JPH08278414A - Back light device - Google Patents

Abstract

PURPOSE: To suppress the concentration of incident light at the corner of a light transmission plate enclosed by a light source and to prevent the occurrence of unequal luminance by forming a notch at the corner of this light transmission plate. CONSTITUTION: This back light device 1 is constituted by disposing the bar- shaped light source 3 bent to an L shape along the adjacent light incident end faces 2a, 2b of the light transmission plate 2 made of an acrylic resin to a rectangular shape. The notch C of a rectangular shape is formed at the corner of the light transmission plate 2 enclosed by the light source 3. This notch C is formed by cutting off the corner of the light transmission plate 2 perpendicularly in such a manner that its one cut face 4a is right angled to the one light incident end face 2a and that the other cut face 4b is perpendicular to the other light incident end face 2a. The back light device 1 constituted in such a manner is capable of making light incident on the light transmission plate 2 from the two light incident end faces 2a, 2b with the one light source 3. In addition, the concentration of the incident light at the corner is prevented by forming the notch C at the corner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge light type backlight device in a liquid crystal display device.

[0002]

2. Description of the Related Art As a conventional edge-light type backlight device, a rod-shaped light source 13 bent into an L-shape as shown in FIG. 5 is provided on two adjacent end surfaces 14a, 14b of a rectangular light guide plate 14. Those arranged so as to straddle are known. According to this type of backlight device, 1
Since light can be incident on the light guide plate 14 from two different directions by one light source 13, it is possible to realize high brightness with an inexpensive and simple device configuration.

[0003]

However, while the above-mentioned conventional backlight device can realize high brightness with one light source 13, as shown in FIG. 6, the corner of the light guide plate 14 surrounded by the light source 13 is provided. Since incident light is concentrated on a portion, there is a problem that the portion becomes extremely bright and causes uneven brightness. This problem also occurs when the corners of the light guide plate 15 are cut into an arc shape as shown in FIG. An object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a high-brightness backlight device without uneven brightness.

[0004]

In order to achieve the above object, the first backlight device of the present invention is provided with a light source along the light incident end faces of the light guide plate arranged behind the display section. In the backlight device configured as described above, a notch is formed in a corner of the light guide plate surrounded by the light source (claim 1).

A second backlight device of the present invention is
In a backlight device in which a light source is provided along adjacent light incident end faces of a light guide plate arranged behind a display unit, a semi-transmissive layer is formed on a corner end face of the light guide plate surrounded by the light source. (Claim 2)

In the first and second backlight devices, it is preferable that the light source is a light source formed by bending the light guide plate at a substantially right angle so as to straddle adjacent light incident end faces of the light guide plate. 3). Examples of this type of light source include an L-shaped light source formed by bending one place in the middle at a substantially right angle, and a U-shaped light source formed by bending two places in the middle at a substantially right angle in the same direction.

[0007]

In the first backlight device, light having a large incident angle on the end surface of the cutout portion of the light guide plate is reflected,
Only light whose incident angle to the end face of the cutout portion is close to a right angle is incident on the light guide plate. As a result, the concentration of incident light is suppressed at the corners of the light guide plate surrounded by the light source, and uneven brightness is prevented.

Further, in the second backlight device, since the semi-transmissive layer is formed on the end face of the corner portion of the light guide plate, the concentration of incident light at the corner portion of the light guide plate surrounded by the light source is suppressed, and the brightness is reduced. The occurrence of unevenness is prevented.

Further, if a light source is used as the light source, which is formed by bending the light incident end faces of the light guide plates which are adjacent to each other so as to be bent at a substantially right angle, the light guide plate is moved from the adjacent light incident end faces of one light source. Light can be incident. For example, if an L-shaped light source is used, light can be incident on the light guide plate from two directions with one light source. Further, if the U-shaped light source is used as the light source, it is possible to allow light to enter the light guide plate from three directions with one light source.

[0010]

EXAMPLES Examples of the present invention will be described below.
FIG. 1A is a plan view of a main part showing a first embodiment of a backlight device according to the present invention, and FIG. 1B is a partially enlarged view of FIG. The backlight device 1 shown in FIG. 1 includes a rectangular light guide plate 2 made of an acrylic resin and having adjacent light incident end faces 2a, 2a.
A rod-shaped light source 3 is provided which is bent in an L shape along b. A right-angled notch C is formed at a corner of the light guide plate 2 surrounded by the light source 3. This notch C
Is the corner of the light guide plate 2 so that the one cut surface 4a is perpendicular to the one light incident end surface 2a and the other cut surface 4b is perpendicular to the other light incident end surface 2a. It is cut off at a right angle (θ = 90 °) (see FIG. 1 (b)).

In the backlight device of the first embodiment constructed as described above, one light source 3 is used for two light incident end faces 2.
Since light can be made incident on the light guide plate 2 from a and 2b, high brightness can be realized with an inexpensive and simple device configuration. Moreover, since the notch C is formed at the corner of the light guide plate 2 surrounded by the light source 3, as shown in FIG. 1B, the incident angle of the notch C on the cut surfaces 4a and 4b is 45 degrees or more. Since the light L is reflected, incident light is not concentrated on the corner of the light guide plate 2 surrounded by the light source 3 and the inconvenience that this part becomes extremely bright does not occur. Therefore, the brightness of the entire light guide plate 2 can be made uniform. Also, the cut surface 4 of the notch C
Since the light whose incident angles to a and 4b are close to right angles enter the light guide plate 2, all the light from the bent portion of the light source 3 is not wasted.

FIG. 2 is an exploded perspective view showing a second embodiment of the backlight device according to the present invention. In the backlight device 5 according to the second embodiment, a groove 7 serving as a light source holding portion is formed across the edge portions of the light guide plate 6 which are adjacent to each other,
An L-shaped light source 8 having an intermediate portion bent substantially at a right angle is held in the groove 7. The cross section of the groove 7 is U-shaped. Further, the two outer surfaces 10a and 10b along the groove 7 of the light guide plate 6 are designed to have an ideal reflection shape that allows the light from the light source 8 held in the groove 7 to be efficiently incident into the light guide plate 6. And these outer surfaces 10a, 1
The reflectors 11 and 12 are attached to 0b. A diffusion sheet (not shown) is arranged along the surface of the light guide plate 6 on the side where the groove 7 is formed. Then, a reflector made of the same material as the reflectors 11 and 12 attached to both outer side surfaces 10a and 10b is attached to a portion of the diffusion sheet that overlaps the groove 7.

In this backlight device 5, the inner peripheral side surface of the groove 7 has two light incident end surfaces 9 of the light guide plate 6.
a and 9b. A notch C having a right-angled shape is formed in the corner surrounded by the light source 8 as in the first embodiment.

In the backlight device 5 of the second embodiment constructed as described above, the groove 7 is formed over the edge portions of the light guide plate 6 which are adjacent to each other. The light source 8 can be accurately positioned and easily mounted on the light guide plate 6.

Further, the both outer side surfaces 10a of the light guide plate 6,
Since 10b is designed in advance to have an ideal reflection shape in order to allow the light from the light source 8 to enter the light guide plate 6 efficiently, the reflectors 11 and 12 can be simply attached to the outer side surfaces 10a and 10b. Can have an ideal reflection shape and can be stably held in a state where an ideal distance from the light source 8 is maintained.
Then, the reflector provided on the diffusion sheet prevents light from leaking from the groove 7.

Therefore, according to the structure of the second embodiment, the light from the light source 8 is made to enter the light guide plate 6 more efficiently than in the case of the first embodiment, and the backlight device of higher brightness is obtained. Can be realized. Moreover, even in this case, the light L having an incident angle of 45 degrees or more on the cut surface of the cutout portion C of the light guide plate 6 is reflected, and only the light whose incident angle on the cut surface of the cutout portion C is close to a right angle inside the light guide plate 6. Since the incident light is incident on, the concentration of incident light at the corners of the light guide plate 6 surrounded by the light source 8 is suppressed, and uneven brightness is prevented.

3 (a) and 3 (b) show a modified embodiment of the backlight device of the first embodiment, in which the adjacent light incident end faces 2a, 2b of the light guide plate 2 are obliquely traversed. The structure of the notch C formed by cutting off the corner stepwise is shown. By cutting off the corners of the light guide plate 2 in a stepwise manner in this manner, the angle 17 of the light guide plate 2 can be separated from the light source 3 to reduce the amount of incident light, and at the same time, the angle 17 of the light guide plate 2 can be reduced.
Can be effectively used as a backlight of the liquid crystal display panel P up to near. Notch C shown in FIGS. 3 (a) and 3 (b)
This structure can be effectively applied to the backlight device of the second embodiment.

FIG. 4 is a partial perspective view showing a third embodiment of the backlight device of the present invention. In this example, a part of light is transmitted to the corner end face of the light guide plate 16 which is cut in an arc shape. The semi-transmissive film 17 having characteristics is attached by a method such as printing or vapor deposition. If the semi-transmissive film 17 is formed on the end surface of the corner of the light guide plate 16 as in this example, the amount of incident light can be reduced, and at the same time, the corners of the light guide plate 16 can be effectively used as the backlight of the liquid crystal display panel P. Since it can be used for, the wasted space can be reduced. Further, instead of attaching the semi-transmissive film 17 to the corner end surface of the light guide plate 16, the corner end surface of the light guide plate 16 may be subjected to frost processing to form that portion as a ground glass semi-transmissive film layer.

The backlight device of the present invention is not limited to the above-mentioned embodiment, and instead of the L-shaped light sources 3 and 8, a U-shaped light source is incident on the three light guide plates 2 and 6. You may arrange | position along an end surface. In that case, it is desirable to form the cutouts C in the two corners of the light guide plates 2 and 6 that are surrounded by the U-shaped light source. Further, in that case, it is desirable that the groove 7 in the second embodiment be formed in a U shape in accordance with the shape of the light source.

Further, the angle θ of the notch C does not necessarily have to be 90 °, and may be an acute angle, that is, an angle less than 90 °. Further, by using the space of the cutout portion C, columns or ribs for supporting the backlight device, or a structure such as a light source retainer may be arranged.

[0021]

In summary, according to the present invention, the following excellent effects can be exhibited. (1) According to the backlight device of the first aspect, the substantially right-angled cutouts are formed at the corners of the light guide plate surrounded by the light source. Since light reflected without entering the light guide plate is generated, it is possible to prevent the incident light from concentrating on the corners of the light guide plate surrounded by the light source, and to make the brightness of the entire light guide plate uniform. .

(2) According to the backlight device of the second aspect, since the semi-transmissive layer is formed on the end face of the corner of the light guide plate surrounded by the light source, the amount of light incident on the corner of the light guide plate is increased. Therefore, it is possible to prevent the incident light from concentrating on the corners of the light guide plate surrounded by the light source and to make the brightness of the entire light guide plate uniform.

(3) According to the backlight device described in claim 3, light can be incident on the light guide plate from the light incident end faces that are adjacent to each other by one light source. High brightness can be realized with a cheaper and simpler device configuration than the case of the item 2).

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a backlight device of the present invention, (a) is a perspective view, and (b) is a partially enlarged plan view of (a).

FIG. 2 is an exploded perspective view showing a second embodiment of the backlight device of the present invention.

FIG. 3 is a partial plan view showing a modified embodiment of the backlight device of the present invention.

FIG. 4 is a partial perspective view showing a third embodiment of the backlight device of the present invention.

FIG. 5 is a perspective view showing an example of a conventional backlight device.

6 is a partially enlarged plan view of FIG.

FIG. 7 is a partial plan view of another conventional backlight device.

[Explanation of symbols]

 1 backlight device 2 light guide plate 2a light incident end face 2b light incident end face 3 light source 5 backlight device 6 light guide plate 8 light source 9a light incident end face 9b light incident end face 16 light guide plate 17 semi-transmissive film (semi-transmissive layer) C notch L Optical P liquid crystal display panel (display section)

Claims (3)

[Claims] 1. A backlight device comprising a light source disposed along adjacent light incident end faces of a light guide plate arranged behind a display part, wherein a notch is provided at a corner of the light guide plate surrounded by the light source. A backlight device characterized by comprising: 2. A backlight device comprising a light source provided along adjacent light incident end faces of a light guide plate arranged behind a display unit, wherein a corner end face of the light guide plate surrounded by the light source is semi-finished. A backlight device comprising a transparent layer. 3. The backlight device according to claim 1, wherein the light source is formed by bending an intermediate portion of the light guide plate at a substantially right angle so as to straddle adjacent light incident end faces of the light guide plate.