JP2800625B2 - Lighting equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display having an illumination function.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 6 (a), a liquid crystal display device having an illumination function is provided with a planar illumination device 1 on the back of a liquid crystal display body 2 and usually illuminates constantly. 6B, or a transflective sheet 4 is disposed between the liquid crystal display 2 and the illuminating device 1 as shown in FIG. 6B so that it can be used both for lighting and non-lighting. I was

[0003]

However, such a conventional liquid crystal display device having an illuminating function is illuminated when a constant transmissive light is used and a semi-transmissive and semi-reflective sheet is used. There is a problem that the display is dark and the contrast is low both when the device is turned on and when the device is not turned on.

In order to solve such a conventional problem, the present invention arranges an illumination device on an object to be illuminated, for example, in front of a liquid crystal display panel, so that the illumination device can be turned on and off. In both cases, the object is to increase the contrast of the object to be illuminated and enhance the visibility.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an illuminating device arranged on the front of a liquid crystal display panel which is an object to be illuminated.

The illuminating device has a transparent light guide and a light source disposed on an end face side of the light guide, and one surface of the light guide has a light exit side plane and the light exit side. A plane in a direction parallel to a plane, and an uneven shape formed by a plane in a direction perpendicular to the light-emitting side plane are provided, and light rays from the light source propagate through the light guide, and The light is emitted from the uneven portion to illuminate the object to be illuminated, and is emitted through the light guide. Where
"The light-emitting side plane, a plane parallel to the light-emitting side plane, and
Concavo-convex shape formed by the light emitting side plane and the vertical surface
The shape is a plane parallel to the light-emitting side plane and the light-emitting side plane.
Surface and a surface substantially perpendicular to the light exit side plane.
The “substantially parallel surface” refers to the light emitting side
Refers to a plane that is generally parallel to the plane,
Indicates a plane substantially perpendicular to the light-emitting side plane.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a lighting device 1 is arranged on a front surface of a liquid crystal display 2. A reflection plate 3 is arranged on the back of the liquid crystal display 2 to constitute a reflection type liquid crystal display. The illuminating device 1 has a function of projecting a light beam on the liquid crystal display 2 side and transmitting the light beam reflected by the reflection plate 3 with almost no dispersion. This is because the lighting device 1 is turned off when there is sufficient external light, and in this case, the lighting device 1 is effective as a mere transparent plate so as not to reduce the visibility and not to affect the display quality. is there. When used in a dark place where external light is not sufficient, the lighting device 1 illuminates the liquid crystal display 2 and the light reflected by the reflector 3 is applied to the lighting device 1.
However, as in the case of turning off the light, it functions as a mere transparent plate and is transmitted as it is, which is effective for maintaining high visibility.

In a transmission type liquid crystal display device in which an illumination device is arranged on the back of a liquid crystal display, a light beam from the illumination device passes through the liquid crystal display only once to generate a contrast between a bright portion and a dark portion. In a reflection type liquid crystal display device in which a lighting device as in the present invention is disposed in front of a liquid crystal display, light rays from the lighting device pass through the liquid crystal display once, are reflected by a reflector, and are transmitted again. This is effective for obtaining higher visibility by increasing the contrast.

FIG. 2A shows an embodiment for realizing the above-described lighting device. A light source 12 is arranged on at least one end face of the light guide 11. The light guide 11 is shown in FIG.
As shown in (b), a protrusion 13 on the rib is provided on one surface of the transparent plate substantially in parallel with the light source 2, and each surface of the protrusion 13 is substantially perpendicular to a surface substantially parallel to the light emitting side plane 14. It consists only of faces. The light guide 11 is formed of a transparent material having a refractive index of 1.4 or more. The light rays from the light source 12 enter the end face 15 as shown by the light rays 16a and 16b, and then repeat the total reflection in the light guide 11, and emit the light only from the side surface of the projection 13. More can illuminate the liquid crystal display.

The transparent material forming the light guide 11 is a transparent resin such as acrylic resin or polycarbonate resin, an inorganic transparent material such as glass, or a composite thereof.
It is formed by a method such as injection molding, photo-curing resin, etching, bonding a film on a transparent resin or a glass flat plate.

As shown in FIG. 3A, the light beam incident from the end face 15 has an optical axis of 45 degrees or less due to refraction with respect to the axis of the light guide 11 in the long side direction. In order to achieve this, a height higher than the width of the projection 13 is required. In the case below that, the light ray is emitted to the upper surface of the illuminating device along the path as shown in FIG. However, when the ratio greatly exceeds one-to-one, not only is optically meaningless, but also a problem arises in that manufacturing becomes difficult. As described above, it is desirable that the ratio of the width and the height of the protrusion 13 be exactly one to one.

Since the visible light has a wavelength of about 380 nm to 700 nm, the width of the projection 13 and the height of the projection 13 need to be about 5 μm or more to prevent a spectral stripe pattern from being generated by interference due to diffraction. Since the size of the pixel of the liquid crystal display is 200 μm to 300 μm, the size should be 100 μm or less in order to prevent the occurrence of a stripe pattern due to interference with the pixel. In addition to the above, the size of the projection 13 is about 10 for convenience in manufacturing.
It is desirable that the thickness be in the range of μm to 50 μm.

By adjusting the density of the projections 13 on the light guide 11, uniformity of the irradiation luminance can be improved.
Actually, the projections 13 are arranged sparsely in the vicinity of the light source 12, and are arranged densely continuously as the projections 13 are separated. In this case, a method of varying the density by keeping the size of the projection 13 constant, a method of varying the size by keeping the density constant, a method of varying both, and the like are adopted.

Another embodiment is shown in FIG. Protrusion 13
The same effect as that of the rib can be obtained also when the is formed in a prismatic shape. The side surface of the projection 13 perpendicular to the light source 12 is irradiated with the light beam at a critical angle or more, and is totally reflected and has no relation to the emitted light. When a prism having a square bottom surface is formed on a substantially rectangular light guide plate 11 as shown in FIG. 4B, a light source 12 is arranged on two adjacent sides and a light beam incident from the two sides is Light can be emitted from each side.

FIG. 5A shows another embodiment in which the projections 13 are formed in a columnar shape. The light beam irradiated to the cylindrical surface of the projection 13 at a critical angle or less emits light, and the light beam irradiated at the critical angle or more repeats reflection at the cylindrical surface, then inverts at the bottom surface of the protrusion 13 and further reflects at the cylindrical surface. By repeatedly repeating the path that travels through the light guide plate. Light rays emitted from the cylindrical surface are different from those in the case of the prism shown in FIG.
As shown in (b), the irradiation range can be widened.

[0016]

According to the present invention, as described above,
In an application such as a portable computer terminal, it is possible to provide a liquid crystal display device which has high contrast even when turned on without turning off the lighting in a bright place for power saving.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing another embodiment of the present invention.

FIG. 5 is a view showing another embodiment of the present invention.

FIG. 6 is a diagram showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 照明 Illumination device 2 ‥‥‥ Liquid crystal display 3 ‥‥‥ Reflector 11 光 Light guide 12 光源 Light source 13 突起 Projection 14 光 Light emitting side surface 15 ‥‥ End face 16 ‥‥ Light ray

Claims (1)

(57) [Claims] 1. An illumination device for illuminating an object to be illuminated, wherein the illumination device has a transparent light guide, and a light source disposed on an end face side of the light guide. On one surface, an uneven surface formed by a light emitting side plane, a surface parallel to the light emitting side plane, and a surface perpendicular to the light emitting side plane is provided, and the light from the light source is the light guide. A lighting device, which propagates through a body, emits light from the uneven portion, illuminates the object to be illuminated, and passes through the light guide to be emitted.