Lighting device, vehicle lighting system

Abstract

To suppress generation of a dark region in a light distribution pattern in a luminaire.SOLUTION: A luminaire includes: a light source 10; a light condensing part for condensing light so that light emitting from the light source focuses on a predetermined position; a liquid crystal element 15 arranged at a position including a focal point; a first polarizing element 12 arranged on a light incident surface side of the liquid crystal element; a second polarizing element 17 arranged on a light emission surface side of the liquid crystal element; a projection lens 18 for enlarging and projecting an image generated by the liquid crystal element, the first polarizing element and the second polarizing element; and an optical filter 19 arranged on a light path leading to the liquid crystal element from the light source. The light source has a light emission peak at equal to or less than 450nm, and the optical filter is a low pass filter in which the relative transmission factor at equal to or less than 435nm is equal to or less than 0.1%, and the relative transmission factor at equal to or less than 450nm is equal to or less than 17%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a lighting device and a vehicle lighting system. [Background technology]

[0002] Japanese Patent Application Laid-Open Publication No. 2019-128449 (Patent Document 1) describes a vehicle headlamp (illumination device) that uses a liquid crystal element to variably control a light distribution pattern. In this vehicle headlamp, light emitted from a light source is concentrated and incident on a liquid crystal element, where a bright and dark image is formed. The image is then enlarged and projected by a lens, thereby variably setting the light distribution pattern of the light irradiated ahead of the vehicle. This vehicle headlamp uses an LED element as the light source, which emits light over a wide angle. Therefore, the light is concentrated by a focusing means such as a lens or reflector and incident on the liquid crystal element. However, as the cumulative usage time increases, a dark area (a relatively low brightness area) may appear in part of the light distribution pattern, corresponding to the vicinity of the focus where the illuminance of the light is relatively high. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-128449 Summary of the Invention [Problem to be solved by the invention]

[0004] One of the objects of a specific aspect of the present disclosure is to provide a technique capable of suppressing the occurrence of dark areas in a light distribution pattern of a lighting device. [Means for solving the problem]

[0005] [1] An illumination device according to one aspect of the present disclosure includes: (a) a light source; (b) a focusing unit that focuses light emitted from the light source so that the light is focused at a predetermined position; (c) a liquid crystal element disposed at a position including the focus; (d) a first polarizing element disposed on the light-incident side of the liquid crystal element; (e) a second polarizing element disposed on the light-exit side of the liquid crystal element; (f) a projection lens that enlarges and projects an image generated by the liquid crystal element, the first polarizing element, and the second polarizing element; and (g) an optical filter disposed on an optical path from the light source to the liquid crystal element; (h) the light source has an emission peak at 450 nm or less; and (i) the optical filter is a low-pass filter having a relative transmittance of 0.1% or less at 435 nm or less and a relative transmittance of 17% or less at 450 nm or less. [2] An illumination device according to one aspect of the present disclosure includes: (a) a light source; (b) a focusing unit that focuses light emitted from the light source so that the light is focused at a predetermined position; (c) a liquid crystal element disposed at a position including the focus; (d) a first polarizing element disposed on the light-incident side of the liquid crystal element; (e) a second polarizing element disposed on the light-exit side of the liquid crystal element; and (f) a projection lens that enlarges and projects an image generated by the liquid crystal element, the first polarizing element, and the second polarizing element; and (g) the light source has a short-wavelength emission intensity peak in a wavelength range of 450 nm or more, and the emission intensity in a wavelength range of 435 nm or less is 0.1% or less compared to the emission intensity peak in the wavelength range of 450 nm or more, and the emission intensity at 450 nm is 17% or less compared to the emission intensity peak in the wavelength range of 450 nm or more. [3] One aspect of the present disclosure is a vehicle lighting system including the lighting device described in [1] or [2] above and a controller connected to the lighting device for controlling its operation.

[0006] According to the above configuration, it is possible to suppress the occurrence of dark areas in the light distribution pattern of the lighting device or the vehicle lighting system using the lighting device. [Brief explanation of the drawings]

[0007] [Figure 1]Fig. 1(A) is a diagram showing the configuration of a vehicle lighting system according to one embodiment, and Fig. 1(B) is a diagram showing the configuration of a vehicle lighting system according to a modified embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of the configuration of a liquid crystal element. [Figure 3] FIG. 3 is a diagram showing the emission spectrum (spectral radiant intensity) of light emitted from a light source. [Figure 4] FIG. 4 is a diagram showing how the electro-optical characteristics of the liquid crystal element change over time. [Figure 5] 5(A) to 5(C) are diagrams showing the optical spectra of lighting devices using various optical filters. [Figure 6] 6(A) and 6(B) are diagrams showing the optical spectra of various optical filters. [Figure 7] FIG. 7 is a diagram showing the results of calculation of the in-plane irradiance distribution of light incident on a liquid crystal element. DETAILED DESCRIPTION OF THE INVENTION

[0008] Fig. 1(A) is a diagram showing the configuration of a vehicle lighting system according to one embodiment. The vehicle lighting system shown in Fig. 1(A) includes a vehicle lighting device (lamp unit) 1, a controller 2, and a camera 3. This vehicle headlamp system detects the positions of vehicles ahead, pedestrians' faces, and the like present around the vehicle based on images captured by the camera 3, and sets a certain range including the position of the vehicle ahead as a dimming range (or non-illumination range) and sets the remaining range as a light illumination range to selectively illuminate the vehicle, and also illuminates various shapes of light onto the road surface.

[0009] The vehicle lamp 1 is disposed at a predetermined position in the front of the vehicle and emits light to illuminate the area ahead of the vehicle. Although one vehicle lamp 1 is provided on each side of the vehicle, only one is shown here.

[0010] The controller 2 controls the operation of the light source 10 and the liquid crystal element 15 of the vehicle lamp 1. The controller 2 is realized by using a computer system having, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and by running a predetermined operation program on the computer system. The controller 2 of this embodiment turns on the light source 10 in accordance with the operating state of a light switch (not shown) installed at the driver's seat, sets a light distribution pattern in accordance with objects detected by the camera 3, such as a forward vehicle (an oncoming vehicle or a preceding vehicle), a pedestrian, a road sign, or a white line on the road, and supplies a control signal to the liquid crystal element 15 to form an image corresponding to this light distribution pattern.

[0011] The camera 3 captures an image of the space ahead of the vehicle and generates an image, and performs a predetermined image recognition process on this image to detect the position, range, size, type, etc. of the target object, such as the vehicle ahead. The detection results from the image recognition process are supplied to the controller 2 connected to the camera 3. The camera 3 is installed in a predetermined position inside the vehicle's cabin (for example, above the windshield) or in a predetermined position outside the vehicle's cabin (for example, inside the front bumper). If the vehicle is equipped with a camera for another purpose (for example, an automatic braking system, etc.), that camera may be used in common.

[0012] The image recognition processing function of the camera 3 may be performed by the controller 2. In this case, the camera 3 outputs the generated image to the controller 2, and the controller 2 performs image recognition processing based on this image. Alternatively, both the image and the result of the image recognition processing based on the image may be supplied from the camera 3 to the controller 2. In this case, the controller 2 may further perform its own image recognition processing using the image obtained from the camera 3.

[0013] 1(A) includes a light source 10, reflectors (reflective members) 11 and 13, a polarizing beam splitter (first polarizing element) 12, a quarter-wave plate 14, a liquid crystal element 15, an optical compensation plate 16, a polarizing plate (second polarizing element) 17, a projection lens 18, and an optical filter 19. These elements are integrated into one unit, for example, housed in a single housing. The light source 10 and the liquid crystal element 15 are each connected to a controller 2.

[0014] The light source 10 emits light under the control of the controller 2. The light source 10 includes a light emitting element such as several white LEDs (Light Emitting Diodes) and a drive circuit. However, the configuration of the light source 10 is not limited to this. For example, the light source 10 may be a laser element, or a light source commonly used in vehicle lighting fixtures such as an incandescent lamp or a discharge lamp.

[0015] Reflector 11 is disposed in correspondence with light source 10, and reflects and collects light emitted from light source 10 so that the light is focused at the position of liquid crystal element 15 (for example, approximately at the center of liquid crystal element 15 in the thickness direction), and guides the light toward polarizing beam splitter 12, where it is incident on liquid crystal element 15. Reflector 11 is, for example, a reflecting mirror having an ellipsoidal reflecting surface. In this case, light source 10 can be disposed near the focal point of the reflecting surface of reflector 11. Note that a lens may be used as a light collecting unit instead of reflector 11.

[0016] The polarizing beam splitter 12 is a transflective polarizing element that transmits light polarized in a specific direction out of the incident light and reflects light polarized in a direction perpendicular to that direction, and is disposed obliquely with respect to the light incident surface on the light incident side of the liquid crystal element 15. For example, a wire grid polarizing element or a multilayer film polarizing element can be used as this polarizing beam splitter 12.

[0017] The reflector 13 is provided at a position where the light reflected by the polarizing beam splitter 12 can be incident, and reflects and collects the incident light so that it is focused at the position of the liquid crystal element 15, causing it to enter the polarizing beam splitter 12.

[0018] The quarter-wave plate 14 is disposed on the optical path between the polarizing beam splitter 12 and the reflector 13, and imparts a phase difference to the incident light. In this embodiment, the light reflected by the polarizing beam splitter 12 passes through the quarter-wave plate 14, is reflected by the reflector 13, and passes through the quarter-wave plate 14 again, rotating the polarization direction by 90° and re-entering the polarizing beam splitter 12. This puts the re-entering light in a state where it is more easily transmitted through the polarizing beam splitter 12, thereby improving the light utilization efficiency.

[0019] 1(B), a half-wave plate 14a can be used instead of the quarter-wave plate 14. In this case, the half-wave plate 14a is disposed at a position where the light reflected by the polarizing beam splitter 12 does not enter the half-wave plate 14a, but where the light reflected by the reflector 13 enters the half-wave plate 14a.

[0020] The liquid crystal element 15 is disposed at a position including the focal points of the light reflected and collected by each of the reflectors 11 and 13, and is disposed so that the light is incident thereon. The liquid crystal element 15 includes a plurality of pixel units (light modulation units) that can be controlled independently of each other. In this embodiment, the liquid crystal element 15 has a driver (not shown) for applying a drive voltage to each pixel unit. The driver applies a drive voltage to the liquid crystal element 15 to individually drive each pixel unit based on a control signal supplied from the controller 2. As shown in the figure, light incident on the liquid crystal element 15 is incident at a wide angle with respect to the light incident surface of the liquid crystal element 15. Specifically, the light is incident at a wide angle of about 40° to 60° with respect to the normal direction of the light incident surface.

[0021] Optical compensator 16 compensates for the phase difference of light transmitted through liquid crystal element 15 and increases the degree of polarization, and is disposed on the light exit surface side of liquid crystal element 15. Specifically, the phase difference of optical compensator 16 is set so that the phase difference combined with the phase difference of liquid crystal layer 15 is 0 or a value close to 0. Note that optical compensator 16 may be omitted.

[0022] The polarizing plate 17 is disposed on the light exit surface side of the liquid crystal element 15. An image corresponding to the light distribution pattern of the light irradiated ahead of the vehicle is formed by the polarizing beam splitter 12, the polarizing plate 17, and the liquid crystal element 15 disposed therebetween.

[0023] The projection lens 18 is disposed at a position where light reflected and condensed by the reflectors 11 and 13 and transmitted through the liquid crystal element 15 can enter, and projects this incident light ahead of the vehicle. The projection lens 18 is disposed so that its focal point is formed on the liquid crystal layer of the liquid crystal element 15. The optical axis of the projection lens 18 is aligned with the left-right direction in the drawing, as indicated by the dashed line in the drawing.

[0024] The optical filter 19 is disposed between the polarizing beam splitter 12 and the liquid crystal element 15. This optical filter 19 attenuates or passes components of a specific wavelength range from the light incident on the liquid crystal element 15. In principle, the optical filter 19 can be disposed at any position on the optical path from the light source 10 to the liquid crystal element 15. For example, the optical filter 19 can be disposed between the light source 10 and the reflector 11, or between the reflector 11 and the polarizing beam splitter 12. The optical filter 19 may be a filter made of an optical multilayer film. The optical filter 19 may have a transmission spectrum that is approximately equal when observed from the front and when observed from an oblique angle. The optical filter 19 may also have a transmission spectrum that is different when observed from the front and when observed from an oblique angle, with a longer cutoff wavelength when observed from an oblique angle. Furthermore, the optical filter 19 preferably contains a light-absorbing material. When the optical filter 19 is disposed between a light-collecting part such as the reflector 11 and the liquid crystal element 15, it is preferable to use an optical filter whose transmission spectrum has little dependency on the angle of incidence, such as a glass filter containing a light-absorbing material, which can prevent the emission spectrum of light incident on the liquid crystal element 15 from varying depending on the angle of incidence.

[0025] 2 is a schematic cross-sectional view showing an example of the configuration of a liquid crystal element. Here, a segment display type liquid crystal element is shown as an example. Specifically, the illustrated liquid crystal element 15 includes a first substrate 51 and a second substrate 52 arranged opposite each other, a plurality of wirings 53, a common electrode (counter electrode) 54, an insulating layer (insulating film) 55, a plurality of pixel electrodes 56, alignment films 57 and 58, and a liquid crystal layer 59.

[0026] The first substrate 51 and the second substrate 52 are, for example, rectangular substrates in a plan view, and are arranged opposite each other. Each substrate may be, for example, a light-transmitting substrate such as a glass substrate or a plastic substrate. Spherical spacers (not shown) made of, for example, a resin film are dispersed between the first substrate 51 and the second substrate 52, and these spherical spacers maintain the gap between the substrates at a desired size (for example, about several μm). Instead of the spherical spacers, pillars made of, for example, resin may be provided on the first substrate 51 side or the second substrate 52 side and used as spacers. In this embodiment, the first substrate 51 is arranged opposite the polarizing plate 17, and the second substrate 52 is arranged opposite the polarizing beam splitter 12. That is, the first substrate 51 side is the light-emitting side of the liquid crystal element 15, and the second substrate 52 is arranged opposite the light-incident side of the liquid crystal element 15.

[0027] A plurality of wiring sections 53 are provided on one surface of the second substrate 52 below the insulating layer 55. These wiring sections 53 are formed by appropriately patterning a transparent conductive film such as indium tin oxide (ITO). Each wiring section 53 is used to apply a voltage to each pixel electrode 56 from a driver.

[0028] The common electrode 54 is provided on one surface of the first substrate 51. The common electrode 54 is provided integrally with and faces each of the pixel electrodes 56 of the second substrate 52. The common electrode 54 is formed by appropriately patterning a transparent conductive film made of, for example, indium tin oxide (ITO).

[0029] The insulating layer 55 is provided on one surface of the second substrate 52 above the wiring 53 so as to cover them. In this embodiment, the insulating layer 55 is provided so as to cover substantially the entire one surface of the second substrate 52. This insulating layer 55 is, for example, a SiO2 film or a SiON film, and can be formed by a vapor phase process such as a sputtering method or a solution process. Note that an organic insulating film may also be used as the insulating layer 55. The thickness of the insulating layer 55 is, for example, about 1 μm.

[0030] A plurality of pixel electrodes 56 are provided on one surface of the second substrate 52, above the insulating layer 55. These pixel electrodes 56 are formed by appropriately patterning a transparent conductive film made of, for example, indium tin oxide (ITO). In this embodiment, a pixel portion is formed in the portion where each pixel electrode 56 faces the common electrode 54.

[0031] Each pixel electrode 56 is physically and electrically connected to one of the wiring portions 53 via a through-hole provided in the insulating layer 55. By providing each pixel electrode 56 and each wiring portion 53 in different layers in this way, there is no need to provide wiring between the pixel electrodes 56, which reduces the gaps between the pixel electrodes 56 and improves the aperture ratio and the amount of transmitted light. This also increases the degree of freedom in the layout of each wiring portion 53.

[0032] The alignment film 57 is disposed on one surface of the first substrate 51, covering the pixel electrodes 56. The alignment film 58 is disposed on one surface of the second substrate 52, covering the common electrode 54. These alignment films 57, 58 regulate the alignment state of the liquid crystal layer 59. Each alignment film 57, 58 has been subjected to a uniaxial alignment treatment, such as rubbing, and has a uniaxial alignment regulation force that determines the alignment of the liquid crystal molecules in the liquid crystal layer 59 along that direction. The alignment treatment directions of the alignment films 57, 58 are set, for example, to be alternate (anti-parallel). The pretilt angle near the interface between each alignment film 57, 58 and the liquid crystal layer 59 is, for example, approximately 89°. In this embodiment, an alignment film made of alicyclic polyimide or alicyclic polyamic acid is used.

[0033] The liquid crystal layer 59 is provided between the first substrate 51 and the second substrate 52. The liquid crystal layer 59 is made of, for example, a nematic liquid crystal material having fluidity. The liquid crystal layer 59 is made of, for example, a liquid crystal material having negative dielectric anisotropy and refractive index anisotropy of approximately 0.13. The thickness of the liquid crystal layer 59 can be, for example, approximately 4 μm.

[0034] The liquid crystal element 15 is not particularly limited in terms of its internal structure or driving method, as long as it can freely modulate transmitted light to form a desired image. For example, while the above-mentioned configuration example shows an example in which the wiring portion and the pixel electrodes are formed on separate layers, this is not limiting and they may be formed on the same layer. The liquid crystal element 15 may be an active matrix liquid crystal element in which a thin film transistor is associated with each pixel, or a simple matrix liquid crystal element in which multiple striped transparent electrodes are arranged opposite each other and each overlapping area of ​​the transparent electrodes is used as a pixel portion. Furthermore, the liquid crystal element 15 may be a segment display liquid crystal element having multiple pixel electrodes of any shape provided on one substrate and one (or multiple) counter electrodes provided on the other substrate. In this case, either multiplex driving or static driving may be used as the driving method.

[0035] 3 is a diagram showing the emission spectrum (spectral radiant intensity) of light emitted from a light source. The white LED used in light source 10 of this embodiment includes a blue LED and a yellow phosphor placed at a position where the light emitted from the blue LED is incident. The blue LED excites the yellow phosphor, and white light is obtained by mixing the blue and yellow colors. As shown in the diagram, the light emitted from light source 10 has a peak wavelength of 440 nm for the wavelength peak showing the maximum intensity. The peak wavelength of the second emission peak is around 545 nm.

[0036] Figure 4 shows the change over time in the electro-optical characteristics of a liquid crystal element. In this example, a constant amount of power was supplied to the light source 10 of the vehicle lamp 1 shown in Figure 1(A) to emit light, and the liquid crystal element 15 was placed in a light-transmitting state. After a specific period of time, the liquid crystal element 15 was removed and placed between polarizers in a crossed Nicol configuration, with the transmission axes of the polarizers and the alignment direction of the liquid crystal element 15 at a 45° angle. The electro-optical characteristics of the liquid crystal element 15 in the substrate normal direction were measured. A soluble polyimide-type vertical alignment film was used as the alignment film for the liquid crystal element 15. The measurement points were within a 3-mm diameter area centered on the position where the liquid crystal element 15 was irradiated with light at the highest illuminance.

[0037] Over time, the electro-optical characteristics change, and a tendency for transmittance to decrease at an applied voltage of 12 V is observed. After 60 hours (60H), the maximum achievable transmittance is equivalent to that of the initial state (0H). However, the maximum transmittance decreases with time, at 150 hours (150H), 320 hours (320H), and 500 hours (500H). For liquid crystal element 15 aged for more than 60 hours, the transmittance decreased to a degree that was visible at the measurement point, even when directly observing the liquid crystal element 15 without a polarizer. For liquid crystal element 15 aged for more than 150 hours, the area around the measurement point turned yellow in appearance. Furthermore, the threshold voltage at around 2.5 V also changed. When a liquid crystal element with a similar configuration using a polyamic acid-type vertical alignment film was used, the transmittance decreased slightly, but the tendency for transmittance to decrease over time was similar.

[0038] Such light degradation is a phenomenon specific to the use of a configuration in which light is incident on the liquid crystal element 15 at a wide angle and condensed to form a focus at the position of the liquid crystal element 15, such as in the vehicle lamp 1 of this embodiment. This phenomenon is not seen in configurations that are based on the premise that parallel or diffused light is incident on the liquid crystal element, such as in conventional applications such as liquid crystal projectors. This is because the illuminance at a specific position on the liquid crystal element is not that high in conventional applications.

[0039] A component analysis of the alignment film near the measurement point was performed on the liquid crystal element 15 in its initial state and on the liquid crystal element 15 after 500 hours of light irradiation. In this embodiment, the alignment film is assumed to be made by polymerizing low-molecular-weight materials, carboxylic acid dianhydride and diamine, to produce polyamic acid, a precursor of polyimide, and then obtaining polyimide. The component analysis revealed a significant increase in low-mass, i.e., low-molecular-weight materials, such as carboxylic acid, and a decrease in high-mass (polymeric) components originating from polyimide.

[0040] In other words, it is believed that the polyimide alignment film, which controls the alignment of liquid crystal molecules in the liquid crystal layer, was decomposed by light irradiation, causing the alignment control force to disappear and further turning yellow. Note that the alignment film of this embodiment is assumed to be a soluble polyimide, so the imidization rate is approximately 100%, and it is believed that no carboxylic acid dianhydride or diamine is present as an impurity. This also supports the belief that the decomposition of polyimide due to light irradiation is the main cause of the above-mentioned deterioration phenomenon.

[0041] 5(A) to 5(C) and 6(A) to 6(B) are diagrams showing the optical spectra of lighting devices using various optical filters considered in this embodiment. Note that these diagrams show the optical spectra of light emitted from the light source 10 having the emission optical spectrum shown in FIG. 3 after passing through each optical filter.

[0042] 5A is a low-pass filter that cuts off ultraviolet light of wavelengths below 400 nm. The transmittance in the wavelength range below 400 nm is 0.1% or less, and the transmittance in the wavelength range above 440 nm is 90%, so that in the wavelength range above 400 nm, a spectrum is obtained in which the light intensity of the original emission spectrum of light source 10 is slightly reduced.

[0043] The optical filter shown in Figure 5(B) is a low-pass filter that cuts off light of 465 nm or less. The transmittance in the wavelength range of 465 nm or less is 0.1% or less, and the transmittance in the wavelength range of 530 nm or more is 90%.

[0044] The optical filter shown in Figure 5(C) is a high-pass filter that cuts off light of 485 nm or longer. The transmittance in the wavelength range of 485 nm or longer is 0.1% or less, and the transmittance in the wavelength range of 380 nm or shorter is 90%.

[0045] 6(A) is a high-pass filter that cuts off light of 575 nm or longer. The transmittance in the wavelength range of 575 nm or longer is 0.1% or less, and the transmittance in the wavelength range of 430 nm to 450 nm is 50%.

[0046] The optical filter shown in Figure 6(B) is a high-pass filter that cuts off light of 435 nm or less. The transmittance in the wavelength range of 435 nm or more is 0.1% or less, and the transmittance in the wavelength range of 470 nm or more is 90%.

[0047] The effect of each of the optical filters described above in suppressing the deterioration phenomenon of the liquid crystal element 15 was confirmed. The light emitted from the light source 10 was continuously irradiated onto the liquid crystal element 15 through each optical filter for a period of time that would necessarily cause deterioration (a decrease in transmittance) if no optical filter was used, and then the appearance of the liquid crystal element 15 was observed. Note that when an optical filter is placed, the illuminance of the transmitted light irradiating the liquid crystal element 15 decreases accordingly, so this decrease was compensated for by adjusting the irradiation time so that the same integrated light intensity was obtained for all optical filters. When no optical filter was placed, the illuminance of the liquid crystal element 15 at the measurement point was 0.181 W / mm 2 The irradiation time is 500 hours, and the cumulative light intensity is 325800 J / mm 2 is.

[0048] Visual observations revealed that a decrease in transmittance at high-illuminance measurement points was observed when using the optical filters with the characteristics shown in Figures 5(A), 5(C), and 6(A). On the other hand, no decrease in transmittance was observed when using the optical filters with the characteristics shown in Figures 5(B) and 6(B). All optical filters that showed no decrease in transmittance had a common characteristic of a transmittance of 0.1% or less in the wavelength range of 435 nm or less. Furthermore, the optical filter with the characteristics shown in Figure 6(B) had a transmittance of 17% or less at wavelengths of 450 nm or less. Therefore, it was found that by using an optical filter that satisfies these two conditions as the optical filter 19 in the vehicle lamp 1, it is possible to suppress the decrease in transmittance due to light degradation in the high-illuminance region where incident light focuses on the liquid crystal element 15.

[0049] Furthermore, even if a light source having a peak wavelength of an emission peak on the short wavelength side in the wavelength range of 450 nm or more is used as light source 10, by using one in which the emission intensity at 435 nm or less is 0.1% or less of the emission intensity of the peak wavelength on the short wavelength side and the emission intensity at 450 nm is 17% or less, it is considered possible to suppress the decrease in transmittance by a similar mechanism even if optical filter 19 is omitted.

[0050] FIG. 7 shows the results of calculating the in-plane irradiance distribution of light incident on the liquid crystal element. In the figure, the vertical axis Y and the horizontal axis X indicate the in-plane position of the liquid crystal element 15. The position with the highest radiant intensity is the origin (center). This irradiance pattern had the same shape as the dark area caused by photodegradation of the liquid crystal element 15 that occurs when the optical filter 19 is not used. The area where this decrease in transmittance is recognized is ±6 mm from the origin of the X axis, and the irradiance at the edge of this area is 0.18 W / mm 2 , the irradiance at the origin. 2 0.023W / mm 2 The cumulative light intensity was 41,400 J / mm 2 is presumed to be the threshold value for determining whether photodegradation occurs or not.

[0051] According to the above-described embodiment, it is possible to suppress partial photodegradation of the liquid crystal element in the vehicle lamp (illumination device), thereby suppressing the occurrence of dark areas in the light distribution pattern of the irradiated light. In particular, when an optical system that reuses reflected light from a polarizing beam splitter is used as in the present embodiment, the intensity of the light incident on the liquid crystal element becomes higher, which is likely to cause photodegradation of the alignment film. However, by using the above-described configuration, it is possible to suppress partial photodegradation of the liquid crystal element.

[0052] The present disclosure is not limited to the above-described embodiments, and various modifications can be made within the scope of the present disclosure. For example, the configuration of the vehicle lamp is not limited to the configuration of the above-described embodiments. The configuration of the liquid crystal element is also not limited to the configuration of the above-described embodiments.

[0053] Furthermore, while the above-described embodiments have cited vehicle lamps as an example of a lighting device, the scope of application of the present disclosure is not limited to this. For example, the configuration according to the present disclosure can be applied to various lighting devices such as street lights, railroad crossing lighting devices, and direction guide lighting devices. Furthermore, the optical system of the vehicle lamp is not limited to the configuration of the above-described embodiments. [Explanation of symbols]

[0054] 1: Vehicle lamp, 2: Controller, 3: Camera, 10: Light source, 11, 13: Reflector, 12: Polarizing beam splitter, 14: 1 / 2 wavelength plate, 15: Liquid crystal element, 16: Optical compensation plate, 17: Polarizing plate, 18: Projection lens, 19: Optical filter, 51: First substrate 51, 52: Second substrate, 53: Wiring section, 54: Common electrode (counter electrode), 55: Insulating layer (insulating film), 56: Pixel electrode, 57, 58: Alignment film, 59: Liquid crystal layer

Claims

1. A light source and a focusing unit that focuses light emitted from the light source so as to form a focus at a predetermined position; a liquid crystal element disposed at a position including the focal point; a first polarizing element disposed on the light incident surface side of the liquid crystal element; a second polarizing element disposed on the light exit surface side of the liquid crystal element; a projection lens that enlarges and projects an image generated by the liquid crystal element, the first polarizing element, and the second polarizing element; an optical filter disposed on an optical path from the light source to the liquid crystal element; Including, the light source has an emission peak at 450 nm or less, the optical filter is a low-pass filter having a relative transmittance of 0.1% or less at 435 nm or less and a relative transmittance of 17% or less at 450 nm or less; Lighting equipment.

2. The light source is configured using a white LED. The lighting device according to claim 1 .

3. The irradiance at the position of the focus is 0.023 W / mm ２ That's all.

3. The lighting device according to claim 1 or 2.

4. the liquid crystal element is configured using an alignment film made of alicyclic polyimide and / or alicyclic polyamic acid; The lighting device according to any one of claims 1 to 3.

5. the first polarizing element is a transflective polarizing plate, The polarizing plate may further include a reflector that reflects and collects light incident from the light source and reflected by the first polarizing element, and that collects the light and makes the light incident on the first polarizing element. The lighting device according to any one of claims 1 to 4.

6. the optical filter has an equal transmission spectrum when observed from the front and when observed obliquely; The lighting device according to any one of claims 1 to 5.

7. the optical filter has a transmission spectrum that differs between when observed from the front and when observed obliquely, and has a longer cutoff wavelength when observed obliquely; The lighting device according to any one of claims 1 to 5.

8. The optical filter is configured using an optical multilayer film. The lighting device according to any one of claims 1 to 7.

9. A light source and a focusing unit that focuses light emitted from the light source so as to form a focus at a predetermined position; a liquid crystal element disposed at a position including the focal point; a first polarizing element disposed on the light incident surface side of the liquid crystal element; a second polarizing element disposed on the light exit surface side of the liquid crystal element; a projection lens that enlarges and projects an image generated by the liquid crystal element, the first polarizing element, and the second polarizing element; Including, the light source has an emission intensity peak on the short wavelength side in a wavelength range of 450 nm or more, an emission intensity in a wavelength range of 435 nm or less relative to the emission intensity peak in the wavelength range of 450 nm or more being 0.1% or less, and an emission intensity at 450 nm relative to the emission intensity peak in the wavelength range of 450 nm or more being 17% or less; Lighting equipment.

10. 10. A vehicle lighting system comprising: the lighting device according to claim 1; and a controller connected to the lighting device for controlling its operation.

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