JP2009138151A - Colored powder and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide colored powder having excellent coloring power and excellent aggregation resistance and a method for producing the powder. <P>SOLUTION: The colored powder comprises colored particles containing one kind of polymer and a metal oxide. Not less than 70 number% of the colored particle is a colored particle (P) satisfying the condition P or colored particle (Q) satisfying the condition Q, and the colored powder contains 5-35 number% colored particle (P) and ≥60 number% colored particle (Q). Condition P: the occupied area ratio of the metal oxide existing in the area S<SB>1</SB>near the surface of the cross-section to the metal oxide existing in the inner area S<SB>2</SB>surrounded by the area S<SB>1</SB>near the surface is ≥65 areal% and ≤100 areal%, and condition Q: the occupied area ratio is ≥30 areal% and <65 areal%. In the conditions P and Q, SA<SB>1</SB>is the total occupied area of individual metal oxide in the area S<SB>1</SB>near the surface, and SA<SB>2</SB>is the total occupied area of individual metal oxide in the inner area S<SB>2</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a colored powder containing a metal oxide and a dispersion stabilizer thereof and a method for producing the same.

Colored powders in which a metal oxide powder is contained in a binder resin are widely used as, for example, display materials for powder displays such as paints, electrophotographic toners, and electronic papers, and cosmetics.
These colored powders, in particular when charged with colored powders such as electrophotographic toners and display materials for powder displays, are required to have excellent coloring power as well as excess. It is required that charging and aggregation are suppressed and that the powder mobility by the electric field is high.

  Conventionally, as the colored powder, for example, colored particles constituting the colored powder, in which a colorant is uniformly dispersed in a binder resin (for example, see Patent Documents 1 and 2) or the like. In addition, a material in which a colorant is contained locally in a region near the surface (for example, see Patent Document 3) has been proposed.

However, in the case of colored particles in which the colorant is uniformly dispersed in the binder resin, the colorant may be exposed unevenly on the surface of the colored particles. In order to obtain a sufficiently good coloring power, there is a problem that the powder mobility is inferior, resulting in inferior powder mobility. There is also a problem that high productivity cannot be obtained because a large amount of colorant needs to be added.
In addition, in the colored particles containing the colorant localized in the region in the vicinity of the surface, the individual colored particles have high uniformity in chargeability, and the degree of overcharging and aggregation is suppressed to a small level. Although there was excellent mobility, there was a problem that sufficient coloring power could not be obtained.

JP-A-1-105958 Japanese Patent Laid-Open No. 10-260554 JP-A-6-126146

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a colored powder having excellent coloring power and excellent agglomeration resistance and a method for producing the same. is there.

The colored powder of the present invention is a colored powder comprising colored particles containing at least one polymer and a metal oxide,
70% by number or more of the colored particles constituting the colored powder are either colored particles (P) satisfying the following condition P or colored particles (Q) satisfying the following condition Q,
The colored powder contains 5 to 35% by number of colored particles (P) and 60% by number or more of colored particles (Q).
Conditions P: a metal oxide present in the region near the surface S ₁ in its cross-section occupied area ratio [SA ₁ / (SA with the metal oxides present in the interior region S ₂ surrounded by the region near the surface S _{1 1} + SA ₂ ) × 100] is 65 area% or more and 100 area% or less.
Conditions Q: a metal oxide present in the region near the surface S ₁ in its cross-section occupied area ratio [SA ₁ / (SA with the metal oxides present in the interior region S ₂ surrounded by the region near the surface S _{1 1} + SA ₂ ) × 100] is 30 area% or more and less than 65 area%.
[However, in the above conditions P and Q, SA ₁ is the total occupied area of the individual metal oxides in the surface vicinity region S ₁ , and SA ₂ is the occupied area of the individual metal oxides in the internal region S ₂ . Is the sum of ]

  In the colored powder of the present invention, the colored particles (P) preferably have a number-based average major axis of 1.2 to 5 times the number-based average major axis of the colored particles (Q).

  In the colored powder of the present invention, the metal oxide is preferably titanium oxide.

In the colored powder of the present invention, the colored particles contain a metal oxide dispersant, and the metal oxide dispersant has a side chain group bonded to the main chain. Comb-shaped polymer consisting of
It is preferable that the side chain group group includes a side chain group represented by any of the following (A) to (D).
(A) at least one side chain group represented by -AZ, and at least one side chain group represented by -BZ (a) at least one side chain group represented by -AZ, and at least one- A side chain group represented by CZ (c) at least one side chain group represented by -BZ, and at least one side chain group represented by -CZ (d) at least one side represented by -CZ. In the above, A represents a polyester group [A] represented by the following general formula (A), B represents a polyester group [B] represented by the following general formula (B), and C Is a group containing a polyester group [A] and a polyester group [B], and Z is each —R ² OH, —R ³ SO ₃ H, or —R ⁴ COOH (where R ^{2 to} R ⁴ are each Represents an alkyl group.).

[In the above general formulas (A) and (B), k is an integer of 1 to 5, j is an integer of 2 to 8 greater than k, and m and n are each an integer of 1 to 1,000. is there. ]

  In the colored powder of the present invention, the content ratio of the polyester group [A] and the polyester group [B] in the polymer constituting the metal oxide dispersant is polyester group [A] / polyester group [B]. ] Is preferably 20/80 to 50/50 by mass ratio.

  In the colored powder of the present invention, the metal oxide preferably has a number average particle size of 20 to 80 nm.

  Moreover, in the colored powder of this invention, it is preferable that the said metal oxide dispersing agent is contained 1-15 mass parts with respect to 100 mass parts of polymers.

  Moreover, in the colored powder of this invention, it is preferable that the said metal oxide is contained 5-30 mass parts with respect to 100 mass parts of polymers.

  In the colored powder of the present invention, the polymer main chain constituting the metal oxide dispersant preferably has a polyalkyleneimine, polyallylamine or polyamide structure.

  Moreover, in the colored powder of the present invention, the particle diameter of the colored particles is preferably 2 to 30 μm in terms of number-based average major axis.

The method for producing the colored powder of the present invention comprises:
A method for producing the above colored powder,
The metal oxide is mixed and dispersed in a polymerizable monomer that forms the polymer to prepare a metal oxide dispersed oil phase liquid, and the metal oxide dispersed oil phase liquid is suspended in an aqueous medium. It is characterized in that it undergoes a step of performing a polymerization treatment in a heated state.

According to the coloring powder of the present invention, since the colored particles occupied area ratio indicating the existence ratio in the region near the surface S ₁ of the metal oxide is in a certain high range (P) is contained 5 to 35% by number In addition, the individual colored particles have a high uniformity of chargeability. Therefore, overcharge and aggregation are suppressed, and the powder mobility by the electric field is excellent, and the occupied area ratio is higher than the specific high range. Since 60% by number or more of colored particles (Q) in a low range are contained, sufficiently excellent coloring power can be obtained with a small amount of colorant.
Further, since the colored particles (P) and the colored particles (Q) are contained in a total of 70% by number or more, the charging uniformity of the individual colored particles becomes extremely high, and a small amount of the colorant ensures the charging. Excellent productivity can be obtained and high productivity can be obtained.

In addition, in the colored powder in which the average major axis of the colored particles (P) and the colored particles (Q) according to the present invention is defined, the presence of the colorant (metal oxide) in the relatively small diameter particles is near the surface region S. _When it is limited to only ₁ , the coloring power is inferior, and relatively small-diameter particles are colored particles (Q) in which the colorant is dispersed not only in the surface vicinity region S ₁ but also in the internal region S _2. specifically the large diameter of the particles for many colorant near the surface area S ₁ is a dispersed colored particles (P), effectively superior color strength with a small amount of the coloring agent is obtained.

When the colored powder of the present invention contains a comb-shaped polymer having a specific shape and properties as a metal oxide dispersant (hereinafter, also referred to as “comb-structured dispersant”), In the vicinity of the surface region S ₁ , a state in which the metal oxide is dispersed with high dispersibility and is not exposed to the outermost surface is obtained. As a result, sufficient fluidity as a powder is obtained.
In addition, when the colored powder is applied to an application in which the colored powder is charged and used like a display material for electrophotography or a powder display, even if it is driven repeatedly by applying voltage for a long time, it is electrostatic. There is no specific aggregation, and excellent charging characteristics can be exhibited.

The reason why a state in which the metal oxide is dispersed with high dispersibility in the near-surface region S ₁ by using a comb-structured dispersant as the dispersant is that the main chain depends on the polarity of the main chain of the dispersant. The metal oxide is adsorbed on the portion, and the side chain group is a polyester group [A] having a structure in which a short carbon chain is sandwiched between a carbonyl group and a carboxylic acid ester group as a whole, and a longer carbon chain is a carbonyl group. The balance between hydrophilicity and hydrophobicity is controlled within a suitable range by containing a polyester group [B] having a structure sandwiched between carboxylic acid ester groups. That is, it is presumed that high dispersion stability is obtained for the metal oxide, and that the metal oxide is easily oriented in the region near the surface S ₁ of the particle. In particular, in the colored powder produced by the production method of the present invention, it is considered that the metal oxide is easily attracted to the surface where the polar group at the end of the side chain group is an interface with water, and the above effect is high. Demonstrated.

According to the method for producing a colored powder of the present invention, a specific colored powder composed of colored particles (P) and colored particles (Q) can be obtained.
This is because when a metal oxide-dispersed oil phase liquid is dispersed in an aqueous medium by applying a mechanical shearing force or the like, it is dispersed and suspended as oil droplets. When the polymerization treatment is performed, the metal oxide moves and diffuses in each oil droplet so that it is oriented on the surface. However, since the individual oil droplets cause a difference in the heat conduction rate from the aqueous medium, It is considered that colored particles having different dispersion states are generated.
That is, in the process in which the metal oxide moves and diffuses toward the surface, depending on the oil droplets, the polymerization reaction proceeds until the polymerization reaction thickens before a part of the metal oxide reaches the surface vicinity region S _1. from such oil droplets, the state in which the metal oxide remaining in the interior region S _2, i.e. occupied area ratio of 30 area of the metal oxide present in the surface region near S ₁ compared to the inner region S ₂ in the cross section It is considered that colored particles (Q) having a ratio of not less than 65% and less than 65 area% are generated.

  Hereinafter, the present invention will be specifically described.

The colored powder of the present invention comprises a binder resin composed of at least one polymer and a metal oxide, and the metal oxide acts as a main component of the colorant, such as white and black. It exhibits achromatic colors or chromatic colors such as red and blue.
These colored powders are used as, for example, display materials for powder displays such as electrophotographic toner and electronic paper, paints, and cosmetics.

The shape of the colored particles constituting the colored powder of the present invention is not particularly limited, but preferably has a true spherical shape to a substantially spherical shape. Here, the colored particles having a true spherical shape to a substantially spherical shape have a shape in which the ratio of the major axis to the minor axis of the colored particles is about 1: 1 to 4: 1 in terms of major axis: minor axis. .
However, the major axis of the colored particle refers to the width of the particle that maximizes the interval between the parallel lines when the cross-sectional image of the colored particle is sandwiched between two parallel lines. The width of the particle | grains to which the line segment concerning the said colored particle | grains of a long diameter perpendicular line becomes the maximum.
The colored powder of the present invention occupies the metal oxide 12 existing in the surface vicinity region S ₁ in the cross section and the metal oxide 12 existing in the inner region S ₂ surrounded by the surface vicinity region S _1. area ratio, i.e. the colored particles present rate of 100% by area or less than 65 area% (P) (see FIG. 1 (a).) in the region near the surface S ₁ of the metal oxide is contained 5 to 35% by number And 60% by number or more of colored particles (Q) (see FIG. 1 (b)) having an occupied area ratio of 30 area% or more and less than 65 area% are contained, and further, the colored particles (P) and the colored particles are contained. The particles (Q) are 70% by number or more in total. Thus, since the colored particles (P) and the colored particles (Q) are contained in a total of 70% by number or more, it can be particularly suitably used as a display material for electrophotographic toner and powder display.
Note that the metal oxide 12 on the surface near the area S ₁ in its cross-section occupied area ratio SR between the metal oxide 12 present inside the area S ₂ surrounded by the region near the surface S ₁ of the formula ( SR): SR = [SA ₁ / (SA ₁ + SA ₂ ) × 100].
However, in the above formula (SR), SA ₁ is the sum of the occupied areas of the individual metal oxides 12 in the surface vicinity region S ₁ , and SA ₂ is the occupied area of the individual metal oxides 12 in the inner region S ₂ . It is the sum.

The content (number%) of the colored particles (P) and the colored particles (Q) in the colored powder of the present invention is calculated by the following method.
That is, first, after embedding the colored powder in a photocurable resin, an ultrathin section having a set thickness of 100 nm is prepared at an acceleration voltage of 200 kV with an ultramicrotome “EM UC6” (manufactured by LEICA), and the ultrathin section is transmitted. A cross-sectional photograph is taken with a scanning electron microscope (TEM) “2000FX” (manufactured by JEOL Ltd.), and the cross-sectional photograph is matched with the image of the metal oxide 12 by image analysis software “LUZEX AP” (manufactured by Nireco). The binarization process was performed as follows.
Next, a near-surface region S ₁ surrounded by a closed curve a composed of the circumference of the colored particles and a closed curve b formed by a set of points separated from each point on the closed curve a by a distance 0.1 times the major axis R, For the inner region S ₂ surrounded by the closed curve b, the total area SA ₁ (nm ² ) of the individual metal oxides 12 in the near-surface region S _{1 and} the occupation of the individual metal oxides 12 in the inner region S ₂ The occupation area ratio SR (= [SA ₁ / (SA ₁ + SA ₂ ) × 100]) was calculated from the total area SA ₂ (nm ² ). However, the “major axis R of the colored particles” refers to the width of the particle that maximizes the interval between the parallel lines when the image of the colored particles in the cross-sectional photograph is sandwiched between two parallel lines.
And when this occupied area ratio SR is 65 area% or more and 100 area% or less, it is set as colored particles (P), and when the occupied area ratio SR is 30 areas% or more and less than 65 area%, colored particles (Q). And conducting this investigation on 100 colored particles extracted indiscriminately from the cross-sectional photograph, and measuring the number p of colored particles (P) and the number q of colored particles (Q) in 100, respectively, The number p or the number q is calculated as a content percentage of the colored particles (P) or the colored particles (Q) in the colored powder in number%.

  When the content of the colored particles (P) in the colored powder of the present invention is less than 5% by number, there is a possibility that sufficient powder mobility may not be obtained due to poor aggregation resistance. If the content of the colored particles (P) exceeds 35% by number, sufficient coloring power may not be obtained.

[Metal oxide]
The colored particles constituting the colored powder of the present invention contain a highly dispersible metal oxide with respect to the binder resin. Examples of the metal oxide contained in the colored particles include titanium oxide and magnetite. And hematite, and titanium oxide is particularly preferable.

Such a metal oxide is preferably hydrophobized.
Due to the hydrophobization of the metal oxide, a high affinity with the binder resin that is hydrophobic can be obtained, and therefore the dispersibility in the binder resin can be improved. Is less likely to peel off or drop off.
Examples of the metal oxide hydrophobizing agent include silicone oils such as isobutyltrimethoxysilane, octyltrimethoxysilane, and dimethylsilicone oil.

  The metal oxide contained in the colored particles constituting such a colored powder is dispersed in fine particles in the binder resin, and the number average particle diameter is preferably in the range of 20 to 80 nm, More preferably, it is 30-50 nm.

  The number average particle size of the fine particles of the metal oxide is measured as follows. That is, a photograph of a metal oxide was taken at a magnification of 30,000 with a scanning electron microscope (SEM), the photograph image was captured with a scanner, and the image processing analyzer “LUZEX AP” (manufactured by Nireco) The metal oxide in the photographic image is binarized, the horizontal ferret diameter for 100 primary particles is calculated, and the average value is taken as the number average particle diameter.

  The metal oxide in the colored particles is preferably contained in an amount of 5 to 30 parts by mass, more preferably 8 to 15 parts by mass with respect to 100 parts by mass of the polymer.

[Comb structure dispersant]
The colored particles constituting the colored powder of the present invention preferably contain a metal oxide dispersant, and the metal oxide dispersant has specific shapes and properties as described below. Particularly preferred is a comb-shaped structure dispersant having the following.
That is, this comb-shaped structure dispersing agent has a function of allowing a metal oxide to exist in a state dispersed in a binder resin, and has a comb-shaped structure in which a side chain group is bonded to a main chain. It consists of a polymer, and includes the side chain groups shown in any of the following (A) to (D) as this side chain group.

(A) At least one side chain group represented by -AZ (hereinafter also referred to as "side chain group -AZ") and at least one side chain group represented by -BZ (hereinafter referred to as "side chain group"). Also referred to as “-BZ”.)
(A) Side chain group -AZ and at least one side chain group represented by -CZ (hereinafter also referred to as "side chain group -CZ")
(C) Side chain group -BZ and side chain group -CZ
(D) Side chain group -CZ

  In the above, A represents the polyester group [A] represented by the general formula (A), B represents the polyester group [B] represented by the general formula (B), and C represents A group containing a polyester group [A] and a polyester group [B] is shown.

The polyester group [A] and the polyester group [B] are obtained, for example, by ring-opening polymerization of lactones.
And k in the said general formula (A) is an integer of 1-5, j in the said general formula (B) is an integer of 2-8 larger than k.

Further, m in the general formula (A) and n in the general formula (B) are each an integer of 1 to 1,000, more preferably an integer of 5 to 100.
When m and n are in the above-mentioned range, an appropriate affinity for the binder resin can be obtained, and therefore a good dispersibility of the metal oxide in the binder resin can be obtained.

In the above, when a plurality of polyester groups [A] and / or polyester groups [B] are contained in the side chain group of the comb-shaped structural dispersant, the general formula ( K in A) is the same integer, and for all polyester groups [B], j in the general formula (B) showing this is the same integer.
Further, m in the general formula (A) representing the polyester group [A] may be different among all the polyester groups [A] contained in the side chain group of the comb structure dispersant, and similarly. , N in the general formula (B) representing the polyester group [B] may be different among all the polyester groups [B] contained in the side chain group of the comb structure dispersant.

  In the comb structure dispersant, the polyester group [A] contained in the side chain group is preferably a repeating polymer of valerolactone units in which k in the above general formula (A) is 4, and the polyester group [B] Is preferably a repeating polymer of caprolactone units in which j in the general formula (B) is 5.

In the above (a) to (d), the carbonyl group side of the polyester group [A] in the side chain group -AZ may be bonded to the main chain, or the carboxylic acid ester group side may be bonded to the main chain.
The polyester group [B] in the side chain group -BZ may be bonded to the main chain on the carbonyl group side or on the main chain on the carboxylic acid ester group side.

Further, as C in the side chain group -CZ, a plurality of polyester groups [A] and polyester groups [B] may be included, and specifically, -ABABZ, -ABABAZ, -BABABZ,- ABABABZ can be used.
In the side chain group -CZ, even if each carbonyl group side of the polyester group [A] and the polyester group [B] constituting C is bonded to the main chain, each carboxylic acid ester group side is the main chain. It may be combined in a state of facing to. However, the orientation of all the polyester groups [A] and polyester groups [B] constituting one side chain group -CZ is in a state where the carbonyl group side is directed to the main chain, or the carboxylic acid ester group side is the main chain. It is necessary to be in a state where it is directed to

  In the side chain group -CZ, one chain length is, for example, the sum of m in the general formula (A) representing the polyester group [A] and n in the general formula (B) representing the polyester group [B] For example, it is preferably within 1,000.

In the above (a) to (d), Z is a hydrophilic group, specifically, —R ² OH, —R ³ SO ₃ H, or —R ⁴ COOH, respectively.
Here, R < ² > -R < ⁴ > shows an alkyl group, respectively.
In the comb-shaped structure dispersant, each terminal Z of the plurality of side chain groups may be the same or different from each other, and the degree of orientation on the surface of the colored particles between the metal oxides is uniform. The plurality of terminals Z are preferably the same as each other.

The content ratio of the polyester group [A] and the polyester group [B] in the comb structure dispersant is 20/80 to 50/50, preferably 30/70 in terms of mass ratio of polyester group [A] / polyester group [B]. ~ 40/60.
When the content ratio of the polyester group [A] and the polyester group [B] is in the above range, the metal oxide can be reliably dispersed with high dispersibility in the binder resin.

  The ratio of the side chain group in the comb structure dispersant varies depending on the type and molecular weight of the main chain described later, and the molecular weight of the polyester group [A] and the polyester group [B], but the main chain / (polyester group [A ] + Polyester group [B]) is preferably 1/10 to 1/100 by mass ratio.

The main chain in the comb structure dispersant is not particularly limited as long as it is a polymer containing a polycondensable functional group, and among them, polyamines such as polyalkyleneimine and polyallylamine, or those having a polyamide structure (hereinafter, “ Also referred to as “polyamide chain”).
Examples of the polyalkyleneimine constituting the main chain include polyethyleneimine, polypropyleneimine, poly-1,1-dimethylethyleneimine, poly-1,2-butyleneimine, poly-2,3-butyleneimine and the like. it can.
The polyamide chain has a repeating unit represented by the following general formula (1).
Formula (1): —CO—R ⁵ —CO—NH—R ⁶ —NH—
However, in the said General formula (1), R < ⁵ >, R < ⁶ > is an organic group respectively.

  The molecular weight of the main chain is 300 to 100,000 as a peak molecular weight, and preferably 600 to 15,000.

  The comb-shaped dispersant is composed of each side chain group bonded to the main chain carbon atom or nitrogen atom by forming an amide bond, a urethane bond, or an ester bond. Yes.

The content of the comb structure dispersant in the colored particles is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the polymer, for example.
When the content of the comb-shaped structure dispersant with respect to the content of the metal oxide is in the above range, the colored powder may be dispersed in the binder resin with a sufficiently high dispersibility. it can.

[Binder resin]
The binder resin is not particularly limited as long as it contains at least a polymer.
Specific examples of the polymer constituting such a binder resin include, for example, styrene resins, acrylic resins such as alkyl acrylates and alkyl methacrylates, styrene-acrylic copolymer resins, or olefin resins. Particularly preferred are styrene resins and acrylic resins. These can be used alone or in combination of two or more.
Moreover, in addition to the resin which consists of the above polymers, it can contain a polyester resin, a silicone resin, an amide resin, or an epoxy resin.

[Colorant]
The colored particles constituting the colored powder of the present invention may further contain an appropriate chromatic / achromatic dye or pigment other than the metal oxide as a colorant.
In the colored particles constituting the colored powder of the present invention, when titanium oxide is used as the metal oxide, the titanium oxide acts as a white pigment. When magnetite is used as the metal oxide, the magnetite acts as a black pigment. When hematite is used as the metal oxide, the hematite acts as a red pigment.
As a method of adding a dye or pigment other than a metal oxide as a colorant to the colored particles constituting the colored powder of the present invention, in the method for producing a colored powder to be described later, a polymerizable single resin to form a binder resin is used. Examples of the method include dissolving or dispersing a metal oxide and a comb structure dispersant in the polymer.

[Method for producing colored powder]
The method for producing the colored powder of the present invention is not particularly limited, and it is produced by separately producing colored particles (P) and colored particles (Q) and then mixing them in a desired ratio. Alternatively, the color particles (P) and the color particles (Q) may be produced by a method of producing them all at once.
The colored particles (P) and / or the colored particles (Q) are produced by a pulverization method in which, for example, a binder resin, a metal oxide, and, if necessary, a metal oxide dispersant are kneaded and pulverized. It may be prepared by a polymerization method in which a polymerizable monomer to form a binder resin, a metal oxide, and, if necessary, a dispersant for metal oxide are mixed and dispersed, and a polymerization process is performed. May be.
Further, the ratio of the metal oxide present in the surface vicinity region S ₁ can be adjusted by further mixing the metal powder as an external additive with the colored powder produced by the above method. .
Among these, the method of suspension polymerization using the above-described comb-shaped dispersant as the metal oxide dispersant, which can collectively produce the colored particles (P) and the colored particles (Q), is the most. Preferably mentioned. That is, a metal oxide, a comb structure dispersant, and a polymerization initiator are added to at least one type of polymerizable monomer that should form a binder resin, and then the polymerizable monomer is mixed with a homomixer or the like. These are dissolved or dispersed in a polymer to prepare a uniform metal oxide dispersed oil phase liquid, and then the metal oxide dispersed oil phase liquid is added to an aqueous medium to which a dispersion stabilizer has been added in advance. For example, by applying mechanical shearing force, the metal oxide dispersed oil phase liquid is dispersed as oil droplets in an aqueous medium to obtain a suspended state, then heated to polymerize, and after the polymerization reaction is completed, the dispersion stability A colored powder can be obtained by removing the agent, washing and drying.
By granulating in the aqueous medium in this manner, the metal oxide is oriented on the surface of the colored particles that form the colored powder formed because the end of the side chain group of the comb-shaped dispersant is hydrophilic. be able to.

And according to such a manufacturing method, the colored powder which consists of colored particles (P) and colored particles (Q) can be obtained.
This is because the metal oxide-dispersed oil phase liquid is dispersed as oil droplets in an aqueous medium, and when such a polymer droplet is polymerized, the metal oxide is oriented on the surface in each oil droplet. However, it is considered that colored particles having different dispersion states of the metal oxide are generated because the difference in heat conduction rate from the aqueous medium is caused by individual oil droplets.
That is, in the process in which the metal oxide moves and diffuses toward the surface, depending on the oil droplet, the polymerization reaction proceeds until the thickening occurs before the metal oxide reaches the near-surface region S _1. From the oil droplets, it is considered that colored particles (Q) with the metal oxide remaining in the internal region S ₂ are generated.
It is considered that whether each of the oil droplets generates colored particles (P) or colored particles (Q) depends on the type and amount of the metal oxide dispersant used.
Also, the smaller the particle size of the oil droplets, the higher the heat conduction rate from the aqueous medium, so that thickening during polymerization occurs earlier, and the metal oxide tends to remain in the internal region S _2. It is considered that the metal oxide tends to be localized in the surface vicinity region S ₁ as the droplet has a larger particle size.

The method for dispersing the metal oxide in the polymerizable monomer and the method for dispersing the metal oxide-dispersed oil phase liquid in the aqueous medium are not particularly limited. For example, an ultrasonic disperser, a high-speed stirring type disperser, and the like. Etc. can be used.
As the dispersed particle diameter for dispersing the metal oxide in the polymerizable monomer, the primary particle diameter is preferably 20 to 80 nm.
In addition, since the particle size of the oil droplets in which the metal oxide dispersed oil phase liquid is dispersed in the aqueous medium finally becomes the particle size of the colored particles constituting the colored powder, it is controlled so as to have a desired particle size. And disperse.

  Here, the “aqueous medium” refers to a medium composed of 50 to 100% by mass of water and 0 to 50% by mass of a water-soluble organic solvent. Examples of the water-soluble organic solvent include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran, and alcohol-based organic solvents that do not dissolve the resulting binder resin are preferable.

(Polymerizable monomer)
As a polymerizable monomer for obtaining a polymer constituting the binder resin, for example, styrene monomers such as styrene, methylstyrene, methoxystyrene, butylstyrene, phenylstyrene, chlorostyrene; methyl acrylate, acrylic acid (Meth) acrylic acid ester monomers such as ethyl, butyl acrylate, ethyl hexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethyl hexyl methacrylate; carboxylic acid monomers such as acrylic acid and fumaric acid The body can be used. These can be used alone or in combination of two or more.

(Polymerization initiator)
In the method for producing a colored powder of the present invention, examples of the polymerization initiator for obtaining the binder resin include an appropriate radical polymerization initiator, and for example, an oil-soluble polymerization initiator can be used. Examples of the oil-soluble polymerization initiator include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carboxyl). Nitrile), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile and other azo or diazo polymerization initiators; benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate , Cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis- (4,4- t-butylperoxycyclohexyl) propane, tris- ( Examples thereof include peroxide-based polymerization initiators such as (t-butylperoxy) triazine and polymer initiators having a peroxide in the side chain.

(Dispersion stabilizer)
In the method for producing a colored powder of the present invention, the dispersion stabilizer for dispersing oil droplets by the metal oxide dispersed oil phase liquid in the aqueous medium is not particularly limited, and examples thereof include tricalcium phosphate and magnesium phosphate. Zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica, alumina and the like. Furthermore, what is generally used as surfactant, such as polyvinyl alcohol, gelatin, methylcellulose, sodium dodecylbenzenesulfonate, these ethylene oxide adducts, and higher alcohol sodium sulfate, can be used.

[Chain transfer agent]
In the method for producing a colored powder of the present invention, a generally used chain transfer agent can be used for the purpose of adjusting the molecular weight of the binder resin. The chain transfer agent is not particularly limited, and examples thereof include mercaptans such as 2-chloroethanol, octyl mercaptan, dodecyl mercaptan, and t-dodecyl mercaptan, and styrene dimers.

[Particle size of colored particles]
Although the particle diameter of the colored particles constituting the colored powder of the present invention varies depending on the application, for example, when used as an electrophotographic toner, the average major axis based on the number is preferably 3 to 11 μm. For example, when a colored powder is used as a display material for electronic paper, the average major axis based on the number is preferably 2 to 30 μm.
If the particle size of the colored particles is excessive, the gap between the particles becomes large and the resulting coloring power is low. On the other hand, when the particles of the colored powder are too small, the aggregation resistance is poor and the fluidity is low.
This particle size can be controlled by adjusting the particle size of the oil droplets by the metal oxide dispersed oil phase liquid dispersed in the aqueous medium.

The number-based average major axis of the colored particles is measured and calculated as follows.
That is, first, after embedding the colored powder in a photocurable resin, an ultrathin section having a set thickness of 100 nm is prepared at an acceleration voltage of 200 kV with an ultramicrotome “EM UC6” (manufactured by LEICA), and the ultrathin section is transmitted. A cross-sectional photograph is taken with a scanning electron microscope (TEM) “2000FX” (manufactured by JEOL Ltd.), and the cross-sectional photograph is matched with a metal oxide image by image analysis software “LUZEX AP” (manufactured by Nireco) Then, the long diameter R is measured for each of the 100 colored particles in the cross-sectional photographic image, and the number average value is calculated to obtain a number-based average long diameter.
The average major axis of the colored particles (P) in the colored powder is calculated based on the number of colored particles (P) satisfying the condition P among the colored particles contained in 100 selected colored particles. . Similarly, the average major axis of the colored particles (Q) is calculated based on the number of colored particles (Q) satisfying the condition Q among the colored particles contained in 100 selected colored particles.

According to color powder described above, the colored particles occupied area ratio indicating the existence ratio in the region near the surface S ₁ of the metal oxide is in a certain high range (P) is contained 5 to 35% by number Therefore, the charged property of each colored particle has high uniformity, and for this reason, overcharge and aggregation are suppressed, the powder mobility by electric field is excellent, and the occupation area ratio is higher than the specified high range. In addition, since the colored particles (Q) in the lower range contain 60% by number or more, a sufficiently excellent coloring power can be obtained with a small amount of the colorant.
Further, since the colored particles (P) and the colored particles (Q) are contained in a total of 70% by number or more, the charging uniformity of the individual colored particles becomes extremely high, and a small amount of the colorant ensures the charging. Excellent productivity can be obtained and high productivity can be obtained.

In the colored powder having an average major axis of the colored particles (P) and the colored particles (Q) is defined, relatively small diameter of the particles present limited to the near-surface region S ₁ of the colorant (metal oxide) In that case, the coloring power is inferior, and the relatively small-diameter particles are colored particles (Q) in which the colorant is dispersed not only in the vicinity of the surface region S ₁ but also in the internal region S ₂ . particles for many colorant near the surface area S ₁ is a dispersed colored particles (P), effectively superior color strength with a small amount of the coloring agent is obtained.

Further, when the colored powder contains a comb-type structural dispersant as the metal oxide dispersant, the metal oxide is dispersed with high dispersibility in the surface vicinity region S ₁ and is not exposed to the outermost surface. A state is obtained, and thereby, accumulation of electrostatic charges on the surface is suppressed, so that high aggregation resistance is obtained. As a result, sufficient fluidity as a powder is obtained.
In addition, when the colored powder is applied to an application in which the colored powder is charged and used like a display material for electrophotography or a powder display, even if it is driven repeatedly by applying voltage for a long time, it is electrostatic. There is no specific aggregation, and excellent charging characteristics can be exhibited.

The reason why a state in which the metal oxide is dispersed with high dispersibility in the near-surface region S ₁ by using a comb-structured dispersant as the dispersant is that the main chain depends on the polarity of the main chain of the dispersant. The metal oxide is adsorbed on the portion, and the side chain group is a polyester group [A] having a structure in which a short carbon chain is sandwiched between a carbonyl group and a carboxylic acid ester group as a whole, and a longer carbon chain is a carbonyl group. The balance between hydrophilicity and hydrophobicity is controlled within a suitable range by containing a polyester group [B] having a structure sandwiched between carboxylic acid ester groups. That is, it is presumed that high dispersion stability is obtained for the metal oxide, and that the metal oxide is easily oriented in the region near the surface S ₁ of the particle. In particular, in the colored powder produced by the production method of the present invention, it is considered that the metal oxide is easily attracted to the surface where the polar group at the end of the side chain group is an interface with water, and the above effect is high. Demonstrated.

  Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

<Example 1>
100 parts by mass of methyl methacrylate, 20 parts by mass of titanium oxide “STT-30D” (manufactured by Titanium Industry Co., Ltd.) hydrophobized with silicone oil (hereinafter referred to as “titanium oxide [1]”) Comb type structural dispersant (X-1) 5 parts by weight and 2,2′-azobisisobutyronitrile 2 parts by weight are mixed with a high shear force “TK type homomixer” (special machine (Kako Kogyo Co., Ltd.) was stirred and mixed at a rotational speed of 6,000 rpm to prepare a metal oxide dispersed oil phase liquid [1] that was uniformly dissolved or dispersed.
Meanwhile, 2.5 parts of polyvinyl alcohol “GH-23” (manufactured by Nippon Synthetic Chemical Co., Ltd.) is dissolved in 250 parts of ion-exchanged water (aqueous medium), and the above metal oxide dispersed oil phase liquid [1] is added thereto. The mixture was stirred at 10,000 rpm for 20 minutes with a “TK homomixer” (manufactured by Tokushu Kika Kogyo Co., Ltd.) in a nitrogen gas atmosphere at 60 ° C., and the metal oxide dispersed oil phase liquid [1] was oiled in an aqueous medium. Dispersed as drops. Thereafter, while stirring with a paddle stirring blade, a polymerization reaction was performed at 60 ° C. for 3 hours, and then the liquid temperature was set to 80 ° C. to perform a polymerization reaction for 10 hours to perform polymerization treatment of the polymerizable monomer. Thereafter, the reaction system was filtered to separate a solid content, and 500 parts of ion-exchanged water was newly added, heated to 50 ° C., slurried, and washed with water for 10 minutes. This water washing was repeated 5 times, and the solid content was separated by filtration and then dried at 50 ° C. for one day with a dryer to obtain a colored powder [1].
When the content ratio of the colored particles (P) and the colored particles (Q) in the colored powder [1] was measured by the method described above, it was found that 15 number% of the colored particles (P) were contained. Table 2 shows the content of the colored particles (P) and the colored particles (Q) and the average major axis based on the number.
Here, the number-based average major axis of the colored particles (P) and the colored particles (Q) was measured by the method described above. The same applies to the following.

[Comb-shaped structure dispersant (X-1)]
As shown in Table 1, the comb structure dispersant (X-1) is composed of a side chain group having a configuration of -AZ and -BZ on a main chain composed of polyethyleneimine (abbreviated as "PEI" in Table 1). The side chain groups having the following structure are each independently bonded such that A: B is 30/70 by mass ratio and main chain: side chain (AZ + BZ) is 1/56 by mass ratio. It is made of a polymer having a comb structure of 35,000. However, A _{is, - (CO (CH 2)} 4 O) 35 -, B _{is, - (CO (CH 2)} 5 O) 65 -, Z is - (CH _{2) 12} OH.

<Examples 2 to 14>
In Example 1, instead of the comb structure dispersant (X-1), the comb structure dispersants (X-2) to (X-14) described in detail below were used in the same manner. Thus, colored powders [2] to [14] were obtained.
Table 2 shows the content of the colored particles (P) and the colored particles (Q) and the number-based average major axis in these colored powders [2] to [14].

[Comb-shaped structure dispersant (X-2)]
As shown in Table 1, the comb-shaped structural dispersant (X-2) has a side chain group having a configuration of -AZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 38,100 that is independently bonded such that A: B is 30/70 by mass and main chain: side chain (AZ + BZ) is 1/62 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 5 O) 50 -, B _{is, - (CO (CH 2)} 6 O) 50 -, Z is - (CH _{2) 4} OH.

[Comb-shaped structure dispersant (X-3)]
As shown in Table 1, the comb structure dispersant (X-3) has a side chain group having a configuration of -AZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 39,500, which is independently bonded such that A: B is 30/70 by mass and main chain: side chain (AZ + BZ) is 1/65 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 50 -, B _{is, - (CO (CH 2)} 7 O) 50 -, Z is - (CH _{2) 4} OH.

[Comb-shaped structure dispersant (X-4)]
As shown in Table 1, the comb-shaped structural dispersant (X-4) has a side chain group having a configuration of -AZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 190,000, independently bonded such that A: B is 20/80 by mass and main chain: side chain (AZ + BZ) is 1/633 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 300 -, B _{is, - (CO (CH 2)} 5 O) 700 -, Z is - (CH _{2) 4} OH.

[Comb-shaped structure dispersant (X-5)]
As shown in Table 1, the comb-shaped structural dispersant (X-5) has a side chain group having a configuration of -AZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 27,000, independently bonded such that A: B is 20/80 by mass and main chain: side chain (AZ + BZ) is 1/43 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 10 -, B _{is, - (CO (CH 2)} 5 O) 90 -, Z is - (CH _{2) 12} OH.

[Comb-shaped structure dispersant (X-6)]
As shown in Table 1, the comb structure dispersant (X-6) is a side chain group having a configuration of -AZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 30,000, each independently bonded such that A: B is 50/50 by mass and main chain: side chain (AZ + BZ) is 1/49 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 35 -, B _{is, - (CO (CH 2)} 5 O) 65 -, Z is - (CH _{2) 4} OH.

[Comb structure dispersant (X-7)]
As shown in Table 1, the comb-shaped structural dispersant (X-7) has a side chain group having a configuration of -AZ and a side chain group having a configuration of -ABZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 104,000, which is independently bonded such that A: B is 30/70 by mass and main chain: side chain (AZ + ABZ) is 1/171 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 35 -, B _{is, - (CO (CH 2)} 5 O) 65 -, Z is - (CH _{2) 4} OH.

[Comb-shaped structure dispersant (X-8)]
As shown in Table 1, the comb-shaped structural dispersant (X-8) has a side chain group having a configuration of -AZ and a side chain group having a configuration of -ABZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 59,000, which is independently bonded such that A: B is 50/50 by mass and main chain: side chain (AZ + ABZ) is 1/97 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 35 -, B _{is, - (CO (CH 2)} 5 O) 65 -, Z is - (CH _{2) 4} OH.

[Comb structure dispersant (X-9)]
As shown in Table 1, the comb-shaped structural dispersant (X-9) has a side chain group having a configuration of -ABZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 71,000, which is independently bonded such that A: B is 30/70 by mass and main chain: side chain (ABZ + BZ) is 1/116 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 35 -, B _{is, - (CO (CH 2)} 5 O) 65 -, Z is - (CH _{2) 4} OH.

[Comb-shaped structure dispersant (X-10)]
As shown in Table 1, the comb structure dispersant (X-10) has a side chain group having a configuration of -ABZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 59,000, which are independently bonded such that A: B is 50/50 by mass and main chain: side chain (ABZ + BZ) is 1/97 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 35 -, B _{is, - (CO (CH 2)} 5 O) 65 -, Z is - (CH _{2) 4} OH.

[Comb-shaped structure dispersant (X-11)]
As shown in Table 1, the comb structure dispersant (X-11) is a side chain group having a configuration of -ABABZ and a side chain group having a configuration of -ABABZ in the main chain made of polyethyleneimine (PEI). And the side chain groups having the configuration of -BABZ are independently bonded such that A: B is 30/70 by mass ratio and the main chain: side chain (ABAZ + ABABZ + BABZ) is 1/164 by mass ratio. It is composed of a comb-shaped polymer having a peak molecular weight of 100,000. However, A _{is, - (CO (CH 2)} 4 O) 35 -, B _{is, - (CO (CH 2)} 5 O) 65 -, Z is - (CH _{2) 4} OH.

[Comb-shaped structure dispersant (X-12)]
As shown in Table 1, the comb structure dispersant (X-12) has a side chain group having a configuration of -ABAZ and a side chain group having a configuration of -ABABZ in the main chain made of polyethyleneimine (PEI). And the side chain groups having the configuration of -BABZ are independently bonded such that A: B is 50/50 by mass ratio, and the main chain: side chain (ABAZ + ABABZ + BABZ) is 1/97 by mass ratio. It is made of a comb-shaped polymer having a peak molecular weight of 59,000. However, A _{is, - (CO (CH 2)} 4 O) 35 -, B _{is, - (CO (CH 2)} 5 O) 65 -, Z is - (CH _{2) 4} OH.

[Comb-shaped structure dispersant (X-13)]
As shown in Table 1, the comb structure dispersant (X-13) is composed of a side chain group having a structure of -AZ and -BZ on a main chain composed of polyallylamine (abbreviated as "PAA" in Table 1). The side chain groups having the following structure are each independently bonded such that A: B is 30/70 by mass ratio and main chain: side chain (AZ + BZ) is 1/56 by mass ratio. It is made of a polymer having a comb structure of 35,000. However, A _{is, - (CO (CH 2)} 4 O) 35 -, B _{is, - (CO (CH 2)} 5 O) 65 -, Z is - (CH _{2) 12} OH.

[Comb structure dispersant (X-14)]
As shown in Table 1, the comb structure dispersant (X-14) is composed of a side chain group having a structure of -AZ and -BZ on a main chain composed of polycaprolactam (abbreviated as "PCL" in Table 1). The side chain groups having the following structure are each independently bonded such that A: B is 30/70 by mass ratio and main chain: side chain (AZ + BZ) is 1/56 by mass ratio. It is made of a polymer having a comb structure of 35,000. However, A _{is, - (CO (CH 2)} 4 O) 35 -, B _{is, - (CO (CH 2)} 5 O) 65 -, Z is - (CH _{2) 12} OH.

<Example 15>
A colored powder [15] was obtained in the same manner as in Example 1 except that the addition amount of the comb-shaped structural dispersant (X-1) was changed from 5 parts by mass to 45 parts by mass.
Table 2 shows the content of the colored particles (P) and the colored particles (Q) and the number-based average major axis in the colored powder [15].

<Example 16>
In Example 1, instead of titanium oxide [1], titanium oxide “MT-500” (manufactured by Teica) hydrophobized with octylsilane (hereinafter referred to as “titanium oxide [2]”). A colored powder [16] was obtained in the same manner except that was used.
Table 2 shows the contents of the colored particles (P) and the colored particles (Q) and the number-based average major axis in the colored powder [16].

<Example 17>
A colored powder [17] was obtained in the same manner as in Example 1 except that methyl methacrylate was changed to styrene.
Table 2 shows the content of the colored particles (P) and the colored particles (Q) and the number-based average major axis in the colored powder [17].

<Example 18>
A colored powder [18a] was obtained in the same manner as in Example 1 except that the comb structure dispersant (X-1) was not used. This colored powder [18a] was a colored powder containing 70% by number of colored particles [Q] having an occupied area ratio SR of 30 area% or more and less than 65 area%.

(Synthesis Example 1 of Binder Resin Particles)
-First stage polymerization (soap-free emulsion polymerization):
Into a 1-liter four-necked flask equipped with a thermometer and a nitrogen inlet tube, 100 parts by mass of styrene (St) and 300 parts by mass of water are added and mixed, and further stirred under a nitrogen stream. The temperature was raised to 80 ° C. Next, 0.5 part by mass of potassium persulfate was added to this mixed solution, and the mixture was reacted for 6 hours while maintaining at 80 ° C. to obtain a dispersion [A] of polymer particles. When the polymer particles in the dispersion [A] of the polymer particles were observed with an electron micrograph, the polymer particles were spherical, the average particle size was 0.41 μm, and the relative standard deviation (CV value). Was 1.8%. The solid content in the polymer particle dispersion [A] was 24.2% by mass.
-Second stage polymerization:
Into a 1-liter four-necked flask equipped with a thermometer and a nitrogen introduction tube, 120.2 parts by mass of styrene (St) and 1.0 part by mass of benzoyl peroxide were added and dissolved. To the solution, 300 parts by mass of water, 3.3 parts by mass of “New Coal 707SN” (manufactured by Nippon Emulsifier Co., Ltd.) and 0.1 parts by mass of sodium nitrite were added and mixed for 10 minutes under strong stirring.
Next, 34.6 parts by mass of the polymer particles in the dispersion [A] of the polymer particles obtained by the first-stage polymerization were added to this mixed solution, and the mixture was gently stirred at 50 ° C. for 30 minutes. The mixture was reacted at 0 ° C. for 2 hours to obtain a dispersion [B] of polymer particles. When the polymer particles in the dispersion [B] of the polymer particles were observed with an electron micrograph, the polymer particles were spherical, the average particle diameter was 1.83 μm, and the relative standard deviation (CV value). Was 4.8%. The solid content in the dispersion [B] of polymer particles was 33.2% by mass.
-Third stage polymerization:
Next, in the same apparatus, 124.2 parts by mass of styrene (St) and 1.0 part by mass of benzoyl peroxide are mixed and dissolved, and further 200 parts by mass of water, “New Coal 707SN” ( 3.3 parts by mass of Nippon Emulsifier Co., Ltd. and 0.1 parts by mass of sodium nitrite were added and mixed for 10 minutes under strong stirring.
Next, 15.6 parts by mass of polymer particles in the dispersion [B] of polymer particles obtained by the second stage polymerization were added to this mixed solution, and the mixture was gently stirred at 50 ° C. for 30 minutes. By reacting at 2 ° C. for 2 hours, a binder resin particle dispersion [C] containing the binder resin particles [C] was obtained. The solid content in the binder resin particle dispersion [C] was 32.1% by mass.
When the binder resin particles [C] in the binder resin particle dispersion [C] were observed with an electron micrograph, the binder resin particles [C] were spherical and had an average particle diameter of 4.31 μm. The relative standard deviation (CV value) was 5.9%.

(Synthesis Example 2 of Binder Resin Particles)
・ Soap-free emulsion polymerization:
In a 1-liter four-necked flask equipped with a thermometer and a nitrogen inlet tube, 99 parts by mass of styrene (St) as a monomer, 1 part by mass of sodium 4-vinylbenzenesulfonate (NaSS), and water 400 Then, the mixture was stirred and mixed, and further heated to 80 ° C. while stirring under a nitrogen stream. Next, 0.5 parts by mass of potassium persulfate is added to the mixed solution, and the mixture is reacted for 6 hours while maintaining at 80 ° C., whereby a binder resin particle dispersion [D] containing the binder resin particles [D] is obtained. Obtained. The solid content in the binder resin particle dispersion [D] was 20.1% by mass.
When the binder resin particle [D] in the binder resin particle dispersion [D] is observed by an electron micrograph, the binder resin particle [D] is a true sphere having a substantially constant particle diameter. The average particle size was 0.12 μm, and the relative standard deviation (CV value) was 8.2%.

(Example of preparation of colorant dispersion)
In a solution obtained by stirring and dissolving 9.2 parts by mass of sodium n-dodecyl sulfate in 160 parts by mass of ion-exchanged water, titanium oxide “MT-500B” (manufactured by Teica) (hereinafter referred to as “titanium oxide [3 ) ") 20 parts by weight are gradually added, and then dispersed using a stirrer" CLEARMIX "(manufactured by M Technique Co., Ltd.), whereby the colorant dispersion [E] is obtained. Obtained.

(Example of colored powder production)
155 parts by weight of the binder resin particle dispersion [C], 49.5 parts by weight of the binder resin particle dispersion [D], 2000 parts by weight of ion-exchanged water, and 11.3 parts by weight of the colorant dispersion [E]. The mixture was stirred in a 5-liter four-necked flask equipped with a temperature sensor, a condenser, a nitrogen introducing device and a stirring device, adjusted to 30 ° C., 49 parts by weight of sodium chloride was added to this solution, and the pH was adjusted to 8. It was adjusted to 0, stirred for 3 hours, and then heated and stirred for 3 hours at a liquid temperature of 90 ° C. ± 2 ° C., followed by fusing to obtain a colored powder [18b]. This colored powder [18b] was a colored powder containing only colored particles [P] having an occupied area ratio SR of approximately 100 area%.

The colored powder [18] was obtained by mixing the colored powder [18a] and the colored powder [18b] at a mass ratio of 10:90.
Table 2 shows the contents of the colored particles (P) and the colored particles (Q) and the number-based average major axis in the colored powder [18].

<Comparative Examples 1-11>
In Example 1, instead of the comb structure dispersant (X-1), the comb structure dispersant (Y-1) to the comb structure dispersant (Y-11) described in detail below were used. In the same manner as above, comparative colored powders [19] to [29] were obtained.
Table 3 shows the contents of the colored particles (P) and the colored particles (Q) in these comparative colored powders [19] to [29] and the number-based average major axis.

[Comb-shaped structure dispersant (Y-1)]
As shown in Table 1, the comb structure dispersant (Y-1) is a side chain group having a configuration of -AZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 38,000, which is independently bonded such that A: B is 30/70 by mass and main chain: side chain (AZ + BZ) is 1/62 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 7 O) 20 -, B _{is, - (CO (CH 2)} 8 O) 80 -, Z is - (CH _{2) 12} OH.

[Comb structure dispersant (Y-2)]
As shown in Table 1, the comb-shaped structural dispersant (Y-2) has a main chain composed of polyethyleneimine (PEI) and a side chain group having a configuration of -AZ as a main chain: side chain (AZ). Is a comb-shaped polymer having a peak molecular weight of 32,000, which are independently bonded to each other so that the mass ratio is 1/52. However, A _{is, - (CO (CH 2)} 4 O) 50 -, Z is - (CH _{2) 12} OH.

[Comb-shaped structure dispersant (Y-3)]
As shown in Table 1, the comb-shaped structural dispersant (Y-3) has a side chain group having a configuration of -AZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 394,000, which is independently bonded such that A: B is 30/70 by mass and the main chain: side chain (AZ + BZ) is 1/11311 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 5 O) 1200 -, B _{is, - (CO (CH 2)} 6 O) 1000 -, Z is - (CH _{2) 12} OH.

[Comb-shaped structure dispersant (Y-4)]
As shown in Table 1, the comb-shaped structural dispersant (Y-4) has a side chain group having a configuration of -AZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 614,000, which is independently bonded such that A: B is 30/70 by mass and main chain: side chain (AZ + BZ) is 1/1022 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 5 O) 500 -, B _{is, - (CO (CH 2)} 6 O) 1500 -, Z is - (CH _{2) 12} OH.

[Comb-shaped structure dispersant (Y-5)]
As shown in Table 1, the comb-shaped structural dispersant (Y-5) has a side chain group having a configuration of -AZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 24,000, independently bonded such that A: B is 30/70 by mass and main chain: side chain (AZ + BZ) is 1/38 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 20 -, B _{is, - (CO (CH 2)} 3 O) 80 -, Z is - (CH _{2) 12} OH.

[Comb-shaped structure dispersant (Y-6)]
As shown in Table 1, the comb-shaped structural dispersant (Y-6) has a side chain group having a configuration of -AZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 37,000, independently bonded such that A: B is 20/80 by mass and main chain: side chain (AZ + BZ) is 1/61 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 20 -, B _{is, - (CO (CH 2)} 9 O) 80 -, Z is - (CH _{2) 12} OH.

[Comb-shaped structure dispersant (Y-7)]
As shown in Table 1, the comb-shaped structural dispersant (Y-7) has a side chain group having a configuration of -AZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 90,000, each independently bonded such that A: B is 10/90 by weight and main chain: side chain (AZ + BZ) is 1/149 by weight. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 20 -, B _{is, - (CO (CH 2)} 5 O) 80 -, Z is - (CH _{2) 12} OH.

[Comb-shaped structure dispersant (Y-8)]
As shown in Table 1, the comb-shaped structural dispersant (Y-8) has a side chain group having a configuration of -AZ and a side chain group having a configuration of -BZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 33,000, which is independently bonded such that A: B is 70/30 by weight and main chain: side chain (AZ + BZ) is 1/54 by weight. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 20 -, B _{is, - (CO (CH 2)} 5 O) 80 -, Z is - (CH _{2) 12} OH.

[Comb structure dispersant (Y-9)]
As shown in Table 1, the comb-shaped structural dispersant (Y-9) has a side chain group having a configuration of -AZ and a side chain group having a configuration of -ABZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 110,000, independently bonded such that A: B is 70/30 by mass and main chain: side chain (AZ + ABZ) is 1/181 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 20 -, B _{is, - (CO (CH 2)} 5 O) 80 -, Z is - (CH _{2) 12} OH.

[Comb-shaped structure dispersant (Y-10)]
As shown in Table 1, the comb-shaped structural dispersant (Y-10) has a side chain group having a configuration of -BZ and a side chain group having a configuration of -ABZ in the main chain made of polyethyleneimine (PEI). Is a comb having a peak molecular weight of 45,000 that is independently bonded such that A: B is 80/20 by mass and main chain: side chain (ABZ + BZ) is 1/74 by mass. It consists of a polymer of structure. However, A _{is, - (CO (CH 2)} 4 O) 20 -, B _{is, - (CO (CH 2)} 5 O) 80 -, Z is - (CH _{2) 12} OH.

[Comb structure dispersant (Y-11)]
As shown in Table 1, the comb structure dispersant (Y-11) is a side chain group having a configuration of -ABABZ and a side chain group having a configuration of -ABABZ in the main chain made of polyethyleneimine (PEI). And a side chain group having a configuration of -BABZ is independently bonded such that A: B is 80/20 in a mass ratio and main chain: side chain (ABAZ + ABABZ + BABZ) is 1/74 in a mass ratio. It is made of a comb-shaped polymer having a peak molecular weight of 45,000. However, A _{is, - (CO (CH 2)} 4 O) 20 -, B _{is, - (CO (CH 2)} 5 O) 80 -, Z is - (CH _{2) 12} OH.

<Comparative Example 12>
A colored powder [30] for comparison was obtained in the same manner as in Example 1 except that the comb-shaped structural dispersant (X-1) was not used.
Table 3 shows the contents of the colored particles (P) and the colored particles (Q) in the comparative colored powder [30] and the number-based average major axis.

<Comparative Example 13>
166 parts by mass of terephthalic acid, 415 parts by mass of isophthalic acid, 96 parts by mass of trimellitic acid, 1300 parts by mass of polyoxyethylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane and 75 parts by mass of ethylene glycol Into a four-necked flask equipped with a stirrer, condenser, and thermometer, and under a nitrogen gas stream, add 0.07% by mass of dibutyltin oxide based on the total acid components, and water produced by dehydration condensation. While removing, a polyester resin was obtained by reacting at 230 ° C. for 15 hours. The obtained polyester resin had a softening point temperature of 155 ° C., a glass transition temperature measured by DSC method of 62 ° C., and an acid value of 10.
50 parts of the polyester resin, 50 parts of rutile white titanium dioxide (hereinafter referred to as “titanium oxide [4]”) hydrophobized with isobutyltrimethoxysilane, and 185 parts of methyl ethyl ketone with Desper. After pre-dispersing, dispersion was performed with “Eiger Motor Mill M-1000” (manufactured by Eiger) to obtain a master solution of a titanium oxide dispersion. Thereafter, the solid content of the master solution of the titanium oxide dispersion was adjusted to 35% by mass using methyl ethyl ketone. The ratio of the white pigment (titanium oxide [4]) in the solid content was 50% by mass, and the white pigment was finely dispersed in the master solution. Furthermore, 60 parts of the above polyester resin was dissolved in 114.3 parts of the master solution of the obtained titanium oxide dispersion by stirring with a desper, and the solid content was adjusted to 55% by mass with methyl ethyl ketone. This is called titanium oxide [4] dispersion. The ratio of the white pigment in solid content was 20 mass%.
While adding 545.5 parts of titanium oxide [4] dispersion, 66.7 parts of methyl ethyl ketone, 43 parts of isopropyl alcohol, and 40 parts of 16.4% sodium hydroxide aqueous solution, they are mixed well, and stirring is continued. 680 parts of water were added. Thereafter, the solvent and a part of water were distilled off under reduced pressure to obtain an aqueous slurry of white resin particles. The obtained slurry was subjected to solid-liquid separation by a skimming method using a centrifugal separator, and a wet cake was freeze-dried to obtain a comparative colored powder [31].
The content of the colored particles (P) and the colored particles (Q) and the number-based average major axis in this comparative colored powder [31] were measured by the method described above. Table 3 shows the content of the colored particles (P) and the colored particles (Q) and the number-based average major axis.

<Comparative example 14>
40 parts by mass of titanium oxide [1], 50 parts by mass of methyl methacrylate, and 10 parts by mass of dioctyl sodium sulfosuccinate as a dispersing agent were mixed and dispersed for 2 hours using a ball mill to disperse titanium oxide into fine particles. A titanium oxide dispersion was obtained.
30 parts by mass of this titanium oxide dispersion, 70 parts by mass of methyl methacrylate, 20 parts by mass of ethylene glycol dimethacrylate and 0.2 parts by mass of 2,2-azobis-2,4-dimethylvaleronitrile as a polymerization initiator were mixed. A monomer composition was prepared.
The above monomer composition is added to and mixed with an aqueous medium in which 10 parts by mass of polyvinyl alcohol (saponification degree: 87%) is added to 50 parts by mass of water, and this is stirred at 2,000 rpm in a homomixer. The monomer droplets were adjusted to about 7 μm. Next, this dispersion is transferred to a reaction apparatus equipped with a stirrer and a thermometer, heated to 55 ° C. and subjected to a polymerization reaction at this temperature for 5 hours, and then cooled to room temperature, and the result obtained by suction filtration. The resin resin powder was separated. After washing with appropriate amounts of warm water and methanol, it was dried at room temperature to obtain a comparative colored powder [32].
The content of the colored particles (P) and the colored particles (Q) and the number-based average major axis in this comparative colored powder [32] were measured by the method described above. Table 3 shows the content of the colored particles (P) and the colored particles (Q) and the number-based average major axis.

<Comparative Example 15>
85 parts by mass of styrene (manufactured by Wako Pure Chemical Industries, Ltd.), 15 parts by mass of n-butyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd.), 0.4 parts by mass of divinylbenzene (manufactured by Wako Pure Chemical Industries, Ltd.), azonitrile compound “V-65” A monomer dispersion [1] was prepared by uniformly mixing 5 parts by mass (manufactured by Wako Pure Chemical Industries, Ltd.) and 40 parts by mass of titanium oxide [1].
Subsequently, 100 parts by mass of the obtained monomer dispersion [1] was accommodated in a homogenizer together with 1,000 parts by mass of an aqueous sodium dodecylbenzenesulfonate (100 ppm) and 20 parts by mass of tricalcium phosphate (TCP) at 10,000 rpm. For 30 minutes.
Furthermore, the obtained dispersion was heated to 70 ° C. while stirring at low speed using a stirring blade, and polymerization was carried out for 6 hours. After completion of the polymerization, in order to remove the TCP adhering to the obtained particle surface, it was washed with dilute hydrochloric acid, and the dilute hydrochloric acid was removed by decantation. The resulting slurry was then dispersed in 1,000 mL of water and then filtered. By repeating this washing operation consisting of dispersion and filtration five times, a comparative colored powder [33] was obtained.
The content of the colored particles (P) and colored particles (Q) and the number-based average major axis in this comparative colored powder [33] were measured by the method described above. Table 3 shows the content of the colored particles (P) and the colored particles (Q) and the number-based average major axis.

<Comparative Example 16>
Titanium oxide [1] 20 parts by mass, polyester resin 100 parts by mass, dispersant “T-77” (Hodogaya Chemical Co., Ltd.) 1 part by mass was mixed using “Henschel mixer” (Mitsui Mining Co., Ltd.), then 110 After melt-kneading using a twin-screw kneading extruder set at ° C., the obtained kneaded product is cooled, coarsely pulverized using a “hammer mill” (manufactured by Hosokawa Micron), and further a mechanical pulverizer “Turbo Mill T” -400 "(manufactured by Turbo Kogyo Co., Ltd.) was finely pulverized and then classified with an air classifier to obtain a colored powder [34] for comparison.
The content of the colored particles (P) and the colored particles (Q) and the number-based average major axis in the comparative colored powder [34] were measured by the method described above. Table 3 shows the content of the colored particles (P) and the colored particles (Q) and the number-based average major axis.

<Comparative Example 17>
Dispersant solution was prepared by dissolving 2.5 parts by mass of polyvinyl alcohol “GH-23” (manufactured by Nippon Synthetic Chemical Co., Ltd.) in 250 parts by mass of ion-exchanged water. A monomer solution consisting of 100 parts by mass of styrene, 2 parts by mass of 2,2′-azobisisobutyronitrile and 0.5 parts by mass of sodium dodecylbenzenesulfonate was added to this dispersant solution, and nitrogen was added at 60 ° C. The mixture was stirred for 20 minutes at 10,000 rpm with a “TK homomixer” (manufactured by Tokushu Kika Kogyo Co., Ltd.) under a gas atmosphere, and the monomer solution was dispersed as oil droplets in an aqueous medium.
Then, after stirring for 3 hours at 60 ° C. while stirring with a paddle stirring blade, the liquid temperature was set to 80 ° C. and polymerization was performed for 10 hours. Thereafter, the reaction system was filtered to separate a solid content, and 500 parts by mass of ion-exchanged water was newly added, heated to 50 ° C., reslurried, and washed with water for 10 minutes. This water washing was repeated 5 times, the solid content was separated by filtration, and then dried at 50 ° C. for one day with a dryer to obtain precursor particles containing no colorant.
Then, 20 parts by mass of titanium oxide [1] was added to 100 parts by mass of the precursor particles, and mixed with a Henschel mixer for 40 minutes to obtain a colored powder [35].
The content of the colored particles (P) and the colored particles (Q) and the number-based average major axis in the comparative colored powder [35] were measured by the method described above. Table 3 shows the content of the colored particles (P) and the colored particles (Q) and the number-based average major axis.

  Using the above colored powders [1] to [18] and comparative colored powders [19] to [35], the coloring power evaluation and the aggregation resistance evaluation described in detail below were performed. The results are shown in Tables 2 and 3.

[Evaluation of coloring power]
A colored powder [1] to [18] and a colored powder for comparison [19] to [35] are respectively provided on the adhesive layer side of a transparent adhesive tape “Transparent beautiful color” (manufactured by Sumitomo 3M) of 1 cm × 3 cm square. ] 1 g was adhered, excess powder was removed by air spray, and a state in which one layer of colored powder adhered to the tape was created. The transmission density of this adhesive tape sample was determined as “X-rite 341” (X− Rite), and the average value was calculated for five points at the center and four corners. If the average value of the transmission density is 2.50 or more, it is determined that the coloring power is sufficient.

[Aggregation resistance evaluation]
(1) Colored powder external additive treatment Hydrophobic silica (number average primary particles) was added to the colored powders [1] to [18] obtained above and the colored powders [19] to [35] for comparison. 1% by mass (diameter = 12 nm) and 0.3% by mass hydrophobic titania (number average primary particle size = 20 nm) are added and mixed with a Henschel mixer, and the colored powder [1 ′] to [18 '] And comparative external additive-treated colored powders [19'] to [34 '] were obtained.
(2) Creation of electrostatic image display device substitute tester An electrostatic image display device substitute tester was produced as follows. That is, a pair of glass substrates provided with an indium oxide electrode having a thickness of about 500 mm was adjusted with a spacer so that the distance was 100 μm, and each of the above-mentioned colored powders [1 ′] to [18 ′] treated with external additives And the externally-treated colored powder [19 '] to [34'] for comparison are placed in a 2.5 cm × 2 cm particle-encapsulating cell provided in the center of the glass substrate, and the glass substrate periphery is bonded with epoxy Adhering with a coloring agent and encapsulating colored powder, electrostatic image display device substitute testing machines [1] to [18] and comparative electrostatic image display device substitute testing machines [19] to [35] were produced. . The filling rate of the colored powder between the glass substrates was adjusted to 25% by volume.
(3) Measurement of anti-aggregation properties of the electrostatic image display device substitute testing machines [1] to [18] and the comparative electrostatic image display device substitution test machines [19] to [35] prepared as described above. After applying a DC bias of ± 500 V to one glass substrate 500 times, when a voltage of −500 V is applied, the other glass substrate to which no bias is applied is applied to the one glass substrate to which the bias is applied. The mass of the moved colored powder was measured, and the moving ratio was calculated. If this movement ratio is 95% or more, it is judged that the electric field mobility is sufficient and, therefore, the aggregation resistance is sufficient.

  As described above, according to the colored powders [1] to [18] according to Examples 1 to 18, it was confirmed that excellent coloring power and aggregation resistance were obtained.

It is sectional drawing for description which shows the colored particle which comprises the colored powder of this invention, the particle | grains shown by (a) are colored particles (P), and the particle | grains shown by (b) are colored particles (Q). is there.

Explanation of symbols

12 Metal oxide S ₁ Surface vicinity area S ₂ Internal area

Claims (11)

A colored powder comprising colored particles containing at least one polymer and a metal oxide,
70% by number or more of the colored particles constituting the colored powder are either colored particles (P) satisfying the following condition P or colored particles (Q) satisfying the following condition Q,
The colored powder contains 5 to 35% by weight of colored particles (P) and 60% by number or more of colored particles (Q).
Conditions P: a metal oxide present in the region near the surface S ₁ in its cross-section occupied area ratio [SA ₁ / (SA with the metal oxides present in the interior region S ₂ surrounded by the region near the surface S _{1 1} + SA ₂ ) × 100] is 65 area% or more and 100 area% or less.
Condition Q: Occupied area ratio [SA ₁ / (SA) between the metal oxide present in the near-surface region S ₁ and the metal oxide present in the internal region S ₂ surrounded by the near-surface region S ₁ in the cross section ₁ + SA ₂ ) × 100] is 30 area% or more and less than 65 area%.
[However, in the above conditions P and Q, SA ₁ is the total occupied area of the individual metal oxides in the surface vicinity region S ₁ , and SA ₂ is the occupied area of the individual metal oxides in the internal region S ₂ . Is the sum of ]   2. The colored powder according to claim 1, wherein the colored particles (P) have a number-based average major axis of 1.2 to 5 times the number-based average major axis of the colored particles (Q). .   The colored powder according to claim 1, wherein the metal oxide is titanium oxide. The colored particles contain a metal oxide dispersant, and the metal oxide dispersant is composed of a polymer having a comb structure in which a side chain group is bonded to a main chain,
The colored powder according to any one of claims 1 to 3, wherein the side chain group group includes a side chain group represented by any one of the following (A) to (D).
(A) at least one side chain group represented by -AZ, and at least one side chain group represented by -BZ (a) at least one side chain group represented by -AZ, and at least one- A side chain group represented by CZ (c) at least one side chain group represented by -BZ, and at least one side chain group represented by -CZ (d) at least one side represented by -CZ. In the above, A represents a polyester group [A] represented by the following general formula (A), B represents a polyester group [B] represented by the following general formula (B), and C Is a group containing a polyester group [A] and a polyester group [B], and Z is each —R ² OH, —R ³ SO ₃ H, or —R ⁴ COOH (where R ^{2 to} R ⁴ are each Represents an alkyl group.).

[In the above general formulas (A) and (B), k is an integer of 1 to 5, j is an integer of 2 to 8 greater than k, and m and n are each an integer of 1 to 1,000. is there. ]   The content ratio of the polyester group [A] and the polyester group [B] in the polymer constituting the dispersant for metal oxide is such that the polyester group [A] / polyester group [B] is 20/80 to 50 / The colored powder according to claim 4, wherein the colored powder is 50.   The colored powder according to any one of claims 1 to 5, wherein the metal oxide has a number average particle diameter of 20 to 80 nm.   The colored powder according to any one of claims 4 to 6, wherein the metal oxide dispersant is contained in an amount of 1 to 15 parts by mass with respect to 100 parts by mass of the polymer.   The colored powder according to claim 1, wherein the metal oxide is contained in an amount of 5 to 30 parts by mass with respect to 100 parts by mass of the polymer.   The coloring according to any one of claims 4 to 8, wherein the main chain of the polymer constituting the dispersant for metal oxide has a polyalkyleneimine, polyallylamine or polyamide structure. powder.   The colored powder according to any one of claims 1 to 9, wherein the colored particles have a number-based average major axis of 2 to 30 µm. A method for producing the colored powder according to any one of claims 1 to 10,
The metal oxide is mixed and dispersed in a polymerizable monomer that forms the polymer to prepare a metal oxide dispersed oil phase liquid, and the metal oxide dispersed oil phase liquid is suspended in an aqueous medium. A method for producing a colored powder, which comprises a step of polymerizing in a wet state.