阅读说明：本技术 一种具有极低介电损耗的液晶组合物及其高频组件 (Liquid crystal composition with extremely low dielectric loss and high-frequency assembly thereof ) 是由 李建 胡明刚 李娟利 车昭毅 莫玲超 张璐 安忠维 万丹阳 杨晓哲 杨诚 史凤娇 于 2020-04-14 设计创作，主要内容包括：本发明提出一种液晶组合物以及包含其的高频组件,液晶组合物包含一种或多种选自结构通式(Ⅰ)的化合物,以及一种或多种选自结构通式(Ⅱ)所示的化合物：其中,R-(1)为碳原子数为1～10的烷基,或碳原子数为2～10的烯基、氟化烷基、氟化烯基、环烷基；X-(1)、X-(2)、X-(3)其中之一为甲基或氯,另外两个为氢；k、m、n、p为0或1；环A为苯环、环己烷或环己烯；其中,R-(2)、R-(3)为碳原子数为1～10的烷基,或碳原子数为2～10的烯基、氟化烷基、氟化烯基、环烷基、卤素或NCS；环A、环B为苯环、环己烷或环己烯。本发明的液晶组合物能够在高频下获得较大的介电调谐率和极低的介电损耗及高的品质因子,拓展向列相工作温度范围、降低旋转粘度、并获得较大的低频介电常数。(The invention provides a liquid crystal composition and a high-frequency component comprising the same, wherein the liquid crystal composition comprises one or more compounds selected from the compounds shown in a structural general formula (I) and one or more compounds selected from the compounds shown in a structural general formula (II): wherein R is 1 An alkyl group having 1 to 10 carbon atoms, or an alkenyl group, a fluorinated alkyl group, a fluorinated alkenyl group, or a cycloalkyl group having 2 to 10 carbon atoms; x 1 、X 2 、X 3 One of which is methyl or chlorine and the other two are hydrogen; k. m, n and p are 0 or 1; ring A is benzene ring, cyclohexane or cyclohexene; wherein R is 2 、R 3 Is alkyl with 1-10 carbon atoms, or alkenyl, fluorinated alkyl, fluorinated alkenyl, cycloalkyl, halogen or NCS with 2-10 carbon atoms; the ring A and the ring B are benzene rings, cyclohexane or cyclohexene. The liquid crystal composition can obtain larger dielectric tuning rate, extremely low dielectric loss and high quality factor under high frequency, expand the nematic phase working temperature range, reduce the rotational viscosity and obtain larger low-frequency dielectric constant.)

1. A liquid crystal composition for high frequency components, comprising one or more compounds selected from the group consisting of compounds represented by the general structural formula (i), and one or more compounds selected from the group consisting of compounds represented by the general structural formula (ii):

wherein R is₁An alkyl group having 1 to 10 carbon atoms, or an alkenyl group, fluorinated alkyl group, fluorinated alkenyl group or cycloalkyl group having 2 to 10 carbon atoms; x₁、X₂、X₃One of which is methyl or chlorine and the other two are hydrogen; k. m, n and p are 0 or 1; ring A is benzene ring, cyclohexane or cyclohexene;

wherein R is₂、R₃Is alkyl with 1-10 carbon atoms, or alkenyl, fluorinated alkyl, fluorinated alkenyl, cycloalkyl, halogen or NCS with 2-10 carbon atoms; the ring A and the ring B are benzene rings, cyclohexane or cyclohexene.

2. The liquid crystal composition of claim 1, wherein the compound of formula (i) comprises one or more compounds selected from the group consisting of compounds of formulae i-a to i-L:

3. the liquid crystal composition of claim 1, wherein the compound of formula (ii) is selected from the following structures:

4. the liquid crystal composition as claimed in any one of claims 1 to 3, wherein the mass ratio of the compound represented by the general structural formula (I) is 50% to 99%, and the mass ratio of the compound represented by the general structural formula (II) is 1% to 40%.

5. The liquid crystal composition according to any one of claims 1 to 3, wherein the liquid crystal composition comprises 0 to 30% by mass of a compound represented by the general structural formula (III);

wherein R is₁An alkyl group having 1 to 10 carbon atoms, or an alkenyl group, a fluorinated alkyl group or a fluorinated alkenyl group having 2 to 10 carbon atoms; x₄、X₅、X₆Is H or F; k. m and n are 0 or 1; ring A is a benzene ring or cyclohexane or cyclohexene.

6. The liquid crystal composition of any one of claims 1 to 3, further comprising 0.001 to 1% of an additive.

7. The liquid crystal composition of claim 6, wherein the additive comprises a 2, 6-di-tert-butylphenol antioxidant or a light stabilizer.

8. The liquid crystal composition according to any of claims 1 to 3, wherein the liquid crystal composition has a vertical dielectric loss value tan δ_⊥Less than or equal to 0.008 and the quality factor eta more than or equal to 40.

9. A high-frequency component comprising the liquid crystal composition according to any one of claims 1 to 8.

Technical Field

The invention belongs to the technical field of liquid crystal materials, and particularly relates to a liquid crystal composition with extremely low dielectric loss and a high-frequency component comprising the same, which are suitable for the fields of filters, adjustable frequency selection surfaces, microwave phase shifters, microwave phased array antennas and the like.

Background

Liquid crystal materials are widely used in electro-optical display devices. In recent years, liquid crystal materials have also been proposed for use in high frequency components, such as microwave phase shifters. Liquid crystal based microwave phase shifters are reported, for example, in the following documents:

Muller S.et al.(2004).Tunable passive phase shifter for microwave applications using highly anisotropic liquid crystals.Microwave Symposium Digest,2004 IEEE MTT-S International.

in a microwave phase shifter, the dielectric tuning rate of the liquid crystal material determines the tuning capability of the microwave device. The liquid crystal material has a dielectric tuning rate (τ) determined by the dielectric anisotropy (Δ ∈) of the liquid crystal material at high frequencies and the dielectric constant (∈) in the direction parallel to the molecules_∥) Determining that:

τ＝Δε/ε_∥

dielectric loss of a liquid crystal material is an important factor affecting the insertion loss of its microwave device. In order to obtain a high performance liquid crystal microwave device, the dielectric loss of the liquid crystal material must be reduced. For liquid crystal materials, the loss tangent varies with the liquid crystal molecular director according to the electric field director, i.e., the loss in the major axis and minor axis directions of the liquid crystal molecules varies, and the maximum loss value, i.e., max (tan δ) is generally used when calculating the loss of the liquid crystal material_∥,tanδ_⊥) As a loss of liquid crystal material.

In order to comprehensively evaluate the performance parameters of the liquid crystal material under microwave, a quality factor (eta) parameter is introduced:

η＝τ/max(tanδ_∥,tanδ_⊥)

liquid crystal materials for high frequency components require large dielectric tuning rate (τ), low loss (tan δ)_∥,tanδ_⊥) High quality factor (η). The liquid crystal material for the high-frequency component disclosed in the prior art has a large dielectric loss value, so that the insertion loss of the high-frequency component is large, the working efficiency of the device is low, and the liquid crystal material becomes a technical bottleneck of industrialization of a microwave device based on liquid crystal. Therefore, the problem of reducing the dielectric loss of the liquid crystal material is urgently needed to be solved.

In addition, in order to meet practical application, the liquid crystal material for high frequency components is required to have a wider operating temperature range, and particularly, the low temperature operating temperature is required to be improved. In order to meet the requirement of fast switching operation of a high-frequency component, the liquid crystal material is required to have lower rotational viscosity. In order to satisfy the requirement that the high-frequency component works under the driving of an electric field, the liquid crystal material is required to have a proper dielectric constant under a low frequency, such as 1 KHz.

Since the dielectric constant of a liquid crystal material at high frequencies is related to the birefringence of the liquid crystal, it is shown by the following formula:

in order to obtain a higher dielectric constant, a liquid crystal material having a high birefringence is also required.

The conventional commercial high-birefringence Liquid crystal materials, for example, in the papers entitled "chromatography and Applications of chemical Liquid Crystals in Microwave devices" of Molecular Crystals and Liquid Crystals and 2011, 542(1):196/[718] -203/[725], have the disadvantages of low tuning rate and large loss at high frequency, such as E7 and E44 containing cyanobiphenyl and terphenyl Liquid Crystals.

Patent CN103443245A discloses a liquid crystal medium containing a bis-diphenylacetylene liquid crystal material, such as a structure represented by the following formula:

although the compound has a high quality factor at high frequency, its rotational viscosity (. gamma.) is high₁) As high as 2100 mPas, it causes a defect of slow response speed. Further, the dielectric constant of this compound is small at low frequencies, only 0.8.

In patent CN 103429704 a, fluorophenylacetylene liquid crystal compounds:

although this compound has a large birefringence (. DELTA.n.0.35) and a good performance at high frequencies, its rotational viscosity (. gamma.) is high₁When 1300mPa · s is obtained, the response speed becomes slow.

CN107955630A and CN105368465A disclose that the molecular end is NCS group, andthe liquid crystal composition with the molecular skeleton of fluorine substituted benzene ring has larger dielectric constant and tuning rate at high frequency, but has larger dielectric loss value; in the disclosed embodiment thereof, the maximum dielectric loss tan delta_⊥(19GHz) is 0.01 or more.

CN110499163A, US2019292458A1 disclose liquid crystal compositions based on NCS groups at the ends of the molecules and fluorine substituted benzene rings in the molecular skeleton, in the examples disclosed, the maximum dielectric loss tan delta_⊥(19GHz)≥0.083。

Disclosure of Invention

Technical problem to be solved

In order to overcome the problems of the background art, the present invention proposes a liquid crystal composition having a large dielectric tuning rate at high frequencies, an extremely low dielectric loss, a wide nematic phase temperature range, a low rotational viscosity, and a large dielectric constant at low frequencies, and a high frequency device comprising the same.

(II) technical scheme

In order to solve the above technical problems, the present invention provides a liquid crystal composition for high frequency components, comprising one or more compounds selected from the group consisting of compounds represented by the general structural formula (i), and one or more compounds selected from the group consisting of compounds represented by the general structural formula (ii):

wherein R is₁An alkyl group having 1 to 10 carbon atoms, or an alkenyl group, fluorinated alkyl group, fluorinated alkenyl group or cycloalkyl group having 2 to 10 carbon atoms; x₁、X₂、X₃One of which is methyl or chlorine and the other two are hydrogen; k. m, n and p are 0 or 1; ring A is benzene ring, cyclohexane or cyclohexene;

wherein R is₂、R₃Is an alkyl group having 1 to 10 carbon atoms or a C-group2-10 alkenyl, fluoroalkyl, fluoroalkenyl, cycloalkyl, halogen or NCS; the ring A and the ring B are benzene rings, cyclohexane or cyclohexene.

Further, the compounds of general structural formula (I) comprise one or more compounds selected from the group consisting of compounds of general structural formulae I-A to I-L:

further, the compound represented by the general structural formula (ii) is selected from the following structures:

furthermore, the mass ratio of the compound shown in the structural general formula (I) is 50-99%, and the mass ratio of the compound shown in the structural general formula (II) is 1-40%.

Further, the liquid crystal composition comprises 0 to 30 mass percent of a compound represented by the general structural formula (III);

wherein R is₁An alkyl group having 1 to 10 carbon atoms, or an alkenyl group, a fluorinated alkyl group or a fluorinated alkenyl group having 2 to 10 carbon atoms; x₄、X₅、X₆Is H or F; k. m and n are 0 or 1; ring A is a benzene ring or cyclohexane or cyclohexene.

Further, the liquid crystal composition also comprises 0.001-1% of additive.

Further, the additive includes a 2, 6-di-tert-butylphenol antioxidant or a light stabilizer.

Further, the vertical dielectric loss value tan. delta. of the liquid crystal composition_⊥Less than or equal to 0.008 and the quality factor eta more than or equal to 40.

In addition, the invention also provides a high-frequency component, which comprises the liquid crystal composition.

(III) advantageous effects

The invention provides a liquid crystal composition with a large dielectric tuning rate at high frequency, extremely low dielectric loss, a wide nematic phase temperature range, low rotational viscosity and a large dielectric constant at low frequency, and a high-frequency component comprising the same. The liquid crystal composition can obtain larger dielectric tuning rate, extremely low dielectric loss and high quality factor under high frequency, can expand the nematic phase working temperature range, reduce the rotational viscosity and obtain larger low-frequency dielectric constant, and is suitable for the fields of filters, phase shifters, phased array radars, 5G communication and the like.

Detailed Description

In order to make the objects, contents and advantages of the present invention clearer, the following detailed description of the embodiments of the present invention will be given in conjunction with examples.

The invention provides a liquid crystal composition for a high-frequency component, which comprises one or more compounds selected from the group consisting of compounds represented by a structural general formula (I), a structural general formula (II) and a structural general formula (III); wherein the content of the first and second substances,

wherein R is₁An alkyl group having 1 to 10 carbon atoms, or an alkenyl group, fluorinated alkyl group, fluorinated alkenyl group or cycloalkyl group having 2 to 10 carbon atoms; x₁、X₂、X₃One of which is methyl or chlorine and the other two are hydrogen; k. m, n and p are 0 or 1; ring A is benzene ring, cyclohexane or cyclohexene;

wherein R is₂、R₃Is alkyl with 1-10 carbon atoms, or alkenyl, fluorinated alkyl, fluorinated alkenyl, cycloalkyl, halogen or NCS with 2-10 carbon atoms; the ring A and the ring B are benzene rings, cyclohexane or cyclohexene;

wherein R is₁An alkyl group having 1 to 10 carbon atoms, or an alkenyl group, a fluorinated alkyl group or a fluorinated alkenyl group having 2 to 10 carbon atoms; x₄、X₅、X₆Is H or F; k. m and n are 0 or 1; ring A is a benzene ring or cyclohexane or cyclohexene.

Further preferred compounds of general structural formula (I) are those of the following structure:

wherein I-A to I-J are further preferably selected from the following structures:

compared with the high-frequency liquid crystal composition based on isothiocyanates, the compound shown in the structural general formula (I) is characterized in that lateral fluorine atom substituent groups do not exist in molecules; the compound uses methyl, ethyl and chlorine atoms with large volume and relatively weak polarity as lateral substituent groups, thereby not only greatly reducing dielectric loss, but also reducing melting point and improving low-temperature compatibility of the liquid crystal composition.

The compounds of the general structural formula (ii) are further preferably of the following structure:

the compound represented by the general structural formula (II) is composed of 2 rings, has the characteristics of low viscosity, low melting point and low dielectric loss, can further improve the low-temperature compatibility of the liquid crystal composition, greatly reduces the viscosity of the liquid crystal composition and simultaneously reduces the dielectric loss.

More preferred structural formulas II-A are the following specific compounds:

wherein II-B is further preferably a compound of the following structure:

wherein II-C is further preferably a compound of the following structure:

preferred specific compounds of the compound of the general structural formula (III) have the following structures:

the compound shown in the structural general formula (III) has a wider liquid crystal phase range, lower viscosity and larger dielectric constant, especially has larger dielectric constant at low frequency of 1KHz, and can play a role in adjusting the liquid crystal phase range and the dielectric constant at low frequency of the composition.

In a preferred embodiment of the present invention, the liquid crystal composition comprises one or more compounds of the general structural formula (I) and one or more compounds of the general structural formula (II). In another preferred embodiment of the present invention, the liquid crystal composition comprises one or more compounds of the general structural formula (I), one or more compounds of the general structural formula (II) and one or more compounds of the general structural formula (III).

The liquid crystal composition preferably comprises 50-99%, preferably 60-95%, more preferably 70-90% of the compound shown in the general formula (I) and 1-40%, preferably 5-30%, particularly preferably 10-20% of the compound shown in the general formula (II) based on the total amount of the composition. The liquid crystal composition of the invention can also comprise 0-30%, preferably 5-25%, particularly preferably 10-20% of the compound shown in the general formula (III) based on the total weight of the composition.

The liquid crystal composition of the present invention may further comprise 0.001 to 1% of additives, such as 2, 6-di-tert-butylphenol antioxidants, light stabilizers T770, and the like.

The liquid crystal composition according to the present invention is composed of a plurality of compounds, preferably 3 to 20 compounds, more preferably 5 to 18 and still more preferably 7 to 15 compounds. These compounds may be mixed by conventional means: weighing various compounds according to a predetermined mass ratio, heating, and uniformly mixing by adopting stirring modes such as magnetic stirring or ultrasonic wave and the like until all components are completely dissolved; and then filtering to obtain the product. The liquid-crystalline compositions can also be prepared in other conventional ways, for example using so-called premixes, or using so-called "multi-bottle" systems, the ingredients of which are themselves ready-to-use mixtures.

The performance of the liquid crystal at high frequency is tested by adopting a test method reported in the literature: penischke, A. (2004). Capacity qualification method for conversion of liquid crystals up to 35 GHz. microwave Conference,2004.34th European.

Liquid crystals were introduced into Polytetrafluoroethylene (PTFE) or fused silica capillaries, and the filled capillaries were introduced into the middle of a chamber with a resonance frequency of 19 GHz. The input signal source is then applied and the results of the output signal are recorded with a vector network analyzer. The change in the resonance frequency and the Q factor between the capillary filled with the liquid crystal and the blank capillary was measured, and the dielectric constant and the loss tangent were calculated. The dielectric constant components perpendicular and parallel to the liquid crystal director are obtained by the alignment of the liquid crystal in a magnetic field, the direction of which is set accordingly and then rotated correspondingly by 90 °.

Preferred liquid crystal compositions of the present invention have a tuning rate τ of 0.25 or greater, more preferably 0.30 or greater; preferred liquid crystal materials have a vertical dielectric loss tan delta_⊥0.008% or less, more preferably tan delta_⊥Less than or equal to 0.007; the material quality factor eta is more than or equal to 40, preferably more than or equal to 50. The preferred nematic phase temperature range of the liquid crystal composition is 0-90 ℃ or above, and the more preferred nematic phase temperature range is-10-100 ℃ or above; the preferred liquid crystal compositions have a rotational viscosity γ 1. ltoreq.1200 mPas, more preferably 1000 mPas; preferred liquid crystal compositions have a dielectric constant at low frequency 1KHz of 7.0 or greater, more preferably 8.0 or greater.

The liquid crystal composition according to the invention is very suitable for the preparation of microwave components, such as phase shifters, which can be tuned by applying a magnetic or electric field. These phase shifters can be operated in the UHF range (0.3-1GHz), the L range (1-2GHz), the S range (2-4GHz), the C range (4-8GHz), the X range (8-12GHz), the Ku range (12-18GHz), the K range (18-27GHz), the Ka range (27-40GHz), the V range (50-75GHz), the W range (75-110GHz) and at most 1 THz. The construction of phase shifters according to the present application is known to the expert. Typically a loaded line phase shifter, an inverted microstrip, a fin line (Finline) phase shifter, preferably an Antipodal (Antipodal) fin line phase shifter, a slotted phase shifter, a microstrip line phase shifter or a coplanar waveguide (CPW) phase shifter is used. These components may implement a re-reconfigurable antenna array.

Wherein "%" represents "mass percent", the measurement characteristics in examples are as follows: Δ n: anisotropy of birefringence at 20 ℃ and 589 nm; t is_ni: clearing the bright spots; tm: melting point; gamma ray₁: rotational viscosity at 20 ℃; Δ ε: dielectric anisotropy at 20 ℃, 1KHz and 19 GHz.

Example 1

TABLE 1 example 1 compositions and Properties

Example 2

Table 2 example 2 composition and properties

Example 3

Table 3 example 3 composition and properties

Example 4

Table 4 example 4 composition and properties

Example 5

TABLE 5 example 5 compositions and Properties

Example 6

TABLE 6 example 6 compositions and Properties

Comparative example 1

CN107955630A discloses a liquid crystal composition for high frequency components, the components of which are selected from fluorine substituted isothiocyanato liquid crystal compounds. In example 1 thereof, the following compositions and performance parameters are disclosed:

compared with the comparative example 1, the dielectric loss of the embodiment of the invention is greatly reduced, and the quality factor is multiplied.

Comparative example 2

In patent CN105368465A, example 15 discloses a composition containing fluorine-substituted isothiocyanato liquid crystal compound and its properties such as high frequency dielectric constant:

compared with the comparative example 2, the dielectric loss of the embodiment of the invention is greatly reduced, and the quality factor is multiplied.

Comparative example 3

In patent CN110499163A, example N52 discloses a composition containing fluorine-substituted isothiocyanato liquid crystal compound and its properties such as high frequency dielectric constant:

compared with the comparative example 3, the dielectric loss of the embodiment of the invention is greatly reduced, and the quality factor is greatly increased.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.