Micro-lens array optical mold and manufacturing method thereof

Abstract

The invention relates to a micro-lens array optical mold and a manufacturing method thereof. The method comprises the following steps: processing a brass pressure head; the WC-Co powder is obtained; wC-Co powder is put into a hard alloy mold body, a hard alloy mold plane pressing head is adopted for a lower mold, a brass pressing head is adopted for an upper mold, pressing is conducted for 30-60 min through the single-axial force of 9.8-29.4 KN, and the micro-lens array is re-carved to a WC-Co hard alloy green body; the WC-Co hard alloy green body is placed in a graphite mold, two-step sintering is carried out under vacuum and no pressure by adopting a spark plasma sintering technology, and the surface of the obtained WC-Co hard alloy micro-lens array optical mold is provided with a Co3W3C layer which is completely covered and minimum in thickness by controlling the sintering process; and the Co3W3C layer is removed through polishing, and the micro-lens array optical mold is obtained. According to the invention, the traditional manufacturing process is obviously simplified, the processing efficiency is greatly improved, the manufacturing cost is effectively reduced, and meanwhile, the high precision and excellent mechanical properties of the die are ensured.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of material preparation, and particularly relates to a microlens array optical mold and a manufacturing method thereof. BACKGROUND

[0002] Precise glass forming is a new manufacturing optical element forming technology with high forming precision, high productivity and good uniformity, and is widely used for large-scale replication of optical lenses with microlens array. Under the condition of severe thermodynamics and thermal-chemical coupling, WC-Co cemented carbide is the preferred material for precise die pressing mold. The traditional manufacturing method of WC-Co cemented carbide microlens array optical mold usually relies on laser processing technology. However, this process has problems such as high manufacturing cost and low processing efficiency.

[0003] With the advancement of technology, additive manufacturing and photolithography technology have become the mainstream technology for manufacturing optical molds. However, these technologies still have deficiencies in manufacturing high-precision WC-Co cemented carbide microlens array optical molds, such as large equipment investment, complex process, limited material selection, etc. In addition, the traditional diamond turning technology cannot quickly manufacture WC-Co cemented carbide microlens array optical molds due to the influence of mold material and process error. The specific steps include: first, install the workpiece and rough process according to the set cutting parameters, adjust the cutting parameters after reaching a certain precision, optimize the cutting path for mold finishing, and finally improve the mold surface precision through surface polishing. This process has long cycle, high cost, and high requirements for tool materials. SUMMARY

[0004] The purpose of the present application is to provide a microlens array optical mold and a manufacturing method thereof, which includes the following steps: turning processing a microlens array brass punch; ultrasonic oscillation and mechanical stirring are used to mix WC and Co nano-powder; the mixed powder is pressed into shape by using single-axis pressing process to reproduce the microlens array; the green body is sintered by using spark plasma sintering technology to control the Co3W3C content on the surface of the mold; the surface Co3W3C is removed by using a handheld electric grinder to obtain a WC-Co cemented carbide complex optical mold with nanoscale precision. The microlens array optical mold rapid manufacturing method of the present application significantly simplifies the traditional manufacturing process, greatly improves the processing efficiency, effectively reduces the manufacturing cost, and at the same time ensures the high precision and excellent mechanical properties of the mold.

[0005] The technical solution for achieving the purpose of the present application is a manufacturing method of a microlens array optical mold, which includes the following steps:

[0006] Step (1): processing the brass punch: the brass punch has a structure matched with the microlens array;

[0007] Step (2): Obtain WC-Co powder: Co powder mass fraction 3-10%;

[0008] Step (3): WC-Co cemented carbide green body: Put the WC-Co powder obtained in step (2) into the cemented carbide mold body, use the cemented carbide mold flat pressure head as the lower mold and the brass pressure head prepared in step (1) as the upper mold, use 9.8-29.4 KN uniaxial force to press for 30-60 min, and copy the microlens array to the WC-Co cemented carbide green body;

[0009] Step (4): Put the WC-Co cemented carbide green body into the graphite mold, and use the spark plasma sintering technology to perform two-step sintering under vacuum and no pressure, control the sintering process to make the obtained WC-Co cemented carbide microlens array optical mold surface have a completely covered Co3W3C layer with minimum thickness;

[0010] Step (5): Polish the Co3W3C layer on the surface of the WC-Co cemented carbide microlens array optical mold to obtain the microlens array optical mold.

[0011] Further, the brass pressure head body in step (1) is cylindrical with a diameter of 15±1 mm, and the structure of the brass pressure head surface matched with the microlens array is a 5×5 orthogonal arrangement of microlens arrays.

[0012] Further, step (2) is specifically: weigh the WC powder and Co powder, put them into the conical flask in turn and pour anhydrous ethanol, mix the powders based on ultrasonic oscillation and mechanical stirring, put the obtained slurry in a vacuum drying box until it is completely dried and solidified, and obtain the WC-Co powder by grinding through a 100 mesh sieve.

[0013] Further, the particle size of the WC powder weighed in step (2) is 100±50 nm, and the particle size of the Co powder weighed is 100-500 nm.

[0014] Further, step (4) two-step sintering is specifically:

[0015] First step sintering: heating rate 50-100℃ / min, sintering temperature 700-1200℃, holding time 3-8 min;

[0016] Second step sintering: heating rate 50-100℃ / min, sintering temperature 1300-1500℃, holding time 3-8 min, mold surface reaction: 3WC+Co→Co3W3C+C;

[0017] After holding, cool down to 900℃ at a cooling rate of 50℃ / min, and then cool down with the furnace.

[0018] Further, the step (4) graphite mold comprises a graphite mold upper pressing head, a graphite mold lower pressing head and a graphite mold main body part;

[0019] The graphite mold main body part is a hollow cylinder, the graphite mold main body part is provided with the graphite mold upper pressing head and the graphite mold lower pressing head respectively, and a vacuum environment is formed; the WC-Co hard alloy green body to be sintered is placed on the graphite mold lower pressing head.

[0020] Further, the step (5) utilizes a handheld electric grinder, adopts a wool polishing head and a grinding paste with a mesh number of 350-20000 to polish the WC-Co hard alloy microlens array optical mold to remove the surface Co3W3C.

[0021] A microlens array optical mold is prepared by the method.

[0022] Compared with the prior art, the present application has the following advantages:

[0023] The manufacturing method of the present application designs the structure of the brass pressing head according to the optical microlens array, presses the green body, utilizes the discharge plasma sintering technology to prepare the WC-Co hard alloy mold, removes the surface Co3W3C by using the handheld electric grinder and the polishing paste, improves the mold surface quality to the nanometer level, and makes the morphology deviation reach the submicron level; the Co3W3C content is controlled by adjusting the final sintering temperature, and the WC-Co complex optical mold with the nanometer surface quality and the submicron morphology deviation can be produced by polishing. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a WC-Co hard alloy complex optical mold production flow chart.

[0025] Figure 2 It is a WC-Co hard alloy complex optical mold surface SEM graph before polishing.

[0026] Figure 3 It is a WC-Co hard alloy complex optical mold surface SEM graph after polishing.

[0027] Figure 4 It is a microlens array brass pressing head schematic diagram.

[0028] Figure 5 It is a microlens array green body pressing schematic diagram.

[0029] Figure 6 It is a graphite mold schematic diagram.

[0030] Figure 7 It is a microlens array optical mold schematic diagram.

[0031] BRIEF DESCRIPTION OF DRAWINGS:

[0032] 11-micro-lens array brass punch, 12-WC-Co powder, 13-cemented carbide die flat punch, 14-cemented carbide die body, 21-graphite die upper punch, 22-WC-Co cemented carbide green body, 23-graphite die lower punch, 24-graphite die body part. DETAILED DESCRIPTION

[0033] The application will be further described in detail below with reference to the accompanying drawings.

[0034] The micro-lens array optical mold rapid manufacturing method of the application processes a micro-lens array structure on a brass round bar, the surface quality of which reaches the nanometer level, and the morphology deviation is sub-micron level; WC and Co powders are mixed according to the design ratio, and the micro-lens array is accurately copied to the WC-Co cemented carbide green body by using the single-axis pressing process; the green body is sintered in two steps under vacuum by using the spark plasma sintering technology, and the final sintering temperature is used to control the content of Co3W3C on the surface; finally, the mold is polished by using a handheld electric grinder to remove the Co3W3C on the surface, and a WC-Co cemented carbide complex optical mold is obtained. The mold can realize high-precision optical surface and excellent mechanical properties without additional processing or modification steps, and is suitable for efficient manufacturing of various optical components.

[0035] The system suitable for the micro-lens array optical mold rapid manufacturing method of the application includes a micro-lens array brass rod, an ultrasonic platform, a vacuum drying box, a hydraulic press, a handheld electric grinder, a spark plasma sintering furnace and a graphite mold. The brass rod is low in cost and easy to process, and can meet the processing requirements of the micro-lens array surface, as shown in FIG. 1. The WC and Co powders are mixed on the ultrasonic platform. The mixed slurry is solidified in the vacuum drying box. The micro-lens array of the brass rod is copied to the green body by using the hydraulic press. The micro-lens array green body is placed in the graphite mold and then transferred to the spark plasma sintering furnace for sintering. The surface morphology of the mold after sintering is shown in FIG. 2. The surface of the mold is polished by using the handheld electric grinder. The surface morphology of the mold after polishing is shown in FIG. 3. Figure 1 Figure 2 Figure 3 The graphite mold is a special pressureless sintering mold with a through hole in the center of the main body. When the WC-Co green body is placed on the lower end cover, it is flush with the position of the through hole. The upper and lower end covers are the same in size, and the size can be adjusted according to actual requirements, as shown in FIG. 4. The metal mold for pressing the WC-Co green body is shown in FIG. 5, which is a punch with a flat lower die and a main body. Figure 6 Figure 5

[0036] The micro-lens array optical mold rapid manufacturing method of the application includes the following steps:

[0037] Step i: Obtain a micro-lens array brass punch.

[0038] ​​​​The micro-lens array setting is based on the design of the turning parameters, and the micro-lens 5*5 array brass indenter is turned out, the surface quality reaches the nanometer level, the morphology deviation reaches the sub-micron level, the unit lens diameter is 2mm, the depth is 60μm, and the curvature radius is 8.363mm.

[0039] Step ii: Obtain WC-Co powder.

[0040] According to the proportion that the mass fraction of Co powder is less than 10%, WC powder with a particle size of 100nm and Co powder with a particle size of 500nm are weighed respectively, and are put into conical bottles and poured into appropriate amount of anhydrous ethanol. The powders are mixed by ultrasonic oscillation and mechanical stirring. The obtained slurry is placed in a vacuum drying box with a temperature setting of 120℃, and after complete drying and curing, it is sieved by a 100 mesh sieve to obtain WC-Co powder.

[0041] Step iii: Pressing.

[0042] The WC-Co powder is loaded into a hard alloy mold, and a uniaxial pressure of 9.8-29.4KN is applied to the micro-lens array brass indenter by a hydraulic press, as shown in Figures 4-5 , and after 1h, the micro-lens array green body is removed and taken out.

[0043] Step iv: Sintering.

[0044] The micro-lens array green body is loaded into a graphite mold, and a two-step sintering is carried out under vacuum and pressure by using discharge plasma sintering technology, and the obtained micro-lens array optical mold has a surface composition as shown in Figure 2 .

[0045] The whole sintering process includes: pre-sintering, holding, final sintering, secondary holding, and cooling five stages.

[0046] Pre-sintering stage: in a vacuum environment, the temperature is raised at a rate of 100℃ / min, and the sintering temperature is 700-1200℃.

[0047] Holding stage: keep at the pre-sintering temperature for 3-8min.

[0048] Final sintering: the temperature is raised at a rate of 100℃ / min, and the sintering temperature is 1300-1400℃.

[0049] Secondary holding: keep at the final sintering temperature for 3-8min.

[0050] Cooling stage: the temperature is lowered at a rate of 50℃ to 900℃, and then the furnace is cooled.

[0051] After cooling, the WC-Co hard alloy micro-lens array mold is taken out.

[0052] Step v: polishing is performed.

[0053] Polishing is performed using a hand-held electric grinder and polishing paste with a mesh size of 350-20000, as shown in Figure 3 After polishing, the Co3W3C on the WC-Co surface is removed.

[0054] The micro-lens array optical mold rapid manufacturing method of the present application is effective, and can quickly and in large quantities manufacture micro-lens array molds meeting requirements.

[0055] The micro-lens array optical mold rapid manufacturing method of the present application is not only limited to the manufacture of micro-lens array optical molds, but also applicable to the manufacture of optical molds of other micro-structures.

[0056] The micro-lens array optical mold rapid manufacturing method of the present application, through the five links of turning the pressing head, powder mixing, pressing the green body, sintering and polishing, reduces production cost, simplifies the process and has high processing efficiency.

[0057] Obviously, the above examples are merely examples for clearly illustrating but not limiting the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments are not required to be exhausted. The changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for manufacturing a microlens array optical mold, characterized in that, Includes the following steps: Step (1): Machining the brass indenter: The brass indenter has a structure that matches the microlens array; Step (2): Obtain WC-Co powder: Co powder mass fraction 3-10%; Step (3): WC-Co cemented carbide green blank: Place the WC-Co powder obtained in step (2) into the cemented carbide mold body. The lower mold uses a cemented carbide mold flat pressure head, and the upper mold uses a brass pressure head prepared in step (1). Press with a uniaxial force of 9.8-29.4KN for 30-60min to replicate the microlens array onto the WC-Co cemented carbide green blank. Step (4): Place the WC-Co cemented carbide green blank in a graphite mold and perform two-step sintering under vacuum and pressureless conditions using spark plasma sintering technology. Control the sintering process so that the surface of the obtained WC-Co cemented carbide microlens array optical mold has a fully covered Co3W3C layer with the smallest thickness. Step (5): Polishing removes the Co3W3C layer on the surface of the WC-Co hard alloy microlens array optical mold to obtain the microlens array optical mold.

2. The method according to claim 1, characterized in that, The brass indenter in step (1) is cylindrical in shape with a diameter of 15±1mm. The brass indenter surface and the microlens array are matched by a 5×5 orthogonally arranged microlens array.

3. The method according to claim 1, characterized in that, Step (2) is as follows: Weigh WC powder and Co powder, put them into an Erlenmeyer flask and pour in anhydrous ethanol. Mix the powders by ultrasonic oscillation and mechanical stirring. Place the obtained slurry in a vacuum drying oven until it is completely dried and solidified. Grind it through a 100-mesh sieve to obtain WC-Co powder.

4. The method according to claim 3, characterized in that, In step (2), the WC powder with a particle size of 100±50nm and the Co powder with a particle size of 100-500nm are weighed.

5. The method according to claim 4, characterized in that, Step (4) involves two sintering steps: First step sintering: heating rate is 50-100℃ / min, sintering temperature is 700-1200℃, and holding time is 3-8min; The second step is sintering: the heating rate is 50-100℃ / min, the sintering temperature is 1300-1500℃, the holding time is 3-8min, and the reaction occurs on the mold surface: 3WC+Co→Co3W3C+C; After holding at the temperature, the temperature is reduced to 900℃ at a rate of 50℃ / min, and then cooled with the furnace.

6. The method according to claim 5, characterized in that, Step (4) The graphite mold includes an upper graphite mold pressure head, a lower graphite mold pressure head, and a main body of the graphite mold; The main body of the graphite mold is a hollow cylinder. The upper and lower parts of the main body of the graphite mold are respectively equipped with an upper graphite mold pressure head and a lower graphite mold pressure head, forming a vacuum environment. The WC-Co cemented carbide green blank to be sintered is placed on the lower graphite mold pressure head.

7. The method according to claim 4, characterized in that, Step (5) Use a handheld electric grinder with a wool polishing head and polishing paste with a mesh size of 350-20000 to polish and remove Co3W3C from the surface of the WC-Co hard alloy microlens array optical mold.

8. A microlens array optical mold, characterized in that, Prepared using the method described in any one of claims 1-7.

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