Salt bath composition for chemical strengthening, strengthening method thereof and IOX glass product

Abstract

The invention discloses a salt bath composition for chemical strengthening, a strengthening method of the salt bath composition and an IOX glass product, and the salt bath composition for chemical strengthening comprises the following components in percentage by mass: 50-99.9% of metal nitrate and more than 0.1% of inhibitor, the inhibitor is used for providing inhibiting ions into the salt bath composition so as to inhibit corrosion of the salt bath composition to a salt bath container and formation of metal oxides, defects are prevented from being formed on the surface of IOX glass, and the yield of the IOX glass is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of glass surface treatment, and particularly relates to a salt bath composition for chemical strengthening, a strengthening method thereof, and a strengthened material product. Background Art

[0002] Glass has excellent optical, mechanical, and chemical resistance properties. However, when the thickness of the glass decreases, its mechanical strength drops significantly. To improve the mechanical strength of thin glass with a thickness less than 2 mm, ion exchange (IOX) is usually performed on the glass. The glass is placed in a molten nitrate salt bath at a temperature above 330°C, and large ions in the salt bath replace small ions in the glass to form a "pinch" effect on the glass surface, thereby generating compressive stress to improve the strength of the glass.

[0003] During IOX of glass, surface punctate particle defects often occur. Curiously, through microscopic observation, it can be found that more than 20% of these punctate defects are in a convex state, and the other part is concave. This phenomenon first appeared in soda-lime-silica glass. With the development of the industry, glasses with larger IOX scales, such as sodium-aluminum-silica, lithium-aluminum-silica glass, and glass-ceramics, have been used, and larger-scale IOX has also accelerated the deterioration and poisoning of the salt bath. Therefore, adding ion sieves, sodium metaphosphate anhydrous, and other substances to the salt bath to remove waste ions and restore the salt bath has become a necessary measure. Practice has proved that the use of ion sieves and sodium metaphosphate anhydrous increases the occurrence frequency of the above-mentioned punctate defects. Whether this defect is caused by changes in the glass material, salt bath management, or related to additives such as ion sieves and sodium metaphosphate anhydrous has not been effectively solved.

[0004] This defect results in a high batch of defective products. When defects occur, usually about 70% of the glass in one furnace of IOX has problems, and it is very difficult to rework, and the rework yield is also very low. Usually, an effective method to solve this problem is to replace the entire salt bath material and use a new salt bath to perform IOX on the glass again. However, such a solution is extremely costly, environmentally unfriendly, and unscientific, and the cause of this problem has always been unclear, which has become a pain point in the industry. Summary of the Invention

[0005] Through a large number of studies, it is found that the punctate defects are mainly caused by the reaction between NO3 - ions in the salt bath and the IOX crucible (stainless steel) when there is a relatively large amount of OH - in the salt bath. The cause analysis is as follows: 1. Metal element release mechanism: The crucibles used for IOX and the glass carrier brackets are both made of stainless steel. In the strong oxidizing environment of the nitrate salt bath, the surface protective film of the stainless steel (such as M2O3, where M is a metal element such as Cr, Fe, etc.) is damaged; metal ions are at high temperature and react with NO3- Under the action of an oxidizing agent, an oxidation reaction occurs to produce M 3+ ions: M + 3NO3 - → M 3+ + 3NO2 + 3O 2- (Equation 1) Sodium phosphate anhydrous is a salt of a strong base and a weak acid, and the ion sieve is a neutral substance. However, both are prone to absorbing water in the air, thereby generating OH - on the surface. When sodium phosphate anhydrous and the ion sieve are added to the salt bath, OH - also enters the salt bath. OH - makes the salt bath slightly alkaline, further promoting the corrosion of stainless steel and the dissolution of M.

[0006] 2. Formation and transformation of M 3+ → M(OH)3 colloid: M 3+ undergoes a hydrolysis reaction in a weakly alkaline environment to form Fe(OH)3 colloid: M 3+ + 3OH − → M(OH)3↓ (Equation 2) Since the salt bath is a high-temperature system, M(OH)3 quickly dehydrates and transforms into extremely fine particles of M2O3: 2M(OH)3 → M2O3 + 3H2O (>200 °C) (Equation 3) The particle size of these M2O3 particles is usually between 10 and 100 nanometers, and they settle slowly and are suspended in the salt bath.

[0007] 3. Particle migration and glass surface deposition mechanism: Convection in the molten salt and changes in the interfacial tension make it easy for M2O3 particles to aggregate towards the glass surface; During the IOX process, the glass surface has a high surface energy and a high stress gradient, becoming an "active site" for impurity adsorption. The particles are pressed into the glass surface layer by the surface stress, forming a "semi-embedded" attachment structure; Some particles fall off during the embedding process, thus forming sunken dot-like defects.

[0008] Summary of the defect mechanism: Stainless steel releases metal elements in the oxidizing salt bath, and after being colloidalized and transformed into M2O3 particles in an alkaline environment, they are deposited and embedded in the glass surface, finally forming stable defects with some convex points and some depressions.

[0009] Based on the above research, aiming at the "root cause" of the problem, the purpose of the present invention is to effectively avoid the erosion of the salt bath composition on the container surface during the batch chemical strengthening process, prevent the occurrence of (Equation 2), or the reverse of (Equation 2), so as to avoid the formation of dot-like defects on the glass surface and improve the yield of the glass.

[0010] To achieve the above object, the present invention provides a salt bath composition for chemical strengthening, which comprises, by mass percentage: 50% - 99.9% of metal nitrate and more than 0.1% of inhibitor; The inhibitor is used to inhibit the corrosion of the stainless steel layer on the container surface and the dissolution of M during the chemical strengthening IOX process. In this application, there is no upper limit on the content of the inhibitor. The role of the inhibitor is to change the environment of the salt bath composition, so that the free M ions in the salt bath composition do not form oxide particles, and at the same time reduce the dissolution of metal elements from the container material, avoiding the appearance of surface dot-like particles on the glass after IOX and improving the yield rate of IOX glass. In this application, the content of the inhibitor is preferably 0.1 - 1.5%, and further preferably 0.8 - 1.5%.

[0011] Furthermore, the inhibitor includes a hydrogen - donating substance, which is used to provide hydrogen ions to the salt bath composition. The hydrogen ions can change the slightly alkaline environment of the salt bath to be neutral or weakly acidic. According to the foregoing causes, when there is not enough OH - in the salt bath composition, the forward reaction of (Equation 2) will be inhibited, thereby inhibiting the formation of colloids and metal oxides in the high - temperature salt bath, avoiding the "protrusion" defect caused by the attachment of metal oxides to the glass surface; at the same time, inhibiting the formation of colloids can also avoid the "depression" defect caused by the shedding of metal oxides after being pressed into the glass surface layer by surface stress; since the reaction of (Equation 2) cannot occur effectively or occurs reversely, the remaining metal M in the salt bath is in a small amount of ionic state, so it will not cause the forward reaction of (Equation 1) to occur, reducing the erosion of the salt bath on the container. In summary, by adding a hydrogen - donating substance to the salt bath composition for chemical strengthening, the dot - like defects that have troubled the industry for a long time can be greatly eliminated, and the yield rate of IOX glass can be greatly improved. There is no upper limit on the content of the hydrogen - donating substance, and it is preferably 0.1 - 1.5%, and further preferably 0.8 - 1.5%.

[0012] Further, the formation temperature of the salt bath composition for chemical strengthening is the first temperature. When the salt bath composition for chemical strengthening is less than or equal to the first temperature, the hydrogen-supplying substance is used to provide hydrogen ions to the salt bath composition; wherein, the first temperature is 380-470°C, and it is held statically at this temperature for 12-36 h. The hydrogen-supplying substance in this application will decompose when the temperature is higher than 380-470°C, and its activity is too low when the temperature is lower than 380-470°C; both of the above will cause the hydrogen-supplying substance in the salt bath to be unable to release sufficient hydrogen ions, thereby affecting the salt bath effect and further affecting the yield rate of the IOX glass finished product. A sufficiently long static time is beneficial to the sedimentation of the metal oxides that have been formed in the salt bath, avoiding the suspension of metal oxide particles adhering to the glass surface after the glass enters the salt bath. The static time is also one of the key points of the present invention.

[0013] Further, the working temperature of the salt bath composition for chemical strengthening is the second temperature. When the salt bath composition for chemical strengthening is at the second temperature, the strengthening treatment time of the salt bath composition is 0.5-12 h; Wherein, the second temperature is 360-600°C. The second temperature is the temperature during chemical strengthening and is a process condition of IOX, which is different from the first temperature; it should be noted that the time and temperature of IOX are related to the type of glass. Different types of glass correspond to different times and temperatures of IOX. When the glass is lithium aluminosilicate glass, preferably 370-500°C, and more preferably 380°C.

[0014] Further, the second temperature is 450-540°C, and the strengthening treatment time is 3-7 h; further, the second temperature is 500-530°C. In some embodiments, when the temperature is between 450-540°C, or further, between 500-530°C, the salt bath composition can achieve better effects. Further, the metal nitrate includes, by mass percentage of the salt bath composition: 0-89.99% sodium nitrate, 0-89.99% potassium nitrate.

[0015] Further, the salt bath composition for chemical strengthening includes, by mass percentage of the salt bath composition: 0-89.99% sodium nitrate, 0-89.99% potassium nitrate, preferably including 50-89.99% sodium nitrate, 0-39.99% potassium nitrate, 0.03%-0.1% lithium nitrate.

[0016] Further, the metal nitrate further includes an antibacterial component, and the antibacterial component includes at least one of silver nitrate, copper nitrate, and zinc nitrate.

[0017] Sodium nitrate is one of the components of the salt bath composition. An appropriate content of sodium nitrate can ensure that there are sufficient sodium ions to exchange with lithium ions in the glass, thereby increasing the depth of the ion exchange layer. If the content of sodium ions is too low, the corresponding content of potassium ions will be too high, affecting the exchange of potassium ions and lithium ions and reducing the depth of the ion exchange layer; conversely, if the content of sodium ions is too high, the corresponding content of potassium ions will be too low, affecting the exchange of potassium ions and sodium ions and reducing the surface compressive stress of the glass.

[0018] Optionally but not necessarily, the mass percentage of sodium nitrate in the active component can be 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74% or 75%, or within the numerical range formed by any two of the above specific values as endpoints.

[0019] Potassium nitrate is one of the components of the salt bath composition. Only by providing a sufficient content of potassium nitrate in the salt bath composition can it meet the rapid exchange of potassium ions and sodium ions in the glass during the chemical strengthening process and improve the surface compressive stress of the glass. The radius of potassium ions (1.38 Å) is larger than that of sodium ions (0.95 Å) and lithium ions (0.76 Å). After replacement, it causes "jamming expansion" on the glass surface, forming a compressive stress layer and significantly improving the impact resistance and scratch resistance.

[0020] Optionally but not necessarily, the mass percentage of potassium nitrate in the active component can be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%, or within the numerical range formed by any two of the above specific values as endpoints.

[0021] Lithium nitrate is mixed in the salt bath in a relatively small proportion and is used to adjust the ionic activity of the molten salt or assist in a specific crystallization process. In the strengthening of lithium-containing glass ceramics, lithium nitrate can promote the exchange of lithium ions and sodium / potassium ions and enhance the depth of the stress layer.

[0022] Optionally but not necessarily, the mass percentage of potassium nitrate in the active component can be 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, or within the numerical range formed by any two of the above specific values as endpoints.

[0023] In the current continuous strengthening process, the addition of phosphates and the application of ion sieves will make the salt bath alkaline, causing corrosion problems. By adding hydrogen-supplying substances to neutralize this alkalinity, it is expected to solve such problems.

[0024] Furthermore, the hydrogen-supplying substances include one or more of silicic acid, sulfuric acid, and boric acid.

[0025] Treatment with strong acids may lead to uneven corrosion and defects, while silicic acid may be milder. Therefore, the hydrogen donor is preferably silicic acid or a mixture containing silicic acid.

[0026] Furthermore, when the hydrogen donor is silicic acid, the mass percentage of the silicic acid is 0.1% - 1.5%. Preferably, the mass percentage of the silicic acid is 0.1% - 0.8%.

[0027] However, adding silicic acid may cause some problems: 1. The decomposition temperature of silicic acid is around 150°C. If the temperature of the combined salt bath is raised above 300°C and then silicic acid is added, the silicic acid will decompose quickly, resulting in the inability of the combined salt bath's pH to decrease and the loss of the ability to adjust the pH; 2. Silicic acid may decompose into silicon dioxide, affecting the composition of the salt bath; 3. It may combine with cations in the salt bath to form precipitates and may also affect the ion exchange during the strengthening process. Therefore, when the hydrogen donor is selected as silicic acid, it is necessary to strictly control the relevant ratios of the salt bath composition for chemical strengthening and the temperatures of various processes.

[0028] The present invention also provides a method for preparing a salt bath composition for chemical strengthening, which is used to prepare the above-mentioned salt bath composition for chemical strengthening, and includes the following steps: Mix metal nitrate, a hydrogen donor, and possible other salt bath components to form a salt bath composition; Heat the salt bath composition to a first temperature to form a molten salt bath composition with or without precipitation; Keep the molten salt bath composition at the first temperature for a reaction, and the hydrogen donor provides hydrogen ions to the molten salt bath composition to make the molten salt bath composition reach neutral or weakly acidic; Among them, the first temperature is 380 - 470°C, and the reaction is kept at this temperature for 12 - 36 h.

[0029] Furthermore, it also includes the following step: stir the salt bath composition heated to the first temperature. The stirring method is to stir clockwise at least part of the molten salt bath composition, and the number of stirring times is more than 20 r. Through stirring, the components can be mixed more evenly.

[0030] Furthermore, a method for preparing a salt bath composition for chemical strengthening, which is used to prepare the above-mentioned salt bath composition for chemical strengthening, is characterized in that it includes the following steps: Mix metal nitrate and possible other salt bath components; Heat the mixture to the first temperature to form a molten composition with or without precipitation; Add an inhibitor to the molten composition; Keep the molten salt bath composition at the first temperature for a reaction, and the inhibitor provides inhibitory ions to the molten salt bath composition. Among them, the first temperature is 380 - 470 °C, and the heat preservation reaction is carried out at this temperature for 12 - 36 h.

[0031] Further, mix the metal nitrate and possible other salt bath components; Heat the mixture to the first temperature to form a molten composition with or without precipitation; Add an inhibitor to the molten composition; Keep the molten salt bath composition under heat preservation reaction at the first temperature, and the hydrogen - supplying substance provides hydrogen ions to the molten salt bath composition to make the molten salt bath composition acidic; Among them, the first temperature is 380 - 470 °C, and the heat preservation reaction is carried out at this temperature for 12 - 36 h.

[0032] Further, a salt bath composition for chemical strengthening is also provided, including the following steps: Raise the molten salt bath composition to the second temperature Immerse the IOX glass to be treated into the molten salt bath composition for ion exchange between the molten salt bath composition and the glass to strengthen the glass; Monitor the pH value of the mixed salt bath; If the pH of the mixed salt bath is greater than or equal to 8, lower the temperature of the mixed salt bath to the third temperature, then add an additional hydrogen - supplying substance and keep it under heat preservation; Among them, the second temperature is 360 - 600 °C, and the strengthening treatment time is 0.5 - 12 h; The additional hydrogen - supplying substance is 0.1% - 1.5% of the mass of the mixed salt bath; The third temperature is 380 - 470 °C, and the heat preservation is carried out at this temperature for 18 - 36 h; In each round of strengthening treatment, the mass of the glass put in is 1% - 5% of the mass of the mixed salt bath.

[0033] Further, a chemical strengthening method is provided, which also includes the following steps: when adding the hydrogen - supplying substance and / or after adding the hydrogen - supplying substance, stir the salt bath composition. The stirring method is to stir at least part of the salt bath composition in a molten state clockwise, and the number of stirring times is more than 20 r. Through stirring, the components can be mixed more evenly.

[0034] Further, in each round of strengthening treatment, ion sieves are also added in an amount of 0.5% - 1% of the mass of the mixed salt bath. As an impurity ion adsorption material, the ion sieve can effectively solve the problems existing in using sodium phosphate and / or potassium phosphate as impurity ion removal materials. In the use of the salt bath, the free alkali metal cations existing in the ion sieve network structure are used for ion exchange with the impurity ions in the salt bath, enabling the impurity ions in the salt bath to diffuse into the interior of the ion sieve channels and be selectively absorbed by the ion sieve. The selective ion exchange of the ion sieve and the ion exchange carried out during glass chemical strengthening can be synchronized, and the ion sieve can be completely non-contact with the glass sample.

[0035] Preferably, the third temperature is 400 - 450 °C.

[0036] In the present invention, the glass to be IOX can be selected as glass or glass-ceramics containing a crystalline phase.

[0037] The present invention also provides a strengthened material product obtained by strengthening with the above-mentioned salt bath composition for chemical strengthening.

[0038] Compared with the prior art, the present invention has the following beneficial effects: 1. The salt bath composition for chemical strengthening provided by the present invention includes an inhibitor, which can inhibit the corrosion of the surface of the stainless steel container and the dissolution of metal elements by the salt bath composition under suitable process conditions, improving the yield of IOX glass.

[0039] 2. The salt bath composition for chemical strengthening provided by the present invention includes a hydrogen-supplying substance, which can continuously supply hydrogen ions during the salt bath process to change the acidity and alkalinity of the salt bath composition, making the salt bath that should maintain alkalinity at high temperature become acidic or neutral. When the salt bath composition maintains neutrality or acidity, it will inhibit the formation of colloids and metal oxides in the high-temperature salt bath, avoiding the "protrusion" defect caused by the attachment of metal oxides to the glass surface; at the same time, inhibiting the formation of colloids and metal oxides can also avoid the "depression" defect caused by the shedding of metal oxides after being pressed into the glass surface layer by the surface stress; in summary, by adding a hydrogen-supplying substance to the salt bath composition for chemical strengthening, the dot-like defects that have plagued the industry for a long time can be greatly eliminated, and the yield of IOX glass can be greatly improved.

[0040] 3. The present application also optimizes the preparation method of the salt bath composition. In the present application, when preparing the salt bath composition, the inhibitor is first mixed with metal nitrates and then heated to the first temperature. Through reasonable temperature control in the present application, the yield of the product can still be maintained at a high level even after multiple rounds of chemical strengthening, greatly reducing the processing cycle; at the same time, while effectively avoiding the corrosion of the glass surface by the alkaline salt bath, the transmittance of IOX glass is increased, and the B value and haze are reduced.

[0041] 4. The present application also optimizes the processing technology of IOX glass. By detecting the pH value of the mixed salt bath and adding an inhibitor to the mixed salt bath to change the salt bath environment, the purpose of improving the yield rate is achieved. In the present application, the salt bath environment can be changed through a specific process, thereby inhibiting the generation of dot-like defects. There is no need to adopt the method in the prior art of replacing the entire salt bath material and using a brand-new salt bath to process IOX glass. Compared with the prior art, the cost is extremely low, and it is more environmentally friendly and scientific. Specific Embodiments

[0042] The corresponding test methods and explanations of relevant measurement methods involved in the application are as follows: Salt Bath pH Test Method Take an appropriate amount of the molten salt bath to be measured for pH from the strengthening furnace. After the molten salt bath cools down, accurately weigh 1.00 g of the cooled solid substance into a 50 ml beaker, add 10 ml of deionized water, and shake until the solid substance dissolves. Use a pH meter to measure the pH of the obtained solution, which is recorded as the pH of the salt bath. In the present invention, an existing probe pH meter can be used for the pH meter, such as the Leici PHS-2F type pH meter.

[0043] In the present application, referring to the national standard "GB / T 7962.12-2010 Test Methods for Colorless Optical Glass - Part 12: Spectral Transmittance", a haze meter is used to test the transmittance, haze, and b value of the microcrystalline glass of the present application. Specifically, use a haze meter to test the transmittance, haze, and b value of 5 microcrystalline glass pieces of the same batch for light of different wavelengths. Take the average values of the b values and haze measured for the 5 microcrystalline glass pieces, which are respectively recorded as the b value result and haze result of the microcrystalline glass. Take the average value of the transmittance of the 5 microcrystalline glass pieces measured for light at a wavelength of 550 nm, which is recorded as the transmittance result of the microcrystalline glass at a wavelength of 550 nm. The haze meter used in the test of the present application is the Konica Minolta Spectrophotometer CM-3600A from Japan. The light receiving optical system is transmission, the spectral splitting method is a plane diffraction grating, the wavelength range is 360 nm - 740 nm, the wavelength interval is 10 nm, the illumination light source is a pulsed xenon lamp × 4, the environmental temperature where the instrument is placed is 24 °C, and the air humidity is 40%.

[0044] In the present application, according to the different strengthening processes, it includes the glass to be IOX and IOX glass. The glass to be IOX refers to the glass before it undergoes IOX, and the IOX glass refers to the glass that has undergone IOX.

[0045] IOX glass appearance inspection: Visually observe the tempered micro-ceramic glass under a white fluorescent lamp with an illumination of 2000 Lux. Keep the glass 1 cm to 3 cm away from the black background, tilt the glass 30 to 80 degrees, and observe at a distance of 30 cm to 50 cm from the glass surface.

[0046] Please note that commonly used glasses for IOX include but are not limited to soda-lime-silicon, soda-aluminum-silicon, lithium-aluminum-silicon, magnesium-aluminum-silicon system glasses and microcrystalline glass. The present invention is also applicable to the processing of various IOX glasses.

[0047] In the prior art, when the glass is at IOX, surface defects such as point-like particles often occur. What is puzzling is that through microscopic observation, it can be found that more than 20% of these point-like defects are convex, while the other part is concave. This phenomenon first appeared on soda-lime-silica glass. With the development of the industry, glasses with larger IOX scales, such as sodium aluminum silicon, lithium aluminum silicon glass and microcrystalline glass, have been used. Larger scale IOX has also caused the salt bath to deteriorate and poison. Therefore, it is necessary to add ion sieves, anhydrous sodium phosphate and other substances to the salt bath to remove junk ions and restore the salt bath. Practice has shown that the use of ion sieves and anhydrous sodium phosphate increases the frequency of the above-mentioned point-like defects. Whether this defect is caused by changes in glass materials, salt bath management, or additives such as ion sieves and anhydrous sodium phosphate, it has not been effectively solved.

[0048] This defect causes a high rate of defective batches. When defects occur, usually about 70% of a batch of IOX glass has problems, and rework is difficult and the rework yield is also low. Usually, the effective way to solve this problem is to replace the entire salt bath material and use a brand new salt bath to re-IOX glass. However, such a solution is extremely costly, environmentally unfriendly, and unscientific. The cause of this problem is still unclear and has become a pain point in the industry.

[0049] The applicant has found through extensive research that point defects are mainly caused by the presence of more OH- in the salt bath and the presence of NO3 - It is caused by the reaction between ions and IOX crucible (stainless steel). The cause analysis is as follows: 1. Metal element release mechanism: The container crucible and glass carrier support used by IOX are made of stainless steel. In the strong oxidizing environment of nitrate salt bath, the protective film on the surface of stainless steel (such as M2O3, M is Cr, Fe and other metal elements) is destroyed; metal ions react with NO3 at high temperature. - Oxidation reaction occurs under the action of oxidant to generate M 3+ ion: M+3NO3 - →M 3+ +3NO2+3O2- (Formula 1) Sodium phosphate anhydrous is a salt of a strong base and a weak acid, and the ion sieve is a neutral substance. However, both are prone to absorb water in the air, thus generating OH on the surface - When sodium phosphate anhydrous and the ion sieve are added to the salt bath, OH - also enters the salt bath accordingly. OH - makes the salt bath alkaline, further promoting the corrosion of stainless steel and the dissolution of M.

[0050] 2. Formation and transformation of M 3+ →M(OH)3 colloid: M 3+ undergoes a hydrolysis reaction in a weakly alkaline environment to generate Fe(OH)3 colloid: M 3+ +3OH - →M(OH)3↓(Formula 2) Since the salt bath is a high-temperature system, M(OH)3 quickly dehydrates and transforms into extremely fine particles of M2O3: 2M(OH)3→M2O3+3H2O (>200 °C)(Formula 3) The particle size of these M2O3 particles is usually between 10 and 100 nanometers, with slow sedimentation and suspension in the salt bath.

[0051] 3. Particle migration and glass surface deposition mechanism: Convection in the molten salt and changes in the interfacial tension make it easy for M2O3 microparticles to aggregate towards the glass surface; During the IOX process, the glass surface has a high surface energy and a high stress gradient, becoming an "active site" for impurity adsorption. The particles are pressed into the glass surface layer by the surface stress, forming a "semi-embedded" attachment structure; Some particles fall off during the embedding process, thus forming sunken dot-like defects.

[0052] Summary of the defect mechanism: Stainless steel releases metal elements in the oxidative salt bath, and after being colloidized and transformed into M2O3 microparticles in an alkaline environment, they are deposited and embedded on the glass surface, finally forming a defect with some convex points and some depressions that is stable.

[0053] Based on the above research, aiming at the "root cause" of the problem, the object of the present invention is to effectively avoid the erosion of the container surface by the salt bath composition during the batch chemical strengthening process, prevent the occurrence of (Formula 2), or the reverse occurrence of (Formula 2), so as to avoid the formation of dot-like defects on the glass surface and improve the yield of the glass.

[0054] To achieve the above object, the present invention provides a salt bath composition for chemical strengthening, including by mass percentage: 50% to 99.9% of metal nitrate and more than 0.1% of inhibitor; The inhibitor is used to inhibit the corrosion of the stainless steel layer on the surface of the container and the dissolution of M during the chemical strengthening of the IOX process. In this application, there is no upper limit on the content of the inhibitor. The role of the inhibitor is to change the environment of the salt bath composition, so that the free M ions in the salt bath composition do not form oxide particles, and at the same time reduce the dissolution of metal elements from the container material, avoiding the appearance of surface dot-like particles on the glass after IOX and improving the yield of IOX glass. In this application, the content of the inhibitor is preferably 0.1 to 1.5%, and further preferably 0.8 to 1.5%.

[0055] Furthermore, the inhibitor includes a hydrogen-supplying substance, and the hydrogen-supplying substance is used to provide hydrogen ions to the salt bath composition. The hydrogen-supplying substance is used to provide hydrogen ions to the salt bath composition. Hydrogen ions can change the slightly alkaline environment of the salt bath to be neutral or weakly acidic. According to the aforementioned causes, when there is not enough OH - in the salt bath composition, the forward reaction of (Equation 2) will be inhibited, thereby inhibiting the formation of colloids and metal oxides in the high-temperature salt bath, avoiding the "protrusion" defect caused by the attachment of metal oxides to the glass surface; at the same time, inhibiting the formation of colloids can also avoid the "depression" defect caused by the detachment of metal oxides after being pressed into the glass surface layer by surface stress; since the reaction of (Equation 2) cannot occur effectively or occurs reversely, the remaining metal M in the salt bath is in a small amount of ionic state, so it will not cause (Equation 1) to occur in the positive direction, reducing the erosion of the salt bath on the container. In summary, by adding a hydrogen-supplying substance to the salt bath composition for chemical strengthening, the dot-like defects that have troubled the industry for a long time can be greatly eliminated, and the yield of IOX glass can be greatly improved. There is no upper limit on the content of the hydrogen-supplying substance, and it is preferably 0.1 to 1.5%, and further preferably 0.8 to 1.5%.

[0056] Furthermore, the formation temperature of the salt bath composition for chemical strengthening is the first temperature. When the salt bath composition for chemical strengthening is less than or equal to the first temperature, the hydrogen-supplying substance is used to provide hydrogen ions to the salt bath composition; wherein, the first temperature is 380 to 470 °C, and it is kept standing at this temperature for 12 to 36 h. The hydrogen-supplying substance in this application will decompose when the temperature is higher than 380 to 470 °C, and its activity is too low when the temperature is lower than 380 to 470 °C; both of the above will cause the hydrogen-supplying substance in the salt bath to be unable to release enough hydrogen ions, thus affecting the salt bath effect and further affecting the yield of the IOX glass finished product. A sufficiently long standing time is beneficial to the sedimentation of the metal oxides that have already formed in the salt bath, avoiding the attachment of suspended metal oxide particles to the glass surface after the glass enters the salt bath. The standing time is also one of the key points of the present invention.

[0057] Further, the working temperature of the salt bath composition for chemical strengthening is the second temperature. When the salt bath composition for chemical strengthening is at the second temperature, the strengthening treatment time of the salt bath composition is 0.5 to 12 h; Among them, the second temperature is 360 to 600 °C. The second temperature is the temperature during chemical strengthening and is a process condition of IOX, which is different from the first temperature. It should be noted that the time of IOX is related to the temperature and the type of glass. Different types of glass correspond to different times and temperatures of IOX. When the glass is LAS glass, preferably it is 370 to 500 °C, and more preferably it is 380 °C.

[0058] Further, the second temperature is 450 - 540 °C, and the strengthening treatment time is 3 to 7 h; Further, the second temperature is 500 - 530 °C. In some embodiments, when the temperature is between 450 - 540 °C, or further, between 500 - 530 °C, the salt bath composition can achieve better effects. Further, the metal nitrate includes, based on the mass percentage of the salt bath composition: 0 to 89.99% of sodium nitrate, 0 to 89.99% of potassium nitrate; preferably, it includes: 50 to 89.99% of sodium nitrate, 0 to 39.99% of potassium nitrate, 0.03% to 0.1% of lithium nitrate.

[0059] Further, the metal nitrate further includes an antibacterial component, and the antibacterial component includes at least one of silver nitrate, copper nitrate, and zinc nitrate.

[0060] Sodium nitrate is one of the components of the salt bath composition. An appropriate content of sodium nitrate can ensure that there are sufficient sodium ions to exchange with lithium ions in the glass, thereby increasing the depth of the ion exchange layer. If the content of sodium ions is too low, the corresponding content of potassium ions is too high, which affects the exchange of potassium ions and lithium ions and reduces the depth of the ion exchange layer; conversely, if the content of sodium ions is too high, the corresponding content of potassium ions is too low, which affects the exchange of potassium ions and sodium ions and reduces the surface compressive stress of the glass.

[0061] Optionally but not absolutely, the mass percentage of sodium nitrate in the active component can be 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, or 75%, or within the numerical range formed by any two of the above specific values as endpoints.

[0062] Potassium nitrate is one of the components of the salt bath composition. Only by providing a sufficient potassium nitrate content in the salt bath composition can it meet the requirement of rapid exchange of potassium ions with sodium ions in the glass during the chemical strengthening process, thereby increasing the surface compressive stress of the glass. The radius of potassium ions (1.38 Å) is larger than that of sodium ions (0.95 Å) and lithium ions (0.76 Å). After replacement, it causes "jamming expansion" on the glass surface, forming a compressive stress layer, which significantly improves the impact resistance and scratch resistance.

[0063] Optionally but not necessarily, the mass percentage of potassium nitrate in the active components can be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%, or within the numerical range formed by any two of the above specific values as endpoints.

[0064] Lithium nitrate is mixed in the salt bath in a relatively small proportion to adjust the ionic activity of the molten salt or assist in a specific crystallization process. In the strengthening of lithium-containing glass-ceramics, lithium nitrate can promote the exchange of lithium ions with sodium / potassium ions and enhance the depth of the stress layer.

[0065] Optionally but not necessarily, the mass percentage of potassium nitrate in the active components can be 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, or within the numerical range formed by any two of the above specific values as endpoints.

[0066] In the current continuous strengthening process, the addition of phosphates and the application of ion sieves will make the salt bath alkaline, leading to corrosion problems. By adding hydrogen-supplying substances to neutralize this alkalinity, it is expected to solve such problems.

[0067] Furthermore, the hydrogen-supplying substances include one or more of silicic acid, sulfuric acid, and boric acid.

[0068] Treatment with strong acids may cause uneven corrosion and defects, while silicic acid may be milder. Therefore, the hydrogen-supplying substance is preferably silicic acid or a solution containing silicic acid.

[0069] Furthermore, when the hydrogen-supplying substance is silicic acid, the mass percentage of the silicic acid is 0.1% - 1.5%. Preferably, the mass percentage of the silicic acid is 0.1% - 0.8%.

[0070] However, adding silicic acid may bring some problems: 1. The decomposition temperature of silicic acid is around 150°C. If the temperature of the combined salt bath is raised above 300°C and then silicic acid is added, the silicic acid will decompose quickly, resulting in the inability of the combined salt bath to lower the pH and lose the ability to adjust the pH; 2. Silicic acid may decompose into silicon dioxide, affecting the composition of the salt bath; 3. It may combine with the cations in the salt bath to form precipitates and may also affect the ion exchange in the strengthening process. Therefore, when the hydrogen donor is selected as silicic acid, it is necessary to strictly control the relevant ratios of the salt bath composition for chemical strengthening and the temperatures of various processes.

[0071] The present invention also provides a method for preparing a salt bath composition for chemical strengthening, which is used to prepare the above-mentioned salt bath composition for chemical strengthening, and includes the following steps: Mix metal nitrate, a hydrogen donor, and possible other salt bath components to form a salt bath composition; Heat the salt bath composition to a first temperature to form a molten salt bath composition with or without precipitates; Keep the molten salt bath composition at the first temperature for a reaction, and the hydrogen donor provides hydrogen ions to the molten salt bath composition to make the molten salt bath composition acidic; Among them, the first temperature is 380 - 470°C, and the reaction is kept at this temperature for 12 - 36 hours.

[0072] Furthermore, it further includes the following step: stir the salt bath composition heated to the first temperature. The stirring method is to stir clockwise at least part of the molten salt bath composition, and the number of stirrings is more than 20 r. Through stirring, the components can be mixed more evenly.

[0073] Furthermore, a method for preparing a salt bath composition for chemical strengthening, which is used to prepare the salt bath composition for chemical strengthening as described in any one of claims 1 - 8, is characterized in that it includes the following steps: Mix metal nitrate and possible other salt bath components; Heat the mixture to the first temperature to form a molten composition with or without precipitates; Add an inhibitor to the molten composition; Keep the molten salt bath composition at the first temperature for a reaction, and the inhibitor provides inhibitory ions to the molten salt bath composition; Among them, the first temperature is 380 - 470°C, and the reaction is kept at this temperature for 12 - 36 hours.

[0074] Furthermore, mix metal nitrate and possible other salt bath components; Heat the mixture to the first temperature to form a molten composition with or without precipitates; Add a hydrogen donor to the molten composition; Keep the molten salt bath composition at a first temperature for a reaction, and the hydrogen donor provides hydrogen ions to the molten salt bath composition to make the molten salt bath composition acidic; Wherein, the first temperature is 380 - 470 °C, and the reaction is carried out at this temperature for 12 - 36 h.

[0075] Furthermore, a salt bath composition for chemical strengthening is also provided, including the following steps: Raise the molten salt bath composition to a second temperature Immerse the IOX glass to be treated into the molten salt bath composition to perform ion exchange between the molten salt bath composition and the glass, and strengthen the glass; Monitor the pH value of the mixed salt bath; If the pH of the mixed salt bath is greater than or equal to 8, lower the temperature of the mixed salt bath to a third temperature, then add an additional hydrogen donor and keep it warm; Wherein, the second temperature is 360 - 600 °C, and the strengthening treatment time is 0.5 - 12 h; The additional hydrogen donor is 0.1% - 1.5% of the mass of the mixed salt bath; The third temperature is 380 - 470 °C, and it is kept warm at this temperature for 18 - 36 h; In each round of strengthening treatment, the mass of the glass put in is 1% - 5% of the mass of the mixed salt bath.

[0076] Furthermore, a chemical strengthening method is provided, which also includes the following steps: when adding the hydrogen donor and / or after adding the hydrogen donor, stir the salt bath composition. The stirring method is to stir at least part of the salt bath composition in a molten state clockwise, and the number of stirring times is more than 20 r. Through stirring, the components can be mixed more evenly.

[0077] Furthermore, in each round of strengthening treatment, 0.5% - 1% of the ion sieve of the mass of the mixed salt bath is also put in. The ion sieve, as an impurity ion adsorption material, can effectively solve the problems existing in using sodium phosphate and / or potassium phosphate as impurity ion removal materials. In the use of the salt bath, the free alkali metal cations existing in the ion sieve network structure perform ion exchange with the impurity ions in the salt bath, enabling the impurity ions in the salt bath to diffuse into the ion sieve channel interior and be selectively absorbed by the ion sieve. The selective ion exchange of the ion sieve and the ion exchange carried out during glass chemical strengthening can be synchronized, and the ion sieve can be completely non - contact with the glass sample.

[0078] Preferably, the third temperature is 400 - 450 °C.

[0079] In the present invention, the IOX glass can be selected as ordinary glass or glass-ceramics.

[0080] The salt bath composition for chemical strengthening provided by the present invention includes an inhibitor, which, under appropriate process conditions, can inhibit the corrosion of the surface of the stainless steel container by the salt bath composition and the dissolution of metal elements, thereby improving the yield of the IOX glass.

[0081] The salt bath composition for chemical strengthening provided by the present invention includes a hydrogen-supplying substance, which can continuously supply hydrogen ions during the salt bath process to change the acidity and alkalinity of the salt bath composition, making the salt bath that should maintain alkalinity at high temperature become acidic or neutral, inhibiting the formation of colloids in the high-temperature salt bath, and avoiding the "protrusion" defect caused by adhering to the glass surface; at the same time, inhibiting the formation of colloids can also avoid the "depression" defect caused by falling off after being pressed into the glass surface layer by surface stress; in summary, adding a hydrogen-supplying substance to the salt bath composition for chemical strengthening can greatly eliminate the dot-like defects that have troubled the industry for a long time and greatly improve the yield of the IOX glass.

[0082] This application also optimizes the production method of the salt bath composition. In this application, when preparing the salt bath composition, the inhibitor is first mixed with metal nitrate and then heated to the first temperature. Through reasonable temperature control in this application, the yield of the product can still remain at a high level even after multiple rounds of chemical strengthening, greatly reducing the processing cycle; at the same time, while effectively avoiding the corrosion of the glass surface by the alkaline salt bath, the transmittance of the IOX glass is increased, and the B value and haze are reduced.

[0083] This application also optimizes the processing technology of the IOX glass. By detecting the yield of the mixed salt bath, when the yield of the mixed salt bath is less than or equal to a specific value, an inhibitor is added to change the environment of the salt bath, so as to achieve the purpose of improving the yield; in this application, the environment of the salt bath can be changed through a specific process, thereby inhibiting the generation of dot-like defects, without the need to replace the entire salt bath material as in the prior art and use a new salt bath to process the IOX glass. Compared with the prior art, the cost is extremely low, and it is more environmentally friendly and scientific.

[0084] The salt bath composition for chemical strengthening provided by the present invention can generate hydrogen ions under appropriate process conditions. When using a stainless steel crucible to hold the molten salt bath mainly composed of nitrate, the hydrogen ions continuously neutralize OH - It can avoid the erosion of the salt bath OH in the strong oxidation environment of the molten nitrate - on the stainless steel crucible, and further avoid the formation of metal compounds by the metal elements released due to the erosion to pollute the salt bath, thereby improving the yield of the glass product.

[0085] The salt bath composition for chemical strengthening provided by the present invention needs to be heated to a temperature between 380 and 470 °C first. By keeping the hydrogen - supplying substance in the present application within the temperature range of 380 - 470 °C, it is possible to avoid the decomposition of the hydrogen - supplying substance when the temperature is higher than 380 - 470 °C, and the situation where the activity is too low when the temperature is lower than 380 - 470 °C. This ensures that the hydrogen - supplying substance in the salt bath can continuously release sufficient hydrogen ions, keeping the OH - content within a stable range, guaranteeing the salt bath effect and further ensuring the quality of the chemically strengthened glass products. The hydrogen - supplying substance in the salt bath composition for chemical strengthening provided by the present invention is preferably silicic acid or a solution containing silicic acid. When silicic acid is within the temperature range of 380 - 470 °C, it has good dispersibility, does not cause local pH fluctuations, and avoids affecting the uniformity of the ion - exchange reaction. At the same time, it can also avoid the decomposition of silicic acid at an appropriate temperature, preventing the problem of impurity precipitation. This not only ensures the pH - regulating ability of silicic acid but also avoids introducing impurities.

[0086] When the salt bath composition for chemical strengthening provided by the present invention is used for strengthening, the chemical strengthening time needs to be guaranteed to be 0.5 - 12 h. When the reaction time is 0.5 - 12 h, it can effectively avoid local pH fluctuations and ensure the uniformity of the ion - exchange reaction.

[0087] This application also optimizes the production method of the salt bath composition. In this application, when preparing the salt bath composition, the hydrogen - supplying substance is first mixed with metal nitrate and then heated to the first temperature. Through reasonable temperature control in this application, even after multiple rounds of chemical strengthening, the pH of the salt bath can still be maintained within an appropriate range, greatly reducing the processing cycle. At the same time, while effectively avoiding the corrosion of the glass surface by the alkaline salt bath, it improves the transmittance of the IOX glass, reduces the B value and haze.

[0088] The processing technology of the salt bath processing is optimized. By detecting the yield rate of the mixed salt bath, when the pH of the mixed salt bath is greater than or equal to 8, hydrogen - supplying substances such as silicic acid are added to regulate the pH. And when adding hydrogen - supplying substances to the high - temperature chemical strengthening salt bath in this application, a method of adding hydrogen - supplying substances while cooling is adopted. The temperature range for adding while cooling is 380 - 470 °C. As mentioned above, when the temperature is within this range, the added hydrogen - supplying substance can maintain sufficient activity and will not decompose. Therefore, the processing technology in this application can effectively control the pH of the mixed salt bath within an appropriate range and improve the utilization rate of the salt bath solution.

[0089] In the present application, the hydrogen donor is preferably silicic acid or a solution containing silicic acid. The raw material of silicic acid is in powder form. By mixing the powdered silicic acid and metal nitrate powder and placing them in a toughening furnace and heating to a first temperature, a salt bath composition in at least a partially molten state is obtained. The first temperature is 380 - 470 °C, and it is kept standing at this temperature for 12 - 36 h to obtain a salt bath composition in at least a partially molten state.

[0090] When the salt bath composition for chemical strengthening provided by the present invention is used for chemical strengthening, the temperature needs to be first heated to between 360 - 600 °C, preferably between 380 - 470 °C. The hydrogen donor in the present application will decompose when the temperature is higher than 380 - 470 °C, and its activity is too low when the temperature is lower than 380 - 470 °C; both of the above will cause the hydrogen donor in the salt bath to be unable to release sufficient hydrogen ions, resulting in a high content of OH - in the salt bath, affecting the salt bath effect and further affecting the quality of the strengthened glass product.

[0091] In some embodiments, when the silicic acid is between 380 - 470 °C, the dispersibility of the silicic acid is good, and it will not cause local pH fluctuations, avoiding affecting the uniformity of the ion exchange reaction; at the same time, it can also avoid the problem that high temperature will accelerate the decomposition of silicic acid and generate silicon dioxide precipitation, not only ensuring the pH adjustment ability of silicic acid, but also avoiding the introduction of silicon dioxide impurities.

[0092] When the salt bath composition for chemical strengthening provided by the present invention is used for strengthening, the chemical strengthening time needs to be guaranteed to be 0.5 - 12 h, preferably between 4 - 7 h. When the strengthening time is between 4 - 7 h, it can effectively avoid local pH fluctuations and ensure the uniformity of the ion exchange reaction.

[0093] In some embodiments of the present application, the processing technology of the salt bath processing is optimized. By detecting the yield rate of the mixed salt bath, when the pH of the mixed salt bath is greater than or equal to 8, hydrogen donors such as silicic acid are added to regulate the pH; and when adding hydrogen donors to the high-temperature chemical strengthening salt bath in the present application, a method of adding hydrogen donors while cooling is adopted. The temperature range for adding while cooling is 380 - 470 °C. As described above, when the temperature is within this range, the added hydrogen donor can maintain sufficient activity and will not decompose, and can effectively control the pH of the mixed salt bath within a suitable range.

[0094] In the present application, the salt bath composition basically does not contain carbonates and / or chlorides. "Basically does not contain" means that the salt bath composition of the present application does not actively add substances containing carbonates and / or chlorides, and the content of carbonates and / or chlorides as impurities is less than 1000 ppm. The carbonates in the present application are, for example, potassium carbonate, sodium carbonate, lithium carbonate, etc., and the chlorides are, for example, potassium chloride, sodium chloride, lithium chloride, etc. In some embodiments of the present application, the carbonate is at least one of potassium carbonate, sodium carbonate, and lithium carbonate. In some embodiments of the present application, the chloride is at least one of potassium chloride, sodium chloride, and lithium chloride.

[0095] Example 1 A method for strengthening a salt bath composition for chemical strengthening, the steps are as follows, Step 1: Weigh 69.98% sodium nitrate, 29.34% potassium nitrate, 0.03% lithium nitrate, 0.25% silver nitrate, 0.25% copper nitrate, and 0.15% silicic acid according to the mass ratio of the salt bath composition for chemical strengthening; Step 2: Raise the temperature of sodium nitrate, potassium nitrate, lithium nitrate, silver nitrate, copper nitrate, and silicic acid to the first temperature of 380 °C and keep it warm for 12 h to obtain a mixed salt bath; Step 3: Raise the temperature of the mixed salt bath to the second temperature of 530 °C, and put the microcrystalline glass and the ion sieve into the mixed salt bath in batches to carry out strengthening treatment on the microcrystalline glass. The strengthening time is 5 h. Among them, the masses of the microcrystalline glass and the ion sieve are 3% and 0.5% of the mixed salt bath respectively; Step 4: Repeat Step 3, and use the same mixed salt bath to carry out strengthening treatment on multiple batches of microcrystalline glass, a total of six batches, and monitor the pH of the mixed salt bath during the strengthening process.

[0096] Example 2 A method for strengthening a salt bath composition for chemical strengthening, the steps are as follows, Step 1: Weigh 69.98% sodium nitrate, 29.19% potassium nitrate, 0.03% lithium nitrate, 0.25% silver nitrate, 0.25% zinc nitrate, and 0.3% silicic acid according to the mass ratio of the salt bath composition for chemical strengthening; Step 2: Raise the temperature of sodium nitrate, potassium nitrate, lithium nitrate, silver nitrate, zinc nitrate, and silicic acid to the first temperature of 420 °C and keep it warm for 24 h to obtain a mixed salt bath; Step 3: Raise the temperature of the mixed salt bath to the second temperature of 530 °C, and put the microcrystalline glass and the ion sieve into the mixed salt bath in batches to carry out strengthening treatment on the microcrystalline glass. The strengthening time is 7 h. Among them, the masses of the microcrystalline glass and the ion sieve are 3% and 0.5% of the mixed salt bath respectively; Step 4: Repeat Step 3, use the same mixed salt bath to strengthen multiple rounds of glass ceramics, for a total of six rounds, and monitor the pH of the mixed salt bath during the strengthening process.

[0097] Example 3 A strengthening method for a salt bath composition for chemical strengthening, the steps are as follows: Step 1: Weigh 69.98% sodium nitrate, 28.74% potassium nitrate, 0.03% lithium nitrate, 0.30% silver nitrate, 0.10% copper nitrate, 0.10% zinc nitrate, and 0.75% silicic acid according to the mass ratio of the salt bath composition for chemical strengthening. Step 2: Raise the temperature of sodium nitrate, potassium nitrate, lithium nitrate, silver nitrate, copper nitrate, zinc nitrate, and silicic acid to the first temperature of 450 °C and hold for 27 h to obtain a mixed salt bath. Step 3: Raise the temperature of the mixed salt bath to the second temperature of 530 °C, put the glass ceramics and the ion sieve into the mixed salt bath in batches, and strengthen the glass ceramics. The strengthening time is 6 h. Among them, the masses of the glass ceramics and the ion sieve are 3% and 0.5% of the mixed salt bath respectively. Step 4: Repeat Step 3, use the same mixed salt bath to strengthen multiple rounds of glass ceramics, for a total of six rounds, and monitor the pH of the mixed salt bath during the strengthening process.

[0098] Example 4 A strengthening method for a salt bath composition for chemical strengthening, the steps are as follows: Step 1: Weigh 69.98% sodium nitrate, 28.69% potassium nitrate, 0.03% lithium nitrate, 0.30% silver nitrate, 0.10% copper nitrate, 0.10% zinc nitrate, and 0.8% silicic acid according to the mass ratio of the salt bath composition for chemical strengthening. Step 2: Raise the temperature of sodium nitrate, potassium nitrate, lithium nitrate, silver nitrate, copper nitrate, zinc nitrate, and silicic acid to the first temperature of 460 °C and hold for 30 h to obtain a mixed salt bath. Step 3: Raise the temperature of the mixed salt bath to the second temperature of 530 °C, put the glass ceramics and the ion sieve into the mixed salt bath in batches, and strengthen the glass ceramics. The strengthening time is 5 h. Among them, the masses of the glass ceramics and the ion sieve are 3% and 0.5% of the mixed salt bath respectively. Step 4: Repeat Step 3, use the same mixed salt bath to strengthen multiple rounds of glass ceramics, for a total of six rounds, and monitor the pH of the mixed salt bath during the strengthening process.

[0099] Example 5 A strengthening method for a salt bath composition for chemical strengthening, the steps are as follows: Step 1: Weigh 69.98% sodium nitrate, 28.29% potassium nitrate, 0.03% lithium nitrate, 0.25% copper nitrate, 0.25% zinc nitrate, and 1.2% silicic acid according to the mass ratio of the salt bath composition for chemical strengthening; Step 2: Heat sodium nitrate, potassium nitrate, lithium nitrate, copper nitrate, zinc nitrate, and silicic acid to the first temperature of 460 °C and hold for 30 h to obtain a mixed salt bath; Step 3: Raise the temperature of the mixed salt bath to the second temperature of 530 °C, and put the microcrystalline glass and ion sieve into the mixed salt bath in batches to perform strengthening treatment on the microcrystalline glass. The strengthening time is 5 h. Among them, the masses of the microcrystalline glass and the ion sieve are 3% and 0.5% of the mixed salt bath respectively; Step 4: Repeat Step 3, use the same mixed salt bath to perform strengthening treatment on multiple rounds of microcrystalline glass, a total of six rounds, and monitor the pH of the mixed salt bath during the strengthening process.

[0100] Example 6 A strengthening method for a salt bath composition for chemical strengthening, the steps are as follows: Step 1: Weigh 69.98% sodium nitrate, 28.19% potassium nitrate, 0.03% lithium nitrate, 0.25% copper nitrate, 0.25% zinc nitrate, and 1.3% silicic acid according to the mass ratio of the salt bath composition for chemical strengthening; Step 2: Heat sodium nitrate, potassium nitrate, lithium nitrate, copper nitrate, zinc nitrate, and silicic acid to the first temperature of 470 °C and hold for 36 h to obtain a mixed salt bath; Step 3: Raise the temperature of the mixed salt bath to the second temperature of 530 °C, and put the microcrystalline glass and ion sieve into the mixed salt bath in batches to perform strengthening treatment on the microcrystalline glass. The strengthening time is 4 h. Among them, the masses of the microcrystalline glass and the ion sieve are 3% and 0.5% of the mixed salt bath respectively; Step 4: Repeat Step 3, use the same mixed salt bath to perform strengthening treatment on multiple rounds of microcrystalline glass, a total of six rounds, and monitor the pH of the mixed salt bath during the strengthening process.

[0101] Example 7 A strengthening method for a salt bath composition for chemical strengthening, the steps are as follows: Step 1: Weigh 69.98% sodium nitrate, 27.89% potassium nitrate, 0.03% lithium nitrate, 0.25% silver nitrate, 0.25% copper nitrate, 0.1% zinc nitrate, and 1.5% silicic acid according to the mass ratio of the salt bath composition for chemical strengthening; Step 2: Heat sodium nitrate, potassium nitrate, lithium nitrate, silver nitrate, copper nitrate, zinc nitrate, and silicic acid to the first temperature of 470 °C and hold for 36 h to obtain a mixed salt bath; Step 3: Raise the temperature of the mixed salt bath to the second temperature of 530°C. Put the glass-ceramics and the ion sieve into the mixed salt bath in turns, and perform strengthening treatment on the glass-ceramics for 4 hours. Among them, the masses of the glass-ceramics and the ion sieve are 3% and 0.5% of the mixed salt bath respectively; Step 4: Repeat Step 3, and perform strengthening treatment on multiple rounds of glass-ceramics using the same mixed salt bath, for a total of six rounds, and monitor the pH of the mixed salt bath during the strengthening process.

[0102] Example 8 A strengthening method for a salt bath composition for chemical strengthening, the steps are as follows. Step 1: Weigh 69.98% sodium nitrate, 28.74% potassium nitrate, 0.03% lithium nitrate, 0.30% silver nitrate, 0.10% copper nitrate, 0.10% zinc nitrate, and 0.75% boric acid according to the mass ratio of the salt bath composition for chemical strengthening; Step 2: Raise the temperature of sodium nitrate, potassium nitrate, lithium nitrate, silver nitrate, copper nitrate, zinc nitrate, and boric acid to the first temperature of 450°C and keep it warm for 27 hours to obtain a mixed salt bath; Step 3: Raise the temperature of the mixed salt bath to the second temperature of 530°C. Put the glass-ceramics and the ion sieve into the mixed salt bath in turns, and perform strengthening treatment on the glass-ceramics for 6 hours. Among them, the masses of the glass-ceramics and the ion sieve are 3% and 0.5% of the mixed salt bath respectively; Step 4: Repeat Step 3, and perform strengthening treatment on multiple rounds of glass-ceramics using the same mixed salt bath, for a total of six rounds, and monitor the pH of the mixed salt bath during the strengthening process.

[0103] Example 9 A strengthening method for a salt bath composition for chemical strengthening, the steps are as follows. Step 1: Weigh 69.98% sodium nitrate, 28.74% potassium nitrate, 0.03% lithium nitrate, 0.30% silver nitrate, 0.10% copper nitrate, 0.10% zinc nitrate, and 0.75% sulfuric acid according to the mass ratio of the salt bath composition for chemical strengthening; Step 2: Raise the temperature of sodium nitrate, potassium nitrate, lithium nitrate, silver nitrate, copper nitrate, zinc nitrate, and sulfuric acid to the first temperature of 450°C and keep it warm for 27 hours to obtain a mixed salt bath; Step 3: Raise the temperature of the mixed salt bath to the second temperature of 530°C. Put the glass-ceramics and the ion sieve into the mixed salt bath in turns, and perform strengthening treatment on the glass-ceramics for 6 hours. Among them, the masses of the glass-ceramics and the ion sieve are 3% and 0.5% of the mixed salt bath respectively; Step 4: Repeat Step 3, and perform strengthening treatment on multiple rounds of glass-ceramics using the same mixed salt bath, for a total of six rounds, and monitor the pH of the mixed salt bath during the strengthening process.

[0104] Comparative Example 1 A method for strengthening a salt bath composition for chemical strengthening, the steps are as follows: Step 1: Weigh 69.98% sodium nitrate, 29.49% potassium nitrate, 0.03% lithium nitrate, 0.25% silver nitrate, and 0.25% copper nitrate according to the mass ratio of the salt bath composition for chemical strengthening; Step 2: Raise sodium nitrate, potassium nitrate, lithium nitrate, silver nitrate, copper nitrate and silicic acid to the first temperature of 530 °C and keep it warm for 5 h to obtain a mixed salt bath; Step 3: Put the microcrystalline glass and ion sieve into the mixed salt bath in batches to strengthen the microcrystalline glass. The strengthening time is 5 h. Among them, the masses of the microcrystalline glass and the ion sieve are 3% and 0.5% of the mixed salt bath respectively; Step 4: Repeat Step 3, use the same mixed salt bath to strengthen multiple rounds of microcrystalline glass, a total of six rounds, and monitor the pH of the mixed salt bath during the strengthening process.

[0105] Comparative Example 2 A method for strengthening a salt bath composition for chemical strengthening, the steps are as follows: Step 1: Weigh 69.98% sodium nitrate, 29.49% potassium nitrate, 0.03% lithium nitrate, 0.25% silver nitrate, and 0.25% zinc nitrate according to the mass ratio of the salt bath composition for chemical strengthening; Step 2: Raise sodium nitrate, potassium nitrate, lithium nitrate, silver nitrate, zinc nitrate and silicic acid to the first temperature of 510 °C and keep it warm for 5 h to obtain a mixed salt bath; Step 3: Raise the temperature of the mixed salt bath to the second temperature of 530 °C, put the microcrystalline glass and ion sieve into the mixed salt bath in batches to strengthen the microcrystalline glass. The strengthening time is 5 h. Among them, the masses of the microcrystalline glass and the ion sieve are 3% and 0.5% of the mixed salt bath respectively; Step 4: Repeat Step 3, use the same mixed salt bath to strengthen multiple rounds of microcrystalline glass, a total of six rounds, and monitor the pH of the mixed salt bath during the strengthening process.

[0106] Comparative Example 3 A method for strengthening a salt bath composition for chemical strengthening, the steps are as follows: Step 1: Weigh 69.98% sodium nitrate, 29.49% potassium nitrate, 0.03% lithium nitrate, 0.10% silver nitrate, 0.30% copper nitrate, and 0.10% zinc nitrate according to the mass ratio of the salt bath composition for chemical strengthening; Step 2: Raise sodium nitrate, potassium nitrate, lithium nitrate, silver nitrate, copper nitrate, zinc nitrate and silicic acid to the first temperature of 490 °C and keep it warm for 5 h to obtain a mixed salt bath; Step 3: Raise the temperature of the mixed salt bath to the second temperature of 530°C. Put the glass-ceramics and the ion sieve into the mixed salt bath in turns, and perform strengthening treatment on the glass-ceramics for 5 hours. Among them, the masses of the glass-ceramics and the ion sieve are 3% and 0.5% of the mixed salt bath respectively; Step 4: Repeat Step 3, and perform strengthening treatment on multiple rounds of glass-ceramics using the same mixed salt bath, with a total of six rounds. Monitor the pH of the mixed salt bath during the strengthening process.

[0107] Tables 1-7 summarize the mixed salt bath formulations and the corresponding reaction parameters of the above examples and comparative examples.

[0108] Table 1

[0109] Table 2

[0110] Table 3

[0111] Table 4

[0112] It can be seen from the results in Table 3 that, compared with the comparative example without the addition of the hydrogen donor substance, the pH of the mixed salt bath in the example did not rise above 8 after the fifth round of strengthening. At the same time, by regulating the ratio of the mixed salt bath, the first temperature, the heat preservation time, and the strengthening time, the increase in the pH of the mixed salt bath can be further inhibited. Especially in Example 3, after the sixth strengthening, the pH of the mixed salt bath is only 8.01. This is because in the example of the present invention, the strengthening salt composition is improved, silicic acid is introduced, and silicic acid and nitrate are heated together to reduce the thermal decomposition of silicic acid. After adding silicic acid, a floating substance is formed on the surface of the salt bath. After keeping warm for a long enough time, the floating substance decomposes, avoiding adsorption on the glass surface. Through the introduction of silicic acid, the reduction of silicic acid decomposition, and the avoidance of the influence of the floating substance, the example of the present invention effectively reduces the pH of the salt bath, reduces the corrosion of the surface of the glass to be IOX caused by the increase in the pH of the salt bath during the industrial continuous production process, and improves the strengthening effect of the mixed salt bath on the glass to be IOX. Therefore, the glass strengthened in the example of the present invention has a higher yield rate, transmittance, and lower B value and haze.

[0113] Using the mixed salt bath of Preferred Embodiment 3, consisting of 69.98% sodium nitrate, 28.74% potassium nitrate, 0.03% lithium nitrate, 0.10% copper nitrate, 0.10% zinc nitrate, and 0.75% silicic acid, as the object, after strengthening multiple rounds of IOX glass to be strengthened, the pH of the mixed salt bath has risen above 8. At this time, the temperature of the salt bath is 530 °C. Before the next round of strengthening, the temperature of the mixed salt bath is reduced to the third temperature, and then an additional hydrogen-supplying substance (accounting for 0.1% - 1.5% of the mass of the mixed salt bath) is added and kept warm, and the pH is adjusted to 6 - 7. The specific parameters are shown in Table 5.

[0114] Table 5

[0115] Experiments were carried out with reference to the substances in Table 6 and Table 7. The substances in Table 7 are the same as those in Table 6, except for the composition. Only the specific values and results are listed in Table 7, without a table header.

[0116] Table 6

[0117] Table 7

[0118] From these results, it can be seen that adding 0.1% - 0.8% of silicic acid to the mixed salt bath with a higher pH and keeping it warm at 420 - 450 °C for 24 - 36 h can effectively adjust the pH of the mixed salt bath to an appropriate range. After such treatment, the corrosion of the IOX glass surface caused by too high pH of the salt bath can be reduced.

[0119] In summary, the present invention effectively avoids the corrosion of the IOX glass surface by the alkaline salt bath by introducing the hydrogen-supplying substance silicic acid into the salt bath composition. At the same time, it overcomes three major difficulties in using silicic acid to control the pH during the chemical strengthening process: 1. Large pH volatility: During batch production, each chemical strengthening will cause a large increase in pH; 2. Easy decomposition of silicic acid at high temperature: After the pH exceeds the standard, after using a sufficient amount of silicic acid for neutralization, the pH decreases slightly, but the decrease is too small; 3. Decomposition reaction of nitrate: When the temperature of the molten salt is above 450 °C, due to the decomposition reaction of nitrate, the pH of the molten salt is likely to increase. Combining with a specific temperature control method, the decomposition of silicic acid and the adsorption of silicate on the IOX glass surface are inhibited, and the pH of the salt bath can still be maintained within an appropriate range after multiple rounds of chemical strengthening. After up to six rounds of chemical strengthening, the pH of the salt bath will not exceed 8. While effectively avoiding the corrosion of the glass surface by the alkaline salt bath, the transmittance of the IOX glass is improved, and the B value and haze are reduced. In addition, the present invention also provides a method for adding silicic acid to regulate the pH and controlling the temperature to inhibit the decomposition of silicic acid when the pH of the mixed salt bath is greater than or equal to 8, effectively controlling the pH of the mixed salt bath within an appropriate range.

[0120] Finally, it should be noted that in the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0121] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A salt bath composition for chemical strengthening, characterized in that, The salt bath composition for chemical strengthening comprises, by mass percentage: 50% - 99.9% of metal nitrate and more than 0.1% of inhibitor; The inhibitor is used to inhibit the generation of defects on the glass surface during the chemical strengthening process.

2. The salt bath composition for chemical strengthening according to claim 1, characterized in that, The inhibitor includes hydrogen - donating substances, and the hydrogen - donating substances are used to provide hydrogen ions to the salt bath composition.

3. The salt bath composition for chemical strengthening according to claim 2, characterized in that, The formation temperature of the salt bath composition for chemical strengthening is the first temperature. When the salt bath composition for chemical strengthening is less than or equal to the first temperature, the hydrogen - donating substances are used to provide hydrogen ions to the salt bath composition; Wherein, the first temperature is 380 - 470 °C.

4. The salt bath composition for chemical strengthening according to claim 2, characterized in that, The working temperature of the salt bath composition for chemical strengthening is the second temperature. When the salt bath composition for chemical strengthening is at the second temperature, the strengthening treatment time of the salt bath composition is 0.5 - 12 h; Wherein, the second temperature is 360 - 600 °C.

5. The salt bath composition for chemical strengthening according to claim 4, characterized in that, The second temperature is 450 - 540 °C, and the strengthening treatment time is 3 - 7 h.

6. The salt bath composition for chemical strengthening according to claim 1, wherein The metal nitrate comprises, by mass percentage of the salt bath composition: 0 - 89.99% of sodium nitrate, 0 - 89.99% of potassium nitrate.

7. The salt bath composition for chemical strengthening according to claim 1, characterized in that, The salt bath composition for chemical strengthening comprises, by mass percentage of the salt bath composition: 50 - 89.99% of sodium nitrate, 0 - 39.99% of potassium nitrate, 0.03% - 0.1% of lithium nitrate.

8. The salt bath composition for chemical strengthening according to claim 1, wherein The metal nitrate further includes an antibacterial component, and the antibacterial component includes at least one of silver nitrate, copper nitrate and zinc nitrate.

9. The salt bath composition for chemical strengthening according to claim 2, characterized in that, The hydrogen - donating substances include one or more of silicic acid, sulfuric acid, and boric acid.

10. The salt bath composition for chemical strengthening according to claim 1, wherein The composition further contains one or more of halides, sulfates, phosphates, carbonates, borates, silicates, antimonates, hydroxides.

11. The salt bath composition for chemical strengthening according to claim 9, characterized in that, The hydrogen - donating substance is silicic acid with a mass percentage of 0.1% - 1.5%.

12. A method for preparing a salt bath composition for chemical strengthening, which is used to prepare the salt bath composition for chemical strengthening according to any one of claims 1 to 11, characterized in that, Including the following steps: Mix metal nitrate, inhibitor and possible other salt bath components to form a salt bath composition; Heat the salt bath composition to the first temperature to form a molten salt bath composition with or without precipitation; Keep the molten salt bath composition at the first temperature for a heat - preservation reaction, and the inhibitor provides inhibitory ions to the molten salt bath composition; Wherein, the first temperature is 380 - 470 °C, keep the heat - preservation reaction for 12 - 36 h at this temperature, and the pH value of the mixed salt bath is < 7.

13. The method for preparing a salt bath composition for chemical strengthening according to claim 12, characterized in that, It further includes the following steps: Stir the salt bath composition heated to the first temperature.

14. A method for preparing a salt bath composition for chemical strengthening, which is used to prepare the salt bath composition for chemical strengthening according to any one of claims 1 to 12, characterized in that, Including the following steps: Mix metal nitrate and possible other salt bath components; Heat the mixture to the first temperature to form a molten composition with or without precipitation; Add an inhibitor to the molten composition; Keep the molten salt bath composition at the first temperature for a heat - preservation reaction, and the inhibitor provides inhibitory ions to the molten salt bath composition; Wherein, the first temperature is 380 - 470 °C, keep the heat - preservation reaction for 12 - 36 h at this temperature, and the pH value of the mixed salt bath is < 7.

15. A chemical strengthening method using the salt bath composition for chemical strengthening according to any one of claims 1 to 11, characterized in that, Including the following steps: Raise the molten salt bath composition to the second temperature; Immerse the glass in a molten salt bath composition to effect ion exchange (IOX) between the molten salt bath composition and the glass, and perform IOX strengthening treatment on the glass; Monitor the pH value of the mixed salt bath; If the pH of the mixed salt bath is greater than or equal to 8, lower the temperature of the mixed salt bath to a third temperature, then add an additional inhibitor and keep it warm, and adjust the pH of the salt bath composition to 6 - 7; Wherein, the second temperature is 360 - 600 °C, and the strengthening treatment time is 0.5 - 12 h; The additional inhibitor is 0.1% - 1.5% of the mass of the mixed salt bath; The third temperature is 380 - 470 °C, and keep it warm at this temperature for 18 - 36 h; In each round of strengthening treatment, the mass of the glass input is 1% - 5% of the mass of the mixed salt bath.

16. The chemical strengthening method according to claim 15, wherein It further includes the following steps: Stir the salt bath composition when adding the inhibitor and / or after adding the inhibitor.

17. The chemical strengthening method according to claim 15, wherein, In each round of strengthening treatment, an ion sieve with a mass of 0.5% - 1% of the mixed salt bath is also input.

18. An IOX glass product, characterized in that, Obtained by strengthening with the salt bath composition for chemical strengthening described in any one of claims 1 - 11.

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