TWI570220B - A liquid crystal composition, and a display element or a display using the liquid crystal composition - Google Patents

Description

Liquid crystal composition and display element or display using the same

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.

For the dynamic picture display application, eliminating the image sticking and smearing, the liquid crystal is required to have a fast response speed, so the liquid crystal is required to have a low rotational viscosity γ ₁ ; in addition, for the portable device, in order to reduce the energy consumption of the device, It is desirable that the driving voltage of the liquid crystal be 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 the elastic constant of the liquid crystal. In relation to the thickness of the liquid crystal cell, the decrease in the thickness of the cell reduces the fall time (t _off ), while in different display modes, the liquid crystal molecules move in different ways. The three modes of TN, IPS and VA are respectively the average elastic constant K and the torsional elasticity. The 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, the liquid crystal is also due to the intermolecular The interaction forces form 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, and some are almost impossible to find. They also have a significant impact on the interaction between liquid crystal molecules. These effects are very Subtle, so far has not formed a 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 using the liquid crystal composition, 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 employed in the present invention are: 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, one or more formulas IV compound, Here, R ₁ , R ₂ and R ₃ are a linear alkyl group having 1 to 5 carbon atoms, R ₄ is H or a linear alkyl group having 1 to 3 carbon atoms, and n is 0, 1, and 2.

The liquid crystal composition provided by the 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.

The content of the compound of the formula I in the liquid crystal composition provided by the invention is 5-30%, the mass percentage of the compound of the formula II is 5-20%, and the mass percentage of the compound of the formula III is 5-30%. The IV compound has a mass percentage of 20 to 50%.

The liquid crystal composition provided by the present invention is further improved in that the compound of the formula I is a compound of the formula I1 to I4, the compound of the formula II is a compound of the formula II1 to II5, and the compound of the formula III is a compound of the formula III1 to III3. The compound of formula IV is a compound of formula IV1 to IV4,

The above compounds of the formulae I1 to I4 have a dielectric anisotropy Δ ε of between 25 and 30, and at the same time have a low rotational viscosity, a clearing point of 120 ° C or more, and a Δn of 0.2 or more. The compound of the formula I is advantageous for increasing the liquid crystal composition Δε, increasing the clearing point, and increasing Δn.

Polyalkyl number of chain carbon atoms Ⅱ1 ~ Ⅱ5 compound of the above formula, the clearing point of the liquid crystal C _p will be higher, but at the same time increases the viscosity.

A compound of formula with a compound represented by the above formulas Ⅱ Ⅲ1 ~ Ⅲ3 compared to a higher clearing point C _p, low viscosity, in particular, has a larger spring constant. Helps improve response speed.

The above compounds of the formulae IV1 to IV4 have a very low rotational viscosity γ ₁ , a near-neutral dielectric anisotropy Δ ε, 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 invention may further comprise one or more compounds of the formula V, and the mass percentage thereof is from 1 to 15%. R ₅ and R ₆ are an alkyl group or alkoxy group having 1 to 5 carbon atoms, and X ₁ is H or F.

A further improvement of the above technical means is that the compound of the formula V is a compound of the formula V1 to V8,

The V1 to V7 compounds all have large elastic constants K (both K11, K22, and K33 are large), high clearing point C _p (higher than 200 ° C), but also have a large viscosity γ ₁ , which can be used for adjustment. The K value parameter of the liquid crystal and the clearing point C _p . The dielectric anisotropy Δ ε of the V1 to V7 compound is substantially close to neutral, and the V1 to V4 compound has a lateral fluorine atom, which is advantageous for improving the mutual solubility of the liquid crystal.

The liquid crystal composition provided by the present invention may further comprise a compound of the formula VI, and the content thereof is 1% to 20% by mass. R ₇ is a linear alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, and X ₂ and X ₃ are H or F.

The compound of formula VI is further defined as a compound of the following formula VI1 - VI3:

The compounds represented by formulas VI1 to VI3 generally have good mutual solubility 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 12. The optical anisotropy Δn is within a suitable range, and as the fluorine atom substituent increases, VI1, VI2, and VI3 have a decreasing tendency, which is close to or slightly larger than Δn of the mixed liquid crystal, and is between 0.11 and 0.13.

When the ratio of each component of the liquid crystal composition is different, a slightly different performance is exhibited, such as dielectric anisotropy Δ ε, optical anisotropy Δn, and a transition temperature of a liquid crystal which is converted into a liquid. C _p and stability at low temperatures will 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 may also be added with dopants of various functions, and the dopant content 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 represents an integer from 1 to 10.

Chiral agents are preferred (left or right):

The invention further relates to a liquid crystal display element or display comprising any of the above liquid crystal compositions, the liquid crystal 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 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 (mpas) at 20 ° C, VHR (%) represents charge retention (5V, 60Hz, 20°C), ρ(×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 microns).

The structure of the liquid crystal monomer in the embodiment of the present invention 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, It is recorded 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 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 (7)

A liquid crystal composition comprising one or more compounds of formula I, one or more compounds of formula II, one or more compounds of formula III, one or more compounds of formula IV, and further comprising a compound of formula VI, Wherein R ₁ , R ₂ and R ₃ are straight-chain alkyl groups having 1 to 5 carbon atoms, R ₄ is H or a linear alkyl group having 1 to 3 carbon atoms, and n is 0, 1, 2; R ₇ is a linear alkyl group having 1 to 5 carbon atoms and an alkenyl group having 2 to 5 carbon atoms; X ₂ and X ₃ are H or F; and the content of the compound of the formula I is 5 to 30% by mass. The compound of formula II has a mass percentage of 5-20%, the mass percentage of the compound of formula III is 5-30%, the mass percentage of the compound of formula IV is 20-50%, and the mass percentage of the compound of formula VI is 1-20%. . The liquid crystal composition according to claim 1, wherein the compound of the formula I is a compound of the formula I1 to I4, the compound of the formula II is a compound of the formula II1 to II5, and the compound of the formula III is a compound of the formula III1 to III3. The compound of formula IV is a compound of 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 1 to 15%. R ₅ and R ₆ are an alkyl group or alkoxy group having 1 to 5 carbon atoms, and X ₁ is H or F. The liquid crystal composition according to claim 3, wherein the compound of the formula V is a compound of the formula V1 to V8, The liquid crystal composition according to claim 1, wherein the compound of the formula VI is a compound of the formula VI1 to VI3, R ₇ is a linear alkyl group having 1 to 5 carbon atoms and an alkenyl group having 2 to 5 carbon atoms. 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 according to claim 6, wherein the liquid crystal composition has a mass percentage of the compound of the formula I of 6 to 24%, and the mass percentage of the compound of the formula II is 6 to 15%, and the mass of the compound of the formula III The percentage content 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%, and the mass percentage of the compound of formula VI is 5-20%.