KR101543568B1 - Coating composition and antireflection film forming method using the same - Google Patents

Abstract

The present invention relates to a water-dispersible metal oxide having a pH of 9 to 12, which contains a basic stabilizer having a pKa of 9 to 13, an isoelectric point adjusting agent having a pKa of 7 to 11 and a hardening accelerator having a pKa of 6 to 12, ) Solution and a method for forming an antireflection film using the coating composition.
According to the present invention, it is possible to provide an antireflection film of a nanoporous metal oxide film capable of controlling a wide range of refractive index in a low-temperature production process at a temperature of 10 to 150 DEG C and having a high weather resistance and mechanical strength, Can be provided.

Description

[0001] The present invention relates to a coating composition and an antireflection film forming method using the same,

The present invention relates to a coating composition and a method for forming an antireflection film using the same, and more particularly, to an antireflection film for a nano-porous metal oxide film having a high refractive index and a high refractive index, And a method for forming an antireflection film using the same.

In general, nanoporous films are widely applied to a carrier, such as a catalyst or a protein, a gas / liquid separation membrane, and a low refractive optical film. Particularly, a low refractive optical film is widely used in the field of antireflection.

A wet antireflective coating method using a solution in which nanoparticles are dispersed has attracted much attention in recent years. In this case, there is a limit in reducing the thickness of the thin film due to the size of particles constituting the actual thin film. When a solution of nanoparticles dispersed uniformly on an optical component such as glass or a transparent film, the nanoparticles meet and connect with each other as the solvent evaporates, forming a nanoporous network structure containing many nano-sized pores.

In the case of the antireflection film, although it has many advantages in the case of having a low refractive index, there is a great restriction in practical application because the antireflection film has a very weak mechanical strength. The porosity and mechanical strength are inversely proportional to each other. As the porosity increases, the mechanical strength of the film becomes weaker. As a result, a film having a low refractive index, that is, a high porosity and a high mechanical strength Is very difficult. Therefore, a high heat treatment at 450 to 500 ° C or more may be performed to induce chemical bonding between nanoparticles to obtain high durability of the antireflection film.

On the other hand, a method for producing an antireflection film on a polymer film requiring a process under milder conditions is very limited. In these cases, low process temperatures are required, often resulting in catalyst problems. Generally, heating of polymer films to high temperature causes physical and chemical modification of the film, and except for some special films, only the temperature of less than 120 ° C is applicable to the process. In addition, ammonia gas (mainly used in the form of NH ₄ OH), which is a catalyst used as a silica production catalyst, promotes the condensation reaction between silanol present on the silica surface to increase the durability of the antireflection film, And a yellowing of the transparent polymer film due to the chemical reaction between the ammonia and the polymer occurs in the process.

Another problem is difficulty in controlling the porosity of the antireflection film. Large particles are used to impart porosity. However, it is accompanied by a low mechanical strength of the antireflection film. Conversely, when a binder is used to impart mechanical strength, the gap between the particles is filled. A high refractive index due to the high refractive index. That is, an organic binder or a crosslinking agent is added to the nanoparticle dispersion solution to increase the mechanical strength of the manufactured antireflection film by increasing the connectivity or adhesiveness between the nanoparticles, while the refractive index of the film is increased It has a negative effect on the characteristics of the antireflection film, such as an increase in the thickness of the antireflection film. US Publication No. 20130034722 (published on Mar. 23, 2013) shows that the binder increases the adhesion between individual silica particles to produce a highly porous film, but its utility is limited.

In addition, attempts have been made to inject a crosslinking agent after forming a porous nanoparticle assembly structure having a low mechanical strength formed at first. However, due to the effect of covering the surface of the antireflection film and filling the pores, a high refractive index and a low AR effect That is, a film showing a decrease in the reflectance reduction effect is obtained. In recent years, attempts have been made to increase the strength of nanoparticle structures by injecting gaseous compounds, such as SiCl ₄ or TEOS (tetraethylorthosilicate), which are easily hydrolyzed, into the gaseous state. However, this phenomenon also increases the refractive index It is not easy to control at each reaction step leading to injection, hydrolysis and condensation of the sample as well as chemical vapor deposition (CVD) and atomic layer deposition (ALD) equipment in order to produce an antireflection film Economy is greatly reduced.

In addition, nanoporous metal oxide films have a high hydrophilicity on the surface, indicating that they are very vulnerable in high humidity environments. Although the amorphous silica has a solubility in a neutral aqueous solution at room temperature, it has a porosity of more than 50%, and a nanoporous thin film made of hydrophilic nano-sized silica having a very large surface area of only a few hundred nanometers in thickness Are vulnerable to water.

In order to solve the problems of the prior art as described above, the present invention provides a nano-porous metal oxide film having a low refractive index, which can control a wide range of refractive index in a low-temperature manufacturing process at 10 to 150 ° C or less, Reflection film of the present invention. Another object of the present invention is to provide an antireflection film exhibiting high light transmittance. Other objects of the present invention can be easily understood from the following description of the embodiments.

According to an aspect of the present invention, there is provided a process for preparing a curable composition comprising a basic stabilizer having a pKa of 9 to 13, an isoelectric point adjusting agent having a pKa of 7 to 11, a curing accelerator having a pKa of 6 to 12 And a water-dispersed metal oxide solution having a pH of 9 to 12, wherein the water-dispersed metal oxide solution is contained.

The water-dispersed metal oxide solution may be composed of any one of water-dispersed alumina (AlOx) solution, water-dispersed silica (SiOx) solution, water-dispersed ceria (CeOx) solution and water-dispersed titania (TiOx) solution or a mixture thereof.

The water-dispersed metal oxide solution may be an aqueous solution containing 1 to 5 wt% of metal oxide particles having a size of 1 to 1,000 nm.

The basic stabilizer may be any one of metal hydroxide and organic hydroxide or a mixture thereof.

The isoelectric point adjusting agent may be any one of ammonium hydroxide, primary amine, secondary amine and tertiary amine, or a mixture thereof.

The curing accelerator may be an aqueous solution of a complex salt of an acid and a base.

The curing accelerator may be selected from the group consisting of tetraalkyl ammonium acetate, tetraalkyl ammonium salt, tetraalkyl ammonium salt, tetraalkyl ammonium salt, tetraalkyl ammonium salt, ammonium salt, ammonium salt, ammonium salt, ammonium salt, ammonium salt, acetoamidine hydrochloride, or a mixture thereof.

The coating composition may comprise 0.1-3.0 wt.% Of Al ³⁺ ions relative to the metal oxide.

The coating composition may include laponite, which is a plate-like nanoparticle 0.1 to 5.0% by weight based on the metal oxide.

According to another aspect of the present invention, there is provided a method of making a coating composition, comprising: applying a coating composition according to one aspect to a substrate; Drying the coating composition applied to the substrate to form a nanoporous metal oxide film; And aging the nanoporous metal oxide film at a temperature of 10 to 150 DEG C and a relative humidity of 30 to 80%.

Further comprising the step of forming a hard coating layer on the substrate by coating the acrylic hard coating, the melamine hard coating, the epoxy hard coating, the organic hybrid hard coating or a mixture thereof before applying the coating composition .

Wherein the top layer of the substrate has a functional group selected from the group consisting of a silanol group, a hydroxyl group, a siloxane group, an ether group, an ester group, a carbonyl group, a carboxyl group, a carbonate group, an amide group, a urea group, a urethane group, and a sulfone group The method comprising the steps of:

The step of applying the coating composition to a substrate may be carried out by any suitable process known in the art such as slit die coating, dip coating, gravure coating, spining coating, roll coating, bar coating, The coating composition may be applied to the substrate by any one of spray coating, flow coating, and the like.

According to the coating composition of the present invention and the method of forming an antireflection film using the same, it is possible to provide a nano-porous metal oxide film having a low refractive index, which can control a wide range of refractive index in a low temperature manufacturing process at 10 to 150 ° C, It is possible to provide an antireflection film and to provide an antireflection film exhibiting high light transmittance.

1 is a flow chart illustrating a method of forming an antireflective film using a coating composition according to one embodiment of the present invention.

The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated and described in detail in the drawings. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but is to be understood to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention, And the scope of the present invention is not limited to the following examples.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings, wherein like or corresponding elements are denoted by the same reference numerals, and redundant explanations thereof will be omitted.

The coating composition according to the present invention comprises a basic stabilizer having a pKa of 9 to 13, a water-dispersed metal having a pH of 9 to 12 containing an isoelectric point adjusting agent having a pKa of 7 to 11 and a hardening accelerator having a pKa of 6 to 12 And a metal oxide solution. Here, the water-dispersed metal oxide solution may be any one of a water-dispersed alumina (AlOx) solution, a water-dispersed silica (SiOx) solution, a water-dispersed ceria (CeOx) This is an example only, not necessarily so.

The water-dispersed metal oxide solution may be an aqueous solution containing 1 to 5 wt% of metal oxide particles having a size of 1 to 1,000 nm, preferably 6 to 150 nm. When the particle size is increased, the hardness and permeability of the fabricated nanoporous metal oxide film is lowered. If the particle size is smaller, the porosity of the nanoporous metal oxide film can not be ensured. If the concentration of the metal oxide particle is dependent on the production method of the film, . For example, the concentration of the metal oxide particles is suitably in the range of 4 to 5 wt% when spin coating is used, and 1.5 to 2 wt% is suitable when using bar coating or gravure coating Do. Also, the usable particle size can be determined according to the wavelength band of light for improving the transmittance. Metal oxide particles with a size of 100 nm or less lower the reflectance mainly in the range of UV to visible light and metal oxide particles with a size of 100 nm or more can be used to lower the reflectance of visible light to NIR to FIR wavelength band. However, if the particles of the metal oxide are too large, they may be disadvantageously dispersed in the solution for a long time because the particles are heavy.

A basic stabilizer may be added to the aqueous solution to adjust the pH to 9 to 12, preferably 10 to 10.5, in order to impart long-term stable dispersibility. In this pH region, for example, the silanol group on the silica surface is ionized, and the negative charge is generated, so that the repulsive force between the colloid particles is increased and the stability of the solution is greatly improved. The basic stabilizer used should have a pKa in the range of 9 to 13, and the boiling point thereof should be 100 ° C or less, which is the boiling point of water as a solvent. If the boiling point such as 2-methoxyethanol is mixed with a solvent higher than water, The boiling point may be below the boiling point of 2-methoxyethanol or below its azeotrope temperature. Thus, the basic stabilizer may be any one of metal hydroxide and organic hydroxide, or a mixture thereof. Here, the metal hydroxide may be KOH, NaOH or the like, and the organic hydroxide may be NH ₄ OH, N (CH ₃ ) ₄ OH, or the like.

An isoelectric point adjuster is added to adjust the isoelectric point of the dispersed nano metal oxide particles. At this time, the isoelectric point adjusting agent added has a pKa in the range of 7 to 11, and its boiling point is equal to or lower than the drying temperature of the nanoporous metal oxide film. The isoelectric point adjusting agent may be any one of ammonium hydroxide, primary amine, secondary amine, tertiary amine, or a mixture thereof. The isoelectric point adjusting agent may be, for example, ammonium hydroxide, ethylamine, propylamine, butylamine, pentylamine, tetramethylethylenediamine or N, N-dimethylethylenediamine. It is preferable to adjust the pKa value and addition amount of the charge control agent such that the isoelectric point is adjusted to be pH 9 or less, preferably pH 8 or less. If it is higher than the above range, the stability of the solution is greatly degraded due to the progress of the gelation. Particularly, in the case of polyamines such as hexamethylenetetramine or tris (2-aminoethyl) amine, the stability of the solution is greatly reduced even by the addition of a small amount, which is caused by the double layer disturbance of the surface of the metal oxide due to their high charge effect.

The gelled initial state nanoporous metal oxide film can further accelerate the condensation reaction to achieve higher mechanical strength. As described above, the basic stabilizer or isoelectric point controlling agent, such as basic amines and amines, is a good catalyst for the silanol condensation reaction, as well as a curing accelerator having a pKa of 6 to 12 as an additional catalyst, Better effect can be obtained if it is contained.

The condensation reaction can be accelerated by dehydroxylation and deprotonation reaction under an acid or base catalyst. Suitable catalysts preferably have amphoteric characteristics of acid and base and buffering function of pH. The buffering function of pH plays a very important role in preserving the stability of the present coating composition. Thus, the curing accelerator may be an aqueous solution of a complex salt of an acid and a base, and may be a tetraalkyl ammonium acetate, tetraalkyl ammonium salt, tetraalkyl ammonium salt, tetraalkyl ammonium salt, ammonium acetate, ammonium formate, ammonium carbonate, ammonium fluoride, hydrazine monohydrochloride, guanidine hydrochloride, ethylenediamine hydrochloride, hydrazinium chloride, hydroxylamine hydrochloride, acetoamidine hydrochloride, or a mixture thereof.

In addition, in consideration of the weather resistance of the antireflection film by the nano-porous metal oxide film, it is required to enhance stability against moisture. For this purpose, the doping of iron, titanium or aluminum may be considered for the metal oxide film, but the use of aluminum is preferred in view of the transparency and the refractive index of the oxide, and the coating composition may contain Al ³⁺ ions. For this purpose, various aluminates such as AlCl ₃ , Al (NO ₃ ) and various aluminum salts and sodium aluminate can be used. Considering the reactivity with the nano metal oxide and the compatibility with the above-mentioned coating composition, ammonium hexafluoroaluminate is most preferable. The concentration of Al ³⁺ ions is preferably 0.1 to 3.0% by weight, more preferably 0.5 to 1.0% by weight, based on the metal oxide. When the content is less than 0.1% by weight, the effect is insufficient. When the content is more than 3.0% by weight, the transmittance of the antireflection film is decreased.

In addition, when adjusting the porosity of the nanoporous metal oxide film, it is possible to increase the porosity while maintaining high mechanical strength, and in particular, improve the transmittance of the antireflection film by adding laponite as the plate-like nanoparticle to the above-mentioned coating composition. Laponite is a plate-like crystalline silicate with a thickness of 0.92 nm and a diameter of about 25 nm and has the property of being well dispersed in an aqueous solution. The addition amount thereof is 0.1 to 5.0% by weight, preferably 1 to 2% by weight, based on the metal oxide.

The coating composition according to the present invention can be produced as an antireflection film having a high mechanical strength and a low refractive index by the following operation. The water-dispersed metal oxide solution will be described as an aqueous dispersion silica solution as an example.

As the nanoparticles in the colloidal sol evaporate, the particles undergo self-assembly, forming a network of three-dimensional networks, and forming nanoporous films. At this time, the basic stabilizer and isoelectric point adjuster, which are added, evaporate at a faster rate than the solvent, and the pH is greatly lowered, so that the gelation proceeds, the porous structure is formed, and the concentration of silicate increases rapidly as the solvent evaporates, It is settled. As a result, bonding between particles can be caused by various chemical reactions on the surface of each particle. Typically, the particles are connected to each other by the condensation reaction of the following formula (1).

[Chemical Formula 1]

Si-OH + Si-OH <---> Si-O-Si + H ₂ O

That is, when the pH is increased, the stability of the solution is improved, and a part of the silica is dissolved and is present as a silicate ion in the solution. The silicate ions are selectively precipitated at the contact between the neighboring silica particles during the drying process, Which is the point at which the free energy between the silica particles is minimized. It can be seen that the strength of the silica net structure increases without a large loss of porosity.

In addition to the mechanical strength in the production of the antireflection film, another important factor is the porosity of the antireflection film. As described above, the refractive index of the antireflection film can be adjusted by changing the porosity. In the self-assembly process, gelation proceeds at an early stage to form a three-dimensional network structure, which exhibits a high refractive index and exhibits a low refractive index. On the other hand, when the gelation is completed at the end of evaporation of the solvent, packing, resulting in a low refractive index and a relatively high refractive index. Therefore, the above effect can be obtained by controlling the gelation point of the silica particles by changing the isoelectric point. Furthermore, inducing gelation at high pH will result in sufficient amount of silicate remaining in the solution, which will further strengthen the connection between the silica particles. However, excessive silicate in the solution may lower the porosity. Therefore, it is preferable that the concentration of silicate ions dissolved in the solution is controlled within 500-1,000 ppm by adjusting the pH as set forth above.

As described above, there is a need to provide an antireflection film having high mechanical strength and easily controlling the porosity without adding a binder or a crosslinking agent to fill the pores by inducing proper gelation of the nanosilica colloidal sol in the evaporation process of the solvent The characteristics of the antireflection film prepared according to the physical properties such as melting point and boiling point as well as the chemical characteristics such as pH and pKa of the acid or basic catalyst are greatly changed and it is very effective in the production of the antireflection film.

1 is a flow chart illustrating a method of forming an antireflective film using a coating composition according to one embodiment of the present invention.

As shown in FIG. 1, the method for forming an antireflective film using the coating composition according to the present invention comprises the steps of (S11) coating a coating composition on a substrate, drying the coating composition applied to the substrate to form a nanoporous metal oxide film (S12); and aging the nanoporous metal oxide film at a temperature of 10 to 150 DEG C and a relative humidity of 30 to 80% (S13). Here, the coating composition is a coating composition according to the present invention, which has been described in detail hereinabove, so that a duplicate description will be omitted.

By applying the coating composition to the substrate (S11), a slit die coating, a dip coating, a gravure coating, a sping coating, a roll coating, a bar coating, The coating composition may be applied to the substrate by any of the methods of coating, spray coating, and flow coating. The substrate is preferably a transparent thermoplastic polymer film or sheet as the light transmittance is higher, and the higher the heat resistance and the mechanical strength, the better. The base material is not limited to the thermoplastic polymer film but can also be used as a substrate of an inorganic material such as glass. In this case, the drying temperature can be increased due to the heat resistance of a more excellent base material, and an antireflection film having better mechanical strength can be obtained.

When the mechanical strength of the substrate such as the polymer film and the sheet substrate is low prior to the step (S11) of applying the coating composition to the substrate, the substrate may be coated with an acrylic hard coating, a melamine hard coating, an epoxy hard coating, Or a mixture of any of these materials. Before the coating composition is applied, the top layer of the substrate may contain a silanol group, a hydroxyl group, a siloxane group, an ether group, an ester group, a carbonyl group, a carboxyl group, a carbonate group, an amide group, Urethane group or sulfone group. If necessary, activation of these functional groups can be maximized through alkali treatment, acid treatment, plasma treatment or primer treatment such as aminosilane.

The thickness of the antireflection film of the porous nano metal oxide film by the applied coating composition can be controlled within the range of 50 to 500 nm, and in order to maximize the antireflection effect in the visible light region, the thickness is preferably 80 to 150 nm.

According to the step of drying the coating composition (S12), the coated film can be dried by room temperature drying, physical heating using heat such as a heater, or chemical heating using a chemical, and heating conditions, , And as long as the characteristics such as the deformation of the substrate due to heat do not occur, the higher the temperature, the better, and the longer the drying time is in the limit of economical efficiency. The antireflection film produced by the present invention does not decrease the refractive index even if it is heated up to the softening point temperature of 650 DEG C (soda lime glass). Typically, the drying temperature of the thermoplastic polymer substrate is maintained at a temperature of 80 to 150 ° C, preferably 120 to 150 ° C for 2 to 5 minutes, and when the substrate is glass, Preferably from 120 DEG C to 650 DEG C, which is the softening point temperature of the glass, and the time can be maintained for 2 to 5 minutes.

A chemical drying method may be used to facilitate the low temperature drying of the film to which the coating composition is applied. When the film coated with the coating composition is dried, the vapor of a chemical drying agent is applied to the film, or the film is applied to a film, followed by heating, the hardness and scratch resistance of the produced antireflection film are improved. Unlike the ammonia strengthening method of the nanoporous metal oxide film, this method does not cause a decrease in light transmittance. Chemical drying agents include 2,2-dichloropropane, 2,2-dimethoxypolane, trimethyl orthoformate, and triethyl orthoformate, among which 2,2-dichloropropane is preferred. The above-mentioned chemical drying agents react with moisture in the antireflection film to decompose into acetone, alcohol, hydrochloric acid, etc., and remove water to promote the condensation reaction between the metal oxide particles.

According to the step of aging the nanoporous metal oxide film (S13), durability and scratch resistance are greatly increased. The aging condition is a temperature of 10 to 150 DEG C, preferably 40 to 80 DEG C, and a relative humidity of 30 to 80% It takes place in a relatively high temperature and high humidity environment and requires a period of several hours to several days. This is similar to the hydrothermal treatment method, but it is different from the hydrothermal treatment method which requires the temperature of 120 ° C or higher and the supersaturated water vapor pressure, and the equipment such as the autoclave is not required. More importantly, the mechanical strength and scratch resistance of the antireflective coating treated under the conditions of lower temperature and relative humidity exhibit similar performance to the antireflective coating treated by the hydrothermal method, while the optical properties, i.e., transmittance and reflectivity, .

It is known that the strengthening of the nanoporous film by the hydrothermal reaction occurs due to the capillary condensation phenomenon. This reaction is not only performed in the hydrothermal treatment process having the saturated vapor pressure of the water vapor, The reaction of dissolution and reprecipitation is continuously occurring. Metal oxide nanoparticle assemblies absorb moisture in the daily atmosphere and contain a certain amount of water. Most importantly, most of the water is filled in the contact point between the nanoparticles in which the capillary phenomenon is most pronounced in the metal oxide aggregate exist. This phenomenon, known as capillary condensation, is observed in a variety of places around us, including silica gel as a desiccant, activated carbon used to remove pollutants in the air, and woody parts of plants, and its behavior is well represented by the Calvin equation do.

[Equation 1]

Where P is the standard state vapor pressure of the liquid, γ is the surface tension, Vm is the molar volume of the liquid, and r is the radius of the capillary.

The vapor pressure (Pcap) of the liquid present in the capillary between the two nanoparticles becomes lower than the standard state vapor pressure (Po) of the liquid, and the water vapor in the atmosphere can be present as a liquid in the capillary, The smaller the radius, r, is, the more easily this phenomenon occurs. Therefore, by adjusting the water vapor pressure and temperature of the appropriate external environment and the size of the nanoparticles, very small nano-droplets can be selectively positioned at the contact points of the respective metal oxide particles in the nano metal oxide assembly.

Therefore, at the relatively low relative humidity conditions defined in the present invention, the dissolution and reprecipitation of the metal oxide occurs at the contact points of the particles much more selectively than the hydrothermal reaction conditions. Also, the rate of rapid reaction at relatively low temperatures can be left to a small amount of the catalysts used in the condensation reactions involved in the coating compositions, which can be selectively added to the contact points of the metal oxide particles during drying of the nanoporous metal oxide film It is filled and can be seen as already existed.

According to the coating composition and the method for forming an antireflection film using the same according to the present invention, a nanoporous metal having a low refractive index, which can control a wide range of refractive index in a low-temperature manufacturing process at 10 to 150 ° C or less and has high weather resistance and mechanical strength An antireflection film of an oxide film can be provided, and an antireflection film exhibiting high light transmittance can be provided.

Although the present invention has been described with reference to the accompanying drawings, it is to be understood that various changes and modifications may be made without departing from the spirit of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

Claims (13)

dispersed metal oxide solution of pH 9 to 12 containing a basic stabilizer having a pKa of 9 to 13, an isoelectric point adjusting agent having a pKa of 7 to 11 and a hardening accelerator having a pKa of 6 to 12 &Lt; / RTI &gt; The method according to claim 1,
The water-dispersed metal oxide solution may contain,
A water-dispersed ceria (CeOx) solution, and a water-dispersed titania (TiOx) solution, or a mixture thereof, wherein the water-dispersed alumina (AlOx) solution, the water-dispersed silica (SiOx) solution, The method according to claim 1,
The water-dispersed metal oxide solution may contain,
Wherein the coating solution is an aqueous solution containing 1 to 5 wt% of metal oxide particles having a size of 1 to 1,000 nm. The method according to claim 1,
The basic stabilizer,
Wherein the metal hydroxide is selected from the group consisting of metal hydroxide and organic hydroxide, or a mixture thereof. The method according to claim 1,
The isoelectric point adjusting agent may be,
Ammonium hydroxide, primary amine, secondary amine, tertiary amine, or a mixture thereof. The method according to claim 1,
The curing accelerator,
Lt; RTI ID = 0.0 &gt; acid / base. &Lt; / RTI &gt; The method of claim 6,
The curing accelerator,
tetraalkyl ammonium formate, tetraalkyl ammonium formate, tetraalkyl ammonium formate, ammonium acetate, ammonium formate, ammonium carbonate, ammonium fluoride, hydrazine monohydrochloride, guanidine hydrochloride, pyridine hydrochloride, ethylenediamine hydrochloride, hydrazinium chloride, hydroxylamine hydrochloride or acetoamidine hydrochloride &Lt; / RTI &gt; or mixtures thereof. The method according to claim 1,
The coating composition may comprise,
0.1 to 3.0% by weight of Al &lt; ^{3 +} &gt; ions relative to the metal oxide. The method according to claim 1,
The coating composition may comprise,
And 0.1 to 5.0% by weight, based on the metal oxide, of lamellar nanoparticles. Applying the coating composition according to any one of claims 1 to 9 to a substrate;
Drying the coating composition applied to the substrate to form a nanoporous metal oxide film; And
And aging the nanoporous metal oxide film at a temperature of 10 to 150 DEG C and a relative humidity of 30 to 80%. The method of claim 10,
Further comprising the step of forming a hard coat layer on the substrate by coating any one of acrylic hard coating, melamine hard coating, epoxy hard coating, and organic hybrid hard coating or a mixture thereof before applying the coating composition , And a method for forming an antireflection film using the coating composition. The method of claim 10,
Wherein the top layer of the substrate has a functional group selected from the group consisting of a silanol group, a hydroxyl group, a siloxane group, an ether group, an ester group, a carbonyl group, a carboxyl group, a carbonate group, an amide group, a urea group, a urethane group, and a sulfone group Wherein the coating composition is applied to the substrate. The method of claim 10,
Wherein the step of applying the coating composition to the substrate comprises:
Coating processes such as slit die coating, dip coating, gravure coating, spining coating, roll coating, bar coating, spray coating, flow coating, A method for forming an antireflection film using a coating composition, wherein the coating composition is applied to the substrate by any one of the methods.

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