JP2015044721A - Processing method of glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating a glass substrate, in which a molar ratio of the content of one alkali ion to that of another alkali ion in the vicinity of the surface of the glass substrate is adjusted.SOLUTION: The method for treating the glass substrate comprises the steps of: disposing the first glass substrate 4c and the second glass substrate 4d, each of which contains alkali metal oxide and which are different in the molar ratio of the content of one alkali metal oxide to that of another alkali metal oxide, in a stacked state to prepare the stacked substrates 4; placing the stacked substrates 4 between a cathode 2 and an anode 3 so that the second main surface of the first glass substrate 4c is contacted with the anode 3 and the main surface to be positioned in the outermost part of the second glass substrate 4d is separated from/opposed to the cathode 2; and impressing a DC voltage between the cathode 2 and the anode 3 to generate corona discharge so that alkali ions in the first glass substrate 4c and those in the second glass substrate 4d are moved toward the anode 3 and the molar ratio of the content of one alkali ion to that of another alkali ion in the surface layer parts of both of the first glass substrate 4c and the second glass substrate 4d is changed before the corona discharge is generated.

Description

  The present invention relates to a method for processing a glass substrate, and more particularly, to a method for processing a surface layer portion of a glass substrate having one or more alkali metal oxides in composition.

In a solar cell (hereinafter referred to as a CIGS solar cell) using a Cu (In, Ga) Se semiconductor (hereinafter referred to as a CIGS semiconductor), the CIGS semiconductor film is formed on a glass substrate containing an alkali metal oxide. It is known that alkali ions (for example, Na ⁺ and K ⁺ ) that have migrated from a glass substrate into a semiconductor and diffused serve as carriers and contribute to an increase in battery efficiency. Therefore, examination of the composition of the glass substrate in consideration of migration and diffusion of alkali ions has been performed.

  The glass composition required for the glass substrate varies depending on the CIGS semiconductor film forming process (temperature and time). Further, even in a glass substrate having the same composition, the content of alkali elements from the surface to a depth of several μm. Is different, it is confirmed that the amount of migration and diffusion of alkali ions to the CIGS semiconductor is different.

  Therefore, in order to obtain desired battery characteristics while suppressing costs, the composition of the entire glass substrate is not changed, but the content of each alkali ion in the vicinity of the surface (surface layer part several μm deep from the surface) There is a need to adjust the molar ratio.

Conventionally, as a method for changing the composition of only the surface layer portion of a glass substrate, a method of immersing with a molten salt containing desired ions to perform ion exchange and chemical strengthening is known (see, for example, Patent Document 1). .
However, the molten salt treatment is costly because of batch processing. In addition, it is difficult to finely adjust the molar ratio of the content of each alkali ion.

JP 2010-202514 A

  The present invention has been made to solve such a problem, and can adjust the molar ratio of the content of each alkali ion in the vicinity of the surface of the glass substrate and can be processed only on one side. The purpose is to provide a simple and easy method.

  The processing method of the glass substrate of this invention is 1 type (s) or 2 or more types on the 1st main surface of the 1st glass substrate which consists of 1st glass containing 1 type, or 2 or more types of alkali metal oxides. At least one second glass substrate made of a second glass, wherein the molar ratio of the content of each of the alkali metal oxides is different from the molar ratio in the first glass. The stacking substrate in which the first glass substrate and the second glass substrate are stacked and the second substrate of the first glass substrate is disposed between the positive electrode and the negative electrode. Between the positive electrode and the negative electrode, and the main surface located on the outermost part of the second glass substrate is spaced apart from and opposed to the positive electrode. The process of generating a corona discharge by applying a DC voltage to Characterized in that it obtain.

  In the method for processing a glass substrate of the present invention, in the step of generating the corona discharge, one or more alkali ions in the first glass substrate and the second glass substrate are respectively used as the negative electrode. The molar ratio of each content of alkali ions can be changed in the surface layer portion on the first main surface side of the first glass substrate. In the first glass substrate, the total mole of each content of alkali ions is preferably substantially constant before and after the step of generating the corona discharge. In the second glass, the molar ratio of the content of sodium oxide to the content of the alkali metal oxide other than sodium oxide is larger than the molar ratio in the first glass, and the corona discharge is performed. In the generating step, the molar ratio of the content of sodium ions to the content of alkali ions other than sodium ions can be increased in the surface layer portion on the first main surface side of the first glass substrate. In the second glass, the molar ratio of the content of potassium oxide to the content of alkali metal oxides other than potassium oxide is larger than the molar ratio in the first glass, and the corona discharge is performed. In the generating step, the molar ratio of the content of potassium ions to the content of alkali ions other than potassium ions can be increased in the surface layer portion on the first main surface side of the first glass substrate.

  Moreover, in the processing method of the glass substrate of this invention, it is preferable that the said positive electrode has an electrode area smaller than the said negative electrode. The positive electrode is a wire-like electrode, and the wire-like electrode can be arranged in parallel to the outer main surface of the second glass substrate located at the outermost part of the stacked substrate. The positive electrode is a needle-like electrode, and the needle-like electrode can be disposed perpendicular to the outer main surface of the second glass substrate located at the outermost part of the stacked substrate.

  Furthermore, in the processing method of the glass substrate of this invention, it can hold | maintain in the atmosphere which mainly has air or nitrogen between the said positive electrode and the said negative electrode. Moreover, it is preferable that the temperature of the stacked substrate is normal temperature to 400 ° C.

  In the present invention, “corona discharge” means that a necessary and sufficient DC voltage (corona discharge start voltage) is applied between the positive electrode and the negative electrode to separate the glass substrate from the object to be processed. This refers to a continuous discharge caused by the generation of a non-uniform electric field around the arranged positive electrode. This discharge is a local discharge (partial discharge) in which ionization of gas existing between the electrodes is locally limited, and is an aggregate of a number of streamers, and continues while maintaining the above-described DC voltage. Occur. When the voltage is increased, the corona discharge progresses toward the negative electrode, and when one streamer approaches or arrives at the negative electrode, it immediately shifts to a spark discharge. In the present invention, basically, corona discharge that does not shift to spark discharge is performed.

  In the present invention, the “alkali ion” refers to an alkali metal ion constituting an alkali metal oxide contained in the first glass and the second glass constituting the first glass substrate and the second glass substrate.

  According to the processing method of the present invention, in the stacked substrate in which the first glass substrate and the second glass substrate are stacked, the second glass substrate of the first glass substrate disposed on the negative electrode side is in contact. The molar ratio of the content of alkali ions in the vicinity of the main surface can be adjusted without changing the composition of the entire first glass substrate. Further, it is possible to process only one side and is an inexpensive method.

An example of the surface treatment apparatus used for embodiment of this invention is shown, FIG.1 (a) is a front view which shows schematic structure, FIG.1 (b) is a top view which shows arrangement | positioning of the positive electrode with respect to a stacking board | substrate. It is. 2A shows another example of the surface treatment apparatus used in the embodiment of the present invention, FIG. 2A is a front view showing a schematic configuration, and FIG. 2B shows the arrangement of the positive electrode with respect to the stacked substrate. It is a top view. It is a figure which shows the processing method of the Example of this invention. In Example 1, it is a graph which shows the result of having measured the element density | concentration in the depth direction in the upper surface side surface layer part of a KBSi board | substrate. In Example 2, it is a graph which shows the result of having measured the element concentration in the depth direction in the upper surface side surface layer part of a NaBSi board | substrate.

Embodiments of the present invention will be described below.
In the embodiment of the processing method of the present invention, first, at least one second glass substrate is placed on the first main surface which is one main surface of the first glass substrate, and thus obtained. The stacked substrate is placed between the positive electrode and the negative electrode on the outermost main surface of the glass substrate disposed on the outermost side of the second glass substrate, that is, on the non-contact side that is not in contact with another glass substrate. The main surface is arranged so as to be separated from the positive electrode, and the second main surface which is the other main surface of the first glass substrate is in contact with the negative electrode.
Note that each of the first glass substrate and the second glass substrate is a substrate made of glass containing one kind or two or more kinds of alkali metal oxides. And the 1st glass which comprises a 1st glass substrate, and the 2nd glass which comprises a 2nd glass substrate differ in the molar ratio of content of each 1 type, or 2 or more types of alkali metal oxides. ing.

After the stacked substrates are arranged in this way, a DC voltage is applied between the positive electrode and the negative electrode to generate a corona discharge between the electrodes, and the generated corona discharge causes the first glass substrate and the second glass substrate. One kind or two or more kinds of alkali ions are moved toward the negative electrode. Since the first glass constituting the first glass substrate and the second glass constituting the second glass substrate both contain one or more alkali metal oxides in the composition, corona discharge Thus, one or more kinds of alkali metal ions (alkali ions) constituting the alkali metal oxide contained in the first glass and the second glass are contained in the first glass substrate and the second glass. It moves in the substrate toward the negative electrode. In such movement of alkali ions, the ease of movement varies depending on the type of alkali ions. Further, in the vicinity of the interface between the first glass substrate and the second glass substrate, the second glass substrate so as to compensate for the charge of the cation desorption portion formed by the movement of alkali ions in the first glass substrate. The alkali ions move from the interface to the first glass substrate. As a result, the molar ratio of the content of each alkali ion can be changed in the surface layer portion of the first glass substrate on the interface side with the second glass substrate.
In addition, the said surface layer part of a 1st glass substrate shall say the part to the depth of 0.5-1.6 micrometers from the surface, for example.

Specifically, the first glass and the second glass are at least one of lithium oxide (Li ₂ O), sodium oxide (Na ₂ O), and potassium oxide (K ₂ O) as an alkali metal oxide. When lithium ions (Li ⁺ ), sodium ions (Na ⁺ ), and potassium ions (K ⁺ ) that are alkali metal ions constituting these alkali metal oxides are contained in the first glass by corona discharge, It moves toward the negative electrode in the substrate and the second glass substrate, respectively. As a result, the molar ratio of the content of each of lithium ions, sodium ions, and potassium ions in the surface portion of the first main surface in contact with the second glass substrate of the first glass substrate is before corona discharge treatment. Change.
Here, the molar ratio of the content of each of lithium ions, sodium ions, and potassium ions changes before and after the treatment, the content of each alkali ion before and after the treatment, a and A for lithium ions, and about the sodium ions When b and B and potassium ions are c and C, a: b: c ≠ A: B: C. That is, one of the three inequalities of a: b ≠ A: B, a: c ≠ A: C, and b: c ≠ B: C holds.

<Stacked substrate to be processed>
The stacked substrates to be treated by the method of the present invention are one or two in composition on a first glass substrate composed of a first glass containing one or more alkali metal oxides in composition. A second glass substrate made of a second glass containing a plurality of alkali metal oxides and having a molar ratio of the content of each of the alkali metal oxides different from that of the first glass. It is. The first glass substrate and the second glass substrate are preferably stacked in direct contact with each other.

  The number of the second glass substrates arranged on the first glass substrate is preferably one from the viewpoint of the efficiency of the processing operation, but may be two or more as long as it is thin. . The thickness of the entire stacked substrate is set to a thickness that allows alkali ions to move by corona discharge. In the case of the processing conditions described later, specifically, it is preferably 0.5 to 5 mm. Then, the thickness and number of the second glass substrates can be adjusted in accordance with the thickness of the first glass substrate so that the thickness of the entire stacked substrate falls within such a range. The plurality of glass substrates constituting the second glass substrate are preferably stacked in direct contact with each other.

Examples of the alkali metal oxide contained in the first glass and the second glass include lithium oxide (Li ₂ O), sodium oxide (Na ₂ O), and potassium oxide (K ₂ O) as described above. It is done. The first glass and the second glass can contain SiO ₂ in addition to these alkali metal oxides. _Furthermore, it may contain _{Al 2 O 3, B 2 O} 3 and the like.

The composition of the first glass and the second glass is not particularly limited as long as it contains at least one of the alkali metal oxides. From the viewpoint of ease of processing, for example, mol% based on the oxide. A silicate glass, aluminosilicate glass, or borosilicate glass (borosilicate glass) containing 0.5 to 20 mol% of at least one of sodium oxide (Na ₂ O) and potassium oxide (K ₂ O) Can be mentioned.

As the first glass, lithium oxide _(Li 2 O), and one or more selected from the group consisting of sodium oxide _(Na 2 O) and potassium oxide _(K 2 O), the glass containing SiO ₂ Can be mentioned. For example, as represented by mol% based on oxides, the SiO ₂ 45 to 80%, the _{Al 2 O 3 0~18%, B} 2 O 3 0 to 15% 0 to 15% of Li ₂ O, Na ₂ O and 0 to 20% _{K 2} O with _{0~15% (Li 2 O + Na} 2 O + K 2 O) 5-20% of MgO 0 to 12% 0 to 12% of CaO, the SrO 0 to 12 %, BaO 0 to 10%, ZrO ₂ 0 to 5%, and TiO ₂ 0 to 5%. In addition, this glass composition is a composition suitable as glass which comprises the glass substrate for an above described CIGS solar cell.
Hereinafter, each component which comprises this glass is demonstrated. In addition, all represent mol% of an oxide basis.

SiO ₂ is a component constituting the skeleton of glass. When the content ratio of SiO ₂ is 45% or more, the heat resistance and chemical durability of the glass are good, and the average thermal expansion coefficient is low. The content ratio of SiO ₂ is more preferably 55% or more. On the other hand, when the content ratio of SiO ₂ is 80% or less, the glass viscosity and the meltability are good. The content ratio of SiO ₂ is more preferably 75% or less.

Al ₂ O ₃ is not an essential component, but is contained in order to increase the glass transition temperature, improve the weather resistance, heat resistance and chemical durability, increase the Young's modulus, and improve the ion migration speed. Is a good ingredient. The content ratio of Al ₂ O ₃ is preferably 0.5% or more, more preferably 1% or more. On the other hand, when the content ratio of Al ₂ O ₃ is 18% or less, the glass viscosity and the meltability are good. The content ratio of Al ₂ O ₃ is more preferably 15% or less.

B ₂ O ₃ is not an essential component, but may be contained for improving meltability at high temperatures or glass strength. When the content ratio of B ₂ O ₃ is 15% or less, the expansion characteristics during semiconductor film formation and the devitrification characteristics during glass production are good.

Na ₂ O is a component that contributes to improving the power generation efficiency of the CIGS solar cell. Moreover, while improving the meltability of glass, it has a sodium ion which moves by corona discharge. When the content ratio of Na ₂ O is 20% or less, the average thermal expansion coefficient does not become too large, and the solubility and devitrification characteristics are good. Further, since the chemical durability and Young's modulus are kept high, a good glass can be obtained. The content ratio of Na ₂ O is more preferably 16% or less. Further, the content ratio of Na ₂ O is preferably 0.1% or more, and more preferably 10% or more.

Since K ₂ O has the same effect as Na ₂ O, it can be contained in an amount of 15% or less. When the content ratio of K ₂ O is 15% or less, the average thermal expansion coefficient does not become too large, and the solubility and devitrification characteristics are good. Further, since the chemical durability and Young's modulus are kept high, a good glass can be obtained. The content ratio of K ₂ O is more preferably 12% or less.

Furthermore, since Li ₂ O has the same effect as Na ₂ O, it can be contained in an amount of 15% or less. When the content ratio of Li ₂ O is 15% or less, the average thermal expansion coefficient does not become too large, and the solubility and devitrification characteristics are good. Further, since the chemical durability and Young's modulus are kept high, a good glass can be obtained. The content ratio of Li ₂ O is more preferably 12% or less.

The total content of Li ₂ O, Na ₂ O and K ₂ O (Li ₂ O + Na _{2) is} improved in order to improve the treatment effect by corona discharge, improve the melting property of glass, and improve the power generation efficiency of CIGS solar cells. O + K ₂ O) is 5% to 20%. Preferably it is 8% or more. However, if (Li ₂ O + Na ₂ O + K ₂ O) exceeds 20%, the glass transition temperature may be too low. (Li ₂ O + Na ₂ O + K ₂ O) is preferably 15% or less.

  MgO can be contained because it has the effect of lowering the viscosity at the time of melting the glass and promoting the melting. When the content ratio of MgO is 12% or less, the average thermal expansion coefficient is not too large and the production characteristics are good. The content ratio of MgO is more preferably 8% or less.

  CaO can be contained because it has an effect of reducing the viscosity at the time of melting the glass and promoting the melting. When the content ratio of CaO is 12% or less, the average thermal expansion coefficient is not too large and the production characteristics are good. The content ratio of CaO is preferably 9% or less.

  SrO can be contained because it has the effect of reducing the viscosity at the time of melting the glass and promoting the melting. When the content ratio of SrO is 12% or less, the average thermal expansion coefficient is not too large and the production characteristics are good. Moreover, since the glass containing SrO has a high density and is brittle, the content ratio of SrO is preferably 8% or less.

  BaO can also be contained because it has the effect of reducing the viscosity at the time of melting the glass and promoting the melting. When the content ratio of BaO is 10% or less, the average thermal expansion coefficient is not too large and the production characteristics are good. Moreover, since the glass containing BaO has high density and is brittle, the content ratio of BaO is preferably 8% or less.

  From the viewpoint of lowering the viscosity at the time of melting the glass and promoting the melting, the total content of MgO, CaO, SrO and BaO (MgO + CaO + SrO + BaO) is preferably 3.5% or more. More preferably, it is 5% or more. When (MgO + CaO + SrO + BaO) is 27% or less, devitrification is difficult and manufacturing characteristics are good.

ZrO ₂ can be contained because it has an effect of reducing the viscosity at the time of melting the glass and promoting the melting. When the content ratio of ZrO ₂ is 5% or less, devitrification is difficult and manufacturing characteristics are good. The content ratio of ZrO ₂ is preferably 5% or less. Further, the content ratio of ZrO ₂ is preferably 0.5% or more.

TiO ₂ can be contained for improving the meltability of the glass. When the content ratio of TiO ₂ is 5% or less, devitrification is difficult and manufacturing characteristics are good.

Examples of the second glass include one or more selected from the group consisting of lithium oxide (Li ₂ O), sodium oxide (Na ₂ O), and potassium oxide (K ₂ O), and glass containing SiO _2. Can do. Na _{2 O: K} 2 O (molar ratio) = 3: 7-8: is preferably 2. For example, as represented by mol% based on oxides, the SiO ₂ 50 to 80%, the _{Al 2 O 3 0.5~15%, B} 2 O 3 0-10%, a Na ₂ O 10 to 16%, 0 to 8% of K ₂ O, 0 to 12% of Li ₂ O, 0 to 10% of CaO, 0 to 12% of MgO, and 10% in total of SrO, BaO, ZrO ₂ , ZnO, SnO _{2 and the} like The glass which contains less can be mentioned. About the effect | action of each component which comprises this glass, a more preferable content rate, the reason, etc., it is the same as that of the description about the said 1st glass.

An example of a composition preferable as the first glass and an example of a composition preferable as the second glass are shown in Table 1, respectively.

  If the shape of the 1st glass substrate and 2nd glass substrate comprised from the 1st glass and 2nd glass which have such a composition is a shape which has a pair of main surface mutually parallel, it is flat form However, a curved plate shape may be used, but a flat plate shape in which the pair of main surfaces are flat surfaces is preferable.

<Positive electrode and negative electrode>
In the embodiment of the present invention, the positive electrode, which is one electrode to which a DC voltage is applied, is disposed on the outermost side among one or two or more second glass substrates constituting the stacked substrate. The glass substrate is disposed at a position separated from the main surface (for example, the upper surface) outside the glass substrate by a predetermined distance. The negative electrode, which is the other electrode to which the DC voltage is applied, is the first main surface on the side not in contact with the second glass substrate in the first glass substrate constituting the stacked substrate that is the object to be processed. It arrange | positions so that two main surfaces (for example, lower surface) may be contacted.

  The distance between the upper surface of the second glass substrate disposed on the outermost side and the positive electrode varies depending on the shape of the positive electrode, the applied voltage, and the like, but the larger the distance, the smaller the discharge current and the weaker the corona discharge. , Larger than 0 mm and 30 mm or less is preferable. Furthermore, since the discharge current becomes parabolically and corona discharge becomes stronger as the distance is shorter, it is more preferably greater than 0 mm and not greater than 10 mm.

  Here, the positive electrode preferably has a smaller electrode area than the negative electrode. The “electrode area” refers to the area of the electrode projected on the main surface of the second glass substrate constituting the stacked substrate that is the object to be processed for the positive electrode, and the first glass for the negative electrode. The area in contact with the second main surface of the substrate. As described later, when the positive electrode is an assembly of a plurality of wire-like electrodes or needle-like electrodes, the “electrode area” is the sum of the “electrode areas” for each wire-like electrode or each needle-like electrode. Say.

  As the positive electrode, a wire-like electrode or a needle-like electrode having a sharp portion at the tip can be used. One of these wire-like electrodes and needle-like electrodes may be used alone, or an assembly in which a plurality of wire-like electrodes and needle-like electrodes are arranged at a predetermined interval may be used as the positive electrode. In this way, by using an assembly in which a plurality of wire-like electrodes or needle-like electrodes are arranged at a predetermined interval as the positive electrode, uniform processing of the stacked substrates becomes possible.

  An example of an apparatus used in the processing method of the present invention is shown in FIGS. 1 (a) and 2 (a) are front views schematically showing the configuration of the processing apparatus 1, and FIGS. 1 (b) and 2 (b) explain the arrangement of the positive electrode with respect to the stacked substrate. It is a top view for doing. In the processing apparatus 1 shown in FIG. 1, a wire electrode 2 a is provided as the positive electrode 2, and in the processing apparatus 1 shown in FIG. 2, a needle electrode 2 b is provided as the positive electrode 2. In these drawings, reference numeral 3 denotes a negative electrode, and reference numeral 4 denotes a stacked substrate which is a workpiece. The stacked substrate 4 is formed by superposing one sheet of the second glass substrate 4b on the first main surface (for example, the upper surface) of the first glass substrate 4a. In these drawings, reference numeral 5 denotes a DC power source, and reference numeral 6 denotes an ammeter for monitoring a current flowing through the circuit.

  In the processing apparatus 1 shown in FIG. 1, the wire-like electrode 2a, which is the positive electrode 2, is preferably thin from the viewpoint of the ease of occurrence of corona discharge, but the wire-like electrode 2a has a strength and ease of handling. The diameter is preferably 0.03 to 0.1 mm. Further, the wire electrode 2 a is preferably arranged in parallel to the upper surface of the stacked substrate 4. When a plurality of wire-like electrodes 2a are used as the positive electrode 2, each wire-like electrode 2a is larger than 0 mm as shown in FIG. 1 (b), and the distance between the second glass substrate 4b and the wire-like electrode 2a It is preferable to arrange them on a plane parallel to each other and at the same interval d and parallel to the upper surface of the stacked substrate 4 for uniform processing. As will be described later, when the stacked substrate 4 is moved in parallel to the wire-like electrode 2a, the processing unevenness is alleviated, so that the interval between the wire-like electrodes 2a can be made larger.

  When the single wire-like electrode 2a is disposed alone as the positive electrode 2, the stacked substrate 4 is uniformly processed in the surface direction, and the alkali ions in the first main surface side surface layer portion of the first glass substrate 4a are treated. In order to change the molar ratio of each content uniformly in the plane direction, it is preferable to move the negative electrode 3 integrated with the stacked substrate 4 relative to the wire electrode 2a which is the positive electrode 2. . Specifically, it is preferable to move the negative electrode 3 in a direction orthogonal to the arrangement direction of the wire-like electrode 2a with the stacked substrate 4 placed thereon. This motion is more preferably a linear motion or a reciprocating linear motion, but it may be a rotational motion or a rocking motion.

  In the processing apparatus 1 shown in FIG. 2, it is preferable that the needle-like electrode 2b which is the positive electrode 2 has a root portion having a diameter of 0.1 to 2 mm, and the tip of the needle-like electrode 2b is formed at the second glass substrate 4b. It is preferable to arrange it toward the top surface and perpendicular to the top surface. When a plurality of needle-like electrodes 2b are used as the positive electrode 2, each needle-like electrode 2b is parallel to each other and perpendicular to the upper surface of the second glass substrate 4b, and the tip is equal from the upper surface of the second glass substrate 4b. It is preferable to arrange the distances. Further, as shown in FIG. 2 (b), each needle electrode 2b is arranged in a staggered manner with an interval d larger than 0 mm and approximately the same as the distance between the second glass substrate 4b and the needle electrode 2b. A uniform arrangement such as a shape or a grid shape is preferable for uniformly treating the surface of the stacked substrate 4. When the stacked substrate 4 is moved in parallel to the needle-like electrode 2b, the processing unevenness is alleviated, so that the interval between the needle-like electrodes 2b can be made larger.

As the angle (tip angle) of the tip of the needle-like electrode 2b is smaller and sharper, the electric field intensity directly below increases, so the electric field strength near the positive electrode 2 is adjusted by adjusting the tip angle of the needle-like electrode 2b. it can. The tip angle of the needle-like electrode 2b is preferably 1 to 15 degrees, and more preferably 1 to 9 degrees.
In the wire-like electrode 2a and the needle-like electrode 2b, when a corrosion-resistant conductive film such as gold, platinum or other noble metal is provided on the surface, the electric field strength becomes uniform and the durability as an electrode is improved.

In the processing apparatus 1 shown in FIG. 1 and FIG. 2, the negative electrode 3 has a shape matching the lower surface of the first glass substrate 4a constituting the stacked substrate 4 that is the object to be processed, such as a flat plate shape or a curved plate shape. . Moreover, the thing which contacts uniformly with the 1st glass substrate 4a in a surface, such as a mesh-shaped thing which has a perforated part, may be used.
By disposing such a negative electrode 3 in contact with the lower surface of the first glass substrate 4a, the conductivity to the first glass substrate 4a is improved, so that the applied voltage can be increased. By providing a conductive film such as ITO on the surface of the negative electrode 3 in contact with the first glass substrate 4a, the conductivity can be further improved.

  Next, processing conditions (temperature of the glass substrate, processing atmosphere, etc.) in the embodiment of the present invention will be described.

<Temperature of stacked substrate>
The temperature of the stacked substrate, that is, the temperature of the first glass substrate and the second glass substrate constituting the stacked substrate is preferably from room temperature to 400 ° C. By setting the temperature to 400 ° C. or lower, deformation of the first and second glass substrates and deterioration of the electrodes can be prevented. The temperature range is lower than the glass transition point, and the glass exhibits a solid state having a sufficiently high viscosity, so that the alkali ions in the first and second glass substrates do not move excessively, Since the moving direction is limited to the direction toward the negative electrode which is the electric field direction, the efficiency of the treatment by corona discharge is high. The temperature of the stacked substrate is more preferably 100 to 300 ° C. However, when the glass transition point is 400 ° C. or lower, the temperature of the stacked substrate is more preferably lower.

<Applied voltage>
The DC voltage applied between the positive electrode and the negative electrode is a voltage that generates corona discharge from the positive electrode. The applied voltage varies depending on the shape of the positive electrode and the temperature of the stacked substrate as the object to be processed, but is in the range of 3 to 12 kV. When the applied voltage is less than 3 kV, corona discharge hardly occurs. When the applied voltage exceeds 12 kV, arc discharge tends to occur and it is difficult to continue corona discharge.

In the embodiment of the present invention, the current flowing through the stacked substrate, which is the object to be processed, by applying such a DC voltage includes both a current due to the movement of electrons and a current due to the movement of alkali ions. The current flowing through the stacked substrate in the process is preferably in the range of 0.01 to 0.5 mA, and the amount of electricity per unit area is preferably in the range of 10 to 500 mC / cm ² .

<Processing atmosphere>
An atmosphere mainly composed of air or nitrogen can be maintained between the positive electrode and the negative electrode on which the stacked substrate as the object to be processed is arranged. Here, the “atmosphere mainly composed of air or nitrogen” refers to a gas state in which the content ratio of air or nitrogen exceeds 50% by volume of the entire atmospheric gas.
As described above, the negative electrode is disposed so as to be in contact with the second main surface (for example, the lower surface) of the first glass substrate, and the conductivity between the negative electrode and the first glass substrate is improved. There is no need for an atmosphere of a plasma forming gas such as helium or argon. That is, corona discharge is generated around the positive electrode in an atmosphere mainly composed of air or nitrogen, and the stacked substrate can be processed by this discharge.

In the embodiment of the present invention, the stacking substrate in which the second glass substrate is placed on the first glass substrate is thus subjected to the treatment by corona discharge, so that the first glass and the second glass substrate are processed. The alkali ions contained in the alkali metal oxide contained in the glass No. 2 can be moved toward the negative electrode. Then, in the vicinity of the interface between the first glass substrate and the second glass substrate, the second glass substrate so as to compensate for the charge of the cation desorption portion formed by the movement of alkali ions in the first glass substrate. As the alkali ions move from the interface to the first glass substrate, the molar ratio of the content of each alkali ion in the surface layer portion on the interface side of the first glass substrate is changed as compared with that before the treatment. Can be made.
In the embodiment of the present invention, the molar ratio of the content of each alkali ion in the surface layer portion on the interface side of the first glass substrate changes before and after the treatment by corona discharge, but the content of each alkali ion. The total mole of is preferably substantially constant before and after the treatment. That is, before and after the treatment by corona discharge, it is preferable that the total mole of the content of each alkali ion in the first glass substrate is substantially constant both in the surface layer part and in the entire glass substrate. Note that “substantially constant” means that an error of plus or minus 5% is allowed.

In the specific treatment, as the composition of the first glass and the second glass (average composition of the whole glass), the content of sodium oxide in the second glass with respect to the content of alkali metal oxides other than sodium oxide By making the molar ratio larger than the molar ratio in the first glass, the corona discharge treatment causes the surface layer portion of the first glass substrate to have a sodium ion content of alkali ions other than sodium ions. The molar ratio to the content can be increased.
Moreover, by making the molar ratio of the content of potassium oxide in the second glass with respect to the content of the alkali metal oxide other than potassium oxide larger than the molar ratio in the first glass, the corona discharge treatment allows the first In the surface layer part of the glass substrate, the molar ratio of the content of potassium ions to the content of alkali ions other than potassium ions can be increased.

  Examples of the present invention will be specifically described below, but the present invention is not limited to these examples.

Example 1
As shown in FIG. 3, a borosilicate glass substrate (main surface is 25 mm × 25 mm) containing 70% SiO ₂ , 10% B ₂ O ₃ and 20% K ₂ O in terms of mol% based on oxide. A rectangular bismuth glass containing 70% SiO ₂ , 10% B ₂ O ₃ and 20% Na ₂ O on a rectangular (thickness 1 mm) (hereinafter referred to as KBSi substrate 4c) A stacked substrate 4 in which substrates having the same size and the same thickness as 4c (hereinafter referred to as NaBSi substrate 4d) are disposed is disposed between the acicular electrode 2b of the positive electrode 2 and the negative electrode 3, and corona discharge is performed. The processing by.

  In this processing apparatus 1, the negative electrode 3 is a grounded flat electrode (electrode material carbon, electrode size 25 mm × 25 mm), and the stacked substrate 4 is placed on the negative electrode 3 with the KBSi substrate 4c on the lower side. Placed and placed horizontally. Further, one needle-like electrode 2b having a diameter of 1 mm at the base was disposed so that the tip thereof was directed to the stacked substrate 4 and was perpendicular to the upper surface of the stacked substrate 4, that is, the surface of the NaBSi substrate 4d. The distance between the tip of the needle electrode 2b and the surface of the NaBSi substrate 4d was 5 mm. The needle-like electrode 2b was prepared by coating the surface of a needle-like body made of iron (carbon steel) with chromium having a thickness of 0.05 μm by sputtering and then coating with platinum having a thickness of 1 μm. . Further, an air atmosphere was provided between the needle-like electrode 2b, which is the positive electrode 2, and the negative electrode 3.

  Thus, a voltage was applied between the acicular electrode 2b, which is the positive electrode 2, and the negative electrode 3 by the DC power source 5 while heating the stacked substrate 4 to 200 ° C. The applied voltage was increased to 4.5 kV over 18 minutes, and the treatment was continued at this voltage for 720 minutes. During processing, when the current value was measured with an ammeter (not shown) installed in the circuit, the maximum current value was 9 μA and the average current value was 7.5 μA.

After performing the surface treatment for 720 minutes, the composition of the upper surface portion of the stacked substrate 4 in contact with the NaBSi substrate 4d of the KBSi substrate 4c disposed on the lower side is determined by C ₆₀ -XPS (X-ray photoelectron spectroscopy). Examined. In the measurement of C ₆₀ -XPS, XPS is performed while etching the upper surface of the treated KBSi substrate 4c by ion sputtering of C ₆₀ , and the content ratio (concentration) of elements such as alkali in the upper surface side surface portion of the KBSi substrate 4c. Was examined in the depth direction. The measurement results are shown in the graph of FIG.

It can be seen from the graph of FIG.
That is, in the upper surface side surface layer portion of the lower KBSi substrate, there was sodium (Na) that did not exist before the treatment, and its concentration became maximum at a position of a depth of 200 to 300 nm from the surface, It gradually decreases as the depth increases. In addition, the concentration of potassium (K) in the upper surface portion increases as the depth increases, and the corona discharge treatment causes potassium ions existing in the KBSi substrate to move toward the negative electrode. It shows that. Furthermore, the total concentration of Na and K is almost constant regardless of the depth from the surface.

From such measurement results, the following considerations can be obtained.
The presence of Na in the upper surface layer portion of the lower KBSi substrate is caused by the corona discharge treatment so that sodium ions contained in the upper NaBSi substrate move toward the negative electrode across the interface with the KBSi substrate. It shows that it is introduced into the substrate. Since the total concentration of Na and K is almost constant regardless of the depth from the surface in the surface layer on the upper surface side of the KBSi substrate, the introduction of sodium ions beyond the interface causes the introduction of the KBSi substrate. This is considered to be performed so as to compensate for the charge of the cation desorption portion formed as the potassium ion moves toward the negative electrode in the upper surface side surface layer portion.

Example 2
The KBSi substrate 4c used in Example 1 was placed on the NaBSi substrate 4d used in Example 1 in an overlapping manner. This stacked substrate was placed between the positive electrode 2 and the negative electrode 3 of the processing apparatus 1 shown in FIG. 3 and processed by corona discharge. The treatment conditions by corona discharge were the same as in Example 1.

After the treatment, the composition of the surface layer portion of the NaBSi substrate 4d disposed on the lower side in contact with the KBSi substrate 4c was examined by C ₆₀ -XPS in the same manner as in Example 1, and the content ratio of elements such as alkali (Concentration) was measured in the depth direction. The measurement results are shown in the graph of FIG.

From the graph of FIG.
That is, in the upper surface side surface layer portion of the lower NaBSi substrate, potassium (K) that was not present before the treatment is present, and the concentration thereof decreases as the depth from the surface increases. In addition, the concentration of sodium (Na) in the upper surface portion increases as the depth increases, and sodium ions existing in the NaBSi substrate before the treatment move toward the negative electrode by the corona discharge treatment. It shows that. Furthermore, the total concentration of Na and K is almost constant regardless of the depth from the surface.

Considerations obtained from the measurement results are shown below.
The presence of K in the upper surface layer portion of the lower NaBSi substrate is due to the fact that potassium ions contained in the upper KBSi substrate move across the interface with the NaBSi substrate toward the negative electrode by the corona discharge treatment. It shows that it is introduced into the substrate. Since the total concentration of Na and K is substantially constant regardless of the depth from the surface in the upper surface side surface portion of the NaBSi substrate, the introduction of potassium ions beyond the interface is performed on the NaBSi substrate. It is thought that it is performed so as to compensate for the charge of the cation desorption portion formed as the sodium ion moves toward the negative electrode in the upper surface side surface layer portion.

  Further, comparing the concentration of Na in the surface layer portion of the upper surface side of the KBSi substrate in Example 1 with the concentration of K in the surface layer portion of the upper surface side of the NaBSi substrate in Example 2, the latter is larger. Is considered to depend on the ease of movement of cations in the lower glass substrate. That is, the sodium ion that is the cation of the lower NaBSi substrate in Example 2 has a smaller ionic radius than the potassium ion that is the cation of the lower KBSi substrate in Example 1, and is directed to the negative electrode by corona discharge treatment. Therefore, a cation desorption portion is easily formed in the upper surface side surface layer portion of the lower glass substrate. Therefore, the amount of potassium ions, which are cations introduced from the upper glass substrate so as to compensate for the charge of such a cation desorption portion, also increases, and as a result, the concentration of K in the upper surface portion of the lower NaBSi substrate Is expected to increase.

According to the treatment method of the present invention, the molar ratio of the content of one or more alkali ions in the vicinity of the surface of the glass substrate can be adjusted without changing the composition of the entire substrate. Moreover, the process of only one side of a glass substrate is possible.
Therefore, by using the method of the present invention, in the glass substrate for a semiconductor film of a CIGS solar cell, the molar ratio of the alkali ion content in the surface layer portion can be adjusted inexpensively and easily.

  DESCRIPTION OF SYMBOLS 1 ... Surface treatment apparatus, 2 ... Positive electrode, 2a ... Wire-like electrode, 2b ... Needle-like electrode, 3 ... Negative electrode, 4 ... Stacked substrate, 4a ... 1st glass substrate, 4b ... 2nd glass substrate, 5 ... DC power supply.

Claims (10)

Containing one or more alkali metal oxides on the first main surface of the first glass substrate made of the first glass containing one or more alkali metal oxides, A step of stacking and arranging at least one second glass substrate made of a second glass in which the molar ratio of the content of each alkali metal oxide is different from the molar ratio in the first glass;
A stacked substrate in which the first glass substrate and the second glass substrate are arranged to overlap each other, and a second main surface of the first glass substrate is in contact with the negative electrode between a positive electrode and a negative electrode. And a main surface located on the outermost part of the second glass substrate is disposed so as to be opposed to the positive electrode, and then a DC voltage is applied between the positive electrode and the negative electrode to corona. A method for treating a glass substrate, comprising: a step of generating electric discharge.   In the step of generating the corona discharge, one or more alkali ions in the first glass substrate and the second glass substrate are moved toward the negative electrode, respectively, and the first glass substrate The processing method of the glass substrate of Claim 1 which changes the molar ratio of each content of an alkali ion in the surface layer part of the said 1st main surface side.   3. The glass substrate processing method according to claim 2, wherein a total mole of each content of alkali ions in the first glass substrate is substantially constant before and after the step of generating the corona discharge. In the second glass, the molar ratio of the content of sodium oxide to the content of alkali metal oxides other than sodium oxide is larger than the molar ratio in the first glass,
In the step of generating corona discharge, the molar ratio of the content of sodium ions to the content of alkali ions other than sodium ions is increased in the surface layer portion on the first main surface side of the first glass substrate. The processing method of the glass substrate of Claim 2 or 3. In the second glass, the molar ratio of the content of potassium oxide to the content of alkali metal oxides other than potassium oxide is larger than the molar ratio in the first glass,
In the step of generating the corona discharge, the molar ratio of the content of potassium ions to the content of alkali ions other than potassium ions is increased in the surface layer portion on the first main surface side of the first glass substrate. The processing method of the glass substrate of Claim 2 or 3.   The glass substrate processing method according to claim 1, wherein the positive electrode has a smaller electrode area than the negative electrode.   The glass according to claim 6, wherein the positive electrode is a wire-like electrode, and the wire-like electrode is arranged in parallel to the outer main surface of the second glass substrate located on the outermost part of the stacked substrate. Substrate processing method.   The glass according to claim 6, wherein the positive electrode is a needle-like electrode, and the needle-like electrode is disposed perpendicular to the outer main surface of the second glass substrate located on the outermost part of the stacked substrate. Substrate processing method.   The processing method of the glass substrate of any one of Claims 1-8 by which the atmosphere mainly consisting of air or nitrogen is hold | maintained between the said positive electrode and the said negative electrode.   The processing method of the glass of any one of Claims 1-9 whose temperature of the said stacked substrate is normal temperature-400 degreeC.

Images