Preparation Of Cholesteric Liquid Crystal Based Device And Application Research In Color Regulation

Cholesteric liquid crystal（CLC）has excellent external field responsiveness due to its periodic spiral structure,which can achieve pitch regulation and control under a variety of external field（such as temperature,electric field,and pressure）stimuli,and thus achieve the regulation of the reflected wavelength.At present,researchers have realized the color regulation of liquid crystal devices by using the electric field stimulation responsiveness of CLC texture state or pitch.However,it is mainly applied to reflective display devices,and little research has been done on its application in the fields of reflective protection,visual sensors,and intelligent windows.In this paper,based on the two systems of polymer dispersed cholesteric liquid crystal（PDCLC）and polymer stabilized cholesteric liquid crystal（PSCLC）,two color control devices with multi-color variable and continuous band change were prepared and applied to visual force-sensitive sensors,ultraviolet reflective protective devices and patterned displays,respectively.The specific research contents are as follows:Firstly,the single-color variable devices were prepared by PDCLC system.The color of the devices was changed by the electric field stimulation response of CLC texture.The effects of the content of chiral agent and UV exposure power on the electrical response of the devices were investigated.The results show that the content of chiral agent is in direct proportion to the threshold voltage required for the device to achieve electrochromism.When the exposure power reaches 70%,the polymer network can be formed stably and the electrical response of the device is the best.The multi-color variable device is designed by using three single color-changing devices which are colored as red（R）,green（G）and blue（B）in a 90-degree rotating and stacking structure,and the directional conversion of at least seven colors is realized through the circuit regulating device.Secondly,a multi-band continuously variable device was prepared by using the PSCLC system,and the reflection band was adjusted by using the electric field stimulation response of the CLC pitch.Through the exploration of the experimental formula and preparation process such as monomer content,exposure time,electrode square resistance,and interval scale,it was found that when the monomer concentration was 12% and the exposure time was 4 min,using the conductive glass with square resistance of 200 Ω/□ and the liquid crystal cell with interval size of 10 μm,the polymer network density of the prepared device was the most appropriate,the band change range was the largest,and the performance was the most stable.The initial center wavelength of the device based on the PSCLC system can be changed by adjusting the chiral agent content.Under the above optimal conditions,when the content of chiral agent is 3.14%,the central reflection wavelength of the device can be changed from 453.6 nm to 692.9 nm by applying the DC voltage of 0 ～ 220 V,and the continuous dynamic change of the device color from violet to red is achieved.When the observation angle is within the range of 25 to 70,the reflection peak of the device does not shift significantly,and the electrical response performance is almost unchanged after dozens of reversible cycle tests,showing good viewability and cycle stability.Finally,according to the material characteristics and color change characteristics of the two devices,the application performance in the fields of sensor,protection and display is studied respectively.The device based on the PDCLC system was applied to the pixelated display with independent and controllable single-pixel color,and the preparation of the bionic color-changing device which realizes the high matching between the color and the environment by adjusting the proportion.In addition,the device was used for the visual force-sensitive sensor in combination with the color-changing property of CLC force sensor.A device based on a PSCLC system is applied to a near infrared reflection type temperature adjusting device and an ultraviolet reflection type protective device by adjusting a reflection wave band through a chiral agent,and patterning control of a color developing region of the device is realized through division of electrode regions,so that the device is applied to the field of patterned displays.