JP2009300508A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the power consumption of a backlight, or to improve the brightness of an image displayed on a liquid crystal display panel, with respect to a liquid crystal display device for use as an in-vehicle display device. <P>SOLUTION: The liquid crystal display device has: the liquid crystal display panel including a first substrate; a second substrate; and liquid crystal interposed between the first substrate and the second substrate; and a backlight for irradiating light the directivity of which is improved. The liquid crystal display device includes a triangular prism array or a trapezoidal prism array disposed between the liquid crystal display panel and the backlight. The triangular prism array is an isosceles triangular prism array. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having directivity in two or three directions as light emitted from a liquid crystal display panel.

Conventionally, the directivity of light emitted from a liquid crystal display panel is set to an angle within a predetermined range in the horizontal direction or the vertical direction in order to realize a high viewing angle.
However, when the liquid crystal display device is used as an in-vehicle display, the image displayed on the liquid crystal display panel only needs to be visible from two directions including the driver and the front passenger seat, or three directions including the middle of the rear seat.
Therefore, when a liquid crystal display panel having a high viewing angle is used as an in-vehicle display, most of the light emitted from the liquid crystal display panel is emitted in an unnecessary direction.
In general, a liquid crystal display device includes a backlight for irradiating light to the liquid crystal display panel. In order to effectively use the light emitted from the backlight, the liquid crystal display device is directed to the light emitted from the backlight. It is known to have sex. (See Patent Document 1 below)
On the other hand, a two-screen display device applying the principle of a parallax barrier type stereoscopic display device is also known. (See Patent Document 2 below)

As prior art documents related to the invention of the present application, there are the following.
Japanese Patent Application No. 2007-177895 JP 2005-78080 A

As described above, when a liquid crystal display panel having a high viewing angle is used as a vehicle-mounted display, most of the light emitted from the liquid crystal display panel is emitted in an unnecessary direction. This means that power consumption is wasted in the backlight in order to irradiate light emitted in an unnecessary direction.
If the light emitted in this unnecessary direction can be reduced, the power consumption of the backlight can be reduced or the luminance of the image displayed on the liquid crystal display panel can be improved.
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to reduce the power consumption of a backlight in a liquid crystal display device used for a vehicle-mounted display, or a liquid crystal display. An object of the present invention is to provide a technique capable of improving the luminance of an image displayed on a display panel.
The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
The present invention relates to a liquid crystal display panel having a first substrate, a second substrate, and a liquid crystal sandwiched between the first substrate and the second substrate, and a back irradiated with light having improved directivity. And a triangular prism array or a trapezoidal prism array disposed between the liquid crystal display panel and the backlight.
In the liquid crystal display device of the present invention, a backlight having directivity that emits light in one direction is used, and light emitted from the backlight by using a triangular prism array or a trapezoidal prism array. The directionality of the display is made in two or three directions, so that the image displayed on the liquid crystal display panel can be seen from the two directions including the driver and the front passenger seat, or the middle of the rear seat. .

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
ADVANTAGE OF THE INVENTION According to this invention, in the liquid crystal display device used for a vehicle-mounted display, it becomes possible to reduce the power consumption of a backlight or to improve the brightness | luminance of the image displayed on a liquid crystal display panel.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In all the drawings for explaining the embodiments, parts having the same functions are given the same reference numerals, and repeated explanation thereof is omitted.
[Example 1]
FIG. 1 is a diagram showing a schematic configuration of a liquid crystal display device according to Embodiment 1 of the present invention.
In FIG. 1, 10 is a liquid crystal display panel, 11 is a triangular prism array, and 12 is a backlight. Here, the backlight irradiates light with improved directivity in the Z direction in FIG.
In this embodiment, light (light beam) irradiated perpendicularly from the backlight 12 toward the liquid crystal display panel 10 is separated into two-direction light beams by the obtuse triangular prism array 11 and enters the liquid crystal display panel 10. Is done.
The light beams in the two directions have gaps when exiting from the triangular prism array 11, but overlap in the direction toward the liquid crystal display panel 10 to become highly uniform light in two directions. If there is a problem in uniformity, a diffusion plate may be provided on the lower surface of the liquid crystal display panel 10 to improve the uniformity. Thereby, the light irradiated from the liquid crystal display panel 10 also becomes a light beam in two directions.
As shown in FIG. 2, when the refractive index of the triangular prism array 11 is 1.53, the base angle of each triangular prism element 11a is 37 degrees, and the apex angle is 106 degrees, as shown in FIG. In the angle distribution, the deviation from the vertical direction is ± 30 degrees.

FIG. 3 is a graph showing the horizontal relative luminous intensity distribution of light emitted from the backlight 12 of the present embodiment and the horizontal relative luminous intensity distribution of light passing through the triangular prism array 11.
FIG. 3 is a graph showing the angle dependency in the X direction shown in FIG. 1. The vertical axis in FIG. 3 is the horizontal relative luminous intensity (Br), and the horizontal axis in FIG. 3 is the light emission angle (φ). 3A shows the horizontal relative luminous intensity distribution of the light emitted from the backlight 12, and FIG. 3B shows the horizontal relative luminous intensity distribution of the light that has passed through the triangular prism array 11. FIG.
As shown in FIG. 3, the horizontal relative luminous intensity distribution of the light beam emitted from the backlight 12 has a peak luminous intensity in the direction of 0 degree (so-called vertical direction), but has passed through the triangular prism array 11. The peak light intensity of the light is ± 30 degrees from the front.
FIG. 4 is a graph showing the vertical relative luminous intensity distribution of the light beam that has passed through the triangular prism array 11 in the horizontal direction of 30 degrees. The vertical axis in FIG. 4 represents the vertical relative luminous intensity (Br), and the horizontal axis in FIG. Is the light emission angle (φ). 3 and 4 are graphs when the triangular prism element 11a has a refractive index of 1.53, a base angle of 37 degrees, and an apex angle of 106 degrees.
From FIG. 4, it can be seen that the light distribution that has passed through the triangular prism array 11 in the horizontal direction 30 degrees (φ = 30 °) has a light distribution restricted in the vertical direction.
3 and 4, the light emitted from the liquid crystal display panel 10 of this embodiment has a strong light distribution in the direction of ± 30 degrees in the horizontal direction (or left and right direction), and the vertical direction. It can be seen that the light distribution is also limited (or in the vertical direction).
It can be seen that this light distribution is an ideal distribution if there is a head of a driver seat and a passenger seat in the direction of ± 30 degrees in the horizontal direction (or left and right direction).

FIG. 5 is a graph showing the horizontal relative luminous intensity distribution when the base angle of the prism element 11a of the triangular prism array 11 is changed.
FIG. 5 is a graph showing the angle dependency in the X direction shown in FIG. 1. The vertical axis of FIG. 5 is the horizontal relative luminous intensity (Br), and the horizontal axis of FIG. 5 is the light emission angle (φ).
5, A in FIG. 5 shows the horizontal relative luminous intensity distribution of the light emitted from the backlight 12, B in FIG. 5 shows the base angle of the triangular prism element 11a is 37 degrees (θ shown in FIG. 6 is 37), the horizontal relative luminous intensity distribution of the light that has passed through the triangular prism array is shown in FIG. 5C, where the triangular prism element 11a has a base angle of 32 degrees (θ shown in FIG. 6 is 32 degrees). The horizontal relative luminous intensity distribution of the light that has passed through the prism array is shown in FIG. 5D, where D in FIG. 5 indicates that the light that has passed through the triangular prism array whose triangular prism element 11a has a base angle of 27 degrees (θ shown in FIG. FIG. 5E shows the horizontal relative luminous intensity distribution, and the horizontal relative luminous intensity distribution of the light that has passed through the triangular prism array whose triangular prism element 11a has a base angle of 22 degrees (θ is 22 degrees in FIG. 6).
As can be seen from FIG. 5, by changing the base angle of the triangular prism element 11a, the directivity in the two directions can be changed in the range of ± 10 degrees to ± 30 degrees. In FIG. 5, the directivity angles in the left-right direction are the same because the triangular prism element 11a is an isosceles triangle, and the triangular prism element 11a has a triangular shape whose lengths of each side are not equal. If a prism is used, the angle of directivity in the left-right direction can be changed.

[Example 2]
The liquid crystal display device of the present embodiment uses a trapezoidal prism array 13 instead of the triangular prism array 11 in the above-described embodiment.
FIG. 7 is a diagram for explaining a trapezoidal prism element 13a constituting the trapezoidal prism array 13 of the present embodiment. The trapezoidal prism element 13a of this embodiment is obtained by flatly cutting the apex portion of the triangular prism element 11a.
FIG. 8 is a graph showing the horizontal relative luminous intensity distribution of the light that has passed through the trapezoidal prism array 13 of Example 2 when the cut amount (ΔH / H) of the trapezoidal prism element 13a is changed. FIG. 8 is a graph showing the angle dependency in the X direction shown in FIG. 1, where the vertical axis in FIG. 8 is the horizontal relative luminous intensity (Br), and the horizontal axis in FIG. 8 is the light emission angle (φ).
8, A in FIG. 8 shows the horizontal relative luminous intensity distribution of the light emitted from the backlight 12, B in FIG. 8 shows the base angle (θ in FIG. 6) of the triangular prism element 11a is 37 degrees. The horizontal relative luminous intensity distribution of the light that has passed through the prism array 11 is shown in FIG. 8C where the base angle (θ in FIG. 7) of the trapezoidal prism element 13a is 37 degrees and the apex angle cut amount is 10% (ΔH / H = 0.1), the horizontal relative luminous intensity distribution of the light that has passed through the prism array 13 is shown in FIG. 8D, where the base angle (θ in FIG. 7) of the trapezoidal prism element 13a is 37 degrees, and the vertical angle cut amount The horizontal relative luminous intensity distribution of the light that has passed through the prism array 13 that is 20% (ΔH / H = 0.2) is represented by E in FIG. 8 and 37 in the base angle (θ in FIG. 7) of the trapezoidal prism element 13a. Of light passing through the prism array 13 having a vertex angle cut amount of 30% (ΔH / H = 0.3). In FIG. 8, F is a prism having a trapezoidal prism element 13a having a base angle (θ) of 37 degrees and a vertex angle cut amount of 40% (ΔH / H = 0.4). The horizontal relative luminous intensity distribution of the light that has passed through the array 13 is shown.

In FIG. 8, the refractive index (n) of the prism element 13a is 1.53, and the base angle (θ in FIG. 7) is 37 degrees. Therefore, when there is no cut, the above-described prism array 11 is formed, and the irradiated light has directivity in the direction of ± 30 degrees in the horizontal direction.
As shown in C of FIG. 8 to F of FIG. 8, as the cut amount (ΔH / H) is increased, the light emitted from the prism array 13 is forward (so-called vertical direction), that is, an angle of 0 degrees. Directivity also appears.
As shown in FIG. 8D, when the cut amount is 20%, the directivity of the light irradiated from the prism array 13 in the left and right directions of 30 degrees and the three directions in the front is almost equal. If there is a human head in the center of the driver seat, passenger seat, and rear seat in the direction of ± 30 degrees to the left and right, the light distribution of the trapezoidal prism array 13 having the trapezoidal prism element 13a shown in FIG. It can be seen that this is a distribution. That is, it is possible to provide a liquid crystal display device having a light directivity that is most suitable for a driver's seat, a passenger seat, and a rear seat person to simultaneously view images.

[Example 3]
FIG. 9 is a cross-sectional view showing the schematic structure of the liquid crystal display device according to the third embodiment of the present invention.
As shown in FIG. 9, the liquid crystal display panel 10 includes a liquid crystal layer (LC) sandwiched between a first substrate (SUB1) and a second substrate (SUB2). A first polarizing plate (POL1) is provided on the first substrate (SUB1), and a second polarizing plate (POL2) is provided on the second substrate (SUB2).
In this embodiment, a trapezoidal prism array 13 is arranged on the liquid crystal display panel 10 side.
In FIG. 9, the trapezoidal prism array 13 is disposed between the first polarizing plate (POL1) and the first substrate (SUB1).
Then, as shown in FIG. 9B in an enlarged view of the portion A in FIG. 9, the orientation of each prism element 13a of the trapezoidal prism array 13 is opposite to that in the first and second embodiments. It is provided to become. In FIG. 9B, 15 is an air layer, 16 is an air layer or resin, BM is a black matrix, and BEF is a brightness enhancement film.
In the present embodiment, the trapezoidal prism array 13 is described. However, the same effect can be obtained with the triangular prism array 11, and the effect can be easily understood from the description of the trapezoidal prism array 13. I will omit it.
In this embodiment, the directivity of the light emitted from the prism array 13 has the effect of converging the light beam on the liquid crystal display panel 10 in addition to the directivity in the 30 ° left and right directions and the three forward directions. . That is, the light shielded by the black matrix (BM) can be used, and the liquid crystal display panel 10 is further brightened.

As described above, for example, a two-screen liquid crystal display device shown in FIG. 10 is known. The present invention can also be applied to such a two-screen liquid crystal display device.
FIG. 10 is a diagram illustrating the principle of the two-screen display device, in which A is an image for an observer of KA, B is an image for an observer of KB, BARIA is a parallax barrier, THBA Is a slit-like opening of a parallax barrier (BARIA).
In FIG. 10, the distance (T1 in FIG. 10) between the parallax barrier (BARIA) and the image plane on which the images A and B are formed, and the width (THBA) of the opening (THBA) in the parallax barrier (BARIA) By appropriately setting T2), it is possible to display different images for the KA observer and the KB observer, for example, a movie for the KA observer and navigation information for the KB observer. .
In the above description, the light emitted from the backlight 12 is assumed to be a parallel light beam that is vertically irradiated toward the liquid crystal display panel 10, but the light emitted from the backlight 12 is a parallel light beam. Need not be. For example, the light emitted from the backlight 12 has a peak luminous intensity in a specific angular direction (a direction of 0 degrees, a so-called vertical direction) in the relative luminous intensity distribution in the X direction (so-called horizontal relative luminous intensity distribution) shown in FIG. Even when the light intensity is ± 15 degrees clockwise around a specific angle, even if the light intensity is 50% or less relative to the peak light intensity, the same effects as those of the above-described embodiments can be obtained. Note that the specific angular direction may be an angle other than the 0 degree direction (so-called vertical direction).

As described above, in this embodiment, the light emitted from the backlight 12 has directivity in two directions including the driver seat and the passenger seat, or in the three directions including the middle of the rear seat. The irradiation light emitted from the backlight 12 can be used effectively.
Therefore, the power consumption of the backlight 12 can be reduced when displaying with the same luminance as the conventional liquid crystal display device, and the liquid crystal display panel 10 is displayed when displaying with the same power consumption as the conventional liquid crystal display device. It is possible to improve the luminance of the displayed image.
As mentioned above, the invention made by the present inventor has been specifically described based on the above embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Of course.

It is a figure which shows schematic structure of the liquid crystal display device of Example 1 of this invention. It is a figure which shows the triangular prism element which comprises the triangular prism array of Example 1 of this invention. It is a graph which shows the horizontal relative luminous intensity distribution of the light irradiated from the backlight of Example 1 of this invention, and the horizontal relative luminous intensity distribution of the light which passed the triangular prism array. It is a graph which shows the perpendicular | vertical relative luminous intensity distribution of the light which passed through the triangular prism array in horizontal direction 30 degree | times. It is a graph which shows the horizontal relative luminous intensity distribution of the light which passed through the triangular prism array of Example 1 of this invention when changing the base angle of a triangular prism element. It is a figure which shows the triangular prism element which comprises the triangular prism array of Example 1 of this invention. It is a figure which shows the trapezoid prism element which comprises the trapezoid prism array of Example 2 of this invention. It is a graph which shows the horizontal relative luminous intensity distribution of the light which passed the trapezoid prism array of Example 2 of this invention when the cut amount of a trapezoid prism element was changed. It is sectional drawing which shows the principal part sectional structure of the liquid crystal display device of Example 3 of this invention. It is a figure for demonstrating the principle of a 2 screen liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display panel 11 Triangular prism array 11a Triangular prism element 12 Backlight 13 Trapezoid prism array 13a Trapezoid prism element 15 Air layer 16 Air layer or resin SUB1, SUB2 Substrate LC Liquid crystal layer BM Black matrix POL1, POL2 Polarizing plate BEF brightness enhancement film KA, KB observer A image for observer (KA) B image for observer (KB) BARIA parallax barrier THBA slit-like opening of parallax barrier

Claims (12)

A liquid crystal display panel having a first substrate, a second substrate, and a liquid crystal sandwiched between the first substrate and the second substrate;
A liquid crystal display device having a backlight that emits light with improved directivity,
A liquid crystal display device comprising a triangular prism array disposed between the liquid crystal display panel and the backlight.   The liquid crystal display device according to claim 1, wherein each prism element of the triangular prism array is an isosceles triangular prism element.   The liquid crystal display device according to claim 1, further comprising a diffusion plate disposed between the liquid crystal display panel and the triangular prism array.   2. The liquid crystal display device according to claim 1, wherein the triangular prism array is arranged such that a base of each triangular prism element is on the liquid crystal display panel side. A first polarizing plate disposed on the first substrate of the liquid crystal display panel;
The first substrate of the liquid crystal display panel is disposed on the backlight side;
The liquid crystal display device according to claim 4, wherein the triangular prism array is disposed between the first substrate and the first polarizing plate. A liquid crystal display panel having a first substrate, a second substrate, and a liquid crystal sandwiched between the first substrate and the second substrate;
A liquid crystal display device having a backlight that emits light with improved directivity,
A liquid crystal display device comprising a trapezoidal prism array disposed between the liquid crystal display panel and the backlight.   The liquid crystal display device according to claim 6, wherein each prism element of the trapezoidal prism array is a trapezoidal prism element in which an apex angle of an isosceles triangle is cut flat.   The liquid crystal display device according to claim 6, further comprising a diffusion plate disposed between the liquid crystal display panel and the trapezoidal prism array.   The liquid crystal display device according to claim 6, wherein the trapezoidal prism array is arranged such that a base of each trapezoidal prism element is on the liquid crystal display panel side. A first polarizing plate disposed on the first substrate of the liquid crystal display panel;
The first substrate of the liquid crystal display panel is disposed on the backlight side;
The liquid crystal display device according to claim 9, wherein the trapezoidal prism array is disposed between the first substrate and the first polarizing plate.   The light emitted from the backlight has a peak luminous intensity in a specific angular direction in a horizontal relative luminous intensity distribution, and is relative to the peak luminous intensity when it is ± 15 degrees or more clockwise around the specific angle. The liquid crystal display device according to any one of claims 1 to 10, wherein the luminous intensity is 50% or less.   The liquid crystal display device according to claim 9, wherein the specific angle is a direction perpendicular to the liquid crystal display panel.

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