KR20140011909A - Electrowetting device and method of fabricating the same - Google Patents

Abstract

The present invention relates to an electrowetting device and a manufacturing method thereof capable of implementing reduction of driving voltage at low costs, and an electrowetting device of the present invention comprises: a first substrate; a first electrode formed on the first substrate; an insulating layer formed on the first electrode; a second substrate bonded to the first substrate; a second electrode formed on the second substrate to face the insulating layer; and oil and water disposed between the insulating layer and the second electrode. In an electrowetting device using electrowetting phenomenon caused by voltage supply between the first and second electrodes, the insulating layer includes: a first insulating layer formed on the first substrate, on which the first electrode is formed, by a nanoparticle deposited film of oxide nanoparticles having a high dielectric constant; and a second insulating layer formed on the first insulating layer by a polymer brush having high water repellency.

Description

ELECTROWETTING DEVICE AND METHOD OF FABRICATING THE SAME [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrowetting device to which an electrowetting technique is applied, and a manufacturing method thereof.

The electrowetting technique is a technique for obtaining a desired effect by controlling the electrostatic wettability (wetting property) to generate deformation or displacement of the liquid. An electro-wetting device is an electro-wetting device, and an electrowetting display (EWD) is an electro-wetting phenomenon. EWD is characterized by a simple structure using water and colored oil as a display medium. It has a fast response time and a potential to cope with moving picture display, and is used for a variety of applications such as electronic books and digital signage display devices Application is expected.

1A and 1B are cross-sectional views illustrating the configuration and operation of a conventional EWD.

A first electrode 2 is formed on a first substrate 1 and a hydrophobic (water repellent) insulating film 3 is formed on the first electrode 2. A lattice-shaped partition wall (Colored oil) 4 is filled in the portion surrounded by the partition wall and the second substrate 7 on which the second electrode 6 is formed is filled with the water 5 on the upper portion.

FIG. 1A shows a case where no voltage is applied between the first and second electrodes 2 and 6. FIG. The state in which the colored oil 4 is present on the side of the insulating film 3 rather than the water 5 is maintained from the viewpoint of the surface tension and the state in which the colored oil 4 spreads over the entire pixel (Cancerous state).

FIG. 1B shows a case where a voltage is applied between the first and second electrodes 2 and 6. FIG. 1B, the electrostatic energy at the interface of the insulating film 3 changes due to the application of a voltage between the first and second electrodes 2 and 6, and the contact angle of the insulating film surface with water decreases. As a result, The coloring oil 4 is pushed out and the pixel becomes bright. By turning on / off the voltage as described above, the brightness and darkness of the pixel are produced, thereby functioning as a display body.

In the conventional EWD, the insulating film 3 may have a single-layer structure as shown in Fig. 2A and a two-layer structure as shown in Fig. 2B. As shown in FIG. 2A, in the case where the insulating film 3 has a one-layer structure, it is often formed of a fluorine resin. When the insulating film 3 has a two-layer structure as shown in FIG. 2B, And a fogging film 3b (see, for example, Patent Documents 1 and 2).

However, in the conventional EWD, when the insulating film 3 is composed of one layer of fluororesin, the relative dielectric constant of the fluororesin is as low as about 2, which causes a problem that the driving voltage becomes relatively high. In order to solve this problem, there has been proposed a method of dividing an insulating film into a high-permittivity portion and a high-volatility portion. However, since the high-permittivity layer needs to be formed by using an expensive vacuum device, the manufacturing cost is high. In addition, although a method of forming a high-dielectric layer by a coating method has been proposed, there is a problem that it can not be applied to a resin substrate because it must be heated to a high temperature of 300 캜 or more to cure the high-dielectric layer.

Patent Document 1: JP-A-2004-028708 Patent Document 2: JP-A-2008-1706318

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide an electrowetting device capable of realizing a reduction in driving voltage at a low cost and a manufacturing method thereof.

According to an aspect of the present invention, there is provided an electrowetting device comprising a first substrate, a first electrode formed on the first substrate, an insulating film formed on the first electrode, A second electrode formed on the second substrate so as to face the insulating film; and oil and water disposed between the insulating film and the second electrode, wherein the first and second electrodes An insulating film formed on the first substrate on which the first electrode is formed, the first insulating film being formed of a nanoparticle deposition film of oxide nanoparticles having a high dielectric constant; And a second insulating film formed on the first insulating film by a polymer brush having high water-solubility.

A manufacturing method of an electrowetting device according to an embodiment of the present invention includes a first substrate, a first electrode formed on the first substrate, an insulating film formed on the first electrode, and a second electrode bonded to the first substrate, A plasma display apparatus comprising: a substrate; a second electrode formed on the second substrate so as to face the insulating film; and oil and water disposed between the insulating film and the second electrode, Wherein the step of forming the insulating film comprises forming a first electrode on the first substrate and a second electrode on the first substrate, the method comprising the steps of: Forming a first insulating film on the first insulating film; and forming the second insulating film made of a polymer brush having high water-solubility on the first insulating film.

The nanoparticle deposition film of the oxide nanoparticles is formed of particles having a particle diameter of 10 nm to 50 nm.

The oxide nanoparticles are barium titanate and synthesized by a sol-gel method.

The polymer brush is formed of a fluorine-based material and is formed by living radical polymerization.

The insulating film is formed at 150 DEG C or lower.

According to the electrowetting device and the manufacturing method thereof of the present invention, the first layer of the insulating film formed by the two-layer structure is formed of the nanoparticle deposition film of the oxide nanoparticles and the second layer of the insulating film is formed of the polymer brush, The driving voltage can be reduced at a low cost.

Further, according to the electrowetting device and the manufacturing method of the present invention, since the insulating film can be used by a coating method and can be cured at a low temperature, it can be applied to a plastic flexible substrate.

1A and 1B are cross-sectional views illustrating the configuration and operation of a conventional EWD.
2A and 2B are cross-sectional views illustrating an example of the configuration of an insulating film in a conventional EWD.
3 is a partial cross-sectional view showing an EWD according to an embodiment of the present invention.
4 is a characteristic diagram of a voltage-white region illustrating the effect of the EWD according to the embodiment of the present invention.

3 is a partial cross-sectional view showing an EWD as an electrowetting device according to an embodiment of the present invention.

The EWD of the present invention has a two-layer insulating film 3 formed on a first electrode 2 formed on a first substrate 1. The insulating film 3 having a two-layer structure includes a first insulating film 3A formed of a high-permittivity high-k film and a second insulating film 3B formed on the first insulating film 3A and formed of a high- . The first insulating film 3A is formed of a nanoparticle deposition film formed of an oxide nanoparticle and an adhesive, and the second insulating film 3B is formed of a polymer brush.

The EWD of the present invention is not limited to the structure shown in FIG. 3, but may be formed on the surface of the second substrate 7 to be bonded to the first substrate 1, such as a conventional EWD shown in FIG. And an oil 4 and water 5 disposed between the insulating film 3 and the second electrode 6. The first electrode 2 and the second electrode 6 are disposed between the first electrode 2 and the second electrode 6, A display device using an electrowetting phenomenon by voltage application is constituted.

The nanoparticle deposition film of the oxide nanoparticles as the first insulating film 3A is formed by a coating method using a coating liquid containing oxide nanoparticles and the polymer brush as the second insulating film 3B is a fluorine based material and is formed by living radical polymerization . The nanoparticle deposition film of the oxide nanoparticles as the first insulating film 3A and the polymer brush forming the second insulating film 3B are all formed at 150 DEG C or less.

1 and 3, the relationship between the relative dielectric constant and the film thickness of the insulating film 3 when a voltage is applied between the first electrode 2 and the second electrode 6 will be examined. When a voltage V is applied between the first electrode 2 and the second electrode 6, the contact angle? Can be expressed by the following equation (1). The initial contact angle in the equation (1) below, θ _0, the first insulating film (3A) and the second the relative dielectric constant of the film thickness of the insulating film 3, the sum of the insulating film (3B) d, insulating film 3 ε _r, dielectric constant of a vacuum Is defined as ε ₀ , and the gas-liquid interface energy of water is defined as γ _LG .

According to the expression (1), it is preferable to increase the relative permittivity (? _R ) of the insulating film (3) and reduce the film thickness (d) in order to reduce the driving voltage of the device, .

Accordingly, in the present invention, a nanoparticle deposition film of oxide nanoparticles having a high relative dielectric constant ( _r ) as the first insulating film 3A is used, and a fluorine-based nanoparticle deposition film capable of exhibiting a high water- Polymer brushes are used. In this manner, the first insulating film (3A) the oxide is formed in a nanoparticle deposited film of nanoparticles, the second insulating film (3B) is to use the insulating film 3 is formed of a fluorine-based polymer brushes, the relative dielectric constant (ε _r) And the film thickness d is made thin, so that the driving voltage can be reduced.

As described above, according to the embodiment of the present invention, the first insulating film 3A of the insulating film 3 formed in a two-layer structure is formed of a nanoparticle deposition film of oxide nanoparticles, and the second insulating film 3B is formed of a polymer brush The driving voltage of the device can be reduced. Further, since the insulating film 3 can be formed by a coating method and does not require a vacuum device, reduction in driving voltage can be realized at low cost. Since the insulating film 3 can be cured at a low temperature of 150 DEG C or less, the insulating film 3 can be applied to a plastic substrate.

In the present invention, the oxide nanoparticle means a compound having one or more kinds of metal atoms and oxygen atoms bound to each other and having crystallinity. Examples of the oxide nanoparticles having relatively high relative dielectric constant include titanium oxide, zirconium oxide, Aluminum and the like. Further, in order to increase the specific dielectric constant, it is preferable to use barium titanate, which is mainly composed of barium and titanium, as the metal element. Barium titanate is represented by the general formula ABO ₃ , and barium (Ba) is included in the metal element A and titanium (Ti) is contained in the metal element B. However, in order to further improve the characteristics such as the relative dielectric constant, a part or all of barium At least one or more kinds of titanium (Ti) selected from Group 1B, Group 2A, Group 2B, Group 3A, Group 4B, Group 5B, and Group 8 of the Periodic Table of Elements may be partially or entirely replaced with Group 4A Group, group 4B, and group 5B. The ratio of the number of atoms of the metal element A, the metal element B, and the oxygen element does not necessarily have to be 1: 1: 3.

The synthesis of the oxide nanoparticles can be carried out using any known method, and a method which is very suitable for the constituent materials of the nanoparticles and the particle diameter can be appropriately selected. The preparation of the oxide nanoparticles may be carried out by any of the breakdown method, which is a method of crushing the bulk of a solid, and the buildup method, which is a synthetic method, from a raw material at an atomic or molecular level. However, It is more preferable to use a build-up method that is easier to control. Specific examples of the build-up method include a vapor phase synthesis method such as a chemical vapor deposition (CVD) method, an electrostatic spray-CVD (ES-CVD) method, a particle synthesis method using a nanoreaction field such as reverse micelle and a liquid phase synthesis method such as a sol- . Of these, the oxide nanoparticles synthesized by the sol-gel method described later can be stably dispersed in a coating liquid for forming a nanoparticle deposition film over a long period of time. Therefore, it is possible to produce a stable coating liquid, From the viewpoint of forming a film, a sol-gel method is most preferable as a method of synthesizing oxide nanoparticles.

Hereinafter, as an example of the synthesis of oxide nanoparticles using the sol-gel method, barium titanate (Ba) is described as an A metal element, and oxide nanoparticles of titanium (Ti) as a B metal element are described.

First, a precursor solution is prepared by dissolving barium alkoxide and titanium alkoxide in a reaction solvent such that the molar ratio of Ba / Ti is approximately 1.

The barium alkoxide that can be used is a compound represented by the general formula Ba (OR1) ₂ , wherein R1 is -C _n H2 _{n +1} , _n is an integer of 1 to 10, -CH (CH ₃ ) ₂ , -C ₂ H ₄ OCH ₃ , -C ₂ H ₄ OC ₂ H ₅ , -CH ₂ OCH ₃ , -CH ₂ OC ₂ H ₅ and -C ₂ H ₄ OC ₂ H ₄ OC ₂ H ₅ . Specific examples of barium alkoxides there may be mentioned barium ethoxide _{(R1 = C 2 H 5)} , barium isopropoxide _{(R1 = CH (CH 3)} 2) or the like. Also, it is not necessary to be an alkoxide from the beginning, but it may be converted into an alkoxide after dissolving metal barium, barium chloride, barium oxide, barium acetate, barium hydroxide and the like in a reaction solvent.

The titanium alkoxide that can be used is a compound represented by the general formula Ti (OR2) ₄ , wherein R2 is -C _n H _{2n +1} , -CH (CH ₃ ) ₂ , -C ₂ H ₄ OCH ₃ , -C ₂ H ₄ OC ₂ H ₅ , -CH ₂ OCH ₃ , -CH ₂ OC ₂ H _5, and -C ₂ H ₄ OC ₂ H ₄ OC ₂ H ₅ . Examples of the titanium alkoxide, titanium ethoxide _{(R2 = C 2 H 5)} , titanium isopropoxide _{(R2 = CH (CH 3)} 2) , and the like. Furthermore, it is not necessary to be an alkoxide from the beginning, but it is also possible to dissolve metallic titanium, titanium chloride, titanium oxalate, titanium hydroxide or the like in a reaction solvent and convert it into an alkoxide.

The concentration of barium alkoxide and titanium alkoxide in the precursor solution is not particularly limited, but is preferably 0.5 mol / L or more, more preferably 1 mol / L or more in view of working efficiency. When it is less than 0.5 mol / L, generation of nanoparticles of barium titanate takes time, which is disadvantageous in working efficiency.

As the solvent to be used for preparing the precursor solution, any solvent capable of dissolving the barium alkoxide and the titanium alkoxide in the above concentrations can be used, the kind and concentration of the barium alkoxide and titanium alkoxide to be used and the formation of the nanoparticle deposition film (For example, methanol, ethanol, 2-methoxyethanol, 2-ethoxyethanol, 2-propanol, 2-ethoxyethanol and the like), and the like. Phenol and the like), a ketone type (methyl ethyl ketone, acetyl acetone (pentane-2,4-dione), acetone, etc.), and a mixed solvent obtained by mixing arbitrary two or more kinds of them in an arbitrary ratio. .

Then, the precursor solution prepared as described above is hydrated and aged at a temperature of 150 ° C or lower until the growth of the particles is finished to form crystallized barium titanate nanoparticles. Hydrolysis and polycondensation reactions of barium alkoxide and titanium alkoxide proceed to hydrolysis of the precursor solution to produce a crystalline gel of barium titanate.

The water used for the hydrolysis may be added to the precursor solution in the air or in the form of steam generated by heating the water, but may be added in the form of a predetermined amount of liquid to control the addition amount, May also be added as a solution dissolved in water. If necessary, an aqueous solution of an acid such as an inorganic acid, an organic acid, a hydroxide, an organic amine, or an alkali may be added.

The method of adding water is not particularly limited, but it is preferable to add the precursor solution while stirring so that the concentration distribution of water in the precursor solution becomes uniform. When the concentration distribution of water becomes nonuniform, the hydrolysis and polycondensation reaction progress locally, so that the particle size of the obtained oxide nanoparticles becomes uneven and the dispersion state of the oxide nanoparticles may decrease.

The amount of water to be added is preferably 1 to 80 times the number of moles of barium alkoxide or titanium alkoxide in the precursor solution. When the addition amount is less than 1 times the number of moles of barium alkoxide and titanium alkoxide in the precursor solution, the hydrolysis and polycondensation reaction hardly proceeds. Even if the aging condition is more than 80 times, the aging condition is optimized. However, since the rate of hydrolysis and polycondensation reaction is too high, the oxide nanoparticles that can be locally advanced can be remarkably heterogeneous in particle size, There is a possibility that the dispersed state of the catalyst may be lowered.

By performing aging after the syringe, alcohol or water is released from the generated gel, and a bond of titanium and barium through the oxygen is formed, so that barium titanate nanoparticles having crystallinity are produced. As the aging temperature is high, the formation of barium titanate nanoparticles is accelerated. However, since the evaporation rate of alcohol or water is remarkably accelerated at 150 ° C or more, there is a problem that the gel is dried before the formation of barium titanate nanoparticles have. Therefore, the aging temperature is preferably 150 DEG C or lower, more preferably 100 DEG C or lower.

Thereafter, the barium titanate nanoparticles obtained as described above are dispersed in the dispersion medium in a wet state with the reaction solvent without being completely dried, whereby the nanoparticles of the barium titanate nanoparticles as the oxide nanoparticles are uniformly dispersed Can be obtained.

The oxide nanoparticles in the coating liquid are preferably 10 to 100 nm in crystallite diameter (primary particle size) calculated from Scherrer's equation from the result of X-ray diffraction measurement, and more preferably 10 to 50 nm . When the thickness is less than 10 nm, the crystal structure of the oxide nanoparticles is incomplete and the relative dielectric constant lowers, and the effect of increasing the relative dielectric constant of the nanoparticle deposited film may be insufficient. On the other hand, The number of voids between the nanoparticles increases in the particle deposition film, and the relative dielectric constant and the insulation property may decrease.

It is preferable that the value obtained by dividing the average particle diameter (aggregated particle diameter) of the oxide nanoparticles in the coating liquid by the dynamic light scattering method specified by JIS-Z8826 by the primary particle diameter is 2.0 or less, more preferably 1.5 or less . When the value obtained by dividing the aggregate particle diameter by the primary particle diameter is more than 2.0, the dispersion stability of the oxide nanoparticles in the coating liquid remarkably decreases and cohesive particles are mixed in the nanoparticle-deposited film, so that the insulating property of the nanoparticle- There is a risk of degradation.

By mixing particles of two or more types of oxide nanoparticles having different average particle diameters in an arbitrary ratio and controlling the particle diameter distribution of the oxide nanoparticles in the coating liquid, it is possible to improve the filling property of the oxide nanoparticles in the nanoparticle deposition film, It is also possible to obtain an insulating film having a high dielectric constant.

The coating solution in which the oxide nanoparticles thus obtained are dispersed is applied onto an arbitrary substrate and dried, and the adhesive is impregnated into the gap between the oxide nanoparticles to obtain a nanoparticle deposited film. The coating method can be carried out by an existing method, and can be carried out by coating methods such as spin coating, dip coating, bar coating, and gravure coating. The drying is not particularly limited as long as the solvent of the coating liquid volatilizes and the treatment time, but from the viewpoint of use of the plastic resin base, the drying is preferably carried out at 150 캜 or lower. It is also possible to dry under reduced pressure or vacuum to lower the drying temperature.

As the adhesive for enhancing the strength and insulation of the nanoparticle deposited film, conventional thermosetting resins or ultraviolet ray curable resins can be used, and examples thereof include epoxy resins and phenol resins. The impregnation of the adhesive with the nanoparticle-deposited film can be carried out by immersing the nanoparticle-deposited film on the surface of the nanoparticle-deposited film or by adjusting the viscosity of the adhesive to a proper viscosity and solid content concentration with a solvent. The resin of the adhesive may be mixed in advance in the coating liquid in which the oxide nanoparticles are dispersed. In order to exhibit the adhesive effect after impregnating the adhesive with the above-mentioned method, it is necessary to remove the solvent and cure by the heat treatment or the ultraviolet ray irradiation treatment, but there is no particular limitation in the method.

The thickness of the nanoparticle deposited film needs to be appropriately adjusted according to the intended performance and the use conditions. The drive voltage of the EWD can be lowered by decreasing the film thickness of the insulating film, but the insulating property is lowered on the other hand. For example, if the thickness of the nanoparticle deposition film is made smaller than 100 nm, the driving voltage of the EWD can be reduced. However, there is a possibility that sufficient insulating property can not be obtained as the insulating film of the EWD, and reliability as an electronic device may be remarkably lowered. In addition, for example, if it is larger than 2000 nm, the insulating property becomes high, but the drive voltage of the EWD may be high-voltage.

The polymer brush in the present invention means that a plurality of graft polymer chains have a structure in which the graft polymer chains are elongated in a direction perpendicular to the substrate surface at a high density. The term "living radical polymerization" refers to a polymerization reaction in which the chain transfer reaction and the termination reaction do not substantially occur in the radical polymerization reaction, and the chain growth terminal remains active even after all of the radical polymerizable monomers are reacted. In this polymerization reaction, since the polymerization activity is maintained at the end of the resulting aggregate even after completion of the polymerization reaction, the polymerization reaction can be started again by adding a radical polymerizable monomer. The living radical polymerization is characterized in that an aggregate having an arbitrary average molecular weight can be synthesized by controlling the concentration ratio between the radical polymerizable monomer and the polymerization initiator, and the molecular weight distribution of the resulting aggregate is extremely narrow Japanese Patent Application Laid-Open No. 2011-81187, paragraph 0013,0017).

A representative example of living radical polymerization used in the present invention is atom transfer radical polymerization (ATRP). For example, an atom-transferring living radical polymerization of a radically polymerizable monomer is carried out using a halogenated copper / ligand complex in the presence of a polymerization initiator. Radical radical polymerizable monomer proceeds in a reversible growth by withdrawing the polymer terminal halogen by the copper halide / ligand complex, and the molecular weight distribution is regulated by reversible activation / inactivation to a sufficient frequency.

The radical polymerizable monomer used in the living radical polymerization has an unsaturated bond capable of carrying out radical polymerization in the presence of an organic radical. Examples of the monomer include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, , Benzyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, 2-methoxyethyl methacrylate, butoxyethyl methacrylate, methoxytetraethylene glycol methacrylate, Hydroxypropyl methacrylate, 2-hydroxypropyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, tetrahydroperfuryl methacrylate, 2-hydroxy- Methacrylate-based monomers such as acrylate, diethylene glycol methacrylate, polyethylene glycol methacrylate and 2- (dimethylamino) ethyl methacrylate. Murray; Acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, benzyl acrylate, cyclohexyl acrylate, Acrylate, n-octyl acrylate, 2-methoxyethyl acrylate, butoxy ethyl acrylate, methoxytetraethylene glycol acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, Hydroxypropyl acrylate, diethylene glycol acrylate, polyethylene glycol acrylate, 2- (dimethylamino) ethyl acrylate, 2-hydroxypropyl acrylate, N, N-dimethylacrylamide, N-methylolacrylamide and N-methylolmethacrylamide. Rate-based monomers; Styrene, styrene derivatives (e.g., o-, m-, p-methoxystyrene, o-, m-, pt-butoxystyrene, o-, m-, p- chloromethylstyrene, etc.) (For example, vinyl acetate, vinyl propionate, vinyl benzoate and vinyl acetate), vinyl ketones (e.g., vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone) , N-vinylpyrrolidone, N-vinylpyrrole, N-vinylcarbazole and N-vinylindyl), (meth) acrylic acid derivatives (for example, acrylonitrile, methacrylonitrile, acrylamide, iso Vinyl chloride, vinyl chloride, vinylidene chloride, tetrachlorethylene, hexachloroprene, vinyl fluoride), and the like can be given as examples of the vinyl monomer. These various radical polymerizable monomers may be used alone, or two or more kinds thereof may be used in combination.

The polymerization initiator is not particularly limited, and those generally known for living radical polymerization can be used. Examples of the polymerization initiator include p-chloromethylstyrene, alpha -dichloroxylene, alpha, alpha -dichloroxylene, alpha, alpha -dibromoxylene, hexakis (alpha -bromomethyl) benzene, benzyl chloride, benzyl bromide, 1- Benzyl halides such as bromo-1-phenylethane and 1-chloro-1-phenylethane; Methyl-2-bromopropionate, ethyl-2-bromopropionate, methyl-2-bromopropionate, ethyl-2-bromo ISO butyrate ( EBIB), and the like; p-toluenesulfonyl chloride (TsCl); Alkyl halides such as tetrachloromethane, tribromomethane, 1-vinylethyl chloride, and 1-vinylethyl bromide; And halogenated derivatives of phosphoric acid esters such as dimethylphosphoric chloride. These various polymerization initiators may be used alone, or two or more of them may be used in combination.

The halogenated copper giving a halogenated copper / ligand complex is not particularly limited, and a commonly known one for living radical polymerization can be used. Examples of the halogenated copper include CuBr, CuCl, CuI and the like. These various types of halogenated copper may be used singly or two or more kinds thereof may be used in combination. The ligand compound giving the copper halide / ligand complex is not particularly limited, and a commonly known ligand compound can be used for the living radical polymerization. Examples of the ligand compound include triphenylphosphane, 4,4'-dinonyl 2,2'-dipyridine (dNbipy), N, N, N ', N'N'-pentamethyldiethylenetriamine, , 4,7,10,10-hexamethyltriethylenetetramine, etc. These various ligand compounds may be used alone or in combination of two or more.

The EWD of the present invention described above can be formed based on the following conditions.

The insulating film has a two-layer structure, the lower layer is a nanoparticle deposition film, and the upper layer is a film having higher water solubility than the lower layer.

· Nanoparticle deposition film is completed with oxide nanoparticles and adhesive.

The oxide nanoparticles and the adhesive may form a laminated structure.

The thickness of the nanoparticle deposition film is preferably 100 nm or more, more preferably 500 nm or more.

Capacitance density as a capacitor of the nanoparticle deposition film is 10 nF / cm ² Or more.

The leakage current of the EWD formed by using the nanoparticle deposition film is preferably 2 × 10 ^-6 A · cm ² or less at a voltage of 50 V DC or less.

The size of the nanoparticles is preferably 50 nm or less.

The particle diameter of the nanoparticles is preferably one kind or two or more kinds.

The oxide nanoparticles are preferably synthesized by a sol-gel method.

It is preferable that the oxide nanoparticles are monodispersed in the coating liquid used for forming the insulating film (the average particle diameter required from the dynamic light scattering method of the oxide nanoparticles in the coating liquid is the crystallite diameter required from the X-ray diffraction measurement results of the oxide nanoparticles Removed to 2 or less).

The solid concentration of the oxide nanoparticles in the coating liquid is preferably 10% by mass or less.

The nanoparticle deposition film is formed by a coating method, and the high water film is formed by dipping in a polymerization solution.

The oxide is barium titanate.

The thickness of the high water film is preferably 4 nm or more (inclusive of the initiator part), more preferably 10 nm to 30 nm.

· The upper layer of water film is finished with a polymer brush.

Polymer brushes are fluorine-based materials.

Polymer brushes are formed by living radical polymerization.

• The insulating film (nano-deposited film, high-water film) is formed at 150 ° C or less.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

< Example >

First, a method of synthesizing oxide nanoparticles of barium titanate nano-particles using a sol-gel method will be described.

Synthesis of Barium Titanate Nanoparticles

0.5 mol / L of Ba (OC ₂ H ₅ ) ₂ and Ti (OCH (CH ₃ ) ₂ ) ₄ were dissolved in a mixed solvent of methanol and 2-methoxyethanol (volume ratio 3: 2) The precursor solution of barium nanoparticles was adjusted.

Then, the electric precursor solution was kept at -30 캜, and a water-methanol mixed solution (1: 1) (vol%) was added dropwise with stirring to perform hydrolysis.

Further, the amount of the water / methanol mixed solution (hydrolyzed solution) was adjusted so that the number of moles of water in the hydrolyzate was 10, 15, 20, 40, 75 and 100 times the number of moles of Ba or Ti in the precursor solution.

After the completion of the hydrolysis, the temperature was raised to 30 占 폚 at a rate of 0.5 占 폚 / min, and the solution was immediately aged at 30 占 폚 for 10 days to crystallize the gel to obtain oxide nanoparticles of barium titanate. The gel obtained after the completion of aging was extracted and ultrasonically dispersed in 2-methoxyethanol to prepare a coating liquid containing 4.5 mass% of barium titanate nano-particles.

The crystallite diameter (primary particle diameter) of the obtained oxide nanoparticles was measured by X-ray diffraction measurement (X'Pert Pro manufactured by SPECTRITH Co., Ltd.) of a gel composed of oxide nanoparticles and using Scherrer's equation Respectively. The average particle size (aggregated particle size) of the oxide nanoparticles dispersed in the coating liquid was measured by a particle size distribution analyzer (Nano-ZS manufactured by Marl Reflective Products) according to the dynamic light scattering method. Table 1 shows the evaluation results of the primary particle diameter and the aggregated particle diameter.

Types of oxide nanoparticles A B C D E F The molar ratio of water in the hydrolysis solution (H ₂ O / Ti) 10 15 20 40 75 100 Primary particle size (nm) 6 10 17 31 44 60 Agglomerated particle size (nm) 8 12 16 32 49 95 Coagulation degree (coagulation particle size / first order inclusion) 1.3 1.2 0.9 One 1.1 1.6

< Example  1>

Oxide nanoparticles Sedimentary membrane  formation

A deposited film of oxide nano-particles, which is the first insulating film 3A, is deposited on ITO of an ITO glass substrate in which the first substrate 1 shown in Fig. 3 is glass and the first electrode 2 is ITO, A coating liquid containing 4.5% by mass of the particles B and an epoxy resin solution containing 4.7% by weight of an epoxy resin as a solvent were formed by spin coating.

An oxide nanoparticle coating liquid was coated on the ITO by a spin coating method, and then an epoxy resin solution was applied by an intergranular adhesive by spin coating, followed by heat treatment at 150 占 폚 to form a deposited film of oxide nanoparticles. Here, the application of the oxide nanoparticles was carried out by rotating the first spin coating at a speed of 1000 rpm x 10 sec, the number of revolutions and the time of the second spin coating at 3000 rpm x 20 sec. The application of the epoxy resin solution was carried out at 1000 rpm x 10 sec for the first spin coating and for 3 rpm x 20 sec for the second spin coating.

The coating solution of the oxide nanoparticles, the application of the epoxy resin solution and the heat treatment at 150 DEG C were repeated several times to form a deposited oxide nanoparticle film having a film thickness of about 1000 nm.

Oxide nanoparticles Sedimentary membrane  Electrical properties (capacitance density, Relative permittivity , Withstand voltage)

The relative dielectric constant and the capacitance density of the obtained oxide nanoparticle deposited film were obtained by forming an aluminum electrode having a diameter of about 5 mm on the surface of the oxide nanoparticle deposition film by vacuum evaporation and then applying the aluminum electrode and the ITO electrode to an impedance analyzer HP4192A of the product), and the capacitance was measured in a frequency range of 10 Hz to 1 MHz. The capacitance was calculated from the electrostatic capacitance value at 1 kHz as a typical value by using the thickness of the oxide nanoparticle deposited film and the aluminum electrode size. The results are shown in Table 2.

In order to evaluate the withstanding voltage at the time of driving the voltage of the EWD with respect to the withstand voltage, it is preferable that evaluation is made such that water is filled between the oxide nanoparticle deposition film and the electrode 6 corresponding to the insulating film 3 as in the structure shown in Fig. And a predetermined voltage was applied to the cell. In the evaluation cell, the oxide nanoparticle deposition film surface and the ITO surface of the new glass substrate were opposed to each other with a gap of 10 mu m, an aqueous solution of 0.09 mass% of sodium dodecyl sulfate (SDS) was filled as water therebetween, And the four sides of the cell were sealed with resin so as not to leak. Each of the ITO surfaces of the evaluation cell was connected to a pA meter (HP4140B manufactured by Agilent Technologies), and a predetermined voltage of 0 to 100 V was applied for 1 minute, and the current value was measured as a leakage current. When the leakage current exceeds 2 × 10 ^-6 A · cm ² , the voltage exceeding 2 × 10 ^-6 A · cm ² is defined as the withstand voltage since the ITO electrode is discolored and insulated by the electrochemical reaction. The results are shown in Table 2.

< Example  2 to 4, Comparative Example  1 to 2>

Each oxide nanoparticle deposition film was formed in the same manner as in Example 1, except that the kinds of the oxide nanoparticles were changed to A, C, D, E and F shown in Table 1, and the respective oxide nanoparticles The electrical properties (capacitance density, dielectric constant, withstand voltage) of the deposited film were evaluated. The results are shown in Table 2.

< Comparative Example  3>

Commercially available barium titanate particles (BT-01 as a chemical reagent) having an average particle diameter of primary particles of about 100 nm were used as oxide nanoparticles, and this was dispersed in 2-methoxyethanol so as to have a barium titanate concentration of 4.5 mass% To prepare a coating liquid of oxide nanoparticles. The oxide nanoparticle deposition film was formed in the same manner as in Example 1 except that the above-mentioned coating liquid was used, and the electrical properties (capacitance density, dielectric constant, withstand voltage) of the oxide nanoparticle deposition film were evaluated in the same manner as in Example 1. [ The results are shown in Table 2.

< Comparative Example  4>

A fluorine-based resin thin film having a film thickness of about 300 nm is formed by spin coating a sieve of Asahi Glass on ITO of an ITO glass substrate in which the first substrate 1 shown in Fig. 3 is glass and the first electrode 2 is ITO . Electrical properties (capacitance density, specific permittivity, withstand voltage) of the formed small-sized resin thin film were evaluated in the same manner as in Example 1. The results are shown in Table 2.

Type of insulating film Film thickness
(nm) Capacity density
(nF / cm ²⁾ Relative permittivity Withstand voltage
(V) Example 1 Sol gel particle B (primary particle diameter: 10 nm) + epoxy resin 1100 11 14 50 Example 2 Sol gel particle C (primary particle diameter: 17 nm) + epoxy resin 1120 11 14 50 Example 3 Sol gel particle D (primary particle diameter: 31 nm) + epoxy resin 1100 17 20 55 Example 4 Sol gel particle E (primary particle diameter: 44 nm) + epoxy resin 1200 11 16 38 Comparative Example 1 Sol gel particle A (primary particle diameter: 6 nm) + epoxy resin 1200 7 9 40 Comparative Example 2 Sol gel particle F (primary particle diameter: 60 nm) + epoxy resin 1100 10 13 12 Comparative Example 3 Commercial particle BT-01 (primary particle diameter 100 nm) + epoxy resin 1200 30 43 5 Comparative Example 4 Fluorine-based resin (sidewall of Asahi Glass) 300 3 One 60

Referring to Table 2, the insulating films formed of the oxide nanoparticle deposited films formed in Examples 1, 2, 3, and 4 of the present invention all had a capacitance density of 10 nF / cm 2 or more and were made of the fluororesin of Comparative Example 4 It is sufficiently high as compared with the capacity density of the insulating film, and the withstand voltage becomes equal to that of Comparative Example 4. [

In Comparative Example 1, since the primary particle diameter of the oxide nanoparticles is too small, the relative dielectric constant of the oxide nanoparticle itself decreases due to the size effect, and the capacitance density and the relative dielectric constant of the oxide nanoparticle deposited film decrease accordingly . Since the difference between the capacitance density of Comparative Example 1 and the capacitance density of Comparative Example 4 is small, the effect of reducing the driving voltage of the EWD is limited when the insulating film of Comparative Example 1 is used for the insulating film of EWD.

In Comparative Example 2, since the primary particle size of the oxide nanoparticles is too large, the filling property of the nanoparticles in the oxide nanoparticle deposited film is lowered, and the withstand voltage is remarkably lowered. Therefore, when Comparative Example 2 is used for the insulating film of EWD, the durability against the voltage of EWD is remarkably lowered and the reliability as an electronic device is lowered.

In Comparative Example 3, since commercial oxide nanoparticles heat-treated at a high temperature are used, the capacitance density and the relative dielectric constant of the nanoparticle deposited film are increased, but the chargeability of the particles is poor and the withstand voltage is remarkably low, Do.

As described above, the insulating film formed of the oxide nanoparticle deposition film according to the present invention can remarkably lower the driving voltage of the EWD as compared with the insulating film formed of the fluororesin of the prior art, and the durability against the voltage is equal to that of the prior art I have the ability.

< Example  5>

The oxide nanoparticle deposition film of Example 3 was used as the first insulating film 3A in Fig. 3 to form a polymer brush of the second insulating film 3B of Fig. 3, and an EWD panel for evaluation was produced.

Fluorine Polymer Of a brush  formation

The formation of the polymer brush which is the second insulating film 3B will be described. The method of forming the polymer brush is not particularly limited, and can be carried out by using a known method. First, on the oxide nanoparticle deposition film of Example 3, lattice-shaped pixel partitions were formed as if the pixels were separated by Japanese chemical SU-8. The initiator layer provided between the deposition film of the oxide nanoparticles as the first insulating film 3A and the polymer brush as the second insulating film 3B contained 38 g of ethanol, 2 g of ammonia water (28%), 2-bromo- , And 0.4 g of onyroxyhexyl triethoxysilane (BHE) were immersed in a glass substrate at room temperature overnight, followed by drying, in a solution containing a deposited film of oxide nanoparticles and a pixel partition wall. The polymer brushes were prepared by mixing ethyl-2-bromo ISO butylate as a polymerization initiator, tripropylethyl methacrylate as a monomer, CuBr as a catalyst, 4,4'-dinonyl 2,2'-dipyridine (dNbipy ) Was adjusted to 1: 1000: 12: 24, and the reaction was carried out at 90 DEG C for 3 hours. The film thickness of the formed polymer brush was about 20 nm. The substrate thus formed had high transparency.

Fabrication of counter substrate

A second electrode 6 was formed on the second substrate 7 and an outer peripheral bulkhead was formed of Japanese Chemical Agent SU-8 to prevent leakage of water / oil in the form of surrounding the substrate.

EWD  Production of panels

A dodecane solution containing 0.09% by mass of an aqueous solution of sodium dodecyl sulfate (manufactured by Kanto Chemical Co.) and 0.11 mol / L of a blue dye (OIL BLUE L manufactured by Kanto Chemical Co., Ltd.) was mixed at a ratio of 9: 1, The dodecane solution and the aqueous solution were separated. Thereafter, a second substrate on which an electrode and an outer circumferential rib are formed is placed on the bottom of the bath containing the solution, and a first substrate on which electrodes, deposited oxide films of oxide nanoparticles, pixel barrier ribs and fluorinated polymer brushes are formed, The first substrate and the second substrate were adhered and mixed in an aqueous solution, and the peripheral portion of the substrate was sealed with TB-3184M made by Surly Bond. In the EWD panel for evaluation produced in this way, an appropriate amount of the dodecane solution and the aqueous solution were sealed in the pixel portion, and the conversion of the coloring / non-coloring state could be favorably carried out by turning off / on the voltage.

< Comparative Example  5>

A fluororesin of Comparative Example 4 was used as the water-repellent insulating film of EWD, and a counter substrate and an electrowetting display device were produced as in Example 5.

EWD The relationship of the voltage to the white area area

According to the fifth embodiment of the present invention, for example, when the pixel size is 500 mu m, as shown in Fig. 2, the white region (non-colored region) can be enlarged with a lower voltage than that of Comparative Example 5, Is increased to 50% of the entire pixel, the voltage ratio can be reduced to about 1/5 of that of the conventional example.

Further, the present invention can be widely applied not only to a display device but also to other devices using an electrowetting technique.

1: first substrate 2: first electrode
3: insulating film 3a, 3A: first insulating film
3b, 3B: second insulating film 4: oil
5: water 6: second electrode
7: second substrate

Claims (11)

A first substrate,
A first electrode formed on the first substrate,
An insulating film formed on the first electrode,
A second substrate bonded to the first substrate,
A second electrode formed on the second substrate so as to face the insulating film,
And oil and water disposed between the insulating film and the second electrode,
An electrowetting device using an electrowetting phenomenon by applying a voltage between the first and second electrodes,
The insulating film
A first insulating layer formed of a nanoparticle deposition film of oxide nanoparticles having a high dielectric constant on a first substrate on which the first electrode is formed;
And a second insulating film formed on the first insulating film, the second insulating film being made of a polymer brush having high water-solubility. The method according to claim 1,
Wherein the nanoparticle deposition film of the oxide nanoparticles is formed of particles having a particle diameter of 10 nm to 50 nm. The method according to claim 1,
Wherein the oxide nanoparticles are barium titanate. The method according to claim 1,
Wherein the polymer brush is formed of a fluorine-based material. A first substrate,
A first electrode formed on the first substrate,
An insulating film formed on the first electrode,
A second substrate bonded to the first substrate,
A second electrode formed on the second substrate so as to face the insulating film,
And oil and water disposed between the insulating film and the second electrode,
A manufacturing method of an electrowetting device using an electrowetting phenomenon by applying a voltage between the first and second electrodes,
The step of forming the insulating film
Forming a first insulating film made of a nanoparticle deposition film of oxide nanoparticles having a high dielectric constant on a first substrate on which the first electrode is formed;
And forming the second insulating film made of a polymer brush having high water-solubility on the first insulating film. The method of claim 5,
Wherein the nanoparticle deposition film of the oxide nanoparticles is formed of particles having a particle diameter of 10 nm to 50 nm. The method of claim 5,
Wherein the oxide nano particles are barium titanate. The method of claim 5,
Wherein the oxide nanoparticles are synthesized by a sol-gel method. The method of claim 5,
Wherein the polymer brush is formed of a fluorine-based material. The method of claim 5,
Wherein the polymer brush is formed by living radical polymerization. The method of claim 5,
Wherein the insulating film is formed at 150 DEG C or less.

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