Viewing angle symmetric light modulation device and application thereof

Abstract

This invention provides a viewing angle-symmetrical optical modulation device and its application. The viewing angle-symmetrical optical modulation device includes at least two layers of guest-host liquid crystal dimming devices and a waveplate with an optical path length equivalent to 1 / 2λ, the waveplate being located between the at least two layers of guest-host liquid crystal dimming devices. The optical modulation device of this invention has advantages such as a centrally symmetrical viewing angle, a wide superposition angle, low operating voltage, simple structure, and low production cost. This invention also provides an application of the viewing angle-symmetrical optical modulation device.

Description

Technical Field

[0001] This invention relates to the field of liquid crystal dimming technology, and more specifically, to a viewing angle symmetrical light modulation device and its application. Background Technology

[0002] When shooting with lenses from devices like mobile phones, cameras, and drones, if the light is too strong, the aperture must be stopped down. However, this can lead to insufficient exposure, making it difficult to achieve the necessary exposure combination. When the scene is too bright, a slower shutter speed may not be possible. In such cases, using a neutral density (ND) filter solves this problem. ND filters reduce the amount of light passing through the lens, preventing overexposure and allowing the photographer to express their intentions. ND filters are categorized by their ability to block light, usually expressed in "stops," such as ND2 (1 stop), ND4 (2 stops), and ND8 (3 stops). Each stop reduces the amount of light passing through the filter by half. The choice of ND filter level depends on the light intensity of the shooting environment and the desired effect. Traditional ND filters only reduce the amount of light passing through the lens and do not affect the color tone. Superficially, the color tone of these filters transitions from gray to black; the higher the number, the stronger the ability to reduce light.

[0003] Traditional ND filters are made of optical glass. When using different levels of ND filters, the appropriate level is typically selected and placed in front of the lens. High-end digital cameras use built-in ND filters, and ND filters are standard equipment on professional broadcast-grade camcorders. In photography and videography using equipment including cameras, mobile phone lenses, drone lenses, and CCD (Charge Coupled Device) cameras, filters serve as additional lenses for filtering natural light. They can filter transmitted light, eliminating the effects of light brightness in different environments, achieving various special image effects, and improving the overall photographic and video quality.

[0004] Guest-host type liquid crystal dimming elements are a type of dimming element that can achieve high light utilization efficiency without a polarizer. Guest-host liquid crystals consist of a dichroic dye (guest body) dissolved in a liquid crystal (host body) with a specific orientation. The dichroic dye absorbs different wavelengths of visible light, thus causing the dimming device to display different colors. Typically, dichroic dyes exhibit anisotropic absorption of visible light along their long and short axes, resulting in two states within the dimming device: an absorbing state and a non-absorbing state. When subjected to an electric field, the orientation of the dichroic dye changes along with the orientation of the liquid crystal molecules, thereby altering the absorption of visible light by the dichroic dye in different directions.

[0005] Using guest-master type liquid crystal dimming elements as ND filters: Guest-master type liquid crystal dimming elements can achieve stepless dimming. When used as ND filters, multiple ND filters can be integrated into one unit, eliminating the need for frequent ND filter switching. However, single-layer master type liquid crystal dimming elements have high light transmittance, making it difficult to achieve small ND values. The inventors of this invention discovered that using double-layer and multi-layer guest-master type liquid crystal dimming elements stacked together achieves switching between multiple ND values. However, the inventors also discovered that guest-master type liquid crystal dimming elements have the disadvantage of non-central symmetry in viewing angle, and that the adjustable angle is more limited when double-layer and multi-layer guest-master type liquid crystal dimming elements are stacked. To address these problems in the prior art, this invention provides a viewing angle symmetrical light modulation device, which has the advantages of a centrally symmetrical viewing angle, wide stacking angle, low operating voltage, simple structure, and low production cost. Summary of the Invention

[0006] The purpose of this invention is to provide a symmetrical optical modulation device with a centrally symmetrical viewing angle, as well as advantages such as a wide superposition angle, low operating voltage, simple structure, and low production cost.

[0007] To achieve the above-mentioned objective, the present invention provides a symmetrical optical modulation device, which includes at least two layers of guest-host liquid crystal dimming devices and a waveplate with an optical path equivalent to 1 / 2λ, wherein the waveplate with an optical path equivalent to 1 / 2λ is located between the at least two layers of guest-host liquid crystal dimming devices.

[0008] In some embodiments of the present invention, the viewing angle symmetrical light modulation device includes two guest-host liquid crystal dimming devices, namely a first guest-host liquid crystal dimming device and a second guest-host liquid crystal dimming device. The first guest-host liquid crystal dimming device includes a first substrate, a first conductive layer, a first alignment layer, a first guest-host liquid crystal composition, a second alignment layer, a second conductive layer, and a second substrate. The second guest-host liquid crystal dimming device includes a third substrate, a third conductive layer, a third alignment layer, a second guest-host liquid crystal composition, a fourth alignment layer, a fourth conductive layer, and a fourth substrate. Both the first guest-host liquid crystal composition and the second guest-host liquid crystal composition contain parent liquid crystal and dichroic dye.

[0009] In some embodiments of the present invention, the friction directions of the first orientation layer and the second orientation layer are opposite, the friction directions of the third orientation layer and the fourth orientation layer are opposite, and the friction directions of the second orientation layer and the third orientation layer are the same.

[0010] In some embodiments of the present invention, the angle between the fast axis or slow axis direction of the waveplate with an optical path equivalent to 1 / 2λ and the friction direction of the second orientation layer is 0 to 90 degrees.

[0011] In some embodiments of the present invention, the parent liquid crystal comprises:

[0012] One or more compounds of general formula I

[0013] as well as

[0014] One or more compounds of general formula II

[0015]

[0016] in,

[0017] R M1 and R M2 Each can independently represent -H, a straight-chain or branched alkyl group containing 1-12 carbon atoms, One or more non-adjacent -CH2- groups of the straight-chain or branched alkyl group containing 1-12 carbon atoms may be independently replaced by -O-, -CO-, -CO-O- or -O-CO-.

[0018] R A Indicates a straight-chain or branched alkyl group containing 1-12 carbon atoms. One or more non-adjacent -CH2- in the straight-chain or branched alkyl group containing 1-12 carbon atoms can be independently replaced by -CH=CH-, -C≡C-, -O-, -CO-, -CO-O- or -O-CO-;

[0019] Z M1 and Z M2 Each can be represented independently as a single bond, -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CH=CH-, -C≡C-, -CH2CH2-, or -(CH2)4-;

[0020] Z A1 and Z A2 Each can independently represent a single bond, -CH2CH2-, -CF2CF2-, -CF2O-, -OCF2-, -CO-O-, -O-CO-, -O-CO-O-, -CH=CH-, -CF=CF-, -CH2O-, or -OCH2-;

[0021] L A1 and L A2 Each can be represented independently as -H or -F;

[0022] X A The terms "halogen", "halogenated alkyl" or "alkoxy" containing 1-5 carbon atoms, and "halogenated alkenyl" or "alkoxy" containing 2-5 carbon atoms are used to indicate halogens.

[0023] ring ring and ring Each represents independently in, One or more of the -CH2- can be replaced by -O-. At most one hydrogen atom can be replaced by a halogen.

[0024] ring and ring Each represents independently in, and One or more -CH2- bonds can be replaced by -O- bonds, and one or more single bonds in a ring can be replaced by double bonds. One or more -H can be replaced by -CN, -F or -Cl, and one or more -CH= in a ring can be replaced by -N=;

[0025] n M1 Represents 0, 1, 2, or 3, and when n M1 When the number is 2 or 3, the ring They can be the same or different, Z M2 They can be the same or different;

[0026] n A Represents 0, 1, 2, or 3, and when n A When the number is 2 or 3, the ring They can be the same or different, Z A1 They can be the same or different.

[0027] In some embodiments of the present invention, the parent liquid crystal contains at least two Z... A2 Compounds of general formula I with single bonds.

[0028] In order to obtain an optical modulation device with a centrally symmetrical viewing angle, a wide superposition angle, and a low operating voltage, in some embodiments of the present invention, the parent liquid crystal contains at least three types of L... A1 and L A2 All are compounds of general formula I with -F; in some embodiments of the present invention, the parent liquid crystal contains at least four L... A1 and L A2 All are compounds of general formula I with -F; in some embodiments of the present invention, the parent liquid crystal contains at least five L... A1 and L A2 All are compounds of general formula I with -F.

[0029] In some embodiments of the present invention, the compounds of general formula I are selected from the group consisting of the following compounds:

[0030]

[0031]

[0032]

[0033]

[0034] as well as

[0035]

[0036] in,

[0037] R A1 It refers to straight-chain or branched alkyl or alkoxy groups containing 1-12 carbon atoms.

[0038] X A1 It represents -F, fluoroalkyl or alkoxy groups containing 1-5 carbon atoms, and fluoroalkenyl or alkenyloxy groups containing 2-5 carbon atoms;

[0039] L A3 L A4 and L A5 Each can be represented independently as -H or -F.

[0040] In some embodiments of the present invention, L A1 and L A2 Both represent -F.

[0041] In some embodiments of the present invention, the compounds of general formula II are selected from the group consisting of the following compounds:

[0042]

[0043]

[0044] as well as

[0045] in,

[0046] R M11 and R M21 Each can be independently represented as a straight-chain or branched alkyl or alkoxy group containing 1 to 12 carbon atoms.

[0047] In order to obtain an optical modulation device with a centrally symmetric viewing angle, a wide superposition angle, and a low operating voltage, in a preferred embodiment of the present invention, the compound of general formula II is selected from the group consisting of compounds of general formula II-1, general formula II-2, general formula II-7, general formula II-8, general formula II-13, general formula II-16, general formula II-17 and general formula II-20.

[0048] In some embodiments of the present invention, the compound of general formula II accounts for not less than 20% and not more than 60% of the total weight of the parent liquid crystal.

[0049] In some embodiments of the present invention, the parent liquid crystal comprises: 20-60% by weight of one or more compounds of general formula II, and 50-80% by weight of one or more compounds of general formula I.

[0050] In some embodiments of the present invention, the first orientation layer and the second orientation layer are both parallel oriented.

[0051] In some embodiments of the present invention, the second orientation layer and the third orientation layer are both parallel oriented.

[0052] In some embodiments of the present invention, the first guest-host liquid crystal composition and the second guest-host liquid crystal composition are the same.

[0053] In some embodiments of the present invention, the first guest-host liquid crystal composition and the second guest-host liquid crystal composition are different.

[0054] In some embodiments of the present invention, the clearing point of both the first guest-host liquid crystal composition and the second guest-host liquid crystal composition is greater than 85°C, and the absolute value of dielectric anisotropy is greater than 5.

[0055] In order to obtain an optical modulation device with a centrally symmetrical viewing angle, a wide superposition angle, and a low operating voltage, in some embodiments of the present invention, the dichroic dye accounts for 0.01%-8% of the weight percentage of the first guest-host liquid crystal composition or the second guest-host liquid crystal composition; in some embodiments of the present invention, the dichroic dye accounts for 0.1%-5% of the weight percentage of the first guest-host liquid crystal composition or the second guest-host liquid crystal composition; in some embodiments of the present invention, the dichroic dye accounts for 0.1%-3% of the weight percentage of the first guest-host liquid crystal composition or the second guest-host liquid crystal composition.

[0056] In some embodiments of the present invention, the first guest-host liquid crystal composition or the second guest-host liquid crystal composition may further contain 0.001%-5% by weight of a chiral dopant. In some embodiments of the present invention, the chiral dopant accounts for 0.001%-2% of the total weight of the first guest-host liquid crystal composition or the second guest-host liquid crystal composition. In some embodiments of the present invention, the chiral dopant accounts for 0.001-1% of the total weight of the first guest-host liquid crystal composition or the second guest-host liquid crystal composition.

[0057] In some embodiments of the present invention, the first substrate, the second substrate, the third substrate, and the fourth substrate are each independently a rigid transparent substrate. In some embodiments of the present invention, the rigid transparent substrate is glass or a hard film layer, wherein the hard film layer may be a transparent plastic film or a transparent plastic sheet.

[0058] In some embodiments of the present invention, the dichroic dye molecule is selected from one or more of azo dyes, anthraquinone dyes, phthalocyanine dyes, cyanine dyes, indigo dyes, arylmethanes, nitro groups, and nitroso groups.

[0059] In some embodiments of the present invention, the dichroic dye is selected from one or more of azo dyes, anthraquinone dyes, and combinations thereof.

[0060] The stabilizers mentioned below can be added to the parent liquid crystal of the present invention.

[0061]

[0062]

[0063]

[0064] Preferably, the stabilizer is selected from the stabilizers shown below.

[0065]

[0066] In embodiments of the present invention, the stabilizer preferably accounts for 0-5% of the total weight of the parent liquid crystal; more preferably, the stabilizer accounts for 0-2% of the total weight of the parent liquid crystal; and as a particularly preferred embodiment, the stabilizer accounts for 0.001-1% of the total weight of the parent liquid crystal.

[0067] To obtain an optical modulation device with a centrally symmetrical viewing angle, a wide superposition angle, low operating voltage, simple structure, and low production cost, the waveplate with an optical path equivalent to 1 / 2λ described in this invention is a waveplate with an optical path of 1 / 2λ or a combination of multiple waveplates with an optical path of 1 / 4λ; in some embodiments of this invention, the waveplate with an optical path equivalent to 1 / 2λ is a combination of at least three waveplates with an optical path of 1 / 4λ; in some embodiments of this invention, the waveplate with an optical path equivalent to 1 / 2λ is a combination of three waveplates with an optical path of 1 / 4λ.

[0068] In the embodiments of the present invention, selecting a waveplate with a shorter optical path length (equivalent to 1 / 2λ) is beneficial for improving the color shift of the symmetrical optical modulator. When the waveplate with an optical path length equivalent to 1 / 2λ is a combination of three waveplates with an optical path length of 1 / 4λ, the color shift of the symmetrical optical modulator is lower than that of the waveplate with an optical path length of 1 / 2λ. When the waveplate with an optical path length equivalent to 1 / 2λ is a combination of six waveplates with an optical path length of 1 / 8λ, the color shift of the symmetrical optical modulator is lower than that of the waveplate with an optical path length equivalent to 1 / 2λ formed by combining three waveplates with an optical path length of 1 / 4λ.

[0069] In the symmetrical optical modulator of the present invention, the fast axis direction of the waveplate with an optical path equivalent to 1 / 2λ forms an angle of 30-60 degrees with the rubbing direction of the second orientation layer, preferably 45°. Figure 1 As shown.

[0070] The symmetrical optical modulator of the present invention comprises a first substrate, a first conductive layer, a first alignment layer, a first host-guest liquid crystal composition, a second alignment layer, a second conductive layer, a second substrate, a waveplate with an optical path equivalent to 1 / 2λ, a third substrate, a third conductive layer, a third alignment layer, a second host-guest liquid crystal composition, a fourth alignment layer, a fourth conductive layer, and a fourth substrate stacked together. The detailed structure is described below. Figure 2 As shown.

[0071] In the symmetrical optical modulation device of this invention, the light rays passing through the first layer of host-guest liquid crystal dimming device vibrate along the long axis of the parent liquid crystal molecules. After passing through a waveplate with an optical path equivalent to 1 / 2λ, the vibration direction rotates by 90°. The light rays from the two polarization directions are superimposed, exhibiting a centrally symmetrical effect, such as... Figure 3 As shown. Among them, the waveplate with an optical path equivalent to 1 / 2λ can be a waveplate with an optical path of 1 / 2λ or a combination of three waveplates with an optical path of 1 / 4λ.

[0072] Compared with the prior art, the optical modulation device of the present invention has the advantages of centrally symmetrical viewing angle, wide superposition angle, low operating voltage, simple structure, and low production cost.

[0073] Another aspect of the present invention provides an application of the aforementioned symmetrical optical modulation device in a neutral density filter. Attached Figure Description

[0074] Figure 1 This is a schematic diagram showing the angle between the waveplate (with an optical path equivalent to 1 / 2λ) and the friction direction of the orientation layer in the optical modulator of the present invention with a symmetrical perspective.

[0075] Figure 2 A schematic diagram illustrating the structure of the optical modulator with symmetrical perspective according to the present invention.

[0076] Figure 3 A schematic diagram illustrating the working principle of the symmetrical optical modulator of the present invention.

[0077] Figure 4 This is a schematic diagram of the optical modulation device of Comparative Example 1 of the present invention.

[0078] Figure 5 This diagram illustrates the viewing angles of the optical modulation device in Comparative Example 1 of the present invention when the pre-tilt angles of the first and second layer liquid crystal dimming devices are symmetrical, with and without power applied.

[0079] Figure 6 This diagram illustrates the viewing angles of the optical modulation device in Comparative Example 1 of the present invention when the pre-tilt angles of the first and second layer liquid crystal dimming devices are asymmetrical, with and without power applied.

[0080] Figure 7 This is a schematic diagram showing the structure of the optical modulation device in Embodiment 1 of the present invention.

[0081] Figure 8 This diagram illustrates the viewing angles of the optical modulation device of Embodiment 1 of the present invention when the pretilt angles of the first and second layer liquid crystal dimming devices are symmetrical, with and without power applied.

[0082] Figure 9 This diagram illustrates the viewing angles of the optical modulation device in Embodiment 1 of the present invention when the pretilt angles of the first and second layer liquid crystal dimming devices are asymmetrical, with and without power applied.

[0083] Figure 10 This is a schematic diagram showing the structure of the optical modulation device in Embodiment 2 of the present invention.

[0084] Figure 11 This is a schematic diagram showing the viewing angles of the optical modulation device of Embodiment 2 of the present invention when the pretilt angles of the first and second layer liquid crystal dimming devices are symmetrical, with and without power applied.

[0085] Figure 12 This diagram illustrates the viewing angles of the optical modulation device in Embodiment 2 of the present invention when the pretilt angles of the first and second layer liquid crystal dimming devices are asymmetrical, with and without power applied. Detailed Implementation

[0086] The abbreviated codes for each test item in the embodiment are as follows:

[0087] t -40℃ Low-temperature storage time (h)

[0088] Cp (Clearing point, °C, nematic-isotropic phase transition temperature)

[0089] Δn Optical anisotropy (589nm, 25℃)

[0090] Δε dielectric anisotropy (1kHz, 25℃)

[0091] T on Open state transmittance

[0092] T off Off-state transmittance

[0093] in,

[0094] Cp: ​​Obtained by testing with a melting point apparatus.

[0095] Δn: Optical anisotropy was obtained by measuring Abbe refractometer under sodium lamp (589nm) light source at 25℃.

[0096] Δε=ε||-ε⊥, where ε|| is the dielectric constant parallel to the molecular axis and ε⊥ is the dielectric constant perpendicular to the molecular axis. Test conditions: 25℃, 1KHz, TN type test box with a thickness of 7μm.

[0097] Transmittance and radar images under different conditions and viewing angles were measured by DMS505 at 25°C.

[0098] t -40℃ Liquid crystal was poured into a 7µm TN cell and placed in a -40°C freezer. Its low-temperature performance was continuously observed and recorded.

[0099] In the host-guest liquid crystal composition of the present invention, the host liquid crystal is a nematic liquid crystal composition, and the various liquid crystal components contained therein are all compounds known in the art, and those skilled in the art can synthesize these compounds by conventional methods.

[0100] In the guest-host liquid crystal dimming device of the present invention, the dichroic dye in the guest-host liquid crystal composition can be formulated from a single dye into a combined dye, and form a guest-host liquid crystal composition with the parent liquid crystal. The dichroic dye is an azo dye or anthraquinone dye or a combination of both. In some embodiments, the dichroic dye is selected from one or more of the dyes listed in Table 1. All of the dyes are commercially available.

[0101] Table 1. Dye molecular structure and maximum absorption wavelength

[0102]

[0103]

[0104]

[0105] One or more single dyes are selected as needed to formulate a dye composition, which is then mixed and dissolved with liquid crystal molecules in a certain proportion using conventional methods such as heating, ultrasound, and suspension to obtain a host-guest liquid crystal composition.

[0106] In the following embodiments, for ease of representation of each liquid crystal compound, the group structures of the liquid crystal compounds are represented by the codes listed in Table 2:

[0107] Table 2. Group structure codes of liquid crystal compounds

[0108]

[0109] Take the following compound with the following structural formula as an example:

[0110]

[0111] If the structural formula is represented by the codes listed in Table 2, it can be expressed as: 3CWO2, where 3 in the code represents the number of C atoms in the left-end alkyl group, that is, the alkyl group is -C3H7; C in the code represents cyclohexyl; W in the code represents 2,3-difluorophenylene; O in the code represents oxygen atoms; and 2 in the code represents the number of C atoms in the right-end alkyl group, that is, the alkyl group is -C2H5.

[0112] Structure of a symmetrical optical modulator

[0113] The structure of the symmetrical optical modulator of the present invention is as follows: Figure 2 As shown. The first guest-host liquid crystal dimming device includes a first substrate, a first conductive layer, a first alignment layer and a second alignment layer, a second conductive layer and a second substrate, with a first guest-host liquid crystal composition poured between the first and second alignment layers. The second guest-host liquid crystal dimming device includes a third substrate, a third conductive layer, a third alignment layer and a fourth alignment layer, a fourth conductive layer and a fourth substrate, with a second guest-host liquid crystal composition poured between the third and fourth alignment layers. A waveplate with an optical path equivalent to 1 / 2λ is disposed between the first and second guest-host liquid crystal dimming devices. Parallel alignment layers are coated on the inner surfaces of the first and second conductive layers to control the orientation of the guest-host liquid crystal composition.

[0114] Comparative Example 1

[0115] The parent liquid crystal 1 for comparison was prepared according to the compounds and weight percentages listed in Table 3. It was filled between the two substrates of the liquid crystal cell and its performance was tested. The test data are shown in the table below:

[0116] Table 3. Composition and proportions of the parent liquid crystal 1

[0117]

[0118] Comparative Example 1 provides an optical modulation device comprising first and second guest-host liquid crystal dimming devices, wherein the cell thickness of both the first and second guest-host liquid crystal dimming devices is 9µm, and the stacking arrangement is as follows: Figure 4As shown, two guest-host liquid crystal dimming devices are vertically stacked, with the light modulation device appearing black. 0.6 wt% dye 1 + 0.6 wt% dye 7 + 0.8 wt% dye 23 (dye numbers and structures are shown in Table 1) are added to the parent liquid crystal 1 to form a guest-host liquid crystal composition. This composition is then filled into the liquid crystal dimming device of Comparative Example 1 for performance testing. The transmittance of the light modulation device of Comparative Example 1 is shown in Table 4, its transmittance at different viewing angles in the dark state is shown in Table 5, and its transmittance at different viewing angles in the bright state is shown in Table 6.

[0119] When the pre-tilt angles of the first and second layer liquid crystal dimming devices are symmetrical, the viewing angles of the light modulation device when it is powered on and not powered on are as follows: Figure 5 When the pre-tilt angles of the first and second layer liquid crystal dimming devices are asymmetrical, the viewing angles of the light modulation device when it is powered on and not powered on are as follows: Figure 6 It is evident that the viewing angles obtained by the superposition of the dual-layer host and guest liquid crystal dimming devices are not centrally symmetrical, but rather left-right symmetrical, which has certain drawbacks when applied to ND filters.

[0120] Table 4. Transmittance of dye liquid crystal in Comparative Example 1

[0121]

[0122] Table 5. Transmittance at different viewing angles in the dark state (0V)

[0123]

[0124] Table 6. Transmittance at different viewing angles in bright state (4V)

[0125]

[0126] In this invention patent, Phi is the angle in the azimuth plane (horizontal plane), ranging from 0 to 360°; Theta is the angle in the pitch plane (vertical plane), ranging from 0 to 180°.

[0127] As can be seen from the results in Tables 5 and 6, the transmittance of the comparative examples in both the dark and bright states at a 35° Theta angle is symmetrical from left to right and not neutrally symmetrical.

[0128] Example 1

[0129] The parent liquid crystal of Example 1 was prepared according to the compounds and weight percentages listed in Table 7, and its performance was tested by filling it between the two substrates of the liquid crystal cell. The test data are shown in the table below:

[0130] Table 7. Composition and proportions of the parent liquid crystal

[0131]

[0132]

[0133] An optical modulation device according to Embodiment 1 is provided, comprising first and second guest-host liquid crystal dimming devices and a waveplate with an optical path equivalent to 1 / 2λ. The cell thickness of both the first and second guest-host liquid crystal devices is 9µm. The dimming devices are black, and the two guest-host liquid crystal dimming devices are stacked in parallel. The intermediate waveplate with an optical path equivalent to 1 / 2λ is a single 1 / 2λ waveplate, whose fast axis direction forms a 45° angle with the friction direction of the second alignment layer. Figure 7 As shown.

[0134] A host-guest liquid crystal composition was formed by adding 0.6 wt% dye 1, 0.6 wt% dye 7, and 0.8 wt% dye 23 (the dye numbers and structures are shown in Table 1) to the parent liquid crystal. This host-guest liquid crystal composition was then filled into the liquid crystal dimming device of Example 1, and performance tests were performed. The transmittance of the light modulation device of Example 1 is shown in Table 8; its transmittance at different viewing angles in the dark state is shown in Table 9, and its transmittance at different viewing angles in the bright state is shown in Table 10.

[0135] When the pretilt angles of the first and second layer liquid crystal dimming devices are symmetrical, the viewing angles of the light modulation device, whether powered on or off, are centrally symmetrical, such as... Figure 8 As shown; when the pretilt angles of the first and second layer liquid crystal dimming devices are asymmetrical, the viewing angle of the entire light modulation device without power is symmetrical from left to right, as shown. Figure 9 As shown.

[0136] Table 8. Transmittance of dye-based liquid crystals

[0137]

[0138] Table 9. Transmittance at different viewing angles in the dark state (0V)

[0139]

[0140]

[0141] Table 10. Transmittance at different viewing angles in bright state (4V)

[0142]

[0143] It is evident that after the double-layer host-guest liquid crystal dimming device is superimposed with a waveplate whose optical path is equivalent to 1 / 2λ, the overall optical center symmetry of the optical modulation device can be achieved through the symmetrical superposition method of pretilt angle, making it more effective when applied to ND filters.

[0144] Example 2

[0145] The parent liquid crystal of Example 2 was prepared according to the compounds and weight percentages listed in Table 11, and its performance was tested by filling it between the two substrates of the liquid crystal cell. The test data are shown in the table below:

[0146] Table 11. Composition and proportions of the parent liquid crystal

[0147]

[0148]

[0149] The optical modulation device provided in Embodiment 2 includes first and second guest-host liquid crystal dimming devices. The cell thickness of both the first and second guest-host liquid crystal dimming devices is 7 μm. The dimming devices are black. The two guest-host liquid crystal dimming devices are stacked in parallel. The intermediate waveplate, with an optical path equivalent to 1 / 2λ, is formed by stacking three waveplates with an optical path of 1 / 4λ. The fast axis directions of these three waveplates form angles of 50°, 90°, and 120° with the friction direction of the second alignment layer, respectively. The specific stacking method is described in [details omitted]. Figure 10 .

[0150] 0.6% dye 1 + 0.6% dye 7 + 0.8% dye 23 (dye numbers and structures are shown in Table 1) were added to the parent liquid crystal 2 to form a host-guest liquid crystal composition. The host-guest liquid crystal composition was filled into the liquid crystal dimming device of Example 2, and performance tests were performed. The transmittance of the light modulation device of Example 2 is shown in Table 12; its transmittance at different viewing angles in the dark state is shown in Table 13, and its transmittance at different viewing angles in the bright state is shown in Table 14.

[0151] When the pretilt angles of the first and second layer liquid crystal dimming devices are symmetrical, the viewing angles of the light modulation device, whether powered on or off, are centrally symmetrical, such as... Figure 11 As shown; when the pretilt angles of the first and second layer liquid crystal dimming devices are asymmetrical, the viewing angle of the entire light modulation device without power is symmetrical from left to right, as shown. Figure 12 As shown.

[0152] Table 12. Transmittance of dye-based liquid crystals

[0153]

[0154] Table 13. Transmittance at different viewing angles in the dark state (0V)

[0155]

[0156] Table 14. Transmittance at different viewing angles in bright state (4V)

[0157]

[0158] As can be seen from the comparison between Comparative Example 1 and Examples 1-2, after the double-layer host-guest liquid crystal device is superimposed with a waveplate whose optical path is equivalent to 1 / 2λ, the overall optical center symmetry of the device can be achieved through the symmetrical superposition method, which has a better effect when applied to ND filters.

[0159] All materials used in this invention are commercially available and can be purchased from retail sources.

[0160] The applicant declares that this invention illustrates the symmetrical optical modulator and its applications through embodiments. However, the descriptions of the above embodiments are only for the purpose of helping and understanding the method and core ideas of this invention. This invention is not limited to the above embodiments, that is, it does not mean that this invention must rely on the above embodiments to be implemented. The disclosure of the specification should not be construed as a limitation of this invention. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials and structures of the product of this invention, additions of auxiliary components, and selection of specific methods, all fall within the protection scope and disclosure scope of this invention.

Claims

1. A viewing angle symmetrical optical modulation device, the optical modulation device comprising at least two layers of guest-host liquid crystal dimming devices and a waveplate with an optical path equivalent to 1 / 2λ, the waveplate being located between the at least two layers of guest-host liquid crystal dimming devices.

2. The optical modulation device according to claim 1, characterized in that, The optical modulation device includes two layers of guest-master liquid crystal dimming devices, namely a first guest-master liquid crystal dimming device and a second guest-master liquid crystal dimming device. in, The first guest-host liquid crystal dimming device includes a first substrate, a first conductive layer, a first alignment layer, a first guest-host liquid crystal composition, a second alignment layer, a second conductive layer, and a second substrate; The second guest-host liquid crystal dimming device includes a third substrate, a third conductive layer, a third alignment layer, a second guest-host liquid crystal composition, a fourth alignment layer, a fourth conductive layer, and a fourth substrate. Both the first guest-host liquid crystal composition and the second guest-host liquid crystal composition contain parent liquid crystal and dichroic dye.

3. The optical modulation device according to claim 1 or 2, characterized in that, The first orientation layer and the second orientation layer have opposite friction directions, the third orientation layer and the fourth orientation layer have opposite friction directions, and the second orientation layer and the third orientation layer have the same friction direction.

4. The optical modulation device according to claim 1, characterized in that, The angle between the fast or slow axis direction of the waveplate with an optical path equivalent to 1 / 2λ and the friction direction of the second orientation layer is 0 to 90 degrees.

5. The optical modulation device according to any one of the preceding claims, characterized in that, The parent liquid crystal comprises: One or more compounds of general formula I as well as One or more compounds of general formula II in, R M1 and R M2 Each can independently represent -H, a straight-chain or branched alkyl group containing 1-12 carbon atoms, One or more non-adjacent -CH2- groups of the straight-chain or branched alkyl group containing 1-12 carbon atoms may be independently replaced by -O-, -CO-, -CO-O- or -O-CO-. R A Indicates a straight-chain or branched alkyl group containing 1-12 carbon atoms. One or more non-adjacent -CH2- in the straight-chain or branched alkyl group containing 1-12 carbon atoms can be independently replaced by -CH=CH-, -C≡C-, -O-, -CO-, -CO-O- or -O-CO-; Z M1 and Z M2 Each can be represented independently as a single bond, -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CH=CH-, -C≡C-, -CH2CH2-, or -(CH2)4-; Z A1 and Z A2 Each can independently represent a single bond, -CH2CH2-, -CF2CF2-, -CF2O-, -OCF2-, -CO-O-, -O-CO-, -O-CO-O-, -CH=CH-, -CF=CF-, -CH2O-, or -OCH2-; L A1 and L A2 Each can be represented independently as -H or -F; X A The terms "halogen", "halogenated alkyl" or "alkoxy" containing 1-5 carbon atoms, and "halogenated alkenyl" or "alkoxy" containing 2-5 carbon atoms are used to indicate halogens. ring ring and ring Each represents independently in, One or more of the -CH2- can be replaced by -O-. At most one hydrogen atom can be replaced by a halogen. ring and ring Each represents independently in, and One or more -CH2- bonds can be replaced by -O- bonds, and one or more single bonds in a ring can be replaced by double bonds. One or more -H can be replaced by -CN, -F or -Cl, and one or more -CH= in a ring can be replaced by -N=; n M1 Represents 0, 1, 2, or 3, and when n M1 When the number is 2 or 3, the ring They can be the same or different, Z M2 They can be the same or different; n A Represents 0, 1, 2, or 3, and when n A When the number is 2 or 3, the ring They can be the same or different, Z A1 They can be the same or different.

6. The optical modulation device according to any one of the preceding claims, characterized in that, The compound of general formula II accounts for not less than 20% and not more than 60% of the total weight of the parent liquid crystal.

7. The optical modulation device according to any one of the preceding claims, characterized in that, The parent liquid crystal comprises: one or more compounds of general formula II accounting for 20-50% of the total weight of the parent liquid crystal, and one or more compounds of general formula I accounting for 50-80% of the total weight of the parent liquid crystal.

8. The optical modulation device according to any one of the preceding claims, characterized in that, The first guest-host liquid crystal composition and the second guest-host liquid crystal composition may be the same or different.

9. The optical modulation device according to any one of the preceding claims, characterized in that, The dichroic dye accounts for 0.01%-8% of the weight of either the first guest-host liquid crystal composition or the second guest-host liquid crystal composition.

10. The optical modulation device according to any one of the preceding claims, characterized in that, The first substrate, the second substrate, the third substrate, and the fourth substrate are each independently a rigid transparent substrate; preferably, the rigid transparent substrate is glass or a hard film layer, wherein the hard film layer may be a transparent plastic film or a transparent plastic sheet.

11. The optical modulation device according to any one of the preceding claims, characterized in that, The dichroic dye molecule is selected from one or more of azo dyes, anthraquinone dyes, phthalocyanine dyes, cyanine dyes, indigo dyes, arylmethanes, nitro groups, and nitroso groups. Preferably, the dichroic dye is selected from one or more of azo dyes, anthraquinone dyes, and combinations thereof.

12. The optical modulation device according to claim 1, characterized in that, The waveplate with an optical path equivalent to 1 / 2λ is a waveplate with an optical path of 1 / 2λ or a combination of multiple waveplates with an optical path of 1 / 4λ; preferably, the waveplate with an optical path equivalent to 1 / 2λ is a combination of at least three waveplates with an optical path of 1 / 4λ.

13. The application of a viewing angle symmetrical optical modulation device according to any one of claims 1-12 in a neutral density filter.

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