Three-dimensional crystallized glass, three-dimensional chemically strengthened glass, and methods for producing these
阅读说明：本技术 三维形状的晶化玻璃、三维形状的化学强化玻璃以及它们的制造方法 (Three-dimensional crystallized glass, three-dimensional chemically strengthened glass, and methods for producing these ) 是由 李清 今北健二 小池章夫 前田枝里子 于 2019-02-22 设计创作，主要内容包括：本发明提供一种三维形状的晶化玻璃,所述三维形状的晶化玻璃用于容易地制造不易损伤且透明性优异的三维形状的化学强化玻璃。本发明的三维形状的晶化玻璃含有晶体,所述三维形状的晶化玻璃的以厚度0.8mm换算的光透射率为80％以上,并且以氧化物基准的质量％表示,所述三维形状的晶化玻璃含有：45％～74％的SiO<Sub>2</Sub>、1％～30％的Al<Sub>2</Sub>O<Sub>3</Sub>、1％～25％的Li<Sub>2</Sub>O、0～10％的Na<Sub>2</Sub>O、0～5％的K<Sub>2</Sub>O、合计0～15％的SnO<Sub>2</Sub>和ZrO<Sub>2</Sub>中的任意一种以上、以及0～12％的P<Sub>2</Sub>O<Sub>5</Sub>。(The present invention provides a three-dimensional crystallized glass for easily producing a three-dimensional chemically strengthened glass which is less likely to be damaged and has excellent transparency. The three-dimensional crystallized glass of the present invention contains crystals, has a light transmittance of 80% or more in terms of a thickness of 0.8mm and is expressed by mass% based on oxides, and contains: 45% -74% of SiO 2 1 to 30 percent of Al 2 O 3 1 to 25% of Li 2 O, 0-10% of Na 2 O, 0 to 5% of K 2 O, SnO in an amount of 0 to 15% in total 2 And ZrO 2 At least one of them, and 0-12% of P 2 O 5 。)
1. A three-dimensional-shaped crystallized glass which is a three-dimensional-shaped crystallized glass containing crystals, wherein,
the light transmittance of the three-dimensional crystallized glass in terms of thickness of 0.8mm is 80% or more, and
the three-dimensionally shaped crystallized glass contains, in mass% on an oxide basis:
45 to 74 percent of SiO2、
1 to 30 percent of Al2O3、
1 to 25 percent of Li2O、
0 to 10% of Na2O、
0 to 5% of K2O、
SnO in an amount of 0 to 15% in total2And ZrO2At least one of them, and
0 to 12% of P2O5。
2. The crystallized glass of three-dimensional shape according to claim 1, wherein the crystallized glass of three-dimensional shape contains, in mass% on an oxide basis:
58 to 74 percent of SiO2、
5 to 30 percent of Al2O3、
1 to 14 percent of Li2O、
0 to 5% of Na2O、
0 to 2% of K2O、
SnO in a total amount of 0.5 to 12%2And ZrO2At least one of them, and
0 to 6% of P2O5。
3. The crystallized glass of three-dimensional shape according to claim 2, wherein the crystallized glass of three-dimensional shape contains, in mass% on an oxide basis:
58 to 70 percent of SiO2、
15 to 30 percent of Al2O3、
2% -10% of Li2O、
0 to 5% of Na2O、
0 to 2% of K2O、
0.5 to 6 percent of SnO2、
0.5 to 6 percent of ZrO2And, and
0 to 6% of P2O5And is and
Na2O+K2o is 1 to 5 percent.
4. The crystallized glass of three-dimensional shape according to claim 1, wherein the crystallized glass of three-dimensional shape contains, in mass% on an oxide basis:
45 to 70 percent of SiO2、
1 to 20 percent of Al2O3、
10% -25% of Li2O、
0 to 10% of Na2O、
0 to 5% of K2O、
0 to 15% of ZrO2And, and
0 to 12% of P2O5。
5. The three-dimensional crystallized glass according to any one of claims 1 to 3, wherein the three-dimensional crystallized glass contains β -spodumene crystals.
6. The crystallized glass of three-dimensional shape according to claim 1 or 2, wherein the crystallized glass of three-dimensional shape contains petalite crystals.
7. The three-dimensionally shaped crystallized glass according to claim 1 or 4, wherein the three-dimensionally shaped crystallized glass contains lithium metasilicate crystals.
8. The crystallized glass of three-dimensional shape according to any one of claims 1 to 7, wherein the Vickers hardness of the crystallized glass of three-dimensional shape is 780 or more.
9. A three-dimensional chemically strengthened glass having a compressive stress layer on a surface thereof, wherein,
the three-dimensional chemically strengthened glass is crystallized glass containing crystals,
the transmittance of the three-dimensional chemically strengthened glass in terms of thickness of 0.8mm is 80% or more, and
the chemically strengthened glass having a three-dimensional shape contains, in mass% on an oxide basis:
45 to 74 percent of SiO2、
1 to 30 percent of Al2O3、
1 to 25 percent of Li2O、
0 to 10% of Na2O、
0 to 5% of K2O、
SnO in an amount of 0 to 15% in total2And ZrO2At least one of them, and
0 to 12% of P2O5。
10. The chemically strengthened glass having a three-dimensional shape according to claim 9, wherein the chemically strengthened glass having a three-dimensional shape contains, in mass% on an oxide basis:
58 to 74 percent of SiO2、
5 to 30 percent of Al2O3、
1 to 14 percent of Li2O、
0 to 5% of Na2O、
0 to 2% of K2O、
SnO in a total amount of 0.5 to 12%2And ZrO2At least one of them, and
0 to 6% of P2O5。
11. The chemically strengthened glass having a three-dimensional shape according to claim 9, wherein the chemically strengthened glass having a three-dimensional shape contains, in mass% on an oxide basis:
45 to 70 percent of SiO2、
1 to 20 percent of Al2O3、
10% -25% of Li2O、
0 to 10% of Na2O、
0 to 5% of K2O、
0 to 15% of ZrO2And, and
0 to 12% of P2O5。
12. The three-dimensionally shaped, chemically strengthened glass according to claim 9 or 10, wherein the three-dimensionally shaped, chemically strengthened glass contains β -spodumene crystals.
13. The three-dimensionally shaped chemically strengthened glass according to claim 9 or 11, wherein the three-dimensionally shaped chemically strengthened glass contains lithium metasilicate.
14. The chemically strengthened glass having a three-dimensional shape according to any one of claims 9 to 13, wherein the chemically strengthened glass having a three-dimensional shape has a Vickers hardness of 800 or more.
15. The three-dimensionally shaped chemically strengthened glass according to any one of claims 9 to 14, wherein the three-dimensionally shaped chemically strengthened glass has a surface compressive stress of 600MPa or more and a depth of compressive stress of 80 μm or more.
16. A method for producing a glass for chemical strengthening, comprising heating a glass to crystallize the glass, heating the obtained crystallized glass and bending the glass,
the glass contains, in mass% on an oxide basis:
45 to 74 percent of SiO2、
1 to 30 percent of Al2O3、
1 to 25 percent of Li2O、
0 to 10% of Na2O、
0 to 5% of K2O、
SnO in an amount of 0 to 15% in total2And ZrO2At least one of them, and
0 to 12% of P2O5。
17. The method for producing a glass for chemical strengthening according to claim 16, wherein the glass is crystallized by heating, and the obtained crystallized glass is bent while heating,
the glass contains, in mass% on an oxide basis:
58 to 74 percent of SiO2、
5 to 30 percent of Al2O3、
1 to 14 percent of Li2O、
0 to 5% of Na2O、
0 to 2% of K2O、
SnO in a total amount of 0.5 to 12%2And ZrO2At least one of them, and
0 to 6% of P2O5And is and
Na2O+K2o is 1 to 5 percent.
18. The method for producing a glass for chemical strengthening according to claim 16, wherein the glass is crystallized by heating, and the obtained crystallized glass is bent while heating,
the glass contains, in mass% on an oxide basis:
45 to 70 percent of SiO2、
1 to 20 percent of Al2O3、
10% -25% of Li2O、
0 to 10% of Na2O、
0 to 5% of K2O、
0 to 15% of ZrO2And, and
0 to 12% of P2O5。
19. A method for producing a chemically strengthened glass, wherein the glass for chemical strengthening obtained by the method according to any one of claims 16 to 18 is chemically strengthened.
Technical Field
The present invention relates to a three-dimensional crystallized glass having high transparency and excellent chemical strengthening properties, and a method for producing the same. The present invention also relates to a chemically strengthened glass having a three-dimensional shape and a method for producing the same.
Background
Thin and strong chemically strengthened glass is used as cover glass for display devices of mobile devices such as mobile phones and smart phones, and as cover glass for on-vehicle display members such as instrument panels and head-up displays (HUDs). In these display devices, a three-dimensional (curved) cover glass is sometimes required to improve operability and visibility. The cover glass having a three-dimensional shape is manufactured by a method of heating a flat glass plate and performing bending molding (also referred to as three-dimensional molding) using a molding die (see patent document 1).
Disclosure of Invention
Problems to be solved by the invention
The chemical strengthening properties of crystallized glass are strongly influenced by the glass composition and precipitated crystals. The indefiniteness and transparency of crystallized glass are strongly affected by the glass composition and the precipitated crystal. Therefore, in order to obtain a crystallized glass excellent in both chemical strengthening properties and transparency, it is necessary to finely adjust the glass composition and precipitated crystals.
As a method for obtaining a three-dimensionally shaped crystallized glass, a method of bending and crystallizing an amorphous glass, a method of crystallizing an amorphous glass and then processing the amorphous glass into a three-dimensional shape by a method such as grinding, and a method of crystallizing an amorphous glass and then bending may be considered.
In the method of bending an amorphous glass and then crystallizing the amorphous glass, since the amorphous glass is heated after the molding, the amorphous glass is easily deformed and a dimensional change occurs when the amorphous glass is crystallized, and thus it is difficult to obtain a desired shape. The method of crystallizing amorphous glass and then processing the crystallized amorphous glass into a three-dimensional shape by grinding or the like requires a long time for cutting, and therefore, the production efficiency is not high.
Therefore, it is preferable to crystallize the amorphous glass and then bend the amorphous glass. However, crystallized glass generally has a higher softening temperature than amorphous glass, and is difficult to bend. In addition, when a transparent crystallized glass is heated to a high temperature to be bent, there is a problem that crystals in the crystallized glass grow excessively and transparency is lowered.
In view of the above circumstances, an object of the present invention is to provide a three-dimensional crystallized glass for easily producing a three-dimensional chemically strengthened glass which is less likely to be damaged and has excellent transparency.
Another object of the present invention is to provide a three-dimensional chemically strengthened glass which is obtained by chemically strengthening the three-dimensional crystallized glass, is less likely to be damaged, and has excellent transparency.
Another object of the present invention is to provide a method for producing a chemically strengthened glass which is the three-dimensional crystallized glass.
Means for solving the problems
The present invention provides a three-dimensional crystallized glass containing crystals, wherein the three-dimensional crystallized glass has a light transmittance of 80% or more in terms of a thickness of 0.8mm and is expressed by mass% based on oxides, and the three-dimensional crystallized glass contains: 45 to 74 percent of
Further, the present invention provides a three-dimensional chemically strengthened glass having a compressive stress layer on a surface thereof, wherein the three-dimensional chemically strengthened glass is a crystallized glass containing crystals, and the three-dimensional chemically strengthened glass has a transmittance of 80% or more in terms of a thickness of 0.8mm and is expressed by mass% based on oxides, and the three-dimensional chemically strengthened glass contains: 45 to 74 percent of
Further, the present invention provides a method for producing a glass for chemical strengthening, which comprises heating a glass to crystallize the glass, and heating the obtained crystallized glass and bending the glass to form a glass, wherein the glass comprises, in mass% based on oxides: 45 to 74 percent of
Further, the present invention provides a method for producing a chemically strengthened glass, comprising heating a glass to crystallize the glass, heating the obtained crystallized glass and bending the glass, and then chemically strengthening the glass, wherein the glass comprises, in mass% based on oxides: 45 to 74 percent of
Effects of the invention
According to the present invention, a three-dimensional crystallized glass can be obtained which is used for easily producing a three-dimensional chemically strengthened glass which is less likely to be damaged and has excellent transparency.
The chemically strengthened glass of the present invention is hardly damaged and has excellent transparency, and can be easily produced by chemically strengthening the crystallized glass of the present invention having a three-dimensional shape.
Further, according to the method for producing a chemically strengthened glass of the present invention, the crystallized glass of the three-dimensional shape of the present invention can be obtained.
Drawings
Fig. 1 is a perspective view showing an example of the shape of the three-dimensional glass of the present invention.
Fig. 2 is a perspective view showing an example of the shape of the three-dimensional glass of the present invention.
Fig. 3 is a perspective view showing an example of the shape of the three-dimensional glass of the present invention.
FIG. 4 is a diagram showing an example of an X-ray diffraction pattern of a crystallized glass.
FIG. 5 is a diagram showing an example of an X-ray diffraction pattern of a crystallized glass.
Fig. 6(a) and (b) are schematic views showing a method of testing bending formability of crystallized glass, in which fig. 6(a) shows a state before bending, and fig. 6(b) shows a state of bending by heating.
Detailed Description
Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the embodiments described below. In the following drawings, members and portions that perform the same function are sometimes described with the same reference numerals, and redundant description may be omitted or simplified. The embodiments shown in the drawings are schematically illustrated for the purpose of clearly explaining the present invention, and do not necessarily indicate actual dimensions or scales precisely.
In the present specification, "to" indicating a numerical range is used in a meaning including numerical values described before and after the range as a lower limit value and an upper limit value.
In the present specification, "amorphous glass" and "crystallized glass" are collectively referred to as "glass".
In the present specification, the term "amorphous glass" means a glass in which a diffraction peak indicating a crystal is not observed by a powder X-ray diffraction method.
In the present specification, the term "crystallized glass" refers to a glass in which crystals are precipitated by heat treatment of "amorphous glass", and contains crystals.
In the powder X-ray diffraction measurement, CuK α rays are used to measure 2 θ in the range of 10 ° to 80 °, and when a diffraction peak appears, the precipitated crystal is identified by, for example, a three-line method.
In the present specification, "chemically strengthened glass" refers to glass after being subjected to a chemical strengthening treatment, and "glass for chemical strengthening" refers to glass before being subjected to a chemical strengthening treatment.
In the present specification, the "basic composition of the chemically strengthened glass" refers to the glass composition of the glass for chemical strengthening. The glass composition of the portion of the chemically strengthened glass deeper than the depth of compressive stress (DOL) was the same as the basic composition of the chemically strengthened glass except that the ion exchange treatment was performed extremely.
In this specification, unless otherwise specified, the glass composition is represented by mass% on an oxide basis, and mass% is abbreviated as "%".
In the present specification, "substantially not contained" means that the impurity level contained in the raw material or the like is not higher than that, that is, the impurity is not intentionally added. In the present specification, when a component is described as not substantially containing it, the content of the component is, for example, less than 0.1%.
In the present specification, the term "stress distribution" refers to a graph in which a compressive stress value is expressed by a depth from a glass surface as a variable. In the stress distribution, the tensile stress is expressed as a negative compressive stress.
The "compressive stress value (CS)" can be determined by flaking a cross section of glass and analyzing the flaked sample using a birefringence imaging system. As the birefringent imaging system, there is, for example, a birefringent imaging system Abrio-IM manufactured by tokyo instruments. In addition, measurement may be performed using photoelastic of scattered light. In this method, CS can be measured by making light incident from the surface of the glass and analyzing the polarized light of the scattered light. As a stress measuring instrument using the scattered light photoelastic, for example, there is a scattered light photoelastic stress meter SLP-1000 manufactured by prototype manufacturing.
"depth of layer of compressive stress (DOL)" is the depth at which the value of Compressive Stress (CS) is zero.
Hereinafter, the compressive stress at DOL/4 may be referred to as CS1The compressive stress at a depth of DOL/2 is referred to as CS2。
The depth at which the compressive stress value reaches CS/2 is DOL1M to be represented by1Set to DOL from the glass surface to the depth1The slope of the stress distribution within the range of (a).
m1＝(CS-CS/2)/(0-DOL1)
M to be represented by2The slope of the stress distribution in the range from the depth DOL/4 to the depth DOL/2 is set.
m2＝(CS1-CS2)/(DOL/4-DOL/2)
M to be represented by3The slope of the stress distribution in the range from the depth DOL/2 to the depth DOL is set.
m3＝(CS2-0)/(DOL/2-DOL)
In the present specification, "internal tensile stress (CT)" means a tensile stress value at 1/2 depth of the sheet thickness t.
In the present specification, "light transmittance" refers to the average transmittance of light having a wavelength of 380nm to 780 nm.
In the present specification, "haze value" means a value measured using a C light source and according to JIS K3761: 2000 haze value measured.
In the present specification, "vickers hardness" is a hardness in JIS R1610: vickers hardness (HV0.1) specified in 2003.
The "fracture toughness value" is a value obtained in accordance with JIS R1607: fracture toughness value by indenter press-in method (IF method) specified in 2010.
In the present specification, the "three-dimensional shape" refers to a shape obtained by bending a flat plate. The three-dimensional shape is not limited to a shape having a uniform thickness as a whole, and may be a shape having portions having different thicknesses.
< three-dimensional shape of crystallized glass >
Fig. 1 is a perspective view showing an example of a three-dimensionally shaped crystallized glass (hereinafter, also referred to as "the present three-dimensionally shaped glass") according to the present embodiment. Although FIG. 1 is depicted as concave, the present three-dimensional shape of the glass may also be convex. In fig. 1, the central portion shows a flat glass plate, but the entire three-dimensional glass plate may be curved. As shown in fig. 2 and 3, the three-dimensional glass may have a three-dimensional shape composed of a plurality of R-shapes.
Since this three-dimensional glass has high transparency, it is suitable for a cover glass of a display portion of a mobile terminal or the like. When the light transmittance in terms of thickness 0.8mm of the three-dimensional glass is 80% or more, the screen is easily visible when the glass is used as a cover glass for a portable display, and therefore, the light transmittance in terms of thickness 0.8mm is preferably 85% or more, more preferably 86% or more, and particularly preferably 88% or more. The higher the light transmittance in terms of 0.8mm thickness of the three-dimensional glass, the more preferable, but the three-dimensional glass is usually 91% or less or 90% or less. 90% is the same light transmittance as that of ordinary amorphous glass.
The haze value of the three-dimensional glass in terms of a thickness of 0.8mm is preferably 1.5% or less, more preferably 1.2% or less, still more preferably 1% or less, most preferably 0.8% or less, and most preferably 0.5% or less. On the other hand, in the case where the haze is difficult to be reduced without reducing the crystallization rate, the haze value in the case where the thickness of the present three-dimensional shaped glass is 0.8mm is preferably 0.05% or more, more preferably 0.1% or more, in order to improve the mechanical strength and the like.
Since this three-dimensional glass is crystallized glass, it has higher strength than amorphous glass. In addition, the three-dimensional glass has high Vickers hardness and is not easy to damage.
In order to improve the abrasion resistance, the vickers hardness of the three-dimensional glass is preferably 680 or more, more preferably 700 or more, still more preferably 740 or more, still more preferably 780 or more, and particularly preferably 800 or more.
However, since the vickers hardness is too large, the glass may be difficult to be processed, and therefore, the vickers hardness of the present three-dimensional glass is preferably 1100 or less, more preferably 1050 or less, and further preferably 1000 or less.
The crystallized glass constituting the glass having a three-dimensional shape (hereinafter, may be simply referred to as "present crystallized glass") contains crystals, but preferably contains lithium aluminosilicate crystals or lithium silicate crystals. In the case of containing lithium aluminosilicate crystals or lithium silicate crystals, these crystals are also ion-exchanged by chemical strengthening treatment, and high strength can be obtained. Examples of the lithium aluminosilicate crystal include β -spodumene crystal and petalite crystal. Examples of the lithium silicate crystal include a lithium metasilicate crystal and a lithium disilicate crystal.
When it is desired to increase the strength after chemical strengthening, the crystallized glass preferably contains β -spodumene crystals. In the case where it is intended to improve transparency and formability while maintaining chemical strengthening properties, the crystallized glass preferably contains lithium metasilicate crystals.
β spodumene crystalThe body is represented by LiAlSi2O6And is a crystal showing diffraction peaks at bragg angles (2 θ) of 25.55 ° ± 0.05 °, 22.71 ° ± 0.05 ° and 28.20 ° ± 0.05 ° in an X-ray diffraction pattern.
Fig. 2 shows an example of an X-ray diffraction pattern of a crystallized glass (glass for chemical strengthening) containing β -spodumene crystals and a crystallized glass (glass for chemical strengthening) obtained by chemically strengthening the crystallized glass. In FIG. 2, the solid line is an X-ray diffraction pattern obtained by measurement of a crystallized glass plate before strengthening, and a diffraction line of a β -spodumene crystal represented by a black circle in FIG. 2 is observed. The dotted line indicates an X-ray diffraction pattern obtained by measuring a crystallized glass (chemically strengthened glass) plate after chemical strengthening. The position of the diffraction peak is shifted to the low angle side by chemical strengthening, which is considered to be because: ion exchange between small ions in the crystal and large ions in the molten salt occurs, and the lattice spacing becomes large.
However, the inventors of the present invention have compared powder X-ray diffraction patterns before and after chemical strengthening, and as a result, such a shift of diffraction lines is not observed. This is considered to be because: the change in lattice spacing due to the chemical strengthening treatment is generated only in the vicinity of the surface of the glass plate, and the change due to the chemical strengthening treatment is not generated in the internal crystal.
The crystallized glass containing β -spodumene crystals tends to have a larger surface Compressive Stress (CS) by chemical strengthening as compared with crystallized glass containing other crystals. It is considered that the crystal structure of β -spodumene crystals is dense, and therefore, the compressive stress generated by the change in the crystal structure accompanying the replacement of ions in the precipitated crystals with larger ions by the ion exchange treatment for chemical strengthening becomes large.
It is known that the crystal growth rate of β -spodumene crystals is fast. Therefore, the crystallized glass containing β -spodumene crystals tends to have large crystals, and thus has low transparency and a large haze value in many cases. However, since the present three-dimensional shaped glass contains a large amount of fine crystals, it has high transparency and a small haze value.
The lithium metasilicate crystal is represented by Li2SiO3The crystal shows diffraction peaks at Bragg angles (2 theta) of 26.98 + -0.2, 18.88 + -0.2, and 33.05 + -0.2 in an X-ray diffraction pattern. FIG. 3 shows an example of an X-ray diffraction pattern of a crystallized glass containing lithium metasilicate crystals.
The crystallized glass containing lithium metasilicate crystals has a higher fracture toughness value than amorphous glass, and is less likely to undergo severe fracture even when a large compressive stress is formed by chemical strengthening. The amorphous glass capable of precipitating lithium metasilicate crystals may precipitate lithium disilicate crystals depending on heat treatment conditions and the like, and when lithium metasilicate crystals and lithium disilicate crystals are contained together, transparency is lowered. Therefore, in order to improve transparency, the crystallized glass containing lithium metasilicate preferably does not contain lithium disilicate. Here, "does not contain lithium disilicate" means that no diffraction peak of lithium disilicate crystals is observed in the above X-ray diffraction measurement.
In the case where the bending temperature is to be lowered, the crystallized glass preferably contains petalite crystals or lithium metasilicate crystals. Since the crystallized glass containing these crystals has a low crystallization temperature and a low softening temperature, the molding temperature tends to be easily lowered.
In order to improve the mechanical strength, the crystallization rate of the crystallized glass is preferably 10% or more, more preferably 15% or more, further preferably 20% or more, and particularly preferably 25% or more. On the other hand, in order to improve transparency, the crystallization ratio of the crystallized glass is preferably 70% or less, more preferably 60% or less, and particularly preferably 50% or less. The small crystallization rate is also preferable in that the bending by heating is easy.
The crystallization rate can be calculated from the X-ray diffraction intensity by the Reed-Bord method. The Reed-Burd method is described in the Crystal analysis Manual edited by the edit Committee of the Japan Crystal society, Crystal analysis Manual (Co-ordinated Press, 1999 journal, pages 492 to 499).
The average particle diameter of the precipitated crystals of the crystallized glass is preferably 300nm or less, more preferably 200nm or less, still more preferably 150nm or less, and particularly preferably 100nm or less. The average particle diameter of the precipitated crystal can be calculated from the powder X-ray diffraction intensity by the Reed-Bord method.
It is known that a crystallized glass containing β -spodumene crystals has a small thermal expansion coefficient, and in the case where the crystallized glass contains β -spodumene, the average thermal expansion coefficient in the range of 50 ℃ to 350 ℃ is preferably 30 × 10-7Not more than 25/° C, more preferably 25 × 10-7Not more than 20 × 10 c, more preferably not more than 20-7Not more than/° C, particularly preferably 15 × 10-7The average coefficient of thermal expansion in the range of 50 ℃ to 350 ℃ is usually 10 × 10-7Above/° c.
On the other hand, when the crystallized glass contains lithium metasilicate crystals, the average thermal expansion coefficient of the crystallized glass in the range of 50 ℃ to 350 ℃ is preferably 10 × 10-7More preferably 11 × 10 deg.C or higher, and still more preferably 11 × deg.C or higher-7More preferably 12 × 10℃ or higher, and still more preferably 12 × DEG C or higher-7It is preferably at least 13 × 10℃, particularly preferably 13 × DEG C-7Since the crystallized glass is easily broken by heat treatment when the coefficient of thermal expansion is too large, the average coefficient of thermal expansion of the crystallized glass is preferably 160 × 10 in the range of 50 to 350 ℃ when the crystallized glass contains lithium metasilicate crystals-7Preferably 150 ℃ or lower, and more preferably 150 × 10-7Preferably 140 × 10℃ or less, more preferably 140 × DEG C or less-7Below DEG C.
The crystallized glass preferably has a fracture toughness value of 0.8 MPa-m1/2More preferably 1MPa · m or more1/2When the fracture toughness value of the crystallized glass is within this range, the fragments are less likely to scatter when the tempered glass is broken.
The Young's modulus of the crystallized glass is preferably 80GPa or more, more preferably 86GPa or more, still more preferably 90GPa or more, and particularly preferably 100GPa or more. By increasing the young's modulus, the fragments are less likely to scatter when the tempered glass is broken.
When the crystallized glass contains lithium aluminosilicate crystals, the crystallized glass preferably contains 58 to 74% of SiO in terms of mass% based on oxides25 to 30 percent of Al2O31 to 14% of Li2O, 0-5% of Na2O, 0 to 2% of K2O, SnO in an amount of 0.5 to 12% in total2And ZrO2At least one of them, and 0-6% of P2O5And more preferably 2% to 14% of Li is contained in the above composition2O, in addition, Na2O and K2Total of O content (Na)2O+K2O) is more preferably 1% to 5%.
Further, the crystallized glass preferably contains 58 to 70% of SiO215 to 30 percent of Al2O32 to 10% of Li2O, 0-5% of Na2O, 0 to 2% of K2O, 0.5-6% SnO20.5 to 6 percent of ZrO2And 0 to 6% of P2O5And Na2O+K2O is 1 to 5 percent.
That is, the three-dimensional glass is preferably a glass obtained by crystallizing an amorphous glass having the above composition.
When the crystallized glass contains lithium silicate crystals, the crystallized glass preferably contains, in terms of mass% based on oxides and in terms of mass% based on oxides: 45 to 75 percent of
< chemically strengthened glass >
The present three-dimensionally shaped glass is preferably chemically strengthened. A three-dimensionally shaped chemically strengthened glass of the present embodiment (hereinafter, may be referred to as "present strengthened glass") obtained by chemically strengthening the present three-dimensionally shaped glass will be described.
When the surface Compressive Stress (CS) of the tempered glass is 600MPa or more, the tempered glass is not easily broken by deformation such as bending, and therefore, it is preferable. The surface compressive stress of the tempered glass is more preferably 800MPa or more.
When the depth of compressive stress (DOL) of the present tempered glass is 80 μm or more, it is preferable because cracking is less likely to occur when damage occurs on the surface. The DOL of the present tempered glass is preferably 100 μm or more.
Further, when the maximum depth (hereinafter, sometimes referred to as "50 MPa depth") at which the compressive stress value becomes 50MPa or more is 80 μm or more, the crack is less likely to occur even when the material is dropped onto a hard surface such as asphalt, and therefore, the maximum depth is more preferable. The depth of 50MPa is more preferably 90 μm or more, and particularly preferably 100 μm or more.
In the present strengthened glass, DOL is formed from the surface to the depth of the glass1The slope m of the stress distribution in the range of (1)1Preferably-50 MPa/μm or less, more preferably-55 MPa/μm or less, and still more preferably-60 MPa/μm or less. The chemically strengthened glass is a glass having a compressive stress layer formed on the surface thereof, and a tensile stress is generated in a portion away from the surface thereof, so that the stress distribution thereof has a negative slope from the surface having a zero depth toward the inside. Thus, m1Is negative, by m1The absolute value of (a) is large, and a stress distribution in which the surface compressive stress CS is large and the internal tensile stress CT is small can be obtained.
Slope m of stress distribution in the range from depth DOL/4 to depth DOL/22Is negative. Slope m for suppressing scattering of fragments at the time of breakage of tempered glass2Preferably-5 MPa/μm or more, more preferably-3 MPa/μm or more, and still more preferably-2 MPa/μm or more. m is2If the amount is too large, the depth of 50MPa may be small, and the dropping strength of the asphalt may be insufficient. To increase the depth of 50MPa, m2Preferably-0.3 MPa/μm or less, more preferably-0.5 MPa/μm or less, and still more preferably-0.7 MPa/μm or less.
In the present tempered glass, the slope m of the stress distribution in the range from DOL/2 to DOL in depth3Is negative. M for suppressing scattering of broken pieces at the time of breakage of the tempered glass3Preferably at least-5 MPa/μm, more preferably at least-4 MPa/μm, even more preferably at least-3.5 MPa/μm, and particularly preferably at least-2 MPa/μm. m is3When the absolute value of (A) is too small, the depth of 50MPa becomes small, and the film is liable to crack when damaged. To increase the depth of 50MPa, m3Preferably-0.3 MPa/μm or less, more preferably-0.5 MPa/μm or less, and still more preferably-0.7 MPa/μm or less.
Slope m2And slope m3Ratio of m2/m3When the ratio is 2 or less, deep can be obtainedDOL is preferred because it simultaneously achieves a small CT. m is2/m3More preferably 1.5 or less, and still more preferably 1 or less. M for preventing cracks from occurring at the end faces of the tempered glass2/m3Preferably 0.3 or more, more preferably 0.5 or more, and further preferably 0.7 or more.
When the internal tensile stress (CT) of the tempered glass is 110MPa or less, fragments are not easily scattered when the tempered glass is broken, and therefore, the tempered glass is preferable. CT is more preferably 100MPa or less, and still more preferably 90MPa or less. On the other hand, when CT is reduced, CS becomes small, and it tends to be difficult to obtain sufficient intensity. Therefore, the CT is preferably 50MPa or more, more preferably 55MPa or more, and still more preferably 60MPa or more.
The four-point bending strength of the tempered glass is preferably 900MPa or more.
Here, the four-point bending strength was measured using a test piece of 40mm × 5mm × 0.8mm under the conditions of a lower span of 30mm, an upper span of 10mm, and a crosshead speed of 0.5 mm/min. The average of 10 test pieces was taken as the four-point bending strength.
The light transmittance and haze value of the tempered glass are substantially the same as those of glass having a three-dimensional shape before chemical tempering, and therefore, the explanation thereof is omitted. In addition, the present tempered glass preferably contains β -spodumene crystals, as in the case of a three-dimensional glass before chemical tempering.
The Vickers hardness of the present tempered glass tends to be larger than that of a glass having a three-dimensional shape before tempering.
The vickers hardness of the present tempered glass is preferably 720 or more, more preferably 740 or more, still more preferably 780 or more, and still more preferably 800 or more. The Vickers hardness of the tempered glass is usually 950 or less.
< glass composition >
Here, the glass composition of the crystallized glass will be explained. The composition of the crystallized glass is the same as that of the amorphous glass before the crystallization treatment as a whole.
The present tempered glass is a glass obtained by chemically tempering a glass having a three-dimensional shape including the present crystallized glass, and the composition of the present tempered glass is the same as that of the present crystallized glass described below as a whole except that the glass is subjected to an extreme ion exchange treatment.
The crystallized glass contains, in mass% based on oxides: 45 to 74 percent of
When the crystallized glass contains lithium aluminosilicate crystals, the crystallized glass preferably contains, in terms of mass% based on oxides: 58 to 74 percent of SiO25 to 30 percent of Al2O31 to 14% of Li2O, 0-5% of Na2O, 0 to 2% of K2O, SnO in an amount of 0.5 to 12% in total2And ZrO2At least one of them, and 0-6% of P2O5And in the above composition, it is more preferable to contain 2% to 14% of Li2O, in addition, Na2O and K2Total of O content (Na)2O+K2O) is more preferably 1% to 5%.
In addition, the present crystallized glass preferably further contains, in mass% based on oxides: 58 to 70 percent of SiO215 to 30 percent of Al2O32 to 10% of Li2O, 0-5% of Na2O, 0 to 2% of K2O, 0.5-6% SnO20.5 to 6 percent of ZrO2And 0 to 6% of P2O5And Na2O+K2O is 1 to 5 percent.
When the crystallized glass contains lithium silicate crystals, the crystallized glass preferably contains, in terms of mass% based on oxides and in terms of mass% based on oxides: 45 to 75 percent of
Hereinafter, these preferable glass compositions will be described.
SiO2Is a component forming the network structure of the glass. In addition, SiO2Is a component for improving chemical durability, and is a constituent of lithium aluminosilicate crystal and also a constituent of lithium silicate crystal.
Al2O3Al is a component effective for increasing the surface compressive stress generated by chemical strengthening2O3Is an essential component. In addition, Al2O3Is a constituent of lithium aluminosilicate crystals. Al (Al)2O3Is 1% or more, preferably 2% or more, more preferably 5% or more, and still more preferably 8% or more, in the case where β -spodumene crystals are to be precipitated, Al is contained2O3The content of (b) is more preferably 15% or more, and still more preferably 20% or more. On the other hand, Al2O3When the content of (b) is too large, the devitrification temperature of the glass becomes high. Al (Al)2O3The content of (b) is 30% or less, preferably 25% or less. To lower the forming temperature, Al2O3The content of (b) is more preferably 20% or less, and still more preferably 15% or less.
Li2O is a component for forming a surface compressive stress by ion exchange, is a constituent component of the lithium aluminosilicate crystal and the lithium silicate crystal, and is an essential component.
Li2The content of O is 1% or more, preferably 2% or more, and more preferably 4% or more. To increase the amount of precipitated lithium metasilicate crystals, Li2The content of O is more preferably 10% or more, and further more preferablyPreferably 15% or more, and particularly preferably 20% or more. Li in the case of containing lithium metasilicate2The content of O is preferably 25% or less, more preferably 22% or less, and further preferably 20% or less. On the other hand, to precipitate lithium aluminosilicate crystals, Li2The content of O is preferably 14% or less, and Li is preferable when β -spodumene crystal is to be precipitated2The content of O is preferably 10% or less, more preferably 8% or less, and further preferably 6% or less.
In the case where the crystallized glass contains β -spodumene crystals, Li2O and Al2O3Content ratio of (A) to (B) Li2O/Al2O3When the content is 0.3 or less, the transparency is preferably high.
Na2O is a component for improving the meltability of the glass.
Na2O is not an essential component, but Na is contained in the crystallized glass2The content of O is preferably 0.5% or more, more preferably 1% or more. Na (Na)2When O is too large, the lithium aluminosilicate crystals or lithium silicate crystals are less likely to precipitate or the chemical strengthening property is lowered, so that Na in the crystallized glass is contained2The content of O is preferably 15% or less, more preferably 12% or less, still more preferably 10% or less, Na is added for the purpose of precipitating β -spodumene crystals2The content of O is preferably 5% or less, more preferably 4% or less, and further preferably 3% or less.
K2O and Na2O is also a component for lowering the melting temperature of the glass and may contain K2And O. The crystallized glass contains K2In case of O, K2The content of O is preferably 0.5% or more, more preferably 1% or more. To lower the forming temperature, K2The content of O is more preferably 1.5% or more, and still more preferably 2% or more.
In addition, Na2O and K2Total content Na of O2O+K2O is preferably 1% or more, more preferably 2% or more.
K2When O is too much, the chemical strengthening property is deteriorated, so that K is contained in the crystallized glass2In case of O, K2The content of O is preferably 8%The content is preferably 7% or less, more preferably 6% or less, and particularly preferably 5% or less. In addition, in order to easily precipitate lithium aluminosilicate crystals, K2The content of O is preferably 2% or less. In this case, Na2O and K2Total content Na of O2O+K2When the amount of O is excessive, the transparency may be deteriorated during the heat treatment. In order to improve the transparency, the total content is preferably 5% or less, more preferably 4% or less, and still more preferably 3% or less.
In the crystallized glass containing lithium metasilicate, K is used for the purpose of satisfying both the chemical strengthening property and the precipitation of lithium metasilicate crystals2The content of O is preferably 4% or less, more preferably 3% or less, and particularly preferably 2% or less.
ZrO2And SnO2The crystal nucleus is not an essential component, but is preferably contained in the crystallization treatment as a component constituting the crystal nucleus. SnO for nucleation2And ZrO2SnO in total amount of2+ZrO2Preferably 0.5% or more, more preferably 1% or more. SnO for improving transparency by forming a large number of crystal nuclei2+ZrO2Preferably 3% or more, more preferably 4% or more, further preferably 5% or more, particularly preferably 6% or more, and most preferably 7% or more. For precipitating lithium metasilicate, ZrO is preferably contained2. ZrO in this case2The content is preferably 1% or more, more preferably 2% or more, further preferably 4% or more, particularly preferably 6% or more, and most preferably 7% or more. In addition, SnO is used for suppressing devitrification at the time of melting glass2+ZrO2Preferably 15% or less, more preferably 14% or less. SnO is a substance which is less likely to cause defects in glass caused by unmelted material2+ZrO2Preferably 12% or less, more preferably 10% or less, still more preferably 9% or less, and particularly preferably 8% or less.
SnO in case where β -spodumene crystal is desired to be precipitated2The content of (b) is preferably 0.5% or more, more preferably 1% or more, and still more preferably 1.5% or more. SnO2When the content of (A) is 6% or less, the glass composition is less likely to cause generation of crystal grainsIt is preferable that defects due to the melt are not present, and more preferably 5% or less, and still more preferably 4% or less.
SnO2Or a component for improving the sun-shine resistance (ソラリゼーション resistance). For inhibition of solarization, SnO2The content of (b) is preferably 1% or more, more preferably 1.5% or more.
ZrO in case where β -spodumene crystal is desired to be precipitated2The content of (b) is preferably 0.5% or more, more preferably 1% or more. In this case, ZrO2When the content of (b) is more than 6%, devitrification is liable to occur during melting, and there is a possibility that the quality of the chemically strengthened glass is deteriorated. ZrO (ZrO)2The content of (b) is preferably 6% or less, more preferably 5% or less, and further preferably 4% or less.
In the crystallized glass containing lithium metasilicate, ZrO for precipitating lithium metasilicate crystals2The content is preferably 1% or more, more preferably 2% or more, further preferably 4% or more, particularly preferably 6% or more, and most preferably 7% or more. Wherein ZrO is used for suppressing devitrification at the time of melting2The content of (b) is preferably 15% or less, more preferably 14% or less, still more preferably 12% or less, and particularly preferably 11% or less.
When β -spodumene crystal is desired to be precipitated, SnO is also contained2And ZrO2In the case of (2), SnO is used for improving transparency2SnO ratio of amount to the total amount thereof2/(SnO2+ZrO2) Preferably 0.3 or more, more preferably 0.35 or more, and further preferably 0.45 or more.
In addition, SnO is used for improving strength2/(SnO2+ZrO2) Preferably 0.7 or less, more preferably 0.65 or less, and still more preferably 0.60 or less.
TiO2TiO may be contained for crystallization of crystal nucleus-forming components of the glass2When β -spodumene crystals are desired to be precipitated, TiO is added2In the case of (2) TiO2The content of (b) is preferably 0.1% or more, more preferably 0.15% or more, and further preferably 0.2% or more. On the other hand, TiO2Is in large amountAt 5%, the glass is likely to devitrify during melting, and the quality of the chemically strengthened glass may be deteriorated, so that TiO is likely to2The content of (b) is preferably 5% or less. More preferably 3% or less, and still more preferably 1.5% or less.
In the case where it is desired to precipitate lithium metasilicate crystals, TiO is added2In the case of (2) TiO2The content of (b) is preferably 0.5% or more, more preferably 0.1% or more, further preferably 2% or more, particularly preferably 3% or more, and most preferably 4% or more. On the other hand, TiO2When the content of (b) is more than 10%, devitrification is liable to occur during melting, and the quality of the chemically strengthened glass may be deteriorated, so that TiO may be used2The content of (b) is preferably 10% or less. More preferably 8% or less, and still more preferably 6% or less.
In addition, the glass contains Fe2O3In the case where TiO is contained in the glass2When a compound called an ilmenite compound is formed, yellow or brown coloration is easily produced. Fe2O3Generally contained in glass as an impurity, and therefore TiO is used for preventing coloration2The content of (b) is preferably 1% or less, more preferably 0.5% or less, further preferably 0.25% or less, and particularly preferably substantially no TiO2。
P2O5Is not an essential component, but P2O5Has the effect of promoting phase separation of the glass to promote crystallization, and may contain P2O5. In the presence of P2O5In case of (2) P2O5The content of (b) is preferably 0.1% or more, more preferably 0.5% or more, still more preferably 1% or more, and particularly preferably 2% or more. In the case where it is desired to precipitate lithium metasilicate crystals, P2O5The content of (b) is more preferably 4% or more, still more preferably 5% or more, and particularly preferably 6% or more. On the other hand, P2O5When the content of (b) is too large, acid resistance is lowered. Thus, P2O5The content of (b) is 15% or less, preferably 14% or less, more preferably 12% or less, further preferably 11% or less, more preferably 10% or less, particularly preferably 8% or less, most preferably7% or less, particularly in the case of a chemically strengthened glass containing β -spodumene crystal, P is added to prevent scattering of fragments at the time of breakage2O5The content of (b) is preferably 6% or less, more preferably 5% or less, further preferably 4% or less, particularly preferably 3% or less, and most preferably 2% or less. When importance is attached to acid resistance, it is preferable that P is not substantially contained2O5。
B2O3Is a component for improving the chipping resistance and improving the meltability of the glass for chemical strengthening or the chemically strengthened glass, and may contain B2O3。B2O3B is not an essential component but is contained in order to improve the meltability2O3In case of (B)2O3The content of (b) is preferably 0.5% or more, more preferably 1% or more, and further preferably 2% or more. On the other hand, B2O3When the content of (B) is more than 5%, striae are generated during melting, and the quality of the glass for chemical strengthening is liable to be deteriorated, so that B2O3The content of (b) is preferably 5% or less, more preferably 4% or less, still more preferably 3% or less, and particularly preferably 1% or less. In order to improve acid resistance, it is preferable that B is not substantially contained2O3。
MgO is a component that increases the surface compressive stress of chemically strengthened glass, suppresses scattering of fragments when the strengthened glass is broken, and may contain MgO. When MgO is contained, the content of MgO is preferably 0.5% or more, and more preferably 1% or more. On the other hand, in order to suppress devitrification at the time of melting, the content of MgO is preferably 5% or less, more preferably 4% or less, and further preferably 3% or less.
CaO is a component that improves the meltability of the glass, and may be contained in order to prevent devitrification at the time of melting and improve the meltability while suppressing an increase in the thermal expansion coefficient. When CaO is contained, the content of CaO is preferably 0.5% or more, and more preferably 1% or more. On the other hand, in order to improve the ion exchange characteristics, the content of CaO is preferably 4% or less, more preferably 3% or less, and particularly preferably 2% or less.
SrO is a component that improves the meltability of the glass, and also improves the light transmittance of the crystallized glass by increasing the refractive index of the glass to bring the refractive index of the glass phase remaining after crystallization close to the refractive index of the precipitated crystal. When SrO is contained, the SrO content is preferably 0.1% or more, more preferably 0.5% or more, and still more preferably 1% or more. On the other hand, when the SrO content is too large, the ion exchange rate decreases, and therefore, the SrO content is preferably 3% or less, more preferably 2.5% or less, further preferably 2% or less, and particularly preferably 1% or less.
BaO is a component that improves the meltability of the glass, and is also a component that improves the light transmittance of the crystallized glass by increasing the refractive index of the glass to bring the refractive index of the glass phase remaining after crystallization close to the refractive index of the lithium aluminosilicate crystal phase. When BaO is contained, the content of BaO is preferably 0.1% or more, more preferably 0.5% or more, and further preferably 1% or more. On the other hand, when the BaO content is too large, the ion exchange rate decreases, so the BaO content is preferably 3% or less, more preferably 2.5% or less, further preferably 2% or less, and particularly preferably 1% or less.
ZnO is a component that lowers the thermal expansion coefficient of the glass to increase chemical durability, and also increases the refractive index of the glass to make the refractive index of the glass phase remaining after crystallization close to the refractive index of the lithium aluminosilicate crystal phase to increase the light transmittance of the crystallized glass, and therefore ZnO may be contained. When ZnO is contained, the content of ZnO is preferably 0.5% or more, more preferably 1% or more, still more preferably 1.5% or more, and particularly preferably 2% or more. On the other hand, in order to suppress devitrification at the time of melting, the content of ZnO is preferably 4% or less, more preferably 3% or less, and further preferably 2% or less.
Y2O3、La2O3、Nb2O5And Ta2O5All of them have the effect of suppressing scattering of broken pieces at the time of glass breakage, and Y may be contained for increasing the refractive index2O3、La2O3、Nb2O5And Ta2O5. When these components are contained, Y2O3、La2O3、Nb2O5Total of contents of (A) Y2O3+La2O3+Nb2O5Preferably 0.5% or more, more preferably 1% or more, still more preferably 1.5% or more, and particularly preferably 2% or more. In addition, Y is added to the glass so that the glass is not easily devitrified during melting2O3+La2O3+Nb2O5Preferably 4% or less, more preferably 3% or less, still more preferably 2% or less, and particularly preferably 1% or less.
Y2O3、La2O3、Nb2O5And Ta2O5Total content of (A) Y2O3+La2O3+Nb2O5+Ta2O5Preferably 0.5% or more, more preferably 1% or more, still more preferably 1.5% or more, and particularly preferably 2% or more. In addition, Y is for making the glass less susceptible to devitrification during melting2O3+La2O3+Nb2O5+Ta2O5Preferably 4% or less, more preferably 3% or less, still more preferably 2% or less, and particularly preferably 1% or less.
In addition, CeO may be contained2。CeO2Has the effect of oxidizing glass and contains a large amount of SnO2In the case of (2), SnO may be suppressed2Is reduced to SnO as a coloring component to suppress coloring. In the presence of CeO2In case of (5) CeO2The content of (b) is preferably 0.03% or more, more preferably 0.05% or more, and still more preferably 0.07% or more. In the use of CeO2In the case of an oxidizing agent, CeO2When the content of (A) is too large, the glass is liable to be colored, so that CeO is used for the purpose of improving transparency2The content of (b) is preferably 1.5% or less, more preferably 1.0% or less.
Further, the coloring component may be added within a range not to inhibit achievement of the desired chemical strengthening property. Examples of the coloring component include: co3O4、MnO2、Fe2O3、NiO、CuO、Cr2O3、V2O5、Bi2O3、SeO2、Er2O3、Nd2O3As a suitable ingredient.
The total content of the coloring components is preferably 1% or less. When it is desired to further improve the light transmittance of the glass, it is preferable that these components are not substantially contained.
In addition, SO may be appropriately contained3Chlorides and fluorides as fining agents in glass melting. Preferably not containing As2O3. In the presence of Sb2O3In the case of (1), Sb2O3The content of (B) is preferably 0.3% or less, more preferably 0.1% or less, and most preferably Sb is not contained2O3。
< method for producing glass for chemical strengthening >
The method for producing a glass for chemical strengthening according to the present embodiment is a method for producing a glass for chemical strengthening in which an amorphous glass is heated to be crystallized, and the obtained crystallized glass is heated and bent. The glass having a three-dimensional shape can be produced by the method for producing a glass for chemical strengthening of the present invention.
The method for producing a chemically strengthened glass according to the present embodiment is a method for producing a chemically strengthened glass in which an amorphous glass is heated to be crystallized, and the obtained crystallized glass is heated and simultaneously bent and then chemically strengthened. The chemically strengthened glass having a three-dimensional shape according to the present embodiment can be obtained by the method for producing a chemically strengthened glass according to the present embodiment.
(production of amorphous glass)
The amorphous glass can be produced by the following method, for example. The following manufacturing method is an example of a case of manufacturing a chemically strengthened glass sheet.
Glass raw materials are formulated to obtain glass of a desired composition, and heated and melted in a glass melting furnace. Then, the molten glass is homogenized by bubbling, stirring, addition of a fining agent, or the like, formed into a glass sheet having a predetermined thickness by a known forming method, and slowly cooled. Alternatively, the sheet-like member may be formed by: the molten glass is formed into a block, slowly cooled, and then cut.
Examples of the method for forming the plate-like glass include: float process, press process, fusion process and downdraw process. Particularly, in the case of manufacturing a large glass plate, the float method is preferable. In addition, a continuous forming method other than the float method, such as a fusion method and a downdraw method, is also preferable.
(crystallization treatment)
The amorphous glass obtained by the above steps is subjected to a heat treatment, thereby obtaining a crystallized glass.
The heat treatment is preferably performed by a two-step heat treatment as follows: raising the temperature from room temperature to a first treatment temperature for a certain time, and then maintaining the temperature at a second treatment temperature higher than the first treatment temperature for a certain time. The heat treatment may be performed by the following three-step heat treatment: raising the temperature from room temperature to a first treatment temperature and holding for a certain time, then holding for a certain time at a second treatment temperature higher than the first treatment temperature, and further holding for a certain time at a third treatment temperature higher than the second treatment temperature.
In the case of the two-step heating treatment, the first treatment temperature is preferably a temperature region in which the nucleation rate increases for the glass composition, and the second treatment temperature is preferably a temperature region in which the crystal growth rate increases for the glass composition. In addition, as for the holding time at the first treatment temperature, it is preferable to hold for a long time so that a sufficient number of crystal nuclei are generated. By forming a large number of crystal nuclei, the size of each crystal becomes small, and a crystallized glass having high transparency is obtained.
The first treatment temperature is, for example, 550 to 800 ℃ and the second treatment temperature is, for example, 850 to 1000 ℃, and the temperature is maintained at the first treatment temperature for 2 to 10 hours and then at the second treatment temperature for 2 to 10 hours.
The crystallized glass obtained by the above steps is ground and polished as necessary to form a crystallized glass plate. When the crystallized glass plate is cut into a predetermined shape and size or chamfered, if the cutting or chamfering is performed before the chemical strengthening treatment is performed, a compressive stress layer is also formed on the end face by the chemical strengthening treatment thereafter, which is preferable.
(bending Forming)
The bending method may be any method selected from conventional bending methods such as a self-weight forming method, a vacuum forming method, and a press forming method. In addition, two or more bending methods may be used in combination.
The self-weight forming method comprises the following steps: the glass sheet is set on a forming mold, and then the glass sheet is heated and fitted to the forming mold by gravity, thereby being bent and formed into a predetermined shape.
The vacuum forming method is as follows: a glass plate is set on a forming mold, the periphery of the glass plate is sealed, then the space between the forming mold and the glass plate is decompressed, and the pressure difference is applied to the front surface and the back surface of the glass plate, thereby carrying out bending forming. At this time, the upper surface side of the glass plate can be additionally pressurized.
The press forming is as follows: a glass plate is placed between forming molds (a lower mold and an upper mold), and the glass plate is heated to apply a pressing load between the upper and lower forming molds, thereby bending and forming the glass plate into a predetermined shape.
In any of the above methods, the glass is deformed by applying a force in a state where the glass is heated.
The bending (hot bending) temperature is, for example, 700 to 1100 ℃, preferably 750 to 1050 ℃. Further, when the thermal bending temperature is high relative to the highest temperature of the crystallization treatment, thermal deformation is likely to occur, and therefore, it is preferable from the viewpoint of dimensional accuracy. The difference between the maximum temperature of crystallization and the thermal bending temperature is preferably 10 ℃ or more, more preferably 30 ℃ or more. On the other hand, when the thermal bending temperature is too high relative to the crystallization temperature, the light transmittance may be lowered by bending. Therefore, the difference between the maximum temperature of the crystallization treatment and the thermal bending temperature is preferably 120 ℃ or less, more preferably 100 ℃ or less, still more preferably 90 ℃ or less, and particularly preferably 60 ℃ or less.
The decrease in light transmittance due to bending is preferably 3% or less, more preferably 2% or less, still more preferably 1.5% or less, and particularly preferably 1% or less.
In order to maintain high transparency of the final glass, it is advantageous that the light transmittance before thermal bending is high, and the light transmittance in terms of a thickness of 0.8mm is preferably 85% or more. More preferably 87% or more, and particularly preferably 89% or more.
(chemical strengthening treatment)
The chemical strengthening treatment is as follows: metal ions having a small ionic radius (typically Na ions or Li ions) in the glass sheet are replaced with metal ions having a large ionic radius (typically Na ions or K ions for Li ions and K ions for Na ions) by bringing the glass into contact with a metal salt (for example, potassium nitrate) by a method such as dipping in a melt containing a metal salt having a large ionic radius (typically Na ions or K ions for Na ions or K ions).
In order to accelerate the chemical strengthening treatment, it is preferable to use "Li — Na exchange" in which Li ions and Na ions in the glass are exchanged. In order to form a large compressive stress by ion exchange, "Na — K exchange" in which Na ions and K ions in the glass are exchanged is preferably used.
Examples of the molten salt used for the chemical strengthening treatment include nitrates, sulfates, carbonates, chlorides, and the like. Among them, examples of the nitrate include: lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, silver nitrate, and the like. Examples of the sulfate include: lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, silver sulfate, and the like. Examples of the carbonate include: lithium carbonate, sodium carbonate, potassium carbonate, and the like. Examples of chlorides include: lithium chloride, sodium chloride, potassium chloride, cesium chloride, silver chloride, and the like. These molten salts may be used alone or in combination of two or more.
The treatment conditions such as time and temperature of the chemical strengthening treatment are appropriately selected in consideration of the glass composition, the type of molten salt, and the like.
The present tempered glass is preferably obtained by, for example, the following two-step chemical tempering treatment.
First, the three-dimensional glass is immersed in a metal salt containing Na ions (for example, sodium nitrate) at about 350 to about 500 ℃ for about 0.1 to about 10 hours. This causes ion exchange between Li ions in the three-dimensional glass and Na ions in the metal salt, thereby forming a compressive stress layer having a surface compressive stress of 200MPa or more and a compressive stress depth of 80 μm or more, for example. When the surface compressive stress introduced by this treatment is greater than 1000MPa, it is difficult to increase DOL while maintaining low CT in the present strengthened glass finally obtained. Therefore, the surface compressive stress introduced by this treatment is preferably 900MPa or less, more preferably 700MPa or less, and further preferably 600MPa or less.
Next, the glass after the above treatment is immersed in a metal salt containing K ions (for example, potassium nitrate) at about 350 to about 500 ℃ for about 0.1 to about 10 hours. As a result, a large compressive stress is generated in a portion of the compressive stress layer formed by the previous process, for example, at a depth of about 10 μm or less.
According to such a two-step treatment, a preferable stress distribution having a surface compressive stress of 600MPa or more can be easily obtained.
Or first immersed in a metal salt containing Na ions, then held at 350 to 500 ℃ for 1 to 5 hours in the atmosphere, and then immersed in a metal salt containing K ions. The temperature is preferably 425 ℃ to 475 ℃, more preferably 440 ℃ to 460 ℃.
By being maintained at a high temperature in the atmosphere, Na ions introduced from the metal salt into the inside of the glass by the initial treatment are thermally diffused in the glass, thereby forming a more preferable stress distribution.
Alternatively, instead of being immersed in a metal salt containing Na ions and then kept in the atmosphere, the metal salt may be immersed in a metal salt containing Na ions and Li ions (for example, a mixed salt of sodium nitrate and lithium nitrate) at 350 to 500 ℃ for 0.1 to 20 hours.
By being immersed in a metal salt containing Na ions and Li ions, ion exchange of Na ions in the glass and Li ions in the metal salt occurs, forming a more preferable stress distribution, thereby improving the asphalt drop strength.
In the case of performing such a two-step or three-step strengthening treatment, the total treatment time is preferably 10 hours or less, more preferably 5 hours or less, and still more preferably 3 hours or less, from the viewpoint of production efficiency. On the other hand, in order to obtain a desired stress distribution, the total treatment time needs to be 0.5 hours or more, and more preferably 1 hour or more.
The chemically strengthened glass having a three-dimensional shape according to the present embodiment obtained as described above is particularly useful as a cover glass used for mobile devices such as mobile phones and smart phones. Further, the present invention is also useful for a cover glass of a display device such as a television, a personal computer, or a touch panel, which is not intended to be carried. The glass is also useful as a cover glass for interior decoration of automobiles, airplanes, and the like.
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