Photothermal conversion member

Abstract

A photothermal conversion member according to one embodiment of the present invention is capable of performing heating without affecting the transmission and reception of light and without using low-power heating or exclusive heating power. The photothermal conversion member includes a base material with infrared transparency and an infrared-absorbing heat generation layer supported by the base material. When viewed in the normal direction of the base material, the infrared-absorbing heat generation layer may include a pattern section that is patterned, and the infrared-absorbing heat generation layer may include a second portion of an oxide that contains nickel and phosphorus and constitutes a protrusion.

Description

Photothermal conversion materials

[0001] The present invention relates to a light-to-heat conversion member.

[0002] Patent Document 1 discloses a snow-melting outdoor LED device that can quickly and reliably prevent snow and ice buildup, frost buildup, freezing, etc., and ensure good visibility. This outdoor LED device uses an LED lighting device, and mixes infrared light with the illumination light from the light-emitting surface of the LED lighting device.

[0003] Patent Document 2 discloses a window film that is easy to install and can accelerate the drying of the window surface by promoting the evaporation of condensation that occurs. This window film has a hydrophilic outermost surface and a heat-generating layer that contains a near-infrared absorbing material and generates heat by absorbing near-infrared rays.

[0004] JP 2018-049467 A JP 2019-070247 A

[0005] In devices that handle optical signals, such as light-emitting devices and light-receiving devices, anything blocking the light in the optical path can impede their function. For example, in cold regions, frost on the device surface (such as the exterior cover) that is in the optical path can affect the transmission and reception of light. For this reason, a resistance heater for heating the exterior is installed inside the device as a means to prevent frost. However, because a resistance heater for heating the exterior requires a large amount of power, a low-power heating means or a heating means that does not require dedicated power for heating is desired to achieve low power consumption.

[0006] An object of the present invention is to provide a photothermal conversion member that can be heated with low power or without using dedicated heating power, without affecting the transmission and reception of light.

[0007] One aspect of the present invention is a photothermal conversion member having an infrared-transparent substrate and an infrared-absorbing heat-generating layer supported on the substrate. With this configuration, infrared light from light that reaches the infrared-absorbing heat-generating layer or light that passes through the substrate is absorbed by the infrared-absorbing heat-generating layer. This absorption of infrared light causes the infrared-absorbing heat-generating layer to generate heat with low power or without the use of dedicated heating power.

[0008] In the above-mentioned photothermal conversion member, the infrared absorbing heat generating layer may have a patterned patterned portion when viewed in the normal direction of the substrate. In this case, when viewed in the normal direction of the substrate, the substrate may be exposed in a non-patterned portion in an area where the patterned infrared absorbing heat generating layer is not located. This allows heat to be generated in the patterned portion of the infrared absorbing heat generating layer and improves the light transmittance in the non-patterned portion.

[0009] In the above light-to-heat conversion member, the infrared absorbing and heat generating layer preferably has a plurality of protrusions protruding in a direction away from the substrate.

[0010] In the above-described photothermal conversion member, the infrared absorbing heat generating layer may have a first portion containing nickel and phosphorus, and a second portion of an oxide containing nickel and phosphorus that constitutes the convex portion.

[0011] In the photothermal conversion member, the first portion may be located closer to the substrate than the second portion, and the surface of the first portion facing the second portion may have an uneven structure. In this case, the second portion may be provided so as to further protrude away from the substrate from a portion of the first portion that protrudes away from the substrate.

[0012] In the above photothermal conversion member, the second portion may be a modified version of the first portion, and the second portion may be formed continuously with the first portion.

[0013] In the above-described photothermal conversion member, the substrate may be a cover for the light-receiving optical system or the light-projecting optical system, which is disposed between the light-receiving optical system that receives infrared rays projected from the light-projecting optical system. In this way, an infrared-absorbing heat-generating layer is provided on the cover for the light-receiving optical system or the light-projecting optical system, and the cover is heated by the heat generated by the infrared-absorbing heat-generating layer.

[0014] According to the present invention, it is possible to provide a photothermal conversion member that can be heated with low power or without using power dedicated to heating, without affecting the transmission and reception of light.

[0015] FIG. 1 is a schematic cross-sectional view illustrating the configuration of a photothermal conversion member according to this embodiment; FIG. 2 is a schematic cross-sectional view illustrating the configuration of a photothermal conversion member according to this embodiment; FIG. 3 is a schematic plan view illustrating an example of a pattern of an infrared absorbing heat generating layer; FIG. 4 is a schematic plan view illustrating an example of a pattern of an infrared absorbing heat generating layer; FIG. 5 is a schematic plan view illustrating an example of a pattern of an infrared absorbing heat generating layer; FIG. 6 is a schematic view illustrating an example of a configuration of a photoelectric sensor; FIG. 7 is a schematic view illustrating an example of a configuration of a photoelectric sensor; FIG. 8 is a schematic view illustrating an example of a configuration of a photoelectric sensor; FIG. 9 is a schematic cross-sectional view illustrating the configuration of an infrared absorbing heat generating layer; FIG. 10 is a diagram showing a secondary electron image (surface observation image 1) obtained by observing the main surface on the second portion side of the infrared absorbing heat generating layer of a photothermal conversion member according to Production Example 1 (example of the present invention) with a scanning electron microscope in the normal direction of the main surface. 7A and 7B are diagrams illustrating the characteristics of an infrared absorbing heat generating layer.

[0033] Fig. 7C is a diagram illustrating the characteristics of an infrared absorbing heat generating layer. Fig. 7D is a diagram illustrating the characteristics of an infrared absorbing heat generating layer. Fig. 7E is a diagram illustrating the characteristics of an infrared absorbing heat generating layer. Fig. 7F is a diagram illustrating the characteristics of an infrared absorbing heat generating layer. Fig. 7G ...

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same components will be designated by the same reference numerals, and the description of components that have already been described will be omitted as appropriate.

[0017] (Configuration of Photothermal Conversion Member) FIGS. 1A and 1B are schematic cross-sectional views illustrating the configuration of a photothermal conversion member according to this embodiment. The photothermal conversion member 1 according to this embodiment has an infrared-transparent substrate 40 and an infrared absorbing and heat-generating layer 10 supported on the substrate 40. The substrate 40 may be a flexible film or a hard substrate. Examples of materials used for the substrate 40 include resin materials such as PC (polycarbonate), PE (polyethylene), and PET (polyethylene terephthalate), as well as glass. The flexibility of the substrate 40 allows the photothermal conversion member 1 to be easily positioned on curved portions.

[0018] The infrared absorbing heat generating layer 10 is supported by the substrate 40 and generates heat by absorbing infrared rays. For example, a compound of an inorganic metal material (e.g., an oxide) is used as the infrared absorbing heat generating layer 10. Preferred examples of the compound of the inorganic metal material include nickel-based compounds (oxide compounds of nickel-phosphorus electroless plating, oxides of nickel-phosphorus alloys, nickel oxide, etc.). The infrared absorbing heat generating layer 10 is made of a material that efficiently absorbs infrared rays and generates heat, and a material with a high emissivity is preferable, while a low reflectivity is preferable. The reflectivity is preferably 5% or less, for example.

[0019] In the photothermal conversion member 1 in which the infrared absorbing heat generating layer 10 is supported on the substrate 40, the infrared rays of the light that reaches the infrared absorbing heat generating layer 10 or the light that passes through the substrate 40 are absorbed by the infrared absorbing heat generating layer 10. The absorption of infrared rays by the infrared absorbing heat generating layer 10 causes the infrared absorbing heat generating layer 10 to generate heat with low power or without using power dedicated to heating, and the heat is transferred to the substrate 40.

[0020] The infrared absorbing heat generating layer 10 may be provided uniformly on the surface of the substrate 40, or may be formed in a pattern as shown in Fig. 1B. When the infrared absorbing heat generating layer 10 is provided uniformly on the surface of the substrate 40, it is sufficient that the layer has a film thickness and composition that allows light of a specific wavelength (e.g., infrared) to pass through. When the infrared absorbing heat generating layer 10 is formed in a pattern, a patterned portion PT and a non-patterned portion NPT are provided. The patterned infrared absorbing heat generating layer 10 will be described later.

[0021] In order to obtain an efficient temperature rise due to heat generation in the photothermal conversion member 1, the base material 40 is preferably a material with low heat dissipation and thermal conductivity, and the preferred thermal conductivity of the base material 40 is 0.4 W / mK or less. The base material 40 needs to be a material that transmits infrared rays, and the higher the infrared transmittance, the better.

[0022] 2A to 3B are schematic plan views showing examples of patterns of the infrared absorbing heat generating layer, as viewed in the normal direction of the substrate 40 (first direction: the Z1-Z2 direction shown in FIGS. 1A and 1B).

[0023] 2A shows an example of a grid pattern. That is, this photothermal conversion member 1 has a patterned portion PT in which an infrared absorbing heat generating layer 10 is provided in a grid pattern on the surface of a substrate 40, and a non-patterned portion NPT in which the infrared absorbing heat generating layer 10 is not provided or which has a configuration different from that of the patterned portion PT.

[0024] The lattice openings 10a are an example of non-patterned portions NPT. The larger the area of ​​the openings 10a, the greater the amount of light transmitted through the photothermal conversion member 1, but the less infrared light is absorbed by the infrared absorbing and heat generating layer 10, resulting in less heat generation. Conversely, the smaller the area of ​​the openings 10a, the less light is transmitted through the photothermal conversion member 1, but the more infrared light is absorbed by the infrared absorbing and heat generating layer 10, resulting in more heat generation.

[0025] 2B shows an example of a dotted pattern. This photothermal conversion member 1 has a patterned portion PT where a dotted infrared absorbing heat-generating layer 10 is provided on the surface of the substrate 40, and a non-patterned portion NPT where no infrared absorbing heat-generating layer 10 is provided. The shape of the dots in the patterned portion PT formed by the infrared absorbing heat-generating layer 10 may be circular, elliptical, or polygonal, such as rectangular. The larger the area of ​​the dotted patterned portion PT, the less light transmits through the photothermal conversion member 1, but the greater the amount of infrared radiation absorbed by the infrared absorbing heat-generating layer 10, resulting in a greater amount of heat generation. Conversely, the smaller the area of ​​the dotted patterned portion PT, the greater the amount of light transmittance through the photothermal conversion member 1, but the less infrared radiation absorbed by the infrared absorbing heat-generating layer 10, resulting in a smaller amount of heat generation.

[0026] 3A shows an example of a concentric pattern. This photothermal conversion member 1 has a pattern portion PT in which multiple infrared absorbing heat-generating layers 10 are concentrically arranged on the surface of a substrate 40, and a non-pattern portion NPT in which no infrared absorbing heat-generating layer 10 is provided. The larger the area of ​​the concentric pattern portion PT, the less light transmits through the photothermal conversion member 1, but the greater the amount of infrared light absorbed by the infrared absorbing heat-generating layer 10 and the greater the amount of heat generated. Conversely, the smaller the area of ​​the concentric pattern portion PT, the greater the amount of light transmittance through the photothermal conversion member 1, but the less infrared light is absorbed by the infrared absorbing heat-generating layer 10 and the less heat generated.

[0027] FIG. 3B shows an example of an opening pattern. This photothermal conversion member 1 has, on the surface of the substrate 40, a patterned portion PT where the infrared absorbing heat-generating layer 10 is provided, and a non-patterned portion NPT where the infrared absorbing heat-generating layer 10 is not provided. An example of the non-patterned portion NPT is an opening 10b. In the example shown in FIG. 3B, the shape of the opening 10b is circular, but this is not limited to this. Furthermore, the position of the opening 10b is not limited to the center of the substrate 40. The larger the area of ​​the opening 10b, the greater the amount of light transmitted through the photothermal conversion member 1, but the less infrared light is absorbed by the infrared absorbing heat-generating layer 10, and the less heat is generated. Conversely, the smaller the area of ​​the opening 10b, the less light is transmitted through the photothermal conversion member 1, but the more infrared light is absorbed by the infrared absorbing heat-generating layer 10, and the more heat is generated.

[0028] In any of the above patterns, the pattern shape is composed of a portion where the infrared absorbing heat generating layer 10 is provided (pattern portion PT) and a portion where the infrared absorbing heat generating layer 10 is not provided (non-pattern portion NPT).

[0029] The non-patterned portion NPT may be the openings 10a, 10b where the infrared absorbing heat generating layer 10 is not provided, or may be a portion where the infrared absorbing heat generating layer 10 is provided but where the amount of light transmitted through the infrared absorbing heat generating layer 10 is less than that of the patterned portion PT. For example, the patterned portion PT and the non-patterned portion NPT may be configured by differences in the layer thickness or layer composition of the infrared absorbing heat generating layer 10.

[0030] The infrared absorbing heat generating layer 10 can be patterned, and its infrared absorption (heat generation) properties can be adjusted by adjusting the area ratio between the patterned portion PT and the non-patterned portion NPT. More specifically, by adjusting the area ratio between the patterned portion PT and the non-patterned portion NPT, as well as their respective shapes and arrangements, it is possible to set the heat generation efficiency, light and infrared transmittance according to the shape and required characteristics of the product. A protective layer or heat-retaining layer may be added to the surface of the infrared absorbing heat generating layer 10, thereby further improving and optimizing the temperature rise characteristics due to heat generation, transmittance, and weather resistance.

[0031] 4A to 6B are schematic diagrams showing configuration examples of photoelectric sensors. The photoelectric sensor 100A shown in Fig. 4A includes a light-projecting optical system 110 that emits light, a light-receiving optical system 120 that receives the light, and a photothermal converting member 1 provided between the light-projecting optical system 110 and the light-receiving optical system 120. The photoelectric sensor 100A is a transmission-type photoelectric sensor that detects the presence or absence of an object between the light-projecting optical system 110 and the light-receiving optical system 120 based on whether or not light (e.g., infrared light) emitted from the light-projecting optical system 110 toward the light-receiving optical system 120 is blocked.

[0032] In the photoelectric sensor 100A, a photothermal conversion member 1 is attached to a cover 130 (a photoelectric sensor cover on the light-receiving optical system 120 side) provided on the light-receiving optical system 120 on the side of the light-projecting optical system 110. The photothermal conversion member 1 is attached to the back surface of the cover 130 (downstream in the direction of travel of light emitted from the light-projecting optical system 110) with an adhesive member 140 such as OCA (Optically Clear Adhesive). The infrared absorbing and heat-generating layer 10 of the photothermal conversion member 1 is patterned. It is preferable that the infrared absorbing and heat-generating layer 10 of the photothermal conversion member 1 be disposed on the side of the light-projecting optical system 110 (upstream in the direction of travel of light).

[0033] In this photoelectric sensor 100A, light emitted from the light-projecting optical system 110 passes through the cover 130 and is irradiated onto the photothermal conversion member 1. A portion of the infrared rays of the irradiated light is absorbed by the pattern portion PT of the infrared absorbing heat generating layer 10 of the photothermal conversion member 1, thereby generating heat. The heat generated in the pattern portion PT of the infrared absorbing heat generating layer 10 is transferred to the cover 130, heating the cover 130. Heating the cover 130 suppresses condensation on the surface of the cover 130. The infrared rays that have passed through the non-pattern portion NPT of the infrared absorbing heat generating layer 10 pass through the base material 40 and reach the light-receiving optical system 120.

[0034] In the photoelectric sensor 100A, heat can be generated without using dedicated heating power by absorbing infrared rays in the patterned portion PT of the infrared absorbing heat generating layer 10 of the photothermal conversion member 1, thereby heating the cover 130. Furthermore, the infrared rays of the light emitted from the light projecting optical system 110 pass through the non-patterned portion NPT of the patterned infrared absorbing heat generating layer 10 and the substrate 40, and therefore do not affect the reception of infrared rays by the light receiving optical system 120. Therefore, the function of the transmission type photoelectric sensor can be exhibited while suppressing condensation on the cover 130.

[0035] 4B includes a light-projecting optical system 110 that emits light, a light-receiving optical system 120 that receives the light, and a photothermal converting member 1 provided between the light-projecting optical system 110 and the light-receiving optical system 120. Similar to the photoelectric sensor 100A, the photoelectric sensor 100B is a transmission-type photoelectric sensor that detects the presence or absence of an object between the light-projecting optical system 110 and the light-receiving optical system 120 based on whether or not light (e.g., infrared light) emitted from the light-projecting optical system 110 toward the light-receiving optical system 120 is blocked.

[0036] In the photoelectric sensor 100B, the photothermal conversion member 1 is attached to a cover 130 (photoelectric sensor cover on the light-receiving optical system 120 side) provided on the light-projecting optical system 110 side of the light-receiving optical system 120. The photothermal conversion member 1 is attached to the back surface of the cover 130 with an adhesive member 140 such as OCA. The infrared absorbing and heat-generating layer 10 of the photothermal conversion member 1 is not patterned and has a uniform configuration. It is preferable that the infrared absorbing and heat-generating layer 10 of the photothermal conversion member 1 be disposed on the light-projecting optical system 110 side (upstream in the direction of light travel).

[0037] In this photoelectric sensor 100B, light emitted from the light-projecting optical system 110 passes through the cover 130 and is irradiated onto the photothermal conversion member 1. A portion of the infrared rays of the irradiated light is absorbed by the infrared absorbing heat generating layer 10 of the photothermal conversion member 1, thereby generating heat. The heat generated in the infrared absorbing heat generating layer 10 is transferred to the cover 130, heating the cover 130. Heating the cover 130 suppresses condensation on the surface of the cover 130. The uniform infrared absorbing heat generating layer 10 is configured to allow a portion of the infrared rays to pass through. The infrared rays that pass through the infrared absorbing heat generating layer 10 pass through the substrate 40 and reach the light-receiving optical system 120.

[0038] In the photoelectric sensor 100B, heat can be generated without using dedicated heating power by absorbing infrared rays in the infrared absorbing heat generating layer 10 of the photothermal conversion member 1, thereby heating the cover 130. Furthermore, the infrared rays of the light emitted from the light projecting optical system 110 pass through the uniform infrared absorbing heat generating layer 10 and the base material 40, and therefore do not affect the reception of infrared rays by the light receiving optical system 120. Therefore, the function of the transmission type photoelectric sensor can be exhibited while suppressing condensation on the cover 130.

[0039] 5A includes a light-projecting optical system 110 that emits light such as infrared rays, a light-receiving optical system 120 that receives the light from the light-projecting optical system 110, a photothermal converting member 1 provided between the light-projecting optical system 110 and the light-receiving optical system 120, and an infrared projector 150. Similar to the photoelectric sensor 100A, the photoelectric sensor 100C is a transmission-type photoelectric sensor that detects the presence or absence of an object between the light-projecting optical system 110 and the light-receiving optical system 120 based on whether or not light (e.g., infrared rays) emitted from the light-projecting optical system 110 toward the light-receiving optical system 120 is blocked.

[0040] In the photoelectric sensor 100C, the photothermal conversion member 1 is attached to a cover 130 (a photoelectric sensor cover on the light-receiving optical system 120 side) provided on the light-projecting optical system 110 side of the light-receiving optical system 120. The photothermal conversion member 1 is attached to the back surface of the cover 130 with an adhesive member 140 such as OCA. The infrared absorbing heat-generating layer 10 of the photothermal conversion member 1 is patterned. The infrared absorbing heat-generating layer 10 of the photothermal conversion member 1 is preferably disposed on the side of the light-projecting optical system 110 (upstream in the direction of light travel). Furthermore, the infrared projector 150 is disposed so that infrared rays can be irradiated from the substrate 40 side of the photothermal conversion member 1 toward the infrared absorbing heat-generating layer 10.

[0041] In this photoelectric sensor 100C, light emitted from the light projecting optical system 110 passes through the cover 130 and is irradiated onto the photothermal conversion member 1. A portion of the infrared rays in the irradiated light is absorbed by the infrared absorbing heat generating layer 10 of the photothermal conversion member 1, thereby generating heat. Also in the photoelectric sensor 100C, infrared rays irradiated from the infrared projector 150 are irradiated onto the infrared absorbing heat generating layer 10 through the substrate 40 of the photothermal conversion member 1. It is preferable to use an LED light source, which consumes little power, as the infrared projector 150. The infrared rays irradiated from this infrared projector 150 are absorbed by the infrared absorbing heat generating layer 10, thereby promoting further heat generation.

[0042] The heat generated in the infrared absorbing heat generating layer 10 is transferred to the cover 130, heating the cover 130. Heating the cover 130 suppresses condensation on the surface of the cover 130. The infrared rays that have passed through the infrared absorbing heat generating layer 10 pass through the base material 40 and reach the light receiving optical system 120.

[0043] In the photoelectric sensor 100C, the infrared absorbing heat generating layer 10 of the photothermal conversion member 1 absorbs the infrared rays emitted from the light-projecting optical system 110, thereby generating heat without using dedicated heating power. Furthermore, the infrared rays emitted from the low-power infrared projector 150 promote further heating of the infrared absorbing heat generating layer 10. This ensures reliable heating of the cover 130. Furthermore, the infrared rays emitted from the light-projecting optical system 110 pass through the patterned infrared absorbing heat generating layer 10 and the substrate 40, and therefore do not affect reception of the infrared rays by the light-receiving optical system 120. Therefore, the functionality of the transmission-type photoelectric sensor can be exhibited while suppressing condensation on the cover 130.

[0044] The photoelectric sensor 100D illustrated in Fig. 5B includes a light-projecting optical system 110 that emits light, a light-receiving optical system 120 that receives the light, and a photothermal conversion member 1 provided between the light-projecting optical system 110 and the light-receiving optical system 120. The photoelectric sensor 100D differs from the photoelectric sensor 100C in Fig. 5A in that the infrared absorbing and heat-generating layer 10 of the photothermal conversion member 1 is disposed closer to the light-receiving optical system 120 (downstream in the direction of light travel) than the substrate 40, and closer to the low-power infrared projector 150.

[0045] In the photoelectric sensor 100D, the patterned infrared absorbing heat generating layer 10 of the photothermal conversion member 1 is positioned closer to the infrared projector 150 than the substrate 40, so that heating is promoted more efficiently in the pattern portion PT of the infrared absorbing heat generating layer 10 by the infrared rays irradiated from the infrared projector 150, which has lower power than the photoelectric sensor 100C in FIG. 5A.

[0046] Furthermore, in the photoelectric sensor 100D, the patterned infrared-absorbing heat-generating layer 10 of the photothermal conversion member 1 is positioned closer to the light-receiving optical system 120 than the substrate 40. Therefore, the infrared light emitted from the light-projecting optical system 110 passes through the substrate 40 and then the non-patterned portion NPT of the infrared-absorbing heat-generating layer 10, thereby not affecting the reception of the infrared light by the light-receiving optical system 120. Furthermore, because the infrared light emitted from the light-projecting optical system 110 is irradiated first onto the substrate 40 and then onto the patterned portion PT of the infrared-absorbing heat-generating layer 10, heating due to heat generation by the patterned portion PT of the infrared-absorbing heat-generating layer 10 can be suppressed more effectively than in the photoelectric sensor 100C of FIG. 5A . This reduces the amount of heat constantly generated by the infrared-absorbing heat-generating layer 10, and allows the heating of the infrared-absorbing heat-generating layer 10 to be relatively increased and adjusted by the infrared light irradiated from the low-power infrared projector 150. This allows the transmission-type photoelectric sensor to function while suppressing condensation on the cover 130 due to seasonal variations.

[0047] 5C includes a light-projecting optical system 110 that emits light, a light-receiving optical system 120 that receives the light, and a photothermal converting member 1 provided between the light-projecting optical system 110 and the light-receiving optical system 120. Similar to the photoelectric sensor 100A, the photoelectric sensor 100E is a transmission-type photoelectric sensor that detects the presence or absence of an object between the light-projecting optical system 110 and the light-receiving optical system 120 based on whether or not light (e.g., infrared light) emitted from the light-projecting optical system 110 toward the light-receiving optical system 120 is blocked.

[0048] In the photoelectric sensor 100E, a cover 130 (a photoelectric sensor cover on the light-receiving optical system 120 side) provided on the light-projecting optical system 110 side of the light-receiving optical system 120 is used as the base material 40, and the infrared absorbing heat generating layer 10 is attached to the back surface (the surface opposite to the light-projecting optical system 110) of the cover 130. The infrared absorbing heat generating layer 10 is patterned.

[0049] The infrared absorbing heat generating layer 10 may be formed directly on the surface of the cover 130 using the cover 130 as the substrate 40, or may be formed by transfer. In the case of formation by transfer, the infrared absorbing heat generating layer 10 is formed and patterned on a release material, and only the infrared absorbing heat generating layer 10 is transferred onto the surface of the cover 130 and the release material is peeled off.

[0050] In this photoelectric sensor 100E, light emitted from the light-projecting optical system 110 passes through the cover 130 and is irradiated onto the photothermal conversion member 1. A portion of the infrared rays of the irradiated light is absorbed by the infrared absorbing heat generating layer 10 of the photothermal conversion member 1, thereby generating heat. The heat generated in the infrared absorbing heat generating layer 10 is transferred to the cover 130, heating the cover 130. Heating the cover 130 suppresses condensation on the surface of the cover 130. The infrared rays that pass through the infrared absorbing heat generating layer 10 reach the light-receiving optical system 120.

[0051] In the photoelectric sensor 100E, the infrared absorbing and heat-generating layer 10 of the photothermal conversion member 1 absorbs infrared rays, generating heat without using dedicated heating power, thereby heating the cover 130. Furthermore, because the cover 130 is used as the substrate 40, infrared attenuation is suppressed and a thinner design is possible compared to when the cover 130 and substrate 40 are separate components. The infrared rays emitted from the light-projecting optical system 110 pass through the non-patterned portion NPT of the patterned infrared absorbing and heat-generating layer 10 and do not affect reception of the infrared rays by the light-receiving optical system 120. Therefore, the cover 130 can function as a transmission-type photoelectric sensor while suppressing condensation. While the photoelectric sensor 100E has a patterned infrared absorbing and heat-generating layer 10 formed on the surface of the cover 130, a uniform, unpatterned infrared absorbing and heat-generating layer 10 may be formed directly or by transfer on the surface of the cover 130, as described above.

[0052] 6A includes a light-projecting optical system 110 that emits light, a light-receiving optical system 120 that receives the light, a first photothermal converting member 1A provided between the light-projecting optical system 110 and the light-receiving optical system 120, and a second photothermal converting member 1B provided between the first photothermal converting member 1A and the light-receiving optical system 120. Similar to the photoelectric sensor 100A, the photoelectric sensor 100F is a transmission-type photoelectric sensor that detects the presence or absence of an object between the light-projecting optical system 110 and the light-receiving optical system 120 based on whether or not light (e.g., infrared light) emitted from the light-projecting optical system 110 toward the light-receiving optical system 120 is blocked.

[0053] In the photoelectric sensor 100F, a first photothermal converting member 1A is attached to a first cover 130A (a photoelectric sensor cover on the light projecting optical system 110 side) provided on the light receiving optical system 120 side of the light projecting optical system 110. The first photothermal converting member 1A is attached to the back surface of the first cover 130A with an adhesive member 140 such as OCA. The infrared absorbing and heat generating layer 10 of the first photothermal converting member 1A is patterned. It is preferable that the infrared absorbing and heat generating layer 10 of the first photothermal converting member 1A be disposed on the light projecting optical system 110 side (upstream in the direction of light travel).

[0054] Furthermore, in the photoelectric sensor 100F, a second photothermal converting member 1B is attached to a second cover 130B (a photoelectric sensor cover on the light receiving optical system 120 side) provided on the light projecting optical system 110 side of the light receiving optical system 120. The second photothermal converting member 1B is attached to the back surface of the second cover 130B (downstream in the direction of travel of light emitted from the light projecting optical system 110) with an adhesive member 140 such as OCA. The infrared absorbing and heat generating layer 10 of the second photothermal converting member 1B is patterned. It is preferable that the infrared absorbing and heat generating layer 10 of the second photothermal converting member 1B be disposed on the light projecting optical system 110 side (upstream in the direction of travel of light).

[0055] In this photoelectric sensor 100F, light emitted from the light-projecting optical system 110 is irradiated onto the first photothermal converting member 1A. A portion of the infrared rays of the irradiated light is absorbed by the infrared absorbing heat-generating layer 10 of the first photothermal converting member 1A, thereby generating heat. The heat generated by the infrared absorbing heat-generating layer 10 of the first photothermal converting member 1A is transferred to the first cover 130A (the photoelectric sensor cover on the light-projecting optical system 110 side), heating the first cover 130A. Heating the first cover 130A suppresses condensation on the surface of the first cover 130A. Light that has passed through the infrared absorbing heat-generating layer 10 of the first photothermal converting member 1A passes through the base material 40 and the first cover 130A and proceeds toward the light-receiving optical system 120.

[0056] Light directed toward the light-receiving optical system 120 passes through the second cover 130B (a cover for the photoelectric sensor on the light-receiving optical system 120 side) and is irradiated onto the second photothermal conversion member 1B. A portion of the infrared rays of the irradiated light is absorbed by the infrared absorbing heat generating layer 10 of the second photothermal conversion member 1B, thereby generating heat. The heat generated in the infrared absorbing heat generating layer 10 is transferred to the second cover 130B, heating the second cover 130B. Heating the second cover 130B suppresses condensation on the surface of the second cover 130B. The infrared rays that have passed through the infrared absorbing heat generating layer 10 pass through the base material 40 and reach the light-receiving optical system 120.

[0057] In the photoelectric sensor 100F, infrared rays, which are a portion of the light emitted from the light-projecting optical system 110, can heat the infrared absorbing heat generating layers 10 of the first photothermal conversion member 1A and the second photothermal conversion member 1B. This makes it possible to heat the first cover 130A and the second cover 130B without using electric power. Furthermore, the infrared rays of the light emitted from the light-projecting optical system 110 pass through the patterned infrared absorbing heat generating layer 10 and the base material 40, and therefore do not affect the reception of the infrared rays by the light-receiving optical system 120. Therefore, the function of a transmission-type photoelectric sensor can be exhibited while suppressing condensation on the first cover 130A and the second cover 130B.

[0058] 6B includes a light-projecting optical system 110 that emits light, a light-receiving optical system 120 that receives the light, and a photothermal converting member 1 provided between the light-projecting optical system 110 and the light-receiving optical system 120. Similar to the photoelectric sensor 100A, the photoelectric sensor 100G is a transmission-type photoelectric sensor that detects the presence or absence of an object between the light-projecting optical system 110 and the light-receiving optical system 120 based on whether or not light (e.g., infrared light) emitted from the light-projecting optical system 110 toward the light-receiving optical system 120 is blocked.

[0059] In the photoelectric sensor 100G, a photothermal conversion member 1 is attached to a cover 130 (a photoelectric sensor cover on the light-receiving optical system 110 side) provided on the light-receiving optical system 120 side of the light-projecting optical system 110. The photothermal conversion member 1 is attached to the back surface of the cover 130 (upstream side in the direction of travel of light emitted from the light-projecting optical system 110) with an adhesive member 140 such as OCA. The infrared absorbing and heat-generating layer 10 of the photothermal conversion member 1 is patterned. It is preferable that the infrared absorbing and heat-generating layer 10 of the photothermal conversion member 1 be disposed on the light-projecting optical system 110 side (upstream side in the direction of travel of light).

[0060] In this photoelectric sensor 100G, light emitted from the light-projecting optical system 110 is irradiated onto the photothermal conversion member 1. A portion of the infrared rays of the irradiated light is absorbed by the infrared absorbing heat-generating layer 10 of the photothermal conversion member 1, thereby generating heat. The heat generated in the infrared absorbing heat-generating layer 10 is transferred to the cover 130, heating the cover 130. Heating the cover 130 suppresses condensation on the surface of the cover 130. Light that has passed through the infrared absorbing heat-generating layer 10 of the photothermal conversion member 1 passes through the base material 40 and the cover 130 and heads toward the light-receiving optical system 120.

[0061] In the photoelectric sensor 100G, heat can be generated without using dedicated heating power by absorbing infrared rays in the infrared absorbing heat generating layer 10 of the photothermal conversion member 1, thereby heating the cover 130. Furthermore, the infrared rays of the light emitted from the light projecting optical system 110 pass through the patterned infrared absorbing heat generating layer 10 and the substrate 40, and therefore do not affect the reception of infrared rays by the light receiving optical system 120. Therefore, the function of the transmission type photoelectric sensor can be exhibited while suppressing condensation on the cover 130.

[0062] In this way, by applying the photothermal conversion member 1 according to this embodiment to the photoelectric sensors 100A-100G, there is no need for a heating device, such as a resistance heater, which requires a large amount of power to suppress condensation, frost, and snow accumulation, or for the associated harness and power supply. Furthermore, there is no need for a canopy to prevent snow accumulation. This allows the photoelectric sensors 100A-100G to achieve low power consumption, a simplified structure, and improved design. Furthermore, the infrared absorbing and heat generating layer 10 may be made conductive. This allows current to be applied to the infrared absorbing and heat generating layer 10 within the range of low power consumption, allowing the infrared absorbing and heat generating layer 10 to function as a resistance heater and auxiliary heating means.

[0063] 7A and 7B are schematic cross-sectional views illustrating the configuration of the infrared absorbing heat generating layer, with Fig. 7B showing an enlarged schematic cross-sectional view of part A in Fig. 7A.

[0064] 7A and 7B, the substrate 40 is a plate-shaped member with its thickness direction in the Z direction and its length direction in the X direction, and an infrared-absorbing heat-generating layer 10 is provided on one side (Z1 side) of the main surface of the substrate 40. The infrared-absorbing heat-generating layer 10 in FIG. 7A has a patterned portion PT and a non-patterned portion NPT. FIG. 7B shows an enlarged portion of portion A of the patterned portion PT of the infrared-absorbing heat-generating layer 10. The infrared-absorbing heat-generating layer 10 includes a film-like first portion 20 proximal to the substrate 40, and a second portion 30 located on one side (Z1 side) of the first portion 20 away from the substrate 40. The infrared-absorbing heat-generating layer 10 has multiple protrusions C protruding in the direction away from the substrate 40 (Z1 direction).

[0065] 7B, the pattern portion PT of the infrared absorbing heat generating layer 10 has a surface shape of an independent convex portion on the second portion 30 side (Z1 side). In the independent convex portion surface shape, a basic structure is formed in which multiple convex portions C protruding independently of one another are aligned in the in-plane direction, and bottom portions B are positioned so as to surround each convex portion C. The tip of the convex portion C on the Z1 side is a sharp portion S.

[0066] Because the surface shape of the infrared-absorbing heat-generating layer 10 is a convex-independent type, light irradiated onto the surface of the infrared-absorbing heat-generating layer 10 on the second portion 30 side (Z1 side) penetrates into the gaps between adjacent convex portions C and is absorbed by the sides and bottoms B of the convex portions C, making it difficult for the light to return to the irradiated light side (Z1 side). Therefore, the infrared-absorbing heat-generating layer 10 has excellent light absorption function. Specifically, when light in the wavelength range of 0.8 μm to 2.0 μm (hereinafter also referred to as "NIR: near-infrared") is irradiated onto the main surface of the infrared-absorbing heat-generating layer 10 on the second portion 30 side (Z1 side), the total reflectance (average NIR total reflectance Rt) is easily 2% or less.

[0067] Because the infrared absorbing heat generating layer 10 has such a light absorbing function, in one embodiment, the average NIR total reflectance Rt on the infrared absorbing heat generating layer 10 side is 2% or less. The average NIR total reflectance Rt of the infrared absorbing heat generating layer 10 according to this embodiment may be preferably 1% or less, more preferably 0.7% or less, and particularly preferably 0.5% or less.

[0068] Furthermore, because the surface of the infrared absorbing heat generating layer 10 on the second portion 30 side (Z1 side) has an independent convex shape, there is little possibility of through holes being formed in the infrared absorbing heat generating layer 10 in the stacking direction (Z direction) between the first portion 20 and the second portion 30. This eliminates the need to excessively increase the thickness of the first portion 20, and makes it possible to keep the heat capacity of the infrared absorbing heat generating layer 10 low. Therefore, the infrared absorbing heat generating layer 10 has a light-to-heat conversion function (heat generation function) based on its excellent light absorption function and a rapid heating function based on its low heat capacity, and the infrared absorbing heat generating layer 10 can be used as a light absorbing member, a light-to-heat conversion member, a heating member, or a heat collecting member that limits the heat generating portion by light-to-heat conversion to only the pattern portion PT.

[0069] The first portion 20 may include nickel-phosphorus plating. When the infrared absorbing heat generating layer 10 is manufactured by chemically altering (modifying) the nickel-phosphorus plating, the phosphorus concentration of the nickel-phosphorus plating of the first portion 20 may affect the surface shape of the first portion 20 and the shape of the second portion 30. The average thickness of the first portion 20 may be 6 μm or less. The average thickness of the first portion 20 directly affects the heat capacity of the infrared absorbing heat generating layer 10, and may therefore affect the heat transfer response and temperature rise / fall response of the infrared absorbing heat generating layer 10 after photothermal conversion. In the infrared absorbing heat generating layer 10 according to this embodiment, the average thickness of the first portion 20 may be 6 μm or less, thereby enabling the infrared absorbing heat generating layer 10 to have good heat transfer response and temperature rise / fall response after photothermal conversion.

[0070] The second portion 30 may contain nickel and phosphorus. In this case, the phosphorus content may preferably be 4.5% by mass or more and 7% by mass or less. In a preferred example, the second portion 30 includes a nickel-phosphorus-plated modified portion continuous with the first portion 20. When the second portion 30 includes a nickel-phosphorus-plated modified portion continuous with the first portion 20, peeling between the first portion 20 and the second portion 30 is less likely to occur, suppressing deterioration of the light absorption function and the photothermal conversion function (heat generation function) based on the light absorption function. Furthermore, even if the first portion 20 and the second portion 30 have different thermal expansion coefficients, the continuous structure of the first portion 20 and the second portion 30 makes it less likely for the difference in thermal expansion coefficients to promote peeling between the first portion 20 and the second portion 30. The average thickness of the second portion 30 may be 2 μm or less. From the perspective of reducing the size and thickness of the infrared absorbing and heat generating layer 10, a small thickness of the infrared absorbing and heat generating layer 10 is preferred. (For example, it is effective for application to small devices such as optical waveguides and MEMS.)

[0071] The structure of the pattern portion PT of the infrared absorbing heat generating layer 10 will be described in more detail below using a manufacturing example (Manufacturing Example 1) of a photothermal conversion member 1 having an infrared absorbing heat generating layer 10. Figure 7C shows a secondary electron image (surface observation image 1) obtained by observing the main surface of the second portion of the infrared absorbing heat generating layer of a photothermal conversion member according to Manufacturing Example 1, an example of the present invention, with a scanning electron microscope in the normal direction to the main surface. Figure 7D shows a secondary electron image obtained by observing the main surface of the second portion of the infrared absorbing heat generating layer of a photothermal conversion member according to Manufacturing Example 1 (an example of the present invention) with a scanning electron microscope in a direction tilted from the normal direction to the main surface. Figure 7E shows a secondary electron image obtained by observing the cross section of the photothermal conversion member according to Manufacturing Example 1 (an example of the present invention) with a scanning electron microscope. Figure 7F shows a view similar to Figure 7E, with symbols indicating shape features added.

[0072] The photothermal conversion member 1 according to this manufacturing example was manufactured as follows. First, a nickel-phosphorus electroless plating layer was formed on a strike-plated layer (underlayer 21) formed by nickel strike plating on a stainless steel substrate 40, using a nickel-phosphorus electroless plating solution with a different composition. The member thus obtained was then washed with hydrogen peroxide (1 mol / dm 3 about) and copper ions (0.1 mol / dm 3 The nickel-phosphorus electroless plating layer was modified by immersing the substrate for 4 to 5 minutes in an acidic mixed solution (liquid temperature: about 30°C) containing ammonium hydroxide (about 100%) and having a pH of 1 or less. This resulted in an infrared absorbing heat generating layer 10 having a main portion 22 of the first portion 20 based on the unmodified nickel-phosphorus electroless plating layer and a second portion 30 formed by the modification. The electroless plating solution was diluted with pure water.

[0073] The infrared absorbing heat generating layer 10 included in the photothermal conversion member 1 according to this manufacturing example had the cross-sectional structure shown in Fig. 7E. Specifically, the main portion 22 of the first portion 20, located on a nickel strike-plated layer (underlayer 21) provided as part of the first portion 20 of the infrared absorbing heat generating layer 10 and in contact with the substrate 40, was composed of nickel-phosphorus electroless plating provided on the nickel strike-plated layer (underlayer 21), and the second portion 30 was a modified portion formed by chemically modifying the nickel-phosphorus plating that constituted the main portion 22. Therefore, the second portion 30 was continuous with the first portion 20 (main portion 22).

[0074] Furthermore, the main portion 22 of the first portion 20 is a nickel-phosphorus alloy, and the modified portion of the second portion 30 contains an oxide of the nickel-phosphorus alloy. Because both the first portion 20 and the second portion 30 contain nickel-phosphorus, they have good adhesion and are less likely to peel off from each other due to differences in thermal expansion coefficients or external forces. Furthermore, there is no need to increase the thickness of the infrared absorbing heat generating layer 10, particularly the thickness of the first portion 20, to prepare for excessively deep recesses. Even if the infrared absorbing heat generating layer 10 or the second portion 30 is thin, a good oxide composition and shape can be obtained, providing efficient light absorption and light-to-heat conversion functions.

[0075] As shown in Figures 7C and 7D, the infrared absorbing heat generating layer 10 provided in the photothermal conversion member 1 according to this manufacturing example had a surface shape on the second portion 30 side with independent convex portions. Specifically, the surface shape on the second portion 30 side had a basic structure in which multiple convex portions protruding independently from each other were arranged in the in-plane direction, with the bottoms positioned to surround each convex portion. Also, as shown in the cross-sectional view of Figure 7E, the surface on the Z1 side (the second portion 30 side) of the first portion 20 had an uneven structure, and the second portion 30 was provided so as to protrude further to the Z1 side from the portion of the first portion 20 protruding to the Z1 side (the opposite side to the substrate 40 side).

[0076] This structure will be explained in detail with reference to Fig. 7F. In the cross-sectional view of Fig. 7F, the surface on the Z1 side of the first portion 20 of the infrared absorbing heat generating layer 10 is shown as an uneven line consisting of a bottom B located on the Z2 side and a top T protruding from the bottom B to the Z1 side. In this uneven line, a portion including two bottoms B aligned in the X direction and a top T located between those bottoms B constitutes a protruding portion P.

[0077] 7F , the second portion 30 was provided on the Z1 side of the protruding portion P of the first portion 20, protruding further to have a sharp portion S, and the protruding portion P of the first portion 20 and the second portion 30 together constituted the convex portion C of the infrared absorbing heat generating layer 10. In the secondary electron images of the main surface of the infrared absorbing heat generating layer 10 shown in FIGS. 7C and 7D , a plurality of the convex portions C were lined up in the in-plane direction (the X-Y in-plane direction). As shown in FIG. 7F , the protruding height (length in the Z direction) of these convex portions C included the protruding height (length in the Z direction) of the second portion 30 having the sharp portion S and the protruding height (length in the Z direction) of the protruding portion P of the first portion 20.

[0078] The main surface on the Z1 side of the infrared absorbing heat generating layer 10 having such a structure has a so-called moth-eye structure, and visible light traveling from the Z1 side to the Z2 side of the infrared absorbing heat generating layer 10 enters the gaps between adjacent protrusions C and is absorbed by the walls of the protrusions C, making it less likely to be reflected back to the Z1 side. The same is true for light in the wavelength range of 0.8 μm to 2.0 μm (also known as "NIR: near-infrared") and infrared light, which are easily absorbed by the infrared absorbing heat generating layer 10. Therefore, the infrared absorbing heat generating layer 10 has a light absorption function and a light-to-heat conversion function.

[0079] (Evaluation Samples) Each of the light-to-heat conversion members shown in Table 1 was prepared as an evaluation sample.

[0080]

[0081] Example 1: After forming an electroless nickel-phosphorus plating film on a substrate 40 made of polycarbonate resin, the electroless nickel-phosphorus plating film was subjected to a modification treatment to form an infrared absorbing heat generating layer 10 having a first portion 20 having a structure in which a plurality of protrusions P are arranged, and a second portion 30 protruding further from the protrusions P of the first portion 20. The infrared absorbing heat generating layer 10 used was that shown in Figure 7C. The pattern of the infrared absorbing heat generating layer 10 used was the pattern shown in Figure 2A, with a pattern opening ratio of 50%.

[0082] Comparative Example 1: The same infrared absorbing heat generating layer 10 as in Example 1 was formed on the entire surface of a substrate made of polycarbonate resin. No openings were provided in the infrared absorbing heat generating layer.

[0083] Comparative Example 2: Only a substrate made of polycarbonate resin was used, and the infrared absorbing and heat generating layer 10 was not provided.

[0084] (Evaluation of properties of photothermal conversion member and evaluation of function as transmission type photoelectric sensor) Each evaluation sample of Example, Comparative Example 1, and Comparative Example 2 was placed between the light projecting optical system 110 and the light receiving optical system 120 as shown in Fig. 4A, and the properties of the infrared absorbing heat generating layer 10 and the function as a transmission type photoelectric sensor (photoelectric sensor 100A) were evaluated. Table 2 shows the evaluation results.

[0085]

[0086] As shown in Table 2, the infrared transmittance of the infrared absorbing heat generating layer 10 at room temperature of 26°C was 40%, 0%, and 90% in the Example, Comparative Example 1, and Comparative Example 2, respectively. The infrared reflectance of the infrared absorbing heat generating layer 10 was 3%, 0.2%, and 10%, respectively. In Comparative Example 1, the infrared absorbing heat generating layer 10 was formed on the entire surface of the substrate 40, resulting in a transmittance of 0% and a reflectance of 0.2%, which are the characteristics of the infrared absorbing heat generating layer 10 alone. In Comparative Example 2, the infrared absorbing heat generating layer 10 was formed on the substrate 40 alone, resulting in the transmittance and reflectance of the substrate 40 alone. The Example had a pattern opening ratio of 50% for the infrared absorbing heat generating layer 10, resulting in transmittance and reflectance intermediate between those of the substrate 40 alone and those of the infrared absorbing heat generating layer 10 alone.

[0087] The temperature reached by the infrared irradiating unit shown in Table 2 is the temperature reached when the part irradiated with infrared rays reaches a steady state. More specifically, the temperatures reached by the infrared irradiating unit in Example and Comparative Example 1 indicate the temperatures reached by the infrared absorbing heat generating layer 10 on the substrate 40. Furthermore, the temperature reached by the infrared irradiating unit in Comparative Example 2 indicates the temperature reached by the substrate 40.

[0088] As shown in Table 2, in Comparative Example 1 and Example, at room temperature of 26°C, the temperature reached by the infrared irradiated portion of the infrared absorbing heat generating layer 10 on the substrate 40 reached 50°C, and at room temperature of -5°C, the temperature reached by the infrared irradiated portion of the infrared absorbing heat generating layer 10 on the substrate 40 reached 7°C. On the other hand, in Comparative Example 2, the temperature reached by the infrared irradiated portion of the substrate 40 was almost the same as room temperature at both room temperature of 26°C and room temperature of -5°C, and no temperature rise in the substrate 40 was observed.

[0089] Here, the photothermal conversion members 1 of each of the Example, Comparative Example 1, and Comparative Example 2 were disposed between the light-projecting optical system 110 and the light-receiving optical system 120 as shown in FIG. 4A , and the characteristics of the infrared absorbing heat-generating layer 10 and the function as a transmission-type photoelectric sensor 100A were evaluated. At room temperature of 26°C, no frost formed on the surface of the substrate 40 of each photothermal conversion member 1 in the infrared irradiated portion. On the other hand, as shown in Table 2, the presence or absence of frost on the surface of the substrate 40 of each photothermal conversion member 1 in the infrared irradiated portion at room temperature of −5°C was evaluated as absent (○), absent (○), and present (×) for Comparative Example 1, Example, and Comparative Example 2, respectively. In Comparative Example 1, no frost formed on the surface at both room temperature of 26°C and room temperature of −5°C, but the entire substrate 40 was covered with the infrared absorbing heat-generating layer 10 with a transmittance of 0%, so light reception and detection by the transmission-type photoelectric sensor 100A was not possible (×). In Comparative Example 2, the substrate 40 had an infrared transmittance of 90% at room temperature of 26°C, and light reception and detection was possible with the transmission-type photoelectric sensor 100A (◯). However, at room temperature of -5°C, there was no temperature increase before and after infrared irradiation, and frost formed on the surface of the substrate 40 over time, preventing light reception and detection with the transmission-type photoelectric sensor 100A (×). On the other hand, in the Example, light reception and detection was possible with the photoelectric sensor 100A. This was because heat generated in the patterned portion PT was transferred to the substrate 40 exposed in the non-patterned portion NPT, causing a temperature increase, preventing frost formation on the substrate 40 in the non-patterned portion NPT. As a result, light reception and detection was possible with the transmission-type photoelectric sensor 100A (◯). Furthermore, the heat resistance and gas generation of the infrared absorbing and heat-generating layer 10 were good in all of Comparative Example 1, the Example, and Comparative Example 2 (◯).

[0090] Fig. 8 is a diagram illustrating the characteristics of the photothermal conversion member. The horizontal axis of Fig. 8 represents the aperture ratio of the pattern of the infrared absorbing and heat generating layer 10, the left vertical axis represents the temperature reached by the infrared irradiated portion (the temperature reached when the portion irradiated with infrared rays reaches a steady state), and the right vertical axis represents the infrared transmittance, reflectance, and absorptance of the photothermal conversion member.

[0091] An opening ratio of 0% on the horizontal axis in Fig. 8 corresponds to Comparative Example 1, an opening ratio of 50% corresponds to the example, and an opening ratio of 100% corresponds to Comparative Example 2. The plots marked with triangles in Fig. 8 indicate the temperatures reached by the infrared irradiated portion of the photothermal conversion member 1 after infrared irradiation at a room temperature of 26°C, and the plots marked with circles indicate the temperatures reached by the infrared irradiated portion of the photothermal conversion member 1 after infrared irradiation at a room temperature of -5°C.

[0092] The infrared transmittance is approximately proportional to the aperture ratio of the pattern of the infrared absorbing heat generating layer 10, and the infrared absorptance is approximately inversely proportional to the aperture ratio of the pattern of the infrared absorbing heat generating layer 10. The infrared reflectance is approximately proportional to the aperture ratio of the pattern of the infrared absorbing heat generating layer 10 in the range of about 0.2% to 10%.

[0093] As in Comparative Example 1, the lower the aperture ratio of the pattern of the infrared-absorbing heat-generating layer 10, the lower the infrared reflectance and transmittance and the higher the absorptance. On the other hand, as in Comparative Example 2, the higher the aperture ratio of the pattern of the infrared-absorbing heat-generating layer 10, the higher the infrared reflectance and transmittance and the lower the absorptance. Therefore, in order to increase the amount of heat generated by infrared absorption by the infrared-absorbing heat-generating layer 10, it is sufficient to lower the aperture ratio of the pattern of the infrared-absorbing heat-generating layer 10, but this reduces the transmittance and prevents the photoelectric sensor 100A from functioning properly. On the other hand, if the aperture ratio of the pattern of the infrared-absorbing heat-generating layer 10 is increased, the transmittance increases, which is advantageous for detection by the photoelectric sensor 100A, but the amount of heat generated by the infrared-absorbing heat-generating layer 10 decreases.

[0094] The infrared absorbing heat generating layer 10 of the photothermal conversion member 1 of the embodiment can obtain heating characteristics equivalent to those of Comparative Example 1 while maintaining infrared transmittance. Therefore, by using the infrared absorbing heat generating layer 10 of the embodiment as the cover of the photoelectric sensor 100A, it is possible to suppress frost formation on the cover while allowing the photoelectric sensor 100A to function.

[0095] As an example, a photothermal conversion element 1 is prepared in which an infrared absorbing heat generating layer 10 with a reflectance of 5% or less is formed on an infrared transparent substrate 40 with a thermal conductivity of 0.4 W / mK or less, and when infrared rays with a wavelength of 850 nm to 1550 nm are irradiated onto the infrared absorbing heat generating layer 10, heat generation of 20°C or more above room temperature (normal temperature) can be obtained.

[0096] Furthermore, when the same photothermal conversion member 1 as above was prepared and irradiated with infrared light having a wavelength of 850 nm to 940 nm in a low-temperature environment (around -10°C below freezing), the heat generated could maintain a surface temperature of 5°C or higher. At this time, no frost was observed on the non-patterned portion NPT (see FIG. 2A) or the patterned portion PT (see FIG. 2A) of the infrared absorbing and heat generating layer 10 in the low-temperature environment. This is because the heat generated in the patterned portion PT was also transferred to the non-patterned portion NPT, causing a temperature rise.

[0097] (Application Example) The photothermal conversion member 1 according to this embodiment can be used in an LED traffic light. By attaching the photothermal conversion member 1 to the cover of the LED traffic light, the light emitted from the LED traffic light is not blocked, and the infrared absorbing heat generating layer 10 is made to generate heat by the infrared rays from the LED traffic light. This makes it possible to melt snow and frost adhering to the cover of the LED traffic light with low power consumption.

[0098] Furthermore, the photothermal conversion member 1 according to this embodiment can be used in LED headlights used in vehicles such as cars and motorcycles. By attaching the photothermal conversion member 1 to the cover of the LED headlight, the light emitted from the LED headlight is not blocked, and the infrared absorbing heat generating layer 10 generates heat using infrared rays from the LED headlight. This allows snow and frost adhering to the cover of the LED headlight to melt with low power.

[0099] Furthermore, the photothermal conversion member 1 according to this embodiment can be used for windowpanes of houses and cars. By attaching the photothermal conversion member 1 to the windowpane, the infrared absorbing heat generating layer 10 generates heat using infrared rays from sunlight or indoor lighting. This allows snow and frost adhering to the windowpane to melt without using separate dedicated heating power.

[0100] Although the present embodiment has been described above, the present invention is not limited to these examples. For example, those in which a person skilled in the art appropriately adds or deletes components or modifies the design of the above-described embodiments, or appropriately combines features of the configuration examples of the embodiments, are also included within the scope of the present invention as long as they include the gist of the present invention.

[0101] 1...Photothermal conversion member 1A...First photothermal conversion member 1B...Second photothermal conversion member 10...Infrared absorbing heat generating layer 10a, 10b...Opening 20...First portion 30...Second portion 21...Base layer 22...Main portion 40...Base material 100A to 100G...Photoelectric sensor 110...Light projecting optical system 120...Light receiving optical system 130...Cover 130A...First cover 130B...Second cover 140...Adhesive member 150...Infrared projector NPT...Non-patterned portion PT...Patterned portion C...Convex portion B...Bottom portion T...Top portion P...Protruding portion S...Sharp portion

Claims

1. A photothermal conversion member comprising: a substrate having infrared transparency; and an infrared absorbing and heat generating layer supported on the substrate.

2. The photothermal conversion member according to claim 1, wherein the infrared absorbing and heat generating layer has a patterned portion when viewed in the normal direction of the substrate.

3. The photothermal conversion member according to claim 2, wherein the substrate is exposed in a non-patterned portion in an area where the patterned infrared absorbing and heat generating layer is not located when viewed in the normal direction of the substrate.

4. The photothermal conversion member according to claim 2, wherein the infrared absorbing and heat generating layer has a plurality of protrusions protruding in a direction away from the substrate.

5. The photothermal conversion member according to claim 4, wherein the infrared absorbing heat generating layer has a first portion containing nickel and phosphorus, and a second portion of an oxide containing nickel and phosphorus that constitutes the convex portion.

6. The photothermal conversion member according to claim 5, wherein the first portion is located closer to the substrate than the second portion, and the surface of the first portion facing the second portion has an uneven structure.

7. The photothermal conversion member according to claim 6, wherein the second portion is provided so as to protrude further in the opposite direction from the substrate side than the portion of the first portion that protrudes in the opposite direction from the substrate side.

8. A photothermal conversion member according to claim 5 or claim 6, wherein the second portion is a modified version of the first portion, and the second portion is continuous with the first portion.

9. The photothermal conversion member according to claim 1, wherein the substrate is a cover for the light-receiving optical system or the light-projecting optical system, which is disposed between the light-receiving optical system and the light-projecting optical system, and which receives infrared rays projected from the light-projecting optical system.

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