Hot bending process of large-size unequal-thickness free-form surface lens

Abstract

The invention discloses a hot bending process of a large-size unequal-thickness free-form surface lens. The hot bending process comprises the following steps: (1) designing a hot pressing mold; 2) cutting the glass; 3) after preheating a mold, putting the glass into the mold; (4) after glass preheating is finished, mold pressing is started; 5) annealing the glass; and (6) glass polishing is carried out, the production efficiency of the large-size unequal-thickness free-form surface lens can be greatly improved, the production cost is reduced, and the machining difficulty is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of display devices, and particularly relates to a hot bending process for large-sized freeform lenses with unequal thicknesses. Background Art

[0002] In the process of implementing the present invention, the inventors found that the prior art has at least the following problems:

[0003] With the rapid development of the modern optical field in recent years, people have higher and higher requirements for the quality of imaging, and high-definition display has become particularly important. Among them, freeform lenses with unequal thicknesses play an important role in optical imaging systems. Freeform lenses with unequal thicknesses can effectively correct high-order aberrations, such as spherical aberration and coma, and improve the imaging quality. Secondly, freeform lenses can be designed into asymmetric and irregular shapes to achieve complex optical functions that are difficult to achieve with traditional spherical or aspherical mirrors, and the high degree of freedom in the design of freeform surfaces allows the use of fewer optical elements to achieve the same optical function; currently, there is an increasing demand for large-sized freeform lenses in the field of in-vehicle displays. Although there are relatively many types of lenses in the industry at present, their sizes are generally relatively small, and cold processing is generally the main method. Compared with lenses of general sizes, the processing of large-sized freeform lenses with unequal thicknesses is more difficult, with high costs and low efficiency.

[0004] Currently, it is difficult to process freeform lenses with unequal thicknesses whose outer dimensions are above 200 mm and thicknesses are between 5 mm and 50 mm. The surface shape of the freeform surface is extremely complex, and the accuracy requirements are extremely high. Traditional processing equipment and technologies are difficult to meet the requirements. Errors in processing will cause imaging blurring and distortion, and precise calculation of the tool position coordinates is required to achieve high-precision cutting and forming. Due to the high accuracy requirements of the product, the accuracy requirements for the processing equipment are also relatively high, the processing difficulty is relatively large, and the efficiency is low and the cost is high, and it is not suitable for mass production.

[0005] CN204062851U - Ultra-thin direct-lit LED freeform optical lens backlight module discloses an ultra-thin direct-lit LED freeform optical lens backlight module, including a plurality of freeform optical lenses. The plurality of freeform optical lenses are arranged according to the module size of the direct-lit LED backlight system. The freeform optical lens is an ultra-thin direct-lit LED freeform optical lens, which makes the light emitted by the LED light source form a rectangular light spot with uniform illuminance on the screen, and the distance between the LED light source and the screen is less than or equal to 30 mm. It also cannot solve the above technical problems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a hot bending process for large-sized freeform lenses with unequal thicknesses, which can greatly improve the production efficiency of large-sized freeform lenses with unequal thicknesses, reduce the production cost, and reduce the processing difficulty.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is: a hot bending process for large-sized freeform lenses with unequal thicknesses, comprising the following steps:

[0008] 1) Design a hot pressing mold; 2) Cut the glass; 3) After preheating the mold, place the glass into the mold; 4) Start molding after the glass preheating is completed; 5) Anneal the glass; 6) Polish the glass.

[0009] In the above step 1), design a hot pressing mold according to the actual surface shape of the product. The materials of the mold include tungsten steel, graphite, stainless steel, and aluminum alloy. The machining requirement for the surface shape accuracy of the mold is 5 - 50 μm. The surface of the mold is polished to a roughness within 500 nm. The polished mold surface is coated with a DLC diamond film layer or a TAC triacetate cellulose film, and the film layer thickness is between 300 - 1000 nm.

[0010] In the above step 2), cut the large glass sheet into the planar design size of the product by using a laser or a dicing wheel cutting method. Adopt a CNC edge grinding method to eliminate the bright and sharp areas at the edges of the glass. The ground glass is cleaned by a flat panel washing machine, and then inspected and covered with a protective film.

[0011] In the above step 3), first place the mold in a hot bending device and preheat it to between 200 - 400 °C.

[0012] In the above step 4), after the glass preheating is completed and it is fully softened, start molding. The downward pressing speed of the upper mold: 0.02 mm - 0.5 mm / minute, the pressure value: between 3 N - 30 N. After complete mold closing, hold the pressure for 5 - 40 minutes.

[0013] In the above step 5), start annealing after molding is completed. The annealing rate is 1 °C - 10 °C / minute, and stay at the strain point and annealing point of the glass for 10 - 30 minutes to allow the product to release internal stress.

[0014] In the above step 6), polish the surface of the molded product to remove apparent defects such as orange peel texture, pitting, and foreign objects on the surface.

[0015] In the above step 3), before hot pressing the glass, wipe the surface of the product clean with alcohol or distilled water and dry the surface with an air gun, then place the glass in the mold. At this time, the glass is in a semi-closed mold state. Raise the temperature of the hot bending machine to between 580 °C - 700 °C for preheating, and the preheating time is 30 - 70 minutes.

[0016] In the above step 5), the product extraction temperature is between 80 and 300 °C.

[0017] One of the above technical solutions has the following advantages or beneficial effects, which can greatly improve the production efficiency of large-size free-form lenses with unequal thicknesses, reduce the production cost, and reduce the processing difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the hot bending process of the large-size free-form lens with unequal thicknesses provided in the embodiment of the present invention;

[0019] Figure 2 is Figure 1 a schematic diagram of the hot bending process of the large-size free-form lens with unequal thicknesses; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0021] Embodiment 1

[0022] Refer to Figures 1-2 , a hot bending process for a large-size free-form lens with unequal thicknesses, comprising the following steps:

[0023] 1) Design a hot pressing mold; 2) Cut the glass; 3) After preheating the mold, place the glass into the mold; 4) Start molding after the glass preheating is completed; 5) Anneal the glass; 6) Polish the glass.

[0024] In the above step 1), the hot pressing mold is designed according to the actual surface shape of the product. The materials of the mold include tungsten steel, graphite, stainless steel, and aluminum alloy. The machining accuracy requirement for the mold surface shape is 5-50 μm, and the surface of the mold is polished to a roughness within 500 nm. The polished mold surface is coated with a DLC diamond film layer or a TAC triacetate cellulose film, and the film layer thickness is between 300 and 1000 nm.

[0025] In the above step 2), the large glass sheet is cut into the plane design size of the product by using a laser or a knife wheel cutting method, and the bright edge and sharp area at the edge of the glass are eliminated by using a CNC edge grinding method. The ground glass is cleaned by a flat panel washing machine, and then inspected and covered with a protective film.

[0026] In the above step 3), the mold is first preheated in a hot bending device to between 200 and 400 °C.

[0027] In the above step 4), after the glass is fully softened after preheating, molding begins, the upper mold pressing speed is: 0.02mm ~ 0.5mm / minute, the pressure value is: between 3N and 30N, and the pressure is maintained for 5 to 40 minutes after the mold is completely closed.

[0028] In the above step 5), annealing is started after molding is completed, and the annealing rate is 1°C to 10°C / minute. The glass is kept at the strain point and annealing point for 10 to 30 minutes to allow the product to release internal stress.

[0029] In the above step 6), the surface of the molded product is polished to remove surface defects such as orange peel, pitting, and foreign matter.

[0030] In the above step 3), before hot pressing the glass, wipe the surface of the product clean with alcohol or distilled water and blow dry the surface with an air gun, then put the glass in the mold. At this time, the glass is in a semi-closed mold state, and the temperature of the hot bending machine is raised to between 580℃ and 700℃ for preheating, and the preheating time is 30 to 70 minutes.

[0031] In the above step 5), the product ejection material temperature is between 80 and 300°C.

[0032] Large-sized lenses of different thicknesses and curvatures can be designed and manufactured according to specific optical requirements. The hot bending process can produce lenses with specific optical properties, such as specific refractive index distribution. High temperature causes the glass to soften slowly, and the glass becomes viscous. The plasticity is molded by fine processing of the mold, and then slowly annealed to release the stress in the glass, which helps to reduce the PV value of the product after molding.

[0033] By adopting the above structure, the production efficiency of large-sized free-form surface lenses with unequal thickness can be greatly improved, the production cost can be reduced, and the processing difficulty can be reduced.

[0034] Embodiment 2

[0035] A method for thermally bending large-sized free-form surface lenses with unequal thicknesses, the process is as follows:

[0036] The first process: design the hot pressing mold according to the actual surface shape of the product. The material of the mold can be tungsten steel, graphite, stainless steel, aluminum alloy, etc. The mold surface precision processing requirements are 5-50um, and the mold surface needs to be polished to a roughness of less than 500nm. The polished mold surface also needs to be plated with DLC diamond-like film or TAC triacetate cellulose film and other corrosion-resistant and scratch-resistant materials to protect the mold surface, increase the service life of the mold and reduce the friction coefficient of the mold surface. The film thickness is between 300 and 1000nm.

[0037] The second process: Use laser or cutter wheel cutting to cut large pieces of glass (glass uses low softening point glass) into the flat design size of the product. CNC edge grinding is used to eliminate the bright and sharp areas of the edges. One of the purposes of CNC is to make the glass more tough and not easy to break during the hot bending process. The ground glass needs to be cleaned by a flatbed cleaning machine and then inspected and covered with a protective film.

[0038] The third process: Place the mold in the hot bending equipment and preheat it to between 200 and 400°C. Preheating the mold helps to ensure a more even temperature distribution of the glass in the mold to avoid local high or low temperature affecting the molding effect of the product. Before hot pressing the glass, the surface of the product needs to be wiped clean with alcohol or distilled water and the surface needs to be blown dry with an air gun. Then place the glass in the mold. At this time, the glass is in a semi-closed mold state. Raise the temperature of the hot bending machine to between 580°C and 700°C for preheating. The preheating time is 30 to 70 minutes.

[0039] The fourth process: After the glass is fully softened after preheating, start molding. The upper mold pressing speed is 0.02mm~0.5mm / minute, and the pressure value is between 3N and 30N. It is controlled according to the product size. After the mold is completely closed, the pressure is maintained for 5 to 40 minutes.

[0040] The fifth process: After the molding is completed, annealing begins. The annealing rate is 1℃~10℃ / minute. It needs to stay at the strain point and annealing point of the glass for 10 to 30 minutes to allow the product to fully release the internal stress for better molding. The product ejection temperature is between 80 and 300℃, depending on the actual product.

[0041] The sixth process: The surface of the product after molding needs to be polished to remove surface defects such as orange peel, pitting, foreign matter, etc., to make the product appearance brighter and cleaner, and secondly to improve the transmittance of the product and reduce the surface roughness.

[0042] Large-sized lenses of different thicknesses and curvatures can be designed and manufactured according to specific optical requirements. The hot bending process can produce lenses with specific optical properties, such as specific refractive index distribution. High temperature causes the glass to soften slowly, and the glass becomes viscous. The plasticity is molded by fine processing of the mold, and then slowly annealed to release the stress in the glass, which helps to reduce the PV value of the product after molding.

[0043] By adopting the above structure, the production efficiency of large-sized free-form surface lenses with unequal thickness can be greatly improved, the production cost can be reduced, and the processing difficulty can be reduced.

[0044] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inner", "front", "center", "both ends", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0045] In the present invention, unless otherwise clearly specified and defined, the terms "installed", "set", "connected", "fixed", "swivelly connected", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements. Unless otherwise clearly defined, for those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A hot bending process for a large-sized freeform lens with unequal thicknesses, characterized in that, It includes the following steps: 1) Design a hot pressing mold; 2) Cut the glass; 3) After preheating the mold, place the glass into the mold; 4) Start hot pressing after the glass preheating is completed; 5) Anneal the glass; 6) Polish the glass.

2. The hot bending process of the large-size free-form lens with unequal thicknesses as claimed in claim 1, characterized in that, In the above step 1), design the hot pressing mold according to the actual surface shape of the product. The materials of the mold include tungsten steel, graphite, stainless steel, and aluminum alloy. The precision machining requirement for the surface shape of the mold is 5 - 50um. The surface of the mold is polished to a roughness within 500nm. The polished mold surface is coated with a DLC diamond film or a TAC triacetate cellulose film, and the film thickness is between 300 - 1000nm.

3. The hot bending process of the large-size free-form lens with unequal thicknesses as claimed in claim 2, wherein, In the above step 2), use laser or cutter wheel cutting to cut the large glass sheet into the planar design size of the product. Use CNC edge grinding to eliminate the bright and sharp areas at the edges of the glass. The ground glass is cleaned by a flat panel cleaning machine and then inspected and covered with a protective film.

4. The hot bending process of the large-sized freeform lens with unequal thicknesses as claimed in claim 3, characterized in that, In the above step 3), first place the mold in a hot bending device and preheat it to between 200 - 400°C.

5. The hot bending process of the large-size freeform lens with unequal thicknesses as claimed in claim 4, wherein In the above step 4), after the glass preheating is completed and it is fully softened, start hot pressing. The downward pressing speed of the upper mold: 0.02mm - 0.5mm / minute, the pressure value: between 3N - 30N. After complete mold closing, hold the pressure for 5 - 40 minutes.

6. The hot bending process of the large-size freeform lens with unequal thicknesses as claimed in claim 5, wherein In the above step 5), start annealing after hot pressing is completed. The annealing rate is 1°C - 10°C / minute. Stay at the strain point and annealing point of the glass for 10 - 30 minutes to allow the product to release internal stress.

7. The hot bending process of the large-size free-form lens with unequal thicknesses as claimed in claim 6, characterized in that, In the above step 6), polish the surface of the hot - pressed product to remove apparent defects such as orange peel texture, pitting, and foreign objects on the surface.

8. The hot bending process of the large-sized freeform lens with unequal thicknesses as claimed in claim 7, wherein, In the above step 3), before hot pressing the glass, wipe the product surface clean with alcohol or distilled water and dry the surface with an air gun. Then place the glass in the mold. At this time, the glass is in a semi - closed mold state. Raise the temperature of the hot bending machine to between 580°C - 700°C for preheating, and the preheating time is 30 - 70 minutes.

9. The hot bending process of the large-sized free-form lens with unequal thicknesses as claimed in claim 8, characterized in that In the above step 5), the product ejection and picking temperature is between 80 - 300°C.

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