CN111732956A - Negative liquid crystal composition with excellent low-temperature storage and display performance and application thereof - Google Patents

Abstract

The invention relates to a negative liquid crystal composition with excellent low-temperature storage and display performances and application thereof. The liquid crystal composition comprises liquid crystal compounds of general formulas I, II, III, IV and V. The liquid crystal composition has a great absolute value of negative dielectric anisotropy, has quite good low-temperature intersolubility and low-temperature response speed, has good stability and low viscosity, strong UV resistance, high VHR and high resistivity, and can be applied to display modes such as VA, MVA, PVA, FFS, PSVA, IPS, TFT and the like.

Description

Negative liquid crystal composition with excellent low-temperature storage and display performance and application thereof

Technical Field

The invention relates to a negative liquid crystal composition with excellent low-temperature storage and display performances and application thereof, belonging to the technical field of liquid crystal materials.

Background

Liquid crystal display technology has been widely used in today's society for various size displays. The liquid crystal display has the advantages of high resolution, high brightness, flat display and the like, and is light in weight, low in energy consumption and even flexible display. Therefore, liquid crystals will continue to play an important role in the information technology age.

Currently, there are various display modes in the market, and the more competitive display modes mainly include in-plane switching (IPS), Fringe Field Switching (FFS), and Vertical Alignment (VA). In these display modes, in-plane switching (IPS) and Fringe Field Switching (FFS) are both characterized by a wide viewing angle. When the negative liquid crystal is used in an IPS/FFS display mode, higher transmittance can be obtained, but the response speed is slow because the viscosity of the negative liquid crystal is relatively high.

The IPS display comprises an LC layer between two substrates, with two electrodes arranged on one of the substrates, interleaved with each other, in a comb structure. When a voltage is applied to the electrodes, an electric field parallel to the LC layer is generated between the LC layers, so that the LC molecules are rearranged. For IPS display technology, new liquid-crystalline media with improved properties are required. For the application field of dynamic display, it is particularly necessary to improve the response time and reduce the driving voltage, and for the application in special fields, it is also necessary to increase the operating temperature range. Therefore, low rotational viscosity, large dielectric anisotropy, high clearing point, and large K value are required. Preferably, the dielectric should be higher than 4, very preferably higher than 5, then preferably not higher than 12, in particular not higher than 15, since this is detrimental for a reasonably high resistivity, having an impact on the quality reliability of the liquid crystal material.

Liquid crystal compositions suitable for LCDs and in particular for IPS displays are known, for example, from the following documents: EP0667555, DE19509410, DE19528106, JP07-181439(A), WO9623851 and the like. However, these compositions have significant disadvantages. They mostly result in, among other disadvantages, disadvantageously long response times, have too low resistivity values, and/or require too high operating voltages.

The MVA display is a display in which a local tilt is caused by an electrode having a protrusion. The LC molecules are aligned parallel to the electrode surface in different regions in different directions after the application of voltage, preventing the disclination. Although this arrangement improves the display viewing angle, light transmission is reduced. With the further development of MVA, projections were used only on one side electrode, while the other side electrode had slits, facilitating the transmission of light. The slit electrodes form an uneven electric field after voltage is applied, and the switching state can still be controlled. In order to further increase the light transmittance, the separation slit and the protrusion may be enlarged, which results in an increase in response time. The PVA display has a complete redundancy of protrusions on the electrodes, which are structured by slits, which increases the contrast and improves the light transmission, but this technique is very difficult and the display is also more sensitive to mechanical forces. For many applications, such as displays, tv screens, short response times, high contrast, brightness of the display are required.

The optical characteristics of the liquid crystal before and after the application of a voltage as a dielectric reversibly change. Liquid crystal displays use a wide variety of electro-optic effects. Special liquid-crystalline media are required for the novel VA displays. For example, liquid crystal media with negative dielectric anisotropy need to have a high VHR after UV exposure. The LC phase used in electro-optic displays needs to meet a number of requirements. Of particular importance are chemical and physical stability to moisture, air, such as thermal stability, resistance to infrared radiation, the visible and ultraviolet regions, and direct or alternating electric fields. Further, industrial application of liquid crystal phases requires a suitable temperature range and has a low viscosity.

The liquid crystal material is a rod-like organic compound which has liquid fluidity and crystal anisotropy at a certain temperature, and the inherent optical (refractive index) anisotropy (delta n) and dielectric anisotropy (delta) characteristics of the liquid crystal material are key photoelectric materials for producing display devices. In the prior art, a plurality of liquid crystal compounds are synthesized, but a single liquid crystal compound cannot meet the performance parameters required by various liquid crystal devices such as wide working temperature, large dielectric anisotropy, low rotary viscosity, proper refractive index anisotropy and the like. Therefore, the liquid crystal material used as the liquid crystal medium is a liquid crystal composition. From the viewpoint of the preparation of liquid crystal compositions, liquid crystal compounds of different properties are used to meet these requirements, since the properties of the materials are somewhat restricted, e.g., such short response times as can be achieved with low viscosity values, but usually at the same time the clearing point is reduced; increasing the dielectric anisotropy increases the rotational viscosity, increases the operating temperature, and is difficult to compromise low temperature performance. If liquid crystal compositions with good functions are formed, new products still need to be developed. Therefore, it is necessary to provide a liquid crystal composition to solve the problems of high transmittance, high clearing point, appropriate birefringence anisotropy, high dielectric anisotropy, excellent stability, high VHR and resistivity, low rotational viscosity, and fast response speed required for practical applications.

Although liquid crystal compositions with extremely large negative dielectric anisotropy exist in the prior art, the characteristics of low-temperature intersolubility and fast response cannot be simultaneously considered, for example: the compound proposed in CN108315017 has a very large absolute value of negative dielectric anisotropy, but as the technology advances, the low temperature display performance and other aspects cannot fully meet the market demand.

Disclosure of Invention

In view of the above-mentioned deficiencies of the prior art, the present invention provides a negative liquid crystal composition having excellent low-temperature storage and display properties. The liquid crystal composition has great negative dielectric anisotropy based on polar compounds, and the clearing point is more than 70 ℃. The invention ensures that the display can have a short response time at very high or very low temperatures, while improving stability, especially without image sticking over long periods of operation.

A negative liquid crystal composition having excellent low-temperature storage and display properties, said liquid crystal composition comprising a liquid crystal compound of the following general formula I, II, III, IV, V:

wherein, R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 are respectively and independently selected from a substituted or unsubstituted straight-chain or branched-chain alkyl, an alkoxy or an ether oxygen group of C1-C15, a substituted or unsubstituted straight-chain or branched-chain alkenyl or an alkenyloxy group of C2-C15, wherein the substituent is selected from F, Cl, Br, I, O, S, CN, OH, -CH ═ CH-, or C ≡ C-;

rings A, B, C, D, E, F, G, H each independently represent a saturated or unsaturated cyclohexyl group, a fluorine-substituted or unsubstituted phenyl group, an oxygen-containing hexacyclic group;

l1, L2, L3, L4, L5 and L6 respectively and independently represent H, F, S, CN, Cl, Br, I, C1-C3 alkyl or alkoxy, CF3 or CF 3O;

m, n, p, q, t each independently represent 0, 1 or 2;

z1, Z2 and Z3 are selected from

-C ≡ C-, -CH ═ CH-, -CF ═ CF-, -COO-, -OCO-, -OOC-, -CF2O-, or-CH 2O-, wherein n is 1 or 2;

the weight ratio of the compound of the general formula I to the liquid crystal composition is 1-20%, preferably 1-18%, more preferably 1-15%;

the weight ratio of the compound of the general formula II to the liquid crystal composition is 1-60%, preferably 1-55%, more preferably 1-50%;

the weight ratio of the compound of the general formula III in the liquid crystal composition is 1-50%, preferably 1-45%, more preferably 1-40%;

the weight ratio of the compound of the general formula IV to the liquid crystal composition is 1-30%, preferably 1-25%, more preferably 1-20%;

the weight ratio of the compound of the general formula V to the liquid crystal composition is 1-10%, preferably 1-8%, more preferably 1-5%.

Preferably, the compound of formula i is selected from the following formulae:

ring B is selected from fluorine substituted or unsubstituted phenyl, oxygen-containing hexacyclic group, saturated or unsaturated cyclohexyl;

Z₂is selected from-CH₂CH₂-、-CF₂O-, or-CH₂O-；

m represents 0 or 1.

More preferably, the compound having the general formula ia is selected from at least one of the following structural formulae:

preferably, the compound of formula ii is iia:

wherein R is₁、R₂Each independently selects a substituted or unsubstituted straight-chain or branched-chain alkyl group, an alkoxy group or an ether oxygen group of C1-C15, a substituted or unsubstituted straight-chain or branched-chain alkenyl group or an alkenyloxy group of C2-C15;

ring A is selected from fluorine substituted or unsubstituted phenyl, oxygen-containing hexacyclic group, saturated or unsaturated cyclohexyl;

L₁selected from F, S, Cl, CN;

Z₁is selected from-CH₂CH₂-、-CF₂O-, or-CH₂O-；

q and t are selected from 0 or 1.

More preferably, the compound of formula ii is selected from at least one of the following structural formulae:

at least one compound in the general formula IA is matched with one or more compounds with the same connecting group in the general formula IIA for use, so that the low-temperature intersolubility and the low-temperature display effect of the liquid crystal composition can be obviously improved.

Preferably, the compound of formula iii has the following structural formula:

preferably, the compound of formula iv is selected from the following formulae:

wherein, R7 and R8 are respectively and independently selected from C1-C15 substituted or unsubstituted straight-chain or branched-chain alkyl, alkoxy or ether oxygen radical, C2-C15 substituted or unsubstituted straight-chain or branched-chain alkenyl or alkenyloxy.

Preferably, the compound of formula iv has the following structural formula:

preferably, the compound of formula v is selected from the following formulae:

wherein R is₉、R₁₀Each independently selected from a substituted or unsubstituted linear or branched alkyl group of C1-C15, an alkoxy group or an ether oxygen group, a substituted or unsubstituted linear or branched alkenyl group of C2-C15 or an alkenyloxy group.

Preferably, the compound of formula v has the following structural formula:

the invention provides a liquid crystal display device, which comprises the liquid crystal composition.

The invention provides an application of the liquid crystal display device in VA, MVA, PVA, FFS, PSVA, IPS and TFT display modes.

Has the advantages that:

the liquid crystal composition provided by the invention has extremely low threshold voltage, extremely large absolute value of negative dielectric anisotropy, good stability and low-temperature intersolubility, higher clearing point, wider nematic phase temperature range, shorter response time, high VHR and resistivity, and good UV resistance, and is mainly applied to display modes such as VA, MVA, PSA, IPS, FFS, TFT and the like.

The liquid crystal composition provided by the invention has a nematic phase temperature range: -40-120 ℃. The crystal precipitation does not occur when the alloy is stored for more than 1 month at low temperature of-40 ℃, 30 ℃, 20 ℃ and 0 ℃, and the low-temperature display performance is excellent. Normal at high temperature, no bad display phenomenon below 10 ℃ lower than the clearing point.

The flowing viscosity of the liquid crystal composition provided by the invention at 20 ℃ is measured by using a rotary rotor viscometer, and v 20 of the liquid crystal composition at 20 ℃ is less than or equal to 100 mPas.

The liquid crystal composition provided by the invention has delta n of 0.07-0.27.

The liquid crystal composition provided by the invention has dielectric anisotropy delta of-3 to-16.

The rotational viscosity of the liquid crystal composition provided by the invention at 20 ℃ is tested by using an INSTEC physical property tester of American INSTEC (China constant quotient), the model of ALCT-PP1 is that gamma 1 is less than or equal to 300 mPa.s.

The liquid crystal composition provided by the invention has an extremely low threshold voltage of 1.0-2.5V. Has high VHR before and after UV.

Detailed Description

The invention provides a liquid crystal composition with a great absolute value of negative dielectric anisotropy, good low-temperature stability and UV resistance, which is mainly applied to display modes such as VA, MVA, PVA, FFS, PSVA, IPS, TFT and the like.

The liquid crystal composition provided by the invention is prepared by adopting a traditional method, and is prepared by mixing two or more compounds at a proper temperature; or dissolving the components in an organic solvent such as acetone, chloroform, methanol, etc., and removing the solvent by distillation.

The liquid crystal composition provided by the invention also needs to be added with proper additives, such as an anti-ultraviolet agent, an antistatic agent, an antioxidant, an antifoaming agent and the like.

The present invention is described below with reference to specific embodiments. The following examples are illustrative of the present invention and are intended to illustrate the invention without limiting it. Other combinations and various modifications within the spirit or scope of the present invention may be made without departing from the spirit or scope of the present invention.

The ingredients used in the following examples can be obtained by conventional methods.

The liquid crystal compositions in the following examples were prepared by a conventional method.

The liquid crystal composition in the following examples was tested by a conventional method to obtain various performance parameters, and the liquid crystal display material includes upper and lower glass substrates carrying transparent electrodes and a liquid crystal medium sandwiched therebetween.

The percentages in the examples represent percentages by weight, unless otherwise specified.

Cp (. degree. C.) represents the clearing point.

DELTA.n represents the optical anisotropy at 20 ℃ of 589 nm.

Δ represents the dielectric anisotropy at 25 ℃.

γ 1 (mPas) represents the rotational viscosity at 20 ℃.

Vo (V) represents the threshold voltage at 20 ℃.

Example E1:

TABLE 1 formulation composition and parameters for example E1

Example E2:

TABLE 2 formulation composition and parameters for example E2

Example E3:

TABLE 3 formulation composition and parameters for example E3

Example E4:

TABLE 4 formulation composition and parameters for example E4

Example E5:

TABLE 5 formulation composition and parameters for example E5

Example E6:

TABLE 6 formulation composition and parameters for example E6

Example E7:

TABLE 7 formulation compositions and parameters for example E7

Example E8:

TABLE 8 formulation composition and parameters for example E8

Example E9:

TABLE 9 formulation compositions and parameters for example E9

Example E10:

TABLE 10 formulation compositions and parameters for example E10

Example E11:

TABLE 11 formulation compositions and parameters for example E11

Comparative example M1:

TABLE 12 formulation composition and parameters for comparative example M1

Referring to the above example, inventive example E4 compares to comparative example M1 at Cp, △ n, V₀Example E4, with approximate values of △, had a lower rotational viscosity both samples were poured into the same VA liquid crystal cell under identical conditions and tested for power consumption after 6min UV and high temperature power consumption at 60 ℃ as follows:

watch 13

According to the above data results, the post-UV power consumption and the high-temperature power consumption of example E4 are significantly improved over comparative example M1.

Comparative example M2:

TABLE 14 formulation composition and parameters for comparative example M2

Referring to the above example, comparative example M2 compares to example E4 in the first two categoriesThe compound does not contain CN, the absolute value of negative dielectric anisotropy is lower, and the crystallization phenomenon does not occur when the compound is stored at the low temperature of 0-40 ℃ for more than 1 month under the condition of consistent single crystal content in the example E4, while the voltage of the compound in the comparative example M2 is higher, and the first compound contains a connecting group of CH₂CH₂Of the second class, containing no linking group CH₂CH₂So that crystallization occurs when the compound is stored at-30 ℃ or below for 10 days.

Comparative example M3:

TABLE 14 formulation composition and parameters for comparative example M3

By way of example, comparative example M3 compares with example E4, M3 does not contain a group II compound, V₀The Cp and △ have large increasing range, and the crystallization phenomenon appears after the liquid crystal composition is stored for 1 day at the low temperature of-20 ℃, so the liquid crystal composition has poor normal-temperature and low-temperature display and does not have practical application value.

With reference to the above examples, the liquid crystal compositions proposed by the present invention have class i and class ii compounds with the following characteristics: firstly, F, S in dibenzothiophene in the II compounds and CN on cyclohexyl are used as electron-withdrawing groups to promote the distribution of the density of electron clouds in molecules along the Y-axis direction, F on benzene rings and CN on the cyclohexyl in the I compounds can promote the distribution of the density of electron clouds in molecules along the Y-axis direction, and the negative dielectric constant absolute value of the system is increased and the voltage can be obviously reduced under the combined action of the F on benzene rings and the CN on the cyclohexyl; secondly, the connecting bond in the two compounds can change the original linear molecular conformation into a broken line type, and the connecting bond with the cyclohexyl can greatly increase the steric hindrance effect, so that the intermolecular attraction and the molecular repulsion are balanced. The linking groups of the two compounds in the liquid crystal composition are required to be consistent,is also CH₂O、CH₂CH₂Or CF₂And O, the main conformations of the two compounds are similar, so that the two compounds have similar intermolecular forces, and therefore, the balance of the intermolecular forces can be more easily achieved under the condition of slow low-temperature molecular motion, and the low-temperature stability is ensured. The liquid crystal composition provided by the invention has an extremely large absolute value of negative dielectric anisotropy, and also has excellent low-temperature storage and low-temperature display performances, a higher clearing point, proper optical anisotropy, a wider nematic term temperature range, low viscosity, low power consumption and high response speed. Can be used for display modes such as VA, MVA, PVA, PSVA, IPS, FFS, TFT and the like.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The above-described embodiments of the invention are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and not by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (10)

1. A negative liquid crystal composition having excellent low-temperature storage and display properties, wherein the liquid crystal composition comprises liquid crystal compounds of the following general formulae I, II, III, IV, V:

wherein R is₁、R₂、R₃、R₄、R₅、R₆、R₇、R₈、R₉、R₁₀Independently selects C1-C15 substituted or unsubstituted straight chain or branched chain alkyl, alkoxy or ether oxygen radical, C2-C15 substituted or unsubstituted straight chain or branched chain alkenyl or alkenyloxy radical, wherein the substituent is selected from F, Cl, Br, I, O, S, CN, OH;

rings A, B, C, D, E, F, G, H each independently represent a saturated or unsaturated cyclohexyl group, a fluorine-substituted or unsubstituted phenyl group, an oxygen-containing hexacyclic group;

L₁、L₂、L₃、L₄、L₅、L₆each independently represents H, F, S, CN, Cl, Br, I, alkyl or alkoxy of C1-C3, CF₃Or CF₃O；

m, n, p, q, t each independently represent 0, 1 or 2;

Z₁、Z₂、Z₃is selected from

-C≡C-、-CH＝CH-、-CF＝CF-、-COO-、-OCO-、-OOC-、-CF₂O-, or-CH₂O-, wherein n is 1 or 2;

the compound of the general formula I accounts for 1-20% of the liquid crystal composition by weight;

the compound of the general formula II accounts for 1-60% of the liquid crystal composition by weight;

the compound of the general formula III accounts for 1-50% of the liquid crystal composition by weight;

the compound of the general formula IV accounts for 1-30% of the liquid crystal composition by weight;

the weight ratio of the compound of the general formula V in the liquid crystal composition is 1-10%.

2. The liquid crystal composition of claim 1, wherein the compound of formula i is selected from the following formulae:

ring B is selected from fluorine substituted or unsubstituted phenyl, oxygen-containing hexacyclic group, saturated or unsaturated cyclohexyl;

Z₂is selected from-CH₂CH₂-、-CF₂O-, or-CH₂O-；

m represents 0 or 1.

3. The liquid crystal composition of claim 2, wherein the compound having the formula ia is selected from at least one of the following structural formulae:

4. the liquid crystal composition of claim 1, wherein the compound of formula ii is iia:

wherein R is₁、R₂Each independently selects a substituted or unsubstituted straight-chain or branched-chain alkyl group, an alkoxy group or an ether oxygen group of C1-C15, a substituted or unsubstituted straight-chain or branched-chain alkenyl group or an alkenyloxy group of C2-C15;

ring A is selected from fluorine substituted or unsubstituted phenyl, oxygen-containing hexacyclic group, saturated or unsaturated cyclohexyl;

L₁selected from F, S, Cl, CN;

Z₁is selected from-CH₂CH₂-、-CF₂O-, or-CH₂O-；

q and t are selected from 0 or 1.

5. The liquid crystal composition of claim 4, wherein the compound of formula II is selected from at least one of the following structural formulas:

6. the liquid crystal composition of claim 1, wherein the compound of formula iii is selected from the following formulae:

wherein R is₅、R₆Each independently selected from a substituted or unsubstituted linear or branched alkyl group of C1-C15, an alkoxy group or an ether oxygen group, a substituted or unsubstituted linear or branched alkenyl group of C2-C15 or an alkenyloxy group.

The compound of the general formula III is selected from at least one of the following structural formulas:

7. the liquid crystal composition of claim 1, wherein the compound of formula iv is selected from the following formulas:

wherein R is₇、R₈Each independently selected from a substituted or unsubstituted linear or branched alkyl group of C1-C15, an alkoxy group or an ether oxygen group, a substituted or unsubstituted linear or branched alkenyl group of C2-C15 or an alkenyloxy group.

The compound of the general formula IV is selected from at least one of the following structural formulas:

8. the liquid crystal composition of claim 1, wherein the compound of formula v is selected from the following formulae:

wherein R is₉、R₁₀Each independently selected from a substituted or unsubstituted linear or branched alkyl group of C1-C15, an alkoxy group or an ether oxygen group, a substituted or unsubstituted linear or branched alkenyl group of C2-C15 or an alkenyloxy group.

The compound of formula v has the following structural formula:

9. a liquid crystal display device comprising the liquid crystal composition according to any one of claims 1 to 11.

10. Use of a liquid crystal display device according to claim 9 in VA, MVA, PVA, FFS, PSVA, IPS and TFT display modes.