KR101079723B1 - Anti-reflective and superhydrophilic film structure and its manufacturing method - Google Patents

Abstract

PURPOSE: An anti-reflective and ultra hydrophilic film structure and a manufacturing method thereof are provided to be applied to various fields like a display, a window, a solar cell by being easily and simply manufactured. CONSTITUTION: A rare earth hydroxide nano rod is deposited and annealed on a substrate. A film structure, in which a rare earth hydroxide nano rod layer is coated on the substrate, is obtained. A silica nano particle is deposited and annealed on an obtained film structure. Rare earth hydroxide is a hydration lanthanum.

Description

Anti-reflective and superhydrophilic film structure and manufacturing method thereof {Antireflective and Superhydrophilic Film Structure and Process of Preparing the Same}

The present invention relates to an antireflective and superhydrophilic film structure and a method of manufacturing the same. More specifically, the present invention relates to an antireflective and superhydrophilic film structure coated with a rare earth hydroxide nanorod layer and a silica nanoparticle layer on a substrate and a method for producing the same simply and easily.

Antireflective coatings have received a great deal of attention in the fields of optics and optoelectronics such as coated displays and windows and solar cover glass. For this purpose, various films made of inorganic, polymer, and inorganic / polymer hybrid materials have been developed, but manufacturing a low refractive index thin film with precise control of thickness, roughness and mechanical strength still presents many problems. Have.

Reflection is n _f = ( n _s n ₀ ) ^1/2 ( n _f , n _s and n ₀ are the refractive indices of the antireflective film, substrate and transmission medium, respectively) It can be greatly suppressed when it is 1/4 of the light wavelength. Thus, for a glass substrate with n _s = 1.52, n _f of the antireflective film should be 1.23 to achieve zero reflectivity. However, since there are no materials with sufficiently low refractive indices, antireflective coatings have typically been performed with multilayer thin film films using either reversely charged nanoparticles or with polyelectrolytes. Compared to multilayer films where a more complex coating process is required, single layer antireflective coatings may be much simpler to perform, but have limited functionality that exhibits minimal reflection in narrow wavelength bands. As one of the methods for providing a broadband antireflection surface including a visible light band, a method of effectively lowering the film's regulation rate by forming a nanoporous structure using nanoparticles has been introduced. However, only limited inorganic materials have been tried for this method.

In addition to antireflection, surface porosity and roughness are closely related to the wettability of the solid surface. For example, hydrophilicity increases with increasing illuminance for hydrophilic materials. Due to the potential for use in the field of self cleaning and biocompatibility, the unique water-repellent properties of superhydrophobic surfaces and the antifogging properties of superhydrophilic surfaces have attracted much attention. However, the high illuminance required to achieve superhydrophobicity or superhydrophilicity leads to extensive scattering of the light that proceeds and conflict with antireflection. Therefore, it is difficult to manufacture a film having both superhydrophilicity and antireflection.

The present inventors have diligently researched to develop a film having both superhydrophilicity and antireflection. As a result, the present invention can achieve superhydrophilicity and antireflection simultaneously by coating a rare earth hydroxide nanorod layer and a silica nanoparticle layer on a substrate. It was found that the present invention was completed.

Accordingly, an object of the present invention is to provide an antireflective and superhydrophilic film structure coated with a rare earth hydroxide nanorod layer and a silica nanoparticle layer on a substrate.

Another object of the present invention is to provide a method for producing the film structure simply and easily.

The present invention relates to an antireflective and superhydrophilic film structure coated with a rare earth hydroxide nanorod layer and a silica nanoparticle layer on a substrate.

As the rare earth hydroxide, yttrium hydroxide, lanthanum hydroxide, cerium hydroxide, gadolium hydroxide, europium hydroxide, and the like may be used, and lanthanum hydroxide is most preferred.

Glass, quartz, silicon, silica, mica, ITO, a polymer, etc. may be used as the substrate, but is not limited thereto.

In the film structure, the film composed of the rare earth hydroxide nanorod layer and the silica nanoparticle layer coated on the substrate has a thickness of 1/4 of the visible wavelength, that is, about 100 to 200 nm, for the anti-reflective application. It is desirable to increase evanescent interference.

In addition, the rare earth hydroxide nanorods preferably have a diameter of about 20 to 30 nm, an average length of about 100 to 250 nm, and the diameter of the silica nanoparticles is preferably 7 to 20 nm.

In the film structure according to the present invention, a rare earth hydroxide nanorod is irregularly self-stacked on a substrate to form a plurality of pores smaller than an optical wavelength on the surface, which is an effective refractive index of an antireflection film. It serves to reduce.

In addition, the film structure according to the present invention exhibits superhydrophilicity by depositing the silica nanoparticle layer on the rough porous surface of the rare earth hydroxide layer.

On the other hand, the present invention relates to a method of manufacturing a film structure coated with a rare earth hydroxide nanorod layer and a silica nanoparticle layer on a substrate, the production method of the present invention

(i) depositing and annealing the rare earth hydroxide nanorods on the substrate to obtain a film structure coated with the rare earth hydroxide nanorods layer on the substrate; And

(ii) depositing and annealing the silica nanoparticles on the film structure obtained in step (i).

As the rare earth hydroxide, yttrium hydroxide, lanthanum hydroxide, cerium hydroxide, gadolium hydroxide, europium hydroxide, and the like may be used, and lanthanum hydroxide is most preferred.

Glass, quartz, silicon, silica, mica, ITO, a polymer, etc. may be used as the substrate, but is not limited thereto.

In the step (i), the substrate is immersed in an aqueous suspension of the rare earth hydroxide nanorods produced by hydrolysis of rare earth oxychloride (REOCl) to deposit the rare earth hydroxide nanorods on the substrate and then annealed to form the rare earth hydroxide nanorod layer. Obtain a coated film structure.

The aqueous suspension of the rare earth hydroxide nanorods produced by hydrolysis of rare earth oxidized chlorides is well dispersed in the rare earth hydroxide nanorods, so that when the substrate is immersed in the aqueous suspension of the rare earth hydroxide nanorods, the rare earth hydroxide nanorods are randomized on the substrate. Self-stacking to form a porous, coarse rare earth hydroxide nanorod film. The film exhibits antireflection properties by significantly reducing reflection loss in the visible region.

The above immersion process may be repeated to increase the thickness of the film while keeping the size of the pores formed on the surface much smaller than the optical wavelength.

The annealing temperature is preferably 250 to 300 ° C., and when the annealing temperature exceeds 300 ° C., the structural and morphological collapse of the rare earth hydroxide nanorods occurs, resulting in an increase in film compactness and a significant decrease in transmittance.

The rare earth oxidized chloride (REOCl) may be easily prepared by reacting the rare earth oxide (RE ₂ O ₃ ) with hydrogen chloride (HCl) according to a known method.

The rare earth hydroxide nanorods preferably have a diameter of about 20 to 30 nm and an average length of about 100 to 250 nm.

In step (ii), the film structure obtained in step (i) is again immersed in a suspension of silica nanoparticles to deposit silica nanoparticles on the rare earth hydroxide nanorod layer and then annealed to form a rare earth hydroxide nanorod on the substrate. A film structure coated with a layer and a silica nanoparticle layer is obtained.

As the suspension of the silica nanoparticles, an aqueous suspension of the silica nanoparticles, an isopropanol suspension, and the like may be used, but is not limited thereto.

When the film structure obtained in step (i) is immersed in the suspension of silica nanoparticles, the silica nanoparticles are deposited on the highly porous and rough surface of the rare earth hydroxide nanorod layer, so that the silica nanoparticle layer is formed without significant change in film thickness. Formed, the resulting film exhibits superhydrophilicity and antifogging properties while maintaining antireflection.

The immersion process can be repeated several times, the annealing temperature is preferably 250 to 300 ℃.

The diameter of the silica nanoparticles is preferably 7 to 20 nm.

The film structure coated with the rare earth hydroxide nanorod layer and the silica nanoparticle layer on the substrate according to the present invention may be used in various fields such as display, window, solar cell, etc., having antireflection, superhydrophilicity, and anti-fogging property.

In addition, according to the manufacturing method of the present invention, the film structure can be easily and easily manufactured in air, and can be applied to various substrates such as large areas or curved surfaces.

1 is an XRD pattern of each of a glass slide (cf) coated 1 to 4 times with LaOCl (a), La (OH) ₃ powder (b) and La (OH) ₃ nanorods.
FIG. 2 is a scanning electron microscopy (SEM) image of the surface and cross-section of each of the glass slides (ad) coated 1 to 4 times with La (OH) ₃ nanorods.
3 is a transmission (a) and reflectance (b) spectrum of each of the glass slides 1-4 coated 1 to 4 times with La (OH) ₃ nanorods.
4 is a photograph of each of the glass slides 1-4 coated 1 to 4 times with La (OH) ₃ nanorods under sunlight.
5 is a transmission spectrum (a) and surface and cross-sectional SEM images (bc) after heat treatment of glass slides coated with La (OH) ₃ nanorods at 300 ° C. and 500 ° C.
FIG. 6 is a view showing the surface and cross-sectional SEM images of a glass substrate coated with La (OH) ₃ nanorods and a glass substrate coated with La (OH) ₃ / SiO ₂ and the shape of water droplets.
7 is a transmission spectrum of a glass substrate (a) coated with La (OH) ₃ nanorods and a glass substrate (b) coated with La (OH) ₃ / SiO ₂ .
8 is a photograph comparing the antifogging effect of a glass substrate (right) coated with La (OH) ₃ / SiO ₂ and an uncoated glass substrate (left).

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention, it is apparent to those skilled in the art that the scope of the present invention is not limited to these examples.

Example 1 La (OH) ₃  Preparation of Nano Rods

La ₂ O ₃ was added to the concentrated HCl solution and uniformly stirred to form a clear solution, after which the solution was evaporated and the resulting powder was heated with intermittent grinding at 550 ° C. for 24 hours to give LaOCl powder. LaOCl (0.5 g) was added to distilled water (100 ml) and refluxed under nitrogen gas for 12 hours. Then, centrifugation at 2000 rpm for 10 minutes to remove the precipitated particles to prepare a super suspension containing La (OH) ₃ nanorods.

Example 2: La (OH) ₃  Fabrication of Glass Substrates Coated with Nanorods

The glass slides were washed with H ₂ O ₂ / H ₂ SO ₄ (1: 3 volume ratio) solution for 30 minutes and washed with water. The glass substrate was immersed in an aqueous suspension containing La (OH) ₃ nanorods obtained in Example 1, kept at room temperature for 10 hours in a closed flask, washed with plenty of water and dried at 100 ° C. for 1 hour. Primary coating of La (OH) ₃ film was performed. To increase the film thickness, the same procedure was repeated 2-4 times. Immersion time was 2 hours from the secondary deposition process. The glass substrate coated with La (OH) ₃ nanorod was then heated at 300 ° C. for 5 hours to improve mechanical properties.

On the other hand, several glass substrates were heated at 400-500 degreeC for 5 hours, and the thermal stability of the transparent film was investigated.

X-ray diffraction (XRD) patterns of each of the glass slides (cf) coated 1 to 4 times with LaOCl (a), La (OH) ₃ powder (b) and La (OH) ₃ nanorods 1 is shown. Compared to La (OH) ₃ powder in FIG. 1, the XRD patterns of glass slides coated with La (OH) ₃ nanorods are characteristic for (100), (110), (200) and (300) reflections. Only diffraction peaks are shown, suggesting that the nanorods are preferentially oriented in the ( hk 0) plane. The relative increase in diffraction intensity with the number of depositions is due to the increase in film thickness.

In addition, the surface and cross-sectional scanning electron microscopy (SEM) images of each of the glass slides (ad) coated 1 to 4 times with La (OH) ₃ nanorods are shown in FIG. 2 (scale bar for cross-sectional images). = 100 nm). It can be seen from FIG. 2 that the high aspect ratio La (OH) ₃ nanorods do not aggregate on the substrate surface regardless of the number of depositions. The size of the La (OH) ₃ nanorods is very regular, about 20-30 nm in diameter, and about 200 nm in average length. Visible light scattering can be avoided by the absence of particles of a size similar to or larger than the visible wavelength. As can be seen in the cross-sectional SEM image of the film, the average thickness of the film was about 120 nm for one coating and increased to about 150, 180 and 200 nm for two, three and four repeated coating processes, respectively. .

The root mean square (RMS) of the roughness of the surface coated with La (OH) ₃ nanorods was measured by atomic force microscopy. As the film thickness increased from about 120 nm to 200 nm, the root mean square of the roughness of the produced film increased linearly from about 24 nm to 55 nm, which was small enough to provide high optical transparency. The increase in surface roughness is related to the degree of irregular lamination on the substrate which increases with the number of depositions.

In comparison to the uncoated glass slide, the transmittance (a) and reflectance (b) spectra of each of the glass slides 1-4 coated 1 to 4 times with La (OH) ₃ nanorods are shown in FIG. 3. As shown in FIG. 3, the coated glass slide exhibited significantly reduced reflection loss throughout the visible region. Glass substrates coated with La (OH) ₃ nanorods also exhibited transmittances of 97-98% at about 450 nm. In addition to very high levels of transmission, very low levels of reflectance have been achieved at certain visible wavelengths. A minimum reflectance of about 1-1.8% satisfies the conditions of the antireflective coating on the glass substrate. The maximum suppression wavelength of reflection can be adjusted to 500-750 nm by varying the number of depositions (ie, film thickness).

A photograph taken of the glass slides 1-4 coated 1 to 4 times with La (OH) ₃ nanorods under sunlight is shown in FIG. 4. The left side of the glass substrate is an uncoated portion. In FIG. 4, the readability of the white letters behind the glass portion coated with the La (OH) ₃ nanorod is considerably better than that after the untreated glass portion, and thus it is confirmed that the reflection is suppressed. While many antireflective surfaces tend to suffer from color perception under certain lighting conditions, the four deposited films exhibited blue light under daylight or fluorescent lamps, one of the commonly used light sources.

The transmittance spectra (a) and surface and cross-sectional SEM images (bc) after heat treatment of the glass slides coated with La (OH) ₃ nanorods at 300 ° C. (b) and 500 ° C. (c) are shown in FIG. 5, respectively ( Scale bar = 100 nm). As shown in FIG. 5, no significant change was observed in the shape and film thickness of the nanorods after the film was heat treated at 300 ° C., and there was no significant difference in transmittance and maximum transmission wavelength. On the other hand, treatment at 500 ° C. resulted in structural and morphological collapse of the La (OH) ₃ nanorods, resulting in increased film compactness and significantly reduced transmittance.

Example 3: La (OH) ₃  Nanorods and SiO ₂  Preparation of Glass Substrates Coated with Nanoparticles

The glass substrate coated with the La (OH) ₃ nanorod obtained in Example 2 was immersed in an isopropanol suspension containing 1.0 wt.% SiO ₂ nanoparticles for 20 seconds and then rapidly washed with deionized water to make SiO ₂ nanoparticles. Was adsorbed. The dipping process was repeated twice and dried at 100 ° C. for 1 hour. Glass slides coated with La (OH) ₃ nanorods and SiO ₂ nanoparticles (La (OH) ₃ / SiO ₂ ) films were heated at 300 ° C. for 5 hours to enhance mechanical properties.

Surface and cross-sectional SEM images of the glass substrate coated with La (OH) ₃ nanorods obtained in Example 2 and the glass substrate coated with La (OH) ₃ / SiO ₂ and the shape of water droplets are shown in FIG. 6. Shown in Compared to La (OH) ₃ film, there was no significant change in thickness after coating with SiO ₂ nanoparticles, indicating that the La (OH) ₃ nanorod layer provides a very porous and rough surface for the silica layer. .

The wettability of the produced films is indicated by the water droplet contact angle (WCA) and the rate of water spreading on the surface. The WCA of the La (OH) ₃ film increased from about 23 ° to about 59 ° with the number of depositions, and such contact angle is not much different from that of the glass itself. On the other hand, when the La (OH) ₃ nanorod layer having a WCA of 27.2 ° was coated with SiO ₂ nanoparticles, the WCA of the La (OH) ₃ / SiO ₂ film became about 0 ° within 0.5 seconds after dropwise addition to the surface. . Considering that the WCA of the planar SiO ₂ surface is about 20 °, it is clear that this change is due to typical superhydrophilicity. Such superhydrophilicity was maintained without light.

The transmittance spectra of the glass substrate (a) coated with La (OH) ₃ nanorods and the glass substrate (b) coated with La (OH) ₃ / SiO ₂ are shown in FIG. 7. No significant change in transmittance and maximum transmission wavelength was observed after surface modification with SiO ₂ nanoparticles in FIG. 7.

In addition, the coating of silica nanoparticles on La (OH) ₃ nanorod film increased the mechanical durability and adhesion of the film.

Glass slides partially coated with La (OH) ₃ / SiO ₂ were cooled to 3 ° C. or below at −5 ° C. and then exposed to a humid environment (about 50% relative humidity) and then photographed La (OH) ₃ / SiO Photographs of the glass substrate (right) coated with ₂ and the uncoated glass substrate (left) are shown in FIG. 8. As shown in FIG. 8, the untreated portion of the glass slide immediately steamed and scattered light, while the portion coated with La (OH) ₃ / SiO ₂ remained transparent, demonstrating the anti-fogging effect.

Claims (18)

An antireflective and superhydrophilic film structure coated with a rare earth hydroxide nanorod layer and a silica nanoparticle layer on a substrate. The film structure according to claim 1, wherein the rare earth hydroxide is lanthanum hydroxide. The film structure of claim 1, wherein the substrate is glass, quartz, silicon, silica, mica, ITO, or a polymer. The film structure according to claim 1, wherein the film composed of the coated rare earth hydroxide nanorod layer and the silica nanoparticle layer has a thickness of 100 to 200 nm. The film structure according to claim 1, wherein the rare earth hydroxide nanorods have a diameter of 20 to 30 nm and an average length of 100 to 250 nm. The film structure according to claim 1, wherein the silica nanoparticles have a diameter of 7 to 20 nm. The film structure according to any one of claims 1 to 6, wherein a silica nanoparticle layer is deposited on the rough porous surface of the rare earth hydroxide nanorod layer. A method of manufacturing a film structure coated with a rare earth hydroxide nanorod layer and a silica nanoparticle layer on a substrate,
(i) depositing and annealing the rare earth hydroxide nanorods on the substrate to obtain a film structure coated with the rare earth hydroxide nanorods layer on the substrate; And
(ii) depositing and annealing silica nanoparticles on the film structure obtained in step (i). 9. A process according to claim 8, wherein the rare earth hydroxide is lanthanum hydroxide. The method of claim 8, wherein the substrate is glass, quartz, silicon, silica, mica, ITO or a polymer. 10. The rare earth of claim 8, wherein in step (i) the substrate is immersed in an aqueous suspension of rare earth hydroxide nanorods produced by hydrolysis of rare earth oxychloride (REOCl) to deposit rare earth hydroxide nanorods on the substrate and then annealed to provide a rare earth. A method for producing a film structure coated with a hydroxide nanorod layer. The method according to claim 11, wherein the thickness of the film is increased by repeating the dipping process. The method according to claim 8, wherein the annealing temperature in step (i) is 250 to 300 ° C. The method according to claim 8, wherein the rare earth hydroxide nanorods have a diameter of 20 to 30 nm and an average length of 100 to 250 nm. The rare earth hydroxide nanorod according to claim 8, wherein the film structure obtained in step (ii) in step (ii) is immersed in a suspension of silica nanoparticles to deposit silica nanoparticles on the rare earth hydroxide nanorod layer and then annealed. A method for producing a film structure coated with a layer and a silica nanoparticle layer. The method of claim 15, wherein the suspension of silica nanoparticles is an aqueous suspension of isopropanol or isopropanol suspension. The method according to claim 8, wherein the annealing temperature in step (ii) is 250 to 300 ° C. The method according to claim 8, wherein the silica nanoparticles have a diameter of 7 to 20 nm.

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