JP2005121700A - Fluid and device using the fluid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To promote operation speed of an anisotropic fluid by using a charge transfer complex. <P>SOLUTION: The anisotropic fluid contains a dielectric fluid having dielectric constant anisotropy and the charge transfer complex capable of accelerating the dielectric fluid by applying an electric field in a mixed state. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fluid that can be controlled by an electric field and a device using the fluid, and more particularly, to a fluid in which another substance is mixed with a base material having dielectric anisotropy and a device using the fluid.

  A liquid crystal display device is known in which light scattering fine particles are dispersed in a liquid crystal and an electric field is applied to control the position of the fine particles, for example, by electrophoresis, thereby switching the display.

  Japanese Patent Application Laid-Open No. 2003-098556 discloses a display device in which light scattering fine particles are dispersed in a medium having a dielectric anisotropy and flowing by an electric field and accommodated between a pair of substrates. A transparent electrode is selectively formed on one substrate, and an opaque electrode is selectively formed on a region other than the display opening on the other substrate. A voltage is applied between the electrodes, an electric field is applied to the medium, and display is controlled.

  FIG. 6A reproduces a part of the proposal of Japanese Patent Laid-Open No. 2003-098556. A stripe-shaped opaque electrode 102 is disposed on the surface of one transparent substrate 101, and a stripe-shaped transparent electrode 106 in the intersecting direction is disposed on the surface of the other transparent substrate 105. The alignment films 103 and 107 are applied so as to cover the electrodes 102 and 106. Both substrates are opposed to each other through a spacer 109, and accommodate a liquid crystal 112 in which light scattering fine particles 114 are dispersed in a space between the substrates. A liquid crystal is a medium having a dielectric anisotropy and flowing by an electric field. A region where the transparent electrode 106 exists and the opaque electrode 102 does not exist forms a display region.

  A voltage is applied between the opaque electrode 102 and the transparent electrode 106. For example, the medium and the fine particles receive an electric attractive force from the anode and an electric repulsive force from the cathode. When the fine particles are attracted to the transparent electrode 106, light is scattered in the display area, and white display is performed. When the fine particles are attracted to the opaque electrode 102, the display area becomes transparent. When the light absorption film 116 is formed on the outer surface of the substrate 105, black display is obtained.

  Selective display is possible depending on which electrode the fine particles are attracted to. Even if the applied voltage is removed, the display form has a memory function. Instead of the striped simple matrix, a transparent electrode on the entire surface and an opaque electrode for defining an opening may be used.

JP 2003-098556 JP Yokota et al., Transactions of the Japan Society of Mechanical Engineers (C), Vol. 66, No. 642 (2002-2), pp 627/633 Motor). An electrically insulative (dielectric) electroconjugate liquid having a specific chemical structure such as dibutyl decanedioate generates an active flow when a DC high voltage is applied. A jet is generated from the high potential side electrode to the low potential side electrode.

  As shown in FIG. 6B, decanedioic acid dibutyl 124 which is an electric conjugate fluid is housed in a cell 123 having a ground potential terminal 121 and a high voltage terminal 122. When the ground terminal 121 is grounded and a high voltage is applied to the high voltage terminal 122, an electric conjugate liquid jet 126 is generated from the high voltage terminal 122 toward the ground terminal 121.

As shown in FIG. 6C, when the rotor of the micromotor is arranged in the center of the circular container 123 and the high voltage terminal 122 and the ground terminal 121 are periodically arranged as the stator electrodes around the rotor, A motor can be configured. By generating a jet between the stator electrodes, a jet flow as indicated by an arrow 128 is generated, and the rotor 129 can be rotated.
Yokota et al., Transactions of the Japan Society of Mechanical Engineers (C) Volume 66, No. 642 (2002-2), pp 627/633 Generally, organic crystals are composed of neutral molecules, which are van der Waals forces. It is agglomerated. In some cases, organic molecules are in the form of positive ions or negative ions to form salts with inorganic ions or other organic ions. In this case as well, organic molecules usually have a closed shell structure and do not have unpaired electrons.

  However, some organic molecules have a stable radical charge state. A crystal containing a positive or negative organic radical ion of an organic molecule, not as an impurity, is called a charge transfer complex.

  In general, organic solids are insulators that are difficult to conduct electricity. This is because many organic solid components do not have unpaired electrons. In recent years, research progress has led to the development of substances that conduct electricity even when they are organic solids. Such conductive organic solids (also called synthetic metals) include roughly two types. One is a conjugated polymer, and the other is a charge transfer complex. However, not all conjugated polymers and charge transfer complexes are conductive.

  Research on conductive charge transfer complexes was started by Akamatsu et al.'S report that perylene bromine is a highly conductive organic semiconductor. In 1972, TTF · TCNQ, which shows metallic conductivity, was synthesized. In 1980, a superconducting phenomenon was confirmed in TMTSF / PF6.

  The charge transfer complex is a conductor having strong electron correlation and electron lattice interaction and low dimensionality compared to ordinary metals. For this reason, many new phenomena have been found.

  The moving speed of a medium having a dielectric anisotropy, such as liquid crystal when an electric field is applied, and flowing due to the electric field cannot be said to be sufficiently high.

  An object of the present invention is to provide a fluid with enhanced operating speed.

  Another object of the present invention is to provide an apparatus using this fluid.

  Yet another object of the present invention is to promote the operating speed of anisotropic fluids with charge transfer complexes.

  According to one aspect of the present invention, there is provided a fluid containing a dielectric fluid having dielectric anisotropy and a charge transfer complex capable of accelerating the dielectric fluid by applying an electric field in a mixed state.

  According to another aspect of the present invention, the counter substrate, the fluid held in the space between the counter substrates, an electrode capable of applying an electric field to the fluid, and the fluid between the counter substrates are operatively disposed. And a micromachine having an actuated actuator.

  According to still another object of the present invention, there is provided a display device having a counter substrate, a pair of electrodes formed on the counter substrate, and the fluid held in a space between the counter substrates. Is done.

  When the charge transfer complex is added to a fluid having dielectric anisotropy, the moving speed of the fluid can be accelerated when an electric field is applied. The transfer rate is accelerated by increasing the amount of charge transfer complex added and increasing the electric field.

  The present inventors have found that by adding a charge transfer complex to a liquid crystal, the movement speed of the liquid crystal when an electric field is applied is accelerated. In the experiment, donor n-butylisoquinolinium iodide (BIQI) was used as a charge transfer complex.

  FIG. 1A is a plan view showing a configuration of a sample cell used in the experiment. T-shaped transparent electrodes 3 and 6 made of indium-tin oxide (ITO) were formed on the surfaces of the transparent glass substrates 1 and 2. The transparent electrodes 3 and 6 form a wide intersection on the transparent substrates 1 and 2. FIG. 1B shows the cross-sectional shape of the intersection used for observation. A vertical alignment film was applied so as to cover the transparent substrates 1 and 2 and the transparent electrodes 3 and 6, and heat treatment was performed to form vertical alignment films 4 and 7 made of polyimide with an alkyl chain having a thickness of 500 mm. The glass substrates 1 and 2 were bonded together so that the vertical alignment films 4 and 7 were opposed to each other, and an experimental sample cell 10 was produced.

  Liquid crystal 8 mixed with BIQI was injected into the space defined by the opposing glass substrates 1 and 2. The liquid crystal used has positive dielectric anisotropy. BIQI molecules have the same size as liquid crystal molecules. The distance between the substrates was 75 μm. In the experiment, no scattering fine particles were added to the liquid crystal, and the change (movement) of the liquid crystal during voltage application was observed with a polarizing microscope.

  The amount of BIQI added was changed to (S1) 0 wt%, (S2) 0.0009968 wt%, (S3) 0.0049188 wt%, (S4) 0.0070979 wt%, (S5) 0.03835 wt%. Samples were prepared. Hereinafter, the characteristics of each sample are also indicated by S1, S2, S3, S4, and S5.

  FIG. 1C shows the form of observation. The liquid crystal cell 10 is sandwiched and observed between a pair of polarizers P1 and P2 arranged in a crossed Nicol arrangement of a polarizing microscope. A direct-current voltage was applied between the electrodes on the two glass substrates, and observation was performed with a polarizing microscope having a crossed Nicol arrangement. The liquid crystal molecules have an elongated shape and are optically anisotropic. The alignment state of the liquid crystal molecules can be observed by observing with a polarizing microscope.

  Assuming that the speed of movement of the liquid crystal can be roughly estimated by following a portion in the same alignment state as an image, the speed was measured by image processing. It is considered that the amount of change in the image reflects the moving speed of the fluid. In each sample cell in which the amount of BIQI added was changed, the voltage applied between the electrodes was changed, and the amount of change in the image was observed.

  FIG. 2A shows an image change amount when the applied voltage is changed from 10 V to 50 V in arbitrary units. The horizontal axis indicates the applied voltage in the unit V, and the vertical axis indicates the change amount of the image in an arbitrary unit.

  The amount of BIQI added increases in the order of the sample cells S1, S2, S3, S4, and S5. In the sample cell S1 to which no BIQI is added, the amount of change in the image hardly increases even when the applied voltage is increased. In Samples S2-S5 to which BIQI is added, the image clearly changes as the voltage is applied, and the amount of change in the image at the rising portion increases as the applied voltage increases.

  Further, in the sample cells S2 to S4 with a small addition amount, the change amount of the image once increases with the increase of the applied voltage and then decreases. As the addition amount increases, the maximum image change amount increases, and the applied voltage indicating the maximum value gradually moves to the high voltage side. Increasing the amount of BIQI added is thought to increase the moving speed of the liquid crystal. BIQI will have the function of accelerating liquid crystal molecules.

  If the liquid crystal molecules change the orientation direction, observation as an image becomes impossible. It is unclear from this experiment whether the phenomenon showing the peak indicates the moving speed of the liquid crystal or the orientation change of the liquid crystal molecules in the liquid crystal.

  FIG. 2B shows a sample cell in which the range of applied voltage is expanded to 5 to 100 V and the addition amount of BIQI is further increased, (S6) 0.1805 wt%, (S7) 0.254 wt%, and (S8) 0.5973 wt. % Added.

  In the sample cell in which the amount of BIQI added is 0.03835 wt% or more, a large amount of change in the image is obtained, but the maximum value is that of the amount added 0.03835 wt%, and more BIQI is added. However, the amount of change in the image is not clearly increased. That is, the increase in the amount of change in the image due to the added amount of BIQI is considered to be saturated at a concentration of about 0.04 wt%. In the range of 5 V to 50 V, the applied voltage also increases as the applied voltage increases, but the amount of change in the image does not increase clearly even when a higher voltage is applied. With regard to the applied voltage, it is considered that the change amount of the moving image is almost saturated at about 50V.

  Considering only from the experimental results, it can be effective to reduce the waste of the BIQI addition amount of about 0.04 wt% or less and the applied voltage of about 50 V or less. Practically, the liquid crystal can be speeded up with a small addition amount of 0.6 wt% or less, and the cost increase is slight.

  It is considered that the phenomenon that the maximum value of the change amount of the image increases as the amount of BIQI added increases suggests that the moving speed of the liquid crystal increases as the amount of BIQI added increases. In order to observe the movement speed of the liquid crystal more accurately, an experiment was conducted in which fine particles were added to the liquid crystal and the movement of the fine particles was directly observed instead of the amount of change in the image. If the microparticles are suspended in the liquid crystal and the movement speed of the liquid crystal increases, the movement speed of the microparticles will also increase.

  FIG. 3A schematically shows the configuration of the sample cell in which the experiment was performed. Striped electrodes 3 are formed on the upper glass substrate 1, and striped electrodes 6 are formed on the lower glass substrate 2 in the intersecting direction. The distance between the glass substrates is about 75 μm. Both substrates were made to face each other, and liquid crystal added with BIQI was injected between them. 0.20 wt% of white fine particles were added to the liquid crystal. In order to observe the fine particles, the concentration of the fine particles is about two orders of magnitude lower than the fine particle concentration normally employed in the electrophoretic display element.

  The amount of BIQI added was (S11) 0 wt%, (S13) 0.0049188 wt%, (S14) 0.0070997 wt%, and (S15) 0.03835 wt%. The first digit of the sample number corresponds to the BIQI concentration of samples S1-S5. The moving speed of the fine particles was measured in the vicinity D outside the intersection of the electrodes 3 and 6. A DC voltage was applied between the electrodes on the two glass substrates, and the movement speed of the fine particles was observed under a microscope.

  FIG. 3B schematically shows how the fine particles move. The fine particles have a property of moving from one electrode to the other electrode. However, in the vicinity of the intersection of the electrodes, the particles once moved from one substrate to the other substrate side as shown in the figure are outside. Reflux and move in a loop. When the applied voltage is reversed, the direction of movement is also reversed.

  FIG. 3C is a graph showing the observation results. The horizontal axis indicates the voltage applied between the electrodes in the unit V, and the horizontal axis indicates the moving speed of the fine particles in μm / sec. The applied voltage was changed in the range of 5V to 100V. In the sample cell S11 to which no BIQI is added, the moving speed hardly increases even when a voltage is applied. As shown by samples S13, S14, and S15, the moving speed at the same applied voltage increases as the amount of BIQI added increases. If the moving speed of the liquid crystal increases, the moving speed of the fine particles will also increase. Further, the moving speed increases almost linearly with the increase of the applied voltage.

  FIG. 3D is a graph in which the speed at an applied voltage of 100 V is plotted against the added amount of BIQI. The rate tends to saturate with increasing BIQI addition.

  From this result, it is considered that when BIQI is added to the liquid crystal, the liquid crystal increases the moving speed under the application of an electric field, and the moving speed of the fine particles increases accordingly. The increase in the moving speed of the fine particles with the increase in the amount of BIQI added is considered that BIQI is accelerated by the electric field, and BIQI accelerates the liquid crystal.

  When the BIQI addition amount is about 0.04 wt% or less and the applied voltage is 100 V or less, the saturation phenomenon as seen in FIGS. 2A and 2B does not occur. The results of this experiment observing the velocity of the fine particles will more accurately indicate the movement speed of the liquid crystal. Saturation and re-degradation as seen in FIGS. 2A and 2B may indicate a change in alignment of liquid crystal molecules.

  It is considered that the moving speed of the liquid crystal and the moving speed of the fine particles can be selected to desired values by selecting the amount of BIQI added to the liquid crystal and appropriately selecting the applied voltage.

  In the light-scattering fine particle dispersed liquid crystal display cell, the moving speed of the fine particles greatly affects the switching of the display. If BIQI is added to the liquid crystal, it is expected that BIQI accelerates the liquid crystal according to the electric field, and the liquid crystal accelerates (or conveys) the fine particles, so that display switching can be accelerated.

  FIG. 4A shows a configuration of a liquid crystal display cell in consideration of the result of the above experiment. A pair of substrates 1 and 2 face each other to constitute a liquid crystal cell 10. The substrate 1 is a transparent substrate, and a metal opaque electrode 3 made of, for example, Mo is formed on the surface thereof. The opaque electrode 3 defines an opening. A vertical alignment film 4 is applied so as to cover the substrate 1 and the opaque electrode 3.

  The substrate 2 is, for example, a glass substrate, and the light absorption layer 5 is formed on the entire surface thereof. A transparent electrode 6 such as ITO (indium tin oxide) is formed on the light absorption layer 5 in a shape corresponding to the opening. A vertical alignment film 7 is applied so as to cover the transparent electrode 6 and the light absorption layer 5. A liquid crystal 8 in which BIQI of about 0.005 wt% to 0.05 wt% and fine particles 9 having a particle diameter of about 6 μm are mixed is injected into the space defined by the counter substrate. The liquid crystal has positive dielectric anisotropy. BIQI molecules have the same size as liquid crystal molecules. The distance between the substrates is about 50 μm to 200 μm, for example, about 75 μm.

  FIG. 4B schematically shows a state in which a voltage having a polarity that attracts the fine particles 9 is applied to the transparent electrode 6. The fine particles 9 are distributed on the transparent electrode 6 below the opening of the opaque electrode 3, and external light incident on the opening is reflected by the fine particles 9 to make the observer recognize the opening white.

  FIG. 4C shows a state in which a voltage having a polarity that attracts the fine particles 9 is applied to the opaque electrode 3. The fine particles 9 aggregate in a region below the opaque electrode 3 and are excluded from the opening. For this reason, the inside of the opening is transparent, and light incident from the outside passes through the liquid crystal layer 8 and is absorbed by the light absorption layer 5 below. The observer recognizes the opening in black. In this way, black and white can be selectively displayed.

  In the cell structure of FIG. 4A, the addition amount of BIQI to the liquid crystal was (S21) 0 wt% and (S25) 0.038 wt%, and 20 wt% of fine particles having a particle diameter of 6 μm were added to the liquid crystal. This fine particle-dispersed liquid crystal was injected between glass substrates, a DC voltage of 100 V was applied, and reflection response characteristics were evaluated. In addition, LCD-5000 (made by Otsuka Electronics) was used for the response characteristic evaluation of reflection.

  In FIG. 4D, the dotted line shows the characteristic of sample S21 to which no BIQI was added, and the solid line shows the characteristic of sample S25 to which BIQI was added by 0.038 wt%. Sample S21 had a rise of 5.3 sec and a fall of 6.8 sec. Sample S25 had a rise of 5.6 sec and a fall of 3.9 sec. The sample cell S25 has substantially the same rise as the sample cell S21, but the fall time is shortened to ½. Although the difference in characteristics as expected from the above experimental results was not observed, the characteristics were clearly improved.

  Further, when the same voltage was applied, the sample cell S5 to which BIQI was added at 0.038 wt% was superior in black level. This suggests that the fine particles move greatly with respect to the same voltage, and the fine particles are excluded from the opening region. This suggests that the addition of the charge transfer complex can lower the driving voltage. In addition, it is speculated that increasing the amount of the charge transfer complex added can shorten the display switching time and lower the switching voltage of the fine particle display type liquid crystal display device.

  In the structure shown in FIG. 4A, the opaque electrode formed on the upper substrate can have a stripe shape or a shape surrounding the display portion. A switching element such as a transistor may be connected to form an active matrix. The area other than the display portion may be covered with a black matrix or the like. The transparent electrode on the lower substrate can be a full-surface electrode in the case of an active matrix. The fine particles to be added are not limited to spherical particles having a particle size of about 6 μm. Various fine particles and microcapsules can be added.

  The charge transfer complex added to the liquid crystal is not limited to BIQI. N, N'-octamethylene-di-3.5-lutidinium iodide (ODLI2), n-octylisoquinolinium iodide (OIQI), etc., which function as donors as well as BIQI could be used.

  In the vicinity of the crossing electrode, the liquid crystal added with the charge transfer complex is refluxed. Using this reflux, a micromachine such as a micromotor can be created.

  FIG. 5A schematically shows the movement of the liquid crystal around the electrode intersection. An electric field having a polarity in which the liquid crystal moves in a direction from the lower electrode 6 toward the upper electrode 3 is applied. The liquid crystal on the lower electrode 6 moves toward the upper electrode 3 as indicated by an arrow. A loop-like flow occurs at the electrode end. If the polarity of the electric field is reversed, the direction of movement is reversed.

  FIG. 5A is a plan view schematically showing the configuration of the micromotor. The electrodes 3 and 6 are disposed so as to intersect with each other, and the rotor 20 is disposed so as to be rotatable in the vicinity of the intersecting portion. By applying a voltage between the electrodes 3 and 6, movement of the liquid crystal added with the charge transfer complex occurs, and the rotor 20 is rotated.

  For example, the rotor diameter is 10 μm to 1000 μm, more preferably 50 μm to 200 μm, the applied voltage is 20 V to 300 V, preferably 50 V to 200 V, and the rotor of the micromotor is rotated. While applying the DC voltage, the rotor 20 continues to rotate in the same direction. If the polarity of the applied voltage is reversed, the rotation of the rotor 20 is reversed. A micromotor can be configured with a simple configuration.

  In addition, it is possible to create not only a micro motor but also a micro machine that operates by receiving a force from a moving liquid crystal.

  As shown in FIG. 5B, for example, it is possible to replace the rotor 20 with an actuator 21 and operate a switch.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

It is the top view, sectional drawing, and perspective view which show roughly the composition of the sample cell used for experiment, and the form of observation. It is a graph which shows the result of having observed the change of the animation using the sample cell of FIG. It is the top view and graph which show the structure of another sample cell roughly. It is sectional drawing which shows the structure of liquid crystal display cell by an Example, operation | movement, and the graph which shows the response characteristic measured using this cell. It is the schematic top view which shows the mode of the movement of the crossing electrode vicinity of the liquid crystal which added the charge transfer complex, and the top view which shows schematically the structure of the micromachine by another Example. It is sectional drawing and a top view which show roughly the structure of the apparatus using the fine particle dispersion type | mold liquid crystal display device and electric field conjugate liquid by a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper substrate 2 Lower substrate 3, 6 Electrode 4, 7 Vertical alignment film 5 Light absorption layer 8 Liquid crystal material 9 Fine particle 10 Liquid crystal cell 20 Rotor 21 Actuator

Claims (9)

A fluid comprising a dielectric fluid having dielectric anisotropy and a charge transfer complex capable of accelerating the dielectric fluid by applying an electric field in a mixed state. The charge transfer complex comprises at least one of n-butylisoquinolinium iodide, N, N′-octamethylene-di-3,5-lutidinium iodide, and n-octylisoquinolinium iodide. The fluid of claim 1 comprising. The fluid according to claim 1 or 2, wherein the dielectric fluid is a liquid crystal. Furthermore, the fluid of any one of Claims 1-3 which disperse | distributed the microparticles | fine-particles which have a different characteristic from the said dielectric fluid. The fluid according to claim 4, wherein the fine particles have light scattering properties. A counter substrate;
The fluid according to any one of claims 1 to 5, held in a space between the counter substrates,
An electrode capable of applying an electric field to the fluid;
An actuator operably disposed in the fluid between the opposing substrates;
A micromachine with The micromachine according to claim 6, wherein the actuator is a rotor of a micromotor. A counter substrate;
A pair of electrodes formed on the counter substrate;
The fluid according to claim 3 or 4, which is held in a space between the counter substrates.
A display device. The display device according to claim 8, wherein the pair of electrodes includes a transparent electrode formed on one substrate and an opaque electrode selectively formed on the other substrate.

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