JPH08151233A - Transparent heating body - Google Patents

Abstract

PURPOSE: To obtain a transparent heating body excellent in durability, heat insulating performance, etc., and suitable for automobile glass, etc., by forming a transparent electroconductive film having a specific composition, a compound oxide film and an over-coat film on a transparent base body. CONSTITUTION: This transparent heating body is produced by coating a transparent electroconductive film having ZnO as a main ingredient containing 1-15atom% Ga based on Zn on a transparent base body consisting of glass, a plastic, etc., by using a vacuum evaporation, etc., and further forming a compound oxide film of Si and Zr and an over-coat film on the upper layer of the transparent electroconductive film. The over-coat film is a film selected from a nitride film, a nitride oxide film of at least one metal selected from Cr, Ti, Zr and Hf and a lower oxide film of at least one metal selected from Ti, W, Mo, Nb, Ta and V. A specific resistance can be lowered by allowing to contain a metal selected from Si, Ti, Zr, Hf, Y and La in the transparent electroconductive film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent heating element.

[0002]

In recent years, automotive glass, in the field of architectural glass, design design property, comfort, for the purpose of air-conditioning load reduction, etc., but the addition of the heat ray reflection performance is being requested, the conventional SnO ₂ A transparent conductive film such as a contained In ₂ O ₃ (ITO) film or a ZnO film does not have sufficient heat ray reflection performance.

Further, while the glass for automobiles is required to have anti-fogging / melting ice performance, when the glass for automobiles (EHW) with anti-fog / ice-melting function is used as a security component, the performance and durability thereof are required. Sex must be guaranteed.

With a conductive film in which the film is broken or the film resistance is increased due to deterioration, it is no longer possible to generate the rated amount of heat generation, or in extreme cases, the broken part of the film abnormally heats up and foams the intermediate film. It can also lead to glass breakage.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks of the prior art, has high reliability and durability, and can be manufactured at low cost. The purpose is to provide the attached transparent heating element.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, in which Zn is formed on a transparent substrate.
Zn whose Ga content is 0.1 to 15 atomic% with respect to
A transparent heating element comprising a transparent conductive film containing O as a main component, wherein a composite oxide film of Si and Zr and a specific overcoat film are formed on the transparent conductive film. The overcoat film is a nitride film or oxynitride film of at least one metal selected from the group consisting of Cr, Ti, Zr and Hf, and Ti, W, Mo, Nb,
Provided is a transparent heating element, which is a film selected from lower oxide films of at least one metal selected from the group consisting of Ta and V.

In the present invention, from the viewpoints of reliability, durability, cost, and heat ray reflection performance, the transparent conductive film (hereinafter referred to as the GZO film) contains ZnO as a main component and Ga as an additive with respect to Zn. It is important to use those containing 0.1 atomic% or more and 15 atomic% or less.

As the GZO film, one having a low specific resistance can be efficiently produced and the durability is improved.
Those containing at least one metal selected from the group consisting of i, Zr, Hf, Y and La are preferable, and the content ratio thereof is preferably 0.01 to 10 atom% with respect to Zn. .

From the viewpoint of durability, the GZO film has an X content.
It is preferable that the line diffraction pattern has a diffraction peak due to the (002) plane, and the half width of the diffraction line due to the (002) plane is 0.6 ° or less.

The thickness of the GZO film is 100 to 10000Å
It is preferred that If it is less than 100 Å, long-term reliability against energization is insufficient, and if it exceeds 10,000 Å, the film formation time becomes long, and productivity and material cost increase, which is not preferable.

After the GZO film is formed, the resistance changes by reversibly exchanging water with the atmosphere during storage until the next step or during actual use to adsorb and desorb water. As a result of the examination, it became clear that the above-mentioned tendency to occur.

As a result of further study, the transparent conductive film was formed from the environment by forming a composite oxide film of Si and Zr (hereinafter referred to as SZO film) and a specific overcoat film on the GZO film. It has been newly found that the effect of effectively suppressing the amount of water reaching the inside and, as a result, significantly stabilizing the resistance of the transparent conductive film and improving the reliability and durability is exhibited.

The SZO film used in the present invention has a ratio of Si to Zr in terms of oxide of SiO ₂ / ZrO ₂ molar ratio of 10/90 to 98/2, particularly 20/80 to 9.
It is preferably 0/10 because water diffusion can be effectively suppressed.

The thickness of the SZO film is preferably 50Å to 3000Å. When it is less than 50Å, it is difficult to secure the reliability and durability of the GZO film, and when it exceeds 3000Å, productivity is deteriorated and the material cost is increased, which is not preferable.

The specific overcoat film is composed of Cr, T
A nitride film, an oxynitride film of at least one metal selected from the group consisting of i, Zr and Hf, and Ti, W and M
It is a film selected from lower oxide films of at least one metal selected from the group consisting of o, Nb, Ta and V.

The thickness of the above specific overcoat film is
It is preferably 10Å to 500Å. When it is less than 10 Å, the effect of reducing the solar radiation transmittance is lost, and when it exceeds 500 Å, the visible light transmittance is significantly lowered, which is not preferable.

Examples of the constitution of the transparent heating element of the present invention include a transparent substrate, a GZO film, a specific overcoat film, and an SZO film, which are laminated in this order. When laminated with the above configuration,
This is preferable because the GZO film is less likely to undergo unintended oxidation and to eliminate problems such as eliminating oxygen defects that contribute to conductivity. Of course, the implementation is not limited to this stacking order.

Depending on the film forming conditions and use conditions, the water adsorbed on the surface of the substrate before film forming may penetrate into the transparent conductive film, causing a change in resistance value. In that case The above-mentioned specific overcoat film is
It is also effective to use it between the ZO film and the substrate.

When the above specific overcoat film is used,
In addition to the effect of stabilizing the resistance and improving the reliability and durability, it is possible to simultaneously provide the effect of selectively blocking the heat ray component in sunlight. That is, the specific overcoat film has a wavelength of 400 to 700 nm.
Has a feature that absorption is small in the visible region and absorption is large in the near infrared / infrared region over 700 to 2100 nm. Therefore, the effect of selectively reducing the transmission of the heat ray component of the sun with respect to the visible range can be provided.

In particular, a nitride film or an oxynitride film of at least one metal selected from the group consisting of Ti, Zr and Cr is excellent in the ability to selectively block the heat ray component in sunlight. It is preferable that Ti, Zr and Cr
A nitride film of at least one metal selected from the group consisting of is particularly preferable.

The heat ray reflection performance required in recent years is 65% in the case of a laminated glass obtained by adhering two 2 mm-thick clear glasses through 0.76 mm-thick polyvinyl butyral, in terms of sunlight transmittance. It is the following.

When stacking the oxide films, the GZ
When an O film or a nitride film is present, the GZO film or the nitride film may be oxidized to increase the specific resistance or deteriorate the selective transmission performance in the visible region and the infrared region.
In order to prevent such deterioration of performance, directly below the oxide film,
It is also possible to insert a metal film constituting the oxide film or a metal film layer such as Ti very thinly, which is an effective means for exhibiting the intended performance.

The thickness of the ultra-thin metal film layer varies depending on the material, but is generally 10 to 50 Å, and is usually determined with the upper limit being the thickness that can be oxidized and made transparent during the formation of the oxide film. .

In the transparent heating element of the present invention, heat generation power adjustment, transmission / reflection color tone adjustment, heat ray reflection performance adjustment, durability / reliability improvement, suppression of characteristic changes during processes requiring high temperature,
It is necessary to adjust the film thickness of each of the GZO film, the SZO film, and the specific overcoat film depending on the purpose of preventing scratches, etc.
The ZO film is 100 to 5000 Å, and the SZO film is 10 to 3
000Å, specific overcoat film is 50-700Å
Is.

As the transparent substrate used in the present invention,
Examples thereof include glass and plastics.

The transparent substrate is like soda lime glass,
When an alkali metal is contained as the component, in order to prevent the diffusion of the alkali metal from the substrate to the conductive film during film formation or heat treatment, Si, Al, Z is formed on the substrate surface.
It is preferable to form an underlayer whose main component is an oxide or nitride of a metal such as r.

In the transparent heating element of the present invention, for the purpose of adjusting the appearance, a film for adjusting the transmission / reflection color tone and the visible light reflectance is provided between the GZO film and the transparent substrate or on the GZO film. It is also possible to provide.

For the purpose of adjusting the adhesiveness when forming a laminated structure or a multi-layer structure together with another substrate, or when attaching the lead-out portion of the electrode lead,
An adhesive force adjusting layer may be separately provided on the outermost layer.

The method of forming the GZO film of the present invention is not particularly limited, and a physical vapor deposition method such as a sputtering method or a vacuum vapor deposition method or a chemical vapor deposition method such as a CVD method may be used. The physical vapor deposition method is preferable because the film characteristics can be obtained.

In particular, the magnetron sputtering method using a high-density plasma effective for promoting crystallinity as an activation means, the low-voltage sputtering method using a high magnetic field, and the plasma-activated deposition method have low resistance and heat resistance. It is preferably used because a film having excellent properties can be obtained.

The transparent heating element of the present invention can be heated by Joule heat by providing at least two electrodes for energization, applying a DC and / or AC voltage to the electrodes.

Further, in the transparent heating element of the present invention, if necessary, detection means can be provided for the purpose of temperature control during electric heating, abnormal heat generation, and abnormality detection such as cracking of the transparent heating element. .

[0033]

【Example】

[Example 1] As a transparent substrate, a sufficiently washed clear glass (10 cm x 10 cm x 2 mm thick) was prepared, and electrodes were formed on the opposite sides by screen printing and firing on the substrate (step 1).

Next, a 1500 Å-thick GZO film was formed on this substrate by the DC sputtering method. The target used at this time had a Ga addition amount of 5.
ZnO so that 0 atomic% and Si are 0.05 atomic%.
Ga ₂ O ₃ and SiO ₂ are added to each of the
This is a target in which Ga ₂ O ₃ held at a temperature of 00 ° C. or more for 60 minutes or more is sufficiently dissolved in ZnO, the pressure during sputtering is 1 mTorr, and the sputtering gas is Ar gas. The composition of the obtained GZO film was almost the same as that of the target used (step 2).

Next, a TiN film having a film thickness of 50Å in an Ar / N ₂ mixed gas and an SZO (SiO ₂ : 66.7 mol%) film having a film thickness of 200Å in an O ₂ gas are sequentially formed on the GZO film. Formed (step 3). The substrate was not heated during any film formation.

In this embodiment, the direct current method is shown as the sputtering method, but it goes without saying that this may be performed by the high frequency method.

Finally, a 0.76 mm-thick polyvinyl butyral (PVB) film was used to cut out a portion of the electrode corresponding to the bronze glass (10 cm × 8.5 cm × 2 mm thick).
Combined with glass, PVB / SZO / TiN
A transparent heating element of laminated glass having a structure of / GZO / glass was formed (step 4).

When the resistance between the electrodes of this transparent heating element was measured, it was 102.4 Ω (initial value). When a voltage of 33.3 V was applied between the electrodes and an energization test was carried out at a heat generation amount per unit area of 1500 W / m ² , the resistance value and the appearance did not change and were constant even after 6 weeks.

Further, SZO / T obtained in the steps up to step 3
Table 1 shows the optical performance of the glass having a structure of iN / GZO / glass. As shown in Table 1, the solar radiation transmittance reduction width was 12%, and it was confirmed that the solar cell had sufficient heat ray reflection performance.

(Comparative Example 1) In steps 2 and 3 of Example 1, instead of forming the GZO film, the TiN film and the SZO film, an in-line type sputtering apparatus equipped with Zn and Ag targets was used. A transparent laminated glass heating element having a structure of glass / PVB / ZnO / Ag / ZnO / glass was prepared in the same manner as in Example 1 except that a conductive film having a high transmittance composed of three layers of / Ag / ZnO was formed. Formed.

In this case, the ZnO layer was formed by reactive sputtering in a mixed gas atmosphere of Ar and O ₂ with Zn as a target. The Ag layer targets Ag,
The film was formed in a pure Ar atmosphere. The film thickness of each layer was 450Å, 100Å, and 450Å in order from the substrate side.

When the resistance between terminals was measured in the same manner as in Example 1, the initial value was 7.1Ω. In addition, a voltage of 8.8 V is applied between the electrodes, and the heat generation amount per unit area: 1,50
When an energization test was performed at 0 W / m ² , the appearance did not change, but the resistance between terminals increased to 12.9Ω after 3 weeks. When the current-carrying test was conducted subsequently, it exceeded 100 Ω in 6 weeks.

(Comparative Example 2) In steps 2 and 3 of Example 1, instead of forming the GZO film, the TiN film and the SZO film, an in-line type sputtering apparatus equipped with an ITO target was used to obtain a film thickness of 2400Å. Ito film is formed and I
A glass with a TO film was obtained.

In this case, the sputtering gas is A
Using a mixed gas of r and 2% by volume of O ₂ with respect to Ar, the mixture was introduced by a mass flow meter so that the pressure in the film forming chamber during sputtering was 2 mTorr. The substrate was not heated during the film formation.

When the sheet resistance distribution in a 30 cm square substrate surface was measured, there was a variation of ± 30%. When a voltage of 22 V was applied between the electrodes, almost no heat was generated in the high resistance portion, and it was confirmed that there was a problem in the function as electrothermal glass.

Example 2 In the same manner as in steps 1 to 4 of Example 1, a laminated glass transparent heating element having a structure of glass / PVB / SZO / TiN / GZO / glass was prepared.
In this embodiment, the GZO film has a thickness of 600 Å, and TiN is
Change the film from 0 to 200Å and change the SZO film from 0 to 500Å
Changed. Each of the produced transparent heating elements was subjected to a high temperature durability test at 100 ° C. for 2 months, and the resistance increase rate was measured. FIG. 1 shows the change in resistance increase rate over time.

As is clear from FIG. 1, the presence of the TiN film and the SZO film significantly improves the durability.

[Example 3] In the same manner as in steps 1 to 4 of Example 1, a laminated glass transparent heating element having a structure of glass / PVB / SZO / TiN / GZO / glass was prepared.
In this embodiment, the GZO film has a thickness of 600 Å, and TiN is
Change the film from 0 to 100Å and change the SZO film from 0 to 200Å
Changed. A heat treatment test was performed at 600 ° C. for 5 minutes on each of the produced transparent substrates, and the resistance increase rate was measured. FIG. 2 shows the change in resistance increase rate with time.

As is clear from FIG. 2, the presence of the TiN film and the SZO film significantly improves the durability.

[Example 4] In steps 1 to 4 of Example 1, a GZO film (600Å), a TiN film (50Å), an SZ film
Glass / PVB / SZ was formed in the same manner except that an O film (200 Å) was formed and the pressure during sputtering of the GZO film was changed.
A transparent heating element of laminated glass having a structure of O / TiN / GZO / glass was prepared.

Further, a transparent heating element having the same structure was prepared by changing the pressure during sputtering of the GZO film in the same manner as described above except that a target containing no SiO ₂ was used.

At this time, the relationship between the pressure during sputtering of the GZO film and the specific resistance of the formed GZO film was investigated. The results are shown in Fig. 3.

As is apparent from FIG. 3, by adding a very small amount of SiO ₂ , it is possible to obtain a film having a low specific resistance even if the pressure during sputtering is closer to the bad condition side.

Next, the pressure during sputtering of the GZO film was 5.
A transparent heating element of laminated glass in the case of 0 × 10 ⁻⁵ Torr was subjected to a high temperature durability test at 100 ° C. for 2 months, and the resistance increase rate was measured. FIG. 4 shows the change in resistance increase rate with time.

As is apparent from FIG. 4, the durability is remarkably improved by adding SiO ₂ .

[Embodiment 5] In steps 1 to 4 of Embodiment 1, the laminated glass having the structure of glass / PVB / SZO / CrN / GZO / glass is transparent in the same manner except that the TiN film is replaced with a CrN film. A heating element was produced.

In this embodiment, the GZO film is 600 Å
The CrN film was changed from 0 to 200Å and the SZO film was changed from 0 to 200Å. Each of the produced transparent heating elements was subjected to a high temperature durability test at 100 ° C. for 2 months, and the resistance increase rate was measured. FIG. 5 shows the change over time in the rate of increase in resistance.

As is clear from FIG. 5, the presence of the SZO film and the CrN film significantly improves the durability.

In Example 5, the CrN film was replaced with ZrN.
When the same procedure was performed by replacing the film or CrON film,
Similar results were obtained.

[Example 6] In steps 1 to 4 of Example 1, the TiN film was replaced with a chromium oxynitride film (CrON film),
A transparent heating element of laminated glass having a structure of glass / PVB / CrON / SZO / GZO / glass was prepared in the same manner except that the order of film formation with the SZO film was reversed.

In this embodiment, the GZO film is 600 Å
, SZO film is 200Å, CrON film is 0-20
Change with 0Å. Each of the produced transparent heating elements was subjected to a high temperature durability test of 100 ° C. for 2 months,
The rate of resistance increase was measured. FIG. 6 shows the change in resistance increase rate with time.

As is apparent from FIG. 6, the presence of the SZO film and the CrON film significantly improves the durability.

[Embodiment 7] In steps 2 to 3 of Embodiment 1, the thickness of the GZO film is changed to 600Å and the TiN film is changed to the WO _3-X film (a partially reduced tungsten oxide film). Glass / PVB / SZO / W in the same manner as in Example 1.
A transparent heating element of laminated glass having a structure of O _3−x / GZO / glass was prepared.

It is known that a tungsten oxide film formed under a reducing condition generally selectively absorbs or reflects light having a wavelength of about 1 μm and is excellent in heat shielding performance. In this example, when forming a WO _3-X film, the water pressure in the sputtering film formation chamber was 3.2 × 10 ^-5 Torr, the sputtering gas was a mixed gas of Ar and O _2, and the target was a metal. Direct current sputtering was performed using tungsten. At this time, the amount of O ₂ in the sputtering gas was made small, and the conditions were adjusted so that the tungsten oxide film could take in water and absorb infrared light.

In this embodiment, the GZO film is 600
Å, the WO _3-X film was 200 Å, and the SZO film was 200 Å. The produced transparent heating element was subjected to a high temperature durability test at 100 ° C. for 2 months, and the resistance increase rate was measured. FIG. 7 shows the change over time in the rate of increase in resistance.

As is clear from FIG. 7, the presence of the SZO film and the WO _3-X film markedly improves the durability.

[0067]

[Table 1]

[0068]

The transparent heating element of the present invention has low cost, high reliability and durability, and excellent heat ray shielding performance.

[Brief description of drawings]

FIG. 1 is a graph showing the high temperature durability of the transparent heating element of Example 2.

FIG. 2 is a graph showing the high temperature durability of the transparent heating element of Example 3.

FIG. 3 is a graph showing the film forming pressure dependency of the high temperature durability of the transparent heating element of Example 4.

FIG. 4 is a graph showing high temperature durability of the transparent heating element of Example 4.

FIG. 5 is a graph showing high temperature durability of the transparent heating element of Example 5.

FIG. 6 is a graph showing high temperature durability of the transparent heating element of Example 6.

FIG. 7 is a graph showing high temperature durability of the transparent heating element of Example 7.

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

Claims (2)

[Claims] 1. A transparent heating element comprising a transparent substrate and a transparent conductive film mainly composed of ZnO having a Ga content relative to Zn of 0.1 to 15 atomic%, which is coated on the transparent substrate. A complex oxide film of Si and Zr and a specific overcoat film are formed on the upper layer of the film, and the specific overcoat film is at least one metal selected from the group consisting of Cr, Ti, Zr and Hf. Of a nitride film, an oxynitride film, and a lower oxide film of at least one metal selected from the group consisting of Ti, W, Mo, Nb, Ta, and V. Characteristic transparent heating element. 2. The transparent conductive film is made of Si, Ti, Zr, H.
at least 1 selected from the group consisting of f, Y and La
The transparent heating element according to claim 1, wherein the transparent heating element contains a kind of metal.