KR20070008977A - Electrophoretic particle and electrophoretic display using the same - Google Patents

Abstract

An electrophoretic particle and an electrophoretic display using the same are provided to improve the mobility of particles and the image quality and decrease a driving voltage by preventing electrophoretic particles from clumping using a lubricant added to an outer surface of the particles. An electrophoretic display displays an image by applying an electric field between substrates facing each other. An electrophoretic particle(10) includes a polymer resin(11), a coloring agent(13), and a carbon nanotube(12). The electrophoretic particle(10) further includes a lubricant(15) at its outer surface. The electrophoretic particle(10) further includes an electrification control agent.

Description

Electrophoretic Particles and Electrophoretic Display Using the Same

1 is a cross-sectional view of a wet electrophoretic display using a conventional microcapsule,

2 is a cross-sectional view of a conventional dry electrophoretic display,

3 is a cross-sectional view of a conventional electrophoretic particle,

4 is a cross-sectional view of the electrophoretic particles according to an embodiment of the present invention,

5 is a cross-sectional view of an electrophoretic particle according to another embodiment of the present invention,

6a and 6b are cross-sectional views of the electrophoretic particles formed with a lubricant according to another embodiment of the present invention.

※ Explanation of the main symbols in the drawing

10: electrophoretic particle 11: polymer resin

12: carbon nanotube 13: colorant

14: charge control agent 15: lubricant

The present invention relates to an electrophoretic particle and an electrophoretic display using the same, wherein carbon nanotubes are added to greatly increase the amount of electrophoretic particles, and prevent aggregation of the electrophoretic particles, thereby improving the mobility of the particles and improving the image. It relates to an electrophoretic particle having a lubricant added to the outside of the particle so as to increase the quality and lower the driving voltage and an electrophoretic display using the same.

Today, the need for a transformation into a way of communicating and sharing information that corresponds to an information society that requires a new paradigm is accelerating technological development of electronic paper that can be bent as a flexible display and entering the commercial development stage. .

The electrophoretic display, which has the advantage of being bent as a flexible display, is much cheaper to produce than a conventional flat panel display and can be driven with very little energy because it does not require backlighting or continuous recharging like liquid crystal displays. Even ahead of it. In addition, the electronic paper is very sharp, has a wide viewing angle, and has a memory function that does not completely disappear even in the absence of power.

These great advantages make it possible for electronic paper to be used in a wide range of applications, such as e-books with paper-like sides and moving illustrations, self-renewable newspapers, reusable paper displays for mobile phones, disposable TV screens and electronic wallpaper. It has a huge potential market.

The technical approach for the electronic paper implementation is largely liquid crystal method, organic EL, reflective film reflective display, electrophoresis, twist ball, electrochromic method, mechanical reflective indicator, and double twist ball method. In the phase change of, there is no voltage threshold and it has a critical defect.Electrochromic devices also have low chemical stability when the colored layer is exposed to air and moisture, and the response speed is high due to the diffusion rate of ions in the electrolyte. Due to the slow drawback, the electrophoretic display technology that is currently attracting the most attention is an electrophoretic display using an electrophoretic phenomenon.

The electrophoretic phenomena can be divided into wet and dry methods.

Representative of the wet method is a display device using a microcapsules proposed by MIT Media Lab and E-Ink, which was established separately from the company (US Patent No. 5961804, etc.).

1 is a cross-sectional view showing the schematic structure. As shown, 200-300 μm in diameter containing ink particles of a specific color with specific charge (103a) and ink particles of different colors (or colored dielectric fluid, 103b) and transparent dielectric fluid 104 having opposite charges. The transparent microcapsules 100 were prepared. These microcapsules are mixed with the binder 107 to be positioned between the upper and lower transparent electrodes 105 and 106 and a voltage is applied to display characters or images by the method described above.

However, this wet method has a problem in realizing a video due to the slow response speed of about 100ms due to the viscous resistance of the liquid, and also has a problem in that a large portion of the upper part of the capsule is shielded by a binder or partially consumed so that the light efficiency is relatively low. . In addition, the specific gravity between the two charged electrophoretic particles and the dielectric fluid should be kept the same, and the physical and chemical treatments for charge attachment to prevent aggregation between the two charged electrophoretic particles and to have electrophoretic mobility Additionally required. In other words, a chemical or physical polymer coating or a polymer ball is produced, followed by a complex process of two or three steps for introducing white and introducing functional groups that facilitate the attachment of charge control agents.

Figure 2 is a cross-sectional view of a dry electrophoretic display to solve this problem. As shown, the dry electrophoretic display encapsulates two types of electrophoretic particles 116 having different colors and charging characteristics between the transparent substrates 111 and 112 having the electrodes 114 and 115 formed on one surface thereof, and the upper and lower electrodes. Electrophoretic charged from the electrodes 114 and 115 of the upper and lower plates having different electric potentials after forming a electrophoretic particle by applying a voltage to (114, 115) and causing the electrophoretic particles to strike each other to give an electric charge due to a collision. It comprises one or more pixels separated from each other by the partition wall 113 to give an electric field to the particle group to display the image.

The dry electrophoretic display does not have a material with high viscosity such as liquid in the pixel space, so the response speed is considerably fast, which is suitable for the implementation of a video.

3 is a cross-sectional view of a conventional electrophoretic particle. As shown, the electrophoretic particles consist of a binder resin 120 comprising a charge control agent 121 and a colorant 122. Since electrophoretic particles have a close relationship with the actual charge voltage, the charge control agent other than the particle resin is introduced to control the charge amount in order to have a large charge amount as shown.

However, the charge control agent has a limit amount that can enter the particle and the limit amount is low, there is a problem in increasing the amount of charge is required to improve it.

On the other hand, as the amount of charge increases, the driving voltage is lowered, whereas aggregation between particles is likely to occur. Therefore, there is a need for a method of preventing such agglomeration and improving particle mobility and improving image quality at the same time.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an electrophoretic particle to which carbon nanotubes are added, and a method for producing the same, which greatly improves the charge amount of the electrophoretic particle.

In addition, by preventing the aggregation phenomenon between the electrophoretic particles to improve the mobility of the particles, to improve the image quality and to lower the driving voltage, to provide an electrophoretic particles with a lubricant added to the outside and a method of manufacturing the same. do.

The present invention for achieving the above object,

An electrophoretic particle used in an electrophoretic display for displaying an image by applying an electric field between opposing substrates, the electrophoretic particle comprising a polymer resin, a colorant, and carbon nanotubes is provided.

In addition, it provides an electrophoretic particle, characterized in that it further comprises a lubricant to the outside, further comprising a charge control agent.

In addition, the amount of the lubricant is characterized in that the weight of the polymer resin of 1-10% by weight, the carbon nanotubes are characterized in that the polymer resin, characterized in that the carbon nanotubes are multi-layered carbon nanotubes It provides an electrophoretic particle.

In addition, the colorant is characterized in that the carbon black or titanium oxide (TiO2), the lubricant comprises silica (SiO ₂ ), the lubricant provides electrophoretic particles, characterized in that it comprises a transparent ceramic powder. .

In addition, an electrophoretic display for displaying an image by applying an electric field between opposing substrates, the electrophoretic display comprising the electrophoretic particles are used, characterized in that the electrophoretic method is dry Provides an electrophoretic display.

Hereinafter, with reference to the drawings will be described the present invention in more detail.

4 is a cross-sectional view of an embodiment of an electrophoretic particle 10 according to the present invention. As shown, the electrophoretic particles 10 according to the present invention comprises a carbon nanotube 12, a colorant 13 and a polymer resin (11).

The manufacturing method can be prepared simply by kneading and pulverizing the polymer resin (11), carbon nanotubes (12) and the colorant (13), or by dispersing the colorant and polymer resin in the liquid phase during the polymerization of the polymer resin (11). In addition, it may be prepared according to the method for producing electrophoretic particles used in the technical field of the present invention. Although not shown, it is obvious that the electrophoretic particles formed by coating the carbon nanotubes 12 and the colorant 13 on the outside of the polymer resin 11 are also included in the present invention.

The polymer resin 11 preferably binds the carbon nanotubes 12 and the colorant to determine the shape of the electrophoretic particles and selects a resin capable of imparting chargeability.

Examples of the resin that may be used as the polymer resin 11 include urethane, nylon, fluorine, silicone, melamine, phenol, styrene, styrene acryl, urethane acryl, and the like, and preferably PMMA (poly methyl). methcrylate), polyethylene terephthalate (PETE), polystyrene (PS), polyethylene, polypropylene, phenolic resin, Du Pont Elvax resin (ethylene-vinyl acetate copolymer), polyester, polyacrylate, poly Methacrylate, ethylene acrylic acid or methacrylic acid copolymers (Nucrel Resins-Dupont, Primacor Resins-Dow Chemical) acrylic acid copolymers and trimers (Elvacite Resins, DuPont). In addition, as these copolymers, materials useful for high shear melting homopolymers and / or pigment phase separation include, but are not limited to, polyethylene, polypropylene, polymethylmethacrylate, polyisobutylmethacrylate, polystyrene, Polybutadiene, polyisoprene, polyisobutylene, polylauryl methacrylate, polystearyl methacrylate, polyisobornyl methacrylate, poly-t-butyl methacrylate, polyethyl methacrylate, polymethyl Acrylate, polyethyl acrylate, polyacrylonitrile and copolymers of two or more such materials.

In particular, acrylic urethane resins, acrylic silicone resins, acrylic fluorine resins, acrylic urethane silicone resins, acrylic urethane fluorine resins, fluorine resins, and silicone resins are suitable from the viewpoint of controlling adhesion to the substrate.

As the positive charge imparting resin, a nylon resin, an epoxy resin or a styrene acrylic resin is suitable, and as a negative charge imparting resin, a fluorine resin, a silicone resin or an acrylic urethane fluorine resin is suitable.

As the colorant 13, various organic and inorganic pigments and dyes can be used. More preferably, the following coloring agent is used.

Black pigments include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, and the like. For white expression, titanium oxide (TiO ₂ ) is typically used.

Examples of the yellow pigments include sulfuric acid, zinc sulfur, cadmium yellow, yellow iron oxide, mineral first yellow, nickel titanium yellow, navel yellow, naphthol yellow-S, benza yellow-G, benza yellow-10G, and benzidine. Yellow-G, benzidine yellow-GR, quinoline yellow lake, permanent yellow-NCG, tartrazine lake, and the like.

Examples of the orange pigment include red sulfur lead, molybdenum orange, permanent orange GTR, pyrazolone orange, balkan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK.

Examples of the red pigment include bengal (red pigment), cadmium red, podium, mercury sulphide, cadmium, permanent red 4R, lithol red, pyrazolone red, watching red, calcium salt, lake red D Brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B.

Purple pigments include manganese purple, first violet B, methyl violet lake, and the like. Blue pigments include ecru, blue cobalt blue, alkaline blue lake, victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partial chlorine, and first. Sky Blue, Indanthrene Blue BC.

Green pigments include chromium green, chromium oxide, pigment green B, malachite green lake, final yellow green G, and the like. As the extender pigment, baryte powder, barium carbonate, clay, silica, white carbon, etc. , Talc, alumina white and so on.

Further, various dyes such as alkaline, acidic, disperse, and direct dyes include nigrosine, methylene blue, rose bengal, quinoline yellow, ultramarine blue, and the like. These colorants can be used alone or in combination of a plurality.

The carbon nanotubes 12 are one of the great features of the present invention. As the carbon nanotubes 12 are added to the electrophoretic particles, a large charge amount is applied to the electrophoretic particles, thereby lowering the driving voltage.

Since the structure of the carbon nanotubes is several to several hundred nm in diameter and tens to hundreds of micrometers in length, the carbon nanotubes can be placed in the space of the polymer chain and the colorants of the polymer resin 11, so that the carbon nanotubes ( 12), the increase in the total volume of electrophoretic particles is negligible. Therefore, it is possible to accumulate a large amount of charge compared to the increase in the volume of the electrophoretic particles.

In addition, carbon nanotubes exhibit an extremely high specific storage capacity (400 to 1000 mAh / g), and thus can accumulate a large amount of charge compared to the added mass. Electrophoretic particles are very useful as an additive to increase the charge amount of the electrophoretic particles because the driving voltage increases by the increase of the mass.

Carbon nanotubes are roughly classified into multilayer carbon nanotubes (MWNT) and single layer carbon nanotubes (SWNT). As the name suggests, multilayer carbon nanotubes consist of two or more concentric cylinders, and single-layer carbon nanotubes consist of single-layered concentric cylinders, and can be added to electrophoretic particles without being limited to a kind, preferably multilayer carbon nanotubes. Do. These can also be mixed and added. As the addition amount, about 1-10% of the weight of the polymer resin 11 is sufficient, preferably about 5%.

The carbon nanotubes 12 may be purchased and used commercially, or may be manufactured separately and used. Since the manufacturing method is disclosed in Japanese Patent Laid-Open Nos. 1999-77943 and 2004-88463, and the like.

The incorporation of the carbon nanotubes 12 may be spray coated only on the surface after the particle polymerization (not shown). More preferably, it is more efficient to increase the amount of charge by dispersing the polymer resin by liquid phase mixing during polymerization.

Another effect obtained by adding the carbon nanotubes 12 is an increase in the mechanical strength of the electrophoretic particles.

Carbon nanotubes have a form in which a single layer of graphite is wound and have sp2 bonds such as graphite, so that the bond strength is strong and the measured Young's modulus in the longitudinal direction is greater than 1 TPa, thereby increasing the mechanical strength of the electrophoretic particles. Let's go. In addition, it can also serve as a ring connecting the low-molecular chains of the polymer resin (11) to connect the particle resins with each other can also enhance the mechanical shock resistance of the particles and maintain the shape of the electrophoretic particles continuously You can.

Figure 5 is a cross-sectional view of the electrophoretic particles according to another embodiment of the present invention.

As shown, the electrophoretic particles may be further added to the charge control agent (14). Although not limited to the charge control agent 14, as the negative charge control agent, for example, salicylic acid metal complexes, metal-containing azo dyes, oil-soluble dyes containing metal ions or metal atoms, quaternary ammonium salt compounds, Calixarene compounds, boron-containing compounds (boron benzyl acid complex), nitroimidazole derivatives, and the like. Examples of the positive charge control agent include nigrosine dyes, triphenylmethane compounds, quaternary ammonium salt compounds, polyamine resins, imidazole derivatives, and the like. In addition, metal oxides such as ultrafine silica, ultrafine titanium oxide, ultrafine alumina, nitrogen-containing cyclic compounds such as pyridine and derivatives thereof, salts, resins containing various organic pigments, fluorine, chlorine, nitrogen and the like can also be used as charge control agents. .

6a and 6b are cross-sectional views of electrophoretic particles according to another embodiment of the present invention.

As shown, it is characterized in that the lubricant 15 is applied to the outside of the electrophoretic particles according to the embodiment described above.

Electrophoretic particles have a problem that the driving voltage is increased as the amount of charging increases between the particles having different charging characteristics. In addition, due to the properties of the polymer resin 11 used as a material of the electrophoretic particles, there is a problem of sticking between the particles or the electrode and the partition (if present).

The lubricant 15 is intended to improve the fluidity of the electrophoretic particles by preventing agglomeration between the electrophoretic particles and sticking to the electrodes and the partition walls.

Silica (SiO ₂ ) is most preferred as the lubricant 15, and transparent ceramic powder may be used. Barium titanate (BaTiO _3), strontium titanate (SrTiO _3), calcium titanate (CaTiO _3), lead titanate (PbTiO _3), titanium dioxide (TiO _2), tin dioxide (SnO _2), Calcium oxide (CaO), magnesium oxide (MgO), aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), gamma iron oxide, magnesium silicate (MgSiO ₃ ), magnetite (Fe ₃ O ₄ ), zirconia (ZrO ₂ ), boron oxide (B ₂ O ₃ ), nickel ferrite, zinc ferrite, nickel zinc ferrite and barium ferrite (BaFe ₂ O ₄ ) It may be at least one or more selected from the group consisting of. The particle diameter of the lubricant 15 is preferably selected within the range of 50 nm to 10 μm.

The method of forming the lubricant 15 may be a mechanochemical method of immobilization by applying mechanical energy such as pouring the lubricant 15 into the surface of the polymer resin 11 or the lubricant 15 on the surface of the polymer resin 11. ) By applying mechanical energy to the thermal energy, a mechano-fusion method for diffusion-immobilization, or a graft method for chemically bonding magnetic particles to the surface of the parent particle. It is also possible to use a general coating method.

The above embodiments are described in detail to make the present invention easier to understand and are not intended to limit the present invention. Therefore, modified electrophoretic particles that can be added typically are also included in the present invention.

The electrophoretic particles of the present invention can be used without limitation to electrophoretic displays that display an image by applying an electric field between opposing substrates, known in the art. That is, it can be applied to a wet type electrophoretic display and can also be used as particles that move in microcapsules. It can be used more suitably for dry electrophoretic display.

As described above, the present invention can add a carbon nanotube to the electrophoretic particles to significantly improve the charge amount of the electrophoretic particles without significantly increasing the volume and mass of the electrophoretic particles, low-polymerization chain of polymer number It can also serve as a ring to connect the particle resins with each other, thereby enhancing the mechanical impact resistance of the particles, and can maintain the shape of the electrophoretic particles continuously, and the lubricant on the outside of the electrophoretic particles By forming a, it is possible to prevent the aggregation phenomenon between the electrophoretic particles to improve the mobility of the particles, to improve the quality of the image and to provide the effect of lowering the driving voltage.

Claims (11)

An electrophoretic particle used in an electrophoretic display for displaying an image by applying an electric field between opposing substrates, the electrophoretic particle comprising a polymer resin, a colorant, and carbon nanotubes. The electrophoretic particle of claim 1, further comprising a lubricant externally. The electrophoretic particle of claim 1, further comprising a charge control agent. The electrophoretic particle of claim 1 or 2, wherein the amount of the lubricant is 1-10% by weight based on the weight of the polymer resin. The electrophoretic particle according to any one of claims 1 to 3, wherein the carbon nanotubes are contained in a polymer resin. The electrophoretic particle according to any one of claims 1 to 3, wherein the carbon nanotubes are multilayer carbon nanotubes. The electrophoretic particle according to any one of claims 1 to 3, wherein the colorant is carbon black for black expression or titanium oxide (TiO ₂ ) for white expression. The electrophoretic particle of claim 2, wherein the lubricant comprises silica (SiO ₂ ). The electrophoretic particle of claim 2, wherein the lubricant comprises a transparent ceramic powder. An electrophoretic display in which at least one kind of electrophoretic particles are injected between opposing substrates and an electric field is applied to move the particles to display an image. The electrophoretic particles are electrophoretic display comprising the electrophoretic particles of any one of claims 1 to 3. 11. The electrophoretic display of claim 10, wherein the electrophoretic method is a dry method.

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