KR20080107864A - Process for producing a micrcapsule for color electronic ink - Google Patents

Abstract

A manufacturing method of a color polymethyl metacrylate microcapsule is provided to be used in order to implement color electronic paper using an electrophoretic deposition and to have clear color and an electric charge. A manufacturing method of a color polymethyl metacrylate microcapsule comprises steps of: manufacturing color polymethyl methacylate particles by dying the polymethyl methacylate particles using disperse dyes; coating titania in the color polymethyl methacylate particles by absorbing and reacting the color polymethyl methacylate particles and a titanium butoxide; manufacturing a core material by reacting PMMA nano particles coated by the titania with a charge control agent; and obtaining a color PMMA microcapsule by adding the core material into a mixed solution including a gelatin-B and an arabian gum and being capsulated by a coacervation method.

Description

Process for producing a microcapsule for color electronic ink

1 is a schematic diagram showing a process of adsorbing titania particles to colored polymethyl methacrylate (PMMA) particles of the present invention.

Figure 2 shows a transmission electron microscope (TEM) image of the color polymethyl methacrylate (PMMA) microcapsules prepared according to the present invention.

Figure 3 shows a TEM image of colored polymethylmethacrylate (PMMA) microcapsules coated with polyvinyl alcohol on ITO glass prepared according to the present invention.

The present invention relates to a method for producing multicolored microcapsules capable of realizing color on electronic paper, in particular a dyeing method.

In general, an electronic paper display is a display device having the advantages of paper and a modern display, and can be applied to a display such as an electronic book, an electronic newspaper, an electronic magazine, and an information display medium of a mobile communication device.

The implementation of electronic paper can be classified into paper display technology based on existing display technology such as liquid crystal and paper display technology based on new technology having paper texture. Current representative electronic papers include twist ball type displays using electrostatic charge-filled hemispherical twist balls (called "Gyricon" balls), electrophoretic displays using electrophoresis and microcapsules, and cholesterol liquid crystals. There are three types of cholesteric liquid crystal displays used.

The Gyricon Display was developed by the Xerox Palo Alto Research Center (PARC) in 1975. This type of display has millions of tiny balls dispersed in oil-filled elastomer matrix cavities between transparent plastic sheets on which indium-tin oxide (ITO) electrodes are formed. Silver is black that absorbs light and the other is white that reflects light, and the white and black areas of the ball have opposite charges. Since the polarities of the two regions are opposite, the ball rotates due to the polarity of the electric field applied from the outside to create a black / white image. At this time, the specific gravity of the ball and oil is almost the same, so when the ball is positioned by the electric field, the ball does not move easily. ). The light reflection efficiency for white light is about 20%, which is about half of newspapers, and the gray image can be observed by partial rotation of the ball at a medium driving voltage, and the thin zircon display layer is very stable. More than 3 million runs are possible. However, the biggest problem with the Zircon display is that there is no voltage threshold in the phase change of the ball, which means that the ball can change the phase of the ball to some degree, which actually limits the resolution and the pixels. As the number increases, the field adjustment of the display becomes very complicated.

Electrophoresis can be classified into a particle type and a capsule type. In the particle type, the charged particles are dispersed in a colored colloidal suspension, and their electrophoresis is a basic operation principle. In other words, when a positive voltage is applied, the negatively charged particles move to the surface to display the color of the particles. When a negative voltage is applied, the particles move in the opposite direction to display the color of the fluid. When the particles do not move in the fluid, they exhibit bistable stability. In the case of particulates, cohesion of particulates was a major obstacle to commercialization. In 1997, E-ink used a microcapsule to solve this problem. In order to solve the problem caused by the particle shape, the capsule-type microcapsules containing 200-300 μm in diameter containing ink fine particles and colored dielectric fluids are prepared and mixed with a binder to be placed between upper and lower transparent electrodes. When a positive voltage is applied, the negatively charged ink fine particles move to the surface to display the color of the fine particles, and when a negative voltage is applied, the fine ink particles move downward to see the color of the fluid. At this time, by adjusting the specific gravity of the microparticles and the dielectric fluid of the dispersion medium to be almost the same, a mixture in which the particles are uniformly dispersed, and a transparent capsule is coated to obtain a stable capsule. The microcapsule electrophoretic display has the characteristics closest to the paper texture, and the gray scale can be realized by controlling the movement of particles by controlling the driving voltage, and can exhibit a much higher resolution than the silicon display. However, like the Zircon display, E-ink's encapsulation, based on the passive driving principle, has no voltage threshold, which limits its resolution.

The cholesteric liquid crystal display was developed by Kent Display in 1993 and can be viewed outdoors using a cholesteric liquid crystal capable of expressing color by selectively reflecting light of different wavelengths. It is a display. A voltage is applied between the two electrodes containing the cholesteric liquid crystal to switch between a transparent state that does not reflect light and a state that reflects light, and each of the R, G, and B liquid crystals in a stacked structure. Colors can be expressed by selectively reflecting colors or by combining them transparently. The cholesteric liquid crystal display consumes a lot of power, but if the image is not deleted, the display has a storage capability of maintaining the image on the display for at least one year, and in particular, a video display is possible.

However, the electronic paper using the conventional liquid crystal has advantages of ease of display / erase, color implementation, and quick response speed. However, many challenges remain to be solved, such as ease of viewing of paper texture and minimizing power consumption.

The present invention is to provide a color polymethyl methacrylate (hereinafter referred to as "PMMA") microcapsules that can be used for the implementation of color electronic paper using electrophoresis method. It is characterized by the fact that the colored particles are made of polymer and made with inorganic titanium oxide (TiO ₂ ).

The present invention is also encapsulated with gelatin type B and gum arabic after mixing colored PMMA particles and TiO ₂ nanoparticles prepared using PMMA particles and disperse dyes. It is intended to provide a method of making colored PMMA microcapsules.

In order to achieve the above object, according to a preferred embodiment of the present invention, the method comprises the steps of: (a) dyeing the PMMA particles with a disperse dye to produce colored PMMA nanoparticles; (b) adsorbing the color PMMA nanoparticles with titanium butoxide to coat titania on the color PMMA nanoparticles; (c) reacting the PMMA nanoparticles coated with titania with a charge control agent to prepare a core material; And (d) adding the core material to a mixed solution containing gelatin-B and gum arabic to encapsulate it with a coacervation method to obtain color PMMA microcapsules. This is provided.

According to another suitable embodiment of the present invention, the mixed solution in the step (d) preferably contains a surfactant cetyltrimethylammonium bromide (cetyltrimethylammonium bromide).

According to another suitable embodiment of the present invention, the titania particles are made of a core material consisting of polymethylmethacrylate particles dyed with a disperse dye deposited on the surface, and a wall material including gelatin-B and gum arabic. Colored polymethyl methacrylate microcapsules are provided.

Hereinafter, the present invention will be described in more detail.

Color PMMA microcapsules of the present invention comprises the steps of (a) dyeing the PMMA particles with a disperse dye to prepare colored PMMA particles; (b) adsorbing the colored PMMA particles and titanium butoxide to coat the titania on the colored PMMA particles; (c) reacting the PMMA nanoparticles coated with titania with a charge control agent to produce a core material; And (d) adding the shim material to a mixed solution containing gelatin-B and gum arabic to encapsulate it with a coacervation method to obtain colored PMMA microcapsules.

1 is a schematic diagram showing a process of adsorbing a titania precursor 2 to colored PMMA particles 1 of the present invention. The monodisperse polymer colloidal particles (1) prepared according to the present invention, that is, a titanium oxide precursor (2) was deposited on the surface of the PMMA particles (1) by an adsorption reaction between positively charged color PMMA particles and titanium butoxide. The gel reaction uniformly deposits titania on the colored PMMA particles.

Monodisperse PMMA colloidal particles are prepared by addition and polymerization of an ionic initiator, monomer, ionic monomer and crosslinking agent, followed by lyophilization. In this case, the polymerization may use an emulsion polymerization method in which no surfactant is added. 2,2'-azobis (2-methylpropionamidine) dihydrochloride (hereinafter abbreviated as "AIBA") as an ionic initiator, methyl methacrylate (hereinafter abbreviated as "MMA") as a monomer, [2- (methacyloxy) ethyl] trimethylammonium chloride (hereinafter abbreviated as "MOTAC") was used as the ionic monomer, and ethylene glycol dimethacrylate (hereinafter abbreviated as "EGDMA") was used as a crosslinking agent. .

The monodisperse polymer colloidal nanoparticles may be uniformly produced in different sizes of about 30 nm to 500 nm depending on the amount of the ionic monomer added. Therefore, the amount of ionic monomer added is adjusted according to the desired particle size. The MOTAC used as the ionic monomer used in the present invention charges the surface of the prepared nanoparticles, controls the size and charge density of the nanoparticles, and improves stability. Although the addition amount of MOTAC which is an ionic monomer is not specifically limited, It is preferable to use in the range of 0.1-1 g.

The polymerization temperature is 60 to 80 ° C, preferably 70 ° C, and the polymerization time is 10-30 hours, preferably 20 hours. The prepared nanoparticles are charged because they use an emulsion-free emulsion polymerization method.

Disperse dyes used for dyeing fibers were dyed by hydrogen bonds or van der Waals interactions, and thus the fibers were dyed. The monodisperse PMMA colloidal particles were dyed with disperse dyes to prepare colored PMMA particles. The dyeing of PMMA particles is performed by adding a dye to a solution in which PMMA particles are dispersed, and dyeing the water: dispersant with a dye solution having a weight ratio of 5 to 40: 1. Since the dyeing method using a disperse dye is performed at a high temperature of about 80 to 125 ℃, the degree of crosslinking should be adjusted in consideration of the stability of the PMMA particles during the dyeing process. In the present invention, the content of the crosslinking agent is preferably added in an amount of 4-6% by weight based on the monomer, and more preferably 5% by weight, for proper degree of crosslinking. The crosslinking agent can be suitably used as long as it is conventionally used in this field.

Organic-inorganic nanoparticles are prepared by depositing a titania precursor on the surface of the polymer to the prepared colored PMMA particles. The structure of the titania precursor used in the present invention is an anatase type, and the titanium butoxide is dissolved in an ethanol solution containing a stabilizer. The titania precursor is uniformly deposited to a thickness of 25 nm to 35 nm on the surface of the colored PMMA particles through hydrolysis and condensation reaction as in Equation 1 below.

[Equation 1]

PMMA particles coated with titania are first introduced into a mixed oil having a halocarbon and isopar G (isopar-G) in a weight ratio of 17:13, and then dispersed by ultrasonic waves. In addition, as the charge control agent, the brand name OLOA 1200 (polybutene succinimide) and BYK-140 were added to prepare a shim material. Charge control agents OLOA 1200 and BYK-140 are preferably used less than 0.1g each.

The microcapsules are made of a shell material by crosslinking the prepared shim material with gelatin-B and glutaraldehyde. The prepared shim material is added to a solution in which cetyltrimethylammonium bromide, which is a surfactant, is added to the mixed solution obtained by mixing and stirring gelatin-B and arabic rubber, and is collected by the surfactant. The collected shim material is prepared in microcapsules by crosslinking of additionally added crosslinking agent glutaraldehyde and gelatin-B by a coacervation method. The TEM image of the prepared colored PMMA microcapsules is shown in FIG. 2. The prepared color PMMA microcapsules are coated with ITO glass with polyvinyl alcohol and driven by applying electricity. TEM images of microcapsules coated with polyvinyl alcohol are shown in FIG. 3.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the embodiments according to the present invention can be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. do.

Example

Example 1

PMMA  Preparation of Particles

0.25 g of AIBA as an ionic initiator, 10 g of PMMA as a monomer, 100 ml of water, 1 g of [2- (methacyloxy) ethyl] trimethylammonium chloride (hereinafter abbreviated as MOTAC) as an ionic monomer, and 1 g of EGDMA as a crosslinking agent were added thereto. Polymerized. A 250 ml round flask equipped with a stirrer, reflux condenser and nitrogen injection system was used and AIBA initiator was added to the reactor with stirring at 300 rpm. Then, the polymerization was carried out at 70 ° C. for 11 hours. After the polymerization, the particles were purified by centrifugation / redispersion three times or more in distilled water. Finally lyophilized to obtain PMMA particles.

PMMA  Dyeing of particles

0.72 g of a dispersion dye was dispersed in 90 ml of an aqueous solution in which 9 g of PMMA particles were dispersed, and then adjusted to pH 4.5 with an aqueous 30 wt% acetic acid solution. In a 250 ml round flask, the dye was first added to the solution in which the particles were dispersed, and the pH of the solution was adjusted with an aqueous 30% acetic acid solution. After the temperature was raised to 110 ° C. at a rate of 1 ° C./min near pH 4.5, the temperature was maintained for 1 hour and dyed, and the temperature of the dye solution was lowered at room temperature. The stained particles were washed by centrifugation with water and lyophilized.

Preparation of Shim Materials

Halocarbon (Halocarbon) / isopaa-G was mixed in a weight ratio of 17:13 to prepare 9g of oil, and the colored PMMA nanoparticles and TiO ₂ particles prepared above were added to the oil and mixed. Then, disperse ultrasonically for 10 minutes. Simul material was prepared by further adding 0.08 g of OLOA 1200 and 0.07 g of BYK140.

Preparation of Microcapsules

33g of 3% by weight gelatin-B solution was prepared by mixing gelatin-B 0.99g and distilled water 30.01g. In addition, a mixture of 1.2 g of gum arabic and 38.8 g of distilled water was used to prepare 40 g of gum arabic at 3 wt%. The prepared gelatin-B solution and the gum arabic solution were mixed for 10 minutes at a rotational speed of 450 rpm. 0.2 g of cetyltrimethylammonium bromide was dispersed in 40 g of distilled water, and then poured into a solution in which the gelatin-B and the gum arabic were mixed, followed by the core material. Then, an appropriate amount of acetic acid was adjusted to pH 3.7. 6 ml of a crosslinking agent glutaraldehyde was added at 5 ° C. or lower, followed by stirring for 1 hour to prepare color PMMA microcapsules.

Although the present invention has been described in detail only with respect to specific examples, it is apparent to those skilled in the art that various changes and modifications can be made within the technical spirit of the present invention, and the present invention is limited by these modifications and variations. This doesn't work.

The nanoparticles prepared according to the present invention have a vivid color, are charged, and have high electrophoretic mobility. Therefore, using the nanoparticles of the present invention can realize a vivid color in the electronic paper.

Claims (3)

(a) dyeing the polymethyl methacrylate particles with a disperse dye to prepare colored polymethyl methacrylate particles; (b) adsorbing the colored polymethylmethacrylate particles with titanium butoxide to coat titania on the colored polymethylmethacrylate particles; (c) reacting the PMMA nanoparticles coated with titania with a charge control agent to prepare a core material; And (d) adding the core material to a mixed solution containing gelatin-B and gum arabic and encapsulating it by a coacervation method to obtain color PMMA microcapsules. Manufacturing Method The method of claim 1, wherein the mixed solution in step (d) comprises cetyltrimethylammonium bromide, which is a surfactant, for preparing colored polymethylmethacrylate microcapsules. Colored polymethylmethacrylate microcapsule, characterized in that the titania particles consist of a core material consisting of polymethylmethacrylate particles dyed with a disperse dye deposited on the surface, and a wall material comprising gelatin-B and gum arabic. .

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