WO2025254111A1 - Chemically strengthened glass, crystallized glass, and glass - Google Patents

Abstract

The present invention relates to a chemically strengthened glass which is a crystallized glass, wherein the composition of the central part in the thickness direction contains, in molar percentages in terms of oxides, 62-75% of SiO₂, 2.2-6.0% of Al₂O₃, more than 0% and not more than 3% of P₂O₅, 20-27% of Li₂O, more than 0% and not more than 5% of Na₂O, 0-1% of K₂O, 0-2% of MgO, 0-2% of CaO, 0-1% of SrO, 1-4.2% of ZrO₂, 0-1% of SnO₂, and substantially no Y₂O₃, while satisfying {[K₂O]/[Na₂O]} is 0-0.3 and[{[Al₂O₃}]/[ZrO₂]} - {[B₂O₃]/[P₂O₅]}] is 0.5-1.5.

Description

Chemically strengthened glass, crystallized glass, and glass

The present invention relates to chemically strengthened glass, crystallized glass, and glass.

BACKGROUND ART Thin, high-strength chemically strengthened glass is used as a cover glass for displays of electronic devices such as mobile phones and smartphones.
Chemically strengthened glass is glass that has been brought into contact with a molten salt composition such as sodium nitrate to cause ion exchange between alkali metal ions contained in the glass and alkali metal ions with a larger ionic radius contained in the molten salt composition, thereby forming a compressive stress layer from the surface to the interior of the glass.

Among electronic device housings that use chemically strengthened glass as the cover glass, mobile devices in particular require the cover glass to be resistant to shatter when the housing is dropped from hand to the floor. To evaluate this shatter resistance, a "drop strength test" is used, in which the electronic device housing or a simulated structure is allowed to fall freely and the height at which it breaks is evaluated.

In Patent Document 1, in order to increase the strength measured by the drop strength test in chemically strengthened glass, the compressive stress value CS ₅₀ at a depth of 50 μm from the glass surface and the compressive stress value CS ₉₀ at a depth of 90 μm are considered important.

In addition, it is known that increasing the fracture toughness value K1c of glass can increase the strength measured in glass drop strength tests, and glass ceramics with a crystalline phase are known to have a high fracture toughness value.

As examples of glass-ceramics, Patent Document 2 discloses glass-ceramics having a fracture toughness value K1c of 1.13 MPa·m ^1/2 or more and containing lithium disilicate crystals as a crystalline phase. Patent Document 3 also discloses glass-ceramics that satisfy a specific composition range and have a fracture toughness value K1c of more than 1.0 MPa·m ^1/2 .

International Publication No. 2013/243574 Chinese Patent Application Publication No. 118771728 Chinese Patent Application Publication No. 118834018

As described in Patent Document 1, drop strength tests have previously been conducted by freely dropping electronic device housings or simulated structures onto #80 sandpaper or #180 sandpaper. This is because #80 and #180 have been used as sandpaper grits, taking into account that the coarser the grit of the sandpaper, i.e., the smaller the grit number, the lower the crack height.

In contrast to this, in recent years, attention has begun to be paid to evaluation of the results when an electronic device housing or a simulated structure thereof is allowed to fall freely onto sandpaper of a coarser grit, #60.
It was also found that glass that exhibits high strength when dropped onto #80 sandpaper or #180 sandpaper does not necessarily exhibit high strength when dropped onto #60 sandpaper.

Therefore, an object of the present invention is to provide chemically strengthened glass having high strength characteristics in a #60 sandpaper set drop strength test.
Another object of the present invention is to provide glass-ceramics before chemical strengthening treatment that can be made into chemically strengthened glass having the above-mentioned properties, and glass before crystallization treatment that can be made into the above-mentioned glass-ceramics.

The #60 sandpaper set drop strength test produces deeper cracks than the #80 sandpaper set drop strength test and the #180 sandpaper set drop strength test, and is therefore a test under more severe conditions. As mentioned above, in the #180 sandpaper set drop strength test and the #80 sandpaper set drop strength test, it has been considered important to have a large _CS50 and _CS90 , respectively.

Based on this idea, it is estimated that in the #60 sandpaper set drop strength test, it is important to increase the compressive stress value at a depth of more than 90 nm from the glass surface.

However, in order to increase the compressive stress value at deeper positions, it is necessary to increase the overall compressive stress applied to the glass, which in turn increases the tensile stress applied to the glass, causing fragments to fly violently when the glass shatters.

In response to this, the inventors conducted extensive research and discovered that the above problem can be solved by using crystallized glass that has a high fracture toughness value K1c and that has a small tensile stress value CT due to chemical strengthening treatment, and thus completed the present invention.
Based on previous findings, it was predicted that glass that exhibits excellent results in a #60 sandpaper set drop strength test would have a high compressive stress value, i.e., a high tensile stress value corresponding to the high compressive stress value. However, the present invention surprisingly found that the above-mentioned problem can be solved by using the opposite, a low tensile stress value.

That is, the gist of this embodiment relates to the following.
[1] A crystallized glass having a crystalline phase,
The composition of the center of the thickness direction is expressed as mole percentage based on oxides:
SiO ₂ 62-75%,
Al ₂ O ₃ 2.2-6.0%,
P ₂ O ₅ more than 0% and less than 3%,
Li ₂ O 20-27%,
Na ₂ O more than 0% and less than 5%,
K ₂ O 0-1%,
MgO 0-2%,
CaO 0-2%,
SrO 0-1%,
ZrO ₂ 1 to 4.2%, and SnO ₂ 0 to 1%,
Substantially does not contain Y ₂ O ₃ ,
Using the content ratio of K ₂ O and Na ₂ O expressed in mole percentage, the value represented by {[K ₂ O]/[Na ₂ O]} is 0 to 0.3;
A chemically strengthened glass in _which the value represented by [{[Al ₂ O ₃ ]/[ZrO _{2 ]}-{[B 2 O 3 ]/[P 2 O 5 ]}] is 0.5 to 1.5, using the contents of Al 2 O 3 , ZrO 2 , B} 2 O 3 and P ₂ O ₅ expressed in mole percentage.
[2] A crystallized glass having a crystalline phase,
The composition of the center of the thickness direction is expressed as mole percentage based on oxides:
SiO ₂ 62-75%,
Al ₂ O ₃ 2.2-6.0%,
Li ₂ O 20-27% and ZrO ₂ 1-4.2%,
Chemically strengthened glass having an average tensile stress value CT _ave of 60 MPa or less, calculated by {I _CT /L _CT } using the tensile stress integral value I _CT (MPa·μm) and the thickness direction length L _CT (μm) of the tensile stress region.
[3] The average value CT ave of the tensile stress calculated by {I _CT /L _CT } using the tensile stress integral value I _CT (MPa · μm) and the plate thickness direction length L _CT (μm) of the tensile stress _region is 60 MPa or less. The chemically strengthened glass according to [1].
[4] The crystalline phase comprises at least one crystal selected from the group consisting of Li ₂ Si ₂ O ₅ , LiAlSi ₂ O ₆ , LiAlSi ₄ O ₁₀ , Li ₃ PO ₄ , and β-quartz solid solution. Chemically strengthened glass according to any one of [1] to [3].
[5] The chemically strengthened glass according to any one of [1] to [4], having a fracture toughness value K1c of 1.3 MPa · m ^{1 / 2} or more.
[6] The chemically strengthened glass according to any one of [1] to [5], wherein the compressive stress value CS ₅₀ at a depth of 50 μm from the surface is 220 MPa or less.
[7] The chemically strengthened glass according to any one of [1] to [6], wherein the compressive stress value CS ₁₅₀ at a depth of 150 μm from the surface is −100 MPa or more.
[8] The chemically strengthened glass according to any one of [1] to [7], wherein the value of Y represented by the following formula is 10 or more.
Y=0.1×α−0.05×CT _ave
α=200×K1c-100
CT _ave =I _CT /L _CT
I _CT : Integrated value of tensile stress (MPa μm)
_LCT : Length of tensile stress area in the thickness direction (μm)
K1c: fracture toughness value (MPa·m ^1/2 )
[9] The chemically strengthened glass according to any one of [1] to [8], wherein the depth K-DOL from the surface of the compressive stress layer by K ions is 3 μm or more.
[10] The chemically strengthened glass according to any one of [1] to [9], wherein the compressive stress layer depth DOL is 100 μm or more.
[11] When the glass thickness is t (μm), the compressive stress layer depth DOL is {t × 0.15} μm or more. Chemically strengthened glass according to any one of [1] to [10].
[12] The Na ion concentration [Na] ₁₀₀ at a depth of 100 μm from the surface is 2.5 mol% or more;
The chemically strengthened glass according to any one of [1] to [11], wherein a compressive stress value CS ₁₀₀ at a depth of 100 μm from the surface is 30 MPa or less.
[13] Using the Na ion concentration [Na] ₁₀₀ at a depth of 100 μm from the surface and the Na ion concentration [Na] ₅₀ at a depth of 50 μm from the surface, the ratio represented by {[Na] ₅₀ /[Na] ₁₀₀ } is 1.4 or less. [14] The chemically strengthened glass according to any one of [1] to [12].
[14] The chemically strengthened glass according to any one of [1] to [13], wherein the compressive stress value _CS0 at the outermost surface is 300 to 700 MPa.
[15] The chemically strengthened glass according to any one of [1] to [14], having a Young's modulus of 105 GPa or more.
[16] The chemically strengthened glass according to any one of [1] to [15], wherein the average crack height measured by a sandpaper set drop strength test under the following conditions is 40 cm or more.
(conditions)
The test specimen is an electronic device equipped with chemically strengthened glass, or an electronic device simulation structure that integrates chemically strengthened glass with a housing that holds the chemically strengthened glass. The drop test is performed by dropping the test specimen onto #60 sandpaper with the chemically strengthened glass facing downward. The test specimen is dropped from a height of 15 cm. If the chemically strengthened glass in the test specimen does not break upon dropping, the drop height is increased by 5 cm and the process is repeated. The height at which the chemically strengthened glass in the test specimen first breaks is defined as the crack height. The drop test is performed on 10 test specimens, and the average of the crack heights is defined as the average crack height.
[17] The chemically strengthened glass according to any one of [1] to [ ₁₆ ], wherein the value represented by {[Al ₂ O ₃ ]/[Na ₂ O]}, using the content ratios of Al ₂ O ₃ and Na 2 O expressed in mole percentage, is greater than 0 and 2.3 or less.
[18] The chemically strengthened glass according to any one of [1] to [17], wherein the value represented by {[Li ₂ O] / [ZrO ₂ ]} is 8 or more, using the content ratio of Li _{2 O} and ZrO 2 expressed in mole percentage.
[19] The chemically strengthened glass according to any one of [1] to [18], wherein the crystallization rate is 40% by mass or more.
[20] The chemically strengthened glass according to any one of [1] to [19], wherein the average particle size of the crystals constituting the crystalline phase is 10 to 100 nm.
[21] The chemically strengthened glass according to any one of [1] to [20], wherein the transmittance of light having a wavelength of 600 nm is 80% or more when converted into a thickness of 0.6 mm.

[22] A crystallized glass having a crystalline phase,
The composition is expressed as mole percentage based on oxides.
SiO ₂ 62-75%,
Al ₂ O ₃ 2.2-6.0%,
P ₂ O ₅ more than 0% and less than 3%,
Li ₂ O 20-27%,
Na ₂ O more than 0% and less than 5%,
K ₂ O 0-1%,
MgO 0-2%,
CaO 0-2%,
SrO 0-1%,
ZrO ₂ 1 to 4.2%, and SnO ₂ 0 to 1%,
Substantially does not contain Y ₂ O ₃ ,
Using the content ratio of K ₂ O and Na ₂ O expressed in mole percentage, the value represented by {[K ₂ O]/[Na ₂ O]} is 0 to 0.3;
A crystallized glass having a value of 0.5 to 1.5, where the content ratios of Al ₂ O ₃ , ZrO ₂ , B ₂ O ₃ and P ₂ O ₅ are expressed in mole percentage, that is, [{[Al ₂ O ₃ ]/[ZrO ₂ ]}-{[B ₂ O ₃ ]/[P ₂ O ₅ ]}].
[23] The crystallized glass according to [22], wherein the crystalline phase contains at least one crystal selected from the group consisting of Li ₂ Si ₂ O ₅ , LiAlSi ₂ O ₆ , LiAlSi ₄ O ₁₀ , Li ₃ PO ₄ , and β-quartz solid solution.
[24] The crystallized glass according to [22] or [23] above, having a fracture toughness value K1c of 1.2 MPa·m ^1/2 or more.
[25] The crystallized glass according to any one of [22] to [24] above, having a Young's modulus of 105 GPa or more.
[26] The crystallized glass according to any one of the above [ ₂₂ ] to [ ₂₅ ], wherein the value represented by {[Al ₂ O ₃ ]/[Na ₂ O]} is greater than 0 and 0.23 or less, using the content ratio of Al 2 O ₃ and Na 2 O expressed in mole percentage.
[27] The crystallized glass according to any one of [22] to [26], wherein the value represented by {[Li ₂ O]/[ZrO ₂ ]} is 8 or more, using the content ratio of Li _{2 O} and ZrO 2 expressed in mole percentage.
[28] The crystallized glass according to any one of [22] to [27], wherein the crystallization rate is 40 mass % or more.
[29] The crystallized glass according to any one of [22] to [28], wherein the average grain size of the crystals constituting the crystalline phase is 10 to 100 nm.
[30] The crystallized glass according to any one of [22] to [29] above, which has a transmittance of 80% or more for light with a wavelength of 600 nm when converted into a glass with a thickness of 0.6 mm.

[31] The composition is expressed in mole percentage based on oxides:
SiO ₂ 62-75%,
Al ₂ O ₃ 2.2-6.0%,
P ₂ O ₅ more than 0% and less than 3%,
Li ₂ O 20-27%,
Na ₂ O more than 0% and less than 5%,
K ₂ O 0-1%,
MgO 0-2%,
CaO 0-2%,
SrO 0-1%,
ZrO ₂ 1 to 4.2%, and SnO ₂ 0 to 1%,
Substantially does not contain Y ₂ O ₃ ,
Using the content ratio of K ₂ O and Na ₂ O expressed in mole percentage, the value represented by {[K ₂ O]/[Na ₂ O]} is 0 to 0.3;
A glass in which the value represented by [{[Al ₂ O _{3 ]} /[ZrO _{2 ]}-{[B 2 O 3 ] /} [P ₂ O ₅ ]}], where the content ratios of Al ₂ O ₃ , ZrO ₂ , B 2 O 3 and P ₂ O ₅ are expressed in mole percentage _, is 0.5 to 1.5.
[32] The glass according to [31] above, wherein the value represented by {[Al ₂ O ₃ ]/[Na ₂ O]}, using the content ratios of Al ₂ O ₃ and Na ₂ O expressed in mole percentage, is greater than 0 and not greater than 0.23.
[33] The glass according to [31] or [32], wherein the value represented by {[Li ₂ O]/[ZrO ₂ ]}, using the content ratio of Li ₂ O and ZrO ₂ expressed in mole percentage, is 8 or more.

According to the present invention, chemically strengthened glass can be obtained that exhibits high strength characteristics in a #60 sandpaper set drop strength test. Furthermore, it is possible to obtain crystallized glass that becomes chemically strengthened glass with the above characteristics when subjected to chemical strengthening treatment, and glass that becomes the above crystallized glass when subjected to crystallization treatment.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the embodiments described below.
In this specification, the term "to" indicating a range of values is used to mean that the values before and after it are included as the lower and upper limits. Furthermore, in this specification, "mass %" and "wt %" and "parts by mass" and "parts by weight" have the same meaning.

In this specification, the composition of the center of the chemically strengthened glass in the thickness direction is the same as the composition of the glass before chemical strengthening treatment, and except in cases where extreme ion exchange treatment has been performed, the glass composition deeper than the compressive stress layer depth DOL of the chemically strengthened glass can be considered to be the same as the composition of the center of the chemically strengthened glass in the thickness direction. Also, in this specification, the composition of the crystallized glass is the same as the composition of the amorphous glass (mother glass) before crystals are precipitated.
In other words, the composition of the amorphous glass before crystallization, the composition of the crystallized glass after the crystallization treatment, and the composition of the center of the thickness direction of the chemically strengthened glass after the above-mentioned crystallized glass has been further subjected to a chemical strengthening treatment can all be considered to be the same.
Regarding glass-ceramics, the composition of the glass before crystallization and the composition of the amorphous phase (residual glass phase) in the glass-ceramics are strictly different. The composition of the amorphous phase in the glass-ceramics is determined from the composition of the glass-ceramics and the composition and content of the crystalline phase.

Chemically strengthened glass
The chemically strengthened glass according to this embodiment is a crystallized glass having a crystalline phase, that is, a crystallized glass having an ion-exchanged compressive stress layer on its surface by undergoing a chemical strengthening treatment.

As a first aspect of the chemically strengthened glass according to this embodiment, the composition of the center portion in the thickness direction satisfies the following in terms of mole percentage based on oxides.
SiO ₂ 62-75%,
Al ₂ O ₃ 2.2-6.0%,
Li ₂ O 20 to 27%, and ZrO ₂ 1 to 4.2%.

In addition to the above, the first aspect of the chemically strengthened glass according to this embodiment has an average tensile stress CT _ave of 60 MPa or less, calculated by {I _CT /L _CT } using the tensile stress integral I _CT (MPa·μm) and the thickness direction length L _CT (μm) of the tensile stress region.

In a second aspect of the chemically strengthened glass according to this embodiment, the composition at the center in the thickness direction satisfies the following in terms of mole percentage based on oxides.
SiO ₂ 62-75%,
Al ₂ O ₃ 2.2-6.0%,
P ₂ O ₅ more than 0% and less than 3%,
Li ₂ O 20-27%,
Na ₂ O more than 0% and less than 5%,
K ₂ O 0-1%,
MgO 0-2%,
CaO 0-2%,
SrO 0-1%,
ZrO ₂ 1-4.2%,
SnO ₂ 0-1%; and
_It contains substantially no _Y2O3 .

In addition to the above, in the second aspect of the chemically strengthened glass according to the present embodiment, in the composition at the center in the thickness direction, using the content ratios of K ₂ O and Na ₂ O expressed in mole percentage, the value represented by {[K ₂ O] / [Na ₂ O]} is 0 to 0.3, and using the content ratios of Al ₂ O ₃ , ZrO ₂ , B ₂ O ₃ and P ₂ O ₅ expressed in mole percentage, the value represented by [{[Al ₂ O ₃ ] / [ZrO ₂ ]} - {[B ₂ O ₃ ] / [P ₂ O ₅ ]}] is 0.5 to 1.5.

The present invention has discovered that in order to have high strength characteristics in a #60 sandpaper set drop strength test, it is important to use chemically strengthened crystallized glass that has a high fracture toughness value K1c and a low average tensile stress value CT _ave .
As mentioned above, based on previous findings, it was predicted that glass that excels in the #60 sandpaper set drop strength test would be glass with a high compressive stress value, i.e., glass with a high tensile stress value corresponding to a high compressive stress value. However, the present invention surprisingly achieved the opposite: that is, that the above-mentioned problem can be solved by a low tensile stress value.

First, in the #60 sandpaper set drop strength test, a part of the glass comes into contact with the abrasive grains of the sandpaper simulating a floor surface, causing a crack. The crack then propagates from that point. It is presumed that the propagation of the crack depends on whether the tensile stress at the tip of the crack is sufficient to counter the energy required for the crack to propagate. In actual drop strength tests, the glass does not break the instant it comes into contact with the sandpaper; rather, the crack propagates as the glass is bent when it bounces off the sandpaper. However, strictly speaking, cracks caused by contact with the sandpaper and crack propagation caused by bending stress cannot be separated, so variability remains. Therefore, in this specification, the average crack height measured in the #60 sandpaper set drop strength test using 10 test specimens is used to indicate the strength characteristics of the #60 sandpaper set drop strength test.

In order to solve the above problem, the fracture toughness value K1c is examined. The fracture toughness value K1c is a value proportional to the Young's modulus and the surface energy.
Young's modulus reflects the properties of the glass-ceramic itself, and the surface energy is thought to be significantly affected by chemical strengthening in addition to the properties of the glass-ceramic itself.
Therefore, in this embodiment, the presence of crystalline phase increases the Young's modulus of the glass, resulting in high rigidity and small bending. As a result, the concentrated stress at the crack tip is reduced, which is thought to be one of the reasons for the excellent strength in the #60 sandpaper set drop strength test. In addition, in order to achieve a high Young's modulus, it is important to use crystallized glass with a crystalline phase. Among them, for example, lithium disilicate (lithium disilicate, Li ₂ Si ₂ O ₅ ) crystals and petalite (LiAlSi ₄ O ₁₀ ) crystals are suitable as the crystalline phase.

Furthermore, because the chemically strengthened glass according to this embodiment is glass-ceramic, the presence of grain boundaries due to the crystals and cleavage planes resulting from the crystal structure inhibit the propagation of cracks. As a result, more energy is required for crack propagation than in amorphous glass. Therefore, by optimizing the crystallization rate of the glass-ceramic, the average particle size of the crystals that make up the crystalline phase, the type of crystals that make up the crystalline phase, etc., the energy required for the above-mentioned crack propagation can be increased, resulting in superior strength in a #60 sandpaper set drop strength test.

Next, the average value of tensile stress CT _ave is a value calculated by {I CT /L _{CT }} using the integral value of tensile stress I _CT (MPa·μm) and the length of the tensile stress region in the plate thickness direction L _CT ( _μm ).
Here, the inventors focused on the depth of cracks that occurred in a #60 sandpaper set drop strength test, and found that the depth was greater than 120 μm, reaching approximately 150 μm.
Generally, a depth of 150 μm from the surface falls within the tensile stress region of chemically strengthened glass. The smaller the absolute value of the tensile stress, the less cracks propagate in this region. Based on this, in this embodiment, it has been conceived that by lowering the average tensile stress CT _ave , excellent strength can be achieved in a #60 sandpaper set drop strength test.

In light of the above, a first aspect of this embodiment relates to chemically strengthened glass obtained by chemically strengthening glass-ceramics having a crystalline phase with an average tensile stress CT _ave of 60 MPa or less. The composition of the center portion in the thickness direction, which becomes glass-ceramics by heat treatment and has an average tensile stress CT _ave of 60 MPa or less by chemical strengthening, can be 62-75% SiO ₂ , 2.2-6.0% Al ₂ O ₃ , 20-27% Li ₂ O 2 , and 1-4.2% ZrO ₂ .

In addition, a second aspect of the chemically strengthened glass according to this embodiment is a crystallized glass having a crystalline phase, in which the composition of the center portion in the thickness direction satisfies a specific range or relationship. This allows for both a high K1c and a low average tensile stress CT _ave , and achieves excellent strength in a #60 sandpaper set drop strength test.

In addition, if only chemically strengthened glass having a small tensile stress is to be obtained, it is possible to suppress the diffusion of Na ions and K ions used in ion exchange by shortening the time for performing the ion exchange treatment or by lowering the temperature of the molten salt for ion exchange.
However, when the above method is adopted, the value of the compressive stress layer depth DOL also becomes small, and if a crack occurs in the glass, it becomes more likely to break.
In contrast, in both the first and second aspects of this embodiment, the chemically strengthened glass is made of crystallized glass having a crystalline phase, and the composition of the center portion in the thickness direction is set to a specific range. This makes it possible to realize a low average tensile stress CT _ave without excessively increasing the compressive stress value, even when ions diffuse to a sufficient depth to form a compressive stress layer.

<composition>
The composition of the center of the chemically strengthened glass in the thickness direction, i.e., the composition of the chemically strengthened crystallized glass, will be described below. The content ratio of each component is expressed as mole percentage based on oxide unless otherwise specified.
The composition of the chemically strengthened glass can be identified by a conventionally known method. For example, the composition can be identified by wet chemical analysis or quantitative analysis using a fluorescent X-ray calibration curve.

_SiO2 is a component that constitutes the glass network and also a component that constitutes lithium disilicate crystals.
The SiO ₂ content in chemically strengthened glass is 62 to 75%. Here, from the viewpoint of facilitating the formation of lithium disilicate crystals, the content is 62% or more, preferably 64% or more, more preferably 66% or more, and even more preferably 68% or more. Also, from the viewpoint of facilitating the formation of lithium disilicate crystals and increasing the meltability of the glass, the content is 75% or less, preferably 73% or less, more preferably 72% or less, even more preferably 70% or less, and particularly preferably 69% or less.

Li ₂ O is a constituent component of lithium disilicate crystals, and is also a component that generates compressive stress near the surface of the crystallized glass when Li ions constituting Li ₂ O are ion-exchanged with Na ions.
The content of Li ₂ O in chemically strengthened glass is 20 to 27%. Here, from the viewpoint of facilitating the formation of lithium disilicate crystals and increasing compressive stress, the content is 20% or more, preferably 21% or more, more preferably 22% or more, and even more preferably 23% or more. Furthermore, from the viewpoint of facilitating the formation of lithium disilicate crystals and the chemical durability of the glass, the content is 27% or less, preferably 26.5% or less, more preferably 26% or less, even more preferably 25% or less, and particularly preferably 24% or less.

Al ₂ O ₃ is a component that improves ion exchangeability when chemical strengthening treatment is carried out and increases the surface compressive stress after chemical strengthening treatment.
The content of Al ₂ O ₃ in chemically strengthened glass is 2.2 to 6.0%. Here, from the viewpoint of performing chemical strengthening treatment appropriately, the content is 2.2% or more, preferably 2.4% or more, more preferably 2.5% or more, more preferably 2.6% or more, even more preferably 2.8% or more, and particularly preferably 3.2% or more. Furthermore, from the viewpoint of facilitating the formation of lithium disilicate crystals, the content is 6.0% or less, preferably 5.5% or less, more preferably 5.0% or less, and even more preferably 4.5% or less.

_ZrO2 is a thickening component that increases the viscosity during melting, and also increases the surface compressive stress due to ion exchange. In addition, it has been found that by incorporating an appropriate amount of _ZrO2 , phase separation can be favorably controlled to facilitate crystallization while maintaining high transparency. As a result, when the glass is made into crystallized glass, the crystallization degree can be increased while maintaining high transparency, resulting in higher strength.
The content of ZrO ₂ in chemically strengthened glass is 1 to 4.2%. Here, from the viewpoint of controlling phase separation and acting as a thickening component to slow the growth rate of crystals that become crystalline phases and form fine crystals, thereby achieving higher transparency of the glass, the content is 1% or more, preferably 1.5% or more, more preferably 1.6% or more, even more preferably 1.7% or more, even more preferably 2.0% or more, and particularly preferably 2.5% or more. Also, from the viewpoint of suppressing devitrification during melting, the content is 4.2% or less, preferably 4.0% or less, more preferably 3.8% or less, even more preferably 3.5% or less, even more preferably 3.0% or less, 2.5% or less, or 2.4% or less.

Furthermore, the content of ZrO ₂ in the chemically strengthened glass according to this embodiment is preferably 1 to 10% by mass when expressed as a mass percentage based on the oxide. Here, from the viewpoint of controlling phase separation and acting as a thickening component to slow the growth rate of crystals that become crystalline phases and form fine crystals, thereby achieving higher transparency of the crystallized glass, the content is preferably 1% by mass or more, more preferably 2.5% by mass or more, even more preferably 3.2% by mass or more, and even more preferably 3.7% by mass or more. Furthermore, from the viewpoint of suppressing devitrification during melting, the content is preferably 10% by mass or less, more preferably less than 5% by mass, even more preferably 4.8% by mass or less, and may be 4.5% by mass or less, or may be 4.4% by mass or less.

P ₂ O ₅ is a component that promotes crystallization.
The content of P ₂ O ₅ in chemically strengthened glass is preferably more than 0% and not more than 3%. Here, from the viewpoint of facilitating crystallization, the content is preferably more than 0%, i.e., P ₂ O ₅ is preferably contained, more preferably 0.2% or more, even more preferably 0.5% or more, even more preferably 0.7% or more, and particularly preferably 0.8% or more. Furthermore, from the viewpoint of suppressing phase separation during melting and a decrease in acid resistance, the content is preferably 3% or less, more preferably 2.5% or less, even more preferably 2.0% or less, and most preferably 1.5% or less.

Na ₂ O is a component that generates compressive stress by ion-exchanging Na ions constituting Na ₂ O with K ions, and the inclusion of a small amount of Na 2 O can sometimes increase the stability of the glass.
The content of Na ₂ O in chemically strengthened glass is preferably more than 0% and not more than 5%. Here, from the viewpoint of increasing compressive stress and improving stability, the content is preferably more than 0%, that is, Na ₂ O is preferably contained, more preferably 0.5% or more, even more preferably 1.0% or more, and even more preferably 2.0% or more. Furthermore, from the viewpoint of maintaining chemical durability, the content is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

K ₂ O is a component that enhances chemical strengthening properties and suppresses phase separation.
The content of K ₂ O in chemically strengthened glass is preferably 0 to 1%. Here, the content of K ₂ O may be 0%, that is, not contained, but if K ₂ O is contained, from the viewpoint of enhancing the stability of the glass, the content is preferably 0.02% or more, more preferably 0.2% or more, and even more preferably 0.4% or more. Furthermore, from the viewpoint of maintaining chemical durability, the content is preferably 1% or less, more preferably 0.9% or less, even more preferably 0.8% or less, even more preferably 0.7% or less, and particularly preferably 0.6% or less.

MgO is a component that improves the meltability of glass.
The MgO content in chemically strengthened glass is preferably 0 to 2%. Here, the MgO content may be 0%, i.e., not contained. However, if MgO is contained, from the viewpoints of meltability and strength, the content is preferably 0.03% or more, more preferably 0.2% or more, and even more preferably 0.4% or more. Furthermore, from the viewpoint of maintaining good ion exchange performance, the content is preferably 2% or less, more preferably 1.5% or less, and even more preferably 1.0% or less.

CaO is a component that improves the meltability of glass.
The CaO content in chemically strengthened glass is preferably 0 to 2%. Here, the CaO content may be 0%, i.e., not contained, but when CaO is contained, from the viewpoints of meltability and strength, the content is preferably 0.03% or more, more preferably 0.2% or more, and even more preferably 0.4% or more. Furthermore, from the viewpoint of maintaining good ion exchange performance, the content is preferably 2% or less, more preferably 1.5% or less, even more preferably 1.0% or less, and particularly preferably 0.8% or less.

SrO is a component that improves the meltability of glass.
The SrO content in chemically strengthened glass is preferably 0 to 1%. Here, the SrO content may be 0%, i.e., not contained. However, if SrO is contained, from the viewpoints of meltability and strength, the content is preferably 0.03% or more, more preferably 0.2% or more, and even more preferably 0.4% or more. Furthermore, from the viewpoint of maintaining good ion exchange performance, the content is preferably 1% or less, more preferably 0.9% or less, and even more preferably 0.7% or less.

_SnO2 is a fining agent during melting and also a component that generates crystal nuclei.
The content of SnO ₂ in chemically strengthened glass is preferably 0 to 1%. Here, the content of SnO may be 0%, that is, not contained. However, when SnO ₂ is contained, it acts as a component that generates crystal nuclei and forms fine crystals. From the viewpoint of realizing high transparency of the glass, the content is preferably 0.02% or more, more preferably 0.1% or more, and even more preferably 0.2% or more. In addition, from the viewpoint of suppressing defects due to unmelted material, the content is preferably 1% or less, more preferably 0.9% or less, even more preferably 0.7% or less, and most preferably 0.5% or less.

B ₂ O ₃ is a component that improves chipping resistance and melting properties.
The content of B ₂ O ₃ in chemically strengthened glass is preferably 0 to 4%. Here, the content of B ₂ O ₃ may be 0%, that is, not contained, but if B ₂ O ₃ is contained, from the viewpoint of obtaining good chipping resistance and meltability, the content is preferably 0.3% or more, more preferably 0.5% or more, even more preferably 1.0% or more, and particularly preferably 1.5% or more. Furthermore, from the viewpoint of suppressing the occurrence of striae and phase separation during melting and maintaining the quality of the chemically strengthened glass, the content is preferably 4% or less, more preferably 3.5% or less, even more preferably 3.0% or less, and even more preferably 2.5% or less.

ZnO is a component that enhances the meltability of glass.
The ZnO content in chemically strengthened glass is preferably 0 to 2%. Here, the ZnO content may be 0%, i.e., not contained, but if ZnO is contained, from the viewpoint of obtaining good meltability, the content is preferably 0.2% or more, more preferably 0.5% or more, and even more preferably 1.0% or more. Furthermore, from the viewpoint of improving weather resistance, the content is preferably 2% or less, more preferably 1.8% or less, even more preferably 1.6% or less, and even more preferably 1.4% or less.

_TiO2 is a thickening component that increases the viscosity when melted, and also a component that increases UV resistance.
The content of TiO ₂ in chemically strengthened glass is preferably 0 to 1%. Here, the content of TiO ₂ may be 0%, that is, it may not be contained, but if TiO ₂ is contained, it acts as a thickening component, slowing the growth rate of crystals that become crystalline phases and forming fine crystals. From the viewpoint of realizing high transparency of the glass, the content is preferably 0.01% or more, more preferably 0.1% or more, and even more preferably 0.3% or more. In addition, from the viewpoint of suppressing a decrease in the haze value due to coloring, the content is preferably 1% or less, more preferably 0.8% or less, and even more preferably 0.6% or less.

Y ₂ O ₃ is a thickening component that increases the viscosity during melting, and also a component that increases the mechanical strength of the glass. It also increases the refractive index. On the other hand, Y ₂ O ₃ has the effect of inhibiting the formation of crystal nuclei.
Therefore, it is preferable that the chemically strengthened glass according to this embodiment does not substantially contain Y ₂ O _3. In this specification, "substantially not containing" means that the content is below the impurity level contained in raw materials, etc., that is, it is not intentionally added, and the content is, for example, less than 0.01%.

Furthermore, other components such as coloring components may be added as appropriate within a range that does not inhibit the achievement of the desired properties of the chemically strengthened glass. Examples _{of the} other components include _BaO , _La2O3 , _Nb2O5 , _Ta2O5 , _CeO2 , _Co3O4 , _MnO2 , _Fe2O3 , _NiO , _CuO , _Cr2O3 , _{V2O5 , Bi2O3} , _{SeO2 , Er2O3 , and Nd2O3 .}
The total content of the other components in the chemically strengthened glass is preferably 0.2% or less. Furthermore, if the light transmittance of the chemically strengthened glass is desired to be higher, it is preferable that the glass does not substantially contain any coloring components.

Furthermore, as a fining agent used during melting of the glass, SO ₃ , chlorides, fluorides, As ₂ O ₃ , Sb ₂ O ₃ and the like may be appropriately contained. The content of each of the fining agents is preferably 0.3% or less, more preferably 0.1% or less, and most preferably, substantially no fining agents are contained.

The chemically strengthened glass according to this embodiment preferably has a composition at the center in the thickness direction that satisfies 62 to 75% of SiO ₂ , 2.2 to 6.0% of Al ₂ O ₃ , 20 to 27% of Li ₂ O 2 , and 1 to 4.2% of ZrO ₂ .
In addition to the above, it is more preferable to satisfy one or more of the following: more than 0% and 3% or less P ₂ O ₅ , more than 0% and 5% or less Na ₂ O , 0-1% K ₂ O , 0-2% MgO , 0-2% CaO , 0-1% SrO , 0-1% SnO ₂ , and substantially no Y ₂ O ₃ ; it is even more preferable to satisfy three or more, even more preferably to satisfy five or more, particularly preferably to satisfy seven or more, and it is particularly preferable to satisfy all eight.

In addition to the content ratios of each component, the chemically strengthened glass according to this embodiment more preferably satisfies one or more of the following relationships (1) to (4) expressed using the content ratios of each component, more preferably satisfies two or more, even more preferably satisfies three or more, and particularly preferably satisfies all four.
Among these, it is even more preferable to satisfy (1) and (2).

(1) The value represented by {[K ₂ O]/[Na ₂ O]} is 0 to 0.3.
(2) The value represented by [{[Al ₂ O ₃ ]/[ZrO ₂ ]}-{[B ₂ O ₃ ]/[P ₂ O ₅ ]}] is 0.5 to 1.5.
(3) The value represented by {[Al ₂ O ₃ ]/[Na ₂ O]} is greater than 0 and not greater than 0.23.
(4) The value represented by {[Li ₂ O]/[ZrO ₂ ]} is 8 or more.

Of the above relationships, in (1), the value represented by {[K ₂ O]/[Na ₂ O]} is 0 to 0.3. This value contributes to the exchange characteristics of K ions. Therefore, the chemically strengthened glass according to this embodiment does not need to contain K ₂ O, that is, the value may be 0.03 or more, or may be 0.05 or more, if K ₂ O is contained. On the other hand, from the viewpoint of reducing the charging characteristics, the value is preferably 0.3 or less, more preferably 0.27 or less, even more preferably 0.25 or less, and particularly preferably 0.23 or less.

In the above relationship (2), the value represented by [{[Al ₂ O ₃ ]/[ZrO ₂ ]}-{[B ₂ O ₃ ]/[P ₂ O ₅ ]}] is 0.5 to 1.5. Here, the value represented by {[Al ₂ O ₃ ]/[ZrO ₂ ]} is an index of the K ion or Na ion exchange characteristics, and the value represented by {[B ₂ O ₃ ]/[P ₂ O ₅ ]} is an index of the ease of crystallization nucleation. The difference between these values can be used as an index of the chemical strengthening characteristics of the crystallized glass.
Therefore, the value represented by [{[Al ₂ O ₃ ]/[ZrO ₂ ]}-{[B ₂ O ₃ ]/[P ₂ O ₅ ]}] is preferably 0.5 or more, more preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.8 or more, and particularly preferably 0.9 or more, from the viewpoint of improving chemical strengthening characteristics. Also, from the viewpoint of facilitating crystallization nucleation, the value is preferably 1.5 or less, more preferably 1.3 or less, more preferably 1.2 or less, even more preferably 1.1 or less, and particularly preferably 0.9 or less.
The value of {[Al ₂ O ₃ ]/[ZrO ₂ ]}, which is an index of the K ion and Na ion exchange properties, is preferably 0.7 to 3.0. Here, the value is preferably 0.7 or more, more preferably 0.8 or more, even more preferably 0.9 or more, even more preferably 1.0 or more, and particularly preferably 1.1 or more. The value is preferably 3.0 or less, more preferably 2.0 or less, even more preferably 1.5 or less, and even more preferably 1.2 or less.

Of the above relationships, in (3), the value represented by {[Al ₂ O ₃ ]/[Na ₂ O]} is greater than 0 and less than or equal to 2.3. This value contributes to the Na ion exchange properties and alkali resistance. Since the chemically strengthened glass according to this embodiment preferably contains Al ₂ O ₃ , the value is preferably greater than 0. However, from the viewpoint of improving the Na ion exchange properties, the value is more preferably 0.1 or greater, even more preferably 0.3 or greater, and most preferably 0.5 or greater. On the other hand, from the viewpoint of improving the alkali resistance, the value is preferably 2.3 or less, more preferably 1.9 or less, even more preferably 1.7 or less, even more preferably 1.2 or less, and particularly preferably 1.0 or less.

Of the above relationships, in (4), the value represented by {[Li ₂ O]/[ZrO ₂ ]} is 8 or more, preferably 8 to 20. This value contributes to the Li ion exchange properties and alkali resistance. From the viewpoint of improving the Li ion exchange properties, the value is preferably 8 or more, more preferably 9 or more, even more preferably 11 or more, and particularly preferably 13 or more. On the other hand, from the viewpoint of improving the alkali resistance, the value is preferably 20 or less, more preferably 17 or less, even more preferably 15 or less, and particularly preferably 14 or less.

<Crystalline phase>
The chemically strengthened glass according to this embodiment is crystallized glass having a crystalline phase.
The crystalline phase is not particularly limited, and examples thereof include Li ₂ Si ₂ O ₅ (lithium disilicate crystal), LiAlSi ₂ O ₆ (β-spodumene crystal), LiAlSi ₄ O ₁₀ (petalite crystal), Li ₃ PO ₄ (lithium phosphate crystal), β-quartz solid solution (Li _x Al _x Si _3-x O ₆ ; including bergerite crystal), Li ₂ SiO ₃ (lithium metasilicate crystal), LiAlSiO ₄ (eucryptite crystal), Al _4+2x Si _2-2x O _10-x (0.2≦x≦0.5, mullite crystal), etc. However, the crystalline phase is not limited to these and may be appropriately selected according to the desired properties.

Among these, from the viewpoint of increasing the strength of the chemically strengthened glass, in particular obtaining a higher fracture toughness value K1c, it is preferable that the crystalline phase contains at least one crystal selected from the group consisting of Li ₂ Si ₂ O ₅ , _{LiAlSi 2 O 6} , LiAlSi ₄ O ₁₀ , Li ₃ PO ₄ , and β-quartz solid solution, more preferably contains at least one crystal of _{Li 2} Si 2 O ₅ and LiAlSi ₄ O 10, and even more preferably contains Li 2 Si ₂ O ₅ .

For example, from the perspective of facilitating ion exchange during chemical strengthening treatment, the crystalline phase may consist solely of lithium disilicate crystals, but may also contain β-spodumene crystals, petalite, β-quartz, lithium metasilicate, etc.

Furthermore, if a higher strength crystallized glass is desired, the crystalline phase may consist solely of lithium disilicate crystals, but may also contain β-spodumene crystals, petalite, β-quartz, lithium metasilicate, mullite, etc.

Furthermore, if higher transparency is desired, the crystalline phase may consist solely of lithium disilicate crystals, but may also contain petalite, β-quartz, lithium metasilicate, lithium phosphate, etc.

The type of crystals that make up the above crystalline phase can be selected primarily depending on the composition of the crystallized glass and the crystallization conditions.

The presence of the crystalline phase can be confirmed by the presence of diffraction peaks indicating crystals in the XRD pattern obtained by powder X-ray diffraction (XRD). By heat-treating amorphous glass (mother glass) in which no diffraction peaks indicating crystals are observed, crystallized glass having a crystalline phase in which crystals are precipitated can be obtained. Furthermore, chemical strengthening of the crystallized glass does not significantly affect the crystalline phase.
The XRD measurement is performed using CuKα radiation in the range of 2θ = 10° to 80°. From the diffraction pattern and diffraction intensity obtained as a result of the measurement, Rietveld analysis is performed to identify the crystalline structure of the crystals constituting the crystalline phase, the content ratio of each crystalline phase, and the total content ratio of the crystalline phases (degree of crystallinity). The Rietveld method is described in "Crystal Analysis Handbook" edited by the Editorial Committee of the Crystallographic Society of Japan (Kyoritsu Shuppan, 1999, pp. 492-499).

When the crystalline phase contains lithium disilicate crystals, the content of lithium disilicate crystals in the crystalline phase is preferably 60% by mass or more, and more preferably 60 to 100% by mass. From the perspective of achieving higher strength, the content is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more. The content may also be 100% by mass, meaning that the crystalline phase consists solely of lithium disilicate crystals. From the perspective of bendability, other crystals may also be included, in which case the content of lithium disilicate crystals in the crystalline phase may be 95% by mass or less, or 85% by mass or less.

The crystallization rate in the chemically strengthened glass according to this embodiment, that is, the content ratio of the crystalline phase (crystallinity), is preferably 40% by mass or more, more preferably 40 to 80% by mass. Here, from the viewpoint of achieving higher strength, the crystallization rate is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. Furthermore, from the viewpoint of maintaining high transparency and three-dimensional formability, the content ratio of the crystalline phase is preferably 80% by mass or less, more preferably 70% by mass or less, and more preferably 65% by mass or less.
In addition, when the chemically strengthened glass according to this embodiment contains two or more types of crystals as a crystalline phase, the crystallization rate means the total content ratio thereof.
The crystallization rate can be adjusted by the composition of the crystallized glass, the temperature, time, temperature rise rate, etc. during crystallization.

In the chemically strengthened glass according to this embodiment, the average particle size of the crystals constituting the crystalline phase is preferably 10 to 100 nm. From the viewpoint of achieving higher strength, the average particle size is preferably 10 nm or more, more preferably 20 nm or more, even more preferably 30 nm or more, and even more preferably 40 nm or more. From the viewpoint of achieving higher transparency, the average particle size is preferably 100 nm or less, more preferably 90 nm or less, even more preferably 80 nm or less, and even more preferably 60 nm or less.
The average particle size can be measured by observation with a scanning electron microscope (SEM). The average particle size can also be adjusted by adjusting the heat treatment conditions.
The average particle size can be adjusted by the temperature and time during crystallization, the cooling rate during glass molding, and the like.

<Reinforcement layer>
The chemically strengthened glass according to this embodiment is crystallized glass having an ion-exchange layer on the surface thereof. By ion exchange, a compressive stress layer is formed on the outermost surface thereof, and a tensile stress layer is formed inside the outermost surface thereof.

In the chemically strengthened glass according to this embodiment, the average value CT ave of the tensile stress calculated by {I _CT /L _CT } using the tensile stress integral value I _CT (MPa·μm) and the thickness direction length L _CT ( _μm ) of the tensile stress region is preferably small.
As mentioned above, the cracks that occur in the #60 sandpaper set drop strength test are deep and fall within the tensile stress region of chemically strengthened glass. Therefore, by reducing the average tensile stress CT _ave in this region, the propagation of the cracks can be suppressed, and excellent strength in the #60 sandpaper set drop strength test can be achieved.

From the above viewpoint, the average value CT _ave of the tensile stress of the chemically strengthened glass according to this embodiment is preferably 60 MPa or less, more preferably 50 MPa or less, and even more preferably 40 MPa or less. Although the lower limit is not particularly limited, from the viewpoint of obtaining a certain or higher compressive stress value, the average value CT _ave of the tensile stress may be 10 MPa or more, or 20 MPa or more.
The average value of the tensile stress CT _ave is partly affected by the conditions of the chemical strengthening treatment, but can also be adjusted by the composition of the central part in the thickness direction of the chemically strengthened glass.

The stress profile, such as the average tensile stress value CT _ave and the compressive stress value, can be measured using, for example, a scattered light photoelastic stress meter (SLP) or a film stress measurement (FSM).

Methods using a scattered light photoelastic stress meter (SLP) can measure compressive stress resulting from Li-Na exchange inside the glass, which is a region several tens of micrometers or more deep from the glass surface. On the other hand, methods using a glass surface stress meter (FSM) can measure compressive stress resulting from Na-K exchange in the glass surface layer, which is a shallow region several tens of micrometers or less from the glass surface (see, for example, WO 2018/056121 and WO 2017/115811).

The maximum tensile stress value CT _max of the chemically strengthened glass according to this embodiment is preferably 120 MPa or less, more preferably 30 to 110 MPa. Here, from the viewpoint of achieving superior strength in a #60 sandpaper set drop strength test, the maximum tensile stress value CT _max is preferably 120 MPa or less, more preferably 110 MPa or less, even more preferably 100 MPa or less, and even more preferably 80 MPa or less. Further, although the lower limit is not particularly limited, from the viewpoint of obtaining a compressive stress value of a certain level or more, the maximum tensile stress value CT _max may be 30 MPa or more, 40 MPa or more, or 50 MPa or more.

The tensile stress integral value I _CT of the chemically strengthened glass according to this embodiment is preferably 8000 to 33000 MPa μm. Here, from the viewpoint of achieving superior strength in a #60 sandpaper set drop strength test, the tensile stress integral value I _CT is preferably 8000 MPa μm or more, more preferably 12000 MPa μm or more, even more preferably 15000 MPa μm or more, and even more preferably 18000 MPa μm or more. Furthermore, from the viewpoint of achieving superior strength in a #60 sandpaper set drop strength test, the tensile stress integral value I _CT is preferably 33000 MPa μm or less, more preferably 30000 MPa μm or less, even more preferably 28000 MPa μm or less, and even more preferably 25000 MPa μm or less.

The value of Y represented by the following formula of the chemically strengthened glass according to this embodiment is preferably 10 or more, more preferably 10 to 50.
Y=0.1×α−0.05×CT _ave
In the above formula, α and CT _ave are expressed by the following formulas.
α=200×K1c-100
CT _ave =I _CT /L _CT
Here, I _CT means the integral value of tensile stress (MPa·μm), L _CT means the length of the tensile stress region in the plate thickness direction (μm), and K1c means the fracture toughness value (MPa·m ^1/2 ).

The value of Y indicates the resistance to deep cracks.
From the viewpoint of realizing superior strength in a #60 sandpaper set drop strength test, the value of Y is preferably 10 or more, more preferably 15 or more, and even more preferably 20 or more. From the viewpoint of reducing the transmittance of the glass, the value of Y is preferably 50 or less, more preferably 40 or less, and even more preferably 30 or less.

The compressive stress value _CS50 at a depth of 50 μm from the surface of the chemically strengthened glass according to this embodiment is preferably 220 MPa or less. Here, in order to achieve a lower average tensile stress CT _ave in order to achieve better strength in a #60 sandpaper set drop strength test, the compressive stress value _CS50 is preferably 220 MPa or less, more preferably 200 MPa or less, even more preferably 170 MPa or less, even more preferably 140 MPa or less, and particularly preferably 110 MPa or less. In addition, from the viewpoint of preventing cracking due to deformation such as bending, the compressive stress value _CS50 is preferably 10 MPa or more, more preferably 30 MPa or more, even more preferably 50 MPa or more, and most preferably 80 MPa or more.
The compressive stress value _CS50 can be adjusted by the molten salt, temperature, time, etc. used in the chemical strengthening treatment. The same applies to the compressive stress value _CS0 at the outermost surface and the compressive stress values _CS50 , _CS100 , and _CS150 at depths of 50 μm, 100 μm, and 150 μm from the surface.

The compressive stress value CS ₁₀₀ of the chemically strengthened glass according to this embodiment at a depth of 100 μm from the surface is preferably 30 MPa or less, more preferably 0 to 30 MPa. From the viewpoint of preventing spontaneous destruction due to excessive tensile stress, the compressive stress value CS ₁₀₀ is preferably 30 MPa or less, more preferably 25 MPa or less, even more preferably 20 MPa or less, and even more preferably 15 MPa or less. From the viewpoint of preventing cracking due to deformation such as bending, the compressive stress value CS ₁₀₀ is preferably 0 MPa or more, more preferably 5 MPa or more, and even more preferably 10 MPa or more.

The compressive stress value CS ₁₅₀ at a depth of 150 μm from the surface of the chemically strengthened glass according to this embodiment is preferably -100 MPa or more, more preferably -100 to 0 MPa. Here, from the viewpoint of improving the #60 sandpaper set drop strength, the compressive stress value CS ₁₅₀ is preferably -100 MPa or more, more preferably -80 MPa or more, even more preferably -70 MPa or more, even more preferably -60 MPa or more, and most preferably -50 MPa or more. Also, from the viewpoint of improving the #60 sandpaper set drop strength, the compressive stress value CS ₁₅₀ is preferably 0 MPa or less, more preferably -10 MPa or less, even more preferably -20 MPa or less, and most preferably -30 MPa or less.

The compressive stress value _CS0 at the outermost surface of the chemically strengthened glass according to this embodiment is preferably 300 to 700 MPa. Here, from the viewpoint of increasing the bending test strength, the compressive stress value _CS0 is preferably 300 MPa or more, more preferably 400 MPa or more, and even more preferably 500 MPa or more. From the viewpoint, the compressive stress value _CS0 is preferably 700 MPa or less, more preferably 650 MPa or less, and even more preferably 600 MPa or less.

The compressive stress layer depth DOL of the chemically strengthened glass according to this embodiment is preferably {0.15 × t} μm or more, and more preferably {0.15 × t + 10} μm or more and {0.15 × t + 70} μm or less, where t (μm) is the thickness of the glass. Here, from the viewpoint of preventing cracks when scratches occur on the surface of the chemically strengthened glass, the compressive stress layer depth DOL is preferably {0.15 × t} μm or more, more preferably {0.15 × t + 10} μm or more, even more preferably {0.15 × t + 20} μm or more, and even more preferably {0.15 × t + 25} μm or more. Further, from the viewpoint of improving the productivity of the strengthening process, the compressive stress layer depth DOL is preferably {0.15 × t + 70} μm or less, more preferably {0.15 × t + 50} μm or less, and even more preferably {0.15 × t + 40} μm or less.
The compressive stress layer depth DOL can be adjusted by the molten salt, temperature, time, etc. used in the chemical strengthening treatment. In this specification, the compressive stress layer depth (DOL) is the depth at which the surface compressive stress (CS) becomes zero.

From the perspective of improving ball drop strength and drop strength, it is preferable that the chemically strengthened glass of this embodiment has a compressive stress layer in which Li ions are ion-exchanged with Na ions and then Na ions are ion-exchanged with K ions. In this case, a surface compressive stress is imparted to the portion close to the surface of the glass due to the ion exchange of Na ions with K ions, and a deep compressive stress is imparted to the portion deeper than that due to the ion exchange of Li ions with Na ions.

In chemically strengthened glass to which the above-described surface compressive stress and deep compressive stress have been imparted, the depth from the surface of the compressive stress layer due to K ions, K-DOL, is preferably 3 μm or more, and more preferably 3 to 10 μm. From the viewpoint of improving bending strength, the K-DOL is preferably 3 μm or more, more preferably 4 μm or more, even more preferably 5 μm or more, and even more preferably 6 μm or more. Furthermore, from the viewpoint of reducing electrostatic chargeability, the K-DOL is preferably 10 μm or less, more preferably 9 μm or less, even more preferably 8 μm or less, and even more preferably 7 μm or less.

In the chemically strengthened glass according to this embodiment, the Na ion concentration [Na] ₁₀₀ at a depth of 100 μm from the surface is preferably 2.5 mol% or more, more preferably 2.7 to 5 mol%. From the viewpoint of improving drop strength, the Na ion concentration [Na] ₁₀₀ is preferably 2.5 mol% or more, more preferably 2.7 mol% or more, even more preferably 3.0 mol% or more, and particularly preferably 3.5 mol% or more. From the viewpoint of improving the efficiency of the manufacturing process, the Na ion concentration [Na] ₁₀₀ is preferably 5 mol% or less, more preferably 4.5 mol% or less, and even more preferably 4.0 mol% or less.

In the chemically strengthened glass according to this embodiment, the Na ion concentration [Na] ₅₀ at a depth of 50 μm from the surface is preferably 3 mol% or more, more preferably 3 to 6 mol%. From the viewpoint of drop strength, the Na ion concentration [Na] ₅₀ is preferably 3 mol% or more, more preferably 3.3 mol% or more, and even more preferably 3.6 mol% or more. From the viewpoint of improving the efficiency of the manufacturing process, the Na ion concentration [Na] ₅₀ is preferably 6 mol% or less, more preferably 5.5 mol% or less, even more preferably 5.2 mol% or less, and even more preferably 4.9 mol% or less.

In the chemically strengthened glass according to this embodiment, the Na ion concentration [Na] ₁₀₀ at a depth of 100 μm from the surface is 2.5 mol% or more, and the compressive stress value CS ₁₀₀ at a depth of 100 μm from the surface is 30 MPa or less. From the viewpoint of improving drop strength, it is preferable.

In the chemically strengthened glass according to this embodiment, the ratio expressed as {[Na] ₅₀ /[Na] 100 }, where [Na] 100 is the Na ion concentration at a depth of 100 μm from the surface and [Na] ₅₀ is the Na ion concentration at a depth of _{50 μm} from the surface, is preferably 1.4 or less, more preferably 1.05 to 1.4. From the viewpoint of improving the efficiency of the manufacturing process, the ratio is preferably 1.4 or less, more preferably 1.35 or less, and even more preferably 1.3 or less. Furthermore, from the viewpoint of improving drop strength, the ratio is preferably 1.05 or more, more preferably 1.1 or more, and even more preferably 1.2 or more.

<Characteristics/Properties>
The Young's modulus of the glass according to this embodiment is preferably 105 GPa or more, more preferably 105 to 130 GPa. From the viewpoint of high strength, the Young's modulus is preferably 105 GPa or more, more preferably 110 GPa or more, and even more preferably 115 GPa or more. From the viewpoint of high strength, the higher the Young's modulus, the better, but is not particularly limited, and may be, for example, 130 GPa or less.
The Young's modulus in this specification can be measured by an ultrasonic method.

The transmittance of light having a wavelength of 600 nm when converted to a thickness of 0.6 mm of the chemically strengthened glass according to this embodiment is preferably 80% or more, more preferably 80 to 98%. From the viewpoint of visibility when the chemically strengthened glass is used as a cover glass, the transmittance is preferably 80% or more, more preferably 85% or more, even more preferably 90% or more, and most preferably 95% or more. The higher the transmittance, the better, but it may be, for example, 98% or less.
The transmittance can be adjusted by the crystal species, the degree of crystallinity, and the glass composition.
In addition, when the thickness of the chemically strengthened glass is not 0.6 mm, the transmittance for 0.6 mm can be calculated from the measured transmittance using Lambert-Beer law.
In addition, in the case of chemically strengthened glass having a thickness t of more than 0.6 mm, the thickness may be adjusted to 0.6 mm by polishing, etching, or the like, and the value obtained by actually measuring the transmittance may be used.

The haze value of the chemically strengthened glass according to this embodiment is preferably 0.20% or less, more preferably 0.05 to 0.20%. Here, from the viewpoint of visibility when the chemically strengthened glass is used as a cover glass, particularly a three-dimensional cover glass, the haze value is preferably 0.20% or less, more preferably 0.17% or less, even more preferably 0.15% or less, even more preferably 0.13% or less, particularly preferably 0.10% or less, and particularly preferably 0.09% or less. The smaller the haze value, the better, but it may be, for example, 0.05% or more.
The above-mentioned haze value can be adjusted by the crystal species, the degree of crystallization, and the glass composition.
In this specification, the haze value refers to a value calculated using a C light source and measured in accordance with JIS K 7136:2000, converted into a 0.7 mm thickness of chemically strengthened glass. If the actual thickness of the chemically strengthened glass is not 0.7 mm, the haze value can be converted into a 0.7 mm thickness using the Lambert-Beer law based on the measured value. If the plate thickness t is greater than 0.7 mm, the plate thickness of the chemically strengthened glass may be adjusted to 0.7 mm by polishing, etching, or the like.

The chemically strengthened glass according to this embodiment has an effect of having a high average crack height as measured by a sandpaper set drop strength test under the following conditions. Specifically, the average crack height is preferably 60 cm or more, more preferably 80 cm or more, and the higher the better.
(conditions)
The test specimen is an electronic device equipped with chemically strengthened glass, or an electronic device simulation structure integrating chemically strengthened glass with a housing holding the chemically strengthened glass. The drop test is performed by dropping the test specimen onto #60 sandpaper with the chemically strengthened glass of the test specimen facing downward. The test specimen is dropped from a height of 15 cm. If the chemically strengthened glass of the test specimen does not break upon dropping, the drop height is increased by 5 cm and the process is repeated. The height at which the chemically strengthened glass of the test specimen first breaks is defined as the crack height. The drop test is performed on 10 test specimens, and the average of the crack heights is defined as the average crack height.

Regarding the fracture toughness value K1c of the chemically strengthened glass according to this embodiment, although it is difficult to measure the fracture toughness value K1c of crystallized glass, it is generally considered to be almost the same as the fracture toughness value K1c of the crystallized glass before chemical strengthening treatment.
Therefore, the fracture toughness value K1c of the chemically strengthened glass according to this embodiment is preferably 1.0 MPa m ^1/2 or more, more preferably 1.2 MPa m ^1/2 or more, even more preferably 1.3 MPa m ^1/2 or more, and even more preferably 1.35 MPa m ^1/2 or more. The upper limit is not particularly limited, but may be, for example, 2.0 MPa m ^1/2 or less.

<Glass-ceramics>
The crystallized glass according to this embodiment is a glass having a crystalline phase, and is the glass before chemical strengthening treatment of the chemically strengthened glass described above in the <<Chemically strengthened glass>>.

As one aspect of the crystallized glass according to this embodiment, the composition satisfies the following in terms of mole percentage based on oxides.
SiO ₂ 62-75%,
Al ₂ O ₃ 2.2-6.0%,
P ₂ O ₅ more than 0% and less than 3%,
Li ₂ O 20-27%,
Na ₂ O more than 0% and less than 5%,
K ₂ O 0-1%,
MgO 0-2%,
CaO 0-2%,
SrO 0-1%,
ZrO ₂ 1-4.2%,
SnO ₂ 0-1%,
Substantially does not contain Y ₂ O ₃ ,
Using the content ratio of K ₂ O and Na ₂ O expressed in mole percentage, the value represented by {[K ₂ O]/[Na ₂ O]} is 0 to 0.3;
Using the content ratios of Al ₂ O ₃ , ZrO ₂ , B ₂ O ₃ and P ₂ O ₅ expressed in mole percentage, the value represented by [{[Al ₂ O ₃ ]/[ZrO ₂ ]}-{[B ₂ O ₃ ]/[P ₂ O ₅ ]}] is 0.5 to 1.5.

The crystallized glass according to this embodiment does not show any significant changes in the overall composition of the glass, the crystalline phase such as the degree of crystallization, or the characteristics and physical properties (other than strength) compared to chemically strengthened glass after chemical strengthening treatment, and can be considered to be the same.
That is, the composition and crystalline phase of the crystallized glass according to this embodiment are the same as those described in the <Composition> and <Crystalline Phase> of the above <Chemically Strengthened Glass>, and preferred aspects are also the same.

Furthermore, the characteristics and physical properties of the crystallized glass according to this embodiment, other than the average crack height measured by a #60 sandpaper set drop strength test, are the same as those described in the "Characteristics and Physical Properties" section of "Chemically Tempered Glass" above, and the same applies to preferred aspects.

The fracture toughness value K1c of the crystallized glass according to this embodiment is preferably 1.0 MPa m ^1/2 or more from the viewpoint of obtaining high strength, more preferably 1.2 MPa m ^1/2 or more, even more preferably 1.3 MPa m ^1/2 or more, and even more preferably 1.35 MPa m ^1/2 or more. The upper limit is not particularly limited, but may be, for example, 2.0 MPa m ^1/2 or less. Here, the fracture toughness value K1c can be adjusted by the crystal species, crystallinity, and glass composition. The fracture toughness value K _IC in this specification can be measured by the pre-crack introduction fracture test method (SEPB method: Single-Edge-Precracked-Beam method) specified in JIS R 1607:2015.

The peak positions in the X-ray diffraction (XRD) pattern of the surface of the crystallized glass shift before and after chemical strengthening. Specifically, for example, by performing chemical strengthening, the peak positions derived from lithium disilicate crystals shift to a lower angle by about 0.02 to 0.10°. Such a peak shift means that Li ions constituting the crystalline phase are also ion-exchanged with Na ions.
However, the above does not have a significant effect on the physical properties and characteristics other than strength.

Glass
The glass according to this embodiment is a pre-crystallization glass suitable for obtaining the crystallized glass described in the above <<Crystalline Glass>>.
In one aspect of the glass according to this embodiment, the composition expressed in mole percentage based on oxides satisfies the following.
SiO ₂ 62-75%,
Al ₂ O ₃ 2.2-6.0%,
P ₂ O ₅ more than 0% and less than 3%,
Li ₂ O 20-27%,
Na ₂ O more than 0% and less than 5%,
K ₂ O 0-1%,
MgO 0-2%,
CaO 0-2%,
SrO 0-1%,
ZrO ₂ 1-4.2%,
SnO ₂ 0-1%,
Substantially does not contain Y ₂ O ₃ ,
Using the content ratio of K ₂ O and Na ₂ O expressed in mole percentage, the value represented by {[K ₂ O]/[Na ₂ O]} is 0 to 0.3;
Using the content ratios of Al ₂ O ₃ , ZrO ₂ , B ₂ O ₃ and P ₂ O ₅ expressed in mole percentage, the value represented by [{[Al ₂ O ₃ ]/[ZrO ₂ ]}-{[B ₂ O ₃ ]/[P ₂ O ₅ ]}] is 0.5 to 1.5.

The glass according to this embodiment does not show a significant change in the overall composition of the glass compared to the crystallized glass after crystallization, and can be considered to be the same. Also, as described above, the crystallized glass according to this embodiment does not show a significant change in the overall composition of the glass compared to the chemically strengthened glass after chemical strengthening treatment, and can be considered to be the same.
That is, the composition of the glass according to this embodiment is the same as that described in the <Composition> section of the above <<Chemically strengthened glass>>, and preferred aspects are also the same.

《Application》
The chemically strengthened glass according to this embodiment is useful as a cover glass for electronic devices such as mobile devices such as mobile phones and smartphones. It is also useful as a cover glass for electronic devices that are not intended for portability, such as televisions, personal computers, and touch panels, as well as elevator walls and wall surfaces (full-surface displays) of buildings such as houses and buildings. It is also useful as a construction material such as window glass, a tabletop, the interior of automobiles and airplanes, and their cover glass, as well as for curved housings.
Furthermore, the crystallized glass according to this embodiment becomes extremely useful for the above-mentioned applications by undergoing chemical strengthening treatment.
Furthermore, the glass according to this embodiment becomes extremely useful for the above-mentioned applications by undergoing crystallization treatment and chemical strengthening treatment.

<<Methods for producing glass, crystallized glass, and chemically strengthened glass>>
The glass according to this embodiment can be produced by blending raw materials to obtain a desired composition and by a conventionally known method. That is, the method for producing the glass according to this embodiment includes the following step 1:
The crystallized glass according to this embodiment can be produced by heat-treating amorphous glass to crystallize it. That is, the method for producing crystallized glass according to this embodiment includes the following steps 1 and 2.
The chemically strengthened glass according to this embodiment can be produced by chemically strengthening glass-ceramics. That is, the method for producing chemically strengthened glass according to this embodiment includes the following steps 1 to 3.

Step 1: A step for producing amorphous glass. Step 2: A step for crystallizing the amorphous glass obtained in step 1 to obtain crystallized glass. Step 3: A step for chemically strengthening the crystallized glass obtained in step 2 to obtain chemically strengthened glass.

Each process is explained below.

<Process 1>
Step 1 is a step of producing amorphous glass, and a specific method can be a conventionally known method.
That is, when obtaining amorphous glass, for example, glass raw materials are mixed to obtain a desired composition and heated and melted in a glass melting furnace. Thereafter, the molten glass is homogenized by bubbling, stirring, adding a clarifier, etc., and formed into a desired shape by a known forming method, and then slowly cooled. Alternatively, the molten glass may be formed into a block shape, slowly cooled, and then cut and processed into a desired shape.
Examples of glass forming methods include the float method, the press method, the fusion method, and the down-draw method.
The slow cooling method may be, for example, a method of cooling to room temperature at a rate of 0.1 to 2°C/min. The slow cooling may be performed by holding the material at a specific temperature for a specific period of time and then cooling to room temperature. Specifically, for example, the material may be held at 420 to 550°C for 10 to 180 minutes and then cooled to room temperature at a rate of 0.1 to 2°C/min.

Furthermore, the above-mentioned desired composition is the same as the preferred embodiment described in the "Composition" section of the above-mentioned "Chemically Strengthened Glass."

<Process 2>
Step 2 is a step of obtaining crystallized glass by crystallizing the amorphous glass obtained in step 1. This results in crystallized glass having a crystalline phase and a desired composition.

The heat treatment for crystallization is not particularly limited as long as it produces the desired crystals, but may be, for example, a two-stage heat treatment in which the temperature is raised from room temperature to a first treatment temperature and held for a certain period of time, and then held for a certain period of time at a second treatment temperature that is higher than the first treatment temperature. After the two-stage heat treatment, a three-stage heat treatment may be performed in which the temperature is held for a certain period of time at a third treatment temperature. Alternatively, a single-stage heat treatment may be performed in which the temperature is held at a specific treatment temperature and then cooled to room temperature.

When using a two-stage heat treatment, the first treatment temperature is preferably in a temperature range where the crystal nucleation rate is high for that glass composition. Furthermore, the second treatment temperature is preferably in a temperature range where the crystal growth rate is high for that glass composition.

When using a three-stage heat treatment, it is preferable that the first and second treatment temperatures be temperatures at which the crystal nucleation rate is high, and the third treatment temperature be a temperature at which the crystal growth rate is high. Alternatively, the first treatment temperature may be a temperature at which the crystal nucleation rate is high, and the second and third treatment temperatures may be temperatures at which the crystal growth rate is high.

In the two-stage and three-stage heat treatments, it is preferable to maintain the first treatment temperature for a long time so that a sufficient number of crystal nuclei are formed. By generating a large number of crystal nuclei, the size of each crystal becomes smaller, resulting in highly transparent crystallized glass.

More specifically, in the case of a two-stage treatment, the first treatment temperature may be held at 500°C to 700°C for 1 to 6 hours, and then the second treatment temperature may be held at 600°C to 800°C for 1 to 6 hours.

More specifically, in the case of a three-stage process, the material may be held at a first processing temperature of, for example, 450°C to 600°C for 1 to 6 hours, then held at a second processing temperature of, for example, 500°C to 650°C for 1 to 6 hours, and then held at a third processing temperature of, for example, 600°C to 800°C for 1 to 6 hours.

More specifically, in the case of a one-stage treatment, the temperature may be held at 500°C to 800°C for 1 to 6 hours, for example.

The crystallized glass obtained in step 2 may be ground and polished as needed. Furthermore, if the crystallized glass obtained is to be cut to a predetermined shape and size or chamfered, it is preferable to perform the cutting or chamfering before carrying out the chemical strengthening treatment in the next step, step 3. This allows a compressive stress layer to be formed on the cut or chamfered surface during the subsequent chemical strengthening treatment.

<Step 3>
Step 3 is a step of subjecting the crystallized glass obtained in step 2 to a chemical strengthening treatment to obtain chemically strengthened glass.
Chemical strengthening is a process in which glass is brought into contact with a metal salt (e.g., potassium nitrate) by immersion in a melt of a metal salt containing metal ions with a large ionic radius (typically Na ions or K ions), thereby replacing metal ions with a small ionic radius (typically Li ions or Na ions) in the glass with metal ions with a large ionic radius (typically Na ions or K ions for Li ions, and K ions for Na ions).

In order to speed up the chemical strengthening process, it is preferable to use "Li-Na exchange," which exchanges Li ions in the glass for Na ions. The crystallized glass in this embodiment contains a crystalline phase, but a compressive stress layer is formed not only in the amorphous phase but also when the Li that makes up the crystalline phase is converted to Na.

In addition, to create greater compressive stress through ion exchange, it is preferable to use "Na-K exchange," in which Na ions in the glass are exchanged for K ions.

Examples of molten salts for carrying out the chemical strengthening treatment include nitrates, sulfates, carbonates, and chlorides.
Examples of nitrates include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, and silver nitrate.
Examples of sulfates include lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, and silver sulfate.
Examples of carbonates include lithium carbonate, sodium carbonate, and potassium carbonate.
Examples of chlorides include lithium chloride, sodium chloride, potassium chloride, cesium chloride, and silver chloride.
These molten salts may be used alone or in combination of two or more kinds.

When both Li-Na exchange and Na-K exchange are performed, a mixed molten salt of lithium nitrate, sodium nitrate, and potassium nitrate may be used. In this case, the mixing ratio of lithium nitrate, sodium nitrate, and potassium nitrate is not particularly limited, but for example, for a total of 100 parts by mass of lithium nitrate, sodium nitrate, and potassium nitrate, 0.002 to 0.5 parts by mass of lithium nitrate, 20 to 70 parts by mass of sodium nitrate, and 30 to 80 parts by mass of potassium nitrate are preferred.

The processing conditions for the chemical strengthening process, such as time and temperature, can be selected taking into consideration the glass composition and type of molten salt. For example, the crystallized glass obtained in step 2 can be chemically strengthened, preferably at 500°C or less, for 20 hours or less. It is also possible to perform the chemical strengthening process in two or more stages.

The present invention will be explained below by way of test examples, but the present invention is not limited thereto.
Examples 1 to 4 are working examples, and Examples 5 to 8 are comparative examples.

<<Examples 1 to 8>>
Glass raw materials were mixed to obtain the glass compositions (glass materials A to G) shown in Table 1 in mole percent based on oxides, and weighed out to obtain 600 g of glass. The mixed glass raw materials were then placed in a platinum crucible, placed in an electric furnace at 1550°C, melted for about 5 hours, degassed, and homogenized.
The obtained molten glass was poured into a mold, kept at 470°C for 1 hour, and then cooled to room temperature at a rate of 0.5°C/min to obtain a glass block. Note that blanks in the glass composition in Table 1 indicate that no additives were added.

The resulting glass blocks were each processed into plates measuring 50 mm x 50 mm x 0.6 mm thick, and then underwent a two- or three-stage crystallization process. Specifically, the first and second processes, or the first, second and second processes, were carried out at the temperatures and holding times listed under "Crystallization Conditions" in Table 1. The blocks were then cooled to room temperature to obtain crystallized glass. Note that a "-" in the "Crystallization Conditions" section of Table 1 indicates that the third heat treatment was not carried out.

The resulting crystallized glass was subjected to ion exchange treatment using the molten salt, temperature, and time listed under "Tempering Conditions" in Table 2 to obtain chemically tempered glass.

"evaluation"
<Transmittance>
The transmittance of the crystallized glass was measured using a spectrophotometer (product name U-4100) manufactured by Hitachi High-Tech Corporation. Specifically, the transmittance of light with a wavelength of 600 nm was measured. The thickness of the crystallized glass was 0.6 mm. The results are shown in Table 2.

<X-ray diffraction: precipitated crystals>
The crystallized glass was subjected to powder X-ray diffraction analysis under the following conditions, and the crystallization rate, precipitated crystals, and their content ratios were determined by Rietveld analysis. The results are shown in Table 1, where only the main crystal species is listed for the crystalline phase. Here, the main crystal species refers to the type of crystal that is most abundant among the crystals that make up the crystalline phase.
Measuring device: Rigaku SmartLab
X-rays used: Cu-Kα rays Measurement range: 2θ = 10° to 80°
Speed: 10°/min Step: 0.02°

<composition>
Composition analysis of the obtained crystallized glass and chemically strengthened glass confirmed that there was no significant change from the glass composition before crystallization and that it was the same as the glass composition shown in Table 1. Therefore, although "composition" is shown in Table 1, this represents the composition of all the amorphous glass before crystallization, the crystallized glass, and the chemically strengthened glass after the crystallized glass was chemically strengthened at the center in the thickness direction.

<Young's modulus>
The Young's modulus of the crystallized glass was measured by an ultrasonic method using an ultrasonic thickness gauge (manufactured by Olympus Corporation, product name 38DL). The results are shown in Table 1. It was confirmed that the Young's modulus of the chemically strengthened glass after chemical strengthening treatment was also approximately the same as that of the crystallized glass.

<Fracture toughness value K1c>
The fracture toughness value K _IC of the crystallized glass was measured using a strength testing machine (Shimadzu Corporation, Autograph AGS-X) according to the pre-crack introduction fracture test method (SEPB method: Single-Edge-Precracked-Beam method) specified in JIS R1607:2015. The results for the crystallized glass are shown in Table 1. In addition, the fracture toughness value K _IC for chemically strengthened glass was not measured, but as a reference value, the fracture toughness value K _IC values that are the same as those for the crystallized glass are shown in parentheses in Table 2.

<Stress profile>
The stress profile in the depth direction of the chemically strengthened glass was measured using a measuring instrument SLP-2000 manufactured by Orihara Seisakusho Co., Ltd.
Based on the above stress profile, the compressive stress value CS ₅₀ (MPa) at a depth of 50 μm from the surface, the compressive stress value CS ₁₀₀ (MPa) at a depth of 100 μm from the surface, the compressive stress value CS ₁₅₀ (MPa) at a depth of 150 μm from the surface, the compressive stress layer depth DOL (μm), the depth K-DOL (μm) from the surface of the compressive stress layer due to K ions, the maximum value of tensile stress CT _max (MPa), and the average value CT _ave (MPa) of the tensile stress obtained from the integrated value I _CT (MPa μm) and the thickness direction length L _CT of the tensile stress region are shown in Table 2.
Table 2 also shows the values of α and Y, which are evaluation parameters calculated using the average tensile stress CT _ave (MPa) and the above-mentioned fracture toughness value K1c according to the following formula.
Y=0.1×α−0.05×CT _ave
α=200×K1c-100
CT _ave =I _CT /L _CT
I _CT : Integrated value of tensile stress (MPa μm)
_LCT : Length of tensile stress area in the thickness direction (μm)
K1c: fracture toughness value (MPa·m ^1/2 )

<Na ion concentration>
The Na ion concentration [Na] ₁₀₀ at a depth of 100 μm from the surface of the chemically strengthened glass and the Na ion concentration [Na] ₅₀ at a depth of 50 μm from the surface were analyzed using an electron probe microanalyzer (EPMA).
In this embodiment, the Na profile in the thickness direction of the chemically strengthened crystallized glass was obtained by the following method.
First, the chemically strengthened glass was embedded in resin, a cross section was prepared on a plane parallel to the thickness direction of the chemically strengthened glass, and the cross section was mirror-polished to obtain a measurement sample. The surface of the cross section of the obtained chemically strengthened glass measurement sample was analyzed by EPMA.
The EPMA analysis was performed using a JXA-8500F manufactured by JEOL Ltd. In the EPMA analysis, a line scan analysis was performed along the thickness direction of the chemically strengthened glass of the measurement sample.
The results are shown in Table 2. In addition to the values of [Na] ₅₀ and [Na] ₁₀₀ , Table 2 also lists the ratio expressed as {[Na] ₅₀ /[Na] ₁₀₀ }. Note that the chemically strengthened glass of Example 7 was not measured, and therefore is indicated as "-" in Table 2.

<#60 sandpaper set drop strength>
The electronic device simulation structure was prepared by attaching 4 g of chemically strengthened glass (50 mm x 50 mm x 0.6 mm) to 26 g of aluminum plate (70 mm x 70 mm x 2 mm thick) using 30 mm x 30 mm double-sided tape, resulting in a total weight of 31 g. The double-sided tape used was a differential type removable double-sided tape (Double Face (registered trademark) DF8350, manufactured by Toyochem Co., Ltd.).
The test specimen was placed in the test apparatus with the chemically strengthened glass facing downward and dropped onto #60 sandpaper. The test specimen was dropped from a height of 15 cm. If the chemically strengthened glass did not break, the drop height was increased by 5 cm and the drop process was repeated. The height at which the chemically strengthened glass first broke in the test specimen was taken as the crack height. For each test example, the drop test was performed on 10 test specimens, and the average of the crack heights was taken as the average crack height. The results are shown in Table 2.

From the above results, it can be seen that the chemically strengthened glass according to this embodiment can achieve both a high fracture toughness value K1c and a low average tensile stress CT _ave by satisfying a specific composition range. As a result, high strength characteristics were achieved in the #60 sandpaper set drop strength test.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on Japanese patent applications filed on June 7, 2024 (Patent Application No. 2024-092882), December 24, 2024 (Patent Application No. 2024-227177), and March 31, 2025 (Patent Application No. 2025-058529), the contents of which are incorporated herein by reference.

Claims (33)

It is a crystallized glass having a crystalline phase,
The composition of the center of the thickness direction is expressed as mole percentage based on oxides:
SiO ₂ 62-75%,
Al ₂ O ₃ 2.2-6.0%,
P ₂ O ₅ more than 0% and less than 3%,
Li ₂ O 20-27%,
Na ₂ O more than 0% and less than 5%,
K ₂ O 0-1%,
MgO 0-2%,
CaO 0-2%,
SrO 0-1%,
ZrO ₂ 1 to 4.2%, and SnO ₂ 0 to 1%,
Substantially does not contain Y ₂ O ₃ ,
Using the content ratio of K ₂ O and Na ₂ O expressed in mole percentage, the value represented by {[K ₂ O]/[Na ₂ O]} is 0 to 0.3;
A chemically strengthened glass in _which the value represented by [{[Al ₂ O ₃ ]/[ZrO _{2 ]}-{[B 2 O 3 ]/[P 2 O 5 ]}] is 0.5 to 1.5, using the contents of Al 2 O 3 , ZrO 2 , B} 2 O 3 and P ₂ O ₅ expressed in mole percentage. It is a crystallized glass having a crystalline phase,
The composition of the center of the thickness direction is expressed as mole percentage based on oxides:
SiO ₂ 62-75%,
Al ₂ O ₃ 2.2-6.0%,
Li ₂ O 20-27% and ZrO ₂ 1-4.2%,
Chemically strengthened glass having an average tensile stress value CT _ave of 60 MPa or less, calculated by {I _CT /L _CT } using the tensile stress integral value I _CT (MPa·μm) and the thickness direction length L _CT (μm) of the tensile stress region. The chemically strengthened glass according to claim 1 or 2, wherein the crystalline phase contains at least one crystal selected from the group consisting of Li ₂ Si ₂ O ₅ , LiAlSi ₂ O ₆ , LiAlSi ₄ O ₁₀ , Li ₃ PO ₄ , and β-quartz solid solution. The chemically strengthened glass according to claim 1 or 2, having a fracture toughness value K1c of 1.3 MPa·m ^1/2 or more. 2. The chemically strengthened glass according to claim 1, wherein the average value CT _ave of the tensile stress obtained by {I _CT /L _CT } using the tensile stress integral value I _CT (MPa·μm) and the plate thickness direction length L _CT (μm) of the tensile stress region is 60 MPa or less. The chemically strengthened glass according to claim 1 or 2, having a compressive stress value CS ₅₀ at a depth of 50 μm from the surface of 220 MPa or less. The chemically strengthened glass according to claim 1 or 2, wherein a compressive stress value CS ₁₅₀ at a depth of 150 μm from the surface is −100 MPa or more. The chemically strengthened glass according to claim 1 or 2, wherein the value of Y represented by the following formula is 10 or more.
Y=0.1×α−0.05×CT _ave
α=200×K1c-100
CT _ave =I _CT /L _CT
I _CT : Integrated value of tensile stress (MPa μm)
_LCT : Length of tensile stress area in the thickness direction (μm)
K1c: fracture toughness value (MPa·m ^1/2 ) Chemically strengthened glass according to claim 1 or 2, in which the depth (K-DOL) from the surface of the compressive stress layer formed by K ions is 3 μm or more. Chemically strengthened glass according to claim 1 or 2, in which the compressive stress layer depth DOL is 100 μm or more. Chemically strengthened glass according to claim 1 or 2, wherein the compressive stress layer depth DOL is {t x 0.15} μm or greater, where t (μm) is the thickness of the glass. The Na ion concentration [Na] ₁₀₀ at a depth of 100 μm from the surface is 2.5 mol% or more,
The chemically strengthened glass according to claim 1 or 2, having a compressive stress value CS ₁₀₀ at a depth of 100 μm from the surface of 30 MPa or less. 3. The chemically strengthened glass according to claim 1, wherein the ratio represented by {[Na] ₅₀ /[Na] ₁₀₀ } is _1.4 or less, where [Na] _{100 is the Na ion concentration at a depth of 100 μm from the surface and [Na] 50} is the Na ion concentration at a depth of 50 μm from the surface. The chemically strengthened glass according to claim 1 or 2, wherein the compressive stress value _CS0 at the outermost surface is 300 to 700 MPa. Chemically strengthened glass according to claim 1 or 2, having a Young's modulus of 105 GPa or more. The chemically strengthened glass according to claim 1 or 2, having an average crack height of 40 cm or more measured by a sandpaper set drop strength test under the following conditions.
(conditions)
The test specimen is an electronic device equipped with chemically strengthened glass, or an electronic device simulation structure that integrates chemically strengthened glass with a housing that holds the chemically strengthened glass. The drop test is performed by dropping the test specimen onto #60 sandpaper with the chemically strengthened glass facing downward. The test specimen is dropped from a height of 15 cm. If the chemically strengthened glass in the test specimen does not break upon dropping, the drop height is increased by 5 cm and the process is repeated. The height at which the chemically strengthened glass in the test specimen first breaks is defined as the crack height. The drop test is performed on 10 test specimens, and the average of the crack heights is defined as the average crack height. The chemically strengthened glass according to claim 1 or 2, wherein the value represented by {[Al ₂ O ₃ ]/[Na ₂ O]}, using the contents of Al ₂ O ₃ and Na ₂ O expressed in mole percentage, is greater than 0 and not greater than 2.3. The chemically strengthened glass according to claim 1 or 2, wherein a value represented by {[Li ₂ O]/[ZrO ₂ ]}, using the content ratios of Li ₂ O and ZrO ₂ expressed in mole percentage, is 8 or more. Chemically strengthened glass according to claim 1 or 2, having a crystallization rate of 40% by mass or more. The chemically strengthened glass according to claim 1 or 2, wherein the average particle size of the crystals constituting the crystalline phase is 10 to 100 nm. Chemically strengthened glass according to claim 1 or 2, having a transmittance of 80% or more for light with a wavelength of 600 nm when converted into a glass with a thickness of 0.6 mm. A crystallized glass having a crystalline phase,
The composition is expressed as mole percentage based on oxides.
SiO ₂ 62-75%,
Al ₂ O ₃ 2.2-6.0%,
P ₂ O ₅ more than 0% and less than 3%,
Li ₂ O 20-27%,
Na ₂ O more than 0% and less than 5%,
K ₂ O 0-1%,
MgO 0-2%,
CaO 0-2%,
SrO 0-1%,
ZrO ₂ 1 to 4.2%, and SnO ₂ 0 to 1%,
Substantially does not contain Y ₂ O ₃ ,
Using the content ratio of K ₂ O and Na ₂ O expressed in mole percentage, the value represented by {[K ₂ O]/[Na ₂ O]} is 0 to 0.3;
A crystallized glass having a value of 0.5 to 1.5, where the content ratios of Al ₂ O ₃ , ZrO ₂ , B ₂ O ₃ and P ₂ O ₅ are expressed in mole percentage, that is, [{[Al ₂ O ₃ ]/[ZrO ₂ ]}-{[B ₂ O ₃ ]/[P ₂ O ₅ ]}]. 23. The glass-ceramics according to claim 22, wherein the crystalline phase comprises at least one crystal selected from the group consisting of Li ₂ Si ₂ O ₅ , LiAlSi ₂ O ₆ , LiAlSi ₄ O ₁₀ , Li ₃ PO ₄ , and β-quartz solid solution. The crystallized glass according to claim 22 or 23, having a fracture toughness value K1c of 1.2 MPa·m ^1/2 or more. Ceramics according to claim 22 or 23, having a Young's modulus of 105 GPa or more. 24. The crystallized glass according to claim 22 or 23, wherein the value expressed by {[Al ₂ O ₃ ]/[Na ₂ O]}, using the content ratios of Al ₂ O ₃ and Na ₂ O expressed in mole percentage, is greater than 0 and not greater than 0.23. 24. The crystallized glass according to claim 22 or 23, wherein the value expressed by {[ _Li2O ]/[ _ZrO2 ]}, where _Li2O and _ZrO2 are contained in mole percentage, is 8 or more. Ceramics according to claim 22 or 23, having a crystallization rate of 40% by mass or more. Ceramics according to claim 22 or 23, wherein the average grain size of the crystals constituting the crystalline phase is 10 to 100 nm. Ceramics according to claim 22 or 23, having a transmittance of 80% or more for light with a wavelength of 600 nm when converted to a thickness of 0.6 mm. The composition is expressed as mole percentage based on oxides,
SiO ₂ 62-75%,
Al ₂ O ₃ 2.2-6.0%,
P ₂ O ₅ more than 0% and less than 3%,
Li ₂ O 20-27%,
Na ₂ O more than 0% and less than 5%,
K ₂ O 0-1%,
MgO 0-2%,
CaO 0-2%,
SrO 0-1%,
ZrO ₂ 1 to 4.2%, and SnO ₂ 0 to 1%,
Substantially does not contain Y ₂ O ₃ ,
Using the content ratio of K ₂ O and Na ₂ O expressed in mole percentage, the value represented by {[K ₂ O]/[Na ₂ O]} is 0 to 0.3;
A glass in which the value represented by [{[Al ₂ O _{3 ]} /[ZrO _{2 ]}-{[B 2 O 3 ] /} [P ₂ O ₅ ]}], where the content ratios of Al ₂ O ₃ , ZrO ₂ , B 2 O 3 and P ₂ O ₅ are expressed in mole percentage _, is 0.5 to 1.5. The glass according to claim 31, wherein the value expressed by {[Al ₂ O ₃ ]/[Na ₂ O]}, where the content ratios of Al ₂ O ₃ and Na ₂ O are expressed as mole percentages, is greater than 0 and not greater than 0.23. The glass according to claim 31 or 32, wherein the value expressed by {[Li ₂ O]/[ZrO ₂ ]}, where the content ratio of Li ₂ O and ZrO ₂ is expressed in mole percentage, is 8 or more.