JP2007016189A - Transparent composite material and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent composite material capable of easily controlling a refractive index of a filling material, regardless of a kind of a stock material thereof, and having enough excellent transparency, by keeping the transparency when the composite material is mixed into various kinds of resins of which the refractive indices are different from one another. <P>SOLUTION: This composite material is given by adding a hollow filling material to a transparent material, wherein a size of the filling material is not less than 1 nm and not more than 380 nm and the filling material and the transparent material have such a relation as to satisfy formula (1) (V<SB>1</SB>is a volume of a stock material part of the filling material; V<SB>2</SB>is a volume of a hollow part of the filling material; n<SB>1</SB>is a refractive index of a stock material part of the filling material; n<SB>2</SB>is a refractive index of a hollow part of the filling material; and n<SB>m</SB>is a refractive index of the transparent material). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a composite material having excellent transparency in which nano-sized particles are dispersed in a transparent material, and a method for producing the same.

  Examples of transparent resins that can be used for optical applications such as organic glass and plastic lenses include methacrylic resins, polycarbonate resins, styrene resins, and epoxy resins. Organic glass has characteristics that are superior in impact resistance, light weight, and moldability compared to inorganic glass. Methacrylic resins have high light transmittance, low light scattering properties, excellent transparency and weather resistance, and polycarbonate resins have excellent impact resistance, so their use and usage increases. ing.

  Japanese Patent No. 3559894 discloses a resin comprising a transparent resin composition in which fine silica particles (filler) having a diameter equal to or smaller than a visible light wavelength are blended with a transparent amorphous organic polymer for the purpose of improving rigidity and the like. A made window is disclosed. In the resin composition, for example, an acrylic resin is dissolved in a methyl ethyl ketone solvent, silica fine particles (filler) are added and mixed in this solution, and then ethanol is added as a coagulating solvent to add silica fine particles (filled) into the acrylic resin. It is obtained by precipitating a transparent resin composition in which a material is dispersed.

  Japanese Patent Application Laid-Open No. 2004-292698 discloses that in a resin composition in which composite metal oxide fine particles (filler) composed of two or more kinds of metal oxides are dispersed in a resin, the composite is obtained depending on the composition ratio of a plurality of metal oxide species. By adjusting the refractive index in the metal oxide fine particles (filler) and making the refractive index difference between the resin and the metal oxide 0.05 or less, a transparent resin composite can be obtained for various resin matrices. Presented.

  Japanese Patent No. 3357881 discloses an artificial marble in which a glass filler (filler) is dispersed in a synthetic resin to give transparency, and the refractive index of the synthetic resin is adjusted by adjusting the proportion of each component of the glass filler (filler). It is shown that an artificial marble excellent in appearance quality and durability can be obtained by matching with the above.

Patent No. 3559894 JP2004-292698 Japanese Patent No. 3357881

  In the conventional composite materials as described above, it has been difficult to obtain transparent composite materials by using fine particles (fillers) having a constant composition for various resins having different refractive indexes. In order to obtain a transparent composite material, it is necessary to uniformly disperse nano-sized fine particles (filler) in the resin. For this purpose, the affinity with the resin that forms the matrix is generally improved on the surface of the fine particles (filler). It is necessary to perform surface modification treatment. However, the reactivity between the surface modification agent such as silane coupling agent and the fine particles (filler) varies depending on the material of the fine particles (filler). It is required to search for processing conditions separately. Therefore, there has been a demand for the development of fine particles having a constant material and adjustable refractive index obtained by a simple method.

  The present invention can easily control the refractive index of the filler regardless of the type of material, ensures transparency when blended with various resins having different refractive indexes, and is sufficiently transparent. An object is to provide a transparent composite material.

The present invention has been made in view of the above-mentioned problems, and hollow fine particles having a size of 1 nm or more and 300 nm or less are used as the filler of the composite material. ₁ and V ₂ , where the refractive index is n ₁ and n _2, and the refractive index of the transparent material that is the matrix is _nm , so that each satisfies the following formula, the material of the fine particles is constant. However, the inventors have found that a transparent composite material can be obtained, and have reached the present invention.

Difference above the refractive index n _m of transparent material comprising the apparent refractive index of the fine particles nf = a _{(V 1 n 1 + V 2} n 2) / (V 1 + V 2) and the matrix Δn = | n _f -n _m | is 0.05 or less, and can be easily realized by changing the ratio of the size of the hollow portion to the material portion. That is, according to the present invention, regardless of the types of the transparent material and filler constituting the transparent composite material, only the form control of changing the size ratio of the hollow portion to the raw material portion of the filler. The refractive index can be controlled with a transparent material having various different refractive indexes, and the transparency can be ensured based on the refractive index control based on the form control, and the transparency is sufficiently high. It is possible to provide an excellent composite material.

  The “hollow part” means an internal cavity part of the filler, and the “material part” means a meat part that is a substantial part of the filler. 1 is a portion indicated by reference numeral “2” in the filler shown in FIG. 1, and the raw material portion is a portion indicated by reference numeral “1” in the filler shown in FIG.

  As described above, according to the present invention, the refractive index of the filler can be easily controlled regardless of the type of material, and transparency is ensured when blended with various resins having different refractive indexes. In addition, a transparent composite material that is sufficiently excellent in transparency can be provided.

  Hereinafter, other features and advantages of the present invention and details of the present invention will be described based on the best mode for carrying out the invention.

(Transparent composite)
In general, as a means for obtaining a transparent composite material, many methods for approximating the refractive index of a filler and a transparent material (matrix) serving as a matrix are taken. However, when using fillers of micron order or larger, such as glass fiber, the refractive index of the base material and filler should be approximately the same in all wavelengths of visible light to ensure sufficient transparency. And must be practically difficult.

  On the other hand, when nano-sized fine particles (nanoparticles) are used as the filler, the tolerance of the refractive index difference from the base material necessary to ensure sufficient transparency increases. This is because when the particle size is reduced, the scattering of visible light is also reduced. In this respect, it is advantageous to obtain a transparent composite material by using nanoparticles as a filler. The size of the nanoparticles needs to be smaller than 380 nm, which is the minimum wavelength of visible light.

  If a transparent resin is used as the base material to make a transparent resin composite and the mechanical and thermal properties of the composite are to be improved, if the size of the nanoparticles is smaller than 1 nm, the effect of improving the physical properties is poor. Since aggregation control becomes difficult, the particle size is preferably 1 nm or more.

If the difference Δn = | n _f −n _m | between the apparent refractive index n _f of the nanoparticles and the refractive index n _{m of the} base material is larger than 0.05, light scattering at the interface between the two becomes remarkable, and transparency is improved. Since it decreases rapidly, Δn = | n _f −n _m | needs to be 0.05 or less. However, Δn = | n _f −n _m | is more preferably set to 0.03 or less when it is assumed to be applied to a portion that requires higher transparency than that of window glass for automobiles.

  The material type constituting the hollow nanoparticles is not particularly limited, and for example, silica, alumina, hematite, titania, and calcia can be used. In particular, it has good crystallinity, is nano-sized, has a high aspect ratio, and can freely form a hollow part depending on a production method such as the hydrothermal synthesis method shown below. Alumina, which can freely control the ratio, is preferable.

  For example, in the case of boehmite, which is a kind of alumina, it can be obtained by the following hydrothermal synthesis, particles having a hollow part can be easily obtained, and the ratio between the hollow part and the material part can be freely controlled. It is.

(Method for producing hollow boehmite nanoparticles)
<Formation of reaction mixture>
First, an aqueous alkali solution is added to an aqueous aluminum metal salt solution to form an aluminum hydroxide gel-like substance in the resulting reaction mixture.

  Aluminum salts constituting the aluminum metal salt aqueous solution include aluminum chloride anhydrate, aluminum chloride hexahydrate, aluminum bromide, aluminum bromide hexahydrate, aluminum iodide, aluminum nitrate nonahydrate, aluminum lactate At least one aluminum metal salt selected from sodium aluminum sulfate 12 hydrate (sodium alum), aluminum perchlorate nonahydrate, aluminum isopropoxide, aluminum s-butoxide, aluminum t-butoxide, etc. The Aluminum chloride hexahydrate, aluminum nitrate nonahydrate, aluminum bromide hexahydrate, sodium aluminum sulfate 12 water, among the above listed, easy to obtain in the market, easy to handle, and inexpensive Japanese (sodium alum) and aluminum isopropoxide are preferred.

  Alkaline aqueous solution is added to the reaction system in order to promote hydrolysis of the aluminum metal salt. Examples of the alkali compound constituting it include sodium hydroxide, potassium hydroxide, calcium hydroxide, and barium hydroxide. At least one selected from can be exemplified. In particular, sodium hydroxide is preferable.

  In addition, the alkali which produces | generates a salt insoluble in water as a by-product in a reaction mixture is removed suitably. It is preferable that the usage-amount of an alkali compound is 2-4 times by molar ratio with respect to aluminum metal salt. If it is less than 2 times, the reaction raw material is insufficient for heat treatment to produce a reaction product, the reaction solution does not gel, and particles may not be obtained with good yield. On the other hand, if it is 4 times or more, the pH is too high, and the alkali dissolves the gel, which may increase adhesion and aggregation particles.

  The concentration of the aluminum metal salt aqueous solution is preferably 1.0M-3.0M, and the concentration of the alkaline aqueous solution is preferably 4.0M-10.0M. This makes it possible to easily realize the formation of a gel-like substance in the reaction mixture of the aluminum metal salt aqueous solution and the alkaline aqueous solution. The concentration of the metal salt in the aluminum metal salt aqueous solution is preferably 1.0M to 3.0M as described above, but the concentration of each aluminum metal salt solubility upper limit is more preferable in terms of productivity.

  It is preferable that the capacity | capacitance of aluminum metal salt aqueous solution and alkaline aqueous solution is equal, or there are few alkaline aqueous solutions. This is because when the concentration of the aqueous alkali solution is thin and the amount of the solution is too large, gelation becomes difficult. If the concentration of the aluminum metal salt and the capacity of the aluminum metal salt and the alkaline aqueous solution are fixed, the subsequent form control only needs to change the concentration of the alkaline aqueous solution. More preferably, the capacities are equal.

  By passing through the above steps, the gel substance can be produced in the reaction mixture. As a result, in the growth process of boehmite particles by the heat treatment shown below, the boehmite particles in the growth process were fixed in the gel substance, and the adhesion and aggregation between the particles were suppressed, and the particle size distribution width was narrowed. Nano-sized boehmite particles can be obtained.

<Heat treatment>
Next, after generating the above-described reaction mixture containing the gel substance, the first heat treatment to the fourth heat treatment are sequentially performed. In addition, since the following heat processing is performed in the state in which the boehmite particle in the growth process was fixed in the gel-like substance, a very narrow particle size distribution width (standard deviation) can be realized.

  The first heat treatment is performed by heating the reaction mixture to a first temperature not lower than room temperature. The first heat treatment is mainly for accelerating the hydrolysis of the alkali metal salt generated in the reaction mixture and promoting the formation of a gel-like substance in the reaction mixture. The temperature is preferably from room temperature (25 ° C.) to 140 ° C., but considering the reaction time, it is preferably 120 ° C. to 140 ° C. When the first heat treatment is performed at a temperature exceeding 140 ° C., boehmite particles having irregular lengths are generated, and the particle size distribution width (standard deviation) of the boehmite particles cannot be reduced even if the subsequent heat treatment is performed. There is a case. The heat treatment time is preferably 24 or more, and if it is less than 24 hours, the effect of reducing the standard deviation is not observed.

  After the first heat treatment, a second heat treatment is performed. This second heat treatment is mainly performed to obtain boehmite particles having a high aspect ratio. The second heat treatment requires the reaction mixture to be performed at a temperature higher than the temperature of the first heat treatment. Specifically, the second heat treatment can be performed at a temperature of 140 ° C to 250 ° C. It is preferable that it is 250 degreeC. If it is less than 140 ° C., not only will it take time to produce particles, but also the standard deviation of the particle size distribution will increase. At 250 ° C or higher, it is advantageous to produce particles with a small aspect ratio, but the heat resistance and pressure-resistant containers of commercial ordinary grade autoclaves will reach the limit at 250 ° C, and a large amount of energy is required for 250 ° C Since it is required, the temperature is preferably 250 ° C or lower.

  The time in the second heat treatment depends on the absolute value of the set temperature, but is preferably within 10 to 30 minutes including the temperature rising stage. The heating exceeding the specified time not only significantly deteriorates the standard deviation of the particle size distribution, but also the needle-like particles become spindle-shaped and the plate-like particles become granular, leading to a loss of aspect ratio.

  After the second heat treatment, a third heat treatment is performed. This third heat treatment is mainly performed in order to narrow the particle size distribution width (standard deviation) of the boehmite particles. In the third heat treatment, the treatment is preferably performed at a temperature lower than that of the second heat treatment, and is set to 130 ° C. or lower, more preferably to room temperature or lower. The cooling from the temperature of the second heat treatment is preferably performed as quickly as possible, for example, by placing the container in which the heat treatment is performed in running water. Specifically, it is preferably within 10 minutes. The heat treatment time at this stage is preferably 10 minutes or more including the time required for the cooling. This makes it possible to further narrow the particle size distribution width (standard deviation) of the target boehmite particles.

  After the third heat treatment, a fourth heat treatment is performed. This fourth heat treatment mainly grows the high aspect ratio boehmite particles. It is necessary to set the temperature in the temperature range of 100 ° C to 180 ° C. When the temperature is higher than 180 ° C., not only the particle size distribution width is expanded and the standard deviation is deteriorated, but also the acicular particles become spindle-shaped, the plate-like particles become granular, and the aspect ratio may be lost. Specifically, in the fourth heat treatment, if the heat treatment is performed at a temperature of 180 ° C. or higher, the generated particles are re-dissolved and recrystallized (Ostwald ripening), and the particle shape and particle size distribution width become uncontrollable In some cases, the particle size distribution width may be deteriorated. Moreover, a yield may deteriorate that temperature is less than 100 degreeC. The processing time is 4 hours to 1 week, and the heating time varies depending on the set temperature.

  After said heat processing, the container containing the said reaction product is stood to cool, and the boehmite particle | grains and solution which were produced | generated using the centrifuge are isolate | separated. Then, to remove by-product salts, centrifugal washing with sodium nitrate aqueous solution (0.5M) (3 times), centrifugal water washing (1 time), water methanol mixed solution (volume ratio water: methanol = 0.5: 9.5) After performing centrifugal washing once, drying is performed to evaporate methanol, and then dispersed in water to obtain a target boehmite nanoparticle dispersion.

  By performing the four-stage heat treatment as described above, boehmite particles having a minor axis length of 1 to 10 nm, a major axis length of 20 to 400 nm, and an aspect ratio of 5 to 80 can be obtained. In addition, the standard deviation of these dimensional characteristic values can be suppressed to within 10%. Therefore, when the boehmite particles are contained in a predetermined resin to produce a resin composition, variations in physical properties can be reduced, and an article with stable quality can be made from the resin composition.

  The boehmite particles obtained as described above were embedded in an epoxy resin and the section was observed with a transmission electron microscope. As a result, it was confirmed that the boehmite particles were hollow needle-like particles as shown in Photo 1.

  The minor axis length of the boehmite particles can be controlled by changing the set values of the temperature and time of the fourth heat treatment described above. Also, the boehmite particles obtained by the above-mentioned process are mixed again in the raw material aluminum metal salt aqueous solution, and further added with an alkaline aqueous solution to create a dispersion of boehmite particles in the gel substance of aluminum hydroxide. Then, when the first to fourth heat treatment steps described above are performed, boehmite newly grows around the added boehmite nanoparticles, and the short axis length can be increased. In addition, even if such a process is taken, the boehmite particles maintain a hollow structure, and there is hardly any change in the size of the hollow part. By these methods, the ratio of the hollow part and the raw material part of boehmite nanoparticles can be controlled.

  According to the boehmite particles obtained as described above, the size of the hollow portion can be freely controlled, so that the apparent refractive index can be controlled. Therefore, even when blended into transparent materials having various refractive indexes by the refractive index control, the refractive index difference from the transparent material can be 0.05 or less as described above, and sufficient transparency is ensured. A transparent composite material can be obtained.

(Transparent composite manufacturing method)
Next, the manufacturing method of the said transparent composite material is demonstrated. Examples of the method for producing the transparent composite material include the following three methods.

  As a first production method, the hollow needle-like inorganic nanoparticles are dispersed and mixed in an organic solvent together with a dispersant to prepare a nanoparticle dispersion, and then the dispersion and a separately prepared transparent material are mixed and melted. The desired transparent composite material is obtained by kneading. As the kneader, a twin-screw extruder, a vacuum micro-kneader extruder, a lab plast mill, or the like can be used, which is selected and determined according to the type of the nanoparticles and the type of solvent being dispersed.

  As a second production method, the nanoparticle dispersion liquid and an organic solvent containing a resin are mixed and stirred, and only the solvent is quickly distilled off under high temperature and reduced pressure, whereby the nanoparticles are uniformly dispersed. A transparent composite material is obtained. Stirring is continued until the viscosity of the solution increases as the solvent decreases, but stirring is no longer possible. Accordingly, the nanoparticles in the transparent composite material can be more uniformly dispersed without agglomeration.

  As a third production method, the nanoparticle dispersion liquid and a transparent monomer are mixed, and then the monomer is polymerized to obtain a target transparent composite material. Also in this method, the nanoparticles in the transparent composite material can be more uniformly dispersed without agglomeration.

  In particular, hollow needle-like inorganic nanoparticles such as boehmite particles exhibit hydrophilicity because they have many hydroxyl groups on the surface. Therefore, it is generally difficult to uniformly disperse in transparent resins such as methacrylic resins, polycarbonate resins, styrene resins, and epoxy resins, which have strong hydrophobic properties. Therefore, in order to disperse in these transparent resins, the surface of the nanoparticles is modified with a silane coupling agent, an organophosphate dispersant, etc., and further dispersed in an organic solvent which is a good solvent for the transparent resin It is better to add it to the transparent resin.

  In addition, as a method for obtaining the above nanoparticle dispersion liquid, a solvent replacement method using a difference in boiling point between water and an organic solvent can be used. However, a dry powder is obtained by freeze-drying the aqueous dispersion liquid of hollow needle-like inorganic nanoparticles. Thereafter, a method of adding a dry powder, an organic phosphate ester dispersant, and the like to the organic solvent and mixing and stirring is easier. In this case, in order to obtain a more uniform dispersion state, a method of applying ultrasonic waves to the nanoparticle dispersion is effective.

Example 1
Place aluminum chloride hexahydrate (2.0M, 40ml, 25 ° C) in a Teflon beaker equipped with a mechanical stirrer, and maintain sodium hydroxide (700rpm) while maintaining at 10 ° C in a constant temperature bath. 5.10M, 40ml, 25 ° C) was added dropwise over about 6 minutes. Stirring was continued for another 10 minutes after the completion of dropping, and the pH of the solution was measured after the stirring was finished (pH = 7.08). The solution was replaced with an autoclave equipped with a Teflon liner, sealed, and aged in an oven at 120 ° C. for 24 hours (first heat treatment). After completion of the first heat treatment, the autoclave was transferred to an oil bath and heated at 180 ° C. for 30 minutes (second heat treatment).

  After completion of the second heat treatment, the autoclave was put into running water and rapidly cooled (about 10 ° C.) (third heat treatment). After completion of the third heat treatment, the autoclave was again placed in an oven and heated at 160 ° C. for 1 day (fourth heat treatment). Thereafter, the autoclave was cooled with running water, and the supernatant was removed by centrifugation (30000 rpm, 30 min), followed by centrifugal water washing 3 times and water methanol mixed solution (volume ratio water: methanol, 0.5: 9.5) centrifugal washing once. Then, colorless crystals were obtained by drying using a freeze dryer.

When the size of the particles was examined using a transmission electron microscope (TEM), it was acicular particles having a minor axis length (diameter) a = 6 nm, and the size of the hollow portion was b = 2 nm. Therefore, the volume ratio of the fine particle material portion to the hollow portion was V ₁ : V ₂ = 0.889: 0.111. As a result of analyzing the particles with an X-ray diffraction apparatus (XRD), it was confirmed that the particles had a boehmite structure. Further, the refractive index n _{f of the} particles was 1.58 when examined by the immersion method.

  The boehmite particles obtained as described above (3.3 g) were placed in about 100 g of THF and stirred well, and then subjected to an ultrasonic disperser for 40 minutes. After adding 0.1 g of hebutoxyethyl acid phosphate (product name JP-506H, manufactured by Johoku Chemical Industry Co., Ltd.) and stirring well, the dispersion of boehmite particles stably dispersed in THF was put on an ultrasonic disperser for 60 minutes. I was able to get it.

In a reaction vessel equipped with a decompressor, mechanical stirrer, and reflux, the above boehmite particle dispersion solution (Boehmite 10.2 wt%), 130 g, polycarbonate resin (Mitsubishi Engineering Plastics, trade name Novalex 7030A, refractive index n _m = 1.58) ) 115 g, dichloromethane was added as an additional solvent and stirred. Next, THF was removed as the solvent by gradually reducing the pressure in the system using a vacuum line, and then the temperature was further raised to completely remove the solvent to obtain a polycarbonate resin composition. The obtained resin composition was dried and then subjected to hot press molding to obtain a test piece (2 mm thick) for optical property evaluation.

When the haze value of this test piece with respect to the standard light A was measured with a haze meter (HM-65 manufactured by Murakami Color Research Laboratory), as shown in Table 1, it showed an extremely excellent transparency of 1%. In this case, the difference in refractive index between the matrix resin and the nanoparticles was Δ _n = 0.00.

(Example 2)
A boehmite particle and a resin composition in which it was dispersed in a polycarbonate resin were obtained in the same manner as in Example 1 except that the fourth heat treatment temperature was 140 ° C. The results of measuring these physical properties in the same manner as in Example 1 are as shown in Table 1. The haze value was 6%, indicating good transparency. In this case, the refractive index difference Δn = 0.03 between the matrix resin and the nanoparticles.

(Example 3)
A boehmite particle and a resin composition in which it was dispersed in a polycarbonate resin were obtained in the same manner as in Example 1 except that the fourth heat treatment temperature was 180 ° C. The results of measuring these physical properties in the same manner as in Example 1 are as shown in Table 1, and the haze value was 12%, indicating a relatively good transparency such that a fluoroscopic image could be confirmed. In this case, the refractive index difference Δn = 0.05 between the matrix resin and the nanoparticles.

Example 4
Boehmite particles were obtained in the same manner as in Example 1 except that the fourth heat treatment temperature was 110 ° C. Under an inert gas stream, 500 ml of the solvent THF, 80 g of methyl methacrylate, 25 g of acrylic acid and 0.5 mol% of the polymerization initiator AIBIN were added to the flask, and the solution was heated to 80 ° C. 105 g of boehmite particle dispersion (boehmite 10.2 wt%) was added, and the temperature of 80 ° C. was kept while stirring for 18 hours. After completion of the reaction, the temperature was returned to room temperature, and excess n-hexane was added to precipitate the polymer, followed by filtration to obtain a methacrylic acid resin composition. The obtained resin composition was dried to form a powder, which was subjected to overheat press molding to obtain a test piece (2 mm thick) for optical property evaluation.

Incidentally, made by same operation that was not added boehmite particle dispersion in the above operation was n _m = 1.49 Examination of refractive index with an Abbe refractometer.

  The results of measuring the material properties in the same manner as in Example 1 are as shown in Table 1, and the haze value was 1%, indicating extremely excellent transparency. In this case, the difference in refractive index between the matrix resin and the nanoparticles was Δn = 0.00.

(Comparative Example 1)
A polycarbonate resin composition was obtained in the same manner as in Example 1 except that the boehmite nanoparticle dispersion to be added was changed to that obtained in Example 4.

  The results of measuring the physical properties of the materials in the same manner as in Example 1 are as shown in Table 1. The haze value was 27%, which was considerably inferior in transparency. In this case, the refractive index difference Δn = 0.09 between the matrix resin and the nanoparticles.

(Comparative Example 2)
Except that the fourth heat treatment temperature was 200 ° C., boehmite particles and a resin composition in which the boehmite particles were dispersed in a polycarbonate resin were obtained in the same manner as in Example 1. The results of measuring these physical properties in the same manner as in Example 1 are as shown in Table 1. The haze value was 22%, which was considerably inferior in transparency. In this case, the refractive index difference Δn = 0.06 between the matrix resin and the nanoparticles.

(Comparative Example 3)
An acrylic resin composition was obtained in the same manner as in Example 4 except that the boehmite particle dispersion used in Example 2 was used. The results of measuring these physical properties in the same manner as in Example 1 are shown in Table 1. The haze value was 23%, which was considerably inferior in transparency. In this case, the refractive index difference Δn = 0.06 between the matrix resin and the nanoparticles.

  The present invention has been described in detail above with reference to specific examples. However, the present invention is not limited to the above contents, and various modifications and changes can be made without departing from the scope of the present invention.

  For example, the resin composition of the present invention contains an antioxidant and a heat stabilizer (including hindered phenols, hydroquinones, thioethers, phosphites, and their substitution products and combinations thereof), ultraviolet absorption, if necessary. Agents (for example, resorcinol, salicylate, benzotriazole, benzophenone, etc.), lubricants, mold release agents (for example, silicon resin, montanic acid and salts thereof, stearic acid and salts thereof, stearyl alcohol, stearylamide, etc.), dyes (for example, nitrocin) , Coloring agents containing facials (for example, cadmium sulfide, phthalocyanine, etc.), additive additives (for example, silicon oil), crystal nucleating agents (for example, talc, kaolin, etc.), etc. can be added alone or in appropriate combination. .

  Specifically, in order to improve thermal stability, partially acrylated polyphenols represented by hindered phenols such as Irganox 1010 and 1076 (manufactured by Ciba-Geigy), Sumilizer GS, and GM (manufactured by Sumitomo Chemical Co., Ltd.) An appropriate amount of a heat stabilizer such as a phosphorus compound typified by phosphites such as Irgafos 168 (manufactured by Ciba Geigy) may be added.

It is a figure which shows one structural aspect of the filler in the transparent composite material of this invention. It is a TEM photograph which shows one structural aspect of the filler in the transparent composite material of this invention.

Explanation of symbols

a Outside diameter of boehmite nanoparticles
b Hollow part diameter of boehmite nanoparticles
1 Material part of boehmite nanoparticles
2 Hollow part of boehmite nanoparticles
n ₁ Boehmite nanoparticle material refractive index
n ₂ Boehmite nanoparticles hollow refractive index
Volume fraction of material part of V ₁ boehmite nanoparticles
Volume fraction of hollow part of V ₂ boehmite nanoparticles

Claims (8)

In a composite material in which a hollow filler is added to a transparent material, the size of the filler is 1 nm or more and 380 nm or less, and the volume of the material part and the hollow part of the filler is V ₁ , V ₂ , refractive index N ₁ and n _2, and the refractive index of the transparent material is _nm , each of which satisfies the following formula.
  2. The transparent composite material according to item 1, wherein the filler is hollow needle-like inorganic nanoparticles, and the transparent material is a resin transparent material.   The transparent composite material according to claim 1, wherein the hollow needle-like inorganic nanoparticles are alumina.   The transparent composite material according to claim 3, wherein the hollow needle-shaped inorganic nanoparticles are boehmite.   The transparent composite material according to claim 3 or 4, wherein the alumina is obtained by hydrothermal synthesis. A method for producing a transparent composite material according to any one of claims 1 to 5,
A step of producing a nanoparticle dispersion by dispersing and mixing the hollow needle-like inorganic nanoparticles in an organic solvent together with a dispersant;
A method for producing a transparent composite material, wherein the transparent composite material is produced by melt-kneading the transparent material and the nanoparticle dispersion. A method for producing a transparent composite material according to any one of claims 1 to 5,
A step of producing a nanoparticle dispersion by dispersing and mixing the hollow needle-like inorganic nanoparticles in an organic solvent together with a dispersant;
A step of dispersing and mixing the transparent material in an organic solvent to produce a transparent material dispersion;
A step of obtaining the transparent composite material by mixing the nanoparticle dispersion and the transparent material dispersion and distilling off the solvent;
A method for producing a transparent composite material, comprising: A method for producing a transparent composite material according to any one of claims 1 to 5,
A step of producing a nanoparticle dispersion by dispersing and mixing the hollow needle-like inorganic nanoparticles in an organic solvent together with a dispersant;
The step of obtaining the transparent composite material by blending the nanoparticle dispersion liquid with respect to the monomer of the transparent material and advancing polymerization;
A method for producing a transparent composite material, comprising: