CN105219400B - Liquid-crystal composition and the display element or display using the liquid-crystal composition - Google Patents

Abstract

The invention discloses a liquid crystal composition and a display element or display using the liquid crystal composition. The liquid crystal composition contains one or more compounds of general formula I, general formula II, general formula III and general formula IV, Among them, R ₁ , R ₂ , and R ₃ represent straight-chain alkyl groups with 1-5 carbon atoms, R ₄ represents H or straight-chain alkyl groups with 1-3 carbon atoms, and n is 0, 1, or 2. The liquid crystal composition has fast response speed, large dielectric anisotropy, moderate optical anisotropy, good stability to light and heat, and is especially suitable for IPS liquid crystal display devices.

Description

Liquid crystal composition and display element or display using the liquid crystal composition

technical field

The invention relates to a liquid crystal composition and a liquid crystal display element or a liquid crystal display comprising the liquid crystal composition.

Background technique

At present, the application range of liquid crystal compounds is expanding more and more widely, and it can be applied to various types of displays, electro-optic devices, sensors, and the like. There are various types of liquid crystal compounds used in the above-mentioned display fields, among which nematic liquid crystals are most widely used. Nematic liquid crystals have been used in passive TN, STN matrix displays and systems with TFT active matrix.

For the application field of thin film transistor technology (TFT-LCD), although the market has been huge in recent years and the technology has gradually matured, people's requirements for display technology are also constantly improving, especially in achieving fast response and reducing driving voltage to reduce power consumption etc. As one of the important optoelectronic materials of liquid crystal display, liquid crystal material plays an important role in improving the performance of liquid crystal display.

As a liquid crystal material, it is required to have good chemical and thermal stability as well as stability to electric fields and electromagnetic radiation. As a liquid crystal material for thin film transistor technology (TFT-LCD), it not only needs to have the above stability, but also has a wide temperature range of nematic phase, suitable birefringence anisotropy, very high resistivity, good Excellent UV resistance, high charge retention and low vapor pressure.

For dynamic picture display applications, liquid crystals are required to have a very fast response speed to eliminate afterimages and trailing of the display picture, so liquid crystals are required to have a low rotational viscosity γ ₁ ; in addition, for portable devices, in order to reduce equipment energy consumption, it is desirable that liquid crystals The driving voltage of the liquid crystal is as low as possible; and for displays such as TVs, the driving voltage requirements for liquid crystals are not so low.

The viscosity of the liquid crystal compound, especially the rotational viscosity γ ₁ , directly affects the response time of the liquid crystal after the power is applied. Both the rising time (t _on ) and the falling time (t _off ) are proportional to the rotational viscosity γ ₁ of the liquid crystal. The time (t _on ) is related to the liquid crystal cell and the driving voltage, which can be adjusted by increasing the driving voltage and reducing the thickness of the liquid crystal cell; while the falling time (t _off ) has nothing to do with the driving voltage, but is mainly related to the elastic constant of the liquid crystal It is related to the thickness of the liquid crystal cell, the drop of the cell thickness will reduce the fall time (t _off ), and the movement of liquid crystal molecules is different under different display modes. The three modes of TN, IPS and VA are respectively different from the average elastic constant K, twist The elastic constant and bending elastic constant are inversely proportional to each other.

According to the theory of liquid crystal continuum, after various liquid crystals are deformed under the action of external force (electric field, magnetic field), they will "rebound" back to their original shape through the interaction between molecules; The interaction forces form "viscosity". Small changes in liquid crystal molecules will cause obvious changes in the performance of conventional parameters of liquid crystals. Some of these changes have certain rules, and some are almost difficult to find the rules. They will also have obvious effects on the interaction between liquid crystal molecules. These effects are very Subtle, so far there is no perfect theoretical explanation.

The viscosity of liquid crystals is related to the molecular structure of liquid crystals. It is one of the important tasks of liquid crystal formulation engineers to study the relationship between the viscosity of liquid crystal systems formed by different liquid crystal molecules and the molecular structure of liquid crystals.

Contents of the invention

The technical problem to be solved in the present invention is to provide a liquid crystal composition and a liquid crystal display element or a liquid crystal display using the liquid crystal composition. Anisotropy Δε, moderate optical anisotropy Δn, high heat and light stability, good UV resistance, high charge retention and low vapor pressure.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A liquid crystal composition comprising one or more compounds of general formula I, one or more compounds of general formula II, one or more compounds of general formula III, one or more compounds of general formula IV,

Wherein, R ₁ , R ₂ , and R ₃ are straight-chain alkyl groups with 1-5 carbon atoms, R ₄ is H or straight-chain alkyl groups with 1-3 carbon atoms, and n is 0, 1, or 2.

The liquid crystal composition provided by the present invention has Δn[589nm, 25°C]>0.08, Δε[1KHz, 25°C]>2, clearing point Cp>70.0°C, rotational viscosity γ ₁ [25°C] at 40-110mPa·s between.

In the liquid crystal composition provided by the present invention, the mass percent content of the compound of general formula I is 5-30%, the mass percent content of the compound of general formula II is 5-20%, and the mass percent content of the compound of general formula III is 5-30%. , the mass percent content of the compound of general formula IV is 20-50%.

The further improvement of the liquid crystal composition provided by the present invention lies in that the compound of general formula I is the compound of formula I1-I4, the compound of general formula II is the compound of formula II1-II5, the compound of general formula III is the compound of formula III1-III3, The compound of general formula IV is the compound of formula IV1～IV4,

The dielectric anisotropy Δε of the above-mentioned compounds of general formulas I1-I4 is between 25-30, and at the same time has low rotational viscosity, clearing point above 120°C, and Δn above 0.2. The compound of general formula I is beneficial to increase the liquid crystal composition Δε, increase the clearing point, and increase Δn.

The above-mentioned compounds of the general formula II1-II5 have more carbon atoms in the alkyl chain, and the clearing point CP of the liquid crystal will be higher, but at the same time, the viscosity will increase.

Compared with the compound represented by formula II, the compounds represented by the above-mentioned formulas III1-III3 have higher clearing point CP, lower viscosity, and especially larger elastic constants. It is beneficial to improve the response speed.

The above-mentioned compounds of formulas IV1-IV4 have very low rotational viscosity γ ₁ , close to neutral dielectric anisotropy Δε, and small optical anisotropy Δn, and have advantages in improving liquid crystal viscosity and low-temperature performance. Different alkyl substituents have influence on the rotational viscosity γ ₁ and the clearing point CP of the liquid crystal. Generally, a longer alkyl chain or alkenyl chain will increase the rotational viscosity γ ₁ of the liquid crystal and increase the clearing point CP.

One or more compounds represented by formula V can also be added to the liquid crystal composition provided by the present invention, and its mass content is 1-15%,

R ₅ and R ₆ are alkyl or alkoxy groups having 1 to 5 carbon atoms, and X ₁ is H or F.

The further improvement of the above technical scheme is that the compound of formula V is a compound of formula V1-V8,

Compounds Ⅴ1 to Ⅴ7 all have large elastic constants K (K11, K22, and K33 are all relatively large), high clearing point CP (higher than 200°C), but also have relatively large viscosity γ1, which can be used to adjust the liquid crystal. K value parameter and clearing point CP. The dielectric anisotropy Δε of compounds V1 to V7 is basically close to neutral, and compounds V1 to V4 have lateral fluorine atoms, which is beneficial to improve the mutual solubility of liquid crystals.

The liquid crystal composition provided by the present invention may also contain the compound of formula VI, and its mass content is 1-20%,

R ₇ is a straight-chain alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms, and X ₂ and X ₃ are H or F.

The compound shown in formula VI is further limited to the compound of following formula VI1-VI3:

Compounds represented by formulas VI1-VI3 generally have good miscibility with other liquid crystals. With the increase of fluorine atom substituents, the dielectric anisotropy Δε of VI1, VI2, and VI3 gradually increases. VI1 is about 5, and VI3 reaches about 12. ; The optical anisotropy Δn is within an appropriate range, with the increase of the fluorine atom substituents VI1, VI2, and VI3 tend to decrease, which is close to or slightly greater than the Δn of the mixed liquid crystal, and is between 0.11 and 0.13.

When the proportions of the components of the above-mentioned liquid crystal composition are different, they will show slightly different properties, such as dielectric anisotropy Δε, optical anisotropy Δn, transition temperature point CP of liquid crystal nematic phase into liquid, low temperature The lower stability will be different, and can be applied to different types of display devices, but the same feature is that its rotational viscosity γ ₁ is low. Applied to liquid crystal display devices, fast response can be achieved.

Dopants with various functions can also be added to the liquid crystal compound provided by the present invention. The dopant content is preferably between 0.01% and 1%. These dopants are mainly antioxidants, ultraviolet absorbers, and chiral agents.

Antioxidant, UV absorber preferred:

S represents the integer of 1-10.

Chiral agent preferred (left-handed or right-handed):

The present invention also relates to a liquid crystal display element or display comprising any one of the above-mentioned liquid crystal compositions, and the display element or display is an active matrix display element or display, a passive matrix display element or display. The liquid crystal display element or display is preferably an active matrix addressed liquid crystal display element or display.

The active matrix display element or display is specifically a TN-TFT or IPS-TFT liquid crystal display element or display.

Owing to having adopted above-mentioned technical scheme, the technical progress that the present invention obtains is:

The liquid crystal composition provided by the invention has low viscosity, can realize fast response, and has moderate dielectric anisotropy Δε, moderate optical anisotropy Δn, and high stability to heat and light.

The liquid crystal material comprising the liquid crystal composition provided by the invention not only has good chemical and thermal stability, but also stability to electric field and electromagnetic radiation. Moreover, as a liquid crystal material for thin-film transistor technology (TFT-LCD), it also has a wide nematic phase temperature range, suitable birefringence anisotropy, very high resistivity, good UV resistance, and high charge retention. efficiency and low vapor pressure.

detailed description

The present invention will be described in further detail below in conjunction with specific examples, but the present invention is not limited to the following examples. The methods are conventional methods unless otherwise specified. The raw materials can be obtained from public commercial sources unless otherwise specified. Said percentages are all mass percentages unless otherwise specified.

In the following examples,

CP stands for clearing point, which is directly measured by WRX-1S thermal microanalyzer, and the heating rate is set at 3°C/min. Δn represents optical anisotropy (589nm, 20°C), Δε represents dielectric anisotropy (25°C, 1KHz, HP4284A, 5.2 micron TN left _- handed box), γ1 represents rotational viscosity (mpas) at 20°C, VHR (% ) represents the charge retention rate (5V, 60Hz, 20°C), ρ(×10 ¹³ Ω·cm) represents the resistivity (20°C), the voltage retention rate VHR (%) tester and the resistivity ρ(×10 ¹³ Ω cm) are both TOYO06254 and TOYO6517 liquid crystal physical property evaluation systems (test temperature 20°C, time 16ms, test box 7.0 microns).

The structure of the liquid crystal monomer in the application example of the present invention is represented by a code, and the code representation methods of the liquid crystal ring structure, terminal group, and linking group are shown in Table (1) and Table (2) below.

Table (1): Corresponding codes of the ring structure

Table (2): Corresponding codes of terminal groups and linking groups

End group and linking group corresponding code

C _n H _2n+1 - no C _n H _2n+1 O- nO -CF ₂ O- Q -F f -CH ₂ =CH ₂ - V

Example: Expressed as 3CCV1,

Write it as 3B B(3F)B(3F,5F)QB(3F,5F)F.

Example 1

Example 2

Example 3

Example 4

Example 5

Example 6

Example 7

It can be seen from the above examples that the liquid crystal composition of the present invention has a relatively low rotational viscosity γ ₁ and can be used for liquid crystal display to achieve fast response. It is especially suitable for liquid crystal materials used in TN and IPS modes.

Claims (6)

1. A liquid crystal composition, characterized in that: comprising one or more compounds of general formula I, one or more compounds of general formula II, one or more compounds of general formula III, one or more compounds of general formula IV compounds, Wherein, R ₁ , R ₂ , and R ₃ are linear alkyl groups with 1 to 5 carbon atoms, R ₄ is H or a linear alkyl group with 1 to 3 carbon atoms, and n is 0, 1, or 2; It also contains the compound of formula V, and its mass content is 1-15%, R ₅ and R ₆ are alkyl or alkoxy groups with 1 to 5 carbon atoms, and X ₁ is H or F; It also contains the compound of formula VI, and its mass content is 1-20%, R ₇ is a straight-chain alkyl group with 1 to 5 carbon atoms, or an alkenyl group with 2 to 5 carbon atoms; X ₂ and X ₃ are H or F; The mass percentage content of the compound of the general formula I is 5-30%, the mass content of the compound of the general formula II is 5-20%, the mass content of the compound of the general formula III is 5-30%, and the mass content of the compound of the general formula IV is 20-50%. 2. The liquid crystal composition according to claim 1, wherein the compound of general formula I is a compound of formula I1-I4, the compound of general formula II is a compound of formula II1-II5, and the compound of general formula III is a compound of formula III1-III3 The compound of general formula, the compound of general formula IV is the compound of formula IV1～IV4, 3. The liquid crystal composition according to claim 1, characterized in that: the compound of formula V is a compound of formula V1～V8, 4. The liquid crystal composition according to claim 1, characterized in that: the compound of formula VI is a compound of formula VI1-VI3, R ₇ is a linear alkyl group having 1 to 5 carbon atoms, or an alkenyl group having 2 to 5 carbon atoms. 5. A liquid crystal display element or display comprising the liquid crystal composition according to any one of claims 1 to 4, characterized in that: the display element or display is an active matrix display element or display, a passive matrix display element or display. 6. The liquid crystal display element or display according to claim 5, characterized in that: in the liquid crystal composition, the mass percentage of the compound of general formula I is 6-24%, and the mass percentage of the compound of general formula II is 6-15% , the mass percentage of the compound of formula III is 5-20%, the mass percentage of the compound of formula IV is 25-45%, the mass percentage of the compound of formula V is 5-14%, the mass percentage of the compound of formula VI The content is 5-20%.