Chemically strengthened glass and glass for chemical strengthening

Chemically strengthened glass and chemically strengthened glass

The present invention relates to chemically strengthened glass.

In recent years, in order to increase the protection and aesthetics of display devices of mobile devices such as mobile phones, smart phones, personal digital assistants (PDAs), and tablet terminals, cover glass containing chemically strengthened glass has been used.

In chemically strengthened glass, the strength tends to increase as the surface compressive stress (value) (CS) or the depth (DOL) of the compressive stress layer increases. On the other hand, in order to maintain a balance with the surface compressive stress, an internal tensile stress (CT) is generated inside the glass, so that the CT increases as CS or DOL increases. When glass with a large CT is broken, it becomes a violent cracking system with a large number of fragments, and the risk of scattering of fragments increases.

Therefore, for example, Patent Document 1 discloses the formula (10) indicating the allowable limit of the internal tensile stress of tempered glass, and chemically tempered glass with little scattering of fragments even if the strength of the chemically tempered glass is increased by adjusting the following CT'. was said to be obtained. The internal tensile stress CT' described in Patent Document 1 is derived by the following formula (11) using the measured values of CS and DOL'.

CT'-38.7×ln(t)+48.2 (10)

CS×DOL'=(t-2×DOL')×CT' (11)

Here, DOL' corresponds to the depth of the ion exchange layer.

<p><patcit num="0001"><text>Specification of US Patent No. 8075999</text></patcit></p>

<p>According to the study of the present inventors, the method of Patent Document 1 sometimes lacks strength of chemically strengthened glass. This is because the influence of the glass composition is not sufficiently taken into account; the above formula for calculating CT' approximates the stress profile linearly; it is assumed that the point at which the stress becomes zero is equal to the depth of the ion diffusion layer, etc. This is thought to be the cause. The present invention improves these problems and provides a chemically strengthened glass with higher strength.</p>

<p>A first aspect of the present invention is a chemically strengthened glass having a surface compressive stress (CS) of 300 MPa or more, and a compressive stress value (CS) at a depth of 90 µm from the glass surface.₉₀) is 25 MPa or more, or the compressive stress value (CS) at a depth of 100 µm from the glass surface₁₀₀) is 15 MPa or more,</p><p>SiO in the imitation composition of the chemically strengthened glass₂, Al₂O₃, B₂O₃, P₂O₅, Li₂O, Na₂O, K₂O, MgO, CaO, SrO, BaO and ZrO₂It is a chemically strengthened glass in which the value of X calculated based on the following formula using the content by the molar percentage expression of the oxide basis of each component of is 30000 or more.</p><p>X=SiO₂×329+Al₂O₃×786+B₂O₃×627+P₂O₅×(-941)+Li₂O×927+Na₂O×47.5+K₂O×(-371)+MgO×1230+CaO×1154+SrO×733+ZrO₂×51.8</p><p>A first aspect of the present invention is a chemically strengthened glass having a surface compressive stress (CS) of 300 MPa or more, and a compressive stress value (CS) at a depth of 90 µm from the glass surface.₉₀) is 25 MPa or more, or the compressive stress value (CS) at a depth of 100 µm from the glass surface₁₀₀) is 15 MPa or more,</p><p>SiO in the imitation composition of the chemically strengthened glass₂, Al₂O₃, B₂O₃, P₂O₅, Li₂O, Na₂O, K₂O, MgO, CaO, SrO, BaO and ZrO₂The chemically strengthened glass may be a chemically strengthened glass in which the value of Z calculated based on the following formula using the oxide-based molar percentage expression of each component of the component is 20000 or more.</p><p>Z=SiO₂×237+Al₂O₃×524+B₂O₃×228+P₂O₅×(-756)+Li₂O×538+Na₂O×44.2+K₂O×(-387)+MgO×660+CaO×569+SrO×291+ZrO₂×510</p><p>It is preferable that the chemically strengthened glass of a 1st aspect is plate-shaped whose plate|board thickness t is 2 mm or less.</p><p>A second aspect of the present invention is a chemically strengthened glass having a surface compressive stress (CS) of 300 MPa or more and satisfying the following formulas (1) and (2).</p><p>StL(t)a×t+7000 (unit: MPa μm) (1)</p><p>a30000 (unit: MPa μm/mm) (2)</p><p>(Here, t is the plate thickness (mm), and StL(t) is the value of St Limit when the plate thickness is t)</p><p>As for the chemically strengthened glass of the said 2nd aspect, it is preferable that a35000.</p><p>In the second aspect, chemically strengthened glass having a surface compressive stress (CS) of 300 MPa or more and chemically strengthened glass satisfying the following formulas (3), (4) and (5) may be used.</p><p>CTL(t)-b×ln(t)+c (unit: MPa) (3)</p><p>b14 (unit: MPa) (4)</p><p>c48.4 (unit: MPa) (5)</p><p>(Here, t is the plate thickness (mm), and CTL(t) is the value of CT Limit when the plate thickness is t)</p><p>It is preferable that the chemically strengthened glass of a 2nd aspect is plate-shaped whose plate|board thickness t is 2 mm or less.</p><p>The chemically strengthened glass of the second aspect has a compressive stress value (CS) at a depth of 90 µm from the glass surface.₉₀) is 25 MPa or more, or the compressive stress value (CS) at a depth of 100 µm from the glass surface₁₀₀) is preferably 15 MPa or more.</p><p>A third aspect of the present invention has an average crack height of 250 mm or more by a drop test on sand to be described later, the number of fractures by an indenter indentation test to be described later is 30 or less, a plate thickness t is 0.4 to 2 mm, and the surface It is chemically strengthened glass whose compressive stress (CS) is 300 MPa or more, and the depth (DOL) of a compressive stress layer is 100 micrometers or more.</p><p>The chemically strengthened glass of the present invention is the product (CS) of the square of the compressive stress value at a depth of 100 µm from the glass surface and the plate thickness t (mm)₁₀₀×t²) is preferably 5 MPa·mm 2 or more.</p><p>In the chemically strengthened glass of the present invention, the area Sc (MPa·µm) of the compressive stress layer is preferably 30000 MPa·µm or more.</p><p>In the chemically strengthened glass of the present invention, the depth d of the portion where the magnitude of the internal compressive stress is 1/2 of the surface compressive stress (CS)._his preferably 8 µm or more.</p><p>In the chemically strengthened glass of the present invention, the position d where the compressive stress is maximum_MIt is preferable to be in the range of 5 micrometers from this glass surface.</p><p>The chemically strengthened glass of the present invention preferably has a compressive stress layer depth (DOL) of 110 µm or more.</p><p>In addition, in the chemically strengthened glass of the present invention, the compressive stress value CS at the depth of the glass surface side of 20 µm from the DOL_DOL_-20ΔCS calculated by the following formula using_DOL_-20It is preferable that (unit: MPa/micrometer) is 0.4 or more.</p><p>ΔCS_DOL_-20=CS_DOL_-20/20</p><p>In addition, in the chemically strengthened glass of the present invention, CS₉₀and CS₁₀₀ΔCS calculated by the following formula using_100-90It is preferable that (unit: MPa/micrometer) is 0.4 or more.</p><p>ΔCS₁₀₀_-90=(CS₉₀-CS₁₀₀)/(100-90)</p><p>In the chemically strengthened glass of the present invention, the fracture toughness value (K1c) of the glass having the imitation property of the chemically strengthened glass is 0.7 MPa·m^1/2 more preferably.</p><p>In the chemically strengthened glass of the present invention, the area St (MPa·µm) of the inner tensile layer is preferably StL(t) (MPa·µm) or less.</p><p>(Here, t is the plate thickness (mm), and StL(t) is the value of St Limit when the plate thickness is t)</p><p>The chemically strengthened glass of the present invention preferably has an internal tensile layer stress CT (MPa) of CTL (t) (MPa) or less.</p><p>(Here, t is the plate thickness (mm), and CTL(t) is the value of CT Limit when the plate thickness is t)</p><p>In the chemically strengthened glass of the present invention, the imitation of the chemically strengthened glass is SiO₂50 to 80% of Al₂O₃1 to 30%, B₂O₃0 to 6%, P₂O₅0 to 6%, Li₂0 to 20% O, Na₂0 to 8% O, K₂0-10% O, 0-20% MgO, 0-20% CaO, 0-20% SrO, 0-15% BaO, 0-10% ZnO, TiO₂0 to 5%, ZrO₂It is preferable to contain 0 to 8%.</p><p>In addition, the present invention is an oxide-based molar percentage expression, SiO₂63 to 80%, Al₂O₃7 to 30%, B₂O₃0 to 5%, P₂O₅0 to 4%, Li₂5 to 15% O, Na₂4 to 8% O, K₂0 to 2% O, 3 to 10% MgO, 0 to 5% CaO, 0 to 20% SrO, 0 to 15% BaO, 0 to 10% ZnO, TiO₂0 to 1%, ZrO₂contains 0 to 8%,</p><p>Ta₂O₅, Gd₂O₃, As₂O₃, Sb₂O₃does not contain</p><p>SiO₂, Al₂O₃, B₂O₃, P₂O₅, Li₂O, Na₂O, K₂O, MgO, CaO, SrO, BaO and ZrO₂It also relates to a glass for chemical strengthening in which the value of X calculated based on the following formula using the oxide-based molar percentage expression of each component is 30000 or more.</p><p>X=SiO₂×329+Al₂O₃×786+B₂O₃×627+P₂O₅×(-941)+Li₂O×927+Na₂O×47.5+K₂O×(-371)+MgO×1230+CaO×1154+SrO×733+ZrO₂×51.8</p><p>In the above-mentioned glass for chemical strengthening, ZrO by mole percentage expression based on oxide₂It is preferable that the content of is 1.2% or less.</p><p>In addition, K by mole percentage expression on an oxide basis₂It is preferable that content of O is 0.5 % or more.</p><p>In addition, B by mole percentage expression based on oxide₂O₃It is preferable that the content of is 1% or less.</p><p>In addition, Al by mole percentage expression based on oxide₂O₃It is preferable that the content of is 11% or less.</p><p>Moreover, loss-of-clarity temperature T is 10, a viscosity⁴It is preferable that it is below the temperature T4 used as dPa*s.</p>

<p>The present invention provides a high-strength chemically strengthened glass in which scattering of fragments due to breakage is suppressed.</p>

1 is a conceptual diagram showing a stress profile of chemically strengthened glass, (a) is a diagram showing an example of a stress profile of chemically strengthened glass, (b) is an enlarged view of the left half of the stress profile of (a), (c) is a figure which shows the depth of the position where the compressive stress in each of profiles A and B becomes maximum. 2 is a schematic diagram showing a state of preparing a sample for measuring the surface compressive stress (CS) of chemically strengthened glass, (a) shows a sample before polishing, (b) shows a flaked sample after polishing do. 3 is a schematic diagram showing a test method for a drop test on sand. 4 is a graph plotting the relationship between chemically strengthened glass or DOL and average crack height of glass. 5 is a graph plotting the relationship between the CT and average crack height of chemically strengthened glass or glass. 6 is a graph plotting the relationship between CT and average crack height of chemically strengthened glass. 7 is a graph plotting the relationship between the surface compressive stress value CS and the average crack height of chemically strengthened glass or glass. 8 is a compressive stress value CS of chemically strengthened glass or glass₉₀It is a graph plotting the relationship between and average crack height. 9 shows the compressive stress values CS of chemically strengthened glass or glass;₁₀₀It is a graph plotting the relationship between and average crack height. 10 is a compressive stress value CS of chemically strengthened glass or glass;₁₀₀and the product of the square of the thickness t (CS₁₀₀×t²) and the average crack height is a plotted graph. 11 is a graph showing test results of a four-point bending test for chemically strengthened glass. 12 is a graph plotting the relationship between CS and bending strength for chemically strengthened glass. 13 is a graph plotting the relationship between DOL and bending strength for chemically strengthened glass. 14 is a graph showing the stress profile of a hypothetical chemically strengthened glass. 15 shows an example of measurement of St Limit and CT Limit, (a) is a graph showing the relationship between the area St of the internal tensile stress layer and the number of fractures, (b) is an enlarged view of the portion surrounded by dotted lines in (a) , (c) is a graph showing the relationship between the internal tensile stress CT and the number of fractures, and (d) is an enlarged view of the portion surrounded by the dotted line in (c). It is explanatory drawing of the sample used for fracture toughness value measurement by the DCDC method. Fig. 17 is a diagram showing a K1-v curve showing the relationship between the stress intensity coefficient K1 and the crack propagation rate v used for fracture toughness value measurement by the DCDC method. 18 is a graph plotting the relationship between St Limit and X value for chemically strengthened glass. 19 is a graph plotting the relationship between St Limit and Z value for chemically strengthened glass. 20 is a graph plotting the relationship between St Limit and Young's modulus for chemically strengthened glass. 21 is a graph plotting the relationship between the X value and the Z value for chemically strengthened glass. 22 is a graph plotting the ST Limit of chemically strengthened glass with respect to the thickness t. 23 is a graph plotting the CT Limit of chemically strengthened glass with respect to the plate thickness t.

Hereinafter, the chemically strengthened glass of the present invention will be described in detail.

&lt;First form&gt;

First, the chemically strengthened glass according to the first aspect will be described.

The first aspect has a surface compressive stress (CS) of 300 MPa or more, and a compressive stress value (CS) at a depth of 90 µm from the glass surface.₉₀) is 25 MPa or more, or the compressive stress value (CS) at a depth of 100 μm from the glass surface.₁₀₀) is 15 MPa or more chemically strengthened glass.

This aspect is SiO in the mother composition of the said chemically strengthened glass₂, Al₂O₃, B₂O₃, P₂O₅, Li₂O, Na₂O, K₂O, MgO, CaO, SrO, BaO and ZrO₂The value of X calculated based on the following formula is 30000 or more, and/or the value of Z calculated based on the following formula is 20000 or more using the content by the molar percentage expression of each component of the oxide basis.

X=SiO₂×329+Al₂O₃×786+B₂O₃×627+P₂O₅×(-941)+Li₂O×927+Na₂O×47.5+K₂O×(-371)+MgO×1230+CaO×1154+SrO×733+ZrO₂×51.8

Z=SiO₂×237+Al₂O₃×524+B₂O₃×228+P₂O₅×(-756)+Li₂O×538+Na₂O×44.2+K₂O×(-387)+MgO×660+CaO×569+SrO×291+ZrO₂×510

The chemically strengthened glass of the first aspect has a compressive stress layer formed on its surface by chemical strengthening treatment (ion exchange treatment). In the chemical strengthening treatment, the surface of glass is ion exchanged to form a surface layer in which compressive stress remains. Specifically, alkali metal ions with a smaller ionic radius (typically Li ions or Na ions) existing near the surface of the glass plate by ion exchange at a temperature below the glass transition point are converted to alkali ions with a larger ionic radius (typically, ions). is Na ion or K ion for Li ion, and K ion for Na ion). Thereby, a compressive stress remains on the surface of glass, and the intensity|strength of glass improves.

In the first aspect, the surface compressive stress (CS) of the chemically strengthened glass is 300 MPa or more. When a smartphone or a tablet PC is dropped, a tensile stress is generated on the surface of the cover glass, and the size thereof reaches about 350 MPa. At this time, if CS is 300 MPa or more, since the tensile stress generated by dropping is canceled, it becomes difficult to break, so it is preferable. CS of the chemically strengthened glass is preferably 350 MPa or more, more preferably 400 MPa or more, and still more preferably 450 MPa or more.

On the other hand, the upper limit of the CS of the chemically strengthened glass is not particularly limited, but if the CS is too large, the risk of scattering of fragments or the like increases if the CS is too large, for example, 2000 It is MPa or less, Preferably it is 1500 MPa or less, More preferably, it is 1000 MPa or less, More preferably, it is 800 MPa or less.

In addition, CS of chemically strengthened glass can be suitably adjusted by adjusting chemical strengthening conditions, a composition of glass, etc.

In addition, CS of the chemically strengthened glass in 1st aspect is value CS by the following two types of measurement methods._F and CS_ABy , it is defined as follows. Compressive stress value at a depth of x μm from the glass surface (CS_x) is the same for

CS=CS_F=1.28×CS_A

Here, CS_Fis a value measured with a surface stress meter FSM-6000 manufactured by Orihara Seisakusho Co., Ltd. and obtained by an attached program FsmV of the surface stress meter.

Also, CS_Ais a value measured by the following procedure using the birefringent imaging system Abrio-IM manufactured by Tokyo Instruments Corporation. As shown in Fig. 2, a cross section of chemically strengthened glass having a size of 10 mm x 10 mm or more and a thickness of about 0.2 to 2 mm is polished in a range of 150 to 250 µm to be exfoliated. As a polishing procedure, grind to about plus 50 μm of the target thickness with a #1000 diamond electrodeposition grindstone, then grind to about plus 10 μm of the target thickness using a #2000 diamond electrodeposition grindstone, and finally mirror finish with cerium oxide to achieve the desired thickness. For the sample thinned to about 200 μm produced as described above, measurement was performed in transmitted light using monochromatic light of λ = 546 nm as a light source, and the phase difference (retardation) of chemically strengthened glass was measured by a birefringent imaging system. It measures and calculates a stress by using the obtained value and following formula (A).

F=δ/(C×') Formula (A)

In formula (A), F is the stress (MPa), δ is the retardation (retardation) (nm), C is the photoelastic constant (nm cm)^-1MPa) and d' indicate the thickness (cm) of the sample.

In addition, the present inventors have found that chemically strengthened glass (hereinafter also referred to as high DOL glass) having a DOL of a predetermined value or more and a compressive stress value at a predetermined depth inside the compressive stress layer is greater than or equal to a predetermined value has excellent drop resistance on sand found out to have In addition, it was found that such high DOL glass has high drop resistance on sand even when CT is relatively large.

From the above viewpoints, in the first aspect, the compressive stress value (CS) of the chemically strengthened glass at a depth of 90 µm from the glass surface₉₀) is preferably 25 MPa or more, and more preferably 30 MPa or more. In addition, the compressive stress value of the chemically strengthened glass at a depth of 100 μm from the glass surface (CS₁₀₀) is preferably 15 MPa or more, and more preferably 20 MPa or more. In addition, in the chemically strengthened glass of the first aspect, the product CS of the square of the compressive stress value at a depth of 100 µm from the glass surface and the plate thickness t (mm)₁₀₀×t²It is preferable that is 5 MPa·mm 2 or more.

CS₉₀If it is 25 MPa or more, it can have sufficient resistance to destruction caused by scratches caused by collision with sharp objects such as sand that may collide with chemically strengthened glass in a practical scene, that is, drop resistance on sand this is excellent In addition, the present inventors, CS₉₀It has been found that, in this chemically strengthened glass of 25 MPa or more, a chemically strengthened glass having high drop resistance on sand can be provided even if the CT is relatively large.

CS₉₀Silver is more preferably 30 MPa or more, still more preferably 35 MPa or more, still more preferably 40 MPa or more, particularly preferably 45 MPa or more, and most preferably 50 MPa or more.

On the other hand, CS₉₀Although the upper limit of is not particularly limited, from the viewpoint of safety at the time of destruction, for example, 250 MPa or less, preferably 200 MPa or less, more preferably 150 MPa or less, particularly preferably 100 MPa or less, , most preferably 75 MPa or less.

As above, CS₁₀₀Silver is more preferably 20 MPa or more, still more preferably 23 MPa or more, still more preferably 26 MPa or more, particularly preferably 30 MPa or more, and most preferably 33 MPa or more. CS₁₀₀The upper limit of is not particularly limited, but from the viewpoint of safety at the time of destruction, for example, 200 MPa or less, preferably 150 MPa or less, more preferably 100 MPa or less, particularly preferably 75 MPa or less, , most preferably 50 MPa or less.

Also, CS₁₀₀×t²is preferably 5 MPa mm or more, more preferably 7 MPa mm or more, still more preferably 10 MPa mm or more, particularly preferably 15 MPa mm or more, and most preferably 20 MPa or more. · mm2 or more. CS₁₀₀×t²Although the upper limit of is not particularly limited, from the viewpoint of safety at the time of destruction, for example, 120 MPa · mm 2 or less, preferably 100 MPa · mm 2 or less, more preferably 80 MPa · mm 2 or less, particularly preferably It is preferably 60 MPa·mm 2 or less, and most preferably 40 MPa·mm 2 or less.

In the chemically strengthened glass of the first aspect, the depth d of the portion where the magnitude of the internal compressive stress is 1/2 of the surface compressive stress (CS)_hIt is preferable that (refer FIG. 1(b)) is 8 micrometers or more. d_hWhen is 8 µm or more, the resistance to a decrease in the strength of the bending strength when a scratch is made is improved. d_hPreferably it is 8 micrometers or more, More preferably, it is 10 micrometers or more, More preferably, it is 12 micrometers or more, Especially preferably, it is 15 micrometers or more. On the other hand, d_hThe upper limit of is not particularly limited, but from the viewpoint of safety at the time of destruction, for example, 70 µm or less, preferably 60 µm or less, more preferably 50 µm or less, still more preferably 40 µm or less, Especially preferably, it is 30 micrometers or less.

In the chemically strengthened glass of the first aspect, the depth d of the position where the compressive stress is maximum_MIt is preferable that (refer FIG. 1(c)) exists in the range of 10 micrometers or less from the glass surface. d_MWhen it is located in a part deeper than 10 micrometers from this glass surface, the effect of the improvement of the bending strength by a chemical strengthening process cannot fully be acquired, and there exists a possibility that it may lead to bending strength fall. d_Mis preferably 10 µm or less, more preferably 8 µm or less, and still more preferably 5 µm or less.

1st aspect WHEREIN: It is preferable that DOL is 100 micrometers or more. If the DOL is 100 µm or more, it can have sufficient resistance to destruction caused by scratches caused by collision with sharp objects such as sand that may collide with chemically strengthened glass in a practical scene. DOL becomes like this. More preferably, it is 110 micrometers or more, More preferably, it is 120 micrometers or more, Especially preferably, it is 130 micrometers or more.

On the other hand, the upper limit of the DOL is not particularly limited, but from the viewpoint of safety at the time of destruction, it is, for example, 200 µm or less, preferably 180 µm or less, more preferably 160 µm or less, particularly preferably 150 µm or less. μm or less.

In addition, DOL can be suitably adjusted by adjusting chemical strengthening conditions, the composition of glass, etc.

In the chemically strengthened glass of the present invention, the compressive stress value CS at the depth of the glass surface side of 20 µm from the DOL_DOL_-20ΔCS calculated by the following formula using_DOL_-20It is preferable that (unit: MPa/micrometer) is 0.4 or more.

ΔCS_DOL_-20=CS_DOL_-20/20

ΔCS_DOL_-20By making it 0.4 or more, it is possible to increase the bending strength (bending strength after scratching) after making a flaw with an acute angle object. ΔCS_DOL_-20Silver is more preferably 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.2 or more, 1.4 or more, 1.5 or more, step by step. On the other hand, ΔCS_DOL_-20Although the upper limit of is not particularly limited, from the viewpoint of safety of crushing, it is, for example, 4.0 or less, preferably 3.0 or less, more preferably 2.0 or less, still more preferably 1.7 or less, and typically 1.6 or less.

In addition, in the chemically strengthened glass of the present invention, CS₉₀and CS₁₀₀ΔCS calculated by the following formula using_100-90It is preferable that (unit: MPa/micrometer) is 0.4 or more.

ΔCS₁₀₀_-90=(CS₉₀-CS₁₀₀)/(100-90)

ΔCS₁₀₀_-90By making it 0.4 or more, it is possible to increase the bending strength (bending strength after scratching) after making a flaw with an acute angle object. ΔCS₁₀₀_-90Silver is more preferably 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.2 or more, 1.4 or more, 1.5 or more, step by step. On the other hand, ΔCS₁₀₀_-90Although the upper limit of is not particularly limited, from the viewpoint of safety of crushing, it is, for example, 4.0 or less, preferably 3.0 or less, more preferably 2.0 or less, still more preferably 1.7 or less, and typically 1.6 or less.

In addition, the DOL of the chemically strengthened glass in 1st aspect is the depth from the glass surface of the part where stress becomes zero in a stress profile, It is measured by the surface stress meter FSM-6000 manufactured by Orihara Seisakusho, and is attached to the program FsmV. It is a value interpreted by Measurement can also be carried out using a flaky sample as shown in Fig. 2(b) using a birefringent imaging system Abrio-IM manufactured by Tokyo Instruments Corporation.

In the chemically strengthened glass of the first aspect, the value of the area Sc (MPa·µm) of the compressive stress layer is preferably 30000 MPa·µm or more. When the value of the area Sc (MPa μm) of the compressive stress layer is 30000 MPa μm or more, by introducing larger CS and DOL, collision with sharp objects such as sand that may collide with chemically strengthened glass in a practical scene It is possible to obtain a chemically strengthened glass having sufficient resistance to destruction caused by scratches caused by the Sc is more preferably 32000 MPa μm or more, and below, stepwise 34000 MPa μm or more, 36000 MPa μm or more, 38000 MPa μm or more, 40000 MPa μm or more, 42000 MPa μm or more, 44000 MPa μm or more As mentioned above, 46000 MPa·micrometer or more is more preferable.

In addition, Sc (MPa·μm) of the chemically strengthened glass in the first aspect is the value Sc by the following two types of measurement methods_F and Sc_ABy , it is defined as follows.

Sc=Sc_F=1.515×Sc_A

Here, Sc_Fis a value calculated using a value measured by a surface stress meter FSM-6000 manufactured by Orihara Seisakusho Co., Ltd. and analyzed by the attached program FsmV, Sc_Ais the above-mentioned CS_A It is a value obtained by the measurement using the birefringent imaging system Abrio-IM, which is a method similar to the measurement, and a flaked sample.

In addition, in the first aspect, the area St (MPa·μm) of the internal tensile layer of the chemically strengthened glass is the value St by the following two types of measurement methods._F and St_ABy , it is defined as follows.

St=St_F=1.515×St_A

Here, St_Fis a value calculated using a value measured with a surface stress meter FSM-6000 manufactured by Orihara Seisakusho Co., Ltd. and analyzed by the attached program FsmV, and St_Ais the above-mentioned CS_A It is a value obtained by the measurement using the birefringent imaging system Abrio-IM, which is a method similar to the measurement, and a flaked sample. As above, the stress profile was produced by two methods,_F or St_Acan be calculated to obtain St.

Fig. 1 (a) shows a conceptual diagram of Sc and St. Sc and St are theoretically equivalent values, and it is preferable to calculate it so that 0.95&lt;Sc/St&lt;1.05.

Further, in the first aspect, SiO in the mother composition of chemically strengthened glass₂, Al₂O₃, B₂O₃, P₂O₅, Li₂O, Na₂O, K₂O, MgO, CaO, SrO, BaO and ZrO₂A value of X calculated based on the following formula is 30000 or more, and/or a value of Z calculated based on the following formula is 20000 or more, using the content in terms of the molar percentage expression of each component based on the oxide of am.

In addition, the imitation property of chemically strengthened glass is a composition of the glass (henceforth chemical strengthening glass) before chemical strengthening. Here, the portion having the tensile stress of the chemically strengthened glass (hereinafter also referred to as the tensile stress portion) is the portion not subjected to ion exchange. When the thickness of the chemically strengthened glass is sufficiently large, the tensile stress portion of the chemically strengthened glass has the same composition as that of the glass before chemical strengthening. In that case, the composition of the tensile stress portion can be regarded as pseudo-composition. In addition, the preferable form of the imitation|imitation property of chemically strengthened glass is mentioned later.

X=SiO₂×329+Al₂O₃×786+B₂O₃×627+P₂O₅×(-941)+Li₂O×927+Na₂O×47.5+K₂O×(-371)+MgO×1230+CaO×1154+SrO×733+ZrO₂×51.8

Z=SiO₂×237+Al₂O₃×524+B₂O₃×228+P₂O₅×(-756)+Li₂O×538+Na₂O×44.2+K₂O×(-387)+MgO×660+CaO×569+SrO×291+ZrO₂×510

The present inventors found that the X value and Z value calculated based on the above formula correlate well with the number of fragments (number of fractures) generated at the time of destruction (shattering) of chemically strengthened glass, and the larger the X value and Z value, the better. , it was found experimentally that the number of fractures at the time of glass breakage tends to decrease.

Based on the above findings, in the chemically strengthened glass of the first aspect, from the viewpoint of making glass with a smaller number of crushes and higher safety, the X value is preferably 30000 MPa·µm or more, and below, 32000 MPa·µm or more in stages , 34000 MPa or more, 36000 MPa or more, 38000 MPa or more, 40000 MPa or more, 42000 MPa or more, 44000 MPa or more, 45000 MPa or more, 46000 MPa or more desirable.

In addition, from the same viewpoint, it is preferable that the Z value is 20000 MPa· or more, and then, in stages, 22000 MPa· or more, 24000 MPa· or more, 26000 MPa· or more, 28000 MPa· or more, 29000 MPa· or more It is more preferable that it is micrometer or more and 30000 MPa·micrometer or more.

The X value and Z value can be adjusted by the amount of each component in the composition of the chemically strengthened glass. In the first aspect, although the imitation property of the chemically strengthened glass is not particularly limited, the chemical strengthening treatment for imparting the chemical strengthening properties described above to the glass after chemical strengthening is applicable, and the value of X is 30000 or more; and/or a glass composition in which the value of Z is 20000 or more may be appropriately selected.

In addition, the Y value calculated based on the following formula is correlated with the number of fragments (number of fractures) generated at the time of destruction (breaking) of chemically strengthened glass. It has been found experimentally that there is a tendency to lose.

Y=SiO₂×0.00884+Al₂O₃×0.0120+B₂O₃×(-0.00373)+P₂O₅×0.000681+Li₂O×0.00735+Na₂O×(-0.00234)+K₂O×(-0.00608)+MgO×0.0105+CaO×0.00789+SrO×0.00752+BaO×0.00472+ZrO₂×0.0202

Based on the above findings, even when the glass is broken, the Y value is preferably 0.7 or more, and more preferably 0.75 or more, in the chemically strengthened glass of the first form, from the viewpoint of providing a glass with a small number of fractures and higher safety, , more preferably 0.77 or more, particularly preferably 0.80 or more, and most preferably 0.82 or more.

The glass for chemical strengthening of the present invention has a devitrification temperature T and a viscosity of 10⁴It is preferable that it is below the temperature T4 used as dPa*s. When loss-of-clarity temperature T is higher than T4, it is because it is easy to generate|occur|produce the quality fall by loss-of-clarity at the time of glass plate shaping|molding by a float method etc.

When the chemically strengthened glass of the first aspect is plate-shaped (glass plate), the plate thickness (t) is not particularly limited, but in order to enhance the effect of chemical strengthening, for example, it is 2 mm or less, preferably 1.5 mm or less, more preferably 1 mm or less, still more preferably 0.9 mm or less, particularly preferably 0.8 mm or less, and most preferably 0.7 mm or less. Further, the plate thickness is, for example, 0.1 mm or more, preferably 0.2 mm or more, more preferably 0.4 mm or more, and still more preferably, from the viewpoint of obtaining the effect of sufficient strength improvement by chemical strengthening treatment. is 0.5 mm or more.

Further, the chemically strengthened glass of the first aspect may have a shape other than a plate shape depending on the applied product, use, or the like. Moreover, a glass plate may have the frame shape etc. from which the thickness of an outer periphery differs. In addition, the said glass plate has two main surfaces and the cross section which adjoins these and forms plate|board thickness, and two main surfaces may form the mutually parallel flat surface. However, the form of a glass plate is not limited to these, For example, two main surfaces do not need to be mutually parallel, Moreover, one or both all or part of two main surfaces may be a curved surface. More specifically, a flat glass plate without curvature may be sufficient as a glass plate, and the curved glass plate which has a curved surface may be sufficient as it, for example.

According to the first aspect, even if CT or St is large, the number of crushing is smaller and a chemically strengthened glass with high safety is obtained.

For example, when a mobile device such as a smartphone is accidentally dropped, it collides with an impact object (hereinafter also referred to as an acute-angle object) having a small impact portion such as sand, and chemically strengthened glass as a cover glass Since there are comparatively many opportunities for breakage, even when it collides with an acute-angle object, chemically strengthened glass which is hard to break is calculated|required.

The chemically strengthened glass according to the first aspect is also excellent in resistance to breakage due to scratches caused by collision with sharp objects such as sand that may collide in a practical scene (resistance to falling on sand).

&lt;Second form&gt;

Next, the chemically strengthened glass according to the second aspect will be described.

One of the chemically strengthened glasses of the second aspect is chemically strengthened glass having a surface compressive stress (CS) of 300 MPa or more and satisfying the following formulas (1) and (2).

StL(t)a×t+7000 (unit: MPa μm) (1)

a30000 (unit: MPa μm/mm) (2)

(Here, t is the plate thickness (mm), and StL(t) is the value of St Limit when the plate thickness is t)

Here, StL(t) is a value obtained by the following measurement. For glass of 25 mm × 25 mm × plate thickness t (mm), chemical strengthening treatment is performed under various chemical strengthening treatment conditions so that the internal tensile stress area (St; unit MPa μm) is changed, and various internal tensile stress areas ( St; a chemically strengthened glass having a unit MPa·) is produced. Then, using a diamond indenter having an indenter angle of 60 degrees facing each other, each of these chemically strengthened glasses is destroyed by an indenter indentation test holding a load of 3 to 10 kgf for 15 seconds, and the fragments of the chemically strengthened glass after destruction The number (number of crushing) is measured respectively. Then, the internal tensile stress area (St; unit MPa·μm) in which the number of fractures becomes 10 is defined as St Limit value = StL(t) when the plate thickness is t(mm). When the number of fractures exceeds 10, using the Stn value, which is the St value of the maximum number of crushing n, which is less than 10, and the Stm value, which is the St value of the St value of the minimum number of fractures, m, exceeding 10, StL(t) by the following formula Define the value.

StL(t) value=Stn+(10-n)×(Stm-Stn)/(mn)

When using chemically strengthened glass having a size larger than 25 mm × 25 mm, an area of 25 mm × 25 mm is displayed in the chemically strengthened glass, and the StL(t) measurement is performed within the area.

Further, StL(t) depends on the plate thickness t(mm) and a, and a is a parameter dependent on the glass composition. StL(t) changes linearly with respect to t, and its slope can be described as a parameter a that changes with composition. Further, by setting the value of a to 30000 MPa·μm/mm or more, even when larger CS and DOL are introduced, it is possible to obtain a crushing mode with fewer crushing numbers and higher safety.

The value of a is more preferably 32000 MPa·μm/mm or more, and below, stepwise 34000 MPa·μm/mm or more, 36000 MPa·μm/mm or more, 38000 MPa·μm/mm or more, 40000 MPa·μm or more. /mm or more, 42000 MPa·μm/mm or more, 44000 MPa·μm/mm or more, 46000 MPa·μm/mm or more, 48000 MPa·μm/mm or more, and 50000 MPa·μm/mm or more are more preferable.

Moreover, in the chemically strengthened glass of this embodiment, when a is larger than 53000 MPa·micrometer/mm, the devitrification temperature of the glass becomes high, and there exists a possibility that productivity may deteriorate in glass manufacture. Therefore, it is preferable that the value of a is 53000 MPa·micrometer/mm or less.

Further, one of the chemically strengthened glasses of the second aspect is a chemically strengthened glass having a surface compressive stress (CS) of 300 MPa or more and satisfying the following formulas (3), (4) and (5).

CTL(t)-b×ln(t)+c (unit: MPa) (3)

b14 (unit: MPa) (4)

c48.4 (unit: MPa) (5)

(Here, t is the plate thickness (mm), and CTL(t) is the value of CT Limit when the plate thickness is t)

Here, CTL(t) is a value obtained by the following measurement. Specifically, for glass of 25 mm × 25 mm × plate thickness t (mm), chemical strengthening treatment is performed under various chemical strengthening treatment conditions so that the internal tensile stress CT (unit: MPa) is changed, and various internal tensile stress CT A chemically strengthened glass having (unit: MPa) is produced. Then, each of these chemically strengthened glasses is destroyed by an indenter indentation test holding a load of 3 to 10 kgf for 15 seconds using a diamond indenter having an indenter angle of 60 degrees facing each other, and the fragments of the chemically strengthened glass after destruction The number (number of crushing) is measured respectively. And the internal tensile stress CT (unit: MPa) in which the number of fractures became 10 is prescribed|regulated as CT Limit value = CTL(t) at the time of plate|board thickness t (mm). When the number of crushing exceeds 10, using the CTn value, which is the CT value of the maximum number of fractures n, which is less than 10, and the CTm value, which is the CT value of the minimum number of fractures, m, which is more than 10, CTL(t) by the following formula Define the value.

CTL(t) value=CTn+(10-n)×(CTm-CTn)/(mn)

When chemically strengthened glass having a size larger than 25 mm × 25 mm is used, an area of 25 mm × 25 mm is displayed in the chemically strengthened glass, and the above-mentioned CTL(t) measurement is performed within the area.

Also, CTL(t) depends on the plate thickness t (mm), b and c, and b and c are parameters dependent on the glass composition. CTL(t) decreases with increasing t, and can be described using natural logarithms as in Equation (3). According to this embodiment, by setting the values of b and c to be 14 MPa or more and 48.4 MPa or more, respectively, even when CS and DOL larger than before are introduced, it is possible to obtain a shredding mode with fewer shredding numbers and higher safety.

The value of b is more preferably 14 MPa or more, and below, stepwise 15 MPa or more, 16 MPa or more, 17 MPa or more, 18 MPa or more, 19 MPa or more, 20 MPa or more, 21 MPa or more, 22 MPa or more, 23 MPa or more, 24 MPa or more, 25 MPa or more, 26 MPa or more, 27 MPa or more, 28 MPa or more, 29 MPa or more, 30 MPa or more are preferable.

The value of c is more preferably 48.4 MPa or more, and then, in steps of 49 MPa or more, 50 MPa or more, 51 MPa or more, 52 MPa or more, 53 MPa or more, 54 MPa or more, 55 MPa or more, 56 MPa or more, 57 MPa or more, 58 MPa or more, 59 MPa or more, 60 MPa or more, 61 MPa or more, 62 MPa or more, 63 MPa or more, 64 MPa or more, 65 MPa or more are preferable.

In the chemically strengthened glass of the present embodiment, when b is larger than 35 MPa and c is larger than 75 MPa, the devitrification of the glass generally deteriorates, and there is a fear that productivity may deteriorate in glass manufacture. Accordingly, the CTL(t) is preferably smaller than -35×ln(t)+75.

In addition, St value and CT value are the value St measured by the surface stress meter FSM-6000 manufactured by Orihara Seisakusho, and analyzed by the attached program FsmV._F and CT_F, or the value St obtained by measurement using the birefringent imaging system Abrio-IM and flaked samples._A and CT_AUsing , each is defined as follows:

St=St_F=1.515×St_A

CT = CT_F=1.28×CT_A

Here, CT_Fis a value equivalent to the value CT_CV interpreted as FsmV, and is different from CT' obtained by the following formula (11).

CS×DOL'=(t-2×DOL')×CT' (11)

Here, DOL' corresponds to the depth of the ion exchange layer. The above formula for calculating CT' approximates the stress profile linearly and assumes that the point at which the stress becomes zero is equal to the depth of the ion diffusion layer, so there is a problem that it is estimated to be larger than the actual internal tensile stress. , which is not suitable as an index of the internal tensile stress in the present embodiment.

The chemically strengthened glass of the second aspect has a compressive stress layer formed on its surface by a chemical strengthening treatment (ion exchange treatment).

The chemically strengthened glass of the second aspect has a surface compressive stress (CS) of 300 MPa or more. Here, the reason for limitation of CS in the chemically strengthened glass of the second aspect and the preferable numerical range are the same as those of the first aspect.

Further, CS in the chemically strengthened glass of the second aspect₉₀, CS₁₀₀ and CS₁₀₀×t²The preferable numerical range of , and the technical effects accompanying it are the same as those of the first aspect. In particular, the compressive stress value (CS) at a depth of 90 μm from the glass surface₉₀) is 25 MPa or more, or the compressive stress value (CS) at a depth of 100 µm from the glass surface₁₀₀) is 15 MPa or more, it can have sufficient resistance to destruction caused by scratches caused by collision with sharp objects such as sand that may collide with chemically strengthened glass in a practical scene, that is, on sand It can be made of chemically strengthened glass with excellent drop resistance.

In addition, d in the chemically strengthened glass of the second aspect_h and d_MThe preferable numerical range of , and the technical effects accompanying it are the same as those of the first aspect.

In addition, the preferable numerical range of DOL in the chemically strengthened glass of the second aspect and the technical effects accompanying it are the same as those of the first aspect.

In addition, the preferable numerical ranges of Sc and St in the chemically strengthened glass of a 2nd aspect, and the technical effect accompanying it are the same as that of the 1st aspect.

Further, the chemically strengthened glass of the second aspect is preferably in the form of a plate having a plate thickness t of 2 mm or less. The preferable numerical range of the plate|board thickness t in the chemically strengthened glass of 2nd aspect, and the technical effect accompanying it are the same as that of 1st aspect.

In addition, the chemically strengthened glass of a 2nd aspect can take various shapes other than plate shape similarly to the chemically strengthened glass of a 1st aspect.

&lt;Third form&gt;

Next, the chemically strengthened glass according to the third aspect will be described.

In the third aspect, the average crack height by a drop test on sand under the following conditions is 250 mm or more,

The number of crushed pieces by the indenter indentation test under the following conditions is 30 or less,

The plate thickness t is 0.4 to 2 mm,

Surface compressive stress (CS) is 300 MPa or more, and

It relates to chemically strengthened glass having a compressive stress layer depth (DOL) of 100 μm or more.

The average crack height of the chemically strengthened glass according to the drop test on sand in the third aspect is 250 mm or more, preferably 300 mm or more, and more preferably 350 mm from the viewpoint of having excellent drop resistance on sand. More than that. Here, the average crack height of the chemically strengthened glass in the third aspect shall be measured by a drop test on sand under the following conditions.

Drop test conditions on sand:

Chemically tempered glass (50 mm x 50 mm x plate thickness t (mm)) on a rigid nylon MOC plate (50 mm x 50 mm, weight: 54 g) with sponge double-sided tape (50 mm x 50 mm x thickness 3 mm) It is joined through and a measurement sample is produced. Next, 1 g of silica sand (No. 5 silica sand manufactured by Takeori Co., Ltd.) is evenly sprinkled on the SUS plate having a size of 15 cm × 15 cm, and the prepared measurement sample is chemically tempered glass down, It is dropped from a predetermined height (fall height) to the surface. The drop test is carried out by increasing the height by 10 mm starting from the drop height: 10 mm, and the height at which the chemically strengthened glass is broken is defined as the crack height (unit mm). The drop test is performed 5 times or more about each example, and let the average value of the crack height in a drop test be an average crack height (unit: mm).

In addition, the number of crushing by the indentation test of the chemically strengthened glass in the third aspect is 30 or less, preferably 20 or less, from the viewpoint of becoming a safer fracture (crushing) even if it is broken (crushed). , More preferably, it is 10 or less, More preferably, it is 5 or less, Especially preferably, it is 2 or less. Here, the number of fractures of the chemically strengthened glass in the third aspect shall be measured by an indenter indentation test under the following conditions.

Indenter indentation test conditions:

With respect to chemically strengthened glass of 25 mm × 25 mm × plate thickness t (mm), using a diamond indenter having an indenter angle of 60 degrees facing angle, by an indenter indentation test holding a load of 3 to 10 kgf for 15 seconds, The chemically strengthened glass is destroyed, and the number of crushing of the chemically strengthened glass after destruction is measured. When using chemically strengthened glass having a size larger than 25 mm × 25 mm, an area of 25 mm × 25 mm is displayed in the chemically strengthened glass, and an indenter indentation test and the number of crushes are measured within the area. When the chemically strengthened glass has a curved shape, a size of 25 mm x 25 mm as a projected area is displayed on the curved surface of the chemically strengthened glass, and an indenter press-in test and the number of crushing are performed within the area.

In addition, the chemically strengthened glass of the third aspect is plate-shaped (glass plate), and the plate thickness (t) is, for example, 2 mm or less, preferably 1.5, from the viewpoint of enabling a remarkable strength improvement by chemical strengthening. mm or less, more preferably 1 mm or less, still more preferably 0.9 mm or less, particularly preferably 0.8 mm or less, and most preferably 0.7 mm or less. In addition, the said plate|board thickness is 0.3 mm or more from a viewpoint of obtaining the effect of sufficient intensity|strength improvement by a chemical strengthening process, Preferably it is 0.4 mm or more, More preferably, it is 0.5 mm or more.

The chemically strengthened glass of the third aspect has a surface compressive stress (CS) of 300 MPa or more. Here, the reason for limitation of CS in the chemically strengthened glass of the third aspect and the preferable numerical range are the same as those of the first aspect.

In addition, the DOL in the chemically strengthened glass of the third aspect has sufficient resistance to destruction caused by scratches caused by collision with sharp objects such as sand that may collide with the chemically strengthened glass in a practical scene. is 100 μm or more from the viewpoint. DOL becomes like this. More preferably, it is 110 micrometers or more, More preferably, it is 120 micrometers or more, Especially preferably, it is 130 micrometers or more.

Further, CS in the chemically strengthened glass of the third aspect₉₀, CS₁₀₀ and CS₁₀₀×t²The preferable numerical range of , and the technical effects accompanying it are the same as those of the first aspect.

In addition, d in the chemically strengthened glass of the third aspect_h and d_MThe preferable numerical range of , and the technical effects accompanying it are the same as those of the first aspect.

In addition, the preferable numerical ranges of Sc and St in the chemically strengthened glass of a 3rd aspect, and the technical effect accompanying it are the same as that of the 1st aspect.

The chemically strengthened glass according to the third aspect is chemically strengthened glass having a small number of crushes and high safety even when CT or St is large.

&lt;Glass for chemical strengthening&gt;

Then, the glass for chemical strengthening of this invention is demonstrated.

Hereinafter, the glass composition of the glass for chemical strengthening may be referred to as the imitation composition of the chemically strengthened glass.

When the thickness of the chemically strengthened glass is sufficiently large, the portion having the tensile stress of the chemically strengthened glass (hereinafter also referred to as the tensile stress portion) is a portion that has not been ion exchanged. It has the same composition as glass. In that case, the composition of the tensile stress portion of the chemically strengthened glass can be regarded as the imitation composition of the chemically strengthened glass.

Although the composition of glass can also be simply calculated|required by the semi-quantitative analysis by a fluorescent X-ray method, it can measure with wet analysis methods, such as ICP emission analysis, more precisely.

In addition, unless otherwise indicated, content of each component shall be expressed by the molar percentage expression of an oxide basis.

As the composition for the chemically strengthened glass of the present invention (the imitation composition of the chemically strengthened glass of the present invention), for example, SiO₂50 to 80% of Al₂O₃1 to 30%, B₂O₃0 to 5%, P₂O₅0 to 4%, Li₂3 to 20% O, Na₂0 to 8% O, K₂0 to 10% O, 3 to 20% MgO, 0 to 20% CaO, 0 to 20% SrO, 0 to 15% BaO, 0 to 10% ZnO, TiO₂0 to 1%, ZrO₂It is preferable to contain 0 to 8%.

For example, SiO₂63 to 80%, Al₂O₃7 to 30%, B₂O₃0 to 5%, P₂O₅0 to 4%, Li₂5 to 15% O, Na₂4 to 8% O, K₂0 to 2% O, 3 to 10% MgO, 0 to 5% CaO, 0 to 20% SrO, 0 to 15% BaO, 0 to 10% ZnO, TiO₂0 to 1%, ZrO₂0 to 8% of Ta₂O₅, Gd₂O₃, As₂O₃, Sb₂O₃glass that does not contain

This glass for chemical strengthening, X=SiO₂×329+Al₂O₃×786+B₂O₃×627+P₂O₅×(-941)+Li₂O×927+Na₂O×47.5+K₂O×(-371)+MgO×1230+CaO×1154+SrO×733+ZrO₂It is preferable that the value of X calculated based on x51.8 is 30000 or more.

Also, Z=SiO₂×237+Al₂O₃×524+B₂O₃×228+P₂O₅×(-756)+Li₂O×538+Na₂O×44.2+K₂O×(-387)+MgO×660+CaO×569+SrO×291+ZrO₂It is preferable that the value of Z calculated based on x510 is 20000 or more.

SiO₂is a component constituting the skeleton of glass. Moreover, it is a component which improves chemical durability, is a component which reduces the crack generation when a flaw (indentation) occurs on the glass surface, and SiO₂The content of is preferably 50% or more. SiO₂The content of is more preferably 54% or more, 58% or more, 60% or more, 63% or more, 66% or more, 68% or more in stages. On the other hand, SiO₂If the content of is more than 80%, the meltability is remarkably reduced. SiO₂The content of is 80% or less, more preferably 78% or less, still more preferably 76% or less, particularly preferably 74% or less, and most preferably 72% or less.

Al₂O₃Silver is a component that improves the friability of chemically strengthened glass. Here, the high friability of glass means that the number of fragments when glass is broken is small. It can be said that the glass with high friability is high in safety since it is hard to scatter fragments when it is destroyed. Also, Al₂O₃Since silver is an effective component for improving ion exchange performance during chemical strengthening and increasing the surface compressive stress after strengthening, Al₂O₃The content of is preferably 1% or more. Al₂O₃Silver is a component that increases the Tg of the glass, and is also a component that increases the Young's modulus. Al₂O₃The content of is more preferably 3% or more, 5% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, 13% or more in stages. On the other hand, Al₂O₃The acid resistance of glass will fall that content is more than 30 %, or loss-of-clarity temperature will become high. In addition, the viscosity of the glass increases and the meltability decreases. Al₂O₃The content of is preferably 30% or less, more preferably 25% or less, still more preferably 20% or less, particularly preferably 18% or less, and most preferably 15% or less. On the other hand, Al₂O₃When content of is large, the temperature at the time of glass melting becomes large, and productivity falls. When considering the productivity of glass, Al₂O₃The content of is preferably 11% or less, and is preferably 10% or less, 9% or less, 8% or less, 7% or less in steps.

B₂O₃Silver is a component that improves the chipping resistance of chemically strengthened glass or chemically strengthened glass, and also improves meltability. B₂O₃is not required, but B₂O₃In order to improve meltability, content in the case of containing it becomes like this. Preferably it is 0.5 % or more, More preferably, it is 1 % or more, More preferably, it is 2 % or more. On the other hand, B₂O₃When the content of is more than 5%, streaks are generated during melting and the quality of the glass for chemical strengthening is likely to deteriorate, so 5% or less is preferable. B₂O₃The content of is more preferably 4% or less, still more preferably 3% or less, and particularly preferably 1% or less. In order to improve acid resistance, it is preferable not to contain.

P₂O₅is a component that improves ion exchange performance and chipping resistance. P₂O₅It is not necessary to contain P₂O₅Content in the case of containing it becomes like this. Preferably it is 0.5 % or more, More preferably, it is 1 % or more, More preferably, it is 2 % or more. On the other hand, P₂O₅When the content of is more than 4%, the crushability of the chemically strengthened glass is lowered, and the acid resistance is remarkably lowered. P₂O₅The content of is preferably 4% or less, more preferably 3% or less, still more preferably 2% or less, particularly preferably 1% or less. In order to improve acid resistance, it is preferable not to contain.

Li₂O is also a component that forms a surface compressive stress by ion exchange, and is a component that improves the friability of chemically strengthened glass.

Li ions on the glass surface are exchanged for Na ions, and the CS₉₀In the case of performing the chemical strengthening treatment to be 30 MPa or more, Li₂The content of O is preferably 3% or more, more preferably 4% or more, still more preferably 5% or more, particularly preferably 6% or more, and typically 7% or more. On the other hand, Li₂When the content of O is more than 20%, the acid resistance of the glass is remarkably reduced. Li₂The content of O is preferably 20% or less, more preferably 18% or less, still more preferably 16% or less, particularly preferably 15% or less, and most preferably 13% or less.

On the other hand, by exchanging Na ions on the glass surface with K ions, the CS₉₀In the case of performing the chemical strengthening treatment to be 30 MPa or more, Li₂When the content of O is more than 3%, the magnitude of the compressive stress decreases, and CS₉₀It becomes difficult to achieve this 30 MPa or more. In this case, Li₂The content of O is preferably 3% or less, more preferably 2% or less, still more preferably 1% or less, particularly preferably 0.5% or less, and most preferably Li₂It is substantially free of O.

In addition, in this specification, "substantially does not contain" means that it does not contain except unavoidable impurities contained in a raw material etc., ie, does not contain it intentionally. Specifically, it points out that content in a glass composition is less than 0.1 mol%.

Na₂O is a component that forms a surface compressive stress layer by ion exchange and improves the meltability of glass.

Li ions on the glass surface are exchanged for Na ions, and the CS₉₀When performing the chemical strengthening treatment to be this 30 MPa or more, Na₂Although it is not necessary to contain O, when attaching importance to the meltability of glass, you may contain it. Na₂The content in the case of containing O is preferably 1% or more. Na₂Content of O becomes like this. More preferably, it is 2 % or more, More preferably, it is 3 % or more. On the other hand, Na₂When the content of O is more than 8%, the surface compressive stress formed by ion exchange is remarkably reduced. Na₂The content of O is preferably 8% or less, more preferably 7% or less, still more preferably 6% or less, particularly preferably 5% or less, and most preferably 4% or less.

On the other hand, by exchanging Na ions on the glass surface with K ions, the CS₉₀When performing the chemical strengthening treatment used as this 30 MPa or more, Na is essential, and the content is 5 % or more. Na₂The content of O is preferably 5% or more, more preferably 7% or more, still more preferably 9% or more, particularly preferably 11% or more, and most preferably 12% or more. On the other hand, Na₂When the content of O is more than 20%, the acid resistance of the glass is remarkably reduced. Na₂The content of O is preferably 20% or less, more preferably 18% or less, still more preferably 16% or less, particularly preferably 15% or less, and most preferably 14% or less.

In the case of simultaneously ion-exchanging Li ions and Na ions, Na ions and K ions on the glass surface by a method such as immersion in a mixed molten salt of potassium nitrate and sodium nitrate, Na₂The content of O is preferably 10% or less, more preferably 9% or less, still more preferably 7% or less, particularly preferably 6% or less, and most preferably 5% or less. Also, Na₂Content of O becomes like this. Preferably it is 2 % or more, More preferably, it is 3 % or more, More preferably, it is 4 % or more.

K₂O may be contained in order to improve ion exchange performance. K₂Content in the case of containing O becomes like this. Preferably it is 0.5 % or more, More preferably, it is 1 % or more, More preferably, it is 2 % or more, Especially preferably, it is 3 % or more. On the other hand, K₂When the content of O is more than 10%, the friability of chemically strengthened glass decreases, so that K₂The content of O is preferably 10% or less. K₂The content of O is more preferably 8% or less, still more preferably 6% or less, particularly preferably 4% or less, and most preferably 2% or less.

MgO is a component that increases the surface compressive stress of chemically strengthened glass and improves friability, and is preferably contained. Content in the case of containing MgO becomes like this. Preferably it is 3 % or more, More preferably, it is 4 % or more, 5 % or more, 6 % or more, 7 % or more, and 8 % or more in steps below. On the other hand, when the content of MgO is more than 20%, the glass for chemical strengthening is easily devitrified at the time of melting. The MgO content is preferably 20% or less, more preferably 18% or less, 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, and 10% or less in stages.

CaO is a component that improves the meltability of the chemically strengthened glass, and is a component that improves the crushability of the chemically strengthened glass, and may be contained. Content in the case of containing CaO becomes like this. Preferably it is 0.5 % or more, More preferably, it is 1 % or more, More preferably, it is 2 % or more, Especially preferably, it is 3 % or more, Most preferably, it is 5 % or more. . On the other hand, since ion exchange performance will fall remarkably when content of CaO becomes more than 20 %, 20 % or less is preferable. Content of CaO becomes like this. More preferably, it is 14 % or less, More preferably, it is 10 % or less, 8 % or less, 6 % or less, 3 % or less, and 1 % or less in steps.

SrO is a component that improves the meltability of the chemically strengthened glass, and is a component that improves the friability of the chemically strengthened glass, and may be contained. The content in the case of containing SrO is preferably 0.5% or more, more preferably 1% or more, still more preferably 2% or more, particularly preferably 3% or more, and most preferably 5% or more. . On the other hand, when the content of SrO exceeds 20%, the ion exchange performance is remarkably deteriorated, so 20% or less is preferable. Content of SrO becomes like this. More preferably, it is 14 % or less, More preferably, it is 10 % or less, 8 % or less, 6 % or less, 3 % or less, and 1 % or less in steps.

BaO is a component that improves the meltability of the chemically strengthened glass, and is a component that improves the friability of the chemically strengthened glass, and may be contained. The content in the case of containing BaO is preferably 0.5% or more, more preferably 1% or more, still more preferably 2% or more, particularly preferably 3% or more, and most preferably 5% or more. . On the other hand, when content of BaO becomes more than 15 %, ion exchange performance will fall remarkably. It is preferable that content of BaO is 15 % or less, More preferably, it is 10 % or less, 8 % or less, 6 % or less, 3 % or less, and 1 % or less in steps.

ZnO is a component which improves the meltability of glass, and you may contain it. Content in the case of containing ZnO becomes like this. Preferably it is 0.25 % or more, More preferably, it is 0.5 % or more. On the other hand, when the content of ZnO exceeds 10%, the weather resistance of the glass is remarkably reduced. The content of ZnO is preferably 10% or less, more preferably 7% or less, still more preferably 5% or less, particularly preferably 2% or less, and most preferably 1% or less.

TiO₂is a component that improves the crushability of chemically strengthened glass, and may be contained. TiO₂Content in the case of containing it becomes like this. Preferably it is 0.1 % or more, More preferably, it is 0.15 % or more, More preferably, it is 0.2 % or more. On the other hand, TiO₂When the content of is more than 5%, devitrification tends to occur at the time of melting, and there is a possibility that the quality of the chemically strengthened glass may be deteriorated. TiO₂It is preferable that content of is 1 % or less, More preferably, it is 0.5 % or less, More preferably, it is 0.25 % or less.

ZrO₂is a component that increases the surface compressive stress by ion exchange, has an effect of improving the friability of the glass for chemical strengthening, and may be contained. ZrO₂Content in the case of containing it becomes like this. Preferably it is 0.5 % or more, More preferably, it is 1 % or more. On the other hand, ZrO₂When the content of is more than 8%, devitrification tends to occur at the time of melting, and there is a possibility that the quality of the chemically strengthened glass may be deteriorated. ZrO₂The content of is preferably 8% or less, more preferably 6% or less, still more preferably 4% or less, particularly preferably 2% or less, and most preferably 1.2% or less.

Y₂O₃, La₂O₃, Nb₂O₅is a component that improves the crushability of chemically strengthened glass, and may be contained. Each content in the case of containing these components is preferably 0.5% or more, more preferably 1% or more, still more preferably 1.5% or more, particularly preferably 2% or more, and most preferably 2.5% or more. % or more. On the other hand, Y₂O₃, La₂O₃, Nb₂O₅When the content of each is more than 8%, the glass tends to devitrify at the time of melting, and there is a possibility that the quality of the chemically strengthened glass may be deteriorated. Y₂O₃, La₂O₃, Nb₂O₅The content of each is preferably 8% or less, more preferably 6% or less, still more preferably 5% or less, particularly preferably 4% or less, and most preferably 3% or less.

Ta₂O₅, Gd₂O₃Silver may be contained in a small amount in order to improve the crushability of chemically strengthened glass, but since the refractive index and reflectance become high, 1% or less is preferable, 0.5% or less is more preferable, and it is still more preferable not to contain it.

In addition, when coloring glass and using it, you may add a coloring component in the range which does not impair achievement of a desired chemical strengthening characteristic. As a coloring component, Co₃O₄, MnO₂, Fe₂O₃, NiO, CuO, Cr₂O₃, V₂O₅, Bi₂O₃, SeO₂, TiO₂, CeO₂, Er₂O₃, Nd₂O₃ etc. are mentioned as suitable.

Content of a coloring component is a molar percentage expression on an oxide basis, and the range of 7 % or less in total is preferable. When it exceeds 7 %, it becomes easy to devitrify glass, and it is unpreferable.

This content becomes like this. Preferably it is 5 % or less, More preferably, it is 3 % or less, More preferably, it is 1 % or less. When giving priority to the visible light transmittance|permeability of glass, it is preferable not to contain these components substantially.

As a fining agent at the time of melting of glass, SO₃, a chloride, a fluoride, etc. may be contained as appropriate. As₂O₃It is preferable not to contain silver. Sb₂O₃When it contains, 0.3 % or less is preferable, 0.1 % or less is more preferable, and it is most preferable not to contain it.

In addition, the chemically strengthened glass of the present invention can impart antibacterial properties by having silver ions on the surface.

In addition, the glass for chemical strengthening of the present invention has a fracture toughness value (K1c) of 0.7 MPa·m^1/2 It is preferable that it is more than 0.75 MPa·m^1/2 It is more preferable that it is more than 0.77 MPa·m^1/2 More preferably, it is more than 0.80 MPa·m^1/2 It is particularly preferable that it is more than 0.82 MPa·m^1/2 More than that is most preferable. The fracture toughness value (K1c) is 0.7 MPa·m^1/2 If it is more than that, the number of crushing at the time of destruction of glass can be suppressed effectively.

Incidentally, the fracture toughness value (K1c) in the present specification is a fracture toughness value obtained by measuring the K1-v curve by the DCDC method, which will be described in detail in Examples to be described later.

Further, in the chemically strengthened glass of the present invention, it is preferable that the area St (MPa·µm) of the inner tensile layer is StL(t) (MPa·µm) or less. When St is StL(t) or less, the number of fractures decreases even if it is actually destroyed.

Moreover, in the chemically strengthened glass of this invention, it is preferable that internal tensile stress CT (MPa) is CTL(t) (MPa) or less. If the CT is CTL(t) or less, the number of fractures decreases even if it is actually destroyed.

Further, in the present invention, the Young's modulus of the chemically strengthened glass is 70 GPa or more, and the compressive stress value (CS) on the outermost surface of the chemically strengthened glass.₀) and the compressive stress value at a depth of 1 μm from the glass surface (CS₁) is preferably 50 MPa or less. In this way, since it is hard to generate|occur|produce the curvature at the time of performing the grinding|polishing process of the glass surface after a chemical strengthening process, it is preferable.

The Young's modulus of the glass for chemical strengthening is more preferably 74 GPa or more, particularly preferably 78 GPa or more, and still more preferably 82 GPa or more. Although the upper limit of Young's modulus is not specifically limited, For example, it is 90 GPa or less, Preferably it is 88 GPa or less. The Young's modulus can be measured, for example, by an ultrasonic pulse method.

Also, CS₀and CS₁The difference between is preferably 50 MPa or less, more preferably 40 MPa or less, still more preferably 30 MPa or less.

Also, CS₀Silver becomes like this. Preferably it is 300 MPa or more, More preferably, it is 350 MPa or more, More preferably, it is 400 MPa or more. On the other hand, CS₀Although the upper limit of is not specifically limited, For example, it is 1200 MPa or less, Preferably it is 1000 MPa or less, More preferably, it is 800 MPa or less.

Also, CS₁Silver becomes like this. Preferably it is 250 MPa or more, More preferably, it is 300 MPa or more, More preferably, it is 350 MPa or more. On the other hand, CS₁Although the upper limit of is not specifically limited, For example, it is 1150 MPa or less, Preferably it is 1100 MPa or less, More preferably, it is 1050 MPa or less.

The chemically strengthened glass of the present invention can be produced, for example, as follows.

First, glass to be subjected to chemical strengthening treatment is prepared. The glass to be subjected to the chemical strengthening treatment is preferably the glass for chemical strengthening of the present invention. Glass to be subjected to chemical strengthening treatment can be produced by a conventional method. For example, the raw material of each component of glass is combined, and it heat-melts in a glass melting kiln. Then, glass is homogenized by a well-known method, it shape|molds into desired shapes, such as a glass plate, and cools slowly.

As a shaping|molding method of a glass plate, the float method, the press method, the fusion method, and the down-draw method are mentioned, for example. In particular, the float method suitable for mass production is preferable. In addition, continuous molding methods other than the float method, that is, the fusion method and the down-draw method are also preferable.

Then, the shape|molded glass is grinded and grind|polished as needed, and a glass substrate is formed. In addition, when cutting a glass substrate to a predetermined shape and size, or performing chamfering of a glass substrate, before performing the chemical strengthening process mentioned later, if cutting or chamfering of a glass substrate is performed, by the subsequent chemical strengthening process Since a compressive stress layer is also formed in the cross section, it is preferable.

The chemically strengthened glass of the present invention can be produced by subjecting the obtained glass plate to a chemical strengthening treatment, followed by washing and drying.

Chemical strengthening treatment can be performed by a conventionally well-known method. In the chemical strengthening treatment, the glass plate is brought into contact with a melt of a metal salt (for example, potassium nitrate) containing a metal ion (typically, a K ion) having a large ionic radius by immersion or the like, thereby reducing the small ionic radius in the glass plate. Metal ions (typically Na ions or Li ions) are replaced by metal ions with large ionic radii.

Although a chemical strengthening process (ion exchange process) is not specifically limited, For example, it can perform by immersing a glass plate in molten salt, such as potassium nitrate heated to 360-600 degreeC for 0.1-500 hours. Moreover, as heating temperature of molten salt, 375-500 degreeC is preferable, and, as for the immersion time of the glass plate in molten salt, it is preferable that it is 0.3-200 hours.

Examples of the molten salt for performing the chemical strengthening treatment include nitrate, sulfate, carbonate, and chloride. Among these, lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, silver nitrate etc. are mentioned as a nitrate. Lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, silver sulfate etc. are mentioned as a sulfate. Lithium carbonate, sodium carbonate, potassium carbonate, etc. are mentioned as a carbonate. Lithium chloride, sodium chloride, potassium chloride, cesium chloride, silver chloride etc. are mentioned as a chloride. These molten salts may be used independently and may be used in combination of multiple types.

In the present invention, the treatment conditions of the chemical strengthening treatment are not particularly limited, and the properties and composition of the glass, the type of molten salt, and the surface compressive stress (CS) and the depth of the compressive stress layer (DOL) desired for the chemically strengthened glass finally obtained. ), and the like, may be selected in consideration of chemical strengthening properties, etc.

In the present invention, the chemical strengthening treatment may be performed only once, or the chemical strengthening treatment may be performed multiple times (multi-stage strengthening) under two or more different conditions. Here, for example, as the first step chemical strengthening treatment, after chemical strengthening treatment is performed under a condition in which CS is relatively low, as the second step chemical strengthening treatment, chemical strengthening treatment is performed under a condition in which CS is relatively high. , while increasing the CS of the outermost surface of the chemically strengthened glass, the internal tensile stress area (St) can be suppressed, and as a result, the internal tensile stress (CT) can be suppressed slightly lower.

The chemically strengthened glass of the present invention is particularly useful as a cover glass used for mobile devices such as mobile phones, smartphones, personal digital assistants (PDAs), and tablet terminals. In addition, the cover glass of display devices such as televisions (TVs), personal computers (PCs), and touch panels that are not intended for portability, elevator walls, wall surfaces of buildings such as houses and buildings (full-surface displays), window glass, etc. It is useful as a building material for construction materials, table tops, interiors of automobiles and airplanes, etc., as cover glass thereof, and also for applications such as housings having a curved shape instead of a plate shape by bending or molding.

[Example]

Hereinafter, although an Example demonstrates this invention, this invention is not limited by these. In addition, about each measurement result in a table|surface, a blank shows that it is unmeasured.

(Production of chemically tempered glass)

Chemically strengthened glasses of Examples S-1 to S-13, S-15 to S-29, and S-31 to S-53 shown in Tables 1 to 9, and the glasses of Examples S-14 and S-30 are described below. It was produced as

First, for Examples S-1 to S-6, S-13 to S-23, and S-30 to S-33, a glass plate is produced in a float kiln so as to have each glass composition expressed in mole percentages based on oxides shown in the table. did. Glass raw materials such as oxides, hydroxides, carbonates or nitrates were appropriately selected and melted in a melting kiln, and molded to a plate thickness of 1.1 to 1.3 mmt by a float method. The obtained plate glass was cut|disconnected and ground, and finally both surfaces were processed into mirror surfaces, and the plate glass of 50 mm long x 50 mm x plate thickness t (mm) was obtained. In addition, plate|board thickness t (mm) is shown in the table|surface.

In addition, with respect to the glasses of Examples S-7 to S-12, S-24 to S-29, and S-34 to S-53, the glass plate was converted into a platinum crucible so that each glass composition of the oxide-based molar percentage indicated in the table was obtained. Made by melting. Glass raw materials generally used, such as oxide, hydroxide, carbonate, or nitrate, were appropriately selected and weighed so as to be 1000 g as glass. Next, the mixed raw materials were put in a platinum crucible, put into a resistance heating electric furnace at 1500 to 1700° C., and melted for about 3 hours, followed by defoaming and homogenization. The obtained molten glass was poured into a shape member, held at a temperature of +50°C of the glass transition point for 1 hour, and then cooled to room temperature at a rate of 0.5°C/min to obtain a glass block. The obtained glass block was cut and ground, and finally both surfaces were mirror-finished to obtain a plate-shaped glass having a length of 50 mm x a width of 50 mm x a plate thickness of t (mm). In addition, plate|board thickness t (mm) is shown in the table|surface.

Then, chemically strengthened glass was obtained by chemically strengthening each glass of Examples S-1 to S-13, S-15 to S-29, and S-31 to S-53. The chemical strengthening treatment conditions of each glass are shown in the table.

In addition, about the glass of Examples S-14 and S-30, the chemical strengthening process was not performed.

For each chemically strengthened glass of Examples S-1 to S-13 and S-15 to S-27, the surface compressive stress CS (unit: MPa), the thickness of the compressive stress layer DOL (unit: μm), and the internal tensile stress CT (unit: MPa), compressive stress value CS at a depth of x μm from the glass surface_x(unit: MPa), the product of the compressive stress value at a depth of x μm from the glass surface and the square of the plate thickness t (mm), CS_x×t²(unit: MPa mm2), the depth d from the glass surface at which the compressive stress value is 1/2 of the surface compressive stress_h(unit: mu m) was measured with a surface stress meter FSM-6000 manufactured by Orihara Seisakusho Co., Ltd. and an attached program FsmV. For Examples S-28 to S-29 and S-31 to S-37, S-39, S-42, and S-44, the above-described birefringent imaging system Abrio-IM manufactured by Tokyo Instruments Co., Ltd. and thin slice samples were used. By technique, CS, DOL, CT, CS_x, CS_x×t², d_hwas measured. For S-38, S-40, S-41, S-43, S-45 to S-53, CS was measured with a surface stress meter FSM-6000 manufactured by Orihara Seisakusho Co., Ltd., and further, Abrio described above -DOL, CT, CS by technique using IM and lamella samples_x, CS_x×t², d_hwas measured. These results are shown in a table|surface.

In addition, for some examples, Sc value (unit: MPa·), ΔCS_100-90(Unit: MPa/), CS_DOL-20(Unit: MPa), ΔCS_DOL-20(unit: MPa/μm) is combined and shown.

In addition, for each example of Examples S-1 to S-53, X and Z values were calculated based on the composition of the glass. In addition, for each chemically strengthened glass of Examples S-1 to S-13, S-15 to S-29, and S-31 to S-53, based on the glass composition before the chemical strengthening treatment (the imitation composition of the chemically strengthened glass) Thus, X and Z values were calculated. These results are shown in a table|surface.

&lt;Devitrification temperature T&gt;

The glass before chemical strengthening was grind|pulverized, classified using the sieve of 4 mm mesh and 2 mm mesh, and after wash|cleaning with pure water, it dried and obtained cullet. 2 to 5 g of cullet is placed on a platinum plate, kept at a constant temperature for 17 hours in an electric furnace maintained at a constant temperature, taken out to the atmosphere at room temperature, cooled, and the operation of observing the presence or absence of devitrification with a polarizing microscope is repeated, The temperature T was estimated. The result is shown in Table 1. Here, the description that the devitrification temperature T is T1 to T2 means that T1 is devitrified and T2 is devitrified.

&lt;T4&gt;

For glass before chemical strengthening, the viscosity was 10 by rotational viscometer (according to ASTM C 965-96).⁴The temperature T4 used as dPa*s was measured. A result is shown in a table|surface. In addition, the numerical value attached with * is a calculated value.

&lt;Sand Drop Test&gt;

Subsequently, the following test methods for each chemically strengthened glass of Examples S-1 to S-13, S-15 to S-29, and S-31 to S-45 and the glass of Examples S-14 and S-30 was subjected to a drop test on the sand, and the average crack height (unit: mm) was measured.

Fig. 3 shows a schematic diagram showing the test method of the drop test on sand. In addition, in the description regarding the test method of the following drop test on sand, chemically strengthened glass is also described as "glass".

First, the glass 13 (50 mm × 50 mm × plate thickness t (mm)) on the hard nylon MOC plate 11 (50 mm × 50 mm × thickness 18 mm, weight: 54 g) was applied with a sponge double-sided tape ( 12) (#2310 by Sekisui Chemical Co., Ltd., 50 mm x 50 mm x thickness 3 mm) was interposed and joined, and the measurement sample 1 (total weight: 61 g) was produced. Next, 1 g of silica sand 22 (No. 5 silica sand manufactured by Takeori Co., Ltd.) is evenly spread on the SUS plate 21 of 15 cm×15 cm size, and the prepared measurement sample 1 is placed under the glass 13. It was dropped from a predetermined height (fall height) onto the surface of the SUS plate 21 on which the silica sand 22 was sprinkled. The drop test started from drop height: 10 mm, and was implemented by raising the height by 10 mm, and the height at which the glass 13 broke was made into the crack height (unit mm). The drop test was performed 5 to 10 times for each example, and the average value of the crack height in the drop test was taken as the average crack height (unit: mm). These results are shown in a table|surface.

4 shows a graph plotting the relationship between the chemically strengthened glass or glass of Examples S-1 to S-35 or the DOL (unit: μm) and the average crack height (unit: mm).

5 shows a graph plotting the relationship between the CT (unit: MPa) and the average crack height (unit: mm) of the chemically strengthened glass or glass of Examples S-1 to S-35.

In addition, among the chemically strengthened glasses of Examples S-1 to S-35 in FIG. 6 , for an example having a DOL of less than 50 μm, the relationship between the CT (unit: MPa) of the glass and the average crack height (unit: mm) was plotted. show the graph.

7 shows a graph plotting the relationship between the surface compressive stress value CS (unit: MPa) and the average crack height (unit: mm) of the chemically strengthened glass or glass of Examples S-1 to S-35. 8, the compressive stress value CS of the chemically strengthened glass or glass of Examples S-1 to S-35 at a depth of 90 µm from the glass surface₉₀A graph plotting the relationship between (unit: MPa) and average crack height (unit: mm) is shown. In addition, in FIG. 9, the compressive stress value CS of the chemically strengthened glass or glass of Examples S-1 to S-35 at a depth of 100 µm from the glass surface₁₀₀A graph plotting the relationship between (unit: MPa) and average crack height (unit: mm) is shown.

10, the compressive stress value CS of the chemically strengthened glass or glass of Examples S-1 to S-35 at a depth of 100 μm from the glass surface₁₀₀Product of (unit: MPa) and the square of plate thickness t (mm) (CS₁₀₀×t²) (unit: MPa·mm 2 ) and the average crack height (unit: mm) are plotted graphs.

<tables num="1"><img file="KR20180098473A_D0001.tif" /></tables>

<tables num="2"><img file="KR20180098473A_D0002.tif" /></tables>

<tables num="3"><img file="KR20180098473A_D0003.tif" /></tables>

<tables num="4"><img file="KR20180098473A_D0004.tif" /></tables>

<tables num="5"><img file="KR20180098473A_D0005.tif" /></tables>

<tables num="6"><img file="KR20180098473A_D0006.tif" /></tables>

<tables num="7"><img file="KR20180098473A_D0007.tif" /></tables>

<tables num="8"><img file="KR20180098473A_D0008.tif" /></tables>

<tables num="9"><img file="KR20180098473A_D0009.tif" /></tables>

From the results in Tables 1 to 9 and Figs. 4 to 6, it is understood that in the region where the DOL is around 0 to 50 µm, the average crack height tends to slightly lower as the DOL increases. In addition, in the region where the DOL is less than 50 μm, it can be seen that the average crack height tends to decrease as the CT increases. On the other hand, in the case where the DOL is 100 µm or more, it is understood that the average crack height tends to be high.

7 to 9, the average crack height has a small correlation with CS, and the internal compressive stress CS₉₀, CS₁₀₀It can be seen that the correlation with CS₉₀, CS₁₀₀When it exceeds 30 MPa and 20 MPa, respectively, the average crack height will be about 300 mm or more, and it turns out that a significant strength improvement can be achieved.

From Fig. 10, the average crack height is CS₁₀₀×t²It can be seen that the correlation with CS₁₀₀×t²When is more than 5 MPa·mm 2 , it can be seen that the average crack height is about 300 mm or more, and a significant improvement in strength can be achieved.

&lt;Indenter press fit test&gt;

For the chemically strengthened glass of Examples S-19 and Examples S-36 to S-53 having a size of 25 mm × 25 mm × plate thickness t (mm), a diamond indenter having an indenter angle of 60 degrees facing angle was used. , the chemically strengthened glass was destroyed by an indenter indentation test holding a load of 3 to 10 kgf for 15 seconds, and the number of crushing of the chemically strengthened glass after destruction was measured. These results are shown in Table 4 and Tables 7-9.

&lt;Four-point bending test after or without scratches&gt;

A glass plate having the same glass composition as in Example S-1 and having a thickness of 1.1 to 1.3 mm was produced by the float method under the same conditions as in Example S-1. The obtained plate glass was cut|disconnected and grind|ground, and finally it processed into double-sided mirror surface, and obtained the plate-shaped glass of length 5mm x width 40mm x thickness 1.0mm. Thereafter, chemical strengthening treatment was performed under the respective chemical strengthening conditions shown in the columns of Examples 4PB-1 to 4PB-6 of Table 10 to prepare each chemically strengthened glass of Examples 4PB-1 to 4PB-6.

Further, a glass block having the same glass composition as in Example S-7 was produced by melting a platinum crucible under the same conditions as in Example S-7. The obtained glass block was cut and ground, and finally both surfaces were processed to a mirror surface to obtain a plate-shaped glass having a length of 5 mm x a width of 40 mm x a thickness of 0.8 mm. Thereafter, chemical strengthening treatment was performed under the respective chemical strengthening conditions shown in the columns of Examples 4PB-7 to 4PB-9 of Table 10 below to prepare each chemically strengthened glass of Examples 4PB-7 to 4PB-9.

In addition, the strengthening temperature (unit: degreeC) in Table 10 is the temperature of the molten salt at the time of a chemical strengthening process. In addition, the salt concentration is KNO on a weight basis in the molten salt used at the time of chemical strengthening treatment.₃ratio of =(KNO₃/KNO₃+Na₂O) x 100 (unit: %). In addition, strengthening time shows the immersion time (unit: time) of the glass in molten salt.

In addition, for each chemically strengthened glass of Examples 4PB-1 to 4PB-9, the surface compressive stress (CS, unit: MPa) and the thickness of the compressive stress layer (DOL, unit: μm) were measured by Orihara Seisakusho Co., Ltd. surface stress. It was measured by the system FSM-6000 and the attached program FsmV. Further, based on the obtained CS and DOL, the internal tensile stress (CT, unit: MPa) was calculated. These results are shown in Table 10 and Table 11.

<tables num="10"><img file="KR20180098473A_D0010.tif" /></tables>

For each chemically strengthened glass of Examples 4PB-1 to 4PB-9, a diamond indenter (indenter angle of facing angle: 110°) was pressed for 15 seconds with a load of 0.5Kgf, 1Kgf, 1.5Kgf, or 2Kgf, to prevent scratches on the glass surface. paid Next, a four-point bending test was performed under the conditions of a lower span of 30 mm, an upper span of 10 mm, and a crosshead speed of 0.5 mm/min, and the breaking stress (MPa) in each scratching condition was measured. Table 11 shows the breaking stress values (bending strength, unit: MPa) in the case of not making a scratch and performing a four-point bending test at the time of each indenter press-in load. In Fig. 11, (a) to (i) respectively show test results for each chemically strengthened glass of Examples 4PB-1 to 4PB-9.

<tables num="11"><img file="KR20180098473A_D0011.tif" /></tables>

Fig. 12 shows a plot of the relationship between the breaking strength and CS when no scratches are made. From FIG. 12 , it can be seen that, when CS is 300 MPa or more, the breaking strength when not scratched can achieve 350 MPa or more. When a smartphone or a tablet PC is dropped, a tensile stress is generated on the surface of the cover glass, and the size thereof reaches about 350 MPa. For this reason, it is preferable that CS is 300 MPa or more. Fig. 13 shows a plot of the relationship between the breaking strength and DOL at the time of making a 2 kgf flaw in Examples 4PB-1 to 4PB-9. In chemically strengthened glass having a DOL of 100 µm or more, the breaking strength is 200 MPa or more even after being scratched with 2 kgf by a diamond indenter (indenter angle of facing angle: 110°), and even after scratching with a higher load, higher It maintains breaking strength, and it appears that it has higher reliability as a cover glass even in the state with a flaw, for example. DOL becomes like this. Preferably it is 100 micrometers or more, More preferably, it is 110 micrometers or more, More preferably, it is 120 micrometers or more, Especially preferably, it is 130 micrometers or more.

From the above results, CS₉₀, CS₁₀₀ and CS₁₀₀×t²It can be seen that when each of more than 30 MPa, more than 20 MPa, and more than 5 MPa · mm 2 , a clear strength improvement can be achieved for the drop test on sand. Also, CS₉₀, CS₁₀₀ and CS₁₀₀×t²It can be seen that, when each of more than 50 MPa, more than 30 MPa, and more than 7 MPa · mm 2 , a significant strength improvement can be achieved for the drop test on sand. Further, it can be seen that, when CS is more than 300 MPa, the breaking strength sufficiently exceeds 350 MPa, and sufficient breaking strength can be achieved as a cover glass.

14 shows the stress profile of a hypothetical chemically strengthened glass having a plate thickness of 1 mm. In addition, Table 12 shows CS, DOL, CT, Sc, and St of each profile. The reinforcement profiles of FIGS. 14 and 12 are prepared by the following formula.

F(x)=α+ERFC(β×x)-CT

Also, x is the depth from the glass surface, and the function ERFC(c) is the complementary error function. The values of the constants α and β are shown in Table 12.

<tables num="12"><img file="KR20180098473A_D0012.tif" /></tables>

Chemically strengthened glass having these profiles is expected to achieve high strength with respect to the drop test on sand and cross-sectional bending, from the above results. Higher CS values and higher CS₉₀, CS₁₀₀The more chemically strengthened glass introduced, the higher the strength is expected, and from Table 12, it can be seen that the Sc value of the chemically strengthened glass of the present invention is about 30000 MPa· or more. In this case, the St value is the same as the Sc value as described above. If breakage occurs, it is desirable for the glass to break more safely, and for this purpose, the St Limit value to be described later is preferably a larger value.

&lt;Relationship between X, Y, and Z values and the number of fractures of glass&gt;

In order to evaluate the relationship between the glass composition and the friability of chemically strengthened glass, chemically strengthened glasses having various St values under various chemical strengthening conditions were prepared, and the relationship between the number of fractures at break and the St value was investigated. Specifically, for glass of 25 mm × 25 mm × thickness t (mm), chemical strengthening treatment is performed under various chemical strengthening treatment conditions so that the internal tensile stress area (St; unit MPa·) is changed, and various internal tensile stress areas A chemically strengthened glass having (St; unit MPa·) was produced. Then, the internal tensile stress area (St; unit MPa·) in which the number of fractures was 10 was defined as the St Limit value, and the internal tensile stress CT (unit: MPa) in which the number of fractures was 10 was defined as the CT Limit value. When the number of fractures exceeds 10, the St Limit value is calculated by the following formula using the Stn value, which is the St value of the maximum number of fractures n, which is less than 10, and the Stm value, which is the St value, of the minimum number of fractures, m, that exceeds 10. stipulated.

St Limit value=Stn+(10-n)×(Stm-Stn)/(mn)

In addition, when the number of fractures exceeds 10, using the CTn value, which is the CT value of the maximum number of fractures n, which is less than 10, and the CTm value, which is the CT value of the minimum number of fractures, m, which is more than 10, the CT Limit by the following formula Values were defined.

CT Limit value=CTn+(10-n)×(CTm-CTn)/(mn)

Incidentally, the St value and the CT value are measured with a surface stress meter FSM-6000 manufactured by Orihara Seisakusho Co., Ltd. and analyzed by the attached program FsmV._F, CT_F or the value St obtained by measurement using the birefringent imaging system Abrio-IM and flaked samples._A, CT_Ais defined as follows using

St=St_F=1.515×St_A

CT = CT_F=1.28×CT_A

Here, CT_Fis a value equivalent to CT_CV, which is interpreted as FsmV.

15 and Table 13 show examples of measurement when t is 1 mm. Fig. 15 shows an example of measurement of St Limit and CT Limit, (a) is a graph showing the relationship between the area St (MPa·) of the internal tensile stress layer and the number of fractures when the plate thickness (t) is 1 mm and (b) is an enlarged view of the portion surrounded by the dotted line in (a). In addition, (c) is a graph showing the relationship between the internal tensile stress CT (MPa) and the number of fractures when the plate thickness (t) is 1 mm, (d) is an enlarged view of the portion surrounded by the dotted line in (c) . StL10 of (b) and CTL10 of (d) respectively represent an internal tensile stress area (St; unit MPa·) and internal tensile stress (CT; unit MPa) when the number of fractures becomes 10.

<tables num="13"><img file="KR20180098473A_D0013.tif" /></tables>

Glass with a larger St Limit value or CT Limit value is a glass with improved friability. In addition, the St Limit value and the CT Limit value are indicators for indicating the degree of friability, and do not prescribe the allowable limit of the crushing mode.

It carried out similarly to the said method, and calculated|required the St limit value. It is shown in Tables 14-15.

For glass before chemical strengthening, Young's modulus E (unit: GPa), fracture toughness value K1c (unit: MPa·m by DCDC method)^1/2) are shown together in Tables 14 to 15.

In addition, the Young's modulus E was measured by the ultrasonic pulse method (JIS R1602).

In addition, fracture toughness values were obtained from MY He, MR Turner and AG Evans, Acta Metall. Mater. 43 (1995) 3453., by the DCDC method, using a sample of the shape shown in FIG. 16 and Tensilon UTA-5kN manufactured by Orientec Co., Ltd., as shown in FIG. 17, stress expansion Coefficient K1 (unit: MPa m^1/2) and the crack propagation rate v (unit: m/s), measure the K1-v curve, regress and extrapolate the obtained RegionIII data to a linear equation, and calculate the fracture toughness as the stress intensity factor K1 of 0.1 m/s. It was taken as the value K1c.

For each of Examples CT-1 to CT-27, X, Y, and Z values were calculated from the following formulas based on the composition of the glass before chemical strengthening (imitation of chemically strengthened glass). These results are shown in Tables 14-15.

X=SiO₂×329+Al₂O₃×786+B₂O₃×627+P₂O₅×(-941)+Li₂O×927+Na₂O×47.5+K₂O×(-371)+MgO×1230+CaO×1154+SrO×733+ZrO₂×51.8

Y=SiO₂×0.00884+Al₂O₃×0.0120+B₂O₃×(-0.00373)+P₂O₅×0.000681+Li₂O x 0.00735 + Na₂O×(-0.00234)+K₂O×(-0.00608)+MgO×0.0105+CaO×0.00789+SrO×0.00752+BaO×0.00472+ZrO₂×0.0202

Z=SiO₂×237+Al₂O₃×524+B₂O₃×228+P₂O₅×(-756)+Li₂O×538+Na₂O×44.2+K₂O×(-387)+MgO×660+CaO×569+SrO×291+ZrO₂×510

For the chemically strengthened glasses of Examples CT-1, CT-5, CT-7 to CT-12, CT-14 to CT-19, and CT-21 to CT-24, the St Limit when the thickness t is 1 mm and A graph plotting the relationship between X values is shown in FIG. 18, a graph plotting the relationship between St Limit and Z value when thickness t is 1 mm is shown in FIG. 19, and St Limit and Young's modulus when thickness t is 1 mm are shown in FIG. A graph plotting the relationship is shown in FIG. 20, and a graph plotting the relationship between the X value and the Z value is shown in FIG. 21, respectively.

<tables num="14"><img file="KR20180098473A_D0014.tif" /></tables>

<tables num="15"><img file="KR20180098473A_D0015.tif" /></tables>

From the results in Tables 14 to 15 and FIGS. 18 to 21, it can be seen that the X value and Z value and the St Limit at 1 mm are correlated with high precision, and are parameters indicating the friability at the time of chemically strengthened glass breakage with high precision. have. In addition, it was found that the greater the X value and the Z value, the greater the St Limit. Here, as the St Limit of the chemically strengthened glass increases, even if the chemically strengthened glass is destroyed, it is shown that the number of fractures is small and a safer fracture is achieved. For example, if the X value and the Z value are 30000 or more and 20000 or more chemically strengthened glass, respectively, the St Limit is greater than 30000 MPa, for example, as described above, Sc or St is 30000 MPa or more, 1 mm high-strength chemical strengthening Also in the example of glass, it can be said that more safety|safety glass can be implement|achieved with sufficiently few crushing numbers at the time of the breakage of glass.

Glasses were prepared as follows so that each glass composition expressed in mole percentages based on oxides shown in Examples 2-1 to 2-53 of Tables 16 to 20 was obtained. Glass raw materials generally used, such as oxide, hydroxide, carbonate, or nitrate, were appropriately selected and weighed so as to be 1000 g as glass. Then, the mixed raw materials were put in a platinum crucible, put into a resistance heating electric furnace at 1500 to 1700° C., melted for about 3 hours, defoamed, and homogenized. The obtained molten glass was poured into a shape member, held at a temperature of +50°C of the glass transition point for 1 hour, and then cooled to room temperature at a rate of 0.5°C/min to obtain a glass block. The obtained glass block was cut, ground and polished, and the following measurement was performed.

The density measurement was performed by the in-liquid weighing method (Method for measuring the density and specific gravity of JIS Z8807 solid).

The linear expansion coefficient α and the glass transition point Tg were measured according to the method of JIS R3102 "Test method for average coefficient of linear expansion of glass".

Young's modulus E, synthesis modulus G, and Poisson's ratio were measured by ultrasonic pulse method (JIS R1602).

In addition, an X value, a Y value, and a Z value are shown about Examples 2-1 to 2-53.

Moreover, while estimating loss-of-clarity temperature T similarly to the above, a viscosity is 10⁴The temperature T4 used as dPa*s was measured.

These results are shown in Tables 16-20.

Also, the examples described in Example 2-51 are examples described in the specification of US Patent Application Publication No. 2015/0259244.

For Examples 2-1, 2-3 to 2-50, and 2-52, the X value is 30000 or more, and even when larger CS and DOL are introduced, the number of fractures at the time of glass breakage is sufficiently small. is an example that can be realized. On the other hand, in Example 2-2 and Example 2-51, the value of X is 30000 or less.

For Examples 2-1, 2-3 to 2-50, and 2-52, the Z value is 20000 or more, and even when larger CS and DOL are introduced, the number of fractures at the time of glass breakage is sufficiently small. is an example that can be realized. On the other hand, in Example 2-2 and Example 2-51, the Z value is 20000 or less.

<tables num="16"><img file="KR20180098473A_D0016.tif" /></tables>

<tables num="17"><img file="KR20180098473A_D0017.tif" /></tables>

<tables num="18"><img file="KR20180098473A_D0018.tif" /></tables>

<tables num="19"><img file="KR20180098473A_D0019.tif" /></tables>

<tables num="20"><img file="KR20180098473A_D0020.tif" /></tables>

&lt;Relationship between glass plate thickness, St, CT, and the number of glass fractures&gt;

In order to evaluate the relationship between the glass plate thickness and the friability of chemically strengthened glass, chemically strengthened glass with various St values and CT values was produced by various compositions and chemical strengthening conditions, and the plate thickness at breakage, the number of fractures, and the St value and CT values were investigated. Specifically, for glass of 25 mm × 25 mm × thickness t (mm), various chemical strengthening treatments such that the internal tensile stress area (St; unit MPa·) or internal tensile stress CT (unit: MPa) is changed Chemical strengthening treatment was performed under the conditions, and chemically strengthened glass having various internal tensile stress areas (St; unit MPa·μm) or internal tensile stress CT (unit: MPa) was produced. Then, using a diamond indenter having an indenter angle of 60 degrees facing angle, each of these chemically strengthened glasses is destroyed by an indenter indentation test holding a load of 3 kgf for 15 seconds, and the number of glass fragments after breaking (the number of fractures) ) were measured respectively. Then, the internal tensile stress area (St; unit MPa·) in which the number of fractures was 10 was defined as the St Limit value, and the internal tensile stress CT (unit: MPa) in which the number of fractures was 10 was defined as the CT Limit value. When the number of crushing exceeds 10, the St Limit value is calculated by the following formula using the Stn value, which is the St value of the maximum number of fractures n, which is less than 10, and the Stm value, which is the St value, of the minimum number of fractures, m, that exceeds 10. stipulated.

St Limit value=Stn+(10-n)×(Stm-Stn)/(mn)

In addition, when the number of fractures exceeds 10, using the CTn value, which is the CT value of the maximum number of fractures n, which is less than 10, and the CTm value, which is the CT value of the minimum number of fractures, m, which is more than 10, the CT Limit by the following formula Values were defined.

CT Limit value=CTn+(10-n)×(CTm-CTn)/(mn)

In addition, St value and CT value are the values St measured by the surface stress meter FSM-6000 manufactured by Orihara Seisakusho and analyzed by the attached program FsmV._F, CT_F or the value St obtained by measurement using the birefringent imaging system Abrio-IM and flaked samples._A, CT_Ais defined as follows using

St=St_F=1.515×St_A

CT = CT_F=1.28×CT_A

Here, CT_Fis a value equivalent to CT_CV, which is interpreted as FsmV.

Tables 21 and 22 show the values of St Limit and CT Limit for each chemically strengthened glass and sheet thickness of Examples CT-5, CT-16, CT-17 and CT-26. 22 and 23 are diagrams in which the ST Limit and CT Limit of each chemically strengthened glass of Examples CT-5, CT-16, CT-17 and CT-26 are plotted against the plate thickness t (mm), respectively. .

From Table 21 and FIG. 22, it can be seen that the St Limit tends to increase linearly with respect to the plate thickness, and is approximated by the following equation.

St(a, t)=a×t+7000 (unit: MPa μm)

In addition, it can be seen that the constant a in the above formula changes depending on the chemically strengthened glass. Here, the larger the value of a, the larger the ST Limit in each plate thickness, and even if larger CS and DOL are introduced, it can be used as chemically strengthened glass with a smaller number of crushing.

From Table 22 and FIG. 23, it can be seen that the CT Limit tends to decrease with increasing plate thickness, and is approximated by the following equation.

CT(b, c, t)=-b×ln(t)+c (unit: MPa)

In addition, it can be seen that the constants b and c in the above formula change depending on the chemically strengthened glass, and b tends to monotonically increase with respect to c. 23 , the larger the values of b and c, the larger the CT Limit in each plate thickness, and even if larger CS and DOL are introduced, it can be used as chemically strengthened glass with a smaller number of fractures.

<tables num="21"><img file="KR20180098473A_D0021.tif" /></tables>

<tables num="22"><img file="KR20180098473A_D0022.tif" /></tables>

Although this invention was demonstrated in detail with reference to the specific form, it is clear for those skilled in the art that various changes and correction are possible without departing from the mind and range of this invention.

In addition, this application is a Japanese patent application filed on January 21, 2016 (Patent Application No. 2016-01002) and a Japanese Patent Application filed on October 18, 2016 (Patent Application No. 2016-204745) It is based on, and is incorporated by reference in its entirety.

1: measurement sample 11: MOC Edition 12: Sponge double-sided tape 13: glass 21: SUS version 22: quartz sand