Liquid crystal composition and liquid crystal optical element comprising same

Abstract

The present application provides a liquid crystal composition and a liquid crystal optical element comprising same. The liquid crystal composition comprises at least one compound of formula I and at least one compound of formula II and / or at least one compound of formula III and / or at least one compound of formula IV. The liquid crystal composition may further comprise a chiral agent and a photosensitizer. The present invention further provides a liquid crystal optical element comprising the liquid crystal composition of the present invention. By manufacturing a liquid crystal optical element using the liquid crystal composition of the present invention, the manufacturing process difficulty of a polymerizable cholesteric liquid crystal optical element can be reduced, and the diffraction efficiency of the optical element can be improved.

Description

Liquid crystal composition and liquid crystal optical element comprising the thereof

[0001] Cross-referencing related documents

[0002] This application claims priority to Chinese Patent Application No. 2024112228065, filed on September 2, 2024, entitled "Liquid Crystal Composition and Liquid Crystal Optical Element Containing the Thereof", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application belongs to the field of liquid crystal display materials, specifically relating to liquid crystal compositions and liquid crystal optical elements containing the same. Background Technology

[0004] Liquid crystals (LCs), as anisotropic optical materials, can introduce phase delay into polarized light, making them an important material for fabricating waveplates (or phase retarders). Polymerizable liquid crystals can be used to manufacture passive (LC polymer) optical elements. Passive LC waveplates are ultra-thin and lightweight polymer films that have undergone UV stabilization. Holographic optical elements (HOEs) made from polymerizable cholesteric liquid crystals can achieve compact and lightweight near-eye display modules.

[0005] Currently, most polymerizable liquid crystals are researched using a single type of liquid crystal monomer. These studies include off-axis lenses, liquid crystal gratings, and phase modulation, but are not limited to other areas of research and application. In these studies and applications, the liquid crystal monomer is mixed with chiral agents, photosensitizers, or other additives such as co-initiators, antioxidants, and UV stabilizers in specific proportions. These components are mixed by heating or using solvents, and then coated onto a glass substrate, wafer, or plastic substrate using blade coating or spin coating. The resulting optical element is then exposed to the desired surface. This method of using only one type of liquid crystal monomer to fabricate liquid crystal optical elements limits the feasibility of the process to flexible liquid crystal monomers with low birefringence and low phase transition temperatures. Using unsuitable molecules can cause rapid crystallization after coating, rendering the designed function ineffective. In terms of performance, birefringence directly determines the reflection wavelength bandwidth of polymerizable liquid crystal gratings or off-axis lenses; higher birefringence results in a wider reflection wavelength bandwidth. Using only a single liquid crystal monomer makes it difficult to simultaneously achieve both fabrication feasibility and performance improvements. The commonly used liquid crystal monomer in the research and production of liquid crystal optical components is RM257, which is only just sufficient for experimental fabrication and functional demonstration. The structural formula of RM257 is as follows: Summary of the Invention

[0006] To address the problem that existing technologies often struggle to simultaneously satisfy both manufacturing feasibility and performance improvement with a single liquid crystal monomer, this invention provides a liquid crystal composition that can reduce the manufacturing difficulty of polymerizable cholesteric liquid crystal optical elements and improve the diffraction efficiency of optical elements.

[0007] In a first aspect, embodiments of this application provide a liquid crystal composition comprising:

[0008] The liquid crystal composition comprises at least one compound of formula I and / or at least one compound of formula II and / or at least one compound of formula III and / or at least one compound of formula IV:

[0009] At least one compound of formula I

[0010] At least one compound of formula II

[0011] At least one compound of formula III

[0012] At least one compound of formula III

[0013] Wherein, n1, n2, m1, m2, n3, m3, n4, and m4 represent 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, respectively; where, when n1, n2, m1, m2, n3, m3, n4, and m4 represent 0, p11, p12, p21, and p22 represent 0, and when n1, n2, m1, and m2 are not 0, p11, p12, p21, p22, p31, p32, p41, and p42 represent 1; X11, X21, X22, Y21, Y22, X31, X32, Y31, Y32, X41, and X42 represent H, F, CH3, Cl, or Br, respectively.

[0014] Based on the total weight of the liquid crystal composition, the weight percentage of compound I is 10% to 90%, compound II is 1% to 70%, compound III is 1% to 70%, and compound IV is 1% to 60%.

[0015] As another embodiment of this application, the compound of formula I has the following structural formula:

[0016] As another embodiment of this application, the compound of formula II has the following structural formula:

[0017] Wherein, n21, n22, m21, and m22 represent 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, respectively.

[0018] As another embodiment of this application, the compound of formula III has the following structural formula:

[0019] Wherein, n31, n32, m31, and m32 represent 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, respectively.

[0020] As another embodiment of this application, the compound of formula IV has the following structural formula:

[0021] Wherein, n41, n42, m41, and m42 represent 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, respectively.

[0022] In another embodiment of this application, compounds of formula I, formula II, formula III and formula IV are combined in a certain weight ratio to form a liquid crystal composition.

[0023] In another embodiment of this application, the compound of formula I is 10% to 80% by weight, the compound of formula II is 1% to 60% by weight, the compound of formula III is 1% to 60% by weight, and the compound of formula IV is 1% to 50% by weight.

[0024] In another embodiment of this application, the compound of formula I is 10% to 70% by weight, the compound of formula II is 1% to 50% by weight, the compound of formula III is 1% to 50% by weight, and the compound of formula IV is 1% to 40% by weight.

[0025] In another embodiment of this application, the liquid crystal composition, in addition to including compounds of formula I, II, III, and IV, also includes a chiral agent or a photosensitizer; the chiral agent can be a dextrorotatory chiral agent or a levorotatory chiral agent. For example, the chiral agent is selected from one or more of S811, S5011, S2011, R811, R5011, and R2011, to achieve the transformation of the composition from a nematic liquid crystal phase to a cholesteric liquid crystal phase with a specific reflection wavelength; the photosensitizer is selected from one or more of UV651, TPO, and rose red.

[0026] The chemical names or structural formulas of the chiral agents used in this application are shown in Table 1:

[0027] Table 1

[0028] The chemical names or structural formulas of the photosensitizers used in this application are shown in Table 2:

[0029] Table 2

[0030] Secondly, this application also provides a planar optical device, a polymerizable liquid crystal material used in the optical device, and a method for fabricating the optical device.

[0031] This application has the following beneficial effects:

[0032] 1. Compared with the prior art, the present invention reduces the phase transition temperature from crystal to liquid crystal phase of the liquid crystal composition material. During the fabrication of liquid crystal optical elements, the composition liquid crystal material can always maintain the liquid crystal phase state, and a complete cholesteric liquid crystal thin film optical element is formed after final exposure.

[0033] 2. Using liquid crystal phase preservation during the process can improve the film-forming properties of liquid crystal materials during the fabrication of optical components, resulting in a more uniform film and higher diffraction efficiency consistency.

[0034] 3. The liquid crystal composition of the present invention has a high birefringence, which makes the grating element made by the liquid crystal composition of the present invention have higher diffraction efficiency. Detailed Implementation

[0035] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are merely some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application. In the following embodiments, unless otherwise stated, the specific conditions of the test methods are generally implemented according to conventional conditions or conditions recommended by the manufacturer; raw materials and reagents are obtained commercially or prepared using publicly available information.

[0036] Liquid crystal material preparation: Compounds represented by Formulas I, II, III, and IV are weighed using an electronic balance according to weight percentages. The weighed liquid crystal composition is then homogenized by heating, or mixed with dichloromethane as a solvent, wherein the volume ratio of dichloromethane to the liquid crystal composition is 4:1 to 10:1.

[0037] Add 0.1-2% by weight of a photosensitizer, such as UV651 or TPO. The amount of chiral agent added for the corresponding wavelength is determined according to the formula:

[0038] Where λ represents the response wavelength. denoted by , p represents the average refractive index of the liquid crystal, c represents the pitch of the liquid crystal, and HTP represents the helical torsional constant.

[0039] Tables 2 and 3 list the formulations of the liquid crystal compositions in different embodiments.

[0040] Table 2

[0041] Table 3

[0042] Table 4

[0043] The liquid crystal compositions provided in this application consist of four components represented by four general formulas. The optimal performance of the compositions includes compounds represented by formulas I, II, III, and IV. Compositions formed by mixing compounds represented by formulas II, III, and IV in pairs with compounds represented by formula I, or individually with compounds represented by formula I, also show improved performance. Compositions obtained by mixing compounds represented by formulas III and IV with compounds represented by formula I show the greatest improvement in the important parameter birefringence Δn, but the phase transition temperature is also relatively high, posing significant challenges in industrial production. Compositions obtained by mixing compounds represented by formula II with compounds represented by formula I show a certain degree of improvement in birefringence Δn, but the phase transition temperature is also relatively high, resulting in some improvement in both performance and industrial production. Compositions formed by mixing compounds represented by formulas II with compounds represented by formula I, as well as compositions formed by mixing compounds represented by formulas III and IV with compounds represented by formula I, all show improved performance and reduced production difficulty compared to using only compounds represented by formula I as materials. Compositions obtained by mixing compounds represented by formulas I, II, III, and IV are optimal in terms of both performance and manufacturing process. (The difficulty of the production process is basically determined by the phase transition temperature. The higher the phase transition temperature, the more difficult it is, and the lower the phase transition temperature, the easier it is. The parameters Tcr and Tcn mentioned below represent the phase transition temperature.)

[0044] Table 5

[0045] In Table 5, Δn represents the birefringence of the liquid crystal; Tcr represents the temperature at which the liquid crystal transitions from the crystal phase to the liquid phase; Tcn represents the temperature at which the liquid crystal transitions from the crystal phase to the nematic phase; η represents the diffraction efficiency; and d represents the thickness of the liquid crystal film.

[0046] As can be seen from Table 5, the phase transition temperature of the embodiments of this application is close to or lower than room temperature, which ensures that the liquid crystal composition can maintain its complete optical properties in the cholesteric helical structure for a relatively long time after spin coating. In contrast, the comparative example using a single liquid crystal monomer crystallizes in a short time, losing the cholesteric helical structure and its optical properties. When the comparative example and the embodiment are made into liquid crystal gratings of the same thickness, it can be clearly seen that the diffraction grating of the embodiment is significantly improved.

[0047] Secondly, this application also provides a planar optical device, a polymerizable liquid crystal material used in the optical device, and a method for fabricating the optical device.

[0048] Traditional cholesteric liquid crystal HOW, PVG, and other optical devices use acrylate liquid crystal monomers that undergo photopolymerization. For example, the commonly used liquid crystal monomer RM257 is formulated into a dichloromethane solution for use as a liquid crystal optical material. Alternatively, RM257 can be mixed with some common polymerizable liquid crystals to form composite liquid crystal compositions, which can lower the crystallization temperature of the liquid crystal material. However, the change in the refractive index of the liquid crystal material is not significant, or the increase is limited, thus the improvement in the optical performance of the liquid crystal material is limited. The liquid crystal compositions of the present invention, composed of compounds represented by Formulas I, II, III, and IV, not only increase the temperature range of the liquid crystal phase and lower the crystallization temperature of the liquid crystal material, but also increase the magnitude of birefringence, an important optical performance parameter of the liquid crystal material. The increase in birefringence of the liquid crystal material results in higher diffraction efficiency in the HOW, PVG, and other optical devices made from it.

[0049] The method for manufacturing optical components includes the following steps:

[0050] Prepare a first substrate, which can be a glass substrate or a plastic substrate. Apply an alignment layer to the substrate by spin coating or blade coating. The alignment layer is bright yellow or other materials that can be aligned by polarized visible light or UV light (common alignment layer materials also include SD1, ATA0042, ATA2, etc.).

[0051] A blue laser is used to align the alignment layer according to the designed pattern.

[0052] The prepared liquid crystal composition or a mixture of liquid crystal composition and dichloromethane is applied to an aligned substrate by means of blade coating or spin coating, and then cured with blue light or UV light to obtain an optical device.

[0053] The structural formula for brilliant yellow is as follows:

[0054] The structural formula for ATA0042 is as follows:

[0055] The ATA2 structure is as follows:

[0056] The SD1 structure is as follows:

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A liquid crystal composition, characterized in that, The liquid crystal composition comprises at least one compound of formula I and / or at least one compound of formula II and / or at least one compound of formula III and / or at least one compound of formula IV: At least one compound of formula I At least one compound of formula II At least one compound of formula III At least one compound of formula III Wherein, n1, n2, m1, m2, n3, m3, n4, and m4 represent 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, respectively; where, when n1, n2, m1, m2, n3, m3, n4, and m4 represent 0, p11, p12, p21, and p22 represent 0, and when n1, n2, m1, and m2 are not 0, p11, p12, p21, p22, p31, p32, p41, and p42 represent 1; X11, X21, X22, Y21, Y22, X31, X32, Y31, Y32, X41, and X42 represent H, F, CH3, Cl, or Br, respectively. Based on the total weight of the liquid crystal composition, the weight percentage of compound I is 10% to 90%, compound II is 1% to 70%, compound III is 1% to 70%, and compound IV is 1% to 60%.

2. The liquid crystal composition according to claim 1, characterized in that, Compound I has the following structural formula:

3. The liquid crystal composition according to claim 1, characterized in that, Compound II has the following structural formula: Wherein, n21, n22, m21, and m22 represent 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, respectively.

4. The liquid crystal composition according to claim 1, characterized in that, Compound III has the following structural formula: Wherein, n31, n32, m31, and m32 represent 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, respectively.

5. A liquid crystal composition as claimed in claim 1, characterized in that, Compound IV has the following structural formula: Wherein, n41, n42, m41, and m42 represent 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, respectively.

6. The liquid crystal composition according to claim 1, characterized in that, The weight percentage of compound I is 10%–80%, the weight percentage of compound II is 1%–60%, the weight percentage of compound III is 1%–60%, and the weight percentage of compound IV is 1%–50%.

7. The liquid crystal composition according to claim 1, characterized in that, The liquid crystal composition also includes a chiral agent or a photosensitizer.

8. The liquid crystal composition according to claim 7, characterized in that, The chiral agent is selected from one or more of S811, S5011, S2011, R811, R5011, and R2011, and the photosensitizer is selected from one or more of UV651, TPO, and rose red.

9. A liquid crystal optical element, characterized in that, It comprises a liquid crystal composition according to any one of claims 1 to 7.

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