JPH07333423A - Permselective membrane - Google Patents

Abstract

PURPOSE:To produce a permselective membrane which can be formed by a simple process by using an inexpensive material excellent in weather resistance by constituting the film of titanium oxide having an oxygen-deficient anatase structure. CONSTITUTION:This permselective membrane is obtd. by forming a single TiO2-x layer by using titanium oxide which is inexpensive and excellent in weather resistance and absorbs UV rays so that the film causes deficit of oxygen. The obtd. layer has a reflecting function for heat rays and can be produced by a simple process. In this case, for example, a thin film 2 of titanium oxide is formed by magnetron sputtering on a transparent glass substrate 1. When the glass coated with this permselective membrane is used as window glass, the glass absorbs UV rays to shield the inside of the window glass so that deterioration of foods or fiber can be prevented. Further, external heat rays are reflected by the glass to increase the cooling efficiency of the room, or heat rays inside the window are reflected to the inside so that the heating efficiency for the room is improved. This saves energy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permselective film provided on a window glass of a vehicle or a window glass of a building, and more particularly to a material thereof.

[0002]

2. Description of the Related Art Conventionally, in this type of film, as shown in, for example, Japanese Patent Application Laid-Open No. 51-150507, a film utilizing the infrared reflecting function of a metal thin film such as aluminum is disclosed. Japanese Patent Laid-Open No. 58-12857, wherein a high refractive index substance such as zirconium oxide and a low refractive index substance such as silicon dioxide are laminated and heat rays are reflected by optical interference. As described above, there are some that utilize the selective permeability of a transparent conductive material such as indium oxide.

[0003]

However, the metal thin film is inferior in weather resistance and the infrared reflection function is deteriorated unless a protective film is provided. In addition, the transparency with respect to visible light decreases unless the film thickness is made extremely thin. In the optical interference film, the control of the refractive index and the film thickness of each laminated film is strict, and the film forming process is complicated. Further, although the transparent conductive material is excellent in characteristics, it has a problem that the material is expensive.

The present invention solves the drawbacks of the above conventional products such as low weather resistance, complicated film forming process, and expensive material, and thus uses an inexpensive material excellent in weather resistance and uses a simple process. It is an object to provide a permselective membrane that can be formed into a film.

[0005]

In order to achieve the above-mentioned object, the present invention uses titanium oxide, which is a material that absorbs ultraviolet light, is inexpensive and has excellent weather resistance, and is positively oxygen-deficient in the film. By producing a TiO _{2 -x} single layer, a selective transmission film having a heat ray reflecting function and a simplified film forming process is obtained.

[0006]

[Function] The selective transmission referred to here is 0.3 to 2.4 μm.
Of sunlight with a wavelength range of 0.38 to 0.78 μm, which is visible light that human eyes can perceive, keeps transparency by transmitting light and deteriorates food and fiber. That is, it absorbs ultraviolet light having a shorter wavelength than visible light and reflects infrared light having a longer wavelength than visible light, which is mainly converted into heat energy and called a heat ray accompanied by temperature rise.

On the inside of the window glass provided with such a selective transmission film, ultraviolet light is blocked by absorption to prevent deterioration of foods, fibers and the like, and heat rays from the outside are reflected to the outside to improve cooling efficiency. By reflecting the heat rays from the inside, the heating efficiency is increased and energy saving is achieved.

The absorption of light having a short wavelength (light having high energy) means that electrons are excited from the valence band of the semiconductor to the conduction band by the energy of light. The lowest energy for exciting this electron (longest wavelength of absorbed light) corresponds to the energy gap (band gap) between the valence band and the conduction band.

The titanium oxide of the present invention has a band gap of about 3.5 eV (0.35-0.36 μm) and absorbs ultraviolet light.

Reflecting light having a long wavelength (electromagnetic waves having a low frequency) means reacting to a low frequency,
This means that there are free electrons in the film that are hardly affected by the restoring force. In semiconductor materials such as titanium oxide, only a few free electrons are present due to thermal excitation, but by actively inducing oxygen deficiency, surplus electrons of titanium without a binding partner are reflected as free electrons. I can carry it. However, the wavelength of light that can be reflected by free electrons depends on the concentration of free electrons, and if a large amount of free electrons are present in the film, the light in the visible light region is also reflected and the film becomes opaque like a metal film. . Therefore, it is necessary to control the concentration of free electrons in the film in order to reflect only light with a wavelength in the infrared region or more, and the presence of metallic titanium that is not bonded to oxygen and that can emit excess electrons. The ratio a needs to be 0.05 ≦ a ≦ 0.15, and more preferably 0.05 ≦ a ≦
It is in the range of 0.09.

Further, the sheet resistance ρ (Ω / □) of the film depends on the free electron concentration and mobility in the film, and in order to reflect only light having a wavelength in the infrared light region or more in titanium oxide, 1 X10 ³ ≤ρ≤1 × 10 ⁴ , preferably 1 × 10 ³ ≤ρ≤4 × 1
It is in the range of 0 ³ .

Further, the film thickness cannot be made too thick in order to maintain transparency in visible light, and cannot be made too thin in order to increase the reflectance in infrared light. Therefore, the film thickness t (μ
As m), 0.01 ≦ t ≦ 10.0 is desirable, and 0.5 ≦ t ≦ 5 is preferable.

[0013]

EXAMPLE There are three types of crystal forms of titanium oxide, anatase, brookite and rutile, and rutile is the most stable crystal form. A comparison of the physical properties of anatase and rutile is as follows. Anatase type Rutile type Tetragonal system Tetragonal system Tetragonal system Specific gravity 3.84 4.26 Refractive index 2.52 2.71 Mohs hardness 5.5-6 6-7 Dielectric constant 31 114 Melting point 700-1000 ° C 1640 ° C Transfer to rutile Next, a specific manufacturing method will be described with reference to FIG.
The titanium oxide thin film 2 was formed on the transparent glass substrate 1 by the magnetron sputtering method. The sputtering conditions are as follows: in a vacuum chamber evacuated to 5 × 10 ^-6 Torr or less,
A gas in which 1.8% of oxygen was mixed with argon was introduced into the vacuum chamber at a flow rate of 5 × 10 ⁻³ Torr, and RF power of 1.0 kW was applied to the metal titanium as a target to form a film. The substrate temperature was room temperature and the film thickness was 0.2 μm. The crystal structure of this film was mainly TiO ₂ having an anatase structure from the X-ray diffraction pattern. In addition, the abundance ratio of metallic titanium not bonded to oxygen in the film was 0.07 by XPS analysis. The sheet resistance of the film was 2 × 10 ³ (Ω / □) by the 4-probe method.

FIG. 2 shows the transmittance and reflectance spectra in the wavelength range of 0.2 to 2.6 μm. As can be seen from the figure, the transmittance is high and the reflectance is low in the visible light region of 0.38 to 0.78 μm. 0.78μ in the infrared region
When it is m or more, the transmittance is low and the reflectance is high. Further, in the ultraviolet region of 0.38 μm or less, the transmittance is low due to absorption. Therefore, this film is a good selective transmission film having a heat ray reflecting function.

As a comparative example, FIG. 3 shows the transmittance and reflectance spectra when the oxygen mixture ratio of the introduced gas during film formation is 2% and the abundance ratio of metallic titanium is 0.04. The oxygen mixture ratio is 1. The existence ratio of metallic titanium is set to 5% and is set to 0.1.
FIG. 4 shows the transmittance and reflectance spectra of the sample No. 7.

As can be seen from FIG. 3, when the abundance ratio of metallic titanium is 0.05 or less, the titanium oxide becomes transparent titanium oxide having no heat ray reflecting function and only the interference pattern appears.

Further, as can be seen from FIG. 4, when the abundance ratio of metallic titanium is 0.15 or more, it becomes a state close to that of a metallic film and becomes opaque in the visible light region. Therefore, by controlling the abundance ratio of metallic titanium in the range of 0.05 to 0.15, it is possible to obtain a selective transmission film having a good heat ray reflecting function.

As a method for forming the thin film, a vapor phase method such as a sputtering method, a vacuum vapor deposition method, a CVD method or the like, and a wet method such as dipping, spraying or coating can be used.

[0019]

As described above, according to the present invention,
The following effects are achieved.

(1) Since titanium oxide, which is a stable material, is used, the weather resistance is good.

(2) Since titanium oxide, which is an inexpensive material, is used, the cost can be reduced.

(3) Since the titanium oxide single layer has selective permeability, the film forming process can be shortened and the workability is extremely good.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a glass substrate on which a selective transmission film according to an embodiment of the present invention is formed.

FIG. 2 is a characteristic diagram of transmittance and reflectance of a selective transmission film according to an example of the present invention.

FIG. 3 is a characteristic diagram of transmittance and reflectance of a selective transmission film according to a comparative example.

FIG. 4 is a characteristic diagram of transmittance and reflectance of a selective transmission film according to a comparative example.

[Explanation of symbols]

 1 glass substrate 2 titanium oxide thin film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location E06B 9/24 A

Claims (5)

[Claims] 1. A selective transmission film, which is transparent to visible light, absorbs ultraviolet light, and reflects infrared light, is composed of titanium oxide having an anatase structure with oxygen deficiency. Permeable membrane. 2. The titanium oxide Ti according to claim 1,
The x value of O _2−x is 0 <x ≦ 0.5, and the abundance ratio a of the metal Ti that does not bind to oxygen contained in the film is 0.05 ≦ a ≦ 0.15. Selectively permeable membrane. 3. The selective permeation film according to claim 1, wherein the sheet resistance ρ (Ω / □) of the selective permeation film is 1 × 10 ³ ≦ ρ ≦ 1 × 10 ⁴ . 4. The selective permeation film according to claim 1, wherein a film thickness t (μm) of the selective permeation film is 0.01 ≦ t ≦ 10.0. 5. The selective permeation film according to claim 1, wherein the selective permeation film is formed on a glass plate.