JPH06289391A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To increase a contrast and visibility both at the time of lighting of an illumination device and at the time of non-lighting of this illumination device by providing the liquid crystal display device with a liquid crystal display panel and the illumination device arranged atop this panel. CONSTITUTION:The illumination device 1 is arranged on the front surface of a liquid crystal display body 2 and a reflection plate 3 is arranged behind this liquid crystal display body 3, by which the reflection type liquid crystal display device is constituted. The illumination device 1 has the function to project rays to the liquid crystal display body 2 side and to allow the transmission of almost all the rays reflected by this reflection plate 3 without dispersion. The liquid crystal display device is used by putting out the illumination device 1 when there is sufficient external light. The illumination device 1 acts as a mere transparent plate at this time. The visibility is thus maintained and the display quality is not affected. The illumination device 1 illuminates the liquid crystal display body 2 with light when the device is used by lighting the illumination device in a dark place. The reflected light by the reflection plate 3 transmits the illumination device as it is as the illumination device acts as the mere transparent plate in the same manner as the illumination device is put out and, therefore, the high visibility is maintained.

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 device having a lighting function.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display device having an illumination function, a planar illumination device 1 is arranged on the back surface of a liquid crystal display body 2 as shown in FIG. 6 is used, or a semi-transmissive / semi-reflective sheet 4 is placed between the liquid crystal display 2 and the lighting device 1 as shown in FIG. 6 (b) so that it can be used for both lighting and non-lighting. Was there.

[0003]

However, such a conventional liquid crystal display device having a lighting function consumes a large amount of power when the lighting is constantly turned on and used. There is a problem that the display is dark and the contrast is low both when the device is turned on and when it is not turned on.

Therefore, in order to solve such a conventional problem, the present invention arranges the illuminating device on the front surface of the liquid crystal display body to provide a high contrast both when the illuminating device is turned on and when it is not turned on. It is an object to provide a high liquid crystal display device.

[0005]

In order to solve the above-mentioned problems, a liquid crystal display device of the present invention comprises (1) a liquid crystal display panel and an illuminating device arranged on the upper surface thereof.

(2) The illuminating device has a light guide and a light source arranged on an end face of the light guide, and the light emitting side surface of the light guide is substantially perpendicular to a surface substantially parallel to the light emitting side surface. It is characterized in that an uneven shape formed by a flat surface is provided.

[0007]

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

Further, in the transmissive liquid crystal display device in which the illumination device is arranged on the back surface of the liquid crystal display body, light rays from the illumination device pass through the liquid crystal display body only once to generate contrast in bright and dark areas. In a reflection type liquid crystal display device in which an illuminating device such as the present invention is arranged in front of a liquid crystal display body, a light beam from the illuminating device is transmitted through the liquid crystal display body once, then reflected by a reflection plate and transmitted again. The higher contrast makes it more effective to obtain high visibility.

FIG. 2 (a) shows an embodiment for realizing the illumination device as described above. The 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 a rib is provided on one surface of the transparent plate substantially parallel to the light source 2, and each surface of the protrusion 13 is substantially perpendicular to a surface substantially parallel to the light output side plane 14. It consists only of faces. The light guide 11 is made of a transparent material having a refractive index of 1.4 or more. The light beam from the light source 12 is incident from the end face 15 as shown by the light beam 16a and the light beam 16b, and then the total reflection is repeated in the light guide 11 to be emitted only from the side surface of the protrusion 13, so that the light emitted from the back surface of the illumination device is emitted. In addition, the liquid crystal display can be illuminated.

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

As shown in FIG. 3A, since the light ray 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, it is applied to the side surface of the protrusion 13. In order to do so, a height higher than the width of the protrusion 13 is required. In the case of less than that, the light ray is emitted to the upper surface of the illuminating device by the path as shown in FIG. However, if the ratio exceeds one-to-one significantly, not only is it optically meaningless, but there is also the problem that manufacturing becomes difficult. From the above, it is desirable that the protrusion 13 has a width-height ratio of about 1: 1.

The width and height of the protrusions 13 are required to be about 5 μm or more in order that the wavelength of visible light is about 380 nm to 700 nm, so that a spectral stripe pattern does not occur due to interference due to diffraction. Moreover, since the size of the pixel of the liquid crystal display is 200 μm to 300 μm, it should be 100 μm or less in order to prevent the occurrence of a stripe pattern due to interference with this pixel. In addition to the above contents, the size of the protrusion 13 is approximately 10 due to manufacturing convenience.
It is desirable that the thickness is not less than μm and not more than 50 μm.

By adjusting the density of the projections 13 on the light guide 11, the uniformity of the irradiation brightness can be improved.
Actually, the protrusions 13 are arranged sparsely in the vicinity of the light source 12, and are continuously arranged densely as they are separated. In this case, a method of changing the density by making the size of the protrusions 13 constant, a method of changing the size by making the density constant, a method of changing both of them are used.

Another embodiment is shown in FIG. Protrusion 13
Even when formed into a prismatic shape, the same effect as the rib can be obtained. Since the side surface of the protrusion 13 which is perpendicular to the light source 12 is irradiated with a light ray at a critical angle or more, it is totally reflected and has nothing to do with the emitted light. As shown in FIG. 4B, when a prism having a square bottom surface is formed on the light guide plate 11 having a substantially rectangular shape, the light sources 12 are arranged on two adjacent sides, and light rays incident from the two sides are projected on the projection 13. Light can be emitted from each side.

As another embodiment, FIG. 5A shows a case where the projection 13 is formed in a cylindrical shape. Light rays irradiated on the cylindrical surface of the protrusion 13 at a critical angle or less are emitted, and light rays irradiated at a critical angle or more repeat reflection on the cylindrical surface, then are inverted on the bottom surface of the projection 13 and are reflected on the cylindrical surface. Repeatedly, the path of traveling inside the light guide plate is traced again. The light beam emitted from the cylindrical surface is shown in FIG. 5 as compared with the case of the prism shown in FIG.
The irradiation range can be widened as shown in (b).

[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 that does not deteriorate the display quality even when the light is turned off and used in a bright place to save power and has a high contrast even when turned on.

[Brief description of 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 diagram showing another embodiment of the present invention.

FIG. 6 is a diagram showing a conventional technique.

[Explanation of symbols]

 1 ...... Illuminator 2 ...... Liquid crystal display 3 ‥ ‥ Reflector 11 ‥ ‥ Light guide 12 ‥ Light source 13 ‥ Protrusion 14 ‥ Light exit side 15 ‥ ‥ End face 16 ‥

Claims (2)

[Claims] 1. A liquid crystal display device comprising a liquid crystal display panel and an illuminating device disposed on an upper surface thereof. 2. The illuminating device has a light guide and a light source arranged on an end face of the light guide, and a light exit side surface of the light guide is substantially perpendicular to a surface substantially parallel to the light exit side surface. The liquid crystal display device according to claim 1, wherein an uneven shape formed by the surface is provided.