Aspherical mold surface structure

Abstract

The utility model provides a kind of aspherical mould core surface structure, including aspherical mould core, and first diamond film layer, second diamond film layer and third diamond film layer are arranged from inside to outside starting from the surface of aspherical mould core, the thickness of first diamond film layer, second diamond film layer and third diamond film layer increases in turn, the hardness of diamond-like film layer on the surface of aspherical mould core is increased in turn by the increase of thickness, first diamond film layer is as soft film layer, so that first diamond film layer can form close combination with aspherical mould core, second diamond film layer is as transition layer, in the cold and hot alternating impact of moulding process, transition layer can play buffering effect through its thickness and hardness characteristics, relieve thermal stress concentration, significantly improve the thermal shock resistance of overall film layer, hard film layer can enhance wear protection to mould core surface, reduce friction coefficient, resist the friction damage of high-temperature glass in moulding process.

Description

Technical Field

[0001] This utility model relates to the field of glass technology, specifically to a surface structure of an aspherical mold core. Background Technology

[0002] Aspherical glass lenses, with their excellent optical properties, are widely used in camera lenses, automotive optical systems, and other fields. Currently, mass production often employs a multi-station isothermal molding process for batch manufacturing. This process involves placing glass raw materials into a precision mold and, under an oxygen-free, nitrogen-filled atmosphere, sequentially undergoing four stages: preheating, pressurizing, annealing, and cooling / demolding, to complete the hot-pressing molding of a single aspherical glass lens. The number of times the mold completes this process is defined as the mold core's lifespan.

[0003] The aforementioned molding process places stringent requirements on the performance of the core component, the mold core. On one hand, the mold undergoes continuous alternating hot and cold shocks during molding, placing extremely high demands on the thermal shock resistance of the mold core's surface coating. On the other hand, to achieve glass molding deformation, the molding temperature must be set near the glass's sag temperature, and a certain pressure must be applied. At this point, the glass exhibits viscoelastic characteristics, combining solid elastic deformation and liquid viscous flow. If the mold core surface is not coated, the high-temperature glass is prone to sticking or adhering to the mold core surface. This not only affects the uniformity of glass elongation and the release process of the formed lens, but also leads to appearance defects such as flow marks and spots on the lens, or deviations in surface accuracy due to uneven deformation. In severe cases, it can even cause lens breakage and damage to the surface finish and precision of the mold core. Therefore, the mold core coating, which comes into direct contact with the high-temperature glass, must possess high hardness, high elastic modulus, and a low high-temperature coefficient of friction.

[0004] Currently, the mainstream molding die body material in the industry is tungsten carbide (tungsten steel). The coating schemes for its working surface are mainly divided into two categories: one is a single-layer diamond-like carbon (DLC) film, and the other is a Pt-Ir precious metal film. DLC films are existing technology; for example, Chinese patent CN113066714A discloses a film layer and its formation method. However, existing single-layer DLC films have inherent defects such as poor thermal shock resistance and easy delamination. In application, this easily leads to unstable surface accuracy of the molded lens, difficulty in release, and consequently, poor lens function and appearance, significantly shortening the mold's lifespan. While Pt-Ir precious metal films can alleviate adhesion problems to some extent, their usage cost is extremely high, and their adhesion to the tungsten carbide mold body is poor. During long-term cyclic use, the coating is still prone to peeling off, making it difficult to meet the economic and stability requirements of large-scale production.

[0005] In summary, existing surface coating solutions for tungsten carbide mold cores all have significant shortcomings and cannot simultaneously meet the comprehensive requirements of multi-station isothermal molding processes for coating thermal shock resistance, adhesion, hardness, and economy. There is an urgent need for a new mold core coating structure adapted to this process to overcome the deficiencies of existing technologies and ensure the production quality of glass aspherical lenses and the service life of molds. Utility Model Content

[0006] In view of the shortcomings of the existing technology, the purpose of this utility model is to propose an aspherical mold core surface structure to solve the problems mentioned in the background section above.

[0007] This utility model is achieved through the following technical solution: An aspherical mold core surface structure includes an aspherical mold core, and a first type of diamond film layer, a second type of diamond film layer, and a third type of diamond film layer disposed from the inside to the outside starting from the surface of the aspherical mold core, wherein the thickness of the first type of diamond film layer, the second type of diamond film layer, and the third type of diamond film layer increases sequentially.

[0008] Furthermore, the thickness of the first type of diamond film is 10nm~30nm; the thickness of the second type of diamond film is 30nm~40nm; and the thickness of the third type of diamond film is 80nm~170nm.

[0009] Furthermore, the thickness of the first type of diamond film is 30 nm; the thickness of the second type of diamond film is 40 nm; and the thickness of the third type of diamond film is 150 nm.

[0010] Furthermore, the aspherical mold core includes a planar portion and an aspherical contour portion, wherein the angle between the tangent of the aspherical contour portion and the planar portion is less than 60°.

[0011] Furthermore, when the included angle is 0°-24°, the thickness of the third type of diamond film is 140nm-170nm; when the included angle is 24°-48°, the thickness of the third type of diamond film is 100nm-140nm; and when the included angle is greater than 48°, the thickness of the third type of diamond film is 80nm-100nm.

[0012] Furthermore, the aspherical mold core is made of tungsten carbide.

[0013] The beneficial effects of this utility model are as follows: A surface structure for an aspherical mold core includes an aspherical mold core and a first type of diamond film layer, a second type of diamond film layer, and a third type of diamond film layer disposed from the inside to the outside of the surface of the aspherical mold core. The thickness of the first type of diamond film layer, the second type of diamond film layer, and the third type of diamond film layer increases sequentially. Through the increase in thickness, the hardness of the diamond-like film layer on the surface of the aspherical mold core increases sequentially. The first type of diamond film layer serves as a soft film layer, enabling it to form a tight bond with the aspherical mold core. The second type of diamond film layer serves as a transition layer. During the alternating hot and cold impacts of the molding process, the transition layer can play a buffering role through its own thickness and hardness characteristics, alleviating thermal stress concentration and significantly improving the overall thermal shock resistance of the film layer. The third type of diamond film layer serves as a hard film layer, which can enhance the wear resistance protection of the mold core surface, reduce the coefficient of friction, and resist frictional damage to the high-temperature glass during the molding process. Attached Figure Description

[0014] Figure 1 This is a cross-sectional view of the surface structure of an aspherical mold core according to the present invention.

[0015] The above figures include the following reference numerals: 1. Aspherical core; 11. Aspherical contour portion; 12. Planar portion; 2. Type I diamond film; 3. Type II diamond film; 4. Type III diamond film. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the description of these embodiments is intended to aid in understanding this utility model, but does not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.

[0017] Reference Figure 1 As shown, an aspherical mold core surface structure includes an aspherical mold core 1, and a first type of diamond film layer 2, a second type of diamond film layer 3, and a third type of diamond film layer 4 disposed from the inside to the outside starting from the surface of the aspherical mold core 1, wherein the thickness of the first type of diamond film layer 2, the second type of diamond film layer 3, and the third type of diamond film layer 4 increases sequentially.

[0018] The first type of diamond film layer 2, as a soft film layer, has the thinnest thickness and the lowest hardness. Its softness is more suitable for the surface of the aspherical mold core 1, and it can form a tight bond with the aspherical mold core 1. This solves the problem of poor bonding force and easy detachment between the existing single-layer diamond-like film or Pt-Ir precious metal film and the aspherical mold core 1, and provides a stable adhesion foundation for the overall film layer.

[0019] The second type of diamond film layer 3 serves as a transition layer, with a thickness between the first type of diamond film layer 2 and the third type of diamond film layer 4. It can effectively bear and release the internal stress of the third type of diamond film layer 4. At the same time, during the alternating hot and cold impacts of the molding process, the second type of diamond film layer 3 can play a buffering role through its own thickness and hardness characteristics, alleviate the concentration of thermal stress, significantly improve the overall thermal shock resistance of the film layer, and avoid the cracking and delamination defects caused by stress concentration in existing single-layer diamond-like films.

[0020] The third type of diamond film layer 4, as a hard film layer, has the largest thickness and the highest hardness. Its thickened design can fully utilize the advantages of high hardness and high density, enhance the wear resistance protection of the surface of the aspherical mold core 1, and resist the frictional damage of the high-temperature glass during the molding process. At the same time, the high-hardness third type of diamond film layer 4 can maintain a small surface roughness and high-temperature friction coefficient, reduce the adhesion between the glass and the aspherical mold core 1, ensure the uniformity of glass elongation, facilitate the lens release after molding, reduce quality problems such as flow marks and surface accuracy deviations, and avoid lens breakage or surface accuracy damage to the aspherical mold core 1.

[0021] The thickness of the first type of diamond film layer 2 is 10nm~30nm; the thickness of the second type of diamond film layer 3 is 30nm~40nm; and the thickness of the third type of diamond film layer 4 is 80nm~170nm. Through the matching design of the thickness and function of each layer, the bonding strength, thermal shock resistance, and wear resistance of the film layers are comprehensively improved, enabling the molding core to withstand more than 2000 molding cycles, greatly reducing the molding production cost. The total thickness of the first type of diamond film layer 2 to the third type of diamond film layer 4 is less than 240nm, and the surface shape accuracy of the lens is stable.

[0022] This utility model provides test tables 1 for embodiments and comparative examples 1 and 2. The process equipment is identical, all using commercially available and mature magnetically filtered cathode (FCVA) coating equipment. The surface to be coated is a φ10mm tungsten carbide aspherical mold core 1. The aspherical mold core 1 to be coated is placed in the process chamber of the coating equipment, and the vacuum degree in the process chamber is 10. -5The surface of the aspherical mold core 1 was treated with an ion beam cleaning process at a voltage of 1200V. After ion beam cleaning, the surface of the aspherical mold core 1 was rotated to face the sputtering deposition source window for diamond-like carbon (DLC) film deposition. After deposition, the hot-pressing life was verified using a HOYA MC-LAC130 optical glass preform, and a 20x optical microscope was used to observe how many hot-pressing cycles the coating layer on the mold core surface would undergo adhesion or delamination. The surface roughness and surface accuracy of the aspherical surface before, after (before) deposition, and after deposition were compared and analyzed using a Panasonic UA3P testing equipment. The test results are shown in Table 1.

[0023] Table 1

[0024] In this embodiment: the thickness of the first type of diamond film 2 is 30 nm; the thickness of the second type of diamond film 3 is 40 nm; and the thickness of the third type of diamond film 4 is 150 nm.

[0025] Comparative Example 1: The same coating operation as in the Example was used, but only one diamond-like carbon film layer was deposited, with a thickness of 220 nm.

[0026] Comparative Example 2: Using the same coating operation as in the Example, a multi-layer coating operation was performed. The thickness of the first type of diamond film 2 was 30 nm; the thickness of the second type of diamond film 3 was 40 nm; and the thickness of the third type of diamond film 4 was 300 nm, for a total coating thickness of 370 nm.

[0027] In this embodiment, as shown in Table 1, before coating, the surface roughness Ra of the aspherical mold core 1 was 8.9 nm. After the coating treatment described in the embodiment, the surface roughness Ra of the aspherical mold core 1 decreased to 3.4 nm. After 2000 molding cycles, the surface roughness of the aspherical mold core 1 only slightly increased to Ra 4.9 nm, and was still within the specified range (Ra < 5 nm). At the same time, the lens surface accuracy reached 0.167 μm after 2000 molding cycles, which was slightly higher than 0.151 μm before molding, but the overall change was not significant. The surface of the aspherical mold core 1 remained smooth and intact after 1,000 molding cycles. After 2,000 molding cycles, only slight pitting appeared in the center, and the lens release was normal. Only after 2,500 molding cycles did slight delamination appear on the surface of the aspherical mold core 1. This indicates that the mold core treated with multi-layer DLC coating has significantly improved thermal shock resistance, and its service life can reach more than 2,000 cycles.

[0028] In Comparative Example 1, as shown in Table 1, after 1000 molding cycles, the surface accuracy of the lens increased from 0.114 μm before molding to 0.692 μm, which no longer meets the surface accuracy requirements (PV less than 0.5 μm). The surface roughness of the aspherical mold core 1 also deteriorated from 3.3 nm before molding to 108.5 nm. The film layer also exhibited severe peeling, making separation between the lens and the aspherical mold core 1 difficult and seriously affecting the imaging quality of the aspherical glass lens. Comparative Example 1 demonstrates that the DLC film layer obtained using a single-layer coating has poor thermal shock resistance, significantly reduces the mold's lifespan, and requires decoating and recoating, greatly increasing production costs.

[0029] In Comparative Example 2, as shown in Table 1, after 1000 molding cycles, although the surface roughness of the aspherical mold core 1 only deteriorated from 3.4 nm before molding to 4.8 nm, the lens surface accuracy increased from 0.131 μm before molding to 0.458 μm. This indicates that an excessively thick coating has a significant impact on the change in lens surface accuracy. In particular, after 1500 molding cycles, the film layer showed a relatively serious peeling phenomenon. The reason for this is that due to the excessive thickness of the film layer, the normal force and shear force between the glass and the aspherical mold core 1 are too large during hot pressing, resulting in a large thermal mismatch that leads to film peeling. Consequently, the lens adheres to the aspherical mold core 1, thus affecting the lens release.

[0030] The aspherical mold core 1 includes a planar portion 12 and an aspherical contour portion 11, wherein the angle between the tangent of the aspherical contour portion 11 and the planar portion 12 is less than 60° (i.e., referring to...). Figure 1 The angle A in the aspherical surface is less than 60°, which avoids difficulties in mold core processing and abrupt changes in local contours caused by excessive angles, making the angle change of the aspherical contour 11 smoother. It also makes the flow path of the glass during molding smoother, reducing local accumulation, flow obstruction, or poor venting of glass caused by excessive angles, thereby reducing the risk of appearance defects such as flow marks, spots, and trapped air in the lens. At the same time, the smooth contour angle allows for a more uniform distribution of contact pressure between the glass and the surface of the aspherical mold core 1, and combined with the low coefficient of friction of the diamond-like carbon film, further ensures the surface accuracy and stability of the lens.

[0031] When the included angle is 0°-24°, the thickness of the third type diamond film 4 is 140nm-170nm; when the included angle is 24°-48°, the thickness of the third type diamond film 4 is 100nm-140nm; when the included angle is greater than 48°, the thickness of the third type diamond film 4 is 80nm-100nm.

[0032] The tangent of the aspherical contour portion 11 has a different angle with the planar portion 12. The tangential force of the large-angle film is relatively large. If the thickness of the third type diamond film 4 is too thick, it is easy to peel off. Therefore, the above problem can be avoided by setting each angle to match the thickness of each third type diamond film 4.

[0033] The aspherical mold core 1 is made of tungsten carbide. Tungsten carbide has moderate surface energy and a high coefficient of thermal expansion, which matches the physical properties of the first type of diamond film 2 well. This provides a stable adhesion substrate for the first type of diamond film 2, significantly enhancing the bonding force between the first type of diamond film 2 and the aspherical mold core 1. Furthermore, tungsten carbide exhibits excellent fatigue resistance, which is beneficial for repeated use and increases service life.

[0034] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0035] In the description of this utility model, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0036] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A surface structure for an aspherical mold core, characterized in that: It includes an aspherical mold core (1), and a first type of diamond film layer (2), a second type of diamond film layer (3) and a third type of diamond film layer (4) arranged from the inside to the outside starting from the surface of the aspherical mold core (1), wherein the thickness of the first type of diamond film layer (2), the second type of diamond film layer (3) and the third type of diamond film layer (4) increases sequentially.

2. The surface structure of an aspherical mold core according to claim 1, characterized in that: The thickness of the first type of diamond film (2) is 10nm~30nm; the thickness of the second type of diamond film (3) is 30nm~40nm; and the thickness of the third type of diamond film (4) is 80nm~170nm.

3. The surface structure of an aspherical mold core according to claim 2, characterized in that: The thickness of the first type of diamond film (2) is 30 nm; the thickness of the second type of diamond film (3) is 40 nm; and the thickness of the third type of diamond film (4) is 150 nm.

4. The surface structure of an aspherical mold core according to claim 1, characterized in that: The aspherical mold core (1) includes a planar portion (12) and an aspherical contour portion (11), wherein the angle between the tangent of the aspherical contour portion (11) and the planar portion (12) is less than 60°.

5. The surface structure of an aspherical mold core according to claim 4, characterized in that: When the included angle is 0°-24°, the thickness of the third type diamond film (4) is 140nm-170nm; when the included angle is 24°-48°, the thickness of the third type diamond film (4) is 100nm-140nm; when the included angle is greater than 48°, the thickness of the third type diamond film (4) is 80nm-100nm.

6. The surface structure of an aspherical mold core according to claim 1, characterized in that: The aspherical mold core (1) is made of tungsten carbide.

Images