WO2017221805A1 - 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 α < β is satisfied where α 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 β 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

Tempered glass manufacturing method and tempered glass manufacturing apparatus

The present invention relates to a method for producing tempered glass and an apparatus for producing tempered glass, and more specifically, relates to a method for producing tempered glass for chemically strengthening a glass plate by an ion exchange method and an apparatus for tempered glass.

Conventionally, a tempered glass plate that has been chemically strengthened as a cover glass has been used for touch panel displays mounted on electronic devices such as smartphones and tablet PCs.

Such a tempered glass plate is generally produced by chemically treating a glass plate containing an alkali metal as a composition with a tempering solution to form a compressive stress layer on the surface. Since such a tempered glass sheet has a compressive stress layer on the main surface, the impact resistance to the main surface is improved. On the other hand, a tensile stress layer corresponding to the compressive stress layer of the main surface is formed inside such a tempered glass plate, but if this tensile stress becomes excessively large, cracks on the end face are caused due to this. Damage due to progress (so-called self-destruction) is likely to occur. Further, when the compressive stress layer on the surface of the glass plate is formed to be shallow as a whole in order to reduce such tensile stress, there is a problem that sufficient impact resistance cannot be obtained at the end face.

In order to solve the above problems, a technology has been developed to appropriately set the balance between the compressive stresses of the main surface and the end surface of the tempered glass sheet and reduce the internal tensile stress within an appropriate range. For example, in Patent Document 1, a film that suppresses ion exchange is formed in advance on the main surface, and the progress of chemical strengthening is suppressed as compared to the end surface, so that the compressive stress layer at the end surface is relatively deeper than the main surface. A technique for forming and improving the strength at the end face is disclosed.

JP 2014-208570 A

¡The molten salt used for ion exchange of tempered glass gradually changes in liquid quality due to repeated use. Therefore, when a membrane that suppresses ion exchange is formed as in the technique of Cited Document 1, depending on the quality of the reinforcing liquid used for ion exchange, chemical strengthening is excessive at the location where the membrane that suppresses ion exchange is formed. In some cases, a sufficient compressive stress layer could not be obtained at that location.

On the other hand, depending on the quality of the strengthening liquid used for ion exchange, the membrane that suppresses ion exchange may be eroded early, and the effect of suppressing ion exchange may not be obtained.

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

The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a tempered glass manufacturing method and a tempered glass manufacturing apparatus capable of stably manufacturing a tempered glass plate having high strength. And

The method for producing tempered glass of the present invention is a method for producing tempered glass for exchanging ions on a glass surface layer, and a step of forming an ion permeation suppression film for suppressing ion permeation on at least a part of the surface of the glass; The ion permeation suppression membrane was formed after the first ion exchange step and the first ion exchange step of exchanging ions by bringing the first molten salt into contact with the glass surface on which the ion permeation suppression membrane was formed. And a second ion exchange step of exchanging ions by bringing the second molten salt into contact with the surface of the glass, and hydrogen ions when the first molten salt is mixed with water to make an aqueous solution having a concentration of 20% by mass. When the concentration index is α and the hydrogen ion concentration index is β when the second molten salt is mixed with water to form an aqueous solution having a concentration of 20% by mass, α <β.

In the method for producing tempered glass of the present invention, α ≦ 10.5 is preferable.

In the method for producing tempered glass of the present invention, it is preferable that 9 ≦ β ≦ 12.

In the method for producing tempered glass of the present invention, 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 the second ion exchange step at 350 to 500 ° C. It is preferably immersed in the dimolten salt for 0.1 to 72 hours, and the immersion time in the first ion exchange step is longer than the immersion time in the second ion exchange step.

In the method for producing tempered glass of the present invention, the ions on the glass surface layer are sodium ions, the first molten salt and the second molten salt both contain potassium ions, and an ion permeation suppression film is formed only on the main surface of the glass. The ion permeation suppression film preferably has a composition containing 70% or more of SiO ₂ by mass, and the film thickness of the ion permeation suppression film is preferably 10 to 1000 nm.

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

In the method for producing tempered glass of the present invention, the glass has a glass composition of mass%, SiO ₂ 45 to 75%, Al ₂ O ₃ 1 to 30%, Na ₂ O 0 to 20%, K ₂ O 0 to 20%. It is preferable that it is a glass plate containing%.

The tempered glass manufacturing apparatus of the present invention includes a first salt bath containing a first molten salt for exchanging ions on the glass surface layer, and a second salt containing a second molten salt for exchanging ions on the glass surface layer. A 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, and the second molten salt is mixed with water to give a concentration of 20%. When the hydrogen ion concentration index in the case of an aqueous solution of% is β, α <β.

According to the present invention, by performing ion exchange a plurality of times using a plurality of types of molten salts having different liquid qualities, a high compressive stress can be obtained by sufficiently performing ion exchange even at a film-formed location. In addition, by appropriately adjusting the liquid quality of the molten salt used in each step, rapid erosion of the ion permeation suppression membrane can be prevented, and ion exchange can be appropriately suppressed. Therefore, it is possible to stably manufacture a tempered glass plate having high strength.

It is a figure which shows the process included in an example of the manufacturing method of the tempered glass of this invention. It is a figure which shows the process included in an example of the manufacturing method of the tempered glass of this invention. It is a figure which shows the process included in an example of the manufacturing method of the tempered glass of this invention. It is a figure which shows the process included in an example of the manufacturing method of the tempered glass of this invention. It is a figure which shows the process included in an example of the manufacturing method of the tempered glass of this invention.

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

First, the preparatory process shown in FIG. 1A is performed. The preparation process is a process of preparing the original glass G1. The original glass G1 is a plate-like glass that can be strengthened by using an ion exchange method.

The original glass G1 preferably contains, by mass%, SiO ₂ 45 to 75%, Al ₂ O ₃ 1 to 30%, Na ₂ O 0 to 20%, K ₂ O 0 to 20% as a glass composition. If the glass composition range is regulated as described above, it becomes 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, 0.3 mm or less, 0.2 mm or less, especially 0 mm. 1 mm or less. As the plate thickness of the tempered glass substrate is smaller, the tempered glass substrate can be made lighter, and 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 main surface means a surface facing the plate thickness direction.

The original glass G1 is preferably formed using an overflow downdraw method, and the main surface S is not polished. With the original glass G1 thus formed, a tempered glass plate having high surface quality can be obtained at low cost. In addition, you may select arbitrarily the shaping | molding method and processing state of the original glass G1. For example, the original glass G1 may be formed using a float process, and the main surface S and the end surface E may be polished.

Next, after the above preparation process, the film forming process shown in FIG. 1B is performed. The film forming step is a step of forming the glass with film G2 by forming the ion permeation suppressing film M on at least a part of the surface of the original glass G1. The ion permeation suppression film M is a film layer that suppresses permeation of ions when ion exchange is performed on the surface layer of the original glass G1 in the strengthening process described later. In the present embodiment, the glass with film G2 is formed such that the ion permeation suppression film M is formed only on the front and back main surfaces S, and the end surface E is exposed.

As a material of the ion permeation suppression film M, any material may be used as long as permeation of ions to be ion-exchanged can be suppressed. When the exchanged ions are alkali metal ions, the ion permeation suppression film M is, for example, a film of metal oxide, metal nitride, metal carbide, metal oxynitride, metal oxycarbide, metal carbonitride, or the like. It is preferable. More specifically, as the material of the ion permeation suppressive film M, for _{example, SiO 2, Al 2 O 3} , SiN, SiC, Al 2 O 3, AlN, ZrO 2, TiO 2, Ta 2 O 5, Nb 2 O ₅ , a film containing one or more of HfO ₂ and SnO ₂ .

In particular, it is preferable to use SiO ₂ as the main component of the ion permeation suppression film M because the ion permeation suppression film M can be easily formed at low cost and can function as an antireflection film. Ion permeation suppressive film M is good as a film made of only SiO _2. Specifically, the ion permeation suppression film M may have a composition containing 99% or more of SiO ₂ by mass%.

The thickness of the ion permeation suppression film M is preferably 5 to 300 nm, more preferably 20 to 200 nm, still more preferably 20 to 150 nm, 40 to 120 nm, and most preferably 80 to 100 nm. By setting the thickness of the ion permeation suppression film M in the above range, ion exchange can be suitably performed without permeating ions or blocking ions too much.

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

Next, after the film formation step, the first ion exchange step shown in FIG. 1C is performed. A 1st ion exchange process is a process of chemically strengthening the glass G2 with a film | membrane by the ion exchange method, and obtaining the glass G3 with a film | membrane. Specifically, ion exchange is performed by immersing the film-coated glass G2 in a molten salt T1 containing alkali metal ions. The molten salt T1 in the present embodiment is, for example, a potassium nitrate molten salt.

The molten salt T1 satisfies α ≦ 10.5 when the hydrogen ion concentration index of the aqueous solution when the molten salt T1 is mixed with water to obtain an aqueous solution having a concentration of the molten salt of 20% by mass is α. A salt is preferred. In the present invention, the hydrogen ion concentration index is a value measured when the temperature of the aqueous solution is 25 ° C. By adjusting α as described above, the wear of the ion permeation suppression film M can be suppressed, and the ion exchange of the film-attached glass G2 at the portion where the ion permeation suppression film M is formed can be suppressed. Moreover, in the location where the ion permeation suppression film M of the film-attached glass G2 is not formed, ion exchange can be performed from the glass surface to a deeper area inside than the location where the film is formed.

The α is preferably 5 to 10, more preferably 5.5 to 9.5, and further preferably 6 to 9. α can be measured, for example, by once cooling and solidifying the molten salt, pulverizing and weighing the molten salt to prepare the aqueous solution.

The temperature of the molten salt T1 in the first ion exchange step may be arbitrarily determined, and is, for example, 350 to 500 ° C., preferably 370 to 480 ° C., more preferably 380 to 450 ° C., and further preferably 380 to 400 ° C. . In particular, if the temperature of the molten salt T1 is 400 ° C. or less, it becomes easy to suppress fluctuations in the value of α due to the temperature. The time for immersing the film-coated glass G2 in the molten salt T1 may be arbitrarily determined. For example, it is 0.1 to 150 hours, preferably 0.3 to 100 hours, more preferably 0.5 to 50 hours. It is.

In the first ion exchange step, sodium ions on the surface of the film-coated glass G2 and potassium ions in the molten salt T1 are exchanged to obtain a film-reinforced glass G3 having a compressive stress layer C on the surface. Here, in the surface of the film-coated glass G2, the portion (main surface S) where the ion permeation suppression film M is provided is suppressed in ion exchange compared to the exposed portion E where the surface of the original glass G1 is exposed. The depth of the compressive stress layer is reduced. In other words, in the exposed portion E, the ion exchange can proceed more easily than the portion where the ion permeation suppression film M is provided, and the depth of the compressive stress layer is increased. In this way, the tempered glass with film G3 has a smaller compressive stress layer at the end surface than the main surface, and therefore has a lower internal tensile stress than the tempered glass reinforced entirely and at the end portion. High impact resistance. Therefore, the damage resulting from the progress of the crack from the end can be suitably suppressed.

However, there may be a case where sufficient compressive stress cannot be obtained at a location where ion exchange is suppressed by the ion permeation suppression membrane M only by the processing of the first ion exchange step. Therefore, after the first ion exchange step, the second ion exchange step described below is performed to increase the compressive stress at the location where the ion permeation suppression film M is formed.

The second ion exchange step is a step of chemically strengthening the film-coated glass G2 again by an ion exchange method, as shown in FIG. 1D. Specifically, the tempered glass with film G3 is immersed in a molten salt T2 containing alkali metal ions to perform ion exchange to obtain the tempered glass with film G4. The molten salt T2 in the present embodiment is, for example, a potassium nitrate molten salt.

The molten salt T2 is a salt in which α <β, where β is the hydrogen ion concentration index of the aqueous solution when the molten salt T2 is mixed with water to form an aqueous solution having a concentration of the molten salt of 20% by mass. is there. By setting the value of β in such a range, it is possible to appropriately perform ion exchange at the film formation location, and to increase the compressive stress at the film formation location.

Note that β is preferably 9 to 12, more preferably 9.5 to 11.5, and still more preferably 10 to 11. The value of β can be measured by the same method as α described above. If the value of β is within the above range, undesirable alteration such as cloudiness on the glass surface can be prevented in the second ion exchange step.

The temperature of the molten salt T2 in the second ion exchange step may be arbitrarily determined, and is, for example, 350 to 500 ° C, preferably 370 to 480 ° C, more preferably 380 to 450 ° C. If the temperature of molten salt T2 is 450 degrees C or less, it will become easy to suppress the fluctuation | variation of the value of (alpha) resulting from temperature. The time for immersing the tempered glass with film G3 in the molten salt T2 may be arbitrarily determined. For example, it is 0.1 to 72 hours, preferably 0.3 to 50 hours, more preferably 0.5 to 24. It's time.

In the second ion exchange step, since the value of β is set higher than α, the ion exchange at the film formation location of the ion permeation suppression membrane M is easier to proceed than in the first ion exchange step. . Therefore, the tempered glass with film G4 that has undergone the process of the second ion exchange step has a greater compressive stress at the location where the ion permeation suppression film M is formed than the tempered glass with film G3 before the process. Further, the tempered glass with film G4 has a deeper compressive stress layer at the position where the ion permeation suppression film M is formed than the tempered glass with film G3.

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

When the ion permeation suppression film M also functions as a protective coating or an antireflection film for an electronic device, the tempered glass with film G4 can be directly mounted on an electronic component or the like and used as a product. Depending on the case, the ion permeation suppression film M may be removed. That is, after the second ion exchange step, a removal step of removing the ion permeation suppression membrane M from the tempered glass with film G4 may be performed.

In the removal step, as shown in FIG. 1E, the ion permeation suppression film M is removed from the tempered glass G4 with film to obtain a tempered glass G5.

Specifically, the ion permeation suppression film M is removed by attaching an etching solution to the film-reinforced glass G4. When the ion permeation 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 etchant, and in particular, a hydrofluoric acid solution is used as an etchant. Is preferred. In addition, the peeling method of the ion permeation suppression film M is not limited to the above, and a known method may be used as a method for removing the film provided on the glass plate. For example, the ion permeation suppression film M may be formed by machining such as polishing. It may be removed.

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

When the ion permeation suppression film M is partially removed or partially removed, the etching liquid is partially adhered using a spray, roll, brush, or the like, or the masked tempered glass G4 is partially masked to etch the liquid. It is possible to remove the film by immersing the film in the film.

When removing all of the ion permeation suppression film M, the entire tempered glass with film G4 may be immersed in an etching solution. If the entire tempered glass with film G4 is immersed in the etching solution in this way, tempered glass G5 with further improved strength may be obtained by reducing microcracks that cause damage.

As described above, according to the method for producing tempered glass according to the embodiment of the present invention, the tempered glass G4 and the tempered glass G5 with less damage from the end face can be produced stably and efficiently.

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

Moreover, the film formation location of the ion permeation suppression film M in the glass with film G2 may be arbitrarily determined. For example, when the original glass G1 is chamfered in advance, the ion permeation suppression film M may be formed on the main surface excluding the chamfered surface.

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

Moreover, although the said embodiment demonstrated the case where molten salt T1, T2 was potassium nitrate molten salt as an example, it is not restricted to this, It replaces with the well-known molten salt used for ion exchange of glass, or uses it in combination Good. 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, although the case where the sodium ion and the potassium ion were exchanged and chemically strengthened was illustrated in the said embodiment, you may chemically strengthen by replacement | exchange of arbitrary ions. For example, chemical strengthening may be performed by exchanging lithium ions and sodium ions, or exchanging lithium ions and potassium ions. In this case, the original glass G1 preferably contains 0.5 to 7.5% by mass of LiO ₂ as a glass composition, for example, 3.0% or 4.5%.

In addition, the processing conditions such as the processing temperature and the immersion time in the first ion exchange step and the second ion exchange step may be appropriately determined according to the characteristics required for the tempered glass with film G4 and the tempered glass G5. In addition, it is preferable to adjust the said process conditions so that the depth of the compressive-stress layer of the main surface S of the tempered glass G4 with a film and the tempered glass G5 may become smaller than the depth of the compressive-stress layer of the exposed part 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. The molten salt used in the strengthening step added between the first ion exchange step and the second ion exchange step has 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. When γ, a molten salt satisfying γ <β is preferable.

The manufacturing method of the tempered glass mentioned above can be implemented using the tempered glass manufacturing apparatus provided with the salt bath X1 which accommodated the said molten salt T1, and the salt bath X2 which accommodated the said molten salt T2. The salt baths X <b> 1 and X <b> 2 are, for example, tanks made of a metal casing having an upper opening, and have an internal space filled with the molten salt T. The tempered glass manufacturing apparatus is configured to have a shape and size capable of accommodating the film-coated glass G2 in the salt tub X1 and the film-reinforced glass G3 in the salt tub X2, and can support the film-coated glass G2. An apparatus (not shown) may further be provided. The support device is a jig constituted by a metal frame such as stainless steel, for example. The processing of the first ion exchange step can be performed by immersing the molten glass T2 in the salt bath X1 in a state where the glass G2 with film is supported by the support device. Moreover, the process of said 2nd ion exchange process can be implemented by making it immerse in the molten salt T2 in the salt bath X2 in the state which supported the tempered glass G3 with a support apparatus. Note that the tempered glass manufacturing apparatus may further include a film forming apparatus (not shown) that performs the film forming process. As the film forming apparatus, a known sputter film forming apparatus or the like can be used.

Here, the stress characteristics of the tempered glass can be measured using, for example, FSM-6000 manufactured by Orihara Seisakusho. When the depth of the compressive stress layer of aluminosilicate glass exceeds 100 μm, or when ion exchange between lithium ions and sodium ions is performed, the stress characteristics of tempered glass are measured using, for example, SLP-1000 manufactured by Orihara Seisakusho. can do. When a cross-sectional sample can be prepared by cutting tempered glass, it is desirable to observe the internal stress distribution and confirm the stress depth using, for example, WPA-micro manufactured by Photonic Lattice or Abrio manufactured by Tokyo Instruments. .

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

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

Each sample in Table 1 was produced as follows. First, the glass composition is glass so that it contains 61.6% of SiO ₂ , 19.6% of Al ₂ O ₃ , 0.8% of B ₂ O ₃ , 16% of Na ₂ O, and ₂ % of K ₂ O in mass%. The raw materials are mixed and melted, formed into a 0.8mm-thick plate using the overflow downdraw method, cut into a 50x50mm rectangular shape by scribing, end-face grinding and polishing, and multiple original glasses G1 was obtained. Subsequently, an ion permeation suppression film M having a composition of 100% by mass and SiO ₂ having a thickness of 200 nm is formed on the entire main surfaces of the front and back surfaces of the original glass G1 by sputtering. Attached glass G2 was obtained (film formation step). Next, the obtained film-coated glass G2 was immersed in a potassium nitrate solution under the conditions shown in Table 1 and chemically strengthened to obtain a film-coated tempered glass G3 (first ion exchange step). Subsequently, the obtained tempered glass with film G3 was immersed in a potassium nitrate solution under the conditions shown in Table 1 and chemically strengthened to obtain tempered glass with film G4 (second ion exchange step). Next, the surface of the obtained tempered glass with film G4 was washed and then polished to remove the ion permeation suppression film to obtain tempered glass G5 (removal step).

No. In 6 and 7, the second ion exchange step was omitted.

The following measurement test was performed on each glass sample obtained as described above.

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 surface are stress meters (FSM manufactured by Orihara Seisakusho). -6000LE and FsmXP). Further, a value obtained by subtracting DOL1 from DOL2 was obtained as ΔDOL. It can be said that the larger the value of ΔDOL, the smaller the internal tensile stress, the more difficult it is to self-destruct, and the higher the strength at the end face.

As shown in Table 1, in the sample Nos. 4 and 5 which are comparative examples, since the value of α is larger than β, the ion exchange suppressing film M is severely worn out during the first ion exchange process, and the film formation location As a result, the value of ΔDOL was smaller than that of the example. Samples Nos. 6 and 7, which are comparative examples, do not perform the second ion exchange process and have a relatively large value of α, so that the ion exchange suppression membrane M is worn out during the first ion exchange process. However, as a result of the fact that ion exchange was not sufficiently suppressed at the film formation location, the value of ΔDOL was smaller than that of the example. That is, Samples Nos. 4 to 7 that are comparative examples were all glass that was more easily self-breaking than the Examples.

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

G1 Original glass G2 Glass with glass G3, G4 Tempered glass with film G5 Tempered glass M Ion permeation suppression film T1 First molten salt T2 Second molten salt X1 First salt bath X2 Second salt bath

Claims (8)

1. A method for producing tempered glass for exchanging ions on a glass surface,
   Forming an ion permeation suppressing film for suppressing permeation of the ions on at least a part of the surface of the glass;
   A first ion exchange step of exchanging the ions by bringing a first molten salt into contact with the surface of the glass on which the ion permeation suppression membrane has been formed; and after the first ion exchange step, the ion permeation suppression membrane A second ion exchange step of exchanging the ions by bringing a second molten salt into contact with the surface of the glass film formed,
   When the first molten salt is mixed with water to form an aqueous solution having a concentration of 20% by mass, the hydrogen ion concentration index is α, and the second molten salt is mixed with water to have a concentration of 20% by mass. A method for producing tempered glass, wherein α <β, where β is the hydrogen ion concentration index.
2. The method for producing tempered glass according to claim 1, wherein α ≦ 10.5.
3. The method for producing tempered glass according to claim 1, wherein 9 ≦ β ≦ 12.
4. 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 is added to the second molten salt at 350 to 500 ° C. in the second ion exchange step. Soak for 1 to 72 hours,
   The method for producing tempered glass according to any one of claims 1 to 3, wherein the immersion time in the first ion exchange step is longer than the immersion time in the second ion exchange step.
5. The glass surface ions are sodium ions,
   The first molten salt and the second molten salt both contain potassium ions,
   Forming the ion permeation suppression film only on the main surface of the glass,
   The ion permeation suppression film has a composition containing 70% or more of SiO ₂ by mass%,
   The method for producing tempered glass according to any one of claims 1 to 4, wherein the ion permeation suppression film has a thickness of 5 to 400 nm.
6. The method for producing tempered glass according to any one of claims 1 to 5, further comprising a step of removing the ion permeation suppression film after the second ion exchange step.
7. The glass is a glass plate containing, by mass%, SiO ₂ 45 to 75%, Al ₂ O ₃ 1 to 30%, Na ₂ O 0 to 20%, K ₂ O 0 to 20% as a glass composition. The manufacturing method of the tempered glass of any one of Claim 1 to 6 characterized by these.
8. A first salt bath containing a first molten salt for exchanging ions on the glass surface layer;
   A second salt bath containing a second molten salt for exchanging ions on the glass surface layer,
   When the first molten salt is mixed with water to form an aqueous solution having a concentration of 20% by mass, the hydrogen ion concentration index is α, and the second molten salt is mixed with water to have a concentration of 20% by mass. When the hydrogen ion concentration index in the case of β is β, α <β.

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