Virtual image display device and mobile object

Abstract

This virtual image display device comprises: a backlight having an emission surface for emitting light from a light-emitting diode that has a fluoride red phosphor; a liquid crystal display panel having an incidence surface at which light from the emission surface is incident, a display surface, and a liquid crystal layer provided between the incidence surface and the display surface; a color filter that is disposed on the display surface side or incidence surface side of the liquid crystal display panel; and an optical system for forming, in a user's visual field, a virtual image of an image displayed on the display surface. The incidence surface of the liquid crystal display panel is tilted at an angle θ with respect to the emission surface. The color filter is thinner in accordance with the angle θ than the thickness of the case of a parallel state in which the incidence surface is parallel to the emission surface, and the liquid crystal layer has a smaller birefringent phase difference in accordance with the angle θ than the birefringent phase difference of the case of the parallel state.

Description

Virtual image display device and mobile object

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

[0002] A prior art virtual image display device is described in, for example, Japanese Patent Application Laid-Open No. 2003-222999.

[0003] Japanese Patent Application Laid-Open No. 2016-4141

[0004] The virtual image display device according to the present disclosure includes a backlight including a plurality of light-emitting diodes each 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 using the light that has entered the entrance surface, and a liquid crystal layer located between the entrance surface and the display surface; a color filter disposed on the side of the display surface or the side of the entrance surface of the liquid crystal display panel; and an optical system that directs the image displayed on the display surface into the user's field of view and forms a virtual image, wherein 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 the thickness when the entrance surface is parallel to the exit surface in accordance with the predetermined angle, and the liquid crystal layer has a small birefringence phase difference in accordance with the predetermined angle compared to the birefringence phase difference when the entrance surface is parallel.

[0005] 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.

[0006] The objects, features, and advantages of the present disclosure will become clearer from the following detailed description and drawings. 10A is a cross-sectional view of a main part of a virtual image display device according to an embodiment of the present disclosure. 10B is a side view showing the position of a liquid crystal display panel relative to a backlight. 10C is a side view showing the position of a liquid crystal display panel relative to a backlight. 10D is a side view showing the position of a liquid crystal display panel relative to a backlight. 10E is a diagram showing the color gamut distribution of an example and a comparative example. 10F is a graph showing the change in transmittance with respect to the NTSC ratio. 10G is a front view showing the display state of a virtual image displaying a road sign. 10H is a front view showing the display state of a virtual image displaying a road sign. 10I is a side view showing an example of installation of a chromaticity measuring device. 10I is a graph showing an example of setting a liquid crystal display panel for a wide color gamut HUD. 10I is a graph showing the spectral characteristics of a backlight. 10I is a cross-sectional view of a main part showing an example configuration of a backlight for a HUD. 10I is a front view showing a wide color gamut liquid crystal display panel for a HUD. 10I is a cross-sectional view of a liquid crystal display panel taken along the cross-sectional line XB-XB in FIG. 10A. 10I is an enlarged view of a portion of a color filter. 10I is a cross-sectional view of a color filter. 10I is a graph showing the spectral characteristics of a color filter. FIG. 1 is a cross-sectional view of a main part of a moving object equipped with a virtual image display device; FIG. 2 is a graph of the transmission spectrum of a color filter; FIG. 3 is a graph of color matching functions; FIG. 4 is a graph of the relative energy spectrum of a C light source (standard illuminant C light source); FIG. 5 is a cross-sectional view of a reflective member, explaining the curvature of the reflective member made of a concave mirror; FIG. 6 is a side view of a liquid crystal display panel, explaining the thickness of the color filter and the thickness of the liquid crystal layer when the liquid crystal display panel is tilted with respect to the backlight; and FIG. 7 is a side view of a liquid crystal display panel, explaining the thickness of the color filter and the thickness of the liquid crystal layer when the liquid crystal display panel is tilted with respect to the backlight using another method.

[0007] In the conventional technology of Patent Document 1, when the color gamut is increased from, for example, 45% to 70% in order to improve the brightness of a virtual image, the transmittance of the transmissive liquid crystal display panel decreases by about 40% when the color reproduction gamut of the NTSC (National Television System Committee) standard is taken as the reference (100%). 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.

[0008] 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.

[0009] 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 of this 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 referred to as 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 mobile object such as a vehicle, a ship, or an aircraft. When the virtual image display device 1 is mounted on a mobile object, the user 5 may be a driver, an operator, or a passenger of the mobile object.

[0010] The display unit 2 displays an image to be projected into the field of view 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 the image displayed to the user 5.

[0011] 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 diffuser 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 arranged two-dimensionally (in a matrix) on the main surface 62a. The diffuser 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 diffuser 63 may diffuse light emitted from the plurality of light-emitting diodes 61, thereby allowing the backlight 6 to irradiate the liquid crystal display panel 7 with light with increased uniformity. The exit surface 6a may be the surface of the diffuser 63 facing the liquid crystal display panel 7, or may be the main surface 62a of the base 62.

[0012] Each of the plurality of 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.

[0013] The liquid crystal display panel 7 has a display surface 7 a. The display surface 7 a is a surface that displays images based on an image display signal, and can output images to the optical system 3 side by light emitted from the emission surface 6 a of the backlight 6.

[0014] The liquid crystal display panel 7 may be a known liquid crystal panel. Examples of known liquid crystal panels include in-plane switching (IPS) panels, fringe field switching (FFS) panels, vertical alignment (VA) panels, and electrically controlled birefringence (ECB) panels. The liquid crystal display panel 7 may include a plurality of liquid crystal display elements (pixels each having a liquid crystal layer 7L), two glass substrates arranged to sandwich the plurality of liquid crystal display elements, and a color filter 7C (hereinafter, the color filter may also be referred to as a CF). Instead of the glass substrate, a light-transmitting plastic substrate, ceramic substrate, or the like may be used.

[0015] The control unit 4 controls the backlight 6. The control unit 4 switches each of the plurality of light-emitting diodes 61 between an emitting state and a non-emitting state. The control unit 4 may control the light emission brightness 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 7 a. The control unit 4 may control the light emission brightness of the light-emitting diodes 61 that are in the emitting state based on the background brightness in the field of view of the user 5.

[0016] The control unit 4 may control not only the backlight 6 but also each component of the virtual image display device 1. 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 loads 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 may include a memory unit that stores various information or programs for operating each component of the virtual image display device 1. The memory unit may be configured as, for example, a semiconductor memory. The memory unit may function as a work memory for the control unit 4.

[0017] The optical system 3 is located in the optical path of image light emitted from the display unit 2 and reaching the eyes of the user 5. The optical system 3 projects the image light emitted from the display unit 2 onto the eyes of the user 5, forming a virtual image in the eyes of the user 5. The optical system 3 may enlarge or reduce the image displayed on the display unit 2 to form an image in the eyes of the user 5. The optical system 3 may include a reflecting member. The reflecting member may be a first optical member (also referred to as a first reflecting member) 3a and a second optical member (also referred to as a second reflecting member) 3b. The first reflecting member 3a reflects the image on the exit surface 6a and the image on the display surface 7a toward the second reflecting member 3b. The second reflecting member 3b reflects the image on the exit surface 6a and the image on the display surface 7a reflected by the first reflecting member 3a toward the eyes of the user 5 to form a virtual image. 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 element may include a reflective element including a convex or concave mirror. The optical element may include a reflective element including a free-form reflecting mirror. The free-form reflecting mirror may be a free-form concave mirror. The optical element may include a refractive element including a convex lens or a concave lens. Convex lenses include biconvex lenses, plano-convex lenses, and convex meniscus lenses. Concave lenses include biconcave lenses, plano-concave lenses, and concave meniscus lenses. 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.

[0018] A free-form reflecting mirror can suppress aberrations of its reflected light, and can reduce distortion of virtual images 10Q and 20Q. The free-form reflecting mirror may be an XY polynomial surface (also called an SPS XYP surface) defined by the following formulas (1) and (2). The XY polynomial surface is expanded into polynomials up to the tenth degree that are added to the reference conic surface. Therefore, in formulas (1) and (2), the sum of m and n is 10 or less. In formula (1), z is the sag of the surface parallel to the z-axis (also called the optical axis), c is the vertex curvature, and r is the radial distance (i.e., r ２ = x ２ +y ２ ), k is the conic constant, and C ｊ is a monomial x ｍ y ｎ is the coefficient of

[0019] The first reflecting member 3a and the second reflecting member 3b may each be a concave mirror, and the curvature of the second reflecting member 3b may be smaller than the curvature of the first reflecting member 3a. If the first reflecting member 3a is a concave mirror, the reflected light reflected by the first reflecting member 3a converges toward the second optical member 3b. If the second reflecting member 3b is a concave mirror, the reflected light reflected by the second reflecting member 3b is less likely to be diffused. As a result, it is possible to prevent a decrease in the brightness and resolution of the virtual images 10Q and 20Q.

[0020] When the curvature of the second reflecting member 3b is smaller than that of the first reflecting member 3a, the curvature may be a curvature, or when the concave surface is aspherical, it may be the average curvature of the entire concave surface. The first reflecting member 3a may have a relatively large curvature to converge the image light of the liquid crystal display panel 7, which has a wide angle of view and is diffused. The second reflecting member 3b, which forms a defocused virtual image formed by the reflected light (divergent light) of the image light, may have a relatively small curvature. Therefore, the second reflecting member 3b may be a plane mirror. The curvature of the first reflecting member 3a may be more than 1 time and up to about 3 times the curvature of the second reflecting member 3b, but is not limited to this range.

[0021] The degree of curvature may be defined as follows. When the first reflecting member 3a is a concave mirror, as shown in Fig. 17, in a cross section along the optical axis OA of image light incident on the first reflecting member 3a, the length of a line segment LS that passes over the center of the reflecting surface 3aa and connects both ends is 2 × H, and the maximum length (also referred to as maximum depth) of the direction along the optical axis OA between a point on the reflecting surface 3aa and the line segment LS may be DMAX. If DMAX / H changes depending on how the cross section is taken, the maximum value of DMAX / H when the position of the cross section is changed may be the degree of curvature.

[0022] 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 these refractive indices is called 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 equation 3. This phase difference is called retardation or birefringence phase difference.

[0023] (Math. 3) δ=2πΔnd / λ …(3)

[0024] 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, which is 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 referred to as an image displayed on the display surface 7a. Hereinafter, the image on the exit surface 6a will also be simply referred to as the exit surface 6a. The image on the display surface 7a will also be simply referred to as the display surface 7a. The virtual image 10Q will also be referred to as a light-emitting surface virtual image, and the virtual image 20Q will also be referred to as a 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.

[0025] 2A to 2C are diagrams 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 disposed at predetermined angles θ1 and θ2 with respect to the exit surface 6a of the backlight 6. Since the display surface a and the incident surface 7b of the liquid crystal display panel 7 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. 2A shows a state in which the incident surface 7b of the liquid crystal display panel 7 is disposed parallel to the exit surface 6a of the backlight 6, FIG. 2B shows a state in which the incident surface 7b of the liquid crystal display panel 7 is disposed at a predetermined angle θ1 with respect to the exit surface 6a of the backlight 6, and FIG. 2C shows a state in which the incident surface 7b of the liquid crystal display panel 7 is disposed at an angle θ2 with respect to the exit surface 6a of the backlight 6. Note that these predetermined angles θ1 and θ2 will be collectively referred to as the 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 incident surface 7b of the liquid crystal display panel 7 relative to the exit surface 6a of the backlight 6 is between 10° and 45° is described below.

[0026] The incident surface 7b of the liquid crystal display panel 7 shown in FIG. 2B is disposed at a predetermined angle θ1 with respect to the exit surface 6a of the backlight 6, while the incident surface 7b of the liquid crystal display panel 7 shown in FIG. 2C is disposed at an angle θ2 with respect to the exit surface 6a of the backlight 6 that is larger than the predetermined angle θ1. The angle θ can be set, for example, within a range of 10° to 45°. Here, FIG. 2A shows the case where the angle θ is 0°, FIG. 2B shows the case where the predetermined angle θ1 is 30°, and FIG. 2C shows the case where the angle θ2 is 45°. When the angle θ is 0° shown in FIG. 2A, when the angle θ is 30° shown in FIG. 2B, and when the angle θ is 45° shown in FIG. 2C, the conditions of the liquid crystal layer 7L and the color filter 7C of the liquid crystal display panel 7 that result in an NTSC ratio of 70% can be set.

[0027] The color filter 7C has a thickness in the parallel state such that the NTSC ratio, which is the color reproduction range relative to the standard color gamut, is 70% or more. The liquid crystal layer 7L has a birefringence retardation in the parallel state such that the NTSC ratio, which is the color reproduction range relative to the standard color gamut, is 70% or more. As shown in FIG. 18 , when the angle θ (indicated by θ1 in FIG. 18 ) changes, the optical path length L1 of light passing through the liquid crystal layer 7L of the liquid crystal display panel 7 changes, and the optical path length L2 of light passing through the color filter changes. When the incident surface 7b of the liquid crystal panel 7 is parallel to the exit surface 6a of the backlight 6, the optical path length L1 of light passing through the liquid crystal layer 7L in the tilted state (θ1 > 0°) is Lc0. When the optical path length of light passing through the CF in the parallel state is Lf0, the optical path length L2 of light passing through the CF in the tilted state is Lf0 / cos θ1.

[0028] In the present disclosure, the thickness L2k of the CF in the tilted state is set to Lf0 × cos θ1, so that the optical path length L2 of light passing through the CF in the tilted state is (Lf0 / cos θ1) × cos θ1 = Lf0 (where Lf0 is the thickness at which the NTSC ratio, which is the color reproduction range relative to the standard color gamut, is 70% or more), and the optical path length L2 of light passing through the CF is set to always be the specified thickness Lf0 regardless of the specified angle θ1.

[0029] Therefore, the thickness L2 of the color filter 7C in the tilt direction is always equal to Lf0 (a thickness at which the NTSC ratio, which is the color reproduction range relative to the standard color gamut, is 70% or more) regardless of the specified angle θ1.Therefore, as shown in Figure 19, it can be said that the color filter 7C is configured to have a thickness such that light that follows a path along a direction d2 rotated by a specified angle θ1 around the incident point Pin1 from a direction d1 perpendicular to the incident surface 7b has an NTSC ratio, which is the color reproduction range relative to the standard color gamut, of 70% or more.

[0030] Similarly, by setting the thickness of the liquid crystal layer 7L in the tilted state to Lc0 x cos θ1, the optical path length L1 of light passing through the liquid crystal layer 7L in the tilted state is set to (Lc0 / cos θ1) x cos θ1 = Lc0 (where Lc0 is the thickness at which the NTSC ratio, which is the color reproduction range relative to the standard color gamut, is 70% or more), and the optical path length L1 of light passing through the liquid crystal layer 7L is set to always be the specified thickness Lc0 regardless of the specified angle θ1.

[0031] Therefore, similarly, the liquid crystal layer 7L can be said to be configured to have a birefringence phase difference such that light that follows a path along a direction d2 rotated by a predetermined angle θ1 from a direction d1 perpendicular to the incident surface 7b around the incident point Pin2 has an NTSC ratio, which is the color reproduction range relative to the standard color gamut, of 70% or more.

[0032] When the optical path length L1 in the liquid crystal layer 7L of the liquid crystal display panel 7 and the optical path length L2 in the CF change, 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 predetermined angle θ of the incident surface 7b of the liquid crystal display panel 7 relative to the exit surface 6a of the backlight 6. This is particularly noticeable in a wide color gamut liquid crystal display panel 7 with an NTSC ratio of 60% or more. To correct this, in this embodiment, the CF has a smaller thickness corresponding to the predetermined angle θ relative to the thickness in the parallel state, and the liquid crystal layer 7L has a smaller birefringence phase difference corresponding to the predetermined angle θ relative to the birefringence phase difference in the parallel state. Specifically, the thickness of the CF may be Lf0 × cos θ, where Lf0 is the thickness of the CF in the parallel state and θ is the angle. The birefringence phase difference may be set to R0 × cos θ, where R0 is the birefringence phase difference in the parallel state and θ is the angle. 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 7L in accordance with the spread of the light emitted from the backlight 6.

[0033] The thickness of the color filter 7C may be Lf0 × cos θ or less, or may be 0.8 × Lf0 × cos θ or more and Lf0 × cos θ or less. That is, because the liquid crystal display panel 7 is tilted with respect to the backlight 6, the light of the backlight 6 that is incident on the incident surface 7b of the liquid crystal display panel 7 may be Fresnel reflected at the incident surface 7b and reduced in intensity. Taking this reduction in intensity into consideration, the thickness of the color filter 7C may be reduced to Lf0 × cos θ or less.

[0034] When the refractive index of air is 1.0, the refractive index of the glass substrate that constitutes the liquid crystal display panel 7 is 1.6, and light is incident on the glass substrate from the air side, the reflectance due to Fresnel reflection of S-polarized light vibrating perpendicular to the plane of incidence, the reflectance due to Fresnel reflection of P-polarized light vibrating parallel to the plane of incidence, and their combined reflectance are shown in Table 1. In Table 1, 10° to 70° indicate the angles of incidence.

[0035] From Table 1, it can be seen that if the incident angle is 10° to 70°, the thickness of the color filter 7C may be 0.8×Lf0×cos θ or more and Lf0×cos θ or less. If the incident angle is 10° to 50°, the thickness may be 0.9×Lf0×cos θ or more and Lf0×cos θ or less. Similarly, the birefringence retardation of the liquid crystal layer 7L may be 0.8×R0×cos θ or more and R0×cos θ or less, or 0.9×R0×cos θ or more and R0×cos θ or less.

[0036] The CF is disposed on the display surface 7a side or the incident 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 surface of the CF substrate of the liquid crystal display panel 7 (a substrate facing the array substrate (a substrate on which pixels each including a large number of thin film transistors are arranged in a matrix)) facing the liquid crystal layer 7L. When the CF is disposed on the incident 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 incident surface 7b side of the liquid crystal display panel 7, for example, it may be disposed on the surface of the array substrate of the liquid crystal display panel 7 facing the liquid crystal layer 7L. 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 surface of the CF substrate of the liquid crystal display panel 7 facing the liquid crystal layer 7L.

[0037] FIG. 3 is a diagram showing the color gamut distribution of the LCDs of the example and 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 transmittance, a fluoride red phosphor (K ２ SiF ６ : Mn ４＋ 8 ) (having the spectral characteristics shown by the curve L11 in FIG. 8 ) is combined with the liquid crystal display panel 7 as an example, and a configuration in which a backlight 6 equipped with light-emitting elements of a yellow phosphor (YAG:Ce) (having the spectral characteristics shown by the curve L10 in FIG. 8 ) is combined with the liquid crystal display panel 7 is a comparative example. The transmittance versus NTSC ratio was measured and the results are shown in FIG. 3 .

[0038] Fluoride red phosphor (K ２ SiF ６ : Mn ４＋The backlight 6 equipped with the light-emitting elements 101 (shown in FIG. 10B ) has the spectral characteristics shown by the curve L11 in FIG. 8 . The transmittance was measured as follows: A measurement light source similar to that of the backlight 6 was placed on the side of the array substrate 23b (shown in FIG. 10B ) of the liquid crystal display panel 7, and a spectroluminometer was placed 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 was parallel to the exit surface of the light source. In this state, the light intensity of the light source was kept constant, and the luminance (defined as luminance 1) was measured. Next, without the liquid crystal display panel 7, the light intensity of the light source was kept constant, and the luminance (defined as luminance 2) was measured in the same manner as above. 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 was 388 (nm). The liquid crystal display panel 7 of the example had an NTSC ratio of 70%.

[0039] The backlight 6 having light-emitting elements of a yellow phosphor (YAG:Ce) of the comparative example has the spectral characteristics 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 was 388 (nm). The liquid crystal display panel 7 of the comparative example had an NTSC ratio of 45%.

[0040] In the case of a HUD, sunlight incident on the liquid crystal display panel 7 is reflected by the windshield 12 (shown in FIG. 13 ). To prevent this reflected light from being visible to the user (the driver in FIG. 13 ) 5, it is preferable to set the predetermined angle θ to 10° or greater. Furthermore, if the incident surface 7b of the liquid crystal display panel 7 is tilted relative to the exit surface 6a of the backlight 6 at a predetermined angle θ in the range of 30° to 45°, a virtual image tilted in the direction of travel (e.g., a virtual image having an inverted trapezoidal shape, etc.) is projected. Therefore, the predetermined angle θ at which the reflected sunlight is not perceived by the driver and the virtual image is not projected with excessive tilt may be 10° to 45°. The liquid crystal display panel 7 is set to match the spectral characteristics of the backlight 6, with an NTSC ratio of 70% or greater. The conditions for the liquid crystal display panel 7, i.e., the conditions for the liquid crystal layer 7L and CF, were set so that the NTSC ratio was 70% when the angle θ between the incident surface 7b of the liquid crystal display panel 7 and the exit surface 6a of the backlight 6 was 10° or greater and 45° or less. That is, the liquid crystal layer 7L and CF were set so that the optical path lengths L1 and L2 corresponding to the angle θ were equal to Lc0 and Lf0. The luminance of the image light for the set LCD was measured, and the transmittance of the image light from the LCD was calculated based on the measured luminance. The results shown in Figure 4 were obtained. The luminance was measured at the center of the virtual image. As shown in Figure 4, the transmittance decreased as the NTSC ratio (%) increased, but it was confirmed that the transmittance of the example (KSF-BL + LCD) was higher than that of the comparative example (YAG-BL + LCD).

[0041] 5A and 5B are front views showing the display state of a virtual image displaying a road sign. Fig. 5A shows a display example with the transmittance of the comparative example (YAG-BL-LCD), and Fig. 5B shows a display example with the transmittance of the embodiment (KSF-BL-LD). It can be seen that the display example shown in Fig. 5B is clearer and has higher visibility than the display example shown in Fig. 5A.

[0042] 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 setup of a liquid crystal display panel 7 for a wide color gamut HUD. To confirm the spectral characteristics of each RGB color with respect to changes in angle θ, a measurement light source 9 simulating a backlight 6 was prepared, and the luminance of light emitted from the measurement light source 9 through a CF was measured using a luminance measuring device 10. The measurement results are shown in FIG. 7 . The vertical axis of FIG. 7 represents transmittance, and the horizontal axis represents wavelength. In FIG. 7 , when the angle θ between the incident surface of the CF and 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 represent the spectral transmittance of each RGB color, and the dashed line graphs LR1, LG1, and LB1 represent the spectral transmittance of the backlight 6 for each RGB color. In FIG. 7 , graph LR1 represents the transmittance of red light, graph LG1 represents the transmittance of green light, and graph LB1 represents the transmittance of blue light.

[0043] 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 7L of the liquid crystal display panel 7 also changes depending on the angle θ, so 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.

[0044] For a wide color gamut HUD display, an LCD equipped with a KSF-BL and a liquid crystal display panel 7 is set to an NTSC ratio of 70% to match the spectral characteristics of the backlight 6. The condition is set so that the NTSC ratio is 70% when the angle θ formed between the incident surface 7b of the liquid crystal display panel 7 and the exit surface 6a of the BL is 10° or greater and 45° or less. That is, (1) the conditions (color filter, liquid crystal layer 7L) of the liquid crystal display panel 7 are set so that the NTSC ratio is 70% when the angle θ formed between the incident surface 7b of the liquid crystal display panel 7 and the exit surface 6a of the backlight 6 is 0°. (2) The liquid crystal layer 7L and CF of the liquid crystal display panel 7 are set so that the optical path lengths L1 and L2 corresponding to the angle θ are the same as Lc0 and Lf0 in the parallel state.

[0045] The thickness of the CF and the thickness of the liquid crystal layer 7L of the liquid crystal display panel 7 are adjusted according to the angle θ formed between the incident surface 7b of the liquid crystal display panel 7 and the exit surface 6a of the backlight 6.

[0046] Table 2 below shows an example of the settings of the liquid crystal display panel 7 for a wide color gamut HUD display (70% NTSC ratio). 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 7L (thickness in a direction perpendicular to the layer surface) and the thickness of the CF (thickness in a direction perpendicular to the CF's incident plane) become thinner. The chromaticity values ​​CF(Rx, Ry), CF(Gx, Gy), and CF(Bx, By) obtained by measuring the spectral luminance in a direction perpendicular to the CF's incident plane using the luminance measuring device 10 for angles θ of 0°, 30°, and 45° are shown. The retardation value Δnd in the thickness direction (thickness in a direction perpendicular to the layer surface) of the liquid crystal layer 7L for angles θ of 0°, 30°, and 45° are also shown.

[0047] When the angle θ is 30°, if the thickness of the liquid crystal layer 7L is not corrected, the optical path length L1 is Lc0 / cos30°=1.155×Lc0, so the thickness of the liquid crystal layer 7L is corrected and set to Lc0×cos30°=0.866×Lc0. As a result, Δnd is Δnd0 (retardation in the parallel state)×cos30°=0.866×388=336 (nm). Furthermore, 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. In the case where the angle θ is 45°, the thickness of the liquid crystal layer 7L and the thickness of CF are corrected in the same way.

[0048]

[0049] Using the CF transmission spectrum in Fig. 14, the color matching functions in Fig. 15, and the relative energy spectrum of Illuminant C in Fig. 16, the chromaticity x, y, and thickness of each of the RGB values ​​of the CF shown in Table 3 are calculated using the following definition formula of the XYZ color system. Illuminant C is one of the standard light source specifications defined by the CIE (International Commission on Illumination), and corresponds to standard illuminant C (standard light). Illuminant C has a color temperature of 6774 Kelvin, which is equivalent to daylight that includes a blue sky.

[0050]

[0051] The thickness when θ=30° is (thickness when θ=0°)×cos θ. The same applies when θ=45°.

[0052] The thickness of the liquid crystal layer 23c (7L) 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°, 3.5 μm) × cos 30°, so it is 3.1 μm. Similarly, the thickness of the liquid crystal layer 23c when θ = 45° is 2.5 μm.

[0053] The chromaticity of the CF may be set by selecting the pigment for each color and then adjusting the pigment concentration and the film thickness of the color filter CF. The chromaticity may also be adjusted to satisfy the characteristics shown in Table 4. For angles θ of 0°, 30°, and 45°, the chromaticity values ​​CF(Rx, Ry), CF(Gx, Gy), and CF(Bx, By) of the RGB colors may be set within a range of approximately ±1.7% to ±4.5% of the median value. For angles θ of 0°, 30°, and 45°, the retardation (Δnd) may be set within a range of approximately ±6% of the median value.

[0054]

[0055] 8 is a graph showing the spectral characteristics of the backlight 6. In FIG. 8, the horizontal axis represents wavelength, and the vertical axis represents light intensity (a.u.). When a virtual image is projected against a bright background, such as a snowy road on a clear day, the luminance of the virtual image of the HUD is 10,000 cd / m２ 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 intensity of 1,000,000 cd / m or more. ２ The maximum brightness is 2.3 million cd / m ２ When the conditions for achieving a wide color gamut (70% of NTSC ratio) were confirmed for the backlight 6, 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 type backlight, and curve L11 shows the light intensity at each wavelength of the KSF-LED type backlight. The first peak P1 in curve L11 is the red fluorescent color (K ２ SiF ６ : Mn ４＋ ), and the second peak P2 is due to the green phosphor (βSiAlON).

[0056] 9 is a cross-sectional view of a main portion showing an example of the configuration of a backlight for a HUD. The backlight 16 of this embodiment includes a plurality of light-emitting diodes 17, which are light-emitting elements, a condenser lens 18 that condenses the light emitted from each light-emitting diode 17, and a diffusion film 19 onto 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.

[0057] FIG. 10A is a front view of a wide-color-gamut LCD panel 7 for a HUD. FIG. 10B is a cross-sectional view of the LCD panel 7 taken along the line XB-XB in FIG. 10A. FIG. 10C is an enlarged view of a portion of a color filter (CF). FIG. 11 is a cross-sectional view of the color filter (CF). The color filter (CF) is formed by applying a color resist 20 (shown in FIG. 11) to a glass substrate 21 and then curing it by irradiating it with ultraviolet light to cause a polymerization and cross-linking reaction. A black matrix (BM) and color resist 20 are formed on one side of the glass substrate 21. Unnecessary portions can be dissolved and removed with a developer, forming any desired pattern. The color resist 20 is a blend of pigment, polymer, photosensitive material, and solvent. The pigment may be composed of a mixture of 1 to 10% by weight of a complex such as Ni or Cu, 5 to 15% by weight of an acrylic resin, and a solvent such as cyclohexane or propylene glycol monomethyl ether acetate. In FIG. 11, the color filter is covered with an overcoat layer 22, with the film surface facing downward. The overcoat layer 22 can be made of an acrylic resin having a thickness of 1 to 3 μm, and smoothes the surface of the CF.

[0058] The liquid crystal display panel 7 has a CF substrate 23a and an array substrate 23b, with a liquid crystal layer 23c sandwiched between them. 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 the end exposed to the outside of the array substrate 23b, and a flexible substrate (flexible wiring substrate) 25 is connected to the liquid crystal driver IC 24 for connecting an external device.

[0059] Figure 12 is a graph showing the spectral characteristics of CF. The chromaticity of CF is set by selecting pigments of each color and then adjusting the pigment concentrations and color filter film thicknesses. When the angle θ is 30°, adjustments are made to satisfy the characteristics of graphs LR1, LG1, and LB1 shown in Figure 12. Note that graph LR1 shows the transmittance of red light, graph LG1 shows the transmittance of green light, and graph LB1 shows the transmittance of blue light.

[0060] Next, a setting example of a 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. Furthermore, when the angle θ is 0°, 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 10,000 cd / 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 needs to have a brightness of 1,000,000 cd / m ２ In the prototype, the maximum brightness was 2.3 million cd / m ２ In the backlight 6, a wide color gamut (NTSC ratio of 70%) was confirmed.

[0061] The wide color gamut LCD panel 7 for HUDs is configured by applying color resist 20 to a glass substrate 21, then polymerizing and crosslinking the color resist 20 with ultraviolet light to harden it. Any desired pattern can be formed by dissolving and removing unnecessary portions with a developer. The color resist 20 is a blend of pigment, polymer, photosensitive material, and solvent. Examples of the composition of the color resist 20 in solution include a pigment complex (1-10% by weight) of a metal (such as Ni or Cu), a polymer acrylic resin (5-15% by weight), and a solvent such as cyclohexanone, propylene glycol monomethyl, or ether acetate.

[0062] 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 layer 22 made of acrylic resin with a thickness of 1 to 3 μm is formed to smooth the CF.

[0063] As examples of the CFs used, those having transmittances for each of the RGB colors shown in Table 5 below were used.

[0064]

[0065] 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, part of the configuration of the virtual image display device 1 may be shared with other devices and parts provided in the moving body 100. For example, the windshield 12 of the moving body 100 may be shared as part of the configuration of the virtual image display device 1. For example, the second reflecting member 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 or outside the moving body 100. For example, the virtual image display device 1 may be located inside the dashboard of the moving body 100.

[0066] 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 mobile object 100, the detection device 11 may be located anywhere inside or outside the mobile object 100. For example, the detection device 11 may be located in the dashboard of the mobile object 100. The detection device 11 may output the information related to the eye position of the user 5 to the control unit 4 via, for example, a wired connection, a wireless connection, a CAN (Controller Area Network), or the like.

[0067] The detection device 11 may be configured to include an imaging device. The imaging device may include, for example, a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) 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 the eyebox. The eyebox is an area in real space where the eyes of the user 5 are assumed to be present, taking into account, for example, the physique, posture, and changes in posture of the user 5. The user 5 may include, for example, the driver of the mobile object 100. The detection device 11 may be configured to detect the positions of both eyes of the user 5 in real space based on the captured image generated by the imaging device.

[0068] 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 using the sensor, and to 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 three-dimensional space using two or more sensors.

[0069] The display unit 2 may be configured to include an optical element that allows 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 eyes 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 eyes 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 as a parallax barrier or a lenticular lens. The parallax barrier may be configured to include a liquid crystal panel.

[0070] In this disclosure, "mobile body" includes vehicles, ships, and aircraft. In this disclosure, "vehicle" includes, but is not limited to, automobiles and industrial vehicles, and may also include railroad vehicles, utility vehicles, and fixed-wing aircraft that travel on runways. Automobiles include, but are not limited to, passenger cars, trucks, buses, motorcycles, trolleybuses, and other vehicles that travel 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 are powered by human power. Note that vehicle classifications are not limited to those described above. For example, automobiles may include industrial vehicles that can travel on roads, and the same vehicle may be included in multiple classifications. In this disclosure, the term "watercraft" includes a marine jet, a boat, and a tanker. In this disclosure, the term "aircraft" includes a fixed-wing aircraft and a rotary-wing aircraft.

[0071] According to the virtual image display device and mobile object disclosed herein, 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 view by an optical system. The liquid crystal display panel is disposed with its entrance surface tilted at a predetermined angle relative to the exit surface of the backlight. The color filter has a thickness that is thinner in accordance with the predetermined angle than when 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 in accordance with the predetermined angle compared to the birefringence phase difference in the parallel state. These corrections are due to the fact that, because the liquid crystal display panel is tilted relative to the backlight, the optical path length of the image light passing through the liquid crystal layer and the color filter is longer than when it is parallel. 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 color reproduction range of the three primary colors of the NTSC standard (100%).

[0072] Furthermore, if the liquid crystal display panel is configured to be tilted 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 containing 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 (Korean Fluorescent Phosphor) is a type of line-emitting phosphor that has a wide color gamut and a narrow wavelength spectrum width of the three primary colors RGB (high sharpness of the wavelength spectrum).

[0073] The present disclosure can be implemented with the following configurations (1) to (17).

[0074] (1) A virtual image display device comprising: 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 exiting from the exit surface is incident, a display surface that displays an image by the light that has entered the entrance surface, and a liquid crystal layer located between the entrance surface and the display surface; a color filter disposed on the side of the display surface or the side of the entrance surface of the liquid crystal display panel; and an optical system that directs the image displayed on the display surface into a user's field of view and forms a virtual image, wherein the entrance surface of the liquid crystal display panel is inclined at a predetermined angle with respect to the exit surface of the backlight; the color filter has a thickness that is thinner than a thickness when the entrance surface is parallel to the exit surface, corresponding to the predetermined angle; and the liquid crystal layer has a birefringence phase difference that is smaller than a birefringence phase difference when the liquid crystal layer is parallel, corresponding to the predetermined angle.

[0075] (2) The virtual image display device according to the above configuration (1), wherein the optical system includes a reflecting member.

[0076] (3) The virtual image display device according to the above configuration (2), wherein the reflecting member is a free-form reflecting mirror.

[0077] (4) The virtual image display device according to the above configuration (3), wherein the free-form surface reflecting mirror is a free-form surface concave mirror.

[0078] (5) The virtual image display device described in the above configuration (2), wherein the reflecting members are a first reflecting member located on the side of the liquid crystal display panel and a second reflecting member that reflects the reflected light of the first reflecting member to form the virtual image, the first reflecting member and the second reflecting member are each concave mirrors, and the curvature of the second reflecting member is smaller than the curvature of the first reflecting member.

[0079] (6) The virtual image display device according to any one of the above configurations (1) to (5), wherein the predetermined angle is equal to or greater than 10° and equal to or less than 45°.

[0080] (7) A virtual image display device described in any one of the above configurations (1) to (6), wherein the thickness of the color filter in the parallel state is such that the NTSC ratio, which is the color reproduction range relative to the standard color gamut, is 70% or more.

[0081] (8) The virtual image display device according to the above configuration (7), wherein the thickness of the color filter is Lf0×cosθ or less, where Lf0 is the thickness of the color filter in the parallel state and θ is the predetermined angle.

[0082] (9) The virtual image display device according to the above configuration (8), wherein the thickness of the color filter is equal to or greater than 0.8×Lf0×cos θ and equal to or less than Lf0×cos θ.

[0083] (10) A virtual image display device described in any one of the above configurations (1) to (6), wherein the thickness of the color filter is such that the light that follows a path along a direction rotated by a predetermined angle around the point of incidence from a direction perpendicular to the incident surface has an NTSC ratio, which is the color reproduction range relative to the standard color gamut, of 70% or more.

[0084] (11) A virtual image display device described in any one of the above configurations (1) to (10), wherein the liquid crystal layer has a birefringence phase difference in the parallel state such that the NTSC ratio, which is the color reproduction range relative to the standard color gamut, is 70% or more.

[0085] (12) A virtual image display device described in any one of the above configurations (1) to (9), wherein the birefringence phase difference is set to be equal to or less than R0 × cosθ, where R0 is the birefringence phase difference in the parallel state and θ is the predetermined angle.

[0086] (13) The virtual image display device according to the above configuration (12), wherein the birefringence phase difference is set to be equal to or greater than 0.8×R0×cos θ and equal to or less than R0×cos θ.

[0087] (14) A virtual image display device described in any one of the above configurations (1) to (10), wherein the liquid crystal layer has a birefringence phase difference such that the light that follows a path along a direction rotated by a predetermined angle around the point of incidence from a direction perpendicular to the incident surface has an NTSC ratio, which is the color reproduction range relative to the standard color gamut, of 70% or more.

[0088] (15) A moving body equipped with the virtual image display device according to any one of the above configurations (1) to (14) as a head-up display device.

[0089] (16) The moving body according to the above configuration (15), wherein the optical system includes a reflecting member, and the reflecting member is a windshield.

[0090] (17) The virtual image display device according to the above configuration (16), wherein the optical system includes a concave mirror that faces the liquid crystal display panel at an angle, and the windshield has a concave surface that faces the concave mirror at an angle, and the curvature of the windshield is smaller than the curvature of the concave mirror.

[0091] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described 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 constituting each of the above-described embodiments can be combined as appropriate within the scope of not contradicting each other.

[0092] REFERENCE SIGNS LIST 1 Virtual image display device 2 Display unit 3 Optical system 3a First reflecting member 3b Second reflecting member 4 Control unit 5 User 6 Backlight 6a Exit surface 7 Liquid crystal display panel 7a Display surface 7b Incident surface 7C Color filter 7L Liquid crystal layer 10Q Virtual image 20Q Virtual image 23a CF substrate 23b Array substrate 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 virtual image display device comprising: a backlight including a plurality of light emitting diodes having a fluoride red phosphor and an exit surface from which light from the plurality of light emitting diodes is emitted; 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 directs the image displayed on the display surface into a user's field of vision and forms it as 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.

2. The virtual image display device according to claim 1, wherein the optical system includes a reflecting member.

3. The virtual image display device according to claim 2, wherein the reflecting member is a free-form reflecting mirror.

4. The virtual image display device according to claim 3, wherein the free-form surface reflecting mirror is a free-form surface concave mirror.

5. The virtual image display device of claim 2, wherein the reflective members are a first reflective member located on the side of the liquid crystal display panel, and a second reflective member that reflects the reflected light of the first reflective member to form the virtual image, the first reflective member and the second reflective member are each concave mirrors, and the degree of curvature of the second reflective member is smaller than the degree of curvature of the first reflective member.

6. The virtual image display device according to any one of claims 1 to 5, wherein the predetermined angle is equal to or greater than 10° and equal to or less than 45°.

7. A virtual image display device according to any one of claims 1 to 6, wherein the color filter has a thickness in the parallel state such that the NTSC ratio, which is the color reproduction range relative to the standard color gamut, is 70% or more.

8. The virtual image display device according to claim 7, wherein the thickness of the color filters in the parallel state is Lf0 and the predetermined angle is θ, and the thickness of the color filters is equal to or less than Lf0×cos θ.

9. The virtual image display device according to claim 8, wherein the thickness of the color filter is not less than 0.8×Lf0×cos θ and not more than Lf0×cos θ.

10. A virtual image display device according to any one of claims 1 to 6, wherein the thickness of the color filter is such that the light that follows a path along a direction rotated and moved by the specified angle around the point of incidence from a direction perpendicular to the incident surface has an NTSC ratio, which is a color reproduction range relative to the standard color gamut, of 70% or more.

11. A virtual image display device according to any one of claims 1 to 10, wherein the liquid crystal layer has a birefringence phase difference in the parallel state such that the NTSC ratio, which is the color reproduction range relative to the standard color gamut, is 70% or more.

12. A virtual image display device according to any one of claims 1 to 9, wherein the birefringence phase difference is set to be R0 x cos θ or less, where R0 is the birefringence phase difference in the parallel state, and θ is the specified angle.

13. The virtual image display device according to claim 12, wherein the birefringence phase difference is set to be equal to or greater than 0.8×R0×cos θ and equal to or less than R0×cos θ.

14. A virtual image display device according to any one of claims 1 to 10, wherein the liquid crystal layer has a birefringence phase difference such that the light that follows a path along a direction rotated and moved by the specified angle around the point of incidence from a direction perpendicular to the incident surface has an NTSC ratio, which is a color reproduction range relative to the standard color gamut, of 70% or more.

15. A moving object equipped with a virtual image display device according to any one of claims 1 to 14 as a head-up display device.

16. The vehicle according to claim 15, wherein the optical system includes a reflecting member, and the reflecting member is a windshield.

17. A virtual image display device as described in claim 16, wherein the optical system includes a concave mirror that faces the liquid crystal display panel at an angle, and the windshield has a concave surface that faces the concave mirror at an angle, and the degree of curvature of the windshield is smaller than the degree of curvature of the concave mirror.

Images