JP2011042748A - Nanoparticle dispersed liquid crystal, method for producing the same and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nanoparticle dispersed liquid crystal that is simply produced and a method for producing the same. <P>SOLUTION: The nanoparticle dispersed liquid crystal is obtained by dispersing a nanoparticle that is not treated (chemically modified) to improve compatibility with a liquid crystal material into a liquid crystal material. Since liquid crystal molecules are physically adsorbed on the surfaces of nanoparticles, the nanoparticles are not aggregated each other. The nanoparticle dispersed liquid crystal is extremely simply produced by physical vapor deposition such as sputtering vapor deposition, etc. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a nanoparticle-dispersed liquid crystal and a method for producing the same, and a liquid crystal display device, in particular, a nanoparticle-dispersed liquid crystal in which nanoparticles not subjected to chemical modification are dispersed, a simple method for producing a nanoparticle-dispersed liquid crystal, The present invention relates to a liquid crystal display device including such a nanoparticle-dispersed liquid crystal.

  One approach for realizing high-speed, high-definition, and high-performance liquid crystal displays is to disperse nanoparticles in liquid crystals. Liquid crystals in which nanoparticles are dispersed (nanoparticle-dispersed liquid crystals) are known to have improved response characteristics to electric fields such as an increase in switching speed and a decrease in drive threshold voltage due to an increase in birefringence and dielectric anisotropy. (Non-Patent Documents 1 and 2). However, since the nanoparticles and the liquid crystal are difficult to mix, the nanoparticles tend to aggregate. Therefore, in order to disperse the nanoparticles in the liquid crystal, the compatibility between the liquid crystal and the nanoparticles is a very important parameter.

  Therefore, in order to improve the compatibility between the liquid crystal and the nanoparticles, an appropriate modifying group (such as a mesogenic group) is chemically synthesized on the surface of the nanoparticles. Thereby, the nanoparticles are easily dispersed in the liquid crystal.

  For example, in Patent Document 1, liquid crystal compatible particles in which liquid crystal molecules are formed on the surfaces (surroundings) of nanoparticles are manufactured. Specifically, the liquid crystal compatible particles are formed by reducing metal ions in a solution containing liquid crystal molecules and bonding the liquid crystal molecules to the nanoparticle surface. In the liquid crystal compatible particles formed in this way, since the liquid crystal molecules are chemically bonded to the surfaces of the nanoparticles, the surfaces of the nanoparticles are protected by the liquid crystal molecules. Therefore, the liquid crystal compatible particles are well dispersed in the liquid crystal layer. That is, the nanoparticles are well dispersed in the liquid crystal layer.

  On the other hand, Patent Document 2 discloses a method for producing nanoparticles in an ionic liquid exhibiting special properties. Specifically, nanoparticles are formed in the ionic liquid by sputtering deposition of a target material that is a nanoparticle precursor by sputtering.

  Patent Document 2 also discloses that the particle diameters of the nanoparticles obtained differ depending on the type of ionic liquid used. Specifically, when an imidazolium-based compound having high hydrophilicity is used as the ionic liquid, the particle size of the obtained nanoparticles becomes larger than when an aliphatic compound having high hydrophobicity is used.

  Non-Patent Document 3 discloses a method of dispersing nanoparticles in organic oil by a sputtering method. Specifically, first, a liquid thin film is formed on the surface of the rotating drum by rotating the rotating drum and causing the organic oil in the container to adhere to the surface of the rotating drum. Next, the nanoparticles formed in the chamber are attached to the liquid thin film. The liquid thin film to which the nanoparticles are attached is returned to the container again by the rotation of the rotating drum. By repeating such treatment, the nanoparticles are gradually dispersed in the organic oil in the container.

JP 2004-347618 A (released on December 9, 2004) JP 2007-231306 A (published September 13, 2007)

H. Qi and T. Hegmann. J. Mater. Chem. 18, 3288 (2008). T. Miyama et al., Jpn. J. Appl. Phys., 43, 2580 (2004). M. Wagener and B. Gunther, Progr. Colloid Polym. Sci., 111, 78-81 (1998). S. Kobayashi, T. Miyama, N. Nishida, Y. Sakai, H. Shiraki, Y. Shiraishi and N. Toshima. Journal of Display Technology., 2, 121 (2006).

  However, the method of Patent Document 1 has a problem that a very complicated synthesis process is required to synthesize liquid crystal compatible particles. On the other hand, the methods of Patent Document 2 and Non-Patent Document 3 are not methods of dispersing nanoparticles in liquid crystals.

  Specifically, in Patent Document 1, nanoparticles are dispersed in a liquid crystal only after an appropriate modifying group is imparted to the surface of the nanoparticles. For this reason, in order to disperse nanoparticles in the liquid crystal, chemical synthesis of liquid crystal compatible particles is indispensable. That is, chemical modification (surface modification) for improving the compatibility with the liquid crystal is necessary on the surface of the nanoparticles.

  However, in order to form liquid crystal compatible particles subjected to such chemical modification, it is necessary to study a synthetic route for forming an appropriate modifying group. Moreover, since the liquid crystal compatible particles are chemically synthesized in the solution, it is necessary to remove by-products (such as salts and decomposition products) present in the reaction solution. Therefore, the production of liquid crystal compatible particles requires a very complicated synthesis process. Further, the purity of the synthesized liquid crystal compatible particles is also lowered. Furthermore, even if the synthesis route is established, it is not clear whether the chemically modified nanoparticles (liquid crystal compatible particles) actually have a function of dispersing in the liquid crystal, and the nanoparticles may aggregate. For example, metal nanoparticles having an alkyl group are aggregated without being dispersed in the liquid crystal.

  Thus, the method of Patent Document 1 has a problem in throughput because the manufacturing process is inefficient. In addition, the purity of the synthesized liquid crystal compatible particles is low and the application range is very limited.

  On the other hand, the method of Patent Document 2 merely discloses a method for producing nanoparticles utilizing the special characteristics of an ionic liquid, and there is no description suggesting application to dispersing nanoparticles in liquid crystals. . Specifically, Patent Document 2 discloses a novel method for producing nanoparticles by paying attention to the unique properties of ionic liquids. For this reason, in patent document 2, "ionic liquid" is indispensable.

  However, since a material having liquid crystallinity is generally not an ionic liquid, the ionic liquid and the liquid crystal do not mix well. For this reason, the method of patent document 2 is not suitable for disperse | distributing a nanoparticle in a liquid crystal.

  Moreover, as described in Patent Document 2, the “ionic liquid” is a series of compounds that are liquid at room temperature, regardless of a salt composed only of cations and anions. Further, the “ionic liquid” is stable at high temperature, has a wide liquid temperature range, a vapor pressure is substantially zero, and has ionic properties such as low viscosity and high oxidation / reduction resistance.

  In contrast, “liquid crystal” is a state (phase) of an intermediate substance between a solid and a liquid, and is found in molecules having a rod-like or disk-like shape, and is not dependent on the ionic nature of the molecule. “Liquid crystal” has a finite vapor pressure (sub Pa at room temperature) and develops a liquid crystal phase at a specific temperature or concentration. It has physical properties such as dielectric constant, refractive index, conductivity, and viscosity. Has anisotropy.

  As described above, the “ionic liquid” in Patent Document 2 refers to a special liquid composed of ions, and is completely different from “liquid crystal” in constituent molecules and physical properties. Therefore, “ionic liquid”, which is an essential component in Patent Document 2, cannot be replaced with “liquid crystal”.

  Moreover, since patent document 2 is a manufacturing method of a nanoparticle to the last, the manufactured nanoparticle is collect | recovered from an ionic liquid. That is, Patent Document 2 does not intend to use the nanoparticles in the ionic liquid as they are, in other words, to disperse the nanoparticles in the ionic liquid without removing the ionic liquid.

  On the other hand, the method of Non-Patent Document 3 only discloses a method for retaining nanoparticles in organic oil, and is applied to the dispersion of nanoparticles in volatile liquid crystal or the application of nanoparticle-dispersed liquid crystals. There is no mention that suggests.

  In Non-Patent Document 3, organic oil in a container is scooped up by a rotating drum, and a liquid thin film is formed on the surface of the rotating drum. Then, in order to disperse the nanoparticles in the formed liquid thin film, the process of adhering nanoparticles having a finite size formed by aggregation in the chamber (in the air) is repeated. For this reason, if the nanoparticles grow too much in the air, it becomes extremely difficult to uniformly disperse the nanoparticles in the liquid, and it is necessary to add a surfactant or the like. However, adding impurities that have no affinity for the liquid crystal such as surfactants leads to deterioration of the liquid crystal properties of the material. It is not preferable to apply the method of Document 3 to liquid crystals. Furthermore, in the method of Non-Patent Document 3, a special rotating drum that is not used in the usual sputtering method is indispensable, and it cannot be said that it is simple and versatility is poor. Furthermore, it takes a lot of time to disperse the nanoparticles in the organic oil.

  The present invention has been made in view of the above-mentioned problems, and the object thereof is a nanoparticle-dispersed liquid crystal in which nanoparticles that are not chemically modified are dispersed in a liquid crystal material, and the nanoparticle-dispersed liquid crystal. An object of the present invention is to provide a simple manufacturing method and a liquid crystal display device including the nanoparticle-dispersed liquid crystal.

  As a result of intensive studies, the present inventors have found that nanoparticles can be dispersed in a liquid crystal material by a physical vapor deposition rather than a chemical method as in the past, and the present invention has been completed.

  That is, the method for producing a nanoparticle-dispersed liquid crystal according to the present invention is characterized in that nanoparticles formed from a target material by physical vapor deposition are dispersed in a liquid crystal material in order to solve the above problems.

  When nanoparticles are added to the liquid crystal material, properties such as switching speed, refractive index anisotropy and dielectric anisotropy are improved. However, since the liquid crystal material and the nanoparticles are not easily mixed, the nanoparticles are easily aggregated simply by adding the nanoparticles to the liquid crystal material.

  Therefore, conventionally, the nanoparticles are dispersed in the liquid crystal material by chemically modifying an appropriate modifying group on the surface of the nanoparticles. However, in this case, it is necessary to consider a synthetic route for forming chemically modified nanoparticles. Even if a synthetic route is established, it is unclear whether chemically modified nanoparticles will actually function when added to a liquid crystal material. In addition, depending on the nanoparticles, the nanoparticles may aggregate. That is, the method of chemically modifying the nanoparticle surface has a limited application range and an inefficient manufacturing process.

  On the other hand, according to the above invention, atoms or molecules released from the target material by physical vapor deposition reach the liquid crystal material. The reached atoms or molecules of the target material enter and gather into the liquid crystal material having fluidity. As a result, the atoms or molecules grow in the liquid crystal material and nanoparticles are formed.

  On the other hand, liquid crystal molecules are physically adsorbed on the surface (surroundings) of the grown nanoparticles. For this reason, when the nanoparticle surface is covered to some extent by liquid crystal molecules, the growth of the nanoparticles stops. Furthermore, since the nanoparticle surface is covered with liquid crystal molecules, aggregation of the nanoparticles can be prevented. Accordingly, the nanoparticles can be dispersed in the liquid crystal material without aggregation of the nanoparticles.

  Thus, according to said invention, a nanoparticle is directly formed from a target material by physical vapor deposition. For this reason, it is not necessary to chemically synthesize nanoparticles whose surface is chemically modified as in the prior art, and it is not necessary to remove by-products. Moreover, since the liquid crystal molecules are physically adsorbed on the surface of the nanoparticles, the nanoparticles do not aggregate. Therefore, a nanoparticle-dispersed liquid crystal in which high-purity nanoparticles are dispersed can be easily produced while suppressing aggregation of the nanoparticles without performing chemical modification.

  In the method for producing a nanoparticle-dispersed liquid crystal of the present invention, the physical vapor deposition is preferably sputter vapor deposition.

  According to the above invention, the nanoparticle-dispersed liquid crystal is manufactured by sputter deposition that does not require high temperature and high vacuum (high decompression). Sputter deposition does not require a crucible required for other physical vapor deposition. Thereby, high-purity nanoparticles can be formed in a short sputtering time while preventing thermal decomposition and evaporation of the liquid crystal material. Therefore, the manufacturing time of the nanoparticle-dispersed liquid crystal can be shortened.

  In the method for producing a nanoparticle-dispersed liquid crystal according to the present invention, it is preferable that atoms or molecules emitted from the target material are aggregated in the liquid crystal material to form nanoparticles.

  According to the above invention, nanoparticles are formed in the liquid crystal material. That is, atoms or molecules emitted from the target material do not aggregate before entering the liquid crystal material. Thereby, aggregation of a nanoparticle can be prevented more reliably. Therefore, a nanoparticle-dispersed liquid crystal in which higher-purity nanoparticles are dispersed can be produced.

  In the method for producing a nanoparticle-dispersed liquid crystal according to the present invention, the physical vapor deposition may be performed by bringing the target material and the liquid crystal material close to each other.

  According to the above invention, the target material and the liquid crystal material are close to each other. Thereby, atoms or molecules emitted from the target material can be prevented from aggregating before entering the liquid crystal material. Therefore, a nanoparticle-dispersed liquid crystal in which higher-purity nanoparticles are dispersed can be produced in a short time.

  In the method for producing a nanoparticle-dispersed liquid crystal of the present invention, the physical vapor deposition may be performed in a state where the liquid crystal material is allowed to stand.

  According to said invention, physical vapor deposition is performed in the state which left liquid crystal material still. For this reason, the special rotation roller used by the nonpatent literature 1 is not required. Thereby, a nanoparticle dispersion liquid crystal can be manufactured, without improving vapor deposition apparatuses, such as a sputtering device. Further, it is not necessary to form a liquid thin film on the rotating roller to disperse the nanoparticles. Therefore, a nanoparticle-dispersed liquid crystal can be produced in a shorter time.

  In the method for producing a nanoparticle-dispersed liquid crystal of the present invention, the liquid crystal material preferably exhibits a frustrated phase.

  According to the above invention, a nanoparticle-dispersed liquid crystal in which nanoparticles are dispersed in a liquid crystal material exhibiting a frustrated phase is produced. Moreover, the manufactured nanoparticle-dispersed liquid crystal exhibits a remarkable effect that the temperature range in which the liquid crystal phase (frustrated phase) is expressed is expanded. Therefore, it is possible to produce a nanoparticle-dispersed liquid crystal that overcomes the greatest drawback of the frustrated phase (particularly the blue phase).

  That is, the method for producing a nanoparticle-dispersed liquid crystal of the present invention can be used as a method for expanding the expression temperature range of a liquid crystal material exhibiting a frustrated phase (particularly a blue phase). That is, the method for expanding the expression temperature range of the liquid crystal material exhibiting the frustrated phase (especially the blue phase) is a method of converting the nanoparticles formed from the target material by physical vapor deposition into the liquid crystal material exhibiting the frustrated phase (particularly the blue phase). It is characterized by being dispersed in.

  In order to solve the above problems, the nanoparticle-dispersed liquid crystal of the present invention is characterized in that nanoparticles that have not been subjected to a treatment for improving compatibility with the liquid crystal material are dispersed in the liquid crystal material. .

  According to the above invention, nanoparticles that have not been subjected to a treatment (chemical modification) for improving compatibility with the liquid crystal material are dispersed in the liquid crystal material. For this reason, there is no need to chemically synthesize chemically modified nanoparticles. Therefore, a nanoparticle-dispersed liquid crystal that can be easily produced can be realized.

  In the nanoparticle-dispersed liquid crystal of the present invention, the liquid crystal molecules constituting the liquid crystal material are preferably physically adsorbed on the surface of the nanoparticles.

  According to the above invention, the liquid crystal molecules constituting the liquid crystal material are physically adsorbed on the surfaces of the nanoparticles, and are not chemically bonded (chemically adsorbed) as in the prior art (Patent Document 1). Thereby, even if the nanoparticle surface is not chemically modified, aggregation of the nanoparticles can be prevented. Therefore, it is possible to realize a nanoparticle-dispersed liquid crystal in which nanoparticles are dispersed in a liquid crystal material without aggregation.

  In the nanoparticle-dispersed liquid crystal of the present invention, the liquid crystal material preferably exhibits a frustrated phase.

  According to the above invention, the nanoparticles are dispersed in the liquid crystal material exhibiting the frustrated phase. Moreover, this nanoparticle-dispersed liquid crystal exhibits a remarkable effect that the temperature range in which the liquid crystal phase (frustrated phase) is expressed is expanded. Therefore, it is possible to realize a nanoparticle-dispersed liquid crystal that overcomes the greatest drawback of the frustrated phase (particularly the blue phase).

  In order to solve the above problems, a liquid crystal display device of the present invention is characterized by including a liquid crystal layer containing any one of the above-described nanoparticle-dispersed liquid crystals.

  According to the above invention, since the liquid crystal display device includes the liquid crystal layer including the nanoparticle-dispersed liquid crystal, the liquid crystal display device can be increased in speed, definition, and function.

  As described above, in the method for producing a nanoparticle-dispersed liquid crystal of the present invention, nanoparticles formed from a target material by physical vapor deposition are dispersed in a liquid crystal material. In the nanoparticle-dispersed liquid crystal of the present invention, nanoparticles that have not been subjected to a treatment for improving the compatibility with the liquid crystal material are dispersed in the liquid crystal material. Therefore, there is an effect that the nanoparticle-dispersed liquid crystal can be easily produced by dispersing the nanoparticles without chemical modification.

Figure 5 is the disappearance spectrum of pure 4-pentyl-4-cyanobiphenyl (5CB) and gold deposited 5CB. FIG. 5 is a diagram showing a polarization microscope image showing the phase transition behavior of pure 5CB and gold-deposited 5CB, where (a) is a pure 5CB diagram and (b) is a gold-deposited 5CB diagram. It is a graph which shows the frequency dependence of the dielectric constant of pure 5CB and gold-deposited 5CB, (a) is a dielectric constant of a short-axis direction, (b) is a dielectric constant of a long-axis direction. It is a figure which shows the transmission electron microscope image of 5CB which carried out gold vapor deposition. It is a figure which shows the pure mixed nematic liquid crystal (E47) and the mixed nematic liquid crystal (E47) which carried out gold vapor deposition. It is a figure which shows the transmission electron microscope image of the mixed-type nematic liquid crystal (E47) vapor-deposited. It is a figure which shows the applied frequency dependence of the drive threshold voltage of TN liquid crystal cell using the mixed-type nematic liquid crystal (E47) by which gold vapor deposition was carried out. It is a figure which shows the disappearance spectrum of 5CB which added the silver nanoparticle. It is the reflection spectrum of the liquid crystal which shows a pure cholesteric blue phase, and the liquid crystal which shows the cholesteric blue phase vapor-deposited by gold | metal | money.

  Hereinafter, the present invention will be described with reference to FIGS. The following description shows an embodiment of the present invention, and the present invention is not limited to the following embodiment.

(1) Nanoparticle-dispersed liquid crystal The nanoparticle-dispersed liquid crystal of the present invention comprises a liquid crystal material and nanoparticles that have not been subjected to a treatment (chemical modification) that improves the compatibility with the liquid crystal material. This is a nanoparticle-liquid crystal dispersion system in which nanoparticles are dispersed. The nanoparticle-dispersed liquid crystal of the present invention does not require chemical synthesis of chemically modified nanoparticles. Therefore, a nanoparticle-dispersed liquid crystal that can be easily produced can be realized.
The nanoparticle-dispersed liquid crystal of the present invention is
Here, the liquid crystal material is a material that develops a liquid crystal phase that is an intermediate layer between a solid and a liquid. Liquid crystal materials generally have a vapor pressure as low as sub-Pa at room temperature. Liquid crystal materials have anisotropy in physical properties such as dielectric constant, refractive index, and electrical conductivity. The liquid crystal material applicable to the present invention is not particularly limited as long as it has such properties. The liquid crystal material may be a single substance or a mixture of a plurality of types of liquid crystals. Further, the molecular structure, liquid crystal phase, and physical properties of the liquid crystal material are not particularly limited.

  Specifically, the liquid crystal material may be a lyotropic liquid crystal or a thermotropic liquid crystal. The thermotropic liquid crystal may be any of a calamitic liquid crystal, a discotic liquid crystal, and a sanitic liquid crystal.

  The liquid crystal phase may be a nematic phase, a smectic phase (smectic A phase to I phase), a cholestic phase, a columnar phase, a discotic columnar phase, or a banana phase, or a blue phase or TGB (Twist It may be a frustrated phase such as a Grain Boundary) phase. The blue phase may be any of blue phase I, blue phase II, and blue phase III, and may be a cholesteric blue phase or a smectic blue phase. The frustrated phase is a phase that forms a macro structure including a locally unstable region in the liquid crystal. In other words, the frustrated phase is a phase stably present as a whole in the liquid crystal while having a local alignment contradiction. For example, the blue phase is a typical example of a frustrated phase. The liquid crystal phase may be a chiral liquid crystal phase or an achiral liquid crystal phase.

  Specific liquid crystal molecules are not particularly limited, and cyanobiphenyls, cholesteryls, carbonates, phenyl esters, Schiff bases, benzidines, azoxybenzenes, ferroelectric liquid crystals having a chiral group Various liquid crystal molecules such as liquid crystal polymers can be used. Examples thereof include 4-pentyl-4-cyanobiphenyl (5CB) or mixed liquid crystals such as E-47, E-44, and MLC-6610 provided by Merck.

  Here, the liquid crystal material currently applied to the liquid crystal display field is a thermotropic liquid crystal, and the liquid crystal phase exhibits a nematic phase. Therefore, also in the present invention, the liquid crystal material is preferably a thermotropic liquid crystal and exhibits a nematic phase. As a result, it is possible to realize high speed, high definition and high functionality of the liquid crystal display device.

  In addition, a liquid crystal exhibiting a frustrated phase (particularly a blue phase) exhibits optically or electro-optically unique properties. For example, a liquid crystal exhibiting a blue phase has a very fast response speed of 1 ms or less, is optically isotropic, and has a three-dimensional lattice structure with a period of the order of visible light wavelength. For this reason, a liquid crystal display device using a liquid crystal exhibiting a blue phase has no viewing angle dependency and does not require alignment treatment such as alignment film or rubbing. Accordingly, a liquid crystal display device using a liquid crystal exhibiting a blue phase is attracting a great deal of attention as a next-generation liquid crystal display device that can achieve both a dramatic improvement in performance and a reduction in cost. However, since the liquid crystal exhibiting a blue phase has an extremely narrow temperature range that expresses the liquid crystal phase compared to other liquid crystals, the narrowness of this temperature range precludes the practical application of liquid crystals exhibiting a blue phase. It has become. That is, it is indispensable to expand this temperature range in order to open the way to the practical use of the frustrated phase, particularly the blue phase.

  In the present invention, a nanoparticle-dispersed liquid crystal in which nanoparticles are dispersed in a liquid crystal material exhibiting a frustrated phase, particularly a blue phase (cholestic blue phase), has a higher speed, higher definition, and higher functionality by dispersing the nanoparticles. Can be realized. In addition, the nanoparticle-dispersed liquid crystal exhibits a remarkable effect that the temperature range in which the liquid crystal phase (frustrated phase) appears is expanded. Therefore, it is possible to realize a nanoparticle-dispersed liquid crystal that overcomes the greatest drawback of the liquid crystal material exhibiting a frustrated phase, particularly a blue phase.

  On the other hand, the nanoparticles dispersed in such a liquid crystal material are not particularly limited as long as the particles have a particle diameter (major axis) of 100 nm or less. In the nanoparticle-dispersed liquid crystal of the present invention, the appropriate particle diameter of the nanoparticles is not particularly limited because it varies depending on the type of liquid crystal material. However, the particle diameter of the nanoparticles is preferably 1 nm to 20 nm, more preferably 1 nm to 10 nm, and particularly preferably 1 nm to 5 nm. Thereby, the physical properties of the liquid crystal can be changed without significantly disturbing the alignment of the liquid crystal due to the nanoparticles.

  The nanoparticles may be a pure substance or a mixture. Furthermore, the pure substance may be a simple substance or a compound. The nanoparticles may be any of gas, liquid, and solid, but is preferably solid. As the nanoparticles, a wide range of materials such as metals, metalloids, inorganic oxides, semiconductors, magnetic substances, and organic substances can be used alone or in combination.

  Examples of metals include gold, silver, copper, platinum, palladium, aluminum, tungsten, lead, zinc, cobalt, nickel, indium, aluminum, iron, rhodium, manganese, chromium, molybdenum, cadmium, titanium, ruthenium, and osmium. Is mentioned.

  Examples of the semimetal include bismuth and tellurium.

Examples of the inorganic oxide include Al ₂ O ₃ , MgO, MoO ₃ , Nb ₂ O ₅ , SiO ₂ , SnO ₂ , BaTiO ₃ , TiO ₂ , UO ₂ , V ₂ O ₅ , WO ₃ , ZrO ₂ , Fe. ₂ O ₃ , CuO, CdO, In ₂ O ₃ , Co ₃ O ₄ , HfO _{2 and the} like.

  Examples of the semiconductor include ZnS, CdS, ZnSe, ZnTe, CdTe, CdSe, and the like.

  Examples of the magnetic material include FePt, CoPt, MPt, Mpd, and the like.

  Examples of the organic substance include C60 series and carbon nanotubes.

  In the nanoparticle-dispersed liquid crystal of the present invention, the nanoparticle is not subjected to a treatment for improving the compatibility with the liquid crystal material. Here, the “treatment for improving the compatibility with the liquid crystal material” means that the nanoparticle surface is subjected to some kind of treatment in order to increase the compatibility between the nanoparticles and the liquid crystal material that are difficult to mix with each other. For example, as in Patent Document 1, in order to satisfactorily disperse nanoparticles in liquid crystal, chemical synthesis of liquid crystal molecules or liquid crystal-like molecules on the surface (periphery) of the nanoparticles is shown.

  In the nanoparticle-dispersed liquid crystal of the present invention, it is preferable that the liquid crystal molecules constituting the liquid crystal material are physically adsorbed on the surface of the nanoparticle and not chemically bonded (chemical adsorption) as in the prior art (Patent Document 1). . Thereby, even if the nanoparticle surface is not chemically modified, aggregation of the nanoparticles can be prevented. Therefore, it is possible to realize a nanoparticle-dispersed liquid crystal in which nanoparticles are dispersed in a liquid crystal material without aggregation.

  Note that “physical adsorption” refers to adsorption by physical force without chemical bonding. For example, adsorption by weak intermolecular forces (van der Waals force) such as van der Waals force can be mentioned. Therefore, “liquid crystal molecules are physically adsorbed on the surface of the nanoparticles” indicates a state in which the liquid crystal molecules are physically adsorbed on the nanoparticle surface by van der Waals force or the like. On the other hand, in Patent Document 1, liquid crystal molecules are chemically bonded (chemically adsorbed) to the surfaces of the nanoparticles. Therefore, the surface state of the nanoparticles is completely different between the present invention and Patent Document 1.

  In the nanoparticle-dispersed liquid crystal of the present invention, the nanoparticle content is not particularly limited because it varies depending on the combination of the liquid crystal material and the nanoparticles and the properties of the nanoparticle-dispersed liquid crystal. However, if the content of the nanoparticles is too large, the nanoparticles may aggregate or lose liquid crystallinity. Therefore, it is preferable that the content does not occur. For example, the content of the nanoparticles is preferably 0.1 wt% to 5 wt%, more preferably 0.1 wt% to 3% with respect to the total weight of the nanoparticle-dispersed liquid crystal. Thereby, the nanoparticles are dispersed in the liquid crystal material without aggregation of the nanoparticles and without loss of liquid crystallinity.

  In the nanoparticle-dispersed liquid crystal of the present invention, it is most preferable that the nanoparticles are not aggregated. In other words, it is most preferable that the nanoparticle aggregate formed by the aggregation of nanoparticles does not exist in the nanoparticle-dispersed liquid crystal. Here, the nanoparticle aggregate indicates a mass having a particle diameter larger than 100 nm formed by aggregation of nanoparticles. The nanoparticle aggregate may be present in the nanoparticle-dispersed liquid crystal as long as it does not affect the properties of the nanoparticle-dispersed liquid crystal. For example, 1% by weight or less of nanoparticle aggregates may be present in the nanoparticle-dispersed liquid crystal.

  Since the nanoparticle-dispersed liquid crystal of the present invention has both fluidity and anisotropy like a normal liquid crystal, it can be used as a material for a liquid crystal display device. By including nanoparticles in the liquid crystal, it is possible to improve characteristics such as a decrease in threshold voltage for Fredericks transition, an increase in dielectric anisotropy, and an increase in switching speed. Accordingly, the liquid crystal display device can be increased in speed, definition, and functionality.

  The nanoparticle-dispersed liquid crystal of the present invention can be used alone, but various additives can be added for the purpose of enhancing the functionality of the liquid crystal material. As such an additive, for example, a polymer or a chiral dopant may be added in order to expand the expression range of a liquid crystal material exhibiting a frustrated phase (particularly a blue phase). More specifically, fullerenes, carbon nanotubes, dendrimers, etc. may be added to expand the expression range of the blue phase. In addition, in order to make an additive easy to disperse | distribute to a liquid-crystal material, it is preferable that an additive has an appropriate modification group, such as a mesogen group.

  As described above, in the nanoparticle-dispersed liquid crystal of the present invention, nanoparticles that are not chemically modified are dispersed in the liquid crystal material. For this reason, there is no need to chemically synthesize chemically modified nanoparticles. Therefore, a nanoparticle-dispersed liquid crystal that can be easily produced can be realized.

(2) Method for Producing Nanoparticle-Dispersed Liquid Crystal As described above, the nanoparticle-dispersed liquid crystal of the present invention was chemically modified because nanoparticles that were not chemically modified were dispersed in the liquid crystal material. There is no need to chemically synthesize the nanoparticles. Further, since the vapor pressure of the liquid crystal material is low, it does not evaporate if it is a low vacuum (reduced pressure) of about several Pa. Therefore, the nanoparticle-dispersed liquid crystal of the present invention can be produced very simply by physical vapor deposition.

  That is, the nanoparticle-dispersed liquid crystal of the present invention can be produced by growing atoms and molecules formed from a target material by physical vapor deposition into nanosized particles in a liquid crystal material.

  Here, “physical vapor deposition (PVD)” means that the target material is evaporated by a physical method such as high-temperature heating and sputtering, and atoms or molecules emitted from the target material are attached to the liquid crystal material. Specifically, “physical vapor deposition” includes, for example, sputtering, vacuum vapor deposition, ion plating, and the like.

  On the other hand, the target material used for physical vapor deposition is one in which atoms or molecules are released by physical vapor deposition. That is, the target material is a nanoparticle precursor. The target material may be selected according to the nanoparticles to be formed, and is not particularly limited. For example, as the target material, a wide range of materials such as metals, metalloids, inorganic oxides, semiconductors, magnetic substances, and organic substances exemplified as the above-described nanoparticles can be applied. Thereby, nanoparticles of a wide range of materials can be dispersed in the liquid crystal material.

  Here, in the method for producing a nanoparticle-dispersed liquid crystal of the present invention, an apparatus similar to a method for depositing a target material on a substrate by a dry film forming method such as a chemical vapor deposition method (CVD method) or a physical vapor deposition method (PVD), and It can be implemented in the procedure. For example, a liquid crystal material is used instead of the substrate in physical vapor deposition. Thereby, atoms or molecules released from the target material by physical vapor deposition gather to form nanoparticles, and the nanoparticles can be dispersed in the liquid crystal material.

  However, as described above, the liquid crystal material has a strong self-organization ability, but has fluidity, and thus generally has a finite vapor pressure of about sub-Pa at room temperature. In addition, the liquid crystal material may be decomposed at a high temperature. For example, when the liquid crystal material is 5 CB, the vapor pressure is approximately 0.23 Pa at 90 ° C., and when left at 100 ° C. for several minutes, it decomposes thermally and does not exhibit liquid crystallinity. The boiling point and vapor pressure of the liquid crystal material vary depending on the type of liquid crystal material, the molecular structure of the liquid crystal material, and the like. For this reason, the conditions of physical vapor deposition should just be set according to liquid crystal material, and are not specifically limited. However, the physical vapor deposition is preferably performed under a vacuum condition (degree of vacuum) and a temperature condition such that the liquid crystal material does not evaporate or decompose.

  In consideration of the properties of such a liquid crystal material, the necessity of a crucible, and the ability to form high-purity nanoparticles, physical vapor deposition is preferably sputter deposition (sputtering method). Sputter deposition does not require a very high temperature and does not require a high vacuum such that the liquid crystal material evaporates. That is, sputter deposition can form high purity nanoparticles under low vacuum conditions. Therefore, high-purity nanoparticles can be formed in a short sputtering time while preventing thermal decomposition and evaporation of the liquid crystal material. Therefore, the manufacturing time of the nanoparticle-dispersed liquid crystal can be shortened.

  Here, the configuration of the sputtering apparatus for performing the sputtering deposition is not particularly limited, and a conventionally known deposition apparatus can be used. For example, the sputtering apparatus uses a deposition chamber that can be evacuated, a cathode that is installed on the upper surface of the deposition chamber and that can be loaded with a target material, and an anode that is installed at a position facing the cathode. can do. In this case, the target material is mounted on the cathode, and a container containing the liquid crystal material or a substrate onto which the liquid crystal material is dropped is placed on the anode. Then, a high voltage is applied to the cathode while the inside of the vapor deposition chamber is in a vacuum or a gas atmosphere (for example, argon gas). Thereby, glow discharge is generated in the vapor deposition chamber, and gas ions generated by the glow discharge collide with the target material, whereby atoms or molecules constituting the target material are sputter evaporated. Then, atoms or molecules knocked out from the target material reach the facing liquid crystal material. The reached atoms or molecules invade and gather in the liquid crystal material having fluidity. As a result, the atoms or molecules grow in the liquid crystal material, and nanoparticles are formed and dispersed. That is, this nanoparticle is comprised from the atom or molecule | numerator which comprises the target material. The nanoparticles thus formed are formed directly from the target material, and thus have high purity and no by-products. Moreover, the nanoparticle surface is not chemically modified.

  On the other hand, the liquid crystal molecules constituting the liquid crystal material are physically adsorbed on the surface (surroundings) of the grown nanoparticles. For this reason, when the nanoparticle surface is covered to some extent by liquid crystal molecules, the growth of the nanoparticles stops. Furthermore, since the nanoparticle surface is covered with liquid crystal molecules, aggregation of the nanoparticles can be prevented. Accordingly, the nanoparticles can be dispersed in the liquid crystal material without aggregation of the nanoparticles.

  The principle that nanoparticles are formed from the target material by physical vapor deposition such as sputter vapor deposition, and the formed nanoparticles are dispersed in the liquid crystal material can be explained as follows.

  Usually, when a very small amount of nanoparticles of a certain size is added to a liquid crystal material, the distance between the nanoparticles is large, so that they disperse in the liquid crystal without aggregating or disturbing the alignment of the liquid crystal material. However, if the interaction between the nanoparticles is strong, or if the amount of nanoparticles added is too large (the nanoparticle concentration becomes too high), the nanoparticles aggregate. Therefore, conventionally, the surface of the nanoparticles is treated with a modification group for enhancing compatibility with the liquid crystal material so that the nanoparticles are not physically contacted (aggregated). The

  On the other hand, in the present invention, the atoms, molecules, or clusters composed of a small number thereof constituting the target material are released by physical vapor deposition, and the atoms, molecules, or clusters collide (attach) to the liquid crystal material. For this reason, the alignment of the liquid crystal material is not disturbed when the atom or molecule contacts the liquid crystal material. Further, since the liquid crystal material has fluidity, atoms, molecules, or clusters that collide with the liquid crystal material invade into the liquid crystal material one after another and gather. As a result, nanoparticles as large as several nm are formed in a bottom-up manner. On the other hand, at the stage where the nanoparticles are formed, the liquid crystal molecules constituting the liquid crystal material are bonded to the surface (surroundings) of the grown nanoparticles by physical adsorption. Thus, the liquid crystal molecules physically adsorbed on the surface of the nanoparticles function to prevent nanoparticle growth and to prevent aggregation of the nanoparticles. For this reason, nanoparticle growth stops at a certain size. Therefore, a nanoparticle-dispersed liquid crystal in which the nanoparticles are dispersed in the liquid crystal material without being aggregated is produced.

  As described above, when the nanoparticles are formed by physical vapor deposition, the nanoparticles are basically formed in the liquid crystal material. In this case, the size (particle diameter) of the nanoparticles changes according to the type of the liquid crystal material. That is, in Patent Document 2, an ionic liquid is used as a solvent for attaching the nanoparticle precursor. And the particle diameter of the nanoparticle formed differs according to the kind of the ionic liquid. For example, the particle diameter of the nanoparticles is controlled by the degree of hydrophilicity of the ionic liquid.

  On the other hand, also in the present invention, a liquid crystal material having fluidity like an ionic liquid is used as a solvent for colliding atoms, molecules, or clusters emitted from a target material. For this reason, it grows only to the nanoparticle of the magnitude | size which can be disperse | distributed in the liquid crystal material by the physical property (degree of hydrophilicity, a viscoelastic coefficient, etc.) of liquid crystal material. Therefore, the particle diameter of the nanoparticles can be adjusted according to the type of the liquid crystal material. For example, in Examples described later, when 5CB is used as the liquid crystal material, gold nanoparticles having a particle diameter of about 3 nm are formed. On the other hand, when the mixed nematic liquid crystal E-47 is used as the liquid crystal material, gold nanoparticles of about 1 nm are formed.

  In the method for producing a nanoparticle-dispersed liquid crystal according to the present invention, the content of nanoparticles in the liquid crystal material can be adjusted by the deposition conditions such as the deposition time. As described above, the content of the nanoparticles is not particularly limited because it varies depending on the combination of the liquid crystal material and the nanoparticles and the properties of the nanoparticle-dispersed liquid crystal. That is, the vapor deposition conditions are not particularly limited. However, if the content of the nanoparticles is too large, the nanoparticles may be aggregated. Therefore, it is preferable to set the vapor deposition conditions so that the content does not aggregate. For example, it is preferable to set the deposition conditions so that the content of nanoparticles is 0.1 wt% to 5 wt% with respect to the total weight of the nanoparticle-dispersed liquid crystal, so that the content is 0.1 wt% to 3%. It is more preferable to set vapor deposition conditions. Accordingly, the nanoparticles can be dispersed in the liquid crystal material without aggregation of the nanoparticles.

  In the above description, the manufacturing method in the case of sputter deposition is described. However, in the case of other physical vapor deposition, nanoparticles can be dispersed in the liquid crystal material according to the same principle.

  Thus, in the method for producing a nanoparticle-dispersed liquid crystal according to the present invention, nanoparticles are directly formed from a target material by physical vapor deposition. For this reason, it is not necessary to chemically synthesize nanoparticles whose surface is chemically modified as in the prior art, and it is not necessary to remove by-products. Moreover, since the liquid crystal molecules are physically adsorbed on the surface of the nanoparticles, the nanoparticles do not aggregate. Therefore, a nanoparticle-dispersed liquid crystal in which high-purity nanoparticles are dispersed can be easily produced while suppressing aggregation of the nanoparticles without performing chemical modification.

  For sputtering deposition, for example, a DC sputtering method, an RF sputtering method, a magnetron sputtering method, an ion beam sputtering method, or the like can be used.

  Moreover, the conditions for sputtering deposition (conditions for forming nanoparticles) may be in air or in a gas atmosphere. When performed in a gas atmosphere, a rare gas such as argon gas is generally used. In order to produce higher-purity nanoparticles, it is preferable to evacuate the deposition chamber to a high vacuum and then introduce a rare gas into the deposition chamber. In this case, it is preferable that the liquid crystal material is placed in a load lock chamber beside the vapor deposition chamber (main chamber) during exhaust, and is introduced into the vapor deposition chamber after introduction of the rare gas. Thereby, it is possible to prevent the liquid crystal material from evaporating in the exhaust gas. If nanoparticles are formed by this method, it is possible to produce a large amount of high-purity nanoparticles in a short sputtering time without producing by-products.

  Note that when performing physical vapor deposition, the liquid crystal material need not exhibit a liquid crystal phase, and may be in an isotropic phase. That is, the state of the liquid crystal material when attaching the atoms or molecules constituting the target material may be a liquid crystal phase or an isotropic phase.

  In addition, when performing physical vapor deposition, nanoparticles may be formed by aggregating atoms or molecules released from the target material in the vapor deposition chamber or in the liquid crystal material. It may be formed by agglomeration. However, when nanoparticles are formed in the liquid crystal material, atoms or molecules emitted from the target material do not aggregate before entering the liquid crystal material. Thereby, aggregation of nanoparticles (formation of nanoparticle aggregates) can be prevented more reliably. Therefore, a nanoparticle-dispersed liquid crystal in which higher-purity nanoparticles are dispersed can be produced. Therefore, it is preferable that atoms or molecules emitted from the target material are aggregated in the liquid crystal material to form nanoparticles.

  In addition, the distance between the target material and the liquid crystal material in the physical vapor deposition is not particularly limited, but it is preferable to perform the physical vapor deposition by bringing the target material and the liquid crystal material close to each other. Thereby, atoms or molecules emitted from the target material can be prevented from aggregating before entering the liquid crystal material. Therefore, a nanoparticle-dispersed liquid crystal in which higher-purity nanoparticles are dispersed can be produced in a short time. Note that the distance between the target material and the liquid crystal material is not constant because it varies depending on the deposition conditions, the scale of the deposition apparatus, the type of the target material, and the like. The distance between the target material and the liquid crystal material may not be agglomerated before the atoms or molecules emitted from the target material enter the liquid crystal material, and is preferably 3 to 10 cm, for example, 3 to 5 cm. More preferably.

  Moreover, it is preferable to perform physical vapor deposition in the state which left the liquid material stationary. Thus, when physical vapor deposition is performed in a state where the liquid crystal material is left stationary, a special rotating roller used in Non-Patent Document 1 is not required. Thereby, a nanoparticle dispersion liquid crystal can be manufactured, without improving vapor deposition apparatuses, such as a sputtering device. Further, it is not necessary to form a liquid thin film on the rotating roller to disperse the nanoparticles. Therefore, a nanoparticle-dispersed liquid crystal can be produced in a shorter time. The physical vapor deposition may be performed while stirring the liquid crystal material (sample) in order to improve the dispersibility between the liquid crystal material and the nanoparticles. That is, depending on the properties of the liquid crystal material used, physical vapor deposition can be performed with the liquid crystal material standing or stirring.

  In the method for producing a nanoparticle-dispersed liquid crystal of the present invention, the liquid crystal material is not particularly limited. For example, if the liquid crystal material is a thermotropic liquid crystal as described above and exhibits a nematic phase, it is possible to realize speedup, high definition, and high functionality of an existing liquid crystal display device.

  On the other hand, in the case of a liquid crystal material exhibiting a frustrated phase, particularly a blue phase (cholestic blue phase), in addition to increasing the speed, resolution and functionality of the liquid crystal display device, the liquid crystal phase (frustrated phase) The remarkable effect that the temperature range which expresses expands is shown. Accordingly, it is possible to produce a nanoparticle-dispersed liquid crystal that overcomes the greatest drawbacks of the frustrated phase, particularly the blue phase.

  As described above, in the method for producing a nanoparticle-dispersed liquid crystal according to the present invention, nanoparticles are dispersed (doped) in a liquid crystal material by physical vapor deposition. According to such physical vapor deposition, since the nanoparticles are directly formed from the target material, it is not necessary to chemically modify the surface of the nanoparticles as in the prior art. Therefore, a nanoparticle-dispersed liquid crystal can be manufactured very simply. Further, since no by-product is present in the liquid crystal material, a complicated process for removing the by-product is not necessary, and high-purity nanoparticles are formed. Moreover, the manufacturing process is overwhelmingly advantageous as compared with the case of chemical modification. Therefore, various nanoparticle-liquid crystal dispersion systems can be produced very simply. In addition, since sputter deposition can be applied in particular, the degree of freedom in selecting a target material is very high.

(3) Application of Nanoparticle-Dispersed Liquid Crystal As described above, in the nanoparticle-dispersed liquid crystal and the method for producing the same according to the present invention, the surface of the nanoparticle is chemically treated with a mesogenic group or a thiol group as in the prior art (Patent Document 1). There is no need to qualify. That is, it is possible to highly disperse highly purified nanoparticles in a liquid crystal material without imparting any modification group to the nanoparticles. Moreover, the nanoparticle-dispersed liquid crystal of the present invention can be produced by a very simple technique called physical vapor deposition. For this reason, the selection range of a target material is also abundant. Accordingly, the present invention has a great impact in the field of liquid crystal displays, the field of optical devices using liquid crystals, the development of metamaterials, and the like, and has a very high economic effect.

(A) Liquid crystal display device Since the nanoparticle-dispersed liquid crystal of the present invention has nanoparticles added to the liquid crystal material, the performance of the liquid crystal material can be improved. For example, an increase in birefringence (refractive index anisotropy) and dielectric anisotropy can improve response characteristics to an electric field, such as an increase in switching speed and a decrease in drive threshold voltage. Accordingly, the liquid crystal display device can be increased in speed, definition, and functionality.

  Specifically, the nanoparticle-dispersed liquid crystal of the present invention can be applied to a liquid crystal layer of a conventionally known liquid crystal display device. For example, in a liquid crystal display device including a pair of glass substrates arranged to face each other, a polarizing plate arranged outside each glass substrate, and a liquid crystal layer sealed between the glass substrates, the liquid crystal layer is The nanoparticle-dispersed liquid crystal of the present invention may be contained. This liquid crystal layer may be composed of the nanoparticle-dispersed liquid crystal of the present invention (the conventional liquid crystal layer is replaced with a nanoparticle-dispersed liquid crystal), or the conventional liquid crystal layer may be composed of the nanoparticle-dispersed liquid crystal of the present invention. It may be added. The liquid crystal layer may be composed of a nanoparticle-dispersed liquid crystal. That is, the content of the nanoparticle-dispersed liquid crystal in the liquid crystal layer may be set according to the type of the nanoparticle-dispersed liquid crystal, and is not particularly limited.

  On the other hand, if the liquid crystal material in the nanoparticle-dispersed liquid crystal of the present invention is a liquid crystal material exhibiting a frustrated phase, particularly a blue phase, a liquid crystal display device comprising a liquid crystal layer containing a liquid crystal material exhibiting a frustrated phase, particularly a blue phase It can be applied as As a result, the greatest drawback of the liquid crystal material exhibiting the frustrated phase, particularly the blue phase, can be overcome, and a next generation liquid crystal display device can be realized.

  In such a liquid crystal display device, nanoparticles such as metal or ferroelectric are dispersed in a liquid crystal material, so that birefringence and dielectric anisotropy are improved, threshold voltage is lowered, and response speed is increased. Can be achieved. In addition, since it is possible to produce a nanoparticle-dispersed liquid crystal very simply, the performance of an information display using a liquid crystal material can be improved.

(B) Other applications 1) Laser field In the nanoparticle liquid crystal-dispersed liquid crystal of the present invention, the scattering intensity is increased at a specific wavelength by dispersing nanoparticles of a specific size in the liquid crystal. On the other hand, when a gain medium such as a dye is added to the nematic liquid crystal, an inversion distribution is formed through a random scattering process, and laser oscillation occurs. Since the threshold value at which laser oscillation occurs depends on how efficiently scattering occurs, it is possible to cause laser oscillation at a low threshold value by causing scattering more efficiently by nanoparticles.

2) Optical communication field The feasibility of a material having a variable refractive index or a material having a negative refractive index has been shown by dispersing nanoparticles in an anisotropic medium such as a liquid crystal material. Therefore, such a novel material can be realized using the nanoparticle-dispersed liquid crystal of the present invention.

3) Field of utilizing nanoparticles In the present invention, nanoparticles dispersed in a liquid crystal material can be isolated and taken out. For this reason, this invention is applicable to the manufacturing method of the unmodified nanoparticle which is not chemically modified (surface treatment). That is, unmodified nanoparticles can be produced in the liquid crystal material using the liquid crystal material as a solvent. Moreover, it is also possible to use the produced unmodified nanoparticles themselves for a chemical reaction in a liquid crystal material. Unmodified nanoparticles can be used as functional materials such as highly active photocatalysts, optoelectronic devices, and biomolecular markers.

  Examples of the present invention will be specifically described below. However, liquid crystal molecules, liquid crystal phases, and nanoparticles applicable to the present invention are not limited to the following examples.

[Example 1]
(1) Manufacture and functionalization of nematic liquid crystal 5CB dispersed with gold nanoparticles Approximately 0.3 g of 4-pentyl-4cyanobiphenyl (5CB) is placed on a glass screw tube (body diameter 18 mm) cut to a height of about 7 mm. It was. The reason why the screw tube is cut to a height of 7 mm is to prevent the liquid crystal from spilling and to allow the sputter atoms to efficiently reach the liquid crystal. If the liquid crystal does not spill, there is no problem even if the liquid crystal is added to a flat substrate such as a slide glass. Next, the screw tube without a lid was placed in a sputter deposition apparatus, and sputtering was performed using gold as a target material (deposition chamber atmosphere: air, pressure: 20 Pa, deposition current: about 4.5 mA, Deposition time: 30 seconds to 20 minutes, distance between target material and liquid crystal: 3 cm). After sputtering, the liquid crystal material in the screw tube was collected.

(2) Measurement of color change and absorption spectrum due to gold deposition FIG. 1 shows disappearance spectra of pure 5CB and gold-deposited 5CB. Specifically, FIG. 1 shows absorption spectra when pure 5CB and gold-deposited 5CB are infiltrated into a glass sandwich cell having a thickness of 350 μm and the temperature is set to 40 ° C. and the sample is in an isotropic phase. Although 5CB is originally transparent in the visible light wavelength region, it can be confirmed that it is colored by depositing gold. Absorption has a shoulder in the vicinity of a wavelength of 520 nm and is attributed to surface plasmon absorption of gold nanoparticles, so that it was confirmed that gold nanoparticles were added into 5CB by sputter deposition.

(3) Change in phase transition behavior FIG. 2 is a diagram showing a polarization microscope image showing the phase transition behavior of pure 5CB and gold-deposited 5CB, and (a) is a diagram of 5CB before pure deposition. (B) is a diagram of 5CB deposited by gold for 20 minutes. Specifically, when 5CB before vapor deposition and 5CB gold-deposited for 20 minutes are sealed in a glass sandwich cell having a uniform orientation treatment with a thickness of about 5 mm and the temperature is lowered from 40 ° C. to 1 ° C./min. The polarization microscope image at the time of the phase transition of is shown.

  As shown in FIG. 2, when gold was deposited, changes were observed in the phase transition temperature of 5CB and the behavior during the phase transition. That is, as shown in FIG. 2A, the clearing point was about 35.4 ° C. in 5CB before vapor deposition. On the other hand, as shown in FIG. 2B, the clearing point was about 33 ° C. in 5CB in which gold was deposited for 20 minutes. Further, regarding the behavior at the time of phase transition, as shown in FIG. 2A, in pure 5CB, the phase transition occurs so that the boundary between the liquid crystal and the isotropic phase region scans the visual field. On the other hand, as shown in FIG. 2B, in the gold-deposited one, innumerable domains of about 10 μm appeared, and the domains were adhered while expanding, and finally a uniform texture was obtained. From these results, it was confirmed that the nanoparticles were dispersed in the liquid crystal material without agglomeration, affecting the phase transition behavior.

(4) Change in dielectric constant FIG. 3 is a graph showing the frequency dependence of the dielectric constant of pure 5CB and gold-deposited 5CB, where (a) is the dielectric constant in the minor axis direction, and (b) is The dielectric constant in the major axis direction. That is, it shows the frequency dependence of the dielectric constant of 5 CB deposited with gold measured using an impedance analyzer (Agilent 4294A). The liquid crystal material was sealed in a glass sandwich cell having a cell thickness of about 6 μm subjected to vertical alignment treatment and parallel alignment treatment, and measurement was performed. The measurement conditions are a measurement frequency range: 40 Hz-10 MHz and a modulation amplitude: 300 mV. At the frequency in the measurement range, 5CB originally did not show frequency dependence, but when gold deposition was performed, clear debye-type dielectric relaxation was confirmed between 100 Hz and 1 kHz.

  Such a result is a phenomenon similar to that reported in the example in which metal fine particles surface-modified with liquid crystal-like molecules are added to the liquid crystal (see Non-Patent Document 4), and the Maxwell-Wagner effect in a non-uniform dielectric material. Known as. From this, it was confirmed that the nanoparticles were dispersed in 5CB by sputter deposition, affecting the electrical characteristics.

(5) Observation with Transmission Electron Microscope After 5CB deposited with gold for 20 minutes was diluted with acetone and dried on a carbon grid, observation was performed with a dry transmission electron microscope (Hitachi H-7650, acceleration voltage 100 keV). The reason for dilution with acetone is to remove the liquid crystal of the original solvent. FIG. 4 is a diagram showing a transmission electron microscope image of 5CB deposited with gold. As shown in FIG. 4, when 5CB was gold-deposited, it was confirmed that nanoparticles having a particle size (nanoparticle size) of about 3 nm and an average deviation of 0.49 nm were dispersed without aggregation.

[Example 2]
(1) Production and functionalization of mixed nematic liquid crystal E-47 in which gold nanoparticles are dispersed The liquid crystal to be subjected to sputter deposition is mixed nematic liquid crystal E-47 marketed by Merck & Co. Sputter deposition was performed under the conditions, and after sputtering, the liquid crystal material in the screw tube was collected.

(2) Color Change by Gold Deposition FIG. 5 is a diagram showing a mixed nematic liquid crystal (E-47) on which gold is deposited. That is, FIG. 5 is a view showing a pure mixed nematic liquid crystal (E-47) and a mixed nematic liquid crystal (E-47) obtained by gold deposition (6 minutes, 20 minutes). As shown in FIG. 5, E-47, which was originally clouded by light scattering, was colored yellow by depositing gold. In addition, since the red coloring by the surface plasmon resonance of a gold nanoparticle is not seen, it is estimated that the particle diameter of the disperse | distributed nanoparticle is 1 nm order. Moreover, although not shown in figure, since it became dark, so that vapor deposition time was long, it was confirmed that the density | concentration of a gold nanoparticle becomes high, so that vapor deposition time is long.

(3) Transmission Electron Microscope Observation of Gold Nanoparticles in E-47 After E-47 on which gold was sputter-deposited for 20 minutes was diluted in acetone and dried with a carbon grid, a transmission electron microscope (Hitachi H-7650, Observation was performed with an acceleration voltage of 100 keV. FIG. 6 is a view showing a transmission electron microscope image of E-47 deposited with gold. As shown in FIG. 6, it can be confirmed that nanoparticles having a particle diameter of about 1 nm or less are formed at locations indicated by auxiliary circles in the drawing. Therefore, even when the mixed liquid crystal E-47 was used, it was confirmed that nanoparticles were produced and dispersed in the mixed liquid crystal E-47.

(4) Comparison with Example 1 Compared with the case of sputter deposition on 5CB in Example 1, when the deposition was performed on E-47 as in Example 2, the size of the gold nanoparticles (particle (Diameter) was confirmed to be small. That is, it was confirmed that the size of the formed nanoparticles varies depending on the physical properties of the liquid crystal material.

(5) Reduction of driving threshold voltage in twisted nematic liquid crystal using E-47 liquid crystal by dispersing gold nanoparticles E-47 obtained by sputter-depositing gold for 20 minutes is sealed in a twisted nematic liquid crystal cell, and the electro-optic response of the liquid crystal Characteristics were evaluated. The twisted nematic cell was fabricated by spin-coating polyimide (JSR: AL1254) on each substrate, rubbing in one direction, and then superimposing them so that the rubbing directions were orthogonal. The cell thickness was 9 μm, and an electric field was applied in the cell thickness direction by the opposing ITO transparent electrode. The electro-optic response characteristic was examined by placing the element between orthogonal polarizers and measuring the applied electric field dependence of the transmittance when monochromatic light having a wavelength of 632 nm was incident. FIG. 7 shows threshold voltage values at which the transmittance is 50% when rectangular elements having various frequencies are applied to the element. In E-47 to which gold nanoparticles were added, it was confirmed that the threshold voltage was lower in the frequency range of 20 Hz to 10000 Hz than E-47 to which no nanoparticles were added. The reduction rate of the threshold voltage was about 15% at maximum. From this, the performance of the liquid crystal can be improved by dispersing the nanoparticles.

Example 3
(1) Production and functionalization of nematic liquid crystal 5CB in which silver nanoparticles are dispersed The target material is silver, sputter deposition is performed for 6 minutes under the same conditions as in Example 1, and after sputtering, the liquid crystal material in the screw tube is recovered. .

(2) Coloring of liquid crystal material by silver FIG. 8 is a diagram showing an annihilation spectrum of 5CB to which silver nanoparticles are added. 5CB on which silver was sputter-deposited was sealed in a 350 μm-thick glass sandwich cell, and the temperature was kept at 40 ° C. and measurement was performed using a CCD multichannel spectrometer (Hamamatsu Photonics: PMA-11). Unlike the case where gold was deposited, a large optical loss was confirmed at a wavelength of 450 nm or less. Corresponding to this spectrum, yellow coloring was confirmed in 5CB deposited with silver.

(3) Comparison with Example 1 Pure liquid crystals appear to be clouded by light scattering, whereas in Example 1, gold nanoparticles were dispersed in 5CB, while reddish coloration was observed, while silver was added. In the case of vapor deposition, yellow coloring was confirmed. Since the two samples were uniform with no precipitates, the difference in color between the two samples was due to the difference in the optical properties (complex dielectric constant) of the highly dispersed nanoparticles in the liquid crystal. It is thought to be caused. That is, the optical properties can be changed by changing the constituent atoms of the nanoparticles dispersed in the liquid crystal.

Example 4
(1) Preparation of cholesteric blue liquid crystal in which gold nanoparticles are dispersed A low-molecular mixed liquid crystal ((46.5 wt%) 5CB + (46.5 wt%) JC1041XX + in which the target material is gold and the liquid crystal material expresses a cholesteric blue phase. (7.0 wt%) ISO- (6OBA) ₂ ) was sputter-deposited on 0.0186 g of a liquid crystal material for 5 minutes under the same conditions as in Example 1, and a sample was taken out after sputtering.

(2) Expansion of expression temperature range of cholesteric blue phase Since the cholesteric blue phase forms a three-dimensional periodic structure in a self-organized manner, it exhibits a reflection peak due to Bragg diffraction in the visible light wavelength region. For this reason, it is possible to investigate the expression temperature range of the cholesteric blue phase by measuring the reflection peak while controlling the temperature of the sample.

  Therefore, a low-molecular mixed liquid crystal sputtered with gold was sealed in a glass sandwich cell having a thickness of 6 μm, and a polarizing microscope was observed and a reflection spectrum was measured while the temperature was lowered at 0.1 ° C./min. FIG. 9 is a reflection spectrum of a liquid crystal showing a pure cholesteric blue phase and a liquid crystal showing a gold-deposited cholesteric blue phase. That is, FIG. 9 shows the temperature dependence of the reflection spectrum of the sample. The pure liquid crystal material developed a cholesteric blue phase in the temperature range of approximately 3.2 ° C. On the other hand, the expression temperature of the liquid crystal material to which the gold nanoparticles were added expanded to about 8.2 ° C. This result indicates that the nanoparticles can expand the temperature range of the frustrated phase such as cholesteric blue phase.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  According to the present invention, it is possible to impart a new function to a liquid crystal material by dispersing nanoparticles such as metal, dielectric, and semiconductor in the liquid crystal material. Therefore, the present invention can be used in various fields such as information display field, laser field, optical communication field, and nanoparticle utilization field.

Claims (10)

  A method for producing a nanoparticle-dispersed liquid crystal, characterized in that nanoparticles formed from a target material by physical vapor deposition are dispersed in a liquid crystal material.   The method for producing a nanoparticle-dispersed liquid crystal according to claim 1, wherein the physical vapor deposition is sputter vapor deposition.   The method for producing a nanoparticle-dispersed liquid crystal according to claim 1 or 2, wherein atoms or molecules emitted from the target material are aggregated in the liquid crystal material to form nanoparticles.   The said physical vapor deposition performs the physical vapor deposition by making the said target material and liquid crystal material adjoin, The manufacturing method of the nanoparticle dispersion | distribution liquid crystal of any one of Claims 1-3 characterized by the above-mentioned.   The said physical vapor deposition is performed in the state which left the said liquid-crystal material, The manufacturing method of the nanoparticle dispersion | distribution liquid crystal of any one of Claims 1-4 characterized by the above-mentioned.   The method for producing a nanoparticle-dispersed liquid crystal according to any one of claims 1 to 5, wherein the liquid crystal material exhibits a frustrated phase.   A nanoparticle-dispersed liquid crystal, characterized in that nanoparticles not subjected to a treatment for improving compatibility with the liquid crystal material are dispersed in the liquid crystal material.   8. The nanoparticle-dispersed liquid crystal according to claim 7, wherein the liquid crystal molecules constituting the liquid crystal material are physically adsorbed on the surfaces of the nanoparticles.   9. The nanoparticle-dispersed liquid crystal according to claim 7, wherein the liquid crystal material exhibits a frustrated phase.   A liquid crystal display device comprising a liquid crystal layer containing the nanoparticle-dispersed liquid crystal according to claim 7.