JPH07249316A - Transparent conductive film and transparent substrate using the transparent conductive film - Google Patents

Abstract

PURPOSE:To coat a large surface area at high speed and prevent the deterioration of optical properties during heating treatment at high temperature in an oxidative atmosphere by setting the values of properties of a transparent conductive film consisting of zinc oxide as a main component. CONSTITUTION:A transparent substrate includes a transparent conductive film containing zinc oxide 2 as a main component. The transparent conductive film contains gallium at 0.1-15 atomic % of zinc and has a diffraction peak in an x-ray diffraction pattern by the (002) plane and the half-width of the diffraction line by the (002) plane is 1.2 or less. The specific resistance of the transparent conductive film is 10-2OMEGA'cm or less and the thickness of the film is within 10nm-5mum range. To make the appearance of the substrate good, at least one layer of an undercoat film 3 is formed between the transparent conductive film 2 and the substrate 4 or at least one layer of an overcoat film 1 is formed on the film 2 and the color tone of permeated or reflected light rays, and reflectance of visible light rays can be adjusted by utilizing the intefering phenomena of light and light absorption by the film.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention provides a transparent conductive film having high performance and excellent appearance uniformity and handleability.
The present invention relates to a transparent member having optical selective transmission.

[0002]

2. Description of the Related Art Heretofore, several types of transparent members having optical selective transmission have been known.
One of them is that it particularly effectively reflects infrared rays having a long wavelength of 2 μm or more, which is a radiation wavelength from a heating heat source or an object at room temperature,
There is a so-called Low-E. As the configuration, in order from the outdoor side, a glass, an air layer, a multi-layered configuration of a coated glass having a coat layer on the outdoor side, a Low-E multi-layer glass that reduces a heating load under cold weather, and an outdoor side in order, Sunbelt Low-E is known as a multi-layered structure of a coated glass, an air layer, and a glass in which a coating layer is placed on the indoor side, and which is used for the purpose of heat shield in a warm region. As a transparent member in this category, a transparent substrate coated with a laminated film including a conductive transparent oxide film and a silver film having a film thickness of about 10 nm is known.

As transparent conductive tin oxide, one containing antimony or fluorine as a dopant is known, and a film system using this is industrially produced by a spray method or a CVD method, and is already low- It is also marketed as E-glass. Since these have excellent mechanical and chemical durability, they can be handled in the same manner as uncoated glass, which is an advantage.

However, as a problem resulting from the manufacturing method, when a large area substrate such as that used for a window member is coated, the film thickness and the film quality vary within the surface, and interference fringes appear visually due to uneven optical interference conditions. There are points that will occur. As a countermeasure, it is usually used in a two-layer structure using a layer for canceling the non-uniformity of interference, but still it does not completely eliminate the interference unevenness, and the sputtering method described below in appearance is used. It is considerably inferior to the silver film type.

As a film system using a silver film by the sputtering method, a two-layer film of transparent dielectric layer / silver layer / transparent dielectric layer or a coating film of five or more layers in which these layers are repeatedly laminated is known. There is. This silver-based coat film has a very high reflectance for long-wavelength infrared rays of 2 μm or more, and is one of the most excellent optical properties among the above mentioned in terms of Low-E performance. Also, since the sputtering method is a method that is extremely suitable for performing a uniform coating over a large area,
One of the advantages is that a coated product with stable appearance and characteristics can be obtained. However, silver is the best among various metallic materials in terms of optical selective reflection performance, but inferior in terms of durability because it is mechanically damaged in the post process and corrodes depending on the storage environment. There is a problem that the appearance becomes abnormal.

As a transparent conductive film, tin oxide-doped indium oxide (ITO) is well known. ITO
Can be deposited by a sputtering method, a chemical vapor deposition method (CVD), a spray method or the like. However, since indium is one of rare metals regardless of which method is used, the film material cost is high.
It is difficult to industrially establish it as a window member.

As another transparent conductive film, zinc oxide doped with alumina or the like is known, and a low specific resistance comparable to that of an ITO film, which is on the order of 10 ⁻⁴ Ω · cm, is obtained.
When a low resistance film required for ow-E is formed, it is easily affected by changes in target properties over time, and heat treatment in a non-oxidizing atmosphere is required after the film formation, and the film formation rate is 0.5 nm / sec. Since it is extremely small, such as below, the production speed is slow and there is a fatal problem in applying it to industrial production, and it has not been widely used.

In addition, there is known an interference filter in which a transparent dielectric material is laminated to have a selective reflection characteristic for infrared rays having a long wavelength by optical interference, but the total film thickness is several hundred nm.
Since it becomes thicker and the film thickness of each layer must be controlled with an accuracy of ± 5% or less, it is almost impossible to industrially apply to large area products such as window members.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks of the prior art, enables high-speed coating of a large area by the DC sputtering method, and has mechanical and chemical durability. A high-quality and low-cost optically selective reflection characteristic film, particularly Low, which is improved and does not deteriorate in optical characteristics even in high temperature heat treatment in an oxidizing atmosphere such as an air atmosphere.
-The purpose is to provide a film that is industrially useful as an E film.

[0010]

The present invention has been made to solve the above-mentioned problems, and is a transparent conductive film containing zinc oxide as a main component, the transparent conductive film containing gallium against zinc. 0.1 to 15 atomic% and has a diffraction peak due to the (002) plane in its X-ray diffraction pattern,
In a transparent conductive film in which the half width of the diffraction line by the (002) plane is 1.2 degrees or less, the specific resistance of the transparent conductive film is 10 ^-2.
Provided is a transparent conductive film having a thickness of 10 nm to 5 μm in a range of Ω · cm or less.

The transparent conductive film in the present invention contains gallium in an amount of 0.5 to 12 atom% with respect to zinc, has a diffraction peak due to the (002) plane in its X-ray diffraction pattern, and has a diffraction peak due to the (002) plane. The full width at half maximum of the line is preferably 0.6 degrees or less.

The transparent conductive film in the present invention has a specific resistance of 10 ^-2 Ω · cm or less and a film thickness of 80 nm to 5 μm, preferably 100 nm to 300 nm.

If the film thickness is more than 5 μm, the film formation time becomes long and the cost increases. If the film thickness is less than 80 nm or the specific resistance is more than 10 ^-2 Ω · cm, the Low-E performance becomes insufficient.

There is no problem if the transparent conductive film of the present invention (hereinafter also simply referred to as a conductive film) contains a metal element other than Zn and Ga within a range not impairing the purpose of the present invention, but as far as possible. It is desirable to keep the amount small.

Glass, plastic or the like can be used for the substrate forming the transparent conductive film of the present invention. When the substrate contains an alkali metal as its component, such as soda lime glass, in order to prevent the diffusion of the alkali metal from the substrate to the conductive film during film formation, heat treatment, or long-term use, the conductivity of the substrate and the conductive It is more preferable to form a base layer containing an oxide of a metal such as Si, Al, or Zr as a main component between the films.

The method for forming the conductive film of the present invention is not particularly limited, and it is a physical vapor deposition method such as a sputtering method or a vacuum vapor deposition method, or CVD.
A chemical vapor deposition method such as a chemical vapor deposition method is used, and a physical vapor deposition method capable of obtaining good conductive film characteristics at a lower substrate temperature is preferable. Above all, the sputtering method using high-density plasma as an activation means effective for promoting crystallinity, the low-voltage sputtering method using a high magnetic field, and the plasma-activated vacuum deposition method have low resistance and excellent heat resistance. It is more preferable for obtaining a film.

When the transparent conductive film of the present invention is formed by the sputtering method, the target is not only added with a predetermined amount of gallium oxide in zinc oxide and then sintered, but preferably at a temperature of 1400 ° C. or higher. It is preferable to use a treatment in which gallium oxide is sufficiently dissolved in zinc oxide by performing a treatment for holding it for 2 hours or more. Although the direct current method is shown as the sputtering method in the embodiments, it goes without saying that this may be performed by a high frequency method.

The conductive film of the present invention has low resistance and high heat resistance in the atmosphere even when it is formed by a magnetron DC sputtering method, for example, even when it is formed at a high speed up to 4 nm / sec. Therefore, it also has the effect that the film can be grown at a practical film forming speed.

In the transparent substrate of the present invention, one or more undercoat films are provided between the transparent conductive film layer and the substrate or one or more overcoat films are formed on the transparent conductive film layer for the purpose of adjusting the appearance. By providing a film, the transmission / reflection color tone and the visible light reflectance can be adjusted by utilizing the light interference phenomenon and the film absorption.

The film material of at least one layer of the undercoat film or at least one layer of the overcoat film is, for example, silicon oxide, titanium oxide, zirconium oxide, tin oxide, tantalum oxide, chromium oxide, niobium oxide or boron oxide. , At least one selected from the group consisting of indium oxide, zinc oxide, and cerium oxide, or a metal of titanium, zirconium, hafnium, chromium, or niobium, a nitride of the metal, and an oxynitride of the metal. At least one selected from the group can be used.

The undercoat film and the overcoat film can be effectively used for the purpose other than adjusting the optical characteristics. For example, it is effective for the purpose of imparting durability in order to improve the handleability of the coated product before the combination. In addition, when forming a laminated structure or a multi-layered structure together with another substrate, the purpose is to adjust the adhesiveness with the intermediate film or spacer in the laminated structure, other parts to be assembled, or after forming the transparent substrate, the glass It is also effective for the purpose of imparting heat resistance to withstand a process requiring high temperature such as strengthening and bending of the substrate, and improving reliability for use under high temperature.

The transparent substrate of the present invention can of course be used alone as a substrate having a transparent conductive film formed thereon, but the substrate may be adhered to a plastic plate or a glass plate, strengthened, or laminated. You can also

FIG. 2 is a sectional view showing the structure of the transparent substrate of the present invention. 1 is an overcoat layer, 2 is a gallium-doped zinc oxide layer, 3 is an undercoat layer, and 4 is a substrate.

[0024]

The inventors have determined that the Ga concentration in the ZnO transparent conductive film is G
By controlling the a / Zn atomic ratio to 0.5 to 12% and controlling the crystallinity of the film so that the half-width of the (002) X-ray diffraction line of the film is 0.6 degrees or less, Resistance value is 2 ×
It has been found that a material as low as 10 ⁻⁴ Ω · cm, which is as low as ITO, can be easily obtained even when it is manufactured at high speed with a normal substrate arrangement. Further, they have found that these films do not deteriorate in conductivity after heat treatment in the air at 500 ° C. or higher and have extremely excellent heat resistance in an oxidizing atmosphere.

The simple addition of Ga to ZnO has already been reported (J. Electrochem. Soc, 127, 1636 (198).
0), Jpn.J.Appl.Phys, 24, L781 (1985)). The former is an example in which 1 atomic% of Ga is added to Zn, and the latter is Zn.
Is an example by a sputtering method in which 1 to 4 atomic% of Ga is added. However, in all cases, these are reported examples of comparative examinations of the added film and the non-added film with respect to electrical and optical characteristics, and no examination or description regarding heat resistance is found. Moreover, the conductivity of these films is inferior to that of the conventional Al-added film.

On the other hand, according to the present invention, by controlling the added amount of Ga and the crystallinity of the film, it is possible to greatly improve the electric characteristics and the heat resistance in the atmosphere. That is, it was found that the heat resistance does not appear only when Ga is contained, but it appears only when Ga is contained in an amount within a specific range and the half-value width of X-ray diffraction is not more than the specific value.

In general, it is well known that the addition of a metal of Group 3 of the periodic table to ZnO increases the electron density and thus the conductivity. It is considered that this is because the group 3 or trivalent metal substitutes at the position of divalent Zn to form a shallow electric donor and generate a free electron. At the same time, an increase in electron density due to donor formation can also be explained by the generation of excess Zn at interstitial sites and the generation of oxygen defects. It is presumed that these are mixed in the actual film. Since the ionic radii of the Group 3 element and Zn are not the same, it is conceivable that crystal lattice distortion will occur even when they are replaced.

It is considered that not all the Group 3 elements can be replaced, but some of them are precipitated between crystal lattices or at grain boundaries. This is because the amount of the Group 3 element detected in the film is larger by about one digit than the amount theoretically calculated from the electron density. Since these excess elements cause lattice distortion, it is expected that oxygen vacancies will be generated. It is considered that defects such as oxygen vacancies are reduced by heat treatment in a high-temperature oxygen atmosphere, and at the same time, the electron density generated by the vacancies is also reduced, resulting in an increase in resistance.

In fact, a ZnO film containing a group 3 element of Al, In, and B other than Ga has excellent heat resistance in a non-oxidizing atmosphere, but has extremely poor heat resistance in an oxidizing atmosphere such as the air. As a result of detailed examination of the relationship between the composition and crystallinity of the film and the thermal stability in the atmosphere by X-ray diffraction, the present inventors have found that the additive element is Ga, not simply the Group 3 element,
Moreover, it has been found that a film having a high heat resistance in the atmosphere can be obtained only when the added amount is within a specific range and in addition, the half width of the X-ray diffraction of the film is less than a certain value.

The difference in ionic radius is considered to be the cause of the difference in heat resistance in the atmosphere when the additive element is Al, B, In and Ga. That is, the ionic radii of Al and B are too small compared with Zn, respectively, and conversely In is too large. Since the ionic radius of Ga is the closest to that of Zn, it is considered that the lattice strain in the case of substitution is the smallest. In order to obtain a low resistance film, it is necessary to add a large amount of Al, B and In. In this case, it is considered that the strain increases and oxygen vacancies are generated. It is considered that this defect is easily reduced by high-temperature heat treatment in an oxidizing atmosphere, and at the same time, the number of free electrons generated by the defect is also reduced, so that the resistance is increased.

On the other hand, in the case of a Ga-added film, it is considered that even if a large amount of Ga is added, lattice strain and oxygen defects are less likely to occur, so that the heat resistance in an oxidizing atmosphere is also improved. It was found that the heat resistance also strongly depends on the crystallinity of the film even when Ga is added, and when the film has good crystallinity, that is, when the half width of the X-ray diffraction line is less than a certain value, the heat resistance in an oxidizing atmosphere is remarkably high. It turned out to improve.

[0032]

【Example】

[Examples 1 to 6] A glass substrate (5 cm x
5 cm × 1 mm) by direct current magnetron sputtering using various targets (Ga / Zn ratio of 0.3 to 15 atom%) in which gallium oxide (Ga ₂ O ₃ ) is added to ZnO in an Ar atmosphere. , The film thickness is 80 nm to 100
A 0 nm ZnO transparent conductive film was formed. The target used at this time is, after adding gallium oxide into ZnO,
It is a target having a diameter of 3 inches in which gallium oxide is sufficiently dissolved in ZnO by holding it at a temperature of 1400 ° C. or more for 2 hours or more.

The vacuum apparatus was evacuated to 10 ^-6 Torr or less in advance, and then Ar gas was introduced at 0.01 Torr for sputtering. The substrate temperature was set in the range of room temperature to 300 ° C. The sputtering power was set to 50 W as a standard condition, but was changed to 400 W as an example of high speed film formation.

The Ga content in the produced film was determined by dissolving the ZnO film in a 2N solution of hydrochloric acid and then quantitatively analyzing it by ICP emission spectrometry. The Ga content is expressed in atomic% based on Zn. The specific resistance was calculated from the sheet resistance obtained by the 4-probe method and the film thickness measured by a stylus type film thickness meter.

The X-ray diffraction of the conductive film was performed by using a Kα ray of Cu and using a rate meter using a proportional coefficient tube. X
An example of measurement of line diffraction is shown in FIG. This is G as described later
Regarding Example 3 of ZnO film to which a is added (002) X
It is an enlarged view of the line diffraction peak. As shown in the figure,
The line width (expressed in degrees) of the diffraction line having an intensity half the maximum intensity of the (002) peak is called a half-value width (half-value width). In the case of Example 3 in FIG. 1, the half-value width is 0. .28 degrees.

As the optical properties, the transmittance, reflectance and emissivity were measured by a spectroscope using an integrating sphere.
These conductive films were subjected to a heat treatment test in air under the conditions shown in Table 1. Table 2 shows the heat treatment test in air (500 ° C, 1
The results of measuring the characteristics before (upper) and after (lower) 0 minutes) are shown.

Examples 1 to 6 shown in Table 2 relate to the films when the Ga addition amount is 0.5 to 12 atomic% and the half width of the (002) X-ray diffraction line is 0.6 degrees or less. It is a heat resistance test result. The full width at half maximum of the X-ray diffraction line of the film of Example 3 was 0.28 degrees as shown in FIG. These films have a low emissivity of 0.40 or less when formed, and
The emissivity does not decrease even after heat treatment in the atmosphere at 500 ° C. for 10 minutes, and the emissivity is equivalent or improved on the contrary.

No change in transmittance was observed, and it was found that the film was stable against heat treatment in the atmosphere. Particularly noteworthy is the example of high-speed film formation shown in Example 4, and even when a film is formed at a high speed of 4 nm / sec, a film having a half width of 0.45 degrees and a small half value width of 0. It was found that it had a low emissivity of 32 and was stable even after heat treatment in the atmosphere. As a typical measurement example, the spectral characteristics of the film of Example 3 (film thickness: 200 nm) are shown in FIG.

[Example 7, Comparative Examples 1 to 4] Various Low-
As E, an example using the gallium oxide-doped zinc oxide film according to the present invention (Example 7) and an example using a transparent conductive zinc oxide film using another dopant or another transparent conductive film (Comparative Example 1) The results are shown in Table 3.

Comparative Example 1 is an example using tin oxide-doped indium oxide. In this case, since a film obtained by sputter deposition in a pure Ar atmosphere exhibits slight absorption, it is necessary to introduce a small amount of oxygen into the sputtering atmosphere. There is. However, since the characteristics of the film sensitively depend on the oxygen concentration and gas pressure in the sputtering atmosphere, the obtained film has non-uniform specific resistance, and the Low-E performance also has an in-plane distribution.

Comparative Example 2 is an example using aluminum oxide-doped zinc oxide, which is easily affected by the change in target properties over time, the film characteristics are likely to change, and the film forming rate is extremely low at 0.5 nm / sec or less. There are drawbacks.

Comparative Example 3 is an example using antimony oxide-doped tin oxide, and the range of conditions for obtaining a low resistance film by the sputtering method is narrow, and a film having the required characteristics can be obtained only at an extremely low film forming rate. Can not.

Comparative Example 4 is an example of using fluorine-doped tin oxide by a spray (pyrolysis) method, and it is very difficult to completely eliminate in-plane non-uniformity of resistivity and film thickness due to the fate of the film forming method. Therefore, a film thickness distribution of ± 10% usually occurs. As a result, in a commonly used film thickness of 1000 to 200 nm, a striped interference color unevenness corresponding to the film thickness unevenness is exhibited, the appearance is unsightly, and the commercial value is remarkably reduced.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

[0047]

As can be seen from Table 2, the Ga concentration is Ga
A film having an atomic ratio of Zn / Zn of 0.5 to 12 atomic% exhibits high conductivity of the order of 10 ⁻³ Ω · cm to 10 ⁻⁴ Ω · cm at the time of film formation, and also exhibits good Low-E characteristics. . In addition, these films have a low conductivity and a low conductivity even after heat treatment in the atmosphere.
The E-characteristics do not deteriorate and are equivalent or, on the contrary, improved.
There is no change in the transmittance, indicating that the film is stable in the high temperature atmosphere.

The transparent substrate according to the present invention in which the gallium oxide-doped zinc oxide layer is used as the selective optical reflection layer is more complex than the film system of the selective optical reflector using a thin metal layer such as a thin silver layer. Excellent in handling before layering and layering, long-term reliability during use, and stability against environmental attack.

Since a film can be formed on a large-area substrate with a uniform film thickness and film quality distribution by the DC sputtering method, a large area of, for example, 1 m width or more is required.
It can be applied to window members with E performance, windshields of automobiles, windows of train cars and aircraft, and anti-fog applications such as frozen showcases in stores. Further, since a plurality of small-sized substrates can be arranged side by side to form a film simultaneously, the production efficiency is excellent.

Of the overcoat layer or undercoat layer for the gallium oxide-doped zinc oxide layer,
One or more layers, for example titanium nitride, zirconium nitride,
Absorbs heat rays and visible light such as nitrides such as hafnium nitride and chromium nitride, and precious metals such as gold and platinum.
By using a material selected from the group of reflective materials, the coated transparent substrate of the present invention can be provided with heat ray reflection performance and the visible light transmittance can be adjusted to a value lower than that of the substrate.

Further, the optical interference condition is adjusted by adjusting the film material and the film thickness of both or one of the overcoat layer and the undercoat layer, and with respect to the coated transparent substrate of the present invention. It is also possible to adjust the reflectance and the color tone of transmission and reflection. As a result, for example, the reflectance in the visible range can be lowered so as not to give a dazzling appearance, or a desired reflection color tone can be obtained.

As described above, by controlling the Ga concentration and the half-width of the X-ray diffraction line within a specific range, a transparent conductive film having high conductivity and high transmittance can be realized. The conductivity is not lost at all,
An oxidation resistant transparent conductive film can be obtained. Therefore,
Since these substrates are provided with the elements of high transparency, low resistance, heat resistance in the air, and low cost, they are used as transparent electrodes for various display elements, solar cells and light receiving elements, heat ray reflective films for construction and automobiles. Optimum as a selective transmission film, an electromagnetic wave shielding film, a transparent base for automobiles such as anti-fogging and waterproofing, waterproofing showcases and other constructions, or an antistatic film for photomasks and constructions, etc. Next to
It can be applied to a very wide range of fields.

[Brief description of drawings]

FIG. 1 is a graph showing the full width at half maximum of a (002) X-ray diffraction line of a transparent conductive film of Example 3.

FIG. 2 is a sectional configuration diagram of a transparent substrate of the present invention.

FIG. 3 is a graph showing spectral characteristics of the transparent conductive film of Example 3.

[Explanation of symbols]

 1: Overcoat layer 2: Gallium-doped zinc oxide layer 3: Undercoat layer 4: Substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masami Miyazaki 1150 Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa Prefecture Asahi Glass Co., Ltd. Central Research Laboratory

Claims (7)

[Claims] 1. A transparent conductive film containing zinc oxide as a main component, wherein the transparent conductive film contains gallium in an amount of 0.1 to 0.1.
It contains 15 atomic% and has an X-ray diffraction pattern of (0
The film has a diffraction peak of the (02) plane, a half-value width of the diffraction line of the (002) plane of 1.2 degrees or less, and a specific resistance of the transparent conductive film of 10 ^-2 Ω · cm or less. Is 80 nm
A transparent conductive film having a thickness of ˜5 μm. 2. The transparent conductive film contains gallium in an amount of 0.5 to 12 atom% with respect to zinc, and has an X-ray diffraction pattern having a diffraction peak due to a (002) plane,
2. The transparent conductive film according to claim 1, wherein the half width of the diffraction line by the plane 2) is 0.6 degree or less. 3. A transparent substrate comprising the transparent conductive film according to claim 1 or 2 on the substrate. 4. The undercoat film of one or more layers between the substrate and the transparent conductive film and / or the overcoat film of one or more layers on the transparent conductive film. Transparent substrate. 5. The film material of at least one layer of the undercoat film or at least one layer of the overcoat film is silicon oxide, titanium oxide, zirconium oxide, tin oxide, tantalum oxide, chromium oxide, niobium oxide, boron oxide. 5. The transparent substrate according to claim 4, comprising at least one selected from the group consisting of, indium oxide, zinc oxide, and cerium oxide. 6. The film material of at least one layer of the undercoat film or at least one layer of the overcoat film is a metal of titanium, zirconium, hafnium, chromium, niobium, a nitride of the metal, or an acid of the metal. The transparent substrate according to claim 4, comprising at least one selected from the group consisting of nitrides. 7. A laminated structure or a multi-layer structure comprising the transparent substrate according to any one of claims 3 to 6.