SILICA-TITANIA COMPOSITE OXIDE POWDER

Abstract

A silica-titania composite oxide powder of the present invention has an average particle diameter D (μm) of 0.1 μm or more to 3.0 μm or less, an average refractive index of 1.47 or more at a measurement wavelength of 589 nm, and a minimum absorbance S measured from a dispersion of 30 mass % of silica-titania composite oxide particles in a liquid having the same refractive index as the average refractive index, the minimum absorbance S satisfying the relationship “S<0.026−0.008×D.”

Claims

1. A silica-titania composite oxide powder having an average particle diameter D (μm) in a range of 0.1 μm or more to 3.0 μm or less measured by a laser light scattering method, an average refractive index of 1.47 or more at a measurement wavelength of 589 nm, and a minimum absorbance S measured from a dispersion of 30 mass % silica-titania composite oxide particles in a liquid having the same refractive index as the average refractive index, the minimum absorbance S satisfying the following relationship:
S<0.026−0.008×D.

2. The silica-titania composite oxide powder of claim 1, wherein a ratio of particles having a particle diameter of 5 μm or more measured by a Coulter counter method is 200 ppm or less on a number basis.

3. A method of producing silica-titania composite oxide particles using an alkoxide of silicon and an alkoxide of titanium as materials, the method comprising: mixing the alkoxide of silicon and the alkoxide of titanium to prepare a composite alkoxide material; reacting the composite alkoxide material in the presence of water and a nitrogen-containing basic catalyst to produce particles; separating the produced particles from a liquid component; drying the particles; and firing the dried particles, wherein the particles after the drying and before the firing has a nitrogen content satisfying the following:
Nitrogen content (mass %)<0.19×Ti content+0.35 where the Ti content is the content of Ti expressed in % when the total amount of Ti and Si on a mol basis is 100%.

4. A resin composition comprising the silica-titania composite oxide powder of claim 1 or 2.

5. A dispersion comprising: the silica-titania composite oxide powder of claim 1 or 2; and a solvent dispersing the silica-titania composite oxide powder therein.

Description

EXAMPLES

[0146] The present embodiment will be specifically described by way of examples, but the present invention is not limited to these examples.

[0147] (Measurement of Average Refractive Index and Minimum Absorbance)

[0148] Toluene, 1-bromonaphthalene, 1-chloronaphthalene, diiodomethane, sulfur-containing diiodomethane, 2-methoxyethanol, and benzyl alcohol were blended in various ratios to prepare a plurality of mixed solvents having different refractive indices.

[0149] In a clean 30 ml glass vessel, 14.0 g of each of the mixed solvents was placed, to which the silica-titania composite oxide powder previously dried at 100° C. for 24 hours and weighed 6.0 g was added. Then, the mixture was dispersed using an ultrasonic homogenizer (Sonifier 250 manufactured by BRANSON) at 20 W for one minute, and the resulting dispersion was introduced into a quartz cell (optical path length: 10 mm) for absorbance measurement.

[0150] As a blank sample, a mixed solvent containing no silica-titania composite oxide powder was introduced into a quartz cell.

[0151] Each of the quartz cells was attached to a spectrophotometer (UV-visible spectrophotometer V-650 manufactured by JASCO) equipped with a temperature control folder, and the absorbance was measured to four decimal places under the following conditions.

[0152] Measurement wavelength: 589 nm

[0153] Temperature range: 5° C. to 40° C.

[0154] Measurement temperature increment: 1° C.

[0155] The lowest absorbance measured under the above conditions was determined to be the minimum value, and the value of the absorbance at that time was defined as the minimum absorbance S.

[0156] The refractive index of the mixed solvent having the minimum absorbance at a wavelength of 589 nm at the temperature at which the minimum absorbance was measured was defined as the average refractive index of the silica-titania composite oxide powder.

[0157] For the average refractive index, the refractive index of each of the mixed solvents at a wavelength of 589 nm was previously measured to four decimal places using an Abbe refractometer while changing the measurement temperature in a range of 5° C. to 40° C. was applied as it was.

[0158] (Volume-Based Cumulative 50% Diameter (Average Particle Diameter))

[0159] About 0.1 g of the silica-titania composite oxide powder was weighed with an electronic balance in a 50 mL glass bottle, about 40 ml of distilled water was added thereto, and the powder was dispersed at 40 W for 10 minutes using an ultrasonic homogenizer (Sonifier 250 manufactured by BRANSON). Then, the volume-based cumulative 50% diameter (μm) and coefficient of variation of the silica-titania composite oxide powder were measured with a laser diffraction scattering particle size analyzer (LS-230 manufactured by Beckman Coulter, Inc.).

[0160] (Amount of Coarse Particles of 5 μm or more Measured by Coulter Counter Method) Five 50 mL glass bottles were prepared. In each of the bottles, 1 g of the silica-titania composite oxide powder was weighed with an electronic balance, and 19 g of distilled water or ethanol was added. The powder was dispersed at 40 W for 10 minutes using an ultrasonic homogenizer (Sonifier 250 manufactured by BRANSON) to obtain a measurement sample. The particle diameter of each of the silica-titania composite oxide particles in the samples was measured with a Coulter counter (Multisizer III manufactured by Beckman Coulter, Inc.). At that time, approximately 50,000 particles were measured in each sample, i.e., approximately 250,000 particles in total were measured from the five samples. Among the measured particles, those having particle diameters of 5 μm or more were counted as the count of coarse particles (ppm) relative to the total count of the particles measured.

[0161] (Nitrogen Content)

[0162] The nitrogen content of the dried powder was measured as follows. The dried powder was heated to 950° C. in an oxygen atmosphere, and the nitrogen content was determined using a CHN analyzer (CHN Coder MT-5 manufactured by Anatec Yanaco Cooperation).

Example 1

[0163] In a 200 ml three-neck glass flask, 54.6 g of tetramethoxysilane (methyl orthosilicate manufactured by Tama Chemicals Co., Ltd., hereinafter referred to as “TMOS”) was charged as metal alkoxide, to which 5.5 g of methanol as an organic solvent and 2.2 g of 0.035 mass % hydrogen chloride as an acid catalyst were added. The resulting mixture was stirred at room temperature for 10 minutes with a stirrer to hydrolyze TMOS.

[0164] Subsequently, 8.9 g of titanium tetraisopropoxide (A-1 manufactured by Nippon Soda Co., Ltd., hereinafter referred to as “TPT”)) was charged as metal alkoxide in a 30 ml glass vessel, and 8.9 g of isopropyl alcohol (hereinafter referred to as “IPA”) was added thereto while stirring with a stirrer.

[0165] A diluent of TPT was added to the TMOS hydrolysate being stirred with the stirrer to obtain 80.1 g of a clear composite alkoxide solution.

[0166] The titania content, calculated from the amount of alkoxide used, was 8.0 mol %.

[0167] A stirrer having a propeller blade was installed in a 300 ml four-neck flask, in which 6.1 g of IPA, 43.0 g of methanol, and 9.4 g of 25 mass % aqueous ammonia were charged and stirred while keeping the temperature at 40° C. To the resulting mixture, the composite alkoxide solution and 28.1 g of 25 mass % aqueous ammonia were separately added dropwise. The solution was turned white after 30 minutes from the start of the addition. The supply of the materials was completed in 4.3 hours while controlling the addition rate, and the silica-titania composite oxide particles were grown.

[0168] After the dropwise addition ended, the dispersion was collected in a centrifugal tube and centrifuged at 6000 rpm to obtain a concentrate containing the particles.

[0169] The concentrate, to which pure water was added, was dispersed with a stirrer and heated to 40° C. To this dispersion, 1.0 N hydrogen chloride was added to adjust the pH of the dispersion to 4.

[0170] The dispersion was centrifuged to obtain a concentrate containing particles.

[0171] The obtained concentrate was introduced into a vacuum dryer and kept at 100° C. The weight was stabilized 16 hours after the start of drying. Part of the dried powder was taken out, and the nitrogen content was measured 1.71%. This value was smaller than the value 1.87, calculated from the formula: 0.19×Ti content+0.35, where the charged amount of Ti was 8.0%.

[0172] The dried powder was fired at a heating rate of 5° C./min and a firing temperature of 900° C. for a firing retention time of 12 hours.

[0173] The silica-titania composite oxide powder obtained after the firing was measured with a laser diffraction particle size analyzer, and the average particle diameter was 0.64 μm. The amount of coarse particles of 5 μm or more were measured 46 ppm. The average refractive index of the particles was 1.504. The minimum absorbance S was 0.0135, which was significantly smaller than the value calculated from the formula, 0.026−0.008×D=0.0209, where the average particle diameter was 0.64 μm.

Comparative Example 1

[0174] Silica-titania composite oxide particles were obtained in the same manner as in Example 1 except that the reaction liquid was centrifuged and dried as it was.

[0175] The nitrogen content of the dried powder was 2.11%. This value was larger than the value 1.87, calculated from the formula: 0.19×Ti content+0.35, where the charged amount of Ti was 8.0%.

[0176] The silica-titania composite oxide powder obtained after the firing was measured with a laser diffraction particle size analyzer, and the average particle diameter was 0.64 μm. The amount of coarse particles of 5 μm or more were measured 42 ppm. The average refractive index of the particles was 1.504. The minimum absorbance S was 0.0310, which was larger than 0.0209.

Example 2

[0177] Silica-titania composite oxide particles were obtained in the same manner as in Example 1 except that the supply of the materials was completed in 2.4 hours. The nitrogen content of the dried powder was 1.73%.

[0178] The silica-titania composite oxide powder obtained after the firing was measured with a laser diffraction particle size analyzer, and the average particle diameter was 0.35 μm. The amount of coarse particles of 5 μm or more were measured 84 ppm. The average refractive index of the particles was 1.504. The minimum absorbance S was 0.0148, which was significantly smaller than the value calculated from the formula, 0.026−0.008×D=0.0232, where the average particle diameter was 0.35 μm.

Comparative Example 2

[0179] Silica-titania composite oxide particles were obtained in the same manner as in Example 2 except that the reaction liquid was centrifuged and dried as it was. The nitrogen content of the dried powder was 2.35%.

[0180] The silica-titania composite oxide powder obtained after the firing was measured with a laser diffraction particle size analyzer, and the average particle diameter was 0.35 μm. The amount of coarse particles of 5 μm or more were measured 88 ppm. The average refractive index of the particles was 1.504. The minimum absorbance S was 0.0271, which was larger than 0.0232.

Example 3

[0181] Silica-titania composite oxide particles were obtained in the same manner as in Example 1 except that the dried powder obtained in Example 2 was fired at a firing temperature of 1000° C.

[0182] The silica-titania composite oxide powder obtained after the firing was measured with a laser diffraction particle size analyzer, and the average particle diameter was 0.34 μm. The amount of coarse particles of 5 μm or more were measured 284 ppm. The average refractive index of the particles was 1.504. The minimum absorbance was 0.0139, which was significantly smaller than the value calculated from the formula, 0.026−0.008×D=0.0233, where the average particle diameter was 0.34 μm.

Example 4

[0183] In a 200 ml three-neck glass flask, 51.6 g of TMOS was charged as metal alkoxide, to which 5.5 g of methanol as an organic solvent and 3.7 g of 0.035 mass % hydrogen chloride as an acid catalyst were added. The resulting mixture was stirred at room temperature for 10 minutes with a stirrer to hydrolyze TMOS.

[0184] Subsequently, 14.4 g of TPT was charged as metal alkoxide in a 50 ml glass vessel, and 8.9 g of IPA was added thereto while stirring with a stirrer.

[0185] A diluent of TPT was added to the TMOS hydrolysate stirred with the stirrer to obtain 84.1 g of a clear composite alkoxide solution.

[0186] The titania content calculated from the amount of alkoxide used was 13.0 mol %.

[0187] A stirrer having a propeller blade was installed in a 300 ml four-neck flask, in which 6.1 g of IPA, 43.0 g of methanol, and 9.4 g of 25 mass % aqueous ammonia were charged and stirred while keeping the temperature at 40° C. To the resulting mixture, the composite alkoxide solution and 28.1 g of 25 mass % aqueous ammonia were separately added dropwise. The solution was turned white after 30 minutes from the start of the addition. The supply of the materials was completed in 11.4 hours while controlling the addition rate, and the silica-titania composite oxide particles were grown.

[0188] After the dropwise addition ended, the dispersion was collected in a centrifugal tube and centrifuged at 6000 rpm to obtain a concentrate containing the particles.

[0189] The dispersion was centrifuged to obtain a concentrate containing particles.

[0190] The obtained concentrate was introduced into a vacuum dryer and kept at 100° C. The pressure was reset to the atmospheric pressure after 8 hours from the start of the drying, and the mixture was introduced into a tubular drier (internal volume: 0 4 L) previously heated at 100° C. Then, air having a partial water vapor pressure of 0.3 was allowed to flow at 20 ml/min for four hours. After the introduction of water vapor ended, the mixture was vacuum dried again. The weight was stabilized 16 hours after the start of re-drying. Part of the dried powder was taken out, and the nitrogen content was measured 2.68%. This value was smaller than the value 2.82, calculated from the formula: 0.19×Ti content+0.35, where the charged amount of Ti was 13.0%.

[0191] The dried powder was fired at a heating rate of 5° C./min and a firing temperature of 900° C. for a firing retention time of 12 hours.

[0192] The silica-titania composite oxide powder obtained after the firing was measured with a laser diffraction particle size analyzer, and the average particle diameter was 1.35 μm. The amount of coarse particles of 5 μm or more were measured 28 ppm. The average refractive index of the particles was 1.543. The minimum absorbance S was 0.0123, which was significantly smaller than the value calculated from the formula, 0.026−0.008×D=0.0152, where the average particle diameter was 1.35 μm.

Comparative Example 3

[0193] Silica-titania composite oxide particles were obtained in the same manner as in Example 4 except that the vacuum drying was continued for 16 hours and the mixture was not brought into contact with a gas containing water vapor in the course of the vacuum drying.

[0194] The nitrogen content of the dried powder was 3.04%. This value was smaller than the value 2.82, calculated from the formula: 0.19×Ti content+0.35, where the charged amount of Ti was 13.0%.

[0195] The silica-titania composite oxide powder obtained after the firing was measured with a laser diffraction particle size analyzer, and the average particle diameter was 1.35 μm. The amount of coarse particles of 5 μm or more were measured 24 ppm. The average refractive index of the particles was 1.543. The minimum absorbance S was 0.0168, which was larger than 0.0152.