JP2004302021A - Backlight structure for liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight structure for a liquid crystal display device having a structure which improves luminance with simple configuration and is advantageous for size and thickness reduction as well. <P>SOLUTION: An on overhang section 2b of a light transmission plate 2 is provided with a photodetecting overhang section 2c which projects up to a light emitting section positions of light emitting elements 4 and 6. The photodetecting overhang section 2c is provided with grooves 2d and 2e respectively facing the light emitting elements 4 and 6. The grooves 2d and 2e have photodetecting surfaces 2f and 2g composed of arcuate recessed surfaces and are installed consecutively in such a manner that the arcs of the photodetecting surfaces intersect with each other and are connected in a diametral direction. The height of a coupling 2h is set lower than the photodetecting overhang section 2c in order to set the angle formed by the tangents of the photodetecting surfaces 2f and 2g in the coupling 2h at ≥90°. The light intruding into the coupling 2h is therefore not confined and the luminance is enhanced. The spacing between the light emitting elements is required to be narrowed in order to make the coupling 2h lower. The state easy to miniaturize the structure is thus attained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the structure of a backlight used in a liquid crystal display device, and more particularly to the structure of the light guide plate and the positional relationship between the light guide plate and the light emitting elements.
[0002]
[Prior art]
In the conventional backlight structure of this type of liquid crystal display device, a light guide plate is disposed behind the liquid crystal display panel, and light is irradiated from the back surface side or side end side of the light guide plate through the light guide plate. The liquid crystal display panel was irradiated with light (see Patent Document 1).
[0003]
In addition, a backlight structure of a liquid crystal display device that prevents uneven light emission due to miniaturization by using the reflecting surface of the housing to cause light from the LED to enter and diffuse at the end of the light guide plate has also been proposed. (See Patent Document 2).
[0004]
In addition, in order to reduce illumination unevenness while reducing the number of LEDs used, a backlight structure has also been proposed in which a light introducing portion combining a flat surface and a concave surface and a reflective surface composed of a concave surface are provided on the end surface of the light guide plate. (See Patent Document 3).
[0005]
[Patent Document 1]
JP-A-4-355428 [Patent Document 2]
JP 2000-221502 A [Patent Document 3]
JP-A-9-259623 [0006]
[Problems to be solved by the invention]
In the above prior art, not only simply providing illumination, but also improving the shape of the reflecting surface of the housing and the light introduction part of the light guide plate in order to prevent uneven illumination due to miniaturization, but in recent years it has become thinner and smaller Therefore, it is required to improve the luminance. In order to further reduce the thickness and size and increase the brightness, the shape of the reflection surface and the light introduction part in the prior art is too complicated and there is no room for improvement. If multiple LEDs are provided to increase the brightness, the size is reduced. It was also supposed to inhibit.
[0007]
The present invention has been made in view of the above-mentioned problems of the prior art. A liquid crystal display device having a structure that is advantageous for downsizing and thinning while using a plurality of light emitting elements to improve luminance with a simple shape and configuration. A backlight structure is provided.
[0008]
[Means for Solving the Problems]
The backlight structure of the liquid crystal display device of the present invention is a backlight structure of a liquid crystal display device that illuminates by irradiating the liquid crystal display panel with light from a light emitting element through a light guide plate. And at least two of the light emitting elements are provided, and a projecting portion that projects to a position of the light emitting portion of the light emitting element and introduces light to a direction of the main body of the light guide plate is provided in a part of the light guide plate. In addition, a groove having a light receiving surface formed of an arcuate concave surface facing each of the light emitting elements is provided on an end surface of the projecting portion, and the groove is continuously provided so that the light receiving surface is connected in the radial direction. Yes. According to a second aspect of the present invention, the projecting portion has a light receiving projecting portion that protrudes toward the light emitting element. According to a third aspect of the present invention, the light receiving surface comprising the arcuate concave surface of the groove is centered on a virtual axis that stands upright to the end surface of the light guide plate, and the light emitting element is positioned on the virtual axis. doing. According to a fourth aspect of the present invention, the groove is formed in the same direction as the optical axis toward the main body of the light guide plate facing the liquid crystal display panel. According to a fifth aspect of the present invention, the connecting portion of the groove is set to be lower than the first light receiving overhanging portion protruding toward the light emitting element. According to a sixth aspect of the present invention, the connecting portion of the groove is formed by setting an angle formed by a tangent of an arc formed by the light receiving surface at the connecting portion from 90 degrees to 180 degrees. In addition, as shown in claim 7, the optical axis direction toward the main body portion of the projecting portion of the light guide plate or a part of the side end surface facing the optical axis forms an angle with the optical axis. It is a surface.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The light guide plate in the backlight structure of the liquid crystal display device of the present invention is provided with an overhanging portion, and the overhanging portion is provided with a light receiving overhanging portion protruding to the position of the light emitting portion of the light emitting element disposed on the back side. ing. The light receiving overhanging portion formed by the end face of the overhanging portion is provided with grooves that respectively face at least two light emitting elements. This groove is formed in the same direction as the optical axis toward the main body of the light guide plate facing the liquid crystal display panel. Further, the groove has a light receiving surface formed of an arcuate concave surface, the arcs of the light receiving surface intersect and are connected in a radial direction, and the connecting portion is set to be lower than the light receiving protruding portion. The
[0010]
When light is emitted from the light emitting element to the light guide plate having such a configuration, the irradiated light is introduced into the light guide plate from the light receiving surface formed of an arcuate concave surface. The light introduced from the light receiving surface travels in the optical axis direction of the light guide plate and is reflected in the optical axis direction by the reflecting surface on the inner surface of the protruding portion of the light guide plate, and from the surface side of the light guide plate toward the liquid crystal display panel. Irradiated. In addition, as described above, the height of the connecting portion is set in order to set the angle formed by the tangent to the light receiving surface in the connecting portion to 90 degrees or more. Without being confined, it becomes effective light and can increase luminance. In addition, in order to lower the connecting portion, it is necessary to increase the arc-shaped radius of the light receiving surface and further reduce the center interval, that is, the interval between the light emitting elements.
[0011]
With the positional relationship between the light emitting element and the overhanging portion or the groove configuration as described above, the light from the light emitting element can be used effectively, and the space between the light emitting elements can be narrowed to facilitate the miniaturization.
[0012]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged front view showing a main part of a light guide plate in a backlight structure of a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a backlight structure using the light guide plate shown in FIG. 3 is a plan view of the light guide plate shown in FIGS. 1 and 2, and FIG. 4 is a front view of the light guide plate shown in FIG. 2 is a light guide plate, 4 and 6 are light emitting elements such as LEDs, and 8 is a liquid crystal display panel. The light emitting elements 4 and 6 are arranged on the back side of the light guide plate 2, and the light guide plate 2 is arranged on the back side of the liquid crystal display panel 8.
[0013]
The light guide plate 2 has a main body 2a facing the liquid crystal display panel 8, and protrudes from the end of the main body 2a in the extending direction, and in the direction of the light emitting elements 4 and 6 (on the optical axis toward the main body 2a). On the other hand, it has a projecting portion 2b projecting in the direction of 90 degrees. The end face on the back surface side of the protruding portion 2b protrudes until reaching the position of the light emitting portions 4a and 6a of the light emitting elements 4 and 6, thereby forming a light receiving protruding portion 2c. Further, grooves 2d and 2e facing the light emitting elements 4 and 6 are provided in the light receiving overhang 2c of the overhang 2b. The grooves 2d and 2e are both formed in the same direction as the optical axis toward the main body portion 2d, and are formed so that the cross-sectional shape of the inner surface thereof is the light receiving surfaces 2f and 2g formed of arcuate concave surfaces. Yes. The centers of the circular arc shapes of the light receiving surfaces 2f and 2g are located on a virtual axis that stands upright to the light receiving protruding portion 2c. The light receiving surfaces 2f and 2g have the least reflection when the angle formed between the light from the light emitting element and the tangent line on the light receiving surface is 90 degrees. Further, in the case of an acrylic material that is the material of the light guide plate 2, the reflectance can be reduced within 1% until the angle reaches 46 degrees. Therefore, the arc-shaped center of the light receiving surface is set so that the angle formed by the light from the light emitting element and the tangent line on the light receiving surface is between 90 degrees and 46 degrees.
[0014]
Further, the grooves 2d and 2e are connected in the radial direction so that the arc shapes of the light receiving surfaces 2f and 2g intersect the radial direction. The connecting portion 2h to which the grooves 2d and 2e are connected has a peak shape sandwiched between arcuate concave surfaces extending in the optical axis direction. The height of the connecting portion 2h (the dimension in the thickness direction of the light guide plate 2) is set to be lower than the height of the end surface 2c (that is, the height reaching the light emitting portions 4a and 6a of the light emitting elements 4 and 6). Thus, the angle formed by the tangent lines of the light receiving surfaces 2f and 2g is set to be 90 degrees or more. The setting of the height of the connecting portion 2h will be described in detail later.
[0015]
Further, the projecting portion 2b is provided with inclined surfaces 2i and 2j that form a certain angle with respect to the optical axis at a part of the side end surface facing the optical axis direction or the optical axis. In this embodiment, the angles of the inclined surfaces 2i and 2j are set to 45 degrees with respect to the optical axis.
[0016]
On the other hand, the light emitting elements 4 and 6 are respectively arranged on virtual axes (lines connecting the light receiving surfaces 2f and 2g and the center thereof) standing upright to the end surface 2c of the projecting portion 2b.
[0017]
Next, a light irradiation state in the backlight structure of the liquid crystal display device having the above structure will be described with reference to FIGS. First, as shown in FIGS. 1 and 5, the light 10 and 12 emitted from the light emitting elements 4 and 6 is such that the light receiving surfaces 2 f and 2 g of the grooves 2 d and 2 e facing the light emitting elements 4 and 6 are arcuate concave surfaces. For this reason, there is less reflection compared to a plane, and the light is efficiently introduced into the light guide plate 2. Of the light introduced from the light receiving surfaces 2f and 2g, the light 14 and 16 on the optical axis directed to the main body 2a is reflected as it is or reflected by the reflecting surface 2n of the light guide plate 2 and travels toward the main body 2a. Further, the lights 18 and 20 having an angle of 90 degrees or the like with respect to the optical axis are reflected by the inclined surfaces 2i and 2j to become light in the optical axis direction and travel toward the main body 2a.
[0018]
Further, the light from the light emitting elements 4 and 6 strikes the light receiving surfaces 2f and 2g obliquely as the distance between the light emitting elements 4 and 6 and the light receiving surfaces 2f and 2g increases. For this reason, as shown in FIG. 7, a part of the light traveling from the light emitting elements 4 and 6 toward the longitudinal direction (optical axis direction) of the grooves 2 a and 2 e is reflected to become reflected light 22. Therefore, as shown in FIG. 8, when the walls 2k and 2m are provided at the end of the groove 2d (2e) in the optical axis direction, the reflected light 22 can be taken in. However, in this case, as shown in FIG. 8, the light incident on the walls 2k and 2m is repeatedly reflected within the walls and cannot escape from the walls 2k and 2m. It will be reduced. For this reason, when an experiment was conducted, it was confirmed that the luminance was improved by adopting a structure in which the walls 2k and 2m were not provided at the ends of the grooves 2d and 2e in the optical axis direction.
[0019]
Further, when the angle formed by the tangent lines of the light receiving surfaces 2f and 2g in the connecting portion 2h shown in FIG. 5 is set to 90 degrees or more, the light that has entered the connecting portion 2h is less than 90 degrees shown in FIG. Is no longer confined, and light can escape as shown in FIG. 9 (b), and utilization efficiency can be improved. Thus, in order to set the angle formed by the tangent to 90 degrees or more, it is necessary to lower the connecting portion 2h. For this purpose, the radius R of the light receiving surfaces 2f and 2g shown in FIG. It is a condition to reduce the distance L between them. When the distance L is reduced, the distance between the light emitting elements 4 and 6 arranged on the line connecting the light receiving surfaces 2f and 2g and the center thereof is also reduced, and the miniaturization is facilitated.
[0020]
When the distance L cannot be reduced and the connecting portion 2h becomes high, the bottom portions of the light receiving surfaces 2f and 2g are extended in the radial direction and connected as shown in FIG. It may be configured. In this case, the angle formed by the tangent lines of the light receiving surfaces 2f and 2g is 180 degrees.
[0021]
In the above embodiment, two light emitting elements are provided and two grooves are provided on the light receiving surface so as to correspond to the light emitting elements. However, the number of light emitting elements is further increased depending on the size of the liquid crystal display panel. It is possible to increase the number of grooves according to the number.
[0022]
【The invention's effect】
According to the present invention, the light receiving surface provided in the projecting portion is formed into a groove having an arcuate concave surface to facilitate the introduction of light, and by specifying the position with the light emitting element, the light from the light emitting element can be transmitted with a simple configuration. It can be effectively used to improve the luminance.
[0023]
In addition, since a plurality of light-emitting elements can be arranged close to each other, it is easy to reduce the thickness and size, and the luminance can be improved by increasing the number of light-emitting elements.
[Brief description of the drawings]
FIG. 1 is an enlarged front view showing a main part of a light guide plate in a backlight structure of a liquid crystal display device according to an embodiment of the present invention.
2 is a cross-sectional view showing a backlight structure using the light guide plate shown in FIG. 1. FIG.
3 is a plan view of the light guide plate shown in FIGS. 1 and 2. FIG.
4 is a front view of the light guide plate shown in FIG. 3. FIG.
5 is a front view showing a state where light is incident on the main part of the light guide plate shown in FIG. 1. FIG.
6 is a plan view showing a state where light is incident on the main part of the light guide plate shown in FIG. 3; FIG.
7 is a cross-sectional view showing a state where light is incident and reflected on the main part of the light guide plate shown in FIG. 2;
8 is a cross-sectional view showing a light reflection state inside when the main part of the light guide plate shown in FIG. 7 is changed.
FIGS. 9A and 9B are enlarged front views showing the state of light reflection inside the connecting portion when the angle formed by the tangent is less than 90 degrees, and FIG. 9B when the angle formed by the tangent is greater than 90 degrees.
FIG. 10 is a front view showing a main part of the light guide plate when grooves are connected and an angle formed by a tangent is 180 degrees.
[Explanation of symbols]
2 Light guide plate 2a Main body portion 2b Overhang portion 2c Light receiving overhang portions 2d, 2e Grooves 2f, 2g Light receiving surface 2h Connection portions 2i, 2j Inclined surfaces 4, 6 Light emitting elements 4a, 6a Light emitting portion 8 Liquid crystal display panel

Claims (7)

A backlight structure of a liquid crystal display device that illuminates by irradiating a liquid crystal display panel with light from a light emitting element through a light guide plate,
At least two of the light emitting elements are provided;
Protruding to part of the light guide plate to the light emitting portion position of the light emitting element and introducing light to guide the light guide plate in the direction of the main body,
A groove having a light receiving surface composed of an arcuate concave surface facing each of the light emitting elements is provided on an end surface of the projecting portion,
A backlight structure of a liquid crystal display device, wherein the grooves are continuously provided so that the light receiving surfaces are connected in a radial direction. The backlight structure of the liquid crystal display device according to claim 1, wherein the projecting portion has a light receiving projecting portion projecting toward the light emitting element side. The light-receiving surface formed of an arc-shaped concave surface of the groove is centered on a virtual axis that stands vertically to the light-receiving overhanging portion of the light guide plate, and the light-emitting element is located on the virtual axis. The backlight structure of the liquid crystal display device according to claim 1 or 2. The back of the liquid crystal display device according to any one of claims 1 to 3, wherein the groove is formed in the same direction as an optical axis toward the main body of the light guide plate facing the liquid crystal display panel. Light structure. 5. The liquid crystal display device according to claim 1, wherein a connecting portion of the groove is set to be lower than the light receiving protruding portion protruding toward the light emitting element side. Backlight structure. 6. The liquid crystal display device according to claim 5, wherein the connecting portion of the groove is formed by setting an angle formed by a tangent of an arc formed by the light receiving surface at the connecting portion from 90 degrees to 180 degrees. Backlight structure. The optical axis direction toward the main body in the projecting portion of the light guide plate or a part of the side end surface facing the optical axis is an inclined surface that forms a certain angle with respect to the optical axis. 3. A backlight structure of the liquid crystal display device according to 2.

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