CN113419390B - A bistable electrochromic film and energy-saving display device - Google Patents

Abstract

The invention relates to a bistable electrochromic film and an energy-saving display device, belonging to the technical field of material science. The polymer can replace the traditional PMMA to be used for preparing the electrochromic film, and can remarkably improve the bistable performance of the electrochromic film. The electrochromic device assembled by the electrochromic film has excellent bistable performance, and also has the performances of high sensitivity, quick corresponding color change, high color contrast and reversible color change under the stimulation of voltage.

Description

A bistable electrochromic film and energy-saving display device

technical field

The invention relates to a bistable electrochromic film and an energy-saving display device, belonging to the technical field of material science.

Background technique

Electrochromic devices are an emerging smart display product with huge market potential, and have broad application prospects in the fields of military anti-counterfeiting, biosensors, smart textiles, and energy-saving displays. Among them, the bistable display not only has the ability of general electrochromic devices to change color in response to electricity, but also can maintain the color state for a period of time without fading after the applied voltage is removed, that is, the ability to stabilize the color state. If it can be used in electronic display equipment such as billboards, it may achieve the purpose of energy saving and emission reduction, and relieve the global energy shortage. Therefore, the bistable display is a research hotspot in the field of energy saving at present.

In the field of small molecule color-changing dyes, there are two ways to realize the bistability of electrochromic devices according to different mechanisms: 1) Design the structure of color-changing dyes or ligand compounds to realize the stability of dye molecules in the ground state and excited state 2) The preparation process of each functional layer of the electrochromic device is improved, and the bistable performance of the device is achieved by regulating the charge/electron transfer rate of each functional layer. In the first implementation method, the design and regulation of novel molecular structures are too complicated, and it is very difficult to implement, and it is difficult to mature and put into practical application in a short period of time. In the second implementation, the bistable performance can be brought about by process adjustment, for example, increasing the thickness of the conductive layer, but this will correspondingly reduce the response sensitivity of the electrochromic device.

Fluorane-based small molecule dyes are a class of organic reversible color-changing materials with electro-responsive color change. The color-changing principle is to stimulate the redox reaction of dye molecules by applying an external electric field, and after molecular rearrangement, the structure of the dye changes (expressed as opening and closing of the lactone ring), thereby achieving a reversible change in color. Such electrochromic materials have the advantages of low response voltage, high color sensitivity, and high color contrast. CN201810659625.7 discloses an acid-base responsive electrochromic film and a preparation method thereof. Acid-responsive and base-responsive dyes are used as raw materials, and polymethyl methacrylate (PMMA), plasticizer and electrolyte are mixed to make PMMA condensate. For glue solution, the dye-containing gel solution is coated on the ITO conductive glass by means of coating to obtain a sol film, which is then dried to obtain an acid-base responsive electrochromic film. The electrochromic device assembled with the thin film has excellent response sensitivity and color uniformity. However, after removing the applied voltage, the color rendering state of the film is difficult to maintain for a long time, and the goal of energy saving cannot be achieved. At present, most of the gel materials of electrochromic films are PMMA.

In the prior art, in order to improve the bistable performance of the electrochromic thin film, the method of developing and designing fluorane dyes with new structures is mostly adopted. Since the new fluoran dyes are still in the experimental stage, it will take a long time before large-scale mass production. In addition, the traditional method of adjusting the PMMA process to achieve the bistable performance of the device will greatly reduce the color rendering rate of the device, and it is not a good method. Therefore, the development of bistable electrochromic films with high color sensitivity based on traditional fluoran dyes has become an urgent technical problem to be solved.

SUMMARY OF THE INVENTION

In order to develop a bistable electrochromic film with high color-changing sensitivity based on traditional fluoran dyes, the technical solution of the present invention is as follows:

The first object of the present invention is to provide a method for preparing a bistable electrochromic film, which is characterized in that it comprises the following steps:

Preparation of polymer: dissolve the functional monomer and initiator in solvent A, uniformly mix and defoam to obtain a precursor solution; the precursor solution is heated for polymerization reaction; after the reaction is completed, cooled to room temperature, purified and dried to obtain a polymer;

Preparation of electrochromic film: dissolving the polymer, electrolyte, solvent A and fluoran color-changing dye in volatile solvent B, and ultrasonically stirring to obtain a gel solution; coating the gel solution on a conductive substrate, The electrochromic film can be obtained by volatilizing the volatile solvent B;

Wherein, the functional monomers include essential monomers and auxiliary monomers; the essential monomers contain organic monomers with active groups capable of donating hydrogen, wherein the active groups capable of donating hydrogen include but not limited to hydroxyl groups , amino, active methylene; the auxiliary monomer is one or more of organic monomers, which mainly play the roles of cross-linking, film-forming and transparency adjustment.

Further, the necessary monomer is at least one of hydroxypropyl acrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxyethyl methacrylate, acrylamide, and N-methylol acrylamide.

Further, the auxiliary monomers are methyl acrylate, methyl methacrylate, ethyl methacrylate, butyl acrylate, isooctyl acrylate, N,N-methylenebisacrylamide, polyethylene glycol two At least one of acrylates.

Further, the mass percentage of the essential monomers in all the functional monomers is 1-99%, preferably 70%-90%.

Specifically, in the preparation step of the polymer, the mass ratio of the functional monomer to the solvent A is 20:80 to 60:40;

Further, the mass fraction of the initiator relative to the functional monomer can be selected from 0.1 to 2%.

Further, the temperature of the polymerization reaction can be selected from 40 to 80°C.

Further, in the preparation step of the electrochromic film, the amount of polymer (40%-80%), the amount of electrolyte (10%-50%), and the amount of solvent A (10%-50%).

Further, the time of ultrasonic stirring in the preparation step of the electrochromic film is 5-20 min.

Further, the reaction time in the preparation step of the polymer may be 0.5-12 h.

Further, the defoaming treatment is specifically as follows: defoaming the precursor solution in a nitrogen environment for 1-30 minutes.

Further, the initiator is a mixed system of potassium persulfate, azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, ammonium persulfate and tetramethylethylenediamine.

Further, the fluoran color changing dye is at least one of acid-base responsive fluoran color changing dyes, wherein the mass fraction of the fluoran color changing dye relative to the volatile solvent B is 0.01-0.5%.

Further, the acid-base responsive fluoran-based color-changing dyes include 2'-chloro-6'-(diethylamino)fluoran, 2'-chloro-6'-(diethylamino)-3'-methyl Fluoran, 6'-(diethylamino)-1',3'-dimethylfluoran, and fluorescein.

Further, the thickness of the electrochromic film is 0.1-100 μm.

Further, the electrolyte is tetrabutylammonium hexafluorophosphate (TBAPF6), tetrabutylammonium perchlorate (TBAP), tetraethylammonium perchlorate, tetramethylammonium hexafluorophosphate, mercury chloride, sulfuric acid At least one of barium and lead acetate.

Further, the solvent A is propylene carbonate.

Further, the volatile solvent B is at least one of acetonitrile, dichloromethane and ethanol.

The second object of the present invention is to provide an application of the above electrochromic film in intelligent color changing, flexible display and the like.

The third object of the present invention is to provide an intelligent induction color-changing textile, including a flexible energy-saving display, wherein the flexible energy-saving display adopts the electrochromic film described above to be assembled with clothes and a sensing device through an encapsulation method.

The fourth object of the present invention is to provide an energy-saving display device. The preparation method of the energy-saving display is to combine the above electrochromic film with clothes and a sensing device through an encapsulation method to obtain a smart textile that can sense and display human body functions.

The fifth object of the present invention is to provide a preparation method of a bistable electrochromic device, comprising the following steps:

Preparation of conductive layer solution;

Preparation of counter electrode layer solution;

Assembly of the bistable electrochromic device: uniformly coat the counter electrode layer solution on the conductive substrate to form a counter electrode layer after the solvent is volatilized; evenly spin the conductive layer solution on the counter electrode layer, The solvent is volatilized to form a conductive layer, and the conductive layer is compositely assembled with the film side of the electrochromic film to obtain a bistable electrochromic device.

Wherein, the conductive substrate may be ITO conductive glass.

Further, the preparation of the conductive layer solution: dissolving the electrolyte, solvent A and PMMA in volatile solvent B, and uniformly mixing to obtain a conductive layer solution.

Further, in the preparation step of the conductive layer solution, the relative addition amounts of the components are: the electrolyte (10%-50%), the solvent A (10%-50%) and the PMMA ( 40% to 80%).

Further, the preparation of the counter electrode layer solution: the electrolyte, solvent A, PMMA, p-benzoquinone and hydroquinone are dissolved in the volatile solvent B, and the counter electrode layer solution is obtained by uniform mixing.

Further, in the preparation step of the counter electrode layer solution, the relative addition amounts of the components are respectively: the electrolyte (10%-50%), the solvent A (10%-50%) and the PMMA (40% to 80%).

Further, in the preparation step of the counter electrode layer solution, the mass fraction of the p-benzoquinone relative to the volatile solvent B is 0.1-1%.

Further, in the preparation step of the counter electrode layer solution, the mass fraction of the hydroquinone relative to the volatile solvent B is 0.1-1%.

Further, the thickness of the counter electrode layer is controlled at 0.1-100 μm; preferably, the thickness of the conductive layer can be controlled at 50-500 μm by adjusting the amount of the conductive layer solution.

Beneficial effects of the present invention:

(1) Different from the prior art, a bistable electrochromic film is developed by designing and developing a new type of fluoran dye; the present invention is a unique way to prepare a polymer suitable for electrochromic devices based on functional monomers, and the polymer can replace Traditional PMMA is used for the preparation of electrochromic films and can significantly improve the bistable properties of electrochromic films.

(2) The electrochromic device assembled based on the electrochromic film of the present invention not only has excellent bistable performance, but also exhibits high sensitivity, rapid corresponding color change and high color contrast under voltage stimulation And the performance of reversible color change. Specifically, the driving voltage of the bistable electrochromic film prepared by the present invention is lower than 2V (much lower than the human safety voltage of 36V), and the color development time is 3.4s to 7.3s; It has a steady state time of 0.5-40h to keep the color of the film from fading, shows excellent bistable characteristics, and can be used in the field of energy-saving display.

(3) Compared with the electrochromic film based on PMMA and traditional fluoran dyes in the prior art, the electrochromic film is mechanically brittle and has poor adhesion to the device. The electrochromic film of the present invention has good toughness and has a wide range of bases. It can produce good adhesion with flexible conductive substrates such as PET, and meet the requirements of flexible wearable electronic products, making it suitable for applications in flexible displays, smart display electronic products, energy saving and environmental protection and other fields.

(4) The polymer prepared by the present invention is a block copolymer film (thickness 0.1-100 μm), which is different from the polymer gel material (thickness 0.2-1 mm) obtained by traditional blending. The electrochromic device assembled based on the electrochromic film of the present invention not only has excellent bistable performance, but at the same time, through the weak activity of the active group, the response rate of the electrochromic device is improved compared with the traditional PMMA. , the electrochromic device thus prepared has both excellent bistable performance and electrochromic response performance.

Description of drawings

FIG. 1 is the test photos of the flexible bistable display device of Example 8 before and after discoloration and bending performance.

Detailed ways

The preferred embodiments of the present invention will be described below, and it should be understood that the embodiments are used to better explain the present invention and are not intended to limit the present invention.

Determination of electrochromic properties: Taking air as a reference, Morpho3.2 software was used in conjunction with FX2000 spectrometer to test the transmittance curves of the colorless device and the device after color development, and the transmittance value at the maximum absorption wavelength of small molecule dye at 499nm was determined The final transmittance of the device; the electrochemical workstation was used to drive the device, and the electrochromic performance of the device was tested with an ultraviolet spectrophotometer, and the discoloration performance of the color-changing film was verified according to the discoloration phenomenon.

Example 1 (functional monomer is HPA)

Mix and stir 10 g of hydroxypropyl acrylate (HPA), 40 g of propylene carbonate and 10 mg of azobisisoheptyl nitrile for 1 to 10 minutes to obtain a precursor solution; after the precursor solution is defoamed in a nitrogen environment for 30 minutes, the temperature is raised. to 70° C., maintaining the temperature to react for 3 hours; after the reaction is completed, take out and cool to room temperature, extract with dichloromethane, and dry to obtain a polymer. Mix and dissolve 6g of the above polymer, 2g of tetrabutylammonium perchlorate (TBAP), and 2g of propylene carbonate in 30ml of ethanol, add 0.5g of 2'-chloro-6'-(diethylamino)fluoran, and ultrasonically Stir for 10 minutes to obtain the electrochromic layer gel solution; the above-mentioned gel solution (10 μL) is coated on a piece of ITO conductive glass (1 cm×3 cm), and after the solvent is volatilized, an electrochromic film is obtained, and an electrochromic film of 2 μm is obtained. film.

Mix and dissolve 2.5g tetrabutylammonium perchlorate, 2.5g propylene carbonate and 5g polymethyl methacrylate in 40ml acetonitrile and stir for 6 hours to obtain a conductive layer solution; mix 2g tetrabutylammonium perchlorate, 2g Propylene carbonate and 6 g of polymethyl methacrylate were mixed and dissolved in 40 ml of acetonitrile and stirred for 6 hours, 0.3 g of p-benzoquinone and 0.3 g of hydroquinone were added, and the solution was stirred and dissolved to obtain a counter electrode layer solution; the counter electrode layer solution and The conductive layer solution was sequentially coated on a piece of ITO conductive glass, the thickness of the counter electrode layer after drying was 10 μm, the thickness of the conductive layer was 200 μm, and the electrochromic device was assembled with the above-mentioned conductive substrate after drying.

The device was tested to have an initial transmittance of 45%. Under the driving of 2V voltage, the color development time is 3.7s, and the transmittance changes by 37%. After removing the voltage, it can maintain a stable state for 1 hour.

Comparative Example 1-1 (Conventional PMMA)

The electrochromic device was prepared with reference to the method of Example 1, the only difference being that the polymer of Example 1 was replaced by PMMA for the preparation of the electrochromic film.

After testing, the device has an initial transmittance of 78%. Under the driving of 2V voltage, the color development time is 5.6s, and the transmittance changes by 71%. After removing the voltage, it can maintain a stable state for 0.1 hours.

From Example 1 and Comparative Example 1-1, it can be seen that the polymer prepared based on the functional monomer of the present invention can replace the traditional PMMA and be used for the preparation of electrochromic films and electrochromic devices. The driving voltage of the electrochromic device prepared by the invention is lower than 2V (much lower than the human body safe voltage of 36V), and under voltage stimulation, it exhibits the properties of high sensitivity, rapid corresponding color change, high color contrast and reversible color change.

In particular, compared with the electrochromic film based on PMMA and traditional fluoran dyes of Comparative Document 1-1, the electrochromic film is mechanically brittle and has poor adhesion to the device. The electrochromic film of Example 1 has good toughness and has Wide range of substrate adhesion, can produce good adhesion with flexible conductive substrates such as PET, and can better meet the requirements of flexible wearable electronic products, making it suitable for flexible displays, smart display electronic products, energy saving and environmental protection, etc. field. In addition, the electrochromic device of Example 1 still has a steady state time of 1h to keep the film color from fading after removing the applied voltage after electrification, indicating that it has excellent bistable characteristics and can be used in the field of energy-saving display.

Embodiment 2 (functional monomer: the mass ratio of HPA and MMA is 8:2)

8 g of hydroxypropyl acrylate (HPA), 2 g of methyl methacrylate (MMA), 40 g of propylene carbonate and 10 mg of azobisisoheptanenitrile were stirred for 1 to 10 minutes to obtain a precursor solution; The solution was defoamed for 30 min in a nitrogen environment, then heated to 70°C, and kept at the temperature for 3 hours; after the reaction was completed, it was taken out and cooled to room temperature, and precipitated with deionized water and dried to obtain a polymer. Mix and dissolve 6g of the above polymer, 2g of tetrabutylammonium perchlorate (TBAP) and 2g of propylene carbonate in 30ml of acetonitrile, add 0.5g of 2'-chloro-6'-(diethylamino)fluoran, and ultrasonically Stir for 10 minutes to obtain the electrochromic layer gel solution; the above-mentioned gel solution (10 μL) is coated on a piece of ITO conductive glass (1 cm×3 cm), and after the solvent is volatilized, an electrochromic film is obtained, and an electrochromic film of 2 μm is obtained. film.

Mix and dissolve 2.5g tetrabutylammonium perchlorate, 2.5g propylene carbonate and 5g polymethyl methacrylate in 40ml acetonitrile and stir for 6 hours to obtain a conductive layer solution; mix 2g tetrabutylammonium perchlorate, 2g Propylene carbonate and 6g of polymethyl methacrylate were mixed and dissolved in 40ml of acetonitrile and stirred for 6 hours, 0.3g of p-benzoquinone and 0.3g of hydroquinone were added, and the solution was stirred and dissolved to obtain the counter electrode layer solution; the counter electrode layer solution ( 20 μL) and the conductive layer solution (300 μL) were sequentially coated on a piece of ITO conductive glass (1cm×3cm), the thickness of the counter electrode layer after drying was 10 μm, and the thickness of the conductive layer was 200 μm. Chromatic devices.

The device was tested to have an initial transmittance of 75%. Under the driving of 2V voltage, the color development time is 3.5s, and the transmittance changes by 67%. After removing the voltage, it can maintain a stable state for 3 hours.

Combining Example 1 and Example 2, it can be seen that adding a small amount of MMA monomer is beneficial to improve the film-forming transparency of the device, and the transmittance is significantly improved, from 45% to 75%; and the bistable performance of the device is also greatly improved. , from 1 hour to 3 hours.

Example 3 (Electrochromic film thickness 10 μm - mass ratio of polymer, electrolyte and solvent A)

8g of hydroxypropyl acrylate, 2g of methyl methacrylate, 40g of propylene carbonate and 10mg of azobisisoheptanenitrile were neutralized, and stirred for 1 to 10 minutes to obtain a precursor solution; the above precursor solution was carried out in a nitrogen environment After defoaming treatment for 30 min, the temperature was raised to 70° C., and the temperature was maintained for 3 hours; after the reaction was completed, it was taken out and cooled to room temperature, separated out with deionized water, and dried to obtain a polymer. Mix and dissolve 6g of the above polymer, 3g of tetrabutylammonium perchlorate (TBAP), and 3g of propylene carbonate in 30ml of acetonitrile, add 0.5g of 2'-chloro-6'-(diethylamino)fluoran, and ultrasonically Stir for 10 minutes to obtain an electrochromic layer gel solution; the above gel solution (10 μL) is coated on a piece of ITO conductive glass (1 cm×3 cm), and after the solvent is volatilized, an electrochromic film is obtained, and an electrochromic layer of 10 μm is obtained. film.

Mix and dissolve 2.5g tetrabutylammonium perchlorate, 2.5g propylene carbonate and 4g polymethyl methacrylate in 40ml acetonitrile and stir for 6 hours to obtain a conductive layer solution; mix 2g tetrabutylammonium perchlorate, 2g Propylene carbonate and 6g of polymethyl methacrylate were mixed and dissolved in 40ml of acetonitrile and stirred for 6 hours, 0.3g of p-benzoquinone and 0.3g of hydroquinone were added, and the solution was stirred and dissolved to obtain the counter electrode layer solution; the counter electrode layer solution ( 20 μL) and the conductive layer solution (300 μL) were sequentially coated on a piece of ITO conductive glass (1cm×3cm), the thickness of the counter electrode layer after drying was 10 μm, and the thickness of the conductive layer was 200 μm. Chromatic devices.

The device was tested to have an initial transmittance of 75%. Under the driving of 2V voltage, the color development time is 3.0s, and the transmittance changes by 70%. After removing the voltage, it can maintain a stable state for 3.5 hours.

Combining Example 3 and Example 2, it can be seen that when the polymer mass fraction of the electrochromic layer is reduced from 60% to 50%, the transmittance of the device will increase, from 67% to 70%; The color rate will also increase, from 3.5s to 3.0s; but the bistable performance will decrease, from 3 hours to 2 hours, and the formula should be adjusted accordingly according to the application needs.

Example 4 (the thickness of the conductive layer is 300 μm - the mass ratio of electrolyte, solvent A and PMMA)

8 g of hydroxypropyl acrylate, 2 g of methyl methacrylate, 30 g of propylene carbonate and 10 mg of azobisisoheptanenitrile were stirred for 1 to 10 minutes to obtain a precursor solution; the precursor solution was removed in a nitrogen atmosphere After soaking for 30 min, the temperature was raised to 70° C., and the temperature was maintained for 3 hours; after the reaction was completed, it was taken out and cooled to room temperature, separated out with deionized water, and dried to obtain a polymer. Mix and dissolve 6g of the above polymer, 2g of tetrabutylammonium perchlorate (TBAP) and 2g of propylene carbonate in 30ml of acetonitrile, add 0.5g of 2'-chloro-6'-(diethylamino)fluoran, and ultrasonically Stir for 10 minutes to obtain an electrochromic layer gel solution; apply the above-mentioned gel solution (10 μL) on a piece of ITO conductive glass (1 cm×3 cm), and obtain an electrochromic film after the solvent is volatilized to obtain a 2 μm electrochromic film. Color changing film.

Mix and dissolve 2.5g tetrabutylammonium perchlorate, 2.5g propylene carbonate and 5g polymethyl methacrylate in 40ml acetonitrile and stir for 6 hours to obtain a conductive layer solution; mix 2g tetrabutylammonium perchlorate, 2g Propylene carbonate and 6g of polymethyl methacrylate were mixed and dissolved in 40ml of acetonitrile and stirred for 6 hours, 0.3g of p-benzoquinone and 0.3g of hydroquinone were added, and the solution was stirred and dissolved to obtain the counter electrode layer solution; the counter electrode layer solution ( 20μL) and the conductive layer solution (450μL) were sequentially coated on a piece of ITO conductive glass (1cm×3cm), the thickness of the counter electrode layer after drying was 10μm, and the thickness of the conductive layer was 300μm. Chromatic devices.

Upon testing, the device had an initial transmittance of 77%. Under the driving of 2V voltage, the color development time is 3.9s, and the transmittance changes by 69%. After removing the voltage, it can maintain a stable state for 10 hours.

Combining Example 4 and Example 2, it can be seen that when the thickness of the conductive layer increases from 200 μm to 300 μm, the transmittance and transmittance change of the device hardly change, but the color development time increases from 3.6s to 4.7s. But it is worth noting that the bistable performance will increase significantly, and the steady-state time will increase from 5 hours to 10 hours.

Example 5-1: Selection of different functional monomers

The electrochromic device was prepared by referring to the method of Example 1, except that the monomer types were adjusted and hydroxypropyl acrylate was replaced with methyl methacrylate, hydroxyethyl acrylate, isobutyl acrylate, n-butyl acrylate and methyl methacrylate. Hydroxypropyl acrylate, other conditions are the same as in Example 1, and the properties of the prepared electrochromic device are shown in Table 1.

Table 1 Properties of electrochromic devices

It can be seen from Table 1 that the polymer (monomer) devices containing active hydroxyl groups have better electrochromic properties than the polymer (monomer) devices without active hydroxyl groups. Both the hydroxypropyl acrylate polymer and the hydroxyethyl acrylate polymer in this embodiment have the ability to impart bistable properties to the device. It shows that this type of polymer electrochromic device has potential application value in the field of energy saving.

Example 6-2: Selection of functional monomer ratio

The electrochromic device was prepared with reference to the method of Example 2, the only difference being that the fixed monomer consumption was 10 g, and the amount ratio of hydroxypropyl acrylate (HPA): methyl methacrylate (MMA) was adjusted to 0: 10, 1:9, 2:8, 3:7, 4:6, 5:5, 7:3, 9:1, 10:0, other conditions are the same as in Example 2, see Table 2.

Table 2 Properties of electrochromic devices

It can be seen from Table 2 that the bistable performance first increases and then decreases with the increase of hydroxypropyl acrylate content. In addition, with the increase of hydroxypropyl acrylate content, the color development rate of the device also improved, from 5.6s for PMMA polymer to 3.4s for 9:1 polymer, indicating that the polymer hydroxyl group has the ability to induce accelerated dyes. Color rendering ability.

Considering the comprehensive performance of the electrochromic device, the preferred ratio in this embodiment is 8:2. Under this ratio, the transmittance of the electrochromic device is high (75%), the color development time is short (3.5s), and it has the most excellent bistable performance (3 hours). It shows that the prepared electrochromic device has good electrochromic properties and excellent bistable properties.

Example 7-4: Thickness Optimization of Conductive Layer

The electrochromic device was prepared by referring to the method of Example 4-2, the only difference was that the thickness of the conductive layer was adjusted from 300 μm to 100 μm, 200 μm, 400 μm, 500 μm, 600 μm (150 μL, 300 μL, 600 μL) by adjusting the amount of the conductive layer solution. , 750 μL, 900 μL), other conditions are the same as in Example 4-2, and the properties of the prepared electrochromic device are shown in Table 2.

Table 3 Properties of electrochromic devices

It can be seen from Table 3 that with the increase of the thickness of the conductive layer, the bistable performance of the device will increase significantly, but at the same time the color development time of the device will also increase, which is not conducive to the application of electrochromic devices. However, considering that this patent is intended to apply electrochromic polymers to energy-saving devices, the requirements for color development time are relatively low, so the preferred thickness of the conductive layer in this embodiment is 500 μm. Under the thickness of the conductive layer, the transmittance of the electrochromic device is high (76%), the color development time is short (3.9s), and the bistable performance is better (54 hours). The above examples show that the prepared electrochromic device has good electrochromic performance and excellent bistable characteristics.

Example 8: A flexible bistable display device

Preparation of electrochromic film: dissolving the polymer, electrolyte, solvent A and fluoran color-changing dye in volatile solvent B, and ultrasonically stirring to obtain a gel solution; coating the gel solution on a conductive substrate, The electrochromic film can be obtained by volatilizing the volatile solvent B.

A flexible bistable display device, the preparation method of which is that the polymer, the electrolyte and the fluoran color-changing dye of the present invention are dissolved in a solvent A to form an electrochromic layer solution, and then a transparent conductive layer is formed by a solvent volatilization method. A film is formed on a flexible polyester substrate, and then encapsulated with another flexible polyester substrate coated with a conductive layer and a counter electrode layer. In order to realize the pattern display, the electrochromic layer solution can be applied to the designed pattern position first, or laser etching can be used after the film is formed. The photos of the flexible bistable display device of Example 8 before and after discoloration and bending performance test are shown in FIG. 1 .

The flexible bistable display device can provide targeted responsive discoloration for clothing, display different colors and patterns through power control, and at the same time have good bending performance, which is conducive to the realization of colorful and energy-saving electronic textiles, and meets people's expectations for clothing. The pursuit of individuality.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Anyone who is familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, The protection scope of the present invention should be defined by the claims.

Claims (6)

1. A preparation method of a bistable electrochromic film is characterized by comprising the following steps:

preparation of the polymer: dissolving a functional monomer and an initiator in a solvent A, wherein the mass ratio of the functional monomer to the solvent A is (20:80) - (60: 40); the mass fraction of the initiator relative to the functional monomer is 0.1-2%, and the initiator is uniformly mixed and subjected to defoaming treatment to obtain a precursor solution; heating the precursor solution for polymerization reaction; after the reaction is completed, cooling to room temperature, purifying and drying to obtain a polymer;

preparing an electrochromic film: dissolving the polymer, the electrolyte, the solvent A and the fluoran color-changing dye in a volatile solvent B, wherein the mass ratio of the polymer to the electrolyte to the solvent A is as follows: (40-80): (10-50): (10-50), wherein the fluoran color-changing dye is 2 '-chloro-6' - (diethylamino) fluoran; ultrasonically stirring to obtain gel liquid; coating the gel liquid on a conductive substrate to volatilize the volatile solvent B, thus obtaining the electrochromic film;

wherein the functional monomers comprise at least essential monomers and auxiliary monomers; the essential monomer contains an organic monomer having a reactive group capable of donating hydrogen; the auxiliary monomer is one or more of organic monomers, and has the functions of crosslinking, film forming and transparency adjustment; the necessary monomer is at least one of hydroxypropyl acrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxyethyl methacrylate, acrylamide and N-hydroxymethyl acrylamide; the auxiliary monomer is at least one of methyl acrylate, methyl methacrylate, ethyl methacrylate, butyl acrylate, isooctyl acrylate, N-methylene bisacrylamide and polyethylene glycol diacrylate; the essential monomer accounts for 70-90% of the total functional monomers by mass percent.

2. The method for preparing the bistable electrochromic film according to claim 1, wherein the thickness of the electrochromic film is 0.1-100 μm.

3. The method of claim 1, wherein the initiator is any one of azobisisoheptonitrile, potassium persulfate, azobisisobutyronitrile, benzoyl peroxide, ammonium persulfate and tetramethylethylenediamine mixture.

4. A bistable electrochromic film prepared by the method for preparing a bistable electrochromic film according to claim 1.

5. Use of the electrochromic film of claim 4 in smart color change materials, flexible display products, smart inductive color change textiles.

6. A preparation method of a bistable electrochromic device is characterized by comprising the following steps:

preparing a conducting layer solution;

preparing a counter electrode layer solution;

assembling the bistable electrochromic device: uniformly coating the counter electrode layer solution on a conductive substrate, and volatilizing a solvent to form a counter electrode layer; and (3) uniformly spin-coating the conducting layer solution on the counter electrode layer, volatilizing a solvent to form a conducting layer, and carrying out composite assembly on the conducting layer and the film side of the electrochromic film as claimed in claim 4 to obtain the electrochromic film.

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