JPH05196934A - LCD lighting device - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent uneven brightness due to temperature differences on the display surface. [Structure] The electrode portion of the tubular light source 12 is covered with a heat-dissipating insulating material 17, and the portion of the light source protector 13 corresponding to the insulating material 17 is hollowed out to efficiently dissipate heat from the electrode portion to the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal lighting device used in a liquid crystal display device such as a word processor or a personal computer.

[0002]

2. Description of the Related Art FIG. 2 is an exploded perspective view of a conventional liquid crystal lighting device, FIG. 3 is a perspective view of a tubular light source, and FIG. 4 is an external perspective view showing an example in which the liquid crystal lighting device is used in a desk-top computer. .. In FIGS. 2 and 3, 1 is a light guide plate, 2 is a tubular light source, 3 is a light source protector for covering the tubular light source 2, 4 is a diffusion plate, and 5 is a plastic or metal chassis. Also, FIG.
Among them, P1 is a display unit having a built-in liquid crystal lighting device, P2 is an upper cabinet for housing the same, and P3 is a lower cabinet.

Conventionally, a cold cathode fluorescent tube (CCFT) is used as a tubular light source 2 used in a liquid crystal lighting device (backlight), and in order to insulate and protect a lead wire 6 from an electrode portion in the tube, FIG. As shown in FIG. 7, the structure was such that the cap 7 made of silicone resin was used for covering.

Further, as the liquid crystal lighting device, as shown in FIG. 2, the entire length of the tubular light source 2 is covered with a light source protector 3 made of plastic. This is to prevent the tubular light source 2 from being damaged in a carrying process or the like before being incorporated in the display portion P1 as shown in FIG.

[0005]

Generally, the electrode portion of the tubular light source 2 has a heat generating property. Conventionally, since the entire length of the tubular light source 2 is covered with the light source protector 3, heat is accumulated in the light source protector 3, and this heat is transmitted to the liquid crystal display panel (LCD panel), and the threshold voltage of the liquid crystal in that portion is changed. When the image locally drops and becomes whiter than the other parts of the LCD panel, it causes so-called uneven contrast.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a liquid crystal lighting device that does not cause uneven contrast on the display surface.

[0007]

As shown in FIG. 1, the means for solving the problems according to the present invention is to illuminate the liquid crystal display panel from the rear side, and the tubular light source 12 is provided outside the effective display area L of the liquid crystal display panel. Is disposed around the tubular light source 12, and a hard light source protector 13 that protects the tubular light source 12 from an external force and reflects the light from the tubular light source 12 outside the effective display region L to the effective display region L side. In the provided liquid crystal lighting device, the electrode portion of the tubular light source 12 is covered and protected by an insulating material 17 having a heat dissipation property, and the heat from the insulating material 17 is radiated to both ends of the light source protector 13 to the outside. The heat-dissipating notch 22 is formed.

[0008]

In the above means for solving the problems, the heat generated in the electrode portion of the tubular light source 12 is effectively radiated to the outside from the heat radiation notch 22 of the light source protection body 13 through the insulating material 17 having a heat radiation property. ..

At this time, the electrode portion of the tubular light source 12 is made of the insulating material 1.
7, the light source protector 13 except the electrode part of the tubular light source 12 is provided.
Are mechanically protected from external forces.

[0010]

FIG. 1 is an exploded perspective view of a liquid crystal lighting device showing an embodiment of the present invention.

As shown in the figure, the liquid crystal lighting device of this embodiment illuminates the liquid crystal display plate from the rear by a light guide method, and is a light guide plate disposed on the chassis 10 in parallel with the liquid crystal display plate. 11, a tubular light source 12 arranged at one end of the light guide plate 11 outside the effective display area L of the liquid crystal display plate, and a tubular light source 12 arranged near the tubular light source 12 to protect the tubular light source 12 from external force and to provide an effective display area. A light source protector 13 for reflecting light that goes out of L to the effective display area L side, and the light guide plate 11
And a diffusion plate 14 for making the brightness of the upper illumination surface uniform over the entire surface.

As in the conventional case, the chassis 10 is made of a plastic material or a metal such as aluminum.
1, the tubular light source 12 and the like are formed in a substantially square shape in a plan view so as to support the four sides.

The light guide plate 11 has, for example, a total light transmittance =
It is formed in a rectangular flat plate shape using an acrylic resin of 93% and a refractive index n = 1.49. Here, the arrangement area of the light guide plate 11 is directly used as the effective display area L.

A reflective sheet (not shown) is adhered to the rear surface of the light guide plate 11 for reflecting the backward light inside the light guide plate 11 toward the liquid crystal display plate.

As the tubular light source 12, for example, a cold cathode fluorescent tube (CCFT) having electrode portions at both ends of a glass tube is used.

Both electrode portions of the tubular light source 12 are made of an insulating material 17.
Insulation protection is provided by the (protection cap). Here, since the electrode portions at both ends of the tubular light source 12 have the heat generating property as in the conventional case, it is necessary to secure the heat dissipation thereof. Therefore, it is desirable that the insulating material 17 has the heat dissipation property. The insulating material 17 is exposed from a heat-dissipating notch 22 described later, but when the liquid crystal lighting device is transported before being assembled into the liquid crystal display device, the electrode part of the tubular light source 12 is protected from external force. Since it is necessary to protect the insulating material 17, it is preferable to use a hard material for the insulating material 17. In view of these, as the insulating material 17, specifically, a silicone resin using alumina particles having a good thermal conductivity as a filler is used.

The light source protector 13 is made of a plastic material that is hard and has a high reflectance. The light source protector 13 is arranged so as to surround the tubular light source 12 in front of and behind it, and to the chassis 10 with screws 21.
Fixed by etc. A heat radiation notch 22 for radiating heat from the insulating material 17 to the outside is formed in a portion of the light source protector 13 near the insulating material 17.

The diffusion plate 14 is made of a milky white resin film.

In the figure, reference numeral 18 is a lead wire for supplying electric power to the electrode portion, and 19 is a connector for external connection.

When the liquid crystal lighting device having the above-described structure is incorporated in the display portion P1 of an external device as shown in FIG. 4, from the process of assembling the tubular light source 12 to the process of assembling a liquid crystal display plate (not shown). In addition, some transfer process must be performed. At this time, since the light source protector 13 is formed of a hard plastic material, it is easier to protect the tubular light source 12 from external force as compared with the case where a soft reflecting sheet is used instead of the light source protector 13, and the yield is improved. Can improve.

Further, when the tubular light source 12 is made to emit light when used by being incorporated in the display portion P1 or the like of an external device, the light radiated inward directly enters from the light incident end face of the light guide plate 11 to the inside thereof. .. On the other hand, the light from the tubular light source 12 to the outside is reflected inward by the light source protector 13 and then enters the inside from the light incident end surface of the light guide plate 11.

After that, the incoming light is distributed to the front diffusion plate 14 while repeatedly reflecting inside the light guide plate 11. Then, the light uniformly distributed is radiated to the back surface of the liquid crystal display plate through the diffusion plate 14.

At this time, the electrode portions of the tubular light source 12 generate heat. When this heat is transferred to the liquid crystal display panel through the light source protector 13, the threshold voltage of the liquid crystal in that portion drops,
Contrast unevenness, that is, a whiteout phenomenon occurs, but in this embodiment, since the heat radiation notch 22 is formed in the vicinity of the electrode portion of the light source protector 13, the heat from the electrode portion is not heat radiation 22. Heat is radiated from the outside to the light source protector 13
The temperature is stable, and the threshold voltage of the liquid crystal display panel can be stabilized. Therefore, the display quality of the liquid crystal device using the liquid crystal lighting device can be improved.

Moreover, since the insulating material 17 for protecting the electrode portion is made of a material having a high heat dissipation property, the tubular light source 12
It is possible to radiate heat from the heat radiating notches 22 without the heat being totally trapped, and thus the display quality can be further improved.

In practice, the liquid crystal lighting device is arranged behind the liquid crystal display panel in a state of actual use, and the contrast (luminance ratio) between the central portion of the display surface of the liquid crystal display panel and the portion in the vicinity of the tubular light source 12 on the display surface. As a result of the comparison of (1), it was 1.3 in the present example, compared with 1.6 in the conventional case, and the contrast unevenness was significantly improved.

The present invention is not limited to the above embodiment, and it goes without saying that many modifications and changes can be made to the above embodiment within the scope of the present invention.

For example, although the light guide type using the light guide plate has been described in the above embodiment, the light guide type does not use the light guide plate as long as the liquid crystal display plate is arranged outside the effective display area. May be.

Further, in FIG. 1, the notch 22 is provided with a light source protector 1.
Although the example in which the light source protector 13 is formed only at the local parts at both ends is shown, it goes without saying that the notches 22 may be formed in such a manner that both ends of the light source protector 13 are shortened.

[0029]

As is apparent from the above description, according to the present invention, in the liquid crystal lighting device using the hard light source protector around the tubular light source, the electrode part of the light source is covered with the insulating material having the heat dissipation property. Since the heat radiation notch is formed in the portion of the light source protector corresponding to the insulating material, the heat from the electrode portion can be efficiently radiated to the outside.

Moreover, since the light source protector is made of a hard material, the above heat dissipation can be achieved while protecting the tubular light source.

Therefore, it is possible to prevent defects due to damage to the light source during assembling work, etc., and to prevent the drop in the threshold voltage of the liquid crystal during use to reduce the contrast unevenness due to the white spot phenomenon. It has an excellent effect.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a liquid crystal lighting device showing an embodiment of the present invention.

FIG. 2 is an exploded perspective view of a conventional liquid crystal lighting device.

FIG. 3 is a perspective view of a conventional tubular light source.

FIG. 4 is an external perspective view showing an example in which a lighting device for liquid crystal is used in a desktop computer.

[Explanation of symbols]

 12 tubular light source 13 light source protector 17 insulating material 22 notch for heat dissipation

Claims (1)

[Claims] 1. A liquid crystal display panel is illuminated from the rear side, wherein a tubular light source is disposed behind the effective display area of the liquid crystal display panel, and the tubular light source is protected from an external force around the tubular light source. In a liquid crystal lighting device provided with a hard light source protector that reflects light from the tubular light source to the outside of the effective display area toward the effective display area side, the electrode part of the tubular light source is covered with an insulating material having a heat dissipation property. A liquid crystal lighting device, which is protected, and has heat dissipation notches formed at both ends of the light source protector for radiating heat from the insulating material to the outside.