JPH11278875A - Surface treatment of glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new and useful method of surface treatment to decrease the alkali concn. of a glass surface which satisfies the requirements of quality and cost. SOLUTION: A glass having the glass surface temp. higher than the glass transition temp. of the glass itself is brought into contact with >=0.001 N acidic aq. soln. or its vapor to elute and remove the alkali component in the glass surface layer. Thus, the obtd. glass product has the glass surface layer having a lower alkali concn. than in the center layer part and has a dense surface structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a novel glass surface treatment method.

[0002]

2. Description of the Related Art Glass surface treatment methods widely used at present are roughly classified into a so-called wet coating method in which a solution containing or dispersing a required film-forming component is coated on the glass surface by a method such as spraying or dipping. A so-called dry coating method in which the film forming components are accelerated by vapor deposition or voltage under an atmosphere to coat the glass surface, a so-called dry coating method, where the accelerated particles such as high-energy ions are applied to the glass surface to scrape the glass surface, There is a method of driving.

Further, there is a method of dissolving and removing the glass surface with hydrofluoric acid or the like, or a method of reacting and removing an alkali component of the glass surface layer using SO ₃ or the like. In addition, there is known a method in which an alkali component of a glass surface layer is reactively extracted with water, steam, or the like under pressure at a temperature of about 200 ° C. using a pressure reaction vessel or the like. Among the glass surface treatment methods, a method employed for removing an alkali component of a glass surface layer or reducing its concentration is a method of reacting and removing an alkali component on a glass surface using SO ₃ or the like, This is a method in which an alkali component of a glass surface layer is reactively extracted with water, steam, or the like using a pressure reaction vessel or the like.

[0004]

Among the methods employed to remove or reduce the concentration of the alkali component in the glass surface layer, the alkali component on the glass surface is reacted and removed using SO ₃ or the like. The method can only slightly reduce the concentration of the alkali component to a depth of several tens to several hundreds of nanometers very close to the surface. In addition, in the method in which the alkali component on the glass surface is reactively extracted with water, steam, or the like using a pressure reaction vessel or the like, the amount of the alkali component to be removed is small, and the glass surface becomes rough due to the removal of the alkali component. It becomes a complicated structure, remains as an optical and physical defect, requires reprocessing, and is a dangerous operation at high pressure using a pressure reaction vessel. Furthermore, although these conventional methods can remove and reduce the concentration of an alkali metal, it is generally difficult to remove and reduce the concentration of an alkaline earth metal.

[0005] As described above, in the conventionally known method, cost and cost are reduced.
The technology for reducing the alkali concentration on the glass surface, which is satisfactory in both aspects of glass quality, has not yet been achieved. An object of the present invention is to realize a technique for reducing alkali concentration on a glass surface which is satisfactory in both cost and quality.

[0006]

SUMMARY OF THE INVENTION The present invention is a method for treating the surface of a glass, wherein the temperature of the glass surface is at least equal to or higher than the glass transition point of the glass.
By contacting with an acidic aqueous solution or a vapor generated from the aqueous solution, the alkali component of the glass surface layer is eluted and removed, so that the alkali concentration of the glass surface layer is lower than that of the central layer portion, and a dense surface structure is obtained. A glass surface treatment method characterized by obtaining a glass product having the same.

According to the present invention, when acidic molecules come into contact with glass heated at a high temperature together with water molecules, a reaction or some kind of interaction between water and an alkali component of the glass surface layer progresses, and alkalis are removed from the glass surface. As the components are desorbed, the alkali components dissolved in the high-temperature glass move to the vicinity of the glass surface to compensate for the concentration gradient, and the removal of the alkali components further progresses. It is estimated that the concentration of the component is reduced.

Therefore, the extent to which the concentration of the alkali component is reduced to the inside depends on the reaction between the acidic molecule and the alkali component in the glass, the mobility of the alkali component, the temperature of the glass,
In any case, it is important that the alkali component in the glass be in a sufficiently active state and have a sufficient mobility and a sufficient interaction with acidic molecules and water molecules, although it depends on the treatment time and the like. That is, it is important that the glass be at a sufficiently high temperature level and a sufficiently high flow level.

When the glass is under such high temperature and high fluidity, the chemically bonded or physically missing state of the removed alkali component is immediately complemented by the chemical bonding or movement of other surrounding components. On the other hand, glass will give a dense, high quality surface state without leaving any substantial defects.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The vapor generated from an aqueous solution as referred to in the present invention is a gas generated from an aqueous solution when the aqueous solution is heated, and in most cases, water vapor is a main component. The glass surface layer referred to in the present invention has a depth of 100 from the glass surface.
Refers to a portion smaller than μm.

The alkali component referred to in the present invention means both a so-called alkali metal component and an alkaline earth metal component, and specifically includes lithium, sodium, potassium, rubidium, cesium, fransium, beryllium, magnesium, and calcium. , Strontium, barium, radium and the like.

The central layer portion in the present invention is a portion having a depth of 100 μm or more from the glass surface. The porous body impregnated with the aqueous solution or the vapor generated from the aqueous solution in the present invention is a porous body containing the aqueous solution or the vapor generated from the aqueous solution therein. The hydrophilic substrate impregnated with the aqueous solution or the vapor generated from the aqueous solution in the present invention is a porous body containing the aqueous solution or the vapor generated from the aqueous solution therein. Hereinafter, “acidic aqueous solution or vapor generated from the aqueous solution” is referred to as “acidic aqueous solution or vapor thereof”.

In the present invention, a high-temperature glass in which at least the temperature of the glass surface is maintained at a temperature equal to or higher than the glass transition point is brought into contact with an acidic aqueous solution or its vapor for a certain period of time. At this time, in order to maintain the glass in a high active state,
It is preferable that the glass surface has a viscosity of 10 ² to 10 ⁵ poise, that is, is in a substantially flowable state.

As a method of contacting a high-temperature glass having at least a glass surface temperature equal to or higher than the glass transition point with an acidic aqueous solution or its vapor for a certain period of time, the acidic aqueous solution or its vapor is brought into contact with the glass at a constant temperature. A method of time-spraying or spraying, a method of contacting the glass with a substrate impregnated with an acidic aqueous solution or vapor thereof for a certain period of time, a method of contacting the glass with an acidic aqueous solution produced by a chemical reaction or its vapor for a certain period of time, etc. Any method may be used.

In the method of spraying or spraying the acidic aqueous solution or its vapor, the acidic aqueous solution or its vapor can be sprayed or sprayed on the high-temperature glass at normal pressure or under pressure. At this time, at least the temperature of the glass surface is a high temperature equal to or higher than the glass transition point of the glass, so that the glass exhibits fluidity. In particular, when the viscosity of the glass is 10 ² to 10 ⁵ poise, an acidic aqueous solution or its vapor There is a high possibility that unintended deformation occurs due to contact with the object or gravity. In such a case, it is preferable to carry out by combining some molding means.

From such a viewpoint, a method in which a substrate impregnated with an acidic aqueous solution or a vapor thereof is brought into contact with high-temperature glass is preferable because the glass can be maintained or formed in an intended shape. As the substrate, an acidic aqueous solution or a porous body or a hydrophilic substrate that can be impregnated with the vapor thereof is preferably used. It is more preferable to use hydrophilic porous carbon as the hydrophilic substrate.

In the present invention, it is necessary that the temperature of the glass surface is at least a high temperature equal to or higher than the glass transition point of the glass, and is maintained at such a high temperature under a contact with an acidic aqueous solution or vapor thereof. It is not easy to do so, and generally the temperature drops over time. Therefore, in the present invention, it is important to keep the glass in a temperature range necessary for the surface treatment for a predetermined range of time.

Although this time varies depending on the temperature of the glass, if this time is too short, the alkali component of the glass surface layer comes into contact with the acidic aqueous solution or its vapor to be eluted and removed, and further, the alkali component in the glass. It becomes difficult to diffuse and move. It takes about 3 seconds or more, usually 10 seconds or more, as the time required for the dissolution or the manifestation of the physicochemical phenomenon. Conversely, if this time is too long and the temperature of the glass surface falls below the glass transition point,
If the temperature of the acidic aqueous solution or its vapor is low, the glass may be cracked. Since the cooling rate of the glass cannot be unconditionally determined by the heat capacity of the glass, the ambient temperature, the air flow near the glass surface, and the like, it is desirable to set the processing time according to these requirements. Further, it is also a useful embodiment to reheat the glass cooled in one treatment and raise the surface temperature to at least a predetermined temperature and repeat the treatment.

It is also effective that after the surface treatment of the glass with an acidic aqueous solution or its vapor, the glass is subsequently subjected to a surface treatment with substantially neutral water or steam. In this case, the effect of washing and removing the reaction product of the alkali component and the acidic molecule removed from the glass by the acidic molecule from the glass surface can be obtained. Further, such a step may be repeatedly performed.

In the present invention, the temperature of the glass to be treated is essentially important, and it is necessary that at least the temperature of the glass surface is equal to or higher than the glass transition point, and the specific temperature depends on the glass composition. . In the case of ordinary soda-lime glass, the glass transition point is approximately 500 to 65.
Between 0 ° C. Therefore, in the case of such a soda lime glass, it is desirable to treat at a temperature higher than the above temperature, preferably 900 ° C. or higher. Considering cooling of the glass, the temperature at which the process is started is preferably 1100 ° C. or higher. Since such a suitable temperature level depends on the glass composition, it is desirable to select the temperature level according to the properties of the glass.

The kind of glass used in the present invention is not particularly limited as long as the glass contains an alkali component, and general soda lime glass, borosilicate glass, glass for CRT panel,
Various types of glass such as display glass, substrate glass used for transparent conductive glass, substrate glass used for glass magnetic disks, and crystal glass can be used.

The form and shape of the glass to which the present invention is applied are flat, curved, cylindrical, prismatic, tubular, square tubular, fibrous, panel-like, funnel-like, and any other shapes and shapes. It may be in the form of a glass plate, a glass fiber, a CRT panel, or the like.

[0023]

(Example 1) 1300 ° C. in a porous cylinder (diameter 30 mm, length 1000 mm, sprayed with the aqueous sulfuric acid solution from the outside) having a filter paper impregnated with 0.5 N aqueous sulfuric acid solution spread on the inner surface. The soda lime glass in the molten state is allowed to flow down. The composition of this glass is 71.5% of silica (weight%, the same applies hereinafter) and 1.8 of alumina in terms of oxide.
%, Magnesium oxide 4.2%, calcium oxide 8.9
%, Sodium oxide 13.0%, potassium oxide 0.5
%, Sulfuric anhydride 0.2%, and a glass transition point of about 560.
° C.

The time required for the glass to emerge from the lower end of the cylinder was 30 seconds. The temperature of the glass surface immediately after exiting the cylindrical outlet was 700 ° C. After the obtained glass was gradually cooled to room temperature in an annealing furnace for 24 hours, the result of composition analysis of the surface-treated glass surface by fluorescent X-rays was 73.0% of silica and 2.10% of alumina in terms of oxide. 0%, magnesium oxide 4.0%, calcium oxide 8.6%, sodium oxide 11.5%, potassium oxide 0.5%, and sulfuric anhydride 0.2%. That is, a decrease in sodium oxide is clearly observed.

(Example 2) 70% silica, 2% alumina, 4% magnesium oxide, 9% calcium oxide, 13% sodium oxide, 0.5% potassium oxide, 0.1% iron oxide,
A soda lime glass (glass transition point: about 560 ° C.) composed of 0.2% sulfuric anhydride is melted at 1500 ° C., and then a hydrophilic porous carbon disk (diameter 20 cm, 8 rpm) impregnated with a 2N aqueous sulfuric acid solution. 4)
After 0 seconds, the glass was taken out and transferred onto a hydrophilic porous carbon disk of the same specification as that described above impregnated with separately prepared ion-exchanged water, and taken out after 10 seconds.

The temperature of the glass surface immediately after being taken out is 60
It was 0 ° C. After slowly cooling in the same manner as in Example 1, the surface of the hydrophilic porous carbon in contact with the disk (treated surface) and the surface that had been opened in the air (open surface) were measured by surface analysis using ESCA ( Table 1 shows the relative atomic% (the total of silicon, calcium, and sodium is 100%). Table 1
In the column of ESCA processing time, the depth from the surface of the measurement portion corresponding to each ESCA processing time is shown in parentheses.

[0027]

[Table 1]

As is apparent from Table 1, the amount of each alkali component on the treated surface is effectively reduced with respect to each alkali component on the open surface. For example, in Table 1, when the treatment time is 5 minutes (corresponding to a depth of 20 to 25 nm from the surface), the relative molar concentration of calcium on the open surface is 14%, whereas that on the open surface is reduced to 0%. ing.

[0029]

According to the surface treatment of the present invention, the concentration of the alkali component in the vicinity of the glass surface is reduced to a certain depth, and the original dense surface structure of the glass is maintained.
(1) Reduction of burning phenomenon of glass products, (2) Reduction of inhibiting factors of functional coating such as imparting conductivity to the surface, (3) Reduction of elution of alkali components upon contact with various substances, (4) Reduction of the influence of alkali components on various substances when in contact with the substances, (5) Mechanical properties equal to or better than untreated glass, (6) Possibility of application to refractive index gradient materials And (7) surface treatment can be performed at a low cost because no special chemicals or the like are used, and (8) it can be carried out simultaneously with the molding of a sheet glass or the like, which can be more advantageous in terms of cost. (9) It is possible to flexibly deal with the type and shape of glass, (10) It is not necessary to use a special pressurizing device such as a high-pressure reaction vessel, and it is an inexpensive glass surface treatment method. There are also the effects and advantages of

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Isamu Kaneko 1150 Hazawacho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside Asahi Glass Co., Ltd.

Claims (5)

[Claims] 1. A method for treating the surface of a glass, wherein the glass having a temperature at least equal to or higher than the glass transition point of the glass is treated with an acidic aqueous solution of 0.01 N or more or vapor generated from the aqueous solution. A glass surface treatment characterized by obtaining a glass product having a dense surface structure in which the alkali concentration of the glass surface layer is lower than that of the central layer portion by contacting and eluting and removing an alkali component of the glass surface layer. Method. 2. The viscosity of the surface of glass to be subjected to a surface treatment is 1
^{2. The method} according to claim 1, wherein the glass is brought into contact with an acidic aqueous solution of 0.01 N or more or vapor generated from the aqueous solution in a flowable state at a pressure of 0 ² to 10 ⁵ poise.
The glass surface treatment method according to the above. 3. The method according to claim 1, wherein the aqueous solution having an acidity of 0.01 N or more used for the surface treatment or the vapor generated from the aqueous solution is supplied from the aqueous solution or the porous body impregnated with the vapor. 3. The method for surface treatment of glass according to 2. 4. The method according to claim 1, wherein the aqueous solution of 0.01 N or more used for surface treatment or the vapor generated from the aqueous solution is supplied from the aqueous solution or the hydrophilic substrate impregnated with the vapor. 3. The method for surface treatment of glass according to 1 or 2. 5. The method according to claim 1, further comprising the step of bringing the glass into contact with substantially neutral water or water vapor following the step of bringing the glass into contact with an acidic aqueous solution of 0.01 N or more or vapor generated from the aqueous solution. The method for surface treatment of glass according to claim 1, 2, 3, or 4.