JP3481834B2 - Liquid crystal display - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display having an illumination function. 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 disposed on the back of a liquid crystal display 2, and usually always illuminates. 6 (b), a semi-transmissive and semi-reflective sheet 4 is arranged between the liquid crystal display 2 and the illuminating device 1 for use in both illuminated and non-illuminated states. I was able to do it. However, such a conventional liquid crystal display device having an illumination function uses a semi-transmissive and semi-reflective sheet which consumes a large amount of electric power when the illumination is constantly turned on. In this case, there is a problem that the display is dark and the contrast is low both when the lighting device is turned on and when the lighting 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] In order to solve the above-mentioned problems, a liquid crystal display device of the present invention is characterized in that: (1) a liquid crystal display body and an illuminating device arranged on the front surface thereof. . (2) The lighting device comprises: a transparent light guide ;
And a light source disposed on the end face side of the light guide member, the surface of the liquid crystal display side of the lightguide, light outgoing side plane, the light exit side plane parallel direction of the surface, and the light outgoing side plane Vertical plane
And the light from the light source is provided .
The line propagates through the light guide, and
Illuminate the liquid crystal display by emitting light from the
The light is emitted through the light guide . 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. 2 (b), 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 each surface of the projections 13 is all on 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, total reflection is repeatedly performed in the light guide 11 and emitted only from the side surface of the projection 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 of less than that, the light ray is emitted to the front surface of the lighting device 1 through the path shown in FIG. 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 on the cylindrical surface of the projection 13 at a critical angle or less emits light, and the light beam irradiated on the cylindrical surface at the critical angle or more repeats reflection on the cylindrical surface, inverts on the bottom surface of the protrusion 13, and further reflects on 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. 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] 1 lighting equipment 2 Liquid crystal display 3 Reflector 11 Light guide 12 light source 13 protrusion 14 Light emitting side plane 15 End face 16 rays

Claims (1)

(57) In the liquid crystal display device having a Patent Claims 1. A lighting device arranged in front of the liquid crystal display element and the liquid crystal display element, the illumination apparatus includes a transparent light guide, and a light source disposed on the end face side of the light guide member, the surface of the liquid crystal display side of the lightguide, light outgoing side plane, the light exit side plane parallel direction of the surface, and the light outgoing side plane vertical
The uneven shape formed by the direction of the surface provided, light from the light source, when propagating in the light guide DOO
In addition, the liquid crystal display is emitted from
A liquid crystal display device , which illuminates a body, is reflected, and is emitted through the light guide .