KR20160138896A - Transparent Dielectric Films, Electrostatic Capacity Type Touch Panels and Flexible Displays - Google Patents

Abstract

The object of the present invention is to provide a transparent dielectric film having a high dielectric constant and excellent transparency. The transparent dielectric film of the present invention includes high dielectric constant fine particles having polymer graft chains are arranged two-dimensionally or three-dimensionally through the polymer graft chains. The high dielectric constant fine particles used in the transparent dielectric film of the present invention may be at least one selected among a group consisting of BaTiO3 fine particles, TiO2 and ZrO2 and the like.

Description

Transparent Dielectric Film, Capacitive Touch Panel, and Flexible Display {Transparent Dielectric Films, Electrostatic Capacity Type Touch Panels and Flexible Displays}

The present invention relates to a transparent dielectric film, a capacitive touch panel, and a flexible display.

BACKGROUND ART [0002] Touch panels are widely used in various displays used in televisions, mobile phones, portable information terminals and the like. In the touch panel method, a resistive film type, a capacitive type, and the like are known, but in particular, attention is focused on a capacitive type touch panel capable of multi-input easily.

Conventionally, in a display provided with a capacitive touch panel, a cover material disposed on the upper surface (touch surface side) of the capacitive touch panel is generally made of chemically tempered glass because of its high transparency, high dielectric constant and excellent sensitivity come. However, since the chemically tempered glass is expensive, there is a problem that the manufacturing cost of the display rises. On the other hand, since the chemically tempered glass has not sufficient flexibility, it can not be used as a cover material for a flexible display having a capacitive touch panel. Further, since the dielectric constant of the member disposed between the electrode of the touch panel and the touch surface affects touch sensitivity, there arises a problem that the sensitivity of the touch panel is lowered when a resin film having a general dielectric constant is used as the cover member. Furthermore, even when a resin film having a general permittivity is used as a substrate positioned between the touch panel electrode and the touch panel among the substrates of the touch panel due to the same reason, the sensitivity of the touch panel deteriorates. Therefore, it has been proposed to use a transparent dielectric film in which a high dielectric constant particle such as barium titanate is contained in a resin film as a substrate of a touch panel or a cover material of a flexible display (for example, Patent Document 1).

Patent Document 1: JP-A-2014-203151

However, it is difficult to uniformly disperse the high-dielectric particles in the resin film. For example, a resin film containing high-purity fine particles is produced by molding a resin material containing high-purity fine particles into a film shape. Since the high-purity fine particles may aggregate and / or precipitate in the resin material, It is difficult to obtain a resin film uniformly dispersed. The aggregation of the high-dielectric fine particles in the resin film causes the resin film to become opaque, so that the transparency of the resin film can not be sufficiently secured.

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 a transparent dielectric film having a high dielectric constant and excellent transparency. Another object of the present invention is to provide a capacitive touch panel and a flexible display provided with a transparent dielectric film having such characteristics.

The present inventors have found that the above problems can be solved by arranging the high-molecular fine grains formed with the polymer graft chains in two-dimensional or three-dimensional directions through the polymer graft chain, and accomplished the present invention.

That is, the present invention is a transparent dielectric film characterized in that high-dielectric fine particles formed with a polymer graft chain are arranged two-dimensionally or three-dimensionally through the polymer graft chain.

Further, the present invention is a capacitive touch panel and a flexible display, characterized by having the transparent dielectric film.

According to the present invention, a transparent dielectric film having a high dielectric constant and excellent transparency can be provided. Further, according to the present invention, it is possible to provide a capacitive touch panel and a flexible display provided with a transparent dielectric film having such characteristics.

Fig. 1 shows the results of measurement of light transmittance in the visible region of the self-supporting films obtained in Examples 1 and 2 and Comparative Example 1. Fig.
Fig. 2 shows the measurement results of relative dielectric constants of the self-supporting films obtained in Examples 1 and 2 and Comparative Example 1. Fig.

The transparent dielectric film of the present invention is characterized in that the high-dielectric microparticles formed with the polymer graft chain are arranged two-dimensionally or three-dimensionally through the polymer graft chain.

Here, the term "polymer graft chain" means a polymer chain having two or more chain lengths (degree of polymerization (n) of 2 or more) formed by extending from the surface of the high-dielectric fine particles by polymerization reaction, and is also referred to as a polymer brush .

As used herein, the term " high dielectric particles " means dielectric particles having a relative dielectric constant of 10 or more, preferably 20 or more, more preferably 30 or more. Examples of the high specific gravity particles include BaTiO ₃ (barium titanate) fine particles (relative dielectric constant 1200), TiO ₂ (titanium dioxide) fine particles (relative dielectric constant 100), ZrO ₂ (zirconium oxide) fine particles (relative dielectric constant 30) . These may be used alone or in combination of two or more. Among them, BaTiO ₃ fine particles are preferable from the viewpoint of the dielectric constant of the transparent dielectric film.

In the present specification, "fine particles" means particles having an average particle diameter of 1 μm or less, and "average particle diameter" of fine particles means 50% cumulative particle diameter measured by a laser diffraction particle size distribution measuring apparatus.

As the average particle size of the high-dielectric fine particles becomes smaller, the transparency of the transparent dielectric film can be improved, while the dielectric constant of the particle itself decreases. Therefore, the average particle diameter of the high-dielectric fine particles is preferably 1 nm to 500 nm, more preferably 2 nm to 100 nm, further preferably 3 nm to 50 nm, and most preferably 4 nm to 30 nm.

The high-purity fine particles in which the polymer graft chain is formed can be formed by surface graft polymerization by living radical polymerization. By using this method, a polymer graft chain having a controlled chain length and a chain length distribution can be formed at high density on the surface of the high-dielectric-constant fine particles. In the vicinity of the surface of the high-dielectric fine particles, the polymer graft chain is in a state of being stretched in the direction perpendicular to the surface of the high-dielectric fine particles (rich polymer brush state) due to steric repulsion between adjacent polymer graft chains. Since the steric repulsion between the polymer graft chains is alleviated to some extent from the surface of the high-purity fine particles, the polymer graft chain is in a state of low elongation (semi-lean polymer brush state) compared to the state of the thick polymer brush. In the state of the polymer-rich polymer brush, the graft density of the polymer graft chain is 0.1 strand / nm ² or more, preferably 0.1 to 1.2 strands / nm ² , and in the semi-lean polymer brush state, the graft density of the polymer graft chain is 0.1 strand is a chain / ㎚ ^2, preferably less than 0.01-stranded chain / ㎚ ² 0.1-stranded chain / ㎚ less than ^2.

The graft density of the polymer graft chain can be calculated in accordance with a known method in the art. Specifically, the amount (graft amount) of the polymer graft chain grafted to the high-purity fine grains is determined by elemental analysis. By using the graft amount, the specific gravity and the surface area of the high-purity fine grains and the number average molecular weight of the polymer graft chain, Can be calculated.

It is preferable that the polymer graft chain formed in the high-purity fine particles has only a rich brush state, that is, the graft density of the polymer graft chain is 0.1 strand chain / nm ² or more. By using fine particles having a polymer graft chain only in a rich brush state, properties such as heat resistance of the formed transparent dielectric film can be improved. The polymer graft chain only in the rich brush state can be obtained by adjusting the polymerization degree.

Herein, the term "living radical polymerization" means a polymerization reaction in which a chain transfer reaction and a termination reaction do not substantially occur in a radical polymerization reaction, and the chain growth end remains active even after the radical polymerizable monomer completes the reaction . In this polymerization reaction, the polymerization activity is maintained at the end of the produced polymer even after the completion of the polymerization reaction, and if the radical polymerizable monomer is added, the polymerization reaction can be started again. Further, the living radical polymerization is characterized in that it is possible to synthesize a polymer having an arbitrary average molecular weight by controlling the concentration ratio of the radical polymerizable monomer and the polymerization initiator, and the resulting polymer has a very narrow molecular weight distribution.

A representative example of the living radical polymerization used in the present invention is Atom Transfer Radical Polymerization (ATRP). For example, in the case of performing atom transfer radical polymerization, the polymerization initiator is fixed on the surface of the high-dielectric microparticles, and atom transfer radical polymerization of the radically polymerizable monomer is then performed using a copper halide / ligand complex to form a polymer graft chain All the fine particles can be obtained.

The method of fixing the polymerization initiator to the surface of the high-dielectric fine particles is not particularly limited, and for example, the high-dielectric fine particles may be brought into contact with the polymerization initiator.

The polymerization initiator used in the present invention is not particularly limited as long as it can be fixed on the surface of the high-dielectric fine particles, and those known in the art can be used. The polymerization initiator preferably used in the present invention is a compound having a halogen at the terminal, for example, a compound represented by the following general formula (1) or (2) can be used.

Formula 1

(2)

In the general formulas (1) and (2), R1 is independently an alkyl group of C1 to C3, preferably a methyl group or an ethyl group, R2 is independently a methyl group or an ethyl group, X is a halogen atom, m is an integer of 2 to 10, preferably 3 to 8, and n is an integer of 3 to 10, preferably an integer of 4 to 8. Specific examples of the compound of formula (1) include 2-bromo-2-methyl-N- [3- (triethoxysilyl) propyl] propanamide; BPA, and specific examples of the compound of the general formula (2) include (2-Bromo-2-methyl) propionyloxyhexyltriethoxysilane; BHE and the like.

The radical polymerizable monomer used in the living radical polymerization has an unsaturated bond capable of performing radical polymerization in the presence of an organic radical, and examples thereof include acrylic acid derivatives, methacrylic acid derivatives, styrene derivatives, vinyl acetate and acrylonitrile . Specific examples include methyl methacrylate (MMA), ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, Acrylate, methacrylate, methacrylate, methacrylate, methacrylate, methacrylate, methacrylate, methacrylate, methacrylate, Hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, tetrahydroperfuryl methacrylate, 2-hydroxy-3-phenoxy Methacrylate monomers such as propyl methacrylate, diethylene glycol methacrylate, polyethylene glycol methacrylate and 2- (dimethylamino) ethyl methacrylate; 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, 2-hydroxypropyl acrylate, diethylene glycol acrylate, polyethylene glycol acrylate, 2- (dimethylamino) ethyl acrylate, 2-hydroxypropyl acrylate, N, N-dimethylacrylamide, N-methylolacrylamide and N-methylolmethacrylamide. Murray; Styrene, o-, m-, p-methoxystyrene, o-, m-, pt-butoxystyrene, o-, m-, p-chloromethylstyrene, vinyl propionate, vinyl methyl ketone, vinyl hexyl ketone, methyl Vinyl pyrrolidone, N-vinyl carbazole, N-vinyl indole, acrylonitrile, methacrylonitrile, acrylamide, isopropylacrylamide, methacrylamide, Vinyl chloride, vinylidene chloride, tetrachlorethylene, hexachloroprene, vinyl fluoride, and the like. These may be used alone or in combination of two or more.

Copper halides which provide a copper halide / ligand complex are not particularly limited and those generally used in living radical polymerization can be used. Examples of the halogenated copper include CuBr, CuCl, CuI and the like.

The ligand compound which provides the copper halide / ligand complex is not particularly limited, and those generally known in living radical polymerization can be used. Examples of the ligand compound include triphenylphosphine, 4,4-dinonyl-2,2-dipyridine (dNbipy), N, N, N 2, N 2 -pentamethyldiethylenetriamine (PMDETA) 1,1,4,7,10,10-hexamethyltriethylenetetraamine, and the like.

The amount of the high-dielectric-constant fine particles, the polymerization initiator, the radically polymerizable monomer, the copper halide and the ligand compound to be used in the preparation of the high-molecular-weight graft chain-containing high-purity fine particles may be appropriately adjusted according to their kind and the like, and is not particularly limited. The production conditions may also be appropriately adjusted according to the type of the raw material to be used and the like, and are not particularly limited.

The living radical polymerization may be carried out without solvent, but a solvent generally used in living radical polymerization may be used. Examples of usable solvents include benzene, toluene, anisole, N, N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetone, chloroform, carbon tetrachloride, tetrahydrofuran (THF) Organic solvents such as methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 2-methoxyethanol and 1-methoxy-2-propanol, water and the like. The amount of the solvent can be suitably adjusted according to the kind of the raw material to be used, and is not particularly limited.

The molecular weight of the polymer graft chain formed by the living radical polymerization can be controlled by the reaction temperature, the reaction time, the kind and the amount of the raw material to be used, but the number average molecular weight is generally 500 to 1,000,000, preferably 1,000 to 500,000, And an average molecular weight of 1,000 to 2,000,000, preferably 2,000 to 1,000,000. The molecular weight distribution (M _w / M _n ) of the polymer graft chain is not particularly limited, but is 1.05 to 2.80, preferably 1.20 to 2.50.

The transparent dielectric film of the present invention has a structure in which high-molecular fine grains formed with polymer graft chains having the above-described characteristics are arranged two-dimensionally or three-dimensionally through a polymer graft chain.

Further, the transparent dielectric film of the present invention can be formed as a self-supporting film. Herein, the term "self-supporting film" means a film capable of maintaining a shape sufficiently without using a support.

The transparent dielectric film of the present invention can be produced using methods known in the art. For example, when a solvent casting method is used, a transparent dielectric film is formed by dispersing high-dielectric particles in which a polymer graft chain is formed in a solvent, coating the dispersion on a substrate, and evaporating the solvent, And the like.

There is no particular limitation on the substrate on which the dispersion liquid in which the high-dielectric-constant fine particles are dispersed in the solvent is used, and those known in the art can be used. Examples of the substrate include a glass plate, a stainless plate, a stainless belt, a polyethylene terephthalate (PET) film, and the like. In order to improve the releasability of the transparent dielectric film, these substrates may be subjected to mirror surface processing, surface release agent treatment or the like, if necessary.

The solvent for dispersing the high-dielectric particles in which the polymer graft chain is formed is not particularly limited and those known in the art can be used. Examples of the solvent include aprotic polar solvents such as N, N-dimethylformamide (DMF), N, N-dimethylacetamide, N-methyl-2-pyrrolidone and dimethylsulfoxide; Chlorinated solvents such as dichloromethane, chloroform, 1,2-dichloroethane, chlorobenzene, and dichlorobenzene; Alcohols such as methanol, ethanol and propanol; Alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether and propylene glycol monoethyl ether; toluene; Anisole; Water and the like. These may be used alone or in combination of two or more.

The concentration of the high-molecular fine grains in which the polymer graft chain is formed is not particularly limited, but is generally 0.1 to 30 wt%, preferably 0.5 to 20 wt%, more preferably 1 to 10 wt%.

The amount of dispersion of the dispersion on the substrate is not particularly limited as long as it is appropriately adjusted according to the application in which the transparent dielectric film is used. Further, in order to obtain a transparent dielectric film having a desired thickness, application of the dispersion and evaporation of the solvent may be performed plural times. The thickness of the transparent dielectric film suitable for the cover material of the flexible display is generally 0.1 탆 to 500 탆, preferably 0.5 탆 to 300 탆, more preferably 1 탆 to 250 탆. If the thickness of the transparent dielectric film is thinner than 0.1 占 퐉, mechanical strength usable as a cover material may not be obtained. On the other hand, when the thickness of the transparent dielectric film exceeds 500 탆, flexibility and transparency of the transparent dielectric film may be impaired. Further, the thickness of the transparent dielectric film can be adjusted by laminating the transparent dielectric film obtained by the casting method, heating, pressing and integrating.

The conditions for evaporating the dispersion are not particularly limited and may be appropriately adjusted according to the type of the solvent used as the dispersion. Generally, the solvent is heated to a temperature higher than the boiling point of the solvent.

Since the transparent dielectric film of the present invention manufactured as described above uses the high-dielectric fine particles formed with the polymer graft chain, the high dielectric constant film is uniformly dispersed in the transparent dielectric film without aggregation of the high-dielectric fine particles, Not only transparency.

The volume fraction of the high dielectric fine particles in the transparent dielectric film of the present invention is not particularly limited, but is preferably 2 vol.% To 30 vol.%, More preferably 3 vol.% To 20 vol.%, Still more preferably 4 vol. To 15 vol%, and most preferably from 5 vol% to 12 vol%. In the present specification, the 'volume fraction of high-dielectric particles' refers to the volume fraction of high-dielectric particles calculated by TGA (thermogravimetry). Specifically, the volume fraction of the high-dielectric-constant fine particles can be obtained from the amount of the residue at 450 DEG C by raising the temperature of the transparent dielectric film to 450 DEG C at 10 DEG C / min.

In the transparent dielectric film of the present invention, chemical bonds may be formed between the polymer graft chains of the high-dielectric fine particles adjacent to each other. For example, a radically polymerizable monomer used for living radical polymerization may be a monomer obtained by introducing a functional group crosslinked or polymerized by external stimuli such as light or heat into a side chain, and an external stimulus such as light or heat is applied to the self- A chemical bond can be formed between the polymer graft chains of the adjacent microparticles. As a result, the mechanical properties of the transparent dielectric film can be improved.

The transparent dielectric film of the present invention has a relative dielectric constant (25 DEG C) of 3.5 or more, preferably 4.0 or more at a frequency of 1 kHz. The relative dielectric constant can be measured by a commercially available relative dielectric constant measuring apparatus.

In the transparent dielectric film of the present invention, the average value of the light transmittance in the visible region (wavelength 400 nm to 800 nm) is 80% or more. In particular, the transparent dielectric film of the present invention has a light transmittance at 550 nm of 80% or more, preferably 85% or more. Herein, the term 'light transmittance' means a rate at which light is transmitted through a transparent dielectric film having a thickness of 100 μm, and a larger value indicates higher transparency. The light transmittance can be measured by a commercially available light transmittance measuring apparatus.

Since the transparent dielectric film of the present invention has a high dielectric constant and is excellent in transparency, it can be used as a cover material for various displays having a capacitive touch panel. In particular, since the transparent dielectric film of the present invention is excellent in flexibility, it can be applied as a cover material of a flexible display having capacitive touch panels. The transparent dielectric film of the present invention can also be applied as a substrate of a capacitive touch panel. Furthermore, since the transparent dielectric film of the present invention is excellent in heat resistance, surface hardness and retardation value as disclosed in Japanese Patent Application No. 2014-212174 filed on October 17, 2014 by the present applicants, It can also be used as a substrate for flexible displays.

<Examples>

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto.

Example 1

1.5 ml of ammonia water was added to 15.5 g of a 2-methoxyethanol dispersion of barium titanate (BaTiO ₃ ) fine particles having an average particle size of 7 nm (a content of BaTiO ₃ fine particles of 8 wt%, manufactured by JGC Catalysts and Chemicals Ltd.) Min. Then, 1.00 g of a polymerization initiator (BPA) dissolved in 2.0 g of 2-methoxyethanol was slowly dropped into the mixed solution, and the mixture was stirred at 40 占 폚 for 18 hours. Subsequently, the solvent was removed from the mixed solution by using an evaporator, and a small amount of water was added thereto. The mixture was centrifuged at 4500 rpm for 10 minutes to obtain BaTiO ₃ fine particles (hereinafter referred to as BPA-BaTiO ₃ fine particles ).

Then, 500 mg of MMA, 6.00 g of DMF and 33.7 mg of PMDETA were added to 204.9 mg of BPA-BaTiO ₃ fine particles and stirred under ice bath using a homogenizer. Next, this mixed solution was put into a two-necked flask, degassed three times by freeze-thaw method, and 24.6 mg of CuBr was added thereto, followed by nitrogen substitution and polymerization was carried out at 70 ° C for 1 hour. After completion of the reaction, the mixed solution was bubbled to deactivate (inactivate, deactivate) Cu. Next, the mixed solution was dissolved in THF, reprecipitated in a mixed solution of methanol / 0.1 M aqueous EDTA solution (volume ratio 20/1), and centrifuged at 4500 rpm for 10 minutes. After repeating three times the reprecipitation, and centrifuged to thereby give a by overnight vacuum drying at 80 ℃, BaTiO ₃ fine particles (hereinafter omitted as "PMMA-BaTiO ₃ fine particle") is a chain formed of PMMA.

The molecular weight of the PMMA (polymer graft chain) separated by immersing the PMMA-BaTiO ₃ fine particles obtained above in hydrofluoric acid and dissolving the BaTiO ₃ fine particles was evaluated using a GPC measuring device (product of JASCO Corporation, LC-2000plus). Polystyrene was used as a standard sample and UV detector was used as a detector. As a result, the number average molecular weight was 39,500 and the weight average molecular weight (Mw) was 92,000.

The graft density of the PMMA-BaTiO ₃ fine particles was calculated in accordance with a method known in the art, and as a result, it was 0.18 strands / nm ² .

Next, a dispersion containing 1 wt% of PMMA-BaTiO ₃ fine particles was prepared using anisole as a solvent. This dispersion was then applied to a substrate at room temperature and then dried at 80 DEG C under vacuum to obtain a self-supporting film having a thickness of 100 mu m.

It was confirmed that the obtained self-supporting film could be wound on a rod having a diameter of 6 mm and had sufficient flexibility. Further, the volume fraction of BaTiO ₃ fine particles was calculated by TGA (thermogravimetry) with respect to the self-supporting film, and as a result, the volume fraction of BaTiO ₃ fine particles was found to be 10.0 vol%. As a result of measurement of small angle X-ray scattering (SAXS) and observation of TEM (Transmission Electron Microscope) on the self-supporting film, PMMA-BaTiO ₃ fine particles were uniformly dispersed As shown in Fig.

Example 2

As the polymerization conditions, PMMA-BaTiO ₃ fine particles were produced in the same manner as in Example 1 except that the mixing ratio (mass ratio) of the BPA-BaTiO ₃ fine particles and MMA was adjusted to 1:10 and the polymerization time was changed to 3 hours To obtain a self-supporting film.

The PMMA-BaTiO ₃ fine particles thus obtained were evaluated for the molecular weight of PMMA (polymer graft chain) in the same manner as in Example 1. The number average molecular weight was 38700 and the weight average molecular weight (Mw) was 61800.

The graft densities of the PMMA-BaTiO ₃ fine particles were calculated according to a method known in the art and found to be 0.43 strands / nm ² .

Next, a dispersion containing 1 wt% of PMMA-BaTiO ₃ fine particles was prepared using anisole as a solvent. This dispersion was then applied to a substrate at room temperature and then dried at 80 DEG C under vacuum to obtain a self-supporting film having a thickness of 100 mu m.

It was confirmed that the obtained self-supporting film could be wound on a rod having a diameter of 6 mm and had sufficient flexibility. Further, the volume fraction of BaTiO ₃ fine particles was calculated by TGA (thermogravimetry) with respect to the self-supporting film, and as a result, the volume fraction of BaTiO ₃ fine particles was found to be 4.7 vol%. Further, as a result of measurement of incineration X-ray scattering (SAXS) and observation of a scanning electron microscope (TEM) on the self-supporting film, it was confirmed that the PMMA-BaTiO ₃ fine particles were uniformly dispersed without being agglomerated.

Example 3

As the polymerization conditions, PMMA-BaTiO ₃ fine particles were produced in the same manner as in Example 1 except that the mixing ratio (mass ratio) of the BPA-BaTiO ₃ fine particles and MMA was adjusted to 1: 4 and the polymerization time was changed to 3 hours To obtain a self-supporting film.

The PMMA-BaTiO ₃ fine particles thus obtained were evaluated for the molecular weight of PMMA (polymer graft chain) in the same manner as in Example 1. The number average molecular weight was 125000 and the weight average molecular weight (Mw) was 159100.

The graft densities of the PMMA-BaTiO ₃ fine particles were calculated in accordance with a method known in the art and found to be 0.10 strand / nm ² .

Next, a dispersion containing 1 wt% of PMMA-BaTiO ₃ fine particles was prepared using anisole as a solvent. This dispersion was then applied to a substrate at room temperature and then dried at 80 DEG C under vacuum to obtain a self-supporting film having a thickness of 100 mu m.

It was confirmed that the obtained self-supporting film could be wound on a rod having a diameter of 6 mm and had sufficient flexibility. In addition, a result of calculation by the volume content of the BaTiO ₃ particles with respect to the free-standing film to TGA (thermogravimetric measurement), the volume content of the BaTiO ₃ particles was 6.2 vol%. Further, as a result of measurement of incineration X-ray scattering (SAXS) and observation of a scanning electron microscope (TEM) on the self-supporting film, it was confirmed that the PMMA-BaTiO ₃ fine particles were uniformly dispersed without being agglomerated.

Example 4

As PMMA-BaTiO ₃ fine particles were produced in the same manner as in Example 1 except that the mixing ratio (mass ratio) of BPA-BaTiO ₃ fine particles to MMA was adjusted to be 1: 4 and the polymerization time was changed to 20 hours To obtain a self-supporting film.

The PMMA-BaTiO ₃ fine particles obtained above were evaluated for the molecular weight of PMMA (polymer graft chain) in the same manner as in Example 1. The number average molecular weight was 64900 and the weight average molecular weight (Mw) was 100700.

The graft density of PMMA-BaTiO ₃ fine particles was calculated according to a method known in the art, and as a result, it was found to be 0.13 strands / nm ² .

Next, a dispersion containing 1 wt% of PMMA-BaTiO ₃ fine particles was prepared using anisole as a solvent. This dispersion was then applied to a substrate at room temperature and then dried at 80 DEG C under vacuum to obtain a self-supporting film having a thickness of 100 mu m.

It was confirmed that the obtained self-supporting film could be wound on a rod having a diameter of 6 mm and had sufficient flexibility. Further, the volume fraction of BaTiO ₃ fine particles was calculated by TGA (thermogravimetry) with respect to the self-supporting film, and as a result, the volume fraction of BaTiO ₃ fine particles was 9.1 vol%. Further, as a result of measurement of incineration X-ray scattering (SAXS) and observation of a scanning electron microscope (TEM) on the self-supporting film, it was confirmed that the PMMA-BaTiO ₃ fine particles were uniformly dispersed without being agglomerated.

Comparative Example 1

Comparative Example 1 to prepare a self-supporting film having a thickness of 100 ㎛ made of only PMMA containing no BaTiO ₃ particles.

It was confirmed that the obtained self-supporting film could be wound on a rod having a diameter of 6 mm and had sufficient flexibility.

Next, for the self-supporting films obtained in Examples 1 and 2 and Comparative Example 1, the light transmittance in the visible region was measured using Shimadzu Corporation V-570. The results are shown in Fig.

The relative permittivity of the self-supporting films obtained in Examples 1 and 2 and Comparative Example 1 was measured at 25 캜 using a Solatron 1255B impedance analyzer connected to a SH2-Z sample holder made by TOYO Corporation. The results are shown in Fig.

As shown in Fig. 1, it was confirmed that the self-supporting films of Examples 1 and 2 had an average value of light transmittance in the visible region of 80% or more and had sufficient transparency. In particular, it was confirmed that the self-supporting film of Example 1 had a light transmittance of at least 85% at 550 nm, which was particularly excellent in transparency.

Also, as shown in Fig. 2, the self-supporting films of Examples 1 and 2 were confirmed to have higher dielectric constants as compared with the self-supporting films of Comparative Example 1. [ In particular, it was confirmed that the self-supporting film of Example 1 had a dielectric constant as high as 4.0 or more at a frequency of 1 kHz and a particularly high dielectric constant.

As can be seen from the above results, according to the present invention, a transparent dielectric film having a high dielectric constant and excellent transparency can be provided. Further, according to the present invention, it is possible to provide a capacitive touch panel and a flexible display having a transparent dielectric film having such characteristics.

Claims (11)

Wherein the high-dielectric-constant fine particles having the polymer graft chain formed thereon are arranged two-dimensionally or three-dimensionally through the polymer graft chain.
The method according to claim 1,
Wherein the high-dielectric-constant fine particles are at least one selected from the group consisting of BaTiO ₃ fine particles, TiO ₂ fine particles, and ZrO ₂ fine particles.
3. The method according to claim 1 or 2,
A transparent dielectric film having a relative dielectric constant of 4 or more at a frequency of 1 kHz.
3. The method according to claim 1 or 2,
And a light transmittance at 550 nm of 80% or more.
3. The method according to claim 1 or 2,
Wherein the volume percentage of the high-dielectric-constant fine particles is from 2 vol% to 30 vol%.
3. The method according to claim 1 or 2,
Wherein the high-dielectric-constant fine particles have an average particle size of 100 nm or less.
3. The method according to any one of claims 1 to 3,
Wherein the polymer graft chain has a graft density of 0.1 strand chain / nm ² or more.
3. The method according to claim 1 or 2,
Wherein the polymer graft chain is formed by living radical polymerization of at least one compound selected from acrylic acid derivatives, methacrylic acid derivatives, styrene derivatives, vinyl acetate and acrylonitrile.
3. The method according to claim 1 or 2,
Wherein chemical bonds are formed between the polymer graft chains of the high-dielectric fine particles adjacent to each other.
A capacitive touch panel having the transparent dielectric film according to any one of claims 1 to 3.
A flexible display having the transparent dielectric film according to any one of claims 1 to 3.

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