Transparent flame-retardant film and quick-response electronic paper

Abstract

A preparation method of the transparent flame-retardant film comprises the following steps: dissolving 3-(hydroxymethylphosphonyl) propionic acid in water to obtain a 3-(hydroxymethylphosphonyl) propionic acid aqueous solution, dissolving polyvinyl alcohol in water to obtain a polyvinyl alcohol aqueous solution, mixing the two aqueous solutions, coating a substrate with a film, and drying to obtain the transparent flame-retardant film. The invention further discloses the quick response electronic paper, and a preparation method of the quick response electronic paper comprises the following steps: constructing the metal template with the micro-cup structure by utilizing a laser etching processing method, placing the metal template on the transparent flame-retardant film, and performing imprinting by utilizing nano-imprinting equipment to manufacture the micro-cup structure. Due to the addition of the 3-(hydroxymethylphosphonyl) propionic acid, the electronic paper microcup has good flame retardance, and the use safety is greatly improved. Due to the addition of the 3-(hydroxymethylphosphonyl) propionic acid, the polarity of the electronic paper microcup is also improved, the response time of the electronic paper is effectively shortened, and the refresh frequency of display is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic paper, and in particular to a transparent flame-retardant film and a fast-response electronic paper. Background Art

[0002] Electronic paper is a general term for reflective paper-like displays that combine the reading comfort of traditional paper with the versatility of modern electronic devices.

[0003] Electrophoretic electronic paper is divided into microcapsule type and microcup type electrophoretic display according to the difference of microcavity that carries electrophoretic particles. The production method of microcup type electronic paper includes: printing microcups with polymer materials, then pouring ink into the microcups, and then sealing the cup mouth. Usually the encapsulation layer is transparent, and the polymer of the microcup structure can be made of non-transparent or even dark material to prevent light from penetrating and improve reflection efficiency. When the electronic paper is working, the upper and lower surfaces of the microcup are connected to electrodes, and voltage is applied to drive the electrophoretic particles in the microcup to move between the electrodes to achieve display.

[0004] However, since the packaged electronic ink mainly contains isomeric alkanes, which are flammable, it is easy to leak during the operation of the electronic paper and cause a fire. Summary of the invention

[0005] The purpose of the present invention is to provide a transparent flame retardant film in view of the defects of the prior art. The preparation method is as follows: 3-(hydroxymethylphosphonyl)propionic acid is dissolved in water to obtain a 3-(hydroxymethylphosphonyl)propionic acid aqueous solution, polyvinyl alcohol is dissolved in water to obtain a polyvinyl alcohol aqueous solution, the above two aqueous solutions are mixed and coated on a substrate, and the transparent flame retardant film is obtained after drying.

[0006] Furthermore, the drying is divided into two stages, the first stage is drying at 70° C. for 4 hours, and the second stage is drying at 100° C. for 3 hours.

[0007] Furthermore, the preparation method of 3-(hydroxymethylphosphonyl)propionic acid is as follows: 2-methyl-1,2-oxophosphine-5-one 2-oxide is hydrolyzed in acetone to obtain 3-(hydroxymethylphosphonyl)propionic acid, and the reaction equation is:

[0008]

[0009] Further, 2-methyl-1,2-oxophosphine-5-one 2-oxide and water were added to acetone at a molar ratio of 1:1 for hydrolysis reaction. The molar ratio of 2-methyl-1,2-oxophosphine-5-one 2-oxide to acetone was 1:3. The hydrolysis reaction was carried out at 60° C. for 2 hours.

[0010] Further, the 3-(hydroxymethylphosphonyl) propionic acid accounts for 10-40wt% of the total mass of polyvinyl alcohol and 3-(hydroxymethylphosphonyl) propionic acid. Further, the 3-(hydroxymethylphosphonyl) propionic acid accounts for 30wt% of the total mass of polyvinyl alcohol and 3-(hydroxymethylphosphonyl) propionic acid.

[0011] Furthermore, the transparent flame retardant film has a thickness of 40 to 50 um.

[0012] A fast-response electronic paper made of a transparent flame-retardant film, the preparation method of which is as follows: a metal template with a microcup structure is constructed by a laser etching method, the metal template is placed on a transparent flame-retardant film, and nanoimprinting equipment is used for imprinting to produce a microcup structure.

[0013] Furthermore, the embossing step is: embossing at a pressure of 200 psi and a temperature of 70-85° C. for 10-30 minutes, then lowering the temperature to 30° C. at a rate of 2° C. / min, maintaining for several minutes, and then removing the pressure to obtain a transparent flame retardant film with a microcup structure.

[0014] Furthermore, the microcup is a regular hexagon with a side length of 10 to 100 μm, and a gap between two regular hexagons is 1 to 50 μm.

[0015] The beneficial effects of the present invention are:

[0016] 1. Due to the addition of 3-(hydroxymethylphosphono) propionic acid, the electronic paper microcup has good flame retardancy, which greatly improves the safety of use.

[0017] The addition of 2.3-(hydroxymethylphosphono) propionic acid also increases the polarity of the electronic paper microcup, effectively shortening the response time of the electronic paper and increasing the refresh rate of the display. At the same time, the process is simple and low-cost, suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a morphology diagram of the electronic paper microcup of the present invention;

[0019] Figure 2 This is the test result of the electronic paper response time of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below by way of examples and comparative examples. The drugs used in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods in the art unless otherwise specified.

[0021] Example 1

[0022] 1 mol of 2-methyl-1,2-oxophosphine-5-one 2-oxide (OP) and 1 mol of water were added to 3 mol of acetone for hydrolysis and reacted at 60°C for 2 hours to obtain 3-(hydroxymethylphosphono)propionic acid (CEP). The reaction equation is:

[0023]

[0024] 3-(Hydroxymethylphosphonyl)propionic acid was dissolved in water to obtain a 30 wt% 3-(hydroxymethylphosphonyl)propionic acid aqueous solution, and polyvinyl alcohol (PVA) was dissolved in water to obtain a 10 wt% polyvinyl alcohol aqueous solution. The two aqueous solutions were mixed and degassed in a planetary deaerator at 2000 rpm / min for 10 minutes to remove bubbles in the composition.

[0025] The mixed solution is coated into a thin film on a conductive ITO (indium tin oxide) substrate and dried in two stages. The first stage is drying at 70°C for 4 hours and the second stage is drying at 100°C for 3 hours. After drying, a transparent flame-retardant film with a thickness of 50 microns is obtained, which ensures a certain mechanical strength.

[0026] The phosphorus element in 3-(hydroxymethylphosphono) propionic acid can form compounds such as phosphoric acid, metaphosphoric acid, and polyphosphoric acid during the combustion process. These compounds have high viscosity and non-flammability, and can form a protective film on the surface of the film to isolate oxygen and heat, thereby preventing combustion. The phosphorus element can also promote the carbonization of the material during the combustion process, forming a carbon layer, which further prevents combustion. The hydroxyl and carboxyl groups in 3-(hydroxymethylphosphono) propionic acid can also promote the dehydration reaction of the material during the combustion process, forming water and carbon layers, which further prevent combustion. Polyvinyl alcohol (PVA) has a high dielectric constant (2-6), which is suitable as a microcup material, and is soluble in water to form a film. The glass transition temperature of the film is moderate, and it is easy to be processed into a microcup structure by hot embossing, which makes it have good processing performance.

[0027] Example 2

[0028] A fast-response electronic paper, the preparation method of which is as follows: a metal template with a microcup structure is constructed by a laser etching method, the metal mold is accurately placed on a transparent flame-retardant film, and a nanoimprinting device is used for hot embossing to produce a microcup structure, the pressure is 200 psi, and the embossing process: time is 90°C for 25 minutes, and then cooled to 30°C at a rate of 2°C / min. After the pressure drops to 0, demolding is performed to obtain a microcup structure. The microcup cavity is 30 μm high, the base thickness is 10 μm, and the microcup structure is 10 μm thick. Figure 1 shown.

[0029] Preparation of PVA blank film: PVA was stirred in 90°C distilled water until completely dissolved, and a 10% PVA aqueous solution was prepared. The aqueous solution was degassed and allowed to stand for 0.5 h. On a smooth, clean, dry glass plate, a film was coated using a film applicator. The film was dried in an oven at 70°C for 12 h to obtain a PVA blank film. A microcup structure was prepared according to the above microcup structure preparation method, and was named sample PVA.

[0030] The microcup structured film samples PVA-1, PVA-2, PVA-3, and PVA-4 were prepared by adding CEP to the total weight of polyvinyl alcohol and CEP at 10-40 wt%. The combustion tests were conducted respectively, and the evaluation and characterization were performed using GB / T2406-2008 "Test Method for Combustion Performance of Plastics - Oxygen Index Method" and GB / T 2408-2008 "Determination of Combustion Performance of Plastics: Horizontal Method and Vertical Method", and the results are shown in Table 1.

[0031] Table 1 PVA / CEP film combustion test results

[0032]

[0033] From the results in Table 1 above, it can be seen that the limiting oxygen index (LOI) of pure polyvinyl alcohol is 18.2%, which is a flammable film material. When the CEP content is 10% (PVA-1), the limiting oxygen index is 24.3%. With the addition of CEP content, the flame retardant performance gradually increases. When the CEP content is 40% (PVA-3), the limiting oxygen index is 27.7%, which is also V-0 level (in the vertical burning test, after the sample is subjected to two 10-second burning tests, the flame is extinguished within 30 seconds, and no burning materials can fall). The vertical burning test shows that the transparent flame retardant film containing CEP20-40wt% has no dripping property.

[0034] Figure 1 The results of the profiler show that the microcup structure of PVA-3 is regular, the microcup is a regular hexagon, the side length is 10 to 100 μm, and the gap between the regular hexagons is 1 to 50 μm. The response time test results are shown in Figure 2, the response time of the microcup prepared by pure PVA embossing to the electronic ink is 195ms, while the response time of the microcup with CEP added is shortened. When the CEP content is 30wt% (PVA-3), the response time is the shortest, which is 62ms. The shorter the response time, the shorter the refresh time of the electronic paper display, the less likely it is to have afterimages, and the better the display effect for users. After adding 3-(hydroxymethylphosphonyl) propionic acid, the response time of the transparent flame retardant film is shortened, which shows that the dielectric properties are improved by the addition of 3-(hydroxymethylphosphonyl) propionic acid, and the polarization properties are enhanced, thereby shortening the response time of the electronic ink in the microcup. This is because the functional groups such as phosphorus atoms, hydroxyl groups and carboxyl groups contained in 3-(hydroxymethylphosphonyl) propionic acid make the polarity of 3-(hydroxymethylphosphonyl) propionic acid itself relatively high, which increases the polarity of the transparent flame retardant film prepared together with PVA, thereby improving the mobility of the electronic ink when power is applied to both ends of the microcup.

[0035] In summary, when the CEP content is 30wt%, the response time is the shortest and it has V-0 level flame retardancy.

[0036] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A transparent flame retardant film, characterized in that: The preparation method is as follows: 3-(hydroxymethylphosphonyl) propionic acid is dissolved in water to obtain a 3-(hydroxymethylphosphonyl) propionic acid aqueous solution, polyvinyl alcohol is dissolved in water to obtain a polyvinyl alcohol aqueous solution, the two aqueous solutions are mixed and coated on a substrate, and a transparent flame retardant film is obtained after drying.

2. The transparent flame retardant film according to claim 1, characterized in that: The 3-(hydroxymethylphosphono)propionic acid accounts for 10-40 wt % of the total mass of the polyvinyl alcohol and the 3-(hydroxymethylphosphono)propionic acid.

3. The transparent flame retardant film according to claim 2, characterized in that: The 3-(hydroxymethylphosphono)propionic acid accounts for 30 wt % of the total mass of the polyvinyl alcohol and the 3-(hydroxymethylphosphono)propionic acid.

4. The transparent flame retardant film according to claim 1, characterized in that: The drying is divided into two stages, the first stage is drying at 70° C. for 4 hours, and the second stage is drying at 100° C. for 3 hours.

5. The transparent flame retardant film according to claim 1, characterized in that: The preparation method of the 3-(hydroxymethylphosphono)propionic acid is as follows: 2-Methyl-1,2-oxophosphine-5-one 2-oxide is hydrolyzed in acetone to obtain 3-(hydroxymethylphosphono)propionic acid. The reaction equation is:

6. The transparent flame retardant film according to claim 4, characterized in that: 2-methyl-1,2-oxophosphine-5-one 2-oxide and water were added to acetone at a molar ratio of 1:1 for hydrolysis reaction. The molar ratio of 2-methyl-1,2-oxophosphine-5-one 2-oxide to acetone was 1:

3. The hydrolysis reaction was carried out at 60° C. for 2 hours.

7. The transparent flame retardant film according to claim 1, characterized in that: The thickness of the transparent flame retardant film is 40-50 um.

8. The fast-response electronic paper prepared from the transparent flame-retardant film according to claim 1, characterized in that The preparation method is as follows: A metal template with a microcup structure is constructed using a laser etching method, the metal template is placed on a transparent flame-retardant film, and nanoimprinting equipment is used for imprinting to produce the microcup structure.

9. The fast response electronic paper according to claim 8, characterized in that: The stamping steps are: The pressing is performed at a pressure of 200 psi and a temperature of 70-85° C. for 10-30 minutes, and then the temperature is lowered to 30° C. at a rate of 2° C. / min. After being maintained for several minutes, the pressure is removed to obtain a transparent flame-retardant film with a microcup structure.

10. The fast response electronic paper according to claim 8, characterized in that: The microcup is a regular hexagon with a side length of 10 to 100 μm, and a gap between two regular hexagons of 1 to 50 μm.

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