JP2003344882A - Coloring particle, electrophoretic particle, electrophoretic display device using the same, and method for manufacturing coloring particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophoretic particle having low specific gravity and excellent dispersibility and showing satisfactory coloring. <P>SOLUTION: The electrophoretic particle is constituted of a colored particle 15 formed by carrying an anionic dye 14 into a porous body particle 12 having meso-pores 13 having substantially uniform diameters and constituted of oxide consisting of at least one of zirconium oxide, aluminum oxide, titanium oxide and tin oxide. The meso-pore having the uniform diameter consists of a meso- pore formed by using an assembled body of amphipathic molecules as a template and the distribution of the diameters of the meso-pores measured by a nitrogen gas adsorption method has a single maximum value and ≥60% pores of total pores have ≤10 nm diameters. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coloring material generally used for recording. More particularly, the present invention relates to electrophoretic particles used in a display device that performs display using electrophoresis, a method for manufacturing the same, and an electrophoretic display device using the same.

More specifically, colored particles prepared by adsorbing anionic dyes uniformly and in large amounts on fine particles of porous oxide having a controlled pore size, color electrophoretic particles composed of the colored particles, The present invention also relates to a manufacturing method thereof, and an electrophoretic display device using the same.

[0003]

2. Description of the Related Art In recent years, with the development of information equipment, the need for low power consumption and thin display devices has increased, and research and development of display devices meeting these needs have been actively conducted. Among them, the liquid crystal display device is capable of electrically controlling the alignment of liquid crystal molecules and changing the optical characteristics of the liquid crystal, and has been actively developed and commercialized as a display device that can meet the above needs. However, in these liquid crystal display devices, the visual burden caused by the viewing angle of the screen, the inconvenience of characters on the screen due to the reflected light, the flicker of the light source, the low brightness, etc. has not been sufficiently solved. For this reason, researches on display devices with less burden on the eyes are being actively studied.

Reflective display devices are expected from the viewpoint of low power consumption and reduction of burden on the eyes. One of them is
Harold D. An electrophoretic display device (US Pat. No. 3,612,758) invented by Lees et al. Is known. FIG. 3 shows the configuration of a conventional electrophoretic display device and its operating principle. This apparatus includes charged electrophoretic particles 31 and an electrophoretic dispersion medium 32 in which a coloring dye is dissolved.
And a pair of electrodes 33, 34 facing each other with this dispersion medium sandwiched therebetween.
It consists of Spacers / partitions 35 are formed between the respective elements in order to keep the distance between the upper and lower substrates constant and prevent bias of electrophoretic particles between the elements. The driving is performed by applying a voltage to the electrophoretic dispersion medium 32 via the electrodes 33 and 34, thereby attracting the electrophoretic particles 31 to an electrode having a polarity opposite to the electric charge of the particles themselves. The display is performed by the color of the electrophoretic particles 31 and the color of the electrophoretic dispersion medium 32 in which a coloring pigment different from the hue of the electrophoretic particles is dissolved. FIG. 3 shows two display states.

Recently, a method has also been proposed in which electrophoretic particles and an electric dispersion medium are enclosed in minute microcapsules, and these are arranged on a substrate to form a display device (US Pat. No. 6).
067185). The feature of this method is that the dispersion system is held in the capsules, so that it can be easily applied and formed on the substrate.

[0006] There are some proposals for electrophoretic particles. For example, Japanese Patent Application Laid-Open No. 2-141730 discloses a method of using metal oxide colloidal particles as electrophoretic particles. Further, in order to prevent sedimentation and separation of the electrophoretic particles and maintain good dispersion for a long time, it has been proposed to reduce the specific gravity of the electrophoretic particles by using a porous material.
Japanese Patent Laid-Open No. 2000-227 discloses electrophoretic particles obtained by coating a porous organic material with an inorganic oxide.
Japanese Patent No. 612 discloses fine particles having a pigment component on the surface and voids inside.

Colored particles obtained by adsorbing a dye on a porous material are considered to be usable as electrophoretic particles, and a coloring composition in which a dye is held on a mesoporous material is disclosed in JP-A-2000-202280. The publication describes mesoporous silica.

[0008]

However, these conventional electrophoretic particles have some problems. That is, in the case of electrophoretic particles obtained by coating a porous organic material with an inorganic oxide, when the pigment layer on the surface becomes thick, the specific gravity increases and the dispersibility is impaired, while when the pigment layer is thin, sufficient coloring is obtained. There was a conflicting problem that there was no Further, in the case of the porous pigment electrophoretic particles, the material is limited, so that the color tone is limited, and since it is necessary to change the material of the pigment to change the color tone, the charge amount of the particles depends on the color. There have been problems such as drastic change and increase in specific gravity when sufficient coloring is obtained. In addition, the porous pigment particles have low mechanical strength and the pigment particles forming the porous electrophoretic particles are separated, resulting in the formation of non-porous particles having a large specific gravity, which adversely affects the display characteristics. There was a problem of affecting. Therefore, electrophoretic particles having a small specific gravity and excellent homogeneity and colorability have been desired.

Against this background, particles in which a dye is supported on a porous material such as a mesoporous material are expected to be suitable for electrophoretic particles. However, for example, when a dye is supported on mesoporous silica particles, which is the most common mesoporous material, since the isoelectric point of silica is as low as about 2.0, a sufficient positive charge is not generated on the particle surface, which is an industrial factor. However, it has a major drawback that it cannot adsorb well the anionic dye which is most widely used as a dye for ink.

The present invention has been made in view of the above problems, and provides colored particles that are microscopically homogeneous, have a small specific gravity, excellent dispersibility, and exhibit sufficient coloring, and a method for producing the colored particles. That is the purpose. Another object of the present invention is to provide electrophoretic particles composed of the colored particles, which are excellent in dispersibility and exhibit sufficient coloring. Another object of the present invention is to provide an electrophoretic display device using the electrophoretic particles.

[0011]

That is, the present invention comprises an oxide of one or more of zirconium oxide, aluminum oxide, titanium oxide and tin oxide having mesopores of substantially uniform diameter. It is a colored particle comprising an anionic dye carried on the constituted porous particles.

In the present invention, the mesopores having a uniform diameter are preferably formed by using an aggregate of amphipathic molecules as a template. Further, it is preferable that the amphipathic molecule is a surfactant. Further, it is preferable that the distribution of the diameters of the mesopores obtained by the nitrogen gas adsorption measurement has a single maximum value, and 60% or more of the pores are included in the range of 10 nm.

The present invention is also an electrophoretic particle composed of colored particles having the above characteristics. The present invention also includes a composition containing colored particles having the above characteristics.

Another aspect of the present invention is to hydrolyze and condense one or more starting materials of zirconium oxide, aluminum oxide, titanium oxide and tin oxide in the presence of an amphipathic material. A step of producing a precursor of a porous body composed of an oxide-organic compound complex, a step of producing a porous body by removing an amphipathic substance from the precursor, and an anionic dye in the porous body And a step of supporting the colored particles.

Here, as the material used as the raw material of the oxide, an alkoxide or an inorganic salt of at least one element selected from zirconium, aluminum, titanium and tin is preferably used.

Further, the present invention is an electrophoretic display device having electrophoretic particles, a dispersion medium for dispersing the electrophoretic particles, and a pair of electrodes for moving the electrophoretic particles, The electrophoretic particles have mesopores of substantially uniform diameter, zirconium oxide, aluminum oxide,
An electrophoretic display device characterized in that it is composed of colored particles in which an anionic dye is carried on porous particles composed of an oxide composed of one or more kinds of titanium oxide and tin oxide. Is.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
FIG. 1 is a diagram schematically showing the electrophoretic particles of the present invention. In FIG. 1, 11 indicates one electrophoretic particle. As shown in FIG. 1, the electrophoretic particles of the present invention have mesopores 13 having a substantially uniform diameter, and are composed of at least one of zirconium oxide, aluminum oxide, titanium oxide, and tin oxide. Porous particles 12 composed of
It is composed of colored particles 15 carrying an anionic dye 14. A is an enlarged view of a portion B of the colored particles 15, and C is an enlarged view of a portion of A.

The material preferably used in the present invention is an oxide composed of at least one of zirconium oxide, aluminum oxide, titanium oxide and tin oxide. Other materials can be used as long as they are colorless (white) and exhibit good anionic dye adsorption.
According to the study by the present inventors, the isoelectric point of oxide is 5.0.
The above materials tend to show a good adsorption amount of the anionic dye, and conversely, when an oxide of less than this is used, the adsorption amount of the anionic dye is insufficient, and sufficient color development can be obtained. The tendency that cannot be accepted is recognized. Regarding the isoelectric point of oxides, see, for example, Langmuir, Vol. 13, Vol. 63.
It is described on page 15. Specifically, the isoelectric point is the pH at which the surface charge of an oxide becomes 0 in an aqueous solution.
PPZC (Pristine point)
Also referred to as to of zero charge). The isoelectric point is measured, for example, by potentiometric titration. The isoelectric points of the oxides are about 8 for zirconium oxide, about 9 for aluminum oxide, and about 12 for magnesium oxide. The isoelectric point of silica is about 2.0.

There are no particular restrictions on the arrangement of the pores. Although FIG. 1 shows pores arranged in a two-dimensional hexagonal structure, the arrangement of pores is not limited to this. For example, in addition to this, a cubic structure, a three-dimensional hexagonal structure, or the like can be used. Moreover, even if the pore diameter is uniform and the arrangement is random, it can be favorably used for the electrophoretic particles of the present invention.

The above-mentioned method for producing colored particles is carried out by hydrolyzing and condensing at least one raw material selected from zirconium oxide, aluminum oxide, titanium oxide and tin oxide in the presence of an amphipathic substance. A step of preparing a precursor of a porous body composed of an oxide-organic compound complex, and removing amphipathic substances from the precursor to have mesopores of uniform diameter, zirconium oxide, aluminum oxide, oxidation This is performed by using a step of forming a porous body composed of an oxide composed of at least one of titanium and tin oxide, and a step of supporting an anionic dye on the porous body.

The mesopore region preferably has a uniform pore size as the pore size of the porous particles. Mesopores are based on the IUPAC classification and have pore diameters of 2 nm to 50 nm. In the case of a microporous substance having a diameter smaller than this, the dyes that can be supported in the pores are limited to those having a relatively small size, while in the case of a macroporous substance having a diameter larger than this, inside the pores. The dye molecules may associate with each other, resulting in a decrease in color tone.

To evaluate the pore size distribution in the porous particles,
Generally, a method of measuring an adsorption isotherm of a gas such as nitrogen is used. From the obtained adsorption isotherm, Berret-Jo
It is calculated by the yner-Halenda (BJH) analysis method or the like. The mesopores of the porous material particles used for the electrophoretic particles of the present invention have a single maximum value of the distribution of pore diameters determined by the BJH method from the nitrogen gas adsorption measurement, and have 60% or more. The pores are included in the range of 10 nm, preferably 5 nm. When using a porous material particles having a wider pore size distribution than this, unevenness in the amount of dye adsorption occurs, or the color tone of the particles decreases,
There is a problem that the specific gravity changes depending on the particles, which may deteriorate the display characteristics.

The uniform-sized mesopores in the electrophoretic particles of the present invention can be formed by various methods. However, they are aggregates of amphipathic molecules, particularly surfactant molecules. The oxide-organic compound composite (mesostructure) prepared by using a certain micelle as a template is generally prepared by removing the organic component, and exhibits favorable properties.

As a method for producing a mesostructure using a surfactant micelle as a template, a known method can be used. The production method varies depending on the element forming the oxide, but basically, in the presence of a surfactant,
This is a method of hydrolyzing at least one substance that is a raw material of zirconium oxide, aluminum oxide, titanium oxide, and tin oxide. As the surfactant, for example, a nonionic surfactant such as a block copolymer containing polyethylene oxide as a hydrophilic group can be used.

For example, Angewandte Chem
IE International Edition
Vol. 35, p. 1102, describes the method of making mesoporous alumina in the Journal of Material.
s Chemistry, Volume 6, Page 89,
The manufacturing method of mesoporous zirconia is Chemical C
Ommunifications, 1998, page 1471, describes the process for producing mesoporous tin oxide, Angew.
and Chemie Magazine International
Al Edition, Vol. 34, p. 2014, describes methods for producing mesoporous titanium oxide. In addition to this, Nature magazine, Volume 396, Volume 15
Page 2 describes a method for making various mesoporous oxides by using a poly (alkylene oxide) block copolymer as a template, and when this method is used, the mesoporous material formed is not in powder form. First, it must be crushed into a powder of a desired size and used.

There are various methods for removing the organic component from the composite, such as calcination, ultraviolet light irradiation, oxidative decomposition with ozone, extraction with a supercritical fluid, and extraction with a solvent, but a method that does not destroy the pore structure. If so, either method can be favorably used.

The anionic dye is adsorbed on the porous particles made of oxides made of one or more of zirconium oxide, aluminum oxide, titanium oxide and tin oxide, prepared as described above. The dye is not particularly limited, and basically any dye can be used as long as it is an anionic dye having a particle size smaller than that of mesopores.

Specific examples of anionic dyes include dyes such as direct blue and acid yellow.

As a method for adsorbing a dye, a method in which the above-mentioned porous material powder is dispersed in an aqueous solution of the dye and then separated and washed is simple and common, but other than this method, the structure is not destroyed. Any method can be used as long as it can introduce the dye into the pores. The amount of anionic dye introduced into the pores is determined by the surface charge density of the oxide. Therefore,
It is possible to control the adsorption amount of the dye by controlling the surface charge density of the inorganic substance, that is, by controlling the pH of the dye aqueous solution.

Since the pore diameter in the porous oxide material used in the present invention is sufficiently larger than the size of most dye molecules, the pH at the time of dye adsorption, the dye concentration, and the charge per dye molecule. If the conditions such as the amount are the same, the amount of dye adsorbed is almost the same regardless of the type of dye, and therefore the surface charge density of particles after dye adsorption is almost constant regardless of the dye. Therefore, the characteristics of the electrophoretic particles do not change significantly even if the type of dye changes, and it is possible to display different color tones under substantially the same driving conditions.

As described above, since the amount of dye adsorbed is determined by the charge density on the surface of the particle, the dye is not adsorbed in a large amount in the pores so as to form an aggregate. And high color development can be achieved. The present inventors believe that the dye molecules are adsorbed within the particles in a state close to that of the dye molecules, as schematically shown in FIG. The amount of the dye adsorbed is preferably in the range of 5 to 30% by weight based on the weight of the porous body.

The shape of the electrophoretic particles of the present invention is most preferably spherical as shown in FIG. 1, but other shapes can be applied as long as display characteristics are not deteriorated. For example, a gyroid shape, a disk shape, a hexagonal particle, a flake shape or the like can be applied. The size of each particle is not particularly limited, but is preferably in the range of 50 nm to 100 μm, more preferably 0.2 μm to 10 μm. If the particle size is too large, it becomes difficult to move by electrostatic force, and the display characteristics may be degraded.

The specific gravity of the electrophoretic particles may be 0.6 to 2.0, preferably 0.6 to 1.5,
It is more preferably 0.7 to 1.2. A known method can be used as the method for measuring the specific gravity, but a simple method in which the specific gravity is dispersed in a solution having a known specific gravity and the degree of sedimentation is determined may be used. In order to obtain uniform particles, the produced particles may be classified.

Further, for the purpose of preventing the particles from aggregating, adjusting the specific gravity, etc., a surface coating not shown in FIG. 1 may be applied to each electrophoretic particle. As an example of the coating method, a spray coating method, i
An n-situ polymerization method, a sputtering method, a plating method and the like can be mentioned.

FIG. 2 schematically shows an example of an electrophoretic device using the electrophoretic particles of the present invention. The electrophoretic device may be a known one and is not particularly limited. At least the electrophoretic particles 21 of the present invention and a dispersion medium 2 in which the electrophoretic particles are dispersed.
2 and the substrate 26 on which the electrode 23 or 24 is formed. By applying an electric field, the particles move in either direction of the upper and lower electrodes, and display is performed according to the color tone of the particles and the dispersion medium.

Further, when it is desired to manufacture a display device compatible with multiple colors, it can be realized by using particles prepared by using dyes of different colors. In this case, when the specific gravity of the particles changes depending on the type of dye used, it can be dealt with by adjusting the specific gravity of the dispersion medium.

[0037]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the embodiments of the present invention are not limited to the description of the examples.

Example 1 In this example, porous alumina particles were prepared by using a poly (alkylene oxide) block copolymer as a nonionic surfactant, and a blue dye was adsorbed to prepare blue electrophoretic particles. It is an example.

2.1 mmol of poly (alkylene oxide) block copolymer (trade name Pluronic L
64, manufactured by BASF) was dissolved in 25 ml of anhydrous sec-butanol, 21 mmol of aluminum tri-sec-butoxide was further dissolved, and the mixture was stirred until it became homogeneous to give a solution A. 42 mmol of pure water was mixed with 10 ml of anhydrous sec-butanol to prepare a solution B.

Solution B was slowly added to Solution A with stirring, and the mixture was further stirred for 3 hours, diluted 5-fold with anhydrous sec-butanol, and further stirred for 24 hours. The final product was washed with ethanol, dried at room temperature for 24 hours, further dried at 100 ° C for 6 hours and finally 400 ° C.
The powder was baked for 4 hours to obtain powder particles.

X-ray alumina particles produced by the above procedure
As a result of analysis using a line diffraction analysis, a diffraction peak corresponding to a face spacing of 6.9 nm was observed, and it was confirmed that it had a three-dimensional pore structure.

Further, as a result of conducting an experiment of nitrogen gas adsorption on this powder sample, the specific surface area obtained from the adsorption isotherm shows a large value of 441 m ² / g, and BJH
As a result of calculating the pore size distribution by the method, the pore size distribution was 3.
It showed a single dispersion having a sharp maximum at 5 nm, and the distribution curve was within the range of 2 nm to 7 nm in particle size. From this, it was confirmed that the produced porous alumina had mesopores having a substantially uniform diameter. In addition, it was confirmed by infrared absorption analysis that no organic component remained in the powder after firing.

Next, an anionic dye is adsorbed on the porous alumina particles. Add appropriate amount of hydrochloric acid to adjust pH to 1.
100 mg of the above-treated porous alumina particles were dispersed in 30 g of a 0.075 wt% aqueous solution of Direct Blue 199 adjusted to 0, and a magnetic stirrer was used to
The dye was adsorbed by stirring for a time.

Next, the particles thus adsorbing the dye are washed to remove the dye excessively adsorbed on the surface. The washing was carried out by repeating the steps of centrifuging the particles having adsorbed the dye, removing the supernatant washing liquid, redispersing in ethanol, and again centrifuging to remove the supernatant washing liquid. By washing 5 times, particles in which the dye hardly eluted in the supernatant washing liquid were produced. The washed particles were dried at room temperature to obtain bright blue porous alumina particles. By CHN elemental analysis, the amount of adsorbed dye was determined to be 12% of the powder weight, and it was confirmed that a sufficient amount of adsorption was achieved.

When the particles after adsorbing the dye were evaluated by X-ray diffraction analysis, a diffraction peak was observed at the same position as that observed in the particles before adsorbing the dye, and the three-dimensional pore structure was observed even after adsorbing the dye. It was confirmed that it was retained. As a result of measurement of nitrogen gas adsorption on the powder sample after dye adsorption, a specific surface area of 248 m ² / g, which was smaller than that before dye adsorption, was obtained. The pore size distribution obtained by the BJH method from the adsorption isotherm shows that there is almost no change in the maximum value compared to that before adsorption of the dye, but the proportion of pores with a smaller diameter increases compared to before adsorption of the dye. Was. This clearly indicates the adsorption of dye into the internal pores.
From the porous alumina particles supporting the dye produced through the above steps, particles having a particle size of 2 μm to 3 μm were classified to obtain electrophoretic particles.

Next, in order to evaluate the electrophoretic characteristics of the porous alumina particles carrying the dye produced through the above steps, the electrophoretic apparatus as shown in FIG. 2 was used for evaluation. Isoparaffin (trade name: Isopar, manufactured by Exxon) was used as the insulating liquid (dispersion medium) 22. Isoparaffin contained succinimide (trade name: OLOA1200, manufactured by Chevron Co.) as a charge control agent. The dye-supported porous alumina particles produced in this example showed good dispersion in the insulating liquid, and the particles did not precipitate even when the solution was left standing, and thus a good fine particle dispersion composition was obtained. I was able to get Also, the adsorbed dye did not elute. The electrophoretic particles produced in this example moved well between the electrodes by applying an electric field to the upper and lower electrodes, and exhibited good display characteristics. It was also confirmed that the particles did not aggregate with the driving, and that good driving characteristics lasted for a long time.

Example 2 This example is an example in which a yellow dye is adsorbed on the porous alumina particles produced in Example 1 to produce yellow electrophoretic particles. Under the same procedure and conditions as in Example 1, particles of porous alumina having pores of uniform diameter were prepared.

100 mg of these particles was adjusted to pH 1.0, and a 0.075 wt% aqueous solution 3 of Acid Yellow 23 was prepared.
It was dispersed in 0 g and stirred with a magnetic stirrer for 1 hour to adsorb the dye. The particles thus adsorbing the dye were washed 5 times with ethanol according to the same procedure as in Example 1 to prepare final dye-supported porous alumina particles. The dye was hardly eluted in the supernatant washing liquid after the fifth washing. The washed sample was dried at room temperature to obtain bright yellow porous alumina particles. By CHN elemental analysis, the amount of adsorbed dye was determined to be 11% of the powder weight, and it was confirmed that a sufficient amount of adsorption was achieved.

The particles after adsorbing the dye were evaluated by X-ray diffraction analysis. As a result, a diffraction peak was observed at the same position as that observed in the particles before adsorbing the dye, and the three-dimensional pore structure was observed even after adsorbing the dye. It was confirmed that it was retained. As a result of measurement of nitrogen gas adsorption on the powder sample after dye adsorption, a specific surface area of 260 m ² / g, which was smaller than that before dye adsorption, was obtained. The pore size distribution obtained by the BJH method from the adsorption isotherm shows that there is almost no change in the maximum value compared to that before adsorption of the dye, but the proportion of pores with a smaller diameter increases compared to before adsorption of the dye. Was. This clearly indicates the adsorption of dye into the internal pores.
From the porous alumina particles supporting the dye produced through the above steps, particles having a particle size of 2 μm to 3 μm were classified to obtain electrophoretic particles.

When the particles were dispersed in the same insulating liquid as used in Example 1, good dispersion was obtained, the particles did not precipitate even when the solution was allowed to stand, and the adsorbing dye from the particles. Did not elute. Also in the case of the electrophoretic particles produced in this example, the characteristics were evaluated under the same driving conditions as in Example 1, using the electrophoretic device having the same configuration as that used in Example 1. As a result, even in the case of the yellow particles of this example, by applying an electric field to the upper and lower electrodes, the particles moved well between the electrodes and exhibited good display characteristics. It was also confirmed that the particles did not aggregate with the driving, and that good driving characteristics lasted for a long time.

Almost no difference in characteristics between the yellow particles produced in this example and the blue particles produced in Example 1 was observed,
This example shows that the use of the colored particles of the present invention as electrophoretic particles makes it possible to move electrophoretic particles having different tones under the same conditions.

Example 3 This example is an example of producing yellow electrophoretic particles by adsorbing a yellow dye to porous zirconia particles produced using a cationic surfactant.

10 mol / l aqueous solution of zirconyl chloride octahydrate (manufactured by Aldrich) 10
To 0 ml, 86 ml of a 0.1 mol / l aqueous solution of cetyltrimethylammonium chloride (manufactured by Tokyo Kasei) was added and stirred for 15 minutes to prepare a solution A.

An aqueous ammonia solution (concentration: 0.88 g / ml) was added to the solution A with stirring until the pH became 11.5, and the mixture was further stirred for 1 hour to obtain a gel-like solid precipitation product. . The mixed solution containing the precipitated component was transferred to a closed container and stirred at 100 ° C. in the container for 72 hours.
Then, the mixed solution containing the precipitation product was allowed to cool to room temperature, washed with pure water while suction-filtered until the surfactant did not elute, and then dried at 60 ° C. for 24 hours.

As a result of analyzing this powder sample by X-ray diffraction analysis, a diffraction peak corresponding to a 3.8 nm plane interval was observed, and an absorption band derived from a surfactant was observed in infrared absorption analysis. Therefore, the formation of the surfactant-zirconia nanocomposite was confirmed. The nanocomposite powder was calcined in air at 400 ° C. for 6 hours to remove the surfactant, and powder particles were obtained.

The calcined zirconia powder produced by the above procedure was analyzed by X-ray diffraction analysis. As a result, a diffraction peak corresponding to an interplanar spacing of 3.6 nm was observed, although it was slightly broad, and three-dimensional. It was confirmed to have a fine pore structure. In addition, it was confirmed by infrared absorption analysis that no organic component remained in the powder after firing. As a result of conducting an experiment of nitrogen gas adsorption on this powder sample,
The specific surface area obtained from the adsorption isotherm showed a large value of 360 m ² / g, and the pore size distribution was calculated by the BJH method. As a result, the pore size distribution showed a single dispersion with a sharp maximum at 2.9 nm. Moreover, the distribution curve was within the range of the pore diameter of 2 nm to 7 nm. From this, it was confirmed that the produced porous zirconia had mesopores having a substantially uniform diameter.

100 mg of these particles was adjusted to pH 1.0, and a 0.075 wt% aqueous solution 3 of Acid Yellow 23 was prepared.
It was dispersed in 0 g and stirred with a magnetic stirrer for 1 hour to adsorb the dye. The particles thus adsorbing the dye were washed 5 times with ethanol according to the same procedure as in Example 1 to obtain final dye-supported porous zirconia particles. The dye was hardly eluted in the supernatant washing liquid after the fifth washing. The washed sample was dried at room temperature to obtain bright yellow porous zirconia particles. By CHN elemental analysis, the amount of adsorbed dye was determined to be 10% of the powder weight, and it was confirmed that a sufficient amount of adsorption was achieved.

When the particles after adsorbing the dye were evaluated by X-ray diffraction analysis, diffraction peaks similar to those observed for the particles before adsorbing the dye were observed, and the three-dimensional pore structure after adsorbing the dye had a three-dimensional pore structure. It was confirmed that it was retained. As a result of measurement of nitrogen gas adsorption on the powder sample after dye adsorption, a specific surface area of 208 m ² / g, which was smaller than that before dye adsorption, was obtained. The pore size distribution obtained by the BJH method from the adsorption isotherm shows that there is almost no change in the maximum value compared to that before adsorption of the dye, but the proportion of pores with a smaller diameter increases compared to before adsorption of the dye. Was. This clearly indicates the adsorption of dye into the internal pores.
From the porous zirconia particles supporting the dye produced in the above steps, particles having a particle size of 2 μm to 3 μm were classified to obtain electrophoretic particles.

When the particles were dispersed in the same insulating liquid as used in Examples 1 and 2, good dispersion was obtained.
The particles did not precipitate even when the solution was allowed to stand, and the adsorbed dye did not elute from the particles. Also in the case of the electrophoretic particles produced in this example, the characteristics were evaluated using the electrophoretic device having the same configuration as that used in Examples 1 and 2. As a result, even in the case of the yellow particles of this example, by applying an electric field to the upper and lower electrodes, the particles moved well between the electrodes and exhibited good display characteristics. It was also confirmed that the particles did not aggregate with the driving, and that good driving characteristics lasted for a long time.

Example 4 This example is an example of producing blue electrophoretic particles by adsorbing a blue dye on porous tin oxide particles produced by using a neutral amine as a surfactant.

To a solution of 0.54 g of octadecylamine dissolved in 36 g of isopropyl alcohol was added 3.5 g of tin tetraisopropoxide, and the mixture was stirred for 1 hour to completely dissolve it and obtain a uniform solution. This solution was left at room temperature in a saturated steam atmosphere for 60 hours to gradually hydrolyze tin tetraisopropoxide. The white precipitate formed was filtered, thoroughly washed with pure water, and then dried at 40 ° C. to obtain a white powder.

As a result of X-ray diffraction analysis of the obtained powder, a diffraction peak corresponding to an interplanar spacing of 5.6 nm was observed, and an absorption band derived from octadecylamine was observed in infrared absorption analysis. More, surfactant-
The formation of tin oxide nanocomposite was confirmed. This nanocomposite powder was heated in air at 300 ° C for 6
Firing was performed for an hour to remove the surfactant.

The tin oxide powder produced by the above-mentioned procedure was replaced with X
As a result of analysis using a line diffraction analysis, a diffraction peak corresponding to a face spacing of 5.1 nm was observed although it was broad, and it was confirmed that it had a three-dimensional pore structure. In addition, it was confirmed by infrared absorption analysis that no organic component remained in the powder after firing. As a result of carrying out an experiment of nitrogen gas adsorption on this powder sample, the specific surface area obtained from the adsorption isotherm showed a large value of 314 m ² / g, and the pore size distribution was calculated by the BJH method.
The pore size distribution showed a single dispersion having a sharp maximum at 2.2 nm, and the distribution curve was within the range of pore sizes of 1.5 nm to 6 nm. From this, it was confirmed that the produced porous tin oxide had mesopores having a substantially uniform diameter.

Direct Blue 199 was adsorbed to the porous tin oxide particles by the same method as in Example 1, and the excessively adsorbed dye was washed with ethanol to be removed. The washed particles were dried at room temperature to obtain bright blue porous tin oxide particles. CHN elemental analysis confirmed that the amount of adsorbed dye in the final product was 8% of the powder weight, and confirmed that a sufficient amount of adsorption was achieved.

When the particles after adsorbing the dye were evaluated by X-ray diffraction analysis, almost the same diffraction peaks as observed in the particles before adsorbing the dye were observed, and the three-dimensional pore structure remained after adsorbing the dye. It was confirmed that it was retained. As a result of measurement of nitrogen gas adsorption on the powder sample after dye adsorption, a specific surface area of 188 m ² / g, which was smaller than that before dye adsorption, was obtained. The pore size distribution obtained by the BJH method from the adsorption isotherm shows that there is almost no change in the maximum value compared to that before adsorption of the dye, but the proportion of pores with a smaller diameter increases compared to before adsorption of the dye. Was. This clearly indicates the adsorption of dye into the internal pores.
Dye-supporting porous tin oxide particles produced in the above steps were classified into particles having a particle size of 2 μm to 3 μm to obtain electrophoretic particles.

Next, using the same apparatus and dispersion medium as those used in Examples 1 to 3, the electrophoretic properties of the dye-supported porous tin oxide particles produced by the above steps were evaluated. The dye-supported porous tin oxide particles produced in this example showed good dispersion in the insulating liquid, and the particles did not precipitate even when the solution was left standing, and the adsorbed dye was eluted. I didn't do it. The electrophoretic particles produced in this example moved well between the electrodes by applying an electric field to the upper and lower electrodes, and exhibited good display characteristics. It was also confirmed that the particles did not aggregate with the driving, and that good driving characteristics lasted for a long time.

Example 5 In this example, a poly (alkylene oxide) block copolymer was used as a nonionic surfactant to prepare a porous titanium oxide by a casting method, which was pulverized into a powder and then a blue dye was added. This is an example in which blue electrophoretic particles are produced by adsorption.

1.0 g of poly (alkylene oxide) block copolymer (trade name Pluronic P12
3, manufactured by BASF) was dissolved in 10 g of ethanol, and 1.9 g of titanium tetrachloride was slowly added to this solution while vigorously stirring. The obtained mixed solution was transferred to a petri dish and kept in an atmosphere having a relative humidity of 80% for 1 day.

This was baked at 300 ° C. for 6 hours,
Removal of the surfactant was performed. The fired sample was finely pulverized and classified into particles having a particle diameter of 2 μm to 3 μm. As a result of X-ray diffraction analysis of this powder, a relatively broad diffraction line having a center at a position corresponding to a structural period of about 11 nm was observed, and this powder sample had a three-dimensional pore structure. It was confirmed that In addition, it was confirmed by infrared absorption analysis that no organic component remained in the powder after firing.

As a result of conducting an experiment of nitrogen gas adsorption on this powder sample, the specific surface area obtained from the adsorption isotherm is 2
It showed a large value of 24 m ² / g, and the pore size distribution was calculated by the BJH method. As a result, the pore size distribution was 6.5 nm.
The distribution curve was in the range of 2 nm to 10 nm in pore diameter. From this, it was confirmed that the produced porous titanium oxide had mesopores having a substantially uniform diameter.

Direct Blue 199 was adsorbed to the porous titanium oxide particles by the same method as in Example 1, and the excessively adsorbed dye was removed by washing with ethanol. The washed powder sample was dried at room temperature to obtain a vivid blue porous titanium oxide powder. CHN elemental analysis confirmed that the amount of adsorbed dye in the final product was 8% of the powder weight, and confirmed that a sufficient amount of adsorption was achieved.

When the particles after adsorbing the dye were evaluated by X-ray diffraction analysis, diffraction peaks similar to those observed for the particles before adsorbing the dye were observed, and the three-dimensional pore structure remained after adsorbing the dye. It was confirmed that it was retained. As a result of measurement of nitrogen gas adsorption on the powder sample after dye adsorption, a specific surface area of 188 m ² / g, which was smaller than that before dye adsorption, was obtained. The pore size distribution obtained by the BJH method from the adsorption isotherm shows that there is almost no change in the maximum value compared to that before adsorption of the dye, but the proportion of pores with a smaller diameter increases compared to before adsorption of the dye. Was. This clearly indicates the adsorption of dye into the internal pores.

Next, using the same apparatus and dispersion medium as those used in Examples 1 to 4, the electrophoretic characteristics of the dye-supporting porous titanium oxide particles prepared by the above steps were evaluated. The dye-supported porous titanium oxide particles produced in this example exhibit good dispersion in the insulating liquid, the particles do not precipitate even when the solution is left standing, and the adsorbed dye is eluted. I didn't do it. The electrophoretic particles produced in this example moved well between the electrodes by applying an electric field to the upper and lower electrodes, and exhibited good display characteristics. It was also confirmed that the particles did not aggregate with the driving, and that good driving characteristics lasted for a long time.

Comparative Example 1 Nonionic surfactant (polyoxyethylene 10 cetyl ether, trade name Brij56, SIGMA CHE
3.3 g (manufactured by MICAL) was dissolved in 128 ml of pure water, and 20 ml of 35% concentrated hydrochloric acid was added to prepare an acidic solution of the surfactant. After adding 2.2 ml of tetraethoxysilane at room temperature to this surfactant solution and stirring for 3 minutes,
It was transferred to a fluororesin pressure vessel and reacted at 80 ° C. for 1 week to obtain a precipitate. The precipitate was thoroughly washed with pure water and dried, and the obtained powder was calcined in air at 550 ° C. for 10 hours to obtain a white powder.

As a result of analyzing this powder using X-ray diffraction analysis, it was confirmed that this powder was mesoporous silica having a pore structure of a two-dimensional hexagonal structure, and the (100) plane spacing was 5 It was confirmed to be 0.3 nm. Further, as a result of conducting an experiment of nitrogen gas adsorption on this powder sample, the specific surface area obtained from the isotherm adsorption line shows a large value of 856 m ² / g, and the result of calculating the pore size distribution by the BJH method shows that Pore size distribution is 3.8n
It shows a monodispersion with a sharp maximum in m, and the distribution curve is in the range of pore diameters from 2 nm to 7 nm. From this, the prepared mesoporous silica has a substantially uniform pore diameter. Was confirmed. In addition, it was confirmed by infrared absorption analysis that no organic component remained in the powder after firing.

100 mg of the mesoporous silica particles
Was dispersed in 30 g of a 0.075 wt% aqueous solution of Direct Blue 199 whose pH was adjusted to 1.0, and stirred with a magnetic stirrer for 1 hour to try to adsorb the dye. Next, as in Example 1, this dispersion solution was separated by centrifugation and redispersed in ethanol to remove the dye excessively adsorbed on the surface. The washed mesoporous silica particles obtained in this comparative example showed almost no coloration, and it was found that the dye was hardly supported in the pores.

[0077]

As described above, according to the present invention,
By supporting an anionic dye on a porous material particle having a uniform diameter of mesopores and made of an oxide composed of one or more of zirconium oxide, aluminum oxide, titanium oxide, and tin oxide, It is possible to provide colored particles having excellent dispersion performance and sufficient coloring.

Further, according to the production method of the present invention, the above-mentioned colored particles can be produced by a simple method. Also,
INDUSTRIAL APPLICABILITY The present invention can provide electrophoretic particles composed of the above colored particles, which are excellent in dispersibility and exhibit sufficient coloring. Further, the present invention can provide an electrophoretic display device using the electrophoretic particles described above.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of electrophoretic particles of the present invention.

FIG. 2 is a schematic diagram showing a configuration of an electrophoretic display device of the present invention.

FIG. 3 is a schematic diagram showing a configuration of a conventional electrophoretic display device and its operating principle.

[Explanation of symbols]

11 Electrophoretic particles 12 Porous particles 13 Mesopores 14 Anionic dye 15 Colored particles 21 Colored electrophoretic particles 22 Dispersion medium for electrophoresis 23, 24 electrodes 25 partitions 26 Substrate 31 Electrophoretic particles 32 Dispersion medium for electrophoresis 33, 34 electrodes 35 bulkhead 36 board

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09D 17/00 C09D 17/00 (72) Inventor Akira Kuriyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Kiya Non-Incorporated (72) Inventor Tomonari Horikiri 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F-term (reference) 4J037 AA22 AA25 EE02 EE03 EE28

Claims (9)

[Claims] 1. Having mesopores of substantially uniform diameter,
A colored particle comprising a porous particle composed of an oxide composed of one or more kinds of zirconium oxide, aluminum oxide, titanium oxide and tin oxide, and carrying an anionic dye. 2. The colored particle according to claim 1, wherein the mesopores having a uniform diameter are pores formed by using an aggregate of amphipathic molecules as a template. 3. The colored particle according to claim 1, wherein the amphipathic molecule is a surfactant. 4. The distribution of diameters of the mesopores obtained by nitrogen gas adsorption measurement has a single maximum value, and 60
% Or more of pores are included in the range of 10 nm, The colored particle according to any one of claims 1 to 3. 5. An electrophoretic particle comprising the colored particle according to any one of claims 1 to 4. 6. A composition comprising the colored particles according to any one of claims 1 to 4. 7. An oxide-organic compound complex is obtained by hydrolyzing and condensing a raw material of at least one of zirconium oxide, aluminum oxide, titanium oxide and tin oxide in the presence of an amphipathic substance. And a step of removing the amphipathic substance from the precursor to form a porous body, and a step of supporting an anionic dye on the porous body. A method for producing colored particles, comprising: 8. The method for producing colored particles according to claim 7, wherein the substance as a raw material of the oxide is an alkoxide or an inorganic salt of at least one element selected from zirconium, aluminum, titanium and tin. 9. An electrophoretic display device comprising electrophoretic particles, a dispersion medium for dispersing the electrophoretic particles, and a pair of electrodes for moving the electrophoretic particles, wherein the electrophoretic particles are The porous material particles having mesopores of substantially uniform diameter and made of an oxide composed of at least one kind of zirconium oxide, aluminum oxide, titanium oxide, and tin oxide are mixed with an anionic dye. An electrophoretic display device, characterized in that the electrophoretic display device is composed of supported colored particles.