TWI820620B - A kind of liquid crystal composition and its application - Google Patents

Abstract

The present invention provides a liquid crystal composition and its application. The liquid crystal composition contains compounds represented by general formulas I to IX. When the nine liquid crystal compounds of general formula I to general formula IX of the present invention are combined according to specific proportions, they have synergistic effects. The obtained liquid crystal composition has a lower voltage change rate and a higher clearing point, and can achieve ultra-high clearing point. Wide-temperature operation is especially suitable for PDLC-type displays. It can overcome the technical shortcomings of existing PDLC displays with narrow operating temperatures, especially difficulty in driving at low temperatures, and broaden its application range.

Description

A kind of liquid crystal composition and its application

The present invention relates to the technical field of liquid crystal materials, and in particular, to a liquid crystal composition and its application.

Liquid crystal is an organic substance with a certain degree of order between the solid state and the liquid state, and has photoelectric dynamic scattering properties. Liquid crystals have a variety of liquid crystal phase states, such as cholesteric phase, various smectic phases, nematic phase, etc. At present, the application fields of liquid crystal compounds have been significantly expanded to various types of display devices, electro-optical devices, electronic components, sensors, etc. Nematic liquid crystal compounds have been the most widely used in flat panel displays. LCD displays use liquid crystal mixtures with required material properties such as operating temperature range, thermal stability, photostability, switching time and contrast ratio.

Polymer Dispersed Liquid Crystal (PDLC) is a mixture of low molecular liquid crystals and prepolymers, which undergo a polymerization reaction under certain conditions to form micron-sized liquid crystal droplets that are evenly dispersed in the polymer network. The dielectric anisotropy of liquid crystal molecules is used to obtain materials with electro-optical response characteristics, which mainly work between the scattering state and the transparent state. Compared with traditional liquid crystal devices, polymer dispersion displays have many advantages, such as no need for polarizers and alignment layers, simple preparation processes, and easy production of large-area flexible displays. In recent years, as PDLC has become more and more widely used in various fields, the corresponding requirements for liquid crystal materials have become higher and higher. Various characteristic parameters of liquid crystal materials, such as optical anisotropy (△n), dielectric anisotropy (△ε), clearing point (Cp), etc., will affect the overall working conditions of PDLC. The voltage change rate (dv/dt) is a parameter that characterizes the change of the driving voltage of the liquid crystal device with temperature. A good voltage change rate at low temperature can ensure that the liquid crystal display can work normally at low temperature.

Therefore, research on liquid crystal materials with high and wide temperature properties has important application value.

The invention provides a liquid crystal composition and its application. The liquid crystal composition has good voltage change rate (dv/dt) characteristics at low temperatures, has a high clearing point, and can realize ultra-wide temperature operation.

The present invention provides a liquid crystal composition, which contains the following components in terms of weight percentage: 3%~9% of the compound represented by general formula I; 41%~47% compounds represented by general formula II; 1%~5% of the compound represented by general formula III; 5%~10% of the compound represented by general formula IV; 10%~15% of the compound represented by general formula V; 1%~5% of the compound represented by general formula VI; 10%~15% of the compound represented by general formula VII; 1%~5% of the compound represented by general formula VIII; 2%~7% of the compound represented by general formula IX,

The structures of the general formulas I to IX are as follows: I II III IV V VI VII VIII IX

Among them, R ₁ , R ₂₁ , R ₂₂ , R ₃₁ , R ₃₂ , R ₄₁ , R ₄₂ , R ₅ , R ₆₁ , R ₆₂ , R ₇₁ , R ₇₂ , R ₈₁ , R ₈₂ , R ₉₁ and R ₉₂ are the same or different, each independently represents a linear alkyl group of C ₁ to C ₁₂ .

Further, the R ₁ , R ₂₁ , R ₂₂ , R ₃₁ , R ₃₂ , R ₄₁ , R ₄₂ , R ₅ , R ₆₁ , R ₆₂ , R ₇₁ , R ₇₂ , R ₈₁ , R ₈₂ , R ₉₁ and R ₉₂ is the same or different, and each independently represents a straight-chain alkyl group of C ₂ to C ₅ , such as ethyl, n-propyl, n-butyl, n-pentyl.

Further, the compound represented by the general formula I is selected from one or two types of formula I-1 to formula I-2: I-1 I-2;

and / or,

The compound represented by the general formula II is selected from one or more of formula II-1 to formula II-4: II-1 II-2 II-3 II-4;

and / or,

The compound represented by the general formula III is selected from one or two types of formula III-1 to formula III-2: III-1 III-2;

and / or,

The compound represented by the general formula IV is selected from one or two types of formula IV-1 to formula IV-2: IV-1 IV-2;

and / or,

The compound represented by the general formula V is selected from one or more of the formulas V-1 to V-4: V-1 V-2 V-3 V-4;

and / or,

The compound represented by the general formula VI is selected from one or more of formula VI-1 to formula VI-4: VI-1 VI-2 VI-3 VI-4;

and / or,

The compound represented by the general formula VII is selected from one or more of formulas VII-1 to formula VII-4: VII-1 VII-2 VII-3 VII-4;

and / or,

The compound represented by the general formula VIII is selected from one or more of formula VIII-1 to formula VIII-4: VIII-1 VIII-2 VIII-3 VIII-4;

and / or,

The compound represented by the general formula IX is selected from one or more of the formulas IX-1 to IX-4: IX-1 IX-2 IX-3 IX-4.

Further, in terms of weight percentage, the liquid crystal composition includes the following components: 5%~7% of the compound represented by general formula I; 43%~46% compounds represented by general formula II; 2%~3% of the compound represented by general formula III; 6%~9% compounds represented by general formula IV; 12%~14% of the compound represented by general formula V; 3%~5% of the compound represented by general formula VI; 13%~15% of the compound represented by general formula VII; 3%~5% of the compound represented by general formula VIII; 4%~5% of the compound represented by general formula IX.

Further, in order to improve the stability of the liquid crystal composition against heat and light, especially ultraviolet light, the liquid crystal composition also includes one or more of an ultraviolet absorber, a hindered amine light stabilizer, and a hindered phenolic antioxidant; Preferably, the ultraviolet absorber is selected from one or more types of benzotriazoles, benzophenones, triazines, and benzoate esters.

Further, in order to improve the display effect of the liquid crystal display device, the liquid crystal composition may also include one or more dichroic dyes; preferably, the dichroic dyes are selected from azos and anthraquinones. One or several.

The liquid crystal composition of the present invention has good low-temperature voltage change rate (dv/dt) and high clearing point, can be used in various display mode devices, and can broaden the operating temperature range of liquid crystal display devices. The display mode device is preferably a PDLC type liquid crystal display device or a dye PDLC type liquid crystal display device.

The preparation method of the liquid crystal composition of the present invention is not particularly limited. It can be produced by mixing two or more compounds using conventional methods, such as by mixing different components at high temperatures and dissolving each other, wherein the liquid crystal composition is dissolved in the solvent used for the compound and mixed, and then distilled out the solvent under reduced pressure; or the liquid crystal composition of the present invention can be prepared according to a conventional method, such as adding a smaller component at a higher temperature. Dissolve it in the main component with a larger content, or dissolve each component in an organic solvent, such as acetone, chloroform or methanol, etc., and then mix the solution to remove the solvent.

The compounds involved in the present invention are all known compounds, which are commercially available or provided by Beijing Bayi Spacetime Liquid Crystal Technology Co., Ltd.

The compounds represented by general formula I to general formula IX in the present invention:

The compound represented by the general formula I has high dielectric anisotropy (△ε) and moderate mutual solubility; the compound represented by the general formula II has large optical anisotropy (△n), moderate clearing point ( Cp), good mutual solubility, and excellent overall performance; the compound represented by the general formula III has large optical anisotropy (△n) and high clearing point (Cp); the compound represented by the general formula IV has high Clearing point (Cp), high optical anisotropy (△n); the compound represented by the general formula V has high dielectric anisotropy (△ε), moderate optical anisotropy (△n), and Excellent low-temperature mutual solubility; the compound represented by the general formula VI has good low-temperature mutual solubility and moderate optical anisotropy (△n); the compound represented by the general formula VII has excellent low-temperature mutual solubility and can significantly improve the liquid crystal combination The low-temperature properties of the material; the compound represented by the general formula VIII has a moderate clearing point (Cp), moderate optical anisotropy (△n), and good low-temperature miscibility; the compound represented by the general formula IX has a very high clearing point Bright spot (Cp), moderate optical anisotropy (Δn).

The invention has the following beneficial effects:

The inventor has conducted extensive research on the photoelectric properties and physical properties of existing liquid crystal compounds, and unexpectedly discovered that when the nine selected liquid crystal compounds of general formula I to general formula IX are combined according to specific ratios, they have synergistic effects, and the resulting The liquid crystal composition has a low voltage change rate and a high clearing point, and can achieve ultra-wide temperature operation. It is especially suitable for PDLC displays and can overcome the narrow operating temperature of existing PDLC displays, especially those that are difficult to drive at low temperatures. technical deficiencies and broaden its application scope.

The following examples are used to illustrate the invention but are not intended to limit the scope of the invention.

Unless otherwise stated, the percentages in the present invention are weight percentages; the temperature unit is degrees Celsius; △n represents optical anisotropy (25°C); ε _∥ and ε _⊥ represent parallel and perpendicular dielectric constants (25°C, 1000Hz) respectively; △ε represents dielectric anisotropy (25℃, 1000Hz); Cp represents the clearing point of the liquid crystal composition (℃); Vth25 represents the threshold voltage (V) at 25℃; Vth-20 represents the threshold voltage at -20℃ (V); dv/dt represents the ratio of the threshold voltage change to the temperature change between -20°C and 25°C (mV/°C).

In the following examples, the group structure in the liquid crystal compound is represented by the code shown in Table 1. Table 1 group code Group name C 1,4-Cyclohexyl P 1,4-phenylene U 2,6-difluoro-1,4-phenylene G 2-Fluoro-1,4-phenylene D 2,6-dioxo-1,4-cyclohexyl Z Ester group T Alkynyl -O- O oxygen substituent -CN EN Cyano C _n H _2n+1 or C _m H _2m+1 n or m alkyl

Take the following compound structure as an example: Represented as: 3DUCN Represented as: 3CCZPC2

In the following examples, the liquid crystal composition is prepared using a thermal dissolution method, which includes the following steps: Use a balance to weigh the liquid crystal compound in percentage by weight. There is no specific requirement for the order of weighing and adding. Usually, the melting point of the liquid crystal compound is from high to low. Weigh and mix in sequence, heat and stir at 60~100°C to melt each component evenly, then filter, rotary evaporate, and finally package to obtain the target sample.

In the following examples, the weight percentage of each component in the liquid crystal composition and the performance parameters of the liquid crystal composition are shown in the following table.

In the following examples, all components involved are known liquid crystal compounds and can be provided by Beijing 800 million Spacetime.

Example 1 Table 2 Category compound code Weight percentage (%) Performance parameters Parameter value I 2DUCN 6 Cp 129 II 2UTPP3 20 △n 0.242 II 4UTPP3 10 △ε 12.6 II 5UTPP3 14 Vth25 1.82 III 3CPTP2 3 Vth-20 2.69 IV 3CGPC3 4 dv/dt 15.8 IV 5CGPC3 4 V 3PZUCN 7 V 5PZUCN 6 VI 3PZP5 4 VII 5CZPO2 13 VIII 3CPZP5 4 IX 3CCZPC3 5

Example 2 Table 3 Category compound code Weight percentage (%) Performance parameters Parameter value I 2DUCN 2 Cp 129 I 3DUCN 5 △n 0.242 II 2UTPP3 twenty two △ε 12.8 II 5UTPP3 twenty two Vth25 1.81 III 3CPTP2 3 Vth-20 2.68 IV 3CGPC3 3 dv/dt 15.8 IV 5CGPC3 5 V 3PZUCN 7 V 5PZUCN 6 VI 3PZP5 4 VII 5CZPO2 8 VII 3CZPO2 4 VIII 3CPZP3 4 IX 3CCZPC3 5

Example 3 Table 4 Category compound code Weight percentage (%) Performance parameters Parameter value I 2DUCN 6 Cp 130 II 2UTPP3 26 △n 0.244 II 4UTPP3 20 △ε 12.9 III 3CPTP2 3 Vth25 1.77 IV 3CGPC3 4 Vth-20 2.63 IV 5CGPC3 4 dv/dt 15.6 V 4PZUCN 14 VI 3PZP5 3 VII 5CZPO2 12 VIII 3CPZP5 4 IX 3CCZPC5 4

Example 4 Table 5 Category compound code Weight percentage (%) Performance parameters Parameter value I 5DUCN 3 Cp 130 II 2UTPP3 20 △n 0.242 II 4UTPP3 10 △ε 12.5 II 5UTPP3 11 Vth25 1.83 III 4CPTP2 3 Vth-20 2.86 III 5CPTP2 2 dv/dt 18.7 IV 3CGPC3 4 IV 4CGPC3 4 IV 5CGPC3 2 V 2PZUCN 3 V 3PZUCN 3 V 4PZUCN 3 V 5PZUCN 6 VI 3PZP5 4 VII 5CZPO2 15 VIII 3CPZP3 5 IX 3CCZPC3 2

Example 5 Table 6 Category compound code Weight percentage (%) Performance parameters Parameter value I 2DUCN 4 Cp 127 I 5DUCN 5 △n 0.239 II 3UTPP3 20 △ε 12.3 II 4UTPP3 10 Vth25 1.8 II 5UTPP3 17 Vth-20 2.85 III 5CPTP1 4 dv/dt 19.1 IV 3CGPC3 2 IV 5CGPC3 3 V 3PZUCN 5 V 5PZUCN 5 VI 2PZP3 1 VI 3PZP3 1 VI 2PZP5 2 VI 3PZP5 1 VII 5CZPO2 10 VIII 5CPZP3 2 VIII 3CPZP3 1 VIII 2CPZP5 1 VIII 3CPZP5 1 IX 3CCZPC3 5

Example 6 Table 7 Category compound code Weight percentage (%) Performance parameters Parameter value I 2DUCN 8 Cp 131 II 2UTPP3 20 △n 0.241 II 4UTPP3 10 △ε 12.8 II 5UTPP3 17 Vth25 1.82 III 3CPTP2 1 Vth-20 2.89 IV 3CGPC3 4 dv/dt 19.5 IV 7CGPC3 4 V 3PZUCN 6 V 5PZUCN 6 VI 3PZP5 1 VII 2CZPO3 3 VII 3CZPO2 4 VII 4CZPO2 4 VII 7CZPO2 4 VIII 2CPZP5 1 IX 3CCZPC3 1 IX 5CCZPC3 2 IX 3CCZPC4 2 IX 3CCZPC5 2

Comparative example 1

The only difference between the liquid crystal composition of this comparative example and Example 1 is that the type I compound 2DUCN in Example 1 is replaced by an equal amount of the type V compound 5PZUCN. The weight percentage of each type of compound in the liquid crystal composition of this comparative example and the performance parameters of the liquid crystal composition are shown in Table 8. Table 8 Category compound code Weight percentage (%) Performance parameters Parameter value II 2UTPP3 20 Cp 132 II 4UTPP3 10 △n 0.248 II 5UTPP3 14 △ε 13.5 III 3CPTP2 3 Vth25 1.73 IV 3CGPC3 4 Vth-20 3.23 IV 5CGPC3 4 dv/dt 27.3 V 3PZUCN 7 V 5PZUCN 12 VI 3PZP5 4 VII 5CZPO2 13 VIII 3CPZP5 4 IX 3CCZPC3 5

Comparative example 2

The only difference between the liquid crystal composition of this comparative example and Example 1 is that the V-type compounds 3PZUCN and 5PZUCN in Example 1 are replaced by an equal amount of the I-type compound 2DUCN. The weight percentage of each component in the liquid crystal composition of this comparative example and the performance parameters of the liquid crystal composition are shown in Table 9. Table 9 Category compound code Weight percentage (%) Performance parameters Parameter value I 2DUCN 19 Cp 121 II 2UTPP3 20 △n 0.231 II 4UTPP3 10 △ε 10.5 II 5UTPP3 14 Vth25 1.99 III 3CPTP2 3 Vth-20 3.47 IV 3CGPC3 4 dv/dt 26.9 IV 5CGPC3 4 VI 3PZP5 4 VII 5CZPO2 13 VIII 3CPZP5 4 IX 3CCZPC3 5

The performance parameters of the liquid crystal compositions obtained in Example 1, Comparative Example 1 and Comparative Example 2 are summarized and compared. The results are shown in Table 10. Table 10 Performance parameters CP △n △ε Vth25 Vth-20 dv/dt Example 1 129 0.242 12.6 1.82 2.69 15.8 Comparative example 1 132 0.248 13.5 1.73 3.23 27.3 Comparative example 2 121 0.231 10.5 1.99 3.47 26.9

Through comparison, it can be seen that the low-temperature voltage change rate of the liquid crystal composition not containing Class I compounds and the liquid crystal composition not containing Class V compounds is significantly higher than that of Example 1, indicating that the combination of Class I compounds and Class V compounds can significantly improve the performance of liquid crystals. Low temperature voltage change rate (dv/dt) characteristics of the composition.

Comparative example 3

The difference between the liquid crystal composition of this comparative example and Example 1 is that the compounds represented by Type IV, Type VII and Type VIII in Example 1 are replaced with other types of liquid crystal compounds. Table 11 Category compound code Weight percentage (%) Performance parameters Parameter value 1 2DUCN 6 Cp 133 II 2UTPP3 20 △n 0.244 II 4UTPP3 10 △ε 12.7 II 5UTPP3 14 Vth25 1.83 III 3CPTP2 3 Vth-20 2.83 3CPPC3 4 dv/dt 18.2 5CPPC3 4 V 3PZUCN 7 V 5PZUCN 6 VI 3PZP5 4 5CZP3 13 3CPZPO2 4 IX 3CCZPC3 5

The performance parameters of the liquid crystal compositions obtained in Example 1 and Comparative Example 3 are summarized and compared. The results are shown in Table 12. Table 12 Performance parameters CP △n △ε Vth25 Vth-20 dv/dt Example 1 129 0.242 12.6 1.82 2.69 15.8 Comparative example 3 133 0.244 12.7 1.83 2.83 18.2

Through comparison, it can be seen that compared with Example 1, the low-temperature voltage change rate of the liquid crystal composition of Comparative Example 3 is increased, indicating that the compounds represented by Class IV, VII, and VIII have synergistic effects on the low-temperature voltage change rate of the liquid crystal composition. Optimization effect.

Comparative example 4

The difference between the liquid crystal composition of this comparative example and Example 1 is that the contents of the compounds represented by each category are different. Table 13 Category compound code Weight percentage (%) Performance parameters Parameter value I 2DUCN 2 Cp 138 II 2UTPP3 20 △n 0.231 II 4UTPP3 10 △ε 9.1 II 5UTPP3 10 Vth25 2.43 III 3CPTP2 1 Vth-20 3.79 IV 3CGPC3 4 dv/dt 24.7 IV 5CGPC3 4 V 3PZUCN 4 V 5PZUCN 4 VI 3PZP5 9 VII 5CZPO2 18 VIII 3CPZP5 6 IX 3CCZPC3 8

The performance parameters of the liquid crystal compositions obtained in Example 1 and Comparative Example 4 are summarized and compared. The results are shown in Table 14. Table 14 Performance parameters CP △n △ε Vth25 Vth-20 dv/dt Example 1 129 0.242 12.6 1.82 2.69 15.8 Comparative example 4 138 0.231 9.1 2.43 3.79 24.7

Comparison shows that compared with Example 1, the low-temperature voltage change rate of the liquid crystal composition of Comparative Example 4 is significantly increased.

Comparative example 5

The weight percentage of each component in the liquid crystal composition of this comparative example and the performance parameters of the liquid crystal composition are shown in Table 15. Table 15 compound code Weight percentage (%) Performance parameters Parameter value 2UTPP3 20 Cp 129 4UTPP3 10 △n 0.241 5UTPP3 10 △ε 12.4 3CPTP2 6 Vth25 1.98 3CPO1 3 Vth-20 3.60 3PZGCN 8 dv/dt 29.5 2CPZGCN 4 3CPZGCN 4 4CPZGCN 4 5CPZGCN 4 3PZP5 12 5CZPO2 12 3CCZPC3 3

The performance parameters of the liquid crystal compositions obtained in Example 1 and Comparative Example 5 are summarized and compared. The results are shown in Table 16. Table 16 Performance parameters CP △n △ε Vth25 Vth-20 dv/dt Example 1 129 0.242 12.6 1.82 2.69 15.8 Comparative example 5 129 0.241 12.4 1.98 3.60 29.5

It can be seen from comparison that: compared with Comparative Example 5, when having the same level of dielectric anisotropy, optical anisotropy and clearing point, the liquid crystal composition provided in Example 1 has low voltage change rate characteristics. It is easier to drive under low temperature (-20℃).

Although the present invention has been described in detail above with general descriptions, specific embodiments and tests, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. . Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims (10)

A liquid crystal composition, characterized in that, in terms of weight percentage, the liquid crystal composition contains the following components: 3% to 9% of the compound represented by the general formula I; 41% to 47% of the compound represented by the general formula II Compounds; 1% to 5% of compounds represented by general formula III; 5% to 10% of compounds represented by general formula IV; 10% to 15% of compounds represented by general formula V; 1% to 5% of compounds represented by general formula VI 10% to 15% of the compound represented by the general formula VII; 1% to 5% of the compound represented by the general formula VIII; 2% to 7% of the compound represented by the general formula IX, the general formula I to The structure of Formula IX is as follows:

Among them, R ₁ , R ₂₁ , R ₂₂ , R ₃₁ , R ₃₂ , R ₄₁ , R ₄₂ , R ₅ , R ₆₁ , R ₆₂ , R ₇₁ , R ₇₂ , R ₈₁ , R ₈₂ , R ₉₁ and R ₉₂ are the same or different, each independently represents a linear alkyl group of C ₁ to C ₁₂ . _The liquid crystal composition according to claim 1, wherein R ₁ , R ₂₁ , R ₂₂ , R ₃₁ , R 32 , R ₄₁ , R ₄₂ , R ₅ , R ₆₁ , R ₆₂ , R ₇₁ , R ₇₂ , R ₈₁ , R ₈₂ , R ₉₁ and R ₉₂ are the same or different, and each independently represents a C ₂ to C ₅ linear alkyl group. The liquid crystal composition according to claim 1, wherein the compound represented by the general formula I is selected from one or two of the formulas I-1 to I-2:

And/or, the compound represented by the general formula II is selected from one or more of the formulas II-1 to II-4:

And/or, the compound represented by the general formula III is selected from one or two types of formula III-1 to formula III-2:

The liquid crystal composition according to claim 1, wherein the compound represented by the general formula IV is selected from one or two of formulas IV-1 to formula IV-2:

And/or, the compound represented by the general formula V is selected from one or more of the formulas V-1 to V-4:

And/or, the compound represented by general formula VI is selected from one or more of formula VI-1 to formula VI-4:

The liquid crystal composition according to claim 1, wherein the compound represented by the general formula VII is selected from one or more of formulas VII-1 to VII-4:

And/or, the compound represented by the general formula VIII is selected from one or more of formula VIII-1 to formula VIII-4:

And/or, the compound represented by the general formula IX is selected from one or more of the formulas IX-1 to IX-4:

The liquid crystal composition according to claim 1, wherein, in terms of weight percentage, the liquid crystal composition includes the following components: 5% to 7% of the compound represented by the general formula I; 43% to 46% of the general formula I Compounds represented by II; 2%~3% compounds represented by general formula III; 6%~9% compounds represented by general formula IV; 12%~14% compounds represented by general formula V; 3%~5% Compounds represented by general formula VI; 13% to 15% of compounds represented by general formula VII; 3% to 5% of compounds represented by general formula VIII; 4% to 5% of compounds represented by general formula IX. The liquid crystal composition according to claim 1, wherein the liquid crystal composition further includes one or more of an ultraviolet absorber, a hindered amine light stabilizer, and a hindered phenolic antioxidant. The liquid crystal composition according to claim 1, wherein the liquid crystal composition further includes a dichroic dye. An application of the liquid crystal composition according to any one of claims 1 to 8 in a display mode device. The application as claimed in claim 9, wherein the display mode device is a PDLC type liquid crystal display device or a dye PDLC type liquid crystal display device.