Non-isothermal step-type hot pressing method and step-type hot pressing device

Abstract

The present invention belongs to the technical field of glass hot pressing, and in particular to a non-isothermal step-by-step hot pressing method and a step-by-step hot pressing device. The non-isothermal step-by-step hot pressing method includes the following steps: heating, a translation table drives one of the lower molds to be located at a forming station; in a vacuum environment or an inert gas environment, a first heating component is used to heat the upper mold to a first predetermined temperature, and a second heating component is used to heat the lower mold and the glass element located at the forming station to a second predetermined temperature; hot pressing, a lifting table drives the translation table to move upward so that the lower mold located at the forming station is clamped with the upper mold, and the embossing force of the force structure is applied to the lower mold; cooling, the temperature of the upper mold and the lower mold located at the forming station is reduced at a predetermined cooling rate so that the glass element with the replicated microstructure is annealed; demolding, the lifting table drives the translation table to descend so that the lower mold unloads the embossing force of the force structure. The present invention can improve the hot pressing efficiency of glass elements.

Description

Technical Field

[0001] The present invention belongs to the technical field of glass hot pressing, and in particular relates to a non-isothermal step-type hot pressing method and a step-type hot pressing device. Background Art

[0002] Glass micro-optical components such as microlens arrays, Fresnel lenses, transmission gratings and diffraction optical elements are in increasing demand in aerospace, national defense and security, green energy, space sensing, laser radiation, fiber optic communications, biomedicine and consumer electronics. The targeted development of efficient and low-cost manufacturing technologies for high-quality glass micro-optical components is a key development direction both domestically and internationally.

[0003] Ultra-precision grinding, micro-milling, laser direct writing, ion beam lithography, electron beam lithography, chemical etching, and precision hot stamping are the primary methods for manufacturing glass micro-optical components. Due to the inherent brittleness and low fracture toughness of optical glass, ultra-precision grinding and micro-milling suffer from severe tool wear, subsurface damage, and low processing efficiency. Laser direct writing suffers from poor surface quality and surface composition variations. Ion beam lithography and electron beam lithography have extremely low processing efficiency and difficulty in processing complex curved structures. Chemical etching requires the use of strong acids and is hazardous.

[0004] Precision hot embossing not only has the advantages of cross-micro-nanoscale manufacturing, net forming, high manufacturing efficiency, low cost, and green environmental protection, but also has high surface replication fidelity. Therefore, combined with ultra-precision mold micro-nano manufacturing technology, it is expected to achieve high-quality, low-cost green manufacturing of glass micro-optical components.

[0005] However, current glass hot pressing is performed with a single mold and a single cavity, that is, only one piece of glass can be processed in one process, resulting in low molding efficiency. Summary of the Invention

[0006] The purpose of the embodiments of the present application is to provide a non-isothermal step-type hot pressing method, aiming to solve the problem of how to improve the efficiency of glass component molding.

[0007] To achieve the above objectives, the technical solution adopted in this application is:

[0008] In a first aspect, a non-isothermal step-type hot pressing method is provided for molding a glass element located at a forming station, the non-isothermal step-type hot pressing method comprising the following steps:

[0009] Prepare an upper mold having a microstructure and located at the forming station, a lower mold carrying the glass element, a translation stage for driving the lower mold to move, a lifting platform, and a force-applying structure connected to the upper mold, wherein the translation stage is located below the upper mold, and a plurality of lower molds are linearly and spaced apart on the translation stage, and the lifting platform is used to drive the translation stage to rise or fall;

[0010] Heating, the translation stage drives one of the lower molds to be located at the forming station; in a vacuum environment or an inert gas environment, using a first heating component to heat the upper mold to a first predetermined temperature, and using a second heating component to heat the lower mold and the glass element located at the forming station to a second predetermined temperature;

[0011] Hot pressing, the lifting platform drives the translation platform to move upward, so that the lower mold located at the forming station is clamped with the upper mold, and the embossing force of the force-applying structure is applied to the lower mold, so that the glass element replicates the microstructure;

[0012] Cooling, reducing the temperature of the upper mold and the lower mold located at the forming station at a predetermined cooling rate to anneal the glass element having the replicated microstructure;

[0013] Demolding, the lifting platform drives the translation platform to descend, so that the lower mold can unload the stamping force of the force-applying structure;

[0014] The translation stage drives each of the lower molds to be located at the forming station in sequence, and repeats the heating step, the hot pressing step, the cooling step and the demoulding step.

[0015] In a second aspect, a step-by-step hot pressing device is provided, which has a forming station and is used to implement the non-isothermal step-by-step hot pressing method. The step-by-step hot pressing device includes:

[0016] A mold structure includes an upper mold located at the forming station and having a microstructure, a translation platform located below the upper mold, a lower mold located on the translation platform and carrying a glass element, and a lifting platform connected to the translation platform, wherein a plurality of lower molds are provided, each mold being linearly arranged on the translation platform in sequence, and the translation platform is used to drive each lower mold to be positioned at the forming station in sequence;

[0017] a heating structure comprising a first heating assembly connected to and used for heating the upper mold and a second heating assembly connected to and used for heating the lower mold; and

[0018] The force-applying structure is vertically slidably disposed at the forming station and connected to the upper mold. The lifting platform drives the translation platform to rise, so that the lower mold located at the forming station is clamped with the upper mold, and the embossing force of the force-applying structure is applied to the lower mold, so that the glass element replicates the microstructure.

[0019] The beneficial effects of the present application are as follows: the non-isothermal step-by-step hot pressing method includes heating, hot pressing, cooling and demolding. By arranging multiple lower molds on a translation table, and each lower mold is sequentially molded and hot pressed with the upper mold, multiple glass elements can be formed in one processing process, and the microstructure on the upper mold is sequentially replicated on the glass element, thereby improving the molding efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or exemplary technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 This is a flow chart of the non-isothermal step hot pressing method provided in an embodiment of the present application;

[0022] Figure 2 yes Figure 1 Schematic diagram of changes in temperature, pressure and displacement of the upper mold and the lower mold in the non-isothermal step hot pressing method;

[0023] Figure 3 is a schematic diagram of the three-dimensional structure of a step-type hot pressing device provided in another embodiment of the present application;

[0024] Figure 4 yes Figure 3 Explosion diagram of a step-type hot pressing device;

[0025] Figure 5 yes Figure 3 A front view schematic diagram of the mold structure and force structure.

[0026] Among them, the reference numerals in the figures are:

[0027] 100. Step-by-step hot pressing device; 101. Hot pressing chamber; 102. Vacuum chamber; 20. Force-applying structure; 21. First-stage gravity unit; 22. Second-stage gravity unit; 23. Guide pillar; 30. Mold structure; 31. Upper mold; 32. Lower mold; 52. Translation stage; 51. Lifting platform; 53. Sliding platform; 41. In-situ observation structure for temperature distribution; 42. In-situ observation structure for shape and contour; 211. First slide; 212. First weight; 221. Second slide; 222. Second weight; 24. Pressure ball; 60. Heating structure; 61. First heating assembly; 62. Second heating assembly; 200. Glass element; 63. Guide pillar and sleeve; 421. XZ translation stage; 422. XY tilt stage; 423. XYR translation stage; DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit this application.

[0029] It should be noted that when a component is referred to as being "fixed on" or "disposed on" another component, it may be directly on the other component or indirectly on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The terms "upper", "lower", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of description and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances. The terms "first" and "second" are only used for the purpose of convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0030] See also Figures 1 to 2 The present invention provides a non-isothermal step-type hot pressing method for hot pressing a glass element 200, wherein the glass element 200 is an optical glass element 200, such as BK7, and the glass element 200 is located at a forming station. The non-isothermal step-type hot pressing method includes the following steps:

[0031] See also Figures 3 to 5S1: Heating; prepare the upper mold 31, lower mold 32, translation stage 52, lifting stage 51, force-applying structure 20, first heating assembly 61, and second heating assembly 62. The upper mold 31 is connected to the force-applying structure 20 and is located at the forming station and has a microstructure. The lower mold 32 carries the glass element 200 and is connected to the translation stage 52. The translation stage 52 is used to drive the lower mold 32 to move horizontally so that the lower mold 32 is directly below the upper mold 31. The lifting stage 51 can drive the translation stage 52 upward to mate the upper mold 31 and the lower mold 32, or drive the translation stage 52 downward to separate the lower mold 32 from the upper mold 31. Multiple lower molds 32 are linearly and spaced apart along the horizontal movement direction of the translation stage 52. The translation stage 52 drives one of the lower molds 32 to a forming station. In a vacuum environment or an inert gas environment, the upper mold 31 is heated to a first predetermined temperature using a first heating assembly 61. The first predetermined temperature can be higher than the glass transition temperature of the glass element 200, and the temperature of the upper mold 31 is maintained at the first predetermined temperature. The lower mold 32 and the glass element 200 located in the forming station are heated to a second predetermined temperature using a second heating assembly 62. The temperature of the lower mold 32 is maintained at the second predetermined temperature, and the second predetermined temperature can be no higher than the glass transition temperature. It will be understood that the upper mold 31, lower mold 32, translation stage 52, lifting platform 51, force-applying structure 20, first heating assembly 61, and second heating assembly 62 are all located within the vacuum chamber 102 of the hot press chamber 101. The vacuum chamber 102 can be evacuated or filled with an inert gas.

[0032] S2: Hot pressing: The lifting platform 51 drives the translation platform 52 to move upward, so that the lower mold 32 located at the forming station is clamped with the upper mold 31. The upper surface of the glass element 200 abuts the microstructure, and the upper mold 31 softens the upper surface of the glass element 200 through heat conduction. The embossing force of the force-applying structure 20 is then applied to the lower mold 32, so that the microstructure is replicated on the upper surface of the glass element 200.

[0033] S3: Cooling: The temperatures of the upper mold 31 and the lower mold 32 located in the forming station are reduced at a predetermined cooling rate to anneal the glass element 200 having the replicated microstructure. During the cooling step, the heating power of the first heating assembly 61 can be reduced to slowly lower the temperature of the glass element 200. The cooling rate can be 20°C / min or 50°C / min, depending on practical circumstances and is not limited herein.

[0034] S4: demoulding, the lifting platform 51 drives the translation platform 52 to descend, so that the lower mold 32 unloads the stamping force of the force-applying structure 20;

[0035] See also Figures 3 to 5The translation stage 52 drives each lower mold 32 to be positioned at a forming station in sequence, and repeats the heating step, the hot pressing step, the cooling step and the demolding step in sequence, so that multiple glass elements 200 can be processed in one forming process, thereby improving the processing efficiency of the glass elements 200.

[0036] See also Figures 3 to 5 It is understandable that cooling the upper mold 31 first can avoid excessive microstructural stress on the glass element 200, while keeping the upper mold 31 at a certain temperature to facilitate heating for the next molding, thereby improving heating efficiency and molding efficiency.

[0037] See also Figures 3 to 5 The non-isothermal step-by-step hot pressing method provided in this embodiment includes heating, hot pressing, cooling and demolding. By arranging multiple lower molds 32 on the translation stage 52, and each lower mold 32 is sequentially clamped and hot pressed with the upper mold 31, multiple glass elements 200 can be formed in a single processing process, and the microstructure on the upper mold 31 is sequentially replicated on the glass elements 200, thereby improving the molding efficiency.

[0038] It is understandable that the lower mold 32 that is not in the forming station can be preheated first, so that after it is moved to the forming station, the heating time can be shortened, thereby improving the molding efficiency.

[0039] Optionally, in the hot pressing step S2 , the upper mold 31 and the lower mold 32 are maintained and pressed for a certain period of time under the action of the force-applying structure 20 so that the microstructure is fully replicated on the upper surface of the glass element 200 .

[0040] See also Figures 3 to 5 In some embodiments, the first predetermined temperature is greater than the second predetermined temperature. Optionally, the softening point of BK7 glass is 550 degrees, the first predetermined temperature may be 600 degrees, and the second predetermined temperature may be 520 degrees.

[0041] At the beginning of the S2 hot pressing step, the lifting platform 51 drives the translation platform 52 to rise, leaving a gap of 0.5 mm between the upper surface of the glass element 200 and the lower surface of the upper mold 31. The vacuum pump starts working until the gas pressure in the vacuum chamber 102 is lower than 1 Pa. When the system stabilizes, the upper mold 31 and the lower mold 32 are heated respectively by the first heating component 61 and the second heating component 62. Optionally, the first heating component 61 and the second heating component 62 can both be ceramic heating plates, which can achieve rapid heating of the upper mold 31 and the lower mold 32, and monitor their heating temperature in real time through thermocouples embedded in the lower mold 32 and the upper mold 31. When the temperature of the upper mold 31 approaches the target imprinting temperature T B (first predetermined temperature), the temperature of the lower mold 32 reaches the preheating temperature T P(second predetermined temperature), and T P <T B , adjust the heating power to keep the upper and lower mold 32 temperatures constant at T P and T B , and maintain it for a period of time to improve the uniformity of the temperature distribution of the upper mold 31 and the lower mold 32. Since the first predetermined temperature is greater than the second predetermined temperature, when the upper surface of the glass element 200 contacts the upper mold 31, the upper mold 31 can soften the upper surface of the glass element 200, while the temperature of other parts of the glass element 200 is lower, reducing the temperature difference of the glass element 200 during subsequent cooling and annealing, thereby reducing the internal stress of the glass element 200.

[0042] See also Figures 1 to 2 In some embodiments, the force-applying structure 20 includes a first-stage gravity unit 21 slidably disposed in a vertical direction at the forming station and connected to the upper mold 31, and a second-stage gravity unit 22 slidably disposed in a vertical direction at the forming station; the hot pressing step includes the following steps:

[0043] S21: The lifting platform 51 drives the lower mold 32 to move upward a first distance, so that the first-level gravity unit 21 is loaded on the lower mold 32, and the upper mold 31 softens the upper surface of the glass element 200; the lifting platform 51 moves upward, so that the glass element 200 maintains contact with the upper mold 31, and realizes the imprinting force loading of the first-level gravity unit 21. Since the surface temperature of the upper mold 31 is relatively high, the shallow upper surface of the glass element 200 is quickly heated and softened, while the temperature of the bottom layer below the glass element 200 is consistent with that of the lower mold 32, which is beneficial to controlling the internal stress of the glass element 200.

[0044] S22: The lifting platform 51 drives the lower mold 32 to continue moving upward by a second distance, so that the first-stage gravity unit 21 and the second-stage gravity unit 22 are both loaded on the lower mold 32. The glass element 200 in the viscoelastic state gradually fills the groove of the microstructure under the action of the first-stage gravity unit 21 and the second-stage gravity unit 22, so that the glass element 200 replicates the microstructure.

[0045] Optionally, the first distance may be 1 mm, 3 mm or 5 mm.

[0046] Optionally, the second distance may be 1 mm, 3 mm or 5 mm.

[0047] It can be understood that both the first-stage gravity unit 21 and the second-stage gravity unit 22 apply the imprinting force to the glass element 200 by their own gravity, without the need for an additional driver, and the force application process is smooth and reliable.

[0048] See also Figures 3 to 5Optionally, in the cooling step, the upper mold 31 is provided with an upper cooling block, and the lower mold 32 is provided with a lower cooling block. The upper cooling block and the lower cooling block are provided with cooling channels. By adjusting the flow rate of the coolant or cooling gas in the cooling channel, the cooling rate of the upper mold 31 and the lower mold 32 can be adjusted.

[0049] See also Figures 3 to 5 In some embodiments, the demoulding step comprises the following steps:

[0050] S31: The lifting platform 51 drives the translation platform 52 downward by the second distance, allowing the lower mold 32 to unload the imprinting force of the second-stage gravity unit 22. The imprinting force of the first-stage gravity unit 21 is maintained, so that the imprinting force F3 is applied to the surface of the glass element 200. This prevents microstructural relaxation of the glass element 200 under low viscosity conditions, which could cause deformation and damage to the surface of the glass element 200. It is understood that after the upper and lower molds 31 and 32 are closed for a period of time, the heating power of the first heating assembly 61 and the nitrogen flow rate in the upper cooling block are adjusted to slowly lower their temperature. During the annealing process, the lifting platform 51 drives the translation platform 52 downward to unload the second-stage gravity unit 22.

[0051] S32: The lifting platform 51 drives the translation platform 52 to continue moving downward by the first distance, so that the lower mold 32 is unloaded from the embossing force of the first-stage gravity unit 21, while the upper mold 31 and the lower mold 32 remain in the mold-clamped state. When the temperature of the upper mold 31 reaches TF, the lifting platform 51 drives the translation platform 52 to continue moving downward, unloading the first-stage gravity unit 21. The gravity-loaded embossing force between the upper mold 31 and the lower mold 32 drops to 0 N, but the upper mold 31 and the lower mold 32 remain in contact, so that the microstructure of the glass element 200 maintains its shape. At the same time, the heating power of the ceramic heater of the first heating assembly 61 is further reduced, and the flow rate of the nitrogen gas in the upper cooling block is increased to increase its cooling rate.

[0052] S33: The lifting platform 51 drives the translation platform 52 to continue moving downward, separating the upper mold 31 from the lower mold 32. Specifically, when the temperature of the upper mold 31 and the glass element 200 drops to T4, the pressure is released, and the lifting platform 51 moves downward, completely separating the glass element 200 from the upper mold 31, and the lower mold 32 from the upper mold 31.

[0053] See also Figures 3 to 5In some embodiments, in step S31, the upper mold 31 and the glass element 200 are cooled at a first cooling rate; in step S32, the upper mold 31 and the glass element 200 are cooled at a second cooling rate, wherein the second cooling rate is greater than the first cooling rate, the first cooling rate mainly puts the glass element 200 into an annealing state, and the second cooling rate mainly achieves rapid cooling of the glass element 200.

[0054] In some embodiments, in the S1 heating step, the upper mold 31 and the lower mold 32 are kept at the first predetermined temperature and the second predetermined temperature for a predetermined time, respectively. The predetermined time can be 1 minute, 3 minutes or 5 minutes, which is selected according to actual conditions and is not limited here.

[0055] See also Figures 3 to 5 After all glass components 200 of the same batch have been formed, nitrogen is introduced into the vacuum chamber 102. The heating power of the ceramic heater of the second heating assembly 62 is further reduced, and the nitrogen flow rate of the lower cooling block is increased to accelerate the cooling of each lower mold 32 and each glass component 200. When the temperature of each lower mold 32 drops to 200°C, the lower mold 32 is maintained at a constant temperature, the vacuum chamber 102 is opened, and each glass component 200 is removed for quality inspection. Thus, it can be seen that the non-isothermal step hot pressing method can shorten the molding cycle by reducing the holding, contact, and pressure holding times, accelerating the heating and cooling rates, increasing the demolding temperature, and avoiding multiple loading and unloading of the glass components 200, thereby improving manufacturing efficiency.

[0056] See also Figure 2 , during the hot pressing process of the glass element 200, at time t B When the upper mold 31 or the lower mold 32 is heated to T B , that is, the first predetermined temperature, t B Keep warm until t2, D At t, the imprinting force gradually increases until the first-stage gravity unit 21 and the second-stage gravity unit 22 are fully loaded. E To t3, maintain pressure, t3 to t F Annealing is performed, and the second-stage gravity unit 22 is unloaded, and the temperature of the upper mold 31 and the lower mold is reduced to T F At t F At t4, the first-stage gravity unit 21 is unloaded and rapidly cooled.

[0057] See also Figures 3 to 5The present invention also proposes a step-by-step hot pressing device 100, which is used to implement the above-mentioned non-isothermal step-by-step hot pressing method. For the specific implementation steps of this method, please refer to the above-mentioned embodiment. Since this step-by-step hot pressing device 100 adopts all the technical solutions of all the above-mentioned embodiments, it also has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0058] See also Figures 3 to 5 In some embodiments, the step-type hot pressing device 100 includes: a mold structure 30 , a heating structure 60 and a force-applying structure 20 .

[0059] See also Figures 3 to 5 The mold structure 30 includes an upper mold 31 located at a forming station and provided with a microstructure, a translation platform 52 located below the upper mold 31, a lower mold 32 located at the translation platform 52 and carrying a glass element 200, and a lifting platform 51 connected to the translation platform 52. A plurality of lower molds 32 are provided, and each mold is linearly arranged on the translation platform 52 in sequence. The translation platform 52 is used to drive each lower mold 32 to be located at the forming station in sequence; the translation platform 52 can drive the lower mold 32 to slide in a horizontal direction, and a linear encoder is provided on the lifting platform 51 to accurately control the rising or falling distance of the lifting platform 51.

[0060] See also Figures 3 to 5 The translation platform 52 and the lifting platform 51 are both located on the sliding platform 53. The sliding platform 53 drives the translation platform 52 and the lifting platform 51 to move horizontally through the principle of the ball screw. The two ends of the translation platform 52 are connected to the sliding platform through two guide pillars and guide sleeves 63. The lifting platform 51 is located between the two guide pillars and guide sleeves 63.

[0061] See also Figures 3 to 5The heating structure 60 includes a first heating component 61 connected to and used for heating the upper mold 31 and a second heating component 62 connected to and used for heating the lower mold 32; it can be understood that the first heating component 61 and the second heating component 62 have the same structural layout. The first heating component 61 or the second heating component 62 includes two silicon nitride ceramic heating plates, a copper plate, a tungsten plate and a fused quartz plate. The silicon nitride ceramic heating plate has excellent high-temperature oxidation resistance, high durability, and high heating power, but there is a problem of uneven surface temperature distribution. Because copper has high thermal conductivity, heat can be quickly transferred from the ceramic heating plate to the copper plate, and finally a uniform temperature distribution is obtained on the surface of the copper plate. Moreover, placing a fused quartz plate with extremely low thermal conductivity under the copper plate for insulation can reduce heat loss. On the other hand, a high-strength tungsten plate is used to cover the copper plate to prevent it from bending and deforming under the action of concentrated force. Through the segmented temperature-controlled heating test of the first heating component 61 or the second heating component 62, it was found that the heating rate can reach 500°C / min, the maximum temperature can reach 1000°C, the temperature control accuracy is 0.5°C, the temperature uniformity is within ±3°C, and it has excellent repeatability.

[0062] See also Figures 3 to 5 The force-applying structure 20 is slidably arranged in the vertical direction at the forming station and connected to the upper mold 31. The lifting platform 51 drives the translation platform 52 to rise, so that the lower mold 32 located at the forming station is clamped with the upper mold 31, and the embossing force of the force-applying structure 20 is loaded on the lower mold 32, so that the glass element 200 replicates the microstructure.

[0063] See also Figures 3 to 5 In some embodiments, the step-type hot pressing device 100 also includes a support frame arranged at the forming station, and the force-applying structure 20 includes a first-stage gravity unit 21 that is slidably connected to the support frame in a vertical direction and connected to the upper mold 31, and a second-stage gravity unit 22 that is slidably connected to the support frame in a vertical direction, and the second-stage gravity unit 22 is located above the first-stage gravity unit 21.

[0064] See also Figures 3 to 5 The first-stage gravity unit 21 and the second-stage gravity unit 22 have similar structures and both include weights. The weight of the weights can be adjusted to precisely control the stamping and holding forces. Using F1-grade weights, the theoretical error can be controlled within 1mN. The lifting platform 51 has a motion resolution of up to 50nm and a linear encoder with an accuracy of up to 5nm. A fuzzy PID control algorithm is used to achieve precise loading of vertical displacement, thereby completing actions such as hot pressing, holding pressure, and demolding.

[0065] See also Figures 3 to 5Optionally, the support frame includes multiple guide columns 23 arranged in the vertical direction, the first-stage gravity unit 21 includes a first weight 212 and a first slide 211, the second-stage gravity unit 22 includes a second weight 222 and a second slide 221, the first slide 211 and the second slide 221 are both slidably connected to each guide column 23, and the second slide 221 is located above the first slide 211.

[0066] See also Figures 3 to 5 Optionally, a pressure ball 24 is provided at the lower end of the second-stage gravity unit 22, and the pressure ball 24 is connected to the end face of the second weight 222, so that the first-stage gravity unit 21 and the second-stage gravity unit 22 are kept in point-to-face contact through the pressure ball 24, which is conducive to making the stamping force of the first-stage gravity unit 21 and the stamping force of the second-stage gravity unit 22 collinear in the vertical direction, thereby improving the hot pressing accuracy of the glass element 200.

[0067] See also Figures 3 to 5 It can be understood that the lifting platform 51 drives the translation platform 52 to move upward until the corresponding lower mold 32 pushes up the upper mold 31, and the first-stage gravity unit 21 slides upward along the guide columns 23, so that the embossing force of the first-stage gravity unit 21 is fully applied to the glass element 200. The lifting platform 51 continues to drive the translation platform 52 to rise until the first slide 211 abuts against the pressure ball 24 and pushes up the second-stage gravity unit 22, and the second-stage gravity unit 22 slides upward along the guide columns 23, so that the embossing forces of the first-stage gravity unit 21 and the second-stage gravity unit 22 are fully applied to the glass element 200.

[0068] See also Figures 3 to 5 In some embodiments, the step-by-step hot pressing device 100 further includes an in-situ temperature distribution observation structure 41 and an in-situ shape contour observation structure 42 , and the in-situ temperature distribution observation structure 41 and the in-situ shape contour observation structure 42 are respectively located on both sides of the translation stage 52 .

[0069] See also Figures 3 to 5The temperature distribution in-situ observation structure 41 includes an infrared thermal imager; the shape contour in-situ observation structure 42 includes an ultra-depth-of-field microscope and a CCD camera. The Z slide, XYR slide and XY tilt stage 422 are used to adjust the position of the temperature distribution in-situ observation structure 41 or the shape contour in-situ observation structure 42 to ensure that the camera is just focused on the glass element 200. The temperature distribution in-situ observation structure 41 is used to record the surface temperature of the glass element 200, the upper mold 31 and the lower mold 32 during the hot stamping process, and its measurement accuracy can reach ±2°C. The shape contour in-situ observation structure 42 is used to record the side video of the glass element 200 during the hot stamping molding process, and then extract the edge contour of the microstructure in the video based on the principle of topological structure analysis. After image processing, the thickness, side contour shape, microstructure top surface curvature, filling rate and other information of the glass element 200 are obtained. The sampling frequency can reach 30Hz and the measurement accuracy can reach 0.5 microns.

[0070] The above are merely optional embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A non-isothermal step-type hot pressing method for molding a glass element at a forming station, characterized in that: The non-isothermal step-type hot pressing method comprises the following steps: Prepare an upper mold having a microstructure and located at the forming station, a lower mold carrying the glass element, a translation stage for driving the lower mold to move, a lifting platform, and a force-applying structure connected to the upper mold, wherein the translation stage is located below the upper mold, and a plurality of lower molds are linearly and spaced apart on the translation stage, and the lifting platform is used to drive the translation stage to rise or fall; Heating, the translation stage drives one of the lower molds to be located at the forming station, and the lower mold that is not in the forming station is preheated first; in a vacuum environment or an inert gas environment, the upper mold is heated to a first predetermined temperature using a first heating component, and the lower mold and the glass element located at the forming station are heated to a second predetermined temperature using a second heating component, wherein the first predetermined temperature is higher than the glass transition temperature of the glass element, the second predetermined temperature is not higher than the glass transition temperature, and the first predetermined temperature is greater than the second predetermined temperature; Hot pressing, the lifting platform drives the translation platform to move upward, so that the lower mold located at the forming station is clamped with the upper mold, and the embossing force of the force-applying structure is applied to the lower mold, so that the glass element replicates the microstructure; The force-applying structure includes a first-stage gravity unit slidably disposed in a vertical direction at the forming station and connected to the upper mold, and a second-stage gravity unit slidably disposed in a vertical direction at the forming station; the hot pressing step includes the following steps: S21: the lifting platform drives the lower mold to move upward by a first distance, so that the first-stage gravity unit is loaded on the lower mold, so that the upper mold softens the upper surface of the glass element; S22: The lifting platform drives the lower mold to continue to move upward by a second distance, so that the first-stage gravity unit and the second-stage gravity unit are both loaded on the lower mold, so that the glass element replicates the microstructure; the first-stage gravity unit and the second-stage gravity unit both apply an imprinting force to the glass element through their own gravity; Cooling, reducing the temperature of the upper mold and the lower mold located at the forming station at a predetermined cooling rate to anneal the glass element having the replicated microstructure; Demolding, the lifting platform drives the translation platform to descend, so that the lower mold can unload the stamping force of the force-applying structure; The translation stage drives each of the lower molds to be located at the forming station in sequence, and repeats the heating step, the hot pressing step, the cooling step and the demoulding step.

2. The non-isothermal step hot pressing method according to claim 1, wherein: The demoulding step comprises the following steps: S31: the lifting platform drives the translation platform to move downward by the second distance, so that the lower mold unloads the imprinting force of the second-stage gravity unit; S32: the lifting platform drives the translation platform to continue to move downward by the first distance, so that the lower mold is unloaded from the imprinting force of the first-stage gravity unit, and the upper mold and the lower mold remain in a mold-clamping state; S33: The lifting platform drives the translation platform to continue to move downward to separate the upper mold and the lower mold.

3. The non-isothermal step hot pressing method according to claim 2, wherein: In the step S31, the upper mold and the glass element are cooled at a first cooling rate; in the step S32, the upper mold and the glass element are cooled at a second cooling rate, and the second cooling rate is greater than the first cooling rate.

4. The non-isothermal step hot pressing method according to any one of claims 1 to 3, wherein: In the heating step, the upper mold and the lower mold are kept at the first predetermined temperature and the second predetermined temperature for a predetermined time, respectively.

5. A step-type hot pressing device having a forming station and used to implement the non-isothermal step-type hot pressing method according to any one of claims 1 to 4, characterized in that: The step-by-step hot pressing device comprises: A mold structure includes an upper mold located at the forming station and having a microstructure, a translation platform located below the upper mold, a lower mold located on the translation platform and carrying a glass element, and a lifting platform connected to the translation platform, wherein a plurality of lower molds are provided, and each lower mold is linearly arranged on the translation platform in sequence, and the translation platform is used to drive each lower mold to be positioned at the forming station in sequence; A heating structure comprising a first heating assembly connected to and used for heating the upper mold and a second heating assembly connected to and used for heating the lower mold; a support frame, disposed at the forming station; and A force applying structure is slidably disposed on the forming station in a vertical direction and connected to the upper mold; The force-applying structure includes a first-stage gravity unit slidably connected to the support frame and connected to the upper mold in a vertical direction, and a second-stage gravity unit slidably connected to the support frame in a vertical direction, wherein the second-stage gravity unit is located above the first-stage gravity unit; The lifting platform drives the translation platform to rise, so that the lower mold located at the forming station is clamped with the upper mold, and the embossing force of the force-applying structure is applied to the lower mold, so that the glass element replicates the microstructure.

6. The step-type hot pressing device according to claim 5, characterized in that: The step-by-step hot pressing device further comprises a temperature distribution in-situ observation structure and a shape contour in-situ observation structure, and the temperature distribution in-situ observation structure and the shape contour in-situ observation structure are respectively located on both sides of the translation stage.

7. The step-type hot pressing device according to claim 5, wherein: The step-type hot pressing device further comprises a hot pressing box having a vacuum cavity, and the mold structure, the heating structure and the force-applying structure are all located in the vacuum cavity.

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