JP2004191934A - Electrophotographic positively charged toner and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic positively charged toner which has its electrification potential not impaired because the charge control agent therein is not coated even when the toner particles are made spherical by melting the particle surfaces in a hot air current after the toner is kneaded, pulverized and classified and thus the toner maintains sufficient tribo-charging capability for good image formation, excellent transfer efficiency, excellent charge build-up performance and excellent charge stability upon continuous printing, and to provide a manufacturing method thereof. <P>SOLUTION: The electrophotographic positively charged toner contains: a core toner obtained by mixing a binder resin, a wax, a colorant and the charge control agent as principal materials and making the toner particles spherical by heat treatment; and at least fine silica particles as an external additive. The charge control agent contains resin having a quaternary ammonium salt group as a functional group and a nigrosine dye. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

The present invention relates to a toner for developing an electrostatic latent image used in an electrophotographic image forming apparatus and the like, and more particularly to a positively charged toner for electrophotography and a method for manufacturing the same.

In the development process, toner for developing an electrostatic latent image used in an electrophotographic copying machine, a printer, or the like is used in a developing process. The image is visualized by being transported and attached to the image. This toner image is transferred from the photoreceptor surface to a transfer medium (paper or the like) in the next transfer step, is fixed in a fixing step, and is discharged as a print image printed on the transfer medium (paper or the like). . Generally, the developing process is roughly classified into a two-component developing method using a combination of a toner and a carrier and a one-component developing method using a toner alone.

  Each of the toners used in the developing method is generally prepared by dispersing a carbon black, a pigment, and the like as a colorant in a binder resin made of a thermoplastic resin containing a natural resin by hot-melt kneading, and then dry-pulverizing the particles. Used as For example, after kneading and dispersing the colorant in a binder resin containing a styrene acrylic copolymer as a main component with a stirrer such as a kneader, an extruder and a Banbury mixer, finely pulverize the particles to about 5 to 20 μm. And Further, a magnetic toner such as magnetite which is further contained during the kneading and dispersion is used as a magnetic toner.

  In any of the toners used in the developing method, a positive or negative charge is applied and held corresponding to the positive or negative charge polarity of the photoreceptor surface before the electrostatic latent image is formed. There is a need. The charge-imparting ability for this purpose can utilize the frictional charge inherent to the material such as the binder resin and the colorant, which are the components of the toner, but is generally obtained by the inherent frictional charge such as the material. Since the amount of charge applied is often too small for good image formation, an image developed only by the frictional charge tends to have background stains or become unclear. Therefore, in practice, in order to impart to the toner the triboelectric charge necessary for good image formation, a charge control agent such as a dye, a pigment, or a specially adjusted organic compound, which makes it easy to impart charge, is used. It is common to add substances referred to as: As such charge control agents, there are materials corresponding to charge imparting ability of positive and negative polarities, respectively, and various types are known.

  Among them, as the positive charge adjuster, various azine compounds, nigrosine dyes, triphenylmethane dyes, dyes such as phthalocyanine pigments, and quaternary ammonium salt compounds, quaternary ammonium bases or amine groups Resin or the like is a well-known material and has been conventionally used. These charge control agents are often used alone. Above all, the positive charge control agent of the nigrosine dye is often used alone, but the chemical structure is complicated, and the chemical stability is poor as a substance. There is a problem that chemical decomposition or alteration is likely to occur due to factors such as mechanical shock, charging stability is impaired, charging ability is reduced, and the original charge providing ability cannot be exhibited.

  Further, when the quaternary ammonium salt compound, the quaternary ammonium base, or the polymer compound (resin) containing a positively-charged functional group such as an amine group is used as the charge adjusting agent, the dye-based compound is used. There is no problem during hot melt kneading, but the friction charge imparting ability is considerably lower than the former, so the amount of charge control agent added is large in order to obtain the amount of charge necessary for good image formation alone. There is a need to. However, particularly in the case of the resin-based charge control agent, if the added amount is too large, there is a problem that the anti-offset property is impaired, and the adjustment of the added amount is extremely difficult. Details of these charge control agents are described in the following patent documents.

  In addition, the styrene-acrylic copolymer or polyester resin, which is generally used frequently as a binder resin, generally exhibits negative charge in the developing step, so that the resin itself exhibits a negative charge. Because the toner is adjusted to be positively charged, the positive charge providing ability of the toner is not always sufficient and stable compared to the negative charge providing ability. For example, when continuous printing is used, charge deterioration is likely to occur due to the separation of the charge adjusting agent from the toner, and as a result, the toner on the photoconductor due to image defects such as print density reduction, background contamination, or charge deterioration is likely to occur. A problem called the filming phenomenon may occur. As described above, the toner obtained by dry pulverization to which the conventional charge controlling agent is added, particularly the positively charged toner, has to be said to be insufficient from the viewpoint of maintaining a stable positive charge providing ability for a long period of time.

In recent years, in order to cope with higher image quality of electrophotographic copying machines, printers and the like, the toner used in the electrophotographic apparatus has been reduced in particle size. In the conventional dry pulverization method, there are problems such as a decrease in fluidity and a non-uniform chargeability due to a reduction in particle size, a deterioration in image quality, a decrease in transfer efficiency, and the like. In order to solve these problems, a wet granulation method by suspension or emulsion polymerization of a binder resin has been developed, and even a toner having a small particle size can be obtained without a decrease in fluidity, and has already been put to practical use. ing.
JP-A-62-1210472 JP-A-63-60458 JP-A-3-80259 JP-A-5-119509 JP-A-11-241353 JP-A-11-242360 JP-A-2000-214633 JP-A-2001-92188

  However, in these wet granulation methods, impurities such as a surfactant and a polymerization initiator added at the time of granulation are likely to remain in the toner particles after granulation, and may adversely affect the chargeability, the insulating property, and the like. Many. Further, in the above wet polymerization granulation method, usable binder resins are limited, so that selectivity of the resins is narrow. Further, there is a problem that the degree of freedom of the molecular weight distribution is limited.

  On the other hand, in the conventional dry pulverization method, a method for introducing the toner after kneading and pulverization classification into a hot air stream and melting and spheroidizing the particle surface to solve the problems such as the decrease in the fluidity is also known. As is already known, the problem of this method is that the toner charge decreases due to the spheroidization of the toner surface due to the melting. That is, the charging ability is reduced by melting and covering the charge adjusting agent present and exposed on the surface with the molten resin due to the surface melting of the toner particles.

  The present invention has been made in view of the above points, and even if the toner after kneading and pulverization and spheroidization by melting the particle surface in a hot air stream is coated with a charge adjusting agent, the chargeability thereof is increased. Positively charged toner for electrophotography having excellent triboelectricity required for good image formation, excellent transfer efficiency, excellent charge start-up performance and charge stability after continuous printing without lowering the toner, and a method for producing the same. Offer.

  According to the present invention, the above object includes a core toner obtained by subjecting a binder resin, a wax, a colorant, and a charge control agent as main components to sphering treatment by heat treatment, and at least silica fine particles as an external additive. In a positively charged toner for electrophotography, the charge control agent is achieved by providing a positively charged toner for electrophotography containing a resin having a quaternary ammonium base as a functional group and a nigrosine dye.

  According to the present invention, based on 100 parts by weight of the binder resin, the charge control agent has 2 to 10 parts by weight of a resin having a quaternary ammonium base as a functional group, and 0.5 to 5 parts by weight of a nigrosine-based resin. It is preferable to use a positively charged toner for electrophotography according to claim 1 containing a dye.

According to the present invention, a resin having a quaternary ammonium base as a functional group is a styrene acrylic copolymer containing a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2): A positively charged toner for electrophotography according to claim 1 or 2, wherein the toner is mainly composed of a coalesced resin (wherein R ¹ and R ² are a hydrogen atom or a methyl group, R ³ is an alkylene group, R ⁴ , R ⁵ and R ⁶ each represent an alkyl group, the repeating unit represented by the following formula (1) is 65 to 97% by weight, and the repeating unit represented by the following formula (2) is 35 to 3% by weight; And the weight average molecular weight is in the range of 2,000 to 10,000).

  According to the present invention, the binder resin is more preferably a positively charged toner for electrophotography according to any one of claims 1 to 3, wherein the binder resin is mainly composed of a styrene acrylic copolymer resin.

  According to the present invention, the colorant contains carbon black having a pH of 8.0 or more in an amount of 3 to 6 parts by weight based on 100 parts by weight of the binder resin. It is more preferable to use a positive charging toner for electrophotography.

  According to the present invention, a binder resin, a wax, a colorant, and a charge control agent are mainly used for producing the positively charged toner for electrophotography according to any one of claims 1 to 5 of the claims. After mixing and stirring as a component material, a kneaded product obtained by hot-melt kneading is pulverized and classified into a core toner, and the core toner is sphericalized by hot air treatment, and then mixed with at least silica fine particles as an external additive. The above object is achieved by a method for producing a charged toner.

  According to the present invention, a positive electrophotographic toner containing a binder resin, a wax, a colorant, and a charge control agent as main components and subjected to a sphering treatment by a heat treatment, and at least silica fine particles as an external additive. In the charged toner, the charge adjusting agent was a positively charged toner for electrophotography containing a resin having a quaternary ammonium base as a functional group and a nigrosine dye, so that the toner after kneading and pulverization was classified in a hot air stream. Even if the particles are formed into a spheroid by melting the surface, the charge controlling agent is coated and the chargeability is not reduced, and the frictional charge necessary for good image formation is obtained, the transfer efficiency is excellent, the charge rising performance and A positively charged toner for electrophotography having excellent charge stability after continuous printing and a method for producing the same can be provided.

  Hereinafter, the positively charged toner for electrophotography of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments described below unless it exceeds the gist. FIG. 1 is a schematic sectional view of a processing apparatus for spheroidizing a positively charged toner for electrophotography according to the present invention. FIG. 2 is an SEM photograph (magnification: 800 times) of the positively charged toner for electrophotography of the present invention before spheroidizing. FIG. 3 is an SEM photograph (× 800) of the positively charged toner for electrophotography after the spheroidizing process according to the present invention.

  The electrophotographic positively charged toner of the present invention has a binder resin, a wax, a colorant, and a charge control agent as main components, and after mixing and stirring these materials, pulverizes a kneaded product obtained by hot-melt kneading, The core toner obtained by the classification is subjected to a spheroidizing treatment, and then a treatment of mixing an external additive such as silica fine particles in order to further improve the fluidity of the toner. Hereinafter, each material of the binder resin, the wax, the colorant, and the charge adjusting agent will be sequentially described.

(Binder resin)
As the binder resin used in the present invention, a resin mainly composed of a general thermoplastic resin having good fixability, which is well known as a binder resin, can be used. For example, a resin containing a polyester resin, a polystyrene resin, a styrene-acryl copolymer resin, an epoxy resin, a vinyl chloride resin, a vinyl acetate resin alone, a mixture thereof, or two or more copolymer resins as a main component is used. In particular, the styrene acrylic copolymer resin has excellent compatibility when the charge control agent according to the present invention described later is based on a styrene acrylic copolymer resin, and the charge control agent is released when the toner is repeatedly used. This is preferable because it is effective in preventing such a situation. For example, in the case of a styrene-acrylic copolymer resin, in order to satisfy both good fixability and offset resistance of the toner, a weight molecular weight distribution in the range of 2000 to 900,000, a low molecular weight of several thousand and a hundred thousand Resins each having a peak distribution in the high molecular weight region are preferred.

(wax)
The positively charged toner for electrophotography of the present invention contains waxes for the purpose of improving the offset resistance. Known waxes such as polyethylene wax, polypropylene wax, beeswax, and carnauba wax can be used as such waxes. The amount of the wax added is preferably in the range of 1 to 7 parts by weight based on 100 parts by weight of the binder resin. If the amount is less than 1 part by weight, the offset resistance becomes poor, and if the amount is more than 7 parts by weight, toner particles tend to aggregate.

(Colorant)
As the colorant contained in the positively charged toner for electrophotography of the present invention, carbon black, lamp black, iron black, other known dyes, pigments and the like can be used alone or in combination. When carbon black is used as the colorant, the amount is preferably in the range of 3 to 6 parts by weight based on 100 parts by weight of the binder resin.

  It was found that when the pH value of the carbon black used in the toner according to the present invention was made alkaline at 8.0 or more, the triboelectricity exhibited positive polarity. The pH of the carbon black is measured on the mud. It is mainly affected by the number of surface oxygen-containing groups of carbon black or the amount of mixed ash (metal oxide and other residues). Generally, channel black is acidic and furnace black is known to be neutral to alkaline.

(Charge control agent)
As the charge adjusting agent contained in the positively charged toner for electrophotography of the present invention, a resin having a quaternary ammonium base as a functional group and a nigrosine dye are used in combination. As the former resin, a positive charge adjusting agent described in detail in JP-A-63-60458 can be used. As described in the above publication, the weight average molecular weight Mw of this resin (copolymer) is 2,000 to 10,000. When the weight average molecular weight Mw is smaller than 2,000, the charge amount under a high-temperature and high-humidity environment is greatly reduced, and offset tends to occur during fixing. If it is larger than 10,000, the compatibility with the binder resin becomes poor, and it becomes difficult to obtain a uniform dispersion. In the present invention, a weight average molecular weight Mw of 3000 to 8000 is particularly preferred. Since the viscosity of the resin affects the kneading property and the fixing property with the binder resin, the viscosity is preferably 50 to 10,000 poise at 130 ° C., and more preferably 100 to 5,000 poise at 130 ° C. The content ratio of this resin in the toner is preferably 2 to 10 parts by weight based on 100 parts by weight of the binder resin. If the amount is less than 2 parts by weight, it is difficult to obtain a charge amount necessary for good image formation, and there is a disadvantage that toner scattering is severe. If the amount is more than 10 parts by weight, problems such as a decrease in environmental resistance, a decrease in compatibility, and occurrence of offset tend to occur. As such a resin having a quaternary ammonium base as a functional group, a resin having a charge adjustment function, trade name of Acrybase FCA-201-PS manufactured by Fujikura Kasei Co., Ltd. is preferable.

  The latter nigrosine-based dye is a black-based dye, which has been well known as a charge control agent, and is considered to be composed of a mixture of a plurality of azine compounds. The content of the dye in the toner is preferably 0.5 to 5 parts by weight based on 100 parts by weight of the binder resin. When the amount is less than 0.5 part by weight, it is difficult to obtain a charge amount required for good image formation, and when the amount is more than 5 parts by weight, the toner is easily separated from the toner and the charge amount becomes unstable. In addition to the above main components of the binder resin, wax, colorant, and charge control agent, a small amount of crystalline magnetic material may be added, if necessary, for the purpose of increasing the hardness of the toner particles.

  Other examples of the charge control agent according to the present invention include fatty acid-modified nigrosine dye, metal-containing nigrosine dye, metal-containing fatty acid-modified nigrosine dye, chromium complex of salicylic acid, and quaternary ammonium compound.

(External additives)
Examples of the external additives in the present invention include tetrafluoroethylene fine particles, zinc stearate, a lubricant such as titanium oxide, an abrasive such as cerium oxide and silicon carbide, a fluidity imparting agent for hydrophobic silica, carbon black, and tin oxide. The conductivity-imparting agent may be appropriately added to the core toner as needed. As described above, the toner of the present invention is subjected to a spheroidizing treatment in order to improve the lack of fluidity of the core toner. However, in order to form a good image, it is necessary to further increase the fluidity. Hydrophobic silica is mixed as an external additive for improving fluidity.

(Example 1)
Hereinafter, the positively charged toner for electrophotography of the present invention and the method for producing the same will be specifically described, and the toner according to the present invention will be evaluated by evaluating the examples according to the present invention and comparative examples not belonging to the present invention. Explain that is excellent. In the following description, all parts are by weight.

(Binder resin): Styrene / n-butyl acrylate copolymer resin
(Mitsui Chemicals CPR250) 100 parts (wax): Low molecular weight polypropylene (Mitsui Chemicals High Wax NP-055)
5 parts (colorant): carbon black (Legal 330R manufactured by Cabot) 6 parts (charge adjusting agent): Nigrosine dye (Bontron N-01 manufactured by Orient Chemical Co.) 2 parts Resin having a quaternary ammonium base as a functional group ( Acrybase FCA-201-PS manufactured by Fujikura Kasei Co., Ltd. 3 parts (High Wax, Regal, Bontron and Acrybase are registered trademarks, respectively)

  After thoroughly mixing and stirring the mixed material having the above composition with a Henschel mixer, hot-melt kneading with a twin-screw extruder, cooling the resulting kneaded material to room temperature, coarsely crushing, pulverizing and classifying, thereby obtaining an average A black, spherical, untreated core toner having a volume particle size of 10 μm and a particle size distribution of 5 to 20 μm was obtained. FIG. 2 shows an SEM photograph of the core toner that has not been processed into a spherical shape. It was found that the unprocessed toner shown in FIG. The cause was thought to be the angular shape of each particle as seen in FIG.

The method of sphering the core toner without sphering will be described below. As shown in the schematic sectional view of the apparatus for spheroidizing a positively charged toner for electrophotography according to the present invention shown in FIG. 1, air 102 sent from a blower 1 is introduced into a hot air generator 2 at 400 ° C. and a hot air flow of 0.1 mm. The hot air 103 is formed into hot air 103 at a rate of ^{2 to} 0.3 m ³ / min and is emitted from the hot air jet nozzle 4 to the first cyclone 7 through the introduction pipe 2-1. On the other hand, the unprocessed core toner particles 10 are conveyed by a predetermined amount of high-pressure air 101 from the powder metering device 3 and sent into the toner radiating device 5. It is injected. The jetted core toner particles 10 are instantaneously brought into contact with the hot air 103 adjusted to the above-mentioned temperature, are uniformly heated, and are spheroidized. The toner particles 10 spheroidized by the heat treatment are immediately cooled by the cooling air 104, do not adhere to the inner wall of the first cyclone 7 equipped with the cooling water circulation jacket 7-1, and have no aggregation between the particles. When the toner is sent to the second cyclone 8 with the cooling water circulation jacket 8-1 via the introduction pipe, the spheroidized toner is further cooled and collected in the toner container 9. The cooling air 105 passes through the upper opening of the second cyclone 8 to a bag filter (not shown). FIG. 3 shows an SEM photograph of the spheroidized toner collected by the sphering apparatus. The heat-treated spheroidized toner shown in FIG. 3 has a spherical shape with no corners as shown, indicating that the fluidity of the toner is improved. However, although the fluidity has been improved, it has not yet been at the level required for good image formation.

  According to the spheroidizing treatment of the toner according to the present invention, a resin having a quaternary ammonium base as a functional group and a nigrosine dye are used in combination as a charge control agent. As described above, the charge control agent is taken into the binder resin whose surface is melted by the heat treatment accompanying the spheroidization and coated, so that the charge imparting ability is not reduced. That is, in the toner of the present invention, one of the charge control agents is a resin, and the resin as the charge control agent adheres to and covers the surface of the binder resin that is the core of the toner before the spheroidizing treatment. Therefore, even with the heat treatment during the spheroidizing treatment, the resin as the charge control agent melts first and fuses with the binder resin, and the resin as the charge control agent is still on the outermost surface of the toner, It is not coated with the resin, and the charge providing ability works effectively. Conversely, long-term stabilization of the charge-imparting ability can be obtained by firmly fixing the resin as the charge adjusting agent to the binder resin.

  However, since the charge-imparting ability of the resin as the charge control agent according to the present invention is considerably lower than that of a nigrosine dye or the like, considering the occurrence of a new problem caused by adding a large amount of this resin alone. It has been found that the effect of using Nigrosine in combination with a high charge-imparting ability level is great, and the present invention has been made.

  To 100 parts of the spheroidized toner obtained by the sphering treatment, 0.5 parts of hydrophobic silica (NA50Y manufactured by Nippon Aerosil Co., Ltd.) was added as an external additive to further increase the fluidity of the toner by 20 liters. The mixture was mixed at 1800 rpm for 3 minutes with a Henschel mixer, and externally added. The static bulk density of the toner according to the present invention obtained by this treatment was 0.45, and extremely high fluidity was obtained (Table 1).

  Next, 5 parts of the toner of the present invention and 100 parts of a ferrite carrier having an average particle diameter of about 60 μm and coated with a silicone resin were mixed and stirred to prepare a two-component developer. The charge amount of this two-component developer was measured by a blow-off charge amount measuring device CF-100 manufactured by Toshiba Chemical Corporation. As a result, the charge amount was 55 μC / g. The rise time until reaching the charge amount was 3 seconds (Table 1). Next, continuous printing evaluation of 50,000 sheets was performed in a high-temperature and high-humidity environment of 35 ° C.-85% RH using a printer equipped with a positively charged organic photoreceptor using this developer. The same toner according to the present invention used for the developer was used as the replenishment toner used in the evaluation test.

(Examples 2 to 4)
The contents of the resin having a functional group having a nigrosine dye and a quaternary ammonium base as the charge control agents of Examples 2, 3, and 4 were 0.6 parts and 2 parts, respectively, with respect to 100 parts of the binder resin. Example 1 was the same as Example 1 except that the combination was changed to a more preferable content ratio within the scope of claim 2 as in parts and 5 parts, 5 parts and 10 parts.

(Example 5)
Example 1 was the same as Example 1 except that the content ratio of the resin having a quaternary ammonium base as a functional group as a charge control agent was out of the range described in claim 2.

(Example 6)
Example 1 was the same as Example 1 except that the content ratio of the nigrosine dye as a charge control agent was out of the range described in claim 2.

(Comparative Example 1)
The procedure was the same as in Example 1 except that the spheroidizing treatment was not performed.

(Comparative Example 2)
The procedure was the same as in Example 3 except that the spheroidizing treatment was not performed.

(Comparative Example 3)
Example 1 was the same as Example 1 except that a resin having a quaternary ammonium base as a functional group was not used as a charge control agent.

(Comparative Example 4)
Example 1 was the same as Example 1 except that no nigrosine dye was used as a charge control agent.

  Tables 1 and 2 show the print evaluation results. From these tables, even in the evaluation under the severe environmental conditions as described above, the column of Example 1 shows that the charge amount, the rise time change, and the image quality, which are the physical properties of the toner at the initial stage and after 50,000 sheets. It can be seen that there is little change in the image density of the solid portion and the density of the background stain in the non-image portion, and the transfer efficiency is always maintained at 95% or more, and a stable print quality can be obtained. In Examples 2 to 4 in which the combination of the charge adjusting agent content ratios was changed as described above, the static bulk density indicating the fluidity was as good as that of Example 1. Also, regarding other evaluation results, the change in the charge amount and the rise time as the toner physical properties at the initial stage and after 50,000 sheets, the change in the solid image density and the non-image stain density as the image quality are small. It is also shown that the transfer efficiency is always maintained at 95% or more and a stable printing quality is obtained. It can be seen that Examples 5 and 6 are not better than the evaluation results of Examples 1 to 4, but are more improved than Comparative Examples 1 to 4.

  On the other hand, the evaluation results of Comparative Examples 1 to 4 show that from Tables 1 and 2, the initial charge amount was small, the charge rise time was considerably slow, the solid image density was low, and the background smear density was high. In addition, the change in the charge amount and the rise time, which are the physical properties of the toner at the initial stage and after 50,000 sheets, the change in the image quality of the solid portion and the background density of the non-image portion, which are the image quality, are large, and the transfer efficiency is low and stable It is shown that the desired print quality cannot be obtained.

  In the following examples, the positively charged toner for electrophotography according to the present invention may contain 3 to 6 parts by weight of carbon black having a pH value of 8.0 or more as a colorant with respect to 100 parts by weight of the binder resin. The invention according to claims 5, 8, 10, and 11 described in the preferred claims will be described. In the following description, all parts are by weight.

(Example 7)
(Binder resin)
Styrene / n-butyl acrylate copolymer resin
(Dianal FB-1157 manufactured by Mitsubishi Rayon Co., Ltd.) 100 parts (wax)
5 parts of low molecular weight polypropylene (High Wax NP-055 manufactured by Mitsui Chemicals, Inc.) (colorant)
Carbon black (Cabot Co., Ltd. Legal 330R: pH-8.5) 4 parts (Charge control agent)
Nigrosine dye (Bontron N-01 manufactured by Orient Chemical Co., Ltd.) 1 part Resin having quaternary ammonium base as a functional group (Acrybase FCA-201-PS manufactured by Fujikura Kasei Co., Ltd.) 4 parts

  After thoroughly mixing and stirring the mixed material having the above composition with a Henschel mixer, hot-melt kneading with a twin-screw extruder, cooling the obtained kneaded material to room temperature, crushing, pulverizing and classifying, thereby obtaining an average volume. A black core toner having a particle size of 10 μm and a particle size distribution of 5 to 20 μm was obtained. To 100 parts of the core toner obtained above, 0.5 part of hydrophobic silica (NA50Y manufactured by Nippon Aerosil Co., Ltd.) as an external additive for imparting fluidity was 2,000 rpm using a 20 liter Henschel mixer. After mixing for 3 minutes, the mixture was externally added to obtain a toner of the present invention. Next, 5 parts of the toner of the present invention and 100 parts of a ferrite carrier having an average particle diameter of about 60 μm and coated with a silicone resin were mixed and stirred to prepare a two-component developer.

  The charge amount of this developer was measured by a blow-off charge amount measuring device CF-100 manufactured by Toshiba Chemical Corporation. As a result, the charge amount was 45.5 μC / g (Table 3). The rise time required to reach the charge amount was 4 seconds (Table 3). Next, using the toner of the present invention obtained by the above-mentioned external addition process, under a high temperature / high humidity environment of 35 ° C.-85% RH using a non-magnetic one-component developing type printer equipped with a positively charged organic photoreceptor. The continuous printing evaluation of 10,000 sheets was performed. The same toner according to the present invention was used as the replenishment toner used in the present evaluation test.

(Examples 8 to 10)
The scope of the invention according to claim 5, wherein the content of the carbon black as the coloring agent in Examples 8, 9, and 10 is 3 parts, 5 parts, and 6 parts with respect to 100 parts of the binder resin. In this case, the procedure was the same as in Example 7, except that the combination was changed to a combination with a different content from that of Example 7.

(Examples 11 to 13)
Carbon black, which is a colorant of Examples 11, 12, and 13, is manufactured by Columbia Chemical Co., Ltd. Raven 420 (pH-9) and Raven 1020 (pH-8.3) each having a pH value of 8.0 or more. The same procedure as in Example 7 was carried out except that Black Pearls 880 (pH-8) manufactured by Cabot Corporation was used.

(Comparative Examples 5 to 7)
Carbon black, which is a coloring agent of Comparative Examples 5, 6, and 7, was manufactured by Raben 8000 (pH-2.4) manufactured by Columbia Chemical Co., Ltd., and Black Pearls L (pH-2) manufactured by Cabot Co., which exhibited a PH value outside the range of the present invention. .5), and the same as Example 7 except that Regal 400 (pH-4) manufactured by the company was used.

(Comparative Examples 8 to 10)
The content of carbon black as a colorant in Comparative Examples 8, 9, and 10 is 2 parts, 7 parts, and 9 parts with respect to 100 parts of the binder resin. The procedure was the same as in Example 7, except for the following.

  Table 3 shows the print evaluation. From this table, even in the evaluation under the severe environmental conditions as described above, the column of Example 7 shows that the charge amount, which is the physical property of the toner at the initial stage and after 10 k (k is 000) sheets, and its rise. It can be seen that there is little change over time and image density in solid areas and image density in non-image areas, which are image quality, and stable print quality can be obtained. Examples 8 to 10 in which the combination of the content ratios of carbon black was changed as described above and Examples 11 to 13 in which the combination of the carbon blacks having different pHs were changed as described above were as good as Example 7. Other evaluation results also show little change in the amount of charge and its rise time, which are the physical properties of the toner at the initial stage and after 10k sheets, and little change in the image quality of the solid portion and the background density of the non-image portion, which is the image quality. It can be seen that the obtained printing quality is obtained.

  On the other hand, the evaluation results of Comparative Examples 5 to 10 show that from Table 3, the initial charge amount is small, the charge rise time is considerably slow, the solid image density is low, and the background smear density is considerably high. In addition, a change in the amount of charge and its rise time, which are the physical properties of the toner, and the change in the rise time of the toner, and the change in the image density of the solid portion and the background density of the non-image portion, which are the image quality, are large, so that stable printing quality cannot be obtained. It is shown. From the comparison between Examples 7 to 13 and Comparative Examples 5 to 10, it can be seen that the pH value of the colorant in the positively charged toner for electrophotography according to the present invention should be 8.0 or more.

FIG. 1 is a schematic cross-sectional view of a sphering apparatus for a positively charged toner for electrophotography according to the present invention. SEM photograph of positively charged toner for electrophotography before spheroidization SEM photograph of positively charged toner for electrophotography after spheroidizing treatment according to the present invention

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Blower 2 Hot-air generator 3 Powder supply device 4 Injection nozzle 5 Toner radiation device 6 Radiation nozzle 7 First cyclone 8 Second cyclone 9 Toner container 101 Air 102 Air 103 High-temperature high-pressure air 104 Air 105 Air

Claims (6)

  In the positively charged electrophotographic toner, the core toner comprising a binder resin, a wax, a colorant, and a charge control agent as main components and subjected to sphering treatment by heat treatment, and at least silica fine particles as an external additive, A positively charged toner for electrophotography, wherein the adjusting agent contains a resin having a quaternary ammonium base as a functional group and a nigrosine dye.   The charge control agent contains 2 to 10 parts by weight of a resin having a quaternary ammonium base as a functional group and 0.5 to 5 parts by weight of a nigrosine dye based on 100 parts by weight of the binder resin. The positively charged toner for electrophotography according to claim 1, wherein: A resin having a quaternary ammonium base as a functional group is mainly composed of a styrene acrylic copolymer resin containing a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2). The positively charged toner for electrophotography according to claim 1 or 2, wherein R ¹ and R ² are a hydrogen atom or a methyl group, R ³ is an alkylene group, R ⁴ , R ⁵ and R ⁶ are Each represents an alkyl group, the repeating unit represented by the following formula (1) is 65 to 97% by weight, the repeating unit represented by the following formula (2) is 35 to 3% by weight, and the weight average molecular weight is 2000 In the range of 10,000 to 10,000).
  The positively charged toner for electrophotography according to any one of claims 1 to 3, wherein the binder resin contains a styrene acrylic copolymer resin as a main component.   5. The colorant according to claim 1, wherein the colorant contains 3 to 6 parts by weight of carbon black having a pH of 8.0 or more based on 100 parts by weight of the binder resin. 6. Positive charge toner for electrophotography.   6. In producing the positive charge toner for electrophotography according to any one of claims 1 to 5, after mixing and stirring a binder resin, a wax, a colorant, and a charge adjusting material as main components, hot-melt kneading. A method for producing a positively charged toner for electrophotography, comprising pulverizing and classifying the kneaded product obtained as described above to obtain a core toner, spheroidizing the core toner by hot air treatment, and then mixing at least silica fine particles as an external additive.