JP7564729B2 - Liquid crystal light modulator, liquid crystal display device, and stereoscopic image display device - Google Patents

Description

(1) Published in the Proceedings of the 67th Spring Meeting of the Japan Society of Applied Physics, 12a-PA1-7, 2020, p. 03-047, published by the Japan Society of Applied Physics on February 28, 2020.

(2) Applicable under Article 30, Paragraph 2 of the Patent Act. Published online on August 3, 2020 by the Society for Information Display, in the proceedings of the 57th International Display Week Symposium, SID Symposium Digest of Technical Papers, Volume 51, Issue 1, pp. 17-20.

(3) Oral presentation at the 57th International Display Week Symposium held online by the Society for Information Display on August 6, 2020 (presentation number: 3-5)

(4) Published online on October 9, 2020 by the Institute of Image Information and Television Engineers, in the Technical Report of the Institute of Image Information and Television Engineers, Volume 44, Number 26, IDY2020-35, pp. 17-20.

(5) Oral presentation at the invited lecture of the "Display General" Information Display Study Group of the Institute of Image Information and Television Engineers, held online by the Institute of Image Information and Television Engineers (ITE) on October 16, 2020.

(6) Published online on October 22, 2020 by the Japanese Liquid Crystal Society, in the Proceedings of the 2020 Japanese Liquid Crystal Society Online Research Presentation, 2I03, 2020, pp. 61-62.

(7) Oral presentation at the 2020 Japanese Liquid Crystal Society Online Research Presentation held online by the Japanese Liquid Crystal Society on October 30, 2020 (presentation number: 2I03)

(8) Applicable under Article 30, Paragraph 2 of the Patent Act. Published online on December 10, 2020 by the International Display Workshop, Inc. (IDW'20) Proceedings of the International Display Workshops, Volume 27, LCT7-1, 2020, pp. 91-94.

(9) Oral presentation at the 27th International Display Workshops (IDW'20), held online by the International Display Workshops (IDW'20) on December 10, 2020 (presentation number: LCT7-1)

The present invention relates to a liquid crystal light modulator, and a liquid crystal display device and a stereoscopic image display device that use this liquid crystal light modulator.

A spatial light modulator (SLM) is a device that spatially modulates the phase and amplitude of light by arranging optical elements (light modulation elements) as pixels in a two-dimensional matrix, and is widely used in fields such as display technology, recording technology, and laser processing. For example, spatial light modulators that use liquid crystal or magneto-optical materials as optical elements to change the polarization direction of light (rotate the light), or DMD (Digital Mirror Device) type devices that have a movable tiny mirror for each pixel to change the reflection direction of light have been developed, and research is being conducted on miniaturizing pixels to achieve higher definition and smaller size. Among them, spatial light modulators that use liquid crystal as an optical element, which has a large angle of rotation, i.e. a high degree of light modulation, and is relatively easy to manufacture, are widely used in liquid crystal displays (LCDs) and the like. For applications in stereoscopic image display devices and the like, spatial light modulators are required to have an even greater number of pixels and higher resolution. In particular, in holography systems (e.g., Non-Patent Documents 1 and 2), it is desirable to make the pixel pitch (pixel length) at most about 2 μm, or even finer, in order to obtain a sufficient viewing angle.

As shown in FIG. 5, an optical element using liquid crystals (liquid crystal optical element) is provided with a liquid crystal layer 20 and a pair of electrodes 3 and 4 arranged above and below the liquid crystal layer 20, depending on the driving method, and generates a vertical electric field by applying a voltage to the liquid crystal layer 20. In addition, alignment films 21 and 22 are provided in contact with the top and bottom of the liquid crystal layer 20 to control the orientation of the liquid crystal molecules 2. For example, in the case of a twisted nematic (TN) method, the liquid crystal layer 20 in an electric field-free state is arranged vertically so that the liquid crystal molecules 2 are tilted in slightly different directions in the film surface direction and twisted 90 degrees, as shown in the right side of FIG. 5. On the other hand, when a voltage is applied from the electrodes 3 and 4 to generate an electric field perpendicular to the film surface, the liquid crystal layer 20 has the liquid crystal molecules 2 standing vertically along the electric field, as shown in the left side of FIG. 5. Polarizers 71 and 72 are arranged in a parallel Nicol arrangement above and below such a liquid crystal optical element, and one polarized component of light (linearly polarized light) L is incident on the liquid crystal layer 20 through the polarizer 71. When no voltage is applied, the liquid crystal layer 20 changes the polarization direction of the transmitted light L by 90°, so that the light L is blocked by the polarizer (analyzer) 72, but when a voltage is applied, the polarization direction does not change and the light L passes through the polarizer 72.

In a spatial light modulator (hereinafter referred to as a liquid crystal light modulator) using such liquid crystal optical elements as pixels, one of a pair of electrodes (electrode 3 below the liquid crystal layer 20 in FIG. 5) is generally arranged two-dimensionally at a distance from each other as a pixel electrode provided for each pixel, and the other (electrode 4) is provided on the entire surface as an electrode (counter electrode) common to all pixels. The liquid crystal light modulator has a transistor formed of a TFT (thin film transistor) or a MOSFET (metal oxide semiconductor field effect transistor) and a driving circuit having a storage capacitance below the pixel electrode 3, and is electrically connected to the pixel electrode 3. Depending on the signal line input to the driving circuit, the pixel electrodes 3 are each set to a predetermined potential difference or the same potential with respect to the counter electrode 4, and the liquid crystal layer 20 generates or has no electric field in the area directly above each pixel electrode 3. As a result, light passes through the polarizer 72 for each pixel to display light (white) or is blocked to display dark (black). In addition, since no electric field is generated in the liquid crystal layer 20 in the gaps between the pixel electrodes 3, the liquid crystal light modulator is provided with a lattice-shaped black matrix along the boundaries between the pixels as non-openings. Therefore, miniaturization of the pixels of the liquid crystal light modulator is mainly restricted by the drive circuit. In particular, LCOS (Liquid Crystal On Silicon)-SLMs, in which the transistors are made of MOSFETs, are limited to reflective liquid crystal light modulators (for example, Patent Document 1) because the drive circuit is formed on a Si substrate, but the pixels can be miniaturized more easily than TFTs, and have been realized to a pitch of about 3 μm.

On the other hand, in liquid crystal light modulators, as pixels become finer and the ratio of the thickness of the liquid crystal layer (cell thickness) to the pixel length becomes higher, the effect of leakage electric fields between adjacent bright and dark pixels becomes greater, and the display contrast decreases. In detail, since the counter electrode 4 is formed wide with respect to the pixel electrodes 3 partitioned for each pixel, a weak electric field is generated that spreads outward to a certain extent from the pixel electrode 3 of the pixel to which voltage is applied and heads diagonally toward the counter electrode 4. If the pixel length is short, this diagonal electric field reaches the pixel electrode 3 (opening) of the adjacent pixel to which no voltage is applied. Furthermore, the electric field also leaks in the in-plane (horizontal) direction between the pixel electrodes 3, 3 of the adjacent bright display pixel and dark display pixel. Due to these leakage electric fields, even in the opening of the pixel to which no voltage is applied, the liquid crystal molecules 2 rise diagonally, resulting in an incomplete display that does not show the original (complete) dark or bright display.

In order to suppress leakage electric fields between pixels in a liquid crystal light modulator, a liquid crystal light modulator has been disclosed in which walls made of a dielectric that separate the liquid crystal layer are provided along the boundaries of the pixels (Non-Patent Documents 3 and 4). Alternatively, a liquid crystal light modulator has been disclosed in which unevenness is formed on a transparent substrate, a counter electrode is formed on the substrate, and the counter electrode is protruded so that the thickness of the liquid crystal layer at the boundaries between pixels is minimized (Patent Document 2). The electric field that flows diagonally from the pixel electrode of a pixel to which a voltage is applied to the counter electrode and the electric field that flows horizontally to the pixel electrode of an adjacent pixel are blocked or trapped by the protruding counter electrode at the non-aperture, making it difficult for them to reach the aperture of a pixel to which no voltage is applied, thereby weakening these leakage electric fields.

Patent No. 4643786 JP 2020-64192 A

Tomoyuki Mishina, "Research Trends in Spatial Image Reproduction 3D Images," NHK STRL R&D, No. 151, pp. 10-17, May 2015 Fai Mok, Joseph Diep, Hua-Kuang Liu, Demetri Psaltis, “Real-time computer-generated hologram by means of liquid-crystal television spatial light modulator”, Optics Letters, Volume 11, Issue 11, pp. 748-570, 1986 Yoshitomo Isomae, Yosei Shibata, Takahiro Ishinabe, Hideo Fujikake, “Design of 1-μm-pitch liquid crystal spatial light modulators having dielectric shield wall structure for holographic display with wide field of view”, Optical Review, Volume 24, Issue 2, pp . 165-176, April 2017 Yoshitomo Isomae, Yosei Shibata, Takahiro Ishinabe, Hideo Fujikake, “Experimental study of 1-μm-pitch light modulation of a liquid crystal separated by dielectric shield walls formed by nanoimprint technology for electronic holographic displays”, Optical Engineering, Volume 57, Issue 6 , 061624, June 2018

In the development of narrow-pixel-pitch liquid crystal light modulators such as those in Non-Patent Documents 3 and 4 and Patent Document 2, especially when the miniaturization of the current MOSFETs that constitute the driving circuits is exceeded, operation experiments are conducted using liquid crystal light modulators with a fixed pattern in which light and dark pixels are arranged alternately, for example. In order to connect an external power supply to both poles of such liquid crystal light modulators, the one-dimensional light and dark pattern (see Non-Patent Document 4, for example) in which band-shaped pixel electrodes are arranged in a stripe shape, or the light and dark pattern of pixel electrodes in which the electrodes arranged in a stripe shape are arranged in two rows in the longitudinal direction, is limited. In particular, unlike nematic liquid crystals, there is no established general orientation simulation method for ferroelectric liquid crystals (FLCs), so experimental devices are required for narrow pixel pitch verification, etc. In addition, in the development of stereoscopic image displays, a spatial light modulator with a large number of pixels arranged two-dimensionally is required. A two-dimensional light-dark pattern with three or more rows can be realized, for example, by forming wiring that connects to an external power supply through an insulating film with contact holes formed under the pixel electrodes, but it is not easy to fabricate such a multilayer wiring structure for an experimental device.

The present invention was devised in consideration of the above problems, and aims to provide a liquid crystal light modulator with a simple configuration that can display a desired image without a drive circuit, as well as a liquid crystal display device and a stereoscopic image display device equipped with such a liquid crystal light modulator.

In other words, the liquid crystal optical modulator of the present invention comprises a liquid crystal layer, and upper and lower electrodes which sandwich the liquid crystal layer from above and below and apply a voltage in the vertical direction, and further comprises a common electrode having a plurality of openings formed between the lower electrode and the liquid crystal layer, and an electrode interlayer insulating film which has an opening formed inside the opening in a planar view and insulates the common electrode from the lower electrode , and an insulating layer is embedded in the openings formed in the common electrode and the electrode interlayer insulating film, and the insulating layer has a structure in which the dielectric constant and/or thickness of the material varies depending on the opening .

With this configuration, the liquid crystal light modulator has a common electrode that is located closer to the liquid crystal layer than the lower electrode, so that the lower electrode is located only in the openings of the common electrode, and the opening pattern of the common electrode can create the desired two-dimensional light and dark pattern.

The liquid crystal display device according to the present invention comprises the liquid crystal light modulator and a polarizer arranged above or below the liquid crystal light modulator, and displays an image by irradiating the side on which the polarizer is arranged with light. Alternatively, the liquid crystal display device according to the present invention comprises the liquid crystal light modulator and two polarizers arranged above and below the liquid crystal light modulator, and displays an image on the other side by irradiating light from either above or below. With this configuration, the liquid crystal display device can display a desired image by the opening pattern of the common electrode of the liquid crystal light modulator.

The stereoscopic image display device according to the present invention comprises the liquid crystal display device, a light source that irradiates light onto the liquid crystal display device, and a power source that is connected to the upper electrode, lower electrode, and common electrode of the liquid crystal light modulator of the liquid crystal display device. With this configuration, the stereoscopic image display device can display a stereoscopic image based on a desired two-dimensional pattern.

The liquid crystal light modulator according to the present invention provides a simply configured liquid crystal display device capable of displaying a desired image without a drive circuit, and can also configure fine pixels within a range corresponding to the processing accuracy of the common electrode. The liquid crystal display device and stereoscopic image display device according to the present invention can display a desired image with fine pixels.

1 is an external view illustrating a structure of a liquid crystal optical modulator according to a first embodiment of the present invention. 1 is a schematic diagram illustrating a structure of a liquid crystal optical modulator according to a first embodiment of the present invention, and is a partial cross-sectional view of FIG. 2 is a plan view of a common electrode of the liquid crystal light modulator shown in FIG. 1 . 2 is a schematic diagram of a display pattern of a liquid crystal display device including the liquid crystal light modulator shown in FIG. 1 . 1A and 1B are schematic diagrams illustrating the operation of a liquid crystal optical element in a twisted nematic type liquid crystal light modulator. 1A and 1B are diagrams illustrating changes in polarization characteristics due to differences in phase difference. 1A is a schematic diagram illustrating another structure of the liquid crystal optical modulator according to the first embodiment of the present invention, and is a partial cross-sectional view of FIG. 1A is a schematic diagram illustrating another structure of the liquid crystal optical modulator according to the first embodiment of the present invention, and is a partial cross-sectional view of FIG. 1A and 1B are schematic diagrams illustrating the structure and operation of a liquid crystal display device including a liquid crystal optical modulator according to a first embodiment of the present invention. 1 is a schematic diagram illustrating a structure of an integral type stereoscopic image display device according to an embodiment of the present invention. 1 is a schematic diagram illustrating a structure of a holographic stereoscopic image display device according to an embodiment of the present invention. 5A to 5C are schematic diagrams illustrating the structure and operation of a liquid crystal display device including a liquid crystal optical modulator according to a modified example of the first embodiment of the present invention. 5A to 5C are schematic diagrams illustrating a structure of a projection type display device including a liquid crystal light modulator according to a modified example of the first embodiment of the present invention. FIG. 4 is a schematic diagram illustrating the structure of a liquid crystal optical modulator according to a second embodiment of the present invention, and corresponds to the partial cross-sectional view of FIG. 13 is a time chart of voltages applied to a liquid crystal optical modulator according to a second embodiment of the present invention and its modified example. FIG. 13 is a schematic diagram illustrating a structure of a liquid crystal optical modulator according to a modified example of the second embodiment of the present invention, and corresponds to the partial cross-sectional view of FIG. FIG. 11 is a partial cross-sectional view illustrating a structure of a liquid crystal optical modulator according to a third embodiment of the present invention. 11A to 11C are schematic diagrams illustrating the structure and operation of a liquid crystal display device including a liquid crystal optical modulator according to a third embodiment of the present invention. 13A to 13C are schematic diagrams illustrating the structure and operation of a liquid crystal display device including a liquid crystal optical modulator according to a third embodiment of the present invention. 13 is a time chart of a voltage applied to a liquid crystal optical modulator according to a third embodiment of the present invention. 4 is a plan view illustrating the planar shape of a common electrode of a sample of a liquid crystal optical modulator according to the first embodiment of the present invention and an observation position for a simulation. FIG. 4 shows the potential distribution and liquid crystal orientation in a cross section of a sample of the liquid crystal optical modulator according to the first embodiment of the present invention. 3 shows the electric potential distribution and liquid crystal orientation in a plane of a sample of the liquid crystal optical modulator according to the first embodiment of the present invention. 3 is a two-dimensional distribution diagram of liquid crystal orientation and transmittance in a plane of a sample of the liquid crystal optical modulator according to the first embodiment of the present invention. FIG. 13A and 13B are plan views for explaining the planar shapes of the common electrodes of samples of liquid crystal optical modulators according to the second embodiment and the modified examples of the present invention, and the observation positions for the simulation. 13 shows the potential distribution and liquid crystal orientation in a cross section of a sample of a liquid crystal optical modulator according to a second embodiment of the present invention. FIG. 11 is a two-dimensional distribution diagram of the transmittance of a sample of a liquid crystal optical modulator according to a second embodiment of the present invention. 13 shows the potential distribution and liquid crystal orientation in a cross section of a sample of a liquid crystal optical modulator according to a modified example of the second embodiment of the present invention. FIG. 11 is a two-dimensional distribution diagram of the transmittance of a sample of a liquid crystal optical modulator according to a modified example of the second embodiment of the present invention.

The following describes the configuration for realizing the liquid crystal optical modulator and liquid crystal display device according to the present invention with reference to the drawings. The liquid crystal optical modulator and its elements shown in the drawings may be exaggerated in size and positional relationship, and may be simplified in shape, in order to clarify the explanation.

First Embodiment
As shown in Fig. 1 and Fig. 2, the liquid crystal light modulator 10 according to the first embodiment of the present invention includes a liquid crystal layer 20, an upper electrode 41 and a lower electrode 31 sandwiching the liquid crystal layer 20 from above and below, a common electrode 32 with an opening 32a formed between the lower electrode 31 and the liquid crystal layer 20, and an inter-electrode insulating film 52 insulating the common electrode 32 from the lower electrode 31. The liquid crystal light modulator 10 further includes alignment films 21 and 22 respectively in contact with the upper and lower surfaces of the liquid crystal layer 20, a transparent substrate 61 above the upper electrode 41, and a transparent substrate 62 below the lower electrode 31. The liquid crystal light modulator 10 is a transmissive spatial light modulator that transmits light (visible light) incident on the entire surface from either above or below and emits it to the other side, changing the polarization direction of the light in a predetermined partial area. The liquid crystal light modulator 10 is also applied to a liquid crystal display device that displays a fixed pattern shown in Fig. 4 as an image. For the sake of simplicity, the liquid crystal light modulator 10 is illustrated with a display pattern of 96 pixels in 12 rows and 8 columns. Each element constituting the liquid crystal light modulator according to this embodiment will be described in detail below.

(Liquid crystal layer)
The liquid crystal layer 20 is made of a liquid crystal material, and examples of such known materials are those applied to liquid crystal display devices such as twisted nematic (TN) type (see FIG. 5), vertical alignment (VA) type, or ferroelectric liquid crystal (FLC) type. If the liquid crystal layer 20 is of the TN type, a liquid crystal having a positive dielectric anisotropy (p-type liquid crystal) is applied, and if the liquid crystal layer 20 is of the VA type, a liquid crystal having a negative dielectric anisotropy (n-type liquid crystal) is applied. Here, the liquid crystal layer 20 will be described as being of the TN type. In the liquid crystal layer 20 in a no-field state (initial state), as shown on the right side of FIG. 5, the liquid crystal molecules 2 try to fall in different directions by 90° in the plane along the respective surface characteristics due to the upper alignment film 21 and the lower alignment film 22, so that they are aligned up and down by changing their orientation little by little in the in-plane direction. The liquid crystal molecules 2 aligned up and down in such a twisted manner cause the liquid crystal layer 20 to generate a phase difference between the mutually orthogonal polarized components in the transmitted light. On the other hand, when a vertical electric field is applied to the liquid crystal layer 20, the liquid crystal molecules 2 rise at an angle according to the strength of the electric field, and at maximum, they rise vertically, and the phase difference δ of the transmitted light becomes 0. The thickness (cell thickness) of the liquid crystal layer 20 is designed in the range of about 0.5 to 5 μm according to the liquid crystal material, etc., so that the desired optical characteristics are obtained. In the liquid crystal light modulator 10, which is a transmissive spatial light modulator, it is preferable that the phase difference δ is at maximum π (in the no electric field state in the TN type, and when the maximum driving voltage is applied in the VA type). However, if the cell thickness is large, the response speed of the liquid crystal light modulator 10 becomes slow.

As shown in FIG. 6, the polarization characteristics of the transmitted light change with a period of 2π due to the phase difference δ. When the phase difference δ of the liquid crystal layer 20 is π, linearly polarized light becomes linearly polarized light with a 90° difference in the polarization direction, and right-handed circularly polarized light becomes left-handed circularly polarized light, as shown on the right side of FIG. 5. In addition, when the electric field is weak (not maximum), the liquid crystal molecules 2 of the liquid crystal layer 20 rise obliquely, and modulate the light with a phase difference of less than π according to the rise angle. In FIG. 5, linearly polarized light is incident on the liquid crystal layer 20, but when the liquid crystal driving method is the TN method or VA method (see FIG. 12) as shown in FIG. 5, it is preferable to provide a retarder between the upper and lower polarizers 71 and 72 to compensate for the phase difference of light caused by the liquid crystal layer 20, as described later, and to have circularly polarized light incident on the liquid crystal light modulator 10.

(Alignment film)
The alignment films 21 and 22 are provided in contact with the top and bottom of the liquid crystal layer 20 in order to control the orientation of the liquid crystal molecules 2. In the liquid crystal light modulator 10, the alignment film 21 is formed on the surface of the upper electrode 41 (the surface on the liquid crystal layer 20 side), and the alignment film 22 is formed on the surface of the common electrode 32 and the surface of the electrode interlayer insulating film 52 exposed in the opening 32a of the common electrode 32. The alignment films 21 and 22 are organic films such as polyimide or inorganic films such as silicon oxide (SiO _x ), and are formed to a thickness of about several tens to 100 nm using a known material corresponding to the liquid crystal driving method. In this embodiment, as the TN method, the alignment films 21 and 22 are each formed on the surface (the surface in contact with the liquid crystal layer 20) with minute grooves or the like along one direction and a direction perpendicular thereto (alignment treatment), and further, as necessary, are subjected to alignment treatment so that the liquid crystal molecules 2 stand up while tilting in the same direction when a voltage is applied. For example, polyimide is formed into a film by a coating method and then oriented by a rubbing method or UV irradiation, while SiO _x is formed into a film by oblique deposition and simultaneously oriented.

(Top electrode, bottom electrode)
The lower electrode 31 and the upper electrode 41 are provided to generate an electric field in the vertical direction in the liquid crystal layer 20. In the present invention, a display pattern is formed by a common electrode 32 described later, and the lower electrode 31 and the upper electrode 41 Both are provided as a single continuous film shared by all pixels.

Since the liquid crystal light modulator 10 according to this embodiment is a transmission type spatial light modulator, both the lower electrode 31 and the upper electrode 41 are formed of a transparent electrode material so as to transmit light (visible light). The transparent electrode material is made of a known conductive oxide such as indium zinc oxide (IZO), indium tin oxide (ITO), tin oxide (SnO ₂ ), antimony oxide-tin oxide (ATO), zinc oxide (ZnO), fluorine-doped tin oxide (FTO), indium oxide (In ₂ O ₃ ), indium gallium zinc oxide (IGZO), etc. Alternatively, a nanocarbon material such as graphene or a carbon nanotube, or a conductive polymer such as PEDOT/PSS (Poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate)) can also be applied. The electrodes 31, 41 made of these transparent electrode materials preferably have a thickness of 20 nm or more so as to obtain sufficient conductivity, and are formed by a known method such as sputtering, vacuum deposition, coating, etc. Alternatively, a metal electrode material may be formed to a thickness of 10 nm or less so as to allow sufficient light transmission.

(Common electrode)
The common electrode 32 is provided between the lower electrode 31 and the liquid crystal layer 20 so as to prevent the electrode 31 and the electrode 41 from partially generating an electric field in the liquid crystal layer 20. In other words, the common electrode 32 has an opening 32a formed therein so as to leave an area for generating an electric field. In the liquid crystal light modulator 10 according to this embodiment, the opening 32a of the common electrode 32 becomes a bright display pixel shown by a white square in FIG. 4. As shown in FIG. 3, in this embodiment, the opening 32a is a square with a side length of l _a in a plan view (xy plane), and is two-dimensionally arranged vertically and horizontally. It is preferable that the opening 32a is large in order to increase the aperture ratio of the pixel. On the other hand, in order to prevent the common electrode 32 from being separated, the width (p _x -l _a , p _y -l _a ) between the openings 32a of adjacent pixels is designed to be such that it does not break. In addition, if the area where no electric field is generated, which is a pixel for dark display, is small compared to the thickness (cell thickness) of the liquid crystal layer 20, leakage electric field from the pixel for bright display is likely to occur. The region that will become the dark display pixel is a (2p _x - l _a ) × (2p _y - l _a ) region (outside the opening 32 a ) on the common electrode 32. Therefore, it is preferable to design the pixel lengths p _x and p _y in the x and y directions according to the cell thickness.

The common electrode 32 preferably has a thickness of 5 nm or more. On the other hand, in order to reduce the step at the edge of the opening 32a and more preferably to flatten the surface of the alignment film 22 formed on the common electrode 32, it is preferable that the common electrode 32 has a smaller thickness, specifically 20 nm or less, particularly when the alignment film 22 is an inorganic film. In addition, the common electrode 32 is selected from the above-mentioned electrode materials so as to transmit light like the lower electrode 31, and is formed by a known method according to the material, and is processed into a desired planar shape by photolithography, and etching or lift-off method, printing, etc.

(Electrode Interlayer Insulation Film)
The electrode interlayer insulating film 52 is provided between the lower electrode 31 and the common electrode 32 to insulate them. The electrode interlayer insulating film 52 can be made of known inorganic insulating materials provided in semiconductor elements, such as oxide films such as SiO ₂ , MgO, and Al ₂ O ₃ , and Si ₃ N ₄ , MgF _{2 ,} etc. The thickness of the electrode interlayer insulating film 52 is designed according to the maximum potential difference between the lower electrode 31 and the common electrode 32 so as not to cause dielectric breakdown. Specifically, when the potential difference is 10 V, it is preferable to use SiO ₂ (relative dielectric constant: about 4) and have a thickness of 50 nm or more. On the other hand, as the electrode interlayer insulating film 52 becomes thicker, it is necessary to increase the voltage applied to the liquid crystal light modulator 10. Therefore, the thickness of the electrode interlayer insulating film 52 is preferably less than 20% of the thickness (cell thickness) of the liquid crystal layer 20, and is preferably thinner within a range that does not cause dielectric breakdown. As described later, the liquid crystal light modulator 10 is driven by shorting the upper electrode 41 and the common electrode 32, so that the potential difference between the electrodes 31-32 is the same as the potential difference between the electrodes 31-41, i.e., the voltage applied to the liquid crystal light modulator 10. Alternatively, the electrode interlayer insulating film 52 may be made of a high dielectric constant (High-κ) insulating material that is used for the gate oxide film of a fine MOSFET (metal oxide semiconductor field effect transistor). Examples of high dielectric constant insulating materials include HfSiO ₄ , ZrSiO ₄ , HfO ₂ , ZrO ₂ , and cubic crystal phase HfO ₂ (see Japanese Patent No. 5652926). If the electrode interlayer insulating film 52 has a high relative dielectric constant, the decrease in the voltage applied to the liquid crystal layer 20 on the opening 32a relative to the voltage applied to the liquid crystal light modulator 10 is suppressed. As a result, the voltage applied to the liquid crystal optical modulator 10 can be reduced, and accordingly, the potential difference between the electrodes 31 and 32 becomes smaller, so that the thickness of the electrode interlayer insulating film 52 can be reduced to some extent.

(Transparent substrate)
The transparent substrate 61 is a base for forming the upper electrode 41 and the alignment film 21, and the transparent substrate 62 is a base for forming the lower electrode 31, the electrode interlayer insulating film 52, the common electrode 32, and the alignment film 22. Furthermore, the transparent substrates 61 and 62 are a base for supporting the liquid crystal layer 20. The transparent substrates 61 and 62 are made of a known transparent substrate material that transmits light, and the transparent substrate 61 is made of a material that is resistant to the film formation conditions (temperature, atmosphere, etc.) of the upper electrode 41 and the alignment film 21, and the transparent substrate 62 is made of a material that is resistant to the film formation and processing conditions of the lower electrode 31, the common electrode 32, etc. Specific examples of the material include SiO ₂ (silicon oxide, glass), sapphire, polycarbonate (PC), etc. Alternatively, the transparent substrates 61 and 62 are made of a flexible plastic substrate such as a transparent polyimide film so that the liquid crystal light modulator 10 has flexibility depending on its application. In this case, it is preferable that the electrodes 31, 32, and 41 are made of a flexible nanocarbon material or conductive polymer among the transparent electrode materials.

(Method of manufacturing a liquid crystal optical modulator)
The liquid crystal light modulator according to this embodiment can be manufactured in accordance with a known method for manufacturing a transmissive liquid crystal light modulator. That is, electrodes 41, 31, 32, etc. are formed on the transparent substrates 61 and 62, respectively, and then the alignment films 21 and 22 are formed. The transparent substrates 61 and 62 are then superimposed so that the alignment films 21 and 22 face each other, and a liquid crystal material is filled between them. The liquid crystal light modulator 10 can be easily manufactured because only one layer of the common electrode 32 needs to be patterned, and is also suitable as an experimental device.

As shown in FIG. 7, the liquid crystal light modulator 10 according to this embodiment may also be formed in the opening 32a so that the height position of the surface is aligned with the common electrode 32. With this configuration, the surface can be made flat, particularly when the alignment film 22 is made of an inorganic film, and even if the common electrode 32 is made thick, no steps are generated on the surface of the alignment film 22. The part of the electrode interlayer insulating film 52 in the opening 32a (embedded insulating layer 5a) does not have to be made of the same insulating material as the part between the common electrode 32 and the lower electrode 31, and is selected from the insulating materials listed as the material of the electrode interlayer insulating film 52. The embedded insulating layer 5a preferably has a high relative dielectric constant, particularly when the common electrode 32 is thick. Such a liquid crystal light modulator 10 can be manufactured, for example, by forming a film of the material of the common electrode 32 on the electrode interlayer insulating film 52, forming a mask on the film with an area for forming the opening 32a, forming the opening 32a by etching, and then forming the material of the embedded insulating layer 5a from above and removing the mask. Alternatively, the liquid crystal light modulator 10 can be manufactured by forming a mask on the electrode interlayer insulating film 52 to cover the area where the opening 32a is to be formed, etching the electrode interlayer insulating film 52 to the thickness of the common electrode 32, depositing the material of the common electrode 32 on top of it, and then removing the mask.

The liquid crystal light modulator 10 according to this embodiment may include an electrode interlayer insulating film 52A having an opening formed in accordance with the opening 32a of the common electrode 32, as shown in FIG. 8. The electrode interlayer insulating film 52A may be made of the same material and thickness as the electrode interlayer insulating film 52. However, in order to reduce the step of the surface of the alignment film 22 at the edge of the opening 32a, it is preferable that the electrode interlayer insulating film 52A has a smaller thickness, similar to the common electrode 32. The opening of the electrode interlayer insulating film 52A has a planar shape that is the same as or smaller than the opening 32a. Such a liquid crystal light modulator 10 can be manufactured by etching the common electrode 32 from above a mask that leaves an area where the opening 32a is to be formed, and then etching the electrode interlayer insulating film 52A in succession. Alternatively, the liquid crystal light modulator 10 can be manufactured by forming a mask covering the area where the opening 32a is to be formed on the lower electrode 31, sequentially depositing the materials of the electrode interlayer insulating film 52A and the common electrode 32 from above, and removing the mask. In addition, a buried insulating layer 5a (see FIG. 7) may be provided in the opening 32a of the common electrode 32 and the opening of the electrode interlayer insulating film 52A to flatten the surface on which the alignment film 22 is formed.

(Liquid crystal display device)
The liquid crystal light modulator 10 according to the first embodiment of the present invention is used in a liquid crystal display device in the same manner as a general transmissive liquid crystal light modulator. As shown in FIG. 9, the liquid crystal display device 100 according to the embodiment of the present invention includes the liquid crystal light modulator 10 and polarizing plates (polarizers) 71 and 72 arranged above and below the liquid crystal light modulator 10. Furthermore, since the liquid crystal light modulator 10 is of the TN type, the liquid crystal display device 100 preferably includes retardation plates 73 and 74 between the liquid crystal light modulator 10 and the polarizing plates 71 and 72, respectively. Furthermore, when the liquid crystal display device 100 displays a full-color image, the liquid crystal display device 100 includes a color filter array 75 in which color filters of red (R), green (G), and blue (B) are arranged in a stripe or mosaic pattern on the light emission side of the liquid crystal light modulator 10 (see FIG. 10). The liquid crystal display device 100 may further include a lattice-shaped black matrix along the center between pixels together with the color filter array 75. The color filter array 75 does not have to switch colors for each pixel of the liquid crystal light modulator 10. For example, four pixels (2×2) may be used as one pixel (pixel length 2l _a ) in the liquid crystal display device 100. Such a liquid crystal display device 100 can display five gradations, 0% (black), 25%, 50%, 75%, and 100% (white), depending on the light and dark patterns of each of the four pixels of the liquid crystal light modulator 10. The liquid crystal display device 100 can be irradiated with light from either the top or bottom to display an image on the other side, and will be described here as being irradiated with light from above to display an image below. The light irradiated to the liquid crystal display device 100 can be selected according to the purpose from outside light, indoor light, or a surface light source incorporating a light emitting element such as a light emitting diode (LED) as in the backlight of a general liquid crystal display.

The upper polarizing plate (polarizer) 71, i.e., on the light incidence side, converts the non-polarized light L _uP incident from the outside into one polarized component of light (linearly polarized light in one direction). In the liquid crystal display device 100, the polarizing plate 71 is arranged with its transmission axis in the horizontal direction (90°) in FIG. 9 (with its absorption axis at 0°), and transmits linearly polarized light with a vibration direction of 90°. The lower polarizing plate (analyzer) 72, i.e., on the light emission side, transmits polarized light with a predetermined direction out of the light emitted from the liquid crystal light modulator 10, and displays it. In the liquid crystal display device 100, the polarizing plate 72 is arranged with its transmission axis in the same direction as the polarizing plate 71, i.e., in a parallel Nicol arrangement. The polarizer 71 on the light incidence side may be a polarization conversion element that outputs all of the incident non-polarized light L _uP as linearly polarized light with one direction (vibration direction 90°). The polarization conversion element is composed of a polarization separation film and a half-wave plate.

The retardation plates 73 and 74 are provided to compensate for the phase difference of light caused by the liquid crystal layer 20, and λ/2 retardation plates (1/2 wavelength plates) or λ/4 retardation plates (1/4 wavelength plates) are applied. The refractive index of the liquid crystal changes depending on the orientation of the liquid crystal molecules due to the optical anisotropy of the liquid crystal molecules. Specifically, when the liquid crystal molecules 2 stand vertically as shown on the left side of FIG. 5, the phase difference δ due to the polarization component is 0, whereas when the liquid crystal molecules 2 are tilted or fall horizontally as shown on the right side of FIG. 5, a phase difference occurs. In this embodiment, as described above, the phase difference δ of the liquid crystal layer 20 is set to π (= λ/2) when the liquid crystal molecules 2 are horizontal at the maximum. In this embodiment, since a dark display is performed when a phase difference occurs in the liquid crystal layer 20, a phase difference change occurs depending on the angle of the liquid crystal molecules 2, and light may leak when viewed from an oblique angle. Therefore, it is preferable to compensate for the phase difference caused by the liquid crystal layer 20 with the retardation plates 73 and 74. Here, the retardation plates 73 and 74 are both λ/4 retardation plates, and are arranged with their slow axes oriented at 45° and 135°, respectively, relative to the transmission axis of the polarizing plate 71.

(Operation of Liquid Crystal Light Modulator)
The operation of the liquid crystal light modulator according to the first embodiment will be described with reference to FIG. 9 and, where appropriate, FIG. 5. When the driving method is the TN method, VA method, or the like, liquid crystal behaves the same regardless of whether the electric field is directed upward or downward, and generally, liquid crystal deteriorates if a voltage is continuously applied with a constant polarity, so it is preferable to apply an AC voltage. As shown in FIG. 9, in the liquid crystal light modulator 10, an AC power source 91 is connected between the electrodes 31 and 41, and the upper electrode 41 and the common electrode 32 are short-circuited to have the same potential, and further, the terminal of the AC power source 91 on the upper electrode 41 side is connected to GND (0 V). Then, the liquid crystal layer 20 is applied with voltage from the upper and lower electrodes 31 and 41, so that an electric field in the vertical direction (represented by an upward arrow with hatching in the figure) is generated. However, since the common electrode 32 arranged closer to the liquid crystal layer 20 than the lower electrode 31 is at the same potential as the upper electrode 41, no electric field is generated in the region between the common electrode 32 and the upper electrode 41, and an electric field is generated only in the region (above the opening 32a) where there is no common electrode 32. Since the liquid crystal layer 20 is of the TN type, the liquid crystal molecules 2 stand upright above the opening 32a where an electric field is generated.

Here, in the liquid crystal light modulator 10, the voltage applied to the liquid crystal layer 20 above the opening 32a is smaller than the voltage of the AC power source 91 (potential difference between the electrodes 31-41) because the liquid crystal layer 20 and the lower electrode 31 are separated by the interelectrode insulating film 52. Hereinafter, the potential of the upper electrode 41 is represented as V0 (=0V), the potential of the lower electrode 31 as V1, the potential of the common electrode 32 as V2 (=V0=0V), and the potential on the lower surface of the liquid crystal layer 20 above the opening 32a as V5 for a brief explanation. Here, the potential drop due to the alignment films 21 and 22 is ignored because their thickness is sufficiently small compared to the liquid crystal layer 20. Therefore, the potential on the upper surface of the liquid crystal layer 20 is set to the same potential V0 as the upper electrode 41. Similarly, the potential on the lower surface of the liquid crystal layer 20 above the common electrode 32 (outside the opening 32a) is set to the same potential V2 (=0V) as the common electrode 32. When a voltage V _DD (V1=V _DD ) is applied between the electrodes 31 and 41, a potential difference ΔV (=|V1-V5|) between V1 and V5 is proportional to the distance d between the liquid crystal layer 20 and the lower electrode 31, i.e., the thickness of the inter-electrode insulating film 52, as expressed by the following formula (1). E _D is the electric field generated in the inter-electrode insulating film 52, and is inversely proportional to the relative dielectric constant of the inter-electrode insulating film 52. Therefore, the voltage V DD (≧V LC +ΔV) of the AC power supply 91 is set in accordance with the relative dielectric constant and thickness of the inter-electrode insulating film 52 so that a voltage (maximum driving voltage) V _LC at which the liquid crystal molecules 2 stand upright and the phase difference _δ of the liquid crystal layer 20 becomes ₀ is applied to the liquid crystal layer 20 (V5≧V _LC ).
ΔV= _ED d...(1)

In this way, the electrodes below the liquid crystal layer 20 are arranged in two layers with the electrode interlayer insulating film 52, which is a dielectric, sandwiched therebetween, and openings 32a are formed in the common electrode 32 on the side closer to the liquid crystal layer 20. This allows a vertical electric field to be locally generated in a two-dimensional pattern corresponding to the arrangement of the openings 32a, and the liquid crystal layer 20 (liquid crystal molecules 2) can be placed in one of two operating states for each region.

The liquid crystal layer 20 may be a surface stabilized ferroelectric liquid crystal (SSFLC). Since ferroelectric liquid crystal has spontaneous polarization, such a liquid crystal light modulator 10 is connected to, for example, two DC power sources in order to generate electric fields in opposite directions on the common electrode 32 and the opening 32a of the liquid crystal layer 20. The first power source has a positive pole connected to the lower electrode 31 and a negative pole connected to the GND and the upper electrode 41, respectively, and the second power source has a positive pole connected to the GND and the upper electrode 41 and a negative pole connected to the common electrode 32, respectively. If the voltage applied to the liquid crystal layer 20 that generates an upward electric field of a required strength is represented as _VLC1 , and the voltage applied to the liquid crystal layer 20 that generates a downward electric field is represented as _VLC2 , the voltages _VDD1 and _VDD2 of the first and second power sources are set to _VDD1 ≧ _VLC1 +ΔV and _VDD2 ≧ _VLC2 . Since it is preferable to input linearly polarized light to the liquid crystal optical modulator 10, the liquid crystal display device 100 does not include the retardation plates 73 and 74.

(Operation of Liquid Crystal Display Device)
The operation of the liquid crystal display device according to this embodiment will be described. Unpolarized light L _uP incident on the liquid crystal display device 100 from above is converted into light L with a regular vibration direction before it is incident on the liquid crystal light modulator 10. First, the polarizing plate 71 converts the light L into linearly polarized light in a 90° direction (with a double arrow indicating the polarization direction), and the linearly polarized light is converted into left-handed circularly polarized light (left-handed circularly polarized light) by the retardation plate 73. The left-handed circularly polarized light L passes through the transparent substrate 61 and the upper electrode 41, etc., and enters the liquid crystal layer 20. The light L incident on the common electrode 32 (outside the opening 32a) in the no-field state has a phase difference δ of π in this region, so that it is modulated from left-handed circularly polarized light to right-handed circularly polarized light when passing through the liquid crystal layer 20 (see FIG. 6), and then passes through the common electrode 32 to the transparent substrate 62 in sequence to be emitted downward from the liquid crystal light modulator 10. The light L that has become right-handed circularly polarized light and is output from the liquid crystal light modulator 10 is converted by the retardation plate 74 into linearly polarized light in the 0° direction (perpendicular to the paper surface in FIG. 9 ) and is completely blocked by the polarizing plate 72 with its absorption axis direction of 0° (transmission axis direction 90). On the other hand, the light L that is incident on the opening 32a where an electric field is generated has a phase difference δ of 0 in this region, so it transmits as left-handed circularly polarized light and is output downward from the liquid crystal light modulator 10, is converted by the retardation plate 74 into linearly polarized light in the 90° direction, transmits through the polarizing plate 72, and is output from the liquid crystal display device 100.

In this way, the liquid crystal display device 100 equipped with the liquid crystal light modulator 10 can receive light from the entire surface and extract it to the opposite side only from the area where the openings 32a of the common electrode 32 are formed. Therefore, a desired image can be displayed depending on the pattern of the openings 32a formed in the common electrode 32.

The liquid crystal display device 100 can also emit light from the entire surface. To achieve this, the common electrode 32 is disconnected from the upper electrode 41 so that a voltage equal to or greater than the maximum driving voltage _VLC is applied to the entire liquid crystal layer 20, i.e., both above the opening 32a and above the common electrode 32 (outside the opening 32a). Then, as an example, the common electrode 32 is shorted to the lower electrode 31 and connected to a terminal on the non-GND side of the AC power supply 91. At this time, the voltage of the AC power supply 91 is set so that the potential difference between the potential V5 on the lower surface of the liquid crystal layer 20 above the opening 32a and the potential V0 (=0V) of the upper electrode 41 is equal to or greater than the maximum driving voltage _VLC . Alternatively, as shown in FIG. 9, the connection to the terminal of the AC power supply 91 may be switched by switching with a switch 94, so that the lower electrode 31 and the common electrode 32 are connected to GND (0V) and the upper electrode 41 is connected to a terminal on the non-GND side of the AC power supply 91.

The liquid crystal display device 100 may be configured such that the slow axis of the retarder 74 is arranged at 45°, the same as the retarder 73, and the transmission axis of the polarizer 72 is arranged at 0° (cross-Nicol arrangement with respect to the polarizer 71), so that linearly polarized light in the 0° direction is extracted from the area where the opening 32a is formed. In addition, when the liquid crystal layer 20 of the liquid crystal light modulator 10 is of the VA type, the phase difference δ is 0 in the non-electric field state (see the modified example shown in FIG. 12, which will be described later), so the liquid crystal display device 100 is arranged with one of the slow axis of the retarder 74 or the transmission axis of the polarizer 72 in a different direction. Note that the liquid crystal display device 100 may be configured such that the orientation of the polarizers 71, 72 or the retarders 73, 74 is changed and black and white are inverted to extract light from outside the opening 32a of the common electrode 32, depending on the application.

The liquid crystal display device 100 according to this embodiment can display a two-dimensional image (see FIG. 4) of a fixed pattern due to the arrangement of the openings 32a in the common electrode 32 on the surface (polarizing plate 72) on the light exit side. Furthermore, by providing a color filter array 75 (see FIG. 10) on the light exit side of the liquid crystal light modulator 10, a full-color image can be displayed. As described above, the light source can be external light, indoor light, or a general lighting device. Therefore, the liquid crystal display device 100 can be installed, for example, by attaching it to the window glass of a building, and can display an image on the indoor side with the outdoor side as the light entrance side. Note that when the AC power supply 91 (see FIG. 9) is turned off, the entire surface does not transmit light, so the entire surface is displayed black. On the other hand, the liquid crystal display device 100 can transmit light on the entire surface and be transparent by switching the connection of the AC power supply 91 as described above. Alternatively, the liquid crystal display device 100 can be installed, for example, by attaching it to the glass plate in front of a show window, and can display an image on the outside by the lighting in the show window. By switching the connection of the AC power supply 91, the exhibits in the show window can be viewed from outside without displaying an image. Furthermore, as described above, the liquid crystal display device 100 has flexibility by using flexible substrates for the transparent substrates 61 and 62, and can be attached to curved surfaces for installation. In this way, the liquid crystal display device 100 can be widely used for posters, advertisements, signs, etc.

(3D image display device)
The liquid crystal light modulator according to the present invention can be applied to an integral type stereoscopic image display device (hereinafter, stereoscopic image display device). As shown in FIG. 10, the stereoscopic image display device 200 according to the embodiment of the present invention further includes a light source device 80, a color filter array 75, a lens array 85, and an AC power source 91 (see FIG. 9) in addition to the liquid crystal display device 100. The AC power source 91 is as described in the liquid crystal display device 100. The light source device 80 includes a light emitting element such as an LED and a light guide plate, as in the case of a general backlight, and irradiates the liquid crystal display device 100 with white light as a parallel light beam having a diameter that includes the entire light incidence surface of the liquid crystal light modulator 10. The light emitting element of the light source device 80 may be a white LED or the like, but in order to improve color reproducibility, it is preferable to include light emitting elements of single colors R, G, and B. In addition, the stereoscopic image display device 200 may be configured such that the light source device 80 irradiates linearly polarized light instead of the liquid crystal display device 100 including the polarizing plate 71 on the light incidence side, and for this purpose, the light source device 80 further includes a polarizer or a polarization conversion element. The color filter array 75 is arranged on the light output side of the liquid crystal light modulator 10, with R, G, and B color filters arranged in stripes or mosaics to match the pixels of the liquid crystal light modulator 10. The lens array 85 is an optical element array that spatially samples elemental images, and is arranged on the light output side of the liquid crystal display device 100, with elemental lenses arranged two-dimensionally. The resolution of the stereoscopic image display device 200 increases as the arrangement pitch of the elemental lenses of the lens array 85 becomes narrower, while the parallax information increases as the number of pixels of the liquid crystal light modulator 10 facing one elemental lens increases. Therefore, it is preferable that the pixels of the liquid crystal light modulator 10 are dense and numerous. In addition, the shorter the focal length f of the elemental lenses of the lens array 85 is relative to the diameter Φ, i.e., the smaller the F value is, the wider the viewing angle Ψ of the stereoscopic image can be as expressed by the following formula (2).
Ψ=2tan ^-1 (Φ/2f)...(2)

In this way, the integral type stereoscopic image display device 200 equipped with the liquid crystal display device 100 according to this embodiment can display a full-color stereoscopic image with a simple configuration. In addition, the stereoscopic image display device 200 can be switched to white light by emitting light from the entire surface of the liquid crystal display device 100 as described above.

(Holography Device)
The liquid crystal light modulator according to the present invention can also be used in a holographic stereoscopic image display device (hereinafter, referred to as a holographic device). As shown in Fig. 11, a holographic device 200B according to an embodiment of the present invention includes a liquid crystal light modulator 10B, a light source device 8 that irradiates linearly polarized light, an AC power source 91, and, if necessary, a magnifying optical system 86. The holographic device 200B forms a monochromatic stereoscopic image at a position at a predetermined distance using the light emission surface (lower surface) of the liquid crystal layer 20 of the liquid crystal light modulator 10B as a hologram surface.

The liquid crystal light modulator 10B is a spatial light phase modulator, and modulates the phase of light having a predetermined polarization direction, i.e., the incident light L, for each region (pixel). For this purpose, the liquid crystal layer 20 has the slow axis set to the polarization direction of the light L by the upper and lower alignment films 21 and 22 (omitted in FIG. 11). The liquid crystal layer 20 is preferably made to have a thickness (cell thickness) such that the amount of change in the phase of the transmitted light is π in a non-electric field state in the case of the TN method, and in a state in which the maximum driving voltage V _LC is applied in the case of the VA method. The liquid crystal light modulator 10B also includes a common electrode 32B in which openings 32a are arranged so as to form a pattern of a computer-generated hologram (CGH) (see Non-Patent Document 2). The pattern of the openings 32a and the individual planar shapes of the common electrode 32B are not particularly limited, and may be separated into two or more by the openings 32a, for example, but is formed so as not to generate any discontinuous parts with edges that are difficult to connect to the power source 91.

The light source device 8 includes a light source 81, an optical system 84, and a polarizer 71. The light source 81 is a monochromatic light source, and it is preferable to use a laser light source such as a semiconductor laser (LD) or a gas laser so as to irradiate light with a phase-aligned light (coherent light). The optical system 84 is a beam expander or the like, and converts the light irradiated by the light source 81 into a parallel light beam having a diameter that encompasses the entire light incidence surface of the liquid crystal light modulator 10B. As described in the liquid crystal display device 100, the polarizer 71 may be a polarization conversion element that converts the incident non-polarized light L _uP into linearly polarized light L in one direction. The light source device 8 may apply a polarized laser to the light source 81 instead of the polarizer 71. The magnifying optical system 86 is composed of one or more lenses, and is arranged on the light emission side of the liquid crystal light modulator 10B to output a stereoscopic image of a desired size.

When coherent linearly polarized light L enters the liquid crystal light modulator 10B, the phase of either the light that has passed through the liquid crystal layer 20 where an electric field is generated above the opening 32a of the common electrode 32B, or the light that has passed through the liquid crystal layer 20 in an electric field-free state above the common electrode 32B (outside the opening 32a) changes, resulting in two lights with different phases being emitted. Then, the lights with the same phase interfere with each other to form a three-dimensional image. Furthermore, if the liquid crystal layer 20 has a cell thickness such that the phases differ by π, the light that has passed through the common electrode 32B and the light that has passed through the opening 32a can be offset by interference to produce a dark display.

Here, the viewing zone angle Ψ in the holography device depends on the pixel length p (λ: wavelength of light) as expressed by the following formula (3). That is, in the holography device 200B, the viewing zone angle Ψ depends on the pitch of the openings 32a in the common electrode 32B, and the finer the pattern of the openings 32a in the common electrode 32B, the wider the viewing zone angle Ψ can be. For example, in the case of blue light (λ=408 nm) in the short wavelength region of visible light, in order to satisfy Ψ≧30°, p≦0.8 μm.
Ψ=2sin ^-1 (λ/2p)...(3)

The holography device according to this embodiment may further include retardation plates 73, 74 and a polarizing plate 72 above and below the liquid crystal light modulator 10B, similar to the liquid crystal display device 100 (see FIG. 9), and only the light that has passed through the liquid crystal layer 20 above the opening 32a may be emitted by the polarizer 72, causing interference between these lights. Also, an LED or the like may be used as the light source 81 of the light source device 8.

A three-plate color holography device can be formed by providing three holography devices 200B that output images of the respective colors R, G, and B, and further providing a color synthesis optical system (see FIG. 6 in Non-Patent Document 1). In each of the holography devices 200B, the light source device 8 irradiates one of red light, green light, and blue light, and the liquid crystal light modulator 10B has a common electrode 32B formed in a pattern corresponding to the color image of the light irradiated by the light source device 8. The three holography devices 200B may share an AC power source 91. The color synthesis optical system is a dichroic prism or two dichroic mirrors. The three holography devices 200B are arranged so that the positions at which the images of the respective colors output by each of them are formed are aligned. Alternatively, a time-division color holography device can be formed by stacking three liquid crystal light modulators 10B each having a common electrode 32B formed in a pattern corresponding to the images of the respective colors R, G, and B, and providing a light source device that alternately irradiates light of each color. For example, when the light source device is emitting red light, the red liquid crystal light modulator 10B is driven. By turning off the power to the other two liquid crystal light modulators 10B, the phase difference δ across the entire surface becomes 0 or π, and the total becomes 0 or 2π, so there is no effect on the modulation of the red light.

In this way, the holography device 200B equipped with the liquid crystal light modulator 10B can display a three-dimensional image with a simple configuration. Furthermore, by providing three holography devices 200B that display images of the respective colors R, G, and B, a full-color three-dimensional image can be displayed.

(Projection type display device)
The liquid crystal display device 100 according to this embodiment includes a light source device 80A (see FIG. 13) that irradiates light on one side and a projection lens (magnifying optical system) 86A (see FIG. 13) on the other side, and can be used as a projection type display device (projector) that projects an image on a screen by connecting an AC power source 91 to the liquid crystal light modulator 10. The light source device 80A and the projection lens 86A can be those used in known liquid crystal projectors. In order to display a full-color image, the liquid crystal display device 100 further includes a color filter array 75 (see FIG. 10), and includes a light source such as a laser or LED of three colors R, G, and B and a color synthesis optical system, or a mercury lamp, so that the light source device 80A irradiates white light. Alternatively, as in the three-panel color holography device described above, a configuration can be used that includes three liquid crystal display devices 100 in which the common electrode 32 is formed into a pattern corresponding to the R, G, and B color images, and a monochrome light source device that irradiates each liquid crystal display device 100 with light of each color, and the emitted light of each color is combined in a color combining optical system and projected onto a screen via a projection lens 86A.

(Modification)
The liquid crystal light modulator according to the above embodiment is a transmissive spatial light modulator, but it may also be a reflective spatial light modulator. A liquid crystal light modulator according to a modification of the first embodiment of the present invention and a liquid crystal display device including the same will be described below with reference to Fig. 12. The same elements as those in the first embodiment (see Figs. 1 to 11) are given the same reference numerals and will not be described.

The liquid crystal light modulator 10A according to the modified first embodiment of the present invention includes a liquid crystal layer 20A, an upper electrode 41 and a lower electrode 31A sandwiching the liquid crystal layer 20A from above and below, a common electrode 32 provided between the lower electrode 31A and the liquid crystal layer 20A, and an inter-electrode insulating film 52 insulating the common electrode 32 from the lower electrode 31A. The liquid crystal light modulator 10A further includes alignment films 21 and 22 respectively in contact with the upper and lower surfaces of the liquid crystal layer 20A, a transparent substrate 61 on the upper electrode 41, and a substrate 62A below the lower electrode 31A. The liquid crystal light modulator 10A is a reflective spatial light modulator that reflects light incident on the entire surface from above and emits it upward, changing the polarization direction of the light in a predetermined partial area.

The liquid crystal layer 20A can be made of the same liquid crystal material as the liquid crystal layer 20 of the above embodiment. Here, the liquid crystal layer 20A is of the VA type, and in the absence of an electric field, the liquid crystal molecules 2 are upright and the phase difference δ is 0. The liquid crystal molecules 2 tilt at an angle according to the strength of the electric field in the vertical direction, and when the maximum driving voltage V _LC is applied, they assume a horizontal posture along the film surface direction, and the phase difference δ is maximized. In the liquid crystal light modulator 10A, which is a reflective spatial light modulator, the light L goes back and forth within the liquid crystal layer 20A and is emitted, so it is preferable to design the cell thickness to π/2 so that the phase difference δ is π in the round trip. Therefore, the cell thickness is smaller than that of a transmissive liquid crystal light modulator, and the response speed can be increased.

The liquid crystal light modulator 10A is a reflective spatial light modulator, and the lower electrode 31A is formed of a general metal electrode material such as metals such as Cu, Al, Au, Ag, Ta, Cr, Pt, Ru, or alloys thereof, since it does not need to transmit light, and two or more of the above metals or alloys may be laminated. The lower electrode 31A is preferably made of a material with high light reflectivity in a sufficient thickness so that it has a high reflectivity for light incident from above. Alternatively, the liquid crystal light modulator 10A may be configured to have a light-transmitting lower electrode 31 as in the above embodiment, and to reflect light L by the substrate 62A below it or a reflective film (not shown) provided further below it. Since the substrate 62A does not need to transmit light, in addition to the transparent substrate 62 of the above embodiment, a Si substrate, a metal plate, a plastic plate, or the like can be applied. Also, as in the above embodiment, flexible plastic substrates are applied to the substrates 61 and 62A so that the liquid crystal light modulator 10A has flexibility depending on its application. In this modified example, a light-transmitting lower electrode 31 and a transparent substrate 62 may be provided below the liquid crystal layer 20A, and light may be incident from below and reflected by the upper electrode 41 or the substrate thereon (transparent substrate 61). In other words, the common electrode 32 and the electrode interlayer insulating film 52 may be disposed on the light incident side of the liquid crystal layer 20A.

In the operation of the liquid crystal light modulator 10A according to this modification, the generation of an electric field by application of a voltage from an AC power supply 91 is the same as in the liquid crystal light modulator 10 according to the above embodiment (see FIG. 9). In this modification, the liquid crystal layer 20A is of the VA type, so that the liquid crystal molecules 2 stand upright outside the opening 32a (above the common electrode 32) in the electric field-free state, as shown in FIG. 12.

The liquid crystal light modulator 10A according to the modified embodiment of the present invention is used in a liquid crystal display device in the same manner as a general reflective liquid crystal light modulator. As shown in FIG. 12, the liquid crystal display device 100A according to the modified embodiment of the present invention includes a liquid crystal light modulator 10A and a polarizing plate (polarizer) 72 arranged on the light input/output side (top) of the liquid crystal light modulator 10A, and preferably further includes a retardation plate 73 between the liquid crystal light modulator 10A and the polarizing plate 72. In addition, when displaying a full-color image, the liquid crystal display device 100A includes a color filter array 75 (see FIG. 10) on the light input/output side of the liquid crystal light modulator 10A.

(Operation of Liquid Crystal Display Device)
The operation of the liquid crystal display device according to this modification will be described. As in the liquid crystal display device 100 according to the above embodiment (see FIG. 9), the non-polarized light L _uP incident on the liquid crystal display device 100A from above is converted into left-handed circularly polarized light by the polarizing plate 72 and the retardation plate 73, and passes through the transparent substrate 61 and the upper electrode 41, etc., and enters the liquid crystal layer 20A. The light L incident on the common electrode 32 (outside the opening 32a) in the electric field-free state has a phase difference δ of 0 in this region, so it passes through as left-handed circularly polarized light and reaches the lower electrode 31A. The left-handed circularly polarized light is changed to right-handed circularly polarized light when reflected by the lower electrode 31A, passes through the liquid crystal layer 20A again from below, and further passes through the upper electrode 41 and the transparent substrate 61, and enters the retardation plate 73. The retardation plate 73 converts the right-handed circularly polarized light into linearly polarized light in the 0° direction, so the linearly polarized light L is blocked by the polarizing plate 72 and does not exit. On the other hand, the light L incident on the opening 32a where the electric field is generated has a phase difference δ of π/2 in this region, so that when it passes through the liquid crystal layer 20A, it changes from left-handed circularly polarized light to linearly polarized light in the 0° direction (see FIG. 6 ) and reaches the lower electrode 31. The state of linearly polarized light does not change when it is reflected, so the light L linearly polarized in the 0° direction enters the liquid crystal layer 20A again from below. The liquid crystal layer 20A then returns the 0° linearly polarized light to left-handed circularly polarized light, and the retarder 73 converts it to linearly polarized light in the 90° direction, so that the linearly polarized light L passes through the polarizer 72 and is emitted upward from the liquid crystal display device 100A.

In this way, the liquid crystal display device 100A equipped with the liquid crystal light modulator 10A can receive natural light such as external light on its entire surface and extract light only from the area on the same side (polarizing plate 72) where the openings 32a of the common electrode 32 are formed, so that the desired image can be displayed by the pattern of the openings 32a, just like the liquid crystal display device 100 equipped with the transmissive liquid crystal light modulator 10.

The liquid crystal display device 100A can emit light from the entire surface by switching the connection between the electrodes 31, 41, and 32 and the AC power supply 91, as in the liquid crystal display device 100. As described in the above embodiment, the connection of the common electrode 32 is switched to disconnect the short circuit with the upper electrode 41 and short circuit with the lower electrode 31. Alternatively, an AC power supply having a voltage smaller than that of the AC power supply 91 ( _VLC or more and less than _VDD ) may be connected to the common electrode 32, taking into account the potential difference ΔV between V1 and V5. As such an AC power supply, a power supply device 92 is provided as shown in FIG. 12. The power supply device 92 receives a voltage from the AC power supply 91 and outputs a voltage smaller than this voltage in synchronization with the AC power supply 91.

In the liquid crystal display device 100A, one polarizing plate 72 serves as both a polarizer and an analyzer, so the light reflected and emitted from the liquid crystal light modulator 10A on the opening 32a must be in the same polarization state as the light entering the liquid crystal light modulator 10A from above (light source). When the TN method is applied, a transmissive liquid crystal light modulator 10 is provided with electrodes 31, 41 and transparent substrates 61, 62 that transmit light above and below, and the liquid crystal layer 20 is designed to have a cell thickness such that the phase difference δ is π/2 in the absence of an electric field. A retardation plate 74 is placed below the liquid crystal light modulator 10 (see FIG. 9), and a reflector is placed below that.

(Projection type display device)
A liquid crystal display device including the liquid crystal light modulator 10A according to this modification can be used in a projection display device (projector) in the same manner as in the above embodiment. As shown in FIG. 13, such a liquid crystal display device 100C includes a polarizing beam splitter 76 on the light input/output side of the liquid crystal light modulator 10A, and is configured so that the phase difference between the light incident on the liquid crystal light modulator 10A and the light output from the opening 32a (voltage application area) is π. The projection display device 200C includes a light source device 80A and a projection lens 86A disposed on the side and above the polarizing beam splitter 76, respectively, in the liquid crystal display device 100C, and an AC power source 91 connected to the liquid crystal light modulator 10A. In order to display a full-color image, the liquid crystal display device 100C further includes a color filter array 75, and the light source device 80A irradiates white light. The light source device 80A irradiates the polarizing beam splitter 76 with unpolarized light L _uP from the side, and the S-polarized light (linearly polarized light L perpendicular to the paper surface) reflected by the polarizing beam splitter 76 is incident on the retardation plate 73 on the liquid crystal light modulator 10A. Then, of the light modulated by the liquid crystal light modulator 10A and emitted from the retardation plate 73, the P-polarized light passes through the polarizing beam splitter 76 and is emitted via the projection lens 86A. Alternatively, as described in the above embodiment, a three-plate projection display device may be used.

The liquid crystal light modulator 10A according to this modification is provided with a common electrode 32B on which a computer-generated hologram pattern is formed, similar to the liquid crystal light modulator 10B according to the embodiment (see FIG. 11), and can be used in a holography device. In the holography device according to the modification provided with such a reflective liquid crystal light modulator 10A, the light source device 8 is arranged so that the incident light is slightly tilted into the liquid crystal light modulator 10A so that the optical paths of the incident light and the outgoing light do not coincide. Alternatively, the holography device is provided with a half mirror (non-polarizing beam splitter) tilted at 45° on the light input/output side (top) of the liquid crystal light modulator 10A, and light L is input from the light source device 8 arranged above it at an incident angle of 0°, and the light emitted from the liquid crystal light modulator 10A is reflected to the side by the half mirror. Alternatively, the holography device according to this modification may be similar to the liquid crystal display device 100C (see FIG. 13) in that it has a phase difference plate 73 on the liquid crystal light modulator 10A and a polarizing beam splitter 76 on top of that instead of a half mirror, and only the light that has passed through the liquid crystal layer 20A above the opening 32a is emitted, causing these lights to interfere with each other. Also, to display a full-color stereoscopic image, a three-plate color holography device is configured by having three holography devices that output images of the colors R, G, and B, and a color synthesis optical system, as in the above embodiment.

As described above, the liquid crystal light modulator according to the first embodiment of the present invention and its modified example can provide a liquid crystal display device that has a simple configuration, has fine pixels, and displays a desired image. Furthermore, an integral type stereoscopic image display device using such a liquid crystal display device can provide more parallax information and higher resolution. Furthermore, a holography device using such a liquid crystal display device can provide a stereoscopic image with a wide viewing angle.

Second Embodiment
The liquid crystal light modulator according to the first embodiment and its modified example displays a binary black and white value, but can also display gradations including intermediate tones without increasing the signal. The liquid crystal light modulator according to the second embodiment will be described below. The same elements as those in the first embodiment (see FIGS. 1 to 13) are given the same reference numerals and description thereof will be omitted.

As shown in FIG. 14, in the liquid crystal light modulator 10E according to the second embodiment of the present invention, in the region where at least some of the openings 32a of the common electrode 32 are formed, the electrode interlayer insulating film 52B has holes of a predetermined depth formed so that the thickness varies for each opening 32a. In FIG. 14, there is no hole in the opening 32a on the left side, and a hole is formed in the opening 32a on the right side so that the thickness is half.

The inter-electrode insulating film 52B may have a minimum thickness of 0, i.e., a through hole. On the other hand, the inter-electrode insulating film 52B may have a maximum thickness without a hole, or may be embedded into the opening 32a (see FIG. 7). The liquid crystal light modulator 10E can display a gray scale that is one more than the number of thickness steps (including thickness 0) of the inter-electrode insulating film 52B. Here, the voltage V _DD applied between the electrodes 31-41 (potential V0 of the upper electrode 41=0V) is set to a voltage that makes the potential V7 on the lower surface of the liquid crystal layer 20 in the maximum thickness region of the inter-electrode insulating film 52B a predetermined value (minimum driving voltage V _LC ') described below (see FIG. 15). When such a voltage V _DD is applied between the electrodes 31-41, a hole is formed in the inter-electrode insulating film 52B at each opening 32a, with a depth such that the potential on the lower surface of the liquid crystal layer 20 becomes a desired value (V _LC ' or less than V _LC ). In particular, the deepest hole, i.e., the minimum thickness of the electrode interlayer insulating film 52B, is formed so that the potential V5 at the lower surface of the liquid crystal layer 20 in this region becomes the maximum drive voltage _VLC . Furthermore, when there are many gradations, the electrode interlayer insulating film 52B having a higher relative dielectric constant is more likely to have many thickness steps.

The liquid crystal light modulator 10E according to this embodiment is applied to a transmissive liquid crystal display device (see FIG. 9) in the same manner as the liquid crystal light modulator 10 according to the first embodiment. When a voltage V _DD is applied from an AC power source 91, as shown in FIG. 15, the potential V5 on the lower surface of the liquid crystal layer 20 in the region where the thickness of the inter-electrode insulating film 52B is the smallest (the hole is the deepest) becomes the maximum driving voltage V _LC . As described above, the potential on the lower surface of the liquid crystal layer 20 above the opening 32a drops relative to the potential V1 (=V _DD ) of the lower electrode 31 in proportion to the distance d between the liquid crystal layer 20 and the lower electrode 31. Therefore, for each opening 32a, a voltage corresponding to the thickness of the inter-electrode insulating film 52B at that opening 32a is applied to the liquid crystal layer 20 thereon. As a result, for each opening 32a, the liquid crystal layer 20 thereon has a tilt of the liquid crystal molecules 2 corresponding to the thickness of the inter-electrode insulating film 52B directly below it. In such a liquid crystal display device, light (e.g., left-handed circularly polarized light) incident on the opening 32a of the liquid crystal light modulator 10E passes through the liquid crystal layer 20 with its polarization state changed by a phase difference δ (TN mode: 0≦δ<π, VA mode: 0<δ≦π) corresponding to the thickness of the electrode interlayer insulating film 52B in this region. Then, the amount of light corresponding to the changed polarization state passes through the polarizing plate 72 and is emitted. When a voltage V _LC ' is applied to the liquid crystal layer 20 above the opening 32a where the electrode interlayer insulating film 52B has the maximum thickness, the phase difference becomes such that the second darkest desired grayscale (next to black) is displayed.

In this way, while the liquid crystal light modulator 10E has an integrated lower electrode 31 as a whole, the lower surface of the liquid crystal layer 20 above each opening 32a can be set to a desired potential, and the liquid crystal layer 20 can have a different phase difference δ. Similarly to the liquid crystal display device 100 according to the first embodiment, the liquid crystal display device including the liquid crystal light modulator 10E can receive light from the entire surface, extract light only from the area where the opening 32a of the common electrode 32 on the opposite side is formed, and further extract light with a different amount for each opening 32a, so that a desired image can be displayed by the pattern of the opening 32a and the thickness of the opening 32a of the electrode interlayer insulating film 52B. Similarly to the liquid crystal display device 100, the liquid crystal display device including the liquid crystal light modulator 10E can emit light from the entire surface by connecting the common electrode 32 and the lower electrode 31 to GND and connecting the upper electrode 41 to a non-GND terminal of the AC power supply 91. In this embodiment, the voltage of the AC power supply 91 is set so that a voltage equal to or greater than the maximum drive voltage _VLC is applied to the liquid crystal layer 20 in the region where the thickness of the inter-electrode insulating film 52B at the opening 32a is at its maximum.

(Modification)
In this embodiment, the gray scale display is possible not only by the difference in thickness of the inter-electrode insulating film separating the liquid crystal layer and the lower electrode, but also by the difference in the relative dielectric constant. As shown in Fig. 16, in the liquid crystal light modulator 10F according to the modified example of the second embodiment of the present invention, an opening is also formed in the inter-electrode insulating film 52C in the region where the opening 32a of the common electrode 32 is formed, and embedded insulating layers (insulating layers) 5b, 5c made of insulating materials having different relative dielectric constants are formed for each opening 32a.

The embedded insulating layers 5b and 5c are selected from the insulating materials listed as the material of the electrode interlayer insulating film 52. Here, the embedded insulating layer 5b made of the same material as the electrode interlayer insulating film 52C is provided in the left opening 32a, and the embedded insulating layer 5c made of an insulating material with a higher relative dielectric constant (high dielectric constant insulating material) is provided in the right opening 32a. The liquid crystal light modulator 10F can display one more gradation than the number of types of materials (levels of relative dielectric constant) of the embedded insulating layers 5b and 5c. The material and thickness of the embedded insulating layers 5b, 5c are designed so that when a voltage V _DD is applied between the electrodes 31-41 (potential V0 of the upper electrode 41 = 0V), the potential V5 at the underside of the liquid crystal layer 20 in the area where the embedded insulating layer with the highest dielectric constant is provided drops to the maximum drive voltage V _LC , and the potential V7 at the underside of the liquid crystal layer 20 in the area where the embedded insulating layer with the lowest dielectric constant is provided drops to the minimum drive voltage V _LC ' (see Figure 15).

The liquid crystal light modulator 10F according to this modified example is applied to a transmissive liquid crystal display device (see FIG. 9) in the same manner as the liquid crystal light modulator 10E according to the above embodiment. A liquid crystal display device including the liquid crystal light modulator 10F can extract light only from the area where the opening 32a of the common electrode 32 is formed, and can further extract light with a different amount for each opening 32a. Also, like a liquid crystal display device including the liquid crystal light modulator 10E, a liquid crystal display device including the liquid crystal light modulator 10F can emit light from the entire surface by connecting the common electrode 32 and the lower electrode 31 to GND and connecting the upper electrode 41 to the non-GND terminal of the AC power supply 91.

This modified example may be combined with the above embodiment to change the thickness of each of the embedded insulating layers 5b and 5c. Also, holes of different depths in the electrode interlayer insulating film 52B of the above embodiment shown in FIG. 14 may be filled with an insulating material having a different dielectric constant than the electrode interlayer insulating film 52B to form a flat surface. When filled with an insulating material having a higher dielectric constant than the electrode interlayer insulating film 52B, a higher voltage is applied to the liquid crystal layer 20 on the area where the electrode interlayer insulating film 52B is thinner. Conversely, when filled with an insulating material having a lower dielectric constant than the electrode interlayer insulating film 52B, a higher voltage is applied to the liquid crystal layer 20 on the area where the electrode interlayer insulating film 52B is thicker.

A liquid crystal display device including the liquid crystal light modulators 10E and 10F according to this embodiment and the modified example can be used in integral and holographic stereoscopic image display devices, similar to the liquid crystal display devices 100 and 100B according to the first embodiment (see Figures 10 and 11). The liquid crystal light modulators 10E and 10F can also be reflective spatial light modulators by including a lower electrode 31A and a substrate 62A that reflect light (see Figure 12).

As described above, the liquid crystal optical modulator according to the second embodiment of the present invention and its modified example can provide a liquid crystal display device that displays a desired image with fine pixels, as in the first embodiment, and further provides high image quality through multi-tone display of the image.

Third Embodiment
In the liquid crystal light modulators according to the first and second embodiments and their modifications, the common electrode can be disposed on either the light incident side or the light exiting side of the liquid crystal layer. Thus, by providing the common electrode on both sides of the liquid crystal layer and forming different opening patterns, two types of images can be displayed. The liquid crystal light modulator according to the third embodiment will be described below. The same elements as those in the first and second embodiments (see FIGS. 1 to 16) are given the same reference numerals and description thereof will be omitted.

(Liquid crystal light modulator)
17, the liquid crystal light modulator 10D according to the third embodiment of the present invention includes a liquid crystal layer 20, an upper electrode 41 and a lower electrode 31 sandwiching the liquid crystal layer 20 from above and below, a common electrode 32 with an opening 32a formed between the lower electrode 31 and the liquid crystal layer 20, a common electrode 42 with an opening 42a formed between the upper electrode 41 and the liquid crystal layer 20, an electrode interlayer insulating film 52 that insulates the common electrode 32 from the lower electrode 31, and an electrode interlayer insulating film 51 that insulates the common electrode 42 from the upper electrode 41. The liquid crystal light modulator 10D further includes alignment films 21 and 22 that contact the upper and lower surfaces of the liquid crystal layer 20, respectively, a transparent substrate 61 above the upper electrode 41, and a transparent substrate 62 below the lower electrode 31. That is, the liquid crystal light modulator 10D has a configuration in which the common electrode 42 and the electrode interlayer insulating film 51 are added between the upper electrode 41 and the liquid crystal layer 20 of the liquid crystal light modulator 10 according to the first embodiment. The liquid crystal light modulator 10D is a transmissive spatial light modulator that transmits light incident on the entire surface from either above or below and emits it to the other side, changing the polarization direction of the light in a predetermined partial area, similar to the liquid crystal light modulator 10. The liquid crystal light modulator 10D is also applied to a liquid crystal display device that displays two fixed patterns as images.

The common electrode 42 is provided between the upper electrode 41 and the liquid crystal layer 20, and like the common electrode 32, prevents the electrodes 31, 41 from partially generating an electric field in the liquid crystal layer 20. That is, the common electrode 42 has an opening 42a formed therein to open up an area in which an electric field is generated. The common electrode 42 can be configured in the same manner as the common electrode 32, except that the arrangement pattern of the openings 42a is different from that of the common electrode 32. The openings 42a are formed in pixels that brightly display the image to be displayed, and this image can be independent of the fixed pattern due to the arrangement of the openings 32a of the common electrode 32. The planar shape of the openings 42a may be the same as or different from that of the openings 32a. The electrode interlayer insulating film 51 is provided between the upper electrode 41 and the common electrode 42 to insulate them, and like the electrode interlayer insulating film 52, is selected from the insulating materials described above and designed to an appropriate thickness.

(Liquid crystal display device)
The liquid crystal light modulator 10D according to the third embodiment of the present invention is used in a liquid crystal display device in the same manner as the liquid crystal light modulator 10 according to the first embodiment. As shown in Fig. 18A and Fig. 18B, the liquid crystal display device 100D according to the embodiment of the present invention includes the liquid crystal light modulator 10D and polarizing plates (polarizers) 71 and 72 arranged above and below the liquid crystal light modulator 10D, and preferably further includes retardation plates 73 and 74 between the liquid crystal light modulator 10D and the polarizing plates 71 and 72, respectively. In addition, when the liquid crystal display device 100D displays a full-color image, a color filter array 75 is provided on the output side of the liquid crystal light modulator 10D (see Fig. 10). The liquid crystal display device 100D can be irradiated with light from either the top or bottom to display an image on the other side, and will be described here as being irradiated with light from above to display an image below.

(Operation of Liquid Crystal Light Modulator and Liquid Crystal Display Device)
The operation of the liquid crystal light modulator and the liquid crystal display device according to the third embodiment will be described with reference to Figs. 18A, 18B, and 19. As shown in Fig. 18A, the liquid crystal light modulator 10D has an AC power supply 91 connected between the electrodes 31 and 41, and the common electrode 32 and the common electrode 42 are short-circuited and connected to a power supply device 93. The power supply device 93 receives a voltage from the AC power supply 91 and outputs a voltage smaller than this voltage in synchronization with the AC power supply 91. Furthermore, the terminal of the AC power supply 91 on the upper electrode 41 side is connected to GND (0V). Here, the potentials of the electrodes 31, 41, 32, and 42 are represented as V1, V4, V2, and V3, the potential on the lower surface of the liquid crystal layer 20 above the opening 32a of the common electrode 32 is represented as V5, and the potential on the upper surface of the liquid crystal layer 20 below the opening 42a of the common electrode 42 is represented as V6. Here, the potential drop due to the alignment films 21 and 22 is ignored because their thickness is sufficiently small compared to the liquid crystal layer 20. Moreover, the electrode interlayer insulating film 51 and the electrode interlayer insulating film 52 have the same structure (dielectric constant, thickness).

When a voltage V _DD (V4=0V, V1=V _DD ) is applied between the electrodes 31 and 41, no voltage is applied to the liquid crystal layer 20 between the common electrodes 32 and 42 (outside the opening 32a and outside the opening 42a) that are shorted to the same potential (V2=V3). As described in the first embodiment, the potential V5 on the lower surface of the liquid crystal layer 20 above the opening 32a of the common electrode 32 drops by a potential difference ΔV (=|V1-V5|) with respect to the potential V1 of the lower electrode 31 (see FIG. 19), and the potential difference ΔV depends on the thickness and relative dielectric constant of the inter-electrode insulating film 52 that separates the liquid crystal layer 20 and the lower electrode 31. Since the inter-electrode insulating film 51 and the inter-electrode insulating film 52 have the same structure, the potential difference between V4 and V6 can also be expressed as ΔV. That is, V5=V _DD -ΔV, V6=ΔV. Therefore, a voltage of |V5-V6|=V _DD -2ΔV is applied to the liquid crystal layer 20 below the opening 42a and above the opening 32a. The voltage V DD (≧V LC +2ΔV) of the AC power supply 91 is set so that a voltage (maximum driving voltage) V _LC is applied (|V5-V6|≧V _LC ) at which the liquid crystal molecules 2 stand upright in this region and the phase difference _δ of the _liquid crystal layer 20 becomes 0. With this configuration, a vertical electric field (represented by a hatched upward arrow in the figure) is generated in the region of the liquid crystal layer 20, causing the liquid crystal molecules 2 to stand upright.

On the other hand, above the opening 32a and below the common electrode 42 (outside the opening 42a), a voltage with a potential difference |V5-V3| is applied to the liquid crystal layer 20. In order to apply the maximum driving voltage _VLC to this region as well, the potential V3 of the common electrode 42 is set to _ΔV , that is, the voltage V _DD ' (=ΔV) of the power supply device 93 is set so that |V5-V3|=|V5-V6|≧VLC. Therefore, V2=V3=ΔV. At this time, above the common electrode 32 (outside the opening 32a) and below the opening 42a, the potential difference is |V2-V6|=0V, and no voltage is applied to the liquid crystal layer 20. In this way, in the liquid crystal light modulator 10D, an electric field is generated only in the region without the common electrode 32 (above the opening 32a), and is not affected by the presence or absence of the opening 42a of the upper common electrode 42. As a result, when the maximum drive voltage V _LC is applied to the liquid crystal layer 20 above the opening 32 a, the liquid crystal molecules 2 stand upright and the phase difference δ becomes 0, while in other regions (outside the opening 32 a), the phase difference δ becomes maximum (π) in the absence of an electric field.

When natural light L _uP is incident on the liquid crystal display device 100D from above in this state of the liquid crystal optical modulator 10D, the light L that has been converted into left-handed circularly polarized light by the polarizer 71 and the retarder 73 enters the liquid crystal layer 20, as described in the first embodiment with reference to Fig. 9. Then, the light L is converted into 90° linearly polarized light only from the region where the openings 32a of the common electrode 32 are formed, and is extracted downward from the liquid crystal display device 100D, so that a desired image can be displayed by the pattern of the openings 32a.

Next, the liquid crystal light modulator 10D switches the connection to the AC power source 91 connected between the electrodes 31 and 41 using the switches 95a and 95b, and connects the terminal of the AC power source 91 on the lower electrode 31 side to GND (0V) as shown in Fig. 18B. When a voltage V _DD is applied between the electrodes 31 and 41 in this state, V1=0V and V4=V _DD , so that the potentials V1 and V4 are switched. Also, |V1-V5|=|V4-V6|=ΔV, so that V5=ΔV and V6=V _DD -ΔV, so that the potentials V5 and V6 are switched. Also, a current of voltage V _DD '(=ΔV) is input from the power supply device 93 to the common electrodes 32 and 42 as in Fig. 18A, so that V2=V3=ΔV.

Similar to FIG. 18A, no voltage is applied to the liquid crystal layer 20 between the common electrodes 32 and 42 (outside the opening 32a and outside the opening 42a). A voltage of |V5-V6|=V _DD -2ΔV≧V _LC is applied to the liquid crystal layer 20 below and above the opening 42a, so that an electric field in the vertical direction (represented by a hatched downward arrow in the figure) is generated. On the other hand, above the opening 32a and below the common electrode 42 (outside the opening 42a), the potential difference is |V5-V3|=0V, so that no voltage is applied to the liquid crystal layer 20. On the other hand, a voltage of a potential difference |V2-V6|≧V _LC is applied to the liquid crystal layer 20 above the common electrode 32 (outside the opening 32a) and below the opening 42a, so that an electric field is generated. In this way, in the liquid crystal light modulator 10D, an electric field is generated only in the region without the common electrode 42 (below the opening 42a), and is not affected by the presence or absence of the opening 32a in the lower common electrode 32. As a result, in the liquid crystal layer 20, the maximum drive voltage _VLC is applied below the opening 42a, causing the liquid crystal molecules 2 to stand upright and the phase difference δ to be 0, while in other regions (outside the opening 42a), the phase difference δ is maximum (π) in the absence of an electric field.

When the liquid crystal optical modulator 10D is in this state, and natural light L _uP is incident on the liquid crystal display device 100D from above, the light becomes linearly polarized in a 90° direction only from the area in which the openings 42a of the common electrode 42 are formed, and is extracted downward from the liquid crystal display device 100D, so that the desired image can be displayed depending on the pattern of the openings 42a.

In this way, the liquid crystal light modulator 10D provides the upper electrode of the liquid crystal layer 20 in two layers with a dielectric sandwiched therebetween, as with the lower electrode, and forms an opening 42a in the common electrode 42 closer to the liquid crystal layer 20. Furthermore, by configuring the connection so that the terminals of the AC power supply 91 can be switched when a voltage is applied between the electrodes 31-41, it is possible to locally generate an electric field in a two-dimensional pattern corresponding to the desired arrangement of the openings 32a in the common electrode 32 or the openings 42a in the common electrode 42. As a result, the liquid crystal display device 100D can selectively display two types of images corresponding to the patterns of the openings 32a in the common electrode 32 and the openings 42a in the common electrode 42.

The liquid crystal display device 100D can also emit light from the entire surface, similarly to the liquid crystal display device 100 according to the first embodiment. To this end, for example, in FIG. 18A (V4=0V, V1=V _DD ), the common electrode 32 is disconnected from the common electrode 42 by a switch 94, and the connection to the power supply device 93 is switched to the power supply device 92. The power supply device 92 receives a current from the AC power supply 91, similarly to the power supply device 93, and outputs a current of voltage V _DD -ΔV in synchronization with the AC power supply 91. That is, since V2=V _DD -ΔV and V3=V _DD '=ΔV, V2=V5 and V3=V6. In addition, the potential difference is |V2-V3|=V _DD -2ΔV≧V _LC , and the voltage V _LC is also applied to the liquid crystal layer 20 between the common electrodes 32 and 42 (outside the opening 32a and outside the opening 42a).

In this embodiment, the liquid crystal layer 20 may be of the VA type or a surface stabilized ferroelectric liquid crystal (SSFLC) as in the liquid crystal light modulator 10 according to the first embodiment. When electric fields in opposite directions are generated on the common electrode 32 and on the opening 32a of the liquid crystal layer 20 using ferroelectric liquid crystal, as described above, the positive pole of the first power supply is connected to the lower electrode 31 and the negative pole to the GND and the upper electrode 41, respectively, and the positive pole of the second power supply is connected to the GND and the upper electrode 41, respectively, and the negative pole is connected to the common electrode 32. Furthermore, in order to make the potential on the upper surface of the liquid crystal layer 20 uniform (V3=V6), the negative pole of the third power supply is connected to the common electrode 42 and the positive pole to the GND (and the upper electrode 41). If the voltage applied to liquid crystal layer 20 which generates an upward electric field of the required strength is denoted as _VLC1 and the voltage applied which generates a downward electric field is denoted as _VLC2 , then the voltages _VDD1 , _VDD2 , _VDD3 of the first, second and third power supplies are _VDD1 ≥ _VLC1 + 2ΔV, _VDD2 ≥ _VLC2 + ΔV and _VDD3 = ΔV. When electric fields of opposite directions are to be generated below common electrode 42 and below opening 42a of liquid crystal layer 20, the connections to the DC power supplies are interchanged between the upper and lower electrodes.

The liquid crystal display device 100D according to this embodiment can selectively display two fixed pattern two-dimensional images by the arrangement of the openings 32a in the common electrode 32 or the openings 42a in the common electrode 42 on the surface (polarizing plate 72) opposite to the surface to which external light or the like is incident. Furthermore, by providing a color filter array 75 (see FIG. 10) on the light output side of the liquid crystal light modulator 10D, a full-color image can be displayed. In this case, the arrangement of the openings 32a, 42a of both the common electrode 32 and the common electrode 42 is designed so that pixels of each color are arranged in accordance with the area facing the color filters of each color of R, G, and B in the color filter array 75. Furthermore, the liquid crystal display device 100D can be used in integral type and holographic type stereoscopic image display devices (see FIGS. 10 and 11) like the liquid crystal display devices 100 and 100B according to the first embodiment. In a holographic stereoscopic image display device (holographic device), a stereoscopic image can be displayed on one side of the common electrodes 32 and 42, and a two-dimensional image can be displayed on the other side. The liquid crystal light modulator 10D can also be a reflective spatial light modulator by placing a reflector on the side opposite the light incident side, or by providing a lower electrode 31A and a substrate 62A that reflect light (see FIG. 12).

(Modification)
The liquid crystal display device 100D according to this embodiment may not include the power supply device 93, and the common electrodes 32, 42 may be connected to GND (0 V) together with the upper electrode 41 (FIG. 18A) or the lower electrode 31 (FIG. 18B). In this liquid crystal display device 100D, the electrode interlayer insulating film 51 and the electrode interlayer insulating film 52 of the liquid crystal optical modulator 10D may be configured as in the liquid crystal optical modulators 10E and 10F according to the second embodiment and their modified examples (see FIGS. 14 and 16), allowing multi-tone display.

As described above, the liquid crystal optical modulator according to the third embodiment of the present invention and its modified example can provide a liquid crystal display device that has fine pixels and displays a desired image, as in the first embodiment, and can also selectively display two different images.

To confirm the effects of the present invention, a simulation was performed to observe the optical output characteristics of a sample simulating the liquid crystal optical modulator according to the first embodiment of the present invention shown in Figure 2.

(Sample creation)
Sample 1 was composed of, from the bottom, a glass substrate, a lower electrode: ITO (thickness 20 nm), an electrode interlayer insulating film: _SiO2 film (thickness 50 nm), a common electrode: ITO (thickness 20 nm), an alignment film, a liquid crystal layer (thickness 1 μm), an alignment film, an upper electrode: ITO film (thickness 20 nm), and a glass substrate. The common electrode was in a checkered pattern with two square openings of 0.8 μm squares formed diagonally at a pitch of 1.0 μm, as shown on the coordinate plane in FIG. 20. The liquid crystal layer was made of homogeneously aligned nematic liquid crystal, and the upper and lower alignment films were made of polyimide-based materials and were rubbed in the y direction (90° direction) of FIG. 20.

(measurement)
Using a liquid crystal simulator (LCDMaster, manufactured by Shintech), the upper electrode and common electrode of sample 1, and one terminal of the AC power supply were fixed to 0 V, the other terminal was connected to the lower electrode, and an AC voltage of ±7 V and 1 kHz was applied. The potential distribution and liquid crystal orientation were obtained in a cross section along the yz direction on the dashed line in FIG. 20 as a cross-sectional distribution, and in a cross section along the xy plane 10 nm above the surface of the common electrode as a planar distribution. Furthermore, a polarizing plate (polarizer) was placed above sample 1 (light incident side) with the transmission axis in the 45° direction, and a polarizing plate (analyzer) was placed below (light exit side) with the transmission axis in the 135° direction. Then, a laser beam with a wavelength of 633 nm was irradiated from above the upper polarizing plate, and a planar distribution of the transmittance reflecting the entire thickness of the liquid crystal layer was obtained.

Figure 21 shows the electric potential distribution and liquid crystal orientation in a cross section, and Figure 22 shows the electric potential distribution and liquid crystal orientation in a plane. Figure 23 also shows the planar distribution of transmittance together with the liquid crystal orientation of Figure 22. Equipotential lines in the electric potential distribution diagram are in 1V increments. Figure 21 also shows the upper and lower electrodes with long white dashed lines, the common electrode with a white dashed line, and the surface of the electrode interlayer insulating film at the opening of the common electrode (the interface with the liquid crystal layer) with a dotted line. In Figures 22 and 23, the outline of the opening of the common electrode is shown with a white dotted line.

21 and 22, the potential at the interface of the liquid crystal layer with the common electrode is 0V, and the potential at the interface of the common electrode opening with the interlayer insulating film is a maximum of approximately +4V at the center of the opening. In FIG. 22, the equipotential lines within the opening of the common electrode are +3V, +2V, and +1V, from the inside. The electric field generated between the opening and the upper electrode, which has a potential of 0V, causes the liquid crystal molecules above the opening to rise from the substrate surface and tilt, with the higher the potential, the closer to vertical they become. On the other hand, the area where the electric field leaks outside the opening is narrow, and even in the leaked area, the tilt of the liquid crystal molecules is small.

As shown in Figure 23, the polarizing plates arranged in a crossed Nicol arrangement above and below Sample 1 display white in the area where the liquid crystal molecules maintain a horizontal orientation, and display gray to black in the area where the liquid crystal molecules stand up. The transmittance decreases as the orientation (long axis direction) of the liquid crystal molecules approaches vertical, and the display becomes black. In some areas above the opening of the common electrode, the transmittance becomes almost 0% and the display becomes black due to the large (close to vertical) angle of the liquid crystal molecules. In addition, because there is electric field leakage from the opening toward the common electrode with a potential of 0V, some of the liquid crystal molecules near the outside of the opening also stand up, and a black display was confirmed outside the opening. However, this is limited to a range of less than 0.2 μm outside the opening, and it is difficult to say that it generally extends to the opening of the adjacent pixel. On the other hand, there was an area above the opening of the common electrode where the liquid crystal molecules were oriented in an oblique direction due to electric field leakage in a diagonal direction in a plan view. In particular, in the area adjacent to the common electrode (outside the opening) in the y direction, the liquid crystal molecules tilt in the y direction, overlapping with the 90° direction, which is the orientation direction in the yz electric field-free state, resulting in a large tilt (small rise angle). As a result, the shape of the area displayed in black is smaller than the shape of the opening of the common electrode, and some parts are recessed inward.

As described above, it was confirmed that the liquid crystal optical modulator according to the first embodiment of the present invention can separate black and white display even in an area with one side less than 1 μm square, which is shorter than the cell thickness, and in particular, the area in which no electric field is to be displayed can be relatively easily secured by the common electrode.

As in Example 1, the optical output characteristics of samples simulating the liquid crystal optical modulator according to the second embodiment of the present invention and its modified example shown in Figures 14 and 16 were observed by simulation.

(sample)
Samples 2 and 3 were made up of, from the bottom up, a glass substrate, a lower electrode: ITO (thickness 20 nm), an electrode interlayer insulating film: _SiO2 film (thickness 100 nm), a common electrode: ITO (thickness 20 nm), an alignment film, a liquid crystal layer (thickness 1 μm), an alignment film, an upper electrode: ITO film (thickness 20 nm), and a glass substrate. The common electrode had a shape in which four square openings, each 0.8 μm square, were arranged in a 2×2 pattern with a pitch of 1.0 μm, as shown on the coordinate plane in FIG. 24. Sample 2 further thinned the electrode interlayer insulating film to a thickness of 20 nm in the two openings diagonally opposite the common electrode (area a1 in FIG. 24) (see FIG. 14). On the other hand, in sample 3, the inter-electrode insulating film was completely removed in two openings on the diagonal corners of the common electrode (region a1 in FIG. 24), and a high dielectric constant insulating material (κ=40) having a thickness of 100 nm, the same as the inter-electrode insulating film, and a relative dielectric constant 10 times that of the inter-electrode insulating film (κ=4) was filled in the vacant space (see FIG. 16). The rest of the configuration was the same as that of the sample in Example 1.

(measurement)
For each of Samples 2 and 3, the upper electrode, the common electrode, and one terminal of the AC power supply were fixed to 0 V, the other terminal was connected to the lower electrode, and an AC voltage of ±5 V and 1 kHz was applied, and the potential distribution and liquid crystal orientation were determined in the same manner as in Example 1. Furthermore, polarizing plates were placed above and below Samples 2 and 3, and laser light was irradiated to determine the planar distribution of transmittance, in the same manner as in Example 1. The potential distribution and liquid crystal orientation in the cross section of Sample 2 are shown in FIG. 25, and the planar distribution of transmittance is shown in FIG. 26. The potential distribution and liquid crystal orientation in the cross section of Sample 3 are shown in FIG. 27, and the planar distribution of transmittance is shown in FIG. 28.

In FIG. 25, the potential of the interface between the liquid crystal layer and the 100 nm thick electrode interlayer insulating film on the left opening of the common electrode was about +2.5 V at the center of the opening. On the other hand, the potential of the interface between the 20 nm thick electrode interlayer insulating film on the right opening was more than +4 V at the center of the opening, and the drop from the AC power supply voltage was small. As a result, the liquid crystal molecules rose almost vertically on the right opening, whereas they were tilted on the left opening. In addition, the rise angle was small at the periphery on both openings, as in Example 1. In Sample 2 in which such an electric field was generated, as shown in FIG. 26, the region of the 20 nm thick electrode interlayer insulating film displayed black, and the region of the 100 nm thick electrode interlayer insulating film displayed gray intermediate tone. In FIG. 26 and FIG. 28 described later, the edge of the opening of the common electrode appears as a bright (white) line because the orientation of the liquid crystal molecules at the interface with the electrode of the liquid crystal layer was fixed horizontally due to the setting of the simulation conditions. Therefore, in samples 2 and 3, the liquid crystal molecules adjacent to the edge of the opening in the common electrode, which is 20 nm high (thickness), are also fixed horizontally, and this portion displays white. The same is true for sample 1 in Example 1, but in Figure 23, the display scale is wide, with a transmittance of 0 to 70%, making the white display at the edge of the opening difficult to see.

In FIG. 27, the potential of the interface between the liquid crystal layer and the electrode interlayer insulating film on the left opening of the common electrode was about +2.5 V at the center of the opening. On the other hand, the potential of the interface between the high dielectric constant insulating material film on the right opening was more than +4 V at the center of the opening, and the drop from the AC power supply voltage was small. As a result, the liquid crystal molecules rose almost vertically on the right opening, whereas they were tilted on the left opening. In addition, the rise angle was small at the periphery on both openings, as in Example 1. Sample 2 in which such an electric field was generated displayed black in the area where the high dielectric constant insulating material film (κ=40) was provided, and displayed gray intermediate tones in the area of the electrode interlayer insulating film (κ=4), as shown in FIG. 28.

In this way, it was confirmed that the liquid crystal optical modulator according to the second embodiment of the present invention and its modified example is capable of displaying grayscale levels using a common power source.

The above describes various embodiments for implementing the liquid crystal optical modulator, liquid crystal display device, and stereoscopic image display device of the present invention, but the present invention is not limited to these embodiments, and various modifications are possible within the scope of the claims.

100, 100A, 100B, 100C, 100D Liquid crystal display device 10, 10A, 10B, 10D, 10E, 10F Liquid crystal light modulator 200 Stereoscopic image display device 200B Holographic device (stereoscopic image display device)
Reference Signs List 200C Projection display device 20, 20A Liquid crystal layer 2 Liquid crystal molecules 21, 22 Alignment film 31, 31A Lower electrode 32, 32B Common electrode 32a Opening 41 Upper electrode 42 Common electrode 42a Opening 51 Inter-electrode insulating film 52, 52A, 52B, 52C Inter-electrode insulating film 5a, 5b, 5c Buried insulating layer (insulating layer)
61, 62 Transparent substrate 62A Substrate 71, 72 Polarizing plate (polarizer)
73, 74 Retardation plate 75 Color filter array 80, 80A Light source device (light source)
8 Light source device (light source)
85 Lens array 91 AC power supply (power supply)
92, 93 Power supply unit

Claims (7)

A liquid crystal light modulator comprising: a liquid crystal layer; and upper and lower electrodes sandwiching the liquid crystal layer from above and below to apply a voltage in a vertical direction,
a common electrode having a plurality of openings formed therein between the lower electrode and the liquid crystal layer; and an electrode interlayer insulating film having openings formed inside the openings in a plan view, the electrode interlayer insulating film insulating the common electrode and the lower electrode, the openings being filled with an insulating layer;
A liquid crystal light modulator , wherein the insulating layer has a material with a relative dielectric constant and/or a thickness that varies depending on the opening . a common electrode having a plurality of openings formed therein between the upper electrode and the liquid crystal layer; and an electrode interlayer insulating film having openings formed inside the openings in a plan view, the electrode interlayer insulating film insulating the common electrode and the upper electrode, the openings being filled with an insulating layer;
the insulating layer has a material with a dielectric constant and/or a thickness that varies across the opening;
2. The liquid crystal light modulator according to claim 1, wherein the common electrodes above and below the liquid crystal layer have different arrangements of the plurality of openings in a plan view. 3. The liquid crystal light modulator according to claim 1 , wherein the common electrode has a plurality of openings arranged in a pattern of a computer generated hologram. 4. A liquid crystal display device comprising: a liquid crystal light modulator according to claim 1 ; and a polarizer disposed above or below the liquid crystal light modulator, the liquid crystal display device displaying an image by irradiating light onto the side on which the polarizer is disposed. 4. A liquid crystal display device comprising a liquid crystal light modulator according to claim 1 and two polarizers arranged above and below the liquid crystal light modulator, the liquid crystal display device being irradiated with light from either above or below and displaying an image on the other side. 6. A stereoscopic image display device comprising: a liquid crystal display device according to claim 4 ; a light source that irradiates light onto the liquid crystal display device; and a power source that is connected to an upper electrode, a lower electrode, and a common electrode of a liquid crystal optical modulator of the liquid crystal display device. 4. A stereoscopic image display device comprising: a liquid crystal light modulator according to claim 1; a light source that irradiates the liquid crystal light modulator with polarized light; and a power source that is connected to an upper electrode, a lower electrode, and a common electrode of the liquid crystal light modulator.

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