Light control device

Abstract

This light control device (10) is a vehicle light control device that adjusts the amount of light entering a vehicle cabin (1a), and comprises a vehicle windshield (11) configured to include a light control material that changes color in response to ultraviolet light and decolorizes in response to visible light and / or heat, a light-emitting unit (30) that emits ultraviolet light at the windshield (11) from the inside of the vehicle cabin (1a), and a control unit (70) that controls the emission of the ultraviolet light by the light-emitting unit (30) on the basis of an emission mode including the illuminance and emission time of the ultraviolet light. The control unit (70) alternately modulates the illuminance of the ultraviolet light emitted at the windshield (11) from the light irradiation unit (30) between one state and another state.

Description

Dimming device

[0001] This disclosure relates to a dimming device.

[0002] Conventionally, anti-glare devices that utilize a material capable of changing the transmittance of visible light in a vehicle's windshield are known.

[0003] For example, Patent Document 1 describes a technique for reducing the transmittance of external light by irradiating a windshield containing a photochromic material that changes color when exposed to ultraviolet light with ultraviolet light to achieve a colored state.

[0004] Patent No. 6392651

[0005] A windshield containing a photochromic material restores the transmittance of ambient light and becomes colorless when anti-glare is not required, thereby ensuring the driver's visibility. However, if the colored state due to ultraviolet irradiation continues, the photochromic material deteriorates, and the ambient light transmittance of the windshield does not fully recover, which can make it difficult to ensure visibility while driving. For this reason, it is necessary to suppress the deterioration of the photochromic material in a windshield containing a photochromic material, but the technology described in Patent Document 1 above cannot suppress the deterioration of the photochromic material.

[0006] This disclosure aims to suppress the deterioration of a photochromic material in a windshield that includes such material, thereby preventing glare while ensuring the driver's field of vision.

[0007] One aspect of the present disclosure is a vehicle light control device for adjusting the amount of light incident into a vehicle interior, comprising: a vehicle windshield comprising a light-adjusting material that is colored in response to ultraviolet light and decolorized in response to at least one of visible light or heat; a light irradiation unit that irradiates the windshield with ultraviolet light from inside the vehicle; and a control unit that controls the irradiation of ultraviolet light by the light irradiation unit based on an irradiation pattern including the illuminance and irradiation time of the ultraviolet light, wherein the control unit alternately modulates the illuminance of the ultraviolet light irradiated onto the windshield from the light irradiation unit between one state and another state.

[0008] According to this disclosure, in a windshield containing a photochromic material, the deterioration of the photochromic material is suppressed, and glare can be prevented while ensuring the driver's field of vision.

[0009] This is a block diagram showing an example of the schematic configuration of a dimming device according to one embodiment of the present disclosure. This is a diagram showing an example of the arrangement of each component of the dimming device according to one embodiment. This is a diagram illustrating an example of the change in the light transmittance of the windshield when dimming by the dimming device. This is a cross-sectional view and a front view showing an example of the schematic configuration of the windshield in a dimming device according to one embodiment. This is a cross-sectional view showing another example of the schematic configuration of the windshield in a dimming device according to one embodiment. This is a diagram showing an example of the irradiation pattern of ultraviolet light in a dimming device according to one embodiment. This is a diagram showing another example of the irradiation pattern of ultraviolet light in a dimming device according to one embodiment. This is a diagram illustrating an example of the coloring behavior of a photochromic material. This is a diagram illustrating an example of the decolorization behavior of a photochromic material. This is a flowchart illustrating an example of the operation of a dimming device according to one embodiment. This is a graph illustrating the effects of an embodiment by comparing an embodiment with a comparative example of one embodiment. This is a flowchart illustrating an example of the operation of a dimming device according to the above modified example.

[0010] (Embodiment) (Configuration) The dimming device according to the embodiment of the present disclosure will be described below with reference to the drawings. The following figures are schematic diagrams, and the size and shape of each part have been exaggerated or simplified as appropriate to facilitate understanding. First, the configuration of the dimming device according to the embodiment will be described with reference to Figures 1A and 1B. The dimming device 10 provided in the vehicle 1 has a dimming function that adjusts the intensity (light quantity) of external light (visible light) such as sunlight that enters the vehicle interior 1a from the outside. As shown in Figure 1A, the dimming device 10 includes a windshield 11, a light irradiation unit 30, an external illuminance measuring unit 60, a control unit 70, and a storage unit 80.

[0011] The windshield 11 is a front windshield for a vehicle, positioned planarly on the front side of the vehicle 1, i.e., in front of the driver, and includes a light-adjusting member 20 that can change the light transmittance. The windshield 11 has a multi-layer structure, with the light-adjusting member 20 as one of the layers.

[0012] The dimming member 20 is a sheet-like or plate-like member and is provided on the windshield 11. The dimming member 20 is formed by including a dimming material, and the action of this dimming material changes the visible light transmittance in the windshield 11, thereby preventing glare from the light entering the vehicle interior 1a from the windshield 11.

[0013] The dimming member 20, which includes a dimming material, has optical properties that cause it to change color in response to ultraviolet light and to decolorize in response to at least one of visible light or heat. When the dimming material in the dimming member 20 changes color, its visible light transmittance (hereinafter also simply referred to as "light transmittance") decreases, and when it decolorizes, its light transmittance increases (restores). Therefore, the dimming member 20 has a photoresponsiveness in which its light transmittance decreases upon reception of ultraviolet light and increases upon reception of at least one of visible light or heat. For example, when the dimming member 20 is irradiated with ultraviolet light, it changes color (light transmittance decreases), and when the ultraviolet irradiation stops, it decolorizes (light transmittance increases) in response to at least one of sunlight or temperature. Note that when decolorizing, not only the outside temperature but also the temperature inside the vehicle compartment 1a may have an effect.

[0014] Thus, the windshield 11 contains a light-modulating material that decreases in light transmittance in response to ultraviolet light and increases in light transmittance in response to at least one of visible light or heat. As will be described in more detail later, the light-modulating member 20 is formed by including, for example, a photochromic compound (photochromic material) as the light-modulating material.

[0015] The dimming member 20 has a normal anti-glare region 21 that contributes to normal anti-glare and a temporary anti-glare region 22 that contributes to temporary (as needed) anti-glare. Normal anti-glare refers to, for example, anti-glare from normal sunlight during the day, while temporary anti-glare refers to, for example, anti-glare from very strong sunlight or from light sources other than sunlight (e.g., headlights of oncoming cars).

[0016] The normal anti-glare region 21 is a region that can be continuously colored (a state in which light transmittance is reduced) while the vehicle 1 is in operation, and the temporary anti-glare region 22 is a region that can be temporarily colored (as needed) while the vehicle 1 is in operation. In this embodiment, the photochromic material included in the normal anti-glare region 21 and the photochromic material included in the temporary anti-glare region 22 have different decolorization rates, that is, different rates of increase in light transmittance after ultraviolet irradiation is stopped. Details of the photochromic material will be described later.

[0017] The normal anti-glare area 21 is the upper part (ceiling 2 side) of the two areas obtained by dividing the windshield 11 vertically, and the temporary anti-glare area 22 is the lower part (dashboard 4 side) of these two areas, that is, the area other than the normal anti-glare area 21. The normal anti-glare area 21 corresponds to the upper area 111 of the windshield 11, and the temporary anti-glare area 22 corresponds to the non-upper area 112 of the windshield 11. Therefore, the normal anti-glare area 21 is colored by ultraviolet light irradiated onto the upper area 111, and the temporary anti-glare area 22 is colored by ultraviolet light irradiated onto the non-upper area 112.

[0018] The light irradiation unit 30 irradiates ultraviolet (UV) light onto the windshield 11 equipped with a dimming member 20 from inside the vehicle (inside the passenger compartment 1a). The ultraviolet light from the light irradiation unit 30 causes the windshield 11 (dimming member 20) to become colored, reducing its light transmittance and dimming the interior of the passenger compartment 1a. The light irradiation unit 30 is a UV irradiation device and is installed in a position (for example, on the ceiling 2) where the direction of irradiation of ultraviolet light onto the windshield 11 is below horizontal, as shown in Figure 2. The light irradiation unit 30 is installed, for example, directly on the ceiling 2 or indirectly via a predetermined member. Preferably, the light irradiation unit 30 is installed above the driver (for example, the driver's seat 3). The light irradiation unit 30 also has an ultraviolet (UV) light source unit 31 and a drive unit 32.

[0019] The UV light source unit 31 is a light source that irradiates the windshield 11 with light and is composed of one or more light-emitting elements. Examples of light-emitting elements include, but are not limited to, ultraviolet light-emitting diodes (UV-LEDs) and ultraviolet laser diodes (UV-LDs). The UV light source unit 31 is also connected to a rotating member (not shown) and is rotatable in the vertical and horizontal directions. The drive unit 32 has a light source drive circuit that supplies a drive signal to the UV light source unit 31 regarding the ultraviolet irradiation pattern. The drive unit 32 also has an actuator drive circuit that supplies a drive signal to the actuator of the rotating member regarding the rotation angle. The drive unit 32 generates a drive signal in response to a control signal from the control unit 70 and supplies the drive signal to the UV light source unit 31 and the rotating member.

[0020] In other words, the light irradiation unit 30 changes the irradiation pattern, including whether or not ultraviolet light is emitted (irradiated) by the UV light source unit 31, the intensity of the ultraviolet light, and the irradiation time, based on a drive signal corresponding to a control signal from the control unit 70.

[0021] Furthermore, the light irradiation unit 30 drives the actuator of the rotating member based on the drive signal supplied from the drive unit 32, thereby rotating the UV light source unit 31. In other words, it changes the irradiation angle, i.e., the irradiation range, of the ultraviolet light emitted by the UV light source unit 31. As a result, the light irradiation unit 30 irradiates not only the upper region 111 of the windshield 11 but also the non-upper region 112 with ultraviolet light, and in addition to the normally anti-glare region 21, it can temporarily color the anti-glare region 22 as needed.

[0022] Furthermore, the rotating member that changes the direction of ultraviolet irradiation may be, for example, a member that rotates the light irradiation unit 30 (UV irradiation device) itself. This allows for even more diverse variations in the irradiation range.

[0023] The external illuminance measuring unit 60 is equipped with an illuminance meter and measures the brightness (illuminance) outside the vehicle (outdoors). The external illuminance measuring unit 60 is installed, for example, at the lower part of the windshield 11 on the passenger compartment 1a side (for example, on the instrument panel). The external illuminance measuring unit 60 may be installed at any position on the outdoor side of the vehicle 1, or it may be used in conjunction with the illuminance meter for controlling the lighting of the headlights (automatic lights). The external illuminance measuring unit 60 transmits a signal (illuminance signal) indicating the external illuminance of the vehicle 1 to the control unit 70.

[0024] The control unit 70 comprises one or more processors and memory (RAM and ROM) for storing programs executable by the processors. The control unit 70 is a microcomputer that, for example, reads a program from memory using the processor and executes processing according to the program to realize control and various functions in the dimming device 10. The microcomputer functions as a plurality of information processing circuits (data acquisition unit 71, irradiation control unit 72) in the dimming device 10. These information circuits may be implemented in software or configured with one or more hardware components to execute each information processing. Furthermore, the control unit 70 is not limited to a microcomputer, and a single-board computer or the like can be used.

[0025] The control unit 70 is connected to each part of the dimming device 10 and various sensors and switches of the vehicle 1 so as to be able to communicate information, and can control each part of the dimming device based on the state of the vehicle 1. The control unit 70 is installed, for example, in the vehicle's dashboard 4, but is not limited to that, and may be installed, for example, in the light irradiation unit 30 (ultraviolet irradiation device).

[0026] The control unit 70 controls the dimming inside the vehicle cabin 1a by controlling the change in the light transmittance of the windshield 11. For example, the control unit 70 controls the irradiation of ultraviolet light by the light irradiation unit 30 based on the irradiation mode, which includes the illuminance and irradiation time of the ultraviolet light. There are two types of irradiation modes: a continuous irradiation mode in which ultraviolet light is irradiated onto the light irradiation unit 30 continuously at a constant illuminance for a predetermined time (continuous irradiation), and a modulated irradiation mode in which ultraviolet light is irradiated onto the light irradiation unit 30 while alternatingly modulating the illuminance between one state and another state (modulated irradiation).

[0027] In this disclosure, the light irradiation unit 30 only needs to be capable of modulated irradiation of ultraviolet light onto the windshield 11. Therefore, the control unit 70 only needs to be configured to control the ultraviolet irradiation by the light irradiation unit 30 based on the above-mentioned modulated irradiation mode, that is, to alternately modulate the illuminance of the ultraviolet light irradiated onto the windshield from the light irradiation unit 30 between one state and another state.

[0028] In the above modulated irradiation configuration, the irradiance of ultraviolet light emitted from the light irradiation unit 30 is modulated between one state and another state according to a predetermined modulation pattern. In other words, the control unit 70 modulates the irradiance of ultraviolet light emitted from the light irradiation unit 30 to the windshield 11 based on a predetermined modulation pattern.

[0029] For example, the modulation pattern is such that state 1 is the ON state where ultraviolet light is irradiated from the light irradiation unit 30, and state 2 is the OFF state where ultraviolet light is not irradiated from the light irradiation unit 30 (ultraviolet irradiance = 0 mW / cm²). ２ ) and the on state and the off state are alternately modulated in an intermittent irradiation pattern. Alternatively, for example, the modulation pattern may be a strong irradiation state in which one state is irradiated with relatively strong ultraviolet light from the light irradiation unit 30, and the other state is a weak irradiation state in which ultraviolet light of relatively weak irradiation (weaker irradiation than the strong irradiation state) is irradiated from the light irradiation unit 30, and the strong and weak irradiation states are alternately modulated in a strong-weak irradiation pattern.

[0030] The control unit 70 supplies control signals to the drive unit 32 of the light irradiation unit 30 indicating the irradiation mode (illuminance, irradiation time) and irradiation range. As a result, the light irradiation unit 30 irradiates ultraviolet light within the irradiation range indicated by the control signals, according to the irradiation mode indicated by the control signals. The control unit 70 may also supply control signals to the drive unit 32 of the light irradiation unit 30 to control whether or not ultraviolet light is emitted from the UV light source unit 31.

[0031] The memory unit 80 stores various data used by the control unit 70 to control each component of the dimming device 10. For example, the memory unit 80 stores dimming data 80a as data used for dimming control by the control unit 70. In this example, the dimming data 80a consists of continuous data 81 used for dimming control in continuous irradiation mode and modulated data used for dimming control in modulated irradiation mode. Note that the dimming data 80a only needs to include modulated data.

[0032] The memory unit 80 stores multiple continuous irradiation modes as continuous data 81 from the dimming data 80a, which include at least the illuminance and irradiation time of ultraviolet light for controlling continuous irradiation by the light irradiation unit 30. The continuous data 81 is data that associates each continuous irradiation mode with illuminance data indicating the illuminance (brightness) outside the vehicle 1. In other words, the memory unit 80 stores multiple continuous data 81 composed of combinations of illuminance data and continuous irradiation modes.

[0033] The illuminance data in the continuous data 81 is numerical data that shows the expected external illuminance (lx) for each environmental condition such as season, weather, and time of day (e.g., morning, noon, afternoon). The illuminance data in the continuous data 81 corresponds to the ultraviolet irradiation pattern required to change the windshield 11 from a decolorized state to a colored state suitable for anti-glare under the external illuminance environment indicated by the illuminance data. The illuminance data in the continuous data 81 may be a fixed value, but it is preferable to set it as a numerical range considering the amount of data in the continuous data 81.

[0034] The memory unit 80 also stores multiple modulation irradiation modes as modulation data 82, which include at least the illuminance and irradiation time of ultraviolet light for controlling the modulation irradiation by the light irradiation unit 30. The modulation irradiation mode in the modulation data 82 will correspond to the modulation pattern of the illuminance. For example, when the illuminance of ultraviolet light is modulated by the intermittent irradiation pattern, the modulation irradiation mode in the modulation data 82 may include at least the illuminance and irradiation time of ultraviolet light in the ON state (ON time) and the time to be in the OFF state (OFF time to stop ultraviolet light irradiation). The modulation irradiation mode may include the illuminance of ultraviolet light in the OFF state (0 mW / cm²). ２ ) may include.

[0035] When the modulation pattern is the intensity modulation irradiation pattern, the modulation data may include, as the modulation irradiation mode, the illuminance and irradiation time of ultraviolet rays in the strong irradiation state, and the illuminance and irradiation time of ultraviolet rays in the weak irradiation state.

[0036] The modulation data 82 stored in the storage unit 80 is data in which each modulation irradiation mode is associated with illuminance data indicating the outdoor illuminance (brightness) of the vehicle 1. That is, the storage unit 80 stores a plurality of modulation data 82 constituted by combinations of illuminance data and modulation irradiation modes. The illuminance data among the modulation data 82 is numerical data indicating the same external illuminance (lx) as the illuminance data in the continuous data 81. The illuminance data in the modulation data 82 is associated with a modulation irradiation mode as an irradiation mode of ultraviolet rays for maintaining the windshield 11 in a coloring state suitable for anti-glare in an environment of the external illuminance indicated by the illuminance data. Note that the illuminance data in the modulation data 82 may be a fixed value, but considering the data amount of the modulation data 82, it is preferably a numerical range.

[0037] Next, the information processing circuit included in the control unit 70 will be described. The control unit 70 includes a data acquisition unit 71 and an irradiation control unit 72. The data acquisition unit 71 acquires data related to dimming control from each device that can communicate with the control unit, and outputs it to the irradiation control unit 72. For example, the data acquisition unit 71 acquires an illuminance signal indicating the external illuminance from the external illuminance measurement unit 60, and outputs it to the irradiation control unit 72.

[0038] The irradiation control unit 72 reads out the dimming data 80a from the storage unit 80, and controls the irradiation of ultraviolet rays by the light irradiation unit 30 based on the illuminance and irradiation time indicated by the irradiation mode of the read dimming data 80a. The irradiation control unit 72 reads out the irradiation mode of the dimming data 80a (continuous data 81, modulation data 82) corresponding to the external illuminance from the storage unit 80 based on the illuminance signal output by the data acquisition unit 71.

[0039] The irradiation control unit 72 generates a control signal indicating the illuminance and irradiation time included in the read irradiation mode (continuous irradiation mode, modulated irradiation mode), and supplies it to the light irradiation unit 30 (drive unit 32). Thereby, under the control of the control unit 70, the light irradiation unit 30 irradiates the windshield 11 with ultraviolet rays in an irradiation mode (illuminance, irradiation time) corresponding to the current outdoor illuminance. That is, the control unit 70 can control the ultraviolet ray irradiation by the light irradiation unit 30 according to the outdoor illuminance by using the dimming data 80a, and contribute to energy saving by minimizing the irradiation amount of ultraviolet rays. That is, the dimming device 10 can change the light transmittance of the windshield 11 according to various environmental conditions and perform dimming in the passenger compartment 1a.

[0040] Hereinafter, ultraviolet irradiation control according to each irradiation mode (continuous irradiation mode, modulated irradiation mode) will be described in detail with reference to FIG. 2. FIG. 2 is a diagram for explaining the change in the light transmittance of the windshield 11 during dimming (when irradiating ultraviolet rays) in the dimming device 10. The horizontal axis represents the irradiation time of ultraviolet rays by the light irradiation unit 30, and the vertical axis represents the light transmittance (%) of the windshield 11.

[0041] The irradiation control unit 72 controls the ultraviolet ray irradiation in the light irradiation unit 30 based on the continuous data 81 (continuous irradiation mode according to the external illuminance) during the period Pr from the start of dimming. As shown in FIG. 2, when continuous irradiation is performed from the light irradiation unit 30 to the windshield 11 during the period Pr, the dimming member 20 in the windshield 11 quickly colors to a coloring state suitable for anti-glare, and the light transmittance of the windshield 11 can be controlled to a value (target value) suitable for anti-glare. That is, the irradiation control unit 72 performs dimming control to color the windshield 11 at the start of dimming (bleached state) and quickly reach the target value of the light transmittance based on the continuous data 81 including the continuous irradiation mode.

[0042] In this embodiment, the irradiation control unit 72 uses continuous data 81 to control the continuous irradiation of ultraviolet light in an irradiation mode (irradiation intensity, irradiation time) corresponding to the outdoor illuminance, thereby bringing the light transmittance of the windshield 11 to a target value. By controlling the light transmittance of the windshield 11 to a target value (to achieve a colored state suitable for anti-glare), the luminous transmittance of the windshield 11 during coloring (dimming) can be set to a specific range. Here, luminous transmittance is a value defined by JIS T7333:2018. The luminous transmittance of the windshield 11 during coloring (dimming) changes depending on the coloring or decolorization of the dimming material in the dimming member 20, i.e., the light transmittance.

[0043] The control of ultraviolet irradiation using continuous data 81 will now be explained in more detail. The irradiation control unit 72 identifies the illuminance data corresponding to the external illuminance indicated by the illuminance signal from the continuous data 81, and reads the continuous irradiation pattern associated with the identified illuminance data from the storage unit 80. The irradiation control unit 72 generates a control signal indicating the illuminance and irradiation time included in the read continuous irradiation pattern and supplies it to the light irradiation unit 30 (drive unit 32). As a result, the light irradiation unit 30 can continuously irradiate the windshield 11 with ultraviolet light according to the irradiation time (period Pr) and illuminance indicated by the continuous irradiation pattern corresponding to the current outdoor illuminance, and quickly reach the target value of light transmittance. Note that the control signal indicating the irradiation time in continuous irradiation may be a control signal indicating the length of the irradiation time (seconds) when the irradiation time is measured in the light irradiation unit 30. Also, when the irradiation time is measured in the irradiation control unit 72, it may be a control signal indicating the start and end of the irradiation time.

[0044] Furthermore, the irradiation control unit 72 controls ultraviolet irradiation in the light irradiation unit 30 based on the modulation data 82 (modulated irradiation mode according to external illuminance) during the period Pm after the light transmittance of the windshield 11 has reached the target value.

[0045] As shown in Figure 2, modulated irradiation is performed on the windshield 11 from the light irradiation unit 30 during period Pm, thereby maintaining the colored state of the dimming member 20. This ensures that the light transmittance of the windshield 11 is stably maintained at the target value when it is colored (dimmed). In other words, the irradiation control unit 72 modulates the illuminance of the ultraviolet light irradiated by the light irradiation unit 30 so that the visible transmittance of the windshield 11 during coloring (dimming) is maintained within a predetermined range. This ensures that even when the windshield 11 is colored, glare can be prevented while maintaining the driver's field of vision of the vehicle 1. Furthermore, as will be described in more detail later, by maintaining the light transmittance at the target value and controlling the visible transmittance to be constant within the above-mentioned specific range during the period (period Pm) in which the colored state of the windshield 11 is maintained, the deterioration of the dimming member 20 can be suppressed more reliably.

[0046] Here, the specific range of luminous transmittance described above will be explained in detail. To ensure the driver's field of vision, it is preferable that the luminous transmittance of the windshield 11 when it is tinted be 5% or more. Furthermore, to provide an anti-glare effect, it is preferable that the luminous transmittance of the windshield 11 when it is tinted be 20% or less. This ensures that the driver's field of vision is more reliably ensured while also providing a more reliable anti-glare effect. Moreover, it is more preferable that the luminous transmittance of the windshield 11 when it is tinted be within the range of 8% to 18%, in line with Category 3 spectacle lenses specified in JIS T7333:2018. This ensures that the driver's field of vision is more reliably ensured even when the windshield 11 is tinted, and further improves the anti-glare effect.

[0047] The control of ultraviolet irradiation using modulated data 82 will be explained in more detail. The irradiation control unit 72 identifies the illuminance data corresponding to the external illuminance indicated by the illuminance signal from the modulated data 82, and reads the modulated irradiation mode associated with the identified illuminance data from the storage unit 80. The irradiation control unit 72 generates a control signal indicating the illuminance and irradiation time included in the read modulated irradiation mode and supplies it to the light irradiation unit 30 (drive unit 32). If the modulation pattern of the modulated irradiation mode is an intermittent irradiation pattern, the irradiation control unit 72 generates a control signal indicating the illuminance and irradiation time of ultraviolet light in the ON state (ON time) and the OFF time to stop ultraviolet irradiation and turn it OFF. If the modulation pattern of the modulated irradiation mode is a strong / weak irradiation pattern, the irradiation control unit 72 generates a control signal indicating the illuminance and irradiation time of ultraviolet light in the strong irradiation state and the illuminance and irradiation time of ultraviolet light in the weak irradiation state included in the read modulated irradiation mode. As a result, the light irradiation unit 30 can maintain the light transmittance at the target value by modulating ultraviolet light irradiation to the windshield 11 according to the irradiation time (period Pr) and illuminance indicated by the modulated irradiation mode corresponding to the current outdoor illuminance.

[0048] Thus, the irradiation control unit 72 may continuously irradiate the windshield 11 with ultraviolet light from the light irradiation unit 30 without modulating the illuminance of ultraviolet light until the light transmittance of the windshield 11 reaches a predetermined target value (period Pr), i.e., until it determines that the target value has not been reached. When it determines that the light transmittance of the windshield 11 has reached the target value, it may modulate the illuminance of the ultraviolet light irradiated by the light irradiation unit 30. In other words, by continuously irradiating the windshield 11 at a constant illuminance, the light transmittance is reduced to the target value by coloring the windshield 11, and by modulated irradiation, the colored state of the windshield 11 is maintained and the light transmittance is kept at the target value. As a result, the dimming device 10 can suppress the deterioration of the dimming member 20 by modulated irradiation, color the windshield 11 (dimming member 20) in a short time, and quickly exert an anti-glare effect.

[0049] Here, the control of ultraviolet irradiation by the light irradiation unit 30 in the modulated irradiation mode will be explained in more detail. It is preferable that the irradiation control unit 72 supplies a control signal to the light irradiation unit 30 so that the modulation period (modulation period) of the ultraviolet irradiance in the modulated irradiation mode is constant. In other words, in each modulation pattern of the modulated irradiation mode (intermittent irradiation pattern or strong / weak irradiation pattern), it is preferable that the irradiance of the ultraviolet light irradiated by the light irradiation unit 30 is modulated at a constant period. This allows the irradiation control unit 72 to modulate the irradiance of the ultraviolet light irradiated by the light irradiation unit 30 with high precision. The modulation period is defined as the time from one state (on state / strong irradiation state) to another state (off state / weak irradiation state) and back to one state. In other words, one set of on state / off state in the intermittent irradiation pattern and one set of strong irradiation state / weak irradiation state in the strong / weak irradiation pattern constitutes one period. The modulation period is defined by the irradiation time for each state (for the off state, the irradiation stop time).

[0050] For example, the irradiation control unit 72 may supply a control signal to the light irradiation unit 30 at a specific frequency in each modulation irradiation mode (intermittent irradiation pattern, intensity irradiation pattern). This improves the accuracy of the modulation period. For example, in each modulation pattern in the modulation irradiation mode, the frequency that defines the modulation period of ultraviolet irradiance is preferably 30 Hz or higher, and more preferably 50 Hz or higher. By setting the above frequency to 30 Hz or higher, the visibility of changes in ultraviolet irradiance (flickering) in the light source unit 31 of the light irradiation unit 30 can be suppressed. Furthermore, by setting the above frequency to 50 Hz or higher, the visibility of flickering in the light source unit 31 can be suppressed more reliably. The frequency that defines the modulation period is also called the "repetition frequency".

[0051] For example, the irradiation control unit 72 may use a pulse generator, a waveform generator, or a function generator when generating a control signal indicating the modulated irradiation mode for each modulation pattern. This improves the accuracy of the frequency that defines the modulation period. For example, when generating a control signal indicating the modulated irradiation mode for an intermittent irradiation pattern, the irradiation control unit 72 may, for example, set an on-time and an off-time in a pulse generator and supply a control signal to the light irradiation unit 30 at a specific frequency (for example, 30 Hz or higher). As a result, the illuminance of the ultraviolet light emitted by the light irradiation unit 30 is modulated in a rectangular wave manner. That is, the modulation between the on-state and the off-state becomes rectangular wave-like. Therefore, the on-state and the off-state can be clearly switched.

[0052] For example, when generating a control signal indicating a modulated irradiation pattern of strong and weak irradiation, the irradiation control unit 72 may set the irradiation time in the strong irradiation state and the irradiation time in the weak irradiation state in a waveform generator, function generator, etc., and supply a control signal to the light irradiation unit 30 at the above-mentioned specific frequency (for example, 30 Hz or higher). This modulates the intensity of the ultraviolet light irradiated by the light irradiation unit 30 in a sinusoidal manner in the strong and weak irradiation pattern. That is, the modulation of the strong irradiation state and the weak irradiation state is sinusoidally modulated. In this case, for example, the midpoint (half value) between the peak irradiance (maximum irradiance) in the strong irradiation state and the peak irradiance (minimum irradiance) in the weak irradiation state may be set to 0, with a positive amplitude representing the strong irradiation state and a negative amplitude representing the weak irradiation state.

[0053] This allows for a smooth change in illuminance from the peak illuminance (maximum illuminance) in the strong illumination state to the peak illuminance (minimum illuminance) in the weak illumination state. As a result, changes in the color state of the windshield 11 become less visible, and the color state of the windshield 11 can be maintained more reliably and consistently. Therefore, the light transmittance of the windshield 11 can be maintained more reliably and consistently. Note that the modulation between the strong illumination state and the weak illumination state may be triangular wave. In this case as well, changes in the color state of the windshield 11 become less visible, and the color state of the windshield 11 can be maintained more reliably and consistently.

[0054] Furthermore, the irradiation control unit 72 can control the irradiation range of ultraviolet light emitted by the light irradiation unit 30 (the colored area on the windshield 11) according to the outdoor illuminance. In principle, the control unit 70 determines the irradiation range of ultraviolet light from the light irradiation unit 30 to be the upper region 111 of the windshield 11. In certain cases (for example, when the sun is low in the sky in the morning or evening and sunlight directly enters the occupants' faces from the non-upper region 112), the control unit 70 may determine the irradiation range of ultraviolet light from the light irradiation unit 30 to be the upper region 111 and the non-upper region 112 of the windshield 11, that is, the entire surface of the windshield 11 on the inside of the passenger compartment 1a (hereinafter referred to as "the entire surface of the windshield 11").

[0055] For example, the control unit 70 may control the illumination range based on outdoor illuminance, or it may determine whether or not to include the temporary anti-glare area 22 in the illumination range based on the current light transmittance in the normal anti-glare area 21 (upper area 111) and the temporary anti-glare area 22 (non-upper area 112), respectively. If control is performed based on light transmittance, the dimming device 10 only needs to be equipped with a visible light transmittance meter.

[0056] The irradiation control unit 72 generates a control signal indicating the determined irradiation range and supplies it to the drive unit 32 of the light irradiation unit 30. This controls the irradiation range of ultraviolet light irradiated from the light irradiation unit 30 onto the windshield 11 depending on whether the vehicle 1 is in motion or not.

[0057] Thus, in the dimming device 10, the windshield 11 contains a dimming material (for example, a photochromic material), and the windshield 11 is colored and the light transmittance is adjusted as appropriate by ultraviolet irradiation performed by the light irradiation unit 30 based on a control signal from the control unit 70. In other words, the dimming device 10 adjusts the amount of ambient light incident into the vehicle interior 1a by changing the light transmittance of the dimming member 20, thereby dimming the light inside the vehicle interior 1a.

[0058] Next, the configuration of the windshield 11 will be described in detail with reference to Figure 3A. As shown on the left side of Figure 3A, the windshield 11 has a multi-layer structure and includes a transparent substrate 12 made of glass, a light-adjusting member 20, and a specific light-blocking member 13. The transparent substrate 12 can be made of, for example, green-colored glass and may have properties that absorb heat and block ultraviolet rays. The light-adjusting member 20 and the specific light-blocking member 13 are arranged adjacent to each other between two opposing transparent substrates 12 and are provided as an interlayer sandwiched between the transparent substrates 12.

[0059] The specific light-blocking member 13 is positioned in front of the dimming member 20, i.e., on the outdoor side. The specific light-blocking member 13 is a sheet-like member with a base material such as PVB (polyvinyl butyral) resin, and exhibits high adhesion even when the windshield 11 is subjected to a strong impact, preventing the transparent substrate 12 from shattering. The specific light-blocking member 13 is also coated (or mixed) with an ultraviolet-blocking material that blocks at least ultraviolet rays. This blocks ultraviolet rays that enter the dimming member 20 from outside the vehicle 1, prevents unintended discoloration of the dimming member 20, and reduces deterioration of interior parts of the passenger compartment 1a and sunburn of occupants due to exposure to ultraviolet rays. Preferably, the specific light-blocking member 13 blocks 99.9% or more of light in the ultraviolet wavelength range.

[0060] The specific light-blocking member 13 is preferably configured to block infrared rays in addition to ultraviolet rays. In other words, it is preferable that an infrared-blocking material that blocks infrared rays is applied (or mixed) to it. This reduces the heat felt by occupants due to exposure to infrared rays inside the vehicle interior 1a. The specific light-blocking member 13 is preferably configured to block 90% or more of light in the infrared wavelength range, for example.

[0061] The dimming member 20 is positioned behind the specific light blocking member 13, i.e., on the side facing the vehicle interior 1a. The dimming member 20 is made of a resin composition containing a photochromic compound. The dimming member 20 is, for example, a sheet or plate-shaped member based on a PVB resin containing a photochromic compound. The sheet or plate-shaped member may be sandwiched between transparent substrates or attached to the vehicle interior side of the transparent substrate.

[0062] As shown on the right side of Figure 3A, the dimming member 20 has a surface area that is almost identical to that of the rearmost (passenger compartment 1a) transparent substrate 12, and is positioned planarly in front of the driver of the vehicle 1. Therefore, ultraviolet light emitted from the light irradiation unit 30 is irradiated onto the dimming member 20 via the surface of the rearmost transparent substrate 12 (the surface 11a of the windshield 11).

[0063] Furthermore, the area of ​​the normal anti-glare region 21 in the dimming member 20 is smaller than the temporary anti-glare region 22. Specifically, the normal anti-glare region 21 is the area above the driver's line of sight in the vehicle 1, while the temporary anti-glare region 22 is the area other than the normal anti-glare region 21, including the driver's line of sight (the area below the normal anti-glare region 21). As a result, it is possible to maintain a state of low visible light transmittance (colored state) in the normal anti-glare region 21 while keeping the driver's field of vision good, thereby reducing glare while driving.

[0064] Here, the distribution of the normal anti-glare area 21 and the temporary anti-glare area 22 will be explained in more detail. As shown in the front view on the right side of Figure 3A, in this example, it is preferable that the normal anti-glare area 21 (upper area 111) is separated from the temporary anti-glare area 22 by a virtual line L10 located above a virtual line L1 that passes through point P1, which indicates the reference position of the driver's line of sight. Point P1 is the point obtained by projecting point V1, which is the reference point for test areas A and B as defined in the annex of JIS R3212 (1998), onto the windshield 11.

[0065] In the above annex, point V1 is defined as follows: • Point V1 with point R as the origin: A point located 68 mm in the +X direction, 5 mm in the +Y direction, and 665 mm in the +Z direction from point R. • Point R (Seating Reference Point): Point R is the position of point H (hip joint point of the model) or an equivalent design standard position when a human body model specified in ISO 6549 (1980) is seated on the seat (for seats adjustable fore-aft, it is at the rearmost position; for seats adjustable for height, it is at the lowest position; for seats where the seat back angle and seat cushion mounting angle are adjustable, it is at the design standard angle). • X-axis: A horizontal plane passing through point R, parallel (lengthwise) to the vehicle centerline, passing through point R.

[0066] +X: Rear direction of the vehicle, -X: Front direction of the vehicle; Y-axis: Horizontal plane passing through point R, perpendicular to the X-axis. +Y: Right direction of vehicle movement, -Y direction: Left direction of vehicle movement; Z-axis: Vertical plane passing through point R, perpendicular to the X and Y axes. +Z: Up direction of vehicle, -Z direction: Down direction of vehicle

[0067] • Vehicle centerline: This is defined as the straight line when the vehicle is placed on a flat surface. (1) For vehicles with four or more wheels, it is the straight line passing through the center of the line segment connecting the design center points of the left and right front wheels and the left and right rear wheels. (2) For three-wheeled vehicles (one front wheel), it is the straight line passing through the midpoint of the line segment connecting the design center points of the left and right rear wheels and the design center point of the front wheel (the same applies to vehicles with one rear wheel). (3) For vehicles with caterpillar tracks, it is the straight line equidistant from the centerlines of the left and right caterpillar tracks.

[0068] In this embodiment, it is preferable that the normal anti-glare region 21 be the region above the virtual straight line L1 passing through point P1, that is, the region that does not include point P1. In other words, it is preferable that the normal anti-glare region 21 (upper region 111) of the windshield 11 is the region above the driver's line of sight of the vehicle 1. This makes it possible to continuously provide anti-glare while maintaining good visibility for the driver while driving.

[0069] For example, it is preferable that the area above the virtual line L10, which is parallel to the virtual line L1 and located above the virtual line L1, be designated as the normal anti-glare area 21, excluding point P1. As described above, by coloring the temporary anti-glare area 22 (non-upper area 112) that includes point P1 (driver's eye level) as needed, temporary anti-glare can be provided against very strong sunlight or light sources other than sunlight, such as the headlights of oncoming vehicles. Furthermore, by designating the area above point P1 as the normal anti-glare area 21, it is possible to reliably prevent glare from sunlight while ensuring the driver's field of vision, even in vehicles where the windshield 11 extends to the roof 2.

[0070] Furthermore, for example, if the windshield 11 does not extend to the ceiling 2, the vertical width (height) of the anti-glare area 21 may be within 20% of the vertical width of the windshield 11, i.e., the height H of the windshield 11. This minimizes the colored area of ​​the windshield 11 while the vehicle 1 is in motion, reducing glare while ensuring the driver's field of vision is sufficient to see the external environment.

[0071] Furthermore, in the colored state in the normal anti-glare region 21 and the temporary anti-glare region 22, that is, when dimming is controlled by the control unit 70 (irradiation control unit 72), the light transmittance is controlled to a target value based on the dimming data 80a (continuous data 81, modulated data 82), so that the luminous transmittance is preferably 5% to 20%, and more preferably 8% to 18%. This ensures that even when the windshield 11 is in a colored state while the vehicle 1 is in operation, glare is reliably reduced while ensuring the driver's field of vision, and the deterioration of the dimming material, i.e., the photochromic compound, contained in the windshield 11 (dimming member 20) can be suppressed. For example, if the area above point P1 is the normal anti-glare region 21, glare can be more reliably reduced by setting the luminous transmittance to about 5%. Also, if point P1 is included in the normal anti-glare region 21, glare can be reliably reduced while ensuring the driver's field of vision by setting the luminous transmittance to 8% to 18%.

[0072] Furthermore, with respect to the photochromic material (e.g., photochromic material) that reacts to ultraviolet light and changes color in the photochromic member 20, the photochromic material constituting the normal anti-glare region 21 (upper region 111) may have a lower light transmittance when colored than the photochromic material constituting the temporary anti-glare region 22 (non-upper region 112). In other words, the target value of the light transmittance when colored in the normal anti-glare region 21 may be set lower than that of the temporary anti-glare region 22, thereby lowering the luminous transmittance in the normal anti-glare region 21 compared to the temporary anti-glare region 22. This reduces the amount of sunlight incident in the upper region 111 of the windshield, where there is a high probability of sunlight near noon, which is necessary for anti-glare. In addition, the increase in light transmittance in the non-upper region of the windshield 11, including point P1 which indicates the reference point of the driver's line of sight, is appropriately suppressed, ensuring visibility.

[0073] The light transmittance of the windshield 11 when colored may be controlled, for example, by the concentration of the photochromic material in each region of the photochromic member 20 (normal anti-glare region 21, temporary anti-glare region 22), or by the thickness of each region. For example, the concentration of the photochromic material in the normal anti-glare region 21 may be higher than the concentration of the photochromic material in the temporary anti-glare region 22, or the thickness of the normal anti-glare region 21 may be increased compared to the thickness of the temporary anti-glare region 22. Alternatively, the light transmittance of the windshield 11 when colored may be controlled by the illuminance of ultraviolet light emitted from the light irradiation unit 30 under the control of the control unit 70 (irradiation control unit 72).

[0074] In the case where the windshield 11 extends to the ceiling 2 in the vehicle 1, the entire area above point P1, which indicates the reference point of the driver's line of sight, may be designated as the normal anti-glare area 21, and the dimming member 20 may be formed such that the light transmittance of the normal anti-glare area 21 when colored is lower than that of the temporary anti-glare area 22.

[0075] Furthermore, the temporary anti-glare region 22 in the dimming member 20 is the region that includes point P1, which indicates the reference position of the driver's line of sight, that is, the region within the driver's field of view, and the light transmittance of the temporary anti-glare region 22 when it is not colored (completely colorless) should be 70% or more. This ensures that the field of view necessary for the driver to check traffic conditions, etc.

[0076] As will be described in more detail later, in the dimming device 10 according to this embodiment, of the regions obtained by dividing the windshield 11 into two upper regions, the first region in which the dimming material (photochromic material) has a fast decolorization rate is the non-upper region 112 corresponding to the temporary anti-glare region 22, and the second region in which the decolorization rate is slower than that of the first region is the upper region 111 corresponding to the normal anti-glare region 21. In other words, the photochromic material included in the non-upper region 112 (temporary anti-glare region 22) corresponding to the first region may have a faster decolorization rate than the photochromic material included in the upper region 111 (normal anti-glare region 21) corresponding to the second region. To put it another way, in this embodiment, the normal anti-glare region 21 (upper region 111 of the windshield 11) of the dimming member 20 may contain a dimming material (for example, a photochromic compound) whose rate of increase in light transmittance (decolorization rate) is slower than that of the temporary anti-glare region 22 (non-upper region 112).

[0077] As a result, the light transmittance of the normal anti-glare region 21, which corresponds to the upper region 111 where the amount of incident sunlight is relatively high, remains reduced (colored) for a long time even after ultraviolet irradiation stops. On the other hand, the temporary anti-glare region 22, which corresponds to the non-upper region 112, quickly becomes colorless, ensuring visibility. Therefore, it is possible to prevent glare while ensuring the driver's visibility, further contributing to energy saving by suppressing the amount of ultraviolet irradiation, and suppressing deterioration of the windshield. In particular, if the non-upper region 112 is a region that includes point P1 which indicates the reference position of the driver's line of sight, the rapid color removal ensures that both glare prevention and the driver's visibility are ensured more reliably.

[0078] Note that the windshield 11 is not limited to the configuration illustrated in Figure 3A. As shown in Figure 3B, a specific light-blocking member 13 may be placed at the position where the interlayer of the windshield 11 is positioned, and a light-adjusting member 20 may be placed on the outermost surface of the windshield 11 on the vehicle interior 1a side. In this case, the light-adjusting member 20 is attached to the surface of the transparent substrate 12 on the vehicle interior 1a side. When installing the light-adjusting member 20 in the vehicle interior 1a, a hard coat may be applied to improve abrasion resistance and scratch resistance while maintaining its original properties. The example configuration of the windshield 11 shown in Figure 3B allows for easy placement and replacement of the light-adjusting member 20 compared to the example configuration shown in Figure 3A. For example, the light-adjusting device 10 may further include side windshields 110 (see Figure 1B) containing a photochromic compound, which are provided on the left and right sides of the windshield 11. In this case, the side windshields 110 may contain a photochromic compound similar to that of the anti-glare region 21 and contribute to continuous anti-glare during driving.

[0079] Next, the irradiation range of ultraviolet rays on the windshield 11 will be described. In this embodiment, when the vehicle 1 is in operation, the dimming device 10 will, in principle, irradiate the upper region 111 of the surface 11a of the windshield 11 with ultraviolet rays from the light irradiation unit 30, and depending on the ambient light conditions (intensity of sunlight, presence of light sources other than sunlight), etc., the entire surface 11a of the windshield 11 will be irradiated with ultraviolet rays from the light irradiation unit 30. In other words, as shown in Figure 3A, when the vehicle is in operation, the light irradiation unit 30 irradiates the upper region 111 (normal anti-glare region 21) with ultraviolet rays 31a, and if necessary, as shown in Figure 3B, irradiates the entire surface 11a of the windshield 11 (normal anti-glare region 21 and temporary anti-glare region 22) with ultraviolet rays 31a.

[0080] As shown in Figure 4A, with the illumination range, when the vehicle 1 is in operation, only the normal anti-glare area 21 is colored, and the light transmittance is reduced only in the upper area 111, thereby reducing glare while ensuring the driver's visibility. Furthermore, with the illumination pattern shown in Figure 4B, both the normal anti-glare area 21 and the temporary anti-glare area 22 are colored, reducing the light transmittance across the entire surface of the windshield 11. As a result, the incidence of external light into the passenger compartment 1a is suppressed over a wide area of ​​the windshield 11, thereby more reliably reducing glare for the driver. As described above, the illumination range is determined by the control unit 70 according to the external light conditions, and under the control of the control unit 70, the movable member of the light irradiation unit 30 rotates to irradiate ultraviolet light into the determined illumination range.

[0081] Here, the control unit 70 (irradiation control unit 72) may, during dimming control, perform modulated or continuous irradiation of ultraviolet light from the light irradiation unit 30 to the non-upper region 112 corresponding to the temporary anti-glare region 22, where the decolorization speed is faster than that of the normal anti-glare region 21. In other words, the irradiation control unit 72 may irradiate the non-upper region 112 from the light irradiation unit 30 with ultraviolet light whose illuminance is modulated by a modulation pattern (intermittent irradiation pattern or intensity-variable irradiation pattern), or irradiate with ultraviolet light continuously at a constant illuminance. This allows, for example, continuous irradiation to quickly color the temporary anti-glare region 22, which has a fast decolorization speed, as needed, thereby bringing the light transmittance of the non-upper region 112 of the windshield 11 to a target value. Furthermore, after the light transmittance of the non-upper region 112 reaches the target value, modulated irradiation can stably maintain the light transmittance at the target value. In addition, deterioration of the windshield 11, which includes the dimming material, can be suppressed.

[0082] Furthermore, during dimming control, the irradiation control unit 72 may, for example, modulated ultraviolet irradiation from the light irradiation unit 30 to the upper region 111 corresponding to the normal anti-glare region 21, where the decolorization speed is faster than that of the temporary anti-glare region 22. In other words, the irradiation control unit 72 may irradiate the upper region 111 from the light irradiation unit 30 with ultraviolet light whose illuminance is modulated by a modulation pattern (intermittent irradiation pattern or strong / weak irradiation pattern). This makes it possible to maintain the light transmittance of the upper region 111 of the windshield 11 at a target value while continuously and stably coloring the normal anti-glare region 21, where the decolorization speed is slow, and suppressing the deterioration of the windshield 11, which includes the dimming material.

[0083] Furthermore, in this embodiment, the modulation patterns (intermittent irradiation patterns, intensity-based irradiation patterns) of the modulation irradiation mode in the modulation data 82 may differ for each irradiation range, i.e., between the upper region 111 and the non-upper region 112. In other words, the irradiation control unit 72 may irradiate the non-upper region 112 from the light irradiation unit 30 with ultraviolet light whose illuminance is modulated with a modulation pattern corresponding to the non-upper region 112, based on the modulation data 82. Alternatively, the irradiation control unit 72 may irradiate the upper region 111 from the light irradiation unit 30 with ultraviolet light whose illuminance is modulated with a modulation pattern corresponding to the upper region 111, based on the modulation data 82.

[0084] As described above, in the windshield 11, the decolorization rate of the light-adjusting material included in the light-adjusting member 20, i.e., the recovery rate of visible light transmittance, differs between the upper region 111 and the non-upper region 112. Therefore, for example, the modulation period in the modulated irradiation mode may differ between the upper region 111 and the non-upper region 112. More specifically, the modulation period in the modulated irradiation mode may be set faster than the decolorization rate of the light-adjusting material included in the light-adjusting member 20. This allows the colored state to be maintained by modulated irradiation, so that in an intermittent irradiation pattern, the ON state is reached and ultraviolet irradiation is performed before the irradiation area becomes decolorized. Also, in an intensity-intensity irradiation pattern, ultraviolet irradiation in an intensity state is performed before the irradiation area becomes decolorized. As a result, changes in the colored state become less visible in each irradiation area (upper region 111, non-upper region 112), and modulated irradiation can be performed to maintain light transmittance so that the colored state of each irradiation area appears constant to the human eye.

[0085] Furthermore, for example, the irradiation time in the modulated irradiation mode may differ for each irradiation area. Specifically, the on-state time in the intermittent irradiation pattern corresponding to the region containing a photochromic material with a fast decolorization rate, i.e., the non-upper region 112, may be longer than the on-state time in the intermittent irradiation pattern corresponding to the region containing a photochromic material with a slow decolorization rate, i.e., the upper region 111. In other words, in modulated irradiation of the upper region 111, the on-state time in the intermittent irradiation pattern may be shorter than that of the non-upper region 112.

[0086] Similarly, the duration of the high-intensity irradiation state in the intensity-variable irradiation pattern corresponding to the non-upper region 112 may be longer than the duration of the high-intensity irradiation state in the intensity-variable irradiation pattern corresponding to the upper region 111. In other words, in modulated irradiation of the upper region 111, the duration of the high-intensity irradiation state in the intensity-variable irradiation pattern may be shorter than that of the non-upper region 112.

[0087] In the upper region 111 (normal anti-glare region 21), which is a region where the recovery speed of light transmittance (decolorization speed) is slow, the colored state of the normal anti-glare region 21 lasts longer than that of the temporary anti-glare region 22, even in the off state (state where ultraviolet irradiation is stopped) or the weak irradiation state. Therefore, by shortening the time of the on state or strong irradiation state in the modulation pattern in the upper region 111 compared to the non-upper region 112, energy consumption due to ultraviolet irradiation and deterioration of the light-modulating material contained in the light-modulating member 20 can be suppressed.

[0088] Whether or not vehicle 1 is in operation can be determined by the state of the main switch and shift lever related to starting the engine of vehicle 1. For example, the irradiation control unit 72 may consider vehicle 1 to be in operation if the main switch is ON and the shift lever is in a range other than parking, and may consider it to be in a non-operational state (not in operation (e.g., parked)) if these conditions are not met. The state of the main switch and shift lever can be acquired, for example, by the data acquisition unit 71 and output to the irradiation control unit 72.

[0089] Next, the photochromic compound used in the dimming member 20 will be described. A photochromic compound is a compound whose molecular structure changes in response to light or heat, reversibly producing two isomers with different colors and absorption spectra.

[0090] In this embodiment, the normal anti-glare region 21 (upper region 111 of the windshield 11) of the dimming member 20 contains a photochromic compound with a slower decolorization rate (restoration rate of light transmittance) compared to the temporary anti-glare region 22 (non-upper region 112). Therefore, the increase in light transmittance of the normal anti-glare region 21 is gradual after UV irradiation is stopped, and the colored state can be maintained for a predetermined period even after UV irradiation is stopped. Consequently, as described above, the illuminance and irradiation time of UV light required to maintain the colored state can be suppressed for the normal anti-glare region 21. In other words, by suppressing the illuminance and irradiation time, the cumulative amount of UV light (= illuminance × irradiation time) required to maintain the colored state can be suppressed, contributing to energy saving. By using a photochromic material with a slower decolorization rate in the normal anti-glare region 21 compared to the temporary anti-glare region 22, it is possible to prevent glare while ensuring the driver's visibility, suppress the deterioration of the dimming material contained in the windshield, and, as described above, contribute to energy saving by suppressing the amount of UV irradiation.

[0091] Furthermore, the temporary anti-glare region 22 contains a photochromic compound that decolorizes faster than the normal anti-glare region 21, thereby reducing glare for the driver while quickly securing the driver's field of vision. In this embodiment, for example, the dimming member 20 can use a light-returning type (P-type) photochromic compound or a heat-returning type (T-type) photochromic material. Light-returning type photochromic materials have high thermal stability, and their molecular structure changes reversibly only in response to light. In other words, the dimming device 10 can use a photochromic material that reacts to visible light and increases (decolorizes) the visible light transmittance in response to visible light as the dimming material constituting the windshield 11. In the dimming device 10 according to this embodiment, it is preferable to include at least a light-returning type photochromic compound as the dimming material constituting the windshield 11, and a heat-returning type photochromic compound may also be used in combination.

[0092] Furthermore, heat-recovering photochromic materials stably decolorize upon blocking light or heat, restoring their light transmittance. In other words, the dimming device 10 can use a photochromic material that reacts to heat and increases its visible light transmittance as the dimming material that constitutes the windshield 11.

[0093] First, let's describe the light-reflecting type photochromic material. The light-reflecting type photochromic compound used in the light-adjusting member 20 is not particularly limited, but for example, diarylethene-based, fulgide-based, and other photochromic compounds can be used.

[0094] For example, diarylethene derivatives, as shown in reaction equation (1) below, produce a closed ring form and develop color when irradiated with ultraviolet light, resulting in a change in their absorption spectrum. Specifically, along with the color development, the absorption band of the absorption spectrum appears in the visible light region. Furthermore, when the closed ring form of the diarylethene derivative is irradiated with visible light or infrared light, it reverts to its original open ring form, and along with the decolorization, the absorption spectrum returns to its original state. In other words, the ring-opening and ring-closing reactions occur reversibly due to the action of light, and the optical state changes between a colored state and a transparent state.

[0095]

[0096] As described above, the photochromic compounds contained in the normal anti-glare region 21 and the temporary anti-glare region 22 are different.

[0097] For example, in the temporary anti-glare region 22, a diarylethene derivative in which the substituent R in the above reaction formula (1) is a cyano group (reaction formula (2) below) can be used.

[0098]

[0099] For example, in the anti-glare region 21, a diarylethene derivative (reaction formula (3) below) in which the substituent R in the above reaction formula (1) is a methyl group can be used.

[0100]

[0101] The diarylethene derivative of reaction formula (2) above (hereinafter referred to as "diarylethene derivative A") exhibits a faster decolorization rate than the diarylethene derivative of reaction formula (3) above (hereinafter referred to as "diarylethene derivative B"). Here, the decolorization rate is the speed at which the colored state changes to a transparent state when ultraviolet irradiation is stopped and visible light to infrared light is irradiated (external light is irradiated) (speed of the decolorization reaction).

[0102] For example, in an environment where a windshield 11 containing diarylethene derivative A in the temporary anti-glare region 22 is irradiated with visible light of 550 nm wavelength as ambient light, the light transmittance at the time when ultraviolet irradiation stops, when the degree of coloration of the temporary anti-glare region 22 is at its maximum (light transmittance is at its minimum), is about 5%. Furthermore, after the ultraviolet irradiation stops, the degree of coloration of the temporary anti-glare region 22 gradually decreases (light transmittance gradually increases), and the time until the light transmittance reaches 50% (coloration reduction time) is about 2 seconds. Approximately 5 seconds after the ultraviolet irradiation stops, the light transmittance of the temporary anti-glare region 22 containing diarylethene derivative A exceeds 80%, and the temporary anti-glare region 22 becomes almost colorless.

[0103] For example, when a windshield 11 containing diarylethene derivative B in the normal anti-glare region 21 is irradiated with ultraviolet light at a wavelength of 550 nm, the light transmittance at the time the ultraviolet irradiation stops is about 5%, similar to diarylethene derivative A. On the other hand, the time it takes for the color to gradually decrease in the normal anti-glare region 21 containing diarylethene derivative B is about 30 seconds. Furthermore, after 55 to 60 seconds after the ultraviolet irradiation stops, the light transmittance of the normal anti-glare region 21 exceeds 80%, and it becomes almost colorless.

[0104] Thus, diarylethene derivative A used in the temporary anti-glare region 22 has a color decay time that is 1 / 15 that of diarylethene derivative B, meaning its decolorization speed is 15 times faster than that of diarylethene derivative B. Therefore, diarylethene derivative A can be suitably used in the temporary anti-glare region 22, which includes point P1 that indicates the reference position of the driver's line of sight, and which requires immediate restoration to a transparent state after the cessation of ultraviolet irradiation in order to ensure visibility.

[0105] Furthermore, since diarylethene derivative B has a longer color decay time than diarylethene derivative A (15 times longer), the colored state of the normal anti-glare region 21 is maintained with a shorter irradiation time than the temporary anti-glare region 22. Thus, diarylethene derivative B can be suitably used in the normal anti-glare region 21, which does not include point P1, a reference point for the driver's line of sight, where it is necessary to continuously maintain a colored state and provide anti-glare while the vehicle 1 is in operation, while suppressing the amount of ultraviolet irradiation to contribute to energy saving and suppressing deterioration of the windshield (deterioration of the light-adjusting material).

[0106] Furthermore, since the light-returning photochromic material's light transmittance is restored (decolorized) by light (visible light, infrared light) after UV irradiation stops, the decolorization speed is not affected by temperature (ambient temperature, etc.). Therefore, for example, when a driver requires good visibility, such as when driving on a curved road, the light transmittance is quickly restored by irradiation with strong sunlight or other light sources.

[0107] In this embodiment, the dimming member 20 can use, for example, "DAE1", "DAE12", or "DAE18" (all manufactured by Yamada Chemical Industries, Ltd.) as a light-returning (photoisomer) photochromic material. Of these, those with a slow decolorization speed can be used in the normal anti-glare region 21, and those with a fast decolorization speed can be used in the temporary anti-glare region 22.

[0108] Next, a heat-returning (T-Type) photochromic material will be described. The heat-returning photochromic compound used in the dimming member 20 is not particularly limited, but for example, photochromic compounds such as spiro-based compounds (spiropyran, spirooxazine) can be used. When a heat-returning photochromic material is used in the dimming member 20, a material with a slow decolorization rate should be used in the normal anti-glare region 21, and a material with a fast decolorization rate should be used in the temporary anti-glare region 22.

[0109] For example, spiro compounds, as shown in reaction equation (4) below, isomerize from a closed ring to an open ring when irradiated with ultraviolet light (or light containing ultraviolet light such as sunlight), becoming a metastable merocyanine compound that is colored. The merocyanine compound reverts to the stable original closed ring state and becomes decolorized when light is blocked or heat is applied. In other words, the ring-opening reaction caused by ultraviolet light and the ring-closing reaction caused by light blocking or heat occur reversibly, and the optical state changes between a colored state and a transparent state.

[0110]

[0111] In this embodiment, the dimming member 20 can use, for example, "TCP-0054", "TCP-0021", "TCP-0024", or "TCP-0033" (all manufactured by Yamada Chemical Industry Co., Ltd.) as a heat-returning (thermally decolorizing) photochromic material. Of these, those with a slow decolorization speed can be used in the normal anti-glare region 21, and those with a fast decolorization speed can be used in the temporary anti-glare region 22.

[0112] Here, an example of the coloring and decolorization behavior of a heat-rebound type photochromic material is explained using Figures 5A and 5B. Figure 5A shows an example of the coloring behavior of a heat-rebound type photochromic material, and Figure 5B shows an example of the decolorization behavior of the same heat-rebound type photochromic material as in Figure 5A. In Figures 5A and 5B, the transmitted light intensity of visible light (wavelength 550 nm in this example) related to the level of light transmittance is shown on the vertical axis, and the passage of time is shown on the horizontal axis. This example shows an example of the behavior (change in optical state) of a heat-rebound type photochromic material in which the increase in light transmittance is relatively gradual.

[0113] In the example shown in Figure 5A, a 200 μm thick PMMA resin film containing a thermal photochromic material was irradiated with ultraviolet light at a temperature of 30°C and a visible light wavelength of 550 nm. The ultraviolet irradiation intensity was 3.6 mW / cm². ２ Furthermore, "TCP-0033, manufactured by Yamada Chemical Industry Co., Ltd." was added to the PMMA resin film as a heat-recovering type photochromic material, in an amount equivalent to 5 wt% of the PMMA resin.

[0114] As shown in Figure 5A, if ultraviolet irradiation is started at time t1, 5 seconds after the start of the transmitted light intensity measurement, the transmitted light intensity will be almost halved (to about 0.5) 10 seconds after time t1 (15 seconds after the start of measurement). If ultraviolet irradiation is continued further, the transmitted light intensity will become very low, to about 0.2 to 0.3, 40 seconds after time t1 (45 seconds after the start of measurement).

[0115] Furthermore, Figure 5B shows the decolorization behavior of the heat-rebound type photochromic material when ultraviolet irradiation to the PMMA resin film in the example of Figure 5A is stopped. As shown in Figure 5B, after the cessation of ultraviolet irradiation at time t2, the transmitted light intensity is very weak at 0.2, but it gradually increases, reaching about 0.5 after 100 seconds, and recovering to 0.8 after 400 seconds. For the heat-rebound type photochromic material in this example, the time until the transmitted light intensity exceeds 0.5 (coloration reduction time) is about 100 seconds. In other words, even after stopping ultraviolet irradiation, a glare-preventing colored state is maintained for about 100 to 150 seconds.

[0116] Thus, a heat-recovering type photochromic material with a gradual increase in light transmittance can be suitably used in the normal anti-glare region 21, where it is necessary to continuously maintain a colored state during the operation of the vehicle 1 to prevent glare, contribute to energy saving by suppressing the amount of ultraviolet irradiation, and suppress deterioration of the windshield.

[0117] Furthermore, in order to ensure visibility, the temporary anti-glare region 22, which needs to be restored to a transparent state immediately after the cessation of ultraviolet irradiation, may use a heat-recovery type photochromic material that increases light transmittance more rapidly. For example, to increase the light transmittance in the temporary anti-glare region 22 more rapidly, the dimming device 10 may be equipped with a heating device (heater). For example, by heating the temporary anti-glare region 22 with the heating device after a certain period of ultraviolet irradiation, the decolorization rate of the heat-recovery type photochromic material may be increased, and the light transmittance may be increased rapidly.

[0118] The heat-returning photochromic material restores its light transmittance (decolorizes) with temperature after ultraviolet irradiation stops. Therefore, even in situations where visible light or infrared light is not irradiated (for example, inside a tunnel or at night), irradiation with visible light or other sources is not required to restore (decolorize) the light transmittance. Consequently, it can be suitably used for glare prevention from light sources other than sunlight (such as light emitted from lighting fixtures), and can further contribute to energy saving. As described above, the windshield 11 may use both a light-returning photochromic material and a heat-returning photochromic material. Specifically, a light-returning photochromic material may be used in the normal anti-glare region 21 and a heat-returning photochromic material in the temporary anti-glare region 22, or a heat-returning photochromic material may be used in the normal anti-glare region 21 and a light-returning photochromic material in the temporary anti-glare region 22. Even when using both light-returning and heat-returning photochromic materials, it is sufficient if the decolorization rate in the normal anti-glare region 21 is slower than the decolorization rate in the temporary anti-glare region 22.

[0119] Next, we will explain how to suppress the degradation of the light-adjusting material (in this example, a photochromic material) in the windshield 11. When a photo-returning type (P-Type) photochromic material absorbs ultraviolet light in its colored state, i.e., in its cyclic form, byproducts are generated. Hereinafter, these byproducts will also be referred to as "colored products." As shown in the reaction formula (5) below, for example, when ultraviolet light is irradiated onto a cyclic form of a diarylethene derivative in which the substituent R is a cyano group (see reaction formula (2) above), the cyclic form absorbs the ultraviolet light and colored products are generated.

[0120]

[0121] The by-products (colored substances) generated by ultraviolet irradiation of the closed-ring structure are irreversible structures; even when irradiated with visible light or infrared light, a ring-opening reaction does not occur, and the structure does not revert to the open-ring structure. In other words, once the closed-ring structure changes into a colored substance, the coloring becomes irreversible and does not disappear. This irreversible coloring state caused by the colored substance corresponds to the degradation of the photochromic material. If a windshield 11 containing a light-returning type photochromic material is continuously irradiated with ultraviolet light, and the absorption of ultraviolet light by the closed-ring structure continues, the photochromic material will degrade (colored substances will be generated), and a region (transmittance fixed region) will be created in the windshield 11 where the light transmittance does not recover due to the irreversible coloring state. In the transmittance fixed region, the windshield 11 should normally become decolorized and the light transmittance should recover due to visible light (sunlight, etc.) after the ultraviolet irradiation stops, but due to the degradation of the photochromic material, the light transmittance does not recover sufficiently, which may make it difficult to maintain visibility while driving.

[0122] More specifically, as shown in Figures 4A and 4B, the surface 11a of the windshield 11 corresponds to the ultraviolet irradiation surface. Therefore, in the region of the photochromic member 20 on the surface 11a (ultraviolet irradiation surface) side in the thickness direction, continuous irradiation with ultraviolet light causes the closed ring body of the photochromic material to absorb ultraviolet light, resulting in the formation of a colored substance, and the degradation of the photochromic material progresses more rapidly compared to other regions. As a result, in the region on the ultraviolet irradiation surface side, the density of the colored substance increases earlier than in other regions of the photochromic member 20, creating a transmittance fixed region and hindering the restoration of light transmittance. When a transmittance fixed region occurs on the ultraviolet irradiation surface (surface 11a) side of the photochromic member 20, the light transmittance does not fully recover even in situations where anti-glare is not required. Therefore, in order to ensure the driver's visibility, measures such as replacing the photochromic member 20 become necessary. Furthermore, if the density of the colored material increases on the UV-irradiated surface, the irradiated UV light will have difficulty reaching the area in front of the light-adjusting member 20 (the area on the specific light-blocking member 13 side), and the ring-closed body of the photochromic material will absorb UV light and deteriorate only in the area on the surface 11a side.

[0123] From the above, in a windshield 11 using a photochromic material, it is necessary to suppress the deterioration of the photochromic material in the region on the ultraviolet irradiation surface (surface 11a) side, that is, the occurrence of irreversible coloring due to the coloring agent, particularly in the photochromic member 20. Therefore, in order to suppress the deterioration of the photochromic material, the photochromic device 10 according to this embodiment performs modulated ultraviolet irradiation when the windshield 11 is colored (photochromic), for example, when maintaining the colored state. As described above, modulated irradiation differs from continuous irradiation in which ultraviolet irradiation is continued at a constant illuminance, in which the illuminance of ultraviolet light irradiated from the light irradiation unit 30 to the windshield 11 is modulated. In other words, the illuminance of ultraviolet light is periodically switched between an on state and an off state, or between a strong irradiation state and a weak irradiation state, depending on the modulation pattern (intermittent irradiation pattern, strong / weak irradiation pattern).

[0124] In modulated ultraviolet irradiation, during periods when the ultraviolet irradiance is reduced (or stopped), the amount of coloration (number of closed rings) of the photochromic material on the ultraviolet irradiation surface (surface 11a) side of the dimming member 20 is reduced. As a result, ultraviolet light can more easily reach the front side of the dimming member 20 (the side of the specific light blocking member 13), i.e., the area on the sunlight irradiation side, compared to continuous irradiation. Therefore, the amount of coloration (number of closed rings) of the photochromic material can be increased in the area of ​​the dimming member 20 on the sunlight irradiation side.

[0125] In other words, when dimming control is performed, the illuminance of ultraviolet light irradiated from the light irradiation unit 30 to the windshield 11 is modulated, which reduces the bias in the coloring (ring-closing reaction) of the photochromic material within the dimming member 20, allowing ultraviolet light to be irradiated to the front side of the dimming member 20, i.e., the side that receives sunlight. As a result, the dimming member 20 can color not only the photochromic material on the side that receives sunlight, but also the photochromic material on the side that receives sunlight. This suppresses the degradation of the photochromic material in the dimming member 20 and slows down the increase in the density of the colored material on the side that receives sunlight. As a result, the occurrence of an irreversible colored state on the side that receives sunlight (the side that receives sunlight) of the dimming member 20, i.e., the occurrence of a transmittance fixed region, can be delayed. As described above, the dimming device 10 according to this embodiment suppresses the degradation of the dimming material (photochromic material) contained in the windshield 11 (dimming member 20) by performing modulated irradiation of ultraviolet light on the windshield, thereby maintaining the light transmittance in the decolorized state and preventing glare while ensuring the driver's visibility. Furthermore, by maintaining the light transmittance of the windshield 11 at a target value during modulated irradiation to maintain the colored state of the windshield 11 and controlling the luminous transmittance to be constant within the above-mentioned specific range (5% to 20%), the degradation of the photochromic material can be suppressed more reliably.

[0126] (Operation) Next, the operation of the dimming device 10 will be explained with reference to Figure 6. The operation of the dimming device 10 shown in the flowchart of Figure 6 starts, for example, when the vehicle's power switch is turned ON, and ends when the power switch is turned OFF. During the period when the power switch is ON, for example, the control unit 70 periodically controls the irradiation of ultraviolet light to the normal anti-glare area 21 by the light irradiation unit 30.

[0127] In step S601, the data acquisition unit 71 of the control unit 70 checks whether a predetermined time has elapsed since the previous control process (S601). If it determines that the predetermined time has elapsed and it is time to execute the control process (Yes in S601), it acquires an illuminance signal indicating the outdoor illuminance from the external illuminance measurement unit 60 (S602) and outputs it to the irradiation control unit 72. If the data acquisition unit 71 determines that the predetermined time has not elapsed (No in S601), it waits until the predetermined time has elapsed.

[0128] The illuminance signal may be transmitted by the external illuminance measurement unit 60 in response to a request from the data acquisition unit 71, or the external illuminance measurement unit 60 may spontaneously transmit it to the data acquisition unit 71 in accordance with the cycle of the control processing described above. The data acquisition unit 71 may also output data for determining the operating state (the state of the main switch and the shift lever) to the irradiation control unit 72 along with the illuminance signal.

[0129] The illumination control unit 72 determines whether the outdoor illuminance indicated by the input illuminance signal is equal to or greater than a predetermined value (S603). This predetermined value may be, for example, the average illuminance value during the daytime, or it may be a brightness level that does not require the headlights to be turned on. If the illumination control unit 72 determines that the outdoor illuminance is equal to or greater than the predetermined value (YES in S603), it reads continuous data 81 from the storage unit 80 as dimming data 80a corresponding to the outdoor illuminance and generates a control signal based on the continuous illumination pattern indicated by the continuous data 81 (S604).

[0130] Specifically, the irradiation control unit 72 reads the continuous irradiation pattern (illuminance and irradiation time) of the continuous data 81 corresponding to the outdoor illuminance, and generates a control signal indicating the continuous irradiation pattern and irradiation range (normal anti-glare area 21). For example, the illuminance and irradiation time in the continuous irradiation pattern of the continuous data 81 can be appropriately set according to the outdoor illuminance to values ​​that can control the light transmittance of the irradiation range to the target value, that is, values ​​that can set the luminous transmittance to the specific range (5% or more and 20% or less).

[0131] The irradiation control unit 72 transmits the generated control signal (continuous irradiation mode, irradiation range) to the drive unit 32 of the light irradiation unit 30 and controls the light irradiation unit 30 to perform continuous irradiation of ultraviolet light based on the control signal (S605). As a result, ultraviolet light is continuously irradiated from the light irradiation unit 30 to the normal anti-glare area 21 (upper area 111) of the windshield 11 according to the continuous irradiation mode corresponding to the outdoor illuminance. In other words, based on the irradiation mode (illuminance, irradiation time) read by the control unit 70, the windshield 11 becomes colored and the light transmittance is reduced to the target value.

[0132] On the other hand, when the irradiation control unit 72 determines that the outdoor illuminance is below a specified value (NO in S603), it transmits a control signal to the drive unit 32 of the light irradiation unit 30 to stop the irradiation of ultraviolet light (S606). This allows the light irradiation unit 30 to stop irradiating ultraviolet light in response to changes in weather or a decrease in outdoor illuminance due to the passage of time, thereby suppressing unnecessary energy consumption.

[0133] The irradiation control unit 72 determines whether the change in the light transmittance of the windshield 11 has reached a target value (S607). If the irradiation time in the continuous irradiation mode has elapsed, the irradiation control unit 72 determines that the light transmittance has reached the target value (YES in S607) and reads the modulated data 82 from the storage unit 80 as dimming data 80a corresponding to the outdoor illuminance (S608). Specifically, the irradiation control unit 72 reads the modulated irradiation mode of the modulated data 82 according to the outdoor illuminance and the normal anti-glare area 21 (upper area 111) which is the irradiation range, and generates a control signal indicating the modulated irradiation mode and the irradiation range (normal anti-glare area 21). For example, the illuminance in the ON state in the modulated irradiation mode of the intermittent irradiation pattern of the modulated data 82, or the illuminance in the strong irradiation state / weak irradiation state in the modulated irradiation mode of the strong / weak irradiation pattern, can be appropriately set according to the outdoor illuminance to an illuminance that can maintain the light transmittance at the target value.

[0134] The irradiation control unit 72 transmits the generated control signal (modulated irradiation mode, irradiation range) to the drive unit 32 of the light irradiation unit 30 and controls the light irradiation unit 30 to perform modulated irradiation of ultraviolet light based on the control signal (S609). As a result, ultraviolet light is modulated and irradiated from the light irradiation unit 30 to the normal anti-glare area 21 (upper area 111) of the windshield 11 according to the modulated irradiation mode corresponding to the outdoor illuminance. In other words, the colored state (light transmittance) of the windshield 11 is maintained based on the modulated irradiation mode (illuminance, irradiation time) read by the control unit 70, and the change in light transmittance is maintained at the target value. That is, the luminous transmittance of the windshield 11 is maintained within the above-mentioned specific range. On the other hand, if the irradiation time in the continuous irradiation mode has not elapsed, the irradiation control unit 72 determines that the light transmittance has not reached the target value (NO in S607) and waits for the irradiation time to elapse.

[0135] For example, the specified values ​​for outdoor illuminance used in the determination in step S603 may be stepped. For instance, the irradiation control unit 72 may include the temporary anti-glare region 22 as the ultraviolet irradiation range when the outdoor illuminance is above a predetermined first specified value and above a second specified value that indicates a higher illuminance than the first specified value (for example, when the ambient light (sunlight, etc.) is very strong).

[0136] (Examples) The embodiments of this disclosure described above will be explained in more detail below with reference to examples and comparative examples.

[0137] First, windshields to be subjected to ultraviolet irradiation were fabricated according to the examples and comparative examples. Specifically, a windshield was fabricated by placing a specific light-blocking member and a light-adjusting member between two transparent substrates made of green glass. The specific light-blocking member was made of PVB (polyvinyl butyral) resin in which an ultraviolet absorber (UVA) was dispersed. The light-adjusting member was made of PVB (polyvinyl butyral) resin in which a light-returning type photochromic compound was dispersed. A diarylethene derivative (DAE12, manufactured by Yamada Chemical Industry Co., Ltd.) was used as the light-returning type photochromic compound.

[0138] [Example 1] The above windshield was subjected to a 24-hour ultraviolet irradiation test according to Example 1, with the irradiation pattern shown in Table 1 below (total 2140 seconds) considered as one cycle. A visible light wavelength of 550 nm (illuminance 20 mW / cm²) was used as simulated sunlight. ２ The windshield was continuously irradiated with ultraviolet light. Specifically, the windshield, which was in a decolorized state, was continuously irradiated with ultraviolet light in a continuous irradiation mode to color it. In the continuous irradiation mode, the illuminance was set to 10 mW / cm². ２ The irradiation time was set to 40 seconds. Subsequently, the colored windshield was subjected to modulated ultraviolet irradiation for 1620 seconds using a modulated irradiation pattern to maintain the colored state. In the above modulated irradiation method, the irradiance of ultraviolet light (on state / off state) was modulated at a frequency of 5 Hz. The irradiance of ultraviolet light in the on state was 10 mW / cm². ２ The device was periodically switched between the on and off states for 0.1 seconds each. After the modulated irradiation, ultraviolet irradiation was stopped for 480 seconds.

[0139] [Comparative Example 1] The above windshield was subjected to a 24-hour ultraviolet irradiation test according to Comparative Example 1, with the irradiation pattern shown in Table 1 below (total 2140 seconds) considered as one cycle. A visible light wavelength of 550 nm (illuminance 20 mW / cm²) was used as simulated sunlight. ２ The system was continuously irradiated with ultraviolet light. Specifically, the windshield, which was in a decolorized state, was continuously irradiated with ultraviolet light in a continuous irradiation mode to color the windshield, and this colored state was maintained. In the above continuous irradiation mode, the illuminance was set to 6 mW / cm². ２ The irradiation time was set to 1660 seconds. After continuous irradiation, ultraviolet irradiation was stopped for 480 seconds.

[0140]

[0141] The visual transmittance during the ultraviolet irradiation test (24 h) according to each irradiation mode of Example 1 and Comparative Example 1 shown in Table 1 above, and the changes in the visible light transmittance before and after the test are shown in Table 2 below. The visual transmittance was measured in accordance with JIS T7333:2018 for the windshield maintained in the colored state. Also, the visible light transmittance before and after the test was measured as the transmittance of simulated sunlight with a wavelength of 550 nm.

[0142]

[0143] As shown in Table 2, during the ultraviolet irradiation test, in any irradiation mode of Example 1 and Comparative Example 1, the visual transmittance of the windshield 11 in the colored state was 4.3%. That is, the visual transmittance of the windshield became a state where the anti-glare effect could be exhibited due to ultraviolet irradiation. Further, as a result of Example 1 in which an irradiation mode including modulated irradiation of ultraviolet rays was carried out, the visible light transmittance in the bleached state of the windshield decreased by 12% (from 88% before the test to 76% after 24 hours of the test). On the other hand, as a result of Comparative Example 1 in which an irradiation mode without modulated irradiation of ultraviolet rays (only continuous irradiation was carried out) was carried out, the visible light transmittance in the bleached state of the windshield decreased by 15% (from 88% before the test to 73% after 24 hours of the test). That is, by carrying out the modulated irradiation of ultraviolet rays, the decrease in the light transmittance of the windshield in the bleached state was suppressed by 3% compared with the case where only continuous irradiation was carried out.

[0144] 〔Example 2〕An ultraviolet irradiation test for 24 hours according to Example 2 was carried out on the above windshield with an irradiation mode (total 1840 seconds) shown in Table 3 below as one cycle. In addition, visible light with a wavelength of 550 nm (irradiance 20 mW / cm ２ ) was constantly irradiated as simulated sunlight. Specifically, continuous irradiation of ultraviolet rays was carried out on the windshield in the bleached state by a continuous irradiation mode to make the windshield in the colored state. In the above continuous irradiation mode, the irradiance was 3.6 mW / cm ２The irradiation time was set to 40 seconds. Subsequently, the now-colored windshield was subjected to modulated ultraviolet irradiation for 1620 seconds using a modulated irradiation pattern to maintain its colored state. In the above modulated irradiation mode, the ultraviolet irradiance in the ON state was 3.6 mW / cm². ２ And, at a frequency of 0.05 Hz, the illuminance of ultraviolet light (on state / off state (illuminance 0 mW / cm²) ２ The circuit was modulated. That is, it was periodically switched between an on state and an off state for 10 seconds each. After that, the ultraviolet irradiation was stopped for 180 seconds.

[0145] [Comparative Example 2] The above windshield was subjected to a 24-hour ultraviolet irradiation test according to Comparative Example 2, with the irradiation pattern shown in Table 3 below (total 1800 seconds) considered as one cycle. A visible light wavelength of 550 nm (illuminance 20 mW / cm²) was used as simulated sunlight. ２ The windshield was continuously irradiated with ultraviolet light in a continuous irradiation mode. Specifically, the windshield, which was in a decolorized state, was continuously irradiated with ultraviolet light in a continuous irradiation mode to color it, and the colored state was maintained. After that, the ultraviolet irradiation was stopped for 180 seconds. In the above continuous irradiation mode, the illuminance was 3.6 mW / cm². ２ The irradiation time was set to 1620 seconds (27 minutes).

[0146]

[0147] Table 4 below shows the luminous transmittance during the ultraviolet irradiation test (24h) for each irradiation mode shown in Table 3 for Example 2 and Comparative Example 2, and the change in visible light transmittance before and after the test. Similar to Example 1 and Comparative Example 1, the luminous transmittance of the colored windshield was measured in accordance with JIS T7333:2018. The visible light transmittance before and after the test was measured as the transmittance of simulated sunlight with a wavelength of 550 nm.

[0148]

[0149] As shown in Table 4, during the UV irradiation test in Example 2, the luminous transmittance of the colored windshield was 10%. In other words, the luminous transmittance of the windshield was in a more desirable state (within the range of 8% to 18%), ensuring better visibility for the driver while providing glare prevention. In Comparative Example 2, during the irradiation test, the luminous transmittance of the windshield during the period it was maintained in the colored state was 7.8%, which was also in a desirable state (within the range of 5% to 20%).

[0150] Furthermore, in Example 2, which involved irradiation including modulated ultraviolet light, the visible light transmittance of the windshield in its decolorized state decreased by 2% from the value before the test (88%) to the value after the 24-hour test (86%). In contrast, in Comparative Example 2, which involved irradiation without modulated ultraviolet light (continuous irradiation only), the visible light transmittance of the windshield in its decolorized state decreased by 8% from the value before the test (88%) to the value after the 24-hour test (80%). In other words, in Example 2, which involved modulated ultraviolet light irradiation, the decrease in visible light transmittance before and after the test in the decolorized windshield was suppressed by 6% compared to Comparative Example 2, which involved continuous irradiation only. Therefore, in Example 2, the decrease in visible light transmittance in the windshield was 1 / 4 of that in Comparative Example 2.

[0151] Furthermore, in Example 2, the decrease in light transmittance before and after the test in the decolorized windshield was half that of Example 1. This is because the ultraviolet irradiance (3.6 mW / cm²) in the irradiation mode of Example 2 was ２ ) is the ultraviolet irradiance (10 mW / cm²) in the irradiation mode of Example 1. ２ This is thought to be due to the fact that it is smaller than ) and that in Example 2, the visible transmittance of the windshield is kept constant in a desirable state (within the range of 5% to 20%) during the period in which the colored state is maintained (1620 seconds).

[0152] From the above results, it was found that when modulated ultraviolet irradiation was performed (Examples 1 and 2), the degradation of the photochromic material (generation of by-products (colored bodies)) was suppressed compared to when only continuous irradiation was performed (Comparative Examples 1 and 2). In other words, it was found that modulated ultraviolet irradiation of a windshield suppresses the degradation of the photochromic material in a windshield containing a photochromic material, thereby suppressing the occurrence of an irreversible colored state (a state in which light transmittance does not return to normal) in the windshield, and thus providing glare prevention while ensuring the driver's visibility.

[0153] Furthermore, even when modulated ultraviolet irradiation was performed, as shown in the results of Example 2, it was found that by setting the luminous transmittance of the colored windshield within a specific range (5% to 20%), the degradation of the photochromic compound (generation of by-products (colored bodies)) was further suppressed compared to when the luminous transmittance was outside the above specific range (Example 1). In other words, by modulating ultraviolet irradiation of the windshield and setting the luminous transmittance of the colored windshield within the above specific range, it is possible to more reliably secure the driver's field of vision while preventing glare, and furthermore, it is possible to more reliably suppress the degradation of the photochromic material in a windshield containing a photochromic material.

[0154] Figure 7 is a graph showing the change in visible light transmittance (wavelength 550 nm) at the time of decolorization when the above ultraviolet irradiation test is continued according to the irradiation methods (Table 3) of Example 2 and Comparative Example 2. As shown in Figure 7, in the irradiation method of Example 2, in which the visible light transmittance in the colored state of the windshield is within the above specific range (10%) and modulated irradiation is performed, the degradation of the photochromic compound is reliably suppressed, and it takes about 270 hours for the visible light transmittance to decrease to around 60%. In contrast, in the irradiation method of Comparative Example 1, in which only continuous irradiation is performed, the degradation of the photochromic compound progresses easily, and the visible light transmittance decreases to around 60% in about 70 hours. In other words, in the irradiation method of Example 2, the degradation of the photochromic compound is delayed for 3 to 4 times longer than in Comparative Example 2, that is, the degradation of the photochromic material can be suppressed.

[0155] (Modification) In the above embodiment, of the regions obtained by dividing the windshield 11 into two upper regions, the first region in which the photochromic material decolorizes quickly is designated as the non-upper region 112, and the second region in which the decolorization speed is slower than that of the first region is designated as the upper region 111. However, the disclosure is not limited thereto. For example, if the upper region 111 includes point P1, the upper region 111 may be designated as the first region (the region in which the photochromic material decolorizes quickly), and the non-upper region 112 may be designated as the second region (the region in which the photochromic material decolorizes slowly). In other words, the photochromic material included in the upper region 111 of the windshield 11 may decolorize faster than the photochromic material included in the non-upper region 112.

[0156] In this case, the control unit 70 (irradiation control unit 72) can determine the irradiation range of ultraviolet light emitted from the light irradiation unit 30. When the vehicle 1 is in operation (in the driving state), the irradiation range may be the upper region 111 (normal anti-glare region 21), and when the vehicle 1 is not in operation (in the non-driving state), the irradiation range may be the entire surface (surface 11a) of the windshield 11, including the upper region 111 and the non-upper region 112 (temporary anti-glare region 22). This ensures that the driver's visibility is reliably maintained by the photochromic material with a fast decolorization rate exhibiting an anti-glare effect while the vehicle 1 is in operation, while the photochromic material with a slow decolorization rate exhibits a heat-shielding effect that suppresses the temperature rise inside the vehicle interior 1a when the vehicle is not in operation (when parked). Therefore, when dimming control is performed by ultraviolet irradiation when the vehicle is not in operation, the amount of ultraviolet irradiation can be kept to the minimum necessary, contributing to energy saving. Note that when dimming for heat shielding when the vehicle is not in operation, it is not necessary to reduce the light transmittance as quickly as when it is anti-glare. Therefore, modulated irradiation can be performed from the start of dimming control without continuous irradiation.

[0157] Here, the operation of the dimming device 10 according to this modified example will be explained using Figure 8. Figure 8 is a flowchart illustrating an example of the operation of the dimming device 10 according to this modified example. The control unit 70 performs the same processing as in steps S601 to S603 in steps S801 to S803.

[0158] When the irradiation control unit 72 determines that the outdoor illuminance is above a specified value (YES in S803), it sets (determines) the ultraviolet irradiation range (normal anti-glare area 21 or both the normal anti-glare area 21 and the temporary anti-glare area 22) according to the operating state (operating state or non-operating state) determined based on the state of the main switch and the shift lever, and generates a control signal indicating the irradiation range (S804). The irradiation control unit 72 reads continuous data 81 from the storage unit 80 as dimming data 80a corresponding to the outdoor illuminance, similar to step S604, and generates a control signal indicating the continuous irradiation mode (S805). For example, the continuous irradiation mode in the continuous data 81 is divided into the irradiation mode of the normal anti-glare area 21 and the irradiation mode of the temporary anti-glare area 22, and the irradiation control unit 72 may select the continuous irradiation mode based on the irradiation range set in step S804. In this case, the illuminance of the continuous irradiation mode of the normal anti-glare area 21 may be set higher than the illuminance of the continuous irradiation mode of the temporary anti-glare area 22. On the other hand, if the irradiation control unit 72 determines that the outdoor illuminance is below a specified value (NO in S803), it transmits a control signal to the drive unit 32 of the light irradiation unit 30 to stop the irradiation of ultraviolet light, similar to step S606 above (S806).

[0159] The irradiation control unit 72 transmits the generated control signal (continuous irradiation mode, irradiation range) to the drive unit 32 of the light irradiation unit 30 and controls the light irradiation unit 30 to perform continuous irradiation of ultraviolet light based on the control signal (S807). Subsequently, in steps S808 to S810, the same processing as in steps S607 to S609 is performed. In step S809, the irradiation control unit 72 reads the modulated irradiation mode of the modulated data 82 according to the irradiation range set in step S804 (normal anti-glare area 21 or both the normal anti-glare area 21 and the temporary anti-glare area 22), and generates a control signal indicating the modulated irradiation mode and irradiation range (normal anti-glare area 21). The illuminance of the modulated irradiation mode of the normal anti-glare area 21 may be set higher than the illuminance of the modulated irradiation mode of the temporary anti-glare area 22.

[0160] (Effects of the Embodiment) (1) The dimming device 10 is a dimming device for a vehicle that adjusts the amount of light incident into the vehicle interior 1a, and comprises a vehicle windshield 11 made of a dimming material that reacts to ultraviolet light to change color and reacts to at least one of visible light or heat to decolorize, a light irradiation unit 30 that irradiates the windshield 11 with ultraviolet light from inside the vehicle interior 1a, and a control unit 70 that controls the irradiation of ultraviolet light by the light irradiation unit 30 based on the irradiation mode including the illuminance and irradiation time of the ultraviolet light, wherein the control unit 70 alternately modulates the illuminance of the ultraviolet light irradiated onto the windshield 11 from the light irradiation unit 30 between one state and another state. As a result, modulated irradiation of ultraviolet light is performed when dimming is controlled, and the dimming material (photochromic material) is evenly colored in the thickness direction of the dimming member 20 of the windshield 11, thereby suppressing the concentration of by-products (colored bodies) due to continuous irradiation of ultraviolet light from rising unevenly towards the surface 11a side of the windshield 11. In other words, modulated irradiation can suppress the deterioration of the photochromic material in the windshield 11. Furthermore, by suppressing the deterioration of the photochromic material, the reduction in light transmittance in the decolorized state can be suppressed, thereby preventing glare while ensuring the driver's visibility.

[0161] (2) In the dimming device 10, the control unit 70 modulates the illuminance of ultraviolet light irradiated onto the windshield 11 from the light irradiation unit 30 based on a predetermined modulation pattern, and the modulation pattern may be an intermittent irradiation pattern in which one state is an ON state in which ultraviolet light is irradiated from the light irradiation unit 30, and the other state is an OFF state in which ultraviolet light is not irradiated from the light irradiation unit 30, and the ON state and the OFF state are alternately modulated. This provides a period in which ultraviolet light irradiation is stopped during modulated ultraviolet light irradiation, which further suppresses the deterioration of the dimming material and suppresses energy consumption due to ultraviolet light irradiation by suppressing the amount of ultraviolet light irradiation. (3) In the dimming device 10, the above modulation pattern may be a strong irradiation pattern in which one state is a strong irradiation state in which relatively strong illuminance ultraviolet light is irradiated from the light irradiation unit 30, and the other state is a weak irradiation state in which relatively weak illuminance ultraviolet light is irradiated from the light irradiation unit 30, and the strong irradiation state and the weak irradiation state are alternately modulated. This creates a period where the intensity of ultraviolet light is reduced, which further suppresses the degradation of light-adjusting materials and reduces energy consumption due to ultraviolet irradiation by suppressing the amount of ultraviolet radiation.

[0162] (4) In the dimming device 10, the control unit 70 may modulate the intensity of ultraviolet light in a sinusoidal or triangular wave manner in the intensity irradiation pattern. This makes it difficult to see changes in the colored state of the windshield 11, and makes it possible to maintain a constant colored state of the windshield 11 more reliably. (5) In the dimming device 10, the frequency that defines the modulation period of the illuminance in the modulation pattern may be 30 Hz or higher. This makes it possible to suppress the visibility of changes (flickering) in the ultraviolet light intensity in the light source unit 31 of the light irradiation unit 30. (6) In the dimming device 10, the modulation period between one state and the other state in the modulation pattern may be faster than the decolorization rate of the dimming material. This makes it difficult to see changes in the colored state of the windshield 11, and modulated irradiation can be controlled so that the colored state appears constant to the human eye.

[0163] (7) In the dimming device 10, the luminous transmittance of the windshield 11 changes depending on whether the dimming material is colored or decolorized, and the control unit 70 may modulate the illuminance of ultraviolet rays emitted by the light irradiating unit 30 so that the luminous transmittance of the windshield 11 when it is colored is maintained within a predetermined range. This suppresses deterioration of the dimming member and prevents glare while ensuring the driver's field of vision of the vehicle 1 even when the windshield 11 is colored. (8) In the dimming device 10, the control unit 70 may modulate the illuminance of ultraviolet rays emitted by the light irradiating unit 30 so that the luminous transmittance of the windshield 11 when it is colored is maintained at 5% or more. This makes it possible to more reliably ensure the driver's field of vision while more reliably exhibiting the anti-glare effect. (9) In the dimming device 10, the control unit 70 may modulate the illuminance of ultraviolet rays emitted by the light irradiating unit 30 so that the luminous transmittance of the windshield 11 when it is colored is maintained at 20% or less. This ensures a clearer view for the driver while also providing a more reliable anti-glare effect.

[0164] (10) In the dimming device 10, if the control unit 70 determines that the visible light transmittance of the windshield 11 has not reached a predetermined target value, it may continuously irradiate the windshield 11 with ultraviolet light from the light irradiation unit 30 without modulating the illuminance of the ultraviolet light. If it determines that the luminous transmittance has reached the target value, it may modulate the illuminance of the ultraviolet light irradiated by the light irradiation unit 30. As a result, the dimming device 10 can suppress the deterioration of the dimming member 20 by modulated irradiation, and by continuous irradiation, quickly control the light transmittance of the windshield 11 to the target value and the luminous transmittance when colored to a specific range, thereby quickly exhibiting an anti-glare effect.

[0165] (11) In the dimming device 10, of the two regions into which the windshield 11 is divided, the dimming material contained in the first region (temporary anti-glare region 22) has a faster decolorization rate than the dimming material contained in the second region (normal anti-glare region 21). The control unit 70 may irradiate the first region from the light irradiation unit 30 with ultraviolet light whose illuminance is modulated in an intermittent irradiation pattern corresponding to the first region, or irradiate it with ultraviolet light at a constant illuminance, and irradiate the second region from the light irradiation unit 30 with ultraviolet light whose illuminance is modulated in an intermittent irradiation pattern corresponding to the second region. Furthermore, the on-state time in the intermittent irradiation pattern corresponding to the first region is longer than the on-state time in the intermittent irradiation pattern corresponding to the second region. As a result, by performing continuous irradiation, the light transmittance of the first region (normal anti-glare region 21), which has a faster decolorization rate, can be quickly brought to the target value as needed, and after the target value is reached, the light transmittance can be stably maintained at the target value by modulated irradiation of the intermittent irradiation pattern. Furthermore, by modulating the intermittent irradiation pattern, the light transmittance in the second region (normal anti-glare region 21), where the decolorization speed is slow, can be continuously and stably maintained at the target value while suppressing the deterioration of the windshield 11, which includes the photochromic material. In addition, by making the on-state time shorter than in the first region (on-state time in the first region > on-state time in the second region) in the intermittent irradiation pattern corresponding to the second region where the decolorization speed is slow, energy consumption due to ultraviolet irradiation and deterioration of the photochromic material contained in the photochromic member 20 can be suppressed.

[0166] (12) In the dimming device 10, the control unit 70 irradiates the first region from the light irradiation unit 30 with ultraviolet light whose illuminance is modulated with an intensity-varying irradiation pattern corresponding to the first region, or irradiates it with ultraviolet light at a constant illuminance, and irradiates the second region from the light irradiation unit 30 with ultraviolet light whose illuminance is modulated with an intensity-varying irradiation pattern corresponding to the second region, and the time of the strong irradiation state in the intensity-varying irradiation pattern corresponding to the first region may be longer than the time of the strong irradiation state in the intensity-varying irradiation pattern corresponding to the second region. This allows the light transmittance of the first region (normal anti-glare region 21), which has a fast decolorization speed, to reach the target value as needed by performing continuous irradiation, and after reaching the target value, the light transmittance can be stably maintained at the target value by modulated irradiation of the intensity-varying irradiation pattern. Furthermore, the deterioration of the windshield 11 including the dimming material can be suppressed while continuously and stably maintaining the light transmittance of the second region (normal anti-glare region 21), which has a slow decolorization speed, at the target value by modulated irradiation of the intensity-varying irradiation pattern. Furthermore, in the intensity irradiation pattern corresponding to the second region where the decolorization speed is slow, by making the on-state time shorter than that of the first region (on-state time of the first region > on-state time of the second region), energy consumption due to ultraviolet irradiation and deterioration of the light-adjusting material contained in the light-adjusting member 20 can be suppressed. (13) In the light-adjusting device 10, the lower of the two regions obtained by dividing the windshield 11 into upper and lower halves, the non-upper region 112, is the first region, and the upper region 111, the upper region, is the second region. This allows the normal anti-glare region 21, which corresponds to the upper region 111 where the amount of incident sunlight is relatively large, to be kept colored for a longer period even after ultraviolet irradiation is stopped, while the temporary anti-glare region 22, which corresponds to the non-upper region 112, can be quickly decolorized to ensure visibility.

[0167] (14) In the dimming device 10, the photochromic material contained in the upper region 111, which is the upper of the two regions obtained by dividing the windshield 11 into upper and lower halves, decolorizes faster than the photochromic material contained in the non-upper region 112, which is the lower region other than the upper region 111. The control unit 70 can determine the irradiation range of ultraviolet light irradiated from the light irradiation unit 30. When the vehicle 1 is in operation, the irradiation range may be the upper region 111, and when the vehicle 1 is not in operation, the entire surface of the windshield 11 (the entire surface 11a), including the upper region 111 and the non-upper region 112, may be irradiated. This ensures glare prevention and visibility for the driver while driving, and when dimming control is used to shield the interior of the vehicle 1a from heat, the amount of ultraviolet light irradiated can be kept to the minimum necessary, contributing to energy saving.

[0168] 1...Vehicle, 1a...Passenger compartment, 2...Ceiling, 3...Driver's seat, 4...Dashboard, 5...Steering column, 10...Dimming device, 11...Windshield, 12...Transparent substrate, 13...Specific light blocking member, 20...Dimming member, 21...Normal anti-glare area, 22...Temporary anti-glare area, 30...Light irradiation unit, 31...UV light source unit, 32...Drive unit, 40...Driver monitor, 60...External illuminance measurement unit, 70...Control unit, 71...Data acquisition unit, 72...Irradiation control unit, 80...Storage unit, 80a...Dimming data, 81...Continuous data, 82...Modulation data, 111...Upper area, 112...Non-upper area

Claims

1. A vehicle light control device for adjusting the amount of light incident into the interior of a vehicle, comprising: a vehicle windshield comprising a light-adjusting material that changes color in response to ultraviolet light and decolorizes in response to at least one of visible light or heat; a light irradiation unit that irradiates the windshield with ultraviolet light from the interior of the vehicle; and a control unit that controls the irradiation of ultraviolet light by the light irradiation unit based on an irradiation pattern including the illuminance and irradiation time of the ultraviolet light, wherein the control unit alternately modulates the illuminance of the ultraviolet light irradiated onto the windshield from the light irradiation unit between one state and another state.

2. The dimming device according to claim 1, wherein the control unit modulates the illuminance of ultraviolet light irradiated onto the windshield from the light irradiation unit based on a predetermined modulation pattern, the modulation pattern being an intermittent irradiation pattern in which the first state is an ON state in which ultraviolet light is irradiated from the light irradiation unit, and the other state is an OFF state in which ultraviolet light is not irradiated from the light irradiation unit, and the ON state and the OFF state are alternately modulated.

3. The dimming device according to claim 1, wherein the control unit modulates the illuminance of ultraviolet light emitted by the light irradiation unit based on a predetermined modulation pattern, the modulation pattern being a strong irradiation state in which one state is irradiated with relatively strong ultraviolet light from the light irradiation unit, and the other state is irradiated with relatively weak ultraviolet light from the light irradiation unit, and the device alternately modulates between the strong irradiation state and the weak irradiation state.

4. The dimming device according to claim 3, wherein the control unit modulates the intensity of ultraviolet light in a sinusoidal or triangular wave manner in the intensity-varying irradiation pattern.

5. The dimming device according to any one of claims 2 to 4, wherein the modulation pattern has a frequency of 30 Hz or higher that defines the modulation period of the illuminance.

6. The dimming device according to any one of claims 2 to 4, wherein the modulation pattern has a modulation period between the first state and the other state that is faster than the decolorization rate in the dimming material.

7. The dimming device according to any one of claims 1 to 4, wherein the luminous transmittance of the windshield changes depending on the coloring or decolorization of the dimming material, and the control unit modulates the illuminance of ultraviolet light emitted by the light irradiating unit so that the luminous transmittance of the windshield is maintained within a predetermined range when the windshield is colored.

8. The dimming device according to claim 7, wherein the control unit modulates the illuminance of ultraviolet light emitted by the light irradiating unit so that the visible transmittance of the windshield is maintained at 5% or more when the windshield is colored.

9. The dimming device according to claim 8, wherein the control unit modulates the illuminance of ultraviolet light emitted by the light irradiating unit so that the visible transmittance of the windshield is maintained at 20% or less when the windshield is colored.

10. The dimming device according to claim 7, wherein the control unit determines that the visible light transmittance of the windshield has not reached a predetermined target value, and continuously irradiates the windshield with ultraviolet light from the light irradiation unit without modulating the illuminance of ultraviolet light, and modulates the illuminance of ultraviolet light irradiated by the light irradiation unit when it determines that the visible light transmittance has reached the target value.

11. The dimming device according to claim 2, wherein, of the two regions obtained by dividing the windshield into two, the dimming material included in the first region has a faster rate of decolorization than the dimming material included in the second region, the control unit irradiates the first region from the light irradiation unit with ultraviolet light whose illuminance is modulated according to the intermittent irradiation pattern corresponding to the first region, or irradiates it with ultraviolet light at a constant illuminance, the light irradiation unit irradiates the second region from the light irradiation unit with ultraviolet light whose illuminance is modulated according to the intermittent irradiation pattern corresponding to the second region, and the time of the ON state in the intermittent irradiation pattern corresponding to the first region is longer than the time of the ON state in the intermittent irradiation pattern corresponding to the second region.

12. The dimming device according to claim 3, wherein, of the two regions obtained by dividing the windshield into two, the dimming material included in the first region has a faster rate of decolorization than the dimming material included in the second region, the control unit irradiates the first region from the light irradiation unit with ultraviolet light whose illuminance is modulated according to the intensity irradiation pattern corresponding to the first region, or irradiates it with ultraviolet light at a constant illuminance, the light irradiation unit irradiates the second region from the light irradiation unit with ultraviolet light whose illuminance is modulated according to the intensity irradiation pattern corresponding to the second region, and the time of the high irradiation state in the intensity irradiation pattern corresponding to the first region is longer than the time of the high irradiation state in the intensity irradiation pattern corresponding to the second region.

13. The dimming device according to claim 11 or 12, wherein the lower of the two regions obtained by dividing the windshield into upper and lower sections is the first region, and the upper region is the second region.

14. The photochromic material contained in the upper region, which is the upper of the two regions obtained by dividing the windshield into upper and lower halves, decolorizes faster than the photochromic material contained in the lower region other than the upper region, the control unit is capable of determining the irradiation range of ultraviolet light irradiated from the light irradiation unit, the irradiation range being the upper region when the vehicle is in operation, and the entire surface of the windshield including the upper region and the lower region when the vehicle is not in operation, the dimming device according to any one of claims 1 to 4.

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