Reflection type optical scale for encoder and reflection type optical encoder

Abstract

To provide a reflection type optical scale for an encoder capable of suppressing undulation.SOLUTION: Provided is a reflection type optical scale 10 for an encoder that has a disk-shaped metal base material 1 having a first surface, and a second surface that opposes the first surface, and a low-reflection layer 2 disposed in a pattern shape along a circumferential direction of the metal base material 1 in a first surface side of the metal base material 1, where the thickness of the metal base material 1 is 0.3 mm or more and 1.1 mm or less, and the undulation of the reflection type optical scale for an encoder is 30 μm or smaller.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a reflective optical scale for an encoder and a reflective optical encoder. [Background technology]

[0002] Conventionally, optical encoders have been used in servo motors equipped with a control mechanism, etc. Optical encoders are classified into transmissive encoders and reflective encoders, and reflective encoders have the advantage that the optical path is shorter than that of transmissive encoders, making them easier to miniaturize and thin, and that they are easier to assemble because they do not require positioning of the light-emitting element and the light-receiving element.

[0003] A reflective optical encoder includes a reflective optical scale, a light source such as an LED that irradiates the scale with light, and a photodetector that detects reflected light from the scale. The reflective optical scale has reflective areas (highly reflective areas) and non-reflective areas (lowly reflective areas) arranged alternately, and the reflectance of light in the reflective areas is higher than that in the non-reflective areas (see, for example, Patent Document 1). As a result, the intensity of light reflected from the scale and incident on the photodetector varies depending on the change in the position of the scale. The photodetector detects the intensity of light that occurs when the position of the scale moves in the length measurement direction. The reflective optical encoder processes displacement information of the position of this scale according to the detected intensity of light, and can obtain position information. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-241248 A Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, reflective optical scales are manufactured by singulating a polygonal body in which a plurality of reflective optical scales are arranged side by side. When the substrate constituting the polygonal body is a metal substrate, the metal substrate is often singulated by etching in the singulation process because the processing accuracy is good. However, singulation by etching the metal substrate is disadvantageous in terms of cost.

[0006] Therefore, it has been considered to reduce the etching cost by reducing the thickness of the metal substrate. Furthermore, the thinner the metal substrate, the more accurate the etching process. However, if the metal substrate is thin, the reflective optical scale becomes difficult to handle. Furthermore, if the metal substrate is thin, the metal substrate itself is likely to undulate or warp, which may cause the reflective optical scale to undulate or warp. Furthermore, when etching a metal substrate, a bridge is usually provided on the outer periphery of the reflective optical scale to connect the reflective optical scale to the frame. After etching, the bridge is cut to separate the reflective optical scale into individual scales. In this case, bridge marks are generated on the reflective optical scale. The bridge marks become burrs or protrusions, causing partial distortion of the reflective optical scale.

[0007] The present invention has been made in consideration of the above circumstances, and has as its main object to provide a reflective optical scale for an encoder that is capable of suppressing waviness. [Means for solving the problem]

[0008] One embodiment of the present disclosure provides a reflective optical scale for an encoder having a disk-shaped metal substrate having a first surface and a second surface opposite to the first surface, and a low-reflection layer arranged in a pattern along the circumferential direction of the metal substrate on the first surface side of the metal substrate, wherein the thickness of the metal substrate is 0.3 mm or more and 1.1 mm or less, and the waviness of the reflective optical scale for an encoder is 30 μm or less.

[0009] Another embodiment of the present disclosure provides a reflective optical encoder comprising the above-mentioned reflective optical scale for an encoder, a light source that irradiates measurement light onto the surface of the reflective optical scale for an encoder on which the low-reflection layer is disposed, and a photodetector that detects reflected light from the reflective optical scale for an encoder. Effect of the Invention

[0010] The reflective optical scale for an encoder according to the present disclosure has the advantage that it is possible to suppress waviness. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic top view illustrating a reflective optical scale for an encoder in the present disclosure. [Diagram 2] FIG. 2 is a partially enlarged cross-sectional view illustrating a reflective optical scale for an encoder in the present disclosure. [Diagram 3] 1A and 1B are schematic diagrams illustrating undulations of a reflective optical scale for an encoder. [Figure 4] 1A and 1B are schematic diagrams illustrating undulations of a reflective optical scale for an encoder. [Diagram 5] 1 is a schematic cross-sectional view illustrating a reflective optical scale for an encoder according to the present disclosure. [Figure 6] 1 is a schematic perspective view illustrating a reflective optical encoder according to the present disclosure. [Figure 7] FIG. 2 is a schematic top view illustrating a reflective optical scale polygon for an encoder according to the present disclosure. [Figure 8] 1 is a schematic cross-sectional view illustrating a punching device used in a singulation step in a manufacturing method for a reflective optical scale for an encoder in the present disclosure. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present disclosure includes a reflective optical scale for an encoder and a reflective optical encoder in the embodiments. Hereinafter, the embodiments of the present disclosure will be described with reference to the drawings. However, the present disclosure can be implemented in many different forms, and should not be interpreted as being limited to the description of the embodiments exemplified below. In addition, in the drawings, the width, thickness, shape, etc. of each part may be shown diagrammatically compared to the actual form in order to make the explanation clearer, but these are merely examples and do not limit the interpretation of the present disclosure. In addition, in this specification and each figure, the same reference numerals are attached to elements similar to those described above with respect to the previously mentioned figures, and detailed explanations may be omitted as appropriate.

[0013] In this specification, when describing an aspect in which another component is disposed on a certain component, the term "above" or "below" includes both cases in which another component is disposed directly above or below a certain component so as to be in contact with the component, and cases in which another component is disposed above or below a certain component with another component interposed therebetween, unless otherwise specified. In addition, in this specification, when describing an aspect in which another component is disposed on the surface of a certain component, the term "on the surface side" or "on the surface" includes both cases in which another component is disposed directly above or below a certain component so as to be in contact with the component, and cases in which another component is disposed above or below a certain component with another component interposed therebetween, unless otherwise specified.

[0014] Furthermore, in this specification, the "reflective optical scale for an encoder" may be simply referred to as the "optical scale".

[0015] The reflective optical scale for an encoder, the reflective optical encoder, and the polygonal reflective optical scale body for an encoder according to the present disclosure will be described in detail below.

[0016] A. Reflective optical scale for encoders The reflective optical scale for an encoder in the present disclosure comprises a disk-shaped metal substrate having a first surface and a second surface opposite to the first surface, and a low-reflection layer arranged in a pattern along the circumferential direction of the metal substrate on the first surface side of the metal substrate, wherein the thickness of the metal substrate is 0.3 mm or more and 1.1 mm or less, and the waviness of the reflective optical scale for an encoder is 30 μm or less.

[0017] FIG. 1 is a schematic top view showing an example of a reflective optical scale for an encoder in the present disclosure. FIG. 2(a) is an enlarged cross-sectional view of the dotted frame a portion in FIG. 1 taken along the line AA. As illustrated in FIG. 1 and FIG. 2(a), the reflective optical scale for an encoder 10 has a disk-shaped metal substrate 1 having a first surface 1a and a second surface 1b facing the first surface 1a, and a low-reflection layer 2 arranged in a pattern along the circumferential direction of the metal substrate 1 on the first surface 1a side of the metal substrate 1. The thickness T1 of the metal substrate 1 is within a predetermined range. The reflective optical scale for an encoder 10 has a holed disk shape, and low-reflection regions R2, which are regions where the low-reflection layer 2 is provided, and high-reflection regions R1, which are regions where the low-reflection layer 2 is not provided, are alternately arranged in the circumferential direction. The low-reflection region R2 has the metal substrate 1 and the low-reflection layer 2 in the thickness direction of the reflective optical scale for an encoder 10. The high-reflection region R1 has the metal substrate 1. The reflectance of light in the high-reflection region R1 is higher than the reflectance of light in the low-reflection region R2. Note that the reflectance of light in the high-reflection region R1 and the reflectance of light in the low-reflection region R2 indicate the reflectance at the same wavelength and the same incident angle.

[0018] According to the present disclosure, the thickness of the metal base material is within a predetermined range and is relatively thick, thereby suppressing undulation and warping. Furthermore, since the waviness of the reflective optical scale for an encoder is equal to or less than a predetermined value, the accuracy of the reflective optical scale for an encoder can be improved, and the accuracy of a reflective optical encoder including the reflective optical scale for an encoder can be improved.

[0019] Moreover, the reflective optical scale for an encoder in the present disclosure is preferably manufactured by punching a polygonal body, as described below. In the case of punching a polygonal body, unlike etching a polygonal body, there is no need to provide a bridge connecting the reflective optical scale for an encoder and a frame, so bridge marks are not generated. Therefore, the occurrence of partial distortion can be suppressed. In addition, there is no need to reduce the thickness of the metal base material in order to reduce costs and improve accuracy. Therefore, the metal base material can be made thick, and as described above, waviness and warping can be suppressed. In addition, it is advantageous in terms of cost compared to etching a polygonal body.

[0020] Hereinafter, each configuration of the reflective optical scale for an encoder according to the present disclosure will be described.

[0021] 1. Waviness of reflective optical scales for encoders The waviness of the reflective optical scale for an encoder in the present disclosure is 30 μm or less, preferably 20 μm or less, and more preferably 15 μm or less. When the waviness is within the above range, the accuracy of a reflective optical encoder including the reflective optical scale for an encoder can be improved. On the other hand, the smaller the waviness, the better, and there is no particular lower limit.

[0022] In this specification, the "waviness" of the reflective optical scale for an encoder is defined as follows: First, a circle of a given radius R is drawn centered on the center of the reflective optical scale for an encoder, and a three-dimensional measuring machine is used to acquire data on the locus of the circle with the circumferential component as X and the height component as Y. Next, a Fourier transform is performed, and the difference between the maximum and minimum values ​​of the Y component for the second-order component is defined as the waviness.

[0023] In the present disclosure, by defining "waviness" as described above, waviness can be appropriately evaluated. The reason for this will be described below.

[0024] For example, as shown in FIG. 3(a), when the reflective optical scale for an encoder is placed horizontally, the coordinate measuring machine acquires data as shown in FIG. 3(b). When this data is Fourier transformed, the first and second order components as shown in FIG. 3(c) are obtained. On the other hand, when the reflective optical scale for an encoder is placed at an angle, as shown in FIG. 4(a), the coordinate measuring machine acquires data as shown in FIG. 4(b). When this data is Fourier transformed, the first and second order components as shown in FIG. 4(c) are obtained. When the reflective optical scale for an encoder is placed at an angle, the difference between the maximum and minimum values ​​of the Y component in FIG. 4(b) may be larger than when the reflective optical scale for an encoder is placed horizontally, and as a result, the difference between the maximum and minimum values ​​of the Y component for the first order component in FIG. 4(c) may be larger. In contrast, the difference between the maximum and minimum values ​​of the Y component for the second-order component is approximately the same whether the reflective optical scale for an encoder is placed horizontally or tilted. Therefore, by using the second-order component, the ripple can be appropriately evaluated regardless of the state in which the reflective optical scale for an encoder is placed when measuring the ripple.

[0025] Furthermore, since the first-order component has a period of one rotation, even if the difference between the maximum and minimum values ​​of the Y component for the first-order component is relatively large, it may be possible to correct it in a reflective optical encoder equipped with a reflective optical scale for an encoder. In contrast, since the second-order component has a period of 1 / 2 rotation, it is difficult to correct it in a reflective optical encoder equipped with a reflective optical scale for an encoder. Therefore, it can be said that waviness can be appropriately evaluated by using the second-order component.

[0026] In addition, in this specification, "distortion" of the reflective optical scale for an encoder refers to a state in which the surface of the reflective optical scale for an encoder is significantly rough in a partial area of ​​the surface of the reflective optical scale for an encoder. Distortion also refers to a spacing that is smaller than that of waviness. Specifically, distortion is defined as a spacing that is 1 / 10 or less (mm) of the outer diameter of the reflective optical scale for an encoder, or 2.5 mm, whichever is larger.

[0027] Here, the waviness is found by the following method. First, a circle with a radius of 10.5 mm is drawn with the center of the reflective optical scale for an encoder as the center, and data is acquired on the locus of the circle with the circumferential component as X and the height component as Y using a three-dimensional measuring machine. Next, a Fourier transform is performed, and the difference between the maximum and minimum values ​​of the Y component for the secondary component is taken as the waviness. Note that if the outer diameter of the reflective optical scale for an encoder is small, it may not be possible to draw the circle with a radius of 10.5 mm. Therefore, if the radius of the reflective optical scale for an encoder is 10.5 mm or less, the radius of the circle is determined as the radius of the reflective optical scale for an encoder multiplied by 0.875. Also, if the reflective optical scale for an encoder is a perforated disk shape and the inner diameter of the reflective optical scale for an encoder is large, it may not be possible to draw the circle with a radius of 10.5 mm. Therefore, if the inner radius of the reflective optical scale for encoder is 10.5 mm or more, a circle is drawn 5 mm inward from the outer circumference of the reflective optical scale for encoder, centered on the center of the reflective optical scale for encoder. For the three-dimensional measuring machine, for example, a one-shot 3D shape measuring machine VR-6000 series manufactured by Keyence Corporation is used. The measurement surface is the surface on the low reflection layer side of the reflective optical scale for encoder.

[0028] In addition, in this specification, "waviness" and "distortion" are distinguished from surface texture parameters defined in JIS B0601:2013. In JIS B0601:2013, the following surface texture parameters are defined: profile curve parameters (Pa, Pz, etc.) obtained from a profile curve, roughness parameters (Ra, Rz, etc.) obtained from a roughness curve, and waviness parameters (Wa, Wz, etc.) obtained from a waviness curve. The profile curve, roughness curve, and waviness curve are curves obtained by applying a profile curve filter to a measured profile curve. The profile curve parameters, roughness parameters, and waviness parameters are obtained from a reference length portion of the profile curve. Therefore, the profile curve parameters, roughness parameters, and waviness parameters can be said to represent surface texture in a microscopic region. In contrast, in this specification, "waviness" is obtained by applying a Fourier transform as described above. In addition, "waviness" is determined by the above method, and can be said to represent the height difference in the macro area of ​​the reflective optical scale for encoders. Therefore, "waviness" is different from the surface texture parameters specified in JIS B0601:2013.

[0029] Methods for adjusting the waviness of a reflective optical scale for an encoder include, for example, when punching a multi-sided body as described below, a method for adjusting the waviness of the metal substrate to be processed that constitutes the multi-sided body, and a method for adjusting the hardness of the punching blade.

[0030] If the waviness of the metal substrate to be processed is small, the waviness of the reflective optical scale for encoder will also be small. Specifically, the waviness of the metal substrate to be processed is 30 μm or less, may be 20 μm or less, or may be 10 μm or less. The method for determining the waviness of the metal substrate to be processed is the same as the method for determining the waviness of the reflective optical scale for encoder described above.

[0031] Furthermore, if the punching blade is hard, the waviness of the reflective optical scale for encoder tends to be reduced.

[0032] 2. Shape of reflective optical scale for encoder The reflective optical scale for an encoder in the present disclosure is typically used as an optical scale for a rotary encoder. The reflective optical scale for an encoder is disk-shaped. The reflective optical scale for an encoder may be, for example, a disk-shaped with a hole having a central hole, or may not have a central hole.

[0033] When the reflective optical scale for an encoder in the present disclosure is disk-shaped with a hole, the outer diameter of the reflective optical scale for an encoder in a plan view is, for example, 15 mm or more, and may be 20 mm or more. On the other hand, the outer diameter of the reflective optical scale for an encoder is, for example, 70 mm or less, and may be 60 mm or less. Specifically, the outer diameter of the reflective optical scale for an encoder may be, for example, 15 mm or more and 70 mm or less, or 20 mm or more and 60 mm or less.

[0034] In the above case, the inner diameter of the reflective optical scale for an encoder is, for example, not less than 5 mm and not more than 20 mm in plan view.

[0035] The outer diameter of the reflective optical scale for encoders is calculated from the coordinates of three points. Specifically, three points are selected arbitrarily on the outer circumference of the reflective optical scale for encoders, an approximation circle is calculated from the coordinates of the three points, and the diameter of the approximation circle is taken as the outer diameter.

[0036] The inner diameter of the reflective optical scale for encoders is calculated from three-point coordinates. Specifically, any three points on the inner circumference of the reflective optical scale for encoders are selected, an approximation circle is calculated from the three-point coordinates, and the diameter of the approximation circle is determined as the inner diameter.

[0037] The process capability index Cp, which indicates the inner diameter dimensional accuracy of the reflective optical scale for an encoder, is preferably 1.33 or more, and more preferably 1.6 or more. If the process capability index Cp is within the above range, the inner diameter dimensional accuracy is excellent. Therefore, when attaching the reflective optical scale for an encoder to a rotating shaft, it is possible to suppress misalignment between the center of the rotating shaft and the center of the reflective optical scale for an encoder, that is, eccentricity. This reduces eccentricity errors and improves the accuracy of the reflective optical encoder.

[0038] Here, the process capability index Cp, which indicates the inner diameter dimensional accuracy of the reflective optical scale for encoder, is calculated from the standard deviation by the following formula. Cp=(UL) / 6σ =[(A+α)-(A-α)] / 6σ =α / 3σ In the above formula, σ is the standard deviation, U is the upper limit specification value, L is the lower limit specification value, A is the reference value, and α is the difference between the upper limit specification value or the lower limit specification value and the reference value, i.e., the tolerance. The standard deviation σ is found from the measured values ​​of the inner diameters of five samples. The tolerance α is set to 0.015. This is because if the tolerance α is greater than 0.015 mm, the eccentricity error increases and the accuracy of the reflective optical encoder deteriorates.

[0039] Furthermore, the inner diameter dimensional tolerance of the reflective optical scale for an encoder is preferably, for example, 0.007 mm or less. With the inner diameter dimensional tolerance within the above range, it is possible to suppress misalignment between the center of the rotating shaft and the center of the reflective optical scale for an encoder when attaching the reflective optical scale for an encoder to the rotating shaft, i.e., eccentricity. This reduces eccentricity errors and improves the accuracy of the reflective optical encoder.

[0040] Here, the inner diameter dimensional tolerance refers to the difference between the maximum and minimum values ​​of the inner diameter measurements of five samples. The method for determining the inner diameter measurements of the five samples is as described above.

[0041] As a method for adjusting the inner diameter dimensional accuracy of the reflective optical scale for an encoder, for example, when punching out the polygonal body as described below, the central hole of the reflective optical scale for an encoder is also punched out, and the accuracy of the punching die can be adjusted.

[0042] In addition, the process capability index Cp, which indicates the outer diameter dimensional accuracy of the reflective optical scale for the encoder, is preferably 1.33 or more. When the process capability index Cp is in the above range, the following advantages are obtained. In general, when attaching the reflective optical scale for the encoder to a rotating shaft, the reflective optical scale for the encoder is fixed using an adhesive. At this time, the adhesive often overflows. Therefore, the overflowing adhesive may creep up and contaminate the surface of the reflective optical scale for the encoder, which may result in a decrease in the encoder accuracy, i.e., the reading accuracy. In order to suppress the contamination by the adhesive, the outermost peripheral edge of the low reflection layer may be disposed inward in the reflective optical scale for the encoder. However, in that case, the angle detection accuracy may not be ensured. Therefore, in order to simultaneously suppress the surface contamination of the reflective optical scale for the encoder and ensure the angle detection accuracy, it is important that the process capability index Cp, which indicates the outer diameter dimensional accuracy of the reflective optical scale for the encoder, is 1.33 or more so that there is a certain space between the outermost peripheral edge of the low reflection layer and the outer diameter of the reflective optical scale for the encoder.

[0043] Here, the method for determining the process capability index Cp, which indicates the outer diameter dimensional accuracy of the reflective optical scale for an encoder, is similar to the method for determining the process capability index Cp, which indicates the inner diameter dimensional accuracy of the reflective optical scale for an encoder described above.

[0044] Furthermore, the difference between the outer diameter and the inner diameter, i.e., the outer / inner diameter difference, is, for example, 8 mm or more and 13 mm or less. If the outer / inner diameter difference is within the above range, undulation or warping of the optical scale that occurs during punching can be suppressed.

[0045] 3.Metal base material (1) Thickness In the present disclosure, the thickness of the metal substrate is 0.3 mm or more, preferably 0.32 mm or more, and more preferably 0.35 mm or more. By setting the thickness of the metal substrate within the above range, undulation and warping can be suppressed. Furthermore, if the thickness of the metal substrate is within the above range, the strength of the reflective optical scale for an encoder is sufficient. On the other hand, the thickness of the metal substrate is 1.1 mm or less, preferably 0.50 mm or less, more preferably 0.47 mm or less, and even more preferably 0.45 mm or less. If the thickness of the metal substrate is within the above range, the reflective optical scale for an encoder can be manufactured by punching the polygonal body. Specifically, the thickness of the metal substrate is 0.3 mm or more and 1.1 mm or less, preferably 0.32 mm or more and 0.50 mm or less, more preferably 0.32 mm or more and 0.47 mm or less, and even more preferably 0.35 mm or more and 0.45 mm or less. The thickness of the metal substrate refers to the average thickness of the metal substrate.

[0046] Here, the "thickness" of each component refers to the thickness obtained by a general measurement method. Examples of thickness measurement methods include a stylus method in which the thickness is calculated by tracing the surface with a stylus to detect unevenness, and an optical method in which the thickness is calculated based on the spectral reflectance spectrum. Specifically, the thickness can be measured using a stylus-type film thickness meter "P-15" manufactured by KLA-Tencor. The thickness is calculated by averaging the thickness measurements at multiple points on the component. For example, in the case of a metal substrate, the average thickness measurement value at two points symmetrical to the center of the disk-shaped metal substrate may be used.

[0047] (2) Shape The metal substrate in the present disclosure is disk-shaped. The metal substrate may be, for example, a perforated disk-shaped substrate having a central hole, or may not have a central hole.

[0048] When the metal substrate is a perforated disk, the outer diameter of the metal substrate in plan view is, for example, 15 mm or more, and may be 20 mm or more. On the other hand, the outer diameter of the metal substrate is, for example, 70 mm or less, and may be 60 mm or less. Specifically, the outer diameter of the metal substrate may be, for example, 15 mm or more, 70 mm or less, and 20 mm or more, and 60 mm or less.

[0049] In the above case, the inner diameter of the metal base material in plan view is, for example, 5 mm or more and 20 mm or less.

[0050] In the above case, the difference between the outer diameter and the inner diameter, i.e., the outer / inner diameter difference, is, for example, 8 mm or more and 13 mm or less. If the outer / inner diameter difference is within the above range, undulation or warping of the optical scale that occurs during punching can be suppressed.

[0051] (3)Reflectance The reflectance of the first surface of the metal substrate is, for example, 50% or more, may be 55% or more, or may be 60% or more. Meanwhile, the reflectance of the first surface of the metal substrate is, for example, 100% or less. Specifically, the reflectance of the first surface of the metal substrate is, for example, 50% or more and 100% or less, may be 55% or more and 100% or less, or may be 60% or more and 100% or less. If the reflectance is within the above range, the difference between the reflectance in the high reflection region and the reflectance in the low reflection region becomes large, so that erroneous detection by the photodetector can be prevented and the detection accuracy of the signal can be improved.

[0052] In this specification, the reflectance refers to the reflectance of the detection light used in the optical encoder. When the wavelength of the incident light on the first surface of the metal layer is within a range of 500 nm to 1000 nm, it is more preferable that the reflectance at the incident angle is within the above range at 5° to 70°.

[0053] The reflectance is measured using Shimadzu's SolidSpec 3700DUV ultraviolet-visible near-infrared spectrophotometer. The irradiation beam size is approximately 6mm x 15mm. Both P-polarized and S-polarized light are measured, and the sum is averaged to calculate the 45° linear polarization and calculate the reflectance.

[0054] (4) Sauce In the present disclosure, the metal substrate may have a sagging on the outer peripheral edge on the first surface side. FIG. 2(b) is an enlarged cross-sectional view of the line BB in the dotted frame b in FIG. 1. In FIG. 2(b), the metal substrate 1 has a sagging P on the outer peripheral edge on the first surface 1a side. A reflective optical scale for an encoder having a sagging on the outer peripheral edge on the first surface side of the metal substrate is usually manufactured by punching a polygonal body. Therefore, as described above, no bridge marks are generated, and partial distortion can be suppressed. In addition, the metal substrate can be made thick, and waviness and warping can be suppressed. In addition, it is advantageous in terms of cost.

[0055] Furthermore, when the metal base material is a perforated disk, it may have a sagging on the inner peripheral edge on the first surface side.

[0056] (5) Material The material of the metal substrate is preferably one that satisfies the above-mentioned reflectance, and examples thereof include stainless steel (SUS), copper, and aluminum.

[0057] 4.Low reflective layer The low reflective layer in the present disclosure is disposed on the first surface side of the metal base in a pattern along the circumferential direction of the metal base.

[0058] (1)Reflectance The reflectance of light incident on the low reflection region, which is a region where a low reflection layer is provided, may be lower than the reflectance of light incident on the high reflection region where no low reflection layer is provided. Specifically, the reflectance of the low reflection region may be lower than the reflectance of the first surface of the metal base material. In the low reflection region, the reflectance at any wavelength in the range of 500 nm to 1000 nm is, for example, 10% or less, or may be 5% or less, or may be 1% or less. On the other hand, the reflectance of the low reflection region is, for example, 0% or more. Specifically, the reflectance of the low reflection region is, for example, 0% or more and 10% or less, or may be 0% or more and 5% or less, or may be 0% or more and 1% or less. If the reflectance is within the above range, the difference between the reflectance in the high reflection region and the reflectance in the low reflection region can be increased.

[0059] In the low reflection region, when the wavelength of incident light is anywhere in the range of 500 nm or more and 1000 nm or less, it is more preferable that the reflectance at an incident angle anywhere in the range of 5° or more and 70° or less is within the above range.

[0060] (2) Layer composition The low-reflection layer is not particularly limited in its configuration as long as it satisfies the above-mentioned reflectance. In particular, the low-reflection layer preferably has a metal chromium film, and a chromium oxide film and a chromium nitride film arranged in random order on the surface of the metal chromium film opposite to the metal substrate from the metal substrate side. Such a three-layered low-reflection layer can reduce the reflectance of the low-reflection region to the above-mentioned range. Moreover, if only metal chromium is prepared, a chromium oxide film and a chromium nitride film can be easily formed by using reactive sputtering or the like. Furthermore, the above-mentioned low-reflection layer can easily perform high-definition patterning compared to a silicon oxide film.

[0061] In this specification, "a chromium oxide film and a chromium nitride film arranged in any order on the surface of the metal chromium film opposite the metal substrate" means that the chromium metal film, the chromium oxide film, and the chromium nitride film may be arranged in this order, or the chromium metal film, the chromium nitride film, and the chromium oxide film may be arranged in this order.

[0062] For example, in Fig. 5(a), the low-reflective layer 2 has, from the metal substrate 1 side, a metal chromium film 2c, a chromium nitride film 2b, and a chromium oxide film 2a. On the other hand, in Fig. 5(b), the low-reflective layer 2 has, from the metal substrate 1 side, a metal chromium film 2c, a chromium oxide film 2a, and a chromium nitride film 2b.

[0063] In the low reflection layer, the film located on the outermost surface opposite to the metal substrate is preferably a chromium oxide film or a chromium nitride film, and more preferably a chromium oxide film, because the reflectance of the low reflection region can be more effectively reduced.

[0064] Hereinafter, the "low-reflective layer in which a metal chromium film, a chromium nitride film, and a chromium oxide film are arranged in this order" will be referred to as a first specification low-reflective layer, and the "low-reflective layer in which a metal chromium film, a chromium oxide film, and a chromium nitride film are arranged in this order" will be referred to as a second specification low-reflective layer.

[0065] (a) Low-reflection layer of the first specification In the low-reflection layer of this specification, a metal chromium film, a chromium nitride film, and a chromium oxide film are arranged in this order from the metal substrate side. In the low-reflection region having the low-reflection layer of this specification, the reflectance at any wavelength within the range of 500 nm to 1000 nm can be reduced to 5% or less, especially 0.5% or less. In addition, the change in reflectance with respect to the change in wavelength is gradual, making it easy to control the reflectance.

[0066] (i) Metal Chromium Film In this specification, the metal chromium film is disposed on the first surface of the metal substrate. The metal chromium film is a layer made of metal chromium. The metal chromium film is a layer that does not substantially transmit light irradiated from a light source, and preferably has a transmittance of 0.0% or more and 1.0% or less. The transmittance is measured using a spectrophotometer "MPC-3100" manufactured by Shimadzu Corporation. The thickness of the metal chromium film is, for example, preferably 40 nm or more, more preferably 70 nm or more.

[0067] The metal chromium film can be formed by a physical vapor deposition (PVD) method such as sputtering, ion plating, or vacuum deposition.

[0068] (ii) Chromium nitride film The chromium nitride film in this specification is disposed between the metallic chromium film and the chromium oxide film. Unlike chromium oxide nitride and chromium oxide nitride carbide, the chromium nitride film is mainly composed of chromium and nitrogen and contains substantially no impurities other than chromium and nitrogen.

[0069] In the chromium nitride (CrNx) film, x, which represents the atomic ratio of Cr to N, is preferably 0.4 or more and 1.1 or less.

[0070] When the ratio of all elements contained in the chromium nitride film is taken as 100 atomic %, the ratio of chromium and nitrogen is preferably 80 atomic % or more and 100 atomic % or less, and more preferably 90 atomic % or more and 100 atomic % or less. The chromium nitride film may contain impurities such as hydrogen, oxygen, and carbon.

[0071] Chromium nitride film thickness (T N ) is preferably, for example, 5 nm or more and 100 nm or less, and more preferably 10 nm or more and 80 nm or less. O ) in relation to the wavelength of 850 nm, T N and T O It is preferable that the sum of T is 40 nm or more. N and T OThe sum of the thickness and the thickness is preferably 20 nm or more. With such a thickness, the reflectance of the low reflection region can be easily reduced to a desired range, compared with a case where the thickness is outside the above range. Furthermore, the thickness of the chromium nitride film is preferably 10 nm or more and 80 nm or less. It becomes easy to reduce the reflectance in the entire range from green to infrared, that is, the reflectance in the range of about 500 nm to 1000 nm.

[0072] Chromium nitride can be formed by physical vapor deposition (PVD) methods such as reactive sputtering, ion plating, and vacuum deposition. When using reactive sputtering, nitrogen is introduced into argon (Ar) gas, and a chromium nitride film can be formed by reactive sputtering using a Cr target. In this case, the composition of the chromium nitride film can be controlled by controlling the ratio of Ar gas and nitrogen gas.

[0073] (iii) Chromium oxide film The chromium oxide film in this specification is disposed on the opposite side of the chromium nitride film to the metallic chromium film. The chromium oxide film is mainly composed of chromium and oxygen, and unlike chromium oxide nitride and chromium oxide nitride carbide, it contains substantially no impurities other than chromium and oxygen.

[0074] In the chromium oxide (CrOy) film, y, which represents the atomic ratio of Cr to O, is preferably 1.4 or more and 2.1 or less.

[0075] Specifically, when the ratio of all elements contained in the chromium oxide film is taken as 100 atomic %, the ratio of chromium and oxygen is preferably 80 atomic % or more and 100 atomic % or less, and more preferably 90 atomic % or more and 100 atomic % or less. The chromium oxide film may contain impurities such as hydrogen, nitrogen, and carbon.

[0076] The thickness of the chromium oxide film is not particularly limited, and is preferably 5 nm to 100 nm, more preferably 10 nm to 80 nm. The sum of the thickness of the chromium oxide film and the thickness of the chromium nitride film is as described above. Furthermore, the thickness of the chromium oxide film is preferably 10 nm to 65 nm. It becomes easy to reduce the reflectance in the entire range from green to infrared, that is, the reflectance in the range of about 500 nm to 1000 nm.

[0077] Chromium oxide can be formed by physical vapor deposition (PVD) such as reactive sputtering, ion plating, and vacuum deposition. When using reactive sputtering, oxygen is introduced into argon (Ar) gas, and a chromium oxide film can be formed by reactive sputtering using a Cr target. In this case, the composition of the chromium oxide film can be controlled by controlling the ratio of Ar gas to oxygen gas.

[0078] (b) Second specification low-reflection layer In the low-reflection layer of this specification, a metal chromium film, a chromium oxide film, and a chromium nitride film are arranged in this order from the metal substrate side. In the low-reflection region having the low-reflection layer of this specification, the reflectance at any wavelength within the range of 500 nm to 1000 nm can be reduced to 5% or less, especially 1% or less.

[0079] (i) Metal Chromium Film The metal chromium film in this specification is similar to the metal chromium film in the low reflection layer in the first specification described above, and therefore a description thereof will be omitted here.

[0080] (ii) Chromium oxide film The chromium oxide film in this specification is disposed between the metallic chromium film and the chromium nitride film.

[0081] The thickness of the chromium oxide film is not particularly limited, and is preferably 5 nm to 60 nm, more preferably 10 nm to 50 nm. As described later, the sum of the thickness of the chromium oxide film and the thickness of the chromium nitride film is preferably within a predetermined range. Furthermore, the thickness of the chromium oxide film is preferably 5 nm to 35 nm, since it is easy to reduce the reflectance in the entire range from green to infrared, that is, the reflectance in the range from 500 nm to 1000 nm.

[0082] The physical properties, composition and method of formation of the chromium oxide film are similar to those of the chromium oxide film in the low reflection layer of the first specification, and therefore a description thereof will be omitted here.

[0083] (iii) Chromium nitride film The chromium nitride film in this specification is disposed on the opposite side of the chromium oxide film to the metallic chromium film.

[0084] Chromium nitride film (T N The thickness of the chromium oxide film (T O ) in relation to the wavelength of 850 nm, T N and T O It is preferable that the sum of is 30 nm or more. When the wavelength is 550 nm, T N and T O The sum of these is preferably 15 nm or more. Furthermore, the thickness of the chromium nitride film is preferably 10 nm or more and 60 nm or less. This makes it easy to reduce the reflectance over the entire range from green to infrared, that is, the reflectance over the range of about 500 nm to 1000 nm.

[0085] The method for forming the chromium nitride film is the same as that for the chromium nitride film in the low reflection layer of the first specification described above, and therefore a description thereof will be omitted here.

[0086] (3) Formation method The method for forming the low reflective layer is not particularly limited, but the low reflective layer can be formed by selective etching or lift-off.

[0087] In the case of selective etching, for example, a metal chromium film is first formed on a first surface of a metal base material by a sputtering method or the like, and then a chromium nitride film and a chromium oxide film are formed. Next, the metal chromium film, the chromium nitride film, and the chromium oxide film are patterned by photolithography and etching.

[0088] In the case of the lift-off method, for example, a resist pattern is first formed on the first surface of the metal substrate, and a metal chromium film, a chromium nitride film, and a chromium oxide film are formed by a known vacuum film forming method such as sputtering. The resist pattern is then removed to lift off the metal chromium film, the chromium nitride film, and the chromium oxide film formed directly on the resist pattern, thereby obtaining patterns of the metal chromium film, the chromium nitride film, and the chromium oxide film.

[0089] (4) Placement The reflective optical scale for an encoder according to the present disclosure preferably does not have a low-reflection layer in a region extending from the outer circumferential surface of the metal substrate to a depth of 500 μm inward, thereby making it possible to suppress peeling or cracking of the low-reflection layer.

[0090] Specifically, the distance between the outer peripheral surface of the metal substrate and the outer peripheral surface of the low-reflection layer is preferably 500 μm or more, more preferably 550 μm or more, and even more preferably 600 μm or more. If the distance is within the above range, peeling and cracking of the low-reflection layer can be easily suppressed. On the other hand, the distance is, for example, preferably 1500 μm or less, more preferably 1000 μm or less, and even more preferably 900 μm or less. If the distance is within the above range, the increase in size of the reflective optical scale for encoder can be suppressed. Specifically, the distance is, for example, preferably 500 μm or more and 1500 μm or less, more preferably 550 μm or more and 1000 μm or less, and even more preferably 600 μm or more and 900 μm or less.

[0091] 5. Other layer configurations The reflective optical scale for an encoder according to the present disclosure may have other layers in addition to the above-mentioned metal substrate and low-reflection layer. For example, the reflective optical scale for an encoder according to the present disclosure may have a protective layer between the metal substrate and the low-reflection layer.

[0092] The protective layer is preferably transparent and has a function of protecting the metal substrate. By providing the protective layer, there is no risk that the surface of the metal substrate becomes rough and the surface roughness increases during etching when forming the low reflection layer in a pattern. Therefore, diffuse reflection of light can be suppressed. The protective layer may be provided over the entire area of ​​the metal substrate in a plan view, or may be provided in a partial area.

[0093] The material for the protective layer is not particularly limited as long as it is transparent and can protect the metal substrate, and may be either an organic material or an inorganic material.

[0094] The organic material preferably contains a resin. The resin used in the protective layer is not particularly limited as long as it is a resin that can provide a transparent protective layer, and examples thereof include ionizing radiation curable resins that are cured by irradiation with ionizing radiation such as ultraviolet rays and electron beams, and thermosetting resins that are cured by heating. Specifically, novolac resins, polyolefin resins, polyester resins, urethane resins, polyimide resins, acrylic resins, and epoxy resins are preferred. Of the novolac resins, phenol novolac resins are preferred. This is because they have excellent electrical properties and can suppress defects caused by charging. Of the acrylic resins, trifunctional or higher acrylates such as pentaerythritol tetraacrylate and dipentaerythritol tetraacrylate are preferred. This is because they can enhance photocurability. Of the epoxy resins, epoxy acrylate resins having a fluorene structure are preferred. This is because they improve heat resistance, adhesion, and chemical resistance. Of the epoxy resins, cardo epoxy resins are also preferred. This is because they can provide excellent transparency, heat resistance, surface hardness, and flatness. The organic material may contain, in addition to the resin, a polymerization initiator, various additives, and the like.

[0095] Examples of inorganic materials include inorganic compounds. Examples of inorganic compounds include oxides, oxynitrides, nitrides, oxycarbides, and oxycarbonitrides of metal elements or nonmetal elements such as silicon, aluminum, magnesium, calcium, potassium, tin, sodium, titanium, boron, yttrium, zirconium, cerium, and zinc. Silicon dioxide (SiO2) is particularly preferred. The inorganic compounds may be used alone or in any combination of the above materials.

[0096] 6. Manufacturing method of reflective optical scale for encoder The manufacturing method of a reflective optical scale for an encoder in the present disclosure preferably comprises a multi-sided body production step of producing a multi-sided body having a metal substrate to be processed, the multi-sided body having a first surface and a second surface opposite to the first surface and a thickness of 0.3 mm or more and 1.1 mm or less, and a patterned low-reflection layer that is multi-sidedly attached to the first surface side of the metal substrate to be processed and arranged in a circular pattern, the multi-sided body having a planned outer circumferential punching line for the reflective optical scale for an encoder outside the outer circumferential surface of each of the low-reflection layers and having a waviness of 30 μm or less, and a singulation step of punching out the multi-sided body along the planned outer circumferential punching line to singulate it, to obtain the reflective optical scale for an encoder.

[0097] 7 is a schematic top view showing an example of a multi-faceted body in the present disclosure. The multi-faceted body 50 has a metal substrate 51 to be processed having a thickness within a predetermined range, and a patterned low-reflection layer 2 arranged in a circumferential shape and multi-faceted on a first surface side of the metal substrate 51 to be processed. In the multi-faceted body 50, a planned outer periphery punching line L of the reflective optical scale for an encoder is arranged outside the outer periphery of each low-reflection layer 2. In the singulation step, the reflective optical scale for an encoder is obtained by punching out along the planned outer periphery punching line L to be singulated.

[0098] (1) Multi-faceted body manufacturing process In this process, a multi-sided body is produced which has a metal substrate to be processed, which has a first surface and a second surface opposite the first surface and a thickness of 0.3 mm or more and 1.1 mm or less, and patterned low-reflection layers which are circumferentially arranged and multi-sidedly attached to the first surface side of the metal substrate to be processed, which has a planned peripheral punching line for a reflective optical scale for an encoder outside the outer circumferential surface of each of the low-reflection layers and has a waviness of 30 μm or less.

[0099] The waviness of the polygonal body is similar to the waviness of the reflective optical scale for encoder described above.

[0100] The thickness of the metal substrate to be processed is the same as the thickness of the metal substrate. The reflectance of the first surface of the metal substrate to be processed is the same as the reflectance of the first surface of the metal substrate. The size of the metal substrate to be processed in plan view is not particularly limited as long as the patterned low reflection layer can be attached to multiple surfaces.

[0101] The method for forming the patterned low reflective layer on multiple surfaces on the first surface side of the metal base material to be processed is the same as the method for forming the low reflective layer described above.

[0102] For example, as shown in FIG. 7, in the polygonal mounting body 50, the planned peripheral punching line L of the reflective optical scale for an encoder is disposed outside the peripheral surface of each low-reflection layer 2. The distance D1 between the planned peripheral punching line L of the reflective optical scale for an encoder and the peripheral surface of the low-reflection layer 2 is, for example, preferably 500 μm or more, more preferably 550 μm or more, and particularly preferably 600 μm or more. If the distance D1 is within the above range, peeling or cracking of the low-reflection layer during punching can be suppressed. On the other hand, the distance D1 is, for example, preferably 1500 μm or less, more preferably 1000 μm or less, and even more preferably 900 μm or less. If the distance D1 is within the above range, the size of the reflective optical scale for an encoder can be suppressed from increasing. Specifically, the distance D1 is, for example, preferably 500 μm or more and 1500 μm or less, more preferably 550 μm or more and 1000 μm or less, and further preferably 600 μm or more and 900 μm or less.

[0103] In addition, a polygonal body for manufacturing a perforated disk-shaped reflective optical scale for an encoder may be provided with an inner peripheral planned punching line for punching out a central hole of the reflective optical scale for an encoder.

[0104] (2) Singulation process In this step, the polygonal body is punched out along the planned outer circumferential punching lines to be divided into individual pieces, thereby obtaining a reflective optical scale for an encoder.

[0105] 8(a) and 8(b) are schematic diagrams showing an example of a punching device used in the singulation process. First, as shown in FIG. 8(a), the multi-faceted body 50 is placed on a lower stage 62 having a lower blade 61. Next, as shown in FIG. 8(b), the lower stage 62 is moved upward and the upper stage 63 having an upper blade 64 is moved downward and pressed in, thereby punching out the multi-faceted body 50. At this time, although not shown, the position of the upper blade 64 is aligned with the outer peripheral punching planned line and the inner peripheral punching planned line of the multi-faceted body 50. In addition, it is preferable that a pressing member 65 is disposed at a position opposite to the upper blade 64. During punching, the metal substrate to be processed is sandwiched between the upper blade 64 and the pressing member 65, and punching can be performed with less burrs and sagging. In this manner, individual reflective optical scales 10 for encoders are obtained.

[0106] In this step, the width of the clearance is preferably, for example, 0.020 mm or less, more preferably 0.017 mm or less, and even more preferably 0.015 mm or less. If the width of the clearance is within the above range, peeling or cracking of the low reflection layer during punching can be suppressed. On the other hand, the width of the clearance is preferably, for example, 0.003 mm or more, more preferably 0.004 mm or more, and even more preferably 0.006 mm or more. By having the width of the clearance within the above range, the load on the blade of the punching device can be reduced. Specifically, the width of the clearance is preferably, for example, 0.003 mm or more and 0.020 mm or less, more preferably 0.004 mm or more and 0.017 mm or less, and even more preferably 0.006 mm or more and 0.015 mm or less. The width of the clearance refers to the distance C in the width direction between the end face of the upper blade 64 and the end face of the lower blade 61 as shown in FIG. 8(b).

[0107] B. Reflective Optical Encoder The reflective optical encoder of the present disclosure comprises the above-mentioned reflective optical scale for the encoder, a light source that irradiates measurement light onto the surface of the reflective optical scale for the encoder on which the low-reflection layer is arranged, and a photodetector that detects reflected light from the reflective optical scale for the encoder.

[0108] Fig. 6 is a schematic perspective view showing an example of a reflective optical encoder in the present disclosure. The reflective optical encoder 100 includes a reflective optical scale 10 for an encoder, a light source 21, and a photodetector 22. In Fig. 6, a fixed slit 23 is disposed between the photodetector 22 and the reflective optical scale 10 for an encoder.

[0109] According to the present disclosure, since the above-described reflective optical scale for an encoder is provided, the accuracy of the reflective optical encoder can be improved.

[0110] Hereinafter, the reflective optical encoder according to the present disclosure will be described in detail with respect to each of its components.

[0111] 1. Reflective optical scale for encoders The reflective optical scale for an encoder is similar to that described above in "A. Reflective optical scale for an encoder," and therefore will not be described here.

[0112] 2.Light source Examples of light sources include LEDs (light emitting diodes) and lasers. The wavelength λ of light emitted from the light source is, for example, in the green to infrared region, that is, about 500 nm or more and 1000 nm or less. The angle of incidence of the light on the optical scale is, for example, 5° or more and 70° or less.

[0113] 3. Photodetector The photodetector detects light reflected by the optical scale. The photodetector includes a light receiving element such as a photodiode or an image sensor. An example of the light receiving element is a photoelectric conversion element.

[0114] 4.Other The reflective optical encoder of the present disclosure may include a fixed slit between the photodetector and the reflective optical scale for the encoder. By providing the fixed slit, the change in the amount of light received by the photodetector increases, and the detection sensitivity can be improved. The fixed slit may be provided between the light source and the reflective optical scale for the encoder.

[0115] C. Reflective optical scale multi-faceted body for encoder The multi-sided reflective optical scale body for an encoder in the present disclosure has a first surface and a second surface opposite to the first surface, and comprises a metal substrate to be processed having a thickness of 0.3 mm or more and 1.1 mm or less, and a patterned low-reflection layer that is multi-sidedly attached to the first surface side of the metal substrate to be processed and arranged in a circumferential shape, with a planned peripheral punching line for the reflective optical scale for an encoder being located outside the outer circumferential surface of each of the low-reflection layers, and with a waviness of 30 μm or less.

[0116] The reflective optical scale polygonal body for encoders in the present disclosure is similar to that described above in "A. Reflective optical scale for encoders 6. Manufacturing method of reflective optical scale for encoders," so description thereof will be omitted here.

[0117] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present disclosure and exhibits similar effects is included in the technical scope of the present disclosure. EXAMPLES

[0118] The present disclosure will be further described below with reference to examples and comparative examples.

[0119] [Example 1] First, a 0.37 mm thick stainless steel substrate was prepared with a mirror finish. A protective layer was formed by applying a protective layer resin composition containing a cardo epoxy resin to the mirror finish surface of the stainless steel substrate and curing the composition. A low-reflection layer having a metallic chromium layer, a chromium nitride layer, and a chromium oxide layer in this order from the protective layer side was then formed in a pattern. This resulted in a multi-faceted body.

[0120] Next, the multi-faceted body was roughly cut so that the outer diameter was about 100 mm to 250 mm. Next, alignment was performed using optical alignment marks, and the roughly cut workpiece was punched along the outer peripheral punching planned line and the inner peripheral punching planned line. In this way, a reflective optical scale for an encoder was obtained. The design value of the outer diameter was 24 mm, and the design value of the inner diameter was 15 mm.

[0121] [Example 2] A reflective optical scale for an encoder was produced in the same manner as in Example 1, except that the design value of the inner diameter was set to 6 mm.

[0122] [Example 3] A reflective optical scale for an encoder was produced in the same manner as in Example 1, except that the thickness of the SUS substrate was 0.30 mm.

[0123] [Example 4] A reflective optical scale for an encoder was produced in the same manner as in Example 1, except that the thickness of the SUS substrate was 1.10 mm.

[0124] [Comparative Example 1] A reflective optical scale for an encoder was produced in the same manner as in Example 1, except that the polygonal body was subjected to etching instead of punching.

[0125] [Comparative Example 2] A reflective optical scale for an encoder was produced in the same manner as in Example 1, except that the thickness of the SUS substrate was 0.20 mm and the polygonal body was etched instead of punched.

[0126] [Comparative Example 3] A reflective optical scale for an encoder was produced in the same manner as in Example 1, except that the thickness of the SUS substrate was 1.20 mm and the polygonal body was etched instead of punched.

[0127] [evaluation] (1) Waviness of reflective optical scale for encoder The waviness of the reflective optical scale for encoder was measured by the method described above in "A. Reflective optical scale for encoder 1. Waviness of reflective optical scale for encoder".

[0128] (2) Process capability index Cp, which indicates the inner diameter dimensional accuracy of the reflective optical scale for encoders The process capability index Cp, which indicates the inner diameter dimensional accuracy of the reflective optical scale for encoder, was determined by the method described above in "A. Reflective optical scale for encoder 2. Shape of reflective optical scale for encoder".

[0129] (3) Bridge marks The reflective optical scale for encoder was visually observed for the presence or absence of bridge marks.

[0130] (4) Encoder accuracy A reflective optical encoder was produced using a reflective optical scale for an encoder. The period, pulse width, and inter-pulse phase difference of the encoder output waveform were measured for the reflective optical encoder, and the degree of error and variation was confirmed by comparing them with the design values. The evaluation criteria are shown below. A: The accuracy was sufficient. B: The accuracy was slightly lacking. C: The accuracy was insufficient.

[0131] [Table 1]

[0132] From Table 1, it can be confirmed that when the thickness of the metal substrate is within a specified range and the waviness of the reflective optical scale for encoder is within a specified range, the encoder accuracy is good.

[0133] That is, the present disclosure provides the following inventions. [1] A disk-shaped metal substrate having a first surface and a second surface opposite to the first surface; a low-reflection layer disposed in a pattern along a circumferential direction of the metal base on the first surface side of the metal base; A reflective optical scale for an encoder, comprising: The thickness of the metal substrate is 0.3 mm or more and 1.1 mm or less, A reflective optical scale for an encoder, wherein the undulation of the reflective optical scale for an encoder is 30 μm or less. [2] The reflective optical scale for an encoder according to [1], which is a perforated disk having a central hole. [3] The reflective optical scale for encoders described in [2] has a process capability index Cp, which indicates the inner diameter dimensional accuracy, of 1.33 or more. [4] [1] to [3], and a light source that irradiates a measurement light onto a surface of the reflective optical scale for an encoder on which the low-reflection layer is disposed; a photodetector for detecting reflected light from the reflective optical scale for encoder; A reflective optical encoder comprising: [Explanation of symbols]

[0134] 1 … Metal base material 2…Low reflective layer 10... Reflective optical scale for encoders 50... Reflective optical scale multi-faceted body for encoder 100... Reflective optical encoder

Claims

1. A disk-shaped metal substrate having a first surface and a second surface opposite to the first surface; a low-reflection layer disposed in a pattern along a circumferential direction of the metal base on the first surface side of the metal base; A reflective optical scale for an encoder, comprising: The thickness of the metal base material is 0.3 mm or more and 1.1 mm or less, A reflective optical scale for an encoder, wherein the undulation of the reflective optical scale for an encoder is 30 μm or less.

2. 2. The reflective optical scale for an encoder according to claim 1, which is in the form of a perforated disk having a central hole.

3. 3. The reflective optical scale for an encoder according to claim 2, wherein a process capability index Cp indicating inner diameter dimensional accuracy is 1.33 or more.

4. A reflective optical scale for an encoder according to any one of claims 1 to 3; a light source that irradiates a measurement light onto a surface of the reflective optical scale for an encoder on which the low-reflection layer is disposed; and a photodetector for detecting reflected light from the reflective optical scale for encoder; A reflective optical encoder comprising:

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