TWI410478B - Liquid crystal composite and device with faster electro-optical response characteristics - Google Patents

Abstract

The present invention discloses a liquid crystal composite comprising a liquid crystal composition as a host and a plurality of carbon nanotubes as a dopant, wherein the carbon nanotubes are dispersed in the liquid crystal composition. The average length of the carbon nanotubes is equal to or less than 1 &mgr;m. The present invention also discloses a device comprising the mentioned liquid crystal composite.

Description

Liquid crystal composite and device with rapid photoelectric reaction characteristics

The present invention relates to a liquid crystal composite and a liquid crystal device, and more particularly to a liquid crystal composite and device having rapid photoelectric reaction characteristics.

Heretofore, a general liquid crystal cell (LC cell) constituting a flat panel display is manufactured by the following procedure: First, an electrode and an alignment film are successively formed to have a switching element, a color filter, etc. On the glass substrate, these alignment layers are then disposed relative to each other and disposed between two glass substrates having a fixed pitch. Except for the liquid crystal sealing, the periphery of the glass substrate is sealed with an adhesive to form a liquid crystal cell. Further, the two glass substrates are maintained at a constant value by a spacer, and after the liquid crystal composite is filled in the gap to form a liquid crystal layer, the liquid crystal sealing is sealed with an adhesive, thereby forming a liquid crystal cell.

For the liquid crystal cell manufactured in this manner, the liquid crystal layer is usually contaminated by ionic impurities, which are usually derived from the fabrication of the device or the material itself, and this ionic impurity greatly affects the display quality. However, the contamination of the above impurities cannot be avoided in the conventional liquid crystal device, and thus the conventional liquid crystal display still has hidden defects such as uneven display quality and reduced reliability.

On the other hand, the display quality of a liquid crystal display depends on the liquid crystal mixture. Physical parameters such as elastic deformation constant, anisotropic dielectric constant, optical anisotropy, conductivity, and rotational viscosity. The reaction characteristics of liquid crystal displays are mainly determined by the relaxation process of liquid crystal molecules. In the essential physical parameters of many liquid crystal materials, the rotational viscous coefficient is the most important parameter in the design of fast response liquid crystal devices. Therefore, new liquid crystal composites and eutectic mixtures having a reduced rotational viscous coefficient still need to be developed in order to improve the photoelectric reaction characteristics of the elements.

In view of the above background, in order to meet the industrial needs, the present invention provides a novel liquid crystal composite and liquid crystal device having rapid photoelectric reaction characteristics.

One of the features of the present invention is to provide a liquid crystal host doped with a short carbon nanotube. The truncated carbon nanotube can avoid the problem of entanglement and aggregation, and play a good and stable dispersion in the liquid crystal composite. An important role.

Another feature of the present invention resides in that a suitable amount of carbon nanotubes is added to the liquid crystal to adsorb ionic impurities in the liquid crystal, so that the driving voltage is lowered by the decrease in the concentration of the ionic impurities.

Still another feature of the present invention resides in the addition of a carbon nanotube in the liquid crystal to reduce the rotational viscous coefficient, thereby shortening the reaction time.

According to the features described above, the present invention can further fine tune the carbon in the liquid crystal The doping concentration of the nanotubes is to reduce the driving voltage and the reaction time. For the liquid crystal of E7 and the short multi-wall carbon tube used in the present case, the doping concentration is preferably 0.010-0.075 wt% at 25-55 ° C. And at this concentration range, the doping concentration of the 0.050 wt% multi-wall carbon nanotube can exhibit the most ideal viscosity coefficient and ion concentration of the liquid crystal composite at 25-55 °C.

The direction of the invention discussed herein is a liquid crystal composite and device having fast photoelectric response characteristics. In order to thoroughly understand the present invention, a detailed composition and apparatus thereof will be set forth in the following description. Obviously, the practice of the invention is not limited to the specific details that are apparent to those skilled in the art. On the other hand, well-known components or devices are not described in detail to avoid unnecessarily limiting the invention. The preferred embodiments of the present invention are described in detail below, but the present invention may be widely practiced in other embodiments, and the scope of the present invention is not limited by the scope of the following patents. .

In the past ten years, novel nanomaterials have attracted great attention, taking carbon nanotubes as an example. Among them, single-walled carbon nanotubes and multi-walled carbon nanotubes are two typical carbon nanotubes with highly perfect structure. The tube type, the single-walled carbon nanotube tube is a seamless cylindrical tube wrapped by a single graphite sheet, and the multi-walled carbon nanotube tube is composed of an array of concentric cylindrical tubes. Single-walled carbon nanotubes and multi-walled carbon nanotubes are powered Arc-discharge, laser ablation, chemical vapor deposition (CVD) or gas-phase catalytic process (HiPco). It is common for the diameter of the carbon nanotube to be between 0.4 and 3 nm for a single-walled carbon nanotube and about 1.4 to 100 nm for a multi-walled carbon nanotube. The length is 5-100 μm.

Due to the unique structure, electrical and mechanical properties of carbon nanotubes, and the aqueous solution of multi-walled carbon nanotubes has lyotropic liquid crystallinity, carbon additives can be widely used in condensed optical materials. Dopants, this move also opens up new horizons in the field of optical applications. In the present invention, the photoelectric characteristics of a nematic LC device can be corrected by mixing a fine additive such as a carbon nanotube into a nematic liquid crystal host. Compared with the characteristics of undoped planar-aligned nematic liquid crystal cells, the experimental results indicate that the horizontal alignment nematic liquid crystal cell doped with multi-walled carbon nanotubes has a lower critical DC voltage and can Therefore, the driving voltage is lowered. In addition, similar phenomena can be observed in twisted-nematic boxes incorporating single-walled carbon nanotubes or multi-walled carbon nanotubes.

However, there are still some bottlenecks in the development of the above composites, such as the problem that phase separation of carbon nanotubes in the liquid crystal causes phase separation. In fact, the carbon nanotubes do not spontaneously suspend in the polymer or remain suspended in the liquid crystal, so the physical and chemical properties of the carbon nanotubes play an important role. color. However, this challenge is very difficult. For single-walled carbon nanotubes, a bundle or a bundle of tens of nanometers is formed due to the mutual attraction of van der Waals between the nanotubes. The above aggregates, and it is quite difficult to disperse the aggregates. In addition, these bundles will entangle each other like spaghetti. However, these shearing aggregates can be separated by shearing, and it is very difficult to further separate the nanotubes forming the aggregate. For general carbon tube or polymer composites, these limiting factors can introduce various functional groups on the surface of the carbon nanotube to improve the dispersibility of the carbon tube in the composite. As mentioned in the prior art, the density of ionic impurities is a key factor for obtaining high quality liquid crystal display elements. In addition, due to the expensive surface modification, the application value of the original carbon nanotubes as additives is thus reduced. Therefore, the chemical modification of the carbon nanotubes is not a perfect solution to the problem of dispersion of the nanotubes in the liquid crystal composite.

The present invention provides a preferred solution for the combined use of physical processing procedures: shortening the length of the carbon nanotubes and shortening the carbon nanotubes by strong shear stress agitation. For raw or surface-modified carbon nanotubes, the shortening procedure described above avoids entanglement and aggregation of the nanotubes prior to use. In addition, the more important role of the shortened carbon nanotubes is to obtain good and stable after the mixing process. The state of distribution. Furthermore, compared with a display element generally comprising a liquid crystal composite having no shortened carbon nanotubes, the shortened carbon nanotubes are connected to each other in a positive or negative electrode or lined up to form a bridge, and cause a component Short circuit or damage. In addition, reducing the doping concentration of the carbon nanotubes can also reduce the formation of entangled agglomerates.

A first embodiment of the present invention discloses a liquid crystal composite comprising a liquid crystal composition and a plurality of carbon nanotubes; wherein the liquid crystal formulation is the main body and the carbon nanotubes are The dopants are dispersed and incorporated into the liquid crystal formulation, and the dispersion range of more than 80% of the carbon tubes is on the nanometer scale. Further, the liquid crystal formulation is a calamitic liquid crystal containing a nematic LC, a smectic LC or a chiral phase thereof. In addition, the carbon nanotubes may be selected from one of the following groups: single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), or multi-walled carbons. Multi-walled carbon nanotube (MWCNT). Wherein the average length of the carbon nanotubes is less than or equal to 1 μm, and the concentration of the carbon nanotubes in the liquid crystal composite is less than or equal to 0.100 wt%, so below the percolation limit [for high anisotropy] At low doping concentrations of ~1% for anisotropic multi-walled carbon tubes, it can be assumed that each nanotube is independent in the liquid crystal medium. Acting and providing a strong local anchoring to the liquid crystal director.

On the other hand, the addition of a carbon nanotube to the liquid crystal composite suppresses the ion-charge effect, and can sequentially lower the driving voltage, avoid image sticking, and change the dynamic response.

First example:

The reaction characteristics of liquid crystal displays are mainly determined by the retardation process of liquid crystal molecules. In designing fast-reacting liquid crystal devices, the rotational viscous coefficient plays an important role in the essential physical parameters of most liquid crystal materials. Several methods have been available to measure the rotational viscous coefficient of liquid crystal materials, but most still require expensive measuring instruments, and many physical properties remain unknown in liquid crystal materials. Sugimura et al. developed a measurement system that applies a DC voltage and measures the induced transient current. This data provides a simple and accurate method for obtaining the rotational viscous coefficient of the liquid crystal, and is not limited to horizontal alignment or The nematic liquid crystal state is reversed; however, there is a deficiency in the method proposed by Sugimura, that is, the method still relies on the known dielectric constant in liquid crystal materials.

In order to understand how the carbon nanotubes affect the dynamic reaction characteristics of liquid crystal molecules, it is first necessary to know the change of the rotational viscous coefficient in the liquid crystal cell doped with carbon nanotubes, which is closely related to the rotation behavior of the liquid crystal. In the present invention, we have established a set of formulas and calculated undoped and doped carbon nanotube tubes. The rotational viscosity coefficient of the crystal. Both the experimental results and the numerical analysis show that the rotational viscous coefficient in the liquid crystal can be lowered by the carbon nanotube additive. More importantly, it has been found in the system provided by the present invention that the relaxation process of the liquid crystal is not only related to the rotational viscous coefficient, but also closely related to the ion concentration. The observations in this experiment show that in low-resistance nematic liquid crystals, the high doping concentration of multi-walled carbon tubes (0.100 wt%) leads to a significant increase in ion concentration, which in turn increases the field-screening effect. . This increase in ion concentration causes an image-sticking effect after the applied voltage is removed, thereby also slowing down the speed of the liquid crystal relaxation process.

The liquid crystal used in the present invention is a liquid crystal mixture having the lowest melting point which is generally commercially available, and E7 (having a phase sequence of Cr 5 ° C N 58.5 ° C I). The effective application of the carbon nanotubes in the field of liquid crystals relies on the uniform dispersibility of the carbon nanotubes in the liquid crystal composite solution, and this ability does not thereby destroy the original properties of the liquid crystal. The material used in the liquid crystal device of the present invention is four high-purity multi-wall carbon nanotubes of different doping concentrations in the E7 liquid crystal, and the device is plated with indium-tin oxide (indium-tin oxide). The conductive glass in which the ITO is an electrode is filled with a nematic liquid crystal composite doped with a multi-walled carbon tube, and the effective conductive area in which the upper and lower substrates overlap is 0.25 cm ² . In order to improve the effect of horizontal alignment by using a small pretilt angle (~2°±0.2°), a layer of polymer alignment agent polyimide is coated on the outer layer of the conductive glass indium tin oxide. Frictional alignment in a parallel manner. Discussed herein are liquid crystal cells prepared using a 9 μm spherical spacer. The DC pulse voltage is applied to the two electrodes of the liquid crystal cell at different temperatures, and the applied voltage generates a transient current in the E7 pure liquid crystal and the E7/carbon nanotube two liquid crystal cells, and the transient current passes through a series of load resistors. It is detected and displayed by a digital storage oscilloscope. It is worth mentioning that there is no significant difference in the phase transition temperature between the low doped liquid crystal sample and the pure nematic liquid crystal sample.

When the applied voltage V is much greater than the threshold voltage V _th and the length of the deformation of the liquid crystal layer (~ 0.3 μm) is much smaller than the thickness of the liquid crystal cell, the photoelectric response characteristics calculated liquid crystal cell may be assumed that the electric field E (nematic director field nematic liquid crystal field guide shaft n is uniformly distributed in most of the cell area. Therefore, consider the time-dependent function n = (sin θ( t ), 0, cos θ( t )), where θ( t ) is the inclination angle of the guide axis to the surface of the vertical substrate. If the elastic moment is neglected and the rotation of the liquid crystal molecules is limited to one-dimensional scale, the equation of motion can be written as: γ ₁ (dθ( t )/d t )=-ε ₀ Δε E ² sin θ( t )cos θ( t Where γ ₁ is the rotational viscous coefficient; ε ₀ is the permittivity of free space; Δ ε is the dielectric constant of the unequal orientation; for nematic E7, these coefficients are all positive. By integrating the above equation of motion, the dynamic behavior of θ( t ) can be obtained. When V is greater than V _th and n is parallel to the electric field E such that the free energy is at a minimum, a stable tilt angle can be obtained. The rotation of n causes the dielectric constant to change and produces a significant displacement current I _d Here, A is the area of the electrode, ε is the effective dielectric constant, and ε _⊥ is the dielectric constant orthogonal to the liquid crystal conduction axis.

The first picture shows a typical transient current induced by a DC voltage in an E7 pure liquid crystal cell. It can be noted that the measurement of the transient current I ( t ) is contributed by the following two: one is the above-mentioned electric displacement current I _d , which is redirected by the liquid crystal director (reorientation) It is induced, and the second is the conduction current generated by the movement of the impurity charge. For the cyano-containing nematic liquid crystal E7, it is known that it has a relatively high concentration of ionic impurities, so the conduction current caused by the ionic impurities is not negligible. The transient current can be described by the mathematical formula of I ( t )= I _d + A σ E exp(- t / t ₀ ), where σ is the conductivity of the ion charge in the liquid crystal cell, and t ₀ is the transition of the ion across the liquid crystal cell. time. The peak current I _p and the peak time t _p are measured at θ( t )=45°, and can be written as the following expressions: versus Note that both I _p and t _p can be derived from the experimental values of the transient current. Therefore, once the dielectric anisotropy Δ ε is a known value, the rotational viscous coefficient γ ₁ can be determined using equation (2). The pretilt angle θ ₀ can also be determined by equation (3). Unfortunately, the anisotropic dielectric constant of the nematic liquid crystal/carbon nanotube sample is unknown, so the rotational viscous coefficient of the low doped liquid crystal composite solution cannot be directly calculated using equation (2). We use the crystal rotation technology to independently measure the pre-tilt angle of the undoped and doped liquid crystal cell, and found that the addition of a small amount of carbon tube has no obvious effect on the pretilt angle. If the pretilt angle θ ₀ is known, the rotational viscous coefficient can be known by the following equation in an unknown case. Where X ≡ A (ε ₀ Δε) ² /2γ ₁ represents the intercept of the ordinate of the I _p / E ³ pair 1 / E ² graph obtained by equation (2), and Y ≡ γ ₁ log (tan θ ₀ ) / ε ₀ Δ ε represents a slope expression expressed by equation (3) where t _p is a numerator and 1 / E ² is a denominator. Taking the nematic liquid crystal E7 as an example, the schematic diagram of the first figure illustrates the relationship between I _p / E ³ and t _p versus 1 / E ² and the linear fit to the ordinate intercept via the inference and the information of the slope Y. . Using Equation (4), the rotational viscous coefficient in the liquid crystal composite solution at various temperatures and carbon nanotube doping concentrations can be calculated, as shown in Table 1. Table 1 clearly shows that the rotational viscous coefficient decreases as the doping concentration of the multilayer wall carbon nanotubes in the liquid crystal body increases.

For a planar-aligned liquid crystal cell, the relaxation time of the liquid crystal due to the electric field shutdown can be expressed as: τ _decay (γ ₁ / K ₁₁ ) d ² , where d is a cell gap, about 9 μm in the present invention; K ₁₁ is an elastic constant of splay, and for E7, K ₁₁ It is 11.7×10 ^-12 N; and the rotational viscosity coefficient γ ₁ is 0.232 Pa at 20 ° C. s, its ratio to K ₁₁ is called the viscoelastic coefficient. If the doped carbon nanotube does not significantly affect the change in K ₁₁ in the liquid crystal, γ ₁ can be lowered when the applied voltage is removed and a faster relaxation time is caused. In order to confirm the above meaning, the present invention performs an electro-optic relaxation experiment at 30 ° C, and the experimental results are referred to the second figure. From the second figure, the relaxation process of the liquid crystal in the dilute solution with a carbon nanotube doping concentration of about 0.010 wt% to 0.050 wt% can be seen. The experimental results show that the relaxation rate is faster than that of the undoped sample. This finding provides good evidence that the carbon nanotube additive can be used to reduce the rotational viscous coefficient in nematic liquid crystals. However, when the doping concentration of the multi-walled carbon nanotubes is as high as 0.100 wt%, even if the rotational viscous coefficient is further lowered, the relaxation time is longer than that of the pure liquid crystal or the sample with low doping. In order to reasonably explain the relaxation process of the liquid crystal cell at a high doping concentration, the ion concentration is further measured in this experiment. The third figure shows the current reaction phenomenon caused by the ion motion in the liquid crystal cell. The figure clearly shows that the current signal of the sample with a doping concentration of 0.050 wt% is weaker than that of the pure liquid crystal sample and the sample with a doping concentration of 0.100 wt%. . In addition, the current signal corresponds to the inverse phenomenon of the triangular waveform opposition, and the polarity of the sample in the pre-pure pure liquid crystal sample and the doping concentration of 0.100 wt% is reversed. According to the previous study of the present invention, this observation indicates that the effective electric field across the liquid crystal cell is reduced before the polarity of the applied electric field is reversed because the internal electric field is caused by the charge adsorbed by the interface between the alignment layer and the liquid crystal layer. And will offset the applied electric field whether in pure liquid crystal samples or highly doped samples.

The instantaneous change of the effective electric field in pure liquid crystals and highly doped samples can be observed by crossed polarized optical microscope. In the beginning, because the nematic liquid crystal guide axis is perpendicular to the substrate, a darkness is observed. After a few seconds, the effective electric field decreases and the birefringence increases due to the re-steering of the adsorbed ions and the guide axis, resulting in optical delay. It is almost equivalent to the case of no applied voltage. When the applied electric field is turned off, the birefringence still exists due to the internal electric field. This phenomenon illustrates the famous image residual effect. Please refer to the fourth figure, which shows that when the doping concentration of the multi-walled carbon nanotubes is gradually increased from less than 0.050 wt%, the ion concentration in E7 is gradually increased. Gradually decreasing, however, when the concentration of the carbon tube in E7 is higher than 0.08 wt%, the ionic charge effect is increased by the incorporation of the carbon nanotube. In the previous study of the present invention, it was found that the concentration of the carbon nanotubes in E7 was 0.05 wt%, which suppressed the screening effect and sequentially lowered the driving voltage. The experimental results of this time show the optimum doping concentration of the carbon nanotubes in the nematic liquid crystal of high ion impurity concentration, and at this doping concentration, the liquid crystal device can achieve the effect of simultaneously reducing the driving voltage and the reaction time.

There are two possible reasons for correcting the rotational viscous coefficient after adding a carbon nanotube to a liquid crystal sample. The first is the difference in the rotational viscous coefficient between a pure nematic liquid crystal and a liquid crystal composite solution doped with a small amount of carbon nanotubes: when a liquid crystal cell doped with a carbon nanotube is subjected to a strong electric field, the liquid crystal Both molecules and carbon nanotubes experience a moment due to their dielectric anisotropy. Due to the differences in dielectric anisotropy and aspect ratio between pure liquid crystal samples and liquid crystal samples with additives, The two are not the same in the mechanical reaction characteristics, so it affects the change of the rotational viscous coefficient. Another possible reason is that mixing the carbon tube in the liquid crystal disturbs the order parameter and thus changes the rotational viscous coefficient in the material. It is worth mentioning that this experiment also detects commercially available nematic liquid crystals with high resistivity and finds similar behavior for the reduction of the rotational viscous coefficient on liquid crystals with carbon nanotube additives. To thoroughly understand this phenomenon depends on further research work.

The effect of adding a carbon nanotube to the liquid crystal body, or by The doping of the carbon nanotubes improves the interaction of the liquid crystal devices depending on the details between the nanotubes and the liquid crystal body. Whether it is liquid crystal or carbon nanotubes, the choice of different material types also produces different effects. For example, the type, purity, and aspect ratio of the carbon nanotubes strongly dominate the interaction between the liquid crystal molecules and the carbon nanotubes.

Second example:

A similar investigation of similar effects was performed on a sample of ZLI-4792 (manufactured by Merck) using a single cell-cell measurement method. The results show that four important physical parameters closely related to the characteristics of the liquid crystal device are When the concentration of the multi-walled carbon nanotubes was 0.071 wt%, it decreased. Compared to E7, the concentration of ionic impurities in ZLI-4792 is relatively low, meaning that the measurement data for the four important physical properties of the ZLI-4792 sample shown in Table 2 is relatively easy and reliable.

As shown in Table 2, when the ZLI-4792 sample at 24 °C contains a uniformly dispersed carbon nanotube at a concentration of 0.07 wt%, the rotational viscosity coefficient of the sample is 127 mPa from the original pure liquid crystal state. s drops to 114 mPa. s. General recognition Therefore, in the absence of an applied electric field, the liquid crystal solution doped with a small amount of carbon nanotubes is ordered to a higher degree than the undoped mesomaterial; however, the experimental results reveal that in the presence of an electric field, The possible trend of the effect of doping carbon nanotubes is to reduce the orientation order parameter, which is presumed to be caused by the dielectric reaction of liquid crystal molecules and carbon nanotubes with different electric fields and the inconsistent re-steering between the two. This demonstrates that in the liquid crystal host, the addition of a small amount of carbon nanotubes can be used to suppress the ionic charge effect while also reducing the rotational viscous coefficient.

For liquid crystal displays, lowering the drive voltage can improve the performance and industrial benefits of the display. The addition of a carbon nanotube can be used in the liquid crystal to adsorb ions in the liquid crystal and thus reduce the ion concentration; however, the ion concentration does not always decrease as the carbon nanotube doping concentration increases. In a specific carbon nanotube concentration range, the ion concentration increases with the carbon nanotube doping amount; on the other hand, the rotational viscous coefficient and reaction time will always follow the carbon nanotube Increase and decrease. The performance of the liquid crystal display can also be improved by the reduction of the driving voltage and the reaction time, so the selection of the carbon nanotube doping concentration becomes very important. Table 1 is the rotational viscous coefficient data table corresponding to the doping concentration of various multi-wall carbon nanotubes at different temperatures of E7 liquid crystal. In addition, please refer to the fourth figure and Table 1. When the doping concentration range of the multi-wall carbon nanotubes is 0.010-0.075 wt%, the ion concentration and the rotational viscous coefficient are relatively low. Therefore, in the present invention, 0.010-0.075 wt% is selected as E7. A preferred doping concentration of a multi-walled carbon nanotube in a liquid crystal. Referring to the fourth figure, in the above range, when the carbon nanotube doping concentration is 0.050 wt%, the rotational viscous coefficient and the ion concentration have the most ideal lower values.

However, as described above, whether it is a liquid crystal or a carbon nanotube, the difference in the use of the materials may also have different effects. The ion concentration and the rotational viscous coefficient change with the increase of the carbon nanotube doping concentration, and the same trend is observed in any liquid crystal and carbon nanotube material selection, but the preferred range and the most The ideal carbon nanotube doping concentration will still vary with material selection.

For several types of carbon nanotubes and liquid crystals, when the doping concentration of the carbon nanotubes increases, the ion concentration in the liquid crystal composite decreases and then increases, and is further greater than the original ion concentration at zero doping. c ₀ and a notch-up curve in which the minimum value of ion concentration c _m corresponds to a specific carbon nanotube doping concentration w _m . Therefore, the most desirable carbon nanotube doping concentration range selected in the liquid crystal composite of the present invention is between the first doping concentration w ₁ and the second doping concentration w ₂ , wherein w ₁ < w _m < w ₂ , the ion concentration corresponding to w ₁ and w ₂ is half of the sum of c ₀ and c _m and less than c ₀ . On the other hand, the rotational viscous coefficient in the liquid crystal composite decreases as the doping concentration of the carbon nanotubes increases. In order to achieve a high quality liquid crystal display, the ion concentration and the rotational viscous coefficient need to be as low as possible. Therefore, the present invention discloses an ideal carbon nanotube doping concentration w _op which is actually in a liquid crystal composite, and w _m w _op w ₂ , this conclusion is valid regardless of whether the carbon nanotubes and liquid crystals are selected from any material.

A second embodiment of the present invention discloses a liquid crystal device comprising a first electrode, a second electrode and a liquid crystal composite. In addition, at least one of the first electrode and the second electrode is transparent, and a liquid crystal composite is disposed between the first electrode and the second electrode, the liquid crystal composite comprising: (a) a liquid crystal formulation, The liquid crystal formulation is used as a host, and (b) a plurality of carbon nanotubes as dopants, the carbon nanotubes being dispersedly doped in the liquid crystal formulation, wherein the average length of the carbon nanotubes If the doping concentration of the carbon nanotube is greater than or equal to zero, when the doping concentration of the carbon nanotube is increased, the ion concentration in the liquid crystal formulation first decreases and then increases, and the increasing trend is followed by further the carbon nanotube is greater than zero when a doping concentration c _0, and forming a plasma concentration profile having a recess upwardly of c _m is the minimum value, which corresponds to a certain minimum value c _m the doped carbon nanotube a heterogeneous concentration w _m , wherein the doping concentration of the carbon nanotube is greater than or equal to the first doping concentration w ₁ and less than or equal to the second doping concentration w ₂ , wherein w ₁ < w _m < w ₂ , and w ₁ and w ₂ correspond to a half value of the sum of the ion concentrations c ₀ and c _m .

As mentioned above, the carbon nanotubes are connected or lined up to form a bridge in the positive and negative electrodes and cause short-circuiting or damage to the components. This embodiment provides a method for overcoming this obstacle by reducing the gap of the liquid crystal cell or the distance between the first electrode and the second electrode. In a preferred example, if the first electrode and the second electrode The distance between the ranges of 10 and 150 μm, the average length of the carbon tubes is equal to or less than 1 μm. If the distance between the first electrode and the second electrode is less than or equal to 10 μm, the average length of the shortened carbon nanotubes is less than or equal to 500 nm. If the distance between the first electrode and the second electrode is less than or equal to 5 μm, the average length of the shortened carbon nanotube is less than or equal to 200 nm.

In addition, if the doping concentration of the carbon nanotubes in the liquid crystal composite is less than or equal to 0.1 wt%, the problem of aggregation of the carbon nanotubes can be reduced. In addition, the liquid crystal device is a display device including one of the following groups: direct drive, multiplex drive, twisted nematic (TN) of active matrix, hybrid-aligned nematic (hybrid-aligned nematic) , HAN), vertical alignment (VA), planar nematic, super-TN (STN), optically compensated bend (OCB), transverse electric field In-plane switching (IPS), fringe-field switching (FFS) and other types of liquid crystal display modes.

Obviously, many modifications and variations of the present invention are possible in the light of the scope of the appended claims. It is implemented in other embodiments. The above is only the preferred embodiment of the present invention, and is not intended to limit the scope of the patent application of the present application; Equivalent changes or modifications made in the spirit of the present invention should be included in the scope of the following application.

The first figure is a liquid crystal composite with a concentration of 0.05 wt% of a pure E7 liquid crystal cell (solid icon: ■, ●) and a carbon nanotube at 30 ° C according to the first example of the present invention (open icon: □, ○) A plot of I _p / E ³ versus t _p versus 1 / E. Among them, the square icon (■, □) and the circular icon (●, ○) are the trend graphs of I _p / E ³ and t _p versus 1 / E , respectively, the solid line is a linear fit, and the illustration is 30 At °C, the pure E7 liquid crystal cell is induced by the DC current of 12 V; the second picture is the first example of the present invention. At 30 ° C, the pure E7 liquid crystal cell and the E7/carbon nanotube composite are on the multi-layer wall. The optical relaxation condition of the carbon nanotubes doping concentration is 0.01-wt%, 0.05-wt% and 0.10-wt%; the third figure is the first example of the invention, at 30 ° C, doping various kinds in E7 liquid crystal Multilayer wall carbon nanotube concentration (0.00 wt%; 0.01 wt%; 0.05 wt%; 0.10 wt%) of a liquid crystal composite whose current signal is induced by a triangular waveform voltage; the fourth figure is an example of the present invention The relationship between the doping concentration of the multi-walled carbon nanotubes doped in the E7 liquid crystal and the ion density in the liquid crystal at 30 ° C.

Claims (18)

A liquid crystal composite comprising: an E7 liquid crystal formulation, wherein the E7 liquid crystal formulation is a nematic liquid crystal and has a phase sequence of Cr 5 ° C N 58.5 ° C I, and the E7 liquid crystal formulation is used as a main body ( Host); and a plurality of carbon nanotubes dispersed and doped in the E7 liquid crystal formulation, wherein the carbon nanotubes have an average length of less than or equal to 1 micrometer, and the carbon nanotubes are doped The concentration range is between 0.010 and 0.075 wt%. The liquid crystal composite according to claim 1, wherein the doping concentration of the carbon nanotubes is increased, and the rotational viscosity in the E7 liquid crystal formulation is reduced. The liquid crystal composite according to claim 1, wherein the carbon nanotube system is a single-walled carbon nanotube (SWCNT) or a double-walled carbon nanotube (double-walled carbon nanotube). , DWCNT) or multi-walled carbon nanotube (MWCNT). The liquid crystal composite according to claim 1, wherein the carbon nanotube tube is a multi-wall carbon nanotube. The liquid crystal composite according to claim 5, wherein the multi-walled carbon nanotube has a doping concentration of 0.05 wt% in the E7 liquid crystal formulation. The liquid crystal composite according to claim 1, wherein the carbon nanotubes having a dispersion range of more than 80% are on a nanometer scale. A liquid crystal device comprising: a first electrode; a second electrode, at least one of the first electrode and the second electrode being transparent; a liquid crystal composite, the liquid crystal composite being placed in the liquid crystal Between an electrode and the second electrode, the liquid crystal composite comprises: (a) an E7 liquid crystal formulation, wherein the E7 liquid crystal formulation is a nematic liquid crystal and has a phase sequence of Cr 5 ° C N 58.5 ° C I, and The E7 liquid crystal formulation is used as a host and (b) a plurality of carbon nanotubes as dopants, and the carbon nanotubes are dispersed and doped in the E7 liquid crystal formulation, wherein the average of the carbon nanotubes The length is less than or equal to 1 micron, and the doping concentration of the E7 carbon nanotube is between 0.010 and 0.075 wt%. The liquid crystal device according to claim 7, wherein the carbon nanotube is a single-walled, double-walled or multi-walled carbon nanotube. The liquid crystal device according to claim 7, wherein the carbon nanotube tube is a multi-wall carbon nanotube. The liquid crystal composite according to claim 9, wherein the doping concentration of the multi-wall carbon nanotube in the E7 liquid crystal formulation is preferably 0.05 wt%. The liquid crystal device according to claim 7, wherein the average length of the carbon nanotubes decreases as the distance between the first electrode and the second electrode decreases. The liquid crystal device according to claim 7, wherein the first electrode and the second electrode are between 10 micrometers and 150 micrometers, and the carbon nano The average length of the tubes is equal to or less than 1 micron. The liquid crystal device according to claim 7, wherein the distance between the first electrode and the second electrode is less than or equal to 10 micrometers, and the shortened average length of the carbon nanotubes is less than or equal to 500 nanometers. The liquid crystal device according to claim 7, wherein the distance between the first electrode and the second electrode is less than or equal to 5 micrometers, and the shortened average length of the carbon nanotubes is less than or equal to 200 nanometers. The liquid crystal device according to claim 7, wherein the liquid crystal composite comprises a rod-like liquid crystal. The liquid crystal device according to claim 7, wherein more than 80% of the carbon nanotube dispersion range is on a nanometer scale. The liquid crystal device according to claim 7, wherein the liquid crystal device is selected from the following display device types: a spatial light modulator, a wavelength filter, and an adjustable optical attenuator ( Variable optical attenuator (VOA), optical switch, light valve, color shutter, lens, and lens with tunable focus. The liquid crystal device according to claim 7, wherein the liquid crystal device is a display device, and the device comprises one of the following groups: direct drive, multiplex drive, active matrix twisted nematic (TN), Mixed arrangement nematic (HAN), vertical alignment (VA), planar nematic, super-twisted nematic (STN), optical compensation bend alignment (OCB), lateral electric field drive (IPS), lateral edge electric field drive (FFS) liquid crystal display mode.