WO2017179360A1

WO2017179360A1 - Method for manufacturing tempered glass and device for manufacturing tempered glass

Info

Publication number: WO2017179360A1
Application number: PCT/JP2017/010479
Authority: WO
Inventors: 田中　敦; 睦深田; 清貴木下; 利之梶岡
Original assignee: 日本電気硝子株式会社
Priority date: 2016-04-12
Filing date: 2017-03-15
Publication date: 2017-10-19
Also published as: JP6827652B2; CN108463443A; CN108463443B; TW201738192A; JPWO2017179360A1

Abstract

This method for manufacturing tempered glass by performing ion exchange on the surface layer of glass is characterized by including: a step of forming, on at least a portion of the surface of glass, an ion permeation suppression film that suppresses permeation of ions; and a step of bringing molten salt into contact with the surface of the glass on which the ion permeation suppression film is formed and performing ion exchange. The molten salt has a pH of 6.5 or higher when mixed with water to produce an aqueous solution with 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 plate 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 on the main surface is formed inside such a tempered glass plate. 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 face of the tempered glass plate and reduce the internal tensile stress within an appropriate range. For example, in Patent Document 1, by forming a film that suppresses ion exchange in advance on the main surface and suppressing the progress of chemical strengthening compared to the end surface, the compressive stress layer on 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. 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 A step of bringing the molten salt into contact with the surface of the glass on which the ion permeation suppressing film is formed and exchanging ions, and the molten salt is mixed with water to form an aqueous solution having a molten salt concentration of 20% by mass. In this case, the pH is 6.5 or more.

In the method for producing tempered glass of the present invention, the molten salt preferably has a pH of 6.7 to 10 when mixed with water to obtain an aqueous solution having a molten salt concentration of 20% by mass. .

The method for producing tempered glass of the present invention preferably further comprises a step of adjusting the pH value when an aqueous solution is prepared by adding a basic substance to the molten salt.

In the method for producing tempered glass of the present invention, it is preferable that the ions on the glass surface layer are sodium ions, the molten salt contains potassium ions, and the basic substance contains potassium hydroxide.

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%. %, And an ion permeation suppressing film is formed only on the main surface of the glass, and the formed glass is immersed in a molten salt at 370 to 480 ° C. for 0.1 to 72 hours for ion exchange. It is preferable.

In the method for producing tempered glass according to the present invention, the ion permeation suppression film preferably contains SiO ₂ as a main component.

It is preferable that the method for producing tempered glass of the present invention further includes a step of adjusting the pH value of the aqueous solution by controlling the temperature of the molten salt.

The tempered glass manufacturing apparatus of the present invention is a tempered glass manufacturing apparatus provided with a salt bath containing molten salt for exchanging ions on the glass surface layer, and the molten salt is mixed with water so that the concentration of the molten salt is The pH when the aqueous solution is 20% by mass is 6.5 or more.

The tempered glass manufacturing apparatus of the present invention further includes a film forming apparatus that forms an ion permeation suppressing film that suppresses permeation of ions on at least a part of the surface of the glass, and a support apparatus that supports the formed glass. The support device is preferably configured to be dipped in a salt bath while supporting the glass.

According to the present invention, by appropriately adjusting the molten salt used for the chemical strengthening of glass, ion exchange is not excessively suppressed at the location where the ion permeation suppression film is formed, and the tempered glass plate has high strength. Can be manufactured stably.

FIG. 1A shows an example of a method for producing tempered glass of the present invention. FIG. 1B shows an example of a method for producing the tempered glass of the present invention. FIG. 1C shows an example of a method for producing the tempered glass of the present invention. FIG. 1D shows an example of a method for producing the tempered glass of the present invention. FIG. 2 is a flowchart showing another example of the method for producing tempered glass according to the present 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 glass that can be tempered 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.

The original glass G1 is preferably formed using an overflow downdraw method, and its 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 film-coated glass G2 has the ion permeation suppression film M formed only on the front and back main surfaces S, and the end face 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 metal oxide, metal nitride, metal carbide, metal oxynitride, metal oxycarbide, metal carbonitride film, or the like. Is preferred. 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 forming process, the strengthening process shown in FIG. 1C is performed. The tempering step is a step of chemically strengthening the film-coated glass G2 by an ion exchange method to obtain a film-coated tempered glass G3. Specifically, ion exchange is performed by immersing the film-coated glass G2 in a molten salt T containing alkali metal ions.

In the present invention, when the molten salt T is mixed with water to form an aqueous solution having a concentration of the molten salt of 20% by mass, the pH value of the aqueous solution (hereinafter referred to as pH at the time of aqueous solution) is 6. It is a salt of 5 or more. By setting the pH at the time of aqueous solution in the above range, ions to be exchanged can be appropriately permeated through the ion permeation suppression membrane M, and ion exchange can be appropriately performed at the film forming location. The aqueous pH is preferably 6.7 to 10, more preferably 6.8 to 8.5, and still more preferably 7.0 to 8.0. From the viewpoint of suppressing a reduction in surface strength of the tempered glass with film G3, it is preferable that the pH when water is in the range of 7.0 to 8.0. The pH at the time of aqueous solution 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 molten salt T in the present embodiment is, for example, potassium nitrate molten salt, but a well-known molten salt used for ion exchange of glass may be used.

In the present invention, it is preferable to carry out the adjustment step of adjusting the pH of the molten salt T when it is in water within the above range before or after the strengthening step. In the adjustment step, for example, the pH at the time of aqueous solution can be adjusted by adding an additive to the molten salt T. 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.

The temperature of the molten salt in the strengthening step may be arbitrarily determined, and is, for example, 350 to 500 ° C., preferably 370 to 480 ° C. Further, the time for immersing the film-coated glass G2 in the molten salt T may be arbitrarily determined, and is, for example, 0.1 to 72 hours, preferably 0.5 to 24 hours.

In the tempering step, sodium ions on the surface of the film-coated glass G2 and potassium ions in the molten salt T 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, a 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 deeper compressive stress layer at the end surface than the main surface, and therefore has a lower internal tensile stress than the tempered glass strengthened 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.

In addition, when the above-described inorganic composition material is adopted as the ion permeation suppression film M, it is melted as compared with a conventional organic protective film or the like even when immersed in the molten salt T with the film provided. It is difficult to deteriorate the salt T.

The processing conditions such as the processing temperature and the dipping time in the tempering step may be appropriately determined according to the characteristics required for the tempered glass with film G3. The processing conditions are preferably adjusted so that the depth of the compressive stress layer on the main surface S of the tempered glass G3 with film is smaller than the depth of the compressive stress layer on the exposed portion E.

Since the ion permeation suppression film M also functions as a protective coating or an antireflection film for electronic devices, the tempered glass G3 with a film can be used as a product as it is, but the ion permeation suppression film M can be used depending on the application. It may be peeled off. In the peeling step shown in FIG. 1D, the ion permeation suppression film M is peeled from the tempered glass G3 with film to obtain a tempered glass plate G4.

Specifically, the ion permeation suppression film M is removed by attaching an etching solution to the tempered glass with film G3. When the ion permeation suppression film M is a film containing SiO ₂ , for example, a solution containing fluorine, TMAH, EDP, KOH, or the like can be used as an etchant, and a hydrofluoric acid solution is particularly preferably used as an etchant. . 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 films 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, etc., or the masked tempered glass G3 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 G3 may be immersed in an etching solution. If the entire tempered glass with film G3 is immersed in the etching solution in this way, there are cases where a tempered glass plate G4 with further improved strength can 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 G3 and the tempered glass G4 with less damage from the end face can be efficiently produced.

The material of the ion permeation suppression film M described above is an example, and any material may be used as long as the film can suppress permeation of ions exchanged in the strengthening process.

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.

The manufacturing method of the tempered glass mentioned above can be implemented using the tempered glass manufacturing apparatus provided with the salt bath X which accommodated the said molten salt T. FIG. The salt tub X is, for example, a tank made of a metal casing having an upper opening, and has an internal space filled with the molten salt T. The said tempered glass manufacturing apparatus is further provided with the support apparatus (not shown) which is comprised by the shape and dimension which can be accommodated in the salt tub X, and can support the glass G2 with a film | membrane. The support device is a jig constituted by a metal frame such as stainless steel, for example. By immersing in the molten salt T in the salt bath X in a state where the glass G2 with film is supported by the support device, the treatment of the strengthening step can be performed. 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.

FIG. 2 is a flowchart showing another example of the method for producing tempered glass according to the present invention. As shown in FIG. 2, the method includes a preparation step S1, a film formation step S2, a molten salt generation step S3, a pH measurement step S4, a determination step S5, a pH adjustment step S6, a strengthening step S7, and a peeling step S8. . The preparation step S1, the film formation step S2, and the peeling step S8 are the same as the example in FIG. Molten salt production | generation process S3 is a process which heats and melts metal nitrate (for example, potassium nitrate etc.), and obtains molten salt T. FIG.

PH measurement step S4 is performed after the molten salt generation step S3. In the pH measurement step S4, the pH when the molten salt T is mixed with water to make an aqueous solution having a concentration of 20% by mass is measured. For example, an off-the-shelf pH meter is used for measuring the pH.

In the determination step S5, it is determined whether or not the pH value of the molten salt T measured in the pH measurement step S4 is suitable for the strengthening step S7. This determination is made by comparison with a predetermined reference value. The reference value is set according to various conditions such as dimensions, thickness, DOL, and CS of the tempered glass. For example, when the reference value of pH is 6.5, when the measured pH value of the molten salt T is 6.5 or more (Yes in determination step S5), the process proceeds to the next strengthening step S7. When the measured pH value of the molten salt T is less than 6.5 (No in the determination step S5), the pH adjustment step S6 is performed before the strengthening step S7.

In the pH adjustment step S6, at least one step such as a step of adding a basic substance to the molten salt T, a step of immersing the film-adjusting member for pH adjustment in the molten salt T, or a step of controlling the temperature of the molten salt T. To adjust the pH value of the molten salt T.

In the step of adding a basic substance to the molten salt T, as in the example of FIG. 1, a basic substance having a pH higher than 7 when mixed with water is added to the molten salt T, and the molten salt T Adjust the pH.

In the step of immersing the membrane-attached member for pH adjustment in the molten salt, the membrane-attached member is immersed in the molten salt T, and the membrane-attached member is melted when the pH of the molten salt T reaches a desired value. Remove from salt T. pH membrane with members for adjustment, for example, be constituted by a glass substrate having a film made of SiO ₂ is desired, it may be used after forming the SiO ₂ film on the metal substrate. By immersing the glass substrate including the SiO ₂ film in the molten salt T, the pH value can be lowered. That is, the hydroxide ions in the molten salt T break Si—O bonds in the SiO ₂ film. By this reaction, hydroxide ions are reduced, and the pH of the molten salt T is lowered. The SiO ₂ film is desirably formed on a glass or metal substrate by sputtering, but is not limited thereto, and may be formed by wet coating or spin coating.

In the step of controlling the temperature of the molten salt T, the pH value of the molten salt T can be increased by maintaining the molten salt T at a temperature equal to or higher than its boiling point. For example, in the case where the molten salt T of potassium nitrate is maintained at a temperature higher than the boiling point, a part of the potassium nitrate is changed to potassium nitrite. Since this potassium nitrite has deliquescence, moisture (H ₂ O) in the atmosphere is taken into the molten salt T. In this case, since hydrogen ions move toward the metal salt bath X made of stainless steel or the like, as a result, hydroxide ions remain in the molten salt T, and the concentration of hydroxide ions in the molten salt T is reduced. Presumed to rise. When the molten salt T is constituted by mixing potassium nitrate and sodium nitrate, the boiling point changes depending on the concentration, but the present inventors have found that this phenomenon occurs at approximately 450 ° C. or higher. When the pH of the molten salt T reaches a target value (above the reference value), the molten salt T is maintained at a temperature below the boiling point. Thereby, the change in pH value of the molten salt T is eliminated, and the molten salt T can be maintained at a desired pH value.

In the strengthening step S7, the film-coated glass G2 is immersed in the molten salt T accommodated in the salt bath X, as in the example of FIG. After immersion for a certain time, the tempered glass with film G3 is taken out from the salt bath X. The tempered glass with film G3 becomes the tempered glass plate G4 after the peeling step S8.

In addition, this invention is not limited to the structure of the said embodiment, It is not limited to the above-mentioned effect. The present invention can be variously modified without departing from the gist of the present invention.

In the above tempered glass manufacturing method, the example in which the tempering step S7 is executed after the pH adjusting step S6 has been shown. However, the present invention is not limited to this, and the pH adjusting step S6 and the tempering step S7 may be executed simultaneously. . For example, in the pH adjusting step S6, the tempered glass with film G3 may be reinforced by immersing the molten salt T in the molten salt T while maintaining the molten salt T at a temperature equal to or higher than the boiling point. In this case, the pH value of the molten salt T may change greatly during strengthening. As a measure for suppressing changes in pH value, it is desirable that the salt bath X be made of quartz. According to this, since hydrogen ions do not come out of the molten salt T, a change in pH value can be suppressed as compared with the metal salt bath X.

Moreover, if the process of molten salt production | generation process S3 is before pH measurement process S4, you may implement in parallel with the process of preparatory process S1 and film-forming process S2, or of preparatory process S1 and film-forming process S2. It may be performed before the start.

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

In Tables 1 and 2, Nos. 1 to 8 show examples of the present invention, and Nos. 9 to 18 show comparative examples.

Each sample in Table 1 and Table 2 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 were mixed and melted, and molded using an overflow downdraw method to obtain a plurality of original glasses having a thickness of 0.4 mm. Next, after forming a film of 100% SiO ₂ having the film thickness shown in Tables 1 and ₂ as an ion permeation suppression film on both main surfaces of the original glass by sputtering, 20 × 50 mm by scribe cleaving. The glass with a film | membrane which has an exposed part in an end surface was obtained by cutting out into the rectangular shape of a dimension. The samples No. 10 to 18 were cut as described above without performing the film formation. Subsequently, the obtained glass with a film was immersed in a 430 ° C. potassium nitrate solution having a pH at the time of water listed in Table 1 for 5 hours to chemically strengthen, washed with pure water and naturally dried, and then No. 1 in Table 1. 1 to 18 tempered glass plate samples were obtained.

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

Main surface compressive stress value CS, main surface stress depth DOL, and internal tensile stress CT were measured with a stress meter (FSM-6000LE and FsmXP manufactured by Orihara Seisakusho).

The falling ball test was carried out by placing the edge of a tempered glass plate sample having a size of 65 mm in length and 130 mm in width created in the same manner as described above on a frame-shaped jig having an open center portion made of paper bakelite. A steel ball was dropped on the center of the glass, and the height at which it was damaged by a single collision was recorded. Specifically, from a height of 15 cm, a steel ball is dropped in increments of 5 cm, the height at which the tempered glass is broken is recorded, the height at which the tempered glass is broken is Weibull plotted, and the height at which the breakage probability has reached 63% is recorded. Obtained as an average value. In addition, each sample grind | polished the end surface beforehand with the 800th grindstone. Further, the tempered glass of each sample was placed on a jig so that the margin of each side was 5 mm.

As shown in Tables 1 and 2, Sample No. 9, which is a comparative example, has a pH under water that is smaller than 6.5. Therefore, ion exchange is excessively suppressed by the ion permeation suppression membrane, and the surface compressive stress value CS and The surface compressive stress depth DOL could not be obtained. On the other hand, as a result of appropriately adjusting the pH of each sample of the example, a compressive stress layer having an appropriate surface compressive stress value and surface compressive stress depth was formed on the surface on which the ion permeation suppression film was formed.

Further, as shown in Table 1 and Table 2, each sample of the example was prepared by strengthening with an ion permeation suppression film formed on the main surface and an exposed portion on the end surface, and therefore compression of the surface and end surface The balance of stress is suitably set, and as a result, the internal tensile stress CT is reduced as compared with the samples of Comparative Examples No. 10 to 18 which are not formed with an ion permeation suppression film and are strengthened with pH under water conditions under the same conditions. It is harder to self-destruct.

Table 3 below shows the change of the pH of the molten salt with respect to the immersion time when the glass plate on which the SiO ₂ film is formed is immersed in molten potassium nitrate held at a predetermined temperature (temperature below the boiling point). Show. Sample No. shown in Table 3 Each of the molten salts 21 to 24 contains 600 g of potassium nitrate and 13.6 g of sodium nitrate. Furthermore, sample no. The 21 molten salt contains 0.10 g of potassium hydroxide. Sample No. The 22 molten salt contains 0.60 g of potassium hydroxide. Sample No. The molten salt of No. 23 was obtained by adding 6.00 g of potassium hydroxide to Sample No. The 24 molten salt contains 0.05 g of potassium hydroxide. The pH value of the molten salt shown in Table 3 is a value when the molten salt is a 20% by mass aqueous solution. As shown in Table 3, each sample No. From 21 to 24, it was found that the pH value of the molten salt decreased with the passage of time. From this, it can be seen that the glass plate on which the SiO ₂ film is formed can be effectively used as an adjusting material for lowering the pH value of the molten salt in the pH adjusting step.

The present inventors conducted a test for confirming the influence of the salt bath containing the molten salt T on the pH of the molten salt. In this test, the molten salt is accommodated in a quartz salt bath (beaker) and a stainless steel salt bath, and the pH value is measured when the molten salt is made into a 20% by mass aqueous solution after a certain period of time. did. The molten salt contains 600 g of potassium nitrate. In this test, the temperature of the molten salt was maintained below the boiling point. The test results are shown in Table 4 below. As shown in Table 4, the molten salt accommodated in the quartz salt tub has a smaller degree of change (increase) in pH with the passage of time than that accommodated in the stainless steel salt tub. I understand.

The present inventors conducted a test to confirm the relationship between temperature and pH change in molten salt. In this test, the temperature of the potassium nitrate molten salt was set to 400 ° C., 430 ° C., and 460 ° C., and the pH value of the molten salt (20% by mass aqueous solution) after a lapse of a fixed time was measured. The test results are shown in Table 5 below. As shown in Table 5, it can be seen that the higher the temperature of the molten salt, the greater the change (increase) in the pH of the molten salt with respect to the elapsed time. This test confirmed that the pH of the molten salt can be adjusted by controlling the temperature of the molten salt in the pH adjustment step.

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 film G3 Tempered glass with film G4 Tempered glass plate M Ion permeation suppression film T Molten salt X Salt bath

Claims

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 step of bringing the molten salt into contact with the surface of the glass on which the ion permeation suppression film is formed and exchanging the ions,
The molten salt has a pH of 6.5 or more when mixed with water to form an aqueous solution having a concentration of 20% by mass.
The tempered glass production according to claim 1, wherein the molten salt has a pH of 6.7 to 10 when mixed with water to form an aqueous solution having a concentration of the molten salt of 20% by mass. Method.
The method for producing tempered glass according to claim 1 or 2, further comprising a step of adjusting a pH value when a basic substance is added to the molten salt to obtain the aqueous solution.
The glass surface ions are sodium ions,
The molten salt contains potassium ions,
The method for producing tempered glass according to claim 3, wherein the basic substance contains potassium hydroxide.
The glass contains, by mass% as a glass composition, a glass plate containing SiO 2 45 ~ 75%, Al 2 O 3 1 ~ 30%, Na 2 O 0 ~ 20%, the K 2 O 0 ~ 20%,
Forming the ion permeation suppression film only on the main surface of the glass,
The method for producing tempered glass according to any one of claims 1 to 4, wherein the ion exchange is performed by immersing the formed glass in the molten salt at 370 to 480 ° C for 0.1 to 72 hours. .
The ion transmission suppressing layer includes SiO 2 as a main component, method for producing a tempered glass according to any one of claims 1 to 5.
The method for producing tempered glass according to any one of claims 1 to 6, further comprising a step of adjusting a pH value of the aqueous solution by controlling a temperature of the molten salt.
A tempered glass manufacturing apparatus comprising a salt bath containing molten salt for exchanging ions on the glass surface layer,
The molten salt has a pH of 6.5 or more when mixed with water to form an aqueous solution having a concentration of 20% by mass.
A film forming apparatus for forming an ion permeation suppressing film for suppressing permeation of the ions on at least a part of the surface of the glass;
A support device for supporting the glass that is formed into a film,
The tempered glass manufacturing apparatus according to claim 8, wherein the support device is configured to be dipped in the salt bath while supporting the glass.