JPS5934589A - Light emitting diode display - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light emitting diode display device with an easy-to-design reflective surface and an effective display surface.

In a conventional light emitting diode display device that displays numbers, characters, figures, etc. using light emitting diodes, as shown in FIG. 1, a light emitting diode (2) is placed and fixed on a substrate (1). It was covered with a reflective frame (3) made of white resin molding. However, in such a light emitting diode display, 1
4 display windows (4 J to form one picture)
) The upper opening of the bar-shaped level display has a rectangular shape, and the upper opening of the bar-shaped level display has a tip-like shape, and is often not circular. Therefore, the reflective surface 15) (57 was almost vertical or curved, rounded, or multi-stepped.
These were determined based on experiments and the experience of engineers.

In addition, for lighting equipment such as light bulbs or floodlights, reflectors are manufactured by simulating the optical path using a large computer.
Light-emitting diode display devices have diversified display contents and formats, and if they cannot respond promptly, they will lose their commercial value, so large computers are not suitable for such trendy items.

The present invention solves problems with light-emitting diode display devices such as brightness and luminance distribution on the display surface, and also solves problems with light-emitting diode display devices (2).
Noting that the luminance distribution is approximately heart-shaped even though the light emission originates from the Pn junction (6), this was done using a method that can also be applied to a small computer (the Seiko computer using a microprocessor). Figure 2 a) is a luminance distribution diagram of a light emitting diode, which will be described below in detail. What is the brightness at a certain distance in front of the light emitting diode when the direction parallel to the substrate is 90 degrees? Relative values are shown. (7) is a characteristic curve for a gallium phosphorous light-emitting diode, which is arranged so that the VCPn junction is approximately parallel to the substrate as shown in Figure 1, but since the element is almost transparent to the emitted color, the The area where most of the emission is from 50 to 60, which is the upper side of the device from the Pn junction.
degree. The lower part (90 degrees) and the upper part (0 degrees) of the element are dark, but this is because there are electrodes on the surface. Therefore, when looking at the brightness distribution from +90 degrees to 190 degrees, it becomes almost heart-shaped as mentioned above. ing. This is a common characteristic of light emitting diodes whose elements are substantially transparent with respect to the color of the emitted light.

The above-mentioned luminance distribution is relatively well known, but although there are attempts to modify the luminance distribution by processing the device itself to make it more advantageous for display, there are few attempts to use this distribution as is. . The present invention was made by paying attention to the fact that the reflective surface (51(5)) is directly affected within the range of 15 degrees to 75 degrees within this brightness distribution.Based on this brightness distribution, When calculating the brightness on the display surface with respect to the optical path, if you try to express this brightness distribution with a specific function using the light emitting diode as the base point, you will find several functional formulas VC.
7 or becomes a high-order function, making it difficult to process with microprogramming. Therefore, by providing a virtual light point (F5) directly above the light emitting diode 02, the brightness distribution could be approximated as a quadratic function (parabola or ellipse). However, if the board is a general printed circuit board (based on GAX epoxy resin, paper epoxy resin, phenol resin, etc.), one side of the light emitting diode from the position of the Pn junction size, 8g (0.28 to 0.4
xtg) 0.5 to 2.2 times the height of the light emitting diode, and considering the molding error of the reflective frame, which will be described later, the virtual light point should be placed at a position 15 to 2.5 times the height of the light emitting diode from the substrate. Just place it. Cross mark (81f81-) in Figure 2(a)
... is the original function (coordinate axis transformation @) b = (Sinθ-0,1
4Co sθ) 10.22coa2θ This is the magnitude of brightness calculated using a parabolic function. Furthermore, by normalizing this function, it is possible to match the focal point position with the virtual light point, so the brightness b-aoO in the range of 5 degrees to 80 degrees
It can be expressed by a simple formula such as 8eo2(θ/2). Even if it is expressed using a parabolic function, the applied angle is only slightly different, so
The luminance expressed in this way is expressed as b (θ) [10°
The following explanation will be continued assuming that 〈θ〈80°〕J.

FIG. 2 (presented) is an explanatory diagram showing the relationship between the reflective surface +151 and the display surface aD according to the embodiment of the present invention, and is drawn for comparison with the luminance distribution in FIG. 2(a). This reflective surface (15
+ corresponds to the reflective surface (5) from the slope or curved surface of the reflective frame (3) in Figure 9!1, and is made of Noryl resin, ABSP
It consists of a white resin molded product such as jA resin. And display screen IO
indicates the position of the surface of this reflective frame (3) or the position when a filter or the like is placed on the surface. Conventionally, such a reflective surface (151) was used to effectively guide the light emitted from the light emitting diode σ2 to the display surface 10, but in the present invention, the luminance distribution from the virtual light point [F] is as shown in FIG. × of a)
It is provided to effectively guide light from a light source such as the marks (81f81-...) to the display surface 161.

The effect of such a reflective surface ff51 will be explained.

The light emitted from the virtual light point [F] hits the reflective surface (151),
There, it is reflected and guided to the display surface (161).At this time, the distribution of light on the display surface 1161 is determined by the optical path and the brightness of each optical path. However, in the embodiment of the present invention, the light distribution on the display surface 1G is determined by the light coming directly from the light emitting diode (17J) and the reflected light from the reflective surface +151 (however, the light source can be obtained as the sum of the above virtual light point 0).

Let's take an arbitrary optical path as an example. To explain it specifically, 1
It will look like this: First, the coordinates are set at the center position of the light emitting diode 02 as the origin, and the ICX axis in the direction of the substrate, X4iII]
The direction perpendicular to the VC is the y-axis, and the reflecting surface a51 is y-, f(
3) (However, f(2) is a function of the linear (plane) or quadratic (curved surface) of Assume that the display surface circle is parallel to the X axis and has a y-intercept y2. Virtual light point (P)
As mentioned above, is given by the size of the light emitting diode, so this coordinate is (0, yO),! Knee J7+.

Then, find the coordinates of each intersection. The formula for light (1) emitted from virtual light point ()1 is y-xtanθ+yO (where θ is
Since it is an angle with respect to the axis and is an angle to which the brightness equation applies, it is expressed as 101'≦θ≦80° (taken as equation 0).The position where this light hits the reflecting surface [151] is 0.
It can be easily given by solving the simultaneous equations of the formula and the 0 formula, so if this coordinate fr: (x+, ylp), the reflected light (■)
The formula is y-yt~tan (2tan-'(=1/f
' (xl)) -tan tanθ) (x-x
1) (■format) and l), display surface (X at +61
Since the coordinates can be easily calculated by setting them to y-y2 in the formula 0, let these coordinates be (X2., y2).

If the coordinates are determined in this way, the brightness is (initial brightness)/(
distance), so the brightness bd at the display surface (X2.y2)
From t d−r g(X)/((X?+(y' MO)2
)・((X2-Xl)2+(72'11)2)di4.

Therefore, the brightness unevenness can be determined by finding this in the range of θ from 30 degrees to 80 degrees and comparing it with the tolerance of brightness variation (for example, light diffusion of a filter) on the display surface (161). Repetitive calculations such as this are the most efficient operation of microprogramming, so even if you use a high-level language such as BASIC, calculations can be compared in a short processing time. Reflective surface aS with uneven brightness
It is also possible to search for functions.

As described above, the present invention provides a light emitting diode display device including a light emitting diode that is substantially transparent to the emitted light color mounted and fixed on a substrate, and a reflective surface surrounding one light emitting diode, in which the reflective surface is arranged above the light emitting diode. Since it is configured to have an effect on the light emitted from the virtual light point provided, it is possible to evaluate numerically that it is bright and uniform on the display surface, and conversely, it is possible to use the light from the light emitting diode efficiently. It is easy to design display devices that can be used.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a light emitting diode display device, Figure 2 (a
) is a luminance distribution diagram of a light emitting diode, and FIG. 2(c) is an explanatory diagram showing the relationship between a reflective surface and a display surface in an embodiment of the invention. (1)...Substrate, (21[+2...Light emitting diode, (3)...Reflection frame, [5)(51(+51...
Reflective surface, (g)...virtual light spot. Packing light intensity

Claims (1)

[Scope of Claims] 1) A light emitting diode display device comprising a light emitting diode that is substantially transparent to the light emitting color and fixed on a substrate, and a reflective surface surrounding the light emitting diode, wherein the reflective surface is a light emitting diode. A light emitting diode display device characterized in that it is configured to have an effect on light emitted from a virtual light point provided above. 2) The virtual light point is a light point whose brightness distribution is obtained by a quadratic function Ej with the virtual light point as the focal point, and is simulated as the original light source emitted from the light emitting diode. - The light-emitting diode display device according to item 1 of the claimed scope, which features a hand.