WO2018097096A1 - Reinforced glass plate and method for producing reinforced glass plate - Google Patents

Abstract

This method for producing a reinforced glass plate includes forming a compressive stress layer by carrying out ion exchange on at least a portion of the surface of a glass plate to be reinforced. The method is characterized by comprising an ion exchange step for carrying out ion exchange until compressive stress becomes at least 200 MPa at a position 50 µm deep from the surface of the compressive stress layer.

Description

Tempered glass plate, method for producing tempered glass plate

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

Conventionally, a tempered glass plate that has been chemically strengthened is used as a cover glass plate 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 (for example, Patent Document 1, 2).

The tempered glass having a compressive stress layer on the 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 the compressive stress (CS) of the compressive stress layer increase.

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

JP-T-2015-523310 JP 2014-001124 A

However, the damage modes (fracture modes) of tempered glass actually mounted on smartphones and tablet computers are various, and in specific damage modes, the tensile stress (CT) and the depth of the compressive stress layer (DOL) are not necessarily set. It has not always been preferable to restrict the size as small as in the past.

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

The method for producing a tempered glass plate of the present invention is a method for producing a tempered glass plate in which at least a part of the surface of the glass plate for tempering is ion-exchanged to form a compressive stress layer, and the depth in the compressive stress layer is from the surface. 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 producing a tempered glass sheet of the present invention, in the ion exchange step, ions are increased 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. Exchange processing is preferable.

In the method for producing a tempered glass plate of the present invention, the ion exchange step includes a first ion exchange step in which the tempered glass plate is brought into contact with the molten salt at the first temperature to perform ion exchange, and the tempered glass plate at the second temperature. A second ion exchange step in which ion exchange is performed by contacting the molten salt, and before the first ion exchange step, at least a part of the surface of the reinforcing glass is previously provided with an ion exchange prevention film for preventing ion exchange. 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 performing the second ion exchange step after the removing step.

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

In the method for producing a tempered glass sheet of the present invention, the first temperature is preferably higher than 430 ° C. and the second temperature is preferably 430 ° C. or lower.

In the method for producing a tempered glass sheet 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 sheet of the present invention, in the ion exchange step, it is preferable to perform ion exchange by bringing the tempered glass sheet into contact with a molten potassium nitrate salt having a sodium ion concentration of 50000 ppm or less continuously for 10 hours or more.

The tempered glass plate of the present invention is characterized in that a compressive stress deep layer having a compressive stress of 200 MPa or more at a depth of 50 μm is provided 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 of the deep compressive stress layer is 400 MPa or more and the depth is deeper than 100 μm.

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

The tempered glass sheet of the present invention preferably has a compressive stress shallow layer shallower than the compressive stress deep layer in at least a part of the surface of the surface where the compressive stress deep layer is not formed.

In the tempered glass sheet of the present invention, the compressive stress shallow layer preferably has a depth of 35 to 60 μm and a maximum value of the compressive stress 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 board which concerns on 1st embodiment of this invention. It is a figure which shows the manufacturing method of the tempered glass board which concerns on 1st embodiment of this invention. It is a figure which shows the manufacturing method of the tempered glass board which concerns on 1st embodiment of this invention. It is a figure which shows the manufacturing method of the tempered glass board which concerns on 1st embodiment of this invention. It is a figure which shows the manufacturing method of the tempered glass board which concerns on 1st embodiment of this invention. It is a top view of the glass plate for reinforcement | strengthening which concerns on embodiment of this invention. It is a top view of the glass plate for reinforcement provided with the ion exchange prevention film concerning the embodiment of the present invention. It is a figure which shows the manufacturing method of the tempered glass board which concerns on 2nd embodiment of this invention. It is a figure which shows the manufacturing method of the tempered glass board which concerns on 2nd embodiment of this invention. 1 is a schematic diagram of a test apparatus for measuring a break height according to an embodiment of the present invention. It is a figure which shows the relationship between the depth from the surface, and the magnitude | size of a compressive stress about a tempered glass board.

<First embodiment>
Hereinafter, the manufacturing method of the tempered glass board of embodiment of this invention is demonstrated. 1a to 1e are diagrams showing an example of a method for producing a tempered glass sheet according to the present invention.

First, the preparatory process shown in FIG. 1a is performed. The preparation step is a step of preparing the reinforcing glass plate G1. The strengthening glass plate G1 is a plate-like glass plate that can be strengthened using an ion exchange method. 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 as shown in FIGS. 1a and 2. FIG. 2 is a plan view of the reinforcing glass plate G1 in the thickness direction. Moreover, FIG. 1a is AA arrow sectional drawing of the glass plate G1 for reinforcement | strengthening 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 the main surface S, the end surface E, and the chamfered surface B.

The glass sheet G1 for strengthening 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 plate composition. Is preferred. If the glass plate composition range is regulated as described above, it is 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, particularly 0.9 mm or less. In addition, a tempered glass board can be reduced in weight, so that the board | plate thickness of a tempered glass board is small, and as a result, thickness reduction and weight reduction of a device can be achieved. In such a case, the thickness of the strengthening 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, particularly 0.8 mm or less. It is still better if it is 1 mm or less. Moreover, if productivity etc. are considered, it is preferable that the plate | board thickness of the glass plate G1 for strengthening is 0.01 mm or more.

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

The strengthening glass plate G1 is, for example, glass formed using an overflow downdraw method. In addition, you may select arbitrarily the shaping | molding method and processing state of the glass plate G1 for reinforcement | strengthening. For example, the reinforcing glass plate G1 may be glass formed using a float method. Further, the main surface S, the end surface E, and the chamfered surface B may be polished.

Next, after the above preparation step, the film forming step shown in FIG. The film forming process is a process of forming the ion-exchange preventing film M on at least a part of the surface of the reinforcing glass sheet G1 to obtain the reinforcing glass sheet G1m with film. In this embodiment, as shown in FIG. 3, the ion exchange prevention film M is formed in the center part S1 of the front and back main surfaces of the reinforcing glass plate G1. 1b corresponds to a cross-sectional view taken along the line AA in FIG. Of the surface of the strengthening glass plate G1, the peripheral portion other than the central portion S1 is exposed. The peripheral portion is a portion including an outer peripheral region S2, a chamfered surface B, and an end surface E surrounding the central portion S1 of the main surface S. The ion exchange preventive membrane M is a membrane layer that suppresses or blocks the permeation of ions when performing ion exchange on the surface layer of the reinforcing glass plate G1 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 the permeation of ions to be ion exchanged can be suppressed or blocked. When the ion to be exchanged is an alkali metal ion, the ion exchange preventing film M is, for example, a metal oxide, metal nitride, metal carbide, metal oxynitride, metal oxycarbide, metal carbonitride film, or the like. Is preferred. Carbon materials, metals, and alloys that are excellent in heat resistance and chemical durability can also be used as the ion exchange preventing film M. More specifically, as the material of the ion exchange preventing 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 , A film containing one or more of SnO ₂ , carbon nanotube, graphene, diamond-like carbon, and stainless steel can be obtained. Further, the ion exchange preventing film M is preferably an amorphous film whose crystallinity hardly changes during the ion exchange treatment.

The ion exchange preventing film M includes a film that suppresses ion permeation, that is, does not completely block. For example, ZrO ₂ , SnO ₂ , ITO film, or AlN can be used as the material of the ion exchange preventing film M. However, since the crystallinity of a film made of these materials is likely to change at a high temperature, the ion permeability may be easily changed during the ion exchange process.

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

The thickness of the ion exchange preventing film M may be any thickness as long as ion permeation can be blocked and suppressed. However, if the thickness of the ion exchange preventing film M is excessive, the film formation time, material cost, and the like increase, and therefore it is preferable to form the ion exchange preventing film M as thin as possible so that ion permeation can be blocked and suppressed. Specifically, the film thickness of the ion exchange preventing film M is preferably, for example, 1 to 5000 nm, and more preferably 50 to 4000 nm.

The film formation method of the ion exchange preventive film M is a PVD method (physical vapor deposition method) such as a sputtering method or a vacuum deposition method, a CVD method (chemical vapor deposition method) such as a thermal CVD method or a plasma CVD method, or dip coating. A wet coating method such as a method or a slit coating method can be used. A sputtering method is particularly preferable. When the sputtering method is used, the ion exchange preventing film M can be easily and uniformly formed. The deposition location of the ion exchange preventing film M may be set by an arbitrary method. For example, film formation can be performed with the peripheral edge masked. Alternatively, the ion exchange preventing film M previously formed into a sheet shape may be bonded to the main surface of the strengthening glass plate G1 to form a film.

In the present embodiment, an example will be described in which an ion exchange preventing 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.

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

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

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

The compressive stress deep layer C1 is a compressive stress layer having a compressive stress CS (50) at a depth of 50 μm of 200 MPa or more. 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 is over 430 ° C., preferably 440 to 500 ° C., more preferably 450 to 490 ° C. Further, the time for immersing the glass sheet for reinforcing glass G1m in the molten salt T1 is, for example, 10 to 200 hours, preferably 12 to 170 hours, more preferably 24 to 100 hours. By performing the ion exchange treatment at a relatively high temperature in this way, a deep compressive stress layer can be formed on the peripheral edge in a short time.

In addition, the molten salt T1 may increase the concentration of Na ions during repeated use, 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. In order to increase the depth of the compressive stress deep layers C1 and C2 efficiently, the Na ion concentration of the molten salt T1 is preferably regulated to 50000 ppm or less, more preferably 30000 ppm or less, and even more preferably 20000 ppm or less. . The Na ion concentration in the molten salt T1 can be adjusted by adding potassium nitrate or the like.

In addition, the tempered glass board G2 provided with the ion exchange prevention film M obtained when the process of the first ion exchange process is completed is referred to as a tempered glass board G2m with a film.

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

As a polishing apparatus used for polishing, a well-known double-side polishing machine or single-side polishing machine can be used. When removing the ion exchange preventing film M by polishing, only the ion exchange preventing film M may be polished, or the glass plate portion may be polished together with the ion exchange preventing film M.

Etching methods such as dry etching and wet etching can be used.

When dry etching is used, it is particularly preferable to use plasma of Ar, O ₂ , CH ₄ , BC ₁₃ , C ₁₂ , SF ₆ or the like.

As an etchant used for wet etching, for example, a solution containing fluorine, TMAH, EDP, KOH, NaOH, or the like can be used as the etchant, and a hydrofluoric acid solution is particularly preferably used as the etchant. In the case where only the ion exchange preventing film M is removed without changing the glass dimensions using a hydrofluoric acid solution, the concentration of HF in the hydrofluoric acid solution is preferably 10% or less.

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

Next, after the film removal step, the second ion exchange step shown in FIG. 1e is performed. The second ion exchange step is a step of obtaining a tempered glass sheet G2b by forming a relatively shallow compressive stress shallow layer D in a region where the compressive stress layer is not formed in the first ion exchange step. In the present embodiment, as shown in FIG. 1e, the tempered glass plate G2 is immersed in a molten salt T2 containing alkali metal ions, and a compressive stress is applied to the entire region (center portion S1) where the ion exchange preventing film M is formed. A shallow layer D is formed. The molten salt T2 is, for example, a potassium nitrate molten salt.

The compressive stress deep layer C1 formed in the peripheral edge part is changed into a compressive stress deep layer C2 due to a slight variation in characteristics due to contact with the molten salt T2 by the above-described treatment. In this embodiment, even after the fluctuation, the compressive stress deep layer C2 is a compressive stress layer having a compressive stress CS (50) at a depth of 50 μm of 200 MPa or more. 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 first ion exchange step. By performing the ion exchange treatment at a relatively low temperature in this manner, 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 less, more preferably 390 to 430 ° C., and further 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.

In addition, it is preferable to maintain the Na ion concentration of the molten salt T2 within a certain range similarly to the molten salt T1. Further, the Na ion concentration of the molten salt T2 is preferably regulated to 30000 ppm or less, more preferably 20000 ppm or less, and further preferably 10,000 ppm or less. Thus, by adjusting the Na ion concentration of the molten salt T2, the maximum value of the compressive stress in the compressive stress deep layer C2 and the compressive stress shallow layer D can be easily increased.

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 ion exchange process twice as described above, the compressive stress deep layer C2 that is a relatively deep compressive stress layer and the compressive stress shallow layer D that 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 sheet G2b, for example, a deep compressive stress deep layer C2 can be formed at the peripheral edge where breakage tends to occur, and high damage resistance can be obtained, and at the same time, shallow compression can be achieved at the central portion S1. It is possible to suppress the increase in internal tensile stress by forming the shallow stress layer D and suppress the increase in tensile stress formed inside the tempered glass sheet G2. Further, since the tensile stress is reduced in the central portion S1, it is difficult to form fine fragments as compared with 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.

The tempered glass plate G2 (G2a, G2b) has the above-described compression stress deep layer C (C1, C2), and thus has high strength in a specific failure mode at the formation site of the layer. The specific failure mode means that a sharp protrusion is present at the tip of the tempered glass sheet G2, and the protrusion breaks through the compressive stress layer on the surface and reaches the internal tensile stress layer. It refers to a failure mode in which cracks develop and break 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, the temperature and immersion time of the molten salt T2 in the second ion exchange step are examples, and the compression stress depth layer C to be formed is You may adjust arbitrarily so that it may become a stress layer whose compressive stress CS (50) in the depth of 50 micrometers is 200 Mpa or more.

Moreover, 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 tempering tank (molten salt). In this case, the difference between the temperature of the molten salt at the time of performing the first ion exchange step and the temperature of the molten salt at the time of performing the second ion exchange step tends to be within a range of ± 5 ° C.

In addition, although the said embodiment demonstrated the case where the compressive-stress deep layer C1 formed by the process of a 1st ion exchange process has the reinforcement | strengthening characteristic that the compressive stress CS (50) in 50 micrometers in depth is 200 Mpa or more, it demonstrated as an example. As long as it has the characteristics at the time of becoming the compressive stress deep layer C2 through the process of the second ion exchange process, it does not have to have the above characteristics at the time of the process of the first ion exchange process.

Further, after the second ion exchange step, a finishing process may be performed (not shown). In the finishing process, the surface of the tempered glass sheet G2b, for example, at least one of the main surface S and the end surface E is polished. When the dimension or surface state of the tempered glass sheet G2b is not a desired state such as a product standard due to the processing of the second ion exchange step, it can be brought into a desired state by performing the processing of such a finishing process.

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

It should be noted that a processing step for performing processing such as cutting processing, drilling processing, polishing processing, etching processing, etc. may be provided before and after the arbitrary steps shown above. Moreover, before and after the arbitrary steps shown above, the glass plate may be appropriately washed and dried.

Moreover, in the said embodiment, although the case where molten salt T1, T2 was potassium nitrate molten salt was demonstrated as an example, it is not restricted to this, It replaces with well-known molten salt used for the ion exchange of a glass plate, or combines. It may be used.

In addition, the ion exchange treatment is not limited to the immersion in the molten salt as described above, and may be performed by applying a molten salt, for example.

Further, the magnitude of the compressive stress and the depth of each layer in the above-described compressive stress deep layers C1 and C2 and the compressive stress shallow 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 deep compressive stress layer C (C1, C2) is formed only at the peripheral edge of the tempered glass sheet G2 has been described as an example, but the deep compressive stress layer is formed on the entire outer surface of the tempered glass sheet G2. C may be formed. 4a and 4b are diagrams showing an outline of a method for producing a tempered glass sheet according to the 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. Then, in 2nd embodiment, the process of a film-forming process is abbreviate | omitted, and as shown to FIG. 4 b, the process of an ion exchange process is implemented with respect to the glass plate G1 for reinforcement | strengthening which does not have the ion-exchange prevention film M. According to such a process, the tempered glass board 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. Examples 1 to 6 are examples of the present invention. 7 to 9 are comparative examples. The following examples are merely illustrative, and the present invention is not limited to the following examples.

First, each sample no. 1 to 9 were produced. As a glass composition, 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 material was prepared so that it might become a glass containing 1.4% O, 4.8% MgO, and 0.2% SnO ₂ and melted at 1600 ° C. for 21 hours using a platinum pot. Thereafter, the obtained molten glass was formed by flow-down molding from a refractory molded body using an overflow downdraw method to form a 0.4 mm thick plate to obtain a strengthening glass plate.

Next, among the obtained reinforcing glass plates, the sample No. For 1 to 3, 5, and 7, an ion exchange preventing film containing 70% SiO _{2 and} 30% Al ₂ O _{3 by} mass was formed in accordance with the process shown in FIG. 1b. Then, 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). Subsequently, sample No. which has an ion exchange prevention film In 1-3, 5, and 7, the film was removed by polishing (removal step). Then, no. Samples 1 to 3, 5, 7, and 8 were again immersed in potassium nitrate molten salt under the conditions shown in Table 1 for ion exchange treatment (second ion exchange step).

Each material obtained as described above was subjected to the following characteristic measurement and strength test.

Maximum value CSmax of compressive stress in the peripheral portion and the central portion shown in Table 1, calculated depth DOL_C of each compressive stress layer, depth DOL_Z at which actual compressive stress becomes zero, compressive stress CS at a depth of 50 μm (50 The tensile stress CT was measured using a surface stress meter FSM-6000LE manufactured by Orihara Seisakusho and application software FsmV. DOL_C is a hypothetical calculated value that assumes that the compressive stress changes linearly in the depth direction, and DOL_Z is a value that changes by bending the compressive stress in the depth direction. Is a measured value. Further, when a negative number is written 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 measured using a test apparatus J shown in FIG. The test apparatus J includes a hammer H that collides with a tempered glass plate G2 that is a 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 includes, 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 has an arm part and a head part. The arm portion is a long member having a constant cross-sectional shape in the extending 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 to be rotatable around one end by a fastener such as a bolt. A head part is a member which is provided in the side part of the other end of an arm part, and contacts the tempered glass board G2. Specifically, the head portion is a member made of stainless alloy. The head portion includes a convex portion extending in the extending direction of the arm portion, and contacts the end surface portion of the tempered glass sheet G2 at the tip of the convex portion.

Hereinafter, a test method using the test apparatus J will be described. First, the tempered glass plate G2 is installed in 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, a 100th sandpaper SP is placed on the surface of the tempered glass plate G2 so that the head portion of the hammer H collides so that the abrasive surface abuts the tempered glass plate G2. Next, the hammer H is swung up to a predetermined height. Next, the hammer H swung up 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 raising the swinging height f of the hammer H until the tempered glass plate G2 is broken. Thus, 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 dropped.

According to the test using the above-described test apparatus J, it is possible to measure the damage resistance in the specific mode at the peripheral edge. In addition, since the magnitude | size of the collision energy added to a sample becomes large according to the raising height f, it can be said that it has the high damage resistance in the said mode, so that the value of the damage height fb is large.

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

Here, the above No. Nos. 1 to 9 are for reference only. FIG. 6 shows the relationship between the depth from the surface at the peripheral edge of the tempered glass sheet and the magnitude of the compressive stress for each of 2 to 4, 6, and 7. When the stress value is positive on the vertical axis in the figure, it indicates that compressive stress is acting, and when it is negative, tensile stress is acting. It shows that. As can be seen from FIG. In Nos. 2 to 4 and 6, no. In comparison with 7, it can be seen that the value of the compressive stress gradually decreases with respect to the depth. And No. In Nos. 2 to 4 and 6, no. It can be seen that the compressive stress is applied to a position deeper than 7.

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

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

Claims (12)

A method for producing a tempered glass plate that forms a compressive stress layer by ion exchange of at least part of the surface of the tempered glass plate,
The manufacturing method of the tempered glass board characterized by including the ion exchange process which performs the said ion exchange until the compressive stress in the position of 50 micrometers deep from the surface becomes 200 Mpa or more in the said compressive-stress layer. In the ion exchange step, the ion exchange treatment is performed until the maximum value of the compressive stress in the compressive stress layer is 400 MPa or more and the depth from the outer surface of the layer becomes deeper than 100 μm. The manufacturing method of the tempered glass board of description. The ion exchange step includes
A first ion exchange step in which the glass plate for strengthening is brought into contact with the molten salt at the first temperature to perform ion exchange;
A second ion exchange step in which ion exchange is performed by bringing a glass sheet for strengthening into contact with a molten salt at a second temperature, and before the first ion exchange step, at least a part of the surface of the glass for strengthening A film forming step in which an ion exchange preventing film for preventing exchange is provided in advance;
A removal step of removing the ion exchange prevention film after the first ion exchange step,
The manufacturing method of the tempered glass board of Claim 1 or 2 which implements said 2nd ion exchange process after the said removal process. The second temperature is lower than the first temperature;
The method for producing a tempered glass sheet according to claim 3, wherein an ion exchange treatment time in the first ion exchange step is longer than an ion exchange treatment time in the second ion exchange step. The first temperature exceeds 430 ° C .;
The method for producing a tempered glass sheet according to claim 4, wherein the second temperature is 430 ° C. or less. The method for producing a tempered glass sheet according to claim 3, wherein a difference between the first temperature and the second temperature is within ± 5 ° C. 7. The ion exchange process according to claim 1, wherein in the ion exchange step, the strengthening glass plate is continuously subjected to ion exchange for 10 hours or more by contacting with a potassium nitrate molten salt having a sodium ion concentration of 50000 ppm or less. Method for manufacturing a tempered glass sheet. A tempered glass sheet having a deep compressive stress layer having a compressive stress at a depth of 50 μm of 200 MPa or more on at least a part of the outer surface. The tempered glass sheet according to claim 8, wherein the maximum value of the compressive stress of the deep compressive stress layer is 400 MPa or more and the depth is deeper than 100 µm. The tempered glass sheet according to claim 8 or 9, comprising the deep compressive stress layer along the peripheral edge. The tempered glass sheet according to any one of claims 8 to 10, which has a compressive stress shallow layer shallower than the compressive stress deep layer in at least a part of a region of the surface where the compressive stress deep layer is not formed. The tempered glass sheet according to claim 11, wherein the shallow compressive stress layer has a depth of 35 to 60 µm and a maximum compressive stress of 600 to 1500 MPa.

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