TW201442964A - Method for molding glass substrate - Google Patents

Abstract

Provided is a method for press-molding a glass substrate using a molding die, and inexpensively obtaining a glass molded article having high molded surface smoothness and high quality. The present invention is provided with: a surface processing step for placing a glass substrate having a pair of principal faces and comprising a glass containing an alkali oxide in the composition thereof between a first electrode and a second electrode, generating a corona discharge by applying a direct-current voltage so that the first electrode is a positive electrode and the second electrode is a ground or a negative electrode, and causing at least one species of alkali ion to move toward the second principal face side, which is the ground side or the negative electrode side, in a surface part on the first principal face side, which is the positive electrode side of the glass substrate; and a molding step for placing a molding die so that a press face abuts on the first principal face of the glass substrate, the surface of which has been processed in the surface processing step, and press-molding the glass substrate while maintaining the glass substrate at a predetermined temperature. The present invention furthermore has a mold release step for cooling the glass substrate and the molding die after the molding step, and separating the press face of the molding die from the first principal face of the glass substrate.

Description

Method for forming glass substrate Field of invention

The present invention relates to a method for forming a glass substrate, and more particularly to a method for producing a glass substrate having a molding surface having a high shape stability by press molding at a low cost.

Background of the invention

In recent years, as a method of producing a glass optical element such as a lens and a crucible, a press molding method is employed in which a glass material which has been heated and softened is pressurized using a mold (hereinafter also referred to as a "forming mold"). And formed. Further, a glass substrate for use in a magnetic recording medium or the like is produced by press molding using a molding die. The press forming method is formed by sequentially transferring the pressed surface of the forming mold such as a smooth mold surface of high precision to the glass material to have a smooth and high-quality forming surface, and the cost is obtained. a low and highly productive method, the steps of: heating and softening the glass material; the step of pressurizing and forming using a forming mold; and separating the forming mold from the glass formed body after cooling (hereinafter referred to as "off The steps of the module").

In the press forming method described, in order to prevent the forming mold from melting In the case of a glass which has been softened at a high temperature, a press-formed surface which is processed with high precision is protected, and a forming surface of a glass molded body having a high smoothness is obtained, and a release film is applied to the pressed surface of the molding die. . For the release film, in addition to the release property from the glass, the adhesion to the molding die, the smoothness of the surface, and the high hardness, etc., the Cr plating film, the Ni plating film, the carbon film, and the like have been used. A noble metal film such as Ir or Re. Further, in Patent Document 1, a boron nitride film is proposed as a release film having high hardness and excellent durability against thermal cycling, and in particular, does not chemically react with lead-containing glass.

However, in the case of such release films, there is a problem that the cost of the material itself becomes high and the operation cost of the film formation is high.

Further, Patent Document 2 discloses a method of forming a metal salt such as a higher fatty acid on at least a mold surface (pressing surface) of a molding die in the molding of a glass substrate for a magnetic recording medium. The layer is formed to improve the mold release property between the mold and the glass substrate of the formed body.

However, in this method, in order to prevent the residue of the release agent from being accumulated on the pressed surface of the mold and transferred onto the glass substrate, not only the film thickness of the release agent layer is difficult to control, but also needs to be formed each time. The release agent is applied to form a release agent layer having a desired thickness, so that there is a problem that work efficiency is not good.

Advanced technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 5-147954

Patent Document 2: Japanese Patent Laid-Open Publication No. 2004-131315

Summary of invention

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a method for forming a glass molded body having a high smoothness and high quality of a molded surface by press molding a glass substrate using a molding die.

The method for molding a glass substrate of the present invention comprises the step of: a surface treatment step of disposing a glass substrate having a pair of main faces and having a glass containing a basic oxide in a composition between the first electrode and the second electrode; And the first electrode is a positive electrode and the second electrode is a ground or a negative electrode, and a DC voltage is applied to the glass substrate to cause corona discharge, and the surface portion on the first main surface side of the glass substrate positive electrode side is formed. And moving the at least one type of alkali ions toward the second main surface side of the ground or the negative electrode side; and the forming step of arranging the forming mold so that the pressing surface and the glass substrate subjected to the surface treatment by the surface treatment step are The first main surface abuts and is press-formed while maintaining the glass substrate at a predetermined temperature.

In the method for forming a glass substrate of the present invention, it is preferred to have a demolding step of cooling the glass substrate and the forming mold after the forming step, and the pressing surface of the forming mold from the glass substrate The first main surface is separated. Further, the forming step is preferably carried out in a gas atmosphere mainly composed of nitrogen.

In the method for forming a glass substrate of the present invention, in the surface treatment step, the glass substrate is preferably disposed such that the first main surface and the foregoing The first electrode is separated and the second main surface is in contact with the second electrode, and a DC voltage is applied to the first electrode as a positive electrode and the second electrode is a ground or a negative electrode to cause corona discharge. Further, in the surface treatment step, the first electrode is preferably a linear electrode, and the linear electrode is preferably disposed such that its length is parallel to the first main surface of the glass substrate.

Further, in the surface treatment step, it is preferable that the first electrode and the second electrode are held in a gas atmosphere mainly composed of air or nitrogen. Further, the temperature of the glass substrate is preferably from room temperature to glass transition point Tg. Further, it is preferable that the second electrode is integrated with the glass substrate, and is moved in parallel with respect to an arrangement surface of the first electrode that is parallel to the first main surface. In addition, the glass substrate is preferably made of a glass material containing a basic oxide and an alkaline earth oxide in a total amount of more than 15% by mass.

According to the forming method of the present invention, a glass molded body having high surface smoothness and high quality can be obtained by press forming, and in the demolding step after forming, the pressed surface of the forming mold is used from the glass substrate. The force required for demolding the first main surface of the pressing surface (hereinafter, also referred to as "release force") is extremely small, so that it is not necessary to form a release film of carbon or precious metal on the pressed surface of the forming mold. The mold release treatment such as applying a release agent or the like is carried out at a low cost.

Further, as described above, since the mold releasing force of the molding die is extremely small, there is no possibility that the pressed surface of the glass substrate is deformed by adhesion to the molding die at the time of demolding, and the shape stability is high. And due to the release force When the reduction, the mechanical deterioration of the forming mold is also suppressed, so that the use period of the forming mold becomes long, which not only reduces the cost, but also saves the time required for the mold replacement, so the productivity is improved.

1‧‧‧ surface treatment equipment

2‧‧‧1st electrode (positive electrode)

2a‧‧‧Linear electrode

2b‧‧‧needle electrode

3‧‧‧2nd electrode (ground or negative)

4‧‧‧ glass substrate

5‧‧‧DC power supply

6‧‧‧ galvanometer

10‧‧‧Forming device

11‧‧‧ Lower mold

12‧‧‧Upper mold

13‧‧‧Forming mould

14‧‧‧Mold body

14a‧‧‧Compressed noodles

15‧‧‧ glass substrate

15a‧‧‧1st main surface of the glass substrate

D‧‧‧ interval

Fig. 1A is a front view showing a schematic configuration of an example of a surface treatment apparatus used in the surface treatment step of the embodiment of the present invention.

Fig. 1B is a plan view showing the arrangement of the first electrode of the glass substrate in an example of the surface treatment apparatus used in the surface treatment step of the embodiment of the present invention.

Fig. 2A is a front view showing a schematic structure of another example of the surface treatment apparatus used in the surface treatment step of the embodiment of the present invention.

Fig. 2B is a plan view showing the arrangement of the first electrode of the glass substrate in another example of the surface treatment apparatus used in the surface treatment step of the embodiment of the present invention.

Fig. 3 is a cross-sectional view showing an example of a molding apparatus used in the molding step of the embodiment of the present invention.

Figure 4 is a graph showing the change in temperature and pressing force of the forming mold in the case of the glass substrate without the surface treatment step.

Fig. 5 is a graph showing the temporal change of the measured values of the temperature and the pressing force of the forming molds (the upper mold and the lower mold) in the first embodiment.

Fig. 6 is a view showing a cross-sectional shape of a pressed surface (forming surface) of the glass substrate after demolding in the first embodiment.

Fig. 7 is a graph showing the change in the measured values of the temperature and the pressing force of the forming mold (upper mold and lower mold) in the comparative example.

Fig. 8 is a view showing a cross-sectional shape of a pressed surface (forming surface) of a glass substrate after demolding in a comparative example.

Fig. 9 is a graph showing the relationship between the molding temperature and the release force generated for each of the glass substrates having surface treatment and surface treatment.

Form for implementing the invention

In the present specification, the basic oxide means an alkali metal oxide, the alkali ion means an alkali metal ion, the alkaline earth oxide means an alkaline earth metal oxide, and the alkaline earth ion means an alkaline earth metal ion. Hereinafter, embodiments of the present invention will be described.

The method for molding a glass substrate according to an embodiment includes a surface treatment step and a molding step. The surface treatment step is performed between the first electrode and the second electrode, and a glass substrate having a pair of main faces (the first main surface and the second main surface) and made of a glass containing an alkali oxide is disposed. The first electrode is a positive electrode and the second electrode is a ground or a negative electrode. A DC voltage is applied to the glass substrate to cause corona discharge, and the surface layer portion on the first main surface side of the glass substrate positive electrode side is made. At least one type of alkali ion moves toward the second main surface side of the ground or the negative electrode side. Further, the forming step is such that the forming die is disposed such that the pressing surface abuts against the first main surface of the glass substrate subjected to the surface treatment step, and the glass substrate is maintained at a predetermined temperature. Press the shaper. Further, the method for forming a glass substrate according to the embodiment further includes a mold release step of cooling the mold after the forming step, and separating the pressed surface of the mold from the first main surface of the glass substrate.

According to the molding method of the embodiment of the present invention, in the surface treatment step, a DC voltage is applied to the glass substrate to cause corona discharge, and the alkali ions are oriented in the surface layer portion on the first main surface side of the glass substrate positive electrode side. By moving the second main surface of the ground or the negative electrode side, a low alkali concentration region can be formed on the surface layer portion of the positive electrode side of the glass substrate, and the low alkali concentration region is a ratio of alkali ions to other regions (for example, Glass matrix) is low. Further, in the low alkali concentration region, as the content ratio of the alkali ions decreases, the content ratio of SiO ₂ becomes higher than that in other regions. Here, the "glass matrix" means a glass material constituting a glass substrate before the surface treatment. In the case of a glass substrate, the region other than the low alkali concentration region subjected to the surface treatment may be a glass composition which is approximately the same as the glass matrix.

Then, the surface treatment is performed in such a manner that the glass substrate having the low alkali concentration region formed on the surface layer portion on the first main surface side is disposed in the molding step so that the pressing surface and the first main surface can be disposed. When it is held at a predetermined temperature (hereinafter, also referred to as "forming temperature") which is maintained at a glass transition point Tg of the glass substrate, it is pressurized by the smooth pressing surface of the molding die, whereby the glass substrate is The press molding is performed, and the first main surface of the pressed surface is a surface having high smoothness.

In the subsequent demolding step, the pressed surface of the forming mold is separated (released) from the first main surface of the glass substrate, but at this time, the releasing force required for demolding is as small as nearly zero, and The situation after the glass substrate which has not been subjected to surface treatment is significantly reduced as compared with the case after press forming.

The reason why the mold release force is extremely small is estimated to be caused by the reason shown below.

Usually, when the glass substrate which has not been surface-treated is press-formed at the aforementioned forming temperature, the pressed surface of the forming mold and the pressed surface of the glass substrate are fused at the time of pressing, and the releasing force occurs in the demolding step. This is because the temperature at which the pressed surface of the forming mold and the pressed surface of the glass substrate start to melt (hereinafter referred to as "melting start temperature") is lower than the forming temperature.

However, according to the present embodiment, in the surface layer portion on the first main surface side of the pressed surface of the glass substrate, as described above, the content ratio of the alkali ions is lowered and the content ratio of the SiO ₂ is relatively low due to the surface treatment. When it becomes high, the melting start temperature becomes higher than the melting start temperature of the glass substrate which is not subjected to the surface treatment.

On the other hand, since the forming temperature depends on the glass substrate, the glass substrate is fixed regardless of the presence or absence of the surface treatment. Further, the aforementioned forming temperature applicable to the formation of the glass substrate has a predetermined range. In the case of a glass substrate which is not subjected to surface treatment, the melting start temperature is approximately equal to or lower than the lower limit of the forming temperature range. However, in the case of the glass substrate to which the surface treatment is applied, the melting start temperature becomes a high temperature exceeding the lower limit of the molding temperature range, so that the molding temperature can be appropriately set to a temperature lower than the melting start temperature. Therefore, since the glass substrate to which the surface treatment is applied can be formed at a molding temperature <melting start temperature and can be press-molded at a temperature lower than the melting start temperature, there is no possibility between the pressed surface of the forming mold and the glass substrate. The occurrence of the fusion occurs, and therefore, the releasing force required for demolding is extremely small to almost zero. The measurement of the release force will be described in further detail later.

As described, the forming method according to the embodiment is formed by press forming Since the mold release force of the subsequent molding die is extremely small (nearly close to 0), the shape stability of the molding surface of the pressed surface of the glass substrate is good, and deformation of the cross-sectional shape toward the separation direction does not occur. Further, since the above-mentioned reduction in the releasing force, the mechanical deterioration of the forming mold is also suppressed, so that the service life becomes long and the cost can be reduced.

Hereinafter, each step of the embodiment of the present invention will be described.

[Surface treatment steps]

In the surface treatment step, first, a glass substrate having a pair of main faces and composed of a glass containing a basic oxide is disposed between the first electrode and the second electrode. The glass substrate is disposed such that one of the main faces (first main faces) is separated from the first electrode, and the other main face (second main face) is in contact with the second electrode. Then, a DC voltage is applied so that the first electrode is a positive electrode and the second electrode is a ground or a negative electrode, so that corona discharge occurs between the electrodes, and the first main surface side close to the positive electrode of the glass substrate is generated by the corona discharge generated. In the surface layer portion, at least one type of alkali ions is moved toward the second main surface side of the ground or the negative electrode side. In the surface layer portion on the first main surface side, the ratio of the alkali ion content (hereinafter, also referred to as "concentration concentration") is reduced, and the concentration of alkali ions is formed to be higher than that of the other alkali ions. A low alkali concentration region of the region (eg, glass matrix).

In the present embodiment, the surface treatment of the glass substrate is carried out by corona discharge as described above. In the surface treatment by corona discharge, there is no case where the electrode described later is in contact with the surface to be treated of the glass substrate. Therefore, when corona discharge is used, the surface treatment of the glass substrate can be performed without damaging the surface to be processed.

In addition, when the glass constituting the substrate contains an alkali ion and also contains an alkaline earth ion, the surface layer portion of the positive electrode side of the glass substrate is not only alkali ions but also alkaline earth ions moving toward the ground or the negative electrode side. In the low alkali concentration region of the surface layer portion of the positive electrode side of the glass substrate, not only the concentration of the alkali ions but also the concentration of the alkaline earth ions is lower than other regions. However, since the moving distance per unit time is larger than that of the alkaline earth ions, the ions which are moved by the corona discharge are representative of alkali ions. Therefore, it is described as a low concentration region of alkali ions.

Further, when the glass substrate contains a plurality of basic oxides in its composition, a plurality of alkali ions move toward the ground or the negative electrode side, and as a result, a region in which each alkali ion has a lower concentration than other regions is formed on the glass substrate. The surface layer. However, since sodium ions among the alkali ions are most likely to move and the effect of lifting release due to movement is large, in the surface treatment step, the alkali ions which are moved by the corona discharge are mainly sodium ions, thereby For the purpose of forming a low concentration region of sodium ions.

<glass substrate>

The glass substrate subjected to the surface treatment in the surface treatment step is composed of a glass material containing a basic oxide in the composition, that is, a glass substrate. The composition of the glass substrate is not particularly limited as long as it has at least one basic oxide. From the viewpoint of easiness of surface treatment, it is preferred to contain a basic oxide and a base in a total amount of more than 15% by mass. Tus oxides.

The glass material described above is exemplified by the mass % of the oxide based on the oxide, and contains 50 to 80% of SiO ₂ , 0.5 to 25% of Al ₂ O ₃ , and 0 to 10% of B. ₂ O ₃ , 10 to 16% Na ₂ O, 0 to 8% K ₂ O, 0 to 16% Li ₂ O, 0 to 10% CaO, 0 to 12% MgO, and others total less than 10 % of SrO, BaO, ZrO ₂ , ZnO and SnO _{2 ,} etc. Hereinafter, each component constituting the glass will be described. In addition, "%" means mass%.

SiO ₂ is a component of the skeleton of the glass. When the content ratio of SiO ₂ is less than 50%, the stability as glass may be lowered, or the weather resistance may be lowered. Therefore, the content ratio of SiO ₂ is preferably 60% or more. It is preferably 62% or more, and particularly preferably 63% or more.

When the content ratio of SiO ₂ exceeds 80%, the viscosity of the glass increases, and there is a fear that the meltability is remarkably lowered. The content ratio of SiO ₂ is preferably 76% or less, more preferably 74% or less.

Al ₂ O ₃ is a component that increases the moving speed of alkali ions. When the content ratio of Al ₂ O ₃ is less than 0.5%, there is a fear that the moving speed of the alkali ions is lowered. Therefore, the content ratio of Al ₂ O ₃ is preferably 1% or more, more preferably 2.5% or more, and particularly preferably 4% or more, and most preferably 6% or more.

When the content ratio of Al ₂ O ₃ exceeds 25%, the viscosity of the glass becomes high, and it is feared that homogeneous melting becomes difficult. Therefore, the content ratio of Al ₂ O ₃ is preferably 20% or less. It is preferably 16% or less, and particularly preferably 14% or less.

Although B ₂ O ₃ is not an essential component, it is a component which can also be contained in order to improve the meltability at a high temperature or the strength of glass. When B ₂ O ₃ is contained, the content ratio is preferably 0.5% or more, more preferably 1% or more.

Further, the content ratio of B ₂ O ₃ is 10% or less. Since B ₂ O ₃ tends to evaporate due to coexistence with an alkali component, it is difficult to obtain a homogeneous glass. The content ratio of B ₂ O ₃ is preferably 6% or less, more preferably 1.5% or less. In particular, in order to improve the homogeneity of the glass, it is preferred that B ₂ O ₃ is not contained.

Na ₂ O is a component that enhances the meltability of glass and has a main ion (sodium ion) that moves due to corona discharge. If the content ratio of Na ₂ O is less than 10%, it is difficult to obtain the effect of moving alkali ions due to corona discharge. Therefore, the content ratio of Na ₂ O is preferably 11% or more, and more preferably 12% or more.

The content ratio of Na ₂ O is 16% or less. If it exceeds 16%, the glass transition point Tg will decrease, and the strain point will become lower, which may result in poor heat resistance or weather resistance. Therefore, the content ratio of Na ₂ O is preferably 15% or less, more preferably 14% or less, and particularly preferably 13% or less.

Although K ₂ O is not an essential component, it may be contained because it is a component which enhances the meltability of glass and is a component which is easily moved by corona discharge. When K ₂ O is contained, the content ratio thereof is preferably 1% or more, and more preferably 3% or more.

Further, the content ratio of K ₂ O is 8% or less. If the content ratio of K ₂ O exceeds 8%, there is a fear that the weather resistance will be lowered. Therefore, it is preferably 5% or less.

Li ₂ O is also an essential component of K ₂ O, but may be contained because it is a component which enhances the meltability of glass and is a component which is easily moved by corona discharge. When Li ₂ O is contained, the content ratio thereof is preferably 1% or more, and more preferably 3% or more.

Further, the content of Li ₂ O is 16% or less. If the content ratio of Li ₂ O exceeds 16%, there is a fear that the strain point becomes too low. Therefore, the content ratio of Li ₂ O is preferably 14% or less, and particularly preferably 12% or less.

The alkaline earth oxide is a component which enhances the meltability of the glass and is also a component effective for the adjustment of Tg.

Among the alkaline earth oxides, although MgO is not an essential component, it is a component which raises the Young's modulus of the glass to increase the strength and improve the meltability. Therefore, it is preferred to contain more than 1% of MgO. The content ratio of MgO is preferably 3% or more, and more preferably 5% or more.

Further, the content ratio of MgO is 12% or less. If the content ratio of MgO exceeds 12%, there is a fear that the stability of the glass is impaired. Therefore, the content ratio of MgO is preferably 10% or less, and preferably 8% or less.

Although CaO is not an essential component, when CaO is contained, the content ratio is typically 0.05% or more. Further, the content ratio of CaO is 10% or less. If the content ratio of CaO exceeds 10%, there is a fear that the amount of movement of alkali ions due to corona discharge is lowered. Therefore, the content ratio of CaO is preferably 6% or less, more preferably 2% or less, and particularly preferably 0.5% or less.

In order to increase the meltability of the glass and to stabilize the corona discharge by the adjustment of Tg, the total ratio (total amount) of the content ratio of the basic oxide to the alkaline earth oxide is more than 15%. should. The total content ratio of the basic oxide to the alkaline earth oxide is preferably 17% or more, particularly preferably 20% or more, and the upper limit is preferably 35%.

The glass constituting the glass substrate subjected to the surface treatment in the surface treatment step may contain other components. When the component is contained, the total content of the components is preferably 10% or less, preferably 5% or less. It is particularly preferable to consist essentially of the above components. Further, the glass containing each of these components may suitably contain SO ₃ , a chloride, a fluoride or the like as a clarifying agent at the time of melting.

In addition, the glass transition temperature Tg in the glass material is preferably It is roughly in the range of 400~700 °C. However, the glass transition temperature Tg in the glass material of the glass substrate used in the molding method of the present invention is not limited thereto.

The shape of the glass substrate composed of the glass material is not particularly limited as long as it has a shape of a pair of main faces. Further, it may be a flat plate having a flat main surface, or a pair of curved surfaces having a curved main surface. Examples of the glass substrate include a glass substrate used as a glass optical element such as an optical lens, a lens array, and a reflection plate. In addition, in the present specification, the flat or curved glass substrate is also referred to as a "glass substrate", and an example in which the glass substrate is a glass substrate will be described below.

<first electrode and second electrode>

In the surface treatment step, for example, the first electrode and the second electrode connected to the DC power source are disposed to face each other with a predetermined interval therebetween, and the glass substrate is disposed between the electrodes. That is, the glass substrate is disposed such that the first main surface (for example, the upper surface) of the glass substrate is separated from the first electrode by a predetermined distance, and the second main surface (for example, the lower surface) is in contact with the second electrode. Then, a DC voltage is applied so that the first electrode is a positive electrode and the second electrode is a ground or a negative electrode, so that corona discharge occurs between the electrodes.

The distance between the upper surface of the glass substrate and the first electrode that is the positive electrode varies depending on the shape of the first electrode and the applied voltage. However, the larger the distance, the smaller the discharge current and the weaker the corona discharge. It is made larger than 0 mm, and preferably 30 mm or less. In other words, the closer the distance is, the larger the discharge current will be parabolically and the corona discharge will become stronger, so it is preferably larger than 0 mm and 10 mm or less.

Here, the electrode area of the first electrode which is the positive electrode is preferably smaller than the electrode area of the second electrode which is the ground or the negative electrode. In addition, the "electrode area" means that the first electrode of the positive electrode refers to the projected area of the main surface of the glass substrate of the object to be processed, and the second electrode which is grounded or the negative electrode means the glass and the glass. The area of contact of the second main surface of the substrate. In the case where the first electrode is a collection of a plurality of linear or needle-shaped electrodes, the "electrode area" refers to the total of the "electrode areas" for each of the linear electrodes or the respective needle electrodes.

A linear electrode or a needle-shaped electrode having a sharp portion at the tip end may be used as the first electrode of the positive electrode. These linear electrodes and the needle electrodes may be used singly or in a plurality of intervals at predetermined intervals (pitch), and the aggregates may be used as the first electrode. As described above, the surface of the glass substrate can be uniformly treated by disposing a plurality of linear electrodes or needle electrodes at a predetermined interval (pitch) from each other as the first electrode.

Examples of the apparatus used in the surface treatment step are shown in Fig. 1A, Fig. 1B, and Figs. 2A and 2B. 1A and 2A are front views schematically showing the structure of the surface treatment apparatus 1. Fig. 1B and Fig. 2B are plan views of the surface treatment apparatus 1 for explaining the arrangement of the first electrode with respect to the glass substrate. In the surface treatment apparatus 1 shown in FIG. 1A, the linear electrode 2a is provided as the first electrode 2 of the positive electrode. Further, in the surface treatment apparatus 1 shown in FIG. 2A, a needle electrode 2b is provided as the first electrode 2. In addition, in FIG. 1A, FIG. 1B, FIG. 2A, and FIG. 2B, the code|symbol 3 shows the 2nd electrode which is a ground or a negative electrode, and the code|symbol 4 shows the glass substrate of the to-be-processed object. Also, symbol 5 represents a DC power source, and symbol 6 represents an ammeter for monitoring the current through the circuit.

In the surface treatment apparatus 1 shown in FIG. 1A, from the corona discharge From the viewpoint of easiness of occurrence, the linear electrode 2a of the first electrode 2 is preferably thin, and the diameter of the linear electrode 2a is preferably 0.03 to 0.8 mm from the viewpoint of strength and ease of handling. And 0.1~0.7mm is preferred. Moreover, it is preferable that the linear electrode 2a is arranged such that its longitudinal direction is parallel to the upper surface of the glass substrate 4. When a plurality of linear electrodes 2a are used as the first electrode 2, as shown in FIG. 1B, each linear electrode 2a is spaced apart by a distance of 0 mm and a distance d between the glass substrate 4 and the linear electrode 2a. And parallel to each other and disposed on a plane parallel to the upper surface of the glass substrate 4, it is preferable to uniformly treat the upper surface of the glass substrate 4. As will be described later, when the glass substrate 4 is moved in parallel with respect to the arrangement surface of the linear electrode 2a which is parallel to the upper surface of the glass substrate 4, the processing unevenness is alleviated by the parallel movement of the glass substrate 4, so the respective linear electrodes 2a The interval can be larger.

In the case where the single linear electrode 2a is separately disposed as the first electrode 2, in order to uniformly treat the surface of the glass substrate 4, the concentration of alkali ions in the low alkali concentration region formed in the surface layer portion of the positive electrode side is contained. The distribution is uniform, and it is preferable to make the second electrode 3 integrated with the glass substrate 4 to move relative to the linear electrode 2a of the first electrode 2. The second electrode 3, which is grounded or negative, is moved in parallel with respect to the arrangement surface of the linear electrode 2a parallel to the upper surface of the glass substrate 4, that is, it is preferably perpendicular to the discharge direction of the corona discharge. On the movement. Further, it is preferable that the second electrode 3 of the ground or the negative electrode moves in a direction perpendicular to the longitudinal direction of the linear electrode 2a in a state in which the glass substrate 4 is loaded. Although the motion is preferably linear or round-trip motion, it can also be a rotary motion or a rocking motion.

Furthermore, it is desirable to use the widely used so-called "corona" (Crotron.scorotron) The coring discharge charging unit is similarly provided with a cylindrical or even square casing. A gate electrode can also be provided. Due to the action of the shield and the gate electrode, the flow of ions of the corona discharge can be controlled, thereby improving the uniformity of processing on the glass substrate and improving the processing efficiency.

In the surface treatment apparatus 1 shown in FIG. 2A, the diameter of the base portion of the needle electrode 2b of the first electrode 2 is preferably 0.1 to 2 mm, and is preferably arranged such that the sharp portion of the front end of the needle electrode 2b faces the glass substrate 4. Above, and its length direction is perpendicular to the top. When a plurality of needle electrodes 2b are used as the first electrode 2, it is preferable that each of the needle electrodes 2b is arranged in parallel with each other so that the longitudinal direction thereof is perpendicular to the upper surface of the glass plate 4, and the front end portion thereof is apart from the upper surface of the glass substrate 4. Isometric. Further, as shown in FIG. 2B, the arrangement position of each of the needle electrodes 2b is larger than 0 mm, and is spaced apart from the distance between the glass substrate 4 and the needle electrode 2b by a distance d, and is a bird shape or a lattice shape. The uniform arrangement is ideal for uniformly treating the surface of the surface of the glass substrate 4. When the glass substrate 4 is moved in parallel with respect to the surface parallel to the upper surface of the glass substrate 4 where the front end portion of the needle electrode 2b is located, since the movement of the glass substrate 4 can alleviate the processing unevenness, the interval between the respective needle electrodes 2b can be Bigger.

The angle (the front end angle) of the sharp portion of the front end of the needle electrode 2b is the smaller the acute angle, and the electric field strength immediately below becomes larger. Therefore, by adjusting the front end angle of the needle electrode 2b, the positive electrode can be adjusted. The electric field strength near the electrode 2. The front end angle of the needle electrode 2b is preferably 1 to 15 degrees, and preferably 1 to 9 degrees.

When the linear electrode 2a and the needle electrode 2b are provided with a conductive film having corrosion resistance such as gold, platinum, or other noble metal, the electric field is strong. The uniformity of the degree will become good and the durability as an electrode will increase.

In the surface treatment apparatus 1 shown in FIG. 1A and FIG. 2A, the second electrode 3 which is a ground or a negative electrode is preferably in the form of a flat plate or a curved plate, and has a second main surface of the glass substrate 4 to which the object to be processed is attached (below The shape of the person. Further, it may be a mesh having a perforated portion or the like, and may be uniformly contacted with the glass substrate 4 in the plane.

By disposing the second electrode 3 in contact with the lower surface of the glass substrate 4, the conductivity of the glass substrate 4 is improved, so that the applied voltage can be increased. In the second electrode 3, by providing a conductive film such as ITO on the contact surface with the glass substrate 4, the conductivity can be further improved. Next, the conditions of the surface treatment (temperature of the glass substrate, processing gas atmosphere, etc.) will be described.

<surface treatment conditions>

The temperature of the glass substrate in the surface treatment step is preferably from normal temperature to the glass transition point Tg. By setting the temperature to be lower than Tg, it is possible to form a low alkali concentration region having a sufficient thickness in the surface layer portion of the glass substrate without causing deformation of the glass substrate and deterioration of the processing member. Further, since the temperature range is not more than Tg, and the glass is in a solid state in which the viscosity is sufficiently large, there is no possibility that the alkali ions in the glass substrate are excessively moved, and the direction of movement of the alkali ions is limited to the electric field. Since the direction is grounded or the direction of the negative side, the surface treatment by corona discharge is highly efficient. The temperature of the glass substrate is preferably 25 to 400 ° C, preferably 100 to 300 ° C. However, when the Tg is 400 ° C or lower, the temperature of the glass substrate is preferably lower.

The DC voltage applied between the first electrode and the second electrode is such that the first electrode is a positive electrode and the second electrode is a ground or a negative electrode, and the electrodes are The voltage at which the corona discharge occurs is more specifically the voltage at which the corona discharge is generated by the first electrode of the positive electrode. The applied voltage also changes depending on the shape of the first electrode and the temperature of the glass substrate of the object to be processed, but it is preferably in the range of 3 to 12 kV. Corona discharge is less likely to occur if the applied voltage is less than 3 kV. On the other hand, once the applied voltage exceeds 12 kV, arc discharge easily occurs, and it is difficult to continue the corona discharge. Therefore, the applied voltage is preferably 5 to 10 kV.

In the surface treatment step, the current flowing in the glass substrate as the object to be processed due to the application of the DC voltage includes the current generated by the movement of the electrons and the current generated by the movement of the cation containing the alkali ions. By. The current flowing through the glass substrate is preferably in the range of 0.01 to 1000 mA, and preferably 0.1 to 100 mA. Further, the amount of electricity per unit area is preferably in the range of 10 to 500 mC/cm ² , preferably 50 to 400 mC/cm ² , more preferably 100 to 300 mC/cm ² .

In the surface treatment step, the treatment time, that is, the time during which the corona discharge is continued, depends on the applied voltage, the distance between the first electrode and the second electrode, and the shape and arrangement of the first electrode. 1 to 100 hours, preferably 2 to 10 hours.

In the surface treatment step, the first electrode and the second electrode disposed between the glass substrate of the object to be treated can be held in a gas atmosphere mainly composed of air or nitrogen. Here, the "gas environment mainly composed of air or nitrogen" means a gas state in which the content ratio of air or nitrogen exceeds 50% by volume of all gases in the gaseous environment.

As described above, the second electrode that is grounded or negatively disposed is placed in contact with the second main surface (for example, the lower surface) of the glass substrate, and the second electrode and the glass are disposed. The electrical conductivity between the substrates has been improved, so that it is not necessary to provide a gas atmosphere such as a plasma of krypton and argon. That is, the surface of the glass substrate can be treated by corona discharge around the first electrode in a gas atmosphere mainly composed of air or nitrogen.

[Forming step]

In the forming step, the forming mold is disposed such that the pressing surface (mold surface) abuts against the first main surface of the glass substrate, and is pressed and formed by holding the glass substrate at a predetermined temperature; The glass-based system has been subjected to surface treatment by the aforementioned surface treatment steps and a region having a low alkali concentration has been formed on the surface portion.

<Forming device>

An example of a molding apparatus used in the molding step of the embodiment is shown in Fig. 3 . FIG. 3 is a cross-sectional view schematically showing the configuration of the forming apparatus 10.

The molding apparatus 10 is provided with a fixed mold 11 and a molding die 13 having an upper mold 12, and the upper mold 12 is disposed to face the lower mold 11. The upper mold 12 is configured to be movable up and down, and the mold body 14 is provided on the lower surface of the upper mold 12 opposite to the lower mold 11. Then, the glass substrate 15 which has been subjected to the surface treatment in the surface treatment step is held in such a manner that the second main surface thereof faces downward and is placed on the lower mold 11, and the pressed surface of the mold body 14 is pressed. 14a is in contact with the first main surface (the main surface on the side where the low alkali concentration region is formed) 15a.

Further, in the molding apparatus 10, the glass substrate 15 and the molding die 13 (particularly, the mold body 14) are heated to a predetermined temperature at which press molding can be performed, and in order to maintain the temperature, the adjacent ones or the like Waiting nearby, A heating mechanism such as an electric heater (not shown) is disposed. Further, a pressurizing mechanism (not shown) is provided, and the upper mold 12 is lowered and a load (pressure) is applied thereto to press the pressing surface 14a of the mold body 14 against the glass substrate 15 . The pressed surface is the first main surface 15a. Further, the forming apparatus 10 described above is disposed in a chamber (not shown) that has been controlled to a nitrogen gas atmosphere or the like. Further, in the case of molding in the atmosphere, a structure having no chamber can be provided. Further, the heating means is not limited to an electric heater, and may be electromagnetic induction heating or the like as long as the glass substrate 15 or the like can be heated and held at a predetermined temperature. In other words, the pressurizing mechanism may be any mechanism as long as it can press the pressing surface 14a of the mold main body 14 against the pressed surface of the glass substrate 15.

The upper mold 12 and the lower mold 11 above the forming mold 13 may be composed of a well-known mold material such as stainless steel and tungsten carbide (WC). The constituent material is not particularly limited as long as it has hardness and durability which can be used as a mold.

The mold body 14 disposed on the lower surface of the mold 12 opposite to the lower mold 11 is a press surface 14a which is in contact with the glass substrate 15 and is pressed, and is formed to fit the glass substrate 15 for molding. The shape of the first main surface 15a is formed into a mirror surface by, for example, polishing. Then, by pressing the press surface 14a which is formed into a mirror surface, the surface of the press surface 14a is transferred onto the first main surface 15a of the glass substrate 15 to form a smooth surface. Therefore, the mold body 14 having the pressing surface 14a is preferably composed of a material having excellent heat resistance and mold release property to the glass and having mechanical strength and durability. As a material constituting the mold body 14 described above, for example, a glass stone Ink-like carbon, stainless steel, tantalum carbide (SiC) and tungsten carbide (WC).

In the forming step, the glass substrate 15 and the forming mold 13 (particularly the mold body 14) are lowered in a state where they have been heated to a predetermined temperature at which press forming is possible, and the pressed surface 14a of the mold body 14 is tight. It is pressed against the pressed surface of the glass substrate 15, that is, the first main surface 15a, and is pressurized by a predetermined pressing force.

The heating temperature (forming temperature) T at the time of molding is a temperature at which the glass material (glass matrix) constituting the glass substrate 15 is softened to a level that can be press-formed, and therefore it is preferably set to be 50 higher than the glass transition point Tg of the glass material. Temperature of ~150 °C. The molding temperature T is preferably set to a temperature 50 to 100 ° C higher than Tg from the viewpoint of obtaining a glass molded body having high surface smoothness and high quality, and is particularly preferably at a temperature 70 to 80 ° C higher than Tg. .

The gas atmosphere in which the glass substrate 15 is press-molded, for example, the gas atmosphere in the chamber (not shown) in which the molding apparatus 10 is disposed is preferably a gas atmosphere mainly composed of nitrogen. Here, the "nitrogen-based gas atmosphere" means a gas state in which the nitrogen content ratio exceeds 50% by volume of all gases in the gas atmosphere, and preferably a gas atmosphere in which the nitrogen content ratio is approximately 100% by volume.

The pressing force per unit area of the pressed surface of the glass substrate 15 to be pressed is preferably in the range of 0.01 MPa to 10 MPa, and preferably 0.1 MPa to 5 MPa. In addition, there is also a time when the pressing force is called "pressing pressure". By setting the pressing force (pressing pressure) in this range, the smooth shape of the pressed surface 14a of the mold main body 14 can be favorably transferred and formed on the glass substrate 15 without damaging the glass substrate 15 and the mold main body 14. It The pressed surface is the first main surface 15a.

Further, the pressing time in the forming step, that is, the pressing time, depends on the pressing force and the heating temperature T during molding, but is preferably from 1 to 900 seconds, preferably from 1 to 300 seconds.

[Mold release step]

After the glass forming process and the forming mold are cooled in the demolding step, the glass mold and the forming mold are cooled, and then the upper mold is raised, and the pressed surface of the mold body is pressed from the pressed surface (forming surface) of the glass substrate. Separation (release) on the main surface.

At this time, in the surface layer portion of the first main surface, which is the surface to be pressed of the glass substrate, a low alkali concentration region is formed by surface treatment, and in the low alkali concentration region, the mold release force occurs. The melting start temperature is higher than that before the surface treatment, that is, compared with the region other than the low alkali concentration region of the glass substrate.

Here, the predetermined temperature above the Tg of the glass substrate, that is, the forming temperature of the glass substrate, has a predetermined temperature range, and in the glass substrate not subjected to the surface treatment, the melting start temperature is approximately the lower limit of the forming temperature range. The temperature below the value. However, in the glass substrate to which the surface treatment has been applied, the melting initiation temperature becomes higher than the lower limit of the forming temperature range of the glass substrate. Therefore, in the method of the present embodiment, the molding temperature of the glass substrate can be appropriately set to a temperature lower than the melting start temperature, and the first main surface of the mold body can be formed with the low alkali concentration region. The release force of the face separation is approximately close to zero. Therefore, at the time of demolding, there is no deformation due to adhesion to the mold body on the first main surface of the glass substrate. Occurs, so the shape that has been formed during the forming step is stably maintained. Moreover, since the mold release force is extremely small as described above, damage to the mold body and mechanical deterioration can be prevented.

Here, the mold release force per unit area of the above-mentioned mold body is measured by, for example, the method described below.

That is, the following steps are continuously performed: a forming step of performing press forming using the forming apparatus 10 shown in Fig. 3; and a demolding step of cooling the upper mold 12 after forming, and pressing the pressed surface of the mold body 14 14a is separated from the first main surface 15a of the glass substrate 15. At this time, if the temperature of the upper mold 12 and the lower mold 11 is continuously measured and the pressing force (pressing pressure) per unit surface of the upper mold 12 is obtained, for example, in the case of a glass substrate which is not subjected to the surface treatment step, The chart shown in Figure 4.

In the graph showing the pressing pressure of the upper mold shown in FIG. 4, in the forming step of the forming temperature T of the glass, after the upper pressing mold 12 and the lower mold 11 are applied with the predetermined pressing force (pressing pressure) P, The pressing pressure will become negative, and after further slowing down, a change portion (a) will be generated, which will rise sharply and return to the original zero. In the demolding step, the changing portion (a) indicates that the pressing surface 14a of the mold main body 14 is pulled close to the first main surface 15a of the glass base 15, and is released. The absolute value of the difference between the pressing pressure of the lowest point in the changing portion (a) and the pressing pressure at the time point returning to the vicinity of the original zero can be taken as the releasing force per unit area. As the unit of the releasing force per unit area, Pa or N/cm ^{2 which is the} same as the pressing pressure can be used. Further, in the graph showing the pressing pressure of the upper mold in Fig. 4, the baseline after demolding is not 0, but this does not indicate the state of pressurization.

Example

Hereinafter, the embodiments of the present invention will be specifically described, but the present invention is not limited to the embodiments.

Example 1

The substrate of bismuth borate glass (manufactured by OHARA INC., trade name: L-BAL42, square having a main surface of 10 mm × 10 mm and thickness of 2 mm, Tg: 506 ° C, softening point: 607 ° C) was placed in Fig. 1A. The first electrode (positive electrode) 2 and the second electrode (ground) 3 of the surface treatment apparatus 1 shown are subjected to surface treatment by corona discharge.

Further, in the surface treatment apparatus 1, the second electrode 3 is a grounded flat electrode (the electrode material is tungsten and the electrode size is 10 mm × 10 mm), and the glass substrate 4 of the same size is placed on the second electrode 3 2 electrodes 3 are arranged horizontally. The first electrode 2 is composed of one linear electrode 2a (the electrode material is tungsten) having a diameter of 0.5 mm, and is disposed such that its longitudinal direction is parallel to one side of the glass substrate 4. Further, the distance between the linear electrode 2a and the upper surface of the glass substrate 4 was 5 mm, and the second electrode 3 on which the glass substrate 4 was placed was stroked at a speed of 5 mm/sec and 100 mm, on a horizontal surface and in a line shape. The longitudinal direction of the electrode 2a reciprocates in a direction perpendicularly intersecting. Further, an atmospheric gas atmosphere is provided between the linear electrode 2a of the first electrode 2 and the second electrode 3.

In this manner, the glass substrate 4 was heated to 200 ° C and maintained at this temperature, and a voltage of 6 kV was applied between the linear electrode 2a and the second electrode 3 by the DC power source 5, and the treatment was continued for 2.4 hours in this state. . In addition, In the surface treatment, the current value was measured by a current meter 6 provided on a circuit that connects the second electrode 3 and the DC power source 5, and it was found to be 0.4 mA and fixed.

Next, after the glass substrate subjected to the surface treatment as described above was subjected to press molding using the molding apparatus 10 shown in FIG. 3, the pressed surface 14a of the mold main body 14 was separated from the glass substrate 15 by the aforementioned method. The release force per unit area. In addition, the cross-sectional shape of the first main surface 15a which is the pressed surface of the glass substrate 15 after demolding was measured by a non-contact three-dimensional measuring apparatus (manufactured by Sanying Optical Co., Ltd., device name: NH-3). In addition, the measurement of the cross-sectional shape was performed in the range of 7 mm of the center part of the glass substrate of one side 10 mm.

Here, the mold body 14 is made of glass graphite, and the pressed surface 14a is made into mirror polishing by grinding. Further, the heating temperature (forming temperature) T at the time of press molding is set to be 440 ° C higher than the glass transition point Tg of the glass material (glass substrate) constituting the glass substrate 15 by (Tg + 74 ° C), and The pressure (pressing pressure) was 2 MPa, and the pressing time was set to 60 seconds. Further, the chamber was set to a nitrogen gas atmosphere (oxygen concentration: 15 ppm).

The temperature change of the upper mold 12 (the mold body 14) and the lower mold 11 and the measured value of the pressing pressure by the upper mold 12 are shown in Fig. 5. Moreover, the cross-sectional shape of the pressed surface of the glass substrate 15 after peeling is shown in FIG. As is apparent from the graph of FIG. 5, in the glass substrate 15 of the first embodiment, the release force per unit area required to separate the pressed surface 14a of the mold body 14 from the glass substrate 15 is substantially zero. Moreover, as shown in Fig. 6, it is understood that the pressed surface of the glass substrate 15 after the mold release has a flat surface having a height difference of about 3 μm, and the flat and smooth shape formed by press molding is maintained after the mold release. No deformation occurred during demolding.

Comparative example 1

A substrate of bismuth borate glass having the same composition as in Example 1 (manufactured by OHARA INC., trade name: L-BAL42, a glass substrate having a main surface of 10 mm × 10 mm and a thickness of 2 mm) was used. The glass substrate was subjected to press molding in the same manner as in Example 1 without performing surface treatment, and then the pressed surface 14a of the mold main body 14 was separated from the glass substrate 15 in the same manner as in Example 1. The release force per unit area. Further, in the same manner as in Example 1, the cross-sectional shape of the pressed surface of the glass substrate 15 after demolding was measured by a non-contact three-dimensional measuring device.

The temperature change of the upper mold 12 (the mold main body 14) and the lower mold 11 and the measured value of the pressing pressure by the upper mold 12 are shown in Fig. 7 . Moreover, the cross-sectional shape of the pressed surface of the glass substrate 15 after peeling is shown in FIG. As is apparent from the graph of Fig. 7, in the glass substrate 15 of Comparative Example 1, the releasing force required to separate the pressed surface 14a of the mold body 14 from the glass substrate 15 is about 75 N per unit area (1 cm ² ), that is, A large release force occurs. Further, as shown in Fig. 8, the pressed surface (molding surface) of the glass substrate 15 after demolding has a trapezoidal shape having a height of about 20 μm and a width of about 6 μm at the center portion, which is in close contact with the pressed surface 14a of the mold body 14. Therefore, the molding surface of the glass substrate 15 after demolding is deformed.

Example 2 and Comparative Example 2

In order to confirm the surface treatment by corona discharge, the melting start temperature at which the mold release force occurred was moved to the high temperature side, and the experiment shown below was performed. That is, for a glass substrate that has not been surface-treated (manufactured by OHARA INC., trade name: L-BAL42, the main surface is a square of 10 mm × 10 mm and a thickness of 2 mm), and the forming temperature shown in Fig. 3 is used to make the forming temperature at 550 to 580 ° C under a nitrogen gas atmosphere. The change in the range was carried out, and after press forming under the conditions of a pressing pressure of 2 MPa and a pressing time of 60 seconds, the releasing force per unit area was measured by the aforementioned method (Comparative Example 2). Further, in the same manner as in Example 1, the same glass substrate was used, and the molding temperature was changed in the range of 580 to 600 ° C in a nitrogen gas atmosphere, and the pressing pressure was 2 MPa and the pressing time was 60 seconds. After press forming under the conditions, the mold release force per unit area was measured by the above method (Example 2).

The measurement results of these are shown in Fig. 9. Fig. 9 is a graph showing the relationship between the molding temperature and the mold release force which is produced by surface treatment and surface treatment without a surface treatment. From the graph, it was confirmed that in Comparative Example 2, when a glass substrate which was not subjected to surface treatment was used, when press forming was carried out at 880 ° C (Tg + 74 ° C) as the molding temperature T, 0.8 MPa occurred. In the case where the glass substrate having been subjected to the surface treatment is used in the second embodiment, the mold release force per unit area (80 N/cm ² ) or more is almost the same at the molding temperature of 580 ° C. No release force will occur.

Industrial availability

According to the forming method of the present invention, a glass molded body having high surface smoothness and high quality can be obtained by press forming, and in addition, in the demolding step after forming, the pressed surface of the forming mold is pressed from the glass substrate. Since the release force of the first main surface is extremely small, it is not necessary to perform a release treatment for forming a release film of carbon or a noble metal and a release agent on the pressed surface of the molding die. It can be formed at low cost. Therefore, it is suitable as an inexpensive and highly reliable forming method for producing a glass optical element or the like.

10‧‧‧Forming device

11‧‧‧ Lower mold

12‧‧‧Upper mold

13‧‧‧Forming mould

14‧‧‧Mold body

14a‧‧‧Compressed noodles

15‧‧‧ glass substrate

15a‧‧‧1st main surface of the glass substrate

Claims (9)

A method for molding a glass substrate, comprising: a surface treatment step of disposing a glass substrate having a pair of main faces and comprising a glass containing a basic oxide in a composition between the first electrode and the second electrode; In the case where the first electrode is a positive electrode and the second electrode is a ground or a negative electrode, a DC voltage is applied to the glass substrate to cause corona discharge, and the surface portion of the first main surface side of the glass substrate positive electrode side is in the surface layer portion. And moving the at least one alkali ion toward the second main surface side of the ground or the negative electrode side; and the forming step of arranging the forming mold such that the pressing surface and the glass substrate subjected to the surface treatment by the surface treatment step are The first main surface abuts and is press-formed while maintaining the glass substrate at a predetermined temperature. The method for forming a glass substrate according to claim 1, which has a demolding step of cooling the glass substrate and the forming mold after the forming step, and the pressing surface of the forming mold from the glass The first main surface of the substrate is separated. A method of forming a glass substrate according to claim 1 or 2, wherein the forming step is carried out in a gas atmosphere mainly composed of nitrogen. The method of forming a glass substrate according to any one of claims 1 to 3, wherein in the surface treatment step, the glass substrate is disposed such that a first main surface is separated from the first electrode and a second main surface is The second electrode is in contact with the first electrode as a positive electrode and the second electrode as a ground or a negative electrode The DC voltage is applied in such a way that corona discharge occurs. The method of forming a glass substrate according to claim 4, wherein in the surface treatment step, the first electrode is a linear electrode, and the linear electrode is disposed in parallel with the first main surface of the glass substrate. . The method of forming a glass substrate according to claim 4 or 5, wherein in the surface treatment step, the first electrode and the second electrode are held in a gas atmosphere mainly composed of air or nitrogen. The method for forming a glass according to any one of claims 4 to 6, wherein in the surface treatment step, the temperature of the glass substrate is a normal temperature to a glass transition point Tg. The method for molding a glass substrate according to any one of claims 5 to 7, wherein the second electrode and the glass substrate are integrated with each other, and the first electrode and the first electrode are formed in the surface treatment step. The arrangement faces parallel to the first main faces are moved in parallel. The glass forming method according to any one of claims 1 to 8, wherein the glass-based system is composed of a glass material containing a basic oxide and an alkaline earth oxide in a total amount of more than 15% by mass.