JPH0449645Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a lighting device used as a backlight of a display using liquid crystal.

[Conventional technology]

A conventional lighting device used as a backlight for a liquid crystal display has a configuration as shown in FIGS. 3 and 4. In other words, it is composed of a fluorescent tube 11, a reflecting mirror 12 provided below the fluorescent tube 11 and having a curved surface having a quadratic cross section, and a diffuser plate 13 provided on the front surface of the fluorescent tube 11. Direct light from a fluorescent tube 11 and reflected light reflected by a reflecting mirror 12 are applied to a diffuser plate 13, where they are converted into diffused light.

In such a lighting device, uniform illumination light cannot be obtained because the central part is particularly bright, so the diffuser plate 13 is
A thick part 13a is formed in the center of the thick part 1.
By utilizing the scattering of light within 3a, the diffusion effect at the center is enhanced to obtain uniform illumination. However, even with this level of increase in the diffusion effect, it is still inevitable that the central area will become brighter, and uniform illumination cannot be obtained. Further, by strengthening the diffusion effect of the diffuser plate as a whole, it is possible to further increase the diffusion effect in the thick portion 13a, but the whole becomes dark and sufficient brightness cannot be obtained.

[Problem that the invention attempts to solve]

The problem that the present invention aims to solve is that it is composed of a line light source such as a fluorescent tube, a curved reflector provided on the back side of the line light source, and a diffuser plate placed on the front side of the line light source. An object of the present invention is to provide a lighting device that can provide bright and uniform illumination by increasing the amount of light that reaches the vicinity of the end of a diffuser plate.

[Means for solving problems]

The illumination device of the present invention consists of a linear light source, a curved reflecting mirror, and a diffuser plate, and by arranging a laminated light guide plate on the back side of the linear light source, light from the linear light source to the reflecting mirror is directed. By transmitting light at the periphery using this light guide plate, the amount of light at the periphery is increased, and bright and uniform surface illumination can be obtained.

〔Example〕

Next, an embodiment of the lighting device of the present invention will be described based on the drawings. FIG. 1 is a divided perspective view of an embodiment of the present invention, in which 1 is a line light source such as a fluorescent tube, and 2 is a line light source 1.
Curved reflector plate installed on the back side (lower side in the drawing), 3
4 is a diffuser plate, and 4 is a laminated light guide plate installed between the linear light source 1 and the reflecting plate 2, which is made by laminating a large number of thin plate-like bodies made of transparent material. The emission part 4b is located at the periphery of the reflector (a part away from the light source 1).

According to this embodiment, the light from the linear light source 1 is directed upward and reaches the diffuser plate 3 directly, and is directed downward and is reflected by the reflector 2 and is reflected by the laminated light guide plate 4.
The light enters from the entrance part 4a, is transmitted in a direction away from the linear light source 1 by the light guide plate, is emitted from the exit part 4b, is reflected by the reflector plate 2, and is then diffused either directly or across the light guide plate 4 in a direction perpendicular to it. Reach board 3. In this way, the light emitted from the linear light source 1 and traveling in the opposite direction (downward) to the diffuser plate 3 is transmitted in a direction away from the linear light source 1 through the light guide plate 4, and then reflected by the reflector plate 2 and then directed to the diffuser plate. Reach the periphery of 3. This increases the amount of light in the periphery where the amount of light decreases, making it possible to provide uniform illumination as a whole. In this way, without thickening the central diffuser plate or installing a light intensity adjusting plate on the front side of the light source to block direct light, we are able to utilize the light intensity in bright areas without reducing it, and use the light intensity in the peripheral areas as is. Since the amount of light is increased, bright and uniform surface illumination is possible.

In the laminated light guide plate 4 used in this embodiment, it is preferable that a transparent layer having a higher refractive index than this is provided between the thin plate-like bodies so that light is totally reflected within the layer and the transmittance thereof is increased. For example, it is conceivable to bond each plate-like plate with a transparent adhesive having a high refractive index to form a laminate. Furthermore, the luminance distribution on the diffuser plate 3 can be made preferable by adjusting the arrangement positions of the entrance part 4a and the exit part 4b of the light guide plate 4.

Further, the curved reflector may have an arcuate cross section, or may have a quadratic or other curved cross section, so to speak, an aspherical shape. Alternatively, it may have a Fresnel shape.

Figure 2 shows the luminance distribution of the lighting device of the present invention, where φ ₁ is direct light only, φ ₁ + φ ₂ is direct light φ ₁ plus reflected light φ ₂ , and φ ₁ + φ ₂ + φ ₃ is Furthermore, light φ ₃ from the light guide plate 4 is added. As shown in this figure, φ ₁ +φ ₂ +φ ₃ has an extremely flat luminance distribution.

[Effect of idea]

The lighting device of the present invention directs direct light to the diffuser plate without attenuation, and uses a laminated light guide plate to guide light from the light source toward the reflector plate to dark areas such as the periphery. Since the brightness on the diffuser plate is made uniform, bright and uniform surface illumination can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view of one embodiment of the present invention;
The figure is a graph showing the luminance distribution of the same example, FIG.
FIG. 4 is an exploded perspective view and a sectional view of a conventional lighting device, respectively. 1...Line light source, 2...Reflector, 3...Diffusion plate,
4...Laminated light guide plate, 4a...Incidence part, 4b...Emission part.

Claims (1)

[Scope of utility model registration request] In an illumination device comprising a linear light source, a diffuser plate disposed on the front side of the linear light source, and a curved reflector plate disposed on the back side of the linear light source, 1. A lighting device comprising: a laminated light guide plate that is substantially parallel to the diffuser plate and has an entrance portion near the periphery of the reflector plate and has an output portion close to a peripheral portion of the reflector plate.