Manufacturing method of reflective metal code disc

Abstract

The invention provides a manufacturing method of a reflective metal code disc, which comprises the following steps of: sequentially plating a first layer of chromium film, a dielectric film and a low-reflection film on the surface of a stainless steel base material, and removing the low-reflection film which does not need to be reserved on the surface through a uniform glue exposure, development and etching process, thereby obtaining the reflective metal code disc. Therefore, a high-reflection area with the reflectivity larger than 90% and a low-reflection area with the reflectivity smaller than 1% are formed on the surface of the metal code disc, and finally the reflection-type metal code disc is obtained through cutting.

Description

Technical Field

[0001] The present invention relates to the technical field of code disk processing, and specifically relates to a manufacturing method of a reflective metal code disk. Background Art

[0002] With the diversification of application fields and scenarios of photoelectric encoders, the external environment of some photoelectric encoder applications is relatively harsh. The photoelectric encoders assembled with common glass code disks and resin code disks have unstable performance characteristics (such as code disk fogging, deformation, etc.) in these harsh environments. Given the stable characteristics of metals, the demand for metal encoder code disks is gradually increasing. The types of metal code disks are mainly divided into transmissive metal code disks and reflective metal code disks.

[0003] While putting forward higher requirements for the seismic resistance of the code disk, with the miniaturization of servo motors, the thick automated robotic arms are gradually evolving and upgrading towards fine automated mechanical joints, which also puts forward higher requirements for the miniaturization of photoelectric encoders. The glass transmissive code disks used in traditional photoelectric encoders require a long optical path to achieve the emission and reception of optical signals, which also results in a large volume and long length of the traditional photoelectric encoder body and cannot well meet the needs of the newly added miniaturized application scenarios. In recent years, the industry solution proposed by Nikon in Japan is to optimize the original long-distance transmissive optical path into a short-distance reflective optical path by using a metal reflective code disk, effectively shortening the optical path distance by nearly 50%, and finally achieving the miniaturization of the photoelectric encoder and better meeting the multi-scenario application requirements.

[0004] Currently, for conventional metal reflective code disks, a low-reflection film layer, such as a chromium film, is directly plated on the surface of a metal substrate. Through a photolithography subtraction process, the part of the surface low-reflection film layer that is removed is the metal substrate area. Currently, there are stainless steel code disks and aluminum code disks for metal code disks, and their corresponding metal substrates are stainless steel substrates and aluminum substrates. The reflectivity of the stainless steel substrate is only about 60%. For example, a manufacturing method of a high-precision reflective metal code disk is disclosed in Patent CN116430682A. A low-reflection film layer is plated on the surface of a stainless steel substrate by magnetron sputtering, and photolithography is performed on the surface of the low-reflection film layer to form a code disk pattern, obtaining a stainless steel substrate with a code disk pattern; the reflectivity of the low-reflection film layer at 850 nm is ≤2%, and the reflectivity of the reflection area of the conventional stainless steel substrate can only reach about 60%. The reflectivity of the aluminum substrate is close to 90%, meeting the requirements of some customers for high reflectivity, but the roughness and surface flatness of the aluminum substrate are poor, affecting the accuracy of the aluminum code disk. Summary of the Invention

[0005] The present invention provides a method for manufacturing a reflective metal code disk. By sequentially depositing a first chromium film, a dielectric film, and a low-reflection film on the surface of a stainless-steel substrate, and then through the processes of spin coating, exposure, development, and etching, the unnecessary low-reflection film on the surface is removed, thereby forming a high-reflection area with a reflectivity greater than 90% and a low-reflection area with a reflectivity less than 1% on its surface. Finally, the reflective metal code disk is obtained by cutting.

[0006] To solve the above technical problems, the technical solution of the present invention is as follows: A method for manufacturing a reflective metal code disk, comprising the following steps: (1) Coating: Sequentially deposit a first chromium film, a dielectric film, and a low-reflection film on the surface of a stainless-steel substrate; (2) Etching pattern: According to a preset pattern, perform spin coating, exposure, and development on the surface of the coated stainless-steel substrate, and then etch to remove the low-reflection film, expose the dielectric film, form a code disk pattern, and obtain an intermediate product; (3) Cutting the product: Use a laser cutting process to cut the intermediate product into a reflective metal code disk.

[0007] The dielectric film is a silicon material composite film layer.

[0008] The silicon material composite film layer includes SiO2 and Si3N4.

[0009] The thickness of the first chromium film is 1000 - 1500 Å, the thickness of the dielectric film is 9000 - 10000 Å, and the thickness of the low-reflection film is 1600 - 2300 Å.

[0010] The reflectivity of the low-reflection film at 850 nm < 1%.

[0011] The low-reflection film includes a second chromium film and a chromium oxide film layer deposited in sequence, where the thickness of the second chromium film is 1000 - 1500 Å, and the thickness of the chromium oxide film layer is 600 - 800 Å.

[0012] The reflectivity of the dielectric film at 800 nm - 900 nm > 90%.

[0013] Coat the film by magnetron sputtering method.

[0014] In step (2), a subtractive etching process is used for etching.

[0015] Before coating, polish and clean the surface of the stainless-steel substrate.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In the present invention, a first chromium film, a dielectric film, and a low-reflection film are sequentially deposited on the surface of a stainless-steel substrate, and then through the processes of spin coating, exposure, development, and etching, the unnecessary low-reflection film on the surface is removed, so as to form a high-reflection area composed of the stainless-steel substrate, the first chromium film, and the dielectric film and a low-reflection area composed of the stainless-steel substrate, the first chromium film, the dielectric film, and the low-reflection film on its surface. Finally, a reflective metal code disk is obtained by cutting.

[0017] (2) In the present invention, in the low-reflection area composed of the stainless-steel substrate, the first chromium film, the dielectric film, and the low-reflection film, the low-reflection film is a second chromium film and a chromium oxide film layer deposited sequentially. The surface reflectivity of the chromium oxide film layer is relatively low, and the reflectivity at 850 nm is <1%. The second chromium film plays a role in blocking light, preventing light from penetrating into the lower dielectric film and reflecting between the dielectric film and the second chromium film, thereby affecting the product performance. The low-reflection film is removed during etching, so that a high-reflection area composed of the stainless-steel substrate, the first chromium film, and the dielectric film is formed. Among them, the dielectric film is a silicon material composite film layer, and the surface reflectivity is relatively high, and the reflectivity at 800 nm - 900 nm is >90%. Moreover, the dielectric film can protect the first chromium film from being etched, and the first chromium film also plays a role in blocking light, preventing part of the light from passing through the first chromium film and reflecting between the stainless-steel substrate and the first chromium film, thereby affecting the product performance.

[0018] (3) In the present invention, the thickness of the first chromium film is 1000 - 1500 Å, the thickness of the dielectric film is 9000 - 10000 Å, the thickness of the second chromium film is 1000 - 1500 Å, and the thickness of the chromium oxide film layer is 600 - 800 Å, ensuring the product performance of the metal code disk while meeting the reflectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the film layer structure after coating the stainless-steel substrate in the present invention; Figure 2 It is a schematic diagram of the stainless-steel substrate after etching the pattern after coating in the present invention; Figure 3 It is a schematic diagram of the reflectivity of the high-reflection area at different wavelengths in the present invention; Figure 4 It is a schematic diagram of the reflectivity of the low-reflection area at different wavelengths in the present invention; Figure 5 It is an enlarged schematic diagram of the intermediate product obtained after etching the pattern in the present invention; In the figure: 1 - stainless-steel substrate, 2 - first chromium film, 3 - dielectric film, 4 - second chromium film, 5 - chromium oxide film layer, 6 - low-reflection area, 7 - high-reflection area. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0021] Embodiment 1 The manufacturing method of the reflective metal code disk provided by the present invention includes the following steps: (1) Coating: A first chromium film 2, a dielectric film 3 and a low-reflection film are sequentially deposited on the surface of the stainless steel substrate 1 by magnetron sputtering, as Figure 1 shown.

[0022] Specifically, before coating, the surface of the stainless steel substrate is polished and cleaned; further, the cleaning steps are: ultrasonically cleaning the stainless steel substrate with an alkaline solution, rinsing with pure water, and finally drying with IPA evaporation. The cleaned substrate is placed on the coating fixture, and the edge of the product is fixed with a special buckle to protect the product from detaching from the coating fixture during the coating process. The magnetron sputtering coating method is adopted, and then the coating starts.

[0023] In this embodiment, the thickness of the first chromium film is 1000 - 1500 Å; the dielectric film is a silicon material composite film layer. Specifically, the silicon material composite film layer includes SiO2 and Si3N4, and the thickness of the dielectric film is 9000 - 10000 Å. The surface of the dielectric film is a high-reflection region 7, and its reflectivity at 800 nm - 900 nm is > 90%, as Figure 3 shown. Further, the silicon material composite film layer is formed by stacking SiO2 + Si3N4 + SiO2. The magnetron sputtering coating method is adopted, a silicon target is selected, argon gas is introduced, and O2 or N2 is mixed during the reaction to achieve the deposition of SiO2 or Si3N4, thereby forming a film stack on the surface of the first chromium film.

[0024] The thickness of the low-reflection film is 1600 - 2300 Å, and the low-reflection film includes a second chromium film 4 and a chromium oxide film layer 5 deposited in sequence. The thickness of the second chromium film is 1000 - 1500 Å, and the thickness of the chromium oxide film layer is 600 - 800 Å. The surface of the coated stainless steel product is light blue (mainly for 850 nm light source), and its surface (the surface of the low-reflection film) is a low-reflection region 6, and the reflectivity at 850 nm is < 1%, as Figure 4 shown.

[0025] (2) Etching pattern: According to the preset pattern, spin coating, exposure, and development are performed on the surface of the coated stainless steel substrate, and then the low-reflection film is etched away to expose the dielectric film, forming a code disk pattern, as Figure 5As shown, an intermediate product is obtained. In this intermediate product, the stainless-steel substrate, the first chromium film, and the dielectric film together form a high-reflection region, and the stainless-steel substrate, the first chromium film, the dielectric film, and the low-reflection film together form a low-reflection region. In this embodiment, the preset pattern is a regular line pattern, and the low-reflection region and the high-reflection region are arranged in an approximate 1:1 ratio, and the line tolerance can be controlled within ±1 μm. Before etching the pattern, the coated product is cleaned. After cleaning, a process of spin coating, exposure, development, and etching is used to remove the parts that are not required for the pattern, and subtractive etching process is used for etching.

[0026] (3)Cutting the product: The intermediate product is cut into a reflective metal code disc by a laser cutting process. The two most important dimensions during cutting are the cutting dimensions of the inner and outer circles of the product and the coaxiality between the cutting circle of the product and the product pattern; in this embodiment, the cutting dimension accuracy of the inner and outer circles of the product and the coaxiality between the cutting circle of the product and the product pattern are both controlled within ±0.0075 mm; before cutting the product, the product after etching the pattern is cleaned again.

[0027] Comparative Example 1 The manufacturing method of the reflective metal code disc in this comparative example is basically the same as that in Example 1, except that the thickness of the first chromium film is less than 1000 Å. When the reflective metal code disc prepared in this comparative example is used, the signal fluctuates; this is because the first chromium film mainly plays a role in blocking light. If its thickness is too thin, some light will pass through and be reflected between the film layer and the substrate, thus affecting the product performance.

[0028] Comparative Example 2 The manufacturing method of the reflective metal code disc in this comparative example is basically the same as that in Example 1, except that: the film thickness deviation of the dielectric film is 5%, that is, the film thickness of the dielectric film is less than 8550 Å or the film thickness of the dielectric film is greater than 9500 Å, and the reflectivity of its surface is lower than 90%.

Claims

1. A manufacturing method of a reflective metal code disk, characterized in that It includes the following steps: (1) Coating: successively deposit a first chromium film, a dielectric film, and a low-reflection film on the surface of the stainless-steel substrate; (2) Etching pattern: according to a preset pattern, perform spin coating, exposure, and development on the surface of the coated stainless-steel substrate, and then etch away the low-reflection film to expose the dielectric film, forming a code disk pattern to obtain an intermediate product; (3) Cutting the product: use a laser cutting process to cut the intermediate product into a reflective metal code disk.

2. The manufacturing method of the reflective metal code disk according to claim 1, characterized in that: The dielectric film is a silicon material composite film layer.

3. The manufacturing method of the reflective metal code disk according to claim 2, wherein: The silicon material composite film layer includes SiO2 and Si3N4.

4. The manufacturing method of the reflective metal code disk according to claim 1, characterized in that: The thickness of the first chromium film is 1000 - 1500 Å, the thickness of the dielectric film is 9000 - 10000 Å, and the thickness of the low-reflection film is 1600 - 2300 Å.

5. The manufacturing method of the reflective metal code disk according to claim 1, wherein: The reflectivity of the low-reflection film at 850 nm is < 1%.

6. The manufacturing method of the reflective metal code disc according to claim 1, characterized in that: The low-reflection film includes a second chromium film and a chromium oxide film layer deposited successively, where the thickness of the second chromium film is 1000 - 1500 Å and the thickness of the chromium oxide film layer is 600 - 800 Å.

7. The manufacturing method of the reflective metal code disk according to claim 1, characterized in that: The reflectivity of the dielectric film at 800 nm - 900 nm is > 90%.

8. The manufacturing method of the reflective metal code disk according to claim 1, characterized in that: Coating is carried out by magnetron sputtering method.

9. The manufacturing method of the reflective metal code disk according to claim 1, wherein: Subtractive etching process is used for etching the pattern.

10. The manufacturing method of the reflective metal code disk according to claim 1, characterized in that: Before coating, the surface of the stainless-steel substrate is polished and cleaned.

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