CN102615894B - Flexible liquid crystal thin film and preparation method thereof - Google Patents

Abstract

The invention discloses a flexible liquid crystal film and a preparation method thereof, belonging to the technical field of liquid crystals. The flexible liquid crystal film is divided into five layers, wherein the bottom layer is a black light-absorbing coating, and above the black light-absorbing coating are a lower transparent electrode layer, an interface layer, a liquid crystal layer, and an upper transparent electrode layer. The preparation process includes: preparation of an upper transparent electrode layer with a display pattern, preparation of an interface layer, preparation of a liquid crystal box, liquid crystal pouring and preparation of a liquid crystal film. The invention has the advantages of simple preparation process and is suitable for large-area display applications. The prepared flexible liquid crystal film realizes the bistable control of the cholesteric liquid crystal by means of interface stabilization, and reduces the control voltage, the color of the film is full, and the conductive electrode is processed by etching technology, and the flexible character liquid crystal film is completed. preparation.

Description

A kind of flexible liquid crystal film and preparation method thereof

technical field

The invention relates to a flexible liquid crystal film and a preparation method thereof, belonging to the technical field of liquid crystals.

Background technique

Due to its lightness, thinness, flexibility and impact resistance, flexible display devices are especially suitable for mobile phones, personal digital assistants (PDAs), notebook computers, e-books, electronic posters, car dashboards, RF identification systems, sensors, etc. . Utilizing the flexible and bendable characteristics makes the engineering design not limited to planarization, and can realize diversified appearance display modes. At present, there are several ways to realize flexible display, such as organic electroluminescent display, electrophoretic display, and liquid crystal display. Among them, the reflective cholesteric liquid crystal display adopts Bragg selective reflection and bistable characteristics of cholesteric liquid crystal, which makes it have the advantages of low power consumption, long image storage time under zero electric field and no need for backlight. Compared with several other methods, the reflective cholesteric liquid crystal display is a passive display, which is more in line with the requirements of future substitutes for paper books and newspapers. Although the Bragg selective reflection characteristics of cholesteric liquid crystals were discovered very early, it was not until Yang et al. at the University of Kent discovered that adding a small amount of polymer to cholesteric liquid crystals, under the stabilizing effect of the polymer network, can realize P state and FC The zero-field stability characteristics of the state, this is the discovery of the bistable characteristics of cholesteric liquid crystals.

At present, the flexible cholesteric liquid crystal film is composed of liquid crystal dispersed in the polymer, using the principle of polymer phase separation or microcapsule emulsification, using inkjet or screen printing technology to coat and control the thickness of the film at the same time, the film is dried and then coated. The device was prepared. Among them, it is difficult to control the particle size of microcapsules uniformly during the preparation of microcapsules; the emulsion made is not stable enough; the printing and coating operation process is complicated, and the film thickness is not easy to control; and the preparation process also involves processes such as solvent volatilization and drying. Time-consuming.

Contents of the invention

The object of the present invention is to provide a flexible liquid crystal film and a preparation method thereof. The flexible liquid crystal film stabilizes the surface of the liquid crystal through an interface stabilizing layer to realize the bistable control of the cholesteric liquid crystal, and the control voltage is low and the color is full , for preparing flexible display devices for characters and pictures. The preparation method has a simple process and is suitable for large-area display applications.

The present invention is achieved through the following technical scheme, a flexible liquid crystal film, characterized in that the flexible liquid crystal film is divided into five layers, wherein the bottom layer is a black light-absorbing coating, and the black light-absorbing coating is sequentially formed on top of the black light-absorbing coating It is the lower transparent electrode layer, the interface layer, the liquid crystal layer, and the upper transparent electrode layer. The thickness of the black light-absorbing coating is 0.1-2mm, and the visible light reflectance is below 5%. It consists of the following components and mass percentages: : 10-60% black light-absorbing substance, 90-40% binder, and the sum of the mass percentages of the above-mentioned components is 100%; the lower transparent electrode layer has a surface sheet resistance lower than 5000 , Indium tin oxide polyethylene terephthalate conductive (ITO-PET) film, indium tin oxide polyethylene conductive (ITO-PE) film with visible light transmittance above 80%, indium fluorine oxide polyethylene terephthalate Ethylene glycol formate conductive (FTO-PET) film, fluorine indium oxide polyethylene conductive (FTO-PE) film, nano-silver polyethylene terephthalate conductive film or nano-silver polyethylene conductive film; The interface layer has a thickness of 0.1-3 , consists of the following components and mass percentages: polymer 5-35%, acrylate monomer 0-15%, the rest is solvent, and the sum of the mass percentages of the above-mentioned components is 100%; The liquid crystal layer thickness described is 3-10 , is composed of commercialized cholesteric liquid crystals; spacers are also distributed in the interface layer and the liquid crystal layer, the content of the spacers is 1%-5% of the mass of the interface layer solution, and the spacers have a particle size of 3 -10 TiO ₂ or SiO ₂ spherical particles; the material of the upper transparent electrode layer is the same as the material of the lower transparent electrode layer, one material at the same time, or two different materials at the same time.

The above-mentioned black light-absorbing substance is carbon black, black organic pigment or black organic dye; the adhesive is commercial acrylic resin, phenolic resin, epoxy resin or silicone resin; the polymer in the above-mentioned interface layer is UV-curable adhesive NOA65, UV curing adhesive NOA10, UV curing adhesive CBU226, polyvinyl alcohol, polyvinyl formal or polyvinyl butyral; acrylate monomers are methyl acrylate, methyl methacrylate, methyl One or both of hydroxyethyl acrylate and butyl methacrylate; the solvent is methyl ethyl ketone, acetone or cyclohexanone; the commercialized cholesteric liquid crystal is that the pitch does not vary with temperature between 0-50°C Cholesteric liquid crystal with variable Bragg reflection wavelength between 380-660nm.

The preparation method of above-mentioned flexible liquid crystal film is characterized in that comprising following process:

1) Preparation of the upper transparent electrode layer with a display pattern: the polyester film or polyethylene film black sheet coated with black paint is used to hollow out the characters or patterns to be displayed as a mask, and the flexible film electrode is processed by photolithography technology. The conductive layer on the surface is etched to prepare an upper transparent electrode layer without a conductive layer where characters or graphics are expected to be displayed;

2) Preparation of the interface layer: dissolve the polymer component and the acrylate monomer component of the interface layer in an appropriate solvent such as water, acetone, methyl ethyl ketone or cyclohexanone to form a uniform layer with a mass fraction of 20%-60%. solution, stir and disperse _SiO2 or _TiO2 spacers with uniform particle size into the solution to form a coating solution with a mass fraction of 1%-5%; use a lead screw to evenly coat the coating solution on the lower transparent electrode layer conductive surface, and then place it under a UV lamp for radiation curing;

3) Preparation of the liquid crystal cell: put the interface layer of the lower transparent electrode layer distributed with spacers upward, and press the conductive surface of the upper transparent electrode layer with the display pattern down on the lower transparent electrode layer, and then use epoxy resin glue, silicone resin Adhesive or polyacrylic acid glue is used as a sealant to seal the edge, leaving two opposite ports for subsequent liquid crystal pouring, and finally cured in an oven at 50-80°C to obtain a liquid crystal cell;

4) Liquid crystal perfusion: Use one port reserved for the liquid crystal box to evacuate, use the other port reserved for the liquid crystal box to perfuse the liquid crystal, absorb the cholesteric liquid crystal according to the dosage of 1-3g/ ^dm2 , and use it under vacuum The needle pours the liquid crystal into the liquid crystal cell, and acts on the outside of the liquid crystal cell with a pressure of 1-10MPa to assist in pouring the liquid crystal evenly, and then glues and solidifies the two ports of the liquid crystal cell with sealant;

5) Preparation of liquid crystal film: Coat a layer of black light-absorbing coating on the transparent electrode layer under the liquid crystal cell poured in step 4), and finally use conductive silver glue to draw electrodes from the two conductive electrodes respectively to obtain a flexible liquid crystal film.

The advantage of the present invention is that the liquid crystal injection method is used to realize the preparation of the flexible liquid crystal film, which avoids the processes of liquid crystal wrapping, drying and coating in the polymer phase separation method or the microcapsule emulsification method, and the preparation process is simple, and is suitable for large-area display application. The prepared flexible liquid crystal film realizes the bistable control of the cholesteric liquid crystal by means of interface stabilization, and reduces the control voltage, the color of the film is full, and the conductive electrode is processed by etching technology, and the flexible character liquid crystal film is completed. preparation.

Description of drawings

Fig. 1 is a schematic structural diagram of a flexible liquid crystal film prepared by Example 1 of the present invention.

In the figure: 1 is a black coating, 2 is a lower transparent electrode layer, 3 is an interface layer, 4 is an upper transparent electrode layer, 5 is a liquid crystal layer, 6 is a spacer, and 7 is a wire.

Fig. 2 is a photo of the P state of the flexible liquid crystal film prepared in Fig. 1 .

Fig. 3 is a photograph of the FC state of the flexible liquid crystal film prepared in Fig. 1 .

Detailed ways

The cholesteric liquid crystal commodity model that the embodiment of the present invention adopts: BN1-12B-460-4; BN1-12B-550-4; BN1-12B-640-4, all by Shijiazhuang Chengzhi Yonghua Display Materials Co., Ltd. supply.

Example 1:

The square resistance of 5×10cm ² is 200 Spin-coating a layer of 15 on the ITO-PET film The thick positive photoresist is exposed for more than 15 minutes by using a UV curing instrument with a wavelength of 220nm and a radiation intensity of 1200μw/ ^cm2 through a mask plate, so that the photoresist in the exposed part is polymerized. Wash off the polymerized photoresist with a developer, and clean it with deionized water. Put the conductive film into an etching solution that is uniformly mixed with 10ml of concentrated hydrochloric acid with a concentration of 37% and 10ml of deionized water, rinse the residual hydrochloric acid with deionized water, and corrode the ITO without photoresist protection, and obtain An upper transparent electrode layer with a display pattern.

The 0.1g particle size is 3 The SiO ₂ spacer was added to 4.9g of UV-curable NOA65 solution, and stirred for 20min under mechanical stirring at a speed of 500rmp to obtain a coating solution with a mass fraction of the spacer of 2%; the reuse specification was 3 The lead screw is used to evenly coat the coating solution on the conductive surface of the lower transparent electrode layer, and then place it under an ultraviolet lamp for radiation curing to obtain an interface layer.

Put the side of the lower transparent electrode layer with spacers facing up, and the conductive side of the upper transparent electrode layer is laminated on the lower transparent electrode layer, and then glue the opposite sides with epoxy resin, and finally cure at 50 ° C, that is Get the LCD box.

Use a needle to absorb 1g of cholesteric liquid crystal, pour it into the liquid crystal cell, and then pour the liquid crystal evenly in the liquid crystal cell under vacuum with a pressure of 1MPa, and then bond and cure the other two sides of the liquid crystal cell with epoxy resin , and then coat a layer of black coating on the non-conductive surface of the lower transparent electrode layer, and finally use conductive silver glue to draw electrodes from the two conductive electrodes respectively to obtain a flexible liquid crystal thin film device.

Example 2:

The difference from Example 1 is: using 800 ITO-PET film, the particle size of 0.1g is 6 The SiO ₂ spacer is added to 3.2g of UV-curable CBU226 solution to obtain a coating solution with a spacer mass fraction of 3%; the reuse specification is 6 The lead screw is coated, the liquid crystal cell is solidified at 60° C., and the liquid crystal cell is uniformly perfused with liquid crystal under vacuum with a pressure of 3 MPa; the others are the same as in Example 1.

Example 3:

The difference with embodiment 1 is: use 1500 ITO-PET film, the particle size of 0.1g is 10 The SiO ₂ spacer was added to 2.4g of UV-curable CBU226 solution to obtain a coating solution with a mass fraction of 4% of the spacer; the reuse specification was 10 The lead screw is coated, the liquid crystal cell is cured at 70° C., and the liquid crystal cell is uniformly perfused with a pressure of 6 MPa under vacuum; the others are the same as in Example 1.

Example 4:

The difference with embodiment 1 is: using 2000 ITO-PET film, the particle size of 0.1g is 6 The SiO ₂ spacer is added to 1.9g of UV-curable CBU226 solution to obtain a coating solution with a mass fraction of 5% of the spacer; the reuse specification is 6 The lead screw was coated and the liquid crystal cell was solidified at 80° C., and the liquid crystal cell was uniformly poured into the liquid crystal under vacuum with a pressure of 9 MPa; the others were the same as in Example 1.

Claims (3)

1. A flexible liquid crystal film is characterized in that the flexible liquid crystal film is divided into five layers, wherein the bottom layer is a black light-absorbing coating, and the black light-absorbing coating is followed by a lower transparent electrode layer, an interface layer, and a liquid crystal layer. layer, and the upper transparent electrode layer, the thickness of the black light-absorbing coating is 0.1-2mm, the visible light reflectance is below 5%, and it is composed of the following components and mass percentages: 10-60% of black light-absorbing material Binder 90-40%, and the sum of the mass percentages of the above components is 100%; the lower transparent electrode layer has a surface sheet resistance lower than , Tin oxide indium polyethylene terephthalate conductive film with a visible light transmittance of more than 80%, tin oxide indium polyethylene conductive film, fluorine oxide indium polyethylene terephthalate conductive film, fluorine oxide indium polyethylene terephthalate conductive film, Indium polyethylene conductive film, nano-silver polyethylene terephthalate conductive film or nano-silver polyethylene conductive film; the interface layer is the thickness , consists of the following components and mass percentages: polymer 5-35%, acrylate monomer 0-15%, the rest is solvent, and the sum of the mass percentages of the above-mentioned components is 100%; The thickness of the liquid crystal layer is , is composed of commercialized cholesteric liquid crystals; spacers are also distributed in the interface layer and the liquid crystal layer, and the content of the spacers is 1%-5% of the mass of the interface layer solution, and the spacers are particle diameters TiO ₂ or SiO ₂ spherical particles; the material of the upper transparent electrode layer and the material of the lower transparent electrode layer are one material at the same time, or two different materials at the same time. 2. according to the described flexible liquid crystal film of claim 1, it is characterized in that, black light-absorbing substance is carbon black, black organic pigment or black organic dye; Binding agent is commercialized acrylic resin, phenolic resin, epoxy resin or It is silicone resin; the polymer in the interface layer is UV curing adhesive NOA65, UV curing adhesive NOA10, UV curing adhesive CBU226, polyvinyl alcohol, polyvinyl formal or polyvinyl butyral; acrylates The monomer is one or both of methyl acrylate, methyl methacrylate, hydroxyethyl methacrylate, and butyl methacrylate; the solvent is butanone, acetone, or cyclohexanone; the commercialized Cholesteric liquid crystal is a cholesteric liquid crystal whose helical pitch does not change with temperature between 0-50°C and whose Bragg reflection wavelength is between 380-660nm. 3. A preparation method of the flexible liquid crystal film according to claim 1, characterized in that comprising the following processes: 1) Preparation of the upper transparent electrode layer with a display pattern: the polyester film or polyethylene film black sheet coated with black paint is used to hollow out the characters or patterns to be displayed as a mask, and the flexible film electrode is processed by photolithography technology. The conductive layer on the surface is etched to prepare an upper transparent electrode layer without a conductive layer where characters or graphics are expected to be displayed; 2) Preparation of the interface layer: dissolve the polymer component and the acrylate monomer component of the interface layer in an appropriate solvent such as water, acetone, methyl ethyl ketone or cyclohexanone to form a uniform layer with a mass fraction of 20%-60%. solution, stir and disperse _SiO2 or _TiO2 spacers with uniform particle size into the solution to form a coating solution with a mass fraction of 1%-5%; use a lead screw to evenly coat the coating solution on the lower transparent electrode layer conductive surface, and then place it under a UV lamp for radiation curing; 3) Preparation of the liquid crystal cell: put the interface layer of the lower transparent electrode layer with spacers facing up, and press the conductive surface of the upper transparent electrode layer with the display pattern down on the lower transparent electrode layer, and then use epoxy resin glue, silicone resin Adhesive or polyacrylic acid glue is used as a sealant to seal the edge, leaving two opposite ports for subsequent liquid crystal pouring, and finally cured in an oven at 50-80°C to obtain a liquid crystal cell; 4) Liquid crystal perfusion: Use one port reserved for the liquid crystal box to evacuate, use the other port reserved for the liquid crystal box to perfuse the liquid crystal, absorb the cholesteric liquid crystal according to the dosage of 1-3g/ ^dm2 , and use it under vacuum The needle pours the liquid crystal into the liquid crystal cell, and acts on the outside of the liquid crystal cell with a pressure of 1-10MPa to assist in pouring the liquid crystal evenly, and then glues and solidifies the two ports of the liquid crystal cell with sealant; 5) Preparation of liquid crystal film: Coat a layer of black light-absorbing coating on the transparent electrode layer under the liquid crystal cell poured in step 4), and finally use conductive silver glue to draw electrodes from the two conductive electrodes respectively to obtain a flexible liquid crystal film.