An electronic paper electrophoretic fluid encapsulation composition with high dielectric performance and an encapsulation method thereof

Abstract

The application provides an electronic paper electrophoretic fluid packaging composition with high dielectric property and a packaging method thereof. The electronic paper electrophoretic fluid packaging composition is a photocuring composition composed of a photocuring polyurethane resin, a cyclodextrin, a photocuring agent and an active diluent. After the photocuring composition is uniformly mixed, a thin film is formed on a glass plate by spin coating. The surface of a microcavity containing electronic ink is covered with the thin film on one side of the glass plate, and the film is cured by irradiation with ultraviolet light. After the glass plate is removed, a packaged microcup display window is obtained. The thin film formed after the photocuring composition is cured is transparent, has high dielectric constant, strong polarity, high hydrophilicity and excellent mechanical flexibility. The packaged microcup display window not only has stable performance, but also has high dielectric property. The preparation method is simple, pollution-free, low in cost, easy to operate, non-toxic and harmless, friendly to the environment, and extremely suitable for large-area popularization and application.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high polymer composite material, and relates to an electrophoretic fluid encapsulation composition and an encapsulation method thereof. BACKGROUND

[0002] Electronic paper, also known as digital paper, is an ultra-thin and ultra-light display screen, that is, it is understood as a "display device as thin as paper, soft and erasable". In an image, electronic paper is a thin film, and a layer of charged substance "painted" on the film is electronic ink. Compared with traditional paper or flat displays, electronic paper has the advantages of high resolution, high contrast, low power consumption and bistability, and has a wide application prospect in the market. It can be applied to outdoor billboards, wearable device displays, and even has a broad application prospect in the fields of medical health or military. In order to realize the display of electronic paper, a relatively low driving voltage, a relatively fast response time, and a relatively high brightness and contrast are often required. For micro-cup type electronic paper, electronic ink containing conductive particles is first injected into a micro-cup array, then the cup opening is encapsulated, and then two electrodes are respectively placed on the upper and lower surfaces of the micro-cup array containing the electronic ink. A voltage is applied to drive the black and white particles to move up and down to realize the display effect.

[0003] The refresh rate and driving voltage of electronic paper display are closely related to the material and structure of the encapsulation layer / micro-cup array. The driving voltage applied between the two electrodes is partially distributed to the micro-cup bottom, partially distributed to the encapsulation layer, and partially distributed to the electrophoretic fluid. The encapsulation layer is composed of a high-transparency polymer. Since the polymer is not conductive, the voltage share acting on the electrophoretic fluid at the rated driving voltage is reduced, the movement rate of the conductive particles of the electronic paper is reduced, the refresh rate of the display is low, and the response speed is slow. SUMMARY

[0004] To solve the problem of the encapsulation layer polymer not being conductive in the background art, which leads to the movement rate of the conductive particles of the electronic paper being reduced, the refresh rate of the display being low, and the response speed being slow, the present application provides an electronic paper electrophoretic fluid encapsulation composition with high dielectric performance and an encapsulation method thereof.

[0005] The present application provides an electronic paper electrophoretic fluid encapsulation composition with high dielectric performance, which comprises the following components in weight percentage: 55-85% of a photocurable polyurethane resin, 1-40% of cyclodextrin, 3-5% of a photocuring agent, and 5-10% of an active diluent; the cyclodextrin is alpha-cyclodextrin, beta-cyclodextrin or gamma-cyclodextrin.

[0006] Preferably, the photocurable polymer prepolymer is a photocurable acrylate prepolymer, a photocurable polyurethane prepolymer or a photocurable epoxy resin prepolymer with a viscosity of 300-500 Pa / s.

[0007] Preferably, the photocuring polymer prepolymer is a photocuring polyurethane prepolymer, and its structure is as follows:

[0008]

[0009] wherein R is an alkyl group containing 1-6 carbon atoms.

[0010] Preferably, the active diluent is 1,6-hexanediol diacrylate. This is because the active diluent uses monomers containing more functional groups, which can not only increase the reactivity, but also impart crosslinked structure to the cured film; monofunctional monomers can only produce linear polymers after polymerization, while multifunctional monomers can produce high crosslinking networks.

[0011] Preferably, the mass percentage of the photocuring polyurethane resin and cyclodextrin is 100:25. The photocuring composition using the above components has the highest dielectric constant, the fastest response speed, and also reaches a good level of light transmittance.

[0012] The application also provides a packaging method of an electronic paper electrophoretic liquid packaging composition with high dielectric properties, comprising the following steps:

[0013] Step one, mix the photocuring polyurethane resin, cyclodextrin and active diluent with each other, and make them uniformly mixed by alternately performing magnetic stirring and ultrasonic stirring, then add a photocuring agent, and perform defoaming by using a planetary defoaming instrument to remove bubbles in the mixed solution;

[0014] Step two, take a certain amount of the mixed solution to the center of a pretreated glass plate in a film applicator, and spin coat the solution into a thin film at room temperature by using a spin coating method;

[0015] Step three, cover the thin film of the glass plate on the surface of a microcavity containing electronic ink, and irradiate and cure the film by using ultraviolet light, then remove the glass plate, and obtain a packaged microcup display window.

[0016] Further, in step one, the rotation speed of the planetary defoaming instrument is 1800-2000 r / min, and the defoaming time is 10-15 min.

[0017] Further, in step two, the thickness of the thin film is 4-6 μm.

[0018] Further, in step three, the ultraviolet light used for irradiation and curing has a wavelength of 320-400 nm and a power of 700-1000 W, and the irradiation time is 3-5 min.

[0019] Compared with the prior art, the electronic paper electrophoretic fluid packaging composition of the present application is a photocuring composition composed of a photocuring polyurethane resin, cyclodextrin, a photocuring agent and an active diluent. After the photocuring composition is uniformly mixed, a thin film is spin-coated on a glass plate, the surface of a microcavity filled with electronic ink is covered with the thin film on one side of the glass plate, and the thin film is cured into a film by irradiation with ultraviolet light. After the glass plate is removed, a packaged microcup display window is obtained. The thin film formed after the photocuring composition is cured is transparent, has high dielectric constant, strong polarity and high hydrophilicity, and has excellent mechanical flexibility. The thin film not only has good adhesion to the microcup substrate, but also does not react with and interact with the electrophoretic fluid in the microcup electronic paper display. The packaged microcup display window not only has stable performance, but also has high dielectric performance. The present application solves the problems of low movement rate of conductive particles of electronic paper, low refresh rate of display and slow response speed caused by the non-conductivity of the polymer of the packaging layer. The present application uses material blending and spin coating process to prepare the film at room temperature. The preparation method is simple, pollution-free, low in cost and easy to operate, avoids the complex physical and chemical processing technology, is non-toxic and harmless, friendly to the environment, and is extremely suitable for large-area popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The surface electron microscope image of the microcup display window packaged in Example 1.

[0021] Figure 2 The graph of the relationship between the dielectric constant and the frequency of the thin film prepared in Examples 1-5 of the present application.

[0022] Figure 3 The light transmittance curve of the thin film prepared in Examples 1-5 and Comparative Example 1 of the present application.

[0023] Figure 4 The response time comparison graph of the thin film prepared in Examples 1-5 of the present application. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0025] The present application provides an electronic paper electrophoretic fluid packaging composition with high dielectric performance, which comprises the following components by weight percentage: photocuring polyurethane resin 55-85%, cyclodextrin 1%-40%, photocuring agent 3%-5%, and active diluent 5%-10%.

[0026] The light-cured polymer prepolymer is a light-cured acrylate prepolymer, a light-cured polyurethane prepolymer or a light-cured epoxy resin prepolymer with a viscosity of 300-500 Pa / s; the cyclodextrin is α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin; and the reactive diluent is 1,6-hexanediol diacrylate.

[0027] Preferably, the light-cured polymer prepolymer is a light-cured polyurethane prepolymer with the structure of:

[0028]

[0029] R1, R2 and R3 are alkyl groups containing 1-6 carbon atoms.

[0030] For the polymer prepolymer, the longer the chain length, the greater the molecular weight, the stronger the polarity, the better the mechanical flexibility, and the better the adhesion to the micro-cup substrate, therefore, R1, R2 and R3 in the light-cured polyurethane prepolymer are preferably alkyl groups containing 6 carbon atoms.

[0031] Preferably, the mass percentage of the light-cured polyurethane resin to the cyclodextrin is 100:25. The light-cured composition using the above components has the highest dielectric constant, the best light transmittance and the fastest response speed.

[0032] The application also provides a packaging method of the electronic paper electrophoretic liquid packaging composition with high dielectric property, which comprises the following steps:

[0033] In step one, the light-cured polyurethane resin, the cyclodextrin and the reactive diluent are mixed with each other, and are uniformly mixed by alternately performing magnetic stirring and ultrasonic treatment, then the light-cured agent is added, and the mixed solution is degassed by using a planetary degassing instrument to remove the bubbles in the mixed solution; the rotation speed of the planetary degassing instrument is 1800-2000 r / min, and the degassing time is 10-15 min.

[0034] In step two, a certain amount of the mixed solution is taken to the center of a glass plate pretreated by a film calender, and a thin film is formed by using a spin coating method at room temperature; the thickness of the thin film is 4-6 μm.

[0035] In step three, the thin film of the glass plate is covered on the surface of a micro-cavity chamber containing electronic ink, and is irradiated by ultraviolet light with a wavelength of 320-400 nm and a power of 700-1000 W for 3-5 min to make it cured into a film, and then the glass plate is removed to obtain a packaged micro-cup display window.

[0036] The application is further described below in combination with specific examples and comparative examples. The structure of the light-cured polyurethane prepolymer is as follows:

[0037]

[0038] R1, R2, R3 are each alkyl groups containing 6 carbon atoms.

[0039] The photo-curing agent is 2-hydroxy-2-methyl propiophenone; the active diluent is 1,6-hexanediol diacrylate.

[0040] Example 1

[0041] The photo-curing polyurethane resin 100g, β-cyclodextrin 5g, photo-curing agent 5g, active diluent 10g are weighed. That is, the mass percentage of the photo-curing polyurethane resin and the cyclodextrin is 100:5, and the weight percentage of each component is calculated as follows: photo-curing polyurethane resin 83.3%, cyclodextrin 4.2%, photo-curing agent 4.2%, and active diluent 8.3%.

[0042] First, the photo-curing polyurethane resin, cyclodextrin, and active diluent are mixed with each other, and are uniformly mixed by alternating magnetic stirring and ultrasonic treatment. Then, the photo-curing agent is added, and the mixed solution is degassed by a planetary degassing instrument at 2000r / min for 10min to remove the bubbles in the mixed solution. Then, a certain amount of the mixed solution is taken to the center of a glass plate pretreated by a film calender, and a thin film is formed on the glass plate by a spin coating method at room temperature. The thin film has a thickness of 5μm. The thin film on one side of the glass plate is covered on the surface of a microcavity containing electronic ink, and is irradiated by ultraviolet light with a wavelength of 360nm and a power of 700W for 3min to cure the thin film into a film. Then, the glass plate is removed to obtain a microcup display window encapsulated.

[0043] Example 2

[0044] In this example, the photo-curing polyurethane resin 100g, β-cyclodextrin 10g, photo-curing agent 5g, and active diluent 10g are weighed. That is, the mass percentage of the photo-curing polyurethane resin and the cyclodextrin is 100:10, and the weight percentage of each component is calculated as follows: photo-curing polyurethane resin 80%, cyclodextrin 4%, photo-curing agent 4%, and active diluent 8%.

[0045] The other conditions are the same as those in Example 1.

[0046] Example 3

[0047] In this example, the photo-curing polyurethane resin 100g, β-cyclodextrin 15g, photo-curing agent 5g, and active diluent 10g are weighed. That is, the mass percentage of the photo-curing polyurethane resin and the cyclodextrin is 100:15, and the weight percentage of each component is calculated as follows: photo-curing polyurethane resin 76.9%, cyclodextrin 11.6%, photo-curing agent 3.8%, and active diluent 7.7%.

[0048] The other conditions are the same as those in Example 1.

[0049] Example 4

[0050] In this embodiment, 100g of photocuring polyurethane resin, 20g of β-cyclodextrin, 5g of photocuring agent and 10g of active diluent are weighed. That is, the mass percentage of photocuring polyurethane resin to cyclodextrin is 100:20, and the weight percentage of each component is calculated as follows: photocuring polyurethane resin 74.1%, cyclodextrin 14.8%, photocuring agent 3.7%, and active diluent 7.4%.

[0051] The other aspects are the same as those of Example 1.

[0052] Example 5

[0053] In this embodiment, 100g of photocuring polyurethane resin, 25g of β-cyclodextrin, 5g of photocuring agent and 10g of active diluent are weighed. That is, the mass percentage of photocuring polyurethane resin to cyclodextrin is 100:25, and the weight percentage of each component is calculated as follows: photocuring polyurethane resin 71.4%, cyclodextrin 17.9%, photocuring agent 3.6%, and active diluent 7.1%.

[0054] The other aspects are the same as those of Example 1.

[0055] Comparative Example 1

[0056] In this comparative example, 100g of photocuring polyurethane resin, 5g of photocuring agent and 10g of active diluent are weighed. That is, no cyclodextrin is used in the photocuring composition.

[0057] The surface electron microscope image of the encapsulated micro-cup display window of Example 1 of the present application is shown in Figure 1 The thickness of the photocured film is uniform.

[0058] The graph of the relationship between the dielectric constant and the frequency of the film prepared in Examples 1-5 is shown in Figure 2 The graph of the transmittance of the film prepared in Examples 1-5 and Comparative Example 1 is shown in Figure 3 The comparative graph of the response time of the film prepared in Examples 1-5 is shown in Figure 4 The performance comparison table of the film prepared in Examples 1-5 and Comparative Example is shown in Table 1.

[0059] It can be seen that although the light transmittance of the films prepared in Examples 1-5 is not as good as that of Comparative Example 1, the dielectric constant of the films prepared in Examples 1-5 is higher than that of Comparative Example 1, the response time of the films prepared in Examples 1-5 is less than that of Comparative Example 1, that is, the response speed of the films prepared in Examples 1-5 is higher than that of Comparative Example 1. And with the increase of the weight ratio of cyclodextrin in Examples 1-5, the dielectric constant of the prepared film is higher, the light transmittance is lower, the response time is smaller, and the response speed is faster. The light-cured composition with a mass ratio of light-cured polyurethane resin to cyclodextrin of 100:25 is used to obtain a film with the highest dielectric constant, the fastest response speed, and a good light transmittance.

[0060] Table 1 Performance comparison table of films prepared in Examples 1-5 and Comparative Example

[0061] Item Transparency (550 nm) Response time (ms) Dielectric constant (1 KHZ) Example 1 87.2 122 5.1 Example 2 86.8 113 5.8 Example 3 84.5 104 6.8 Example 4 83.1 96 7.6 Example 5 83.2 81 8.1 Comparative Example 1 91.6 165 4.8

[0062] It is found that increasing the dielectric constant of the polymer layer can increase the response speed of the particles. The reason is that the cup bottom and the encapsulation layer are in close contact with the electrode surface. After electrification, under the action of the electric field, the polymer is polarized, the side in contact with the electrode generates induced electrons opposite to the electrode, and the side close to the electrophoretic fluid generates induced charges the same as the electrode. The surface of these charged polymers is equivalent to an extended electrode, which attracts particles with opposite charges, thus increasing the movement rate of the particles. Therefore, the higher the dielectric constant of the electronic paper electrophoretic fluid encapsulation composition, that is, the higher the dielectric performance of the encapsulated micro-cup display window formed by curing the film, the faster the conductive particles of the prepared electronic paper device exhibit the response speed.

[0063] The film formed by curing the electronic paper electrophoretic fluid encapsulation composition of the present application is transparent, has high dielectric constant, strong polarity, high hydrophilicity, and excellent mechanical flexibility. Not only does it have good adhesion to the micro-cup substrate, but it also does not react with or interact with the electrophoretic fluid in the micro-cup electronic paper display. The encapsulated micro-cup display window not only has stable performance, but also has high dielectric performance. According to the above examples, the dielectric constant of the film of the present application can reach more than 8 compared with pure light-cured resin, which has outstanding technical effects and significant progress.

[0064] The above-described examples are only used to illustrate the technical solutions of the present application, but not to limit them. Although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can modify the technical solutions described in the foregoing examples, or make equivalent substitutions for part of the technical features. These modifications or substitutions do not change the essence of the corresponding technical solutions, and are within the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A packaging method of an electronic paper electrophoretic fluid packaging composition having high dielectric properties, characterized by, It comprises the following steps: Step one, weigh the light-cured polymer prepolymer, cyclodextrin, active diluent, mix them together, and mix them uniformly by alternating magnetic stirring and ultrasonic, then add light-cured agent, and then use planetary defoaming instrument to remove bubbles in the mixed solution; The high dielectric performance electronic paper electrophoretic liquid packaging composition comprises the following components by weight percentage: light-cured polymer prepolymer 83.3%, cyclodextrin 4.2%, light-cured agent 4.2%, and active diluent 8.3%; Or light-cured polymer prepolymer 80%, cyclodextrin 8%, light-cured agent 4%, and active diluent 8%; Or light-cured polymer prepolymer 76.9%, cyclodextrin 11.6%, light-cured agent 3.8%, and active diluent 7.7%; or light-cured polymer prepolymer 74.1%, cyclodextrin 14.8%, light-cured agent 3.7%, and active diluent 7.4%; or light-cured polymer prepolymer 71.4%, cyclodextrin 17.9%, light-cured agent 3.6%, and active diluent 7.1%; The cyclodextrin is α-cyclodextrin, β-cyclodextrin, or γ-cyclodextrin; The light-cured polymer prepolymer is a light-cured polyurethane prepolymer with a viscosity of 300-500 Pa·s, and the structure of the light-cured polymer prepolymer is: Wherein, R1, R2, R3 are alkyl groups containing 1-6 carbon atoms; Step two, take a certain amount of mixed solution to the center of the pretreated glass plate in the film applicator, and use the spin coating method at room temperature to spin coat a thin film; Step three, cover the glass plate thin film on one side on the surface of the microcavity containing electronic ink, and use ultraviolet light to irradiate and cure into a film, then take off the glass plate, and get the packaged microcup display window.

2. The encapsulation method of the electronic paper electrophoretic fluid encapsulation composition with high dielectric properties according to claim 1, characterized in that: In step one, the rotation speed of the planetary defoaming instrument is 1800-2000 r / min, and the defoaming time is 10-15 min.

3. The encapsulation method of the electronic paper electrophoretic fluid encapsulation composition with high dielectric property according to claim 2, characterized in that: In step two, the thickness of the thin film is 4-6 μm.

4. The encapsulation method of the electronic paper electrophoretic fluid encapsulation composition with high dielectric property according to claim 3, characterized in that: In step three, the ultraviolet light irradiation curing uses ultraviolet light with a wavelength of 320-400 nm and a power of 700-1000 W for irradiation for 3-5 min.

5. The method of encapsulating the high dielectric electronic paper electrophoretic fluid encapsulation composition according to claim 1, characterized in that: The active diluent is 1,6-hexanediol diacrylate.

6. The method of encapsulating the high dielectric performance electronic paper electrophoretic fluid encapsulation composition according to claim 1, characterized in that: The mass percentage of the light-cured polymer prepolymer and cyclodextrin is 100:25.

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