CN118546310A - An electronic paper electrophoretic liquid packaging composition with high dielectric properties and packaging method thereof - Google Patents

Abstract

The invention provides a high dielectric property electronic paper electrophoresis liquid packaging composition and a packaging method thereof, wherein the electronic paper electrophoresis liquid packaging composition is a photocuring composition consisting of photocuring polyurethane resin, cyclodextrin, a photocuring agent and an active diluent, after uniformly mixing the photo-curing composition, spin-coating a film on a glass plate, covering one side of the film of the glass plate on the surface of a micro-chamber filled with electronic ink, curing the film by ultraviolet irradiation, and taking down the glass plate to obtain the packaged micro-cup display window. The film formed by curing the photo-curing composition is transparent, has high dielectric constant, strong polarity and high hydrophilicity, has excellent mechanical flexibility, and has stable performance and high dielectric property after packaging. The preparation method provided by the invention is simple, pollution-free, low in cost, easy to operate, nontoxic and harmless, environment-friendly and extremely suitable for large-area popularization and application.

Description

An electronic paper electrophoretic liquid packaging composition with high dielectric properties and packaging method thereof

Technical Field

The invention belongs to the technical field of polymer composite materials and relates to an electrophoretic liquid packaging composition and a packaging method thereof.

Background Art

Electronic paper, also known as digital paper, is an ultra-thin and ultra-light display screen, which can be understood as a "display that is as thin as paper, soft, and rewritable." Figuratively speaking, electronic paper is a thin film, and the layer of charged material "coated" on the film is electronic ink. Compared with traditional paper or flat display, electronic paper has the advantages of high resolution, high contrast, low power consumption, and bistable state. It has a wide range of application prospects in the market. It can not only be used in outdoor billboards and wearable device displays, but also has broad application prospects in the medical and health or military fields. In order to realize the display of electronic paper, a lower driving voltage, a faster response time, and a higher brightness and contrast are often required. For microcup electronic paper, firstly, the electronic ink containing conductive particles is injected into the microcup array, and then the cup mouth is sealed. Then, two electrodes are placed on the upper and lower surfaces of the microcup array containing electronic ink, and voltage is applied to drive the black and white particles to move up and down to achieve the display effect.

The refresh rate and driving voltage of the electronic paper display are closely related to the material and structure of the encapsulation layer/microcup array. Part of the driving voltage applied between the two electrodes is allocated to the bottom of the microcup, part to the encapsulation layer, and the other part to the electrophoretic fluid. The encapsulation layer is composed of highly transparent polymers. Since the polymer is not conductive, under the rated driving voltage, the voltage share acting on both ends of the electrophoretic fluid is reduced, the movement rate of the conductive particles in the electronic paper is reduced, the refresh rate of the display is low, and the response speed is slow.

Summary of the invention

In order to solve the problem that the encapsulation layer polymer is not conductive, resulting in a reduced movement rate of the electronic paper conductive particles, a low display refresh rate and a slow response speed, the present invention provides an electronic paper electrophoretic liquid encapsulation composition with high dielectric properties and a encapsulation method thereof.

The invention provides an electronic paper electrophoretic liquid encapsulation composition with high dielectric properties, comprising 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 α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin.

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.

Preferably, the photocurable polymer prepolymer is a photocurable polyurethane prepolymer, and its structure is:

Wherein, R is an alkyl group containing 1 to 6 carbon atoms.

Preferably, the active diluent is 1,6-hexanediol diacrylate. This is because the active diluent uses monomers containing more functional groups, which not only increases the reaction activity but also gives the cured film a cross-linked structure; monofunctional monomers can only obtain linear polymers after polymerization, while multifunctional monomers can obtain a highly cross-linked network.

Preferably, the mass percentage of the photocurable polyurethane resin to cyclodextrin is 100:25. The photocurable composition of the above components can obtain a film with the highest dielectric constant, the fastest response speed, and a good light transmittance.

The present invention also provides a method for encapsulating an electronic paper electrophoretic liquid encapsulation composition with high dielectric properties, comprising the following steps:

Step 1, weighing a photocurable polyurethane resin, cyclodextrin, and an active diluent, mixing them with each other, and mixing them evenly by alternating magnetic stirring and ultrasound, adding a photocuring agent, and then degassing with a planetary degasser to remove bubbles in the mixed solution;

Step 2: Take a certain amount of the mixed solution to the center of the pre-treated glass plate in the coating machine, and spin-coat it into a thin film at room temperature by spin coating;

Step 3: Cover one side of the glass plate film on the surface of the micro-chamber containing the electronic ink, and cure it with ultraviolet light to form a film, remove the glass plate, and obtain a packaged micro-cup display window.

Furthermore, in the step 1, the rotation speed of the planetary deaerator is 1800-2000r/min, and the deaeration time is 10-15min.

Furthermore, in the step 2, the film thickness is 4-6 μm.

Furthermore, in the step three, the ultraviolet light curing is performed by irradiating with ultraviolet light of 320-400nm wavelength and 700-1000W power for 3-5 minutes.

Compared with the prior art, the electronic paper electrophoretic liquid encapsulation composition of the present invention is a photocurable composition composed of a photocurable polyurethane resin, cyclodextrin, a photocuring agent, and a reactive diluent. After the photocurable composition is evenly mixed, it is spin-coated on a glass plate into a thin film, and one side of the glass plate film is covered on the surface of a micro-chamber containing electronic ink, and cured by ultraviolet light to form a film. After removing the glass plate, a packaged micro-cup display window can be obtained. The film formed by the photocurable composition of the present invention after curing is transparent, has a high dielectric constant, strong polarity, high hydrophilicity, and excellent mechanical flexibility. It not only has good adhesion to the micro-cup substrate, but also does not chemically react or interact with the electrophoretic liquid in the micro-cup electronic paper display. The encapsulated micro-cup display window not only has stable performance, but also has high dielectric properties. The present invention solves the problem that the current encapsulation layer polymer is not conductive, resulting in a reduced movement rate of the electronic paper conductive particles, a low refresh rate of the display, and a slow response speed. The present invention adopts material blending and spin coating process to prepare the film at room temperature. The preparation method is simple, pollution-free, low-cost, easy to operate, avoids the complex process of physical and chemical processing, is non-toxic and harmless, is environmentally friendly, and is extremely suitable for large-scale promotion and application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a surface electron microscope image of the encapsulated microcup display window of Example 1.

FIG. 2 is a graph showing the relationship between the dielectric constant and frequency of the films prepared in Examples 1-5 of the present invention.

FIG3 is a light transmittance curve diagram of the films prepared in Examples 1-5 of the present invention and Comparative Example 1.

FIG. 4 is a comparison chart of the response times of the films prepared in Examples 1-5 of the present invention.

DETAILED DESCRIPTION

In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, this application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

The invention provides an electronic paper electrophoretic liquid encapsulation composition with high dielectric properties, comprising the following components in percentage by weight: 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 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; the cyclodextrin is α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin; and the active diluent is 1,6-hexanediol diacrylate.

Preferably, the photocurable polymer prepolymer is a photocurable polyurethane prepolymer, and its structure is:

Wherein, R ₁ , R ₂ and R ₃ are alkyl groups containing 1 to 6 carbon atoms.

For the polymer prepolymer, the longer the chain length, the larger the molecular weight, the stronger the polarity, the best mechanical flexibility, and the better the adhesion to the microcup substrate. Therefore, R ₁ , R ₂ , and R ₃ in the photocurable polyurethane prepolymer are preferably alkyl groups containing 6 carbon atoms.

Preferably, the mass percentage of the photocurable polyurethane resin to the cyclodextrin is 100:25. The photocurable composition of the above components can obtain a film with the highest dielectric constant, the best light transmittance and the fastest response speed.

The present invention also provides a method for encapsulating an electronic paper electrophoretic liquid encapsulation composition with high dielectric properties, the steps of which are as follows:

Step 1, weighing a photocurable polyurethane resin, cyclodextrin, and an active diluent, mixing them with each other, and mixing them evenly by alternating magnetic stirring and ultrasound, adding a photocuring agent, and then degassing with a planetary deaerator to remove bubbles in the mixed solution; the rotation speed of the planetary deaerator is 1800-2000r/min, and the degassing time is 10-15min;

Step 2: Take a certain amount of the mixed solution to the center of the pre-treated glass plate in the coating machine, and spin-coat it into a thin film at room temperature by spin coating; the film thickness is 4-6μm;

Step 3: Cover one side of the glass plate film on the surface of the micro-chamber containing electronic ink, irradiate it with ultraviolet light with a wavelength of 320-400nm and a power of 700-1000W for 3-5 minutes to solidify it into a film, remove the glass plate, and obtain a packaged micro-cup display window.

The present invention is further described below in conjunction with specific examples and comparative examples. Wherein, the structure of the photocurable polyurethane prepolymer is:

Wherein, R ₁ , R ₂ and R ₃ are all alkyl groups containing 6 carbon atoms.

The photocuring agent is 2-hydroxy-2-methylpropiophenone; the active diluent is 1,6-hexanediol diacrylate.

Example 1

Weigh 100g of photocurable polyurethane resin, 5g of β-cyclodextrin, 5g of photocuring agent, and 10g of active diluent. That is, the mass percentage of photocurable polyurethane resin and cyclodextrin is 100:5. After calculation, the weight percentages of each component are: 83.3% of photocurable polyurethane resin, 4.2% of cyclodextrin, 4.2% of photocuring agent, and 8.3% of active diluent.

Firstly, photocurable polyurethane resin, cyclodextrin and active diluent are mixed with each other, and after being mixed evenly by alternating magnetic stirring and ultrasound, photocuring agent is added, and then a planetary degasser is used to degas at 2000r/min for 10 minutes to remove bubbles in the mixed solution; then a certain amount of the mixed solution is taken to the center of a glass plate pretreated in a coating machine, and a thin film is spin-coated at room temperature by spin coating, and the film thickness is 5μm; one side of the glass plate film is covered on the surface of a micro-chamber containing electronic ink, and irradiated under ultraviolet light with a wavelength of 360nm and a power of 700W for 3 minutes to solidify it into a film, and the glass plate is removed to obtain a packaged microcup display window.

Example 2

In this embodiment, 100 g of photocurable polyurethane resin, 10 g of β-cyclodextrin, 5 g of photocuring agent, and 10 g of active diluent are weighed. That is, the mass percentage of photocurable polyurethane resin and cyclodextrin is 100:10. After calculation, the weight percentages of the components are: 80% of photocurable polyurethane resin, 4% of cyclodextrin, 4% of photocuring agent, and 8% of active diluent.

The rest is the same as in Example 1.

Example 3

In this embodiment, 100 g of photocurable polyurethane resin, 15 g of β-cyclodextrin, 5 g of photocuring agent, and 10 g of active diluent are weighed. That is, the mass percentage of photocurable polyurethane resin and cyclodextrin is 100:15. After calculation, the weight percentages of the components are: 76.9% of photocurable polyurethane resin, 11.6% of cyclodextrin, 3.8% of photocuring agent, and 7.7% of active diluent.

The rest is the same as in Example 1.

Example 4

In this embodiment, 100 g of photocurable polyurethane resin, 20 g of β-cyclodextrin, 5 g of photocuring agent, and 10 g of active diluent are weighed. That is, the mass percentage of photocurable polyurethane resin and cyclodextrin is 100:20. After calculation, the weight percentages of the components are: 74.1% of photocurable polyurethane resin, 14.8% of cyclodextrin, 3.7% of photocuring agent, and 7.4% of active diluent.

The rest is the same as in Example 1.

Example 5

In this embodiment, 100 g of photocurable polyurethane resin, 25 g of β-cyclodextrin, 5 g of photocuring agent, and 10 g of active diluent are weighed. That is, the mass percentage of photocurable polyurethane resin and cyclodextrin is 100:25. After calculation, the weight percentages of the components are: 71.4% of photocurable polyurethane resin, 17.9% of cyclodextrin, 3.6% of photocuring agent, and 7.1% of active diluent.

The rest is the same as in Example 1.

Comparative Example 1

In this comparative example, 100 g of photocurable polyurethane resin, 5 g of photocuring agent, and 10 g of reactive diluent were weighed, that is, cyclodextrin was not used in the photocurable composition.

The surface electron microscope image of the packaged microcup display window of Example 1 of the present invention is shown in FIG1 , and the thickness of the film after light curing is uniform.

The relationship between the dielectric constant and frequency of the films prepared in Examples 1-5 of the present invention is shown in Figure 2, the transmittance curves of the films prepared in Examples 1-5 and Comparative Example 1 are shown in Figure 3, and the response time comparison of the films prepared in Examples 1-5 is shown in Figure 4. The performance comparison table of the films prepared in Examples 1-5 and Comparative Example is shown in Table 1.

It can be seen that: although the light transmittance of the films prepared in Examples 1-5 of the present invention is not as good as that of Comparative Example 1, the dielectric constants of the films prepared in Examples 1-5 of the present invention are higher than that of Comparative Example 1, and the response time of the films prepared in Examples 1-5 is shorter 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 as the weight ratio of cyclodextrin in Examples 1-5 increases, the higher the dielectric constant of the prepared film, the lower the light transmittance, the shorter the response time, and the faster the response speed. The photocurable composition with a mass percentage of photocurable polyurethane resin and cyclodextrin of 100:25 is used, and the obtained film has the highest dielectric constant, the fastest response speed, and the light transmittance also reaches a good level.

Table 1 Comparison of the properties of the films prepared in Examples 1-5 and Comparative Examples

project Light transmittance (550nm) Response time (ms) Dielectric constant (1KHZ) 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

The study found that increasing the dielectric constant of the polymer layer can increase the response speed of the particles. The reason is that the bottom of the cup and the encapsulation layer are in close contact with the electrode surface respectively. After power is turned on, under the action of the electric field, the polymer is polarized, and the side in contact with the electrode produces induced electrons opposite to the electrode, while the side close to the electrophoretic liquid produces the same induced charge as the electrode. These charged polymer surfaces are equivalent to extended electrodes, attracting particles with opposite charges, thereby increasing the movement rate of the particles. Therefore, the higher the dielectric constant of the electronic paper electrophoretic liquid encapsulation composition, that is, the higher the dielectric properties of the cured film, that is, the encapsulated microcup display window, the faster the response speed of the conductive particles of the prepared electronic paper device will be.

The film formed by the electronic paper electrophoretic liquid encapsulation composition of the present invention after curing is transparent, has a high dielectric constant, strong polarity, high hydrophilicity, and excellent mechanical flexibility. It not only has good adhesion to the microcup substrate, but also does not chemically react or interact with the electrophoretic liquid in the microcup electronic paper display. The encapsulated microcup display window not only has stable performance, but also has high dielectric properties. As verified by the above examples, the dielectric constant of the film of the present invention can reach up to 8 or more compared with pure photocurable resin, which has outstanding technical effects and significant progress.

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 (9)

1. An electronic paper electrophoretic liquid encapsulation composition with high dielectric properties, characterized in that it comprises the following components in weight percentage: 55-85% of photocurable polymer prepolymer, 1%-40% of cyclodextrin, 3%-5% of photocuring agent, and 5%-10% of active diluent; the cyclodextrin is α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin. 2. The electronic paper electrophoretic liquid encapsulation composition with high dielectric properties according to claim 1, characterized in that 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. 3. The electronic paper electrophoretic liquid encapsulation composition with high dielectric properties according to claim 2, characterized in that: the photocurable polymer prepolymer is a photocurable polyurethane prepolymer, and its structure is: Wherein, R is an alkyl group containing 1 to 6 carbon atoms. 4 . The electronic paper electrophoretic liquid encapsulation composition with high dielectric properties according to claim 1 , wherein the active diluent is 1,6-hexanediol diacrylate. 5. The electronic paper electrophoretic liquid encapsulation composition with high dielectric properties according to claim 2, characterized in that the mass percentage of the photocurable polyurethane resin and cyclodextrin is 100:25. 6. A method for encapsulating the high dielectric performance electronic paper electrophoretic liquid encapsulation composition according to any one of claims 1 to 5, characterized in that it comprises the following steps: Step 1, weighing a photocurable polyurethane resin, cyclodextrin, and an active diluent, mixing them with each other, and mixing them evenly by alternating magnetic stirring and ultrasound, adding a photocuring agent, and then degassing with a planetary degasser to remove bubbles in the mixed solution; Step 2: Take a certain amount of the mixed solution to the center of the pre-treated glass plate in the coating machine, and spin-coat it into a thin film at room temperature by spin coating; Step 3: Cover one side of the glass plate film on the surface of the micro-chamber containing the electronic ink, and cure it with ultraviolet light to form a film, remove the glass plate, and obtain a packaged micro-cup display window. 7. The encapsulation method of the electronic paper electrophoretic liquid encapsulation composition with high dielectric properties according to claim 6, characterized in that: in the step 1, the rotation speed of the planetary degassing instrument is 1800-2000r/min, and the degassing time is 10-15min. 8. The packaging method of the electronic paper electrophoretic liquid packaging composition with high dielectric properties according to claim 7, characterized in that: in the step 2, the film thickness is 4-6 μm. 9. The encapsulation method of the electronic paper electrophoretic liquid encapsulation composition with high dielectric properties according to claim 8, characterized in that: in the step 3, the ultraviolet light curing is performed under ultraviolet light with a wavelength of 320-400nm and a power of 700-1000W for 3-5 minutes.