TWI900909B - A negative dielectric anisotropic liquid crystal composition containing an additive - Google Patents

Abstract

The present invention belongs to the field of liquid crystal material technology and specifically relates to a liquid crystal composition with negative dielectric anisotropy containing an additive and its application in the field of liquid crystal displays. The liquid crystal composition comprises one or more compounds of Formula I, one or more additives for compounds of Formula II, and one or more compounds of Formula III. The composition exhibits an appropriate clearing point, appropriate optical anisotropy, and appropriate negative dielectric anisotropy, as well as a large elastic constant, a small rotational viscosity, a long low-temperature storage time, a fast response speed, and very high light and heat stability. In particular, the composition can maintain stable display after long periods of backlight exposure without producing defects such as residual images.

Description

A negative dielectric anisotropic liquid crystal composition containing an additive

The present invention relates to the field of liquid crystal display technology. More specifically, it relates to a liquid crystal composition with negative dielectric anisotropy containing an additive and its application in the field of liquid crystal display.

TFT-LCD (thin-film transistor liquid crystal display) is the most mature technology in the flat-panel display field, with widespread application in mobile phones, tablets, laptops, in-vehicle displays, industrial control displays, televisions, and other display applications. AMOLED (active-matrix organic light-emitting diode) display technology has also been continuously developing in recent years. Its high brightness, high contrast, bendability, and flexibility have led to its widespread adoption in small-sized display devices such as smartphones and smart wearables, gradually replacing TFT-LCD in these applications. However, due to technical challenges such as lifespan and reliability, AMOLED technology still primarily utilizes TFT-LCD in medium- and large-sized display devices such as computer monitors, in-vehicle displays, and televisions.

LCD displays are categorized as either positive or negative based on the dielectric anisotropy of the liquid crystal material. Positive dielectric anisotropy refers to a dielectric anisotropy greater than zero, while negative dielectric anisotropy refers to a dielectric anisotropy less than zero. In recent years, both negative dielectric anisotropic liquid crystal display materials and their display modes have become a research focus in the field of liquid crystal material technology. However, due to the inherent characteristics of negative dielectric anisotropy, these materials exhibit slower response times and lower reliability than their positive counterparts, leading to a higher risk of image artifacts. Therefore, improving the reliability and response speed of negative dielectric anisotropic liquid crystal materials is a topic worthy of continued research.

In recent years, people's demand for the visual experience brought by television has been continuously increasing. Resolution has been continuously improving, and has developed from 4K to 8K. The size of TVs has also been increasing. 65-inch TVs have gradually replaced 55-inch TVs to become the mainstream products in the market, and there is a trend of development towards 75-inch and 85-inch TVs in the future. Mini LED (sub-millimeter light-emitting diode) technology is a key direction of recent research and development in the new display industry. Compared with traditional side-backlit LCD TVs, LCD TVs with Mini LED backlighting have improved contrast, brightness, color gamut, and viewing angles. In 2021, mainstream TV brands have released TVs equipped with Mini LED backlighting, and the future application of LCD TVs with Mini LED as backlighting will also become more and more extensive. Mini LED backlights offer exceptionally high brightness, with a 4K display boasting a brightness of 1800 nits. This requires the liquid crystal material to resist aging under prolonged exposure to high-brightness backlights, placing even higher demands on its reliability.

To address one or more of the above-mentioned technical deficiencies, the present invention provides a negative dielectric anisotropic liquid crystal composition containing an additive. The composition exhibits an appropriate clearing point, appropriate optical anisotropy, and appropriate negative dielectric anisotropy. It also features a large elastic constant, a low rotational viscosity, a long low-temperature storage time, a fast response speed, and very high light and heat stability. In particular, it maintains stable display even after prolonged backlight exposure without causing defects such as image artifacts.

To achieve the above-mentioned beneficial technical effects, the present invention provides an additive-containing negative dielectric anisotropic liquid crystal composition, comprising one or more compounds of Formula I, one or more additives for compounds of Formula II, and one or more compounds of Formula III.

wherein _R1 represents H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an alkenyloxy group having 2 to 10 carbon atoms; _R2 represents an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an alkenyloxy group having 2 to 10 carbon atoms; and _Z1 represents a single bond, _-CH2- , _{-CH2- CH2-} , or _-CH2O- ; express or , and at least one single bond in the ring structure can be replaced by a double bond; p and q each independently represent any integer from 1 to 15; relative to a liquid crystal composition not containing the compound represented by formula I and the compound represented by formula II, the added concentration of the compound represented by formula I is 10 to 200 ppm, and the added concentration of the compound represented by formula II is 50 to 1000 ppm.

The second object of the present invention is to provide a liquid crystal display element/liquid crystal display, which is mainly an active matrix display mode.

The technical solution provided by this invention features an appropriate clearing point, appropriate optical anisotropy, and appropriate negative dielectric anisotropy. It also possesses a large elastic constant, a low rotational viscosity, and a fast response speed. In particular, it can maintain a stable display even after prolonged backlight exposure, without producing defects such as residual images. The liquid crystal display element or liquid crystal display provided by this invention has a fast response speed and no residual images after prolonged backlight exposure, making it ideally suited for Mini LED backlight displays.

The present invention provides an additive-containing negative dielectric anisotropic liquid crystal composition, comprising one or more compounds of Formula I, one or more additives for compounds of Formula II, and one or more compounds of Formula III.

wherein _R1 represents H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an alkenyloxy group having 2 to 10 carbon atoms; _R2 represents an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an alkenyloxy group having 2 to 10 carbon atoms; and _Z1 represents a single bond, _-CH2- , _{-CH2- CH2-} , or _-CH2O- ; express or , and at least one single bond in the ring structure can be replaced by a double bond; p and q each independently represent any integer from 1 to 15; relative to a liquid crystal composition not containing the compound represented by formula I and the compound represented by formula II, the added concentration of the compound represented by formula I is 10 to 200 ppm, and the added concentration of the compound represented by formula II is 50 to 1000 ppm.

In the liquid crystal composition of the present invention, preferably, the compound represented by the aforementioned formula I is selected from the group consisting of compounds represented by the following formulas I-1 to I-15,

In the liquid crystal composition of the present invention, preferably, the compound represented by the aforementioned formula II is selected from the group consisting of compounds represented by the following formulas II-1 to II-15.

In the liquid crystal composition of the present invention, preferably, the ratio of the compound represented by formula I to the compound represented by formula II in the liquid crystal composition is less than or equal to 1:3.

In the liquid crystal composition of the present invention, the ratio of the compound represented by Formula I to the compound represented by Formula II is preferably 1:3 to 1:15. More preferably, the ratio of the compound represented by Formula I to the compound represented by Formula II is 1:5 to 1:13. Even more preferably, the ratio of the compound represented by Formula I to the compound represented by Formula II is 1:6 to 1:10.

The liquid crystal composition of the present invention is preferably a compound represented by the aforementioned formula III, wherein R ₁ represents H, express 、 、 、 or .

In the liquid crystal composition of the present invention, preferably, the compound represented by the aforementioned formula III is selected from the group consisting of compounds represented by the following formulas III-1 to III-30.

In the liquid crystal composition of the present invention, preferably, the compound represented by the aforementioned formula III is a compound represented by formula III-21 to III-30.

In the liquid crystal composition of the present invention, the mass content of the compound represented by the aforementioned formula III is preferably 1-20%; more preferably, the mass content of the compound represented by the aforementioned formula III is 5-15%.

The liquid crystal composition of the present invention preferably further comprises one or more compounds represented by formula IV.

Here, R ₃ and R ₄ each independently represent a chain alkyl group having 1 to 10 carbon atoms, a chain alkoxy group having 1 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms.

In the liquid crystal composition of the present invention, preferably, the compound represented by the aforementioned formula IV is selected from the group consisting of compounds represented by the following formulas IV-1 to IV-12.

In the liquid crystal composition of the present invention, preferably, the mass content of the compound represented by the aforementioned formula IV is 30-60%; more preferably, the mass content of the compound represented by the aforementioned formula IV is 35-50%.

The liquid crystal composition of the present invention preferably further comprises one or more compounds represented by formula V.

Here, R ₅ and R ₆ each independently represent a chain alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or a chain alkoxy group having 1 to 10 carbon atoms.

In the liquid crystal composition of the present invention, preferably, the compound represented by the aforementioned formula V is selected from the group consisting of compounds represented by the following formulae V-1 to V-24,

In the liquid crystal composition of the present invention, the mass content of the compound represented by the aforementioned formula V is preferably 1-30%; more preferably, the mass content of the compound represented by formula V is 5-25%.

The liquid crystal composition of the present invention preferably further comprises one or more compounds represented by formula VI.

wherein R ₇ and R ₈ each independently represent a chain alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or a chain alkoxy group having 1 to 10 carbon atoms; and m represents 0 or 1.

In the liquid crystal composition of the present invention, preferably, the compound represented by the aforementioned formula VI is selected from the group consisting of compounds represented by the following formulae VI-1 to VI-14.

In the liquid crystal composition of the present invention, preferably, the mass content of the compound represented by the aforementioned formula VI is 5-25%; more preferably, the mass content of the compound represented by formula VI is 9-21%.

The liquid crystal composition of the present invention preferably further comprises one or more compounds represented by formula VII.

Here, R ₉ and R ₁₀ each independently represent a chain alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or a chain alkoxy group having 1 to 10 carbon atoms.

In the liquid crystal composition of the present invention, preferably, the compound represented by the aforementioned formula VII is selected from the group consisting of compounds represented by the following formulae VII-1 to VII-9.

In the liquid crystal composition of the present invention, the mass content of the compound represented by the aforementioned formula VII is preferably 5-20%; more preferably, the mass content of the compound represented by the aforementioned formula VII is 6-16%.

The liquid crystal composition of the present invention preferably further comprises one or more compounds represented by formula VIII.

wherein R ₁₁ and R ₁₂ each independently represent a chain alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or a chain alkoxy group having 1 to 10 carbon atoms; and n represents 0 or 1.

In the liquid crystal composition of the present invention, preferably, the compound represented by the aforementioned formula VIII is selected from the group consisting of compounds represented by the following formulas VIII-1 to VIII-24.

In the liquid crystal composition of the present invention, preferably, the mass content of the compound represented by the aforementioned formula VIII is 5-15%; more preferably, the mass content of the compound represented by formula VIII is 6-12%.

The liquid crystal composition of the present invention preferably further comprises one or more compounds represented by formula IX.

Here, R ₁₃ and R ₁₄ each independently represent an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an alkenyloxy group having 2 to 10 carbon atoms.

In the liquid crystal composition of the present invention, preferably, the compound represented by the aforementioned formula IX is selected from the group consisting of compounds represented by the following formulas IX-1 to IX-16.

In the liquid crystal composition of the present invention, preferably, the mass content of the compound represented by the aforementioned formula IX is 5-15%; more preferably, the mass content of the compound represented by the formula IX is 9-15%.

The liquid crystal composition of the present invention preferably further comprises one or more compounds represented by formula X.

Here, R ₁₅ and R ₁₆ each independently represent a chain alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or a chain alkoxy group having 1 to 10 carbon atoms.

In the liquid crystal composition of the present invention, preferably, the compound represented by the aforementioned formula X is selected from the group consisting of compounds represented by the following formulas X-1 to X-15.

In the liquid crystal composition of the present invention, preferably, the mass content of the compound represented by the aforementioned formula X is 15-25%; more preferably, the mass content of the compound represented by the aforementioned formula X is 20-25%.

The liquid crystal composition of the present invention preferably further comprises one or more compounds represented by formula XI.

wherein R ₁₇ and R ₁₈ each independently represent a chain alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or a chain alkoxy group having 1 to 10 carbon atoms; and r represents 0 or 1.

In the liquid crystal composition of the present invention, preferably, the compound represented by the aforementioned formula XI is selected from the group consisting of compounds represented by the following formulas XI-1 to XI-23.

In the liquid crystal composition of the present invention, the mass content of the compound represented by the aforementioned formula XI is preferably 1-20%; more preferably, the mass content of the compound represented by the aforementioned formula XI is 4-16%.

The liquid crystal composition of the present invention preferably further comprises one or more polymerizable compounds.

In the liquid crystal composition of the present invention, preferably, the polymerizable compound is selected from the group consisting of compounds represented by the following formulae RM-1 to RM-8.

In the liquid crystal composition of the present invention, the polymerizable compound preferably comprises a compound represented by formula RM-1. Furthermore, RM-1 is preferably added in an amount of 0.01-0.5% based on 100% of the total mass of the liquid crystal composition.

[Liquid crystal display element or liquid crystal display]

The present invention also relates to a liquid crystal display element or liquid crystal display comprising any of the above-mentioned liquid crystal compositions; the display element or display is an active matrix display element or display.

The aforementioned active matrix display element or display can specifically include, for example, IPS-TFT, FFS-TFT, or VA-TFT liquid crystal display elements or other TFT displays, and is particularly suitable for VA-TFT mode liquid crystal display elements or liquid crystal displays.

The liquid crystal display device or liquid crystal display of the present invention includes the liquid crystal composition disclosed in the present invention and is particularly suitable for Mini LED backlight displays.

Embodiment

To more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

In the present invention, the preparation methods are conventional methods unless otherwise specified. The raw materials used are available from publicly available commercial channels unless otherwise specified. Percentages are by mass. Temperature is in degrees Celsius (°C). The specific meanings of other symbols and the test conditions are as follows: Tni represents the clearing point of the liquid crystal (°C), as measured by DSC quantitative method; △n represents the optical anisotropy, △n= _ne - _no , where _no is the refractive index of ordinary light and _ne is the refractive index of extraordinary light, and the test conditions are 25±2°C and 60±2°C. 589nm, as measured by Abbe refractometer; △ε represents the dielectric anisotropy, △ε= _ε∥ - _ε⊥ , where _ε∥ is the dielectric constant parallel to the molecular axis, ε _⊥ is the dielectric constant perpendicular to the molecular axis, measured at 25±0.5°C, a 20-micron antiparallel cell, and an INSTEC: ALCT-IR1. _γ1 represents the rotational viscosity (mPa·s), measured at 25±0.5°C, a 20-micron perpendicular cell, and an INSTEC: ALCT-IR1. _K11 represents the splay elastic constant, and _K33 represents the flexural elastic constant, measured at 25°C, an INSTEC: ALCT-IR1, and a 20-micron antiparallel cell. VHR represents the voltage holding ratio (%), measured at 60±2°C, a voltage of ±5V, a pulse width of 10ms, and a voltage holding time of 16.7ms. The test equipment used was a TOYO Model 6254 LCD performance comprehensive tester.

Image artifacts: The LCD device was tested after undergoing a backlight aging test. Backlight aging test method: The liquid crystal composition was poured into a test box, which was placed on a backlight panel and powered on for 500 hours. The temperature was controlled at 60°C and the backlight intensity was 25,000 nits. A black and white checkerboard pattern was then fired at room temperature for 2 hours, and the image artifacts were observed at 127 grayscale levels.

◎No residue left

○ There is a very small amount of residue, which is an acceptable level.

△ There are residues, which is an unacceptable level.

× There are some residues, quite bad.

The liquid crystal composition is prepared as follows: Each liquid crystal monomer is weighed according to a specific ratio and placed in a stainless steel beaker. The stainless steel beaker containing each liquid crystal monomer is placed on a magnetic stirrer to heat and melt. Once the liquid crystal monomers in the stainless steel beaker are mostly melted, a magnetic rotor is added to the stainless steel beaker to stir the mixture evenly. After cooling to room temperature, the liquid crystal composition is obtained.

The liquid crystal monomer structures of the embodiments of the present invention are represented by codes. The codes for the liquid crystal ring structures, end groups, and linking groups are shown in Tables 1 and 2 below.

For example:

, whose code is Sc-CpX3O-O2; , its code is CC-3-V; , its code is CPY-2-O2; , its code is CY-3-O2; , its code is CCY-3-O2; , its code is CLY-3-O2; , its code is PP-1-2V; , its code is CPP-3-2; , whose code is COY-3-O2.

The present invention is described below using the following specific embodiments:

Matrix 1

The formula of the liquid crystal composition and its corresponding properties are shown in Table 3 below.

Matrix 2

The formula of the liquid crystal composition and its corresponding properties are shown in Table 4 below.

Matrix 3

The formula of the liquid crystal composition and its corresponding properties are shown in Table 5 below.

Matrix 4

The formula of the liquid crystal composition and its corresponding properties are shown in Table 6 below.

Matrix 5

The formula of the liquid crystal composition and its corresponding properties are shown in Table 7 below.

Matrix 6

The formula of the liquid crystal composition and its corresponding properties are shown in Table 8 below.

Table 8 Formula and corresponding properties of matrix 6 liquid crystal composition

Matrix 7

The formula of the liquid crystal composition and its corresponding properties are shown in Table 9 below.

Matrix 8

The formula of the liquid crystal composition and its corresponding properties are shown in Table 10 below.

Using the above-mentioned liquid crystal composition as a matrix, the content of the compound represented by Formula I-7 or Formula II-3 was adjusted as an example or comparative example. Many additives are commonly used in liquid crystal compositions. The following three additives, D-1 to D-3, were added to the liquid crystal composition as examples, and compared with the compounds represented by Formula I and Formula II. The improvement in reliability of the liquid crystal composition is shown in Table 11.

The liquid crystal compositions provided in the above examples and comparative examples were subjected to backlight aging reliability tests, as well as VHR and image retention tests, to examine their reliability under long-term backlighting and high-temperature environments.

The aforementioned backlight aging experiments demonstrate that the liquid crystal composition provided in this application exhibits an appropriate clearing point, appropriate optical anisotropy, and appropriate negative dielectric anisotropy. It also possesses a large elastic constant, a low rotational viscosity, and a fast response speed. In particular, it maintains a stable display even after prolonged backlight exposure, without exhibiting defects such as residual images. The liquid crystal display element or liquid crystal display provided by this invention exhibits a fast response speed and lacks residual images even after prolonged backlight exposure, making it ideally suited for Mini LED backlight displays.

Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Persons skilled in the art will appreciate that other variations or modifications may be made based on the above description. It is not possible to list all possible implementations here. Any obvious variations or modifications derived from the technical solution of the present invention remain within the scope of protection of the present invention.

Claims (9)

A negative dielectric anisotropic liquid crystal composition containing an additive, comprising one or more compounds of Formula I, one or more compounds of Formula II, and one or more compounds selected from Formulas III-1 to III-30; I II wherein p and q each independently represent any integer from 1 to 15; relative to a liquid crystal composition not containing the compound represented by Formula I and the compound represented by Formula II, the added concentration of the compound represented by Formula I is 10 to 200 ppm, and the added concentration of the compound represented by Formula II is 50 to 1000 ppm; the ratio of the added amount of the compound represented by Formula I to the compound represented by Formula II is 1:5 to 1:13; III-1 III-2 III-3 III-4 III-5 III-6 III-7 III-8 III-9 III-10 III-11 III-12 III-13 III-14 III-15 III-16 III-17 III-18 III-19 III-20 III-21 III-22 III-23 III-24 III-25 III-26 III-27 III-28 III-29 III-30; the mass content of the one or more compounds selected from Formula III-1 to Formula III-30 is 5-15%, and the liquid crystal composition further comprises one or more compounds represented by Formula IV-6 or Formula IV-7, IV-6 IV-7 The mass content of the compound represented by formula IV-6 or formula IV-7 is 35-50%. The liquid crystal composition according to claim 1 further comprises one or more compounds represented by formula V, V wherein R ₅ and R ₆ each independently represent a chain alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or a chain alkoxy group having 1 to 10 carbon atoms. The liquid crystal composition according to claim 1 further comprises one or more compounds represented by formula VI, VI wherein R ₇ and R ₈ each independently represent a chain alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or a chain alkoxy group having 1 to 10 carbon atoms; and m represents 0 or 1. The liquid crystal composition according to claim 1 further comprises one or more compounds represented by formula VII, VII wherein R ₉ and R ₁₀ each independently represent a chain alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or a chain alkoxy group having 1 to 10 carbon atoms. The liquid crystal composition according to claim 1 further comprises one or more compounds represented by formula VIII, VIII wherein R ₁₁ and R ₁₂ each independently represent a chain alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or a chain alkoxy group having 1 to 10 carbon atoms; and n represents 0 or 1. The liquid crystal composition according to claim 1 further comprises one or more compounds represented by formula IX, IX wherein R ₁₃ and R ₁₄ each independently represent an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an alkenyloxy group having 2 to 10 carbon atoms. The liquid crystal composition according to claim 1 further comprises one or more compounds represented by formula X, X wherein R ₁₅ and R ₁₆ each independently represent a chain alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or a chain alkoxy group having 1 to 10 carbon atoms. The liquid crystal composition according to claim 1 further comprises one or more compounds represented by formula XI, XI wherein R ₁₇ and R ₁₈ each independently represent a chain alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or a chain alkoxy group having 1 to 10 carbon atoms; and r represents 0 or 1. A liquid crystal display element comprises the liquid crystal composition according to any one of claims 1 to 8, wherein the liquid crystal display element is an active matrix display element or a passive matrix display element.