A high-transmittance low-haze glass composition, a glass-ceramic and a method for preparing the same

Abstract

This invention provides a high-transmittance, low-haze glass composition, a glass preparation method, and a microcrystalline glass. The glass composition comprises the following components in molar percentage: SiO2: 69%~78%; Al2O3: 3%~5%; Li2O: 18%~24%; Na2O: 0.1%~3%; K2O: 0.1%~2.5%; B2O3: 0%~3%; CaO: 0%~1.5%; MgO: 0%~1.5%; ZnO: 0%~1.5%; BaO: 0%~1.5%; ZrO2: 0.5%~3%; P2O5: 0.1%~1%; TiO2: 0%~1%; SnO2: 0%~1%. This invention minimizes the performance difference between the glass phase and the microcrystalline phase by controlling the type, content, and size of the microcrystalline phase. At the same time, it utilizes the advantages of glass and ceramics to produce a microcrystalline glass with high transmittance and low haze, thus expanding the application of microcrystalline glass in the field of transparent glass. It can be applied to touch display, electronic optics, astronomical telescopes, bio-microcrystalline materials, architectural decoration and other fields.

Description

Technical Field

[0001] This invention relates to the field of glass manufacturing, and more particularly to a high transmittance, low haze glass composition, microcrystalline glass, and a method for preparing the same. Background Technology

[0002] Due to its excellent optical, mechanical, and chemical stability, glass has been widely used as a cover and backplate protective material for touch display products. With the iterative updates of terminal products such as mobile phones, televisions, and iPads, screen sizes are increasing while product thickness is decreasing, placing increasingly higher demands on the mechanical properties of cover and backplate glass, especially its strength. Since its inception, cover and backplate glass has undergone product iterations, including soda-lime glass, primary-strengthened medium-aluminum and / or high-aluminum glass, secondary-strengthened lithium aluminum silicon glass, and chemically strengthened transparent microcrystalline glass, all aimed at improving the impact resistance, drop resistance, and scratch resistance of cover glass.

[0003] Glass-ceramics possess the high transmittance and chemical stability of some glass materials, as well as the high strength and thermal stability of some ceramic materials. However, due to the simultaneous existence of both a glassy phase and a microcrystalline phase, the properties of glass-ceramics differ from those of glass and ceramics. This is mainly because the microscopic morphology and structure of the glassy and microcrystalline phases are significantly different. The atoms in the glassy phase are disordered in the short range but ordered in the long range, while the atoms in the microcrystalline phase are arranged in a certain ordered manner. Microstructure determines properties, therefore, the two differ in optical properties, mechanical properties, and chemical stability. In comparison, the glassy phase has better optical properties such as visible light transmittance and optical uniformity, but poorer mechanical strength such as scratch resistance and drop resistance. The microcrystalline phase has excellent mechanical properties such as hardness, strength, and thermal shock resistance, but its haze and visible light transmittance are difficult to control. In particular, when nucleation heat treatment and crystallization heat treatment are not performed properly, the visible light transmittance of glass products decreases significantly, resulting in translucency or even opacity and loss of transparency. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing high transmittance and low haze microcrystalline glass, glass and glass composition thereof, in order to solve the technical problems of low transmittance and poor haze in the existing microcrystalline glass manufacturing process.

[0005] To achieve the above objectives, the present invention provides a glass composition comprising, by molar percentage, the following components: SiO2: 69%~78%; Al2O3: 3%~5%; Li2O: 18%~24%; Na2O: 0.1%~3%; K2O: 0.1%~2.5%; B2O3: 0%~3%; CaO: 0%~1.5%; MgO: 0%~1.5%; ZnO: 0%~1.5%; BaO: 0%~1.5%; ZrO2: 0.5%~3%; P2O5: 0.1%~1%; TiO2: 0%~1%; SnO2: 0%~1%.

[0006] Preferably, the above composition satisfies the following conditions: A: 0.17~0.25; B: 0.2%~3.1%; C: 0.21~0.38; D: 0.29~0.48; E: 0%~2%, wherein:

[0007]

[0008] Preferably, the composition is as follows: SiO2: 69%~74%; Al2O3: 3.5%~5%; Li2O: 19%~24%; Na2O: 0.1%~2%; K2O: 0.1%~2%; B2O3: 0%~2%; CaO: 0%~1%; MgO: 0%~1%; ZnO: 0%~1%; BaO: 0%~1%; ZrO2: 1%~2.5%; P2O5: 0.3%~1%; TiO2: 0%~0.5%; SnO2: 0%~0.5%; A: 0.18~0.24%; B: 1%~2.6%; C: 0.28~0.37%; D: 0.41~0.48%; E: 0%~1%.

[0009] More preferably, the composition is as follows: SiO2: 69%~73%; Al2O3: 3.7%~4.8%; Li2O: 19%~23%; Na2O: 0.1%~1.5%; K2O: 0.1%~1.5%; B2O3: 0%~0.5%; CaO: 0%~0.5%; MgO: 0%~0.5%; ZnO: 0%~0.5%; BaO: 0%~0.5%; ZrO2: 1.5%~2.5%; P2O5: 0.6%~1%; TiO2: 0%~0.4%; SnO2: 0%~0.4%; A: 0.18~0.23%; B: 1%~2%; C: 0.30~0.37%; D: 0.42~0.48%; E: 0%~0.5%.

[0010] To achieve the above objectives, the present invention also provides a method for preparing microcrystalline glass, comprising the following steps:

[0011] Step 1: After the above-mentioned materials are prepared and mixed, the basic glass is manufactured.

[0012] Step 2: Treat the base glass at a nucleation temperature of 500℃~650℃ for 0.1h~4h;

[0013] Step 3: Treat the base glass after nuclear heat treatment at a crystallization temperature of 700℃~800℃ for 0.5h~8h.

[0014] Preferably, the process further includes step four: placing the microcrystalline glass in molten salt at 380℃~500℃ for 0.3h~6h of chemical strengthening heat treatment.

[0015] Preferably, the molten salt is a pure sodium molten salt and / or a mixed sodium-potassium molten salt.

[0016] Preferably, the molten salt is a mixed molten salt of NaNO3 and KNO3, wherein the mass fraction of NaNO3 molten salt is 5% to 100% and the mass fraction of KNO3 molten salt is 0% to 95%.

[0017] To achieve the above objectives, the present invention also provides a microcrystalline glass, which is prepared by the above preparation method, wherein the main crystalline phases in the microcrystalline glass are lithium disilicate crystalline phase and lithium feldspar crystalline phase, and a small amount of lithium metasilicate crystalline phase.

[0018] Preferably, lithium disilicate crystals account for 40% to 60% of the total crystallization, lithium feldspar crystals account for 30% to 60% of the total crystallization, and lithium metasilicate crystals account for ≤5% of the total crystallization.

[0019] Preferably, the total crystal content of the microcrystalline glass is 70% to 90%.

[0020] Preferably, the average grain size of the microcrystalline phase is ≤60nm.

[0021] This invention minimizes the performance difference between the glass phase and the microcrystalline phase by controlling the type, content, and size of the microcrystalline phase. It also utilizes the advantages of glass and ceramics to provide a high-transmittance, low-haze microcrystalline glass and its manufacturing method. This expands the application of microcrystalline glass in the field of transparent glass and can be widely used in touch display, electronic optics, astronomical telescopes, bio-microcrystalline materials, architectural decoration and other fields. Attached Figure Description

[0022] Figure 1 This is an X-ray diffraction analysis result diagram of one embodiment.

[0023] Figure 2 This is an example of the appearance morphology of a microcrystalline phase. Detailed Implementation

[0024] This invention provides a glass composition, a glass preparation method, and a microcrystalline glass. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] The endpoints and any values ​​disclosed in this invention are not limited to the precise range or value, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] The first aspect of the present invention provides a glass composition comprising, in molar percentage, the following components: SiO2: 69%~78%; Al2O3: 3%~5%; Li2O: 18%~24%; Na2O: 0.1%~3%; K2O: 0.1%~2.5%; B2O3: 0%~3%; CaO: 0%~1.5%; MgO: 0%~1.5%; ZnO: 0%~1.5%; BaO: 0%~1.5%; ZrO2: 0.5%~3%; P2O5: 0.1%~1%; TiO2: 0%~1%; SnO2: 0%~1%.

[0027] More preferably, the above composition satisfies the following conditions: A: 0.17~0.25; B: 0.2%~3.1%; C: 0.21~0.38; D: 0.29~0.48; E: 0%~2%, wherein:

[0028]

[0029] SiO2 forms the basic framework of glass as silicon-oxygen tetrahedra [SiO4], stabilizing the network structure of the base glass and glass-ceramics, thus giving them better mechanical properties and chemical stability. The SiO2 content is 69%~78% molar percentage, more preferably 69%~74%, and even more preferably 69%~73%. Limiting the SiO2 content controls the appropriate melting and forming temperatures. Furthermore, in this invention, SiO2 serves as the source of silicon during the crystallization heat treatment stage to form the lithium feldspar and lithium disilicate phases. An appropriate amount of SiO2 is used to form a microcrystalline phase with a total crystallization content of 80%~90%, and the remainder is used to form the glass phase. The spatial network structure of the SiO2 used to form the microcrystalline phase is altered, slightly deviating from the SiO2 framework structure used to form the glass phase and base glass. For example, in the lithium feldspar phase, some Si in the silicon-oxygen tetrahedra [SiO4] is altered. 4+ Grid point positions are determined by AI3+ Li + The crystal phase maintains charge balance within the network structure. At this point, the crystal phase structure differs from the silicon-oxygen tetrahedral [SiO4] framework structure of the glass phase and the base glass. The SiO2 content should not be too low. If it is too low, the chemical stability of the glass-ceramic is poor, and the total microcrystalline phase content is low. During the crystallization heat treatment stage, the silicon source supply for forming the lithium feldspar and lithium disilicate crystal phases is insufficient, making it difficult to form a high proportion of microcrystalline phases and thus failing to achieve the technical effect of improving transmittance and reducing haze as described in this invention. Simultaneously, the SiO2 content should not be too high. If it is too high, the viscosity of the molten glass increases significantly, the melting temperature of the base glass rises, and clarification and homogenization become difficult. Furthermore, excessive SiO2 content promotes the formation of undesirable crystal phases such as β-quartz and / or β-quartz solid solutions during the crystallization heat treatment stage, increasing the difficulty of the crystallization heat treatment process, reducing the visible light transmittance of the product, and increasing haze, thus limiting the application of transparent glass-ceramics.

[0030] Al₂O₃ exists in the base glass in two forms: aluminum-oxygen tetrahedral [AlO₄] and aluminum-oxygen hexahedral [AlO₆]. It is a network intermediate oxide. 3+Ions compete for non-bridging oxygen provided by alkali metal oxides such as Li₂O, Na₂O, and K₂O, and alkaline earth metal oxides such as CaO, MgO, ZnO, and BaO, forming aluminum-oxygen tetrahedra [AlO₄]. Together with silicon-oxygen tetrahedra [SiO₄], they constitute the basic framework of the base glass, thereby improving the mechanical properties and chemical stability of the glass. This also helps to appropriately increase the high-temperature viscosity of the molten glass during the forming stage to suit various forming processes. Furthermore, the volume of aluminum-oxygen tetrahedra [AlO₄] is larger than that of silicon-oxygen tetrahedra [SiO₄], thus expanding the basic framework structure in the glass. This facilitates ion exchange between small-radius ions on the glass surface and large-radius ions in the molten salt during the chemical strengthening heat treatment stage, increasing surface compressive stress and deepening the ion exchange depth, thereby improving the mechanical properties of the glass. The Al₂O₃ content is 3% to 5% by molar percentage, more preferably 3.5% to 5%, and even more preferably 3.7% to 4.8%. An appropriate amount of Al2O3 is used as the source of aluminum when forming a 30%–60% lithopone crystalline phase. The Al2O3 content should not be too low; if it is, the high-temperature viscosity of the glass is low, making the molten glass too fluid for many forming processes other than casting, such as calendering and float glass, which require suitable high-temperature viscosity within the forming temperature range. Furthermore, too low an Al2O3 content reduces the precipitation of lithopone crystals, failing to utilize the interlocking effect of forming twin phases to force microcracks to change their propagation path, thus reducing the drop resistance of the glass-ceramic. Conversely, the Al2O3 content should not be too high; excessively high Al2O3 content increases the high-temperature viscosity of the glass, making high-temperature melting more difficult, and may even lead to the formation of undesirable crystalline phases such as β-nepheline and β-spodumene, resulting in decreased transmittance and transformation into translucent or even opaque glass.

[0031] Li₂O belongs to the glass network outer oxide category, Li + Ions residing in the cavities of the glass structure network can provide free oxygen, increasing the O / Si ratio in the glass structure, breaking the bonds of the basic silicon-oxygen tetrahedra [SiO4] in the glass framework, thereby reducing the high-temperature viscosity of the glass and making it easier to melt. Li + Ionic radius < Na + Ionic radius < K + Ionic radius; the smaller the radius, the higher the chemical reactivity, and Li + The ionic potential of the ion is much higher than that of Na. + Ions, K + The ions are large, therefore Li + The fluxing power of ions is greater than that of Na. + Ions, K +The ions need to be much larger, specifically manifested in the lower melting temperature of this invention. The Li2O content is 18%~24% by molar percentage, more preferably 19%~24%, and even more preferably 19%~23%. An appropriate amount of Li2O is used as the source of lithium when forming a lithium feldspar crystal phase with a crystallization amount of 30%~60%, a lithium disilicate crystal phase of 40%~60%, and a lithium metasilicate crystal phase of ≤5%. The Li2O content should not be too low; if it is too low, the lithium source supply will be insufficient, resulting in a low total crystal phase content, which is not conducive to forming a bicrystalline interlocking structure and maximizing the high strength and high toughness characteristics of the microcrystalline phase in the glass-ceramic. If the crystal phase content is too low, microcrack propagation does not need to bypass the crystal propagation, reducing strength. Furthermore, in the chemical strengthening heat treatment stage, a low Li2O content makes it difficult for the Li2O used for large-radius ion exchange with the molten salt to reach the desired concentration. + Insufficient ion content reduces surface compressive stress and ion exchange depth, resulting in decreased drop resistance of the glass-ceramic. The Li₂O content should not be too high; excessively high content leads to excessively low high-temperature viscosity of the base glass, making the molten glass too fluid for many forming processes other than casting, such as calendering and float glass. Furthermore, Li… + The accumulation of ions makes the base glass prone to phase separation and crystallization during the forming stage, increasing the difficulty of base glass preparation. In addition, the high content of Li2O will reduce the corrosion resistance, acid resistance, alkali resistance and water resistance of the glass-ceramic. Due to the formation of excessive lithium metasilicate, a longer crystallization time and / or a higher crystallization temperature are required in the crystallization heat treatment stage to improve the visible light transmittance of the glass-ceramic and reduce the haze of the glass-ceramic.

[0032] Na₂O is an oxide on the glass network, free in the silicon-oxygen tetrahedron and aluminum-oxygen tetrahedron network structure of the glass. It provides free oxygen to break the bonds in the glass framework network structure, lowering the melting temperature of the base glass and facilitating its melting and refining. The Na₂O content is 0.1%~3% by molar percentage, more preferably 0.1%~2%, and even more preferably 0.1%~1.5%. An appropriate amount of Na₂O can be used to reduce the viscosity of the base glass, which is beneficial for its melting and refining. Furthermore, in the chemical strengthening heat treatment process of glass-ceramics, smaller Na₂O radii can be achieved on the surface of the glass-ceramics. + K in ions and molten salts with larger radii +Ion exchange further extends the ion exchange depth, increasing the compressive stress on the surface of the glass-ceramic, thereby improving its ability to prevent crack propagation and its drop resistance. The Na₂O content should not be too low; if it is too low, the effect of auxiliary chemical strengthening heat treatment on improving the ion exchange depth and surface compressive stress strength is limited. The Na₂O content should also not be too high. As the Na₂O content increases, it first gradually reduces the total content of the lithium feldspar and lithium disilicate phases, while increasing the content of the glass phase. Subsequently, with further increases in Na₂O content, Na₂O will also participate in the formation of the microcrystalline phase, generating undesirable phases such as nepheline. An increase in the glass phase content will cause the glass-ceramic properties to become more biased towards the glass phase, gradually losing the mechanical property advantages of the microcrystalline phase.

[0033] K₂O is also an oxide in the glass network, and its role in the base glass is similar to that of Na₂O. + The radius of the ion is greater than that of Na + The large of the ions, K + Ions are more effective than sodium in reducing the high-temperature viscosity of base glass. + Ion difference. The K2O content, by molar percentage, is 0.1% to 2.5%, more preferably 0.1% to 2%, and even more preferably 0.1% to 1.5%. An appropriate amount of K2O can reduce the tendency of the base glass to crystallize during the forming stage, because K... + Ions can reduce the surface tension of the base glass, thereby slowing down the hardening rate of the base glass and widening the forming temperature range. The K2O content should not be too high, otherwise the glass phase content will increase, inhibiting the formation of lithium feldspar and lithium disilicate crystal phases and reducing the total amount of microcrystalline phase.

[0034] B2O3 exists in glass in two forms: boron-oxygen trigonal [BO3] and boron-oxygen tetrahedron [BO4]. It can lower the melting temperature of the base glass. An appropriate amount of B2O3 is beneficial to the growth of lithium feldspar and lithium disilicate crystal phases, especially promoting the formation of crystal phases with high aspect ratios, thus improving the chemical durability and mechanical strength of the glass-ceramic. The B2O3 content is 0%~3% molar percentage, more preferably 0%~2%, and even more preferably 0%~0.5%. B2O3 does not participate in the formation of the microcrystalline phase but remains in the glass phase. When there is insufficient free oxygen in the glass phase, i.e., insufficient bridging oxygen supply, boron exists in the form of boron-oxygen trigonal [BO3] and does not participate in the construction of the framework structure of the base glass. The boron-oxygen trigonal [BO3] is less rigid than the boron-oxygen tetrahedron [BO4], allowing the glass framework structure to withstand a certain degree of deformation when subjected to external impact, macroscopically manifested as resistance to the formation of microcracks. Furthermore, the presence of the boron-oxygen triangle [BO3] buffers the structure and properties of the two different phases: the dense microcrystalline phase and the amorphous glassy phase. However, the B2O3 content should not be too high, as this increases the proportion of the glassy phase in the microcrystalline phase. In addition, due to the problem of boron volatilization, the glass surface is prone to stratification during the melting process. To ensure the chemical homogeneity of the glass melt, measures such as surface overflow, deep flow channels, enhanced stirring, and platinum channels are required, which increases production costs and production difficulty.

[0035] CaO is a divalent network oxide that can increase the chemical stability and mechanical strength of glass. The CaO content is 0% to 1.5% by molar percentage, more preferably 0% to 1%, and even more preferably 0% to 0.5%. The CaO content should not be too high, as excessively high CaO content increases the tendency of the base glass to crystallize during the forming stage, which is not conducive to subsequent nucleation heat treatment and crystallization heat treatment to form microcrystalline glass with high transmittance and low haze.

[0036] MgO is an oxide on the glass network. An appropriate amount of MgO can reduce the crystallization tendency of the base glass and slow down its crystallization rate. The MgO content, by molar percentage, is 0% to 1.5%, more preferably 0% to 1%, and even more preferably 0% to 0.5%. The MgO content should not be too high. If it is too high, undesirable crystalline phases such as magnesium aluminum spinel may form after nucleation and crystallization heat treatments, leading to a decrease in the transmittance, haze, and other properties of the glass-ceramic.

[0037] ZnO is used as an intermediate oxide, with zinc-oxygen octahedrons [ZnO6] as the network exooxide. When there is sufficient free oxygen in the glass, zinc-oxygen tetrahedra [ZnO4] can be formed and enter the glass network structure, making the glass network structure denser, thereby improving the chemical and thermal stability of the glass-ceramic. The ZnO content is 0%~1.5% by molar percentage, more preferably 0%~1%, and even more preferably 0%~0.5%. The ZnO content should not be too high, as excessive ZnO content will result in a high glass phase content in the glass-ceramic and may lead to devitrification.

[0038] BaO is a divalent network exooxide that can increase the refractive index, density, luster, and chemical stability of glass. The BaO content is 0% to 1.5% by molar percentage, more preferably 0% to 1%, and even more preferably 0% to 0.5%. The BaO content should not be too high, as excessive BaO content will severely corrode refractory materials and make it difficult to melt the base glass.

[0039] Although ZrO2 significantly increases the high-temperature viscosity of the base glass and causes stratification of the molten glass due to its heavy weight, it plays an important role in this invention. Firstly, ZrO2 acts as a nucleating agent for the lepidolite crystal phase. During the nucleation heat treatment stage, phase separation of the base glass leads to the formation of ZrO2 single crystals. As a nucleation agent, ZrO2 lowers the crystallization kinetic energy and energy barrier of the lepidolite crystals. Al... 3+ Ion substitution of Si in silicon-oxygen tetrahedra [SiO4] 4+ The grid point position, Li + Ion-filled Al 3+The network gaps near the ions neutralize the charge, promoting the precipitation of lithium feldspar crystals. Secondly, ZrO2 inhibits the precipitation of lithium metasilicate and lithium disilicate crystals and refines the grain size of the lithium metasilicate and lithium disilicate phases. This is because ZrO2 promotes the formation of the lithium feldspar phase, and the growth of the lithium feldspar phase competes for Li2O in the lithium metasilicate and lithium disilicate phases, thereby inhibiting the formation of these two phases and destroying their crystal structure, refining the grain size, and making the transparent glass-ceramic meet the condition that the grain size of the microcrystalline phase is smaller than the wavelength of visible light. Thirdly, when the lithium feldspar crystals formed by ZrO2 grow to a sufficiently large size, they will collide with the lithium metasilicate and lithium disilicate crystals, reducing the crystallization rate of these two phases. The ZrO2 content is 0.5% to 3% by molar percentage, more preferably 1% to 2.5%, and even more preferably 1.5% to 2.5%. The ZrO2 content should not be too low. If it is too low, the content of the lithium feldspar crystal phase will be too low, and the interlocking twin structure of the lithium feldspar and lithium disilicate crystal phases cannot be formed to improve the ability of the glass-ceramic to prevent crack propagation. This will also reduce the effect of inhibiting and refining the lithium disilicate crystal phase, making it difficult to control the size of the lithium disilicate crystal phase, reducing the transmittance and haze of the glass-ceramic, and causing the glass to become translucent, opaque, or even devitrified. The ZrO2 content should not be too high. If it is too high, there will be too many nucleating agents. During the basic glass forming stage, crystallization and devitrification are easy. During the crystallization heat treatment stage, the lithium feldspar crystal phase will crystallize and grow uncontrollably, leading to devitrification of the glass-ceramic and loss of the possibility of high transparency under visible light.

[0040] P2O5 serves as the nucleating agent. The formation mechanism of the lithium disilicate crystal phase involves the reaction of P2O5 with Li2O to form lithium orthophosphate (Li3PO4) crystals, which in turn induces the reaction of Li2O and SiO2 in the glass to form metastable lithium metasilicate (Li2SiO3) and stable lithium disilicate (Li2SiO5). During the crystallization heat treatment stage, the lithium metasilicate and lithium disilicate crystal phases undergo epitaxial growth around the lithium orthophosphate (Li3PO4) nuclei. After sufficient crystallization time, the metastable lithium metasilicate crystal phase transforms into the stable lithium disilicate crystal phase. The P2O5 content is 0.1% to 1% by molar percentage, more preferably 0.3% to 1%, and even more preferably 0.6% to 1%. The P2O5 content should not be too high. If it is too high, it will cause crystallization of the base glass during the forming stage, making it difficult to obtain glass-ceramics with high transmittance through nucleation heat treatment and crystallization heat treatment. At the same time, it will cause excessive precipitation of lithium metasilicate crystalline phase during the crystallization heat treatment stage, requiring the crystallization temperature to be increased and the crystallization time to promote the transformation of lithium metasilicate crystalline phase into lithium disilicate crystalline phase. In addition, if P2O5 is too high, it will also reduce the crystallization activation energy and energy barrier of undesirable crystalline phases such as β-quartz, leading to the precipitation of undesirable crystalline phases and making it difficult to control the visible light transmittance and haze of glass-ceramics.

[0041] TiO2 is an intermediate oxide in glass, which can enter the glass network structure in the form of titanium oxide tetrahedra [TiO4] or reside outside the glass network in the form of titanium oxide octahedra [TiO6], thereby improving the refractive index and chemical stability of the glass. Furthermore, TiO2 can act as a nucleating agent, exhibiting good solubility during the nucleation heat treatment stage. This promotes the unstable decomposition of the glass, reduces the liquid-liquid surface energy, and causes phase separation in the base glass. This allows TiO2 to crystallize with alkali metal or alkaline earth metal ions to form nuclei, promoting the development of the phase interface and lowering the activation energy and potential barrier for nucleation. Additionally, a small amount of TiO2 can give the base glass a yellowish tint, complementing the bluish tint of the lithium feldspar and lithium disilicate phases, balancing the b-value, and resulting in a neutral tone for the glass-ceramic. The TiO2 content is 0% to 1% by molar percentage, more preferably 0% to 0.5%, and even more preferably 0% to 0.4%. The TiO2 content should not be too high, as an excessively high nucleating agent content makes it difficult to control the crystallization rate and grain size during the crystallization heat treatment stage.

[0042] SnO2, as a clarifying agent, is beneficial for improving defects such as streaks and bubbles generated during the melting process of base glass. The SnO2 content is 0% to 1% by molar percentage, more preferably 0% to 0.5%, and even more preferably 0% to 0.4%. The SnO2 content should not be too high, as it will form dispersed suspended particles, which will form crystal nuclei and cause glass opacity.

[0043] To achieve better glass properties, the components should preferably also meet the following conditions:

[0044]

[0045] A is used to control the amount of bridging oxygen and non-bridging oxygen in glass-ceramics. The more bridging oxygen there is, the more oxygen ions act as "bridges," sharing vertices between two or more network polyhedra, resulting in a tighter glass network and higher mechanical strength. Conversely, the more non-bridging oxygen there is, the looser the glass network, the larger the network voids, and the easier it is for network-modifying ions to move within these voids, leading to an increase in the glass's thermal expansion coefficient and electrical conductivity. In this invention, bridging oxygen is mainly used to link network formations such as silicon-oxygen tetrahedra [SiO4], aluminum-oxygen tetrahedra [AlO4], and boron-oxygen tetrahedra [BO4] in the glass phase, as well as the lithium feldspar, lithium metasilicate, and lithium disilicate phases in the microcrystalline phase. A suitable A value is used to find a balance between the high mechanical strength of glass due to bridging oxide and the fast migration rate of network-modified ions in glass due to non-bridging oxide. The former forms a robust glass phase network and a dense microcrystalline phase to enhance the bulk strength of the glass-ceramic, while the latter increases the porosity of the glass network and improves the mobility of oxides on the outside of the glass network. During the chemical heat treatment stage, it enhances the ion exchange between small-radius ions on the glass surface and large-radius ions in the molten salt, thereby forming higher compressive stress and a deeper ion exchange depth on the glass surface, improving the drop resistance and crack propagation prevention ability of the glass-ceramic. The chemically strengthened glass-ceramics of this invention achieve high drop resistance because: 1) the high strength and high proportion of microcrystalline phases improve the bulk strength of the glass-ceramics; 2) the interlocking structure of the lithium feldspar and lithium disilicate phases forms a twin-phase structure, enhancing the strength of the microcrystalline phase and further improving the bulk strength of the glass-ceramics; 3) the high strength and high toughness of the microcrystalline phases cause microcracks generated by external impacts to preferentially bypass the microcrystalline phases and propagate along the glass phase, extending the crack propagation path; 4) after chemical strengthening and heat treatment, the glass phase, through the "squeezing effect" generated by the ion exchange between small-radius ions on the glass surface and large-radius ions in the molten salt, forms an ion exchange depth of ≥100µm and a compressive stress of ≥200MPa in the glass, so that after a drop, the compressive stress layer must be overcome before the glass-ceramics bulk is destroyed. The calculated value of A is 0.17~0.25, more preferably 0.18~0.24, and even more preferably 0.18~0.23. The larger the value of A, the more free oxygen and non-bridging oxygen, resulting in an increased glass phase content and inhibiting the formation of lithium feldspar and lithium disilicate crystal phases. The smaller the value of A, the less free oxygen and the more bridging oxygen, leading to a higher melting temperature of the base glass and greater difficulty in crystallization.

[0046]

[0047] B is used to control the content of alkali metal oxides other than Li₂O in the glass-ceramic. Na₂O and K₂O are both oxides in the glass network, providing free oxygen in the glass, breaking bonds in the glass framework network structure, and lowering the melting temperature of the base glass. However, Na₂O and K₂O are different from Li₂O. The latter not only provides free oxygen but also participates in the formation of the lithium feldspar and lithium disilicate crystal phases. Excessive Na₂O and K₂O remain in the glass phase after nucleation and crystallization heat treatments. Therefore, B needs to be within a suitable range. B is calculated to be 0.2% to 3.1%, more preferably 1% to 2.6%, and even more preferably 1% to 2%. B should not be too high. If it is too high, too much free oxygen is provided, leading to an increase in non-bridging oxygen, increasing the glass phase content, failing to achieve the purpose of the present invention of a high proportion of crystal phases to improve the mechanical strength of the glass-ceramic, and generating undesirable crystal phases such as nepheline crystal phases. B should not be too low. If it is too low, it will not be conducive to further extending the ion exchange depth and increasing the compressive stress value generated on the surface of the glass-ceramic during the chemical strengthening heat treatment process. This will not improve the glass-ceramic's ability to prevent crack propagation and its drop resistance.

[0048]

[0049] C is used to control the amount of lithium feldspar crystals precipitated in glass-ceramics. Lithium feldspar (molecular formula...) Using lithium, aluminum, and silicon as sources, and ZrO2 as a nucleating agent, Al… 3+ Substitution of Si in [SO4] tetrahedron 4+ The grid point positions, and Li + Filling Al 3+ The electrical properties are neutralized in the nearby network gaps, forming petalite. C needs to be within a suitable range, calculated to be 0.21~0.38, more preferably 0.28~0.37, and even more preferably 0.30~0.37. C should not be too low; if it is too low, the supply of nucleating agent and lithium source will be insufficient, resulting in too little petalite crystal phase formation, or even difficulty in formation. Consequently, the total microcrystalline phase content will be too low, and it will be difficult to form the interlocking structure of the twin phases to enhance the bulk strength of the glass-ceramic. Furthermore, if the number of zirconia crystal nuclei is too small, they cannot compete for the Li in the already formed lithium metasilicate and lithium disilicate phases. + The effect of C on refining the grain size of lithium disilicate is limited. C should not be too high, otherwise the number of crystal nuclei and Li sources will be too large, making it difficult to control the grain size during the crystallization heat treatment stage, and the microcrystalline glass will easily become translucent or even devitrified.

[0050]

[0051] D is used to control the amount of lithium disilicate crystals in the glass-ceramic. During the nucleation heat treatment stage, P2O5 reacts with Li2O to form lithium orthophosphate (Li3PO4) crystals. During the crystallization heat treatment stage, Li2O in the glass is induced to react with SiO2, simultaneously forming lithium metasilicate and lithium disilicate crystal phases. The lithium metasilicate crystal phase is metastable and further transforms into the lithium disilicate crystal phase. Lithium disilicate is derived from lithium and silicon, with P2O5 as the nucleating agent. D needs to be within a suitable range; calculated, D is 0.29~0.48, more preferably 0.41~0.48, and even more preferably 0.42~0.48. D should not be too low; if it is too low, the supply of nucleating agent and lithium source will be insufficient, resulting in too few lithium disilicate crystals forming, failing to fully utilize the high strength and high toughness advantages of the glass-ceramic, and preventing the formation of a bicrystalline interlocking structure with the litharge crystal phase. D should not be too high. If it is too high, there will be too much supply of nucleating agent and lithium source, which will make crystallization difficult to control. After crystallization heat treatment, the glass is prone to opacity, which will reduce the transmittance of visible light and increase the haze.

[0052]

[0053] E is used to control the total content of divalent alkaline earth metal oxides in the glass-ceramic. In this invention, alkaline earth metal oxides do not participate in, or are not intended to participate in, the formation of the microcrystalline phase. As a component of the glass phase, such as the spinel crystal phase, the formation of the spinel crystal phase is not intended to disrupt the twin-crystal interlocking structure of the lithopone and lithium disilicate crystal phases. E needs to be within a suitable range. A suitable E can reduce the tendency of the base glass to crystallize during the forming stage. E is calculated to be 0%~2%, more preferably 0%~1%, and even more preferably 0%~0.5%. E should not be too high. If it is too high, the percentage of the glass phase in the weight of the glass-ceramic will be too high, and the high strength and high toughness of the microcrystalline phase cannot be fully utilized.

[0054] More preferably, by molar percentage, are the following components: SiO2: 69%~74%; Al2O3: 3.5%~5%; Li2O: 19%~24%; Na2O: 0.1%~2%; K2O: 0.1%~2%; B2O3: 0%~2%; CaO: 0%~1%; MgO: 0%~1%; ZnO: 0%~1%; BaO: 0%~1%; ZrO2: 1%~2.5%; P2O5: 0.3%~1%; TiO2: 0%~0.5%; SnO2: 0%~0.5%; A: 0.18~0.24%; B: 1%~2.6%; C: 0.28~0.37%; D: 0.41~0.48%; E: 0%~1%.

[0055] The following components are further preferred by molar percentage: SiO2: 69%~73%; Al2O3: 3.7%~4.8%; Li2O: 19%~23%; Na2O: 0.1%~1.5%; K2O: 0.1%~1.5%; B2O3: 0%~0.5%; CaO: 0%~0.5%; MgO: 0%~0.5%; ZnO: 0%~0.5%; BaO: 0%~0.5%; ZrO2: 1.5%~2.5%; P2O5: 0.6%~1%; TiO2: 0%~0.4%; SnO2: 0%~0.4%; A: 0.18~0.23%; B: 1%~2%; C: 0.30~0.37%; D: 0.42~0.48%; E: 0%~0.5%.

[0056] The second aspect of the present invention provides a method for preparing colored transparent microcrystalline glass, comprising four steps: basic glass manufacturing, nucleation heat treatment, crystallization heat treatment, and chemical strengthening heat treatment.

[0057] 1) Basic glass manufacturing: After the above-mentioned material design, batching and mixing, the basic glass is manufactured.

[0058] The manufacturing of base glass involves preparing colorless and transparent glass from raw materials such as industrial-grade minerals and chemically pure materials. Except for the annealing stage, where crystal nucleation is completed or partially completed due to process connections, the base glass does not undergo phase separation due to nucleating agents and / or Li. + Ion accumulation leads to crystallization in glass, which manifests as fogging, translucency, opacity, or even devitrification. The final base glass product is colorless and transparent with uniform chemical and optical properties.

[0059] The manufacturing of basic glass involves processes such as melting, clarification, homogenization, forming, annealing, and cooling. The melting, clarification, and homogenization processes are used to prepare chemically homogeneous molten glass at 1400℃~1650℃, which can be achieved in air-fired furnaces, oxygen-enriched / oxygen-full-fired furnaces, all-electric furnaces, electric-assisted furnaces, crucible furnaces, and electric + oxygen-enriched / oxygen-full-fired furnaces.

[0060] This invention adds nucleating agents such as ZrO2, P2O5, and TiO2 to the base glass. Only when the nucleating agents are uniformly distributed within the base glass can a uniformly distributed microcrystalline phase be formed during the nucleation and crystallization heat treatment stages. This prevents excessive local nucleating agent content from causing microcrystalline phase concentration, which can lead to unnecessary stress concentration in the glass-ceramic and reduce the mechanical properties of the product. Additionally, the Li2O introduced into the base glass in this invention serves as a lithium source for forming lithium feldspar and lithium disilicate crystals. While its molar percentage content is relatively high, the production raw material Li2CO3 is lightweight and prone to stratification during the batch mixing stage. Furthermore, due to the low mass of Li... +Lightweight and highly reactive ions tend to concentrate in the upper layer of the molten glass during the melting, clarification, and homogenization stages. This uneven composition leads to localized semi-permeability or devitrification in certain areas during nucleation and crystallization heat treatments due to higher levels of nucleating agents or Li₂O. This results in inconsistent chemical composition and optical properties of the glass-ceramic, with localized high haze. Therefore, necessary measures are required to address the issue of molten glass homogenization. These measures are not limited to one, multiple, or combinations thereof, including adding bubbling and stirring devices, adding surface overflow devices, adding bottom discharge devices, setting deep flow channels, or adding platinum channels.

[0061] The forming process involves transforming glass from a liquid to a solid state at 1000℃~1200℃. The forming method can be one of the following: float glass, overflow glass, casting glass, flat drawing glass, slot drawing glass, vertical rolling glass, or horizontal rolling glass. The formed sample can be either a sheet or a block.

[0062] The annealing process described herein aims to eliminate internal stress in the base glass at temperatures ranging from 500℃ to 650℃, preventing cracks from forming due to differences in surface and internal stress. In addition to eliminating internal stress, the annealing process in this invention can be combined with nucleation heat treatment to achieve the nucleation process of the base glass. However, since the annealing temperature range is not included in the crystallization heat treatment temperature range, even if annealing and nucleation heat treatment are intentionally combined, only crystal nuclei with a size of 1-5 nanometers can be formed in the base glass. The appearance, optical properties, and mechanical properties of the product after annealing and / or nucleation heat treatment are the same as or close to those of the untreated product. Therefore, limited by existing testing methods, it is not ruled out that complete nucleation heat treatment of the base glass can be achieved during the annealing stage, or that a small number or most of the crystal nuclei can be formed during the annealing stage, in order to rationally integrate the production process and reduce energy consumption and production costs.

[0063] 2) Nucleation heat treatment: The prepared base glass is treated at a nucleation temperature of 500℃~650℃ for 0.1h~4h, the nucleation temperature is more preferably 520℃~630℃, and the nucleation time is more preferably 0.5h~4h.

[0064] The purpose of the nucleation heat treatment is to achieve uniform nucleation within the base glass. During this stage, the nucleating agent promotes the unstable decomposition of the base glass, reduces the liquid-liquid surface energy, and induces phase separation, such as silicon-rich, zirconium-rich, and phosphorus-rich phases. This facilitates liquid-phase crystallization and unstable decomposition, promoting phase interface development and lowering the activation energy / barrier for nucleation, thus achieving uniform nucleation of the nucleating agent within the base glass. In this invention, ZrO2, P2O5, and TiO2 are primarily used as nucleating agents. During the nucleation heat treatment stage, a large number of zirconium oxide, lithium orthophosphate, and titanium oxide nuclei are formed, providing a basis for the epitaxial growth of the lithopone, lithium metasilicate, and lithium disilicate phases along these nuclei.

[0065] The aforementioned nucleation heat treatment ensures that ZrO2, P2O5, and TiO2 nucleating agents achieve nucleation at sufficient temperature and for a sufficient time. The more nuclei formed, the more crystals will grow around the nuclei, and the higher the percentage of crystals by weight in the glass-ceramic. Secondly, given a fixed volume, the more nuclei there are, the less space there is for each nucleus to grow into a crystal. When the crystal reaches a certain size, it will collide with other crystals, inhibiting growth and making it difficult to grow larger. This results in finer grain size. When the grain size is much smaller than the wavelength of visible light, transparent glass-ceramics can be obtained.

[0066] The nucleation heat treatment temperature range is 500℃~650℃. If the nucleation temperature is too low, it is insufficient to provide the activation energy required for nucleation or to overcome the energy barrier required for nucleation, thus preventing glass phase separation. If the nucleation temperature is too high, the nucleation rate is too fast, resulting in an insufficient number of crystal nuclei. The lithium feldspar, lithium metasilicate, and lithium disilicate phases rapidly grow around the crystal nuclei at high temperatures, losing the possibility of forming a high proportion of crystals. Furthermore, the size of these crystals may even exceed the visible light wavelength, leading to translucency or even devitrification of the glass.

[0067] The method of nucleation heat treatment of the base glass can be as follows: placing the base glass in a heat treatment furnace and heating it from room temperature to the nucleation temperature at a heating rate of 5℃ / min to 50℃ / min; directly placing the base glass in a heat treatment furnace that has already been heated to the nucleation temperature; or directly placing the base glass at a temperature between room temperature and the nucleation temperature and then heating it to the nucleation temperature at a heating rate of 5℃ / min to 50℃ / min. The above methods achieve the same technical effect.

[0068] The nucleation heat treatment time ranges from 0.1 h to 4 h. If the nucleation time is too short, the total number of crystal nuclei formed will be small. Furthermore, for the bicrystalline microcrystalline glass of this invention, various nucleating agents such as ZrO2 and P2O5 are introduced. These nucleating agents have different phase separation and nucleation mechanisms. ZrO2 forms single crystals of zirconium oxide in the initial stage of nucleation, while P2O5 leads to the formation of separated lithium orthophosphate crystal phases, serving as epitaxial centers for heterogeneous nucleation of lithium metasilicate and lithium disilicate. Clearly, the activation energy or energy barrier required for nucleation by these nucleating agents is different, and consequently, the optimal temperature and time for nucleation heat treatment are not entirely the same. Therefore, only when the nucleation time is sufficient can the nucleating agents fully exert their nucleation effect, forming a sufficient number of crystal nuclei in the base glass to facilitate sufficient crystal growth during the crystallization heat treatment stage. Therefore, the use of a multi-step nucleation heat treatment process in this invention to achieve optimal nucleation is not excluded. Although the number of nuclei initially grows exponentially when the nucleation time is short, the growth rate of the number of nuclei gradually slows down to near zero as the nucleation time increases, limited by the amount of nucleating agent. Therefore, the nucleation time should not be too long for the purpose of energy saving and cost reduction.

[0069] The nucleation heat treatment in this invention can maintain a constant temperature at a specific nucleation temperature, or it can fluctuate continuously within a nucleation temperature range, or it can exhibit a stepwise change within a nucleation temperature range. These methods achieve the same technical effect. The following scenarios are not limited to: 1) isothermal treatment at T1 nucleation temperature for t1 time; 2) continuous temperature fluctuations and / or cooling within the nucleation temperature range of 500℃ to 650℃; 3) isothermal treatment at T1 nucleation temperature for t1 time, followed by heating to T2, and isothermal treatment at T2 nucleation temperature for t2 time; 4) isothermal treatment at T1 nucleation temperature for t1 time, followed by cooling to T2, and isothermal treatment at T2 nucleation temperature for t2 time; 5) isothermal treatment at T1 nucleation temperature for t1 time, followed by heating to T2, isothermal treatment at T2 nucleation temperature for t2 time, followed by heating to T3, and isothermal treatment at T3 nucleation temperature for t3 time; 6) isothermal treatment at T1 nucleation temperature for t1 time, followed by cooling to T2, isothermal treatment at T2 nucleation temperature for t2 time, cooling to T3, and isothermal treatment at T3 nucleation temperature for t3 time. The nucleation temperatures of T1, T2, and T3 range from 500℃ to 650℃, and the sum of the nucleation times of t1, t2, and t3 ranges from 0.1h to 4h.

[0070] 3) Crystallization heat treatment: The base glass after nucleation heat treatment is treated at a crystallization temperature of 700℃~800℃ for 0.5h~8h, the crystallization temperature is more preferably 720℃~780℃, and the crystallization time is more preferably 1h~4h.

[0071] The main purpose of the crystallization heat treatment is to grow the crystal nuclei in the base glass into crystals. This process involves two stages: first, the nucleation process is not fully completed during the nucleation heat treatment stage; second, the crystals grow to a sufficiently large size, and mutual collisions reduce the crystallization rate. Furthermore, the present invention uses a biphase system of lithium feldspar crystals and lithium disilicate crystals. During crystal growth, there is competition and / or mutual promotion between the two phases. The competition arises because both phases require Li... + Ions form their respective crystal phases, and in the process of competition, they will continuously destroy the crystal structure of the other to meet their own growth needs. The mutual promotion is that after the competition, the two crystal phases will refine their respective grain size to meet the basic requirement of transparent microcrystalline glass that the grain size is smaller than the wavelength of visible light. At the same time, the two crystal phases will fuse together in the process of mutual competition and / or mutual promotion to form an interlocking structure, which is microscopically manifested as the formation of spherical interlocking crystals. This is beneficial to improving the glass's drop resistance and preventing crack propagation.

[0072] The method of performing crystallization heat treatment on the base glass that has undergone nucleation heat treatment can be as follows: the base glass is heated from the nucleation temperature to the crystallization temperature at a heating rate of 5℃ / min to 50℃ / min; the base glass is first cooled from the nucleation temperature to room temperature and then heated to the crystallization temperature at a heating rate of 5℃ / min to 50℃ / min; or the base glass is first cooled to a temperature between room temperature and the nucleation temperature and then heated to the crystallization temperature at a heating rate of 5℃ / min to 50℃ / min. The technical effects achieved by the above methods are the same.

[0073] The crystallization heat treatment temperature range is 700℃~800℃. If the crystallization temperature is too low, the crystal growth process will either stop at the nucleation stage or, due to the small size of the microcrystalline phase, the mass percentage of crystals in the glass-ceramic will be too low, failing to fully utilize the high strength and high toughness advantages of the microcrystalline phase. The crystallization temperature should not be too high, because at higher temperatures, the crystallization process is difficult to control, and the microcrystalline phase will rapidly grow epitaxially along the crystal nucleus, resulting in a size exceeding the visible light wavelength, causing opacity or even devitrification in a short period of time.

[0074] The crystallization heat treatment time ranges from 0.5 h to 8 h. Not limited by theory, the formation mechanism of the lithium feldspar crystal phase is that, with the assistance of a nucleating agent, Al... 3+ Substitution of Si in [SiO4] tetrahedron 4+ The grid point positions, and Li + Filling Al 3+ The electrical properties are neutralized in the nearby network gaps, forming a lithium feldspar crystal phase. The formation mechanism of the lithium disilicate crystal phase is that P2O5 reacts with Li2O to form lithium orthophosphate Li3PO4 crystals, which induces Li2O in the glass to react with SiO2 to form metastable lithium metasilicate Li2SiO3 and stable lithium disilicate Li2SiO5. During the crystallization heat treatment stage, the lithium metasilicate crystal phase will complete the transformation to the lithium disilicate crystal phase. Therefore, the crystallization heat treatment time should not be too short to meet the requirements of crystal growth. Specifically, it is necessary to achieve the generation of lithium feldspar crystal phase and lithium disilicate crystal phase, and complete or partially complete the transformation of the undesirable lithium metasilicate crystal phase to the lithium disilicate crystal phase.

[0075] The crystallization heat treatment in this invention can maintain a constant temperature at a specific crystallization temperature, or it can fluctuate continuously within a crystallization temperature range, or it can exhibit a step-like change within a crystallization temperature range. These methods achieve the same technical effect. The following scenarios are not limited to: 1) isothermal treatment at crystallization temperature T1 for time t1; 2) continuous fluctuation within the crystallization temperature range of 700℃~800℃; 3) isothermal treatment at crystallization temperature T1 for time t1, then heated to T2, and isothermal treatment at crystallization temperature T2 for time t2; 4) isothermal treatment at crystallization temperature T1 for time t1, then cooled to T2, and isothermal treatment at crystallization temperature T2 for time t2; 5) isothermal treatment at crystallization temperature T1 for time t1, then heated to T2, crystallized at crystallization temperature T2 for time t2, then heated to T3, and isothermal treatment at crystallization temperature T3 for time t3; 6) isothermal treatment at crystallization temperature T1 for time t1, then cooled to T2, isothermal treatment at crystallization temperature T2 for time t2, then cooled to T3, and isothermal treatment at crystallization temperature T3 for time t3. The crystallization temperatures of T1, T2, and T3 range from 700℃ to 800℃, and the sum of the crystallization times of t1, t2, and t3 ranges from 0.5h to 8h.

[0076] To further enhance the performance of the microcrystalline glass, preferably, it also includes:

[0077] 4) Chemical strengthening heat treatment: The glass-ceramic is placed in molten salt at 380℃~500℃ for 0.3h~6h of chemical strengthening heat treatment, with a more preferred chemical strengthening temperature of 430℃~470℃ and a more preferred chemical strengthening time of 2h~4h. The molten salt can be pure sodium molten salt and / or a mixed sodium-potassium molten salt, preferably a mixed molten salt of NaNO3 and KNO3, with NaNO3 accounting for 5%~100% by mass and KNO3 accounting for 0%~95% by mass, to complete the manufacture of glass-ceramic with high transmittance and low haze.

[0078] The chemical strengthening heat treatment involves placing the microcrystalline glass, after nucleation and crystallization heat treatment, in a salt bath containing alkali metal and / or alkaline earth metal ions. The alkali metal ions with larger ionic radii in the salt bath replace the alkali metal and / or alkaline earth metal ions with smaller ionic radii on the surface of the microcrystalline glass, thereby imparting compressive stress to the microcrystalline glass product and further improving the strength of the microcrystalline glass product.

[0079] The molten salt can be one or more of NaNO3, KNO3, Na2SO3, K2SO3, NaCl, and KCl, preferably one or more of NaNO3 and KNO3.

[0080] The molten salt may be a pure sodium molten salt and / or a mixed sodium-potassium molten salt, preferably a mixed molten salt of NaNO3 and KNO3, wherein the NaNO3 content is 5% to 100% by mass and the KNO3 content is 0% to 95% by mass.

[0081] The temperature and time of chemical strengthening heat treatment should not be too high or too long. Under prolonged chemical strengthening, the lithium feldspar and lithium disilicate phases in the glass-ceramic will... + The ions will be Na + Ions and / or K + Ion substitution leads to "decrystallization" and / or the formation of new, undesirable crystalline phases. Compared to the state before chemical strengthening following crystallization heat treatment, the crystalline phase content per unit area of ​​the ion exchange region on the surface of the chemically strengthened glass-ceramic is reduced, and is also lower than the crystalline phase content per unit area inside the glass-ceramic. Using molten sodium... + Li on the surface of ion-substituted microcrystalline glass + Taking ions as an example, Na + Ions will not only be used to replace free Li in the glassy phase + Ions can even be used to replace Li in microcrystalline phases such as lithium feldspar and / or lithium disilicate phases. + Ions cause the microcrystalline phase to be "de-crystallized," transforming into a glassy phase and / or a sodium carbonate crystalline phase. The former reduces the crystalline phase content per unit area of ​​the ion exchange region, while the latter, being an undesirable crystalline phase, can cause surface haze, leading to reduced haze. Furthermore, a sodium-rich surface layer reduces the glass's chemical durability, including its resistance to corrosion, acids, water, and alkalis, making the microcrystalline glass susceptible to corrosion and surface damage during long-term use, thus reducing its transmittance, haze, and lifespan. Additionally, excessively high temperatures and / or prolonged periods during chemical strengthening heat treatment can cause the molten salt to decompose, lose its activity, and pollute the environment.

[0082] The third aspect of the present invention also provides a microcrystalline glass, wherein the microcrystalline glass prepared by the above preparation method has a main crystalline phase formed after crystallization heat treatment as a lithium disilicate crystalline phase and a lithium feldspar crystalline phase, and a small amount of lithium metasilicate crystalline phase, with an average grain size ≤60nm, a total crystal content of 70%~90%, a lithium disilicate crystalline phase accounting for 40%~60% of the total crystal content, a lithium feldspar crystalline phase accounting for 30%~60% of the total crystal content, and a lithium metasilicate crystalline phase accounting for ≤5% of the total crystal content.

[0083] The main crystalline phases of the microcrystalline glass are lithium disilicate and lithium feldspar. The conditions for the microcrystalline glass to be transparent are: firstly, the grain size is much smaller than the wavelength of visible light; secondly, the birefringence of the crystals is low; and thirdly, the refractive index difference between the glass phase and the crystals is small. By controlling the nucleation and crystallization heat treatments, the grain size of the microcrystalline phase can be made much smaller than the wavelength of visible light. In this invention, after nucleation and crystallization heat treatments, the average grain size of the microcrystalline phase is ≤60nm, the birefringence of the lithium disilicate and lithium feldspar phases is low, and the refractive index difference between them and the glass phase is small, thus possessing the basic conditions for obtaining transparent microcrystalline glass.

[0084] The total crystal content of the microcrystalline glass is 70%~90%. Under the premise of meeting the requirements of transmittance and haze, the high strength and high toughness of the microcrystalline phase in the microcrystalline glass are brought into full play. At the same time, the interlocking structure formed by the bicrystalline phase causes the microcracks generated when the microcrystalline glass is subjected to external impact to bend the path when passing through the crystal, which prolongs the crack propagation path and prevents the crack from propagating. This results in a significant increase in the strength of the glass body when the microcrystalline glass is used as a cover glass.

[0085] The lithium disilicate crystalline phase has a rod-shaped microstructure. When the content of the lithium disilicate crystalline phase is high, the glass-ceramic exhibits the best mechanical properties, such as high bending strength and strong fracture toughness. Therefore, in this invention, the lithium disilicate crystalline phase accounts for 40-60% of the total crystal content. When the proportion is low, the interlocking of crystals cannot force the microcracks to change their propagation path. When the proportion is high, the content of the lithopone crystalline phase is low, that is, the Al2O3 content introduced into the base glass is low, resulting in the high-temperature viscosity of the base glass being too low. The glass melt has too strong a fluidity and is difficult to apply to many forming processes other than casting, such as calendering and float glass.

[0086] The lithium feldspar crystal phase is a monoclinic crystal with a three-dimensional framework structure consisting of a layered structure with folded Si2O6 layers connected by Li and Al tetrahedra. This enhances the network space structure of the glass and improves the thermal shock resistance of the glass-ceramic. The lithium feldspar crystal phase accounts for 30% to 60% of the total crystal content. The content should not be too high, otherwise the Al2O3 content introduced into the base glass will be too high, leading to an increase in the high-temperature viscosity of the glass, increasing the difficulty of high-temperature melting, and even forming undesirable crystal phases such as β-nepheline and β-spodumene.

[0087] The bicrystalline phases of lithium feldspar and lithium disilicate exhibit mutual competition and / or mutual promotion during crystallization heat treatment. The competition arises because both phases require Li. +Ions form their respective crystal phases, and in the process of competition, they will continuously destroy the crystal structure of the other to meet their own growth needs. The mutual promotion is that after the competition, the two crystal phases will refine their respective grain size to meet the basic requirement of transparent microcrystalline glass that the grain size is smaller than the wavelength of visible light. At the same time, the two crystal phases will fuse together in the process of mutual competition and / or mutual promotion to form an interlocking structure, which is microscopically manifested as the formation of spherical interlocking crystals. This is beneficial to improving the glass's drop resistance and preventing crack propagation.

[0088] The lithium metasilicate crystal phase, which appears simultaneously with the lithium disilicate crystal during the crystallization heat treatment stage, is an undesirable crystal phase. This is because lithium metasilicate crystal is metastable and its refractive index differs significantly from that of the glass phase, which would significantly reduce visible light transmittance and increase haze. During the crystallization heat treatment stage, most of the lithium metasilicate can be transformed into lithium disilicate. The lithium metasilicate crystal phase accounts for ≤5% of the total crystallization amount, thus minimizing its impact on visible light transmittance and haze.

[0089] The present invention will be described in detail below through examples. Unless otherwise specified, the methods used are conventional methods in the art.

[0090] The main crystalline phases of the microcrystalline glass are lithium disilicate crystals and lithium feldspar crystals, as well as a small amount of lithium metasilicate crystals, which were tested using an Empyrean multi-functional X-ray diffractometer.

[0091] The average grain size of the microcrystalline phase of the glass-ceramic is ≤60nm, and it was tested using a COXEM desktop scanning electron microscope.

[0092] The microcrystalline glass, converted to 1 mm, has a visible light transmittance of ≥80% in the visible light wavelength range of 380nm~720nm, a value of CRE: -1~-0.1, and a value of CRE: 0.4~5. It was tested using a Datacolor 650 ultra-high precision benchtop spectrophotometer in accordance with the standard ISO13468-1:1996.

[0093] The microcrystalline glass, when converted to 1 mm, has a haze of ≤4%, and was tested using an Everfine haze meter.

[0094] The coefficient of thermal expansion of the microcrystalline glass is 7.0 × 10⁻⁶. -6 / ℃~8.0×10 -6 / ℃, tested using a DIL402 ExpedisSupreme linear thermal expansion tester.

[0095] The microcrystalline glass has a Vickers hardness ≥ 700 kgf / mm². 2 The indentation method of the Matsuzawa Vickers hardness tester was used for testing.

[0096] The surface compressive stress of the microcrystalline glass is ≥200MPa, and the ion exchange depth is ≥100µm. It is tested using FSM6000LEUV+SLP2000.

[0097] Table 1 Glass Compositions

[0098]

[0099]

[0100] Continued from Table 1: Glass Compositions

[0101]

[0102]

[0103] Continued from Table 1: Glass Compositions

[0104]

[0105]

[0106] Continued from Table 1: Glass Compositions

[0107]

[0108]

[0109] Taking Example 1 as an example, the mass percentage of oxides was calculated according to the molar percentage of oxides in Example 1 in Table 1, as shown in Table 2.

[0110] Table 2 Chemical composition (wt%) of the base glass and glass-ceramic in Example 1

[0111]

[0112] According to the chemical composition of the base glass and microcrystalline glass in Table 2, the glass raw materials were accurately weighed and thoroughly mixed to form a glass batch. The batch was placed in a crucible made of platinum-rhodium alloy and melted in a high-temperature electric furnace at 1520℃ for 4 hours. During the melting process, the chemical homogeneity of the glass melt was improved by stirring. The batch was then poured into a heat-resistant stainless steel mold to form a glass block with a length × width × height of 160 × 80 × 15 mm. The block was then placed in an annealing furnace and annealed at 520℃ for 2 hours. After cooling to room temperature in the furnace, the block was cut, ground, rough polished, and fine polished to form a glass sheet with a length × width × height of 160 × 80 × 0.65 mm, thus obtaining the base glass.

[0113] The base glass was placed in a crystallization furnace and heated from room temperature to 540°C at a heating rate of 10°C / min, and held at 540°C for 4 hours for nucleation heat treatment. Subsequently, the base glass was heated from 540°C to 750°C at a heating rate of 5°C / min and held for 4 hours for crystallization heat treatment. The glass was then cooled to room temperature in the furnace to obtain microcrystalline glass. The microcrystalline glass was then placed in a mixed molten salt containing 30wt% NaNO3 and 70wt% KNO3 by weight and subjected to chemical strengthening heat treatment at 430°C for 4 hours with ion exchange, yielding chemically strengthened microcrystalline glass. Relevant tests were performed on the microcrystalline glass, and the X-ray diffraction analysis results are as follows: Figure 1 As shown, the morphology of the microcrystalline phase is as follows: Figure 2 As shown, the main crystalline phases are lithium feldspar and lithium disilicate. The visible light transmittance is 89.2%, the CRE a value is -0.2, the CRE b value is 1.1, the haze after conversion to 1 mm is 0.2%, and the coefficient of thermal expansion is 7.2 × 10⁻⁶. -6 At / ℃, the Vickers hardness is 721 kgf / mm². 2 The surface compressive stress is 262 MPa, and the ion exchange depth is 164 µm.

[0114] Taking Example 10 as an example, a glass sheet with a thickness of 160×80×0.65mm (length×width×height) was obtained after different nucleation heat treatments and crystallization heat treatments. The total content of the main crystalline phase, the content of the lithium feldspar crystalline phase, the content of the lithium disilicate crystalline phase, the transmittance, and the haze are shown in Table 3.

[0115] Table 3 Nucleation heat treatment and crystallization heat treatment

[0116]

[0117]

[0118] Continued from Table 3: Nucleation Heat Treatment and Crystallization Heat Treatment

[0119]

[0120] Continued from Table 3: Nucleation Heat Treatment and Crystallization Heat Treatment

[0121]

[0122]

[0123] Taking Example 43 as an example, the product after nucleation heat treatment and crystallization heat treatment was subjected to chemical strengthening heat treatment according to Table 4 to obtain a glass sheet with a thickness of 160×80×0.65mm (length x width x height). The results are as follows.

[0124] Table 4. Heat treatment for strengthening microcrystalline glass

[0125]

[0126]

[0127] Continued from Table 4: Heat Treatment for Strengthening Microcrystalline Glass

[0128]

[0129] The preferred embodiments of the present invention have been described in detail above. It should be understood that the application of the present invention is not limited to the examples described above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a microcrystalline glass includes the following steps: Step 1: Prepare and mix the materials according to the formula of the glass composition to complete the manufacturing of the basic glass; Step 2: Treat the base glass at a nucleation temperature of 520℃~600℃ for 0.1h~4h; Step 3: Treat the base glass after nucleation heat treatment at a crystallization temperature of 700℃~800℃ for 0.5h~8h; Step two specifically adopts at least one of the following methods: 1) isothermal treatment at T1 nucleation temperature for t1 time, then heating to T2, and isothermal treatment at T2 nucleation temperature for t2 time; 2) isothermal treatment at T1 nucleation temperature for t1 time, then cooling to T2, and isothermal treatment at T2 nucleation temperature for t2 time. The nucleation temperatures of T1 and T2 range from 520℃ to 600℃, and the sum of the nucleation times of t1 and t2 ranges from 0.1h to 4h. The glass composition comprises, by molar percentage, the following components: SiO2: 69%~74%; Al2O3: 3.5%~5%; Li2O: 19%~24%; Na2O: 0.1%~2%; K2O: 0.1%~2%; B2O3: 0%~2%; CaO: 0%~1%; MgO: 0%~1%; ZnO: 0%~1%; BaO: 0%~1%; ZrO2: 1%~2.5%; P2O5: 0.3%~1%; TiO2: 0%~0.5%; SnO2: 0%~0.5%.

2. The preparation method according to claim 1, characterized in that: The glass composition satisfies the following condition: A: 0.17~0.25; B：0.2%~3.1%； C：0.21~0.38； D：0.29~0.48； E: 0%~2%, of which: ； ； ； ； 。 3. The preparation method according to claim 2, characterized in that: A：0.18~0.24； B：1%~2.6%； C：0.28~0.37； D：0.41~0.48； E：0%~1%。 4. The preparation method according to claim 3, characterized in that: The glass composition comprises, by molar percentage, the following components: SiO2: 69%~73%; Al2O3: 3.7%~4.8%; Li2O: 19%~23%; Na2O: 0.1%~1.5%; K2O: 0.1%~1.5%; B2O3: 0%~0.5%; CaO: 0%~0.5%; MgO: 0%~0.5%; ZnO: 0%~0.5%; BaO: 0%~0.5%; ZrO2: 1.5%~2.5%; P2O5: 0.6%~1%; TiO2: 0%~0.4%; SnO2: 0%~0.4%; A：0.18~0.23； B：1%~2%； C：0.30~0.37； D：0.42~0.48； E：0%~0.5%。 5. The preparation method according to any one of claims 1-4, characterized in that, Also includes Step 4: Place the glass-ceramic in molten salt at 380℃~500℃ for chemical strengthening heat treatment for 0.3h~6h.

6. The preparation method according to claim 5, characterized in that, The molten salt is a pure sodium molten salt or a sodium-potassium mixed molten salt.

7. The preparation method according to claim 6, characterized in that: The mixed molten salt is a mixed molten salt of NaNO3 and KNO3, wherein the mass fraction of NaNO3 molten salt is 5%~100% and the mass fraction of KNO3 molten salt is 0%~95%.

8. A microcrystalline glass, prepared by the method of any one of claims 1-7, wherein, The main crystalline phases in the glass-ceramic are lithium disilicate and lithium feldspar, as well as a small amount of lithium metasilicate.

9. The microcrystalline glass according to claim 8, characterized in that: Lithium disilicate crystals account for 40% to 60% of the total crystallization, lithium feldspar crystals account for 30% to 60% of the total crystallization, and lithium metasilicate crystals account for ≤5% of the total crystallization.

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