JP2000128581A - Antifouling film and its formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the surface reflectance, to maintain good photocatalysis and to prevent fouling by providing a titanium oxide film having fine reggednesses on the surface on a transparent substrate through a transparent electrically conductive film. SOLUTION: An SnO2 film as a transparent electrically conductive film having <=100 nm thickness is formed on a transparent substrate 1 (glass substrate), and a TiO2 film 3 having the ruggednesses of <=200 nm depth on the surface and having 0.1-5 μm thickness is formed on a transparent electrically conductive film 2 to obtain an antifouling film. The fine rugged layer 5 on the antifouling film surface is preferably formed from the fine TiO2 grains 4 having 50 nm to 1 μm diameters by a film forming method. When the transparent electrically conductive film of an n-type semiconductor is brought into contact with the film of TiO2 as a nearly intrinsic semiconductor, light is absorbed in the TiO2, an excited electron is attracted toward the transparent electrically conductive film, and hence the photocatalysis is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antifouling film and a method for forming the same, and more particularly to an antifouling film applicable to optical windows such as solar cells, greenhouses and screens, and a method for forming the same.

[0002]

_2. Description of the Related Art Heretofore, antifouling and air purification coatings have been provided by a coating film using TiO ₂ as a photocatalytic material.
However, in this case, since the reflectance is large (about 20%) due to the optical characteristic of the TiO ₂ material having a large refractive index,
It has been difficult to apply it to optical windows such as solar cells, greenhouses and screens.

On the other hand, a method of improving optical characteristics by mixing with SiO ₂ or the like has been attempted, but has a problem that photocatalytic characteristics are deteriorated. Further, since the sintering method is used for the production of the photocatalyst film, the temperature cannot be lowered (such as tempered glass). Furthermore, when mixed with a paint, there is a problem that long-term durability is lacking.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has provided a TiO ₂ film having fine irregularities of 200 nm or less in depth on a transparent substrate via a transparent conductive film. It is an object of the present invention to provide an antifouling film capable of reducing surface reflectance and maintaining good photocatalytic properties by adopting such a configuration.

Further, the present invention provides a method for forming an antifouling film comprising a step of forming a transparent conductive film on a transparent substrate and a TiO ₂ film having a layer of fine irregularities having a depth of 200 nm or less on the surface. The object of the present invention is to provide a method for forming an antifouling film capable of reducing surface reflectance in the same manner as described above and maintaining good photocatalytic properties by forming a layer having irregularities by a fine particle film forming method. And

[0006]

Means for Solving the Problems A first invention of the present application is directed to a transparent substrate, a transparent conductive film formed on the transparent substrate, and a fine pattern having a depth of 200 nm or less formed on the transparent conductive film. And a TiO ₂ film having various irregularities.

The second invention of the present application is directed to a method of forming an antifouling film comprising a step of forming a transparent conductive film on a transparent substrate and forming a TiO ₂ film having a layer of fine irregularities with a depth of 200 nm or less on the surface. This is a method for forming an antifouling film, characterized by forming a layer having irregularities by a fine particle film forming method.

In the present invention, the thickness of the transparent conductive film is preferably 100 nm or less, more preferably 20 to 80.
nm. The reason is that if it is less than 20 nm, the antireflection effect is reduced, and if it exceeds 80 nm, color unevenness occurs due to the interference effect. The reason for using a transparent conductive film in the present invention is as follows. That is, in order to improve the photocatalytic properties, it is important to separate charges (holes and electrons) generated in the TiO ₂ film. Since the transparent conductive film is an n-type semiconductor and TiO ₂ is almost an authentic semiconductor, TiO ₂
When a transparent conductive film is brought into contact with the film, electrons excited by absorbing light in TiO ₂ are attracted to the transparent conductive film side.
As a result, the photocatalytic properties are improved.

In the present invention, the thickness of the layer having irregularities on the surface of the TiO ₂ film is preferably 200 nm or less, more preferably 80 to 180 nm. The reason for this is that as shown in FIG.
If the thickness exceeds 0 nm, light scattering occurs, which causes a decrease in transparency and a decrease in transmittance. FIG. 2 shows a wavelength of 550 nm.
3 shows the relationship between the thickness of the surface layer and the reflectance.

In the present invention, the thickness of the TiO ₂ film is a thickness necessary for light absorption. The thicker the better, the better, but the thinner the better from the viewpoint of photocatalytic properties, there is an appropriate value. In general,
The thickness of the TiO ₂ film is preferably 0.1 μm or more, more preferably 1.5 μm to 5 μm, and about 3 μm is appropriate. The reason for this is that if it is less than 1.5 μm, the light absorption is insufficient, and if it exceeds 5 μm, the photocatalytic properties are poor.

In the present invention, the diameter of the fine particles made of TiO ₂ is 125 nm or more, which is 0.5 times or more as an optical film thickness of 500 nm which is a wavelength at which the conversion efficiency of the photoelectric conversion device using amorphous silicon becomes high. It is desirable that the thickness be 50 nm or more. In addition,
Assuming that the diameter of the fine particles is D, D = λ / 2n. Here, λ: wavelength, n: refractive index. When λ = 500 nm and n =, D = 500/2 × 2 = 125 nm. On the other hand, if the diameter of the fine particles is too large, it becomes technically difficult to make contact between the photoelectric conversion film and the back electrode containing the fine particles.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An antifouling film according to one embodiment of the present invention will be described below with reference to FIG. However, the constituent materials, film thicknesses, and the like described in the following examples are merely examples, and do not specify the scope of the present invention.

Reference numeral 1 in the drawing denotes a refractive index of 1.5, a thickness of 1.
1 shows a 1 mm glass substrate (transparent substrate). On this glass substrate 1, a SnO ₂ film (transparent conductive film) 2 having a refractive index of 2.0 and a thickness of 70 nm is formed. The SnO ₂ film 2
A TiO ₂ film 3 having a refractive index of 2.8 and a thickness of 3 μm is formed thereon. The surface of the TiO ₂ film 3 is a layer 5 having a refractive index of 1.6 having fine particles 4 made of TiO _2, and has irregularities with a depth (F) of 160 nm.

The antifouling film having such a structure is formed as follows.

First, a SnO ₂ film 2 was formed on a glass substrate 1. Next, SnO ₂ was placed on the surface in a vacuum vessel (not shown).
As shown in FIG. 3, the glass substrate 1 having the film 2 is set on the crucible 6 containing the Ti raw material 5 with the SnO ₂ film 2 face down, and then the Ti raw material is set. 5 was heated to 2500 ° C. Before opening a vapor deposition shutter (not shown), oxygen gas is introduced at a controlled pressure of 10 mTorr, and plasma is excited by a high frequency of 13.56 MHz. The high frequency input power was 100 W. Then, the Ti raw material 5 was supercooled and aggregated to grow particles, which were applied to the surface of the SnO ₂ film 2. When a continuous film is formed on the glass substrate 1, as shown in FIG. 4, the glass substrate is set with the surface of the SnO ₂ film 2 facing down and directly above the container containing the TiO ₂ raw material, ₍₂₎ Sublimation of the raw material by electron beam heating and activation of the deposited particles by O ₂ plasma.

According to the antifouling film according to the above embodiment,
SnO on the substrate 1_TwoRefractive index 2.8, thickness through film 2
3 μm TiO_TwoA film 3 is provided, and the TiO_TwoSurface of membrane 3
Is TiO_TwoLayer having a refractive index of 1.6 having fine particles 4 composed of
5 has a configuration with unevenness having a depth of 160 nm.
As a result, an appropriate anti-reflection effect due to the unevenness of
The surface reflectivity was reduced from 20% to 10%.
Wear. Also, TiO_TwoTiO on the surface of film 3_TwoConsisting of fine particles
Since the layer 5 having the element 4 is formed, TiO _TwoInside
The electrons excited by absorbing light are SnO_TwoPull to membrane 2 side
As a result, photocatalytic properties are improved. Furthermore, glass
Substrate 1 and TiO_TwoA function as an anti-reflection film between the films 3
SnO having_TwoSince the film 2 is formed, the glass substrate
1 and TiO _TwoThe reflectance between the films 3 can be reduced.

In the formation of the antifouling film according to the above embodiment, a fine particle film forming method is used to form the layer 5 having the fine particles 4 made of TiO _2. Can be

[0018]

As described above in detail, according to the present invention, a TiO ₂ film having fine unevenness with a depth of 200 nm or less is provided on a transparent substrate via a transparent conductive film. In addition, it is possible to provide an antifouling film capable of reducing surface reflectance and maintaining good photocatalytic properties.

Further, according to the present invention, an antifouling film comprising a step of forming a transparent conductive film on a transparent substrate and a TiO ₂ film having a layer of fine unevenness having a depth of 200 nm or less on the surface. By forming a layer having irregularities by a fine-particle film forming method, it is possible to provide a method for forming an antifouling film capable of reducing surface reflectance and maintaining good photocatalytic properties as described above.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an antifouling film according to one embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a TiO ₂ film thickness (surface layer thickness) of the antifouling film of FIG. 1 and reflectance.

FIG. 3 is an explanatory view of a method for forming a TiO ₂ film containing fine particles on a glass substrate in the antifouling film according to the present invention.

FIG. 4 is an explanatory view of a method for continuously forming a TiO ₂ film containing fine particles on a glass substrate in the antifouling film according to the present invention.

[Explanation of symbols]

1 ... glass substrate (transparent substrate), 2 ... SnO ₂ film, 3 ... TiO ₂ film, fine particles composed of 4 ... TiO _2, 5 ... Ti raw material, 6 ... crucible.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayoshi Murata 5-717-1, Fukahori-cho, Nagasaki-shi, Nagasaki F-term in Nagasaki Research Laboratory, Mitsubishi Heavy Industries, Ltd. 4G047 CA02 CB04 CC03 CD02 4G059 AA01 AC01 AC12 AC22 EA02 EB03 GA01 GA04 GA12 5F051 BA17 FA02 FA03 GA02 GA03 GA16 HA03

Claims (3)

[Claims] 1. A transparent substrate, a transparent conductive film formed on the transparent substrate, and a TiO ₂ film formed on the transparent conductive film and having fine unevenness with a depth of 200 nm or less on the surface. An antifouling film characterized by the following. 2. An antifouling film, wherein the thickness of the transparent conductive film is 100 nm or less. 3. A Ti having a transparent conductive film on a transparent substrate and a layer having fine unevenness with a depth of 200 nm or less on the surface.
A method for forming an antifouling film, comprising a step of forming an O ₂ film, wherein a layer having irregularities is formed by a fine particle film forming method.