JPH11133890A - Led display device and led display system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a contrast ratio by forming a sectional shape of a louver to a curved surface shape in its upper side tip part and adding minute ruggedness to the surface of the curved surface shape. SOLUTION: The section of the louver 311 is formed into the nearly curved surface shape in the upper side tip part of the louver 311 so as to enlarge an radiation angle of light emitted from an LED arranged upward it. Thus, a surface area viewed from a viewer side is increased, and a reflection surface of external light is formed large. Particularly, on the upper side tip part 307 of the louver 311, reflection light is observed remarkably since the reflection light of the external light directly turns toward the viewer side. Furnher, by making the upper side tip part 317 of the louver 321 section have the curved surface shape having the ruggedness, an adverse effect due to the reflection surface is reduced. Although the surface of the curved surface shape having the ruggedness forms the reflection surface, it diffusedly reflects the external light by the minute ruggedness, and the reflection light directly turning toward the viewer is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LED display having a plurality of light emitting diodes arranged therein and having a louver for reducing the influence of sunlight or the like radiated to each light emitting diode, and particularly to an LED display having a wide viewing angle. The present invention relates to a high-contrast LED display in which the influence of extraneous light is reduced while reducing the influence of external light.

[0002]

2. Description of the Related Art Light emitting diodes (hereinafter, also referred to as LEDs) capable of emitting RGB (red, green, blue) light with an ultra-high brightness of over 1000 mcd have been developed. As a result, a full-color LED display using LEDs with low power consumption and long life has become possible. Such an LED display device can emit light with high luminance.

[0003] For this reason, attention has been paid to an LED display that can be used with high brightness even in a place where external light is relatively strong, such as outdoors or semi-outdoors, which are listed as platforms on train stations.

FIG. 4 is a schematic front view of an LED display device. Specifically, each light emitting diode 4 capable of emitting RGB light
02 is arranged as a pixel in a 16 × 16 dot matrix. In the case of dynamic driving, a common driver or a segment driver, which is a driving unit 406 of the LED display device, is driven based on video data, and a desired LE is driven.
By turning on D, a desired image or the like can be displayed. A louver 40 is provided on the stage for each pixel to reduce external light such as sunlight from being directly applied to the LED.
1 is arranged. Such an LED display device as a whole can be an LED display device with improved contrast. Louver 401 provided on LED display
Is determined by selecting a desired angle, length, width and thickness for the purpose of shielding incident light from a certain angle such as sunlight.

On the other hand, an LED display device is often installed at a position higher than a viewer such as a billboard. Further, the louver 401 is formed of resin or metal, but needs to have a certain strength. Therefore, the louver 401 as a light shielding member needs a certain length and thickness.

[0006]

However, if the length of the louver 301 is long and the louver 301 is thick, the louver 301 shown in FIG.
For a viewer below the front of the LED display (A) (the position of the viewer's eyes is shown in the figure), the LED is used.
The light emission of 302 (displaying a part of the light emitting diode) is shaded by the louver 301. Therefore, the range that can be visually recognized by a viewer may be narrowed. In particular, if the installation position of the LED display such as a billboard is relatively high, a slight difference in elevation angle greatly affects the visible range. In addition, when LEDs that emit RGB light are arranged close to each other to use mixed color light emission,
LED3 partially constituting a pixel by louver 301
Occlusion of 02 causes a problem that a desired emission color cannot be obtained.

In particular, when LEDs emitting RGB light are emitted by mixing colors of different light emitting diodes, the distance between the light emitting diodes is increased. Although a mixed color is observed as one pixel by a viewer, a large distance is generated between the louver and each of the LEDs arranged in close proximity. Therefore, the color mixing will be more greatly destroyed at the position of the viewer.

In these cases, the cross-sectional shape of the louver 311 as shown in FIG. 3 (B) is such that the upper end 307 of the louver is formed in a curved shape, so that the light emission of the LED 312 (part of the light emitting diode is displayed) is shaded by the louver 311. , And the viewing range can be widened.
However, the LED display device having such a configuration significantly reduces the contrast ratio. Therefore, an object of the present invention is to provide an LED display device which solves the above-mentioned problems.

[0009]

The present invention is an LED display device in which a plurality of light emitting diodes are arranged and a louver is arranged between the light emitting diodes. In particular, this is an LED display device in which the cross-sectional shape of the louver forms the upper end portion of the louver into a curved shape and the surface of the curved shape has fine irregularities.

According to a second aspect of the present invention, there is provided an LED display device having a plurality of light emitting diodes arranged and a louver arranged between the light emitting diodes;
Driving means for driving the ED display. In particular, the upper end of the louver is placed above the LE.
D has a curved surface shape that increases the emission angle of the emitted light, and the curved surface shape has irregularities that irregularly reflect and reduce reflected light that goes directly to the viewer.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The inventor of the present invention
The present invention has been found to be able to increase the emission angle of light emitted from the LED and significantly improve the contrast ratio of the LED display device by making the louver serving as a light shielding member used in the LED display device a specific shape. It came to accomplish.

That is, the cross section of the louver is formed in a substantially curved shape so that the emission angle of the light emitted from the LED disposed above the upper end of the louver is increased.
The louver itself is originally provided so as to protrude so that the LED is not directly exposed to extraneous light. For this reason, if the cross-sectional shape of the upper end portion of the louver is a specific shape as shown in FIG. 3B, the viewer side (the eye position of the viewer in FIG. 3B) as shown in FIG. ), The surface area for reflection of extraneous light is increased. Particularly, at the upper end portion 307 of the louver, the reflected light is remarkably observed because the external light is reflected directly to the viewer side. In addition, since the cross section of the upper end portion of the louver has a curved surface shape, the reflection surface is widened and the reflection surface is always formed regardless of a change in the sun angle.

The present invention employs a louver 321 as shown in FIG.
By forming the upper end portion 317 of the cross section into a curved shape having irregularities, the adverse effects of the reflection surface are reduced. The curved surface having irregularities forms a reflecting surface, but irregularly reflects due to minute irregularities and reduces reflected light directed toward the viewer. Thereby, the contrast ratio can be improved while preventing the louver 321 from lowering the viewing angle.

FIGS. 1 and 2 show an example of the LED display device of the present invention. FIGS. 1 and 2 show RGB (red 102,
LED that can emit green 112 and blue 122) respectively
Is a part in which one blue pixel, two green pixels and two red pixels are used and arranged as a pixel in a 16 × 16 dot matrix on the substrate. A louver 101 made of aluminum alloy is placed between rows of each pixel so that direct incidence of sunlight is reduced.
It is arranged at an angle of 6 ° with respect to the perpendicular to the ED display surface.
Light emitting diode 202, substrate 20 on which internal circuits are arranged
Case 203 for protecting 4, 206 etc. from the outside
The inside is partially covered with a filler 205. This constitutes an LED display device.

The tip of the louver 201 of the present invention is thin so that each picture element is less concealed particularly to a viewer viewed from below and a viewing angle can be obtained, and the cross section is formed in a semicircular shape having an upwardly convex shape. It has been formed. Further, the louver 201 is made of an aluminum alloy, and irregularities are formed on the surface of the louver 201 by applying a matting agent-containing black paint containing fine silicon oxide particles to the louver 201. The formed LED display device can not only increase the viewing angle from the viewer, but also improve the contrast ratio of the entire LED display device. Hereinafter, the configuration of the present invention will be described in detail.

(Lovers 101, 201, 321) The louvers 101, 201, 321 used in the present invention are for suppressing external light such as sunlight from being directly radiated to the light emitting diode, and are made of various materials and shapes. Or on the LED display surface at a desired angle.

The upper end portion 317 of the louver 321 used in the present invention is a portion of the louver 321 projecting to the outside so as not to directly irradiate the light mainly irradiated with the external light to the light emitting diode 322. In particular, in the present invention, the light emitting diode 32 arranged above the louver 321 by its upper end 317.
2 is difficult to block the light emitted, and the radiation angle increases (ie,
(Elevation angle becomes smaller).

The upper end portion 31 of the louver 321 of the present invention
The curved surface shape provided in 7 refers to a convex curved surface formed at the top of the louver tip where at least external light is incident when the LED display is viewed from the side. More specifically, those having various curved surface shapes such as a semicircular shape, an elliptical shape, and a parabolic shape are exemplified. With the curved shape, the viewing angle can be increased while increasing the strength of the upper end portion 317 of the louver 321.

The louver 321 used in the present invention
The fine unevenness formed in the curved shape of the cross section of the upper end portion may be any as long as it can prevent a decrease in the contrast ratio caused by the direct reflection of extraneous light toward the viewer side. Therefore, the louver 321 itself may be provided with irregularities, or the upper end 317 of the louver 321 may be provided.
May be formed by applying a coating film or the like in which fine irregularities are formed on the convex curved surface provided on the substrate. According to JIS B0601, such fine unevenness has a roughness curve cutoff value (λc) of 0.8 mm and a reference length of the roughness curve of 2.
Arithmetic average roughness (Ra) is 1 to 50 μm under the condition of 40 mm
Is more preferable, and more preferably, 2 to 10 μm. The ten-point average roughness (Rz) is preferably in the range of 5 to 100 μm, and more preferably in the range of 10 to 50 μm. A curved surface having such unevenness is clearly different from a smooth surface not subjected to the unevenness treatment in light scattering.

Light from sunlight or the like has a sun angle irradiated from above the LED display device. Therefore, it is desirable that the louvers 101, 201, and 321 are attached to the LED display surface at a certain angle. By adjusting the angle as desired in consideration of the place of use and the time of use, the rate at which the light emitting diodes are directly radiated to the sun by the louvers 101, 201, and 321 changes.

Specific materials of the louvers 101, 201, 321 include polycarbonate resin, ABS resin, epoxy resin, phenol resin, etc., aluminum and copper alone, and Mg, Si, Fe, Cu, Mn,
An alloy containing a desired amount of another metal such as Cr, Zn, Ni, Ti, Pb, or Sn is preferably used.

Particularly, polycarbonate containing glass fiber is a louver 101 having high strength, heat resistance and weather resistance.
201 and 321 can be formed relatively easily.
Further, by containing a coloring agent, the louver 101,
201 and 321 themselves can be colored in a dark color such as black. On the other hand, in order to further improve the strength of the louvers 101, 201, and 321, glass fibers may be contained in a large amount of 10% or more. Louvers 101 and 20 formed of resin containing a large amount of glass fiber
In Nos. 1 and 321, glass fibers may be visible on the surface of the louver. For this reason, the ratio of reflection at the upper end 307 of the louver containing glass fiber by external light such as sunlight increases. In this case, even if the louver 311 contains a coloring agent, the contrast ratio may be reduced.
Therefore, when a resin in which glass fibers are contained in the resin is used as the louver 321 of the present invention, a decrease in the contrast ratio can be suppressed more remarkably.

Similarly, the louvers 101, 20
Even when used as 1, 321, the light reflected by the metal surface can be covered with black paint to improve the contrast ratio. However, on a relatively smooth metal surface, even if the applied paint surface itself is a dark color system, it may be totally reflected and the contrast ratio may be reduced. Therefore, the louvers 101 and 20 formed of metal are used.
1, 321 the upper end surface itself or louver 1
By applying a matting agent-containing coloring agent containing fine particles or the like to the upper end portions of 01, 201, and 321, a decrease in the contrast ratio can be more remarkably suppressed.

It is preferable that the louvers 101, 201, and 321 have a structure in which the angles of the louvers 101, 201, and 321 can be changed so that the angles can be changed in accordance with the viewing distance. In this case, it can be selected as desired depending on the viewing angle and the distance. Preferably, such an angle is
A range of 0 ° to 10 ° below the vertical line of the display surface (viewer side) is preferable. Also, the louvers 101, 201, 3
Not only 21 but also the entire LED display device can be configured to be inclined with the ground plane. In addition, the unevenness | corrugation provided in the curved surface of the upper end part of a louver can also be given to the whole louver and the whole body.

(Light emitting diodes 102, 202, 32)
2) For the light emitting diodes 102, 202, and 322, various semiconductor light emitting elements molded with resin or the like are suitably used. One type of LED chip disposed in the light emitting diode may emit a single color, or a plurality of LEDs may emit a single color or multicolor. Specifically, the liquid phase growth method,
ZnS, S on the substrate by HDVPE method or MOCVD method
iC, GaN, GaP, ZnSe, GaAsP, GaAs
lAs, InGaN, GaAlN, AlInGaP, A
A light emitting layer formed of a semiconductor such as lInGaN is preferably used. Examples of the semiconductor structure include a homostructure having a MIS junction, a PIN junction, and a PN junction, a heterostructure, and a double heterostructure. The emission wavelength can be variously selected from ultraviolet light to infrared light depending on the material of the semiconductor layer and the degree of mixed crystal thereof.

Further, a single quantum well structure or a multiple quantum well structure having a thin film where a quantum effect occurs can be provided as desired. The light emitting diode mold is preferably provided to protect each LED chip and the like from the outside. As a material of the mold member, a transparent resin having excellent weather resistance such as an epoxy resin or a urea resin, or an inorganic material such as silicon oxide or titanium oxide is preferably used.

Further, by including a diffusing agent in the mold member, the directivity from the light emitting diode can be reduced and the viewing angle can be increased. As the diffusing agent, barium titanate, titanium oxide, aluminum oxide, silicon oxide and the like are suitably used. Further, by forming the mold member into a desired shape, it is possible to have a lens effect of converging or diffusing light emitted from the light emitting diode. Therefore, a structure in which a plurality of mold members are stacked may be used. Specifically, it is a convex lens shape, a concave lens shape, or a shape obtained by combining a plurality of them. Further, the mold member may contain a coloring pigment or a coloring dye to serve as a filter that cuts out wavelengths not desired.

When the use of the LED display device is considered outdoors, it is preferable to use a gallium nitride compound semiconductor for the green and blue colors, and to use a gallium-aluminum-arsenic-based semiconductor or aluminum-indium-oxide semiconductor for the red color. It is preferable to use a gallium-phosphorus semiconductor. Further, a nitride-based compound semiconductor (Al _a In _b Ga _1-ab N, 0 ≦ a, capable of emitting light with a relatively short wavelength with high efficiency)
It is also possible to use a light-emitting diode in which 0 ≦ b, a + b ≦ 1) and a phosphor (for example, YAG: Ce) that emits light when excited by its emission wavelength.

Further, a multi-color light emitting diode in which a plurality of LED chips having different wavelengths are arranged on the stem as desired, and which are electrically connected to inner leads or the like so that each of them can be driven independently can be used. For example, two blue LED chips and one green and one red LED chip can be configured. In order to use a light emitting diode as a color display device, a red light emission wavelength is 610 nm to 700 nm, a green light emission wavelength is 495 nm to 565 nm, and a blue light emission wavelength is 430 nm to 490 n.
It is preferable to use an LED chip using a semiconductor of m.

(Today 103, 203) Today 10
Reference numerals 3 and 203 denote mechanically protecting the LEDs 202 arranged in a desired shape such as a matrix shape on the substrate 204 and the substrate on which the driving means 206 are arranged from the outside, and forming the LED 202 in a desired size. Can be. As a material for the casings 103 and 203, a polycarbonate resin, an ABS resin, an epoxy resin, a phenol resin, or the like is preferable from the viewpoint of ease of molding. In addition, the body 103, 2
The inner surface of No. 03 may be roughened to increase the bonding area, or may be subjected to plasma treatment to improve the adhesion to the filler.

(Substrate 204) The substrate 204 can be suitably used for fixing the light emitting diodes 202 in a desired arrangement. The substrate 204 on which the light emitting diodes 202 are arranged is used for arranging the respective light emitting diodes 202 in a desired shape and electrically connecting them. In some cases, the substrate 204 also serves as a substrate on which the driving means 206 is arranged. Is also good. The arrangement of the light emitting diodes 202 can be in a matrix when used as a video display or the like. Also, as long as the louvers 101, 201, and 321 as the light shielding member of the present invention can be arranged, the light emitting diodes 102, 202,
321 may be arranged. The substrate is preferably one having high mechanical strength and low thermal deformation. Specifically, a printed circuit board using ceramics, glass, an aluminum alloy, or the like can be suitably used. Since the surface of the substrate on which the light emitting diodes are mounted coincides with the LED display surface, it is preferable that the surface is colored to improve the contrast. In addition, unevenness may be applied to improve the adhesion to the filler.

(Filler 205) As the filler 205,
Good adhesion to the light emitting diode 202, the housing 203, the substrate 204 on which the light emitting diode is disposed, the light shielding member 201, and the like is required. In addition, mechanical strength and weather resistance are required to protect the internal circuit. Specific examples of such a filler 205 include an epoxy resin, a urethane resin, and a silicone resin. Further, in order to improve the contrast ratio, these resins may contain a coloring dye or coloring pigment of a dark color such as black. Further, a heat conduction member may be included for the purpose of improving heat conduction. Since the heat conducting member is also arranged between the light emitting diodes 202, it is required that the heat conducting member does not conduct electricity.
Specific examples include copper oxide and silver oxide.

(Driving Means 206) The driving means 206 includes:
It is electrically connected to an LED display having a lighting circuit and the like and having a plurality of light emitting diodes 202 arranged thereon. In the case of the dynamic drive, specifically, an LED display arranged in a matrix or the like is driven by an output pulse from a drive circuit. As the driving circuit, a RAM (Random Ac) for temporarily storing input display data is used.
cess memory), a gradation control circuit for calculating a gradation signal for lighting the light emitting diode 202 to a predetermined brightness from the data stored in the RAM, and an output signal of the gradation control circuit for switching to emit light. A driver for lighting the diode 202 can be used.

The driving means can be formed relatively easily using a central processing unit or the like. The gradation control circuit calculates a lighting time of the light emitting diode from data stored in the RAM and outputs a pulse signal. A gray scale signal which is a pulse signal output from the gray scale control circuit is input to a driver of the light emitting diode 202 to switch the driver. The light emitting diode 202 can be turned on when the driver is turned on, and can be turned off when the driver is turned off. By controlling the lighting time of each light emitting diode 202, desired video data or the like can be displayed.
Hereinafter, examples of the present invention will be described, but it goes without saying that the present invention is not limited to only specific examples.

(Example 1) InGaN (emission wavelength: 525 nm) and InGaN were used as semiconductors of a light emitting layer used for an LED chip capable of emitting green, blue and red light, respectively.
(Emission wavelength 470 nm), AlGaInP (emission wavelength 6
60 nm). Each LED chip was electrically connected to the lead frame using a gold wire and an Ag paste, and then covered with an epoxy resin as a convex lens-shaped mold portion to form light emitting diodes capable of emitting RGB light. As shown in FIG. 1, two pixels of red, two green and one blue light constitute one pixel. They were arranged in a 16 × 16 pixel dot matrix on a printed circuit board and soldered to the conductive pattern of the board. This was arranged and fixed inside a casing made of polycarbonate containing glass fiber.

On the other hand, as shown in FIG. 3C, the upper end of the plate-shaped louver made of polycarbonate containing 10% glass fiber, into which extraneous light is incident, is formed into a convex semicircular curved surface. Further, the surface of the convex semicircular shape has a shape with fine irregularities. The fine unevenness formed in the curved shape of the louver can be formed relatively easily by integral molding using a mold. By matching the concave portion provided inside the casing with the end of the louver, the light emitting diode was held on the substrate on which the light emitting diodes were arranged, substantially perpendicular to the substrate. A part of the louver is inserted between rows of light emitting diodes constituting pixels arranged in a matrix. Except for the tip of the light emitting diode, the housing, the light emitting diode, the substrate and a part of the light shielding plate were filled with silicon rubber.
Then, it was cured at room temperature to form an LED display. Next, this LED display is electrically connected to the driving means, and L
An ED display was formed.

LE was measured by a luminance measuring device (BM-7 manufactured by TOPCON).
The luminance of the D display was measured. The projector was placed at an angle of 55 ° on the louver with respect to a line perpendicular to the surface of the LED display. 3. Place the luminance meter in front of the LED display device.
Dark luminance was measured at a distance of 5 m. 53 when fully lit
08 (cd / m ² ) and the dark luminance is 130 (cd / m ² )
Met. The contrast ratio is about 1/40. In addition,
The semi-circular louver upper and lower ends are JIS
As a result of measurement under the conditions of a cutoff value of 0.8 mm and a length of 2.40 mm according to B0601, the arithmetic average roughness (R
a) 3.943 μm, ten-point average roughness (Rz) 20.15
μm.

(Comparative Example 1) An LED display device was formed in the same manner as in Example 1, except that the louver surface was not subjected to unevenness processing, and the LED display device as shown in FIG. 3B was used. The upper end of the louver measured in the same manner as in Example 1 had an arithmetic average roughness (Ra) of 0.2511 μm and a ten-point average roughness (R).
z) was a smooth surface of 2.645 μm. When the luminance was measured in the same manner as in Example 1, it was found that the luminance was 5577 (c
d / m ² ), and the dark luminance was 225 (cd / m ² ). As in the first embodiment, the contrast ratio is about 1/24.

Comparative Example 2 An LED display device was formed in the same manner as in Example 1 except that the cross-sectional shape of the upper end portion of the louver was not a convex semicircular shape but a rectangular shape as shown in FIG. The surface roughness of the louver is almost the same as in Comparative Example 1. When the luminance of the formed LED display device was measured in the same manner as in Example 1, the luminance was 5301 (cd / m 2) at the time of full lighting.
² ) and the dark luminance was 124 (cd / m ² ). The contrast ratio was about 1/43.

The LED display of Example 1 was placed at a height of about 15 m together with the LED displays formed in Comparative Examples 1 and 2. After installing the LED display, a test was conducted to confirm the color shift due to the difference in the viewing distance. In Comparative Example 2, about 6 mL from the position A where the LED constituting the pixel due to the color mixture is partially shielded by the louver and the color is changed
In Comparative Example 1 and Example 1, no color misregistration was observed even at the position B near the ED display side. From this, it can be seen that in the structure in which the cross section of the upper end portion of the louver has a convex curved shape, the visible range is greatly expanded. From the above results, the present invention can provide an LED display that achieves both a wide viewing angle and an improvement in contrast ratio.

[0041]

According to the present invention, by forming the cross section of the upper end portion of the louver into a curved shape, the viewing angle can be increased while maintaining the strength. Further, it is possible to suppress direct reflected light generated by the upper end portion of the louver being formed into a curved surface by being scattered by fine irregularities formed on the curved surface. Therefore, according to the present invention, both a wide viewing angle and an improvement in contrast ratio can be achieved.

[Brief description of the drawings]

FIG. 1 is a partial schematic plan view showing an LED display device of the present invention.

FIG. 2 is an LED according to the invention in the section AA in FIG. 1;
It is a typical sectional view showing a display.

FIG. 3 is a schematic explanatory view for explaining an effect of the present invention, and FIG. 3A is a schematic diagram of an LED display using a general louver shown for comparison with the present invention. FIG. 3B is a schematic cross-sectional view of an LED display in which the upper end of the louver shown in FIG. 3B has a curved surface shape for comparison, and FIG. FIG. 2 is a schematic sectional view of the LED display device.

FIG. 4 is a schematic perspective view of an LED display device shown for comparison with the present invention.

[Explanation of symbols]

101, 201, 321... Louver having a convex vertical cross section at the tip and having fine irregularities 102... Light emitting diode capable of emitting R (red) 112. Light emitting diode capable of emitting G (green) 122: Light-emitting diodes capable of emitting B (blue) light 103, 203, 403: Housing 204: Substrate on which light-emitting diodes are disposed 205: Fillers 206, 406: Driving means 301, Reference numeral 401: a louver having a rectangular vertical cross section at the tip 311: a louver having a convex vertical cross section at the tip 302, 312, 322, 402: light emitting diode 307: fine irregularities on the surface Certain upper tip 317: Upper tip with a smooth surface

Claims (2)

[Claims] 1. An LED display in which a plurality of light emitting diodes are arranged and a louver is arranged between the light emitting diodes, wherein the cross-sectional shape of the louver is such that an upper end portion of the louver is formed in a curved shape and the curved shape is formed. An LED display characterized in that the surface of the LED has fine irregularities. 2. An LED having a plurality of light-emitting diodes disposed therein and a louver disposed between the light-emitting diodes, and driving means for driving the LED displays.
An ED display device, wherein an upper end portion of the louver has a curved surface shape for increasing a radiation angle of light emitted from an LED disposed above the louver, and the curved surface shape is irregularly reflected to directly go to a viewer. L having irregularities for reducing reflected light
ED display device.