JPH0624087Y2 - Lighting device and liquid crystal display device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of Invention] (Industrial field of application) The present invention uses a bent fluorescent lamp as a light source, and a lighting device suitable as a backlight for an LCD TV or a liquid crystal meter, and an illumination device for the same. The liquid crystal display device used.

(Prior Art) Liquid crystal televisions, liquid crystal meters, and the like are designed to display the liquid crystal surface by shining light from the back surface of the liquid crystal display panel. As such a backlight, a liquid crystal surface having a predetermined spread is used. An illumination device that can illuminate with a uniform brightness as a whole is required.

As a backlight of this kind, conventionally, a lamp is housed as a light source in a casing having a quadric surface on the bottom surface and a reflecting surface on the inner surface, and the light from the lamp is reflected by the reflecting surface to open the casing. The illuminating device adapted to emit the light to the outside through the light diffusing and transmitting plate installed in is adopted.

And as the above-mentioned light source, there is one using a hot cathode or cold cathode fluorescent lamp, and such a fluorescent lamp is superior in luminous efficiency to an incandescent lamp and generates less heat, has a long life, and has a long discharge. Since it has a path, it has an advantage that the light emitting area is large and the light distribution is likely to be uniform.

Particularly in the case of a fluorescent lamp, it is easy to form the discharge path into a bent shape, for example, a U-shape or a W-shape, so that at least two linear portions of such a bent fluorescent lamp are substantially parallel to each other. With the arrangement, the light emitting surface is widened in plan view, so that there is an advantage that the display surface having a predetermined spread can be easily illuminated with uniform brightness.

By the way, when the above-mentioned curved fluorescent lamp is used as a light source, the curved fluorescent lamp is provided in a casing whose bottom surface forms a reflecting surface of a quadric surface.
The book is housed in such a manner that the straight portions of the book are substantially parallel to each other and that they are substantially parallel to the bottom surface.

However, in the case of such an illuminating device, the brightness of the light diffusion / transmission plate installed in the opening of the casing is not uniform throughout, and it is bright just above the bent bulb and becomes darker as it goes away from the bulb. There is a defect. In particular,
In a portion where a plurality of straight line portions are arranged in parallel, it is bright just above the bulb, and the brightness is lowered between these straight line portions.

In order to eliminate such brightness unevenness, the bottom surface of the casing is provided with a protrusion located between the linear portions of the bulb and extending along the linear portion. The protrusion has a reflecting surface and a cross-sectional shape of It has a substantially triangular shape. When such a protrusion is provided, the light emitted from each straight part of the bulb is
The light is reflected toward the portions of the light diffusion / transmission plate located between the linear portions of the bulb, and therefore the luminance of the portions located between the linear portions can be increased, which is effective in preventing uneven brightness. .

(Problems to be solved by the invention) However, in the case where a protrusion is provided on the bottom surface of the casing as described above, if the protrusion is formed with a uniform height in the longitudinal direction, the position between the linear portions is increased. It is effective to increase the brightness of the shaded area, but it was found that unevenness occurs in the brightness along the straight line portion.

That is, in the case of a bent fluorescent lamp having a U shape, a W shape, or the like, the density of light emitting portions is high in the bent portion when viewed in plan. Therefore, when viewed from the surface of the light diffusion / transmission plate, the portion facing the bent portion has higher brightness than the portion facing the straight portion.

When the protrusion is formed with a uniform height in the longitudinal direction, the light emitted from the bent portion is difficult to diffuse far, and the brightness decreases as it approaches the end of the straight portion, that is, the electrode sealing portion. There is a problem to do.

The present invention is intended to provide an illumination device in which the brightness from the bent portion to the end portion on the electrode sealing side of the straight portion is also equalized, and the entire luminance distribution is uniform, and a liquid crystal display device using the same. is there.

[Constitution of device]

(Means for Solving the Problems) In the lighting device of the present invention, the height of the protrusion formed of the reflection surface formed on the bottom surface of the casing is gradually lowered as it approaches the bent portion of the bent fluorescent lamp. Is characterized by.

In addition, the liquid crystal display device of the present invention is characterized in that the lighting device is provided on the back surface of the liquid crystal display panel.

(Operation) According to the present invention, since the height of the protrusion is lowered as it approaches the bend of the bent fluorescent lamp, the proportion of the light emitted from the bend reflected and blocked by the protrusion is low. Therefore, the light emitted from the bent portion reaches the end of the straight portion, so that the brightness of the portion facing the bent portion is reduced and the brightness of the portion facing the straight portion is reduced. It becomes higher, and the brightness distribution becomes uniform as a whole.

Therefore, in the liquid crystal display device of the present invention using such an illuminating device as a backlight, the brightness of the display surface of the liquid crystal display panel can be made uniform over the entire surface.

(Embodiment) The present invention will be described below based on an embodiment shown in FIGS. 1 to 3.

In the figure, reference numeral 1 denotes a casing, which is made of synthetic resin such as polycarbonate and has a gutter-shaped cross section having a quadratic curve. A partition projection 2 is integrally formed and formed in the center of the bottom surface of the casing 1 along the longitudinal direction. The projection 2 has a substantially triangular cross section as shown in FIG. 2, and its height is gradually changed along the longitudinal direction as shown in FIG. The bottom surface and the projection 2 of the casing 1 are entirely formed as a reflection surface 3.

A bent fluorescent lamp 5 is housed in such a casing 1. In this embodiment, a U-shaped fluorescent lamp 5 is used. That is, 6 is a U-shaped bent valve, and this valve 6 has straight portions 8a and 8b which are substantially parallel to each other at both ends of a U-shaped bent portion 7. Cold cathode type electrodes 9a, 9b are sealed to these linear portions 8a, 8b,
Further, caps 10a and 10b are attached to the ends. A phosphor coating (not shown) is formed on the inner surface of the bulb 6, and a predetermined amount of mercury and a rare gas for starting such as argon or xenon are enclosed in the bulb 6.

The fluorescent lamp 5 having such a structure is provided in the casing 1
The linear portions 8a, 8b are housed so as to be substantially parallel to the bottom surface of the casing 1. In this case, the straight line portions 8a, 8b of the U-shaped valve 6 which are substantially parallel to each other are arranged along the above-mentioned protrusion 2, and the protrusion 2 is interposed between these straight line portions 8a, 8b, that is, the protrusion 2 Are installed so as to distinguish between the adjacent straight line portions 8a and 8b.

The protrusion 2 is cut off at a portion facing the bent portion 7 of the U-shaped valve 6.

The fluorescent lamp 5 has fixed notches 11a and 11b formed on the side wall 4 of the casing 1 at the bases 10a and 10b at both ends.
It is attached to the casing 1 by being fitted to the casing 1 and fixed by an appropriate means such as an adhesive.

A light diffusion / transmission plate 12 is attached to the upper opening of the casing 1. The light diffusing and transmitting plate 12 has a milky white color such as acrylic resin to perform a light diffusing action, and the inner surface (or the outer surface) of the light diffusing and transmitting plate 12 is provided with a valve 6a.
A thick portion 13 is formed in a portion facing to. The thick portion 13 gradually becomes thinner as it goes away from the valve 6.

In front of such a light diffusing and transmitting plate 12, a back surface of a known liquid crystal display panel (not shown) is provided so as to face it.

The operation of the embodiment having such a configuration will be described.

When the fluorescent lamp 5 is energized and turned on, it emits light along the shape of the U-shaped bulb 6.

A part of the light emitted from the bulb 6 is reflected by the reflecting surface 3 on the bottom surface of the casing 1 and directed toward the light diffusion / transmission plate 12 at the upper end, and the rest of the light goes directly to the light diffusion / transmission plate 12. Therefore, almost all of the light emitted from the lamp 5 is emitted to the outside through the light diffusion / transmission plate 12.

In this case, since the reflecting surface 3 of the casing 1 forms a quadric surface, the light reflected by the reflecting surface 3 has a substantially uniform brightness with respect to the opening of the casing 1. Refracts and reflects.

Further, since the protrusion 2 is interposed between the linear portions 8a and 8b of the U-shaped bulb 6 which are substantially parallel to each other, the protrusion 2 reflects upward the light emitted from the linear portions 8a and 8b, respectively. ,
The light diffusion / transmission plate 12 facing between the straight portions 8a and 8b.
Increase the brightness above. In other words, if there is no protrusion 2,
On the light diffusion / transmission plate 12, the brightness is reduced at the portion facing between the straight line portions 8a and 8b, and uneven brightness occurs in the direction orthogonal to the straight line portions 8a and 8b. The reflection effect of the protrusion 2 compensates for the brightness of the portion of the light diffusion / transmission plate 12 facing between the linear portions 8a and 8b, and reduces the uneven brightness in the direction orthogonal to the linear portions 8a and 8b. To do.

On the other hand, since the thick portion 13 is formed on the inner surface of the light diffusion / transmission plate 12, the thick portion 13 faces directly above the bulb 6, so that the light transmission amount is reduced in the thick portion, and the thick portion 13 is formed. Since the wall thickness becomes thinner as the distance from the portion 13 increases, the light transmission amount increases. Therefore,
The light diffusion / transmission plate 12 itself also has an effect of eliminating uneven brightness.

In this embodiment, the height of the protrusion 2 formed between the substantially parallel straight portions 8a and 8b of the U-shaped valve 6 is set to the valve 6
Of the bulb 6 is gradually lowered so that it becomes higher on the ends of the straight portions 8a and 8b, that is, on the electrodes 9a and 9b side. The brightness on the plate 12 can be reduced.

That is, in the bent portion 7 of the bulb 6, since the density of the light emitting area is high, the brightness on the light diffusing and transmitting plate 12 is equal to that of the straight portions 8a, 8a.
Since the protrusion 2 has a height higher than that of the end portion of b, and the protrusion 2 has a light reflecting action, if the protrusion 2 is high on the bent portion 7 side of the bulb 6, the reflecting action becomes too strong and the light diffusing / transmitting plate. The luminance on 12 is higher than that at the ends of the straight portions 8a and 8b.

On the other hand, when the protrusion 2 is lowered on the bent portion 7 side, the reflection action becomes weaker, and in addition, the light emitted from the bent portion 7 of the bulb 6 is not disturbed by the protruding portion 2 on the way, so that the straight portions 8a, 8b are formed. Therefore, the uneven brightness along the longitudinal direction of the straight portions 8a and 8b can be eliminated.

From this, the brightness distribution on the light diffusion transmission plate 12 is reduced uneven brightness in the direction orthogonal to the straight line portions 8a, 8b and the direction along the straight line portions 8a, 8b, and is uniform over the entire surface. Can be bright.

For this reason, the liquid crystal display panel arranged in front of the light diffusing and transmitting plate 12 has a uniform luminance distribution on its display surface.

In the above embodiment, the casing 1 is made of synthetic resin such as polycarbonate, and the casing 1
Although the projection 2 is integrally formed on the bottom surface of the casing, the present invention is not limited to this, and as shown as another embodiment in FIG. The part 20 may be fixed and configured.

The height of the protrusions 2 and 20 is determined by the distance and length between the linear portions of the valve. In the above embodiment, the case where the projections 2 and 20 are inclined in a substantially linear shape and the height thereof gradually changes has been described, but the height is not limited to a uniform change, but changes in a curved shape. It may be a thing that changes while repeating a certain amount of elevation, or a thing that changes in a stepwise manner.

The bent fluorescent lamp is not limited to the U-shaped one, but may be W-shaped or the like.

Further, the electrode is not limited to the cold cathode type, but may be the hot cathode type, and the bulb may be filled with only a rare gas without containing mercury.

[Effect of device]

As described above, according to the present invention, the height of the protrusion is lowered as it approaches the bent portion of the bent fluorescent lamp. Therefore, the ratio of the light emitted from the bent portion reflected and shielded by the protruding portion As the light emitted from the bent portion reaches the end of the straight portion, the brightness of the portion facing the bent portion is reduced and the light is emitted toward the end portion of the straight portion. The brightness of the part becomes high, and therefore the brightness distribution becomes uniform as a whole.

Further, in the liquid crystal display device of the present invention using such an illuminating device as a backlight, the brightness of the liquid crystal display panel can be made uniform over the entire surface.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention, FIG. 1 is an exploded perspective view of the whole, FIG. 2 is a sectional view, and FIG. 3 is a sectional view taken along line III-III in FIG. FIG. 4 is a sectional view showing another embodiment of the present invention. 1 ... Casing, 2, 20 ... Protrusion, 3 ... Reflective surface, 5 ... Fluorescent lamp, 6 ... Bulb, 7 ... Bend, 8a, 8b ... Straight part, 9
a, 9b ... Electrodes, 12 ... Light diffusion / transmission plate, 13 ... Thick parts.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location G09F 9/00 333 Z 6447-5G 336 F 6447-5G

Claims (2)

[Scope of utility model registration request] 1. A bent fluorescent lamp in which at least two linear portions are parallel to each other is housed in a casing whose bottom surface is a reflecting surface, and the bottom surface of the casing is between the linear portions of the fluorescent lamp. A light diffusing and transmitting plate provided at the opening of the casing by providing a projection formed of a reflecting surface located along this straight line portion and reflecting the light from the fluorescent lamp by the reflecting surface of the bottom surface and the reflecting surface of the projection. In the lighting device configured to emit light through the projection, a projection formed of a reflective surface formed on the bottom surface of the casing has a height that is gradually lowered as it approaches the bent portion of the bent fluorescent lamp. apparatus. 2. A liquid crystal display device, wherein the lighting device according to claim 1 is provided on a back surface of a liquid crystal display panel.