JP2005157168A - Electrostatic charge image developing magnetic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive charge type electrostatic charge image developing magnetic toner containing a charge control agent which is a composition prepared by mixing a nigrosine base with a xylene resin and a specified magnetic material, wherein the charge control agent and the magnetic material are uniformly dispersed in the toner, and capable of forming a fog-free clear image of high image density. <P>SOLUTION: In the electrostatic charge image developing magnetic toner containing at least a binder resin, the magnetic material and the charge control agent, the composition prepared by mixing the nigrosine base with the xylene resin is contained as the charge control agent and a BET specific surface area of the magnetic material by a nitrogen adsorption method is 3.0-9.0 m<SP>2</SP>/g. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic toner for developing an electrostatic image used for developing an electrostatic latent image in an electronic copying machine, a laser beam printer, or the like in which an image is formed using an electrophotographic method, an electrostatic recording method, or the like. About.

  Conventionally, as a method for developing an electrostatic latent image formed on an electrostatic image carrier such as an electrophotographic photosensitive member or an electrostatic recording member, it can be roughly divided into liquid development in which fine toner is dispersed in an electrically insulating liquid. Two methods are known: a method using an agent (wet development method) and a method using a toner in which a colorant or magnetic powder is dispersed in a binder resin (dry development method). In the dry development method, a method using a two-component developer composed of carrier particles and a toner and a method using a one-component developer composed of only a toner (usually magnetic toner) are known.

The toner for developing an electrostatic charge image used in these dry development methods usually uses a styrene resin or a polyester resin as a binder resin, kneaded with a colorant such as a dye, a pigment, and a magnetic material, and then cooled. Then, it is manufactured through pulverization and classification steps.
Magnetic powders such as magnetite and ferrite are usually used as colorants for magnetic toners. Magnetic powders are required to have appropriate magnetic properties (saturation magnetization, remanent magnetization, coercive force, etc.) and coloring power, and most of them use magnetite (iron trioxide: Fe ₃ O ₄ ). (For example, see Non-Patent Document 1)
The particle diameter of the toner for developing an electrostatic charge image usually has an average particle diameter of about 1 to 30 μm. Further, as carrier particles used in the two-component developer, iron powder, ferrite, magnetite, etc., which are coated with a hydrophobic resin as required, are used.

  The electrostatic image developing toner as described above is required to hold positive or negative charges depending on the polarity of the electrostatic latent image to be developed. In order to retain the charge in the toner for developing an electrostatic image, triboelectric charging properties such as a binder resin as a toner component and the above-described colorant can be used. Therefore, the image obtained by development is easily fogged and unclear. For this reason, a material called a charge control agent is generally added to the toner in order to impart desirable charging characteristics to the toner.

  Representative examples of conventional charge control agents include those that impart positive chargeability to the toner, such as basic dyes such as nigrosine dyes and triarylmethane dyes, quaternary ammonium salts, organic tin oxides, As an electron donating substance such as a polymer having an amino group or a toner having a negative chargeability, a metal-containing dye such as a metal complex of a monoazo dye or a chromium-containing organic dye (copper phthalocyanine green, chromium-containing monoazo dye) is used. Can be given.

  In many cases, an organic photoreceptor is used as a photoreceptor of an electrophotographic copying machine or printer, and a positively chargeable toner is used as a developer for a copying machine using the organic photoreceptor. However, many of the positively chargeable charge control agents used for producing the positively chargeable toner are hydrophilic, and the charge amount tends to decrease under high humidity conditions, while the charge amount decreases under high humidity conditions. Many that do not have the problem that the charge amount becomes unnecessarily high under low humidity. For example, triarylmethane-based dyes exhibit excellent positive chargeability at normal temperature and humidity, but tend to cause a decrease in charge amount at high temperatures and high humidity, and depending on the choice of toner components, charging is not possible at low temperatures and low humidity. It may be uniform. Further, the quaternary ammonium salt has a low charge imparting ability, and the image density may be lowered as the number of copies is increased under high temperature and high humidity.

  Nigrosine dye, on the other hand, has high charging performance and is a relatively excellent charge control agent, but has poor dispersibility in the toner resin and is difficult to disperse uniformly. The required performance as a charge control agent is such that image density decreases, fogging easily occurs, or toner scattering occurs in the machine as the number of copies increases. It is difficult to obtain something that satisfies the conditions sufficiently. In order to solve these problems, a technique (for example, refer to Patent Document 1) such as rake or acid modification of nigrosine dye has been proposed. When such treatment is performed, charge control in the toner is performed. It may cause a decrease in the dispersibility of the agent or the fluidity of the toner.

In addition, since nigrosine dye uses nitrobenzene and aniline as raw materials, the manufactured nigrosine dye also contains a trace amount of aniline and nitrobenzene as a residue. These residues not only adversely affect the characteristics of the toner, such as fogging on the image, image density reduction during toner replenishment, and in-machine scattering, but are also preferable for problems such as deterioration in quality due to heating and the environment. It is preferable to use after removing as much as possible. (For example, see Patent Documents 2 and 3)
However, the process for removing aniline and nitrobenzene is complicated and the production process becomes complicated, and it is difficult to use as a charge control agent for toner in terms of cost.
“Basics and Applications of Electrophotographic Technology” Corona, June 15, 1988, P.475 Japanese Patent Laid-Open No. 3-131868 JP-A-6-230611 JP 2002-311652 A

  Thus, the nigrosine dye is a relatively excellent charge control agent, but has various problems. To solve these problems, the charge amount is sufficiently high, the temperature and humidity dependence during development is small, the toner characteristics are not deteriorated by the heat stress before use, the dispersibility to the binder resin is good, and the development characteristics There is a need for a positively chargeable magnetic toner that is excellent in durability and durability.

  An object of the present invention is to provide a positively charged magnetic toner for developing an electrostatic image having excellent characteristics that does not have the above-described problems, that is, a frictional charge amount between a toner and a carrier, and a toner carrier such as a toner and a developing sleeve. It is an object of the present invention to provide a positively chargeable magnetic toner for developing an electrostatic image capable of forming a toner image having high quality and stability, which is not affected by temperature and humidity and has a stable quality.

  Another object of the present invention is to provide a positively chargeable magnetic toner for developing an electrostatic image having a stable triboelectric charge amount even when the number of copies is increased, no fogging, and no toner scattering in the apparatus.

  Another object of the present invention includes a charge control agent, which is a composition formed by mixing a nigrosine base and a xylene resin, and a specific carbon black, and the charge control agent and the magnetic material are uniformly dispersed in the toner. It is an object of the present invention to provide a positively charged magnetic toner for developing an electrostatic image capable of forming a clear image having a high image density and free from fogging.

  Furthermore, an object of the present invention is to provide a positively chargeable magnetic toner for developing an electrostatic charge image containing a charge control agent which does not deteriorate the toner characteristics due to thermal stress during toner storage.

  As a result of intensive studies, the present inventors have used the composition obtained by mixing the nigrosine base and the xylene resin in the toner by using a charge control agent and a magnetic material having a specific BET specific surface area in the toner. The inventors have found that it can be achieved and have arrived at the present invention.

That is, the first invention contains, as a charge control agent, a composition obtained by mixing a nigrosine base and a xylene resin in an electrostatic charge image developing toner containing at least a binder resin, a magnetic material, and a charge control agent. And a magnetic toner for developing an electrostatic image, wherein the magnetic material has a BET specific surface area of 3.0 to 9.0 m ² / g as measured by a nitrogen adsorption method.

  According to a second aspect of the present invention, there is provided the magnetic material for developing an electrostatic charge image according to the first aspect, wherein the content of aniline in the charge control agent is 100 ppm or less and the content of nitrobenzene is 50 ppm or less. Toner.

  The third invention is the magnetic toner for developing an electrostatic image according to the first or second invention, wherein the xylene resin has a number average molecular weight of 800 to 1800.

  According to a fourth aspect of the present invention, there is provided a magnetic toner for developing an electrostatic charge image according to any one of the first to third aspects of the present invention, wherein the mixing ratio of the nigrosine base and the xylene resin is 20:80 to 70:30. It is.

A fifth invention is the magnetic toner for developing an electrostatic charge image according to any one of the first to fourth inventions, wherein the magnetic material has a bulk density of 0.15 to 0.40 g / cm ^3. is there.

  As described above, by using a charge control agent, which is a composition obtained by mixing a nigrosine base and a xylene resin, and a magnetic material having specific physical properties as a material for a magnetic toner for developing an electrostatic image, the charge control agent is obtained. And a magnetic toner for developing an electrostatic image in which a magnetic material is uniformly dispersed. The electrostatic toner for developing an electrostatic image of the present invention contains almost no aniline and nitrobenzene in the charge control agent, and a magnetic material having a specific BET specific surface area in combination with the charge control agent. In addition, it is possible to obtain a copy image having a good image density from the beginning and having no fog, and no decrease in the image density is observed even when a large number of copies are stacked. Further, the magnetic toner for developing an electrostatic charge image of the present invention does not change with heating, and can obtain a good toner which is not changed in characteristics due to heating stress during commercial storage, after purchase or during storage or transportation. Can do. In addition, since the charge control agent and magnetic substance of the present invention have good distribution properties, it is easy to reuse classified fine powder, which contributes greatly to resource saving and cost reduction during toner production. .

Hereinafter, the present invention will be described in more detail.
The charge control agent of the present invention can be obtained by mixing a conventionally known nigrosine base and a xylene resin.
Nigrosine base is prepared by oxidizing aniline and aniline hydrochloride as raw materials with nitrobenzene in the presence of iron chloride, iron and hydrochloric acid at 160 ° C to 180 ° C to obtain crude nigrosine, and then adding an aqueous alkaline solution to the reaction. It is prepared by separating the dye aniline layer, then base-treating with alkali, washing with water, filtering, drying and grinding. The nigrosine dye is made insoluble in water by being made into a base, and is hardly affected by humidity. The nigrosine base obtained here has an aniline content of about 2000 ppm to 4000 ppm and a nitrobenzene content of about 200 to 500 ppm.
Here, the nigrosine base is preferably pulverized to 30 μm or less. If it is larger than 30 μm, it will be difficult to uniformly disperse in the xylene resin.

  In the present invention, a commercially available nigrosine base can also be used. Specifically, Bontron N-01, N-07, Nigrosine Base EX manufactured by Orient Chemical Co., Ltd., CHUO CCA-1 manufactured by Chuo Synthetic Chemical Co., etc. can be used.

If a large amount of nitrobenzene remains in the nigrosine base, charge due to polarization is stored in the nigrosine base, which tends to aggregate, resulting in a decrease in the dispersibility and distribution of the nigrosine base in the binder resin. . This is because nitrobenzene has a high relative dielectric constant. Therefore, it is important to remove nitrobenzene in the nigrosine base.
Nitrobenzene in the nigrosine base can be removed by dissolving the nigrosine base in alcohol and washing. As a preferable alcohol to be used, it is preferable to use methanol, ethanol or the like in view of the fact that the solvent can be easily removed. Thereby, the nitrobenzene content in the nigrosine base can be reduced to 50 ppm or less. After removing and washing with alcohol, filtration, drying, and in some cases, pulverization and pulverization may be performed.
When removing nitrobenzene in a commercially available nigrosine base, the nigrosine base may be dissolved in alcohol and treated in the same manner as described above.

  Nitrobenzene can also be removed during the nigrosine-based manufacturing process, which is a preferable process for simplifying the manufacturing process and reducing costs. In the nigrosine base manufacturing process, the base is treated with alkali, washed with water, and then added with alcohol to remove nitrobenzene in the nigrosine base, followed by filtration, drying, and in some cases grinding and crushing. That's fine.

The xylene resin that can be used in the present invention is preferably a thermoplastic xylene resin represented by the following chemical formula. The —OH group in the xylene resin becomes an important functional group for reducing the aniline content of the charge control agent of the present invention.
That is, the aniline remaining in the nigrosine base reacts with the —OH group in the xylene resin to form a tertiary amine structure. As a result, the aniline in the nigrosine base reacts with the xylene resin, so that the aniline content in the charge control agent of the present invention is reduced to 100 ppm or less. The presence of a tertiary amine is very useful for improving water resistance and oil resistance.

 From this, it is preferable that the hydroxyl value (OH value) of the xylene resin which can be used by this invention is 100-200 (mgKOH / g), More preferably, it is 110-170 (mgKOH / g). If the hydroxyl value is less than 100 (mgKOH / g), unreacted aniline may remain, and the aniline content in the charge control agent will exceed 100 ppm. On the other hand, if the hydroxyl value is larger than 200 (mgKOH / g), since —OH groups are excessively present, they are easily affected by moisture, and the environmental stability as a charge control agent is lowered. Problems such as in-machine scattering due to a decrease in the charge amount, an increase in fogging, and an excessive increase in the charge amount under low temperature and low humidity may occur.

Moreover, it is preferable to use a thing with an average molecular weight of 800-1800, More preferably, it is 1000-1400. By using in this range, the nigrosine base can be dispersed well. When the average molecular weight is 800 or less, it is easy to cause a dispersion failure of the nigrosine base, and when the average molecular weight is higher than 1800, the softening temperature becomes high and it is necessary to mix with the nigrosine base at a high temperature. Or productivity will deteriorate.
Specific preferred xylene resins include thermoplastic xylene resins such as Nicanol HP-100, HP-70, and HP-150 manufactured by Mitsubishi Gas Chemical Company.

The composition of the present invention can be obtained by mixing these nigrosine base and xylene resin. As a mixing method, (1) a method in which a nigrosine base is added after being dissolved in a solvent that is soluble in the xylene resin, and the mixture is mixed in the solution. (2) the xylene resin is melted using a kneader or the like. There is a method of adding and mixing nigrosine base in a heated state. Specifically:
(1) Dissolve nigrosine base and xylene resin in a solvent, mix with heating for 1-2 hours near the boiling point of the solvent, remove the solvent, drain into water, filter, wash with water and dry To obtain a composition. Here, the aniline in the nigrosine base reacts with the xylene resin to produce a partially amine-modified xylene resin, so that the composition from which the aniline can be removed hardly contains the remaining aniline. The composition obtained here is in a state where the nigrosine base is dispersed in the xylene resin. Further, if necessary, the composition may be made into a desired particle size through a pulverization step to be a charge control agent.
As the solvent specifically used here, any solvent that dissolves both xylene resin and aniline can be used, but among them, a cellosolve type solvent such as propylene glycol monomethyl ether is preferably used.

(2) The nigrosine base and the xylene resin are put into a kneader such as a heating kneader or a Banbury mixer and mixed thoroughly, and melt kneading is performed at a temperature equal to or higher than the softening temperature of the xylene resin. This disperses the nigrosine base in the xylene resin. At this time, the aniline contained in the nigrosine base reacts with the xylene resin, and a partly amine-modified xylene resin is produced, so that the composition from which the aniline can be removed contains little residual aniline. Become. The composition obtained here is in a state where the nigrosine base is dispersed in the xylene resin. Furthermore, the composition may be used as a charge control agent by roughly crushing and pulverizing the composition to adjust to a desired particle size.

  When the mixing ratio of the nigrosine base and the xylene resin is in the range of 20:80 to 70:30, a good charge control agent can be obtained. If the ratio of nigrosine base is less than 20, it will be difficult to impart a good positive charge as a charge control agent, and if the ratio of nigrosine base exceeds 70, it will be difficult to remove the remaining aniline, The amount of aniline in the charge control agent may be greater than 100 ppm.

  The amount of the charge control agent used in the magnetic toner for developing an electrostatic charge image of the present invention varies depending on the type of the binder resin used, but is usually 0.1 to 10 parts by weight, preferably 100 parts by weight of the binder resin. Is 0.5 to 5 parts by weight, more preferably 0.8 to 3 parts by weight. The particle size of the charge control agent may be 30 μm or less in terms of volume average particle size, and more preferably 2 μm or more and 15 μm or less. If it is less than 2 μm, the toner will be excessively charged, making it difficult to use. If it is larger than 15 μm, it may be difficult to uniformly disperse and mix in the toner.

  In the magnetic toner for developing an electrostatic charge image of the present invention, as the charge control agent, other charge control agents that can impart positive chargeability to the toner can be used in addition to the nigrosine dye. Such a charge control agent may be any known charge control agent that has been conventionally known to be capable of imparting positive chargeability to the toner. Ammonium salt compounds and triphenylmethane basic dyes are preferred.

Examples of the magnetic material that can be used in the magnetic toner for developing an electrostatic charge image of the present invention include iron oxide such as magnetite, maghemite, and ferrite, or a compound of a divalent metal and iron oxide, iron, cobalt, nickel, and the like. Powders of such metals or alloys of these metals such as aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium and These mixtures can be mentioned. Among these, magnetite (triiron tetroxide: Fe ₃ O ₄ ) is preferable. Moreover, the addition amount of 5-120 weight part with respect to 100 weight part of binder resin normally, Preferably 60-100 weight part is good.

The magnetic material that can be used in the magnetic toner for developing an electrostatic charge image of the present invention needs to have a BET specific surface area of 3.0 to 9.0 m ² / g by a nitrogen adsorption method. More preferably, it is 4.0-8.0 m < ² > / g. The BET specific surface area of the magnetic material is an important characteristic that determines the dispersibility and distribution in the binder resin. In particular, the charge control agent obtained by mixing xylene resin and nigrosine base maintains good chargeability, good dispersibility in the binder resin, and good distribution, while maintaining good color development and color reproducibility. It is important in getting.
If the value of the BET specific surface area is larger than 9.0 m ² / g, the resistance of the magnetic material decreases, the toner charge amount decreases, the fog on the image increases, or the toner is scattered in the machine. There is a risk of causing. Further, it becomes difficult to uniformly disperse and distribute the magnetic material in the binder resin. On the other hand, if the value of the BET specific surface area is smaller than 3.0 m ² / g, the image cannot be sufficiently colored, and the resistance becomes high and an excessive increase in the charge amount occurs. Defects such as density reduction occur.

  The BET specific surface area of the magnetic material used in the magnetic toner of the present invention was measured using a multi-sorve 12 manufactured by Yuasa Ionics Co., Ltd., which is a gas adsorption method (flow method). A nitrogen-helium mixed gas was used as the carrier gas. And the BET specific surface area was computed from the value of the desorption peak.

In addition to the above characteristics, the magnetic material used in the magnetic toner of the present invention also has an important value of oil absorption, and the oil absorption is preferably 20 to 35 ml / 100 g. Within this range, dispersion and distribution of the magnetic material in the binder resin can be preferably performed.
Furthermore, the value of the bulk density is preferably in the range of 0.15 to 0.40 g / cm ³ , and the dispersion and distribution of the magnetic substance in the binder resin can be preferably performed.
Here, the amount of oil absorption is obtained based on the amount of boiled linseed oil consumed by dropping the boiled linseed oil onto 5 g of the magnetic material sample and mixing it until the whole becomes a hard, uniform putty-like mass.
Oil absorption (ml / 100 g) = [boiled linseed oil consumption (ml) / sample weight (g)] × 100
The bulk density was measured using a powder tester (PT-E) manufactured by Hosokawa Micron Corporation with an amplitude of 1 mm and a sieving time of 3 minutes.

  As a component of the magnetic toner for developing an electrostatic image of the present invention, a binder resin, which is a known material constituting the toner, is used in addition to the charge control agent and the magnetic material of the present invention. In addition to the magnetic substance, carbon black, conventionally known pigments and dyes can be used in combination as the colorant. If necessary, the magnetic toner for developing electrostatic images further contains a release agent, a lubricant, a fluidity improver, an abrasive, a conductivity-imparting agent, an image peeling preventing agent, and the like.

Any binder resin can be used as the binder resin used in the magnetic toner for developing an electrostatic charge image of the present invention as long as it is known as a binder resin for a toner for developing an electrostatic charge image. Examples of binder resins that can be used include homopolymers of styrene and its derivatives such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, and the like. Styrene-styrene derivative copolymer such as polymer; styrene-vinyl naphthalene copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-α-chloromethyl methacrylate copolymer, Styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene- Acrylonitrile-indene copolymer, etc. Styrene copolymer; polyvinyl chloride, phenol resin, natural modified phenol resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy Examples thereof include resins, polyvinyl butyral, terpene resins, coumarone indene resins, and petroleum resins.
Among these, styrene homopolymers, styrene-styrene derivative copolymers, styrene-acrylic acid copolymers, and styrene-methacrylic acid copolymers are particularly preferable.

  As a comonomer for a styrene monomer of a styrene-acrylic acid copolymer or a styrene-methacrylic acid copolymer, for example, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, Examples include 2-ethylhexyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, and the like.

A crosslinked styrene copolymer is also a preferred binder resin. Examples of the comonomer used together with styrene to produce a crosslinked styrene-based copolymer include the styrene derivatives, acrylic acid, methacrylic acid, acrylic acid ester or methacrylic acid ester, acrylonitrile, methacrylonitrile, acrylamide, etc. A monocarboxylic acid having a double bond or a substituted product thereof; for example, a dicarboxylic acid having a double bond such as maleic acid, methyl maleate, butyl maleate, dimethyl maleate and the substituted product thereof; for example, vinyl chloride, vinyl acetate, Vinyl esters such as vinyl benzoate; ethylene-based olefins such as ethylene, propylene and butylene; vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; for example vinyl methyl ether and vinyl ethyl ether , Vinyl ethers such as vinyl isobutyl ether; vinyl monomers are used alone or two or more kinds.

  As the crosslinking agent, compounds having two or more polymerizable double bonds are mainly used. For example, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1, Carboxylic acid esters having two double bonds such as 3-butanediol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone; and three or more A compound having a vinyl group is used alone or as a mixture. These crosslinking agents are used in an amount of about 0.01 to 5 parts by weight, more preferably about 0.03 to 3 parts by weight with respect to 100 parts by weight of other monomer components.

The binder resin is a styrene having at least one peak in a region of 3 × 10 ^{3 to} 5 × 10 ⁴ in a molecular weight distribution measured by GPC, and having at least one peak or shoulder in a region of 10 ⁵ or more. A copolymer is preferred from the viewpoint of fixability. The binder resin having such a molecular weight distribution can be produced by mixing two or more kinds of resins having different average molecular weights, and can also be produced by using the crosslinking agent as a crosslinked resin. .

The molecular weight distribution by GPC is measured, for example, under the following conditions. Moreover, it can measure similarly about xylene resin.
The column is stabilized in a 40 ° C. heat chamber, and tetrahydrofuran (THF) as a solvent is allowed to flow through the column at this temperature at a flow rate of 1 ml / min, and about 100 μl of a sample solution dissolved in THF is injected for measurement. In measuring the molecular weight of a sample, the molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the number of counts.

As a standard polystyrene sample for preparing a calibration curve, for example, a standard polystyrene sample having a molecular weight of about 10 ² to 10 ⁷ manufactured by Tosoh Corporation or Showa Denko is used, and it is appropriate to use at least about 10 standard polystyrene samples. . An RI (refractive index) detector is used as the detector. As the column, it is preferable to combine a plurality of commercially available polystyrene gel columns. For example, combinations of shodex GPC KF-801, 802, 803, 804, 805, 806, 807, 800P manufactured by Showa Denko KK, TSKgel G1000H (HXL), G2000H (HXL), G3000H (HXL) manufactured by Tosoh Corporation, A combination of G4000H (HXL), G5000H (HXL), G6000H (HXL), G7000H (HXL), and TSKguardcolumn can be given.

  The measurement sample is prepared as follows. That is, after putting a sample in THF and leaving it to stand for several hours, the sample is sufficiently shaken, mixed well with THF until the sample is no longer united, and further allowed to stand for 12 hours or more. At this time, the standing time in THF is set to be 24 hours or longer. Then, GPC measurement was performed on a sample processing filter (pore size 0.45 to 0.5 μm, for example, Mysori Disc H-25-5 manufactured by Tosoh Corp., Excro Disc 25CR manufactured by Gelman Science Japan Ltd., etc.). Sample for use. The sample concentration is adjusted so that the resin component is 0.5 to 5 mg / ml.

  In the production of the vinyl polymer, a polymerization initiator is used. Any conventionally known polymerization initiator can be used as the polymerization initiator. Examples of the polymerization initiator include benzoyl peroxide, lauroyl peroxide, tertiary butyl hydroperoxide, tertiary butyl peroxybenzoate, ditertiary butyl peroxide, cumene hydroperoxide, dicumyl peroxide, azoisobutyro Nitrile, azobisvaleronitrile and the like are usually preferably used. The use ratio of the initiator to the vinyl monomer is generally 0.2 to 5% by weight. The polymerization temperature is appropriately selected according to the type of monomer and initiator used.

  A polyester resin can also be used as a binder resin for the toner for developing an electrostatic charge image of the present invention. Examples of the alcohol component constituting the polyester resin include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, , 6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, hydrogenated bisphenyl A, diols such as bisphenol derivatives, and polyhydric alcohols such as glycerin, sorbit and sorbitan.

  As the acid component, divalent carboxylic acids such as benzene dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and phthalic anhydride or anhydrides thereof; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid, or Further, succinic acid substituted with an alkyl group having 16 to 18 carbon atoms or an anhydride thereof; unsaturated dicarboxylic acid such as fumaric acid, maleic acid, citraconic acid, itaconic acid, or an anhydride thereof. Examples of the trivalent or higher carboxylic acid include trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid and anhydrides thereof.

  A preferred alcohol component is a bisphenol derivative represented by the general formula 1, and a preferred acid component is phthalic acid, terephthalic acid, isophthalic acid or its anhydride, succinic acid, n-dodecenyl succinic acid or its anhydride, fumaric acid, Dicarboxylic acids such as maleic acid and maleic anhydride, and tricarboxylic acids such as trimellitic acid or its anhydride.

  Further, in the case of using the pressure fixing method, a binder resin for pressure fixing toner can be used, for example, polyethylene, polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer. Examples thereof include a polymer, an ionomer resin, a styrene-butadiene copolymer, a styrene-isoprene copolymer, a linear saturated polyester, and paraffin.

  The particle diameter of the magnetic toner for developing an electrostatic charge image of the present invention is preferably 1 to 30 μm, and more preferably 3 to 15 μm in weight average particle diameter. In particular, toner particles having a particle size of 5 μm or less are contained in 12 to 60% by number, toner particles having a particle size of 8 to 12.7 μm are contained in 1 to 33% by number, and toner particles having a particle size of 16 μm or more. Is more preferably 2.0% by weight or less, and the toner has a weight average particle diameter of 4 to 12 μm from the viewpoint of development characteristics. The toner particle size distribution can be measured using, for example, a Coulter counter.

  As described above, the magnetic toner of the present invention is further used in the production of toners such as a release agent, a lubricant, a fluidity improver, an abrasive, a conductivity imparting agent, and an image peeling prevention agent as necessary. Known additives can be added internally or externally. Examples of these additives include, for example, low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, and sazol wax. And wax-like substances such as paraffin wax, which are usually added to the toner in an amount of about 0.5 to 5% by weight.

Also, as the lubricant, polyvinylidene fluoride, zinc stearate, etc., as the fluidity improver, silica, aluminum oxide, titanium oxide, silicon aluminum co-oxide, silicon titanium co-oxide produced by the dry method or wet method And those obtained by hydrophobizing these, and as abrasives, silicon nitride, cerium oxide, silicon carbide, strontium titanate, tungsten carbide, calcium carbonate, and hydrophobized ones of these are used as conductivity imparting agents. Examples include carbon black and tin oxide. In addition, fine powders of fluorine-containing polymers such as polyvinylidene fluoride are preferable from the viewpoints of fluidity, abrasiveness, charge stability, and the like.

  In the magnetic toner of the present invention, hydrophobized silica, hydrophobized aluminum oxide, hydrophobized silicon aluminum co-oxide or hydrophobized silicon titanium co-oxide as an external additive It is preferable to use fine powder as an external additive. Examples of the hydrophobization treatment of the silica fine powder include treatment with a silane coupling agent such as silicone oil, dichlorodimethylsilane, hexamethyldisilazane, and tetramethyldisilazane. Moreover, it is preferable to use positively-charged silica having a positive tribo-charge relative to the iron powder carrier when measured by the blow-off method. In order to obtain this positively chargeable silica, it may be treated with a silicone oil having an organo group having at least one nitrogen atom in the side chain, or a nitrogen-containing silane coupling agent. The amount of the hydrophobized silica fine powder used is 0.01 to 10%, preferably 0.03 to 5%, based on the developer weight.

  The magnetic toner of the present invention can be manufactured using a conventionally known toner manufacturing method. In general, the above-described toner constituent materials are sufficiently mixed by a mixer such as a ball mill or a Henschel mixer, and then kneaded thoroughly using a thermal kneader such as a hot roll kneader, a uniaxial or biaxial extruder. After cooling and solidifying, a method of coarsely pulverizing mechanically using a pulverizer such as a hammer mill, then finely pulverizing with a jet mill or the like and then classifying is preferable. However, the method for producing the toner is not limited to this method, and the method for producing the toner by the so-called microcapsule method, the method of dispersing the toner after dispersing other toner constituent materials in the binder resin solution, and the binder, Other methods such as a polymerization toner manufacturing method in which a predetermined material is mixed with a monomer forming a resin, and emulsion or suspension polymerization is performed to obtain a toner can be arbitrarily employed.

  Furthermore, if necessary, the classified toner and the external additive are sufficiently mixed using a mixer such as a Henschel mixer, and the toner for electrostatic charge development of the present invention can be produced through a sieving step.

  The magnetic toner of the present invention can be mixed with a carrier and used as a two-component developer. The carrier that can be used with the magnetic toner of the present invention may be any conventionally known carrier. Examples of the carrier that can be used include magnetic powders such as iron powder, ferrite powder, and nickel powder, and those whose surfaces are treated with a resin or the like. Examples of the resin covering the carrier surface include styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, acrylic acid ester copolymer, methacrylic acid ester copolymer, fluorine-containing resin, silicone-containing resin, and polyamide. Examples thereof include a resin, an ionomer resin, a polyphenylene sulfide resin, and a mixture thereof. Among these, fluorine-containing resins and silicone-containing resins are particularly preferable because they hardly form spent toner.

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

[Production example 1 of nigrosine base]
Crude nigrosine was obtained by oxidizing and reacting aniline and aniline hydrochloride with nitrobenzene at 160 to 180 ° C. in the presence of iron chloride, iron and hydrochloric acid. Furthermore, after neutralizing the crude nigrosine, aniline and sodium hydroxide solution were added to make a base treatment, and then the precipitates of nigrosine and iron hydroxide were separated by screw decanter centrifugation and the iron hydroxide precipitate was removed. The obtained liquid was washed with water. After washing with water, in order to remove the remaining nitrobenzene, the mixture was further stirred and washed while heating to 60 ° C., filtered, dried, and pulverized to a mean particle size of 7 μm with a nigrosine base. 1 was obtained. The nitrobenzene content was 50 ppm, and the aniline content was 2500 ppm.

[Production example 2 of nigrosine base]
A commercially available nigrosine base CCA-1 (manufactured by Chuo Gosei Chemical Co., Ltd.) was dissolved in methanol and stirred for 30 minutes while heating to 60 ° C. to remove nitrobenzene. Furthermore, it wash | cleaned with methanol, filtered and dried, and it grind | pulverized by the jet mill to the average particle diameter of 6 micrometers, and obtained the nigrosine base 2. The nitrobenzene content was 40 ppm and the aniline content was 2000 ppm.

  The characteristic values of the nigrosine bases 1 and 2 are summarized in Table 1.

[Charge control agent production example 1]
To 3000 g of propylene glycol monomethyl ether, 600 g of a xylene resin (HP-100 manufactured by Mitsubishi Gas Chemical Co., Ltd .: average molecular weight 1200) was added, and sufficiently mixed and dissolved. 400 g of the nigrosine base 1 obtained above was added thereto, and then the mixture was stirred and mixed for 2 hours while maintaining the liquid temperature at 70 to 80 ° C. Further, the temperature was raised above the boiling point of the solvent (120 ° C.) to remove propylene glycol monomethyl ether. Furthermore, after washing | cleaning with water and drying, it grind | pulverized with the sample mill and the composition of 750g was obtained. (Average particle diameter 7.5 μm) This is designated as charge control agent 1.
When the aniline content and the nitrobenzene content contained in the charge control agent 1 were analyzed by gas chromatography, the aniline content was 25 ppm and the nitrobenzene content was 10 ppm.

[Charge control agent production examples 2 to 6, 8]
Except for the conditions shown in Table 2, charge control agents 2 to 6 were obtained in the same manner as in charge control agent production example 1. The charge control agent 8 is a charge control agent obtained in the same manner as the charge control agent 1 except that rosin maleic anhydride resin (Marquide resin NO.33 manufactured by Arakawa Chemical Co., Ltd.) is used instead of xylene resin. The characteristic values of the obtained charge control agent are shown in Table 2.

[Charge Control Agent Production Example 7]
600 g of xylene resin (HP-100 manufactured by Mitsubishi Gas Chemical Company) and 400 g of the nigrosine base obtained above were mixed and kneaded at 140 ° C. for 30 minutes using a pressure kneader. After taking out and cooling, it was pulverized by a sample mill and a jet mill to obtain 700 g of a composition. (Average particle diameter 7.7 μm) This is designated as charge control agent 7. When the aniline content and the nitrobenzene content contained in the charge control agent 7 were analyzed by gas chromatography, the aniline content was 50 ppm and the nitrobenzene content was 20 ppm.

The nitrobenzene content and aniline content in nigrosine in Examples and Comparative Examples were both measured using Gas Chromatograph Agilent (formerly Hewlett Packard) Model 6890 and using HP-INNOWAX as a column.

Styrene-n-butyl acrylate copolymer 100 parts by weight Magnetic substance 1 (magnetite) 70 parts by weight Charge control agent 1 2.5 parts by weight Low molecular weight polypropylene wax 2.5 parts by weight were premixed with a Henschel mixer and then biaxial The mixture that had been put into a heating kneader, kneaded and extruded was cooled at room temperature, and coarsely pulverized with a hammer mill to obtain a chip-like pulverized product (hereinafter referred to as “chip”). Subsequently, this was finely pulverized by a jet mill pulverizer, led to a classifier, and a portion having an average particle size of 10 μm was taken out as a fine powder for toner to obtain a classified toner (toner base particle).

  In order to investigate the dispersibility in the nigrosine-based binder resin, a predetermined amount of chips, classified toner base particles and classified fine powder are dissolved in a predetermined amount of chloroform, and the absorbance (wavelength: 567 nm) of the supernatant is measured. The content of nigrosine base in the charge control agent in the classified toner base powder and classified fine powder was determined from the value of the calibration curve. The contents of the nigroshi base were 0.56%, 0.56% and 0.58%, respectively.

  Note that the calibration curve is based on the addition amount of nigrosine base of 0.5 to 2.5 parts by weight, the addition amount of magnetic substance is 40 parts by weight, the polypropylene wax is 1.4 parts by weight, and the rest is styrene which is a binder resin. -As a n-butyl acrylate copolymer, a magnetic toner was prepared in the same manner as in the above example except that the total amount was 100 parts by weight, and a predetermined amount of the toner was dissolved in a predetermined amount of chloroform. Then, the absorbance (wavelength: 567 nm) of the supernatant was measured in the same manner as in the example, and the absorbance value was plotted in association with the added amount value. When forming the supernatant liquid, the magnetic powder can be sufficiently precipitated by leaving the prepared liquid on the magnet.

The content of the magnetic substance in the magnetic toner can be easily obtained by burning in air and obtaining the residue. Although the approximate magnetic substance content can be calculated from the residual rate, it can be calculated in consideration of the proportion of weight increase due to the oxide for more accurate calculation.
For example, in the case of magnetite, since the left ones to be Fe ₂ O _3, than this in terms with Fe ₂ O ₃ original magnetite (Fe ₃ O _4, i.e. Fe O.Fe ₂ O ₃ ) content can be calculated. That is, the Fe content in the Fe ₂ O ₃ content may be obtained and further converted into the amount of Fe ₃ O ₄ . The composition of the magnetic material itself is analyzed in advance to confirm the composition of the original magnetic material, and the state of the oxide of the magnetic material may be further grasped.
For example, about 5 g of a magnetic toner sample containing magnetite is weighed in a crucible, set in an electric furnace at 700 ° C. and left in the air for about 2 hours to completely burn, and after left to cool, the remaining weight is measured. The rate [%] is required. Since what is obtained as a residue at that time is Fe ₂ O ₃ , the content may be obtained by converting this to Fe ₃ O ₄ . At this time, when the Fe ₂ O ₃ residue is 40%, the numerical value obtained by conversion to Fe ₃ O ₄ is 40.6%. That is, the molecular weight of Fe ₂ O ₃ is 159.7, and the atomic weight of Fe ₂ is 111.7 because the atomic weight of Fe is 55.85. Accordingly, the proportion of Fe in Fe ₂ O ₃ is 69.9%. 69.9% of the residual rate is Fe content. Fe ₃ O ₄ has a molecular weight of 231.55, of which the atomic weight of Fe is 167.55, so the proportion of Fe is 72.4%. 72.4% of the residual rate is Fe content. Here, the amount of Fe in the residual rate of 40% is 29.4% (40 × 0.699), and when converted to the amount of Fe ₃ O _{4, the} content is 40.6% (29.4 ÷ 0.724). Can be sought.
By calculating the residual ratio of the toner base particles, classified fine powder and toner chip before fine pulverization by this quantitative analysis, the distribution of the magnetic substance into the toner can be quantified. It can be seen that the distribution is good if there is almost no difference in the content of the magnetic substance in the toner base particles, classified fine powder and toner chip. On the other hand, it can be confirmed that a toner having a large difference in the content of the magnetic substance in the toner base particles and the classified fine powder causes poor distribution.
The content of the magnetic substance in the obtained toner base powder and classified fine powder in the chips thus obtained was 39.9%, 39.8%, and 40.0%.

[Examples 2 to 9, Comparative Examples 1 to 5]
Performed in the same manner as in Example 1 except that the charge control agent 1 and the magnetic material 1 were changed to the charge control agents and magnetic materials described in Tables 2 and 3, respectively, in the chip, in the classified toner base particles, and in the classification. The content of nigrosine base and the content of magnetic substance in the fine powder were determined. The results are shown in Table 4.

From Table 4, the toners (Examples 1 to 9) obtained by combining the charge control agents (1 to 7) of the present invention and the magnetic materials (1 to 4) are obtained in the chips, classified toner base particles, and In any of the classified fine powders, the content of nigrosine base and the content of the magnetic substance are the same as the addition amount at the time of blending, and this shows that the distribution property to the binder resin is good.
On the other hand, the content of nigrosine base and the content of magnetic substance in the toners (Comparative Examples 1 to 5) that do not satisfy the above combination are less than the addition amount in the toner base particles, while increasing in the classified fine powder. Both show that the dispersibility of the nigrosine base and the magnetic material is poor.
It is estimated that the deterioration of partitioning is caused by the amount of nitrobenzene, the amount of aniline in the nigrosine base, and the specific surface area of the magnetic substance. In order to obtain good distribution, both the characteristics of the charge control agent and the characteristics of the magnetic material are important. And even if one is bad, good distribution cannot be obtained. In addition, when the specific surface area of the magnetic material is large, the image quality deteriorates.
If the distribution of the nigrosine base and the magnetic substance in the charge control agent is poor, a stable quality toner cannot be obtained when the classified fine powder is returned to the raw material and reused, so the classified fine powder cannot be reused. It becomes.

  Furthermore, 0.3 parts by weight of hydrophobic silica (Aerosil R972) and 0.5 parts by weight of tungsten carbide (WC-10 manufactured by Nippon Shin Metal Co., Ltd.) were added to 100 parts by weight of these toner base powders. After mixing, the toner was examined for changes over time. (Examples 1-9, Comparative Examples 1-5)

 The test of change with time in heating was carried out by leaving the toner in a dryer at 50 ° C. for 3 days (72 hours) to promote heat deterioration, and then using a commercially available copying machine (Canon Co., NP3050). It was based on the continuous shooting of 10,000 sheets under the environmental condition of RH and 50RH. The image densities at the initial and 10,000 copies were 1.41 and 1.42, respectively, and the fog at the initial and 10,000 copies was 0.6 and 0.7, respectively. Furthermore, there was no scattering of the toner particles in the machine after copying 10,000 sheets, and there was no stain on the obtained image.

The fog was measured by measuring the reflectance with a photovolt. 1.5% or less is a good value.
Further, the scattering of the toner in the machine was performed by checking whether or not the scattered toner was present on the transfer charger of the copying machine. When toner scattering is observed on the transfer charger, image contamination is caused.

  From Table 5, when developed using the toner after the heat deterioration acceleration test, the toners of the present invention (Examples 1 to 9) and the comparative toners (Comparative Examples 1 to 5) are not significantly different in image density. In the toner of the present invention, even after the heat deterioration acceleration test, fog generation and toner scattering are not observed when copying 10,000 sheets, whereas the comparative toner shows fog from the beginning of copying. There was scattering in the aircraft, and the image was dirty. This heat deterioration is presumed to be due to the deterioration of the uniform dispersibility of the nigrosine dye due to the presence of a large amount of nitrobenzene and aniline and the deterioration of the uniform dispersibility of the magnetic substance.

Claims (5)

A magnetic toner for developing electrostatic images containing at least a binder resin, a magnetic material, and a charge control agent, containing a composition obtained by mixing a nigrosine base and a xylene resin as a charge control agent, and nitrogen adsorption of the magnetic material A magnetic toner for developing an electrostatic image, wherein the BET specific surface area is 3.0 to 9.0 m ² / g according to the method.  2. The magnetic toner for developing electrostatic images according to claim 1, wherein the content of aniline in the charge control agent is 100 ppm or less and the content of nitrobenzene is 50 ppm or less.  The magnetic toner for developing an electrostatic charge image according to claim 1 or 2, wherein the xylene resin has a number average molecular weight of 800 to 1800.  The magnetic toner for developing an electrostatic charge image according to any one of claims 1 to 3, wherein a mixing ratio of the nigrosine base and the xylene resin is 20:80 to 70:30. The magnetic toner for developing an electrostatic charge image according to any one of claims 1 to 4, wherein the magnetic material has a bulk density of 0.15 to 0.40 g / cm ³ .