Display device and control method for display device

Abstract

A display device (1) comprises: an image display body (10) having a display function layer (11) the light scattering property of which is increased by receiving ultraviolet light and decreased by receiving specific visible light which is visible light in a specific wavelength region; a first projector (20) that projects ultraviolet light onto the image display body (10); and a second projector (40) that projects visible light having an arbitrary wavelength onto a light projection region (10c) on the image display body (10) in which the light scattering property of the display function layer (11) has been increased, to thereby display a visible light image having an arbitrary shape and color component in the light projection region (10c). The first projector (20) projects the ultraviolet light in an overlapping manner onto at least a specific light projection region (15), within the light projection region (10c) onto which the visible light is projected during the display of the visible light image, onto which the specific visible light is projected.

Description

Display device and control method for display device

[0001] This disclosure relates to a display device and a method for controlling the display device.

[0002] In recent years, display devices have been developed that use technology to display images on transparent glass such as car windshields and building windows. Patent Document 1 discloses a display device that has a display functional layer whose light scattering properties increase when exposed to ultraviolet light, which is then projected onto the image display body to create a screen (make it opaque), and then projected onto the image display body to display an image related to the visible light (visible light image).

[0003] Patent No. 7063081

[0004] When displaying visible light images, visible light from various wavelength ranges can be projected onto the image display surface for color representation. A non-transparent image display surface becomes transparent (non-screened) when the light scattering properties of the display functional layer decrease upon reception of visible light, but the rate of decrease in light scattering properties (degree of transparency progression) differs depending on the wavelength of visible light. As a result, the light scattering properties in the display functional layer become non-uniform, and the brightness of the visible light image being displayed may partially decrease, causing uneven brightness. However, the display device described in Patent Document 1 was unable to suppress brightness unevenness in the visible light image.

[0005] Therefore, the present disclosure aims to provide a technology that can equalize the light scattering properties of the display function layer during the display of a visible light image, thereby suppressing the occurrence of brightness unevenness in the visible light image.

[0006] A display device according to one aspect of the present disclosure includes: an image display body having a display function layer whose light scattering properties increase when it receives ultraviolet light and decrease when it receives specific visible light, which is visible light in a specific wavelength range; an ultraviolet light projection unit that projects ultraviolet light onto the image display body; and a visible light projection unit that projects visible light of an arbitrary wavelength onto a projection area on the image display body where ultraviolet light has been projected and the light scattering properties of the display function layer have increased, thereby displaying a visible light image with arbitrary shape and color components within the projection area, wherein the ultraviolet light projection unit superimposes ultraviolet light onto at least a specific projection area onto which the specific visible light is projected, among the projection areas onto which visible light is projected during the display of the visible light image.

[0007] Furthermore, a control method for a display device according to one aspect of the present disclosure is a control method for a display device that projects ultraviolet light onto an image display body having a display function layer whose light scattering properties increase when it receives ultraviolet light and decrease when it receives specific visible light which is visible light in a specific wavelength range, projects visible light of an arbitrary wavelength onto a projection area on the image display body where the light scattering properties of the display function layer have increased due to the projection of ultraviolet light, and displays a visible light image with arbitrary shape and color components within the projection area, wherein during the display of the visible light image, ultraviolet light is superimposed on at least the specific projection area onto which the specific visible light is projected among the projection areas onto which visible light is projected.

[0008] According to this disclosure, the light scattering properties of the display function layer can be made uniform during the display of a visible light image, thereby suppressing the occurrence of brightness unevenness in the visible light image.

[0009] This is a perspective view showing the schematic configuration of a display device according to the first embodiment of this disclosure. This is a cross-sectional view showing the schematic configuration of the image display body shown in Figure 1. This is a cross-sectional view showing the schematic configuration of the display function layer in a transparent state. This is a cross-sectional view showing the schematic configuration of the display function layer in an opaque state. This is a diagram showing the absorption spectrum of an azobenzene molecule (cis isomer) in the display function layer. This is a schematic diagram showing an example of a visible light image on the image display body. This is a schematic diagram illustrating an example of a visible light and ultraviolet light projection pattern in a display device according to the first embodiment. This is a schematic diagram illustrating another example of an ultraviolet light projection pattern in a display device according to the first embodiment. This is a flowchart showing an example of a control method for a display device according to the first embodiment of this disclosure. This is a flowchart showing an example of a control method for a display device according to a first modification of the first embodiment of the present invention. This is a schematic diagram illustrating an example of ultraviolet light and visible light projection control in a display device according to a second modification of the first embodiment of the present invention. This is a flowchart showing an example of a control method for a display device according to a second modification of the first embodiment of the present invention. This is a perspective view showing the schematic configuration of a display device according to the second embodiment of the present invention.

[0010] Embodiments of the present invention will be described below with reference to the drawings. Note that the drawings are schematic and may differ from actual ones. Furthermore, the embodiments of the present invention described below are illustrative examples of devices and methods for realizing the technical concept of the present invention, and the technical concept of the present invention is not limited to the structure, arrangement, etc., of the components described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims described in the patent claims.

[0011] 1. Figure 1 of the first embodiment is a perspective view showing the schematic configuration of a display device 1 according to the first embodiment of the present invention. The display device 1 of this embodiment comprises an image display body 10, a first projector (an example of an ultraviolet light emitting unit) 20, a second projector (an example of a visible light emitting unit) 40, and a control unit 50.

[0012] The image display body 10 is a thin plate-shaped member whose optical state changes between a transparent state and an opaque state, and has a front surface 10a facing the first projector 20 and the second projector 40, and a back surface 10b opposite the front surface 10a. The image display body 10 changes from a transparent state (non-screen state) to an opaque state (screen state) when it receives ultraviolet light, and changes from an opaque state to a transparent state when it receives visible light in a specific wavelength range. The image display body 10 may be attached, for example, to the windshield of an automobile. A detailed description of the image display body 10 will be given later.

[0013] The first projector 20 is a projector that emits ultraviolet light and has an arbitrary ultraviolet light source (UV light source), and is positioned opposite the front surface 10a of the image display unit 10. The first projector 20 is an ultraviolet light projection unit that projects ultraviolet light onto the image display unit 10, and for example, emits ultraviolet light with a wavelength of around 365 nm. The first projector 20 projects ultraviolet light onto the front surface 10a of the image display unit 10, changing the ultraviolet light projection area 10c on the image display unit 10 from a transparent state to an opaque state (screen state).

[0014] The second projector 40 is a color projector and is positioned opposite the front surface 10a of the image display unit 10. The second projector 40 has any visible light source such as a laser, mercury lamp, or LED, and emits visible light for image projection as a visible light projection unit, which is light of one of three colors: blue (for example, a wavelength of around 450 nm), green (for example, a wavelength of around 530 nm), and red (for example, a wavelength of around 630 nm), or light of a combination of two or more colors. The second projector 40 projects visible light onto the projection area 10c of the first projector 20 of the image display unit 10, thereby displaying an image 60, which is a visible light image of any color and shape, on the non-transparent image display unit 10. In other words, the second projector 40 is a visible light projection unit that projects visible light of an arbitrary wavelength onto the projection area 10c on the image display body 10, which has been made opaque (screen state) by the projection of ultraviolet light, and displays a visible light image (image 60 in this example) with arbitrary shape and color components within the projection area 10c.

[0015] The control unit 50 controls the operation of the first projector 20 and the second projector 40. The control unit 50 communicates with a higher-level control device (not shown) and switches the first projector 20 and the second projector 40 between emitting light and not emitting light. The control unit 50 communicates with the higher-level control device and sends a predetermined signal or command to the first projector 20 to instruct it to emit ultraviolet light. As a result, under the instruction of the control unit 50, ultraviolet light is emitted onto the front surface 10a of the image display unit 10, making the emitted light area 10c opaque (screened). The control unit 50 also communicates with the higher-level control device and sends image information to the second projector 40. As a result, under the instruction of the control unit 50, visible light is emitted onto the emitted light area 10c and a visible light image (for example, image 60) is displayed.

[0016] For example, the control unit 50 sends image information indicating the color components of a visible light image to the second projector 40. The image information may include image color signals as image color information indicating the color components of each pixel of the visible light image (for example, image 60). In this example, the second projector 40 projects visible light of a wavelength corresponding to the color components of the visible light image (image 60) indicated by the image information (image color signals) sent by the control unit 50 onto the projection area 10c of the image display unit 10. As a result, image 60 is displayed within the projection area 10c of the image display unit 10. For example, the control unit 50 may send a projection pattern composed of image color signals as image information to the first projector 20. Details of the projection pattern will be described later.

[0017] In the display device 1, the first projector 20 and the second projector 40 emit ultraviolet light and visible light for projecting a visible light image (image 60 in this example) respectively, based on the control of the control unit 50, so that the image 60 displayed on the image display body 10 is contained within the ultraviolet light emission area 10c on the image display body 10.

[0018] The control unit 50 may include one or more processors and memory (RAM and ROM) for storing programs executable by the processors. The control unit 50 may be a microcomputer that, for example, reads a program from memory using the processor, executes processing according to the program, and sends and receives various signals and commands to and from each projector (first projector 20, second projector 40), thereby realizing control of each projector in the display device 1. The control unit 50 is not limited to a microcomputer, and a single-board computer or the like can be used. The control unit 50 is connected to each projector of the display device 1 and a higher-level control device (not shown) so as to be able to communicate information. When the image display unit 10 is installed inside a car (for example, on the windshield), the control unit 50 may be installed inside the car (on the dashboard, etc.). However, it is not limited to this, and the control unit 50 may be a portable information terminal device for the user. Furthermore, the control unit 50 may be capable of communicating with a higher-level control device (not shown) that serves as an image (video) source, such as a video recorder or a personal computer, and may be capable of receiving video signals, computer signals, etc., as image (video) signals.

[0019] Next, with reference to Figure 2, the image display body 10 of the display device 1 will be described in detail. Figure 2 is a cross-sectional view showing the schematic configuration of the image display body 10. The image display body 10 of this embodiment includes a display function layer 11, a dimming layer 12, and an ultraviolet light shielding layer 13. The display function layer 11 is arranged on the transparent substrate 101 side that forms the front surface 10a of the image display body 10, and the ultraviolet light shielding layer 13 is arranged on the transparent substrate 102 side that forms the back surface 10b of the image display body 10. The dimming layer 12 is arranged between the display function layer 11 and the ultraviolet light shielding layer 13. In other words, the image display body 10 may be configured in which the display function layer 11, the dimming layer 12, and the ultraviolet light shielding layer 13 are stacked in this order from the transparent substrate 101 side to the transparent substrate 102 side. Note that the image display body 10 only needs to include at least transparent substrates 101, 102 and the display function layer 11.

[0020] The display function layer 11 is a film material whose optical state changes between a transparent state and an opaque state. The display function layer 11 has optical properties in which its light scattering increases when it receives ultraviolet light and decreases when it receives visible light. When the display function layer 11 receives ultraviolet light, it becomes opaque due to the increase in light scattering, and when it receives visible light, it returns to a transparent state due to the decrease in light scattering. As a result, the image display body 10 can reversibly change between a transparent state (non-screen state) and an opaque state (screen state). As will be described in more detail later, the light scattering of the display function layer 11 decreases when it receives visible light in a specific wavelength range. The display function layer 11 in this embodiment is a liquid crystal film containing host liquid crystal molecules 91 and azobenzene molecules 92.

[0021] The light-adjusting layer 12 is a transparent film component whose light absorption increases when exposed to ultraviolet light. The light-adjusting layer 12 contains a photochromic material and has optical properties that cause it to change color from colorless to gray (or black) when exposed to ultraviolet light, as its light absorption increases. The light-adjusting layer 12 also has optical properties that cause it to return to colorless from gray when it is not exposed to ultraviolet light, as its light absorption decreases. By providing the light-adjusting layer 12 between the display function layer 11 and the ultraviolet light shielding layer 13, background light such as sunlight and headlights can be reduced. In other words, contrast is maintained even in bright environments, and the visibility of visible light images is improved.

[0022] The ultraviolet light shielding layer 13 is a transparent film member that shields ultraviolet light. The ultraviolet light shielding layer 13 is formed of a transparent resin containing an ultraviolet light reflector or an ultraviolet light absorber, and shields light in the wavelength range near ultraviolet light by reflecting or absorbing it. The ultraviolet light shielding layer 13 is positioned on the transparent substrate 102 side that forms the back surface 10b of the image display body 10, and prevents ultraviolet light from entering the display function layer 11 from the back surface 10b of the image display body 10. Therefore, for example, when the image display body 10 is attached to the windshield of a car, it is possible to prevent the image display body 10 from becoming opaque due to sunlight or headlights.

[0023] The transparent substrate 101 forms the front surface 10a of the image display unit 10. The transparent substrate 102 forms the back surface 10b of the image display unit 10. The transparent substrates 101 and 102 are protective substrates that protect the display function layer 11, the dimming layer 12, and the ultraviolet light shielding layer 13. The transparent substrates 101 and 102 only need to have transparency that does not hinder the visibility of the image 60 projected onto the non-transparent image display unit 10, and may be, for example, glass substrates. Alternatively, the transparent substrates 101 and 102 may be transparent resin substrates formed from transparent resin. Furthermore, the transparent substrate 102 may also serve to prevent ultraviolet light entering from the outside from reaching the display function layer 11, in place of the ultraviolet light shielding layer 13. In this case, the transparent substrate 102 may be formed from a material that shields ultraviolet light, or a film that shields ultraviolet light may be attached to it.

[0024] Next, the display function layer 11 of the image display unit 10 will be described in detail with reference to Figures 3A to 3C. Figure 3A is a cross-sectional view showing the schematic configuration of the display function layer 11 in a transparent state together with the transparent substrates 101 and 102, and Figure 3B is a cross-sectional view showing the schematic configuration of the display function layer 11 in a non-transparent state together with the transparent substrates 101 and 102. Figure 3C is a graph showing the absorption spectrum of the azobenzene molecule 92.

[0025] As described above, the display function layer 11 in this embodiment is a liquid crystal film containing host liquid crystal molecules (hereinafter referred to as liquid crystal molecules 91) and azobenzene molecules 92. When azobenzene molecules 92 are exposed to ultraviolet light, their structure changes from the trans form 92a to the cis form 92b, and when exposed to visible light in a specific wavelength range, their structure changes from the cis form 92b to the trans form 92a. When azobenzene molecules 92 change to the cis form 92b, they bend and disrupt the arrangement of liquid crystal molecules 91. Therefore, when ultraviolet light is projected onto the display function layer 11 in a state where the liquid crystal molecules 91 are arranged substantially perpendicular to the thickness direction of the display function layer 11 (see Figure 3A) and the liquid crystal phase is in the nematic phase, the liquid crystal molecules 91 change to a focal conic state and their arrangement is disrupted, changing to a scattering state (see Figure 3B), and the light scattering ability increases. On the other hand, when visible light in a specific wavelength range is projected onto the display functional layer 11, in which the liquid crystal molecules 91 are in a scattering state (see Figure 3B) and the liquid crystal molecules are in a focal conic state, the liquid crystal molecules 91 change to an aligned state (see Figure 3A), the liquid crystal phase changes to a nematic phase, and the light scattering properties decrease.

[0026] The visible light in a specific wavelength range that reduces the light scattering properties of the display functional layer 11 (hereinafter also referred to as "specific visible light") is the visible light in the absorption wavelength range of the azobenzene molecule 92 that has been converted to the cis isomer 92b upon exposure to ultraviolet light. As shown in Figure 3C, the azobenzene molecule 92 that has been converted to the cis isomer 92b has high absorbance of visible light in the wavelength range of approximately 400 nm to 570 nm. In other words, the visible light in the wavelength range of approximately 400 nm to 570 nm, which is the absorption wavelength range of the azobenzene molecule 92 that has been converted to the cis isomer 92b, corresponds to the specific visible light. That is, when the display functional layer 11 contains azobenzene molecule 92, the visible light with a color component corresponding to blue or green becomes the specific visible light that reduces the light scattering properties of the display functional layer 11. When the azobenzene molecule 92 receives blue or green visible light as the specific visible light, its structure changes from the cis isomer 92b to the trans isomer 92a, and the light scattering properties of the display functional layer 11 decrease. Therefore, the image display unit 10 in this example changes from an opaque state (screen state) to a transparent state (non-screen state) when it receives blue or green visible light.

[0027] As shown in FIG. 3C, although the azobenzene molecule 92 changed to the cis form 92b slightly absorbs visible light (visible light other than specific visible light) exceeding 570 nm, its light scattering property does not significantly decrease. That is, when visible light (non-specific visible light) other than blue and green, which does not correspond to a specific wavelength region, is projected, the rate of decrease in the light scattering property in the display functional layer 11 is very slow, and the degree of progress of transparency is very low. The second projector 40, which is a color projector, projects visible light of any one of the three primary colors (red, green, and blue), or two or more colors, onto the light projection region 10c of the image display body 10 to display a visible light image. In the display functional layer 11, the rate of decrease in the light scattering property is clearly different between the region that receives specific visible light (blue light, green light) and the region that receives non-specific visible light (red light).

[0028] In a conventional display device, due to the difference in the rate of decrease in the light scattering property in the display functional layer, the light scattering property in the display functional layer becomes non-uniform, and partial transparency progresses in the image display body, resulting in uneven brightness in the image region of the visible light image being displayed. In a conventional display device, for example, in a region of the display functional layer that receives blue or green visible light, which is specific visible light, the decrease in the light scattering property progresses more rapidly than in a region that receives other visible light (for example, red light). At this time, in the region of the light projection region of the image display body where specific visible light is projected, transparency (non-screening) progresses faster than in other regions. Therefore, in a conventional display device, the brightness of the image region corresponding to the region where specific visible light is projected in the visible light image being displayed decreases, resulting in uneven brightness in the visible light image, which may be recognized by the user as variations in the visibility (shading) of the visible light image.

[0029] Therefore, during the display of the image 60 in the light projection region 10c of the image display body 10, the display device 1 according to the present embodiment additionally projects ultraviolet light onto the region of the light projection region 10c where specific visible light is projected. Thereby, the light scattering property of the display functional layer 11 can be made uniform, and the occurrence of uneven brightness in the visible light image can be suppressed.

[0030] The operation of the display device 1, which emits additional ultraviolet light while displaying a visible light image on the image display unit 10, will be described below with reference to Figures 4A to 4C. Figure 4A is a diagram showing an example of an image 600, which is a visible light image using three visible light colors: red, green, and blue. Figure 4B is a diagram explaining an example of image information used for additional ultraviolet light emission, along with its generation process. Figure 4C is a diagram explaining another example of image information used for additional ultraviolet light emission.

[0031] Similar to image 60 shown in Figure 1, image 600 is displayed in the light-emitting area 10c of the image display unit 10, which has become opaque due to ultraviolet light emitted from the first projector 20. As shown in Figure 4A, the visible light image (image 600) in this example includes a red image 61 composed of red light and having pixels that show red as a color component (red pixels), a green image 62 composed of green light and having pixels that show green as a color component (green pixels), and a blue image 63 composed of blue light and having pixels that show blue as a color component (blue pixels).

[0032] As described above, the image display unit 10, on which a visible light image (image 600) is displayed, contains azobenzene molecules 92 having the absorption spectrum shown in Figure 3C in the display function layer 11, and blue and green visible light become specific visible light. In other words, the green image 62 and the blue image 63 are image regions (specific color image regions) of the visible light image 600 that contain color components corresponding to specific visible light. Furthermore, the region of the light-emitting region 10c of the image display unit 10 that includes the specific color image regions, the green image 62 and the blue image 63, becomes the specific light-emitting region 15 on which specific visible light is emitted. The specific light-emitting region 15 is the region on which specific visible light is emitted, and because the decrease in light scattering properties in the display function layer 11 is more likely to progress, it is more likely to become transparent compared to other regions within the light-emitting region 10c. For example, the specific light-emitting region 15 may be the smallest region that includes the entire image region (green image 62 and blue image 63 in this example) composed of pixels corresponding to specific visible light in the image 600. In this example, the specific light projection area 15 is an area containing cool-colored pixels that make up the green image 62 and the blue image 63.

[0033] In the display device 1 according to the present embodiment, during the display of the image 600 which is a visible light image, ultraviolet light is superimposed and projected onto at least the specific projection area 15 where specific visible light is projected, out of the light projection area 10c where visible light is projected. That is, during the display of the image 600, additional ultraviolet light is projected onto an area in the light projection area 10c that is likely to be transparent (where the reduction in light scattering property in the display functional layer 11 tends to progress). When additional ultraviolet light is projected, the integrated light amount of the ultraviolet light projected onto the specific projection area 15 increases more than that of other areas. During the display of the visible light image, the azobenzene molecules 92 in the display functional layer 11 are maintained in the cis form 92b (or return from the trans form 92a to the cis form 92b). Therefore, when additional ultraviolet light is projected, the reduction in the light scattering property in the display functional layer 11 that receives the specific visible light is suppressed, and the light scattering property of the display functional layer 11 can be made uniform during the display of the visible light image. Thus, the occurrence of luminance unevenness in the visible light image can be suppressed.

[0034] Hereinafter, referring to FIG. 4B, the operations of each component of the display device 1 from the display of the visible light image to the additional projection of ultraviolet light will be described in sequence.

[0035] When the display device 1 displays a visible light image (image 600 in this example) on the image display body 10, the second projector 40, which is a color projector, projects visible light of a wavelength corresponding to the color components of the visible light image indicated by the projection pattern (image information) sent by the control unit 50 onto the projection area 10c. For example, the projection pattern may be composed of an image color signal indicating the color components of each pixel of the visible light image. For example, the image color signal may indicate the pixel value of each pixel of the visible light image. The pixel value may be, for example, an RGB value indicating the RGB (Red / Green / Blue) elements of one pixel. The image color signal may be an RGB signal indicating the color components of each pixel using one of the three primary colors (red, green, blue) or a combination of two or more colors. Of the RGB values ​​indicated by the image color signal, the R value corresponds to red light, the G value corresponds to green light, and the B value corresponds to blue light among the visible light emitted by the second projector 40. For example, the projection pattern may indicate the shape of a visible light image by a combination of image color signals (pixel values). The second projector 40 emits visible light of wavelengths corresponding to the color components of each pixel in the visible light image indicated by the projection pattern and projects it into the projection area 10c of the image display unit 10. As a result, a visible light image with the color and shape corresponding to the projection pattern is displayed in the projection area 10c.

[0036] As shown in Figure 4B, the projection pattern 160 in this example corresponds to a visible light image (image 600) and is composed of image color signals that indicate the color component (e.g., pixel value) of each pixel in image 600 (red image 61, green image 62, and blue image 63). For example, the projection pattern 160 is composed of image color signals (RGB signals) that indicate the RGB values ​​of each pixel in image 600. The projection pattern 160 includes a red pixel pattern 161, a green pixel pattern 162, and a blue pixel pattern 163, each composed of image color signals that indicate the color component of each pixel in the red image 61, green image 62, and blue image 63, respectively. The red pixel pattern 161 is formed by image color signals that indicate the pixel values ​​of the red pixels constituting the red image 61, the green pixel pattern 162 is formed by image color signals that indicate the pixel values ​​of the green pixels constituting the green image 62, and the blue pixel pattern 163 is formed by image color signals that indicate the pixel values ​​of the blue pixels constituting the blue image 63.

[0037] The second projector 40 emits visible light (red light, green light, blue light) of wavelengths corresponding to red, blue, and green, respectively, according to the color components shown by the red pixel pattern 161, green pixel pattern 162, and blue pixel pattern 163 in the light projection pattern 160. As a result, an image 600 having a predetermined shape (three rounded rectangles in this example) and color components shown by the light projection pattern is displayed in the light projection area 10c of the image display unit 10. In this example, the second projector 40 projects specific visible light (blue light, green light) into a specific light projection area 15 within the light projection area 10c based on the light projection pattern. As a result, a specific color image area (green image 62 and blue image 63 in this example), which is an image area containing color components corresponding to the specific visible light, is displayed in the specific light projection area 15.

[0038] The light projection pattern 160 is generated, for example, in the control unit 50 and sent to the second projector 40. When the control unit 50 receives an image signal (video signal, computer signal, etc.) from a higher-level control device (image source), it may generate a light projection pattern corresponding to the image (original image) indicated by the received signal and send it to the second projector 40. The control unit may generate the light projection pattern 160 according to the number of pixels, aspect ratio, and color components (pixel values) of each pixel of the original image. As a result, the second projector 40 can display a visible light image corresponding to the original image on the image display unit 10.

[0039] Furthermore, in the display device 1 according to this embodiment, the control unit 50 extracts specific image information indicating the specific color image region (green image 62 and blue image 63) from the visible light image from the image information (light projection pattern) and sends it to the first projector 20. Specifically, the control unit 50 extracts pixels constituting the specific color image region (green image 62 and blue image 63) that is the target of additional ultraviolet light projection from the light projection pattern 160 corresponding to the visible light image, and sends the ultraviolet light projection pattern 180 generated based on this to the first projector 20. As a result, the display device 1 can have the first projector 20 additionally project ultraviolet light onto the specific light projection region 15 onto which the specific visible light is projected.

[0040] As shown in Figure 4B, the control unit 50 may extract the image color signals of each pixel corresponding to a specific color image region (green image 62 and blue image 63) from the light projection pattern 160 to generate a specific color pattern 170, and generate an ultraviolet light projection pattern 180 based on the specific color pattern 170. The specific color pattern 170 and the ultraviolet light projection pattern 180 correspond to the specific image information. As shown in Figure 4B, in this example, the control unit 50 generates a specific color pattern 170 that includes only the green pixel pattern 162 and the blue pixel pattern 163 from the light projection pattern 160, which show the color components corresponding to specific visible light. The specific color pattern 170 is composed of image color signals corresponding to the green image 62 and the blue image 63 included in the specific light projection region 15. For example, the control unit 50 sets the R value to 0 in the pixel value (RGB value) indicated by the image color signal (RGB signal) that constitutes the light projection pattern 160. In other words, the image color signals representing color components other than the specific visible light (red light in this example) are removed from the projection pattern 160, and only the image color signals corresponding to the pixel values ​​(G value and B value) representing the color components corresponding to the specific visible light are extracted. As a result, a specific color pattern 170 is generated that contains only the image color signals corresponding to the green image 62 and the blue image 63 (specific color image region).

[0041] When the control unit 50 generates a specific color pattern 170, it generates an ultraviolet light projection pattern 180 based on it. The ultraviolet light projection pattern 180 is an ultraviolet light projection pattern for determining the specific light projection area 15 that the first projector 20 will target for additional ultraviolet light projection. The ultraviolet light projection pattern 180 only needs to be configured so that the first projector 20 can determine whether or not each pixel of the visible light image (image 600) corresponds to a specific visible light (whether or not it is a target for ultraviolet light projection). For this reason, as shown in Figure 4B, the ultraviolet light projection pattern 180 in this example is a projection pattern that grayscales the image color signal (RGB value) indicating the color component of each pixel in the specific color pattern 170, and shows the specific color image area (green image 62 and blue image 63) that is the target for additional ultraviolet light projection in black, and the image area that is not the target for additional ultraviolet light projection in white.

[0042] The control unit 50 performs grayscale conversion according to the intensity of visible light at wavelengths corresponding to the image color signals of each pixel constituting the specific color pattern 170, specifically the green pixel pattern 162 and the blue pixel pattern 163, based on the pixel values ​​(RGB values) indicated by these values. This generates an ultraviolet light projection pattern 180 that includes a first projection pixel pattern 182 corresponding to the green pixel pattern 162, which shows the position of the green image 62 in the visible light image (image 600) in grayscale, and a second projection pixel pattern 183 corresponding to the blue pixel pattern 163, which shows the position of the blue image 63 in the image 600 in grayscale. The control unit 50 sends the generated ultraviolet light projection pattern 180 to the first projector 20.

[0043] The first projector 20 additionally projects ultraviolet light to a specific projection area 15 within the projection area 10c based on the ultraviolet light projection pattern. Specifically, the first projector 20 identifies specific color image areas (green image 62 and blue image 63) in the visible light image (image 600) displayed in the projection area 10c according to the ultraviolet light projection pattern 180, and projects ultraviolet light to the specific projection area 15 that includes the specific color image areas. This suppresses the decrease in the light scattering properties of the display function layer 11 due to the reception of specific visible light in the specific projection area 15, uniformizes the light scattering properties within the display function layer 11, and suppresses the occurrence of brightness unevenness in the visible light image (image 600).

[0044] The first projector 20 may determine the position of a specific color image region (green image 62 and blue image 63) displayed in the projection area 10c based on the ultraviolet light projection pattern 180, derive the range of a specific projection area 15 that includes the entire specific color image region based on this, and project ultraviolet light onto the specific projection area 15. At this time, the first projector 20 may, for example, obtain the pixel coordinates of the specific color image region based on the pixels constituting the first projection pixel pattern 182 and the second projection pixel pattern 183 in the ultraviolet light projection pattern 180, and project ultraviolet light onto the specific projection area 15 based on these pixel coordinates. However, it is not limited to this, and the first projector 20 may project ultraviolet light according to the shape of the specific projection area 15 (green image 62 and blue image 63) based on the ultraviolet light projection pattern 180. Furthermore, when the first projector 20 projects ultraviolet light evenly within a specific projection area 15 based on the ultraviolet light projection pattern 180, the intensity of the ultraviolet light (mW / cm²) is calculated based on blue light, which is most easily absorbed by the display function layer 11. ２ ) should be set. In other words, ultraviolet light of an intensity that can suppress the decrease in the light scattering properties of the display function layer 11 in the image area of ​​the blue image 63 should be projected onto the specific projection area 15. The ultraviolet light intensity corresponding to the blue image 63 is the reference ultraviolet light intensity (reference ultraviolet light intensity) for additional projection, and may be a predetermined value.

[0045] As described above, in the display device 1 according to this embodiment, the first projector 20 superimposes ultraviolet light onto at least a specific light-emitting region 15 on which specific visible light is emitted, within the light-emitting region 10c on which visible light is emitted during the display of the visible light image. As a result, the first projector 20 reliably emits additional ultraviolet light onto specific color image regions (green image 62 and blue image 63) within the specific light-emitting region 15, increasing the integrated amount of emitted ultraviolet light and suppressing the decrease in the light scattering properties of the display function layer 11 due to the reception of specific visible light (maintaining light scattering properties). Therefore, the light scattering properties in the display function layer 11 can be made uniform, and the occurrence of brightness unevenness in the image 600 can be reduced. Furthermore, in order to suppress brightness unevenness by emitting high-intensity ultraviolet light that can bring the light scattering properties of the display function layer 11 to their functional upper limit (saturating the light scattering properties) over the entire light-emitting area 10c including the image 600 during additional light emission, a powerful ultraviolet light source is required, which may increase the size of the display device 1 and reduce its suitability as an in-vehicle device. By narrowing the target of additional light emission to a specific light-emitting area 15, it is possible to suppress the increase in size of the display device 1 and improve its suitability as an in-vehicle device.

[0046] The control unit 50 also sends image information (light projection pattern 160) indicating the color components of a visible light image (image 600) to the second projector 40, and extracts a specific color pattern 170 from the light projection pattern 160 that indicates a specific color image region (green image 62 and blue image 63), which is an image region containing a color component corresponding to a specific visible light in the visible light image, and sends an ultraviolet light projection pattern 180 (specific image information) based on this specific information to the first projector 20. The second projector 40 also projects visible light with a wavelength corresponding to the color components of the visible light image shown by the light projection pattern 160 into the light projection area 10c, and the first projector 20 may superimpose ultraviolet light onto the specific color image region (green image 62 and blue image 63) displayed in the specific light projection area 15 in the light projection area 10c based on the ultraviolet light projection pattern 180 corresponding to the specific image information. This ensures that additional ultraviolet light is projected in accordance with the shape of the specific color image region within the specific light projection area 15, thereby more reliably increasing the integrated amount of ultraviolet light projected onto the green image 62 and the blue image 63. As a result, the light scattering properties of the display function layer 11 can be more reliably made uniform during the display of the visible light image, thereby more reliably suppressing the occurrence of brightness unevenness in the visible light image.

[0047] Furthermore, the ultraviolet light projection pattern generated by the control unit 50 in this disclosure is not limited to the ultraviolet light projection pattern 180 that indicates the position of a specific color image region. For example, the control unit 50 may generate a projection pattern that shows different ultraviolet light intensities according to the color components of the specific color image region and send it to the first projector 20. As a result, the first projector 20 can project additional ultraviolet light of different intensities according to the color components of the specific color image region (green image 62 and blue image 63).

[0048] As shown in Figure 4C, the ultraviolet light projection pattern 280 may include a green conversion pattern 282, which is a grayscale conversion of the pixel values ​​indicated by the image color signals constituting the green pixel pattern 162 extracted in the specific color pattern 170, and a blue conversion pattern 283, which is a grayscale conversion of the pixel values ​​indicated by the image color signals constituting the blue pixel pattern 163. The green conversion pattern 282 and the blue conversion pattern 283 indicate the positions of the image regions (the specific color image regions) of the green image 62 and blue image 63 in the visible light image (image 600), respectively, that is, the positions of the specific light projection region 15 within the light projection region 10c. Furthermore, the green conversion pattern 282 and the blue conversion pattern 283 each indicate the intensity of the ultraviolet light projected onto the specific light projection region 15 during additional projection, based on the grayscale gradation. The ultraviolet light projection pattern 280 indicates that the closer the grayscale gradation of each pixel is to black (lower gradation), the greater the ultraviolet light intensity. In this way, within the visible light image 600 projected within the light projection area 10c, the intensity of ultraviolet light projected in areas where the gradation of the R, G, and B pixel values ​​is low, that is, where the intensity of visible light projection is weak for each of the R, G, and B colors, can be reduced, thereby further suppressing brightness unevenness in the display.

[0049] As described above, the azobenzene molecule 92 absorbs blue light more readily than green light among the specific visible light. The ultraviolet light projection pattern 280 sets the gradation of the green conversion pattern 282 corresponding to the green image 62 formed by green light to be higher (closer to white) than the gradation of the blue conversion pattern 283 corresponding to the blue image 63 formed by blue light, thereby projecting ultraviolet light with a lower intensity than the region corresponding to the blue image 63 within the specific color image region. Based on the ultraviolet light projection pattern 180, the first projector 20 may project ultraviolet light of different intensities to the specific projection area 15 (or the green image 62 and blue image 63 (specific color image region) within the specific projection area 15) according to the color components of the specific color image region (green image 62 and blue image 63). Specifically, ultraviolet light with a lower intensity than the region corresponding to the blue image 63 may be projected to the region corresponding to the green image 62. This allows for the projection of high-intensity ultraviolet light onto a blue image 63, which is projected with blue light, the most easily absorbed light in the display function layer 11, within a specific projection area 15 of the projection area 10c. At the same time, it allows for the projection of lower-intensity ultraviolet light onto a green image 62, which is projected with green light, the least easily absorbed light in the display function layer 11, than the area projected onto the blue image 63. In other words, by suitably adjusting the integrated light amount of the image area within the specific projection area 15 based on the visible light absorption rate of the display function layer 11, the light scattering properties in the display function layer 11 can be made uniform with high precision, and brightness unevenness in the visible light image (image 600) can be suppressed with higher precision.

[0050] In the display device 1, when erasing a visible light image, the first projector 20 stops emitting ultraviolet light, and under the control of the control unit 50, the second projector 40 emits specific visible light (for example, blue light with a wavelength of around 450 nm) over the entire surface of the image display body 10, thereby changing the ultraviolet light emission area 10c on the image display body 10 from an opaque state to a transparent state. This allows for quick visibility from inside the vehicle, for example, when the image display body 10 is installed on the windshield of a car. When ultraviolet light emission is stopped, the light scattering properties of the display function layer 11 decrease over time due to specific visible light (in this example, blue or green visible light) contained in sunlight or white illumination light, and the image display body 10 gradually becomes transparent (non-screen state), erasing the visible light image (for example, image 600) within the emission area 10c.

[0051] Next, an example of a control method for the display device 1 will be described with reference to Figure 5. Figure 5 is a flowchart showing an example of the control flow for displaying a visible light image and additionally emitting ultraviolet light, which is performed by the control unit 50 in the display device 1. For example, the control unit 50 may start control for displaying a visible light image and additionally emitting ultraviolet light based on receiving an image signal indicating a visible light image (e.g., image 600) from a higher-level control device (not shown).

[0052] As shown in Figure 5, the control unit 50 screens (makes opaque) the image display body 10 having the display function layer 11 by emitting ultraviolet light (S1). For example, the control unit 50 sends a predetermined signal to the first projector 20 to instruct the emission of ultraviolet light, and the ultraviolet light source of the first projector 20 emits ultraviolet light and projects ultraviolet light onto the image display body 10 (light-emitting area 10c) having the display function layer 11. As a result, the display function layer 11 receives the ultraviolet light and its light scattering properties increase, causing the light-emitting area 10c of the image display body 10 to become opaque (screened).

[0053] Next, the control unit 50 projects visible light of an arbitrary wavelength from the second projector 40 onto the image display unit 10 onto which ultraviolet light is projected, and displays a visible light image (image 600) with an arbitrary shape and color components within the projection area 10c (S2). For example, the control unit 50 sends image information (projection pattern 160) to the second projector 40 that indicates the shape of the visible light image (image 600) and the color components of each pixel, which is generated based on the image signal received from a higher-level control device (not shown). As a result, visible light of a wavelength corresponding to the color components of the visible light image indicated by the projection pattern 160 (red pixel pattern 161, green pixel pattern 162, and blue pixel pattern 163) is projected from the second projector 40 onto the image display unit 10 (projection area 10c).

[0054] Next, the control unit 50 extracts specific image information from the image information (light projection pattern 160) that indicates a specific color image region containing color components corresponding to specific visible light (blue light, green light) within the visible light image (S3), and generates an ultraviolet light projection pattern based on the extracted specific image information (S4). For example, the control unit 50 extracts a specific color pattern 170 as specific image information from the light projection pattern 160 that indicates a specific color image region corresponding to the green image 62 and the blue image 63 within the visible light image (image 600), and generates an ultraviolet light projection pattern 180 (or ultraviolet light projection pattern 280) based on this.

[0055] Next, the control unit 50 outputs an ultraviolet light projection pattern (ultraviolet light projection pattern 180 or ultraviolet light projection pattern 280) based on specific image information (specific color pattern 170) to the second projector (S5), and projects ultraviolet light onto the image display unit 10 based on the ultraviolet light projection pattern (S6). For example, the control unit 50 sends an ultraviolet light projection pattern 180 based on specific image information (specific color pattern 170) to the first projector 20, and the first projector 20 projects ultraviolet light onto a specific projection area 15 including a specific color image area (green image 62 and blue image 63). Alternatively, the control unit 50 may send an ultraviolet light projection pattern 280 based on the specific color pattern 170 to the first projector 20, and the first projector 20 projects ultraviolet light onto the specific color image area (green image 62 and blue image 63). As described above, the ultraviolet light projection pattern 280 indicates the intensity of ultraviolet light corresponding to the color components of specific color image regions (green image 62 and blue image 63) using grayscale gradations. Therefore, by sending the ultraviolet light projection pattern 280 to the first projector 20, the control unit 50 can make the intensity of ultraviolet light projected over the specific color image regions (green image 62 and blue image 63) in the specific projection area 15 different according to the color components of the specific color image regions.

[0056] 1-1. First Modified Example As described above, the display device 1 may, while displaying a visible light image (image 600), additionally project ultraviolet light onto a specific projection area 15 within the projection area 10c on the image display body 10. In other words, the first projector 20 in the display device 1 may project ultraviolet light onto the visible light image (image 600) displayed within the projection area 10c on the image display body 10. That is, ultraviolet light may be projected (additional projection) not only onto specific color image areas (green image 62 and blue image 63) within the specific projection area 15, but also onto image areas using visible light that do not correspond to specific visible light (red image 61). As described above, the azobenzene molecule 92, which has become the cis isomer 92b in the display function layer 11, also absorbs a small amount of visible light outside the absorption wavelength range (for example, red light). Therefore, by additionally illuminating ultraviolet light even in image areas on the image display unit 10 that are made of visible light that does not correspond to specific visible light (non-specific visible light), brightness unevenness in the visible light image can be further suppressed.

[0057] For example, the control unit may generate an ultraviolet light projection pattern 180 that has been converted to grayscale according to the intensity of visible light at wavelengths corresponding to the red pixel pattern 161, green pixel pattern 162, and blue pixel pattern 163 of the image color signal (RGB value) indicating the color component of each pixel in the projection pattern 160. As a result, the ultraviolet light projection pattern 180 becomes a projection pattern that indicates the respective positions of the red image 61, green image 62, and blue image 63 in the image 600 displayed in the projection area 10c of the image display unit 10, that is, the area to be projected with ultraviolet light in the additional projection.

[0058] Furthermore, the control unit 50 may calculate the intensity of ultraviolet light during additional illumination according to the color component of each pixel of the visible light image (image 600) being displayed. More specifically, the control unit 50 may calculate the intensity of ultraviolet light during additional illumination (ultraviolet light intensity from the ultraviolet light source of the first projector 20) based on the wavelength of visible light corresponding to the color component of each pixel of the visible light image (image 600) being displayed (wavelength of the visible light source in the second projector 40). This makes it possible to create an intensity difference in the intensity of ultraviolet light emitted to each pixel of the visible light image displayed in the illumination area 10c of the image display unit 10. Therefore, the light scattering properties of the display function layer can be made even more uniform with higher precision, and the occurrence of brightness unevenness in the visible light image can be suppressed even more reliably.

[0059] In this modified example, the intensity of ultraviolet light projected (additional projection) to a visible light image (e.g., image 600) displayed in a specific projection area by the first projector 20 may be weighted by the molar extinction coefficient according to the color component of each pixel constituting the visible light image. For example, the control unit 50 sets the ultraviolet light intensity (I) corresponding to the blue light (blue image 63) where absorption by the azobenzene molecule 92 in cis form 92b is greatest. Ｂ ) is used as a reference, and the ultraviolet light intensity (I) corresponding to red light (red image 61) is used. Ｒ ) and ultraviolet light intensity (I) corresponding to green light (green image 62) Ｇ You may calculate the ultraviolet light intensity (I) corresponding to blue light. More specifically, you can calculate the ultraviolet light intensity (I) corresponding to blue light. Ｂ The ultraviolet light intensity to be additionally projected onto each pixel of a visible light image (for example, image 600) may be calculated by multiplying the ratio of the molar extinction coefficients of red light and green light at each wavelength of the azobenzene molecule by ε, using ε as a reference. In calculating the ultraviolet light intensity corresponding to the color component of each pixel of the visible light image, the wavelengths from the visible light source of the second projector 40 (light source wavelength) are set to 630 nm for red light, 532 nm for green light, and 467 nm for blue light. In this example, the molar extinction coefficient of the azobenzene molecule at wavelength λ is set to ε λ Let's assume that.

[0060] Specifically, the control unit 50 controls the ultraviolet light intensity (I) corresponding to the blue light (blue image 63). Ｂ), based on this, the ultraviolet light intensity I corresponding to red light Ｒ and the ultraviolet light intensity I corresponding to green light Ｇ may be calculated as in the following formulas (1) and (2). The ultraviolet light intensity (I Ｂ ) may be the above reference ultraviolet light intensity. I Ｒ = I Ｂ × ε ６３０ / ε ４６７ ... (Formula 1) I Ｇ = I Ｂ × ε ５３２ / ε ４６７ ... (Formula 2)

[0061] Thus, in this example, among the visible light images (image 600) displayed in the light projection area 10c of the image display body 10, the intensity of the ultraviolet light additionally projected onto the red image 61 by red light and the green image 62 by green light can be made smaller than the intensity of the ultraviolet light additionally projected onto the blue image 63 by blue light (the visible light most easily absorbed in the display functional layer 11). Also, the intensity of the ultraviolet light additionally projected onto the red image 61 by red light can be made smaller than the intensity of the ultraviolet light additionally projected onto the green image 62 by green light.

[0062] The control unit 50 includes the ultraviolet light projection pattern 180 including the red pixel pattern 161, the green pixel pattern 162, and the blue pixel pattern 163 gray-scaled as described above, and data on the ultraviolet light intensity, that is, the ultraviolet light intensities corresponding to the red image 61 and the green image 62 (ultraviolet light intensity I Ｒ and ultraviolet light intensity I Ｇ) and may be sent to the first projector 20. As a result, the intensity of ultraviolet light projected (additional projection) from the first projector 20 onto the visible light image (e.g., image 600) becomes an intensity weighted by the molar extinction coefficient according to the color component of each pixel constituting the visible light image. As a result, ultraviolet light of a suitable intensity according to the visible light absorption degree of the display function layer 11 is additionally projected onto each pixel of the visible light image, and the integrated amount of ultraviolet light additionally projected onto each pixel can be adjusted with high precision. In other words, the integrated amount of additionally projected ultraviolet light can be increased or decreased according to the color component of each pixel of the visible light image. Therefore, the display device 1 according to this modified example can further reliably homogenize the light scattering properties of the display function layer according to the visible light absorption degree of the display function layer 11, and further suppress the occurrence of brightness unevenness in the visible light image.

[0063] Figure 6 is a flowchart showing an example of operation control of the display device 1 in this modified example. In this modified example, the control unit 50 of the display device 1 generates an ultraviolet light projection pattern 180 including a grayscale red pixel pattern 161, a green pixel pattern 162, and a blue pixel pattern 163 based on image information (light projection pattern 160) (S13). Next, the control unit 50 calculates the intensity of ultraviolet light in the additional projection based on the color component of each pixel in the visible light image (S14). For example, as described above, the control unit 50 calculates the ultraviolet light intensity (ultraviolet light intensity I) weighted by the molar extinction coefficient according to the wavelength of visible light corresponding to the color component of each pixel constituting the visible light image (image 600). Ｒ and ultraviolet light intensity I Ｇ The control unit 50 calculates the intensity of ultraviolet light projected onto the visible light image, weighting it by the molar extinction coefficient according to the color component of each pixel constituting the visible light image.

[0064] Next, the control unit 50 processes the ultraviolet light projection pattern 180 generated in step S13 and the calculated ultraviolet light intensity (ultraviolet light intensity I Ｒ and ultraviolet light intensity I Ｇ) is sent to the first projector 20 (S15), and the first projector 20 emits additional ultraviolet light based on the ultraviolet light emission pattern 180 and the ultraviolet light intensity (S16). For example, the control unit 50 emits ultraviolet light intensity I, which is a predetermined reference ultraviolet light intensity. Ｂ and the calculated ultraviolet light intensity (ultraviolet light intensity I Ｒ and ultraviolet light intensity I Ｇ Based on the above, ultraviolet light may be additionally projected onto each pixel of the visible light image shown by the ultraviolet light projection pattern 180. In other words, when additional light is projected, ultraviolet light of an intensity weighted by the molar extinction coefficient according to the color component of each pixel constituting the visible light image may be projected onto each pixel of the visible light image displayed on the image display unit 10. Steps S11 and S12 in Figure 6 are equivalent to steps S1 and S2 in Figure 5, so their explanation is omitted.

[0065] In this modified example, similar to the first embodiment, the specific light projection area 15 is targeted for additional ultraviolet light projection, and the ultraviolet light intensity corresponding to the green image 62 is defined as the ultraviolet light intensity I, which is weighted by the molar extinction coefficient according to the color component of each pixel in the visible light image. Ｇ Only the calculated ultraviolet light intensity I may be calculated. In this case, the control unit 50 will calculate the ultraviolet light intensity I Ｇ The ultraviolet light projection pattern 280 is then sent to the first projector 20. This allows ultraviolet light to be superimposed onto the specific color image area within the specific projection area based on the information indicating the specific color image area.

[0066] 1-2. Second Modification In the first modification, the intensity of ultraviolet light additionally projected onto each pixel of the visible light image was calculated according to the color component of each pixel to adjust the magnitude of the integrated amount of ultraviolet light at each pixel. However, the method for adjusting the integrated amount of ultraviolet light at each pixel of the visible light image is not limited to this in this disclosure. The display device 1 may also calculate the length of the projection time of the ultraviolet light additionally projected onto each pixel of the visible light image according to the color component of each pixel to adjust the magnitude of the integrated amount of ultraviolet light additionally projected onto each pixel. For example, when the display device 1 superimposes ultraviolet light onto a visible light image (image 600) displayed in the projection area 10c on the image display body 10 (additional projection), the length of the projection time during which ultraviolet light is projected onto the visible light image may be set according to the color component of each pixel (red pixel, green pixel, blue pixel) of the visible light image.

[0067] In other words, in the display device 1, the first projector 20, which is an ultraviolet light emission unit, emits ultraviolet light in addition to the visible light image (image 600) displayed in the light emission area 10c on the image display body 10. The duration of the emission of the ultraviolet light emitted in addition to the visible light image may be set according to the color component of each pixel constituting the visible light image. This allows the cumulative amount of ultraviolet light emitted to each pixel of the visible light image to be adjusted by changing the length of the additional emission time of ultraviolet light according to the absorption rate of visible light in the display function layer 11, thereby further reliably uniformizing the light scattering properties of the display function layer 11 and further reliably suppressing brightness unevenness in the visible light image. As will be described in more detail later, in this modified example, by adjusting the cumulative amount of ultraviolet light by changing the length of the additional emission time of ultraviolet light, it is possible to provide a period in the first projector 20 when the ultraviolet light source is turned off, thereby suppressing energy consumption in the display device 1.

[0068] When the display device 1 superimposes ultraviolet light onto a visible light image (image 600) displayed in the light-emitting area 10c on the image display body 10, the length of the emission time for which ultraviolet light is emitted onto the visible light image may be set according to the color components of each image area of ​​each pixel (red pixel, green pixel, blue pixel) that constitutes the visible light image. In this example, the length of the emission time for ultraviolet light superimposed onto specific color image areas (green image 62 and blue image 63) and non-specific color image areas (red image 61) within the specific light-emitting area 15 in the light-emitting area 10c on which the visible light image (image 600) is displayed may be set according to the color components (wavelength of the emitted visible light) of each image area of ​​the visible light image.

[0069] Figure 7 illustrates the control of the ultraviolet light emission time according to this modified example along the time axis. Figure 7 shows the on / off switching of ultraviolet light emission (presence or absence of ultraviolet light emission) and visible light emission (presence or absence of visible light emission) in the display device 1, along with the light (visible light, ultraviolet light) emitted to each pixel of the visible light image in the emission area 10c. As described above, the presence or absence of ultraviolet light and visible light emission is controlled by the control unit 50. In Figure 7, the red image 61 composed of red pixels in the visible light image is referred to as the "R pixel area," the green image 62 composed of green pixels is referred to as the "G pixel area," and the blue image 63 composed of blue pixels is referred to as the "B pixel area." In this example, the intensity of ultraviolet light emitted from the first projector 20 to the image display unit 10 is (mW / cm²). ２ ) is constant.

[0070] As shown in Figure 7, the period from time t0 to time t1 is the screening (opacity reduction) period for the image display unit 10. During the screening period, the first projector 20 projects ultraviolet light onto the entire light-emitting area 10c of the image display unit 10 (projection on), making the light-emitting area 10c opaque. During the screening period, opacity reduction (screening) is not yet complete in the light-emitting area 10c of the image display unit 10. Therefore, a visible light image cannot be displayed. For this reason, as shown in Figure 7, the period from time t0 to time t1 is the blackout period in the second projector 40, during which the visible light source is turned off, and no visible light is projected onto the image display unit 10 (projection off), and the visible light image (R pixel area, G pixel area, B pixel area) is not displayed.

[0071] In this example, at time t1, a predetermined time after time t0, the screening (opacification) of the light-emitting area 10c is completed, and the screening period ends. Therefore, as shown in Figure 7, at time t1, the first projector 20 stops emitting ultraviolet light (turns off). Therefore, as shown in Figure 7, at time t1, the ultraviolet light source of the first projector 20 is turned off, and the off period begins. On the other hand, at time t1, with the end of the screening period, it becomes possible to display a visible light image. Therefore, the off period for the visible light source in the second projector 40 ends, and under the control of the control unit 50, the emission of visible light onto the image display unit 10 (light-emitting area 10c) begins. Therefore, as shown in Figure 7, red light, green light, and blue light are emitted from the second projector 40 onto the light-emitting area 10c, and a visible light image (image 600) consisting of R pixel area, G pixel area, and B pixel area is displayed on the image display unit 10.

[0072] At time t2, after a predetermined time has elapsed from time t1, the first projector 20, under the control of the control unit 50, begins to emit additional ultraviolet light at time t2. In other words, the blackout period of the first projector 20 ends at time t2. In this example, the display function layer 11 contains azobenzene molecules 92, and blue light and green light correspond to specific visible light. Under the control of the control unit 50, the first projector 20 begins to emit additional ultraviolet light to the B pixel region (blue image 63) where blue light is emitted at time t2. This starts the additional emission time from time t2. The control unit 50 may determine the length of the additional emission time of ultraviolet light for each pixel of the visible light image according to the absorption degree of visible light in the display function layer 11. Specifically, pixels that emit visible light with a high absorption degree in the display function layer 11 among the specific visible light may be given priority as targets for additional emission of ultraviolet light. The first projector 20, under the control of the control unit 50, should start projecting additional ultraviolet light until the transparency in the B pixel area becomes visible (the brightness unevenness of the visible light image becomes visible).

[0073] Furthermore, at time t3, after a predetermined time has elapsed from time t2, the first projector 20 begins to additionally project ultraviolet light onto the G pixel region (green image 62) onto which green light is projected. Under the control of the control unit 50, the first projector 20 should begin additionally projecting ultraviolet light onto the G pixel region after the end of the screening period until transparency is visible in the G pixel region (brightness unevenness of the visible light image is visible), and such that the end of the additional projection time for the G pixel region (green image 62) falls within the additional projection time for the B pixel region (blue image 63). Furthermore, at time t4, after a predetermined time has elapsed from time t3, the first projector 20 begins additionally projecting ultraviolet light onto the R pixel region onto which red light is projected. The first projector 20, under the control of the control unit 50, may start additional ultraviolet light projection to the R pixel region at any timing within the range where transparency is visible in the R pixel region (brightness unevenness of the visible light image) and the end of the additional light projection time for the R pixel region (red image 61) falls within the additional light projection time for the B pixel region (blue image 63).

[0074] The start of ultraviolet light projection to the G pixel area and R pixel area at time t3 and time t4 may be determined according to the ultraviolet light intensity during the screening period, the visible light intensity for displaying the visible light image, and the wavelengths of green or red light, respectively. As shown in Figure 7, at time t4, the first projector 20 stops additionally projection of ultraviolet light to the G pixel area. At time t5, after a predetermined time has elapsed from time t4, the first projector 20 stops additionally projection of ultraviolet light to the R pixel area, and at time t6, after a predetermined time has elapsed from time t5, the first projector 20 stops additionally projection of ultraviolet light to the B pixel area. As a result, additional ultraviolet light projection ends at time t6.

[0075] As shown in Figure 7, in this example, the longest period of additional ultraviolet light projection by the first projector 20 (from time t2 to time t6), i.e., the additional projection time, is the additional projection time to the B pixel region where blue light, which is most easily absorbed by the display function layer 11, is projected (from time t2 to time t6). In other words, the additional projection time to the B pixel region corresponds to the additional projection time of ultraviolet light by the first projector 20. In Figure 7, the additional projection time is when both ultraviolet light from the first projector 20 and visible light from the second projector 40 are projected onto the respective image regions of the visible light image (red image 61, green image 62, and blue image 63) that are the target of the additional projection. In Figure 7, the projection of ultraviolet light and visible light during the projection time in each image region of the visible light image (image 600) is indicated by black shading and the notation "UV + VL". Furthermore, in the display function layer 11, the additional UV light emission time to the G pixel region, where green light (the second most easily absorbed light after blue light) is emitted, is the second longest after the additional UV light emission time to the B pixel region, while the additional UV light emission time to the R pixel region, where red light (which has relatively low absorption) is emitted in the display function layer 11, is the shortest. Therefore, in this example, when additional UV light is emitted, the integrated amount of UV light in the B pixel region is the largest, followed by the integrated amount of UV light in the G pixel region, and the integrated amount of UV light in the R pixel region is the smallest. In other words, the integrated amount of UV light emitted to each pixel of the visible light image can be suitably adjusted according to the absorption degree of visible light in the display function layer 11, and the integrated amount can be increased for pixel regions where visible light with high absorption is emitted. Alternatively, an interval (additional UV light emission time to the B pixel region only) may be provided between the additional UV light emission time to the G pixel region and the additional UV light emission time to the R pixel region.

[0076] Furthermore, in the visible light image (image 600), the pixels corresponding to visible light with higher absorption in the display function layer 11 become transparent more quickly. Therefore, in this example, additional light projection to the B pixel region (blue image 63), where blue light is projected, is started earliest, followed by additional light projection to the G pixel region (green image 62), and finally to the R pixel region (red image 61). This allows additional ultraviolet light projection to be started in the projection area 10c of the image display unit 10 before transparency in each pixel region becomes visible (brightness unevenness occurs). The additional light projection time for the G pixel region (green image 62) and the R pixel region (red image 61) only needs to be set within the additional light projection time for the B pixel region (blue image 63).

[0077] Furthermore, in the first projector 20 and the second projector 40, similar to general projectors, a constant intensity of light (e.g., the highest intensity light) is always emitted from the light source (ultraviolet light source, visible light source), and the intensity of the light projected onto the image display surface is adjusted by a spatial light modulator such as a DMD (Digital Micromirror Device). Therefore, adjusting the magnitude of the light intensity projected onto the image display surface 10 does not change the amount of energy consumed. In contrast, in this example, in order to adjust the cumulative amount of ultraviolet light projected onto each pixel of the visible light image (image 600) by changing the length of the additional ultraviolet light projection time, a period of time during which the ultraviolet light source is turned off (off period from time t1 to time t2) can be provided. Therefore, an effect of suppressing energy consumption (energy saving effect) can be achieved. In addition, because there is an off period, the amount of heat generated from the ultraviolet light source is reduced, making it possible to miniaturize cooling components such as heat sinks and fans. Therefore, the display device 1 according to this modified example can be made more suitable as an in-vehicle device.

[0078] Figure 8 is a flowchart showing an example of operation control of the display device 1 in this modified example. In this modified example, the control unit 50 of the display device 1 generates an ultraviolet light projection pattern corresponding to the visible light image (S23), similar to step S13 (see Figure 6), and derives the ultraviolet light projection time based on the color component of each pixel of the visible light image (S24). For example, the control unit 50 may calculate the period during which the ultraviolet light is off after the screening period, and at the end of the off period, calculate the length of the additional projection time (length between time t2 and time t6). The additional projection time may be calculated based on the ultraviolet light intensity during the screening period, the visible light intensity related to the display of the visible light image, the wavelength of blue light, etc. The control unit 50 may also calculate the length of the additional projection time, i.e., the length of the additional projection time to the B pixel area, based on the wavelength of blue light, the intensities of visible light and ultraviolet light, etc. Similarly, the lengths of the additional projection time to the G pixel area and the R pixel area may be calculated based on the wavelengths of green light and red light, and the intensities of visible light and ultraviolet light, respectively. The duration of the ultraviolet light source's off period during the display of the visible light image, and the length of the additional light emission time for the R pixel area, G pixel area, and B pixel area, may be predetermined. The control unit 50 may determine the start timing of additional light emission so that the additional light emission of ultraviolet light begins in the order of B pixel area, G pixel area, and R pixel area. Alternatively, the additional light emission time for the B pixel area may be set to be the longest, followed by the additional light emission time for the G pixel area, and then the shortest for the R pixel area.

[0079] Next, the control unit 50 sends the ultraviolet light projection pattern and the duration of additional projection (start timing and end timing of additional projection) to each pixel area of ​​the R pixel area, B pixel area, and G pixel area to the first projector 20 (S25). The first projector 20 then projects ultraviolet light onto the visible light image (image 600) displayed in the projection area 10c based on the projection pattern and the duration of additional projection. Steps S21 and S22 in Figure 8 are equivalent to steps S1 and S2 in Figure 5, so their explanation is omitted.

[0080] Thus, under the control of the control unit 50, the display device 1 superimposes ultraviolet light onto the visible light image (image 600) in the light projection area 10c on the image display body 10, and the length of the projection time of the ultraviolet light superimposed onto the visible light image may be set according to the color component of each pixel constituting the visible light image. In this modified example, the cumulative amount of ultraviolet light projected onto each pixel of the visible light image can be adjusted by changing the length of the additional ultraviolet light projection time according to the visible light absorption rate of the display function layer 11, thereby further reliably uniformizing the light scattering properties of the display function layer 11 and further reliably suppressing brightness unevenness in the visible light image. In addition, in this modified example, since the cumulative amount of ultraviolet light is adjusted by changing the length of the additional ultraviolet light projection time, the ultraviolet light source in the first projector 20 can be turned off. This reduces the amount of heat generated from the ultraviolet light source, resulting in energy saving effects and miniaturization of cooling components, further improving the suitability of the display device 1 as an in-vehicle device.

[0081] Furthermore, the control unit 50 may control the first projector 20 to periodically repeat periods of UV light being turned off and periods of additional UV light projection (additional projection time) while displaying a visible light image. This makes it possible to suppress brightness unevenness in the visible light image even more reliably while suppressing energy consumption.

[0082] 2. Second Embodiment Next, a second embodiment of the present disclosure will be described with reference to Figure 9. This embodiment is an embodiment in which the display device 1 is equipped with a third projector 30 that emits visible light (specific visible light) for erasing a visible light image displayed on an image display body 10. The third projector 30 is a projector that emits specific visible light and is positioned opposite the front surface 10a of the image display body 10. As a specific visible light emitting unit, the third projector 30 emits, for example, specific visible light (blue light) with a wavelength of around 450 nm. The third projector 30 emits specific visible light onto the image display body 10, which is in an opaque state, and changes the ultraviolet light emitting area 10c on the image display body 10 from an opaque state to a transparent state.

[0083] As described above, the display function layer 11 becomes cloudy due to increased light scattering when it receives ultraviolet light, and returns to a transparent state when it receives specific visible light, as its light scattering decreases. Therefore, by emitting specific visible light (blue light) from the third projector 30, the ultraviolet light emission area 10c on the image display body 10 can be made transparent (non-screen state), and the display of the visible light image can be terminated. According to the configuration of this embodiment, by providing a dedicated projector that emits visible light to erase the visible light image, the visible light image can be reliably erased, and the control by the control unit 50 can be simplified, reducing the processing load.

[0084] (Effects of the Embodiment) (1) In this disclosure, the display device 1 includes an image display body 10 having a display function layer whose light scattering increases when it receives ultraviolet light and whose light scattering decreases when it receives specific visible light which is visible light in a specific wavelength range; a first projector 20 that projects ultraviolet light onto the image display body 10; and a second projector 40 that projects visible light of an arbitrary wavelength onto a projection area 10c on the image display body 10 where ultraviolet light has been projected and the light scattering of the display function layer 11 has increased, thereby displaying a visible light image (image 600) with an arbitrary shape and color components within the projection area 10c. The first projector 20 superimposes ultraviolet light onto at least a specific projection area 15 on which the specific visible light is projected, among the projection area 10c on which the visible light is projected. The display device 1, under the control of the control unit 50, overlays ultraviolet light onto at least the specific light-emitting region 15 on which the specific visible light is emitted, within the light-emitting region 10c on which the visible light is emitted during the display of a visible light image (image 600). With this configuration, additional ultraviolet light is reliably emitted onto the specific light-emitting region 15 (region including cool-colored pixels) on which the specific visible light is emitted, increasing the integrated amount of emitted ultraviolet light and suppressing the decrease in light scattering properties in the display function layer 11 (maintaining light scattering properties). As a result, the light scattering properties in the display function layer 11 can be made uniform, and the occurrence of brightness unevenness in the image 600 can be reduced.

[0085] (2) The display device 1 further includes a control unit 50 that controls the operation of the first projector 20 and the second projector 40. The control unit 50 sends image information (light projection pattern 160) indicating the color components of a visible light image (image 600) to the second projector 40. The control unit 50 extracts specific image information (specific color pattern 170, ultraviolet light projection pattern 180) from the image information that indicates specific color image regions (green image 62 and blue image 63), which are image regions of the visible light image (image 600) that contain color components corresponding to specific visible light, and sends this to the first projector 20. The second projector 40 projects visible light of a wavelength corresponding to the color components of the visible light image indicated by the image information onto the light projection region 10c. The first projector 20 may superimpose ultraviolet light onto the specific color image region displayed in the specific light projection region 15 in the light projection region 10c based on the specific image information. The display device 1, under the control of the control unit 50, projects visible light of a wavelength corresponding to the color component onto the projection area 10c based on image information (projection pattern 160) indicating the color component of the image 600. It extracts specific image information (specific color pattern 170, ultraviolet light projection pattern 180) from the image information that indicates a specific color image region (green image 62 and blue image 63), which is an image region of the image 600 containing the color component corresponding to the specific visible light. Based on the information indicating the specific color image region, it may project ultraviolet light onto the specific color image region displayed in the specific projection area 15 in the projection area 10c. With this configuration, additional ultraviolet light can be reliably projected in accordance with the shape of the green image 62 and blue image 63 (image region composed of cool-colored pixels) within the specific projection area 15 onto which the specific visible light is projected, thereby more reliably increasing the integrated amount of ultraviolet light projected onto the green image 62 and blue image 63. Therefore, the light scattering properties of the display function layer 11 can be more reliably made uniform during the display of a visible light image, thereby more reliably suppressing the occurrence of brightness unevenness in the visible light image.

[0086] (3) In the display device 1, the first projector 20 may project ultraviolet light of different intensities onto the specific color image region according to the color components of the specific color image region. The display device 1 may, under the control of the control unit 50, set the intensity of the ultraviolet light projected onto the specific color image region to different intensities according to the color components of the specific color image region. With this configuration, the integrated amount of light in the image region within the specific projection region 15 can be suitably adjusted based on the visible light absorption rate of the display function layer 11 to uniformize the light scattering properties in the display function layer 11 with high precision, and brightness unevenness of the visible light image (image 600) can be suppressed with higher precision. (4) In the display device 1, the first projector 20 projects ultraviolet light onto the visible light image (image 600) displayed in the projection region 10c on the image display body 10, and the intensity of the ultraviolet light projected onto the visible light image may be weighted by the molar extinction coefficient according to the color components of each pixel constituting the visible light image. The display device 1 superimposes ultraviolet light onto a visible light image (image 600) in the light-emitting area 10c on the image display body 10, and the intensity of the ultraviolet light emitted onto the visible light image may be weighted by the molar extinction coefficient according to the color component of each pixel constituting the visible light image. With this configuration, the integrated amount of additionally emitted ultraviolet light can be increased or decreased according to the color component of each pixel of the visible light image (image 600), further reliably making the light scattering properties of the display function layer 11 uniform in accordance with the visible light absorption degree of the display function layer 11, and further suppressing the occurrence of brightness unevenness in the visible light image.

[0087] (5) In the display device 1, the first projector 20 superimposes ultraviolet light onto a visible light image (image 600) displayed in the light projection area 10c on the image display body 10, and the length of the projection time of the ultraviolet light superimposed on the visible light image may be set according to the color component of each pixel constituting the visible light image. The display device 1, under the control of the control unit 50, superimposes ultraviolet light onto a visible light image (image 600) in the light projection area 10c on the image display body 10, and the length of the projection time of the ultraviolet light superimposed on the visible light image may be set according to the color component of each pixel constituting the visible light image. With this configuration, the cumulative amount of ultraviolet light projected onto each pixel of the visible light image can be adjusted by changing the length of the additional ultraviolet light projection time according to the visible light absorption rate of the display function layer 11, thereby further reliably making the light scattering properties of the display function layer 11 uniform and further reliably suppressing brightness unevenness of the visible light image. Furthermore, by adjusting the cumulative amount of ultraviolet light by changing the length of the additional ultraviolet light emission time, it is possible to set a period during which the ultraviolet light source is turned off, thereby suppressing energy consumption in the display device 1.

[0088] 1 Display device 10 Image display unit 10a Front 10b Back 101 Transparent substrate 102 Transparent substrate 10c Light projection area 11 Display function layer 12 Dimming layer 13 Ultraviolet light shielding layer 15 Specific light projection area 20 First projector 30 Third projector 40 Second projector 50 Control unit 60, 600 Image 61 Red image 62 Green image 63 Blue image 160 Light projection pattern 161 Red pixel pattern 162 Green pixel pattern 163 Blue pixel pattern 170 Specific color pattern 180 Ultraviolet light projection pattern 182 First light projection pixel pattern 183 Second light projection pixel pattern 280 Ultraviolet light projection pattern 282 Green conversion pattern 283 Blue conversion pattern

Claims

1. A display device comprising: an image display body having a display functional layer whose light scattering properties increase when it receives ultraviolet light and decrease when it receives specific visible light which is visible light in a specific wavelength range; an ultraviolet light projection unit that projects ultraviolet light onto the image display body; and a visible light projection unit that projects visible light of an arbitrary wavelength onto a projection area on the image display body where ultraviolet light has been projected and the light scattering properties of the display functional layer have increased, thereby displaying a visible light image with arbitrary shape and color components within the projection area, wherein the ultraviolet light projection unit superimposes ultraviolet light onto at least a specific projection area where the specific visible light is projected, among the projection areas onto which visible light is projected during the display of the visible light image.

2. The display device according to claim 1, further comprising a control unit for controlling the operation of the ultraviolet light projection unit and the visible light projection unit, wherein the control unit sends image information indicating the color components of the visible light image to the visible light projection unit, extracts specific image information from the image information indicating a specific color image region which is an image region containing the color components corresponding to the specific visible light from the visible light image and sends it to the ultraviolet light projection unit, the visible light projection unit projects visible light of a wavelength corresponding to the color components of the visible light image indicated by the image information onto the projection area, and the ultraviolet light projection unit superimposes ultraviolet light onto the specific color image region displayed in the specific projection area within the projection area based on the specific image information.

3. The display device according to claim 2, wherein the ultraviolet light projection unit projects ultraviolet light of different intensities onto the specific color image region according to the color components of the specific color image region.

4. The display device according to claim 2, wherein the ultraviolet light projection unit projects ultraviolet light onto the visible light image displayed within the projection area on the image display body, and the intensity of the ultraviolet light projected onto the visible light image is weighted by the molar extinction coefficient according to the color component of each pixel constituting the visible light image.

5. The display device according to claim 2, wherein the ultraviolet light projection unit projects ultraviolet light onto the visible light image displayed within the projection area on the image display body, and the length of the projection time of the ultraviolet light projected onto the visible light image is set according to the color component of each pixel constituting the visible light image.

6. A control method for a display device that displays a visible light image with arbitrary shape and color components within a projection area, wherein ultraviolet light is projected onto an image display body having a display function layer whose light scattering properties increase when it receives ultraviolet light and decrease when it receives specific visible light which is visible light in a specific wavelength range, and visible light of an arbitrary wavelength is projected onto a projection area on the image display body where the light scattering properties of the display function layer have increased due to the projection of ultraviolet light, the control method for a display device that, during the display of the visible light image, superimposes ultraviolet light onto at least a specific projection area where the specific visible light is projected from the projection area where visible light is projected.

7. A control method for a display device according to claim 6, comprising: projecting visible light of a wavelength corresponding to the color component onto the projection area based on image information indicating the color component of the visible light image; extracting specific image information from the image information that indicates a specific color image area which is an image area of ​​the visible light image that includes the color component corresponding to the specific visible light; and superimposing ultraviolet light onto the specific color image area displayed in the specific projection area within the specific projection area based on the information indicating the specific color image area.

8. A control method for a display device according to claim 7, wherein the intensity of ultraviolet light projected onto the specific color image region is set to a different intensity according to the color components of the specific color image region.

9. A control method for a display device according to claim 8, comprising superimposing ultraviolet light onto the visible light image in the light projection area on the image display body, and weighting the intensity of the ultraviolet light projected onto the visible light image by the molar extinction coefficient according to the color component of each pixel constituting the visible light image.

10. A control method for a display device according to claim 7, comprising superimposing ultraviolet light onto the visible light image in the light projection area on the image display body, and setting the duration of the ultraviolet light superimposed onto the visible light image according to the color component of each pixel constituting the visible light image.

Images