JP2009192695A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method for stably forming images of high quality over a long period without any occurrence of fog in the image forming method by a direct transfer type image forming apparatus directly transferring toner images formed on an electrostatic latent image carrier on an image support. <P>SOLUTION: In the image forming method, the image support is obtained which carries the toner images by directly transferring the toner images formed by clearly imaging electrostatic latent images formed on the electrostatic latent image carrier with toner on the image support, and then the toner images are fixed on the image support. The toner contains at least coloring particles and external additive particulates. The external additive particulates consist of a composite oxide containing silicon atoms, and a titanium atoms and/or aluminum atoms. An existence rate of the silicon atoms on the surface layer is higher than that of the silicon atoms in the whole. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming method using electrophotography.

In recent years, in electrophotographic image forming methods, with the evolution of networks that can easily transmit digital data, the creation of original images has become commonplace, developing from the act of simple copying. . In the creation of this original image, formation of a high-quality image is required, and a printer that is reduced in size and weight is demanded due to circumstances such as use near a desk.
By the way, in the electrophotographic image forming method, the electrostatic latent image formed on the electrostatic latent image carrier is visualized with toner to obtain a toner image, and the toner image is transferred to the intermediate transfer member. In general, the image is transferred onto an image support such as paper and fixed to form an image.
In particular, in a full-color image forming apparatus formed using toners of four or more colors of yellow, magenta, cyan and black, this intermediate transfer method is adopted as a very preferable method from the viewpoint of easy color superposition. (For example, see Patent Document 1 and Patent Document 2).

  However, depending on such an intermediate transfer method, an intermediate transfer member is required, so that there is a problem that the apparatus becomes large.

  In order to eliminate the disadvantages of this increase in size, an image of a direct transfer system in which a toner image formed on an electrostatic latent image carrier is directly transferred onto an image support such as paper without using an intermediate transfer member. A forming apparatus has been proposed. This direct transfer type image forming apparatus has an advantage that it can be miniaturized.

  However, in the image forming apparatus adopting such a direct transfer method, the toner image is directly transferred from the electrostatic latent image carrier during the transfer, so that there is no problem when the conventional intermediate transfer member is used. There is a problem that fog occurs.

JP-A-6-27734 JP 2002-229270 A

  The present invention has been made based on the above circumstances, and an object of the present invention is to provide a direct transfer type image in which a toner image formed on an electrostatic latent image carrier is directly transferred onto an image support. An object of the present invention is to provide an image forming method capable of forming a high-quality image stably over a long period of time without causing fog in an image forming method using a forming apparatus.

As a result of detailed analysis of the fog problem that occurs when the present inventors directly transfer the toner image formed on the electrostatic latent image carrier to the image support, It was estimated that fog was generated and the fog was transferred onto the image support together with the toner image, and as a result, fog was generated in the resulting image.
In addition, since fog is not completely transferred at the time of transfer, when an image is formed by adopting an intermediate transfer method, the fog is hardly transferred by a plurality of transfer processes and can be obtained. It seems that the occurrence of fog in the image could be suppressed.

  As a result of intensive studies to solve this problem, the present inventors have found that the external additive fine particles contained in the toner are overcharged because they are made of a relatively insulating material such as silica. In order to solve the problem of fog generation in this direct transfer method, it is assumed that the toner has a low charge amount distribution and there is a toner with a low charge amount, and as a result, fog is generated. Have found that it is effective to use fine external additive particles that are not overcharged or capable of leaking overcharged charges.

In the image forming method of the present invention, a toner image formed by developing an electrostatic latent image formed on an electrostatic latent image carrier with a toner is directly transferred onto the image support to carry the toner image. In an image forming method for obtaining an image support and then fixing the toner image to the image support,
The toner contains at least colored particles and external additive fine particles,
The external additive fine particles are composed of a composite oxide containing silicon atoms and titanium atoms and / or aluminum atoms, and the abundance ratio of silicon atoms in the surface layer is greater than the abundance ratio of silicon atoms in the whole. It is also characterized by high.
Here, the composite oxide represents an oxide containing two or more kinds of metal atoms.

In the image forming method of the present invention, the image supporting member carrying the toner image is a step of visualizing the electrostatic latent image formed on the electrostatic latent image bearing member with the toner of different colors. Can be obtained by repeatedly forming a color toner image on the electrostatic latent image carrier and transferring the color toner image directly to the image support.
In the image forming method of the present invention, the image support carrying the toner image is a toner image formed by developing the electrostatic latent image formed on the electrostatic latent image carrier with toner. The step of transferring directly to the image support may be obtained by repeating the step of using a different color toner twice or more to form a color toner image on the image support.

In the image forming method of the present invention, the external additive fine particles, when the abundance ratio of silicon in the entire atom R _1, the existence ratio of silicon atoms in the surface layer and the R _2, coefficients (R ₁₎ / (R ₂ ) is preferably 0.7 or less.

In the image forming method of the present invention, the external additive fine particles preferably have a total content mass of titanium atoms and aluminum atoms larger than the content mass of silicon atoms.
The external additive fine particles preferably have a number average primary particle diameter of 20 to 200 nm.

  According to the image forming method of the present invention, the toner contains the specific external additive fine particles, and the specific external additive fine particles have an abundance ratio of silicon atoms in the surface layer of the total presence of silicon atoms. The ratio is higher than the ratio, and the occurrence of excessive charging is suppressed, which suppresses the presence of toner having a low charge amount due to a sharp charge amount distribution, resulting in fog and the like. And high-quality images can be formed stably over a long period of time.

The reason why the specific external additive fine particles contained in the toner can suppress the occurrence of fogging by suppressing excessive charging while having sufficient chargeability is presumed as follows.
That is, silica, which is an oxide of silicon atoms, has a structure that is easily charged and easily retains charges, but charges are accumulated due to the structure that easily retains charges.
On the other hand, since oxides of titanium atoms and aluminum atoms have relatively low resistance, charges can be leaked, but it is difficult to retain the charges.
The specific external additive fine particles used in the present invention have a sufficient charge-imparting ability for the colored particles because the surface layer has a large number of oxides having silicon atoms (hereinafter referred to as “silica component”) oriented. And a structure in which a relatively low resistance component such as an oxide having a titanium atom and / or an aluminum atom (hereinafter referred to as “titania and / or alumina component”) is oriented. Therefore, excessive charge generated by the silica component in the surface layer can be suppressed by leaking inside the external additive fine particles by the titania and / or alumina component present inside. It is guessed.

  Although fogging can be suppressed by using, for example, fine particles having a relatively low resistance due to metal oxides such as titanium oxide and aluminum oxide as external additive fine particles, the charge imparting ability to the colored particles constituting the toner can be suppressed. Good chargeability and fluidity cannot be obtained, such as fluctuation depending on environmental fluctuations.

  Hereinafter, the present invention will be described in detail.

(Image forming method)
In the image forming method of the present invention, a toner image formed by developing an electrostatic latent image formed on an electrostatic latent image carrier with a toner is directly transferred onto the image support to carry the toner image. In a method of obtaining an image support and then fixing the toner image to the image support, the toner contains at least colored particles and external additive fine particles, and the external additive fine particles are silicon. It is composed of a composite oxide containing atoms and titanium atoms and / or aluminum atoms, and the silicon atoms have a higher proportion of silicon atoms in the surface layer than the silicon atoms in the whole. .
Hereinafter, such external additive fine particles are also referred to as “specific external additive fine particles”.
Since the specific external additive fine particles are those in which silicon atoms are surface-oriented, the toner obtained by externally adding the colored particles to the colored particles does not cause a packing phenomenon or the like even when stored still, It exhibits excellent flow characteristics similar to that of a toner externally treated with silica.

[Specific external additive fine particles]
In specific external additive fine particles, “the presence ratio of silicon atoms in the surface layer is higher than the existence ratio of silicon atoms in the whole” means that more silicon atoms are present on the surface. Specifically, the coefficient (R ₁ ) / (R ₂ ) is less than ₁ when the abundance ratio of silicon atoms in the whole is R ₁ and the abundance ratio of silicon atoms in the surface layer is R _2. Say.
The coefficient (R ₁ ) / (R ₂ ) of the silicon atom is preferably 0.7 or less, more preferably 0.5 or less, and particularly preferably 0.25 or less.

The abundance ratio R ₁ of silicon atoms in the whole specific external additive fine particles is determined by the XRF (XRF) apparatus “XRF-1800” (Shimadzu Corporation) for the contained mass of silicon atoms, titanium atoms and / or aluminum atoms in the whole. ) And calculated as a mass fraction.
Specifically, the following steps (1) to (3) are performed.
(1) First, as a sample for preparing a calibration curve, a known amount of silicon dioxide is added to 100 parts by mass of styrene powder to produce a pellet for measuring silicon atoms. Similarly, a known amount of oxidation is added to 100 parts by mass of styrene powder. A titanium atom measurement pellet to which titanium is added and / or an aluminum atom measurement pellet in which a known amount of aluminum oxide is added to 100 parts by mass of styrene powder is prepared.
(2) Next, each of the produced silicon atom measurement pellets, titanium atom measurement pellets and / or aluminum atom measurement pellets was subjected to X-ray fluorescence analysis, and each silicon pellet, titanium oxide or aluminum oxide in styrene powder was analyzed. A calibration curve is created based on the peak intensity obtained from
(3) Thereafter, the sample of the specific external additive fine particles is subjected to fluorescent X-ray analysis, and the obtained peak intensity is collated with a calibration curve, whereby the content of silicon atoms, titanium atoms and / or aluminum atoms is quantified. The
In this measurement, the Kα peak angle of the element to be measured was determined from the 2θ table and used. The X-ray generation part conditions are target: Rh, tube voltage: 40 kV, tube current: 95 mA, filter: none, and spectroscopic system conditions are slit: standard, attenuator: none, spectral crystal: (Si = PET, Ti = LiF, Al = PET), detector: (Si = FPC, Ti = SC, Al = FPC).

On the other hand, the abundance ratio R ₂ of silicon atoms in the surface layer of the specific external additive fine particles is determined by the inclusion of silicon atoms, titanium atoms and aluminum atoms in the surface layer from the surface to a depth of several nanometers (about 10 atomic layers). The mass is measured by an X-ray photoelectron spectrometer “ESCA-1000” (manufactured by Shimadzu Corporation), and is calculated as a mass fraction.
Specifically, calibration curves were created for silicon atoms, titanium atoms, and aluminum atoms in the same manner as in (1) and (2) of the measurement using the X-ray fluorescence (XRF) apparatus, and the following measurement conditions were used. Samples of specific external additive fine particles were measured by X-ray photoelectron spectroscopy.
-Measurement conditions-
X-ray intensity: 30 mA, 10 kV
Analytical depth; Normal mode Quantitative element; Si, Ti and Al elements simultaneously quantitatively analyzed

In the specific external additive fine particles, the abundance ratio of silicon atoms in the whole is preferably 1 to 49%, more preferably 1 to 20%.
Moreover, in the specific external additive fine particles, the abundance ratio of silicon atoms in the surface layer from the surface to a depth of several nanometers is preferably 70 to 100%, more preferably 80 to 100%.
If the abundance ratio of silicon atoms in the whole external additive fine particles is less than 1%, the resulting external additive fine particles may not have sufficient chargeability, or toner obtained by external addition treatment to colored particles On the other hand, if the existing ratio of silicon atoms in the entire external additive fine particles exceeds 49%, the resulting external additive fine particles may not be able to sufficiently suppress overcharge. is there. Moreover, when the abundance ratio of silicon atoms in the surface layer is less than 70%, the charge imparting ability to the colored particles may be low.

[Average particle diameter of external additive fine particles]
The specific external additive fine particles preferably have a number average primary particle size of 10 to 500 nm, more preferably 20 to 300 nm, and particularly preferably 20 to 200 nm.
When the number average primary particle diameter is in the above range, the charge on the surface of the colored particles can be stabilized, and the specific external additive fine particles themselves can be held on the surface of the colored particles with high stability.

The number average primary particle size of the specific external additive fine particles is measured using a scanning electron microscope (SEM).
Specifically, an SEM photograph magnified 30,000 times is captured by a scanner, and external additive fine particles present on the toner surface of the SEM photograph image are analyzed by an image processing analyzer “LUZEX AP” (manufactured by Nireco). Binarization is performed, and the horizontal ferret diameter is calculated for 100 external additive fine particles, and the average value is taken as the number average primary particle diameter.
When the number average primary particle diameter of the external additive fine particles is small and exists as an aggregate on the toner surface, the particle diameter of the primary particles forming the aggregate is measured.

[Specific surface area of external additive fine particles]
The specific external additive fine particles preferably have a BET specific surface area of ² to 100 m ² / g.
Note that the BET specific surface area is a specific surface area calculated by using a BET adsorption isotherm from an adsorption amount of gas molecules having a known adsorption occupation area such as nitrogen gas.
When the BET specific surface area of the external additive fine particles is within the above range, the external additive fine particles can stably act as an external additive without being excessively embedded in the colored particles or detached from the surface of the colored particles. An environment is formed.

The BET specific surface area of the specific external additive fine particles is a value measured by a multipoint method (7-point method) using an automatic specific surface area measuring device “GEMINI 2360” (manufactured by Shimadzu Micromeritics).
Specifically, first, 2 g of the external additive fine particles are filled into a straight sample cell, and the inside of the cell is replaced with nitrogen gas (purity 99.999%) for 2 hours as a pretreatment, and then the external additive is added by the measuring apparatus main body. It is calculated by adsorbing and desorbing nitrogen gas (purity 99.999%) on the fine particles.

[Bulk density of external additive fine particles]
The specific external additive fine particles preferably have a bulk density of 100 to 400 g / L.
The bulk density is a value obtained by dividing the mass of the filled external additive fine particles by the volume when the external additive fine particles are filled in a container having a known volume. This means the degree of existence of voids formed between the external additive fine particles per unit volume when the agent fine particles are filled.
When the bulk density of the specific external additive fine particles is within the above range, the obtained toner ensures a space between the toner particles, so that packing due to stationary storage is unlikely to occur. Sufficient fluidity can be reliably maintained.

The bulk density of the specific external additive fine particles is a value measured by a Kawakita-type bulk density measuring device “IH-2000 type” (manufactured by Seishin Enterprise Co., Ltd.).
Specifically, 50 g of a sample (specific external additive fine particles) is placed on a 120-mesh sieve, the sieve is vibrated for 90 seconds at a vibration strength of 6, and after dropping the sample into a 100 mL container, the vibration is stopped. After standing for 30 seconds, the container is ground and the mass is measured to calculate the bulk density.

[Hydrophobicity of external additive fine particles]
The specific external additive fine particles preferably have a hydrophobicity of 30% or more.
When the degree of hydrophobicity of the specific external additive fine particles is 30% or more, there is an advantage that sufficient chargeability can be obtained even in a high temperature and high humidity environment.

The degree of hydrophobicity of specific external additive fine particles is a value measured as follows.
That is, 50 mL of water is put into a 200 mL beaker, and 0.2 g of external additive fine particles (sample) are added, and methanol is added from a burette whose tip is immersed in water at the time of dropping while stirring with a magnetic stirrer. From the amount (Me) of methanol dropped when the external additive fine particles (sample) that initially floated completely settled, calculation is performed using the following formula (1).
Formula (1): Degree of hydrophobicity (%) = [Me (mL) / (50 + Me (mL))] × 100

The specific external additive fine particles have a higher proportion of silicon atoms in the surface layer than the whole.
As specific external additive fine particles, specifically, those having a structure in which a surface layer made of a silica component is formed on the surface of a core particle made of titania and / or an alumina component are structurally effective. It is preferable because it tends to be obtained. In addition, it is preferable that the said core particle consists of an oxide also containing a silicon atom.
In such a form, the surface layer of the silica component may not necessarily completely cover the core particles, and the silica component abundance ratio measured by mass with an X-ray photoelectron spectrometer is 70 to 100%. It is preferable that it is 80% to 100%.

The abundance ratio of silica is specifically determined by a method for measuring the abundance ratio R ₂ of silicon atoms in the surface layer of the specific external additive fine particles described above using an X-ray photoelectron spectrometer “ESCA-1000” (manufactured by Shimadzu Corporation). It is measured in the same manner as above.

[Method for producing external additive fine particles]
The method for producing the specific external additive fine particles used in the image forming method of the present invention is not particularly limited, and examples thereof include pyrogenic processes such as a gas phase method and a flame hydrolysis method; a sol-gel method. A plasma method; a precipitation method; a hydrothermal method; a mining process (bergmaennische Verfahren); and a combination of these methods. In terms of easy adjustment of the site where atoms are present, a thermal decomposition method Is preferable, and in particular, a production method employing a gas phase method disclosed in Japanese Patent No. 32025573 can be given.
The method for producing external additive fine particles by the vapor phase method is a method for producing external additive fine particles by introducing raw materials of external additive fine particles into a high-temperature flame in a vapor state or a powder state and oxidizing them. is there.

When the specific external additive fine particles having silicon atoms oriented on the surface are produced by a method in which the raw material is introduced into a high-temperature flame in a vapor state (hereinafter, also referred to as “vapor phase method using vapor”), for example, a high temperature In the flame, steam vaporized by heating the titanium atom source and / or aluminum atom source is introduced in advance, and after vapor growth to some extent, vapor vaporized by heating the silicon atom source is introduced. Is preferable from the viewpoint of production stability.
Examples of the silicon atom source include silicon halides such as silicon tetrachloride, or organosilicon compounds. Examples of the titanium atom source include titanium sulfate and titanium tetrachloride. Further, examples of the aluminum atom source include , Aluminum chloride, aluminum sulfate, sodium aluminate and the like.

On the other hand, in the case of producing specific external additive fine particles having silicon atoms oriented on the surface by a method of introducing raw materials into a high-temperature flame in a powder state (hereinafter also referred to as “powder vapor phase method”). For example, a powder that forms core particles in a high-temperature flame (hereinafter also referred to as “core particle-forming powder”) and a powder that is modified on the surface to form a surface layer (hereinafter referred to as “modifying powder”) In other words, it is preferable to make the core particle-forming powder larger than the modifying powder from the viewpoint of production stability.
This is because the core particle-forming powder and the modifying powder are introduced into the same high-temperature flame, and a plurality of powders aggregate and grow in the high-temperature flame, and grow into particles having a large diameter. It is considered that by making the modifying powder fine particles, the heat receiving area of the modifying powder is increased, and the modifying powder is more easily melted. Therefore, for example, by controlling the temperature of the high temperature flame, the degree of association / growth of the core particle forming powder can be suppressed to a small level, and the conditions for melting and adhering the modifying powder can be found without any special trial and error. it can.
In the above, it is considered that the core particle-forming powder and the modifying powder are simultaneously introduced into a high-temperature flame to modify the surfaces of each other.

In this production method, particles made of a metal oxide such as titania and / or an alumina component are used as the core particle forming powder. The core particle forming powder may be made of an oxide containing silicon atoms.
The core particle-forming powder using a metal oxide can be obtained, for example, by burning a raw material of the metal oxide in a flame. Examples of the metal oxide raw material include those mentioned above as the titanium atom source and the aluminum atom source. These can be used alone or in combination in any combination.
On the other hand, as the modifying powder, one made of silica is used, and specifically, one obtained by burning the silicon atom source mentioned above in a high temperature flame is preferably used. In addition, it is preferable to use an amorphous thing from a viewpoint of environmental safety as a silica.
It is preferable that the silica is bonded and fused before the prototype of the silica cannot be observed on the surface of the core particle by heat.

FIG. 1 is a schematic view showing an example of a production facility for producing external additive fine particles constituting the toner used in the image forming method of the present invention by a powder vapor phase method. The production equipment for producing the specific external additive fine particles according to the present invention by a vapor phase method using powder is not limited to this.
In the case of producing the external additive fine particles by the gas phase method using this powder, for example, when producing the external additive fine particles containing silicon atom, titanium atom and aluminum atom, specifically, as follows: Can get to.

That is, first, the core particle forming powder A housed in the core particle forming powder A tank 21A and the modifying powder B housed in the tank 21B for modifying powder B, respectively, It is introduced into a main burner 26 having a spray nozzle attached to its tip through introduction pipes 23A and 23B by fixed supply pumps 22A and 22B, and further sprayed into a combustion furnace 27 together with an oxygen / steam mixed gas D and ignited by an auxiliary flame. Thus, the high temperature flame 28 is formed.
Then, external additive fine particles are generated by combustion, and the external additive fine particles are cooled in the flue 29 together with the exhaust gas, separated from the exhaust gas by the cyclone 30 and the bag filter 32, and collected by the collectors 31 and 33, respectively. . The exhaust gas separated from the external additive fine particles is exhausted by the exhaust fan 34.
In FIG. 1, 21D is a tank for oxygen / water vapor mixed gas D, and 23D is an introduction pipe for oxygen / water vapor mixed gas.

FIG. 2 is a schematic view showing an example of a production facility for producing the external additive fine particles constituting the toner used in the image forming method of the present invention by a vapor phase method using steam. The production equipment for producing the specific external additive fine particles according to the present invention by the vapor phase method using steam is not limited to this.
In the case of producing external additive fine particles by the vapor phase method using vapor, for example, when producing external additive fine particles containing silicon atoms, titanium atoms, and aluminum atoms, specifically, as follows: Obtainable.

(1) First, a silicon atom source, a titanium atom source, and an aluminum atom source are introduced from a raw material inlet 1 and heated in an evaporator 2 to be vaporized to be vapor related to silicon, vapor related to titanium, and aluminum Get steam.
(2) Next, these vapors are introduced into the mixing chamber 3 together with an inert gas (not shown) such as nitrogen, and then dry air and / or oxygen gas and hydrogen gas are mixed at a predetermined ratio. Thus, a mixed gas is obtained, and this mixed gas is introduced from the combustion burner 4 into a combustion flame (not shown) formed in the reaction chamber 5.
(3) A particle containing silicon atoms, titanium atoms and aluminum atoms is generated by performing a combustion treatment at a temperature of 1000 ° C. to 3000 ° C. in the combustion flame.
(4) After the produced particles are cooled in the cooler 6, the gaseous reaction product is separated and removed in the separator 7. At this time, in some cases, hydrogen chloride adhering to the particle surface is removed in wet air. further,
In the treatment chamber 8, the hydrogen chloride is deoxidized, and is collected by a filter, and the composite oxide particles are collected in the silo 9.

In the manufacturing method as described above, the flow rate ratio of the steam related to silicon introduced into the combustion flame, the steam related to titanium and the steam related to aluminum, the timing of introduction of each steam into the combustion flame, the combustion time, the combustion Since the influence of temperature, combustion atmosphere, and other combustion conditions is reflected in the state of orientation of silicon atoms on the surface of specific external additive fine particles, in the present invention, titanium atoms and aluminum atoms are oriented inside. In order to orient the silicon atoms on the surface, it is preferable to adjust these conditions in a complex manner.
The state in which the silicon atoms are oriented on the surface is, for example, that the timing of introduction of the steam related to silicon introduced into the combustion flame is delayed, or the concentration of the steam related to silicon in all the flowing steam is reacted. It is obtained by making it high in the second half.
Specifically, in the combustion flame, the concentration of the steam related to silicon in the steam having a relatively low electrical resistance preceded by the steam related to titanium and / or the steam related to aluminum (or the total steam flowing in the first half of the reaction). After the crystal has grown to some extent, the silicon-related vapor having a relatively high electrical resistance is introduced (the concentration of the silicon-related vapor in the whole vapor flowing in the second half of the reaction is increased). Is preferable from the viewpoint of production stability.

Although the obtained composite oxide particles may be used as external additive fine particles as they are, it is preferable to subject the composite oxide particles to a hydrophobization treatment.
Examples of the hydrophobic treatment method include the following dry methods.
That is, the hydrophobizing agent is diluted with a solvent such as tetrahydrofuran (THF), toluene, ethyl acetate, methyl ethyl ketone, acetone ethanol and hydrogen chloride saturated ethanol, and the composite oxide particles are forcibly stirred with a blender, etc. Add the diluted solution by dripping or spraying, and mix well. In that case, apparatuses such as a kneader coater, a spray dryer, a Kalmar processor, and a fluidized bed can be used.
Next, the obtained mixture is transferred to a vat or the like and dried by heating in an oven or the like. Then, it is sufficiently crushed again by a mixer or jet mill. The obtained crushed material is preferably classified as necessary. In the above-described method, when a hydrophobic treatment is performed using a plurality of types of hydrophobizing agents, the treatment may be performed using each of the hydrophobizing agents simultaneously or separately.
In addition to such a dry method, the composite oxide particles are immersed in an organic solvent solution of a coupling agent and then dried; the composite oxide particles are dispersed in water to form a slurry, and then hydrophobic. A hydrophobizing treatment may be performed using a wet method such as a method in which an aqueous solution of an agent is dropped and then the composite oxide particles are precipitated, dried by heating, and crushed.
In the hydrophobization treatment as described above, the temperature during heating is preferably 100 ° C. or higher. When the temperature at the time of heating is less than 100 ° C., the condensation reaction between the composite oxide particles and the hydrophobizing agent becomes difficult to complete.

  Examples of the hydrophobizing agent used in the hydrophobizing treatment include those used as usual surface treating agents such as silane coupling agents such as hexamethyldisilazane, titanate coupling agents, silicone oil, and silicone varnish. . Furthermore, a fluorine-based silane coupling agent, a fluorine-based silicone oil, a coupling agent having an amino group or a quaternary ammonium base, a modified silicone oil, or the like can also be used. These hydrophobizing agents are preferably used in a state dissolved in a solvent such as ethanol.

[Other external additive fine particles]
The external additive fine particles contained in the toner used in the image forming method of the present invention are not limited to the specific external additive fine particles as described above, and other external additive fine particles may be used in combination. .
When other external additive fine particles are used in combination, 50% by mass or more of all external additive fine particles are the specific external additive fine particles according to the present invention. When the specific external additive fine particles are less than 50% by mass of the total external additive fine particles, the high chargeability or excessive antistatic property of the specific external additive fine particles is offset by the influence of the other external additive fine particles. There is a risk of being.

As other external additive fine particles, various inorganic fine particles, organic fine particles and lubricants can be used. For example, inorganic fine particles such as silica, titania, and alumina are preferably used as the inorganic fine particles, and these inorganic fine particles are hydrophobized with a silane coupling agent or a titanium coupling agent. Is preferred. As the organic fine particles, spherical particles having a number average primary particle diameter of about 10 to 2,000 nm can be used. As the organic fine particles, polymers such as polystyrene, polymethyl methacrylate, and styrene-methyl methacrylate copolymer can be used.
As these other external additive fine particles, various types may be used in combination.

[Addition treatment of external additive fine particles]
The toner can be obtained by adding the external additive fine particles as described above to the colored particles to form the toner.
In the addition of the external additive fine particles, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used as a mixing device used for adding the external additive fine particles.

[Addition ratio of external additive fine particles]
The addition ratio of the external additive fine particles is preferably 0.1 to 2.0% by mass with respect to the colored particles.

〔toner〕
The toner used in the image forming method of the present invention contains colored particles and specific external additive fine particles.

[Method for producing colored particles]
The method for producing the colored particles constituting the toner is not particularly limited, and includes a pulverization method, a suspension polymerization method, an emulsion polymerization aggregation method, a dissolution suspension method, a polyester molecular extension method, and other known methods. Can be mentioned. The colored particles constituting the toner are preferably obtained by an emulsion aggregation method, and in particular, miniemulsion polymerization aggregation in which miniemulsion polymerization particles are associated (aggregated / fused) with resin particles having a multistage polymerization configuration by emulsion polymerization. It is preferably obtained by the method.

  Specifically, for example, the miniemulsion polymerization aggregation method is a polymerization property in which a release agent is dissolved in a polymerizable monomer in an aqueous medium in which a surfactant having a critical micelle concentration or less is dissolved. The monomer solution is formed into oil droplets (10 to 1000 nm) using mechanical energy to prepare a dispersion, and a water-soluble polymerization initiator is added to the obtained dispersion to cause radical polymerization. This is a method of obtaining colored particles by associating (aggregating / fusing) the obtained binder resin fine particles. In this miniemulsion polymerization aggregation method, instead of adding a water-soluble polymerization initiator, or while adding the water-soluble radical polymerization initiator, the oil-soluble radical polymerization initiator is added to the monomer solution. It may be added inside. Further, the binder resin fine particles can be composed of two or more layers made of binder resins having different compositions. In this case, the first prepared by miniemulsion polymerization treatment (first-stage polymerization) according to a conventional method. It is possible to employ a method in which a polymerization initiator and a polymerizable monomer are added to a dispersion of resin particles, and this system is polymerized (second-stage polymerization).

As a method for producing colored particles, specifically showing an example of using a miniemulsion polymerization aggregation method,
(1) Dissolving / dispersing a colorant and, if necessary, a toner particle constituent material such as a release agent and a charge control agent in a polymerizable monomer serving as a binder resin to obtain a polymerizable monomer solution Dispersion step (2) Polymerization step in which a polymerizable monomer solution is converted into oil droplets in an aqueous medium and a dispersion of binder resin fine particles is prepared by a mini-emulsion method (3) Salting out of the binder resin fine particles in an aqueous medium Agglomeration and fusing step for agglomerating and fusing to form agglomerated particles (4) aging step for aggregating the agglomerated particles with thermal energy to adjust the shape and obtaining a dispersion of colored particles (5) a dispersion of colored particles Cooling step for cooling (6) Filtration and washing step for solid-liquid separation of the colored particles from the cooled dispersion of colored particles and removal of the surfactant from the colored particles (7) Washed colored particles It is comprised from the drying process which dries.

  Here, the “aqueous medium” means that the main component (50% by mass or more) is made of water. Examples of components other than water include organic solvents that dissolve in water, such as methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran. Among these, alcohol-based organic solvents such as methanol, ethanol, isopropanol, and butanol, which are organic solvents that do not dissolve the resin, are particularly preferable.

[Binder resin]
When the colored particles constituting the toner of the present invention are produced by a pulverization method, a dissolution suspension method or the like, various known resins can be exemplified as the binder resin constituting the colored particles of the toner.
In addition, when the colored particles constituting the toner of the present invention are produced by a suspension polymerization method, a miniemulsion polymerization aggregation method, an emulsion polymerization aggregation method, or the like, a polymerizable monomer for obtaining each resin constituting the toner Examples of the body include various known polymerizable monomers such as vinyl monomers. Moreover, as a polymerizable monomer, it is preferable to use what has an ionic dissociation group in combination. Furthermore, as the polymerizable monomer, a cross-linked binder resin can be obtained using a polyfunctional vinyl monomer.

[Colorant]
As the colorant constituting the colored particles of the toner of the present invention, a known inorganic or organic colorant can be used.
The amount of the colorant added is 1 to 30% by mass, preferably 2 to 20% by mass, based on the colored particles.

(Internal additive)
The colored particles constituting the toner of the present invention may contain a release agent and a charge control agent as necessary. Various known compounds can be used as the release agent and charge control agent.

[Particle size of colored particles]
The particle diameter of the colored particles constituting the toner particles used in the image forming method of the present invention is preferably 3 to 8 μm in number average particle diameter. In the case of forming colored particles by a polymerization method, the particle size is controlled by the concentration of the aggregating agent, the amount of the organic solvent added, the fusing time, and the composition of the polymer itself in the above-described toner production method. can do.
The number average particle size is 3 to 8 μm, so that reproducibility of fine lines and high image quality of photographic images can be achieved, and the amount of toner consumption can be reduced as compared with the case of using a large particle size toner. Can do.

(Developer)
The toner used in the image forming method of the present invention can be used as a magnetic or non-magnetic one-component developer, but may be used as a two-component developer by mixing with various known carriers.
The volume average particle diameter of the carrier is preferably 20 to 100 μm, more preferably 25 to 80 μm. The volume average particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

The above developers are used in image forming methods such as the following [1] and [2].
[1] The process of visualizing the electrostatic latent image formed on the electrostatic latent image carrier with toner is repeated twice or more using toners of different colors, so that the color on the electrostatic latent image carrier is An image forming method in which a toner image is formed, and the color toner image is directly transferred to an image support to obtain an image support carrying the toner image, and the toner image is fixed to the image support.

[2] The step of directly transferring the toner image formed by developing the electrostatic latent image formed on the electrostatic latent image carrier onto the image support 2 using toners of different colors. An image forming method in which a color toner image is formed on an image support repeatedly to obtain an image support carrying the toner image, and the toner image is fixed to the image support.

  Such an image forming method can be executed in the following image forming apparatus.

[Image forming apparatus]
FIG. 3 is an explanatory diagram showing an example of the configuration of the image forming apparatus used in the image forming method of the present invention.
This image forming apparatus is a so-called direct transfer type full-color image forming apparatus that uses four intermediate image forming units 18Y, 18M, 18C, and 18Bk along the conveying belt 15A and does not use an intermediate transfer member.

Each of the image forming units 18Y, 18M, 18C, and 18Bk is formed by forming a photoconductive layer made of a conductive layer and an organic photoconductor (OPC) on the outer peripheral surface of a cylindrical substrate, and a drive source (not shown) Photosensitive drums 10Y, 10M, 10C, and 10Bk that are rotated counterclockwise by the power from the motor or following the conveyor belt 15A and the conductive layer is grounded, and the photosensitive drums 10Y, 10M, 10C, and 10Bk. A uniform potential is applied to the surfaces of the photosensitive drums 10Y, 10M, 10C, and 10Bk by corona discharge having the same polarity as that of the toner and disposed in a direction orthogonal to the moving direction of the toner. The chargers 11Y, 11M, 11C, and 11Bk are scanned in parallel with the rotation axes of the photosensitive drums 10Y, 10M, 10C, and 10Bk. Exposure devices 12Y, 12M, 12C, and 12Bk made of, for example, polygon mirrors, which form latent images by performing image exposure based on image data on the surfaces of the photosensitive drums 10Y, 10M, 10C, and 10Bk charged to And a developing device 13Y, 13M, 13C, 13Bk that conveys the toner held on the surface to the surfaces of the photosensitive drums 10Y, 10M, 10C, 10Bk. It is said that.
In FIG. 3, 19Y, 19M, 19C, and 19Bk are cleaning devices.

  Here, the yellow toner image is formed by the image forming unit 18Y, the magenta toner image is formed by the image forming unit 18M, and the cyan toner image is formed by the image forming unit 18C. According to the unit 18Bk, a black toner image is formed.

As the transport belt 15A for transporting the image support P, a conductive film such as carbon black is added to a polymer film such as polyimide, polycarbonate, PVdF, or a synthetic rubber such as silicon rubber or fluoro rubber to impart conductivity. These may be used, and may be in the form of a drum or a belt, but is preferably in the form of a belt from the viewpoint of freedom in device design.
The surface of the conveyor belt 15A is preferably appropriately roughened, and for example, the ten-point surface roughness Rz is preferably 0.5 to 2 μm. By making the surface of the transport belt 15A rough in this way, the adhesion between the image support P and the transport belt 15A becomes high, and the image support P swings on the transport belt 15A. Is suppressed, and the transferability of the toner image from the photosensitive drums 10Y, 10M, 10C, and 10Bk to the image support P can be improved.

  In such an image forming apparatus, first, the toner images of the respective colors formed on the photosensitive drums 10Y, 10M, 10C, and 10Bk of the image forming units 18Y, 18M, 18C, and 18Bk are conveyed at the same timing. A color toner image is formed on the image support P by sequentially transferring and superimposing on the image support P conveyed by 15A by the transfer units 14Y, 14M, 14C, and 14Bk.

The image support P on which the color toner image is carried has a predetermined interval from the discharging portion by the AC discharger 15B provided on the downstream side of the transfer region with the image forming unit 18Bk of the transfer belt 15A and the transfer portion 15D. Due to the separation action of the separation claw 15C provided via the separation claw 15C, the separation claw 15C is separated from the conveyance belt 15A and conveyed to the conveyance unit 15D.
In the fixing device 16, the image support P is sandwiched in the nip portion N formed by the heating roll 16 a and the pressure roll 16 b and heat and pressure are applied, so that the image support P is superposed on the image support P. After the color toner image is fixed, it is discharged out of the apparatus.

(Image support)
The image support used in the image forming method of the present invention is a support for holding a toner image, and specifically, coating of plain paper, fine paper, art paper, coated paper, etc. from thin paper to thick paper. Various kinds of printed paper, commercially available Japanese paper, postcard paper, plastic films for OHP, cloth, and the like can be used, but the invention is not limited to these.

According to the image forming method as described above, the toner contains specific external additive fine particles, and the specific external additive fine particles have an abundance ratio of silicon atoms in the surface layer of the silicon atoms in the whole. It is higher than the abundance ratio, and the occurrence of overcharging is suppressed, which suppresses the presence of toner with a low charge amount due to a sharp charge amount distribution, resulting in fog and the like. And a high-quality image can be stably formed over a long period of time.
The reason why the specific external additive fine particles contained in the toner can suppress the occurrence of fogging by suppressing excessive charging while having sufficient chargeability is that the specific external additive fine particles are contained in the surface layer. Silica is easily charged by the silicon atoms present and sufficient chargeability is obtained due to the property of easily retaining charges, but excessive due to charge leakage into the particles due to titanium atoms and / or aluminum atoms present inside the silica. This is presumably because charging can be suppressed.

  As mentioned above, although embodiment of this invention was described concretely, embodiment of this invention is not limited to said example, A various change can be added.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

[Production Example 1 of resin particle dispersion]
(First stage polymerization)
A 5 L reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen introducing device was charged with a solution prepared by dissolving 8 g of sodium dodecyl sulfate in 3 L of ion-exchanged water and stirred at a stirring speed of 230 rpm under a nitrogen stream. The internal temperature was raised to 80 ° C. After the temperature rise, a solution in which 10 g of potassium persulfate was dissolved in 200 g of ion-exchanged water was added, the temperature was again set to 80 ° C., 480 g of styrene, 250 g of n-butyl acrylate, 68.0 g of methacrylic acid and n-octyl-3- Polymeric monomer solution containing 16.0 g of mercaptopropionate was added dropwise over 1 hour, then polymerized by heating and stirring at 80 ° C. for 2 hours, and resin particle dispersion containing resin particles (1h) A liquid (1H) was prepared.

(Second stage polymerization)
A 5 L reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introducing device was charged with a solution prepared by dissolving 7 g of sodium polyoxyethylene-2-dodecyl ether sulfate in 800 ml of ion-exchanged water and heated to 98 ° C. , 260 g of the above resin particle dispersion (1H), 245 g of styrene, 120 g of n-butyl acrylate, 1.5 g of n-octyl-3-mercaptopropionate, 67 g of the release agent “HNP-11” at 90 ° C. Add the dissolved polymerizable monomer solution, and mix and disperse for 1 hour using a mechanical disperser “CREARMIX” (M Technique Co., Ltd.) with a circulation path to prepare a dispersion containing emulsified particles (oil droplets). did.
Next, an initiator solution in which 6 g of potassium persulfate was dissolved in 200 ml of ion-exchanged water was added to this dispersion, and the system was heated and stirred at 82 ° C. for 1 hour to polymerize the resin particles (1 hm ) Containing resin particle dispersion (1HM) was prepared.

(3rd stage polymerization)
A solution prepared by dissolving 11 g of potassium persulfate in 400 ml of ion-exchanged water was added to the above resin particle dispersion (1HM), and styrene 435 g, n-butyl acrylate 130 g, methacrylic acid 33 g and n were added at a temperature of 82 ° C. -A polymerizable monomer solution consisting of 8 g of octyl-3-mercaptopropionate was added dropwise over 1 hour. After completion of the dropwise addition, polymerization was carried out by heating and stirring for 2 hours, followed by cooling to 28 ° C. to obtain a resin particle dispersion [A] containing resin particles a. The particle diameter of the resin particles a in the resin particle dispersion [A] was measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.). The volume-based median diameter was 150 nm. It was. Moreover, it was 45 degreeC when the glass transition point temperature of this resin particle a was measured.

[Production Example 1 of Colorant Fine Particle Dispersion]
While stirring a solution obtained by dissolving 90 g of sodium dodecyl sulfate in 1600 ml of ion-exchanged water, 420 g of carbon black “Regal 330R” (manufactured by Cabot) is gradually added, and then a stirrer “Clearmix” (M Technique Co., Ltd.). Dispersion of colorant fine particles [Bk] was prepared.

[Production Example 1 of colored particles]
In a 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction device, 300 g of resin particle dispersion [A], 1400 g of ion-exchanged water, and dispersion of colorant fine particles [Bk ] And 120 g of sodium polyoxyethylene-2-dodecyl ether sulfate dissolved in 120 ml of ion-exchanged water, the temperature of the solution was adjusted to 30 ° C., and 5N sodium hydroxide aqueous solution was added to adjust the pH. Adjusted to 10. Next, an aqueous solution in which 35 g of magnesium chloride was dissolved in 35 ml of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring, and the temperature was raised after holding for 3 minutes. The particle growth reaction was continued while maintaining the temperature at 90 ° C. In this state, the particle size of the associated particles is measured with “Coulter Multisizer III”, and when the desired particle size is reached, an aqueous solution in which 150 g of sodium chloride is dissolved in 600 ml of ion-exchanged water is added to increase particle growth. Further, the fusion between the particles was allowed to proceed until the average circularity was 0.965 as measured by “FPIA-2100” by heating and stirring at a liquid temperature of 98 ° C. as a fusion step. Thereafter, the solution was cooled to 30 ° C., hydrochloric acid was added to adjust the pH to 4.0, and stirring was stopped.

  The colored particles produced in the above process are solid-liquid separated with a basket-type centrifuge “MARK III model number 60 × 40” (Matsumoto Kikai Co., Ltd.) to form a wet cake of colored particles. Was washed with ion exchange water at 45 ° C. until the electrical conductivity of the filtrate reached 5 μS / cm using the basket-type centrifuge, and then transferred to “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.). It dried until it became 5 mass%, and colored particle [Bk] was obtained.

[Production Example 1 of External Additive Fine Particles]
Using the production apparatus shown in FIG. 2, silicon tetrachloride vapor [A], titanium tetrachloride vapor [B], and aluminum chloride vapor [C] are not flowed at the flow rates shown in the initial introduction amount column of Table 1. A composite containing silicon atoms, titanium atoms and aluminum atoms introduced into a reaction chamber together with an active gas and burned for 0.3 seconds at a combustion temperature of 2,000 ° C. with a mixture of hydrogen and air mixed at a predetermined ratio Particles were generated and collected by a filter after cooling.
The obtained composite particles were dechlorinated by heating at 500 ° C. for 1 hour in an oven in an air atmosphere, and 500 parts by mass of this was charged into a high-speed stirring mixer equipped with a jacket for heating and stirring at 500 rpm. Then, 25 parts by mass of pure water was sprayed and supplied under sealing, and the mixture was further stirred for 10 minutes. Subsequently, 25 parts by mass of hexamethyldisilazane was added, and the mixture was stirred for 60 minutes in a sealed state, and then aerated with nitrogen at 150 ° C. with stirring to remove the generated ammonia gas and the remaining treatment agent. External additive fine particles [1] comprising composite oxide particles were obtained.
Table 1 shows the coefficient (R ₁ ) / (R ₂ ), number average primary particle size, BET specific surface area, bulk density, and degree of hydrophobicity of the obtained external additive fine particles [1]. The coefficient (R ₁ ) / (R ₂ ), number average primary particle size, BET specific surface area, bulk density, and degree of hydrophobicity are calculated based on the above measurement procedure.

[Production Examples 2 to 5 of external additive fine particles]
In Production Example 1 of the external additive fine particles, silicon tetrachloride vapor [A], titanium tetrachloride vapor [B] and aluminum chloride vapor [C] were initially introduced from the main route as shown in Table 1 as reaction raw materials. Introduced into the reaction chamber at the flow rate shown in the quantity column, and introduced into the reaction chamber at the flow rate shown in the late introduction quantity column of Table 1 from another route (not shown) as the late raw material of the reaction, to form silicon atoms, titanium atoms and aluminum External additive fine particles [2] to [5] were obtained in the same manner except that composite particles containing atoms were produced.
Table 1 shows the coefficient (R ₁ ) / (R ₂ ), number average primary particle diameter, BET specific surface area, bulk density, and degree of hydrophobicity of the obtained external additive fine particles [2] to [5].

[Production Examples 6 to 10, 13 to 15 of External Additive Fine Particles]
In the external additive fine particle production example 1, the external additive fine particles [6] to [6] to [6] are similarly produced except that the raw material introduced into the reactor of the combustion burner is changed to the raw materials shown in Table 1 and the mixing ratio thereof. 10] and external additive fine particles [13] to [15].
Coefficients (R ₁ ) / (R ₂ ), number average primary particle diameter, BET specific surface area, bulk density of the obtained external additive fine particles [6] to [10] and external additive fine particles [13] to [15] Table 1 shows the degree of hydrophobicity.

[Production Example 11 of External Additive Fine Particles]
Titanium dioxide particles [t] obtained in the same manner as in Production Example 14 of external additive fine particles and silica powder [s] obtained in the same manner as in Production Example 13 of external additive fine particles were previously 9% by mass. 1 is mixed in a resin bag, put into a tank using the manufacturing apparatus shown in FIG. 1, and conveyed through an introduction pipe together with air as a carrier gas at a supply rate of 4 kg / hour, and a nozzle Erupted from. At this time, the flow velocity of the air nozzle was 48 m / sec.
After the reaction, cooling air was introduced into the combustion furnace so that the high-temperature residence time in the combustion furnace was 0.3 seconds or less, and then the fine powder produced using a polytetrafluoroethylene bag filter [P ] Was collected.
The collected fine powder [P] is dechlorinated by heating in an oven at 500 ° C. for 1 hour in an air atmosphere, and 500 parts by mass of this is charged into a high-speed stirring mixer with a jacket for heating and cooling, and 500 rpm While being stirred at 25 ° C., 25 parts by mass of pure water was sprayed in a sealed state, and then stirring was continued for 10 minutes. Subsequently, 25 parts by mass of hexamethyldisilazane was added, and stirring was performed for 60 minutes in a sealed state, followed by stirring and heating to remove the generated ammonia gas and the remaining treating agent while ventilating nitrogen at 150 ° C., External additive fine particles [11] were obtained.
Table 1 shows the coefficient (R ₁ ) / (R ₂ ), number average primary particle diameter, BET specific surface area, bulk density, and degree of hydrophobicity of the obtained external additive fine particles [11].

[Production Example 12 of External Additive Fine Particles]
In the external additive fine particle production example 11, the aluminum dioxide [a] obtained in the same manner as the external additive fine particle production example 15 was used instead of the titanium dioxide particles [t]. External additive fine particles [12] were obtained.
Table 1 shows the coefficient (R ₁ ) / (R ₂ ), number average primary particle size, BET specific surface area, bulk density, and degree of hydrophobicity of the obtained external additive fine particles [12].

[Toner Production Examples Bk1 to Bk15]
Toner particles [Bk1] to [Bk15] were prepared by adding external additive fine particles [1] to [15] to the colored particles [Bk] so as to have the addition amounts shown in Table 2 and mixing with a Henschel mixer. . Note that the shape and particle size of these toner particles did not change depending on the addition of the external additive fine particles. The toners [Bk1] to [Bk4] and [Bk6] to [Bk12] are toners according to the present invention, and the toners [Bk5] and [Bk13] to [Bk15] are comparative toners.

[Developer Production Examples 1 to 15]
Each of the toners [1] to [15] is mixed with a ferrite carrier having a volume average particle diameter of 60 μm coated with a silicone resin so that the toner concentration becomes 6%, thereby developing agents [1] to [15]. Was prepared.

[Examples 1-11, Comparative Examples 1-4]
Using the developer [1] to [15] obtained as described above, the image forming apparatus shown in FIG. 3 is used, and A4 size plain paper is used as an image support, as described below. Evaluation was performed. The results are shown in Table 2.

[Evaluation of fog]
A test in which a character image having a pixel rate of 7%, a human face photo image, a solid black image, and a solid white image are formed in each 1/4 area under a high temperature and high humidity environment (temperature 33 ° C., humidity 80% RH). An image (image with a pixel rate of 10%) is printed in an intermittent mode of 50,000 sheets, and a reflection densitometer “RD-918” (manufactured by Macbeth) is used for the solid white image area of the 50,000th test image. Then, the absolute reflection density at 20 arbitrary positions is measured, and the average image density D1, which is the arithmetic average value, is calculated. Similarly, the average image density D0 of plain paper on which no image is formed is calculated. D1-D0) was evaluated as fog density. The results are shown in Table 2.
In addition, if the fog density is 0.005 or less, it can be said that the fog is not a practical problem.

  As is clear from the results in Table 2, in Examples 1 to 11 according to the image forming method of the present invention, it was confirmed that generation of fog was suppressed regardless of environmental conditions such as temperature and humidity.

It is the schematic which shows an example of the manufacturing equipment which manufactures the external additive fine particle which comprises the toner used for the image forming method of this invention by the gaseous-phase method by powder. It is the schematic which shows an example of the manufacturing equipment which manufactures the external additive fine particle which comprises the toner used for the image forming method of this invention by the vapor phase method by a vapor | steam. 1 is a cross-sectional view illustrating an example of a configuration of an image forming apparatus used in an image forming method of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw material inlet 2 Evaporator 3 Mixing chamber 4 Combustion burner 5 Reaction chamber 6 Cooler 7 Separator 8 Processing chamber 9 Silo 10Y, 10M, 10C, 10Bk Photosensitive drum 11Y, 11M, 11C, 11Bk Charger 12Y, 12M, 12C, 12Bk Exposing devices 13Y, 13M, 13C, 13Bk Developing devices 14Y, 14M, 14C, 14Bk Transfer device 15A Conveying belt 15B AC neutralizer 15C Separating claw 15D Conveying section 16 Fixing device 16a Heating roll 16b Pressure rolls 18Y, 18M, 18C, 18Bk Image forming units 19Y, 19M, 19C, 19Bk Cleaning device N Nip part P Image supports 21A, 21B, 21D Tanks 22A, 22B Metering supply pumps 23A, 23B, 23D Introducing tube A Core particle forming powder B Modification Powder D oxygen / steam mixed gas 26 main bar Over 27 combustion furnace (reaction tube)
28 High-temperature flame 29 Flue 30 Cyclone 32 Bag filter 31, 33 Recovery unit 34 Blower

Claims (6)

The electrostatic latent image formed on the electrostatic latent image carrier is visualized with toner, and the toner image formed is directly transferred onto the image support to obtain an image support carrying the toner image. In an image forming method for fixing the toner image to an image support,
The toner contains at least colored particles and external additive fine particles,
The external additive fine particles are composed of a composite oxide containing silicon atoms and titanium atoms and / or aluminum atoms, and the abundance ratio of silicon atoms in the surface layer is greater than the abundance ratio of silicon atoms in the whole. An image forming method characterized by being high.   The image support carrying the toner image is subjected to a static image by repeating the process of developing the electrostatic latent image formed on the electrostatic latent image carrier with toner twice or more using different color toners. 2. The image forming method according to claim 1, wherein a color toner image is formed on the electrostatic latent image carrier, and the color toner image is directly transferred to an image support.   The image support carrying the toner image includes a step of directly transferring the toner image formed by visualizing the electrostatic latent image formed on the electrostatic latent image support to the image support. The image forming method according to claim 1, wherein the image forming method is obtained by forming a color toner image on the image support by repeating two or more times using different color toners.   4. The image forming method according to claim 1, wherein the external additive fine particles have a total content of titanium atoms and aluminum atoms larger than that of silicon atoms. 5. The external additive fine particles, the abundance ratio of silicon in the entire atoms when R _1, the existence ratio of silicon atoms in the surface layer and R _2, the coefficient _{(R 1) / (R 2} ) is 0.7 or less The image forming method according to claim 1, wherein the image forming method is provided.   The image forming method according to claim 1, wherein the external additive fine particles have a number average primary particle diameter of 20 to 200 nm.