TW201936258A - Method for fabricating micro-cell structures - Google Patents

Abstract

A method for fabricating micro-cell structures is provided and includes steps of: providing a liquid crystal mixture; performing a heating step on the liquid crystal mixture at a temperature ranging from 75 DEG C to 110 DEG C; 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 light-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; and performing a light curing step on the liquid crystal mixture by emitting an ultraviolet light so that the liquid crystal particles and the network light-curing adhesive further form a plurality of micro-cell structures.

Description

Method for manufacturing microcellular structure

The present invention relates to a method for producing a microcellular structure, and more particularly to a method for producing a microcellular structure for treating a liquid crystal mixture.

The scattering type liquid crystal light valve has been quite mature in the past ten years. The most important application product is Polymer-Dispersed Liquid Crystal (PDLC), which is polymer and liquid crystal. The mixture is composed of phase separation, and most of the processes are by using ultraviolet light or using a thermal effect to cause phase separation of the mixed material, thereby obtaining a scattering type liquid crystal light valve which is in a scattering state without an applied voltage. The switching between the scattering state and the penetrating state is obtained by applying a voltage, and this type of scattering type liquid crystal light valve needs to continuously apply a voltage to fix the transmittance of the light valve.

If a negative-type liquid crystal material doped with a salt-based ionic material (for example, a negative-type cholesteric liquid crystal material) is used, the uniformity and chaos of the cholesteric liquid crystal arrangement can be directly controlled by high and low-frequency voltages without going through the unwinding structure. The cholesteric liquid crystal is switched to a light-transmitting planar planar structure or a scattered focal-conic structure, and retains its bistable characteristics. Since the driving principle is direct switching between structures, the material switching speed is fast (about several hundred microseconds), the voltage is small, the contrast is relatively high, the molecular dispersion liquid crystal is high, and the material and surface treatment are high. The tolerance is quite good.

Therefore, 遂 began to have researchers trying to apply the above technology to smart windows. By applying different voltages to the cholesteric liquid crystal to form transparent planar planar textures or scattered focal-conic textures, the smart window can produce light transmission (corresponding to a planar spiral structure) )or The effect of opacity (corresponding to the focal cone structure). However, no researchers have yet developed suitable production methods to commercialize smart windows.

Therefore, it is necessary to provide a manufacturing method of the microcellular structure to solve the problems of the conventional technology.

An object of the present invention is to provide a method for fabricating a microcellular structure, which determines a thermal phase separation temperature and a thermal phase separation time of a thermally induced phase separation step according to a ratio of a bright region ratio change of the liquid crystal mixture, so as to facilitate It is required to produce a microcellular structure with different transmittances, which can be applied to smart windows.

Another object of the present invention is to provide a method for manufacturing a microcellular structure, which is a light-cured mesh-like photocurable adhesive as a support material between a first transparent substrate and a second transparent substrate, thereby A plurality of microcellular structures may be disposed on the first transparent substrate and the second transparent substrate.

To achieve the above various objects, the present invention provides a method for producing a microcellular structure comprising the steps of: providing a liquid crystal mixture comprising: 15% by weight to 91% by weight of a negative liquid crystal material; 0.0001% by weight to 5% by weight of a salt An ionic material; 3 wt% to 40 wt% of a chiral molecular material; and 5 wt% to 40 wt% of a photocurable material; performing a heating step, heating the liquid crystal mixture to between 40 and 150 degrees Celsius; Performing a heat-induced phase separation step, holding the liquid crystal mixture at a thermal phase separation temperature for a thermal phase separation time, so that the liquid crystal mixture forms a plurality of liquid crystal particles and a reticulated photocurable gel, wherein the thermal phase is separated The temperature and the thermal phase separation time are determined according to a change ratio of a bright region ratio of the liquid crystal mixture; and a photocuring step is performed, and the liquid crystal mixture is irradiated with an ultraviolet light to make the liquid crystal particles and the reticulated light curing adhesive A plurality of microcellular structures are further formed.

In one embodiment of the invention, a bright region ratio of the liquid crystal mixture is proportional to a ratio of a portion of the liquid crystal particles distributed in the liquid crystal mixture.

In an embodiment of the invention, the brightness ratio change ratio is a rate of change of the bright area ratio of the liquid crystal mixture as a function of per unit time.

In one embodiment of the invention, the rate of change of the bright area ratio varies from -1% to +1% per second.

In an embodiment of the invention, the negative liquid crystal material comprises at least one of negative liquid crystals MLC 2081, MLC 2078, ZLI-2806, and ZLI 2293.

In an embodiment of the invention, the salt ion material comprises at least one of the salt ions TBATFB, R6G, NaCl, KNO ₃ and CaSO ₄ .

In an embodiment of the invention, the chiral molecular material comprises at least one of chiral molecules S811, R811, S1011, R1011, S5011, and R5011.

In an embodiment of the invention, the photocurable adhesive material comprises at least one of photocurable adhesives NOA63, NOA65, NOA73, and NOA81.

In an embodiment of the invention, after the heating step, a setting step is further included to dispose the heated liquid crystal mixture between a first transparent substrate and a second transparent substrate.

In an embodiment of the invention, the photocuring step is performed with the ultraviolet light having an intensity of 0.1 to 100 mW/cm ² for 0.1 to 20 minutes.

10‧‧‧ method

11~14‧‧‧Steps

20‧‧‧Smart windows

21‧‧‧Microcellular structure

22‧‧‧First transparent substrate

23‧‧‧Second transparent substrate

211‧‧‧ liquid crystal particles

211A‧‧‧Negative liquid crystal material

211B‧‧‧ Salt ionic materials

211C‧‧‧Chiral Molecular Materials

212‧‧‧Net light curing adhesive

Fig. 1 is a flow block diagram showing a method of manufacturing a microcellular structure according to an embodiment of the present invention.

2A is a schematic cross-sectional view showing a microcellular structure (the liquid crystal particles are in a steady state of a planar spiral structure) disposed between two light-transmissive substrates according to an embodiment of the present invention.

FIG. 2B is a schematic cross-sectional view showing the microcellular structure 21 (the liquid crystal particles are in a steady state of the focal conic structure) disposed between the two transparent substrates according to an embodiment of the present invention.

Fig. 3 is a graph showing the relationship between the ratio of the bright regions and the liquid crystal particle size with respect to the thermal phase separation time in the case of using the thermal phase separation temperature of 10 °C.

Figures 4A to 4F: Electron microscopy with different thermal phase separation times (0 seconds, 37 seconds, 55 seconds, 120 seconds, 170 seconds, and 195 seconds) using a thermal phase separation temperature of 10 °C photo.

Figures 5A to 5F: using a hot phase separation temperature of 15 ° C and a thermal phase of 55 seconds In the case of the separation time, there are electron micrographs of the ratios of the different photocurable gel materials (15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, and 40 wt%, respectively).

Fig. 6 is a graph showing experimental data of the transmittance of the microcellular structure of the embodiment switched between bistable states. .

The above and other objects, features and advantages of the present invention will become more <RTIgt; Furthermore, the directional terms mentioned in the present invention, such as upper, lower, top, bottom, front, rear, left, right, inner, outer, side, surrounding, central, horizontal, horizontal, vertical, longitudinal, axial, Radial, uppermost or lowermost, etc., only refer to the direction of the additional schema. Therefore, the directional terminology used is for the purpose of illustration and understanding of the invention.

Referring to FIG. 1, a manufacturing method 10 for a microcellular structure according to an embodiment of the present invention mainly comprises the following steps 11 to 14: providing a liquid crystal mixture comprising: 15 wt% to 91 wt% of a negative liquid crystal material; 0.0001 wt. % to 5 wt% of a salt-based ionic material; 3 wt% to 40 wt% of a chiral molecular material; and 5 wt% to 40 wt% of a photocurable adhesive material (Step 11); performing a heating step to heat the liquid crystal mixture Between 40 degrees Celsius and 150 degrees Celsius (step 12); performing a heat-induced phase separation step, holding the liquid crystal mixture at a thermal phase separation temperature for a thermal phase separation time to form the liquid crystal mixture into a plurality of Liquid crystal particles and a reticulated light-curing adhesive, wherein the thermal phase separation temperature and the thermal phase separation time are determined according to a ratio of change of a bright region ratio of the liquid crystal mixture (step 13); and a photocuring step is performed to the liquid crystal The mixture is irradiated with an ultraviolet light to further form a plurality of microcellular structures with the liquid crystal particles and the reticulated gel (step 14). The details of the implementation of the above-described steps of an embodiment and the principles thereof will be described in detail below.

Referring to FIG. 1, a method 10 for fabricating a microcellular structure according to a first embodiment of the present invention is first performed in a step 11 of providing a liquid crystal mixture comprising: 15 wt% to 91 wt% of a negative liquid crystal material; 0.0001 wt% to 5wt% of a salt ion 3 wt% to 40 wt% of a chiral molecular material; and 5 wt% to 40 wt% of a photocurable adhesive material. In this step 11, the above negative liquid crystal material, salt ion material, chiral molecular material and photocurable rubber material are provided and mixed to prepare the liquid crystal mixture. In one embodiment, the negative liquid crystal material is a negative cholesteric liquid crystal material having at least two steady states (at least a light-transmitting planar planar structure and a focal-conic structure that is scattered) .

In one embodiment, the negative liquid crystal material comprises, for example, a negative liquid crystal MLC2081 (available from Merck), MLC 2078 (available from Merck), and ZLI-2806 (by Merck ( At least one of Merck) and ZLI2293 (available from Merck).

In one embodiment, the salt ion material comprises at least one of a salt ion TBATFB (tetrabutyltetrafluoroborate), R6G, NaCl, KNO ₃ and CaSO ₄ , wherein the molecular formula of R6G is as follows.

R6G:

In one embodiment, the chiral molecular material comprises at least one of chiral molecules S811, R811, S1011, R1011, S5011, and R5011, the molecular formula is as follows:

S811:

R811:

S1011:

R1011:

R5011/S5011 (R5011 and S5011 are symmetric with each other, so they are only represented by one structure):

In one embodiment, the photocurable adhesive material comprises photocurable adhesive NOA63 (available from Norland Products, Inc.), NOA65 (available from Norland Products), NOA73 (available from NO. At least one of Norland Products (available from Norland Products) and NOA 81 (available from Norland Products).

Continuingly, the method 10 for fabricating a microcellular structure according to an embodiment of the present invention is followed by step 12: performing a heating step of heating the liquid crystal mixture between 40 and 150 degrees Celsius. In this step 12, the liquid crystal mixture can be heated to about 90 degrees Celsius to facilitate subsequent heat-induced phase separation steps.

A method for fabricating a microcellular structure according to an embodiment of the present invention is followed by a step 13 of performing a thermal phase separation step, holding the liquid crystal mixture at a thermal phase separation temperature for a thermal phase separation time to cause the liquid crystal mixture Forming a plurality of liquid crystal particles and a reticulated light-curing gel, wherein the thermal phase separation temperature and the thermal phase separation time are determined according to a ratio of a bright region ratio change of the liquid crystal mixture. In this step 13, the thermal phase separation temperature and the thermal phase separation time of the liquid crystal mixture will vary depending on the material selected for the liquid crystal mixture. On the other hand, even if the same material is used, if different thermal phase separation temperatures are used, the required thermal phase separation time will be affected. Detailed experimental data will be described in the following paragraphs.

The method 10 for manufacturing a microcellular structure according to an embodiment of the present invention is finally a step 14 of performing a photocuring step, and irradiating the liquid crystal mixture with ultraviolet light to further form the plurality of liquid crystal particles and the network photocurable adhesive. Microcellular structure. In this step 14, for example, the photocuring step is performed by irradiating the ultraviolet light with an intensity of 0.1 to 100 mW/cm ² for 0.1 to 20 minutes, and the main purpose is to cause the reticulated photocurable adhesive to have a curing effect, thereby serving as the micro-curing effect. The support structure of the cystic structure. The foregoing support structure can be used to support two transparent substrates (ie, the first transparent substrate and the second transparent substrate) of the smart window. On the other hand, since the liquid crystal particles in the microcellular structure are pinned by the mesh-shaped light-curing adhesive, a large-sized smart window can be pre-made, and then cut into small-sized smart windows according to user requirements. Without causing the microcellular structures to leak out of the cut.

Referring to Figures 1, 2A and 2B together, FIG. 2A is a schematic cross-sectional view showing the microcellular structure 21 (the liquid crystal particles are in a steady state of the planar spiral structure) disposed between the two transparent substrates according to an embodiment of the present invention. And FIG. 2B is a schematic view showing a microcellular structure 21 (the liquid crystal particles are in a steady state of the focal conic structure) disposed between the two transparent substrates according to an embodiment of the present invention. In an embodiment, the heating step further comprises a setting step of disposing the heated liquid crystal mixture between a first transparent substrate 22 and a second transparent substrate 23. In other words, when the manufacturing method 10 of the microcellular structure of the present invention is applied to the production of a smart window 20, the liquid crystal mixture can be disposed between the two light-transmissive substrates after the heating step, and then the micro-cellization can be completed through the subsequent steps. The structure 21 includes the liquid crystal particles 211 and the network curing adhesive 212, wherein each liquid crystal particle 211 comprises a negative liquid crystal material 211A, a salt ion material 211B and a chiral molecular material 211C, which can be applied with different voltages. To switch the steady state in the microcellular structure, thereby changing the degree of light transmission of the smart window.

Hereinafter, how the method for producing the microcellular structure of the present invention determines the thermal phase separation temperature and the thermal phase separation time of the heat-induced phase separation step according to the rate of change of the bright region ratio of the liquid crystal mixture. First, it should be noted that the microcellular structures are mainly composed of two parts, and the liquid crystal particles and the cured network curing adhesive are contained. In general, by providing different voltages and the liquid crystal particles, the liquid crystal particles are switched between a light-transmitting planar planar structure or a scattered focal-conic structure, thereby Light passes through the liquid crystal particles or blocks the light from being blocked by the liquid crystal particles. The cured web-like light-curing gel is a structure for supporting the whole, which is substantially opaque. It can be seen from the above that if the regions or proportions of the liquid crystal particles in the microcellular structure are larger, the liquid crystal particles form a steady state of the light-transmitting planar spiral structure, and have a larger ratio of bright regions (because they are transparent) The larger the light area is, the brighter or clearer the overall appearance is, that is, the relationship is roughly proportional); on the contrary, if the area or proportion of the network light-curing adhesive in the microcellular structure is larger, although it may have a larger The supporting effect, but when the liquid crystal particles form a steady state of the light-transmitting planar spiral structure, the smaller the bright area ratio (since the smaller the light-permeable area, the darker or more blurred the overall appearance).

In the method for fabricating a microcellular structure according to an embodiment of the present invention, in order to make the microcellular structures have a support structure sufficient to support the substrate, the rate of change of the bright region ratio of the liquid crystal mixture is used to determine the heat-induced phase separation step. Parameters. Please refer to Fig. 3 and Figs. 4A to 4F. Fig. 3 is a graph showing the relationship between the ratio of bright areas and the liquid crystal particle size with respect to the thermal phase separation time when the temperature is separated by 10 °C; 4A to 4F In the case of using a hot phase separation temperature of 10 ° C, electron micrographs at different thermal phase separation times (in the order of 0 seconds, 37 seconds, 55 seconds, 120 seconds, 170 seconds, and 195 seconds). As can be seen from Fig. 3 and Figs. 4A to 4F, the bright area ratio has a large growth ratio before about 55 seconds, mainly because the liquid crystal mixture has a remarkable phase separation effect during this period. However, after 55 seconds, the ratio of the bright areas did not change significantly, but it can be seen from the 4D to 4F graph that the liquid crystal particles began to aggregate into larger liquid crystal particles, which adversely affected the support effect of the network light curing adhesive. influences. Therefore, when the phase separation is about to be completed or just completed (for example, about 55 seconds in this embodiment), the ratio of the liquid crystal particles to the curing adhesive is not large, so that the retaining wall is not made small by photocuring. From this, it can be seen that, when the heat-induced phase separation step is performed, the thermal phase separation temperature and the thermal phase separation time can be determined according to the rate of change of the brightness ratio of the bright region to obtain a microcellular structure having a high support effect and a ratio of highlight regions. For example, in this embodiment, for example, the brightness ratio change rate of the bright area may be designed as a ratio of change of the bright area ratio of the liquid crystal mixture with each unit time, such as when the brightness ratio change rate reaches every second. When the system changes by -1% to +1%, the thermal phase separation temperature corresponding to the state and the thermal phase separation time are set as parameters used in the heat-induced phase separation step.

It is worth mentioning that, according to the user's needs, for example, when the user wants to obtain the microcellular structure with a low proportion of bright areas, the heat-induced phase separation step may also be determined according to a change ratio of a bright area ratio of the liquid crystal mixture. The parameters used. Referring to Figure 3, for example, using a thermal phase separation temperature of 10 ° C and a thermal phase separation time of about 37 seconds, the microcellular structures having a lower ratio of bright regions can be obtained. In addition, the microcellular structure having a low proportion of bright regions can also have the advantage of higher support strength.

In addition, the manufacturing method 10 of the microcellular structure of the embodiment of the present invention is also The thickness of the reticulated gel can be controlled by adjusting the proportion of the photocurable material. Please refer to Figures 5A to 5F. Figures 5A to 5F are the ratios of different photocurable adhesive materials in the case of using a thermal phase separation temperature of 15 ° C and a thermal phase separation time of 55 seconds (in order of 15 wt%). , electron micrographs of 20 wt%, 25 wt%, 30 wt%, 35 wt% and 40 wt%). As can be seen from the 5A to 5F drawings, when the proportion of the photocurable adhesive material is larger, the thickness of the reticulated light-curable adhesive (the black region in the 5A to 5F drawings) is larger. When the thickness of the reticulated gel is larger, the proportion of a bright region of the liquid crystal mixture also decreases. It can be seen that, in addition to determining the thermal phase separation temperature and the thermal phase separation time through a ratio of the bright region ratio change of the liquid crystal mixture, the bright regions of the microcellular structures can also be adjusted by the ratio of the photocurable adhesive material. proportion.

In one embodiment, the thermal phase separation temperature is, for example, between 10 and 25 ° C, such as 11 ° C, 12 ° C, 13 ° C, 15 ° C, 17 ° C, 19 ° C, 21 ° C, 23 ° C or 24 °C. In another embodiment, the thermal phase separation time is, for example, between 40 and 75 seconds, such as 42 seconds, 45 seconds, 48 seconds, 52 seconds, 56 seconds, 60 seconds, 64 seconds, 67 seconds, 70 seconds or 72 seconds.

An example is given below to demonstrate that the microcellular structure produced by the method for producing a microcellular structure of the present invention does have the above-described effects.

First, a liquid crystal mixture comprising 62.3 wt% of negative liquid crystal MLC 2081, 1 wt% of a salt ion TBATFB, 16.7 wt% of a chiral molecule R811, and 20 wt% of a photocurable adhesive NOA65 was provided. The liquid crystal mixture is then heated to 110 ° C, at which time the liquid crystal mixture is in an isotropy state. Next, the liquid crystal mixture at 110 ° C was injected into the sample cell, and the temperature was lowered to 15 degrees for 50 seconds. Finally, irradiating 5 (mW/cm ² ) of ultraviolet light (band about 365 nm) for 15 minutes, the particle size can be made between 50 and 100 microns, and the thickness of the reticulated gel is only 0.1. Microcytochemical structures of the examples between 10 microns.

Next, a voltage test was performed on the above-described microcellular structure. Please refer to Fig. 6. Fig. 6 is a graph showing experimental data of the transmittance of the microcytization structure switched between the bistable states of the embodiment. When the AC voltage of 60 Hz is applied at 60 volts, the microcellular structure of the embodiment can be switched to the scattering state, and can be in focus after releasing the voltage. Steady state of a cone-conic structure. When the AC voltage of 6 kHz is applied at 120 volts, the microcellular structure of the embodiment can be switched to a light transmitting state and can be in a steady state of a planar planar structure after the voltage is released.

The present invention has been disclosed in its preferred embodiments, and is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application.

Claims (10)

A method for producing a microcellular structure, comprising the steps of: providing a liquid crystal mixture comprising: 15 wt% to 91 wt% of a negative liquid crystal material; 0.0001 wt% to 5 wt% of a salt ion material; and 3 wt% to 40 wt% a chiral molecular material; and 5 wt% to 40 wt% of a photocurable material; performing a heating step, heating the liquid crystal mixture to between 40 and 150 degrees Celsius; performing a heat-induced phase separation step, The liquid crystal mixture is maintained at a thermal phase separation temperature for a thermal phase separation time to form the liquid crystal mixture to form a plurality of liquid crystal particles and a reticulated photocurable gel, wherein the thermal phase separation temperature and the thermal phase separation time are A ratio of change in the brightness ratio of the liquid crystal mixture is determined; and a photocuring step is performed, and the liquid crystal mixture is irradiated with an ultraviolet light to further form the plurality of microcellular structures with the liquid crystal particles and the reticulated light curable gel. The method for producing a microcellular structure according to claim 1, wherein a ratio of a bright region of the liquid crystal mixture is proportional to a ratio of a portion of the liquid crystal particles distributed in the liquid crystal mixture. The method for producing a microcellular structure according to claim 2, wherein the brightness ratio change ratio is a rate of change of the bright area ratio of the liquid crystal mixture as a function of per unit time. The method for producing a microcellular structure according to claim 3, wherein the rate of change of the bright area ratio varies by -1% to +1% with the passage per second. The method for producing a microcellular structure according to claim 1, wherein The negative liquid crystal material includes at least one of negative liquid crystals MLC 2081, MLC 2078, ZLI-2806, and ZLI 2293. The method for producing a microcellular structure according to claim 1, wherein the salt ion material comprises at least one of salt ions TBATFB, R6G, NaCl, KNO ₃ and CaSO ₄ . The method for producing a microcellular structure according to the first aspect of the invention, wherein the chiral molecular material comprises at least one of chiral molecules S811, R811, S1011, R1011, S5011 and R5011. The method for producing a microcellular structure according to claim 1, wherein the photocurable adhesive material comprises at least one of photocurable adhesives NOA63, NOA65, NOA73, and NOA81. The method for manufacturing a microcellular structure according to claim 1, wherein the heating step further comprises a setting step of disposing the heated liquid crystal mixture on a first transparent substrate and a second transparent substrate. Between light substrates. The method for producing a microcellular structure according to claim 1, wherein the photocuring step is performed by irradiating the ultraviolet light with an intensity of 0.1 to 100 mW/cm ² for 0.1 to 20 minutes.