JP2011022210A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure the visibility of an image, and to suppress the deterioration of image contrast. <P>SOLUTION: A liquid crystal display panel 25, an inorganic phase difference panel 26, a polarizing plate 27, and mirrors 28 and 29 are disposed on an optical axis AOL in this order. The device magnifies and projects display light from the liquid crystal display panel 25 to front glass 15, and reflects the light toward a driver 14 by means of the front glass 15. The liquid crystal display panel 25 is disposed in a direction rotated around a horizontal axis by an inclination angle α from a direction perpendicular to the optical axis AOL. The inorganic phase difference film formed on the surface of the base material of the inorganic phase difference panel 26 is disposed so that a refractive index ellipsoid with refractive index anisotropy is parallel or at an angle with respect to the base material, thereby compensating for a phase difference of transmitted display light. The inorganic phase difference panel 26 is disposed in a direction rotated around a horizontal axis by an inclination angle β from a direction perpendicular to the optical axis AOL. The inclination angle β is suitably adjusted taking into account the inclination angle α of the liquid crystal display panel 25 and the inclination angle of the liquid crystal molecules of the liquid crystal display panel 25. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a display device that projects image display light onto a reflecting plate such as a glass plate and observes a virtual image through the reflecting plate, and more particularly to a head-up display device using a windshield of an automobile or an aircraft.

  A head-up display (HUD) that allows image display light (hereinafter simply referred to as display light) to be reflected by the windshield toward the driver so that images of instruments such as speedometers can be observed. An apparatus is known (see Patent Documents 1 to 3). In the HUD device, the instrument image is displayed as a virtual image through the windshield. Therefore, the driver can observe the images of the instruments together with the normal forward visual field with almost no change in the line-of-sight direction or diopter.

  The optical unit used in the HUD device is composed of a liquid crystal display panel, a light source, a projection optical system, and the like. A transmissive liquid crystal display panel is used. A backlight provided behind the liquid crystal display panel serves as a light source, and light transmitted through the liquid crystal display panel enters the projection optical system as display light. A concave mirror or the like is used for the projection optical system, and the display light reflected by the concave mirror is further reflected by the windshield and directed to the driver.

  In such a HUD device, external light such as sunlight or headlights of an oncoming vehicle may enter the windshield, travel in the reverse direction of the display light, and be reflected by the liquid crystal display panel. When the liquid crystal display panel is arranged perpendicular to the optical axis, external light reflected by the liquid crystal display panel travels along the display light path and enters the driver's field of view, affecting the image visibility. I'll be stuck.

  Therefore, it is necessary to arrange the liquid crystal display panel so as to be inclined from the direction perpendicular to the optical axis so that the external light reflected by the liquid crystal display panel does not travel the path of the display light. However, when the liquid crystal display panel is tilted, the light from the light source is transmitted obliquely through the liquid crystal display panel, so that the contrast of the image based on the display light is lowered. In this case, it is necessary to suppress a decrease in contrast of the image.

  In the first place, the HUD device is required to be able to visually recognize an image when it is used in a bright condition on a clear day. The contrast of the image is increased, and a black portion (low luminance portion) is made black (low luminance). There is also a need.

  Therefore, in order to suppress a decrease in image contrast, for example, when the driving method of the liquid crystal display panel is a TN (Twisted Nematic) method, it is conceivable to attach a WV (Wide View) film to the liquid crystal display panel (non-patent document). 1).

Japanese Patent Laid-Open No. 03-239639 JP 05-254360 A JP 2002-287076 A

Hiroyuki Mori, 3 others, “Development of FUJIFILM WV film Wideview SA”, [online], FUJIFILM Corporation, Research Report No. 46, 2001 Research Report, [Search June 4, 2009], Internet (URL: http://www.fujifilm.co.jp/rd/report/rd046/pack/pdf/ff_rd046_009.pdf)

  However, when suppressing the contrast reduction of an image with a WV film, since the WV film is stuck on the liquid crystal display panel, optimal adjustment cannot be performed, and variations such as luminance cannot be suppressed. Further, the WV film is weak to heat and ultraviolet rays and easily deteriorates. As described above, there are various problems when a WV film is applied to suppress a reduction in contrast of an image.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a head-up display device (display device) that secures image visibility and suppresses a decrease in image contrast.

  In order to achieve the above object, in the display device of the present invention, light from a light source transmitted through a liquid crystal display panel is reflected toward the observer by a reflector arranged so as to face the observer, An image displayed on the liquid crystal display panel is a display device that is visually recognized by the observer as a virtual image. The display device is arranged so that the tilt can be adjusted, and transmits the light transmitted through the liquid crystal display panel toward the reflector. An optical compensation plate made of an inorganic material that compensates for the phase difference of the light is provided, and the liquid crystal display panel is arranged to be inclined from a direction perpendicular to the optical axis.

  The liquid crystal display panel is preferably a VA type in which liquid crystal molecules are aligned substantially perpendicular to the substrate surface when no voltage is applied. Moreover, it is preferable that it is a head-up display apparatus.

  According to the display device of the present invention, since the liquid crystal display panel is disposed so as to be tilted from the direction perpendicular to the optical axis, external light such as sunlight transmitted through the reflecting plate reverses the path of the display light. Even when the light is reflected by the liquid crystal display panel, the external light reflected by the liquid crystal display panel does not return to the path of the display light. That is, it is possible to prevent the visibility of the image from being affected by the external light reflected by the liquid crystal display panel.

  In addition, since an optical compensator is provided that transmits the light transmitted through the liquid crystal display panel and compensates for the phase difference of the light, the contrast of the image due to the liquid crystal display panel being inclined is reduced. Can be suppressed. Furthermore, since the optical compensation plate is made of an inorganic material, it is less likely to deteriorate than when it is made of an organic material.

  Further, when the liquid crystal display panel is of a VA method in which liquid crystal molecules are aligned substantially perpendicular to the substrate surface when no voltage is applied, compared to the case of using a TN method, High contrast can be achieved. Furthermore, by using a substrate having a high thermal conductivity and high heat dissipation as the substrate of the liquid crystal display panel, the liquid crystal display panel can be prevented from reaching a high temperature. That is, high image quality can be realized without being influenced by the use environment.

It is the schematic of the motor vehicle carrying a head-up display apparatus. It is the schematic which shows the structure of a head-up display apparatus.

  A head-up display device (hereinafter abbreviated as a HUD device) 11 shown in FIG. 1 is built in a dashboard 13 of an automobile 12 and displays instruments such as a speedometer value in front of a driver (observer) 14. To do.

  The HUD device 11 enlarges and projects the display light from the built-in small liquid crystal display panel 25 (see FIG. 2) on the windshield (reflecting plate) 15 and reflects the light toward the driver 14 by the windshield 15. According to the HUD device 11, an image is not formed on the windshield 15 and a real image is displayed, but a virtual image 16 is displayed at a position over the windshield 15 when viewed from the driver 14. The position where the virtual image 16 is displayed is, for example, 2 m or more away from the driver 14, and the driver 14 sees the virtual image 16 without moving the line of sight while driving and without adjusting the focus of the eyes. Can do.

  As shown in FIG. 2, the HUD device 11 includes a display light generation unit 21 that generates display light and a housing 22 to which the display light generation unit 21 is attached. The display light generation unit 21 includes a light source 24, a liquid crystal display panel 25, an inorganic retardation plate 26, and a polarizing plate 27 in a cylindrical unit body 23. These 24 to 27 are arranged on the optical axis (axis of lens) AOL of the illumination light emitted from the light source 24 in the order of signs, and guide the display light from the liquid crystal display panel 25 into the housing 22. A concave mirror 28 and a plane mirror 29 are provided in the housing 22. These mirrors 28 and 29 guide the display light from the liquid crystal display panel 25 to the windshield 15.

  The light source 24 is made of, for example, a white LED, and uniformly irradiates the liquid crystal display panel 25 from behind. The light source 24 is not limited to the white LED that emits the white illumination light, but may emit the illumination light of a desired color. For example, it may be composed of single-color LEDs such as red, green, and blue, and some of these single-color LEDs may be combined to display an image in a desired color. Further, the light source 24 is not limited to an LED, and other known lamps may be used.

  The liquid crystal display panel 25 is a VA (Vertical Alignment) type transmissive liquid crystal display panel, and transmits illumination light irradiated from the back surface to generate display light having image information.

  In a VA liquid crystal display panel, nematic liquid crystal is sealed between vertical alignment films, and liquid crystal molecules are aligned substantially perpendicularly to the substrate when no voltage is applied to the liquid crystal layer. If the liquid crystal molecules are aligned substantially perpendicular to the substrate, light passes through the liquid crystal layer almost without being affected by the liquid crystal molecules, so the black color displayed in this state is crossed so as to sandwich the liquid crystal layer. The characteristics of the polarizing plate provided in the Nicol arrangement are substantially the same, and a very high contrast is realized. As described above, the VA system is advantageous in comparison with the TN system in that high contrast is realized.

  The liquid crystal display panel 25 displays values of various instruments such as a speedometer, a tachometer, a water temperature gauge, and a fuel gauge. The image displayed on the liquid crystal display panel 25 is enlarged and projected as a virtual image in front of the windshield 15.

  The liquid crystal display panel 25 is cantilevered at its lower end by a fixing rubber 30 provided on the unit main body 23, and its inclination is adjusted by an inclination adjustment mechanism 31 provided outside the unit main body 23. Is done.

  The tilt adjusting mechanism 31 includes a guide pole 32 provided in parallel with the optical axis AOL, metal fittings 33 and 34 for fixing both ends of the guide pole 32, a coil spring 35 fitted in the guide pole 32, and a liquid crystal display panel. 25 and an adjustment screw 36 for adjusting the inclination of 25. The tilt adjustment mechanism 31 is formed at the upper end portion of the liquid crystal display panel 25 and acts on an adjustment piece 25 a protruding outside the unit main body 23 through an opening formed in the unit main body 23, so that the liquid crystal display panel 25 Adjust the tilt.

  The guide pole 32 is inserted through a through hole formed in the adjustment piece 25a, and restricts the direction in which the adjustment piece 25a moves to two dimensions. The coil spring 35 is disposed between the adjustment piece 25a and the metal fitting 33, and biases the adjustment piece 25a toward the metal fitting 34 side. The adjustment screw 36 is attached to a screw hole formed in the metal fitting 34 so that the tip end thereof is in contact with the adjustment piece 25a, and advances and retreats by rotation. When the adjustment screw 36 moves forward, the adjustment piece 25a moves in the direction in which the coil spring 35 contracts. On the other hand, when the adjustment screw 36 is retracted, the adjustment piece 25a moves in the direction in which the coil spring 35 extends. That is, the tilt of the liquid crystal display panel 25 is adjusted by the rotation of the adjusting screw 36.

  The liquid crystal display panel 25 is adjusted in inclination by the inclination adjusting mechanism 31 and arranged in a direction rotated by an inclination angle α (for example, 4 to 5 °) from the direction perpendicular to the optical axis AOL to the center of the horizontal axis. Yes. The image displayed on the liquid crystal display panel 25 is a modification of the image to be displayed when the liquid crystal display panel 25 is directly viewed, corresponding to the inclination angle α.

  The inorganic retardation film 26 is formed by forming an inorganic retardation film (not shown) on the surface of a flat substrate (not shown) by vapor deposition or sputtering, and transmitting the liquid crystal display panel 25 obliquely. Transmits light. In the inorganic retardation film, a refractive index ellipsoid (not shown) having refractive index anisotropy is arranged to be inclined with respect to the base material, and compensates for a phase difference of transmitted display light. Thereby, the contrast and viewing angle characteristics of the image displayed in front of the driver 14 are enhanced.

  The inorganic phase difference plate 26 is rotatably provided around the horizontal axis, and is arranged in a direction rotated by an inclination angle β from a direction perpendicular to the optical axis AOL. The tilt angle β is appropriately adjusted in consideration of the tilt angle α of the liquid crystal display panel 25 and the tilt angle of the liquid crystal molecules of the liquid crystal display panel 25.

  The polarizing plate 27 transmits the display light from the liquid crystal display panel 25 and adjusts the amount of display light. The polarizing plate 27 is arranged in a direction rotated by an inclination angle γ from the direction perpendicular to the optical axis AOL to the center of the horizontal axis. The tilt angle γ is substantially the same as the tilt angle α of the liquid crystal display panel 25, and is appropriately adjusted based on the amount of display light. The tilt adjustment of the polarizing plate 27 is realized by providing projections (not shown) at the four corners of the frame that supports the polarizing plate 27, and changing the height of each projection by shaving.

  The concave mirror 28 is disposed with the concave surface serving as a reflection surface directed toward the liquid crystal display panel 25, and reflects display light from the liquid crystal display panel 25 so as to diverge toward the flat mirror 29. The flat mirror 29 reflects the display light reflected by the concave mirror 28 toward the windshield 15. The surface shape of the concave mirror 28 is a non-rotationally symmetric aspherical shape, and the display light is reflected by the concave mirror 28 to correct image distortion.

  The display light reflected so as to diverge by the concave mirror 28 passes through the opening 22 a formed in the housing 22 and the opening 13 a formed in the dashboard 13 and is enlarged and projected onto the windshield 15. The optical axis AOL is folded back toward the plane mirror 29 by the concave mirror 28 and is folded back toward the windshield 15 by the plane mirror 29. Further, the windshield 15 is folded back toward the driver 14.

  Although the display light is enlarged and projected using the concave mirror 28, it is sufficient if the display light can be enlarged and the lens may be used without using the concave mirror.

  In addition, the liquid crystal display panel 25, the inorganic retardation plate 26, and the polarizing plate 27 are arranged in a direction rotated about the horizontal axis from the direction perpendicular to the optical axis AOL, but rotated about the vertical axis. The tilting direction is arbitrary, for example, it is arranged in the direction.

  Further, the case where a so-called O-plate is used as the inorganic phase difference plate 26 has been described as an example. However, as long as the phase difference of transmitted display light can be compensated, the O-plate is not limited. For example, a so-called C-plate in which the refractive index in the in-plane direction of the substrate has a different characteristic from the refractive index in the thickness direction of the substrate may be used.

11 Head-up display device (HUD device)
14 Driver (observer)
15 Windshield (reflector)
16 Virtual Image 21 Display Light Generation Unit 24 Light Source 25 Liquid Crystal Display Panel 26 Inorganic Retardation Plate 31 Tilt Adjustment Mechanism AOL Optical Axis

Claims (3)

The light from the light source that has passed through the liquid crystal display panel is reflected toward the observer by a reflector arranged so as to face the observer, and the image displayed on the liquid crystal display panel is displayed as a virtual image to the observer. In a display device that is visually recognized,
An optical compensator formed of an inorganic material that is arranged so as to be capable of adjusting the tilt and transmits the light transmitted through the liquid crystal display panel toward the reflector and compensates for the phase difference of the light,
The liquid crystal display panel is arranged to be inclined from a direction perpendicular to the optical axis.   The display device according to claim 1, wherein the liquid crystal display panel is of a VA type in which liquid crystal molecules are aligned substantially perpendicular to the substrate surface when no voltage is applied.   The display device according to claim 1, wherein the display device is a head-up display.

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