TW201811709A - Reinforced glass production method and reinforced glass production apparatus - Google Patents

Abstract

Provided is a reinforced glass production method that exchanges ions in a glass surface layer, the method comprising: a step for forming, on at least a part of the surface of glass, an ion permeation-inhibiting film that inhibits ion permeation; a first ion-exchange step for exchanging ions by bringing a first molten salt into contact with the surface of the glass on which the ion permeation-inhibiting film has been formed; and a second ion-exchange step for, after the first ion-exchange step, exchanging ions by bringing a second molten salt into contact with the surface of the glass on which the ion permeation-inhibiting film has been formed, the method being characterized in that [alpha] < [beta] is satisfied where [alpha] is the hydrogen ion concentration index for an aqueous solution that is prepared by mixing the first molten salt with water and has a concentration of 20 mass%, and [beta] is the hydrogen ion concentration index for an aqueous solution that is prepared by mixing the second molten salt with water and has a concentration of 20 mass%.

Description

   Method for manufacturing strengthened glass and device for manufacturing strengthened glass   

The present invention relates to a method for manufacturing a strengthened glass and a device for manufacturing a strengthened glass, and more specifically to a method for manufacturing a strengthened glass and a device for strengthening a glass by chemically strengthening a glass plate by an ion exchange method.

Conventionally, in a touch panel display mounted on an electronic device such as a smart phone or a tablet PC, a chemically strengthened tempered glass plate has been used as a cover glass.

Such a strengthened glass plate is generally manufactured by chemically treating a glass plate containing an alkali metal as a composition with a strengthening liquid, and forming a compressive stress layer on the surface. Since such a strengthened glass plate has a compressive stress layer on the main surface, the impact resistance to the main surface is improved. On the other hand, in such a strengthened glass sheet, a tensile stress layer corresponding to the compressive stress layer on the main surface is formed. However, if the tensile stress becomes excessively large, it will easily occur due to this. Breakage (so-called spontaneous failure) caused by progression of cracks on the end face. Further, in order to reduce such a tensile stress, when forming a compressive stress layer on the surface of a glass plate having a relatively low integrity, there is a problem that sufficient impact resistance cannot be obtained at the end surface.

In order to solve the problems as described above, a technology is being developed to appropriately set the balance between the compressive stress of the main surface and the end surface of the strengthened glass plate and reduce the internal tensile stress to an appropriate range. For example, Patent Document 1 discloses that by forming a membrane that inhibits ion exchange in advance on the main surface, the progress of chemical strengthening is suppressed compared to the end surface, and a deep compressive stress layer is formed on the end surface relative to the main surface, thereby improving Technology of strength in the face.

    [Prior technical literature]         [Patent Literature]    

[Patent Document 1] Japanese Patent Laid-Open No. 2014-208570

The molten salt used for ion exchange of strengthened glass changes its liquid properties slowly due to repeated use. Therefore, as in the technique cited in Document 1, if a membrane that inhibits ion exchange is formed, the chemical strengthening of the site where the membrane that inhibits ion exchange is formed is excessively suppressed due to the liquid nature of the strengthening liquid used in the ion exchange. On the other hand, there may be cases where a sufficient compressive stress layer cannot be obtained.

On the other hand, due to the liquid nature of the strengthening liquid used in ion exchange, the membrane that inhibits ion exchange will be eroded early, and the effect of inhibiting ion exchange may not be obtained.

That is, there is still room for improvement in a method for stably producing tempered glass having high strength.

The present invention is an invention completed in consideration of such circumstances, and an object of the present invention is to provide a method and a device for manufacturing a strengthened glass that can stably manufacture a strengthened glass plate having a high strength.

The manufacturing method of the strengthened glass of the present invention is a method of manufacturing strengthened glass that exchanges ions on the surface of the glass, and is characterized by comprising the following steps: forming an ion penetration inhibiting film that can inhibit the penetration of ions into a film; A step of at least a part of a surface of glass; a first ion-exchange step of contacting a first molten salt with a surface of a glass formed with an ion penetration inhibiting film to exchange ions; and after the first ion-exchange step, The second ion-exchange step in which a molten salt contacts the surface of the glass on which the ion penetration suppression film is formed to exchange ions, the hydrogen ion concentration index when the first molten salt is mixed with water to make an aqueous solution having a concentration of 20% by mass is set to α, the hydrogen ion concentration index when the second molten salt was mixed with water to make an aqueous solution having a concentration of 20% by mass was set to β, and at this time α <β.

In the method for producing a strengthened glass of the present invention, α ≦ 10.5 is preferred.

In the method for manufacturing a strengthened glass of the present invention, it is preferably 9 ≦ β ≦ 12.

In the method for manufacturing a strengthened glass of the present invention, it is preferable that the glass is immersed in the first molten salt at 350 to 500 ° C for 0.1 to 150 hours in the first ion exchange step, and then immersed in 350 to 500 in the second ion exchange step. In the second molten salt at 500 ° C. for 0.1 to 72 hours, the immersion time in the first ion exchange step is longer than the immersion time in the second ion exchange step.

In the method of manufacturing the strengthened glass of the present invention, it is preferable that the ions on the surface of the glass are sodium ions, the first molten salt and the second molten salt both contain potassium ions, and the ion penetration suppression film is formed only on the main surface of the glass. The ion penetration suppression film has a composition containing 70% or more of SiO ₂ in terms of mass%, and the film thickness of the ion penetration suppression film is 10 to 1000 nm.

In the method for producing a strengthened glass of the present invention, it is preferable to further include the step of removing the ion penetration suppression film after the second ion exchange step.

In the method for manufacturing the strengthened glass of the present invention, it is preferred that the glass-based glass plate contains SiO ₂ 45 to 75%, Al ₂ O ₃ 1 to 30%, and Na ₂ O as a glass composition. 0 ~ 20%, K ₂ O 0 ~ 20%.

The tempered glass manufacturing apparatus of the present invention includes a first salt bath for storing a first molten salt for exchanging ions of a glass surface layer, and a first salt bath for receiving a second molten salt for exchanging ions of a glass surface layer. A two-salt bath, the hydrogen ion concentration index when mixing the first molten salt with water to make an aqueous solution with a concentration of 20% by mass is α, and the hydrogen ion when mixing the second molten salt with water to make an aqueous solution with a concentration of 20% by mass The concentration index is set to β, where α <β.

According to the present invention, since a plurality of types of molten salts having different liquid properties are used for ion exchange a plurality of times, ion exchange can be sufficiently performed even in a portion where a film has been formed, and a high compressive stress can be obtained. In addition, by appropriately adjusting the liquid properties of the molten salt used in each step, the rapid erosion of the ion penetration suppression membrane can be prevented, and ion exchange can be appropriately suppressed. Therefore, it is possible to stably manufacture a strengthened glass plate having high strength.

G1‧‧‧Original glass

G2‧‧‧ Glass with film

G3, G4 ‧‧‧ Tempered Glass with Film

G5‧‧‧Tempered glass

M‧‧‧Ion penetration suppression membrane

T1‧‧‧The first molten salt

T2‧‧‧Second Molten Salt

X1‧‧‧The first salt bath

X2‧‧‧Second Salt Bath

[Fig. 1A] A diagram showing steps included in an example of a method for producing a strengthened glass of the present invention.

[Fig. 1B] A diagram showing steps included in an example of a method for producing a strengthened glass of the present invention.

[FIG. 1C] A diagram showing steps included in an example of a method for producing a strengthened glass of the present invention.

[Fig. 1D] A diagram showing steps included in an example of a method for producing a strengthened glass of the present invention.

[Fig. 1E] A diagram showing steps included in an example of a method for producing a strengthened glass of the present invention.

    [Best Mode for Implementing Invention]    

Hereinafter, the manufacturing method of the tempered glass which concerns on embodiment of this invention is demonstrated. FIG. 1 is a diagram showing an example of a method for producing a strengthened glass of the present invention.

First, the processing of the preparation steps shown in FIG. 1A is performed. The preparation step is a step of preparing the original glass G1. The original glass G1 is a sheet-shaped glass that can be strengthened using an ion exchange method.

The original glass G1 is preferably a glass composition containing 45 to 75% of SiO ₂ , Al ₂ O ₃ 1 to 30%, Na ₂ O 0 to 20%, and K ₂ O 0 to 20%. When the glass composition range is specified as described above, it is easy to achieve both ion exchange performance and devitrification resistance at a high level.

The thickness of the original glass G1 is, for example, 1.5 mm or less, preferably 1.3 mm or less, 1.1 mm or less, 1.0 mm or less, 0.8 mm or less, 0.7 mm or less, 0.6 mm or less, 0.5 mm or less, 0.4 mm or less, and 0.3 mm or less. It is less than or equal to 0.2 mm, particularly less than or equal to 0.1 mm. The smaller the thickness of the strengthened glass substrate, the lighter the strengthened glass substrate can be. As a result, the device can be made thinner and lighter. In consideration of productivity and the like, the thickness of the original glass G1 is preferably 0.01 mm or more.

The dimensions of the main surface of the original glass G1 are, for example, 480 × 320 mm to 3350 × 3950 mm. Here, the term "main surface" means a surface opposed to the thickness direction of the plate.

The original glass G1 is formed by using an overflow down-draw method, and its main surface S is preferably not ground. As long as the original glass G1 formed in this manner, a strengthened glass plate having low cost and high surface quality can be obtained. The forming method or processing state of the original glass G1 can also be arbitrarily selected. For example, the original glass G1 can be formed by a float method, and the main surface S and the end surface E can also be ground.

Next, after the above-mentioned preparation step, the processing of the film formation step shown in FIG. 1B is performed. The film forming step is a step of forming the ion penetration suppression film M on at least a part of the surface of the original glass G1 and obtaining the film-attached glass G2. In the strengthening step described later, the ion penetration suppressing film M is a film layer that suppresses the penetration of ions when performing ion exchange on the surface layer of the original glass G1. In this embodiment, the glass G2 with the film is formed with the ion penetration suppression film M only on the front main surface and the back main surface S, and the end surface E is exposed.

As a material of the ion penetration suppression film M, any material can be used as long as it can suppress the penetration of ions undergoing ion exchange. When the ions to be exchanged are alkali metal ions, the ion penetration suppressing film M is made of, for example, a film of a metal oxide, a metal nitride, a metal carbide, a metal oxynitride, a metal carbonitride, or a metal carbonitride. Better. More specifically, the material system of the ion penetration suppression film M may include, for example, SiO ₂ , Al ₂ O ₃ , SiN, SiC, Al ₂ O ₃ , AlN, ZrO ₂ , TiO ₂ , Ta ₂ O ₅ , Nb. One or more types of ₂ O ₅ , HfO ₂ , and SnO ₂ are used to form a film.

In particular, when SiO _{2 is} used as the main component of the ion penetration suppression film M, it is preferable because the ion penetration suppression film M can be formed inexpensively and easily, and can also function as an antireflection film. The ion penetration suppression film M may be a film made of only SiO ₂ . Specifically, the ion penetration suppression film M may have a composition containing 99% or more of SiO ₂ by mass%.

The thickness of the ion penetration suppression film M is preferably 5 to 300 nm, more preferably 20 to 200 nm, more preferably 20 to 150 nm, 40 to 120 nm, and most preferably 80 to 100 nm. By setting the thickness of the ion penetration suppression film M to the above-mentioned range, there is no case where the ion penetrates or the ions are blocked too much, so that ion exchange can be suitably performed.

The film formation method of the ion penetration suppression film M is a CVD method (chemical vapor deposition method) such as a PVD method (physical vapor deposition method) such as a sputtering method or a vacuum evaporation method, a thermal CVD method, or a plasma CVD method. ), A wet coating method such as a dip coating method or a slit coating method. In particular, a sputtering method and a dip coating method are preferred. When the sputtering method is used, the ion penetration suppression film M can be easily and uniformly formed. The film formation site of the ion penetration suppression film M can be set by any method. For example, film formation can be performed on a non-film-forming portion (the end face E in the present embodiment) in a state where a mask is applied in advance.

Next, after the above-mentioned film forming step, the processing of the first ion exchange step shown in FIG. 1C is performed. The first ion exchange step is a step of chemically strengthening the glass G2 with a membrane by an ion exchange method, so that a glass G3 with a membrane can be obtained. Specifically, the membrane-attached glass G2 is immersed in a molten salt T1 containing an alkali metal ion to perform ion exchange. The molten salt T1 in this embodiment is, for example, a potassium nitrate molten salt.

When the molten salt T1 is mixed with water to form an aqueous solution having a concentration of 20% by mass of the molten salt, and when the hydrogen ion concentration index of the aqueous solution is α, a salt having α ≦ 10.5 is preferred. The hydrogen ion concentration index in the present invention is a value measured in a state of 25 ° C. By adjusting α as described above, the loss of the ion penetration suppression film M is suppressed, and the ion exchange of the glass G2 with the film in the portion where the ion penetration suppression film M has been formed can be suppressed. In addition, compared with the portion where the film has been formed, ion exchange can be performed from the glass surface to a deeper region in the portion where the ion penetration suppression film M of the glass G2 with the film has not been formed.

The aforementioned α system is preferably 5 to 10, more preferably 5.5 to 9.5, and even more preferably 6 to 9. The α system can be measured by, for example, once the molten salt is cooled, solidified, pulverized, and measured, and then the aqueous solution can be prepared.

The temperature of the molten salt T1 in the first ion exchange step can be arbitrarily set, for example, 350 to 500 ° C, preferably 370 to 480 ° C, still more preferably 380 to 450 ° C, and more preferably 380 to 400 ° C. In particular, when the temperature of the molten salt T1 is 400 ° C. or lower, it becomes easy to control the fluctuation of the α value due to the temperature. The time for immersing the glass G2 with the film in the molten salt T1 can be arbitrarily set, and is, for example, 0.1 to 150 hours, preferably 0.3 to 100 hours, and more preferably 0.5 to 50 hours.

In the above-mentioned first ion exchange step, sodium ions on the surface of the glass G2 with the film are exchanged with potassium ions in the molten salt T1 to obtain a glass-reinforced glass G3 having a compressive stress layer C on the surface. Here, among the surfaces of the glass G2 with the film, compared with the exposed portion E exposed from the surface of the original glass G1, the portion (the main surface S) where the ion penetration suppression film M is provided is suppressed because of ion exchange. The depth of the compressive stress layer will become smaller. In other words, since the ion exchange in the exposed portion E is easier than that in the portion provided with the ion penetration suppressing film M, the depth of the compressive stress layer becomes larger. In this way, compared to the main surface, the strengthened glass G3 with a film has a larger depth of the compressive stress layer on the end surface. Therefore, compared with the strengthened glass that is strengthened on the entire surface, the internal tensile stress is smaller and it has High impact resistance. Therefore, it is possible to suitably suppress breakage due to the progress of cracks from the ends.

However, when only the above-mentioned first ion exchange step is performed, because the ion penetration suppressing membrane M is used, a sufficient compressive stress may not be obtained in the portion where the ion exchange is suppressed. Therefore, next, after the above-mentioned first ion-exchange step, the processing of the second ion-exchange step described below is performed, so that the compressive stress in the film-forming portion of the ion penetration suppression film M is increased.

As shown in FIG. 1D, the second ion exchange step is a step of chemically strengthening the glass G2 with the membrane by an ion exchange method. Specifically, the reinforced glass G3 with a film is immersed in a molten salt T2 containing an alkali metal ion to perform ion exchange, so that the reinforced glass G4 with a film can be obtained. The molten salt T2 in this embodiment is, for example, a potassium nitrate molten salt.

Molten salt T2 is a salt of α <β when the molten salt T2 is mixed with water to prepare an aqueous solution having a concentration of 20% by mass of the molten salt. When the hydrogen ion concentration index of the aqueous solution is β. By setting the value of β to such a range, since ion exchange can be performed moderately in the film formation site, the compressive stress in the film formation site can be increased.

However, the above-mentioned β series is preferably 9-12, more preferably 9.5-11.5, and even more preferably 10-11. The value of β can be measured in the same manner as the aforementioned α. When the value of β is within the above range, it is possible to suppress undesirable deterioration such as white turbidity on the glass surface in the second ion exchange step.

The temperature of the molten salt T2 in the second ion exchange step can be arbitrarily set, for example, 350 to 500 ° C, preferably 370 to 480 ° C, and more preferably 380 to 450 ° C. When the temperature of the molten salt T2 is 450 ° C. or lower, it becomes easy to control the fluctuation of the α value due to the temperature. The time for immersing the reinforced glass G3 with a film in the molten salt T2 can be arbitrarily set, and is, for example, 0.1 to 72 hours, preferably 0.3 to 50 hours, and more preferably 0.5 to 24 hours.

In the above-mentioned second ion exchange step, since the β value is set higher than α, the ion exchange in the film formation site of the ion penetration suppression membrane M becomes easier than in the first ion exchange step. Therefore, compared with the strengthened glass G3 with a film before the treatment, the compressive stress in the film-forming site of the ion penetration suppression film M will be changed in the strengthened glass G4 with a film that has undergone the second ion exchange step. Big. Moreover, compared with the strengthened glass G3 with a film, the compressive stress layer of the strengthened glass G4 with a film in the film formation part of the ion penetration suppression film M becomes deeper.

In the present invention, it is preferable that the adjusting step of adjusting α and β to the above-mentioned range is performed in a previous step or a subsequent step of each of the first ion exchange step and the second ion exchange step. In the adjustment step, α and β can be adjusted by, for example, adding an additive to the molten salt T1 or T2. The additive system is, for example, an alkaline substance. The alkaline substance in the present invention is a substance having a hydrogen ion index (pH) of more than 7 when mixed with water. As the additive, a simple substance or a combination of, for example, KOH and NaOH can be used.

When the ion transmission suppression film M can also function as a protective coating or an anti-reflection film for electronic devices, the reinforced glass G4 series with a film can be directly used as a product and mounted on electronic parts, but it can also be used according to the application. To remove the ion penetration inhibiting film M. That is, after the second ion exchange step, a removal step of removing the ion penetration suppression film M from the strengthened glass G4 with a film may be performed.

In the removing step, as shown in FIG. 1E, the ion penetration suppression film M is removed from the strengthened glass G4 with a film, so that a strengthened glass G5 can be obtained.

Specifically, the strengthened glass G4 with a film is attached to an etching solution to remove the ion penetration suppressing film M. When the ion penetration suppression film M is a film containing SiO ₂ , for example, a solution containing fluorine, TMAH, EDP, KOH, NAOH, or the like can be used as an etching solution, and a hydrofluoric acid solution is preferably used as the etching solution. . The method for removing the ion penetration suppression film M is not limited to the above, and a known method can be used as a method for removing the film provided on the glass plate, and the ion penetration suppression can be removed by mechanical processing such as polishing. Film M.

In the peeling step, only the ion penetration suppression film M on one main surface side may be removed, or the ion penetration suppression film M on both main surfaces may be removed. In addition, the ion penetration suppression film M may be partially removed on each main surface, and the ion penetration suppression film M may be entirely removed.

When the ion penetration suppression film M is removed on one side or partly, a spray, roller, bristles, or the like can be used to partially attach the etching solution, or to partially shield the reinforced glass G4 with the film and make It is immersed in an etching solution, thereby removing the film.

When the ion penetration suppressing film M is removed in its entirety, it is preferable that the entire tempered glass G4 with the film is immersed in an etching solution. When the whole reinforced glass G4 with a film is immersed in the etchant as described above, a strengthened glass G5 that reduces the micro-cracks that cause breakage and further increases the strength is obtained.

As described above, according to the method for manufacturing a strengthened glass according to an embodiment of the present invention, it is possible to stably and efficiently manufacture a strengthened glass G4 and a strengthened glass G5 with a film having less damage from an end surface.

The material of the ion penetration suppression film M described above is an example, and any material may be used as long as it can suppress the penetration of the exchanged ions in the first ion exchange step.

In addition, the film formation site of the ion penetration suppression film M in the glass G2 with a film can be arbitrarily set. For example, when the original glass G1 is chamfered in advance, an ion penetration suppression film M may be formed on a main surface other than the chamfered surface.

In addition, before or after any of the steps shown above, a processing step for performing any of cutting processing, end surface processing, and hole processing may be provided. In addition, before and after any of the steps shown above, the glass plate may be appropriately washed and dried.

Moreover, in the said embodiment, although the case where the potassium nitrate molten salt was used as the molten salt T1, T2 is demonstrated, it is not limited to this, It can replace the well-known molten salt used for ion exchange of glass, or it can use it in combination . For example, the molten salts T1 and T2 may be a mixed salt of a potassium nitrate molten salt and a sodium nitrate molten salt.

Moreover, in the said embodiment, although the case of performing chemical strengthening by exchanging sodium ion and potassium ion was illustrated, you may perform chemical strengthening by arbitrary ion exchange. For example, lithium ion and sodium ion may be exchanged, or lithium ion and potassium ion may be exchanged for chemical strengthening. In this case, the glass G1 is preferably a glass composition containing 0.5 to 7.5% of LiO ₂ in terms of mass%, for example, 3.0% or 4.5%.

The processing conditions such as the processing temperature and the immersion time in the first ion exchange step and the second ion exchange step are appropriately set in accordance with the characteristics required for the strengthened glass G4 and strengthened glass G5 with a film. The above-mentioned processing conditions are preferably adjusted so that the depth of the compressive stress layer of the main surface S of the strengthened glass G4 and the strengthened glass G5 with the film is smaller than the depth of the compressive stress layer of the exposed portion E.

Further, a plurality of additional strengthening steps may be provided between the first ion exchange step and the second ion exchange step or after the second ion exchange step. In the strengthening step added between the first ion exchange step and the second ion exchange step, the molten salt used is a hydrogen ion concentration index when the molten salt is mixed with water to make an aqueous solution having a concentration of 20% by mass. It is preferable that the molten salt is γ <β.

The manufacturing method of the said tempered glass can be implemented using the tempered glass manufacturing apparatus provided with the salt bath X1 containing the said molten salt T1, and the salt bath X2 containing the said molten salt T2. The salt baths X1 and X2 are, for example, grooves formed of a metal case with an opened upper portion, and have an internal space filled with molten salt T. This tempered glass manufacturing device is formed in a shape and size that each can store a glass G2 with a film in the salt bath X1, and a glass G3 that can store a film with a film in the salt bath X2. A support device (not shown) of the glass G2 with a film is suitable. The supporting device is a jig composed of a metal frame such as stainless steel. In a state where the glass G2 with the membrane is supported by the supporting device, the treatment in the first ion exchange step can be performed by immersing the glass G2 in the salt bath X1 in the molten salt T1. In the state where the reinforced glass G3 with the membrane is supported by the supporting device, the treatment in the second ion exchange step can be performed by immersing the molten salt T2 in the salt bath X2. In addition, it is preferable that the tempered glass manufacturing apparatus further includes a film forming apparatus (not shown) capable of performing the processing of the film forming step described above. As a film-forming apparatus, a well-known sputtering film-forming apparatus etc. can be used.

Here, the stress characteristics of tempered glass can be measured using, for example, FSM-6000 manufactured by Ohara Corporation. When the depth of the compressive stress layer of the aluminosilicate glass exceeds 100 μm, or when ion exchange between lithium ions and sodium ions is performed, the stress characteristics of the strengthened glass can be measured using, for example, SLP-1000 manufactured by Ohara Corporation. When the cross-section sample can be prepared by cutting tempered glass or the like, it is preferable to use WPA-micro manufactured by Photonic-lattice or Abrio manufactured by Tokyo Instruments to observe the internal stress distribution and confirm the stress depth.

    [Example]    

Hereinafter, the present invention will be described in detail based on examples.

In Table 1, Nos. 1 to 3 represent examples of the present invention, and Nos. 4 to 7 represent comparative examples.

Each sample in Table 1 was prepared in the following manner. First, as a glass composition system, glass raw materials are mixed and melted so that they contain SiO ₂ 61.6%, Al ₂ O ₃ 19.6%, B ₂ O ₃ 0.8%, Na ₂ O 16%, and K ₂ O 2%. The overflow down-draw method is used to form a plate with a thickness of 0.8 mm, and a 50 × 50 mm rectangular shape is cut by scribe cutting, and the end surface is ground and ground to obtain multiple original materials. Glass G1. Next, an ion penetration suppression film M having a composition containing 100% by mass of SiO ₂ and having a thickness of 200 nm was formed on the two main surfaces of the front and back sides of the obtained original glass G1 by sputtering. As a whole, glass G2 with a film is obtained (film formation step). Next, the obtained film-added glass G2 was immersed in a potassium nitrate solution to perform chemical strengthening according to the conditions in Table 1, thereby obtaining a film-added strengthened glass G3 (first ion exchange step). Next, the obtained glass-reinforced glass G3 is immersed in a potassium nitrate solution to perform chemical strengthening according to the conditions in Table 1, thereby obtaining the glass-reinforced glass G4 (second ion exchange step). . Next, after the surface of the obtained reinforced glass G4 with a film is washed, it is polished to remove the ion penetration suppressing film, thereby obtaining a strengthened glass G5 (removal step).

The second ion exchange step is omitted in Nos. 6 and 7.

For each glass sample obtained as described above, the following measurement test was performed.

The compressive stress CS of the compressive stress layer formed on the main surface of the tempered glass G5, the depth DOL1 of the compressive stress layer on the main surface, and the depth DOL2 of the compressive stress layer on the end face were measured using a stress gauge (FSM- 6000LE and FsmXP). The value obtained by subtracting DOL1 from DOL2 is determined as ΔDOL. The larger the value of ΔDOL, the smaller the internal tensile stress is, and it is not easy to spontaneously break, and it can be said to have glass with high strength at the end surface.

As shown in Table 1, Sample Nos. 4 and 5 of the comparative example had a value of α greater than β. Therefore, in the first ion-exchange step, the ion-exchange suppression membrane M was drastically depleted, and the DOL at the film-forming site was changed. As a result, the value of ΔDOL becomes smaller than that of the example. In addition, in Sample Nos. 6 and 7 of the comparative example, since the second ion-exchange step was not performed and the value of α was relatively large, the ion-exchange suppression membrane M was severely depleted in the first ion-exchange step. Ion exchange cannot be sufficiently suppressed in the membrane portion, and as a result, the value of ΔDOL becomes smaller than in the Examples. That is, compared with the examples, the samples Nos. 4 to 7 of the comparative examples are all glass which is liable to spontaneously break.

    [Industrial availability]    

The tempered glass plate and the manufacturing method thereof of the present invention are suitable as a glass substrate for a touch panel display and the like, and a manufacturing method thereof.

Claims (8)

    A method for manufacturing strengthened glass, which is a method for manufacturing strengthened glass that exchanges ions on the surface of a glass, and is characterized by having the following steps: forming an ion penetration inhibiting film capable of inhibiting the penetration of the aforementioned ions into a film A step of at least a part of a surface of glass; a first ion-exchange step of contacting a first molten salt with a surface of the glass on which the aforementioned ion penetration suppression film is formed to exchange the ions; and after the first ion-exchange step A second ion exchange step in which a second molten salt is brought into contact with a surface of the glass on which the ion penetration suppression film is formed to exchange the ions, the first molten salt is mixed with water to make an aqueous solution with a concentration of 20% by mass The hydrogen ion concentration index at this time was set to α, and the hydrogen ion concentration index when the second molten salt was mixed with water to make an aqueous solution having a concentration of 20% by mass was set to β, and at this time α <β.         The method for manufacturing a strengthened glass according to claim 1, wherein α ≦ 10.5.         The method for manufacturing tempered glass according to claim 1 or 2, wherein 9 ≦ β ≦ 12.         The method for manufacturing a strengthened glass according to any one of claims 1 to 3, wherein the glass is immersed in the first molten salt at 350 to 500 ° C for 0.1 to 150 hours in the first ion exchange step, and then in the foregoing The second ion exchange step is immersed in the second molten salt at 350 to 500 ° C. for 0.1 to 72 hours. The immersion time in the first ion exchange step is longer than the immersion time in the second ion exchange step.     The method for manufacturing strengthened glass according to any one of claims 1 to 4, wherein the ions of the glass surface layer are sodium ions, the first molten salt and the second molten salt both contain potassium ions, and the ion penetration suppression film The film is formed only on the main surface of the glass. The ion penetration suppression film has a composition containing 70% or more of SiO ₂ by mass%. The film thickness of the ion penetration suppression film is 5 to 400 nm.     The method for producing a strengthened glass according to any one of claims 1 to 5, further comprising the step of removing the ion penetration suppression film after the second ion exchange step.     The method for manufacturing a strengthened glass according to any one of claims 1 to 6, wherein the aforementioned glass-based glass plate contains SiO ₂ 45 to 75%, Al ₂ O ₃ 1 to 1% by mass as a glass composition. 30%, Na ₂ O 0-20%, K ₂ O 0-20%.     A tempered glass manufacturing device, comprising: a first salt bath containing a first molten salt for exchanging ions of a glass surface layer; and a second salt containing a second molten salt for exchanging ions of a glass surface layer. A bath, wherein the hydrogen ion concentration index when the first molten salt is mixed with water to make an aqueous solution with a concentration of 20% by mass is α, and the hydrogen ion when the second molten salt is mixed with water to make an aqueous solution with a concentration of 20% by mass The concentration index is set to β, where α <β.