Reflection-type optical scale for encoder, reflection-type optical encoder, and laminate for reflection-type optical scale for encoder

Abstract

The invention relates to a reflective optical scale for an encoder, a reflective optical encoder, and a laminate for a reflective optical scale for an encoder. A reflective optical scale for an encoder, which has, in this order in the thickness direction, a high reflective layer, a protective layer, and a low reflective layer provided in a pattern, and which has a low reflective region, which is a region where the low reflective layer is provided, and a high reflective region, which is a region where the protective layer is exposed, when the film thickness of the protective layer is d ([mu] m) and the incident angle of the incident light to the protective layer is theta (degree), the following formula (1) is satisfied. D = m [lambda] / [2n * cos {Arcsin (sin [theta] / n)}] (1) (in the formula, n is the refractive index of the protective layer, [lambda] is the wavelength ([mu] m) of incident light, and m is a number satisfying 0 < m < = 0.3 or p-0.3 < = m < = p + 0.3 (p is an integer of 1-3). )

Description

[0001] This application is a divisional application. The original application has the Chinese national application number 202380067296.6, the application date is September 21, 2023, and the invention title is "Reflective optical scale for encoder, reflective optical encoder and laminate for reflective optical scale of encoder". Technical Field

[0002] This invention relates to a reflective optical scale for encoders, a reflective optical encoder, and a laminate for a reflective optical scale for encoders. Background Technology

[0003] Previously, optical encoders were used in servo motors and other devices with control mechanisms. Optical encoders include transmissive and reflective types, but compared to transmissive encoders, reflective encoders have the following advantages: shorter optical path, easier miniaturization and thinning, and easier assembly as they do not require positioning of the light-emitting or light-receiving elements. 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 the reflected light from the scale. In the reflective optical scale, reflective areas (high-reflection areas) and non-reflective areas (low-reflection areas) are alternately arranged, with the reflectivity of light in the reflective areas being higher than that in the non-reflective areas. Therefore, the intensity of the light reflected from the scale and incident on the photodetector varies depending on the scale's position. The photodetector detects the intensity of light caused by the scale's movement in the measuring direction. The reflective optical encoder processes the displacement information of the scale based on the detected light intensity, thereby acquiring position information.

[0004] In the reflective and non-reflective regions formed on a reflective optical scale, in order to prevent false detection by the photodetector and improve the detection accuracy of the signal, it is necessary to increase the reflectivity of the reflective region and decrease the reflectivity of the non-reflective region.

[0005] For example, Patent Document 1 discloses a reflector, characterized in that, in the reflector for an optical encoder, a reflective film for reflecting light, a protective layer for protecting the reflective film, and a pattern forming film having a lower light reflectivity than the reflective film and having a slit pattern are sequentially stacked on a substrate.

[0006] Patent Document 2 discloses a reflective optical scale for an encoder, which, with the aim of sufficiently reducing the reflectivity in low-reflection areas, alternately arranges high-reflection areas and low-reflection areas on a substrate. The low-reflection areas include low-reflection portions having: a chromium metal film disposed on one surface of the substrate; and a chromium oxide film and a chromium nitride film disposed in different orders on the surface of the chromium metal film opposite to the substrate. The reflectivity of light incident from the side of the reflective optical scale for the encoder opposite to the substrate in the high-reflection areas is higher than that in the low-reflection areas.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2005-241248

[0010] Patent Document 2: WO2021 / 201024 Publication Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] Conventionally, when forming a patterned low-reflection layer on a high-reflection layer containing metal or the like, the low-reflection layer is formed directly on the high-reflection layer, and a resist pattern is formed on the low-reflection layer, for example, by photolithography. The resist pattern is then used as a mask for etching, thereby obtaining the patterned low-reflection layer. However, during the etching of the low-reflection layer, sometimes the surface of the high-reflection layer becomes rough, resulting in increased surface roughness, or etching residue is formed on the surface of the high-reflection layer, leading to a decrease in the reflectivity of light incident on the high-reflection region. Therefore, the inventors of this application investigated providing a protective layer between the high-reflection layer and the low-reflection layer. However, a new discovery has been made: even with a protective layer, the reflectivity of light incident on the high-reflection region sometimes decreases.

[0013] The present invention was made in view of the above circumstances, and its main objective is to provide a reflective optical scale for an encoder that can improve the reflectivity of light incident on a high-reflectivity region.

[0014] Methods for solving problems

[0015] One embodiment of this disclosure provides a reflective optical scale for an encoder, which has a high reflective layer, a protective layer and a low reflective layer arranged in a pattern in the thickness direction. The reflective optical scale for an encoder has a low reflective region as the area where the low reflective layer is provided and a high reflective region as the area where the protective layer is exposed. When the film thickness of the protective layer is set to d (μm) and the incident angle of the incident light on the protective layer is set to θ (°), the following equation (1) is satisfied.

[0016] d=mλ / [2n×cos{Arcsin(sinθ / n)}] (1)

[0017] (In the formula, n is the refractive index of the protective layer, λ is the wavelength (μm) of the incident light, and m is a number that satisfies 0 < m ≤ 0.3 or p - 0.3 ≤ m ≤ p + 0.3 (p is an integer greater than 1 and less than 3).)

[0018] Another embodiment of this disclosure provides a reflective optical scale for an encoder, wherein a high-reflectivity layer, a protective layer containing an organic material, and a low-reflectivity layer arranged in a pattern are sequentially provided in the thickness direction. The scale includes: a low-reflectivity region, which is a region where the high-reflectivity layer, the protective layer, and the low-reflectivity layer are provided; and a high-reflectivity region, which is a region where the high-reflectivity layer and the protective layer are provided. The protective layer has a film thickness of 0.16 μm or more and 1.0 μm or less, and the reflectivity of the high-reflectivity region is 40% or more when the wavelength of the measuring light source is set to 850 μm.

[0019] Another embodiment of this disclosure provides a reflective optical scale for an encoder, wherein a high-reflectivity layer, a protective layer containing an organic material, and a low-reflectivity layer arranged in a pattern are sequentially provided in the thickness direction. It has: a low-reflectivity region, which is a region provided with the high-reflectivity layer, the protective layer, and the low-reflectivity layer; and a high-reflectivity region, which is a region provided with the high-reflectivity layer and the protective layer. The reflectivity of the low-reflectivity region is 2% or less when the wavelength of the measuring light source is set to 850 μm, and the S / N ratio expressed by the following formula is 30 or more.

[0020] S / N ratio = Reflectance of high-reflection area / Reflectance of low-reflection area

[0021] Another embodiment of this disclosure provides a reflective optical encoder, characterized in that it comprises: a reflective optical scale for the encoder; a light source for illuminating measuring light onto a surface of the reflective optical scale for the encoder on the side where the low-reflection layer is disposed; and a photodetector for detecting reflected light from the reflective optical scale for the encoder.

[0022] Another embodiment of the present invention provides a laminate for a reflective optical scale for an encoder, which is a laminate for manufacturing the above-mentioned reflective optical scale for an encoder. The laminate has a high reflective layer, a protective layer and a low reflective layer forming layer in sequence in the thickness direction. When the thickness of the protective layer is set to d (μm) and the incident angle of the incident light on the protective layer is set to θ (°), the following formula (1) is satisfied.

[0023] d=mλ / [2n×cos{Arcsin(sinθ / n)}] (1)

[0024] (In the formula, n is the refractive index of the protective layer, λ is the wavelength (μm) of the incident light, and m is a number that satisfies 0 < m ≤ 0.3 or p - 0.3 ≤ m ≤ p + 0.3 (p is an integer greater than 1 and less than 3).)

[0025] Another embodiment of this disclosure provides a laminate for a reflective optical scale for an encoder, which is used to manufacture the aforementioned reflective optical scale for an encoder. The laminate has a high reflective layer and a protective layer in sequence in the thickness direction. When the thickness of the protective layer is set to d (μm) and the incident angle of the incident light on the protective layer is set to θ (°), the following equation (1) is satisfied.

[0026] d=mλ / [2n×cos{Arcsin(sinθ / n)}] (1)

[0027] (In the formula, n is the refractive index of the protective layer, λ is the wavelength (μm) of the incident light, and m is a number that satisfies 0 < m ≤ 0.3 or p - 0.3 ≤ m ≤ p + 0.3 (p is an integer greater than 1 and less than 3).)

[0028] Invention Effects

[0029] In this disclosure, the following effect is achieved: a reflective optical scale for an encoder is provided that can improve the reflectivity of light incident on a highly reflective region. Attached Figure Description

[0030] Figure 1 This is a schematic cross-sectional view illustrating the reflective optical scale used in the encoder of this disclosure.

[0031] Figure 2 These are schematic perspective views and partial enlarged views illustrating the reflective optical encoder of this disclosure.

[0032] Figure 3 This is a schematic cross-sectional view illustrating the reflective optical scale used in the encoder of this disclosure.

[0033] Figure 4 This is a schematic cross-sectional view illustrating the reflective optical scale used in the encoder of this disclosure.

[0034] Figure 5 This is a graph showing the relationship between the thickness of the protective layer and the average reflectivity in Experimental Example A and Experimental Example B.

[0035] Figure 6 This is a graph showing the relationship between the thickness of the protective layer and the average standard reflectance in Experimental Example A and Experimental Example B.

[0036] Figure 7 The results are the reflectance measurements of the measured light wavelength and incident angle as described in Examples and Reference Example 1.

[0037] Figure 8 The results are the reflectance measurements of Comparative Example 1 and Comparative Example 2 when the wavelength and angle of incidence of the measured light change.

[0038] Figure 9 This is a schematic cross-sectional view of the reflective optical scale laminate for encoders in this disclosure. Detailed Implementation

[0039] This disclosure includes, in its embodiments, a reflective optical scale for an encoder, a reflective optical encoder, and a laminate for a reflective optical scale for an encoder. Hereinafter, embodiments of this disclosure will be described with reference to the accompanying drawings. However, this disclosure can be implemented in many different ways and is not limited to the description of the embodiments illustrated below. Furthermore, regarding the drawings, to make the explanation clearer, the width, thickness, shape, etc., of each part are sometimes schematically shown compared to the actual form; however, this is merely an example and does not limit the interpretation of this disclosure. Additionally, in this specification and the drawings, for figures that have already appeared, the same reference numerals are used for the same elements as before, and detailed descriptions are sometimes appropriately omitted.

[0040] In this specification, when describing the configuration of other components on a certain component, the simple expression "on..." or "below..." includes, unless otherwise specified, both cases where the other component is configured to be directly above or below a certain component in connection with it, and cases where the other component is configured above or below a certain component while being separated by another component. Similarly, in this specification, when describing the configuration of other components on the surface of a certain component, the simple expression "on the side of..." or "on...the surface" includes, unless otherwise specified, both cases where the other component is configured to be directly above or below a certain component in connection with it, and cases where the other component is configured above or below a certain component while being separated by another component.

[0041] Additionally, in this specification, "reflective optical scale for encoder" is sometimes abbreviated as "optical scale".

[0042] As described above, the inventors of this application investigated the problem that the reflectivity of light incident on the high-reflectivity region decreases even when a protective layer is provided between the high-reflectivity layer and the low-reflectivity layer. The results showed that by adjusting the thickness of the protective layer to a predetermined range where the light reflected from the surface of the protective layer and the light reflected at the interface between the protective layer and the high-reflectivity layer mutually enhance each other, the reflectivity of light incident on the high-reflectivity region can be improved, thus completing the present invention.

[0043] The following provides a detailed description of the reflective optical scale for encoders, the reflective optical encoder, and the laminate for the reflective optical scale for encoders as disclosed herein.

[0044] A-1. Encoder with reflective optical scale

[0045] Figure 1 (a) is a schematic cross-sectional view showing an example of an encoder using a reflective optical scale in this disclosure. Figure 1 The encoder shown in (a) uses a reflective optical scale 10 in the thickness direction D. T The protective layer comprises a high-reflection layer 1, a protective layer 2, and a low-reflection layer 3 arranged in a pattern, and has a low-reflection region R1, which is the area where the low-reflection layer 3 is disposed, and a high-reflection region R2, which is the area where the protective layer 2 is exposed. A feature of this disclosure is that the film thickness d of the protective layer 2 meets a specified range. Figure 1 The encoder in (a) is configured with alternating low-reflection regions R1 and high-reflection regions R2 using a reflective optical scale. The low-reflection region R1 has a high-reflection layer 1, a protective layer 2, and a low-reflection layer 3. The high-reflection region R2 has a high-reflection layer 1 and a protective layer 2. Furthermore, Figure 1 (b) shows the measurement of light from Figure 1 The encoder in (a) is incident on the low-reflection layer 3 side of the reflective optical scale 10. Light L1, irradiated from the light source, is reflected at the surface of the protective layer 2 and at the interface between the high-reflection layer 1 and the protective layer 2. The reflectivity of the light at the high-reflection region R2 is higher than that at the low-reflection region R1. It should be noted that the reflectivity of the light at the high-reflection region R2 and the low-reflection region R1 represent the reflectivity at the same wavelength and the same angle of incidence.

[0046] Figure 2 (a) is a schematic perspective view showing an example of a reflective optical encoder equipped with a reflective optical scale for encoders as described in this disclosure. Figure 2 (b) is viewed from above. Figure 2 (a) is a partial enlarged view of a reflective optical encoder. The reflective optical encoder 100 of this disclosure includes a reflective optical scale 10 for the encoder, a light source 21, and a photodetector 22. Figure 2In (a), the fixed slit 23 is positioned between the photodetector 22 and the reflective optical scale 10 for the encoder.

[0047] The encoder in this disclosure uses a reflective optical scale to improve the reflectivity of light incident on a high-reflectivity region by adjusting the film thickness d of the protective layer 2 to a specified range.

[0048] The following is a detailed description of the reflective optical scale for the encoder disclosed herein.

[0049] 1. Protective layer

[0050] The protective layer in this disclosure is disposed between the high-reflectivity layer and the low-reflectivity layer. The protective layer is transparent and also functions to protect the high-reflectivity layer. By providing the protective layer, during etching when the low-reflectivity layer is patterned, there is no need to worry about the surface roughness of the high-reflectivity layer increasing. Therefore, diffuse reflection of light can be suppressed.

[0051] In this disclosure, when the incident angle of the incident light on the protective layer is set to θ (°), the thickness d (μm) of the protective layer is adjusted to satisfy the following equation (1).

[0052] d=mλ / [2n×cos{Arcsin(sinθ / n)}] (1)

[0053] (In the formula, n is the refractive index of the protective layer, λ is the wavelength (μm) of the incident light, and m is a number that satisfies 0 < m ≤ 0.3 or p - 0.3 ≤ m ≤ p + 0.3 (p is an integer greater than 1 and less than 3).)

[0054] It should be noted that the reason for increasing the reflectivity of light incident on the high-reflectivity region by setting the thickness of the protective layer within the aforementioned range is as follows: The refractive index is in the relationship of air < ​​protective layer < high-reflectivity layer, thus resulting in fixed-end reflections at each interface, with a phase shift of π. When the light reflected at the air-protective layer interface is in phase with the light reflected at the protective layer-high-reflectivity layer interface, the reflected light best suppresses the attenuation of reflectivity. The condition for phase consistency of the reflected light is a film thickness that satisfies the above formula.

[0055] In equation (1) above, the incident angle θ is the incident angle of the incident light onto the protective layer. As will be described later, the incident angle of the light on the optical scale 10 may vary depending on its position relative to the light source 21. Figure 3 In equation (1) above, the incident angle θ is the angle of incidence at the scale position (e.g., the position of the main pattern) where the strongest reflectivity is desired. For example, it can be 0°, 20°, 40°, or 55°.

[0056] In the above formula (1), n ​​is the refractive index of the protective layer, and λ is the wavelength (μm) of the incident light, which can be any wavelength in the range of 0.38μm or more and 1.0μm or any wavelength in the range of 0.50μm or more and 1.0μm or less.

[0057] In the above formula (1), m is a number that satisfies 0 < m ≤ 0.3 or p - 0.3 ≤ m ≤ p + 0.3 (p is an integer greater than or less than 1 and less than 3). p is 1, 2 or 3, preferably 1 or 2, and more preferably 1.

[0058] like Figure 2 As shown in (b), the optical scale 10 sometimes has different angles of incidence of light depending on its position relative to the light source 21. Figure 3 (a) and Figure 3 (b) are respectively used to explain Figure 2 A schematic cross-sectional view of the optical scales for the angles of incidence of light at P1 and P2 in (b). Figure 3 (a) and Figure 3 As shown in (b), the incident angle θ1 of the light at position P1 is larger than the incident angle θ2 of the light at position P2, which is closer to the light source 21. The incident angle is the angle between the perpendicular line from the surface of the protective layer and the emission direction of the light L1 from the light source.

[0059] As described above, the inventors of this application have discovered that the reflectivity deviation sometimes increases depending on the position of the high-reflectivity region in the optical scale. In this disclosure, m in the above formula (1) is preferably within the range of greater than 0 and less than 0.3, greater than 0.7 and less than 1.3, greater than 1.9 and less than 2.3, or greater than 3.0 and less than 3.3. By keeping m within the above range, it is also possible to reduce the reflectivity deviation caused by the position of the high-reflectivity region as described above.

[0060] As for the material used as the protective layer, there are no particular limitations as long as it is transparent and can protect the high-reflectivity layer. It can be any of the organic or inorganic materials, with organic materials being preferred.

[0061] The reason is that the etching process used to adjust the shape of the optical scale to the specified shape is easy. In addition, although it also depends on the type of high-reflectivity layer, it has excellent adhesion to high-reflectivity layers compared to inorganic materials. Furthermore, the protective layer made of organic materials has excellent anti-fouling properties, so impurities (contaminants) do not easily adhere to the surface, and the adhesion between the protective layer and other layers on the side opposite to the substrate is also good.

[0062] Furthermore, compared to inorganic materials, it can sometimes suppress crack formation and is easy to adjust to the thickness specified above. In addition, it is superior in terms of cost compared to inorganic materials. Furthermore, compared to inorganic materials, the contact angle is higher, thus improving the antifouling function. Specifically, the contact angle of the protective layer with water can be set within the range described later.

[0063] In this disclosure, the protective layer can be a single layer or a multilayer consisting of two or more layers. When the protective layer consists of two layers, from the viewpoint of antifouling, it is preferable to place a protective layer made of organic material on the outermost surface (the side opposite to the substrate) and a protective layer made of inorganic material on the other side.

[0064] The organic material preferably includes a resin. The resin used as the protective layer is not particularly limited as long as it can produce a transparent protective layer; examples include ionizing radiation-curing resins that cure under ionizing radiation such as ultraviolet light or electron beams, and thermosetting resins that cure by heating. Specifically, phenolic varnish resins, polyolefin resins, polyester resins, urethane resins, polyimide resins, acrylic resins, and epoxy resins are preferred. Among phenolic varnish resins, phenolic varnish resins are preferred because they have excellent electrical properties and can suppress adverse conditions caused by electrical charge. Among acrylic resins, trifunctional or higher acrylates such as pentaerythritol tetraacrylate and dipentaerythritol tetraacrylate are preferred because they improve photocurability. Among epoxy resins, epoxy acrylate resins with a fluorene structure are preferred because they improve heat resistance, adhesion, and chemical resistance. Phenolic cardoyl epoxy resins are also preferred as epoxy resins. This is because it imparts excellent transparency, heat resistance, surface hardness, and flatness. In addition to resins, organic materials may also contain polymerization initiators or various additives.

[0065] Inorganic materials include inorganic compounds. Examples of inorganic compounds include oxides, nitrides, nitrides, carbides, and nitrides of metallic or nonmetallic elements such as silicon, aluminum, magnesium, calcium, potassium, tin, sodium, titanium, boron, yttrium, zirconium, cerium, and zinc. Silicon dioxide (SiO2) is particularly preferred. Inorganic compounds can be used alone or in mixtures of the above materials in any proportion.

[0066] The protective layer and the high-reflectivity layer are preferably in direct contact. Furthermore, the refractive index of the protective layer is preferably lower than that of the high-reflectivity layer. The refractive index of the protective layer can be, for example, 1.1 or higher and 3.0 or lower, 1.1 or higher and 1.65 or lower, or 1.5 or higher and 1.65 or lower.

[0067] Furthermore, the refractive index mentioned above refers to the refractive index of light with respect to the peak wavelength of the light source. The refractive index is the value obtained by dividing the speed of light in a vacuum by the speed of light in a substance (more accurately, the phase velocity), and it is an indicator describing the way light travels within a substance. One method for measuring the refractive index is using an ellipsometer. An ellipsometer is an analytical device that measures the changes in the polarization state of incident and reflected light relative to a sample.

[0068] The protective layer preferably has water-repellent properties. Even if water containing substances that cause dirt buildup adheres to the surface of the protective layer, the substances causing dirt buildup can be removed by repelling the water. Therefore, the decrease in reflectivity caused by dirt adhering to highly reflective areas can be suppressed.

[0069] The protective layer in this disclosure has a water contact angle of, for example, 50 degrees or more and 90 degrees or less, preferably 62 degrees or more and 90 degrees or less, and more preferably 73 degrees or more and 90 degrees or less.

[0070] When the water contact angle is within the above-mentioned range, the antifouling performance is improved. On the other hand, when the water contact angle is smaller than the above-mentioned range, the water repellency becomes insufficient, and therefore excellent antifouling performance may not be obtained. On the other hand, when the water contact angle is larger than the above-mentioned range, in the case of using an organic film in a low-reflection layer, defects such as dents may occur during coating, which may become the cause of defects.

[0071] Here, the water contact angle is measured according to the provisions of JIS R3257:1999.

[0072] 2. High reflectivity layer

[0073] The high-reflectivity layer in this disclosure has high reflectivity. Examples of such high-reflectivity layers include a metal substrate and a metal film disposed on one side of the substrate.

[0074] Examples of metal substrates include stainless steel (hereinafter referred to as SUS), aluminum, and copper.

[0075] In this disclosure, a SUS substrate is preferably used. Since SUS contains metallic chromium, directly patterning a low-reflection layer containing a chromium film onto an SUS substrate can easily lead to roughness due to etching, and chromium etching residue is also easily generated. Therefore, the effects of forming a protective layer—namely, suppressing surface roughness of the high-reflection layer caused by etching and suppressing the generation of etching residue—can be obtained more significantly.

[0076] The lower limit for the thickness of such a metal substrate is preferably 0.05 mm or more, and particularly preferably 0.1 mm or more. On the other hand, the upper limit for the thickness of the aforementioned metal substrate is preferably 0.5 mm or less.

[0077] The high-reflectivity layer in this disclosure can be a metal film disposed on one side of a substrate.

[0078] Examples of substrates used in this case include glass and resin. In addition to the above, a metal different from the metal film can also be used as the substrate. Among these, a glass substrate is preferred. This is because glass has a low coefficient of linear expansion, which helps to suppress dimensional changes associated with temperature variations in the operating environment.

[0079] Furthermore, the aforementioned metal film is preferably composed of a metal with high reflectivity. Examples of metals include chromium, silver, aluminum, rhodium, gold, copper, and alloys with these metals as the main component. Among these, a chromium film is preferred. A chromium film is a layer containing chromium.

[0080] The thickness of the metal film can be, for example, 0.05 μm or more and 0.3 μm or less, or 0.1 μm or more and 0.2 μm or less.

[0081] 3. Low-reflectivity layer

[0082] In this disclosure, the low-reflection layer is patterned on the side of the protective layer opposite to the high-reflection layer. As a low-reflection layer, its composition is not particularly limited as long as the reflectivity of light incident on the low-reflection region is less than the reflectivity of light incident on the high-reflection region. For example, the low-reflection layer can be an inorganic film or an organic film.

[0083] In this invention, a three-layer structure is preferably provided, starting from the high-reflectivity layer side, consisting of a chromium film, a chromium oxide film, and a chromium nitride film formed on the chromium film in different orders. With such a low-reflectivity layer, the reflectivity of light incident on the low-reflectivity region can be reduced to 10% or less, preferably 5% or less, and further to 1% or less, at any wavelength within the wavelength range of 380 nm to 1000 nm, particularly 500 nm to 1000 nm. On the other hand, the reflectivity of the aforementioned low-reflectivity region is, for example, 0% or more. Specifically, the reflectivity of the aforementioned low-reflectivity region is, for example, 0% to 10% or less, preferably 0% to 5% or less, more preferably 0% to 1% or less, and particularly more preferably 0% to 0.5% or less.

[0084] It should be noted that the reflectivity of the aforementioned low-reflection region preferably meets the range described above at any angle within the incident angle range of 5° to 70°. Therefore, the difference between the reflectivity of the high-reflection region and the low-reflection region can be increased. Furthermore, if only metallic chromium is prepared, chromium oxide and chromium nitride films can be easily formed using reactive sputtering or the like. Moreover, high-precision patterning can be performed more easily compared to silicon oxide films.

[0085] In this specification, "chromium oxide film and chromium nitride film formed on a metallic chromium film in different orders" means that they can be formed in the order of metallic chromium film, chromium oxide film and chromium nitride film, or in the order of metallic chromium film, chromium nitride film and chromium oxide film.

[0086] For example, Figure 4 The encoder shown in (a) uses a reflective optical scale 10 with a low-reflection layer 3 comprising a chromium film 3c, a chromium nitride film 3b formed on the chromium film 3c, and a chromium oxide film 3a formed on the chromium nitride film 3b. On the other hand, Figure 4 The encoder shown in (b) has a low-reflection layer 3 for a reflective optical scale 10, which has a chromium metal film 3c, a chromium oxide film 3a formed on the chromium metal film 3c, and a chromium nitride film 3b formed on the chromium oxide film 3a.

[0087] The outermost surface of the low-reflection region is preferably the surface of a chromium oxide film or a chromium nitride film, with a particular preference for the surface of a chromium oxide film. This is because it can more effectively reduce the reflectivity in the low-reflection region.

[0088] Hereinafter, the "low-reflection layer with a chromium metal film, a chromium nitride film, and a chromium oxide film arranged in sequence" will be referred to as the first specification of low-reflection layer, and the "low-reflection layer with a chromium metal film, a chromium oxide film, and a chromium nitride film arranged in sequence" will be referred to as the second specification of low-reflection layer.

[0089] (i) First-grade low-reflectivity layer

[0090] The low-reflection layer of this specification comprises, sequentially from the substrate side, a chromium metal film, a chromium nitride film, and a chromium oxide film. The low-reflection region of this low-reflection layer can reduce the reflectance of any wavelength within the range of 380 nm to 1000 nm, particularly 500 nm to 1000 nm, irradiated by a light source, to 5% or less, particularly 0.5% or less. Furthermore, the reflectance change with wavelength is relatively gradual, making reflectance control easier. Specifically, the reflectance can be reduced to 0% or less and 5% or less, particularly to 0% or less and 0.5% or less. The following provides a detailed description of each layer.

[0091] (a) Chromium film

[0092] In this specification, a metallic chromium film is disposed on the protective layer. The metallic chromium film is a layer containing metallic chromium. The metallic chromium film is a layer that substantially prevents light from passing through when irradiated by a light source, and its transmittance is preferably 1.0% or less. The transmittance can be measured using a spectrophotometer (MPC-3100) manufactured by Shimadzu Corporation. The film thickness is, for example, 40 nm or more, preferably 70 nm or more. Specifically, the film thickness is, for example, 40 nm or more and 500 nm or less, preferably 70 nm or more and 200 nm or less.

[0093] Here, the "thickness" of each component refers to the thickness obtained through general measurement methods. Examples of thickness measurement methods include stylus-based methods that calculate thickness by tracing and detecting unevenness on a surface with a stylus, and optical methods that calculate thickness based on spectroscopic reflectance spectra. Specifically, the thickness can be measured using a stylus-type film thickness gauge P-15 manufactured by KLA-Tencor Co., Ltd. It should be noted that the thickness can be the average of thickness measurements taken at multiple locations on the component in question.

[0094] Methods for forming metallic chromium films include physical vapor deposition (PVD), such as sputtering, ion plating, and vacuum evaporation.

[0095] (b) Chromium nitride film

[0096] In this specification, the chromium nitride film is positioned between the metallic chromium film and the chromium oxide film. Unlike chromium oxynitride and chromium oxynitrogen carbide, the main components of the chromium nitride film are chromium and nitrogen, and it does not contain any impurities other than chromium and nitrogen.

[0097] The value of x, which represents the atomic ratio of Cr to N in a chromium nitride (CrNx) film, is preferably 0.4 or more and 1.1 or less.

[0098] Furthermore, regarding the chromium nitride film, the overall purity of the film is set to 100 atomic%, with the ratio of chromium to nitrogen ranging from 80% to 100%, and preferably ranging from 90% to 100%. Impurities may include, for example, hydrogen, oxygen, and carbon.

[0099] The film thickness (T) of chromium nitride film N The preferred thickness is in the range of 5 nm to 100 nm, and particularly preferred is in the range of 10 nm to 80 nm. Furthermore, the film thickness (T) of the chromium oxide film described later... O In the relationship between T and ), at a wavelength of 850nm, N With T O The total wavelength is preferably 40nm or higher, and when the wavelength is 550nm, T N With T OThe total thickness is preferably 20 nm or more. If this film thickness range is within such a range, compared to cases outside this range, the reflectivity in the low-reflectivity region can be easily reduced to 10% or less, particularly 5% or less. Specifically, the reflectivity can be reduced to 0% or more and 10% or less, particularly to 0% or more and 5% or less. Furthermore, the film thickness (T) of the chromium nitride film... N It is easy to reduce the reflectivity of the entire violet to infrared (380nm to 1000nm) region, especially the green to infrared (500nm to 1000nm) region. Therefore, it is preferable to be in the range of 10nm to 80nm.

[0100] Methods for forming chromium nitride include physical vapor deposition (PVD) such as reactive sputtering, ion plating, and vacuum evaporation. In reactive sputtering, nitrogen is introduced into argon (Ar) gas, and a chromium nitride film is formed using a Cr target. The composition of the chromium nitride film can be controlled by adjusting the ratio of Ar to nitrogen.

[0101] (c) Chromium oxide film

[0102] Chromium oxide film is formed on chromium nitride film. Its main components are chromium and oxygen. Unlike chromium oxynitride and chromium oxynitrocarbonide, it does not contain impurities other than chromium and oxygen.

[0103] The value of y, which represents the atomic ratio of Cr to O in a chromium oxide (CrOy) film, is preferably 1.4 or more and 2.1 or less.

[0104] Specifically, for chromium oxide films, the overall purity is set to 100 atomic percent, with the ratio of chromium to oxygen ranging from 80% to 100%, and a purity range of 90% to 100% being preferred. Impurities may also include hydrogen, nitrogen, carbon, etc.

[0105] The thickness of the chromium oxide film is not particularly limited, but is preferably in the range of 5 nm to 100 nm, and particularly preferably in the range of 10 nm to 80 nm. Furthermore, the film thickness (T) of the chromium oxide film... O ) and the film thickness (T) of chromium nitride film N The total film thickness is preferably within the range described in "(i) the low-reflection layer of the first specification (b) the chromium nitride film". Furthermore, regarding the film thickness (T) of the chromium oxide film... O To easily reduce reflectivity across the entire violet-infrared region (380nm to approximately 1000nm), and especially in the green-infrared region (500nm to approximately 1000nm), a range of 10nm to 65nm is preferred.

[0106] Methods for forming chromium oxide include physical vapor deposition (PVD) such as reactive sputtering, ion plating, and vacuum evaporation. In reactive sputtering, oxygen is introduced into argon (Ar) gas, and a chromium oxide film is formed using a Cr target. The composition of the chromium oxide film can be controlled by adjusting the ratio of Ar to oxygen.

[0107] (ii) Second-grade low-reflection layer

[0108] The low-reflection layer of this specification comprises, sequentially from the protective layer side, a chromium metal film, a chromium oxide film, and a chromium nitride film. The low-reflection region of this specification's low-reflection layer can reduce the reflectance of light irradiated from a light source to 5% or less, and particularly to 1% or less, at any wavelength within the range of 380 nm to 1000 nm, especially 500 nm to 1000 nm. Specifically, it can reduce the reflectance to 0% or less and 5% or less, and particularly to 0% or less and 1% or less. Each layer will be described in detail below.

[0109] (a) Chromium film

[0110] In this specification, the metallic chromium film is formed on the substrate. The details of the metallic chromium film are the same as those in "(i) Low-reflection layer (a) metallic chromium film of the first specification" above, so the description is omitted here.

[0111] (b) Chromium oxide film

[0112] In this specification, the chromium oxide film is disposed between the metallic chromium film and the chromium nitride film. The film thickness is not particularly limited, but is preferably in the range of 5 nm to 60 nm, and particularly preferably in the range of 10 nm to 50 nm. Furthermore, it is preferable to satisfy the relationship with the film thickness of the chromium nitride film described later. This is because it is possible to more reliably reduce the reflectance at any wavelength within the wavelength range of 380 nm to 1000 nm, particularly 500 nm to 1000 nm, to 10% or less, particularly 5% or less. Specifically, the reflectance can be reduced to 0% or less and 10% or less, particularly to 0% or less and 5% or less.

[0113] Furthermore, regarding the film thickness (T) of the chromium oxide film... O This can easily reduce the reflectivity of the entire violet to infrared region (above 380nm and below approximately 1000nm), especially the green to infrared region (above 500nm and below approximately 1000nm). Therefore, a range of 5nm to 35nm is preferred.

[0114] The other physical properties, composition and formation methods of the chromium oxide film are the same as those in “(i) Low reflectance layer of first specification (c) Chromium oxide film” above, so the description is omitted here.

[0115] (c) Chromium nitride film

[0116] The chromium nitride film of this specification is formed on a chromium oxide film. The film thickness of the chromium nitride film of this specification is not particularly limited, but is preferably in the range of 5 nm to 100 nm, and particularly preferably in the range of 10 nm to 80 nm. Furthermore, regarding the film thickness (T) of the chromium oxide film... O In the relationship between T and ), at a wavelength of 850nm, N With T O The total wavelength is preferably 30nm or more, and when the wavelength is 550nm, T N With T O The total thickness is preferably 15 nm or more. Furthermore, regarding the film thickness (T) of the chromium nitride film in this specification... N This can easily reduce the reflectivity of the entire violet to infrared region (380nm to about 1000nm), especially the entire green to infrared region (500nm to about 1000nm). Therefore, it is preferable to use a range of 10nm to 60nm.

[0117] The method for forming the low-reflection layer disclosed herein is not particularly limited and can be fabricated by selective etching or lift-off. Specifically, a chromium film is formed on a protective layer disposed on a high-reflection layer, for example by sputtering, followed by the formation of a chromium nitride film and a chromium oxide film. Then, the chromium film, chromium nitride film, and chromium oxide film are patterned by photolithography and etching, thereby fabricating a patterned low-reflection layer. Examples of etching include dry etching based on plasma etching, which involves plasma-injecting a reactive gas containing chlorine and oxygen using a high-frequency electric field, or wet etching based on a cerium ammonium nitrate solution.

[0118] Alternatively, as another method, a resist pattern is formed on the protective layer, and a metallic chromium film, a chromium nitride film, and a chromium oxide film are formed using a known vacuum film-forming method such as sputtering. Then, it can also be formed by removing the resist pattern, thereby peeling off the metallic chromium film, chromium nitride film, and chromium oxide film formed directly above the resist pattern, thereby obtaining the pattern of the chromium nitride film and the chromium oxide film.

[0119] 4. Low-reflection areas

[0120] Regarding the low-reflection region of this disclosure, the reflectance at any wavelength within the range of 380 nm to 1000 nm, particularly 500 nm to 1000 nm, is, for example, less than 10%, less than 5%, less than 2%, less than 1.5%, or less than 1%. Specifically, the aforementioned reflectance of the low-reflection region in this disclosure is, for example, more than 0% to less than 10%, more than 0% to less than 5%, more than 0% to less than 2%, more than 0% to less than 1.5%, or more than 0% to less than 1%. It should be noted that the reflectance of the low-reflection region preferably meets the above range at any angle within the range of 0° to 70°. The outermost surface of the low-reflection region is preferably the surface of the chromium oxide film or chromium nitride film of the low-reflection layer, and particularly preferably the surface of the chromium oxide film. This is because the reflectance in the low-reflection region can be reduced more effectively.

[0121] 5. High reflectivity areas

[0122] The high-reflectivity region in this disclosure is the area where the aforementioned protective layer is exposed, and the reflectivity of light incident from the low-reflectivity layer side of the encoder reflective optical scale is higher than that of the low-reflectivity region.

[0123] Regarding the highly reflective region, when the incident light is any wavelength within the range of 380 nm to 1000 nm, particularly within the range of 500 nm to 1000 nm, the reflectivity is preferably 50% or more, and more preferably 60% or more, within the range of incident angle of 0° to 70°. Specifically, the reflectivity of the aforementioned highly reflective region in this disclosure is, for example, 50% or more and 100% or less, preferably 60% or more and 100% or less.

[0124] 6. S / N ratio

[0125] As described above, the encoder using a reflective optical scale in this disclosure can improve the reflectivity of high-reflectivity areas, and thus improve the S / N ratio expressed by the following formula.

[0126] S / N ratio = Reflectance of high-reflection area / Reflectance of low-reflection area

[0127] It should be noted that the reflectivity of the high-reflectivity region and the reflectivity of the low-reflectivity region in the above formula represent the reflectivity under the same wavelength and the same incident angle.

[0128] In this disclosure, the S / N ratio can be 30 or more, wherein it can be 35 or more, preferably 40 or more, and particularly preferably 60 or more.

[0129] 7. Optical scale

[0130] The optical scale in this disclosure can be used for both rotary encoders and linear encoders. It is preferred for rotary encoders. The top view shape of the optical scale is not limited; for example, for rotary encoders, the shape can be approximately annular or circular, and for linear encoders, the shape can be approximately rectangular.

[0131] The manufacturing method of the optical scale in this disclosure includes, for example, a step of preparing the aforementioned high-reflectivity layer; a step of forming the aforementioned protective layer on the high-reflectivity layer; and a step of forming a low-reflectivity layer in a pattern on the side of the protective layer opposite to the side of the high-reflectivity layer.

[0132] A-2. Other methods of using reflective optical scales in encoders

[0133] This disclosure also includes other methods that differ from the method of using a reflective optical scale for an encoder described in “A-1. Reflective Optical Scale for Encoder” above.

[0134] 1. First other method

[0135] The first other aspect of this disclosure is a reflective optical scale for an encoder, wherein a high-reflectivity layer, a protective layer containing organic material, and a low-reflectivity layer arranged in a pattern are sequentially provided in the thickness direction. It has: a low-reflectivity region, which is a region where the high-reflectivity layer, the protective layer, and the low-reflectivity layer are provided; and a high-reflectivity region, which is a region where the high-reflectivity layer and the protective layer are provided. The film thickness of the protective layer is 0.16 μm or more and 1.0 μm or less, and the reflectivity of the high-reflectivity region is 40% or more when the wavelength of the measuring light source is set to 850 μm.

[0136] In this method, since the thickness of the protective layer is within the range described above, high reflectivity can be maintained even when the high reflectivity layer is provided with the protective layer containing organic materials.

[0137] In this embodiment, the protective layer comprises an organic material. The organic material described above is the same as that described in "A-1. Reflective Optical Scale for Encoders," therefore, the description is omitted here.

[0138] In addition, in this method, the thickness of the protective layer is 0.16 μm or more and 1.0 μm or less.

[0139] In this method, the lower limit of the film thickness of the protective layer is not particularly limited as long as it is 0.16 μm or more, preferably 0.18 μm or more, and more preferably 0.20 μm or more. In addition, the upper limit of the film thickness of the protective layer is not particularly limited as long as it is 1.0 μm or less, preferably 0.6 μm or less, and more preferably 0.33 μm or less.

[0140] In this method, when the wavelength of the measuring light source is set to 850 μm, the reflectivity in the aforementioned high-reflectivity region is 40% or more, preferably 45% or more, and particularly more preferably 50% or more.

[0141] Except for the aspects related to the material of the protective layer, the thickness of the protective layer, and the reflectivity of the high-reflectivity region when the wavelength of the measuring light source is set to 850 μm, the content described in the above-mentioned item "A-1. Reflective optical scale for encoder" is the same, so the description here is omitted.

[0142] 2. Other methods

[0143] The second alternative aspect of this disclosure is a reflective optical scale for an encoder, wherein a high-reflectivity layer, a protective layer containing organic material, and a low-reflectivity layer arranged in a pattern are sequentially provided in the thickness direction. It has: a low-reflectivity region, which is a region provided with the high-reflectivity layer, the protective layer, and the low-reflectivity layer; and a high-reflectivity region, which is a region provided with the high-reflectivity layer and the protective layer. The reflectivity of the low-reflectivity region is 2% or less when the wavelength of the measuring light source is set to 850 μm, and the S / N ratio expressed by the following formula is 30 or more.

[0144] S / N ratio = Reflectance of high-reflection area / Reflectance of low-reflection area

[0145] In this method, the S / N ratio is above 30, meaning there is a large difference in reflectivity between the high-reflectivity and low-reflectivity regions, thus preventing false detections by the photodetector. As a result, for reflective optical encoders, the optical scale is easy to read, exhibiting excellent encoder characteristics.

[0146] In this embodiment, the protective layer comprises an organic material. The organic material described above is the same as that described in "A-1. Reflective Optical Scale for Encoders," therefore, the description is omitted here.

[0147] In this method, the S / N ratio is 30 or more, more preferably 35 or more, more preferably 40 or more, and particularly preferably 60 or more.

[0148] In this method, there is no particular limitation as long as the reflectivity in the low-reflection region is 2% or less when the wavelength of the measuring light source is set to 850 μm, preferably 1% or less, and particularly preferably 0.5% or less.

[0149] Except for the aspects related to the material of the protective layer, the S / N ratio, and the reflectivity in the low-reflection region when the wavelength of the measuring light source is set to 850 μm, the content described in the above-mentioned item "A-1. Reflective optical scale for encoder" is the same, so the description here is omitted.

[0150] B. Reflective optical encoder

[0151] This disclosure provides a reflective optical encoder, characterized by comprising: a reflective optical scale for an encoder; a light source that illuminates measuring light onto a surface of the reflective optical scale for an encoder on the side where the low-reflection layer is disposed; and a photodetector that detects reflected light from the reflective optical scale for an encoder. Figure 2 (a) is a schematic perspective view showing an example of a reflective optical encoder of this disclosure. Regarding Figure 2 (a) has been described in “A. Reflective Optical Scale for Encoder” above, and therefore the description is omitted here. The encoder of this disclosure has the aforementioned reflective optical scale for encoder, thus the difference between the reflectivity in high-reflectivity areas and low-reflectivity areas is large, thereby preventing false detections by the photodetector 22. As a result, for the reflective optical encoder 100, the optical scale 10 is easy to read, exhibiting excellent encoder characteristics.

[0152] 1. Encoder uses a reflective optical scale.

[0153] As a reflective optical scale for encoders, it is the same as described in "A. Reflective optical scale for encoders" above, so the description here is omitted.

[0154] 2. Light source

[0155] The light source can be, for example, an LED (light-emitting diode) or a laser. The wavelength λ of the light L1 emitted from the light source can be, for example, in the violet to infrared region (around 380 to 1000 nm) or in the green to infrared region (around 500 nm to 1000 nm). The angle of incidence of the light relative to the optical scale 10 is, for example, between 0° and 70°.

[0156] The wavelength λ of the light L1 from the light source used in this disclosure is the same as the wavelength λ of the light used in the above-mentioned "A. Reflective Optical Scale for Encoder" to determine the film thickness of the protective layer.

[0157] 3. Photodetector

[0158] A photodetector detects the light reflected by an optical scale. A photodetector may include, for example, a light-receiving element (e.g., a photoelectric conversion element) such as a photodiode or a camera element.

[0159] 4. Other

[0160] The reflective optical encoder disclosed herein can also include a fixed gap between the photodetector and the reflective optical scale for the encoder. By setting the fixed gap, the variation in the amount of light received by the photodetector increases, thereby improving detection sensitivity. The fixed gap can also be set between the light source and the reflective optical scale for the encoder.

[0161] C-1. Encoder with reflective optical scale using a laminated body

[0162] Figure 9 This is a schematic cross-sectional view of the reflective optical scale laminate for encoders in this disclosure. Figure 9 The encoder reflective optical scale laminate 50 shown is used to manufacture the encoder reflective optical scale described above. It has a high reflective layer 1, a protective layer 2 and a low reflective layer forming layer 30 in sequence in the thickness direction D. When the thickness of the protective layer is set to d (μm) and the incident angle of the incident light to the protective layer is set to θ (°), the following equation (1) is satisfied.

[0163] d=mλ / [2n×cos{Arcsin(sinθ / n)}] (1)

[0164] (In the formula, n is the refractive index of the protective layer, λ is the wavelength (μm) of the incident light, and m is a number that satisfies 0 < m ≤ 0.3 or p - 0.3 ≤ m ≤ p + 0.3 (p is an integer greater than 1 and less than 3).)

[0165] The thickness of the protective layer of the laminated body for such an encoder reflective optical scale is within the range specified above. Therefore, by patterning the layer for forming the low-reflectivity layer, it is possible to manufacture the aforementioned encoder reflective optical scale that can improve the reflectivity of light incident on the high-reflectivity region. Furthermore, by making m within the range of greater than 0 and less than 0.3, greater than 0.7 and less than 1.3, greater than 1.9 and less than 2.3, or greater than 3.0 and less than 3.3, it is also possible to reduce the reflectivity deviation caused by the position of the high-reflectivity region as described above.

[0166] 1. High reflectivity layer and protective layer

[0167] The high-reflectivity layer and protective layer in this disclosure are the same as those described in "A. Reflective optical scale for encoder" above, so the description here is omitted.

[0168] 2. Layer for forming low-reflection layer

[0169] The low-reflection layer forming layer in this disclosure is a layer prior to the patterning process for forming the aforementioned patterned low-reflection layer, and is preferably disposed on the entire surface of the protective layer opposite to the high-reflection layer side. The layer structure of the low-reflection layer forming layer is the same as that of the aforementioned patterned low-reflection layer, therefore its description is omitted here.

[0170] C-2. Encoders using reflective optical scales and other methods using laminated structures.

[0171] This invention also includes other methods that differ from the reflective optical scale laminate for encoders described in “C-1. Laminate for Reflective Optical Scale for Encoder” above.

[0172] The encoder reflective optical scale laminate in this method is used to manufacture the encoder reflective optical scale. It has a high reflective layer and a protective layer in sequence in the thickness direction. When the thickness of the protective layer is set to d (μm) and the incident angle of the incident light to the protective layer is set to θ (°), the following formula (1) is satisfied.

[0173] d=mλ / [2n×cos{Arcsin(sinθ / n)}] (1)

[0174] (In the formula, n is the refractive index of the protective layer, λ is the wavelength (μm) of the incident light, and m is a number that satisfies 0 < m ≤ 0.3 or p - 0.3 ≤ m ≤ p + 0.3 (p is an integer greater than 1 and less than 3).)

[0175] The encoder reflective optical scale laminate of this method is the same as the above-mentioned "C-1. Encoder reflective optical scale laminate" except for the point about the low-reflection layer formation layer, so the description here is omitted.

[0176] It should be noted that this disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and structures having substantially the same structure and function as the technical concept described in the claims of this disclosure are included within the technical scope of this disclosure.

[0177] Example

[0178] The following examples, Experimental Example A, Experimental Example B, Examples, and Comparative Examples, further illustrate this disclosure.

[0179] (Experimental Example A and Experimental Example B)

[0180] For a laminate containing a metallic chromium layer (refractive index 3.2) as a high-reflectivity layer and an organic protective layer (refractive index n = 1.58) with a film thickness d (μm) on the high-reflectivity layer as a protective layer, the reflectivity (R0, R1, R2, R3) when light with wavelength λ = 850 nm is incident from the protective layer side at incident angles θ (θ = 0°, 20°, 40°, and 55°) is calculated by simulation. 20 R 40 R 55 ).

[0181] At this point, the thickness d of the protective layer is set to the value of m that is changed by setting the incident angle θ = 0° in the following formula (1).

[0182] d=mλ / [2n×cos{Arcsin(sinθ / n)}] (1)

[0183] In addition, calculate R0 and R 20 R 40 R 55 The average value (average reflectance R) ave And the difference between the maximum and minimum reflectivity (reflectivity difference ΔR). Then, calculate R0, R... 20 R 40 and R 55 The standard reflectance (R′0, R′) obtained by dividing the simulated reflectance at θ=0° without a protective layer (65.3%) is... 20 、R′ 40 and R′ 55 ), and the average standard reflectance (average standard reflectance R′) ave The difference between the maximum and minimum standard reflectance (standard reflectance difference ΔR′) is also shown. It should be noted that the simulated reflectance (65.3%) at θ=0° without the aforementioned protective layer is the reflectance of an ideal high-reflectance layer without any etching residue on its surface. The results are shown in Tables 1 to 3. Furthermore, the film thickness d (μm) of the protective layer and the average reflectance R′ are also shown. ave The curve illustrating the relationship (%) is shown in the figure. Figure 5 The film thickness d (μm) of the protective layer is shown in relation to the average standard reflectance R′. ave The curve illustrating the relationship (%) is shown in the figure. Figure 6 .

[0184] [Table 1]

[0185]

[0186] [Table 2]

[0187]

[0188] [Table 3]

[0189]

[0190] As shown in Tables 1 to 3, when the film thickness d of the protective layer satisfies the above condition (1) (Experimental Example A), the average standard reflectance R′ ave The reflectance was above 72%, confirming that the decrease in reflectance was suppressed. Furthermore, compared to Experimental Example B2 (m = 1.4), Experimental Examples A1–9 (0.7 ≤ m ≤ 1.3) showed a smaller standard reflectance difference ΔR′, confirming that the deviation in reflectance of light incident on the high reflectance region was suppressed. Similarly, Experimental Examples A12–16 (1.9 ≤ m ≤ 2.3) showed a smaller standard reflectance difference ΔR′ compared to Experimental Examples B4 (m = 2.4), B5 (m = 2.5), A10 (m = 1.7), and A11 (m = 1.8). Experimental Examples A18–20 (3.0 ≤ m ≤ 3.3) showed a smaller standard reflectance difference ΔR′ compared to Experimental Example A17 (m = 2.9).

[0191] (Example)

[0192] First, a SUS substrate (400 μm thick) with a mirror finish was prepared as a high-reflectivity layer. Next, a protective layer forming composition containing cardoyl epoxy resin was coated onto the mirror-finished surface of the SUS substrate and cured to form a protective layer with a thickness of 0.27 μm and a refractive index of 1.58. Then, a low-reflectivity layer was formed in a pattern, consisting of a chromium layer, a chromium nitride layer, and a chromium oxide layer sequentially from the protective layer side. This yielded an evaluation scale.

[0193] The surface roughness, gloss (60° gloss value), and reflectance of the high-reflectivity area obtained by the evaluation scale were measured using the following method. Additionally, the average value and range of reflectance were calculated. The results are shown in Table 4. It should be noted that the protective layer thickness (0.27 μm) is the value of m = 1.0 under the conditions set in (1) above, where the incident angle θ = 0° and the wavelength of the incident light = 0.85 μm.

[0194] [Reflectivity]

[0195] Reflectivity was measured using a Shimadzu SolidSpec-3700 spectrophotometer. The measurement wavelength was set to 850 nm, the wavelength to be (p-polarized light + s-polarized light) / 2, and the angle of incidence (the angle between the perpendicular line from the surface of the evaluation component to the direction of the incident light) was set to 5°–70°. The size of the illumination beam was approximately 6 mm × 15 mm.

[0196] Surface roughness

[0197] According to JIS B 0601-1994, the arithmetic mean roughness Ra, maximum height Ry, and ten-point mean roughness Rz were measured.

[0198] [Gloss]

[0199] The 60° specular gloss was measured using a HANDY GLOSSMETER PG-II (NIPPON DENSHOKU) according to JIS Z8741.

[0200] [Angle of contact with water]

[0201] The determination was carried out in accordance with the provisions of JIS R3257:1999.

[0202] The contact angle is 31° in the case of mirror SUS without a protective layer (Comparative Example 2 in Table 4). When an inorganic material protective layer is formed on mirror SUS, the contact angle is 62°. When an organic material protective layer is formed on mirror SUS, the contact angle is 73° (Example 1 in Table 4) and 75° (Comparative Example 1 in Table 4), and the average contact angle for a specified thickness (0.16 μm to 1.0 μm) is 74.3°.

[0203] (Comparative Example 1)

[0204] Except that the thickness of the protective layer was 1.0 μm, an evaluation scale was manufactured using the same method as in Example 1, and the surface roughness, gloss, and reflectivity of the high-reflectivity area were measured. The results are shown in Table 4.

[0205] The thickness of the protective layer (1.0 μm) is the value of m = 3.7 when the incident angle θ = 0° and the wavelength of the incident light = 0.85 μm are set in (1) above.

[0206] (Comparative Example 2)

[0207] As a high-reflectivity layer, a SUS substrate (400 μm thick) with a mirror finish was prepared. Next, a chromium film was formed without a protective layer. Then, the substrate was etched with acid for 6 minutes, and the effect of etching on the surface roughness of the high-reflectivity layer was investigated. The surface roughness, gloss, and reflectivity of the high-reflectivity layer after etching were measured. The results are shown in Table 4.

[0208] (Refer to Examples 1 to 4)

[0209] For the high-reflectivity layer (SUS substrate with mirror finish), acid etching was performed at the times shown in Table 4, and the surface roughness, gloss, and reflectivity of the high-reflectivity layer after etching were measured. The results are shown in Table 4.

[0210] [Table 4]

[0211]

[0212] Based on the results in Table 4, it was confirmed that Example 1 achieved a higher reflectivity than Comparative Example 1 and Comparative Example 2. In Comparative Example 2, chromium residue was observed after etching of the chromium film, and it is speculated that the reduced reflectivity was due to the influence of this etching residue. It should be noted that the residue did not disappear even with extended etching time.

[0213] It should be noted that in the above reflectivity measurement, the size of the irradiated beam was relatively large, approximately 6 mm × 15 mm. However, the size of the light-receiving part (high reflectivity area) of an actual encoder is, for example, less than 100 μm, and typically as small as about 50 μm. In cases where the surface roughness of the high reflectivity layer is rough, as in Comparative Example 2, it is assumed that the smaller the beam size, the worse the reflectivity. Therefore, it is speculated that the reflectivity increase effect brought about by this disclosure is actually more significant.

[0214] [Angle-dependent evaluation of reflectivity]

[0215] For the high-reflectivity region of the evaluation scale used in the above embodiments, Comparative Example 1, Comparative Example 2, and Reference Example 1, the wavelength of the measurement light was varied from 400 nm to 900 nm, and the incident angle was varied from 5° to 70°, and the reflectivity was measured. The results are shown in Figure 7(a) (Example). Figure 7 (b) (Refer to Example 1) Figure 8 (a) (Comparative Example 1) Figure 8 (b) (Comparative Example 2).

[0216] like Figure 7 As shown in (a), the high-reflectivity areas in the evaluation scale of the embodiment exhibit the same degree of reflectivity and incident angle dependence as Reference Example 1 (mirror-finished SUS substrate). Figure 8 As shown in (a), it is confirmed that without controlling the thickness of the protective layer, the incident angle dependence of reflectivity increases due to thin-film interference. Figure 8 As shown in (b), the reflectivity of the high-reflectivity region is reduced without a protective layer. It is speculated that this is because the surface roughness of the high-reflectivity layer after etching is large.

[0217] That is, the following invention can be provided in this disclosure.

[0218] [1] A reflective optical scale for an encoder, wherein a high-reflection layer, a protective layer, and a low-reflection layer arranged in a pattern are sequentially provided in the thickness direction, and the reflective optical scale for an encoder has a low-reflection region as the area where the low-reflection layer is provided and a high-reflection region as the area where the protective layer is exposed.

[0219] When the thickness of the protective layer is set to d (μm) and the incident angle of the incident light on the protective layer is set to θ (°), the following equation (1) is satisfied.

[0220] d=mλ / [2n×cos{Arcsin(sinθ / n)}] (1)

[0221] (In the formula, n is the refractive index of the protective layer, λ is the wavelength of the incident light (μm), and m is a number that satisfies 0 < m ≤ 0.3 or p - 0.3 ≤ m ≤ p + 0.3 (p is an integer greater than 1 and less than 3).)

[0222] [2] The reflective optical scale for encoders as described in [1], wherein m is in the range of greater than 0 and less than 0.3, greater than 0.7 and less than 1.3, greater than 1.9 and less than 2.3, or greater than 3.0 and less than 3.3.

[0223] [3] A reflective optical scale for an encoder as described in [1] or [2], wherein the protective layer comprises an organic material.

[0224] [4] An encoder reflective optical scale as described in any one of [1] to [3], wherein the high reflective layer is a metal substrate.

[0225] [5] A reflective optical scale for an encoder as described in any one of [1] to [4], wherein the low-reflection layer has a chromium film, a chromium oxide film and a chromium nitride film arranged in different orders from the protective layer side.

[0226] [6]. A reflective optical encoder, characterized in that it comprises: a reflective optical scale for an encoder as described in any one of claims [1] to [5]; a light source that illuminates the measuring light onto a surface of the reflective optical scale for an encoder on the side where the low-reflection layer is disposed; and a photodetector that detects the reflected light from the reflective optical scale for an encoder.

[0227] [7]. A laminate for a reflective optical scale for an encoder, which is used to manufacture a reflective optical scale for an encoder as described in any one of [1] to [5], wherein the laminate has a high-reflection layer, a protective layer and a low-reflection layer forming layer in sequence in the thickness direction.

[0228] When the thickness of the protective layer is set to d (μm) and the incident angle of the incident light on the protective layer is set to θ (°), the following equation (1) is satisfied.

[0229] d=mλ / [2n×cos{Arcsin(sinθ / n)}] (1)

[0230] (In the formula, n is the refractive index of the protective layer, λ is the wavelength (μm) of the incident light, and m is a number that satisfies 0 < m ≤ 0.3 or p - 0.3 ≤ m ≤ p + 0.3 (p is an integer greater than 1 and less than 3).)

[0231] [8] A reflective optical scale for an encoder, wherein a high-reflection layer, a protective layer containing an organic material, and a low-reflection layer arranged in a pattern are sequentially provided in the thickness direction, and the scale has: a low-reflection region, which is a region provided with the high-reflection layer, the protective layer, and the low-reflection layer; and a high-reflection region, which is a region provided with the high-reflection layer and the protective layer, wherein the film thickness of the protective layer is 0.16 μm or more and 1.0 μm or less, and the reflectivity of the high-reflection region is 40% or more when the wavelength of the measuring light source is set to 850 μm.

[0232] [9] A reflective optical scale for an encoder, wherein a high-reflection layer, a protective layer containing an organic material, and a low-reflection layer arranged in a pattern are sequentially provided in the thickness direction, and the scale has: a low-reflection region, which is a region provided with the high-reflection layer, the protective layer, and the low-reflection layer; and a high-reflection region, which is a region provided with the high-reflection layer and the protective layer, wherein the reflectivity of the low-reflection region is 2% or less when the wavelength of the measuring light source is set to 850 μm, and the S / N ratio expressed by the following formula is 30 or more.

[0233] S / N ratio = Reflectivity of high-reflectivity area / Reflectivity of low-reflectivity area.

[0234]

[10] As described in [9], the encoder uses a reflective optical scale, wherein,

[0235] The thickness of the aforementioned protective layer is 0.16 μm or more and 1.0 μm or less.

[0236] When the wavelength of the light source is set to 850 μm, the reflectivity in the aforementioned high-reflectivity region is above 40%.

[0237]

[11] A reflective optical scale for an encoder as described in any one of [1] to [5] or any one of [8] to

[10] , wherein the contact angle of the protective layer with water is 50° or more and 90° or less.

[0238]

[12] . A laminate for a reflective optical scale for an encoder, which is a laminate for a reflective optical scale for an encoder used in manufacturing any one of [1] to [5] or any one of [8] to

[11] , wherein,

[0239] The laminate has a high-reflectivity layer and a protective layer sequentially in the thickness direction.

[0240] When the thickness of the protective layer is set to d (μm) and the incident angle of the incident light on the protective layer is set to θ (°), the following equation (1) is satisfied.

[0241] d=mλ / [2n×cos{Arcsin(sinθ / n)}] (1)

[0242] (In the formula, n is the refractive index of the protective layer, λ is the wavelength (μm) of the incident light, and m is a number that satisfies 0 < m ≤ 0.3 or p - 0.3 ≤ m ≤ p + 0.3 (p is an integer greater than 1 and less than 3).)

[0243] Explanation of reference numerals in the attached figures

[0244] 1…High reflectivity layer

[0245] 2…protective layer

[0246] 3…Low-reflection layer

[0247] 3a…chromium oxide film

[0248] 3b…Chromium nitride film

[0249] 3C… Metallic chromium film

[0250] 10…Reflective optical scale for encoders

[0251] 50…Laminated body for reflective optical scales for encoders

[0252] 100…Reflective optical encoder

Claims

1. A reflective optical encoder, characterized in that, have: The encoder uses a reflective optical scale; A light source illuminates the surface of the encoder's reflective optical scale, on the side where a low-reflection layer is configured, with measuring light; and A photodetector detects reflected light from the reflective optical scale of the encoder. The encoder uses a reflective optical scale that has, in the thickness direction, a high-reflectivity layer, a protective layer, and a low-reflectivity layer arranged in a pattern. The encoder uses a reflective optical scale that has a low-reflection area, which is the region where the low-reflection layer is disposed, and a high-reflection area, which is the region where the protective layer is exposed. When the thickness of the protective layer is set as d in μm and the incident angle of the incident light on the protective layer is set as θ in °, the following equation (1) is satisfied. The protective layer comprises organic materials and has a water contact angle of 73° or greater and 90° or less. The high-reflectivity layer is a stainless steel substrate. d=mλ / [2n×cos{Arcsin(sinθ / n)}] (1) In the formula, n is the refractive index of the protective layer, λ is the wavelength of the incident light in μm, m is a number that satisfies 0 < m ≤ 0.3 or p - 0.3 ≤ m ≤ p + 0.3, and p is an integer greater than 1 and less than 3.

2. The reflective optical encoder as described in claim 1, wherein, The value of m is within the range of greater than 0 and less than 0.3, greater than 0.7 and less than 1.3, greater than 1.9 and less than 2.3, or greater than 3.0 and less than 3.

3.

3. The reflective optical encoder as described in claim 1, wherein, The low-reflection layer has a metallic chromium film, and chromium oxide film and chromium nitride film arranged in different orders from the protective layer side.

4. A laminated body for a reflective optical scale for an encoder, which is used to manufacture a reflective optical scale for an encoder as described in any one of claims 1 to 3, wherein, The laminate has, in the thickness direction, a high-reflectivity layer, a protective layer, and a low-reflectivity layer forming layer, in sequence. When the thickness of the protective layer is set as d in μm and the incident angle of the incident light on the protective layer is set as θ in °, the following equation (1) is satisfied. d=mλ / [2n×cos{Arcsin(sinθ / n)}] (1) In the formula, n is the refractive index of the protective layer, λ is the wavelength of the incident light in μm, m is a number that satisfies 0 < m ≤ 0.3 or p - 0.3 ≤ m ≤ p + 0.3, and p is an integer greater than 1 and less than 3.

5. A reflective optical encoder, characterized in that, have: The encoder uses a reflective optical scale; A light source illuminates the surface of the encoder's reflective optical scale, on the side where a low-reflection layer is configured, with measuring light; and A photodetector detects reflected light from the reflective optical scale of the encoder. The encoder uses a reflective optical scale that, in the thickness direction, has a high-reflectivity layer, a protective layer containing organic material, and a low-reflectivity layer arranged in a pattern. It has: a low-reflection region, which is a region provided with the high-reflection layer, the protective layer, and the low-reflection layer; and a high-reflection region, which is a region provided with the high-reflection layer and the protective layer. The protective layer has a thickness of 0.16 μm or more and 1.0 μm or less. When the wavelength of the measuring light source is set to 850 μm, the reflectivity in the high-reflectivity region is above 40%. The protective layer comprises organic materials and has a water contact angle of 73° or greater and 90° or less. The high-reflectivity layer is made of stainless steel substrate.

6. A laminated body for a reflective optical scale for an encoder, which is used to manufacture a reflective optical scale for an encoder as described in any one of claims 1 to 3 or claim 5, wherein, The laminate has a high-reflectivity layer and a protective layer sequentially in the thickness direction. When the thickness of the protective layer is set as d in μm and the incident angle of the incident light on the protective layer is set as θ in °, the following equation (1) is satisfied. d=mλ / [2n×cos{Arcsin(sinθ / n)}] (1) In the formula, n is the refractive index of the protective layer, λ is the wavelength of the incident light in μm, m is a number that satisfies 0 < m ≤ 0.3 or p - 0.3 ≤ m ≤ p + 0.3, and p is an integer greater than 1 and less than 3.

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