JP4137803B2 - Display element - Google Patents

Description

  The present invention relates to a display element having high-speed response and wide-field display performance.

  Liquid crystal display elements have the advantage of being thin, light and low in power consumption among various display elements, and can be used for OA (Office Automation) devices such as TV, video, and other image display devices, monitors, word processors and personal computers. Widely used.

  Conventionally, as a liquid crystal display method of a liquid crystal display element, for example, a display mode using a TN (twisted nematic) mode using a nematic liquid crystal, a ferroelectric liquid crystal (FLC), or an antiferroelectric liquid crystal (AFLC). A polymer dispersion type liquid crystal display mode is known.

  Among them, conventionally used liquid crystal display elements include, for example, TN (twisted nematic) mode liquid crystal display elements using nematic liquid crystal, and the liquid crystal display elements using the TN mode. Have drawbacks such as a slow response and a narrow viewing angle. These disadvantages greatly hinder CRT (cathode ray tube) from surpassing.

  In addition, the display mode using FLC or AFLC has advantages such as quick response and wide viewing angle, but it has major drawbacks in terms of shock resistance, temperature characteristics, etc. It has not yet been realized.

  Furthermore, the polymer dispersion type liquid crystal display mode using light scattering does not require a polarizing plate and can display a high luminance, but the viewing angle cannot be controlled by the phase plate, and the response characteristic is not necessary. There is little advantage over the TN mode.

  In any of these display methods, the liquid crystal molecules are aligned in a certain direction, and the appearance differs depending on the angle with respect to the liquid crystal molecules. Each of these display systems uses rotation of liquid crystal molecules due to application of an electric field, and the liquid crystal molecules rotate in an aligned manner, so that it takes time to respond. In the case of a display mode using FLC or AFLC, although it is advantageous in terms of response speed and viewing angle, irreversible alignment breakage due to external force becomes a problem.

  On the other hand, a display method based on electronic polarization using a secondary electro-optic effect has been proposed in contrast to these display methods utilizing the rotation of molecules by applying an electric field.

  The electro-optic effect is a phenomenon in which the refractive index of a substance is changed by an external electric field. The electro-optic effect includes an effect proportional to the first order of the electric field and an effect proportional to the second order, which are called the Pockels effect and the Kerr effect, respectively. In particular, the secondary electro-optic effect called the Kerr effect has been applied to high-speed optical shutters from an early stage, and has been put to practical use in special measuring instruments. The Kerr effect was discovered by J. Kerr in 1875. So far, materials such as organic liquids such as nitrobenzene and carbon disulfide have been known as materials showing the Kerr effect. These materials are used for, for example, high electric field strength measurement of power cables and the like in addition to the optical shutter described above.

  After that, it was shown that the liquid crystal material has a large Kerr constant, and a basic study for application to a light modulation element, a light polarization element, and an optical integrated circuit was performed, and the Kerr constant exceeding 200 times that of the nitrobenzene was shown. Liquid crystal compounds have also been reported.

  In such a situation, application to a display device of the Kerr effect is being studied. Since the Kerr effect is proportional to the second order of the electric field, it can be expected to drive at a relatively low voltage, and essentially exhibits a response characteristic of several microseconds to several milliseconds. Application is expected.

  Under such circumstances, for example, in Patent Document 1, Patent Document 2, and Non-Patent Document 1, a medium made of a liquid crystal substance is sealed between a pair of substrates, and an electric field parallel or perpendicular to the substrates is applied. It has been proposed to induce the Kerr effect and apply it as a display element.

In such a display element, polarizing plates whose absorption axes are orthogonal to each other are arranged outside each of the substrates, and the medium is optically isotropic when no voltage is applied to realize black display. When applied, birefringence occurs, resulting in a change in transmittance, thereby performing gradation display. For this reason, the contrast in the normal direction of the substrate can realize a very high value.
JP 2001-249363 A (published September 14, 2001) Japanese Patent Laid-Open No. 11-183937 (published July 9, 1999) Shiro Matsumoto, 3 others, “Fine droplets of liquid crystals in a transparent polymer and their response to an electric field”, Appl. Phys., 1996, Lett. 69, p. 1044-1046 Takashi Kato and two others, “Fast and High-Contrast Electro-optical Switching of Liquid-Crystalline Physical Gels: Formation of Oriented Microphase-Separated Structures”, Adv. Funct. Mater., April 2003, vol. 13. No. 4, p313-317 Kazuya Saito, 1 other person, “Thermodynamics of unusual thermotropic liquid crystals that are optically isotropic”, Liquid Crystals, 2001, Vol. 5, No. 1. p.20-27 Jun Yamamoto, “Liquid Crystal Microemulsion”, Liquid Crystal, 2000, Vol. 3, No. 3, p.248-254 Yukihide Shiraishi, 4 others, “Palladium nanoparticles protected with liquid crystal molecules—Preparation and application to guest-host mode liquid crystal display devices”, Polymer Papers, December 2002, Vol. 59, No. 12, p. .753-759 Hirotsugu kikuchi, 4 others, "Polymer-stabilized liquid crystal blue phases", p. 64-68, [online], September 2, 2002, Nature Materials, vol. 1, [Search July 10, 2003], Internet <URL: http://www.nature.com/naturematerials> Makoto Yoneya, “Searching for Nanostructured Liquid Crystal Phase by Molecular Simulation”, Liquid Crystal, 2003, Vol. 7, No. 3, p.238-245 D. Demus, 3 other editions, “Handbook of Liquid Crystals Low Molecular Weight Liquid Crystal”, Wiley-VCH, 1998, vol. 2B, p. 887-900 D. Demus, 3 other editions, “Handbook of Liquid Crystals Low Molecular Weight Liquid Crystal”, Wiley-VCH, 1998, vol. 1, p. 484-485 Eric Grelet, 3 others, “Structural Investigations on Smectic Blue Phases”, PHYSICAL REVIEW LETTERS, The American Physical Society, April 23, 2001, vol. 86, no. 17, p3791-3794 Jun Yamamoto, "Liquid Crystal Science Laboratory 1st: Identification of Liquid Crystal Phase: (4) Lyotropic Liquid Crystal", Liquid Crystal, 2002, Vol. 6, No. 1, p.72-83 Junichi Yamamoto, 1 outside, “Organic electro-optic material”, National Technical Report, December 1976, vol. 22, no. 6, p. 826-834

  However, according to a detailed examination by the inventors of the present application, it has been found that a display element having the above-described conventional configuration may exhibit a phenomenon of decreasing contrast (white display luminance / black display luminance). It turned out that there was a problem in the practicality of televisions and personal computer monitors using the element.

  According to the study by the inventors of the present application, the following two factors can be cited as factors that cause the contrast to decrease.

  First, when power is turned on in a conventional display element using a medium that exhibits optical anisotropy by application of an electric field as a display medium or a display device including the display element, the ambient temperature is If the temperature is low, the medium does not reach the temperature at which it should be driven, and the physical state of the medium may be different from the state that the medium should have at the time of driving the element. . For example, when the medium must be driven in an isotropic phase state immediately above the phase transition temperature of the nematic-isotropic phase, the medium may be in a nematic state lower than the phase transition temperature when the power is turned on. is there. In this case, when nematics that have optical anisotropy even when no electric field is applied must transmit black due to the optical anisotropy when black display must be achieved in an isotropic state when no electric field is applied. Will end up. Therefore, in such a case, good black display cannot be performed and the contrast is lowered. Of course, the display element can be overheated by a heater or a light source (backlight) to obtain a good display, but it is not easy to raise the temperature and stabilize it instantaneously.

  The other is that in the bulk region away from the substrate interface inside the cell, even if the medium (display medium) realizes an optically isotropic state, the molecules constituting the medium are firmly adsorbed by the substrate at the substrate interface. Therefore, there are cases where the optically isotropic state may not be realized. For example, when driving at a temperature of 0.1 K just above the nematic-isotropic phase transition temperature, the vicinity of the substrate interface is in a nematic state.

  In any case, near the substrate interface, due to the adsorption phenomenon, the physical state of the medium is different from the state that should originally have when the element is driven, and is different from the bulk region inside the cell that is away from the substrate interface. The medium in the vicinity of the interface causes a phenomenon that light is transmitted even during black display, and as a result, the contrast is lowered.

  The present invention has been made in view of the above-mentioned problems, and the object thereof is a display element that does not cause the above-described problems, that is, a display element that does not deteriorate contrast and has excellent high-speed response and viewing angle characteristics. Is to provide.

Display element according to the present invention, in order to solve the above problems, and at least one of the pair of transparent substrates, being interposed between the pair of substrates, and the medium optical anisotropy is expressed by the application of an electric field, Of the pair of substrates, at least one of the substrates is provided with at least one polarizing plate disposed on a side opposite to the surface facing the medium, and the medium exhibits optical isotropy when no electric field is applied. A display element that performs display by exhibiting optical anisotropy when an electric field is applied, wherein at least one of the pair of substrates has at least one horizontal alignment treatment on a surface facing the other substrate. It is characterized by being applied in parallel or perpendicular to the absorption axis of the polarizing plate or by being subjected to a vertical alignment treatment.

According to the above configuration, the absorption axis of at least one polarizing plate on the surface of the at least one of the pair of substrates facing the other substrate, that is, at least one of the pair of substrates. By performing a horizontal alignment process or a vertical alignment process in a direction parallel or perpendicular to the absorption axis of any polarizing plate disposed on the side opposite to the surface facing the medium, for example, the ambient temperature is Low, when the power is turned on, the medium does not reach the temperature at which it should be driven, and the medium is placed in the orientation even when the physical state of the medium is different from the state at the time of driving. Since it can be oriented in the direction (orientation processing direction), the optical contribution due to the medium (medium whose physical state is different from the original driving state) can be eliminated, and the temperature of the display element is increased. Also in until it becomes possible to realize a good display. Further, according to the above configuration, even when the desired driving temperature is reached, light leakage due to molecules adsorbed on the substrate interface does not occur, and high contrast can be obtained. Therefore, according to the above configuration, there is an effect that it is possible to provide a display element excellent in high-speed response and viewing angle characteristics without lowering contrast. The medium exhibits optical isotropy when no electric field is applied, and exhibits optical anisotropy when a voltage is applied. Therefore, according to the above configuration, by applying an electric field, the shape of the refractive index ellipsoid of the medium can be changed between when no electric field is applied and when an electric field is applied, and the direction of optical anisotropy is constant. The display can be performed by changing the degree of optical anisotropy (degree of orientation order, refractive index). Therefore, according to the said structure, there exists an effect that the display element which has a wide viewing angle characteristic and a high-speed response characteristic is realizable.

  In addition, in order to solve the above problems, the display element according to the present invention includes at least a pair of electrodes for applying an electric field substantially parallel to the substrate to the medium, and the alignment treatment direction in the horizontal alignment treatment is the above. It is characterized in that it forms an angle of less than 45 degrees ± 10 degrees with respect to the direction of electric field application by the electrodes.

  As described above, in the display element in which the electric field is applied substantially parallel to the substrate, the alignment process direction in the horizontal alignment process forms an angle of less than 45 degrees ± 10 degrees with respect to the electric field application direction by the electrodes. The effect is that the rate can be maximized.

  The display element includes at least a pair of electrodes for applying an electric field substantially parallel to the substrate to the medium on one of the pair of substrates, and a horizontal alignment film is provided on the surface of the other substrate. It is desirable.

  When an alignment film is formed on the electrode, the voltage effectively applied to the medium, that is, the display medium is reduced. Furthermore, the effect is not as great as when the horizontal alignment film is formed on the surfaces of both substrates, but can also be obtained when the horizontal alignment film is formed only on one substrate surface.

  Accordingly, at least one pair of electrodes for applying an electric field substantially parallel to the substrate to the medium is provided on only one surface of the substrate, for example, one substrate facing the other substrate, and the other substrate surface, that is, Since the horizontal alignment film is provided on the surface of the substrate on the non-electrode-forming side, the voltage drop due to the alignment film does not occur, and the black luminance can be reduced without increasing the drive voltage of the element. Play. Further, according to the above configuration, even when the desired driving temperature is reached, light leakage due to molecules adsorbed on the substrate interface does not occur, and there is an effect that a high contrast can be obtained.

  In the display element, it is preferable that the surfaces of the pair of substrates facing each other are subjected to a horizontal alignment process in parallel or antiparallel to each other.

  Since the surfaces of the pair of substrates facing each other are subjected to horizontal alignment processing in parallel or antiparallel, the contrast can be maximized, for example, the black luminance can be further reduced. There is an effect. In the present invention, “parallel” means that the alignment treatment directions are parallel and the same direction, and “anti-parallel” means that the alignment treatment directions are parallel and opposite (reverse). This case shall be shown.

Further, the medium may have an alignment order equal to or less than the wavelength of light when no electric field is applied.

If the alignment order is less than the wavelength of light, it is optically isotropic. Therefore, the display in by using a medium which is orientational order when no voltage is applied (when no electric field is applied) becomes less than the wavelength of light, when no voltage is applied (the absence of an applied electric field) when a voltage is applied and (when an electric field is applied) There exists an effect that a state can be varied reliably.

  Further, the medium may have an ordered structure exhibiting cubic symmetry.

  The medium may be composed of molecules exhibiting a cubic phase or a smectic D phase.

  The medium may be made of a liquid crystal microemulsion.

  The medium may be composed of a lyotropic liquid crystal exhibiting a micelle phase, a reverse micelle phase, a sponge phase, or a cubic phase.

  The medium may be composed of a liquid crystal fine particle dispersion system exhibiting a micelle phase, reverse micelle phase, sponge phase, or cubic phase.

  The medium may be a dendrimer.

  The medium may be composed of molecules exhibiting a cholesteric blue phase.

  The medium may be composed of molecules exhibiting a smectic blue phase.

  In any of the above substances, the optical anisotropy changes when an electric field is applied. Therefore, any of the above substances can be used as the medium.

  As described above, the display element according to the present invention has a surface facing the other substrate of at least one of the pair of substrates and the other substrate of at least one of the pair of substrates. The surface of the opposing surface is subjected to a horizontal alignment treatment parallel or perpendicular to the absorption axis of at least one polarizing plate, or a vertical alignment treatment, for example, at a low ambient temperature, when power is turned on. Even if the medium does not reach the temperature to be driven and the physical state of the medium is different from the original driving state, the medium is moved in the orientation direction (orientation processing direction). ), The optical contribution due to the medium (medium whose physical state is different from the original driving state) can be eliminated, and before the temperature of the display element rises. Even, it is possible to realize a good display. Further, according to the above configuration, even when the desired driving temperature is reached, light leakage due to molecules adsorbed on the substrate interface does not occur, and high contrast can be obtained. Therefore, according to the above configuration, there is an effect that it is possible to provide a display element excellent in high-speed response and viewing angle characteristics without lowering contrast.

  An embodiment of the present invention will be described with reference to FIGS. 1 to 13 as follows.

  FIG. 1A is a cross-sectional view schematically showing a schematic configuration of a main part of the display element according to the present embodiment in a voltage non-application state (OFF state), and FIG. It is sectional drawing which shows typically schematic structure of the principal part of the display element concerning this Embodiment in an ON state. FIG. 2 is a diagram for explaining the relationship among the polarizing plate absorption axis, the electric field (orientation) direction, and the rubbing direction in the display element. Further, FIG. 3 is a diagram illustrating an example of an electrode structure in the display element and a relationship between the electrode structure and a polarizing plate absorption axis.

  As shown in FIGS. 1 (a) and 1 (b), the display element according to the present embodiment includes a pair of substrates (hereinafter referred to as a pixel substrate 11 and a counter substrate 12) that are arranged to face each other and at least one of them is transparent. And a cell structure in which a medium layer 3 made of a medium that is optically modulated by applying an electric field (hereinafter referred to as medium A) is sandwiched between the pair of substrates as an optical modulation layer. Yes.

  Further, as shown in FIGS. 1A and 1B, the pixel substrate 11 and the counter substrate 12 have substrates 1 and 2 as medium holding means (optical modulation layer holding means), respectively. A configuration in which polarizing plates 6 and 7 are respectively provided on the outside of the substrates 1 and 2 (outside of the pixel substrate 11 and the counter substrate 12), that is, on the surface opposite to the facing surfaces of both the substrates 1 and 2. Have.

  Of the pair of substrates 1 and 2, at least one substrate is made of a transparent substrate such as a glass substrate having translucency, and the other substrate of the pair of substrates 1 and 2 is the other substrate. 2 is an electric field applying means for applying an electric field (lateral electric field) substantially parallel to the substrate 1 to the medium layer 3 as shown in FIGS. 1 (a) and 1 (b). The electrodes 4 and 5 are arranged to face each other.

  The electrodes 4 and 5 are made of an electrode material such as a transparent electrode material such as ITO (indium tin oxide). In the present embodiment, for example, the line width is 5 μm, the distance between electrodes (electrode interval) is 5 μm, and the thickness is 0. It is set to 3 μm. However, the electrode material, the line width, the distance between the electrodes, and the thickness are merely examples, and are not limited thereto. As an example of the electrodes 4 and 5, for example, as shown in FIG. 3, a comb-shaped electrode in which the comb-tooth portions 4a and 5a are opposed to each other is arranged. There is no particular limitation as long as an electric field can be applied to the medium layer 3.

  Further, on the surface of the substrate 1 facing the substrate 2, that is, on the surface of the pixel substrate 11 facing the counter substrate 12, a rubbing alignment film 8 (dielectric thin film) is provided on the electrode. 4 and 5 so as to cover the entire surface of the substrate 1 facing the substrate 2.

  An alignment film 9 (dielectric thin film) that has been subjected to rubbing treatment on the surface of the substrate 2 facing the substrate 1, that is, on the surface of the counter substrate 12 facing the pixel substrate 11, also has the substrate. 2 over the entire surface facing the substrate 1.

  As shown in FIG. 2, the alignment films 8 and 9 have a rubbing direction of either one of the absorption axes 6a and 7a of the polarizing plates 6 and 7 (see FIG. 3, polarizing plate absorption axis). As the rubbing process, a horizontal rubbing process (horizontal alignment process) in which the alignment process direction is the in-plane direction of the substrate is performed so as to coincide with the absorption axis.

  2 and 3, the polarizing plates 6 and 7 are arranged so that the polarizing plate absorption axis directions thereof are orthogonal to each other, and the polarizing plate absorption axes of the polarizing plates 6 and 7 are An angle of 45 degrees is formed with respect to the electric field application direction of the electrodes 4 and 5.

In the display element according to the present embodiment, as shown in FIG. 1B, the medium layer 3 exhibits optical anisotropy due to an increase in the degree of orientational order in the direction of electric field application, and the transmittance changes. It can function as a shutter-type display element. Therefore, with respect to the polarizing plate absorption axis directions orthogonal to each other, the anisotropic direction gives the maximum transmittance when forming an angle of 45 degrees. Note that the transmittance (P) when the orientation in which the optical anisotropy of the medium A develops exists at an angle of ± θ (degrees) to the polarizing plate absorption axis is P (%) = Sin ² ( 2θ). If the transmittance when θ is 45 degrees is 100%, it is felt that the human eye has the maximum luminance when the transmittance is approximately 90% or more. If θ is 35 degrees <θ <55 degrees, it is felt that the human eye has the maximum luminance. That is, as shown in the present embodiment, in a display element in which an electric field is applied, for example, substantially parallel to the substrate 1, the polarizing plate absorption axis direction, in other words, the alignment treatment direction (rubbing direction) in the horizontal alignment treatment is The transmittance can be maximized by forming an angle of less than 45 degrees ± 10 degrees, more preferably less than 45 degrees ± 5 degrees, and most preferably 45 degrees with respect to the direction of electric field application by the electrodes 4 and 5. it can.

  In the present embodiment, as shown in FIGS. 2 and 3, the polarizing plates 6 and 7 provided on both the substrates 1 and 2 are orthogonal to each other and the polarizing plates 6 and 7 are orthogonal to each other. Is formed at an angle of 45 degrees between the polarizing plate absorption axis and the electrodes 4 and 5 (comb portions 4a and 5a).

  Therefore, in the display element, the electric field application direction by the electrodes 4 and 5 forms an angle of 45 degrees with the polarizing plate absorption axis direction of the polarizing plates 6 and 7 and the rubbing direction of the alignment films 8 and 9.

  In the present embodiment, as shown in FIG. 2, the rubbing directions in the alignment films 8 and 9 are parallel to each other as long as they coincide with the polarizing plate absorption axis of the polarizing plates 6 and 7 ( The orientation (treatment) directions of each other may be parallel and the same direction), and anti-parallel (anti-parallel), that is, the orientation (treatment) directions of each other are parallel and opposite (reverse). It may be present or orthogonal.

  Each of the alignment films 8 and 9 used in the present embodiment may be an organic film or an inorganic film, and improves the degree of alignment order of the molecules 10 constituting the medium A. As long as the molecules 10 can be aligned in a desired direction, the alignment is not particularly limited. However, when the alignment films 8 and 9 are formed of an organic thin film, a good alignment effect is exhibited. Therefore, it is more desirable to use an organic thin film as the alignment films 8 and 9. Among such organic thin films, polyimide has high stability and reliability, and exhibits an extremely excellent alignment effect. Therefore, by using polyimide as an alignment film material, a display element having better display performance is provided. be able to.

  A commercially available horizontal alignment film can be used as the alignment films 8 and 9.

  Further, the alignment films 8 and 9 may have a functional group having photosensitivity (hereinafter referred to as a photofunctional group) because the alignment control is easy. Examples of the photofunctional group include a cinnamate system and a chalcone system that perform a dimerization reaction, and an azo system that performs an isomerization reaction, but the present invention is not limited thereto.

  When the alignment films 8 and 9 have a photofunctional group, the surfaces of the pixel substrate 11 and the counter substrate 12, that is, the surfaces of the alignment films 8 and 9 are irradiated with polarized ultraviolet rays (hereinafter referred to as polarized ultraviolet light irradiation). ) To develop the alignment regulating force, the desired alignment treatment can be easily performed.

  In the display element, for example, the pixel substrate 11 and the counter substrate 12 are bonded to each other with a sealing agent (not shown) through a spacer such as a plastic bead or a glass fiber spacer (not shown) as necessary. The medium A is encapsulated.

The medium A used in the present embodiment is a medium whose optical anisotropy changes when an electric field is applied. When an electric field E _j is applied to the material from the outside, an electric displacement D _ij = ε _ij · E _j is generated, and at that time, a slight change is also seen in the dielectric constant (ε _ij ). Since the square of the refractive index (n) is equivalent to the dielectric constant at the frequency of light, the medium A can also be said to be a substance whose refractive index changes when an electric field is applied.

  As described above, the display element according to the present embodiment performs display using a phenomenon (electro-optic effect) in which the refractive index of a substance is changed by an external electric field. Unlike liquid crystal display elements that utilize the fact that they rotate together, the direction of optical anisotropy hardly changes, and the degree of optical anisotropy changes (mainly electronic polarization and orientation polarization). Is displayed.

  As the medium A, a substance exhibiting the Pockels effect or the Kerr effect is optically isotropic when no electric field is applied (may be macroscopically isotropic). May be a substance that exhibits optical anisotropy when no electric field is applied, and disappears when the electric field is applied, and is optically isotropic (as long as it is macroscopically isotropic) It may be a substance exhibiting good). Typically, it is optically isotropic when no electric field is applied (it should be isotropic when viewed macroscopically), and optical modulation (especially, it is desirable that birefringence is increased by applying an electric field) by applying an electric field. It is a medium to express.

  The Pockels effect and the Kerr effect (which are themselves observed in the isotropic phase state) are electro-optic effects that are proportional to the primary or secondary electric field, respectively, and are in the isotropic phase when no voltage is applied. Although optically isotropic, in the voltage application state, in the region where an electric field is applied, the long axis direction of the compound molecules is oriented in the electric field direction, and birefringence is expressed, thereby modulating the transmittance. be able to. For example, in the case of a display method using a substance exhibiting the Kerr effect, by controlling the bias of electrons within one molecule by applying an electric field, each randomly arranged individual molecule rotates and becomes oriented. Is advantageous in that the response speed is very fast and the molecules are arranged randomly, and there is no viewing angle limitation. The medium A that is roughly proportional to the primary or secondary electric field can be treated as a substance exhibiting the Pockels effect or the Kerr effect.

  Examples of the substance exhibiting the Pockels effect include, but are not limited to, organic solid materials such as hexamine. As the medium A, various organic materials and inorganic materials exhibiting the Pockels effect can be used.

  Moreover, as a substance which shows a Kerr effect, following structural formula (1)-(4)

Although the liquid crystalline substance shown by these is mentioned, it does not specifically limit.

  The Kerr effect is observed in a medium transparent to incident light. For this reason, the substance showing the Kerr effect is used as a transparent medium. Usually, a liquid crystalline substance shifts from a liquid crystal phase having a short-range order to an isotropic phase having random orientation at a molecular level as the temperature rises. In other words, the Kerr effect of liquid crystalline substances is not a nematic phase, but a phenomenon seen in liquids in the isotropic phase state above the liquid crystal phase-isotropic phase temperature. The liquid crystalline substance is used as a transparent dielectric liquid. Is done.

  A dielectric liquid such as a liquid crystal substance is in an isotropic phase state as the use environment temperature (heating temperature) by heating is higher. Therefore, when a dielectric liquid such as a liquid crystal substance is used as the medium, in order to use the dielectric liquid in a liquid state that is transparent, that is, transparent to visible light, for example, (1) medium layer 3 may be provided with heating means such as a heater (not shown), and the dielectric liquid may be heated to the clearing point or higher by the heating means. (2) Thermal radiation from the backlight, The dielectric liquid may be used by heating it above its clearing point by light conduction and / or heat conduction from the peripheral driving circuit (in this case, the backlight or the peripheral driving circuit functions as a heating means). (3) A sheet heater (heating means) may be bonded to at least one of the substrates 1 and 2 as a heater and heated to a predetermined temperature. Furthermore, in order to use the dielectric liquid in a transparent state, a material having a clearing point lower than the lower limit of the operating temperature range of the display element may be used.

  The medium A preferably contains a liquid crystalline substance. When a liquid crystalline substance is used as the medium A, the liquid crystalline substance is a transparent liquid that shows a macroscopic isotropic phase. However, microscopically, it is desirable to include a cluster which is a molecular group having a short-range order arranged in a certain direction. Since the liquid crystalline substance is used in a state transparent to visible light, the cluster is also used in a state transparent (optically isotropic) to visible light.

  Therefore, as described above, the display element may be temperature-controlled using heating means such as a heater, or the medium layer 3 may be made of a polymer material as described in Patent Document 2. The liquid crystalline material may be divided into small areas using, for example, a diameter of 0.1 μm or less, and the liquid crystalline material is a micro droplet having a diameter smaller than the wavelength of light. Alternatively, it may be made transparent by suppressing light scattering, or a liquid crystalline compound exhibiting a transparent isotropic phase at the use environment temperature (room temperature) may be used. Light scattering can be ignored when the diameter of the liquid crystalline substance, and further, the diameter (major axis) of the cluster is 0.1 μm or less, that is, smaller than the wavelength of light (incident light wavelength). Therefore, for example, if the diameter of the cluster is 0.1 μm or less, the cluster is also transparent to visible light.

  The medium A is not limited to a substance exhibiting the Pockels effect or the Kerr effect as described above. For this reason, the medium A has an ordered structure in which the molecular arrangement has cubic symmetry of a scale equal to or smaller than the wavelength of light (for example, nanoscale), and is optically isotropic cubic phase (non-patent document) You may have literature 3 * 6-8). The cubic phase is one of the liquid crystal phases of the liquid crystalline substance that can be used as the medium A. As the liquid crystalline substance exhibiting the cubic phase, for example, the following structural formula (5)

BABH8 etc. which are shown by these. When an electric field is applied to such a liquid crystalline substance, the fine structure is distorted and optical modulation can be induced.

  BABH8 shows a cubic phase composed of an ordered structure having cubic symmetry of a scale below the wavelength of light in a temperature range of 136.7 ° C. or more and 161 ° C. or less. The BABH 8 has an ordered structure equal to or less than the wavelength of light, and exhibits optical isotropy when no voltage is applied in the above temperature range, whereby good black display can be performed under crossed Nicols.

  On the other hand, when a voltage is applied between the electrodes 4 and 5 (comb-shaped electrodes) while controlling the temperature of the BABH 8 to 136.7 ° C. or more and 161 ° C. or less using, for example, the heating means described above, cubic symmetry is obtained. Distortion occurs in the structure (ordered structure). That is, the BABH8 is isotropic in the above temperature range when no voltage is applied, and anisotropy is exhibited when a voltage is applied.

  As a result, birefringence occurs in the medium layer 3, so that the display element can perform good white display. Note that the direction in which birefringence occurs is constant, and its magnitude changes with voltage application. The voltage transmittance curve showing the relationship between the voltage applied between the electrodes 4 and 5 (comb electrodes) and the transmittance is a temperature range of 136.7 ° C. or higher and 161 ° C. or lower, that is, a wide temperature range of about 20K. Becomes a stable curve. For this reason, when the BABH 8 is used as the medium A, temperature control can be performed very easily. That is, since the medium layer 3 made of BABH8 is a thermally stable phase, it does not exhibit abrupt temperature dependence and is extremely easy to control the temperature.

  Further, as the medium A, it is also possible to realize a system that is optically isotropic, in which liquid crystal molecules are filled with aggregates that are radially aligned with a size equal to or smaller than the wavelength of light. As a technique, the liquid crystal microemulsion described in Non-Patent Document 4 or the liquid crystal / fine particle dispersion system described in Non-Patent Document 5 (mixed system in which fine particles are mixed in a solvent (liquid crystal), hereinafter simply referred to as a liquid crystal fine particle dispersion system). ) Method can also be applied. When an electric field is applied to these, a set of radial orientations is distorted, and optical modulation can be induced.

  Any of these liquid crystalline substances may be liquid crystalline as a single substance, or may be liquid crystalline by mixing a plurality of substances. Other non-liquid crystalline substances may be mixed. Furthermore, a polymer / liquid crystal dispersion material as described in Non-Patent Document 1 can also be applied. Further, a gelling agent as described in Non-Patent Document 2 may be added.

  The medium A preferably contains a polar molecule. For example, nitrobenzene or the like is suitable as the medium A. Nitrobenzene is also a type of medium that exhibits the Kerr effect.

  Hereinafter, examples of the substance or the form of the substance that can be used as the medium A will be shown, but the present invention is not limited to the following examples.

[Smectic D phase (SmD)]
The smectic D phase (SmD) is one of liquid crystal phases of a liquid crystalline material that can be used as the medium A, has a three-dimensional lattice structure, and has a lattice constant equal to or less than the wavelength of light. For this reason, the smectic D phase is optically isotropic.

  Examples of liquid crystalline substances exhibiting a smectic D phase include the following general formulas (6) and (7) described in Non-Patent Document 3 or Non-Patent Document 8.

ANBC16 represented by the following. In the general formulas (6) and (7), m represents an arbitrary integer, specifically, m = 16 in the general formula (6), m = 15 in the general formula (7), and X Represents a —NO ₂ group.

  The ANBC16 exhibits a smectic D phase in a temperature range of 171.0 ° C. to 197.2 ° C. When an electric field is applied to the ANBC 16 in the above temperature range in which the ANBC 16 exhibits a smectic D phase, the ANBC 16 molecules themselves have dielectric anisotropy, so that the molecules are distorted in the lattice structure as the molecules move in the direction of the electric field. That is, the optical anisotropy appears in ANBC16. Note that the material is not limited to ANBC16, and any material exhibiting a smectic D phase can be applied as the medium A of the display element according to the present embodiment.

[Liquid crystal microemulsion]
A liquid crystal microemulsion is an O / W microemulsion proposed in Non-Patent Document 4 (a system in which water is dissolved in oil in the form of water droplets in an oil, and the oil becomes a continuous phase). A generic term for a system (mixed system) in which oil molecules are replaced with thermotropic liquid crystal molecules.

  Specific examples of the liquid crystal microemulsion include, for example, pentylcyanobiphenyl (5CB) which is a thermotropic liquid crystal exhibiting a nematic liquid crystal phase and a lyotropic (lyotropic) liquid crystal which exhibits a reverse micelle phase, which are described in Non-Patent Document 4. There is a mixed system with an aqueous solution of didodecyl ammonium bromide (DDAB). This mixed system has a structure represented by schematic views as shown in FIGS.

  In this mixed system, the diameter of reverse micelles is typically about 50 mm, and the distance between the reverse micelles is about 200 mm. These scales are about an order of magnitude smaller than the wavelength of light. In addition, reverse micelles exist randomly in three-dimensional space, and 5CB are radially oriented around each reverse micelle. Therefore, this mixed system is optically isotropic.

  When an electric field is applied to a medium composed of this mixed system, the molecule itself tends to move in the direction of the electric field because there is dielectric anisotropy in 5CB. That is, orientation anisotropy appears in a system that is optically isotropic because it is oriented radially around a reverse micelle, and optical anisotropy appears. The liquid crystal microemulsion is not limited to the above-described mixed system, and is optically isotropic when no voltage is applied, and exhibits optical anisotropy when voltage is applied. It can be applied as the medium A.

[Lyotropic LCD]
The lyotropic liquid crystal means a liquid crystal of another component system in which the main molecules forming the liquid crystal are dissolved in a solvent having other properties (such as water or an organic solvent). The specific phase is a phase that is optically isotropic when no electric field is applied. Examples of such a specific phase include a micelle phase, a sponge phase, a cubic phase, and a reverse micelle phase described in Non-Patent Document 11. FIG. 10 shows a classification diagram of the lyotropic liquid crystal phase.

  Surfactants that are amphiphilic substances include substances that develop a micelle phase. For example, an aqueous solution of sodium decyl sulfate, which is an ionic surfactant, an aqueous solution of potassium palmitate, and the like form spherical micelles. Further, in a mixed solution of polyoxyethylene nonylphenyl ether, which is a nonionic surfactant, and water, micelles are formed by the nonylphenyl group acting as a hydrophobic group and the oxyethylene chain acting as a hydrophilic group. In addition, micelles are formed even in an aqueous solution of a styrene-ethylene oxide block copolymer.

  For example, spherical micelles exhibit a spherical shape by packing molecules (forming molecular aggregates) in all spatial directions. Further, since the size of the spherical micelle is equal to or less than the wavelength of light, it does not show anisotropy and looks isotropic. However, when an electric field is applied to such spherical micelles, the spherical micelles are distorted, so that anisotropy is expressed. Therefore, a lyotropic liquid crystal having a spherical micelle phase can also be applied as the medium A of the display element according to this embodiment. The same effect can be obtained by using not only the spherical micelle phase but also other micelle phases, that is, string-like micelle phase, elliptical micelle phase, rod-like micelle phase, and the like as the medium A.

  Further, it is generally known that reverse micelles in which a hydrophilic group and a hydrophobic group are exchanged are formed depending on the conditions of concentration, temperature, and surfactant. Such reverse micelles optically show the same effects as micelles. Therefore, by applying the reverse micelle phase as the medium A, an effect equivalent to that obtained when the micelle phase is used is obtained. The liquid crystal microemulsion described above is an example of a lyotropic liquid crystal having a reverse micelle phase (reverse micelle structure).

  Further, an aqueous solution of pentaethylene glycol-dodecyl ether, which is a nonionic surfactant, has a concentration and temperature range showing a sponge phase and a cubic phase as shown in FIG. Such a sponge phase or cubic phase is a transparent substance because it has an order equal to or less than the wavelength of light. That is, a medium composed of these phases is optically isotropic. When a voltage is applied to a medium composed of these phases, the orientation order changes and optical anisotropy appears. Therefore, a lyotropic liquid crystal having a sponge phase or a cubic phase can also be applied as the medium A of the display element according to this embodiment.

[Liquid crystal fine particle dispersion]
The medium A may be, for example, a liquid crystal fine particle dispersion system in which latex particles having a diameter of about 100 mm whose surface is modified with a sulfate group are mixed in an aqueous solution of a nonionic surfactant pentaethylene glycol-dodecyl ether. Good. In the liquid crystal fine particle dispersion system, a sponge phase is expressed. However, the medium A used in the present embodiment may be a liquid crystal fine particle dispersion system that expresses the aforementioned micelle phase, cubic phase, reverse micelle phase, or the like. In addition, by using the DDAB in place of the latex particles, an alignment structure similar to the liquid crystal microemulsion described above can be obtained.

[Dendrimer]
A dendrimer is a three-dimensional hyperbranched polymer having a branch for each monomer unit. Since dendrimers have many branches, they have a spherical structure when the molecular weight exceeds a certain level. This spherical structure is a transparent material because it has an order equal to or less than the wavelength of light, and its optical orientation is manifested by changing the orientation order when a voltage is applied. Therefore, a dendrimer can also be applied as the medium A of the display element according to this embodiment. Further, by using the dendrimer in place of DDAB in the liquid crystal microemulsion described above, an alignment structure similar to that of the liquid crystal microemulsion described above can be obtained. The medium thus obtained can also be applied as the medium A.

[Cholesteric blue phase]
It is known that the cholesteric blue phase has a three-dimensional periodic structure in the helical axis, and the structure has high symmetry (see, for example, Non-Patent Documents 6 and 7). The cholesteric blue phase is an almost transparent substance because it has an order equal to or less than the wavelength of light, and its orientation order is changed by application of a voltage, and optical anisotropy appears. That is, the cholesteric blue phase is optically substantially isotropic, and the liquid crystal molecules tend to move in the electric field direction when an electric field is applied, so that the lattice is distorted and anisotropy is expressed.

  In addition, as a substance showing a cholesteric blue phase, for example, “JC1041” (trade name, mixed liquid crystal manufactured by Chisso Corporation) is 48.2 wt%, “5CB” (4-cyano-4′-pentylbiphenyl, nematic liquid crystal). 47.4% by weight and “ZLI-4572” (trade name, a chiral dopant manufactured by Merck & Co., Inc.) at a ratio of 4.4% by weight are known. The composition exhibits a cholesteric blue phase in the temperature range of 330.7K to 331.8K.

[Smectic blue phase]
The smectic blue (BP _Sm ) phase has a highly symmetric structure (for example, see Non-Patent Document 7, Non-Patent Document 10 and the like) and has an order of less than the wavelength of light, as does the costic blue phase. Therefore, it is a substantially transparent substance, and the orientational order is changed by application of voltage, and optical anisotropy is developed. That is, the smectic blue phase is optically substantially isotropic, and the liquid crystal molecules tend to move in the direction of the electric field when an electric field is applied, so that the lattice is distorted and anisotropy is expressed.

In addition, as a substance which shows a smectic blue phase, FH / FH / HH-14BTMHC etc. which are described in the nonpatent literature 10 are mentioned, for example. The material exhibits a BP _Sm 3 phase at 74.4 ° C. to 73.2 ° C., a BP _Sm 2 phase at 73.2 ° C. to 72.3 ° C., and a BP _Sm 1 phase at 72.3 ° C. to 72.1 ° C. . Since the BP _Sm phase has a highly symmetric structure as shown in Non-Patent Document 7, it generally exhibits optical isotropy. Further, when an electric field is applied to the substance FH / FH / HH-14BTMHC, the lattice is distorted by the liquid crystal molecules moving in the direction of the electric field, and the substance exhibits anisotropy. Therefore, the same substance can be used as the medium A of the display element according to this embodiment.

  As described above, the substance that can be used as the medium A in the display element according to the present embodiment only has to change its optical anisotropy (refractive index, degree of orientation order) by applying an electric field. For example, it may be a substance exhibiting Pockels effect or Kerr effect, and may be composed of molecules exhibiting any of cubic phase, smectic D phase, cholesteric blue phase, and smectic blue phase. It may be a lyotropic liquid crystal or a liquid crystal fine particle dispersion system showing any of a phase, a sponge phase, and a cubic phase. The medium A may be a liquid crystal microemulsion, a dendrimer (dendrimer molecule), an amphiphilic molecule, a copolymer, or a polar molecule other than the above.

  The medium is not limited to a liquid crystalline substance, and preferably has an ordered structure (alignment order) that is equal to or less than the wavelength of light when a voltage is applied or no voltage is applied. If the ordered structure is less than the wavelength of light, it is optically isotropic. Therefore, by using a medium whose ordering structure is equal to or less than the wavelength of light when a voltage is applied or when no voltage is applied, the display state can be reliably changed between when no voltage is applied and when a voltage is applied.

  Hereinafter, in this embodiment, pentylcyanobiphenyl (5CB) represented by the structural formula (1) is used as the medium A. However, the medium A is not limited to this. Instead of the above 5CB, the various substances described above can be applied.

  According to the present embodiment, ITO is used as the electrodes 4 and 5, the line width is 5 μm, the distance between the electrodes is 5 μm, the thickness of the medium layer 3 (that is, the distance between the substrates 1 and 2) is 10 μm, and the medium A 5CB is used, and the above 5CB is maintained at a temperature just above the phase transition of the nematic isotropic phase (a temperature slightly higher than the phase transition temperature, for example, +0.1 K) by an external heating device (heating means), and voltage is applied. As a result, the transmittance could be changed. In addition, said 5CB shows a nematic phase at the temperature below 33.3 degreeC, and an isotropic phase at the temperature beyond it.

  Next, with respect to the display principle of the display element according to the present embodiment, FIGS. 1 (a) and 1 (b), FIGS. 4 (a) and 4 (b), FIG. 6, and FIGS. This will be described below with reference.

  In the following description, a transmissive display element is mainly used as the display element, which is optically isotropic and preferably isotropic when no electric field is applied. The case where a substance exhibiting sex is used will be described as an example, but the present invention is not limited to this.

  FIG. 4A is a main part plan view schematically showing the configuration of the display element according to the present embodiment in the electric field non-application state (OFF state), and FIG. 4B is a voltage application state (ON). It is a principal part top view which shows typically the structure of the said display element in a state. 4A and 4B show the configuration of one pixel in the display element, and the illustration of the configuration of the counter substrate 12 is omitted for convenience of explanation. The electrodes 4 and 5 may be comb-shaped electrodes as shown in FIG. 3 and are particularly limited as long as they can apply an electric field substantially parallel to the substrates 1 and 2. Is not to be done. Moreover, the arrow in a figure shows a polarizing plate absorption axis.

  Further, FIG. 6 is a graph showing the relationship between the applied voltage and the transmittance in the display element shown in FIGS. 1A and 1B, and FIGS. The difference in display principle between a display element that performs display using a change in mechanical anisotropy and a conventional liquid crystal display element is the average of the medium when no voltage is applied (OFF state) and when a voltage is applied (ON state). 7 is a sectional view schematically showing the shape of a refractive index ellipsoid (indicated by the shape of the cut surface of the refractive index ellipsoid) and its principal axis direction, and FIGS. A cross-sectional view of a display element that performs display using a change in optical anisotropy due to voltage application when no voltage is applied (OFF state), a cross-sectional view of the display element when a voltage is applied (ON state), TN ) Cross-sectional view of the liquid crystal display element with no voltage applied, and the voltage of the TN liquid crystal display element Cross-sectional view when applied, cross-sectional view when no voltage is applied to a VA (Vertical Alignment) liquid crystal display element, cross-sectional view when a voltage is applied to the VA-type liquid crystal display element, and IPS (In Plane Switching) liquid crystal display A cross-sectional view when no voltage is applied to the element and a cross-sectional view when a voltage is applied to the IPS liquid crystal display element are shown.

In general, the refractive index in a material is not isotropic and varies depending on the direction. This anisotropy of the refractive index is in a direction parallel to the substrate surface (in-plane direction), the opposing direction of the electrodes 4 and 5, the direction perpendicular to the substrate surface (substrate normal direction), and parallel to the substrate surface. An arbitrary orthogonal coordinate system (X ₁ , X ₂ , X ₃ ) is used where the direction (in-plane direction of the substrate) and the direction perpendicular to the opposing direction of the electrodes 4 and 5 are x, y, and z directions, respectively. The following relational expression (1)

(N _ji = n _ij , i, j = 1,2,3)
(Refractive index ellipsoid) (for example, refer nonpatent literature 12). Here, when the above relational expression (1) is rewritten using the coordinate system (Y ₁ , Y ₂ , Y ₃ ) in the principal axis direction of the ellipsoid, the following relational expression (2)

Indicated by n ₁ , n ₂ , n ₃ (hereinafter referred to as nx, ny, nz) are called main refractive indexes, and correspond to half the length of the three main axes in the ellipsoid. Considering a light wave traveling in a direction perpendicular to the Y ₃ = 0 plane from the origin, this light wave has polarization components in the directions of Y ₁ and Y _2, and the refractive indexes of the respective components are nx and ny, respectively. . In general, for light traveling in an arbitrary direction, the plane that passes through the origin and is perpendicular to the traveling direction of the light wave is considered to be the cut surface of the refractive index ellipsoid, and the principal axis direction of this ellipse is the component direction of the polarization of the light wave. Yes, half the length of the main axis corresponds to the refractive index in that direction.

  First, regarding a difference in display principle between a display element that performs display using a change in optical anisotropy due to application of an electric field and a conventional liquid crystal display element, a TN system, a VA system, and an IPS are used as conventional liquid crystal display elements. The method will be described as an example.

  As shown in FIGS. 7C and 7D, in the TN liquid crystal display element, a liquid crystal layer 105 is sandwiched between a pair of substrates 101 and 102 that are arranged to face each other. It has a configuration in which transparent electrodes 103 and 104 (electrodes) are provided, and when no voltage is applied, the major axis direction of the liquid crystal molecules in the liquid crystal layer 105 is twisted and aligned, but when a voltage is applied, The major axis direction of the liquid crystal molecules is aligned along the electric field direction. In this case, the average refractive index ellipsoid 105a has a direction in which the principal axis direction (major axis direction) is parallel to the substrate surface (in-plane direction) as shown in FIG. 7C when no voltage is applied. When the direction and voltage are applied, as shown in FIG. 7D, the principal axis direction faces the normal direction of the substrate surface. That is, the shape of the refractive index ellipsoid 105a does not change between when no voltage is applied and when the voltage is applied, and the principal axis direction changes (the refractive index ellipsoid 105a rotates).

  As shown in FIGS. 7E and 7F, the VA liquid crystal display element has a liquid crystal layer 205 sandwiched between a pair of substrates 201 and 202 arranged in opposition to each other. It has a configuration in which transparent electrodes (electrodes) 203 and 204 are provided, and when no voltage is applied, the major axis direction of the liquid crystal molecules in the liquid crystal layer 205 is aligned in a direction substantially perpendicular to the substrate surface. When a voltage is applied, the major axis direction of the liquid crystal molecules is aligned in a direction perpendicular to the electric field. As shown in FIG. 7E, the average refractive index ellipsoid 205a in this case, when no voltage is applied, the principal axis direction (major axis direction) faces the normal direction of the substrate surface, and FIG. As shown in FIG. 5, when a voltage is applied, the principal axis direction is in a direction parallel to the substrate surface (in-plane direction of the substrate). In other words, in the case of a VA liquid crystal display element, as in the case of a TN liquid crystal display element, the shape of the refractive index ellipsoid 205a does not change between when no voltage is applied and when a voltage is applied, and the principal axis direction changes. (Refractive index ellipsoid 205a rotates).

  In addition, as shown in FIGS. 7F and 7G, the IPS liquid crystal display element has a configuration in which a pair of electrodes 302 and 303 are arranged to face each other on the same substrate 301, and is not shown. By applying a voltage to the liquid crystal layer sandwiched between the counter substrate and the electrodes 302 and 303, the orientation direction of the liquid crystal molecules in the liquid crystal layer (the principal axis direction (major axis direction) of the refractive index ellipsoid 305a) ), And different display states can be realized when no voltage is applied and when a voltage is applied. That is, in the case of the IPS mode liquid crystal display element, similarly to the TN mode and VA mode liquid crystal display elements, when no voltage is applied as shown in FIG. 7 (f) and when a voltage is applied as shown in FIG. The shape of the refractive index ellipsoid 305a does not change, but its principal axis direction changes (the refractive index ellipsoid 305a rotates).

  Thus, in the conventional liquid crystal display element, the liquid crystal molecules are aligned in some direction even when no voltage is applied, and display is performed by changing the alignment direction by applying a voltage (modulation of transmittance). Yes. That is, although the shape of the refractive index ellipsoid does not change, the display is performed by utilizing the fact that the principal axis direction of the refractive index ellipsoid is rotated (changed) by voltage application. That is, in the conventional liquid crystal display element, the degree of alignment order of liquid crystal molecules is constant, and display (modulation of transmittance) is performed by changing the alignment direction.

  On the other hand, a display element that performs display using a change in optical anisotropy due to application of an electric field, including the display element according to the present embodiment, is as shown in FIGS. The shape of the refractive index ellipsoid 3a when no voltage is applied is spherical, that is, optically isotropic (nx = ny = nz, orientation order = 0), and anisotropy (nx by applying a voltage) > Ny, orientational order> 0). Note that nx, ny, and nz are the main refractive index in the direction parallel to the substrate surface (in-plane direction of the substrate) and the opposing direction of the electrodes 4 and 5, respectively, and the direction perpendicular to the substrate surface (substrate normal direction) ), The main refractive index in the direction parallel to the substrate surface (in-plane direction of the substrate) and perpendicular to the opposing direction of the electrodes 4 and 5.

  As described above, the display element according to the present embodiment performs display by modulating the degree of orientation order, for example, while the direction of optical anisotropy is constant (the voltage application direction does not change). The display principle is greatly different from that of a liquid crystal display element.

  As shown in FIG. 1A, the display element according to the present embodiment has a medium A (medium layer 3) sealed between the substrates 1 and 2 when no voltage is applied to the electrodes 4 and 5. Indicates an isotropic phase and is optically isotropic, so that black is displayed.

  On the other hand, as shown in FIG. 1 (b), when a voltage is applied to the electrodes 4 and 5, each molecule 10 of the medium A has its long axis direction along the electric field formed between the electrodes 4 and 5. The birefringence phenomenon appears because of the orientation. By this birefringence phenomenon, the transmittance of the display element can be modulated in accordance with the voltage between the electrodes 4 and 5.

  Note that the voltage required to modulate the transmittance of the display element increases at a temperature sufficiently far from the phase transition temperature (transition point), but a voltage of about 0 to 100 V is sufficient at a temperature immediately above the transition point. It is possible to modulate the transmittance.

For example, according to Non-Patent Document 9 and Non-Patent Document 12, if the refractive index in the electric field direction and the refractive index in the direction perpendicular to the electric field direction are n // and n⊥, respectively, the birefringence change (Δn = n // − n⊥) and the external electric field, that is, the electric field E (V / m) is expressed by the following relational expression (3)
Δn = λ · B _k · E ² (3)
It is represented by Here, λ is the wavelength (m) of incident light in vacuum, B _k is the Kerr constant (m / V ² ), and E is the applied electric field strength (V / m).

  The Kerr constant B is known to decrease with a function proportional to 1 / (T-Tni) as the temperature (T) increases, and even if it can be driven with a weak electric field strength near the transition point (Tni). As the temperature (T) rises, the required electric field strength increases rapidly. For this reason, the voltage necessary for modulating the transmittance increases at a temperature sufficiently far from the transition point (a temperature sufficiently higher than the transition point), but at a temperature immediately above the phase transition, the transmission is performed at a voltage of about 100 V or less. The rate can be modulated sufficiently.

  However, as a result of studies by the inventors of the present application, it has been found that when display is performed by modulating the degree of orientation order, the contrast may be lowered in some cases.

  According to the study by the inventors of the present application, the following two factors can be cited as factors that cause the contrast to decrease.

  First, when power is turned on in a conventional display element using a medium A that exhibits optical anisotropy by application of an electric field as a display medium or a display device including the display element, the ambient temperature If the temperature of the medium A is low, the temperature at which the medium A is originally driven has not been reached, and the physical state of the medium A may be different from the state that the medium A should originally have at the time of driving the element. Is mentioned. For example, when the medium A is in an isotropic phase state just above the nematic-isotropic phase transition temperature and must be driven originally, the medium A is in a nematic state lower than the phase transition temperature when the power is turned on. There is. In this case, when nematics that have optical anisotropy even when no electric field is applied must transmit black due to the optical anisotropy when black display must be achieved in an isotropic state when no electric field is applied. Will end up. Therefore, in such a case, good black display cannot be performed and the contrast is lowered. Of course, the display element can be overheated by a heater or a light source (backlight) to obtain a good display, but it is not easy to raise the temperature and stabilize it instantaneously.

  The other is that even if the medium A (display medium) realizes an optically isotropic state in a region away from the substrate interface, the molecules constituting the medium A by the substrate 1 at the substrate interface, particularly the substrate 1 interface. For example, since 10 is firmly adsorbed, an optically isotropic state may not be realized. For example, when driving at a temperature of 0.1 K just above the nematic-isotropic phase transition temperature, the vicinity of the substrate interface is in a nematic state.

  In any case, near the substrate interface, due to the adsorption phenomenon, the physical state of the medium A is different from the state that should originally have at the time of driving the element, and is different from the bulk region in the cell away from the substrate interface. The medium A in the vicinity of the substrate interface causes a phenomenon that light is transmitted even during black display, resulting in a problem that the contrast is lowered.

  Even in the display element according to the present embodiment, the nematic liquid crystal phase is precipitated at a temperature lower than the transition point in the same manner as the conventional display element. However, according to the display element according to the present embodiment, for example, when the ambient temperature is lower than the transition point when the power is turned on and the medium A does not reach the temperature that should be driven, the deposited nematic liquid crystal phase Is the alignment (treatment) direction in the alignment films 8 and 9, in this case, as shown in FIG. 5, in order to align in the polarizing plate absorption axis direction (indicated by an arrow in the figure), the nematic liquid crystal phase That is, there is no optical contribution from a medium whose physical state is different from the original driving state. As a result, it was possible to realize a good black display until the temperature of the display element rose due to the heater and the backlight.

  That is, according to the present embodiment, even if optical anisotropy is manifested when no voltage is applied, the opposing surfaces of the pixel substrate 11 and the counter substrate 2 are parallel or orthogonal to one polarizing plate absorption axis. The optical contribution can be eliminated by applying a horizontal alignment treatment in the direction to be performed and keeping the direction of optical anisotropy, that is, the alignment direction parallel or orthogonal to the polarizing plate absorption axis. . That is, in the present embodiment, the surfaces of the pixel substrate 11 and the counter substrate 12 facing each other are subjected to a horizontal alignment process, so that the medium A at the substrate interface, strictly speaking, the molecules constituting the medium A 10 is a temperature lower than the element driving temperature and is oriented along the orientation (treatment) direction in the orientation treatment.

  In addition, according to the display element according to the present embodiment, even when the desired driving temperature range is reached, light leakage during black display due to molecules adsorbed on the substrate interface is not observed, and high contrast is realized. I was able to. As a result, a display element excellent in high-speed response and viewing angle characteristics could be obtained without reducing the contrast.

  As described above, the rubbing directions of the substrates 1 and 2 are preferably orthogonal, parallel or antiparallel, but more preferably parallel or antiparallel. Contrast can be maximized by performing horizontal alignment treatment on both the substrates 1 and 2 and making the horizontal alignment directions parallel or anti-parallel to each other. As a result, the black luminance can be further reduced. It was.

  In this embodiment, the alignment films 8 and 9 and the rubbing process are performed on both the substrates 1 and 2 (the pixel substrate 11 and the counter substrate 12). Even when rubbing is performed, it can be obtained. In this case, when the alignment films 8 and 9 are formed on both the substrates 1 and 2, that is, the effect as the alignment treatment is not performed on both the substrates 1 and 2, the electrodes 4 and 5 are formed. If the alignment film (alignment film 9) is formed only on the substrate 2 on the side opposite to the substrate 1, a voltage drop derived from the alignment film 8 on the substrate 1 side does not occur, and the drive voltage of the element increases. There are no practical advantages. Even when the desired driving temperature was reached, light leakage due to molecules adsorbed on the substrate interface did not occur, and high contrast could be obtained. Even when the desired driving temperature was reached, light leakage due to molecules adsorbed on the substrate interface did not occur, and high contrast could be obtained.

  On the other hand, for comparison, as shown in FIGS. 11A and 11B, the alignment films 8 and 9 are not formed and the configuration is the same as that of the present embodiment except that the alignment treatment is not performed. Using the display element, when the ambient temperature was lower than the transition point when the power was turned on, the leakage of light during black display until the temperature of the display element rose was examined.

  FIG. 11A is a cross-sectional view schematically showing a schematic configuration of a main part of a comparative display element in a voltage non-application state (OFF state), and FIG. 11B is a voltage application state (ON state). It is sectional drawing which shows typically schematic structure of the principal part of the display element for a comparison in. FIG. 12A is a main part plan view schematically showing the state of the medium of the display element for comparison at a temperature lower than the driving temperature, and FIG. 12B is a plan view shown in FIG. It is explanatory drawing which shows the relationship between the polarizing plate absorption axis and electric field (alignment) direction in a display element.

  When the alignment treatment is not performed, as shown in FIG. 12A, the nematic liquid crystal phase deposited at low temperature is randomly oriented, and the orientation direction of the molecules 10 of the deposited nematic liquid crystal phase is the substrate. It faces all directions in the in-plane direction, that is, the direction parallel to the substrate surface. As a result, light leakage occurred, and a large increase in black luminance occurred even when no voltage was applied until the desired driving temperature was reached during heating by the backlight and heater. Even when the desired driving temperature is reached, light leakage due to molecules adsorbed on the interface of the substrate occurs, so that high contrast cannot be obtained.

  In Patent Document 1, in order to increase the Kerr effect, a polarizing plate is arranged on the outer surface of the substrate so that the absorption axis directions thereof are parallel or orthogonal to each other and form an angle of 45 degrees with the rubbing direction. Disposing is disclosed. However, even with this configuration, the optical contribution of a medium whose physical state is different from the original driving state cannot be lost, a good black display cannot be obtained, and high contrast can be obtained. There wasn't. Specifically, when ΔT = 0.1K, when 50V is applied when white and when 0V is applied when black, a contrast of 500 or more is obtained according to the present invention, whereas in the configuration of Patent Document 1, Only a contrast of 200 or less was obtained. The contrast can be easily measured by, for example, “EZContrast” manufactured by ELDIM (France). Therefore, from the above results, in the display element that performs display by modulating the orientation order, for example, with the direction of the optical anisotropy being constant (the voltage application direction does not change), the polarizing plate absorption axis direction and the orientation of the substrate surface It turns out that the said effect can be acquired because a process direction has a specific relationship.

  Note that in this embodiment mode, the description has been mainly given of the transmissive display element as an example, but the present invention is not limited to this, and may be a reflective display element.

  FIG. 13 shows an example of a schematic configuration of a reflective display element according to this embodiment to which the present invention is applied.

  In the reflective display element, the pixel substrate 11 is provided with a reflective layer 21 on one substrate 1 made of, for example, a glass substrate, and an insulating layer 22 is interposed on the reflective layer 21 as necessary. For example, electrodes 4 and 5 (for example, comb-shaped electrodes) such as ITO are provided. Other configurations are as described above. As the insulating layer 22, an organic film such as an acrylic resin; an inorganic film such as silicon nitride or silicon oxide can be used. The reflective layer 21 may be an aluminum or silver thin film. In the above configuration, the reflective layer 21 can reflect light incident from the other substrate 2 made of a transparent substrate such as a glass substrate, and thus functions as a reflective display element.

  When the display element according to this embodiment is used as a reflective display element, the electrodes 4 and 5 are not limited to transparent electrode materials such as ITO as in the case of using as a transmissive display element. Various conventionally known materials can be used as the electrode material, such as a metal electrode material such as aluminum. Further, the line width of the electrodes 4 and 5 and the distance between the electrodes (electrode spacing) are not particularly limited, and can be arbitrarily set according to, for example, the gap between the substrate 1 and the substrate 2. .

  Furthermore, in the present embodiment, the case where a glass substrate is used as the substrate 1 or 2 has been described as an example. However, the present invention is not limited to this, and at least of the substrates 1 and 2, One substrate may be a transparent substrate, and various conventionally known substrates can be used, for example.

  The substrates 1 and 2 are not limited to those conventionally used as substrates, and may be, for example, in the form of a film or may have flexibility, at least As long as one side is transparent and the medium A can be held (clamped) between the substrates, that is, in the inside, various materials should be used depending on the type of the medium A, the state of the phase, and the like. Can do.

  In this embodiment, as a specific example, a case where a material that is optically isotropic when no electric field is applied and that exhibits optical anisotropy when an electric field is applied is used as a medium A will be described as an example. However, the present invention is not limited to this, and as described above, the medium A may be a material that loses anisotropy by application of an electric field and exhibits optical isotropy. is there.

  Hereinafter, as the medium A, a specific example in which anisotropy disappears when an electric field is applied and the material is optically isotropic will be described.

  In this specific example, transparent electrodes 4 and 5 made of ITO and an orientation made of polyimide are provided on the surface of one of the two transparent substrates 1 and 2 made of a glass substrate facing the substrate 2. And a transparent dielectric substance 4′-n-alkoxy-3′-nitrobiphenyl-4-carboxylic acid (ANBC-22) is enclosed as a medium A between the substrates 1 and 2 did. The thickness of the medium layer 3 in the display element was adjusted to 4 μm by previously spreading plastic beads on the opposing surfaces of the substrates 1 and 2. The electrodes 4 and 5 are comb electrodes as shown in FIG.

  As described above, the polarizing plates 6 and 7 have the absorption axes 6a and 7a orthogonal to each other, the absorption axes 6a and 7a in the polarizing plates 6 and 7, and the combs in the electrodes 4 and 5 that are comb-shaped electrodes. Each of the tooth portions 4a and 5a was provided on the outside of the substrates 1 and 2 (on the opposite side of the facing surface) so as to form an angle of about 45 degrees with the electrode extending direction.

  The display element thus obtained is maintained at a temperature in the vicinity of the smectic C phase-cubic phase transition (up to about 10K on the low temperature side of the phase transition temperature) by an external heating device (heating means), and voltage is applied ( When an alternating electric field of about 50 V (greater than 0 up to several hundred kHz) was performed, the transmittance could be changed. That is, it was possible to change to an isotropic cubic phase (dark state) by applying a voltage to the smectic C phase (bright state) exhibiting optical anisotropy when no voltage was applied.

  Moreover, substantially the same results were obtained even when electrodes were provided on the substrates 1 and 2 and an electric field in the normal direction of the substrate surface was generated. That is, substantially the same result was obtained not only in the horizontal direction of the substrate surface but also in the normal direction of the substrate surface.

  As described above, the medium A used in the display element according to this embodiment has optical anisotropy when no electric field is applied, and the optical anisotropy disappears when the electric field is applied. You may use the medium which shows.

  According to the display element according to the present embodiment, light leakage during black display due to molecules adsorbed on the substrate interface was not observed, and high contrast could be realized. As a result, a display element excellent in high-speed response and viewing angle characteristics could be obtained without reducing the contrast.

  That is, even if the optical anisotropy of the medium A in the bulk region can be eliminated by applying an electric field, the molecule 10 (medium A) adsorbed on the substrate interface has a large adsorbing force. It is not easy to disappear. However, according to the configuration of the present invention, there is an effect of eliminating the optical contribution due to the optical anisotropy in the vicinity of the substrate interface, and therefore, a high contrast can be obtained as described above.

  The medium A may have positive dielectric anisotropy or negative dielectric anisotropy. When a medium having a positive dielectric anisotropy is used as the medium A, the medium A needs to be driven by an electric field substantially parallel to the substrates 1 and 2, but a medium having a negative dielectric anisotropy is applied. This is not always the case. For example, the substrate 1 or 2 can be driven by an oblique electric field, and can also be driven by a vertical electric field. In this case, the shape, material, and arrangement position of the electrodes may be appropriately changed. If an electric field is applied vertically using a transparent electrode, it is advantageous in terms of aperture ratio.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to FIGS. 14 (a) to 14 (c) to FIG. In the present embodiment, differences from the first embodiment will be mainly described, and components having the same functions as those used in the first embodiment are designated by the same reference numerals. A description thereof will be omitted.

  In the first embodiment, the case where a horizontal alignment process parallel or orthogonal to the polarizing plate absorption axis is performed as an example for the alignment process on the surface of the pixel substrate 11 and the counter substrate 12 is described. As the alignment treatment, a case where vertical alignment is performed will be described as an example.

  FIG. 14A is a main part plan view schematically showing the configuration of the display element according to the present embodiment in an electric field non-application state (OFF state), and FIG. 14B is a voltage application state (ON). 14C is a plan view of a main part schematically showing the configuration of the display element in the state), and FIG. 14C illustrates the relationship among the polarizing plate absorption axis, the electric field (orientation) direction, and the rubbing direction in the display element. FIG. FIG. 15 is a plan view of the main part schematically showing the state of the medium of the display element at a temperature lower than the driving temperature, and FIG. 16 shows the state of the medium of the display element for comparison at a temperature lower than the driving temperature. It is a principal part top view which shows typically.

  For example, as shown in FIGS. 14A to 14C, the configuration of the display element according to the present embodiment is basically the same as that of the first embodiment except for the direction of the alignment treatment in the alignment films 8 and 9. This is the same as the display element described in the above. According to the present embodiment, by performing vertical alignment treatment on the alignment films 8 and 9, for example, when the ambient temperature is lower than the transition point of the medium A when the power is turned on, a nematic liquid crystal phase is precipitated. However, as shown in FIG. 15, the deposited nematic liquid crystal phase molecules 10 are aligned in the normal direction of the substrate, which is the alignment (treatment) direction, and thus there is no optical contribution. That is, according to the display element according to the present embodiment, even if optical anisotropy is exhibited when no voltage is applied, the optical anisotropy is achieved by performing an alignment treatment that realizes vertical alignment. By making this direction perpendicular to the substrate surface, the optical contribution can be eliminated. That is, also in the present embodiment, the surface A of the pixel substrate 11 and the counter substrate 12 facing each other is subjected to the vertical alignment process, so that the medium A at the substrate interface, specifically, the medium A is configured. The molecules 10 can be aligned along the alignment direction in the alignment process at a temperature lower than the element driving temperature, thereby realizing a good black display even when the temperature of the display element is increased by the heater and the backlight. It becomes possible. Even when the temperature was achieved in the driving temperature range, no light leakage was observed during black display, and high contrast could be realized. Even when the desired driving temperature was reached, light leakage due to molecules adsorbed on the substrate interface did not occur, and high contrast could be obtained.

  That is, even when vertical processing is performed as the alignment processing, as shown in the first embodiment, light leakage due to nematic liquid crystal phases precipitated at low temperatures and molecules adsorbed on the substrate interface does not occur. Contrast could be improved.

  On the other hand, when the alignment treatment is not performed, as shown in FIG. 16, the nematic liquid crystal phase deposited at low temperature is randomly oriented, and the orientation direction of the molecules 10 of the deposited nematic liquid crystal phase is in the plane of the substrate. The direction, that is, all the directions parallel to the substrate surface.

  As a result, light leakage occurred, and a large increase in black luminance occurred even when no voltage was applied until the desired driving temperature was reached during heating by the backlight and heater. Even when the desired driving temperature is reached, light leakage due to molecules adsorbed on the interface of the substrate occurs, so that high contrast cannot be obtained.

  From the above results, in the present embodiment as well, in the display element that performs display by modulating the degree of orientational order and the direction of optical anisotropy is constant (the voltage application direction does not change), for example, the polarizing plate absorption axis It turns out that the said effect can be acquired because a direction and the orientation processing direction of a substrate surface have a specific relationship.

  In this embodiment, the alignment films 8 and 9 and the rubbing process are performed on both the substrates 1 and 2 (the pixel substrate 11 and the counter substrate 12). Even when rubbing is performed, it can be obtained. Also in this case, when the alignment films 8 and 9 are formed on both the substrates 1 and 2, that is, the effect as in the case where the alignment treatment is applied to both the substrates 1 and 2 is not obtained, If the alignment film (alignment film 9) is formed only on the substrate 2 opposite to the formed substrate 1, a voltage drop derived from the alignment film 8 does not occur and the drive voltage of the element does not increase. There are great practical advantages. Even when the desired driving temperature was reached, light leakage due to molecules adsorbed on the substrate interface did not occur, and high contrast could be obtained.

  Various materials can be used as the vertical alignment film used in the present embodiment, and examples thereof include polyimide, a silane coupling agent, and lecithin, but are not particularly limited.

  When polyimide or the like is used as the vertical alignment film, for example, a rubbing process may be performed after forming these alignment films on the substrate 1 and / or the substrate 2 to form an alignment film. Further, when a silane coupling agent is used, it may be formed by a pulling method like an LB film.

  Further, as the alignment films 8 and 9, a commercially available vertical alignment film can be used.

  Furthermore, also in this embodiment, as the alignment films 8 and 9, the alignment film having the photofunctional group may be used because the alignment control is easy. Also in the present embodiment, when the alignment films 8 and 9 have a photofunctional group, the surfaces of the pixel substrate 11 and the counter substrate 12, that is, the surfaces of the alignment films 8 and 9 are irradiated with polarized ultraviolet light to regulate alignment. By expressing the force, a desired alignment process can be easily performed.

  In the first and second embodiments, the case where an electric field substantially parallel to the substrate is applied has been described as an example. However, the display element according to the present invention can be driven by an electric field oblique to the substrate. It can also be driven by a vertical electric field. In this case, an electric field may be applied to the medium layer 3 by providing electrodes on both of the pair of substrates (substrates 1 and 2) facing each other and applying an electric field between the electrodes provided on both substrates.

  In the first and second embodiments, a case where either the horizontal alignment process or the vertical alignment process is performed on both the pixel substrate 11 and the counter substrate 12 or any one of the substrates is described. Although described as an example, the molecules 10 at the substrate interface are aligned in the alignment processing direction (rubbing direction) described above, but the intermolecular interaction extends to the bulk region away from the substrate interface inside the cell. In addition, since the alignment direction of the molecules 10 in the bulk region is not changed, a configuration in which one substrate is subjected to horizontal alignment treatment and the other substrate is subjected to vertical alignment treatment may be employed.

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

  The display element of the present invention is a display element excellent in wide viewing angle characteristics and high-speed response characteristics. For example, an image display apparatus such as a television or a monitor, an OA device such as a word processor or a personal computer, a video camera, a digital The present invention can be widely applied to image display devices provided in information terminals such as cameras and mobile phones. In addition, as described above, the display element of the present invention has a wide viewing angle characteristic and a high-speed response characteristic, and can prevent a decrease in contrast, and thus is suitable for large-screen display and moving image display. .

(A) is sectional drawing which shows typically schematic structure of the principal part of the display element concerning one Embodiment of this invention in a voltage no application state, (b) is the said display element in a voltage application state. It is sectional drawing which shows the schematic structure of the principal part typically. It is a figure explaining the relationship between the polarizing plate absorption axis in the said display element, an electric field (orientation) direction, and a rubbing direction. It is a figure explaining an example of the electrode structure in the said display element, and the relationship between this electrode structure and a polarizing plate absorption axis. FIG. 4A is a main part plan view schematically showing the configuration of the display element in a state where no electric field is applied, and FIG. 4B schematically shows the configuration of the display element in a state where a voltage is applied. It is a principal part top view. It is a principal part top view which shows typically the state of the medium of the said display element in the temperature lower than drive temperature. It is a graph which shows the relationship between the applied voltage and the transmittance | permeability in the display element shown to Fig.1 (a) * (b). The difference in display principle between a display element that displays using the change in optical anisotropy due to the application of an electric field and a conventional liquid crystal display element is described as the average refractive index of the medium when no voltage is applied and when a voltage is applied. It is sectional drawing typically shown in the shape of an ellipsoid and the principal axis direction, (a) is a cross section at the time of no voltage application of the display element which displays using the change of the optical anisotropy by the application of an electric field (B) is a cross-sectional view when a voltage is applied to the display element shown in (a), (c) is a cross-sectional view when no voltage is applied to a TN liquid crystal display element, and (d) is a cross-sectional view. It is sectional drawing at the time of the voltage application of the liquid crystal display element shown to (c), (e) is sectional drawing at the time of no voltage application of the VA-type liquid crystal display element, (f) is the liquid crystal display shown to (e). It is sectional drawing at the time of the voltage application of an element, (g) is the interruption at the time of no voltage application of the liquid crystal display element of an IPS system. A diagram, (h) is a cross-sectional view of when a voltage is applied the liquid crystal display device shown in (g). It is a schematic diagram which shows an example of the reverse micelle phase mixing system of liquid crystal microemulsion. It is a schematic diagram which shows the other example of the reverse micelle phase mixing system of liquid crystal microemulsion. It is a classification diagram of a lyotropic liquid crystal phase. (A) is sectional drawing which shows typically schematic structure of the principal part of the display element for a comparison in a voltage non-application state, (b) is a principal part of the said display element for a comparison in a voltage application state. It is sectional drawing which shows a schematic structure typically. (A) is a principal part top view which shows typically the state of the medium of the said display element for a comparison in the temperature below drive temperature, (b) is a polarizing plate absorption axis in the said display element for a comparison, It is explanatory drawing which shows the relationship with an electric field (alignment) direction. It is sectional drawing which shows an example of schematic structure of the reflection type display element concerning one Embodiment of this invention. (A) is a principal part top view which shows typically the structure of the display element concerning other embodiment of this invention in an electric field no application state, (b) is a structure of the said display element in a voltage application state. FIG. 6C is a diagram for explaining a relationship among a polarizing plate absorption axis, an electric field (orientation) direction, and a rubbing direction in the display element. It is a principal part top view which shows typically the state of the medium of the display element concerning other embodiment of this invention in the temperature lower than drive temperature. It is a principal part top view which shows typically the state of the medium of the display element for a comparison in the temperature lower than drive temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Substrate 3 Medium layer 3a Refractive index ellipsoid 4 Electrode 4a Comb portion 5 Electrode 5a Comb portion 6 Polarizing plate 6a Absorption axis 7 Polarizing plate 7a Absorption axis 8 Alignment film 9 Alignment film 11 Pixel substrate 12 Counter substrate 21 Reflection Layer 22 Insulating layer

Claims (13)

At least one of a pair of transparent substrates, a medium sandwiched between the pair of substrates and exhibiting optical anisotropy by application of an electric field, and the medium of at least one of the pair of substrates At least one polarizing plate disposed on the side opposite to the facing surface, and the medium exhibits optical isotropy when no electric field is applied and displays optical anisotropy when an electric field is applied. A display element,
The surface of the at least one of the pair of substrates facing the other substrate is subjected to a horizontal alignment treatment parallel or perpendicular to the absorption axis of at least one polarizing plate, or the vertical alignment treatment is performed. A display element characterized by being applied. Including at least a pair of electrodes for applying an electric field substantially parallel to the substrate to the medium;
The display element according to claim 1, wherein an alignment treatment direction in the horizontal alignment treatment forms an angle of less than 45 degrees ± 10 degrees with respect to an electric field application direction by the electrodes. One of the pair of substrates is provided with at least a pair of electrodes for applying an electric field substantially parallel to the substrate to the medium,
The display element according to claim 1, wherein a horizontal alignment film is provided on the surface of the other substrate.   2. The display element according to claim 1, wherein the surfaces of the opposing surfaces of the pair of substrates are subjected to a horizontal alignment process in parallel or antiparallel to each other. The display element according to claim 1 , wherein the medium has an alignment order equal to or less than a wavelength of light when no electric field is applied . The display element according to claim 1 , wherein the medium has an ordered structure exhibiting cubic symmetry . 2. The display element according to claim 1 , wherein the medium is composed of molecules exhibiting a cubic phase or a smectic D phase . The display element according to claim 1 , wherein the medium is made of a liquid crystal microemulsion . 2. The display element according to claim 1 , wherein the medium is composed of a lyotropic liquid crystal exhibiting a micelle phase, a reverse micelle phase, a sponge phase, or a cubic phase . 2. The display element according to claim 1 , wherein the medium comprises a liquid crystal fine particle dispersion system exhibiting a micelle phase, a reverse micelle phase, a sponge phase, or a cubic phase . The display element according to claim 1 , wherein the medium is made of a dendrimer . The display element according to claim 1 , wherein the medium is made of molecules exhibiting a cholesteric blue phase . The display element according to claim 1 , wherein the medium is composed of molecules exhibiting a smectic blue phase .

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