Optical element, variable focus element, and head-mounted display

Abstract

Provided are an optical element, a variable-focus element, and a head-mounted display, the optical element comprising: a first liquid crystal cell having first liquid crystal molecules and a first electrode; and a second liquid crystal cell having second liquid crystal molecules and a second electrode, the first electrode and the second electrode being configured to be capable of switching between a first state and a second state, the first state being a state in which the second liquid crystal molecules are twisted and the first liquid crystal molecules are vertically aligned, the second state being a state in which the first liquid crystal molecules are twisted and the second liquid crystal molecules are vertically aligned, the azimuthal angle of the alignment direction of the second liquid crystal molecules on the third substrate side in the first state and the azimuthal angle of the alignment direction of the second liquid crystal molecules on the fourth substrate side being, respectively, an angle obtained by rotating the azimuthal angle of the alignment direction of the first liquid crystal molecules on the first substrate side in the second state and the azimuthal angle of the alignment direction of the first liquid crystal molecules on the second substrate side in the second state by 1 / 4 in the same direction.

Description

Technical Field

[0001] The following disclosure relates to optical elements, a zoom element having the aforementioned optical elements, and a head-mounted display having the aforementioned zoom element. Background Technology

[0002] In recent years, for applications such as head-mounted displays, variable focus optical systems have been proposed that combine Pancharatnam-Berry (PB) lenses and switchable half-wave plates (sHWPs). An sHWP is a device capable of switching the polarization state of circularly polarized light, achieved through a liquid crystal.

[0003] As a technology related to variable focus optical systems, for example, Patent Document 1 discloses a display device having a waveguide and a broadband adaptive lens assembly. The waveguide is configured to guide light in a lateral direction parallel to the output surface of the waveguide, and further configured to externally combine the guided light through the output surface. The broadband adaptive lens assembly is configured to internally combine and diffract the externally combined light from the waveguide through the broadband adaptive lens assembly.

[0004] Patent document 2 discloses a variable focus block having an sHWP and multiple liquid crystal lenses.

[0005] Patent document 3 discloses an achromatic polarization switch, which is an achromatic polarization switch for converting linearly polarized light with an initial polarization orientation. It comprises: a first liquid crystal (LC) unit having a first orientation axis with respect to the initial polarization orientation; and a second LC unit having a second orientation axis with respect to the first orientation axis.

[0006] Patent document 4 discloses an optical element having a first stacked birefringent layer and a second stacked birefringent layer, wherein the local optical axes of the first stacked birefringent layer and the second stacked birefringent layer rotate at their respective torsion angles on the thickness of the first layer and the second layer, and are arranged along the interface between the first layer and the second layer.

[0007] In Patent Document 5, for use as a display in a head-mounted display, an optical element composed of a stacked liquid crystal structure that rotates the polarized light of incident circularly polarized light with a wide wavelength and incident angle is proposed.

[0008] Existing technical documents

[0009] Patent documents

[0010] [Patent Document 1]: U.S. Patent No. 2021-501361 [Patent Document 2]: U.S. Patent No. 10379419 [Patent Document 3]: U.S. Patent No. 2009-524106 [Patent Document 4]: U.S. Patent No. 2014-528597 [Patent Document 5]: U.S. Patent No. 10678057 Summary of the Invention

[0011] The technical problem to be solved by the present invention

[0012] In the aforementioned patent documents 1 to 5, there is a problem that it is difficult to realize a device structure that can switch the polarization state of left and right circularly polarized light with wide bandwidth and wide viewing angle, and a device structure that does not switch the polarization state of left and right circularly polarized light, and a device structure that does not switch the polarization state of left and right circularly polarized light.

[0013] The present invention was made in view of the above-mentioned situation, and its object is to provide an optical element capable of switching between polarized light modulation and polarized light non-modulation with a wide bandwidth and a wide viewing angle, a variable focus element having the above-mentioned optical element, and a head-mounted display having the above-mentioned variable focus element.

[0014] Technical solutions for solving technical problems

[0015] (1) An optical element according to one embodiment of the present invention sequentially comprises a first substrate, a first liquid crystal layer containing first liquid crystal molecules, a second substrate, a third substrate, a second liquid crystal layer containing second liquid crystal molecules, and a fourth substrate. The first substrate, the first liquid crystal layer, and the second substrate constitute a first liquid crystal unit, and the third substrate, the second liquid crystal layer, and the fourth substrate constitute a second liquid crystal unit. The first liquid crystal unit has a first electrode for applying a voltage to the first liquid crystal layer at least one of the first substrate and the second substrate, and the second liquid crystal unit has a second electrode for applying a voltage to the second liquid crystal layer at least one of the third substrate and the fourth substrate. The first electrode and the second electrode are configured to apply a voltage to the first liquid crystal layer. The system switches between a first state and a second state. The first state is a state in which the second liquid crystal molecules are twisted and oriented vertically. The second state is a state in which the first liquid crystal molecules are twisted and oriented vertically. The azimuth angle of the orientation direction of the second liquid crystal molecules on the third substrate side in the first state and the azimuth angle of the orientation direction of the second liquid crystal molecules on the fourth substrate side in the first state are respectively obtained by rotating the azimuth angle of the orientation direction of the first liquid crystal molecules on the first substrate side in the second state and the azimuth angle of the orientation direction of the first liquid crystal molecules on the second substrate side in the second state in the same direction by 1 / 4.

[0016] (2) Furthermore, in a certain embodiment of the present invention, the optical element, based on the configuration described in (1) above, also has a negative C plate between the first liquid crystal cell and the second liquid crystal cell.

[0017] (3) Furthermore, in a certain embodiment of the present invention, the optical element is configured as described in (2) above, wherein the retardation Rth in the thickness direction of the negative C plate is -220 nm or more and 0 nm or less.

[0018] (4) Furthermore, in a certain embodiment of the present invention, based on the configuration described in (1), (2) or (3) above, the delay of the first liquid crystal layer in the second state at a wavelength of 550 nm is 200 nm or more and 260 nm or less, and the delay of the second liquid crystal layer in the first state at a wavelength of 550 nm is 210 nm or more and 260 nm or less.

[0019] (5) Furthermore, in a certain embodiment of the present invention, the optical element is based on the configuration described in (1), (2), (3) or (4) above, but the first liquid crystal cell does not have the same configuration as the second liquid crystal cell.

[0020] (6) Furthermore, in a certain embodiment of the present invention, the optical element is configured as described in (1), (2), (3), (4) or (5) above, wherein the first liquid crystal molecule in the second state is oriented with a twist angle of 61° or more and 75° or less, and the second liquid crystal molecule in the first state is oriented with a twist angle of 64° or more and 74° or less.

[0021] (7) Furthermore, in a certain embodiment of the present invention, based on the configuration described in (1), (2), (3), (4), (5), or (6) above, the azimuth angle of the orientation direction of the first liquid crystal molecule on the first substrate side in the second state is -9° or more and 7° or less, and the azimuth angle of the orientation direction of the second liquid crystal molecule on the third substrate side in the first state is 85° or more and 96° or less.

[0022] (8) Furthermore, in a certain embodiment of the present invention, the optical element is provided with a 1 / 4 wavelength film on the side of the first liquid crystal cell opposite to the second liquid crystal cell or on the side of the second liquid crystal cell opposite to the first liquid crystal cell, based on the configuration described in (1), (2), (3), (4), (5), (6), or (7) above.

[0023] (9) Furthermore, in a certain embodiment of the present invention, the 1 / 4 wavelength film has reverse wavelength dispersion characteristics based on the configuration described in (8) above.

[0024] (10) Furthermore, in a certain embodiment of the present invention, based on the configuration described in (8) or (9) above, the in-plane phase difference of the 1 / 4 wavelength film at a wavelength of 450 nm is 0.7 times or more and less than 1 times the in-plane phase difference at a wavelength of 550 nm.

[0025] (11) Furthermore, in a certain embodiment of the present invention, based on the configuration described in (8), (9) or (10) above, the in-plane phase difference of the 1 / 4 wavelength film at a wavelength of 650 nm is more than 1 and less than 1.3 times the in-plane phase difference at a wavelength of 550 nm.

[0026] (12) Furthermore, in a certain embodiment of the present invention, the optical element is configured as described in (8), (9), (10) or (11) above, and the azimuth angle of the hysteresis axis of the quarter-wavelength film is 52° or more and 60° or less.

[0027] (13) Furthermore, in a certain embodiment of the present invention, the optical element is configured as described in (8), (9), (10), (11) or (12) above, and the in-plane phase difference of the 550nm wavelength of the 1 / 4 wavelength film is 90nm or more and 170nm or less.

[0028] (14) Furthermore, in a certain embodiment of the present invention, the optical element is based on the configuration described in (8), (9), (10), (11), (12) or (13) above, wherein the 1 / 4 wavelength film is a first 1 / 4 wavelength film, and a second 1 / 4 wavelength film is provided on the side of the first 1 / 4 wavelength film opposite to the first liquid crystal cell and the second liquid crystal cell.

[0029] (15) Furthermore, in a certain embodiment of the present invention, the second 1 / 4 wavelength film has flat wavelength dispersion characteristics based on the above-described (14) configuration of the optical element.

[0030] (16) Furthermore, in a certain embodiment of the present invention, the optical element is configured as described in (14) or (15) above, and the azimuth angle of the hysteresis axis of the second 1 / 4 wavelength film is 8° or more and 18° or less.

[0031] (17) Furthermore, in a certain embodiment of the present invention, based on the configuration described in (14), (15) or (16) above, the in-plane phase difference of the second 1 / 4 wavelength film with a wavelength of 550 nm is 120 nm or more and 150 nm or less.

[0032] (18) In addition, the variable focus element of other embodiments of the present invention includes the optical element described in (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15), (16) or (17) above; and a Pancharatnam-Berry lens.

[0033] (19) Furthermore, in a certain embodiment of the present invention, the variable focus element is configured as described in (18) above, wherein the Pancharatnam-Berry lens is disposed within the optical element.

[0034] (20) Furthermore, the head-mounted display of other embodiments of the present invention includes the variable focus element described in (18) or (19) above.

[0035] Beneficial effects

[0036] According to the present invention, it is possible to provide an optical element capable of switching between polarized light modulation and polarized light non-modulation with a wide bandwidth and a wide viewing angle, a variable focus element having the above-mentioned optical element, and a head-mounted display having the above-mentioned variable focus element. Attached Figure Description

[0037] Figure 1 This is a cross-sectional schematic diagram of the optical element according to the first embodiment.

[0038] Figure 2 This is a cross-sectional schematic diagram of the first liquid crystal unit and the second liquid crystal unit included in the optical element of the first embodiment.

[0039] Figure 3 This is a schematic diagram illustrating the orientation of liquid crystal molecules in the first and second states of the optical element according to the first embodiment.

[0040] Figure 4 This is a cross-sectional schematic diagram of the optical element in comparison method 1.

[0041] Figure 5 This is a cross-sectional schematic diagram of the optical element in comparison method 2.

[0042] Figure 6 It is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical element of the first embodiment, comparison method 1 and comparison method 2 is modulated.

[0043] Figure 7 This is a cross-sectional schematic diagram illustrating the first state of the optical element according to the first embodiment.

[0044] Figure 8This is a cross-sectional schematic diagram illustrating the second state of the optical element in the first embodiment.

[0045] Figure 9 This is a cross-sectional schematic diagram of the optical element of a variation of the first embodiment 1.

[0046] Figure 10 This is a cross-sectional schematic diagram of the optical element according to the second embodiment.

[0047] Figure 11 This is a cross-sectional schematic diagram of the optical element according to the third embodiment.

[0048] Figure 12 This is a cross-sectional schematic diagram of the first liquid crystal unit and the second liquid crystal unit included in the optical element of the third embodiment.

[0049] Figure 13 This is a schematic diagram illustrating the orientation of liquid crystal molecules in the first and second states of the optical element according to the third embodiment.

[0050] Figure 14 This is a cross-sectional schematic diagram illustrating the first state of the optical element in the third embodiment.

[0051] Figure 15 This is a cross-sectional schematic diagram illustrating the second state of the optical element in the third embodiment.

[0052] Figure 16 This is a cross-sectional schematic diagram of the optical element according to the fourth embodiment.

[0053] Figure 17 This is a cross-sectional schematic diagram of the first liquid crystal unit and the second liquid crystal unit included in the optical element of the fourth embodiment.

[0054] Figure 18 This is a schematic diagram illustrating the orientation of liquid crystal molecules in the first and second states of the optical element according to the fourth embodiment.

[0055] Figure 19 This is a cross-sectional schematic diagram illustrating the first state of the optical element according to the fourth embodiment.

[0056] Figure 20 This is a cross-sectional schematic diagram illustrating the second state of the optical element in the fourth embodiment.

[0057] Figure 21 This is a cross-sectional schematic diagram of the variable focus element according to the fifth embodiment.

[0058] Figure 22 This is an example of a cross-sectional schematic diagram of the PB lens included in the zoom element of the fifth embodiment.

[0059] Figure 23 This is a cross-sectional schematic diagram of the variable focus element of Modified Example 1 of the fifth embodiment.

[0060] Figure 24 This is an enlarged cross-sectional schematic diagram of the variable focus element in Modification 1 of the fifth embodiment. Figure 25 This is a schematic diagram illustrating the orientation of liquid crystal molecules in the first and second states of the optical element of Modified Example 1 of the fifth embodiment.

[0061] Figure 26 This is a plan view showing the orientation pattern of the PB lens provided by the zoom element of the fifth embodiment, modified example 1.

[0062] Figure 27 This is a cross-sectional schematic diagram illustrating the detailed configuration of the variable focus element in Modified Example 1 of the fifth embodiment.

[0063] Figure 28 This is a diagram illustrating the polarization state of the variable focus element in F-2.5 mode of Modified Example 1 of the fifth embodiment.

[0064] Figure 29 This is a cross-sectional schematic diagram of the head-mounted display according to the sixth embodiment.

[0065] Figure 30 This is a perspective view showing an example of the appearance of the head-mounted display according to the sixth embodiment.

[0066] Figure 31 This is a cross-sectional schematic diagram of the optical element in Comparative Example 1.

[0067] Figure 32 This is a cross-sectional schematic diagram of the optical element in Comparative Example 2.

[0068] Figure 33 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical elements of Example 1, Comparative Example 1, and Comparative Example 2 are not modulated.

[0069] Figure 34 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical elements of Example 1, Comparative Example 1, and Comparative Example 2 are modulated.

[0070] Figure 35 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Comparative Example 1 when the incident angle is set to 30° and it is not modulated.

[0071] Figure 36This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Comparative Example 1 is modulated with the incident angle set to 30°.

[0072] Figure 37 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Comparative Example 2 when the incident angle is set to 30° and it is not modulated.

[0073] Figure 38 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Comparative Example 2 is modulated with the incident angle set to 30°.

[0074] Figure 39 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Example 1 when the incident angle is set to 30° and it is not modulated.

[0075] Figure 40 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 1 is modulated with the incident angle set to 30°.

[0076] Figure 41 The graph shows the simulation results of the field of view angle characteristics of the optical elements of Example 1, Comparative Example 1, and Comparative Example 2 under non-modulation and modulation conditions.

[0077] Figure 42 This is a graph showing the Stokes parameter S3 under the first state of the second liquid crystal layer possessed by the optical element of Embodiment 1, in a delayed, unmodulated state.

[0078] Figure 43 A graph showing the Stokes parameter S3 during delayed modulation in the second state of the first liquid crystal layer of the optical element of Embodiment 1.

[0079] Figure 44 This is a graph showing the Stokes parameter S3 in the unmodulated state, representing the twist angle of the second liquid crystal molecules relative to the optical element of Example 1.

[0080] Figure 45 It is a graph showing the Stokes parameter S3 during modulation, which represents the twist angle of the first liquid crystal molecule relative to the optical element of Example 1.

[0081] Figure 46 This is a graph showing the Stokes parameter S3 in the unmodulated state, representing the pre-twist angle of the second liquid crystal molecules relative to the optical element of Example 1.

[0082] Figure 47It is a graph showing the Stokes parameter S3 during modulation, which represents the pre-twist angle of the first liquid crystal molecule relative to the optical element of Example 1.

[0083] Figure 48 This is a graph showing the Stokes parameter S3 in the unmodulated state, representing the azimuth angle of the hysteresis axis of the quarter-wavelength film with reverse wavelength dispersion relative to the optical element of Example 1.

[0084] Figure 49 A graph showing the Stokes parameter S3 during modulation, representing the azimuth angle of the hysteresis axis of the quarter-wavelength film with reverse wavelength dispersion relative to the optical element of Example 1.

[0085] Figure 50 This is a graph showing the unmodulated Stokes parameter S3, representing the phase difference of the quarter-wavelength film with reverse wavelength dispersion relative to the optical element of Example 1.

[0086] Figure 51 This is a graph showing the Stokes parameter S3 during modulation, representing the phase difference of the quarter-wavelength film with reverse wavelength dispersion relative to the optical element of Example 1.

[0087] Figure 52 This is a graph showing the Stokes parameter S3 in the unmodulated state, representing the azimuth angle of the hysteresis axis of the quarter-wavelength film with flat wavelength dispersion relative to the optical element of Example 1.

[0088] Figure 53 It is a graph showing the Stokes parameter S3 during modulation, which represents the azimuth angle of the hysteresis axis of the quarter-wavelength film with flat wavelength dispersion relative to the optical element of Example 1.

[0089] Figure 54 This is a graph showing the unmodulated Stokes parameter S3, representing the phase difference of the quarter-wavelength film with flat wavelength dispersion relative to the optical element of Example 1.

[0090] Figure 55 This is a graph showing the Stokes parameter S3 during modulation, representing the phase difference of the 1 / 4 wavelength film with planar wavelength dispersion possessed by the optical element of Embodiment 1.

[0091] Figure 56 The graph shows the simulation results of the viewing angle characteristics of the optical elements of Example 1, Example 2 and Comparative Example 1 under both non-modulated and modulated conditions.

[0092] Figure 57 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element in Example 2 when the incident angle is set to 30° and it is not modulated.

[0093] Figure 58 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 2 is modulated with the incident angle set to 30°.

[0094] Figure 59 This is a graph showing the relationship between the Stokes parameter S3 of the optical element in the embodiment when it is not modulated and the delay Rth in the thickness direction of the negative C plate.

[0095] Figure 60 This is a graph showing the relationship between the Stokes parameter S3 during modulation of the optical element in the embodiment and the delay Rth in the thickness direction of the negative C plate.

[0096] Figure 61 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light of the optical elements of Examples 1, 3, Comparative Example 1 and Comparative Example 2 when the incident angle is set to 0°.

[0097] Figure 62 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical element of Examples 1, 3, Comparative Example 1 and Comparative Example 2 is modulated with the incident angle set to 0°.

[0098] Figure 63 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Example 3 when the incident angle is set to 30° and it is not modulated.

[0099] Figure 64 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 3 is modulated with the incident angle set to 30°.

[0100] Figure 65 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical element of Example 4, Comparative Example 1, and Comparative Example 2 is not modulated, with the incident angle set to 0°.

[0101] Figure 66 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical element of Example 4, Comparative Example 1, and Comparative Example 2 is modulated with the incident angle set to 0°.

[0102] Figure 67 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element in Example 4 when the incident angle is set to 30° and it is not modulated.

[0103] Figure 68This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 4 is modulated with the incident angle set to 30°.

[0104] Figure 69 This is a schematic diagram illustrating the first orientation process in the manufacturing process of the variable focus element of Example 5.

[0105] Figure 70 This is a schematic diagram illustrating the second orientation process in the manufacturing process of the variable focus element of Example 5.

[0106] Figure 71 This is a schematic diagram illustrating the third orientation process in the manufacturing process of the variable focus element of Embodiment 5.

[0107] Figure 72 This is a schematic diagram illustrating the fourth orientation process in the manufacturing process of the variable focus element of Example 5.

[0108] Figure 73 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical element of Example 6, Comparative Example 1 and Comparative Example 2 is not modulated, with the incident angle set to 0°.

[0109] Figure 74 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical element of Example 6, Comparative Example 1 and Comparative Example 2 is modulated with the incident angle set to 0°.

[0110] Figure 75 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Example 6 when the incident angle is set to 30° and it is not modulated.

[0111] Figure 76 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 6 is modulated with the incident angle set to 30°.

[0112] Figure 77 This is a graph showing the Stokes parameter S3 in the unmodulated state, representing the delay Rth in the thickness direction relative to the first positive C-plate of the optical element in Embodiment 6.

[0113] Figure 78 This is a graph showing the Stokes parameter S3 during modulation, which represents the delay Rth in the thickness direction relative to the first positive C-plate of the optical element in Embodiment 6.

[0114] Figure 79This is a graph showing the Stokes parameter S3 in the unmodulated state, representing the delay Rth in the thickness direction relative to the second positive C-plate of the optical element in Embodiment 6.

[0115] Figure 80 This is a graph showing the Stokes parameter S3 during modulation, which represents the delay Rth in the thickness direction relative to the second positive C-plate of the optical element in Embodiment 6.

[0116] Figure 81 This is a cross-sectional schematic diagram of an optical element having the first configuration of a modified example 2 of the first embodiment.

[0117] Figure 82 This is an example of a cross-sectional schematic diagram of an optical element having a second configuration according to a variation of the first embodiment, Example 2.

[0118] Figure 83 This is an example of a cross-sectional schematic diagram of an optical element having a second configuration according to a variation of the first embodiment, Example 2.

[0119] Figure 84 This is an example of a cross-sectional schematic diagram of an optical element having a second configuration according to a variation of the first embodiment, Example 2.

[0120] Figure 85 This is an example of a cross-sectional schematic diagram of an optical element having a second configuration according to a variation of the first embodiment, Example 2.

[0121] Figure 86 This is an example of a cross-sectional schematic diagram of an optical element with a third configuration having a variation of the first embodiment, Example 2.

[0122] Figure 87 This is an example of a cross-sectional schematic diagram of an optical element with a third configuration having a variation of the first embodiment, Example 2.

[0123] Figure 88 This is an example of a cross-sectional schematic diagram of an optical element with a third configuration having a variation of the first embodiment, Example 2.

[0124] Figure 89 This is an example of a cross-sectional schematic diagram of an optical element with a third configuration having a variation of the first embodiment, Example 2.

[0125] Figure 90 This is an example of a cross-sectional schematic diagram of an optical element with a third configuration having a variation of the first embodiment, Example 2.

[0126] Figure 91 This is an example of a cross-sectional schematic diagram of an optical element with a third configuration having a variation of the first embodiment, Example 2.

[0127] Figure 92 This is an example of a cross-sectional schematic diagram of an optical element having a fourth configuration as described in Modification 2 of the first embodiment.

[0128] Figure 93 This is an example of a cross-sectional schematic diagram of an optical element having a fourth configuration as described in Modification 2 of the first embodiment.

[0129] Figure 94 This is an example of a cross-sectional schematic diagram of an optical element having a fourth configuration as described in Modification 2 of the first embodiment.

[0130] Figure 95 This is an example of a cross-sectional schematic diagram of an optical element having a fourth configuration as described in Modification 2 of the first embodiment.

[0131] Figure 96 This is an example of a cross-sectional schematic diagram of an optical element having a fifth configuration of a variation of the first embodiment, Example 2.

[0132] Figure 97 This is an example of a cross-sectional schematic diagram of an optical element having a sixth configuration of a variation of the first embodiment, Example 2.

[0133] Figure 98 This is an example of a cross-sectional schematic diagram of an optical element having a sixth configuration of a variation of the first embodiment, Example 2.

[0134] Figure 99 This is an example of a cross-sectional schematic diagram of an optical element having a sixth configuration of a variation of the first embodiment, Example 2.

[0135] Figure 100 This is an example of a cross-sectional schematic diagram of an optical element having a sixth configuration of a variation of the first embodiment, Example 2.

[0136] Figure 101 This is an example of a cross-sectional schematic diagram of an optical element having a sixth configuration of a variation of the first embodiment, Example 2.

[0137] Figure 102 This is an example of a cross-sectional schematic diagram of an optical element having a seventh configuration according to a variation of the first embodiment, Example 2.

[0138] Figure 103 This is an example of a cross-sectional schematic diagram of an optical element having a seventh configuration according to a variation of the first embodiment, Example 2.

[0139] Figure 104 This is an example of a cross-sectional schematic diagram of an optical element having a seventh configuration according to a variation of the first embodiment, Example 2.

[0140] Figure 105This is an example of a cross-sectional schematic diagram of an optical element having a seventh configuration according to a variation of the first embodiment, Example 2.

[0141] Figure 106 This is an example of a cross-sectional schematic diagram of an optical element having a seventh configuration according to a variation of the first embodiment, Example 2.

[0142] Figure 107 This is an example of a cross-sectional schematic diagram of an optical element having a seventh configuration according to a variation of the first embodiment, Example 2.

[0143] Figure 108 This is an example of a cross-sectional schematic diagram of an optical element having a seventh configuration according to a variation of the first embodiment, Example 2.

[0144] Figure 109 This is an example of a cross-sectional schematic diagram of an optical element having a seventh configuration according to a variation of the first embodiment, Example 2.

[0145] Figure 110 This is an example of a cross-sectional schematic diagram of an optical element having a seventh configuration according to a variation of the first embodiment, Example 2.

[0146] Figure 111 This is an example of a cross-sectional schematic diagram of an optical element having an eighth configuration as described in Modification 2 of the first embodiment.

[0147] Figure 112 This is an example of a cross-sectional schematic diagram of an optical element having an eighth configuration as described in Modification 2 of the first embodiment.

[0148] Figure 113 This is an example of a cross-sectional schematic diagram of an optical element having an eighth configuration as described in Modification 2 of the first embodiment.

[0149] Figure 114 This is an example of a cross-sectional schematic diagram of an optical element having an eighth configuration as described in Modification 2 of the first embodiment.

[0150] Figure 115 This is an example of a cross-sectional schematic diagram of an optical element having an eighth configuration as described in Modification 2 of the first embodiment.

[0151] Figure 116 This is an example of a cross-sectional schematic diagram of an optical element having an eighth configuration as described in Modification 2 of the first embodiment.

[0152] Figure 117 This is an example of a cross-sectional schematic diagram of an optical element having an eighth configuration as described in Modification 2 of the first embodiment.

[0153] Figure 118This is an example of a cross-sectional schematic diagram of an optical element having a ninth configuration according to a variation of the first embodiment, Example 2.

[0154] Figure 119 This is an example of a cross-sectional schematic diagram of an optical element having a ninth configuration according to a variation of the first embodiment, Example 2.

[0155] Figure 120 This is an example of a cross-sectional schematic diagram of an optical element having a tenth configuration of a variation 2 of the first embodiment.

[0156] Figure 121 This is an example of a cross-sectional schematic diagram of an optical element having a tenth configuration of a variation 2 of the first embodiment.

[0157] Figure 122 This is an example of a cross-sectional schematic diagram of an optical element having a tenth configuration of a variation 2 of the first embodiment.

[0158] Figure 123 This is an example of a cross-sectional schematic diagram of an optical element having a tenth configuration of a variation 2 of the first embodiment.

[0159] Figure 124 This is an example of a cross-sectional schematic diagram of an optical element having a tenth configuration of a variation 2 of the first embodiment.

[0160] Figure 125 This is an example of a cross-sectional schematic diagram of an optical element having a tenth configuration of a variation 2 of the first embodiment.

[0161] Figure 126 This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2.

[0162] Figure 127 This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2.

[0163] Figure 128 This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2.

[0164] Figure 129 This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2.

[0165] Figure 130 This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2.

[0166] Figure 131This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2.

[0167] Figure 132 This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2.

[0168] Figure 133 This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2.

[0169] Figure 134 This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2.

[0170] Figure 135 This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2.

[0171] Figure 136 This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2.

[0172] Figure 137 This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2.

[0173] Figure 138 This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2.

[0174] Figure 139 This is an example of a cross-sectional schematic diagram of an optical element having a twelfth configuration of a variation of the first embodiment, Example 2.

[0175] Figure 140 This is an example of a cross-sectional schematic diagram of an optical element having a twelfth configuration of a variation of the first embodiment, Example 2.

[0176] Figure 141 This is an example of a cross-sectional schematic diagram of an optical element having a twelfth configuration of a variation of the first embodiment, Example 2.

[0177] Figure 142 This is an example of a cross-sectional schematic diagram of an optical element having a twelfth configuration of a variation of the first embodiment, Example 2.

[0178] Figure 143 This is an example of a cross-sectional schematic diagram of an optical element having a twelfth configuration of a variation of the first embodiment, Example 2.

[0179] Figure 144This is an example of a cross-sectional schematic diagram of an optical element having a twelfth configuration of a variation of the first embodiment, Example 2.

[0180] Figure 145 This is an example of a cross-sectional schematic diagram of an optical element having a twelfth configuration of a variation of the first embodiment, Example 2.

[0181] Figure 146 This is an example of a cross-sectional schematic diagram of an optical element having a twelfth configuration of a variation of the first embodiment, Example 2.

[0182] Figure 147 This is an example of a cross-sectional schematic diagram of an optical element having a twelfth configuration of a variation of the first embodiment, Example 2.

[0183] Figure 148 This is an example of a cross-sectional schematic diagram of an optical element having a twelfth configuration of a variation of the first embodiment, Example 2.

[0184] Figure 149 This is an example of a cross-sectional schematic diagram of an optical element having a twelfth configuration of a variation of the first embodiment, Example 2.

[0185] Figure 150 This is an example of a cross-sectional schematic diagram of an optical element having a twelfth configuration of a variation of the first embodiment, Example 2.

[0186] Figure 151 This is an example of a cross-sectional schematic diagram of an optical element having the thirteenth configuration of a variation of the first embodiment, Example 2.

[0187] Figure 152 This is an example of a cross-sectional schematic diagram of an optical element having the thirteenth configuration of a variation of the first embodiment, Example 2.

[0188] Figure 153 This is an example of a cross-sectional schematic diagram of an optical element having the thirteenth configuration of a variation of the first embodiment, Example 2.

[0189] Figure 154 This is an example of a cross-sectional schematic diagram of an optical element having the thirteenth configuration of a variation of the first embodiment, Example 2.

[0190] Figure 155 This is an example of a cross-sectional schematic diagram of an optical element having the fourteenth configuration of a variation of the first embodiment, Example 2.

[0191] Figure 156 This is an example of a cross-sectional schematic diagram of an optical element having the fourteenth configuration of a variation of the first embodiment, Example 2.

[0192] Figure 157This is an example of a cross-sectional schematic diagram of an optical element having the fourteenth configuration of a variation of the first embodiment, Example 2.

[0193] Figure 158 This is an example of a cross-sectional schematic diagram of an optical element having the fourteenth configuration of a variation of the first embodiment, Example 2.

[0194] Figure 159 This is an example of a cross-sectional schematic diagram of an optical element having the fourteenth configuration of a variation of the first embodiment, Example 2.

[0195] Figure 160 This is an example of a cross-sectional schematic diagram of an optical element having a fifteenth configuration of a variation of the first embodiment, 2.

[0196] Figure 161 This is an example of a cross-sectional schematic diagram of an optical element having a fifteenth configuration of a variation of the first embodiment, 2.

[0197] Figure 162 This is an example of a cross-sectional schematic diagram of an optical element having a fifteenth configuration of a variation of the first embodiment, 2.

[0198] Figure 163 This is an example of a cross-sectional schematic diagram of an optical element having a fifteenth configuration of a variation of the first embodiment, 2.

[0199] Figure 164 This is an example of a cross-sectional schematic diagram of an optical element having a fifteenth configuration of a variation of the first embodiment, 2.

[0200] Figure 165 This is an example of a cross-sectional schematic diagram of an optical element having a fifteenth configuration of a variation of the first embodiment, 2.

[0201] Figure 166 This is an example of a cross-sectional schematic diagram of an optical element having a fifteenth configuration of a variation of the first embodiment, 2.

[0202] Figure 167 This is an example of a cross-sectional schematic diagram of an optical element having a fifteenth configuration of a variation of the first embodiment, 2.

[0203] Figure 168 This is an example of a cross-sectional schematic diagram of an optical element having a fifteenth configuration of a variation of the first embodiment, 2.

[0204] Figure 169 This is an example of a cross-sectional schematic diagram of an optical element having a sixteenth configuration of a variation of the first embodiment 2.

[0205] Figure 170This is an example of a cross-sectional schematic diagram of an optical element having a sixteenth configuration of a variation of the first embodiment 2.

[0206] Figure 171 This is an example of a cross-sectional schematic diagram of an optical element having a sixteenth configuration of a variation of the first embodiment 2.

[0207] Figure 172 This is an example of a cross-sectional schematic diagram of an optical element having a sixteenth configuration of a variation of the first embodiment 2.

[0208] Figure 173 This is an example of a cross-sectional schematic diagram of an optical element having a sixteenth configuration of a variation of the first embodiment 2.

[0209] Figure 174 This is an example of a cross-sectional schematic diagram of an optical element having a sixteenth configuration of a variation of the first embodiment 2.

[0210] Figure 175 This is an example of a cross-sectional schematic diagram of an optical element having a sixteenth configuration of a variation of the first embodiment 2.

[0211] Figure 176 This is an example of a cross-sectional schematic diagram of an optical element having the seventeenth configuration of a variation of the first embodiment, Example 2.

[0212] Figure 177 This is an example of a cross-sectional schematic diagram of an optical element having the seventeenth configuration of a variation of the first embodiment, Example 2.

[0213] Figure 178 This is a schematic diagram illustrating the orientation of liquid crystal molecules in the first and second states of the optical element of Example 7.

[0214] Figure 179 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical elements of Examples 1 and 7 are not modulated.

[0215] Figure 180 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical element of Embodiment 1 and Embodiment 7 is modulated.

[0216] Figure 181 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Example 1 when the incident angle is set to 30° and it is not modulated.

[0217] Figure 182 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 1 is modulated with the incident angle set to 30°.

[0218] Figure 183 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Example 7 when the incident angle is set to 30° and it is not modulated.

[0219] Figure 184 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 7 is modulated with the incident angle set to 30°.

[0220] Figure 185 This is a graph showing the Stokes parameter S3 in the unmodulated state, representing the delay Rth in the thickness direction relative to the second C plate of the optical element in Embodiment 7.

[0221] Figure 186 This is a graph showing the Stokes parameter S3 during modulation, representing the delay Rth in the thickness direction relative to the second C plate of the optical element in Embodiment 7.

[0222] Figure 187 This is a graph showing the Stokes parameter S3 in the unmodulated state, representing the delay Rth in the thickness direction relative to the first C-plate of the optical element in Embodiment 7.

[0223] Figure 188 This is a graph showing the Stokes parameter S3 during modulation, which represents the delay Rth in the thickness direction relative to the optical element of Embodiment 7 in the first C-plate.

[0224] Figure 189 This is a graph showing the Stokes parameter S3 in the unmodulated state, representing the delay Rth in the thickness direction of the negative C plate relative to the optical element of Embodiment 7.

[0225] Figure 190 This is a graph showing the Stokes parameter S3 during modulation, which represents the delay Rth in the thickness direction of the negative C plate relative to the optical element of Embodiment 7.

[0226] Figure 191 This is a graph showing the Stokes parameter S3 under non-modulation conditions of the in-plane phase difference Re of the second A plate relative to the optical element of Embodiment 7.

[0227] Figure 192 This is a graph showing the Stokes parameter S3 during modulation of the in-plane phase difference Re of the second A plate relative to the optical element of Embodiment 7.

[0228] Figure 193 This is a graph showing the Stokes parameter S3 in the unmodulated state, representing the azimuth angle of the hysteresis axis of the second A plate relative to the optical element of Embodiment 7.

[0229] Figure 194 It is a graph showing the Stokes parameter S3 during modulation, which represents the azimuth angle of the hysteresis axis of the second A plate relative to the optical element of Embodiment 7.

[0230] Figure 195 This is a graph showing the Stokes parameter S3, under non-modulation conditions, of the in-plane phase difference Re of the first A plate relative to the optical element of Embodiment 7.

[0231] Figure 196 This is a graph showing the Stokes parameter S3 during modulation of the in-plane phase difference Re of the first A plate relative to the optical element of Embodiment 7.

[0232] Figure 197 This is a graph showing the Stokes parameter S3 in the unmodulated state, representing the azimuth angle of the hysteresis axis of the first A plate relative to the optical element of Embodiment 7.

[0233] Figure 198 It is a graph showing the Stokes parameter S3 during modulation, which represents the azimuth angle of the hysteresis axis of the first A plate relative to the optical element of Embodiment 7.

[0234] Figure 199 This is a diagram illustrating the polarization state.

[0235] Figure 200 This is a cross-sectional schematic diagram of the optical element of Modified Example 3 of the first embodiment.

[0236] Figure 201 This is a schematic diagram illustrating the orientation of liquid crystal molecules in the first and second states of the optical element of Modified Example 3 of the first embodiment.

[0237] Figure 202 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical elements of Example 8, Comparative Example 1, and Comparative Example 2 are not modulated.

[0238] Figure 203 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical elements of Example 8, Comparative Example 1, and Comparative Example 2 are modulated.

[0239] Figure 204 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Example 8 when the incident angle is set to 30° and it is not modulated.

[0240] Figure 205 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 8 is modulated with the incident angle set to 30°. Detailed Implementation

[0241] The embodiments of the present invention will now be described. The present invention is not limited to the contents described in the following embodiments, and design changes can be appropriately made within the scope of satisfying the structure of the present invention. Furthermore, in the following description, the same reference numerals are appropriately used for the same parts or parts having the same function in different drawings, and repeated descriptions are appropriately omitted. Various aspects of the present invention can also be appropriately combined without departing from the spirit of the present invention.

[0242] (Definition of the term)

[0243] In this specification, orientation refers to the direction in which the direction of the object is projected onto the substrate surface of the emitting side of the optical element, and is expressed by the angle (azimuth angle) formed between the orientation and the reference orientation. Here, the reference orientation (0°) is set to the horizontal right direction of the liquid crystal panel screen when viewing the optical element from the emitting side. The azimuth angle is a positive angle for counterclockwise direction and a negative angle for clockwise direction. Both counterclockwise and clockwise directions represent the rotation direction when viewing the optical element from the emitting side. Furthermore, the azimuth angle represents the value measured when viewing the optical element from above the emitting side.

[0244] In this specification, two straight lines (including axes, directions, and orientations) being orthogonal means being orthogonal when viewed from above the optical element from the exiting side. Furthermore, one of the two straight lines being inclined relative to the other means that, when viewed from above the optical element from the exiting side, one straight line is inclined relative to the other. Additionally, the angle between two straight lines represents the angle between one straight line and the other when viewed from above the optical element from the exiting side.

[0245] In this specification, two straight lines (including axes, directions, and orientations) are orthogonal if the angle between them is 90°±5°, preferably 90°±3°, more preferably 90°±1°, and particularly preferably 90° (completely orthogonal). Two straight lines are parallel if the angle between them is 0°±5°, preferably 0°±3°, more preferably 0°±1°, and particularly preferably 0° (completely parallel).

[0246] In this specification, the in-plane retardation (in-plane phase difference) Rp is defined by Rp = (ns - nf)d. Furthermore, the thickness retardation Rth is defined by Rth = (nz - (nx + ny) / 2)d. ns refers to the larger of nx and ny, and nf is the smaller. Additionally, nx and ny represent the principal refractive indices in the in-plane direction of the birefringent layer (including the retardation film and the liquid crystal layer), nz represents the principal refractive index in the out-of-plane direction, i.e., the direction perpendicular to the plane of the birefringent layer, and d represents the thickness of the birefringent layer.

[0247] In addition, unless otherwise specified, the measurement wavelength for optical parameters such as principal refractive index and phase difference in this specification is 550nm.

[0248] The embodiments of the present invention will be described below. The present invention is not limited to the contents described in the following embodiments, and appropriate design changes can be made within the scope of satisfying the structure of the present invention.

[0249] (First Implementation)

[0250] Figure 1 This is a cross-sectional schematic diagram of the optical element according to the first embodiment. Figure 2 This is a cross-sectional schematic diagram of the first liquid crystal unit and the second liquid crystal unit included in the optical element of the first embodiment. Figure 3 This is a schematic diagram illustrating the orientation of liquid crystal molecules in the first and second states of the optical element according to the first embodiment.

[0251] like Figures 1-3As shown, the optical element 10 of this embodiment sequentially includes a first substrate 100, a first liquid crystal layer 500 containing first liquid crystal molecules 510, a second substrate 200, a third substrate 300, a second liquid crystal layer 600 containing second liquid crystal molecules 610, and a fourth substrate 400. The first substrate 100, the first liquid crystal layer 500, and the second substrate 200 constitute a first liquid crystal unit 11A, and the third substrate 300, the second liquid crystal layer 600, and the fourth substrate 400 constitute a second liquid crystal unit 11B. The first liquid crystal unit 11A has a first planar electrode 120 and a second planar electrode 220, which serve as the first electrode for applying voltage to the first liquid crystal layer 500, on at least one of the first substrate 100 and the second substrate 200. The second liquid crystal unit 11B has a third planar electrode 320 and a fourth planar electrode 420, which serve as the second electrode for applying voltage to the second liquid crystal layer 600, on at least one of the third substrate 300 and the fourth substrate 400. The first electrode and the second electrode are configured to switch between a first state and a second state. The first state is a state in which the second liquid crystal molecule 610 is twisted and the first liquid crystal molecule 510 is vertically oriented. The second state is a state in which the first liquid crystal molecule 510 is twisted and the second liquid crystal molecule 610 is vertically oriented. The azimuth angle of the orientation direction 611A of the second liquid crystal molecule 611 on the third substrate 300 side in the first state and the azimuth angle of the orientation direction 612A of the second liquid crystal molecule 612 on the fourth substrate 400 side in the first state are respectively: angles obtained by rotating the azimuth angle of the orientation direction 511A of the first liquid crystal molecule 511 on the first substrate 100 side in the second state and the azimuth angle of the orientation direction 512A of the first liquid crystal molecule 512 on the second substrate 200 side in the second state in the same direction by 1 / 4. By adopting this method, in addition to rotating the entire system by 1 / 4, the first state and the second state can be driven in the same way. Polarization modulation can be achieved in one of the first and second states with a wide bandwidth and a wide viewing angle, and polarization non-modulation can be achieved in the other state. That is, it is possible to realize optical elements that can switch between polarized light modulation and polarized light non-modulation with a wide bandwidth and wide viewing angle, and more specifically, it is possible to realize a switchable half-wave plate (sHWP) element.

[0252] Here, if we want to implement SHWP on the liquid crystal layer 1, then as follows Figure 4As shown, consider the configuration of the optical element 10R1 in Comparison Method 1, which uses a liquid crystal cell 11R1 with a TN liquid crystal layer 500R1 having a 90° twist. More specifically, the optical element 10R1 of Comparison Method 1 sequentially includes: a 1 / 4 wavelength film 15R with a hysteresis axis azimuth angle of 75°, a 1 / 2 wavelength film 16R with a hysteresis axis azimuth angle of 15°, a liquid crystal cell 11R1, a 1 / 2 wavelength film 17R with a hysteresis axis azimuth angle of -75°, and a 1 / 4 wavelength film 18R with a hysteresis axis azimuth angle of -15°. Figure 4 This is a cross-sectional schematic diagram of the optical element in comparison method 1.

[0253] Furthermore, if you want to achieve sHWP with two liquid crystal layers, you can consider, for example... Figure 5 As shown, the optical element 10R2 of Comparison Method 2 is configured with a TN liquid crystal layer 500R2 with a 70° twist and a TN liquid crystal layer 500R3 with a -70° twist. Figure 5 This is a cross-sectional schematic diagram of the optical element in comparison method 2.

[0254] Figure 6 It is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical element of the first embodiment, comparison method 1 and comparison method 2 is modulated. Figure 6 This represents the wavelength dependence of the polarization state of the outgoing light when incident right-circularly polarized light (Stokes parameter S3 = +1). The closer to S3 = -1, the more it indicates conversion to left-circularly polarized light. Approaching -1 across the entire wavelength range, it can be considered a broadband modulation.

[0255] While the optical element 10R1 in Comparison Method 1 is easy to design, it is affected by factors such as wavelength dispersion of the TN liquid crystal layer 500R1, which is twisted by 90°. Figure 6 It is difficult to achieve wide bandwidth as shown. Furthermore, while the optical element 10R2 of Comparative Method 2 can achieve wide bandwidth by stacking liquid crystal layers twisted by approximately 70 degrees, it is difficult to achieve wide viewing angle. On the other hand, the optical element 10 of this embodiment can switch between polarized light modulation and polarized light non-modulation with both wide bandwidth and wide viewing angle.

[0256] In the aforementioned Patent Document 1, polarization modulation characteristics are not disclosed at all. Patent Document 1 discloses the structure of a single-layer TN liquid crystal layer, but in this structure, during polarization modulation (when Patent Document 1 is inactive, when the voltage is off), polarization conversion is only performed appropriately at a specific wavelength, and wide-bandwidth polarization conversion cannot be achieved.

[0257] More specifically, in the single-layer structure disclosed in Patent Document 1, during polarization modulation, the liquid crystal molecules are oriented with a 90° twist, while during non-polarization modulation, the liquid crystal molecules are oriented vertically by an applied longitudinal electric field. Because the liquid crystal molecules are oriented with a 90° twist during polarization modulation, there is wavelength dependence, making broadband polarization modulation impossible. Even if broadband polarization modulation could be achieved by adjusting the twist angle of the liquid crystal molecules and the unit thickness of the liquid crystal layer, broadband non-polarization modulation would still be impossible during non-polarization due to residual delay caused by liquid crystal molecules near the substrate. In other words, it is impossible to simultaneously achieve both broadband polarization modulation and non-polarization.

[0258] In Patent Document 5, the modulation characteristics are not disclosed at all. Furthermore, specific physical properties such as those of the phase retardation film are not described. Moreover, since one of the stacked liquid crystal cells in Patent Document 5 is used as a backup, it is assumed to be the same cell design as the other liquid crystal cell.

[0259] The following is a detailed description of this embodiment.

[0260] The orientation direction of the first liquid crystal molecules on the first substrate side refers to the orientation direction of the first liquid crystal molecules that are horizontally oriented near the first substrate. More specifically, when the alignment film disposed on the first liquid crystal layer side of the first substrate is a horizontally oriented film, the orientation direction of the first liquid crystal molecules on the first substrate side refers to the orientation direction of the first liquid crystal molecules located at the interface of the first liquid crystal layer on the first substrate side. When the alignment film disposed on the first liquid crystal layer side of the first substrate is a vertically oriented film, since the liquid crystal molecules located at the interface of the first liquid crystal layer on the first substrate side are vertically oriented, the orientation direction of the first liquid crystal molecules on the first substrate side refers to the orientation direction of the first liquid crystal molecules located further inside the first liquid crystal layer than the interface on the first substrate side and in a horizontally oriented state.

[0261] Similarly, the orientation direction of the first liquid crystal molecules on the second substrate side refers to the orientation direction of the first liquid crystal molecules that are horizontally oriented near the second substrate. More specifically, when the alignment film disposed on the first liquid crystal layer side of the second substrate is a horizontally oriented film, the orientation direction of the first liquid crystal molecules on the second substrate side refers to the orientation direction of the first liquid crystal molecules located at the interface of the first liquid crystal layer on the second substrate side. When the alignment film disposed on the first liquid crystal layer side of the second substrate is a vertically oriented film, since the liquid crystal molecules located at the interface of the first liquid crystal layer on the second substrate side are vertically oriented, the orientation direction of the first liquid crystal molecules on the second substrate side refers to the orientation direction of the first liquid crystal molecules located further inside the first liquid crystal layer than the interface on the second substrate side and in a horizontally oriented state.

[0262] Similarly, the orientation direction of the second liquid crystal molecules on the third substrate side refers to the orientation direction of the second liquid crystal molecules that are horizontally oriented near the third substrate. More specifically, when the alignment film disposed on the second liquid crystal layer side of the third substrate is a horizontally aligned film, the orientation direction of the second liquid crystal molecules on the third substrate side refers to the orientation direction of the second liquid crystal molecules located at the interface of the second liquid crystal layer on the third substrate side. When the alignment film disposed on the second liquid crystal layer side of the third substrate is a vertically aligned film, the liquid crystal molecules located at the interface of the second liquid crystal layer on the third substrate side are vertically oriented. Therefore, the orientation direction of the second liquid crystal molecules on the third substrate side refers to the orientation direction of the second liquid crystal molecules located further inside the second liquid crystal layer than the interface on the third substrate side and in a horizontally oriented state.

[0263] Similarly, the orientation direction of the second liquid crystal molecules on the fourth substrate side is the orientation direction of the second liquid crystal molecules that are horizontally oriented near the fourth substrate. More specifically, when the alignment film disposed on the second liquid crystal layer side of the fourth substrate is a horizontal alignment film, the orientation direction of the second liquid crystal molecules on the fourth substrate side refers to the orientation direction of the second liquid crystal molecules located at the interface of the second liquid crystal layer on the fourth substrate side. When the alignment film disposed on the second liquid crystal layer side of the fourth substrate is a vertical alignment film, since the liquid crystal molecules located at the interface of the second liquid crystal layer on the fourth substrate side are vertically oriented, the orientation direction of the second liquid crystal molecules on the fourth substrate side refers to the orientation direction of the second liquid crystal molecules located further inside the second liquid crystal layer than the interface on the fourth substrate side and in a horizontally oriented state.

[0264] The azimuth angles of the orientation direction of the second liquid crystal molecules on the third substrate side in the first state and the orientation direction of the second liquid crystal molecules on the fourth substrate side in the first state are respectively: angles obtained by rotating the orientation direction of the first liquid crystal molecules on the first substrate side in the second state and the orientation direction of the first liquid crystal molecules on the second substrate side in the second state in the same direction by 1 / 4. Alternatively, the azimuth angles of the orientation direction of the second liquid crystal molecules on the third substrate side in the first state and the orientation direction of the second liquid crystal molecules on the fourth substrate side in the first state are respectively: angles obtained by rotating the orientation direction of the first liquid crystal molecules on the first substrate side in the second state and the orientation direction of the first liquid crystal molecules on the second substrate side in the second state in the positive direction by 1 / 4; or, the azimuth angles of the orientation direction of the second liquid crystal molecules on the third substrate side in the first state and the orientation direction of the second liquid crystal molecules on the fourth substrate side in the first state are angles obtained by rotating the orientation direction of the first liquid crystal molecules on the first substrate side in the second state and the orientation direction of the first liquid crystal molecules on the second substrate side in the second state in the negative direction by 1 / 4.

[0265] Here, 1 / 4 rotation means 80° or more and 100° or less, preferably 85° or more and 95° or less, and more preferably 87° or more and 93° or less.

[0266] The first liquid crystal cell 11A comprises, from the incident side to the emission side, a first substrate 100, a first liquid crystal layer 500 containing first liquid crystal molecules 510, and a second substrate 200. The first substrate 100 comprises a first support substrate 110 and a first planar electrode 120, and the second substrate 200 comprises a second support substrate 210 and a second planar electrode 220.

[0267] The second liquid crystal cell 11B comprises, from the incident side to the emission side, a third substrate 300, a second liquid crystal layer 600 containing second liquid crystal molecules 610, and a fourth substrate 400. The third substrate 300 comprises a third support substrate 310 and a third planar electrode 320, and the fourth substrate 400 comprises a fourth support substrate 410 and a fourth planar electrode 420.

[0268] Examples of insulating substrates such as the first support substrate 110, the second support substrate 210, the third support substrate 310, and the fourth support substrate 410 include glass substrates and plastic substrates. Examples of materials used for the glass substrate include float glass and soda-lime glass. Examples of materials used for the plastic substrate include polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, polycarbonate, and alicyclic polyolefins.

[0269] The first planar electrode 120, the second planar electrode 220, the third planar electrode 320, and the fourth planar electrode 420 can be formed, for example, by forming a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or tin oxide (SnO), or their alloys, in single-layer or multi-layer films by sputtering, and then patterning them using photolithography. In this specification, a planar electrode refers to an electrode in which no slits or openings are provided, at least in the area overlapping with the optical opening of the image element when viewed from above.

[0270] One of the first planar electrode 120 and the second planar electrode 220 is a pixel electrode, and the other is a common electrode. One of the third planar electrode 320 and the fourth planar electrode 420 is a pixel electrode, and the other is a common electrode.

[0271] The first liquid crystal layer 500 contains liquid crystal material. When a voltage is applied to the first liquid crystal layer 500, the orientation state of the first liquid crystal molecules 510 in the liquid crystal material changes according to the applied voltage, thereby changing the polarization state of light passing through the first liquid crystal layer 500.

[0272] The second liquid crystal layer 600 contains liquid crystal material. When a voltage is applied to the second liquid crystal layer 600, the orientation state of the second liquid crystal molecules 610 in the liquid crystal material changes according to the applied voltage, thereby changing the polarization state of light passing through the second liquid crystal layer 600.

[0273] The first liquid crystal molecule 510 and the second liquid crystal molecule 610 can be positive liquid crystal molecules with a positive dielectric constant anisotropy (Δε) as defined by the following formula (L), or they can be negative liquid crystal molecules with a negative dielectric constant anisotropy (Δε). Furthermore, one of the first liquid crystal molecule 510 and the second liquid crystal molecule 610 can be a positive liquid crystal molecule, and the other can be a negative liquid crystal molecule. In this embodiment, the case where the first liquid crystal molecule 510 and the second liquid crystal molecule 610 are positive liquid crystal molecules will be described as an example. Additionally, the long axis direction of the liquid crystal molecule is the direction of the hysteresis axis.

[0274] Δε = (dielectric constant along the long axis of the liquid crystal molecule) - (dielectric constant along the short axis of the liquid crystal molecule) ... (L)

[0275] The first liquid crystal layer 500 contains first liquid crystal molecules 510 twisted and oriented between the first substrate 100 and the second substrate 200. In the second state, the first liquid crystal molecules 510 are twisted and oriented from the first substrate 100 side to the second substrate 200 side.

[0276] The second liquid crystal layer 600 contains second liquid crystal molecules 610 that are twisted and oriented between the third substrate 300 and the fourth substrate 400. In the first state, the second liquid crystal molecules 610 are twisted and oriented from the third substrate 300 side to the fourth substrate 400 side.

[0277] The twisted orientation of the first liquid crystal molecule 510 and the second liquid crystal molecule 610 can be achieved, for example, by adding a chiral agent to the liquid crystal material. There are no particular limitations on the chiral agent; conventionally known chiral agents can be used. For example, S-811 (manufactured by "Melk Co.") can be used.

[0278] In this embodiment, the first liquid crystal molecule 510 and the second liquid crystal molecule 610 are positively oriented liquid crystal molecules with a twisted orientation. Therefore, when the first liquid crystal layer 500 is in a voltage-applied state and the second liquid crystal layer 600 is in a voltage-free state, a first state in which the first liquid crystal molecule 510 is vertically oriented and the second liquid crystal molecule 610 is twistedly oriented can be achieved. Furthermore, when the first liquid crystal layer 500 is in a voltage-free state and the second liquid crystal layer 600 is in a voltage-applied state, a second state in which the first liquid crystal molecule 510 is twistedly oriented and the second liquid crystal molecule 610 is vertically oriented can be achieved. In this embodiment, polarized light is not modulated in the first state and polarized light is modulated in the second state.

[0279] Preferably, the retardation of the first liquid crystal layer 500 in the second state with a wavelength of 550 nm is 200 nm or more and 260 nm or less, and the retardation of the second liquid crystal layer 600 in the first state with a wavelength of 550 nm is 210 nm or more and 260 nm or less. By adopting this method, it is possible to switch between polarized light modulation and polarized light non-modulation with a wider bandwidth. In this specification, the voltage application state in which a voltage of more than a threshold is applied to the liquid crystal layer is also simply referred to as "voltage application state" or "voltage application time", and the voltage-free state in which a voltage less than a threshold is applied to the liquid crystal layer (including no voltage application) is also simply referred to as "voltage-free state" or "voltage-free application time".

[0280] Preferably, the first liquid crystal molecule 510 in the second state is oriented with a twist angle of 61° or more and 75° or less, and the second liquid crystal molecule 610 in the first state is oriented with a twist angle of 64° or more and 74° or less. By employing this method, it is possible to switch between polarized light modulation and polarized light non-modulation with a wider bandwidth. Furthermore, the twist angle of the liquid crystal molecules can be determined using an Axoscan (manufactured by "OptoSynes") by measuring the noise matrix after the liquid crystal layer is emitted.

[0281] The twist angle of the first liquid crystal molecule 510 in the second state refers to the angle formed by the orientation angle of the first liquid crystal molecule 511 on the first substrate 100 side and the orientation angle of the first liquid crystal molecule 512 on the second substrate 200 side. The twist angle of the second liquid crystal molecule 610 in the first state refers to the angle formed by the orientation angle of the second liquid crystal molecule 611 on the third substrate 300 side and the orientation angle of the second liquid crystal molecule 612 on the fourth substrate 400 side.

[0282] Preferably, in the second state, the azimuth angle of the orientation direction 511A of the first liquid crystal molecule 511 on the first substrate 100 side is -9° or more and 7° or less, and in the first state, the azimuth angle of the orientation direction 611A of the second liquid crystal molecule 611 on the third substrate 300 side is 85° or more and 96° or less. By adopting this method, it is possible to switch between polarized light modulation and polarized light non-modulation with a wider bandwidth. For example, the azimuth angle of the orientation direction 511A of the first liquid crystal molecule 511 on the first substrate 100 side in the second state can be set to 0°, and the azimuth angle of the orientation direction 611A of the second liquid crystal molecule 611 on the third substrate 300 side in the first state can be set to 90°.

[0283] Preferably, the first liquid crystal cell 11A has a first alignment film 41 on the first liquid crystal layer 500 side of the first substrate 100 and a second alignment film 42 on the first liquid crystal layer 500 side of the second substrate 200. Preferably, the second liquid crystal cell 11B has a third alignment film 43 on the second liquid crystal layer 600 side of the third substrate 300 and a fourth alignment film 44 on the second liquid crystal layer 600 side of the fourth substrate 400.

[0284] The first alignment film 41 and the second alignment film 42 have the function of controlling the orientation of the first liquid crystal molecules 510 in the first liquid crystal layer 500. When the first liquid crystal layer 500 is in a state where no voltage is applied, the orientation of the first liquid crystal molecules 510 in the first liquid crystal layer 500 is mainly controlled by the action of the first alignment film 41 and the second alignment film 42.

[0285] The third alignment film 43 and the fourth alignment film 44 have the function of controlling the orientation of the second liquid crystal molecules 610 in the second liquid crystal layer 600. When the second liquid crystal layer 600 is in a state where no voltage is applied, the orientation of the second liquid crystal molecules 610 in the second liquid crystal layer 600 is mainly controlled by the action of the third alignment film 43 and the fourth alignment film 44. The first alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44 are also referred to as alignment films below.

[0286] As a material for alignment films, common materials can be used in the field of liquid crystal display panels, such as polymers with polyimide main chains, polymers with polyamic acid main chains, and polymers with polysiloxane main chains. Alignment films can be formed by coating alignment film materials; the coating method is not particularly limited, and for example, flexographic printing or inkjet coating can be used.

[0287] The alignment film can be a horizontally aligned film in which the liquid crystal molecules are aligned approximately horizontally with respect to the film surface, or a vertically aligned film in which the liquid crystal molecules are aligned approximately perpendicularly with respect to the film surface. In this embodiment, the case where the first alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44 are horizontally aligned films will be described.

[0288] The horizontal alignment film has the function of aligning liquid crystal molecules in the liquid crystal layer in a horizontal direction relative to the surface of the horizontal alignment film in the pixel region when no voltage is applied to the liquid crystal layer. Here, the horizontal alignment of the liquid crystal molecules relative to the surface of the horizontal alignment film means that the pretilt angle of the liquid crystal molecules relative to the surface of the horizontal alignment film is 0° to 5°, preferably 0° to 2°, and more preferably 0° to 1°. The pretilt angle of the liquid crystal molecules refers to the angle at which the long axis of the liquid crystal molecules is tilted relative to the main surface of each substrate when no voltage is applied to the liquid crystal layer.

[0289] The vertical alignment film has the function of aligning liquid crystal molecules in the liquid crystal layer in the vertical direction relative to the surface of the vertical alignment film in the pixel region when no voltage is applied to the liquid crystal layer. Here, the vertical alignment of liquid crystal molecules relative to the surface of the vertical alignment film means that the pretilt angle of the liquid crystal molecules relative to the surface of the vertical alignment film is 86° to 90°, preferably 87° to 89°, and more preferably 87.5° to 89°.

[0290] Furthermore, the alignment film can be either an optically aligned film with optical functional groups that has undergone optical alignment treatment, or a rubbing-aligned film that has undergone rubbing treatment. By performing the alignment treatment, the liquid crystal molecules can be pre-tilted.

[0291] The orientation direction of liquid crystal molecules is the direction of the major alignment axis (the direction in which the long axes of molecules in a nematic liquid crystal are average aligned). Therefore, the azimuth angle of the orientation direction 511A of the first liquid crystal molecule 511 on the first substrate 100 side is the same as the azimuth angle of the alignment processing direction of the alignment film (first alignment film 41) disposed on the first liquid crystal layer 500 side of the first substrate 100. The azimuth angle of the orientation direction 512A of the first liquid crystal molecule 512 on the second substrate 200 side is the same as the azimuth angle of the alignment processing direction of the alignment film (second alignment film 42) disposed on the first liquid crystal layer 500 side of the second substrate 200. The azimuth angle of the orientation direction 611A of the second liquid crystal molecule 611 on the third substrate 300 side is the same as the azimuth angle of the alignment processing direction of the alignment film (third alignment film 43) disposed on the second liquid crystal layer 600 side of the third substrate 300. The orientation angle of the second liquid crystal molecule 612 on the fourth substrate 400 side is consistent with the orientation angle of the alignment processing direction of the alignment film (fourth alignment film 44) disposed on the second liquid crystal layer 600 side of the fourth substrate 400.

[0292] Figure 7 This is a cross-sectional schematic diagram illustrating the first state of the optical element according to the first embodiment. Figure 8 This is a cross-sectional schematic diagram illustrating the second state of the optical element according to the first embodiment. In this embodiment, the optical element 10 preferably has a negative C-plate 12 between the first liquid crystal cell 11A and the second liquid crystal cell 11B. By employing this method, thus... Figure 7 As shown, in the first state, the phase difference of the first liquid crystal cell 11A during tilted incidence can be eliminated using the negative C-plate 12. Furthermore, as... Figure 8 As shown, in the second state, the phase difference of the second liquid crystal cell 11B during tilted incidence can be eliminated using the negative C plate 12. As a result, only the undriven liquid crystal layer can be made effective, and polarization modulation and polarization non-modulation can be switched with a wider bandwidth and a wider viewing angle.

[0293] As a negative C plate 12, for example, a stretched cyclic olefin polymer film can be cited.

[0294] The thickness-direction delay Rth of the negative C plate 12 is preferably -220 nm or more and 0 nm or less. By employing this method, it is possible to switch between polarized light modulation and polarized light non-modulation with a wider bandwidth. Sometimes, for ease of manufacturing, the negative C plate 12 has an in-plane phase difference of about a few nanometers, therefore, the in-plane phase difference of the negative C plate 12 is, for example, 0 nm or more and 5 nm or less.

[0295] like Figure 1 As shown, in this embodiment, the optical element 10 preferably has a first 1 / 4 wavelength film 13 on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B or on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A. By employing this method, it is possible to switch between polarized light modulation and polarized light non-modulation with a wider bandwidth.

[0296] In this embodiment, the optical element 10 preferably has a second quarter-wavelength film 14 on the side of the first quarter-wavelength film 13 opposite to the first liquid crystal cell 11A and the second liquid crystal cell 11B. By adopting this method, it is possible to further switch between polarized light modulation and polarized light non-modulation with a wide bandwidth.

[0297] A quarter-wavelength film (specifically, the first quarter-wavelength film 13 and the second quarter-wavelength film 14) only needs to impart an in-plane phase difference of at least 20 nm and less than 240 nm to light with a wavelength of 550 nm.

[0298] Examples of materials that can be used as quarter-wavelength films include photopolymerizable liquid crystal materials. Examples of compositions of photopolymerizable liquid crystal materials include those with photopolymerizable groups such as acrylate groups and methacrylate groups at the ends of the liquid crystal molecule backbone.

[0299] A quarter-wavelength film can be formed, for example, by the following method. First, a photopolymerizable liquid crystal material is dissolved in an organic solvent such as propylene glycol monomethyl ether acetate (PGMEA). Next, the resulting solution is coated onto the surface of a substrate (e.g., a polyethylene terephthalate (PET) film) to form a solution coating. Then, the solution coating is sequentially pre-fired, irradiated with light (e.g., ultraviolet light), and formally fired, thereby forming a quarter-wavelength film.

[0300] Alternatively, a chiral agent can be added to the above-mentioned photopolymerizable liquid crystal material, and the liquid crystal polymerized under a 70° twist can be used as a 1 / 4 wavelength film.

[0301] As a quarter-wavelength membrane, for example, a stretched polymer membrane can also be used. Examples of materials that can be used as polymer films include cyclic olefin polymers, polycarbonate, polysulfone, polyethersulfone, polyethylene terephthalate, polyethylene, polyvinyl alcohol, norbornene, triacetyl cellulose, diethyl cellulose, etc.

[0302] The first quarter-wavelength film 13 preferably has reverse wavelength dispersion characteristics. By employing this method, it is possible to switch between polarized light modulation and polarized light non-modulation over a wider bandwidth. Here, in this specification, "wavelength dispersion of the retardation film" refers to the correlation between the absolute value of the phase difference imparted by the retardation film and the wavelength of the incident light. The property that the absolute value of the phase difference imparted by the retardation film does not change even when the wavelength of the incident light changes in the visible light region is called "flat wavelength dispersion characteristics." Furthermore, the property that the absolute value of the phase difference imparted by the retardation film decreases as the wavelength of the incident light increases in the visible light region is called "positive wavelength dispersion characteristics," and the property that the absolute value of the phase difference imparted by the retardation film increases as the wavelength of the incident light increases in the visible light region is called "reverse wavelength dispersion characteristics."

[0303] The in-plane phase difference of the first quarter-wavelength film 13 at wavelength 450 nm is preferably more than 0.7 times and less than 1 times the in-plane phase difference at wavelength 550 nm. By adopting this method, it is possible to switch between polarized light modulation and polarized light non-modulation in a wider frequency band.

[0304] The in-plane phase difference of the first quarter-wavelength film 13 at a wavelength of 650 nm is preferably more than 1 and less than 1.3 times the in-plane phase difference at a wavelength of 550 nm. By employing this method, it is possible to switch between polarized light modulation and polarized light non-modulation over a wider frequency band.

[0305] Figure 3 The azimuth angle of the hysteresis axis 13A of the first quarter-wavelength film 13 shown is preferably 52° or more and 60° or less. By employing this method, it is possible to switch between polarized light modulation and polarized light non-modulation over a wider frequency band.

[0306] The in-plane phase difference of the first quarter-wavelength film 13 at a wavelength of 550 nm is preferably greater than 90 nm and less than 170 nm. By adopting this method, it is possible to switch between polarized light modulation and polarized light non-modulation in a wider frequency band.

[0307] The second quarter-wavelength film 14 preferably has flat wavelength dispersion characteristics. By employing this method, it is possible to switch between polarized light modulation and polarized light non-modulation over a wider frequency band.

[0308] Figure 3The azimuth angle of the hysteresis axis 14A of the second quarter-wavelength film 14 shown is preferably 8° or more and 18° or less. By adopting this method, it is possible to switch between polarized light modulation and polarized light non-modulation over a wider frequency band.

[0309] The in-plane phase difference of the second quarter-wavelength film 14 at a wavelength of 550 nm is preferably greater than 120 nm and less than 150 nm. By adopting this method, it is possible to switch between polarized light modulation and polarized light non-modulation in a wider frequency band.

[0310] Preferably, the light incident on the optical element 10 is circularly polarized light. By adopting this method, it is possible to realize an optical element 10 that can switch the polarization state of circularly polarized light.

[0311] (Modification 1 of the first embodiment)

[0312] In this modified example, the optical element 10 of the first embodiment described above is further provided with a first positive C-plate on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, and a second positive C-plate on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

[0313] Figure 9 This is a cross-sectional schematic diagram of the optical element in a variation of the first embodiment, Example 1. Figure 9 As shown, the optical element 10 of this embodiment also has a first positive C-plate 19A on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, and a second positive C-plate 19B on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A. By adopting this method, polarization modulation and polarization non-modulation can be achieved with a wider bandwidth.

[0314] like Figure 9 As shown, the second positive C-plate 19B is preferably disposed between the second liquid crystal cell 11B and the first 1 / 4 wavelength film 13. By adopting this method, polarization modulation and polarization non-modulation can be achieved with a wider bandwidth.

[0315] The first positive C-plate 19A and the second positive C-plate 19B can be, for example, thin films obtained by longitudinal and transverse biaxial stretching of thin films containing materials with inherent negative birefringence as components, or thin films coated with liquid crystal materials such as nematic liquid crystals.

[0316] The thickness retardation Rth of the first positive C plate 19A is preferably 0 nm or more and 190 nm or less. By adopting this method, it is possible to switch between polarized light modulation and polarized light non-modulation with a wider bandwidth.

[0317] The thickness retardation Rth of the second positive C plate 19B is preferably 0 nm or more and 220 nm or less. By adopting this method, it is possible to switch between polarized light modulation and polarized light non-modulation with a wider bandwidth.

[0318] For ease of manufacturing, the first positive C-plate 19A and the second positive C-plate 19B sometimes exhibit an in-plane phase difference of several nanometers. Therefore, the in-plane phase difference between the first positive C-plate 19A and the second positive C-plate 19B is, for example, 0 nm or more and 5 nm or less. Furthermore, the thickness direction retardation Rth of the first positive C-plate 19A and the second positive C-plate 19B can be the same or different. Additionally, the in-plane phase difference between the first positive C-plate 19A and the second positive C-plate 19B can be the same or different.

[0319] (Modification 2 of the first embodiment)

[0320] In the above-described variation 1 of the first embodiment, the optical element 10 is described as having a first positive C-plate 19A on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, a second positive C-plate 19B on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A, a first 1 / 4 wavelength film 13, and a second 1 / 4 wavelength film 14. However, it is also possible that the first positive C-plate 19A is not arranged on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, and the phase retardation layer arranged on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A is not limited to the variation 1 of the first embodiment, and may also be arranged in the manner described below.

[0321] <First Composition>

[0322] Figure 81 This is a cross-sectional schematic diagram of an optical element having the first configuration of a variation of the first embodiment, Example 2. Figure 81 As shown, the optical element 10 with the first configuration of the first embodiment 2 has a first A plate 51 and a second A plate 52 disposed further away from the emission side than the first A plate 51 on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A. That is, the optical element 10 has the first A plate 51 and the second A plate 52 sequentially disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A, starting from the side closest to the second liquid crystal cell 11B. Furthermore, the first positive C plate 19A is not disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B.

[0323] The refractive indices (nx, ny, nz) of plate A satisfy either (Equation N1) or (Equation N2). Plate A satisfying (Equation N1) is also called a positive A plate. Plate A satisfying (Equation N2) is also called a negative A plate. First A plate 51 and second A plate 52 are preferably positive A plates. In the case where the first quarter-wavelength film 13 and the second quarter-wavelength film 14 in the first embodiment described above are positive A plates, and both first A plate 51 and second A plate 52 are positive A plates, then in the first embodiment described above, the first quarter-wavelength film 13 corresponds to the first A plate 51, and the second quarter-wavelength film 14 corresponds to the second A plate 52. Furthermore, due to manufacturing variations, a positive A plate may be nx > ny > nz, and a negative A plate may be nz > nx > ny or nx > nz > ny.

[0324] nx > ny = nz ... (Equation N1)

[0325] nz = nx > ny……(Equation N2)

[0326] Here, "nx" is the refractive index in the direction of maximum in-plane refractive index (i.e., the hysteresis axis direction), "ny" is the refractive index in the direction orthogonal to the hysteresis axis in-plane, and "nz" is the refractive index in the thickness direction. Unless otherwise specified, the refractive index refers to the value for light at 23°C and a wavelength of 550 nm. Furthermore, the incident side refers to the side of the optical element where light is incident, and the exiting side refers to the side of the optical element where light exits.

[0327] The first A plate 51 may have reverse wavelength dispersion characteristics, or even flat wavelength dispersion characteristics, or positive wavelength dispersion characteristics (forward wavelength dispersion characteristics), but it is preferred to have reverse wavelength dispersion characteristics. The second A plate 52 may have reverse wavelength dispersion characteristics, flat wavelength dispersion characteristics, or positive wavelength dispersion characteristics, but it is preferred to have flat wavelength dispersion characteristics or positive wavelength dispersion characteristics.

[0328] by Figure 81 Based on the first configuration shown, the phase retardation layer is preferably configured in a manner that satisfies at least one of (conditions 1) to (condition 5) shown below. Furthermore, the refractive index (nx, ny, nz) of the C plate satisfies (Equation N3) or (Equation N4) below. A C plate satisfying (Equation N3) is also called a positive C plate. A C plate satisfying (Equation N4) is also called a negative C plate. Furthermore, due to manufacturing variations, the C plate may also have an in-plane phase retardation Re of several nm.

[0329] nz>nx=ny……(Equation N3)

[0330] nx = ny > nz ... (Equation N4)

[0331] (Condition 1) The optical element 10 has a positive C-plate on at least one side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B and on the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A. By adopting this method, the viewing angle can be improved.

[0332] (Condition 2) When at least one of the first A plate 51 and the second A plate 52 is a positive A plate, the optical element 10 has a positive C plate on at least one of the incident side and the exit side of the positive A plate. By adopting this method, the viewing angle can be improved.

[0333] (Condition 3) When at least one of the first A plate 51 and the second A plate 52 is a negative A plate, the optical element 10 has a negative C plate on at least one of the incident side and the exit side of the negative A plate. By adopting this method, the viewing angle can be improved.

[0334] (Condition 4) When at least one of the first A plate 51 and the second A plate 52 is a negative A plate, the optical element 10 has a positive C plate or a negative C plate between the second liquid crystal cell 11B and the negative A plate. By adopting this method, the viewing angle can be improved.

[0335] (Condition 5) When one of the first A plate 51 and the second A plate 52 is a positive A plate and the other is a negative A plate, there is a positive C plate or a negative C plate between the positive A plate and the negative A plate. By adopting this method, the viewing angle can be improved.

[0336] Based on the first configuration, the following describes configurations (second configuration to seventeenth configuration) that satisfy at least one of the conditions shown in (condition 1) to (condition 5) above.

[0337] <Second Composition>

[0338] Figures 82-85 This is an example of a cross-sectional schematic diagram of an optical element with a second configuration having a variation of the first embodiment, Example 2. Figures 82-85 As shown, in the first configuration described above, the first A plate 51 is a positive A plate 51PA, the second A plate 52 is a positive A plate 52PA, and the second optical element 10 also includes a C plate 61, which is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B or on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A.

[0339] When C-plate 61 is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B, C-plate 61 is preferably a positive C-plate 61PC. When C-plate 61 is disposed on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A and a positive A-plate 52PA is disposed adjacent to the incident side of C-plate 61, C-plate 61 is preferably a positive C-plate 61PC.

[0340] <Third Composition>

[0341] Figures 86-91 This is an example of a cross-sectional schematic diagram of an optical element with a third configuration according to a variation 2 of the first embodiment. For example... Figures 86-91 As shown, in the first configuration described above, the third optical element 10 includes a first A plate 51 (positive A plate 51PA), a second A plate 52 (positive A plate 52PA), and also includes a first C plate 61 and a second C plate 62 disposed further away from the emission side than the first C plate 61. The first C plate 61 is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B, or on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, and the second C plate 62 is disposed on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A.

[0342] When the first C-plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, the first C-plate 61 is preferably a positive C-plate 61PC. When the second C-plate 62 is disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A, and a positive A-plate 52PA is disposed adjacent to the incident side of the second C-plate 62, the second C-plate 62 is preferably a positive C-plate 62PC. Furthermore, Figure 91 The configuration shown is equivalent to the configuration of the first embodiment described above.

[0343] When multiple C-plates are arranged on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, it is preferable that the multiple C-plates are not adjacent to each other. Specifically, it is preferable that at least one A-plate is arranged between the multiple C-plates.

[0344] <Fourth Composition>

[0345] Figures 92-95 This is an example of a cross-sectional schematic diagram of an optical element with a fourth configuration, as described in Modification 2 of the first embodiment. Figures 92-95As shown, in the first configuration described above, the fourth optical element 10 includes a first A plate 51 (positive A plate 51PA) and a second A plate 52 (positive A plate 52PA). It also includes a first C plate 61, a second C plate 62 positioned further from the emission side than the first C plate 61, and a third C plate 63 positioned further from the emission side than the second C plate 62. The first C plate 61 is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B, or on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A. The second C plate 62 and the third C plate 63 are disposed on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A.

[0346] When the first C-plate 61 is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B, the first C-plate 61 is preferably a positive C-plate 61PC. When the third C-plate 63 is disposed on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A and a positive A-plate 52PA is disposed adjacent to the incident side of the third C-plate 63, the third C-plate 63 is preferably a positive C-plate 63PC.

[0347] When multiple C-plates are arranged on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, it is preferable that the multiple C-plates are not adjacent to each other. Specifically, it is preferable that at least one A-plate is arranged between the multiple C-plates.

[0348] <Fifth Composition>

[0349] Figure 96 This is an example of a cross-sectional schematic diagram of an optical element having a fifth configuration according to a variation of the first embodiment, Example 2. Figure 96 As shown, in the first configuration described above, the fifth optical element 10 includes a first A plate 51 (positive A plate 51PA) and a second A plate 52 (positive A plate 52PA), and further comprises: a first C plate 61; a second C plate 62 disposed further from the emission side than the first C plate 61; a third C plate 63 disposed further from the emission side than the second C plate 62; and a fourth C plate 64 disposed further from the emission side than the third C plate 63. The first C plate 61 is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B, or on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A. The second C plate 62, the third C plate 63, and the fourth C plate 64 are disposed on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A.

[0350] When the first C-plate 61 is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B, the first C-plate 61 is preferably a positive C-plate 61PC. When the fourth C-plate 64 is disposed on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, and a positive A-plate 52PA is disposed adjacent to the incident side of the fourth C-plate 64, the fourth C-plate 64 is preferably a positive C-plate 64PC.

[0351] When multiple C-plates are arranged on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, it is preferable that the multiple C-plates are not adjacent to each other. Specifically, it is preferable that at least one A-plate is arranged between the multiple C-plates.

[0352] <Sixth Composition>

[0353] Figures 97-101 This is an example of a cross-sectional schematic diagram of an optical element with a sixth configuration according to a variation of the first embodiment, Example 2. Figures 97-101 As shown, in the first configuration described above, the optical element 10 of the sixth configuration has a first A plate 51 as a positive A plate 51PA, a second A plate 52 as a negative A plate 52NA, and also includes a C plate 61, which is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B or on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A.

[0354] When C-plate 61 is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B, C-plate 61 is preferably a positive C-plate 61PC. When C-plate 61 is disposed on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, and a negative A-plate 52NA is disposed adjacent to the incident side of C-plate 61, C-plate 61 is preferably a negative C-plate 61NC.

[0355] <Seventh Composition>

[0356] Figures 102-110 This is an example of a cross-sectional schematic diagram of an optical element with a seventh configuration, as described in Modification 2 of the first embodiment. Figures 102-110 As shown, in the first configuration described above, the seventh optical element 10 includes a first A plate 51 (positive A plate 51PA), a second A plate 52 (negative A plate 52NA), a first C plate 61, and a second C plate 62 disposed further away from the emission side than the first C plate 61. The first C plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, or on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A, and the second C plate 62 is disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

[0357] When the first C-plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, the first C-plate 61 is preferably a positive C-plate 61PC. When the second C-plate 62 is disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A, and a negative A-plate 52NA is disposed adjacent to the incident side of the second C-plate 62, the second C-plate 62 is preferably a negative C-plate 62NC.

[0358] When multiple C-plates are arranged on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, it is preferable that the multiple C-plates are not adjacent to each other. Specifically, it is preferable that at least one A-plate is arranged between the multiple C-plates.

[0359] <Eighth Composition>

[0360] Figures 111-117 This is an example of a cross-sectional schematic diagram of an optical element having an eighth configuration according to a variation of the first embodiment, Example 2. Figures 111-117 As shown, in the first configuration described above, the optical element 10 of the eighth configuration has a first A plate 51 (positive A plate 51PA) and a second A plate 52 (negative A plate 52NA). It also includes a first C plate 61, a second C plate 62 positioned further from the emission side than the first C plate 61, and a third C plate 63 positioned further from the emission side than the second C plate 62. The first C plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, or on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A. The second C plate 62 and the third C plate 63 are disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

[0361] When the first C-plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, the first C-plate 61 is preferably a positive C-plate 61PC. When the third C-plate 63 is disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A, and a negative A-plate 52NA is disposed adjacent to the incident side of the third C-plate 63, the third C-plate 63 is preferably a negative C-plate 63NC.

[0362] When multiple C-plates are arranged on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, it is preferable that the multiple C-plates are not adjacent to each other. Specifically, it is preferable that at least one A-plate is arranged between the multiple C-plates.

[0363] <Ninth Composition>

[0364] Figures 118-119 This is an example of a cross-sectional schematic diagram of an optical element having a ninth configuration according to a variation of the first embodiment, Example 2. Figures 118-119As shown, in the first configuration described above, the optical element 10 of the ninth configuration has a first A plate 51 (positive A plate 51PA) and a second A plate 52 (negative A plate 52NA). It also includes a first C plate 61, a second C plate 62 positioned further from the emission side than the first C plate 61, a third C plate 63 positioned further from the emission side than the second C plate 62, and a fourth C plate 64 positioned further from the emission side than the third C plate 63. The first C plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, or on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A. The second C plate 62, the third C plate 63, and the fourth C plate 64 are disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

[0365] When the first C-plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, the first C-plate 61 is preferably a positive C-plate 61PC. When the fourth C-plate 64 is disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A, and a negative A-plate 52NA is disposed adjacent to the incident side of the fourth C-plate 64, the fourth C-plate 64 is preferably a negative C-plate 64NC.

[0366] When multiple C-plates are arranged on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, it is preferable that the multiple C-plates are not adjacent to each other. Specifically, it is preferable that at least one A-plate is arranged between the multiple C-plates.

[0367] <Tenth Composition>

[0368] Figures 120-125 This is an example of a cross-sectional schematic diagram of an optical element having the tenth configuration of a variation 2 of the first embodiment. For example... Figures 120-125 As shown, in the first configuration described above, the first A plate 51 is a negative A plate 51NA, the second A plate 52 is a positive A plate 52PA, and the tenth optical element 10 also includes a C plate 61, which is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B or on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A.

[0369] When C-plate 61 is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B, C-plate 61 is preferably a positive C-plate 61PC. When C-plate 61 is disposed on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, and a positive A-plate 52PA is disposed adjacent to the incident side of C-plate 61, the positive C-plate 61 is preferably 61PC.

[0370] <Eleventh Composition>

[0371] Figures 126-138This is an example of a cross-sectional schematic diagram of an optical element having the eleventh configuration of a variation of the first embodiment, Example 2. Figures 126-138 As shown, in the first configuration described above, the eleventh optical element 10 has a first A plate 51 that is a negative A plate 51NA, a second A plate 52 that is a positive A plate 52PA, and includes a first C plate 61 and a second C plate 62 disposed further away from the emission side than the first C plate 61. The first C plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, or on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A, and the second C plate 62 is disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

[0372] When the first C-plate 61 is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B, the first C-plate 61 is preferably a positive C-plate 61PC. When the second C-plate 62 is disposed on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, and a positive A-plate 52PA is disposed adjacent to the incident side of the second C-plate 62, the second C-plate 62 is preferably a positive C-plate 62PC.

[0373] When multiple C-plates are arranged on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, it is preferable that the multiple C-plates are not adjacent to each other. Specifically, it is preferable that at least one A-plate is arranged between the multiple C-plates.

[0374] <Twelfth Composition>

[0375] Figures 139-150 This is an example of a cross-sectional schematic diagram of an optical element having a twelfth configuration of a variation of the first embodiment, Example 2. Figures 139-150 As shown, in the first configuration described above, the twelfth optical element 10 has a first A plate 51 that is a negative A plate 51NA, a second A plate 52 that is a positive A plate 52PA, and includes a first C plate 61, a second C plate 62 disposed further away from the emission side than the first C plate 61, and a third C plate 63 disposed further away from the emission side than the second C plate 62. The first C plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, or on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A. The second C plate 62 and the third C plate 63 are disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

[0376] When the first C-plate 61 is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B, the first C-plate 61 is preferably a positive C-plate 61PC. When the third C-plate 63 is disposed on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, and a positive A-plate 52PA is disposed adjacent to the incident side of the third C-plate 63, the third C-plate 63 is preferably a positive C-plate 63PC.

[0377] When multiple C-plates are arranged on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, it is preferable that the multiple C-plates are not adjacent to each other. Specifically, it is preferable that at least one A-plate is arranged between the multiple C-plates.

[0378] <Thirteenth Composition>

[0379] Figures 151-154 This is an example of a cross-sectional schematic diagram of an optical element having the thirteenth configuration of a variation of the first embodiment, Example 2. Figures 151-154 As shown, in the first configuration described above, the thirteenth optical element 10 includes a first A plate 51 (negative A plate 51NA) and a second A plate 52 (positive A plate 52PA). It also comprises a first C plate 61, a second C plate 62 positioned further from the emission side than the first C plate 61, a third C plate 63 positioned further from the emission side than the second C plate 62, and a fourth C plate 64 positioned further from the emission side than the third C plate 63. The first C plate 61 is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B, or on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A. The second C plate 62, the third C plate 63, and the fourth C plate 64 are disposed on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A.

[0380] When the first C-plate 61 is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B, the first C-plate 61 is preferably a positive C-plate 61PC. When the fourth C-plate 64 is disposed on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, and a positive A-plate 52PA is disposed adjacent to the incident side of the fourth C-plate 64, the fourth C-plate 64 is preferably a positive C-plate 64PC.

[0381] When multiple C-plates are arranged on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, it is preferable that the multiple C-plates are not adjacent to each other. Specifically, it is preferable that at least one A-plate is arranged between the multiple C-plates.

[0382] <The Fourteenth Composition>

[0383] Figures 155-159 This is an example of a cross-sectional schematic diagram of an optical element having the fourteenth configuration of a variation of the first embodiment, Example 2. Figures 155-159 As shown, in the first configuration described above, the first A plate 51 is a negative A plate 51NA, the second A plate 52 is a negative A plate 52NA, and the fourteenth optical element 10 also includes a C plate 61, which is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B or on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A.

[0384] When C-plate 61 is disposed on the side of the first liquid crystal unit 11A opposite to the second liquid crystal unit 11B, C-plate 61 is preferably a positive C-plate 61PC. When C-plate 61 is disposed on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, and a negative A-plate 52NA is disposed adjacent to the incident side of C-plate 61, C-plate 61 is preferably a negative C-plate 61NC.

[0385] <Fifteenth Composition>

[0386] Figures 160-168 This is an example of a cross-sectional schematic diagram of an optical element having the fifteenth configuration of a variation of the first embodiment, Example 2. Figures 160-168 As shown, in the first configuration described above, the optical element 10 of the fifteenth configuration has a first A plate 51 that is a negative A plate 51NA, a second A plate 52 that is a negative A plate 52NA, and includes a first C plate 61 and a second C plate 62 disposed further away from the emission side than the first C plate 61. The first C plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, or on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A, and the second C plate 62 is disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

[0387] When the first C-plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, the first C-plate 61 is preferably a positive C-plate 61PC. When the second C-plate 62 is disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A, and a negative A-plate 52NA is disposed adjacent to the incident side of the second C-plate 62, the second C-plate 62 is preferably a negative C-plate 62NC.

[0388] When multiple C-plates are arranged on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, it is preferable that the multiple C-plates are not adjacent to each other. Specifically, it is preferable that at least one A-plate is arranged between the multiple C-plates.

[0389] <Sixteenth Composition>

[0390] Figures 169-175 This is an example of a cross-sectional schematic diagram of an optical element having a sixteenth configuration of a variation of the first embodiment 2. Figures 169-175As shown, in the first configuration described above, the sixteenth optical element 10 has a first A plate 51 that is a negative A plate 51NA, a second A plate 52 that is a negative A plate 52NA, and includes a first C plate 61, a second C plate 62 that is positioned further away from the emission side than the first C plate 61, and a third C plate 63 that is positioned further away from the emission side than the second C plate 62. The first C plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, or on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A. The second C plate 62 and the third C plate 63 are disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

[0391] When the first C-plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, the first C-plate 61 is preferably a positive C-plate 61PC. When the third C-plate 63 is disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A, and a negative A-plate 52NA is disposed adjacent to the incident side of the third C-plate 63, the third C-plate 63 is preferably a negative C-plate 63NC.

[0392] When multiple C-plates are arranged on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, it is preferable that the multiple C-plates are not adjacent to each other. Specifically, it is preferable that at least one A-plate is arranged between the multiple C-plates.

[0393] <Seventeenth Composition>

[0394] Figures 176-177 This is an example of a cross-sectional schematic diagram of an optical element having the seventeenth configuration of a variation of the first embodiment, Example 2. Figures 176-177 As shown, in the first configuration described above, the seventeenth optical element 10 has a first A plate 51 that is a negative A plate 51NA, a second A plate 52 that is a negative A plate 52NA, and includes a first C plate 61, a second C plate 62 that is positioned further from the emission side than the first C plate 61, a third C plate 63 that is positioned further from the emission side than the second C plate 62, and a fourth C plate 64 that is positioned further from the emission side than the third C plate 63. The first C plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, or on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A. The second C plate 62, the third C plate 63, and the fourth C plate 64 are disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

[0395] When the first C-plate 61 is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, the first C-plate 61 is preferably a positive C-plate 61PC. When the fourth C-plate 64 is disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A, and a negative A-plate 52NA is disposed adjacent to the incident side of the fourth C-plate 64, the fourth C-plate 64 is preferably a negative C-plate 64NC.

[0396] When multiple C-plates are arranged on the side of the second liquid crystal unit 11B opposite to the first liquid crystal unit 11A, it is preferable that the multiple C-plates are not adjacent to each other. Specifically, it is preferable that at least one A-plate is arranged between the multiple C-plates.

[0397] (Modification 3 of the first embodiment)

[0398] In this modified example, the optical element 10 of the first embodiment described above is provided with a first phase reversal film and a second phase reversal film on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

[0399] Figure 200 This is a cross-sectional schematic diagram of the optical element in Modification 3 of the first embodiment. (As shown) Figure 200 As shown, the optical element 10 of this modified example further includes: a first retardation film 71 disposed on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A, and a second retardation film 72 disposed on the side of the first retardation film 71 opposite to the second liquid crystal cell 11B. By adopting this method, a wide viewing angle can be achieved.

[0400] The first phase retardation film 71 and the second phase retardation film 72 are preferably biaxial films. The biaxial films are preferably biaxial films with refractive indices (nx, ny, nz) that satisfy the following (Equation N5) and (Equation N6).

[0401] nx > ny……(Equation N5)

[0402] nz=(nx+ny) / 2……(Equation N6)

[0403] The materials of the first phase retardation film 71 and the second phase retardation film 72 are not particularly limited. For example, materials obtained by stretching a polymer film, materials obtained by fixing the orientation of a liquid crystal material, or thin plates made of inorganic materials can be used.

[0404] The methods for forming the first phase difference film 71 and the second phase difference film 72 are not particularly limited. When formed from a polymer film, solvent casting, melt extrusion, etc., can be used, for example. As long as the desired phase difference is exhibited, stretching can be performed or not. The stretching method is also not particularly limited. In addition to roll stretching, roll compression stretching, tenter frame transverse uniaxial stretching, tilt stretching, and longitudinal and transverse biaxial stretching, special stretching methods that stretch under the shrinkage force of heat-shrinkable films can also be used. Furthermore, when formed from a liquid crystal material, for example, a method of coating the liquid crystal material onto a substrate film that has undergone alignment treatment and then fixing the alignment can be used. As long as the desired phase difference is exhibited, methods such as not performing special alignment treatment on the substrate film or peeling it off from the substrate film after alignment fixation and transferring it to other films can also be used.

[0405] The in-plane phase difference Re of the first phase retardation film 71 at a wavelength of 550 nm is preferably 90 nm or more and 170 nm or less. The in-plane phase difference of the first phase retardation film 71 at a wavelength of 450 nm is preferably more than 1.0 times and less than 1.1 times the in-plane phase difference at a wavelength of 550 nm. The in-plane phase difference of the first phase retardation film 71 at a wavelength of 650 nm is preferably more than 0.9 times and less than 1.0 times the in-plane phase difference at a wavelength of 550 nm.

[0406] The in-plane phase difference Re of the second phase retardation film 72 at a wavelength of 550 nm is preferably 40 nm or more and 210 nm or less. The in-plane phase difference of the second phase retardation film 72 at a wavelength of 450 nm is preferably more than 1.0 times and less than 1.1 times the in-plane phase difference at a wavelength of 550 nm. The in-plane phase difference of the second phase retardation film 72 at a wavelength of 650 nm is preferably more than 0.9 times and less than 1.0 times the in-plane phase difference at a wavelength of 550 nm.

[0407] The difference between the in-plane phase difference Re of the first phase retardation film 71 and the in-plane phase difference Re of the second phase retardation film 72 is preferably 0 nm or more and 10 nm or less. By adopting this method, the first phase retardation film 71 and the second phase retardation film 72 can be constructed with the same film, and wide viewing angle can be achieved more easily.

[0408] Figure 201 This is a schematic diagram illustrating the orientation of liquid crystal molecules in the first and second states of the optical element of Modified Example 3 of the first embodiment. Figure 201The azimuth angle of the hysteresis axis 71 of the first phase retardation film 71 shown is preferably 50° or more and 60° or less. By employing this method, polarization modulation and polarization non-modulation can be switched over a wider frequency band. The azimuth angle of the hysteresis axis 72A of the second phase retardation film 72 is preferably 5° or more and 24° or less. By employing this method, polarization modulation and polarization non-modulation can be switched over a wider frequency band.

[0409] (Second Implementation)

[0410] In this embodiment, the features unique to this embodiment are mainly described, and the descriptions of contents that are repeated in the first embodiment and its variations are omitted. This embodiment is substantially the same as the first embodiment except that it does not have the negative C plate 12.

[0411] Figure 10 This is a cross-sectional schematic diagram of the optical element according to the second embodiment. In the first embodiment described above, the optical element 10 was described in a manner that includes the negative C-plate 12, but... Figure 10 As shown, the optical element 10 may also be without the negative C plate 12. By adopting this method, the optical element 10 can be manufactured in a thin and low-cost manner.

[0412] (Third Implementation)

[0413] In this embodiment, the features unique to this embodiment are mainly described, and the descriptions of contents that are repeated in the first embodiment and its variations, as well as the second embodiment, are omitted. This embodiment is substantially the same as the first embodiment except for the different configurations of the first liquid crystal unit 11A and the second liquid crystal unit 11B.

[0414] Figure 11 This is a cross-sectional schematic diagram of the optical element according to the third embodiment. Figure 12 This is a cross-sectional schematic diagram of the first liquid crystal unit and the second liquid crystal unit included in the optical element of the third embodiment. Figure 13 This is a schematic diagram illustrating the orientation of liquid crystal molecules in the first and second states of the optical element according to the third embodiment. Figure 14 This is a cross-sectional schematic diagram illustrating the first state of the optical element in the third embodiment. Figure 15 This is a cross-sectional schematic diagram illustrating the second state of the optical element in the third embodiment.

[0415] Figures 11-15 The first liquid crystal molecule 510 and the second liquid crystal molecule 610 of the optical element 10 shown in this embodiment are twisted-oriented negative liquid crystal molecules. Therefore, as Figure 14As shown, when the first liquid crystal layer 500 is in a state with no voltage applied and the second liquid crystal layer 600 is in a state with voltage applied, a first state can be achieved where the first liquid crystal molecules 510 are vertically aligned and the second liquid crystal molecules 610 are twistedly aligned. In this first state, the phase difference of the first liquid crystal cell 11A can be eliminated by the negative C-plate 12. Furthermore, as... Figure 15 As shown, when the first liquid crystal layer 500 is in a voltage-applied state and the second liquid crystal layer 600 is in a voltage-free state, a second state can be achieved where the first liquid crystal molecules 510 are twisted and oriented, and the second liquid crystal molecules 610 are vertically oriented. In this second state, the phase difference of the second liquid crystal cell 11B can be eliminated by the negative C plate 12.

[0416] The first orientation film 41, the second orientation film 42, the third orientation film 43, and the fourth orientation film 44 are preferably vertically oriented films.

[0417] (Fourth Implementation)

[0418] In this embodiment, the features unique to this embodiment will be described in detail, while the description of content that is repeated in the first embodiment and its variations, as well as the second to third embodiments, will be omitted. This embodiment is substantially the same as the first embodiment except for the different configuration of the second liquid crystal unit 11B.

[0419] Figure 16 This is a cross-sectional schematic diagram of the optical element according to the fourth embodiment. Figure 17 This is a cross-sectional schematic diagram of the first liquid crystal unit and the second liquid crystal unit included in the optical element of the fourth embodiment. Figure 18 This is a schematic diagram illustrating the orientation of liquid crystal molecules in the first and second states of the optical element according to the fourth embodiment. Figure 19 This is a cross-sectional schematic diagram illustrating the first state of the optical element according to the fourth embodiment. Figure 20 This is a cross-sectional schematic diagram illustrating the second state of the optical element in the fourth embodiment.

[0420] Figures 16-20 The optical element 10 of this embodiment shown has a first liquid crystal molecule 510 that is twisted and oriented positive liquid crystal molecule, and a second liquid crystal molecule 610 that is twisted and oriented negative liquid crystal molecule. Therefore, as Figure 19 As shown, when both the first liquid crystal layer 500 and the second liquid crystal layer 600 are under voltage application, a first state can be achieved where the first liquid crystal molecules 510 are vertically aligned and the second liquid crystal molecules 610 are twistedly aligned. In this first state, the phase difference of the first liquid crystal cell 11A can be eliminated by the negative C-plate 12. Furthermore, as... Figure 20As shown, when both the first liquid crystal layer 500 and the second liquid crystal layer 600 are in a state where no voltage is applied, a second state can be achieved where the first liquid crystal molecules 510 are twisted and oriented, and the second liquid crystal molecules 610 are vertically oriented. In the second state, the phase difference of the second liquid crystal cell 11B can be eliminated by the negative C plate 12.

[0421] The first orientation film 41 and the second orientation film 42 are preferably horizontally oriented films, and the third orientation film 43 and the fourth orientation film 44 are preferably vertically oriented films.

[0422] (Fifth Implementation)

[0423] In this embodiment, the features unique to this embodiment will be described, and the description of content that is repeated in the first embodiment and its variations, as well as the second to fourth embodiments, will be omitted. In this embodiment, a variable focus element having the optical element (sHWP) of the first to fourth embodiments will be described. Figure 21 This is a cross-sectional schematic diagram of the variable focus element according to the fifth embodiment. Figure 21 The zoom element 30 of this embodiment shown includes an optical element 10 and a Pancharatnam Berry lens 20.

[0424] As described above, the optical element 10 of the first to fourth embodiments can modulate circularly polarized light. Furthermore, since the PB lens 20 has different focal lengths in right-handed and left-handed circularly polarized light, a variable-focus element 30 can be realized by combining the optical element 10 and the PB lens 20.

[0425] The PB lens 20 has the function of focusing and diverging circularly polarized light. The PB lens 20 can be manufactured, for example, by the method described in International Publication No. 2019 / 189818.

[0426] Figure 22 This is an example of a cross-sectional schematic diagram of the PB lens included in the variable focus element of the fifth embodiment. For example... Figure 22 As shown, the PB lens 20 includes an optical anisotropy layer 700. As an example, the PB lens 20 targets circularly polarized light, causing the incident light to refract and transmit in a predetermined direction. Furthermore, in Figure 22 In this case, the incident light is set as left-circularly polarized light.

[0427] exist Figure 22 In the portion shown, the optical anisotropy layer 700 has a characteristic from... Figure 22From the left side, there are three regions, R0, R1, and R2, each with a different length Λ of a cycle. Specifically, the length Λ of a cycle decreases in the order of regions R0, R1, and R2. Furthermore, regions R1 and R2 have a configuration where the optical axis is twisted and rotated in the thickness direction of the optical anisotropic layer (hereinafter also referred to as a twist structure). The twist angle in the thickness direction of region R1 is smaller than that of region R2. Region R0 is a region without a twist structure (i.e., the twist angle is 0°). The twist angle is set as the overall twist angle in the thickness direction.

[0428] In optical element 10, when left-circularly polarized light LC1 is incident on region R1 within the plane of optical anisotropic layer 700, it is refracted and transmitted at a predetermined angle relative to the incident direction in the direction of arrow X, i.e., the direction in which the optical axis of liquid crystal molecules 710 continuously rotates and changes. Similarly, when left-circularly polarized light LC2 is incident on region R2 within the plane of optical anisotropic layer 700, it is refracted at a predetermined angle relative to the incident direction in the direction of arrow X before being transmitted. Likewise, when left-circularly polarized light LC0 is incident on region R0 within the plane of optical anisotropic layer 700, it is refracted at a predetermined angle relative to the incident direction in the direction of arrow X before being transmitted.

[0429] Here, regarding the angle of refraction of the optical anisotropic layer 700, due to the 1-period Λ of the liquid crystal alignment pattern in region R2... R2 One period Λ of liquid crystal alignment pattern shorter than region R1 R1 Therefore, as Figure 22 As shown, the angle θ of the transmitted light in region R2 is relative to the angle of refraction of the incident light. R2 The angle θ of the transmitted light is greater than that of region R1 R1 Furthermore, the period Λ of the liquid crystal alignment pattern in region R0 R0 A period Λ of liquid crystal alignment pattern longer than region R1 R1 Therefore, as Figure 22 As shown, for the angle of refraction of the incident light, the angle θ of the transmitted light in region R0 is... R0 The angle θ of the transmitted light is smaller than that of region R1 R1 .

[0430] In the case of optical anisotropy layers with liquid crystal alignment patterns where the orientation of the optical axes of liquid crystal molecules changes continuously as the plane rotates, there is a problem that the diffraction efficiency decreases, i.e., the intensity of the diffracted light weakens, as the diffraction angle increases. Therefore, when the optical anisotropy layer is configured with regions of varying lengths for one cycle in which the orientation of the optical axes of liquid crystal molecules rotates 180° in-plane, the diffraction angle varies depending on the incident position of the light, resulting in differences in the amount of diffracted light depending on the incident position within the plane. That is, regions where the transmitted and diffracted light dims occur depending on the incident position within the plane.

[0431] In contrast, the PB lens 20 of this embodiment has a region where the optical anisotropic layer is twisted and rotated in the thickness direction, and has regions with different magnitudes of twist angles in the thickness direction. Figure 22 In the example shown, the twist angle φ in the thickness direction of region R2 of the optical anisotropy layer 700 R2 The twist angle φ in the thickness direction of region R1 is greater than that of region R1. R1 Furthermore, region R0 does not have a twisted structure in the thickness direction. Therefore, it is possible to suppress the reduction in diffraction efficiency of refracted light.

[0432] exist Figure 22 In the example shown, by giving regions R1 and R2, whose diffraction angles are larger than region R0, a decrease in the amount of light refracted in regions R1 and R2 can be suppressed. Furthermore, by making the twist angle of the twist structure in region R2, whose diffraction angle is larger than that in region R1, a decrease in the amount of light refracted in region R2 can be suppressed. Thus, the amount of transmitted light can be made uniform depending on the incident position within the plane.

[0433] Thus, in the PB lens 20 of this embodiment, in regions within the plane where refraction is high due to the optical anisotropic layer, incident light is refracted within layers with large twist angles in the thickness direction. Conversely, in regions within the plane where refraction is low due to the optical anisotropic layer, incident light is refracted within layers with small twist angles in the thickness direction. In other words, in the PB lens 20, by setting the twist angle in the thickness direction within the plane according to the magnitude of refraction of the optical anisotropic layer, the transmitted light can be brightened. Therefore, according to the PB lens 20, the refraction angle dependence of the amount of transmitted light within the plane can be reduced.

[0434] The angle of light refracted within the plane of the optical anisotropy layer 700 increases with the shortening of one period Λ of the liquid crystal alignment pattern. Furthermore, the twist angle in the thickness direction within the plane of the optical anisotropy layer 700, where the optical axis is rotated 180° along the direction of arrow X in the liquid crystal alignment pattern, has a larger area in the shorter region of one period Λ than in the larger region of one period Λ. As an example in the PB lens 20, such as... Figure 22As shown, the period Λ of the liquid crystal alignment pattern in region R2 of the optical anisotropic layer 700 is 1. R2 Compared to the period Λ of the liquid crystal alignment pattern in region R1 R1 Short, with a twist angle φ in the thickness direction. R2 Larger. That is, region R2 of the optical anisotropy layer 700 on the light incident side refracts light more.

[0435] Therefore, by setting the twist angle φ in the thickness direction within one period Λ of the liquid crystal alignment pattern to be targeted, it is possible to preferably brighten the transmitted light refracted at different angles in different regions within the surface.

[0436] In the PB lens 20, as described above, since the shorter the period Λ of the liquid crystal alignment pattern, the larger the angle of refraction, the shorter the period Λ of the liquid crystal alignment pattern, the larger the twist angle in the thickness direction, thereby making the transmitted light brighter. Therefore, it is preferable that in the PB lens 20, in regions where the length of the period of the liquid crystal alignment pattern is different, there are regions with different arrangements of the length of the period and different arrangements of the twist angle in the thickness direction.

[0437] In summary, the preferred PB lens 20 includes an optical anisotropy layer 700 formed using a liquid crystal composition containing liquid crystal molecules 710. The optical anisotropy layer 700 has a liquid crystal alignment pattern that changes continuously as the orientation of the optical axis from the liquid crystal molecules rotates along at least one in-plane direction. Furthermore, the optical axis has a region that twists and rotates in the thickness direction of the optical anisotropy layer 700, and regions with different sizes of twist angles in the thickness direction.

[0438] When the PB lens 20 preferably has a region with a different length of the aforementioned 1-cycle in the liquid crystal alignment pattern when the orientation of the optical axis from the liquid crystal molecule 710 is rotated 180° in the plane, it is preferred to have a region with a different length of the aforementioned 1-cycle in the liquid crystal alignment pattern.

[0439] Preferably, in the optical anisotropy layer 700, the multiple regions with different lengths of the one-cycle in the liquid crystal alignment pattern are arranged in order of the length of the one-cycle, and the multiple regions with different sizes of the twist angle in the thickness direction are arranged in order of the size of the twist angle in the thickness direction, and have regions whose arrangement direction of the length of the one-cycle is different from the arrangement direction of the size of the twist angle in the thickness direction.

[0440] The optical anisotropic layer 700 preferably has a region with a twist angle of 10° to 360° in the thickness direction.

[0441] Preferably, in the optical anisotropy layer 700, the period of the liquid crystal alignment pattern gradually shortens as the orientation of the optical axis from the liquid crystal molecules 710 in the liquid crystal alignment pattern changes continuously with rotation.

[0442] Preferably, the liquid crystal alignment pattern of the optical anisotropy layer 700 is a concentric circle pattern in one direction that changes from the inside to the outside while the orientation of the optical axis of the liquid crystal molecules 710 rotates continuously.

[0443] Figure 22 The PB lens 20 shown is a PB lens with a torsion angle that varies in the plane, and it is a high-efficiency diffraction element even when the diffraction angle is large. However, the PB lens 20 can also be a PB lens with a torsion angle that does not vary in the plane. Specifically, the PB lens 20 can be a PB lens that is not twisted in the thickness direction or has a fixed torsion angle in the plane. For example, a polarization diffraction grating described in Japanese Patent Application Publication No. 2008-532085 can be used.

[0444] The PB lens 20 is preferably a PB lens having multiple optical anisotropic layers 700, having optical anisotropic layers 700 having different orientations of twist angle in the thickness direction of the optical anisotropic layers 700.

[0445] The PB lens 20 is preferably a PB lens having multiple optical anisotropic layers 700, having optical anisotropic layers 700 having different twist angles in the thickness direction of the optical anisotropic layers 700.

[0446] The preferred PB lens 20 is a PB lens having a multilayer optical anisotropy layer 700, the optical anisotropy layer 700 having a liquid crystal alignment pattern in which the orientation of the optical axis of the liquid crystal molecules 710 is the same as that of each other in at least one direction within the plane.

[0447] The length of one period in the liquid crystal alignment pattern is preferably 50 μm or less.

[0448] The zoom element 30 can be a dual-level zoom element 30A having one set of stacked optical elements 10 and PB lenses 20, or a multi-level zoom element 30B having two or more sets of stacked optical elements 10 and PB lenses 20. In this way, by combining multiple sets of optical elements 10 and PB lenses 20, a zoom element 30B with multi-level tunability can be realized.

[0449] The zoom element 30 can be manufactured, for example, by attaching a PB lens 20, made using the method described in International Publication No. 2019 / 189818, to the optical element 10.

[0450] (Modification 1 of the fifth embodiment)

[0451] In this modified example, the variable focus element 30, in which the PB lens 20 of the fifth embodiment described above is disposed within the optical element 10 and embedded, will be described. Figure 23 This is a cross-sectional schematic diagram of the variable focus element of Modified Example 1 of the fifth embodiment. Figure 24 This is an enlarged cross-sectional schematic diagram of the variable focus element in Modification 1 of the fifth embodiment. Figure 25 This is a schematic diagram illustrating the orientation of liquid crystal molecules in the first and second states of the optical element of Modified Example 1 of the fifth embodiment.

[0452] In this variation, the zoom element 30 is as follows: Figure 23 The image shows a multi-stage variable focus element 30B having two or more stacked bodies consisting of optical elements 10 and PB lenses 20.

[0453] like Figure 24 As shown, in this modified example, the PB lens 20 of the zoom element 30 is disposed within the optical element 10. Thus, by embedding the PB lens 20, an external PB lens 20 is eliminated, thereby significantly reducing manufacturing costs. Furthermore, the thickness of the zoom element 30 can be suppressed. Additionally, in Figure 23 For convenience, optical element 10 and PB lens 20 are shown in the figure.

[0454] like Figure 24 As shown, more specifically, the variable focus element 30 of this modified example includes, from the incident side to the exit side, the following components in sequence: a second 1 / 4 wavelength film 14, a first 1 / 4 wavelength film 13, a first substrate 100, a first liquid crystal layer 500, a second substrate 200, a third substrate 300, a second liquid crystal layer 600, a PB lens 20, and a fourth substrate 400.

[0455] The zoom element 30 may also have a first alignment film 41 between the first substrate 100 and the first liquid crystal layer 500. Furthermore, the zoom element 30 may also have a second alignment film 42 between the second substrate 200 and the first liquid crystal layer 500. Furthermore, the zoom element 30 may also have a third alignment film 43 between the third substrate 300 and the second liquid crystal layer 600. Furthermore, the zoom element 30 may also have a fourth alignment film 44 between the PB lens 20 and the second liquid crystal layer 600.

[0456] In this modified example, the first liquid crystal cell 11A and the second liquid crystal cell 11B have the same configuration as in the first embodiment, and the first alignment film 41, the second alignment film 42, the third alignment film 43 and the fourth alignment film 44 are horizontal alignment films.

[0457] like Figure 25As shown, in this modified example, preferably, the azimuth angle of the orientation direction 512A of the first liquid crystal molecule 512 on the second substrate 200 side in the second state is -9° or more and 7° or less, and the azimuth angle of the orientation direction 612A of the second liquid crystal molecule 612 on the fourth substrate 400 side in the first state is 85° or more and 96° or less. By adopting this method, it is possible to switch between polarized light modulation and polarized light non-modulation with a wider bandwidth.

[0458] In this modified example, the negative C plate 12 is not disposed between the first liquid crystal cell 11A and the second liquid crystal cell 11B, but the negative C plate 12 may also be disposed between the first liquid crystal cell 11A and the second liquid crystal cell 11B.

[0459] The embedded PB lens 20 (PB lens layer) is, in other words, an embedded phase difference layer that is patterned by rotating in-plane in the direction of the hysteresis axis.

[0460] Embedding of a PB lens can be performed, for example, as follows. On a fourth substrate 400, a photosensitive material for forming an embedded PB lens containing a polymer represented by the following general formula (PB-1) is coated, and after forming a PB lens forming film, the PB lens forming film is oriented, thereby embedding the PB lens 20.

[0461] [Formula 1]

[0462]

[0463] (In the above formula, V represents a spacer group, W represents a divalent organic group with photofunctional groups, and R...) 5 (This represents a monovalent group, and p represents an integer greater than or equal to 1.)

[0464] In the above general formula (PB-1), V represents a spacer group. V preferably has an alkylene group with 2 or more carbon atoms, represented by -(CH2)n- (where n is an integer of 2 or more). By adopting this method, a good phase difference can be exhibited. The alkylene group is preferably linear.

[0465] In the above general formula (PB-1), W represents a divalent organic group having a photofunctional group. Examples of divalent organic groups having a photofunctional group include those containing photofunctional groups (photoreaction sites) that undergo photodimerization, photoisomerization, photoFries rearrangement, and photodecomposition. Examples of photofunctional groups capable of photodimerization and photoisomerization include cinnamate, chalcone, coumarin, and stilbene. Examples of photofunctional groups capable of photoisomerization include azophenyl. Examples of photofunctional groups capable of photoFries rearrangement include phenolic ester groups. Examples of photofunctional groups capable of photodecomposition include cyclobutane rings.

[0466] In the above general formula (PB-1), R 5 This indicates a monovalent group. R 5 Preferably, it is a hydrogen atom or a monovalent hydrocarbon group, more preferably a hydrogen atom, methyl or ethyl.

[0467] The orientation processing of the film for forming a PB lens is performed through multiple orientation processes, and the directions of the polarized light irradiated by the multiple orientation processes are different. For example, the orientation processing of the film for forming a PB lens includes: a first orientation process that aligns the film with polarized light at an azimuth angle of 0°; a second orientation process that aligns the film with polarized light at an azimuth angle of 45°; a third orientation process that aligns the film with polarized light at an azimuth angle of 90°; and a fourth orientation process that aligns the film with polarized light at an azimuth angle of 135°.

[0468] Figure 26 This is a planar schematic diagram showing the orientation pattern of the PB lens provided in the variable focus element of Modified Example 1 of the fifth embodiment. For example... Figure 26 As shown, the orientation pattern of the PB lens 20 rotates continuously from the center outwards. Furthermore, when viewed from above, the orientation directions of all liquid crystal molecules 710 at a radius R are identical. In other words, they have a predetermined angular distribution corresponding to their distance from the center. The period P1 of the orientation pattern and the diffraction angle θ are represented by P1 = 2 × λ / sinθ. The shorter the period of the orientation pattern, the greater the diffraction of light. Therefore, to achieve a lens effect that connects the focal points, this is achieved by widening the spacing (smaller diffraction angle) towards the center of the optical element and shortening the spacing (larger diffraction angle) towards the outer periphery.

[0469] The PB lens 20 with different refractive powers D described later can be manufactured by changing the design of the orientation pattern period. In addition, the orientation pattern can also be set based on International Publication No. 2020 / 186123, Japanese Patent Publication No. 2008-532085, etc.

[0470] In this embodiment, the alignment process is described using four exposures. However, the more exposures are performed, the better the diffraction efficiency of the variable focus element 30 becomes. Fabrication based on multi-light alignment using an optical alignment device exhibits good compatibility with existing liquid crystal factories and can be manufactured at high productivity. In this embodiment, the fabrication of the PB lens 20 based on multi-light alignment is described, but alignment patterns can also be fabricated using existing methods such as optical interference and direct laser drawing.

[0471] The phase difference of the embedded PB lens 20 (PB lens layer) is preferably 100 nm or more and 500 nm or less, more preferably 200 nm or more and 350 nm or less, and particularly preferably λ / 2 (i.e., 275 nm). The diffraction efficiency is expressed by the following (Equation 1), and therefore takes the maximum value when Δnd = λ / 2.

[0472] [Mathematical Expression 1]

[0473]

[0474] The multi-stage variable focus element 30, which is composed of multiple stacks of the variable focus element 30 of this modified example, namely the optical element 10 and the PB lens 20 embedded in the optical element 10, has the following characteristics, for example.

[0475] Figure 27 This is a cross-sectional schematic diagram illustrating the detailed configuration of the variable focus element in Modification 1 of the fifth embodiment. (See attached diagram.) Figure 27 As shown, the variable focus element 30 has, from the incident side to the exit side, an optical element 10, a first PB lens 20A1, an optical element 10, a first PB lens 20A1, an optical element 10, a second PB lens 20A2, an optical element 10, a second PB lens 20A2, an optical element 10, a second PB lens 20A2, an optical element 10, a third PB lens 20A3, and an optical element 10 and a third PB lens 20A3.

[0476] The first PB lens 20A1 has a diopter D = ±0.25, the second PB lens 20A2 has a diopter D = ±0.5, and the third PB lens 20A3 has a diopter D = ±1. They exhibit the characteristic of being + (focusing) when right-circularly polarized light is incident, and - (diverging) when left-circularly polarized light is incident.

[0477] Table 1 below describes the state of the optical element 10 and PB lenses 20A1, 20A2 and 20A3 of the zoom element 30 in each mode of the fifth embodiment of Modified Example 1.

[0478] [Table 1]

[0479]

[0480] The F0 mode is explained using Table 1 above. In this mode, all optical elements 10 are in their first state (unmodulated). If right-circularly polarized light is incident, it is directly incident on the first first PB lens 20A1 without modulation by the initial optical element 10. Here, a focusing of 0.25D is received. At this time, the outgoing light becomes left-circularly polarized light. Here, even after passing through the PB lens 20, the direction of the circularly polarized light changes, which is a characteristic of the PB lens 20. Since the optical element 10 is unmodulated, it passes through the second optical element 10 in the state of left-circularly polarized light. In the second first PB lens 20A1, a divergence of -0.25D is generated. As a result, the incident light passes directly through the first four lenses (optical element 10, first PB lens 20A1, optical element 10, and first PB lens 20A1) from the incident side. Similarly, the second PB lens 20A2 and PB lens 20A3 also pass through, and as outgoing light, they also maintain the state of the incident light and exit directly at OD.

[0481] The F1 mode is explained using Table 1 above. In this mode, only the fourth optical element 10 from the incident side is in the second state. In this state, after passing through the initial second PB lens 20A2, it is in the same state as the F0 mode, with left circularly polarized light imparted with 0.5D. Then, it is converted to right circularly polarized light by the optical element in the second state. Next, in the second second PB lens 20A2, it becomes left circularly polarized light imparted with +0.5D, for a total imparted of 1D, and is emitted. After that, left circularly polarized light of 1D is emitted directly. Since it becomes left circularly polarized light after passing through the second second PB lens 20A2, the sign of the third PB lens 20A3 is reversed compared to that in F0.

[0482] Use Table 1 above and Figure 28 Explain the F-2.5's modes. Figure 28 This is a diagram illustrating the polarization state of the variable focus element in Modification 1 of the fifth embodiment in F-2.5 mode. See Table 1 and... Figure 28 As shown, in F-2.5 mode, the light is right-circularly polarized to -0.5D by the first four lenses (optical element 10, first PB lens 20A1, optical element 10 and first PB lens 20A1) from the incident side, and to -2D by the last four lenses (optical element 10, third PB lens 20A3, optical element 10 and third PB lens 20A3) from the exiting side, resulting in a total right-circularly polarized light of -2.5D that is emitted.

[0483] Furthermore, using the same principle, multiple focal lengths can be achieved depending on which optical element 10 is set to the second state of the modulation state. In this modified example, only three conditions are extracted and shown.

[0484] (Modification 2 of the fifth embodiment)

[0485] In the fifth embodiment and its variation 1 described above, a PB lens with a film-like (embedded polymer-like) structure was described. However, the PB lens can also be a liquid crystal layer with fluidity, i.e., a liquid crystal layer that can be driven by voltage. In this variation, the case where the PB lens is a liquid crystal layer that can be driven by voltage will be described.

[0486] As described in the fifth embodiment and its variation 1, the polymer-shaped PB lens cannot change under voltage and is therefore called a passive PB lens. On the other hand, the PB lens formed from a liquid crystal layer with fluidity can be driven by voltage and is therefore called an active PB lens.

[0487] An active PB lens can be fabricated using the following steps. First, the alignment film of one side of a pair of substrates is oriented to form a PB lens pattern. The alignment film of the other side of the substrate is a weak anchoring force alignment film (sliding interface). Furthermore, a transparent electrode is provided on either substrate. When the pair of substrates are bonded together by clamping a liquid crystal layer, the liquid crystal molecules align along the oriented pattern, and the liquid crystal layer also adopts the PB lens pattern orientation. This enables the fabrication of an active PB lens. More preferably, a PSA (Polymer Sustained Alignment) process is subsequently performed to stabilize the alignment of the liquid crystal molecule interface, thereby obtaining an active PB lens with higher alignment stability and reliability.

[0488] An active PB lens has a PB lens pattern when the voltage is OFF, thus focusing or diverging light depending on the incident polarization state. When the voltage is ON, the liquid crystal molecules become vertically aligned, so light neither focuses nor diverges and passes directly through.

[0489] In the zoom element combining an sHWP and a passive PB lens as described in the fifth embodiment and its variation 1, a two-value switching of focusing / diverging is performed. In contrast, in the zoom element combining an sHWP and an active PB lens as described in this variation, a three-value switching of focusing / diverging / transmission is possible. As a result, smoother focus control is possible. Alternatively, the number of layers of voltage drive elements used to achieve the same focal length can be reduced.

[0490] (Sixth Implementation Method)

[0491] In this embodiment, the features unique to this embodiment will be described in detail, and the description of content that is repeated in the first embodiment, its variations, the second to fifth embodiments and their variations will be omitted. In this embodiment, a head-mounted display equipped with a zoom element 30 will be described. Figure 29This is a cross-sectional schematic diagram of the head-mounted display according to the sixth embodiment. Figure 30 A perspective view showing an example of the appearance of the head-mounted display according to the sixth embodiment.

[0492] like Figure 29 as well as Figure 30 As shown, the head-mounted display 1 of this embodiment includes a display panel 1P for displaying images, a phase retardation plate 40, and a zoom element 30. By using the head-mounted display 1, light emitted from the display panel 1P, such as a liquid crystal display device or an organic electroluminescent display device, is converted into circularly polarized light by the phase retardation plate 40, and then viewed by the user U through the zoom element 30.

[0493] The following examples and comparative examples illustrate the effects of the present invention, but the present invention is not limited to these examples.

[0494] (Example 1)

[0495] An optical element 10 of Embodiment 1 with the same configuration as the first embodiment described above is fabricated. Two layers of a first liquid crystal cell 11A and a second liquid crystal cell 11B are overlapped, with a negative C-plate 12 having a thickness retardation Rth of -110 nm stacked between them. The first liquid crystal molecule 510 and the second liquid crystal molecule 610 are positive liquid crystal molecules with a refractive index anisotropy Δn = 0.066. The first alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44 are horizontally aligned films.

[0496] In the second state, the orientation angle of the first liquid crystal molecule 511 on the first substrate 100 side is 0°, and the orientation angle of the first liquid crystal molecule 512 on the second substrate 200 side is 68°. Furthermore, in the first state, the orientation angle of the second liquid crystal molecule 611 on the third substrate 300 side is 90°, and the orientation angle of the second liquid crystal molecule 612 on the fourth substrate 400 side is 158°. Furthermore, the orientation direction 511A of the first liquid crystal molecule 511 on the first substrate 100 side in the second state, the orientation direction 512A of the first liquid crystal molecule 512 on the second substrate 200 side in the second state, the orientation direction 611A of the second liquid crystal molecule 611 on the third substrate 300 side in the first state, and the orientation direction 612A of the second liquid crystal molecule 612 on the fourth substrate 400 side in the first state are consistent with the orientation processing directions of the first alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44, respectively. Therefore, in the embodiment, the orientation directions 511A, 512A, 611A, and 612A are determined according to the orientation processing directions of the first alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44, respectively.

[0497] The first quarter-wavelength film 13 has reverse wavelength dispersion characteristics, and the second quarter-wavelength film 14 has planar wavelength dispersion characteristics. The azimuth angle of the hysteresis axis 13A of the first quarter-wavelength film 13 is 57.2°, and the azimuth angle of the hysteresis axis 14A of the second quarter-wavelength film 14 is 12.2°.

[0498] The first state involves driving the first liquid crystal layer 500 by applying a voltage. In this first state, the voltage applied to the first liquid crystal layer 500 is preferably as high as possible; in this embodiment, 20V is applied. Since the negative C-plate 12 is designed to eliminate the phase difference between the driven liquid crystal layer (first liquid crystal layer 500) and the negative C-plate 12, only the undriven liquid crystal layer (second liquid crystal layer 600) is effective. Therefore, a wide viewing angle and wide bandwidth sHWP can be achieved.

[0499] The second state is the opposite of the first state. By applying a voltage to the second liquid crystal layer 600 to drive it, the liquid crystal layer (first liquid crystal layer 500), which is rotated 90 degrees from the liquid crystal layer (second liquid crystal layer 600) that is effective in the first state, becomes effective. Therefore, the light that has passed through the two 1 / 4 wavelength films (first 1 / 4 wavelength film 13 and second 1 / 4 wavelength film 14) becomes circularly polarized light with a polarization state opposite to that of the light incident on the optical element 10.

[0500] (Comparative Example 1)

[0501] Figure 31 This is a cross-sectional schematic diagram of the optical element in Comparative Example 1. It was fabricated... Figure 31 The optical element 10R1 of Comparative Example 1 is shown. The optical element 10R1 of Comparative Example 1 is the same as the optical element of Comparative Method 1 described above. The optical element 10R1 of Comparative Example 1 comprises, from the incident side to the exit side, the following components in sequence: a 1 / 4 wavelength film 15R with an azimuth angle of 75° for the hysteresis axis, a 1 / 2 wavelength film 16R with an azimuth angle of 15° for the hysteresis axis, a liquid crystal cell 11R1 with a TN liquid crystal layer 500R1 having a 90° twist, a 1 / 2 wavelength film 17R with an azimuth angle of -75° for the hysteresis axis, and a 1 / 4 wavelength film 18R with an azimuth angle of -15° for the hysteresis axis.

[0502] (Comparative Example 2)

[0503] Figure 32 This is a cross-sectional schematic diagram of the optical element in Comparative Example 2. It was fabricated... Figure 32 The optical element 10R2 of Comparative Example 2 is shown. The optical element 10R2 of Comparative Example 2 is the same as the optical element of Comparative Example 2 described above. The optical element 10R2 of Comparative Example 2 has a structure in which a 70° twisted TN liquid crystal layer 500R2 and a -70° twisted TN liquid crystal layer 500R3 are stacked sequentially from the incident side to the emission side.

[0504] (Evaluation of Example 1, Comparative Example 1, and Comparative Example 2)

[0505] For the optical elements (sHWP) of Example 1, Comparative Example 1, and Comparative Example 2, the Stokes parameter S3 of the emitted light when incident with right-circularly polarized light (S3 = +1) was evaluated. Furthermore, in the examples and comparative examples of this specification, unless otherwise specified, the Stokes parameter S3 of the emitted light when incident with right-circularly polarized light (S3 = +1) was evaluated. Figure 33 This is a graph showing the relationship between the Stokes parameter S3 of the optical elements of Example 1, Comparative Example 1 and Comparative Example 2 in the unmodulated state and the wavelength of the emitted light. Figure 34 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light during modulation of the optical elements of Example 1, Comparative Example 1, and Comparative Example 2. Figure 33 and Figure 34 As shown, in Example 1, both during modulation and without modulation, |S3|≥0.9 can be achieved in the wavelength range of 450nm~650nm.

[0506] Figure 35 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Comparative Example 1 when the incident angle is set to 30° and the unmodulated condition. Figure 36 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Comparative Example 1 is modulated with an incident angle set to 30°. Figure 37 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Comparative Example 2 when the incident angle is set to 30° and it is not modulated. Figure 38 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Comparative Example 2 is modulated with the incident angle set to 30°. Figure 39 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Example 1 when the incident angle is set to 30° and it is not modulated. Figure 40 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 1 is modulated with an incident angle set to 30°. Figures 35-40 The values ​​in the figure represent the evaluation results at wavelengths of 450nm, 550nm, and 650nm.

[0507] like Figure 35 and Figure 36 As shown, in Comparative Example 1, |S3|≥0.9 was not achieved in both modulated and unmodulated states. Figure 37 and Figure 38 As shown, in Comparative Example 2, |S3|≥0.9 was approximately achieved during modulation, but |S3|≥0.9 was not achieved during non-modulation. On the other hand, as... Figure 39 and Figure 40 As shown in Example 1, both during modulation and without modulation, |S3|≥0.9 can be achieved in all directions within the range of 450nm to 650nm.

[0508] The viewing angle characteristics of the optical elements of Example 1, Comparative Example 1, and Comparative Example 2 under both non-modulated and modulated conditions were evaluated through simulation. The results are shown below. Figure 41 . Figure 41 The figure shows the simulation results of the viewing angle characteristics of the optical elements of Example 1, Comparative Example 1 and Comparative Example 2 under non-modulation and modulation conditions.

[0509] exist Figure 41 In the unmodulated graph, a wider dense region indicates better characteristics; conversely, in the modulated graph, a wider thin region indicates better characteristics. For example... Figure 41 As shown, in Example 1, it is evident that both unmodulated and modulated viewing angles are good within the wavelength range of 450nm to 650nm. On the other hand, in Comparative Example 1, the viewing angle is good when unmodulated, but highly wavelength-dependent when modulated. In Comparative Example 2, although the viewing angle is good when modulated, the viewing angle is poor when unmodulated.

[0510] To study the design of a suitable liquid crystal cell, optical calculations were performed on the optical element 10 of Example 1 using an LCD-MASTER1D manufactured by Cintec. Based on the simulation results, the range within which modulation and non-modulation ratios of 90% or more can be achieved at an incident angle of 30° and a wavelength of 450nm to 650nm is determined to be the preferred range. Furthermore, for simplicity, the following charts only illustrate data for the worst-case orientation at an incident angle of 30° at wavelengths of 450nm, 550nm, and 650nm.

[0511] First, in order to study the preferred range of the delay Δnd in the second state at a wavelength of 550 nm of the first liquid crystal layer 500 and the delay Δnd in the first state at a wavelength of 550 nm of the second liquid crystal layer 600, the Stokes parameter S3 for the unmodulated delay of the first state of the second liquid crystal layer 600 provided with the optical element 10 of Embodiment 1 and the Stokes parameter S3 for the modulated delay of the second state of the first liquid crystal layer 500 provided with the optical element 10 of Embodiment 1 were obtained by simulation. Figure 42 This is a graph showing the Stokes parameter S3 under non-modulation conditions, representing the delay in the first state of the second liquid crystal layer possessed by the optical element of Embodiment 1. Figure 43 This is a graph showing the Stokes parameter S3 during modulation of the delay in the second state of the first liquid crystal layer possessed by the optical element of Embodiment 1.

[0512] Depend on Figure 42 It is known that the delay of the second liquid crystal layer 600 in the first state at a wavelength of 550 nm is preferably 210 nm or more and 260 nm or less. Furthermore, according to... Figure 43 It is known that the delay in the second state at a wavelength of 550nm of the first liquid crystal layer 500 is preferably 200nm or more and 260nm or less.

[0513] In order to study the preferred range of the twist angle of the first liquid crystal molecule 510 and the second liquid crystal molecule 610, the Stokes parameter S3 for the unmodulated twist angle of the second liquid crystal molecule 610 with respect to the optical element 10 of Embodiment 1 and the Stokes parameter S3 for the modulated twist angle of the first liquid crystal molecule 510 with respect to the optical element 10 of Embodiment 1 were obtained by simulation. Figure 44 This is a graph showing the Stokes parameter S3 when the twist angle of the second liquid crystal molecule relative to the optical element of Example 1 is not modulated. Figure 45 This is a graph showing the Stokes parameter S3 when the twist angle of the first liquid crystal molecule is modulated relative to the optical element of Example 1.

[0514] according to Figure 44 It is known that the second liquid crystal molecule 610 in the first state (non-modulated state) is preferably oriented with a twist angle of 64° or more and 74° or less. Furthermore, according to... Figure 45 It is known that the first liquid crystal molecule 510 in the second state (modulation) is preferably oriented with a twist angle of 61° or more and 75° or less.

[0515] In order to study the preferred range of the pre-twist angle of the first liquid crystal molecule 510 and the second liquid crystal molecule 610, the Stokes parameter S3 for the unmodulated pre-twist angle of the second liquid crystal molecule 610 with respect to the optical element 10 of Embodiment 1 and the Stokes parameter S3 for the modulated pre-twist angle of the first liquid crystal molecule 510 with respect to the optical element 10 of Embodiment 1 were obtained by simulation. Figure 46 This is a graph showing the Stokes parameter S3 when the pre-twist angle of the second liquid crystal molecule relative to the optical element of Example 1 is not modulated. Figure 47 This is a graph showing the Stokes parameter S3 when the pre-twist angle of the first liquid crystal molecule is modulated relative to the optical element of Embodiment 1. Here, the pre-twist angle refers to the azimuth angle of the orientation direction of the liquid crystal molecules in the substrate on the incident side of each liquid crystal cell. Specifically, the pre-twist angle of the first liquid crystal molecule 510 is the azimuth angle of the orientation direction 511A of the first liquid crystal molecule 511 on the first substrate 100 side in the second state. Furthermore, the pre-twist angle of the second liquid crystal molecule 610 is specifically the azimuth angle of the orientation direction 611A of the second liquid crystal molecule 611 on the third substrate 300 side in the first state.

[0516] according to Figure 46 It is known that the preferred pre-twist angle of the second liquid crystal molecule 610, that is, the azimuth angle of the orientation direction 611A of the second liquid crystal molecule 611 on the third substrate 300 side in the first state, is 85° or more and 96° or less. Furthermore, according to... Figure 47 It is known that the preferred pre-twist angle of the first liquid crystal molecule 510, that is, the azimuth angle of the orientation direction 511A of the first liquid crystal molecule 511 on the first substrate 100 side in the second state, is -9° or more and 7° or less.

[0517] according to Figures 42-47 It is known that the optimal values ​​of the delay Δnd, twist angle, and pre-twist angle of the liquid crystal layer are different in the first liquid crystal cell 11A and the second liquid crystal cell 11B, so it is not necessary to stack liquid crystal cells with the same design. That is, it is known that the first liquid crystal cell 11A may not have the same structure as the second liquid crystal cell 11B.

[0518] In order to study the preferred range of the azimuth angle of the hysteresis axis of the quarter-wavelength film with reverse wavelength dispersion (first quarter-wavelength film 13), the Stokes parameter S3 of the azimuth angle of the hysteresis axis of the quarter-wavelength film with reverse wavelength dispersion relative to the optical element 10 of Embodiment 1 was obtained by simulation, both in the unmodulated and modulated states. Figure 48 This is a graph showing the Stokes parameter S3 when the azimuth angle of the hysteresis axis of the quarter-wavelength film with reverse wavelength dispersion relative to the optical element of Example 1 is not modulated. Figure 49 A graph showing the Stokes parameter S3 when the azimuth angle of the hysteresis axis of the quarter-wavelength film with reverse wavelength dispersion relative to the optical element of Example 1 is modulated. (See graph for example.) Figure 48 and Figure 49 As shown, the azimuth angle of the hysteresis axis of the quarter-wavelength film that serves as the reverse wavelength dispersion of the first quarter-wavelength film 13 is preferably 52° or more and 60° or less.

[0519] In order to study the preferred range of the phase difference of the quarter-wavelength film with reverse wavelength dispersion, the wavelength dispersion of the Stokes parameter S3 of the phase difference of the quarter-wavelength film with reverse wavelength dispersion possessed by the optical element 10 of Example 1 was determined by simulation, both in the unmodulated and modulated states. Figure 50 This is a graph showing the Stokes parameter S3 under non-modulation conditions, representing the phase difference of the quarter-wavelength film with reverse wavelength dispersion relative to the optical element of Example 1. Figure 51 This is a graph showing the Stokes parameter S3 when the phase difference of the quarter-wavelength film with reverse wavelength dispersion relative to the optical element of Example 1 is modulated. (As shown) Figure 50 and Figure 51As shown, the phase difference of the quarter-wavelength film serving as the first quarter-wavelength film 13 for reverse wavelength dispersion is preferably 90 nm or more and 170 nm or less.

[0520] In order to study the preferred range of the azimuth angle of the hysteresis axis of the quarter-wavelength film with flat wavelength dispersion (second quarter-wavelength film 14), the wavelength dispersion of the Stokes parameter S3 with respect to the azimuth angle of the hysteresis axis of the quarter-wavelength film with flat wavelength dispersion possessed by the optical element 10 of Embodiment 1 was determined by simulation, both unmodulated and modulated. Figure 52 This is a graph showing the Stokes parameter S3 when the azimuth angle of the hysteresis axis of the quarter-wavelength film with flat wavelength dispersion relative to the optical element of Example 1 is not modulated. Figure 53 This is a graph showing the Stokes parameter S3 when the azimuth angle of the hysteresis axis of the quarter-wavelength film with flat wavelength dispersion relative to the optical element of Example 1 is modulated. (As shown...) Figure 52 and Figure 53 As shown, it can be seen that the azimuth angle of the hysteresis axis of the quarter-wavelength film, which serves as the flat wavelength dispersion of the second quarter-wavelength film 14, is preferably 8° or more and 18° or less.

[0521] In order to study the preferred range of the phase difference of the 1 / 4 wavelength film with planar wavelength dispersion, the wavelength dispersion of the Stokes parameter S3 with respect to the phase difference of the 1 / 4 wavelength film with planar wavelength dispersion of the optical element 10 of Example 1 was determined by simulation, both in the unmodulated and modulated states. Figure 54 This is a graph showing the Stokes parameter S3 under non-modulation conditions, representing the phase difference of a quarter-wavelength film with planar wavelength dispersion relative to the optical element of Example 1. Figure 55 This is a graph showing the Stokes parameter S3 when the phase difference of the quarter-wavelength film with planar wavelength dispersion relative to the optical element of Example 1 is modulated. (As shown...) Figure 54 and Figure 55 As shown, the phase difference of the quarter-wavelength film that serves as the second quarter-wavelength film 14 for planar wavelength dispersion is preferably 120 nm or more and 150 nm or less.

[0522] (Example 2)

[0523] An optical element 10 of Embodiment 2 with the same configuration as the second embodiment described above was fabricated. Specifically, the optical element 10 of Embodiment 2 was fabricated in the same manner as in Embodiment 1, except that the negative C plate 12 was not provided.

[0524] The viewing angle characteristics of the optical elements of Examples 1, 2 and Comparative Example 1 under both unmodulated and modulated conditions were evaluated by simulation. Figure 56 Indicates the result. Figure 56The graph shows the simulation results of the viewing angle characteristics of the optical elements of Example 1, Example 2 and Comparative Example 1 under both non-modulated and modulated conditions.

[0525] exist Figure 56 In the unmodulated graph, a wider dense region indicates better characteristics; conversely, in the modulated graph, a wider thin region indicates better characteristics. For example... Figure 56 As can be seen, although Example 2 is not like Example 1, both unmodulated and modulated images have good viewing angles in the wavelength range of 450nm to 650nm. The optical element 10 of Example 2 can be manufactured inexpensively without the need for a negative C plate 12, and can be made thinner.

[0526] For the optical element (sHWP) of Example 2, the Stokes parameter S3 of the emitted light when incident with right-circularly polarized light (S3 = +1) was evaluated. Figure 57 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element in Example 2 when the incident angle is set to 30° and it is not modulated. Figure 58 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 2 is modulated with the incident angle set to 30°. Figure 57 and Figure 58 The evaluation results are shown at wavelengths of 450 nm, 550 nm, and 650 nm. Figure 57 and Figure 58 As shown in Example 2, both during modulation and without modulation, |S3|≥0.9 can be achieved in all directions within the wavelength range of 450nm~650nm.

[0527] Here, including Example 1, the preferred range of the thickness direction retardation Rth of the negative C plate 12 was investigated. Specifically, for an optical element having the same configuration as the optical element in Example 1, the Stokes parameter S3 was obtained by simulation when the thickness direction retardation Rth of the negative C plate 12 was -300 nm to 0 nm. Here, a thickness direction retardation Rth of 0 nm for the negative C plate 12 indicates a configuration where the negative C plate 12 is not stacked, i.e., the configuration of Example 2. The results are as follows: Figure 59 and Figure 60 As shown.

[0528] Figure 59 This is a graph showing the relationship between the Stokes parameter S3 of the optical element in the embodiment when it is not modulated and the delay Rth in the thickness direction of the negative C plate. Figure 60 This is a graph showing the relationship between the Stokes parameter S3 during modulation of the optical element in the embodiment and the delay Rth in the thickness direction of the negative C plate. Figure 59 and Figure 60The data shown only includes the worst azimuth data for an incident angle of 30° at wavelengths of 450nm, 550nm, and 650nm. According to... Figure 59 and Figure 60 It can be seen that the thickness retardation Rth of the negative C plate 12 is preferably above -220nm and below 0nm.

[0529] (Example 3)

[0530] An optical element 10 of Embodiment 3 with the same configuration as the third embodiment described above was fabricated. Specifically, the first liquid crystal molecule 510 and the second liquid crystal molecule 610 were configured as negative liquid crystal molecules with a twisted orientation and a chiral spacing of 15.7 μm (refractive index anisotropy Δn = 0.079). The first alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44 were configured as vertical alignment films. A pretilt angle of 0° was given to the first substrate 100 side of the first liquid crystal layer 500 (i.e., the azimuth angle of the orientation direction 511A of the first liquid crystal molecule 511 on the first substrate 100 side in the second state was set to 0°, and a pretilt angle of 90° was given to the third substrate 300 side of the second liquid crystal layer 600 (i.e., the azimuth angle of the orientation direction 611A of the second liquid crystal molecule 611 on the third substrate 300 side in the first state was set to 90°). Otherwise, the optical element of Embodiment 3 was fabricated in the same manner as in Embodiment 1.

[0531] The first state involves driving the second liquid crystal layer 600 by applying a voltage. In this first state, the voltage applied to the second liquid crystal layer 600 is preferably as high as possible; in this embodiment, 20V is applied. The negative C-plate 12 is designed to eliminate the phase difference between the undriven liquid crystal layer (first liquid crystal layer 500) and the negative C-plate 12, thus only the driven liquid crystal layer (second liquid crystal layer 600) is effective. Therefore, a wide viewing angle and wide bandwidth sHWP can be achieved.

[0532] The second state is the opposite of the first state. By applying a voltage to the first liquid crystal layer 500 to drive it, the liquid crystal layer (first liquid crystal layer 500) that is 90 degrees rotated from the liquid crystal layer (second liquid crystal layer 600) that is effective in the first state becomes effective. Therefore, the light that has passed through the two 1 / 4 wavelength films (first 1 / 4 wavelength film 13 and second 1 / 4 wavelength film 14) becomes circularly polarized light with a polarization state opposite to that of the light incident on the optical element 10.

[0533] For the optical element (sHWP) of Example 3, the Stokes parameter S3 of the emitted light when incident right-circularly polarized light (S3 = +1) is evaluated. Figure 61 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the incident angle is set to 0° for the optical elements of Examples 1, 3, Comparative Example 1 and Comparative Example 2 in the unmodulated state. Figure 62This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical element of Examples 1, 3, Comparative Example 1 and Comparative Example 2 is modulated with the incident angle set to 0°. Figure 61 and Figure 62 The text indicates the modulation and non-modulation characteristics in the visible light region when the incident angle is set to 0°. For example... Figure 61 and Figure 62 As shown, in Example 3, |S3|≥0.9 can be achieved in the wavelength range of 450nm~650nm in both modulated and unmodulated states.

[0534] Figure 63 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Example 3 when the incident angle is set to 30° and it is not modulated. Figure 64 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 3 is modulated with the incident angle set to 30°. Figure 63 and Figure 64 This indicates the modulation and non-modulation characteristics at wavelengths of 450nm, 550nm, and 650nm when the incident angle is set to 30°. For example... Figure 63 and Figure 64 As shown, in Example 3, |S3|≥0.9 can be achieved in all directions within the wavelength range of 450nm to 650nm, both during modulation and without modulation.

[0535] (Example 4)

[0536] An optical element 10 of Embodiment 4 with the same configuration as the fourth embodiment described above is fabricated. Specifically, the optical element 10 of Embodiment 4 is fabricated in the same manner as in Embodiment 1, except that the second liquid crystal cell 11B of Embodiment 3 is used as the second liquid crystal cell 11B.

[0537] The first state involves driving both the first liquid crystal layer 500 and the second liquid crystal layer 600 by applying a voltage. In this first state, the voltage applied to the first liquid crystal layer 500 and the second liquid crystal layer 600 is preferably as high as possible; in this embodiment, 20V is applied. The negative C-plate 12 is designed to eliminate the phase difference between the driven first liquid crystal layer 500 and the negative C-plate 12, thus only the driven second liquid crystal layer 600 is effective. Therefore, a wide viewing angle and wide bandwidth sHWP can be achieved.

[0538] The second state is the opposite of the first state. By not applying a voltage to either the first liquid crystal layer 500 or the second liquid crystal layer 600, the liquid crystal layer (first liquid crystal layer 500) rotated 90 degrees from the liquid crystal layer (second liquid crystal layer 600) that is effective in the first state becomes effective. Therefore, the light that passes through the two 1 / 4 wavelength films (first 1 / 4 wavelength film 13 and second 1 / 4 wavelength film 14) becomes circularly polarized light with a polarization state opposite to that of the light incident on the optical element 10.

[0539] For the optical element (sHWP) of Example 4, the Stokes parameter S3 of the emitted light when incident right-circularly polarized light (S3 = +1) is evaluated. Figure 65 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the incident angle is set to 0° for the optical elements of Example 4, Comparative Example 1, and Comparative Example 2 without modulation. Figure 66 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical element of Example 4, Comparative Example 1 and Comparative Example 2 is modulated with the incident angle set to 0°. Figure 65 and Figure 66 This indicates the modulation and non-modulation characteristics in the visible light region when the incident angle is set to 0°. For example... Figure 65 and Figure 66 As shown, in Example 4, both during modulation and without modulation, |S3|≥0.9 can be achieved in the wavelength range of 450nm~650nm.

[0540] Figure 67 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element in Example 4 when the incident angle is set to 30° and it is not modulated. Figure 68 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 4 is modulated with the incident angle set to 30°. Figure 67 and Figure 68 The text indicates the modulation and non-modulation characteristics at wavelengths of 450nm, 550nm, and 650nm when the incident angle is set to 30°. For example... Figure 67 and Figure 68 As shown in Example 4, both during modulation and without modulation, |S3|≥0.9 can be achieved in all directions within the wavelength range of 450nm~650nm.

[0541] (Example 5)

[0542] A variable focus element 30 corresponding to Modification 1 of the fifth embodiment described above was fabricated in Example 5. The first liquid crystal molecule 510 and the second liquid crystal molecule 610 are positive liquid crystal molecules with a refractive index anisotropy Δn = 0.066. The first alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44 are horizontal alignment films.

[0543] In the second state, the orientation angle of the first liquid crystal molecule 512 on the second substrate 200 side is 0°, and the orientation angle of the first liquid crystal molecule 511 on the first substrate 100 side is 68°. Furthermore, in the first state, the orientation angle of the second liquid crystal molecule 612 on the fourth substrate 400 side is 90°, and the orientation angle of the second liquid crystal molecule 611 on the third substrate 300 side is 158°.

[0544] The first quarter-wavelength film 13 has reverse wavelength dispersion characteristics, and the second quarter-wavelength film 14 has planar wavelength dispersion characteristics. The hysteresis axis 13A of the first quarter-wavelength film 13 is 57.2°, and the hysteresis axis 14A of the second quarter-wavelength film 14 is 12.2°.

[0545] The zoom element 30 of Embodiment 5 is specifically fabricated as follows. A photosensitive material for forming an embedded PB lens, containing a polymer represented by the above general formula (PB-1), is coated on the fourth substrate 400 of the second liquid crystal cell 11B to form a PB lens forming film.

[0546] Figure 69 This is a schematic diagram illustrating the first orientation process in the manufacturing process of the variable focus element of Example 5. Figure 70 This is a schematic diagram illustrating the second orientation process in the manufacturing process of the variable focus element of Example 5. Figure 71 This is a schematic diagram illustrating the third orientation process in the manufacturing process of the variable focus element of Example 5. Figure 72 This is a schematic diagram illustrating the fourth orientation process in the manufacturing process of the variable focus element of Example 5.

[0547] Next, the PB lens forming film disposed on the fourth substrate 400 is oriented. Specifically, as follows: Figure 69 As shown, the PB lens forming film 900 was oriented using polarized light at an azimuth angle of 0° using a first photomask 810. Next, as... Figure 70 As shown, the PB lens forming film 900 was oriented using polarized light at an azimuth angle of 45° using a second photomask 820. Next, as... Figure 71As shown, the PB lens forming film 900 was oriented using polarized light at an azimuth angle of 90° using a third photomask 830. Finally, as... Figure 72 As shown, the PB lens forming film 900 was oriented using polarized light with an azimuth angle of 135° using a fourth photomask 840. Afterwards, an annealing process was performed, enabling the PB lens 20 to be formed on the fourth substrate 400.

[0548] Using the stack of the fourth substrate 400 and the PB lens 20, the second liquid crystal cell 11B is fabricated in the same manner as in Embodiment 2, and the horizontally aligned first liquid crystal cell 11A and the horizontally aligned second liquid crystal cell 11B are stacked. Then, as the first quarter wavelength film 13, a quarter wavelength film with anti-wavelength dispersion is attached to the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, and as the second quarter wavelength film 14, a quarter wavelength film with flat wavelength dispersion is attached to the side of the first quarter wavelength film 13 opposite to the first liquid crystal cell 11A, thus obtaining the zoom element 30 of Embodiment 5.

[0549] In this embodiment, the incident light is incident on the sHWP before the PB lens 20, switching between right-circularly polarized light and left-circularly polarized light. The PB lens 20 is used to focus or diverge the light according to this polarization state. Therefore, the second 1 / 4 wavelength film 14 and the first 1 / 4 wavelength film 13 are positioned closer to the incident side than the first liquid crystal layer 500 and the second liquid crystal layer 600. Thus, the configuration and axial orientation of each layer differ from those in Embodiment 2.

[0550] The variable focus element 30 of Embodiment 5 is capable of switching between polarized light modulation and polarized light non-modulation with a wide bandwidth and wide viewing angle.

[0551] (Example 6)

[0552] An optical element 10 of Embodiment 6, having the same configuration as Modification 1 of the first embodiment described above, was fabricated. Specifically, a first positive C-plate 19A with a thickness direction retardation Rth of 70 nm is disposed on the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B; a second positive C-plate 19B with a thickness direction retardation Rth of 70 nm is disposed between the second liquid crystal cell 11B and the first 1 / 4 wavelength film 13; and the thickness direction retardation Rth of the negative C-plate 12 is changed to -140 nm. Otherwise, the optical element 10 of Embodiment 6 is fabricated in the same manner as in Embodiment 1. The driving method for the optical element 10 is also the same as in Embodiment 1.

[0553] For the optical element (sHWP) of Example 6, the Stokes parameter S3 of the emitted light when incident right-circularly polarized light (S3 = +1) is evaluated. Figure 73This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light of the optical elements of Example 6, Comparative Example 1, and Comparative Example 2 when the incident angle is set to 0°, in the unmodulated state. Figure 74 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical element of Example 6, Comparative Example 1 and Comparative Example 2 is modulated with the incident angle set to 0°. Figure 73 and Figure 74 This indicates the modulation and non-modulation characteristics in the visible light region when the incident angle is set to 0°. For example... Figure 73 and Figure 74 As shown, in Example 6, |S3|≥0.9 can be achieved in the wavelength range of 450nm~650nm, both during modulation and without modulation.

[0554] Figure 75 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Example 6 when the incident angle is set to 30° and it is not modulated. Figure 76 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 6 is modulated with the incident angle set to 30°. Figure 75 and Figure 76 This indicates the modulation and non-modulation characteristics at wavelengths of 450nm, 550nm, and 650nm when the incident angle is set to 30°. For example... Figure 75 and Figure 76 As shown, in Example 6, both modulated and unmodulated states can achieve |S3|≥0.9 across the entire wavelength range of 450nm to 650nm. Furthermore, Example 6 yielded even better characteristics than Example 1.

[0555] To investigate the preferred range of the retardation Rth in the thickness direction of the first positive C-plate 19A and the second positive C-plate 19B, optical calculations were performed on the optical element 10 of Example 6 using an LCD-MASTER1D manufactured by Sintek. Hereinafter, based on the simulation results, the range in which modulation and non-modulation ratios of 90% or more can be achieved within an incident angle of 30° and a wavelength of 450nm to 650nm is determined to be the preferred range. Furthermore, for simplicity, only data regarding the worst orientation at an incident angle of 30° for wavelengths of 450nm, 550nm, and 650nm are shown in the following charts.

[0556] Figure 77 This is a graph showing the Stokes parameter S3 when the delay Rth in the thickness direction relative to the optical element of Embodiment 6 is not modulated. Figure 78This is a graph showing the Stokes parameter S3 when the delay Rth in the thickness direction of the first positive C-plate of the optical element in Embodiment 6 is modulated. According to... Figure 77 and Figure 78 It can be seen that the thickness retardation Rth of the first positive C plate 19 is preferably above 0 nm and below 190 nm.

[0557] Figure 79 This is a graph showing the Stokes parameter S3 when the delay Rth in the thickness direction relative to the optical element of Embodiment 6 is not modulated. Figure 80 This is a graph showing the Stokes parameter S3 when the delay Rth in the thickness direction of the second positive C-plate of the optical element in Embodiment 6 is modulated. According to... Figure 79 and Figure 80 It can be seen that the thickness retardation Rth of the second positive C plate 19B is preferably above 0 nm and below 220 nm.

[0558] (Example 7)

[0559] Figure 178 This is a schematic diagram illustrating the orientation of liquid crystal molecules in the first and second states of the optical element of Example 7. An optical element 10 having the seventh configuration of Modification 2 of the first embodiment described above was fabricated. Figure 104 The corresponding optical element 10. In the optical element of this embodiment, Figure 178 The azimuth angle of the hysteresis axis 51A of the first A plate 51 (positive A plate) shown is 52.7°, and the azimuth angle of the hysteresis axis 52A of the second A plate 52 (negative A plate) is 10.2°.

[0560] The first A plate 51 has a Re at a wavelength of 550 nm of 140 nm, a Re at a wavelength of 450 nm relative to the Re at a wavelength of 550 nm of 1.01, and a Re at a wavelength of 650 nm relative to the Re at a wavelength of 550 nm of 0.99. Here, Re refers to the in-plane phase difference (Rp).

[0561] The Re of the second A plate 52 is 120nm at a wavelength of 550nm, the Re of the wavelength of 450nm is 1.08 relative to the Re of the wavelength of 550nm, and the Re of the wavelength of 650nm is 0.96 relative to the Re of the wavelength of 550nm.

[0562] The first C-plate 61 (positive C-plate) has an Rth of 75nm at a wavelength of 550nm, a Re at a wavelength of 450nm relative to the Re at a wavelength of 550nm is 1.07, and a Re at a wavelength of 650nm relative to the Re at a wavelength of 550nm is 0.97.

[0563] The second C-plate 62 (negative C-plate) has an Rth of -12.5nm at a wavelength of 550nm, a Re at a wavelength of 450nm relative to the Re at a wavelength of 550nm is 1.01, and a Re at a wavelength of 650nm relative to the Re at a wavelength of 550nm is 0.99.

[0564] The negative C plate 12 has an Rth of 160nm at a wavelength of 550nm, a Re at a wavelength of 450nm relative to the Re at a wavelength of 550nm is 1.01, and a Re at a wavelength of 650nm relative to the Re at a wavelength of 550nm is 0.99.

[0565] The first liquid crystal unit 11A and the second liquid crystal unit 11B are fabricated as follows: A first planar electrode 120, a second planar electrode 220, a third planar electrode 320, and a fourth planar electrode 420 are formed on the first substrate 100, the second substrate 200, the third substrate 300, and the fourth substrate 400, respectively. Furthermore, horizontal alignment films are respectively provided on the first substrate 100, the second substrate 200, the third substrate 300, and the fourth substrate 400 on which the planar electrodes are formed. Additionally, these horizontal alignment films may be pre-tilted by rubbing or other processes.

[0566] A first liquid crystal cell 11A is fabricated by depositing a first liquid crystal layer 500 between a first substrate 100 and a second substrate 200, which are respectively provided with a planar electrode and a horizontal alignment film. A second liquid crystal cell 11B is fabricated by depositing a second liquid crystal layer 600 between a third substrate 300 and a fourth substrate 400, which are respectively provided with a planar electrode and a horizontal alignment film. The first liquid crystal molecule 510 contained in the first liquid crystal layer 500 and the second liquid crystal molecule 610 contained in the second liquid crystal layer 600 are both positive liquid crystal molecules (Δn = 0.070). The thickness of both the first liquid crystal layer 500 and the second liquid crystal layer 600 is 3.4 μm.

[0567] In the second state, the orientation angle of the first liquid crystal molecule 511 on the first substrate 100 side is 0°, and the orientation angle of the first liquid crystal molecule 512 on the second substrate 200 side is 68°. In the first state, the orientation angle of the second liquid crystal molecule 611 on the third substrate 300 side is 90°, and the orientation angle of the second liquid crystal molecule 612 on the fourth substrate 400 side is 158°.

[0568] For the optical element (sHWP) of Example 7, the Stokes parameter S3 of the emitted light when incident right-circularly polarized light (S3 = +1) is evaluated. Figure 179 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical element of Embodiment 1 and Embodiment 7 is not modulated. Figure 180This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical elements of Examples 1 and 7 are modulated. Figure 179 and Figure 180 This indicates the modulation and non-modulation characteristics in the visible light region when the incident angle is set to 0°. For example... Figure 179 and Figure 180 As shown, in Example 7, similar to Example 1, |S3|≥0.9 can be achieved in the wavelength range of 450nm~650nm in both modulated and unmodulated states.

[0569] Figure 181 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Example 1 when the incident angle is set to 30° and it is not modulated. Figure 182 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 1 is modulated with the incident angle set to 30°. Figure 183 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Example 7 when the incident angle is set to 30° and the angle of incidence is not modulated. Figure 184 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 7 is modulated with the incident angle set to 30°. Figures 181-184 The evaluation results are shown at wavelengths of 450 nm, 550 nm, and 650 nm. Furthermore, the range of the gray shaded line in the figure represents |S3| ≥ 0.9, which is the preferred range.

[0570] like Figures 181-184 As shown, in Example 7, both during modulation and without modulation, |S3|≥0.9 can be achieved in all directions within the range of 450nm to 650nm. The characteristics of Example 7 are superior to those of Example 1.

[0571] To study the design of a suitable liquid crystal cell, optical calculations were performed on the optical element 10 of Example 7 using an LCD-MASTER1D manufactured by Cintec. Based on the simulation results, the range within which modulation and non-modulation ratios of 90% or more can be achieved at an incident angle of 30° and a wavelength of 450nm to 650nm is determined to be the preferred range. Furthermore, for simplicity, only the data for the worst-case orientation at an incident angle of 30° at wavelengths of 450nm, 550nm, and 650nm are shown in the following charts.

[0572] First, in order to study the preferred range of the thickness direction delay Rth of the second C plate 62 (negative C plate), the Stokes parameter S3 for the unmodulated thickness direction delay Rth of the second C plate 62 provided with the optical element 10 of Embodiment 7 and the Stokes parameter S3 for the modulated thickness direction delay Rth of the second C plate 62 provided with the optical element 10 of Embodiment 7 were obtained by simulation. Figure 185 This is a graph showing the Stokes parameter S3 when the delay Rth in the thickness direction of the second C plate of the optical element in Embodiment 7 is not modulated. Figure 186 This is a graph showing the Stokes parameter S3 when the delay Rth in the thickness direction of the second C-plate of the optical element in Embodiment 7 is modulated. (See graph for details.) Figure 185 and Figure 186 As shown, the thickness retardation Rth of the second C plate 62 is preferably -170nm or more and 0nm or less.

[0573] In order to study the preferred range of the thickness direction delay Rth of the first C plate 61 (positive C plate), the Stokes parameter S3 for the unmodulated thickness direction delay Rth of the first C plate 61 with respect to the optical element 10 of Embodiment 7 and the Stokes parameter S3 for the modulated thickness direction delay Rth of the first C plate 61 with respect to the optical element 10 of Embodiment 7 were obtained by simulation. Figure 187 This is a graph showing the Stokes parameter S3 when the delay Rth in the thickness direction of the first C-plate of the optical element in Embodiment 7 is not modulated. Figure 188 This is a graph showing the Stokes parameter S3 when the delay Rth in the thickness direction of the first C-plate of the optical element in Embodiment 7 is modulated. (See graph for details.) Figure 187 and Figure 188 As shown, the thickness retardation Rth of the first C plate 61 is preferably 0 nm or more and 230 nm or less.

[0574] In order to study the preferred range of the delay Rth in the thickness direction of the negative C plate 12, the Stokes parameter S3 when the negative C plate 12 is not modulated relative to the optical element 10 of Embodiment 7, and the Stokes parameter S3 when the delay Rth in the thickness direction of the negative C plate 12 is modulated relative to the optical element 10 of Embodiment 7 are obtained by simulation. Figure 189 This is a graph showing the Stokes parameter S3 when the delay Rth in the thickness direction of the negative C plate of the optical element in Example 7 is not modulated. Figure 190 This is a graph showing the Stokes parameter S3 when the delay Rth in the thickness direction of the negative C plate of the optical element in Embodiment 7 is modulated. (See graph for details.) Figure 189 and Figure 190As shown, the thickness retardation Rth of the negative C plate 12 is preferably -350nm or more and 0nm or less.

[0575] In order to study the preferred range of the in-plane phase difference Re of the second A plate 52 (negative A plate), the Stokes parameter S3 for the unmodulated in-plane phase difference Re of the second A plate 52 of the optical element 10 of Embodiment 7 and the Stokes parameter S3 for the modulated in-plane phase difference Re of the second A plate 52 of the optical element 10 of Embodiment 7 were obtained by simulation. Figure 191 This is a graph showing the Stokes parameter S3 when the in-plane phase difference Re of the optical element in Embodiment 7 is not modulated. Figure 192 This is a graph showing the Stokes parameter S3 when the in-plane phase difference Re of the second A plate of the optical element in Embodiment 7 is modulated. Figure 191 as well as Figure 192 As shown, the in-plane phase difference Re of the second A plate 52 is preferably above 92nm and below 140nm.

[0576] In order to study the preferred range of the azimuth angle of the hysteresis axis 52A of the second A plate 52, the Stokes parameter S3 for the non-modulated azimuth angle of the hysteresis axis 52A of the second A plate 52 with respect to the optical element 10 of Embodiment 7, and the Stokes parameter S3 for the modulated azimuth angle of the hysteresis axis 52A of the second A plate 52 with respect to the optical element 10 of Embodiment 7 were obtained by simulation. Figure 193 This is a graph showing the Stokes parameter S3 when the azimuth angle of the hysteresis axis of the second A plate relative to the optical element of Embodiment 7 is not modulated. Figure 194 This is a graph showing the Stokes parameter S3 when the azimuth angle of the hysteresis axis of the second A plate relative to the optical element of Embodiment 7 is modulated. (See graph for details.) Figure 193 and Figure 194 As shown, the azimuth angle of the hysteresis axis 52A of the second A plate 52 is preferably 4° or more and 17° or less.

[0577] In order to study the preferred range of the in-plane phase difference Re of the first A plate 51 (positive A plate), the Stokes parameter S3 for the unmodulated in-plane phase difference Re of the first A plate 51 of the optical element 10 of Embodiment 7 and the Stokes parameter S3 for the modulated in-plane phase difference Re of the first A plate 51 of the optical element 10 of Embodiment 7 were obtained by simulation. Figure 195 This is a graph showing the Stokes parameter S3 when the in-plane phase difference Re of the first A plate relative to the optical element of Embodiment 7 is not modulated. Figure 196This is a graph showing the Stokes parameter S3 when the in-plane phase difference Re of the first plate relative to the optical element of Embodiment 7 is modulated. (See graph for example.) Figure 195 and Figure 196 As shown, the in-plane phase difference Re of the first A plate 51 is preferably above 70nm and below 220nm.

[0578] In order to study the preferred range of the azimuth angle of the hysteresis axis 51A of the first A plate 51, the Stokes parameter S3 for the unmodulated azimuth angle of the hysteresis axis 51A of the first A plate 51 with respect to the optical element 10 of Embodiment 7, and the Stokes parameter S3 for the modulated azimuth angle of the hysteresis axis 51A of the first A plate 51 with respect to the optical element 10 of Embodiment 7 were obtained by simulation. Figure 197 This is a graph showing the Stokes parameter S3 when the azimuth angle of the hysteresis axis of the first A plate relative to the optical element of Embodiment 7 is not modulated. Figure 198 This is a graph showing the Stokes parameter S3 when the azimuth angle of the hysteresis axis of the first A plate of the optical element in Embodiment 7 is modulated. (See graph for details.) Figure 197 and Figure 198 As shown, the azimuth angle of the hysteresis axis 51A of the first plate 51 is preferably 47° or higher and 52° or lower.

[0579] Figure 199 It is a diagram illustrating the polarization state. Figure 185 The horizontal axis of the graph represents the phase difference and angle, while the vertical axis represents the value of "S3," a numerical representation of polarized light known as the Stokes parameter. For example... Figure 199 As shown in the Poincaré sphere, S3 = +1 corresponds to the north pole on the Poincaré sphere in terms of polarization state, representing right-circularly polarized light. S3 = -1 represents the south pole on the Poincaré sphere, representing left-circularly polarized light. That is, in this specification, the closer S3 is to ±1, the better the characteristics.

[0580] Furthermore, this specification describes the optical element 10 that switches between right-circularly polarized light and left-circularly polarized light. Therefore, there are two possible values: when right-circularly polarized light with S3 = +1 enters as incident light, is the incident light directly emitted as right-circularly polarized light with S3 = +1, or is it converted to left-circularly polarized light with S3 = -1 for emission? Therefore, in this specification, two graphs, one for non-modulated conditions and one for modulated conditions, are used to investigate the preferred range.

[0581] Furthermore, this specification targets optical elements with wide bandwidth and wide viewing angle. Therefore, in order to investigate whether it is possible to modulate all circularly polarized light (right-circularly polarized light in this specification) of RGB (red, green, and blue light) in the tilt direction, the incident angle was set to 30°, and S3 was plotted for wavelengths of 450nm, 550nm, and 650nm.

[0582] (Example 8)

[0583] An optical element of Embodiment 8 was fabricated having the same configuration as Modification 3 of the first embodiment described above. The first retardation film 71 and the second retardation film 72 used the same thin film.

[0584] In the optical element of this embodiment, Figure 201 The first phase difference film 71 (biaxial thin film) shown has a hysteresis axis 71A azimuth angle of 57.7 degrees, and the second phase difference film 72 (biaxial thin film) has a hysteresis axis 72A azimuth angle of 15.8 degrees.

[0585] The in-plane phase difference Re at a wavelength of 550 nm for the first phase retardation film 71 and the in-plane phase difference Re at a wavelength of 550 nm for the second phase retardation film 72 are both 140 nm. The in-plane phase difference at a wavelength of 450 nm relative to the in-plane phase difference at a wavelength of 550 nm for the first phase retardation film 71 and the in-plane phase difference at a wavelength of 450 nm relative to the in-plane phase difference at a wavelength of 550 nm for the second phase retardation film 72 are both 1.01. The in-plane phase difference at a wavelength of 650 nm relative to the in-plane phase difference at a wavelength of 550 nm for the first phase retardation film 71 and the in-plane phase difference at a wavelength of 650 nm relative to the in-plane phase difference at a wavelength of 550 nm for the second phase retardation film 72 are both 0.99.

[0586] The first phase difference film 71 and the second phase difference film 72 satisfy the above (Equation N5) and (Equation N6).

[0587] The first liquid crystal unit 11A and the second liquid crystal unit 11B are fabricated as follows: A first planar electrode 120, a second planar electrode 220, a third planar electrode 320, and a fourth planar electrode 420 are formed on the first substrate 100, the second substrate 200, the third substrate 300, and the fourth substrate 400, respectively. Furthermore, horizontal alignment films are respectively provided on the first substrate 100, the second substrate 200, the third substrate 300, and the fourth substrate 400 on which the planar electrodes are formed. Additionally, these horizontal alignment films may be pre-tilted by rubbing or other processes.

[0588] A first liquid crystal cell 11A is fabricated by depositing a first liquid crystal layer 500 between a first substrate 100 and a second substrate 200, which are respectively provided with a planar electrode and a horizontal alignment film. A second liquid crystal cell 11B is fabricated by depositing a second liquid crystal layer 600 between a third substrate 300 and a fourth substrate 400, which are respectively provided with a planar electrode and a horizontal alignment film. The first liquid crystal molecule 510 contained in the first liquid crystal layer 500 and the second liquid crystal molecule 610 contained in the second liquid crystal layer 600 are both positive liquid crystal molecules (Δn = 0.070). The thickness of both the first liquid crystal layer 500 and the second liquid crystal layer 600 is 3.4 μm.

[0589] In the second state, the orientation angle of the first liquid crystal molecule 511 on the first substrate 100 side is 0°, and the orientation angle of the first liquid crystal molecule 512 on the second substrate 200 side is 68°. In the first state, the orientation angle of the second liquid crystal molecule 611 on the third substrate 300 side is 90°, and the orientation angle of the second liquid crystal molecule 612 on the fourth substrate 400 side is 158°.

[0590] For the optical element (sHWP) of Example 8, the Stokes parameter S3 of the emitted light when incident right-circularly polarized light (S3 = +1) is evaluated. Figure 202 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical elements of Example 8, Comparative Example 1, and Comparative Example 2 are not modulated. Figure 203 This is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical elements of Example 8, Comparative Example 1, and Comparative Example 2 are modulated. Figure 202 and Figure 203 The text indicates the modulation and non-modulation characteristics in the visible light region when the incident angle is set to 0°. For example... Figure 202 and Figure 203 As shown, in Example 8, |S3|≥0.9 can be achieved both during modulation and in the non-modulated wavelength range of 450nm to 650nm.

[0591] Figure 204 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle of the optical element of Example 8 when the incident angle is set to 30° and the angle of incidence is not modulated. Figure 205 This is a graph showing the relationship between the Stokes parameter S3 and the azimuth angle when the optical element of Example 8 is modulated with the incident angle set to 30°. Figure 204 and Figure 205 The evaluation results at wavelengths of 450 nm, 550 nm, and 650 nm are shown. Additionally, the range of the shaded area in the gray area of ​​the figure represents the preferred range where |S3| ≥ 0.9.

[0592] like Figure 204 as well as Figure 205 As shown in Example 8, both during modulation and without modulation, |S3|≥0.9 can be achieved in all directions within the range of 450nm to 650nm.

[0593] In the optical element 10 of Embodiment 8, a wide viewing angle can be achieved by using the same biaxial thin film in both the first retardation film 71 and the second retardation film 72. Such an optical element can be manufactured at low cost. Furthermore, the number of thin films can be reduced, which is also considered advantageous in terms of thinning.

[0594] Explanation of reference numerals in the attached figures

[0595] 1: Head-mounted display

[0596] 1P: Display panel

[0597] 10, 10R1, 10R2: Optical elements

[0598] 11A, 11B, 11R1: Liquid crystal units

[0599] 12, 61NC, 62NC, 63NC, 64NC: Negative C plate

[0600] 13, 14, 15R, 18R: 1 / 4 wavelength film

[0601] 13A, 14A, 51A, 52A, 71A, 72A: Hysteresis shafts

[0602] 16R, 17R: 1 / 2 wavelength film

[0603] 19A, 19B, 61PC, 62PC, 63PC, 64PC: Positive C-board

[0604] 20, 20A1, 20A2, 20A3: Pancharatnam-Berry (PB) lenses

[0605] 30, 30A, 30B: Variable zoom element

[0606] 40: Phase Difference Plate

[0607] 41, 42, 43, 44: Orientation film

[0608] 51, 52: Board A

[0609] 51NA, 52NA: Negative A plate

[0610] 51PA, 52PA: Positive A-plate

[0611] 61, 62, 63, 64: Board C

[0612] 71, 72: Phase retardation film

[0613] 100, 200, 300, 400: substrate

[0614] 110, 210, 310, 410: Support base plate

[0615] 120, 220, 320, 420: Full-surface electrode

[0616] 500, 600: Liquid crystal layer

[0617] 500R1, 500R2, 500R3: TN liquid crystal layer

[0618] 510, 511, 512, 610, 611, 612, 710: liquid crystal molecules

[0619] 511A, 512A, 611A, 612A: Orientation direction

[0620] 700: Optical Anisotropy Layer

[0621] 810, 820, 830, 840: Photomasks

[0622] 900: PB lens forming film

[0623] LC0, LC1, LC2: left circular polarization

[0624] R0, R1, R2: Regions

[0625] U: User

Claims

1. An optical element, characterized in that, It comprises, in sequence, a first substrate, a first liquid crystal layer containing first liquid crystal molecules, a second substrate, a third substrate, a second liquid crystal layer containing second liquid crystal molecules, and a fourth substrate. The first substrate, the first liquid crystal layer, and the second substrate constitute a first liquid crystal cell. The third substrate, the second liquid crystal layer, and the fourth substrate constitute a second liquid crystal unit. The first liquid crystal cell has a first electrode for applying voltage to the first liquid crystal layer on at least one of the first substrate and the second substrate. The second liquid crystal cell has a second electrode for applying voltage to the second liquid crystal layer in at least one of the third substrate and the fourth substrate. The first electrode and the second electrode are configured to switch between a first state and a second state. The first state is a state in which the second liquid crystal molecules are twisted and oriented vertically, and the second state is a state in which the first liquid crystal molecules are twisted and oriented vertically. The azimuth angle of the orientation direction of the second liquid crystal molecule on the third substrate side in the first state and the azimuth angle of the orientation direction of the second liquid crystal molecule on the fourth substrate side in the first state are respectively obtained by rotating the azimuth angle of the orientation direction of the first liquid crystal molecule on the first substrate side in the second state and the azimuth angle of the orientation direction of the first liquid crystal molecule on the second substrate side in the second state in the same direction by 1 / 4.

2. The optical element according to claim 1, characterized in that, A negative C-plate is also provided between the first liquid crystal unit and the second liquid crystal unit.

3. The optical element according to claim 2, characterized in that, The thickness retardation Rth of the negative C plate is greater than -220nm and less than 0nm.

4. The optical element according to any one of claims 1 to 3, characterized in that, The delay of the first liquid crystal layer in the second state at a wavelength of 550 nm is greater than 200 nm and less than 260 nm. The delay of the second liquid crystal layer in the first state at a wavelength of 550 nm is greater than 210 nm and less than 260 nm.

5. The optical element according to any one of claims 1 to 3, characterized in that, The first liquid crystal unit does not have the same structure as the second liquid crystal unit.

6. The optical element according to any one of claims 1 to 3, characterized in that, In the second state, the first liquid crystal molecules are oriented with a twist angle of 61° or more and 75° or less. In the first state, the second liquid crystal molecules are oriented with a twist angle of 64° or more and 74° or less.

7. The optical element according to any one of claims 1 to 3, characterized in that, In the second state, the azimuth angle of the orientation direction of the first liquid crystal molecules on the first substrate side is greater than -9° and less than 7°. In the first state, the azimuth angle of the orientation direction of the second liquid crystal molecules on the third substrate side is 85° or more and 96° or less.

8. The optical element according to any one of claims 1 to 3, characterized in that, A 1 / 4 wavelength film is also provided on the side of the first liquid crystal cell opposite to the second liquid crystal cell or on the side of the second liquid crystal cell opposite to the first liquid crystal cell.

9. The optical element according to claim 8, characterized in that, The 1 / 4 wavelength film has reverse wavelength dispersion characteristics.

10. The optical element according to claim 8, characterized in that, The in-plane phase difference of the 1 / 4 wavelength film at a wavelength of 450 nm is more than 0.7 times and less than 1 times the in-plane phase difference at a wavelength of 550 nm.

11. The optical element according to claim 8, characterized in that, The in-plane phase difference of the 1 / 4 wavelength film at a wavelength of 650 nm is more than 1 and less than 1.3 times the in-plane phase difference at a wavelength of 550 nm.

12. The optical element according to claim 8, characterized in that, The azimuth angle of the hysteresis axis of the quarter-wavelength film is above 52° and below 60°.

13. The optical element according to claim 8, characterized in that, The in-plane phase difference of the 1 / 4 wavelength film at a wavelength of 550nm is greater than 90nm and less than 170nm.

14. The optical element according to claim 8, characterized in that, The 1 / 4 wavelength film is the first 1 / 4 wavelength film. A second quarter-wavelength film is also provided on the side of the first quarter-wavelength film opposite to the first liquid crystal cell and the second liquid crystal cell.

15. The optical element according to claim 14, characterized in that, The second 1 / 4 wavelength film has flat wavelength dispersion characteristics.

16. The optical element according to claim 14, characterized in that, The azimuth angle of the hysteresis axis of the second 1 / 4 wavelength film is 8° or more and 18° or less.

17. The optical element according to claim 14, characterized in that, The in-plane phase difference of the second 1 / 4 wavelength film with a wavelength of 550nm is greater than 120nm and less than 150nm.

18. A variable focus element, characterized in that, It possesses: The optical element according to any one of claims 1 to 3; and Pancharatenam-Berry lens.

19. The variable focus element according to claim 18, characterized in that, The Pancharatnam-Berry lens is disposed within the optical element.

20. A head-mounted display, characterized in that, It has the variable focus element as described in claim 18.

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