JP2003233071A - Backlight for liquid crystal display and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight for a liquid crystal display, which is excellent in efficiency and with which a brighter display screen is obtained. <P>SOLUTION: The direct backlight body 10 for the liquid crystal display is constructed with fluorescent tubes 14 placed side-by-side, a housing 13 to house the fluorescent tubes and a diffuser 12 arranged so as to cover an opening part of the housing. A member 15 with a refractive index approximating to that of the glass of the fluorescent tube is filled into the housing. In this case, the member 15 is a rubber-like silicone resin. Thereby efficiency of extracting light from the inside of the fluorescent tubes is improved and luminance is enhanced. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight for a liquid crystal display, which is formed by arranging a plurality of fluorescent tubes on the back surface of a display screen.

[0002]

2. Description of the Related Art Generally, liquid crystal displays are widely used as display devices such as personal computers and television monitors. Recently, in order to obtain a bright display screen, a backlight is often installed on the back surface of a transmissive liquid crystal display to perform display. In particular, in the case of color display, since a color filter is used for the liquid crystal panel, the light transmittance is lowered by using a large number of filters. Therefore, it is necessary to use a backlight. And in recent years, due to the demand for lightness and thinness of liquid crystal displays, it is thinner as a backlight,
There is a need for something that is more compact, bright, uniform, and provides uniform illumination.

FIG. 5 is a sectional view showing the outline of the basic structure of a conventional liquid crystal display backlight. The backlight shown in FIG. 5 is installed on the back surface of the liquid crystal panel unit 1, and includes a plurality of fluorescent tubes 4 arranged side by side, a housing 3 for housing these fluorescent tubes 4, and an entire opening of the housing 3. The diffusion plate 2 is arranged so as to cover it, and is called a direct type. The housing 3 is formed by bending a plate-shaped metal (SUS, Al, etc.), and has a substantially U-shaped cross section. A reflection sheet that reflects the light from the fluorescent tube 4 is attached to the inner surface of the housing 3. The diffusing plate 2 is made of a translucent resin (acrylic, polycarbonate, etc.) containing fine particles of titanium dioxide, calcium carbonate or the like, has a plate thickness of about 2 to 3 mm, and has a direct light generated from the fluorescent tube 4. It has a function of diffusing the reflected light reflected by the reflecting sheet by scattering the contained fine particles. Due to this light diffusion function of the diffusion plate 2, it is possible to obtain uniform illumination without unevenness in brightness. The distance W between the fluorescent tubes 4 is 25 to 30 m.
The inside of the housing 5 is filled with air.

[0004]

However, in such a conventional backlight for a liquid crystal display, the fluorescent tube is made of glass (having a refractive index of about 1.5 to 1.6), and the fluorescent tube inside the housing is used. Since the surroundings of are filled with air (refractive index is almost 1), the light generated in the fluorescent tube passes through the glass part and is radiated into the surrounding air. Since the difference is large, there is a problem in that the proportion of light that is totally reflected in the glass portion increases, and the light extraction efficiency when the generated light is extracted from the fluorescent tube decreases. For this reason, it is difficult to obtain a bright display screen because the brightness of each fluorescent tube is lowered.

Incidentally, Japanese Patent Laid-Open Nos. 5-323312 and 4-79330 disclose that the housing is filled with resin, but the former is for improving the strength of the housing. The latter is for improving the heat dissipation, and is not disclosed about the refractive index of the resin filled in any of them, therefore, it is not intended to improve the light extraction efficiency from the fluorescent tube described above. Absent.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a backlight for a liquid crystal display which is highly efficient and provides a brighter display screen.

[0007]

In order to achieve the above object, the backlight for liquid crystal display according to the present invention comprises:
A liquid crystal composed of a plurality of fluorescent tubes juxtaposed with each other, a housing for accommodating the plurality of fluorescent tubes, and a diffusion plate arranged so as to cover an opening of the housing, the fluorescent tubes being made of glass. In a backlight for a display, a refractive index close to that of the glass, preferably 1.
The inside of the housing is filled with a member having 3 to 1.8.

According to this structure, since the periphery of the fluorescent tube in the housing is filled with a member having a refractive index close to that of the glass of the fluorescent tube, light is totally reflected in the glass portion. Since the ratio becomes low and the extraction efficiency of the light generated in the fluorescent tubes is improved, the brightness of each fluorescent tube is increased and a brighter display screen can be obtained. Further, by improving the efficiency of extracting light from the fluorescent tube, the amount of heat generated together with the light from the fluorescent tube is suppressed, and the periphery of the fluorescent tube is filled with a member, so that heat dissipation is improved. There is also.

It is effective to improve the light extraction efficiency if the member is made of rubber or gel resin or liquid, or if the resin is silicon resin. Also, if the distance d between the juxtaposed fluorescent tubes is 0 <d <20 mm, the energy conversion efficiency of the fluorescent tubes can be improved, so that the brightness of the fluorescent tubes is further improved. Brighter lighting is obtained.

Further, when the pair of side walls of the housing facing each other are constituted by the lamp supporting base and the box body formed by the housing and the diffusion plate has a hermetically sealed structure, the peripheral surface of the fluorescent tube and the members are It is possible to prevent the member from leaking out from the inside of the housing as well as to have good adhesion and good light extraction efficiency.

As a method of manufacturing a backlight, a step of attaching a lamp support base having an injection port to a housing body and closely fixing contact portions thereof, a plurality of side walls in the housing formed of the lamp support base. A step of closely attaching the fluorescent tubes to the lamp support when the fluorescent tubes of the book are juxtaposed, a step of disposing a diffusion plate in the opening of the housing and closely fixing the contact portions thereof to form a box, If a liquid having a refractive index close to that of the glass of the fluorescent tube is filled into the housing from the injection port and then a process of sealing the injection port after filling the liquid, the process is easily and efficiently performed. it can.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a direct type backlight for a liquid crystal display which is a first embodiment of the present invention. As shown in FIG. 1, in this embodiment, the backlight body 10 includes a fluorescent tube 14, a housing 13, and a diffusion plate 12.
Made of. In addition, the mounting portion of each fluorescent tube 14 and the mounting portion of the diffusion plate 12 in the housing 13 are sealed and fixed, and the inside of the housing 13 is in a substantially sealed state. The housing 13 is filled with a member 15 having a refractive index close to the optical refractive index of the glass of the fluorescent tube 14, preferably a refractive index of 1.3 to 1.8.

Member 1 filled in housing 13
5 is made of rubber-like silicon resin and has a refractive index of about 1.4. Since the filled rubber-like resin has a high airtightness in the housing 13 and does not leak to the outside of the housing 13, in order to fill the inside of the housing 13 with resin as much as possible to improve the adhesiveness, A liquid material may be poured into the housing 13 to be filled therein and then cured. Other configurations and operational effects are similar to those of the conventional backlight described above.

By doing so, each fluorescent tube 14 in the housing is covered with the member 15 having a refractive index close to that of glass, and the periphery of the fluorescent tube 14 is filled with the member 15.
Since the critical angle in total reflection of the light generated in the fluorescent tube in the glass portion becomes large and the proportion of the light totally reflected in the glass portion becomes low, it becomes easy to emit light from the fluorescent tube into the surrounding member 15. The light extraction efficiency is improved. The larger the refractive index of the member to be filled, the larger the critical angle and the greater the extraction efficiency, so the larger the refractive index, the better.

Further, since the periphery of each fluorescent tube 14 in the housing 13 is filled with the member 15, and the member 15 is in contact with the peripheral surface of the fluorescent tube 14 and also with the inner surface of the housing 13, heat is generated. Is easily transmitted, and the heat generated from each fluorescent tube 14 along with the light is transmitted from the fluorescent tube 14 to the surrounding members 1.
5, and since it conducts to the housing 13, it also has excellent heat dissipation. Since the member 15 is rubber-like, its shape is stable and easy to handle.

Next, another embodiment of the present invention will be described. FIG. 2 is a sectional view of a direct type backlight according to the second embodiment. In the second embodiment shown in this figure, a member 16 made of a gel-like silicon resin is filled in the housing 13 instead of the rubber-like silicon resin, and this point is the same as the first embodiment of FIG. Is different from
Also in this case, since the degree of airtightness inside the housing 13 is high, the filled gel resin does not leak out of the housing 13 even when the backlight is set up. In this case, since the member 16 is gel-like, the adhesion between the peripheral surface of the fluorescent tube 14 and the member 16 is improved, and the light extraction efficiency is further improved.

FIG. 3 is a cross-sectional view of the third embodiment. In the third embodiment shown in this figure, the inside of the housing 13 is made of rubber-like silicon resin as in the first embodiment described above. Although filled with 15, the distance W ′ between the fluorescent tubes 14 is shorter than the distance W (see FIG. 5) between the fluorescent tubes in the conventional backlight. Note that the other configurations and operational effects are similar to those of the first embodiment.

This is because in the prior art, the brightness of the fluorescent tubes decreases because the energy conversion efficiency of the fluorescent tubes decreases due to the temperature rise due to heat generation, so the distance between the fluorescent tubes is about W = 25 to 30 mm. However, in the present embodiment, since the heat dissipation is good as described above, the temperature rise due to the heat generation due to the light emission of the fluorescent tubes 14 can be suppressed. This is because the distance W ′ can be made shorter than the distance W. The distance W'is set so that the energy conversion efficiency of the fluorescent tube 14 is optimized. In addition,
The distance W ′ (= d) between the fluorescent tubes 14 is 0 <W ′ <2
It is 0 mm.

As a result, the efficiency of extracting light from the fluorescent tube 14 is improved, the amount of the extracted light is increased, and the brightness of the fluorescent tube 14 is increased. At the same time, the energy conversion efficiency of the fluorescent tube 14 is improved. , Because the amount of light generated increases and the brightness of the fluorescent tube 14 increases, and again
Since it is possible to increase the number of the fluorescent tubes 14 arranged side by side, it is effective to obtain brighter illumination.

FIG. 4 is a schematic view of a direct type backlight according to the fourth embodiment, FIG. 4 (a) is an exploded perspective view thereof, and FIG. 4 (b) is a sectional view. In the fourth embodiment shown in these figures, the housing 13 is the rear chassis 13
a and a lamp support base 18 forming a pair of side walls of the housing 13 facing each other, the rear chassis 13a
The upper ends 21 of the both side arm portions 20 are horizontally bent outward. Further, the lamp support 18 is made of trapezoidal plate-shaped glass (or resin), and the fluorescent tubes 14 juxtaposed in the housing 13 are arranged.
Are supported and fixed by respective lamp support holes 19 provided so as to face the pair of lamp support bases 18, respectively. Each fluorescent tube 14 has a lamp support hole 1 through rubber holders (not shown) attached to both ends of the tube.
9 can be attached without creating a gap.

A cylindrical injection port 22 is provided on one side of the lamp support 18, and a member 17 made of a liquid is injected and filled into the housing 13 through the injection port 22. The member 17 filled in the housing 13 has a refractive index close to that of the glass of the fluorescent tube 14, has a high insulating property, and is excellent in translucency. It is oil etc. In addition, each part, the lower surface 23a of both ends of the diffusion plate 12 and the rear chassis 13
the upper surface 23a of the upper end portion 21 of both side arm portions 20a of the a, the diffusion plate 1
2 and the upper surface 2 of each lamp support base 18
3b, side and bottom surfaces 23c of each lamp support base 18 and side surface joints 23c of the rear chassis 13a, each lamp support hole 1
9 are adhesively sealed with an adhesive or the like, and the inside of the housing 13 has a closed structure. The inlet 22
After the member 17 is injected and filled into the housing 13, the member 17 is welded and the tip portion thereof is cut off. Other configurations and operational effects are similar to those of the first embodiment, and FIG.
In (a), the fluorescent tube 14 is omitted.

In this way, the member 17 filled in the housing 13 does not leak to the outside, and since the member 17 is made of liquid, it has excellent adhesion to the peripheral surface of the fluorescent tube 14. Therefore, the light extraction efficiency is high, and the heat dissipation due to heat conduction is also excellent.

The method of manufacturing the above-mentioned backlight according to the fourth embodiment will be described below. The manufacturing procedure consists of four steps. (1) The fluorescent tubes 14 are arranged in the housing 13, and the fluorescent tubes 14 are connected to the lamp supporting holes 1 of the pair of lamp supporting bases 18.
9 is closely attached to and fixed to the diffuser plate 12
Is placed in the opening of the housing 13. (2) Each part, the lower surfaces 23a of both ends of the diffusion plate 12 and the upper surfaces 23a of the upper ends 21 of the both side arm parts 20 of the rear chassis 13a,
The lower surface 23b of both end portions of the diffusion plate 12 and each lamp support base 18
Upper surface 23b of the lamp, side surfaces and lower surfaces 23 of the lamp support bases
c, the side surface joints 23c of the rear chassis 13a, and the lamp support holes 19 are adhesively sealed with an adhesive or the like, so that the diffusion plate 12, the rear chassis 13a, and the lamp support base 18 are integrated. (3) The member 17 is injected and filled into the housing 13 through the injection port 22. (4) After filling, the injection port 22 is sealed by welding and the tip portion is cut off.

[0024]

As described above, in the backlight for a liquid crystal display of the present invention, by filling the housing with a member having a refractive index close to that of glass, the efficiency of extracting the generated light is improved and the fluorescent tube. Since the brightness of the is increased, brighter illumination was obtained. Further, since the periphery of the fluorescent tube is filled with the member, the heat dissipation is also good.

[Brief description of drawings]

FIG. 1 is a sectional view of a backlight for a liquid crystal display which is a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the second embodiment of the present invention.

FIG. 3 is a sectional view of a third embodiment of the present invention.

FIG. 4 is a view showing a backlight which is a fourth embodiment of the present invention, (a) is an exploded perspective view, and (b) is a sectional view.

FIG. 5 is a sectional view of a conventional backlight.

[Explanation of symbols]

10 Backlight body 12 Diffuser 13 housing 14 Fluorescent tube 15, 16, 17 members 18 lamp support 22 Inlet

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mitsuto Kobayashi             3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori             Sanyo Electric Co., Ltd. (72) Inventor Hiroki Sakamoto             3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori             Sanyo Electric Co., Ltd. (72) Inventor Junya Mita             3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori             Sanyo Electric Co., Ltd. (72) Inventor Yuki Muraoka             3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori             Sanyo Electric Co., Ltd. (72) Inventor Satoshi Hayano             3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori             Sanyo Electric Co., Ltd. (72) Inventor Akio Tanishige             3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori             Sanyo Electric Co., Ltd. (72) Inventor Mitsuru Matsumoto             3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori             Sanyo Electric Co., Ltd. (72) Inventor Tetsuyuki Ishida             3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori             Sanyo Electric Co., Ltd. F-term (reference) 2H091 FA32Z FA42Z FB02 FD22                       KA01 LA16 LA17                 3K014 AA02 LA04 LB04

Claims (8)

[Claims] 1. A fluorescent tube comprising a plurality of fluorescent tubes arranged in parallel, a housing for accommodating the plurality of fluorescent tubes, and a diffusion plate arranged so as to cover an opening of the housing. A backlight for a liquid crystal display, wherein the backlight is made of glass, and the inside of the housing is filled with a member having a refractive index close to that of the glass. 2. The refractive index of the member is 1.3 to 1.8.
The backlight for a liquid crystal display according to claim 1, wherein the backlight is in the range. 3. The backlight for a liquid crystal display according to claim 1, wherein the member is a rubber-like or gel-like resin. 4. The backlight for a liquid crystal display according to claim 3, wherein the resin is a silicone resin. 5. The backlight for a liquid crystal display according to claim 1, wherein the member is liquid. 6. A distance d between the juxtaposed fluorescent tubes.
Is 0 <d <20 mm.
5. The backlight for liquid crystal display according to any one of items 5 to 5. 7. The pair of side walls of the housing, which face each other, are constituted by a lamp support, and the box formed by the housing and the diffusion plate is hermetically sealed. 6. The backlight for liquid crystal display according to any one of 6. 8. A step of attaching a lamp support base having a pouring port to a housing body and closely fixing the contact portion thereof.
When a plurality of fluorescent tubes are juxtaposed in the housing having a pair of side walls formed by the lamp support, the fluorescent tubes are closely attached to the lamp support, and a diffusion plate is arranged in the opening of the housing. Together with the step of closely fixing the contact portion to form a box, the step of filling a liquid having a refractive index close to that of the glass of the fluorescent tube into the housing from the inlet, and the step after filling the liquid And a step of sealing the injection port.