JP2005099726A - Toner for forming image, toner container, two-component developer, image forming method and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide toner for forming an image using a black pigment which is safe and harmless for the environment, has high charging performance and can suppress scattering of the toner, to provide a toner container filled with the above toner for forming an image, and to provide a two-component developer using the toner, an image forming method and a process cartridge. <P>SOLUTION: The toner for forming an image contains at least a binder resin and a colorant and is characterized in that: the colorant is a black iron oxide compound containing a Ti component by 10 to 45 mass% in terms of Ti atoms with respect to Fe atoms in the measurement by wavelength dispersive fluorescent X-ray analysis; and the coercive force of the toner is in the range of 2 to 15 kA/m measured in a 398 Am<SP>2</SP>/kg magnetic field for the measurement by a multi-sample rotation type magnetization measurement apparatus. The toner container is charged with the above toner for forming an image. The above toner with a carrier is used for the two-component developer, the image forming method and the process cartridge. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming toner used in an image forming method in electrophotography and the like, more specifically, an image forming toner in which a black iron oxide compound as a specific component is blended as a colorant, a toner container filled with the toner, The present invention relates to a two-component developer using the toner, an image forming method, and a process cartridge.

  Conventionally, various methods have been disclosed as electrophotographic methods (Patent Documents 1 to 3). Generally, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means. Then, the latent image is developed using dry toner, and the toner image is transferred to paper or the like, and then fixed by heating, pressing, or the like to obtain a copy.

  Methods for developing electrical latent images are roughly divided into liquid development methods that use a developer in which various pigments and dyes are finely dispersed in an insulating organic liquid, cascade methods, magnetic brush methods, powder cloud methods, etc. Thus, there is a dry development method using a toner in which a colorant such as carbon black is dispersed in a natural or synthetic resin, and there are a one-component development method and a two-component development method using a carrier.

In recent years, attempts have been made to use black metal compound fine powder having good thermal conductivity as a colorant to replace carbon black. In recent years, the problem of environmental pollution and health damage has become a major issue, and there is an increasing demand for the safety of raw materials used in toners.
Carbon black, which is used in a large amount as a black colorant for toner, contains a very small amount of aromatic hydrocarbon, and in this, carcinogenicity such as 3,4-benzpyrene has been pointed out. Due to the fact that the substance is contained, there is an increasing trend toward safety as a problem for toner using carbon black.

As a low magnetic black pigment replacing carbon black, Patent Document 4 describes a black pigment particle powder composed of polycrystalline particles having a mixed composition of Fe ₂ TiO ₅ and Fe ₂ O ₃ —FeTiO ₃ solid solution. 6 describes a black particle powder having a hematite structure containing Mn.
The black pigment described in Patent Document 4 includes Fe ₂ TiO ₅ and Fe ₂ O ₃ —FeTiO ₃ obtained by coating magnetite with titanium oxide or mixing magnetite and titanium oxide and firing in a non-oxidizing atmosphere. It is related to black pigment particle powder consisting of polycrystalline particles having a mixed composition with a solid solution, and is mainly composed of safe and harmless iron oxide and titanium oxide, so there is no problem with safety. However, since magnetite with strong cohesiveness is the main raw material and magnetite coated with titanium oxide is fired at a high temperature of 700 ° C. or higher, hematite is produced, the color tone is reddish, and the blackness is low. There is a problem in that it is insufficient, and furthermore, only particles that are sintered or coalesced between particles can be obtained and monodispersed uniformly. It was. Further, since the black pigments described in Patent Documents 5 and 6 contain a large amount of Mn, which is an environmental pollutant, it is difficult to say that they are safe and harmless pigments.

Patent Document 7 proposes a mixture of Fe ₂ TiO ₅ and Fe ₂ O ₃ —FeTiO ₃ solid solution having an average particle size of 0.1 to 0.5 μm. This black pigment has an L * value of 18 to 25. Yes, the blackness is not as good as that of carbon black. Patent Documents 8 to 10 propose magnetic iron oxide containing 25 to 30% FeO, which is effective for magnetic toners but cannot be used for non-magnetic two-component development systems. Patent Documents 11 and 12 propose magnetite having a remanent magnetization of 6 Am ² / kg or less, and Patent Document 13 proposes iron oxide particles composed of Ti inside and Ti and Fe on the surface. The saturation magnetization is as high as 80 to 85 Am ² / kg and is effective for magnetic toners, but cannot be used for non-magnetic two-component development systems. Patent Document 14 proposes a rutile TiO ₂ mixed phase crystal with a saturation magnetization of 0.5 to 10 Am ² / kg, a particle size of 0.1 to 0.4 μm, and coated with Fe ₂ TiO _4. Although blackness has been obtained, energy saving has been progressing in recent years, and it is difficult to obtain sufficient fixability when using a thin roller and a low surface pressure fixing device. Can't get. Patent Document 15 proposes a toner containing a metal compound having a saturation magnetization of 30 Am ² / Kg or less and a dielectric loss factor of 50 or less. As a result, a toner having sufficient blackness of the image when the fixing speed is set to a medium speed of about 180 mm / sec as described in the examples can be obtained. The fixing speed is required to be 400 to 600 mm / sec. However, the toner described in Patent Document 15 cannot obtain a sufficient fixing property in a high speed machine, and therefore cannot obtain a sufficient blackness. Further, in Patent Document 16, a toner containing 20 parts by mass or less of a metal compound having a saturation magnetization of 40 Am ² / kg or less has an a * value after fixing of −3.0 to 3.0 and a b * value of −3.0. Toner of 3.0 is proposed, but in this range, red or blue is strong and it cannot be said that carbon black is black. Further, in Patent Document 17, a black hydrous iron oxide powder is devised for black hematite particles, but the core material is essentially manganese, and there remains a problem in safety.

  On the other hand, magnetite is a black pigment mainly composed of safe and harmless iron oxide, but has a high magnetic property, so that there is a problem that particles are reaggregated and it is difficult to obtain a uniform dispersion. In addition, since magnetite has a conductive property, it cannot be used as a colorant for the toner of the above-described two-component development method or non-magnetic one-component development method that requires insulation or high resistance.

Further, methods for heat-fixing a toner image on transfer paper are roughly classified into a contact fixing method and a non-contact fixing method. The former includes heating roller fixing, belt fixing, the latter includes flash fixing, and oven (atmosphere) fixing. .
The heating roller fixing method is a very heat efficient fixing method because the toner image and the heating roller are in direct contact with each other, and the apparatus can be miniaturized, so that it is widely used.
However, in recent years, energy saving has been further advanced, and there are cases where the heat source is turned off during standby when fixing is not performed. In such an apparatus, the heat roller is heated as soon as the heat source is turned on, and it is necessary to reach a desired temperature in a very short time.
For this reason, in order to increase the thermal energy efficiency of the fixing device used in such an apparatus, an attempt has been made to reduce the thickness of the fixing roller on the side in contact with the toner image support surface to 1.0 mm or less (Patent Document 18). 19). This makes it possible to reach the desired temperature in a very short time.
However, when the thickness of the fixing roller is 1.0 mm or less, the mechanical strength of the roller itself is weakened, and when a large load is applied between the rollers, the roller is deformed, so that a large load cannot be applied.
For this reason, the toner used in such a fixing device is required to be fixed at a low temperature that is not comparable to conventional toners.

As a technique for solving this problem, several proposals have conventionally been made.
For example, Patent Document 20 describes a toner for roll fixing in which core particles made of polyester resin and a wax having a polar group are coated with a resin, and the melt viscosity of the polyester resin and the wax is defined. A film fixing toner comprising a specific polyester resin and a release agent, and specifying the melt viscosity of the polyester resin at 80 to 120 ° C., the slope of the graph of the melt viscosity and temperature, and the melt viscosity of the specific release agent is described Patent Document 24 includes a specific polyester resin and a release agent, and defines the melt viscosity of the polyester resin at 80 to 120 ° C., the slope of the graph of the melt viscosity and temperature, and the melt viscosity of the specific release agent. A film fixing capsule toner is described, and Patent Document 25 contains a specific polyester resin, an organometallic compound, and a release agent. A film fixing toner that defines the melt viscosity of a reester resin at 120 to 150 ° C., the slope of the graph of melt viscosity and temperature, and the melt viscosity of a specific release agent is described. A toner composed of a styrene-acrylic resin that defines a relational expression between the melt viscosity and the temperature measured in Step 1 is described. Patent Document 27 describes a toner that contains a specific charge control agent and defines an average viscosity gradient. ing.

  In recent years, the image quality has been increasingly improved, and the toner particle size tends to be small. It is known that when the toner particle size is small, it is difficult to apply pressure to the toner particles even if the pressure is applied between the fixing rollers, so that the fixability is deteriorated. This tendency is particularly noticeable in the case of a fixing device having a low surface pressure.

US Pat. No. 2,297,691 Japanese Patent Publication No.49-23910 Japanese Patent Publication No.43-24748 JP-A-3-2276 JP-A-8-143316 JP 2000-10344 A Japanese Patent No. 2736680 Japanese Patent No. 3101782 Japanese Patent No. 3108823 Japanese Patent No. 3174960 Japanese Patent No. 3224774 Japanese Patent No. 3261888 JP 2000-319021 A JP 2002-129063 A JP 2002-189313 A JP 2002-196528 A JP 2000-10344 A JP 2002-82474 A JP-A-9-222750 Japanese Patent No. 2743476 Japanese Patent Laid-Open No. 3-122661 Japanese Patent Laid-Open No. 4-85550 Japanese Patent Publication No. 8-16804 Japanese Patent Publication No. 8-12459 Japanese Patent Publication No. 7-82250 Japanese Examined Patent Publication No. 7-72809 Japanese Patent Laid-Open No. 10-246989

  Accordingly, the present invention has been made to solve the above problems, and is an image forming toner using a black pigment that is safe and harmless to the environment, has good charging performance, and can suppress toner scattering. The issue is to provide It is another object of the present invention to provide a toner container filled with the image forming toner, a two-component developer using the toner, an image forming method, and a process cartridge. It is another object of the present invention to provide an image forming toner and an image forming method excellent in fixability and heat resistant storage stability even when used in a fixing device using a thin-walled, low surface pressure roller.

  According to the present invention, the following image forming toner, a toner container filled therewith, a two-component developer using the toner, an image forming method, and a process cartridge are provided.

(1) An image-forming toner containing at least a binder resin and a colorant, wherein the colorant is 10 to 45 masses of Fe component in terms of Ti atom with respect to Fe atom in measurement by wavelength dispersion type fluorescent X-ray method. And a coercive force of the toner measured with a multi-sample rotational magnetization measuring device at a measuring magnetic field of 398 Am ² / kg is in the range of 2 to 15 kA / m. Image forming toner.
(2) The toner for image formation as described in (1) above, wherein the saturation magnetization σs of the toner is 0.1 to 5.0 Am ² / kg.
(3) The toner for image formation as described in (1) or (2) above, wherein the true specific gravity of the toner is 1.35 to 1.55.
(4) The image forming toner according to any one of (1) to (3), wherein the toner has a volume specific resistance of 10.9 to 11.4 Log Ωcm.
(5) The toner for image formation as described in any one of (1) to (4) above, wherein the content of the black iron oxide compound in the toner is 21 to 30% by mass.
(6) The image forming toner according to any one of (1) to (5), wherein the toner further contains a zirconium compound composed of zirconium and an aromatic oxycarboxylic acid or a salt thereof.
(7) After fixing the toner on art paper equivalent to ISO 12647-2 TYPE 1 at an adhesion amount of 0.60 to 0.85 mg / cm ² , X-Rite 938 (2 degrees of light source D50) based on the measurement method specified in ISO 12647-1 L * value in the color coordinates after fixing measured by (field of view) is 10 to 28, a * value is -1.0 to 1.0, and b * value is in the range of -1.0 to 1.0. The image forming toner according to any one of (1) to (6), wherein the toner is for image formation.
(8) The toner for image formation as described in any one of (1) to (7) above, wherein the mass average particle diameter D4 is 3 to 10 μm.
(9) The toner for image formation according to any one of (1) to (8), wherein the black iron oxide compound has an average primary area particle size of 0.005 to 1.5 μm.
(10) The MI value (melt index value) measured at 150 ° C. and a load of 2160 g based on JIS K 6760 is 10 to 20 (g / min), wherein (1) to (9) The image forming toner according to any one of the above.
(11) The image forming toner according to any one of (1) to (10), wherein the toner has a glass transition point of 55 to 65 ° C.
(12) The toner according to (1), wherein the toner contains a wax and contains 0.5 to 7% by mass of carnauba wax and / or rice wax and / or ester wax as a wax component. The toner for image formation as described in any one of 11).
(13) The molecular weight distribution of the THF-soluble component by gel permeation chromatography (GPC) has a peak top molecular weight Mp of 3300 to 5500, The image according to any one of (1) to (12) above Toner for forming.
(14) A toner container filled with the image forming toner according to any one of (1) to (13).
(15) A two-component developer comprising the image forming toner according to any one of (1) to (13) and a carrier.
(16) A charging step of applying a voltage to the charging member from the outside to charge the charged member, a step of forming an electrostatic charge image on the charged charged member, and developing the electrostatic charge image with toner to form a toner A developing step for forming an image, a transferring step for applying a voltage to the transfer member from the outside to transfer the toner image onto the transfer member, a cleaning step for cleaning the surface of the charged member after transfer with a cleaning member, and a toner image An image forming method comprising a fixing step of heat fixing, wherein the toner is the image forming toner according to any one of (1) to (13).
(17) The fixing step is a fixing device that heat-fixes the toner image by passing a support holding the toner image between two rollers, and is on the side in contact with the toner image support surface. The image according to (16), wherein the fixing roller has a thickness of 1.0 mm or less and a surface pressure (roller load / contact area) applied between the two rollers is 1.5 × 10 ⁵ Pa or less. Forming method.
(18) The surface of the member to be charged after the toner image is transferred onto the transfer member is cleaned to collect the toner on the surface of the member to be charged, and the collected toner is supplied to the developing means for use in the developing step. The image forming method as described in (16) or (17) above, comprising a recycling system.
(19) Any one of (16) to (18), wherein the charging step includes charging the charged member by bringing the charging member into contact with the charged member and applying a voltage to the charging member from the outside. The image forming method described in 1.
(20) The image forming method according to any one of (16) to (19), wherein, in the transfer step, the charged body and the transfer member are in contact with each other.
(21) In a process cartridge that integrally supports a photosensitive member and at least one unit selected from a charging unit, a developing unit, and a cleaning unit and is detachable from an image forming apparatus main body, the developing unit includes a developer. A process cartridge, wherein the developer contains the image forming toner according to any one of (1) to (13).

  According to the configuration (1), it is possible to provide an image forming toner using a black pigment that is safe and harmless to the environment, has good charging performance, and can suppress toner scattering. Further, even when used in a fixing device using a thin and low surface pressure roller, it is possible to provide an image forming toner excellent in fixability and heat-resistant storage stability.

  According to the configuration (2), toner scattering is good. This is because, for example, when the toner is used as a two-component developer, since the toner has a slight magnetization, a coercive force with the developing sleeve is generated and scattering can be prevented.

  According to the configuration (3), toner scattering and fogging are further improved. This is because, for example, when the toner is used as a two-component developer, the difference in specific gravity is reduced, so that the stirrability between the carrier and the toner is improved and the start-up property of the toner is improved. It is because it becomes possible to improve.

  According to the configuration (4), the dispersion state of the colorant and the like in the toner is good, good charge stability of the toner is obtained, and toner scattering and fogging can be improved.

  According to the configuration of (5), since the content of the black iron oxide compound is 21% by mass or more, sufficient blackness can be obtained. Further, since the content of the black iron oxide compound is 30% by mass or less, it is possible to prevent the specific gravity of the toner from increasing and to improve the developing ability.

  According to the configuration (6), it is possible to obtain a toner having good charging stability and rising property.

  According to the configuration of the above (7), it is possible to obtain a blackness and hue as good as those of carbon black. If it is out of this range, the color tone becomes reddish or yellowish, and good blackness cannot be obtained.

  According to the configuration (8), the low-temperature fixability and the blackness are further improved.

  According to the configuration (9), excellent dispersibility in the toner can be obtained. When the average primary area particle size of the black iron oxide compound is less than 0.005 μm, the toner becomes extremely hard and the grindability is deteriorated, and when it exceeds 1.5 μm, the thermal conductivity may be disadvantageous.

  According to the configuration of (10), the low-temperature fixability is further improved, thereby increasing the blackness, and the effect is remarkable particularly in a fixing method using a low-pressure roller of a high-speed machine or an energy saving system. .

  According to the configuration of (11), both low temperature fixability and storage stability can be achieved.

  According to the configuration of (12), hot offset does not occur even in the oilless mechanism, and the blackness is improved due to good low temperature fixability.

  The configuration (13) is further advantageous for low-temperature fixability. When the peak top molecular weight Mp is less than 3300, the toners are likely to be fused together during pulverization in the production process.

  According to the configuration of (14), it is possible to provide a container for supplying image forming toner using a black pigment that is safe and harmless to the environment, has good charging performance, and can suppress toner scattering. It becomes.

  According to the configuration (15), it is possible to obtain a good developer having good toner charging stability and free from toner scattering and fogging.

  With the configuration (16), it is possible to obtain an image forming method that is safe and harmless to the environment, has good charging performance, and can suppress toner scattering.

  According to the configuration of (17), since the toner has good thermal conductivity, the toner can be raised to a desired temperature in a very short time, and good fixability can be obtained. Can be obtained.

  According to the configuration (18), aggregation of recycled toner can be prevented by the hardness of the minute black iron oxide compound in the toner, and an image forming method with good recyclability can be obtained.

    According to the configuration of (19), it is possible to obtain an image forming method without fusing to the charging member due to the hardness of the minute black iron oxide compound in the toner.

  According to the configuration (20), it is possible to obtain an image forming method without fusing to the transfer member due to the hardness of the minute black iron oxide compound in the toner.

  According to the configuration (21), it is possible to obtain a process cartridge that is safe and harmless to the environment, has good charging performance, and can be reduced in size and can maintain toner, and has good maintainability.

Hereinafter, embodiments of the present invention will be described in detail.
A preferred embodiment of the image forming toner of the present invention is an image forming toner containing at least a binder resin and a colorant, and the colorant converts the titanium component into Fe atoms in terms of Ti atoms in the wavelength dispersive fluorescent X-ray method. It is a black iron oxide compound containing 10 to 45% by mass with respect to the coercive force of the toner at a measuring magnetic field of 398 Am ² / kg in a multi-sample rotary magnetization measuring device in the range of 2 to 15 kA / m. It is.
According to the present invention, it is possible to provide an image forming toner using a black pigment that is safe and harmless to the environment, has good charging performance, and can suppress toner scattering. Further, even when used in a fixing device using a thin and low surface pressure roller, it is possible to provide an image forming toner excellent in fixability and heat-resistant storage stability. In particular, the blackness of the toner is sufficiently high, and the occurrence of toner scattering in the actual machine is very small. The image forming toner of the present invention is particularly preferably used for two-component development.

The so-called toner scattering is a phenomenon in which toner is scattered on the developing sleeve due to generation of reversely charged toner or weakly charged toner, and the coercive force of this toner is in the range of 2 to 15 kA / m, preferably 5 to 10 KA / m. As a result, the carrier and the toner, and the developing sleeve and the toner are held, and the reversely charged toner and the weakly charged toner do not scatter and are re-stirred in the developing unit, thereby obtaining toner that does not cause toner scattering and fogging. Is something that can be done.
When the coercive force of the toner is less than 2 kA / m, toner scattering occurs because the coercive force is low. On the other hand, when the coercive force of the toner exceeds 15 kA / m, the coercive force between the carrier and the toner and between the developing sleeve and the toner is too strong, the developing ability is lowered, and the image density is insufficient. For the measurement of the magneto-magnetic characteristics, a magnetic measurement device BHU-60 manufactured by Riken Denshi Co., Ltd. was used, and when the magnetic field was swept up to a measurement magnetic field of 398 Am ² / kg in toner filled in a cell having an inner diameter of 7 mmφ and a height of 10 mm. From the history curve, the coercive force was obtained.

In order to set the coercive force of the toner to 2 kA / m or more and 15 kA / m or less, for example, a black iron oxide compound containing 10 to 45% by mass with respect to Fe atoms in terms of Ti atoms is contained in the toner at 15 to 40% by mass. It is good to contain in the range. Furthermore, in the toner production method, the colorant is uniformly dispersed by melting and kneading the kneading viscosity in the range of 10 ⁴ to 10 ⁸ poise, and a desired coercive force of the toner can be obtained. Alternatively, a low molecular weight resin not containing a crosslinking component and a black iron oxide compound are processed by a master batch, and then melt kneaded with other materials to form a toner.

A black iron oxide compound containing titanium as a constituent component is used for the colorant of the present invention.
Hereinafter, it explains in detail also including a manufacturing method.

The amount of the titanium compound constituting the black iron oxide compound according to the present invention is required to be within the range of 10 to 45 mass%, preferably 20 to 40 mass% of the titanium component with respect to Fe atoms in terms of Ti atoms. It is.
When the content is less than 10% by mass, the magnetization value of the obtained black pigment particle powder is increased, the coercive force is increased, and the developing ability is decreased. When it exceeds 45% by mass, it is preferable in terms of obtaining low-magnetic black pigment particle powder, but there are disadvantages that the coercive force is not obtained and the L * value is increased because the amount of TiO ₂ produced is increased. The L * value represents lightness, and the L * value is preferably in the range of 10 to 28, more preferably 10 to 15.
In addition, the ratio with respect to Fe atom in Ti atom conversion can be calculated | required by converting the main peak obtained per 1 mol using a wavelength dispersion type | mold fluorescence X-ray-analysis apparatus, and the ratio.
As a wavelength dispersive X-ray fluorescence analysis method, for example, RIX3000 manufactured by Rigaku Corporation is used, and a sample is added to an aluminum ring of 32 mmΦ under the conditions of spectroscopic crystal LiF1, output 50 KV, current 50 mA, target Rh, measurement range 30 mmΦ. Measure by pressure molding.

As the structure of the black iron oxide compound, a polycrystalline particle powder containing a Fe ₂ O ₃ —FeTiO ₃ solid solution is particularly preferable because it is black and has low magnetism.

Further, as an index representing the blackness of the black iron oxide compound, the lightness L * value of the CIE 1976 (L *, a *, b *) uniform perceptual color space is 10 to 28, a * and b as described above. * Is preferably in the range of -1.0 to 1.0.
Further, the saturation magnetization value of the black iron oxide compound is preferably 50.0 Am ² / kg or less.
Further, when the average primary area particle diameter of the black iron oxide compound is in the range of 0.005 to 1.5 μm, particularly in the range of 0.005 to 0.5 μm, excellent dispersibility in the toner is achieved. And high blackness can be obtained. Furthermore, since the thermal conductivity is improved, the low-temperature fixability is improved. Further, if it is less than 0.005 μm, the toner becomes extremely hard and the grindability is deteriorated, and if it exceeds 1.5 μm, it may be disadvantageous for thermal conductivity, so the range of 0.005 to 1.5 μm is preferable.
The average primary area particle size of the black iron oxide compound is, for example, obtained by collecting the black iron oxide compound on a carbon tape, coating it with Pt-Pd, and using an electron microscope such as a Hitachi scanning electron microscope H-9000. An SEM image magnified 15000 times at 10 kv is taken. This image is taken into, for example, a Luzex image analyzer, and the average primary area particle diameter can be calculated from photographs of 50 or more black iron oxide compounds.
The method for obtaining the average primary area particle diameter of the black iron oxide compound in the range of 0.005 to 1.5 μm, particularly in the range of 0.005 to 0.5 μm is shown.

The black iron oxide compound according to the present invention is obtained by reducing, for example, magnetite particle powder whose particle surface is coated with a titanium compound, mixed powder of magnetite particle powder and titanium compound, or hematite particle powder whose particle surface is coated with a titanium compound. Each of the obtained reduced powders can be obtained by a method in which the fired product is pulverized after being heated and fired at a temperature of 700 ° C. or higher in a non-oxidizing atmosphere.
Among these methods, the method using magnetite particle powder whose particle surface is coated with a titanium compound as a raw material is a particularly preferable method in that particles having a small magnetization value are easily obtained and a low-magnetic black colorant is obtained. It is.

Here, as the magnetite particle powder and hematite particle powder, particles of any form such as granular, spherical, and needle-like can be used, and particles having a size of about 0.003 to 1.5 μm can be used. it can.
There is a correlation between the size of the raw material particles and the size of the product particles. When small raw material particles are used, small product particles tend to be obtained. When large raw material particles are used, large product particles tend to be obtained. It is in. By using particles of about 0.003 to 1.5 μm, a black iron oxide compound having an average primary area particle size in the range of 0.005 to 1.5 μm can be obtained.

  As the titanium compound, any of hydrated oxide, hydroxide and oxide of titanium can be used. When mixing with magnetite particle powder, it is preferable to use a water-soluble titanium compound.

As the non-oxidizing atmosphere, N ₂ gas or the like can be used. When the atmosphere is oxidizing, the target black iron oxide compound cannot be obtained.

The heating and firing temperature needs to be 700 ° C. or higher. When the temperature is lower than 700 ° C., the solid phase reaction between iron oxide and titanium compound does not occur sufficiently, and the target black iron oxide compound cannot be obtained.
The pulverization can be performed using a pulverizer such as a commonly used ball mill, attritor, or vibration mill. Thereby, the black iron oxide compound in the range of the target average primary area particle diameter can be obtained.

In the above method, in order to obtain the average primary volume particle diameter of the black iron oxide compound in the range of 0.1 to 0.5 μm, the raw material particles are coated with a known sintering inhibitor in advance before heating and firing. It is effective to leave In this case, it is possible to prevent sintering between the particles and the particles during heating and firing, and a black iron oxide compound having a desired average primary volume particle diameter can be obtained.
As a sintering inhibitor that does not impair various properties of the black pigment particle powder that is the object of the present invention, a compound comprising one or more elements selected from Al, Ti, Si, Zr and P is used. Can do. The amount of the sintering inhibitor is 0.1 to 15.0 atomic% with respect to Fe and Ti. In order to obtain a sufficient sintering prevention effect, it is preferably 0.1 atomic% or more, and when it exceeds 15.0 atomic%, magnetite is mixed in the resulting black pigment particle powder, and low magnetic properties are obtained. It becomes difficult to obtain a black iron oxide compound.

In order to further increase the blackness, it is preferable to fix the black dyed pigment and the blue dyed pigment to the black iron oxide compound using Mechanomyl (Okada Seiko Co., Ltd.) or MechanoFusion System (Hosokawa Micron Co., Ltd.).
Iron black, aniline black, graphite, fullerene etc. as black dye / pigment, cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, fast sky blue, Indanthrene blue BC and the like are exemplified, but not limited thereto.

The true specific gravity of the black oxide compound is preferably 4.0 to 5.0, and the bulk density is preferably in the range of 0.5 to 1.2 g / cm ³ .

In the present invention, the toner saturation magnetization σs is preferably in the range of 0.1 to 5.0 Am ² / kg. In this range, toner scattering is further improved.
This is because in the two-component developer, since the toner has a slight magnetization, a coercive force with the developing sleeve is generated, and scattering thereof can be prevented. If the toner saturation magnetization σs is less than 0.1 Am ² / kg, the effect is insufficient. If the toner saturation magnetization σs exceeds 5.0 Am ² / kg, the magnetism becomes stronger and the developing ability decreases.
The saturation magnetization in the present invention refers to, for example, a measurement magnetic field of 398 Am applied to a toner filled in a cell having an inner diameter of 7 mmφ and a height of 10 mm using a multi-sample rotational magnetization measuring device (Toei Kogyo Co., Ltd. REM-1-10 type). ² / kg, saturation speed at a sweep rate of 1 minute, temperature 25 ° C.
In order to obtain a toner saturation magnetization σs in the range of 0.1 to 5.0 Am ² / kg, for example, a black iron oxide compound containing 10 to 45% by mass with respect to Fe atoms in terms of Ti atoms is contained in 15 to 15%. It is good to contain in the range of 40 mass%. Furthermore, in the toner production method, the colorant is uniformly dispersed by melting and kneading the kneading viscosity in the range of 10 ⁴ to 10 ⁸ poise, and the desired toner saturation magnetization σs can be obtained. Alternatively, a low-molecular weight resin and a black iron oxide compound are processed by a master batch, and then melt-kneaded with other materials to form a toner.

Further, in the present invention, since the true specific gravity of the toner is 1.35 to 1.55, toner scattering and fogging are further improved. This is because in the two-component developer, the difference in specific gravity with the carrier becomes small, so that the stirring property between the carrier and the toner becomes good and the rising property of the toner is improved. It is preferable that the true specific gravity of the carrier is in the range of 1.3 to 2.5 times that of the toner because the effect is high.
If the true specific gravity of the toner is less than 1.35, the effect cannot be sufficiently obtained.
When it exceeds 1.55, the specific gravity of the toner is too large, so that the developing ability is lowered and the image density is insufficient. In addition, true specific gravity was measured using the air comparison type hydrometer (MODEL-930 by Beckman).

  Further, in the present invention, since the volume specific resistance of the toner is 10.9 to 11.4 LogΩcm, the dispersion state of the colorant and the like in the toner is good, and good charging stability of the toner can be obtained. Good scattering and fogging.

  In the present invention, the content of the black iron oxide compound is preferably 21% by mass or more from the viewpoint of obtaining sufficient blackness, and the true specific gravity of the toner becomes excessively large, so that the developing ability is not adversely affected. It is preferable that it is 30 mass% from a viewpoint of doing.

In the image forming toner of the present invention, a charge control agent can be blended in order to control the chargeability.
Examples of the charge control agent in this case include a nigrosine dye, a quaternary ammonium salt, an amino group-containing polymer, a metal-containing azo dye, a salicylic acid complex compound, and a phenol compound. Among them, zirconium and aromatic oxy By using a zirconium compound composed of a carboxylic acid or a salt thereof, a toner having good charging stability and start-up property can be obtained.
As the aromatic oxycarboxylic acid, known compounds can be used, but a compound represented by the following general formula (1) is preferable from the viewpoint of charge imparting ability. This does not simply mean that the charge control agent has excellent charging characteristics, but the oxycarboxylic acid is hydrogen-bonded to the titanium compound of the black iron oxide compound of the present invention by the thermal energy during kneading, and thereby the toner in the toner. This is because the dispersibility of the charge control agent becomes very good. Further, when the black iron oxide compound and zirconium which is the central metal of the charge control agent are well dispersed, the effect of the filler is obtained, and the strength of the toner is increased, which is very advantageous for fusing and fixing.

In the formula, R ¹ , R ² and R ³ each independently represent a monovalent group, or R ¹ and R ² or R ¹ and R ³ have a bond to form a condensed ring with a basic aromatic ring You may do it.
Examples of the monovalent group include a hydrogen atom, a halogen atom, a hydroxyl group, and a monovalent organic group.
Examples of the halogen atom include a fluorine atom and a chlorine atom.
Examples of the monovalent organic group include a carboxyl group, a substituted or unsubstituted alkoxycarbonyl group having 2 to 11 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, and a substituted or unsubstituted group having 1 to 10 carbon atoms. Examples thereof include an alkyl group or an alkenyl group, and a substituted or unsubstituted aryl group having 6 to 18 carbon atoms.
Examples of the substituted or unsubstituted alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the aryl group include a phenyl group.
Among these groups, a hydrogen atom, a chlorine atom, a hydroxyl group, a carboxyl group, a lower alkyl group having 1 to 10 carbon atoms, and the like can be given as examples of preferable groups.

  More specifically, aromatic oxycarboxylic acids represented by the following formulas (2) to (9) can be mentioned as particularly preferable raw material compounds from the viewpoint of imparting charge.

Since the image forming toner of the present invention has sufficient low-temperature fixability and developing ability, the toner is fixed to art paper equivalent to ISO 12647-2 TYPE 1 at an adhesion amount of 0.60 to 0.85 mg / cm ² and then ISO 12647. -1 L-value in the color coordinates after fixing measured by X-Rite 938 (2-degree field of view of the light source D50) based on the specified measuring method is 10 to 28, a * value is -1.0 to 1.0, b * Value is in the range of -1.0 to 1.0, preferably L * value is 10 to 20, more preferably L * value is 10 to 15, and preferably a * value is -0.5 to 0.5. , B * value can be obtained in the range of -0.5 to 0.5. As a result, it is possible to obtain a blackness and hue as good as those of carbon black. Outside this range, reddish or yellowish colors are obtained, and good blackness cannot be obtained. Note that L * represents the total reflected light amount ratio, and the smaller the value, the closer to black, a * Represents redness, and a larger value means stronger redness. b * represents yellowishness, and a larger value means stronger yellowishness. L * represents lightness.

  In addition, the standard value of the color of art paper equivalent to ISO 12647-2 TYPE1 is L * value of 93 ± 3, a * value of 0 ± 2, b * value of -3 ± 2, and glossiness of 65 ± 5 (%). It is. The measured values of the art paper used in the present invention were L * value of 93, a * value of 0.3, b * value of 0.2, and glossiness of 65%.

  In order to obtain such a range, the use of a polyester resin as a binder resin increases the low-temperature fixability and glossiness, thereby making it easier to obtain desired L * values, a * values, and b * values. As the polyester resin, by using a resin containing about 5 to 25% of THF-insoluble matter, the torque at the time of kneading is increased, the dispersibility of the black iron oxide compound is improved, and the desired L * value, a * value, It becomes easier to obtain a b * value. Further, a polyester resin not containing a THF-insoluble component and a black iron oxide compound are mixed at a mass ratio of about 1: 1 to 2: 1, pre-kneaded with a two-roll or the like, pulverized, and master batched. It is also effective to mix this pulverized product with other materials to form a toner. The melt viscosity of the toner at this time is 10 to 20 (g / min) when measured at 150 ° C. and a load of 2160 g, thereby further improving the low-temperature fixability, thereby increasing the blackness. This makes it easier to obtain desired L * values, a * values, and b * values. The effect is particularly remarkable in the low surface pressure fixing method of high speed machines and energy saving systems. If the MI value is less than 10, low-temperature fixability cannot be obtained sufficiently, and if it exceeds 20, it is disadvantageous for hot offset resistance.

  Further, as the molecular weight distribution of the toner, the peak top molecular weight Mp of 3300 to 5500 in the molecular weight distribution of the THF-soluble component by gel permeation chromatography (GPC) is more advantageous for low-temperature fixability, and the desired L * value, It becomes easy to obtain a * value and b * value. If it is less than 3300, toner fusion during pulverization tends to occur during production, and if it exceeds 5500, a sufficient effect on low-temperature fixability cannot be obtained. In order to obtain the MI value and molecular weight distribution in this range, the resin has a peak top molecular weight Mp in the range of 3300 to 7000, and further contains a THF-insoluble content of about 5 to 25%. It is easy to obtain by mixing and kneading to achieve the target molecular weight and MI value. In order to improve the low-temperature fixability, it is also effective to blend a resin not containing a THF-insoluble component. Further, the glass transition point of the toner is preferably 55 to 65 ° C. in order to achieve both low-temperature fixability and storage stability.

  The glass transition temperature Tg was measured using a differential thermal analysis measuring device (DSC measuring device) and DSC-7 (manufactured by Perkin Elmer), and the measuring method was performed according to ASTM D3418-82. The measurement sample is precisely weighed 5 to 10 mg. This is put in an aluminum pan, a standard sample such as aluminum oxide is put as a reference, the temperature is raised once at a rate of temperature rise of 10 ° C / min in the measurement range of 30 to 200 ° C, and the temperature is raised after taking the previous history An endothermic peak of the main peak in the temperature range of 40 to 100 ° C. when the temperature is raised at a rate of 10 ° C./min is obtained. At this time, the point of intersection between the intermediate point line of the baseline before and after the endothermic peak and the differential heat curve is defined as the glass transition temperature Tg in the present invention.

  The MI value (melt index value) of the toner was measured according to JIS-K6760 using a TOYOSEIKI FLOW RATE COUNTER TYPE C-5059D (manufactured by Toyo Seiki) at a load of 2160 g, a measurement temperature of 150 ° C., and a sample amount of 5 g.

In the molecular weight distribution by the gel permeation chromatography (GPC) of the THF soluble component of the toner, the peak top molecular weight Mp was measured under the following conditions with a commercially available monodisperse standard polystyrene as a standard.
Detector: SHODEX RI-71S
Solvent: Tetrahydrofuran Column: KF-G + KF-807Lx3 + KF800D
Flow rate: 1.0 ml / min Sample: 0.25% THF solution

  Further, the toner of the present invention has a mass average particle diameter D4 of 3 to 10 μm, so that the low temperature fixability and blackness are further improved. This is because the thermal conductivity of the toner can be sufficiently obtained by being in this range, and the adhesiveness between the uneven surface of the toner and the fixing paper is enhanced. If it is less than 3 μm, the possibility of inhaling dust increases, which is not preferable from the viewpoint of safety. If it exceeds 10 μm, it is disadvantageous for the thermal conductivity of the toner.

A method for measuring the particle size distribution of the toner particles will be described.
Examples of the measuring device for the particle size distribution of toner particles by the Coulter counter method include Coulter Counter TA-II and Coulter Multisizer II (both manufactured by Coulter). The measurement method is described below.
First, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of an aqueous electrolytic solution. Here, the electrolytic solution is a solution prepared by preparing a 1% NaCl aqueous solution using primary sodium chloride. For example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the measurement device is used to measure the volume and number of toner particles or toner using a 100 μm aperture as an aperture. Volume distribution and number distribution are calculated. From the obtained distribution, the mass average particle diameter (D4) and the number average particle diameter (D1) of the toner can be obtained.
As channels, 2.00 to less than 2.52 μm; 2.52 to less than 3.17 μm; 3.17 to less than 4.00 μm; 4.00 to less than 5.04 μm; 5.04 to less than 6.35 μm; 6 Less than 35 to 8.00 μm; less than 8.00 to less than 10.08 μm; less than 10.08 to less than 12.70 μm; less than 12.70 to less than 16.00 μm; less than 16.00 to less than 20.20 μm; Uses 13 channels of less than 40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm, and targets particles having a particle size of 2.00 μm to less than 40.30 μm.

  Further, the toner may contain a wax, and it is effective for hot offset resistance to contain 0.5 to 7% by mass of carnauba wax and / or rice wax and / or ester wax as a wax component.

  In addition, as a carrier used as a two-component developer by mixing the image forming toner of the present invention, a powder having a particle size of about 30 to 1000 μm mainly composed of glass, iron, ferrite, nickel, zircon, silica or the like. Alternatively, the powder can be used by appropriately selecting from those coated with a styrene-acrylic resin, a silicon resin, a polyamide resin, a polyvinylidene fluoride resin, etc. using the powder as a core material. A diameter of 30 to 80 μm is preferable.

  The toner for image formation of the present invention is filled in a container, and the container filled with the toner is distributed separately from the image forming apparatus, and is generally mounted on the image forming apparatus by a user to form an image. The container is not limited to be used. For example, a conventional bottle type or cartridge or a flexible cartridge capable of volume reduction is used.

The image forming method in the present invention includes a charging step in which a voltage is applied to the charging member from the outside to charge the charged member, a step of forming an electrostatic charge image on the charged charged member, and an electrostatic charge image. The toner is developed with toner to form a toner image, a transfer step in which a voltage is applied to the transfer member from the outside to transfer the toner image onto the transfer member, and the surface of the charged member after transfer is cleaned with a cleaning member. It consists of a cleaning process and a fixing process for fixing the toner image by heating. Specifically, the apparatus is not limited as long as it is an apparatus for forming an image by electrophotography, and includes, for example, a copying machine and a printer.
An example will be described with reference to FIG.
FIG. 1 shows an example of an image forming apparatus used in the present invention. An image forming apparatus, which is a digital copying machine, uses a known electrophotographic system and includes a drum-shaped photosensitive member (1) therein. Around the photoreceptor (1), along with the rotation direction indicated by the arrow A, a charger (2) for carrying out an electrophotographic copying process, an exposure means (3), a developing means (4), a transfer means (5), A cleaning means (6), a recycling means (15), and a fixing means (10) are arranged.

The exposure means (3) forms an electrostatic latent image on the photosensitive member (1) based on the image signal read by the reading means (8) on the original placed on the original table (7) on the upper surface of the copying machine. To do.
The electrostatic latent image formed on the photosensitive member (1) is converted into a toner image by the developing means (4), and the toner image is transferred onto the transfer paper fed from the paper feeding device (9). ) Is electrostatically transferred. The transfer paper on which the toner image is placed is conveyed and fixed to the fixing means (10), and then discharged outside the apparatus.
On the other hand, the untransferred portion and the contaminated photoreceptor (1) are cleaned by the cleaning means (6), and the toner recovered by the cleaning is recovered to the toner hopper by the recycling means (15) and mixed with the replenishing toner. Then, the developer container is returned to the next image forming step.

Further, in order to reduce the generation of ozone in recent years, a contact method is effectively used in the charging process, the transfer process, and the cleaning process, and a charging roller, a charging blade, a transfer belt, a cleaning blade, and the like are used. However, as these inconveniences, the problem that the toner is fused due to direct contact or contact with the photoconductor is likely to occur. In particular, this problem is remarkable in the charging process and the transfer process.
However, since the toner of the present invention contains a fine black iron oxide compound as a colorant, an appropriate shaving effect can be obtained, so that such a problem does not occur.
Further, in the recycling system, the problem that the toner is likely to aggregate due to the pressure of the recycling path in the related art is likely to occur. However, the toner of the present invention is preferable because the aggregation of the recycled toner can be prevented by the hardness of a minute metal material. .
The material of the charging roller, charging blade, transfer belt, and cleaning blade is preferably conductive rubber.

The fixing step of the present invention is a fixing device that heats and fixes a toner image by passing a support holding a toner image between two rollers, and fixes the toner image on the side in contact with the toner image support surface. The roller thickness is 1.0 mm or less, and the surface pressure (roller load / contact area) applied between the two rollers is 1.5 × 10 ⁵ Pa or less, and an example is shown in FIG. Reference numeral (21) represents a fixing roller, and (22) represents a pressure roller. The fixing roller (21) has RTV, silicon rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA), polytetra on the surface of a metal cylinder (23) made of a high thermal conductor such as aluminum, iron, stainless steel or brass. An anti-offset layer (24) such as fluoroethylene (PTFE) is coated. A heating lamp (25) is arranged inside the fixing roller (21). The metal cylinder (26) of the pressure roller (22) is often made of the same material as the fixing roller (21), and its surface is covered with an offset prevention layer (27) such as PFA or PTFA. Although not necessarily required, a heating lamp (28) is disposed inside the pressure roller (22).
Although the fixing roller and the pressure roller are not shown, they are pressed against and rotated by springs at both ends.
A fixing support (S) (transfer paper such as paper) for toner image (T) is passed between the fixing roller (21) and the pressure roller (22) for fixing.

The fixing device used in the present invention improves the temperature rise characteristic of the fixing roller by setting the thickness of the metal cylinder of the fixing roller to 1.0 mm or less, and can rise to a desired temperature in a very short time. Can do.
The preferred thickness of the metal cylinder varies depending on the strength and thermal conductivity of the material used, but is preferably 0.2 to 0.7 mm.

Further, the load (surface pressure) applied between the fixing roller and the pressure roller is preferably 1.5 × 10 ⁵ Pa or less. The surface pressure is a value obtained by dividing the load applied to both ends of the roller by the roller contact area.
The roller contact area is determined by passing a sheet whose surface property greatly changes due to heating, such as OHP paper, between the rollers heated to the fixing temperature, stopping on the way, holding it for several tens of seconds, and then discharging it. Find the area of the location.
A higher surface pressure is advantageous for fixing a toner image. However, in a fixing device in which the thickness of the metal cylinder of the fixing roller is 1.0 mm or less, a large load is not applied because the roller is distorted. The load is 1.5 × 10 ⁵ Pa or less, preferably 0.5 to 1.0 × 10 ⁵ Pa.
Since the toner of the present invention has good thermal conductivity, good fixability can be obtained even when the surface pressure is 1.5 × 10 ⁵ Pa or less, preferably 0.5 to 1.0 × 10 ⁵ Pa. Thereby, an image with a high coloring degree can be obtained.

The process cartridge of the present invention uses the toner of the present invention, and integrally supports the photosensitive member and at least one unit selected from a charging unit, a developing unit, and a cleaning unit, and is detachable from the main body of the image forming apparatus. It is characterized by that.
FIG. 3 shows a schematic configuration of an image forming apparatus having the process cartridge of the present invention.
In the figure, reference numeral (30) denotes the entire process cartridge, (31) denotes a photoreceptor, (32) denotes charging means, (33) denotes developing means, and (34) denotes cleaning means.
In the present invention, the above-described photoreceptor (31) and at least one means selected from a charging means (32), a developing means (33) and a cleaning means (34) are integrally coupled as a process cartridge. The process cartridge is configured to be detachable from a main body of an image forming apparatus such as a copying machine or a printer.

  In the image forming apparatus having the process cartridge of the present invention, the photosensitive member is rotationally driven at a predetermined peripheral speed. In the rotation process, the photosensitive member is uniformly charged with a positive or negative predetermined potential on its peripheral surface by the charging unit, and then receives image exposure light from an image exposing unit such as slit exposure or laser beam scanning exposure. An electrostatic latent image is sequentially formed on the peripheral surface of the body, and the formed electrostatic latent image is then developed with toner by a developing unit, and the developed toner image is transferred between the photosensitive member and the transfer unit from the paper feeding unit. Then, the image is sequentially transferred to the transfer material fed in synchronization with the rotation of the photosensitive member by the transfer means. The transfer material that has received the image transfer is separated from the surface of the photosensitive member, introduced into the image fixing means, and fixed on the image, and printed out as a copy (copy). The surface of the photoconductor after the image transfer is cleaned by removing toner remaining after transfer by a cleaning unit, and after being further neutralized, it is repeatedly used for image formation.

As the binder resin used in the image forming toner of the present invention, all conventionally known resins are used.
For example, polystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene -Styrene such as maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloroacrylic acid methyl copolymer, styrene-acrylonitrile-acrylic acid ester copolymer Resin (monopolymer or copolymer containing styrene or styrene-substituted product), polyester resin, epoxy resin, vinyl chloride resin, rosin-modified maleic acid resin, phenol resin, polyethylene resin, polypropylene resin, petroleum resin, polyurethane resin, Ketone resin, ethylene Examples include ethyl acrylate copolymer, xylene resin, and polyvinyl butyrate resin.
These resins can be used alone or in combination of two or more. Moreover, the manufacturing method of these resin is not specifically limited, either bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization can be used.

In order to make the low temperature fixability of the toner advantageous, it is preferable to use a polyester resin as the binder resin among the above resins.
The polyester resin is obtained by condensation polymerization of alcohol and carboxylic acid.
Examples of the alcohol used include glycols such as ethylene glycol, diethylene glycol, triethylene glycol and propylene glycol, etherified bisphenols such as 1,4-bis (hydroxymeta) cyclohexane and bisphenol A, and other divalent alcohols. Mention may be made of monomers and trihydric or higher polyhydric alcohol monomers.
Examples of carboxylic acids include divalent organic acid monomers such as maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, and malonic acid, 1,2,4-benzenetricarboxylic acid, 1 , 2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methylenecarboxy Mention may be made of trivalent or higher polyvalent carboxylic acid monomers such as propane and 1,2,7,8-octanetetracarboxylic acid.
The Tg of the polyester resin is preferably 55 to 70 ° C.

Various other additives may be added to the toner as necessary.
Examples of the additive include silica, aluminum oxides, and titanium oxides. When the main purpose is to impart high fluidity, the average primary particle diameter is 0.001 to 1 μm, preferably 0.005 to 0.1 μm as hydrophobized silica or rutile type fine particle titanium oxide. It is advantageous to select appropriately. In particular, organosilane surface-treated silica or titania is preferable, and is usually used in a proportion of 0.1 to 5% by mass, preferably 0.2 to 2% by mass.

Next, a method for producing the image forming toner of the present invention will be described.
The toner production method of the present invention includes a step of mechanically mixing a developer component including at least a binder resin (binder resin), a main charge control agent, and a colorant, a step of melt-kneading, and a step of pulverizing. In addition, a known toner manufacturing method having a classification step can be applied.
In addition, in the mechanical mixing step and the melt kneading step, a production method in which powder (by-product) other than the particles that are products obtained in the pulverization or classification step is returned and reused can also be employed. Here, the powder other than the particles to be the product, that is, the by-product is a fine particle or coarse particle other than the component that becomes the product having a desired particle size obtained in the pulverization step after the melt-kneading step, or the next classification step. It means fine particles or coarse particles other than the components that are produced as products having a desired particle size. In the mixing step and the step of melt-kneading such a by-product, the mass ratio of the by-product and other raw materials is mixed at a mass ratio of by-product / other raw materials = 1/99 to 50/50. Is preferred.

  The mixing step mechanically mixes at least a binder resin, a main charge control agent and a colorant, preferably a developer component further containing a by-product. The mixing method may be performed under normal conditions using a normal mixer having rotating blades, and is not particularly limited.

When the above mixing process is completed, the mixture is then charged into a kneader and melt-kneaded. As the melt kneader, a uniaxial or biaxial continuous kneader or a batch kneader using a roll mill can be used.
It is important that this melt-kneading is performed under appropriate conditions that do not cause the molecular chains of the binder resin to be broken. Specifically, the melt kneading temperature should be performed with reference to the softening point of the binder resin. If the temperature is lower than the softening point, cutting is severe, and if the temperature is too high, dispersion does not proceed.

When the above melt-kneading process is completed, the kneaded product is then pulverized. In this pulverization step, it is preferable to first coarsely pulverize and then finely pulverize. At this time, a method of pulverizing by colliding with a collision plate in a jet stream or pulverizing with a narrow gap between a rotor and a stator that rotate mechanically is preferably used.
After the pulverization step is completed, the pulverized product is classified in an air stream by centrifugal force or the like, thereby producing a developer having a predetermined particle size.
In addition to the above methods, the toner may be produced by spray drying, suspension polymerization, emulsion aggregation, dissolution suspension, or the like.

In addition, when preparing the developer, in order to improve the fluidity, storage stability, developability, and transferability of the developer, the hydrophobic silica fine particles listed above are further listed in the developer produced as described above. Inorganic fine particles such as powder may be added and mixed.
For mixing external additives, a general powder mixer is used, but it is preferable to equip a jacket or the like to adjust the internal temperature. In order to change the load history applied to the external additive, the external additive may be added in the middle or gradually. Of course, you may change the rotation speed of a mixer, rolling speed, time, temperature, etc. A strong load may be given first, then a relatively weak load, and vice versa.
Examples of the mixing equipment that can be used include a V-type mixer, a rocking mixer, a Ladige mixer, a Nauter mixer, a Henschel mixer, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these Examples. In the following, parts are based on mass unless otherwise specified.

Production Example of Black Iron Oxide Compound [Production Examples of Black Iron Oxide Compounds 1 to 4, see Table 1]
The mixed powder of granular hematite particle powder and titanium oxide was fired at a firing temperature and firing time shown in Table 1 under a nitrogen atmosphere, and pulverized with a ball mill to obtain black iron oxide compounds 1 to 4.

[Production examples of black iron oxide compounds 5 to 12, see Table 1]
The reduced powder obtained by reducing the hematite particle powder with the surface of the granular hematite particles coated with titanium hydroxide was fired in a nitrogen atmosphere at the firing temperature and firing time shown in Table 1, and pulverized with a ball mill. Thereafter, a black dyed pigment-free metal phthalocyanine blue was fixed to the surface of the black pigment particle particles at 600 ° C. with a mechanofusion system (manufactured by Hosokawa Micron Corporation) to obtain black iron oxide compounds 5-12. The amount of titanium component is a wavelength dispersive X-ray fluorescence analysis method. For example, RIX3000 manufactured by Rigaku Corporation is used, and the sample is an aluminum ring of 32 mmΦ under the conditions of spectroscopic crystal LiF1, output 50 KV, current 50 mA, target Rh, measurement range 30 mmΦ. Measurement was performed by pressure molding.
In the table, the amount of titanium component is a value indicating the Ti component with respect to Fe atoms in terms of Ti atoms.

[Example 1]
The toner formulation is shown below.
Styrene-n-butyl acrylate copolymer (THF insoluble content 30%, Tg 72 ° C.) 58 parts by mass Black iron oxide compound 1 35 parts by mass Carnauba wax 5 parts by mass Charge control agent (chromium azo dye: TRH manufactured by Hodogaya Chemical Co., Ltd.) -1) 2 parts by mass The above formulation was kneaded at a kneading temperature of 160 ° C for 10 minutes using a biaxial extruder, pulverized and classified to give a mass average particle diameter of 10.5 µm. Thereafter, 0.5 part of silica fine powder (R-972: manufactured by Client Japan) was mixed using a Henschel mixer to obtain the toner of Example 1.

  The evaluation method is as follows.

Magnetic properties Using a multi-sample rotational magnetization measurement device (Toei Kogyo Co., Ltd. REM-1-10 type), a toner filled in a cell having an inner diameter of 7 mmφ and a height of 10 mm is measured with a magnetic field of 398 Am ² / kg and a sweep speed of 1 minute The saturation magnetization and the coercive force were determined from the hysteresis curve when swept at a temperature of 25 ° C.

Fog evaluation Fog was judged comprehensively according to the following criteria.
A: Very good. No fogging.
○: Good. Slight fogging △: Possible. Although fogging has occurred, there is practically no problem.
X: Bad. It is terrible.

A method for measuring the particle size distribution of the toner particles will be described.
Examples of the measuring device for the particle size distribution of toner particles by the Coulter counter method include Coulter Counter TA-II and Coulter Multisizer II (both manufactured by Coulter). The measurement method is described below.
First, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of an aqueous electrolytic solution. Here, the electrolytic solution is a solution prepared by preparing a 1% NaCl aqueous solution using primary sodium chloride. For example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the measurement device is used to measure the volume and number of toner particles or toner using a 100 μm aperture as an aperture. Volume distribution and number distribution are calculated. From the obtained distribution, the mass average particle diameter (D4) and the number average particle diameter (D1) of the toner can be obtained.

  As channels, 2.00 to less than 2.52 μm; 2.52 to less than 3.17 μm; 3.17 to less than 4.00 μm; 4.00 to less than 5.04 μm; 5.04 to less than 6.35 μm; 6 Less than 35 to 8.00 μm; less than 8.00 to less than 10.08 μm; less than 10.08 to less than 12.70 μm; less than 12.70 to less than 16.00 μm; less than 16.00 to less than 20.20 μm; Uses 13 channels of less than 40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm, and targets particles having a particle size of 2.00 μm to less than 40.30 μm.

  The glass transition temperature Tg was measured using a differential thermal analysis measuring device (DSC measuring device) and DSC-7 (manufactured by Perkin Elmer), and the measuring method was performed according to ASTM D3418-82. The measurement sample is precisely weighed 5 to 10 mg. This is put in an aluminum pan, a standard sample such as aluminum oxide is put as a reference, the temperature is raised once at a rate of temperature rise of 10 ° C / min in the measurement range of 30 to 200 ° C, and the temperature is raised after taking the previous history An endothermic peak of the main peak in the temperature range of 40 to 100 ° C. when the temperature is raised at a rate of 10 ° C./min is obtained. At this time, the point of intersection between the intermediate point line of the baseline before and after the endothermic peak and the differential heat curve is defined as the glass transition temperature Tg in the present invention.

  The MI value (melt index value) of the toner was measured according to JIS-K6760 using a TOYOSEIKI FLOW RATE COUNTER TYPE C-5059D (manufactured by Toyo Seiki) at a load of 2160 g, a measurement temperature of 150 ° C., and a sample amount of 5 g.

In the molecular weight distribution by the gel permeation chromatography (GPC) of the THF soluble component of the toner, the peak top molecular weight Mp was measured under the following conditions with a commercially available monodisperse standard polystyrene as a standard.
Detector: SHODEX RI-71S
Solvent: Tetrahydrofuran Column: KF-G + KF-807Lx3 + KF800D
Flow rate: 1.0 ml / min Sample: 0.25% THF solution

(1) Fixing evaluation method A fixing device (surface pressure: 0.7 × 10 ⁵ Pa) having the configuration shown in FIG. 2 is mounted on an imagio MF6550 remodeling machine (manufactured by Ricoh Co., Ltd.), and the heater temperature is varied. Copy to obtain a fixed image.
A fixing tape (manufactured by 3M) is applied to the fixed image, and after applying a certain pressure, it is slowly peeled off. The image density before and after that is measured with a Macbeth densitometer, and the fixing rate is calculated by the following equation. The temperature of the fixing roller is lowered step by step, and the temperature at which the fixing rate represented by the following formula becomes 80% or less is defined as the fixing temperature. (Image density = before tape attachment)
Fixing rate (%) = image density after tape peeling / image density × 100
The imagio MF6550 modified machine (manufactured by Ricoh Co., Ltd.) is equipped with a transfer belt, a charging roller, and a recycling system. The hot offset temperature was also examined.

(2) Image Density Evaluation Method A fixing device (surface pressure: 0.7 × 10 ⁵ Pa) having the configuration shown in FIG. 2 is mounted on an imagio MF6550 (manufactured by Ricoh Co., Ltd.), and after 100,000 copies are made. The black part image was measured with a Macbeth densitometer. The higher the image density, the greater the coloring power. The color tone was also examined.

(3) Evaluation Method of Toner Scattering A fixing device (surface pressure: 0.7 × 10 ⁵ Pa) having the configuration shown in FIG. 2 is mounted on an imagio MF6550 (manufactured by Ricoh Co., Ltd.), and 100,000 copies are made. Measure the dirt on the blank paper attached to the inside of the front door with a Macbeth densitometer.
The Macbeth density of white paper is 0.07, and the higher this value, the worse the toner scattering.

(4) Measuring method of average primary area particle size The average value of the values measured from an electron micrograph with a Hitachi transmission electron microscope H-9000 was shown.

[Example 2]
Styrene-methacrylate copolymer (THF insoluble content 0%, Tg75 ° C.) 76 parts by weight Black iron oxide compound 2 18 parts by weight Carnauba wax 4 parts by weight Charge control agent (zinc salicylate: E-84 manufactured by Orient Chemical Industries, Ltd.) ) 2 parts by mass The above formulation was kneaded at a kneading temperature of 150 ° C. for 10 minutes using a biaxial extruder, pulverized and classified to give a mass average particle diameter of 2.5 μm. Thereafter, 1.5 parts of silica fine powder (HDK-1303VP: manufactured by Client Japan) was mixed using a Henschel mixer to obtain a toner of Example 2.

[Example 3]
Styrene-methacrylate copolymer (THF insoluble content 0%, Tg 75 ° C.) 76 parts by weight Black iron oxide compound 2 18 parts by weight Carnauba wax 4 parts by weight Charge control agent (zirconium salicylate: TN-105 manufactured by Hodogaya Chemical) 2 parts by mass The above formulation was kneaded at a kneading temperature of 150 ° C. for 10 minutes using a biaxial extruder, pulverized and classified to give a mass average particle diameter of 2.5 μm. Thereafter, 1.5 parts of silica fine powder (R-972: manufactured by Client Japan) was mixed using a Henschel mixer to obtain a toner of Example 3.

[Example 4]
Polyester resin (THF insoluble content 0%, Tg 55 ° C.) 71 parts by weight Black iron oxide compound 3 21 parts by weight Carnauba wax 6 parts by weight Charge control agent (zirconium salicylate: TN-105 by Hodogaya Chemical Co., Ltd. 2 parts by weight or more) The mixture was kneaded for 10 minutes at a kneading temperature of 150 ° C. using a biaxial extruder, pulverized and classified to a mass average particle diameter of 7.2 μm, and then silica fine powder (R-972: Client Japan) using a Henschel mixer. The toner of Example 4 was obtained by mixing 1.5 parts.

[Example 5]
Black iron oxide compound 4 30 parts by weight Polyester resin (THF insoluble content 20%, Tg70 ° C) 35 parts by weight Polyester resin (THF insoluble content 0.0%, Tg65 ° C) 30 parts by weight Carnauba wax 3 parts by weight Charge control agent ( Zirconium salicylate: TN-105 manufactured by Hodogaya Chemical Co., Ltd. 2 parts by mass The above formulation was kneaded for 10 minutes at a kneading temperature of 130 ° C. using a biaxial extruder, pulverized and classified to a mass average particle diameter of 6.8 μm. . Thereafter, using a Henschel mixer, 0.5 part of silica fine powder (HDK-1303VP: manufactured by Client Japan) and 0.1 part of titanium oxide (SMT-600BI: Taker) were mixed to obtain a toner of Example 5.

[Example 6]
Using polyester resin (Tg; 60 ° C., THF insoluble content 0%), black iron oxide compound 5, polyester resin, and pure water were mixed at a mass ratio of 1: 1: 0.5, and 2 It knead | mixed with this roll. Kneading was performed at 70 ° C., and then the roll temperature was raised to 120 ° C. to evaporate the water and prepare a master batch B in advance.
Masterbatch B 50 parts by mass Styrene-N-butyl acrylate (THF insoluble content 25%, Tg 50 ° C) 10 parts by mass Polyester resin (THF insoluble content 10%, Tg; 55 ° C) 30 parts by mass Rice wax 7 parts by mass Charge control Agent (zirconium salicylate: TN-105 manufactured by Hodogaya Chemical Co., Ltd.) 3 parts by mass The above formulation is kneaded for 10 minutes at a kneading temperature of 150 ° C using a biaxial extruder, pulverized and classified, and a mass average particle size of 5.5 µm It was. Thereafter, using a Henschel mixer, 0.7 part of silica fine powder (R-972: manufactured by Client Japan) and 0.3 part of titanium oxide were mixed to obtain a toner of Example 6.

[Example 7]
Using polyester resin (Tg; 60 ° C., THF insoluble content 0%), black iron oxide compound 6, polyester resin, and pure water were mixed at a mass ratio of 1: 1: 0.5, and 2 It knead | mixed with this roll. Kneading was carried out at 70 ° C., and then the roll temperature was raised to 120 ° C. to evaporate water and prepare a master batch C in advance.
Polyester resin (THF insoluble matter 25%, Tg65 ° C) 36 parts by mass Styrene-methacrylic acid copolymer (THF insoluble matter 0%, Tg62 ° C) 5 parts by mass Masterbatch C 52 parts by mass Ester wax 6 parts by mass Charge control Agent (zirconium salicylate: TN-105 manufactured by Hodogaya Chemical Co., Ltd.) 1 part by mass Kneading, pulverizing and classifying at a kneading temperature of 130 ° C. for 15 minutes using a biaxial extruder with the above formulation, and a mass average particle size of 3.5 μm did. Thereafter, using a Henschel mixer, 0.7 part of silica fine powder (R-972: manufactured by Client Japan) and 0.3 part of titanium oxide were mixed to obtain a toner of Example 7.

[Example 8]
Using polyester resin (Tg; 60 ° C., THF insoluble content 0%), black iron oxide compound 7, polyester resin, and pure water were mixed at a mass ratio of 1: 1: 0.5, and 2 It knead | mixed with this roll. Kneading was performed at 70 ° C., and then the roll temperature was raised to 120 ° C. to evaporate water and prepare a master batch D in advance.
Polyester resin (THF insoluble matter 40%, Tg; 60 ° C.) 32 parts by mass Masterbatch D 58 parts by mass Carnauba wax 6 parts by mass Charge control agent (zirconium salicylate: TN-105 manufactured by Hodogaya Chemical) 4 parts by mass The mixture was kneaded at 130 ° C. for 30 minutes using a biaxial extruder, pulverized and classified to give a mass average particle diameter of 4.2 μm. Thereafter, 1.8 parts of silica fine powder (R-972: manufactured by Client Japan) and 0.5 parts of titanium oxide (Titanium Industry SW-100) were mixed using a Henschel mixer to obtain a toner of Example 8.

[Example 9]
Using polyester resin A (Tg; 65 ° C., THF insoluble content 0%), black iron oxide compound 8, polyester resin, and pure water were mixed at a mass ratio of 1: 1: 0.5, It knead | mixed with two rolls. Kneading was carried out at 70 ° C., and then the roll temperature was raised to 120 ° C. to evaporate water and prepare a master batch E in advance.
Styrene-nbutyl acrylate copolymer (Tg 58 ° C., THF insoluble content 10%) 10 parts by weight Polyester resin A 28 parts by weight Masterbatch E 60 parts by weight Carnauba wax 5 parts by weight Charge control agent (zirconium salicylate: Hodogaya Chemical) Manufactured by TN-105) 2 parts by mass The above formulation was kneaded for 10 minutes at a kneading temperature of 160 ° C. using a biaxial extruder, pulverized and classified to obtain a mass average particle diameter of 4.5 μm. Then, using a Henschel mixer, 3.0 parts of silica fine powder (HDK-1301VP: manufactured by Client Japan) was mixed to obtain a toner.

[Example 10]
Using polyester resin B (Tg; 55 ° C., THF insoluble content 0%), black iron oxide compound 9, polyester resin and pure water were mixed at a mass ratio of 1: 1: 0.5. It knead | mixed with two rolls. Kneading was performed at 70 ° C., and then the roll temperature was raised to 120 ° C. to evaporate water and prepare a master batch F in advance.
Polyester resin (Tg 58 ° C., THF insoluble content 30%) 30 parts by weight Polyester resin B 10 parts by weight Masterbatch F 50 parts by weight Carnauba wax 7 parts by weight Charge control agent (zirconium salicylate: TN-105 manufactured by Hodogaya Chemical) 3 Part by mass The above formulation was kneaded at a kneading temperature of 160 ° C. for 10 minutes using a biaxial extruder, pulverized and classified to give a mass average particle size of 6.0 μm. Thereafter, 2.0 parts of silica fine powder (HDK-1301VP: manufactured by Client Japan) was mixed using a Henschel mixer to obtain a toner.

[Comparative Example 1]
Using polyester resin B (Tg; 55 ° C., THF insoluble content 0%), black iron oxide compound 10, polyester resin, and pure water were mixed at a mass ratio of 1: 1: 0.5. It knead | mixed with two rolls. Kneading was performed at 70 ° C., and then the roll temperature was raised to 120 ° C. to evaporate water and prepare a master batch G in advance.

Polyester resin (Tg 58 ° C., THF insoluble content 30%) 30 parts by weight Polyester resin B 10 parts by weight Masterbatch G 50 parts by weight Carnauba wax 7 parts by weight Charge control agent (zirconium salicylate: TN-105 manufactured by Hodogaya Chemical) 3 Part by mass The above formulation was kneaded at a kneading temperature of 160 ° C. for 10 minutes using a biaxial extruder, pulverized and classified to give a mass average particle size of 6.0 μm. Thereafter, 2.0 parts of silica fine powder (HDK-1301VP: manufactured by Client Japan) was mixed using a Henschel mixer to obtain a toner.

[Comparative Example 2]
Using polyester resin B (Tg; 55 ° C., THF insoluble content 0%), black iron oxide compound 11, polyester resin, and pure water were mixed at a ratio of 1: 1: 0.5, It knead | mixed with the roll. Kneading was performed at 70 ° C., and then the roll temperature was raised to 120 ° C. to evaporate water and prepare a master batch G in advance.
Styrene-n-BMA copolymer (THF insoluble content 20%, Tg 69 ° C.) 10 parts by mass Polyester resin B 30 parts by mass Masterbatch G 50 parts by mass Carnauba wax 7 parts by mass Charge control agent (zirconium salicylate: Hodogaya Chemical) TN-105 manufactured) 3 parts by mass The above formulation was kneaded under a kneading condition at 150 ° C. for 10 minutes using a biaxial extruder, pulverized and classified to give a mass average particle diameter of 6.5 μm. Thereafter, 0.5 part of silica fine powder (R-972: manufactured by Client Japan) and 0.2 part of titanium oxide were mixed using a Henschel mixer to obtain a toner of Comparative Example 2.

[Comparative Example 3]
Polyester resin (THF insoluble matter 20%, Tg59 ° C) 50 parts by weight Polyester resin (THF insoluble matter 0%, Tg59 ° C) 20 parts by weight Black iron oxide compound 12 20 parts by weight Carnauba wax 7 parts by weight Charge control agent ( Zirconium salicylate: TN-105 manufactured by Hodogaya Chemical Co., Ltd. 3 parts by mass The above formulation was kneaded under a kneading condition at 150 ° C. for 10 minutes using a biaxial extruder, pulverized and classified, and a mass average particle of 6.0 μm The diameter. Thereafter, using a Henschel mixer, 0.5 part of silica fine powder (R-972: manufactured by Client Japan) and 1.2 parts of titanium oxide were mixed to obtain a toner of Comparative Example 3.

Developers according to Examples 1 to 10 were prepared by mixing the toners according to the above Examples 1 to 10 and ferrite particles having an average particle diameter of 50 μm with a silicone resin-coated carrier at a concentration of 4.0% toner. Similarly, developers according to Comparative Examples 1 to 3 were prepared.
The evaluation results are shown in Table 2 and Table 3.

  As described above, the toner of the present invention is excellent in toner coloring power, toner scattering, fogging, image density, and the like.

  According to the present invention, an image forming toner using a black pigment that is safe and harmless to the environment, has good charging performance, and can suppress toner scattering, a toner container filled with the image forming toner, A two-component developer using toner, an image forming method, and a process cartridge are provided. Further, according to the toner and the image forming method of the present invention, an image excellent in fixability and heat-resistant storage stability can be formed even when used in a fixing device using a thin-walled, low surface pressure roller.

It is a figure which shows an example of the image forming apparatus used for this invention. It is a figure which shows an example of the fixing device used for this invention. 1 is a diagram showing a schematic configuration of an example of an image forming apparatus having a process cartridge of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device 3 Exposure means 4 Developing means 5 Transfer means 5a Transfer belt 6 Cleaning means 6a Cleaning blade 6b Cleaning brush 7 Document placement table 8 Reading means 9 Paper feed device 10 Fixing means 14 Waste toner tank 15 Recycling means 21 Fixing Roller 22 Pressure roller 23 Metal cylinder 24 Offset prevention layer 25 Heating lamp 26 Metal cylinder 27 Offset prevention layer 28 Heating lamp 30 Process cartridge 31 Photoconductor 32 Charging means 33 Developing means 34 Cleaning means S Adhering support T Toner image

Claims (21)

An image forming toner containing at least a binder resin and a colorant, wherein the colorant contains 10 to 45% by mass of a Ti component with respect to Fe atoms in terms of Ti atoms as measured by a wavelength dispersive X-ray fluorescence method. For forming an image, wherein the coercive force of the toner is a black iron oxide compound and measured with a multi-sample rotational magnetization measuring device at a measuring magnetic field of 398 Am ² / kg in a range of 2 to 15 kA / m. toner. ^2. The image forming toner according to claim 1, wherein the toner has a saturation magnetization [sigma] s of 0.1 to 5.0 Am < ² > / kg.   The image forming toner according to claim 1, wherein a true specific gravity of the toner is 1.35 to 1.55.   The image forming toner according to claim 1, wherein the toner has a volume specific resistance of 10.9 to 11.4 LogΩcm.   5. The image forming toner according to claim 1, wherein a content of the black iron oxide compound in the toner is 21 to 30% by mass.   The image forming toner according to claim 1, wherein the toner further contains a zirconium compound composed of zirconium and an aromatic oxycarboxylic acid or a salt thereof. After fixing the toner on art paper equivalent to ISO 12647-2 TYPE 1 at an adhesion amount of 0.60 to 0.85 mg / cm ² , X-Rite 938 (two-degree field of view of light source D50) based on the measurement method defined by ISO 12647-1 The measured L * value in the color coordinates after fixing is 10 to 28, the a * value is -1.0 to 1.0, and the b * value is in the range of -1.0 to 1.0. The image forming toner according to claim 1.   The image forming toner according to claim 1, wherein a mass average particle diameter D4 is 3 to 10 μm.   9. The image forming toner according to claim 1, wherein the black iron oxide compound has an average primary area particle size of 0.005 to 1.5 [mu] m.   10. The image according to claim 1, wherein the MI value (melt index value) measured at 150 ° C. under a load of 2160 g based on JIS K 6760 is 10 to 20 (g / min). Toner for forming.   The image forming toner according to claim 1, wherein the toner has a glass transition point of 55 to 65 ° C.   12. The toner according to claim 1, wherein the toner contains a wax and contains 0.5 to 7% by mass of carnauba wax and / or rice wax and / or ester wax as a wax component. The toner for image formation as described.   The toner for image formation according to any one of claims 1 to 12, wherein the peak top molecular weight Mp is 3300 to 5500 in the molecular weight distribution of the THF soluble component by gel permeation chromatography (GPC).   A toner container filled with the image forming toner according to claim 1.   A two-component developer comprising the image forming toner according to claim 1 and a carrier.   A charging process in which voltage is applied to the charging member by applying a voltage to the charging member from outside, a process in which an electrostatic image is formed on the charged body to be charged, and a toner image is formed by developing the electrostatic image with toner. A developing step, a transfer step in which a voltage is applied to the transfer member from the outside to transfer the toner image onto the transfer member, a cleaning step in which the surface of the charged member after transfer is cleaned with a cleaning member, and the toner image is heated and fixed. An image forming method comprising a fixing step, wherein the toner is the image forming toner according to claim 1. The fixing step is a fixing device that heats and fixes a toner image by passing a support holding a toner image between two rollers, and the fixing roller on the side in contact with the toner image support surface The image forming method according to claim 16, wherein the surface pressure (roller load / contact area) applied between the two rollers is 1.5 × 10 ⁵ Pa or less.   A recycling system that cleans the surface of the member to be charged after the toner image is transferred onto the transfer member, collects the toner on the surface of the member to be charged, supplies the collected toner to the developing means, and uses it in the developing process. The image forming method according to claim 16 or 17, further comprising:   19. The image forming method according to claim 16, wherein in the charging step, the charging member is brought into contact with the member to be charged and a voltage is applied to the charging member from the outside to charge the member to be charged. .   20. The image forming method according to claim 16, wherein in the transfer step, the member to be charged and the transfer member are in contact with each other. In the process cartridge that integrally supports the photosensitive member and at least one unit selected from a charging unit, a developing unit, and a cleaning unit and is detachable from the image forming apparatus main body, the developing unit holds the developer, 14. A process cartridge, wherein the developer contains the image forming toner according to claim 1.

Images