JP2002196539A - Electrostatic latent image developing black toner, method for producing the same, image forming method and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic latent image developing black toner having no color rendering property and high stability of blackness, an image forming method using the toner and an image forming device using the toner. SOLUTION: The electrostatic latent image developing black toner contains at least plural chromatic colorants and >=80 mass% of the chromatic colorants comprise two chromatic colorants. The two chromatic colorants preferably have the relation of complementary colors and are preferably green and red colorants, blue and orange colorants or purple and yellow colorants.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a black toner for developing an electrostatic latent image used in a copying machine, a printer, etc., utilizing an electrophotographic method, an electrostatic recording method or an electrostatic printing method, and a method for producing the same. The present invention also relates to an image forming method and an image forming apparatus using a black toner for developing an electrostatic latent image.

[0002]

2. Description of the Related Art In an electrophotographic method, an electrostatic latent image is formed on an electrostatic latent image carrier made of a photoconductive photoreceptor by a charging step and an exposure step, and then the electrostatic latent image is formed into a binder. A method is known in which a visible image is formed by developing with a toner composition containing a colorant in a resin, transferring the resulting toner image to an image forming support such as transfer paper, and fixing by heating. ing. As a toner composition used for developing an electrostatic latent image, generally, a composition in which a black colorant such as carbon black is dispersed in a binder resin is often used.

In recent years, in electrophotography, an image forming method of forming a full-color image by superposing a plurality of color toner compositions has been adopted. Such a full-color image is formed. In some cases,
After development with a plurality of color toner compositions, so-called "inking" is performed in which an electrostatic latent image is developed using a black toner.

For example, carbon black or the like has been used as the black toner used for the “inking”. However, the black toner used for the inking is different from other magenta, cyan, and yellow toners. Also, excellent developability and transferability are required, and when the developability and transferability of this black toner are inferior, the fine image formed by inking becomes poor, and the sharpness of a full-color image is sufficiently improved. Can not be expressed.

Conventionally, as such a black toner for forming a full-color image, for example, Japanese Patent Laid-Open No.
No. 7, for example, proposes a toner using carbon black as a colorant. However, since the electrical resistance of carbon black is low, it is difficult to obtain a sufficient charge amount in the obtained black toner, and particularly, a stable charge amount is maintained under conditions such as a low-temperature low-humidity environment or a high-temperature high-humidity environment. It is difficult to perform the task.

In order to solve such a problem, as a technique for forming a full-color image, instead of the above black toner, a plurality of color pigments such as yellow, magenta and cyan are mixed by a subtractive color mixing method. It is known that a toner exhibiting a black color developing function is thereby used. Japanese Patent Application Laid-Open No. 4-309996 discloses a chromatic colorant and a resin for each of yellow, magenta, and cyan. Are produced, and a method for producing a black toner by melt-kneading them is proposed. JP-A-4-356059 discloses an isoindoline-based yellow organic pigment and a quinacridone / perylene-based red pigment. A black toner containing an organic pigment and a phthalocyanine-based blue organic pigment has been proposed. Has a high volume resistivity as compared with carbon black, it is disclosed to exhibit the effect of suppressing the environmental fluctuations of the charge.

However, in the above technique, the degree of coloring power of the obtained black toner is inferior to that of the case of using carbon black, so that a large amount of a chromatic colorant must be contained in the toner. However, in this case, the amount of the chromatic colorant to be added becomes excessive, and the charge controllability of the black toner tends to be insufficient. It becomes difficult to uniformly disperse the chromatic colorant. When the dispersibility of the three chromatic colorants is poor, not only does the formed image have a poor black tint, but also the charging characteristics of the black toner deteriorate. ing.

In order to solve this problem, Japanese Patent Laid-Open Publication No. 2000-2000
JP-A-131879 proposes a toner containing a binder resin having a prescribed acid value, carbon black, a blue pigment, a yellow pigment, a red pigment, and a metal compound of an aromatic oxycarboxylic acid derivative. And JP-A-2000-
JP 112179 proposes a black toner for developing an electrostatic latent image comprising a binder resin, colored particles containing carbon black, a cyan pigment, a magenta pigment and a yellow pigment, and an external additive. It has been proposed to define the concentration of carbon black and each pigment in the particles and the volume average particle size of the colored particles.

However, in the above-mentioned black toner, when used in a high-temperature and high-humidity environment for a long period of time, there is a problem that fog and poor transferability are found in the formed image. . Further, when a black color is formed by mixing three types of colorants as described above, there is a problem that a so-called color rendering property appears in which a black tint appears to change depending on the wavelength of irradiation light. The color changes under light and under illumination light from a fluorescent lamp or the like in a room, and the texture, especially in halftone, deteriorates. It is considered that such a problem of the color rendering properties is caused by the fact that the chromatic colorants in the black toner particles are not uniformly dispersed but are unevenly mixed.

Specifically, for example, in a manufacturing method in which a plurality of chromatic pigments are melt-kneaded and then pulverized to obtain a toner, the dispersion of the pigment added during the melt-kneading is uniform as described above. The properties are different for each pigment,
At the time of pulverization, pulverization points concentrate on specific pigment particles, and as a result, uniform dispersibility cannot be obtained.Particularly, toner particles having a particle size at the bottom of the fine powder side in the toner particle size distribution have dispersibility. There is a problem that uniform dispersion cannot be obtained due to large deviation of the color, which causes color rendering.

Further, when the content ratio of the chromatic colorant in the black toner is increased, the physical properties such as the melt viscosity of the black toner change, which causes a problem of fixing failure. As described above, there has been a demand for the development of a black toner which has a black coloring property higher than that of carbon black as a coloring agent, and has a stable charging characteristic for a long period of time.

In recent years, in response to demands for full-color images and improved resolution in image forming apparatuses, miniaturization of electrostatic latent images has been achieved, and it has been possible to faithfully develop the miniaturized electrostatic latent images. As a toner capable of forming a higher quality image, a toner having a small particle diameter is attracting attention.
In particular, developing, transferring, and developing digital latent images with chromatic toner
In the image forming method for fixing, higher resolution such as further improvement of fine line reproducibility and improvement of gradation reproducibility is required, and in order to meet this demand, a toner having a smaller particle size is required. As a method for obtaining such a small particle size toner, a polymerized toner technology manufactured by a polymerization method has been proposed.

However, for example, a polymerized toner obtained by polymerizing a polymerizable monomer in an aqueous medium has a low electric resistance, and when carbon black is used as a coloring agent, the dispersion diameter of carbon black is also small. Due to its tendency to increase in size, there is a problem that the problem of fogging and poor transfer under a high-temperature and high-humidity environment is liable to occur.For example, black using a plurality of chromatic colorants in the above technology is used. As can be understood from the fact that all of the toner is obtained by a pulverization method, a technique of providing a black toner using a plurality of chromatic colorants by a polymerization method has not been studied so far. .

[0014]

SUMMARY OF THE INVENTION The present invention has been made based on the above circumstances. That is, a first object of the present invention is to provide a black toner for developing an electrostatic latent image having no color rendering property and high blackness stability. A second object of the present invention is to provide a black toner for developing an electrostatic latent image capable of obtaining an appropriate image density and obtaining an image having a stable texture even in halftone. A third object of the present invention is to provide a black toner for developing an electrostatic latent image which does not generate fog and maintains stable transferability even when used under a high temperature and high humidity for a long period of time. It is. A fourth object of the present invention is to provide a black toner for developing an electrostatic latent image having stable toner properties and excellent fixability, while being a toner containing a plurality of chromatic colorants. . A fifth object of the present invention is to provide a black toner for developing an electrostatic latent image, comprising a polymerized toner which achieves the first to fourth objects. A sixth object of the present invention is to provide an image forming method using a toner having excellent characteristics as described above.
A seventh object of the present invention is to provide an image forming apparatus using a toner having the above-described excellent characteristics.

[0015]

The present invention is attained by adopting the structure described in the claims. That is, the black toner for developing an electrostatic latent image according to the present invention (claims 1 to 5) is a black toner containing at least a plurality of chromatic colorants, wherein the chromatic colorant is at least 80% by mass. Is characterized by comprising two types of chromatic colorants, and it is preferable that the two types of chromatic colorants have a complementary color relationship to each other, and furthermore, the two types of chromatic colorants Preferably, the agent comprises a green colorant and a red colorant, a blue colorant and an orange colorant, or a purple colorant and a yellow colorant.

Further, the black toner for developing an electrostatic latent image according to the present invention (claims 6 to 8) is obtained by polymerizing at least a polymerizable monomer in an aqueous medium. It is preferable that the obtained polymer particles and the plurality of chromatic colorants are associated in an aqueous medium, and the chromatic colorant is 10 to 600 n in an aqueous medium.
It is preferably used as a chromatic colorant dispersion dispersed to have a particle size in the range of m.

The black toner for developing an electrostatic latent image according to the present invention (claims 9 to 13) further has a shape coefficient variation coefficient of 1
6% or less, and the number variation coefficient in the number particle size distribution is 27% or less.
The ratio of toner particles in the range of 0 to 1.6 is 65% by number
Preferably, the shape factor is 1.
65% by number of toner particles in the range of 2 to 1.6
It is preferable that the ratio of the toner particles having no corners is 50% by number or more. When the particle size of the toner particles is D (μm), the natural logarithm lnD is plotted on the horizontal axis. In the histogram showing the number-based particle size distribution in which the horizontal axis is divided into a plurality of classes at intervals of 0.23,
Relative frequency (m1) of toner particles included in the most frequent class;
It is preferable that the sum (M) of the relative frequency (m2) of the toner particles included in the class having the second highest frequency after the mode is 70% or more.

The method for producing a black toner for developing an electrostatic latent image according to the present invention (Claims 14 to 16) includes a step of polymerizing at least a polymerizable monomer in an aqueous medium. It is characterized in that a black toner for developing an electrostatic latent image containing a chromatic colorant is obtained, and the polymer particles obtained thereby and the plurality of chromatic colorants are preferably associated with each other in an aqueous medium. The chromatic colorant is
It is preferably used as a chromatic colorant dispersion dispersed in an aqueous medium to a particle size in the range of 10 to 600 nm.

According to the image forming method of the present invention (claim 17),
An image forming method including: developing an electrostatic latent image to form a toner image; and transferring the toner image to an image forming support, and then fixing the toner image with a fixing device having a heating roller. The above-described black toner for developing an electrostatic latent image is used for developing the electrostatic latent image.

The image forming apparatus of the present invention (claim 18)
Image formation for forming an image including a step of forming a toner image by developing an electrostatic latent image and a step of transferring the toner image to an image forming support and then fixing the toner image with a fixing device having a heating roller In the device, for developing the electrostatic latent image,
The black toner for developing an electrostatic latent image is used.

[0021]

According to the present invention, there is provided a black toner for developing an electrostatic latent image (hereinafter also referred to simply as "black toner") which is suitably used for forming a visible image, especially a full-color image, and contains a chromatic color. By making the number of kinds of agents, their content ratio, and the method for producing the black toner specific, a high-quality visible image with excellent black reproducibility and fine line reproducibility can be stably formed. . That is, by using a black toner in which 80% by mass or more of the chromatic colorant is used, color rendering properties do not appear in an image to be formed, and blackness stability is improved. An image having a certain color tone can be obtained even under irradiation light having

Further, since the above-mentioned black toner for developing an electrostatic latent image is obtained by polymerizing a polymerizable monomer in an aqueous medium, toner particles having a small diameter can be obtained. And the image quality of the reproducibility of fine lines and dots can be improved.

In the black toner, the number of kinds of the chromatic colorants contained, the content ratio thereof, and the manufacturing method thereof are specified, and the external structure (shape / particles) of the black toner itself is specified. By setting the diameter or the like to a specific value, a high-quality visible image excellent in black reproducibility and fine line reproducibility, in particular, a color image can be stably formed. That is, the black toner composed of toner particles having a shape coefficient variation coefficient of 16% or less and a number variation coefficient in the number particle size distribution of 27% or less provides excellent developability and transferability. . Further, the charge amount distribution in the toner becomes sharp, and the chargeability between the toner particles of each color can be made uniform. As a result, the adhesion to the image forming support between the toner particles of each color becomes uniform. be able to.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. <Toner> The black toner for developing an electrostatic latent image of the present invention comprises a polymer particle containing, as a colorant, a plurality of types of chromatic colorants such as pigments. At least 80% by mass of the mass is composed of two types of chromatic colorants, and the two types of chromatic colorants have, for example, mutually complementary colors. Here, as a combination of chromatic colorants having a complementary color relationship to each other, a combination of a green colorant and a red colorant, a combination of a blue colorant and an orange colorant, a combination of a purple colorant and a yellow colorant There is. Other appropriate chromatic colorants can be used in combination with these two specific chromatic colorants, but the proportion must be less than 20% by mass of the entire chromatic colorant. .

As a pigment for a red colorant, C.I. I. Pigment Red 2, 3, 5, 6, 7, 15, 15, 16, 48: 3, 53: 1, 57: 1, 12
2, 123, 139, 144, 149, 16
6, 177, 178, 222 and the like. Examples of the pigment for a green colorant to be combined with the pigment for a red colorant include C.I. I. Pigment Green 1, 2, 7, 8, 10, 12, 12, 36, 37, 38 and the like.

Examples of pigments for cyan colorants include C.I. I.
Pigment Blue 15, 15: 2, 15: 3, 1
6, 17 and the like. Orange pigments to be combined with pigments for cyan colorants include C.I. I. Pigment Oranges 31 and 43 and the like.

Examples of pigments for purple colorants include C.I. I. Pigment Violet 1, 2, 3, 5, 19
23 and the like. Examples of the pigment for the yellow colorant to be combined with the pigment for the purple colorant include C.I. I. Pigment Yellow 12, 13, 14, 14, 15, 17, 93, 94, 138, 155, 156, 18
0 and 185. Examples of a pigment for a green colorant or a cyan colorant include C.I. I. Pigment Blue 15, 15: 2, 15: 3, 16, 60, C.I.
I. Pigment Green 7 and the like.

As the dye, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 1
22, C.I. I. Solvent Yellow 19, 44, 7
7, 79, 81, 82, 93, 98, 10
3, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 9
5 and the like, and a mixture thereof can also be used.

The total content of the colorant is 2 to the polymer.
To 20% by mass, and preferably 3 to 15% by mass. As the colorant, a surface-modified colorant may be used. As the surface modifier, a conventionally known one can be used, and specifically, a silane coupling agent, a titanium coupling agent, an aluminum coupling agent and the like can be preferably used. The number average primary particle diameter of the colorant varies depending on the type, but is preferably from 10 to 200 nm.

In order to obtain polymer particles containing a colorant, a method of adding a colorant at the stage of aggregating polymer particles prepared by an emulsion polymerization method by adding an aggregating agent, or polymerizing a monomer is used. A method of obtaining colored particles by adding a colorant at the stage and polymerizing the monomer can be used. When the colorant is added at the stage of preparing the polymer, it is preferable to treat the surface thereof with a coupling agent or the like so as not to inhibit the radical polymerization.

The toner of the present invention may further have a number average molecular weight of, for example, 15 as a fixing property improving agent or a releasing agent.
It is preferable to contain a low-molecular-weight polypropylene having a molecular weight of 00 to 9000, a low-molecular-weight polyethylene, or the like. In particular, a crystalline ester compound represented by the following general formula (1) can be preferably used.

[0032]

Embedded image

(Wherein R ¹ is a hydrocarbon group having 1 to 40, preferably 1 to 20, more preferably 2 to 5 carbon atoms which may have a substituent, and R ² represents a substituent. Represents a hydrocarbon group having 1 to 40, preferably 16 to 30, and more preferably 18 to 26 carbon atoms which may have
An integer of 4, preferably 2 to 4, more preferably 3
To 4, particularly preferably 4. Specific examples include those shown in the following exemplary compounds (1) to (22).

[0034]

Embedded image

[0035]

Embedded image

[0036]

Embedded image

The fixing improver comprising the above ester compound is contained at a ratio of 1 to 30% by mass, preferably 2 to 20% by mass, particularly preferably 3 to 15% by mass, based on the whole toner.

A solution in which a fixing improver is dissolved in a monomer for forming a polymer particle is dispersed in water, and the monomer is polymerized in that state, thereby fixing the polymer in the polymer particle. A polymer particle containing an improving agent is formed, and this is
For example, polymer particles containing a fixing improver can be obtained by salting out / fusion together with the colorant particles.

More specifically, in preparing the polymer particles, the fixing improver is dissolved in a monomer for the polymer particles, and then the miniemulsion polymerization method is used. Can be obtained preferably.

It is preferable that the polymer of the polymer particles has a plurality of polymer components having different molecular weights from the viewpoint of obtaining a good fixing property. In particular, when both the high molecular weight component and the low molecular weight component are present, both the improvement of the offset property and the adhesion to the image forming support such as paper can be obtained.

Specifically, the polymer constituting the polymer particles has a weight average molecular weight of 160,000 to 1,000,000.
It preferably contains at least both a high molecular weight component having a peak or shoulder in the range of 00 and a low molecular weight component having a peak or shoulder in the range of 1,000 to less than 50,000.
It is preferable to use an intermediate molecular weight having a peak or a shoulder in a portion of 5,000 to 100,000,
More preferably, an intermediate molecular weight having a peak or a shoulder at a portion of 25,000 to 75,000 is used.

In such a polymer, better anti-offset properties can be obtained when the release improver is present on the low molecular weight component side than in the high molecular weight component. Although the reason for this is not clear, the high molecular weight component has a high elastic modulus at high temperatures, so that the offset phenomenon itself is unlikely to occur, whereas the low molecular weight component has a high elastic modulus at high temperatures (during fixing). Therefore, it is presumed that good offset resistance can be obtained by the presence of the fixing improver in the low molecular weight component.

In particular, when an intermediate molecular weight is contained, the presence of a fixing improver in the intermediate molecular weight component can improve not only the anti-offset property but also the fixing property. Although the reason for this is not clear, the content of the fixing improver in the low molecular weight component can be reduced by being present in the intermediate molecular weight component. This is presumed to be because the adhesiveness can be maintained without the addition, and the offset resistance is reliably exhibited by maintaining the elastic modulus in the high molecular weight component.

In the above, the molecular weight of the polymer is represented by a molecular weight in terms of polystyrene measured by a GPC (gel permeation chromatography) method using THF (tetrahydrafuran) as a solvent. Specifically, 0.5 to 5 mg, for example, 1 m
g of the measurement sample body, 1 cc of THF was added thereto, and the mixture was stirred at room temperature using a magnetic stirrer or the like to sufficiently dissolve the sample in THF, and the solution was made to have a pore size of 0.45 to 0.50 μm. After filtration through a membrane filter of No. 2, the mixture is injected into a column of GPC.

GPC measurement conditions were as follows: the column was stabilized at 40 ° C., and THF was flowed at a flow rate of 1 cc / min.
About 100 μl of a sample having a concentration of 1 mg / cc is injected into a GPC column for measurement. The column is preferably used in combination with a commercially available polystyrene gel column. For example, Shodex GPC KF-8 manufactured by Showa Denko KK
01, 802, 803, 804, 805, 8
06 or 807 or TSK manufactured by Tosoh Corporation
gel G1000H, G2000H, G3000
H, G4000H, G5000H, G6000H
Or G7000H, TSK guard column
A combination of n and the like can be used. It is preferable to use a refractive index detector (IR detector) or a UV detector as the detector. In measuring the molecular weight of a sample,
The molecular weight distribution of the sample is calculated using a calibration curve created using monodisperse polystyrene standard particles. It is preferable to use about 10 polystyrenes for preparing a calibration curve.

<Shape Factor of Black Toner> In the present invention, the “shape factor” of the toner is represented by the following equation and is an index indicating the degree of roundness of the toner particles.

[0047]

(Equation 1)

Here, the maximum diameter refers to the width of a particle at which the distance between the parallel lines becomes maximum when the projected image of the toner particles on the plane is sandwiched between two parallel lines. The projection area refers to the area of the projected image of the toner particles on the plane. The shape factor was determined by taking a photograph of the toner particles magnified 2000 times with a scanning electron microscope, and based on this photograph, "SCANNING IMAGE ANALYZER"
It is measured by analyzing a photographic image using (manufactured by JEOL Ltd.). In practice, the average value of the shape factors calculated for 100 toner particles is used as the shape factor of the toner.

In the toner of the present invention, the proportion of toner particles having a shape factor in the range of 1.0 to 1.6 is preferably at least 65% by number, more preferably at least 70% by number. More preferably, the shape factor is 1.2 to
The ratio of the toner particles in the range of 1.6 is 65% by number or more, more preferably 70% by number or more. When the ratio of the toner particles having the shape coefficient in the range of 1.0 to 1.6 is 65% by number or more, the uniformity of the triboelectrification in the developer conveying member and the like is increased,
Since the excessively charged toner does not accumulate and the toner is easily exchanged from the surface of the developer conveying member, problems such as a development ghost are less likely to occur. Further, since the toner particles are less likely to be crushed, contamination of the charging member is reduced, and the chargeability of the toner is stabilized.

The method for controlling the shape factor is not particularly limited. For example, a method of spraying toner particles into a hot air flow, a method of repeatedly applying mechanical energy by impact force in a gas phase in a gas phase, or a method of adding a toner particle in a solvent that does not dissolve a toner to impart a swirling flow, and the like. By using this, toner particles having a shape factor adjusted to 1.0 to 1.6 or 1.2 to 1.6 are prepared, and mixed with a normal toner whose shape factor is not particularly adjusted. There is a method to prepare. Further, the shape factor is adjusted to 1.0 to 1.6 or 1.2 to 1.6 by controlling the shape of the whole polymer particles at the stage of preparing the toner particles by a so-called polymerization method. There is a method of adding to normal toner.

<Coefficient of Variation of Shape Factor of Toner> In the present invention, the “coefficient of variation of shape coefficient” of toner is calculated from the following equation.

[0052]

(Equation 2)

[Wherein, S ₁ represents the standard deviation of the shape coefficients of 100 toner particles, and K represents the average value of the shape coefficients. ]

In the black toner of the present invention, the variation coefficient of the shape factor is 16% or less, preferably 14% or less. When the variation coefficient of the shape coefficient is 16% or less, the surface property between the toner particles becomes uniform, so that there is little variation in transferability to the image forming support and stable transferability can be obtained. Further, the toner particles are less likely to be crushed, and the contamination of the charging member is reduced, and the charging property of the toner is stabilized. Therefore, there is little variation in adhesion between the toner particles and the electrostatic latent image carrier, and the toner is stable. An image can be formed. When a color-fixed image is formed via the intermediate transfer body, the density of the toner particles in the toner layer transferred and formed on the intermediate transfer body increases, so that good transferability can be obtained.

A polymerization step of preparing polymer particles constituting the toner, in order to constantly and uniformly control the shape coefficient and the variation coefficient of the shape coefficient of the toner with high stability;
In addition, in the step of controlling the shape by fusing the polymer particles, a method of terminating the process at an appropriate time while monitoring the characteristics of the colorant-containing polymer particles being formed can be used.

Here, "monitoring" means that a measuring device is incorporated in-line and process conditions are controlled based on the measurement result. In other words, when a device for measuring the shape or the like is incorporated inline to form a toner by a polymerization method described later, for example, the shape and particle size of the polymer particles generated while performing sequential sampling in a process such as fusing. The diameter is measured and the reaction is stopped when the desired shape is obtained. In order to perform monitoring, for example, a flow-type particle image analyzer FPIA-
2000 (manufactured by Toa Medical Electronics Co., Ltd.) can be used. This apparatus is suitable because the shape of the polymer particles can be monitored by performing image processing in real time while passing the sample liquid. That is, sampling may be performed from a reaction field using a pump or the like, and the shape or the like may be measured by constantly monitoring, and the reaction may be stopped when the desired shape or the like is obtained.

<Coefficient of Variation in Number of Toner> In the present invention, the particle size distribution and the number variation coefficient of the toner are measured by a Coulter Counter TA or a Coulter Multisizer (manufactured by Coulter). Specifically, a Coulter Multisizer was used, and an interface (manufactured by Nikkaki) for outputting a particle size distribution and a personal computer were connected to this. 100 μm diameter as aperture in Coulter Multisizer
The particle size distribution and average particle size were calculated by measuring the volume and number of toner particles having a particle size of 2 μm or more. The number particle size distribution represents the relative frequency of the toner particles with respect to the particle size, and the number average particle size represents the median size in the number particle size distribution. The “number variation coefficient in the number particle size distribution” of the toner is calculated from the following equation.

[0058]

(Equation 3)

[Wherein, S ₂ represents the standard deviation in the number particle size distribution, and Dn represents the number average particle size (μm). ]

The number variation coefficient of the toner of the present invention is 27% or less, preferably 25% or less. When the number variation coefficient is 27% or less, the surface property between the toner particles of each color becomes uniform, so that there is little variation in transferability to the image forming support and stable transferability can be obtained.
In addition, since toner particles are less likely to be crushed, the contamination of the charging member is reduced, and the charging property of the toner is stabilized, the variation in the adhesion between the toner particles and the electrostatic latent image carrier is small, and the Can be stabilized. And when forming a color fixed image via the intermediate transfer member,
Since the packing density of the toner particles in the toner layer transferred and formed on the intermediate transfer member is increased, good transferability can be maintained.

The method of controlling the number variation coefficient of the toner is not particularly limited. For example, a method of classifying toner particles by wind force can be used, but classification in a liquid is effective for further reducing the number variation coefficient. As a method of classifying in the liquid, there is a method of separating and collecting toner particles using a centrifugal separator, controlling the number of revolutions, and utilizing a difference in sedimentation speed caused by a difference in toner particle diameter. In particular, in the case of producing a toner by a suspension polymerization method described below, a classification operation is indispensable in order to reduce the number variation coefficient in the number particle size distribution to 27% or less. That is, in the suspension polymerization method, it is necessary to disperse the polymerizable monomer in an aqueous medium into oil droplets of a desired size as a toner before polymerization, and the large oil droplet of the polymerizable monomer is required. On the other hand, mechanical shearing by a homomixer or a homogenizer is repeated to reduce oil droplets to a size corresponding to the toner particles. The number particle size distribution becomes wide, and therefore, the particle size distribution of the toner obtained by polymerizing the number particle size becomes wide. For this reason, a classification operation is required.

<Ratio of toner particles without corners> In the toner particles constituting the black toner of the present invention, the ratio of the toner particles without corners needs to be 50% by number or more, and this ratio is 70%. % Is preferable.

When the ratio of the toner particles having no corners is 50% by number or more, the surface property between the toner particles of each color becomes uniform, so that there is little variation in transferability to the image forming support, and the toner is stable. Transferability is obtained. In addition, the amount of toner particles that are easily worn or broken and the number of toner particles having a portion where electric charges are concentrated are reduced, the charge amount distribution is sharpened, the chargeability between the toner particles of each color is stabilized, and a good color image is obtained. Can be formed stably over a long period of time. When a color-fixed image is formed via the intermediate transfer member, the density of the toner particles in the toner layer transferred and formed on the intermediate transfer member increases, so that good transferability can be maintained. .

Here, “toner particles having no corners” refers to toner particles having substantially no protrusions where charges are concentrated or which are easily worn out by stress.
Specifically, the following toner particles are referred to as “toner particles without corners”.
That. That is, as shown in FIG. 1A, when the major axis of the toner particles T is L, a circle C having a radius (L / 10)
In the case where the inside is rolled while being in contact with the peripheral line of the toner particle T at one point and the circle C does not substantially protrude outside of the toner T, the case where the circle C does not substantially extend outside the toner T is referred to as “toner particle having no corner”. That. “Cases that do not substantially protrude” refer to cases where there are no more than one protrusion having a protruding circle. Also,
The “longer diameter of the toner particle” refers to the width of the particle at which the interval between the parallel lines is the largest when the projected image of the toner particle on the plane is sandwiched between two parallel lines. FIGS. 1B and 1C show projected images of the toner particles having corners, respectively.

The ratio of the toner particles having no corners was measured as follows. First, a photograph in which the toner particles were enlarged by a scanning electron microscope was taken, and further enlarged to 15.0.
Obtain a 00x photographic image. Next, the presence or absence of the corners is measured for this photographic image. This measurement was performed for 100 toner particles.

The method for obtaining toner having no corners is not particularly limited. For example, as described above, as a method of controlling the shape coefficient, a method of spraying toner particles into a hot air flow, a method of repeatedly applying mechanical energy by an impact force in a gas phase, or a method of dissolving a toner It can be obtained by adding to a solvent that does not contain and giving a swirling flow. Further, in the polymerization method toner formed by associating or fusing the polymer particles, the surface of the fused particles has many irregularities at the stage of stopping the fusion, and the surface is not smooth. By adjusting the conditions such as the rotation speed of the stirring blade and the stirring time, toner particles having no corners can be obtained. These conditions vary depending on the physical properties of the polymer particles.For example, by setting the rotation speed higher than the glass transition temperature of the polymer particles, the surface becomes smooth and toner having no corners is formed. it can.

Further, in the present invention, the yellow toner, magenta toner, cyan toner, and black toner used for forming a color image have the same toner particle shape and the like (between the toner particles of each color). , The color reproducibility is improved. That is, by satisfying the following expressions (1) to (4), when a color image is formed by the tandem method, it is possible to reduce the variation in the adhesion between the toner particles of each color and the chargeability, and to achieve color reproduction. And a good color image can be formed without image quality deterioration in the transfer step and the fixing step.

[0068]

(Equation 4)

In the above equations (1) to (4), the maximum value and the minimum value of K are the average values (Ky, Km, Kc) of the shape coefficients of the yellow toner, magenta toner, cyan toner, and black toner. , Kb) mean the maximum and minimum values, and the maximum and minimum values of Kσ are the variation coefficients (Kσy, Kσ) of the shape coefficient of each color toner.
m, Kσc, and Kσb) mean the maximum value and the minimum value, and the maximum value and the minimum value of D mean the maximum value and the minimum value of the number average particle diameter (Dy, Dm, Dc, Db) of each color toner. The maximum value and the minimum value of Dσ are the number variation coefficients (Dσy,
Dσm, Dσc, and Dσb).

Further, by using toner particles having a cornerless toner particle ratio of not less than 50% by number and a number variation coefficient in the number particle size distribution of not more than 27% as toner particles constituting each color toner, Since the surface properties between the toner particles of each color are uniform, the chargeability between the toner particles of each color and the adhesion to the electrostatic latent image carrier can be homogenized and transferred to the image forming support. In this case, a good color image can be stably formed for a long time without causing image defects such as dust. When a color-fixed image is formed via the intermediate transfer member, the density of the toner particles in the toner layer transferred and formed on the intermediate transfer member increases, so that good transferability can be maintained. .

<Diameter of Toner Particles> The toner of the present invention preferably has a number average particle diameter of 3 to 8 μm. In the case where toner particles are formed by a polymerization method, the particle size is determined by the concentration of the coagulant, the amount of the organic solvent added, or the fusing time, and the composition of the polymer itself, in the toner manufacturing method described in detail below. Can be controlled by When the number average particle diameter is 3 to 8 μm, the transferability to the image forming support can be improved without the thickness of the toner layer between the colors being excessively large. Further, the transfer efficiency is improved, and the image quality of halftone is improved, and the image quality of fine lines, dots, and the like is improved.

In the toner of the present invention, when the particle diameter of toner particles is D (μm), the natural logarithm InD is plotted on the horizontal axis, and the horizontal axis is divided into a plurality of classes at intervals of 0.23. In the histogram showing the particle size distribution, the sum (M1) of the relative frequency (m1) of the toner particles included in the most frequent class and the relative frequency (m2) of the toner particles included in the class having the second highest frequency after the most frequent class. ) Is preferably 70% or more.

When the sum (M) of the relative frequency (m1) and the relative frequency (m2) is 70% or more, the dispersion of the particle size distribution of the toner particles becomes narrower. Thus, the occurrence of selective development can be reliably suppressed. In the present invention, the histogram showing the number-based particle size distribution includes a natural logarithm lnD (D: particle size of individual toner particles) in a plurality of classes (0 to 0.23: 0.23 to 0.23) at intervals of 0.23. 0.46: 0.46-0.
69: 0.69-0.92: 0.92-1.15: 1.
15-1.38: 1.38-1.61: 1.61-1.
84: 1.84 to 2.07: 2.07 to 2.30: 2.
30 to 2.53: 2.53 to 2.76...) Is a histogram showing the number-based particle size distribution, which is based on the following conditions. Diameter data is
It is transferred to a computer via the / O unit, and is created by the computer using a particle size distribution analysis program.

[Measurement conditions] (1) Aperture: 100 μm (2) Sample preparation method: Electrolyte [ISOTON R-1
1 (manufactured by Coulter Scientific Japan)
An appropriate amount of a surfactant (neutral detergent) is added to 50 to 100 ml, and the mixture is stirred, and 10 to 20 mg of a measurement sample is added thereto. This system is prepared by subjecting it to a dispersion treatment with an ultrasonic disperser for 1 minute.

<Production Method of Toner>
It is preferable that the toner is obtained by polymerizing at least a polymerizable monomer in an aqueous medium, and that it is an associative toner obtained by salting out / fusing at least polymer particles in an aqueous medium. Is preferred. Hereinafter, the method for producing the toner of the present invention will be described in detail.

The toner of the present invention can be obtained by suspension polymerization or emulsion polymerization of a monomer in a liquid (in an aqueous medium) to which an emulsion of a necessary additive is added, to produce fine polymer particles (resin particles). ) Is prepared, and thereafter, an organic solvent, a flocculant and the like are added to the polymer particles to associate the polymer particles. Here, "association" means that a plurality of the polymer particles are fused, and the polymer particles and other particles (for example, colorant particles)
Are fused.

An example of a method for producing the toner of the present invention is as follows. A colorant and a releasing agent, if necessary, are contained in a polymerizable monomer.
Various constituent materials such as a charge control agent and a polymerization initiator are added, and the various constituent materials are dissolved or dispersed in the polymerizable monomer using a homogenizer, a sand mill, a sand grinder, an ultrasonic disperser or the like. The polymerizable monomer in which the various constituent materials are dissolved or dispersed is dispersed in an aqueous medium containing a dispersion stabilizer into oil droplets having a desired size as a toner by using a homomixer or a homogenizer. Thereafter, the stirring mechanism is moved to a reaction device (stirring device), which is a stirring blade, and the polymerization reaction is advanced by heating. After completion of the reaction, the toner of the present invention is prepared by removing the dispersion stabilizer, filtering, washing and drying. The “aqueous medium” in the present invention refers to a medium containing at least 50% by mass of water.

Further, as a method for producing the toner of the present invention, there is a method in which polymer particles are prepared by associating or fusing them in an aqueous medium. This includes:
Although not particularly limited, for example, Japanese Patent Application Laid-Open
65252, JP-A-6-329947, and JP-A-9-15904. That is, a method of associating a plurality of fine particles composed of a polymer and a colorant, such as dispersed particles of a constituent material such as a polymer particle and a colorant, particularly after dispersing these in water using an emulsifier, At the same time as adding a coagulant having a coagulation concentration or more and causing salting-out, the formed polymer itself is heated and fused at a temperature equal to or higher than the glass transition point to gradually grow the particle size while forming fused particles. When the diameter became large, a large amount of water was added to stop the growth of the particle diameter, and the shape was controlled by heating and stirring to smooth the particle surface,
The toner of the present invention can be formed by heating and drying the particles in a fluidized state in a water-containing state. Here, a solvent that is infinitely soluble in water may be added together with the coagulant.

The polymerizable monomers forming the polymer of the polymer particles include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4 -Dichlorostyrene,
p-phenylstyrene, p-ethylstyrene, 2,4-
Dimethylstyrene, p-tert-butylstyrene, p
-N-hexylstyrene, pn-octylstyrene,
pn-nonylstyrene, pn-decylstyrene, p
Styrene or a styrene derivative such as n-dodecylstyrene, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, methacrylic acid 2 -Methacrylate derivatives such as ethylhexyl, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, n acrylate
-Butyl, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate,
Acrylate derivatives such as phenyl acrylate,
Ethylene, propylene, olefins such as isobutylene, vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, halogenated vinyls such as vinylidene fluoride, vinyl propionate, vinyl acetate, vinyl esters such as vinyl benzoate, Vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl hexyl ketone; N-vinyl compounds such as N-vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidone; vinyl There are vinyl compounds such as naphthalene and vinylpyridine, and acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide. These vinyl monomers can be used alone or in combination.

It is more preferable to use a polymerizable monomer for obtaining polymer particles in combination with one having an ionic dissociation group. Monomers having an ionic dissociation group include, for example, a carboxyl group, a sulfonic acid group,
It has a substituent such as a phosphate group as a constituent group of the monomer, specifically, acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, monoalkyl maleate, Itaconic acid monoalkyl ester, styrenesulfonic acid, allylsulfosuccinic acid, 2-acrylamido-2-methylpropanesulfonic acid, acid phosphooxyethyl methacrylate, 3
-Chloro-2-acid phosphooxypropyl methacrylate and the like. In addition, polyfunctional such as divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, etc. A polymer having a crosslinked structure can be obtained by using a hydrophilic vinyl.

These polymerizable monomers can be polymerized using a radical polymerization initiator. In this case, an oil-soluble polymerization initiator can be used in the suspension polymerization method. As the oil-soluble polymerization initiator, 2,2'-azobis- (2,4
-Dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvalero Azo or diazo polymerization initiators such as nitrile and azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide , Dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis-
Examples include peroxide-based polymerization initiators such as (4,4-t-butylperoxycyclohexyl) propane and tris- (t-butylperoxy) triazine, and polymer initiators having a peroxide in a side chain. . When an emulsion polymerization method is used, a water-soluble radical polymerization initiator can be used. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and salts thereof, and hydrogen peroxide.

Examples of the dispersion stabilizer include tricalcium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, and calcium sulfate. , Barium sulfate,
Bentonite, silica, alumina and the like can be mentioned. Further, a surfactant generally used as a surfactant such as polyvinyl alcohol, gelatin, methyl cellulose, sodium dodecylbenzenesulfonate, ethylene oxide adduct, and higher alcohol sodium sulfate can be used as a dispersion stabilizer.

In the present invention, the polymer of the polymer particles preferably has a glass transition point of 20 to 90 ° C.
Those having a softening point of 80 to 220 ° C are preferred. The glass transition point is measured by a differential calorimetric analysis method, and the softening point can be measured by a Koka flow tester. Further, these resins have a number average molecular weight (M.P.) measured by gel permeation chromatography.
n): 1000 to 100000, weight average molecular weight (M
It is preferable that w) be 2000 to 1,000,000. Further, as a molecular weight distribution, Mw / Mn is 1.5 to 10
0, especially 1.8 to 70 are preferred.

The flocculant used when associating the polymer particles in the aqueous medium is not particularly limited, but those selected from metal salts are preferably used. Specifically, as a monovalent metal, for example, a salt of an alkali metal such as sodium, potassium, and lithium, and as a divalent metal, for example, a salt of an alkaline earth metal such as calcium and magnesium, or a divalent metal such as manganese or copper And salts of trivalent metals such as iron and aluminum. Specific examples of the salt include sodium chloride, potassium chloride, lithium chloride,
Examples thereof include calcium chloride, zinc chloride, copper sulfate, magnesium sulfate, and manganese sulfate. These may be used in combination.

It is preferable that these coagulants are added at a concentration higher than the critical coagulation concentration. The critical aggregation concentration is an index relating to the stability of the aqueous dispersion, and indicates the concentration at which aggregation occurs when a coagulant is added. This critical aggregation concentration is
It varies greatly depending on the emulsified component and the dispersant itself. For example, Seizo Okamura et al.
7, 601 (1960), edited by The Society of Polymer Science, Japan, and the like, and a detailed critical aggregation concentration can be determined.
As another method, a desired salt is added to the target particle dispersion at a different concentration, the 、 (zeta) potential of the dispersion is measured, and the salt concentration at which this value changes is defined as the critical aggregation concentration. You can also ask. The amount of the coagulant to be added may be at least the critical coagulation concentration, but is preferably at least 1.2 times, more preferably at least 1.5 times the critical coagulation concentration.

As the "solvent infinitely soluble in water" used together with the coagulant, a solvent which does not dissolve the polymer to be formed is selected. Specific examples include alcohols such as methanol, ethanol, propanol, isopropanol, t-butanol, methoxyethanol and butoxyethanol, nitriles such as acetonitrile, and ethers such as dioxane. Particularly, ethanol, propanol and isopropanol are preferred. The addition amount of the solvent infinitely soluble in water is preferably 1 to 100% by volume based on the polymer-containing dispersion to which the flocculant has been added. In order to make the particle shape uniform, it is preferable to prepare a colored particle, and after the filtration, it is preferable to fluidly dry a slurry in which 10% by mass or more of water is present with respect to the particle. Those having a polar group therein are preferred. It is considered that the reason for this is that the existing water exerts an effect of slightly swelling the polymer in which the polar group is present, so that the shape is particularly easily uniformized.

The toner of the present invention has the above-mentioned constitution, but can contain various additives as required, for example, a charge control agent. Further, an external additive composed of organic fine particles or the like can be added.

The black toner of the present invention may contain a black colorant as long as the conditions for the above colorant are satisfied. As the black colorant, carbon black, a magnetic substance, a dye, a pigment and the like can be arbitrarily used. As the carbon black, channel black, furnace black, acetylene black, thermal black, lamp black and the like are used. As the magnetic material, ferromagnetic metals such as iron, nickel and cobalt, alloys containing these metals, compounds of ferromagnetic metals such as ferrite and magnetite, alloys which do not contain ferromagnetic metals but show ferromagnetism by heat treatment, For example, alloys of a type called a Heusler alloy such as manganese-copper-aluminum and manganese-copper-tin, chromium dioxide, and the like can be used.
This black colorant varies depending on the type thereof, but is preferably used at a ratio of 5 to 45% by mass with respect to all the chromatic colorants.

The charge control agent is, among various known ones,
Those that can be dispersed in water are preferably used. Specific examples include a nigrosine dye, a metal salt of naphthenic acid or a higher fatty acid, an alkoxylated amine, a quaternary ammonium salt compound, an azo metal complex, a metal salt of salicylic acid, and a metal complex thereof.

When the toner of the present invention is used by adding fine particles such as inorganic fine particles and organic fine particles as an external additive, the effect can be surely exhibited. It is presumed that the reason for this is that the embedding and detachment of the external additive from the toner particles can be effectively suppressed, so that the effect appears remarkably. As the above-mentioned inorganic fine particles, inorganic oxide particles such as silica, titania, and alumina are preferable, and these inorganic fine particles are preferably subjected to a hydrophobic treatment with a silane coupling agent, a titanium coupling agent, or the like. The amount of the external additive added to the toner is
It is 0.1 to 5.0% by mass, preferably 0.5 to 4.0% by mass. Various external additives may be used in combination.

The toner of the present invention is used as a one-component magnetic toner containing a magnetic material, for example, when used as a two-component developer by mixing with a so-called carrier, or when a non-magnetic toner is used alone. Any of them can be suitably used, but in the present invention, it is preferable to use as a two-component developer to be used by mixing with a carrier.

<Developing Method> The developing method using the toner of the present invention is not particularly limited. The volume average particle diameter of the carrier that can be used as a two-component developer is 15 to 100.
μm, more preferably 25 to 60 μm. The volume average particle size of the carrier is typically measured by a laser diffraction type particle size distribution analyzer “HEROS (HE) equipped with a wet disperser.
LOS) "(manufactured by SYMPATEC). The carrier is preferably a resin-coated carrier or a so-called resin-dispersed carrier in which magnetic particles are dispersed in a resin. The resin composition for coating is not particularly limited,
For example, an olefin resin, a styrene resin, a styrene / acrylic resin, a silicone resin, an ester resin, a fluorine-containing polymer resin, or the like is used. The resin for constituting the resin dispersion type carrier is not particularly limited, and known resins can be used.
For example, styrene acrylic resin, polyester resin, fluorine resin, phenol resin, and the like can be used.

<Image Forming Apparatus and Image Forming Method> FIG.
1 is a schematic configuration diagram illustrating an example of an image forming apparatus for forming a full-color image using the black toner of the present invention. The image forming apparatus is provided with first, second, third and fourth image forming parts Pa, Pb, Pc and Pd. Each image forming unit has the same configuration, and forms toner images of different colors.

More specifically, the image forming units Pa, Pb,
Pc and Pd are dedicated latent image carriers, specifically, electrophotographic photosensitive drums 1la, 1lb, 1lc, and 11l
d. Each image forming unit Pa, Pb, Pc and Pd
Electrophotographic photosensitive drums 1la, 1lb, 1
The toner images of the respective colors on lc and 1ld are carried on a recording material carrier 20 that moves adjacent to each image forming unit and are conveyed by an image forming support (hereinafter also referred to as “recording material”) 60.
1 is transferred. Further, the toner image transferred and formed on the recording material 601 is overheated and pressed by the fixing device 70 to be fixed. Then, the recording material 601 on which the image is formed is discharged to the tray 61.

Next, the latent image forming section in each image forming section will be described. Photosensitive drums 1la, 1lb, 1lc,
On the outer circumference of 1 ld, there are provided charge removing exposure lamps 12 la and 12 l.
b, 12lc, 12ld, drum chargers 12a, 12
b, 12c, 12d, laser beam exposure device 17 as image exposure means, potential sensors 122a, 122b, 12
2c and 122d are provided. Static elimination exposure lamp 12
The photosensitive drums 1la, 1lb, 1lc, 1ld, which have been neutralized by la, 12lb, 12lc, 12ld, are uniformly charged by the drum chargers 12a, 12b, 12c, 12d and then exposed by the laser beam exposure device 17. As a result, the photosensitive drums 1la, 1lb, 1l
On c and 1ld, an electrostatic latent image that is color-separated according to an image signal is formed. In the image forming apparatus of the present invention, as the image exposing means, in addition to the above-described laser beam exposing device 17, an LED array exposing device or the like has a plurality of light levels other than off in a basic image unit (pixel). A well-known multi-value exposure means capable of irradiating the light can be suitably used.

The electrostatic latent image on the photosensitive drum is developed by developing means to be a toner image of each color. In other words, the developing means includes a plurality of developing devices 13a, 13b, 13a each filled with a predetermined amount of the above-described developer including a yellow toner, a magenta toner, a cyan toner, or a black toner.
c, 13d, and the photosensitive drums 1la, 1
The electrostatic latent images formed on lb, 1lc, and 1ld are developed to form toner images of different colors. here,
The black toner of the present invention is used in the developing device 13d related to the last photosensitive drum 1ld.

Next, the transfer section will be described. The recording material 601 held in the recording material cassette 60 is fed to the recording material carrier 20, which is an intermediate transfer member, via the registration roller 18.

Here, the recording material carrier 20 is a film made of a dielectric resin such as a polyethylene terephthalate resin film sheet (PET sheet), a polyvinylidene fluoride resin film sheet or a polyurethane resin film sheet. An endless shape or a seamless belt having no seams is used. In the case of a belt having a seam, it is preferable to provide a means (not shown) for detecting a seam position so that transfer is not performed on the seam.

When the recording material carrier 20 starts to rotate,
The recording material is conveyed from the registration roller 18 onto the recording material carrier 20. At this time, the image writing signal is turned ON, and a toner image is formed on the first photosensitive drum 1la at a certain timing.

A transfer charger 14a and a transfer pressing member 141a are provided below the first photosensitive drum 1la. The transfer pressing member 14la applies a uniform pressing force toward the photosensitive drum 11a. When the transfer charger 14a applies an electric field, the toner image on the photosensitive drum 1la is transferred onto the recording material 601. At this time, the recording material 601 is
The sheet is held on the recording material carrier 20 by electrostatic attraction, and is conveyed to the second image forming unit Pb.

The second, third, and fourth image forming units Pb,
Regarding Pc and Pd, similarly to the first image forming unit Pa,
Below the photosensitive drums 11b, 11c, 11d, transfer chargers 14b, 14c, 14d and transfer pressing members 141b,
41c and 141d are provided, respectively. And
In the same manner as described above, the toner images of the respective colors formed on the second, third, and fourth photosensitive drums 1lb, 11c, and 11d are sequentially transferred, and the toner layers are stacked (colored) on the recording material 601. Overlapping) is performed. The recording material 601 on which the toner images of all colors have been transferred is discharged by the separation charger 19, detaches from the recording material carrier 20 due to the attenuation of the electrostatic attraction force, and is conveyed to the fixing device 70.

The fixing device 70 includes a heating roller 701, a pressure roller 702, and a heat-resistant cleaning member 70 for cleaning these rollers 701 and 702, respectively.
3, 704, heaters 705, 706 for heating the respective rollers 701, 702, an oil application roller 707 for applying a release agent oil such as polydimethyl silicone to the heating roller 701, and an oil reservoir for supplying the oil. 708, a thermistor 709 for fixing temperature control.

After the transfer step, the photosensitive drums 1la, 1lb,
The developer remaining on 1lc and 1ld is removed by the photoreceptor cleaning units 15a, 15b, 15c and 15d, and is prepared for the subsequent latent image formation. The developer remaining on the recording material carrier 20 is transferred to the belt neutralizer 16.
After removing the electrostatic attraction force, the cleaning device 21 having a nonwoven fabric in this example removes the electrostatic attraction force. As the cleaning device 21, for example, a rotating fur brush, a blade, or a device using these in combination is used.

<Fixing Device> In the image forming method using the black toner of the present invention, a so-called contact heating method is used as a fixing method. Specific examples include a heat-pressure fixing method, a heat-roll fixing method, and a pressure-contact heat fixing method in which fixing is performed by a rotating pressing member including a fixedly disposed heating element.

FIG. 3 is a sectional view showing an example of a fixing device using a hot roll fixing method. This fixing device includes a heating roller 701 and a pressure roller 702 that contacts the heating roller 701. T is a toner image formed on a transfer paper as an image forming support.

The heating roller 701 has a coating layer 712 made of an elastic body or a fluororesin formed on the surface of a metal core 713, and includes a heating member 714 made of a linear heater. The core metal 713 is made of metal and has an inner diameter of 10 to 70 mm. The metal constituting the metal core is not particularly limited, but examples thereof include metals such as iron, aluminum and copper or alloys thereof. The thickness of the core is 0.1 to 15 mm,
Specifically, it is determined in consideration of the balance between the thinning in response to the demand for energy saving and the strength depending on the constituent materials. For example, the same strength as that of a 0.57 mm iron core is used for the aluminum core. To hold in gold,
Its thickness needs to be 0.8 mm.

Further, as the fluororesin constituting the coating layer 712, PTFE (polytetrafluoroethylene) and PFA (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer) can be used. The thickness of the coating layer made of fluororesin is 10 to 500.
μm, and preferably 20 to 400 μm. If the thickness of the coating layer made of fluororesin is less than 10 μm, the function as the coating layer cannot be sufficiently exhibited, and the durability as a fixing device cannot be secured. On the other hand, there is a problem that the surface of the coating layer having a thickness of more than 500 μm is easily scratched by paper dust, and toner or the like adheres to the scratched portion, thereby causing image stains.

As the elastic body constituting the coating layer 712,
It is preferable to use silicone rubber and silicone sponge rubber having good heat resistance such as LTV, RTV, and HTV. In this case, the Asker C hardness of the elastic body constituting the coating layer is less than 80 °, preferably 60 °.
° and the thickness of the coating layer 712 is 0.1 to 30 mm
And preferably 0.1 to 20 mm. When the Asker C hardness of the elastic body constituting the coating layer exceeds 80 °, or when the thickness of the coating layer is less than 0.1 mm, the fixing nip cannot be increased, and the effect of soft fixing is not achieved. (The effect of improving the color reproducibility by the toner layer at the smoothed interface) cannot be exhibited.

As the heating member 713, a halogen heater can be preferably used. The number of the heating members is not particularly limited, and a plurality of heating members can be provided. Thereby, the heat distribution area can be changed according to the size (width) of the transfer paper passing therethrough.

The heating roller 701 shown in FIG. 4 has a central halogen heater 714A for heating the central area,
Edge halogen heater 714 for heating the edge region
B and 714C. When fixing is to be performed on a narrow image forming support, only the central halogen heater 714A is turned on. When fixing is to be performed on a wide image forming support, the central halogen heater 714A and an end Halogen heater 714B
And all of the halogen heaters 714C are energized.

The pressure roller 702 has a coating layer 722 made of an elastic material formed on the surface of a cored bar 721. The elastic body constituting the coating layer 722 is not particularly limited, and examples thereof include various soft rubbers such as urethane rubber and silicone rubber, and sponge rubbers, for example, having good heat resistance such as LTV, RTV, and HTV. It is preferable to use a suitable silicone rubber and silicone sponge rubber. The material constituting the cored bar 721 is not particularly limited, but may be a metal such as aluminum, iron, or copper, or an alloy thereof. In the fixing device of FIG. 3, the pressure roller 702 is not provided with a heating member.

The elastic material constituting the coating layer 722 has Asker C hardness of less than 80 °, preferably less than 60 °, and the thickness of the coating layer 22 is 0.1 to 30 mm, preferably 0.1 to 30 mm. ２０20 mm. If the Asker C hardness of the elastic body constituting the coating layer exceeds 80 °, and if the thickness of the coating layer is less than 0.1 mm, the fixing nip cannot be increased, and the effect of soft fixing may be reduced. Can not demonstrate.

The contact load (total load) between the heating roller 701 and the pressure roller 702 is usually 40 to 350 N, preferably 50 to 300 N, and more preferably 50 to 300 N.
２５０250N. This contact load is applied to the heating roller 70.
The strength is determined in consideration of the strength of 1, that is, the thickness of the core bar 713. For example, in the case of a heating roller having a core bar made of 0.3 mm iron, the heating roller is preferably 250 N or less.

Further, from the viewpoint of offset resistance and fixing property, the nip width is preferably 4 to 10 mm, and the surface pressure of the nip is 0.6 × 10 ⁵ Pa to 1.5.
It is preferably × 10 ⁵ Pa.

An example of the fixing conditions by the fixing device shown in FIG. 3 is as follows. Fixing temperature (surface temperature of heating roller 701)
Is 150 to 210 ° C., and the fixing linear velocity is 80 to 640 m.
m / sec.

The fixing device used in the present invention may be provided with a cleaning mechanism as needed. In this case, as a method of supplying the silicone oil to the upper roller (heating roller) of the fixing unit, a method of supplying and cleaning with a pad, a roller, a web, or the like impregnated with the silicone oil can be used. High heat-resistant silicone oils are used, such as polydimethyl silicone,
Polyphenylmethyl silicone, polydiphenyl silicone and the like are used. Since those having a low viscosity have a large outflow during use, the viscosity at 20 ° C. is 1 to 10
Those having 0 Pa · s are preferably used.

The present invention is remarkably exhibited when an image is formed without supplying the silicone oil or using a fixing device having a very small amount of the supplied silicone oil. Even when silicone oil is supplied, it is preferable that the supply amount is 2 mg or less for an A4 size recording material. By setting the supply amount of the silicone oil to 2 mg / A4 or less, the amount of the silicone oil adhering to the transfer paper (image forming support) after fixing is reduced, making it difficult to fill in the transfer paper with the silicone oil using a ballpoint pen or the like. There is no loss of rewriting. Further, it is possible to avoid problems such as deterioration of the offset resistance with time due to deterioration of the silicone oil and contamination of the optical system and the electrodes by the silicone oil.

Here, the supply amount of the silicone oil is transferred to the fixing device (between the rollers) heated to a predetermined temperature by the transfer paper (A4).
This is an amount (Δw / 100) calculated by measuring a change in mass (Δw) of the fixing device before and after passing 100 sheets of white paper (size white paper) continuously.

The black toner of the present invention has been described above mainly on the case where a full-color image is formed using the black toner. However, the black toner of the present invention may be used for forming a so-called monochrome image which is not a color image. Can be.

<Examples> (Preparation Example 1 of Latex) Dodecyl sulfone, an anionic activator previously prepared, was placed in a 5000 ml separable flask equipped with a stirrer, a temperature sensor, a condenser, and a nitrogen introducing device. Sodium acid salt (SDS) 7.
A solution consisting of 08 g and 3010 g of ion-exchanged water was added.

The temperature inside the reaction vessel was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream. Meanwhile, a monomer solution comprising 70.1 g of styrene, 19.9 g of n-butyl acrylate and 10.9 g of methacrylic acid was prepared. Then, 9.2 g of potassium persulfate (KPS) as a polymerization initiator was added to 200 g of ion-exchanged water.
Was added thereto, and then the temperature was raised to 75 ° C., the monomer solution was added dropwise in 1 hour, and the mixture was heated and stirred at 75 ° C. for 2 hours to produce latex particles. The process up to this point is referred to as “HP step”, and the obtained latex particles are referred to as “latex HP”.

Separately, 105.6 g of styrene and 30.0 g of n-butyl acrylate were placed in a flask having a stirrer.
g, a solution of 6.4 g of methacrylic acid and 5.6 g of n-octyl-3-mercaptopropionate in a solution of 72.0 g of a fixing improver consisting of Exemplified Compound (19) at 80 ° C.
And heated to dissolve. And 1.6 g of SDS is 27
The solution dissolved in 00 ml of water was heated to 80 ° C., and the latex HP obtained in the above-mentioned HP step was converted to a solid content of 2%.
8 g, and a solution obtained by adding a fixing improver to the above monomer is mixed and dispersed by a mechanical disperser (manufactured by CLEARMIX) having a circulation path to the SDS aqueous solution, and contains emulsified particles having a uniform dispersed particle diameter. An emulsion was prepared. Subsequently, a solution in which 5.1 g of KPS as a polymerization initiator was dissolved in 240 ml of ion-exchanged water was added to the dispersion having the latex HP, and 750 ml of water was further added.
The mixture was heated to 80 ° C. and reacted at 80 ° C. for 3 hours to prepare a latex in which an intermediate molecular weight substance was encapsulated using a high molecular weight substance as a core. This step is referred to as “MP step”.

Further, 7.4 g of KPS was added to this latex.
Was dissolved in 200 ml of water, and 300 g of styrene and 95% of butyl acrylate were kept at 80 ° C.
g, 15.3 g of methacrylic acid and n-octyl-3-
A solution containing 10.4 g of mercaptopropionate was added dropwise over 1 hour. And it was made to react for 2 hours, and the target latex particle was obtained. This reaction step is referred to as “LP step”, and the latex particles are referred to as “latex 1”.

<Latex 2> In a flask having a stirrer, 105.6 g of styrene, 30.0 g of n-butyl acrylate, 6.4 g of methacrylic acid and 72.0 g of a fixing improver composed of Exemplified Compound (19) were heated to 80 ° C. Heated to dissolve. Next, 1.6 g of SDS was added to 2700 m
The solution dissolved in 1 l of water is heated to 80 ° C.
28 g of the latex HP obtained in the step is added in an amount equivalent to the solid content, and a solution obtained by adding a fixing improver to the above monomer is mixed and dispersed in the SDS aqueous solution by a mechanical disperser having a circulation path (manufactured by CLEARMIX). Thus, an emulsion containing emulsified particles having a uniform dispersed particle diameter was prepared.

Subsequently, a solution obtained by dissolving 5.1 g of KPS as a polymerization initiator in 240 ml of ion-exchanged water was added to the dispersion containing the latex particles.
The mixture was heated to 80 ° C. and reacted at 80 ° C. for 3 hours to prepare a latex in which a high molecular weight substance was used as a core and an intermediate molecular weight substance was encapsulated. This step is referred to as “HP step”. Further, a solution of 14.8 g of KPS dissolved in 400 ml of water was added to this latex, and while keeping at 80 ° C., 600 g of styrene and 190 g of butyl acrylate were added.
g, 30 g of methacrylic acid and 20.8 g of n-octyl-3-mercaptopropionate were added dropwise over 1 hour. And it was made to react for 2 hours, and the target latex particle was obtained. This reaction process is called "LP
This step is referred to as “latex 2”.

<Preparation of Colored Particles Bk>"Colorant dispersion Bk1" 5.9 g of sodium n-dodecyl sulfate was dissolved in 160 ml of ion-exchanged water with stirring. C. As a red colorant, C.I. I. Pigment Red 122 and C.I. I. Pigment Green 7 and 12.6 g of Pigment Green 7 were gradually added, and dispersed using a mechanical dispersing machine (manufactured by CLEARMIX). The particle size of this dispersion was measured using a laser diffraction particle size analyzer SALD-1000 (manufactured by Shimadzu Corporation), and as a result, it was 150 nm in weight average. This dispersion is referred to as “colorant dispersion Bk1”.

<Colorant dispersion Bk2>"Colorant dispersion Bk2"
1), 14.3 g of Pigment Red 48: 3 as a red colorant and C.I. as a green colorant as chromatic colorants. I. Pigment Green 2 11.5
"Colorant dispersion Bk2" was obtained in the same manner as "Colorant dispersion Bk1" except that g was used. As a result of measuring the particle size of the dispersion, the weight average was 161 nm.

"Adhesive Dispersion Bk3""Colorant Dispersion Bk"
In the preparation of “1”, except that as a chromatic colorant, 14.1 g of a blue colorant, Pigment Blue 15: 3, and 12.6 g of an orange colorant, Pigment Orange 43, were used. "Colorant dispersion Bk3" in the same manner as "agent dispersion Bk1". As a result of measuring the particle size of the dispersion, the weight average was 148 nm.

"Colorant dispersion Bk4""Colorant dispersion B
In the preparation of “k1”, except that 7.8 g of Pigment Violet 19, which is a purple colorant, and 9.8 g of Pigment Yellow 180, which is a yellow colorant, were used as chromatic colorants. "Colorant dispersion Bk4" was obtained in the same manner as in "Liquid Bk1". As a result of measuring the particle size of the dispersion, the weight average was 198 nm.

"Colorant Dispersion Bk5""Colorant Dispersion B
In the preparation of “k1”, 10.2 g of Pigment Red 57: 1 as a red colorant and C.I. I. Pigment Green 10-1
"Colorant dispersion Bk5" was obtained in the same manner as "Colorant dispersion Bk1", except that 0.0 g and 1.8 g of titanium black were used. As a result of measuring the particle size of the dispersion,
The weight average was 220 nm.

In the preparation of “Comparative Colored Dispersion Bk1” and “Colored Dispersion Bk1”, as a chromatic colorant, C.I. I. Solvent Yellow 93-1
0.9 g, Pigment Red 4 which is a magenta colorant
"Comparative colorant dispersion Bk1" in the same manner as "colorant dispersion Bk1", except that 10.9 g of 8: 3 and 9.5 g of pigment blue 15: 3 as a cyan colorant were used. I got it.

"Comparative Colored Dispersion Bk2""Comparative Colored Dispersion Bk1" is the same as "Colorant Dispersion Bk1" except that 42.0 g of carbon black was used as a colorant and no chromatic colorant was added. Agent dispersion Bk2 "was obtained.

(Production Example 1 of Toner) 420.7 g corresponding to the solid content of “latex 1” described above and 90 parts of ion-exchanged water
0 ml and 351 g of “colorant dispersion Bk1”
The mixture was stirred in a 5-liter four-necked flask equipped with a temperature sensor, a cooling tube, a nitrogen introducing device, and a stirring device. After adjusting the temperature to 30 ° C., a 5N aqueous sodium hydroxide solution was added to the solution to adjust the pH to 11.0. Then
12.1 g of magnesium chloride hexahydrate was added to deionized water 1
The aqueous solution dissolved in 000 ml was added with stirring at 30 ° C. for 10 minutes. Thereafter, after standing for 3 minutes, the temperature was raised, and the temperature was raised in 6 minutes until the liquid temperature reached 90 ° C (heating rate: 10 ° C / min). In this state, the particle size of the produced polymer particles is
When the volume average particle size becomes 5.5 μm or more, 80.4 g of sodium chloride is added to 100 parts of ion-exchanged water.
An aqueous solution dissolved in 0 ml was added to stop the particle growth, and the salting-out / fusion was continued by changing the liquid temperature in the range of 80 to 95 ° C and changing the stirring time from 1 hour to 10 hours. Was. Then, at a rate of 8 ° C./min.
After cooling to ° C., hydrochloric acid was added to adjust the pH to 2.0, and the stirring was stopped. The resulting colored particles were filtered, washed repeatedly with ion-exchanged water, then dried at a suction air temperature of 60 ° C. using a flash jet drier, and then dried at a temperature of 40 ° C. using a fluidized bed drier. .
0.8 parts by weight of silica fine particles were externally added and mixed with 100 parts by weight of the obtained colorant particles using a Henschel mixer to obtain a black toner.

(Toner Production Example 2) (Toner Production Example 1) except that “Colorant Dispersion Bk2” was used instead of “Colorant Dispersion Bk1” in (Toner Production Example 1).
"Toner 2" was obtained in the same manner as described above.

(Toner Production Example 3) (Toner Production Example 1) except that “Colorant Dispersion Bk3” was used instead of “Colorant Dispersion Bk1” in (Toner Production Example 1).
"Toner 3" was obtained in the same manner as described above.

(Toner Production Example 4) In (Toner Production Example 1), “latex 2” was used instead of “latex 1”, and “colorant dispersion Bk4” was used instead of “colorant dispersion Bk1”. (Toner Production Example 1)
"Toner 4" was obtained in the same manner as described above.

(Toner Production Example 5) In (Toner Production Example 1), “latex 2” was used instead of “latex 1”, and “colorant dispersion Bk5” was used instead of “colorant dispersion Bk1”. (Toner Production Example 1)
"Toner 5" was obtained in the same manner as described above.

(Production Example 6 of Toner) In this example, polymer particles are prepared by a suspension polymerization method. 165 g of styrene, 35 g of n-butyl acrylate, C.I.
I. Pigment Red 122 and C.I. I. Pigment Green 7, 5.2 g of metal di-t-butylsalicylate, 8 g of styrene-methacrylic acid copolymer, and paraffin wax (mp: 70 ° C.)
Is heated to 60 ° C. and uniformly dissolved at 12000 rpm with a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.).
Dispersed. To this, 10 g of 2,2′-azobis (2,4-valeronitrile) as a polymerization initiator was added and dissolved to prepare a polymerizable monomer composition. Next, 450 g of a 0.1 M sodium phosphate aqueous solution was added to 710 g of ion-exchanged water.
Was added, and 68 g of 1.0 M calcium chloride was gradually added while stirring at 13000 rpm with a TK homomixer to prepare a suspension in which tricalcium phosphate was dispersed.
The polymerizable monomer composition was added to the suspension, and the mixture was stirred with a TK homomixer at 10,000 rpm for 20 minutes to granulate the polymerizable monomer composition. Thereafter, the reaction was performed at 75 to 95 ° C. for 5 to 15 hours using a reactor having a stirring blade. Tricalcium phosphate was dissolved and removed with hydrochloric acid, and then classified in a liquid by a centrifugal sedimentation method using a centrifuge, followed by filtration, washing, and drying. To 100 parts by weight of the obtained colored particles, 1 part by weight of silica fine particles was externally added and mixed with a Henschel mixer to obtain a toner by a suspension polymerization method. This is referred to as “toner 6”.

(Toner Production Example 7) In this example, polymer particles are prepared by a pulverization method. 3. 100 parts by weight of styrene acrylic resin and Pigment Red 57: 1.
8 parts by weight, C.I. I. Pigment Green 7 and 4.0 parts of a fixing improver consisting of Exemplified Compound (9).
Parts by weight with a Henschel mixer, melt-kneaded with a twin-screw extruder, pulverized with a jet mill, and classified with an airflow classifier, and then 0.8 parts by weight of hydrophobic silica with a Henschel mixer. To obtain “Toner 7” by a pulverization method.

(Production Example 1 of Comparative Toner) Production Example 1 of Toner
Of Comparative Example 1, except that “Comparative Colorant Dispersion Bk1” was used instead of “Colorant Dispersion Bk1”, to obtain Comparative Toner 1 in the same manner as in Toner Production Example 1. (Comparative Toner Production Example 2)
Comparative toner 2 was obtained in the same manner as in Toner Production Example 1, except that “Comparative colorant dispersion Bk2” was used instead of “Colorant dispersion Bk1”.

<Evaluation> For each of the toners prepared as described above, a ferrite carrier whose surface was coated with a silicone resin and having a volume average particle diameter of 60 μm was used so that the final toner concentration was 6%. After mixing, a high-speed printer "Stios7075" (manufactured by Konica Corporation)
Of the photoconductor cleaning in the high-speed printer was evaluated by using the modified model No. 1. The conditions are as shown below. Use a laminated organic photoreceptor as the photoreceptor,
In addition, a blade cleaning method was used for cleaning the photoconductor.

Movement speed of photosensitive drum surface: 135 mm / sec. Photosensitive drum surface potential (dark potential): -500 V. Photosensitive drum surface potential (light potential): -100 V. DC bias: -400 V. AC bias: 2 kV. Frequency of AC part: 12 kHz • Repetition frequency of two frequencies: 1.5 kHz • Peripheral surface speed ratio of developing sleeve to photosensitive drum: 1.
7. The amount of the developer in the developing area: 40 mg / cm ²

As the fixing method, a pressure fixing type heat fixing device shown in FIG. 3 was used. Specifically, this fixing device has a 25 μm-thick PFA on a surface of a cylindrical aluminum alloy core bar having an inner diameter of 70 mm, a thickness of 15.0 mm, and a total width of 310 nm.
A coating layer formed by the tube is formed,
A heating roller (701) in which a heater is disposed, and a 7 mm thick steel core having an inner diameter of 60 mm and a wall thickness of 8.0 mm.
and a pressure roller (702) on which a coating layer of silicone rubber (Asker C hardness of 62 mm) is formed, and the nip portion is 12.8 mm. In this fixing device, the printing linear velocity was set to 380 mm / sec.
As a cleaning mechanism of this fixing device, polydiphenyl silicone (having a viscosity of 10 Pa · s at 20 ° C.)
Was used, and the amount of silicone oil applied was 0.6 mg / A4.

[Evaluation of Characteristics] According to the above conditions, 2 million copies of a black solid image, a halftone image with an image density of 0.4, and a white background image were continuously made in a high-temperature and normal-humidity environment (33 ° C./50% RH). After printing, the maximum image density of the solid image and the density of fog on a white background were measured with a Macbeth reflection densitometer. “Durability” is the number of sheets at which the maximum image density is less than 1.2, and “Fog” is 0.0
The smaller number of the sheets having more than 1 was recorded. The “transfer rate” was obtained by forming an image of 60 mg / cm ² on the photoreceptor and measuring the amount of adhesion per unit area transferred to recording paper as a transfer agent. When it is 80% or more, the uniformity of the image density becomes firm and good.

The texture of the solid image and the texture of the halftone were visually determined. Among the 20 judged persons, "A" indicates that the number of persons who have excellent texture is 15 or more, "B" indicates that the number of persons is 10 or more, and 3 persons. Those that were less than were rated "C". The evaluation of the tint was visually determined. The fixing rate was obtained by collecting a 1-inch square solid image having an adhesion amount of 0.6 mg / cm ² ,
It was determined from the image density before and after peeling with a Scotch mending tape (manufactured by Sumitomo 3M). That is, fixing rate = (image density after peeling / image density before peeling) × 100 [%]. Those having a fixing rate of 80% or more were judged to have acceptable performance. The results are shown in Table 1, and the external constitution of each toner is shown in Table 2.

[0146]

[Table 1]

[0147]

[Table 2]

[0148]

According to the present invention, there is provided a black toner for developing an electrostatic latent image suitably used for forming a visible image, especially a full-color image, wherein the number of kinds of chromatic colorants contained, the content ratio thereof and When the method for producing the black toner satisfies specific conditions, a high-quality visible image, particularly a color image, having excellent black reproducibility and fine line reproducibility can be stably formed. That is, 80% by mass thereof
By using a black toner in which the above-mentioned portion is composed of two kinds of chromatic colorants, no color rendering property appears in an image to be formed and the stability of blackness is improved. , An image having a certain color tone can be obtained.

In addition, since the above-mentioned black toner for developing an electrostatic latent image is obtained by polymerizing a polymerizable monomer in an aqueous medium, toner particles having a small diameter can be obtained. And the image quality of the reproducibility of fine lines and dots can be improved.

In the black toner, the number of kinds of chromatic colorants contained, the content ratio thereof, and the manufacturing method thereof are specified, and the external structure (shape / particles) of the black toner itself is specified. With a specific diameter or the like, a high-quality visible image, particularly a color image, having excellent black reproducibility and fine line reproducibility can be stably formed. That is, the black toner composed of toner particles having a shape coefficient variation coefficient of 16% or less and a number variation coefficient in the number particle size distribution of 27% or less provides excellent developability and transferability. . Further, the charge amount distribution in the toner becomes sharp, and the chargeability between the toner particles of each color can be made uniform. As a result, the adhesion to the image forming support between the toner particles of each color becomes uniform. be able to.

[Brief description of the drawings]

FIG. 1A is an explanatory view showing a projected view of a toner particle having no corner, and FIGS. 1B and 1C are explanatory views showing a projected view of a toner particle having a corner.

FIG. 2 is a schematic configuration diagram illustrating an example of an image forming apparatus for performing the image forming method of the present invention.

FIG. 3 is a cross-sectional view illustrating an example of a fixing device using a hot roll fixing method.

FIG. 4 is an explanatory diagram illustrating an example of an arrangement of a halogen heater in a heating roller of a fixing device.

[Explanation of symbols]

Pa, Pb, Pc, Pd Image forming units 1la, 1lb, 1lc, 1d Photosensitive drums 12a, 12b, 12c, 12d Drum chargers 12la, 12lb, 12lc, 12ld Static elimination exposure lamps 122a, 122b, 122c, 122d Potential sensor 13a, 13b, 13c, 13d Developing devices 14a, 14b, 14c, 14d Transfer chargers 141a, 141b, 141c, 141d Transfer pressing members 15a, 15b, 15c, 15d Photoconductor cleaning unit 16 Belt eliminator 17 Laser beam exposure device 18 Registration roller 19 Separation Charger 20 Recording Material Carrier 21 Cleaning Device 60 Recording Material Cassette 601 Recording Material 61 Tray 70 Fixing Device 701 Heating Roller 702 Pressure Roller 703, 704 Cleaning Member 705, 706
Heater 707 Oil application roller 708 Oil reservoir 709 Thermistor 712 Coating layer 713 Core 714 Heating member 714A Central halogen heater 714B and 714C Halogen heater 721 Core metal 722 Coating layer

Claims (18)

[Claims] 1. A black toner for developing an electrostatic latent image containing at least a plurality of chromatic colorants, wherein 80% by mass or more of the chromatic colorant is composed of two types of chromatic colorants. Characteristic black toner for developing electrostatic latent images. 2. The electrostatic latent image developing black toner according to claim 1, wherein the two chromatic colorants have a complementary color relationship with each other. 3. The black toner for developing an electrostatic latent image according to claim 1, wherein the two types of chromatic colorants comprise a green colorant and a red colorant. 4. The black toner for developing an electrostatic latent image according to claim 1, wherein the two chromatic colorants comprise a blue colorant and an orange colorant. 5. The black toner for developing an electrostatic latent image according to claim 1, wherein the two kinds of chromatic colorants comprise a violet colorant and a yellow colorant. 6. A black toner for developing an electrostatic latent image containing at least a plurality of chromatic colorants, obtained by polymerizing at least a polymerizable monomer in an aqueous medium. A black toner for developing an electrostatic latent image according to claim 5. 7. The method according to claim 1, wherein polymer particles obtained by polymerizing at least a polymerizable monomer in an aqueous medium and the plurality of chromatic colorants are associated in an aqueous medium. 7. The black toner for developing an electrostatic latent image according to 6. 8. The chromatic colorant according to claim 1, wherein the chromatic colorant is
8. The black toner for developing an electrostatic latent image according to claim 6, wherein the black toner is used as a chromatic colorant dispersion liquid dispersed so as to have a particle size in a range of from about 600 nm to about 600 nm. 9. The electrostatic element according to claim 6, wherein a variation coefficient of the shape factor is 16% or less, and a number variation coefficient in the number particle size distribution is 27% or less. Black toner for developing latent images. 10. The electrostatic device according to claim 6, wherein a ratio of toner particles having a shape factor in a range of 1.0 to 1.6 is 65% by number or more. Black toner for developing latent images. 11. The electrostatic device according to claim 6, wherein the proportion of toner particles having a shape factor in the range of 1.2 to 1.6 is 65% by number or more. Black toner for developing latent images. 12. The electrostatic latent image developing black toner according to claim 6, wherein the ratio of the toner particles having no corners is 50% by number or more. 13. When the particle size of the toner particles is D (μm), the natural logarithm lnD is plotted on the horizontal axis, and the horizontal axis is 0.2.
In the histogram showing the number-based particle size distribution divided into a plurality of classes at three intervals, the relative frequency (m1) of the toner particles included in the most frequent class and the toner included in the class having the second highest frequency after the most frequent class The sum (M) of the relative frequency (m2) of the particles is 70% or more.
A black toner for developing an electrostatic latent image according to claim 12. 14. An electrostatic device comprising a step of polymerizing at least a polymerizable monomer in an aqueous medium to obtain a black toner for electrostatic latent image development containing at least a plurality of chromatic colorants. A method for producing a black toner for developing a latent image. 15. At least a plurality of chromatic colorants are associated by associating polymer particles obtained by polymerizing at least a polymerizable monomer in an aqueous medium with the plurality of chromatic colorants in an aqueous medium. The method for producing a black toner for developing an electrostatic latent image according to claim 14, wherein a black toner for developing an electrostatic latent image is obtained. 16. The chromatic colorant may contain 1 in an aqueous medium.
The method for producing a black toner for developing an electrostatic latent image according to claim 15, wherein the method is used as a chromatic colorant dispersion liquid dispersed in a particle size range of 0 to 600 nm. 17. An image including a step of forming a toner image by developing an electrostatic latent image and a step of fixing the toner image by a fixing device having a heating roller after transferring the toner image to an image forming support. 14. An image forming method, wherein the black toner for developing an electrostatic latent image according to claim 1 is used for developing the electrostatic latent image. 18. An image comprising a step of forming a toner image by developing an electrostatic latent image and a step of fixing the toner image by a fixing device having a heating roller after transferring the toner image to an image forming support. 14. An image forming apparatus for forming, wherein the black toner for developing an electrostatic latent image according to claim 1 is used for developing an electrostatic latent image.