JP7004222B2 - Manufacturing method of tempered glass plate and tempered glass plate - Google Patents

Description

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

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

Such a tempered glass plate is generally manufactured by chemically treating a glass plate containing an alkali metal as a composition with a tempering liquid to form a compressive stress layer on the surface (for example, Patent Document 1, Patent Document 1, 2).

Tempered glass having a compressive stress layer on its surface has a tensile stress layer formed inside so that the stress balance is balanced. The tensile stress (CT) of the tensile stress layer increases as the depth (DOL) and compressive stress (CS) of the compressive stress layer increase.

For example, when fracture due to a point collision of a sharp indenter tool is assumed as in Patent Document 1, or when fracture due to bending is assumed as in Patent Document 2, if the tensile stress (CT) is excessive, it is strengthened. The glass was thought to be prone to breakage. Therefore, conventionally, it has been preferable to control the depth (DOL) of the compressive stress layer to a certain value or less. For example, in Patent Document 2, it is preferable that the DOL is 35 μm or less.

Japanese Patent Publication No. 2015-523310 Japanese Unexamined Patent Publication No. 2014-001124

However, there are various fracture modes (break modes) of tempered glass actually mounted on smartphones, tablet computers, etc., and in a specific fracture mode, the tensile stress (CT) and the depth of the compressive stress layer (DOL) are not necessarily determined. It is not always preferable to regulate as small as in the past.

The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide a tempered glass plate having high strength and a method for manufacturing the same.

The method for manufacturing a tempered glass plate of the present invention is a method for manufacturing a tempered glass plate in which at least a part of the surface of the tempered glass plate is ion-exchanged to form a compressive stress layer, and the depth from the surface of the compressive stress layer is formed. It is characterized by comprising an ion exchange step of performing ion exchange until the compressive stress at a position of 50 μm becomes 200 MPa or more.

In the method for manufacturing a tempered glass plate of the present invention, in the ion exchange step, ions are formed until the maximum value of the compressive stress in the compressive stress layer is 400 MPa or more and the depth (DOL_Z) from the outer surface of the layer becomes deeper than 100 μm. It is preferable to carry out a replacement process.

In the method for manufacturing a strengthened glass plate of the present invention, the ion exchange step includes a first ion exchange step in which the strengthening glass plate is brought into contact with a molten salt at the first temperature to perform ion exchange, and a second temperature for the strengthening glass plate. Including a second ion exchange step of contacting with the molten salt of the above to perform ion exchange, and prior to the first ion exchange step, an ion exchange prevention film for preventing ion exchange is previously applied to at least a part of the surface of the reinforcing glass. It is preferable to further include a film forming step to be provided and a removing step of removing the ion exchange preventing film after the first ion exchange step, and to carry out the second ion exchange step after the removing step.

In the method for producing a tempered glass plate of the present invention, it is preferable that the second temperature is lower than the first temperature and the ion exchange treatment time in the first ion exchange step is longer than the ion exchange treatment time in the second ion exchange step.

In the method for producing a tempered glass plate of the present invention, it is preferable that the first temperature exceeds 430 ° C and the second temperature is 430 ° C or lower.

In the method for producing a tempered glass plate of the present invention, the difference between the first temperature and the second temperature is preferably within ± 5 ° C.

In the method for producing a tempered glass plate of the present invention, it is preferable that the tempered glass plate is continuously contacted with a molten potassium nitrate salt having a sodium ion concentration of 50,000 ppm or less for 10 hours or more to perform ion exchange in the ion exchange step.

The tempered glass plate of the present invention is characterized by having a compressive stress deep layer having a compressive stress of 200 MPa or more at a depth of 50 μm on at least a part of the outer surface.

In the tempered glass plate of the present invention, it is preferable that the maximum value of the compressive stress in the deep compressive stress layer is 400 MPa or more and the depth thereof is deeper than 100 μm.

The tempered glass plate of the present invention preferably has a deep compressive stress layer along the peripheral edge portion.

It is preferable that the tempered glass plate of the present invention has a compressive stress shallow layer shallower than the compressive stress deep layer in at least a part of the surface where the compressive stress deep layer is not formed.

In the tempered glass plate of the present invention, the compression stress shallow layer preferably has a depth of 35 to 60 μm and a maximum compressive stress value of 600 to 1500 MPa.

According to the present invention as described above, a tempered glass plate having high strength can be obtained.

It is a figure which shows the manufacturing method of the tempered glass plate which concerns on 1st Embodiment of this invention. It is a figure which shows the manufacturing method of the tempered glass plate which concerns on 1st Embodiment of this invention. It is a figure which shows the manufacturing method of the tempered glass plate which concerns on 1st Embodiment of this invention. It is a figure which shows the manufacturing method of the tempered glass plate which concerns on 1st Embodiment of this invention. It is a figure which shows the manufacturing method of the tempered glass plate which concerns on 1st Embodiment of this invention. It is a top view of the reinforcing glass plate which concerns on embodiment of this invention. It is a top view of the reinforcing glass plate provided with the ion exchange prevention film which concerns on embodiment of this invention. It is a figure which shows the manufacturing method of the tempered glass plate which concerns on the 2nd Embodiment of this invention. It is a figure which shows the manufacturing method of the tempered glass plate which concerns on the 2nd Embodiment of this invention. It is a schematic diagram of the test apparatus for measuring the breaking height which concerns on embodiment of this invention. It is a figure which shows the relationship between the depth from the surface and the magnitude of compressive stress about a tempered glass plate.

<First embodiment>
Hereinafter, a method for manufacturing a tempered glass plate according to an embodiment of the present invention will be described. 1a to 1e are views showing an example of the method for manufacturing a tempered glass plate of the present invention.

First, the process of the preparation step shown in FIG. 1a is carried out. The preparation step is a step of preparing the reinforcing glass plate G1. The strengthening glass plate G1 is a plate-shaped glass plate that can be strengthened by using an ion exchange method. As shown in FIGS. 1a and 2, the reinforcing glass plate G1 in the present embodiment is a substantially rectangular glass plate having a main surface S and an end surface E. Note that FIG. 2 is a plan view of the reinforcing glass plate G1 in the plate thickness direction. Further, FIG. 1a is a cross-sectional view taken along the line AA of the reinforcing glass plate G1 in FIG. The reinforcing glass plate G1 is chamfered and has a chamfered surface B between the main surface S and the end surface E. That is, the outer surface of the reinforcing glass plate G1 includes a main surface S, an end surface E, and a chamfered surface B.

The reinforcing glass plate G1 has a glass plate composition of 40% by mass, contains SiO ₂ 45 to 75%, Al ₂ O ₃ 1 to 30%, Na ₂ O 0 to 20%, and K ₂ O 0 to 20%. Is preferable. If the glass plate composition range is regulated as described above, it becomes easy to achieve both ion exchange performance and devitrification resistance at a high level.

The plate thickness of the reinforcing glass plate 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, and particularly 0.9 mm or less. The smaller the thickness of the tempered glass plate, the lighter the tempered glass plate can be, and as a result, the thinner and lighter the device may be. In such a case, the plate thickness of the reinforcing glass plate G1 is 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, and particularly 0. It is even better if it is 1 mm or less. Further, in consideration of productivity and the like, the plate thickness of the reinforcing glass plate G1 is preferably 0.01 mm or more.

The plan view dimension of the reinforcing glass plate G1 can be arbitrarily set, and is, for example, 10 × 10 mm to 3350 × 3950 mm.

The reinforcing glass plate G1 is, for example, glass formed by using an overflow down draw method. The molding method and processing state of the reinforcing glass plate G1 may be arbitrarily selected. For example, the reinforcing glass plate G1 may be glass formed by using the float method. Further, the main surface S, the end surface E, and the chamfered surface B may be polished.

Next, after the preparatory step, the film forming step shown in FIG. 1b is processed. The film forming step is a step of forming an ion exchange preventing film M on at least a part of the surface of the strengthening glass plate G1 to obtain a strengthening glass plate G1m with a film. In the present embodiment, as shown in FIG. 3, the ion exchange prevention film M is formed in the central portion S1 of the front and back main surfaces of the reinforcing glass plate G1. Note that FIG. 1b corresponds to the cross-sectional view taken along the line AA in FIG. Of the surface of the reinforcing glass plate G1, the peripheral portions other than the central portion S1 are exposed. The peripheral edge portion is a portion of the main surface S including the outer peripheral region S2 surrounding the central portion S1, the chamfered surface B, and the end surface E. The ion exchange prevention film M is a film layer that suppresses or blocks the permeation of ions when the ion exchange of the surface layer of the reinforcing glass plate G1 is performed in the first ion exchange step described later.

As the material of the ion exchange preventing film M, any material may be used as long as it can suppress or block the permeation of the ions exchanged with ions. When the ion to be exchanged is an alkali metal ion, the ion exchange prevention film M is, for example, a metal oxide, a metal nitride, a metal carbide, a metal oxynitride, a metal acid carbide, a metal carbonitride film, or the like. Is preferable. Further, carbon materials, metals and alloys having excellent heat resistance and chemical durability can also be used as the ion exchange prevention film M. More specifically, as the material of the ion exchange prevention film M, for example, SiO ₂ , Al ₂ O ₃ , SiN, SiC, AlN, ZrO ₂ , TIO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , HfO ₂ , etc. The film may contain one or more of SnO ₂ , carbon nanotubes, graphins, diamond-like carbon, and stainless steel. Further, the ion exchange prevention film M is preferably an amorphous film whose crystallinity does not easily change during the ion exchange treatment.

The ion exchange prevention film M also includes a membrane that suppresses ion permeation, that is, does not completely block it. As the material of such an ion exchange prevention film M, for example, ZrO ₂ , SnO ₂ , ITO film, and AlN can be used. However, since the crystallinity of the membrane made of these materials tends to change at high temperatures, the ion permeability may easily change during the ion exchange process.

Considering the mechanical strength and cost, it is preferable to use a film containing SiO ₂ as a main component and Al ₂ O ₃ as an ion exchange prevention film M. In this case, the ion exchange prevention film M preferably has a composition containing 20 to 99% of SiO ₂ and 1 to 80% of Al ₂ O ₃ by mass.

The thickness of the ion exchange prevention membrane M may be any thickness as long as it is possible to block and suppress ion permeation. However, if the thickness of the ion exchange prevention film M is excessive, the film formation time, material cost, and the like increase. Therefore, it is preferable to form the ion exchange prevention film M as thin as possible to block and suppress ion permeation. Specifically, the film thickness of the ion exchange prevention film M is preferably, for example, 1 to 5000 nm, and more preferably 50 to 4000 nm.

The film forming method of the ion exchange prevention film M includes PVD method (physical vapor deposition method) such as sputtering method and vacuum vapor deposition method, CVD method (chemical vapor deposition method) such as thermal CVD method and plasma CVD method, and dip coating. Wet coating methods such as the method and the slit coating method can be used. The sputtering method is particularly preferable. When the sputtering method is used, the ion exchange prevention film M can be easily and uniformly formed. The film formation location of the ion exchange prevention film M may be set by any method. For example, the film can be formed with the peripheral portion masked. Further, the ion exchange prevention film M previously formed into a sheet shape may be bonded to the main surface of the reinforcing glass plate G1 to form a film.

In this embodiment, the case where the ion exchange prevention film M containing SiO ₂ and Al ₂ O ₃ and having a film thickness of 100 nm or more and capable of blocking the permeation of alkali metal ions is formed will be described as an example.

Next, after the film forming step, the ion exchange step is performed. In the ion exchange step, ion exchange is performed on at least a part of the surface of the reinforcing glass plate G1 until the compressive stress at a depth of 50 μm from the surface becomes 200 MPa or more to form the compressive stress deep layer C (C1, C2). It is a process to do. The ion exchange step of the present embodiment includes a first ion exchange step shown in FIG. 1c and a second ion exchange step shown in FIG. 1e.

First, the process of the first ion exchange step shown in FIG. 1c is carried out. The first ion exchange step is a step of obtaining a tempered glass plate G2 in which the tempered glass plate G1 is partially chemically strengthened by an ion exchange method. Specifically, the reinforcing glass plate G1 is immersed in the molten salt T1 containing alkali metal ions for ion exchange. The molten salt T1 in the present embodiment is, for example, a molten salt of potassium nitrate.

Here, since ion exchange is not performed in the region (central portion S1) where the ion exchange prevention film M is formed on the surface of the reinforcing glass plate G1, the compressive stress layer is not formed. On the other hand, on the surface of the reinforcing glass plate G1, ion exchange is performed in the region (peripheral portion) where the ion exchange prevention film M is not formed, and the compressive stress deep layer C1 is formed.

The compressive stress deep layer C1 is a compressive stress layer having a compressive stress CS (50) of 200 MPa or more at a depth of 50 μm. Further, in the compressive stress deep layer C1, the maximum value CSmax of the compressive stress is preferably 400 MPa or more, and the depth DOL_Z of the layer is preferably deeper than 100 μm.

The temperature of the molten salt T1 in the first ion exchange step exceeds 430 ° C, preferably 440 to 500 ° C, and more preferably 450 to 490 ° C. The time for immersing the glass plate G1m for strengthening with a film in the molten salt T1 is, for example, 10 to 200 hours, preferably 12 to 170 hours, and more preferably 24 to 100 hours. By performing the ion exchange treatment at such a relatively high temperature, a deep compressive stress layer can be formed on the peripheral portion in a short time.

As the molten salt T1 is used repeatedly, the concentration of Na ions may increase and the ion exchange characteristics may fluctuate. Therefore, it is preferable to maintain the Na ion concentration of the molten salt T1 within a certain range. Further, in order to efficiently increase the depth of the compressive stress deep layers C1 and C2, it is preferable to regulate the Na ion concentration of the molten salt T1 to preferably 50,000 ppm or less, more preferably 30,000 ppm or less, still more preferably 20,000 ppm or less. .. The Na ion concentration in the molten salt T1 can be adjusted by adding potassium nitrate or the like.

The tempered glass plate G2 provided with the ion exchange prevention film M obtained when the treatment of the first ion exchange step is completed is referred to as a tempered glass plate G2m with a film.

Next, after the first ion exchange step, the process of the film removing step shown in FIG. 1d is carried out. The film removing step is a step of removing the ion exchange preventing film M from the tempered glass plate G2m with a film. As a method for removing the ion exchange prevention film M, for example, a method such as polishing or etching can be used.

As the polishing device used for polishing, a well-known double-sided polishing machine or single-sided polishing machine can be used. When the ion exchange prevention film M is removed by polishing, only the ion exchange prevention film M may be polished, or the glass plate portion may be polished together with the ion exchange prevention film M.

As the etching method, a method such as dry etching or wet etching can be used.

When dry etching is used, it is particularly preferable to use plasmas such as Ar, O ₂ , CH ₄ , BC ₁₃ , C ₁₂ , and SF ₆ .

As the etching solution used for wet etching, for example, a solution containing fluorine, TMAH, EDP, KOH, NaOH and the like can be used as the etching solution, and it is particularly preferable to use the hydrofluoric acid solution as the etching solution. When using a hydrofluoric acid solution and removing only the ion exchange prevention film M without changing the dimensions of the glass, it is preferable that the concentration of HF in the hydrofluoric acid solution is 10% or less.

The tempered glass plate G2a obtained as described above has a compressive stress deep layer C1 at the peripheral edge portion. That is, the tempered glass plate G2a is a glass having high breakage resistance at the peripheral portion.

Next, after the film removing step, the process of the second ion exchange step shown in FIG. 1e is carried out. The second ion exchange step is a step of forming a relatively shallow compressive stress shallow layer D in a region where the compressive stress layer was not formed in the first ion exchange step to obtain a tempered glass plate G2b. In the present embodiment, as shown in FIG. 1e, the tempered glass plate G2 is immersed in the molten salt T2 containing alkali metal ions, and the compressive stress is applied to the entire region (central portion S1) where the ion exchange prevention film M is formed. The shallow layer D is formed. The molten salt T2 is, for example, a molten salt of potassium nitrate.

The compressive stress deep layer C1 formed on the peripheral edge portion becomes a compressive stress deep layer C2 with the characteristics slightly changed by coming into contact with the molten salt T2 in the above treatment. In the present embodiment, the compressive stress deep layer C2 is a compressive stress layer having a compressive stress CS (50) of 200 MPa or more at a depth of 50 μm even after the fluctuation. The compressive stress CS (50) at a depth of 50 μm of the compressive stress deep layer C2 is preferably 200 to 500 MPa, more preferably 220 to 450 MPa, and further preferably 250 to 400 MPa.

The temperature of the molten salt T2 in the second ion exchange step is preferably lower than the temperature of the molten salt T1 used in the above-mentioned first ion exchange step. By performing the ion exchange treatment at such a relatively low temperature, it becomes easy to prevent the depth of the compressive stress shallow layer D formed in the central portion S1 from becoming excessive. The temperature of the molten salt T2 is, for example, 430 ° C or lower, more preferably 390 to 430 ° C, and even more preferably 400 to 425 ° C.

The time for immersing the tempered glass plate G2 in the molten salt T2 is, for example, 0.1 to 72 hours, preferably 0.3 to 50 hours, and more preferably 0.5 to 24 hours.

It is preferable that the Na ion concentration of the molten salt T2 is also maintained within a certain range as in the molten salt T1. The Na ion concentration of the molten salt T2 is preferably regulated to 30,000 ppm or less, more preferably 20,000 ppm or less, and even more preferably 10,000 ppm or less. By adjusting the Na ion concentration of the molten salt T2 in this way, the maximum value of the compressive stress in the compressive stress deep layer C2 and the compressive stress shallow layer D can be easily set to a large value.

The maximum value of the compressive stress in the compressive stress deep layer C2 is preferably 400 MPa or more, more preferably 450 to 1500 MPa, and further preferably 500 to 1200 MPa. The depth of the compressive stress deep layer C2 is preferably 100 μm or more, more preferably 100 to 300 μm, and further preferably 100 to 250 μm.

By performing the treatment of the ion exchange process twice as described above, the compressive stress deep layer C2 which is a relatively deep compressive stress layer and the compressive stress shallow layer D which is a relatively shallow compressive stress layer are provided in different regions. A tempered glass plate G2b can be obtained. According to such a tempered glass plate G2b, for example, a deep compressive stress deep layer C2 can be formed in the peripheral portion where the starting point of fracture is likely to be obtained, and high fracture resistance can be obtained, and at the same time, shallow compression is performed in the central portion S1. The stress shallow layer D can be formed to suppress the increase in the internal tensile stress, and the increase in the tensile stress formed inside the tempered glass plate G2 can be suppressed. Further, since the tensile stress is reduced in the central portion S1, it is difficult for the central portion S1 to become finer debris than in the peripheral portion at the time of breakage. Therefore, for example, when the tempered glass plate G2 is used for a display or the like, it is easy to maintain the visibility of the display even after it is damaged.

Since the tempered glass plate G2 (G2a, G2b) has the compressive stress deep layer C (C1, C2) as described above, the tempered glass plate G2 (G2a, G2b) has high strength in a specific breakage mode at the formation site of the layer. In the specific failure mode, a sharp protrusion exists at the drop destination of the tempered glass plate G2, and the protrusion breaks through the compressive stress layer on the surface and reaches the tensile stress layer inside to generate a crack. A failure mode in which a crack propagates and breaks due to internal tensile stress.

The treatment conditions such as the temperature and immersion time of the molten salt T1 in the first ion exchange step and the temperature and immersion time of the molten salt T2 in the second ion exchange step are examples, and the formed compressive stress deep layer C is: It may be arbitrarily adjusted so that the stress layer has a compressive stress CS (50) of 200 MPa or more at a depth of 50 μm.

Further, in order to suppress the manufacturing cost of the tempered glass plate, for example, the first ion exchange step and the second ion exchange step may be performed in the same tempered tank (molten salt). In this case, the difference between the temperature of the molten salt when the first ion exchange step is performed and the temperature of the molten salt when the second ion exchange step is performed tends to be within the range of ± 5 ° C.

In the above embodiment, the case where the compressive stress deep layer C1 formed by the treatment of the first ion exchange step has a strengthening property in which the compressive stress CS (50) at a depth of 50 μm is 200 MPa or more has been described as an example. As long as it has the characteristics when it becomes the compressive stress deep layer C2 after the treatment of the second ion exchange step, it does not have to have the above characteristics at the time of the treatment of the first ion exchange step.

Further, after the second ion exchange step, the finishing process may be further performed (not shown). In the finishing process, at least one of the surface of the tempered glass plate G2b, for example, the main surface S and the end surface E is polished. If the dimensions and surface condition of the tempered glass plate G2b are not in the desired state such as the product standard by the treatment of the second ion exchange step, the desired state can be obtained by carrying out the treatment of such a finishing process.

As described above, according to the method for manufacturing a tempered glass plate according to the embodiment of the present invention, the tempered glass plate G2 (G2m, G2b) having high strength in the above-mentioned specific breakage mode can be stably and efficiently manufactured. ..

Before and after the arbitrary process shown above, a processing process for performing processing such as cutting, drilling, polishing, and etching may be provided. In addition, the glass plate may be appropriately washed and dried before and after any of the steps shown above.

Further, in the above embodiment, the case where the molten salts T1 and T2 are molten salts of potassium nitrate has been described as an example, but the present invention is not limited to this, and a well-known molten salt used for ion exchange of a glass plate is substituted or combined. You may use it.

Further, the ion exchange treatment is not limited to the immersion in the molten salt as described above, and for example, the molten salt may be applied.

Further, the magnitude of the compressive stress and the depth of each layer in the above-mentioned deep compressive stress layers C1 and C2 and the shallow compressive stress layer D can be measured by, for example, a stress meter (FSM-6000LE and FsmV manufactured by Orihara Seisakusho).

<Second embodiment>
In the first embodiment, the case where the compressive stress deep layer C (C1, C2) is formed only on the peripheral edge of the tempered glass plate G2 has been described as an example, but the compressive stress deep layer is formed on the entire outer surface of the tempered glass plate G2. C may be formed. 4a and 4b are diagrams showing an outline of a method for manufacturing a tempered glass plate according to a second embodiment of the present invention.

FIG. 4a is a preparatory step for preparing the reinforcing glass plate G1 in the same manner as in the first embodiment. After that, in the second embodiment, the treatment of the film forming step is omitted, and as shown in FIG. 4b, the treatment of the ion exchange step is carried out on the reinforcing glass plate G1 having no ion exchange prevention film M. By such a treatment, the tempered glass plate G2 (G2c) in which the compressive stress deep layer C (C3) is formed on the entire outer surface can be easily manufactured.

Hereinafter, the tempered glass plate G2 (G2b or G2c) of the present invention will be described based on examples. In Table 1, No. Nos. 1 to 6 are examples of the present invention. 7 to 9 are comparative examples. The following examples are merely examples, and the present invention is not limited to the following examples.

First, each sample No. is as follows. 1 to 9 were prepared. The glass composition is mol%, SiO ₂ 66.3%, Al ₂ O ₃ 11.4%, Na ₂ O 15.2%, B ₂ O ₃ 0.5%, Li ₂ O 0.2%, K ₂ The glass raw materials were prepared so as to be a glass containing O 1.4%, MgO 4.8%, and SnO ₂ 0.2%, and melted at 1600 ° C. for 21 hours using a platinum pot. Then, the obtained molten glass was flow-molded from a refractory molded body using an overflow downdraw method to form a plate having a thickness of 0.4 mm to obtain a reinforcing glass plate.

Next, among the obtained reinforcing glass plates, the sample No. For 1 to 3, 5 and 7, an ion exchange prevention film containing ₂₇₀ % SiO and 30% Al _{2O 330} % by mass was formed according to the steps shown in FIG. 1b. Next, each sample No. 1 to 9 were immersed in a molten potassium nitrate salt under the conditions shown in Table 1 for ion exchange treatment (first ion exchange step). Next, the sample No. having an ion exchange prevention film was added. In 1 to 3, 5 and 7, the film was removed by polishing (removal step). After that, No. The samples 1 to 3, 5, 7, and 8 were again immersed in the molten potassium nitrate under the conditions shown in Table 1 for ion exchange treatment (second ion exchange step).

The following characteristics were measured and strength tests were performed on each of the materials obtained as described above.

Maximum value CSmax of compressive stress at the peripheral and central parts shown in Table 1, calculated depth DOL_C of each compressive stress layer, depth DOL_Z where the compressive stress actually becomes zero, compressive stress CS (50) at a depth of 50 μm. ), The tensile stress CT was measured using a surface stress meter FSM-6000LE manufactured by Orihara Seisakusho and application software FsmV. Note that DOL_C is a hypothetical calculated value calculated on the assumption that the compressive stress changes linearly in the depth direction, and DOL_Z changes the compressive stress by bending in the depth direction. It is a measured value measured as. Further, when a negative number is expressed as CS (50), the numerical value indicates that tensile stress is generated instead of compressive stress at a depth of 50 μm.

The break height fb was determined using the test apparatus J shown in FIG. The test device J includes a hammer H that collides with the tempered glass plate G2 that is the measurement sample, and a support device L that supports the measurement sample.

The support device L is a member that supports the tempered glass plate G2. The support device L is composed of, for example, a support base having an inclined surface and a pin protruding from the inclined surface. The tempered glass plate G2 is supported by the support device L so that the inclined surface and the main surface S are in contact with each other and the pin and the end surface E of the tempered glass plate G2 are in contact with each other.

The hammer H includes an arm portion and a head portion. The arm portion is a long member having a constant cross-sectional shape in the extension direction. Specifically, the arm portion is a rod-shaped member made of aluminum having a length of about 500 mm. The arm portion is arranged so as to be rotatable around one end by a fastener such as a bolt. The head portion is a member provided on the side surface portion of the other end of the arm portion and in contact with the tempered glass plate G2. Specifically, the head portion is a member made of a stainless alloy. The head portion includes a convex portion extending in the extending direction of the arm portion, and the tip of the convex portion comes into contact with the end face portion of the tempered glass plate G2.

Hereinafter, a test method using the test apparatus J will be described. First, the tempered glass plate G2 is installed on the support device L. At this time, the tempered glass plate G2 is installed so that the head portion of the hammer H collides with the peripheral portion of the tempered glass plate G2, more specifically, the chamfered surface B. Next, the 100th sandpaper SP is placed on the surface of the tempered glass plate G2 at a position where the head portion of the hammer H collides so that the abrasive surface abuts on the tempered glass plate G2. Next, the hammer H is rotated to a predetermined height and swung up. Next, the swung up hammer H is dropped to cause the head portion and the tempered glass plate G2 to collide with each other. Then, the above test is repeated while gradually increasing the swing height f of the hammer H until the tempered glass plate G2 is damaged. In this way, the value of the swing-up height f when the tempered glass plate G2 was damaged was measured as the damage height fb. The sandpaper SP was replaced with a new one every time the hammer H was dropped.

According to the test using the above-mentioned test apparatus J, it is possible to measure the breakage resistance of the peripheral portion in the above-mentioned specific mode. Since the magnitude of the collision energy applied to the sample increases with the swing height f, it can be said that the larger the value of the break height fb, the higher the break resistance in the mode.

No. Since the samples 1 to 6 had a compressive stress CS (50) of 200 MPa or more at a depth of 50 μm at the peripheral portion, all of them had a break height fb of 50 mm or more and were glasses having high break resistance. On the other hand, No. The samples 7 to 9 were all glasses having a low breaking height fb and low breaking resistance because the compressive stress CS (50) at a depth of 50 μm at the peripheral portion was less than 200 MPa. In particular, No. In Nos. 7 and 9, it is considered that the compressive stress CS (50) became a small value because the processing time in the first ion exchange step was short. In addition, No. In No. 8, it is considered that the compressive stress CS (50) became a small value because the Na ion concentration of the molten salt T1 in the first ion exchange step was high.

Here, the above No. Of 1 to 9, No. 1 for reference. For each of 2 to 4, 6 and 7, the relationship between the depth from the surface and the magnitude of the compressive stress at the peripheral edge of the tempered glass plate is shown in FIG. If the stress value is a positive value on the vertical axis in the figure, it indicates that compressive stress is acting, and if it is a negative value, tensile stress is acting. Show that. As can be understood from the figure, No. In 2 to 4 and 6, No. In comparison with No. 7, it can be seen that the value of the compressive stress gradually decreases with respect to the depth. And No. In 2 to 4 and 6, No. It can be seen that the compressive stress acts to a position deeper than 7.

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

G1 Tempered glass plate G2 (G2a, G2b, G2c) Tempered glass plate M Ion exchange prevention film T1 First molten salt T2 Second molten salt

Claims (10)

A method for manufacturing a tempered glass plate in which at least a part of the surface of a tempered glass plate is ion-exchanged to form a compressive stress layer.
The compressive stress layer includes an ion exchange step of performing the ion exchange until the compressive stress at a depth of 50 μm from the surface becomes 200 MPa to 400 MPa .
Manufacture of a tempered glass plate characterized by performing an ion exchange treatment in the ion exchange step until the maximum value of the compressive stress in the compressive stress layer is 612 MPa or more and the depth from the outer surface of the layer is deeper than 100 μm. Method. The ion exchange step is
The first ion exchange process in which the reinforcing glass plate is brought into contact with the molten salt at the first temperature to perform ion exchange,
A second ion exchange step in which a reinforcing glass plate is brought into contact with a molten salt at a second temperature to perform ion exchange is included, and the ions are formed on at least a part of the surface of the strengthening glass before the first ion exchange step. A film forming process in which an ion exchange prevention film for preventing exchange is provided in advance, and
After the first ion exchange step, a removal step of removing the ion exchange prevention film is further provided.
The method for manufacturing a tempered glass plate according to claim 1 , wherein the second ion exchange step is carried out after the removal step. The second temperature is lower than the first temperature,
The method for manufacturing a tempered glass plate according to claim 2 , wherein the ion exchange treatment time in the first ion exchange step is longer than the ion exchange treatment time in the second ion exchange step. The first temperature exceeds 430 ° C.
The method for manufacturing a tempered glass plate according to claim 3 , wherein the second temperature is 430 ° C. or lower. The method for manufacturing a tempered glass plate according to claim 2 , wherein the difference between the first temperature and the second temperature is within ± 5 ° C. The invention according to any one of claims 1 to 5 , wherein in the ion exchange step, the tempered glass plate is continuously contacted with a molten salt of potassium nitrate having a sodium ion concentration of 50,000 ppm or less for 10 hours or more to perform ion exchange. How to make a tempered glass plate. At least a part of the outer surface has a compressive stress deep layer having a compressive stress of 200 MPa to 400 MPa at a depth of 50 μm.
A tempered glass plate characterized in that the maximum value of the compressive stress of the deep compressive stress layer is 612 MPa or more and the depth is deeper than 100 μm . The tempered glass plate according to claim 7 , further comprising the compressive stress deep layer along the peripheral edge portion. The tempered glass plate according to claim 7 or 8 , which has a compressive stress shallow layer shallower than the compressive stress deep layer in at least a part of the surface where the compressive stress deep layer is not formed. The tempered glass plate according to claim 9 , wherein the compression stress shallow layer has a depth of 35 to 60 μm and a maximum value of compressive stress of 600 to 1500 MPa.

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