TWI541332B - A liquid crystal composition suitable for coplanar conversion mode and its application - Google Patents

Description

Liquid crystal composition suitable for coplanar conversion mode and application thereof

The present invention belongs to a liquid crystal composition applied to a liquid crystal display element, and more particularly to a liquid crystal composition of an active matrix mode driven coplanar switching mode (IPS) liquid crystal display element and its use in an electrooptical liquid crystal display.

The liquid crystal display element operates by utilizing the optical anisotropy and dielectric anisotropy of the liquid crystal material itself, and has been widely used. Using different characteristics and working modes of liquid crystal materials, the device can be designed into various working modes. Among them, TN mode (twist nematic mode) and STN mode (super twisted nematic) are commonly used in conventional displays. Column mode), ECB mode (electrically controlled birefringence mode), OCB mode (optically compensated bend), IPS mode (in-plane switching mode), VA mode (vertical alignment) , vertical alignment mode) and so on.

In the low information volume, passive driving is generally used, but as the amount of information increases, the display size and the number of display channels increase, and crosstalk and contrast reduction become severe. Therefore, active matrix (AM) driving is generally used. . In the AM-TFT device, the TFT switching device is addressed in a two-dimensional grid, charging the primitive electrode for a limited time during conduction, and then becoming an off state until it is addressed again in the next cycle. Therefore, between the two addressing periods, it is undesirable to change the voltage at the pixel point, otherwise the transmittance of the pixel point will change, resulting in The display is unstable. The discharge rate of the pixel point depends on the electrode capacity and the resistivity of the dielectric material between the electrodes. Therefore, the liquid crystal material is required to have a higher resistivity, and the material is required to have a suitable optical anisotropy Δn (the Δn value is generally between 0.08 and 0.15), and a lower threshold voltage to lower the driving voltage and lower the voltage. The purpose of power consumption; also requires a lower viscosity to meet the needs of fast response. There have been many reports on such liquid crystal compositions, such as foreign patent documents WO9202597, WO9116398, WO9302153, WO9116399 and the like.

In the early 1970s, experimental studies were conducted on the basic electro-optical properties of uniformly aligned, twisted, and nematic liquid crystal IPS modes, characterized by a pair of electrodes fabricated on the same substrate and on the other substrate. Without the electrode, the alignment of the liquid crystal molecules is controlled by the transverse electric field applied between the electrodes, so this mode can also be called the transverse field mode. In the IPS mode, the nematic liquid crystal molecules are uniformly arranged in parallel between the two substrates, and the two polarizing plates are placed orthogonally. In the IPS mode, when no electric field is applied, the incident light is blocked by two orthogonal polarizers and is in a dark state. When an electric field is applied, the liquid crystal molecules are rotated to cause a delay, so that light leaks from the two orthogonal polarizers.

Due to the simplicity of the IPS mode and the wide viewing angle, they are the most attractive way to improve viewing angle characteristics and achieve large-area display.

The coplanar conversion mode (ie, IPS mode) requires only a linear polarizer without the need for a compensation film, but its response speed is too slow to display a fast moving picture. Therefore, compared with the conventional TN-TFT type display mode, the IPS type display uses a liquid crystal to require a faster response speed.

However, based on the complexity of liquid crystal mixed crystal modulation, various aspects of material properties (low optical anisotropy value, high dielectric anisotropy value, high resistivity, etc.) are considered from the viewpoint of liquid crystal composition material modulation. Low rotational viscosity, low melting point, high clearing point, good thermal stability and UV stability, etc. are mutually restrained, and performance on the one hand is often accompanied On the other hand, the performance is lowered, and it is often difficult to prepare a liquid crystal composition having various properties.

Therefore, there is a need for a liquid crystal composition which is required to have low rotational viscosity, fast response speed, suitably high optical anisotropy, high dielectric anisotropy, good thermal stability and ultraviolet stability. At least one of the properties.

SUMMARY OF THE INVENTION An object of the present invention is to provide an IPS mode liquid crystal composition suitable for an active matrix, which is capable of achieving a fast response while having a low rotational viscosity, a suitably high optical anisotropy, and a high dielectric. At least one of anisotropic, good thermal stability, and ultraviolet stability.

In order to accomplish the above object, the present invention provides a liquid crystal composition suitable for a coplanar conversion mode, wherein the liquid crystal composition comprises: one or more Formula I of 25-55% by weight based on the total weight of the liquid crystal composition compound of One or more compounds of the general formula II in an amount of from 20 to 40% by weight based on the total weight of the liquid crystal composition One or more compounds of the formula III in an amount of from 5 to 25% by weight based on the total weight of the liquid crystal composition One or more compounds of the formula IV in an amount of from 5 to 20% by weight based on the total weight of the liquid crystal composition And one or more compounds of the formula V in an amount of from 5 to 25% by weight based on the total weight of the liquid crystal composition Wherein R1, R3, R4, R5, R6 and R7 are the same or different and each independently represents H, an alkyl or alkoxy group having 1 to 7 carbon atoms, and a fluoroalkyl group having 1 to 7 carbon atoms; Or a fluoroalkoxy group or an alkenyl group or alkenyloxy group having 2 to 7 carbon atoms; R2 represents H or an alkyl group or alkoxy group having 1 to 5 carbon atoms; and L1 and L2 are the same or different and each independently Ground represents H or F; n represents 0 or 1.

The liquid crystal composition of the present invention further comprises: 0 to 10% by weight of the total weight of the liquid crystal composition of one or more compounds of the formula VI One or more compounds of the formula VII in an amount of from 0 to 10% by weight based on the total weight of the liquid crystal composition One or more compounds of the formula VIII in an amount of from 0 to 20% by weight based on the total weight of the liquid crystal composition And one or more compounds of the formula IX in an amount of from 0 to 10% by weight based on the total weight of the liquid crystal composition Wherein R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ and R _{14 are the} same or different and each independently represents H, an alkyl group having 1 to 7 carbon atoms or an alkoxy group, and the number of carbon atoms a fluoroalkyl or fluoroalkoxy group of 1-7 or an alkenyl or alkenyloxy group having 2-7 carbon atoms; Express or Wherein said One or more -CH ₂ - may be substituted by -O-, provided that the oxygen atoms are not connected; One or more H may be replaced by F, one or more -CH= may be substituted by -N=; L ₃ represents H or F.

In some embodiments of the invention, it is preferred that the compound of formula I comprises from 30 to 50% by weight of the total weight of the liquid crystal composition; the compound of formula II comprises from 23 to 35 of the total weight of the liquid crystal composition. %; the compound of the formula III accounts for 10-20% by weight of the total weight of the liquid crystal composition; the compound of the formula IV accounts for 5-16% of the total weight of the liquid crystal composition; The compound accounts for 5-18% of the total weight of the liquid crystal composition; the compound of the formula VI accounts for 0-5% of the total weight of the liquid crystal composition; the compound of the formula VII accounts for the total of the liquid crystal composition 0 to 5% by weight; the compound of the formula VIII is 0 to 15% by weight based on the total weight of the liquid crystal composition; and the compound of the formula IX is 0 to 8% by weight based on the total weight of the liquid crystal composition.

In some embodiments of the invention, the compound of Formula I is selected from one or more of the following compounds: ;as well as

In some embodiments of the invention, the compound of Formula II is selected from one or more of the following compounds: ;as well as

In some embodiments of the invention, the compound of Formula III is selected from one or more compounds consisting of: ;as well as

In some embodiments of the invention, the compound of Formula IV is selected from one or more of the following compounds: ;as well as

In some embodiments of the invention, the compound of Formula V is selected from one or more compounds consisting of: ;as well as

In some embodiments of the invention, the compound of Formula VI is selected from one or more compounds consisting of: ;as well as

In some embodiments of the invention, the compound of Formula VII is selected from one or more of the following compounds: ;as well as

In some embodiments of the invention, the compound of Formula VIII is selected from one or more compounds consisting of: ;as well as

In some embodiments of the invention, the compound of Formula IX is selected from one or more of the following compounds: ;as well as

Another aspect of the present invention provides an electro-optical liquid crystal display comprising the liquid crystal composition of the present invention.

A further aspect of the present invention provides an active matrix addressed IPS mode liquid crystal display device comprising the liquid crystal composition of the present invention.

The present invention determines a liquid crystal medium comprising the above liquid crystal composition by a combination experiment with the above compound, and has a fast response speed, a low rotational viscosity, a high clearing point, and a suitably high optical anisotropy. The high dielectric anisotropy and the like, the IPS mode liquid crystal display device using the liquid crystal composition has the advantages of fast response, high-definition bright spot, and low driving voltage.

In general, the clearing point of the IPS mode mobile phone product is between 85-90 ° C, and the larger the dielectric anisotropy value, the lower the corresponding product driving voltage, when the dielectric anisotropy value is greater than 10 (provided that When the thickness of the liquid crystal cell case is about 4 μm, the driving voltage is about 4 V; when the dielectric anisotropy value is between 9 and 10, the driving voltage can be designed to be 4.5 V.

A liquid crystal composition having a clear spot greater than 100 ° C is generally used in an automotive product using an IPS mode.

In some embodiments of the present invention, the clearing point Cp is between 80 and 110 ° C, preferably between 85 and 105 ° C, by optimizing the combination and optimizing the ratio of the liquid crystal composition obtained by optimizing a large number of known liquid crystal compounds; The viscosity η is between 68-90 mPa*s (20 °C), preferably between 70-85 mPa*s (20 °C); the optical anisotropy Δn is between 0.090-0.110 (25 °C), preferably Between 0.095-0.108 (25 ° C); negative dielectric anisotropy Δ ε is between 8-11 (25 ° C), preferably between 8.9-10.6 (25 ° C).

The liquid crystal composition of the present invention may further contain additives known to those skilled in the art and described in the literature, such as multicolor dyes, chiral agents, antistatic agents and the like.

In the present invention, unless otherwise specified, the ratios are all by weight, all temperatures are in degrees Celsius, and the response time data is selected to have a cell thickness of 7 μm.

The invention will now be described in connection with specific embodiments. It is to be understood that the following examples are illustrative of the invention and are not intended to limit the invention. Other combinations and various modifications within the inventive concept can be made without departing from the spirit or scope of the invention.

For ease of expression, in the following examples, the group structure of the liquid crystal composition is represented by the codes listed in Table 1:

Take a compound of the following structural formula as an example:

The structural formula is expressed by the code listed in Table 1, and can be expressed as: nCCGF, where n in the code represents the number of C atoms of the left-end alkyl group, for example, n is "3", that is, the alkyl group is -C ₃ H ₇ ; C in the code represents a cyclohexane group.

The shorthand code for the test project in the following examples is as follows:

Cp (°C): clearing point (nematic-isotropic phase transition temperature)

△n: optical anisotropy (589 nm, 25 ° C)

△ ε: dielectric anisotropy (1 kHz, 25 ° C)

Γ1: torsional viscosity (mPa*s at 20 ° C)

Vth: threshold voltage

Among them, the refractive index anisotropy was measured at 25 ° C under a sodium light (589 nm) light source using an Abbe refractometer; the dielectric test box was a TN90 type, and the cell thickness was 7 μm.

Each component used in the following examples can be synthesized by the inventors of the present application in accordance with a known method, or by a combination of methods in organic synthetic chemistry. These synthetic techniques are conventional, and each of the obtained liquid crystal compounds has been tested to meet the standards of electronic compounds. A method for introducing a target terminal group, a ring structure, and a binding group into a starting material is described in Organic Syntheses (John Wiley & Sons, Inc), Organic Reactions (Organic Reactions, John Wiley & Sons, Inc) In the publications of Comprehensive Organic Synthesis (Pergamon Press) and New Experimental Chemistry Lecture (Maruzen Co., Ltd.).

A liquid crystal composition was prepared in accordance with the ratio of each liquid crystal composition specified in the following examples. The preparation of the liquid crystal composition is carried out according to a conventional method in the art, such as heating, ultrasonic wave, suspension, etc., in a predetermined ratio.

The liquid crystal composition given in the following examples was prepared and studied. The composition of each liquid crystal composition and the test results of its performance parameters are shown below.

Table 2, Table 3 and Table 4 are the test results of the composition, the ratio of the liquid crystal composition of the comparative example, and the performance test between the two substrates filled in the liquid crystal display, in order to facilitate the performance comparison with the liquid crystal composition of the present invention.

Comparative Example 1

The liquid crystal composition of Comparative Example 1 was prepared according to each compound and weight percentage listed in Table 2, and was filled in the performance test between the two substrates of the liquid crystal display. The test data are as follows: Table 2 Liquid crystal composition formula and Test performance

Comparative Example 2

The liquid crystal composition of Comparative Example 2 was prepared according to each compound and weight percentage listed in Table 3, and was filled in the performance test between the two substrates of the liquid crystal display. The test data are as follows:

Comparative Example 3

The liquid crystal composition of Comparative Example 3 was prepared according to each compound and weight percentage listed in Table 4, and was filled in the performance test between the two substrates of the liquid crystal display. The test data are as follows:

Example 1

The liquid crystal composition of Example 1 was prepared according to each compound and weight percentage listed in Table 5, and was filled in the performance test between the two substrates of the liquid crystal display. The test data are as follows:

Example 2

The liquid crystal compositions of Example 2 were prepared according to the respective compounds and weight percentages listed in Table 6, and were filled in the performance test between the two substrates of the liquid crystal display. The test data are shown in the following table:

Example 3

The liquid crystal composition of Example 3 was prepared according to each compound and weight percentage listed in Table 7, and was filled in the performance test between the two substrates of the liquid crystal display. The test data are as follows:

Example 4

The liquid crystal composition of Example 4 was prepared according to each compound and weight percentage listed in Table 8, and was filled in the performance test between the two substrates of the liquid crystal display. The test data are as follows:

The liquid crystal compositions described in Example 1, Example 2, Example 3, and Example 4 correspond to use in different types of IPS-based products, respectively.

Through Comparative Example 1, Example 1 and Example 4, we can see that the voltage, clearing point and optical anisotropy specifications of the liquid crystal composition can be applied to a 4V-driven mobile phone product using the IPS mode. However, referring to Example 1 and Example 4, it can be seen that the rotational viscosity γ1 of Comparative Example 1 is significantly higher, the rotational viscosity γ1 is greater than 100, and the rotational viscosities γ1 of Examples 1 and 4 are between 70 and 80. Therefore, the response speeds of the liquid crystal compositions described in Example 1 and Example 4 have significant advantages.

The liquid crystal compositions described in Comparative Example 2 and Example 2 have good optical anisotropy and a suitably high clearing point, and can be applied to mobile phone products using the IPS mode, but with reference to Comparative Example 2 and Example 2, it can be seen As a result, the dielectric anisotropy of Example 2 was significantly greater than that of Comparative Example 2. When the liquid crystal composition described in Comparative Example 2 was applied to a 4.5V-driven mobile phone type product using the IPS mode, the voltage did not reach the driving requirement. Embodiment 2 can fully satisfy the 4.5V drive. And The rotational viscosity γ1 of Example 2 was also lower than that of Comparative Example 2, and therefore, the response speed of the liquid crystal composition described in Example 2 had a significant advantage.

Also in the case of in-vehicle IPS application, referring to Comparative Example 3 and Example 3, it can be seen that the rotational viscosity γ1 of Example 3 was significantly lower than that of Comparative Example 3.

In summary, the present invention selects the most suitable liquid crystal compound of various liquid crystal compounds by selecting a suitable combination of a strong polar liquid crystal compound, a medium polarity liquid crystal compound and a nonpolar liquid crystal compound, thereby obtaining a liquid crystal product which is most suitable for use in IPS products. .

However, the above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Therefore, it is common knowledge in the technical field or equivalent or easy to be familiar with the technology. The changes and modifications made by the changer without departing from the spirit and scope of this creation shall be covered by the scope of this creation.

Claims (14)

A liquid crystal composition, wherein the liquid crystal composition comprises: 25-55% by weight of the total weight of the liquid crystal composition of one or more compounds of the formula I One or more compounds of the formula II in an amount of from 20 to 40% by weight based on the total weight of the liquid crystal composition One or more compounds of the formula III in an amount of from 5 to 25% by weight based on the total weight of the liquid crystal composition One or more compounds of the formula IV in an amount of from 5 to 20% by weight based on the total weight of the liquid crystal composition And one or more compounds of the formula V in an amount of from 5 to 25% by weight based on the total weight of the liquid crystal composition Wherein R ₁ , R ₃ , R ₄ , R ₅ , R ₆ and R _{7 are the} same or different and each independently represents H, an alkyl group having 1 to 7 carbon atoms or an alkoxy group, and a carbon number of 1 a fluoroalkyl or fluoroalkoxy group of 7 or an alkenyl group or an alkenyloxy group having 2 to 7 carbon atoms; R ₂ represents H or an alkyl group or alkoxy group having 1 to 5 carbon atoms; ; L ₁ and L _{2 are the} same or different and each independently represents H or F; n represents 0 or 1. The liquid crystal composition according to claim 1, wherein the liquid crystal composition further comprises: 0 to 10% by weight of the total weight of the liquid crystal composition of one or more compounds of the formula VI One or more compounds of the formula VII in an amount of from 0 to 10% by weight based on the total weight of the liquid crystal composition One or more compounds of the formula VIII in an amount of from 0 to 20% by weight based on the total weight of the liquid crystal composition And one or more compounds of the formula IX in an amount of from 0 to 10% by weight based on the total weight of the liquid crystal composition Wherein R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ and R _{14 are the} same or different and each independently represents H, an alkyl group having 1 to 7 carbon atoms or an alkoxy group, and the number of carbon atoms a fluoroalkyl or fluoroalkoxy group of 1 to 7 or an alkenyl group or an alkenyloxy group having 2 to 7 carbon atoms; Express or , where, the One or more -CH ₂ - may be substituted by -O-, provided that the oxygen atoms are not connected; One or more H may be replaced by F, one or more -CH= may be substituted by -N=; L ₃ represents H or F. The liquid crystal composition according to claim 2, wherein the compound of the formula I accounts for 30-50% by weight of the total weight of the liquid crystal composition; the compound of the formula II accounts for 23% of the total weight of the liquid crystal composition. -35%; the compound of the formula III accounts for 10-20% by weight of the total liquid crystal composition; the compound of the formula IV accounts for 5-16% of the total weight of the liquid crystal composition; the compound of the formula V accounts for 5-18% of the total weight of the liquid crystal composition; the compound of the formula VI is from 0 to 5% by weight based on the total weight of the liquid crystal composition; the compound of the formula VII is from 0 to 5% by weight based on the total weight of the liquid crystal composition; The compound of the formula VIII is from 0 to 15% by weight based on the total weight of the liquid crystal composition; and the compound of the formula IX is from 0 to 8% by weight based on the total weight of the liquid crystal composition. The liquid crystal composition of claim 3, wherein the compound of the formula I is selected from the group consisting of one or more of the following compounds: ;as well as The liquid crystal composition of claim 3, wherein the compound of the formula II is selected from the group consisting of one or more of the following compounds: ;as well as The liquid crystal composition of claim 3, wherein the compound of the formula III is selected from the group consisting of one or more of the following compounds: ;as well as The liquid crystal composition of claim 3, wherein the compound of the formula IV is selected from the group consisting of one or more of the following compounds: ;as well as The liquid crystal composition of claim 3, wherein the compound of the formula V is selected from one or more of the following compounds: ;as well as The liquid crystal composition of claim 3, wherein the compound of the formula VI is selected from one or more of the following compounds: ;as well as And the compound of formula VII is selected from one or more compounds consisting of: ;as well as And the compound of formula VIII is selected from one or more of the following compounds: ;as well as And the compound of formula IX is selected from one or more of the following compounds: ;as well as The liquid crystal composition according to any one of claims 1 to 9, wherein the liquid crystal composition has an optical anisotropy value Δn of between 0.095 and 0.108. The liquid crystal composition according to claim 10, wherein the liquid crystal composition comprises: 5% of the total weight of the liquid crystal composition of the compound V-2; and the compound V- of 3.5% by weight based on the total weight of the liquid crystal composition. 1; Compound IV-2; 16% by weight of the total weight of the liquid crystal composition of the compound III-3; 36% of the total weight of the liquid crystal composition of the compound I-1; The compound III-4; the compound II-2 which accounts for 11% of the total weight of the liquid crystal composition; the compound II-4 which accounts for 3.5% of the total weight of the liquid crystal composition; the liquid crystal composition A total weight of 7% of the compound II-5; and 7% of the total weight of the liquid crystal composition of the compound II-6. The liquid crystal composition according to claim 10, wherein the liquid crystal composition comprises: 4% by weight of the total weight of the liquid crystal composition of the compound V-2; and 5% of the total weight of the liquid crystal composition of the compound V- 1; Compound V-7, which is 6% by weight based on the total weight of the liquid crystal composition; Compound IV-2, which is 10% by weight based on the total weight of the liquid crystal composition; Compound III-3, which accounts for 10% by weight of the total weight of the liquid crystal composition; The compound I-1 having a total weight of 33% by weight of the composition; the compound 1-2 in an amount of 8% by weight based on the total weight of the liquid crystal composition; the compound II-2 in an amount of 10% by weight based on the total weight of the liquid crystal composition; % of compound II-4; and compound II-5, which is 8% by weight based on the total weight of the liquid crystal composition. The liquid crystal composition according to claim 10, wherein the liquid crystal composition comprises: 5% of the total weight of the liquid crystal composition of the compound VII-2; and 5% of the total weight of the liquid crystal composition of the compound V- 2; compound IV-2; 15% by weight of the total weight of the liquid crystal composition of the compound III-3; 31% of the total weight of the liquid crystal composition of the compound I-1; a compound III-4 which accounts for 9% by weight of the total weight of the liquid crystal composition; a compound II-2 which accounts for 14% by weight of the total weight of the liquid crystal composition; a compound II-4 which accounts for 5% by weight of the total weight of the liquid crystal composition; The compound II-5 was found to have a total weight of 6%. The liquid crystal composition according to claim 10, wherein the liquid crystal composition comprises: Compound V-2 in an amount of 2% by weight based on the total weight of the liquid crystal composition; and Compound V- in an amount of 5% by weight based on the total weight of the liquid crystal composition. 1; Compound IV-2, which is 16% by weight based on the total weight of the liquid crystal composition; Compound III-3, which is 10% by weight based on the total weight of the liquid crystal composition; Compound I-1, which accounts for 34% of the total weight of the liquid crystal composition; 3% by weight of the composition of the compound VI-1; 3% by weight of the total weight of the liquid crystal composition of the compound III-4; 16% by weight of the total weight of the liquid crystal composition of the compound II-2; % of compound II-4; compound II-5 which is 4% by weight based on the total weight of the liquid crystal composition; and compound II-6 which is 4% by weight based on the total weight of the liquid crystal composition.