JPH10104623A - Backlight for LCD - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain lighting of higher luminance than that obtained by using a light shield plate without partially lowering the luminance of a fluorescent tube by passing part of the light emitted by a light source through a light guide plate which is obliquely arranged. SOLUTION: The light guide plate 4 is arranged slantingly above so that part of the light emitted by a fluorescent tube 8 can pass through the light guide plate 4. In the back light body 1, the whole of the light emitted by the fluorescent tube 8 is not made incident directly on the diffusion plate and part of the light passes through the light guide plate 4 and is projected from the upper end surface of the light guide plate 3 and diffused to selectively irradiate a position which is far away from the fluorescent tube 8 and low in luminance. The degree of diffusion of this light is only adjusted according to the finish state of the upper end surface. Consequently, the back light body 1 decreases in high/low difference in luminance due to the difference in the distance of a diffusion plate from the fluorescent tube 8, so that the entire surface of the diffusion plate can be irradiated nearly uniformly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal backlight having high brightness over the entire surface of a diffusion plate.

[0002]

2. Description of the Related Art A liquid crystal is a material having properties of both a solid and a liquid, and is widely used as a liquid crystal display by utilizing a property that a color tone and a light transmittance change with an appropriate temperature change or voltage. . In general, liquid crystal displays can be designed inexpensively and compactly. Small ones are used for digital clocks and dials of calculators and display panels for measuring instruments, and large ones are used for screens such as portable personal computers, word processors and LCD televisions. is there.

A liquid crystal display emits an image by transmitting and reflecting external light, and therefore generally consumes little power except for a color liquid crystal. However, it does not emit light without external light, so it cannot be seen at all in a dark place. For this reason, a liquid crystal display requires auxiliary lighting called a backlight.

[0004]

The backlight of a liquid crystal display has a light source disposed behind it and an original backlight body for directly illuminating the entire surface of the display uniformly, and a light source disposed on a side edge thereof. Through the transparent light guide plate,
An edge light body that emits light from the surface of the light guide plate. The original backlight body has a light source located behind the liquid crystal display, so the entire display becomes thicker, but it is excellent in that it illuminates the entire display with higher brightness and uniformity, and is mainly used as auxiliary lighting. ing.

In a conventional backlight body, fluorescent tubes are arranged in a meandering manner on a reflection plate behind a liquid crystal display,
Light from the fluorescent tube is diffused by passing through a diffuser having an uneven surface to illuminate the entire display. In this illumination method, only the fluorescent tube portion is strongly illuminated and rises white.Therefore, by interposing a light-shielding plate below the diffusion plate, only the fluorescent tube portion is appropriately shielded to make the brightness of the entire display uniform. I have. The light-shielding plate is partially colored so as to shield only the fluorescent tube portion, and the brightness of the backlight is partially reduced by the light-shielding plate.

On the other hand, it is necessary to illuminate a liquid crystal display with as high a brightness as possible in order to obtain a bright screen.
The demands of users for high-brightness lighting become even stronger. However, simply increasing the lux of the fluorescent tube in order to obtain high-luminance illumination has limitations in terms of heat generation and power consumption of the fluorescent tube. It is desirable to obtain illumination.

The present invention has been proposed in order to solve the above-mentioned problems relating to the backlight unit for liquid crystal, and has higher luminance than using a light shielding plate without partially lowering the luminance of the fluorescent tube. It is an object of the present invention to provide a backlight body that obtains the illumination of the above. Another object of the present invention is to provide a liquid crystal backlight body which can illuminate the entire surface of a display substantially uniformly with a simple structure.

[0008]

In order to achieve the above object, a liquid crystal backlight unit 1 according to the present invention comprises a light source located on a reflection plate 2 and a light source located on a reflection plate 2 as shown in FIG. A light guide plate 4 disposed diagonally above and around the
And a diffusion plate 6 (FIG. 3) covering the reflection plate 2. The light source used is a fluorescent tube 8 or a lamp. To cover the entire surface of the wide reflecting plate 2 with these, the fluorescent tube 8 meanders as shown in FIG. .

In the present invention, the light guide plate 4 is disposed obliquely upward so that a part of the light emitted from the light source can pass through the light guide plate. In the backlight body 1, all light emitted from the light source does not directly enter the diffusion plate 6,
Part of the light passes through the light guide plate 4, exits from the upper end face of the light guide plate, is diffused, and selectively irradiates a position far from the light source and having low luminance. The degree of diffusion of the light may be adjusted according to the manner of finishing the upper end face. As a result, in the backlight body 1, the difference in the luminance level due to the difference in the distance from the light source in the diffusion plate 6 is reduced, and the entire surface of the diffusion plate can be irradiated substantially uniformly.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Backlight body 1 for liquid crystal of the present invention
As shown in FIG. 2, a heat-resistant reflective plate 2 is provided. The plate is usually made of a plastic such as white or silver and has a size corresponding to the screen of the liquid crystal display 10. When the fluorescent tube 8 as a light source has a large surface area such as a liquid crystal display 10 such as a notebook computer 12 (FIG. 1), a car navigation system, a word processor or a television, the fluorescent tube 8 meanders so as to illuminate the entire surface of the display. On a small display panel 14 (see FIG. 5) used for a dial of an alarm clock, a display panel of a calculator or a measuring instrument, etc., the vehicle goes straight. When the fluorescent tube 8 is meandered, the interval between the parallel tubes and the meandering shape are determined according to the desired brightness and dimensions of the liquid crystal display 10.

The light guide plate 4 used in the present invention is made of a transparent plastic or glass having excellent light transmittance so that light passing through the light guide plate can be emitted from the upper end face 16 (FIG. 3) and diffused. In addition, it is preferable to finish the end face with fogging. The side shape of the light guide plate 4 may be a linear shape as shown in the drawing,
The curved reflecting plate 2 may be curved along the bottom wall. The light guide plate 4 is, as illustrated in FIG.
If the plate material is adhered or fixed to the light guide plate, the plate material may be made of a polycarbonate resin or an acrylic resin different from that of the reflection plate 2, and the light guide plate may have an inclined end surface or a slightly curved surface.

When the light guide plate is fixed to the reflection plate 2, the light guide plate is a plate-shaped molded product, and a projection of the molded product is inserted into a hole of the reflection plate or reflected by the hole of the molded product. What is necessary is just to insert in the protrusion of a plate. Further, this light guide plate may be formed integrally with the reflection plate 2,
In this case, only the portion of the light guide plate needs to be transparent by partial coloring.

The light guide plate 4 may be disposed obliquely upward on both sides along the fluorescent tube 8. In the case of a spot-shaped light source lamp, the light guide plate 4 is installed in an inverted conical shape surrounding the lamp. Plates are juxtaposed on both sides along the fluorescent tube.
The light guide plate 4 is mounted on the reflecting plate bottom wall 1 so that a part of the light emitted from the fluorescent tube 8 can pass through the light guide plate.
If it is arranged along the eight V-shaped grooves 20 (FIG. 3), it may be bonded, fixed or integrated with the inclined portion of the V-shaped bottom wall of the reflection plate. The groove 20 of the plate bottom wall 18 may be a shallow V-shape as shown, or may be a curved surface so as to reflect light evenly. If the fluorescent tubes are mounted on a flat reflecting plate, the light guide plates may be set so as to be positioned obliquely above the fluorescent tubes by a predetermined mounting plate (not shown).

The diffusion plate 6 used in the present invention is generally a milky white flat plastic plate, and its material is acrylic resin, polyvinyl chloride resin, or the like. At least one surface of the diffusion plate 6 is formed into fine irregularities so that light transmitted through the diffusion plate is widely dispersed. Diffuser 6
Has a size corresponding to the screen of the liquid crystal display 10 covering the entire surface of the fluorescent tube 8 on the reflection plate 2.

[0015]

Next, the present invention will be described based on examples, but the present invention is not limited to the examples. The backlight unit 1 for a liquid crystal according to the present invention, as shown in FIG.
A white reflective plate 2 having a substantially rectangular flat surface is provided, and the plate is a liquid crystal display 10 of a notebook computer 12 (FIG. 1).
Has a surface area equivalent to that of the screen. The bottom wall 18 of the reflection plate 2 has a number of shallow V-shaped grooves 20 as shown in FIG.
Are formed in parallel, and each V-shaped groove is curved and connected in a semicircular plane on both sides of the plate, so that the V-shaped groove 20 as a whole meanders in the plate plane.

The fluorescent tube 8 as a light source is an elongated rod tube as shown in FIG. 2, and is meandering so as to illuminate the entire surface of the liquid crystal display 10. The fluorescent tubes 8 can be uniformly illuminated as far as possible from the diffusion plate 6. Therefore, the fluorescent tubes 8 are arranged along the bottom surface of the V-shaped groove 20 in the bottom wall 18 of the reflection plate. In the fluorescent tube 8, a conductor (not shown) is drawn out from both ends and an appropriate place, and the conductor is connected to a power source.

The light guide plate 4 shown in FIGS. 2 and 3 is made of a transparent plastic having excellent light transmittance, and is formed so that light passing through the light guide plate can be diffused from the upper end face 16 (FIG. 3). The end face is cloudy. Each light guide plate 4 is adhered to the upper side wall surface of the V-shaped groove 20 in the reflection plate 2 so as to be disposed on both sides along the fluorescent tube 8. As each light guide plate 4, a straight plate material is used in a straight portion of the fluorescent tube 8.
In addition, the curved portion of the fluorescent tube may be made of a plate material curved in a semicircular flat shape, or may be composed of only two plate materials formed in a meandering shape as a whole.

Each of the light guide plates 4 arranged obliquely has a lower end surface close to the fluorescent tube 8 but is not in contact with the fluorescent tube. On the other hand, the upper end face 16 of each light guide plate 4 has a V-shaped groove 20.
Even if it is close to the upper end of the frame, it needs to be slightly distant.
The width and thickness of each light guide plate 4 are appropriately determined according to the diameter of the fluorescent tube 8, the depth and the inclination angle of the V-shaped groove 20, and the like.

The flat milky white diffusion plate 6 is mounted horizontally and fixed directly on the reflection plate 2 so as to cover the entire surface of the fluorescent tube 8 on the reflection plate 2, and a light shielding plate is used in the present invention. I haven't. The diffuser plate 6 has its surface formed into fine irregularities, so that the transmitted light is widely dispersed. The diffusion plate 6 is made of a material and a thickness that does not attenuate the transmitted light, and is not particularly required to have heat resistance because it is separated from the fluorescent tube 8.

Since the backlight unit 1 for a liquid crystal has the light guide plate 4 disposed obliquely above the reflection plate 2 behind the display, all the light emitted from the fluorescent tubes 8 does not directly enter the diffusion plate 6. A part of the light passes through the light guide plate 4 arranged obliquely, exits from the upper end face 16 of the light guide plate, and is diffused. This light selectively irradiates a position far from the fluorescent tube 8 and having low brightness. . The degree of diffusion of this light can be adjusted by the manner of finishing the upper end face 16. The backlight body 1 can uniformly illuminate the liquid crystal display 10 with higher luminance than using a conventional light shielding plate.

FIG. 4 shows a modification of the present invention. The backlight body 30 is for a small-sized liquid crystal display panel, and has a white reflecting plate 32 having a shallow V-shaped cross section. The fluorescent tube 34 serving as a light source is a straight and elongated rod tube, and the fluorescent tube is arranged along the V-shaped bottom of the reflection plate 32. Fluorescent tube 3
In step 4, a conductor (not shown) is pulled out from both ends, and the conductor is connected to a power source.

The linear light guide plates 36, 36 are
4, the reflection plate 3
2 is adhered to the upper side of the V-shaped side wall surface. Although the lower end face of each of the obliquely arranged light guide plates 36 is close to the fluorescent tube 34, the light guide plate 36 does not contact the fluorescent tube 34, and the upper end surface thereof is the diffusion plate 3.
A bit far from 8. The milky white diffusion plate 38
It is placed horizontally and fixed on the reflection plate 32 so as to cover the entire surface of the reflection plate 32. The diffuser plate 38 has a surface formed into fine irregularities so that the transmitted light is widely dispersed.

Table 1 below shows the results of measuring the surface luminance at the positions indicated by circles for the backlight body 30 of the present invention and a conventional backlight body using a light-shielding plate.

[0024]

[Table 1] Note: Numerical values are luminance (candela) cd / m ²

From the maximum difference in luminance in Table 1, it is clear that the backlight body 30 of the present invention illuminates the surface of the diffusion plate 38 more uniformly than the conventional backlight body using a light shielding plate. is there. In addition, the backlight body 30 of the present invention also has an advantage that a decrease in luminance is small as compared with the case where a light shielding plate is used.

According to Table 1, in the backlight body 30, all the light emitted from the fluorescent tubes 34 is directly incident on the diffusion plate 38 because the light guide plates 36, 36 are disposed obliquely above the reflection plate 32 behind the display. Turns out not to be. A part of the emitted light passes through the light guide plates 36, 36 arranged obliquely, exits from the upper end face of the light guide plate, and is diffused. This light is selectively located at a position far from the fluorescent tube 34 and at a low luminance. Irradiation.

[0027]

The backlight body for a liquid crystal according to the present invention comprises:
By having a diagonally arranged light guide plate on the reflective plate behind the display, a portion of the light selectively illuminates locations far from the light source and at low brightness. As a result, in the backlight body of the present invention, if the same fluorescent tube is used, higher luminance and uniform illumination can be obtained than in the case where the conventional light shielding plate is used. The backlight body of the present invention has a light source disposed behind the liquid crystal display, so that the entire display is somewhat thicker, but is capable of uniformly illuminating the entire display with higher brightness and is excellent as auxiliary lighting.

The backlight body of the present invention can almost uniformly illuminate the entire display with a simple structure. In this backlight body, fluorescent tubes are arranged in a meandering shape on a liquid crystal reflection plate, and when light from the fluorescent tubes is diffused by passing through a diffuser having an uneven surface, only the fluorescent tube portions are strongly illuminated and become white. Even without a light-shielding plate beneath the diffusion plate, the portion far from the fluorescent tube is selectively and strongly irradiated to make the brightness of the entire display substantially uniform without being lifted.

When the backlight body of the present invention is used,
A bright liquid crystal display can be easily obtained, and it is possible to quickly respond to a user request for high-brightness illumination due to the spread of a color display. Moreover, in the present invention,
There is no need to increase the lux of the fluorescent tube in order to obtain high-luminance illumination, and it is unlikely that a problem will occur with respect to heat generation and power consumption of the fluorescent tube.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a notebook computer in which a backlight body of the present invention is installed behind a liquid crystal display.

FIG. 2 is a plan view illustrating an example of a backlight body according to the present invention.

FIG. 3 is a partial cross-sectional view of a backlight body cut along the line AA in FIG. 2 and further having a diffusion plate mounted thereon.

FIG. 4 is a transverse sectional view showing a modification of the present invention.

FIG. 5 is a schematic plan view of the backlight body of FIG. 4,
The circled number is entered at the measurement position.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 backlight unit for liquid crystal 2 reflection plate 4 light guide plate 6 diffusion plate 8 fluorescent tube 10 liquid crystal display

Claims (5)

[Claims] 1. A reflection plate having a size corresponding to a liquid crystal display surface, a light source located on the reflection plate, a light guide plate disposed obliquely above the light source, and a diffusion plate covering the reflection plate. And a part of the light emitted from the light source passes through the light guide plate arranged obliquely,
A liquid crystal backlight that illuminates the liquid crystal display almost uniformly. 2. A reflection plate having a size corresponding to the surface of a liquid crystal display, a fluorescent tube arranged on the entire surface of the plate by meandering or moving straight on the reflection plate, and a light guide arranged diagonally upward on both sides along the fluorescent tube. It consists of a light plate and a diffusion plate that covers the reflection plate and disperses the transmitted light, and a part of the light emitted from the fluorescent tube passes through the obliquely arranged light guide plate, so that the light passing through the diffusion plate is almost uniform. LCD backlight that illuminates the entire surface of the liquid crystal display. 3. The light guide plate is a plate material adhered to a reflection plate, and the upper end surface is cloudy-finished so that light passing through the plate material can be emitted from the upper end surface and diffused.
Or the backlight body according to 2. 4. The light guide plate is a plate-like molded product, and a projection of the molded product is inserted into a hole of the reflection plate or is inserted into a hole of the reflection product and fixed to the projection of the reflection plate. Or the backlight body according to 2. 5. The backlight body according to claim 1, wherein the light guide plate is formed integrally with the reflection plate, and only a portion of the light guide plate is transparent due to partial coloring.