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A method for measuring liquid crystal torsional elastic constant

A technology of elastic constants and measurement methods, applied in the direction of measuring devices, instruments, scientific instruments, etc., can solve the problems affecting the capacitance value of the liquid crystal layer, the uncertainty of the threshold voltage, and not considered

Active Publication Date: 2020-06-30
HEBEI UNIV OF TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Although simpler than the previous method, the disclination line will move with the voltage, making the threshold voltage uncertain, which still limits the determination of k 22 the accuracy of
None of the above methods consider the influence of the orientation layer on the upper and lower substrate surfaces of the liquid crystal cell on the measurement results, which will cause the voltage actually applied to the liquid crystal layer to be different from the external measurement voltage, and will also affect the capacitance value of the liquid crystal layer

Method used

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  • A method for measuring liquid crystal torsional elastic constant
  • A method for measuring liquid crystal torsional elastic constant
  • A method for measuring liquid crystal torsional elastic constant

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0105] Embodiment 1 (positive liquid crystal):

[0106] When measuring positive liquid crystals (take liquid crystal E7 as an example), pour liquid crystal E7 into PAN, VAN and TN liquid crystal empty cells through capillary action. Use a precision LCR meter (Keysight E4980A) to measure the C-U characteristic curves of PAN, VAN and TN liquid crystal cells at an applied voltage of 0.2-20V and a frequency of 1KHz when the ambient temperature is 20°C. Such as Figure 8 As shown, under low voltage, the total capacitance C of the PAN liquid crystal cell = 0.869nf, and the capacitance C of the liquid crystal layer of the PAN liquid crystal cell is obtained LC-PAN =0.906nf. Such as Figure 9 As shown, the total capacitance C of the VAN liquid crystal cell is 3.196nf, and the capacitance C of the liquid crystal layer of the VAN liquid crystal cell is obtained LC-VAN = 3.34nf. Then the liquid crystal vertical permittivity ε ⊥ =5.015 and parallel permittivity ε / / =18.509. Then ...

Embodiment 2

[0109] Embodiment 2 (negative liquid crystal):

[0110] When measuring negative liquid crystals (take the liquid crystal 81H82300-100 as an example), pour the liquid crystal 81H82300-100 into VAN, PAN and IPS liquid crystal empty cells through capillary action, and the liquid crystal molecule director in the IPS liquid crystal empty cell is on the glass substrate. The included angle between the projection and the IPS electrode period direction is 45°, and the plane of the second ITO electrode layer in the IPS liquid crystal cell includes two coplanar electrodes, and the two coplanar electrodes are not connected to each other; the first alignment layer pair The orientation of the director of the liquid crystal molecules near the alignment layer is a vertical direction, and the angle between the first glass substrate and the first glass substrate in the vertical direction is 89°; The angle between the two glass substrates is 1°. Use a precision LCR meter to measure the C-U char...

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Abstract

The invention relates to a method for measuring a twist elastic constant of liquid crystals. Liquid crystal hollow cells used in the method comprise a PAN (parallel-aligned nematic) liquid crystal hollow cell, a VAN (vertical-aligned nematic) liquid crystal hollow cell, a TN (twisted nematic) liquid crystal hollow cell and an IPS (in-plane switching) liquid crystal hollow cell. The PAN liquid crystal hollow cell, the VAN liquid crystal hollow cell and the TN liquid crystal hollow cell are used when the method is used for measuring a positive liquid crystal material; the PAN liquid crystal hollow cell, the VAN liquid crystal hollow cell and the IPS liquid crystal hollow cell are used when the method is used for measuring a negative liquid crystal material; corresponding capacitance of the liquid crystal cells under different voltages is measured with a C-U method, and in consideration of influence of a PI (polyimide) orientation layer on capacitance of the liquid crystal cells, the parallel dielectric constant epsilon / / , the vertical dielectric constant epsilon perpendicular, the splay elastic constant k11, the bend elastic constant k33 and the twist elastic constant k22 of a to-be-measured nematic liquid crystal material can be obtained precisely.

Description

Technical field: [0001] The invention designs a method for measuring the twisted elastic constant of liquid crystals, which can measure the elastic constants of various positive and negative nematic liquid crystals, and is suitable for measuring the twisted elastic constants of liquid crystals by relevant universities or enterprises. Background technique: [0002] The elastic constant is one of the important physical parameters of the liquid crystal material, which directly affects the important electro-optic effect parameters such as the response time, duty cycle, and threshold voltage of the liquid crystal display device. For nematic liquid crystals, the arrangement of liquid crystal molecular directors has three independent deformations: splay, twist and bend, corresponding to the splay elastic constant k 11 , torsional elastic constant k 22 and the bending elastic constant k 33 . for k 11 and k 33 At present, there are relatively simple methods such as numerical sim...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N27/00
Inventor 叶文江袁瑞李振杰孙婷婷邢红玉朱吉亮
Owner HEBEI UNIV OF TECH