JP2884498B2 - Method for producing titanium oxide electrochromic thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an effective method for producing a titanium oxide electrochromic thin film or material, and its industrial field of application is a window material for controlling the transmittance of solar energy in buildings and vehicles. It is about technology, more specifically, without blinds and curtains,
The present invention relates to a method for manufacturing a titanium oxide-based electrochromic thin film or material capable of automatically controlling incident sunlight.

[0002]

BACKGROUND ART A phenomenon in which color (light transmittance) is reversibly changed by physical stimulus from the outside is called chromism. Among them, reversible color or light transmission that occurs in a substance when a voltage is applied or an electric current is passed. The change in the degree is called electrochromism. Historically,
In 1969, Deb discovered that an amorphous thin film of WO ₃ , a transition metal oxide, exhibited an electrochromic phenomenon, which became well known.

[0003] Applications of practical devices using an electrochromic material exhibiting such an electrochromic phenomenon are broadly classified into display devices and light control devices. This is an application as a light control element. The dimming element is an element that can be used for a window material of a building, a vehicle, or the like and that can freely control the entrance and exit of light and heat from the outside. If such an electrochromic element is used as a window material, the transmittance of the window can be controlled so as to suppress the cooling and heating load and the lighting load of the building as much as possible,
An intelligent window without so-called blinds or curtains can be realized.

By the way, the materials exhibiting such electrochromism are in a wide range from inorganic materials to organic materials, but the materials which are expected to be practically the fastest to date are: Tungsten oxide (WO
₃ ) is used as a chromic material, and prototype products have already been developed. On the other hand, titanium oxide has high mechanical and chemical resistance,
In the field of optics, as a substance having a high refractive index and a high degree of transparency, various production techniques have been studied, and studies on its properties have been actively conducted. Therefore, if such a titanium oxide is used, the development of a new optical element combining its excellent optical characteristics and electrochromic characteristics is expected.

[0005] Further, as the electrochromic characteristics, it is important to determine how much the transmittance changes between coloring and decoloring, and the coloring efficiency as a measure of how efficiently the transmittance changes. It is. For the former change in transmittance, the amount of visible light transmittance integrated by multiplying the transmission spectrum by the sensitivity of the human eye is often used.

However, there have been several reports on the production of a titanium oxide film expected to have the above-mentioned characteristics using a physical vapor deposition method such as a sputtering method, a vacuum vapor deposition method, and an electron beam vapor deposition method. Although performed, the electrochromic properties of the resulting film are:
All were inferior to those obtained by other methods such as the sol-gel method. For example, in the case of a titanium oxide film produced by an electron beam evaporation method, the transmittances at the time of coloring and decoloring are 63% and 75%, respectively, and the variation is small, and the coloring efficiency is 5 cm ² / C and the coloring efficiency of tungsten oxide (WO ₃ ): 60 cm ² / C
In comparison with T.
Seike and J. Nagai: Solar Energy Materials, Vol.2
2 (1991), p.107].

[0007]

Under such circumstances, the present inventors have studied in detail the dependence of various physical properties of a titanium oxide electrochromic thin film by a reactive sputtering method on film forming conditions, and as a result, have grown under a specific condition. If you do
The present inventors have found that a titanium oxide thin film showing a change in transmittance about three times larger than conventionally reported and having a coloring efficiency about six times larger than conventionally reported can be formed. It was completed.

An object of the present invention is to provide a titanium oxide electrochromic thin film which shows a large change in transmittance between coloring and decoloring using a reactive DC magnetron sputtering method and has high coloring efficiency. Another object of the present invention is to provide a method capable of advantageously producing a material.

[0009]

According to the present invention, in order to solve the above-described problems, a reactive titanium compound having a target of metallic titanium is used.
When forming an amorphous titanium oxide electrochromic thin film by the C magnetron sputtering method, the flow rate of argon gas into the sputtering system is set to 1
A gist of the present invention is a method for producing a titanium oxide electrochromic thin film, wherein the sputtering is performed at a pressure of 20 to 230 sccm.

In the method of manufacturing a titanium oxide electrochromic thin film according to the present invention, a method for forming a titanium oxide thin film as a metal oxide by bonding with an atom struck out from titanium as a target material,
It is desirable that oxygen gas be introduced into the sputtering system at a rate of 5 to 20 sccm.
It is adjusted so as to be １１11 Pa.

Further, the present invention provides a transparent substrate having a transparent conductive film formed thereon in order to obtain a material exhibiting excellent electrochromic characteristics comprising a titanium oxide thin film produced by the reactive DC magnetron sputtering method as described above. And forming a titanium oxide electrochromic thin film having an amorphous structure on the transparent conductive film of the substrate according to the method according to claim 1. Is also the gist of this.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a sputtering method for producing an oxide thin film, a sputtering method using a compound target and a reactive sputtering method using a metal target are known. In view of the above, the latter reactive sputtering method is advantageous, and the voltage application method is RF (high frequency).
Although there are a sputtering method and a DC (direct current) sputtering method, the latter DC sputtering method is advantageous in terms of power supply cost and the like. For this reason, in the present invention, a reactive DC magnetron sputtering method is used when producing a titanium oxide thin film.

The present inventors have proposed a titanium oxide film obtained by growing under various growth conditions (sputtering conditions) by diluting lithium perchlorate (LiClO ₄ ) to 1N with propylene carbonate as an electrolytic solution. As a result of performing cyclic voltammetry and evaluating the electrochromic characteristics, the electrochromic characteristics of the obtained titanium oxide film were determined by the flow rate of argon gas introduced into the sputtering system during growth (film formation). Therefore, it was found that the titanium oxide film grown (deposited) showed better chromic characteristics under a large flow rate (high pressure) depending on the total gas pressure. is there.

That is, the flow rate (per second) of the argon gas generally employed in the ordinary reactive sputtering method is as follows:
Although it is about 50 to 100 sccm (abbreviation of standard cubic centimeter), in the present invention, such a flow rate of argon gas per second is set to 120 to 230 sccm.
The sputtering is performed at a high pressure by raising the pressure to 150 sccm, preferably 150 to 200 sccm, thereby realizing a titanium oxide thin film having an amorphous structure having good chromic characteristics. If the flow rate of the argon gas introduced into the sputtering system is too low, a titanium oxide film having insufficient electrochromic properties will be formed as in the related art, and even if the flow rate is too high, Electric discharge also occurs in portions other than the sputter gun, and the titanium oxide film formed under such conditions does not exhibit good chromic characteristics.

By introducing argon gas at such a high flow rate, the total pressure (total gas pressure) in the sputtering system is adjusted to 4 to 11 Pa, preferably 5 to 8 Pa. is there.

Of course, in the present invention, in order to perform reactive DC magnetron sputtering, in a sputtering system, oxygen gas is used to oxidize metal titanium (target) to produce titanium oxide having an amorphous structure. The oxygen gas is introduced into such a sputtering system.
Approximately 20 sccm is sufficient, and the ratio is extremely small as compared with the introduction amount of argon gas. Therefore, the ratio does not substantially affect the total pressure in the sputtering system. It does not adversely affect the electrochromic properties of the titanium oxide film. Of course, if the amount of oxygen gas introduced is too small, it becomes difficult to form a titanium oxide film, and the purpose of introducing oxygen gas is sufficiently achieved with an introduced amount of up to 20 sccm, The introduction of gas is meaningless.

In the thus obtained titanium oxide electrochromic thin film according to the present invention,
Those exhibiting the best properties show extremely good properties, in which the visible light transmittance in the solution changes from 22% to 92%, and the coloring efficiency of such a thin film is 2%.
A value of 9 cm ² / C was obtained, which is about six times higher than the report on the conventional titanium oxide film.

Incidentally, FIG. 1 shows a schematic view of a sputtering apparatus capable of carrying out the present invention, wherein reference numeral 2 denotes a sputtering chamber (sputtering system) having a closed structure, The sputtering chamber 2 is provided with a sputter gun 4 and a substrate supporting manipulator 6, respectively. A plate-shaped target 8 made of metallic titanium is attached to the tip of the sputter gun 4. Although not shown, the sputter gun body behind the target 8 has a conventional shape. Similarly, a magnet (permanent magnet) is arranged so that DC magnetron sputtering similar to that of the related art can be performed by a direct current supplied from a DC power supply.

In the sputtering chamber 2, a substrate 10 on which a titanium oxide thin film is formed can be supported by the manipulator 6 so as to face a target 8 at the tip of the sputtering gun 4 at a predetermined distance. Further, cooling water is fed into the back side of such a substrate 10 through a water cooling pipe 12 and the temperature of the substrate 10 is controlled under the control of a temperature controller. The crystallization of the titanium oxide thin film formed on the substrate is prevented, and an amorphous structure can be obtained.

Further, the sputtering chamber 2 can be maintained at a reduced pressure enough to perform a sputtering operation by a vacuum pump 14, while the argon gas is passed through a mass flow controller 16 under the control of a computer. And a predetermined amount of oxygen gas can be introduced into the sputtering chamber 2.

Therefore, in carrying out the present invention in the sputtering apparatus having such a configuration, after removing the atmosphere in the sputtering chamber 2 by the vacuum pump 14, argon gas is supplied through the mass flow controller 16 to the sputtering chamber. 2, 120-230 scc
m and a flow of oxygen gas, generally between 5 and
The target 8 was introduced at a rate of 20 sccm to perform DC magnetron sputtering.
Are oxidized by the oxygen gas introduced into the sputtering chamber 2 and are deposited as titanium oxide on the surface of the opposing substrate 10 to have a predetermined thickness (for example, 0.1 to 0.1). Thus, a titanium oxide thin film (about 1 μm) is formed.

In order to advantageously obtain an electrochromic material such as an intelligent window material which does not require a blind or a curtain by utilizing the electrochromic properties of the titanium oxide thin film thus formed,
The substrate 10 is made of a transparent material such as glass,
For further energization, a transparent conductive film similar to the conventional one, for example, an ITO (Indium Tin Oxide) film is formed on the surface of the transparent substrate on which the titanium oxide thin film is formed. A titanium oxide thin film is formed thereon.

[0023]

EXAMPLES In order to clarify the present invention more specifically,
Some examples of the present invention will be shown below,
It goes without saying that the present invention is not subject to any restrictions by the description of such embodiments. Further, the present invention may be variously modified based on the knowledge of those skilled in the art without departing from the spirit of the present invention, in addition to the following examples, and in addition to the description in the above embodiment of the present invention. It should be understood that changes, modifications, improvements and the like can be made.

Example 1 A titanium oxide thin film was grown by a reactive DC magnetron sputtering method using an apparatus having the same structure as the sputtering apparatus shown in FIG. The substrate (10) was coated with an ITO film as a transparent conductive film (sheet resistance: 10Ω), size: 11 mm × 11
mm × 1 mm glass plate and target (8)
As for diameter: 50 mm, thickness: 3 mm, purity: 9
A 9.9% metal titanium plate was used. The sputter power supply (DC power supply) is driven in a constant voltage mode, and the current is 0.
Fixed to 2A. Further, during sputtering, the substrate holder (manipulator 6) was cooled with water so that the temperature did not rise.

Then, an argon gas is introduced into the sputtering chamber (2) at a flow rate of 50 to 250 sccm, and the partial pressure of argon, which is a substantial total pressure in the sputtering chamber (2), is adjusted to 2 to 12 Pa. On the other hand, the flow rate of oxygen gas was changed from 10 to 20 sccm, and the target titanium oxide thin film was deposited on a transparent conductive film (ITO film) of a glass plate as the substrate (10) by about 0.4. ~
The film was formed with a thickness of 0.5 μm. During the growth, the film thickness was monitored with a quartz film thickness meter, and after the growth,
The film thickness was measured by a stylus-type film thickness meter, and the growth conditions were calibrated to obtain a predetermined film thickness.

The structure of the titanium oxide thin film on the glass plate obtained by changing the flow rate of the argon gas and the flow rate of the oxygen gas introduced into the sputtering chamber (2) in various manners was determined by using an X-ray. As a result of diffraction, it was confirmed that the film grown under any conditions was not crystallized and had an amorphous structure.
On the other hand, when the supply of the cooling water through the water cooling pipe (12) was stopped and the substrate holder (manipulator 6) was not cooled, all of the generated titanium oxide films were crystallized. It became something. In addition, as a result of examining the composition of the film having the amorphous structure by Rutherford backscattering method, the ratio (atomic ratio) between titanium and oxygen was
When the flow rate of the oxygen gas was in the range of 5 sccc to 20 sccm, the ratio was 1: 2.2, and it was confirmed that a composition close to TiO ₂ was obtained.

Example 2 Various samples obtained by forming a titanium oxide thin film under various conditions in Example 1 were examined for their electrochromic properties by cyclic voltammetry. As the electrolytic solution, a solution obtained by diluting LiClO ₄ to 1N with propylene carbonate was used, and a platinum plate was used as a counter electrode.

Then, as a result of examining the electrochromic characteristics of the titanium oxide film formed under the above various conditions,
It has been found that the characteristics greatly depend on the flow rate of the argon gas introduced into the sputtering chamber. Incidentally, the electrochromic properties of a titanium oxide film formed at a flow rate of argon gas: about 50 to 100 sccm, which is commonly used in ordinary sputtering, are not so good, similarly to those which have been reported conventionally. On the other hand, the higher the flow rate of the argon gas and the higher the pressure, the better the chromic properties were exhibited.

Incidentally, FIG. 2 shows a voltage-current curve (cyclic cyclic voltammetry) in a cyclic voltammetry of a sample grown under the conditions of an argon gas flow rate of 200 sccm, an oxygen gas flow rate of 10 sccm, and a total pressure of 8 Pa. It shows the change in transmittance at 620 nm and the wavelength: 620 nm. As can be seen from this figure, when the potential is lowered, the current starts to flow, and at the same time, the transmittance decreases and the color becomes dark blue. By coloring, and conversely, increasing the voltage, the transmittance increases and returns to a transparent state, showing good electrochromic properties.

Example 3 Under a condition that the flow rate of argon gas is 200 sccm, the flow rate of oxygen gas is 10 sccm, and the total pressure is 8 Pa,
With respect to the sample obtained by forming a film in the same manner as in Example 1, the optical transmission spectra at the time of coloring and decoloring were measured in a solution, and the results are shown in FIG. The spectrum at the time of coloring was measured by applying a potential of -1.9 V, and the spectrum at the time of decoloring was measured while applying a potential of 1 V.

When the visible light spectrum was calculated from the spectrum shown in FIG.
%, And it can be controlled to an arbitrary transmittance in the meantime, and it was recognized that the film had extremely good performance. In addition, considering that the change in visible light transmittance of a film formed by a sputtering method is about 63% and about 75% in a conventional report, a titanium oxide thin film obtained according to the present invention can be used. It is surprising that the change in transmittance is about three times greater.

Example 4 FIG. 4 shows the result of plotting the optical density calculated from the transmittance at the wavelength of 620 nm in FIG. 2 with respect to the injected charge amount. The inclination in the graph shown in FIG. 4 is the coloring efficiency.

Then, based on FIG. 4, the coloring efficiency of the titanium oxide thin film was calculated to be 29 cm ²
/ C. Although this value is lower than the value of about 60 cm ² / C of the tungsten oxide (WO ₃ ) film, about 5 cm reported for a titanium oxide thin film formed by a conventional physical method is used.
It is about 6 times larger than cm ² / C, and it is recognized that it can be used practically.

Further, the flow rate of oxygen gas introduced into the sputtering chamber (2) was fixed at 10 sccm, and the flow rate (total pressure) of argon gas was varied, and the reactive DC magnetron sputtering was performed in the same manner as in Example 1. The coloring efficiency of a film obtained by growing a titanium oxide thin film by the method was examined, and the results are shown in Table 1 below. As is clear from the results, the argon gas flow rate (total pressure) But 150sccm (5Pa) or 200sccm
(8 Pa), it shows good coloring efficiency and is useful as an electrochromic thin film, whereas 50 sccm (2 Pa) and 100 s
ccm (4 Pa) or 250 sccm (12 P
In the case of a), the coloring efficiency is lowered, and it is difficult to say that the film is practically usable.

[0035]

[Table 1]

[0036]

As is apparent from the above description, the present invention provides an excellent dimming characteristic including the infrared region by forming a film by the reactive DC magnetron sputtering method using titanium metal as a target. It shows that it is possible to produce a titanium oxide electrochromic thin film having a useful amorphous structure, and it is also possible to produce a material formed of such a titanium oxide electrochromic thin film, for example, a window material. Is what you do.
According to the present invention, it is possible to form an extremely high-performance film that can control the visible light transmittance from, for example, 22% to 92%.

Further, according to the titanium oxide electrochromic thin film obtained according to the present invention having such characteristics, it is possible to control the solar energy so that the cooling load and the lighting load inside the building can be reduced as much as possible. This makes it possible to significantly reduce costs. In addition, titanium oxide films are also used as materials for various optical materials and wet solar cells, and by combining them, there is a possibility that an element having a new function, which has not existed in the past, can be manufactured. -ing

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a sputtering apparatus capable of performing a reactive DC magnetron sputtering method according to the present invention.

FIG. 2 is a graph showing a cyclic voltammogram of a titanium oxide thin film and a change in transmittance at 620 nm.

FIG. 3 is a graph showing transmittance when a titanium oxide thin film is colored and erased in a solution.

FIG. 4 is a graph showing the relationship between the optical density of a titanium oxide thin film and the amount of injected charge.

[Description of Signs] 2 Sputtering chamber 4 Sputter gun 6 Manipulator 8 Target 10 Substrate 12 Water cooling pipe 14 Vacuum pump 16 Mass flow controller

Claims (4)

(57) [Claims] When a titanium oxide electrochromic thin film having an amorphous structure is formed by reactive DC magnetron sputtering using titanium metal as a target, the flow rate of an argon gas into a sputtering system is set to 120 to 230 sccm. A method for producing a titanium oxide electrochromic thin film. 2. The method for producing a titanium oxide electrochromic thin film according to claim 1, wherein oxygen gas is introduced into said sputtering system at a rate of 5 to 20 sccm. 3. The total pressure in the sputtering system is 4 to
3. The method for producing a titanium oxide electrochromic thin film according to claim 1, wherein the pressure is 11 Pa. 4. A transparent substrate on which a transparent conductive film is formed, and a titanium oxide electrochromic thin film having an amorphous structure is formed on the transparent conductive film of the substrate by the method according to claim 1. A method for producing a titanium oxide electrochromic material, characterized by being formed.