Illuminating unit and display device using the unit

1. An illuminating unit comprising:

a point light source;

a light guide plate having an illuminating surface that is illuminated by light from the point light source;

a light pipe having an incident surface and an emerging portion, the light pipe changing the direction of light incident on the incident surface so that the light emerges from the emerging portion; and

a joining portion that integrally joins the emerging portion and the light guide plate;

wherein the light pipe has an elliptical cylinder shape, and the incident surface has an elliptical shape.

2. An illuminating unit according to claim 1 ; wherein the emerging portion of the light pipe includes an elliptical cylinder shape bus line.

3. An illuminating unit according to claim 1 ; wherein the center of light emitted by the point light source is in the vicinity of at least one of two foci included in the elliptical surface forming the incident surface of the light pipe.

4. An illuminating unit comprising:

a point light source;

a light guide plate having an illuminating surface that is illuminated by light from the point light source;

a light pipe having an incident surface and an emerging portion, the light pipe changing the direction of light incident on the incident surface so that the light emerges from the emerging portion; and

a joining portion that integrally joins the emerging portion and the light guide plate, the joining portion joining a bottom surface of the light pipe and a bottom surface of the light guide plate;

wherein the light pipe has a rectangular parallelpiped shape, and the incident surface has a rectangular shape; and

wherein the center of light emitted from the point light source is disposed in a position separated from at least one side of the rectangular shape incident surface of the light pipe by m/n (where m and n are each irreducible natural numbers other than 1, and m<n).

5. An illuminating unit according to claim 4 ; wherein the thickness of the joining portion becomes larger with increasing distance from the point light source.

6. An illuminating unit according to claim 5 ; wherein the thickness of the joining portion becomes linearly larger with increasing distance from the point light source.

7. An illuminating unit according to claim 5 ; wherein the thickness of the joining portion becomes quadratically larger with increasing distance from the point light source.

8. An illuminating unit according to claim 4 ; further comprising a prism formed in the rectangular shape incident surface of the light pipe, the prism having a depressed shape toward an inner side of the rectangular shape incident surface and having an apex point that coincides with the center of light emitted from the point light source.

9. An illuminating unit according to claim 1 ; further comprising minute scattering structure members provided in a bottom surface of the light guide plate, the haze value of the minute scattering structure members increasing with increasing distance from the light pipe.

10. An illuminating unit comprising:

a point light source;

a light guide plate having an illuminating surface that is illuminated by light from the point light source;

a light pipe having an incident surface to which light from the point light source is made incident, and an emerging portion from which the incident light from the incident surface emerges;

a joining portion that integrally joins the emerging portion and the light guide plate; and

a prism formed in the incident surface of the light pipe, the prism having a depressed shape toward an inner side of the incident surface and having an apex point that coincides with the center of light emitted from the point light source.

11. An illuminating unit according to claim 10 ; wherein the light pipe changes the direction of light incident from the incident surface so that the light emerges from the emerging portion.

12. An illuminating unit according to claim 11 ; wherein the light pipe has an elliptical cylinder shape, and the incident surface has an elliptical shape.

13. An illuminating unit according to claim 10 ; wherein the thickness of the joining portion becomes larger with increasing distance from the point light source.

14. An illuminating unit according to claim 13 ; wherein the thickness of the joining portion becomes linearly larger with increasing distance from the point light source.

15. An illuminating unit according to claim 13 ; wherein the thickness of the joining portion becomes quadratically larger with increasing distance from the point light source.

16. An illuminating unit according to claim 10 ; further comprising minute scattering structure members provided in a bottom surface of the light guide plate, the haze value of the minute scattering structure members increasing with increasing distance from the light pipe.

17. A display device comprising:

one or more display elements; and

an illuminating unit that illuminates the one or more display elements, the illuminating unit comprising a point light source; a light guide plate having an illuminating surface that is illuminated by light from the point light source; a light pipe having an incident surface and an emerging portion, the light pipe changing the direction of light incident on the incident surface so that the light emerges from the emerging portion; and a joining portion that integrally joins the emerging portion and the light guide plate; wherein the light pipe has an elliptical cylinder shape and the incident surface has an elliptical shape.

18. A display device according to claim 17 ; wherein the one or more display elements comprise one or more liquid crystal display elements.