Virtual image display device and mobile object

Abstract

To provide a virtual image display device in which a decrease in transmittance is suppressed even when a color gamut is expanded.SOLUTION: A virtual image display device 1 comprises: a backlight 6 that has an emission surface 6a for emitting light from a light-emitting diode 61 having a fluoride red phosphor; a liquid crystal display panel 7 that has an incidence surface 7b at which the light from the emission surface 6a is incident, a display surface 7a, and a liquid crystal layer 23c located between the incidence surface 7b and the display surface 7a; a color filter CF that is disposed on the display surface 7a side or incidence surface 7b side of the liquid crystal display panel 7; and an optical system 3 for forming, in a visual field of a user 5, an image displayed on the display surface 7a as a virtual image 10Q, 20Q. The incidence surface 7b of the liquid crystal display panel 7 is tilted at an angle θ with respect to the emission surface 6a. The CF is thinner in accordance with the angle θ than the thickness of the case of a parallel state in which the incidence surface 7b is parallel to the emission surface 6a, and the liquid crystal layer 23c has a smaller birefringent phase difference in accordance with the angle θ than the birefringent phase difference of the case of the parallel state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a virtual image display device and a moving object. [Background technology]

[0002] A prior art virtual image display device is described in, for example, US Pat. No. 5,399,326. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-4141 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional technology of Patent Document 1, when the color gamut is increased from, for example, 45% to 70% when the color reproduction gamut of the NTSC (National Television System Committee) standard is taken as the reference (100%) in order to improve the brightness of the virtual image, the transmittance of the transmissive liquid crystal display panel decreases by about 40%. Therefore, there has been a demand for a virtual image display device in which the decrease in transmittance is suppressed even when the color gamut is expanded. [Means for solving the problem]

[0005] The virtual image display device according to the present disclosure includes a backlight including a plurality of light-emitting diodes having a fluoride red phosphor and an exit surface that emits light from the plurality of light-emitting diodes; a liquid crystal display panel having an entrance surface into which the light emitted from the exit surface is incident, a display surface that displays an image by the light incident on the entrance surface, and a liquid crystal layer located between the entrance surface and the display surface; a color filter disposed on the display surface side or the entrance surface side of the liquid crystal display panel; and an optical system that guides the image displayed on the display surface into a user's field of vision and forms a virtual image, wherein the liquid crystal display panel is disposed with the entrance surface inclined at a predetermined angle with respect to the exit surface of the backlight, the color filter has a smaller thickness corresponding to the predetermined angle compared to a thickness when the entrance surface is parallel to the exit surface, and the liquid crystal layer has a smaller birefringence phase difference corresponding to the predetermined angle compared to a birefringence phase difference in the parallel state.

[0006] The moving body according to the present disclosure is configured such that the virtual image display device is equipped as a head-up display device, and the liquid crystal display panel has an NTSC ratio of 70% or more. Effect of the Invention

[0007] According to the virtual image display device and moving body of the present disclosure, unlike the prior art, a decrease in transmittance is suppressed even when the color gamut of the liquid crystal display panel is expanded, and a highly vivid virtual image can be viewed. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a main part of a virtual image display device according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a side view showing the arrangement position of a liquid crystal display panel relative to a backlight. [Diagram 3] FIG. 1 is a diagram showing color gamut distributions of an example and a comparative example. [Figure 4] 1 is a graph showing the change in transmittance with respect to the NTSC ratio. [Diagram 5]FIG. 2 is a front view showing a display state of a virtual image showing a road sign. [Figure 6] FIG. 2 is a side view showing an example of installation of a color measuring device. [Figure 7] 1 is a graph showing an example of settings for a liquid crystal display panel for a wide color gamut HUD. [Figure 8] 1 is a graph showing the spectral characteristics of a backlight. [Figure 9] 1 is a cross-sectional view of a main part showing a configuration example of a backlight for a HUD. [Figure 10A] FIG. 2 is a front view showing a wide color gamut liquid crystal display panel for HUD. [Figure 10B] 10B is a cross-sectional view of the liquid crystal display panel taken along the cutting line XB-XB in FIG. 10A. [Figure 10C] FIG. 2 is an enlarged view of a portion of a color filter. [Figure 11] FIG. 2 is a cross-sectional view of a color filter. [Figure 12] 1 is a graph showing the spectral characteristics of a color filter. [Figure 13] 1 is a cross-sectional view showing a main part of a moving object equipped with a virtual image display device. [Figure 14] 1 is a graph showing the transmission spectrum of a color filter. [Figure 15] 1 is a graph of color matching functions. [Figure 16] 1 is a graph of the relative energy spectrum of Illuminant C (Standard Illuminant C). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The drawings used in the following description are schematic. The dimensional ratios and the like in the drawings do not necessarily correspond to the actual ones.

[0010] FIG. 1 is a cross-sectional view of a main part of a virtual image display device 1 according to an embodiment of the present disclosure. As shown in FIG. 1, the virtual image display device 1 according to the present embodiment includes a display unit 2, an optical system 3, and a control unit 4. The virtual image display device 1 allows a user 5 to view a virtual image. The virtual image display device 1 is also called a head up display (HUD). In the following description, the head up display may be abbreviated as HUD. The virtual image display device 1 may be mounted on a moving body such as a vehicle, a ship, or an aircraft. When the virtual image display device 1 is mounted on a moving body, the user 5 may be a driver, an operator, or a passenger of the moving body.

[0011] The display unit 2 displays an image to be projected into the visual field of the user 5. The display unit 2 may be configured as a transmissive display device. The transmissive display device may be, for example, a liquid crystal device such as an LCD (Liquid Crystal Display) including a backlight (BL) 6 and a liquid crystal display panel 7. The backlight 6 and the liquid crystal display panel 7 are arranged in this order from the side farthest from the user 5 along the optical path of image light of an image displayed to the user 5.

[0012] The backlight 6 may be a direct-type backlight for HUD. 2 SiF 6 :Mn 4 +The (KSF) type backlight 6 includes a plurality of light emitting diodes 61 having a fluoride red phosphor, and an exit surface 6a capable of emitting light from the plurality of light emitting diodes 61. The backlight 6 may include a base 62 and a diffusion plate 63. The base 62 may have a main surface 62a facing the liquid crystal display panel 7, and the plurality of light emitting diodes 61 may be two-dimensionally (in a matrix) arranged on the main surface 62a. The diffusion plate 63 may be located in front of the base 62 (on the left side in FIG. 1 ) and cover the plurality of light emitting diodes 61. The diffusion plate 63 may diffuse the light emitted from the plurality of light emitting diodes 61, so that the backlight 6 can irradiate the liquid crystal display panel 7 with light with improved uniformity. The exit surface 6a may be the surface of the diffusion plate 63 facing the liquid crystal display panel 7, or may be the main surface 62a of the base 62.

[0013] Each of the light emitting diodes 61 includes at least one light source. The light source may be a point light source such as a light emitting diode (LED). The LED includes a mini LED and a micro LED.

[0014] The liquid crystal display panel 7 has a display surface 7a. The display surface 7a is a surface on which a display is performed based on an image display signal, and can output an image to the optical system 3 side by light emitted from the emission surface 6a of the backlight 6.

[0015] The liquid crystal display panel 7 may be a known liquid crystal panel. Examples of known liquid crystal panels include liquid crystal panels of the IPS (In-Plane Switching) type, the FFS (Fringe Field Switching) type, the VA (Vertical Alignment) type, and the ECB (Electrically Controlled Birefringence) type. The liquid crystal display panel 7 may include a plurality of liquid crystal display elements (pixels having a liquid crystal layer), two glass substrates arranged to sandwich the plurality of liquid crystal display elements, and a color filter CF. Instead of the glass substrate, a plastic substrate, a ceramic substrate, or the like having light transmission properties may be used.

[0016] The control unit 4 controls the backlight 6. The control unit 4 switches each of the multiple light-emitting diodes 61 between an emitting state and a non-emitting state. The control unit 4 may control the light emission luminance of the light-emitting diodes 61 that are in the emitting state based on image data of an image to be displayed on the display surface 7a. The control unit 4 may control the light emission luminance of the light-emitting diodes 61 that are in the emitting state based on the background luminance of the field of view of the user 5.

[0017] The control unit 4 may control each component of the virtual image display device 1 as well as the backlight 6. The control unit 4 is configured as, for example, a processor. The control unit 4 may include one or more processors. The processor may include a general-purpose processor that reads a specific program to execute a specific function, and a dedicated processor specialized for a specific process. The dedicated processor may include an application specific integrated circuit (ASIC). The processor may include a programmable logic device (PLD). The PLD may include a field-programmable gate array (FPGA). The control unit 4 may be either a system-on-a-chip (SoC) or a system in a package (SiP) in which one or more processors work together. The control unit 4 includes a storage unit, and may store various information or a program for operating each component of the virtual image display device 1 in the storage unit. The storage unit may be configured as, for example, a semiconductor memory. The storage unit may function as a work memory for the control unit 4.

[0018] The optical system 3 is located in the optical path of the image light emitted from the display unit 2 and reaching the eye of the user 5. The optical system 3 projects the image light emitted from the display unit 2 onto the eye of the user 5, forming a virtual image on the eye of the user 5. The optical system 3 may enlarge or reduce the image displayed on the display unit 2 to form an image on the eye of the user 5. The optical system 3 includes a first optical member (also referred to as a first reflecting section) 3a and a second optical member (also referred to as a second reflecting section) 3b. The first reflecting section 3a reflects the image on the exit surface 6a and the image on the display surface 7a toward the second reflecting section 3b. The second reflecting section 3b reflects the image on the exit surface 6a and the image on the display surface 7a reflected by the first reflecting section 3a toward the eye of the user 5. The number of optical members constituting the optical system 3 is not limited to two, and may be three or more, or may be four or more. The optical members may include a reflecting member including a convex or concave mirror. The optical element may include a reflective element including a freeform mirror. The optical element may include a refractive element including a convex lens or a concave lens. The convex lens includes a biconvex lens, a plano-convex lens, and a convex meniscus lens. The concave lens includes a biconcave lens, a plano-concave lens, and a concave meniscus lens. The optical element is not limited to a reflective element or a refractive element, and may include various other optical elements such as a hologram element.

[0019] Assuming three orthogonal axes, X, Y, and Z, light whose polarization axis is parallel to the X axis and light whose polarization axis is parallel to the Y axis have different refractive indices, and are said to have refractive index anisotropy. The difference between each refractive index is called the birefringence Δn. There is a phase difference between light parallel to the polarization axis X and light parallel to the polarization axis Y, which is expressed by the following formula 1. This phase difference is called retardation or birefringence phase difference.

[0020]

number

[0021] A virtual image 10Q of the image on the exit surface 6a and a virtual image 20Q of the image on the display surface 7a are located at the end of a two-dot chain line extending straight forward (left side in FIG. 1) from the second optical member 3b located closest to the user 5. The image on the exit surface 6a refers to the image on the exit surface 6a observed through the liquid crystal display panel 7 when the display unit 2 is viewed from the front side (left side in FIG. 1) of the display unit 2 along the optical path of the image light. The image on the display surface 7a refers to the image on the display surface 7a observed when the display unit 2 is viewed from the front side of the display unit 2 along the optical path of the image light. The image on the display surface 7a can also be said to be an image displayed on the display surface 7a. Hereinafter, the image on the exit surface 6a is also simply referred to as the exit surface 6a. The image on the display surface 7a is also simply referred to as the display surface 7a. The virtual image 10Q is also referred to as the light-emitting surface virtual image, and the virtual image 20Q is also referred to as the display surface virtual image. The size of the display surface 7a corresponds to the maximum display area of ​​the liquid crystal display panel 7, and is the size of the effective display area that can be displayed. The size of the exit surface 6a corresponds to the size of the maximum lighting area that can be irradiated with light from the light source, corresponding to the effective display area of ​​the liquid crystal display panel 7. The virtual images 10Q and 20Q are formed in the eyes of the user 5. The user 5 can view the virtual images 10Q and 20Q.

[0022] FIG. 2 is a diagram showing the position of the liquid crystal display panel 7 relative to the backlight 6. The incident surface 7b of the liquid crystal display panel 7 is arranged to form predetermined angles θ1 and θ2 with respect to the exit surface 6a of the backlight 6. Since the display surface a of the liquid crystal display panel 7 and the incident surface 7b are generally parallel, the angles θ1 and θ2 may be the inclination angles between the display surface a of the liquid crystal display panel 7 and the exit surface 6a of the backlight 6. FIG. 2(a) shows a state in which the incident surface 7b of the liquid crystal display panel 7 is arranged parallel to the exit surface 6a of the backlight 6, FIG. 2(2) shows a state in which the incident surface 7b of the liquid crystal display panel 7 is arranged at an angle θ1 with respect to the exit surface 6a of the backlight, and FIG. 2(3) shows a state in which the incident surface 7b of the liquid crystal display panel 7 is arranged at an angle θ2 with respect to the exit surface 6a of the backlight 6. Note that these angles θ1 and θ2 are collectively referred to as angle θ. The procedure for setting the NTSC ratio of the reproduced color gamut to the standard color gamut (100%) to be 70% when the angle θ of the entrance surface 7b of the liquid crystal display panel 7 with respect to the exit surface 6a of the backlight 6 is between 10° and 45° is described below.

[0023] The incident surface 7b of the liquid crystal display panel 7 shown in FIG. 2(b) is disposed at an angle θ1 with respect to the exit surface 6a of the backlight 6, and the incident surface 7b of the liquid crystal display panel 7 shown in FIG. 2(c) is disposed at an angle θ2 with respect to the exit surface 6a of the backlight 6, which is larger than the angle θ1. The angle θ can be set, for example, in the range of 10° to 45°. Here, FIG. 2(a) shows the case where the angle θ is 0°, FIG. 2(b) shows the case where the angle θ1 is 30°, and FIG. 2(c) shows the case where the angle θ2 is 45°. When the angle θ=0° shown in FIG. 2(a), the angle θ=30° shown in FIG. 2(b), and the angle θ=45° shown in FIG. 2(c), the conditions of the liquid crystal layer of the liquid crystal display panel 7 and the conditions of the color filter CF that make the NTSC ratio 70% can be set for each of the cases.

[0024] When the angle θ changes, the optical path length L1 of the light passing through the liquid crystal layer of the liquid crystal display panel 7 changes, and the optical path length L2 of the light passing through the color filter (hereinafter also referred to as CF) changes. If the optical path length of the light passing through the liquid crystal layer when the incident surface 7b of the liquid crystal panel 7 is parallel to the exit surface 6a of the backlight 6 is Lc0, the optical path length L1 of the light passing through the liquid crystal layer in the tilted state (θ>0°) is Lc0 / cosθ. If the optical path length of the light passing through the CF in the parallel state is Lf0, the optical path length L2 of the light passing through the CF in the tilted state is Lf0 / cosθ.

[0025] When the optical path length L1 in the liquid crystal layer of the liquid crystal display panel 7 and the optical path length L2 in the CF change, a phenomenon occurs in which the luminance and chromaticity of the virtual image 10Q and the virtual image 20Q change. As a result, the display characteristics of the virtual image change depending on the angle θ of the entrance surface 7b of the liquid crystal display panel 7 with respect to the exit surface 6a of the backlight 6. This becomes noticeable in a liquid crystal display panel 7 with a wide color gamut with an NTSC ratio of 60% or more. In order to correct this, in this embodiment, the CF has a thin thickness corresponding to the angle θ compared to the thickness in the parallel state, and the liquid crystal layer has a small birefringence phase difference corresponding to the angle θ compared to the birefringence phase difference in the parallel state. Specifically, the thickness of the CF may be Lf0×cosθ when the thickness of the CF in the parallel state is Lf0 and the angle is θ. The birefringence phase difference may be set to R0×cosθ when the birefringence phase difference in the parallel state is R0 and the angle is θ. Furthermore, it is preferable to appropriately adjust the spectral characteristics of the liquid crystal display panel 7 and the birefringence retardation of the liquid crystal layer in accordance with the spread of the light emitted from the backlight 6.

[0026] The CF is disposed on the display surface 7a side or the entrance surface 7b side of the liquid crystal display panel 7. When the CF is disposed on the display surface 7a side of the liquid crystal display panel 7, for example, it is disposed on the liquid crystal layer side surface of the CF substrate (substrate facing the array substrate (substrate on which pixels including a large number of thin film transistors are arranged in a matrix)) of the liquid crystal display panel 7. When the CF is disposed on the entrance surface 7b side of the liquid crystal display panel 7, for example, the CF substrate of the liquid crystal display panel 7 may be located on the backlight 6 side. When the CF is disposed on the entrance surface 7b side of the liquid crystal display panel 7, for example, it may be disposed on the liquid crystal layer side surface of the array substrate of the liquid crystal display panel 7. FIG. 2 shows a configuration in which the CF is disposed on the display surface 7a side of the liquid crystal display panel 7, and is disposed on the liquid crystal layer side surface of the CF substrate of the liquid crystal display panel 7.

[0027] FIG. 3 is a diagram showing the color gamut distribution of the LCDs of the example and the comparative example. The LCD is configured to include a backlight 6 and a liquid crystal display panel 7. In order to confirm the color reproduction range and the transmittance, a fluoride red phosphor (K 2 SiF 6 :Mn 4 + 8.) (having the spectral characteristics shown by curve L11 in FIG. 8) is combined with a liquid crystal display panel 7 as an example, and a configuration in which a backlight 6 having light-emitting elements of a yellow phosphor (YAG:Ce) (having the spectral characteristics shown by curve L10 in FIG. 8) is combined with a liquid crystal display panel 7 as a comparative example. The results of measuring the transmittance versus NTSC ratio are shown in FIG. 3.

[0028] Example of fluoride red phosphor (K 2 SiF 6 :Mn 4 +) light emitting element has the spectral characteristic shown by the curve L11 in FIG. 8. The transmittance was measured as follows. A light source for measurement similar to that of the backlight 6 is arranged on the side of the array substrate 23b (shown in FIG. 10B) of the liquid crystal display panel 7, and a spectroluminometer is arranged on the side of the CF substrate 23a (shown in FIG. 10B) of the liquid crystal display panel 7. In this case, the incident surface of the liquid crystal display panel 7 is parallel to the exit surface of the light source. In this state, the light intensity of the light source is kept constant, and the luminance (luminance 1) is measured. Next, in the absence of the liquid crystal display panel 7, the light intensity of the light source is kept constant as above, and the luminance (luminance 2) is measured. The luminance was measured at the center of the virtual image. The light transmittance was measured by calculating (luminance 1) / (luminance 2). The retardation of the liquid crystal display panel 7 is 388 (nm). The liquid crystal display panel 7 of the embodiment had an NTSC ratio of 70%.

[0029] The backlight 6 having the light-emitting element of the yellow phosphor (YAG:Ce) of the comparative example has the spectral characteristic shown by the curve L10 in FIG. 8. The transmittance was measured in the same manner as above. The retardation of the liquid crystal display panel 7 is 388 (nm). The liquid crystal display panel 7 of the comparative example has an NTSC ratio of 45%.

[0030] In the case of HUD, sunlight incident on the liquid crystal display panel 7 is reflected by the windshield 12 (shown in FIG. 13), so in order to prevent the reflected light from being visually recognized by the user (the driver in FIG. 13) 5, it is preferable to set the angle θ to 10° or more. Also, if the entrance surface 7b of the liquid crystal display panel 7 is inclined at an angle θ in the range of 30° to 45° with respect to the exit surface 6a of the backlight 6, a virtual image tilted in the traveling direction (for example, a virtual image having a shape such as an inverted trapezoid) is projected. Therefore, the angle θ at which the reflected light of sunlight is not recognized by the driver and the virtual image is not projected with an excessive tilt may be 10° to 45°. The liquid crystal display panel 7 is set to match the spectral characteristics of the backlight 6, and the NTSC ratio is set to 70% or more. The conditions are set as follows: when the angle θ between the entrance surface 7b of the liquid crystal display panel 7 and the exit surface 6a of the backlight 6 is 10° or more and 45° or less, the condition of the liquid crystal layer and the CF is set such that the NTSC ratio is 70%. That is, the liquid crystal layer and the CF are set so that the optical path lengths L1 and L2 according to the angle θ are the same as Lc0 and Lf0. The brightness of the image light was measured for the set LCD, and the transmittance of the image light of the LCD was calculated based on the measured brightness, and the results shown in FIG. 4 were obtained. The brightness was measured at the center of the virtual image. As shown in FIG. 4, the transmittance decreased as the NTSC ratio (%) increased, but it was confirmed that the transmittance of the embodiment (KSF-BL+LCD) was higher than the transmittance of the comparative example (YAG-BL+LCD).

[0031] Fig. 5 is a front view showing the display state of a virtual image showing a road sign. Fig. 5(a) shows a display example of the transmittance of the comparative example (YAG-BL-LCD), and Fig. 5(b) shows a display example of the transmittance of the embodiment (KSF-BL-LD). It can be seen that the display example shown in Fig. 5(b) is clearer and has higher visibility than the display example shown in Fig. 5(a).

[0032] FIG. 6 is a side view showing an example of the installation of a chromaticity measuring device, and FIG. 7 is a graph showing an example of the setting of a liquid crystal display panel 7 for a wide color gamut HUD. In order to confirm the spectral characteristics of each RGB color with respect to the change in angle θ, a measurement light source 9 simulating a backlight 6 is prepared, and the luminance of the light emitted from the measurement light source 9 through a CF is measured by a chromaticity measuring device 10, and the measurement result is shown in FIG. 7. The vertical axis of FIG. 7 indicates the transmittance, and the horizontal axis indicates the wavelength. In FIG. 7, when the angle θ of the incident surface of the CF with respect to the exit surface of the measurement light source 9 is 0°, the two-dot chain line graph LR, the one-dot chain line LG, and the solid line LB indicate the spectral transmittance of each RGB color, and the dashed lines LR1, LG1, and LB1 indicate the spectral transmittance of the backlight 6 for each RGB color. In FIG. 7, the graph LR1 indicates the transmittance of red light, the graph LG1 indicates the transmittance of green light, and the graph LB1 indicates the transmittance of blue light.

[0033] Since a phenomenon occurs in which the optical path length L2 passing through the CF of the liquid crystal display panel 7 changes depending on the angle θ, and the optical path length L1 passing through the liquid crystal layer of the liquid crystal display panel 7 changes depending on the angle θ, the display characteristics (brightness, chromaticity) of the virtual image differ depending on the angle θ. This becomes noticeable in a wide color gamut liquid crystal display panel 7 with an NTSC ratio of 60% or more.

[0034] For a wide color gamut HUD display, the NTSC ratio of an LCD equipped with a KSF-BL and a liquid crystal display panel 7 is set to 70% in accordance with the spectral characteristics of the backlight 6. The condition is set so that the NTSC ratio is 70% when the angle θ between the entrance surface 7b of the liquid crystal display panel 7 and the exit surface 6a of the BL is 10° or more and 45° or less. That is, (1) when the angle θ between the entrance surface 7b of the liquid crystal display panel 7 and the exit surface 6a of the backlight 6 is 0°, the conditions (color filter, liquid crystal layer) of the liquid crystal display panel 7 are set so that the NTSC ratio is 70%. (2) The liquid crystal layer of the liquid crystal display panel 7 and the CF are set so that the optical path lengths L1, L2 according to the angle θ become the same as Lc0, Lf0 in the parallel state.

[0035] A method for setting the CF will be described below. The thickness of the CF and the thickness of the liquid crystal layer of the liquid crystal display panel 7 are adjusted according to the angle θ formed between the entrance surface 7b of the liquid crystal display panel 7 and the exit surface 6a of the backlight 6.

[0036] The following Table 1 shows an example of the settings of the liquid crystal display panel 7 for wide color gamut HUD display (NTSC ratio 70%). When the angle θ is set to 0°, 30°, and 45°, the optical path lengths L1 and L2 are set to be the same as Lc0 and Lf0 in the parallel state. That is, as the angle θ increases, the thickness of the liquid crystal layer (thickness in a direction perpendicular to the layer surface) and the thickness of the CF (thickness in a direction perpendicular to the incident surface of the CF) become thinner. The chromaticity values ​​CF(Rx, Ry), CF(Gx, Gy), and CF(Bx, By) are shown when the spectral luminance is measured by the luminance measuring device 10 in a direction perpendicular to the incident surface of the CF when the angle θ is 0°, 30°, and 45°. The retardation values ​​Δnd in the thickness direction of the liquid crystal layer (thickness in a direction perpendicular to the layer surface) are also shown when the angle θ is 0°, 30°, and 45°.

[0037] When the angle θ is 30°, if the thickness of the liquid crystal layer is not corrected, the optical path length L1 is Lc0 / cos30°=1.155×Lc0, so the thickness of the liquid crystal layer is corrected and set to Lc0×cos30°=0.866×Lc0. As a result, Δnd is Δnd0 (retardation in parallel state)×cos30°=0.866×388=336 (nm). Also, when the angle θ is 30°, if the thickness of the CF is not corrected, the optical path length L2 is Lf0 / cos30°=1.155×Lf0, so the thickness of the CF is corrected and set to Lf0×cos30°=0.866×Lf0. As a result, the chromaticity values ​​CF(Rx,Ry), CF(Gx,Gy), and CF(Bx,By) are set so that the color purity is slightly reduced. When the angle θ is 45°, the thickness of the liquid crystal layer and the thickness of the CF are corrected in the same manner.

[0038] [Table 1]

[0039] Using the transmission spectrum of CF in Fig. 14, the color matching function in Fig. 15, and the relative energy spectrum of Illuminant C in Fig. 16, the chromaticity x, y, and each thickness of RGB of CF shown in Table 2 are calculated by the following definition formula of the XYZ color system. Illuminant C is one of the standard light source specifications defined by CIE (International Commission on Illumination), and corresponds to standard illuminant (standard light) C. Illuminant C has a color temperature of 6774 Kelvin, which is equivalent to daylight including blue sky.

[0040]

number

[0041] [Table 2] In addition, the thickness when θ=30° is (thickness when θ=0°)×cos θ. The same applies when θ=45°.

[0042] The thickness of the liquid crystal layer 23c is calculated. The retardation in the thickness direction of the liquid crystal layer 23c is (Δn(0.11) of the liquid crystal) × (thickness of the liquid crystal layer) = 388 (nm), so the thickness of the liquid crystal layer 23c is 3.5 (μm). The thickness of the liquid crystal layer 23c when θ = 30° is (thickness of the liquid crystal layer 23c when θ = 0° is 3.5 μm) × cos30°, so it is 3.1 μm. Similarly, the thickness of the liquid crystal layer 23c when θ = 45° is 2.5 μm.

[0043] The chromaticity of the CF may be set by adjusting the pigment concentration and the film thickness of the color filter CF after selecting the pigment of each color. Also, it may be adjusted so as to satisfy the characteristics of Table 2. For angles θ of 0°, 30°, and 45°, the chromaticity values ​​CF(Rx,Ry), CF(Gx,Gy), and CF(Bx,By) of each color of RGB may be set within a range of about ±1.7% to ±4.5% from the median value. For angles θ of 0°, 30°, and 45°, the retardation (Δnd) may be set within a range of about ±6% from the median value.

[0044] [Table 3]

[0045] Fig. 8 is a graph showing the spectral characteristics of the backlight 6. In Fig. 8, the horizontal axis indicates wavelength, and the vertical axis indicates light intensity (au). When a virtual image is projected against a bright background such as a snowy road on a sunny day, the luminance of the virtual image of the HUD is 10000cd / m 2 Considering the transmittance of the liquid crystal display panel 7 and the optical system of the HUD, the backlight 6 for the HUD requires a light transmittance of 1,000,000 cd / m 2 The maximum brightness is 2.3 million cd / m 2 When the conditions for achieving a wide color gamut (70% of NTSC) with the backlight 6 were checked, the results shown in Table 3 above were obtained. In FIG. 8, curve L10 shows the light intensity at each wavelength of the YAG-LED backlight, and curve L11 shows the light intensity at each wavelength of the KSF-LED backlight. The first peak P1 in curve L11 is red fluorescent color (K 2 SiF 6 :Mn 4 + ), and the second peak P2 is due to the green phosphor (βSiAlON).

[0046] 9 is a cross-sectional view of a main part showing an example of the configuration of a backlight for HUD. The backlight 16 of this embodiment includes light-emitting diodes 17 which are a plurality of light-emitting elements, a condenser lens 18 which condenses the light emitted from each of the light-emitting diodes 17, and a diffusion film 19 on which the light emitted from the condenser lens 18 is irradiated. The diffusion film 19 has an exit surface 19a, and the liquid crystal display panel 7 is disposed above the exit surface 19a at an angle θ.

[0047] FIG. 10A is a front view showing a wide color gamut liquid crystal display panel 7 for HUD, FIG. 10B is a cross-sectional view of the liquid crystal display panel 7 seen from the cross-sectional line XB-XB in FIG. 10A, and FIG. 10C is an enlarged view of a part of the CF. FIG. 11 is a cross-sectional view of the CF. The CF is formed by applying a color resist 20 (shown in FIG. 11) to a glass substrate 21, and then irradiating it with ultraviolet light to cause a polymerization and cross-linking reaction and hardening it. A black matrix BM and the color resist 20 are formed on one side of the glass substrate 21, and unnecessary parts can be dissolved and removed with a developer, and formed into any pattern. The color resist 20 is a mixture of a pigment, a polymer, a photosensitive material, and a solvent. The pigment may be composed of a mixture of 1 to 10 weight % of a complex such as Ni or Cu, 5 to 15 weight % of an acrylic resin, and a solvent such as cyclohexane or propylene glycol monomethyl ether acetate. In FIG. 11, the CF is covered with an overcoat layer 22 with the film surface facing downward. The material of the overcoat layer 22 may be an acrylic resin having a thickness of 1 to 3 μm, and the surface of the CF is smoothed.

[0048] The liquid crystal display panel 7 has a CF substrate 23a and an array substrate 23b, and a liquid crystal layer 23c is sandwiched between these substrates. The liquid crystal layer 23c is located between the CF substrate 23a and the array substrate 23b. A CF is formed on the surface of the CF substrate 23a facing the liquid crystal layer 23c. A liquid crystal driver IC 24 is mounted on an end portion exposed to the outside of the array substrate 23b, and a flexible substrate (flexible wiring substrate) 25 for connecting an external device to the liquid crystal driver IC 24 is connected to the liquid crystal driver IC 24.

[0049] Figure 12 is a graph showing the spectral characteristics of CF. The chromaticity of CF is set by adjusting the pigment concentration and the film thickness of the color filter after selecting the pigment of each color. When the angle θ is 30°, adjustment is made to satisfy the characteristics of the curves LR1, LG1, and LB1 shown in Figure 12. The curve LR1 indicates the transmittance of red light, the curve LG1 indicates the transmittance of green light, and the curve LB1 indicates the transmittance of blue light.

[0050] Next, a setting example of the liquid crystal display panel LCP for a wide color gamut HUD will be described. When the angle θ is 30°, the backlight 6 has the spectral characteristics when using KSF-BL and the liquid crystal display panel 7, specifically, the liquid crystal display panel 7 for a wide color gamut HUD has the spectral characteristics of each of the RGB colors. When the angle θ is 0°, the luminance of the virtual image of the HUD is 10000cd / m when projecting a virtual image against a bright background such as a snowy road on a sunny day. 2 The transmittance of the liquid crystal display panel 7 is required to be 1,000,000 cd / m for the backlight 6 for the HUD, taking into consideration the optical system of the HUD. 2 In the prototype, the maximum brightness was 2.3 million cd / m 2 With backlight 6, a wide color gamut (70% NTSC ratio) was confirmed.

[0051] The HUD wide color gamut liquid crystal display panel 7 is configured such that the CF is formed by applying color resist 20 to a glass substrate 21, and then polymerizing and crosslinking the color resist 20 with ultraviolet light to harden it. Any pattern is formed by dissolving and removing unnecessary parts with a developer. The color resist 20 is made of a mixture of pigment, polymer, photosensitive material, and solvent. As an example of the composition of the color resist 20 in solution, the pigment may be a complex of a metal (such as Ni or Cu) (1 to 10% by weight), the polymer may be an acrylic resin (5 to 15% by weight), and the solvent may be cyclohexanone, propylene glycol monomethyl, ether acetate, or the like.

[0052] A black matrix BM made of resin with a thickness of about 1 μm and an OD value of 4 or more is formed to prevent color mixing, and an overcoat 22 made of acrylic resin with a thickness of 1 to 3 μm is formed to smooth the CF.

[0053] As an example of the CF used, the transmittance of each of the RGB colors is shown in Table 4 below.

[0054] [Table 4]

[0055] As shown in FIG. 13, the virtual image display device 1 may be mounted on a moving body 100. When the virtual image display device 1 is mounted on the moving body 100, a part of the configuration of the virtual image display device 1 may be shared with other devices and parts of the moving body 100. For example, the windshield 12 of the moving body 100 may be shared as a part of the configuration of the virtual image display device 1. For example, the second reflecting portion 3b constituting the optical system 3 shown in FIG. 1 may be replaced by the windshield 12 of the moving body 100. The position of the virtual image display device 1 may be arbitrary inside and outside the moving body 100. For example, the virtual image display device 1 may be located in the dashboard of the moving body 100.

[0056] The virtual image display device 1 may further include a detection device 11 that detects the eye position of the user 5. The detection device 11 is configured to detect the eye position of the user 5. The detection device 11 is configured to output information related to the detected eye position to the control unit 4. The information related to the detected eye position is also referred to as eye position information. The control unit 4 may be configured to control the emission or non-emission of each of the multiple light-emitting diodes 61 (see FIG. 1 ) based on the eye position of the user 5 detected by the detection device 11. When the virtual image display device 1 is mounted on a moving body 100, the position of the detection device 11 may be any position inside or outside the moving body 100. For example, the detection device 11 may be located in the dashboard of the moving body 100. The detection device 11 may output information related to the eye position of the user 5 to the control unit 4, for example, via a wired, wireless, CAN (Controller Area Network), or the like.

[0057] The detection device 11 may be configured to include an imaging device. The imaging device may include, for example, a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The imaging device may be configured to be able to capture an image of the face of the user 5. The imaging range of the imaging device includes an eye box. The eye box is an area in real space where the eyes of the user 5 are assumed to exist, taking into account, for example, the physique, posture, and changes in posture of the user 5. The user 5 may include, for example, a driver of the moving body 100. The detection device 11 may be configured to detect the positions of both eyes of the user 5 in real space based on an image generated by the imaging device.

[0058] The detection device 11 may include, for example, a sensor. The sensor may be an ultrasonic sensor, an optical sensor, or the like. The detection device 11 may be configured to detect the position of the head of the user 5 by the sensor, and detect the position of the eyes of the user 5 based on the position of the head. The detection device 11 may be configured to detect the position of the eyes of the user 5 as coordinates in a three-dimensional space by two or more sensors.

[0059] The display unit 2 may be configured to include an optical element for allowing the user 5 to view a stereoscopic image. The optical element may be located between the backlight 6 and the liquid crystal display panel 7 along the optical path of the image light reaching the eye of the user 5. The optical element may be located between the liquid crystal display panel 7 and the optical system 3 along the optical path of the image light reaching the eye of the user 5. The liquid crystal display panel 7 may be configured to display a left eye image and a right eye image having parallax with respect to the left eye image on the display surface 7a. The optical element may be configured to separate the image light emitted from the display surface 7a into left eye image light indicating the left eye image and right eye image light indicating the right eye image. This enables the virtual image display device 1 to allow the user 5 to view a stereoscopic image with reduced degradation in visibility. The optical element may be configured to include a parallax barrier or a lenticular lens. The parallax barrier may be configured to include a liquid crystal panel.

[0060] In the present disclosure, the term "mobile body" includes vehicles, ships, and aircraft. In the present disclosure, the term "vehicle" includes, but is not limited to, automobiles and industrial vehicles, and may include railroad vehicles, lifestyle vehicles, and fixed-wing aircraft that run on runways. Automobiles include, but are not limited to, passenger cars, trucks, buses, motorcycles, trolley buses, and the like, and may include other vehicles that run on roads. Industrial vehicles include industrial vehicles for agriculture and construction. Industrial vehicles include, but are not limited to, forklifts and golf carts. Industrial vehicles for agriculture include, but are not limited to, tractors, cultivators, transplanters, binders, combines, and lawnmowers. Industrial vehicles for construction include, but are not limited to, bulldozers, scrapers, excavators, cranes, dump trucks, and road rollers. Vehicles include those that run by human power. The classification of vehicles is not limited to the above. For example, automobiles may include industrial vehicles that can run on roads, and the same vehicle may be included in multiple classifications. In the present disclosure, the vessel includes a marine jet, a boat, and a tanker. In the present disclosure, the aircraft includes a fixed-wing aircraft and a rotorcraft.

[0061] According to the virtual image display device and the moving body of the present disclosure, the backlight includes a plurality of light-emitting diodes having a fluoride red phosphor and an exit surface that emits light emitted from the plurality of light-emitting diodes. The light emitted from the exit surface is incident on the entrance surface of the liquid crystal display panel, and the incident light passes through a liquid crystal layer driven by a control unit and is displayed as an image on the display surface. The image displayed on the display surface is formed as a virtual image in the user's field of vision by an optical system. The liquid crystal display panel is disposed with the entrance surface inclined at a predetermined angle with respect to the exit surface of the backlight. The color filter has a thin thickness corresponding to the predetermined angle compared to the thickness in a parallel state in which the entrance surface of the liquid crystal display panel is parallel to the exit surface of the backlight, and the liquid crystal layer has a small birefringence phase difference corresponding to the predetermined angle compared to the birefringence phase difference in the parallel state. These corrections are due to the fact that the liquid crystal display panel is inclined with respect to the backlight, and therefore the optical path length of the light of the image passing through the liquid crystal layer and the color filter is longer than that in the parallel state. With the above configuration, a highly clear virtual image can be viewed without significantly reducing the color reproduction range of the liquid crystal display panel relative to the standard (100%) of the color reproduction range of the three primary colors of the NTSC standard.

[0062] In addition, when the liquid crystal display panel is inclined with respect to the backlight, the color gamut of the virtual image tends to narrow and the color purity of the virtual image tends to decrease. However, since the backlight has a plurality of light emitting diodes having a fluoride red phosphor, it is possible to suppress the decrease in color purity of the virtual image. 2 SiF 6 :Mn 4 + This is because KSF (Kindium Fluorescent Sulfide) is a type of line-emitting phosphor with a wide color gamut and a narrow wavelength spectrum width of the three primary colors RGB (high sharpness of the wavelength spectrum).

[0063] The present disclosure can be implemented in the following configurations (1) to (6).

[0064] (1) A backlight including a plurality of light emitting diodes having a fluoride red phosphor and an emission surface that emits light from the plurality of light emitting diodes; a liquid crystal display panel having an incident surface onto which the light emitted from the exit surface is incident, a display surface that displays an image by the light incident on the incident surface, and a liquid crystal layer located between the incident surface and the display surface; a color filter disposed on the display surface side or the light incidence surface side of the liquid crystal display panel; an optical system that guides the image displayed on the display surface into a user's field of vision and forms a virtual image; the liquid crystal display panel is disposed such that the entrance surface is inclined at a predetermined angle with respect to the exit surface of the backlight, the color filter has a thickness that is smaller than a thickness when the incident surface is parallel to the exit surface, the thickness being determined by the predetermined angle; The liquid crystal layer has a birefringence phase difference that is smaller than the birefringence phase difference in the parallel state in accordance with the predetermined angle.

[0065] (2) The virtual image display device according to the above configuration (1), wherein the predetermined angle is equal to or greater than 10° and equal to or less than 45°.

[0066] (3) The virtual image display device according to the above configuration (1) or (2), wherein the thickness of the color filter in the parallel state is Lf0 and the specified angle is θ, and the thickness of the color filter is Lf0×cosθ.

[0067] (4) The virtual image display device according to any one of the above configurations (1) to (3), wherein the birefringence phase difference in the parallel state is set to R0×cosθ, where R0 is the birefringence phase difference and θ is the specified angle, and the color filter has a thickness according to the specified angle.

[0068] (5) The virtual image display device according to any one of the above configurations (1) to (4), wherein the liquid crystal display panel has an NTSC ratio of 70% or more.

[0069] (6) The virtual image display device according to any one of the above configurations (1) to (5) is installed as a head-up display device, The liquid crystal display panel has an NTSC ratio of 70% or more.

[0070] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-mentioned embodiments, and various modifications and improvements are possible within the scope of the gist of the present invention. It goes without saying that all or part of the components of each of the above-mentioned embodiments can be appropriately combined within the scope of not contradicting each other. [Explanation of symbols]

[0071] 1 Virtual image display device 2 Display section 3 Optical system 3a 1st reflection section 3b 2nd reflection section 4. Control Unit 5 User 6 Backlight 6a Output surface 7 Liquid crystal display panel 7a Display surface 7b Incidence plane 10Q Virtual Image 20Q Virtual Image 23a CF board 23b Array board 23c liquid crystal layer 12 Windshield 61 Light Emitting Diode 62 Base 62a Main surface 63 Diffuser θ, θ1, θ2 Predetermined angle CF Color Filter

Claims

1. A backlight including a plurality of light emitting diodes having a fluoride red phosphor and an emission surface that emits light from the plurality of light emitting diodes; a liquid crystal display panel having an incident surface onto which the light emitted from the exit surface is incident, a display surface that displays an image by the light incident on the incident surface, and a liquid crystal layer located between the incident surface and the display surface; a color filter disposed on the display surface side or the light incidence surface side of the liquid crystal display panel; an optical system that guides the image displayed on the display surface into a user's field of vision and forms a virtual image; the liquid crystal display panel is disposed such that the entrance surface is inclined at a predetermined angle with respect to the exit surface of the backlight, the color filter has a thickness that is smaller than a thickness when the incident surface is parallel to the exit surface, the thickness being determined by the predetermined angle; The liquid crystal layer has a birefringence phase difference that is smaller than the birefringence phase difference in the parallel state in accordance with the predetermined angle.

2. The virtual image display device according to claim 1 , wherein the predetermined angle is equal to or greater than 10° and equal to or less than 45°.

3. 3. The virtual image display device according to claim 1, wherein a thickness of the color filter is Lf0×cos θ, where Lf0 is a thickness of the color filter in the parallel state and θ is the predetermined angle.

4. 3. The virtual image display device according to claim 1, wherein the birefringence phase difference is set to R0×cos θ, where R0 is the birefringence phase difference in the parallel state, and θ is the predetermined angle.

5. 3. The virtual image display device according to claim 1, wherein the liquid crystal display panel has an NTSC ratio of 70% or more.

6. The virtual image display device according to claim 1 or 2 is installed as a head-up display device, The liquid crystal display panel has an NTSC ratio of 70% or more.

Images