JP2800628B2 - 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. 9 (a), a liquid crystal display device having an illumination function is such that a planar illumination device 1 is arranged on the back of a liquid crystal display panel 2 and usually illumination is always turned on. 9 or a transflective sheet 4 between the liquid crystal display panel 2 and the lighting device 1 as shown in FIG.
Was arranged so that it can be used for both lighting and non-lighting.

[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.

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 to be illuminated has high contrast and high visibility.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is arranged on a front surface of a liquid crystal display panel which is an object to be illuminated, and a light guide and an end face of the light guide. And a lighting device having a light source.

[0006] In the lighting device of the present invention, the one surface of the light guide may include a light exit side plane, a plane parallel to the light exit side plane, and a plane perpendicular to the light exit side plane. 10 degrees or less
And a light beam from the light source propagates through the light guide and exits from the uneven portion to form the illuminated object. And is emitted through the light guide. Here, “the surface parallel to the light exit side plane”
Is a plane substantially parallel to the light-emitting side plane, that is, substantially parallel
Point to the surface.

The lighting device of the present invention is perpendicular to the plane on the light exit side.
The inclination in the range of 10 degrees or less with respect to the
Is characterized by an inclination in a direction in which the width of the convex portion decreases toward the tip .

The illuminating device according to the present invention is characterized in that the light guide is formed of a material having a different refractive index only in the uneven portion.

[0009] The illumination device of the present invention is characterized in that the ratio of the width to the height of the convex portion of the concave and convex shape is approximately one to one.

The lighting device of the present invention is characterized in that the light guide is arranged between the liquid crystal display panel and the front polarizing plate.

[0011]

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 panel 2. A reflection plate 3 is arranged on the back of the liquid crystal display panel 2 to constitute a reflection type liquid crystal display device. The illuminating device 1 has a function of projecting a light beam on the liquid crystal display panel 2 side and transmitting the light beam reflected by the reflecting plate 3 with almost no dispersion. This is effective when the illuminating device 1 is turned off when there is sufficient external light, and in this case, the illuminating device 1 acts as a mere transparent plate so as not to lower 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 panel 2 and the light reflected by the reflecting plate 3 is used as a mere transparent plate in the same manner as when the lighting device 1 is turned off. Since it functions and transmits as it is, it is effective to maintain 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 panel, light rays from the illumination device are transmitted only once through the liquid crystal display panel 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 panel, light from the lighting device passes through the liquid crystal display panel once, is reflected by the reflector, and is 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 projection 13 on the rib is provided on one surface of the transparent plate substantially in parallel with the light source 12, and each surface of the projection 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 only from the side surfaces of the projections 13. In many cases, the liquid crystal display panel 2 can be illuminated. When a protective sheet or the like is overlaid on the liquid crystal display panel 2 side of the light guide 11 or on the opposite side, a slight air layer is always provided, and this is because light rays repeat total internal reflection inside the light guide 11. Is necessary for

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.

[0015] As shown in FIG.
By using a material having a higher refractive index, a light ray traveling inside the light guide plate 11 like the light ray 16 is refracted when entering the projection 13 and further refracted when exiting from the side surface of the projection 13. The angle of the final output light can be made larger with respect to the output side plane 14. in this case,
It is suitable to form and manufacture by the method of bonding a transparent film having a high refractive index on the above-mentioned transparent resin or glass flat plate.

As shown in FIG. 4A, 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, and is irradiated on the side surface of the projection 13. In order to achieve this, a height higher than the width of the projection 13 is required. In the case below this, the light beam is emitted to the upper surface of the light guide 11 along the path as shown in FIG. 4B, and the visibility is greatly reduced. 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 wavelength of visible light is about 380 nm to about 700 nm, the projections 13 need to have a size of about 5 μm or more in order to prevent the occurrence of spectral stripes due to interference due to diffraction. Further, since the size of the pixel of the liquid crystal display panel 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 contents described above, the size of the protrusion 13 is desirably about 10 μm or more and 50 μm or less for convenience in manufacturing.

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.

FIG. 5A shows another embodiment. 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. 5B, 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. 6A 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. The light rays emitted from the cylindrical surface are different from those of the prism shown in FIG.
As shown in (b), the irradiation range can be widened.

Another embodiment is shown in FIG. The light guide 11 is superimposed directly on the liquid crystal display panel, and the polarizing plate 17 is further superimposed on the light guide 11. Another polarizing plate 18 is disposed below the liquid crystal display panel, and the reflecting plate 3 is disposed further below. It has been found that this configuration improves the visibility.

FIG. 8 shows an example in which a side surface of the projection 13 is provided with an inclination angle of 10 degrees or less. When the inclination angle is large, visibility is reduced because it affects the transmission of light rays in the vertical direction, and illumination performance is reduced because the inclination of the emitted light is large. In the case of, the influence is small, and it is effective as a punch taper when manufacturing by injection molding or the like.

[0023]

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 another embodiment of the present invention.

FIG. 7 is a diagram showing another embodiment of the present invention.

FIG. 8 is a diagram showing another embodiment of the present invention.

FIG. 9 is a sectional view showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 照明 Illumination device 2 ‥‥‥ Liquid crystal display panel 3 反射 Reflector 11 光 Light guide 12 光源 Light source 13 突起 Projection

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-17730 (JP, A) JP-A-5-158034 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/1335 530

Claims (4)

(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. One surface has a light emitting side plane, a plane parallel to the light emitting side plane, and a plane perpendicular to the light emitting side plane .
And an uneven shape formed by a surface having an inclination in a range of 10 degrees or less , wherein the inclination is such that the width of the convex portion of the uneven shape is toward the tip.
The light from the light source propagates through the light guide, exits from the uneven portion, illuminates the illuminated body, and transmits through the light guide. An illuminating device characterized in that the illuminating device is emitted. 2. A lighting device, wherein the light guide according to claim 1 is formed of a material having a different refractive index only in a portion having a concave and convex shape. 3. A lighting device, wherein the ratio of the width to the height of the projection of the uneven shape according to claim 1 or 2 is approximately one to one. 4. An illuminating device, wherein the light guide according to claim 1, 2 or 3 is arranged between an illuminated body and an upper polarizing plate.