Light Emitting Diode Display Panel

This invention relates to a light emitting diode display panel composed of a plurality of light emitting diode elements.

As shown in FIG. 3, prior art display panels using light emitting diodes are typically composed of red (R) and green (G) light emitting diodes each including a stem of 3-5 mm .PHI. in outer diameter and disposed alternately in arrays such that mixed colors can be displayed. With a display panel thus structured, however, only a low brightness can be obtained because the number of light emitting diodes that can be disposed per unit area is limited by their external dimensions. In order to improve the brightness of a display panel, therefore, it may be considered to make use of two-color light emitting diode elements 2 structured as shown in FIG. 4 with two light emitting diode chips 2b and 2c on a single stem 2a emitting light of different colors such as red from one 2b and green from the other 2c. With two-color light emitting diode elements 2 like this, the number of light emitting diode chips per unit area of a display panel can be doubled and hence brighter panels can be made available.

Since the individual chips 2b and 2c of a two-color light emitting diode element 2 are disposed on the stem 2a away from the optical axis of the element 2 as shown in FIG. 4, however, red light and green light are emitted in mutually different directions as shown in FIG. 5 wherein numeral 3b indicates the directional intensity distribution of red light from the red light emitting diode chip 2b of FIG. 4 and numeral 3c indicates that of green light from the green light emitting diode elements like this are arranged as shown in FIG. 6 such that mutually adjacent chips emit different colors, different colors will be seen, depending upon the position of the viewers with respect to the panel. The view from the right-hand side or left-hand side, for example, will see different colors alternately along vertical lines.

It is therefore an object of the present invention to provide a light emitting diode display panel of high brightness from which the color or emitted light does not appear differently, depending on the angle at which it is viewed.

The above and other objects of the present invention are achieved by providing a light emitting diode display panel wherein two-color light emitting diode elements are disposed in matrix formation such that light emitting diode chips of the same color are adjacent to each other in the direction in which two-color light emitting diode chips are aligned but chips of different colors are mutually adjacent along the perpendicular direction. With a light emitting diode display panel thus structured, improved brightness can be obtained and the color of emitted light does not appear differently, depending on the angular position of the viewer with respect to the panel.

The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:

FIG. 1 is a drawing showing the arrangement of two-color light emitting diodes according to the present invention;

FIG. 2 is a schematic sectional view of a display panel according to another embodiment of the present invention;

FIG. 3 is a drawing showing the arrangement of light emitting diodes in a prior art display panel;

FIG. 4 is a sectional view of a two-color light emitting diode element for showing its structures schematically;

FIG. 5 is a schematic drawing of distribution of light intensity from the element of FIG. 4; and

FIG. 6 is a drawing showing another arrangement of two-color light emitting diodes to be compared with that shown in FIG. 1.

FIG. 1 shows an arrangement of two-color light emitting diode elements 2 according to the present invention. The structure and light-emission characteristics of the elements 2 are as explained above by way of FIGS. 4 and 5.

The arrangement shown in FIG. 1 is characterized in that two light emitting diode chips of the same color (red (R) or green (G)) are adjacent each other in the direction indicated by H along which the two light emitting diode chips in each element 2 are aligned and that two light emitting diode chips of different colors are adjacent each other in the perpendicular direction indicated by V. With an arrangement as described above, one can realize a display panel with improved brightness from which the color of emitted light does not appear to change, depending on the angular position of the viewer and with which intermediate colors can be beautifully displayed when seen from a distance.

The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and many modifications and variations are possible in light of the above teaching. For example, FIG. 4 is not intended to limit the type of two-color light emitting diodes in a display panel of the present invention. Also included within the scope of the present invention are two-color light emitting diode elements of wich the chip of each color comprises a pair, each pair having common directionality. FIG. 2 shows still another kind of two-color light emitting diode element within the scope of this invention, having pairs of two-color chips 2b and 2c disposed on a substrate 4, a reflecting plate 5 provided to cover it with a V-shaped holes 6 each corresponding to a pair of these chips 2b and 2c, and a transparent resin material 7 molded in these holes 6. In other words, these types of two-color light emitting diode elements may also be arranged as shown in FIG. 1 to achieve the objects of the present invention.