Liquid crystal panel, optical switching element, and method for manufacturing substrate for liquid crystal panel

Abstract

The invention provides a liquid crystal panel and a method for manufacturing a substrate for the liquid crystal panel, which are suitable for sensors of LiDAR, robots and the like and can operate at a lower voltage than in the prior art. An optical switching element (1A) is provided with a liquid crystal panel (2A) and a diffraction member (3) attached downstream in the direction of incidence of light. The liquid crystal panel (2A) has a liquid crystal (5) and an electrode (6A) between a pair of transparent substrates (4). As shown in (A) in FIG. 2, a pair of electrodes 6A are fixed to both of a pair of transparent substrates 4, and a liquid crystal 5 is interposed therebetween. The electrode (6A) has a transparent spacer (61) and a transparent electrode (62) formed on an upright surface (61a) of the transparent spacer (61), has a positive electrode (6P) and a negative electrode (6M), and is formed in a comb tooth shape on the transparent substrate (4). Through the structure, a liquid crystal panel 2A suitable for polymer-stabilized blue phase liquid crystal is formed.

Description

Technical Field

[0001] The present invention relates to a liquid crystal panel, an optical switch element using the liquid crystal panel, and a method for manufacturing a substrate for a liquid crystal panel. Background Art

[0002] In recent years, the development of autonomous driving technology for automobiles has been progressing, and the development of sensor technology for detecting obstacles around the automobile has become important. In addition, the development of sensor technology has also become important in the detection of grasped objects and obstacles in the field of robots.

[0003] As part of such sensor technology, the development of LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging) that uses laser beams for sensing has attracted much attention. In LiDAR, a light beam is emitted to the outside, and when the light beam hits an obstacle and is reflected, the reflected light is received, and the obstacle is detected using the time delay and phase difference between the emitted light and the reflected light.

[0004] The inventors of the present application proposed an optical switch element that can be used for the LiDAR (Patent Document 1). The optical switch element in Patent Document 1 has a polarization grating mounted on the surface of a liquid crystal panel using polymer-stabilized blue phase liquid crystal, and glass wedges as tilting members mounted on both surfaces thereof.

[0005] The liquid crystal panel in Patent Document 1 forms thin film transparent electrodes on the surfaces of two glass substrates, fills polymer stabilized blue phase liquid crystals between the transparent electrodes, and stabilizes them by light irradiation. The optical switch element in Patent Document 1 uses the polymer stabilized blue phase liquid crystals that can be switched at a higher speed than conventional nematic liquid crystals, thereby achieving high-speed switching.

[0006] [Prior art literature]

[0007] [Patent Document]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2020-106616 Summary of the invention

[0009] Technical problem to be solved by the invention

[0010] The inventors of the present application are currently developing LiDAR using the optical switch element described in Patent Document 1, and are continuing research on the practical application of vehicle-mounted LiDAR in particular. The power source of vehicle-mounted LiDAR is the battery of the vehicle, so when the operating voltage exceeds the battery voltage, a booster or the like is required, which increases the number of components and weight, and is therefore not preferred.

[0011] The optical switch element described in Patent Document 1 realizes high-speed switching by using polymer-stabilized blue phase liquid crystal, but requires a relatively high operating voltage. Therefore, in order to put vehicle-mounted LiDAR into practical use, it is desired to reduce the operating voltage and thus reduce power consumption.

[0012] The present invention aims to provide an optical switch element and a liquid crystal panel for the optical switch element, wherein the optical switch element can be applied to sensors such as LiDAR or robots and can operate at a lower voltage than before. In addition, the present invention aims to provide a method for manufacturing a substrate for such a liquid crystal panel.

[0013] Technical solutions for solving technical problems

[0014] In order to achieve the above-mentioned purpose, the liquid crystal panel of the present invention is a liquid crystal panel that maintains electrodes and liquid crystals between a pair of transparent substrates, and is characterized in that the electrodes are arranged in a plurality of transparent spacers having rising surfaces that rise relative to the inner surfaces of the transparent substrates in a manner that the rising surfaces are opposite to each other, and a transparent electrode that becomes a positive electrode and a transparent electrode that becomes a negative electrode are formed on the opposite rising surfaces, respectively, and a liquid crystal layer filled with the liquid crystal is provided between the transparent electrode that becomes the positive electrode and the transparent electrode that becomes the negative electrode, and the refractive index ellipsoid formed by the director in the liquid crystal has a characteristic of having a major axis along the direction of the electric field when a voltage is applied to the electrodes to generate an electric field.

[0015] In the liquid crystal panel of the present invention, the transparent electrode is arranged on the rising surface (side wall) of the transparent spacer, and a liquid crystal layer is provided between the positive and negative transparent electrodes. Therefore, the direction of the electric field when a voltage is applied to the electrodes can be made parallel to the transparent substrate. Therefore, a voltage can be directly applied to the liquid crystal between the positive electrode and the negative electrode, so that the liquid crystal can be operated with less power.

[0016] Furthermore, since the refractive index ellipsoid formed by the director in the liquid crystal has a property that the major axis is along the direction of the electric field, light incident on the transparent substrate can be effectively delayed by applying a voltage to the electrodes.

[0017] In the liquid crystal panel of the present invention, the liquid crystal in the liquid crystal layer may be a polymer-stabilized blue phase liquid crystal. According to this structure, it is possible to switch at a higher speed than conventional nematic liquid crystals.

[0018] In addition, in the liquid crystal panel of the present invention, the plurality of transparent spacers may be formed into linear or rod-shaped structures extending in a predetermined direction in the plane of the transparent substrate, and periodically arranged at equal intervals in the direction of the electric field. When light passes through the liquid crystal panel having such a periodic structure, a plurality of light beams such as 0th order, ±1st order, ±2nd order, etc. are formed.

[0019] In addition, in the liquid crystal panel of the present invention, the width of the transparent spacer in the direction of the electric field and the width of the liquid crystal layer in the direction of the electric field can be formed to be the same or formed in the range of ±50%. Through this structure, the electrode and the liquid crystal layer composed of the transparent spacer and the transparent electrode can be set as a periodic structure in the direction of the electric field.

[0020] In devices such as liquid crystal displays, it is preferred to generate such high-level light beams (±1 level, ±2 level, etc.) in order to see images at a wide angle relative to the display. However, in liquid crystal panels used in devices such as LiDAR, if high-level light beams are generated, the light will diffuse, which is disadvantageous for this application.

[0021] In the liquid crystal panel of the present invention, by adopting the above structure, the generation of high-level light beams is suppressed and the light is not diffused. It should be noted that in the liquid crystal panel of the present invention, the width of the transparent spacer and the transparent electrode in the direction of the electric field and the width of the liquid crystal layer in the direction of the electric field are preferably within 1 / 4 to 2 times the wavelength of the irradiated light.

[0022] In addition, in the liquid crystal panel of the present invention, if the interval between one electrode of the transparent spacer and one electrode of the transparent spacer adjacent to the transparent spacer (the next transparent spacer) is set as a period ( Figure 2 W5+W6 in ), the period can be set to be more than 1 / 2 times and less than 4 times the wavelength of the light used. In this way, by setting the structure of the transparent spacer to a periodic structure (constant length), if the light used is near-infrared light, the liquid crystal panel can be used for a scanner for LiDAR. In addition, if the light used is visible light, the liquid crystal panel can be used for goggles for VR (Virtual Reality), head-up displays for vehicles, or displays for projecting images onto walls or screens.

[0023] In addition, in the liquid crystal panel of the present invention, the refractive index of the transparent spacer is preferably set to a value between the refractive index of ordinary light and the refractive index of extraordinary light when an electric field is applied to the liquid crystal. Thus, the generation of high-level light beams is suppressed, and even when the incident light entering the liquid crystal panel is tilted, the refractive index contrast becomes smaller, thereby significantly reducing the loss of transmitted light.

[0024] In addition, in each of the above-mentioned liquid crystal panels, it is preferred that the transparent electrode is formed of a raw material with zinc oxide as the main raw material. Here, the main raw material refers to a raw material that accounts for 50% or more of the mass % of the whole raw material. In the liquid crystal panel of the present invention, since a transparent electrode is formed on the rising surface, a portion of the light incident from the transparent substrate passes through the inside of the transparent electrode having a length that is substantially the same as the thickness of the transparent spacer. Therefore, in order to suppress the loss of light passing through the inside of the transparent electrode, it is preferred to use a raw material containing zinc oxide having a higher transparency than ITO.

[0025] Regarding the internal structure of each of the above-mentioned liquid crystal panels, a first mode may be that the transparent spacer and the transparent electrode are provided on the inner surfaces of both sides of a pair of the transparent substrates, and a liquid crystal layer is provided between the transparent spacer on one side and the transparent spacer on the other side. The liquid crystal panel of the first mode is provided with a transparent spacer and a transparent electrode for the liquid crystal panel on a pair of transparent substrates, respectively, and when the transparent spacer is formed by etching or the like, processing becomes easy.

[0026] Regarding the internal structure of each of the above-mentioned liquid crystal panels, a second mode may be that the transparent spacer and the transparent electrode are arranged on the inner surface of the transparent substrate on one side, and a liquid crystal layer is arranged between the transparent spacer and the inner surface of the transparent substrate on the other side. The liquid crystal panel of the second mode arranges the transparent spacer and the transparent electrode on the transparent substrate on one side, but not on the transparent substrate on the other side, so that the structure can be simplified.

[0027] In addition, in each of the above-mentioned liquid crystal panels, the thickness of the transparent spacer can also be formed to be more than 70% and less than 95% of the spacing between a pair of the transparent substrates. According to this structure, it is possible to generate an electric field in the refractive index ellipsoid formed by the director at most of the liquid crystal sandwiched by a pair of transparent substrates. If this ratio is less than 70%, the performance of the liquid crystal panel when used as an optical switch element is reduced. On the contrary, if this ratio exceeds 95%, it is possible that the relative transparent spacers are in contact with each other, or the transparent substrate and the transparent spacer are in contact, and damage may be caused by the contact, so it is not preferred.

[0028] The optical switch element of the present invention uses the above-mentioned liquid crystal panels, and a transmissive diffraction component is mounted on one surface of the transparent substrate. In addition, in the optical switch element of the present invention, the diffraction component can be mounted on the transparent substrate with the direction of the rotation axis of the director of the diffraction component facing the extending direction of the transparent electrode (within ±10°). By setting it as this structure, even if the angle of the incident light is tilted in the extending direction of each electrode, the light transmission efficiency can be kept unchanged.

[0029] In addition, when the surface of the optical switch element on which the diffraction member is mounted is set as the front surface and the other surface is set as the back surface, an optical switch element stack can be formed by mounting the back surface of another optical switch element on the front surface of the optical switch element.

[0030] In addition, in the optical switch element stack, the diffraction component located on the downstream side of the diffraction components installed in the stacked plurality of optical switch elements may be set to have a larger deflection angle than the diffraction component located on the upstream side in the incident direction of light. With this structure, the outgoing angle of the outgoing light can be increased and the outgoing light can be irradiated to a wide range.

[0031] The manufacturing method of the substrate for liquid crystal panels of the present invention is characterized in that it includes: a mask layer forming step, forming a mask layer on the surface of a raw material substrate that becomes the raw material of the substrate for liquid crystal panels; a resist pattern layer forming step, forming a resist pattern layer having a specified pattern on the surface of the mask layer; a first etching step, etching the mask layer into the shape of the resist pattern layer; a second etching step, etching the raw material substrate so that the shape of the pattern becomes a specified thickness and forming a transparent spacer having a rising surface rising on the surface of the transparent substrate; a mask layer removing step, removing the mask layer after the second etching step; a transparent electrode forming step, forming an electrode film for forming a transparent electrode on the surface of the transparent substrate and the transparent spacer including the rising surface; and a selective sputtering etching step, etching the electrode film in the planar portion of the transparent electrode and the transparent spacer so that the electrode film in the rising surface remains to form the transparent electrode.

[0032] Through these steps, a transparent spacer and a transparent substrate can be formed from a raw material substrate, an electrode film can be formed on the rising surface of the transparent spacer, and an unnecessary portion of the electrode film can be etched to form a transparent electrode. In addition, the removal of the resist pattern layer can be performed in the second etching step, or after etching the mask layer in the first etching step, or in the mask layer removal step after the second etching step.

[0033] In addition, the manufacturing method of the substrate for liquid crystal panel of the present invention may also be that in the transparent electrode forming step, the electrode film is formed by ALD technology using Al-doped ZnO as a raw material. Here, ALD (Atomic Layer Deposition) technology is a film forming technology using vacuum, which refers to a technology that uses the properties of atoms, i.e., self-control, to deposit atoms layer by layer. By using this ALD technology to form a film using Al-doped ZnO (AZO), a transparent electrode suitable for the liquid crystal panel and optical switch element of the present invention can be formed.

[0034] Effects of the Invention

[0035] According to the present invention, a liquid crystal panel, an optical switch element using the liquid crystal panel, and a method for manufacturing a substrate for a liquid crystal panel can be provided. The liquid crystal panel can be suitable for sensors such as LiDAR or robots, goggles for VR, head-up displays or projection displays, etc., and can operate at a lower voltage than before. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 (A) is an explanatory diagram showing the appearance of the optical switch element of this embodiment, Figure 1 (B) means Figure 1 An explanatory diagram of the relationship between the electrodes of an optical switch element and the director of a diffraction component.

[0037] Figure 2 (A) means Figure 1 is an explanatory diagram of a part of a cross section of an optical switch element, Figure 2 (B) is to Figure 1 An explanatory diagram schematically showing the state of electrodes of an optical switch element.

[0038] Figure 3 (A) is an explanatory diagram showing the state of the electric field in the liquid crystal panel of the first embodiment, Figure 3 (B) is an explanatory diagram showing a schematic state of the refractive index ellipsoid of the liquid crystal layer.

[0039] Figure 4 It is the relationship between the refractive index of the liquid crystal and the transparent spacer and the square of the electric field and the birefringence difference (the major axis of the refractive index ellipsoid (n e ) and the minor axis (n o ) is a graph of the refractive index difference).

[0040] Figure 5 It is an explanatory diagram showing a cross section of a liquid crystal panel according to the second embodiment.

[0041] Figure 6 (A) indicates stacking Figure 1 An explanatory diagram of a laminated body of an optical switch element, Figure 6 (B) in the formula is Figure 6 An explanatory diagram schematically showing a cross section of a laminated body in (A).

[0042] Figure 7 (A) to (G) are explanatory diagrams showing the method for producing the liquid crystal panel substrate of the present invention. DETAILED DESCRIPTION

[0043] Next, refer to Figures 1 to 6A liquid crystal panel and an optical switch element as an example of an embodiment of the present invention will be described. Figure 1 and Figure 2 As shown in (A) of FIG. 1 , the optical switch element 1A of the first embodiment includes the liquid crystal panel 2A of the first embodiment and a diffraction member 3 mounted on the downstream side of the liquid crystal panel 2A in the incident direction of light.

[0044] like Figure 2 As shown in (A) in the figure, the optical switch element 1A of the first embodiment is provided with an electrode 6A of the first embodiment in a liquid crystal panel 2A in which a liquid crystal 5 is held between a pair of transparent substrates 4. The optical switch element 1A is provided with a diffraction component 3 on one surface of the liquid crystal panel 2A, and a power supply electrode 7 for supplying power is provided on the electrode 6A.

[0045] In this embodiment, quartz glass is used for the transparent substrate 4, and polymer-stabilized blue phase liquid crystal is used for the liquid crystal 5. The polymer-stabilized blue phase liquid crystal has the following properties: when a voltage is applied, the major axis of the refractive index ellipsoid 5a formed by the director is along the direction of the electric field. Here, as far as the major axis direction of the refractive index ellipsoid 5a is concerned, it only needs to be roughly consistent with the direction of the electric field, as long as it can cause the light passing through the liquid crystal panel 2A to be delayed.

[0046] The electrode 6A is provided on both inner surfaces of a pair of transparent substrates 4, and includes a transparent spacer 61 and a transparent electrode 62. The transparent spacer 61 is formed in a linear or rod-like shape extending in a predetermined direction in the plane direction of the transparent substrate 4, and has a rising surface 61a rising relative to the transparent substrate 4, and a transparent electrode 62 is formed on the rising surface 61a.

[0047] In addition, regarding the electrode 6A, a plurality of transparent electrodes 62 and the rising surface 61a are arranged in a manner facing each other, and adjacent transparent electrodes 62 each have a transparent electrode that becomes a positive electrode 6P and a transparent electrode that becomes a negative electrode 6M. The liquid crystal panel 2A of this embodiment is provided with a liquid crystal layer filled with liquid crystal 5 between the transparent electrode that becomes the positive electrode 6P and the transparent electrode that becomes the negative electrode 6M.

[0048] In this embodiment, the transparent spacer 61 used for the electrode 6A is made of quartz glass doped with germanium dioxide (GeO2). In this embodiment, the transparent electrode 62 is made of a material with zinc oxide (ZnO) as the main raw material and Al and Ga added. In this embodiment, the content of zinc oxide is 98% by mass, Al is 2% by mass, and no other additives are added. In addition, ZnO to which Ga is added can be used instead of Al, and pure ZnO treated with hydrogen plasma can also be used.

[0049] In addition, the diffraction component 3 uses a polarization grating as a transmission type diffraction component. In this embodiment, as the diffraction component 3, for example, "Polarization Grating" of Edmund Optics Japan Co., Ltd. can be used. This "Polarization Grating" has the same phase difference as a 1 / 2 wavelength plate, and its optical axis rotates at a constant period. In addition, as Figure 2 As shown in (A) in FIG. 1 , an optical adhesive layer 4 a having the same refractive index as that of the transparent substrate 4 is provided on the outer surface of the transparent substrate 4 .

[0050] like Figure 2 As shown in (A) in FIG. 1 , the electrode 6A is composed of a positive electrode 6P and a negative electrode 6M. Figure 2 As shown in (B) in FIG. 4 , the positive electrode 6P and the negative electrode 6M are formed in a comb-tooth shape when viewed from the out-of-plane direction of the transparent substrate 4 (the direction of viewing the surface of the transparent substrate 4 from the front). Figure 2 As shown in (B) in FIG. 8 , the positive electrodes 6P and the negative electrodes 6M are alternately arranged in the in-plane direction of the transparent substrate 4 (the up-down direction in the figure).

[0051] In this application, in order to easily understand the electrode 6 (refer to Figure 1 In the structure (B) of FIG. 1 , the thickness dimension of each component is compressed and illustrated. For example, Figure 2 In (A), if the vertical scale is set to 1, the horizontal scale is about 1 / 6. The same applies to Figure 3 and Figure 5 In addition, the positive electrode 6P and the negative electrode 6M of the electrode 6A are so sized that their shapes cannot be recognized by naked eyes, but Figure 2 In (B) of FIG. 1 , the positive electrode 6P and the negative electrode 6M are partially enlarged and illustrated so that their shapes can be recognized.

[0052] like Figure 2 As shown in (A), in the liquid crystal panel 2A of the first embodiment, the width W6 of the positive electrode 6P and the negative electrode 6M and the interval W5 between these electrodes are formed to be the same length, which is set to 2 μm in this embodiment. Therefore, the plurality of transparent spacers 61 in this embodiment are periodically arranged at equal intervals in the in-plane direction of the transparent substrate 4 along the direction of the electric field.

[0053] Here, if the distance between a transparent electrode 62 formed on the positive electrode 6P of the transparent spacer 61 and a transparent electrode 62 formed on the negative electrode 6M of the adjacent transparent spacer 61 is Figure 2 The period is the sum of the interval W5 of the liquid crystal in (A) and the width W6 of the transparent spacer 61 and the transparent electrode 62, and the period can be set to be not less than 1 / 2 times and not more than 4 times the wavelength of the light used.

[0054] In such a periodic structure, in addition to the 0th order (the light of the order in which the incident light maintains the original direction and travels), high-order light (±1st order, ±2nd order, ...) is also generated. In this technology, the 0th order light is used, and the high-order light is unnecessary light and needs to be reduced as much as possible.

[0055] In general, when light is incident on a periodic structure, the outgoing light is given by the following equation.

[0056] sinθ=sinθo+m·λ / Λ (1)

[0057] Here, θo is the incident angle defined by the angle with the perpendicular line of the transparent substrate 4;

[0058] θ is the emission angle defined by the angle with the perpendicular line of the transparent substrate 4;

[0059] m is the series (0, ±1, ±2···);

[0060] λ is the wavelength in vacuum;

[0061] Λ is the period of the transparent spacer (W5+W6).

[0062] When the period (W5+W6) is less than 1 / 2 of the wavelength of the light used (e.g., 1.55 μm), no matter what the incident angle θo is, the solution according to formula (1) does not exist (sinθ is greater than 1), and high-level series (±1 times, ±2 times, ...) are no longer generated. Although the desired performance can be obtained, the undesirable situation that the resist exposure and etching processing are extremely difficult occurs. In addition, when the interval (W5+W6) exceeds 4 times the wavelength of the light used, unnecessary series (±1 times, ±2 times, ...) are generated, and there is an undesirable situation that losses occur.

[0063] By setting such a structure, when visible light (wavelength of about 0.3 to 0.7 μm) is used as the light used, the liquid crystal panel 2A can be used for goggles for VR (Virtual Reality), head-up displays for vehicles, or liquid crystal panels for displays that project images onto walls or screens. In addition, when near-infrared light (wavelength of about 0.7 to 2.5 μm) is used as the light used, the liquid crystal panel 2A can be used for scanners for LiDAR or other object detection sensors.

[0064] In addition, the height (thickness) H6 of the rising surface 61a of the positive electrode 6P and the negative electrode 6M is set to 4 μm to 16 μm, and is set to 8 μm in this embodiment. The height H6 of the rising surface 61a is preferably set to 70% or more of the interval H5 between the pair of transparent substrates 4, and is set to 80% in this embodiment. In addition, the angle of the rising surface 61a relative to the transparent substrate 4 is set to 90° in this embodiment, but it can be set within the range of 70° to 90°.

[0065] like Figure 2 As shown in (B) in FIG. 1 , the positive electrode 6P and the negative electrode 6M are connected to the root of the comb teeth with a power supply electrode 7. The voltages of the positive electrode 6P and the negative electrode 6M become positive and negative relative to each other through the power supply electrode 7, and an electric field is generated between the positive electrode 6P and the negative electrode 6M. The positive electrode 6P and the negative electrode 6M can be switched by reversing at a certain time using an external driver (not shown).

[0066] here, Figure 1 (B) in FIG. 1 shows the relationship between the liquid crystal panel 2A and the director D of the diffraction member 3 in the optical switch element 1A of this embodiment. Figure 1 As shown in (B) in the figure, the diffraction component 3 has the following functions: the directing vector D with birefringence rotates in one direction with a specified period around the rotation axis A, and when a circularly polarized light beam is incident, the light beam output in the rotation direction of the circularly polarized light is deflected to the right or left.

[0067] like Figure 1 As shown in (B) in FIG. 1 , in the optical switch element 1A of the present embodiment, the positive electrode 6P and the negative electrode 6M are formed in a comb-tooth shape, and the liquid crystal panel 2A and the diffraction member 3 are combined in such a manner that the extending direction of each electrode is consistent with the rotation axis A of the director D (within ±10°). With this structure, even when the angle of incident light is inclined in the X direction (the extending direction of each electrode) in the figure, the light transmission efficiency can be kept unchanged.

[0068] On the other hand, when the angle of the incident light is inclined in the Y direction (direction of the electric field) in the figure, the transmission efficiency changes according to the period formed by the width W6 of the positive electrode 6P, the negative electrode 6M and the size of the interval W5 between these electrodes, and the refractive index difference between the liquid crystal 5 and the transparent spacer 61 described later. In particular, when the applied voltage becomes higher, the refractive index difference between the liquid crystal 5 and the transparent spacer 61 becomes larger, a high-order light beam is generated, and the transmittance reduction of the 0-order light beam becomes larger.

[0069] Regarding the light transmission efficiency when the angle of light is inclined in the Y direction, the smaller the period determined by the size of W6 and W5, the less degradation, but resist exposure and etching processing become difficult. According to the verification of the inventors of the present application, the width W6 of the positive electrode 6P and the negative electrode 6M and the size of the interval W5 between these electrodes are preferably within 1 / 4 to 2 times the wavelength of the incident light. In addition, it is preferred that the liquid crystal refractive index (n) when no electric field is applied is i ) and the refractive index difference between the transparent spacer 61 and the transparent spacer 61 is within 0.05. Furthermore, it is preferred that the ordinary light (n o ) and extraordinary light (n e ) between the transparent spacer 61 and the refractive index difference therebetween.

[0070] Thus, the smaller the width W6 of the positive electrode 6P and the negative electrode 6M and the interval W5 of these electrodes, the better. However, due to the limitation of manufacturing technology, the current situation is that the width W6 and W5 are in the range of 0.2μm to 6μm as realistic values. In addition, the higher the height H6 of the rising surface 61a, the lower the voltage can be. Therefore, the higher the better. However, due to the reasons of manufacturing technology, the height H6 is in the range of 2μm to 25μm. In addition, the height H6 of the rising surface 61a is preferably set to be more than 70% of the interval H5 between the pair of transparent substrates 4, and is set to 84% in the present embodiment.

[0071] Next, refer to Figure 3 , the state of the electric field in the liquid crystal panel 2A of the first embodiment is described. Figure 3 It is an explanatory diagram showing contour lines and directions of electric fields in a state where voltage is applied to electrodes of the liquid crystal panel 2A.

[0072] like Figure 3 As shown in the figure, if a voltage is applied to the positive electrode 6P and the negative electrode 6M of the electrode 6A, an electric field is generated between the positive electrode 6P and the negative electrode 6M, as shown by the arrow in the figure, from the positive electrode 6P to the negative electrode 6M. The direction of the electric field is parallel to the transparent substrate 4 between the positive electrode 6P and the negative electrode 6M, and is consistent with the in-plane direction of the transparent substrate 4. In addition, the liquid crystal 5 is sandwiched between the electrode 6A located on the left side of the figure and the electrode 6A located on the right side, but the liquid crystal 5 between the electrodes 6A also generates an electric field parallel to the transparent substrate 4.

[0073] In this way, the electric field acts on the liquid crystal 5 in a direction parallel to the transparent substrate 4. In this embodiment, the liquid crystal 5 uses a polymer-stabilized blue phase liquid crystal, such as Figure 3 As shown in (B) in FIG. 1 , the refractive index ellipsoid 5a in the liquid crystal 5 can be arranged parallel to the transparent substrate 4 by applying an electric field. If light is irradiated to the liquid crystal panel 2A in this state, the light passing through the liquid crystal panel 2A can be effectively delayed by the action of the liquid crystal 5.

[0074] On the other hand, when no electric field is applied between the positive electrode 6P and the negative electrode 6M, the refractive index ellipsoid 5a in the liquid crystal becomes a spherical refractive index ellipsoid (not shown) when viewed from the side, and becomes an optically isotropic medium. Even if light is irradiated onto the liquid crystal panel 2A, there will be no delay in the light passing through the liquid crystal panel 2A.

[0075] In this way, by turning on and off the electric field between the positive electrode 6P and the negative electrode 6M, the polymer-stabilized blue phase liquid crystal with high speed can be switched. Therefore, by using the liquid crystal panel 2A of the electrode 6A of this embodiment, an optical switch element 1A capable of high-speed switching can be formed. It should be noted that, for convenience, the electrode 6A is set as the positive electrode 6P and the negative electrode 6M, but in fact, the positive and negative are controlled by an alternating voltage that is reversed in time, so the positive electrode 6P and the negative electrode 6M are alternately replaced.

[0076] In addition, in the liquid crystal panel 2A of the first embodiment, the transparent spacer 61 uses quartz glass doped with germanium dioxide, and its refractive index is adjusted to a specified range of the refractive index of the liquid crystal layer. Thus, even when the incident light is tilted, the refractive index contrast becomes smaller, so it will not couple with the high-order light of ±1st and ±2nd order, and the loss of the transmitted 0th order light can be reduced.

[0077] Specifically, the refractive index of the transparent spacer 61 is adjusted to the refractive index of the liquid crystal, that is, to be n= o (E) to n e Here, n o (E) is the refractive index of ordinary light when an electric field is applied, and ne(E) is the refractive index of extraordinary light when an electric field is applied, which are expressed by the following formula.

[0078] n o (E) = n i -Δn ind (E) / 3(2A)

[0079] n e (E) = n i +2Δn ind (E) / 3(2B)

[0080] Among them, n i is the refractive index when no electric field is applied, Δn ind (E) is the difference between the two refractive indices taking into account the influence of the extended Kerr effect, and is expressed by the following formula.

[0081] Δn ind (E) = Δn S (1-exp[-(E / Es ) 2 ]) (3)

[0082] Here, Δn S represents the saturation refractive index change, E s represents the saturation electric field.

[0083] Figure 4 (A) represents the refractive index of the liquid crystal 5 when no electric field is applied and the refractive index when an electric field is applied. o (E) and n e (E) Graph of the changes in . Figure 4 In the graph (B), the vertical axis is n o (E) and n e The horizontal axis represents the refractive index difference Δn of (E), and the horizontal axis represents the value of the square of the applied voltage. Generally, when an electric field (E) is applied to a blue phase liquid crystal, the Kerr effect, in which the refractive index difference Δn changes in proportion to the square of E, is dominant in a region of small voltage.

[0084] However, in the large voltage region, due to the ordinary light (n o ) and extraordinary light (n e ) is saturated, such as Figure 4 As shown in (B) in FIG. 1 , the refractive index difference Δn also tends to be saturated. Therefore, in this embodiment, in order to accurately derive n under a large voltage, o (E) and n e The refractive index of the transparent spacer 61 is given by using the formula (3). Figure 4 n of (A) o With n e The substance doped in the quartz glass and the doping amount are adjusted by adjusting the value between . Here, germanium dioxide is doped in the quartz glass.

[0085] It should be noted that the electrode 6A in the first embodiment can be formed, for example, by forming a layer doped with germanium dioxide on one surface of quartz glass, etching the shape of the electrode, attaching zinc oxide to the surface, and removing unnecessary zinc oxide by etching. Alternatively, the electrode 6A may be made of quartz glass doped with germanium dioxide from the beginning.

[0086] Next, refer to Figure 5 , the optical switch element 1B, the liquid crystal panel 2B and the electrode 6B according to the second embodiment of the present invention are described. In the liquid crystal panel 2B according to the second embodiment, the electrode 6B is fixed only to one side of the transparent substrate 4, which is different from the electrode 6A according to the first embodiment. In addition, the same reference numerals are attached to the same structures as those in the first embodiment, and detailed descriptions are omitted.

[0087] like Figure 5 As shown, the electrode 6B of the second embodiment is provided with a transparent spacer 61 and a transparent electrode 62 on the inner surface of the transparent substrate 4 on the right side of the figure, and the electrode 6B is not provided on the inner surface of the transparent substrate 4 on the left side of the figure. The liquid crystal 5 is filled between the inner surface of the transparent substrate 4 on the left side of the figure and the transparent spacer 61.

[0088] The electrode 6B of the second embodiment is similar to the electrode 6A of the first embodiment, and includes a positive electrode 6P and a negative electrode 6M, with a liquid crystal layer formed therebetween. Figure 2 The same as (B) in FIG. 1 . In addition, the height (thickness) H6 of the rising surface 61a of the positive electrode 6P and the negative electrode 6M is set to 4 μm to 16 μm, and is set to 16 μm in this embodiment. The height H6 of the rising surface 61a is preferably set to be greater than 70% of the interval H5 between the pair of transparent substrates 4, and is set to 80% in this embodiment.

[0089] In the electrode 6B of the second embodiment, similarly to the first embodiment, the direction of the electric field between the positive electrode 6P and the negative electrode 6M is parallel to the transparent substrate 4 , and an electric field that is consistent with the in-plane direction of the transparent substrate 4 can be generated.

[0090] Next, refer to Figure 6 The optical switch element stack 10 is described. The optical switch element stack 10 is a stack of a plurality of Figure 1 In the present embodiment, eight optical switch elements 1A are stacked, but the number of stacked elements is appropriately selected based on the angle resolution (minimum deflection angle of the switch) and the maximum deflection angle.

[0091] Figure 6 (B) is a schematic representation of Figure 6 FIG. 2 is a cross-sectional view of a liquid crystal panel 2A of an optical switch element stack 10 in FIG. Figure 6 As shown in (B) in FIG. 1 , the optical switch element 1A has a transmissive diffraction member 3 mounted on one surface of a liquid crystal panel 2A.

[0092] The optical switch element stack 10 of this embodiment is formed by arranging the surface on the downstream side of the incident direction of light and mounting the back side of another optical switch element 1A on the surface when the surface on which the diffraction component 3 is mounted is set as the front surface and the other surface is set as the back side.

[0093] In this embodiment, the polarization angle of the diffraction component 3 disposed on the downstream side is set larger than the polarization angle of the diffraction component 3 disposed on the upstream side of the incident direction of the light. For example, the polarization angle of the diffraction component 3 disposed on the upstream side of the incident direction of the light is set to 0.1°, and the polarization angle of the second diffraction component 3 is set to 0.2°, so that the polarization angle increases by 2 times each time toward the downstream side.

[0094] For the diffraction component 3, by changing the polarization angle from the upstream side of the incident direction of the light toward the downstream side, the outgoing angle of the outgoing light can be increased and the outgoing light can be irradiated to a wide range. In addition, this structure is a one-dimensional optical switch element, but by using two groups and rotating them by 90 degrees, a two-dimensional optical switch element can be realized.

[0095] The optical switch element 1A and the optical switch element 1B of this embodiment can both operate at a voltage of about 10 V or less. This allows hybrid vehicles, electric vehicles, and ordinary vehicles with internal combustion engines to operate without using a booster, and thus is an optical switch element suitable for vehicle-mounted LiDAR.

[0096] In the above embodiment, polymer-stabilized blue phase liquid crystal is used as liquid crystal 5, but it is not limited to this. Liquid crystal formed by other materials can also be used as long as the liquid crystal has the characteristic that the major axis of the refractive index ellipsoid 5a is along the direction of the electric field when voltage is applied.

[0097] In addition, in the above embodiment, the transparent spacer 61 uses quartz glass doped with germanium dioxide (GeO2), but it is not limited to this, and a dopant that increases the refractive index of quartz glass, such as phosphorus pentoxide (P2O5) or titanium dioxide (TiO2), may also be used. In addition, in the above embodiment, the transparent electrode 62 uses zinc oxide (ZnO) doped with Al, but it may also be a material containing other additives such as Ga in zinc oxide. Alternatively, in the wavelength region of visible light, ITO (Indium Tin Oxide) may also be used instead of ZnO.

[0098] Next, refer to Figure 7 The method for manufacturing a liquid crystal panel substrate of the present invention is described below. The method for manufacturing a liquid crystal panel substrate of the present embodiment is to manufacture a substrate 40 (see Figure 7 The substrate 40 can be used for a liquid crystal panel having the same structure as the liquid crystal panel 2A or the liquid crystal panel 2B. The substrate 40 in this embodiment is obtained by integrating the transparent substrate and the transparent spacer in the above embodiment.

[0099] The manufacturing method of this embodiment includes: a mask layer forming step, forming a mask layer 42 on the surface of a raw material substrate 41 that becomes a raw material of a transparent substrate and a transparent spacer; a resist pattern layer forming step, forming a resist pattern layer 43 that becomes a pattern of a specified transparent spacer on the surface of the mask layer; a first etching step, etching the mask layer 42 into the shape of the resist pattern layer 43; a second etching step, etching the raw material substrate 41 so that the shape of the pattern becomes a specified thickness and forming a transparent spacer 61 having a rising surface 61a rising on the surface of the transparent substrate 4; a mask layer removing step, removing the mask layer 42 after the second etching step; a transparent electrode forming step, forming an electrode film 44 for forming a transparent electrode on the surface of the transparent substrate 4 and the transparent spacer 61 including the rising surface 61a; and a selective sputtering etching step, leaving the electrode film 44 in the rising surface 61a to form a transparent electrode 62.

[0100] First, in the mask layer forming step, as Figure 7 As shown in (A), a mask layer 42 is formed on the surface of a raw material substrate 41. In the present embodiment, quartz glass is used as the raw material of the raw material substrate 41. In addition, chromium (Cr) is used as the raw material of the mask layer 42. The mask layer 42 is formed on the surface of the raw material substrate 41 using a commonly used sputtering method. Alternatively, the mask layer 42 can also be formed by known electron beam evaporation. As the raw material of the mask layer 42, in addition to chromium (Cr), other metals such as tungsten silicide (WSix) can also be used.

[0101] Next, in the resist pattern layer forming step, as Figure 7 As shown in (B), a resist pattern layer 43 having a pattern of the transparent spacer 61 is formed on the surface of the mask layer 42. The resist pattern layer 43 can be formed by a method such as a photoresist using a known photosensitive film. In this embodiment, a phenolic resin is used as the material of the resist pattern layer 43, but a commercially available photoresist can also be used.

[0102] Next, proceed Figure 7 The first etching step shown in (C) is performed. In the first etching step, the mask layer 42 is formed into the shape of the resist pattern layer 43 using the method of RIE (Reactive Ion Etching). The etching process is, for example, a process in which the chlorine-based gas is made into a plasma state by discharge under reduced pressure, and the mask layer 42 to be etched is etched into a desired shape by the reaction between the generated active species such as ions and neutral radicals and the mask layer 42 to be etched. The etching process may also be a process using an etching solution capable of removing the chromium coating.

[0103] Next, proceed Figure 7The second etching step shown in (D) is performed. In the second etching step, etching is performed to remove the resist pattern layer 43, and the raw material substrate 41 is etched to a thickness required for the transparent spacer 61. In this embodiment, in the second etching step, a method known as reactive ion etching (RIE) is used. In the second etching step, by using RIE using a fluorine-based gas, the raw material substrate 41 can be efficiently processed.

[0104] Then, if Figure 7 As shown in FIG. 8 (E), the mask layer 42 is removed by the mask layer removal step, thereby forming the transparent substrate 4 and the transparent spacer 61 from the raw material substrate 41. The mask layer 42 is removed by an etching process capable of removing the chromium coating.

[0105] Next, proceed Figure 7 The transparent electrode forming step shown in (F) of FIG. In the present embodiment, in the transparent electrode forming step, after the mask layer 42 is removed in the mask layer removing step, an AZO (Al-doped ZnO) film, i.e., an electrode film 44, is formed using the ALD technique on the surface of the transparent substrate 4 and the transparent spacer 61. The electrode film 44 is formed to a thickness of 30 nm to 40 nm so that it can be used as the transparent electrode 62 in the present embodiment.

[0106] Next, proceed Figure 7 In the selective sputtering etching step shown in (G), in the present embodiment, the electrode film 44 in the planar portion of the transparent substrate 4 and the transparent spacer 61 is etched, and the electrode film 44 in the rising surface 61a is left to form the transparent electrode 62. In the selective sputtering etching step of the present embodiment, in dry etching, active species are irradiated from the normal direction of the surface of the transparent substrate 4 and the transparent spacer 61, and etching is performed in a manner that the active species does not contact the rising surface 61a of the transparent spacer 61.

[0107] By this treatment, only the electrode film 44 on the surface of the transparent substrate 4 and the transparent spacer 61 is removed, and the electrode film 44 on the rising surface of the transparent spacer 61 remains, and the electrode film 44 becomes the transparent electrode 62. In this way, in the manufacturing method of this embodiment, the transparent electrode 62 can be efficiently formed on the transparent spacer 61 by the selective sputtering etching step.

[0108] Furthermore, in the above-described embodiment, the resist pattern layer 43 is removed in the second etching step, but the present invention is not limited thereto and may be removed in the first etching step or the mask layer removal step.

[0109] [Explanation of Reference Numerals]

[0110] 1A, 1B...Optical switch element

[0111] 2A, 2B…LCD panel

[0112] 3…Diffractive components

[0113] 4…Transparent substrate

[0114] 4a…Optical bonding layer

[0115] 40...Substrate

[0116] 41…raw material substrate

[0117] 42…Mask layer

[0118] 43…Resist pattern layer

[0119] 44…Electrode membrane

[0120] 5…Liquid crystal (liquid crystal layer)

[0121] 5a…Refractive index ellipsoid

[0122] 6A, 6B...Electrode

[0123] 6P…Positive

[0124] 6M…Negative electrode

[0125] 61…Transparent spacer

[0126] 61a…Standing surface

[0127] 62…Transparent electrode

[0128] 7…Power supply electrode

[0129] 10…Optical switch element laminate

Claims

1. A liquid crystal panel having electrodes and liquid crystals held between a pair of transparent substrates, characterized in that: The electrode is configured by arranging a plurality of transparent spacers having rising surfaces rising relative to the inner surface of the transparent substrate so that the rising surfaces face each other, and forming a transparent electrode serving as a positive electrode and a transparent electrode serving as a negative electrode on the opposing rising surfaces, respectively. A liquid crystal layer filled with the liquid crystal is provided between the transparent electrode serving as the positive electrode and the transparent electrode serving as the negative electrode, The refractive index ellipsoid formed by the director in the liquid crystal has a property of having a major axis along the direction of the electric field when a voltage is applied to the electrodes to generate an electric field.

2. The liquid crystal panel according to claim 1, characterized in that: The liquid crystal in the liquid crystal layer is a polymer-stabilized blue phase liquid crystal.

3. The liquid crystal panel according to claim 1, characterized in that: The plurality of transparent spacers are formed in a linear or rod-like shape extending in a predetermined direction in the plane of the transparent substrate, and are periodically arranged at equal intervals in the direction of the electric field.

4. The liquid crystal panel according to claim 3, characterized in that: The width of the transparent spacer in the direction of the electric field is formed to be the same as or within a range of ±50% of the width of the liquid crystal layer in the direction of the electric field.

5. The liquid crystal panel according to claim 3, characterized in that: If the interval between one electrode of the transparent spacer and one electrode of the transparent spacer adjacent to the transparent spacer is taken as a period, the period is set to be not less than 1 / 2 times and not more than 4 times the wavelength of the light used.

6. The liquid crystal panel according to claim 1, characterized in that: The refractive index of the transparent spacer is set to a value between the refractive index of ordinary light and the refractive index of extraordinary light when an electric field is applied to the liquid crystal.

7. The liquid crystal panel according to claim 1, characterized in that: The transparent electrode is formed of a material mainly containing zinc oxide.

8. The liquid crystal panel according to claim 1, characterized in that: The transparent spacer and the transparent electrode are provided on inner surfaces of both of the pair of transparent substrates, and the liquid crystal layer is provided between one of the transparent spacers and the other of the transparent spacers.

9. The liquid crystal panel according to claim 1, characterized in that: The transparent spacer and the transparent electrode are provided on the inner surface of one of the transparent substrates, and the liquid crystal layer is provided between the transparent spacer and the inner surface of the other transparent substrate.

10. The liquid crystal panel according to claim 1, characterized in that: The transparent spacer is formed to have a thickness not less than 70% and not more than 95% of a distance between the pair of transparent substrates.

11. An optical switch element using the liquid crystal panel according to claim 1, characterized in that: A transmission-type diffraction component is mounted on one surface of the transparent substrate.

12. The optical switch element according to claim 11, characterized in that The diffraction member is mounted on the transparent substrate such that the direction of the rotation axis of the director of the diffraction member faces the extending direction of the transparent electrode.

13. An optical switch element stacked body, comprising the optical switch elements according to claim 11 stacked together, characterized in that: When the surface of the optical switch element on which the diffraction member is mounted is defined as the front surface and the other surface is defined as the back surface, the back surface of another optical switch element is mounted on the front surface of the optical switch element.

14. The optical switch element stack according to claim 13, wherein: The diffraction member mounted on the plurality of stacked optical switch elements is configured such that the deflection angle of the diffraction member located on the downstream side is set larger than that of the diffraction member located on the upstream side in the incident direction of light.

15. A method for manufacturing a substrate for a liquid crystal panel, characterized in that: include: a mask layer forming step of forming a mask layer on a surface of a raw material substrate that becomes a raw material of the liquid crystal panel substrate; a resist pattern layer forming step of forming a resist pattern layer having a predetermined pattern on a surface of the mask layer; A first etching step, etching the mask layer into the shape of the resist pattern layer; a second etching step of etching the raw material substrate so that the shape of the pattern becomes a predetermined thickness and forming a transparent spacer having a rising surface rising on the surface of the transparent substrate; A mask layer removing step, removing the mask layer after the second etching step; a transparent electrode forming step of forming an electrode film for forming a transparent electrode on the surface of the transparent substrate and the transparent spacer including the rising surface; as well as The selective sputtering etching step is to etch the transparent electrode and the electrode film in the planar portion of the transparent spacer to leave the electrode film in the rising surface to form the transparent electrode.

16. The method for manufacturing a liquid crystal panel substrate according to claim 15, wherein: In the transparent electrode forming step, the electrode film is formed by using Al-doped ZnO as a raw material through an atomic layer deposition (ALD) technique.

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