JP6428344B2 - Glass substrate - Google Patents

Description

  The present invention relates to a glass substrate.

In a solar cell, a semiconductor film is formed on a glass substrate as a photoelectric conversion layer.
As a semiconductor used for a solar cell, for example, a group 11-13 compound semiconductor and a group 11-16 compound semiconductor having a chalcopyrite crystal structure, a cubic system 12-16 compound semiconductor, or a hexagonal system group 12-16 A compound semiconductor etc. are mentioned. These compound semiconductors have a large absorption coefficient for light in the visible to near-infrared wavelength range. Therefore, these compound semiconductors are expected as materials for improving the efficiency of thin film solar cells. A typical example is Cu (In, Ga) Se ₂ (hereinafter referred to as CIGS).

  For example, in Patent Document 1, in a CIGS solar cell including a CIGS layer, the presence of an alkali metal such as sodium (Na) in the CIGS layer improves the carrier concentration and improves the energy conversion efficiency. The effect is described. Furthermore, according to Patent Document 1, by using a glass substrate containing one or more alkali metals and providing a back electrode layer containing molybdenum (Mo) and tungsten (W) between the CIGS layer and the glass substrate, It describes that an alkali metal can be diffused from a glass substrate to a CIGS layer.

As described in Patent Document 2, when a compound semiconductor layer is formed on a glass substrate, a heat treatment step of about 500 to 600 ° C. is required.
Patent Document 3 also describes that in order to produce a solar cell with good power generation efficiency, heat treatment at a higher temperature is preferable, and the glass substrate is required to withstand the heat treatment at a high temperature.

International Publication No. 2011/158841 JP 2014-97916 A International Publication No. 2013/111749

In the float process, when the glass substrate is rolled and transported in the slow cooling step, SO ₂ gas (sulfurous acid gas) is blown in the air to the glass plate having a high temperature in order to prevent scratches on the glass substrate surface by the roll. Alternatively, a method may be used in which a sulfate is precipitated on the surface of the glass to protect it by reacting with a glass component. Examples of the sulfate include Na salt, K salt, Ca salt, Sr salt, Ba salt and the like. Usually, a composite of these salts is deposited on the surface of the glass substrate.

The SO ₂ spraying process (hereinafter referred to as SO ₂ process) is a process of spraying SO ₂ gas from the first surface side of the glass substrate formed into a plate shape. The first surface is a surface in contact with the conveying roller. The SO ₂ process may be performed only on the first surface, or may be performed on other surfaces. When SO ₂ gas is sprayed on the surface of the glass substrate, a protective film containing an alkali metal sulfate such as Na or K or an alkaline earth metal sulfate is formed. By forming a protective film on the surface of the glass substrate, it becomes difficult to be scratched during transportation.

As described in Patent Documents 2 and 3, when a compound semiconductor layer is formed on a glass substrate, a heat treatment step of about 500 to 600 ° C. or higher is necessary, compared with general soda lime glass. A glass substrate that is difficult to deform at high temperatures is required.
Among the components of glass, the abundance ratio between alkali metal oxides such as Na and K and alkaline earth metal oxides is higher or equivalent to alkali metal oxides in soda lime glass. The glasses described in Patent Documents 2 and 3 are characterized by an increase in the abundance ratio of alkaline earth metal oxides. This is because the glass transition temperature is generally higher when the alkaline earth metal oxide is more than the alkali metal oxide, and the glass is not deformed to a higher temperature.

The protective film containing sulfate produced by the SO ₂ treatment makes it difficult to scratch the substrate surface. However, glass substrates for CIGS solar cells have many alkaline earth metal oxides as glass components, and precipitated sulfates are also included. There is a tendency for alkaline earth metal sulfate to be relatively high. However, alkaline earth metal sulfates, especially BaSO _4, are difficult to remove by water washing or the like. For example, Patent Document 2 proposes that the mass ratio SrO / BaO of the oxide contained in the glass substrate be specified to be 1 or more in order to facilitate cleaning and removal of the sulfate protective film. According to Patent Document 2, by prescribing such a mass ratio, easily water-soluble SrSO ₄ is preferentially precipitated as compared with BaSO _4, and sulfuric acid is washed by water washing or the like before product shipment. It is described that the salt protective film can be easily removed.

However, SrSO ₄ may be more easily dissolved in water than BaSO ₄ , but there is a demand to remove the sulfate protective film on the substrate surface with higher accuracy as the efficiency of solar cells increases.

  In addition, if the glass substrate breaks during transportation of the glass substrate in the manufacturing process of the solar cell or in the usage environment after manufacturing the solar cell, it leads to a decrease in yield and an increase in the defective product rate. A substrate is desired. In addition, since solar cells are used outdoors, a glass substrate with high acid resistance on the glass surface that can withstand long-term use is desired.

  In order to improve the strength of the glass or the acid resistance of the glass, the composition of the glass substrate itself may be adjusted. However, as described above, in order to use as a substrate for a CIGS solar cell, it is necessary that the substrate be a substrate that is difficult to be deformed even in a heat treatment step of about 500 to 600 ° C. by diffusing an alkali metal into the CIGS layer. Accordingly, there is a need for a glass substrate that simultaneously satisfies the conditions that a sulfate protective film that has a high acid resistance and strength on the glass surface and can be easily removed by washing can be formed.

  An object of the present invention is to provide a glass substrate capable of forming a sulfate protective film that has a high acid resistance and strength on the glass surface and is easier to wash and remove.

According to one embodiment of the present invention, the first substrate surface includes silicon, an alkali metal, an alkaline earth metal, and oxygen, and has a glass transition temperature of 640 ° C. or higher. The first hydrogen ion concentration at any depth from 500 nm to 5000 nm from the substrate surface of X is X [ppm], and the second hydrogen at any depth from 40 nm to 60 nm from the first substrate surface When the ion concentration is set to Y [ppm], an acid resistance test is performed in which the hydrogen ion concentration ratio Y / X is 3.0 or more and the sample is immersed in dilute hydrochloric acid having a concentration of 1 mol / liter maintained at 90 ° C. for 20 hours. A glass substrate having an elution amount of 0.5 mg / cm ² or less and a Vickers hardness Hv of 500 or more is provided.

  According to one embodiment of the present invention described above, it is possible to provide a glass substrate that can form a sulfate protective film that has high acid resistance and strength and is easier to remove by washing.

It is a section schematic diagram of the glass substrate concerning one embodiment of the present invention. It is a conceptual diagram explaining the assumption mechanism in the manufacturing method of the glass substrate which concerns on one Embodiment of this invention. It is a diagram showing the ²⁷ Al-MAS NMR spectra of a glass substrate according to the embodiment.

The aspect which concerns on one Embodiment of this invention is demonstrated below.
FIG. 1 shows a schematic cross-sectional view of a glass substrate 1 of the present embodiment. The dimensions and shape of the glass substrate of the present invention are not limited to the description in the embodiment.

The glass substrate 1 has a first substrate surface 11, contains silicon, an alkali metal, an alkaline earth metal, and oxygen, has a glass transition temperature of 640 ° C. or higher, and has a first substrate surface 11. The first hydrogen ion concentration at any depth from 500 nm to 5000 nm is defined as X [ppm], and the second hydrogen ion concentration at any depth from 40 nm to 60 nm from the first substrate surface 11 is defined as In the case of Y [ppm], when the acid resistance test was performed, the hydrogen ion concentration ratio Y / X was 3.0 or more and the sample was immersed in dilute hydrochloric acid having a concentration of 1 mol / liter maintained at 90 ° C. for 20 hours. The elution amount is 0.5 mg / cm ² or less, and the Vickers hardness Hv is 500 or more. The hydrogen ion concentration can be measured by secondary ion mass spectrometry (SIMS).

In the present embodiment, when the depth at which the first hydrogen ion concentration X is measured, for example, when the depth from the first substrate surface 11 is represented by D1 as shown in FIG. 1, D1 is 500 nm or more and 5000 nm or less. It is.
In this embodiment, when the depth at which the second hydrogen ion concentration Y is measured, for example, when the depth from the first substrate surface 11 is represented by D2 as shown in FIG. 1, D2 is 40 nm or more. 60 nm or less.
The above-mentioned hydrogen ion concentration ratio Y / X is the first hydrogen ion concentration X at any depth in the range of 500 nm to 5000 nm and the second hydrogen at any depth in the range of 40 nm to 60 nm. It is a ratio with the ion concentration Y. The hydrogen ion concentration ratio Y / X may be 3.0 or more.

When the hydrogen ion concentration ratio Y / X is less than 3.0, the effect of promoting the ion exchange reaction (described later) between hydrogen ions and alkali metals and alkaline earth metals cannot be expected. Y / X is preferably 3.5 or more, more preferably 4.0 or more, still more preferably 4.5 or more, and particularly preferably 5.0 or more.
Y / X is preferably 30 or less. If Y / X exceeds 30, the ion exchange reaction between hydrogen ions and alkali metals and alkaline earth metals results in excessive hydrogen ions and the internal structure on the glass surface layer becomes sparse. Therefore, for example, when a heat treatment is performed during film formation in a solar cell manufacturing process, a difference in expansion coefficient is generated between the glass surface and the inside, which may cause cracks in the glass substrate. Y / X is more preferably 25 or less, and still more preferably 22 or less.

When the glass substrate 1 is immersed in dilute hydrochloric acid having a concentration of 1 mol / liter maintained at 90 ° C. for 20 hours as an acid resistance test, the elution amount from the glass surface is 0.5 mg / cm ² or less. When the elution amount exceeds 0.5 mg / cm ² , when the glass substrate is used outdoors, the transparency may not be maintained for a period of, for example, 10 years or longer. Elution amount is more preferably 0.1 mg / cm ² or less, even more preferably at 0.05 mg / cm ² or less, more further preferably 0.02 mg / cm ² or less, particularly preferably 0.01mg / Cm ² or less. Incidentally, the surface area of the glass substrate has, for example, a 1.1mm thickness, if the test piece length of one side is 30 mm, is 3cm × 3cm × 2 + 3cm × 0.11cm × 4 = 19.32cm 2 .

  The Vickers hardness Hv of the glass substrate 1 is preferably 500 or more, more preferably 600 or more, further preferably 650 or more, and particularly preferably 680 or more.

If the glass transition temperature of the glass substrate 1 is 640 degreeC or more, CIGS layer formation in high temperature is possible, and formation of a good quality CIGS layer can be ensured. If the glass transition temperature Tg of the glass substrate 1 is less than 640 ° C., the glass substrate may be deformed in the process of forming the photoelectric conversion layer exposed to a high temperature, and the yield of solar cells may be reduced. The Tg of the glass substrate 1 is more preferably 650 ° C. or higher, further preferably in the order of 660 ° C. or higher and 670 ° C. or higher, and particularly preferably 675 ° C. or higher.
The upper limit value of Tg of the glass substrate 1 is preferably 750 ° C. or lower. If Tg is higher than 750 ° C., the viscosity of the glass raw material at the time of melting increases, which may make it difficult to produce. Furthermore, when Tg is larger than 750 ° C., the expansion coefficient of the glass substrate is decreased. In the process of forming the photoelectric conversion layer, there is a mismatch in the expansion coefficient between the glass substrate and the photoelectric conversion layer, and the photoelectric conversion layer is easily peeled off from the glass substrate, or the other member constituting the solar cell and the glass substrate There is a risk of expansion coefficient mismatch, and the other members may be damaged by long-term use. The Tg of the glass substrate 1 is more preferably 720 ° C. or less, and further preferably 700 ° C. or less.

The glass substrate 1 passes the glass substrate in an atmosphere having a glass transition temperature or higher (640 ° C. or higher), an H ₂ concentration of a [%], and an N ₂ concentration of (100−a) [%]. This is achieved by a process (sometimes referred to as a hydrogen treatment process). However, a is more than 0 and 100 or less, and a is preferably 50 or less. The conditions for the hydrogen treatment process may be set as appropriate so that the hydrogen ion concentration ratio Y / X of the glass substrate 1 after the hydrogen treatment is 3.0 or more.

  The manufacturing method of the glass substrate 1 includes a melting process, a clarification process, a molding process, and a slow cooling process, as well as a conventional glass substrate manufacturing method, in addition to a hydrogen treatment process. The glass substrate 1 is preferably manufactured by a float method or a fusion method (down draw method), and more preferably manufactured by a float method. In the float process, the structure of the glass surface is formed when passing through the slow cooling process from the float bath. Therefore, the glass substrate 1 can be achieved more effectively by providing a hydrogen treatment process between the float bath and the slow cooling process. Furthermore, in the subsequent sulfate protective film formation process (described later), it is possible to form a sulfate protective film that is easier to clean and remove. Moreover, if it is a float process, the plate-shaped and large area glass substrate 1 can be shape | molded easily and stably.

When a sulfate protective film is formed on the first substrate surface 11 of the glass substrate 1, a process of blowing SO ₂ gas onto the first substrate surface 11 (hereinafter referred to as SO ₂ process) is performed in the slow cooling step. Is done. The SO ₂ treatment is performed when the glass substrate 1 is cooled to room temperature in a slow cooling furnace in the slow cooling step, and a sulfate protective film is formed on the first substrate surface 11 of the glass substrate 1. Then, the process (henceforth a cleaning process) which wash | cleans the glass substrate 1 is implemented, and the sulfate protective film formed in the 1st board | substrate surface 11 is removed. After the cleaning step, the glass substrate 1 is appropriately cut to a desired size and provided to a solar cell manufacturing process or the like.

According to the glass substrate 1, it is possible to form a sulfate protective film that has high acid resistance and strength on the glass surface and is easier to remove by washing. Therefore, the sulfate protective film can be more easily removed in the above-described cleaning process. The reason why the sulfate protective film can be easily removed is considered to be because the proportion of the alkali metal salt in the sulfate protective film increases when the SO ₂ treatment is performed.

  In the hydrogen treatment step described above, when the first substrate surface 11 of the glass substrate 1 is exposed to a hydrogen atmosphere at a temperature equal to or higher than the glass transition temperature Tg, dehydration condensation occurs on the first substrate surface 11 and siloxane bonds ( Si—O—Si bond) increases. The reaction formula for dehydration condensation is shown below.

-Si-OH + HO-Si- → -Si-O-Si- + H 2 O

FIG. 2 shows a conceptual diagram showing a mechanism assumed to occur inside the first substrate surface 11 and the substrate when the first substrate surface 11 of the glass substrate 1 is subjected to hydrogen treatment. Yes. In FIG. 2, Si represents a silicon atom, O represents an oxygen atom, H represents a hydrogen atom, R ⁺ represents an alkali metal atom, and R ²⁺ represents an alkaline earth metal atom.

FIG. 2A shows an assumed mechanism of siloxane bond formation by dehydration condensation on the surface layer of the first substrate surface 11.
By increasing the number of siloxane bonds having high bond strength, the Vickers hardness Hv of the glass substrate 1 is increased, and the strength of the glass substrate 1 is improved. As a result, according to the glass substrate 1, the crack in the use environment after manufacture in a solar cell manufacturing process or after solar cell manufacture can be suppressed.
Since the activity of SiO ₂ is larger than the activity of HSiO ₃ ⁻ ions and SiO ₃ ²⁻ ions up to about 9 and is stable, the acid resistance of the glass substrate 1 is improved by increasing the siloxane bond. . If the glass substrate 1 is used as a solar cell substrate, the solar cell can be durable enough to withstand long-term use outdoors.

FIG. 2B shows an assumed mechanism of the ion exchange reaction on the surface layer of the first substrate surface 11.
Due to the dehydration condensation reaction in the surface layer of the first substrate surface 11, the hydrogen ion (H ⁺ ) concentration in the surface layer decreases, and a hydrogen ion concentration gradient is generated between the surface layer and the inside of the glass substrate 1. This concentration gradient becomes a driving force, and H ⁺ diffuses from the inside of the glass substrate 1 to the surface layer. In order to compensate for the reduced charge due to the diffusion of H ⁺ into the surface layer, alkali metals and alkaline earth metals contained in the glass substrate 1 diffuse into the substrate. H ⁺ diffused to the glass surface layer combines with oxygen atoms to newly generate hydroxyl groups.

FIG. 2C shows an assumed mechanism of a dehydration condensation reaction of a hydroxyl group newly generated on the first substrate surface 11.
A dehydration condensation reaction of a newly generated hydroxyl group occurs, and a siloxane bond is formed. In the glass substrate 1 of the present embodiment, it is considered that the reaction of the mechanism as described above (FIGS. 2A to 2C) is repeatedly generated.

The glass substrate 1 of the present embodiment satisfies the relationship that the hydrogen ion concentration ratio Y / X is 3.0 or more. This hydrogen ion concentration ratio is considered to be due to the movement of hydrogen ions, alkali metals, and alkaline earth metals due to the mechanism described above on the first substrate surface 11 and inside the substrate. By satisfying the relationship that the hydrogen ion concentration ratio Y / X is 3.0 or more, siloxane bonds are increased in the surface layer of the first substrate surface 11, and the acid resistance and strength of the glass substrate 1 are increased. Further, in the glass substrate 1 satisfying the relationship that the hydrogen ion concentration ratio Y / X is 3.0 or more, the alkaline earth metal diffuses inward, and the alkaline earth metal concentration in the surface layer of the first substrate surface 11 decreases. To do. As a result, according to the glass substrate 1, the concentration of the alkaline earth metal sulfate contained in the sulfate protective film after the SO ₂ treatment can be reduced. That is, according to the glass substrate 1, it is possible to form a sulfate protective film that is easy to clean and remove.

In the present embodiment, the first molar fraction of sulfate generated when SO ₂ gas is brought into contact with the first substrate surface 11 of the glass substrate 1 at 300 ° C. or higher is expressed as M1 = R ₂ SO ₄ / ( R ₂ SO ₄ + R′SO ₄ ) Further, the second molar fraction of sulfate produced when SO ₂ gas is brought into contact with the first exposed surface exposed by polishing the first substrate surface 11 of 5000 nm or more at 300 ° C. or higher is expressed as M2 = R ₂ SO ₄ / (R ₂ SO ₄ + R′SO ₄ ) However, R is at least one of Na and K, and R ′ is at least one of Mg, Ca, Sr, and Ba. Note that the surface exposed by polishing the first substrate surface 11 by 5000 nm or more is in a state equivalent to the surface not subjected to the above-described hydrogen treatment.
In the glass substrate 1, the ratio M1 / M2 between the first molar fraction M1 and the second molar fraction M2 is preferably 1.00 or more, and more preferably 1.10 or more. When the glass substrate 1 satisfies such a molar fraction ratio M1 / M2, the concentration of the alkali metal sulfate in the sulfate protective film generated after the SO ₂ treatment becomes higher than the concentration of the alkaline earth metal salt. Therefore, the sulfate protective film formed on the glass substrate 1 becomes easier to remove by washing.

When the glass substrate 1 performs the following acid resistance test on the substrate, the amount of elution from the substrate preferably satisfies the relationship shown below.
The glass substrate 1 is cut into a rectangular shape, and six surfaces are mirror-polished to produce a first test piece having a thickness of 1.1 mm and a side length of 30 mm. The amount of elution when the acid resistance test is conducted for 20 hours in dilute hydrochloric acid with a concentration of 1 mol / liter maintained at 90 ° C. is defined as the first elution amount Z1 [μg]. The first test piece is subjected to the above-described hydrogen treatment step after mirror polishing and before being immersed in dilute hydrochloric acid.
The first substrate surface 11 is polished by 5000 nm or more, and after polishing, the glass substrate 1 is cut into a rectangular shape, and six surfaces are further mirror-polished, the thickness is 1.1 mm, and the length of one side is 30 mm. The second elution amount is the second elution amount when an acid resistance test is performed in which two test pieces are prepared and the second test piece is immersed in dilute hydrochloric acid having a concentration of 1 mol / liter maintained at 90 ° C. for 20 hours. Let Z2 [μg].
The ratio Z1 / Z2 between the first elution amount Z1 and the second elution amount Z2 is preferably 0.8 or less, and more preferably 0.7 or less. If the elution amount ratio Z1 / Z2 is satisfied, the acid resistance of the glass substrate 1 can be further improved. If the glass substrate 1 is used as a solar cell substrate, the solar cell can be durable enough to withstand long-term use outdoors.

The glass substrate 1 preferably satisfies the following Vickers hardness relationship.
The Vickers hardness of the first substrate surface 11 is defined as first Vickers hardness Hv1 [N / mm ² ]. The Vickers hardness of the exposed surface exposed by polishing the first substrate surface 11 by 5000 nm or more is defined as second Vickers hardness Hv2 [N / mm ² ]. The measurement of Vickers hardness is performed by the method described in JIS Z 2244 under the condition that the dew point is −50 ° C. and the indentation load is 0.98 N.
In the glass substrate 1, the ratio Hv1 / Hv2 between the first Vickers hardness Hv1 and the second Vickers hardness Hv2 is preferably 1.00 or more.
If it is such Vickers hardness ratio Hv1 / Hv2, the intensity | strength of the glass substrate 1 is high, and it can suppress the crack in the use environment after manufacture in a solar cell manufacturing process, or after solar cell manufacture.

The glass substrate 1 preferably further contains aluminum. If the content of Al ₂ O ₃ in the glass substrate 1 is 7% or more and 20% or less in terms of a mass percentage based on the oxide, the strength of the glass substrate 1 is more preferable.

When the glass substrate 1 further contains aluminum, in the ²⁷ Al-MAS NMR spectrum of the glass substrate 1, it is preferable that the integrated intensity in a predetermined chemical shift satisfies the following relationship.
That is, in the ²⁷ Al-MAS NMR spectrum of the glass substrate 1, the integrated intensity in the range of 20 ppm to 85 ppm is the first integrated intensity α, and the integrated intensity in the range of 10 ppm to 40 ppm is the second integrated intensity β. The integrated intensity in the range of −20 ppm to 15 ppm is defined as a third integrated intensity γ. In this case, the integrated intensity ratio α / (α + β + γ) in the glass substrate 1 is preferably 0.9 or more.
As a method for evaluating the coordination number of aluminum contained in the glass substrate 1, a ²⁷ Al-MAS NMR spectrum can be mentioned. In this embodiment, the detection value in the range of 20 ppm or more and 85 ppm or less is derived from 4-coordinate, the detection value in 10 ppm or more and 40 ppm or less is derived from 5 coordination, and the detection value in the range of −20 ppm or more and 15 ppm or less is determined to be derived from 6 coordination. To do. If the integrated intensity ratio α / (α + β + γ) is 0.9 or more, the aluminum contained in the glass substrate 1 has a high proportion of being contained as a four-coordinate.

In a glass containing Al ₂ O ₃ , alkali metal ions such as Na ⁺ and K ⁺ are more easily coordinated with [AlO ₄ ] ⁻ in the glass than with H ⁺ , and thus a dehydration condensation reaction is used as a driving force. Alkali metal diffusion hardly occurs in the glass interior direction. On the other hand, since the alkaline earth metal is difficult to coordinate with [AlO ₄ ] ⁻ , diffusion of the alkaline earth metal with the dehydration condensation reaction as a driving force to the inside of the glass easily occurs.
For the above reasons, the alkaline earth metal concentration in the surface layer of the first substrate surface 11 decreases, and the proportion of the alkaline earth metal that reacts with the SO ₂ gas in the glass surface layer decreases. Furthermore, when the siloxane bond is increased by the dehydration condensation reaction on the glass surface layer, the number of hydroxyl groups serving as a diffusion path for the alkaline earth metal decreases, and the alkaline earth metal is difficult to diffuse into the glass surface layer. As a result, the ratio of the alkaline earth metal salt in the sulfate produced by the reaction with the SO ₂ gas on the surface layer of the first substrate surface 11 decreases. On the other hand, since alkali metals can be easily diffused through [AlO ₄ ] ⁻ in the glass at a temperature equal to or higher than the glass transition temperature Tg, the alkali metal sulfate easily reacts with the SO ₂ gas. Form. Alkali metal sulfates are more soluble in water and have higher detergency with water than alkaline earth metal salts.

The glass substrate 1 has a mass percentage based on the following oxides at a depth of 5000 nm or more from the first substrate surface 11, and SiO ₂ is 45% to 75%, Al ₂ O ₃ is 7% to 20%, MgO 0% to 15%, CaO 0% to 15%, SrO 0% to 18%, BaO 0% to 18%, Na ₂ O 1% to 20%, K ₂ O Is 0.1% to 20%, ZrO ₂ is 0% to 10.5%, Na ₂ O + K ₂ O is 1.1% to 30%, and MgO + CaO + SrO + BaO is 1% to 40%. It is preferable. With such a composition, the strength and acid resistance of the glass substrate 1 are further improved.

SiO ₂ is a component that forms a glass skeleton. If the content of SiO ₂ is less than 45% by mass (hereinafter simply referred to as “%”), the heat resistance and chemical durability of the glass are lowered, and the average thermal expansion coefficient may be increased. The content of SiO ₂ is preferably 48% or more, more preferably 51% or more.
If the SiO ₂ content exceeds 75%, the high-temperature viscosity of the glass increases, which may cause a problem of deterioration in solubility. The content of SiO ₂ is preferably 70% or less, more preferably 65% or less, and further preferably 60% or less.

Al ₂ O ₃ is a component that increases the glass transition temperature, improves weather resistance (discoloration and solarization), heat resistance and chemical durability, and increases Young's modulus. If the content of Al ₂ O ₃ is less than 7%, the glass transition temperature may be lowered. Moreover, there exists a possibility that an average thermal expansion coefficient may increase. The content of Al ₂ O ₃ is preferably 8% or more, more preferably 10% or more, and further preferably 12% or more.
If the content of Al ₂ O ₃ exceeds 20%, the high-temperature viscosity of the glass increases and the solubility may be deteriorated. Further, the devitrification temperature is increased, and the moldability may be deteriorated. The content of Al ₂ O ₃ is preferably 18% or less, more preferably 15% or less, and still more preferably 14% or less.

  MgO has the effect of lowering the viscosity at the time of melting the glass and promoting the melting. MgO can be contained up to 15% in the glass substrate. The content of MgO is preferably 0.05% or more, more preferably 0.1% or more, and further preferably 0.15% or more. If the MgO content exceeds 15%, the average thermal expansion coefficient may increase. Further, the devitrification temperature may increase. The content of MgO is preferably 10% or less, more preferably 5% or less, and even more preferably 3% or less.

  CaO has the effect of lowering the viscosity at the time of melting the glass and promoting the melting. CaO can be contained up to 15% in the glass substrate. The content of CaO is preferably 1% or more, more preferably 2% or more, still more preferably 3% or more, and particularly preferably 5% or more. If the CaO content exceeds 15%, the average thermal expansion coefficient of the glass may increase. The CaO content is preferably 10% or less, more preferably 9% or less, and even more preferably 8% or less.

  SrO has the effect of lowering the viscosity at the time of melting the glass and promoting the melting. SrO can be contained in the glass substrate up to 18%. The SrO content is preferably 0.5% or more, more preferably 2% or more, still more preferably 5% or more, and particularly preferably 7% or more. If the SrO content exceeds 18%, the average thermal expansion coefficient of the glass increases, the density increases, and the glass may become brittle. The SrO content is preferably 15% or less, more preferably 14% or less, still more preferably 13% or less, and particularly preferably 12% or less.

  BaO has an effect of reducing the viscosity at the time of melting the glass and promoting the melting. BaO can be contained in the glass substrate at 18% or less. The content of BaO is preferably 0.5% or more, more preferably 1% or more, and further preferably 1.5% or more. If the content of BaO exceeds 18%, the average thermal expansion coefficient of the glass substrate may be increased. In addition, the specific gravity increases, the density increases, and the glass may become brittle. The BaO content is preferably 8% or less, more preferably 6% or less, still more preferably 5% or less, and particularly preferably 4% or less.

Na ₂ O is a component that contributes to improving the power generation efficiency of a solar cell including a photoelectric conversion layer such as CIGS. Further, Na ₂ O has an effect of lowering the viscosity at the glass melting temperature and facilitating melting. Na diffuses into the photoelectric conversion layer formed on the glass substrate, and can improve power generation efficiency. If the content of Na ₂ O is less than 1%, the amount of Na diffusion into the photoelectric conversion layer on the glass substrate becomes insufficient, and the power generation efficiency may be insufficient. The content of Na ₂ O is preferably 2% or more, more preferably 2.5% or more, still more preferably 3% or more, and particularly preferably 3.5% or more. If the content of Na ₂ O exceeds 20%, the glass transition temperature decreases, the average thermal expansion coefficient increases, or the chemical durability deteriorates. The content of Na ₂ O is preferably 15% or less, more preferably 11% or less, still more preferably 9% or less, and particularly preferably 7% or less.

K ₂ O exhibits the same effect as Na ₂ O. Furthermore, K ₂ O is a component that promotes the effect that Na ₂ O contributes to the improvement of power generation efficiency of a solar cell including a photoelectric conversion layer such as CIGS. If the content of K ₂ O is less than 0.1%, the power generation efficiency of the solar cell may be insufficient. The content of K ₂ O is preferably 2% or more, more preferably 3% or more, and further preferably 3.5% or more. If the content of K ₂ O exceeds 20%, the diffusion of Na is inhibited, and the power generation efficiency is lowered, or the glass transition temperature is lowered, and the average thermal expansion coefficient may be increased. The content of K ₂ O is preferably 15% or less, more preferably 12% or less, still more preferably 10% or less, and particularly preferably 6% or less.

ZrO ₂ is a component that has the effect of lowering the viscosity at the time of melting the glass, promoting the melting, and increasing the Tg, and may be incorporated up to 10.5%. The ZrO ₂ content is preferably 0.5% or more, more preferably 1% or more, still more preferably 1.5% or more, and particularly preferably 2% or more. If ZrO ₂ is contained up to more than 10.5%, the power generation efficiency is lowered, the devitrification temperature is increased, and the average thermal expansion coefficient of the glass substrate may be increased. The ZrO ₂ content is preferably 9% or less, more preferably 7% or less, and even more preferably 5% or less.

In order to sufficiently lower the viscosity at the glass melting temperature and to improve the power generation efficiency of the CIGS solar cell, Na ₂ O and K ₂ O may be combined up to 30%. The total amount of Na ₂ O and K ₂ O is preferably 5% or more, more preferably 8% or more, and further preferably 9% or more. If the total amount of Na ₂ O and K ₂ O exceeds 30%, Tg is too low and the average thermal expansion coefficient may be too high. The total amount of Na ₂ O and K ₂ O is preferably 20% or less, more preferably 17% or less, still more preferably 15% or less, and particularly preferably 13% or less.

  The total amount of MgO, CaO, SrO and BaO can be made 1 to 40% from the viewpoint of reducing the viscosity at the time of melting the glass and promoting the melting. The total amount of MgO, CaO, SrO and BaO is preferably 6% or more, more preferably 9% or more, further preferably 12% or more, and particularly preferably 14% or more. If the total amount of MgO, CaO, SrO and BaO exceeds 40%, the average thermal expansion coefficient increases, and the devitrification temperature may increase. The total amount of MgO, CaO, SrO and BaO is preferably 30% or less, more preferably 25% or less, and even more preferably 22% or less.

It is preferable that the glass substrate 1 of this embodiment consists essentially of the said composition. In addition, the glass substrate 1 of this embodiment may contain other components typically in 5% or less in the range which does not impair the objective of this invention. For example, for the purpose of improving weather resistance, solubility, devitrification, ultraviolet shielding, etc., the glass substrate 1 is made of B ₂ O ₃ , ZnO, Li ₂ O, WO ₃ , Nb ₂ O ₅ , V ₂ O ₅ , Bi ₂ O _3, MoO _3, and among such _P 2 _{O 5,} it may contain at least any.
In particular, the glass substrate 1 may contain up to 2% of B ₂ O ₃ in order to improve solubility. A glass substrate in which the content of B ₂ O ₃ exceeds 2% is not preferable for the process of forming a photoelectric conversion layer such as a CIGS film because the glass transition temperature is lowered or the average thermal expansion coefficient is decreased. The content of B ₂ O ₃ is preferably 1% or less, more preferably 0.5% or less, and particularly preferably substantially not contained.
In the present specification, “substantially does not contain” means that it is not contained other than inevitable impurities mixed from raw materials or the like, that is, it is not intentionally contained in glass.

In order to improve the chemical durability and the Young's modulus of glass, the glass substrate 1 may contain at least one of Y ₂ O ₃ , La ₂ O ₃ and TiO ₂ in a total of 5% or less.

In order to adjust the color tone of the glass, the glass substrate 1 may contain a colorant such as Fe ₂ O ₃ . The content of such a colorant is preferably 1% or less on an external basis when the glass composition is 100%.
As ₂ O ₃ , Sb ₂ O ₃ , and ZnO are also components that can adjust the color tone of the glass. However, in consideration of environmental load, it is preferable that the glass substrate 1 does not substantially contain As ₂ O ₃ and Sb ₂ O ₃ . In consideration of stable float forming, the glass substrate 1 preferably does not substantially contain ZnO.

In order to improve the solubility and clarity of glass, the glass substrate 1 is at least one selected from the group consisting of SO ₃ , an inorganic compound containing F, an inorganic compound containing Cl, and SnO ₂ . The compound may be added up to a total amount of 2% when the above glass composition is taken as 100%.

The glass substrate 1 by this embodiment can be preferably used for the glass substrate for solar cells, More preferably, it can be used for the glass substrate for CIGS solar cells. In this case, it is possible to make the glass difficult to be scratched in the transporting process when manufacturing the solar cell.
Furthermore, according to the glass substrate 1, when installed outdoors as a solar cell, corrosion of the glass substrate due to acid rain or the like can be prevented.

[Modification of Embodiment]
The present invention is not limited to the embodiment. The present invention includes modifications and improvements as long as the object of the present invention can be achieved.

  The present invention is not limited to an embodiment in which the hydrogen treatment process is performed on the first substrate surface, and includes an embodiment in which the same hydrogen treatment process is performed on the other substrate surfaces. For example, hydrogen treatment may be performed on the second substrate facing the first substrate.

  In the above embodiment, the mode in which the hydrogen treatment is performed on the surface of the first substrate has been described as an example. It may be a glass substrate manufacturing method including a step of passing through. In addition, an atmosphere having a dew point of −10 ° C. or lower passes through an atmosphere in which dry air having a dew point of −10 ° C. or lower is heated and circulated even in a process of passing through an atmosphere substantially free of water vapor. It may be a process of making it.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

The raw materials were prepared so as to have the compositions A, B, C and D shown in Table 1, and a glass substrate was produced by the float process.
During the manufacturing process of the glass substrate, a hydrogen treatment process for performing hydrogen treatment on the surface of the glass substrate was performed. The surface of the glass substrate that had been subjected to hydrogen treatment was used as the first substrate surface. The gas used in the hydrogen treatment step is a mixed gas of hydrogen and nitrogen, and Tables 2 and 3 show the hydrogen concentration in the mixed gas. Tables 2 and 3 show the conditions for the hydrogen treatment. In Table 3, in the comparative example in which the column of hydrogen treatment concentration is displayed as “none”, it means that no hydrogen treatment is performed.

  About the manufactured glass substrate, the physical property etc. were measured with the following method.

(1) Glass transition temperature Tg
The glass transition temperature Tg was measured using a differential thermal dilatometer (TMA) based on JIS R3103-3 (FY2001). The measurement results are shown in Table 2 and Table 3.

(2) Vickers hardness Hv
The manufactured glass substrate was cut into the following sizes to obtain test pieces for measuring Vickers hardness.
Sample size: 30mm x 30mm, thickness 1.1mm
Measurement surface: Polished with a # 1000 grindstone and then mirror-finished with cerium oxide.
For measurement of Vickers hardness, HMV-2 manufactured by Shimadzu Corporation was used.
DP (Dew Point, dew point): obtained by driving a Vickers indenter with a load of F = 0.1 kgf (= 0.98 N) on the first substrate surface of the glass substrate under the condition of an atmosphere having a dew point of −50 ° C. Hv was calculated from the following equation, where d is the average length of the diagonal lines of the Vickers indentation. The method was described in JIS Z 2244.
Hv: 1.8544 × F [kgf] ÷ d ² [mm ² ]
For each test piece, 12 points of indenter were driven in, and the average value of 10 points excluding the maximum and minimum values was defined as Hv.
The Vickers hardness of the surface of the first substrate subjected to the hydrogen treatment was defined as the first Vickers hardness Hv1 [N / mm ² ]. For the glass substrate not subjected to hydrogen treatment, the Vickers hardness measurement was performed on the untreated surface, and the first Vickers hardness Hv1 was measured.
The Vickers hardness of the exposed surface exposed by polishing the first substrate surface of 5000 nm or more was defined as the second Vickers hardness Hv2 [N / mm ² ].
Tables 2 and 3 show the first Vickers hardness Hv1 and the ratio Hv1 / Hv2 between the first Vickers hardness Hv1 and the second Vickers hardness Hv2.

(3) Hydrogen ion concentration The hydrogen ion concentration was analyzed using D-SIMS (secondary ion mass spectrometer). The primary ion was Cs ⁺ . As a measuring apparatus, an apparatus (product name: ADEPT1010) manufactured by ULVAC-PHI Co., Ltd. was used.

The measurement conditions of the hydrogen ion concentration in the range where the depth from the first substrate surface of the glass substrate is up to 2 μm were as follows. The same applies to the untreated surface of the hydrogen treatment.
Acceleration voltage: 3 kV
Beam current: 100 nA
Raster size: 300 × 300 μm ²
Sample angle: 45 °

The measurement conditions of the hydrogen ion concentration in the range where the depth from the surface of the first substrate of the glass substrate exceeds 2 μm and reaches 17 μm are as follows. The same applies to the untreated surface of the hydrogen treatment.
Acceleration voltage: 5 kV
Beam current: 700 nA
Raster size: 300 × 300 μm ²
Sample angle: 45 °

In this example and comparative example, the average value of the hydrogen ion concentration at a depth of 500 nm to 600 nm from the surface of the first substrate was calculated, and the first hydrogen ion concentration was set to X [ppm].
In this example and the comparative example, the average value of the second hydrogen ion concentration at a depth of 40 nm or more and 60 nm or less from the first substrate surface was calculated and defined as Y [ppm].

Table 4 shows the first hydrogen ion concentration X _A [ppm] and the second hydrogen ion concentration Y _A [ppm] in the glass substrate having the composition A (Examples 2 and 3 and Comparative Example 1).

Table 5 shows the first hydrogen ion concentration X _B [ppm] and the second hydrogen ion concentration Y _B [ppm] in the glass substrate having the composition B (Example 5, Comparative Example 2).

  Table 6 shows the glass substrate depth at which the hydrogen ion concentration on the surface of the glass substrate is halved.

  As shown in Table 6, it was found that the hydrogen ion concentration in the surface layer of the glass substrate was increased by performing the hydrogen treatment. It has been found that the hydrogen ion concentration rapidly decreases when no hydrogen treatment is performed.

(4) Element profile Tables 2 and 3 show the concentration ratio of each atom at a depth of 30 nm and a depth of 5000 nm from the first substrate surface of the glass substrate. The concentration of each atom at each depth was measured using an X-ray photoelectron spectrometer (manufactured by ULVAC-PHI Co., Ltd .; product name ESCA5500).
Measurement angle: 75 degrees Depth measurement condition: Pass Energy: 117.4 [eV]
Energy Step: 0.50 [eV / step]
Sputter ion: C ₆₀ ⁺
Sputtering rate: about 1 nm / min (SiO ₂ conversion)
Measurement interval: Every 5 min
The concentration of each element was converted using the profile of the polished product and the calculated glass composition (ac%).

Grinding from the first substrate surface of a glass substrate to 30nm were sputter etched by C ₆₀ ion beam. Grinding from the glass substrate surface to 5000nm, first, after grinding with a water slurry of cerium oxide to 4000 _nm, and sputter etching by _{C 60} ion beam.
The surface Na ratio was the ratio (Na ₃₀ / Na ₅₀₀₀ ) of the Na atom concentration (Na ₃₀ ) at a depth of 30 nm to the Na atom concentration (Na ₅₀₀₀ ) at a depth of ₅₀₀₀ nm.
The surface K ratio was the ratio (K ₃₀ / K ₅₀₀₀ ) of the K atom concentration (K ₃₀ ) at a depth of 30 nm to the K atom concentration (K ₅₀₀₀ ) at a depth of ₅₀₀₀ nm.
The surface Ca ratio was the ratio of the Ca atom concentration (Ca ₃₀ ) at a depth of 30 nm (Ca ₃₀ / Ca ₅₀₀₀ ) to the Ca atom concentration (Ca ₅₀₀₀ ) at a depth of ₅₀₀₀ nm.
The surface Sr ratio was defined as the ratio (Sr ₃₀ / Sr ₅₀₀₀ ) of the Sr atom concentration (Sr ₃₀ ) at a depth of 30 nm to the Sr atom concentration (Sr ₅₀₀₀ ) at a depth of ₅₀₀₀ nm.
The surface Ba ratio was the ratio (Ba ₃₀ / Ba ₅₀₀₀ ) of the Ba atom concentration (Ba ₃₀ ) at a depth of 30 nm to the Ba atom concentration (Ba ₅₀₀₀ ) at a depth of ₅₀₀₀ nm.

(5) Acid resistance The glass substrate after the slow cooling produced without implementing a hydrogen treatment process was cut | disconnected, 6 surfaces were mirror-polished, and the test piece for the acid resistance test of the following size was obtained.
Test piece size: 30 mm x 30 mm, thickness 1.1 mm
The plate-like glass (test piece) was ground by 300 μm to 1000 μm using a # 1000 grindstone. Then, it grind | polished using cerium oxide and made the surface of the test piece the mirror surface. The processing strain adhering to the surface of the test piece after mirror finishing was removed.

The test piece was immersed in 1 mol / liter dilute hydrochloric acid maintained at 90 ° C. for 20 hours, and the weight loss per surface area of the test piece before and after immersion (elution amount [mg / cm ² ]) was measured.
After the surface of the test piece was subjected to hydrogen treatment, the elution amount when the above acid resistance test was performed was defined as a first elution amount Z1 [μg]. The elution amount when the above acid resistance test was carried out without subjecting the test piece to hydrogen treatment was defined as a second elution amount Z2 [μg]. Tables 2 and 3 show the elution amount from the test piece after the hydrogen treatment and the ratio Z1 / Z2 between the first elution amount Z1 and the second elution amount Z2.

(6) Composition of sulfate after SO ₂ treatment: R ₂ O / (R ₂ O + RO)
The surface (non-analytical surface (glass bottom surface)) facing the first substrate surface of the glass substrate was masked with PTFE (polytetrafluoroethylene). The masked glass substrate was placed in a plastic bag with a chuck, and 5 mL of ultrapure water was further added to the bag. The chuck was closed and sonication was performed for 30 minutes under the condition of 28 kHz. After the ultrasonic treatment, the glass substrate was taken out from the bag. Microwave decomposition was performed by adding 5 mL of concentrated nitric acid to the eluate remaining in the bag. After taking out the decomposition solution, the volume was adjusted to 20 mL with ultrapure water. Each element in the constant volume solution was quantified by ICP-MS. As the apparatus, Agilent 8800 manufactured by Agilent Technology Co., Ltd. was used.

Using a glass substrate in which SO ₂ gas is brought into contact with the surface of the first hydrogen-treated substrate in the hydrogen treatment step at a temperature 50 ° C. higher than the glass transition point of the sample, a constant volume liquid is prepared by the above-described method, Quantification was performed. In this case, the first molar fraction of sulfate was M1 = R ₂ SO ₄ / (R ₂ SO ₄ + R′SO ₄ ). R is at least one of Na and K, and R ′ is at least one of Mg, Ca, Sr, and Ba.
Using a glass substrate in which SO ₂ gas is brought into contact with a glass substrate surface that has not been subjected to hydrogen treatment at a temperature 50 ° C. higher than the glass transition point of the sample, a constant volume liquid is prepared by the above-described method and quantified. It was. In this case, the second molar fraction of sulfate was M2 = R ₂ SO ₄ / (R ₂ SO ₄ + R′SO ₄ ).
The SO ₂ treatment conditions are as follows.
Processing temperature: Tg + 50 ° C
Dew point: 45 ° C
Treatment step: Preheating was performed for 5 minutes in an N ₂ atmosphere, and then a 10% by volume SO ₂ gas and a mixed gas of air and argon were sprayed onto the surface of the glass substrate. 10 volume% SO ₂ gas was maintained under the condition of 0.20 L / min and a mixed gas of air and argon was maintained under the condition of 1.40 L / min for 5 minutes. Followed by cooling at room temperature for 5 minutes under N ₂ atmosphere.
Tables 2 and 3 show the ratio M1 / M2 between the first molar fraction M1 and the second molar fraction M2.

(7) Coordination number of aluminum in glass substrate The coordination number of aluminum in the glass substrate of composition A, B, and C was confirmed based on the ²⁷ Al-MAS NMR spectrum. For the measurement of the NMR spectrum, ECA600 manufactured by JEOL RESONANCE was used. The measurement conditions are as follows. FIG. 3 shows the NMR spectrum.
Measurement conditions Probe: 3.2 mm MQMAS probe Measurement method: single pulse method Integration count: 512 times D .: 2 seconds MAS speed: 20 kHz

  In this example, the detection value in the range of 20 ppm or more and 85 ppm or less is derived from 4-coordination, the detection value in 10 ppm or more and 40 ppm or less is derived from 5 coordination, and the detection value in −20 ppm or more and 15 ppm or less is determined to be derived from 6 coordination. did. Integrating in the range of each range, the integrated intensity in the range of 20 ppm to 85 ppm is the first integrated intensity α, the integrated intensity in the range of 10 ppm to 40 ppm is the second integrated intensity β, and is −20 ppm to 15 ppm. The integrated intensity of the range was defined as the third integrated intensity γ. The 4-coordinate integrated intensity ratio was α / (α + β + γ), the 5-coordinate integrated intensity ratio was β / (α + β + γ), and the 6-coordinate integrated intensity ratio was γ / (α + β + γ). The calculated results are shown in Table 7.

As shown in Table 7, 95% or more of the glass substrates having compositions A, B, and C were calculated as 4-coordinate.
In addition, when the measurement by MQ-MAS was implemented separately, the peak derived from aluminum other than 4-coordination was not detected.

  From the above-mentioned results, it was found that the glass substrates of Examples 1 to 7 were glass substrates having high acid resistance and strength on the glass surface and capable of forming a sulfate protective film that was easier to wash and remove.

  The present invention can be used as a glass substrate.

  1 ... Glass substrate, 11 ... First substrate surface.

Claims (5)

A glass substrate,
Having a first substrate surface;
Silicon, an alkali metal, an alkaline earth metal, and oxygen,
The content of Al ₂ O ₃ is 10 % or more by mass percentage based on oxide,
The glass transition temperature is 640 ° C. or higher,
The first hydrogen ion concentration at any depth of 500 nm or more and 5000 nm or less from the surface of the first substrate is X [ppm],
When the second hydrogen ion concentration at any depth from 40 nm to 60 nm from the first substrate surface is Y [ppm],
The hydrogen ion concentration ratio Y / X is 3.0 or more and 8.3 or less,
In the ²⁷ Al-MAS NMR spectrum of the glass substrate,
The integrated intensity in the range of 20 ppm to 85 ppm is defined as the first integrated intensity α,
The integrated intensity in the range of 10 ppm to 40 ppm is defined as the second integrated intensity β,
When the integrated intensity in the range of −20 ppm or more and 15 ppm or less is the third integrated intensity γ,
α / (α + β + γ) is 0.9 or more,
A glass substrate having an elution amount of 0.5 mg / cm ² or less and a Vickers hardness Hv of 500 or more when an acid resistance test is conducted by immersing in dilute hydrochloric acid having a concentration of 1 mol / liter maintained at 90 ° C. for 20 hours. . The first molar fraction of sulfate produced when SO ₂ gas is brought into contact with the first substrate surface at 300 ° C. or higher is M1 = R ₂ SO ₄ / (R ₂ SO ₄ + R′SO ₄ ). Represented by
The second molar fraction of sulfate produced when SO ₂ gas is brought into contact with the first exposed surface exposed by polishing the first substrate surface of 5000 nm or more at 300 ° C. or higher is M2 = R _2. SO ₄ / (R ₂ SO ₄ + R′SO ₄ ),
R is at least one of Na and K;
R ′ is at least one of Mg, Ca, Sr, and Ba;
The ratio M1 / M2 between the first molar fraction M1 and the second molar fraction M2 is 1.00 or more,
The glass substrate according to claim 1. The glass substrate is cut into a rectangular shape, and six surfaces are mirror-polished to produce a first test piece having a thickness of 1.1 mm and a side length of 30 mm. The amount of elution when the acid resistance test was conducted for 20 hours in dilute hydrochloric acid with a concentration of 1 mol / liter maintained at 90 ° C. was defined as the first elution amount Z1 [μg],
The surface of the first substrate is polished by 5000 nm or more, and after polishing, the glass substrate is cut into a rectangular shape, six surfaces are further mirror-polished, the thickness is 1.1 mm, and the length of one side is 30 mm. The second elution amount is the second elution amount when an acid resistance test is performed in which two test pieces are prepared and the second test piece is immersed in dilute hydrochloric acid having a concentration of 1 mol / liter maintained at 90 ° C. for 20 hours. If Z2 [μg],
The ratio Z1 / Z2 between the first elution amount Z1 and the second elution amount Z2 is 0.8 or less,
The glass substrate of Claim 1 or Claim 2. The Vickers hardness of the first substrate surface is defined as a first Vickers hardness Hv1 [N / mm ² ],
When the Vickers hardness of the exposed surface exposed by polishing the first substrate surface of 5000 nm or more is the second Vickers hardness Hv2 [N / mm ² ],
The ratio Hv1 / Hv2 between the first Vickers hardness Hv1 and the second Vickers hardness Hv2 is 1.00 or more.
The glass substrate as described in any one of Claims 1-3.
However, the measurement of Vickers hardness is carried out by the method described in JIS Z 2244 under the condition that the dew point is −50 ° C. and the indentation load is 0.98 N. At a depth of 5000 nm or more from the surface of the first substrate, the mass percentage based on the following oxide:
SiO ₂ 51% or more and 60% or less,
Al ₂ O ₃ of 10 % or more and 14% or less,
MgO 0.05% to 3%,
CaO 5% or more and 8% or less,
SrO 7% to 12%,
BaO is 1.58% or more and 7.65% or less,
Na ₂ O 4.29% or more and 5.93% or less,
K ₂ O of 3.80% or more and 6.10% or less,
ZrO ₂ is contained 2.56% or more and 4.34% or less,
The glass substrate as described in any one of Claims 1-4.

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