JP2007297228A - Method for manufacturing polished glass substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a polished glass substrate by which the surface of a glass substrate is polished while restraining the growth of a dimple, and consequently the glass substrate having flat and smooth surfaces can be obtained and to provide the polished glass substrate manufactured by the manufacturing method. <P>SOLUTION: The method for manufacturing the polished glass substrate comprises the steps of: immersing a cassette 21 where a glass substrate 20 is set in a surface polishing liquid tank 1 filled with a surface polishing liquid 6 containing 40-90 wt.% sulfuric acid and 0.4-4 wt.% hydrofluoric acid and polishing the surface of the immersed glass substrate; washing the surface-polished glass substrate with water in a first water washing tank 2; and immersing the water-washed glass substrate in a post-polishing liquid tank 3 filled with a post-polishing liquid containing 2-30 wt.% hydrofluoric acid and post-polishing the immersed glass substrate until the polished glass substrate has predetermined thickness. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a polished glass substrate in which a glass substrate is immersed in a chemical polishing solution containing hydrofluoric acid and polished to a predetermined glass substrate thickness, and in particular, a polished glass substrate suitable for producing a glass substrate for a liquid crystal display. It relates to a manufacturing method.

  In recent years, glass substrates for liquid crystal displays (hereinafter simply referred to as “glass substrates”) are made as thin as possible (hereinafter simply referred to as “glass thickness”) for the purpose of reducing the energy consumption of display products. It is hoped that. Therefore, conventionally, a method for producing a polished glass substrate in which one side or both sides of a glass substrate is chemically polished with a chemical polishing solution containing hydrofluoric acid to reduce the glass thickness has been performed.

  For example, Patent Document 1 (Japanese Patent Laid-Open No. 2003-20255) shows polishing with a chemical working solution containing hydrofluoric acid and one or more inorganic acids selected from hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid, As an example, an example is shown in which a chemical processing solution containing 5% hydrofluoric acid, 10% hydrochloric acid, and 5% nitric acid is used to polish to a predetermined glass substrate thickness. However, in such a conventional technique, polishing is performed until a predetermined glass substrate thickness is obtained in one step. Therefore, polishing to a desired glass thickness is possible, but the glass substrate surface (hereinafter simply referred to as “glass”). There was a problem with the smoothness of the “surface”. In particular, the micro cracks originally present on the glass surface grow into large depressions (hereinafter referred to as “dimples”) in the course of chemical polishing, and cause a product defect. It was difficult to suppress the occurrence of.

  As means for solving such problems, for example, Patent Document 2 (Japanese Patent Laid-Open No. 2005-343742) discloses a surface polishing liquid containing 10 to 30% by weight of hydrofluoric acid and 20 to 50% by weight of sulfuric acid. Using surface polishing as a pre-polishing that suppresses the growth of scratches with a diameter of 40 μm or more to a diameter of 100 μm or more by polishing at a polishing rate of 1 μm / sec or more for several seconds, and thereafter medium to low concentration hydrofluoric acid A method of post-polishing until a predetermined glass substrate thickness is obtained by immersing in a post-polishing liquid containing. However, according to this method, it is possible to suppress the spread of scratches in the surface polishing as the pre-polishing, but since the contact time with the polishing liquid is short, the entire glass substrate is controlled to be uniformly polished. However, there is a problem that a step of several μm is likely to occur in a smooth portion, which is enlarged in post-polishing.

  Further, in Patent Document 3 (Japanese Patent Laid-Open No. 2004-77640), a plurality of polishing liquids having different chemical polishing rates are used in chemical polishing of a glass substrate, and polishing is performed several times in order from a liquid with a high polishing speed to a liquid with a low polishing speed. Thus, a method for suppressing the generation of dimples has been proposed. However, according to this method, even if it is possible to suppress the generation of dimples, it is necessary to take a number of steps, which is disadvantageous in terms of productivity, equipment cost, etc. .

Patent Document 4 (Japanese Patent Application Laid-Open No. 2005-11894) discloses that when a glass substrate is chemically polished, the glass substrate is immersed in a liquid (inert liquid) that does not react with the polishing liquid, and is inert to the pores existing on the glass surface. A method of suppressing the growth of pores into dimples by chemical polishing after filling with a liquid has been proposed, and examples of inert liquids include perfluoroalkyl compounds. However, according to this method, even though it is possible to suppress the generation of dimples, there is a problem that wastewater treatment is necessary because wastewater containing an organic compound is generated.
JP 2003-20255 A JP 2005-343742 A JP 2004-77640 A JP 2005-11894 A

  An object of the present invention is to solve the problems of the prior art, suppress the dimple growth and polish the surface of the glass substrate to obtain a glass substrate having a smooth glass surface. It is providing the polishing glass substrate manufactured by this.

The present invention provides the following method for producing a polished glass substrate and a polished glass substrate.
(1) A method for producing a polished glass substrate in which a glass substrate is immersed in a polishing liquid containing hydrofluoric acid, and the surface is chemically polished,
A method for producing a polished glass substrate, comprising: dipping a glass substrate in a surface polishing solution containing 40 to 90% by weight sulfuric acid and 0.4 to 4% by weight hydrofluoric acid to perform surface polishing.
(2) A method for producing a polished glass substrate in which a glass substrate is immersed in a polishing liquid containing hydrofluoric acid, and the surface is chemically polished,
After surface polishing by immersing the glass substrate in a surface polishing liquid containing 40 to 90% by weight sulfuric acid and 0.4 to 4% by weight hydrofluoric acid,
A method for producing a polished glass substrate, comprising immersing the glass substrate in a post-polishing liquid containing 2 to 30% by weight of hydrofluoric acid and post-polishing until a predetermined glass substrate thickness is reached.
(3) The method according to (1) or (2) above, wherein the surface polishing liquid is a polishing liquid containing 50 to 85% by weight sulfuric acid and 0.5 to 4% by weight hydrofluoric acid.
(4) The method according to any one of (1) to (3) above, wherein the glass substrate is a glass substrate for liquid crystal display.
(5) A polished glass substrate produced by the method according to any one of (1) to (4) above.

  Examples of the polished glass substrate produced in the present invention include glass substrates for flat panel displays such as liquid crystal displays, organic electroluminescence displays, and plasma panel displays. In particular, glass substrates for liquid crystal displays are suitable. As a material of the glass substrate, all materials generally used for the above glass substrate such as an aluminoborosilicate glass substrate can be polished.

  In the method for producing a polished glass substrate of the present invention, a glass substrate having a smooth glass surface is formed by suppressing dimple growth by immersing the glass substrate in a surface polishing liquid and polishing the surface by chemical polishing. Examples of the surface polishing liquid that can be used for such surface polishing include a surface polishing liquid containing 40 to 90% by weight of sulfuric acid and 0.4 to 4% by weight of hydrofluoric acid, and particularly 50 to 85% by weight of sulfuric acid. A polishing liquid containing 0.5 to 4% by weight of hydrofluoric acid is preferred. The balance of the surface polishing liquid is mainly water, but may contain other solvents, surfactants, stabilizers and other additives. In the surface polishing liquid, when the concentration of sulfuric acid or the concentration of hydrofluoric acid is lower than the above lower limit value, the action of suppressing the growth of dimples becomes weak, and when the concentration of sulfuric acid or the concentration of hydrofluoric acid exceeds the above upper limit value, A step is likely to occur on the glass surface, which is not preferable.

  The temperature of the surface polishing liquid in the surface polishing step is not particularly limited and may be room temperature. However, the higher the temperature, the higher the dimple suppression effect. Therefore, depending on the liquid temperature, the surface polishing step can be performed by heating to 30 to 50 ° C. The immersion time of the polishing liquid is suitably 1 to 90 minutes (preferably 5 to 30 minutes). If it is less than 1 minute, the dimple growth inhibitory effect is not sufficient, and when immersed for a long time of 90 minutes or more, the productivity of polishing of the glass substrate decreases. In this surface polishing step, it is not necessary to polish until a predetermined glass substrate thickness is reached, and it is only necessary to obtain a smooth glass surface.

  By surface polishing with a surface polishing liquid, growth of dimples can be suppressed and a glass substrate having a smooth glass surface can be formed. The mechanism is not clear, but high-viscosity polishing containing a moderate concentration of hydrofluoric acid is a mechanism that prevents microcracks that originally exist on the glass surface from growing and expanding in the process of chemical polishing. It is presumed that the crack disappears in advance by polishing the flat portion by bringing it into contact with the liquid and precipitating and confining the fluoride in the microcrack.

  As a post-polishing step, a glass substrate on which a smooth glass surface is formed by suppressing the dimple growth by surface polishing with the surface polishing liquid is immersed in a post-polishing liquid containing medium to low concentration hydrofluoric acid. A polished glass substrate having a target glass substrate thickness can be produced by post-polishing until a predetermined glass substrate thickness is reached. Thereafter, the polishing liquid is a polishing liquid containing 2 to 30% by weight of hydrofluoric acid, but can contain an inorganic acid other than hydrofluoric acid such as hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid. The remainder of the post-polishing liquid is mainly water, but may contain other solvents, surfactants, stabilizers and other additives.

The post-polishing step is conventional polishing, and is a method for manufacturing a polished glass substrate by polishing until a predetermined glass substrate thickness is reached. Therefore, in the post-polishing step, conditions, operations, and the like in the method of polishing until a predetermined glass substrate thickness that has been conventionally performed can be employed. The temperature of the post-polishing liquid in the post-polishing step is not particularly limited and may be room temperature, but in general, the post-polishing step can be performed at 15 to 50 ° C. The immersion time of the post-polishing liquid is about 30 to 150 minutes, but is the time required for polishing until the target glass substrate thickness is reached.

  By polishing to a predetermined glass substrate thickness in the post-polishing step, a polished glass substrate having a target glass substrate thickness can be produced. In this case, in the present invention, the surface polishing step suppresses the dimple growth and polishes the surface to obtain a smooth glass surface. In this state, the post-polishing step has a predetermined glass substrate thickness. Even if polished up to dimples, no dimples or steps are formed on the glass surface, and a polished glass substrate having a smooth glass surface can be obtained. Therefore, by chemically polishing the glass substrate for liquid crystal display by the above method, it is possible to provide a high-quality product that suppresses the generation of dimples and maintains a good surface state.

According to the present invention, dimple growth is suppressed by dipping a glass substrate in a surface polishing liquid containing 40 to 90% by weight sulfuric acid and 0.4 to 4% by weight hydrofluoric acid to perform surface polishing. A glass substrate having a smooth glass surface can be obtained by polishing the surface of the glass substrate.
Further, by polishing the surface-polished glass substrate that has been surface-polished until a predetermined glass substrate thickness is obtained in a post-polishing step, there is no dimple or step on the glass surface, and a polished glass substrate having a smooth glass surface is obtained. Can be manufactured.
The polished glass substrate obtained by the present invention has a smooth glass surface without dimples or steps on the glass surface, and has a predetermined glass substrate thickness.

An example of a method for producing a glass substrate for a liquid crystal display will be described below with reference to FIG. 1 as an embodiment of the present invention. However, various types of glass substrate, polishing liquid tank, glass substrate holder, etc. used in the embodiment are described below. The operation method of the appliances and devices does not limit the present invention.
In FIG. 1, 1 is a surface polishing bath, 2 is a first washing bath, 3 is a post-polishing bath, 4 is a second washing bath,
5 is a final washing tank.

  The size of the glass substrate 20 for liquid crystal displays varies. The chemical polishing is performed by filling the surface polishing liquid tank 1 filled with the surface polishing liquid 6, the first water washing tank 2 filled with the cleaning water 7, the post-polishing liquid 8 after the polishing liquid tank 3, and the cleaning water 9. The second water washing tank 4 and the final water washing tank 5 filled with the washing water 10 are arranged in the order shown in FIG. 1, and the cassette container 21 containing the glass substrate 20 is connected to the surface polishing liquid tank 1, the first water washing tank 2, and the rear. It carries out by putting in and out of the polishing liquid tank 3, the second water washing tank 4 and the final water washing tank 5 in order.

  First, the cassette 21 is immersed in the surface polishing liquid tank 1 filled with the surface polishing liquid 6, and the surface polishing liquid 6 is stirred from the air diffuser 11 by means such as gas bubbling of nitrogen or air to perform surface polishing. The immersion time of the surface polishing bath 1 is suitably 1 to 90 minutes (preferably 5 to 30 minutes). If it is less than 1 minute, the dimple growth inhibitory effect is not sufficient, and soaking for 90 minutes or longer is not preferable because the productivity of polishing of the glass substrate 20 is lowered. Further, the temperature of the surface polishing liquid is not particularly limited, but it has been found that the dimple suppression effect increases as the temperature increases. Depending on the liquid temperature, it can be carried out by heating to 30-50 ° C.

  Next, the cassette 21 is taken out from the surface polishing liquid tank 1 and immediately immersed in the first washing tank 2 and stirred by means such as gas bubbling from the air diffuser 12 to remove the surface polishing liquid adhered to the glass surface 20. Wash and remove with wash water 7. Subsequently, the cassette 21 is taken out from the first washing tank 2, filled with the post-polishing liquid 8, and then immersed in the polishing liquid tank 3 to perform post-polishing. At this time, the post-polishing liquid 8 is preferably kept in a uniform flow by means such as gas bubbling from the air diffuser 13 or means such as circulating the polishing liquid. If the flow is insufficient, precipitates accumulate on the surface of the glass substrate 20, resulting in uneven polishing speed, non-uniform polishing thickness, and poor surface finish. The treatment with the post-polishing liquid 8 is performed by setting a polishing time according to a predetermined glass thickness.

  When the chemical polishing is finished in the post-polishing liquid tank 3, the cassette 21 is immediately taken out and immersed in the second water-washing tank 4 filled with the washing water 9 to wash the glass substrate 20 with water. The washing water can be stirred by gas bubbling from the air diffuser 14, or the washing water can be circulated to enhance the washing effect. Finally, the cassette 21 is moved to the final rinsing tank 5 and the same operation as that of the first and second rinsing tanks 2 and 4 is performed to complete the chemical polishing.

Example 1:
A sandpaper with an appropriate roughness was laid, and an aluminoborosilicate glass cut into 10 cm square was placed horizontally, and a certain load was applied from above to give artificial scratches to the glass surface. Using samples as samples, the dimple suppression effect was verified.
The test apparatus produced a small substrate storage cassette 21 simulating FIG. 1, a polishing liquid tank, and a water washing tank, and polished the sample according to the method of FIG. 1. After polishing, the surface of the sample was observed under a microscope to observe the size of dimples grown from artificial scratches, and the number was measured. Moreover, it observed visually about the state of the surface of a glass substrate.

Comparative Example 1:
Comparative Example 1 uses the same sample, the treatment with the surface polishing liquid 6 in the surface polishing liquid tank 1, the treatment with the post polishing liquid 8 in the post polishing liquid tank 3 without performing the water washing in the first water washing tank 2, and the second And only the water washing in the final water washing tanks 4 and 5 was performed and compared. Note that the polishing with the post-polishing liquid 8 in the post-polishing liquid tank 3 of Example 1 and Comparative Example 1 were both processed with a polishing liquid containing 10 wt% hydrofluoric acid and 5 wt% sulfuric acid at room temperature for about 50 minutes.

Evaluation method:
For the evaluation method, the suppression effect was judged as satisfying that the number of dimples having a diameter of 50 μm or more was smaller than that of Comparative Example 1 and that the above-described step was not present.

  From the results in Table 1, it can be read that the decreasing tendency of the number of dimples and the tendency of occurrence of a step are determined by the balance between the sulfuric acid concentration, the hydrofluoric acid concentration, and the immersion time in the surface polishing liquid. That is, from the results of RUN 1, 2, 6, 8, and 9, large dimples having a diameter of 150 μm or more were recognized under the conditions of sulfuric acid concentration 60 to 85% by weight and hydrofluoric acid concentration 1.1 to 3.9% by weight. In addition, the total number of dimples is reduced to about 1/2 to 1/7 or less of Comparative Example 1, and no step is generated.

  In addition, in RUN3 having 70% by weight sulfuric acid and a low hydrofluoric acid concentration (0.9% by weight), the number of dimples was reduced to 1/10 of that of Comparative Example 1 by extending the immersion time. It is suggested that the dimple suppression effect is improved by setting it longer.

  Furthermore, RUN4 with a low hydrofluoric acid concentration (0.5% by weight) and RUN5 and RUN7 with low sulfuric acid concentration (50% by weight) have no dimples with a diameter of 150 μm or more, and the total number is up to about 4/5. Reduction is possible.

On the other hand, in RUN12 in which the sulfuric acid concentration exceeds 90% by weight, RUN10,11 in which the hydrofluoric acid concentration exceeds 4% by weight, and RUN13 in which the sulfuric acid concentration is as low as 30% by weight and the hydrofluoric acid concentration is as high as 5.5% by weight,
In either case, although the dimple generation suppression effect is recognized, a step is likely to occur, which is not preferable.
From the above, in order to suppress dimples without causing a step, 40 to 90% by weight of sulfuric acid (preferably 50 to 85% by weight) and 0.4 to 4% by weight of hydrofluoric acid (preferably 0.5 to 4%). It is necessary to perform polishing in a concentration range of (% by weight).

Example 2 (Test results using an actual substrate):
The test was conducted using an aluminoborosilicate glass substrate (4th generation size). The surface of the glass was polished by using an aqueous solution of 70 wt% sulfuric acid and 1.3 wt% hydrofluoric acid as the surface polishing liquid 6 and immersing the glass substrate in this surface polishing liquid. At this time, the temperature of the surface polishing liquid was 15 ° C., the time for immersing the glass substrate in the polishing liquid was about 15 minutes, and the surface polishing liquid was stirred by air bubbling. After the surface polishing, the glass substrate was washed with water. Thereafter, it was processed to a predetermined glass thickness with a post-polishing liquid containing 10% by weight of hydrofluoric acid and 5% by weight of sulfuric acid. As a result, the nonconformity rate in the practical evaluation standard was reduced to 1/3.

Example 3 (Test results using an actual substrate):
The test was conducted using an aluminoborosilicate glass substrate (4th generation size). An aqueous solution of 60 wt% sulfuric acid and 1.4 wt% hydrofluoric acid was used as the surface polishing liquid 6, and the glass surface was polished by immersing the glass substrate in this surface polishing liquid. At this time, the temperature of the surface polishing liquid was 15 ° C., the time for immersing the glass substrate in the surface polishing liquid was about 70 minutes, and the surface polishing liquid was stirred by air bubbling. After the surface polishing, the glass substrate was washed with water. Thereafter, it was processed to a predetermined glass thickness with a post-polishing liquid containing 10% by weight of hydrofluoric acid and 5% by weight of sulfuric acid. As a result, the nonconformity rate in the practical evaluation standard was reduced to 1/20.

  The glass substrate is immersed in a chemical polishing liquid containing hydrofluoric acid, and the surface of the glass substrate is polished to a predetermined glass substrate thickness. In particular, it can be used as a method for producing a glass substrate for a liquid crystal display.

It is a flowchart which shows the manufacturing method of the glass substrate for liquid crystal displays as embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface polishing liquid tank 2 1st water washing tank 3 Post polishing liquid tank 4 2nd water washing tank 5 Final water washing tank 6 Surface polishing liquid 7, 9, 10 Washing water 8 Post polishing liquid 11, 12, 13, 14, 15 Aeration Equipment 20 Glass substrate 21 Cassette

Claims (5)

A method for producing a polished glass substrate in which a glass substrate is immersed in a polishing liquid containing hydrofluoric acid and the surface is chemically polished,
A method for producing a polished glass substrate, comprising: dipping a glass substrate in a surface polishing solution containing 40 to 90% by weight sulfuric acid and 0.4 to 4% by weight hydrofluoric acid to perform surface polishing. A method for producing a polished glass substrate in which a glass substrate is immersed in a polishing liquid containing hydrofluoric acid and the surface is chemically polished,
After surface polishing by immersing the glass substrate in a surface polishing liquid containing 40 to 90% by weight sulfuric acid and 0.4 to 4% by weight hydrofluoric acid,
A method for producing a polished glass substrate, comprising immersing the glass substrate in a post-polishing liquid containing 2 to 30% by weight of hydrofluoric acid and post-polishing until a predetermined glass substrate thickness is reached.   The method according to claim 1 or 2, wherein the surface polishing liquid is a polishing liquid containing 50 to 85 wt% sulfuric acid and 0.5 to 4 wt% hydrofluoric acid.   The method according to claim 1, wherein the glass substrate is a glass substrate for a liquid crystal display.   A polished glass substrate produced by the method according to claim 1.

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