JP2007099931A - Transparent zirconia dispersion liquid, transparent composite material and method for producing transparent composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent zirconia dispersion liquid having improved refractive index and mechanical properties while keeping transparency by using tetragonal zirconia particles of nanometer size and provide a transparent composite material and a method for producing a transparent composite material. <P>SOLUTION: The transparent zirconia dispersion liquid contains tetragonal zirconia particles having a dispersed particle diameter of ≥1 nm and ≤20 nm and a dispersion medium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a zirconia transparent dispersion, a transparent composite, and a method for producing a transparent composite. More specifically, the zirconia transparent dispersion is preferably used as a resin filler, and can maintain transparency while improving refractive index and mechanical properties. The present invention relates to a zirconia transparent dispersion, a transparent composite that can be substituted for glass obtained by combining the zirconia transparent dispersion and a resin, and a method for producing the transparent composite.

  Conventionally, attempts have been made to improve the mechanical properties and the like of a resin by combining it with a resin using an inorganic oxide such as silica as a filler. As a method of combining the filler and the resin, a method of mixing a dispersion in which an inorganic oxide is dispersed in water and / or an organic solvent and a resin is generally used. By mixing by the method, an inorganic oxide particle composite plastic in which inorganic oxide particles are composited as the second phase can be produced.

On the other hand, as a substrate for a flat panel display (FPD) such as a liquid crystal display (LCD), a plasma display (PDP), and an electroluminescence display (EL), a glass substrate has been conventionally used. However, there are problems such as being easy to break, not being bent, large specific gravity, and unsuitable for weight reduction. Therefore, many attempts have been made to use a plastic substrate instead of a glass substrate.
The required properties for plastic substrates for flat panel displays (FPD) include transparency, refractive index, mechanical properties, and the like.

As inorganic oxide fillers for improving the refractive index of plastics, fine particles such as zirconia and titania are used as high refractive index fillers.
Moreover, in order to make an inorganic oxide filler composite with resin, the dispersion liquid of the inorganic oxide filler was developed, and improvement of the refractive index of resin is examined.
For example, a high refractive index and highly transparent film having a thickness of several microns using a zirconia particle composite plastic in which a zirconia particle having a particle size of 10 to 100 nm and a resin are combined has been proposed (for example, see Patent Document 1). ).
Japanese Patent Laying-Open No. 2005-161111

By the way, when evaluating the transparency of a substrate using a conventional plastic compounded with inorganic oxide particles, the thickness of the substrate is taken as the optical path length, and the visible light transmittance at this optical path length is obtained. Therefore, it becomes difficult to maintain transparency as the thickness increases.
For example, in the case of the above-described conventional zirconia particle composite plastic film, since the high refractive index and high transparency are ensured by setting the thickness to several μm, when the thickness is several tens μm or more, It becomes difficult to maintain transparency.
As described above, although the zirconia particle composite plastic film has been studied, the refractive index and transparency when the zirconia particle composite plastic is used as a bulk body have not been studied.

  Furthermore, the crystal structure of zirconia includes monoclinic, tetragonal, and cubic crystals. Among them, when tetragonal crystals are compounded as the second phase, there is a toughening mechanism called martensitic transformation, and mechanical characteristics. Although there is an advantage in terms of improvement, no attempt has been made to compound this tetragonal zirconia with plastic.

  The present invention has been made in order to solve the above-described problems. By using nanometer-scale tetragonal zirconia particles, the refractive index and mechanical properties can be improved and transparency can be maintained. An object is to provide a transparent dispersion, a transparent composite, and a method for producing the transparent composite.

  The inventors of the present invention have made extensive studies on nanometer-grade tetragonal zirconia particles that have a toughening mechanism called martensite transformation when compounded as the second phase and are superior in terms of improving mechanical properties. As a result of overlapping, if a zirconia transparent dispersion containing tetragonal zirconia particles having a dispersed particle diameter of 1 nm or more and 20 nm or less is used, the refractive index, while maintaining the transparency of the composite when composited with a resin, The present inventors have found that mechanical characteristics can be improved and have completed the present invention.

That is, the zirconia transparent dispersion of the present invention is characterized by containing tetragonal zirconia particles having a dispersed particle diameter of 1 nm or more and 20 nm or less.
In this zirconia transparent dispersion, the content of the tetragonal zirconia particles is preferably 1 wt% or more and 70 wt% or less.

The transparent composite of the present invention is characterized in that tetragonal zirconia particles having a dispersed particle diameter of 1 nm or more and 20 nm or less are dispersed in a resin.
In this transparent composite, the content of the tetragonal zirconia particles is preferably 1 wt% or more and 80 wt% or less.

  The method for producing a transparent composite of the present invention is characterized in that the zirconia transparent dispersion of the present invention and a resin are mixed, the resulting mixture is molded or filled, and then the molded or filled is cured. And

According to the zirconia transparent dispersion of the present invention, since tetragonal zirconia particles having a dispersed particle diameter of 1 nm or more and 20 nm or less are contained, it is possible to improve the refractive index and mechanical properties and maintain transparency.
Therefore, when this zirconia transparent dispersion is mixed with a resin, a transparent composite having a high refractive index, excellent transparency, and improved mechanical properties can be easily obtained.

  According to the transparent composite of the present invention, since the tetragonal zirconia particles having a dispersed particle diameter of 1 nm or more and 20 nm or less are dispersed in the resin, the refractive index, transparency and mechanical properties can be improved.

  According to the method for producing a transparent composite of the present invention, the zirconia transparent dispersion of the present invention and a resin are mixed, the resulting mixture is molded or filled, and then the molded or filled is cured. A transparent composite having a high refractive index, excellent transparency, and improved mechanical properties can be easily and inexpensively produced.

The best mode for carrying out the zirconia transparent dispersion and transparent composite of the present invention and the method for producing the transparent composite will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

"Zirconia transparent dispersion"
The zirconia transparent dispersion of the present invention is a dispersion containing tetragonal zirconia particles having a dispersed particle diameter of 1 nm to 20 nm and a dispersion medium.
Here, the reason why the zirconia particles are limited to tetragonal zirconia particles is that, from the standpoint of fine particle synthesis, if the particle size of the fine particles is as small as 20 nm or less, the tetragonal crystals are more than the monoclinic crystals conventionally known. In addition to being stable and having high hardness, the mechanical properties of the transparent composite can be improved. In addition, when the transparent composite is obtained by dispersing zirconia particles in the resin, tetragonal zirconia is used as the transparent composite. This is because when it is added as the second phase, it exhibits high toughness due to volume expansion called martensitic transformation, compared with the case where monoclinic zirconia particles are added.

Further, the reason why the dispersed particle diameter of tetragonal zirconia particles is limited to 1 nm or more and 20 nm or less is that when the dispersed particle diameter is less than 1 nm, crystallinity becomes poor and it is difficult to express particle characteristics such as refractive index. On the other hand, if the dispersed particle diameter exceeds 20 nm, the transparency is lowered in the case of a dispersion or a transparent composite.
Thus, since tetragonal zirconia particles are nano-sized particles, even when these tetragonal zirconia particles are dispersed in a resin to form a transparent composite, light scattering is small, and the transparency of the composite is reduced. It is possible to maintain.

The content of tetragonal zirconia particles is preferably 1% by weight or more and 70% by weight or less, more preferably 1% by weight or more and 50% by weight or less, and further preferably 5% by weight or more and 30% by weight or less.
Here, the reason why the content of tetragonal zirconia particles is limited to 1% by weight or more and 70% by weight or less is that this range is a range in which the tetragonal zirconia particles can take a good dispersion state, and the content is 1% by weight. If it is less than%, the effect as tetragonal zirconia particles is reduced, and if it exceeds 70% by weight, gelation and aggregation precipitation occur, and the characteristics as a dispersion are lost.

The dispersion medium basically contains at least one of water, an organic solvent, a liquid resin monomer, and a liquid resin oligomer.
Examples of the organic solvent include alcohols such as methanol, ethanol, 2-propanol, butanol, and octanol, ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and γ-butyrolactone. Esters such as diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, acetone, Methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, cyclohexanone, etc. Amides, aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, and amides such as dimethylformamide, N, N-dimethylacetoacetamide and N-methylpyrrolidone are preferably used. One of these solvents or Two or more kinds can be used.

As the liquid resin monomer, acrylic or methacrylic monomers such as methyl acrylate and methyl methacrylate, and epoxy monomers are preferably used.
Moreover, as said liquid resin oligomer, a urethane acrylate oligomer, an epoxy acrylate oligomer, an acrylate oligomer, etc. are used suitably.

In addition to the above, the zirconia transparent dispersion may contain other inorganic oxide particles, a dispersant, a dispersion aid, a coupling agent, a resin monomer, and the like as long as the characteristics are not impaired.
As inorganic oxide particles other than tetragonal zirconia particles, monoclinic or cubic zirconia particles, titanium oxide, cerium oxide, zinc oxide, tin oxide, antimony-added tin oxide (ATO), tin-added indium oxide (ITO) Etc.
Examples of the dispersant include phosphate ester type dispersants.

In the zirconia transparent dispersion, when the content of tetragonal zirconia particles is 5% by weight, the visible light transmittance is preferably 90% or more, more preferably 95% or more when the optical path length is 10 mm.
The visible light transmittance varies depending on the content of tetragonal zirconia particles. When the content of tetragonal zirconia particles is 1% by weight, it is 95% or more, and when the content of tetragonal zirconia particles is 40% by weight, it is 80% or more. It is.

"Transparent composite"
The transparent composite of the present invention is a composite in which tetragonal zirconia particles having a dispersed particle diameter of 1 nm or more and 20 nm or less are dispersed in a resin.
The resin may be any resin that is transparent to light in a predetermined wavelength band such as visible light or near infrared, and is thermoplastic, thermosetting, light (electromagnetic wave) curing by visible light, ultraviolet light, infrared light, or the like. And curable resins such as electron beam curable by electron beam irradiation are preferably used.

Examples of this resin include acrylates such as polymethyl methacrylate (PMMA) and polycyclohexyl methacrylate, polycarbonate (PC), polystyrene (PS), polyether, polyester, polyarylate, polyacrylate, polyamide, phenol-formaldehyde ( Phenol resin), diethylene glycol bisallyl carbonate, acrylonitrile / styrene copolymer (AS resin), methyl methacrylate / styrene copolymer (MS resin), poly-4-methylpentene, norbornene polymer, polyurethane, epoxy, silicone, etc. Is mentioned.
An antioxidant, a release agent, a coupling agent, an inorganic filler, and the like may be added to the resin as long as the characteristics are not impaired.

In this transparent composite, the content of tetragonal zirconia particles is preferably 1 wt% or more and 80 wt% or less, more preferably 10 wt% or more and 80 wt% or less, further preferably 10 wt% or more and 50 wt%. % Or less.
Here, the reason why the content of the tetragonal zirconia particles is limited to 1% by weight or more and 80% by weight or less is that the lower limit of 1% by weight is the minimum value of the addition rate that can improve the refractive index and mechanical properties. On the other hand, 80% by weight of the upper limit is the maximum value of the addition rate that can maintain the characteristics (flexibility and specific gravity) of the resin itself.

In this transparent composite, when the content of tetragonal zirconia particles is 25% by weight, the visible light transmittance is preferably 90% or more, more preferably 92% or more when the optical path length is 1 mm.
This visible light transmittance varies depending on the content of tetragonal zirconia particles in the transparent composite. When the content of tetragonal zirconia particles is 1% by weight, it is 95% or more, and when the content of tetragonal zirconia particles is 40% by weight. 80% or more.

Since the tetragonal zirconia particles have a refractive index of 2.15, by dispersing the tetragonal zirconia particles in the resin, the refractive index of the acrylate and the silicone resin is about 1.4, and the refractive index of the epoxy resin is about 1.5. As compared with the above, it is possible to further improve the refractive index of the resin.
Further, tetragonal zirconia particles can be expected to improve the toughness value due to martensitic transformation as compared with monoclinic zirconia particles, and also have high toughness and hardness, and are suitable for improving the mechanical properties of the composite.
Further, since the tetragonal zirconia particles are nano-sized particles, even when they are combined with a resin, light scattering is small and the transparency of the composite material can be maintained.

"Production method of transparent composite"
The transparent composite of the present invention can be produced by the following method.
First, the above-described zirconia transparent dispersion of the present invention and a resin monomer or oligomer are mixed using a mixer or the like to obtain a resin composition in an easily flowable state.
Next, the resin composition is molded using a mold, or filled in a mold or a container, and then the molded body or filling is heated or irradiated with ultraviolet rays, infrared rays, etc. The object is cured.

Here, when the resin monomer or oligomer has a reactive carbon double bond (C = C), it can be polymerized / resinized simply by mixing.
In particular, there are various methods for curing a resin composition containing an ultraviolet (UV) curable resin such as an acrylic resin. Typically, a radical polymerization reaction initiated by heating or light irradiation is used. Mold molding method, transfer molding method and the like. Examples of this radical polymerization reaction include a polymerization reaction by heat (thermal polymerization), a polymerization reaction by light such as ultraviolet rays (photopolymerization), a polymerization reaction by gamma rays, or a method in which a plurality of these are combined.

  An example of the transparent composite of the present invention is an optical element made of a silicone resin. This optical element is manufactured by putting one or a plurality of types of organopolysiloxane, a curing agent, and a catalyst into a mold and thermally curing in the mold to obtain a molded body having a predetermined shape. As the thermosetting reaction, reactions such as condensation crosslinking, peroxide crosslinking, and platinum addition crosslinking can be used. In particular, thermosetting by an addition polymerization reaction using a platinum catalyst is preferable.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.

[Preparation and evaluation of zirconia transparent dispersion]
"Example 1"
To a zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate is dissolved in 40 L (liter) of pure water, dilute ammonia water in which 344 g of 28% ammonia water is dissolved in 20 L of pure water is added with stirring, and the zirconia precursor slurry is added. It was adjusted.
Next, an aqueous sodium sulfate solution in which 300 g of sodium sulfate was dissolved in 5 L of pure water was added to this slurry with stirring. The amount of sodium sulfate added at this time was 30% by weight with respect to the zirconia converted value of zirconium ions in the zirconium salt solution.

Next, this mixture was dried in the air at 130 ° C. for 24 hours using a dryer to obtain a solid.
Next, the solid was pulverized with an automatic mortar or the like and then baked at 500 ° C. for 1 hour in the air using an electric furnace.
Next, the fired product is put into pure water, stirred to form a slurry, washed using a centrifuge, and after sufficiently removing the added sodium sulfate, dried in a dryer, Zirconia particles were prepared.
Next, 87 g of toluene as a dispersion medium and 3 g of CS-141E (manufactured by Asahi Denka Kogyo Co., Ltd.) as a dispersion medium were added to 10 g of the zirconia particles, followed by dispersion treatment, and the zirconia transparent dispersion liquid of Example 1 ( Z1) was prepared.

Subsequently, the dispersed particle diameter of the zirconia particles of this zirconia transparent dispersion and the visible light transmittance of the dispersion were measured.
The dispersion particle size was measured by using a dynamic light scattering particle size distribution measuring device (Malvern) and adjusting the content of zirconia particles in the zirconia transparent dispersion to 1% by weight. The data analysis conditions were such that the particle diameter standard was the volume standard, the refractive index of zirconia as a dispersed particle was 2, 15 and the refractive index of toluene as a dispersion medium was 1.49.

Further, the visible light transmittance of the dispersion liquid was set to a quartz cell (10 mm × 10 mm) with a zirconia content ratio of the above dispersion liquid adjusted to 5 wt% using toluene, and the optical path length of this sample was set to 10 mm. The visible light transmittance at that time was measured using a spectrophotometer (manufactured by JASCO Corporation). Here, the transmittance of 80% or more was “◯”, and the transmittance of less than 80% was “x”.
Table 1 shows the measurement results.
Moreover, the crystal system of the zirconia particles of this dispersion was examined using an X-ray diffractometer.
FIG. 1 shows a powder X-ray diffraction pattern (chart) of zirconia particles. This powder X-ray diffraction pattern confirmed that the crystal system of the zirconia particles was a tetragonal system.

“Comparative Example 1”
A zirconia dispersion (Z2) of Comparative Example 1 was prepared by carrying out a dispersion treatment according to Example 1 except that RC-100 (manufactured by Daiichi Rare Element Co., Ltd.) was used as the zirconia particles.
Subsequently, the dispersed particle diameter and visible light transmittance of the zirconia particles were measured according to Example 1. Table 1 shows the measurement results.

[Preparation of transparent composite]
"Example 2"
To 100 g of the zirconia transparent dispersion of Example 1, 5 g of 1,6-hexanediol diacrylate, 2.5 g of pentaerythritol triacrylate, 2 g of pentaerythritol tetraacrylate, and 0.5 g of benzoyl peroxide as a polymerization initiator are added and vacuum dried. To remove the solvent to prepare a resin composition.
Next, this resin composition was poured into a mold assembled with a glass plate so as to have a thickness of 1 mm, and cured by heating at 60 ° C. for 5 hours and then at 120 ° C. for 2 hours. A transparent composite was prepared.
The zirconia content of this transparent composite was 50% by weight.

"Example 3"
To 100 g of the zirconia transparent dispersion of Example 1, 10 g of silicone oil (a mixture of methylhydrogenpolysiloxane and organopolysiloxane having vinyl groups at both ends) was added, and chloroplatinic acid was added to 100 parts by weight of silicone oil. The solvent was removed by vacuum drying to prepare a resin composition.
Next, this resin composition was poured into a mold assembled with a glass plate so as to have a thickness of 1 mm and cured by heating at 150 ° C. for 2 hours to produce a transparent composite of Example 3.
The zirconia content of this transparent composite was 50% by weight.

Example 4
To 100 g of the zirconia transparent dispersion of Example 1, 7 g of epoxy resin: Epicoat 828 and 3 g of EpiCure 3080 (both manufactured by Japan Epoxy Resins Co., Ltd.) were added, and the solvent was removed by vacuum drying to obtain a resin composition. Was made.
Next, this resin composition was poured into a mold assembled with glass plates so as to have a thickness of 1 mm, and cured by heating at 80 ° C. for 30 minutes, whereby a transparent composite of Example 4 was produced.
The zirconia content of this transparent composite was 50% by weight.

"Comparative Example 2"
To 100 g of the zirconia dispersion of Comparative Example 1, 5 g of 1,6-hexanediol diacrylate, 2.5 g of pentaerythritol triacrylate, 2 g of pentaerythritol tetraacrylate, and 0.5 g of benzoyl peroxide as a polymerization initiator were added and vacuum dried. Solvent removal was performed to prepare a resin composition.
Subsequently, this resin composition was processed according to Example 2, and the transparent composite body of the comparative example 2 was produced.
The zirconia content of this transparent composite was 50% by weight.

“Comparative Example 3”
To 100 g of the zirconia dispersion of Comparative Example 1, 10 g of silicone oil (a mixture of methylhydrogenpolysiloxane and organopolysiloxane each having vinyl groups at both ends) is added, and chloroplatinic acid is added to 100 parts by weight of silicone oil. On the other hand, it was added to 20 ppm, and the solvent was removed by vacuum drying to prepare a resin composition.
Subsequently, this resin composition was processed according to Example 3 to produce a transparent composite of Comparative Example 3.
The zirconia content of this transparent composite was 50% by weight.

“Comparative Example 4”
To 100 g of the zirconia dispersion of Comparative Example 1, 7 g of epoxy resin: Epicoat 828 and 3 g of EpiCure 3080 as a curing agent (both manufactured by Japan Epoxy Resins Co., Ltd.) are added, and the resin composition is removed by vacuum drying. Produced.
Subsequently, this resin composition was processed according to Example 4 to produce a transparent composite of Comparative Example 4.
The zirconia content of this transparent composite was 50% by weight.

“Comparative Example 5”
A transparent composite of Comparative Example 5 was produced by processing according to Comparative Example 2 except that the content of zirconia in the transparent composite was 2% by weight.

“Comparative Example 6”
A transparent composite of Comparative Example 6 was produced by processing according to Comparative Example 3 except that the content of zirconia in the transparent composite was 2% by weight.

“Comparative Example 7”
A transparent composite of Comparative Example 7 was produced by processing according to Comparative Example 4 except that the content of zirconia in the transparent composite was 2% by weight.

"Evaluation of transparent composites"
With respect to each of the transparent composites of Examples 2 to 4 and Comparative Examples 2 to 7, the following apparatus or method was evaluated for three points of visible light transmittance, refractive index, and hardness.

(1) Visible light transmittance Visible light transmittance was measured using a spectrophotometer (manufactured by JASCO Corporation).
Here, the measurement sample was a bulk body having a size of 100 × 100 × 1 mm, the transmittance of 80% or more was “◯”, and the less than 80% was “×”.
(2) Refractive index: Measured with an Abbe refractometer in accordance with Japanese Industrial Standards: JIS K 7142 “Plastic Refractive Index Measuring Method”.
Here, on the basis of the resin to which zirconia is not added, a case where the refractive index is improved by 0.05 or more is indicated by “◯”, and a case where the refractive index is improved by less than 0.05 is indicated by “X”.

(3) Hardness JIS-A hardness was measured using a durometer in accordance with Japanese Industrial Standards: JIS K 7215 “Durometer Hardness Test Method for Plastics”.
Here, it is produced using the zirconia dispersion liquid of Comparative Example 1 and the resins of Comparative Examples 2 to 4, and based on the hardness of each transparent composite having a zirconia content of 50% by weight, it is higher than this reference value. The case was “◯”, and the case lower than this reference value was “x”.
The above evaluation results are shown in Table 2.

According to these evaluation results, in Examples 2 to 4, it was found that the visible light transmittance, refractive index, and hardness were all good.
On the other hand, in Comparative Examples 2 to 7, any one of visible light transmittance, refractive index, and hardness was inferior to Examples 2 to 4.

  The zirconia transparent dispersion of the present invention contains tetragonal zirconia particles having a dispersed particle diameter of 1 nm or more and 20 nm or less, so that the transparent composite containing the zirconia particles and the resin has improved refractive index and mechanical properties. Therefore, the sealing property of the semiconductor laser (LED), the substrate for liquid crystal display device, the substrate for organic EL display device, the substrate for color filter, the substrate for touch panel, the substrate for solar cell, etc. The effect is great not only in the optical sheet, transparent plate, optical lens, optical element, optical waveguide, etc., but also in various other industrial fields.

It is a figure which shows the powder X-ray-diffraction figure of the zirconia particle of Example 1 of this invention.

Claims (5)

  A zirconia transparent dispersion comprising tetragonal zirconia particles having a dispersed particle diameter of 1 nm or more and 20 nm or less.   2. The zirconia transparent dispersion according to claim 1, wherein the content of the tetragonal zirconia particles is 1% by weight or more and 70% by weight or less.   A transparent composite comprising tetragonal zirconia particles having a dispersed particle diameter of 1 nm or more and 20 nm or less dispersed in a resin.   4. The transparent composite according to claim 3, wherein the content of the tetragonal zirconia particles is 1% by weight or more and 80% by weight or less.   A transparent composite comprising the zirconia transparent dispersion according to claim 1 or 2 and a resin, molding or filling the obtained mixture, and then curing the molded body or the filling. Method.

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