JP5975928B2 - Vehicle display device - Google Patents

Description

  The present invention relates to a vehicle display device including a liquid crystal panel.

  In recent years, for example, a vehicle display device has been put into practical use in which a small liquid crystal display unit is provided in a vehicle meter and vehicle information such as fuel consumption information, mileage information, and warning information is centrally displayed on the liquid crystal display unit. .

  In such a vehicle display device, the light emitted from the liquid crystal display unit is reflected by the windshield of the vehicle and enters the driver's field of view, so the information displayed on the liquid crystal display unit is reflected on the windshield. Observed at (window reflection). In particular, when the ambient brightness is low, such as at night, the difference between the brightness of the background through the windshield and the brightness of the information displayed in the window increases, so that the window reflection is observed more prominently. And a driver | operator feels bothersome by getting attention to this window projection.

  In order to prevent such windowing, for example, a louver is provided between the liquid crystal panel constituting the liquid crystal display device and the backlight to limit the emission direction of the light beam emitted from the liquid crystal display device. Cutting light rays directed in the direction of is performed (for example, Patent Document 1).

JP 2005-275262 A

  However, according to the vehicle display device described in Patent Document 1, since it is necessary to provide a louver between the liquid crystal panel constituting the liquid crystal display device and the backlight, the thickness of the display device increases, thereby the weight of the component. An increase occurs. Moreover, since the number of parts is increased by providing a louver, there is a problem that the cost is increased.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vehicle display device in which window reflection is reduced without increasing the number of parts.

  The vehicle display device according to the present invention reduces windowing of information displayed on the liquid crystal display device.

That is, the display device for a vehicle according to the present invention has a liquid crystal layer sandwiched between two transparent electrodes facing each other, and applies a predetermined DC voltage between the two transparent electrodes. When the liquid crystal layer is illuminated from the back side, the light transmittance when the liquid crystal layer is viewed from a predetermined angle direction on the front side with respect to the normal direction of the liquid crystal layer is asymmetric with respect to the normal direction A liquid crystal panel having a characteristic that changes to: a backlight that illuminates the liquid crystal panel from the back side; an image display unit that is arranged in contact with the front side of the liquid crystal panel and outputs image information having color information; The liquid crystal panel is applied with the predetermined DC voltage between the two transparent electrodes, and the side where the light transmittance is reduced with respect to the normal direction is set to the windshield of the vehicle. placed on the side, said image information, said liquid crystal panel And outputting in viewable brightness intermediate brightness in the.

According to the vehicle display device configured as described above, when a DC voltage is applied between the two transparent electrodes facing each other, the liquid crystal layer sandwiched between the two transparent electrodes. The liquid crystal molecules contained in the direction change in the direction corresponding to the magnitude of the applied DC voltage. At this time, when the liquid crystal layer is illuminated from the back side, the transmittance of light traveling through the liquid crystal layer changes according to the direction in which the liquid crystal molecules face. In particular, when a predetermined DC voltage is applied between two transparent electrodes, the transmittance of light traveling in a predetermined angular direction is reduced, so that the transmittance of light is asymmetric with respect to the normal direction of the liquid crystal layer. Change. Therefore, when a predetermined DC voltage is applied between the two transparent electrodes of the liquid crystal panel, the side where the light transmittance is reduced with respect to the normal direction of the liquid crystal panel is installed on the windshield side of the vehicle. Thus, it is possible to reduce the window reflection that occurs when image information having color information that is output to the image display unit disposed so as to be in contact with the front surface side of the liquid crystal panel is reflected on the windshield. Since the image information is output at an intermediate brightness that can be displayed on the liquid crystal panel, the background of the background through the windshield is higher than when the image information is output at a higher brightness. The difference between the brightness and the brightness of the reflection of image information on the windshield can be further reduced, and the window reflection can be reduced to a level at which it does not bother.

The vehicle display device according to claim 2 outputs the image information at an intermediate brightness of brightness that the liquid crystal panel can display at night, and the liquid crystal panel at daytime. Is output at the maximum brightness that can be displayed.

  According to the vehicular display device configured as described above, in the daytime, the image information is output with the maximum brightness, so that the visibility of the display can be increased and the background through the windshield can be increased. Since the difference between the brightness and the brightness of the reflection of the image information on the windshield is reduced, the window reflection can be reduced to a level that does not matter. On the other hand, at night, image information is output at an intermediate brightness, so that the visibility of the display is not reduced, and the brightness of the background through the windshield and the brightness of the image information reflected on the windshield Since the difference between the two can be reduced, the window reflection can be reduced to a level that does not matter.

According to a third aspect of the present invention, the vehicle display device generates the intermediate brightness by adjusting the predetermined DC voltage or adjusting the luminance of the backlight.

  According to the vehicle display device configured as described above, the intermediate brightness of the image information is generated by adjusting the DC voltage applied between the two transparent electrodes or adjusting the luminance of the backlight. Therefore, it is possible to easily generate an intermediate brightness in which window reflection is reduced without using a special component.

According to a fourth aspect of the present invention, the liquid crystal layer includes a twisted matic liquid crystal.

  According to the vehicle display device configured as described above, when a predetermined DC voltage is applied between the two transparent electrodes of the twisted matic liquid crystal, the liquid crystal molecules contained in the liquid crystal layer are applied with the applied DC. Due to the characteristic of directing in the direction corresponding to the magnitude of the voltage, a gradation inversion region in which the transmittance of the liquid crystal panel is reduced can be formed in the direction corresponding to the magnitude of the DC voltage. By installing the liquid crystal panel so that the gradation inversion region faces the windshield, it is possible to reduce windowing.

  According to the vehicle display device of the present invention, there is an effect that it is possible to provide a vehicle display device in which window reflection is reduced without increasing the number of parts.

It is a figure which shows an example of the display apparatus for vehicles. (A) is a figure which shows the structure of the display apparatus for vehicles which concerns on this invention. (B) is a figure which shows the structure of the liquid crystal panel used for the display apparatus for vehicles which concerns on this invention. It is a figure explaining the effect | action of the display apparatus for vehicles which concerns on this invention, (a) is the state of a liquid crystal molecule, incident light, and outgoing light when a DC voltage is not applied between two transparent electrodes of a liquid crystal panel. It is a figure explaining the state of polarized light. (B) is a figure explaining the state of a liquid crystal molecule | numerator when the intermediate voltage is applied between two transparent electrodes of a liquid crystal panel, and the polarization state of incident light and an emitted light. (C) is a figure explaining the state of a liquid crystal molecule | numerator when the maximum voltage is applied between the two transparent electrodes of a liquid crystal panel, and the polarization state of incident light and an emitted light. It is a figure explaining the effect | action of the display apparatus for vehicles which concerns on this invention, (a) is a mode that the transmittance | permeability of the light of a predetermined direction reduces, when an intermediate voltage is applied between the two transparent electrodes of a liquid crystal panel. FIG. FIG. 4B shows the transmittance of light in a direction different from that in FIG. 4A when an intermediate voltage is applied between the two transparent electrodes in a state where the liquid crystal panel of FIG. It is a figure explaining a mode that is reduced. It is a graph which shows the change of the brightness (luminance) of the image with respect to an observation direction when displaying on the display apparatus for vehicles concerning the present invention. (A) is a figure which shows an example of the specific installation layout of the display apparatus for vehicles which concerns on this invention. (B) is a figure which shows an example of the image information displayed on the display apparatus for vehicles of Fig.6 (a). (A) is a figure which shows the mode of the window projection reflected on a windshield, when the image information of FIG.6 (b) is displayed on a liquid crystal panel. (B) is a figure which shows the mode of the window projection reflected on a windshield, when the image information of FIG.6 (b) is reversed upside down and displayed on the liquid crystal panel reversed upside down. (C) is a figure which shows the mode of the window projection reflected on a windshield, when the image information comprised by the halftone gray is displayed on the liquid crystal panel of FIG.7 (b). (D) is a graph which shows the result of having measured the brightness of the window projection reflected in the windshield in each of Drawing 7 (a) and (b).

  Embodiments of a display device for a vehicle according to the present invention will be described below with reference to the drawings.

  Embodiments of the present invention will be described below with reference to FIGS. The image display device of the present invention is configured by a liquid crystal panel and is installed in a vehicle meter cluster, and displays necessary vehicle information. FIG. 1 shows an example of an instrument panel 3 having such an image display device.

  In FIG. 1, a liquid crystal panel 10 constituting an image display device is disposed together with a speedometer 1 and an engine tachometer 2 in an instrument panel 3 installed in a vehicle (not shown). Vehicle information such as fuel consumption information, travel distance information, and warning information is displayed as necessary.

  Embodiment 1 of the present invention will be described below with reference to FIGS. 2 (a) and 2 (b).

[Description of configuration of vehicle display device]
The vehicular display device 20 according to the present invention includes the components shown in FIGS. 2 (a) and 2 (b). Among these, FIG. 2A is a diagram showing a state in which the vehicle display device 20 is mounted on a vehicle (not shown). That is, the vehicle display device 20 generates the image information necessary for driving, the liquid crystal panel 10 and the image information to be displayed on the liquid crystal panel 10, and controls the operation of the liquid crystal panel 10 and the backlight 10g (FIG. 2 (b)) and a display control unit 50 for controlling brightness and brightness. And the liquid crystal panel 10 is arrange | positioned so that the driver | operator 100 can see the image information displayed on the surface 10s side of the liquid crystal panel 10 inside the meter cluster, for example.

That is, as shown in FIG. 2A, the light emitted from the point P _{1 on} the surface 10 s of the liquid crystal panel 10 travels along the optical path A ₃ and is disposed so as to be visually recognized by the driver 100.

On the other hand, of the light emitted from the point P _{1 on} the surface 10 s of the liquid crystal panel 10, the light traveling along the optical path A ₁ reaches the point P ₂ of the windshield 5. Then, the light is regularly reflected at the point P ₂ , travels along the optical path A ₂ , and is visually recognized by the driver 100. In this way, the image that travels along the optical path A ₁ and the optical path A ₂ and is visually recognized by the driver 100 is an image generated by window projection.

[Description of LCD panel configuration]
Next, the internal structure of the liquid crystal panel 10 will be described with reference to FIG.

  The liquid crystal panel 10 has a layered structure as shown in FIG. That is, the alignment films 10e and 10e having fine grooves are bonded to each other on the front surface side and the back surface side of the liquid crystal layer 10f including the liquid crystal molecules 10m with an angular difference of 90 ° from each other. The liquid crystal molecules 10m are regularly aligned along the grooves of the alignment films 10e and 10e, and the direction of the liquid crystal molecules 10m is twisted and arranged between the two alignment films 10e and 10e. That is, the direction of the liquid crystal molecules 10m is twisted by 90 ° between the two alignment films 10e and 10e. The alignment film 10e is generally made of a polymer material called a polyimide film, and the alignment direction is formed by a so-called rubbing process in which the surface of the alignment film 10e is rubbed in a certain direction.

  The liquid crystal layer 10f includes liquid crystal molecules 10m. In this embodiment, twisted nematic (TN) mode TFT liquid crystal molecules (twisted matic liquid crystal) are used as the liquid crystal molecules 10m. The function of the twisted matic liquid crystal will be described later.

Transparent electrodes 10d and 10d are provided outside the alignment films 10e and 10e, respectively. The transparent electrode 10d is an electrode that applies a DC voltage necessary to apply an electric field to the inside of the liquid crystal layer 10f. The transparent electrode 10d needs to have high transparency so as not to disturb the display of the liquid crystal panel 10. Therefore, for example, indium tin oxide ITO (Indium Tin Oxide) produced from indium oxide IN ₂ O ₃ and tin oxide SnO _{2 is} produced by adhering to glass by sputtering.

  A color filter 10c (image display unit) is installed on the transparent electrode 10d on the surface side of the liquid crystal panel 10. The color filter 10c (image display unit) is generally composed of three primary color filters of red (R), green (G), and blue (B), and these three primary color filters are regularly arranged. And the image information produced | generated by the display control part 50 is output to the color filter 10c (image display part), and it is the structure displayed on the display apparatus 20 for vehicles.

  Glass substrates 10b and 10b are installed on the front surface of the color filter 10c (image display unit) and the back surface of the transparent electrode 10d on the back surface 10t side of the liquid crystal panel 10, respectively. The glass substrate 10b is provided in order to prevent the transparent electrodes 10d and 10d from coming into contact with other parts and leaking electricity. As a material for the glass substrate 10b, alkali-free glass is generally used.

  Polarizing filters 10a and 10a are installed outside the glass substrates 10b and 10b. Note that the polarization axes of the two polarizing filters 10a and 10a are set so as to be shifted from each other by 90 °. The direction of the alignment film 10e on the back surface 10t side of the liquid crystal panel 10 and the direction of the polarization axis of the polarizing filter 10a on the back surface 10t side of the liquid crystal panel 10 are the same, and the alignment film on the front surface 10s side of the liquid crystal panel 10 It is assumed that the direction 10e coincides with the direction of the polarization axis of the polarizing filter 10a on the surface 10s side of the liquid crystal panel 10.

  Further, a backlight 10g is installed under the polarizing filter 10a on the back surface 10t side of the liquid crystal panel 10. The backlight 10g is composed of, for example, a cold cathode tube, a white light emitting diode (LED), or a light emitting diode of three colors (RGB).

  At this time, when light emitted from the backlight 10g is incident on the back surface of the liquid crystal panel 10 without applying a DC voltage between the transparent electrodes 10d and 10d, the light passes through the polarizing filter 10a on the back surface 10t side of the liquid crystal panel 10. The polarization direction of the light is twisted by 90 ° while passing through the liquid crystal layer 10f including the liquid crystal molecules 10m of the twisted liquid crystal, and is emitted from the polarization filter 10a on the surface 10s side of the liquid crystal panel 10.

  In the liquid crystal panel 10 configured as described above, when the backlight 10g is turned on, the light emitted from the backlight 10g toward the surface 10s side of the liquid crystal panel 10 is polarized filter 10a, the glass substrate 10b, the transparent electrode 10d, and the alignment. The film 10e, the liquid crystal layer 10f, the alignment film 10e, the transparent electrode 10d, the color filter 10c, the glass substrate 10b, and the polarizing filter 10a are sequentially passed through and emitted from the surface 10s side of the liquid crystal panel 10 to the outside.

Light emitted from the surface 10s side of the liquid crystal panel 10, as described above, proceeds along the optical path A _3, the driver 100, the image visible information output on the color filter 10c (image display portion).

[Description of the behavior of light propagating inside the liquid crystal panel]
Next, the behavior of light propagating through the liquid crystal panel 10 will be described with reference to FIGS.

  FIGS. 3A, 3B, and 3C are diagrams for explaining the state of the liquid crystal molecules 10m when a DC voltage V is applied between the two transparent electrodes 10d and 10d. As described above, the liquid crystal molecules 10m adjacent to the two transparent electrodes 10d and 10d are aligned 90 ° apart from each other on the front surface 10s side and the back surface 10t side in the direction along the grooves of the alignment films 10e and 10e. . In FIG. 3, the drawings are drawn so as to be aligned along the same direction for easy understanding.

  When the DC voltage V is not applied between the two transparent electrodes 10d and 10d, the liquid crystal molecules 10m are aligned in a direction parallel to the two transparent electrodes 10d and 10d, as shown in FIG. .

At this time, since the liquid crystal molecules 10m are twisted by 90 ° between the two transparent electrodes 10d and 10d, the liquid crystal molecules 10m are emitted from the backlight 10g (not shown) and are polarized on the back surface 10t side of the liquid crystal panel 10 on the polarizing filter 10a. Illuminating light _BL incident on the liquid crystal panel 10 through the light travels while changing its polarization direction along the alignment of the liquid crystal molecules 10m. Then, the polarization direction is shifted by 90 ° and passes through the transparent electrode 10 d on the surface 10 s side of the liquid crystal panel 10.

Therefore, since the polarization direction of the light that has passed through the transparent electrode 10d on the surface 10s side of the liquid crystal panel 10 matches the direction of the polarization axis of the polarization filter 10a installed on the surface 10s side of the liquid crystal panel 10, the liquid crystal panel 10 The passed light passes through the polarizing filter 10 a installed on the surface 10 s side of the liquid crystal panel 10. Accordingly, the polarization direction P _L11 of the light that travels along the optical path L ₁ in the illumination light B _L is shifted by 90 ° when the light is emitted from the polarization filter 10a on the surface 10s side of the liquid crystal panel 10, and becomes the polarization direction P _L12. .

Similarly, the polarization direction _{P L21} of the light traveling along the optical path _{L 2} is, when it is emitted from the polarization filter 10a of the surface 10s side of the liquid crystal panel 10 displaced 90 °, along next to the polarization direction _{P L22,} the optical path _{L 3} The polarization direction P _L31 of the traveling light is shifted by 90 ° to become the polarization direction P _L32 when emitted from the polarization filter 10a on the surface 10s side of the liquid crystal panel 10.

When this time observing the liquid crystal panel 10 from the surface 10s side of the liquid crystal panel 10, the brightest image is observed when observed from the normal direction of the liquid crystal panel 10 (the direction along the optical path L _1). This is a state where the liquid crystal panel 10 is displayed brightly. When the observation direction is changed from there, the amount of light emitted toward the observation direction gradually decreases (darkens) in a symmetrical manner in accordance with the observation direction.

  Next, as shown in FIG. 3B, when an intermediate voltage Vmid is applied as the DC voltage V between the two transparent electrodes 10d and 10d, the liquid crystal molecules 10m are placed between the two transparent electrodes 10d and 10d. Thus, it rises in the direction of the electric field generated between the two transparent electrodes 10d, 10d by an amount corresponding to the intermediate voltage Vmid. Then, the higher the intermediate voltage Vmid is, the direction of the liquid crystal molecules 10m is changed in the direction according to the applied intermediate voltage Vmid so that the liquid crystal molecules 10m are directed in the direction orthogonal to the two transparent electrodes 10d and 10d.

At this time, the illumination light _BL emitted from the backlight 10g (not shown), passing through the polarizing filter 10a on the back surface 10t side of the liquid crystal panel 10 and incident on the liquid crystal panel 10 is, for each optical path, the liquid crystal molecules 10m. Takes behavior according to the array state.

First, attention is focused on the light traveling along the optical path L _1. When light traveling along the optical path L ₁ is emitted from the surface 10s side of the liquid crystal panel 10, when observing the liquid crystal panel 10 from opposite directions to the emission direction, the long axis direction of the ellipsoid of the liquid crystal molecules 10m is because it has an overturning direction component with respect to the optical path L _1, are arranged in a state of twisted remained between the liquid crystal molecules 10 m. Therefore, when the light traveling along the optical path L ₁ has the polarization direction P _L11 , the light changes the polarization direction by 90 ° according to the twist of the liquid crystal molecules 10 m, and as light having the polarization direction P _L12 , The light passes through the transparent electrode 10d on the surface 10s side of the liquid crystal panel 10 and the polarizing filter 10a and is emitted to the outside.

At this time, the long axis direction of the ellipsoid of the liquid crystal molecules 10m, the direction component along the optical path L ₁ also has at the same time. When having a component in the direction of the liquid crystal molecules 10m is along the optical path L _1, since the twist between the liquid crystal molecules 10m does not occur, has the property of directly passed through the light incident on the liquid crystal panel 10.

Therefore, the light having the polarization direction _PL11 incident on the liquid crystal panel 10 enters the polarization filter 10a on the surface 10s side of the liquid crystal panel 10 without changing the polarization direction. Then, since the polarization axis of the polarizing filter 10a on the surface 10s side of the liquid crystal panel 10 is shifted by 90 ° from the polarization direction _PL11 , the light that has passed through the liquid crystal panel 10 passes through the polarizing filter 10a on the surface 10s side of the liquid crystal panel 10. It will be blocked.

That is, since only twist light the polarization direction is changed 90 ° in accordance with the liquid crystal molecules 10m is passed through the liquid crystal panel 10, the amount of light passing through the liquid crystal panel 10, along the optical path L ₁ of FIGS. 3 (a) Decreases compared to the amount of light traveling through. The amount of light reduction depends on the direction of the liquid crystal molecules 10m, that is, the magnitude of the DC voltage V applied between the two transparent electrodes 10d and 10d. When the DC voltage V is large, that is, the liquid crystal molecules 10m It gets bigger as you stand up.

Similarly, the light having the polarization direction P _L31 that travels along the optical path L ₃ is the same as the light having the polarization direction P _L32 , but only the light having the polarization direction changed by 90 ° according to the twist of the liquid crystal molecules 10 m. The light passes through the polarizing filter 10a on the surface 10s side of the light and exits to the outside.

Next, attention is focused on the light traveling along the optical path L _2. State light traveling along the optical path L ₂ is when emitted from the surface 10s side of the liquid crystal panel 10, when observing the liquid crystal panel 10 from opposite direction to the emission direction, the liquid crystal molecules 10m is stood up along the optical path L ₂ Are arranged in At this time, since the liquid crystal molecules 10m are not twisted, the light incident on the liquid crystal panel 10 passes through without changing the polarization direction. Therefore, light having a polarization direction P _L21 proceeds inside the liquid crystal panel 10 along the optical path L ₂ while maintaining its polarization direction. Since the polarization axis of the polarizing filter 10a on the surface 10s side of the liquid crystal panel 10 is shifted by 90 ° from the polarization direction _PL21 , the light that has passed through the liquid crystal panel 10 passes through the polarizing filter 10a on the surface 10s side of the liquid crystal panel 10. Blocked. Therefore, light is not emitted in the opposite direction to the optical path L _2, when observing the liquid crystal panel 10 is dark image is observed.

  As described above, when a state in which the intermediate voltage Vmid is applied as the DC voltage V between the two transparent electrodes 10 d and 10 d is created, the brightness of the light that has passed through the liquid crystal panel 10 is in the normal direction of the liquid crystal panel 10. Change asymmetrically.

  Further, as shown in FIG. 3C, when the maximum voltage Vmax is applied as the DC voltage V between the two transparent electrodes 10d and 10d, the liquid crystal molecules 10m are placed between the two transparent electrodes 10d and 10d. The two transparent electrodes 10d and 10d are aligned in a direction perpendicular to the transparent electrodes 10d and 10d.

At this time, since the liquid crystal molecules 10m are aligned along the direction of the electric field, the liquid crystal molecules 10m are not twisted, and the light incident on the liquid crystal panel 10 along the optical paths L1, L2, and L3 maintains the polarization direction. As it is, the liquid crystal panel 10 is passed through. Since the polarization axis of the polarizing filter 10a on the surface 10s side of the liquid crystal panel 10 is shifted by 90 ° from the polarization directions P _L11 , P _L21 , and P _L31 , the light that has passed through the liquid crystal panel 10 is the surface 10s of the liquid crystal panel 10. It is blocked by the polarizing filter 10a on the side.

Therefore, no light is emitted in the direction opposite to the optical paths L ₁ , L ₂ , L ₃ , and a dark image is observed when the liquid crystal panel 10 is observed. This is a state where the liquid crystal panel 10 is displayed darkly. And even if the observation direction is changed from there, the amount of light emitted toward the observation direction is hardly changed, so a dark image is observed regardless of the observation direction.

FIG. 4A shows a state in which the liquid crystal panel 10 is observed from various directions on the surface 10s side when the liquid crystal panel 10 is in the state of FIG. 3B. At this time, when the position of the eye of the observer is in the eye position E ₁ is the direction from the surface 10s of the liquid crystal panel 10 to the eye position E _1, i.e. in a direction along the optical path L ₁ and the optical path L _3, the liquid crystal panel 10 Since more illumination light _BL incident from the rear surface 10t side is emitted, image information output to the color filter 10c (not shown) is brightly observed by being illuminated with this light. The position of the eye position E ₁ is, if the inside region R ₂ of FIG. 4 (a), similarly bright image is observed.

Meanwhile, when the position of the eye of the observer is at the position of the eye position E _2, the direction from the surface 10s of the liquid crystal panel 10 to the eye position E _2, i.e. in a direction along the optical path L _2, the back surface 10t of the liquid crystal panel 10 Since the illumination light _BL incident from the side hardly emits, the image information output to the color filter 10c (not shown) is observed darkly. The position of the eye position E ₂ is, if the interior of the region R ₁ of FIG. 4 (a), similarly dark image is observed.

Next, the left and right sides of the liquid crystal panel 10 are reversed and arranged in the same manner as in FIG. That is, the left end a and the right end b of the transparent electrode 10d on the surface 10s side of the liquid crystal panel 10 shown in FIG. 4A are reversed, and the left end of the transparent electrode 10d on the back surface 10t side of the liquid crystal panel 10 is reversed. Invert c and right end d. Then, as shown in FIG. 4 (b), since the alignment direction of liquid crystal molecules 10m is left Conversely, when the eye position E ₂ is inside the region R _3, are outputted to the color filter 10c (not shown) image information is observed brightly, eye position E ₁ is when it is inside the region R _4, image information outputted to the color filter 10c (not shown) is darkened observed.

  That is, when the intermediate voltage Vmid is applied as the DC voltage V between the two transparent electrodes 10d and 10d, the direction in which the image is observed dark differs depending on the direction in which the liquid crystal panel 10 is installed.

  FIG. 5 is a graph showing changes in brightness (luminance) of an image according to the observation direction θ of the liquid crystal panel 10 when the liquid crystal panel 10 is in the state of FIGS. 3 (a), (b), and (c). It is.

That is, in the state of FIG. 3A, the image brightness I ₁ is observed brightly as shown in FIG. The brightness I ₁ is brightest in the normal direction (θ = 0) of the liquid crystal panel 10 according to the observation direction θ, and gradually attenuates symmetrically from there.

In the state shown in FIG. 3C, the image brightness I ₃ is observed dark without depending on the observation direction θ as shown in FIG.

Thus, when in the state of FIG. 3 (b), the brightness I _P of the image, as shown by a dotted line in FIG. 5, and shall become intermediate brightness of the brightness I ₁ and brightness I ₃ Guessed.

However, actually, the image brightness I ₂ observed at this time has brightness corresponding to the DC voltage V applied between the two transparent electrodes 10d and 10d, as shown in FIG. The liquid crystal panel 10 exhibits left-right asymmetric characteristics with respect to the normal direction (θ = 0 ° direction). That is, in the example shown in FIG. 5, when the observation direction θ is about 30 °, the image brightness I ₂ becomes the highest brightness I ₀ , and when the observation direction θ is about −30 °, the image brightness I ₂ is It becomes the darkest.

At this time, comparing the image brightness I ₂ with the image brightness I _P expected when observed from the same direction, a region where I ₂ <I _P is referred to as a gradation inversion region R _0. To. That is, when the liquid crystal panel 10 is observed from the direction corresponding to the gradation inversion region _R0 , a darker image than the image that is expected to be observed is observed. In this embodiment, this gradation inversion region _R0 is used to reduce the windowing of image information.

The gradation inversion region R ₀ appears not only for image information expressed in gray scale (monochrome information) displayed on the color filter 10c (not shown in FIG. 3) but also in image information having a color. . That is, when image information having an amber color, for example, is displayed on the color filter 10c and an intermediate voltage Vmid is applied between the two transparent electrodes 10d, 10d, even in the same amber, in the gradation inversion region _R0 , Observed as the brightness becomes dark.

Furthermore, two transparent electrodes 10d, by changing the value of the intermediate voltage Vmid applied between the 10d, it is possible to adjust the value of brightness I Brightness I ₀ is the maximum value of _P. That is, when the value of the intermediate voltage Vmid is lowered, the brightness I ₀ becomes brighter, and when the value of the intermediate voltage Vmid is increased, the brightness I ₀ becomes darker. Therefore, for example, an appropriate value of the intermediate voltage Vmid can be set while confirming the degree of window projection and the visibility of display.

[Explanation of working example]
Next, the effect | action of the present Example 1 is demonstrated using FIG. 6, FIG.

FIG. 6A is a typical layout diagram when the vehicle display device 20 is mounted on a vehicle. That is, the liquid crystal panel 10, a vehicle windshield 5 and a predetermined positional relationship (not shown), from the eye range E _R of the driver, so that the image information displayed on the liquid crystal panel 10 can be visually recognized Has been placed. At this time, it is assumed that a voltage of V = Vmid is applied between the two transparent electrodes 10d and 10d of the liquid crystal panel 10.

  The angle condition between the liquid crystal panel 10 and the windshield 5 described in FIG. 6A shows an example of the installation condition of the vehicle display device 20, and is not limited to this value. . That is, the layout is designed for each vehicle on which the vehicle display device 20 is mounted.

Here, the liquid crystal panel 10, as an example, a gray scale ranging from white to black shown in FIG. 6 (b), assumed to be displayed as image information D _1.

FIG. 7A shows the window projection D _1r reflected on the windshield 5 when the image information D ₁ shown in FIG. 6B is displayed on the liquid crystal panel 10 installed as shown in FIG. It is a figure showing a mode. In the example shown in FIG. 7A, it is assumed that the gradation inversion region R ₀ faces the opposite side of the windshield 5. At this time, as shown in FIG. 7A, a noticeable window reflection D _1r occurs in the windshield 5.

7B, the liquid crystal panel 10 shown in FIG. 6A is inverted only up and down without changing the direction of the surface 10s, and the liquid crystal panel 10 shown in FIG. FIG. 7 is a diagram illustrating a state of window reflection D _2r reflected on the windshield 5 when the image information D ₁ shown in FIG. 6B is displayed as the liquid crystal panel 10 ′. In this case, 'because you are, the liquid crystal panel 10' LCD panel 10 of the liquid crystal panel 10 upside down, the image information D ₂ was vertically inverted image information D ₁ are displayed. At this time, the gradation inversion region _R0 faces the windshield 5 side.

When in the state of FIG. 7B, the window reflection _D2r reflected on the windshield 5 is significantly less than the window reflection _D1r observed in the state of FIG.

In FIG. 7A, the amount of light emitted from the liquid crystal panel 10 in the direction toward the windshield 5 is large, and thus the window reflection D _1r is noticeably observed, whereas FIG. Then, since the gradation inversion region R ₀ is installed so as to face the windshield 5 side, the amount of light emitted in the direction toward the windshield 5 is reduced.

  In FIGS. 7 (a) and 7 (b), the brightness of the observed window projection is measured as shown in FIG. 7 (d).

It can be seen that the brightness I ₅ of the window projection in FIG. 7A is very bright over the entire gray scale of the image information D ₁ .

On the other hand, it can be seen that the brightness of the window projection I ₄ in FIG. 7B is very dark over the entire gray scale of the image information D ₂ .

Here, as shown in FIG. 7C, the image information displayed on the liquid crystal panel 10 ′ is uniform in the brightness range that can be displayed by the liquid crystal panel 10 ′, which corresponds to an intermediate brightness. (For example, luminance equivalent to gray 4 shown in FIG. 6B). The image information thus generated to D _3. When the window projection D _3r when the image information D ₃ is displayed on the liquid crystal panel 10 ′ is observed, the window projection D _3r is reduced to a level that is hardly visible as shown in FIG. 7C. Thus, by generating the image information D ₃ in the middle of the luminance, while maintaining the visibility of the image information, it is possible to reduce the window being viewed as.

  Note that the luminance corresponding to the intermediate brightness within the range of brightness that can be displayed by the liquid crystal panel 10 ′ is, as described above, the direct current voltage V applied between the two transparent electrodes 10d and 10d. Can be generated by changing the size of. That is, by increasing the DC voltage V within a range not exceeding the maximum voltage Vmax, it is possible to output darker image information as intermediate brightness. Conversely, by reducing the DC voltage V, brighter image information can be output as intermediate brightness.

  Further, the image information having the intermediate brightness can be generated by adjusting the luminance of the backlight 10g. That is, by storing a predetermined value (color) in the color filter 10c (image display unit) and setting the luminance of the backlight 10g lower than the maximum luminance, the color filter 10c (image) is irradiated with the backlight 10g. The brightness of the light transmitted through the display unit can be set to an intermediate brightness.

Here, in the daytime bright environment, than displaying the image information D ₃ generated in the intermediate luminance, there is a possibility that the visibility of the bottom line image information is degraded. Furthermore, since the background brightness through the windshield 5 is high during the daytime, the window projection is less worrisome than at night. Therefore, in the daytime, image information may be generated and displayed on the liquid crystal panel 10 ′ with the maximum luminance within the brightness range that the liquid crystal panel 10 ′ can display. Then, only at night, the image information is generated and displayed on the liquid crystal panel 10 ′ at a luminance equivalent to the middle of the brightness range that can be displayed by the liquid crystal panel 10 ′, thereby displaying the image regardless of day or night. The visibility of information can be ensured, and the occurrence of window reflection at night can be reduced.

  The daytime and nighttime judgments may be made by judging whether the light switch of the vehicle is on or off, or based on the output of an illuminance sensor that is installed in the vehicle and detects the brightness outside the vehicle. Also good. Moreover, you may carry out using the time information which a vehicle has.

When the gradation inversion region R ₀ , which is a direction in which the transmittance of the liquid crystal panel 10 ′ is reduced, cannot be directed to the windshield 5 due to a request for design of the vehicle or the like, the two transparent electrodes 10 d and 10 d The voltage value of the DC voltage V applied between the electrodes, the alignment direction formed on the alignment film 10e, or the voltage applied between the two transparent electrodes 10d and 10d is directed in a desired direction. By selecting an appropriate type of liquid crystal molecules 10m that changes the ratio, it is possible to appropriately design the direction in which the transmittance is reduced and to realize a vehicle display device that can reduce windowing.

  As described above, according to the vehicular display device 20 according to the first embodiment, when the DC voltage V is applied between the two transparent electrodes 10d and 10d facing each other constituting the liquid crystal panel 10 ′, The liquid crystal molecules 10m having an ellipsoidal shape contained in the liquid crystal layer 10f sandwiched between the two transparent electrodes 10d and 10d change the direction in the direction corresponding to the magnitude of the applied DC voltage V. At this time, when the liquid crystal layer 10f is illuminated from the back surface 10t side, the transmittance of light traveling through the liquid crystal layer 10f changes according to the direction in which the liquid crystal molecules 10m face. In particular, when an intermediate voltage Vmid is applied as a predetermined DC voltage V between the two transparent electrodes 10d, 10d, the transmittance of light traveling in a predetermined angular direction is reduced, and therefore in the normal direction of the liquid crystal layer 10f. On the other hand, the light transmittance changes asymmetrically. Therefore, when the intermediate voltage Vmid is applied as the predetermined DC voltage V between the two transparent electrodes 10d and 10d of the liquid crystal panel 10 ′, the light transmittance is reduced with respect to the normal direction of the liquid crystal panel 10 ′. By installing the side to be mounted on the windshield 5 side of the vehicle, the image information having color information output to the color filter 10c (image display unit) arranged so as to be in contact with the surface side of the liquid crystal panel 10 ′ is obtained. Window reflection caused by reflection on the windshield 5 can be reduced.

  Further, according to the vehicle display device 20 according to the first embodiment, the image information is output at an intermediate brightness among the brightnesses that can be displayed on the liquid crystal panel 10 ′. Compared with the case where it is output in this way, the difference between the brightness of the background through the windshield 5 and the brightness of the image information reflected on the windshield 5 can be further reduced, and the window projection is less concerned. Can be reduced to a level.

  Further, according to the vehicle display device 20 according to the first embodiment, in the daytime, the image information is output with the maximum brightness, whereby the visibility of the display can be increased and the windshield 5 is passed through. Since the difference between the brightness of the background and the brightness of the reflection of the image information on the windshield 5 is reduced, the window reflection can be reduced to a level that does not matter. On the other hand, at night, the image information is output at an intermediate brightness, so that the visibility of the display is not reduced, and the brightness of the background through the windshield 5 and the reflection of the image information on the windshield are reduced. Since the difference in luminance can be reduced, window reflection can be reduced to a level that does not matter.

  In addition, according to the vehicle display device 20 according to the first embodiment, the image information is intermediated by adjusting the DC voltage V applied between the two transparent electrodes 10d and 10d or adjusting the luminance of the backlight 10g. Therefore, it is possible to easily generate an intermediate brightness at which window reflection is reduced without using a special component.

In addition, according to the vehicle display device 20 according to the first embodiment, when Vmid is applied as the predetermined DC voltage V between the two transparent electrodes 10d and 10d included in the twisted liquid crystal, the liquid crystal layer 10f is applied. Gradation inversion in which the transmittance of the liquid crystal panel 10 'is reduced in the direction according to the magnitude of the DC voltage V due to the characteristic that the liquid crystal molecules 10m included are oriented in the direction according to the magnitude of the applied DC voltage V. Region _R0 can be formed. Then, by installing the liquid crystal panel 10 ′ so that the gradation inversion region R ₀ faces the windshield 5 side, it is possible to reduce windowing.

In the description of the embodiment, an example of an image expressed in gray scale from white to black as shown in FIG. 6B as the image information D ₁ is shown on the liquid crystal panel 10. ₁ can also be applied when a color image is displayed. That is, for example, an image having a gradation from dark red to bright red, an image having a gradation from dark green to bright green, an image having a gradation from dark blue to light blue, or a mixture of these colors This can also be applied when displaying a selected image. That is, the image information D ₁ to be displayed on the liquid crystal panel 10, regardless of the color, by displaying at an intermediate brightness in the liquid crystal panel is possible brightness display, it is possible to reduce the window being viewed as .

  Although the embodiments of the present invention have been described in detail with reference to the drawings, the embodiments are only examples of the present invention, and the present invention is not limited to the configurations of the embodiments. Needless to say, design changes and the like within a range not departing from the gist of the invention are included in the present invention.

5 windshield 10 for the liquid crystal panel 20 vehicle display device 50 display control unit 100 the driver _{A 1,} A 2, _{A 3} optical path 10 liquid crystal panels 10a polarizing filter 10b glass substrate 10c color filter (image display unit)
10d transparent electrode 10e alignment film 10f liquid crystal layer 10g backlight 10m liquid crystal molecule 10s surface 10t back surface

Claims (4)

A liquid crystal layer sandwiched between two transparent electrodes facing each other, and when the liquid crystal layer is illuminated from the back side by applying a predetermined DC voltage between the two transparent electrodes, the liquid crystal layer A liquid crystal panel having a characteristic that light transmittance when viewed from a predetermined angle direction on the surface side with respect to the normal direction of the liquid crystal layer changes asymmetrically with respect to the normal direction;
A backlight for illuminating the liquid crystal panel from the back side;
An image display unit that is arranged in contact with the surface side of the liquid crystal panel and outputs image information having color information, and the liquid crystal panel is placed between the two transparent electrodes with the predetermined direct current Apply a voltage, and install the side where the light transmittance becomes small with respect to the normal direction on the windshield side of the vehicle ,
The vehicle display device , wherein the image information is output at a brightness intermediate between brightnesses that can be displayed by the liquid crystal panel .   The image information is output at an intermediate brightness that can be displayed by the liquid crystal panel at night, and at the maximum brightness that the liquid crystal panel can display at daytime. The vehicle display device according to claim 1, wherein The brightness of the intermediate, the predetermined adjustment of the DC voltage, or the display device for a vehicle according to claim 1 or claim 2, wherein the generating the brightness control of the backlight. The vehicular display device according to any one of claims 1 to 3 , wherein the liquid crystal layer includes a twisted matic liquid crystal.