JP2007121663A - Negative charge type encapsulated silica, method for manufacturing same, and toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide negative charge type encapsulated silica excellent in environmental stability and in ability to impart a negative charging property, to provide a manufacturing method by which such negative charge type encapsulated silica can be efficiently manufactured, and to provide toner excellent in charging characteristics. <P>SOLUTION: The encapsulated silica is negative charge type encapsulated silica as an external additive for imparting a negative charging property to toner, and the encapsulated silica is obtained by coating silica particles having an anionic group on the surface with a film derived from a cationic polymerizable surfactant having a cationic group, a hydrophobic group and a polymerizable group, and an anionic polymerizable surfactant having an anionic group, a hydrophobic group and a polymerizable group, wherein the film has the cationic group originating in the cationic polymerizable surfactant on the silica particle side, and has the anionic group originating in the anionic polymerizable surfactant on the side opposite to the silica particle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to negatively chargeable encapsulated silica, a method for producing negatively chargeable encapsulated silica, and a toner.

For the purpose of improving the charging characteristics of the toner, it is common to apply negatively chargeable silica as an external additive to the toner.
As such negatively chargeable silica, a silica particle whose surface has been subjected to a hydrophobic treatment is known (see, for example, Patent Document 1).
However, the conventional negatively chargeable silica improves the moisture resistance by subjecting it to a hydrophobic treatment, but has a problem that the ability to impart negative chargeability to the toner particles is reduced. Further, there has been a problem that when the hydrophobization treatment is performed, the aggregation of the silica particles is promoted, or the primary particles remain without being crushed during the hydrophobization treatment. As a result, there has been a problem that sufficient fluidity cannot be imparted to the toner, resulting in poor charging or fogging. In particular, such a problem is remarkable after use under high humidity or for a long time.

JP 2004-168559 A

  An object of the present invention is to provide negatively charged encapsulated silica having excellent environmental stability and excellent negative chargeability-imparting ability, and such negatively chargeable encapsulated silica can be efficiently produced. It is an object of the present invention to provide a production method and a toner excellent in charging characteristics.

Such an object is achieved by the present invention described below.
The negatively chargeable encapsulated silica of the present invention is a negatively chargeable encapsulated silica as an external additive that imparts negative chargeability to a toner,
Silica particles having an anionic group on the surface, a cationic polymerizable surfactant having a cationic group, a hydrophobic group and a polymerizable group, and an anionic property having an anionic group, a hydrophobic group and a polymerizable group Coated with a film derived from a polymerizable surfactant,
The membrane has a cationic group derived from the cationic polymerizable surfactant on the silica particle side, and an anionic group derived from the anionic polymerizable surfactant on the side opposite to the silica particle. It is characterized by having.
Thereby, it is possible to provide negatively charged encapsulated silica having excellent environmental stability and excellent negative chargeability imparting ability.

The average particle diameter of the negatively chargeable encapsulated silica of the present invention is preferably 8 to 50 nm.
As a result, when added to the toner, it is possible to effectively prevent variation in the charge amount between the toner particles.
In the negatively charged encapsulated silica of the present invention, the membrane is a laminate of at least a cationic layer derived from the cationic polymerizable surfactant and an anionic layer derived from the anionic polymerizable surfactant. It is preferable that it is comprised with the body.
Thereby, the durability (moisture resistance) of the negatively chargeable encapsulated silica can be further improved. Further, the dispersibility in the toner powder can be further improved.

The method for producing the negatively chargeable encapsulated silica of the present invention comprises:
Adding the cationic polymerizable surfactant to the dispersion of silica particles and mixing to obtain a first mixture;
Adding the anionic polymerizable surfactant to the first mixed solution and mixing to obtain a second mixed solution;
And adding a polymerization initiator to the second liquid mixture for polymerization.
Thereby, negatively chargeable encapsulated silica having excellent environmental stability and excellent negative chargeability-imparting ability can be easily obtained.
The method for producing negatively charged encapsulated silica of the present invention is a method for producing negatively charged encapsulated silica of the present invention,
Forming a cation layer by polymerizing the cationic polymerizable surfactant on the silica particles;
A step of laminating the anionic layer by polymerizing the anionic polymerizable surfactant on the cationic layer.
Thereby, negatively chargeable encapsulated silica having excellent environmental stability and excellent negative chargeability-imparting ability can be easily obtained.
The toner of the present invention is characterized in that the negatively chargeable encapsulated silica of the present invention is added as an external additive.
Thereby, it is possible to provide a toner having excellent charging characteristics and environmental characteristics.

Hereinafter, preferred embodiments of a negatively chargeable encapsulated silica, a method for producing negatively chargeable encapsulated silica, and a toner using negatively chargeable encapsulated silica of the present invention will be described in detail with reference to the accompanying drawings.
<Negatively charged encapsulated silica>
Hereinafter, the negatively chargeable encapsulated silica of the present invention will be described.

<First Embodiment>
First, a first embodiment of the negatively chargeable encapsulated silica of the present invention will be described.
FIG. 1 is a diagram showing a first embodiment of negatively chargeable encapsulated silica of the present invention, and FIG. 2 is a diagram showing a process for producing negatively chargeable encapsulated silica according to the first embodiment.
The negatively chargeable encapsulated silica 100 of the present embodiment imparts negative chargeability to the toner. As shown in FIG. 1, the silica particles 1 having an anionic group 11 on the surface are coated with a film 200. It is a thing.
The average particle size of such negatively chargeable encapsulated silica 100 is preferably 8 to 50 nm, and more preferably 12 to 30 nm. When the average particle diameter of the negatively chargeable encapsulated silica 100 is in such a range, when added to the toner, it is possible to effectively prevent the charge amount from varying between the toner particles.

[Silica particles 1]
First, the silica particles 1 will be described.
The silica particles 1 are mainly composed of SiO ₂ (silica), and usually have silanol groups on the surface thereof.
In the present invention, this silanol group may be used as the anionic group on the surface of the silica particles, or may be introduced by surface treatment.

When an anionic group is introduced by surface treatment, for example, a surface treatment agent as shown below can be used.
For example, as a surface treating agent (anionic group-imparting agent) for introducing an anionic group on the surface of silica particles, a sulfur-containing treating agent can be preferably mentioned first.
Examples of the treatment agent containing sulfur include sulfuric acid, fuming sulfuric acid, sulfur trioxide, chlorosulfuric acid, fluorosulfuric acid, amidosulfuric acid, sulfonated pyridine salt, and sulfamic acid. Among them, sulfur trioxide, sulfonated pyridine salt or sulfamine. Sulfonating agents such as acids are preferred. These can be used alone or in admixture of two or more.

In addition, a solvent capable of forming a complex with the sulfur trioxide (a basic solvent such as N, N-dimethylformamide dioxane, pyridine, triethylamine, and trimethylamine, nitromethane, acetonitrile, etc.) and a solvent described later. It is also useful to form a complex with a mixed solvent of one or more kinds.
In particular, if sulfur trioxide itself is too reactive to decompose or alter the resin itself, or it is difficult to control the reaction with a strong acid, a complex of sulfur trioxide and a tertiary amine is used as described above. It is preferable to perform the surface treatment of the silica particles.
In addition, when sulfuric acid, fuming sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, etc. are used alone, silica particles dissolve easily, and it is necessary to suppress the reaction for strong acids that react per molecule. It is necessary to pay attention to the type of solvent and the amount used.

The treatment with the treatment agent containing sulfur is performed by adding a treatment agent containing sulfur, heating to 60 to 200 ° C., and stirring for 3 to 10 hours. At this time, the determination of the amount of the anionic group introduced largely depends on the reaction conditions and the type of the treatment agent containing sulfur.
Furthermore, by treating the sulfonic acid (—SO ₃ H) described above with an alkali compound, silica particles having a sulfonic acid anion group (—SO ₃ ^— ) on the surface can be obtained.

As the alkali compound, a cation is an alkali metal ion or a chemical formula (R ₁ R ₂ R ₃ R ₄ N) ⁺ (R ₁ , R ₂ , R ₃ and R ₄ may be the same or different, and a hydrogen atom, an alkyl group, An alkaline compound that is a monovalent ion represented by (showing a hydroxyalkyl group or an alkyl halide group) is selected. Preferably, an alkaline compound in which the cation is an alkanolamine cation such as lithium ion (Li ⁺ ), potassium ion (K ⁺ ), sodium ion (Na ⁺ ), ammonium ion (NH 4 ⁺ ), and triethanolamine cation. is there.

  Hydroxyl anion is preferably used as the anion of the alkali compound. Specific examples thereof include ammonia, alkanolamine (monoethanolamine, diethanolamine, N, N-butylethanolamine, triethanolamine, propanolamine, aminomethyl). Propanol, 2-aminoisopropanol, etc.) and monovalent alkali metal hydroxides (LiOH, NaOH, KOH).

The amount of the alkali compound added is preferably at least the neutralization equivalent of the sulfonic acid group of the silica particles. Further, for volatile additives such as ammonia and alkanolamine, addition of 1.5 times or more of the neutralization equivalent is generally preferable.
The operation can be performed by placing silica particles having the sulfonic acid group chemically bonded to the surface thereof in an alkali compound and shaking with a paint shaker or the like.

Moreover, a carboxylating agent can also be mentioned suitably as an anionic group provision agent for processing the surface of a silica particle.
As a carboxylating agent, an oxidant such as hypohalite such as sodium hypochlorite or potassium hypochlorite is used to cut a partial bond (C = C, CC) on the surface of silica particles. And by oxidizing.

As an example of the treatment with a carboxylating agent, an appropriate amount of hypohalite such as sodium hypochlorite having an effective halogen concentration of 10 to 30% is added to an aqueous suspension in which silica particles are dispersed, It is performed by heating to 60 to 80 ° C. and stirring for about 5 to 10 hours, preferably 10 hours or more. This operation involves a considerable amount of heat and requires safety precautions.
Then, by treating the silica particles having a carboxylic acid group (-COOH) with an alkaline compound, a carboxylic acid anion group - it may be silica particles having a surface ^(-COO).
The kind of alkali compound and the treatment method with the alkali compound are the same as described above.

The average particle diameter of such silica particles 1 is preferably 5 to 45 nm, and more preferably 9 to 25 nm. As a result, when added to the toner, it is possible to effectively prevent variation in the charge amount between the toner particles.
Further, the amount of the anionic group on the surface of the silica particle 1 is preferably 3 to 100 mmol, more preferably 4 to 20 mmol with respect to 100 g of the silica particles. Thereby, the silica particle 1 can be encapsulated more reliably.

[Membrane 200]
Next, the film 200 will be described.
The membrane 200 includes a cationic polymerizable surfactant 210 having a cationic group 211, a hydrophobic group 212, and a polymerizable group 213, an anionic group 221, a hydrophobic group 222, and a polymerizable group, as will be described in detail later. It is derived from an anionic polymerizable surfactant 220 having a group 223.

As shown in FIG. 1, the membrane 200 includes a cationic group 211 derived from the cationic polymerizable surfactant 210 on the silica particle 1 side, and an anionic polymerizable surfactant 220 on the opposite side of the silica particle 1. And an anionic group 221 derived therefrom.
The membrane 200 covers the silica particle 1 in a state where the anionic group 11 of the silica particle 1 and the cationic group 211 are ionically bonded.

  By the way, conventionally, as the negatively chargeable silica, silica particles whose surface has been subjected to a hydrophobic treatment have been used. However, the conventional negatively chargeable silica improves the moisture resistance by hydrophobizing, but has a problem that the ability to impart negative chargeability (negative chargeability imparting ability) decreases. Further, there has been a problem that when the hydrophobization treatment is performed, the aggregation of the silica particles is promoted, or the primary particles remain without being crushed during the hydrophobization treatment. As a result, there has been a problem that sufficient fluidity cannot be imparted to the toner, resulting in poor charging or fogging. In particular, such a problem is remarkable after use under high humidity or for a long time.

  In contrast, in the negatively charged encapsulated silica of the present invention, silica particles are coated with a film derived from a cationic polymerizable surfactant and an anionic polymerizable surfactant (encapsulated). Therefore, the charge state on the surface of the silica particles can be directly used as the charge state on the film surface. As a result, the negative chargeability imparting ability of the silica particles themselves can be effectively exhibited. In addition, since the film derived from the cationic polymerizable surfactant and the anionic polymerizable surfactant has high environmental stability (particularly moisture resistance), conventional negatively charged silica could not be compatible. It is possible to achieve both excellent environmental stability and excellent ability to impart negative chargeability.

In addition, since the negatively charged encapsulated silica of the present invention is one in which silica particles are coated with the film as described above, the particles can be effectively prevented from becoming coarse due to aggregation or the like. Can be provided with sufficient fluidity.
In addition, since the film derived from the cationic polymerizable surfactant and the anionic polymerizable surfactant that coats the silica particles has high affinity with the toner particles, the resulting negatively charged encapsulated silica Dispersibility in the toner powder can be improved. As a result, the charge amount between the toner particles can be made uniform.

In addition, according to the present invention, since the silica particles and the film are strongly ionically bonded, it is possible to prevent unintentional peeling of the film and the like, and to effectively reduce the charging characteristics of the obtained toner. Can be prevented.
The effects as described above cannot be obtained simply by coating silica particles with a resin or the like.

The cationic group of the cationic polymerizable surfactant is preferably a cationic group selected from the group consisting of a primary amine cation, a secondary amine cation, a tertiary amine cation, and a quaternary ammonium cation. The primary amine cation is a monoalkylammonium cation (RNH ₃ ⁺ ) or the like, the secondary amine cation is a dialkylammonium cation (R ₂ NH ₂ ⁺ ) or the like, and the tertiary amine cation is a trialkylammonium cation (R _3). NH ⁺ ) and the like, and examples of the quaternary ammonium cation include (R ₄ N ⁺ ) and the like. Here, R is a hydrophobic group and a polymerizable group, and examples thereof include those shown below.

Examples of the counter anion of the cationic group include Cl ⁻ , Br ⁻ , and I ⁻ .
In addition, the hydrophobic group of the cationic polymerizable surfactant is preferably selected from the group consisting of an alkyl group, an aryl group, and a group in which these are combined.
The polymerizable group of the cationic polymerizable surfactant is preferably an unsaturated hydrocarbon group, and more specifically, a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, or a vinylene group. Preferably it is selected from the group. Among these, an acryloyl group and a methacryloyl group can be exemplified as preferable examples.
Specific examples of the cationic polymerizable surfactant described above include cationic allyl acid derivatives as described in JP-B-4-65824.

Examples of the cationic polymerizable surfactant used in the present invention include compounds represented by the general formula R _{[4- (l + m + n)]} R ¹ _l R ² _m R ³ _n N ⁺ · X ^−. (R is a polymerizable group, R ¹ , R ² , and R ³ are each an alkyl group or an aryl group, X is Cl, Br, or I, and l, m, and n are each 1 or 0. .) Here, as the polymerizable group, a hydrocarbon group having an unsaturated hydrocarbon group capable of radical polymerization can be preferably exemplified, and more specifically, an allyl group, an acroyl group, a methacryloyl group, a vinyl group, a propenyl group. Group, vinylidene group, vinylene group and the like.

  Specific examples of the cationic polymerizable surfactant include dimethylaminoethyl methyl chloride methacrylate, dimethylaminoethyl benzyl methacrylate methacrylate, methacryloyloxyethyltrimethylammonium chloride, diallyldimethylammonium chloride, 2-hydroxy-3-methacryloxypropyl. Examples thereof include trimethylammonium chloride.

A commercial item can also be used as the above-mentioned cationic polymerizable surfactant. Examples include Acryester DMC (Mitsubishi Rayon Co., Ltd.), Acryester DML60 (Mitsubishi Rayon Co., Ltd.), C-1615 (Daiichi Kogyo Seiyaku Co., Ltd.), and the like.
The cationic polymerizable surfactants exemplified above can be used alone or as a mixture of two or more.

Preferred examples of the anionic group of the anionic polymerizable surfactant include those selected from the group of sulfonic acid groups, sulfinic acid groups, carboxyl groups, carbonyl groups, and salts thereof.
The hydrophobic group of the anionic polymerizable surfactant is preferably selected from the group consisting of an alkyl group, an aryl group, and a group in which these are combined.
The polymerizable group of the anionic polymerizable surfactant is preferably an unsaturated hydrocarbon group, and more specifically, a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, or a vinylene group. Preferably it is selected from the group. Among these, an acryloyl group and a methacryloyl group can be exemplified as preferable examples.

Specific examples of the anionic polymerizable surfactant include anions as described in JP-B-49-46291, JP-B-1-24142, or JP-A-62-104802. Allyl derivatives, anionic propenyl derivatives as described in JP-A-62-221431, JP-A-62-34947 or JP-A-55-11525 Examples thereof include anionic acrylic acid derivatives and anionic itaconic acid derivatives as described in JP-B-46-34898 or JP-A-51-30284.
Examples of the anionic polymerizable surfactant used in the present invention include a general formula (31):

［式中、Ｒ^２１及びＲ^３１は、それぞれ独立して、水素原子又は炭素数１〜１２の炭化水素基であり、Ｚ１は、炭素−炭素単結合又は式−ＣＨ_２−Ｏ−ＣＨ_２−で表される基であり、ｍは２〜２０の整数であり、Ｘは式−ＳＯ_３Ｍ^１で表される基であり、Ｍ^１はアルカリ金属、アンモニウム塩、又はアルカノールアミンである］
で表される化合物、又は式（３２）：

[Wherein, R ²¹ and R ³¹ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, and Z 1 represents a carbon-carbon single bond or a formula —CH ₂ —O—CH ₂ — Wherein m is an integer of 2 to 20, X is a group represented by the formula —SO ₃ M ¹ , and M ¹ is an alkali metal, an ammonium salt, or an alkanolamine]
Or a compound represented by formula (32):

［式中、Ｒ^２２及びＲ^３２は、それぞれ独立して、水素原子又は炭素数１〜１２の炭化水素基であり、Ｄは、炭素−炭素単結合又は式−ＣＨ_２−Ｏ−ＣＨ_２−で表される基であり、ｎは２〜２０の整数であり、Ｙは式−ＳＯ_３Ｍ^２で表される基であり、Ｍ^２はアルカリ金属、アンモニウム塩、又はアルカノールアミンである］
で表される化合物が好ましい。

[Wherein, R ²² and R ³² each independently represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, and D represents a carbon-carbon single bond or a formula —CH ₂ —O—CH ₂ — N is an integer of 2 to 20, Y is a group represented by the formula —SO ₃ M ² , and M ² is an alkali metal, an ammonium salt, or an alkanolamine]
The compound represented by these is preferable.

  The polymerizable surfactant represented by the above formula (31) is described in JP-A-5-320276 or JP-A-10-316909. As a preferable polymerizable surfactant represented by the formula (31), a compound represented by the following formula (310) can be exemplified. Specifically, in the following formulas (31a) to (31d) Mention may be made of the compounds represented.

［式中、Ｒ^３１，ｍ，Ｍ^１は式（３１）で表される化合物と同様］

[Wherein R ³¹ , m and M ¹ are the same as the compound represented by formula (31)]

Moreover, a commercial item can also be used as an anionic polymerizable surfactant. For example, Aqualon HS series (Aqualon HS-05, HS-10, HS-20, HS-1025) from Daiichi Kogyo Seiyaku Co., Ltd. or Adeka Soap SE-10N, SE-20N from Asahi Denka Kogyo Co., Ltd. Can be mentioned.
Adeka Soap SE-10N manufactured by Asahi Denka Kogyo Co., Ltd. is a compound represented by formula (310) in which M ¹ is NH ₄ , R ³¹ is C ₉ H ₁₉ , and m = 10. Adeka Soap SE-20N manufactured by Asahi Denka Kogyo Co., Ltd. is a compound represented by formula (310) in which M ¹ is NH ₄ , R ³¹ is C ₉ H ₁₉ , and m = 20.
Examples of the anionic polymerizable surfactant used in the present invention include a general formula (33):

［式中、ｐは９又は１１であり、ｑは２〜２０の整数であり、Ａは−ＳＯ_３Ｍ^３で表わされる基であり、Ｍ^３はアルカリ金属、アンモニウム塩又はアルカノールアミンである］
で表される化合物が好ましい。式（３３）で表される好ましいアニオン性重合性界面活性剤としては、以下の化合物を挙げることができる。

[In the formula, p is 9 or 11, q is an integer of 2 to 20, A is a group represented by —SO ₃ M ³ , and M ³ is an alkali metal, an ammonium salt or an alkanolamine]
The compound represented by these is preferable. Preferred examples of the anionic polymerizable surfactant represented by the formula (33) include the following compounds.

［式中、ｒは９又は１１、ｓは５又は１０］

[Wherein r is 9 or 11, s is 5 or 10]

Further, as the anionic polymerizable surfactant, other commercially available products can be used. For example, Aqualon KH series (Aqualon KH-5, Aqualon KH-10) from Daiichi Kogyo Seiyaku Co., Ltd. can be mentioned. Aqualon KH-5 is a mixture of a compound represented by the above formula wherein r is 9 and s is 5 and a compound where r is 11 and s is 5. Aqualon KH-10 is a mixture of a compound represented by the above formula wherein r is 9 and s is 10, and a compound where r is 11 and s is 10.
Moreover, as an anionic polymerizable surfactant, the compound represented by the following formula (A) is also preferable.

［上式中、Ｒ^４は水素原子または炭素数１から１２の炭化水素基を表し、ｌは２〜２０の数を表し、Ｍ^４はアルカリ金属、アンモニウム塩、またはアルカノールアミンを表す。］

[In the above formula, R ⁴ represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, l represents a number of 2 to 20, and M ⁴ represents an alkali metal, an ammonium salt, or an alkanolamine. ]

[Production of Negatively Charged Encapsulated Silica 100]
Next, a method for producing negatively charged encapsulated silica according to the first embodiment of the present invention will be described with reference to the accompanying drawings.
The negatively chargeable encapsulated silica 100 as described above can be manufactured, for example, as follows.

First, an aqueous dispersion in which silica particles 1 are dispersed in an aqueous dispersion medium such as water is prepared.
Next, the cationic polymerizable surfactant 210 described above is added to and mixed with this aqueous dispersion to obtain a first mixed liquid (first mixed liquid preparation step).
At this time, in the first mixed solution, as shown in FIG. 2A, the added cationic polymerizable surfactant 210 adsorbs the cationic group 211 to the anionic group 11 of the silica particle 1. It is ionically bound and immobilized.

In this embodiment, the addition amount of the cationic polymerizable surfactant added to the aqueous dispersion is 1.0 to 1.5 times the total number of anionic groups on the surface of the silica particles in the aqueous dispersion. The range of mol is preferable, and the range of 1.0 to 1.2 times mol is more preferable. As a result, the silica particles having an anionic group are strongly ionically bound and can be easily encapsulated. By setting the addition amount to 2 times mol or less, the generation of the cationic polymerizable surfactant not adsorbed on the silica particles can be reduced.
The anionic group 11 on the surface of the silica particle 1 and the cationic group 211 of the cationic polymerizable surfactant 210 are ionically bonded.

Next, the anionic polymerizable surfactant 220 as described above is added to and mixed with the obtained first mixed liquid to obtain a second mixed liquid (second mixed liquid preparing step).
In the second mixed solution, as shown in FIG. 2B, the hydrophobic group 222 and the polymerizable group 223 of the anionic polymerizable surfactant 220 are combined with the hydrophobic group of the cationic polymerizable surfactant 210. 212 is adsorbed by a hydrophobic interaction between the polymerizable group 213 and the anionic group 221 of the anionic polymerizable surfactant 220 is arranged in the direction in which the aqueous dispersion medium exists, that is, in the direction away from the silica particles 1. Is done.

  In this embodiment, the amount of the anionic polymerizable surfactant added to the first mixed solution is preferably in the range of 1.0 to 10 times mol with respect to the added cationic polymerizable surfactant, Preferably, it is the range of 1.0-5.0 times mol. Thereby, the generation of the anionic polymerizable surfactant not adsorbed on the silica particles can be reduced and the encapsulation can be easily performed.

Next, a polymerization initiator is added to the second mixed solution to polymerize the polymerizable groups of the cationic polymerizable surfactant 210 and the anionic polymerizable surfactant 220 (polymerization step). Thereby, as shown in FIG. 1, a film 200 is formed on the surface of the silica particles 1, and a dispersion liquid in which the negatively chargeable encapsulated silica 100 according to the present embodiment is dispersed is obtained.
As such a polymerization initiator, a water-soluble polymerization initiator is preferable, and potassium persulfate, ammonium persulfate, sodium persulfate, 2,2-azobis- (2-methylpropionamidine) dihydrochloride, or 4,4 -Azobis- (4-cyanovaleric acid) and the like.

The addition of the polymerization initiator can be suitably carried out by dropping an aqueous solution in which a water-soluble polymerization initiator is dissolved in pure water.
The polymerization initiator is preferably added in an activated state.
The activation of the polymerization initiator can be preferably carried out by raising the temperature of the second mixed liquid to a predetermined polymerization temperature. The polymerization temperature is preferably in the range of 60 ° C to 90 ° C.
The polymerization reaction is preferably performed using a reaction vessel equipped with an ultrasonic generator, a stirrer, a reflux condenser, a dropping funnel and a temperature controller.

  According to the method as described above, the anionic group on the surface of the silica particles and the cationic group of the cationic polymerizable surfactant are ionically bonded in the polymerization system, and the membrane is formed by a polymerization reaction. Therefore, the arrangement of the cationic polymerizable surfactant and the anionic polymerizable surfactant existing around the silica particles before emulsion polymerization affects the polarization state of the particle surface after polymerization, and therefore extremely It can be controlled with high accuracy.

The dispersion liquid of negatively charged encapsulated silica 100 obtained as described above is isolated by spray drying, filtration drying or the like, and applied to a toner described later.
In addition, you may perform a 1st liquid mixture preparation process, a 2nd liquid mixture preparation process, and a superposition | polymerization process repeatedly. Thereby, it can be set as the film | membrane comprised by the laminated body which laminated | stacked the several layer. Thereby, the durability (moisture resistance) of the film can be improved and the dispersibility in the toner powder can be further improved.
In addition to the cationic polymerizable surfactant and the anionic polymerizable surfactant, a comonomer may be added for the purpose of improving durability and dispersibility in the resin.

  Further, during the polymerization, a polymerizable surfactant (cationic polymerizable surfactant, anionic polymerizable surfactant) and a hydrophobic monomer may be present in the second mixed liquid as necessary. In this case, the film 200 is copolymerized from a polymerizable surfactant and a hydrophobic monomer. Thereby, unintentional peeling etc. of the film | membrane 200 which coat | covers the silica particle 1 can be prevented more effectively.

  The hydrophobic monomer has at least a hydrophobic group and a polymerizable group in its structure, and the hydrophobic group is selected from the group consisting of an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. Can be illustrated. Examples of the aliphatic hydrocarbon group include a methyl group, an ethyl group, and a propyl group. Examples of the alicyclic hydrocarbon group include a cyclohexyl group, a dicyclopentenyl group, a dicyclopentanyl group, and an isobornyl group, and an aromatic hydrocarbon group. Examples thereof include a benzyl group, a phenyl group, and a naphthyl group.

The polymerizable group is an unsaturated hydrocarbon group capable of radical polymerization, and is preferably selected from the group consisting of a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. .
Specific examples of the hydrophobic monomer include styrene and methylstyrene, dimethylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, p-chloromethylstyrene, divinylbenzene, and other styrene derivatives; methyl acrylate, ethyl acrylate, acrylic acid n-butyl, butoxyethyl acrylate, benzyl acrylate, phenyl acrylate, phenoxyethyl acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, tetrahydrofurfuryl acrylate, isobol Monofunctional acrylic esters such as nyl acrylate; methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate , Butoxymethyl methacrylate, benzyl methacrylate, phenyl methacrylate, phenoxyethyl methacrylate, cyclohexyl methacrylate, dicyclopentanyl methacrylate, dicyclopentenyl methacrylate, dicyclopentenyloxyethyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl methacrylate, etc. Monofunctional methacrylate esters of allyl compounds such as allylbenzene, allyl-3-cyclohexanepropionate, 1-allyl-3,4-dimethoxybenzene, allylphenoxyacetate, allylphenylacetate, allylcyclohexane, allyl polycarboxylic acid allyl, etc. ; Ester cheeks of fumaric acid, maleic acid, itaconic acid; radically polymerizable groups such as N-substituted maleimides and cyclic olefins Monomer, and the like that.

As the hydrophobic monomer, those satisfying the above-mentioned required characteristics are appropriately selected, and the addition amount thereof is arbitrarily determined.
The amount of the hydrophobic monomer added is preferably in the range of about 5 to 900 parts by weight, more preferably in the range of 10 to 500 parts by weight, and particularly preferably 15 to 200 parts by weight with respect to 100 parts by weight of the silica particles. Part range.
Moreover, it is also preferable that the film | membrane 200 which coat | covers the silica particle 1 has a repeating structural unit induced | guided | derived from the crosslinkable monomer.

By having a repeating structural unit derived from a crosslinkable monomer, a crosslinked structure is formed in the film 200 and the durability of the film 200 can be improved.
Examples of the crosslinkable monomer include compounds having two or more unsaturated hydrocarbon groups selected from vinyl group, allyl group, acryloyl group, methacryloyl group, propenyl group, vinylidene group, and vinylene group. , Ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, allyl acrylate, bis (acryloxyethyl) hydroxyethyl isocyanurate, bis (acryloxy neopentyl glycol) adipate 1,3-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, propylene glycol diacrylate Rate, polypropylene glycol diacrylate, 2-hydroxy-1,3-diaacryloxypropane, 2,2-bis [4- (acryloxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy) phenyl] propane 2,2-bis [4- (acryloxyethoxy diethoxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy polyethoxy) phenyl] propane, hydroxypentylglycol diacrylate, 1 , 4-butanediol diacrylate, dicyclopentanyl diacrylate, dipentaerythritol hexaacrylate, dipentaerythritol monohydroxypentaacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate , Tetrabromopisphenol A diacrylate, triglycerol diacrylate, trimethylolpropane triacrylate, tris (acryloxyethyl) isocyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate Methacrylate, polyethylene glycol dimethacrylate, propylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate 2-hydroxy-1,3-dimethacryloxypropane, 2,2 -Bis [41- (methacryloxy) phenyl] propane, 2,2-bis [4- (methacryloxyethoxy) phenyl] propane, 2,2-bis [4- (methacryloxyethoxydiethoxy) phenyl] propane, 2, 2-bis [4- (methacryloxyethoxypolyethoxy) phenyl] propane, tetrabromobisphenol A dimethacrylate, dicyclopentanyl dimethacrylate, dipentaerythritol hexamethacrylate, glycerol dimethacrylate, hydroxypentylglycol dipentaglycol dimethacrylate Dipentaerythritol monohydroxypentamethacrylate, ditrimethylolpropane tetramethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, Rig Lise over roll dimethacrylate, trimethylolpropane trimethacrylate, tris (methacryloxyethyl) isocyanurate, allyl methacrylate, divinylbenzene, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, diethylene glycol bis allyl carbonate.
Moreover, it is preferable that the film | membrane 200 which coat | covers the silica particle 1 has a repeating structural unit induced | guided | derived from the monomer further represented by following General formula (1).

The R ² group, which is a “bulky” group derived from the monomer represented by the general formula (1) in the membrane 200, reduces the flexibility of the molecules of the membrane, that is, restricts the mobility of the molecules. The mechanical strength and heat resistance of the film are improved.
In the general formula (1), examples of the alicyclic hydrocarbon group represented by R ² include a cycloalkyl group, a cycloalkenyl group, a benzyl group, a phenyl group, an isobornyl group, a dicyclopentanyl group, a dicyclopentenyl group, and an adamantane. Group, tetrahydrofuran group, naphthyl group, t-butyl group and the like.

As described above, a film having a repeating structural unit derived from a crosslinkable monomer or a film having a repeating structural unit derived from the monomer represented by the general formula (1) has mechanical strength, heat resistance, and solvent resistance. There is an advantage of excellent durability such as property.
Moreover, the following are mentioned as a specific example of the monomer represented by the said General formula (1).

The following hydrophilic monomers can be used together with each polymerizable surfactant. Examples of such hydrophilic monomers include those having a hydroxyl group, an ethylene oxide group, an amide group, or an amino group as a hydrophilic group.
Examples of the hydrophilic monomer include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and 2-hydroxybutyl methacrylate having an OH group, ethyldiethylene glycol acrylate having an ethylene oxide group, polyethylene glycol monomethacrylate, methoxypolyethylene glycol methacrylate, and the like. N-methylaminoethyl methacrylate, N-methylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl methacrylate, amino group-containing N-methylaminoethyl methacrylate, N-N-dimethylacrylamide, etc. Alkylamino esters of acrylic acid or methacrylic acid such as N- (2-dimethylaminoethyl) acrylamide, N- (2-dimethylaminoethyl) methacrylamide, N, N-dimethylaminopropylacrylamide, and other unsaturated amides having an alkylamino group, and vinylpyridine Examples thereof include vinyl ethers having an alkylamino group such as monovinyl pyridines and dimethylaminoethyl vinyl ether; vinyl imidazole and the like, N-vinyl-2-pyrrolidone, and the like.

Second Embodiment
Next, a second embodiment of the negatively chargeable encapsulated silica of the present invention will be described. Hereinafter, the present embodiment will be described with a focus on differences from the above-described embodiments, and description of similar matters will be omitted.
FIG. 3 is a view showing a second embodiment of the negatively chargeable encapsulated silica of the present invention, and FIG. 3 is a view showing a manufacturing process of the negatively chargeable encapsulated silica according to the second embodiment.

[Negatively chargeable encapsulated silica 100 ']
The negatively chargeable encapsulated silica 100 ′ of this embodiment imparts negative chargeability to the toner. As shown in FIG. 3, the silica particles 1 having an anionic group 11 on the surface, and silica And a film 40 covering the particles 1.
In this embodiment, the membrane 40 is composed of a laminate of a cation layer 20 derived from a cationic polymerizable surfactant and an anion layer 30 derived from an anionic polymerizable surfactant. This is different from the above-described embodiment.
By covering the silica particles with the film composed of the laminate as described above, the durability (moisture resistance) of the negatively charged encapsulated silica can be further improved. Further, the dispersibility in the toner powder can be further improved.

The cationic layer 20 has a cationic group 21 derived from a cationic polymerizable surfactant on the silica particle 1 side, and a cationic group 21 ′ derived from a cationic polymerizable surfactant on the opposite side of the silica particle 1. have.
The cation layer 20 covers the silica particle 1 in a state where the anionic group 11 and the cationic group 21 of the silica particle 1 are ionically bonded.

The anion layer 30 is laminated on the cation layer 20 described above, the anionic group 31 derived from the anionic polymerizable surfactant on the cation layer 20 side, and the anionic polymerization on the side opposite to the cation layer 20. And an anionic group 31 ′ derived from a surfactant.
The anion layer 30 is laminated on the cation layer 20 in a state where the cationic group 21 ′ of the cation layer 20 and the anionic group 31 are ionically bonded.

[Production of Negatively Charged Encapsulated Silica 100 ′]
Next, a method for producing negatively charged encapsulated silica according to the first embodiment of the present invention will be described with reference to the accompanying drawings.
The negatively chargeable encapsulated silica 100 ′ as described above can be manufactured, for example, as follows.

(Formation process of cation layer 20)
Hereinafter, formation of the cation layer 20 will be described.
The cationic layer 20 is formed by polymerizing the cationic polymerizable surfactants 2 and 2 ′ on the silica particles 1 having the anionic group 11 on the surface (cation layer 20 forming step).
First, similarly to the first embodiment described above, an aqueous dispersion in which silica particles 1 are dispersed in an aqueous dispersion medium such as water is prepared.

Next, the cationic polymerizable surfactant described above is added to the aqueous dispersion.
At this time, as shown in FIG. 4 (a), the cationic groups 21 of the cationic polymerizable surfactant 2 are arranged so as to face the anionic groups 11 of the silica particles 1, and adsorb with strong ionic bonds. . Further, the hydrophobic group 22 ′ and the polymerizable group 23 ′ of the cationic polymerizable surfactant 2 ′ are caused by the hydrophobic interaction between the hydrophobic group 22 and the polymerizable group 23 of the cationic polymerizable surfactant 2. The cationic groups 21 ′ of the cationic polymerizable surfactant 2 ′ are adsorbed and arranged so as to face the direction in which the aqueous dispersion medium exists, that is, the direction away from the silica particles 1.

  In this state, the polymerization groups 23 and 23 ′ of the adjacent cationic polymerizable surfactants 2 and 2 ′ are polymerized by adding a polymerization initiator as described in the first embodiment. As a result, a cation layer 20 is formed on the surface of the silica particles 1 as shown in FIG. Thereby, the 1st dispersion liquid in which the silica particles 1 coated with the cation layer 20 are dispersed is obtained.

  In this embodiment, the addition amount of the cationic polymerizable surfactant added to the aqueous dispersion is 2.0 to 2.5 times the total number of moles of anionic groups on the surface of the silica particles in the aqueous dispersion. The range of mol is preferable, and the range of 2.0 to 2.2 times mol is more preferable. As a result, the silica particles having an anionic group are strongly ionically bound and can be easily encapsulated.

(Formation process of anion layer 30)
Next, the anion layer 30 is laminated on the cation layer 20 formed as described above (anion layer 30 forming step).
The anion layer 30 is formed by polymerizing the anionic polymerizable surfactants 3 and 3 ′ on the cation layer 20.

First, the anionic polymerizable surfactant as described above is added to the first dispersion obtained by dispersing the silica particles 1 coated with the cation layer 20 as described above.
At this time, as shown in FIG. 4 (c), the anionic group 31 of the anionic polymerizable surfactant 3 is arranged to face the cationic group 21 ′ of the cation layer 20 and adsorbs with a strong ionic bond. To do. Further, the hydrophobic group 32 ′ and the polymerizable group 33 ′ of the anionic polymerizable surfactant 3 ′ are adsorbed by the hydrophobic interaction between the hydrophobic group 32 and the polymerizable group 33 of the anionic polymerizable surfactant 3. The anionic group 31 ′ of the anionic polymerizable surfactant 3 ′ is arranged so as to face the direction in which the aqueous dispersion medium exists, that is, the direction away from the silica particles 1.
In this state, for example, by adding a polymerization initiator, the polymerizable groups 33 and 33 ′ of the adjacent anionic polymerizable surfactants 3 and 3 ′ are polymerized with each other, as shown in FIG. The anion layer 30 is laminated on the layer 20 to form the film 40.

  In this embodiment, the addition amount of the anionic polymerizable surfactant added to the first dispersion is preferably in the range of 1.0 to 10 times mol with respect to the added cationic polymerizable surfactant. Preferably, it is the range of 1.0-5.0 times mol. As a result, the generation of the anionic polymerizable surfactant not adsorbed on the silica particles can be reduced, and the anion layer can be easily formed.

As described above, a dispersion liquid in which the negatively charged encapsulated silica 100 ′ is dispersed is obtained.
The obtained dispersion is isolated by spray drying, filter drying, or the like, as in the first embodiment described above, and applied to the toner described later.
As in the first embodiment, in addition to the polymerizable surfactants, a comonomer, a hydrophobic monomer, a crosslinkable monomer, and the like as described above may be added in each layer forming step.
Further, the cation layer forming step and the anion layer forming step described above may be repeated. Thereby, the particle size of negatively chargeable encapsulated silica can be arbitrarily adjusted. As a result, negatively chargeable encapsulated silica having a suitable particle size can be obtained. Further, the moisture resistance (environmental stability) of the negatively charged encapsulated silica can be improved.

"toner"
Next, the toner provided with the negatively charged encapsulated silica of the present invention as an external additive as described above will be described.
The toner is composed of at least the negatively charged encapsulated silica as the external additive described above and toner particles.
The toner particles include at least a binder resin (hereinafter also simply referred to as “resin”) as a main component.

<Constituent material of toner particles (toner constituent material)>
First, materials constituting the toner particles will be described.
1. Resin (binder resin)
In the present invention, the resin (binder resin) is not particularly limited, and for example, polystyrene, poly-α-methylstyrene, chloropolystyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer. Polymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-acrylic acid ester -Styrene or styrene-substituted styrene resin such as methacrylic acid ester copolymer, styrene-α-chloroacrylic acid methyl copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, styrene-vinyl methyl ether copolymer A homopolymer or copolymer, Polyester resin, epoxy resin, urethane modified epoxy resin, silicone modified epoxy resin, vinyl chloride resin, rosin modified maleic acid resin, phenyl resin, polyethylene resin, polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl Examples include acrylate copolymers, xylene resins, polyvinyl butyral resins, terpene resins, phenol resins, aliphatic or alicyclic hydrocarbon resins. One or more of these can be used in combination.

  Although the softening temperature of resin (resin material) is not specifically limited, It is preferable that it is 50-130 degreeC, It is more preferable that it is 50-120 degreeC, It is further more preferable that it is 60-115 degreeC. In the present specification, the softening temperature is a measurement condition in a Koka type flow tester (manufactured by Shimadzu Corporation): temperature increase rate: 5 ° C./min, softening start temperature defined by a die hole diameter of 1.0 mm. Point to.

2. Colorant The toner particles may contain a colorant in addition to the resin material described above. Examples of the colorant that can be used include pigments and dyes. Examples of such pigments and dyes include carbon black, spirit black, lamp black (CI No. 77266), magnetite, titanium black, chrome lead, cadmium yellow, mineral fast yellow, navel yellow, and naphthol yellow S. , Hansa Yellow G, Permanent Yellow NCG, Chrome Yellow, Benzidine Yellow, Quinoline Yellow, Tartrazine Lake, Red Mouth Lead, Molybdenum Orange, Permanent Orange GTR, Pyrazolone Orange, Benzidine Orange G, Cadmium Red, Permanent Red 4R, Watching Red Calcium salt, eosin lake, brilliant carmine 3B, manganese purple, fast violet B, methyl violet lake, bitumen, cobalt blue, al Reblue Lake, Victoria Blue Lake, First Sky Blue, Indanthrene Blue BC, Ultramarine, Aniline Blue, Phthalocyanine Blue, Calco Oil Blue, Chrome Green, Chrome Oxide, Pigment Green B, Malachite Green Lake, Phthalocyanine Green, Final Yellow Green G, Rhodamine 6G, quinacridone, rose bengal (C.I. No. 45432), C.I. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Modern Tread 30, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 184, C.I. I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Modern Blue 7, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 5: 1, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Basic Green 6, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 180, C.I. I. Pigment Yellow 162, nigrosine dye (CI No. 50415B), metal complex dye, silica, aluminum oxide, magnetite, maghemite, various ferrites, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide, Examples thereof include metal oxides such as magnesium oxide, and magnetic materials containing magnetic metals such as Fe, Co, and Ni, and one or more of these can be used in combination.

  The toner particles may contain wax. The wax is usually used for the purpose of improving releasability. Examples of such wax include plant waxes such as candelilla wax, carnauba wax, rice wax, cotton wax, and wood wax, animal waxes such as beeswax and lanolin, montan wax, ozokerite, and ceresin. Mineral waxes such as mineral waxes, paraffin waxes, microwaxes, microcrystalline waxes, petroleum waxes such as petrolatum waxes, Fischer-Tropsch waxes, polyethylene waxes (polyethylene resins), polypropylene waxes (polypropylene resins) ), Synthetic hydrocarbon waxes such as oxidized polyethylene wax, oxidized polypropylene wax, 12-hydroxystearic acid amide, stearic acid amide, phthalic anhydride imide, chlorinated hydrocarbons Fatty acid amides, esters, ketones, synthetic wax wax such as ether and the like, can be used singly or in combination of two or more of them. Further, as the wax, a crystalline polymer resin having a lower molecular weight may be used. For example, a homopolymer or copolymer of polyacrylate such as poly n-stearyl methacrylate and poly n-lauryl methacrylate (for example, It is also possible to use a crystalline polymer having a long alkyl group in the side chain, such as a copolymer of n-stearyl acrylate-ethyl methacrylate).

The content of the wax in the toner is not particularly limited, but is preferably 1.0 wt% or less, and more preferably 0.5 wt% or less. If the content of the wax is too large, the wax is liberated and coarsened in the finally obtained toner particles, and the toner seeps into the toner particle surface and the transfer efficiency of the toner tends to decrease. Indicates.
The softening point of the wax is not particularly limited, but is preferably 50 to 180 ° C, and more preferably 60 to 160 ° C.

Further, the toner of the present invention may contain a component other than these as a constituent material. Examples of such components include a charge control agent and magnetic powder.
Examples of the charge control agent include a metal salt of benzoic acid, a metal salt of salicylic acid, a metal salt of alkyl salicylic acid, a metal salt of stearic acid, a metal salt of catechol, a metal-containing bisazo dye, a nigrosine dye, a tetraphenylborate derivative, a fourth Examples include quaternary ammonium salts, alkylpyridinium salts, chlorinated polyesters, and nitrohumic acids.

Examples of the magnetic powder include magnetite, maghemite, various ferrites, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide, magnesium oxide, and other metal oxides, and magnetic materials such as Fe, Co, and Ni. The thing etc. which were comprised with the magnetic material containing a metal are mentioned.
In addition to the above materials, the toner may contain, for example, zinc stearate, zinc oxide, cerium oxide, silica, titanium oxide, iron oxide, fatty acid, fatty acid metal salt, and the like.

<Toner production method>
Next, a preferred embodiment of a toner manufacturing method to which the negatively chargeable encapsulated silica of the present invention is applied will be described.
FIG. 5 is a longitudinal sectional view schematically showing an example of the configuration of a kneader and a cooler for producing a kneaded product.
In the following description, a case where toner is manufactured using a kneaded material K7 containing a resin material and a colorant will be described.
The kneaded material K7 can be manufactured using, for example, an apparatus as shown in FIG.

(Kneading process)
The raw material K5 used for kneading contains the components as described above. In particular, when a colorant is included, the colorant tends to embed air, and thus air tends to remain in the composition. However, by kneading in this step, air contained in the raw material K5 (particularly colored) The air entrained by the agent can be efficiently removed, and air bubbles can be effectively prevented from being mixed (remaining) inside the toner particles.
The raw material K5 used for kneading is preferably a mixture of these components.
This embodiment demonstrates the structure which uses a biaxial kneading extruder as a kneading machine.

The kneading machine K1 includes a process part K2 for kneading while conveying the raw material K5, a head part K3 for extruding the kneaded raw material (kneaded material K7) into a predetermined cross-sectional shape, and a raw material K5 in the process part K2. And a feeder K4 to be supplied.
The process part K2 includes a barrel K21, a screw K22 and a screw K23 inserted into the barrel K21, and a fixing member K24 for fixing the head part K3 to the tip of the barrel K21.

In the process part K2, when the screw K22 and the screw K23 rotate, a shearing force is applied to the raw material K5 supplied from the feeder K4, and a uniform kneaded material K7 is obtained.
The total length of the process part K2 is preferably 50 to 300 cm, and more preferably 100 to 250 cm. If the total length of the process part K2 is less than the lower limit, it may be difficult to mix the components in the raw material K5 sufficiently uniformly. On the other hand, when the total length of the process part K2 exceeds the upper limit, depending on the temperature in the process part K2, the number of rotations of the screw K22, the screw K23, and the like, the material K5 is easily denatured by heat, and finally obtained. It may be difficult to sufficiently control the physical properties of the toner.

  Moreover, although the raw material temperature at the time of kneading | mixing changes with compositions etc. of the raw material K5, it is preferable that it is 80-260 degreeC, and it is more preferable that it is 90-230 degreeC. Note that the raw material temperature in the process part K2 may be uniform or may vary depending on the part. For example, the process unit K2 includes a first region having a relatively low set temperature and a second region that is provided on the base end side from the first region and whose set temperature is higher than the first region. You may have.

  In addition, the residence time (time required for passage) of the raw material K5 in the process part K2 is preferably 0.5 to 12 minutes, and more preferably 1 to 7 minutes. If the residence time in the process part K2 is less than the lower limit, it may be difficult to mix the components in the raw material K5 sufficiently uniformly. On the other hand, if the residence time in the process part K2 exceeds the upper limit, the production efficiency is reduced. Depending on the temperature in the process part K2, the rotational speed of the screw K22, the screw K23, etc., the heat of the raw material K5 Modification tends to occur, and it may be difficult to sufficiently control the physical properties of the finally obtained toner.

  The number of rotations of the screw K22 and the screw K23 varies depending on the composition of the binder resin and the like, but is preferably 50 to 600 rpm. If the rotational speeds of the screws K22 and K23 are less than the lower limit, it may be difficult to mix the components in the raw material K5 sufficiently uniformly. On the other hand, when the rotation speed of the screw K22 and the screw K23 exceeds the upper limit value, the molecular chain of the resin may be cut by shearing, and the resin characteristics may be deteriorated.

  Further, in the kneader K1 used in the present embodiment, the inside of the process unit K2 is connected to the pump P via the deaeration port K25. Thereby, the inside of the process part K2 can be degassed, and an increase in the pressure in the process part K2 due to heating or heat generation of the raw material K5 (kneaded material K7) can be prevented. As a result, the kneading process can be performed safely and efficiently. Further, since the inside of the process part K2 is connected to the pump P via the deaeration port K25, it is possible to effectively prevent bubbles (particularly relatively large bubbles) from being contained in the obtained kneaded material K7. And the properties of the finally obtained toner can be made more excellent.

(Extrusion process)
The kneaded material K7 kneaded in the process part K2 is pushed out of the kneader K1 through the head part K3 by the rotation of the screw K22 and the screw K23.
The head part K3 has an internal space K31 into which the kneaded material K7 is fed from the process part K2, and an extrusion port K32 from which the kneaded material K7 is extruded.

The temperature of the kneaded material K7 in the internal space K31 (at least in the vicinity of the extrusion port K32) is not particularly limited, but is preferably a temperature equal to or higher than the softening temperature of the resin material contained in the raw material K5. As a result, the toner particles can be obtained as a mixture of the constituent components more uniformly, and variations in characteristics (charging characteristics, fixing properties, etc.) among the toner particles can be particularly reduced.
The specific temperature of the kneaded material K7 in the internal space K31 (at least the temperature near the extrusion port K32) is not particularly limited, but is preferably 80 to 150 ° C, more preferably 90 to 140 ° C. preferable. When the temperature of the kneaded material K7 in the internal space K31 is a value within the above range, the kneaded material K7 does not solidify in the internal space K31 and is easily extruded from the extrusion port K32.

  In the illustrated configuration, the internal space K31 has a cross-sectional area gradually decreasing portion K33 in which the cross-sectional area gradually decreases in the direction of the extrusion port K32. By having such a cross-sectional area gradually decreasing portion K33, the extrusion amount of the kneaded material K7 extruded from the extrusion port K32 is stabilized, and the cooling rate of the kneaded material K7 in the cooling step described later is stabilized. As a result, the toner produced using the toner has a small variation in characteristics among the toner particles, and has excellent overall characteristics.

(Cooling process)
The softened kneaded material K7 extruded from the extrusion port K32 of the head portion K3 is cooled and solidified by the cooler K6.
The cooler K6 includes rolls K61, K62, K63, and K64, and belts K65 and K66.

The belt K65 is wound around a roll K61 and a roll K62. Similarly, the belt K66 is wound around the roll K63 and the roll K64.
The rolls K61, K62, K63, and K64 rotate around the rotation axes K611, K621, K631, and K641 in the directions indicated by e, f, g, and h in the drawing. Thereby, the kneaded material K7 extruded from the extrusion port K32 of the kneading machine K1 is introduced between the belt K65 and the belt K66. The kneaded material K7 introduced between the belt K65 and the belt K66 is cooled while being formed into a plate shape having a substantially uniform thickness. The cooled kneaded material K7 is discharged from the discharge portion K67. The belts K65 and K66 are cooled by a method such as water cooling or air cooling. When such a belt type is used as the cooler, the contact time between the kneaded product extruded from the kneader and the cooling body (belt) can be increased, and the cooling efficiency of the kneaded product is particularly excellent. Can be.

  By the way, in the kneading step, since shearing force is applied to the raw material K5, phase separation (particularly macrophase separation) is sufficiently prevented, but the kneaded product K7 that has finished the kneading step is not subjected to shearing force. Therefore, depending on the constituent materials of the kneaded product, phase separation (macrophase separation) or the like may occur again if left for a long period of time. Therefore, it is preferable to cool the kneaded material K7 obtained as described above as soon as possible. Specifically, the cooling rate of the kneaded material K7 (for example, the cooling rate when the kneaded material K7 is cooled to about 60 ° C.) is preferably −3 ° C./second or more, and is preferably −5 to −100 ° C. / More preferably it is seconds. Further, the time required from the end of the kneading step (when the shearing force is no longer applied) to the completion of the cooling step (for example, the time required for cooling the temperature of the kneaded product K7 to 60 ° C. or lower) is 20 seconds. Or less, more preferably 3 to 12 seconds.

In the present embodiment, the configuration using a continuous biaxial kneading extruder as the kneading machine has been described, but the kneading machine used for kneading the raw materials is not limited to this. For kneading the raw materials, for example, various kneaders such as a kneader, a batch type triaxial roll, a continuous biaxial roll, a wheel mixer, and a blade type mixer can be used.
In the illustrated configuration, a kneader having two screws has been described. However, the number of screws may be one or three or more. Further, the kneading apparatus may have a disc (kneading disc) portion.

Further, in the present embodiment, the configuration using one kneader has been described, but kneading may be performed using two kneaders. In this case, the heating temperature of the raw material, the rotational speed of the screw, and the like may be different between one kneader and the other kneader.
In the present embodiment, a configuration using a belt type as the cooler has been described. However, for example, a roll type (cooling roll type) cooler may be used. Further, the cooling of the kneaded product extruded from the extrusion port K32 of the kneader is not limited to the one using the above-described cooler, and may be performed by, for example, air cooling.

(Crushing process)
First, the kneaded material K7 that has undergone the cooling process as described above is pulverized to obtain a powder for toner production.
The pulverization method is not particularly limited, and can be performed using various pulverizers and crushers such as a ball mill, a vibration mill, a jet mill, and a pin mill.
The pulverization process may be performed in multiple steps (for example, two stages of a coarse pulverization process and a fine pulverization process).
Moreover, you may perform processes, such as a classification process and a thermal spheroidization process, as needed after such a crushing process.
For the classification treatment, for example, a sieve, an airflow classifier or the like can be used.

(External addition process (external addition process))
Next, the negatively chargeable encapsulated silica of the present invention as described above is applied as an external additive to the obtained toner manufacturing powder.
Thereby, a toner (toner of the present invention) to which the negatively chargeable encapsulated silica of the present invention is applied is obtained. Since the negatively chargeable encapsulated silica of the present invention is particularly excellent in the ability to impart negative chargeability as described above, the obtained toner is easily uniformly negatively charged. Further, since the negatively chargeable encapsulated silica of the present invention has high moisture resistance as compared with the case where conventional negatively chargeable silica is added, the environmental stability of the toner can be made higher.
The content of negatively charged encapsulated silica contained in the toner is preferably 0.1 to 5 parts by weight, and 0.5 to 1.2 parts per 100 parts by weight of toner particles (powder for toner production). More preferred are parts by weight. Thereby, the toner particles can be negatively charged efficiently.

In addition to the negatively charged encapsulated silica described above, for example, positively charged silica, aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, and oxidation can be used as the external additive used for the external addition treatment. Fine particles composed of inorganic materials such as chromium, titania, zinc oxide, alumina, magnetite and other metal oxides, nitrides such as silicon nitride, carbides such as silicon carbide, calcium sulfate, calcium carbonate and aliphatic metal salts, acrylic Examples thereof include fine particles composed of organic materials such as resins, fluororesins, polystyrene resins, polyester resins, and aliphatic metal salts, and fine particles composed of composites thereof.
As the external additive, the surface of the fine particles as described above is subjected to a surface treatment with HMDS, a silane coupling agent, a titanate coupling agent, a fluorine-containing silane coupling agent, silicone oil or the like. It may be used.

The toner produced as described above has a uniform shape and a sharp particle size distribution (small width).
The volume-based average particle diameter of the toner obtained as described above is preferably 2 to 20 μm, and more preferably 4 to 15 μm. When the average particle diameter of the toner is less than the lower limit value, the adhesion force to the surface of the electrostatic latent image carrier (for example, a photoreceptor) is increased, and as a result, the transfer residual toner may be increased. On the other hand, when the average particle size of the toner exceeds the upper limit, the reproducibility of the contour portion of an image formed using the toner, particularly a character image or a light pattern, is deteriorated.
Further, the toner preferably has a standard deviation of the particle size between particles of 1.5 μm or less, more preferably 1.3 μm or less, and even more preferably 1.0 μm or less. When the standard deviation of the particle diameter between the particles is 1.5 μm or less, variations in charging characteristics, fixing characteristics and the like are particularly small, and the reliability of the toner as a whole is further improved.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to this.
For example, in the above-described embodiment, the toner is obtained by pulverizing the kneaded product. However, the present invention is not limited to this, and the toner may be manufactured using, for example, an emulsion polymerization method.

[1] Production of toner (Example 1)
<Manufacture of negatively charged encapsulated silica>
Prior to toner production, negatively chargeable encapsulated silica was produced as follows.
First, silica particles having an anionic group on the surface (manufactured by Nippon Aerosil Co., Ltd .: trade name “AEROSIL200”, specific surface area: 200 m ² / g, amount of anionic group on the surface: 0.12 mmol / g) were prepared. The volume-based average particle size of the silica particles was 8 nm.

  After adding 0.4 parts by weight of dimethylaminoethylmethyl chloride methacrylate as a cationic polymerizable surfactant to an aqueous dispersion in which 15 parts by weight of silica particles are dispersed in 80 parts by weight of ion-exchanged water, and mixed. The sample was irradiated with ultrasonic waves for 15 minutes. Next, Aqualon KH-10 (Daiichi Kogyo Seiyaku Co., Ltd.): 2.1 parts by weight and ion-exchanged water: 20 parts by weight are added and mixed as an anionic polymerizable surfactant, and 30 ultrasonic waves are applied again. Irradiated for 1 minute.

This was put into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a temperature controller, a nitrogen introduction tube and an ultrasonic generator. After raising the internal temperature of the reaction vessel to 80 ° C., a potassium persulfate aqueous solution in which 0.03 parts by weight of potassium persulfate was dissolved as a polymerization initiator in 10 parts by weight of ion-exchanged water was dropped, and nitrogen was introduced, Polymerization was carried out at 80 ° C. for 6 hours. After completion of the polymerization, the pH was adjusted to 8 with a 2 mol / L potassium hydroxide aqueous solution, and the mixture was filtered through a membrane filter having a pore size of 1 μm to remove coarse particles to obtain a target negatively charged encapsulated silica dispersion.
The volume average particle size of the obtained dispersion was measured using a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop Co. As a result, it was 15 nm.
This was centrifuged and dried at room temperature to obtain a powdery negatively charged encapsulated silica powder.

<Manufacture of toner>
First, styrene-acrylic copolymer resin (manufactured by Sekisui Chemical Co., Ltd .: trade name “ESREC P, Grade SE-0040”): 60 parts by weight, phthalocyanine pigment (CI Pigment Blue 15: 3): 40 weights Part was mixed using the flushing method. This was coarsely pulverized to a diameter of about 2 mm to obtain a pigment master batch.

Next, a styrene-acrylic copolymer resin (manufactured by Sekisui Chemical Co., Ltd .: trade name “ESREC P, Grade SE-0040”): 100 parts by weight, pigment masterbatch: 10 parts by weight, di as charge control agent particles -Zinc tert-butyl salicylate (manufactured by Orient Chemical Co., Ltd .: trade name “Bontron E-84”): 1 part by weight, and carnauba wax (molecular weight 850): 3 parts by weight as a wax were prepared.
These components were mixed using a 20 L type Henschel mixer to obtain a raw material for toner production.

Next, this raw material (mixture) was kneaded at a kneading temperature of 120 ° C. using a twin-screw kneading extruder (manufactured by Toshiba Machine Co., Ltd., TEM-41 type).
Thus, the kneaded material extruded from the extrusion port of the biaxial kneading extruder was cooled using a cooler.
The kneaded product cooled as described above was coarsely pulverized (average particle size: 1 to 2 mm), and then finely pulverized. A hammer mill was used for coarse pulverization of the kneaded product, and a jet mill (200 AFG, manufactured by Hosokawa Micron Corporation) was used for fine pulverization. The fine pulverization was performed at a pulverization air pressure: 500 [kPa] and a rotor rotational speed: 7000 [rpm].

The pulverized material thus obtained was classified with an airflow diverter (manufactured by Hosokawa Micron Corporation, 100 ATP).
0.5 parts by weight of the negatively charged encapsulated silica obtained as described above is added to 100 parts by weight of the obtained classified product, mixed and stirred with a Henschel mixer, and the final toner is prepared. Obtained. The finally obtained toner had a volume-based average particle diameter of 7.5 μm.

(Example 2)
Example 1 except that AEROSIL 50 (manufactured by Nippon Aerosil Co., Ltd., specific surface area: 50 m ² / g, amount of anionic group on the surface: 0.12 mmol / g) was used as the silica particles having an anionic group on the surface. In the same manner, a toner was produced. The volume-based average particle size of the silica particles was 30 nm, and the volume-based average particle size of the obtained negatively chargeable encapsulated silica was 45 nm.

(Example 3)
A toner was produced in the same manner as in Example 1 except that negatively charged encapsulated silica was obtained as follows.
First, silica particles having an anionic group on the surface (manufactured by Nippon Aerosil Co., Ltd .: trade name “AEROSIL200”, specific surface area: 200 m ² / g, amount of anionic group on the surface: 0.12 mmol / g) were prepared. The volume-based average particle size of the silica particles was 8 nm.
An aqueous dispersion in which 10 parts by weight of the silica particles were dispersed in 80 parts by weight of ion exchange water was prepared.

The aqueous dispersion was mixed with 1.75 parts by weight of dimethylaminoethyl methyl chloride methacrylate as a cationic polymerizable surfactant with respect to 100 parts by weight of silica particles, and then irradiated with ultrasonic waves for 15 minutes. . Next, 18 parts by weight of benzyl methacrylate and 12 parts by weight of dodecyl methacrylate were mixed and mixed by stirring. Further, 2.25 parts by weight of dimethylaminoethylmethyl chloride methacrylate was added, and ultrasonic waves were irradiated again for 30 minutes. . This was put into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a temperature controller, a nitrogen introduction tube and an ultrasonic generator. After raising the internal temperature of the reaction vessel to 80 ° C., 0.6 parts by weight of 2,2′-azobis (2-methylpropionamidine) dihydrochloride was dissolved in 20 parts by weight of ion-exchanged water as the start of polymerization. A 2′-azobis (2-methylpropionamidine) dihydrochloride aqueous solution was dropped, and polymerization was performed at 80 ° C. for 6 hours while introducing nitrogen. After completion of the polymerization, the pH was adjusted to around 6 with disodium citrate and ultrafiltration was performed to obtain a first dispersion.
Further, 6 parts by weight of Aqualon KH-10 as an anionic polymerizable surfactant was added to and mixed with 15 parts by weight of the particles in the obtained first dispersion, and then irradiated with ultrasonic waves for 15 minutes. Next, 3 parts by weight of Aqualon KH-10 and 20 parts by weight of ion-exchanged water were added and mixed, and ultrasonic waves were irradiated again for 30 minutes.

This was put into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a temperature controller, a nitrogen introduction tube and an ultrasonic generator. After raising the internal temperature of the reaction vessel to 80 ° C., an aqueous potassium persulfate solution in which 0.03 part by weight of potassium persulfate was dissolved as a polymerization start was added dropwise to 10 parts by weight of ion-exchanged water. Polymerization was carried out at 6 ° C. for 6 hours. After the completion of the polymerization, the pH was adjusted to 8, and unreacted substances were removed by ultrafiltration to obtain a dispersion of negatively charged encapsulated silica.
When the volume-based average particle diameter of the obtained dispersion was measured using a laser Doppler system particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop, it was 12 nm.
This was centrifuged and dried at room temperature to obtain a powdery negatively charged encapsulated silica powder.

(Comparative Example 1)
A toner was produced in the same manner as in Example 1 except that the silica particles were not subjected to microencapsulation and the silica particles were hydrophobized as follows.
<Production of hydrophobized silica (negatively chargeable silica)>
100 parts by weight of silica particles (manufactured by Nippon Aerosil Co., Ltd .: trade name “AEROSIL200”, specific surface area 200 m ² / g) are gradually added to a solution obtained by diluting 20 parts by weight of organopolysiloxane (50 cs) with 10,000 parts by weight of hexane. After the reaction at 100 ° C. or higher, the solvent was removed. Thereafter, the pulverized product using a pin-type pulverizer is put into a solution obtained by dissolving 10 parts by weight of 90% methanol water and 10 parts by weight of hexamethylene disilazane in 10,000 parts by weight of hexane. The solvent and by-products were removed to obtain hydrophobic silica powder.
(Comparative Example 2)
The toner was prepared in the same manner as in Example 1 except that silica particles (manufactured by Nippon Aerosil Co., Ltd .: trade name “AEROSIL200”, specific surface area: 200 m ² / g) were directly used as external additives without being encapsulated. Manufactured.

[2] Evaluation Each toner obtained as described above was evaluated for charging uniformity, fogging, and fixing strength.
[2.1] Charge Uniformity The toners obtained in each Example and each Comparative Example were respectively charged into a developing device of a color laser printer (manufactured by Seiko Epson Corporation, LP-9300C). The toner regulating blade of the developing device of the same machine was adjusted so that a predetermined amount of toner (0.65 mg / cm ² ) was supplied from the developing roller to the photoconductor, and the LP9300 was operated.

The charge amount of the toner regulated by the toner regulating blade and conveyed to the photosensitive member was evaluated by analyzing the toner on the developing roller. The charge amount was measured by an E-SPART analyzer manufactured by Hosokawa Micron Corporation. The measurement conditions were a suction flow rate of 0.2 liters / minute, a dust collection air flow rate of 0.6 liters / minute, a blowing nitrogen gas pressure of 0.02 MPa, and the charge amount (Q / m) for each toner was measured. The charge amount distribution was obtained with a toner count of 3000.
The uniformity of the toner charge amount is obtained by dividing the maximum charge amount (Q ₁ / m ₁ ) and the total toner charge amount measured by the measurement count (number) in the number distribution of the charge amount per toner. The smaller the absolute value of the difference from the value (Q ₂ / m ₂ ), the more uniform the charge amount distribution, and the larger the absolute value, the more nonuniform.

[2.2] Cover evaluation A mending tape manufactured by Sumitomo 3M Co., Ltd. is affixed to plain paper manufactured by Fuji Xerox Office Supply Co., Ltd. (product name J). The color of this tape is measured with a color difference meter CR-221 manufactured by Minolta Co., Ltd. (this is the reference value).
Using a color laser printer (manufactured by Seiko Epson Corporation, LP-3000C), the toner to be evaluated is put in a developing machine, and white (solid white) is printed. The printer is stopped during printing and the photosensitive member is taken out. A mending tape is applied to the area between the contact point between the photosensitive member and the transfer belt (transfer nip) and the point adjacent to the developing roller and the photosensitive member (development nip), and the fog toner is attached to the J paper. . The color difference between this tape and the reference value is measured. A smaller color difference means less fogging.
Using the above method, the initial fog (at the time of printing 100 sheets) and the fog after long-term use (at the time of printing 3000 sheets) under the conditions of room temperature (25 ° C., 45% RH), and high temperature and high humidity (30 ° C., 70% % RH), the initial fog was measured.
These results are shown in Table 1.

  As is clear from Table 1, the toners of Examples 1 to 3 were all excellent in charging uniformity and fogging. In addition, the toners of Examples 1 to 3 were excellent in environmental characteristics. On the other hand, all of the toners of the comparative examples were inferior in charging uniformity and fog. Further, the toner of the comparative example was inferior in environmental stability. This is presumably because the added external additive has low environmental stability.

It is a figure which shows 1st Embodiment of the negatively charged encapsulated silica of this invention. It is a figure which shows the manufacturing process of the negatively charged encapsulated silica which concerns on 1st Embodiment of this invention. It is a figure which shows 2nd Embodiment of the negatively charged encapsulated silica of this invention. It is a figure which shows the manufacturing process of the negatively charged encapsulated silica which concerns on 2nd Embodiment of this invention. FIG. 3 is a longitudinal sectional view schematically showing an example of the configuration of a kneader and a cooler used in the toner production method of the present invention.

Explanation of symbols

  K1 ... kneading machine K2 ... process part K21 ... barrel K22, K23 ... screw K24 ... fixing member K25 ... deaeration port K3 ... head part K31 ... internal space K32 ... extrusion port K33 ... cross-sectional area gradually decreasing part K4 ... feeder K5 ... raw material K6 ... Coolers K61, K62, K63, K64 ... Rolls K611, K621, K631, K641 ... Rotating shafts K65, K66 ... Belts K67 ... Discharge part K7 ... Kneaded material 100, 100 '... Negatively charged encapsulated silica 1 ... Silica particles 11 ... anionic group 2, 2'210 ... cationic polymerizable surfactant 21, 21 ', 211 ... cationic group 22, 22', 212 ... hydrophobic group 23, 23 ', 213 ... polymerizable group 221, 31, 31 '... anionic groups 222, 32, 32' ... hydrophobic groups 223, 33, 33 '... Polymerizable group 220,3,3 '... anionic polymerizable surfactant 20 ... cation layer 30 ... anion layer 200,40 ... film

Claims (6)

Negatively charged encapsulated silica as an external additive that imparts negative chargeability to the toner,
Silica particles having an anionic group on the surface, a cationic polymerizable surfactant having a cationic group, a hydrophobic group and a polymerizable group, and an anionic property having an anionic group, a hydrophobic group and a polymerizable group Coated with a film derived from a polymerizable surfactant,
The membrane has a cationic group derived from the cationic polymerizable surfactant on the silica particle side, and an anionic group derived from the anionic polymerizable surfactant on the side opposite to the silica particle. A negatively chargeable encapsulated silica, comprising:   2. The negatively charged encapsulated silica according to claim 1, wherein the negatively charged encapsulated silica has an average particle size of 8 to 50 nm.   2. The membrane comprises at least a laminate of a cationic layer derived from the cationic polymerizable surfactant and an anionic layer derived from the anionic polymerizable surfactant. Or negatively chargeable encapsulated silica according to 2. A method for producing negatively charged encapsulated silica according to claim 1 or 2,
Adding the cationic polymerizable surfactant to the dispersion of silica particles and mixing to obtain a first mixture;
Adding the anionic polymerizable surfactant to the first mixed solution and mixing to obtain a second mixed solution;
A method for producing negatively charged encapsulated silica, comprising: adding a polymerization initiator to the second liquid mixture for polymerization. A method for producing negatively charged encapsulated silica according to any one of claims 1 to 3,
Forming a cation layer by polymerizing the cationic polymerizable surfactant on the silica particles;
And a step of laminating the anionic layer by polymerizing the anionic polymerizable surfactant on the cationic layer.   A toner comprising the negatively chargeable encapsulated silica according to claim 1 as an external additive.

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