JPH10123518A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which contrast is high and visibility is high even both at the time of lighting an illuminator and at the time of non-lighting the illuminator in a thin liquid crystal display device having a lighting function. SOLUTION: A thin illuminator is arranged at the front surface of a liquid crystal display body and a reflection plate is arranged at the rear surface of the liquid crystal body. The illuminator has a light transmission body 11 and a light source 12 arranged at the end face of the light transmission body 11 and light-emitting side flat surfaces 14 and rugged pattern formed by surfaces roughly parallel with the light-emitting flat surfaces and surfaces roughly vertical to the light-emitting side flat surfaces are provided on the surface of the light-emitting side of the light transmission body 11. Thus, in an application like a liquid crystal portable computer terminal, the liquid crystal display device in which display quality is not lowered even though it is used by turning off illumination in a bright place for power saving and contrast is high even at the time of lighting the illuminator is provided.

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 the illumination is constantly turned on, and when a semi-transmissive and semi-reflective sheet that consumes a large amount of power 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.

Therefore, in order to solve such a conventional problem, the present invention arranges an illuminating device in front of a liquid crystal display so that when the illuminating device is turned on and off, the contrast is high and the visibility is high. It is an object to provide a high liquid crystal display device.

[0005]

According to the present invention, there is provided a liquid crystal display device comprising: (1) a liquid crystal display and an illuminating device disposed in front of the liquid crystal display.

(2) The lighting device includes a light guide and a light source disposed on an end face side of the light guide, and a light emitting side plane and a light emitting side plane are provided on a light emitting side surface of the light guide. And an uneven shape formed by a surface substantially parallel to the light emitting side plane and a surface 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. In this case, when there is sufficient external light, the lighting device 1 is turned off and used. In this case, the lighting device 1 acts as a mere transparent plate and does not reduce visibility.
This is effective in not affecting display quality. 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 converted into a mere transparent plate as in the case where the lighting device 1 is turned off. Since it functions and transmits as it is, it is effective to maintain high visibility.

In a transmissive liquid crystal display device in which the lighting device 1 is disposed on the back of the liquid crystal display 2, a light beam from the lighting device 1 transmits through the liquid crystal display 2 only once to generate a contrast between a bright portion and a dark portion. On the other hand, in the reflection type liquid crystal display device in which the lighting device 1 according to the present invention is disposed in front of the liquid crystal display 2, the light from the lighting device 1 passes through the liquid crystal display 2 once and then is reflected by the reflector. Since the light is transmitted once more, the contrast is further increased, which is effective for obtaining high visibility.

FIG. 2A shows an embodiment for realizing the illumination device 1 as described above. A light source 12 is arranged on at least one end face side of the light guide 11. As shown in FIG. 2B, the light guide 11 has rib-like projections 13 provided on one surface of a transparent plate substantially in parallel with the light source 2, and all the surfaces of the projections 13 are arranged with respect to the light emitting side plane 14. It is composed of only a substantially parallel surface and a substantially vertical surface. That is, on the light-emitting side surface of the light guide 11, a light-emitting side plane 14, a surface substantially parallel to the light-emitting side plane 14,
An uneven shape is formed by a surface substantially perpendicular to the light emitting side plane 14. The light guide 11 is formed of a transparent material having a refractive index of 1.4 or more. The light beam from the light source 12 is a light beam 16
a and light rays 16 b, after being incident from the end face 15, the total reflection in the light guide 11 is repeated and emitted only from the side faces of the projections 13, so that more light is emitted from the back surface of the lighting device 1, and the liquid crystal display Can illuminate the body.

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 of a film on a transparent resin or glass flat slope.

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 beam is emitted to the front surface of the lighting device 1 through the path as shown in FIG. 3B, and the visibility is greatly reduced. However, when the value greatly exceeds 対, not only is optically meaningless, but also a problem arises that production becomes difficult. As described above, it is desirable that the ratio of the width to the height of the projection 13 is exactly about the same.

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 changing the density by keeping the size of the projection 13 constant, a method of changing the size while keeping the density constant, a method of changing both of them, 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 is formed on a substantially rectangular light guide 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 projected 13 Light can be emitted from each side of

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. Repeatedly follow the path that travels through the light guide again. 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,
The lighting device is disposed on the front surface of the liquid crystal display device, and the light guide plate has a light emitting side plane on the liquid crystal display side, a surface substantially parallel to the light emitting side plane,
And, since the uneven shape formed by a surface substantially perpendicular to the light emitting side plane is provided, in an application such as a liquid crystal display portable computer terminal, even when used in a bright place for power saving, the display is displayed even when the light is turned off. It is possible to provide a liquid crystal display device with high contrast even during lighting without lowering the quality.

[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 diagram showing another embodiment of the present invention.

FIG. 6 is a diagram showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Illumination device 2 Liquid crystal display body 3 Reflector 11 Light guide 12 Light source 13 Projection 14 Light emission side plane 15 End face 16 Light ray

Claims (1)

[Claims] 1. A liquid crystal display device having a liquid crystal display and a lighting device disposed on a front surface thereof, wherein the lighting device has a light guide and a light source disposed on an end face side of the light guide. The surface on the liquid crystal display side of the light guide is provided with a light emitting side plane, a plane substantially parallel to the light emitting side plane, and a concavo-convex shape formed by a plane substantially perpendicular to the light emitting side plane. Liquid crystal display device.