JPH09219109A - Surface display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a display quality, and inexpensively manufacture a device by almost uniformalizing light emitting brightness of a display surface over the whole surface. SOLUTION: A surface display device is composed of a liquid crystal display panel 3 being a surface display unit, a transparent light conductive plate 5 whose light emitting surface 5a is formed in a rectangular shape and light sources 6 and 6 respectively arranged in close vicinity to both opposed side surfaces 5c and 5c forming the short sides of its light conductive plate 5, and its light conductive plate 5 is formed as a projecting curved surface as a whole in the light emitting direction in the long side direction. This light conductive plate 5 is arranged so that a distance from the liquid crystal display panel 3 gradually separates as its approaches both side surfaces 5c and 5c. In this way, since a surface light source device 4 is arranged on the back face side of the liquid crystal display panel 3 as a back light source, brightness of a display surface is uniformized, and nonuniformity of contrast of a liquid crystal display is eliminated, and high quality display becomes possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface display device such as a liquid crystal display device which requires a light source for backlight illumination.

[0002]

2. Description of the Related Art A surface light source device for illuminating a predetermined plane area almost uniformly is widely used for backlight illumination of a surface display device such as a liquid crystal display device. As the surface light source device, a straight tubular light source is generally arranged close to the side surface of a transparent light guide plate, and the light incident from the light source to the side surface of the light guide plate passes through the inside of the light guide plate and its front surface (light emission surface). ) Is used while being propagated while being reflected by, and being sequentially emitted from the surface to illuminate.

In such a surface light source device, the entire light exit surface of the light guide plate is devised so as to emit light with uniform brightness. For example, the surface light source device shown in FIG.
As disclosed in Japanese Patent No. 241590, the straight tube-shaped light sources 12 are arranged close to both side surfaces forming the short side of the transparent light guide plate 11, and the lower surface of the light guide plate 11 is diffused. The surface 13 is formed, and a white paint is applied to the light diffusing surface 13 by changing the density and / or the size of the application point so that the application area per unit area increases with the distance from the light source 12. .

Therefore, in this surface light source device, the light source 1
Light incident on the inside of the light guide plate 11 from 2 is reflected by the light diffusion surface 13 and the light exit surface (upper surface) 14 and propagates,
When it hits a portion of the light diffusing surface 13 where the white paint is applied, it is diffused and emitted from the light emitting surface 14 to the outside. When it hits a portion not coated with white paint, if the incident angle of the light on the light diffusion surface 13 is larger than the critical angle, it is totally reflected and further propagates inside the light guide plate 11, and if it is smaller than the critical angle, it passes through. It leaks to the outside.

Since the coating area of the white paint per unit area of the light diffusing surface 13 increases with the distance from the light source 12, a large amount of light is diffused by the light diffusing surface 13 and emitted from the light emitting surface 14 to the outside. Become. Thereby, the light source 1
The intensity of light becomes weaker as the distance from 2 increases, and the brightness of the entire light exit surface 14 of the light guide plate 11 is made uniform.

The surface light source device shown in FIG. 5 is disclosed in Japanese Patent Application Laid-Open No. 4-14.
This is another conventional example seen in Japanese Laid-Open Patent Publication No. 0783, that is, the light guide plate 1
The reflecting surface 16 on the lower surface of 5 is formed into a mountain-shaped slope, and the light incident from the straight tubular light source 12 into the light guide plate 15 is reflected by the reflecting surface 1.
The light reflected by 6 and emitted from the emission surface (upper surface) 17 is made uniform over the entire surface.

[0007]

However, all of the conventional surface light source devices with uniform brightness have a problem of high cost. That is, in the surface light source device shown in FIG. 4, the number of steps of applying the white paint to the light diffusion surface 13 of the light guide plate 11 so that the application area per unit area becomes larger as the distance from the light source 12 increases, and it is quite troublesome. It is work.

Further, in the surface light source device shown in FIG. 5, it is necessary to use a metal mold having a chevron-shaped unevenness in order to mold the reflecting surface 16 of the light guide plate 15, and the mold cost is increased and the slope of the sloped surface is increased. There is also the problem that it takes time to make a prototype to determine the angle.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a surface display device, which has a uniform display surface brightness over the entire surface and a high display quality, at low cost. .

[0010]

In order to achieve the above-mentioned object, the present invention has an area display, a transparent light guide plate for guiding light to the area display, and a light source arranged at least close to one side surface thereof. In a surface display device consisting of, the light guide plate,
It is formed to have a convex curved surface as a whole in the direction of emitting light along the direction orthogonal to the side surface, and is arranged so that the distance from the surface display becomes larger as it approaches the side surface.

The light exit surface of the transparent light guide plate is formed into a rectangular shape and is formed into a curved surface that is convex in the direction of light emission along the long side direction thereof. It is advisable to arrange the light sources close to each other. by this,
By simply performing a curved surface process on the light guide plate, the emission brightness of the display surface of the planar display can be made substantially uniform over the entire surface.

By subjecting the back surface of the light guide plate to white treatment, its brightness can be increased as a whole. If the surface display is a liquid crystal display panel and the light guide plate and the light source are provided as the backlight light source, a liquid crystal display device having a uniform brightness on the display surface can be provided at low cost.

[0013]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 3 is a perspective view showing a state in which a liquid crystal display device, which is a surface display device according to an embodiment of the present invention, is attached to an operation panel of an electronic device, and FIG. 1 is an enlarged sectional view taken along the line AA. 2 is a plan view of only the surface light source device.

In FIG. 3, reference numeral 1 denotes an operation panel of an electronic device (for example, an electronic musical instrument), which may also serve as a case (housing). The operation panel 1 has a tapered surface 1a with a loose periphery.
Is provided with a rectangular window hole 1b depressed by
The transparent cover panel 2 is fitted therein. A liquid crystal display device is disposed and held on the back side of the cover panel, and the display can be seen through the cover panel 2.

As shown in FIG. 1, the internal structure is such that a liquid crystal display panel 3 having a rectangular display surface is arranged in parallel below the cover panel 2 at a slight interval and is close to the back surface side. The surface light source device 4 is provided as a backlight light source to form a liquid crystal display device.

The liquid crystal display panel 3 is a unit in which a polarizing plate and a liquid crystal (not shown) are enclosed between two glass substrates 3a and 3b in which drive electrodes for pixels are formed in a matrix.
Both short sides of the pair of holding members 7, 7 are attached to the back surface side of the operation panel 1 in the vicinity of the window hole 1b by a mounting screw 8, and the inside of the window hole 1b of the operation panel 1. It is sandwiched and held by the projecting edge portion 1c extending in the direction.

As shown in FIG. 2, the surface light source device 4 includes a transparent light guide plate 5 having a rectangular light exit surface 5a and opposite side surfaces 5c and 5c forming short sides of the light guide plate 5, respectively. The light guide plate 5 is formed by curving the light guide plate 5 along its long side direction so as to form a convex curved surface as a whole in the light emitting direction. The distance from the liquid crystal display panel 3 is gradually increased as the distance from the surface 5c approaches. For the light guide plate 5, a highly transparent resin such as an acrylic resin is used. In this example, the light exit surface 5a of the light guide plate 5 and the back surface 5b serving as a reflection surface are formed in a convex curved surface having the same curvature, and the thickness of the light guide plate 5 is constant, but the light exit surface 5a and the back surface 5b are the same. The light guide plate 5 can be formed in a lens shape with different curvatures.

The light guide plate 5 of the surface light source device 4 is held by its both short sides being retained by being locked by the shallow groove portions 7b, 7b of the pair of holding members 7, 7. Is fitted and held in the groove portions 7c, 7c formed deeper than the shallow groove portions 7b, 7b of the holding members 7, 7. As the light source 6, an example in which an elongated lamp having a filament 6a is used is shown, but a microminiature fluorescent lamp, a high-intensity LED (it is preferable to arrange a plurality of LEDs), or the like can also be used.

In the surface light source device 4, the light incident from the side surface 5c into the light guide plate 5 by the light emission of the light source 6 is directed to the light exit surface (upper surface) 5a or the back surface (lower surface) 5b thereof as shown in FIG. If the incident angle is larger than the critical angle, the light is totally reflected there and propagates, and if the incident angle is smaller than the critical angle, it is transmitted and emitted to the outside. At that time, the incident angle to the light exit surface 5a formed in a convex curved surface in the light exit direction becomes larger as the incident position is closer to the light source 6 than in the case where it is a flat surface. Thereby, the emitted light is reduced in a region close to the light source 6, and the emitted light is increased as the distance from the light source 6 is increased (closer to the center), so that the decrease of the light intensity can be compensated, and the light of the light guide plate 5 can be compensated. Exit surface 5a
The overall brightness can be made uniform.

When the back surface 5b of the light guide plate 5 is subjected to a white treatment, for example, a white paint is applied or a white resin sheet is attached, the reflection efficiency at the back surface 5b is increased and almost no light is transmitted. The brightness on the side of the light exit surface 5a can be increased and the brightness can be increased. Even if the white treatment is performed in this manner, unlike the conventional example described with reference to FIG. 4, the troublesome work of changing the area of the white portion per unit area is not required, and the white treatment (conduction) is uniformly performed on the entire back surface 5b. Processing such as spray painting or simply pasting white paper on the back surface of the light plate 5)
The work is easy as Further, even if this white treatment is not performed, it is possible to achieve uniform brightness on the light exit surface 5a side.

In the liquid crystal display device shown in FIG. 1, the liquid crystal display panel 3 is illuminated from the back side by the surface light source device 4 with uniform brightness over the entire surface, so that the contrast of the liquid crystal display is uniform. , The display quality can be improved.

In the above embodiment, the light source 6 is arranged close to both side surfaces 5c, 5c forming the short side of the light guide plate 5, but the surface light source device 4 is divided into two parts from the center in the longitudinal direction to the left and right. It is also possible to make only the shape. That is, even in a surface light source device in which a light source is arranged close to one side surface of the light guide plate, the light guide plate may be formed into a curved surface convex in the light emitting direction along the direction orthogonal to the side surface in which the light source is arranged. In this case, the brightness on the light emitting surface side can be made uniform.

[0023]

As described above, in the surface display device according to the present invention, the luminance is substantially uniform over the entire light emitting surface,
Moreover, since it is sufficient to perform a simple curved surface process of applying a bending force while heating the light guide plate, a troublesome process and a special mold are not necessary, and the manufacturing cost can be reduced. Further, when the liquid crystal display device is configured according to the present invention, the brightness of the backlight is uniform over the entire display surface, and therefore, the contrast of the liquid crystal display is not uneven, and it is possible to perform high-quality display that is easy to see.

[Brief description of drawings]

1 is an enlarged cross-sectional view of the liquid crystal display device shown in FIG. 3, taken along the line AA.

FIG. 2 is a plan view of only the surface light source device.

FIG. 3 is a perspective view showing a state in which a liquid crystal display device, which is a surface display device according to an embodiment of the present invention, is attached to an operation panel of an electronic device.

FIG. 4 is a perspective view showing an example of a surface light source device used in a conventional surface display device.

FIG. 5 is a perspective view showing another example of a conventional surface light source device.

[Explanation of reference numerals] 1 ... Operation panel, 2 ... Cover panel, 3 ... Liquid crystal display panel, 4 ... Surface light source device, 5 ... Light guide plate, 5a ... Light emitting surface, 5
b ... back surface, 5c ... short side surface, 6 ... straight tubular light source,
7 ... Holding member, 8 ... Mounting screw

Claims (3)

[Claims] 1. A surface display device comprising a surface display device, a transparent light guide plate for guiding light to the surface display device, and a light source arranged in proximity to at least one side surface thereof. A surface display device characterized in that it is formed into a curved surface as a whole in a direction that emits light along a direction orthogonal to, and is arranged so that the distance from the surface display device increases as it approaches the side surface. . 2. The surface display device according to claim 1, wherein the back surface of the light guide plate is white-treated. 3. The surface display is a liquid crystal display panel,
The surface display device according to claim 1 or 2, wherein the light guide plate and the light source are provided as the backlight light source.