JP2002139865A - Electrophotographic black toner composition, electrophotographic two-component developer and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic black toner composition having high volume resistivity and satisfactory blackness. SOLUTION: The electrophotographic black toner composition consists essentially of toner particles containing at least a colorant and a bonding resin and an additive. The colorant consists of particles having a hematite structure and a pigment whose spectral reflectance has no highest peak in the range of 600-700 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method used in a copying machine or a printer utilizing or applying an electrophotographic method, and a black toner used in the method. In particular, a latent image is formed using a laser beam. The present invention relates to a multicolor image forming method applied to a digital copying machine and a black toner used for the method.

[0002]

2. Description of the Related Art In an electrophotographic development process, a black toner in which a nonmagnetic black pigment such as carbon black is mixed and dispersed in a binder resin is widely used as a developer. 2. Description of the Related Art Conventionally, in electrophotography, a developing method of visualizing an electrostatic latent image formed on a photoconductive photoreceptor using toner can be roughly classified into a two-component developing method and a one-component developing method.
In the two-component developing method, the black toner and the carrier are rubbed to give an electric charge of the opposite sign to the electrostatic latent image to the black toner, and the black toner is attached to the surface of the electrostatic latent image by electrostatic attraction to develop the toner. It is a method to do. On the other hand, the one-component developing method is a method of forming a thin toner layer on a developing roll and thereby visualizing an electrostatic latent image. Since no carrier is required, there is no need to control the concentration of black toner in the developer, and the structure of the developing machine is simple and the size can be reduced. On the other hand, the performance is equivalent to that of the two-component developing method. In order to achieve this, advanced technology is required. As one of the one-component developing methods, a so-called insulating non-magnetic toner using an insulating or high-resistance black toner in which carbon black fine particles are dispersed in a binder resin without using magnetic particles. There is a development method.

The black toner used in the two-component developing method and the insulative non-magnetic toner developing method has an insulating property or a high resistance in the case of the PPC method, which is currently the mainstream in copying machines. And it is required that the volume specific resistance value be 10 ¹² Ω · cm or more.
Furthermore, since the insulating or high-resistance black toner needs to maintain the charge required for development, as described above,
It is strongly required to have a volume resistivity value of 10 ¹² Ω · cm or more. In the case of a low volume specific resistance value, the charge of the toner leaks and the proper charge amount cannot be maintained, and the opposite charge is injected and the charge amount may decrease.
This is to suppress this. If the charge amount is low, the attractive force between the toner carriers is weak, so that the toner is detached and "ground fog" occurs due to the stirring of the developing unit, the mechanical impact force with the photoreceptor, and the like. Conversely, if the charge amount is too high, it remains on the carrier and the amount of toner transferred to the photoreceptor decreases, resulting in a decrease in image density.

[0004] Further, the carrier in the two-component developing method is to impart an appropriate chargeability (charge amount, charge distribution) to the toner,
Maintaining an appropriate chargeability of the toner for a long time,
It is important that the chargeability of the toner is not changed even with changes in humidity or temperature, and various coated carriers having a resin coated on the surface have been proposed. Furthermore, in recent years, there has been a need for higher image quality, and for the purpose of improving the reproducibility of a solid (solid) image, Japanese Patent Application Laid-Open Nos.
JP-A-105264 proposes dispersing a conductive material in a coat film to lower the volume resistivity of the carrier. However, when the volume specific resistance of the carrier decreases, the resistance of the developer in which the toner and the carrier are mixed also decreases.
Injection into the toner of the opposite charge (of the opposite polarity to the proper charge of the toner) occurs, and "ground fog" occurs due to the toner having the reduced charge amount or the toner of the opposite polarity.
Further, the charged charges of the toner leak when left unattended. For example, if a copy is taken immediately after the copier has been left overnight, there is a problem that charge leakage occurs due to the necessity of the copier, the charge amount decreases, and ground fog occurs in the copy.

As described above, the insulating or high-resistance black toner needs to have an insulating property enough to maintain the charge, in particular, a volume specific resistance of 10 ¹² Ω · cm or more. It is strongly demanded that even when the content of the black pigment is increased to increase the degree, the decrease in the charge amount of the black toner can be suppressed. That is, in order to maintain the volume resistivity of the black toner as high as possible, it is strongly required that the volume resistivity of the black pigment be as high as possible.

At present, carbon black fine particles are mainly used as black pigments used in black toners (JP-A-4-142561, JP-A-10-39).
546). However, when carbon black fine particle powder is used, in order to obtain a black toner having a volume resistivity value of 10 ¹² Ω · cm or more, the amount of carbon black fine particle powder used is limited due to its conductivity. For this reason, the obtained black toner has a problem that a sufficient degree of blackness cannot be obtained. The carbon black fine particle powder is itself conductive and has a volume resistivity of 10Ω.
When the toner is used in a large amount to increase the degree of blackness, the volume specific resistance of the black toner decreases, and the toner cannot be used as an insulating or high-resistance toner. Although the details are unknown, even if the carbon black fine particle powder has a toner volume specific resistance value of 10 ¹² Ω · cm or more, the above-described charge leakage is relatively large and ground fogging is likely to occur. This is presumed to be because when the surface of the toner is microscopically observed, the carbon black itself is electrically conductive, so that the charge easily moves. In addition, it has been reported that among the substances generated in the process of manufacturing carbon black fine particle powder, substances suspected of carcinogenicity are included as impurities in the carbon black fine particle powder, and black toner using carbon black fine particle powder has been reported. Safety has been pointed out.

Further, as a black pigment used for a black toner, hematite particle powder containing Mn is used (Japanese Patent Laid-Open No. Hei 10-279314). This particle powder is safe and harmless, and has a volume resistivity value of 1 × 10 ⁶ to 1 × 1.
0 that there is a high resistance ^{8 Ω} · cm. However, the hue is red-brown to black-brown and the degree of blackness is not sufficient. Even when the toner is used, the same hue is obtained, and it is difficult to obtain a satisfactory degree of blackness. If it is contained in a large amount, it is possible to obtain a certain degree of blackness, but in that case, the volume specific resistance value of the toner decreases.

[0008]

A black pigment for a black toner having a high volume resistivity which is capable of suppressing a decrease in the charge amount of the black toner even when the content of the black pigment is increased, is currently available. Although most demanded, a black pigment having such properties has not yet been obtained. An object of the present invention is to achieve the following objects in order to satisfy such a conventional demand. That is, an object of the present invention is to provide a black toner composition for electrophotography having a high volume resistivity and a sufficient blackness. Another object of the present invention is to provide a two-component developer for electrophotography which does not easily cause "ground fogging" even when used with a carrier having a relatively low resistance and can obtain high quality image quality. Still another object of the present invention is to provide an image forming method for developing an electrostatic latent image on an electrostatic latent image carrier with a black toner having a high volume resistivity and a sufficient blackness.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems in the prior art, and as a result, the present invention described below has solved the above-mentioned problems. That is, the present invention provides a particle having a hematite structure having a high volume resistivity and a spectral reflectance of 600 to 700.
The pigment having no maximum peak in the range of nm is simultaneously contained in the toner, so that the volume resistivity value is 10 ¹² Ω.
A black toner composition having a blackness of not less than cm and a sufficient degree of blackness can be obtained. Further, since it hardly shows magnetism, it can be easily used as a developer for a two-component developing method.

The particles having a hematite structure by themselves exhibit a hue of reddish brown to blackish brown. This means that, in terms of spectral reflectance, the reflectance for light having a wavelength of 500 nm or more is higher than the reflectance for light having a wavelength of less than 500 nm. This is a physical property derived from the structure. When a metal atom such as Mn is doped into the particles having the hematite structure, the black hue is slightly improved, which is preferable but not sufficient. On the other hand, of the spectral reflectances in the range of 400 to 700 nm,
By causing a pigment having no maximum peak in the reflectance in the range of 600 to 700 nm to be present in the toner at the same time as the particles having the hematite structure, the toner having only the particles having the hematite structure alone has a hue that is reddish brown or black brown. It can be adjusted and the blackness can be made sufficient.

There are two-component developing methods and one-component developing methods for visualizing the electrostatic latent image formed on the photoconductive photoreceptor using toner. In the developer, the toner is frictionally charged by stirring the toner and the carrier, so that the frictional charge amount of the toner can be controlled by selecting the characteristics of the carrier and the stirring conditions, so that the image quality is highly reliable and excellent. . Also in the present invention, it is preferable that the developer is a two-component developer composed of a carrier and a toner from the viewpoint of reliability of image quality. In particular, when the electric resistance of the carrier is in the range of 1 × 10 ⁸ to 1 × 10 ¹⁵ Ωcm, the electric resistance of the carrier is 1 × 10 ⁸ to 1 × since the reproducibility of the solid (solid) image is good. 10 ¹⁵ Ω · c
It is preferably in the range of m. The above-described carbon black fine particle powder has a relatively large leakage of electric charge, and a toner using the same is liable to cause ground fogging, which is more remarkable when used in combination with the above-described relatively low-resistance carrier. However, in the toner having the constitution according to the present invention, since the resistance of the colorant itself is high, the background fog can be suppressed even when used in combination with the above-described relatively low-resistance carrier.

The means for solving the above problems are as follows. That is, <1> in an electrophotographic toner composition comprising at least toner particles containing a colorant and a binder resin and an additive, the colorant has particles having a hematite structure and a spectral reflectance of 600 to 700 nm. A black toner composition for electrophotography comprising a pigment having no maximum peak.

<2> The pigment has a spectral reflectance of 400 to 5
The black toner composition for electrophotography according to <1>, having a maximum peak in a range of 00 nm.

<3> The black toner composition for electrophotography according to <1>, wherein the particles having a hematite structure are mainly composed of Mn-containing iron.

<4> The Mn content of the particles having a hematite structure is 5 to 4 with respect to the particles having a hematite structure.
The black toner composition for electrophotography according to the above <3>, which is 0% by weight.

<5> The particles having a hematite structure having a volume resistivity of 1 × 10 ⁵ Ω · cm or more.
The black toner composition for electrophotography according to any one of <3>.

<6> The electrophotographic device according to any one of <1> to <4>, wherein the particles having a hematite structure have an average particle diameter in a range of 0.02 to 0.5 μm. It is a black toner composition.

<7> In a two-component developer for electrophotography comprising at least a toner comprising toner particles containing a colorant and a binder resin and an additive, and a carrier, the colorant is a particle having a hematite structure and Reflectivity is 6
An electrophotographic two-component developer comprising a pigment having no maximum peak in the range of 00 to 700 nm.

<8> The electric resistance of the electrophotographic two-component developer is 6.2 × 10 ⁴ under an electric field strength of 2.0 V / μm.
The two-component developer for electrophotography according to the item <7>, wherein the developer is in the range of 1.0 to 10 ¹³ Ω.

<9> The pigment has a spectral reflectance of 400 to 50.
The two-component developer for electrophotography according to <7>, having a maximum peak in a range of 0 nm.

<10> The two-component electrophotographic developer according to <7>, wherein the particles having the hematite structure are mainly composed of Mn-containing iron.

<11> The Mn content of the particles having a hematite structure is 5 to 5% with respect to the particles having a hematite structure.
The two-component developer for electrophotography according to <10>, wherein the amount is 40% by weight.

<12> The particles according to the above <7, wherein the particles having a hematite structure have a volume resistivity of 1 × 10 ⁵ Ω · cm or more.
>, <9>, and <10>.

<13> The particle having the hematite structure having an average particle diameter in the range of 0.02 to 0.5 μm.
The two-component developer for electrophotography according to any one of <7>, <9>, <10>, and <11>.

<14> The developer carried on the developer carrier is transported to the development area, and the electrostatic latent image on the electrostatic latent image carrier is developed with the developer on the developer carrier in the development area. In the image forming method, the developer has a black toner containing at least a binder resin and a colorant, the colorant has particles having a hematite structure, and a spectral reflectance of 600 to 700.
An image forming method comprising a pigment having no maximum peak in the range of nm.

<15> The pigment has a spectral reflectance of 400 to 5
The image forming method according to the item <14>, wherein the image forming method has a maximum peak in a range of 00 nm.

<16> The image forming method according to <14>, wherein the particles having a hematite structure are mainly composed of iron containing Mn.

<17> The Mn content of the particles having a hematite structure is 5 to 5% with respect to the particles having a hematite structure.
The image forming method according to the item <16>, wherein the content is 40% by weight.

<18> The particle according to any one of <14>, <16>, and <17>, wherein the particles having a hematite structure have a volume resistivity of 1 × 10 ⁵ Ω · cm or more. This is an image forming method.

<19> The above <14>, <16>, <17>, and <18>, wherein the particles having a hematite structure have an average particle size in the range of 0.02 to 0.5 μm.
The image forming method according to any one of the above items.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION The toner composition for electrophotography, the two-component developer for electrophotography, and the image forming method of the present invention will be described in detail below. The toner particles used in the present invention comprise at least a colorant and a binder resin, and known binder resins are used.

Examples of the binder resin include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene and isoprene, vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl acetate, and acrylic acid. Α such as methyl, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate
-Examples of homopolymers or copolymers of vinyl ethers such as methylene aliphatic monocarboxylic acid ester, vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether, vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone and the like. Particularly, as typical binder resins, polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene- Maleic anhydride copolymer, polyethylene and polypropylene can be mentioned. Furthermore, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin, and wax can be mentioned. Among them,
It is particularly effective when polyester is used as the binder resin.
For example, a linear polyester resin composed of a polycondensate containing bisphenol A and a polyvalent aromatic carboxylic acid as main monomer components can be preferably used.

The polyester resin used in the present invention is synthesized from a polyol component and a polycarboxylic acid component by polycondensation. As the polyol component used,
Ethylene glycol, propylene glycol, 1,3-
Butanediol, 1,4-butanediol, 2,3 butanediol, diethylene glycol, triethylene glycol, 1,5-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol, hydrogenated bisphenol A, bisphenol -A
Examples include ethylene oxide adducts and bisphenol-A propylene oxide adducts. As the polyol component, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, dodecenylsuccinic acid, trimellitic acid, pyromellitic acid, cyclohexanetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 2,4-naphthalenetricarboxylic acid 1,2,5
Hexanetricarboxylic acid, 1,3-dicarboxyl-2
-Methylenecarboxypropanetetramethylenecarboxylic acid and their anhydrides.

The softening point is 90 to 150 ° C., the glass transition point is 50 to 75 ° C., and the number average molecular weight is 2,000 to 600.
0, weight average molecular weight 8,000 to 150,000, THF insoluble gel content 0 to 30% by weight, acid value 0 to 30, hydroxyl value 0
Resins having a value of from 40 to 40 are particularly preferably used.

Next, the particles having a hematite structure will be described. The particles having a hematite structure according to the present invention are composed of granular particles, and the size of the particles has an average diameter of 0.3.
When it is from 02 to 2 μm, and less than 0.02 μm, it is difficult to disperse because it is a fine particle. If it exceeds 2 μm, it is difficult to obtain a black color because the particle diameter is too large. The volume resistivity of the particle powder is generally 10 ⁵ Ω · cm (1
(At 00 V / cm). The particle shape of the particles is spherical, octahedral, hexahedral, granular, etc., and isotropic particle powder having a sphericity (ratio of average longest diameter to average shortest diameter) of less than 2, needle-like, spindle-like, rice-like, etc. Axis ratio (ratio of average major axis diameter to average minor axis diameter)
Any of two or more anisotropic particle powders can be used.

The particles having a hematite structure according to the present invention are effective by themselves, but particles having a hematite structure containing Mn having a hue closer to black are more preferable. The Mn content is 5 to 40% by weight based on the particles having a hematite structure. If it is less than 5% by weight, it is difficult to obtain the required blackness. If it exceeds 40% by weight, the desired blackness can be obtained, but the blackness is saturated and there is no point in containing more than necessary. Preferably 9 to
It is 35% by weight, more preferably 10 to 20% by weight.

Octahedral particles having a hematite structure containing iron as a main component and containing Mn and having an average particle diameter of 0.05 to 2.0 μm are prepared by using an aqueous ferrous salt solution and an aqueous ferrous salt solution. The suspension containing the ferrous hydroxide colloid obtained by reacting 1.01 to 1.3 equivalents of an aqueous alkali hydroxide solution with respect to Fe ²⁺ is heated to a temperature range of 45 to 100 ° C. A suspension containing magnetite particles is formed by oxidizing the ferrous hydroxide colloid by a magnetite generation reaction in which an oxygen-containing gas is aerated while generating magnetite particles, and the suspension containing the magnetite particles contains Mn or Mn and Fe ²⁺ are added in the form of an aqueous solution, and the total F
Then, the suspension is heated and oxidized under the same conditions as the magnetite formation reaction, so that the surface of the magnetite particles is treated with hydroxide of Mn or Mn and Fe. The magnetite particles coated with a hydroxide and then coated with the hydroxide of Mn or the hydroxide of Mn and Fe are separated by filtration, washed with water, dried, and then heated in a temperature range of 750 to 1000 ° C. Obtained by firing.

The spherical particles having a hematite structure containing iron as a main component and containing Mn and having an average particle diameter of 0.05 to 2.0 μm are formed by using an aqueous ferrous salt solution and an aqueous solution of F in the aqueous ferrous salt solution.
A suspension containing ferrous hydroxide colloid obtained by reacting 0.80 to 0.99 equivalents of an aqueous alkali hydroxide solution with respect to e ²⁺ is heated to a temperature range of 45 to 100 ° C. While the ferrous hydroxide colloid is oxidized by a magnetite generation reaction in which an oxygen-containing gas is passed to generate magnetite particles, a suspension containing magnetite particles is formed, and Mn or Mn is added to the suspension containing the magnetite particles. And Fe ²⁺ in the form of an aqueous solution to add
The suspension is heated and oxidized under the same conditions as the magnetite generation reaction after the presence of Mn of 8 to 150 at. The magnetite particles coated with an oxide and then coated with the hydroxide of Mn or the hydroxide of Mn and Fe are separated by filtration, washed with water, dried, and then heated and calcined in a temperature range of 750 to 1000 ° C. It is obtained by doing.

Various conditions for producing octahedral particles and spherical particles having a hematite structure containing iron as a main component containing Mn will be described. As the ferrous salt aqueous solution, ferrous sulfate, ferrous chloride and the like can be used. As the aqueous solution of the Mn compound, manganese sulfate, manganese chloride, or the like can be used. In order to uniformly coat the surface of the magnetite particles, it is preferable to add the aqueous solution. As the aqueous alkali hydroxide solution, sodium hydroxide, potassium hydroxide, or the like can be used.

The reaction can be oxidized by passing an oxygen-containing gas (eg, air) through the reaction suspension, and is preferably performed in a reactor equipped with a stirring function. The magnetite particles coated with the hydroxide of Mn or the hydroxide of Mn and Fe are then 750-
By heating in a temperature range of 1000 ° C., granular particles having a hematite structure mainly containing iron containing Mn are obtained. When the temperature is lower than 750 ° C., the blackness is insufficient, and
When the temperature exceeds 0 ° C., the particles become too large and the coloring power is not obtained. The atmosphere for the heating and firing is performed in the air. The heating and firing in the air is for oxidizing the magnetite to transform it into a hematite structure.

The amount of the particles having a hematite structure added to the toner ranges from 5 to 50% by weight. Preferably it is in the range of 10 to 30% by weight. If the amount is less than 5% by weight, the blackness is not sufficient. On the other hand, if it is more than 50% by weight, the strength as a toner is reduced, and for example, a toner image fixed by heating and pressure on paper is undesirably dropped from the paper due to bending or the like.

The volume resistivity was measured as follows. Electrometer (KEITHLEY, product name: KEITH
LEY 610C) and a high voltage power supply (FLUKE 415C, product name: FLUKE 415)
Place the sample on the lower plate of the measuring jig which is a pair of 20 cm ² circular plates (made of steel) connected to B) with a thickness of about 1 mm.
Place so as to form a flat layer of ３3 mm. Next, after the upper electrode plate is placed on the sample, a weight of 4 kg is placed on the upper electrode plate in order to eliminate a gap between the samples. In this state, the thickness of the sample layer is measured. Next, a current value is measured by applying a voltage to both electrode plates, and a volume resistivity is calculated based on the following equation. Volume specific resistance = applied voltage × 20 ÷ (current value−initial current value) ÷ sample thickness In the above equation, the initial current is a current value when the applied voltage is 0, and the current value indicates a measured current value.

Next, a pigment having no maximum peak in the range of 600 to 700 nm in the spectral reflectance in the range of 400 to 700 nm will be described. Basically 600-700
Any known pigment can be used as long as it has a small reflectance in the range of nm. Aniline blue, ultramarine blue,
Phthalocyanine blue, malachite green oxalate, C.I. I. Pigment Blue 15: 1, Pigment Blue 15: 3, and the like can be exemplified as typical examples. Specific examples include the following, but are not limited thereto. CIPigment Blue 15: Fasto
gen Blue GS (manufactured by Dainippon Ink), Chromobine SR (manufactured by Nippon Seisakusho) CI Pigment Blue 16: Sumitone Cyamine Bl
ue LG (Sumitomo Chemical Co., Ltd.) CI Pigment Green 7: Phthaloc
yanineGreen (Toyo Ink Co., Ltd.) CI Pigment Green 3
6: Cyanine Green 2YL (manufactured by Toyo Ink Co., Ltd.)
Blue 15:13: Cyanine GGK (Nippon Pigment) C.
I. Pigment Blue 15: 3: Lionol Blue FG-7351 (manufactured by Toyo Ink Co., Ltd.)

The amount added to the toner is in the range of 0.1 to 2.0% by weight. Preferably it is in the range of 0.1 to 1.0% by weight. If the amount is less than 0.1% by weight, the hue is not sufficiently adjusted, and if it is more than 2.0% by weight, the hue of the pigment itself is undesirably produced.

The weight ratio of the hematite to the pigment having no maximum peak in the spectral reflectance range of 600 to 700 nm is preferably in the range of 15: 1 to 50: 1. The spectral reflectance of the pigment was 0.5
g and castor oil (0.7 cc) were kneaded with a Hoover type muller into a paste, and 4.5 g of clear lacquer was added to the paste, kneaded and made into a coating, and the coated piece was applied on a cast-coated paper using a 6-mil applicator ( A coating thickness: about 30 μm) is prepared, and the paint piece is measured with an X-Rite938 (two-degree visual field with a light source D50).

The toner used in the present invention comprises a binder resin, particles having a hematite structure, a pigment having no maximum peak in the range of 600 to 700 nm in spectral reflectance, and a fixing agent as another internal additive. It may include one or more known waxes for imparting properties and one or more known charge control agents for adjusting the charge.

Examples of the wax include paraffin wax and its derivatives, montan wax and its derivatives, microcrystalline wax and its derivatives, Fischer-Tropsch wax and its derivatives, and polyolefin wax and its derivatives. Derivatives are oxides,
Including polymers with vinyl monomers and graft-modified products. In addition, alcohols, fatty acids, vegetable waxes, animal waxes, mineral waxes, ester waxes, acid amides and the like can also be used. Further, a petroleum-based resin may be contained in order to satisfy the pulverizability and heat storage property of the toner. The petroleum-based resin is synthesized from diolefins and monoolefins contained in a cracked oil fraction produced as a by-product from an ethylene plant that produces ethylene, propylene, etc. by steam cracking of petroleum.

Further, long-term storage properties, fluidity, developability,
In order to further improve the transferability, the toner used in the present invention may contain an inorganic powder or a resin powder alone or in combination with the toner surface. As inorganic powder, for example, carbon black, silica, alumina, titania, zinc oxide, as resin powder, PMMA, nylon, melamine, benzoguanamine, spherical particles such as fluorine, and irregular powder such as vinylidene chloride, fatty acid metal salt, etc. Is raised. When added to the surface, the amount of each addition is 0.1 to 4% by weight, more preferably 0.1 to 4% by weight.
It is added so as to have a blending amount of 3 to 3% by weight.

The black toner obtained by mixing the toner particles with the above additives can be produced by a known method. Specifically, it can be obtained by sufficiently mixing the toner particles and the additive with a mixer. As the mixer, a Henschel mixer, a ball mill or the like can be used.

The carrier is not particularly limited as long as it is a known carrier, and iron powder-based carriers, ferrite-based carriers, surface-coated ferrite carriers and the like can be used.
Preferably, a surface-coated carrier can be used. Preferably, the measurement conditions of the resistance of the developer are such that the toner forms a magnetic brush developer layer with a composition of 6 parts with respect to 100 parts of the carrier,
The resistance per unit length in the longitudinal direction of the sleeve (developer carrier) (referred to as “electrical resistance” in the present invention) is 2.
The one measured under an electric field strength of 0 V / μm is used. This electric resistance value is preferably in the range of 6.2 × 10 ^{4 to} 1.0 × 10 ¹⁵ Ω. More preferably 6.2 × 1
0 ^{4 to} 1.0 × 10 ¹⁰ Ω. The electric resistance value in the present invention is the electric resistance in the actual developing nip configuration, and a magnetic brush is formed on the developing sleeve so that an aluminum pipe having the same size as the photoconductor is arranged in the same arrangement as the actual developing nip. When a DC voltage is applied between the sleeve and the aluminum pipe, the resistance obtained from the flowing current is set to the length of the sleeve covered with the developer (unit: c
m). By controlling the resistance of the developer layer in the above range, the reproducibility of the solid image portion is good, and in the region from the low-density portion to the high-density portion, image omission and generation of brush marks are prevented. Can be. 2.
Resistance under electric field strength of 0 V / μm is 1.0 × 10 ¹⁵ Ω
If it is higher than this, the rear end of the halftone is likely to be missing at the boundary where the halftone and the solid image are in contact, and if it is lower than 6.2 × 10 ⁴ Ω, a brush mark is also likely to be generated. The developer is the carrier 10
It is preferable to use the toner in a range of 1 to 20 parts with respect to 0 part.

In the toner used in the present invention, the addition of the internal additive to the inside of the toner particles is performed by a kneading process. It can be produced by a known method of mixing, kneading, and pulverizing a predetermined amount of a binder resin and a predetermined amount of a black composite nonmagnetic particle powder. Specifically, the black composite non-magnetic particles powder and the binder resin, if necessary, a release agent,
After thoroughly mixing a mixture containing a colorant, a charge control agent, and other additives with a mixer, the resin and the like are melted by a heating kneader, kneaded and made compatible to form a black composite nonmagnetic particle powder. Are dispersed and then solidified by cooling to obtain a kneaded resin, and the kneaded resin is pulverized and classified to obtain a black toner having a desired particle size.

As the mixer, a Henschel mixer, a ball mill or the like can be used. The kneading can be performed using various types of heating kneaders. As a heating kneader, three-roll type, single screw type,
A twin screw type and a Banbury mixer type are known.

The method for producing the toner used in the present invention is optional. Examples of the pulverization of the kneaded material include a micronizer, Ulmax, Jet-o-mizer, KTM (Krypton), and turbo mill. Furthermore, there is Formula I Jet-Mill. Classification is performed by elbow jet using the Coander effect, by wind power, and by a hybridization system as a subsequent process.
The shape can be changed by adding a mechanofusion system (manufactured by Hosokawa Micron Corporation), a kryptron system (manufactured by Kawasaki Heavy Industries, Ltd.), or the like.

As a method other than the above known methods, there are a suspension polymerization method and an emulsion polymerization method. In the suspension polymerization method,
Polymerizable monomer and particles having a hematite structure and a pigment having no peak in the range of 600 to 700 nm in spectral reflectance, if necessary, further a polymerization initiator, a crosslinking agent,
A charge controlling agent, a monomer composition obtained by dissolving or dispersing a mixture to which other additives are added is added to an aqueous phase containing a suspension stabilizer while stirring, granulated, polymerized, and polymerized. A black toner having a particle size can be formed. In the emulsion polymerization method, a monomer and particles having a hematite structure and a pigment having no peak in the range of 600 to 700 nm in spectral reflectance are further dispersed in water with a polymerization initiator, if necessary, to carry out polymerization. By adding an emulsifier during the process, a black toner having a desired particle size can be formed.

[0055]

EXAMPLES <Production of Mn-Containing Hematite Particles> 300 l of an aqueous solution of ferrous sulfate having a concentration of 1.30 mol / l were previously prepared in a reactor equipped with a stirrer in 200 l of water and 1 l.
To 60 l of 5.5N aqueous sodium hydroxide solution, add pH
An aqueous ferrous salt solution containing ferrous hydroxide was produced at a temperature of 85 ° C. and a value of 13 or more. 270 l / min at a temperature of 90 ° C. to the aqueous ferrous salt solution containing ferrous hydroxide.
Was passed through for 90 minutes to produce magnetite particles. Next, 100 l of an aqueous solution of ferrous sulfate having a concentration of 1.3 mol / l and 100 l of a manganese sulfate aqueous solution containing 1.3 mol / l were added to 500 l of an aqueous suspension containing 29.6 kg of the magnetite particles (Mn content was reduced to Fe and Mn). 20% by atom) and 46 l of a 11.2N aqueous sodium hydroxide solution (corresponding to the amount for neutralizing the added Mn amount and the added Fe ²⁺ amount), and the pH value was 13 or more, and the temperature was lowered. 90 ° C
At 700 l / min for 180 min.
, And magnetite particles coated with the Fe hydroxide. The produced particles were separated by filtration, washed with water, dried and pulverized by a conventional method to obtain a black powder. Subsequently, the obtained black powder was passed through a continuous electric furnace having a furnace tube made of ceramic to give an average residence time of 900 ° C. and 60 minutes in the air to obtain black powder A.

The obtained black powder A had an average particle size of 0.2
As a result of X-ray fluorescence analysis at 5 μm, the Mn content was 14.8% by weight, and as a result of X-ray diffraction, a hematite peak was observed. The magnetism is 0.8 emu / g when applied with an external magnetic field of 10 kOe, and the volume resistivity is 3.
It was 8 × 10 ⁶ Ω · cm.

Toner 1 79.5 parts of linear polyester (linear polyester selected from terephthalic acid / bisphenol A / ethylene oxide adduct / cyclohexane dimethanol: Tg = 62 ° C., Mn = 4,000, Mw = 35,000) , Acid value = 12, hydroxyl value = 25) Black powder A 15 parts CI Pigment Blue 15: 3 (Lionol Blue FG-7351, manufactured by Toyo Ink Co., Ltd., maximum peak wavelength: 460 nm) 0.5 part Purified granular carnauba wax ( the Toa Kasei Co., Ltd.) 5 parts the above mixture was kneaded by an extruder, was ground in a grinder of a surface grinding method, fine particles in air classifier, the coarse particles classified black toner particles d ₅₀ = 9.1 microns Obtained. The volume specific resistance was 4.6 × 10 ¹⁴ Ω · cm.

Toner 2 CI Pigment Blue 15: 3 in toner 1
ment Blue 15 (Fastogen Blue GS, manufactured by Dainippon Ink,
Black toner particles having a d ₅₀ = 6.5 μm were obtained in the same manner except that the maximum peak wavelength was changed to 460 nm. The volume resistivity was 3.6 × 10 ¹⁴ Ω · cm.

Toner 3 89.5 parts of linear polyester (linear polyester selected from terephthalic acid / bisphenol A / ethylene oxide adduct / bisphenol A / propylene oxide adduct / cyclohexanedimethanol: Tg = 70 ° C., Mn = 4) , 600, Mw = 38,000, acid value = 11, hydroxyl value = 23) Black powder A 10 parts CIPigment Blue 15: 3 (Lionol Blue FG-7351, manufactured by Toyo Ink, maximum peak wavelength: 460 nm) 0 After the above mixture was preliminarily mixed, the mixture was kneaded with an extruder and pulverized with a jet mill. The particles were classified by an air classifier to obtain black toner particles having an average particle size of 7.8 μm. The volume resistivity was 1.8 × 10 ¹⁵ Ω · cm.

Toner 4 A black toner having a d ₅₀ = 6.1 μm was prepared in the same manner as in toner 3, except that the black powder A was changed from 10 parts to 20 parts and the linear polyester was changed from 89.5 parts to 79.5 parts. Particles were obtained. The volume resistivity was 1.6 × 10 ¹⁴ Ω · cm.

Toner 5 A toner was prepared in the same manner as in toner 1 except that CI Pigment Blue 15: 3 was excluded, to obtain black toner particles having d ₅₀ = 7.2 μm. The volume resistivity was 5.6 × 10 ¹⁴ Ω · cm.

Toner 6 83 parts of linear polyester (linear polyester selected from terephthalic acid / bisphenol A / ethylene oxide adduct / bisphenol A / propylene oxide adduct / cyclohexanedimethanol: Tg = 70 ° C., Mn = 4,600) , Mw = 38,000, acid value = 11, hydroxyl value = 23) carbon black (BPL, manufactured by Cabot Corporation) 10 parts low molecular weight polyethylene 7 parts After the above mixture was preliminarily mixed, it was kneaded with an extruder. It was pulverized with a jet mill. The particles were classified by an air classifier to obtain black toner particles having an average particle size of 8.8 μm. The volume resistivity was 3.6 × 10 ¹⁴ Ω · cm. To 100 parts of the toner thus obtained, 1.0 part of negatively chargeable silica and 0.6 part of negatively chargeable titania were added to obtain an externally added toner.

Carrier A The average particle diameter of the particles was 35 μm as measured by the microtrack.
100 parts by weight of 70 emu / g, 2 emu / g and 12 oersted ferrite particles having a saturation magnetization, a remanent magnetization and a coercive force of 3000 oersted,
0.5 part by weight of a styrene-methyl methacrylate copolymer and 14 parts by weight of toluene were placed in a vacuum degassing kneader,
After stirring at a temperature of 90 ° C. for 30 minutes, the pressure was reduced and the toluene was distilled off to form a coating layer, thereby obtaining Carrier A.

Carrier B The average particle diameter of the particles was 35 μm as measured by Microtrack.
100 parts by weight of 70 emu / g, 2 emu / g and 12 oersted ferrite particles having a saturation magnetization, a remanent magnetization and a coercive force of 3000 oersted,
1.2 parts by weight of a styrene-methyl methacrylate copolymer and 14 parts by weight of toluene were placed in a vacuum degassing kneader,
After stirring at a temperature of 90 ° C. for 30 minutes, the pressure was reduced and the toluene was distilled off to form a coating layer and obtain Carrier B. To 100 parts of this carrier A, 6 parts of this externally added toner was added and mixed to obtain a developer. To 100 parts of the carrier B, 6 parts of the externally added toner was added and mixed to obtain a developer.

A commercially available electrophotographic copying machine (A-Color 6)
30, manufactured by Fuji Xerox Co., Ltd.) under a humidity of 85% and a temperature of 28 ° C. in a copy test of 1000 sheets, and then the spectral reflectance of the 1000th solid image was measured. Further, the developer was sampled and the charge amount was measured. The copier was allowed to stand overnight, and the next day, the developer was sampled, the charge amount was measured again, and the fog of the first copy was observed. After a copy test of 30,000 sheets was further performed, the developer was sampled and the charge amount was measured. The copier was allowed to stand overnight, and the next day, the developer was sampled, the charge amount was measured again, and the fog of the first copy was observed. Table 1 shows the results.

[0066]

[Table 1]

In Table 1, the charge amount is a value measured by TB200 (manufactured by Toshiba Corporation). Ground fog is the result of visual observation of a copy. The resistance value of the developer is a value measured by the method described above.

Further, a solid image formed by each toner is converted into an X-Ri image.
Spectral reflectance was obtained by te938 (2 degree field of view of light source D50). The result is shown in FIG. Toners 1-4 show similar reflectance at each wavelength of 400-700 nm, as can be seen from the spectral reflectance of the fixed image solid, and have a satisfactory black hue. The reproducibility of the tone portion was good. In addition, a stable charge amount was also shown. On the other hand, in the toner 5, the reflectance was clearly increased from 550 nm in spectral reflectance, and the hue was black-brown, which was not satisfactory. Also,
The hue of Toner 6 was satisfactory black, but in the actual machine test, the amount of charge was significantly reduced when left overnight after a 30,000-sheet copy test, and ground fogging also occurred in the copy.

[0069]

According to the present invention, it is possible to provide a black toner composition for electrophotography having a high volume resistivity and a sufficient blackness. According to the present invention, it is possible to provide a two-component developer for electrophotography in which "ground fogging" does not easily occur even when a carrier having a relatively low resistance is used and high quality image quality can be obtained. According to the present invention, it is possible to provide an image forming method for developing an electrostatic latent image on an electrostatic latent image carrier with a black toner having a high volume resistivity and a sufficient blackness.

[Brief description of the drawings]

FIG. 1 is a graph showing the spectral reflectance of a solid image by the toner composition of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kotaro Yoshihara 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture F-Xerox Co., Ltd. F-term (reference) 2H005 AA00 CA21 CB03 EA01 FA01

Claims (4)

[Claims] 1. An electrophotographic toner composition comprising at least toner particles containing a colorant and a binder resin, and an additive, wherein the colorant has particles having a hematite structure, and a spectral reflectance of 600 to 700 nm. A black toner composition for electrophotography, comprising a pigment having no maximum peak in the range of. 2. A two-component developer for electrophotography comprising at least a toner comprising toner particles containing a colorant and a binder resin and an additive, and a carrier, wherein the colorant has particles having a hematite structure, and A two-component developer for electrophotography, comprising a pigment having no maximum peak in the range of 600 to 700 nm in reflectance. 3. An electrophotographic two-component developer having an electric resistance of 6.2 × 10 ⁴ under an electric field intensity of 2.0 V / μm.
3. The two-component developer for electrophotography according to claim 2, wherein the value is in the range of 1.0 to 1.010 < ¹³ > [Omega]. 4. An image in which a developer carried on a developer carrier is transported to a developing area, and an electrostatic latent image on the electrostatic latent image carrier is developed with the developer on the developer carrier in the developing area. In the formation method, the developer has at least a black toner containing a binder resin and a colorant, and the colorant has particles having a hematite structure, and a spectral reflectance of 600 to 700 nm. An image forming method comprising a pigment having no maximum peak.