and used as toner base particles.

As the binder resin, generally known resins can be used. From the viewpoint of image transparency, a colorless and transparent resin is more preferable. For example, polystyrene, styrene
Acrylic ester copolymer, styrene-butadiene copolymer, chloride resin, styrene-vinyl acetate copolymer, rosin-modified maleic resin, phenol resin, epoxy resin, polyester resin, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resin , A polyurethane resin, a silicone resin, a rosin ester, a rosin, etc., but the production method of any resin is not particularly limited.

As an example of the charge control agent, when the toner base particles are black, known negative chargeable agents can be used. Specific examples include chromium-containing metal complexes, rhodamine-based dyes, and organic metal complexes such as metal complexes of alkyl-substituted salicylic acids (for example, chromium complexes, aluminum complexes, and zinc complexes of di-tert-butylsalicylic acid). I can do it.

When the toner base particles are other than black, a colorless or light-colored charge control agent which does not affect the color tone of an image is preferred. For example, an organic metal complex such as a metal complex of an alkyl-substituted salicylic acid (for example, a chromium complex, an aluminum complex, or a zinc complex of di-tert-butylsalicylic acid) can be given.

When the toner base particles of the present invention are color toner base particles, three of yellow, cyan and magenta, respectively, are used.
A developer obtained from a color pigment may be used.

In the case of black toner base particles, the above-described three color pigments of yellow, cyan and magenta may be obtained and used in combination. It does not prevent the use of carbon black as a pigment. As carbon black, channel black, furnace black,
All known materials such as lamp black can be used.

It is preferable that the toner base particles of the present invention are mixed with an external additive such as a flow improver or a cleaning aid to form a negatively chargeable toner for electrostatic charge development. A method for producing a negatively chargeable toner for developing an electrostatic image is obtained by adding an external additive to toner base particles and mixing them with a Henschel mixer or the like. The addition amount of the external additive is preferably 0.1 to 5% by weight. The average particle size of the negatively chargeable toner for developing an electrostatic image is suitably 5 to 20 μm.

Any known external additives can be used. For example, 0.01 to 0.5 μm silica, alumina,
Metal oxides such as titanium oxide, abrasives such as silicon carbide and tungsten carbide, lubricants such as fatty acid metal salts such as zinc stearate and aluminum stearate, other polytetrafluoroethylene, polyvinylidene fluoride, polymethyl methacrylate, Fine powders such as polystyrene and silicone, mixtures thereof, and those obtained by subjecting these fine powders to various surface treatments may be used.

The negatively chargeable developer of the present invention is a two-component type developer obtained by mixing the above-mentioned negatively chargeable toner for electrostatic image development with a carrier, and can be obtained by a conventionally known method. And there is no particular restriction.

As the carrier, all known carriers can be used. In general, carriers are roughly classified into conductive carriers and insulating carriers. As a conductive carrier,
Usually, oxidized or unoxidized iron powder is used.

A typical example of the insulating carrier is a carrier in which the surface of a carrier core material particle generally made of a ferromagnetic material is uniformly coated with an insulating resin. Examples of the core material include particles of iron oxide (magnetite), reduced iron, copper, ferrite, nickel, cobalt, and the like, and alloys of these with zinc, aluminum, and the like. Any of known materials such as acrylic resin, epoxy resin, silicone resin, urethane resin, polyacetal resin, polyamide resin, polycarbonate resin, phenol resin, vinyl acetate resin, cellulose resin, polyolefin resin, fluororesin, amino resin, etc. It may be. The carrier preferably has a particle size of about 20 to 200 μm. Generally, the two-component developer preferably contains 1 to 30% of toner. In general, in consideration of the life of the developer and the like, an insulating carrier coated with a resin is superior, and is often used in practice.

[0037]

The present invention will be described below in more detail with reference to Examples and Comparative Examples. However, this does not limit the embodiment of the present invention at all. In Examples and Comparative Examples, parts and% indicate parts by weight and% by weight, respectively.

[Example 1] [Acid pasting treatment] Hosta Palm Pink E
(Quinacridone pigment, Hoechst) 30 parts and 98%
300 parts of sulfuric acid was weighed into a 1 liter glass beaker and stirred for 1 hour to sufficiently dissolve the pigment. The entire amount of the dissolved solution was added dropwise over 1 minute through an aspirator connected to a water flow set to 3.5 kg / cm ² at a gauge pressure. The precipitate was collected by filtration, and washing and filtration were repeated with purified water until the pH reached 6.8, whereby an aqueous paste (B) having a pigment concentration of 30% was obtained.

[Chelating agent treatment] Next, 3 parts of sodium ethylenediaminetetraacetate was added to the aqueous paste (B), and the mixture was stirred for 15 minutes, washed with water and filtered to obtain an aqueous paste having a pigment concentration of 30%. Was dried and pulverized to obtain a treated pigment (D).

[Preparation of Negatively Chargeable Toner for Developing Electrostatic Image] The above treated pigment (D) 3 parts Unsaturated polyester resin (binder resin) 100 parts Negative charge control agent 3 parts Mixing was performed and melt kneading was performed with a twin-screw extruder. After cooling, the mixture was roughly pulverized using a hammer mill and further finely pulverized using a jet mill, and negatively chargeable toner base particles for electrostatic charge development having an average particle diameter of 10 μm were obtained using an air classifier. This toner mother particle 1
To 00 parts, 0.4 part of titanium oxide fine powder having an average particle diameter of 0.05 μm was added and mixed with a Henschel mixer to obtain a negatively chargeable toner for developing an electrostatic image.

[Preparation of Developer] 6 parts of the above toner was added to 100 parts of ferrite, and mixed with a ball mill to obtain a developer.

[Evaluation of Developer] (1) The dispersion state of the pigment in the developer was observed with an optical microscope. As a result, the dispersion state was very good without aggregation. (2) The charge amount of the developer was measured by a blow-off powder charge amount measuring device manufactured by Toshiba Chemical Corporation. As a result, 20-30
It was in the range of μC / g, which was good. (3) A commercially available full-color copying machine (CLC
350, manufactured by Canon Inc.), and color reproducibility and color development were confirmed. As a result, a sufficient image having sufficient color reproducibility and coloring was obtained.

Example 2 [Acid Pasting Treatment] Lionol Blue F
30 parts of G-7351 (phthalocyanine pigment, manufactured by Toyo Ink Mfg. Co., Ltd.) and 300 parts of sulfuric acid were weighed into a 1 liter glass beaker, and stirred for 1 hour to be sufficiently dissolved. The entire amount of the dissolved solution was added dropwise over 1 minute through an aspirator connected to a water flow set to 3.5 kg / cm ² at a gauge pressure. The precipitate was collected by filtration, and washing and filtration were repeated with purified water until the pH reached 7.0, whereby an aqueous paste (B) having a pigment concentration of 40% was obtained.

[Chelating agent treatment] Then, 3 parts of sodium ethylenediaminetetraacetate was added to the aqueous paste (B), and the mixture was stirred for 15 minutes, washed with water and filtered to obtain an aqueous paste having a pigment concentration of 40%. After drying and pulverizing, a treated pigment (D) was obtained. Hereinafter, a developer was obtained in the same manner as in Example 1, and the state of dispersion of the pigment, the change in the amount of charge, and the image were evaluated. The results were the same as those in Example 1.

Example 3 Acid Pasting Treatment Hostaperm Yellow H3G (Benzimidazolone Pigment, Hoechst) 3
5 parts and 300 parts of sulfuric acid were weighed into a 1 liter glass beaker, and stirred for 1 hour to sufficiently dissolve. The entire amount of the dissolved solution was added dropwise over 1 minute through an aspirator connected to a water flow set to 3.5 kg / cm ² at a gauge pressure. The precipitate was collected by filtration, and washing and filtration were repeated with purified water until the pH reached 7.0, whereby an aqueous paste (B) having a pigment concentration of 35% was obtained.

[Chelating Agent Treatment]
To the strike (B), 3 parts of sodium ethylenediaminetetraacetate were added, stirred for 15 minutes, washed with water and filtered to obtain an aqueous paste having a pigment concentration of 35%, and dried and pulverized to obtain a treated pigment (D). Hereinafter, a developer was obtained in the same manner as in Example 1, and the state of dispersion of the pigment, the change in the amount of charge, and the image were evaluated. The results were the same as those in Example 1.

Example 4 [Acid Pasting Treatment] 35 parts of Irgazine DPP RED BO (diketopyrrolopyrrole-based pigment Ciba-Geigy) and 300 parts of sulfuric acid
Was weighed into a 1-liter glass beaker and stirred for 1 hour to dissolve sufficiently. The entire amount of the dissolved solution was added dropwise over 1 minute through an aspirator connected to a water flow set to 3.5 kg / cm ² at a gauge pressure. The precipitate is collected by filtration and adjusted to pH
Washing with purified water and filtration until the pH reached 7.0 gave a treated pigment (D) having a pigment concentration of 35%.

[Chelating agent treatment] Next, 3 parts of ethylenediaminetetraacetic acid sodium salt was added to the treated pigment (D), and the mixture was stirred for 15 minutes, washed with water and filtered to obtain a pigment concentration of 3%.
5% aqueous paste is obtained, dried and pulverized to obtain a treated pigment (D)
I got Hereinafter, a developer is obtained by performing the same processing as in Example 1,
When the dispersion state of the pigment, the change in the amount of charge, and the image were evaluated, the same results as in Example 1 were obtained.

Embodiment 5 [Acid Pasting Treatment] Chromophthal Red A
2B (anthraquinone pigment, Ciba-Geigy) 35
And 300 parts of 98% sulfuric acid were weighed into a 1 liter glass beaker, and stirred for 1 hour to sufficiently dissolve. The entire amount of the dissolved solution was added dropwise over 1 minute through an aspirator connected to a water flow set to 3.5 kg / cm ² at a gauge pressure. The precipitate was collected by filtration, and washed and filtered with purified water until the pH reached 6.8, whereby a treated pigment (D) having a pigment concentration of 35% was obtained.

[Chelating agent treatment] Then, 3 parts of ethylenediaminetetraacetic acid sodium salt was added to 100 parts of the treated pigment (D), and the mixture was stirred for 15 minutes, washed with water and filtered to obtain an aqueous paste having a pigment concentration of 35%. After drying and pulverization, a treated pigment (D) was obtained. Hereinafter, a developer was obtained in the same manner as in Example 1, and the state of dispersion of the pigment, the change in the amount of charge, and the image were evaluated. The results were the same as those in Example 1.

[Comparative Example 1] Hosta Palm Pink E (quinacridone pigment, manufactured by Hoechst) 3 parts Unsaturated polyester resin (same as in Example 1) 100 parts Negative charge control agent 3 parts Henschel mixer Perform pre-mixing with
Melt kneading was performed with a twin-screw extruder. After cooling,
After coarse pulverization using a hammer mill and fine pulverization using a jet mill, colorant-containing fine particles having an average particle size of 10 μm were obtained using an air classifier. To 100 parts of the coloring agent-containing fine particles, 0.4 part of titanium oxide fine powder having an average particle diameter of 0.05 μm was added and mixed with a Henschel mixer to form a toner.

The above toner was added to 6 parts of ferrite for 6 parts.
And the mixture was mixed with a ball mill mixer to obtain a developer. Evaluation was performed in the same manner as in Example 1. Aggregation of the pigment was confirmed in the developer, and the dispersion state was poor. Further, the charge amount of the developer was in the range of 15 to 20 μC / g, which was poor.
It was lower than that. Furthermore, when an image was formed,
Example 1 (Acid pasting treatment,
Compared with the chelating agent treatment, the difference was obvious, and it was confirmed that the transparency was remarkably inferior particularly when an image was formed on an OHP sheet.

[Comparative Examples 2 to 5] Instead of the pigment used in Comparative Example 1, Comparative Example 2: Lionol Blue FG-7351 (phthalocyanine pigment, manufactured by Toyo Ink Mfg. Co.) Comparative Example 3: Hostaperm Comparative Example 4: Irgazine DPP RED BO (Diketopyrrolopyrrole-based pigment, manufactured by Ciba Geigy), Comparative Example 5: Chromophthal Red A2B (Anthraquinone-based pigment, (Ciba-Geigy Co., Ltd.) was used, and a developer was obtained in the same manner as in Comparative Example 1. Evaluation was performed in the same manner. In each case, the same results as in Comparative Example 1 were obtained. In addition, when images obtained using the same pigment in each of the examples, for example, the developers obtained in Example 2 and Comparative Example 2, were compared side by side, a clear decrease in image quality was confirmed.

[0054]

According to the present invention, a negatively chargeable toner mother for developing an electrostatic image using a pigment obtained by first purifying the pigment by acid paste and then capturing a trace amount of metal ions by a chelating agent. The toner and the toner using the toner base particles improved the chargeability of the negatively chargeable developer, and provided a clear image with good color reproducibility, color development and transparency. In particular, this effect is remarkable when an image is formed on a transparent substrate such as a sheet for OHP, and it is possible to provide a clear and transparent image comparable to a dye.

Claims (6)

[Claims] 1. A solution in which a pigment (A) is dissolved in sulfuric acid is poured into water to form fine precipitates, and a chelating agent (C) is added to an aqueous paste (B) obtained by washing and filtering. Negatively chargeable toner base particles for developing an electrostatic image, comprising a treated pigment (D) obtained by mixing, stirring, washing and filtering. 2. The pigment (A) is a quinacridone pigment, a phthalocyanine pigment, a benzimidazolone pigment, a diketopyrrolopyrrole pigment, a perinone pigment, an anthraquinone pigment, a dioxazine pigment, a perylene pigment, or isoindia. 2. The negatively chargeable toner base particles for electrostatic image development according to claim 1, wherein the particles are at least one selected from the group consisting of linone pigments and azo pigments. 3. The negatively chargeable toner base particles for developing an electrostatic image according to claim 1, wherein a solution obtained by dissolving the pigment (A) in sulfuric acid is thrown into continuously flowing water. 4. The treated pigment (D) is an aqueous paste (B).
The chelating agent (C) is added to 100 parts by weight of the pigment content therein.
4. The negatively chargeable toner base particles for developing an electrostatic image according to claim 1, wherein the base particles are processed with 1 to 15 parts by weight. 5. A negatively chargeable toner for developing an electrostatic charge image obtained by mixing the negatively chargeable toner base particles for developing an electrostatic charge image according to claim 1 with an external additive. toner. 6. A negatively chargeable developer comprising a mixture of the negatively chargeable toner for developing an electrostatic image according to claim 5 and a carrier.