A method for adjusting the visible light transmittance of colored microcrystalline glass

Abstract

This invention relates to the field of microcrystalline glass technology, and more particularly to a method for wide-range adjustment of visible light transmittance in colored microcrystalline glass. The method includes the following steps: S1) a crystallization process to induce crystal formation in the base glass; S2) a dimming process; the dimming process includes rapidly heating the crystallized glass to Tmax, followed by rapid cooling. Tmax is greater than or equal to the highest crystallization temperature. This dimming method enables wide-range adjustment of transmittance without degrading the key performance characteristic of the microcrystalline panel: its coefficient of thermal expansion. The dimming method provided by this invention operates within the cooling phase after crystallization, with detection close to the cold end, enabling rapid transmittance adjustment.

Description

Technical Field

[0001] This invention relates to the field of glass-ceramic technology, and more particularly to a method for adjusting the visible light transmittance of colored glass-ceramics. Background Technology

[0002] LAS (Li2O-Al2O3-SiO2) microcrystalline glass refers to microcrystalline glass with a main crystalline phase of Li2O-Al2O3-SiO2, hereinafter referred to as microcrystalline glass. It possesses unique low-expansion characteristics and good impact resistance, making it widely used in kitchen cooktops, appliance covers, and other applications. The area beneath the microcrystalline cover primarily houses various electronic components, such as heating coils, copper coils, buttons, and various light-emitting devices, such as LED indicator lights. Besides providing safety protection during use, the microcrystalline cover must also possess visual shielding functionality; that is, the electronic components beneath the cover should be invisible during use, while the light-emitting devices should be clearly visible when operating. Therefore, high requirements are placed on the visible light transmittance of the microcrystalline glass panel, generally limited to between 0.2% and 2%. A transmittance below 0.2% makes it difficult to clearly display the light-emitting devices; a transmittance above 2% results in undesirable visibility of electronic components. To achieve the aforementioned light-blocking effect, the industry standard practice is to add coloring agents, especially the addition of V element, which can achieve a black appearance. With a visible light transmittance of only 0.2%-2%, its mid-infrared transmittance (1600nm) is still higher than 60%.

[0003] In practice, customer requirements are often more specific, and the transmittance ranges of different customers may not overlap. For example, customer A may require a transmittance of 0.35%-0.70%, while customer B may require 0.8%-1.3%. Current technology struggles to adequately address the issue of visible light transmittance adjustment in microcrystalline glass panels.

[0004] The manufacturing process of glass-ceramics is roughly as follows: glass batch preparation → high-temperature melting → rolling → crystallization → post-processing, which includes, but is not limited to, grinding, polishing, edge grinding, chamfering, screen printing, and surface treatment. Base glass refers to the uncrystallized glass after rolling; glass-ceramics generally refer to glass that has undergone crystallization treatment and formed a large number of micro- and nano-crystalline phases. If the glass batch contains inorganic arsenic compounds, it is called an arsenic-containing sheet; otherwise, it is called an arsenic-free sheet.

[0005] Basic glass thermal analysis results are as follows Figure 1 As shown. Tg is the glass transition temperature, Tp1 is the temperature of the first crystallization peak, corresponding to the precipitation of the first type of crystal, and Tp2 is the temperature of the second crystallization peak, corresponding to the precipitation of the second type of crystal. Depending on the type and degree of crystallinity required, the crystallization temperature Tc is selected as the reference between Tp1 and Tp2, and can be adjusted upwards or downwards.

[0006] The transmittance of glass-ceramics depends on the following factors:

[0007] 1. Colorant Content. The main colorant in glass-ceramics is vanadium pentoxide, with secondary colorants including titanium dioxide and iron oxides. Titanium dioxide is introduced as the primary nucleating agent, determining the performance of the glass-ceramic panel; iron is generally introduced as an impurity in the raw materials. Therefore, the main method for adjusting the colorant content is by regulating the vanadium pentoxide content.

[0008] 2. Crystallization Process. The crystallization process involves inducing crystal formation and growth within the glass. Crystallization temperatures often reach 860-950℃, and coloring is achieved simultaneously with crystallization. Before crystallization, the visible light transmittance of the glass panel is 40%–85%, which drops sharply to below the required 2% after crystallization. Higher temperatures or longer crystallization times result in lower transmittance; however, the coefficient of thermal expansion increases, leading to decreased temperature resistance.

[0009] 3. Thickness of the prepared microcrystalline panel. According to Beer-Lambert law, the greater the thickness of the optical path, the stronger the absorption of visible light and the lower the transmittance. However, the thickness of the microcrystalline panel is one of the main specifications of microcrystalline products. The thickness deviation is generally controlled within ±0.2mm. Taking a conventional 4mm thick microcrystalline panel as an example, the thickness requirement is a fluctuation range of 3.8-4.2mm. Considering the fluctuations caused by the production process, the actual controllable thickness variation range is only 0.2mm. Compared with a 4mm panel thickness, 0.2mm can only achieve a visible light change of about 0.15%, which is insufficient to achieve the purpose of adjusting transmittance. Moreover, the process requirements for thickness control are extremely high.

[0010] Existing processes are ill-suited to the rapid and wide-ranging adjustments required for visible light. First, adjusting the colorant content is an extremely lengthy process. The preparation of glass-ceramics involves several steps: formula adjustment, glass melting, rolling, and crystallization, taking several days. Furthermore, the change in colorant content is gradual, requiring continuous production over extended periods in the glass melting furnace to stabilize the colorant content at a new level. Second, the crystallization process is difficult to alter arbitrarily. Crystallization primarily aims to achieve glass crystallization; arbitrarily changing crystallization parameters will lead to changes in the properties of the glass-ceramics, such as insufficient impact resistance or decreased resistance to rapid temperature changes. Finally, thickness is a strictly controlled parameter, making it difficult to achieve a wide range of transmittance variations by adjusting thickness. Additionally, thickness is related to impact strength and should not be arbitrarily changed. Summary of the Invention

[0011] In view of this, the technical problem to be solved by the present invention is to provide a method for adjusting the visible light transmittance of colored microcrystalline glass, which realizes rapid and wide-range adjustment of visible light transmittance.

[0012] This invention provides a method for adjusting the brightness of colored microcrystalline glass, comprising the following steps:

[0013] S1) Crystallization process, which crystallizes the glass;

[0014] S2) Dimming process;

[0015] The dimming process includes rapid cooling, with a cooling rate of ≥90℃ / min, to adjust the visible light transmittance of the microcrystalline glass and obtain colored microcrystalline glass.

[0016] Optionally, in step S2), before the rapid cooling, a rapid heating process is further included to rapidly heat the crystallized glass to Tmax, so as to adjust the visible light transmittance of the microcrystalline glass and obtain colored microcrystalline glass. Tp2 > Tmax ≥ Tc.

[0017] Optionally, the Tmax is 890–1100℃.

[0018] Optionally, in step S2), the heating rate of the rapid heating is greater than or equal to 60°C / min; the cooling rate of the rapid cooling is greater than or equal to 90°C / min.

[0019] The higher the heat treatment temperature of glass-ceramics, the shorter the required heat treatment time, meaning that high temperatures can improve crystal precipitation efficiency. However, excessively high temperatures or excessively long heat treatment times can lead to phase transformation, severely affecting the performance of the glass-ceramic panel. The inventors surprisingly discovered that rapid heating and cooling after crystallization, as long as Tmax is controlled within a certain range, does not affect the key properties of the glass-ceramics, and the coefficient of thermal expansion remains stable. Tmax should be less than Tp²; otherwise, some crystalline phases in the colored glass-ceramics will transform, leading to a rapid increase in the coefficient of thermal expansion. The aforementioned rapid heating refers to a heating rate greater than 60℃ / min, and rapid cooling refers to a cooling rate greater than 90℃ / min. Clearly, higher heating and cooling rates can shorten the time the glass-ceramics are at high temperatures; conversely, excessively low heating or cooling rates will result in excessively long high-temperature residence time, leading to phase transformation and performance degradation.

[0020] More noteworthy is that by rapidly heating and cooling the crystallized glass, the transmittance of the glass-ceramic can be altered, thereby achieving a wide range of adjustable transmittance.

[0021] Specifically, the inventors discovered that the higher the Tmax, the higher the transmittance; and the greater the heating rate, the higher the transmittance. Simultaneously, there is a "terminal temperature" for rapid cooling starting from Tmax. Below this terminal temperature, the transmittance of the microcrystalline panel is not significantly affected by the cooling rate. For example, below the terminal temperature, rapid cooling at 120℃ / min and conventional cooling at 20℃ / min result in almost identical room-temperature transmittance for the microcrystalline panel. Rapid cooling between Tmax and the terminal temperature can effectively alter the transmittance of the microcrystalline glass; during this cooling range, a higher cooling rate leads to increased transmittance. From the terminal temperature to room temperature, any cooling method can be used with almost no impact on transmittance.

[0022] The inventors discovered that, in order to achieve the effect of the present invention, the rapid cooling is Tmax rapid cooling to the endpoint temperature, and the endpoint temperature is not higher than 750°C;

[0023] Preferably, the final temperature is not higher than 700°C.

[0024] Optionally, an annealing stage can be added after the dimming process to release the thermal stress generated by rapid cooling. The annealing temperature can be the final temperature, or a temperature higher or lower than this temperature, etc.

[0025] Optionally, after the dimming process, a conventional cooling process is set up to gradually cool the glass-ceramic from the final temperature. The conventional cooling process is not limited to a specific cooling rate and can refer to the cooling steps of existing glass-ceramic crystallization processes, such as a cooling rate of 1–40°C / min. Cooling can be achieved through conventional cooling processes, such as forced draft.

[0026] The microcrystalline glass comprises V₂O₅. Vanadium is an essential element for achieving transmittance adjustment in this invention. Colored microcrystalline glass generally achieves its shielding effect on components after crystallization by adding V₂O₅. The visible light transmittance of the base glass is generally >40%. After crystallization, the high-valence vanadium element is reduced, resulting in strong absorption in the visible light range. Therefore, V₂O₅ is necessary for this invention.

[0027] Optionally, the mass content of the V2O5 is 0.01% to 0.50%.

[0028] Preferably, the mass content of V2O5 is 0.01%, 0.02%, 0.03%, 0.04%, 0.10%, 0.20%, 0.30%, 0.40%, or 0.50%.

[0029] Optionally, the microcrystalline glass formulation includes TiO2. TiO2 is one of the important nucleating agents in microcrystalline glass, which can promote crystallization during the crystallization process and improve crystallization efficiency. As a nucleating agent, the content of TiO2 is 2.0 wt% to 4.0 wt%. Specifically, the content of TiO2 is 2.0 wt%, 2.2 wt%, 2.4 wt%, 2.7 wt%, 2.9 wt%, 3.1 wt%, 3.3 wt%, 3.7 wt%, and 4.0 wt%. TiO2 can enhance the coloring effect of vanadium after crystallization; similarly, TiO2 is beneficial for achieving a wider range of transmittance adjustment.

[0030] Optionally, in step S2), a heat preservation process is included between the rapid heating and rapid cooling; the microcrystalline glass panel has a very low thermal conductivity. When the microcrystalline glass is thick, the internal temperature of the microcrystalline panel rises more slowly than the surface. Setting a certain heat preservation time of Tmax is beneficial for the entire microcrystalline panel to reach the Tmax temperature, so as to better achieve transmittance regulation. To avoid crystal growth or phase transformation, the Tmax heat preservation time is less than 10 minutes. The closer Tmax is to Tp2, the shorter the heat preservation time; the closer Tmax is to Tc, the longer the heat preservation time can be.

[0031] Optionally, the rapid heating time is less than or equal to 3 minutes to avoid unwanted crystal growth or phase transformation.

[0032] Optionally, step S2) may further include:

[0033] S3) Cooling. The glass-ceramic is further cooled from the end temperature of the dimming process using cooling methods commonly used in the art. For example, it is cooled gradually at a rate of 1°C / min to 40°C / min.

[0034] Compared with existing technologies, the method provided by this invention enables wide-range adjustment of the visible light transmittance of colored microcrystalline glass. Without changing the crystallization process, the transmittance of the microcrystalline panel is expanded from a single-point value to a controllable adjustment range of >100%. Experimental results show that the dimming method provided by this invention can significantly broaden the light transmittance from a single-point value of 0.515% to 0.465%–1.193%, without significantly deteriorating the key performance characteristic of the microcrystalline panel: its coefficient of thermal expansion.

[0035] Furthermore, the dimming process provided by this invention involves changes made during the cooling phase of the original crystallization process, resulting in a short adjustment time, only a few minutes before cold-end detection. By detecting the transmittance of the cold-end microcrystalline panel and changing the process parameters of the dimming process, rapid transmittance adjustment can be achieved. Even with formula changes, during the gradual change of colorant content, the method of this invention can quickly adjust the transmittance of the microcrystalline panel to maintain the stability of the transmittance of the produced microcrystalline panel during colorant or formula changes. Attached Figure Description

[0036] Figure 1 Thermal analysis curves of the base glass;

[0037] Figure 2 The expansion curves are for the microcrystalline glass prepared in Examples 1-2 and Comparative Example 1. Detailed Implementation

[0038] This invention provides a method for adjusting the brightness of colored microcrystalline glass, comprising the following steps:

[0039] S1) Crystallization process, which crystallizes the glass;

[0040] S2) Dimming process;

[0041] The dimming process includes rapid cooling, with a cooling rate of ≥90℃ / min, to adjust the visible light transmittance of the microcrystalline glass and obtain colored microcrystalline glass.

[0042] This invention is applicable to microcrystalline glass containing V2O5.

[0043] The V2O5 is a colorant for glass-ceramics, and the mass content of the V2O5 is 0.01% to 0.5%, which can be 0.01%, 0.02%, 0.03%, 0.04%, 0.10%, 0.20%, 0.30%, 0.40%, or 0.50%.

[0044] The V2O5 content is preferably 0.015% to 0.35% by mass.

[0045] Wherein, when the glass is an arsenic-free plate, the mass content of V2O5 is preferably 0.015% to 0.04%; when the glass is an arsenic-containing plate, the mass content of V2O5 is preferably 0.2% to 0.35%.

[0046] This invention is applicable to microcrystalline glass containing TiO2. TiO2 can enhance the coloring effect of vanadium after crystallization.

[0047] Wherein, TiO2 is a nucleating agent for glass-ceramics, and the mass content of TiO2 is 2% to 4%, which can be 2.0%, 2.2%, 2.5%, 2.8%, 3.0%, 3.2%, 3.5%, 3.8%, or 4.0%.

[0048] The preferred mass content of TiO2 is 2.7% to 3.2%.

[0049] In this invention, the glass composition also includes conventional additives such as clarifying agents, fluxing agents, and glass clinker batching materials.

[0050] The present invention does not impose any special limitations on the specific types and contents of the clarifying agent, flux, glass clinker batching material, etc., which can be types well known to those skilled in the art, and the contents of each additive can be adjusted according to the requirements.

[0051] In some specific embodiments of the present invention, the microcrystalline glass comprises:

[0052] V2O5, As2O3, TiO2, ZrO2, Li2O, Al2O3, SiO2, flux, and unavoidable impurities.

[0053] In some specific embodiments of the present invention, the microcrystalline glass comprises:

[0054] V2O5, SnO2, TiO2, ZrO2, Li2O, Al2O3, SiO2, flux, and unavoidable impurities.

[0055] In some embodiments of the present invention, the main components of the glass and various additives are first mixed, and then melted at high temperature to melt the glass batch into a uniform, bubble-free high-temperature glass melt. The high-temperature melting temperature can be 1600–1800°C.

[0056] Then, the glass is calendered and rolled into a base glass sheet of a specified thickness using pressure rollers.

[0057] In some embodiments of the present invention, the thickness of the glass plate is 3 to 5 mm, including but not limited to 3 mm, 3.5 mm, 3.8 mm, 4.2 mm or 5 mm, and the visible light transmittance of the base glass plate can be higher than 40%.

[0058] Then, subsequent heat treatment is carried out, through heating and holding, to induce crystallization of the base glass and form microcrystalline glass.

[0059] Crystallization of glass-ceramics is common knowledge in the field of glass-ceramics. The crystallization process can be achieved by heating to Tc (crystallization temperature) and holding at that temperature for a certain period of time; or by heating to Tc (crystallization temperature) and then directly entering the cooling process. It is known to those skilled in the art that a lower temperature holding process or a slow heating process can be inserted into the above-mentioned heating process to achieve "nucleation".

[0060] A typical two-stage crystallization process is as follows:

[0061] First, a nucleation process is performed to nucleate the glass.

[0062] The preferred temperature for the nucleation process is 690–780°C, the preferred holding time for the nucleation process is 3–60 min, and the preferred heating rate before nucleation, i.e., the single heating rate, is 2–30°C / min. The nucleation temperature can be 690°C, 715°C, 725°C, 735°C, 740°C, 745°C, 750°C, or 780°C; the holding time can be 3 min, 10 min, 15 min, 20 min, 25 min, 35 min, 45 min, 55 min, or 60 min; and the heating rate can be 2°C / min, 5°C / min, 10°C / min, 15°C / min, 20°C / min, or 30°C / min.

[0063] As is known to those skilled in the art, the nucleation process does not require constant temperature holding and can be replaced by a heating stage.

[0064] After glass nucleation, it is heated a second time to crystallize the glass, thus completing crystal growth and initial coloring.

[0065] The preferred temperature for the crystallization process is 840–980°C, the preferred heating rate for the crystallization process is 2–30°C / min, and the preferred holding time for the crystallization process is <120min.

[0066] The nucleated base glass is heated to the crystallization temperature Tc at a rate of 2–30 °C / min, preferably 4–15 °C / min, and more preferably 5–10 °C / min. The crystallization temperature is generally in the range of -20 to +120 °C around the Tp1 temperature (meaning a decrease of 20 °C or an increase of 120 °C from the Tp1 temperature), typically 840–980 °C. The preferred crystallization temperature range is 870–930 °C. Tp1 temperature is the first exothermic peak of the base glass and can be measured by DSC or DTA. The crystallization holding time is generally <120 min, preferably 25–45 min. The crystallization process completes the precipitation of crystals in the glass-ceramic, accompanied by a decrease in transmittance from 40%–85% of the base glass to below 2%.

[0067] In some embodiments of the present invention, the temperature of the crystallization process is 890°C, the heating rate of the crystallization process is 5-6°C / min, and the holding time of the crystallization process is 40min.

[0068] This invention incorporates a dimming process after the crystallization process, enabling rapid, wide-range online adjustment of the transmittance of the crystallized glass-ceramic. The dimming process includes rapid heating and rapid cooling.

[0069] The rapid heating rate is preferably greater than or equal to 60°C / min, more preferably greater than or equal to 80°C / min. In some specific embodiments of the present invention, the rapid heating rate is 70 to 150°C / min, preferably 80 to 120°C / min, and can specifically be 80, 90, 100, 110 or 120°C / min.

[0070] This invention rapidly heats the crystallized glass to Tmax. To obtain a large range of transmittance adjustment, Tmax should be as high as possible, but lower than Tp2. Tp2 is the crystallization peak of hydrothermal quartz. Temperatures close to Tp2 will lead to significant precipitation of hydrothermal quartz and a deterioration of the coefficient of thermal expansion. Preferably, Tmax is 890–1100°C, specifically 890, 900, 950, 980, 1000, 1010, 1050, 1060, 1080, or 1100°C.

[0071] It should be noted that when Tmax equals the highest crystallization temperature, rapid cooling is performed directly without rapid heating.

[0072] The rapid cooling rate is preferably greater than or equal to 90°C / min; more preferably greater than or equal to 120°C / min. In some specific embodiments of the present invention, the rapid cooling rate is 90–200°C / min, specifically 95, 100, 110, 120, 130, or 140°C / min.

[0073] The rapid cooling is preferably rapid cooling to the endpoint temperature, which is below 750°C.

[0074] More preferably, the rapid cooling cools the temperature to below 700°C.

[0075] Microcrystalline glass has poor thermal conductivity. When the microcrystalline panel is thick, a heat preservation process can be set between the rapid heating and rapid cooling to ensure that the internal temperature of the microcrystalline panel is close to Tmax. However, increasing the heat preservation time will bring the risk of performance degradation of the microcrystalline panel. Specifically, during the Tmax heat preservation process, a crystal phase transformation occurs, and the coefficient of linear thermal expansion increases, thereby impairing the resistance to thermal shock.

[0076] Preferably, the rapid heating time is less than or equal to 3 minutes.

[0077] The preferred heat preservation time is <10 min.

[0078] Preferably, the total time for the rapid heating and the heat preservation process is less than or equal to 10 minutes. For higher Tmax values, such as 1010°C, providing an appropriate heat preservation time is beneficial for the overall temperature of the microcrystalline panel to reach Tmax, thereby achieving a larger range of transmittance adjustment. Excessive heat preservation time, especially for higher Tmax values, will lead to crystal phase transformation and deterioration of panel performance.

[0079] The aforementioned rapid heating and cooling temperature change rates should be as large as possible to obtain the widest possible transmittance adjustment range; however, excessively large temperature change rates can cause the thermal stress caused by volume changes to accumulate beyond the tolerance of the microcrystalline panel body, leading to cracking. Preferably, the closer the coefficient of thermal expansion of the microcrystalline glass body after the crystallization process is to 0, the greater the temperature change rate it can withstand.

[0080] Preferably, after step S2), the method further includes:

[0081] S3) Cooling.

[0082] The cooling rate can be 1 to 40°C / min, and can be achieved through conventional cooling processes, such as air blowing.

[0083] The present invention does not impose any special limitations on the conventional cooling method and cooling rate, and can use natural cooling or forced air cooling, etc.

[0084] After cooling to room temperature, it can also include conventional post-processing such as cutting and post-processing.

[0085] The post-processing includes, but is not limited to, grinding, polishing, screen printing, and surface treatment.

[0086] The visible light transmittance in this paper was measured by Hunterlab ColorQuest XE, and the visible light range refers to wavelengths of 400-700nm.

[0087] To further illustrate the present invention, a detailed description is provided below with reference to embodiments. However, it should be understood that these descriptions are merely for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims.

[0088] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0089] Examples 1 to 4, and Comparative Example 1, used arsenic-containing glass crystals with the following composition, expressed as a percentage by mass:

[0090] V2O5 0.3%, As2O3 0.8%, TiO2 2.9%, ZrO2 1.6%, Li2O 3.9%, Al2O3 21%, SiO2 64%, and other components 5.3%.

[0091] Example 1

[0092] Crystallization process: 1. Nucleation: Heat from room temperature to 735℃ at a rate of 10℃ / min and hold for 15 minutes to complete the nucleation process; 2. Crystallization: Heat to the crystallization temperature of 890℃ at a rate of 5℃ / min and hold for 40 minutes to complete crystal growth and preliminary coloring.

[0093] Dimming process: The temperature is increased to 1010℃ in about 1 minute at a rate of 120℃ / min, without heat preservation, and then decreased to 700℃ at a rate of 130℃ / min.

[0094] Conventional cooling: The temperature is reduced to 400°C at a rate of 25°C / min for 12 minutes, and then further cooled to room temperature to obtain colored microcrystalline glass.

[0095] The transmittance and coefficient of thermal expansion (DIL) of the microcrystalline panel were tested. The results are shown in Table 1.

[0096] Examples 2-4

[0097] Crystallization process: 1. Nucleation: Heat from room temperature to 735℃ at a rate of 10℃ / min and hold for 15 minutes to complete the nucleation process; 2. Crystallization: Heat to the crystallization temperature of 890℃ at a rate of 5℃ / min and hold for 40 minutes to complete crystal growth and preliminary coloring.

[0098] Dimming process: The parameters for the temperature adjustment process are shown in Table 1.

[0099] Conventional cooling: The parameters of the cooling process are shown in Table 1. Further cooling to room temperature yields colored microcrystalline glass.

[0100] The transmittance and DIL of the microcrystalline panel were tested. The results are shown in Table 1.

[0101] Comparative Example 1

[0102] Comparative Example 1 shows a typical crystallization process for arsenic-containing microcrystalline panels.

[0103] Crystallization process: 1. Nucleation: Heat from room temperature to 735℃ at a rate of 10℃ / min and hold for 15 minutes to complete the nucleation process; 2. Crystallization: Heat to the crystallization temperature of 890℃ at a rate of 5℃ / min and hold for 40 minutes to complete crystal growth and preliminary coloring; 3. Cooling: The parameters of the cooling process are shown in Table 1. Further cool to room temperature to obtain colored microcrystalline glass.

[0104] The transmittance and DIL of the microcrystalline panel were tested. The results are shown in Table 1.

[0105] Table 1 Crystallization process and test results of Examples 1-4 and Comparative Example 1

[0106]

[0107] Figure 2 These are the thermal expansion curves of the microcrystalline glass prepared in Examples 1-2 and Comparative Example 1. Generally, a microcrystalline panel with a linear thermal expansion coefficient <0.5ppm / ℃ can withstand rapid thermal changes above 800℃. Figure 2 As can be seen, after processing by the method described in this invention, the linear thermal expansion coefficient of the microcrystalline glass is <0.2ppm / ℃, and the performance does not change significantly. However, the visible light transmittance is expanded from a single point value of 0.515% to a controllable adjustment range of 0.465 to 1.193% with an amplitude exceeding 100%, and the overall time required does not increase.

[0108] Examples 5-7 and Comparative Examples 2-3 are arsenic-free plates with the following components, in mass percentage:

[0109] V2O5 0.03%, SnO2 0.3%, TiO2 2.9%, ZrO2 1.6%, Li2O 3.9%, Al2O3 21%, SiO2 64%, and other components 6.27%.

[0110] Example 5

[0111] Crystallization process: 1. Nucleation: Heat from room temperature to 735℃ at a rate of 10℃ / min and hold for 15 minutes to complete the nucleation process; 2. Crystallization: Heat to the crystallization temperature of 890℃ at a rate of 5℃ / min and hold for 40 minutes to complete crystal growth and preliminary coloring.

[0112] Dimming: Heat to 980℃ at a rate of 120℃ / min in 45s, hold for 5min, and then cool down to 700℃ at a rate of 120℃ / min.

[0113] Conventional cooling: The temperature is reduced to 400°C at a rate of 25°C / min for 12 minutes, and then further cooled to room temperature to obtain colored microcrystalline glass.

[0114] The transmittance and DIL of the microcrystalline panel were tested. The results are shown in Table 2.

[0115] Examples 6-7

[0116] Crystallization process: 1. Nucleation: Increase the temperature from room temperature to 735℃ at a rate of 10℃ / min and hold for 15 minutes to complete the nucleation process; 2. Crystallization: Increase the temperature to the crystallization temperature of 890℃ at a rate of 5℃ / min and hold for 40 minutes to complete crystal growth and preliminary coloring.

[0117] Dimming process: The parameters for the temperature adjustment process are shown in Table 2.

[0118] Conventional cooling: The parameters of the cooling process are shown in Table 2. Further cooling to room temperature yields colored microcrystalline glass.

[0119] The transmittance and DIL of the microcrystalline panel were tested. The results are shown in Table 2.

[0120] Comparative Example 2

[0121] The Tmax holding time for Comparative Example 2 was longer, 10 minutes.

[0122] Crystallization process: 1. Nucleation: Heat from room temperature to 735℃ at a rate of 10℃ / min and hold for 15 minutes to complete the nucleation process; 2. Crystallization: Heat to the crystallization temperature of 890℃ at a rate of 5℃ / min and hold for 40 minutes to complete crystal growth and preliminary coloring.

[0123] Dimming process: Heat to 980℃ at a rate of 120℃ / min in 45s, hold for 10min, and then cool down to 700℃ at a rate of 120℃ / min.

[0124] Conventional cooling: The temperature is reduced to 400°C at a rate of 25°C / min for 12 minutes, and then further cooled to room temperature to obtain colored microcrystalline glass.

[0125] Comparative Example 3

[0126] Comparative Example 3 shows a typical crystallization process for arsenic-free microcrystalline panels.

[0127] Crystallization process: 1. Nucleation: Heat from room temperature to 735℃ at a rate of 10℃ / min and hold for 15 minutes to complete the nucleation process; 2. Crystallization: Heat to the crystallization temperature of 890℃ at a rate of 5℃ / min and hold for 40 minutes to complete crystal growth and preliminary coloring; 3. Cooling: The parameters of the cooling process are shown in Table 2. Further cool to room temperature to obtain colored microcrystalline glass.

[0128] The transmittance and DIL of the microcrystalline panel were tested. The results are shown in Table 2.

[0129] Table 2 Crystallization process and test results of Examples 5-7 and Comparative Examples 2-3

[0130]

[0131] The results of Examples 1-4 and Comparative Example 1 demonstrate that the method provided by this invention can significantly broaden the light transmittance from a single-point value of 0.515% to 0.465%-1.193%, achieving a visible light adjustment range of 156%, without deteriorating the key performance characteristic of the microcrystalline panel: its coefficient of thermal expansion. Therefore, this invention, by adding a light-adjusting process during the preparation of colored microcrystalline glass and adjusting different heating rates, heating times, Tmax temperatures, holding times, cooling rates, and cooling times, achieves a wide range of transmittance adjustment for microcrystalline glass. This can meet the different transmittance requirements of various customers for different products, and the adjustment method is simple and fast.

[0132] Examples 5-6 and Comparative Examples 2-3 show that while Tmax insulation for a certain period can adjust the transmittance, it has side effects, leading to an increase in the coefficient of linear thermal expansion. Especially at higher temperatures, insulation can cause DIL to increase to over 0.5 ppm / ℃, resulting in a significant decrease in resistance to rapid thermal changes.

[0133] Based on the above findings, this invention achieves rapid and wide-range adjustment of visible light transmittance without changing the current crystallization process or increasing production time.

[0134] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for adjusting the visible light transmittance of a colored microcrystalline glass, comprising the following steps: S1) Crystallization process, which crystallizes the glass; S2) Dimming process; The microcrystalline glass is LAS microcrystalline glass, and the composition of the glass includes V2O5, the mass content of which is 0.01%~0.5%. The dimming process includes rapid cooling, with a cooling rate of ≥90℃ / min, to adjust the visible light transmittance of the microcrystalline glass and obtain colored microcrystalline glass. In step S1), the temperature of the crystallization process is 840~980℃, the heating rate of the crystallization process is 2~30℃ / min, and the holding time of the crystallization process is 25-45min. In step S2), before the rapid cooling, there is a rapid heating process to rapidly heat the crystallized glass to Tmax in order to adjust the visible light transmittance of the microcrystalline glass and obtain colored microcrystalline glass. The heating rate of the rapid heating is 70~150℃ / min. The Tmax is greater than or equal to the crystallization temperature and less than Tp2; Tp2 is the crystallization peak of hydrothermal quartz. The rapid cooling refers to rapid cooling to below 750°C.

2. The method for adjusting the visible light transmittance of colored microcrystalline glass according to claim 1, characterized in that, The Tmax is 890~1100℃.

3. The method for adjusting the visible light transmittance of colored microcrystalline glass according to claim 1, characterized in that, In step S2), a heat preservation process is included between the rapid heating and the rapid cooling; the rapid heating time is less than or equal to 3 minutes; and the heat preservation time is less than 10 minutes.

4. The method for adjusting the visible light transmittance of colored microcrystalline glass according to claim 1, characterized in that, Following step S2), the following is also included: S3) Cooling.

5. The method for adjusting the visible light transmittance of colored microcrystalline glass according to claim 1, characterized in that, Step S1) further includes a nucleation process, wherein the temperature of the nucleation process is 690~780℃ and the holding time of the nucleation process is 3~60min.

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