JP2013149549A - Backlight device and liquid crystal display using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backlight device having a spectrum performance with a simple structure.SOLUTION: The backlight device 1 includes a plurality of light sources 41R-B which emit light of different colors, respectively, a collimation means 42 which emits light of each color emitted from each light source 41R-B by collimating it, and a light guide plate 10 which has an end face 12 into which each of parallel light from the collimation means 42 enters and an emitting face from which the light guided inside is emitted. Since a spacing is provided and arranged between each two light sources 41R-B, the parallel light of each color emitted from the collimation means 42 is emitted in different directions, and the light of each color from the light guide plate 10 is emitted to different directions.

Description

  The present invention relates to a backlight device that guides light emitted from a light source to illuminate a liquid crystal display element, and a liquid crystal display device using the backlight device.

  In a liquid crystal display device, a backlight device that illuminates an image formed by pixels from behind is used. In such a backlight device, white light is used as a light source, and illumination is performed by using a spectral element such as a prism, a hologram (diffraction grating), or a dichroic mirror so that the light is dispersed and incident in front of a pixel. Has been done. In addition, a color filter is disposed in front of a pixel to transmit a frequency component corresponding to the pixel. When a color filter is used, the light use efficiency is reduced. Various techniques for improving it have been developed.

  Patent Document 1 discloses a backlight device that splits white light with a hologram having a diffraction wavelength and angle selectivity and illuminates with a color corresponding to a pixel of a liquid crystal display element. In this backlight device, it is possible to greatly improve the utilization efficiency of a backlight device for liquid crystal display without using a conventional color filter.

  Patent Document 2 describes a display device having an optical path synthesis optical system that emits chief rays of different color lights at different angles.

JP-A-6-308332 JP 2007-328218 A

  When a dichroic mirror is used as a spectroscopic element in a liquid crystal display device, it is difficult to downsize the system and the cost becomes high. In addition, when the spectral element uses a hologram or a prism as in Patent Document 1, when the parallelism of the light source is not good, colors are mixed, or vignetting occurs at a place other than the aperture in the pixel, that is, an unexpected direction. There is a problem in that surface reflection occurs to reduce the efficiency and color mixing. Further, when the intensity is continuously distributed with respect to the wavelength as in the case of a white light source, there has been a problem that vignetting efficiency of an intermediate color of RGB is reduced in a pixel other than the aperture.

  Further, there is a technique of using light sources separated by RGB as in Patent Document 2 and using light beams of respective colors in a substantially parallel manner. Since the light guide plate disclosed in Patent Document 2 exclusively uses the color separation direction as the width direction, a large lens is required, resulting in an increase in the size of the apparatus. Further, in the peripheral region of the lens where the incident angle becomes large, the reflection is increased and the efficiency is lowered. As a measure for increasing the size, it may be possible to divide the light source, but the number of parts is increased, and the reduction in efficiency is similar to the large size.

In order to solve such a problem, the backlight device according to the present invention,
A plurality of light sources that emit light of different colors,
Parallelizing means for collimating and emitting the light of each color emitted from each of the light sources;
A light guide plate having an end face on which the parallel light of each color from the collimating means is incident, and an exit surface for emitting the light guided inside,
By arranging the light sources at intervals, the parallel light of each color emitted from the collimating means is emitted in different directions, and the light of each color from the light guide plate is emitted in different directions. And

Furthermore, the backlight device according to the present invention is:
Further comprising a lens array having a plurality of unit lenses for entering light of each color emitted from the light guide plate,
The light of each color emitted from the unit lens illuminates a different area for each color.

Furthermore, in the backlight device according to the present invention,
Each of the light sources has a shape extending along an end surface of the light guide plate.

Furthermore, in the backlight device according to the present invention,
The collimating means is a cylindrical lens.

Furthermore, in the backlight device according to the present invention,
The collimating means is a concave mirror.

Furthermore, in the backlight device according to the present invention,
An end face of the light guide plate functions as the parallelizing means.

Furthermore, in the backlight device according to the present invention,
At least one of the light sources is an LED.

Furthermore, in the backlight device according to the present invention,
At least one of the light sources includes a laser source that emits a parallel light beam, and a positive lens or a negative lens that expands the parallel light beam emitted by the laser source.

Furthermore, the liquid crystal display device according to the present invention provides:
A plurality of light sources that emit light of different colors,
Collimating means for collimating light of each color emitted from each light source in different directions for each color;
A light guide plate having an end face to which each color parallel light from the collimating means is incident, and an exit face that emits light guided inside;
A liquid crystal display element in which pixels corresponding to each color are arranged;
A lens array having a plurality of unit lenses that enter each color of light emitted from the light guide plate and illuminate the liquid crystal display element,
By arranging the light sources with an interval, the light of each color from the light guide plate is emitted in different directions, and the light of each color emitted from the unit lens illuminates the pixel of the corresponding color. It is characterized by that.

Furthermore, in the liquid crystal display device according to the present invention,
Each of the unit lenses is arranged for each unit pixel group including pixels of all colors.

Furthermore, in the liquid crystal display device according to the present invention,
A color filter is provided between the lens array and the liquid crystal display element.

  In the present invention, light is emitted from the light guide plate in different directions by arranging the light sources at intervals, converting the light into parallel light by the collimating means, and entering the light into the light guide plate. Light emitted from the light guide plate can illuminate the pixels of the liquid crystal display element corresponding to each color. As described above, in the present invention, it is possible to provide a backlight device and a liquid crystal display device that can illuminate pixels corresponding to each color light while adopting a simple configuration. In addition, it is not necessary to provide a spectroscopic element separately, and it is possible to reduce the size and cost.

Sectional drawing of the liquid crystal display device which concerns on embodiment of this invention The top view of the backlight device concerning the embodiment of the present invention. The side view of the light source which concerns on embodiment of this invention The figure which shows the structural example of each color light source which concerns on embodiment of this invention. Sectional drawing of the liquid crystal display device which concerns on other embodiment of this invention. Sectional drawing of the liquid crystal display device which concerns on other embodiment of this invention.

  Now, a backlight device according to an embodiment of the present invention and a liquid crystal display device using the backlight device will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a liquid crystal display device (Example 1) according to an embodiment of the present invention.

  The liquid crystal display device 1 according to the present embodiment includes a light source group 40, a collimator 42 as a parallelizing unit, a light guide plate 10, a lens array 20, and a liquid crystal display element 30. In the configuration of the liquid crystal display device 1, the backlight device refers to a configuration other than the liquid crystal display element 30 or the lens array 20 and the liquid crystal display element 30.

  The light guide plate 10 is a transparent substrate having a thickness in the Z-axis direction in the drawing, guides each color light emitted from the light source group 40 inside, and emits it from the emission surface 13 parallel to the XY plane. FIG. 2 is a top view of the backlight device 1 according to the present embodiment. This figure is a view of FIG. 1 as viewed from the top (in the negative direction of the Z axis), and the appearance of the exit surface 13 of the light guide plate 10 can be seen. The light guide plate 10 has a plurality of convex portions 11 formed on the lower surface thereof, that is, on the surface facing the emission surface 13. The convex portion 11 of the present embodiment is formed in a shape protruding in the positive Z-axis direction by cutting out the surface of the light guide plate 10 in order to guide the light incident on the lower surface of the light guide plate 10 to the output surface 13. Has been. The protrusion 11 may be formed by filling a position corresponding to the notch with a medium having a refractive index different from that of the light guide plate 10. As shown in FIG. 2, they are provided discretely when viewed from the exit surface 13 side. Moreover, these convex parts 11 are increasing the discrete density as they move away from the light source group 40 (X-axis positive direction). With the configuration of the convex portion 11, the light intensity emitted from the light guide plate 10 is made uniform.

  In the present embodiment, the light source group 40 serving as a light emission source includes R (red), G (green), B (blue), and three color light sources 41R to 41B. In the present embodiment, an LED is used for each light source 41. Light emitted from the light sources 41R, G, and B is incident on a collimator 42 as a collimating means with a certain degree of emission angle.

In the present embodiment, it is important that the color light sources 41R, G, and B are arranged, that is, the color light sources 41R to 41B are arranged at intervals in the ZX plane as shown in FIG. The color light sources 41 </ b> R to 41 </ b> B are opposed to the incident surface 12 (the end surface of the light guide plate 10) of the light guide plate 10 and are arranged in parallel with the incident surface 12. 2 shows the shape of each color light source 41R, G, B when viewed from the upper surface side of the light guide plate 10, and FIG. 3 shows the shape when viewed from the side surface side of the light guide plate 10. Yes. Each color light source 41R, G, B in the present embodiment has a line segment shape extending over the entire incident surface 12 of the light guide plate 10 as shown in the figure. In this way, by extending each color light source 41R, G, and B, light emitted from the light source can be easily made uniform in the illuminance distribution of the illuminated portion as compared with the configuration in which the light sources are scattered. It is also possible to increase the total illuminance. Each color light source 41 may be configured by dividing its line segment shape, or emits light in a line segment shape as in this embodiment by forming an aggregate of a plurality of point light sources. It is good also as a structure.

  The collimator 42 functions as a collimating unit that converts light emitted from the color light sources 41R to 41B into parallel light or substantially parallel light. In this embodiment, a cylindrical lens having a positive lens function is employed. doing. This cylindrical lens has a cross-sectional shape shown in FIG. 1 and extends in the Y-axis direction. As described above, when a cylindrical lens is used as a collimator, the illuminance can be made uniform compared to a lens array including a plurality of lenses. In addition, since the cylindrical lens is a single optical element, the cylindrical lens can be easily manufactured and can be easily aligned when attached to the backlight device. The collimating means only needs to have a function capable of collimating the light from each of the color light sources 41R to 41B, and various forms such as a plurality of optical elements may be employed.

  Light having an angle emitted from each of the color light sources 41 </ b> R to 41 </ b> B is collimated by a collimator 42 having a positive lens function and is incident on the incident surface 12 of the light guide plate 10. As described above, since the color light sources 41R to 41B are arranged at intervals in the ZX plane of the paper, each color light incident on the collimator 42 is converted into parallel light emitted in different directions. . Therefore, after being guided by the light guide plate 10, the light emitted from the exit surface 13 of the light guide plate 10 is also emitted in different directions for each color.

  Further, in the present embodiment, as shown in FIG. 1, the incident surface 12 having a narrow cross-sectional width on the XZ plane (for example, a length of cm order when used as a PC display or a TV display) is illuminated. Therefore, the collimator 42 having a relatively small NA value (numerical aperture) can be used. Therefore, unlike an optical element that has to be illuminated over the width direction of the light guide plate as in Patent Document 2 described above, it is possible to suppress a reduction in efficiency due to reflection in the peripheral region of the collimator 42.

  A lens array 20 for illuminating the liquid crystal display element 30 with the light emitted from the light guide plate 10 is disposed on the light emission surface 13 side of the light guide plate 10. The lens array 20 of the present embodiment is composed of unit lenses 21 (positive lenses) arranged in the XY plane. Light emitted from one unit lens 21 is arranged to illuminate a unit pixel group 31 composed of a plurality of color pixels 31R to 31B. In other words, one lens array and one unit pixel group 31 are arranged in a one-to-one relationship.

  The liquid crystal display element 30 to be illuminated has a plurality of unit pixel groups 31 composed of color pixels 31R to 31B corresponding to the light source color in the XY plane. By controlling the liquid crystal display element 30 by a control device (not shown), each pixel 31 is in an on state in which light is transmitted and in an off state in which light is not transmitted, and an image that can be observed with illumination light from the lens array 20 is formed.

Here, since the light emitted from the light guide plate 10 is emitted in different directions as described above, each color light incident on the unit lens 21 can illuminate a different area for each color after being condensed. Become. By arranging the color pixels 31R to 31B described above in different regions for each color, it is possible to illuminate with illumination light of a color corresponding to the color of the pixels 31R to 31B. Note that the order of colors such as R, G, and B can be arbitrary, such as G, R, and B, as long as the order of the color light sources 41 corresponds to the order of the pixels 31.

  As described above, the collimator 42 as the collimating means emits parallel light or substantially parallel light. The degree of parallelism in the emitted light depends on each color light emitted from the light guide plate 10 as a lens array. It is preferable that a region that is different for each color through 20 (specifically, each opening of each color pixel 31R-B to be illuminated (detailed illustration is omitted)) can be illuminated. Specifically, in addition to the degree of parallelism immediately after the collimator 42, a factor (for example, the convex portion 11) that deteriorates the degree of parallelism immediately after the color pixels 31R to 31B is taken into consideration, and a wide range within the area of each color pixel 31R to 31B. Is preferably not projected from the region of each of the color pixels 31R to 31B.

  As described above, in the present embodiment, the light sources 41R to 41B are arranged with a space between them, and are collimated by the collimator 42 as the collimating means and are incident on the light guide plate 10 to thereby exit the light guide plate 10. The light is emitted in different directions. Light emitted from the light guide plate 10 is collected by the lens array 20 and illuminates the pixels 31R to 31B of the liquid crystal display element 30 corresponding to each color. Thus, in this embodiment, it is possible to provide a backlight device and a liquid crystal display device that can illuminate the pixels 31R to 31B for each color light while adopting a simple configuration.

  In this embodiment, the color filter is not used. However, a color filter corresponding to each of the color pixels 31R to 31B may be provided between the liquid crystal display element 30 and the lens array 20. Although it is conceivable that the light utilization efficiency is lowered, it is possible to improve the spectral performance.

  In the present embodiment, each color light source 41R-B uses an LED having a certain emission angle, and a collimator 42 can obtain wide parallel light. However, each color light source 41 includes a laser source instead of the LED. It is also possible to adopt. Moreover, it is good also as utilizing the plasma light source used for PDP (Plasma Display Panel) for each color light source 41. FIG.

  FIG. 4 shows each color light source 41 when the laser source 44 is employed. 4A shows a form using the positive lens 45 to obtain the emission angle α, and FIG. 4B shows a form using the negative lens 46 to obtain the emission angle β. The laser source 44 emits a parallel light beam, but the light beam width is generally narrow. In this embodiment in which light having a certain width is required, it is preferable to give an emission angle to the parallel light flux from the laser source 44. The light to which the emission angle is given enters the collimator 42 as the collimating means, and enters the light guide plate 10 as parallel light having a width.

  In the embodiment described with reference to FIG. 1, the collimator 42 having a positive lens function is used as the collimating means. However, various forms may be adopted as the collimating means. 5 and 6 are diagrams showing a liquid crystal display device according to another embodiment.

  The liquid crystal display device shown in FIG. 5 is an embodiment in which a curve is formed on the incident surface 12 of the light guide plate to function as a collimating means. Light emitted from the color light sources 41R to 41B enters the incident surface 12 and is collimated in different directions for each color. By integrating the collimating means with the light guide plate 10 in this way, it is not necessary to separately provide the collimator 42 and the like as in the above-described embodiment, and the number of parts can be reduced. And, by reducing the number of boundary surfaces due to integration, light loss due to reflection at the boundary surface can be suppressed, and light utilization efficiency can be improved. At the same time, the liquid crystal display device 1 can be downsized.

In the liquid crystal display device shown in FIG. 6, the concave mirror 43 is used. The concave mirror 43 is disposed with the reflection surface facing the light source group 40 and the incident surface 12 of the light guide plate 10, and makes the emitted light from the respective color light sources 41 </ b> R to 41 </ b> B collimate and enter the incident surface 12. The arrangement relationship between the color light sources 41R to 41B and the concave mirror 43 may be reversed. In that case, by changing the arrangement of the colors in the color light sources 41R to 41B, it is possible to make each color parallel light that is the same as that shown in FIG.

  According to such a configuration using the concave mirror 43, it is possible to configure the liquid crystal display device with a layout different from the case where the collimator 42 of FIG. 1 is adopted, and it is possible to provide a wide design freedom. It becomes. In the example of the figure, the concave mirror 43 that performs surface reflection is used. However, the concave mirror that performs internal reflection may be used. In that case, the optical path from each color light source 41R-B to the concave mirror and the light guide plate may be filled with a medium having a refractive index similar to that of the light guide plate 10, and the concave mirror as the collimating means and the light guide plate 10 may be integrated. Is possible.

  Note that the present invention is not limited to these embodiments, and embodiments configured by appropriately combining the configurations of the respective embodiments also fall within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device 10 ... Light guide plate 11 ... Convex part 12 ... Incident surface (end surface)
DESCRIPTION OF SYMBOLS 13 ... Output surface 20 ... Lens array 21 ... Unit lens 30 ... Liquid crystal display element 31 ... Unit pixel group 31R, 31G, 31B ... Each color pixel 41R, 41G, 41B ... Each color light source 42 ... Collimator 43 ... Concave mirror 44 ... Laser source 45 ... Positive lens 46 ... Negative lens

Claims (11)

A plurality of light sources that emit light of different colors,
Parallelizing means for collimating and emitting the light of each color emitted from each of the light sources;
A light guide plate having an end face on which the parallel light of each color from the collimating means is incident, and an exit surface for emitting the light guided inside,
By arranging the light sources at intervals, the parallel light of each color emitted from the collimating means is emitted in different directions, and the light of each color from the light guide plate is emitted in different directions. A backlight device. Further comprising a lens array having a plurality of unit lenses for entering light of each color emitted from the light guide plate,
The backlight device according to claim 1, wherein the light of each color emitted from the unit lens illuminates a different area for each color. The backlight device according to claim 1, wherein each of the light sources has a shape extending along an end surface of the light guide plate. The backlight device according to any one of claims 1 to 3, wherein the collimating unit is a cylindrical lens. The backlight device according to any one of claims 1 to 3, wherein the collimating means is a concave mirror. The backlight device according to any one of claims 1 to 5, wherein an end surface of the light guide plate functions as the collimating means. The backlight device according to any one of claims 1 to 6, wherein at least one of the light sources is an LED. The at least one of the light sources includes a laser source that emits a parallel light beam and a positive lens or a negative lens that expands the parallel light beam emitted by the laser source. The backlight device according to claim 1. A plurality of light sources that emit light of different colors,
Collimating means for collimating light of each color emitted from each light source in different directions for each color;
A light guide plate having an end face to which each color parallel light from the collimating means is incident, and an exit face that emits light guided inside;
A liquid crystal display element in which pixels corresponding to each color are arranged;
A lens array having a plurality of unit lenses that enter each color of light emitted from the light guide plate and illuminate the liquid crystal display element,
By arranging the light sources with an interval, the light of each color from the light guide plate is emitted in different directions, and the light of each color emitted from the unit lens illuminates the pixel of the corresponding color. A liquid crystal display device. The liquid crystal display device according to claim 9, wherein each of the unit lenses is provided for each unit pixel group including pixels of all colors. The liquid crystal display device according to claim 9, wherein a color filter is provided between the lens array and the liquid crystal display element.

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