TWI570225B - A liquid crystal composition and a liquid crystal display device or a - Google Patents

Description

Liquid crystal composition and liquid crystal display element or display thereof

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

At present, the application range of liquid crystal compounds is expanding wider and wider, and it can be applied to various types of displays, photoelectric elements, sensors, and the like. There are many kinds of liquid crystal compounds used in the above display field, and the nematic liquid crystal is most widely used. Nematic liquid crystals have been used in passive TN, STN matrix displays and systems with TFT active matrices.

For the application of thin film transistor technology (TFT-LCD), although the market has been very large in recent years, and the technology has gradually matured, people's requirements for display technology are also constantly improving, especially in achieving rapid response and reducing the driving voltage. Reduce power consumption and other aspects. As one of the important optoelectronic materials for liquid crystal displays, liquid crystal materials play an important role in improving the performance of liquid crystal displays.

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

In the dynamic picture display process, it is desirable to eliminate the image sticking and smearing of the display screen as much as possible, and the liquid crystal has a fast response speed, so the liquid crystal material is required to have a low rotational viscosity γ ₁ ; in addition, for the portable device, To reduce the energy consumption of the device, it is desirable that the driving voltage of the liquid crystal is as low as possible; and for a display such as a television, the driving voltage requirement for the liquid crystal is not so low.

The viscosity of the liquid crystal compound, especially the rotational viscosity γ ₁ directly affects the response time after the liquid crystal is powered on, whether it is the rise time (t _on ) or the fall time (t _off ), which is proportional to the rotational viscosity γ ₁ of the liquid crystal, and rises. The time (t _on ) is related to the liquid crystal cell and the driving voltage, and can be adjusted by increasing the driving voltage and reducing the thickness of the liquid crystal cell; and the falling time (t _off ) is independent of the driving voltage, mainly with the elasticity of the liquid crystal. The constant is related to the cell thickness of the liquid crystal cell, and the drop of the cell thickness reduces the fall time (t _off ). In different display modes, the liquid crystal molecules move in different ways. The TN, IPS, and VA modes are respectively the average elastic constant K, The torsional elastic constant and the bending elastic constant are inversely proportional.

According to the theory of liquid crystal continuum, after different kinds of liquid crystals are deformed by external force (electric field, magnetic field), they will "rebound" back to the original shape through the interaction between molecules; similarly, liquid crystals are also due to mutual interaction between molecules. The force forms a "viscosity". Small changes in liquid crystal molecules can cause significant changes in the performance of conventional parameters of liquid crystals. Some of these changes are regular, some are almost impossible to find, and liquid crystal materials and their ratios also produce interactions between liquid crystal molecules. The obvious effects, these effects are very subtle, and 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 formulators to study the relationship between the viscosity of liquid crystal systems formed by different liquid crystal molecules and the molecular structure of liquid crystals.

The technical problem to be solved by the present invention is to provide a liquid crystal composition and a liquid crystal display element or liquid crystal display comprising the same, which has a low viscosity, can achieve a fast response, and has a large dielectric difference. Directional Δ ε, moderate optical anisotropy Δn, high stability to heat and light, good UV resistance, high charge retention, and low vapor pressure.

In order to solve the above technical problems, the technical means adopted by the present invention is: a liquid crystal composition containing one or more compounds of the formula I, one or more compounds of the formula II, one or more compounds of the formula III, Wherein R ₁ and R ₃ are a linear alkyl group having 2 to 5 carbon atoms; R ₂ is a linear alkyl group having 2 to 5 carbon atoms; and an alkenyl group having 2 to 5 carbon atoms; R ₄ Is H or a linear alkyl group having 1 to 3 carbon atoms; X ₁ and X ₂ are H or F.

The liquid crystal composition provided by the present invention has Δn [589 nm, 25 ° C] > 0.08, Δ ε [1 KHz, 25 ° C] > 2, clearing point C _p > 70.0 ° C, and rotational viscosity γ ₁ [25 ° C] at 40 ~110mPa. Between s.

In the liquid crystal composition provided by the present invention, the mass percentage of the compound of the formula I is 5 to 30%, the mass percentage of the compound of the formula II is 5 to 20%, and the mass percentage of the compound of the formula III is 20 to 50. %.

In the liquid crystal composition provided by the present invention, the compounds of the formula I, the formula II and the formula III are further defined as follows. The compounds of formula I are those of formulas I1 to I4:

The compound of the formula II is a compound of the formula II1 to II3, R ₂ represents a linear alkyl group having 2 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms.

The compound of formula III is a compound of formula III1 to III4,

The dielectric anisotropy Δ ε of the compounds of the formulae I1 to I4 is between 25 and 30, and at the same time has a low rotational viscosity, the clearing point is above 120 ° C, and the Δn is above 0.2. It is beneficial to increase the liquid crystal composition Δ ε, improve the clearing point, and improve Δn.

The compounds represented by the general formulae II1 to II3 generally have good mutual solubility with other liquid crystals, and the dielectric anisotropy Δ ε of II1, II2, II3 gradually increases, and the dielectric anisotropy Δ ε of II3 reaches about 12; optical difference The tropism Δn is within a suitable range, close to the Δn of the mixed liquid crystal, but slightly different, between 0.11 and 0.13.

The compounds of the formulae III1 to III4 have a very low rotational viscosity γ1, a near-neutral dielectric anisotropy Δε, and a small optical anisotropy Δn, which are advantageous in improving liquid crystal viscosity and low temperature performance. Different alkyl substituents have an effect on the rotational viscosity γ ₁ and clearing point C _p of the liquid crystal. Generally, the longer alkyl chain or alkenyl chain increases the rotational viscosity γ _{1 of the} liquid crystal while increasing the clearing point C _p .

The liquid crystal composition provided by the present invention may further contain one or more compounds represented by the formula IV, and the content of the compound represented by the formula IV in the liquid crystal composition is 1 to 25%.

R ₅ represents an alkyl group having 2 to 5 carbon atoms. Multi alkyl chain carbon atoms, the C _p of the liquid crystal will be higher, but at the same time increases the viscosity.

The compounds of formula IV are the following IV1 to IV4 compounds:

The compound of formula IV has a moderate Δ ε (about 6), a high C _p , and a low viscosity is suitable for adjusting the viscosity of liquid crystal, C _p , △ ε

The liquid crystal composition provided by the present invention may further contain one or more compounds represented by the formula V, and the content of the compound represented by the formula V in the liquid crystal composition is 1 to 25%. R ₆ represents an alkenyl group having 2 to 5 carbon atoms.

The compound of the formula V is a compound of the formula V1 to V2,

A compound of formula V with a compound of formula Ⅳ compared with C _p, low viscosity transition temperature higher clearing point, in particular, has a larger spring constant. Helps improve response speed.

Different ratios of the components of the liquid crystal composition may exhibit slightly different properties, such as dielectric anisotropy Δ ε, optical anisotropy Δn, conversion of the nematic phase of the liquid crystal to a liquid transition temperature clearing point C _p , Stability at low temperatures can vary and can be applied to different types of display elements, but the same feature is lower rotational viscosity γ ₁ . Applied to liquid crystal display elements for fast response.

The liquid crystal compound provided by the invention can also add dopants of various functions, and is doped The content of the dopant is preferably between 0.01 and 1%. These dopants are mainly antioxidants, ultraviolet absorbers, and chiral agents.

The antioxidant and the ultraviolet absorber are preferably: S in the above formula is an integer from 1 to 10.

Chiral agents are preferred (left or right):

The invention further relates to a liquid crystal display element or liquid crystal display comprising any of the above liquid crystal compositions; the display element or display being an active matrix display element or display, a passive matrix display element or a display.

The liquid crystal display element or display is preferably an active matrix addressed liquid crystal display element or a liquid crystal display.

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

The technical progress achieved by the present invention is that the liquid crystal composition provided by the invention has low viscosity and can achieve fast response, and has moderate dielectric anisotropy Δ ε and moderate optical difference. Directional Δn, high stability to heat and light.

The liquid crystal material comprising the liquid crystal composition provided by the present invention not only has good chemical and thermal stability and stability against electric fields 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 ultraviolet resistance, and high charge. Maintainability and low vapor pressure.

The present invention will be further described in detail below with reference to specific embodiments, but the invention is not limited to the following examples. The method is a conventional method unless otherwise specified. The raw materials can be obtained from an open commercial route unless otherwise specified. The percentages are all percentages by mass unless otherwise stated.

In the following examples, C _p denotes clearing point, directly WRX-1S microscopic thermal analyzer measurement, is set a heating rate of 3 ℃ / min.

Δn represents optical anisotropy (589 nm, 20 ° C), Δ ε represents dielectric anisotropy (25 ° C, 1 KHz, HP 4284 A, 5.2 μm TN left-handed box), and γ ₁ represents rotational viscosity (mPa.s) at 20 ° C. , VHR (%) represents charge retention (5V, 60Hz, 20 ° C), p (×10 ¹³ Ω.cm) represents resistivity (20 ° C), voltage retention rate VHR (%) of the tester and resistivity ρ ( ×10 ¹³ Ω·cm) are TOYO06254 and TOYO6517 liquid crystal physical property evaluation systems (test temperature 20 ° C, time 16 ms, test box 7.0 μm).

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

Example: Expressed as 3CCV1, Expressed as 3BB(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 low rotational viscosity γ ₁ for liquid crystal display and can achieve a fast response. It is especially suitable for liquid crystal materials for TN and IPS modes.

Claims (8)

A liquid crystal composition comprising one or more compounds of the formula I, one or more compounds of the formula II, one or more compounds of the formula III, Wherein R ₁ and R ₃ are a linear alkyl group having 2 to 5 carbon atoms; R ₂ is a linear alkyl group having 2 to 5 carbon atoms; and an alkenyl group having 2 to 5 carbon atoms; R ₄ Is H or a linear alkyl group having 1 to 3 carbon atoms; X ₁ and X ₂ are H or F; wherein: the mass percentage of the compound of formula I is 5 to 30%, and the mass percentage of the compound of formula II 5 to 20%, the compound of the formula III has a mass percentage of 20 to 50%; and wherein: one or more compounds of the formula IV are further contained, and the mass percentage thereof is 1% to 25%, R ₅ represents an alkyl group having 2 to 5 carbon atoms. The liquid crystal composition according to claim 1, wherein the compound of the formula I is a compound represented by the formulae I1 to I4, the compound of the formula II is a compound represented by the formula II1 to II3, and the compound of the formula III is a formula III1 to III4. Compound, R ₂ represents a linear alkyl group having 2 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms. The liquid crystal composition according to claim 1, wherein the compound represented by the formula IV is a compound of the formula IV1 to IV4, The liquid crystal composition according to claim 1, wherein: the compound of the formula V is further contained, and the mass percentage thereof is from 1% to 25%. R ₆ represents an alkenyl group having 2 to 5 carbon atoms. The liquid crystal composition according to claim 4, wherein the compound of the formula V is a compound of the formula V1 to V2, A liquid crystal display element or display comprising the liquid crystal composition according to any one of claims 1 to 5, wherein the liquid crystal display element or display is an active matrix display element or display, a passive matrix display element or a display. The liquid crystal display element or display of claim 6, wherein: the active matrix display element or display is a TN-TFT or IPS-TFT liquid crystal display element or display. The liquid crystal display element or display according to claim 7, wherein the liquid crystal composition has a mass percentage of the compound of the formula I of 6 to 20%, and the compound of the formula II has a mass percentage of 5 to 15%, and the formula III The mass percentage of the compound is 25 to 45%, the mass percentage of the compound of the formula IV is 5 to 20%, and the mass percentage of the compound of the formula V is 5 to 20%.