JPH09208264A - Glass top for copying machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a glass top for a copying machine on which a transparent conductive film can be easily formed, by thermally decomposing an org. tin compd. containing no chlorine at a specified temp. to form a tin oxide film on the surface of a glass plate subjected to chemically reinforcement. SOLUTION: This glass top for a copying machine is produced by coating a glass plate with a tin oxide film, and the surface roughness Ra of the tin oxide film is controlled to <3nm. The glass plate is preliminarily chemically reinforced and then a tin oxide film is formed on the surface of the glass, preferably to have <=1MΩ/cm<2> surface resistance and >=88% transmittance. It is preferable to form two or more layers including a preventing film against elusion of alkali and a tin oxide film on the glass surface. An org. tin compd. containing no chlorine as the source material is thermally decomposed near the surface of the glass plate to form the tin oxide film. Concerning, the org. tin compd. containing no chlorine, dibutyl tin diacetate or tetrabutyl tin are preferably used. The temp. near the glass plate is preferably controlled to <=500 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a top plate glass for a copying machine used in a copying machine equipped with an automatic document feeder.

[0002]

2. Description of the Related Art In a copying machine equipped with an automatic document feeder,
If static electricity is generated on the top glass during document feeding, the static electricity causes a paper jam, and it becomes impossible to continuously feed the document. Therefore, the surface of the top plate glass
It is covered with a transparent conductive film such as an O film or a tin oxide film and has an antistatic effect to prevent the generation of static electricity. Furthermore, the surface resistance of the top plate glass is 1 MΩ / □ (1 MΩ
Ω / cm ² ) or less is expected. Also,
If the coefficient of friction of the surface of the top plate glass is large, paper jam easily occurs. Therefore, as described in, for example, JP-A-62-293236 and JP-A-63-73234, it is necessary to apply a lubricant to the glass surface of the top plate. Is being done.

However, even if the lubricant is applied, the lubricant peels off as the document passes over the surface of the top plate many times. Therefore, it is required that the friction coefficient is small even when the lubricant is not applied. Furthermore, it is known that the effect of the lubricant increases as the surface of the conductive film becomes smoother. Therefore, in particular, for a tin oxide film having a large surface roughness, the surface is polished to reduce the friction coefficient and to improve the effect of the lubricant.

In order to ensure safety, the glass plate itself is required to have significantly higher strength than ordinary glass plates. Therefore, in order to increase the strength of the glass plate, the glass plate is strengthened. As a strengthening method,
A method of obtaining compressive stress by cooling glass heated above the softening point from the surface, so-called wind-cooling strengthening method, dipping glass in molten salt containing potassium ions, exchanging with sodium ions in the glass, A method of obtaining a surface compressive stress based on the difference in depth, a so-called chemical strengthening method is used.

[0005]

In the prior art, a transparent ceramic film such as an ITO film or a tin oxide film is used as the transparent conductive film. However, in the case of an ITO film, a vacuum device such as a vapor deposition method or a sputtering method is required, which increases the cost. In the case of a tin oxide film, C
A film forming method by thermal decomposition such as a VD method or a spray method is known, and a tin oxide film is formed by spraying a raw material on a glass substrate coming out of the float bath or on a glass substrate coming out of the float bath particularly in terms of cost and productivity. A so-called online film forming method is used. However, in this method, since it is necessary to strengthen the glass after forming the tin oxide film, wind-cooling strengthening causes cracks in the film due to a rapid temperature change, and chemical strengthening increases the temperature. The film is peeled off because it is ion-exchanged by immersing it in the solution.

Therefore, it is conceivable to form a transparent conductive film on a glass substrate which has been previously subjected to air-cooling strengthening or chemical strengthening treatment, but when the processing temperature becomes high, the surface compressive stress layer disappears due to atomic diffusion. Had the problem. In the case of air cooling strengthening, the temperature is 250 ° C to 30 ° C.
This is because the surface compressive stress decreases at 0 ° C. or higher, and in the case of chemical strengthening, the surface compressive stress decreases at a temperature of 500 ° C. to 550 ° C. or higher.

Further, it is necessary to form a transparent conductive film at a temperature of 500 ° C. or lower on a glass substrate that has been chemically strengthened.
As this method, a vapor deposition method, a sputtering method, or the like can be easily considered, but as described above, a vacuum device is required, resulting in high cost and poor productivity.

Further, it is possible to form a tin oxide film on a glass substrate subjected to a chemical strengthening treatment at a temperature of 500 ° C. or lower by a film forming method by thermal decomposition such as a spray method or a CVD method.
However, in many cases, since a raw material containing chlorine such as tin tetrachloride or monobutyltin trichloride is used, there is a problem that the tin oxide film has large irregularities on the surface although the film formation is good. ing. This is because when a tin raw material containing chlorine is formed into a film by a thermal decomposition method, crystal orientation of the tin oxide film generally occurs, columnar orientation is obtained toward the surface, and sharp irregularities on the surface become large. is there. In general, (110), (200), and (211) crystal orientations are recognized in the thin film X-ray diffraction pattern. Therefore, after the tin oxide film is formed, the film surface is polished and smoothed. . Furthermore, by using a raw material containing chlorine, chlorine reacts with sodium, potassium, etc. in the glass to form a salt, which causes defects such as pinholes. Therefore, when using a raw material containing chlorine, an alkali prevention film such as silicon dioxide is required.

As a method of using a chlorine-free organotin compound as a raw material, for example, JP-A-2-307 is known.
No. 65, it relates to infrared-reflecting coated glass, and the glass substrate temperature during film formation is 500 ° C. or higher. Therefore, unlike the present invention, it is difficult to form a film while maintaining the chemical strengthening property.
Although a method of forming a transparent conductive film by a coating method is also conceivable, it has a problem that it is troublesome in terms of temperature but complicated because it requires a large number of steps of coating, drying and baking.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a top plate glass for a copying machine in which a transparent conductive film can be easily formed on the surface. Is what you are trying to do.

[0011]

In order to solve the above-mentioned problems, the present invention is to coat a glass plate with a tin oxide film and set the average surface roughness Ra of this tin oxide film to 3 nm or less. Further, the glass plate is chemically strengthened in advance and a tin oxide film is formed on the surface thereof, the surface resistance is 1 MΩ / □ or less, and the transmittance is 88%.
The above is recommended. In addition, two or more layers including an alkali elution preventive film and a tin oxide film may be formed on the surface of the glass plate.

The chlorine-free organotin compound as a raw material can be thermally decomposed near the surface of the glass plate to form the tin oxide film. The chlorine-free organotin compound may be dibutyltin diacetate or tetrabutyltin, and the organotin compound may be vapor or solution mist. Further, the alkali elution preventing film may be formed of a silicon dioxide film. Further, it is preferable that the tin oxide film contains fluorine or antimony.

The temperature in the vicinity of the glass plate is preferably 500 ° C. or lower. Further, the crystal orientation of the tin oxide does not have a strong peak in (110), (200) and (211) in the X-ray diffraction pattern. Furthermore, the tin oxide is amorphous.

[0014]

Embodiments of the present invention will be described below. The present invention is a top plate glass for a copying machine in which a tin oxide film is formed on the surface of a chemically strengthened glass substrate, and a chlorine-free organotin compound is used as a raw material.
A tin oxide film is formed by thermal decomposition at a temperature of ℃ or less, and the average surface roughness Ra of this tin oxide film is set to 3 nm or less.

As a method for forming the tin oxide film, either a CVD method or a spray method may be used, but the CVD method is preferable in view of the film forming property at a temperature of 500 ° C. or lower. The crystal orientation of a tin oxide film formed from an organic tin compound containing chlorine, which is often used in the CVD method, as a raw material is, for example, Japanese Patent Laid-Open No. 2-23.
X-ray diffraction pattern (11
Strong peaks are obtained at 0), (200), and (211). The surface shape of this tin oxide film is such that columnar crystals are oriented and the surface Ra is about 4 to 10 nm. Then
It can be found that the tin oxide film formed by using a non-chlorine type organic tin compound as a raw material has almost no peak indicating crystal orientation, and the surface Ra is small.

In order to maintain the chemical strengthening property of the glass substrate, the film forming temperature is 5 or more above the decomposition temperature of the organotin compound.
The temperature may be not higher than 00 ° C, but the film formation rate by pyrolysis decreases as the temperature decreases, so in order to improve productivity, 440 ° C to 500 ° C, and more preferably 470 ° C to 5 ° C.
00 ° C is good.

As the raw material, any organic tin compound containing no chlorine may be used, but in the case of forming a film by the CVD method,
It is preferably a liquid and has a high vapor pressure. Furthermore, for safety, an organotin compound having low toxicity is preferable. Therefore, C
When the film is formed by the VD method, it retains its chemical strengthening property.
In order to obtain a film quality that maintains a film forming rate that industrially satisfies productivity under a temperature condition of 0 ° C. or less and that ensures a high transmittance with a low friction coefficient, dibutyltin is used as a chlorine-free organotin compound. Diacetate or tetrabutyltin is preferred. Other chlorine-free organotin compounds include tetramethyltin, tetraethyltin, tributyltin acetate, tributyltin trimethylacetate and dioctyltin diacetate.

Further, since the raw material does not contain chlorine, defects such as pinholes will not occur even if the alkali prevention film is not formed on the glass substrate. It is preferable that an alkali prevention film such as silicon dioxide is formed on the substrate.

To obtain a tin oxide film having a low coefficient of friction,
Although it is not necessary to consider the film thickness of tin oxide, it is necessary that the transmittance of the top plate glass for a copying machine is high, so that the film thickness is 5 nm to 100 nm, more preferably 10 nm.
-30 nm is preferable. Furthermore, when a large amount of oxygen is present in the film forming atmosphere, the oxidation state of the tin oxide film advances, and the transmittance of the tin oxide film increases, so that when the vapor of the organotin compound is supplied onto the glass substrate. It is preferable to mix oxygen.

The conductivity of the tin oxide film is 1 MΩ.
It is sufficient if it is / square or less, but the lower one is preferable. Then, in order to adjust the conductivity of tin oxide, a compound containing fluorine or a compound containing antimony may be mixed in the organic tin compound vapor, and fluorine or antimony may be added to the tin oxide film. Further, although fluorine may be bonded to the organotin compound, it is preferable to mix a gas such as 1,1-difluoroethane with vapor of the organotin compound as a simpler method.

Furthermore, it is more preferable to provide an alkali prevention film of silicon dioxide or the like on the glass substrate, because the effect of preventing sodium and the like in the glass from diffusing into tin oxide and affecting the electrical characteristics can be obtained. Further, the organic tin compound may be supplied not only in the form of vapor but also in the state of solution mist. In this case, fluorine or antimony may be added to the tin oxide film by mixing a compound containing fluorine or a compound containing antimony in the solution.

Ra on the surface may be any value as long as it is 3 nm or less, but it is preferably 2 nm or less, more preferably 1 nm or less in order to reduce the friction coefficient of the surface and enhance the effect after application of the lubricant. When a lubricant is applied to the surface of the tin oxide film thus obtained, the coefficient of friction of the surface becomes very small, which improves the durability of the tin oxide film.

Table 1 below shows film forming conditions (type of tin raw material, tin raw material flow rate, tin raw material temperature, glass substrate temperature, oxygen flow rate, presence / absence of silicon dioxide film) of the top glass for a copying machine according to the present invention. And film forming results (resistivity, transmittance, Ra, friction coefficient after applying lubricant) are shown in Examples 1 to 12 and a comparative example according to the prior art.

[0024]

[Table 1]

In the first embodiment, the size is 100 mm × 10.
A chemically strengthened glass substrate with a 0 mm thick and 3 mm thick potassium nitrate molten salt is heated to 470 ° C., monosilane gas, nitrogen, and oxygen-controlled gas are supplied to the substrate surface, and a silicon dioxide layer with a thickness of 30 nm is mainly used. A film as a component is formed. Then, vapor of dibutyltin diacetate heated to 130 ° C. with nitrogen as a carrier, 3 l / mi
n, oxygen 5 l / min, and 1,1-difluoroethane gas 0.4 l / min are mixed and supplied to the substrate surface. Under such film forming conditions, a tin oxide film having a resistance value of 28 kΩ / □, a transmittance of 91% at a wavelength of 550 nm and an Ra of 0.2 nm can be obtained. Further, a side chain diamino-modified polysiloxane is used as a lubricant on the surface of the tin oxide film with a denatured alcohol.
Apply the solution diluted 50 times. Then, the dynamic friction coefficient of the surface after applying the lubricant becomes 0.02. When the crystal orientation of the tin oxide film obtained in Example 1 was measured by an X-ray diffractometer,
Almost no peak showing crystal orientation was obtained.

In Example 2, the film forming conditions were the same as in Example 1 except that the carrier flow rate of dibutyltin diacetate was set to 4 l / min. Under such film forming conditions, the resistance value is 19 kΩ / □, the transmittance at the wavelength of 550 nm is 90%, and the Ra is
A tin oxide film having a thickness of 0.2 nm is obtained, and the dynamic friction coefficient of the surface after applying the lubricant is 0.02.

In Example 3, the film forming conditions were the same as in Example 1 except that the temperature of dibutyltin diacetate was 150 ° C. and the oxygen flow rate was 10 l / min. Under such film forming conditions, a tin oxide film having a resistance value of 27 kΩ / □, a transmittance of 89% at a wavelength of 550 nm and an Ra of 0.5 nm was obtained, and the dynamic friction coefficient of the surface after applying the lubricant was 0.02. is there.

In Example 4, the film forming conditions were the same as in Example 3 except that the carrier flow rate of dibutyltin diacetate was set to 2 l / min. Under such film forming conditions, the resistance value is 26 kΩ / □, the transmittance at the wavelength of 550 nm is 90%, and Ra is
A tin oxide film having a thickness of 1.0 nm is obtained, and the dynamic friction coefficient of the surface after applying the lubricant is 0.05.

In Example 5, the film forming conditions were the same as in Example 3 except that the carrier flow rate of dibutyltin diacetate was set to 1 l / min. Under such film forming conditions, the resistance value is 90 kΩ / □, the transmittance at the wavelength of 550 nm is 90%, and the Ra is
A tin oxide film having a thickness of 0.8 nm is obtained, and the dynamic friction coefficient of the surface after applying the lubricant is 0.04.

In Example 6, the film forming conditions were the same as in Example 1 except that the substrate temperature was 500 ° C. Under such film forming conditions, a tin oxide film having a resistance value of 25 kΩ / □, a transmittance of 90% at a wavelength of 550 nm and an Ra of 0.2 nm is obtained.
The coefficient of dynamic friction of the surface after applying the lubricant is 0.01.

In Example 7, the film forming conditions were the same as in Example 6 except that the carrier flow rate of dibutyltin diacetate was set to 4 l / min. Under such film forming conditions, a tin oxide film having a resistance value of 9 kΩ / □, a transmittance of 90% at a wavelength of 550 nm and an Ra of 0.7 nm was obtained, and the dynamic friction coefficient of the surface after applying the lubricant was 0.04. is there.

In Example 8, the film forming conditions were the same as in Example 7, except that the substrate temperature was 440 ° C. Under such film forming conditions, a tin oxide film having a resistance value of 283 kΩ / □, a transmittance of 91% at a wavelength of 550 nm and an Ra of 0.3 nm was obtained, and the dynamic friction coefficient of the surface after applying the lubricant was 0.03. is there.

In Example 9, the substrate temperature was set to 470 ° C.,
The film forming conditions were the same as in Example 6 except that the silicon dioxide film was omitted. Under such film forming conditions, the resistance value is 920k.
Ω / □, transmittance at wavelength of 550 nm 89%, Ra = 0.
A 2 nm tin oxide film is obtained, and the dynamic friction coefficient of the surface after coating the lubricant is 0.02.

In Example 10, the film forming conditions were the same as in Example 9 except that the substrate temperature was 550 ° C. Under these film forming conditions, a tin oxide film having a resistance value of 20 kΩ / □, a transmittance of 88% at a wavelength of 550 nm and an Ra of 0.2 nm was obtained, and the dynamic friction coefficient of the surface after applying the lubricant was 0.01. is there.

In Example 11, the film forming conditions were the same as in Example 1, except that the tin raw material was tetrabutyl tin. Under such film forming conditions, a resistance value of 362 kΩ / □ and a wavelength of 550
A tin oxide film having a transmittance of 91% in nm and an Ra of 0.1 nm was obtained, and the dynamic friction coefficient of the surface after applying the lubricant was 0.005.
It is.

In Example 12, the film forming conditions were the same as in Example 11 except that the carrier flow rate of tetrabutyltin was set to 4 l / min. Under such film forming conditions, the resistance value is 27
A tin oxide film having a kΩ / □, a transmittance of 90% at a wavelength of 550 nm and an Ra of 0.1 nm was obtained, and the dynamic friction coefficient of the surface after applying the lubricant was 0.005.

Further, when the strength of the glass substrates obtained in Examples 1, 6 and 10 was evaluated, the glasses obtained in Examples 1 and 6 maintained the chemical strengthening property. The glass obtained in Example 10 had a reduced chemical strengthening property. This is because the substrate temperature is 500 ° C. or lower in Example 1 and Example 6, whereas it is 500 in Example 10.
This is because it is 550 ° C., which exceeds ° C. The glass strength was evaluated by a falling ball test using a hard ball of 535 g.

As a comparative example, except that the tin raw material was monobutyltin trichloride, the vapor of monobutyltin trichloride was 0.5 l / min, the oxygen was 1 l / min, and the 1,1-difluoroethane gas was 0.2 l / min. Is the film forming conditions similar to those in Example 1. Under such film forming conditions, the resistance value is 3 kΩ / □ and the transmittance is 89 at a wavelength of 550 nm.
%, A tin oxide film with Ra of 6 nm is obtained, and the dynamic friction coefficient of the surface after applying the lubricant is 0.45. In addition, strong peaks were obtained at (110), (200), and (211) by X-ray diffraction measurement.

[0039]

As described above, according to the present invention, a tin oxide film having a surface Ra of 3 nm or less can be formed on a chemically strengthened glass substrate at 500 ° C. or less and without polishing, which is easy. The top plate glass for copiers can be obtained. Furthermore,
By applying a lubricant to the surface of the tin oxide film having Ra of 3 nm or less, a top plate glass for a copying machine having a very small friction coefficient can be obtained.

Claims (11)

[Claims] 1. A top plate glass for a copying machine, characterized in that a glass plate is covered with a tin oxide film, and Ra of the surface of the tin oxide film is 3 nm or less. 2. The top plate glass for a copying machine according to claim 1, wherein the glass plate is chemically strengthened in advance, a tin oxide film is formed on the surface thereof, the surface resistance is 1 MΩ / □ or less, and the transmittance is 88% or more. . 3. The top glass for a copying machine according to claim 2, wherein two or more layers including an alkali elution preventive film and a tin oxide film are formed on the surface of the glass plate. 4. The top glass for a copying machine according to claim 1, 2 or 3, wherein a chlorine-free organotin compound as a raw material is thermally decomposed near the surface of the glass plate to form the tin oxide film. 5. The top glass for a copying machine according to claim 4, wherein the organotin compound containing no chlorine is dibutyltin diacetate or tetrabutyltin. 6. The top glass for a copying machine according to claim 5, wherein the organotin compound is vapor or solution mist. 7. The top glass for a copying machine according to claim 3, 4, 5 or 6, wherein the alkali elution preventive film is formed of a silicon dioxide film. 8. The top glass for a copying machine according to claim 4, 5, 6 or 7, wherein the tin oxide film contains fluorine or antimony. 9. The top plate glass for a copying machine according to claim 4, wherein the temperature in the vicinity of the glass plate is 500 ° C. or lower. 10. The crystal orientation of the tin oxide does not have a strong peak in (110), (200), (211) in an X-ray diffraction pattern. Top glass for copiers. 11. The top plate glass for a copying machine according to claim 4, 5, 6, 7, 8, 9 or 10, wherein the tin oxide is amorphous.