LCD pixel

Abstract

To provide a liquid crystal pixel that can suppress the crosstalk between pixels arranged two-dimensionally at a narrow pixel pitch.SOLUTION: The present invention relates to a rectangular liquid crystal pixel 1 having a liquid crystal layer 50 made of a liquid crystal. The initial orientation when no electric field of the liquid crystal is applied intersects with a longer side of the liquid crystal pixel 1. The liquid crystal may include an SSFLC or a nematic liquid crystal. When the liquid crystal includes the SSFLC, a direction of a central axis in a conical molecular motion orbit of the SSFLC may intersect with the longer side of the liquid crystal pixel 1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a liquid crystal pixel, and a spatial light modulator, a two-dimensional image display device, and a three-dimensional image display device that include the same. [Background technology]

[0002] Liquid crystal display elements have been used in various display devices such as televisions and personal computers, and in recent years, development of high-definition display devices such as 4K and 8K has been progressing. Furthermore, there is a demand for even higher pixel counts and higher density for the high image quality of new video services such as VR and AR, and for applications to three-dimensional video displays such as integral and holography methods.

[0003] In particular, when using liquid crystal display elements in a spatial light modulator (SLM) for holographic display, the pixel pitch of the SLM must be sufficiently small, approximately the wavelength of visible light (360 nm to 830 nm), in order to increase the angle at which a 3D image can be viewed (viewing angle). For example, to achieve a viewing angle of 30° or more, an ultra-high density display device with a pixel pitch of approximately 1 μm is required.

[0004] Here, SLM is a device that arranges optical elements (light modulation elements) in a two-dimensional matrix to spatially modulate the phase and amplitude of light, and is widely used in fields such as display technology and recording technology. For liquid crystal, reflective LCOS (Liquid Crystal on Silicon) that uses a substrate (Si backplane) with a silicon (Si)-based pixel selection transistor drive circuit built into each pixel is suitable for high density, but due to the problem of crosstalk between liquid crystal pixels, the pixel pitch is limited to about 3 μm x 3 μm. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Yoshitomo Isomae, Shintaro Aso, Junichi Shibasaki, Ken-ichi Aoshima, Kenji Machida, Hiroshi Kikuchi, Takahiro Ishinabe, Yosei Shibata and Hideo Fujikake, “Superior spatial resolution of surface-stabilized ferroelectric liquid crystals compared to nematic liquid crystals for wide-field-of-view holographic displays,” Jpn. J. Appl. Phys. 59 040901 (2020). Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, research is being conducted to further narrow the pixel pitch of liquid crystal devices, aiming at future application to narrow pixel pitch spatial light modulators for holographic display. So far, research has been conducted on the light modulation characteristics of liquid crystal pixels with pixel pitches up to 1 μm using one-dimensional electrodes with a striped structure, and it has been reported that inter-pixel crosstalk can be suppressed by using ferroelectric liquid crystals (for example, see Non-Patent Document 1). However, when liquid crystal pixels are arranged two-dimensionally with a pitch of 1 μm to 2 μm, the current situation is that no effective inter-pixel crosstalk suppression technology has yet been proposed.

[0007] The present invention has been made in view of the above, and has an object to provide a liquid crystal pixel capable of suppressing crosstalk between pixels arranged two-dimensionally at a narrow pixel pitch. [Means for solving the problem]

[0008] (1) The present invention provides a rectangular liquid crystal pixel (e.g., liquid crystal pixel 1, 1A, 1B described below) having a liquid crystal layer made of liquid crystal (e.g., liquid crystal layer 50, 50B described below), in which the initial orientation of the liquid crystal when no electric field is applied is perpendicular to the long side of the liquid crystal pixel.

[0009] (2) In the liquid crystal pixel of (1), the liquid crystal may include SSFLC or nematic liquid crystal.

[0010] (3) In the liquid crystal pixel of (2), the liquid crystal may include the SSFLC, and the direction of the central axis of the conical molecular motion orbit of the SSFLC (e.g., the central axis C of the FLC molecular motion orbit described below) may be perpendicular to the long side of the liquid crystal pixel.

[0011] (4) In the liquid crystal pixel of (3), the pixel pitch in the short side direction of the liquid crystal pixel may be less than 2 μm, and the pixel pitch in the long side direction of the liquid crystal pixel may be 2 μm or more.

[0012] (5) The present invention also provides a spatial light modulator comprising a liquid crystal pixel according to any one of (1) to (4).

[0013] (6) The present invention also provides a two-dimensional image display device comprising a liquid crystal pixel according to any one of (1) to (4).

[0014] (7) The present invention also provides a three-dimensional image display device comprising a liquid crystal pixel according to any one of (1) to (4).

[0015] (8) The three-dimensional image display device of (7) may be a holographic three-dimensional image display device.

[0016] (9) The three-dimensional image display device of (7) may display an amplitude modulation hologram.

[0017] (10) The three-dimensional image display device of (7) may display a phase modulation type hologram. Effect of the Invention

[0018] According to the present invention, it is possible to provide a liquid crystal pixel capable of suppressing crosstalk between pixels arranged two-dimensionally at a narrow pixel pitch. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a diagram showing a configuration of a liquid crystal pixel according to the first embodiment. [Diagram 2] 1 is a diagram showing the relationship between the direction of a leakage electric field generated between adjacent pixels and the alignment direction of liquid crystal. [Diagram 3] FIG. 13 shows the voltage response of an SSFLC. [Figure 4] FIG. 1 is a diagram showing the relationship between pixel pitch and modulation depth in SSFLC and nematic liquid crystal. [Diagram 5] FIG. 11 is a perspective view of a liquid crystal pixel according to a second embodiment. [Figure 6] FIG. 11 is a cross-sectional view of a liquid crystal pixel according to a second embodiment. [Figure 7] FIG. 11 is a plan view of a two-layer structure electrode of a liquid crystal pixel according to a second embodiment. [Figure 8] 8 is a diagram showing a simulation result of potential distribution in the A1-A1 cross section of FIG. 7. FIG. [Figure 9] 13 is a diagram showing an optical microscope image of a liquid crystal pixel according to the second embodiment. FIG. [Figure 10] 13 is a diagram showing a polarizing microscope image of a liquid crystal pixel according to the second embodiment. FIG. [Figure 11] FIG. 13 is a diagram showing a configuration of a liquid crystal pixel according to a third embodiment. [Figure 12] 13 is a diagram showing a simulation result of the in-plane transmittance distribution and liquid crystal molecule direction of a liquid crystal pixel 1B according to the third embodiment, which is aligned along the x axis. FIG. [Figure 13] FIG. 13 is a diagram showing the results of a simulation of the transmittance distribution and liquid crystal molecule direction in the plane of a liquid crystal pixel aligned along the y axis. [Figure 14] 13 is a diagram showing a simulation result of the transmittance distribution, the liquid crystal molecular direction, and the electric potential distribution in a cross section of a liquid crystal pixel 1B according to the third embodiment, which is aligned along the x axis. FIG. [Figure 15] FIG. 13 is a diagram showing the results of simulating the transmittance distribution, liquid crystal molecular direction, and electric potential distribution in the cross section of a liquid crystal pixel aligned along the y axis. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description of the second and subsequent embodiments, the description of the configurations common to the first embodiment will be omitted as appropriate.

[0021] [First embodiment] FIG. 1 is a diagram showing the configuration of a liquid crystal pixel 1 according to the first embodiment. In FIG. 1, the lower part is a plan view of a lower electrode substrate and a liquid crystal pixel driving electrode, and the upper part is a cross-sectional view of the liquid crystal pixel 1. As shown in FIG. 1, the liquid crystal pixel 1 according to this embodiment is a rectangular liquid crystal pixel arranged two-dimensionally with a narrow pixel pitch of 1 μm×2 μm, and constitutes a transmissive liquid crystal device. Although only 2×2 pixels are shown in FIG. 1, in reality, the electrode arrangement shown in FIG. 1 is structured to continue infinitely. In an example of the liquid crystal pixel according to this embodiment shown in FIG. 1, the pixel pitch in the y-axis direction is 2 μm, and the pixel pitch in the x-axis direction is 1 μm. That is, since the pixel pitch is narrower in the x-axis direction, the magnitude of the leakage electric field generated between adjacent pixels is larger in the x-axis direction. The liquid crystal pixel 1 according to this embodiment is characterized in that it can suppress crosstalk between pixels with a narrow pixel pitch, even though it is arranged two-dimensionally with such a narrow pixel pitch.

[0022] 1, a liquid crystal pixel 1 according to this embodiment includes a lower electrode substrate 11, a liquid crystal pixel driving electrode 10, alignment films 41 and 42, a liquid crystal layer 50, a common transparent electrode 60, and an upper transparent substrate 70. Each of these components will be described below.

[0023] (Lower electrode substrate 11) The lower electrode substrate 11 is disposed in the bottom layer of the liquid crystal pixel 1 according to this embodiment. A liquid crystal pixel driving electrode 10, which will be described later, is provided on this lower electrode substrate 11. Examples of materials that can be used to form the lower electrode substrate 11 include Si, glass, synthetic quartz, and sapphire. Alternatively, a flexible plastic film substrate can be used as the lower electrode substrate 11.

[0024] (Liquid crystal pixel driving electrode 10) The liquid crystal pixel driving electrodes 10 are provided on the lower electrode substrate 11 described above to constitute an active matrix driving backplane. In the example shown in FIG. 1, the pixel pitch is set to 1 μm×2 μm. That is, the liquid crystal pixel driving electrodes 10 are arranged on the lower electrode substrate 11 at a pitch of 1 μm in the x-axis direction and at a pitch of 2 μm in the y-axis direction. The size of the liquid crystal pixel driving electrodes 10 is set to a width of 0.8 μm in the x-axis direction and a width of 1.8 μm in the y-axis direction. However, this is not limited to this, and a preferred pixel pitch is set according to the type of liquid crystal described later, and a preferred pitch and size of the liquid crystal pixel driving electrodes 10 are also set. This pixel pitch will be described in detail later.

[0025] As the electrode material constituting the liquid crystal pixel driving electrode 10, in addition to a highly conductive metal material such as Al, a transparent electrode material or the like can be used. Examples of electrode materials that are transparent in the visible light wavelength range (360 nm to 830 nm) include 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 ) and other known transparent electrode materials such as indium gallium zinc oxide (IGZO) can be used.

[0026] (Alignment films 41, 42) The alignment films 41 and 42 are respectively disposed on the front and back sides of the liquid crystal layer 50 described later. These alignment films 41 and 42 determine the alignment of the entire liquid crystal layer 50 by applying an alignment control force to the liquid crystal located in the vicinity of the upper transparent substrate 70 described later and the liquid crystal located in the vicinity of the lower electrode substrate 11 described above.

[0027] As the material for forming the alignment films 41 and 42, various conventionally known alignment film materials such as polyimide polymers and polyvinyl polymers can be used. In addition to performing alignment treatment by a rubbing method, a photoalignment method, etc. using these alignment film materials, SiO, SiO 2 Alternatively, an obliquely evaporated film of an inorganic material such as a metal oxide may be used. Alternatively, liquid crystal alignment may be performed by treating the surface of each substrate with a surfactant, or by forming a fine pattern on the substrate surface by ion beam irradiation or the like. The alignment treatment direction in this embodiment is the x-axis direction in FIG. 1, that is, the short side direction of a pixel pitch of 1 μm.

[0028] (Liquid crystal layer 50) The liquid crystal layer 50 according to this embodiment is made of a surface stabilized ferroelectric liquid crystal (hereinafter also referred to as SSFLC). The molecular motion orbit of the ferroelectric liquid crystal (hereinafter also referred to as FLC) is conical, and the FLC molecules are usually aligned in a spiral on the molecular motion orbit. However, in an SSFLC, the thickness of the liquid crystal layer is set thin, so that the FLC molecules are confined in a narrow range and can only take two alignment directions on the conical orbit. The liquid crystal layer 50 according to this embodiment suppresses an increase in inter-pixel crosstalk due to the rotation of the FLC molecules in such an SSFLC, depending on the direction of the initial alignment when no electric field is applied.

[0029] Here, Fig. 2 is a diagram showing the relationship between the direction of the leakage electric field generated between adjacent pixels and the alignment direction of the liquid crystal. More specifically, Fig. 2 is a diagram showing the response of FLC molecules 51 to the leakage electric field generated between adjacent pixels together with different liquid crystal alignment treatment directions.

[0030] As shown in Fig. 2, the electric dipole moment 52 of the FLC molecule 51 is oriented in a direction generally perpendicular to the rod-shaped FLC molecule 51. Therefore, when an orientation process is performed in the x-axis direction as shown in (a) of Fig. 2, and the central axis C of the cone-shaped FLC molecular motion orbit is oriented in the x-axis direction, the x-axis direction in which the leakage electric field is large and the electric dipole moment 52 of the FLC molecule 51 are always perpendicular to each other. Therefore, rotation of the FLC molecule 51 due to the leakage electric field between adjacent pixels is unlikely to occur. Therefore, crosstalk between adjacent pixels during display is unlikely to occur.

[0031] 2(b), in contrast, when alignment is performed in the y-axis direction, from the viewpoint of stabilization, a force is generated that rotates the FLC molecules 51 so that the electric dipole moment 52 of the FLC molecules 51 is oriented in a direction parallel to the leakage electric field generated in the x-axis direction between adjacent pixels, resulting in increased crosstalk between adjacent pixels during display.

[0032] Therefore, the liquid crystal pixel 1 according to this embodiment is a two-dimensional arrangement of rectangular liquid crystal pixels using FLC with a pitch of 1 μm×2 μm, with the orientation process direction being the 1 μm pitch direction, and the central axis C of the cone-shaped FLC molecular motion orbit being set to face the 1 μm pitch direction. That is, the liquid crystal layer 50 according to this embodiment has an initial orientation in the direction perpendicular to the long side of the liquid crystal pixel 1, i.e., the x-axis direction, when no electric field is applied. As a result, according to this embodiment, it is possible to realize a two-dimensional liquid crystal pixel with a narrow pixel pitch in which the effects of inter-pixel crosstalk are suppressed.

[0033] FIG. 3 is a diagram showing the voltage response of an SSFLC. As shown in FIG. 3, an SSFLC operates such that the direction of the electric dipole moment of the molecule is reversed according to the polarity of the voltage applied to each pixel. In response to the reversal of the electric dipole moment direction, the FLC molecule 51 operates in two ways, either on the back side or on the front side of the cone-shaped FLC molecular motion orbit 53, which corresponds to the on / off of the pixel. In the example of this embodiment shown in FIG. 3, when +5V is applied, a force acts to direct the electric dipole moment of the FLC molecule 51 upward, and the FLC molecule 51 is accordingly positioned on the back side of the cone-shaped FLC molecular motion orbit 53, while when −5V is applied, a force acts to direct the electric dipole moment of the FLC molecule 51 downward, and the FLC molecule 51 is accordingly positioned on the front side of the cone-shaped FLC molecular motion orbit 53. However, as described above, the x-axis direction in which the leakage electric field is large and the electric dipole moment 52 of the FLC molecule 51 are always perpendicular to each other, so that rotation of the FLC molecule 51 due to the leakage electric field between adjacent pixels is unlikely to occur, and crosstalk between adjacent pixels during display can be suppressed.

[0034] The thickness of the liquid crystal layer 50 needs to be about 2 μm or less so that the helical structure of the FLC is broken down to the SSFLC state. For example, when manufacturing a device with a narrow pixel pitch such as a 1 μm pitch, the thickness of the liquid crystal layer 50 is preferably 0.5 μm to 1.5 μm from the viewpoint of suppressing crosstalk between pixels. If the thickness of the liquid crystal layer 50 is less than 0.5 μm, a sufficient modulation degree cannot be obtained. If the thickness of the liquid crystal layer 50 exceeds 1.5 μm, the influence of the leakage electric field between adjacent pixels becomes large, and crosstalk between pixels increases.

[0035] (Common transparent electrode 60) Returning to FIG. 1, a transparent electrode material can be used for the common transparent electrode 60. Examples of electrode materials that are transparent in the visible light wavelength range (360 nm to 830 nm) include indium zinc oxide (IZO), indium tin oxide (ITO), and tin oxide (SnO 2), antimony oxide-tin oxide (ATO), zinc oxide (ZnO), fluorine-doped tin oxide (FTO), indium oxide (In 2 O 3 ), and other known transparent electrode materials such as indium gallium zinc oxide (IGZO) can be used. These transparent electrode materials are formed into films by conventionally known methods such as sputtering, vacuum deposition, and coating. The thickness is preferably, for example, 20 nm or more so that sufficient conductivity is obtained.

[0036] (Upper transparent substrate 70) The upper transparent substrate 70 may be made of a transparent substrate material such as glass, synthetic quartz, sapphire, etc. Alternatively, the upper transparent substrate 70 may be made of a flexible plastic film.

[0037] Next, a preferred pixel pitch of the liquid crystal pixel 1 according to this embodiment will be described in detail with reference to FIG. 4. FIG. 4 is a diagram showing the relationship between the pixel pitch and the modulation degree R in SSFLC and nematic liquid crystal. More specifically, FIG. 4 is a diagram showing the relationship between the pixel pitch and the modulation degree R when driving voltages of opposite polarity are applied to adjacent pixels, and the SSFLC and nematic liquid crystals are aligned in a predetermined direction with a liquid crystal layer thickness of 1 μm using one-dimensional pixel electrodes arranged in parallel to each other. In FIG. 4, the horizontal axis represents the pixel pitch, and the vertical axis represents the modulation degree R. The modulation degree R is calculated by R=(Tmax-Tmin) / (Tmax+Tmin), where Tmax is the maximum transmittance of visible light for each liquid crystal pixel, and Tmin is the minimum transmittance.

[0038] In Fig. 4, attention is focused on SSFLC. Here, the SSFLC molecules oriented at 0° with respect to the leakage electric field direction corresponds to the initial orientation when no electric field is applied, in which the central axis of the molecular motion orbit of SSFLC is oriented in the leakage electric field direction (larger leakage electric field direction), i.e., in the x-axis direction perpendicular to the long side of the liquid crystal pixel 1, as in this embodiment shown in Fig. 2(a). Moreover, the SSFLC molecules oriented at 90° with respect to the leakage electric field direction corresponds to the initial orientation when no electric field is applied, in which the central axis of the molecular motion orbit of SSFLC is oriented in the direction perpendicular to the leakage electric field direction (larger leakage electric field direction), i.e., in the y-axis direction, as shown in Fig. 2(b).

[0039] In Fig. 4, when comparing the SSFLC molecules oriented at 0° with respect to the leakage electric field direction with the SSFLC molecules oriented at 90° with respect to the leakage electric field direction, it can be seen that when the pixel pitch is smaller than 2 µm, the modulation degree R of the former does not change significantly, whereas the modulation degree R of the latter significantly decreases. In other words, when the pixel pitch is smaller than 2 µm, the influence of inter-pixel crosstalk becomes large in the latter. From this result, it can be said that the preferred pixel pitch for the liquid crystal pixel 1 of this embodiment, in which the central axis direction of the conical molecular motion orbit of the ferroelectric liquid crystal is perpendicular to the long side of the liquid crystal pixel 1 and the initial orientation of the liquid crystal when no electric field is applied is perpendicular to the long side of the liquid crystal pixel 1, is as follows:

[0040] That is, when SSFLC is used as the liquid crystal constituting the liquid crystal layer 50, the pixel pitch in the short side direction is preferably less than 2 μm, and the pixel pitch in the long side direction is preferably 2 μm or more. If the pixel pitch is within the above ranges, a sufficient modulation R can be obtained even when using SSFLC and rectangular liquid crystal pixels arranged two-dimensionally with a narrow pixel pitch. This is different from the nematic liquid crystal NLC shown in FIG. 4, and is a pixel pitch characteristic of SSFLC.

[0041] Here, when a narrow pixel pitch device such as a 1 μm pitch is fabricated, the above-mentioned preferable pixel pitch is considered to be independent of the thickness of the liquid crystal layer. This is because, as described above, when a narrow pixel pitch device such as a 1 μm pitch is fabricated, the thickness of the liquid crystal layer 50 is preferably 0.5 μm to 1.5 μm from the viewpoint of suppressing crosstalk between pixels, and therefore the preferable pixel pitch does not change significantly from the case of the liquid crystal layer thickness of 1 μm used in the experiment of FIG. 4. And, the interval between adjacent pixel electrodes (the gap between electrodes) is only 200 nm in the case of the 1 μm pitch element of FIG. 4, which is 1 / 5 of the distance of the liquid crystal layer thickness of 1 μm. This means that at the boundary between adjacent pixels, the strength of the leakage electric field between adjacent pixels is much greater than the strength of the original liquid crystal driving electric field generated between the upper and lower electrodes. Therefore, even if the liquid crystal layer thickness is 1.5 μm, if the interval between adjacent pixels is the same, it is considered that the effect of suppressing crosstalk between pixels due to the liquid crystal alignment direction can be obtained at a pixel pitch of about the same level as that of the case of the liquid crystal layer thickness of 1 μm.

[0042] As described above, according to this embodiment, it is possible to provide a liquid crystal pixel 1 capable of suppressing crosstalk between pixels arranged two-dimensionally with a narrow pixel pitch. Therefore, the liquid crystal pixel 1 according to this embodiment is preferably used in a spatial light modulator, a two-dimensional image display device, a holographic three-dimensional image display device, and a three-dimensional image display device capable of displaying an amplitude modulation type hologram or a phase modulation type hologram. More specifically, the liquid crystal pixel 1 according to this embodiment is preferably used in a liquid crystal television, a display device for a personal computer, a portable display device, a head-mounted display device for a virtual reality space (VR) or an augmented reality space (AR), a spatial light modulator for a stereoscopic display such as an integral type or a holography type, and the like.

[0043] [Second embodiment] FIG. 5 is a perspective view of a liquid crystal pixel 1A according to the second embodiment. FIG. 6 is a cross-sectional view of the liquid crystal pixel 1A according to the second embodiment. FIG. 7 is a plan view of a two-layer structure electrode 20 of the liquid crystal pixel 1A according to the second embodiment. However, in FIG. 5, the illustration of an upper transparent substrate, an alignment film, and a lower electrode substrate is omitted. Also, in FIG. 7, only 3×3 pixels are shown, but in reality, the electrode arrangement as shown in FIG. 7 continues infinitely. As shown in these FIGS. 5 to 7, the liquid crystal pixel 1A according to the second embodiment has the same configuration as the liquid crystal pixel 1 according to the first embodiment, except that the liquid crystal pixel 1A according to the second embodiment includes a lower electrode substrate 11A and a two-layer structure electrode 20 instead of the lower electrode substrate 11 and the liquid crystal pixel driving electrode 10, as compared with the liquid crystal pixel 1 according to the first embodiment.

[0044] (Lower electrode substrate 11A) As shown in FIG. 6, the lower electrode substrate 11A is disposed at the bottom. A two-layer structure electrode 20, which will be described later, is formed on this lower electrode substrate 11A. As the lower electrode substrate 11A, in addition to a highly conductive metal material such as Al, a transparent electrode material or the like can be used. Examples of electrode materials that are transparent in the visible light wavelength range (360 nm to 830 nm) include 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 ) and other known transparent electrode materials such as indium gallium zinc oxide (IGZO) can be used.

[0045] (Lower electrode 21) The lower electrode 21 is disposed directly above the lower electrode substrate 11A. A known transparent electrode material can be used for the lower electrode 21. Examples of electrode materials that are transparent in the visible light wavelength range (360 nm to 830 nm) include indium zinc oxide (IZO), indium tin oxide (ITO), and tin oxide (SnO 2 ), antimony oxide-tin oxide (ATO), zinc oxide (ZnO), fluorine-doped tin oxide (FTO), indium oxide (In 2 O 3 ), known transparent electrode materials such as indium gallium zinc oxide (IGZO), graphene, carbon nanotubes, etc. can also be used. These transparent electrode materials are formed into films by known methods such as sputtering, vacuum deposition, and coating. The thickness is preferably 20 nm or more so that sufficient conductivity is obtained. In addition, metal materials with high conductivity can be used as thin films with a thickness of less than 10 nm so that light can pass through.

[0046] (insulating layer 23) The insulating layer 23 is disposed directly on the lower electrode 21. The insulating layer 23 is made of a material such as SiO 2 Known insulating materials such as SiO2, MgO, etc. can be used. The thickness of the insulating layer 23 is set to a thickness that does not cause dielectric breakdown depending on the magnitude of the voltage applied to the device. For example, when the potential difference between the lower electrode 21 and the upper electrode 22 described later is 10 V or more, the thickness of the insulating layer 23 is preferably 50 nm or more.

[0047] In order to suppress a decrease in the voltage applied to the liquid crystal layer 50 due to the presence of the insulating layer 23, it is preferable to use a high dielectric constant insulating film (High-k film). 2 As materials having a dielectric constant larger than 40, hafnium silicate, zirconium silicate, hafnium oxide, zirconia, etc. are preferably used. Furthermore, cubic crystal phase HfO 2etc. are more preferably used.

[0048] (upper layer electrode 22) The upper electrode 22 is disposed directly on the insulating layer 23. As the upper electrode 22, in addition to a highly conductive metal material such as Al, a transparent electrode material or the like can be used. Examples of electrode materials that are transparent in the visible light wavelength range (360 nm to 830 nm) include 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 ) and other known transparent electrode materials such as indium gallium zinc oxide (IGZO) can be used.

[0049] The upper electrode 22 is preferably as thin as possible, but is preferably at least 5 nm to 20 nm thick. In this upper electrode 22, upper electrode openings A of any shape are formed. In one example of the liquid crystal pixel 1A according to this embodiment shown in Figs. 5 to 7, the upper electrode openings A are formed in a checkered pattern with a pitch of 1 µm x 2 µm. This upper electrode opening A is formed by a procedure of forming a desired resist pattern on the upper electrode 22 by means of photolithography, electron beam lithography, or the like, etching by a known technique such as ion beam milling, and then peeling off the resist pattern.

[0050] 6 and 7, the pixel pitch P of the liquid crystal pixel 1A according to this embodiment, specifically, the preferred ranges of the pixel pitch Px in the x-axis direction and the pixel pitch Py in the y-axis direction are the same as those in the first embodiment. In this embodiment, the dimensions and arrangement of the upper electrode openings A are set so as to obtain the preferred pixel pitch P (Px, Py).

[0051] As a modified example, after etching and before peeling off the resist pattern, an insulating layer having the same thickness as the upper electrode 22 may be formed to backfill the upper electrode opening A. In this case, the surface becomes flat, so that SiO, SiO 2 This is preferable because it enables the formation of a uniform alignment film 41 made of an obliquely evaporated film of an inorganic material such as a metal oxide. As another modification, after forming the resist pattern, not only the upper electrode 22 but also the insulating layer 23 may be continuously etched so that the depth of the opening reaches the surface of the lower electrode 21. In other words, an opening penetrating both the upper electrode 22 and the insulating layer 3 may be provided.

[0052] Next, a description will be given of the results of a verification experiment carried out on a prototype liquid crystal pixel 1A according to this embodiment having the following configuration. (composition) Lower electrode substrate 11A: glass substrate Lower electrode 21: IZO (thickness 20 nm) Insulating layer 23: SiO 2 (Thickness 320nm, relative dielectric constant 4.0) Upper electrode 22: IZO (thickness 20 nm) Upper electrode opening A: formed in a checkerboard pattern with a pitch of 1 μm x 2 μm by electron beam lithography Dimensions of upper electrode opening A: 1.8 μm × 0.8 μm Alignment films 41, 42: Polyimide-based material Alignment treatment: x-axis alignment (this embodiment) and y-axis alignment by rubbing method, both of which are anti-parallel alignment (x-axis alignment has a pretilt angle of 1.6° with respect to the x-axis direction, and y-axis alignment has a pretilt angle of 1.6° with respect to the y-axis direction). Liquid crystal layer 50: SSFLC (thickness 1 μm) Common transparent electrode 60: ITO (thickness 20 nm) Upper transparent substrate 70: glass substrate Light source: Halogen lamp Polarization means: Linearly polarized polarizing plates are arranged on the entrance and exit sides, and the angle between the polarizing plates on the entrance and exit sides is 90° in a crossed Nicol arrangement.

[0053] As shown in FIGS. 5 and 6, a voltage of −1 V (V 2 ), and a voltage of +9V (V 1 7. A potential distribution simulation was carried out when a voltage of 0 V was applied to the common transparent electrode 60 to perform light modulation. FIG 8 is a diagram showing the results of the potential distribution simulation in the A1-A1 cross section of FIG.

[0054] 8, the potential at the interface between the liquid crystal layer 50 and the two-layer structure electrode 20 was -1 V on the upper electrode 22 and +2 V at the center of the upper electrode opening A. That is, a positive and negative potential distribution was observed in the liquid crystal layer 50 directly above the upper electrode opening A. Therefore, from the potential distribution simulation result, it was confirmed that the two-layer structure electrode 20 according to this embodiment functions effectively as a lower electrode.

[0055] In addition, the prototype two-dimensional liquid crystal device with a pitch of 1 μm×2 μm was subjected to the application of the same voltage as above to display a checkered pattern, and was observed under an optical microscope and a polarizing microscope. Fig. 9 shows an optical microscope image of the two-layer structure electrode 20 of the prototype liquid crystal pixel 1A according to the second embodiment. As shown in Fig. 9, the upper layer electrode 22 constitutes a black pixel electrode, and the upper layer electrode opening A constitutes a white pixel electrode.

[0056] FIG. 10 is a view showing a polarizing microscope image of a prototype liquid crystal pixel 1A according to the second embodiment. (a) in FIG. 10 is a polarizing microscope image of the liquid crystal pixel 1A according to the second embodiment that is aligned in the x-axis direction, and (b) in FIG. 10 is a polarizing microscope image of the liquid crystal pixel that is aligned in the y-axis direction. As is clear from a comparison of (a) and (b) in FIG. 10, the liquid crystal pixel that is aligned in the y-axis direction has a wider white pixel width in the x-axis direction than the liquid crystal pixel 1A that is aligned in the x-axis direction, despite the use of electrodes of the same design as described above. That is, it can be seen that the liquid crystal pixel 1A according to the present embodiment that is aligned in the x-axis direction is better able to suppress inter-pixel crosstalk.

[0057] Therefore, from the results of the polarizing microscope observation, it was confirmed that, with the liquid crystal pixel 1A of this embodiment, by arranging rectangular pixels with a pitch of 1 μm x 2 μm in two dimensions and aligning the orientation treatment direction in the 1 μm pitch direction, i.e., the x-axis direction perpendicular to the long side of the pixel, it is possible to realize a narrow pixel pitch two-dimensional liquid crystal pixel in which the effects of inter-pixel crosstalk are suppressed.

[0058] [Third embodiment] FIG. 11 is a diagram showing the configuration of a liquid crystal pixel 1B according to the third embodiment. In FIG. 11, the lower part is a plan view of the lower electrode substrate 11 and the liquid crystal pixel driving electrode 10, and the upper part is a cross-sectional view of the liquid crystal pixel 1B. However, in FIG. 11, the upper transparent substrate 70 and the alignment films 41 and 42 are omitted. In FIG. 11, only 2×2 pixels are shown, but the x direction and the y direction are periodic boundary conditions, and the electrode arrangement shown in FIG. 11 continues infinitely. As shown in FIG. 11, the liquid crystal pixel 1B according to the third embodiment is different from the liquid crystal pixel 1 according to the first embodiment in that the liquid crystal constituting the liquid crystal layer 50B is a nematic liquid crystal, not an SSFLC, and the other configurations are the same as those of the liquid crystal pixel 1 according to the first embodiment.

[0059] 11, the pixel pitch is 1 μm×2 μm, and the dimensions of the liquid crystal pixel driving electrodes 10 are 0.8 μm×1.8 μm. Also, an example of light modulation operation is shown by applying +5 V only to the electrodes arranged diagonally among the liquid crystal pixel driving electrodes 10, and applying a voltage of 0 V to the common transparent electrode 60.

[0060] In the liquid crystal pixel 1B according to the third embodiment, a general nematic liquid crystal can be used as the nematic liquid crystal constituting the liquid crystal layer 50B. In this embodiment, as in the first embodiment, the initial orientation of the liquid crystal (nematic liquid crystal) when no electric field is applied is set to a direction perpendicular to the long side of the liquid crystal pixel 1B. As a result, according to this embodiment, it is possible to realize a two-dimensional liquid crystal pixel with a narrow pixel pitch in which the influence of inter-pixel crosstalk is suppressed.

[0061] In this embodiment, similarly to the second embodiment, a liquid crystal pixel 1B according to the third embodiment aligned in the x-axis direction and a liquid crystal pixel aligned in the y-axis direction were fabricated as prototypes, and simulations were performed on the transmittance distribution, the liquid crystal molecular direction, and the electric potential distribution when the liquid crystal pixel 1B was subjected to light modulation operation. Specifically, a voltage of +5V was applied only to the diagonally arranged electrodes among the liquid crystal pixel driving electrodes 10, and a voltage of 0V was applied to the common transparent electrode 60 to perform light modulation operation, and simulations were performed on the transmittance distribution, the liquid crystal molecular direction, and the electric potential distribution.

[0062] The simulation was based on the elastic continuum theory of liquid crystals, and simulated the potential distribution and liquid crystal orientation in the liquid crystal layer. The simulation software used was "LCD Master 3D" made by Shintech Co., Ltd. The liquid crystal material was "E7", and the elastic constant K 11 , K 22 and K 33 , relative permittivity ε p and ε s The liquid crystal alignment treatment was horizontal alignment, and both the x-axis alignment and the y-axis alignment were anti-parallel alignment (the pretilt angle with respect to the x-axis direction was 1.6° for the x-axis alignment, and the pretilt angle with respect to the y-axis direction was 1.6° for the y-axis alignment). Elastic constant K 11 :11.0pN Elastic constant K 22 : 10.2pN Elastic constant K 33 :16.9pN Relative permittivity ε p :19.6 Relative permittivity ε s :5.1

[0063] The design dimensions of the simulation model shown in FIG. The transmittance of the common transparent electrode 60, lower electrode substrate 11, and liquid crystal pixel driving electrode 10 was all assumed to be 100%. Since the purpose of this simulation was to verify the effect of suppressing crosstalk between pixels in the liquid crystal layer, the transmittance of the electrodes and substrate was ignored. Therefore, the material and thickness of the electrodes are meaningless in the simulation, and so these were not set as conditions. However, as an item that affects the potential distribution simulation, the relative dielectric constant of the lower electrode substrate (dielectric) was set to 4.0. This is a value assuming a typical silicon substrate.

[0064] In the actual device, there is an alignment film on the lower electrode substrate 11, the liquid crystal pixel driving electrode 10, and the common transparent electrode 60. However, since the thickness of the alignment film is about 100 nm, which is relatively thin compared to the liquid crystal layer thickness, and it is difficult to strictly incorporate information such as the thickness and surface state of the alignment film of the actual device into the simulation, it is not included in the simulation model of FIG. 11. However, as described above, the liquid crystal alignment direction at the upper and lower interfaces of the liquid crystal layer is specified as a function of the alignment film. In addition, the transmittance is defined as the light intensity (%) after the light passes through the polarizer on the incident side and passes through the liquid crystal layer and the analyzer on the output side, with the intensity of the light being 100% as the reference. This value is the TRANSMITTANCE shown in FIG. 12 to FIG. 15.

[0065] FIG. 12 is a diagram showing a simulation result of the transmittance distribution and liquid crystal molecular direction in the plane of the liquid crystal pixel 1B according to the third embodiment oriented along the x axis. FIG. 13 is a diagram showing a simulation result of the transmittance distribution and liquid crystal molecular direction in the plane of the liquid crystal pixel oriented along the y axis. FIG. 14 is a diagram showing a simulation result of the transmittance distribution, liquid crystal molecular direction, and electric potential distribution in the cross section of the liquid crystal pixel 1B according to the third embodiment oriented along the x axis. FIG. 15 is a diagram showing a simulation result of the transmittance distribution, liquid crystal molecular direction, and electric potential distribution in the cross section of the liquid crystal pixel oriented along the y axis. Note that in the plane in FIG. 12 and FIG. 13 means the xy plane. Also, the cross section in FIG. 14 means the X1-X1 cross section in FIG. 12, and the cross section in FIG. 15 means the Y1-Y1 cross section in FIG. 13.

[0066] 12 and 13, the thin, short lines represent the average orientation direction of the nematic liquid crystal molecules in their vicinity. In FIG. 12, it can be seen that the nematic liquid crystal molecules are oriented in the horizontal x-axis direction. In FIG. 13, it can be seen that the nematic liquid crystal molecules are oriented in the vertical y-axis direction. As shown in these figures, the nematic liquid crystal directly above the diagonal liquid crystal pixel drive electrode 10 to which a voltage of +5V is applied forms a black pixel, and the nematic liquid crystal directly above the diagonal liquid crystal pixel drive electrode 10 to which no voltage is applied forms a white pixel.

[0067] As is clear from Figures 12 and 13, in a white pixel, at the boundary with an adjacent pixel in a direction perpendicular to the alignment treatment direction of the nematic liquid crystal molecules, the nematic liquid crystal molecules rotate in-plane due to the influence of the leakage electric field generated in the in-plane direction between the adjacent pixel electrodes, causing blackening. Specifically, in the case of y-axis alignment as shown in Figure 13, the nematic liquid crystal molecules rotate in-plane by 45° or 135° at the boundary with an adjacent pixel in the x-axis direction, causing blackening. Also, in the case of x-axis alignment as shown in Figure 12, the nematic liquid crystal molecules rotate in-plane at the boundary with an adjacent pixel in the y-axis direction, causing blackening.

[0068] Thus, with x-axis orientation, the in-plane rotation of the nematic liquid crystal molecules occurs along the short side of the pixel electrode. In contrast, with y-axis orientation, the in-plane rotation of the nematic liquid crystal molecules occurs along the long side of the pixel electrode. Therefore, it can be seen that the x-axis orientation, in which the in-plane rotation of the nematic liquid crystal molecules occurs along the short side of the pixel, is superior because it reduces the area that becomes black due to crosstalk between pixels.

[0069] From the above results, it was confirmed that even in the liquid crystal pixel 1B of the third embodiment using nematic liquid crystal, inter-pixel crosstalk can be suppressed by setting the initial orientation of the nematic liquid crystal when no electric field is applied in a direction perpendicular to the long side of the liquid crystal pixel 1B.

[0070] The present invention is not limited to the above-described embodiment, and modifications and improvements within the scope of the present invention that can achieve the object of the present invention are included in the present invention. [Explanation of symbols]

[0071] 1,1A,1B LCD pixel 10 Liquid crystal pixel driving electrode 11, 11A Lower electrode substrate 20 Two-layer structure electrode 21 Lower electrode 22 Upper layer electrode 23 Insulating layer 41,42 Alignment film 50,50B liquid crystal layer 51 FLC molecules 52 Electric Dipole Moment 53 FLC molecular motion trajectory 60 Common transparent electrode 70 Upper transparent substrate A Upper layer electrode opening C Central axis of FLC molecular motion orbit P Pixel pitch Px Pixel pitch in the x-axis direction Py y-axis pixel pitch

Claims

1. A device including a plurality of rectangular liquid crystal pixels including a liquid crystal layer made of liquid crystal, The liquid crystal comprises an SSFLC, The device has an initial alignment of the SSFLC when no electric field is applied, which is perpendicular to the long side of the liquid crystal pixel, so that rotation of the SSFLC due to a leakage electric field generated between adjacent liquid crystal pixels is unlikely to occur.

2. The device according to claim 1 , wherein a central axis direction of the cone-shaped molecular motion orbit of the SSFLC is perpendicular to a long side of the liquid crystal pixel.

3. The pixel pitch of the liquid crystal pixel in the short side direction is less than 2 μm, The device according to claim 2 , wherein the pixel pitch in the long side direction of the liquid crystal pixels is 2 μm or more.

4. A device described in any one of claims 1 to 3, wherein the thickness of the liquid crystal layer is 0.5 μm to 1.5 μm.

5. A device as described in any one of claims 1 to 4, which is a spatial light modulator.

6. A device described in any one of claims 1 to 4, which is a two-dimensional image display device.

7. A device described in any one of claims 1 to 4, which is a three-dimensional image display device.

8. The apparatus according to claim 7 , wherein the three-dimensional image display device is a holographic three-dimensional image display device.

9. The apparatus of claim 7 , wherein the three-dimensional image display device displays an amplitude-modulated hologram.

10. The apparatus of claim 7 , wherein the three-dimensional image display device displays a phase-modulating hologram.

Images