阅读说明：本技术 微晶玻璃和化学强化玻璃以及它们的制造方法 (Glass ceramics and chemically strengthened glass, and method for producing same ) 是由 古田仁美 福士恭基 李清 荒井雄介 于 2020-03-13 设计创作，主要内容包括：本发明涉及一种微晶玻璃,其为由包含平均曲率半径为5.0×10～(2)mm以下的最小的R形状和平均曲率半径为1.0×10～(3)mm以上的最大的R形状的多个R形状构成的三维形状的微晶玻璃,其中,对各R形状的圆弧上的1点以上垂直地照射波长为543nm的光,使用双折射测定装置测定的延迟的最大值为20nm/mm以下,并且上述最大的R形状的换算成厚度0.8mm时的雾度值为1.0％以下。(The invention relates to a microcrystalline glass which is prepared by mixing glass with an average curvature radius of 5.0 multiplied by 10 2 minimum R shape and average radius of curvature of mm or less are 1.0X 10 3 A three-dimensional glass ceramic comprising a plurality of R shapes each having a maximum R shape of not less than mm, wherein 1 point or more on the arc of each R shape is perpendicularly irradiated with light having a wavelength of 543nm, the maximum value of retardation measured by a birefringence measuring device is not more than 20nm/mm, and the haze value in terms of the thickness of 0.8mm of the maximum R shape is not more than 1.0%.)

1. A glass ceramic comprising a glass having an average radius of curvature of 5.0 x 10²minimum R shape and average radius of curvature of mm or less are 1.0X 10³A three-dimensional glass ceramic comprising a plurality of R shapes having a maximum R shape of mm or more,

the maximum value of the retardation measured by the following measurement method is 20nm/mm or less, and

a haze value of 1.0% or less in terms of a thickness of 0.8mm of the maximum R shape,

(measurement method)

Light having a wavelength of 543nm is perpendicularly irradiated to 1 point or more on each R-shaped arc, and retardation is measured using a birefringence measurement device, wherein when an angle formed by a tangent to a curved surface at the center of a measurement sample and a tangent to a surface to be measured is 90 ° or more, measurement is not performed.

2. The glass ceramic according to claim 1, wherein the glass ceramic is a glass ceramic containing β -spodumene crystals.

3. The microcrystalline glass according to claim 1 or 2, wherein the microcrystalline glass comprises, 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, and

0 to 2% of K₂O。

4. The glass ceramic according to any one of claims 1 to 3, wherein a light transmittance in terms of a thickness of 0.8mm of the maximum R shape is 85% or more.

5. A chemically strengthened glass having a compressive stress layer on the surface and comprising a glass having an average radius of curvature of 5.0 x 10²minimum R shape and average radius of curvature of mm or less are 1.0X 10³A chemically strengthened glass having a three-dimensional shape comprising a plurality of R shapes each having a maximum R shape of mm or more,

the chemically strengthened glass has a surface compressive stress value of 500MPa or more and a depth of compressive stress layer of 80 μm or more,

the chemically strengthened glass is microcrystalline glass containing crystals,

the maximum value of retardation per 1mm thickness measured by perpendicularly irradiating the central part of the minimum R shape with light with wavelength of 543nm is 20nm/mm or less, and

the haze value of the maximum R shape is 1.0% or less when converted to a thickness of 0.8 mm.

6. The chemically strengthened glass as claimed in claim 5, wherein the glass ceramics contains β -spodumene crystals.

7. The chemically strengthened glass according to claim 5 or 6, wherein the chemically strengthened 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、

0.5 to 12 percent of SnO in total₂And ZrO₂Any one or more of, and

0 to 6% of P₂O₅。

8. The chemically strengthened glass according to any one of claims 5 to 7, wherein the chemically strengthened glass has a light transmittance of 85% or more in terms of a thickness of 0.8 mm.

9. The chemically strengthened glass as claimed in any one of claims 5 to 8, wherein the chemically strengthened glass is used for a cover glass of a display device.

10. A method for producing a three-dimensional glass ceramic, comprising:

by heating and bending the amorphous glass, the glass obtained by the method has an average curvature radius of 5.0 × 10²minimum R shape and average radius of curvature of mm or less are 1.0X 10³A step of forming a three-dimensional amorphous glass having a plurality of R shapes each having a maximum R shape of mm or more; and

a step of crystallizing the three-dimensional amorphous glass by heat treatment to obtain a three-dimensional glass ceramic,

the amorphous 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、

0.5 to 12 percent of SnO in total₂And ZrO₂Any one or more of, and

0 to 6% of P₂O₅。

11. The method for producing a glass ceramic according to claim 10, wherein an absolute value of a difference between an average thermal expansion coefficient in a range of 50 ℃ to 500 ℃ of the amorphous glass and an average thermal expansion coefficient in a range of 50 ℃ to 500 ℃ of a mold material used for the bending is 150 x 10^-7Below/° c.

12. The method for producing a glass-ceramic according to claim 10 or 11, wherein the amorphous glass has an average coefficient of thermal expansion of 20 x 10 in a range of 50 ℃ to 500 ℃^-7170X 10 ℃ C. or higher^-7Below/° c.

13. A method for producing a three-dimensional chemically strengthened glass, the method comprising:

by heating and bending the amorphous glass, the glass obtained by the method has an average curvature radius of 5.0 × 10²minimum R shape and average radius of curvature of mm or less are 1.0X 10³A step of forming a three-dimensional amorphous glass having a plurality of R shapes each having a maximum R shape of mm or more;

crystallizing the three-dimensional amorphous glass by heat treatment to obtain a three-dimensional microcrystalline glass; and

a step of chemically strengthening the three-dimensional glass ceramics,

the amorphous 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、

0.5 to 12 percent in totalSnO₂And ZrO₂Any one or more of, and

0 to 6% of P₂O₅。

Technical Field

The present invention relates to a three-dimensional microcrystalline glass and a chemically strengthened glass having high transparency and excellent strength and formability, and methods for producing the same.

Background

Protective glass for display devices of mobile devices such as mobile phones and smartphones, and protective glass for on-vehicle display members such as instrument panels and head-up displays (HUDs) are required to have excellent strength and transparency. For example, thin, strong chemically strengthened glass is used as the cover glass.

As the glass used for the cover glass, a three-dimensional glass having a plurality of R-shapes is sometimes required in order to improve the handling property and the visibility. As a method for producing a three-dimensionally shaped glass, for example, there is a method of heating a flat glass plate and pressing the same with a forming mold to thereby perform bending forming (also referred to as three-dimensional forming) (patent document 1).

As the glass used for the above-mentioned cover glass, amorphous glass containing no crystal is used, but microcrystalline glass having higher strength has also been proposed (patent document 2). The glass ceramics are glasses in which crystals are precipitated in the glass by heat treatment of the glass.

Examples of the method for obtaining a microcrystalline glass having a three-dimensional shape include: a method of performing bending while precipitating crystals from amorphous glass, a method of crystallizing amorphous glass and then bending it, a method of processing microcrystalline glass into a three-dimensional shape by a method such as grinding, a method of bending amorphous glass and then crystallizing it, and the like (patent documents 3 and 4).

Patent document 2 discloses a method for producing a crystallized glass having a curved surface shape, the method comprising a deformation step: the temperature of the plate-shaped glass is maintained so as to be within a first temperature range, crystals are precipitated from the plate-shaped glass, and at least a part of the plate-shaped glass is deformed into a curved shape by an external force acting on the plate-shaped glass.

Further, patent document 3 discloses a method for producing a curved crystallized glass sheet, the method comprising: a step of producing a curved crystallized glass plate in which a portion of a crystallized glass flat plate in one direction is locally heated to deform the crystallized glass flat plate in a softened state; the crystallization step is to obtain the crystallized glass bent plate by placing the crystallized glass bent plate on a forming mold and heating the same to crystallize the crystallized glass bent plate while deforming the same.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2014/167894

Patent document 2: international publication No. 2019/022034

Patent document 3: japanese patent laid-open publication No. 2017-190265

Patent document 4: japanese patent laid-open No. 2014-141356

Disclosure of Invention

Problems to be solved by the invention

As shown in patent document 1, in a method for producing a glass having a three-dimensional shape by bending, particularly in a bent portion, thermal unevenness occurs during heating due to uneven contact between the glass and a forming mold, and a stress difference (delay) is likely to occur in the glass after forming. In addition, when the cooling rate in the bending is increased in order to improve the productivity, the retardation in the glass after the forming becomes large. When the retardation in the glass becomes large, the glass is easily broken and the strength is lowered.

In addition, in the case of obtaining a microcrystalline glass having a three-dimensional shape, molding is usually performed after crystallization, but depending on the composition of the glass, there is a problem that the haze is deteriorated by heating at the time of molding, and the transparency of the glass is lowered. On the other hand, in the method of performing crystallization after bending, there is a problem that deformation is likely to occur due to heat treatment for crystallization, and transparency is likely to be lowered. Under these circumstances, it is difficult to obtain a glass-ceramic having a three-dimensional shape which is suitable for a cover glass and has excellent transparency, strength and shape stability.

The purpose of the present invention is to provide a three-dimensional shaped glass having excellent strength, transparency and shape stability, and a method for producing the same.

Means for solving the problems

The present inventors have made extensive studies on a glass composition and the like in view of the above-mentioned problems, and as a result, have found a three-dimensional shaped glass excellent in strength, transparency and shape stability and a method for producing the same, and have completed the present invention.

The invention provides a microcrystalline glass which comprises a glass having an average radius of curvature of 5.0 x 10²minimum R shape and average radius of curvature of mm or less are 1.0X 10³A three-dimensional glass ceramic comprising a plurality of R shapes having a maximum R shape of mm or more,

the maximum value of the retardation measured by the following measurement method is 20nm/mm or less, and

the haze value of the maximum R shape is 1.0% or less when converted to a thickness of 0.8 mm.

(measurement method)

Light having a wavelength of 543nm was perpendicularly irradiated to 1 point or more on each R-shaped arc, and retardation was measured using a birefringence measurement device. When the angle formed by the tangent to the curved surface of the center portion of the measurement sample and the tangent to the surface to be measured is 90 ° or more, the measurement is not performed.

The present invention relates to a chemically strengthened glass having a compressive stress layer on the surface and comprising a glass having an average radius of curvature of 5.0 x 10²minimum R shape and average radius of curvature of mm or less are 1.0X 10³maximum R shape of mm or moreA chemically strengthened glass having a three-dimensional shape formed of R-shaped glass particles,

the chemically strengthened glass has a surface compressive stress value of 500MPa or more and a depth of compressive stress layer of 80 μm or more,

the chemically strengthened glass is microcrystalline glass containing crystals,

the maximum value of retardation per 1mm thickness measured by perpendicularly irradiating the central part of the minimum R shape with light with wavelength of 543nm is 20nm/mm or less, and

the haze value of the maximum R shape is 1.0% or less when converted to a thickness of 0.8 mm.

The present invention relates to a method for producing a three-dimensional glass ceramic, the method comprising:

by heating and bending the amorphous glass, the glass obtained by the method has an average curvature radius of 5.0 × 10²minimum R shape and average radius of curvature of mm or less are 1.0X 10³A step of forming a three-dimensional amorphous glass having a plurality of R shapes each having a maximum R shape of mm or more; and

a step of crystallizing the three-dimensional amorphous glass by heat treatment to obtain a three-dimensional glass ceramic,

the amorphous 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、

0.5 to 12 percent of SnO in total₂And ZrO₂Any one or more of, and

0 to 6% of P₂O₅。

The present invention relates to a method for producing a three-dimensional chemically strengthened glass, the method comprising:

by heating and bending the amorphous glass, the glass obtained by the method has an average curvature radius of 5.0 × 10²minimum R shape and average radius of curvature of mm or less are 1.0X 10³A step of forming a three-dimensional amorphous glass having a plurality of R shapes each having a maximum R shape of mm or more;

crystallizing the three-dimensional amorphous glass by heat treatment to obtain a three-dimensional microcrystalline glass; and

a step of chemically strengthening the three-dimensional glass ceramics,

the amorphous 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、

0.5 to 12 percent of SnO in total₂And ZrO₂Any one or more of, and

0 to 6% of P₂O₅。

Effects of the invention

The three-dimensionally shaped glass according to the present invention comprises a glass having an average radius of curvature of 5.0X 10²minimum R shape and average radius of curvature of mm or less are 1.0X 10³And a three-dimensional shape formed by a plurality of R shapes of the maximum R shape of mm or more, wherein the maximum value of the retardation per 1mm thickness measured by perpendicularly irradiating the minimum R shape with light having a wavelength of 543nm is 20nm/mm or less, so that the three-dimensional shape is not easy to break and has excellent strength and forming stability. Further, the haze value when converted to a thickness of 0.8mm by the maximum R shape is 1.0% or less, and the transparency is excellent.

According to the method for producing a three-dimensional glass of the present invention, the step of heating an amorphous glass having a specific composition and bending the same to form an amorphous glass having a three-dimensional shape is followed by the step of crystallizing the same by a heating treatment, whereby the retardation generated during the forming can be reduced and the strength can be improved. In addition, the haze deterioration due to heating during molding can be suppressed, and excellent transparency can be achieved.

Drawings

Fig. 1 is a perspective view showing an example of the shape of the three-dimensional shaped glass of the present invention.

Fig. 2 is a view showing an example of the shape of the three-dimensional shaped glass of the present invention, in which fig. 2 (a) is a front view and fig. 2 (b) is a perspective view.

Fig. 3 is a view showing an example of the shape of the three-dimensional shaped glass of the present invention, wherein fig. 3 (a) is a front view and fig. 3 (b) is a perspective view.

Fig. 4 is a diagram showing an example of an X-ray diffraction pattern of the crystallized glass.

Fig. 5 is a schematic view showing one embodiment of the method for producing a three-dimensional glass of the present invention.

Detailed Description

In the present specification, "to" indicating a numerical range is used in the meaning of including numerical values described before and after the range as a lower limit value and an upper limit value. Unless otherwise specified, "to" is used in the present specification as defined above.

In the present specification, "amorphous glass" and "glass ceramics" are collectively referred to as "glass". In the present specification, "amorphous glass" refers to glass in which a diffraction peak indicating a crystal cannot be observed by a powder X-ray diffraction method. The "glass ceramics" refers to 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.

Hereinafter, "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.

The "basic composition of the chemically strengthened glass" refers to the glass composition of the glass for chemical strengthening. Except for the case where the extreme ion exchange treatment is performed, the glass composition of a portion of the chemically strengthened glass deeper than the depth of compressive stress layer (DOL) is the basic composition of the chemically strengthened glass.

In the present specification, unless otherwise specified, the glass composition is represented by mass% based on oxides, and the 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 the depth from the glass surface indicates the value of compressive stress as a variable. In the stress distribution, the tensile stress is expressed as a negative compressive stress.

"compressive stress value (CS)" or "surface compressive stress value (CS)₀) "can be determined by flaking a cross section of glass and analyzing the flaked sample using a birefringence imaging system. The birefringent imaging system includes, for example, a birefringent imaging system Abrio-IM manufactured by Tokyo instruments. In addition, the "compressive stress value (CS)" or the "surface compressive stress value (CS)₀) "measurement can also be performed by 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, a scattered light photoelastic stress meter SLP-1000 manufactured by prototype manufacture was used.

In the present specification, "depth of compressive stress layer (DOL)" means a depth at which the value of Compressive Stress (CS) is zero. In the present specification, "internal tensile stress (CT)" means a tensile stress value at a depth of 1/2 of the sheet thickness t.

In the present specification, "retardation" refers to a value obtained by irradiating 543nm wavelength light from a direction perpendicular to the principal surface of a glass plate, measuring the retardation using a birefringence meter, and converting the measured retardation into a thickness of 0.55 mm. Examples of the birefringence meter include WPA-100 and WPA-200 manufactured by Photonic Lattice corporation.

In the present specification, "light transmittance" refers to the average transmittance of visible light having a wavelength of 380nm to 780 nm. In addition, "haze value" means a value measured using a C light source and according to JIS K3761: 2000 measured and obtained. "haze value in terms of thickness of 0.8 mm" means a haze value measured after processing to a thickness of 0.8mm when the thickness of the object to be measured is not 0.8 mm. Alternatively, "the haze value when converted to a thickness of 0.8 mm" means a haze value corresponding to a case where the thickness is 0.8mm, which is obtained by calculation from a haze value measured in the original thickness and a haze value measured after processing to change the thickness.

In the present specification, "thermal expansion coefficient" means a coefficient according to JIS R1618: 2002 means an average thermal expansion coefficient in the range of 50 to 500 ℃ as measured with the temperature increase rate set at 10 ℃/min unless otherwise specified. The "glass transition temperature" refers to a value obtained from a thermal expansion curve thereof.

In the present specification, "vickers hardness" means a hardness in JIS R1610: vickers hardness (HV0.1) specified in 2003.

In addition, the "fracture toughness value" can be measured by the DCDC method (Actametall. mat. Vol.43, p. 3453-3458, 1995).

< three-dimensional shaped glass >

The three-dimensionally shaped glass of the present invention includes a three-dimensionally shaped glass-ceramic and a three-dimensionally shaped chemically strengthened glass. In the present invention, the term "three-dimensional shape" means a shape comprising an average radius of curvature of 5.0X 10²minimum R shape and average radius of curvature of mm or less are 1.0X 10³A shape composed of a plurality of R shapes having a maximum R shape of mm or more. The three-dimensional shape in the present invention includes any of a curved shape including a continuous curve, a shape curved in the longitudinal and transverse directions, and a shape having a concavity and a convexity on a plane.

Fig. 1, 2, and 3 are views each showing an example of the three-dimensional glass of the present invention. These figures show a three-dimensional shape glass having a uniform thickness as a whole, but the three-dimensional shape may be a shape having portions with different thicknesses.

The three-dimensional glass 100 in fig. 1 has a peripheral portion 120 around a substantially planar central portion 110, and includes a minimum R-shape between the central portion 110 and the peripheral portion 120, and a maximum R-shape in the substantially planar central portion 110.

Fig. 2 (a) and (b) show glasses of the following shapes: the both end portions of the inner surface (inner coating surface) of the glass include a pair of minimum R shapes having an average curvature radius R1 and curved in a direction away from the outer surface as they go toward the both end portions, and include a maximum R shape having an average curvature radius R2 and curved upward (in the drawing).

Fig. 3 (a) and (b) show glasses of the following shapes: the glass includes, at both end portions of the inner and inner surfaces, a pair of minimum R shapes having an average curvature radius R1 and curved in a direction away from the outer surface as it goes toward both end portions, and includes a maximum R shape having an average curvature radius R2 and curved downward (in the drawing).

The average curvature is a physical index value indicating how much the plane deviates from the plane. The mathematical derivation of the mean curvature is well known and is omitted in this specification. In brief, the average curvature of a surface is defined as the median value between the maximum value and the minimum value of the curvature of a rotating body obtained by rotating a curved surface around a normal vector of the curved surface at a certain point on the surface. The average curvature radius of the surface is defined as the reciprocal of the average curvature.

Specific examples are listed below: the average curvature of any point on the spherical surface of the sphere with the radius R is 1/R. Further, since the maximum curvature is 1/R and the minimum curvature is 0 at an arbitrary point on the cylindrical side surface having the radius R of the bottom surface, the average curvature is 1/2R. Therefore, the value of the average curvature of a certain point on a surface is an important parameter representing the physical shape. The average curvature can be determined by any known method.

The average radius of curvature R1 of the smallest R shape is 5.0X 10²mm or less, preferably 1.0X 10²mm or less, more preferably 5.0X 10¹mm or less. The average curvature radius R1 is preferably 1.0mm or more, more preferably 2.5mm or more, and still more preferably 5.0mmThe above. The minimum bending angle of the R-shape is preferably 1 ° or more, more preferably 10 ° or more, and further preferably 20 ° or more. The minimum bend angle of the R-shape is preferably 89 ° or less, more preferably 80 ° or less, and further preferably 75 ° or less.

The average radius of curvature R2 of the largest R shape is 1.0X 10³mm or more, preferably 2.5X 10³mm or more, more preferably 5.0X 10³Is more than mm. The average curvature radius R2 is preferably 4.0 × 10⁵mm or less, more preferably 2.0X 10⁵mm or less, more preferably 1.0X 10⁵mm or less. The bending angle of the maximum R shape is preferably in a range of more than 0 ° to 10.0 °, more preferably in a range of more than 0 ° to 8.0 °, and further preferably in a range of more than 0 ° to 5.0 °.

The stress remaining inside the three-dimensional shaped glass of the present invention can be evaluated using retardation as an index. For example, the refractive index difference (refractive index anisotropy) between the refractive index of a first linearly polarized light having a predetermined wavelength and the refractive index of a second linearly polarized light perpendicular to the first linearly polarized light, which is measured by a birefringence measuring device, is Δ n, and the thickness of the central portion of the three-dimensional shaped glass is t [ nm ].

In this case, the level of residual stress can also be evaluated from the measured retardation Δ n × t [ nm ]. The retardation is not limited to the case where the thickness (t [ nm ]) of the central portion of the actual three-dimensional shaped glass is used as it is, and may be evaluated in the form of retardation Δ n × d [ nm/mm ] per 1mm thickness. In this case, the calculation can be performed using d ═ t [ nm ]/t [ mm ].

The maximum value of the retardation of the three-dimensional shaped glass of the present invention measured by the following measurement method is 20nm/mm or less, and is preferably 18nm/mm or less, and more preferably 16nm/mm or less. The retardation value may be measured on at least one cross section.

(measurement method)

Light having a wavelength of 543nm was perpendicularly irradiated to 1 point or more on each R-shaped arc, and retardation was measured using a birefringence measurement device. When the angle formed by the tangent to the curved surface of the center portion of the measurement sample and the tangent to the surface to be measured is 90 ° or more, the measurement is not performed.

The magnitude of the retardation depends on the stress in the glass, and a small maximum value of retardation indicates a small stress difference in the glass. The three-dimensional shaped glass of the present invention is less likely to break and is excellent in strength and forming stability by having a maximum value of retardation of 20nm/mm or less. The lower limit of the maximum value of the retardation is not particularly limited, but is usually 1nm/mm or more.

The haze value of the maximum R-shape of the three-dimensional shaped glass of the present invention in terms of thickness of 0.8mm is 1.0% or less, preferably 0.8% or less, more preferably 0.5% or less, further preferably 0.4% or less, very preferably 0.3% or less, and most preferably 0.25% or less. When the haze value is 1.0% or less, excellent transparency can be achieved, and the glass composition is suitable for protective glass of a display portion of a portable terminal or the like.

On the other hand, in the case where it is difficult to reduce the haze without reducing the crystallization rate, the haze value in terms of the thickness of 0.8mm of the maximum R shape is preferably 0.05% or more, more preferably 0.08% or more, in order to improve the mechanical strength and the like.

The light transmittance of the three-dimensional glass of the present invention in terms of the thickness of 0.8mm of the maximum R-shape is preferably 85% or more, more preferably 87% or more, still more preferably 88% or more, and particularly preferably 89% or more. When the light transmittance is 85% or more, the screen is easily seen in the case of a cover glass for a portable display. The higher the light transmittance, the more preferable, but it is usually 91% or less or 90% or less. 91% is the transmittance equivalent to that of ordinary amorphous glass.

The three-dimensional glass of the present invention is microcrystalline glass, and therefore has higher strength and higher vickers hardness than amorphous glass, and is less likely to be damaged. For the abrasion resistance, the vickers hardness is preferably 700 or more, more preferably 740 or more, and further preferably 780 or more. On the other hand, when the vickers hardness is too large, the processing may be difficult, and therefore, the vickers hardness is preferably 1100 or less, more preferably 1050 or less, and further preferably 1000 or less.

< glass ceramics >

The crystallized glass of the present invention is included in the three-dimensional shaped glass, and is a three-dimensional shaped crystallized glass.

In order to suppress warpage during chemical strengthening treatment, the glass ceramics of the present invention preferably have a young's modulus of 80GPa or more, more preferably 85GPa or more, still more preferably 87GPa or more, and particularly preferably 90GPa or more. If the young's modulus is too high, the processing such as polishing becomes difficult, and therefore, in order to improve the processability, the young's modulus is preferably 130GPa or less, more preferably 125GPa or less, and further preferably 120GPa or less.

The value of fracture toughness of the glass ceramics of the present invention is preferably 0.8MPa · m^1/2More preferably 1MPa · m or more^1/2The above. When the fracture toughness value is within the above range, the fragments are less likely to scatter when the tempered glass is fractured.

The microcrystalline glass of the present invention preferably has an average thermal expansion coefficient of 30X 10 in the range of 50 ℃ to 350 ℃^-7Lower than/° C, more preferably 25X 10^-7Not more than/° C, more preferably 20X 10^-7/. degree.C.or less, particularly preferably 15X 10^-7Below/° c. The average coefficient of thermal expansion in the range of 50 ℃ to 350 ℃ is usually 10X 10^-7Above/° c.

The glass ceramic of the present invention preferably contains crystals of lithium aluminosilicate. The microcrystalline glass containing lithium aluminosilicate crystals is also strengthened by chemical strengthening treatment to precipitate crystals, and therefore high strength can be obtained.

When it is desired to further improve the strength after chemical strengthening, the glass ceramics of the present invention are preferably glass ceramics containing β -spodumene crystals. The beta-spodumene crystal is expressed as LiAlSi₂O₆And is a lithium aluminosilicate 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 spectrum.

Fig. 4 shows an example of X-ray diffraction patterns of a glass ceramic containing β -spodumene crystals and a tempered glass ceramic (chemically tempered glass). In fig. 4, the solid line is an X-ray diffraction pattern measured on the crystallized glass plate before strengthening, and a diffraction line of β -spodumene crystals indicated by a black circle in fig. 4 is observed. The broken line indicates an X-ray diffraction pattern measured on a chemically strengthened glass-ceramic (chemically strengthened glass) plate.

The microcrystalline glass containing β -spodumene crystals has a surface compressive stress value (CS) by chemical strengthening as compared with a microcrystalline glass containing other crystals₀) The tendency becomes larger. It is considered that the crystal structure of β -spodumene crystals is dense, and therefore, the effect of chemical strengthening becomes greater due to the large compressive stress generated by the change in the crystal structure when ions in precipitated crystals are replaced with larger ions by the ion exchange treatment for chemical strengthening.

It is known that the crystal growth rate of β -spodumene crystals is fast. Therefore, the microcrystalline glass containing β -spodumene crystals tends to have large crystals, and thus has low transparency and a large haze value in many cases. However, the crystallized glass of the present invention contains a large amount of fine crystals, and has high transparency and a small haze value.

In order to improve the mechanical strength, the crystallization ratio of the crystallized glass of the present invention 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, the crystallization rate is preferably 95% or less, more preferably 90% or less, and particularly preferably 85% or less. By setting the crystallization ratio to 80% or less, the transparency can be improved and the film can be easily bent by heating.

The crystallization rate can be calculated from the X-ray diffraction intensity by the Reed-Bohr 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 glass ceramics of the present invention is preferably 300nm or less, more preferably 200nm or less, and still more preferably 150nm 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.

The glass ceramics of the present invention preferably contain 58 to 74% of SiO in terms of mass% based on oxides₂、5％～30％Al of (2)₂O₃1 to 14% of Li₂O, 0-5% of Na₂O and 0 to 2% of K₂O, and further preferably SnO in a total amount of 0.5 to 12%₂And ZrO₂Any one or more of the above and 0 to 6% of P₂O₅. In the above composition, it is more preferable that 2% to 14% of Li is contained₂O, in addition, Na is particularly preferable₂O+K₂O is 1 to 5 percent.

Further, it is preferable that the microcrystalline glass contains 58% to 70% by mass of SiO based on oxides₂15 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 crystallized glass of the present invention is preferably a glass obtained by crystallizing an amorphous glass having the above composition.

< chemically strengthened glass >

The three-dimensional glass of the present invention is preferably a glass obtained by chemical strengthening. That is, the chemically strengthened glass of the present invention is included in the three-dimensional glass, and is a three-dimensional chemically strengthened glass.

When the surface compressive stress value (CS) of the chemically strengthened glass of the present invention is used₀) It is preferably 500MPa or more because it is less likely to be broken by deformation such as warpage. The surface compressive stress value of the chemically strengthened glass of the present invention is more preferably 600MPa or more, still more preferably 800MPa or more, and particularly preferably 1000MPa or more.

When the depth of compressive stress layer (DOL) of the chemically strengthened glass of the present invention is 80 μm or more, it is not easily broken even when damage is generated on the surface, and therefore, it is preferable. DOL is more preferably 90 μm or more, still more preferably 100 μm or more, and particularly preferably 120 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, it is more preferable. The depth of 50MPa is more preferably 90 μm or more, and particularly preferably 100 μm or more.

When the internal tensile stress (CT) of the chemically strengthened glass of the present invention is 110MPa or less, fragments are less likely to scatter when the strengthened glass is broken, and therefore, the chemically strengthened 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 chemically strengthened glass of the present invention preferably has a 4-point bending strength of 900MPa or more, more preferably 1000MPa or more, and still more preferably 1100MPa or more. Here, the 4-point bending strength was measured using a test piece of 40 mm. times.5 mm. times.0.8 mm 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 value of 10 test pieces was defined as 4-point bending strength.

The light transmittance and haze value of the chemically strengthened glass of the present invention are substantially the same as those of the three-dimensional shaped glass before chemical strengthening. Further, the chemically strengthened glass of the present invention preferably contains β -spodumene crystals, as in the case of the three-dimensional glass before chemical strengthening.

The chemically strengthened glass of the present invention tends to have a higher vickers hardness than the three-dimensional glass before chemical strengthening. The chemically strengthened glass of the present invention has a vickers hardness of preferably 720 or more, more preferably 740 or more, still more preferably 780 or more, and still more preferably 800 or more. The chemically strengthened glass of the present invention has a vickers hardness of usually 950 or less.

< method for producing microcrystalline glass having three-dimensional shape >

The method for producing a three-dimensional microcrystalline glass of the present invention comprises the following steps (1) and (2).

(1) A step of obtaining amorphous glass having a three-dimensional shape by heating and bending the amorphous glass;

(2) a step of obtaining a three-dimensional microcrystalline glass by crystallizing the three-dimensional amorphous glass by heat treatment

Hereinafter, each step will be explained.

(1) A step of providing amorphous glass on a forming mold and obtaining amorphous glass with a three-dimensional shape by heating and forming

The step (1) is a step of obtaining amorphous glass having a three-dimensional shape by bending amorphous glass into a curved shape by bending molding.

(amorphous glass)

The glass composition of the amorphous glass is preferably as follows: the glass composition of the amorphous glass contains 58 to 74 mass% of SiO based on oxides₂5 to 30 percent of Al₂O₃1 to 14% of Li₂O, 0-5% of Na₂O, 0 to 2% of K₂O, SnO accounting for 0.5-12% in total₂And ZrO₂Any one or more of them, and 0 to 6% of P₂O₅. In the above composition, it is more preferable that 2% to 14% of Li is contained₂O, and further, Na is more preferable₂O+K₂O is 1 to 5 percent.

The glass composition of the amorphous glass further preferably contains 58 to 70% by mass of SiO based on oxides₂15 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.

These glass compositions are explained below.

SiO₂Are components that form the network structure of the glass. In addition, SiO₂The component for improving chemical durability is a constituent of lithium aluminosilicate crystal and also a constituent of lithium silicate crystal. SiO 2₂The content of (b) is preferably 58% or more, more preferably 60% or more, and still more preferably 64% or more. On the other hand, when SiO₂When the content of (A) is too large, the meltability is remarkably lowered, and thereforeSiO₂The content of (b) is preferably 74% or less, more preferably 70% or less, still more preferably 68% or less, and particularly preferably 66% or less.

Al₂O₃The component is essential for increasing the compressive stress generated by chemical strengthening. In addition, Al₂O₃Is a constituent of lithium aluminosilicate crystals. Al (Al)₂O₃Is preferably 5% or more, and Al is added when the precipitation of beta-spodumene crystals is desired₂O₃The content of (b) is more preferably 15% or more. Al (Al)₂O₃The content of (b) is more preferably 20% or more. On the other hand, when Al is₂O₃When the content of (b) is too large, the devitrification temperature of the glass becomes high. Al (Al)₂O₃The content of (b) is preferably 30% or less, more preferably 25% or less.

Li₂O is a component that generates compressive stress by ion exchange, and is indispensable as a constituent of lithium aluminosilicate crystals. Li₂The content of O is preferably 1% or more, more preferably 2% or more, and further preferably 4% or more. On the other hand, Li₂The content of O is preferably 14% or less, and when β -spodumene crystals are to be precipitated, it is more preferably 10% or less, still more preferably 8% or less, and particularly preferably 6% or less.

In the case of producing a glass ceramic containing β -spodumene crystals, when Li is used₂O and Al₂O₃Content ratio of (A) to (B) Li₂O/Al₂O₃When the content is 0.3 or less, the transparency is preferably high. This is considered to be because crystallization rapidly proceeds during heat treatment, and the crystal size becomes large.

Na₂O is a component for improving the meltability of the glass. Na (Na)₂O is not essential, but the content thereof is preferably 0.5% or more, more preferably 1% or more. When Na is present₂When O is too much, the precipitation of lithium aluminosilicate crystals is difficult or the chemical strengthening property is lowered, so Na₂The content of O is preferably 5% or less, more preferably 4% or less, and further preferably 3% or less.

K₂O and Na₂Phase OAlso, K may be contained as a component for lowering the melting temperature of the glass₂And O. In the presence of K₂In case of O, K₂The content of O is preferably 0.5% or more, more preferably 1% or more. In addition, Na₂O and K₂Total content Na of O₂O+K₂O is preferably 1% or more, more preferably 2% or more.

When K is₂When the amount of O is too large, lithium aluminosilicate crystals are less likely to precipitate, and therefore the content is preferably 2% or less. In addition, when Na₂O and K₂Total content Na of O₂O+K₂When the amount of O is excessive, the promotion of crystallization is inhibited during heat treatment, and the transparency may be lowered. The total content is preferably 5% or less, more preferably 4% or less, and still more preferably 3% or less, for the purpose of improving transparency.

ZrO₂And SnO₂None of them is essential, but ZrO at the time of crystallization treatment₂And SnO₂It is a component constituting the crystal nucleus, and therefore, it is preferable to contain at least one of them. SnO for nucleation₂And ZrO₂SnO in total amount of₂+ZrO₂Preferably 0.5% or more, more preferably 1% or more. In order to form a large number of crystal nuclei and improve transparency, the total content is more preferably 3% or more, still more preferably 4% or more, still more preferably 5% or more, particularly preferably 6% or more, and most preferably 7% or more. In order to prevent defects caused by unmelted material from being generated in the glass, the total content is preferably 12% or less, more preferably 10% or less, still more preferably 9% or less, and particularly preferably 8% or less.

It is preferable to contain 0.5% or more of SnO for precipitating β -spodumene crystals₂。SnO₂The content of (b) is more preferably 1% or more, and still more preferably 1.5% or more. When SnO₂When the content of (b) is 6% or less, defects due to unmelted material are less likely to occur in the glass, and therefore, the content is preferable. SnO₂The content of (b) is 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). To suppressPreparation of solarization, SnO₂The content of (b) is preferably 1% or more, more preferably 1.5% or more.

Generally, TiO is known₂、ZrO₂As a crystal nucleus forming component of the glass ceramics. According to the investigation of the present inventors, in the present composition, ZrO₂Is more effective than TiO₂High. Alternatively, by adding SnO₂The transparency of the crystallized glass becomes high.

ZrO₂The content of (b) is preferably 0.5% or more, more preferably 1% or more. On the other hand, when ZrO₂When the content of (b) is 6% or less, devitrification is less likely to occur during melting, and deterioration in quality of the chemically strengthened glass can be suppressed. ZrO (ZrO)₂The content of (b) is preferably 6% or less, more preferably 5% or less, and further preferably 4% or less.

In the presence of SnO₂And 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 0.6 or less.

TiO₂Is a crystal nucleus forming component of the glass ceramics, and therefore may contain TiO₂. In the presence of TiO₂In 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, when TiO₂When the content of (3) is 5% or less, devitrification is less likely to occur during melting, and deterioration in quality of the chemically strengthened glass can be suppressed, so that TiO is used as the material for the glass₂The content of (b) is preferably 5% or less. TiO 2₂The content of (b) is more preferably 3% or less, and still more preferably 1.5% 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. Fe₂O₃Usually contained as impurities in the glass becauseFor preventing coloration, TiO₂The content of (b) is preferably 1% or less, more preferably 0.5% or less, still more preferably 0.25% or less, and particularly preferably substantially not contained.

P₂O₅Is not essential, but P₂O₅P may be contained because it has an effect of promoting phase separation of the glass to promote crystallization₂O₅. 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.

On the other hand, when P is₂O₅When the content of (b) is too large, the fracture resistance of the chemically strengthened glass is deteriorated and the acid resistance is remarkably lowered. P₂O₅The 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. In order to further improve the acid resistance, it is preferable that substantially no P is contained₂O₅。

B₂O₃B may be contained in order to improve the chipping resistance and the melting property of the glass for chemical strengthening or the chemically strengthened glass₂O₃。B₂O₃Is not essential, but contains B₂O₃In the case of (B), in order to improve the meltability, B₂O₃The content of (b) is preferably 0.5% or more, more preferably 1% or more, and further preferably 2% or more.

On the other hand, when 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 lowered, so that B₂O₃The content of (b) is preferably 5% or less. B is₂O₃The content of (b) is more preferably 4% or less, still more preferably 3% or less, and particularly preferably 1% or less. In order to improve acid resistance, it is preferable that B is not substantially contained₂O₃。

MgO is a component that increases the compressive stress generated by chemical strengthening, and may contain MgO in order to suppress scattering of fragments when the strengthened glass is broken. 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 for improving the meltability of the glass, and SrO can be contained because the refractive index of the glass is increased to make the refractive index of the residual glass phase after crystallization close to the refractive index of the precipitated crystal, thereby improving the transmittance of the glass ceramic.

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, from this viewpoint, 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 for improving the meltability of the glass, and BaO can be contained because the refractive index of the glass is increased to make the refractive index of the residual glass phase after crystallization close to the refractive index of the lithium aluminosilicate crystal phase to improve the transmittance of the glass ceramic.

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, and therefore, from this viewpoint, 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 for reducing the thermal expansion coefficient of glass and increasing chemical durability. Further, ZnO may be contained because the refractive index of the glass is increased, and the transmittance of the glass ceramics is increased by making the refractive index of the residual glass phase after crystallization close to the refractive index of the lithium aluminosilicate crystal phase.

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 Ta₂O₅Y may be contained to increase 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+Nb₂O₅The content of (b) is preferably 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 (2)₂O₃+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 added to the glass so that the glass is not easily devitrified during melting₂O₃+La₂O₃+Nb₂O₅+Ta₂O₅Preferably 4% or less, more preferably 3% or less, and still more preferably2% or less, particularly preferably 1% or less.

CeO₂Has the effect of oxidizing glass and contains a large amount of SnO₂In the case of (2), SnO may be suppressed₂CeO may be contained because it is reduced to SnO as a coloring component to suppress coloring₂. 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, CeO is used₂When 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 hindering achievement of the desired chemical strengthening property. The coloring component may be, for example, 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 contained₃And chlorides and fluorides as fining agents for melting glass. 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。

When the average thermal expansion coefficient is large, strain and crack are easily generated at the time of cooling, and therefore the average thermal expansion coefficient of the amorphous glass in the range of 50 ℃ to 500 ℃ is preferably 100X 10^-7Lower than/° C, more preferably 80X 10^-7Preferably 60X 10 or less/° C^-7Below/° c. When the average thermal expansion coefficient of the amorphous glass in the range of 50 ℃ to 500 ℃ is small, a mold is produced at the time of formingThe amorphous glass has a poor thermal expansion and cannot be molded into a desired shape. Therefore, the average thermal expansion coefficient of the amorphous glass in the range of 50 ℃ to 500 ℃ is preferably 10X 10^-7/. degree.C.or higher, more preferably 30X 10^-7/. degree.C.or higher, more preferably 40X 10^-7Above/° c.

When the thermal expansion difference between the glass and a mold material for bending to be described later is large, it is necessary to design the mold in consideration of the correction factor in accordance with the target shape. When the average thermal expansion coefficient of the amorphous glass is within the above range, the difference in thermal expansion between the glass and the mold can be reduced when carbon is used as a mold material for bending, and it is not necessary to design the mold by calculating a correction factor from a target shape, and productivity can be improved.

The amorphous glass can be produced by the following method, for example. The following method is an example of a case where a plate-shaped amorphous glass is produced.

Glass raw materials are formulated to give a glass of a preferred 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 of a predetermined thickness by a known forming method, and slowly cooled. Alternatively, the sheet-like member may be formed by: the molten glass was shaped into a block and slowly cooled, and then cut.

As a method for producing the flat glass, for example, a float method, a press method, a fusion method, and a down-draw method can be used. In particular, in the case of producing a large glass plate, the float process is preferable. Further, a continuous forming method other than the float method, such as a fusion method and a downdraw method, is also preferable.

(bending Forming)

The bending is a step of heating the glass to form a bent shape, and rapidly cooling the glass from a high temperature without crystallizing the glass. Examples of the bending method include conventional bending methods such as a self-weight forming method, a vacuum forming method, and a press forming method, and any method can be selected. In addition, two or more bending methods may be used in combination.

The self-weight forming method is as follows: 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 a differential pressure 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 a method as follows: a glass sheet is placed between forming molds (a lower mold and an upper mold), heated, and subjected to a pressing load between the upper and lower forming molds, thereby being bent into a predetermined shape.

In either case, the glass is deformed by applying a force in a state where the glass is heated.

When the temperature for bending (hereinafter, also simply referred to as the hot bending temperature) is low, the desired shape cannot be formed, and therefore the bending temperature is preferably 500 ℃ or higher, more preferably 600 ℃ or higher, further preferably 700 ℃ or higher, and most preferably 750 ℃ or higher. When the temperature for the bending is high, the temperature does not exceed the upper limit of the temperature of the forming machine, and therefore, 1100 ℃ or lower is preferable, 1050 ℃ or lower is more preferable, and 900 ℃ or lower is most preferable.

When the viscosity of the bending (balance viscosity at the time of bending) is low, the bending cannot be formed into a desired shape, and therefore the bending viscosity is preferably 10⁸Pa · s or more, more preferably 10⁹Pa · s or more, most preferably 10¹⁰Pa · s or more. Since it is difficult to maintain a desired shape when the viscosity of the bending is high, the bending viscosity is preferably 10¹³Pa · s or less, more preferably 10¹²Pa · s or less, most preferably 10^11.5Pa · s or less.

Since crystal nucleation and crystal growth occur when the crystallization temperature is close to the thermal bowing temperature, the difference between the crystallization temperature and the thermal bowing temperature is preferably 5 ℃ or more, more preferably 10 ℃ or more, and still more preferably 15 ℃ or more. In order to suppress the decrease in transmittance due to the bending, the difference between the maximum temperature of the crystallization treatment and the thermal bending temperature is preferably 200 ℃ or less, more preferably 150 ℃ or less, further preferably 130 ℃ or less, and particularly preferably 100 ℃ or less.

In the case where it is intended to promote nucleation at the time of hot bending, the difference between the nucleation temperature and the hot bending temperature is preferably 10 ℃ or less. On the other hand, in terms of crystal control in terms of process, nucleation is preferably performed at the time of crystallization treatment, and in this case, the temperature difference is preferably set to 10 ℃ or more.

When the thermal bending temperature is higher than the crystallization temperature, the transmittance may be reduced by bending. The decrease in 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 bending is high, and the light transmittance in terms of a thickness of 0.8mm is preferably 85% or more. The light transmittance in terms of a thickness of 0.8mm is more preferably 87% or more, and particularly preferably 89% or more.

The absolute value of the difference between the average thermal expansion coefficient of the amorphous glass in the range of 50 to 500 ℃ and the average thermal expansion coefficient of the mold material used for bending in the range of 50 to 500 ℃ is preferably 150X 10^-7Lower than/° C, more preferably 100X 10^-7Preferably 50X 10 or less/° C^-7Lower than/° C, and most preferably 30X 10^-7Below/° c.

When the difference in thermal expansion between the mold used for bending and the glass is large, the releasability of the glass is poor, and therefore, the mold design needs to consider a correction factor obtained from the difference between the expansion rate of the glass and the expansion rate of the mold material, and the productivity is lowered. By the absolute value of the difference being 150X 10^-7When the temperature is lower than/° c, the difference in thermal expansion between the mold used for bending and the glass can be reduced, and the mold does not need to be designed according to the target shape, so that the productivity can be improved.

Since the average thermal expansion coefficient of the amorphous glass in the present invention in the range of 50 to 500 ℃ is similar to that of carbon, it is preferable to perform bending using a carbon mold made of carbon. Thus, even without performing a large correction, it is possible to suppress the occurrence of a stress difference during molding, improve the strength, and realize excellent dimensional stability and molding accuracy.

The amorphous glass of the present invention is preferably 170X 10 because a desired shape is not easily obtained when the average thermal expansion coefficient is large in the range of 50 ℃ to 500 ℃^-7/° C or less, more preferably 160X 10^-7Preferably not more than 150X 10/° C^-7Below/° c. In addition, in the case of using a carbon mold, the thermal expansion coefficient is particularly preferably 60 × 10^-7Below/° c. When the thermal expansion coefficient is low, the releasability from the mold is poor, and therefore, it is preferably 20 × 10^-7/. degree.C.or higher, more preferably 30X 10^-7/. degree.C.or higher, more preferably 40X 10^-7Above/° c.

From the viewpoint of suppressing crystal growth during forming, the difference between the glass transition temperature of the amorphous glass in the present invention and the maximum temperature of crystallization treatment is preferably 10 ℃ or more, more preferably 20 ℃ or more, and still more preferably 30 ℃ or more.

(2) A step of obtaining a three-dimensional microcrystalline glass by crystallizing the three-dimensional amorphous glass by heat treatment

The step (2) is a step of obtaining a three-dimensional microcrystalline glass by heating the three-dimensional amorphous glass obtained in the step (1).

The heat treatment in the step (2) is preferably 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.

In the case of using the two-step heating treatment, the first treatment temperature is preferably a temperature range in which the nucleation rate increases for the glass composition, and the second treatment temperature is preferably a temperature range 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 glass-ceramic 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 ℃. The first treatment temperature is maintained for 2 to 10 hours, and then the second treatment temperature is maintained for 2 to 10 hours.

The microcrystalline glass having a three-dimensional shape obtained by the above steps is ground and polished as necessary. When the glass-ceramic plate is cut into a predetermined shape and size or chamfered, if the cutting and chamfering are 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.

< method for producing chemically strengthened glass having three-dimensional shape >

The method for producing a chemically strengthened glass having a three-dimensional shape of the present invention includes the following steps (1) to (3).

(1) A step of obtaining amorphous glass having a three-dimensional shape by heating and bending the amorphous glass;

(2) crystallizing the three-dimensional amorphous glass by heat treatment to obtain a three-dimensional microcrystalline glass;

(3) and (3) chemically strengthening the three-dimensional glass ceramics obtained in step (2).

The steps (1) and (2) are the same as the steps (1) and (2) described above in the < method for producing a microcrystalline glass having a three-dimensional shape >. The step (3) will be explained below.

The chemical strengthening treatment is as follows: metal ions having a small ionic radius (typically Na ions or Li ions) in glass 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 by a method such as dipping in a melt containing a metal salt (for example, potassium nitrate) having a large ionic radius (typically Na ions or K ions for Na ions) or the like.

In order to accelerate the chemical strengthening treatment, it is preferable to use "Li — Na exchange" in which Li ions in the glass are exchanged with Na ions. 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 for the chemical strengthening treatment may be appropriately selected in consideration of the glass composition, the type of molten salt, and the like.

The chemically strengthened glass of the present invention is preferably obtained by, for example, the following two-step chemical strengthening treatment.

First, as a first chemical strengthening treatment, a three-dimensional shape of a glass ceramics 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 glass ceramics and Na ions in the metal salt, and enables formation of, for example, a surface compressive stress value (CS)₀) A compressive stress layer having a depth of the compressive stress layer of not less than 200MPa and not less than 80 μm. On the other hand, when the surface compressive stress value (CS)₀) Above 1000MPa, it is difficult to increase DOL while maintaining low CT. The surface compressive stress value is preferably 900MPa or less, more preferably 700MPa or less, and still more preferably 600MPa or less.

Next, as a second chemical strengthening treatment, the steel sheet 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, a depth of about 10 μm or less.

According to such a two-step process, the surface compressive stress value (CS) is easily obtained₀) A preferred stress distribution of 600MPa or more.

Or may be 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 holding temperature is preferably 325 ℃ or higher, more preferably 340 ℃ or higher. The holding temperature is preferably 475 ℃ or less, and more preferably 460 ℃ or less.

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 held in the atmosphere, the metal salt may be first immersed in a metal salt containing Na ions and then immersed in a metal salt containing Na ions and Li ions (for example, a mixed salt of sodium nitrate and lithium nitrate) at a temperature in the range of 350 ℃ to 500 ℃ for 0.1 hour 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, and a more preferable stress distribution is formed, whereby the asphalt drop strength can be improved.

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. The treatment time is more preferably 1 hour or more.

The three-dimensional glass of the present invention is particularly useful as a cover glass for use in display devices such as mobile devices including mobile phones and smartphones. 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.

Examples

The present invention will be described below with reference to examples, but the present invention is not limited thereto. In the table, the blank column indicates no measurement.

[ evaluation method ]

(glass transition temperature)

The glass transition temperature was measured using a thermal dilatometer (manufactured by Bruker AXS, TD5000 SA).

(delay)

The glass was irradiated with light having a wavelength of 543nm, and the retardation value was measured at one or more positions on each R-shaped arc using a birefringence measurement device (WPA-100, manufactured by Photonic Lattice corporation).

(haze value)

According to JIS K3761: 2000, the maximum haze value of the R shape was measured using a haze meter (HZ-2, manufactured by Kogaku Kogyo Co., Ltd.).

(coefficient of thermal expansion)

The thermal expansion curve was obtained by using a thermal expansion meter (TD 5000SA manufactured by Bruker AXS) and setting the temperature increase rate at 10 ℃/min. Further, the average linear thermal expansion coefficient [ unit: x 10^-7/℃]。

(precipitation of crystals)

The precipitated crystals (main crystals) were identified by measuring powder X-ray diffraction under the following conditions.

A measuring device: SmartLab, manufactured by Nippon corporation

Using X-rays: CuKalpha ray

Measurement range: 2 theta is 10-80 DEG

Speed: 10 °/min

Step length: 0.02 degree

(average radius of curvature)

Average radius of curvature the height direction coordinates of the sample surface with respect to the cross-sectional direction were measured at 0.1mm intervals using a three-dimensional measuring machine ATOS (model: ATOS Triple scan III) manufactured by gom, and then the general formula of an approximate circle was found using the least square method, and finally the average radius of curvature was calculated.

[ production of glass ]

< reference example 1 >

Glass raw materials were prepared so as to obtain 800g of each of glasses having compositions A to I shown in Table 1 in terms of mass% based on oxides, and the glasses were placed in a platinum crucible and put into an electric furnace at 1400 to 1700 ℃ to be melted for 5 hours. The defoamed and homogenized molten glass was poured into a mold, kept at a temperature higher than the glass transition temperature by about 30 ℃ for 1 hour, and then cooled to room temperature at a cooling rate of 0.5 ℃/minute, thereby obtaining a glass gob. From the obtained glass block, a glass plate having a thickness of 0.55mm and a test piece for evaluating glass physical properties were obtained. The surface of the glass plate was subjected to mirror finish.

The results of measuring the glass transition temperature and the thermal expansion coefficient of the obtained glass plate are shown in table 1.

TABLE 1

Compositions B to I are examples of compositions suitable for use in the present invention. When they are subjected to heat treatment, a glass ceramics containing β -spodumene crystals can be obtained. The thermal expansion coefficient of the compositions B to D, F, G is 40X 10^-7/℃～60×10^-7In the range of/° c, when carbon is used as a mold material for bending, the difference in thermal expansion between the glass and the mold can be reduced, and it is not necessary to design the mold according to the calculation of the target shape, so that productivity can be improved.

< example 1 >

Fig. 5 is a schematic view of an embodiment of the method for producing a three-dimensional glass according to the present invention. The glass plate 13 of composition A (80 mm. times.50 mm, R-shaped corner glass plate) was C-chamfered in a range of 0.2mm from the glass end face. Here, the phrase "the corner portions have an R shape" means that when the preform is viewed from directly above, 4 corners have an R shape. A600 # grindstone (manufactured by TOKYO DIA) was used for chamfering so that the surface roughness of the end face (arithmetic average surface roughness of the chamfered portion) was 450 nm.

A carbon female mold 11 and a carbon male mold 12 are prepared, the carbon female mold 11 and the carbon male mold 12 are designed to be capable of molding a curved surface having a curvature radius of 6.0mm and a bending depth of 4.0mm, and a glass plate 13 obtained by chamfering is placed near the center of a glass contact surface of the female mold 11.

The glass plate 13 was preheated, deformed, and cooled while the female mold 11 and the male mold 12 on which the glass plate 13 was placed were fixed to the lower axis and the upper axis of a molding apparatus (manufactured by Toshiba mechanical Co., Ltd., glass element molding apparatus: GMP-315V), respectively.

In the preheating step, the temperature was raised from room temperature to 600 ℃ over 15 minutes. The equilibrium viscosity of the glass plate 13 is about 10 at 600 deg.C¹³Pa · s. Subsequently, the temperature was raised from 600 ℃ to 645 ℃ over 5 minutes. The equilibrium viscosity of the glass plate 13 at 645 deg.C is about 10^11.5Pa·s。

The equilibrium viscosity at the center of the glass plate 13 is maintained at 10¹¹Pa·s～10¹²The punch 12 was moved downward in a state of Pa · s range (temperature was maintained in a range of 640 ℃ to 650 ℃), and the die 11 was pressed at maximum 2000N for 3 minutes. Meanwhile, 20L/min of nitrogen gas was blown through a through hole (not shown) provided in the punch 12 to uniformly shape the glass sheet 14.

Then, it was slowly cooled to 480 ℃ over 20 minutes. The equilibrium viscosity of the glass sheet at 480 ℃ is about 10²¹Pa · s. Subsequently, the male mold 12 was raised at 2 mm/sec and retracted, and the glass plate 14 was naturally cooled to room temperature.

At room temperature, the glass sheet 14 had an average radius of curvature of the smallest R-shape of 6.0mm, a bending depth of 4.0mm, and an average radius of curvature of the largest R-shape of 3.8X 10³mm. The largest R-shape is contained in the approximately parallel portions of the inner and outer surfaces of the glass sheet 14.

The surface of the glass plate 14 having the smallest R-shape was irradiated perpendicularly with light having a wavelength of 543nm, and the retardation was measured. The maximum value of retardation was 22 nm/mm.

< example 2 >

The glass plate 13 of composition B was chamfered in the same manner as in example 1. A glass plate 13 was formed in the same manner as in example 1Bending to obtain the minimum R shape with average curvature radius of 6.0mm, bending depth of 4.0mm, and maximum R shape with average curvature radius of 3.8 × 10³mm glass plate 14. The largest R-shape is contained in the approximately parallel portions of the inner and outer surfaces of the glass sheet 14.

The obtained glass plate 14 was held at 750 ℃ for 4 hours and then at 900 ℃ for 4 hours in a state of being placed on the punch 12, and crystallization was performed by this means, and a microcrystalline glass 15 having a three-dimensional shape was obtained.

The maximum R-shaped retardation of the obtained three-dimensional-shaped glass ceramics 15 was measured in the same manner as in example 1. The maximum retardation of the maximum R shape is 1.9 nm/mm. The haze value of the maximum R-shape was measured, and found to be 0.29%.

< example 3 >

In the same manner as in example 2, the glass plate 13 having the composition B was chamfered and then crystallized by heat treatment in the same manner as in example 2, thereby obtaining a crystallized glass plate. The obtained glass ceramics sheet was placed on a punch 12, and subjected to bending forming under the same conditions as in example 2 to obtain a three-dimensional glass ceramics.

The three-dimensionally shaped glass ceramics obtained had an average radius of curvature of the smallest R-shape of 12900mm, a depth of curvature of 4.2mm and an average radius of curvature of the largest R-shape of 5.7 mm. The haze value of the maximum R-shape was measured, and found to be 3.0%.

< examples 4 to 6 >

Microcrystalline glass having a three-dimensional shape was obtained in the same manner as in example 2, except that the glass composition, crystallization treatment, molding timing, and molding conditions were set as shown in table 2.

The results obtained by evaluating the obtained three-dimensional glass are shown in table 2. In the "crystallization treatment column" in table 2, the two-step treatment conditions are shown to be maintained at the temperature and time described in the upper stage, and then maintained at the temperature and time described in the lower stage. For example, in the above paragraph of "750 ~ 4 hours", in the following paragraph of "920 ~ 4 hours" cases, means at 750 ℃ for 4 hours, and then at 920 ℃ for 4 hours.

In the column of "molding timing", when it is referred to as "before crystallization", it means that the processing is performed in the order of molding and crystallization. In the case of the description "after crystallization", the treatment is performed in the order of crystallization and molding. The "Haze value" represents a Haze value after molding and after crystallization, and the "Δ Haze value" represents a difference between a Haze value (Haze) after molding and after crystallization and a Haze value before molding and before crystallization. "shape deviation" means a deviation from a target shape.

The results of evaluating the obtained glass ceramics are shown in table 2. Examples 2 and 4 are examples, and examples 1, 3, 5 and 6 are comparative examples. The precipitated crystals of examples 2 to 6 were β -spodumene crystals.

TABLE 2

As shown in table 2, the maximum values of retardation of examples 2 and 4, which are three-dimensional shape glasses of the present invention, are 20nm or less, and high strength and shape stability (molding stability) are exhibited as compared with example 1, which is a comparative example. The maximum haze value of the R-form is 1.0% or less, and the transparency is excellent.

Further, examples 2 and 4 produced by bending and crystallizing an amorphous glass satisfying the composition range specified in the present invention can suppress the deterioration of haze caused by heating at the time of molding and can realize high transparency, as compared with examples 3 and 6 obtained by bending and molding after crystallization.

Examples 2 and 4, which were manufactured by bending and crystallizing an amorphous glass satisfying the preferable composition range of the present invention, can obtain samples having small shape variations and a shape close to a target shape.

Therefore, according to the method for producing a three-dimensional glass of the present invention, it is found that the difference in stress generated during molding can be reduced by the heat treatment for crystallization to improve the strength, and the deterioration in haze can be suppressed to realize excellent transparency.

While the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. The present application is based on the japanese patent application (japanese patent application 2019-072736), filed on 5/4/2019, the content of which is incorporated herein by reference.

Industrial applicability

According to the present invention, a three-dimensional shaped glass excellent in strength, transparency and shape stability and a method for producing the same can be provided.

Description of the reference symbols

100 three-dimensional shaped glass

110 center section

120 peripheral part