JPH07235207A - Backlight - Google Patents

Abstract

PURPOSE:To thin a back light and prevent light leakage by making the opening width of a reflecting cover almost the same with the thickness of a light diffusing plate end face, in a structure wherein light is made incident from the side face of the diffusing plate having a reflecting face on its bottom and radiated out of the face opposite to the reflecting face. CONSTITUTION:LED light R emitted out of a LED element 4 goes straight or is reflected on a reflecting sheet 11 or a reflecting end face 1a to be incident upon a diffusing plate 12. The light R is repeatedly reflected between the inner face of a radiating face 18 and a diffusing face 13, which is the bottom of the diffusing plate and the light reaches the radiating face 18 at critical angle or more is radiated to the outside. In this case, a gradation pattern is formed in the diffusing face 13 due to a large number of projected parts formed more densely as the distance from the element 4 is larger and the light is diffused and reflected efficiently and at the same time the brightness of the light R is made uniform. With this structure, since the width X of the opening part of a reflecting cover 1 in the light emitting part and the thickness (t) of the diffusing plate 12 are set almost equal to each other, the gap between them is eliminated to thin the structure and the light R is prevented from leaking outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight of a liquid crystal display section having an LED light source, for example.

[0002]

2. Description of the Related Art Conventionally, many backlights used for illuminating a liquid crystal display unit have been proposed. For example, as shown in FIG. 10, the backlight 100 ′ is L
The ED element 4, the reflection cover 1 ′, and the diffusion plate 12 are provided. The LED element 4 fixes the LED element 4 on the substrate 5, and also fixes it to a part of the reflection cover 1 ′ that reflects the LED light R. The reflection cover 1 ′ is fixed on the substrate 5. The LED element 4 is electrically connected to the lead frame 6 via the lead wire 3. LE
D light source 4 is a COB LED array, LED lamp, L
An ED chip lamp or the like is used. L emitted from the light source
The ED light R is reflected by the reflection sheet 11 and the diffusion surface 13 of the diffusion plate 12.
It is emitted to the outside while reflecting between the. In this way, the diffuser plate 12 functions as a surface light source. Moreover, the total thickness of the conventional backlight is larger than the plate thickness t ′ of the diffusion plate.

[0003]

However, in the conventional example configured as described above, the total thickness of the backlight is limited to a width of at least about 1.5 mm when an LED chip or a COB array is used. However, it has a drawback that it is not suitable as a backlight with a total thickness of about 0.8 mm which is currently required.

Further, in the conventional backlight, the opening width of the light emitting portion reflection cover is wide, and there is a gap between the reflection end surface of the light emitting portion reflection cover and the end surface (emission surface 18) of the diffusion plate 12. It had to be forced. For this reason,
There is a problem that the leakage of light cannot be prevented and the amount of light emitted from the LED is wasted. Therefore, the backlight of the present invention has been made in view of the above circumstances, and an object thereof is to make the total thickness thinner and downsize,
An object of the present invention is to provide a backlight having high light transmission efficiency that prevents leakage of emitted light.

[0005]

In order to solve the above-mentioned problems and to achieve the object, a backlight of the present invention is provided with a light source from a side edge portion of a light diffusing plate member having a reflecting surface on a bottom surface. A backlight for allowing light to enter and to exit from a surface of the light diffusing plate member opposite to the reflecting surface, which is on a space portion formed between a reflection cover holding the light source and the side edge portion. It is characterized in that the distance between the reflecting surfaces provided on the lower surface is made substantially equal to the plate thickness of the light diffusing plate member.

Further, preferably, the reflection cover is formed to have substantially the same thickness as the plate thickness, and a light emitting reflection part for reflecting light from the light source to the light diffusion plate member side and a space part. The light diffusing plate member is characterized in that the light diffusing plate member is fitted in a recess formed in a side edge portion of the light diffusing plate member.

[0007]

Since the backlight according to the present invention is configured as described above, the total thickness can be made thinner and smaller by making the opening width of the reflection cover and the thickness of the end surface of the diffuser plate equal. It is possible to provide a backlight with high light transmission efficiency that prevents leakage of emitted light.

[0008]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is an external view of the backlight of this embodiment. 2 is a plan view of the assembled state of FIG. FIG. 3 is a perspective view showing a configuration of a diffusion plate and a reflection sheet. FIG. 4 is a front view of the light emitting unit reflection cover 1 of FIG. 1. FIG. 5 is a plan view of FIG. 4. FIG. 6 is a side view of the light emitting unit reflection cover 1. Hereinafter, referring to FIGS. 1 to 6,
The structure of the backlight of this embodiment will be described. As shown in FIG. 1, the backlight 100 has an outer shape configured by fitting the light emitting unit reflection cover 1 and the diffusion plate 12 together. At the time of assembling, the fixing projections 15 extending on both side surfaces 9 of the light emitting section reflection cover 1 and the recesses 16 provided on the diffusion plate 12 are fitted to each other to fix them. Further, on the upper part of the reflection cover 1, a collar portion 14 protruding from the side surface portion 9 is formed on both sides, and by this collar portion 14,
The reflective cover 1 is in contact with the diffuser plate 12 so that the reflective cover 1 does not fall downward. Further, the backlight 100 mounts the reflection sheet 11 (see FIG. 3), the light emitting section reflection cover 1 for fixing the LED element 4, and the LED element 4,
A lead frame 6 that is electrically connected via the lead wire 3 and a diffuser plate 12 that reflects and diffuses LED light are provided (see FIG. 4). In addition, the backlight 100 is an LED
It is a backlight provided with two elements 4. The light emitting section reflection cover 1 has a light emitting surface 1b for fixing the reflection section end face 1a, the side surface section 9, the LED element 4 and the lead frame branch section 8.
And a lens 2 that allows the light emitted from the LED element 4 to pass therethrough. The lens 2 is the LED element 4
Is a concave lens. The light emitting part reflection cover 1 is
It is made of PBT mixed with glass material. Further, the reflection cover 1 is configured so that the LED light can be reflected by the reflection end surface 1a and the light emitting surface 1b. Further, a lead frame 6 is interposed between the light emitting unit reflection cover 1 and the reflection sheet 11, and the lead frame for fixing the LED element 4 and the light emitting element 4 are electrically connected via the lead wire 3. The respective lead frames are soldered to the external substrate 5 (see FIGS. 7 and 8) and connected.
The lead frame 6 is preferably made of a flexible material, and is provided so as to be bendable as described later. A diffusion plate 12 is attached to the upper surface of the reflection sheet 11 and faces the opening of the light-emitting reflection cover 1. As shown in FIG. 3, the diffuser plate 12 is provided with a side surface edge portion 14 through which LED light enters, an emission surface 17 on the upper surface portion, and the reflection sheet 11 is attached to the bottom surface portion. The diffusion plate 12 has a certain thickness t.
The light guide path is formed between the emission surface 18 and the reflection sheet 11 so that the LED light is effectively diffused and reflected and emitted. The diffusion surface 13 on the bottom surface of the diffusion plate 12 is formed such that a large number of convex portions become denser as the distance from the side closer to the LED element 4 increases, and a so-called gradation pattern is formed by the convex portions.
It is designed to efficiently diffuse and reflect light. The reflection sheet 11 is made of a flexible material and has the same area as the diffusion plate 12. Then, as shown in FIG. 1, the reflection sheet 11 is fixed to the back surface of the diffusion plate 12 with an adhesive C after the reflection cover 1 is fixed to the diffusion plate 12. Incidentally, one surface S of the reflection sheet 11
Form a reflective surface having a high reflectance.

Further, as shown in FIG. 9 which will be described later, the opening of the light emitting part reflection cover 1 (the reflection part end face 1a and the reflection sheet 1).
The width X (the portion between 1) and the thickness t of the diffusion plate 12 are set to be equal. In FIG. 5, two L's
An extension portion 10 extending from the reflection cover 1 is provided between the ED element 4 and the ED element 4 to reinforce the reflection cover 1 and
It is provided so that the LED light from the two LED elements 4 passes through the lens 2 and then is reflected in the direction of the side surface end portion 17 of the light guide plate 12 to efficiently emit light. The above is the overall configuration of the backlight of this embodiment.

Next, with reference to FIGS. 4 to 6, an assembling process of the backlight of this embodiment will be described. 4 to 6, the lead frame 6 shown in FIG. 4 includes a lead frame branching portion 8 that branches from a lead frame body (not shown) into four. At the end portion of the lead frame branch portion 8, a mounting portion on which the LED element 4 is mounted together with the lead wire 3 and an extension portion further extended from the end portion are provided. To include this lead frame branching section 8,
The light emitting portion reflection cover is molded with the PCB resin mixed with the glass described above (insert molding step).

Next, the extension portion 6 of the lead frame branch portion 8
6 is bent in the direction of the arrow Y, as shown in FIG. Process). In this state, among the four lead frame branch portions 8, the LED chips 4 are respectively bonded to the ends of the two branch portions, and the lead wires 3 are bonded to the other two ends (bonding step). ).

After that, the LED chip 4 and the lead wire 3 are potted to protect them and hardened (potting step). Finally, after cutting off unnecessary portions of the lead frame branching portion 8, product inspection is performed to complete the reflection cover 1 of this embodiment (lead frame cutting step and inspection step).

The backlight of this embodiment is manufactured through the above steps. In addition, the reflection cover 1 and the diffusion plate 1
As shown in FIG. 7, the lead frame 6 protruding rearward in the step of bending the terminal portion after fixing
It is soldered on or inserted into a hole formed in the substrate as shown in FIG. 8 and then soldered and electrically connected.

Next, the optical operation of the backlight of this embodiment will be described. FIG. 9 is a schematic side view of the backlight of this embodiment. In FIG. 9, the LED light R emitted from the LED element 4 goes straight on and enters the diffusion plate 12, or the reflection sheet 11 or the reflection end surface 1
After being reflected by a, they are incident on the diffusion plate 12. The surface of the reflective sheet 11 on which the LED light R is reflected is a reflective surface having a high reflectance as described above. Here, the diffusion plate 1
The LED light R incident on the light source 2 is emitted from the emission surface 18 of the diffusion plate 12.
The light is repeatedly guided between the inner surface of the diffusion plate 13 and the reflection sheet 11 and is guided in the diffusion plate 12 in the direction opposite to the LED element 4. On the way, the light reaching the emitting surface 18 at a critical angle or more is emitted from the emitting surface 18 to the outside. In the process, the light that reaches the irregular reflection portion formed of the convex portion provided on the diffusion surface 13 is irregularly reflected toward the emission surface 18 side there. Therefore, the protrusions are so dense as to move away from the LED element 4, so that only the portion near the LED element does not become bright, and the LE up to the emission surface 18 side.
The D light is formed to be uniform.

(Effects of the Embodiment) As described above, the width X of the opening of the reflection cover 1 is processed to be equal to the plate thickness t of the diffusion plate 12, and the reflection sheet 11 is assembled as a base portion to form the diffusion plate. It is possible to prevent the LED light R from leaking to the outside by eliminating the gap generated between 12 and the light emitting section reflection cover 1.

Further, since the leakage can be prevented, it is possible to prevent the variation in the brightness of the light emitted from the emission surface 18. Further, the lower frame portion of the reflection cover is removed and directly fixed to the reflection sheet 11 so that the width of the opening and the thickness of the diffusion plate are the same, so that the backlight can be downsized.

Further, since it is manufactured by resin insert molding, it is possible to minimize variations in processing accuracy in mass production. The present invention can be applied to the modified or modified embodiment described above without departing from the spirit of the invention. For example, although the configuration of the backlight of the liquid crystal display used for a small device such as a handy terminal or a pager has been described as the application of the present embodiment, it is not limited to this. Further, the roughening of the diffusion surface is not limited to the projection gradation pattern formed by integral molding, and it is also possible to use a gradation pattern for printing a white ink dot pattern or roughening by hairline processing. Needless to say.

[0018]

As described above, according to the backlight of the present invention, by making the opening width of the light emitting section reflection cover and the thickness of the end surface of the diffusion plate equal, the total thickness can be made thinner and the size can be reduced. Therefore, there is an effect that it is possible to provide a backlight having high light transmission efficiency that prevents leakage of emitted light.

[Brief description of drawings]

FIG. 1 is a perspective view showing an outline of a backlight of this embodiment.

FIG. 2 is a plan view of a backlight of this embodiment.

FIG. 3 is a perspective view showing a configuration of a diffusion plate and a reflection sheet.

FIG. 4 is a front view of a light emitting unit reflection cover.

FIG. 5 is a plan view of FIG.

FIG. 6 is a side view of FIG.

FIG. 7 is a diagram showing an example of a mounting form when mounting the backlight of the present embodiment on a substrate.

FIG. 8 is a diagram showing an example of a mounting form when mounting the backlight of the present embodiment on a substrate.

FIG. 9 is a side view showing the outline of the backlight and the operating principle of light according to the present embodiment.

FIG. 10 is a side view showing the outline of a conventional backlight and the operating principle of light.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light emitting part reflective cover 1a Reflective end face 1b Reflective side face 2 Lens 3 Lead wire 4 LED element 5 Mounting board 6 Lead frame 8 Lead frame branching part 9 Reflective cover side part 10 Reflective cover extension part 11 Reflective sheet 12 Diffuser 13 Diffuse surface t Diffuser thickness R Light from light source

Claims (2)

[Claims] 1. A backlight for allowing light of a light source to enter from a side edge portion of a light diffusing plate member having a reflecting surface on a bottom surface and to emit light from a surface opposite to the reflecting surface of the light diffusing plate member. And making the distance between the reflection surfaces arranged on the upper and lower surfaces of the space formed between the reflection cover holding the light source and the side edge substantially equal to the plate thickness of the light diffusion plate member. Backlight characterized by. 2. The reflection cover is formed to have substantially the same thickness as the plate thickness, and a light emitting reflection part for reflecting light from the light source to the light diffusion plate member side; and upper and lower surfaces of the space part. The backlight according to claim 1, further comprising a flange portion that covers at least one of the flange portions, the flange portion being fitted in a concave portion formed in a side edge portion of the light diffusion plate member.