JPH11338187A - Production of electrophotographic toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method of an electrophotographic toner by which the mixing time of toner core particles and external additives can be controlled to the optimum mixing time to effectively obtain the effects of the external additives, and an electrophotographic toner having optimum characteristics for electrophotography can be obtd. SOLUTION: The toner core particles contains a binder resin having two peaks in the mol.wt. distribution with 1.0×10<5> to 2.5×10<5> number average mol.wt. of the peak in the high mol.wt. region and 2.0×10<3> to 3.2×10<3> number average mol.wt. of the peak in the low mol.wt. region. The binder resin has 60 to 70 deg.C glass transition temp. The mixing time of the toner core particles and external additives is controlled to the time t1 or longer which corresponds to the saturation point p1 of the charge amt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrophotographic toner used in an electrophotographic recording system.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic method using a Carlson process has been widely used for image formation using toner. An electrophotographic image forming apparatus to which the Carlson process is applied generally has a charger, an exposure device, a developing device, a fixing device, a cleaner, and a static eliminator provided sequentially around a photosensitive drum having a photosensitive layer on a surface. It is configured.

An image forming process in an electrophotographic image forming apparatus will be described below. In the above device, first,
In a dark place, the surface of the photosensitive drum is uniformly charged by the charger. Next, an original image is projected on the surface of the photosensitive drum by the exposure device. As a result, the charged potential of the portion of the photosensitive drum surface irradiated with light is removed, and an electrostatic latent image is formed on the photosensitive drum surface. Next, the toner in the developing device charged to the polarity opposite to the charged potential on the photosensitive drum is attached to the electrostatic latent image. As a result, a visible image is formed by the toner.

Then, a recording material is superimposed on this visible image,
Corona discharge is performed on the back surface of the recording material by the transfer device, and a charge having a polarity opposite to that of the toner is applied to the recording material. Thereby, the toner image is transferred to the recording material. The transferred toner image is fixed on the recording material by the heat and pressure of the fixing device,
It becomes a permanent image. On the other hand, the residual toner remaining on the photosensitive drum without being transferred to the recording material is removed by the cleaner. Further, in the above-described apparatus, after the electrostatic latent image on the photosensitive drum is neutralized by the neutralizer, the above-described series of processes starting from the charging process by the charger is repeated again to perform continuous image formation. Will be

The toner used in the electrophotographic system to which the Carlson process is applied, that is, the toner for electrophotography, is a colored powder for forming a visible image and has a function of fixing to a recording material. ing. As described above, in the electrophotographic toner having a plurality of functions, it is often difficult to satisfy all functions. For this reason, a problem occurs in the image density in some cases, and a problem occurs in the long-term use stability in some cases.

In order to solve such a problem, an external additive is often added to the toner in order to stabilize various physical properties such as preservability, fluidity, and chargeability.

Generally, fine particles such as external additives exist in a state where primary particles are aggregated to form large secondary particles. Therefore, when obtaining a toner having desired characteristics by adding an external additive to the toner particles,
The problem is how to crush the aggregates (secondary particles) of the external additive and uniformly disperse them in the toner in an optimum state.

[0008] Japanese Patent Application No. 9-35175 discloses a technique for more effectively exhibiting the effect of the external additive in the process of adding the external additive as described above. A technique is described in which the mixing time for mixing is set between the mixing time at which the charging property indicates a singular point and the mixing time at which the storage property indicates a singular point.

[0009]

However, according to the above-mentioned prior art, as shown in FIG. 10, the charge amount of the toner core particles (toner particles) becomes maximum after a certain mixing time, and then decreases greatly. Go. For this reason, the optimal mixing time between the toner core particles and the external additive is limited to a specific time until the mixing time becomes maximum. Therefore, when adding a plurality of external additives having different optimum mixing times, it is difficult to mix all the external additives with the optimum mixing time for each external additive.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to reduce the mixing time between the toner core particles and the external additive so that the effect of the external additive is more effectively exhibited. An object of the present invention is to provide a method for producing an electrophotographic toner which can be set to a mixing time and which can obtain an electrophotographic toner having characteristics optimal for an electrophotographic system.

[0011]

According to a first aspect of the present invention, there is provided a method of manufacturing a toner for electrophotography, comprising mixing toner core particles containing a binder resin with an external additive. A method for producing an electrophotographic toner, wherein the binder resin exhibits a molecular weight distribution having two peaks, and has a number average molecular weight of 1.0 × 10
⁵ to 2.5 × 10 in the range of ^5, a number average molecular weight within the range of 2.0 × 10 ³ ~3.2 × 10 ³ of the low molecular weight side peak, and a glass transition temperature of 60 to 70 ° C. And the mixing time between the toner core particles and the external additive is set to be equal to or longer than the time when the charge amount reaches the saturation point.

According to the above method, since the binder resin having the above-mentioned specific characteristics is used, the state of the toner core particles and the state of the external additive do not substantially change after the middle stage of stirring. Become. Therefore, when the mixing time of the toner core particles and the external additive is equal to or longer than the time when the charge amount of the electrophotographic toner reaches the saturation point, there is no substantial change in the charge amount of the electrophotographic toner. .

On the other hand, when the number average molecular weight and the glass transition temperature of the binder resin are lower than the above numerical ranges,
The saturation point of the charge amount disappears. When the number average molecular weight and the glass transition temperature of the binder resin are higher than the above numerical ranges, the fixing properties are significantly deteriorated, and the resin cannot be practically used.

According to the above method, the mixing time between the toner core particles and the external additive is set to be equal to or longer than the time when the charge amount reaches the saturation point. In addition, all external additives can be mixed under optimum conditions.

In the present specification, the “saturation point” is
It indicates the point in time when the variation of the charge amount of the electrophotographic toner is within ± 10%.

According to a second aspect of the present invention, there is provided a method of manufacturing a toner for electrophotography according to the first aspect of the present invention.
In the method for producing an electrophotographic toner as described above, the external additive contains silica and hydrotalcite.

The initial developer is required to have a rising speed of the charge amount in order to prevent initial fogging. Therefore, in the method of claim 2, silica and hydrotalcite are added to the toner core particles. As a result, it is possible to obtain an electrophotographic toner which has a rapid rise in charge amount, has fluidity and chargeability required for an initial developer, and can prevent generation of initial fog.

According to a third aspect of the present invention, there is provided a method of manufacturing an electrophotographic toner, the second aspect of the present invention being intended to solve the above-mentioned problems.
The method for producing an electrophotographic toner described above is characterized in that the toner core particles are mixed with silica and then mixed with hydrotalcite.

According to a third aspect of the present invention, in the method of the second aspect, the silica is mixed with the toner core particles, and then the hydrotalcite is mixed. As a result, a large amount of hydrotalcite, which greatly contributes to the rise of the charge amount, is present on the surface of each toner core particle. As a result, it is possible to obtain an electrophotographic toner in which the charge amount rises more quickly and the occurrence of initial fog can be more reliably prevented. Further, it is possible to prevent silica from being buried in the toner core particles, and to obtain an electrophotographic toner having sufficient fluidity.

According to a fourth aspect of the present invention, there is provided a method of manufacturing an electrophotographic toner, the second aspect of the invention being intended to solve the above-mentioned problems.
The method for producing an electrophotographic toner described above, wherein the external additive further contains magnetite.

The toner for replenishment is required to have stable charging during long-term use in order to prevent problems such as a decrease in density, toner scattering, and storability. Therefore, in the method of the fourth aspect, magnetite having a function of stabilizing charging is added to the toner core particles in addition to silica and hydrotalcite. This makes it possible to provide an electrophotographic toner that has excellent stability in properties such as fluidity and chargeability in long-term use, has optimal properties as a replenishing toner, and can prevent problems such as a decrease in density, toner scattering, and storage stability. Obtainable.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a toner for electrophotography according to the fourth aspect of the present invention.
The method for producing an electrophotographic toner described above is characterized in that the toner core particles are mixed with hydrotalcite, mixed with magnetite, and then mixed with silica.

According to a fifth aspect of the present invention, in the method of the fourth aspect, an external additive is added to the toner core particles in the order of magnetite, hydrotalcite, and silica. As a result, each external additive is externally added with an optimal mixing time,
An electrophotographic toner can be manufactured under optimal external addition conditions as a replenishing toner. Therefore, each external additive can sufficiently exhibit its function. As a result, it is possible to obtain an electrophotographic toner which can secure charging stability in long-term use, has optimal characteristics as a replenishing toner, and can prevent problems such as a decrease in density, toner scattering, and storage stability.

Hereinafter, the present invention will be described with reference to FIGS.
This will be described in more detail with reference to FIGS. 9 and 10. According to the method for producing an electrophotographic toner of the present invention, in the method for producing an electrophotographic toner in which toner core particles 1 containing a binder resin and an external additive 2 are mixed, the molecular weight distribution having two peaks is used as the binder resin. And the number average molecular weight of the high molecular weight side peak was 1.0 × 10 ^{5 to} 2.5 × 1.
0 ⁵ range, a number average molecular weight of the low molecular weight side peak 2.
Those having a glass transition temperature in the range of 0 × 10 ^{3 to} 3.2 × 10 ³ and 60 to 70 ° C. are used.

FIGS. 1 and 9 show states of the toner core particles 1 and 11 and the external additive 2 when the toner core particles 1 and 11 and the external additive 2 are mixed by a mixer or the like. FIG. 1 shows the state of the toner core particles 1 and the external additive 2 in the production method of the present invention, and FIG. 9 shows the state of the toner core particles 11 and the external additive 2 in the conventional production method. The toner core particles 11 have a number average molecular weight lower than the above numerical range,
It contains a binder resin having a glass transition temperature of less than 60 ° C.

As can be seen from FIGS. 1 and 9, the state of adhesion between the toner core particles (toner core particles 1 and toner core particles 11) and the external additive 2 greatly affects the charge amount of the electrophotographic toner. .

In the production method of the present invention, as shown in FIG. 1, since the binder resin having the above-mentioned specific characteristics is used, the state of the toner core particles 1 and the external additive 2 is not changed after the middle stage of stirring. Does not substantially change. Therefore, as shown in FIG. 2, the mixing time of the toner core particles 1 and the external additive 2 is time t ₁ , and after the charge amount of the electrophotographic toner reaches the saturation point p ₁ , A saturated state where there is no substantial change in the charge amount of the toner for use.

On the other hand, in the conventional method for producing an electrophotographic toner, as shown in FIG. 9, the state of adhesion between the toner core particles 11 and the external additive 2 always changes greatly. Since the toner core particles 11 having a lower number average molecular weight and a lower glass transition temperature than the toner core particles 1 are used, the external additive 2 is embedded in the toner core particles 1 at a later stage of the stirring.
It shows charging characteristics without a saturation point.

Therefore, as shown in FIG. 10, the charge amount of the toner for electrophotography always changes greatly, reaches a maximum, and then decreases greatly. For this reason, the optimal mixing time of the toner core particles 11 and the external additive 2 is limited to a specific time until the charge amount reaches a maximum. Therefore, when adding a plurality of external additives 2 having different optimum mixing times, it is difficult to mix all the external additives 2 with the respective external additives 2 in the optimum mixing time.

[0030] In contrast, in the manufacturing method of the present invention, each of the external additive 2, the toner core particles 1 at the time the charge amount of the toner for electrophotography reaches the saturation point p ₁ t ₁ or more mixing time
, All the external additives 2 can be externally added under optimum conditions.

When producing an electrophotographic toner used as an initial developer, it is desirable to use silica and hydrotalcite as the external additive 2. As a result, it is possible to obtain an electrophotographic toner which has a rapid rise in charge amount, has fluidity and chargeability required for an initial developer, and can prevent generation of initial fog.

The amount of silica and hydrotalcite used is in the range of 0.1 to 0.3 parts by weight of silica and 100 parts by weight of toner core particles 1, and 0.2 to 0.2 parts by weight of hydrotalcite. It is desirably in the range of ~ 0.4 parts by weight. Thereby, the rise of the charge amount of the electrophotographic toner can be further accelerated.

It is desirable that the toner core particles 1 be mixed with hydrotalcite after being mixed with silica.
As a result, the adhesion state between the toner core particles 1 and the external additive 2 was such that, as shown in FIG. 3, a large amount of hydrotalcite particles 2b largely involved in the rise of the charge amount was present on the surface of the toner core particles 1. It is in a state. As a result, it is possible to obtain an electrophotographic toner in which the charge amount rises more quickly and the occurrence of initial fog can be more reliably prevented. Also, unlike the conventional manufacturing method, the previously mixed silica particles 2a are not buried in the toner core particles 1, so that the fluidity of the electrophotographic toner is not impaired.

When producing an electrophotographic toner used as a replenishing toner, it is desirable to use magnetite as the external additive 2 in addition to silica and hydrotalcite. This makes it possible to provide an electrophotographic toner that has excellent stability in properties such as fluidity and chargeability in long-term use, has optimal properties as a replenishing toner, and can prevent problems such as a decrease in density, toner scattering, and storage stability. Obtainable.

The amount of silica, hydrotalcite, and magnetite used is in the range of 0.1 to 0.3 parts by weight of silica based on 100 parts by weight of toner core particles 1.
In addition, it is desirable that the hydrotalcite is in the range of 0.05 to 0.1 part by weight and the magnetite is in the range of 0.1 to 0.3 part by weight. This can further improve the charging stability of the electrophotographic toner during long-term use.

It is desirable that these external additives be mixed with the toner core particles 1 in the order of hydrotalcite, magnetite, and silica. Thereby, each external additive 2
Is externally added at an optimum mixing time, and an electrophotographic toner can be manufactured under optimum external addition conditions as a replenishing toner. As a result, the adhesion state of the toner core particles 1, the silica particles 2a and the hydrotalcite particles 2b as shown in FIG. 4 is obtained. Therefore, each external additive 2 can sufficiently exhibit its function. Accordingly, it is possible to obtain an electrophotographic toner which can ensure the stability of charging during long-term use, has optimal characteristics as a replenishing toner, and can prevent problems such as a decrease in density, toner scattering, and storage stability.

The binder resin in the toner core particles 1 may be, for example, a polystyrene, poly-p-chlorostyrene, polyvinyltoluene, or other styrene or a substituted homopolymer; styrene-p-chlorostyrene copolymer. Copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer Styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, Styrene-acrylonitrile copolymer, styrene-vinyl Tyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid Styrene-based copolymers such as copolymers, styrene-maleic acid half-ester copolymers, styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, Polyester, polyurethane, epoxy resin, polyvinyl butyral, polyamide, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic hydrocarbon resin, alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated resin Raffin,
Paraffin, wax and the like can be used alone or in combination of two or more. Further, the toner core particles 1 contain a colorant such as carbon black, and may further contain, as necessary, a charge control agent or a polyolefin wax such as polyethylenelen wax as an internal additive.

The electrophotographic toner obtained by the production method of the present invention is desirably subjected to a process of obtaining a two-component developer by mixing with a carrier (hereinafter, referred to as developer).

As the carrier, a spherical magnetic carrier is preferably used. Examples of the spherical magnetic carrier include particles obtained by spheroidizing magnetic particles made of a ferromagnetic substance or a paramagnetic substance; particles in which the surface of the magnetic substance particles is coated spherically with a resin or a fatty acid wax; And the like in which the above magnetic particles are dispersed.

The above ferromagnetic material or paramagnetic material includes:
Metals such as iron, chromium, nickel and cobalt; and compounds and alloys of these metals, for example, triiron tetroxide, ferric oxide, chromium dioxide, manganese oxide, ferrite, and manganese-copper alloy. Examples of the resin include a styrene resin, a vinyl resin, an ethyl resin, a rosin-modified resin, an acrylic resin, a polyamide resin, an epoxy resin, and a polyester resin.The fatty acid wax includes palmitic acid. , Stearic acid and the like.

[0041]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1 Styrene-acrylic copolymer (number average molecular weight Mn on high molecular weight side) as binder resin
₁ is 1.0 × 10 ⁵ ≦ Mn ₁ ≦ 2.5 × 10 ⁵ , and the number average molecular weight Mn ₂ on the low molecular weight side is 2.0 × 10 ³ ≦ Mn ₂ ≦
3.2 × 10 ³ , glass transition temperature Tg is 60 ° C. or more and 70
100 ° C.), carbon black as a colorant (manufactured by Degussa; trade name “Printex9”)
0 ") 7 parts by weight, 2 parts by weight of a charge control agent (manufactured by Orient Chemical Co., Ltd .; trade name" Bontron P51 "), and polyethylene len wax (manufactured by Sanyo Chemical Industry Co., Ltd .; trade name" Hymer TP32 ") 2 A part by weight is 400 rpm with a dry mixer (Henschel type mixer).
And mixed. The obtained mixture is 240 r by a twin-screw kneader.
After melt-kneading at pm, the mixture was pulverized and classified by a jet mill. Thereby, the average particle size of the toner core particles 1 is 9 μm.
m were obtained.

The obtained powder and silica as an external additive 2 (manufactured by Nippon Aerosil Co., Ltd .; trade name "R972")
0.2 parts by weight were mixed by a dry mixer (Henschel type mixer) for each external mixing time shown in Table 1.
An electrophotographic toner was obtained.

Next, 145 g of the toner for electrophotography described above.
And 4 kg of a ferrite carrier having an average particle size of 100 μm (a copying machine manufactured by Sharp Corporation; a carrier for a developer dedicated to the trade name “SD-4085”) using a ball mill (V-type mixer) to form each of the developing times shown in Table 1. (Ball mill rotation time) to form a mixed developer to obtain a two-component developer having a toner concentration of 3.5% by weight.

Evaluation of the toner for electrophotography was performed by using the above two-component developer with a copying machine manufactured by Sharp Corporation; trade name "SD-4".
085 "and measuring the change in the charge amount. Table 1 and FIG. 5 show the evaluation results of each sample (electrophotographic toner) in which the external mixing time and the developing time were changed.

[0046]

[Table 1]

From Table 1 and FIG. 5, it can be seen that, in this embodiment, when the external mixing time is 60 seconds or longer, the charging characteristics of the electrophotographic toner are saturated and stabilized. Therefore, in this embodiment, the mixing time of the powder and the external additive 2 may be set to 60 seconds or more at which the charge amount reaches the saturation point. In addition, it can be seen that the magnitude of the saturation charge amount of the electrophotographic toner changes depending on the developing time.

Example 2 A dry mixer was prepared by mixing the electrophotographic toner obtained in Example 1 with 0.2 parts by weight of hydrotalcite (trade name "Alkamizer 4") as an external additive 2. (Henschel type mixer) was mixed for each external addition time shown in Table 2 to obtain an electrophotographic toner.

Next, 145 g of the toner for electrophotography described above.
And 4 kg of a ferrite carrier having an average particle size of 100 μm (copying machine manufactured by Sharp Corp .; developer carrier for exclusive use of trade name “SD-4085”) by a ball mill (V-type mixer) to obtain each developing time shown in Table 2. (Ball mill rotation time) to form a mixed developer to obtain a two-component developer having a toner concentration of 3.5% by weight.

The evaluation of the electrophotographic toner was performed in the same manner as in Example 1. Table 2 shows the evaluation results of each sample (electrophotographic toner) in which the external mixing time and the developing time were changed.

[0051]

[Table 2]

From Table 2 and FIG. 6, it can be seen that in this embodiment, when the external mixing time is 80 seconds or longer, the charging characteristics are saturated and stabilized. Therefore, in this embodiment, the mixing time of the powder and the external additive 2 may be set to 80 seconds or more at which the charge amount reaches the saturation point. That is, the optimal mixing time of the hydrotalcite is 80 seconds or more.

Example 3 The powder obtained in Example 1 was mixed with silica (manufactured by Nippon Aerosil Co., Ltd .; trade name: "External Additive 2") using a dry mixer (Henschel type mixer). R972 ”) 0.2 parts by weight
After mixing for 2 seconds, 0.2 parts by weight of hydrotalcite (trade name “Alkamizer 4”) as an external additive 2 was added and externally added and mixed for 80 seconds to obtain an electrophotographic toner. The mixing time of the powder and the external additive 2 was set to be equal to or longer than the time when the charge amount reached the saturation point.

Next, 145 g of the above-mentioned toner for electrophotography was used.
And 4 kg of a ferrite carrier having an average particle size of 100 μm (copying machine manufactured by Sharp Corporation; developer carrier for exclusive use of trade name “SD-4085”) by using a ball mill (V-type mixer) to obtain each developing time shown in Table 3. (Ball mill rotation time) to form a mixed developer to obtain a two-component developer having a toner concentration of 3.5% by weight.

Evaluation of the electrophotographic toner was performed in the same manner as in Example 1. Table 3 and FIG. 7 show the evaluation results of each sample (toner for electrophotography) in which the developing time was changed.

Example 4 The powder obtained in Example 1 was subjected to hydrotalcite (trade name “Alkamizer 4”) as an external additive 2 using a dry mixer (Henschel type mixer). ) 0.2 parts by weight were added and mixed for 80 seconds, and then 0.2 parts by weight of silica (manufactured by Nippon Aerosil Co., Ltd .; trade name "R972") as external additive 2 was added and externally added and mixed for 60 seconds. Thus, an electrophotographic toner was manufactured. The mixing time of the powder and the external additive 2 was set to be equal to or longer than the time when the charge amount reached the saturation point.

Next, 145 g of the toner for electrophotography described above.
And 4 kg of a ferrite carrier having an average particle size of 100 μm (copying machine manufactured by Sharp Corporation; developer carrier for exclusive use of trade name “SD-4085”) by using a ball mill (V-type mixer) to obtain each developing time shown in Table 3. (Ball mill rotation time) to form a mixed developer to obtain a two-component developer having a toner concentration of 3.5% by weight.

Evaluation of the electrophotographic toner was performed in the same manner as in Example 1. Table 3 and FIG. 7 show the evaluation results of each sample (toner for electrophotography) in which the developing time was changed.

[0059]

[Table 3]

From the comparison of the results of Examples 3 and 4 shown in Table 3 and FIG. 7, it can be seen that a difference occurs in the saturation charge amount by changing the order of external addition. The initial developer preferably has a higher charge saturation value to prevent fogging. From this, it can be seen that in the case of producing an electrophotographic toner used as an initial developer, hydrotalcite may be externally added after silica is externally added.

[Example 5] Unlike the initial developer, the replenishment toner needs to have stable chargeability and fluidity in long-term use in order to prevent a decrease in copy density and improve storage stability. Becomes

Then, the powder obtained in Example 1 was
Using a dry mixer (Henschel type mixer)
Silica as an external additive 2 (manufactured by Nippon Aerosil Co., Ltd .;
After adding 0.2 parts by weight of the trade name “R972” and mixing for 60 seconds, 0.2 parts by weight of hydrotalcite (trade name “Alkamizer 4”) as the external additive 2 and polishing of the photosensitive drum An electrophotographic toner was manufactured by adding 0.2 parts by weight of magnetite (trade name “KBC-100-40”) as an external additive 2 functioning as an agent and externally mixing for 80 seconds. The mixing time of the powder and magnetite was set to be equal to or longer than the time when the charge amount reached the saturation point.

Next, 145 g of the above-mentioned toner for electrophotography was used.
And 4 kg of a ferrite carrier having an average particle diameter of 100 μm (copying machine manufactured by Sharp Corporation; a developer carrier for exclusive use of trade name “SD-4085”) by a ball mill (V-type mixer) for each developing time shown in Table 4. (Ball mill rotation time) to form a mixed developer to obtain a two-component developer having a toner concentration of 3.5% by weight.

The evaluation of the electrophotographic toner was performed in the same manner as in Example 1. Ball mill rotation time (developer conversion time)
Table 4 and FIG. 8 show the evaluation results of the samples (electrophotographic toner) in which was changed, together with the evaluation results of the electrophotographic toner of Example 3.

[0065]

[Table 4]

From the results shown in Table 4 and FIG. 8, the use of magnetite makes it possible to obtain a more stable image quality over a long period of use, and to obtain an electrophotographic toner having optimum characteristics as a replenishing toner. I understand.

In addition, the order of mixing silica, hydrotalcite, and magnetite with the powder obtained in Example 1 was examined in various ways. As a result, the external additive 2 was mixed with the powder obtained in Example 1 in the order of hydrotalcite, magnetite, and silica.
Can be externally added in an optimum mixing time, and the external additive 2 can exhibit its function sufficiently.

[0068]

The method for producing an electrophotographic toner according to claim 1 of the present invention is, as described above, a method for producing an electrophotographic toner in which toner core particles containing a binder resin and an external additive are mixed. The binder resin exhibits a molecular weight distribution having two peaks, and the number average molecular weight of the high molecular weight side peak is in the range of 1.0 × 10 ^{5 to} 2.5 × 10 ⁵ ,
The number average molecular weight of the low molecular weight side peak is from 2.0 × 10 ³ to
A mixture having a glass transition temperature in the range of 3.2 × 10 ³ and a glass transition temperature of 60 to 70 ° C. is used. This is a method that is set for the time to reach.

According to the above method, since the binder resin having the above-mentioned specific characteristics is used, the mixing time of the toner core particles and the external additive at a certain point in time makes it difficult to charge the electrophotographic toner. The amount reaches the saturation point. According to the above method, the mixing time between the toner core particles and the external additive is set to be equal to or longer than the time when the charge amount reaches the saturation point. With this, even when a plurality of types of external additives are used, the mixing time of all the external additives and the toner core particles is set to the optimal mixing time at which the effect of the external additives is more effectively exhibited. Can be
An effect is obtained that an electrophotographic toner having characteristics optimal for the electrophotographic method can be obtained.

The method for producing an electrophotographic toner according to claim 2 of the present invention is a method as described above, wherein the external additive contains silica and hydrotalcite. As a result, an effect is obtained that an electrophotographic toner having a rapid rise in charge amount, having fluidity and chargeability required for an initial developer, and capable of preventing occurrence of initial fog can be obtained.

The method for producing an electrophotographic toner according to claim 3 of the present invention is a method of mixing toner core particles with silica and then mixing with hydrotalcite, as described above. As a result, there is an effect that an electrophotographic toner having a more rapid rise of charging, preventing generation of initial fog more reliably, and having sufficient fluidity can be obtained.

The method for producing an electrophotographic toner according to claim 4 of the present invention is a method wherein the external additive further contains magnetite as described above. This makes it possible to provide an electrophotographic toner that has excellent stability in properties such as fluidity and chargeability in long-term use, has optimal properties as a replenishing toner, and can prevent problems such as a decrease in density, toner scattering, and storage stability. This has the effect that it can be obtained.

The method for producing an electrophotographic toner according to claim 5 of the present invention is, as described above, a method in which toner core particles are mixed with hydrotalcite, mixed with magnetite, and then mixed with silica. is there. As a result, it is possible to obtain a toner for electrophotography that can ensure the stability of charging during long-term use, has optimal characteristics as a replenishing toner, and can prevent problems such as density reduction, toner scattering, and storage stability. To play.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state in which an external additive is externally added to toner core particles with stirring in a method for producing an electrophotographic toner of the present invention, wherein FIG. )
Shows the state in the middle of the stirring, and (c) shows the state in the latter half of the stirring.

FIG. 2 is a graph showing a relationship between a mixing time of an external additive and toner core particles and a charge amount of the electrophotographic toner in the method for producing an electrophotographic toner of the present invention.

FIG. 3 is a schematic view showing a state in which silica particles and hydrotalcite particles as external additives are adhered to toner core particle surfaces in one embodiment of the method for producing an electrophotographic toner of the present invention.

FIG. 4 is a schematic view showing a state in which silica particles and hydrotalcite particles, which are external additives, are attached to the surface of toner core particles in another embodiment of the method for producing an electrophotographic toner of the present invention.

FIG. 5 is a graph showing the relationship between the external addition mixing time, the time for forming a developer, and the charge amount of the electrophotographic toner in one embodiment of the method for producing the electrophotographic toner of the present invention.

FIG. 6 is a graph showing the relationship between the external addition mixing time, the time for forming a developer, and the charge amount of the electrophotographic toner in another example of the method for producing the electrophotographic toner of the present invention.

FIG. 7 is a graph showing the relationship between the developer conversion time and the charge amount of the electrophotographic toner in still another example of the method for producing an electrophotographic toner of the present invention.

FIG. 8 is a graph showing the relationship between the ball mill rotation time (developing agent development time) and the charge amount of the electrophotographic toner in still another example of the method for producing an electrophotographic toner according to the present invention.

FIG. 9 shows a conventional method for producing an electrophotographic toner.
FIGS. 3A and 3B are schematic diagrams showing a state in which an external additive is externally added to toner core particles with mixing, wherein FIG. 3A shows a state at an early stage of stirring, FIG. .

FIG. 10 is a graph showing a relationship between a mixing time of an external additive and toner core particles and a charge amount of the electrophotographic toner in a conventional method for producing an electrophotographic toner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Toner core particle 2 External additive 2a Silica particle 2b Hydrotalcite particle

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshitaka Urata 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Yasuharu Morinishi 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp (72) Inventor Yoyasu Honda 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka

Claims (5)

[Claims] 1. A method for producing an electrophotographic toner, comprising mixing toner core particles containing a binder resin and an external additive, wherein the binder resin exhibits a molecular weight distribution having two peaks, and a high molecular weight peak. Has a number average molecular weight of 1.0
The number average molecular weight of the low molecular weight side peak is in the range of 2.0 × 10 ^{3 to} 3.2 × 10 ³ , and the glass transition temperature is in the range of × 10 ^{5 to} 2.5 × 10 ⁵ . A method for producing a toner for electrophotography, wherein a temperature within a range of 70 ° C. is used, and a mixing time of the toner core particles and the external additive is set to be equal to or longer than a time at which a charge amount reaches a saturation point. 2. The method for producing an electrophotographic toner according to claim 1, wherein said external additive contains silica and hydrotalcite. 3. The method for producing an electrophotographic toner according to claim 2, wherein the toner core particles are mixed with silica and then mixed with hydrotalcite. 4. The method for producing an electrophotographic toner according to claim 2, wherein said external additive further contains magnetite. 5. The method for producing an electrophotographic toner according to claim 4, wherein the toner core particles are mixed with hydrotalcite, mixed with magnetite, and then mixed with silica.