CN106701105B - Dual-frequency driving liquid crystal mixture with low critical switching frequency - Google Patents
Dual-frequency driving liquid crystal mixture with low critical switching frequency Download PDFInfo
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Abstract
The invention discloses a dual-frequency driving liquid crystal mixture with low critical switching frequency, which comprises a first component and a second component,the first component comprises one or more compounds shown in the general formula I:
the second component comprises one or more compounds shown in a general formula II:
Description
Technical Field
The invention belongs to the technical field of liquid crystal materials, and particularly relates to a dual-frequency driving liquid crystal mixture with low critical switching frequency.
Background
The Dual frequency driven liquid crystal (Dual frequency liquid crystal) material has the characteristic that the positive and negative of the dielectric anisotropy can be changed along with the change of the applied frequency. When no external frequency is applied, the dielectric anisotropy value of the liquid crystal is positive; as the frequency of the applied alternating electric field increases, the dielectric anisotropy may change from positive to negative; the frequency value corresponding to the value when the dielectric anisotropy is zero is the critical transition frequency (f)c) The method is an important index for measuring the performance of the dual-frequency liquid crystal. When the external frequency is less than the critical frequency, the liquid crystal molecules are arranged along the direction of the electric field; when the applied frequency is greater than the critical frequency, the liquid crystal molecules are arranged in a vertical electric field; thereby realizing the change of the molecular arrangement mode by controlling the magnitude of the applied frequency.
The double-frequency driving liquid crystal has the characteristics of nematic positive liquid crystal and nematic negative liquid crystal, compared with the common nematic liquid crystal, the double-frequency driving liquid crystal material has larger phase transition and faster response time, the prepared device has sub-microsecond level response speed, the required driving voltage is low, the regulation and control mechanism is simpler, and the double-frequency driving liquid crystal material is applied to the display field, the bistable device and the optical field such as an optical shutter, a self-adaptive optical device and an optical lensAnd the like, and has wide application range. However, of the currently commercially available dual-frequency liquid crystal materialscHigher, higher frequency drive is required to cause large dielectric loss, which affects the stability and lifetime of the device, limiting its application as a high performance photovoltaic material. Therefore, designing novel dual-frequency driving liquid crystal molecules and developing dual-frequency driving liquid crystal materials with low critical switching frequency have important significance for production and application of the dual-frequency driving liquid crystal materials.
Disclosure of Invention
The invention aims to provide a dual-frequency driving liquid crystal mixture with low critical switching frequency, which has the excellent performances of low critical switching frequency, proper viscosity, large dielectric anisotropy constant, wide liquid crystal temperature range and the like.
In order to achieve the purpose, the invention adopts the following technical scheme:
a dual-frequency driven liquid crystal mixture with low critical switching frequency, which comprises a first component and a second component, wherein the first component comprises one or more compounds shown in a general formula I:
in the formula, the terminal group R1、R2Are respectively selected from-CN, -NCS, -OCN and-CnH2n+1、-OCnH2n+1、-SCnH2n+1、-CF3O、-CHF2O, any one of groups formed by replacing any two adjacent methylene groups in alkyl containing 1-10 carbon atoms by vinyl groups, any one of groups formed by replacing any two adjacent methylene groups in alkoxy containing 1-10 carbon atoms by vinyl groups, and n is an integer of 1-20;
the bridge bond A is selected from carbon-carbon single bond, double bond, triple bond, -COO-, -OCO-, -CONH-, - (CH)2)a-、-CH2O, wherein a is an integer of 0-5;
a six-membered ring Z is 
Any one or more of the groups, wherein the number m of the rings is an integer of 1-3;
substituent X1～X4Any one of-H, -F, -Cl and-CN independently;
the second component comprises one or more compounds shown in a general formula II:
in the formula, the terminal group R3、R4Are respectively selected from-CnH2n+1、-OCnH2n+1、-SCnH2n+1、-CF3O、-CHF2O、-CF3Any one of groups formed by replacing any two adjacent methylene groups in alkyl containing 1-10 carbon atoms by vinyl groups, any one of groups formed by replacing any two adjacent methylene groups in alkoxy containing 1-10 carbon atoms by vinyl groups, and n is an integer of 1-20;
the bridge bond B is selected from one or more of a carbon-carbon single bond, a carbon-carbon double bond and a carbon-carbon triple bond;
six-membered ring Y is
Any one or two of the groups, wherein the number m of the rings is an integer of 1-3;
substituent X5、X6Independently selected from any one of-H, -F, -Cl and-CN.
In the invention, the mass fractions of the first component and the second component are respectively 10-50% and 50-90%.
Preferably, the mass fractions of the first component and the second component are 20-40% and 60-80%, respectively.
As a preferable technical scheme of the invention, the compound shown in the general formula I is one or more of compounds shown in I-a-I-j;
as a more preferred embodiment of the present invention, R1、R2Respectively selecting any one of an alkyl chain with 1-10 carbon atoms, an alkoxy chain with 1-10 carbon atoms, a cyano group and an isothiocyanato;
X1～X4each independently selected from a hydrogen atom, a chlorine atom or a fluorine atom;
ring Z is 1, 4-cyclohexylene or 1, 4-phenylene.
As another preferable technical scheme, the compound shown in the general formula II is one or more of compounds shown in II-a-II-f;
as another more preferred embodiment of the present invention, R1、R2Respectively selected from alkyl chains with 1-10 carbon atoms and alkoxy chains with 1-10 carbon atoms;
X5、X6each independently selected from hydrogen atom, chlorine atom or cyano;
ring Y is a 1, 4-cyclohexylene or 1, 4-phenylene group.
The invention utilizes a mixing method to prepare the dual-frequency driving liquid crystal mixture.
The dielectric anisotropy value of the liquid crystal molecules with the dual-frequency driving characteristic is positive under a low-frequency electric field, gradually decreases along with the increase of the frequency, and becomes negative after the critical switching frequency is exceeded. Because the pure double-frequency driving liquid crystal compound has high critical conversion frequency, large viscosity and small negative dielectric constant value under a high-frequency electric field, and is not beneficial to electric field and frequency regulation, some liquid crystal compounds with negative dielectric anisotropy are required to be added to improve the physical properties.
By adopting the technical scheme, the invention provides a novel dual-frequency driving liquid crystal mixture. The mixture is obtained by mixing a plurality of double-frequency liquid crystal compounds with different molecular structures and negative dielectric anisotropy liquid crystal compounds, and the double-frequency driving liquid crystal mixture with excellent performance is obtained by regulating and controlling the variety and the proportion of the two components. The liquid crystal mixture has the characteristics of smaller critical conversion frequency, wider liquid crystal phase temperature range, good thermal stability, proper viscosity, large optical anisotropy and dielectric anisotropy constant and the like, has great significance for the industrial application of the dual-frequency drive liquid crystal material, and has wide application value and market prospect.
Detailed Description
The present invention will be described in further detail with reference to the following examples:
the following examples refer to the proportions of the components in mass fractions, the temperature unit is deg.C, the frequency unit is KHz, and the specific meanings and test conditions of other symbols are as follows:
Δ ∈ denotes a dielectric anisotropy constant, and Δ ∈∥-ε⊥Wherein, epsilon∥Is a dielectric constant, ε, parallel to the long axis of the molecule⊥For the dielectric constant perpendicular to the long axis of the molecule, test conditions: 25 ℃, 1Hz-1MHz, 10.0um parallel orientation box, 10.0um vertical orientation box, precise LCR instrument test.
fcWhich represents the critical switching frequency of the liquid crystal, the magnitude of which is related to the test temperature and generally increases exponentially with increasing temperature. The calculation method comprises the following steps: 25 deg.C,. DELTA.. epsilon. -. epsilon∥-ε⊥The frequency of the corresponding applied electric field is f of the liquid crystal material when the value is equal to 0c。
TIIndicating the clearing point temperature of the liquid crystal; t isNRepresents the nematic phase temperature of the liquid crystal; t ismThe melting point temperature of the liquid crystal is shown. Differential scanning calorimetry was combined with polarizing microscopy.
Δ n represents optical anisotropy, and Δ n ═ no-neWherein n isoRefractive index of ordinary light, neFor the refractive index of extraordinary rays, test conditions: 25 deg.C589nm, Abbe refractometer test;
η represents the kinetic viscosity in mPa · s, test conditions: at 25 ℃ and with a rotational viscometer.
The following examples 1 to 5 were prepared by weighing the liquid crystal compounds of the first component and the second component in proportion, and uniformly mixing them to obtain a dual frequency driving liquid crystal mixture. The small molecule compounds used can be synthesized by known methods or obtained commercially.
Example 1
And (3) modulating a liquid crystal mixture according to the corresponding compounds and mass fractions in the table 1, heating to an isotropic state, oscillating, and performing ultrasonic treatment for more than 1h to ensure that the components are uniformly mixed. The obtained liquid crystal mixture is heated to be clear and respectively filled into parallel-oriented and vertical-oriented liquid crystal boxes with the thickness of 10um for testing the dielectric constant value.
The resulting mixture is a nematic liquid crystal with the following performance parameters: f. ofc＝7.1，TI＝106.3，Tm≤-20，Δn＝0.12，η＝88，Δε＝1.9at 50Hz，Δε＝-1.8at 10KHz。
TABLE 1 component kinds and mass ratios of the dual frequency-driven liquid crystal mixture of example 1
Example 2
And (3) modulating a liquid crystal mixture according to the corresponding compounds and mass fractions in the table 2, heating to an isotropic state, oscillating, and performing ultrasonic treatment for more than 1h to ensure that the components are uniformly mixed. The obtained liquid crystal mixture is heated to be clear and respectively filled into parallel-oriented and vertical-oriented liquid crystal boxes with the thickness of 10um for testing the dielectric constant value.
The resulting mixture is a nematic liquid crystal with the following performance parameters: f. ofc＝5.8，TI＝103.2，Tm≤-20，Δn＝0.10，η＝76，Δε＝2.8at 50Hz，Δε＝-2.2at 10KHz。
TABLE 2 component kinds and mass ratios of the dual frequency-driven liquid crystal mixture of example 2
Example 3
And (3) preparing a liquid crystal mixture according to the corresponding compounds and mass fractions in the table 3, heating to an isotropic state, oscillating, and performing ultrasonic treatment for more than 1 hour to ensure that the components are uniformly mixed. The obtained liquid crystal mixture is heated to be clear and respectively filled into parallel-oriented and vertical-oriented liquid crystal boxes with the thickness of 10um for testing the dielectric constant value.
The resulting mixture is a nematic liquid crystal with the following performance parameters: f. ofc＝2.4，TI＝96.2，Tm≤-20，Δn＝0.13，η＝41，Δε＝4.6at 50Hz，Δε＝-3.8at 10KHz。
TABLE 3 component kinds and mass ratios of the dual frequency-driven liquid crystal mixture of example 3
Example 4
And (3) modulating a liquid crystal mixture according to the corresponding compounds and mass fractions in the table 4, heating to an isotropic state, oscillating, and performing ultrasonic treatment for more than 1h to ensure that the components are uniformly mixed. The obtained liquid crystal mixture is heated to be clear and respectively filled into parallel-oriented and vertical-oriented liquid crystal boxes with the thickness of 10um for testing the dielectric constant value.
The resulting mixture is a nematic liquid crystal with the following performance parameters: f. ofc＝1.5，TI＝87.4，Tm≤-20，Δn＝0.17，η＝49，Δε＝5.4at 50Hz，Δε＝-4.7at 10KHz。
TABLE 4 component kinds and mass ratios of the dual frequency-driven liquid crystal mixture of example 4
Example 5
The liquid crystal mixture was prepared according to the corresponding compounds and mass fractions in table 5, heated to isotropic state and oscillated, and sonicated for more than 1h to ensure uniform mixing of the components. The obtained liquid crystal mixture is heated to be clear and respectively filled into parallel-oriented and vertical-oriented liquid crystal boxes with the thickness of 10um for testing the dielectric constant value.
The resulting mixture is a nematic liquid crystal with the following performance parameters: f. ofc＝0.9，TI＝92.5，Tm≤-20，Δn＝0.16，η＝32，Δε＝6.4at 50Hz，Δε＝-5.9at 10KHz。
TABLE 5 component kinds and mass ratios of the dual frequency-driven liquid crystal mixture of example 5
The experimental results of the above examples show that: the double-frequency driving liquid crystal material with smaller critical conversion frequency can be obtained by mixing according to the formula of the embodiment 1-5, wherein fcThe lowest mixture ratio (example 5) is 0.9KHz, the viscosity and the optical anisotropy are moderate, the dielectric anisotropy constant is large, and the practical dual-frequency driving liquid crystal material can be prepared by further optimizing the components.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (5)
1. A dual-frequency driven liquid crystal mixture with a low critical switching frequency, which consists of the following components in percentage by mass:
2. a dual-frequency driving liquid crystal mixture with low critical switching frequency, its preparation methodThe mixture comprises the following components in percentage by mass:
3. a dual-frequency driven liquid crystal mixture with a low critical switching frequency, which consists of the following components in percentage by mass:
4. a dual-frequency driven liquid crystal mixture with a low critical switching frequency, which consists of the following components in percentage by mass:
5. a dual-frequency driven liquid crystal mixture with a low critical switching frequency, which consists of the following components in percentage by mass:
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| CN108659854A (en) * | 2017-03-29 | 2018-10-16 | 北京八亿时空液晶科技股份有限公司 | A kind of liquid-crystal composition and its application |
| CN107338057B (en) * | 2017-07-10 | 2018-05-04 | 深圳市擎亮科技有限公司 | Dual-frequency liquid crystal composition, liquid crystal handwriting device, display device and light modulating device |
| CN109824543B (en) * | 2017-11-23 | 2022-02-22 | 江苏和成显示科技有限公司 | Compound, liquid crystal composition and application thereof |
| EP3543313B1 (en) * | 2018-03-23 | 2020-10-07 | Merck Patent GmbH | Liquid-crystalline medium |
| US20220399166A1 (en) * | 2019-11-14 | 2022-12-15 | Panasonic Intellectual Property Management Co., Ltd. | Dielectric composition, dielectric film, and capacitor |
| TW202206576A (en) * | 2020-08-06 | 2022-02-16 | 日商Ｄｉｃ股份有限公司 | Liquid crystal composition, and liquid crystal display element, sensor, liquid crystal lens, optical communication equipment, and antenna using same |
| JP7491182B2 (en) | 2020-10-21 | 2024-05-28 | Jnc株式会社 | Liquid crystal composition and device used for phase control of electromagnetic wave signals |
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