Chemically-strengthenable high-refractive optical glass, method for chemically strengthening high-refractive optical glass

Abstract

The application relates to the field of glass strengthening technology, and discloses a chemically-strengthenable high-refractive optical glass and a chemical strengthening method of the high-refractive optical glass. The high-refractive optical glass contains 20-35 mol% of SiO2, 25-45 mol% of TiO2, 5-20 mol% of BaO, 5-25 mol% of alkali metal oxide, 0.5-15 mol% of Nb2O5 and 0.5-5 mol% of ZrO2, with the total mole content of the high-refractive optical glass as the benchmark; the refractive index of the high-refractive optical glass is defined as n1, the refractive index of the high-refractive optical glass after ion exchange is n2, and the difference between n1 and n2 is less than 0.01. The high-refractive optical glass provided by the application has a significantly improved strength after chemical strengthening; the glass can still be subjected to laser cutting processing after being strengthened, and will not have edge collapse when being cut into a special shape.

Description

Technical Field

[0001] This invention relates to the field of glass strengthening technology, specifically to chemically strengthenable high-refractive-index optical glass and a chemical strengthening method for high-refractive-index optical glass. Background Technology

[0002] High-refractive-index optical glass is a core material for achieving miniaturization and high performance in precision optical systems. Its key value lies in its ability to significantly expand the field of view of optical devices, thus making it a material urgently sought after by digital cameras, microscopes, and especially augmented reality (AR) and virtual reality (VR) devices to achieve a more immersive experience.

[0003] To achieve core optical properties such as high refractive index and low dispersion, high-refractive-index glass typically incorporates a large amount of heavy metal ions such as lanthanum, titanium, niobium, and barium. This results in high density, high brittleness, and low strength. Its bending strength is usually much lower than that of ordinary cover glass, making it unable to directly meet the durability requirements of the aforementioned applications.

[0004] Currently, chemical strengthening technology is widely used to improve the mechanical strength of glass covers. Its core principle is to immerse the glass in high-temperature molten salt, causing larger ions in the molten salt to replace smaller ions on the glass surface, thereby forming a protective compressive stress layer.

[0005] However, when ion exchange is applied to high refractive index optical glass, the following serious defects exist: 1) It causes optical distortion: the change in refractive index of the glass before and after strengthening is often greater than 0.01. The fluctuation of refractive index will produce interference fringes, pattern distortion or stray light in the final optical element, which will damage its core optical performance; 2) When the strengthened glass is subjected to precision processing such as laser cutting, it is very easy to cause edge chipping or cracking.

[0006] Therefore, there is an urgent need to develop a high-refractive-index glass that can maintain good optical and mechanical properties even after strengthening. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of low strength of high-refractive glass and poor optical and mechanical properties after strengthening in the prior art.

[0008] To achieve the above objectives, a first aspect of the present invention provides a chemically strengthenable high-refractive-index optical glass, wherein, based on the total molar amount of the high-refractive-index optical glass, the high-refractive-index optical glass contains 20-35 mol% SiO2, 25-45 mol% TiO2, 5-20 mol% BaO, 5-25 mol% alkali metal oxides, 0.5-15 mol% Nb2O5 and 0.5-5 mol% ZrO2; The refractive index of the high refractive index optical glass is defined as n1, and the refractive index of the high refractive index optical glass after ion exchange is defined as n2, wherein the difference between n1 and n2, Δn, is less than 0.01. The strain point temperature of the high-refractive-index optical glass is defined as T. st The characteristic critical temperature of the high refractive index optical glass is T. c T c ≤T st -80℃.

[0009] A second aspect of the present invention provides a chemical strengthening method for high-refractive-index optical glass, the method being carried out using the high-refractive-index optical glass described in the first aspect above, comprising: High-refractive-index optical glass is ion-exchanged with molten salt to obtain reinforced glass; The temperature of the ion exchange is T, where T≤T c ≤T st -80℃; Among them, T c and T st The definition corresponds to the definition described in the first aspect above.

[0010] This invention obtains a chemically strengthenable high-refractive-index optical glass by using a specific ratio of SiO2, TiO2, BaO, Nb2O5, ZrO2 and alkali metal oxides. After strengthening, the strength of the optical glass is increased to more than three times that before strengthening; and the refractive index fluctuation before and after strengthening is less than 0.01, which allows the high-refractive-index optical glass to still be laser-cut after strengthening, and it will not chip when cut into irregular shapes.

[0011] The chemical strengthening method for high-refractive-index optical glass provided by this invention can maximize ion exchange efficiency to improve strength while greatly reducing uncontrollable optical distortion caused by network relaxation; moreover, the method is simple, highly operable, and conducive to industrial production. Attached Figure Description

[0012] Figure 1 This is a cross-sectional view of the chemically strengthenable high-refractive-index optical glass prepared in Example 1 of the present invention before and after laser cutting. Detailed Implementation

[0013] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these 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.

[0014] In this invention, the refractive index is the refractive index of glass tested at a wavelength of 527.5 nm.

[0015] In this invention, the strain point temperature of high refractive index optical glass refers to the temperature at which the glass viscosity is 10. 14.5 The temperature corresponding to dPa·s.

[0016] In this invention, the characteristic critical temperature of high refractive index optical glass is obtained by testing the refractive index change curves at different temperatures after the high refractive index glass has undergone ion exchange (strengthening treatment) for the same heat preservation time, and determining the temperature point at the inflection point of the curve (the point where the second derivative is 0).

[0017] In this invention, the bending strength of the glass is obtained by ball-on-ring (BOR) test.

[0018] In this invention, the difference Δn between n1 and n2 refers to the absolute value of the difference between n1 and n2.

[0019] In this invention, the ion exchange depth is obtained by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS).

[0020] As previously stated, a first aspect of the present invention provides a chemically strengthenable high-refractive-index optical glass, wherein, based on the total molar amount of the high-refractive-index optical glass, the high-refractive-index optical glass contains 20-35 mol% SiO2, 25-45 mol% TiO2, 5-20 mol% BaO, 5-25 mol% alkali metal oxides, 0.5-15 mol% Nb2O5 and 0.5-5 mol% ZrO2; The refractive index of the high refractive index optical glass is defined as n1, and the refractive index of the high refractive index optical glass after ion exchange is defined as n2, wherein the difference between n1 and n2, Δn, is less than 0.01. The strain point temperature of the high-refractive-index optical glass is defined as T. st The characteristic critical temperature of the high refractive index optical glass is T. c T c ≤T st -80℃.

[0021] The chemically strengthenable high-refractive-index optical glass provided by this invention achieves a balance between specific high-refractive-index glass components (25-45 mol% TiO2, 5-20 mol% BaO, 0.5-15 mol% Nb2O5) and the content of SiO2, alkali metal oxides, and ZrO2. This balance enables the glass to exhibit unique structural relaxation behavior during chemical strengthening, thereby generating a definite characteristic critical temperature (T0). c ), and Tc ≤T st -80℃ fundamentally suppresses structural relaxation during the strengthening process, ensuring that the refractive index change Δn of high-refractive glass with specific components is less than 0.01 before and after ion exchange; this allows high-refractive-index optical glass to still be laser-cut after strengthening, and it will not chip when cut into irregular shapes; it can maximize ion exchange efficiency to improve strength while greatly reducing uncontrollable optical distortion caused by network relaxation.

[0022] According to a preferred embodiment, based on the total molar amount of the high-refractive-index optical glass, the high-refractive-index optical glass contains 25-35 mol% SiO2, 30-40 mol% TiO2, 8-15 mol% BaO, 10-21 mol% alkali metal oxides, 3-8 mol% Nb2O5, and 1-5 mol% ZrO2. In this preferred embodiment, the glass achieves a better and more consistent balance in key indicators such as high refractive index, chemical stability, and mechanical strength, resulting in more balanced and stable performance; it also exhibits better chemical strengthening properties and reduces the risk of crystallization during melting and forming processes.

[0023] In a preferred embodiment, the high-refractive-index optical glass does not contain lead, arsenic, or cadmium.

[0024] Preferably, based on the total molar amount of the high-refractive-index optical glass, the total molar content of TiO2 and Nb2O5 is 38-48 mol%. In this preferred case, a more stable glass network structure is formed, which significantly improves the glass forming ability and melt stability, suppresses the precipitation of harmful crystalline phases, and effectively ensures the glass forming ability without causing obvious coloration.

[0025] Preferably, the alkali metal oxide is selected from at least one of Li₂O, Na₂O, and K₂O. In high-refractive-index glass, potassium oxide has a moderate fluxing effect, which can significantly improve the refractive index, transparency, and gloss; sodium oxide can provide an effective fluxing effect, improve the refractive index well, and provide a sodium source for ion exchange; lithium oxide has a strong fluxing effect, provides a lithium source for ion exchange, and can reduce the coefficient of thermal expansion by replacing the other two alkali metals. An appropriate amount of lithium oxide can achieve a higher refractive index without increasing dispersion.

[0026] According to another preferred embodiment, the alkali metal oxide contains at least Na₂O, and the molar ratio of Na₂O to SiO₂ is ≤0.5, preferably ≤0.4. In this preferred embodiment, chemically strengthenable high-refractive-index optical glass, based on sodium-potassium ion exchange in the chemical strengthening process, can achieve higher surface stress, improving glass strength, scratch resistance, and impact resistance; simultaneously, the stress layer depth is moderate, with minimal impact on the refractive index; and the use of sodium-potassium exchange is low-cost, making it suitable for industrial production.

[0027] In a preferred embodiment, the alkali metal oxide further comprises K₂O, and the molar ratio of K₂O to Na₂O is ≤0.5. This preferred embodiment achieves a balance between refractive index, melting performance, and glass stability; more preferably, the ratio is ≤0.42, which further optimizes the glass's resistance to crystallization, chemical stability, and chemical strengthening properties.

[0028] Preferably, the high refractive index optical glass has a refractive index of 1.7-1.9, and more preferably, the high refractive index optical glass has a refractive index greater than 1.78 and less than or equal to 1.9.

[0029] In some embodiments, the flexural strength of the high-refractive-index optical glass is 180-240 MPa.

[0030] In some embodiments, the T of the high refractive index optical glass c The temperature ranges from 420 to 500℃.

[0031] In some embodiments, the T of the high refractive index optical glass st The temperature is 500-600℃.

[0032] As previously described, a second aspect of the present invention provides a method for chemically strengthening high-refractive-index optical glass, wherein the method utilizes the high-refractive-index optical glass described in the first aspect, and includes: High-refractive-index optical glass is ion-exchanged with molten salt to obtain reinforced glass; The temperature of the ion exchange is T, where T≤T c ≤T st -80℃; Among them, T c and T st The definition corresponds to the definition described in the first aspect above.

[0033] During their research, the inventors of this invention discovered that subjecting the chemically strengthenable high-refractive-index optical glass described in the first aspect of the invention to ion exchange at temperature T can fundamentally guarantee the optical uniformity of the glass while ensuring increased strength. The inventors speculate that the possible reason is that at this temperature, the high-refractive-index glass undergoes ion exchange with silicon-oxygen and high-field-strength ions (such as Ti). 4+ 、Nb 5+ Zr 4+ The network composed of (etc.) has very weak mobility and is in a "frozen" state. Ions can exchange slowly, and the glass network itself is difficult to undergo large-scale structural rearrangement to adapt to this change. At this time, the photoelastic effect becomes the main cause of the refractive index change. The compressive stress generated by ion exchange directly and instantly changes the refractive index through the photoelastic coefficient. Once a stable stress layer is formed on the surface, the concentration of alkali metal ions tends to stabilize. Continuing to extend the processing time mainly increases the exchange depth, but does not significantly change the peak stress of the outermost layer. Therefore, the refractive index change (Δn) of the surface layer tends to stabilize.

[0034] The chemical strengthening methods for high-refractive-index optical glass provided by this invention all strictly limit the upper temperature limit to this critical temperature (T). c Under these conditions, while maximizing ion exchange efficiency to enhance intensity, uncontrollable optical distortion caused by network relaxation is completely avoided.

[0035] According to a preferred embodiment, the ion exchange temperature satisfies 350℃≤T≤T c -20℃. Under this preferred condition, the optical uniformity of the high-refractive-index glass can be fundamentally guaranteed while ensuring improved glass strength.

[0036] In a preferred embodiment, the ion exchange time is 2-12 hours, more preferably 4-8 hours; the ion exchange depth is 1-10 μm, preferably 2-7 μm.

[0037] In a preferred embodiment, the flexural strength of the tempered glass is ≥650MPa.

[0038] Preferably, the molten salt contains potassium nitrate, and the potassium nitrate content is 90-100 wt% based on the total mass of the molten salt. In this preferred embodiment, a pure and stable reaction environment is provided for the above-mentioned ion exchange process, ensuring that the ion exchange process is mainly sodium-potassium exchange, which is conducive to achieving the preset stress distribution, exchange depth and refractive index change; at the same time, the high-purity molten salt helps to ensure the ion exchange efficiency.

[0039] In some implementations, the enhancement process can be carried out in an isothermal manner (maintaining a constant temperature for ion exchange) or in a stepped heating manner (e.g., heating at a rate of 1-10°C / h). Regardless of the method used, the temperature during the ion exchange process should be controlled to meet the requirements of the second aspect mentioned above.

[0040] The present invention will be described in detail below through examples. Unless otherwise specified, the instruments, reagents, and materials involved in the following examples are all conventional instruments, reagents, and materials, which can be obtained through legitimate commercial channels. Unless otherwise stated, all reagents used are commercially available analytical grade products.

[0041] Preparation Example 1 This preparation example illustrates the preparation of high-refractive-index optical glass according to the formulations in Table 1 and the following steps: S1: Weigh the corresponding raw materials according to the formula and mix them evenly to obtain the mixture; S2: The mixture is placed in a platinum crucible and melted, clarified, and homogenized at high temperature to obtain a homogeneous melt; The melting temperature is 1500℃, and the holding time is 4 hours; S3: Cast the uniform melt into blocks and anneal it; The annealing temperature is 600℃ and the holding time is 2 hours.

[0042] Table 1

[0043] Note: n1 refers to the refractive index of high-refractive-index optical glass; "-" indicates that the glass does not have a characteristic critical temperature and cannot be measured. T c It refers to the characteristic critical temperature of high refractive index optical glass. It is obtained by placing high refractive index optical glass in pure potassium nitrate molten salt for strengthening treatment, plotting the curve of refractive index versus temperature under the same holding time and different temperature conditions, and determining the temperature point at the inflection point of the curve (the point where the second derivative is 0). T st This refers to the strain point temperature of high-refractive-index optical glass, specifically when the glass viscosity is 10. 14.5 The temperature corresponding to dPa·s.

[0044] Unless otherwise specified, Preparation Examples 2-4 and Comparative Preparation Example 1 were carried out using a method similar to that of Preparation Example 1. The difference is that the formulation for preparing the glass is shown in Table 1, and the parts not listed are the same as those in Preparation Example 1.

[0045] Example 1 This embodiment illustrates the preparation of strengthened glass according to the formulation and process parameters in Table 2, and the following steps: High-refractive-index optical glass is subjected to ion exchange with molten salt (pure potassium nitrate molten salt) at a temperature of T to obtain reinforced glass.

[0046] Table 2

[0047] Continued from Table 2

[0048] Unless otherwise specified, Examples 2-7 and Comparative Examples 1-2 were carried out using methods similar to those in Example 1, except that the formulations and process parameters are as shown in Table 2; and the parts not listed are the same as in Example 1.

[0049] Test example: 1. The properties of the tempered glass prepared in the above embodiments and comparative examples are shown in Table 3: Table 3

[0050] 2. This invention provides, by way of example, comparative images of the cross-sections of the chemically strengthenable high-refractive-index optical glass prepared in Example 1 before and after chemical strengthening (i.e., the strengthened glass prepared in Example 1) after laser cutting, as shown in the figures. Figure 1 As shown: pass Figure 1 It can be seen that the chemically strengthened high-refractive-index optical glass provided by the present invention still has good processability after chemical strengthening by ion exchange and will not exhibit edge chipping.

[0051] The above results show that the chemically strengthenable high-refractive-index optical glass provided by this invention, after strengthening (the ion exchange temperature is T, where T≤T), c ≤T st After being heated to -80℃, the strength of the glass is increased to more than three times that before strengthening; and the fluctuation of the refractive index before and after strengthening is less than 0.01, which allows the high refractive index optical glass to still be laser-cut after strengthening, and it will not chip when cut into irregular shapes.

[0052] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A chemically strengthenable high-refractive-index optical glass, characterized in that, Based on the total molar amount of the high-refractive-index optical glass, the high-refractive-index optical glass contains 20-35 mol% SiO2, 25-45 mol% TiO2, 5-20 mol% BaO, 5-25 mol% alkali metal oxides, 0.5-15 mol% Nb2O5 and 0.5-5 mol% ZrO2; The refractive index of the high refractive index optical glass is defined as n1, and the refractive index of the high refractive index optical glass after ion exchange is defined as n2, wherein the difference between n1 and n2, Δn, is less than 0.

01. The strain point temperature of the high-refractive-index optical glass is defined as T. st The characteristic critical temperature of the high refractive index optical glass is T. c T c ≤T st -80℃.

2. The high refractive index optical glass according to claim 1, characterized in that, Based on the total molar amount of the high-refractive-index optical glass, the high-refractive-index optical glass contains 25-35 mol% SiO2, 30-40 mol% TiO2, 8-15 mol% BaO, 10-21 mol% alkali metal oxides, 3-8 mol% Nb2O5 and 1-5 mol% ZrO2. And / or, the high-refractive-index optical glass is free of lead, arsenic, and cadmium.

3. The high refractive index optical glass according to claim 1, characterized in that, Based on the total molar amount of the high refractive index optical glass, the total molar content of TiO2 and Nb2O5 is 38-48 mol.

4. The high refractive index optical glass according to claim 1, characterized in that, The alkali metal oxide is selected from at least one of Li2O, Na2O, and K2O.

5. The high refractive index optical glass according to claim 4, characterized in that, The alkali metal oxide contains at least Na2O, and the molar ratio of Na2O to SiO2 is ≤0.

5.

6. The high refractive index optical glass according to claim 5, characterized in that, The alkali metal oxide further contains K2O, and the molar ratio of K2O to Na2O is ≤0.

5.

7. The high refractive index optical glass according to any one of claims 1-6, characterized in that, The high-refractive-index optical glass has a refractive index of 1.7-1.9; And / or, the flexural strength of the high-refractive-index optical glass is 180-240 MPa; And / or, the T of the high refractive index optical glass c The temperature is 420-500℃. And / or, the T of the high refractive index optical glass st The temperature is 500-600℃.

8. A chemical strengthening method for high-refractive-index optical glass, characterized in that, This method uses the high refractive index optical glass described in any one of claims 1-7, and includes: High-refractive-index optical glass is ion-exchanged with molten salt to obtain reinforced glass; The temperature of the ion exchange is T, where T≤T c ≤T st -80℃; Among them, T c and T st The definition corresponds to the definition described in any one of claims 1-7.

9. The method according to claim 8, characterized in that, The ion exchange temperature satisfies 350℃≤T≤T c -20℃; And / or, the ion exchange time is 2-12 h, and the ion exchange depth is 1-10 μm; And / or, the flexural strength of the reinforced glass is ≥650MPa.

10. The method according to claim 8 or 9, characterized in that, The molten salt contains potassium nitrate, and the potassium nitrate content is 90-100 wt% based on the total mass of the molten salt.

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