Method for fabricating micro-cell structures

#The present disclosure relates to a method for fabricating micro-cell structures, and more particularly to a method for fabricating micro-cell structures performed on a liquid crystal mixture.

#Scattering-type liquid crystal light valves have been quite mature in the last decade or so, which are mainly used in polymer-dispersed liquid crystals (PDLC). PDLE consists of a mixture of polymers and liquid crystals, and the polymers and the liquid crystals are made using a phase separation method. In most cases of the phase separation method, phase separation of the mixture material occurs by emitting an ultraviolet light or by a thermal process, such that the scattering-type liquid crystal light valves are in a scattering state under no applied voltage. In addition, switching between the scattering state and a light-transmitting state can be achieved by applying a voltage, and an applied voltage is needed to apply in this type of scattering-type liquid crystal light valve so as to fix the light-transmitting state of the light valve.

#If a negative-type liquid crystal material (such as, a negative-type cholesteric liquid crystal material) is doped with salt-type ionic material, the degree of consistency or disorder of a cholesteric liquid crystal alignment can be directly controlled by a high voltage or a low voltage without having to unscrew a structure of the cholesteric liquid crystal alignment, such that the cholesteric liquid crystal is switched to a light-transmitting planar structure or a scattering focal conic structure and retains its bistable properties. Compared with PDLC, the cholesteric liquid crystal has a relatively fast switching speed (about several hundred microseconds), a relative small applied voltage, and a relatively high contrast. Further, the cholesteric liquid crystal has a quite good tolerance of materials and surface treatment.

#FIG. 1 illustrates a flowchart of a method of fabricating micro-cell structures according to an embodiment of the present disclosure.

#FIG. 2A illustrates a schematic cross-sectional diagram of the micro-cell structures (where the liquid crystal particles are in a planar structure stable state) disposed between two transparent substrate according to an embodiment of the present disclosure.

#FIG. 2B illustrates a schematic cross-sectional diagram of the micro-cell structures (where the liquid crystal particles are in a focal conic structure stable state) disposed between two transparent substrate according to an embodiment of the present disclosure.

#The structure and the technical means adopted by the present disclosure to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings. Furthermore, directional terms described by the present disclosure, such as upper, lower, front, back, left, right, inner, outer, side, longitudinal/vertical, transverse/horizontal, and etc., are only directions by referring to the accompanying drawings, and thus the used directional terms are used to describe and understand the present disclosure, but the present disclosure is not limited thereto.

#Referring to FIG. 1, a method 10 for fabricating micro-cell structures of an embodiment of the present disclosure mainly includes steps 11 to 14 of: providing a liquid crystal mixture comprising: 15 wt % to 91 wt % of a negative type liquid crystal material; 0.0001 wt % to 5 wt % of a salt ionic material; 3 wt % to 40 wt % of a chiral molecule material; and 5 wt % to 40 wt % of a photocurable adhesive material (step 11); performing a heating step on the liquid crystal mixture at a temperature ranging from 40° C. to 150° C. (step 12); performing a heat induced phase separation step on the liquid crystal mixture at a thermal phase separation temperature for a thermal phase separation time such that the liquid crystal mixture forms a plurality of liquid crystal particles and a network photo-curing adhesive, wherein the thermal phase separation temperature and the thermal phase separation time are determined by a changing rate of a bright area ratio of the liquid crystal mixture (step 13); and performing a photo-curing step on the liquid crystal mixture by emitting an ultraviolet light so that the liquid crystal particles and the network photo-curing adhesive further form a plurality of micro-cell structures (step 14), The implementation details of the above-described steps and the principles thereof will be described in detail below.

#In one embodiment of the present disclosure, the method 10 for fabricating micro-cell structures has step 11 of: providing a liquid crystal mixture comprising: 15 wt % to 91 wt % of a negative type liquid crystal material; 0.0001 wt % to 5 wt % of a salt ionic material; 3 wt % to 40 wt % of a chiral molecule material; and 5 wt % to 40 wt % of a photocurable adhesive material. In step 11, the negative type liquid crystal material, the salt ionic material, the chiral molecule material, and the photocurable adhesive material are provided and mixed to prepare the liquid crystal mixture. In one embodiment, the negative type liquid crystal material is a negative type cholesteric liquid crystal material and has at least two stable states (at least includes a light-transmitting planar structure or a scattering focal conic structure).