TWI702188B - Barium titanate fine particle powder, dispersion and coating - Google Patents

Abstract

The present invention provides a barium titanate particle powder suitable for optical thin film applications, which can maintain a small particle size and a large dielectric constant, and a method for efficiently producing barium titanate particle powder.

The average particle size of the primary particles of the barium titanate microparticle powder of the present invention is 20-60nm, and the relative permittivity is 300-800. The particle size distribution of the primary particles is divided by the average particle size of the primary particles. It is 0.20~0.25.

Description

Barium titanate fine particle powder, dispersion and coating

The present invention aims to provide a fine particle powder of barium titanate with a high dielectric constant (relative dielectric constant).

Barium titanate with a high dielectric constant is widely used as a dielectric material for multilayer ceramic capacitors and the like.

On the other hand, with respect to optical films used in various displays, it is done by adding inorganic particle fillers such as zirconia to the transparent resin to control the dielectric constant or refractive index.

Even in the TFT for control of liquid crystal displays, due to the low power consumption, as the material of the insulating film and the like, there is a need for fine particles and high dielectric constant.

Therefore, in order to use barium titanate in the aforementioned optical applications, it is sought to ensure the transparency of the film as a resin film containing barium titanate with a fine particle size, and to obtain barium titanate particle powder with a large dielectric constant.

Conventionally, there are known barium titanate particle powders (Patent Documents 1 and 2) that increase the dielectric constant by heat treatment at 500°C or higher, and fine barium titanate particle powders obtained by hydrothermal reaction (Patent Document 3) Wait.

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] JP 2002-211926 A

[Patent Document 2] Japanese Patent Application Publication No. 2005-289668

[Patent Document 3] JP 2007-137759 A

Although barium titanate fine particles satisfying many of the aforementioned characteristics are currently required, they have not yet been obtained.

That is, although the aforementioned Patent Documents 1 and 2 describe heat treatment of barium titanate particle powder in a temperature range of 500° C. or higher, the heat treatment temperature is high, and the particle size may be coarsened.

In addition, it is difficult to say that the barium titanate particle powder produced by the hydrothermal reaction described in Patent Document 3 has a high dielectric constant.

Therefore, in the present invention, it is a technical problem to obtain barium titanate particle powder with a small particle size and a large dielectric constant.

The aforementioned technical problems can be achieved by the present invention as follows.

That is, the present invention is a barium titanate fine particle powder, which is characterized in that the average particle diameter of the primary particles is 20-60 nm and the relative dielectric constant is 300-800 (the present invention 1).

In addition, the present invention is the barium titanate fine particle powder of the present invention 1, wherein the value of the particle size distribution of the primary particles divided by the average particle size of the primary particles is 0.20 to 0.25 (the present invention 2).

In addition, the present invention is the barium titanate fine particle powder of claim 1 or 2, wherein the lattice constant ratio c/a is less than 1.003 (the present invention 3).

In addition, the present invention is a dispersion containing the barium titanate fine particle powder according to any one of the inventions 1 to 3 (the invention 4).

In addition, the present invention is a coating film containing the barium titanate fine particle powder according to any one of the inventions 1 to 3 (the invention 5).

The barium titanate microparticle powder of the present invention is very fine particles and has a high dielectric constant, making it suitable for optical materials.

In addition, in the present invention, when the barium titanate fine particle powder is used to form a resin film, since a sheet with excellent transparency is obtained, it is suitable for use as an optical material.

[Figure 1] Barium titanate fine particles used in Example 1 (before heat treatment).

[Figure 2] Barium titanate fine particles obtained in Example 1 (after heat treatment).

The structure of the present invention will be described in detail below.

The average particle diameter (x) of the primary particles of the barium titanate fine particle powder of the present invention is 20 to 60 nm. By adjusting the average particle size of the barium titanate fine particle powder within the aforementioned range, when a resin film containing the barium titanate fine particle powder is produced, a resin film with excellent transparency can be obtained. Preferably, the average particle size is 22 to 58 nm, more preferably 25 to 55 nm.

Regarding the barium titanate fine particle powder of the present invention, the relative dielectric constant measured by the evaluation method described later is 300 to 800. By adjusting the relative dielectric constant of the barium titanate fine particle powder within the aforementioned range, fine particles with suppressed particle growth can be obtained. More preferably, the relative dielectric constant is 410~750.

The value obtained by dividing the particle size distribution (σ) of the primary particles of the barium titanate fine particle powder of the present invention by the average particle size (x) of the primary particles is preferably 0.20 to 0.25. By adjusting the aforementioned numerical value within the aforementioned range, a barium titanate fine particle powder with excellent particle size distribution is obtained. The more preferable range is 0.205~0.248.

Regarding the crystallinity of the barium titanate fine particle powder of the present invention, when expressed by the lattice constant ratio c/a of the a-axis length (a) and the c-axis length (c) of the lattice constant, the lattice constant ratio is preferred Less than 1.003. The barium titanate fine particle powder having a lattice constant ratio c/a of 1.003 or more is difficult to industrially produce in the particle size system of the present invention.

The specific surface area of the barium titanate fine particle powder of the present invention is preferably 10 to 80 m ² /g. When the particle size is less than 10m ² /g, the particle powder becomes coarse, and the particles have become sintered particles between each other. When the binder is mixed, the dispersibility is easily damaged. It is difficult to industrially produce barium titanate fine particles with a specific surface area value exceeding 80 m ² /g.

The half-value width (FWHM) of the (111) plane calculated from the X-ray diffraction peak of the barium titanate fine particle powder of the present invention is preferably 0.2 to 0.4.

The particle shape of the barium titanate fine particle powder according to the present invention is preferably spherical or granular.

Next, the method for producing the barium titanate fine particle powder of the present invention will be described.

The barium titanate microparticle powder of the present invention can be obtained by heat-treating barium titanate microparticle powder with an average particle size of 10-50 nm produced by hydrothermal reaction in a temperature range of 100-400°C in advance.

In the present invention, although the hydrothermal reaction is not particularly limited, for example, a barium hydroxide aqueous solution is dropped and neutralized in a titanium chloride aqueous solution to obtain a titanium hydroxide colloid, and then the aforementioned titanium hydroxide colloid is put into the barium hydroxide aqueous solution , Heat the resulting mixed solution to generate barium titanate. After cooling and washing, it can be obtained by hydrothermal treatment at a temperature range of 100~250℃, followed by washing, drying and crushing.

In the hydrothermal reaction, barium titanate of different sizes can be produced by changing the reaction temperature, concentration, and pH value.

The average particle diameter of the barium titanate obtained by the hydrothermal reaction is preferably 10-50 nm.

The barium titanate particles (particle size: 10-50 nm) produced by the hydrothermal reaction are heat-treated in the temperature range of 100-400°C to obtain the barium titanate fine particle powder that is the object of the present invention. By adjusting the heat treatment temperature within the aforementioned range, the growth of the particle size of the barium titanate fine particles can be suppressed while increasing the dielectric constant. When the heat treatment temperature is too high, the particles may fuse with each other.

The heat treatment time is preferably 1 to 3 hours.

Next, the dispersion related to the present invention will be described.

As the dispersion medium in the present invention, both aqueous and solvent systems can be used.

As the dispersion medium of the water-based dispersion, water, or alcoholic solvents such as methanol, ethanol, propanol, isopropanol, butanol can be used; methyl cellulose, ethyl cellulose, propyl cellulose, butyl Diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol and other glycol ether solvents; oxyethylene or oxypropylene addition polymers such as ethylene glycol, Alkylene glycol such as propylene glycol and 1,2,6-hexanetriol; water-soluble organic solvent such as glycerin and 2-pyrrolidone. The dispersion media for these water-based dispersions can be used by mixing one or more types according to the intended use.

As a dispersion medium for solvent dispersions, aromatic hydrocarbons such as toluene and xylene; ketones such as methyl ethyl ketone and cyclohexanone; N,N-dimethylformamide, N,N -Dimethylacetamide, N-methylpyrrolidone and other amides; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, Propylene glycol monoethyl ether, etc. Ether alcohols; ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate and other ether acetates; Acetate esters such as ethyl acetate, butyl acetate, isobutyl acetate, etc.; lactate esters such as methyl lactate, ethyl lactate, and propyl lactate; ethylene carbonate, propylene carbonate, γ-butyrolactone And other cyclic esters and various monomers. These dispersing media for solvent-based dispersions can be used by mixing one or more types according to the intended use.

The dispersing machine used to produce the dispersion of the present invention is not particularly limited, and it is preferably a device that can add shear, impact, compression, and/or friction to the powder layer, for example, Roller mills, high-speed rotary mills, classifiers built-in high-speed rotary mills, ball mills, media stirring mills, jet mills, compact shear mills, colloid mills, roller mills, etc.

Regarding the dispersion of the present invention, the barium titanate particle powder contains 0.1 to 60 parts by weight, preferably 0.5 to 50 parts by weight, and more preferably 1 to 40 parts by weight relative to 100 parts by weight of the substrate constituting the dispersion. As the base material for the dispersion of barium titanate particle powder, in addition to the above barium titanate particle powder, it is made of a dispersing medium. If necessary, dispersing agents and additives (resin, defoaming agents, auxiliary agents, etc.) can be added )Wait.

As the dispersant in the present invention, it can be appropriately selected and used according to the type of barium titanate particle powder or dispersing medium used, and organosilicon compounds such as alkoxysilanes, silane coupling agents, and organopolysiloxanes can be used. Surfactants, polymer dispersants, etc., can be used in combination of one or more types.

Examples of the above-mentioned organosilicon compounds include methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, ethyltriethoxysilane, propyl Triethoxysilane, butyl triethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, tetraethoxysilane and tetramethoxysilane such as alkoxysilane, vinyl trimethyl Oxysilane, vinyl triethoxy silane, γ-aminopropyl triethoxy silane, γ-glycidoxy propyl trimethoxy silane, γ-mercaptopropyl trimethoxy silane, γ- Methacryloxypropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane Silane coupling agents such as silane, γ-chloropropyltrimethoxysilane, polysiloxane, methyl hydrogen polysiloxane, modified polysiloxane and other organopolysiloxanes.

Examples of the above-mentioned surfactants include anionic surfactants such as fatty acid salts, sulfate ester salts, sulfonate salts, and phosphate ester salts; polyethylene glycol type such as polyoxyethylene alkyl ethers and polyoxyethylene aryl ethers. Nonionic surfactants, nonionic surfactants such as polyvalent alcohol nonionic surfactants such as sorbitol fatty acid esters; amine salt type cationic surfactant, fourth-level ammonium salt type cationic interface Cationic surfactants such as active agents; amphoteric surfactants such as alkyl dimethylaminoacetic acid betaines and alkyl imidazolines.

As the polymer dispersant, styrene-acrylic acid copolymer, styrene-maleic acid copolymer, polycarboxylic acid and its salt, etc. can be used.

Although the amount of dispersant added depends on the total surface area of the barium titanate particles in the dispersion medium, it also responds to the dispersion of the barium titanate particles. The purpose of the body and the type of dispersant can be adjusted appropriately, but generally speaking, by adding 0.01 to 100% by weight of the dispersant relative to the barium titanate particle powder in the dispersion medium, the barium titanate particle powder can be uniform and It is finely dispersed in the dispersing medium, and at the same time it can improve the dispersion stability. In addition, the above-mentioned dispersant may be directly added to the dispersion medium, or the barium titanate particle powder may be pretreated.

Next, the coating film related to the present invention will be described.

The coating film of the present invention is prepared by adding resin to the aforementioned dispersion, and after mixing, using a coater such as a bar coater or a spin coater to form it on a film such as a PET film.

The resin used is generally acrylic resin, silicone resin, epoxy resin, polyester resin, polyimide resin, polymethylmethacrylate (PMMA), polystyrene (PS), polycarbonate (PC) Wait.

When the coating film using the barium titanate fine particle powder of the present invention is evaluated by the method described below, the total light transmittance is 85% or more, the haze is 0.65 or more, and the transparency is excellent.

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In the present invention, a fine and high dielectric constant barium titanate particle powder is obtained.

In the present invention, by heating the fine barium titanate particle powder after the hydrothermal reaction in a temperature range where it is difficult to produce sintering between the particles, the particle size and lattice constant are compared with the barium titanate particle powder before heat treatment. The half-value width of c/a and (111) reflection is almost unchanged, only the dielectric can be improved constant.

As a factor that affects the dielectric constant of barium titanate particles, it is considered to be the size effect of the particles. When measured by the inventors, the relative dielectric constant of barium titanate particles with a particle size of 175 nm obtained by the hydrothermal reaction is about 130.

It is considered that the growth of the particles by the heat treatment in the present invention is very small, and the increase in the particle size only affects the dielectric constant, and the results of the present invention cannot be explained.

As another reason for the increase in the dielectric constant caused by heat treatment, it is considered that the surface layer of the particles is modified by removing hydroxyl groups. In the low temperature heat treatment, although it is generally impossible to expect a change in characteristics, since the barium titanate particles subjected to the heat treatment in the present invention are nano-sized, it is considered to be a type with a large surface area and a large increase in dielectric constant.

However, if heat treatment can be carried out at a higher temperature and the interior of the particles can be modified, the dielectric constant can be expected to further increase. However, heat treatment at high temperature may cause the particle size to grow rapidly due to the fusion of particles. It is not suitable for the production of barium titanate particles for optical thin film applications.

[Example]

The representative embodiment of the present invention is as follows.

The average particle size (x) of the primary particles of the barium titanate fine particles powder is based on a photograph (50 thousand times magnification) observed with a scanning electron microscope (S-4300, Hitachi, Ltd.). The particle size is measured from about 500 particles , And obtain the particle size distribution (σ) at the same time. Shang, the so-called primary particle The average particle diameter is the diameter of a circle having the same area as the area obtained from the photograph for each particle, and the particle diameter is the average particle diameter of all particles measured. Since there is almost no difference in the measured value of the visual field, each visual field is widely observed at low magnification, and the measurement is performed in the visual field that can be regarded as an average.

The barium titanate fine particle powder was evaluated by powder X-ray diffraction, and the c/a ratio of the lattice constant and the half-value width (FWHM) of the (111) plane were measured.

The specific surface area value is expressed by the value measured by the BET method.

The relative dielectric constant of the barium titanate fine particle powder was measured by the following evaluation method.

That is, a mixture of 2.5 g of barium titanate fine particles powder and 0.5 g of a polyvinyl alcohol aqueous solution with a concentration of 3 wt% is pressed at a pressure of 100 kg/cm ² to produce a disc-shaped pressed powder with a diameter of 25 mm and a thickness of 1 to 2 mm. body. The pressed powder contains moisture, so it is placed in dry air at 50°C for more than 12 hours.

From the weight and volume of the compressed powder after drying, the volume ratio of barium titanate particle powder, PVA and voids is obtained. In addition, the compaction system is adjusted so that the barium titanate fine particles powder becomes 41 to 55 vol%, PVA becomes 0.1 to 3 vol%, and the remainder becomes voids.

For the obtained compact, the relative dielectric constant at 10 MHz was measured at a room temperature of about 25° C. and a humidity of about 40% RH using an impedance analyzer E4991A manufactured by Agilent and a dielectric constant measuring fixture 16453A. The relative permittivity measurement results obtained include barium titanate particles The effect of each component of the sub-powder, PVA and voids, therefore, in the present invention, it is estimated that only barium titanate has an effect from the measured value using logarithmic mixing.

Example 1:

The water and salt barium hydroxide octahydrate (Kanto Chemical (shares) _{system, 97% Ba (OH) 2} .8H 2 O reagent special grade) 1.12kg dissolved in purified water were dripped, and titanium tetrachloride to give an aqueous solution of 688g Titanium hydroxide colloid. Next, 1.28 kg of barium hydroxide octahydrate salt was dissolved and purified in water and kept in a reaction vessel with a temperature of 70°C and a nitrogen atmosphere with a pH of 12.5. Next, the aforementioned titanium hydroxide colloid was put into the aforementioned barium hydroxide aqueous solution in 2 minutes. The mixed solution was heated at 100°C for 0.5 hours to generate barium titanate. After cooling to room temperature, the filtrate is used to wash Ba ions with a suction filter until it is no longer recognized, and then filtered and dried to obtain barium titanate fine particles. The average particle size of the obtained barium titanate fine particle powder was 32 nm. The electron micrograph of the obtained barium titanate fine particle powder is shown in FIG. 1.

The obtained barium titanate particle powder with an average particle diameter of 32 nm was heated in the air at 400° C. for 2 hours using an electric furnace. When the resultant heat-treated powder was observed by SEM, it was sintered at 400°C. Although part of the powder was fused into particles with a size of several tens of nanometers, the particle size was 60 nm or less and the overall particles grew slightly. The electron micrograph of the obtained barium titanate fine particle powder is shown in FIG. 2.

Example 2:

Change the conditions of the hydrothermal reaction to obtain titanium with an average particle size of 46nm Next, the barium titanate particle powder was heat-treated at a temperature of 400° C. by the same method as described in Example 1 to obtain barium titanate particle powder. Table 1 shows many characteristics of the obtained barium titanate fine particles powder.

Example 3:

The conditions of the hydrothermal reaction were changed to obtain barium titanate particle powder with an average particle size of 51 nm. Next, by the same method as described in Example 1, heat treatment at 400°C to obtain barium titanate fine particles powder. Table 1 shows many characteristics of the obtained barium titanate fine particle powder.

Example 4:

Except that the heat treatment temperature was changed to 300°C, the same procedure as in Example 1 was performed to obtain barium titanate fine particles. Table 1 shows many characteristics of the obtained barium titanate fine particle powder.

Example 5:

Except that the heat treatment temperature was changed to 300°C, the same procedure as in Example 2 was carried out to obtain barium titanate fine particles. Table 1 shows many characteristics of the obtained barium titanate fine particle powder.

Example 6:

The conditions of the hydrothermal reaction were changed to obtain barium titanate particle powder with an average particle diameter of 20 nm, and then the barium titanate fine particle powder was obtained by heat treatment at a temperature of 300 ℃ by the same method as described in Example 1. end. Table 1 shows many characteristics of the obtained barium titanate fine particle powder.

Example 7:

The barium titanate particle powder with an average particle diameter of 32nm was heat-treated at a temperature of 100°C in the same manner as described in Example 1, and the relative dielectric constant, c/a ratio, half-value width and The specific surface area was evaluated by the same method as described in Example 1. Table 1 shows many characteristics of the obtained barium titanate fine particle powder.

Comparative example 1:

The relative permittivity, c/a ratio, half-value width, and specific surface area of the barium titanate particle powder with an average particle size of 32 nm before heat treatment obtained in Example 1 were performed in the same manner as described in Example 1. Evaluation. Table 1 shows many characteristics of the obtained barium titanate fine particle powder.

Comparative example 2:

The relative permittivity, c/a ratio, half-value width, and specific surface area of the barium titanate particles with an average particle size of 46 nm before heat treatment obtained in Example 2 were performed in the same manner as described in Example 1. Evaluation. Table 1 shows many characteristics of the obtained barium titanate fine particle powder.

Comparative example 3:

The relative dielectric constant, c/a ratio, half-value width and ratio of the barium titanate particle powder with an average particle size of 51nm before the heat treatment obtained in Example 3 The surface area was evaluated by the same method as described in Example 1. Table 1 shows many characteristics of the obtained barium titanate fine particle powder.

Comparative example 4:

The barium titanate particle powder with an average particle diameter of 32nm was heat-treated at a temperature of 700°C in the same manner as described in Example 1, and the relative dielectric constant, c/a ratio, half-value width and The specific surface area was evaluated by the same method as described in Example 1. Due to the high temperature heat treatment, although the relative dielectric constant is greatly increased, the average particle size is also greatly increased. Table 1 shows many characteristics of the obtained barium titanate fine particle powder.

Comparative example 5:

The relative permittivity, c/a ratio, half-value width, and specific surface area of the barium titanate particle powder that was not heat-treated with an average particle diameter of 62 nm were evaluated in the same manner as described in Example 1. Table 1 shows many characteristics of the obtained barium titanate fine particle powder.

Comparative example 6:

The relative permittivity, c/a ratio, half-value width, and specific surface area of the barium titanate particle powder that was not heat-treated with an average particle diameter of 64 nm were evaluated in the same manner as described in Example 1. Table 1 shows many characteristics of the obtained barium titanate fine particle powder.

Comparative example 7:

With respect to the barium titanate particle powder produced by the solid phase method, the relative dielectric constant was measured by the same method as described in Example 1. As a result, the relative dielectric constant at 10 MHz is approximately 170.

Example 8:

In the barium titanate particle powder obtained in Example 1, zirconia beads (50μm in diameter) were placed in a vertical bead mill (Ultra apex mill manufactured by Shou Giken Co., Ltd.) so as to become 70 vol% of the stirring vessel. UAM-05") in a 0.5 liter stirring vessel made of zirconium oxide, as a dispersant, add a solution of ED153 (manufactured by Kusumoto Chemical) and a solvent PGMEA, circulate and disperse for 1 hour to obtain barium titanate particles Powder dispersion.

Example 9:

The obtained dispersion was mixed with acrylic resin (SB-193 manufactured by Gifu Shellac), and barium titanate/binder (including dispersant) = 6/4 ratio, and coated on Lumirror U-46 (Toray (System), a coating film with a thickness of about 3 μm is produced. For the obtained coating film, the total light transmittance and haze were measured using "Haze Meter NDH 2000" manufactured by Nippon Denshoku Industries Co., Ltd.

Examples 10 and 11:

The barium titanate particle powders of Examples 3 and 6 were flaked according to the method of Example 8 and Example 9. The many characteristics of the obtained sheet are shown in the table 2.

Comparative examples 8, 9:

The barium titanate particle powders of Comparative Examples 1 and 2 were exfoliated according to the methods of Example 8 and Example 9. Table 2 shows many characteristics of the obtained sheet.

It can be clearly understood from Table 2 that the coating film (Examples 9 to 11) using the barium titanate particle powder (Examples) of the present invention has a total light transmittance of 85% or more, and the haze is only lower than that of the substrate. 1.05 or less, excellent transparency.

[Industrial availability]

Since the barium titanate particle powder of the present invention has excellent dispersibility for inhibiting aggregation, it can be suitably used in various dielectric materials.

It is considered that the barium titanate particle powder of the present invention has high dielectric constant In addition, when the barium titanate particle powder and transparent resin are mixed, the amount of barium titanate particle powder used can be suppressed more than before. Moreover, because barium titanate is a fine particle, the transparency necessary for optical film applications is changed. easy.

Claims (4)

A barium titanate fine particle powder, characterized in that the average particle size of the primary particles is 20-60nm, the relative dielectric constant is 300-800, and the particle size distribution of the primary particles divided by the average particle size of the primary particles is 0.20~ 0.25. Such as the barium titanate fine particle powder of claim 1, wherein the lattice constant ratio c/a does not reach 1.003. A dispersion containing the barium titanate fine particle powder of claim 1 or 2. A coating film containing the barium titanate fine particle powder of claim 1 or 2.

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