JPH0555568U - LED surface light source device - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide an LED surface light source device in which direct light from each LED chip is prevented from entering the diffuser plate so that the luminous intensity of light emitted from the diffuser plate can be surely made uniform. To do. [Structure] A plurality of LEs mounted on a printed circuit board 11
A relatively thick plate-shaped light guide 15 made of a transparent material is arranged between the printed circuit board 11 and the diffusion plate 13 and includes a D chip 12 and a diffusion plate 13 arranged so as to cover the LED chip. The LED surface light source device 10 is configured so that the light guide is provided with the conical cutout portion 16 in the upper surface region corresponding to the LED chip.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to an LED surface light source device in which a plurality of LED chips are mounted.

[0002]

[Prior Art]

 Conventionally, as such an LED surface light source device, a device having a structure as shown in FIG. 4, for example, is often used. That is, in FIG. 4, the LED surface light source device 1 includes a printed board 2, a plurality of LED chips 3 mounted on the surface of the printed board 2, and the LED chips 3 above the printed board 2. And a lamp house 5 for preventing light from the LED chip 3 from leaking laterally.

According to the LED surface light source device 1 having such a configuration, by causing each LED chip 3 to emit light, a part of the light emitted from the LED chip 3 is directly emitted as indicated by an arrow in the drawing. To the diffused plate 4 after being partially reflected by the surface of the printed circuit board 2 and the side wall of the lamp house 5 and then incident on the diffuser plate 4, while being diffused by the diffuser plate 4. The light is emitted upward from the entire surface of the diffuser plate 4 through the diffuser plate 4 to act as a surface light source.

[0004]

[Problems to be solved by the device]

 However, in the LED surface light source device 1 configured as described above, the light reaching the lower surface of the diffusion plate 4 from the LED chip 3 has a short distance from the LED chip 3 and is directly incident on the LED chip 3. The light intensity is the highest right above, and the light intensity decreases as it goes to the side, causing unevenness in the light intensity on the entire diffusion plate 4. By diffusing the light with the diffusion plate 4, the light intensity is made uniform. However, it cannot be said that the diffusion plate 4 alone is sufficient for uniformization, and thus uneven illumination occurs.

In view of the above points, the present invention prevents direct light from each LED chip from entering the diffuser plate and ensures that the luminosity of the light emitted from the diffuser plate can be made uniform. It is an object to provide an LED surface light source device.

[0006]

[Means for Solving the Problems]

 In order to achieve the above object, the LED surface light source device according to the present invention is provided with a plurality of LED chips mounted on a printed circuit board and above the printed circuit board so as to cover the LED chips. A relatively thick plate-shaped light guide made of a transparent material is disposed between the printed circuit board and the diffusion plate, and includes a diffusion plate, and the light guide has an upper surface corresponding to the LED chip. It is characterized in that it has a conical notch in the area.

[0007]

[Action]

 According to the above configuration, a part of the light emitted from each LED chip, which is directed upward, is incident on the surface of the conical cutout portion of the light guide at an incident angle exceeding the critical angle and is reflected. As a result, it is possible to prevent the light from directly going upward from the light guide and entering the diffuser plate. Therefore, only the light that does not directly enter the notch of the light guide is then reflected in the light guide, then exits from the upper surface of this light guide, enters the lower surface of the diffusion plate, and is diffused by the action. Since the light is emitted from the upper surface to the outside, only the indirect light from each LED chip is incident on the lower surface of the diffusion plate. Therefore, the light intensity of the light incident on the lower surface of the diffusion plate is sufficient. It is possible to obtain uniform illumination light over the entire area.

[0008]

【Example】

 Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. FIG. 1 shows an embodiment of an LED surface light source device according to the present invention. The LED surface light source device 10 includes a printed circuit board 11, a plurality of LED chips 12 mounted on the surface of the printed circuit board 11, and an LED chip 12 arranged above the printed circuit board 11 so as to cover the LED chip 12. And a lamp house 14 that prevents light from the LED chip 12 from leaking laterally.

The above-mentioned configuration is similar to that of the conventional LED surface light source device 1 shown in FIG. 4, but in the case of the LED surface light source device 10 according to the present invention, a printed circuit board 11 and a diffusion plate 13 are further provided. A relatively thick plate-shaped light guide 15 made of a transparent material is arranged in between.

The light guide 15 is provided with a conical cutout portion 16 in the region of the upper surface corresponding to the LED chip 12 (see FIG. 2) whose axis is a vertical line passing through the LED chip 12. Here, as shown in FIG. 3, the notch 16 reflects light that is incident on the peripheral surface of the notch 16 from each LED chip 12 at an incident angle θ that exceeds the critical angle. At the same time, when the light passing around the notch 16 reaches the upper surface of the light guide 15, its size and inclination angle are selected so that the incident angle θ with respect to this upper surface is reflected beyond the critical angle. ing.

The LED surface light source device 10 according to the present invention is configured as described above, and a part of the light emitted from each LED chip 12 that goes upward is incident on the inside of the light guide 15. By being reflected by the peripheral surface of the concave portion 16 or by the upper surface of the light guide 15, it is possible to prevent the light from directly advancing upward from the light guide 15 and entering the diffusion plate 13. Further, the light incident around the cutout portion 16 is incident on the upper surface of the light guide 15 at an incident angle that exceeds the critical angle, and therefore is reflected by the upper surface of the light guide 15 and accordingly, The light emitted from the LED chip 12 does not directly enter the diffusion plate 13, but enters the light guide 15 from the lower surface of the light guide 15, and then the side wall, the upper surface, the bottom surface of the light guide 15 and the lamp. Only the light reflected at least once by the side wall of the house 14 is incident on the lower surface of the diffusion plate 13, and is diffused by the action of the diffusion plate 13 while being emitted to the outside from the upper surface of the diffusion plate 13. I'm supposed to get it. Thus, only the indirect light from each LED chip 12 is incident on the lower surface of the diffuser plate 13, and the light intensity of the light incident on the lower surface of the diffuser plate 13 can be made sufficiently uniform. Illumination light that is substantially uniform is obtained over the entire area.

[0012]

[Effect of the device]

 As described above, according to the present invention, of the light emitted from each LED chip, a part of the upward light is incident on the surface of the conical cutout portion of the light guide at an incident angle exceeding the critical angle. Since the light is incident and reflected, it is possible to prevent the light from directly traveling upward from the light guide and being incident on the diffuser plate, and thus only the light that does not directly enter the cutout portion of the light guide. After that, after being reflected in the light guide, it is emitted from the upper surface of this light guide, and is emitted from the upper surface to the outside while being diffused by the diffusion plate. Only indirect light from each LED chip will enter. Therefore, the luminosity of the light incident on the lower surface of the diffuser plate is made sufficiently uniform, and almost uniform illumination light is obtained over the entire surface. Thus, according to the present invention, it is possible to prevent the direct light from each LED chip from entering the diffuser plate and to surely make the luminous intensity of the light emitted from the diffuser plate uniform. A device is provided.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of an LED surface light source device according to the present invention.

FIG. 2 is a plan view of a light guide in the apparatus of FIG.

FIG. 3 is a partially enlarged sectional view of one LED chip of FIG.

FIG. 4 is a schematic sectional view showing an example of a conventional LED surface light source device.

[Explanation of symbols]

 10 LED Surface Light Source Device 11 Printed Circuit Board 12 LED Chip 13 Diffusion Plate 14 Lamp House 15 Light Guide 16 Notch

Claims (1)

[Scope of utility model registration request] 1. A plurality of LEs mounted on a printed circuit board
In an LED surface light source device including a D chip and a diffusion plate disposed above the printed circuit board so as to cover the LED chip, a transparent material is provided between the printed circuit board and the diffusion plate. A relatively thick plate-shaped light guide is provided, and the light guide is provided with a conical notch in a region of an upper surface corresponding to the LED chip.
Surface light source device.