TWI785229B - Zirconia based nanoparticles and dispersion solution - Google Patents

Abstract

Zirconia based nanoparticles having D50 of the particle size distribution of 20 nm or less, wherein (1) the particles have a zirconia monoclinic phase, (2) a diffraction peak is substantially absent in the range from 2θ=29.74 degree to 2θ=30.74 degree in the diffraction pattern of X-ray diffraction.

Description

Monoclinic zirconia nanoparticles and dispersion

The present invention relates to a novel monoclinic zirconia-based nanometer particle and a manufacturing method thereof.

Background technique

High refractive index materials are used in various optical components such as lenses, optical filters, and anti-reflection materials. Taking the lens as an example, if the lens has a high refractive index, the corresponding lens thickness reduction, weight reduction, high resolution, etc. can be achieved, and the product will become advantageous.

As for high refractive index materials, in addition to transparent inorganic materials such as glass and ceramics, there are known composite materials obtained by dispersing high refractive index particles using transparent resin as a matrix, especially in the field of low cost and light weight. From the point of view of etc., the composite material as mentioned above is very advantageous.

As the high-refractive-index particles dispersed in the composite material, for example, inorganic oxide particles such as titanium oxide, zirconium oxide, and aluminum oxide are currently used. In particular, titanium oxide, zirconium oxide, etc. have a high refractive index (2.00 or more), but they must also have high transparency when used as an optical material. That is, finer and more stable inorganic oxide particles are required.

Here, in terms of the form of raw materials when manufacturing composite materials In other words, the inorganic oxide particles are usually provided in the form of a dispersion already dispersed in a solvent. Therefore, it is required that individual particles in the dispersion can exhibit a highly dispersed state without aggregating. From such a standpoint, recently, various studies and proposals are being made in order to develop inorganic oxide particles or their dispersion liquids that are more excellent in dispersibility and the like.

For example, known zirconia-based nanoparticles are zirconia nanoparticles coated with two or more coating agents, and are zirconia nanoparticles containing tetragonal zirconia, characterized in that at least one of the coating agents is It is represented by the following formula (I): R ¹ -COOH‧‧‧(I)

[wherein, R ¹ represents a branched chain hydrocarbon group with more than 6 carbon atoms]; and at least one coating agent other than the coating agent shown in formula (I) is the following: having a plurality of selected from the group consisting of hydroxyl, At least one functional group in the group consisting of amine group, mercapto group, carboxyl group, epoxy group and alkoxy group; product with vinyl or phenyl group; silane coupling agent; or the product represented by the following formula (II) Compound: R ² -COOH‧‧‧(II)

[wherein, R ² represents a linear hydrocarbon group having 6 or more carbon atoms] (Patent Document 1).

In addition, for example, there is known a transparent zirconia dispersion liquid characterized by containing tetragonal zirconia particles having a dispersed particle diameter of not less than 1 nm and not more than 20 nm (Patent Document 2).

Furthermore, a method for producing a dispersion solution of inorganic microparticles has been proposed at present. The dispersion solution of inorganic microparticles is dispersed in a solvent with inorganic microparticles having an average particle diameter of primary particles of more than 1 nm and less than 30 nm. It is characterized in that: Use an average particle size of 15 μm or less Above and below 30 μm beads to stir the inorganic microparticles (average particle size of the primary particles is 1nm to 30nm) in the mixed solvent in the solvent in an aggregated state while applying ultrasonic waves, thereby dispersing the aforementioned inorganic microparticles (Patent Document 3 ).

Prior art literature patent documents

[Patent Document 1] Japanese Patent No. 5030694

[Patent Document 2] Japanese Patent Laid-Open No. 2007-99931

[Patent Document 3] Japanese Unexamined Patent Publication No. 2010-23031

Summary of the invention

However, in the dispersions of the prior art, the zirconia nanoparticles are not only monoclinic zirconia, but also tetragonal zirconia. Since the tetragonal phase of zirconia is a quasi-stable phase, it may change to a monoclinic phase over time under certain factors. Once the phase changes to the monoclinic phase and causes volume change (especially volume shrinkage), the physical properties of the coating film formed by the dispersion will be adversely affected. More specifically, after forming a coating film with zirconia nanoparticles containing a tetragonal phase, once the tetragonal phase in the film changes to a monoclinic phase over time, strain occurs in the coating film due to volume change etc. As a result, there is a possibility that the physical properties may be lowered.

From this point of view, zirconia nanoparticles containing less or substantially no tetragonal zirconia are ideal, but such zirconia nanoparticles have not yet been developed, which is the status quo.

Therefore, the main object of the present invention is to provide a zirconia nanoparticle containing less or substantially no tetragonal zirconia.

The inventors of the present case have repeatedly studied carefully in view of the problems of the conventional technology, and found that the nano-particles produced by using a specific zirconia powder as a starting material and a specific method can achieve the above-mentioned purpose, and finally completed the present invention.

That is, the present invention relates to the following zirconia-based nanoparticles and a method for producing the same.

1. A monoclinic zirconia-based nanoparticle, which is a zirconia microparticle with a particle size distribution D50 of 20 nm or less, characterized in that: (1) the zirconia microparticle contains a zirconia monoclinic phase; and (2) the zirconia In the diffraction pattern obtained by powder X-ray diffraction analysis of zirconium particles, there is virtually no diffraction peak in the range of 2θ=29.74~30.74 degrees.

2. The monoclinic zirconia-based nanoparticles according to item 1 above, wherein the content of the zirconia monoclinic crystal phase is 90% by volume or more.

3. The monoclinic zirconia-based nanoparticles according to item 1 or 2 above, wherein the particle size distribution of the powder composed of zirconia fine particles is unimodal, and the particle size distribution D90 is 30 nm or less.

4. A dispersion liquid in which the monoclinic zirconia-based nanoparticles according to any one of the aforementioned items 1 to 3 are dispersed in a solvent.

5. The dispersion as in item 4 above, which further contains a silane coupling agent and a phosphoric acid ester-based dispersant.

6. A method for producing monoclinic zirconia-based nanoparticles, which is a method for producing monoclinic zirconia-based nanoparticles from zirconia powder as described in item 1 above, characterized in that: (1) the aforementioned The a) particle size distribution D50 of zirconia powder is below 900nm, b) the content of zirconia monoclinic phase is 90~95% by volume, and the content of zirconia tetragonal phase is 5~10% by volume; (2) includes the following The above step: in the presence of beads with a particle size distribution D50 of 40 μm or less, the aforementioned zirconia powder is subjected to bead milling treatment.

7. As in the manufacturing method of item 6 above, the bead milling treatment is a wet bead milling treatment carried out in the presence of a solvent.

8. The production method according to item 7 above, wherein the solvent contains a silane coupling agent and a phosphoric acid ester-based dispersant.

9. The production method according to item 6 above, wherein the beads are at least one of metal beads and ceramic beads.

10. The production method according to the aforementioned item 6, which uses particles having a substantially spherical shape as the aforementioned beads.

11. The production method according to item 6 above, wherein the BET specific surface area of the zirconia powder is 70 m ² /g or more.

According to the present invention, there can be provided zirconia nanoparticles containing less or substantially no tetragonal zirconia. More specifically, there can be provided a nanoparticle (monoclinic zirconia particle) that is less or substantially free of tetragonal zirconia (quasi-stable tetragonal) and contains monoclinic zirconia zirconium.

This kind of special nanoparticles can effectively suppress or even prevent the volume change that may be caused by tetragonal zirconia due to phase transition, so the coating film obtained by dispersing it in the liquid phase can also exhibit high reliability. sex.

In addition, since the production method of the present invention uses zirconia particles containing tetragonal zirconia as a starting material and performs bead milling in the presence of specific fine beads, it is possible to produce tetragonal zirconia reliably and efficiently. Nanoparticles that are less or substantially free of tetragonal zirconia and consist essentially of monoclinic zirconia.

Moreover, the nanoparticles obtained by the manufacturing method of the present invention can be in a finely dispersed state at the nanometer level. The reason for this has not been determined, but it is presumed to be realized by the following mechanism of action. That is, although the production method of the present invention uses zirconia containing both a tetragonal phase and a monoclinic phase as a starting material, even if aggregated particles are included, the tetragonal phase changes to a monoclinic phase during the production process. In this case, strain due to volume change occurs in the aggregated particles, and the aggregation is released due to the strain, resulting in finer particles and high dispersibility.

As mentioned above, since the zirconia nanoparticles of the present invention are stable and highly dispersible, for example, they can be suitably used as raw materials for various optical components such as lenses, optical filters, and anti-reflection materials.

10: Bead milling device

11: beads

12: Processed objects

13: Crushing room

14: Stirrer

15: Motor

16: axis

17: Cooling water jacket

18: cooling water

FIG. 1 is a graph showing the X-ray diffraction analysis results of the zirconia nanoparticles obtained in Example 1.

Figure 2 is a graph showing the Raman fraction of the zirconia nanoparticles obtained in Example 1 A graph of a Raman spectrum for optical analysis.

FIG. 3 shows the intensity curve of the zirconia nanoparticles obtained in Example 1 obtained by electron diffraction.

FIG. 4 is a graph showing the particle size distribution of zirconia nanoparticles obtained in Example 1. FIG.

Fig. 5 is a graph showing the relationship between the particle size distribution D90 and the peak ratio of [tetragonal phase (T phase)/monoclinic phase (M phase)] and processing time for the zirconia nanoparticles obtained in Example 1.

FIG. 6 is a diagram (enlarged diagram) showing the X-ray diffraction analysis results of various zirconia-based nanoparticles obtained by using zirconia beads with different particle sizes.

FIG. 7 shows a schematic diagram of the bead milling apparatus used in Example 1.

FIG. 8 shows a schematic diagram of an agitator used in the bead milling apparatus used in Example 1. FIG.

form for carrying out the invention

1. Zirconia-based nanoparticles

The monoclinic zirconia-based nanoparticles of the present invention (nanoparticles of the present invention) are zirconia microparticles with a particle size distribution D50 of 20 nm or less, and are characterized in that: (1) the zirconia microparticles contain a monoclinic crystal phase; and ( 2) In the diffraction pattern obtained by the powder X-ray diffraction analysis of the zirconia microparticles, there is substantially no diffraction peak at 2θ = 29.74~30.74 degrees.

The nanoparticles of the present invention are crystalline zirconia particles, and contain a monoclinic phase as a crystal phase. The content of zirconia monoclinic phase is usually More than 90% by volume is suitable, especially 95-100% by volume. That is, the nanoparticles of the present invention may contain components other than tetragonal zirconia (such as other crystalline phases, amorphous phases, etc.) within the range that does not hinder the effect of the present invention.

As for the crystal phase of the nanoparticles of the present invention, it is characterized in that in the diffraction pattern of the powder X-ray diffraction analysis of the zirconia particles, there is substantially no diffraction peak within 2θ=29.74~30.74 degrees. That is, the diffraction peak of tetragonal zirconia (101 planes) is 2θ=30.24 degrees, and the fact that no diffraction peak of tetragonal zirconia can be identified on the diffraction pattern is one of the characteristics of the nanoparticles of the present invention. As long as such a diffraction peak cannot be identified, the present invention accepts a very small amount of tetragonal zirconia. In addition, as far as the existence of diffraction peaks is concerned, in addition to the case of peaks only in the range of 2θ=29.74~30.74 degrees, there are also wide ranges in the range of 2θ=29.74~30.74 degrees and outside the range Spike situation.

In addition, in the analysis of the nanoparticles of the present invention by Raman spectroscopy, it is preferable not to confirm peaks at wavenumbers 202 cm ^-1 and 267 cm ^-1 . Furthermore, in the intensity graph of the nanoparticles of the present invention obtained by electron diffraction, it is preferable not to confirm the sharp peak originating from the 111t of the tetragonal crystal.

It is conceivable that even if the nanoparticles of the present invention are nano-scale particles, they still have the above-mentioned crystal structure, which not only has high stability but also contributes to high dispersion.

The particle size distribution D50 (average particle diameter) of the nanoparticles of the present invention is less than 20 nm, preferably less than 15 nm. Although the lower limit thereof is not restrictive, it can generally be set to about 1 nm. High transparency can be contributed by having such an average particle diameter.

In addition, although the particle size distribution of the nanoparticles of the present invention is not limited, it is particularly preferred to have a single peak and a particle size distribution D90 of 30 nm or less (especially 25 nm or less). Thereby, high stability and transparency can be exhibited further in the dispersion liquid and its coating film mentioned later.

The nanoparticles of the present invention preferably have a relatively high specific surface area (BET method). More specifically, the specific surface area is usually not less than 70 m ² /g, more preferably not less than 80 m ² /g. In addition, although the upper limit of the specific surface area is not limited, it can usually be set at about 200 m ² /g.

The nanoparticles of the present invention are basically composed of zirconia (ZrO ₂ ), but other components may be attached or composited with other components within the range that does not hinder the effect of the present invention. For example, when the nanoparticles of the present invention are produced by the production method described later, the additives (such as dispersant, coupling agent, etc.) added in the production process can be attached to or composited with the zirconia particles.

The nanoparticles of the present invention can be in any form such as dry powder, dispersion liquid, etc., but the monoclinic zirconia-based nanoparticles (powder) of the present invention are preferably provided in the form of a dispersion liquid dispersed in a solvent. At this time, the solvent is not particularly limited, and examples include: alcohol-based solvents such as methanol, ethanol, isopropanol, and butanol; ketone-based solvents such as ketone, acetone, methyl ethyl ketone, methyl acetone, and methyl isobutyl ketone; isopropyl ether , Methyl celluloid and other ether solvents; propylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate and other glycol ester solvents.

In addition, various additives may be added to the above-mentioned dispersion liquid as needed. For example, additives such as dispersants, coupling agents, and dispersion aids can be used.

The dispersion amount of nanoparticles of the present invention in the dispersion liquid (solid composition Quantity) is not particularly limited, and can be appropriately set in response to the type of solvent used, required viscosity, etc. In the present invention, it is especially preferable to set the dispersion amount within the range of 1 to 50% by weight in the dispersion liquid.

2. Manufacturing method of monoclinic zirconia-based nanoparticles

The manufacturing method of the nanoparticles of the present invention is not particularly limited, and can be suitably manufactured as in the following manufacturing method, for example. That is, the following production method can be suitably adopted: a method for producing nanoparticles of the present invention from zirconia powder, characterized in that: (1) a) the particle size distribution D50 of the above-mentioned zirconia powder is 900 nm or less; b) oxidation The content of the zirconium monoclinic phase is 90-95% by volume, and the content of the tetragonal zirconia phase is 5-10% by volume; (2) comprising the following steps: in the presence of beads with a particle size distribution D50 of 40 μm or less, The aforementioned zirconia powder was subjected to bead milling (bead milling step).

starting material

The production method of the present invention is based on the premise that zirconia powder is used as the starting material. The zirconia powder uses a) a particle size distribution D50 of 900nm or less, b) a content of zirconia monoclinic crystal phase of 90-95% by volume and oxidized A powder with a zirconium tetragonal phase content of 5-10% by volume.

As the zirconia powder, those whose D50 is 900 nm or less are used. The aforementioned D50 is particularly preferably 800 nm or less. At this time, although the lower limit of D50 is not limited, it is generally about 300 nm, and is particularly preferably 400 nm. Therefore, as a starting material, zirconia powder containing zirconia aggregated particles can be used. For example, particle size distribution D50 (average particle size of secondary particles) is 400~700nm The zirconia powder can be suitable as starting material. In addition, the primary particle size of the zirconia powder used as the starting material is not limited, but generally zirconia powder within the range of 1-50 nm (especially 5-30 nm) can be used. In other words, for example, zirconia powder having a secondary particle diameter (D50) within a range of 5 times or more (especially 10 times or more) the crystallite diameter of zirconia can also be used.

Zirconia powder as the starting material can be composed of crystalline zirconia particles, especially the content of zirconia monoclinic phase is 90~95% by volume and the content of zirconia tetragonal phase is 5~10% by volume. Zirconia powder. In this way, stable and finer zirconia particles can be produced by using a raw material containing a specific amount of zirconia tetragonal crystal phase.

In addition, the specific surface area of the zirconia powder as the starting material is not limited, but it is particularly preferable to use a powder with a specific surface area of 70 m ² /g or more (more preferably 80 m ² /g or more). By using zirconia powder having such a specific surface area, highly dispersed nanoparticles can be more reliably produced. In addition, although the upper limit of the specific surface area is not restrictive, it is generally set at about 200 m ² /g, particularly preferably set at 150 m ² /g.

As the zirconia powder having such a crystal structure, physical properties, etc., conventionally known or commercially available ones can be used. In addition, zirconia powder synthesized by conventional production methods can also be used. For example, zirconia synthesized by liquid-phase methods such as hydrolysis, co-precipitation, neutralization, and alkoxide can be used. Especially in the hydrolysis method, after synthesizing the effluent and the zirconia sol by hydrolyzing the zirconium salt, the zirconia powder obtained by temporarily heating the aforementioned sol can be suitably used as a starting material. As mentioned above, the present invention can use known or commercially available general zirconia powders as raw materials without using special raw materials and cost. effective method. That is, the production method of the present invention uses such zirconia powder containing zirconia monoclinic phase and zirconia tetragonal phase as a starting material, and can reliably and efficiently produce monoclinic zirconia-based nanoparticles , there is virtually no diffraction peak in the 2θ=29.74~30.74 degrees of the diffraction pattern.

Bead Milling Steps

The bead milling step is to subject the aforementioned zirconia powder to bead milling in the presence of beads having a particle size distribution D50 of 40 μm or less.

Beads used as media (grinding media) only need to have a particle size distribution D50 within the range of 40 μm or less, preferably 35 μm or less, more preferably 32 μm or less, and most preferably 30 μm or less. When the above-mentioned D50 exceeds 40 μm , there is a possibility that stable and highly dispersible nanoparticles cannot be obtained. In addition, although the above-mentioned lower limit of D50 is not limiting, it is generally sufficient to be about 1 μm, more preferably about 10 μm, and more preferably about 20 μm. The present invention can more efficiently and reliably prepare fine monoclinic zirconia-based nanoparticles by using such relatively fine beads.

The composition of the beads is not particularly limited, and the same materials as those used in conventional bead mills can be used. For example, inorganic material systems such as oxide-based beads such as zirconia, alumina, and silicon oxide, metal-based beads such as nickel, copper, tungsten, and steel, and non-oxide-based beads such as titanium nitride and silicon nitride can be applied. beads. From the viewpoints of lightening, preventing the mixing of impurities, and mixing efficiency, it is particularly preferable to use zirconia beads.

Bead shape Generally, it is suitable to use slightly spherical beads. As such spherical beads, known or commercially available ones can be used. In particular, it is applicable to spherical beads prepared by plasma melting method (thermoplasma melting method). Plasma fusion is a practice Known methods, such as the method disclosed in Japanese Patent Laid-Open No. 2007-4090, etc. can be used. That is, in a plasma gas atmosphere formed under atmospheric pressure, raw material powder of zirconia (such as a powder prepared by a pulverization method) is continuously supplied in a gas phase state, and the surface of the zirconia particles constituting the raw material powder is melted to make the particles Spheroidization, followed by spherical zirconia particles can be produced by a method comprising the step of rapidly cooling the particles by blowing a cooling gas under convective flow of the particles. The spherical zirconia particles obtained by this method are advantageous in that the particle shape is roughly spherical and there are few coarse particles.

The amount of beads used is not limited, but generally speaking, it can be determined by the apparent volume ratio of beads (bead filling rate) relative to the capacity of the space (usually the crushing chamber in the bead mill) filled with beads, According to the model of the bead mill, etc., the bead filling rate can be properly set within the range of 10-90%. Therefore, for example, it may be set within a range of 50 to 70%, and may further be set within a range of 40 to 60%. In addition, for example, as shown in the following examples, when the spherical zirconia beads obtained by the thermoplasma fusion method are used for the beads, it can also be set to satisfy the above-mentioned bead filling rate and relative to 100 parts by weight of the zirconia powder mentioned above. Beads are in the range of 600 to 900 parts by weight.

Bead milling is a method of pulverizing and dispersing the starting material by shearing force or impact force generated by beads (grinding medium), for example, it can be implemented by using a conventional or commercially available bead milling device. Therefore, the model and form of the bead milling device are not particularly limited. For example, the shape of the stirrer installed in the bead mill is not limited, for example, any one of disc type, pin type, single roll type, etc. is acceptable. In addition, the crushing chamber (duct) may be any of vertical type and horizontal type. In addition, the operation mode of the bead mill is not limited, it can be circular, pass, batch any of the formulas.

Commercially available bead milling devices are not limited as long as they can perform bead milling treatment under the conditions of the present invention. For example, Super Apex Mill (manufactured by HIROSHIMA METAL & MACHINERY CO., LTD.), Ultra Apex Mill (manufactured by HIROSHIMA METAL & MACHINERY CO., LTD.), Dual Apex Mill (manufactured by HIROSHIMA METAL & MACHINERY CO., LTD. ), MSC Mill (manufactured by NIPPON COKE & ENGINEERING CO.,LTD.), Nano Getter (manufactured by Ashizawa Finetech Ltd.), MAX Nano Getter (manufactured by Ashizawa Finetech Ltd.), LABSTAR Mini (manufactured by Ashizawa Finetech Ltd.), JBM series (JBM-B035, JBM-C020, JBM-C050, JBM-C200, JBM-C500, JBM-C1000, Waterspout-Combo, JBM-D500, JBM-D1000, JBM-D2000) (all JUST NANOTECH CO., Ltd.).

The operating conditions of the bead mill are based on the conditions of the production method of the present invention (use of specific starting materials and beads), and can be appropriately set depending on the properties of the zirconia powder used, the type of solvent, the type of beads, etc. For example, in the case of a bead mill equipped with a stirrer in the present invention, the peripheral speed of the stirrer can usually be set to about 5-20 m/s, especially 7-15 m/s. The residence time (processing time) is generally set at about 5 to 25 minutes (especially 8 to 20 minutes), but as long as it can ensure that the obtained zirconia particles (powder) are analyzed by X-ray diffraction, the diffraction pattern becomes substantially unrecognizable The time required for the formation of the tetragonal phase of zirconia is sufficient, and is not particularly restricted by the above-mentioned time.

In addition, the bead milling treatment of the present invention can be either dry or wet, and wet bead milling is particularly preferred. In this case, as a solvent other than water, alcohol-based solvents such as methanol, ethanol, isopropanol, and butanol, ketone-based solvents such as ketone, acetone, methyl ethyl ketone, methyl acetone, and methyl isobutyl ketone, isopropyl ether, Various organic solvents such as ether-based solvents such as methyl celluloid, glycol ester-based solvents such as propylene glycol monomethyl ether acetate, and ethylene glycol monoethyl ether acetate.

In addition, in the case of bead milling, various additives may be blended as necessary in addition to the solvent. For example, various additives such as dispersants, coupling agents, binders, and dispersion aids can be blended. In the present invention, it is particularly preferable to include both the dispersant and the coupling agent in the dispersion liquid for the purpose of obtaining high dispersibility and the like.

As the dispersant, any type of dispersant such as nonionic, anionic, or cationic can be used, but anionic dispersants are particularly preferred in the present invention. Anionic dispersants are especially suitable for phosphate ester dispersants. A commercial item can also be used for these dispersants.

The amount of the dispersant to be added is not particularly limited, and can be appropriately set in the range of 0.1 to 100 parts by weight, depending on the type of dispersant to be used, etc., usually within the range of 0.1 to 100 parts by weight relative to 100 parts by weight of the zirconia powder. Therefore, for example, it may be set within a range of 0.4 to 100 parts by weight relative to 100 parts by weight of zirconia powder, and may be set within a range of 0.5 to 20 parts by weight relative to 100 parts by weight of zirconia powder. , can further be set within a range of 1 to 10 parts by weight relative to 100 parts by weight of zirconia powder, for example.

The coupling agent can be, for example, a silane coupling agent, a titanium coupling agent, etc., and a silane coupling agent is particularly suitable for the present invention.

Silane coupling agent is not particularly limited, but can use at least acryl A silane agent with a functional group or a methacryl group is suitable.

As an example, the general formula X _3-n (CH ₃ ) _n Si-RY (but n=1 or 2, R represents an ethylidene or propylidene group, X represents a hydrolyzable group, and Y represents a functional group) can be cited. Show silane coupling agent. Examples of the hydrolyzable group X include alkoxy groups such as methoxy, ethoxy, and 2-methoxyethoxy. Examples of the functional group Y include vinyl groups, epoxy groups, styrene groups, ureido groups, acryl groups, methacryl groups, amine groups, isocyanurate groups, isocyanate groups, and mercapto groups. For example, a silane coupling agent in which R in the above general formula is acryl or methacryl can be used. These silane coupling agents can also use a commercial item.

The amount of the coupling agent added is not particularly limited, but is generally within the range of 2 to 200 parts by weight relative to 100 parts by weight of the zirconia powder, and can be appropriately set depending on the type of dispersant used, etc. Therefore, for example, it may be set within a range of 5 to 100 parts by weight relative to 100 parts by weight of zirconia powder, or may be set within a range of 5 to 50 parts by weight relative to 100 parts by weight of zirconia powder. Furthermore, it is set in the range of 10-20 weight part with respect to 100 weight part of zirconia powder.

After the bead milling treatment, after separation from the beads according to the usual method, it is only necessary to recover the zirconia-based nanoparticles. At this time, when the wet bead milling treatment is performed, it can be recovered in the form of a dispersion liquid in which the zirconia-based nanoparticles are dispersed in the aforementioned solvent. At this time, part or all of the solvent may be replaced with other solvents, or a dispersant may be further added to the solvent, if necessary.

3. Use of zirconia-based nanoparticles

The zirconia-based nanoparticles of the present invention can be used for the same purposes as conventional zirconia nanoparticles.

In particular, in order to make full use of the advantages of the high refractive index of the nanoparticles of the present invention, for example, it can be widely used in various optical parts such as lenses, optical filters, anti-reflection materials, hard coating materials, and refractive index adjustment materials. use. That is, the nanoparticles of the present invention can be used as dispersion materials (especially high refractive index particles) of conventional or commercially available optical components. In this case, the zirconia-based nanoparticles of the present invention may be used alone, or may be used in the form of a composite material containing the zirconia-based nanoparticles of the present invention and a resin component. As for the resin component, various synthetic resins such as polyester resins, polyolefin resins, polyamide resins, acrylic resins, etc. that are used in conventional composite materials can also be used.

Example

Examples are shown below to illustrate the features of the present invention more specifically. However, the scope of the present invention is not limited by the examples.

Example 1

(1) Preparation of zirconia-based nanoparticle dispersion

A dispersion liquid in which zirconia-based nanoparticles were dispersed in a solvent was prepared in the following manner. As the zirconia powder of the starting material, a commercially available product was used. The particle size distribution D50 of this commercial product is in the range of 0.4-0.7 μm, the monoclinic phase is 94% by volume and the tetragonal phase is 6% by volume, and the specific surface area is 80m ² /g. After blending 6 g of this zirconia powder and additives (0.9 g of silane coupling agent and 0.3 g of phosphoric acid ester-based dispersant) into 15 g of methyl ethyl ketone, a bead mill (batch type bead mill, manufactured by Daiken Chemical Industry Co., Ltd.) ) The resulting mixed solution is subjected to bead milling. The above-mentioned apparatus is constituted by the structure shown in Fig. 7, and a single-roller type agitator shown in Fig. 8 is used. As the beads, 50 g of commercially available zirconia beads ("DZB" manufactured by Daiken Chemical Industry Co., Ltd., D50 of particle size distribution 30 μm) spheroidized by the thermal plasma fusion method (44 volumes relative to the volume of the crushing chamber) were used. %), the circumferential speed of the agitator is 10m/s, and the processing time is 15 minutes. In this way, a dispersion liquid containing zirconia-based nanoparticles was obtained.

A schematic diagram of the bead milling device used in Example 1 is shown in FIG. 7 . The bead mill 10 is provided with: a) a crushing chamber (pipe) 13 for containing beads 11 and processed objects (containing dispersion medium) 12; b) an agitator 14 arranged in the crushing chamber 13; c) making the aforementioned A motor 15 for the agitator 14 to rotate; d) a shaft 16 for transmitting the rotational driving force of the motor 15 to the agitator 14; The cooling water 18 flows into the cooling water jacket 17 and absorbs the heat generated during pulverization, then is discharged from the cooling water jacket 17, and returns to the cooling water jacket 17 after cooling down, so as to circulate in this way.

The stirrer 13 is shown in Figure 8 (a), on the position of the central axis, the shaft 16 is installed on the stirrer 14. Fig. 8(b) is a view viewed from the direction of arrow A in Fig. 8(a). As shown in FIG. 8( b ), the agitator 14 used in the embodiment is a single-roller type close to a windmill, and it grinds by rotating clockwise (arrow direction).

(2) Evaluation of zirconia-based nanoparticles

The crystal structure and particle size of the zirconia-based nanoparticles in the obtained dispersion were investigated.

1) Crystal structure

1-1) X-ray diffraction analysis

Powder X-ray diffraction analysis was performed on the powder obtained by drying the dispersion liquid obtained in Example 1. X-ray diffraction device using "MiniFlex 600" (manufactured by Rigaku Corporation). The results of their analysis (shown as "after treatment") are shown in FIG. 1 . In addition, the results of measuring the zirconia powder (starting material) before the treatment in the same manner are also shown in FIG. 1 for comparison. As shown in Figure 1, it can be seen that for the zirconia-based nanoparticles obtained in Example 1, the diffraction peaks in the range of 2θ=29.74~30.74 degrees in the diffraction pattern (especially the diffraction peaks of the zirconia tetragonal crystal phase) disappear.

1-2) Raman spectroscopic analysis

In addition, the crystallinity of the aforementioned powder was investigated by Raman spectroscopy. As a Raman spectrometer, "Raman Microscope RAMAN Touch" (manufactured by Nanophoton Corporation) was used, and the excitation wavelength was 532 nm, and the diffraction grating was 2400 gr/mm. This Raman spectrum (shown as "after treatment") is shown in FIG. 2 . In addition, the results of measuring the zirconia powder (starting material) before the treatment in the same manner are also shown in FIG. 2 for comparison. It can also be clearly seen from FIG. 2 that even with the Raman spectrum, the zirconia-based nanoparticles produced in Example 1 still have no peaks at wavenumbers 202 cm ⁻¹ and 267 cm ⁻¹ originating from the tetragonal zirconia phase.

1-3) Electron diffraction analysis

Furthermore, electron diffraction analysis was performed on the aforementioned powder. Use gold microparticles as a standard sample for plane spacing reference, and obtain length data from the curve of the standard sample. Calculate the positions of the strongest lines 111m and 111t of monoclinic and tetragonal crystals. The intensity curve obtained by electron diffraction is shown in FIG. 3 . The upper panel of FIG. 3 shows the results before treatment (starting material), and the lower panel of FIG. 3 shows the results of the nanoparticles obtained in Example 1. It can also be clearly seen from the results in FIG. 3 that the 111t peak of the tetragonal crystal will not be confirmed in the treated nanoparticles.

2) Granularity

For particle size measurement, a dynamic light scattering type particle size distribution analyzer "Nanotrac Wave EX-150" (manufactured by MicrotracBEL Corp.) was used. Particle size is the volume-based cumulative distribution D50 and D90. The results are shown in Fig. 4. It can also be clearly seen from the results of the frequency distribution and cumulative distribution in Figure 4 that the particle size distribution (frequency distribution) is a single peak, D50 is about 12nm, and D90 is about 20nm.

In addition, the relationship between the particle size distribution D90, processing time and the peak ratio (intensity ratio) of tetragonal crystal/monoclinic crystal was investigated. The results are shown in Figure 5. As shown in Figure 5, as the monoclinic crystal phase of zirconia increases, D90 also decreases. That is, while the tetragonal phase of zirconia decreases, the monoclinic phase of zirconia increases, thus becoming more than 94% by volume of the monoclinic phase of the starting material. In addition, it can be deduced from the results in Fig. 5 that when the tetragonal crystal phase present in the starting material changes to the monoclinic crystal, the unraveling of the aggregated particles of zirconia also contributes to the miniaturization, resulting in high dispersion .

Test example 2

Zirconia-based nanoparticles (comparative sample 1 and comparative sample 2) were prepared in the same manner as in Example 1 using zirconia beads having different average particle diameters D50. The crystal phase of the obtained zirconia-based nanoparticles was investigated by X-ray diffraction analysis in the same manner as in Example 1. As the zirconia beads, D50 of 50 μm (comparative sample 1 user) and D50 of 100 μm (comparative sample 2 user) were used. The results are shown in FIG. 6 . In addition, the analysis results of the zirconia-based nanoparticles obtained in Example 1 are also shown in FIG. 6 .

It can also be clearly seen from the results in Figure 6 that the zirconia-based nano Particles (using bead diameter D50=30μm, symbol A in Figure 6) do not have diffraction peaks in the range of 2θ=29.74~30.74 degrees. In contrast, Comparative Sample 1 (bead diameter D50 = 50 μm, symbol B in Fig. 6) and Comparative Sample 2 (bead diameter D50 = 100 μm, Fig. The symbol C) shows a slight diffraction peak in the range of 2θ=29~30 degrees (especially the range of 2θ=29.74~30.74 degrees).

Test example 3

A dispersion liquid containing zirconia-based nanoparticles was prepared in the same manner as in Example 1, and the particle size distribution change within a certain period of time from immediately after preparation was investigated. The results are shown in Table 1.

From the results in Table 1, it can be clearly seen that the dispersion liquid containing zirconia-based nanoparticles still maintains approximately the same particle size distribution as the original (0 day) after about 6 months after preparation, and has excellent dispersion stability.

Test example 4

A zirconia-based nanoparticle-containing dispersion (dispersion 1) was prepared in the same manner as in Example 1. In addition, use zirconia beads with different average particle diameter D50 particles, and prepared in the same manner as in Example 1, dispersions containing zirconia-based nanoparticles (comparative dispersion 1 and comparative dispersion 2). As the zirconia beads, D50 of 100 μm (comparative dispersion 1 user) and D50 of 50 μm (comparative dispersion 2 user) were used. The transmittance and particle size distribution of each of the obtained dispersion liquids were investigated. For the transmittance, the solvent (MEK) is used as a blank sample (transmittance 100%), and the spectral transmittance at the measurement wavelength of 600nm is measured when the optical path length is 5mm. The particle size distribution was measured in the same manner as in Example 1. These results are shown in Table 2.

It can also be clearly seen from the results in Table 2 that the dispersion liquid 1 of the present invention has a high transmittance of 30% or more (especially 35% or more) due to its fineness and excellent dispersibility. On the other hand, Comparative Dispersion Liquids 1 and 2 had relatively low transmittance because they contained relatively coarse particles.

Claims (5)

A monoclinic zirconia-based nanoparticle, which is a zirconia microparticle with a particle size distribution D50 of 15 nm or less, characterized in that: (1) the zirconia microparticle contains a zirconia monoclinic crystal phase; and (2) the zirconia microparticle In the diffraction pattern obtained by powder X-ray diffraction analysis, there is no diffraction peak in the range of 2θ=29.74~30.74 degrees. For the monoclinic zirconia-based nanoparticles of claim 1, the content of the zirconia monoclinic crystal phase is more than 90% by volume. For the monoclinic zirconia-based nanoparticles of claim 1 or 2, the particle size distribution of the powder composed of zirconia fine particles is unimodal, and the particle size distribution D90 is 30 nm or less. A dispersion liquid, in which the monoclinic zirconia-based nanoparticles according to any one of Claims 1 to 3 are dispersed in a solvent. Such as the dispersion liquid of claim 4, which further contains a silane coupling agent and a phosphoric acid ester-based dispersant.

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