JP2000123958A - Corrosion preventing method for oxide semiconductor, and defogging-defrosting heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent corrosion of an oxide semiconductor even in the case of an electrolytic solution being formed on the surface of the oxide semiconductor due to deliquescence of dew drops and salt by using a metal film containing ion exchangeable material, as a metal film. SOLUTION: Ion exchangeable material is contained in a metal film provided at a part of the surface of an oxide semiconductor. Even in the case of an electrolytic solution being formed by deliquescence of dew drops and salt in environment of high humidity, environment with the sharp change of temperature, environment with attachment of dust containing sea salt grains and salt, or the like, electrolyte is captured by the ion exchange material to make the electrolytic solution low in conductivity. A current flowing to the oxide semiconductor with voltage applied thereto does not therefore flow in and out of the electrolytic solution, so that the semiconductor is not reduced nor corroded. Inorganic ion exchangeable material excellent in heat resistance is used as the ion exchangeable material, preferably such as hydrous antimony oxide, zirconium phosphate, hydrotalite or hydroxyapatite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide semiconductor such as ITO (Indium Tin OXide) used for an anti-fogging and defrosting heater. Even if an electrolytic solution is formed on the surface of the oxide semiconductor due to dew condensation or salt deliquescence in an environment where dusts are contained, etc., a method for preventing the oxide semiconductor from corroding and increasing the resistance and disconnection is used. The present invention relates to an anti-fog and frost heater.

[0002]

2. Description of the Related Art As the name suggests, an oxide semiconductor is an oxide, and is therefore considered to be chemically stable, but is known to corrode in an atmospheric environment. For example, ITO (Indium Tin Oxide) used for an electrode of a liquid crystal display device corrodes and causes a disconnection accident (Japanese Patent Application Laid-Open No. 58-17832).
No. 5). However, this corrosion mechanism was not clear.

[0003] The inventor has found that when an oxide semiconductor to which a voltage is applied is in contact with an electrolyte, a current flowing through the oxide semiconductor flows into and out of the electrolyte, and a current flows from the electrolyte to the oxide semiconductor. (Cathode), it was clarified that reduction and corrosion occur due to electrochemical reaction (Corrosion and Corrosion Prevention Association) (D-203S).

A voltage-applied ATO (Antimony
Electrolyte solution (0.1mol-N) on the surface of doped Tin Oxide
The corrosion mechanism of ATO when (a ₂ SO ₄ aqueous solution) is dropped will be described with reference to FIG. This figure shows the AT
The corrosion behavior of O is schematically shown, in the figure, 15 is a power supply, 16 is an Ag anode, 17 is an Ag cathode, 18 is ATO,
19 is a glass substrate, 20 is a droplet (0.1N-Na ₂ SO ₄₎
Aqueous solution), 21 is an electric current, 22 is an anode portion, 23 is a cathode portion, 24 is the movement of droplets, and 25 is a corroded portion of ATO. In the figure, (a) represents the first step, (b) represents the second step, and (c) represents the third step. In addition,
[1] First step, [2] Second step and [3]
The droplets described in the third step are exaggerated, and the actual size of the droplets is about 3 mm. In the diagrams of [2] the second step and [3] the third step, the voltage is still applied as in [1] the first step.

[1] First step When a voltage is applied between Ag electrodes, the tip of the droplet facing the Ag electrode of the cathode moves toward the Ag electrode of the cathode, and the semi-elliptical droplet is distorted.

[2] Second Step ATO at the tip of the distorted droplet facing the Ag cathode is reduced and corroded. At this time, air bubbles are generated from the leading end of the droplet facing the Ag cathode and the leading end of the droplet facing the Ag anode. These phenomena are thought to be caused by the electrochemical reaction of the following formulas (1) to (4), where ATO at the tip of the droplet facing the Ag electrode on the anode becomes the anode, and ATO at the tip of the droplet facing the Ag electrode on the cathode becomes the cathode. Can be

Anode (ATO at the tip of the droplet facing the Ag anode) 2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻ (generation of O ₂ by electrolysis of water) ‥‥‥ Cathode (facing the Ag cathode) (ATO at the tip of the droplet) 2H ₂ O + 2e → H ₂ + 2OH ⁻ (generation of H ₂ by electrolysis of water) ‥‥ SnO ₂ + 4H ⁺ + 2e → Sn ²⁺ + 2H ₂ O (reduction and corrosion of ATO) ‥‥ [ 3] Third Step When the ATO is corroded and the underlying glass comes into contact with the droplet, the droplet spreads to a corroded portion of the ATO (exposed underlying glass), which is more likely to leak than on the ATO, and as a result, the Ag cathode becomes The ATO at the tip of the opposing droplet corrodes, and the corroded area expands. Note that when the base of the oxide semiconductor is plastic,
Although the spread of the droplets is smaller than in the case of glass, the phenomenon of corrosion of ATO is the same.

[0008] Regarding the corrosion behavior of ITO,
The ITO is reduced and corroded by the following electrochemical reaction shown in the equation.

In ₂ O ₃ + 6H ⁺ + 4e ⁻ → 2In ⁺ + 3H ₂ O ‥‥‥ SnO ₂ + 4H ⁺ + 2e ⁻ → Sn ²⁺ + 2H ₂ O ‥‥‥ Corrosion of an oxide semiconductor in an atmospheric environment by the above corrosion mechanism. Explain the behavior. On the other hand, when no voltage is applied, the oxide semiconductor does not reduce or corrode even when in contact with the electrolytic solution.

The inventor further proceeded with experiments and clarified the corrosion conditions of the oxide semiconductor to which the electrolytic solution was attached and to which voltage was applied as shown in the following (1) and (2).

(1) Corrosion occurs regardless of the pH of the electrolytic solution. Note that when the electrolyte is strongly acidic or strongly alkaline, the oxide semiconductor is corroded by a chemical reaction even when a voltage is not applied. For example, IT in a strongly acidic aqueous solution
O corrosion is caused by the following chemical reaction shown in the following equation.

In ₂ O ₃ + 6H ⁺ + 4e ⁻ → 2In ⁺ + 3H ₂ O ‥‥‥ SnO ₂ + 4H ⁺ → Sn ⁴⁺ + 2H ₂ O ‥‥‥‥‥‥ (2) Corrosion when the conductivity of the electrolyte is large I do. Conversely, if the conductivity of the electrolyte is low, it does not corrode. This is because the current flowing through the oxide semiconductor does not flow into and out of the electrolytic solution, so that an electrochemical reaction does not occur.

For example, if the conductivity is 10 μS / cm (25
° C) does not corrode the oxide semiconductor.

In general, when an oxide semiconductor is exposed to the air, sea salt particles, dust containing salt, and the like adhere. When these salts form an electrolytic solution due to deliquescence or condensation, the oxide semiconductor is reduced and corroded when a voltage is applied to the oxide semiconductor.

FIG. 3 shows a cross section of the heater for anti-fog and frost. In FIG. 3, 1 is a substrate, 2 is a transparent conductive film made of an oxide semiconductor, and 3 is a metal film. A voltage is applied between the two metal films to remove water droplets attached to the oxide semiconductor. In this case, when a water droplet containing a high concentration of salt adheres to the oxide semiconductor, the oxide semiconductor may be corroded by applying a voltage between the two metal films. In particular, in a pinhole existing in the metal film or in a gap between the metal film and the oxide semiconductor, condensation easily occurs due to a capillary condensation phenomenon, so that a high-concentration electrolyte solution containing salt is formed and the oxide semiconductor is corroded.

In order to prevent the oxide semiconductor from corroding, a transparent film such as polyester is attached to the surface of the oxide semiconductor and the metal film. However, if the transparent film is not adhered with good adhesiveness, a gap is formed between the oxide semiconductor and the metal film, so that dew condensation is likely to occur.

Further, in order to prevent corrosion of the oxide semiconductor, it has been proposed to cover the surface of the oxide semiconductor with an insulating film. FIG. 4 is a cross-sectional view of a liquid crystal display device described in JP-A-58-178325, in which 5 is an upper plate, 5 'is a lower plate,
6 is a sealing portion, 7 is an alignment film, 8 is an insulating film, 9 is a liquid crystal,
Reference numeral 0 denotes an upper polarizing plate, 10 'denotes a lower polarizing plate, 11 denotes a transparent conductive film, 12 denotes conductive rubber, 13 denotes a liquid crystal display element driving circuit board, and 14 denotes a conductive pattern. This patent covers the surface of 11 transparent conductive films, such as ITO, exposed to the external environment with an insulating film, such as SiO ₂ . However, when a path such as a pinhole that reaches the oxide semiconductor exists in the insulating film, there is a problem that the electrolyte enters and penetrates the oxide semiconductor through the path.

[0018]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and has been made in an environment of high humidity,
In an environment where temperature changes drastically or in an environment where dust containing sea salt particles or salt adheres, when an electrolyte is formed on the surface of the oxide semiconductor due to dew condensation or salt deliquescence, it is necessary to prevent corrosion of the oxide semiconductor. Aim.

[0019]

When an oxide semiconductor to which a voltage is applied is in contact with an electrolytic solution, the oxide semiconductor is corroded as described above because a current flowing through the oxide semiconductor is applied to the electrolytic solution. This is because they flow in and out. Therefore, preventing current from flowing in and out through the electrolytic solution is a method for preventing corrosion of the oxide semiconductor. Therefore, it is necessary to (1) prevent contact between the oxide semiconductor and the electrolyte, and (2) reduce the conductivity of the electrolyte, that is, remove the electrolyte. As a method therefor, the present invention (1) provides a water-repellent film on the surface of an oxide semiconductor having no metal film,
(2) An ion exchange material is contained in the metal film.

The invention according to claim 1 is characterized in that in a structure in which a metal film is laminated on a part of the surface of an oxide semiconductor, a metal film containing an ion-exchange material is used as the metal film. This is a method for preventing corrosion of an oxide semiconductor.

According to a second aspect of the present invention, there is provided a structure in which a metal film is laminated on a part of the surface of an oxide semiconductor, and a water-repellent film is laminated on a surface of the oxide semiconductor on which no metal film exists. The method for preventing corrosion according to claim 1, which is a method for preventing corrosion.

According to a third aspect of the present invention, the water repellent film is made of S
3. The method according to claim 2, wherein the method is iOF.

According to a fourth aspect of the present invention, the ion exchange material is an inorganic ion exchange material.
It is the corrosion prevention method described.

According to a fifth aspect of the present invention, the inorganic ion exchange material is at least one selected from the group consisting of hydrous antimony oxide, zirconium phosphate, hydrotalcite and hydroxyapatite. It is a prevention law.

According to a sixth aspect of the present invention, there is provided a heater for anti-fog and defrost, wherein a metal film containing an ion-exchange material is laminated on a part of the surface of the oxide semiconductor.

According to a seventh aspect of the present invention, there is provided the semiconductor device according to the first aspect, wherein the oxide semiconductor has an S
The anti-fogging and defrosting heater according to claim 6, wherein the iOF film is laminated.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a water-repellent film is provided on the surface of an oxide semiconductor having no metal film thereon.
As a result, even in a high humidity environment, an environment in which temperature changes drastically, or an environment where dust containing sea salt particles or salt adheres, even if an electrolyte is formed by dew condensation or salt deliquescence, the water-repellent film is an oxide semiconductor. The oxide semiconductor is not corroded because the contact between the oxide semiconductor and the electrolyte is interrupted. In addition, even when the water-repellent film has a passage such as a pinhole reaching the oxide semiconductor, the electrolyte does not contact the oxide semiconductor. Accordingly, current flowing through the oxide semiconductor to which a voltage is applied does not flow into or out of the electrolytic solution, and thus the oxide semiconductor is not reduced or corroded.

Further, in the present invention, a metal film provided on a part of the surface of an oxide semiconductor contains an ion-exchange material. As a result, even if the electrolyte is formed by condensation or deliquescence of salt in environments with high humidity, environments with drastic temperature changes, or environments where dust containing sea salt particles or salt adheres, the ion exchange properties in the metal film can be reduced. The electrolyte is trapped by the material to form a liquid with low conductivity. Accordingly, current flowing through the oxide semiconductor to which a voltage is applied does not flow into or out of the electrolytic solution, and thus the oxide semiconductor is not reduced or corroded.

The oxide semiconductor that is the object of the present invention can be corroded by being electrochemically reduced, such as ITO (indium oxide doped with tin), ATO (tin oxide doped with antimony), AZO (zinc oxide doped with aluminum), In ₂ O ₃ , SnO ₂ , Zn
O, CdO, TiO ₂ , CdIn ₂ O ₄ , Cd ₂ SnO ₄ ,
Zn ₂ SnO _{4 and the} like can be mentioned. The shape of the oxide semiconductor is not particularly limited, and is, for example, a film formed by evaporation, sputtering, or a spray method.

According to the present invention, when a water-repellent film is not laminated on the surface of an oxide semiconductor having no metal film thereon and a metal film mixed with an ion exchange material is provided, the metal film does not exist on the upper portion. There are two cases in which a water-repellent film is stacked over the surface of an oxide semiconductor and a metal film in which an ion exchange material is mixed is provided. The above is used when the adhesion of dust containing sea salt particles or salt is slight, and the above is used when the adhesion of dust containing sea salt particles or salt is severe.

The water-repellent film plays a role in preventing the oxide semiconductor from coming into contact with the electrolytic solution. As the water-repellent film, an inorganic material having excellent heat resistance is used. A specific example is an SiOF film, which is manufactured by plasma CVD. The thickness of the water-repellent film is not particularly limited as long as the water-repellency can be maintained, but is preferably 100 to 1000 ° from the viewpoint of anticorrosion performance and production cost.

Here, the water repellency refers to keeping water away or repelling water.
The evaluation can be made using an angle (water contact angle) formed between the water droplet when the water droplet is put on the coating film and the surface of the water-repellent film. The larger this angle is, the higher the water repellency is, and this angle is 9
It is preferable to rub 0 degrees (Doi, Haruta, "Water-repellent paint", Industrial Materials April 1996 extra edition, Vol.44, No5, p46)
(1996)).

The metal particles are not particularly limited, but silver having excellent conductivity or an alloy mainly containing silver is used. Although the particle size is not particularly limited, a range of 1 to several thousand μm is appropriate from the viewpoint of workability. The thickness of the metal film is not particularly limited, but is several μm to secure conductivity.
A range of a few mm would be appropriate.

As the ion exchange material, an inorganic ion exchange material having excellent heat resistance is used. Inorganic ion exchange materials include cation exchange materials and anion exchange materials.

Here, the cation exchange material is such that the electrolyte ion is a cation (eg, an alkali metal ion such as Na, K, and Li; Ag, Cu, Fe, Pb, Sn, Zn, M
In the case of other metal ions such as g and Ca; ammonium ions such as tetramethylammonium ion and trimethylammonium ion, the anionic exchange material is such that the electrolyte ion is an anion (eg, a halogen ion such as Cl, Br, I, etc.). Oxide ions such as SO ₄ , NO ₃ , and NO ₂ ; organic acid ions such as formic acid, acetic acid, and phthalic acid). Of course, both ion-exchange substances can be used in combination.

Examples of the cation-exchangeable inorganic substance include polyvalent metal acids such as zeolite, antimonic acid, stannic acid, titanic acid, niobic acid, and manganic acid and salts thereof; zirconium phosphate, titanium phosphate, tin phosphate And polybasic metal salts such as cerium phosphate, tin arsenate and titanium arsenate; and heteropoly acids such as molybdic acid and tungstic acid.

Examples of the anion exchangeable inorganic substance include hydrotalcite, hydroxyapatite, hydrated antimony, hydrated iron, hydrated oxide such as hydrated zirconium and hydrated bismuth.

Among these ion-exchange materials, hydrous antimony, zirconium phosphate, hydrotalcite and hydroxyapatite are preferred. Further, these ion exchange substances can be used alone or in combination of two or more.

When the cation-exchange material and the anion-exchange material are used as a mixture, for example, the weight ratio of the cation-exchange material / anion-exchange material is about 9/1 to 1/1. / 9, preferably in the range of about 2/1 to 1/2 is preferable in that it can correspond to any electrolyte.

The ion exchange material mixed with the metal particles is as follows:
Although it can be used in the form of granules, fibers, scales, pellets, etc., it is preferable that the particles be granular in terms of dispersibility. In this case, the particle size is not particularly limited, but the average particle size is about 1000 in terms of uniformity of dispersion, easiness of application, and specific surface area.
μm or less is preferable, and 1 to 1000 μm is more preferable.

The amount of the ion exchange material used is determined by the corrosiveness of the use environment, but is used in the range of 0.1 to 50% by weight of the metal film from the viewpoint of ensuring conductivity.

[0042] The metal film is formed on the surface of the oxide semiconductor by baking. A metal powder, an inorganic ion exchange material, an organic binder, and a solvent are mixed, applied to the surface of the oxide semiconductor, and then baked by maintaining the temperature at a high temperature (for example, 300 ° C.). The ratio between the organic binder and the solvent is not particularly limited, but is, for example, 10% by weight with respect to the total of 80% by weight of the metal powder and the inorganic ion exchange material.

An example in which the present invention is applied to an anti-fog and frost heater will be described below.

Embodiment 1 FIG. 1 is a sectional view of a heater for anti-fog and defrost. In the figure, 1 is a substrate (glass) of a heater for anti-fog and frost, 2 is a transparent conductive film (ITO), and 3 is a metal film (Ag). After an ITO film is formed on one glass substrate by a sputtering method, an Ag film is baked. The thickness of the Ag metal film is 1 mm. Ag
After blending the particles, antimony hydroxide, an organic binder, and a solvent in the following proportions and applying the mixture on ITO, 300 ° C. × 30
Bake for a minute.

Mixing ratio Metal {Ag particles (average particle size = 10 μm) 60% by weight Inorganic ion-exchange material {hydrated antimony hydroxide 20% by weight (average particle size = 10 μm) Organic binder} Polyvinyl alcohol 10 Wt% Solvent ‥‥‥ Isopropyl alcohol 10 wt% A 0.1N-NaCl aqueous solution was dropped on the interface between the Ag film and the ITO, and a voltage of 50 V was applied. As a result, the ITO did not corrode.

Comparative Example 1 An Ag film containing no inorganic ion-exchange material was formed in the same manner as in Example 1, and a 0.1N film was formed on the Ag film / ITO interface.
When a voltage of 50 V was applied after the dropwise addition of the -NaCl aqueous solution, the ITO was corroded.

Embodiment 2 FIG. 2 is a sectional view of a heater for anti-fog and defrost. In the figure, 1 is a substrate (glass) of a heater for anti-fog and frost, 2 is a transparent conductive film (ITO), 3 is a metal film (Ag), and 4 is a water-repellent film (Si).
OF). The thickness of the metal film is 1 mm, and the thickness of the water-repellent film is 500 °. After a film of ITO was formed on the glass substrate 1 by sputtering, SiO 2 was formed by plasma CVD.
F is deposited. Further, an Ag film is baked on ITO having no SiOF film. Note that the conditions for forming the Ag film are the same as those described in Embodiment 1.

After a 0.1N-NaCl aqueous solution was dropped on the Ag film / SiOF interface and on the SiOF, and a voltage of 50 V was applied, the ITO did not corrode.

Comparative Example 2 In the same manner as in Example 2, an Ag film containing no inorganic ion exchange material was formed. Even when SiOF was not present on the ITO, a 0.1N-NaCl aqueous solution was dropped on the interface between the Ag film and the ITO and on the surface of the ITO, and when a voltage of 50 V was applied, the ITO was corroded.

[0050]

According to the present invention, since the water-repellent film is laminated on the surface of the oxide semiconductor, the electrolyte does not come into contact with the oxide semiconductor. Thus, the oxide semiconductor does not corrode. In addition, since the ion-exchange material is contained in the metal film stacked over part of the surface of the oxide semiconductor, the electrolyte is trapped by the ion-exchange material even if an electrolyte is attached through the metal film.
Thus, even when a voltage is applied between the metal films, the current does not flow into and out of the electrolytic solution, so that the oxide semiconductor does not corrode.

According to the first aspect of the present invention, since a metal film containing an ion-exchange material on a part of the surface of the oxide semiconductor is used, corrosion of the oxide semiconductor at the interface between the metal film and the oxide semiconductor is prevented. It has an effect that can be prevented.

According to the second aspect of the present invention, the structure laminated on a part of the surface of the oxide semiconductor has the water-repellent film laminated on the surface of the oxide semiconductor having no metal film on the upper part. Therefore, even when sea salt particles or dust containing salt is attached and an electrolyte is formed by deliquescence or dew condensation, the electrolyte does not contact the oxide semiconductor. Thus, an effect of preventing corrosion of the oxide semiconductor can be obtained.

According to the third aspect of the present invention, since the water-repellent film is SiOF, the contact between the electrolytic solution and the oxide semiconductor can be prevented, and the effect of excellent heat resistance can be obtained.

According to the fourth aspect of the present invention, since the ion-exchange material is an inorganic ion-exchange material, there is an effect that the ion-exchange material is not deteriorated by increasing the temperature when forming a metal film.

According to the fifth aspect of the invention, since an easily available inorganic ion-exchange material is used as the ion-exchange material, there is an effect that the metal film can be easily contained.

According to the sixth aspect of the present invention, since the heater for fogging and frost is formed by laminating a metal film containing an ion exchange material on a part of the surface of the oxide semiconductor, the metal film / oxide Corrosion of the oxide semiconductor at the interface of the semiconductor can be prevented. This has the effect of preventing an increase in the resistance of the heater for anti-fog and frost and a failure in disconnection.

According to the seventh aspect of the present invention, since the SiOF film is laminated on the surface of the oxide semiconductor having no metal film thereon, sea salt particles and dust containing salt adhere to the surface to cause deliquescence and dew condensation. Does not make contact with the oxide semiconductor even when the electrolyte is formed. Accordingly, corrosion of the oxide semiconductor can be prevented, and an effect of preventing an increase in resistance and disconnection failure of the heater for anti-fog and frost can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a heater for anti-fog and defrost according to Embodiment 1 of the present invention.

FIG. 2 is a cross-sectional view of an anti-fog and frost heater according to Embodiment 2 of the present invention.

FIG. 3 is a cross-sectional view of a conventional heater for anti-fog and defrost.

FIG. 4 is a cross-sectional view of a conventional liquid crystal display device.

FIG. 5 is a diagram showing the corrosion behavior (schematic diagram) of ATO (Antimony doped Tin Oxide).

[Explanation of symbols]

1 substrate, 2 transparent conductive film, 3 metal film (containing ion exchange material), 4 water repellent film, 5 upper plate, 5 'lower plate, 6
Seal part, 7 alignment film, 8 insulating film, 9 liquid crystal, 10
Upper polarizer, 10 'Lower polarizer, 11 transparent conductive film, 12 conductive rubber, 13 liquid crystal display element driving circuit board, 14 conductive pattern, 15 power supply, 16 Ag
Anode, 17 Ag cathode, 18 ATO, 19 glass substrate, 20 droplets, 21 current, 22 anode, 23
Cathode, 24 Droplet movement, 25 ATO erosion.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshishin Kiyoshi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation F-term (reference) 3K092 PP20 QA05 QB01 QB04 QB31 QB58 QB61 QB65 QB66 QB69 QC07 QC20 QC25 QC49 RF03 RF12 RF17 RF22 TT31 VV10

Claims (7)

[Claims] 1. A structure in which a metal film is stacked over part of a surface of an oxide semiconductor, wherein a metal film containing an ion-exchange material is used as the metal film. Corrosion prevention law. 2. A structure in which a metal film is stacked on a part of the surface of an oxide semiconductor, in which a water-repellent film is stacked on a surface of the oxide semiconductor on which no metal film exists.
Corrosion prevention method as described. 3. The method according to claim 2, wherein the water-repellent film is SiOF. 4. The method according to claim 1, wherein the ion exchange material is an inorganic ion exchange material. 5. The method according to claim 4, wherein the inorganic ion exchangeable material is at least one selected from the group consisting of antimony hydroxide, zirconium phosphate, hydrotalcite and hydroxyapatite. 6. A heater for fogging and frost, wherein a metal film containing an ion-exchange material is laminated on part of the surface of an oxide semiconductor. 7. The heater for fogging and defrost according to claim 6, wherein the oxide semiconductor is formed by laminating a SiOF film on the surface of the oxide semiconductor having no metal film on the upper surface.