JPH0948641A - Microwave oven, glass for window of the microwave oven and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an electric oven provided with a window glass having an improved visibility by using a glass which is coated with both an electrocoraductive membrane transparent at least in a visible light range and a stainproofing membrane. SOLUTION: This microwave oven is provided with a window glass whose glass base board 1 is coated with both an electroconductive membrane 3 transparent at least in a visible light range and a stainproofing membrane 5. The formation of an alkali barrier membrane 2 consisting of silica or alumina silica between the glass base board 1 and the electroconductive membrane 3 is preferable since this enables the improvement of the adhesion of the electroconductive membrane 3 with the glass base board 1. The production of the window glass is performed as follows: an electroconductive membrane transparent in a visible light range is formed on at least one side of a glass base board 1 for the window glass, which has been washed cleanly, subsequently the whole body is cooled by wind to strength the formed membrane, and a stainproofing membrane containing a fluoride carbon group is formed on the electroconductive membrane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven with improved visibility of cooked foods. For more information,
The present invention relates to a microwave oven provided with a transparent window glass having an electromagnetic wave shielding function and an antifouling function, a window glass plate used therefor, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, a microwave oven has a window for confirming the heating state of food being cooked. However, in order to prevent the microwave of 2.45GHz generated by the magnetron from leaking out of the machine, punching metal is fitted in the window of the microwave oven. The hole diameter of this punching metal is about several millimeters, and the metal portion other than the hole does not transmit light at all.

[0003]

The microwave oven having the above-mentioned conventional structure is capable of confirming the cooking state of food during cooking, but has poor visibility as compared with an oven or the like.

Further, in the conventional microwave oven, the inside of the chamber is self-cleaning (SC) enamel or is coated with a fluororesin, so that the antifouling function is considerably added. No measures have been taken. Therefore, if oil or the like adheres to the surface of the glass plate, it becomes extremely difficult to remove it. In other words, as it is used, dirt gradually accumulates and the visibility deteriorates. Especially in the case of the microwave oven, this drawback is serious.

The present invention is intended to solve the problems of the conventional structure as described above, and it is a first object of the present invention to provide a microwave oven having a window glass with improved visibility. A second object is to provide a microwave oven having a function of preventing microwave leakage. Further, it is a third object to provide a window glass plate capable of achieving the first object or the second object. A fourth object is to provide a method for manufacturing a glass plate for a window, which can achieve the third object.

[0006]

The first means of the present invention for achieving the first object is to provide a glass window provided with both a transparent conductive film and an antifouling film which are transparent at least in the visible light range. A microwave oven is provided.

A second means of the present invention for achieving the second object has a glass window in which double transparent conductive films are installed at least in the visible light region, and faces at least the food heating side. The microwave oven has a conductive film electrically connected to a housing.

A third means of the present invention for achieving the third object is a glass plate for a window of a microwave oven in which transparent conductive films in the visible light region are formed on both front and back surfaces of a glass substrate. Is.

The fourth means of the present invention for attaining the fourth object is to form a transparent conductive film in the visible light region on at least one surface of the washed glass substrate, and thereafter strengthen the whole by air cooling. A method for manufacturing a glass plate for a window of a microwave oven.

[0010]

The first means of the present invention is to use the punching metal which has been used conventionally by using the glass window provided with both the transparent conductive film and the antifouling film in the visible light region. The microwave oven has improved visibility.

The second means of the present invention is a microwave oven in which the food heating side of the double-layered conductive film is electrically connected to the housing, and particularly microwave leakage can be reduced.

A third means of the present invention is a glass plate for windows which is excellent in visibility when used in a microwave oven as a glass plate having transparent conductive films formed on both front and back surfaces of a glass substrate in the visible light region. It acts as.

The fourth means of the present invention is to form a transparent conductive film in the visible light region on at least one surface of a washed glass substrate, and then cool the whole by air to burn the transparent conductive film. The method is to manufacture a glass plate for a window of a microwave oven capable of simultaneously strengthening and glass.

[0014]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described below with reference to FIG. The present embodiment relates to a glass plate for a window of a microwave oven having antifouling property and conductivity.

On both sides of a glass substrate 1 having a size of 200 × 300 cm ² and a thickness of 3.2 mm that has been degreased and washed in advance, 0.5 μm of an alkali barrier film 2 made of alumina silica is formed on both surfaces by a sol-gel method.
It is formed with the thickness of. The firing temperature at this time is 250 ° C-4
It is set to 00 ℃. Further, a conductive inorganic thin film made of tin oxide doped with fluorine is formed thereon as the conductive film 3 by chemical reaction vapor deposition (hereinafter simply referred to as CVD method) with a thickness of 0.5 μm on both sides. This conductive film 3 is
It is transparent at least in the visible light range. Further, the glass plate 4 which has been subjected to the above treatment at about 650 ° C.
Is heated and reinforced by air cooling.

At this time, a silica film using silica may be used in place of the alkali barrier film 2, but it has a drawback that pinholes are larger than those using alumina silica. Although the thickness of the alkali barrier film 2 is 0.5 μm, the thickness can be arbitrarily selected according to the desired durability. Note that there is no problem even if a sol-gel method or a vapor deposition method is used instead of the CVD method. It is also possible to use as the conductive film 3 a conductive inorganic thin film made of tin oxide to which antimony or indium is added as a dopant.

The glass plate 4 thus formed has an area resistance of 9.5 Ω / cm ² and a transmittance of 74% for visible light having a wavelength of 500 nm. The visible light transmittance is 83 to 7 when the thickness of the conductive film 3 is changed in the range of 0.3 to 0.9 μm.
It changes in the range of 1%. Also this glass plate 4
Has a heat resistance of 350 ° C or higher (heat shock resistance of 230 ° C or higher)
The impact resistance is such that even if a 600 g steel ball is dropped from a height of 1.0 m or more, no abnormality is shown. The warp is 0.5m
m or less.

Further, the sheet resistance at this time is 10 to 5 Ω / cm ² depending on the thickness of the conductive film 3 of 0.3 to 0.9 μm.
It was possible to arbitrarily adjust while maintaining the visible light transmittance to some extent. However, an attempt to completely reflected microwaves only on one side, is required sheet resistance of 0.1~1Ω / cm ^2, the visible light transmittance when making those 1 [Omega / cm ² becomes 30% or less Therefore, it is not practical.

Instead of forming a conductive inorganic thin film of tin oxide on the surface of the glass substrate 1 by the CVD method, a metal such as gold, silver, platinum or nickel is thinly vacuum-deposited to form a metal thin film. The material can also be the conductive film 3 that is transparent in the visible light range. This metal thin film has an advantage that it can be easily manufactured by vapor deposition. However, as compared with the conductive film 3 made of tin oxide by using the same area resistance CVD method, the light transmittance is low and the visibility is slightly deteriorated. For example, vacuum deposition of nickel 8
And those with a metal thin film of the Omega / cm ^2, when comparing the tin oxide film of 8ohms / cm ^2, the nickel thin film has a large surface reflection than slightly brown in which tin oxide film charged with a light transmittance of visible low Sex is a little worse.

Next, an antifouling film 5 is formed on the conductive film 3. As the antifouling film 5 having a small surface energy, there are a method of dissolving and coating a fluorocarbon resin containing a fluorocarbon group in an organic solvent and a method of chemically adsorbing a fluorochemical surfactant. Attempts to form a film by the chemical adsorption method, which has excellent adhesion and transparency.

First, the glass plate 4 on which the conductive film 3 is formed is mixed with a substance containing a fluorocarbon group and a chlorosilane group, for example, a non-aqueous solvent such as CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ SiCl ₃ 80% n-hexadecane (toluene, xylene, dicyclohexyl may be used), 12% carbon tetrachloride, 8% chloroform solution dissolved at a concentration of about 10% is prepared by using, and the glass plate 4 is immersed for about 2 hours. To do. At this time,
Since the surface of the glass plate 4 contains many hydroxyl groups,
SiCl of a substance containing a fluorocarbon group and a chlorosilane group
The group reacts with the hydroxyl group, and the dehydrochlorination reaction shown in Chemical formula 1 occurs on the entire surface of the glass plate 4.

[0022]

Embedded image

By this dehydrochlorination reaction, a monomolecular film 5 containing fluorine can be formed on the surface of the glass plate 4 with a film thickness of about 1.5 nm, as shown in FIG. Since this monomolecular film 5 contains fluorine, it has antifouling properties,
It is strongly chemically bonded to the surface of the glass plate 5. If the adsorption time is shortened and air is contacted during the reaction, a chemically adsorbed polymer film is formed. At this time, monomolecular films also polymeric - The film in the point which joins the glass plate surface via a covalent bond is the same, the water and oil repellency is a monomolecular film -CF ₃ group are arranged on the surface Is more expensive.

In order to confirm the peeling resistance of the monomolecular film 5 thus prepared, a cross-cut tape peeling test was conducted. As a result of this test, since the monomolecular film 5 of this example was chemically bonded very strongly, it was not peeled at all. The visible light transmittance of the glass plate 4 on which the conductive film 3 and the monomolecular film 5 were formed was 74% with respect to light having a wavelength of 500 nm. This indicates that the monomolecular film 5 does not absorb light of this wavelength at all.

In this embodiment, fluorocarbon-based surface active agent is used.
CF as an agent_Three(CF₂)₇(CH₂)₂SiCl_ThreeI am using
In addition to the above as a carbonized carbon surfactant, CF_ThreeCH₂O (CH₂)
_FifteenSiCl_Three, CF_Three(CH₂)₂Si (CH_Three)₂(CH₂)_FifteenSiCl_Three, F (CF₂)_Four(CH
₂)₂Si (CH_Three)₂(CH2)₉SiCl_Three, CF _ThreeCOO (CH₂)_FifteenSiCl_Three, CF_Three(CF
₂)_Five(CH₂)₂SiCl_Three, CF_Three(CF₂) 5 (CH₂)₂SiCl_Three, CF_Three(CF₂)₇(CH
₂)₂Si (OCH_Three)_Three, CF_Three(CF₂) 5 (CH₂)₂Si (OC₂H_Five)_ThreeEtc. are available
It can be. Here, instead of the chlorosilyl group,
Use a surfactant that incorporates toxy or ethoxy groups
In some cases, use an acid catalyst or heat treatment during film formation
There is a need.

When expecting a microwave shielding effect, a conductive film 3 having a sheet resistance of 5 to 10 Ω / cm ² is used.
The conductive film provided on the food heating side of the stack is electrically connected to the housing of the microwave oven. At this time, the double conductive film 3 may be formed on both front and back surfaces of one glass substrate 1 as shown in FIG. 1A, or conductive on only one surface of the glass substrate 1. Membrane 3
It is also possible to use two glass plates 4 formed with. However, in order to establish electrical continuity, it is more convenient to use one glass substrate 1 having the conductive films 3 formed on both sides thereof. With the above configuration, most of the microwave generated from the magnetron during cooking can be reflected inward. In addition, the partially absorbed microwave heats the glass plate 4 itself, so that it also has an antifogging effect.

That is, it has a glass window in which a conductive film 3 transparent at least in the visible light region is doubly installed, and at least the conductive film 3 facing the food heating side is electrically connected to the housing. In addition to the wave shielding effect, an anti-fog effect can be added to realize a microwave oven with improved visibility.

When the microwave shielding effect is not expected, the sheet resistance of at least one surface of the conductive film 3 is calculated by the formula 1
It is set to 0 kΩ to several MΩ / cm ² . By doing so, most of the microwaves are transmitted, and only the partially absorbed microwaves can exert the anti-fogging effect.

A glass plate for a window of a microwave oven, in which transparent conductive films in the visible light range are formed on both front and back surfaces of one glass substrate, has an effect of shielding electromagnetic waves almost completely by one plate.

Further, in a glass plate for a window of a microwave oven, in which an alkali barrier film made of silica or alumina silica is formed between the glass base material and the conductive film, the glass base material at the time of temperature rise is changed to the conductive film. The alkali diffusion of is prevented,
It has the effect of preventing the deterioration of the conductivity of the conductive film, and is particularly effective as a window glass plate for an oven microwave oven in which the temperature of the glass window rises.

Further, in the glass plate for a window of a microwave oven in which the antifouling film is formed on the conductive film, there is an effect that it is possible to easily wipe off the cooked food that has adhered and to prevent seizure of the adhered food. It is particularly effective as a window glass plate for an oven microwave oven in which the window temperature rises.

On the other hand, if a method for producing a glass plate for a window of a microwave oven is used, in which a transparent conductive film in the visible light region is formed on at least one surface of the washed glass substrate, and then the whole is air-cooled, a transparent glass film is used. There is an effect that firing of the conductive film and strengthening by air cooling can be performed at the same time.

Further, when the method for manufacturing a glass plate for a window of a microwave oven in which an alkali barrier film made of silica or alumina silica is formed before forming the conductive film, the adhesion of the conductive film to the glass substrate can be improved. effective.

Furthermore, after the air-cooling strengthening step, when a method for manufacturing a glass plate for a window of a microwave oven in which an antifouling film containing a fluorocarbon group is formed on a conductive film, there is almost no organic stain, so that cleaning is performed. Has the effect of being extremely easy. .

Furthermore, in the method for manufacturing a glass plate for a window of a microwave oven, which uses a chemisorption film containing a fluorocarbon group adsorbed by a chemisorption method as an antifouling film,
There is an effect that a film having a very small surface energy that is firmly bonded to the surface of the substrate can be formed.

(Embodiment 2) Next, a second embodiment of the present invention will be described. The present embodiment relates to a microwave oven (hereinafter simply referred to as a microwave oven) in which the glass plate 4 produced in the above-mentioned Embodiment 1 is used as a glass window.

The glass plate 4 is replaced by a window glass of an oven microwave oven.
The outer circumference of the conductive film 3 so that it is completely grounded.
Report on experimental results to confirm microwave leakage amount
I do. The experimental condition at this time was to put it in the microwave oven.
Set a beaker filled with 275 ml of water and set to 600 W
It is supposed to radiate microwave. At this time,
The electric field strength due to microwave leakage on the surface of the lath window is 0.
01mW / cm²It was below. For reference, this microwave
The legal value of the electric field strength due to leakage is 5 mW / cm²Becomes
It is what Also, turn on the switch and one minute later
When the temperature of the glass surface was measured, it was 41 ° C.
Partly absorbed microwave heats the glass window itself
Of. As a result, the generated vapor will stick to the glass window.
Even though it does not condense, it also has an antifogging effect. What
If you heat without heating the cooker,
The microwave leakage in the empty state is 0.05 mW / cm
²It also has a shielding ability that can withstand practical use.
Of.

When a glass plate 4 having a conductive film 3 formed on only one side under the same conditions as in Example 1 was used as the window glass, the electric field strength due to microwave leakage on the surface of the window glass was 3.8 mW. / Cm ² , which was close to the legal specifications.

Further, the reflection ability of the window glass in the infrared region was about 50% at the wavelength of 2 μm.
Therefore, the energy loss can be significantly improved by using the window glass provided with the conductive film 3 facing the food heating side.

Even if the glass plate 4 shown in FIG. 1 is not provided with the antifouling film 5, it has a microwave shielding effect, and the conductive film 3 is electrically insulated from the casing of the microwave oven. Installed, the window glass itself will generate heat by absorbing some microwaves during cooking as explained in the above example, and it will have an anti-fog effect and visibility will be improved. To do.

As a window glass, as shown in FIG. 1, a glass plate having an alkali barrier film 2 on which a conductive film 3 which is transparent in the visible light region is formed, and on which an antifouling film 5 is formed. When 4 is used, the alkali barrier ability is further improved, which is convenient for improving the durability of the antifouling film 5. When an antifouling test is performed on the glass surface of the microwave oven incorporating the glass plate 4 on the food heating side, it is possible to greatly reduce the amount of seizure of the filth compared to the untreated one. The attached dirt can be easily removed by wiping with a cloth. This window glass is 300g /
A rubbing test was conducted 50,000 times with a wet cloth under a pressure of cm ² , but no scratches were found and the water repellent effect was not deteriorated at all. In addition, even dirt due to oil and fat can be easily removed by wiping, and the gloss and transparency are restored. The wettability with water is 120 degrees in contact angle, and the wettability with normal hexane is 85 degrees in contact angle.

As described above, according to this embodiment, the glass plate having a transparent conductive film in the visible light region formed on the surface thereof is used in place of the punching metal used for preventing the leakage of microwaves which has been conventionally used. By using, it is possible to realize a microwave oven having a window having a microwave leakage prevention function and good visibility. Further, by covering the surface of the conductive film with an antifouling film containing a fluorocarbon group, a microwave oven with improved visibility of the viewing window is provided.

At this time, a glass window in which a transparent conductive film is doubly installed at least in the visible light range is manufactured, and at least the conductive film installed facing the food heating side is connected to the casing of the range and the electric power. When it is connected, most of the electromagnetic waves during cooking are reflected to the inside, and the glass plate itself also heats up by absorbing a part of it, so it is possible to add an anti-fog effect in addition to a radio wave shielding effect, and improve visibility. It is more desirable for improvement. In addition,
When expecting the radio wave shielding effect, it is necessary to set the sheet resistance of the transparent conductive film to 5 to 10 Ω / cm ² , but when not expecting it, set the sheet resistance to several tens of kilos to several MΩ / cm ² . If so, most of the electromagnetic waves are transmitted, and only a part of the electromagnetic waves is absorbed and heat is generated, so that only the antifogging effect can be exhibited.

Further, visibility is improved by forming a transparent conductive film having a sheet resistance of 5 to 10 Ω / cm ² at least in the visible light region and further using a glass plate on which an antifouling film is formed. More convenient above.

Further, if transparent conductive films in the visible light range are formed on both the front and back surfaces of the glass, distortion that occurs when the glass is tempered by air can be reduced, and the radio wave shielding effect is also better than that of only one surface. It is convenient because it can be improved several hundred times.

Furthermore, if a transparent conductive film in the visible light region is made of a conductive inorganic thin film or a metal thin film containing tin oxide as a main component, a heat ray reflecting function can be imparted. Furthermore, if a conductive film that reflects light in the infrared region formed on the glass surface and that is transparent in the visible region is installed facing the food heating side, the heat that escapes to the outside can be reduced and the heating It is preferable for improving efficiency.

At this time, even if a transparent film having a transparent conductive inorganic thin film or a metal thin film which is transparent in the visible light region is attached to the outer surface of the glass window to shield electromagnetic waves, the same function can be achieved.

Further, it is preferable to include a fluorocarbon group in the antifouling coating because the surface energy can be reduced.
Further, when the antifouling film is a chemisorption monomolecular film containing a fluorocarbon group, it is possible to further improve the adhesiveness to the base material, which is advantageous in improving the durability and translucency of the antifouling film. .

On the other hand, it is convenient to improve the durability of the transparent conductive film or the antifouling film by forming an alkali barrier film made of silica or alumina silica between the glass substrate and the conductive film. . Further, when a chemisorption monomolecular film is formed, the durability can be further improved if it is formed on the conductive film.

Also, after forming a transparent conductive film in the visible light range on at least one surface of the washed glass substrate, the entire glass substrate is tempered by air cooling, so that the transparent conductive film can be fired and glass strengthened together. Is high.

Furthermore, if the antifouling film containing a fluorocarbon group is immediately formed on the conductive film after the step of strengthening by air cooling, it is convenient for applying the antifouling film because there is no contamination of organic substances. .

When a chemisorption monomolecular film containing a fluorocarbon group is formed by using a chemical adsorption method as the antifouling film, an extremely transparent antifouling film having excellent durability can be formed.

A glass window provided with both a transparent conductive film and an antifouling film at least in the visible light range is provided,
The microwave oven from which the punching metal used in the past is removed has the effect of improving the visibility of the food being cooked.

Further, in a microwave oven having a glass window in which a conductive film transparent at least in the visible light region is doubly installed, and at least the conductive film facing the food heating side is electrically connected to the housing, There is an effect that the microwave leaking from the gap between the glass and the housing can be stably minimized.

Furthermore, in a microwave oven using window glass having transparent conductive films formed on both front and back surfaces in the visible light range, there is an effect that the door can be lightened while ensuring the visibility.

Furthermore, in a microwave oven in which a punching metal is removed by using a window glass having a transparent conductive film formed in the visible light region, which is made of a conductive inorganic thin film or a metal thin film containing tin oxide as a main component, cooking is performed in a microwave oven. It is effective in improving the visibility without impairing the color tone of the food inside.

Further, in a microwave oven in which a transparent conductive film formed on the glass surface in the visible light region reflects light in the infrared light region and faces the food heating side as a window glass, The effect is that the heat radiation from the can be made smaller and the heating efficiency can be improved.

Further, in a microwave oven having a structure in which a transparent film having a transparent conductive inorganic thin film or a metal thin film formed in advance in the visible light region is attached to the outside of the glass window, it is possible to prevent the glass from popping out when the glass is broken and to ensure safety. There is an effect that can improve the sex.

Furthermore, in the microwave oven in which an antifouling coating containing a fluorocarbon group is formed on the innermost outer surface of the glass window,
This has the effect of reducing the adhesion of food stains and making cleaning easier.

At this time, if the antifouling film is a chemically adsorbed monomolecular film containing a fluorocarbon group, it will never come off because it is chemically bonded to the glass surface. Therefore, there is an effect that a microwave oven having a high antifouling effect and a high durability can be provided.

[0061]

The first means of the present invention is to provide a window glass with improved visibility as a constitution having a glass window provided with both a transparent conductive film and an antifouling film at least in the visible light range. A microwave oven equipped with this is realized.

The second means of the present invention has a glass window in which a transparent conductive film is at least doubled in at least the visible light region, and at least the conductive film facing the food heating side is electrically connected to the housing. The microwave oven having the function of preventing the leakage of microwaves is realized as the structure connected to the microwave oven.

A third means of the present invention is a glass plate for windows which is excellent in visibility when used in a microwave oven, as a structure in which transparent conductive films in the visible light region are formed on both front and back surfaces of a glass substrate. It will be realized.

The fourth means of the present invention is to form a transparent conductive film in the visible light region on at least one surface of a washed glass substrate, and then strengthen the whole by air cooling.
It is intended to realize a method for manufacturing a glass plate for a window of a microwave oven capable of simultaneously firing a transparent conductive film and strengthening glass.

[Brief description of drawings]

FIG. 1A is a cross-sectional view showing a glass plate which is an embodiment of the present invention. FIG. 1B is a schematic cross-sectional view showing an antifouling film.

[Explanation of symbols]

 1 glass substrate 2 alkali barrier film 3 conductive film 4 glass plate 5 antifouling film

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshimitsu Kurozawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Tsuneo Shibata, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (15)

[Claims] 1. A microwave oven provided with a glass window provided with both a transparent conductive film and an antifouling film which are transparent at least in a visible light region. 2. A microwave oven having a glass window in which a transparent conductive film is at least doubled in at least a visible light region, and at least the conductive film facing the food heating side is electrically connected to a housing. 3. The microwave oven according to claim 1, wherein a transparent conductive film in the visible light region is formed on both front and back surfaces of the window glass. 4. The microwave oven according to claim 1, wherein the conductive film transparent in the visible light region is a conductive inorganic thin film or a metal thin film containing tin oxide as a main component. 5. The conductive film, which is formed on the glass surface and is transparent in the visible light range, reflects the light in the infrared light range and is installed facing the food heating side. microwave. 6. A transparent film on which a conductive inorganic thin film or a metal thin film which is transparent in the visible light region is formed in advance,
The microwave oven according to claim 1, which is attached to the outside of the glass window. 7. The antifouling film contains a fluorocarbon group.
Microwave oven described in. 8. The microwave oven according to claim 7, wherein the antifouling film is a chemisorption monomolecular film containing a fluorocarbon group. 9. A glass plate for a window of a microwave oven, wherein transparent conductive films in the visible light range are formed on both front and back surfaces of a glass substrate. 10. The glass plate for a window of a microwave oven according to claim 9, wherein an alkali barrier film made of silica or alumina silica is formed between the glass substrate and the conductive film. 11. The glass plate for a window of a microwave oven according to claim 9, wherein an antifouling film is formed on the conductive film. 12. A method for producing a glass plate for a window of a microwave oven, which comprises forming a transparent conductive film in a visible light region on at least one surface of a washed glass substrate, and thereafter strengthening the whole by air cooling. 13. The method for producing a glass plate for a window of a microwave oven according to claim 12, wherein an alkali barrier film made of silica or alumina silica is formed before forming the conductive film. 14. The antifouling film containing a fluorocarbon group is formed on the conductive film after the air cooling strengthening step.
3. The method for producing a glass plate for a window of a microwave oven described in 3. 15. The method for producing a glass plate for a window of a microwave oven according to claim 14, wherein a chemisorption film containing a fluorocarbon group adsorbed by a chemisorption method is used as the antifouling film.