WO2021035586A1 - Strengthened glass ceramic having low surface compressive stress, and raw sheet glass - Google Patents

Abstract

Strengthened glass ceramic having a low surface compressive stress. The surface compressive stress of the strengthened glass ceramic is between 100-450 Mpa; the depth of a compressive stress layer is less than or equal to 180 µm; the maximum value of an internal tensile stress is less than or equal to 180 Mpa; a tensile stress linear density is less than or equal to 60,000 Mpa/mm; a dielectric loss tangent is less than or equal to 9×10-3 under the frequency of 1.8 GHz at room temperature. The strengthened glass ceramic is obtained by performing micro-crystallization heat treatment and ion exchange treatment on a raw sheet glass. The strengthened glass ceramic has high intrinsic strength because of having nanocrystals that are integrally and uniformly distributed, and after the low surface compressive stress is realized by means of chemical strengthening, the strengthened glass ceramic still has high glass anti-fall strength, and therefore can serve as the front and rear protective covers of an electronic device. In the process of industrial production, the strength of the strengthened glass ceramic is less affected by the change of the content of impurity ions, i.e., Na+ and Li+, and the distribution of large alkali metal ions in a salt bath, thereby ensuring that the strengthened glass ceramics produced in large batch are high in strength uniformity.

Description

Strengthened glass ceramic and original glass with low surface compressive stress Technical field

The invention relates to the technical field of glass, in particular to a strengthened glass ceramic and original glass with low surface compressive stress.

Background technique

At present, the protective material of the front and rear covers of electronic devices (such as smart phones, laptops, tablet computers, etc.) is generally glass. In order to make the mobile phone lighter and thinner, the glass used as the protective cover of the mobile phone is getting thinner and thinner. In order to make the light and thin glass reach sufficient strength, the current strengthening method is usually chemical strengthening method, specifically, the large alkali in the salt bath Metal ions, such as potassium ions and sodium ions, exchange sodium and lithium ions inside the glass under high temperature conditions. Finally, due to the effect of the exchanged ion volume difference, compressive stress is generated inside the glass, making it difficult for small cracks/defects on the glass surface to grow Growth, increase the strength of the glass. It should be understood that the process of industrial production of strengthened glass is to place a large number of glass in different batches in the same strengthened furnace with a salt bath for ion exchange, especially high-content sodium ion glass, which is used with the salt bath. As the time lengthens and the amount of glass processed by the salt bath increases, ^{the content of garbage ions Na +} and Li ⁺ in the salt bath will also increase. Although it is only PPM level, it is enough to seriously hinder the progress of normal chemical tempering, leading to follow-up The CS value of the strengthened glass decreases and the strength drops significantly, resulting in uneven strength levels, poor uniformity, and high dispersion of strengthened glass produced in different batches. In addition, due to the uniformity of the distribution of large alkali metal ions in the salt bath, even the strength of strengthened glass produced in the same batch will vary greatly. This makes it difficult to control the quality of the final product. In order to reduce the ^{influence of the changes in the content of garbage ions Na +} and Li ⁺ in the salt bath and the uniformity of the distribution of large alkali metal ions on the uniformity and dispersion of the strength of the final strengthened glass, we must reduce the industrial production of strengthened glass The degree of dependence on the chemical strengthening process, that is to say, the improvement of the strength of the glass cannot be achieved only by chemical strengthening. On the other hand, with the advent of the 5G era, 5G communications also have higher requirements for electronic equipment. Exposure of ordinary glass to high-frequency or ultra-high-frequency electromagnetic fields results in slower transmission speed, attenuation of signal strength, and signal transmission time delay. The glass is required to have low dielectric loss.

Summary of the invention

The technical problem to be solved by the present invention is to provide a strengthened glass ceramic in view of the above-mentioned problems in the prior art. The strengthened glass ceramic is subjected to microcrystallization heat treatment and ion exchange through a raw glass with special physical and chemical characteristics. It is obtained after processing and is strong enough to be used as a front and rear protective cover for electronic equipment. On the one hand, the strengthened glass-ceramic contains a low sodium content, and on the other hand, it has a high intrinsic strength due to its uniformly distributed nanocrystals. Therefore, the strengthened glass-ceramic is obtained by chemical strengthening. The surface compressive stress is low, and it still has high glass drop strength. Therefore, in the industrial production process, the strength of the strengthened glass ceramic with a low CS value is less affected by the ^{changes in the content of the garbage ions Na +} and Li ⁺ in the salt bath and the distribution of the large alkali metal ions, ensuring the final mass production Strength uniformity of strengthened glass ceramics is high. In addition, due to the low sodium content in the strengthened glass ceramic, it also has a low dielectric loss, which meets the new requirements of the high-frequency electromagnetic field on the front and rear cover of the electronic device in the 5G era.

The technical solution adopted by the present invention to solve its technical problems is to provide a strengthened glass ceramic with low surface compressive stress, the surface compressive stress of the strengthened glass ceramic is between 100-450Mpa, and the depth of the compressive stress layer is less than or equal to 180 μm; The maximum internal tensile stress of the strengthened glass ceramic is less than or equal to 180Mpa; the tensile stress linear density of the strengthened glass ceramic is less than or equal to 60000Mpa/mm, and the dielectric loss angle of the strengthened glass ceramic at room temperature and a frequency of 1.8GHz The tangent is less than or equal to 9×10 ^-3 .

As a preference of the strengthened glass ceramic with low surface compressive stress of the present invention, the surface compressive stress of the strengthened glass ceramic is between 200-350Mpa; the depth of the compressive stress layer of the strengthened glass ceramic is less than or equal to 150 μm; the strengthened glass ceramic The maximum internal tensile stress is less than or equal to 150Mpa; the tensile stress linear density of the strengthened glass ceramic is less than or equal to 40000Mpa/mm, and the dielectric loss tangent of the strengthened glass ceramic at room temperature and a frequency of 1.8GHz is less than or equal to 5. ×10 ^-3 .

As a preference for the strengthened glass ceramic with low surface compressive stress of the present invention, the surface compressive stress of the strengthened glass ceramic is between 200-300Mpa; the maximum internal tensile stress of the strengthened glass ceramic is less than or equal to 130Mpa; The tensile stress linear density of the glass ceramic is less than or equal to 34000 mpa/mm, and the dielectric loss tangent of the strengthened glass ceramic at room temperature and a frequency of 1.8 GHz is less than or equal to 3×10 ^-3 .

As a preference of the strengthened glass ceramic with low surface compressive stress of the present invention, the strengthened glass ceramic includes a glass body and a plurality of crystals discretely distributed in the glass body, and the composition of the crystals is Li _{2-2(X+ Y)} ·Mg _X Zn _Y O·Al ₂ O ₃ ·nSiO ₂ or/and Li ₂ O·2SiO ₂ , where n is between 2-10, X+Y≤1, the proportion of the crystal It is 20-80wt%, the size of the crystal is between 6-80nm, and the average size of a plurality of the crystals is less than or equal to 50nm.

As a preference of the strengthened glass ceramics with low surface compressive stress of the present invention, the strengthened glass ceramics, in terms of mole percentage, contain the following components:

60-80% SiO ₂ ;

3-11% Al ₂ O ₃ ;

0.5-8% P ₂ O ₅ and/or B ₂ O ₃ ;

7-18% Li ₂ O;

0.05-2% Na ₂ O;

0.05-2% K ₂ O;

1-6% of ZrO ₂ ;

0-2% TiO ₂ ;

0-1% SnO ₂ .

As a preference of the strengthened glass ceramic with low surface compressive stress of the present invention, the strengthened glass ceramic further includes 0-8 mol% of other oxides, and the other oxides include one of MgO, ZnO and Tm ₂ O ₃ or Many kinds.

As a preference of the strengthened glass ceramics with low surface compressive stress of the present invention, the strengthened glass ceramics, in terms of mole percentage, contain the following components:

68-75% SiO ₂ ;

5-7 mol% Al ₂ O ₃ ;

2-7% P ₂ O ₅ and/or B ₂ O ₃ ;

7.5-15% Li ₂ O;

0.05-1% Na ₂ O;

0.05-1% K ₂ O;

2-5% ZrO ₂ ;

0-1% TiO ₂ ;

0.1-0.5% SnO ₂ .

As a preference for the strengthened glass ceramic with low surface compressive stress of the present invention, the Young’s modulus of the strengthened glass ceramic is greater than or equal to 85 GPa; the equibiaxial flexural strength of the strengthened glass ceramic is greater than or equal to 800 N; the strengthened glass ceramic The X-axis bending strength and Y-axis bending strength are greater than or equal to 450Mpa and 180Mpa, respectively.

As a preferred of the strengthened glass ceramic with low surface compressive stress of the present invention, the isobiaxial flexural strength of the strengthened glass ceramic is 1200N or more.

As a preference of the low surface compressive stress strengthened glass ceramic of the present invention, the average visible light transmittance of the strengthened glass ceramic is greater than or equal to 90%, and the haze of the strengthened glass ceramic is less than or equal to 0.2%.

The present invention also provides an original piece of glass, which can be subjected to microcrystallization heat treatment and ion exchange treatment to produce the above-mentioned strengthened glass ceramic; the original piece of glass, in terms of mole percentage, contains the following ingredient:

60-80% SiO ₂ ;

3-11% Al ₂ O ₃ ;

0.5-8% P ₂ O ₅ and/or B ₂ O ₃ ;

7-18% Li ₂ O;

0-2% Na ₂ O;

0-2% K ₂ O;

1-6% of ZrO ₂ ;

0-2% TiO ₂ ;

0-1% SnO ₂ ;

As a preference of the original glass provided by the present invention, the original glass further includes 0-8 mol% of other oxides, and the other oxides include one or more of _{MgO, ZnO, and Tm 2} O _3.

As a preference of the original glass sheet provided by the present invention, the original glass sheet, in terms of mole percentage, contains the following ingredients:

68-75% SiO ₂ ;

5-7% Al ₂ O ₃ ;

2-7% P ₂ O ₅ and/or B ₂ O ₃ ;

7.5-15% Li ₂ O;

0-1% Na ₂ O;

0-1% K ₂ O;

2-5% ZrO ₂ ;

0-1% TiO ₂ ;

0.1-0.5% SnO ₂ .

As a preference of the original glass provided by the present invention, the original glass does not contain Na ₂ O.

As a preference for the original glass sheet provided by the present invention, the Young's modulus of the original glass sheet is greater than or equal to 80 GPa.

As a preference of the original glass provided by the present invention, the molar volume V _{m of} the original glass is less than or equal to 25.5 cm ³ /mol, and the molar volume V _m =∑x _i M _i /ρ, where x _i and M _i are the respective mole fractions of oxides and molar mass, ρ is the density of the original glass.

As a preference of the original glass provided by the present invention, the microcrystallization heat treatment includes a nucleation process and a crystallization process; the conditions of the nucleation process are: the nucleation temperature is 580-750°C, and the holding time is 0.5-5h The conditions of the crystallization step are: the crystallization temperature is 700-800 degrees ℃, and the holding time is 0.5-5h.

As a preference of the original glass sheet provided by the present invention, the ion exchange treatment is one or more chemical strengthening in a mixed salt bath, and the mixed salt bath contains at least two of potassium salt, sodium salt and lithium salt, The potassium salt includes KNO ₃ and/or KCl, the sodium salt includes NaNO ₃ and/or NaNO ₂ , and the lithium salt includes LiNO ₃ and/or Li ₂ CO ₃ .

As a preference of the original glass provided by the present invention, the mixed salt bath contains the potassium salt, the sodium salt and the lithium salt.

As a preference of the original glass sheet provided by the present invention, the mixed salt bath contains NaNO ₃ and LiNO ₃ , wherein NaNO ₃ accounts for 5% to 75% _{of the mass of the mixed salt bath, and LiNO 3} accounts for the mass of the mixed salt bath. Of 0.05% to 5%.

As a preference for the original glass sheet provided by the present invention, the temperature of the mixed salt bath is 400-550° C., and the total duration of the ion exchange treatment is greater than or equal to 5 hours.

detailed description

The surface of the strengthened glass ceramic provided by the present invention has a compressive stress layer produced by chemical ion exchange strengthening. The surface compressive stress of the strengthened glass ceramic is between 100-450Mpa, preferably between 200-350Mpa, and more preferably between 200-300Mpa; the depth of the compressive stress layer is less than or equal to 180μm, preferably less than or equal to 150μm; The maximum internal tensile stress of the glass ceramic is less than or equal to 180Mpa, preferably, less than or equal to 150Mpa, more preferably, less than or equal to 130Mpa; the tensile stress linear density of the strengthened glass ceramic is less than or equal to 60,000Mpa/mm, preferably, less than or equal to 40,000Mpa / mm, and more preferably, less 34000mpa / mm; the reinforced glass ceramic at room temperature and at a frequency of 1.8GHz the dielectric loss tangent of the angle is less than or equal to 8 × 10 ^-3, preferably less than equal to 5 × 10 ^{- 3} , more preferably, less than or equal to 3×10 ^-3 . The strengthened glass ceramic includes a glass body and a plurality of crystals discretely distributed in the glass body, and the composition of the crystals is Li _2-2(X+Y) ·Mg _X Zn _Y O·Al ₂ O ₃ ·nSiO ₂ or/and Li ₂ O·2SiO ₂ , wherein the value of n is between 2-10, X+Y≤1, the proportion of the crystal is 20-80wt%, and the size of the crystal is 6-80nm In between, the average size of a plurality of the crystals is less than or equal to 50 nm. The Young's modulus of the strengthened glass ceramic is greater than or equal to 85GPa; the isobiaxial flexural strength is greater than or equal to 800N, preferably, greater than or equal to 1200N; the bending strength in the X-axis and the Y-axis are greater than or equal to 450Mpa and 180Mpa, respectively ; The average visible light transmittance is greater than or equal to 90%; the haze is less than or equal to 0.2%.

The crystal composition, crystal size, internal tensile stress, average visible light transmittance, haze, and dielectric loss tangent can all be tested by conventional testing methods in the industry.

Use FSM-6000LE surface stress meter (Japan Orihara Research Institute) to measure the surface compressive stress CS (unit: MPa) and compressive stress layer depth DOL (unit: μm) of strengthened glass ceramics. The measured surface compressive stress is K-Na exchange The resulting surface compressive stress.

Refer to ASTM C-623 to determine the Young's modulus of strengthened glass ceramics, the unit is GPa.

The explanation of the tensile stress linear density is as follows: the strengthened glass ceramic has a tensile stress layer formed in the ion exchange process, and the tensile stress layer has an upper boundary spaced apart from the upper surface of the strengthened glass ceramic and A lower boundary at a certain interval from the lower surface of the strengthened glass ceramic will be perpendicular to the upper boundary and the lower boundary while in the tensile stress layer, and the upper and lower end points shall fall on the upper boundary respectively The magnitude of the tensile stress at a certain point on the line segment on the lower boundary is the Y axis, and the distance between the corresponding point and the upper boundary is the X axis is the curve drawn as the tensile stress curve, and the tensile stress curve is The ratio of the definite integral to the thickness of the strengthened glass ceramic is recorded as the tensile stress linear density, that is, the sum of the tensile stress at each point on the line segment of the strengthened glass ceramic measured by the SLP-1000 stress meter and the strengthened glass ceramic The thickness ratio.

Equivalent biaxial flexural strength is determined by ring-on-ring test. The ring-on-ring test covers the determination of the biaxial strength of advanced brittle materials under the condition of monotonous uniaxial load via concentric ring construction. This type of test has been widely accepted and used to evaluate the surface strength of glass substrates. For the ring-on-ring experiment performed in the embodiments herein, a 30 mm diameter support ring and a 15 mm inch diameter load ring can be used on a sample size of approximately 2 inches by 2 inches. The contact radius of the ring may be about 1.6 mm, and the head speed may be about 1.2 mm/min.

A four-point bending test was performed on strengthened glass ceramics in accordance with ASTM D6272-02. The lower span was 60.0mm, the upper span was 20.0mm, and the displacement speed of the indenter was 4.0mm/min. The pressure and displacement of the indenter were recorded and calculated based on the size of the strengthened glass ceramic. X-axis bending strength and Y-axis bending strength.

The strengthened glass ceramics, in terms of mole percentage, contains the following components: 60-80% SiO ₂ ; 3-11% Al ₂ O ₃ ; 0.5-8% P ₂ O ₅ and/or B ₂ O ₃ ; 7-18% Li ₂ O; 0.05-2% Na ₂ O; 0.05-2% K ₂ O; 1-6% ZrO ₂ ; 0-2% TiO ₂ ; 0-1% SnO ₂ . Preferably, the strengthened glass ceramics, in terms of mole percentage, contains the following components: 68-75% of SiO ₂ ; 5-7 mol% of Al ₂ O ₃ ; 2-7% of P ₂ O ₅ and/or B ₂ O ₃ ; 7.5-15% Li ₂ O; 0.05-1% Na ₂ O; 0.05-1% K ₂ O; 2-5% ZrO ₂ ; 0-1% TiO ₂ ; 0.1-0.5% SnO ₂ . Optionally, the strengthened glass ceramic further includes 0-8 mol% of other oxides, and the other oxides include one or more of _{MgO, ZnO, and Tm 2} O _3.

The method for preparing the strengthened glass ceramic is to prepare the strengthened glass ceramic by subjecting the original glass to microcrystallization heat treatment and ion exchange treatment.

The key of the preparation method is the physical and chemical characteristics of the original glass. Specifically, the original glass includes the following components in mole percentage: 60-80% SiO ₂ ; 3-11% Al ₂ O ₃ ; 0.5-8% P ₂ O ₅ and/or B ₂ O ₃ ; 7-18% Li ₂ O; 0-2% Na ₂ O; 0-2% K ₂ O; 1-6% ZrO ₂ ; 0-2% TiO ₂ ; 0-1% SnO ₂ . Preferably, the original glass contains 68-75% SiO ₂ ; 5-7% Al ₂ O ₃ ; 2-7% P ₂ O ₅ and/or B ₂ O ₃ ; 7.5-15% Li ₂ O; 0-1% Na ₂ O; 0-1% K ₂ O; 2-5% ZrO ₂ ; 0-1% TiO ₂ ; 0.1-0.5% SnO ₂ . Optionally, the original glass further includes 0-8 mol% of other oxides, and the other oxides include one or more of _{MgO, ZnO, and Tm 2} O _3. Optionally, the original glass may not contain Na ₂ O.

The Young's modulus of the original glass is greater than or equal to 80 GPa.

_{The molar volume V m of} the original piece of glass is less than or equal to 25.5 cm ³ /mol, and the molar volume V _m =∑x _i M _i /ρ according to the formula, where x _i and M _i are the moles of each oxide composition, respectively Fraction and molar mass, ρ is the density of the glass ceramic.

The microcrystallization heat treatment includes a nucleation step and a crystallization step; the conditions of the nucleation step are: the nucleation temperature is 580-750°C, and the holding time is 0.5-5h; the conditions of the crystallization step are: crystallization The melting temperature is 700～800℃, and the holding time is 0.5～5h.

The nucleation process specifically includes: heating the original glass to a nucleation temperature of 580-750°C at a rate of 0-10°C/min, and holding it for 0.5-5h.

The crystallization process specifically includes: heating the original glass to a crystallization temperature of 700-800°C at a rate of 5-10°C/min, and holding it for 0.5-5h.

The ion exchange treatment is one or more chemical strengthening in a mixed salt bath, the mixed salt bath contains at least two of potassium salt, sodium salt and lithium salt, and the potassium salt includes KNO ₃ and/or KCl The sodium salt includes NaNO ₃ and/or NaNO ₂ , and the lithium salt includes LiNO ₃ and/or Li ₂ CO ₃ . Optionally, the mixed salt bath includes the potassium salt, the sodium salt, and the lithium salt. Preferably, the temperature of the mixed salt bath is 400-550°C, and the total time of the ion exchange treatment is greater than or equal to 5 hours. Optionally, the mixed salt bath contains NaNO ₃ and LiNO ₃ , wherein NaNO ₃ accounts for 5% to 75% _{of the mass of the mixed salt bath, and LiNO 3} accounts for 0.05% to 5% of the mass of the mixed salt bath.

In order to have a clearer understanding of the technical features, objectives and effects of the present invention, the specific embodiments of the present invention will now be described in detail. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

Example 1-5: Preparation of strengthened glass ceramics from original glass

In Examples 1-5, batches (1000 pieces) of original glass I, original glass II, original glass III, original glass IV, and original glass V were subjected to the above-mentioned microcrystallization heat treatment and ionization. The batches (1000 pieces) of strengthened glass ceramics I, strengthened glass ceramics II, strengthened glass ceramics III, strengthened glass ceramics IV, and strengthened glass ceramics V are prepared by the exchange treatment.

The physical and chemical characteristics of the original glass I to V are shown in the table below.

The parameters involved in the microcrystallization heat treatment and ion exchange treatment of the original glass I, the original glass II, the original glass III, the original glass IV, and the original glass V are shown in the following table.

The composition of the crystals in the prepared strengthened glass ceramic I is Li _1.8 ·Mg _0.1 O·Al ₂ O ₃ ·6SiO ₂ , the largest crystal size is 26 nm, the smallest crystal size is 24 nm, and the average crystal size is 25 nm. The proportion of crystals is 75% of the total mass of strengthened glass ceramic I.

The physical and chemical characteristics of the prepared batches of strengthened glass ceramics I were tested, and the results are shown in the following table.

Physical and chemical characteristics Maximum value Minimum average value Young's modulus/GPa 92.45 91.30 91.88 Equivalent biaxial flexural strength/N 1600 1508 1554 X-axis bending strength/MPa 820 780 800 Y-axis bending strength/MPa 400 380 390 Average visible light transmittance/% 91.8 91.4 91.6 Haze/% 0.080 0.078 0.079 Dielectric loss tangent 0.00510 0.00500 0.00505 Surface compressive stress/MPa 418 406 412 Compressive stress layer depth/μm 176 166 163 Maximum internal tensile stress/Mpa 180 170 175 Tensile stress linear density/Mpa/mm 36366 36150 36258

It can be seen from the above table that the average biaxial flexural strength of the prepared batch of strengthened glass ceramic I is 1554N, and the difference between the maximum value and the minimum value is only 92N; the average value of the X-axis flexural strength is 800MPa, the maximum value The difference between the minimum value and the minimum value is only 40Mpa; the Y-axis bending strength is 390MPa; the difference between the maximum value and the minimum value is only 20MPa, which is enough to show that the bulk of the original glass I produced the bulk of the strengthened glass ceramics I have higher strength uniformity, Low dispersion.

The composition of the crystals in the prepared strengthened glass ceramic II is Li·Mg _0.5 O·Al ₂ O ₃ ·8SiO ₂ , the largest crystal size is 40 nm, the smallest crystal size is 38 nm, the average crystal size is 39 nm, and the crystal The proportion is 40% of the total mass of strengthened glass ceramic II.

The physical and chemical characteristics of the prepared batches of strengthened glass ceramics II were tested, and the results are shown in the following table.

Physical and chemical characteristics Maximum value Minimum average value Young's modulus/GPa 88.60 88.40 88.50 Equivalent biaxial flexural strength/N 1500 1380 1440 X-axis bending strength/MPa 720 676 698 Y-axis bending strength/MPa 340 306 323 Average visible light transmittance/% 91.4 91.2 91.3 Haze/% 0.098 0.096 0.097 Dielectric loss tangent 0.00820 0.00810 0.00815 Surface compressive stress/MPa 360 348 354 Compressive stress layer depth/μm 105 94 99.5 Maximum internal tensile stress/Mpa 142 130 136 Tensile stress linear density/Mpa/mm 29330 29020 29175

It can be seen from the above table that the average biaxial flexural strength of the prepared batch of strengthened glass ceramic II is 1440N, and the difference between the maximum value and the minimum value is only 120N; the average value of the X-axis flexural strength is 698MPa, the maximum value The difference from the minimum value is only 44Mpa; the bending strength in the Y-axis is 323MPa; the difference between the maximum value and the minimum value is only 34MPa, which is enough to show that the strength uniformity of the batches of strengthened glass ceramics produced by batches of original glass II is relatively high.

The crystal composition of the prepared strengthened glass-ceramic III mainly includes Li ₂ O·Al ₂ O ₃ ·8SiO ₂ and a small amount of Li ₂ O·2SiO _{2. The} largest crystal size is 34nm and the smallest crystal size is 32nm. , The average size of crystals is 33nm, and the proportion of crystals is 78% of the total mass of strengthened glass ceramic III.

The physical and chemical characteristics of the prepared batches of strengthened glass ceramic III were tested, and the results are shown in the following table.

Physical and chemical characteristics Maximum value Minimum average value Young's modulus/GPa 90.12 90.08 90.10 Equivalent biaxial flexural strength/N 2120 2010 2065 X-axis bending strength/MPa 890 860 875 Y-axis bending strength/MPa 460 442 451 Average visible light transmittance/% 91.5 91.4 91.45 Haze/% 0.092 0.090 0.091 Dielectric loss tangent 0.00240 0.00230 0.00235 Surface compressive stress/MPa 270 258 264 Compressive stress layer depth/μm 162 148 155 Maximum internal tensile stress/Mpa 158 144 151 Tensile stress linear density/Mpa/mm 51758 51554 51656

It can be seen from the above table that the average biaxial flexural strength of the prepared batch of strengthened glass ceramic III is 2065N, and the difference between the maximum value and the minimum value is only 110N; the average value of the X-axis flexural strength is 875MPa, the maximum value The difference from the minimum value is only 30Mpa; the bending strength in the Y axis is 451MPa; the difference between the maximum value and the minimum value is only 18MPa, which is enough to show that the bulk of the original glass III produced the bulk of the strengthened glass ceramics I have higher strength uniformity.

The crystal composition in the prepared strengthened glass-ceramic IV mainly includes Li ₂ O·2SiO ₂ and a small amount of Li _1.4 ·Zn _0.3 O·Al ₂ O ₃ ·8SiO _{2. The} largest crystal size is 60 nm, and the smallest crystal is The size is 30nm, the average size of crystals is 45nm, and the proportion of crystals is 70% of the total mass of strengthened glass ceramic IV.

The physical and chemical characteristics of the prepared batches of strengthened glass ceramic IV were tested, and the results are shown in the following table.

Physical and chemical characteristics Maximum value Minimum average value Young's modulus/GPa 86.66 86.60 86.63 Equivalent biaxial flexural strength/N 1220 1156 1188 X-axis bending strength/MPa 780 746 763 Y-axis bending strength/MPa 360 342 351

Average visible light transmittance/% 90.8 90.6 90.7 Haze/% 0.140 0.136 0.138 Dielectric loss tangent 0.00470 0.00460 0.00465 Surface compressive stress/MPa 230 216 223 Compressive stress layer depth/μm 122 110 116 Maximum internal tensile stress/Mpa 136 124 130 Tensile stress linear density/Mpa/mm 38280 38070 38175

It can be seen from the above table that the average biaxial flexural strength of the prepared batches of strengthened glass-ceramic IV is 1188N, and the difference between the maximum value and the minimum value is only 64N; the average value of the X-axis flexural strength is 763MPa, the maximum value The difference between the minimum value and the minimum value is only 34Mpa; the Y-axis bending strength is 351MPa; the difference between the maximum value and the minimum value is only 18MPa, which is enough to show that the bulk strength uniformity of strengthened glass ceramics produced by batches of original glass IV is relatively high.

The crystal composition of the prepared strengthened glass ceramic V mainly includes Li ₂ O·2SiO ₂ and a small amount of Li ₂ O·Al ₂ O ₃ ·10SiO _{2. The} largest crystal size is 40 nm, and the smallest crystal size is 34 nm. , The average size of crystals is 37nm, and the proportion of crystals is 60% of the total mass of strengthened glass ceramic V.

The physical and chemical characteristics of the prepared batches of strengthened glass ceramic V were tested, and the results are shown in the following table.

Physical and chemical characteristics Maximum value Minimum average value Young's modulus/GPa 91.00 90.90 90.95 Equivalent biaxial flexural strength/N 1660 1580 1620 X-axis bending strength/MPa 850 826 838 Y-axis bending strength/MPa 380 366 373 Average visible light transmittance/% 91 90 90.5 Haze/% 0.090 0.088 0.089 Dielectric loss tangent 0.00690 0.00680 0.00685 Surface compressive stress/MPa 322 298 310 Compressive stress layer depth/μm 166 156 161 Maximum internal tensile stress/Mpa 172 158 165

Tensile stress linear density/Mpa/mm 44920 44700 44810

It can be seen from the above table that the average biaxial flexural strength of the prepared batches of strengthened glass ceramic V is 1620N, and the difference between the maximum and minimum values is only 80N; the average value of the X-axis flexural strength is 838MPa, the maximum The difference between the minimum value and the minimum value is only 24Mpa; the Y-axis bending strength is 373MPa; the difference between the maximum value and the minimum value is only 14MPa. Low dispersion.

In summary, the batches of strengthened glass ceramics produced by batches of the original glass provided by the present invention have equal biaxial flexural strength, X-axis flexural strength, and Y-axis flexural strength with low dispersion and uniformity. The advantages of high sex. The tempered glass produced by using existing glass usually has a higher CS. Even if the tempered glass is produced in the same batch, the extreme difference between the bending strength in the X-axis and the bending strength in the Y-axis can reach 300MPa. The extreme difference in biaxial flexural strength can reach 1000N.

The embodiments of the present invention are described above, but the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are only illustrative and not restrictive. Under the enlightenment, many forms can be made without departing from the purpose of the present invention and the protection scope of the claims, and these are all within the protection of the present invention.

Claims (21)

A strengthened glass ceramic with low surface compressive stress, characterized in that the surface compressive stress of the strengthened glass ceramic is between 100-450Mpa, and the depth of the compressive stress layer is less than or equal to 180 μm; the internal tensile stress of the strengthened glass ceramic is less than or equal to 180 μm. The maximum value is less than or equal to 180Mpa; the tensile stress linear density of the strengthened glass ceramic is less than or equal to 60000Mpa/mm, and the dielectric loss tangent of the strengthened glass ceramic at room temperature and a frequency of 1.8GHz is less than or equal to 9×10 ^-3 . The strengthened glass ceramic with low surface compressive stress according to claim 1, wherein the surface compressive stress of the strengthened glass ceramic is between 150-380Mpa; the depth of the compressive stress layer of the strengthened glass ceramic is less than or equal to 150 μm; The maximum internal tensile stress of the strengthened glass ceramic is less than or equal to 160Mpa; the tensile stress linear density of the strengthened glass ceramic is less than or equal to 40000Mpa/mm, and the dielectric loss angle of the strengthened glass ceramic at room temperature and a frequency of 1.8GHz The tangent is less than or equal to 8×10 ^-3 . The strengthened glass ceramic with low surface compressive stress according to claim 2, wherein the surface compressive stress of the strengthened glass ceramic is between 180-350Mpa; the maximum value of the internal tensile stress of the strengthened glass ceramic is less than or equal to 140Mpa; the tensile stress linear density of the strengthened glass ceramic is less than or equal to 34000mpa/mm. The strengthened glass ceramic with low surface compressive stress according to claim 1, wherein the strengthened glass ceramic comprises a glass body and a plurality of crystals discretely distributed in the glass body, and the composition of the crystals is Li _{2 -2(X+Y)} ·Mg _X Zn _Y O·Al ₂ O ₃ ·nSiO ₂ or/and Li ₂ O·2SiO ₂ , where n is between 2-10, X+Y≤1, so The proportion of the crystals is 20-80 wt%, the size of the crystals is between 6 and 80 nm, and the average size of a plurality of the crystals is less than or equal to 50 nm. The strengthened glass-ceramic with low surface compressive stress according to claim 1, wherein the strengthened glass-ceramic, in terms of mole percentage, contains the following components: 60-80% SiO ₂ ; 3-11% Al ₂ O ₃ ; 0.5-8% P ₂ O ₅ and/or B ₂ O ₃ ; 7-18% Li ₂ O; 0.05-2% Na ₂ O; 0.05-2% K ₂ O; 1-6% of ZrO ₂ ; 0-2% TiO ₂ ; 0-1% SnO ₂ . The strengthened glass ceramic with low surface compressive stress according to claim 5, wherein the strengthened glass ceramic further includes 0-8 mol% of other oxides, and the other oxides include MgO, ZnO, and Tm ₂ O ₃ One or more of. The strengthened glass ceramic with low surface compressive stress according to claim 5, wherein the strengthened glass ceramic contains the following components in mole percentage: 68-75% SiO ₂ ; 5-7 mol% Al ₂ O ₃ ; 2-7% P ₂ O ₅ and/or B ₂ O ₃ ; 7.5-15% Li ₂ O; 0.05-1% Na ₂ O; 0.05-1% K ₂ O; 2-5% ZrO ₂ ; 0-1% TiO ₂ ; 0.1-0.5% SnO ₂ . The strengthened glass ceramic with low surface compressive stress according to claim 1, wherein the Young's modulus of the strengthened glass ceramic is greater than or equal to 85 GPa; the equibiaxial flexural strength of the strengthened glass ceramic is greater than or equal to 800N; The bending strength in the X-axis direction and the bending strength in the Y-axis direction of the strengthened glass ceramic are respectively greater than or equal to 450Mpa and 180Mpa. The strengthened glass ceramic with low surface compressive stress according to claim 8, wherein the equibiaxial flexural strength of the strengthened glass ceramic is greater than or equal to 1200N. The strengthened glass ceramic with low surface compressive stress according to claim 1, wherein the average visible light transmittance of the strengthened glass ceramic is greater than or equal to 90%, and the haze of the strengthened glass ceramic is less than or equal to 0.2%. An original piece of glass, characterized in that, the strengthened glass ceramic according to any one of claims 1-10 can be obtained after the original piece of glass is subjected to microcrystallization heat treatment and ion exchange treatment; the original piece of glass , In terms of mole percentage, contains the following ingredients: 60-80% SiO ₂ ; 3-11% Al ₂ O ₃ ; 0.5-8% P ₂ O ₅ and/or B ₂ O ₃ ; 7-18% Li ₂ O; 0-2% Na ₂ O; 0-2% K ₂ O; 1-6% of ZrO ₂ ; 0-2% TiO ₂ ; 0-1% SnO ₂ . The original glass according to claim 11, wherein the original glass further includes 0-8 mol% of other oxides, and the other oxides include one or more of _{MgO, ZnO, and Tm 2} O ₃ Kind. 11. The original glass of claim 11, wherein the original glass contains the following components in mole percent: 68-75% SiO ₂ ; 5-7% Al ₂ O ₃ ; 2-7% P ₂ O ₅ and/or B ₂ O ₃ ; 7.5-15% Li ₂ O; 0-1% Na ₂ O; 0-1% K ₂ O; 2-5% ZrO ₂ ; 0-1% TiO ₂ ; 0.1-0.5% SnO ₂ . The original glass of claim 11, wherein the original glass does not contain Na ₂ O. The original glass of claim 11, wherein the Young's modulus of the original glass is greater than or equal to 80 GPa. The original glass of claim 11, wherein the molar volume V _{m of} the original glass is less than or equal to 25.5 cm ³ /mol, and the molar volume V _m =∑x _i M _i /ρ, wherein, x _i and M _i are the respective mole fractions of oxides and molar mass, [rho] is the density of the original glass. The original glass of claim 11, wherein the microcrystallization heat treatment includes a nucleation step and a crystallization step; the conditions for the nucleation step are: the nucleation temperature is 580-750°C, and the holding time It is 0.5-5h; the conditions of the crystallization step are: the crystallization temperature is 700-800°C, and the holding time is 0.5-5h. The original glass according to claim 11, wherein the ion exchange treatment is chemically strengthened one or more times in a mixed salt bath, and the mixed salt bath contains potassium salt, sodium salt, and lithium salt. At least two, the potassium salt includes KNO ₃ and/or KCl, the sodium salt includes NaNO ₃ and/or NaNO ₂ , and the lithium salt includes LiNO ₃ and/or Li ₂ CO ₃ . The original glass of claim 18, wherein the mixed salt bath contains the potassium salt, the sodium salt, and the lithium salt. The original glass according to claim 18, wherein the mixed salt bath contains NaNO ₃ and LiNO ₃ , wherein NaNO ₃ accounts for 5% to 75% of the mass of the mixed salt bath, and LiNO ₃ accounts for the mass of the mixed salt bath. 0.05% to 5% of the mass of the mixed salt bath. The original glass of claim 18, wherein the temperature of the mixed salt bath is 400-550°C, and the total time of the ion exchange treatment is greater than or equal to 5 hours.