Reflective optical scale for encoder and reflective optical encoder

Abstract

To provide a reflective optical scale for an encoder capable of sufficiently reducing a reflectance in a low reflection region.SOLUTION: The present disclosure provides a reflective optical scale for an encoder in which a high-reflectance region and a low-reflectance region are alternately arranged on a substrate, wherein the low-reflectance region has a reflectance of 1% or less at a wavelength of 850 nm, the high-reflectance region is formed by laminating at least one inorganic layer, the reflectance of the high-reflectance region at a wavelength of 850 nm is 60% or more, and the high-reflectance region is formed by laminating at least an inorganic layer containing silver or aluminum, wherein a value of an S / N ratio represented by the following formula is equal to or greater than 15: S / N ratio=reflectance of high reflection region / reflectance of low reflection region SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Optical encoders capable of measuring dimensions with high precision have been used in the field of measuring instruments, etc. Optical encoders are classified into transmissive encoders and reflective encoders, but reflective encoders have a shorter optical path than transmissive encoders, making them easier to make smaller and thinner, and also have the advantage of being easier to assemble as they do not require positioning of the light-emitting element and light-receiving element.

[0003] A reflective optical encoder includes a reflective optical scale, a light source such as an LED that illuminates the scale, and a photodetector that detects light reflected from the scale. The reflective optical scale has alternating reflective areas (highly reflective areas) and non-reflective areas (lowly reflective areas), with the reflectivity of light in the reflective areas being higher than that of the non-reflective areas. As a result, the intensity of light reflected from the scale and incident on the photodetector fluctuates depending on the position of the scale. The photodetector detects the intensity of light that changes as the scale position moves in the measurement direction. The reflective optical encoder processes displacement information about the position of this scale according to the detected light intensity, and can obtain position information.

[0004] In the reflective and non-reflective areas formed on a reflective optical scale, in order to prevent erroneous detection by the photodetector and to increase the signal detection accuracy, it is necessary to make the reflectivity of the reflective areas high and the reflectivity of the non-reflective areas low.

[0005] For example, Patent Document 1 discloses a reflective optical scale in which the non-reflective areas of the reflective optical scale have a multilayer structure in which metal Ti, SiO2, TiO2, and SiO2 are laminated in this order, thereby reducing reflectivity and increasing the difference in the intensity of reflected light in the high-reflection areas and the low-reflection areas. However, the SiO2 film used is expensive, and two types of raw materials, Ti and Si, are required for film formation, which is disadvantageous in terms of cost.

[0006] Furthermore, Patent Document 2 discloses a reflective optical scale in which a partial area on one surface of a substrate having a high surface reflectance is covered with a non-reflective pattern made of a metal oxide film or a metal nitride.

[0007] Patent Document 3 describes the use of chromium or chromium compounds such as chromium oxide and chromium nitride as a material for forming a pattern formation film having a lower light reflectance than a reflective film. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2019-158710 [Patent Document 2] Japanese Utility Model Application Publication No. 61-197510 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-241248 Summary of the Invention [Problem to be solved by the invention]

[0009] As described above, various configurations of reflective optical scales have been proposed, but the inventors have found that the configurations of the low-reflection areas of conventional reflective optical scales for encoders are unable to sufficiently reduce the reflectance in the red / near-infrared range, and therefore further reduction in the reflectance of the low-reflection areas is desired.

[0010] The present invention has been made in consideration of the above circumstances, and its main object is to provide a reflective optical scale for an encoder that can sufficiently reduce the reflectance in a low-reflection region. [Means for solving the problem]

[0011] The present disclosure provides a reflective optical scale for an encoder in which high-reflection regions and low-reflection regions are arranged alternately on a substrate, wherein the low-reflection regions include low-reflection portions having a metal chromium film arranged on one surface of the substrate and a chromium oxide film and a chromium nitride film arranged in any order on the surface of the metal chromium film opposite the substrate, and the high-reflection regions have a higher reflectivity for light incident from the opposite side of the substrate of the reflective optical scale for an encoder than the low-reflection regions.

[0012] According to the present disclosure, a reflective optical scale for an encoder can be provided that has a low-reflection region that has a low-reflection portion consisting of a metal chromium film formed on a substrate and a chromium oxide film and a chromium nitride film formed in any order on the metal chromium film, thereby reducing the reflectivity in the low-reflection region.

[0013] In the present disclosure, the outermost surface of the low-reflection region is preferably the chromium oxide film or the chromium nitride film. Furthermore, the low-reflection region preferably includes the metal chromium film, the chromium nitride film disposed on the surface of the metal chromium film opposite to the substrate, and the chromium oxide film disposed on the surface of the chromium nitride film opposite to the metal chromium film. This is because the reflectance in the low-reflection region can be further reduced.

[0014] In the present disclosure, the highly reflective region preferably has the metal chromium film formed on the substrate, because this allows for a simplification of the manufacturing process, leading to cost reduction.

[0015] In the present disclosure, the highly reflective region may have a metallic silver film or a silver alloy film containing silver as a main component formed on the substrate, because such a metallic silver film or silver alloy film can further increase the reflectance in the highly reflective region.

[0016] In the present disclosure, the reflectance at any wavelength within the wavelength range of 550 nm to 950 nm of the high reflection region can be 60% or more, and the S / N ratio value expressed by the following formula can be 100 or more. S / N ratio = reflectance of high reflection area / reflectance of low reflection area In the above formula, the reflectance of the high reflection region and the reflectance of the low reflection region indicate reflectance at the same wavelength.

[0017] The present disclosure provides a reflective optical encoder comprising the above-mentioned reflective optical scale for an encoder, a light source that irradiates light onto the surface of the reflective optical scale for an encoder on which the low-reflection portion is located, and a photodetector that detects reflected light from the reflective optical scale for an encoder of the light source.

[0018] The reflective optical encoder of the present disclosure includes the above-mentioned reflective optical scale for the encoder, and therefore the difference in reflectivity between the high-reflection area and the low-reflection area can be increased, thereby preventing erroneous detection by the photodetector.

[0019] The present disclosure provides a reflective optical scale for an encoder in which high-reflection regions and low-reflection regions are alternately arranged on a transparent substrate, wherein the low-reflection regions include a light-reflecting portion having a chromium oxide film and a chromium nitride film arranged in any order on one surface of the transparent substrate, and a metal chromium film arranged on the surface of the chromium oxide film or the chromium nitride film opposite the substrate, and the high-reflection regions have a higher reflectivity for light incident from the transparent substrate side of the reflective optical scale for an encoder than the low-reflection regions.

[0020] According to the present disclosure, a reflective optical scale for an encoder can be provided in which the low-reflection region has a light-reflecting portion consisting of a chromium oxide film and a chromium nitride film formed in any order on a transparent substrate, and a metal chromium film formed on the chromium oxide film or the chromium nitride film, thereby reducing the reflectivity in the low-reflection region.

[0021] In the present disclosure, the low-reflection region preferably has the chromium oxide film disposed on one surface of the transparent substrate, the chromium nitride film disposed on the surface of the chromium oxide film opposite to the transparent substrate, and the metal chromium film disposed on the surface of the chromium nitride film opposite to the chromium oxide film, because this makes it possible to further reduce the reflectance in the low-reflection region.

[0022] In the present disclosure, the highly reflective region preferably has the metal chromium film disposed on the surface of the transparent substrate on the side where the light reflecting portion is disposed, because this allows for simplification of the manufacturing process, leading to cost reduction.

[0023] In the present disclosure, the highly reflective region may have a metallic silver film or a silver alloy film mainly composed of silver disposed on the surface of the transparent substrate on the side where the light reflecting portion is disposed, because such a metallic silver film or silver alloy film can further increase the reflectance in the highly reflective region.

[0024] Furthermore, in the present disclosure, the reflectance at any wavelength within the wavelength range of 550 nm to 950 nm of the high reflection region can be 60% or more, and the value of the S / N ratio represented by the following formula can be 15 or more. S / N ratio = reflectance of high reflection area / reflectance of low reflection area In the above formula, the reflectance of the high reflection region and the reflectance of the low reflection region indicate reflectance at the same wavelength.

[0025] The present disclosure provides a reflective optical encoder comprising the above-mentioned reflective optical scale for an encoder, a light source that irradiates light onto the surface of the reflective optical scale for an encoder opposite to the side on which the light-reflecting portion is arranged, and a photodetector that detects reflected light from the reflective optical scale for an encoder of the light source.

[0026] The reflective optical encoder of the present disclosure includes a reflective optical scale for an encoder having the above-mentioned light-reflecting portion, and therefore the difference in reflectivity between the high-reflectivity region and the low-reflectivity region can be increased, thereby preventing erroneous detection by the photodetector.

[0027] The present disclosure further provides a reflective optical scale for an encoder in which high-reflection regions and low-reflection regions are alternately arranged on a transparent substrate, wherein the low-reflection region has a low-reflection portion formed by stacking at least three inorganic layers, and the reflectance in the low-reflection region is 5% or less, and the high-reflection region is formed by stacking at least one inorganic layer, and the reflectance in the high-reflection region is 60% or more, and the value of the S / N ratio represented by the following formula is 6 or more. S / N ratio = reflectance of high reflection area / reflectance of low reflection area [Effects of the Invention]

[0028] The reflective optical scale for an encoder according to the present disclosure has the advantageous effect of being able to sufficiently reduce the reflectance in a low-reflection region. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic cross-sectional view showing an example of a reflective optical scale for an encoder (first embodiment) according to the present disclosure. [Figure 2] 1 is a schematic cross-sectional view showing an example of a reflective optical scale for an encoder (first embodiment) according to the present disclosure. [Figure 3] 1 is a schematic cross-sectional view showing an example of a reflective optical scale for an encoder (first embodiment) according to the present disclosure. [Figure 4] FIG. 1 is a schematic cross-sectional view showing an example of a reflective optical scale for an encoder (second embodiment) according to the present disclosure. [Figure 5] FIG. 1 is a schematic cross-sectional view showing an example of a reflective optical scale for an encoder (second embodiment) according to the present disclosure. [Figure 6] FIG. 1 is a schematic cross-sectional view showing an example of a reflective optical scale for an encoder (second embodiment) according to the present disclosure. [Figure 7] 1A and 1B are a schematic perspective view and a schematic cross-sectional view showing an example of a reflective optical encoder according to the present disclosure. [Figure 8] 1 is a table and graph showing the simulation results of Example 1. [Figure 9] 10 is a table and graphs showing the simulation results of Example 2. [Figure 10] 10 is a table and graph showing the simulation results of Example 3. [Figure 11] 10 is a table and graph showing the simulation results of Example 4. [Figure 12] 1 is a graph showing the simulation results of Comparative Example 1 and a schematic cross-sectional view of a low-reflection region. [Figure 13] 10A and 10B are graphs showing simulation results of Comparative Example 2 and a schematic cross-sectional view of a low-reflection region. [Figure 14] 10 is a graph showing the simulation results of Comparative Example 3 and a schematic cross-sectional view of a low-reflection region. [Figure 15] 10 is a graph showing the simulation results of Comparative Example 4 and a schematic cross-sectional view of a low-reflection region. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present disclosure includes embodiments of a reflective optical scale for an encoder and a reflective optical encoder. Hereinafter, 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 construed as being limited to the description of the embodiments exemplified below. Furthermore, for clarity of explanation, the drawings may schematically depict the width, thickness, shape, etc. of each part compared to the embodiments, but these are merely examples and do not limit the interpretation of the present disclosure. Furthermore, in this specification and each drawing, elements similar to those described above with reference to the previous drawings may be designated by the same reference numerals, and detailed description may be omitted as appropriate. Furthermore, for convenience of explanation, the terms "upper" and "lower" may be used in some cases, but the up-down direction may be reversed.

[0031] Furthermore, in this specification, when a certain component, region, or other structure is said to be "above (or below)" another component, region, or other structure, unless otherwise specified, this includes not only the case where it is directly above (or below) the other structure, but also the case where it is above (or below) the other structure, i.e., the case where another component is included between the other structure and above (or below) the other structure.

[0032] In this specification, the "reflective optical scale for an encoder" may be simply referred to as the "optical scale." Furthermore, the light incident on the optical scale refers to light of wavelength λ that is incident on the optical scale from a light source at an incident angle θ.

[0033] The inventors conducted extensive research into the above-mentioned problems and found that the configuration of a conventional low-reflection area (non-reflection area) in a reflective optical scale for an encoder does not sufficiently reduce reflectance in the red and near-infrared regions. The inventors then conducted research into the configuration of a non-reflection area that can sufficiently reduce reflectance, and found that a configuration having a low-reflection area made of a metal chromium film and a chromium oxide film and a chromium nitride film formed in any order on the metal chromium film can sufficiently reduce the reflectance of light incident on the side opposite the metal chromium film side of the low-reflection area, which led to the completion of the present invention.

[0034] The reflective optical scale for an encoder and the encoder of the present disclosure can include a first embodiment in which light is incident from the side opposite the substrate of the optical scale described below, and a second embodiment in which light is incident from the substrate side.

[0035] A. Reflective optical scale for encoder (first embodiment) The reflective optical scale for an encoder of this embodiment is a reflective optical scale for an encoder in which high-reflection areas and low-reflection areas are arranged alternately on a substrate, and the low-reflection areas include low-reflection portions consisting of a metal chromium film formed on the substrate and a chromium oxide film and a chromium nitride film formed in any order on the metal chromium film, and the high-reflection areas are characterized in that the reflectivity of light incident from the opposite side of the substrate of the reflective optical scale for an encoder is higher than that of the low-reflection areas.

[0036] In the optical scale of this embodiment, the low-reflection region includes a low-reflection portion having a three-layer structure consisting of, from the substrate side, a metal chromium film and a chromium oxide film and a chromium nitride film formed in any order on the metal chromium film, and light incident from a light source located on the side of the optical scale opposite the substrate is reflected by the low-reflection portion, so that the reflectance in the low-reflection region can be reduced to 10% or less, preferably 5% or less, and even 1% or less, at any wavelength within the wavelength range of 550 nm to 950 nm. This makes it possible to increase the difference in reflectance between the high-reflection region and the low-reflection region. In this specification, the reflectance is obtained by measurement using a Scanning Spectrophotometer UV-3100PC (manufactured by Shimadzu Corporation) as a measuring device.

[0037] On the other hand, in a low-reflection portion including a two-layer structure of a metal chromium film and a chromium oxide film, a two-layer structure of a metal chromium film and a chromium nitride film, or a combination of another metal film and a chromium oxide film and / or a chromium nitride film, the reflectance of the low-reflection region cannot be sufficiently reduced.

[0038] Furthermore, if only metallic chromium is prepared, chromium oxide films and chromium nitride films can be easily formed by reactive sputtering, etc. Furthermore, high-resolution patterning can be performed more easily than with silicon oxide films.

[0039] In this specification, the phrase "a chromium oxide film and a chromium nitride film formed in any order on a metal chromium film" means that the metal chromium film, the chromium oxide film, and the chromium nitride film may be formed in this order, or the metal chromium film, the chromium nitride film, and the chromium oxide film may be formed in this order.

[0040] 1(a) and 1(b) are schematic cross-sectional views showing an example of a reflective optical scale for an encoder according to this embodiment. In the optical scale 10 according to this embodiment shown in FIGS. 1(a) and 1(b), high-reflection regions 12 and low-reflection regions 11 are alternately arranged on a substrate 1. The high-reflection regions 12 have a metal chromium film 2 formed on the substrate 1, and light L1 is reflected by the metal chromium film 2. In FIG. 1(a), the low-reflection regions 11 have a first-type low-reflection portion 20A made up of a metal chromium film 2 formed on the substrate 1, a chromium nitride film 3 formed on the metal chromium film 2, and a chromium oxide film 4 formed on the chromium nitride film 3, and light L1 is reflected by the low-reflection portion 20A. On the other hand, in FIG. 1(b), the low-reflection region 11 has a second-type low-reflection portion 20B made up of a metal chromium film 2 formed on the substrate 1, a chromium oxide film 4 formed on the metal chromium film 2, and a chromium nitride film 3 formed on the chromium oxide film 4, and light L1 is reflected by the low-reflection portion 20B.

[0041] The optical scale shown in Figure 1 requires fewer layers, which is advantageous in terms of cost. Furthermore, the reflectance at any wavelength within the wavelength range of 550 nm to 950 nm in the low reflection region can be reduced to 10% or less, preferably 5% or less, and further to 1% or less by adjusting the film thickness.

[0042] (1) Low reflection area The low-reflection region in the present disclosure has a low-reflection portion. The low-reflection portion is composed of a metal chromium film formed on a substrate, and a chromium oxide film and a chromium nitride film formed in any order on the metal chromium film. Specifically, the low-reflection portion is configured such that the metal chromium film, the chromium nitride film, and the chromium oxide film are arranged in this order, or the metal chromium film, the chromium oxide film, and the chromium nitride film are arranged in this order, with the metal chromium film facing the substrate in the optical scale. The outermost surface of the low-reflection region is preferably the surface of the chromium oxide film or the chromium nitride film of the low-reflection portion, and particularly preferably the surface of the chromium oxide film. This is because the reflectance in the low-reflection region can be more effectively reduced.

[0043] Hereinafter, the "low-reflection portion 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 the first specification low-reflection portion, and the "low-reflection portion 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 the second specification low-reflection portion.

[0044] (i) Low-reflection part of the first specification The low-reflection portion of this specification is composed of a metal chromium film, a chromium nitride film, and a chromium oxide film, arranged in this order from the substrate side. The low-reflection region having the low-reflection portion of this specification can reduce the reflectance at any wavelength within the wavelength range of 550 nm to 950 nm of light emitted from a light source to 5% or less, especially 0.5% or less, and the change in reflectance with wavelength is gradual, making it easy to control the reflectance. Each layer is described in detail below.

[0045] (a) Metallic chromium film In this specification, the metal chromium film is provided on a 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 1.0% or less. The transmittance can be measured using a spectrophotometer (MPC-3100) manufactured by Shimadzu Corporation, or the like. The film thickness is, for example, 40 nm or more, or preferably 70 nm or more.

[0046] Here, the "thickness" of each component refers to a 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 film thickness meter P-15 manufactured by KLA-Tencor Corporation. Note that the average value of thickness measurements taken at multiple locations on the component may also be used as the thickness.

[0047] The metal chromium film can be formed by physical vapor deposition (PVD) methods such as sputtering, ion plating, and vacuum deposition.

[0048] (b) Chromium nitride film The chromium nitride film in this specification is placed between the metallic chromium film and the chromium oxide film. Unlike chromium oxynitride and chromium oxynitride carbide, the chromium nitride film is mainly composed of chromium and nitrogen and contains substantially no impurities other than chromium and nitrogen.

[0049] The atomic ratio x of Cr to N in the chromium nitride (CrNx) film is preferably 0.4 or more and 1.1 or less.

[0050] The chromium nitride film has a purity of 80 to 100% by atomic percentage of chromium and nitrogen, preferably 90 to 100%, based on the entire film being 100 atomic %. Impurities such as hydrogen, oxygen, and carbon may be contained.

[0051] The thickness of the chromium nitride film (T N ) is preferably in the range of 5 nm to 100 nm, and particularly preferably in the range of 10 nm to 80 nm. O ) in relation to the wavelength of 850 nm, T N and T O If the sum of and is 40 nm or more and the wavelength is 550 nm, T N and T OThe total of the thicknesses (T) and (T) is preferably 20 nm or more. If the thickness is within this range, the reflectance in the low reflection region can be easily reduced to 10% or less, particularly 5% or less, compared with the case where the thickness is outside the above range. Furthermore, the thickness (T) of the chromium nitride film is N ) is preferably in the range of 10 nm to 80 nm, since this makes it easy to reduce the reflectance over the entire range from green to infrared (about 500 to 1000 nm).

[0052] Chromium nitride can be formed by physical vapor deposition (PVD) methods such as reactive sputtering, ion plating, and vacuum evaporation. 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 adjusting the ratio of Ar gas to nitrogen gas.

[0053] (c) Chromium oxide film The chromium oxide film is formed on the chromium nitride film and is mainly composed of chromium and oxygen. Unlike chromium oxynitride and chromium oxynitride carbide, the chromium oxide film does not substantially contain impurities other than chromium and oxygen.

[0054] The atomic ratio y of Cr to O in the chromium oxide (CrOy) film is preferably 1.4 or more and 2.1 or less.

[0055] Specifically, the chromium oxide film has a purity of 80 to 100% of chromium and oxygen, preferably 90 to 100%, based on 100 atomic % of the entire film. Impurities such as hydrogen, nitrogen, and carbon may be contained.

[0056] The thickness of the chromium oxide film is not particularly limited, but is preferably within the range of 5 nm to 100 nm, and more preferably within the range of 10 nm to 80 nm. In addition, the thickness of the chromium oxide film (T O ) is the thickness of the chromium nitride film (T N) is preferably in the range described above in "(i) Low reflection portion of first specification (b) chromium nitride film." Furthermore, the thickness of the chromium oxide film (T O ) is preferably in the range of 10 nm to 65 nm, since this makes it easy to reduce the reflectance over the entire range from green to infrared (about 500 to 1000 nm).

[0057] Chromium oxide can be formed by physical vapor deposition (PVD) methods such as reactive sputtering, ion plating, and vacuum evaporation. 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 adjusting the ratio of Ar gas to oxygen gas.

[0058] (ii) Low-reflection part of the second specification The low-reflection area of ​​this specification is composed of a metal chromium film, a chromium oxide film, and a chromium nitride film, arranged in this order from the substrate side. The low-reflection area having the low-reflection area of ​​this specification can reduce the reflectance of light irradiated from a light source at any wavelength within the wavelength range of 550 nm to 950 nm to 5% or less, especially 1% or less. Each layer will be described in detail below.

[0059] (a) Metallic chromium film The metal chrome film in this specification is formed on a substrate. The details of the metal chrome film are the same as those in "(ii) Low-reflection part of the first specification (a) Metal chrome film" above, so the explanation will be omitted here.

[0060] (b) Chromium oxide film The chromium oxide film in this specification is disposed between the metal chromium film and the chromium nitride film. The film thickness is not particularly limited, but is preferably within the range of, for example, 5 nm to 60 nm, and particularly preferably 10 nm to 50 nm. Furthermore, it is preferable to satisfy the relationship with the thickness of the chromium nitride film described below, because this more reliably reduces the reflectance at any wavelength within the low-reflectivity wavelength range of 550 nm to 950 nm to 10% or less, particularly 5% or less.

[0061] Furthermore, the thickness of the chromium oxide film (T O ) is preferably in the range of 5 nm to 35 nm, since this makes it easy to reduce the reflectance over the entire range from green to infrared (about 500 to 1000 nm).

[0062] Other details of the physical properties, composition and formation method of the chromium oxide film are the same as those of "(ii) Low reflectivity portion of first specification (c) chromium oxide film" described above, and therefore will not be described here.

[0063] (c) Chromium nitride film The chromium nitride film of this specification is formed on a chromium oxide film. The thickness of the chromium nitride film of this specification is not particularly limited, but is preferably within the range of 5 nm to 100 nm, and more preferably within the range of 10 nm to 80 nm. Furthermore, the thickness of the chromium oxide film (T O ) in relation to the wavelength of 850 nm, T N and T O If the sum of is 30 nm or more and the wavelength is 550 nm, T N and T O The total thickness of the chromium nitride film (T N ) is preferably in the range of 10 nm to 60 nm, since this makes it easy to reduce the reflectance over the entire range from green to infrared (about 500 to 1000 nm).

[0064] (2) Base material In the present disclosure, the material used for the substrate may be, for example, glass, metal, resin, silicon, etc., but a glass substrate using glass is preferable. This is because glass has a small linear expansion coefficient and can suppress dimensional changes that occur due to temperature changes in the usage environment. The shape of the substrate is not limited, and for example, a substrate used for a rotary encoder may have a substantially circular shape in plan view, and a substrate used for a linear encoder may have a substantially rectangular shape in plan view.

[0065] (3) Highly reflective area The configuration of the high-reflection region in this embodiment is not particularly limited as long as it has a higher reflectance than the low-reflection region for light incident from the side opposite the substrate side of the reflective optical scale for an encoder. The reflectance of the high-reflection region at any wavelength within the light wavelength range of 550 nm to 950 nm is preferably 60% or more, more preferably 80% or more, and even more preferably 90% or more. For example, the high-reflection region 12 in FIG. 1 has a metal chromium film 2 disposed on the substrate 1, and reflects light by the metal chromium film.

[0066] (4) Manufacturing method The optical scale of this embodiment can be manufactured by any method, including selective etching and lift-off. Specifically, a metal chromium film is formed on a substrate by, for example, sputtering, and then a chromium nitride film and a chromium oxide film are formed. The chromium nitride film and the chromium oxide film are then patterned by photolithography and etching, thereby producing the optical scale shown in FIG. 1.

[0067] Alternatively, the chromium nitride film and the chromium oxide film can be formed by forming a metal chromium film on a substrate, forming a resist pattern on the metal chromium film, and forming a chromium nitride film and a chromium oxide film by a known vacuum film formation method such as sputtering.The resist pattern is then removed to lift off the chromium nitride film and the chromium oxide film formed directly on the resist pattern, thereby obtaining patterns of the chromium nitride film and the chromium oxide film.

[0068] (5) Variation 1 Fig. 2 is a schematic cross-sectional view showing another example of a reflective optical scale for an encoder according to the present embodiment. In the optical scale 10 according to the present embodiment shown in Fig. 2, high-reflection regions 12 and low-reflection regions 11 are alternately arranged on a substrate 1. A highly reflective metal film 5 and a protective film 6 are formed on the substrate 1 in this order.

[0069] In the high-reflection region 12, light is reflected by the high-reflection metal film 5. On the other hand, in the low-reflection region 11, a low-reflection portion 20 is formed on the protective film 5, the low-reflection portion 20 having a metal chromium film 2, and a chromium oxide film 4 and a chromium nitride film 3 formed in no particular order on the metal chromium film 2.

[0070] (i) Highly reflective metal film The highly reflective metal film is preferably made of a metal having a high reflectance, such as silver, aluminum, rhodium, chromium, and alloys containing these metals as the main component, etc. Metal films having particularly high reflectance in the near-infrared region include gold, copper, and alloys containing these metals as the main component, etc.

[0071] (ii) Protective film When the highly reflective metal film is susceptible to corrosion, it is preferable to form a protective film on the highly reflective metal film. The protective film can be made of the same materials as those commonly used as protective films for optically functional components, such as photosensitive polyimide resins, epoxy resins, acrylic resins, and other photocurable or thermosetting resins, and inorganic materials. Other materials include polymerization initiators and various additives. The thickness of the protective film can be appropriately selected. The protective film can be formed by known coating methods, such as spin coating and die coating.

[0072] (6) Variation 2 3(a) and 3(b) are schematic cross-sectional views showing another example of a reflective optical scale for an encoder according to the present embodiment. The optical scale 10 according to the present embodiment shown in Fig. 3(a) is an embodiment in which a patterned metal chromium film 9 is formed on a laminate including a substrate 1, a metal chromium film 2, and a chromium nitride film 3 and a chromium oxide film 4 formed in no particular order on the metal chromium film 2.

[0073] FIG. 3(b) shows an embodiment in which a highly reflective metal film 5 formed in a pattern on the laminate. The optical scale shown in FIG. 3 has a substrate 1 on which high-reflection regions 12 and low-reflection regions 11 are alternately arranged, and includes a metal chromium layer 9 or a highly reflective metal film 5 in which the high-reflection regions 12 are formed in a pattern. Light is reflected by the metal chromium layer 9 or the highly reflective metal film 5. The low-reflection region 11 includes a metal chromium film 2 formed on the substrate 1 and a low-reflection portion 20 having a chromium nitride film 3 and a chromium oxide film 4 formed in any order on the metal chromium film 2. Light is reflected by the low-reflection portion 20. As shown in FIG. 3(b), if the highly reflective metal film 5 is susceptible to corrosion, a protective film 6 may be formed on the highly reflective metal film 5. In this case, the resist used in patterning the highly reflective metal film can be left as is to serve as the protective film 6. On the other hand, because a metal chromium film has excellent corrosion resistance, a protective film need not be formed on the patterned metal chromium film 9.

[0074] (7)S / N ratio As described above, the reflective optical scale for encoders of this embodiment makes it possible to reduce the reflectance of low-reflection areas, thereby making it possible to increase the S / N ratio expressed by the following formula. S / N ratio = reflectance of high reflection area / reflectance of low reflection area In the above formula, the reflectance of the high reflection region and the reflectance of the low reflection region indicate reflectance at the same wavelength.

[0075] In this embodiment, the S / N ratio can be set to 6 or more, particularly 15 or more, preferably 100 or more, and particularly preferably 200 or more. The basis for the above S / N ratio values ​​will be shown in the examples below.

[0076] (8) Optical scale The optical scale in the present disclosure may be for use in a rotary encoder or a linear encoder.

[0077] B. Encoder (First Embodiment) The present disclosure provides a reflective optical encoder comprising the above-mentioned reflective optical scale for an encoder, a light source that irradiates the reflective optical scale for an encoder with light of wavelength λ, and a photodetector that detects reflected light from the reflective optical scale for an encoder of the light source.

[0078] Fig. 7(a) is a schematic perspective view showing an example of a reflective optical encoder of the present disclosure, and Fig. 7(b) is a schematic cross-sectional view of an optical encoder equipped with an optical scale 10 including the low-reflection region 11 of Fig. 1(a). The reflective optical encoder 100 of the present disclosure includes the above-mentioned reflective optical scale 10 for encoder, and further includes a light source 31 and a photodetector 32. Furthermore, a fixed slit 33 may be included between the photodetector 32 and the reflective optical scale for an encoder 10. By providing the fixed slit 33, the change in the amount of light received by the photodetector 32 increases, thereby improving detection sensitivity. The fixed slit 33 may be provided between the light source 31 and the reflective optical scale for an encoder 10.

[0079] The reflective optical encoder 100 of the present disclosure has a large difference in reflectance between the high-reflection region and the low-reflection region, making it possible to prevent erroneous detection by the photodetector 32. As a result, the reflective optical encoder 100 makes it easy to read the optical scale 10 and has good encoder characteristics. Although FIG. 7 shows a rotary encoder, a linear encoder may also be used. The reflective optical scale for an encoder of the present disclosure will be described in detail below.

[0080] (1) Reflective optical scale for encoders The reflective optical scale for an encoder is similar to that described above in the section "A. Reflective optical scale for an encoder (first embodiment)," and therefore description thereof will be omitted here.

[0081] (2) Light source The light source may be, for example, an LED (light emitting diode), a laser, etc. The wavelength λ of the light L1 emitted from the light source is, for example, in the green to infrared (approximately 500 to 1000 nm) range. The low-reflection areas in the optical scale of the present disclosure can reduce the reflectance of light in these wavelength ranges, but it is particularly effective to reduce the reflectance of light in the red to infrared range (approximately 600 to 1000 nm).

[0082] The incident angle of the light L1 on the optical scale 10 is, for example, not less than 5° and not more than 45°. As shown in FIG. 7(b), the incident angle θ is the angle formed between a perpendicular line P to the surface of the substrate and the emission direction of light L1 from the light source.

[0083] (3) Photodetector The photodetector detects the light L2 reflected by the optical scale. The photodetector includes, for example, a light receiving element (e.g., a photoelectric conversion element) such as a photodiode or an imaging element.

[0084] C. Reflective optical scale for encoder (second embodiment) The reflective optical scale for an encoder of this embodiment is a reflective optical scale for an encoder in which high-reflection areas and low-reflection areas are arranged alternately on a transparent substrate, and the low-reflection areas include a light-reflection portion having a chromium oxide film and a chromium nitride film formed in any order on the transparent substrate, and a metal chromium film formed on the chromium oxide film or the chromium nitride film, and the high-reflection areas have a higher reflectivity of light incident from the transparent substrate side of the reflective optical scale for an encoder than the low-reflection areas.

[0085] A second embodiment of the present disclosure is an embodiment in which light is incident from the transparent substrate side of the optical scale. In this optical scale of this embodiment, the low-reflection region includes a light-reflecting portion having a three-layer structure of a chromium oxide film, a chromium nitride film, and a metal chromium film, formed in any order from the transparent substrate side. Because light is reflected by the light-reflecting portion, the reflectance of light incident from the transparent substrate side in the low-reflection region at any wavelength in the wavelength region of 550 nm to 950 nm can be reduced to 10% or less, preferably 5% or less, and the difference between the reflectance in the high-reflection region and the reflectance in the low-reflection region can be increased.

[0086] On the other hand, in a light-reflecting portion including a two-layer structure of a metal chromium film and a chromium oxide film, a two-layer structure of a metal chromium film and a chromium nitride film, or a combination of another metal film and at least one of a chromium oxide film and a chromium nitride film, the reflectance of the low-reflecting region cannot be sufficiently reduced.

[0087] Furthermore, if only metallic chromium is prepared, chromium oxide films and chromium nitride films can be easily formed by reactive sputtering, etc. Furthermore, high-resolution patterning can be performed more easily than with silicon oxide films.

[0088] Furthermore, since the reflecting surface is covered with glass, it is less susceptible to external damage and has the advantage of being easy to clean.

[0089] In this specification, the phrase "a chromium oxide film and a chromium nitride film formed in any order on a transparent substrate, and a metal chromium film formed on the chromium oxide film or the chromium nitride film" means that the films may be formed in the order of, from the transparent substrate side, the chromium oxide film, the chromium nitride film, and the metal chromium film, or the films may be formed in the order of, from the transparent substrate side, the chromium nitride film, the chromium oxide film, and the metal chromium film.

[0090] 4(a) and 4(b) are schematic cross-sectional views showing an example of a reflective optical scale for an encoder according to this embodiment. In the optical scale 50 according to this embodiment shown in FIGS. 4(a) and 4(b), high-reflection regions 22 and low-reflection regions 21 are alternately arranged on a transparent substrate 7. The high-reflection regions 22 have a metal chromium film 2 formed on the transparent substrate, and light is reflected by the metal chromium film 2. In FIG. 4(a), the low-reflection regions 21 have a first-type light-reflecting portion 20A consisting of a chromium oxide film 4 formed on the transparent substrate 7, a chromium nitride film 3 disposed on the chromium oxide film 4, and a metal chromium film 2 disposed on the chromium nitride film 3. Meanwhile, in FIG. 4(b), the low-reflection region 21 has a second-type light-reflecting portion 20B consisting of a chromium nitride film 3 formed on the transparent substrate 7, a chromium oxide film 4 disposed on the chromium nitride film 3, and a metal chromium film 2 disposed on the chromium oxide film 4. In FIG. 4(c), an anti-reflection film 8 is arranged on the opposite side of the transparent substrate 7 from the light-reflecting portion.

[0091] (1) Low reflection area The low-reflection region may have a light-reflecting portion. The light-reflecting portion is composed of a chromium oxide film and a chromium nitride film formed in any order on a transparent substrate, and a metal chromium film formed on the chromium oxide film or the chromium nitride film. Specifically, the light-reflecting portion may have a chromium oxide film, a chromium nitride film, and a metal chromium film arranged in this order from the transparent substrate side (first specification light-reflecting portion), or a chromium nitride film, a chromium oxide film, and a metal chromium film arranged in this order (second specification light-reflecting portion), with the metal chromium film being arranged on the opposite side of the optical scale from the transparent substrate. In this embodiment, the first specification light reflecting portion is preferable because it can make the low reflection area even lower in reflection.

[0092] (i) First specification light reflecting part The light-reflecting portion in this specification is a chromium oxide film, a chromium nitride film, and a metal chromium film arranged in this order from the transparent substrate side. The compositions and formation methods of the chromium oxide film, chromium nitride film, and metal chromium film can be the same as those explained in the above section "A. Reflective optical scale for encoder (first embodiment) (1) Low-reflection region (i) Low-reflection portion of the first specification," so explanation here will be omitted.

[0093] (a) Chromium oxide film The chromium oxide film of this specification is formed on a transparent substrate. The thickness of the chromium oxide film of this specification is not particularly limited, but is preferably in the range of 5 nm to 100 nm, and particularly in the range of 10 nm to 80 nm. If the thickness is within this range, the reflectance in the low-reflectance region can be reduced compared to when it is outside this range, and further, it becomes easier to reduce the reflectance over the entire region from green to infrared (approximately 500 to 1000 nm).

[0094] (b) Chromium nitride film The chromium nitride film of this specification is placed between the chromium oxide film and the metallic chromium film. The thickness of the chromium nitride film, T N is not particularly limited, but is preferably in the range of 10 nm to 100 nm, and more preferably in the range of 15 nm to 80 nm. In addition, the thickness of the chromium oxide film T O In relation to the wavelength, when the wavelength is 850 nm, T N and T O If the sum of is 30 nm or more and the wavelength is 550 nm, T N and T O The sum of these is preferably 20 nm or more. Furthermore, the range of 20 nm to 80 nm is preferred, as this makes it easier to reduce the reflectance over the entire range from green to infrared (approximately 500 to 1000 nm).

[0095] (c) Metallic chromium film The metal chromium film of this specification is formed on the side of the chromium nitride film opposite the chromium oxide film. A protective film may or may not be placed on the side of the metal chromium film opposite the chromium nitride film. The thickness of the metal chromium film is not particularly limited, but can be the same as that described in the above section "A. Reflective optical scale for encoder (first embodiment) (1) Low-reflection area (i) Low-reflection portion of first specification," so description here will be omitted.

[0096] (ii) Second specification light reflecting part The light-reflecting portion in this specification is a chromium nitride film, a chromium oxide film, and a metal chromium film arranged in this order from the transparent substrate side. The compositions and formation methods of the chromium nitride film, chromium oxide film, and metal chromium film can be the same as those explained in the above section "A. Reflective optical scale for encoder (first embodiment) (1) Low-reflection region (i) Low-reflection portion of first specification," so explanation here will be omitted.

[0097] (a) Chromium nitride film The chromium nitride film of this specification is disposed between the chromium oxide film and the transparent substrate. The thickness of the chromium nitride film is not particularly limited, but is preferably in the range of 5 nm to 80 nm, and more preferably in the range of 10 nm to 60 nm. In addition, the thickness T of the chromium oxide film O In relation to the wavelength, when the wavelength is 850 nm, T N and T O If the sum of is 30 nm or more and the wavelength is 550 nm, T N and T O The total thickness of the chromium nitride film is preferably 15 nm or more. Furthermore, the thickness of the chromium nitride film is preferably within the range of 5 nm to 40 nm, since this makes it easy to reduce the reflectance over the entire range from green to infrared (approximately 500 to 1000 nm).

[0098] (b) Chromium oxide film The chromium oxide film of this specification is formed on a transparent substrate. The thickness of the oxide film is not particularly limited, but is preferably in the range of 5 nm to 80 nm, and more preferably in the range of 10 nm to 60 nm. Furthermore, the thickness of the chromium oxide film is preferably in the range of 10 nm to 45 nm, since this makes it easy to reduce the reflectance over the entire range from green to infrared (approximately 500 to 1000 nm).

[0099] (c) Metallic chromium film The metal chromium film of this specification is formed on the opposite side of the chromium oxide film from the substrate. A protective film may or may not be placed on the opposite side of the metal chromium film from the chromium oxide film. The thickness of the metal chromium film is not particularly limited, but can be the same as that described in the above section "A. Reflective optical scale for encoder (first embodiment) (1) Low-reflection area (i) Low-reflection section of first specification," and therefore will not be described here.

[0100] (2) Highly reflective area The configuration of the high-reflection region in this embodiment is not particularly limited as long as it has a higher reflectance than the low-reflection region for light incident from the transparent substrate side of the reflective optical scale for an encoder. The reflectance of the high-reflection region at any wavelength within the light wavelength range of 550 nm to 950 nm is preferably 60% or more, more preferably 80% or more, and even more preferably 90% or more. For example, the high-reflection region in Figures 4(a) and (b) has a metal chrome film disposed on the transparent substrate, and light is reflected by the transparent substrate and the metal chrome film.

[0101] (3) Transparent base material The transparent substrate preferably has a total light transmittance of 80% or more, more preferably 85% or more, and even more preferably 90% or more in the wavelength range of 550 nm to 950 nm. The thickness of the transparent substrate may be any thickness that allows the desired light transmittance to be exhibited, and is preferably within the range of, for example, 0.1 mm to 2.0 mm.

[0102] Specifically, glass, transparent resin substrates, etc. can be used. Among these, glass is preferred because glass has high strength, a small coefficient of linear expansion, and can suppress dimensional changes caused by temperature changes in the usage environment. Transparent resin substrates include those made of transparent resin materials selected from polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene (PE), polycarbonate (PC), acrylic, polyvinyl chloride, polyvinyl alcohol, polyimide, polyetherimide, polyether ether ketone, epoxy resin, silicone resin, phenolic resin, etc.

[0103] (4) Anti-reflection coating In this embodiment, as shown in Fig. 4(c), an anti-reflection coating 8 may be provided on the transparent substrate 7. By providing an anti-reflection coating, the reflectance in the low-reflection region can be further reduced, and the contrast of the image formed by reflected light from the optical scale can be increased.

[0104] The anti-reflection film may be an organic layer or an inorganic layer as long as it can exhibit a predetermined anti-reflection function. For example, SiO2, MgF2, Al2O 3、 Examples of such a thin film include a thin film with a low refractive index, such as TiO3. Alternatively, a multilayer film can be formed by alternately stacking a thin film made of a high refractive index material (hereinafter referred to as a high refractive index film) and a thin film made of a low refractive index material (hereinafter referred to as a low refractive index film) having a refractive index lower than that of the high refractive index material. However, a low refractive index film is formed on the most visible side of the multilayer film. The number of thin films in the multilayer film and the refractive index of each thin film are not particularly limited.

[0105] (5) Manufacturing method The optical scale of this embodiment can be manufactured by any method, including selective etching and lift-off. Specifically, a chromium nitride film and a chromium oxide film are formed on a transparent substrate by, for example, sputtering, and then patterned by photolithography and etching. Thereafter, a metal chromium film is formed on the patterned chromium nitride film and chromium oxide film, thereby manufacturing the optical scale shown in FIG. The patterning can also be performed by lift-off.

[0106] (6) Variation 1 5(a) and 5(b) are schematic cross-sectional views showing an example of a reflective optical scale for an encoder according to this embodiment. The low-reflection region 21 in the optical scale 50 according to this embodiment shown in FIG. 5 has a light-reflecting portion 20 composed of a chromium oxide film 4 and a chromium nitride film 3 formed in any order on the transparent substrate 7, and a metal chromium film 2 formed on the chromium oxide film or the chromium nitride film. The high-reflection region 22 has a highly reflective metal film 5 formed on the transparent substrate, and light is reflected by the transparent substrate 7 and the highly reflective metal film 5. As shown in FIG. 5(b), if the highly reflective metal film 5 is susceptible to corrosion, it is preferable to form a protective film 6 on the highly reflective metal film 5. An anti-reflection film 8 may be provided on the transparent substrate 7 on the side opposite the light-reflecting portion 20.

[0107] (7) Variation 2 FIGS. 6(a), 6(b), and 6(c) are schematic cross-sectional views showing another example of the reflective optical scale for an encoder according to this embodiment. In the optical scale 50 according to this embodiment shown in FIG. 6(a), the low-reflection region 21 has a light-reflecting portion composed of a chromium oxide film 4 and a chromium nitride film 3 formed in any order on the transparent substrate 7, and a metal chromium film 2 formed on the chromium oxide film or the chromium nitride film. The high-reflection region 22 has a metal chromium film 9 formed in a pattern on the transparent substrate. FIG. 6(b) shows a case in which the high-reflection region 22 has a highly reflective metal film 5 formed in a pattern on the transparent substrate. An anti-reflection film 8 may be provided on the transparent substrate 7 opposite the light-reflecting portion 20 in FIGS. 6(a) and 6(b) (FIG. 6(c)). The provision of an anti-reflection film further enhances the contrast of the image formed by the light reflected from the optical scale. Furthermore, a protective film may be provided on the metal chromium film 2 opposite the chromium nitride film 3 and the chromium oxide film 4.

[0108] (8)S / N ratio As described above, the reflective optical scale for encoders of this embodiment makes it possible to reduce the reflectance of low-reflection areas, thereby making it possible to increase the S / N ratio expressed by the following formula. S / N ratio = reflectance of high reflection area / reflectance of low reflection area In the above formula, the reflectance of the high reflection region and the reflectance of the low reflection region indicate reflectance at the same wavelength.

[0109] In this embodiment, the S / N ratio can be set to 6 or more, particularly 15 or more, preferably 100 or more, and particularly preferably 200 or more. The basis for the above S / N ratio values ​​will be shown in the examples below.

[0110] D. Optical Encoder (Second Embodiment) The present disclosure provides a reflective optical encoder comprising the above-mentioned reflective optical scale for an encoder, a light source that irradiates the reflective optical scale for an encoder with light of wavelength λ, and a photodetector that detects reflected light from the reflective optical scale for an encoder of the light source.

[0111] (1) Reflective optical scale for encoders The reflective optical scale for an encoder is similar to that described above in the section "C. Reflective optical scale for an encoder (second embodiment)," and therefore description thereof will be omitted here.

[0112] (2) Light source and photodetector The light source and photodetector are the same as those described above in the section "B. Reflective optical scale for encoder (first embodiment)", and therefore a description thereof will be omitted here.

[0113] E. Reflective optical scale for encoder (third embodiment) The reflective optical scale for an encoder of this embodiment is a reflective optical scale for an encoder in which high-reflection areas and low-reflection areas are arranged alternately on a transparent substrate, and is characterized in that the low-reflection areas have low-reflection portions formed by stacking at least three inorganic layers, the reflectivity of the low-reflection areas is 5% or less, the high-reflection areas are formed by stacking at least one inorganic layer, the reflectivity of the high-reflection areas is 60% or more, and the value represented by the following formula is 6 or more. S / N ratio = reflectance of high reflection area / reflectance of low reflection area In the above formula, the reflectance of the high reflection region and the reflectance of the low reflection region indicate reflectance at the same wavelength.

[0114] The low-reflection portion constituting the low-reflection region in the present disclosure is a laminate of at least three inorganic layers, which may be metal layers or metal compounds such as metal oxides and metal nitrides. Examples of materials that can be used to form such an inorganic layer include metallic chromium, chromium oxide, chromium nitride, silicon oxide, aluminum oxide, titanium oxide, and magnesium fluoride.

[0115] In the low reflection region, the reflectance at any wavelength within the wavelength range of 550 nm to 950 nm is 5% or less, and particularly preferably 1% or less. Furthermore, the configuration of the high-reflection region is not particularly limited, as long as the reflectance at any wavelength within the wavelength range of 550 nm to 950 nm is 60% or more. For example, the configurations described above in "A. Reflective optical scale for encoder (first embodiment)" and "C. Reflective optical scale for encoder (second embodiment)" can be mentioned.

[0116] The reflectance at any wavelength within the wavelength range of 550 nm to 950 nm in the high reflectance region is 60% or more, preferably 80% or more, and more preferably 90% or more. In this embodiment, the S / N ratio may be 6 or more, particularly 15 or more, preferably 100 or more, and particularly preferably 200 or more.

[0117] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and that provides similar effects is included within the technical scope of the present invention. [Example]

[0118] The present invention will be described in more detail below with reference to examples and comparative examples. Example 1 In the first embodiment, when the low-reflection portion has the first specification (FIG. 1(a)), the thicknesses of the chromium oxide film 4 and chromium nitride film 3 in the low-reflection portion 20 were varied (thickness of the metal chromium film 2 set to 100 nm), and the reflectance was calculated by simulation when light L1 with a wavelength of 850 nm was incident on the low-reflection region 11 from the side opposite the glass (substrate 1). The results are shown in FIG. 8(a). In FIG. 8, △ indicates a reflectance of 20% or less, ◯ indicates a reflectance of 10% or less, and ⊚ indicates a reflectance of 5% or less. FIG. 8(b) shows the wavelength dependence of reflectance when the thickness of the chromium oxide film is 50 nm, the thickness of the chromium nitride film is 30 nm, and the thickness of the metal chromium film is 100 nm.

[0119] In Example 1, the reflectance (wavelength 850 nm) in the high-reflection region where the metal chromium film 2 was disposed was 64.1%. The reflectance (wavelength 850 nm) in the low-reflection region where the film thickness of each layer was adjusted to the above values ​​was 0.3%. The S / N ratio in this case was 214.

[0120] On the other hand, in the high reflection region where silver was disposed as the highly reflective metal film instead of the metal chromium film 2, the reflectance (wavelength 850 nm) was 91.1%. The S / N ratio in this case was 304.

[0121] Example 2 In the second embodiment, when the low-reflection portion has the first specification (FIG. 4(a)), the thicknesses of the chromium oxide film and chromium nitride film of the low-reflection portion 20 were varied (thickness of the metal chromium film: 100 nm), and the reflectance was calculated by simulation when light with a wavelength of 850 nm was incident on the low-reflection region from a transparent substrate (glass). The results are shown in FIG. 9(a). Furthermore, FIG. 9(b) shows the wavelength dependence of reflectance when the thickness of the chromium oxide film is 25 nm, the thickness of the chromium nitride film is 45 nm, and the thickness of the metal chromium film is 100 nm. Note that the thickness of the metal chromium film here refers to the film thickness in the low-reflection region 21, and refers to the thickness of the metal chromium 2 disposed on the surface of the chromium nitride 3 opposite the chromium oxide 4 in the low-reflection region 21.

[0122] In Example 2, the reflectance (wavelength 850 nm) in the high-reflection region where the metal chromium film 2 was disposed was 70.0%, and the reflectance (wavelength 850 nm) in the low-reflection region where the film thickness of each layer was adjusted to the above values ​​was 4.1%. The S / N ratio in this case was 17.

[0123] On the other hand, the reflectance (wavelength 850 nm) in the high reflection region where silver was disposed as the high reflection metal film instead of the metal chromium film 2 was 97.0%. The S / N ratio in this case was 24.

[0124] Example 3 In the first embodiment, when the low-reflection portion conforms to the second specification (FIG. 1(b)), the thicknesses of the chromium oxide film and chromium nitride film in the low-reflection portion were varied (thickness of the metal chromium film: 100 nm), and the reflectance was calculated by simulation when light with a wavelength of 850 nm was incident on the low-reflection region from the side opposite the glass. The results are shown in FIG. 10(a). The wavelength dependence of reflectance when the thickness of the chromium oxide film is 20 nm, the thickness of the chromium nitride film is 40 nm, and the thickness of the metal chromium film is 100 nm is shown in FIG. 10(b).

[0125] In Example 3, the reflectance (wavelength 850 nm) in the high-reflection region where the metal chromium film 2 was disposed was 64.1%, and the reflectance (wavelength 850 nm) in the low-reflection region where the film thickness of each layer was adjusted to the above values ​​was 0.6%. The S / N ratio in this case was 107.

[0126] On the other hand, in the high reflection region where silver was disposed as the highly reflective metal film instead of the metal chromium film 2, the reflectance (wavelength 850 nm) was 91.1%. The S / N ratio in this case was 152.

[0127] Example 4 In the second embodiment, when the low-reflection portion conforms to the second specification (FIG. 4(b)), the thicknesses of the chromium oxide film and chromium nitride film in the low-reflection portion were varied (thickness of the metal chromium film: 100 nm), and the reflectance was calculated by simulation when light with a wavelength of 850 nm was incident on the low-reflection region from the glass side. The results are shown in FIG. 11(a). FIG. 11(b) also shows the wavelength dependence of reflectance when the thickness of the chromium oxide film is 40 nm, the thickness of the chromium nitride film is 20 nm, and the thickness of the metal chromium film is 100 nm. The thickness of the metal chromium film here refers to the film thickness in the low-reflection region 21, and refers to the film thickness of the metal chromium 2 disposed on the surface of the chromium oxide 4 opposite the chromium nitride 3 in the low-reflection region 21.

[0128] In Example 4, the reflectance (wavelength 850 nm) in the high-reflection region where the metal chromium film 2 was disposed was 70.0%, and the reflectance (wavelength 850 nm) in the low-reflection region where the film thickness of each layer was adjusted to the above values ​​was 4.1%. The S / N ratio in this case was 17.

[0129] On the other hand, the reflectance (wavelength 850 nm) in the high reflection region where silver was disposed as the high reflection metal film instead of the metal chromium film 2 was 97.0%. The S / N ratio in this case was 24.

[0130] (Comparative Example 1) 12(b), a thin-film multilayer film having a metal chromium film 52 and a chromium nitride film 53 formed in this order on glass 51 was used to form a low-reflection region. The reflectance of the low-reflection region for light incident from the side opposite the glass (vertical axis) was calculated by simulation according to the film thickness of the chromium nitride film (horizontal axis). The wavelengths were 550 nm, 650 nm, 750 nm, and 850 nm. The results when the thickness of the metal chromium film was 100 nm are shown in FIG. 12(a).

[0131] (Comparative Example 2) As shown in Figure 13(b), a thin-film multilayer film having a metal chromium film 52 and a chromium oxide film 54 formed in this order on glass 51 was used to form a low-reflection region. A simulation was performed to measure the reflectance of the low-reflection region (vertical axis) for light incident from the side opposite the glass as a function of the film thickness of the chromium oxide (horizontal axis). The results for a metal chromium film with a film thickness of 100 nm are shown in Figure 13(a).

[0132] (Comparative Example 3) As shown in Figure 14(b), a simulation was performed on the reflectance (vertical axis) of the low-reflection region of light incident from the glass side as a function of the film thickness (horizontal axis) of the chromium nitride film, where a thin-film multilayer film having a chromium nitride film 53 and a metal chromium film 52 in this order was formed on glass 51 to form a low-reflection region. The results for the metal chromium film with a film thickness of 100 nm are shown in Figure 14(a).

[0133] Comparative Example 4 As shown in Figure 15(b), a simulation was performed on the reflectance (vertical axis) of the low-reflection region of light incident from the glass side as a function of the film thickness (horizontal axis) of the chromium oxide film, where a thin-film multilayer film having a chromium oxide film 54 and a metal chromium film 52 in this order was formed on glass 51 to form a low-reflection region. The results for the metal chromium film with a film thickness of 100 nm are shown in Figure 15(a).

[0134] According to the results of Examples 1 to 4, it was possible to reduce the reflectance in the low-reflection region to 10% or less, particularly to 5% or less. On the other hand, according to the results of Comparative Examples 1 to 4, it was not possible to sufficiently reduce the reflectance compared to the Examples. Furthermore, it was suggested that Examples 1 and 3 had little wavelength dependency of the reflectance change. [Explanation of symbols]

[0135] 1 … Base material 2... Metallic chrome film 3... Chromium nitride film 4... Chromium oxide film 20…Low reflection area 11... Low reflection area (first embodiment) 12 ... Highly reflective area (first embodiment) 21 ... Low reflection area (second embodiment) 22 ... Highly reflective area (second embodiment)

Claims

1. A reflective optical scale for an encoder, in which high-reflection areas and low-reflection areas are alternately arranged on a substrate, the low-reflection region has a reflectance of 1% or less at a wavelength of 850 nm; the high-reflection region is formed by laminating at least one inorganic layer, and the reflectance of the high-reflection region at a wavelength of 850 nm is 60% or more; the highly reflective region is formed by laminating an inorganic layer containing at least silver or aluminum, A reflective optical scale for an encoder, having an S / N ratio value represented by the following formula of 15 or more. S / N ratio = reflectance in high reflection area / reflectance in low reflection area

2. 2. The reflective optical scale for an encoder according to claim 1, wherein the outermost surface of the low-reflection region is the chromium oxide film or the chromium nitride film.

3. 3. A reflective optical scale for an encoder according to claim 1, wherein the low-reflection region has the metal chromium film, the chromium nitride film arranged on a surface of the metal chromium film opposite to the substrate, and the chromium oxide film arranged on a surface of the chromium nitride film opposite to the metal chromium film.

4. 4. The reflective optical scale for an encoder according to claim 1, wherein the S / N ratio is 100 or more.

5. a reflective optical scale for an encoder according to any one of claims 1 to 4; and a light source that irradiates light onto a surface of the reflective optical scale for an encoder opposite to a surface on which a light reflecting portion is disposed; a photodetector that detects reflected light from the light source on the reflective optical scale for encoder; A reflective optical encoder comprising:

Images