JP2014122146A - Production method of alkali aluminosilicate glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of chemically strengthened glass capable of suppressing effectively warp after chemical strengthening, and omitting or simplifying a polishing treatment before chemical strengthening or the like.SOLUTION: In a production method of chemically strengthened glass, which is a method for producing the chemically strengthened glass by chemically strengthening float glass comprising alkali aluminosilicate glass in which the content of AlOis over 5 moles, the alkali aluminosilicate glass is alkali aluminosilicate glass produced by granulating a glass-making feedstock.

Description

  The present invention relates to a method for producing alkali aluminosilicate glass and a method for producing float glass for chemical strengthening.

  In recent years, in a flat panel display device such as a mobile phone or a personal digital assistant (PDA), a thin plate-like cover glass is formed on the front surface of the display so as to be wider than the image display portion in order to enhance the protection and aesthetics of the display. It has been done to arrange. Such flat panel display devices are required to be lightweight and thin, and therefore, it is also required to reduce the thickness of cover glass used for display protection.

  However, as the thickness of the cover glass is reduced, the strength decreases, and the cover glass itself may be broken due to falling in use or while carrying it, which plays the original role of protecting the display device. There is a problem that it becomes impossible. For this reason, in order to improve the scratch resistance of the conventional cover glass, the float glass manufactured by the float process is chemically strengthened to form a compressive stress layer on the surface, thereby improving the scratch resistance of the cover glass.

  It has been reported that the float glass is warped after chemical strengthening and the flatness is impaired (Patent Documents 1 to 3). The warpage is caused by chemical strengthening between a glass surface that is not in contact with molten tin (hereinafter also referred to as a top surface) and a glass surface that is in contact with molten tin (hereinafter also referred to as a bottom surface) during float forming. It is supposed to be caused by different ways of entering.

  Since the warp of the float glass becomes larger as the chemical strengthening becomes stronger, the surface compressive stress was developed to meet the demand for high scratch resistance, the surface compressive stress is 600 MPa or more, and the depth of the compressive stress layer is 15 μm or more. In the chemically strengthened float glass, the problem of warpage becomes more obvious as compared with the conventional chemically strengthened float glass having a surface compressive stress of about 500 MPa and a depth of the compressive stress layer of about 10 μm.

Patent Document 1 discloses a glass strengthening method in which the amount of ions entering the glass during chemical strengthening is adjusted by chemically strengthening after forming a SiO ₂ film on the glass surface. Patent Documents 2 and 3 disclose a method of reducing warpage after chemical strengthening by setting the surface compressive stress on the top surface side within a specific range.

  Further, conventionally, in order to reduce the problem of warpage, chemical strengthening is performed after removing a surface heterogeneous layer by reducing the strengthening stress due to chemical strengthening or grinding or polishing at least one surface of glass. There is a solution.

US Patent Application Publication No. 2011/0293928 International Publication No. 2007/004634 JP 62-191449 A

In the method of chemically strengthening after forming the SiO ₂ film on the glass surface described in Patent Document 1, preheating conditions for chemical strengthening are limited, and depending on the conditions, the film quality of the SiO ₂ film changes to affect the warpage. May give. Further, as described in Patent Documents 2 and 3, the method of setting the surface compressive stress on the top surface side in a specific range has a problem from the viewpoint of the strength of the glass.

  Moreover, the method of grinding or polishing at least one surface of the glass before chemical strengthening is problematic from the viewpoint of improving productivity, and it is preferable to omit these grinding or polishing treatments.

  Accordingly, an object of the present invention is to provide a method for producing chemically strengthened glass, which can effectively suppress warping after chemical strengthening and can omit or simplify the polishing treatment before chemical strengthening. And

  The present inventors have found that the main cause of the difference in the way of chemical strengthening between the bottom surface and the top surface of the float glass is the difference in hydrogen concentration between the top surface and the bottom surface. By using it, the amount of hydrogen in the glass due to water in the glass raw material can be reduced to reduce the difference in hydrogen concentration, and a float glass made of an alkali aluminosilicate glass produced using the glass raw material can be chemically treated. It has been found that by strengthening, the way of chemical strengthening between the top surface and the bottom surface can be balanced, and warpage of the float glass after chemical strengthening can be reduced, and the present invention has been completed.

That is, the present invention is as follows.
1. A method for producing a chemically strengthened glass by chemically strengthening a float glass made of an alkali aluminosilicate glass having an Al ₂ O ₃ content of more than 5 mol%, wherein the alkali aluminosilicate glass granulates a glass raw material. A method for producing chemically tempered glass, characterized in that it is an alkali aluminosilicate glass produced by the method described above.
2. _{2. The} method for producing chemically tempered glass according to item 1, wherein the alkali aluminosilicate glass contains Fe in an amount of 30 ppm or more in terms of total Fe ₂ O ₃ .
3. 3. The method for producing chemically strengthened glass according to 1 or 2 above, wherein the redox of the alkali aluminosilicate glass is 60% or less.
4). 4. The method for producing chemically strengthened glass according to any one of items 1 to 3, wherein the granulation is briquette granulation.
5. A process for producing float glass for chemical strengthening, characterized by granulating a glass raw material.
6). A float glass for chemical strengthening having a bottom surface in contact with a molten metal at the time of forming a float glass to be manufactured and a top surface opposite to the bottom surface, the top surface of the surface layer β-OH at a depth of 5 to 30 μm; 6. The method for producing float glass as described in 5 above, wherein the absolute value of the difference between the bottom surfaces is 0.2 / mm ⁻¹ or less.
7). 7. The method for producing an alkali aluminosilicate glass according to any one of items 4 to 6, wherein the granulation is briquette granulation.
8). A method for producing a float glass for chemical strengthening comprising an alkali aluminosilicate glass having an Al ₂ O ₃ content of more than 5 mol%, wherein the alkali aluminosilicate glass is produced by granulating a glass raw material. A method for producing float glass for chemical strengthening, wherein the glass is silicate glass.

  According to the production method of the present invention, since the granulated glass raw material used for the production of the alkali aluminosilicate glass has voids between the granulated products, dehydration can be promoted at the time of melting, and the water in the glass raw material is By reducing the amount of hydrogen in the glass before chemical strengthening, the difference in hydrogen concentration between the top surface and the bottom surface can be reduced. Thereby, the ease of entering the chemical strengthening between the top surface and the bottom surface can be balanced, and the warp of the float glass after chemical strengthening can be reduced.

  Usually, glass is manufactured by weighing and mixing predetermined raw materials containing silica sand and putting them in a melting furnace. The raw material thrown into the melting kiln is heated from room temperature, heated to a maximum of about 1600-1700 ° C. in the melting kiln, melted, and vitrified.

However, the present inventors have also found that unmelted silica sand tends to be a problem when a raw material of high alumina composition glass having an Al ₂ O ₃ content exceeding 5 mol% is melted. This is considered to be because the reaction between soda and silica sand required to efficiently promote the dissolution of the silica sand is hindered by alumina, and the undissolved silica sand eventually tends to occur. If the silica sand remains undissolved, it may cause defects (for example, bubbles, inhomogeneity, or undissolved matter) in the glass. That is, according to the manufacturing method of the present invention, it is possible to reduce the defects of glass.

  If the circulation and residence time of the molten glass in the melting furnace for melting the glass raw material becomes unstable, a part of the molten glass flows out of the melting furnace before bubbles are released from the molten glass in the melting furnace by the refining agent. There is also a case. Moreover, since the melting of the glass is non-uniform, the effect of the fining agent on the silica sand that has been melted late becomes insufficient, the bubbles do not sufficiently escape from the molten glass, and the glass is liable to have defects.

When the melting of the silica sand is delayed, the unmelted silica sand is trapped by the bubbles generated in the glass melt and gathers near the surface of the glass melt, whereby the SiO in the surface of the glass melt and other portions _A difference occurs in the composition ratio of the _two components, and the homogeneity of the glass decreases.

  However, since the melting point of quartz sand alone is as high as 1723 ° C., it is difficult to melt quartz sand alone by subsequent melting. As a method for reducing the undissolved residue of silica sand, a method of using fine silica sand that is melted at a high temperature is known. When the temperature of the glass raw material is increased to dissolve the silica sand, there is a problem that the glass transmittance decreases due to the increase in Fe redox. In order to make a glass having a low redox and a high transmittance, it is considered important to melt the glass raw material without suppressing the undissolved residue of the silica sand in the initial melting and attaining a high temperature.

According to the method for producing chemically strengthened glass of the present invention, the distance between silica sand (SiO ₂ ) and soda ash (Na ₂ O) contained in the glass raw material is obtained by using the alkali aluminosilicate glass produced from the granulated glass raw material. By using the eutectic reaction of SiO ₂ , Na ₂ O and Al ₂ O ₃ shown in FIG. 1, it is possible to eliminate undissolved silica sand. Therefore, it becomes possible to melt the glass raw material at a low temperature, and it becomes possible to produce chemically strengthened glass with low redox and high transmittance. Here, Redox means Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) × 100%.

The phase diagram of SiO ₂ , Na ₂ O and Al ₂ O ₃ is shown. A portion surrounded by a circle is a portion where SiO ₂ and Na ₂ O are dissolved by a eutectic reaction. FIG. 2 is a diagram showing an outline of the polishing IR method. FIG. 3 is a graph in which β-OH is calculated for a region having a depth of 0 to 40 μm and compared with the 1H / 30Si average count of the region calculated by the SIMS method. In FIG. 3, β-OH was calculated by a mass conversion method. In FIG. 3, the reading error is ± 2.5 to 3.5%. In the graph of FIG. 3, y = 2.9777x + 0.0566 and R ² = 0.985. FIG. 4 is a schematic diagram showing a step of granulating briquettes with a briquetting machine. FIGS. 5A to 5C are schematic diagrams showing a method for evaluating the amount of undissolved silica sand in the initial reaction. 6 (a) and 6 (b) show the results of melting an ungranulated glass raw material at 1450 ° C. 6 (c) and 6 (d) show the results of melting briquette granulated glass raw material at 1450 ° C. FIGS. 7A and 7B show the results of melting an ungranulated glass raw material at 1500 ° C. for 10 minutes. Moreover, FIG.7 (c) and (d) show the result of having melt | dissolved the briquette granulated glass raw material for 10 minutes at 1500 degreeC. FIG. 8 shows the result of analyzing unmelted glass raw material (■) or briquetted granulated (◆) glass raw material for 10 minutes at 1450 ° C. or 1500 ° C. and analyzing the undissolved residue of silica sand (SiO ₂ ). Show. FIG. 9 shows the results of measuring the β-OH of the melted glass by IR method after holding the normal raw material (■) or briquette-granulated raw material (●) at 1550 ° C. for 1 hour.

  The method for producing chemically tempered glass of the present invention is a method for producing chemically tempered glass by chemically strengthening float glass made of alkali aluminosilicate glass, and the alkali aluminosilicate glass is produced by granulating a glass raw material. It is an aluminosilicate glass.

FIG. 1 shows a phase diagram of silica sand (SiO ₂ ), soda ash (Na ₂ O) and Al ₂ O ₃ contained in the high alumina raw material. A reaction product obtained by reacting Na ₂ O and Al ₂ O ₃ has a high melting point and does not dissolve at first unless the temperature is high. When Na ₂ O and SiO ₂ react with each other to form a low melting point reaction product, an effect is obtained that the dissolution rate of SiO ₂ is accelerated by the reaction product, but Na ₂ O is converted to Al ₂ O _3. When consumed in the reaction with the above, such an effect cannot be obtained, and the dissolution rate of SiO ₂ becomes slow. In particular, when the temperature rising rate of the glass raw material is slow, the reaction of Na ₂ O and Al ₂ O ₃ proceeds, and the dissolution rate of SiO ₂ is thought to be slow.

The present inventors have found that the undissolved residue of silica sand (SiO ₂ ) can be eliminated by utilizing the eutectic reaction of SiO ₂ and Na ₂ O. By granulating the glass raw material, the eutectic reaction can be utilized by reducing the distance between SiO ₂ and Na ₂ O in the raw material.

Because eutectic reaction between the silica sand (SiO ₂ ) and soda ash (Na ₂ O) in the raw material accelerates the dissolution of the silica sand, reducing the undissolved residue of the silica sand and enabling the glass raw material to be dissolved at a low temperature. It is possible to obtain a glass with high transmittance without increasing Redox. In addition, by dissolving the granulated glass raw material, initial bubbles such as carbon dioxide escape from the gaps in the glass structure, so that generation of bubbles that cause defects can be suppressed.

The alkali aluminosilicate glass used in the production method of the present invention typically contains 30 ppm or more in terms of total Fe ₂ O ₃ . The redox of the alkali aluminosilicate glass used in the production method of the present invention is preferably 60% or less, and more preferably 50% or less. According to the production method of the present invention, alkali aluminosilicate glass is produced by using a glass raw material obtained by granulating alkali aluminosilicate glass for chemical strengthening even when it is contained in an amount of 30 ppm or more in terms of total Fe ₂ O _3. The redox can be preferably 60% or less, and a chemically tempered glass having a high transmittance can be obtained.

  The float glass is formed by a float process, and has a bottom surface that is in contact with the molten metal at the time of forming and a top surface that faces the bottom surface. The main cause of the warp caused by chemically strengthening the float glass is considered to be a hydrogen concentration difference between the top surface and the bottom surface, as will be described below.

  In the production of glass by the float process, molten glass is continuously supplied from the upstream side to the surface of the molten metal stored in the float bath, and a glass ribbon is formed while forming the glass ribbon from the downstream end of the float bath. A glass ribbon is drawn out and slowly cooled with a layer to produce a plate glass.

In the production of glass by the float process, an apparatus of a type in which a flow path is narrowed is generally used in which a glass tank kiln and a float bath are connected by a canal and a spout.
In this case, since it is necessary to spread the glass in the float bath, molten glass having a higher temperature is poured out onto the surface of the molten metal as compared with another type of apparatus described later.

However, since the dew point of the float bath is low, H _{2 O} diffuses from the glass surface, H _{2 O} diffuses into the atmosphere from the top surface, from the bottom surface H _{2 O} diffuses into the molten metal . Therefore, the float glass produced by such a type of apparatus has a lower hydrogen concentration on the surface (5 to 10 μm) than the hydrogen concentration inside (typically a depth of about 50 μm or more). Since the diffusion coefficient of H ₂ O is higher at higher temperatures, the diffusion amount of H ₂ O from the top surface in contact with an atmosphere having a lower dew point or higher temperature than the bottom surface of the float glass in contact with the lower temperature molten metal The hydrogen concentration on the top surface is lower than the bottom surface of the float glass.

  By the way, when the hydrogen concentration in the glass is high, hydrogen enters the Si—O—Si bond network of the glass in the form of SiOH, and the Si—O—Si bond is broken. When the hydrogen concentration in the glass is high, the Si-O-Si bond is cut off more and the thermal properties such as the glass transition point decrease, so the stress is relaxed during chemical strengthening when the glass is heated at a high temperature. descend.

  Therefore, among the top and bottom surfaces of float glass, the glass surface with a high hydrogen concentration is less stressed during chemical strengthening, and the glass surface with a lower hydrogen concentration is susceptible to stress during chemical strengthening. It will be.

  That is, the closer the hydrogen concentration between the top surface and the bottom surface in the float glass, the smaller the absolute value of the hydrogen concentration difference between the top surface and the bottom surface, the smaller the difference between the top surface and the bottom surface after chemical strengthening. The approach of stress approaches a balanced state, and warpage is reduced.

  Many glass ingredients contain water in all forms. Examples of the form of water contained in the glass raw material include hydroxide, hydrated crystal, and adsorbed water. Moreover, in order to prevent the glass raw material from dancing, it is also common to add water, put it in a kiln, and dissolve it. Glass materials that are not granulated from these raw materials are difficult to drain water in the raw materials, and the hydrogen concentration at the top and bottom surfaces is high. In the present invention, the granulated glass raw material used for the production of the alkali aluminosilicate glass has a large surface area and the presence of voids between the granulated materials, thereby promoting dehydration during melting and the hydrogen concentration in the glass before chemical strengthening. Can be reduced.

  By reducing the hydrogen concentration in the glass before chemical strengthening due to the water in the raw material when melting the glass raw material, the difference in hydrogen concentration between the top surface and the bottom surface can be reduced, and the top surface and the bottom surface It is possible to balance the ease of entering the chemical strengthening, and to reduce the warp of the float glass after the chemical strengthening.

There exists (beta) -OH measured by IR method as a guideline of the moisture content in glass. β-OH is measured by the polishing IR method described below. As shown in FIGS. 2A to 2C, in the polishing IR method, a region where β-OH on the glass substrate surface is to be evaluated is removed by polishing treatment, and the substrate before and after polishing is subjected to IR measurement, and 3500 cm ^−1. Read the absorbance of the Si—OH peak detected in the vicinity.

  Β-OH in the target region is calculated from the difference in absorbance between the Si—OH peaks before and after polishing and the polishing thickness. Compared with the sample before polishing, the sample after polishing shows a decrease in the intensity of the Si—OH peak. This reduced amount corresponds to glass absorption in the polished region.

The absorbance of the Si—OH peak existing in the vicinity of 3500 cm ⁻¹ is calculated by subtracting the absorbance at the base of 3955 cm ⁻¹ from the absorbance of the Si—OH peak top. FIG. 3 is a graph in which β-OH is calculated for a region having a depth of 0 to 40 μm and compared with the 1H / 30Si average count of the region calculated from the SIMS method. In addition, since there is a positive correlation between β-OH and [ ¹ H ⁻ / ³⁰ Si ⁻ ] average count, the surface layer β-OH calculated by the polishing IR method is the same as that of the SIMS method. Can be used to evaluate hydrogen concentration.

In the present invention, specifically, the surface layer β-OH at a depth of 5 to 30 μm calculated by the following steps (1) to (3) is obtained, whereby dehydration of the top surface and bottom surface float glass surfaces is performed. Assess the condition.
(1) The measurement surface of the float glass is polished by 5 μm and IR measurement is performed, and the absorbance of the Si—OH peak is calculated by subtracting the absorbance at the base of 3955 cm ⁻¹ from the absorbance of the Si—OH peak (FIG. 2B). The absorbance of the Si—OH peak top is the absorbance present in the vicinity of 3500 cm ⁻¹ .
(2) Further, the measurement surface of the float glass is polished by 30 μm, and the absorbance of the Si—OH peak is measured in the same manner as in the step (1) (FIG. 2C).
(3) The surface layer β-OH of the target region is calculated by the following equation based on the difference in absorbance between the Si—OH peaks before and after polishing obtained in steps (1) and (2) and the polishing thickness.
(Surface layer β-OH) = [(Si-OH absorbance of 5 μm polishing) − (Si-OH absorbance of 30 μm polishing)] / Polishing thickness (mm)

On the surface of the float glass (depth 0 to several μm), there is little Si—O—Na ^{+ due} to burns. Therefore, the absorbance at the peak top in the vicinity of 3500 cm ⁻¹ used for β-OH calculation may be different between the surface of the float glass and the bulk. Therefore, if the IR spectrum of the surface of the float glass is used for β-OH calculation, the hydrogen concentration cannot be evaluated correctly. According to the polishing IR method, which is a method for measuring the surface layer β-OH of the present invention, the sample from which the surface has been removed can be evaluated by performing IR measurement after polishing the measurement surface of the float glass by 5 μm.

  In the steps (1) to (3), the same glass substrate is polished to prepare samples (A) to (C) in FIG. 2, and from the IR spectra in the samples (B) and (C) in FIG. It is preferable to calculate the surface layer β-OH. Alternatively, a plurality of the same glass substrates may be prepared, the samples shown in FIGS. 2B and 2C may be prepared by changing the polishing thickness, and IR measurement and β-OH calculation may be performed.

The polishing agent used in the polishing, for _{example, CeO 2, SiO 2, Al} 2 O 3 and ZrO ₂ and the like.

  As a method for calculating the polishing thickness, there are a mass conversion method for calculating the polishing thickness from the difference in mass between the glass plates before and after polishing, and a plate thickness conversion method for calculating from the difference in plate thickness before and after polishing. The plate thickness conversion method measures the plate thickness with a plate thickness meter, while the mass conversion method measures the mass of the glass with an electronic balance.

Considering the accuracy of the thickness gauge and the electronic balance, the mass conversion method can calculate the average polished thickness of the glass plate with higher accuracy. Therefore, in this invention, it is preferable to calculate polishing thickness by the mass conversion method which calculates polishing thickness from the mass difference of the glass plate before and behind grinding | polishing.
Alternatively, a laser thickness meter may be used.

In the present invention, the difference between the top surface and the bottom surface of the surface layer β-OH at a depth of 5 to 30 μm determined by the steps (1) to (3) [(surface layer β-OH at a depth of 5 to 30 μm of the bottom surface). − (Surface layer β-OH at a depth of 5 to 30 μm on the top surface)] is preferably 0.2 / mm ⁻¹ or less, 0.15 / mm ⁻¹ or less, 0.12 mm ⁻¹ or less. Or it is more preferable that it is 0.1 mm < ^-1 > or less.

Even if the polishing treatment before chemical strengthening is simplified or omitted by setting the absolute value of the difference between the top surface and the bottom surface of the surface layer β-OH at a depth of 5 to 30 μm to 0.2 / mm ⁻¹ or less. The curvature of the float glass after chemical strengthening can be reduced and excellent flatness can be obtained.

  The IR measurement is performed by a known method using a commercially available apparatus (for example, Nicolet 6700 manufactured by Thermo Fisher Scientific).

3. Granulation Examples of the method for granulating the glass raw material include compression granulation, rolling granulation, fluidized bed granulation, stirring granulation, compression granulation, extrusion granulation, melt granulation, and spray granulation. . Examples of compression granulation include briquetting granulation and tableting (tabletting). Among these, from the viewpoint of production efficiency, compression granulation is preferable, and briquette granulation is more preferable.

  FIG. 4 shows a specific example of the step of granulating briquettes with a briquetting machine. A glass raw material (not shown) is formed from the hopper 1 on the outer peripheral surface, preferably 10 to 50 mm in width, preferably 10 to 50 mm in length, preferably 5 to 30 mm in depth (not shown). By discharging while rotating the swivel wheel 2, an almond-shaped briquette 3 having a width of about 10 to 50 mm, a length of 10 to 50 mm, and a thickness (10 to 60) mm can be granulated.

  The specific gravity of the granulated product obtained by granulating the glass raw material is preferably 2.0 to 2.8, and more preferably 2.2 to 2.6. This is because the eutectic reaction can be promoted by setting the specific gravity of the granulated product to 2.0 to 2.8.

The content of the SiO ₂ component in the granulated product is preferably 40 to 90% by mass, and more preferably 50 to 80% by mass. The granulated product is preferably a raw material mainly composed of an oxide or a carbonate compound. For example, in soda lime silica-based glass, it is preferable to use at least one selected from a raw material group consisting of silica sand, dolomite, limestone, and soda ash.

  Examples of the shape of the granulated product include a spherical shape, a cylindrical shape, an almond shape, a flat plate shape, a flake shape, a cubic shape, and a thread shape. Among these, a shape that is not too long in only one direction, such as a spherical shape, a cylindrical shape, or an almond shape, is preferable.

  The dissolution temperature of the granulated product is preferably 1450 to 1650 ° C, and more preferably 1500 to 1600 ° C. When the melting temperature is 1450 to 1650 ° C., Redox can be suppressed low and a glass with high transmittance can be obtained. The melting temperature of the granulated product can be examined by “Evaluation method of undissolved amount of silica sand in initial reaction” described later in Examples (FIGS. 5A to 5C).

4). The glass glass production method is not particularly limited except that the glass raw material is granulated. Specifically, for example, various raw materials are prepared in an appropriate amount to form a granulated product, and the granulated product is continuously charged into a large kiln. Preferably, heated to 1450-1650 ° C. and melted, then homogenized by defoaming or stirring, formed into a plate shape by a well-known float method, manufactured by slow cooling, cutting to a desired size, and polishing To do. A chemically strengthened glass can be obtained by cutting the molded glass into a predetermined size with a cutting machine and then chemically strengthening the glass.

  In chemical strengthening, alkali metal ions (typically Li ions or Na ions) having a small ion radius on the glass surface are exchanged by ion exchange at a temperature below the glass transition temperature, and alkali ions (typically, This is a process of forming a compressive stress layer on the glass surface by exchanging with K ions. The chemical strengthening treatment can be performed by a conventionally known method.

  The glass used in the production method of the present invention is alkali aluminosilicate glass. Hereinafter, a preferable composition of the alkali aluminosilicate glass will be described.

Alkaline aluminosilicate glass is expressed in terms of oxide-based mole percentage, SiO ₂ 50-50%, Al ₂ O ₃ 0-10%, B ₂ O ₃ 0-4%, MgO 5-30%, ZrO It is preferable that at least 1 selected from ₂ , P ₂ O ₅ , TiO ₂ and La ₂ O ₃ is contained in a total of 0.5 to 10% and Na ₂ O is contained in 1 to 17%.

The content of SiO ₂ is preferably 50 to 80%, more preferably 55 to 75%, and still more preferably 58 to 70%. The content of Al ₂ O ₃ is preferably 0 to 10%, more preferably 1 to 7%, and further preferably 2 to 5%. In addition, for example, the content of Al ₂ O ₃ is preferably 0 to 10%. Al ₂ O ₃ may or may not be contained, but when it is contained, the content is preferably 10% or less. Is the meaning.

The content of B ₂ O ₃ is preferably 0 to 4%, preferably 0.3 to ₃ %, and more preferably 0.5 to 2%. The content of MgO is preferably 5 to 30%, more preferably 10 to 28%, and still more preferably 15 to 25%.

The alkali aluminosilicate glass preferably contains at least one selected from ZrO ₂ , P ₂ O ₅ , TiO ₂ and La ₂ O ₃ . When the alkali aluminosilicate glass contains at least one selected from ZrO ₂ , P ₂ O ₅ and La ₂ O ₃ , the alkali aluminosilicate glass can be whitened. The total amount is preferably 0.5 to 10%.

The content of ZrO ₂ in the alkali aluminosilicate glass is preferably 0 to 5%, and more preferably 0.5 to 3%. The content of P ₂ O ₅ in the alkali aluminosilicate glass is preferably 0 to 10%, more preferably 0.5 to 7%, and further preferably 1 to 6%. The content of TiO ₂ in the alkali aluminosilicate glass is preferably 0 to 10%, more preferably 0.5 to 7%, and further preferably 1 to 6%. The content of La ₂ O ₃ in the alkali aluminosilicate glass is preferably 0 to 2%, and more preferably 0.2 to 1%.

When the alkali aluminosilicate glass contains Na ₂ O, the strength of the glass by the subsequent ion exchange treatment can be increased. The content of Na ₂ O in the alkali aluminosilicate glass is preferably 1 to 17%, more preferably 3 to 11%, and still more preferably 4 to 14%. By making the content of Na ₂ O 1% or more, a desired surface compressive stress layer can be easily formed by ion exchange. Further, it is possible to improve the weather resistance by a 17% or less of Na 2 _O.

Examples of the composition of the alkali aluminosilicate glass used in the production method of the present invention include the following.
(I) 50% to 80% of SiO ₂ , 5 to 25% of Al ₂ O ₃ , 0 to 10% of Li ₂ O, 0 to 18% of Na ₂ O, K ₂ O with a composition expressed in mol% Is represented by a glass (ii) mol% containing 0-10% MgO, 0-15% MgO, 0-5% CaO and 0-5% ZrO ₂ , SiO ₂ 50-74%, Al ₂ O ₃ 5-10%, Na ₂ O 6-14%, K ₂ O 3-11%, MgO 2-15%, CaO 0-6% and ZrO ₂ 0-5% The total content of SiO ₂ and Al ₂ O ₃ is 75% or less, the total content of Na ₂ O and K ₂ O is 12 to 25%, and the total content of MgO and CaO is 7 to 15%. a composition which is displayed at a certain glass (iii) mol%, a SiO ₂ 68 to 80%, the _Al 2 _{O 3} 5 to 10%, a ₂ O 5-15% of _{K 2} O 0 to 1%, glass containing MgO 4 to 15% and ZrO ₂ and 0 to 1%

  The glass obtained by the production method of the present invention is a float glass with a small amount of warping after chemical strengthening. The amount of warp of the float glass can be measured with a three-dimensional shape measuring instrument (for example, manufactured by Mitaka Kogyo Co., Ltd.).

  The amount of warpage is measured as the difference between the highest point and the lowest point when measured with a three-dimensional shape measuring instrument. When it warps in the convex direction of the top surface, it is expressed as plus, and when it warps in the convex direction of the bottom surface, it is expressed as minus. The change in the warp amount of the float glass before and after chemical strengthening can be measured by the Δ warp amount [(warp amount after chemical strengthening) − (warp amount before chemical strengthening)].

[Example 1]
SiO ₂ , alumina, soda ash, calcium carbonate, water mug and other raw materials were prepared so as to be an alkali aluminosilicate glass having the composition 1 shown below, and a briquette machine (trade name CS-25, manufactured by Hosokawa Micron) To prepare briquettes having a diameter of 5 mm, a thickness of 33 mm, and a specific gravity of 2.4, and briquettes having a width of 30 mm × length of 30 mm × thickness of 18 mm and a specific gravity of 2.4.
Composition 1: In terms of mol%, SiO ₂ 65.2%, Al ₂ O ₃ 7.9%, MgO 10.2%, Na ₂ O 12.4%, K ₂ O 3.9%, ZrO ₂ 0. 5%

After holding the obtained briquette or non-granulated glass raw material (normal raw material) at 1550 ° C. for 1 hour at each water vapor concentration shown in Table 1, β-OH of the obtained glass was measured by IR method. . The measurement surface of the glass is polished by 5 μm, IR measurement is performed, and the absorbance of the Si—OH peak is calculated by subtracting the absorbance at the base of 3955 cm ⁻¹ from the absorbance at the top of the Si—OH peak, and further polished by 25 μm. The absorbance of the Si—OH peak was measured.

IR method Measurement condition apparatus: Nicolet 6700 manufactured by Thermo Fisher Scientific
Detector: Electronically cooled DTGS
Integration: 64 times wave number resolution: 4 cm ⁻¹

From the absorbance difference between the Si—OH peaks before and after polishing and the polishing thickness, β-OH in the target region (depth 5 to 30 μm) was calculated by the following formula.
(Surface layer β-OH) = [(Si-OH absorbance of 5 μm polishing) − (Si-OH absorbance of 30 μm polishing)] / Polishing thickness

  The results are shown in Table 1 and FIG. In FIG. 9, the solid line is the result of plotting the data in Table 1, and shows the prediction from the obtained data. In Table 1, “Briquet average” means an average value of “Bricket 5 mmφ × 33 mm” and “Bricket 30 × 30 × 18 mm”.

  Further, a float glass having a thickness of 0.8 mm and a size of 100 mm × 100 mm made of such glass is immersed in potassium nitrate at 435 ° C. so that the compression stress CS on the TOP surface is 750 MPa and the compression stress depth DOL is 40 μm. When the chemical strengthening is performed, the warp of the float glass increases, and the amount of increase is shown in the Δ warp column of Table 1.

  As shown in Table 1 and FIG. 9, it was found that the β-OH concentration of the obtained glass can be reduced by granulating the glass raw material. By reducing the β-OH concentration of the glass, the difference in hydrogen concentration between the top surface and the bottom surface can be reduced, and the ease of chemical strengthening between the top surface and the bottom surface is balanced, and the float after chemical strengthening is increased. Glass warpage can be reduced.

[Example 2]
SiO ₂ and other raw materials were prepared so as to be an alkali aluminosilicate glass having the composition 2 shown below, and further granulated by a briquetting machine (trade name CS-25, manufactured by Hosokawa Micron Corporation). A briquette having a thickness of 15 mm, a thickness of 10 mm, and a specific gravity of 2.4 was prepared.
Composition 2: By mol%, SiO ₂ 68.0%, Al ₂ O ₃ 10.0%, MgO 8.0%, Na ₂ O 14.0%

Using the obtained briquettes, as shown in FIGS. 5A to 5C, the undissolved amount of silica sand in the initial reaction was evaluated by the following procedure.
(1) The cullet 52 (glass layer 300 g) placed in a castable container 51 having an inner size of 150 mm square is melted in an electric furnace set at a temperature to be evaluated [FIG. 5A].
(2) The castable container 51 is once extracted, 125 g of glass raw material 53 is added in a mountain shape, and immediately returned to the electric furnace [FIG. 5 (b)].
(3) After melting the glass raw material 53 for 10 minutes in the electric furnace, the castable container 51 is taken out [FIG. 5 (c)]. Of the melted glass raw material, an analysis region 54 of 80 × 80 × 2.5 mm is analyzed by XRD.

  6 (a) and 6 (b) show the results of melting an ungranulated glass raw material at 1450 ° C. for 3 minutes [FIG. 6 (a)] and 5 minutes [FIG. 6 (b)]. 6 (c) and 6 (d) show the results of melting the briquette granulated glass raw material at 1450 ° C. for 3 minutes [FIG. 6 (c)] and 5 minutes [FIG. 6 (d)]. The numbers in FIGS. 6 (a) to 6 (d) indicate the remaining silica sand ratio (%) with respect to that before heating.

  As shown in FIGS. 6 (a) to 6 (d), it was found that by melting the glass raw material, the dissolution of the silica sand progresses rapidly by the eutectic reaction. It was also found that the generation of bubbles was suppressed when the glass raw material was dissolved because the initial bubbles were removed from the gaps in the structure between the granulated products.

  7 (a) and 7 (b) show the results of melting an ungranulated glass raw material at 1450 ° C. for 3 minutes and 5 minutes. Moreover, the result of having melt | dissolved the glass raw material which carried out briquette granulation for 3 minutes and 5 minutes at 1450 degreeC in FIG.7 (c) and (d) is shown.

  FIGS. 7 (c) and 7 (d) in which the glass raw material is granulated have no scum problem and less melted silica sand than in FIGS. 7 (a) and 7 (b) in which the glass raw material is not granulated. It was found that the occurrence was suppressed.

Table 2 and FIG. 8 show the results of analyzing unmelted glass raw material (normally melted) or briquetted granulated glass raw material at 1450 ° C. or 1500 ° C. for 10 minutes and analyzing the undissolved residue of silica sand (SiO ₂ ). Indicates. In Table 2, “Qz” refers to the undissolved residue of SiO ₂ , and “Cri” refers to the high-temperature crystal phase of Qz. Moreover, in Table 2, “%” indicates the residual silica sand ratio before heating.

  From the results of Table 2 and FIG. 8, it was found that the glass raw material can be melted at a low temperature by granulating the glass raw material.

  In addition, as a result of investigating Redox of the glass (composition 1) obtained by passing the kiln-seal MAX temperature, the Redox at the kiln-compression temperature of 1650 ° C was 50%, and the Redox at 1580 ° C was 10%. Therefore, according to the manufacturing method of this invention, since the granulated glass raw material can be melt | dissolved at the low temperature of 1500 degreeC, it is thought that the glass with the low transmittance | permeability of Redox can be manufactured.

DESCRIPTION OF SYMBOLS 1 Hopper 2 Turning wheel 3 Briquette 51 Castable container 52 Caret 53 Glass raw material 54 Analysis area

Claims (5)

A method for producing a chemically strengthened glass by chemically strengthening a float glass made of an alkali aluminosilicate glass having an Al ₂ O ₃ content of more than 5 mol%, wherein the alkali aluminosilicate glass granulates a glass raw material. A method for producing chemically tempered glass, characterized in that it is an alkali aluminosilicate glass produced by the method described above. Method for producing a chemically strengthened glass according to claim 1, wherein the alkali aluminosilicate glass contains more than 30ppm in total in terms _{of Fe} 2 _{O 3} and Fe.   The method for producing chemically tempered glass according to claim 1 or 2, wherein the redox of the alkali aluminosilicate glass is 60% or less.   The method for producing chemically strengthened glass according to any one of claims 1 to 3, wherein the granulation is briquette granulation. A method for producing a float glass for chemical strengthening comprising an alkali aluminosilicate glass having an Al ₂ O ₃ content of more than 5 mol%, wherein the alkali aluminosilicate glass is produced by granulating a glass raw material. A method for producing float glass for chemical strengthening, wherein the glass is silicate glass.