阅读说明：本技术 基于高强度纳米纤维膜制备液晶显示器背光膜的方法 (Method for preparing liquid crystal display backlight film based on high-strength nanofiber film ) 是由 陈苏 解安全 朱亮亮 于 2020-05-27 设计创作，主要内容包括：本发明公开了一种基于高强度纳米纤维膜制备液晶显示器背光膜的方法其具体的步骤如下：首先使用微流控静电纺丝技术制备了具有独特的纤维-粒子-纤维点线结构的纳米纤维膜,该纳米纤维膜的拉伸强度和弹性模量都有很大的提高；然后在此纳米纤维膜上均匀刮涂数层半导体量子点荧光涂料,经过真空干燥和后期处理后作为显示器背光膜应用到量子点显示器中。该方法设备简单,可操作性强,所得到的量子点液晶显示器表现出了优异的性能,例如宽色域(高达116％),高颜色饱和度,长寿命(60000小时)等。(The invention discloses a method for preparing a backlight film of a liquid crystal display based on a high-strength nanofiber film, which comprises the following specific steps: firstly, a nanofiber membrane with a unique fiber-particle-fiber point-line structure is prepared by using a microfluidic electrostatic spinning technology, and the tensile strength and the elastic modulus of the nanofiber membrane are greatly improved; then, a plurality of layers of semiconductor quantum dot fluorescent paint are uniformly coated on the nanofiber membrane in a blade mode, and the semiconductor quantum dot fluorescent paint is used as a display backlight membrane to be applied to a quantum dot display after vacuum drying and post-processing. The method has simple equipment and strong operability, and the obtained quantum dot liquid crystal display shows excellent performances such as wide color gamut (up to 116%), high color saturation, long service life (60000 hours) and the like.)

1. A method for preparing a backlight film of a liquid crystal display based on a high-strength nanofiber film comprises the following specific steps:

a. preparing monodisperse polymer emulsion by adopting an emulsion polymerization method, centrifuging, drying and grinding the polymer emulsion to obtain polymer nano-particle powder, and ultrasonically dispersing the polymer nano-particle powder into a solvent to obtain nano-particle dispersion liquid;

b. dissolving a spinning polymer in a solvent to obtain a polymer spinning solution;

c. injecting the nanoparticle dispersion liquid and the polymer spinning solution into a T-shaped microfluidic chip through a microfluidic pump for uniform mixing reaction, then allowing the mixture to enter a spinning nozzle for electrostatic spinning through a silicone tube, and setting parameters in the spinning process to prepare the nanofiber membrane with the unique microstructure of fiber-particle-fiber; then the nanofiber membrane is placed in a vacuum drying oven for drying;

d. placing the dried nanofiber membrane in a low-temperature plasma treatment instrument, and carrying out physical and chemical modification on the fiber membrane;

e. dissolving green light emitting semiconductor quantum dots, red light emitting semiconductor quantum dots, transparent optical coating and curing agent in an organic solvent, and stirring to obtain uniform quantum dot liquid fluorescent coating;

f. d, flatly paving the nanofiber membrane treated by the plasma in the step d on an automatic coating instrument, setting the advancing speed of the automatic coating instrument, and dripping the quantum dot liquid fluorescent coating on the nanofiber membrane; and then repeatedly blade-coating to obtain a fiber fluorescent film, and then putting the fiber fluorescent film into a vacuum drying oven for drying to obtain the backlight film of the liquid crystal display.

2. The method according to claim 1, wherein the polymer nanoparticles in step a are poly (styrene-methyl methacrylate-acrylic acid) nanoparticles, poly (styrene-methyl methacrylate-butyl acrylate) nanoparticles, poly (methyl methacrylate-butyl acrylate) nanoparticles or silica nanoparticles; the average particle diameter of the polymer nanoparticles is 40-150 nanometers, and the polymer dispersibility index PDI is 0.001-0.01; the mass fraction of the nanoparticle dispersion liquid is 0.1-0.5%.

3. The method according to claim 1, wherein the centrifugation speed in step a is 12000-16000 rpm, and the centrifugation time is 10-30 min; the solvent in the step a is deionized water, N-dimethylformamide DMF or formic acid solution.

4. The method according to claim 1, characterized in that the spinning polymer in step b is polyamide 66, polycaprolactone, polyurethane, polystyrene, polymethylmethacrylate or polyvinylidene fluoride; the solvent is formic acid solution, ethanol or N, N-dimethylformamide DMF; the mass fraction of the polymer spinning solution is 10-20%.

5. The method of claim 1, wherein the inner diameter of the channel of the microfluidic chip in step c is 300 μm to 600 μm.

6. The method according to claim 1, wherein the parameters during spinning in step c are: the spinning voltage is 10-30 kV; the flow rate of the nanoparticle dispersion liquid is 0.1-0.8 mL/h; the flow rate of the polymer spinning solution is 0.2-1 mL/h; the vertical distance between the needle head and the collector is 8-20 cm; the temperature is 20-40 ℃, and the humidity is 55-65%.

7. The method of claim 1, wherein the nanofibers produced in step c have an average fiber diameter of 150 to 500nm and a tensile strength of 20 to 78 MPa.

8. The method of claim 1, wherein the frequency of the plasma processor in step d is 2.45 to 2.65GHz and the processing time is 180 to 300 seconds.

9. The method of claim 1, wherein the green and red light emitting semiconductor quantum dots in step e are each cadmium selenide, cadmium telluride, or zinc sulfide-coated cadmium selenide; the optical paint is JXHM50E-3 optical paint; the curing agent is HD-50 non-yellowing curing agent; the organic solvent is toluene, dichloromethane or chloroform; the mass ratio of the green light emitting semiconductor quantum dots to the red light emitting semiconductor quantum dots is 3-8: 1; the mass ratio of the quantum dots to the optical coating is 1 (50-60); the mass ratio of the curing agent to the optical coating is 1 (20-25); the mass-volume ratio of the quantum dots to the organic solvent is 0.15-0.25 mg/mL.

10. The method according to claim 1, wherein the advance speed of the automatic coating apparatus in step f is 10 to 50 mm/s; the number of the blade coating layers is 5-10; the temperature of the vacuum drying oven is 20-40 ℃, and the time is 12-24 hours.

Technical Field

The invention belongs to the field of quantum dot liquid crystal display, relates to a method for preparing a liquid crystal display backlight film based on a high-strength nanofiber film, and particularly relates to a method for preparing a high-strength nanofiber film by adopting a microfluidic electrostatic spinning technology, in particular to a method for preparing a long-life quantum dot liquid crystal display backlight film by using the high-strength nanofiber film as a substrate and using semiconductor quantum dots as a color conversion material.

Background

As a zero-dimensional nano material, the quantum dot has many unique properties such as narrow emission wavelength, adjustable color and high fluorescence emission efficiency, and shows great potential in the application field of next-generation displays. In recent years, quantum dot material-based optical devices including LED lighting and quantum dot displays have been commercialized, and especially in the display field, the appearance of quantum dot displays has increased the color gamut of conventional display devices from around 70% to over 110%, greatly increasing the color saturation of the displays. Since sony corporation introduced the first quantum dot television, many display manufacturers worldwide, such as samsung, LG, philips, and hyaline, have invested a lot of investment in the quantum dot display field, which will inevitably lead to a revolution in the display technology field. The quantum dot display not only obviously improves the color gamut value of the display, but also enables the color to be purer and brighter, and better meets the visual enjoyment of people. The Housekeeping professor team of Beijing science and technology university adopts a simple and convenient method to directly coat the organic metal halide perovskite precursor solution and the PVDF solution on the transparent glass, obtains the perovskite quantum dot polymer composite film after vacuum drying, is applied to the backlight film of the display, shows high luminous efficiency and wide color gamut (121 percent of NTSC standard), and obviously improves the color display effect of the display. However, the quantum dot luminescent material of the backlight film obtained by the method is still exposed on the surface of the film, and the quantum dot is extremely unstable, especially the perovskite quantum dot and the semiconductor quantum dot which have high luminescent efficiency are easily damaged by water molecules and oxygen molecules under the high temperature condition to cause fluorescence quenching, and the problem is one of the key problems in the development of the field of quantum dot liquid crystal displays.

The nanofiber membrane is an ideal supporting material for flexible photoelectric devices due to the fact that the nanofiber membrane has large specific surface area, high porosity, excellent strength and flexibility and unique one-dimensional quantum confinement effect. Therefore, the high-stability quantum dot liquid crystal display backlight film prepared by using the high-strength superfine nanofiber film as the substrate material has important significance.

The invention content is as follows:

the invention provides a method for preparing a backlight film of a liquid crystal display based on a high-strength nanofiber membrane, aiming at improving the defects of the prior art, and the backlight film has high mechanical strength (78MPa) and good flexibility (free bending folding) because the substrate material adopts the high-strength nanofiber membrane prepared by a microfluidic electrospinning method. In addition, because abundant pores in the nano fibers are used for coating and protecting the quantum dots, the influence of light, high temperature, humidity and oxygen on the quantum dot luminescent material is effectively reduced, the display effect of the quantum dot display is improved, more importantly, the problem of poor stability which puzzles the quantum dot display for a long time is solved, the service life of the quantum dot display using the backlight film under the normal working condition reaches 60000 hours and exceeds the service life of the quantum dot display reported at present.

The technical scheme provided by the invention is as follows:

the invention prepares the monodisperse nanoparticle-reinforced nanofiber membrane by a microfluidic electrospinning technology, and the strength of the nanofiber membrane is improved by adopting a unique microstructure of fiber-particle-fiber constructed by a new spinning technology. And then, the obtained nanofiber membrane is used as a substrate, an automatic film coating instrument is used for uniformly blade-coating quantum dot fluorescent materials on the nanofiber membrane, and then the backlight membrane of the liquid crystal display is obtained through later simple treatment and is applied to the quantum dot display.

The specific technical scheme of the invention is as follows: a method for preparing a backlight film of a liquid crystal display based on a high-strength nanofiber film comprises the following specific steps:

a. preparing monodisperse polymer emulsion by adopting an emulsion polymerization method, centrifuging, drying and grinding the polymer emulsion to obtain polymer nano-particle powder, and ultrasonically dispersing the polymer nano-particle powder into a solvent to obtain nano-particle dispersion liquid;

b. dissolving a spinning polymer in a solvent to obtain a polymer spinning solution;

c. injecting the nanoparticle dispersion liquid and the polymer spinning solution into a T-shaped microfluidic chip through a microfluidic pump for uniform mixing reaction, then allowing the mixture to enter a spinning nozzle for electrostatic spinning through a silicone tube, setting parameters (such as voltage, flow velocity of the nanoparticle dispersion liquid and the polymer spinning solution, and vertical distance between the spinning nozzle and a collector) in the spinning process, and preparing the nanofiber membrane with the unique microstructure of fiber-particle-fiber; then the nanofiber membrane is placed in a vacuum drying oven for drying;

d. and (3) placing the dried nanofiber membrane in a low-temperature plasma treatment instrument, and carrying out physical and chemical modification on the fiber membrane to improve the hydrophilic performance of the fiber membrane and the cleaning degree of the surface of the fiber membrane.

e. Dissolving green light emitting semiconductor quantum dots, red light emitting semiconductor quantum dots, transparent optical coating and curing agent in an organic solvent, and stirring (generally using a magnetic stirrer) to obtain uniform quantum dot liquid fluorescent coating;

f. d, flatly paving the nanofiber membrane treated by the plasma in the step d on an automatic coating instrument, setting the advancing speed of the automatic coating instrument, and dripping the quantum dot liquid fluorescent coating on the nanofiber membrane; and then repeatedly blade-coating to obtain a fiber fluorescent film, and then putting the fiber fluorescent film into a vacuum drying oven for drying to obtain the backlight film of the liquid crystal display.

Preferably, the polymer nanoparticles in step a are poly (styrene-methyl methacrylate-acrylic acid) nanoparticles, poly (styrene-methyl methacrylate-butyl acrylate) nanoparticles, poly (methyl methacrylate-butyl acrylate) nanoparticles or silica nanoparticles (the surface of which is grafted with abundant carboxyl groups); the average particle diameter of the polymer nanoparticles is 40-150 nanometers, and the polymer dispersibility index PDI is 0.001-0.01; the mass fraction of the nanoparticle dispersion liquid is 0.1-0.5%.

The preparation of the monodisperse polymer emulsion in step a by the emulsion polymerization process was carried out according to the method of our previously published patent "method for preparing polystyrene emulsion CN 108794671A".

Preferably, the centrifugation speed in the step a is 12000-16000 rpm, and the centrifugation time is 10-30 min; the solvent in the step a is deionized water, N-dimethylformamide DMF or formic acid solution.

Preferably, the spinning polymer in step b is polyamide 66 (nylon 66), polycaprolactone, polyurethane, polystyrene, polymethyl methacrylate or polyvinylidene fluoride; the solvent is formic acid solution, ethanol or N, N-dimethylformamide DMF; the mass fraction of the polymer spinning solution is 10-20%.

Preferably, the inner diameter of the channel of the microfluidic chip in the step c is 300-600 μm.

Preferably, the parameters in the spinning process in the step c are as follows: the spinning voltage is 10-30 kV; the flow rate of the nanoparticle dispersion liquid is 0.1-0.8 mL/h; the flow rate of the polymer spinning solution is 0.2-1 mL/h; the vertical distance between the needle head and the collector is 8-20 cm; the temperature is 20-40 ℃, and the humidity is 55-65%.

Preferably, the average fiber diameter of the nanofibers prepared in the step c is 150-500 nm, and the tensile strength is 20-78 MPa.

Preferably, the frequency of the plasma processor in the step d is 2.45-2.65 GHz, and the processing time is 180-300 seconds.

Preferably, the green light and red light emitting semiconductor quantum dots in the step e are cadmium selenide, cadmium telluride or cadmium selenide coated by zinc sulfide; the optical paint is JXHM50E-3 optical paint; the curing agent is HD-50 non-yellowing curing agent; the organic solvent is toluene, dichloromethane or chloroform; the mass ratio of the green light emitting semiconductor quantum dots to the red light emitting semiconductor quantum dots is 3-8: 1; the mass ratio of the quantum dots to the optical coating is 1 (50-60); the mass ratio of the curing agent to the optical coating is 1 (20-25); the mass-volume ratio of the quantum dots to the organic solvent is 0.15-0.25 mg/mL.

Preferably, the advancing speed of the automatic film coating instrument in the step f is 10-50 mm/s; the number of the blade coating layers is 5-10; the temperature of the vacuum drying oven is 20-40 ℃, and the time is 12-24 hours.

Has the advantages that:

the invention uses the high-strength nanometer fiber film as the protective layer of the quantum dot fluorescent material to prepare the quantum dot liquid crystal display backlight film with ultrahigh stability, high temperature resistance, water resistance and long service life, and has the following advantages:

(1) the preparation method of the fiber film quantum dot display backlight film prepared by the invention is simple, the used equipment is convenient to operate, and the used materials are green, safe and pollution-free.

(2) The fiber material of the prepared fiber film quantum dot display backlight film is prepared by a micro-fluidic electrostatic spinning technology, the micro-fluidic technology and an electrospinning technology work cooperatively, the size and microstructure of the nanofiber can be accurately regulated and controlled, and the unique fiber-particle-fiber micro-nano structure is constructed to enhance the tensile strength of the nanofiber.

(3) The substrate adopted by the fiber film quantum dot display backlight film prepared by the invention is a high-strength nanofiber film, the tensile strength reaches 78MPa, and the fiber film quantum dot display backlight film has good flexibility, so that the backlight film can be bent, twisted and folded at will, and has potential application prospects in the field of flexible display.

(4) The color gamut value of the backlight film of the fiber film quantum dot display prepared by the invention reaches 116%, so that the color expression of the display is more accurate and fine, and more complete color expression is provided.

(5) The fiber film quantum dot display backlight film prepared by the invention has high thermal stability and water resistance, and can still maintain good color performance after working for 24 hours at a high temperature of 200 ℃.

(6) The service life of the fiber quantum dot display backlight film prepared by the invention reaches 60000 hours.

Drawings

Fig. 1 is a schematic view of a T-shaped microfluidic chip used for microfluidic electrospinning according to example 1 of the present invention; wherein 1, nano-particle dispersion liquid and 2, polymer spinning liquid.

FIG. 2 is a schematic diagram of a high-strength nanofiber membrane prepared by microfluidic electrospinning according to example 1 of the present invention; wherein, 3, a high-voltage power supply, 4, a roller metal collector and 5, an electrostatic spinning needle.

Fig. 3 is a fluorescence spectrum of the green light emitting zinc sulfide-coated cadmium selenide quantum dot and the red light emitting zinc sulfide-coated cadmium selenide quantum dot in embodiment 1 of the present invention.

FIG. 4 is a schematic view of a coating process in example 1 of the present invention; wherein 6, the nanometer fiber film, 7, the film coating silk rod, 8, the quantum dot fluorescent paint and 9, the automatic film coating instrument base.

Fig. 5 is a schematic structural diagram of a quantum dot display in embodiment 1 of the present invention; 10, an outer frame, 11, an external polarizer, 12, a fiber film quantum dot display backlight film, 13, a blue light backlight source, 14, an internal polarizer, and 15, the outer frame.

Fig. 6 is a CIE chromaticity diagram of a backlight film of a fiber film quantum dot display fabricated in example 1 of the present invention.

Detailed Description

The present invention will be described below with reference to specific examples, but the present invention is not limited to the following examples.