Liquid crystal display element

Abstract

The present invention discloses a liquid crystal display element, comprising two opposing substrates, two opposing conductive layers located within the inner layers of the substrates, and a liquid crystal layer located between the conductive layers, wherein at least one of the two opposing substrates is made of an optically isotropic material; the dielectric anisotropy of the liquid crystal layer is positive, and the liquid crystal layer comprises a liquid crystal alignment film obtained by curing the liquid crystal and a polymerizable compound by irradiation with polarized light, wherein the polymerizable compound further comprises one or more of the following compounds selected from formula I: #imgabs0# The liquid crystal display element is transparent when not energized and foggy when energized.

Description

Technical Field

[0001] The present invention relates to the field of liquid crystal application technology, and more specifically, to a liquid crystal display element. Background Art

[0002] Polymer dispersed liquid crystal (PDLC) is currently widely used in smart windows. It can switch between a transparent state and a scattering state. The scattering state can provide privacy protection and block outdoor sunlight. Currently, the main type of PDLC on the market is the forward PDLC, which is transparent when powered and a scattering state when powered off. However, this display mode is inconsistent with actual usage. Windows need to be transparent in most situations, and transparent forward PDLC consumes electricity in this state. Furthermore, due to its operating principle, when viewed from the side, the transparency of the forward PDLC decreases, appearing cloudy, resulting in a poor viewing angle and a poor visual experience. Reverse PDLC is transparent when powered off and a scattering state when powered on. This significantly saves energy compared to forward PDLC. Furthermore, due to the design of the polymer and molecular arrangement in the device, it has a better viewing angle than forward PDLC.

[0003] The main reason why reverse PDLC can be transparent when not powered is that the liquid crystal molecules are aligned and arranged neatly, thus eliminating light scattering. To align the liquid crystal molecules neatly, the general practice is to use a polyimide alignment film (PI film) to align the liquid crystals neatly through the interface force between the alignment film and the liquid crystal. However, this involves the preparation of the alignment film, which increases the difficulty of the process. At the same time, due to insufficient adhesion between the polyimide film and the glue, insufficient adhesion between the polyimide and the ITO substrate, and insufficient strength of the polyimide film, the reverse PDLC film is prone to peeling, resulting in a decrease in yield and increased costs. Summary of the Invention

[0004] To address the above issues, the present invention provides a liquid crystal display element and develops a photo-aligned reverse PDLC technology. Specifically, the alignment film portion of the reverse PDLC film is removed from the structure of the reverse PDLC film, and the liquid crystal material is changed from negative to positive. After sandwiching the liquid crystal / polymer material between two ITO substrates, during the UV process, linearly polarized ultraviolet light is irradiated to the composite material above the clearing temperature of the liquid crystal / polymer mixture, causing the polymer to preferentially polymerize along the polarization direction of the linear polarization. Once polymerized along the polarization direction, the liquid crystal is horizontally aligned, thereby achieving the purpose of photo-alignment. After UV irradiation, the film is cooled to room temperature, maintaining its transparency and being able to switch between a transparent and scattering state. Furthermore, the present invention overcomes the problem of reverse PDLC devices in the prior art requiring the substrate to be pre-coated with an alignment film, saving the cost of alignment film coating equipment and materials, eliminating environmental pollution caused by solvent volatilization of the alignment film, and reducing the problem of poor reverse PDLC peel strength caused by the alignment film.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A liquid crystal display element comprises two opposing substrates, two opposing conductive layers located within the substrates, and a liquid crystal layer located between the conductive layers, wherein at least one of the two opposing substrates is made of an optically isotropic material.

[0007] The dielectric anisotropy of the liquid crystal layer is positive, and the liquid crystal layer comprises a liquid crystal alignment film obtained by curing the liquid crystal and a polymerizable compound by irradiation with polarized light, wherein the polymerizable compound comprises one or more compounds selected from Formula I:

[0008]

[0009] in,

[0010] R1 and R2 each independently represent Alkyl groups having 1 to 7 carbon atoms, alkoxy groups having 1 to 7 carbon atoms, alkenyl groups having 2 to 7 carbon atoms, alkenyloxy groups having 3 to 7 carbon atoms, fluorine-substituted alkyl groups having 1 to 7 carbon atoms, fluorine-substituted alkoxy groups having 1 to 7 carbon atoms, fluorine-substituted alkenyl groups having 2 to 7 carbon atoms, or fluorine-substituted alkenyloxy groups having 3 to 7 carbon atoms;

[0011] Spa1 and Spa2 each independently represent a single bond, an alkylene group having 1 to 7 carbon atoms, an alkyleneoxy group having 1 to 7 carbon atoms, an alkenylene group having 2 to 7 carbon atoms, an alkenyleneoxy group having 3 to 7 carbon atoms, a fluorine-substituted alkylene group having 1 to 7 carbon atoms, a fluorine-substituted alkyleneoxy group having 1 to 7 carbon atoms, a fluorine-substituted alkenylene group having 2 to 7 carbon atoms, or a fluorine-substituted alkenyleneoxy group having 3 to 7 carbon atoms;

[0012] Z1, Z2, and Z3 each independently represent -C≡C-, -CH2-, -CH2CH2-, -CH2CF2-, -COO-, -CH=CH-, -CF=CF-, -CH2O-, or a single bond;

[0013] Each independently expresses and may be optionally substituted by a F atom or a methyl group;

[0014] L1, L2, and L3 each independently represent an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms, or an alkenyloxy group having 3 to 7 carbon atoms, wherein any one or more H atoms are optionally replaced by F atoms, replace;

[0015] n represents 1 or 2;

[0016] At least one of R1, R2, L1, L2, and L3 represents a polymerizable group.

[0017] Furthermore, the compound of formula I is selected from the group consisting of compounds represented by the following formulas I-1 to I-2,

[0018]

[0019] in,

[0020] R1 and R2 each independently represent Alkyl groups having 1 to 7 carbon atoms, alkoxy groups having 1 to 7 carbon atoms, alkenyl groups having 2 to 7 carbon atoms, alkenyloxy groups having 3 to 7 carbon atoms, fluorine-substituted alkyl groups having 1 to 7 carbon atoms, fluorine-substituted alkoxy groups having 1 to 7 carbon atoms, fluorine-substituted alkenyl groups having 2 to 7 carbon atoms, or fluorine-substituted alkenyloxy groups having 3 to 7 carbon atoms;

[0021] Spa1 and Spa2 each independently represent a single bond, an alkylene group having 1 to 7 carbon atoms, an alkyleneoxy group having 1 to 7 carbon atoms, an alkenylene group having 2 to 7 carbon atoms, an alkenyleneoxy group having 3 to 7 carbon atoms, a fluorine-substituted alkylene group having 1 to 7 carbon atoms, a fluorine-substituted alkyleneoxy group having 1 to 7 carbon atoms, a fluorine-substituted alkenylene group having 2 to 7 carbon atoms, or a fluorine-substituted alkenyleneoxy group having 3 to 7 carbon atoms;

[0022] R3, R4, R5, R6, R7, R8 and R9 each independently represent F, Cl, an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms or an alkenyloxy group having 3 to 7 carbon atoms, wherein any one or more H atoms are optionally replaced by a F atom, replace;

[0023] m represents 0 or 1;

[0024] At least one of R1, R2, R3, R4, R5, R6, R7, R8, and R9 represents a polymerizable group.

[0025] Furthermore, the compound of formula I-1 is selected from the group consisting of compounds represented by the following formulas I-1-1 to I-1-18,

[0026]

[0027]

[0028] The definitions of R1, R2, Spa1 and Spa2 are as described above.

[0029] Furthermore, the compound of formula I-2 is selected from the group consisting of compounds represented by the following formulas I-2-1 to I-2-3,

[0030]

[0031]

[0032] The definitions of R1, R2, Spa1 and Spa2 are as described above.

[0033] Furthermore, the polymerizable compound further comprises at least one selected from the group consisting of acrylic polymers, methacrylic polymers, phenolic resins, polyhydroxystyrene, isocyanate polymers, polyesters, polyethers, cellulose, polyurethane acrylates, epoxy acrylates, polysiloxanes, and thiol compounds.

[0034] Furthermore, the optical anisotropy of the liquid crystal in the mixture of the liquid crystal and the polymerizable compound is in the range of 0.08 to 0.35.

[0035] Furthermore, the polarized light is linearly polarized, and the wavelength range of the light is 313nm-450nm.

[0036] Furthermore, the substrate is made of glass or plastic.

[0037] Furthermore, the electrode material on the substrate is ITO, nanosilver, conductive ink, AZO or carbon nanotubes.

[0038] Furthermore, the thickness of the liquid crystal layer is 2.8-20 μm.

[0039] The beneficial effects of the present invention are as follows:

[0040] The liquid crystal display element provided in the present invention belongs to the photo-aligned reverse PDLC technology, that is, the alignment film portion is removed from the structure of the reverse PDLC film, and the liquid crystal material is also changed from negative liquid crystal to positive liquid crystal. After the liquid crystal / polymer material is sandwiched between two ITO substrates, during the UV process, the composite material is irradiated with linearly polarized ultraviolet light above the clearing temperature of the liquid crystal / polymer mixture, so that the polymer therein preferentially polymerizes along the polarization direction of the linear polarization. After the polymer is polymerized along the polarization direction, the liquid crystal can be horizontally aligned, thereby achieving the purpose of photo-alignment. After the UV irradiation is completed, it is cooled to room temperature, and the film remains transparent and can be switched between a transparent state and a scattering state, realizing the reverse photo-alignment technology. This technology overcomes the problem of the reverse PDLC device in the prior art that an alignment film needs to be pre-coated on the substrate, saves the cost of alignment film coating equipment and materials, eliminates environmental pollution caused by volatilization of the alignment film solvent, and reduces the problem of poor reverse PDLC peel strength caused by the alignment film. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0042] Figure 1 The figure shows a schematic structural diagram of the liquid crystal display element provided by the present invention, wherein 1 is an optically isotropic substrate; 2 is a conductive layer, preferably ITO; and 3 is a liquid crystal layer. DETAILED DESCRIPTION

[0043] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the following detailed description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0044] This embodiment provides a liquid crystal display element, comprising two opposing substrates, two opposing conductive layers located within the inner layers of the substrates, and a liquid crystal layer located between the conductive layers. The liquid crystal display element does not have a polarizer, and at least one (i.e., one or both) of the two opposing substrates is made of an optically isotropic material, and neither substrate has an alignment layer.

[0045] The dielectric anisotropy of the liquid crystal layer is positive, and the liquid crystal layer comprises a liquid crystal alignment film obtained by curing the liquid crystal and a polymerizable compound by irradiation with polarized light, wherein the polymerizable compound comprises one or more compounds selected from Formula I:

[0046]

[0047] in,

[0048] R1 and R2 each independently represent Alkyl groups having 1 to 7 carbon atoms, alkoxy groups having 1 to 7 carbon atoms, alkenyl groups having 2 to 7 carbon atoms, alkenyloxy groups having 3 to 7 carbon atoms, fluorine-substituted alkyl groups having 1 to 7 carbon atoms, fluorine-substituted alkoxy groups having 1 to 7 carbon atoms, fluorine-substituted alkenyl groups having 2 to 7 carbon atoms, or fluorine-substituted alkenyloxy groups having 3 to 7 carbon atoms;

[0049] Spa1 and Spa2 each independently represent a single bond, an alkylene group having 1 to 7 carbon atoms, an alkyleneoxy group having 1 to 7 carbon atoms, an alkenylene group having 2 to 7 carbon atoms, an alkenyleneoxy group having 3 to 7 carbon atoms, a fluorine-substituted alkylene group having 1 to 7 carbon atoms, a fluorine-substituted alkyleneoxy group having 1 to 7 carbon atoms, a fluorine-substituted alkenylene group having 2 to 7 carbon atoms, or a fluorine-substituted alkenyleneoxy group having 3 to 7 carbon atoms;

[0050] Z1, Z2, and Z3 each independently represent -C≡C-, -CH2-, -CH2CH2-, -CH2CF2-, -COO-, -CH=CH-, -CF=CF-, -CH2O-, or a single bond;

[0051] Each independently expresses Among them, the "—" in the aforementioned four groups represents a single bond; and may be optionally substituted by a F atom or a methyl group. For example, the following substituent groups can be listed: (It can be understood that among the substituent groups listed above, the structure only contains “—” and does not contain When “—” indicates a single bond; when a substituent group contains both “—” and When, only represents a single key for connecting keys);

[0052] L1, L2, and L3 each independently represent an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms, or an alkenyloxy group having 3 to 7 carbon atoms, wherein any one or more H atoms are optionally replaced by F atoms, replace;

[0053] n represents 1 or 2;

[0054] At least one of R1, R2, L1, L2, and L3 represents a polymerizable group.

[0055] Wherein, at least one of R1, R2, L1, L2, L3 represents a polymerizable group means that at least one of R1, R2, L1, L2, L3 is selected from a polymerizable group. Preferably, at least one of R1, R2, L1, L2, L3 represents

[0056] In the present invention, unless otherwise specified, among the exemplified groups, All represent connecting single bonds.

[0057] In one example, in the liquid crystal display element, the compound of formula I is selected from the group consisting of compounds represented by the following formulas I-1 to I-2.

[0058]

[0059] in,

[0060] R1 and R2 each independently represent Alkyl groups having 1 to 7 carbon atoms, alkoxy groups having 1 to 7 carbon atoms, alkenyl groups having 2 to 7 carbon atoms, alkenyloxy groups having 3 to 7 carbon atoms, fluorine-substituted alkyl groups having 1 to 7 carbon atoms, fluorine-substituted alkoxy groups having 1 to 7 carbon atoms, fluorine-substituted alkenyl groups having 2 to 7 carbon atoms, or fluorine-substituted alkenyloxy groups having 3 to 7 carbon atoms;

[0061] Spa1 and Spa2 each independently represent a single bond, an alkylene group having 1 to 7 carbon atoms, an alkyleneoxy group having 1 to 7 carbon atoms, an alkenylene group having 2 to 7 carbon atoms, an alkenyleneoxy group having 3 to 7 carbon atoms, a fluorine-substituted alkylene group having 1 to 7 carbon atoms, a fluorine-substituted alkyleneoxy group having 1 to 7 carbon atoms, a fluorine-substituted alkenylene group having 2 to 7 carbon atoms, or a fluorine-substituted alkenyleneoxy group having 3 to 7 carbon atoms;

[0062] R3, R4, R5, R6, R7, R8 and R9 each independently represent F, Cl, an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms or an alkenyloxy group having 3 to 7 carbon atoms, wherein any one or more H atoms are optionally replaced by a F atom, replace;

[0063] m represents 0 or 1;

[0064] At least one of R1, R2, R3, R4, R5, R6, R7, R8, and R9 represents a polymerizable group.

[0065] In a preferred example, the compound of formula I-1 is selected from the group consisting of compounds represented by the following formulas I-1-1 to I-1-18,

[0066]

[0067]

[0068]

[0069] The definitions of R1, R2, Spa1 and Spa2 are as described above.

[0070] In a preferred example, the compound of formula I-2 is selected from the group consisting of compounds represented by the following formulas I-2-1 to I-2-3,

[0071]

[0072] The definitions of R1, R2, Spa1 and Spa2 are as described above.

[0073] In the liquid crystal layer of the present invention, preferably, the added amount of the compound represented by formula I accounts for 3-15% of the total weight of the liquid crystal and the polymerizable compound.

[0074] In the liquid crystal display element disclosed in this embodiment, the polymerizable compound may further include at least one selected from the group consisting of acrylic polymers, methacrylic polymers, phenolic resins, polyhydroxystyrene, isocyanate polymers, polyesters, polyethers, cellulose, urethane acrylates, epoxy acrylates, polysiloxanes, and thiol compounds. Preferably, the polymerizable compound is at least one selected from the group consisting of acrylic polymers, methacrylic polymers, isocyanate polymers, polyesters, polyethers, urethane acrylates, epoxy acrylates, and thiol compounds.

[0075] In the liquid crystal display element disclosed in the present embodiment, the optical anisotropy Δn of the liquid crystal in the mixture of the liquid crystal and the polymerizable compound is in the range of 0.08 to 0.35, preferably 0.10 to 0.25.

[0076] In the liquid crystal display element disclosed in this embodiment, the polarized light of the mixture of the cured liquid crystal and the polymerizable compound is linearly polarized, and the wavelength of the light is in the range of 313 nm to 450 nm.

[0077] In the liquid crystal display element disclosed in this embodiment, the material of the substrate is glass or plastic, preferably an optically isotropic plastic substrate.

[0078] In the liquid crystal display element disclosed in this embodiment, the electrode material on the substrate is ITO, nanosilver, conductive ink, AZO, or carbon nanotubes, preferably ITO.

[0079] In the liquid crystal display element disclosed in this embodiment, the thickness of the liquid crystal material layer is 2.8 to 20 μm.

[0080] The liquid crystal composition used in this embodiment can also be introduced into the electrode gap (also referred to as gap) for controlling the thickness of the liquid crystal layer of the liquid crystal display element. The injection method of the liquid crystal composition is not particularly limited, and for example, the following method can be cited. That is, when a glass substrate is used as the substrate, the following method can be cited: prepare a pair of transparent conductive substrates, apply a sealant to the substrate on one side except for a part, and then paste it on the substrate on the other side with the surface of the conductive layer facing inward, thereby making an empty cell. In addition, the liquid crystal composition is injected under reduced pressure from the part where the sealant is not applied, thereby obtaining a cell injected with the liquid crystal composition. Furthermore, when a plastic substrate or a film is used as the substrate, the following method can be cited: prepare a pair of transparent conductive flexible substrates, drip the liquid crystal composition on the substrate on one side using an ODF (liquid crystal drop injection, One Drop Filling) method, an inkjet method, etc., and then paste the substrate on the other side to obtain a cell injected with the liquid crystal composition. In the liquid crystal display element of the present invention, since the liquid crystal layer has a high adhesion to the vertical liquid crystal alignment film, the substrate can also be not coated with a sealant. When a plastic substrate or film is used as the substrate, the following method can be used: prepare a pair of transparent conductive substrates, laminate them together using a roll-to-roll method, apply a mixture of liquid crystal, polymer, and spacer between the two substrates before rolling, squeeze the spacer into a single layer supporting the substrate using a roller, and place the mixture between the two substrates.

[0081] The gap of a liquid crystal display element can be controlled using the aforementioned spacers, etc. Examples of such methods include introducing a spacer of the target size into the liquid crystal composition as described above, and using a substrate having a column spacer of the target size. Furthermore, when a plastic or film substrate is used as the substrate and the substrates are laminated, the gap can be controlled without introducing a spacer.

[0082] The technical solution of the present invention is described below with reference to some specific embodiments:

[0083] In this manual, unless otherwise specified, percentages refer to mass percentages, temperatures are in degrees Celsius (°C), and the specific meanings of other symbols and test conditions are as follows:

[0084] Cp represents the clearing point of liquid crystal (℃), measured by DSC quantitative method;

[0085] Δn represents optical anisotropy, no is the refractive index of ordinary light, n e The refractive index of extraordinary light was measured at 25±2°C, 589 nm, and an Abbe refractometer.

[0086] Δε represents dielectric anisotropy, Δε=ε ∥ -ε ⊥ , where ε ∥ is the dielectric constant parallel to the molecular axis, ε ⊥ is the dielectric constant perpendicular to the molecular axis, tested at 25±0.5°C, 20 μm parallel cell, INSTEC:ALCT-IR1;

[0087] γ1 represents the rotational viscosity (mPa·s), the test conditions are 25±0.5℃, 20 μm parallel cell, INSTEC:ALCT-IR1 test;

[0088] K 11 is the torsional elastic constant, K 33 is the splay elastic constant, the test conditions are: 25°C, INSTEC:ALCT-IR1, 18 μm vertical cell;

[0089] The preparation method of the liquid crystal / polymerizable compound mixture is as follows: liquid crystal, the compound represented by formula I, and other polymerizable compounds other than the compound represented by formula I are weighed according to a certain ratio and placed in a stainless steel beaker, the stainless steel beaker is placed on a magnetic stirring device to heat, stir and mix, stir the mixture evenly, and cool it to room temperature to obtain the liquid crystal / polymerizable compound mixture.

[0090] The method for preparing a liquid crystal display element involves forming a conductive layer on a substrate, coating a liquid crystal / polymerizable compound mixture on the conductive layer. Spacers are placed on the substrate to control the thickness of the liquid crystal layer. The conductive surface of the substrate with the conductive layer formed on the other side is then roll-to-roll laminated to the substrate coated with the liquid crystal / polymerizable compound mixture. The substrate is then placed in a light-curing oven, where the polymerizable compound undergoes a photopolymerization reaction to produce the liquid crystal display element.

[0091] Characterization method of liquid crystal display elements: Use the WGT-S haze transmittance test to test the haze of the element in the transparent state and the haze in the scattered state after power is applied.

[0092] In the present invention, unless otherwise specified, the raw material compounds used can be obtained from commercial sources.

[0093] The liquid crystal monomer structure of the embodiment of the present invention is represented by a code, and the code representation method of the liquid crystal ring structure, end group, and connecting group is shown in Table 1 and Table 2 below.

[0094] Table 1 Corresponding codes of ring structure

[0095]

[0096] Table 2: Corresponding codes of end groups and linker groups

[0097]

[0098]

[0099]

[0100] LC1 liquid crystal composition

[0101] Table 3

[0102] Serial number Monolithic code content% 1 CC-3-V 35 2 PUQU-3-F 15 3 PGUQU-3-F 5 4 PGUQU-4-F 5 5 PGUQU-5-F 5 6 PGP-3-F 5 7 PGP-3-2V 5 8 PGU-3-F 15 9 CCG-3-F 10

[0103] LC2 liquid crystal composition:

[0104] Table 4

[0105] Serial number Monolithic code content% 1 PP-4-N 15 2 PP-5-N 10 3 PGP-3-N 10 4 PGP-4-N 15 5 PGP-5-N 10 6 PZP-3-N 10 7 PZP-4-N 10 8 CP-3-N 10 9 CPZP-3-N 5 10 CPZP-4-N 5

[0106] LC3 liquid crystal composition:

[0107] Table 5

[0108]

[0109]

[0110] Example 1

[0111] Table 6

[0112]

[0113] The materials in Example 1 were introduced into the preparation method of the liquid crystal / polymerizable compound mixture and the preparation method of the liquid crystal display element, and the haze was characterized by the characterization method of the liquid crystal display element. It can be seen that the liquid crystal display device can achieve the transition from the transparent state to the light scattering state under voltage actuation without using an alignment layer, and is a reverse PDLC.

[0114] Example 2

[0115] Table 7

[0116]

[0117]

[0118] The materials in Example 2 were introduced into the preparation method of the liquid crystal / polymerizable compound mixture and the preparation method of the liquid crystal display element, and the haze was characterized by the characterization method of the liquid crystal display element. It can be seen that the liquid crystal display device can achieve the transition from the transparent state to the light scattering state under voltage actuation without using an alignment layer, and is a reverse PDLC.

[0119] Comparative Example 1

[0120] Table 8

[0121]

[0122] The materials in Comparative Example 1 were incorporated into a method for preparing a liquid crystal / polymerizable compound mixture and a method for preparing a liquid crystal display element, and the haze was measured using the liquid crystal display element characterization method. Compared to Example 1, when polarized UV curing was not used, the resulting liquid crystal display element had a high initial haze after polymerization. Under voltage actuation, this transition from a high haze state to a low haze, transparent state was observed, demonstrating the effect of a positive PDLC.

[0123] Comparative Example 2

[0124] Table 9

[0125]

[0126]

[0127] The materials in Comparative Example 2 were incorporated into a method for preparing a liquid crystal / polymerizable compound mixture and a method for preparing a liquid crystal display element, and the haze was measured using the liquid crystal display element characterization method. Compared to Example 2, it can be seen that when using an optically anisotropic substrate, the resulting liquid crystal display element exhibits a high initial haze. Under voltage actuation, this transition from a high haze state to a low haze transparent state is observed, indicating a positive PDLC.

[0128] Comparative Example 3

[0129] Table 10

[0130]

[0131] The materials in Comparative Example 3 were introduced into the preparation method of a liquid crystal / polymerizable compound mixture and a liquid crystal display element preparation method, and the haze was characterized using the liquid crystal display element characterization method. Comparative Example 2, in which polymerizable compound I was not used, exhibited a high initial haze in the resulting liquid crystal display element after polymerization. Under voltage actuation, the high haze state transitioned to a low haze transparent state, demonstrating a positive PDLC.

[0132] Comparative Example 4

[0133] Table 11

[0134]

[0135]

[0136] The materials in Comparative Example 4 were introduced into the preparation method of a liquid crystal / polymerizable compound mixture and the preparation method of a liquid crystal display element, and the haze was measured using the liquid crystal display element characterization method. In Comparative Example 2, the liquid crystal composition had negative dielectric anisotropy, and the resulting liquid crystal display element exhibited relatively low initial haze and low haze in the driving state after polymerization, failing to achieve the desired technical effect.

[0137] Table 12 shows Examples 3 to 25. The process is the same as that of Example 1. The haze parameters measured in the non-driven state and the driven state are as follows:

[0138] Table 12

[0139]

[0140]

[0141] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A liquid crystal display element, characterized in that: The invention comprises two opposing substrates, two opposing conductive layers located inside the substrates, and a liquid crystal layer located between the conductive layers, wherein at least one of the two opposing substrates is made of an optically isotropic material; The dielectric anisotropy of the liquid crystal layer is positive, and the liquid crystal layer comprises a liquid crystal alignment film obtained by curing the liquid crystal and a polymerizable compound by irradiating linearly polarized ultraviolet light, wherein the polymerizable compound comprises one or more selected from the group consisting of the compounds represented by the following formulas I-1-1 to I-1-18 and the compounds represented by the following formulas I-2-1 to I-2-3, I-1-1； I-1-2； I-1-3； I-1-4； I-1-5； I-1-6； I-1-7； I-1-8； I-1-9； I-1-10； I-1-11； I-1-12； I-1-13； I-1-14； I-1-15； I-1-16； I-1-17； I-1-18； I-2-1； I-2-2； I-2-3； in, R1 and R2 each independently represent 、 、 、 、 、 , an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms, an alkenyloxy group having 3 to 7 carbon atoms, a fluorine-substituted alkyl group having 1 to 7 carbon atoms, a fluorine-substituted alkoxy group having 1 to 7 carbon atoms, a fluorine-substituted alkenyl group having 2 to 7 carbon atoms, or a fluorine-substituted alkenyloxy group having 3 to 7 carbon atoms; and at least one of R1 and R2 represents or ; Spa1 and Spa2 each independently represent a single bond, an alkylene group having 1 to 7 carbon atoms, an alkyleneoxy group having 1 to 7 carbon atoms, an alkenylene group having 2 to 7 carbon atoms, an alkenyleneoxy group having 3 to 7 carbon atoms, a fluorine-substituted alkylene group having 1 to 7 carbon atoms, a fluorine-substituted alkyleneoxy group having 1 to 7 carbon atoms, a fluorine-substituted alkenylene group having 2 to 7 carbon atoms, or a fluorine-substituted alkenyleneoxy group having 3 to 7 carbon atoms.

2. The liquid crystal display element according to claim 1, wherein The polymerizable compound further includes at least one selected from the group consisting of acrylic polymers, methacrylic polymers, phenolic resins, polyhydroxystyrene, isocyanate polymers, polyesters, polyethers, cellulose, polyurethane acrylates, epoxy acrylates, polysiloxanes, and thiol compounds.

3. The liquid crystal display element according to claim 1, wherein The optical anisotropy of the liquid crystal in the mixture of the liquid crystal and the polymerizable compound is in the range of 0.08 to 0.

35.

4. The liquid crystal display element according to claim 1, wherein The wavelength range of the linearly polarized ultraviolet light is 313nm-450nm.

5. The liquid crystal display element according to claim 1, wherein The substrate is made of glass or plastic.

6. The liquid crystal display element according to any one of claims 1 to 5, characterized in that The electrode material on the substrate is ITO, nanosilver, conductive ink, AZO or carbon nanotube.

7. The liquid crystal display element according to any one of claims 1 to 5, characterized in that The thickness of the liquid crystal layer is 2.8-20 μm.

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