LIQUID DISPERSION OF FLUORIDE PARTICLES AND METHOD FOR PRODUCING SAME, AND OPTICAL FILM

Abstract

Provided are a liquid dispersion of fluoride particles, which has low viscosity and excellent dispersibility, and is suitable for producing an optical film such as an antireflection film; a method for producing the same; and an optical film using the same. The liquid dispersion of fluoride particles according to the present invention is that in which particles of a fluoride represented by the chemical formula A.sub.xCF.sub.y (wherein A represents sodium or potassium, C represents silicon or boron, x is 1 or 2, and y is 4 or 6) are dispersed in an aprotic organic solvent having a relative permittivity of 5 to 40, and the optical film according to the present invention is produced by using the liquid dispersion of fluoride particles.

Claims

1. A liquid dispersion of fluoride particles wherein particles of a fluoride represented by the chemical formula AxCFy (wherein A represents sodium or potassium, C represents silicon or boron, x is 1 or 2, and y is 4 or 6) are dispersed in an aprotic organic solvent having a relative permittivity of 5 to 40.

2. The liquid dispersion of fluoride particles according to claim 1, wherein the moisture concentration [a] (% by mass) in the liquid dispersion of fluoride particles relative to 100% by mass of the liquid dispersion of fluoride particles and the relative permittivity [b] of the aprotic organic solvent satisfy the relationship represented by the following inequality (1).
[a]≤0.06e0.15[b]  (1)

3. The liquid dispersion of fluoride particles according to claim 1, wherein the aprotic organic solvent is at least one selected from the group consisting of a ketone solvent, an amine solvent, an ether solvent and an ester solvent.

4. The liquid dispersion of fluoride particles according to claim 3, wherein the ketone solvent is at least one selected from the group consisting of methyl isobutyl ketone, methyl ethyl ketone, methyl butyl ketone, cyclohexanone, methylcyclohexanone and acetylacetone.

5. The liquid dispersion of fluoride particles according to claim 3, wherein the amine solvent is at least one selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide and tetramethyl urea.

6. The liquid dispersion of fluoride particles according to claim 3, wherein the ether solvent is at least one selected from the group consisting of ethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate and tetrahydrofuran.

7. The liquid dispersion of fluoride particles according to claim 3, wherein the ester solvent is at least one selected from the group consisting of methyl acetate, ethyl acetate, butyl acetate and isobutyl acetate.

8. The liquid dispersion of fluoride particles according to claim 1, which contains a dispersant for dispersing the particles of the fluoride in the aprotic organic solvent.

9. The liquid dispersion of fluoride particles according to claim 1, wherein the average dispersion particle size of the particles of the fluoride is in the range of 1 nm to 100 nm.

10. The liquid dispersion of fluoride particles according to claim 1, wherein the content of the particles of the fluoride is in the range of 1% by mass to 30% by mass relative to 100% by mass of the liquid dispersion of fluoride particles.

11. A method for producing a liquid dispersion of fluoride particles, which comprises the steps of: reacting an aqueous sodium salt solution or an aqueous potassium salt solution with a silicofluoride or a borofluoride, thereby obtaining a slurry of fluoride particles represented by AxCFy (wherein A represents sodium or potassium, C represents silicon or boron, x is 1 or 2, and y is 4 or 6); subjecting the slurry of fluoride particles to solid-liquid separation, and washing the resulting solid component of fluoride particles; drying the washed solid component of fluoride particles; and dispersing the dried fluoride particles in an aprotic organic solvent having a relative permittivity of 5 to 40, thereby generating a liquid dispersion of fluoride particles.

12. The method for producing a dispersion of fluoride particles according to claim 11, wherein the step of generating the liquid dispersion of fluoride particles is performed by adjusting the moisture concentration [a] in the liquid dispersion relative to 100% by mass of the liquid dispersion of fluoride particles so that the moisture concentration [a] (% by mass) in the liquid dispersion of fluoride particles and the relative permittivity [b] of the aprotic organic solvent satisfy the relationship represented by the following inequality (1).
[a]≤0.06e0.15[b]  (1)

13. The method for producing a dispersion of fluoride particles according to claim 12, wherein the moisture concentration [a] in the liquid dispersion is adjusted by generating the liquid dispersion of fluoride particles in an atmosphere of inert gas.

14. An optical film comprising a dry cured film of a composition for forming an optical film containing the liquid dispersion of fluoride particles according to claim 1.

15. The liquid dispersion of fluoride particles according to claim 2, wherein the aprotic organic solvent is at least one selected from the group consisting of a ketone solvent, an amine solvent, an ether solvent and an ester solvent.

Description

EXAMPLES

[0098] Suitable Examples of the present invention will be described in detail below. However, materials or mixing amounts mentioned in these Examples do not purport to limit the scope of the present invention only to these unless there is a definitive description.

[Measurement Method of Average Particle Size]

[0099] Using a particle size distribution measuring instrument (Microtrac, Nanotrac UPA, UPA-UZ152, manufactured by MicrotracBEL Corp.), the average particle size of fluoride particles in the liquid dispersion was measured. It is noted that the average particle size (d50) is a particle size defined by the fact that particles having an average dispersion particle size or less accounts for 50% by volume of the entire sample particles.

Measurement principle: dynamic light scattering frequency analysis (FFT-heterodyne method).
Light source: 3 mW, two semiconductor lasers of 780 nm
Set temperature range: 10° C. to 80° C.
Particle size distribution measuring range: 0.8 nm to 6.5406
Measurement target: colloidal particles

[0100] Unless otherwise specified, each average particle size in Examples and Comparative Examples means a volume-equivalent average particle size measured by the above dynamic light scattering method.

(Moisture Measurement Method)

[0101] The moisture concentration in the liquid dispersion of fluoride particles was measured by the Karl Fischer method. A TQV-2200S (trade name) manufactured by Hiranuma Sangyo Co., Ltd. was used as the moisture measuring device. The measurement method was the volumetric titration method based on JIS K 0068 (2001).

(Viscosity Measuring Method)

[0102] The viscosity of the liquid dispersion of fluoride particles was measured using a B-type viscometer. As the B-type viscometer, a DV-I PRIME (trade name) manufactured by Brookfield, USA was used. The measurement was performed based on JIS K 5600-2-2 (2004).

Example 1

[0103] In a 500 cc container made of fluororesin, 190 g of methyl ethyl ketone (reagent), 10 g of sodium hexafluorosilicate (manufactured by Stella Chemifa Corporation) and 2 g of PLYSURF A212C (trade name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a dispersant were mixed to generate a slurry in which sodium hexafluorosilicate was aggregated. Next, the slurry was charged in a bead mill (manufactured by SHINMARU ENTERPRISES CORPORATION) in a nitrogen environment at a dew point of −40° C. or lower, and then a dispersion treatment was performed. Zirconia beads (manufactured by NIKKATO CORPORATION) were used. During the dispersion treatment, the liquid dispersion was sampled at regular intervals to measure the particle size distribution. The dispersion treatment was performed until the average dispersion particle size (volume-equivalent, d50) of the sodium hexafluorosilicate particles stopped decreasing, thus obtaining 180 g of a liquid dispersion of sodium hexafluorosilicate particles (particle concentration: 5% by mass relative to the total mass of the liquid dispersion). The physical properties of the liquid dispersion according to Example 1 are shown in Table 1.

Example 2

[0104] A liquid dispersion according to the present Example was obtained in the same manner as in Example 1, except that N-methyl-2-pyrrolidone (NMP) was used in place of methyl ethyl ketone. The physical properties of the liquid dispersion thus obtained are shown in Table 1.

Comparative Example 1

[0105] In the present Comparative Example, the dispersion treatment in a nitrogen environment was replaced by a dispersion treatment in an atmospheric environment (room temperature of 25° C., relative humidity of 60%). A gel-like dispersion according to the present Comparative Example was obtained in the same manner as in Example 1, except for the above. The physical characteristics of the dispersion thus obtained are shown in Table 1.

Comparative Example 2

[0106] In this Comparative Example, isopropanol (IPA, protic organic solvent) was used in place of methyl ethyl ketone, and no dispersant was used. A liquid dispersion according to the present Comparative Example was obtained in the same manner as in Example 1, except for the above. The physical characteristics of the liquid dispersion thus obtained are shown in Table 1.

Comparative Example 3

[0107] In this Comparative Example, 1-Methoxy-2-propanol (PGME, protic organic solvent) was used in place of methyl ethyl ketone, and no dispersant was used. A liquid dispersion according to the present Comparative Example was obtained in the same manner as in Example 1, except for the above. The physical characteristics of the liquid dispersion thus obtained are shown in Table 1.

TABLE-US-00001 TABLE 1 Average Moisture dispersion Fluoride Organic concentration Viscosity particle size particles solvent Dispersant (% by mass) (mPa .Math. s) (nm) Example 1 Na.sub.2SiF.sub.6 MEK PLYSURFA212C 0.08 0.77 34 Example 2 Na.sub.2SiF.sub.6 NMP None 0.08 34 53 Comparative Na.sub.2SiF.sub.6 MEK PLYSURFA212C 1.40 Unmeasurable 212 Example 1 Comparative Na.sub.2SiF.sub.6 IPA PLYSURFA212C 0.05 140 3,420 Example 2 Comparative Na.sub.2SiF.sub.6 PGME None 0.06 81 1,070 Example 3

Example 3

[0108] 7.3 g of the liquid dispersion produced in Example 1 and 2.9 g of a commercially available acrylate paint were mixed. Further, 0.37 g of 1-hydroxycyclohexyl phenyl ketone was dissolved in the mixed solution to obtain a composition for forming an optical film. Next, 0.1 g of this composition for forming an optical film was diluted with 99.9 g of propylene glycol monomethyl ether to produce a low refractive index paint.

[0109] 500 μl of the diluted low refractive index paint was coated on one surface of a PET film (Lumilar (registered trademark) U34: thickness of 100 μm, manufactured by Toray Industries, Inc.) by spin coating. The coating film was dried at 130° C. and photocured by irradiation with ultraviolet rays at 400 mJ/cm.sup.2, and then an antireflection film (low refractive index layer, optical film) was laminated.

Example 4

[0110] 0.01 g of 1-hydroxycyclohexyl phenyl ketone was dissolved in 0.18 g of a commercially available acrylate paint. Further, 3.10 g of the liquid dispersion produced in Example 1 was mixed with the mixed solution to obtain a composition for forming an optical film. Next, 3.3 g of this composition for forming an optical film was diluted with 6.72 g of propylene glycol monomethyl ether to produce a low refractive index paint.

[0111] 300 μl of the diluted low refractive index paint was coated on one surface of a PET film (Lumilar (registered trademark) T60: thickness of 100 μm, manufactured by Toray Industries, Inc.) by spin coating. The coating film was dried at 130° C. and photocured by irradiation with ultraviolet rays at 400 mJ/cm.sup.2, and then an antireflection film (low refractive index layer, optical film) was laminated.

Example 5

[0112] In this Example, the liquid dispersion produced in Example 2 was used in place of the liquid dispersion produced in Example 1. An antireflection film according to the present Example was laminated in the same manner as in Example 4, except for the above.

Comparative Example 4

[0113] In this Comparative Example, the dispersion produced in Comparative Example was used in place of the liquid dispersion produced in Example 1. An antireflection film according to the present Example was laminated in the same manner as in Example 3, except for the above.

Comparative Example 5

[0114] In this Comparative Example, the dispersion produced in Comparative Example was used in place of the liquid dispersion produced in Example 1. An antireflection film according to the present Example was laminated in the same manner as in Example 4, except for the above.

(Haze Measurement, Total Light Transmittance Measurement and Minimum Light Reflectance Measurement)

[0115] Using an ultraviolet-visible near-infrared spectrophotometer (trade name: V670, manufactured by JASCO Corporation), the haze value of the antireflection film (low reflectance layer), the total light transmittance of the low refractive index layer, and the minimum light reflectance of the antireflection film (low refractive index layer) were measured in accordance with JIS K 7136.

[0116] The physical properties of the antireflection films according to Examples 3 to 5 and Comparative Examples 4 and 5 are shown in Table 2. Each of the numerical values of Examples 3 to 5 and Comparative Example 5 in Table 2 indicates the relative value to the reference value, with optical properties (reference value) of the antireflection film of Comparative Example 4 being 100. Regarding the total light transmittance in Table 2, the higher the numerical value, the better the optical properties of the antireflection film. Regarding the haze and the minimum light reflectance, the smaller the numerical value, the better the optical properties of the antireflection film.

TABLE-US-00002 TABLE 2 Concentration (% by mass) of fluoride Minimum particles contained in Total light light Liquid dispersion antireflection film transmittance Haze reflectance Example 3 Liquid dispersion 20 110 13 47 of Example 1 Example 4 Liquid dispersion 50 116 3 20 of Example 1 Example 5 Liquid dispersion 50 97 16 68 of Example 2 Comparative Liquid dispersion 20 100 100 100 Example 4 of Comparative Example 1 Comparative Liquid dispersion 50 98 25 42 Example 5 of Comparative Example 1