TW201742846A - Glass plate, glass substrate for display and glass substrate for solar cell relating to a glass plate having a lower hydrogen concentration in the surface layer of the glass plate than the inside of the glass plate - Google Patents

Abstract

The present invention is to provide an excellent glass plate in which alkali metal hardly diffuses on the surface of a glass plate and deterioration of properties of a transparent conductive oxide film can be suppressed. The disclosed glass plate has value represented by (surface hydrogen concentration/internal hydrogen concentration) of 0.80 or less, wherein the surface hydrogen concentration is an average value of the hydrogen concentration between the surface of the glass plate and the depth of 0.5~1.5[mu]m, while the internal hydrogen concentration is the hydrogen concentration within a region between the surface of the glass plate and the depth of 0.5~1.5[mu]m after the glass plate removes its surface down to a thickness of 100[mu]m. However, when the glass plate has a thickness below 0.2mm, the internal hydrogen concentration is the hydrogen concentration within a region between the surface of the glass plate and the depth of 0.5~1.5[mu]m after the glass plate removes half of its thickness.

Description

Glass plate, glass substrate for display, and glass substrate for solar cell

FIELD OF THE INVENTION The present invention relates to a glass plate having a lower hydrogen concentration in a surface of a glass plate than a glass plate, a glass substrate for a display, and a glass substrate for a solar cell.

BACKGROUND OF THE INVENTION A problem with photoelectric conversion elements such as liquid crystal displays and solar cells is that various characteristics caused by alkali metals contained in a glass substrate are deteriorated. For example, the alkali metal in the glass substrate is diffused to a transparent conductive oxide film or the like formed on the glass substrate to deteriorate characteristics. Therefore, an alkali-free glass substrate which does not substantially contain an alkali metal oxide is preferably used (Patent Document 1).

On the other hand, since the production cost is low, an alkali glass substrate containing an alkali metal oxide such as soda lime glass is often used. When an alkali glass substrate is used, in order to minimize the diffusion of the alkali metal, it is necessary to form an alkali barrier layer such as a ruthenium oxide film, an aluminum oxide film, a zirconia film, or a mixed oxide film of ruthenium oxide and tin oxide on the glass substrate. A transparent conductive oxide film is formed on the basic barrier layer (Patent Document 2). Prior Technical Literature Patent Literature

Patent Document 1: Japanese Patent No. 3901757 Patent Document 2: International Publication No. 2013/035746

SUMMARY OF THE INVENTION Problems to be Solved by the Invention An alkaline glass substrate contains an alkali metal oxide. Even an alkali-free glass substrate which does not substantially contain an alkali metal oxide has to contain an alkali metal such as Na which cannot be avoided, and it is impossible to achieve a zero content.

However, the alkali metal contained in the alkali-free glass or the alkali glass substrate may diffuse to the transparent conductive oxide film formed on the glass substrate, etc., and the characteristics may deteriorate.

The present inventors believe that the Si-OH group (stanol group) in the glass plate becomes a conduction route of the alkali metal, so that a glass plate having a large amount of stanol groups (a glass plate having a high hydrogen concentration) promotes the alkali metal from The inside of the glass plate is diffused to the surface of the glass plate to increase the amount of alkali metal diffused from the surface of the glass plate to the transparent conductive oxide film, thereby weakening the characteristics.

Accordingly, an object of the present invention is to provide an excellent glass sheet which can suppress the weakening of the characteristics of the transparent conductive oxide film by reducing the stanol group of the surface layer of the glass plate, especially the glass plate, so that the alkali metal does not easily diffuse to the surface of the glass plate. Means to solve the problem

As a result of the intensive research by the present inventors, it has been found that the above problem can be solved by reducing the hydrogen concentration (surface hydrogen concentration) in the vicinity of the surface layer of the glass sheet to at least the hydrogen concentration (internal hydrogen concentration) in the glass, and the present invention has been completed.

That is, the glass plate of the present invention has a value of (the surface layer hydrogen concentration/internal hydrogen concentration) of 0.80 or less, wherein the surface layer hydrogen concentration is an average value of the hydrogen concentration in the region from the surface of the glass plate to a depth of 0.5 to 1.5 μm, and the inside thereof. The hydrogen concentration is the concentration of hydrogen in the region from the surface of the glass plate removed to the depth of 100 μm to the depth of 0.5 to 1.5 μm. However, when the thickness of the glass plate is 0.2 mm or less, the internal hydrogen concentration is the hydrogen concentration in the region from the surface of the glass plate after removing the depth region of the half thickness of the glass plate to a depth of 0.5 to 1.5 μm. Effect of the invention

According to the present invention, a glass plate in which an alkali metal is not easily diffused to the surface of a glass plate can be obtained. Therefore, when the glass plate of the present invention is used as a glass substrate for a display or a glass substrate for a solar cell, it is possible to suppress deterioration of characteristics of the transparent conductive oxide film due to diffusion of an alkali metal.

MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below, but the present invention is not limited to the following embodiments, and modifications may be made without departing from the spirit and scope of the invention. In addition, in the present specification, the symbol "~" in the numerical range is used in the definition that the numerical values described before and after are defined as the lower limit and the upper limit.

<Glass plate> The glass plate of the present embodiment is characterized by a value of (the surface layer hydrogen concentration/internal hydrogen concentration) of 0.80 or less, wherein the surface layer hydrogen concentration is a glass plate surface to a depth of 0.5 to 1.5 μm (hereinafter, The average hydrogen concentration in the "surface layer only" is the area where the internal hydrogen concentration has been removed from the surface of the glass plate to the depth of 100 μm to the depth of 0.5 to 1.5 μm (hereinafter sometimes referred to as " The concentration of hydrogen in the interior"). In addition, unlike the surface layer, the inside is an area in which the hydrogen concentration is almost constant. Further, when the thickness of the glass plate is 0.2 mm or less, the inside refers to the surface of the glass plate after the depth region of the half thickness of the glass plate is removed to a depth of 0.5 to 1.5 μm, and the hydrogen concentration inside is the internal hydrogen concentration.

When a glass sheet is usually applied to an article, a certain processing is generally performed. For example, when used as a glass substrate for a liquid crystal display, a thin film (ITO film) of an indium tin oxide (ITO) compound called ITO is often plated on the glass plate. The film formation temperature of the ITO film is, for example, about 350 °C. Conventional glass plates differ in heating conditions depending on the heating conditions after film formation or before and after film formation, but the amount of alkali metal in the surface of the glass plate to a depth of 10 nm increases. For example, in the case of the amount of Na, the ²³ Na/ ²⁸ Si count ratio obtained by the time-of-flight secondary ion mass spectrometry in the region of the surface of the glass plate to a depth of 10 nm is shown. The average value of the values (surface Na count) becomes larger. In addition, the surface of the glass plate to the depth of 10 nm is a region where Na segregation is remarkable.

On the other hand, in the glass of the present embodiment, the value indicated by (surface hydrogen concentration/internal hydrogen concentration) is set to 0.80 or less, and the surface Na count after heat treatment can be reduced by about 30%. Further, if the value indicated by (surface hydrogen concentration/internal hydrogen concentration) is 0.65 or less, the surface Na count after heat treatment can be reduced by about 50%, which is preferable. More preferably, it is 0.50 or less. Although the value shown in the surface hydrogen concentration/internal hydrogen concentration is as small as possible, there is a limit to effectively reduce the surface hydrogen concentration. Therefore, from the viewpoint of easy production of a glass plate, the value indicated by the surface layer hydrogen concentration/internal hydrogen concentration in the present embodiment is preferably 0.40 or more.

The presence of Si-OH groups (stanol groups) in the glass plate can become a conduction pathway for alkali metals such as Na. Therefore, by reducing the stanol group (which reduces the hydrogen concentration) which is originally present on the surface layer of the glass sheet, it is possible to suppress the diffusion of Na from the inside of the glass sheet to the surface. In other words, by reducing the stanol group of the surface layer of the glass sheet (reducing the hydrogen concentration), Na can be prevented from diffusing to the surface of the glass sheet, and further hindrance of Na diffusion causes deterioration of characteristics of the transparent conductive oxide film.

[Method for Measuring Surface Layer Hydrogen Concentration/Internal Hydrogen Concentration] (Surface hydrogen concentration/internal hydrogen concentration) It can be determined by Secondary Ion Mass Spectrometry (SIMS). The detailed measurement method is explained below.

In order to obtain a quantitative hydrogen concentration profile by SIMS, it is necessary to measure a standard sample of known hydrogen concentration and determine a relative sensitivity factor for converting the count into a concentration. However, this embodiment is expressed by the ratio of (surface hydrogen concentration/internal hydrogen concentration), so there is no need to calculate the relative sensitivity factor. The method of calculating the surface layer hydrogen concentration/internal hydrogen concentration is described below.

The glass plate of the evaluation object from which part of the glass had been cut was ground from the surface to a depth of 100 μm. However, when the thickness of the glass plate is 0.2 mm or less, the depth of the glass plate is half the thickness. The unground glass plate and the ground glass plate are sent to a SIMS device. Used in the primary ion Cs ^+, made of two glass plates ¹ H ^- count and ³⁰ Si ^- counting a sectional view in the depth direction, and then to acquire ³⁰ Si ^- count ¹ H ^- normalization of count ¹ H ^- / ³⁰ Si ^- Count The profile of the depth direction. Using ¹ H ^- / ³⁰ Si ^- counting the depth direction than the cross-sectional surface of the glass plate to FIG obtaining an average depth of ¹ H 0.5 ~ ^{1.5μm -} / ³⁰ Si ^- count ratio.

The average ¹ H ^- / ³⁰ Si ^- count ratio of the surface of the glass plate to the depth of 0.5 to 1.5 μm (surface layer) of the object to be evaluated is "surface hydrogen count", and the surface of the glass plate of the object to be evaluated by grinding 100 μm to a depth of 0.5~ The average ¹ H ^- / ³⁰ Si ^- count ratio of 1.5 μm (internal) is "internal hydrogen count", and the ratio of (surface hydrogen count / internal hydrogen count) is obtained. The value obtained here (surface hydrogen count / internal hydrogen count) is the value of (surface hydrogen concentration / internal hydrogen concentration). As described above, the inner region of the glass plate is different from the surface layer, and is a region in which the hydrogen concentration is almost constant. Therefore, in order to measure the internal hydrogen count, the glass plate is polished from the surface to a depth of 100 μm, or the thickness of the glass plate is 0.2 mm or less. When the thickness of the glass plate is half, even if there is a grinding depth error of, for example, ±10 μm, almost the same can be obtained. Internal hydrogen count value.

The measurement conditions of SIMS are as follows. Device: ADEPT1010 manufactured by ULVAC-PHI, Inc. Primary ion species: Acceleration voltage of Cs ⁺ primary ion: 5kV Current value of primary ion: 500nA Incident angle of primary ion: 60° normal to the surface of the sample : 300 × 300 μm ² Secondary ion polarity: Detection area of negative secondary ions: 60 × 60 μm ² (4% of the grid size of primary ions) Neutralization gun use: Converting the horizontal axis from sputtering time to depth Method: The depth of the analysis pit was measured by a stylus type surface shape measuring instrument (Dektak 150 manufactured by Veeco Co., Ltd.), and the sputtering rate of the primary ions was determined. Using this sputtering rate, the horizontal axis is converted from sputtering time to depth. Field Axis Potential at ¹ H ^- is detected: the optimum value may vary depending on the device. When the measurer sets the value, it must be noted that the background value is adequately blocked. Vacuum in the measurement chamber: 2.0 × 10 ^-9 Torr or less

[Method for Measuring Surface Na Count] The surface Na count value of the glass plate can be calculated by Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). The detailed measurement method is explained below. Further, in the same manner as the alkali metal other than Na, TOF-SIMS can be used to determine the surface alkali metal count value of the glass plate.

The glass plate of the evaluation object and the Si wafer having the SiO ₂ film of a known film thickness are sent to the TOF-SIMS device. Primary ion used in Bi ₃ ^++, ion sputtering using C ₆₀ ^++, to obtain ²³ Na ^{+ 28} Si ^+, and the depth of the counting direction sectional view obtained in the ²⁸ Si ^{+ 23} Na ⁺ count, normalization of the counts ²³ Na ⁺ / ²⁸ Si ⁺ count ratio in the depth direction profile. Next, the Si wafer having a known thickness of the SiO ₂ film ¹⁶ O ⁺ count and the depth direction of the cross-sectional view of FIG. ²⁸ Si ⁺ count, Collocation SiO ₂ film by sputtering rate of C ₆₀ ⁺⁺ ion sputtering . Using the sputtering rate, the horizontal axis of the ²³ Na ⁺ / ²⁸ Si ⁺ count ratio of the glass plate of the evaluation object was converted from the sputtering time to the depth. Then, the average ²³ Na ⁺ / ²⁸ Si ⁺ count ratio in the glass surface to the depth region of 10 nm was determined and used as the value of "surface Na count".

The measurement conditions of TOF-SIMS are as follows. Device: TOF.SIMS5 manufactured by ION-TOF Co., Ltd. Primary ion species: Bi ₃ ⁺⁺ Acceleration voltage of primary ion: 25kV Current value of primary ion: 0.1pA (@10kHz) Grid size of primary ion: 100×100μm ² primary ion Mode: High current bunching mode Secondary ion polarity: Medium and gun use: Sputtered ion species: C ₆₀ ⁺⁺ Accelerated voltage of sputtered ions: 10kV Current value of sputtered ions: 0.8nA (@10kHz) Grid size of sputtered ions: 300 × 300μm ² Measurement mode: noninterlaced mode

The glass plate of this embodiment can use various compositions. Specific examples thereof include aluminosilicate glass, soda lime glass, borosilicate glass, lead glass, basic bismuth glass, aluminoborosilicate glass, and alkali-free glass. Among them, glass containing a large amount of Na such as soda lime glass or aluminosilicate glass is preferable because it is difficult for the glass to diffuse to the surface of the glass plate. Further, in the use of solar cells, soda lime glass is preferred from the viewpoint of production cost. Further, the glass plate of the present embodiment can also be subjected to chemical strengthening treatment and used. For example, in the use of a cover glass for a solar cell, a glass plate such as a soda lime glass or an aluminosilicate glass which is chemically strengthened is preferable from the viewpoint of ensuring strength.

The alkali metal in the glass plate is contained in an unavoidable impurity or by active addition. For example, in the use of an alkali metal such as a liquid crystal display or a solar cell, the alkali metal may be one of the reasons for the performance deterioration, and the alkali metal in the alkali-free glass plate. The content is more than 0 and preferably 1000 ppm by mass or less. In this case, the alkali metal content is preferably 800 ppm by mass or less, more preferably 600 ppm by mass or less. Moreover, from the viewpoint of reducing the viscosity at the time of glass melting and easily producing glass, the lower limit is preferably 10 ppm by mass or more. When the alkali metal is Na, a suitable Na content is also the same as a suitable content of the above alkali metal.

The alkali-free glass can be used for a glass substrate for a display. In the liquid crystal display application, even if the glass plate contains only a small amount of alkali metal, the characteristics of the transparent conductive oxide film may be weakened. Therefore, it is preferable to use the glass plate of the embodiment in which the alkali metal is not easily diffused to the surface of the glass plate. . The alkali metal is particularly preferably Na. The alkali metal content exemplified by Na can be measured by, for example, atomic absorption spectrophotometry or ICP emission spectrometry after dissolving the glass with hydrofluoric acid or the like.

The thickness of the glass plate is not particularly limited. For example, in the use of a liquid crystal display, it is usually preferably 3 mm or less based on the viewpoint of weight reduction, preferably 1 mm or less, more preferably 0.7 mm or less, and particularly preferably 0.4 mm or less. Further, in order to suppress the deflection at the time of the step treatment, it is preferably 0.1 mm or more and more preferably 0.2 mm or more.

Further, the shape of the glass plate of the present embodiment is not particularly limited. For example, a glass plate having a uniform plate thickness, at least one of a front surface and a back surface having a curved shape and a three-dimensional shape such as a bent portion may be used. In the case of a display or a solar cell, since the flatness of the surface is required, it is preferable to use a flat plate having a uniform thickness.

The composition of the glass plate of the present embodiment is not particularly limited, and may be the following glass plate composition. (i) a glass which is an alkali-free glass, expressed as % by mole of oxide, containing SiO ₂ : 50 to 73%, Al ₂ O ₃ : 5 to 27%, B ₂ O ₃ : 0 to 12%, MgO: 0~12%, CaO: 0~15%, SrO: 0~24%, BaO: 0~15% and ZrO ₂ : 0~5%, and MgO+CaO+SrO+BaO: 7~29.5%. (ii) A glass which is an alkali glass (soda-lime glass) expressed by mol% based on an oxide, containing SiO ₂ : 65 to 75%, Al ₂ O ₃ : 0 to 5%, Na ₂ O: 9 ~17%, K ₂ O: 0~2%, MgO: 0~9% and CaO: 0~10%. (iii) A glass which is an alkali glass (aluminum silicate glass), expressed as % by mole of oxide, containing SiO ₂ : 55 to 75%, Al ₂ O ₃ : 5 to 20%, Na ₂ O : 3~20%, K ₂ O: 0~10% and MgO: 0~20% and CaO+SrO+BaO: 0~20%.

<Method for Producing Glass Plate> A method for producing the glass plate of the present embodiment will be described below, but the present invention is not limited thereto. The glass plate of the present embodiment can be produced, for example, by the following steps 1 to 5. Step 1: the step of melting the glass raw material; the step 2: the step of forming the glass plate; the step 3: the step of grinding the formed glass plate; the step 4: the step of performing the dehydration treatment in a dry gas atmosphere; Then the step of etching the surface layer.

(Step 1 and Step 2) The required glass raw material is put into a continuous melting furnace, and the glass raw material is heated and melted and clarified at a desired temperature of 1500 to 1600 ° C, and then supplied to a molding apparatus to form the molten glass into a plate shape, and then Xu cold can make glass plates.

Various methods can be used for forming the glass sheet. For example, various methods such as a down-draw method (such as an overflow down-draw method, a flow-down method, and a re-extension method), a floating glass plate method, a transfer method, a pressing method, and a melting method can be employed.

When it is intended to form a transparent conductive oxide film on a glass plate, the floating glass formed by the floating glass plate method is often produced by a polishing step of polishing a surface in contact with molten tin during molding. Since the polishing step can be replaced by the step 3 described later, the method for producing a glass sheet of the present embodiment is suitable for using a floating glass from the viewpoint of productivity. Further, the glass plate may be directly used as a commercially available product, or may be further subjected to chemical strengthening or physical strengthening in addition to the above steps 1 and 2.

(Step 3) The formed glass plate is ground to remove the deteriorated layer on the surface of the glass plate. The altered layer on the surface of the glass sheet is derived from a modified layer formed by processing in a method of producing a glass sheet. By removing the altered layer of the glass plate, the number of stanol groups (number of hydrogen atoms) present in the surface layer of the glass sheet in the step 4 described later can be appropriately controlled. The amount of polishing is not particularly limited, and it is preferable to polish about 100 μm in order to make the surface of the glass plate in the same state as the inside of the glass. However, when the thickness of the glass plate is 0.2 mm or less, the amount of grinding should be appropriately adjusted.

The polishing method may be a conventionally known polishing method, and the polishing conditions such as the polishing pressure are not limited. For example, cerium oxide or colloidal cerium oxide or the like may be used as the abrasive grains for grinding.

(Step 4) The ground glass plate is subjected to dehydration treatment in a dry gas atmosphere. The dry gas atmosphere is not particularly limited, and examples thereof include a dry nitrogen atmosphere, a dry argon atmosphere, and dry air. The glass plate is heated in the dry gas atmosphere for dehydration treatment. The dehydration treatment is a treatment method in which the stanol group on the surface of the glass plate is released from the system by Si-OH + Si-OH → Si-O-Si + H ₂ O by dehydration condensation. Thereby, the number of stanol groups (number of hydrogen atoms) present in the surface layer of the glass sheet can be reduced, thereby reducing the surface hydrogen concentration.

The heating temperature of the dehydration treatment may be at least a temperature at which the dehydration condensation reaction of the stanol group can be initiated, and the longer the heating time, the more the dehydration condensation reaction progresses. That is, when the heating temperature is low, the number of hydrogen atoms present on the surface or surface layer of the glass sheet can be reduced by elongating the heating time. Further, when the heating temperature is high, the number of hydrogen atoms can be reduced by a short heating time. For example, when the heating temperature is set to 640 ° C, the heating time in a dry nitrogen atmosphere is preferably 25 hours or more, and more preferably 50 hours or more.

(Step 5) Since the heating is performed in a dry gas atmosphere of dehydration treatment, a deteriorated layer is formed on the surface of the glass plate. Therefore, the surface of the glass plate needs to be etched after the dehydration treatment to remove the altered layer. For the etching, for example, hydrofluoric acid or a mixed acid solution of hydrofluoric acid and hydrochloric acid or the like can be used. The etching method is not particularly limited, and examples thereof include a method in which a glass plate is immersed in a chemical solution and a supersonic wave is simultaneously irradiated.

The amount of etching can be estimated from the change in weight of the glass plate before and after etching. If the altered layer is sufficiently removed and the dehydration condensation effect of the step 4 is sufficiently exhibited, it is preferably etched to about 0.2 μm. If the amount of etching is increased, the layer having reduced the hydrogen concentration in the surface layer by the dehydration condensation in the step 4 is accordingly reduced. That is, even if the dehydration condensation of the step 4 is carried out at a constant temperature and for a constant time, if the etching amount is large, the surface hydrogen concentration becomes lower than the temperature and/or at a later time. The same is true for dehydration condensation in a shorter period of time.

The glass plate of the present invention can be produced by the above steps 1 to 5.

When the resulting glass sheet is applied to an article, some treatment is generally applied. For example, when used as a glass substrate for a liquid crystal display, a thin film (ITO film) of an indium tin oxide (ITO) compound called ITO is often plated on a glass plate. The film formation temperature of the ITO film is, for example, about 350 °C. Further, it is also preferable to chemically strengthen the obtained glass plate to form a chemically strengthened glass plate. The chemically strengthened glass plate is a glass plate having an ion-exchanged compressive stress layer on the surface of the glass, for example, a glass plate containing sodium ions is brought into contact with an inorganic salt (molten salt) containing potassium ions. The temperature of the molten salt varies depending on the inorganic salt used, and is usually about 350 to 500 °C. The glass plate of the present embodiment is characterized in that the value shown in the surface layer hydrogen concentration/internal hydrogen concentration is still in the film formation process or after a high temperature process such as a heating step or a chemical strengthening treatment before or after the film formation. Below 0.80. Since the value of (surface hydrogen concentration/internal hydrogen concentration) is small, the alkali metal is less likely to diffuse to the surface layer of the glass, and the deterioration of the characteristics of the transparent conductive oxide film due to the diffusion of the alkali metal can be suppressed. Example

The invention is specifically illustrated by the following examples, but the invention is not limited thereto.

<Evaluation Method> (Surface Hydrogen Concentration/Internal Hydrogen Concentration) The method described in the above [(Surface hydrogen concentration/internal hydrogen concentration) measurement method] was used to derive (surface hydrogen concentration/internal hydrogen concentration) by SIMS. Further, the glass plate was polished from the surface to a depth of 100 μm (error ± 10 μm) to prepare a glass plate for internal hydrogen concentration measurement. This grinding was carried out using a cerium oxide slurry. Further, the drawing interval of the ¹ H ^- / ³⁰ Si ^- count ratio of the glass plate obtained by SIMS was about 0.006 μm each in the depth direction sectional view.

(Surface Na count) The surface Na count was derived by TOF-SIMS according to the method described in the above [Surface Na Count Measurement Method]. Further, when the surface layer Na count was measured, a glass plate obtained by subjecting the obtained glass plate to heat treatment at 350 ° C for 3 hours in an air atmosphere was used as a sample. The heat treatment conditions are longer than the heating conditions generally when the ITO film is formed on the glass plate.

<Example 1> An alkali-free glass plate (thickness: 0.5 mm) having the following composition was surface-polished to a depth of 100 μm. The polishing system uses a cerium oxide slurry. Thereby, the work-affected layer on the surface of the glass plate formed by the method for producing a glass plate is removed, so that the surface of the glass plate is in the same state as the main body. Next, the polished glass plate was subjected to heat treatment at 640 ° C for 25 hours in a dry nitrogen atmosphere having a dew point of minus 50 ° C to carry out dehydration condensation. Then, the glass plate was immersed in a mixed acid solution of 0.2% HF and 0.7% HCl for 4 minutes, and an etching of about 0.2 μm was performed by ultrasonic waves of 100 kHz to remove the altered layer formed by the heat treatment, thereby obtaining an example. 1 glass plate. Further, the etching thickness was calculated from the change in weight of the glass plate before and after the etching treatment. Glass composition (% by mole of oxide standard): SiO ₂ : 65%, Al ₂ O ₃ : 10%, B ₂ O ₃ : 8%, MgO: 5%, CaO: 7%, SrO: 4%

<Example 2> A glass plate of Example 2 was obtained in the same manner as in Example 1 except that the heating time of the heat treatment was 52 hours. <Example 3> A glass plate of Example 3 was obtained in the same manner as in Example 1 except that the heating time of the heat treatment was 120 hours. <Comparative Example 1> A glass plate of Comparative Example 1 was obtained in the same manner as in Example 1 except that the heating time of the heat treatment was set to 0 hours. <Comparative Example 2> A glass plate of Comparative Example 2 was obtained in the same manner as in Example 1 except that the heating time of the heat treatment was changed to 3 hours.

Various evaluations were made for the obtained glass sheets. The results are shown in Table 1. The "reduction rate (%) of surface layer Na" in Table 1 is a value obtained by subjecting the glass plate of Comparative Example 1 which was not subjected to heat treatment in a dry nitrogen atmosphere to the surface layer Na after heat treatment in an air atmosphere. Further, Fig. 1 is a graph showing the relationship between the surface layer hydrogen concentration/internal hydrogen concentration of the glass sheets obtained in the examples and the comparative examples and the surface Na count after heat treatment in an atmospheric environment.

[Table 1]

In the test example, since Comparative Example 1 was not subjected to heat treatment in a dry nitrogen atmosphere, it was a glass plate which was not dehydrated and condensed. As shown in Table 1 and Fig. 1, the glass sheets of the examples (the surface layer hydrogen concentration/internal hydrogen concentration) were all lower than 0.80. As a result, Na (surface Na count) which is present on the surface layer of the glass is reduced by nearly 30% or more than 30%, compared with the glass sheet which has not been dehydrated and condensed in Comparative Example 1, after heat treatment in an atmosphere. Therefore, it can be said that a glass plate which does not easily diffuse Na to the surface of the glass plate is obtained.

The present invention has been described in detail with reference to the specific embodiments thereof, and it is obvious that those skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. The present application is based on a Japanese patent application filed on Apr. 22, 2016, the disclosure of which is hereby incorporated by reference.

Industrial Applicability The alkali metal of the glass plate of the present invention does not easily diffuse to the surface of the glass plate. Therefore, it is suitable for use in applications in which an alkali metal such as Na is weakened, such as a substrate for a display or a substrate for a solar cell.

Fig. 1 is a graph showing the relationship between the surface layer hydrogen concentration/internal hydrogen concentration of each of the glass sheets obtained in the examples and the comparative examples and the surface Na counts of the respective glass sheets after heat treatment.

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Claims (12)

A glass plate having a value of (the surface layer hydrogen concentration/internal hydrogen concentration) of 0.80 or less, wherein the surface layer hydrogen concentration is an average value of the hydrogen concentration in the region from the surface of the glass plate to a depth of 0.5 to 1.5 μm, and the internal hydrogen concentration has been The glass plate removes the surface to the depth of the surface of the glass plate after the depth of 100 μm to a concentration of hydrogen in a region of 0.5 to 1.5 μm; if the thickness of the glass plate is 0.2 mm or less, the internal hydrogen concentration is a depth region at which half of the thickness of the glass plate is removed. The concentration of hydrogen in the area of the rear glass plate to a depth of 0.5 to 1.5 μm. The glass plate of claim 1, wherein the value (the surface hydrogen concentration/internal hydrogen concentration) is 0.40 or more. The glass plate of claim 1 or 2, wherein the value (the surface layer hydrogen concentration/internal hydrogen concentration) is 0.65 or less. The glass plate according to any one of claims 1 to 3, wherein the value (the surface layer hydrogen concentration/internal hydrogen concentration) is 0.50 or less. A glass sheet according to any one of claims 1 to 4 which is a float glass. A glass plate according to any one of claims 1 to 5 which is an alkali-free glass. The glass plate of claim 6 has a Na content of more than 0 and less than 1000 ppm by mass. A glass substrate for a display, comprising the glass plate according to any one of claims 5 to 7. A glass plate according to any one of claims 1 to 5 which is a soda lime glass. A glass sheet according to any one of claims 1 to 5 which is an aluminosilicate glass. The glass sheet of claim 9 or 10 is chemically strengthened. A glass substrate for a solar cell, comprising the glass plate according to any one of claims 9 to 11.