JP7552575B2 - LED display - Google Patents

Description

The technical field of this specification relates to LED displays.

Display devices are used in a wide variety of applications, including televisions, desktop computers, notebook computers, and smartphones. Micro LED displays that use LED elements have been researched and developed. Micro LED displays are made up of tiny light-emitting elements measuring between 1 μm and 100 μm, arranged in a matrix.

In such micro LED displays, screen defects may occur due to partial light emission defects of the LED elements. Patent Document 1 discloses a technique for avoiding image defects. In Patent Document 1, the two light emitting diodes of the LED 300 are connected in parallel, so that the LED 300 has redundancy.

JP 2018-101785 A

As mentioned above, in Patent Document 1, the two light-emitting diodes of the LED 300 are arranged in parallel. This requires a common electrode to integrate the electrodes of the two constituent light-emitting diodes into one, which makes the structure more complicated.

In addition, since the electrodes of the micro LED and the electrodes of the drive circuit that are joined to them are very small, it is desirable from the perspective of mounting accuracy to make these electrodes as large and simple as possible.

The problem that the technology of this specification aims to solve is to provide an LED display that simplifies the structure of the micro LEDs and the electrodes of the drive circuit while avoiding image defects.

The LED display in the first aspect has a monolithic light-emitting element and a drive circuit board having a drive circuit for driving the light-emitting element. The light-emitting element has a pixel light-emitting portion corresponding to one pixel. The pixel light-emitting portion has one or more sub-pixel light-emitting portions. The sub-pixel light-emitting portion has a first partial light-emitting portion and a second partial light-emitting portion connected in parallel. The first partial light-emitting portion has a first p-electrode. The second partial light-emitting portion has a second p-electrode. The drive circuit has one transistor for each sub-pixel light-emitting portion. One electrode of the transistor is electrically connected to the first partial light-emitting portion via the first p-electrode and is electrically connected to the second partial light-emitting portion via the second p-electrode.

In this LED display, one transistor TrR1 is arranged for one subpixel light-emitting portion R1. Since one electrode on the transistor side is electrically connected to two electrodes on the partial light-emitting portion side, the ease of mounting the light-emitting element is improved.

This specification provides an LED display that simplifies the drive circuit while avoiding image defects.

FIG. 2 is a schematic diagram of an LED display D1 according to the first embodiment. 1 is a diagram showing a layered structure of an LED display D1 according to a first embodiment. FIG. 1 is a diagram conceptually showing a band structure and the behavior of electrons and holes in an LED display D1 according to a first embodiment. FIG. 2 is a circuit diagram showing a schematic diagram of a drive circuit CC1 of the LED display D1 of the first embodiment. FIG.

Specific embodiments will be described below with reference to the figures, taking an LED display as an example. However, the technology of this specification is not limited to these embodiments. The layered structure and electrode structure of each layer of the LED display described below are examples. Of course, a layered structure different from that of the embodiment may also be used. Furthermore, the thickness ratios of each layer in each figure are shown conceptually, and do not represent the actual thickness ratios.

(First embodiment)
1. LED Display Fig. 1 is a schematic diagram of an LED display D1 according to a first embodiment. The LED display D1 includes a micro LED element 100 and a drive circuit board 200. As shown in Fig. 1, the micro LED element 100 is a monolithic semiconductor light emitting element.

The micro LED element 100 has a plurality of pixel light emitting portions A1. The pixel light emitting portion A1 is a light emitting area corresponding to one pixel. For this reason, the pixel light emitting portions A1 are arranged in a matrix. The pixel light emitting portion A1 has sub-pixel light emitting portions R1, G1, and B1. The sub-pixel light emitting portions R1, G1, and B1 are areas that emit red, green, and blue light, respectively.

The subpixel light-emitting unit R1 has a first partial light-emitting unit RC1 and a second partial light-emitting unit RC2 connected in parallel. The subpixel light-emitting unit G1 has a first partial light-emitting unit GC1 and a second partial light-emitting unit GC2 connected in parallel. The subpixel light-emitting unit B1 has a first partial light-emitting unit BC1 and a second partial light-emitting unit BC2 connected in parallel.

The first partial light-emitting unit RC1 has a first p-electrode P1a. The second partial light-emitting unit RC2 has a second p-electrode P1b. The first partial light-emitting unit GC1 has a first p-electrode P1c. The second partial light-emitting unit GC2 has a second p-electrode P1d. The first partial light-emitting unit BC1 has a first p-electrode P1e. The second partial light-emitting unit BC2 has a second p-electrode P1f. These p-electrodes may be collectively referred to as p-electrode P1.

In this way, each subpixel light-emitting portion has a first partial light-emitting portion and a second partial light-emitting portion. The first partial light-emitting portion and the second partial light-emitting portion are adjacent regions, and different electrodes are connected to each of them. For example, if the first partial light-emitting portion has a light-emitting defect and does not emit light, the second partial light-emitting portion emits light.

The drive circuit board 200 has a drive circuit CC1. The drive circuit CC1 drives the micro LED element 100.

2. Stacked structure Fig. 2 is a diagram showing the stacked structure of the LED display D1 of the first embodiment. As shown in Fig. 2, the micro LED element 100 has a transparent substrate TS1, a semiconductor layer SM1, a p-electrode P1, an n-electrode N1, and a reflective layer RF1. The micro LED element 100 is a monolithic light emitting element made of a group III nitride semiconductor in which a plurality of light emitting portions are arranged in a matrix in one element.

The transparent substrate TS1 is, for example, sapphire, GaN, or SiC.

The semiconductor layer SM1 has an n-type contact layer 120, a first light-emitting layer 130, a first intermediate layer 140, a second light-emitting layer 150, a second intermediate layer 160, a third light-emitting layer 170, a cap layer 180, and a p-type contact layer 190.

The drive circuit board 200 has a drive circuit CC1. The drive circuit CC1 has transistors TrR1, TrG1, and TrB1. The transistors TrR1, TrG1, and TrB1 are selection transistors that select whether or not to pass current through the partial light-emitting portion.

The subpixel light-emitting portion R1 has an n-type contact layer 120, a first light-emitting layer 130, a first intermediate layer 140, a second light-emitting layer 150, a second intermediate layer 160, a third light-emitting layer 170, a cap layer 180, and a p-type contact layer 190.

The subpixel light-emitting portion G1 has an n-type contact layer 120, a first light-emitting layer 130, a first intermediate layer 140, a second light-emitting layer 150, a second intermediate layer 160, and a p-type contact layer 190.

The subpixel light-emitting portion B1 has an n-type contact layer 120, a first light-emitting layer 130, a first intermediate layer 140, and a p-type contact layer 190.

The p-electrodes P1 are provided on the transparent electrodes TE1. The transparent electrodes TE1 are provided on the p-type contact layer 190. The p-electrodes P1 are arranged in a matrix pattern. Therefore, one transparent electrode TE1 and one p-electrode P1 are arranged in each of the first partial light-emitting section and the second partial light-emitting section. Furthermore, the respective p-electrodes P1 are insulated from each other.

The n-electrode N1 is formed in a rectangular ring-shaped pattern along the outer periphery of the micro LED element 100. A groove is formed by etching on the outer periphery of the micro LED element 100, reaching the n-type contact layer 120, and the n-electrode N1 is provided on the n-type contact layer 120 exposed at the bottom of the groove. There is one n-electrode N1, which is common to each pixel. Therefore, the n-electrode N1 is common to all the first partial light-emitting sections and the second partial light-emitting sections. The material of the n-electrode N1 is, for example, a laminate such as Ti/Al.

The micro LED element 100 does not have grooves to separate each pixel, and the n-electrode N1 is also common to each pixel. This makes it possible to miniaturize the element.

The n-electrode N2 is provided on the drive circuit board 200 side. The n-electrode N2 is electrically connected to the n-electrode N1 of the micro LED element 100.

The p-electrode P2 is provided on the drive circuit board 200 side. The p-electrode P2 is electrically connected to the p-electrode P1 of the micro LED element 100.

The insulating layer I1 is a layer that insulates the multiple p-electrodes P1. The insulating layer I1 also insulates the transparent electrodes TE1 of each partial light-emitting portion.

3. Band Structure and Behavior of Electrons and Holes Fig. 3 is a diagram conceptually showing the band structure and behavior of electrons and holes in the LED display D1 of the first embodiment. In Fig. 3, for ease of explanation, each light-emitting layer is depicted as having a single quantum well structure. Each light-emitting layer may have a multiple quantum well structure.

The holes injected from the p-contact electrode p3 easily enter the third light-emitting layer 170. The holes remain in the third light-emitting layer 170 without escaping from the third light-emitting layer 170. This is because the barrier of the second intermediate layer 160 as viewed from the third light-emitting layer 170 is sufficiently high.

Electrons injected from the n-contact electrode N1 enter the first light-emitting layer 130. The barrier of the first intermediate layer 140 seen from the first light-emitting layer 130 is not very high. Therefore, the electrons can easily move from the first light-emitting layer 130 to the second light-emitting layer 150. The barrier of the second intermediate layer 160 seen from the second light-emitting layer 150 is not very high. Therefore, the electrons can easily move from the second light-emitting layer 150 to the third light-emitting layer 170. The electrons that enter the third light-emitting layer 170 barely move and remain in the third light-emitting layer 170. This is because the barrier adjacent to the third light-emitting layer 170 is sufficiently high.

In this way, electrons tend to exist in the third light-emitting layer 170, and holes tend to exist in the third light-emitting layer 170. In other words, the wave functions of electrons and holes have large amplitudes at the position of the third light-emitting layer 170 and overlap with each other well. For this reason, light is emitted intensively in the third light-emitting layer 170, and not so much in the first light-emitting layer 130 and the second light-emitting layer 150.

When the third light-emitting layer 170 is not present, light is emitted primarily from the second light-emitting layer 150, and not so much from the first light-emitting layer 130.

4. Circuit Diagram 4-1. Circuit Configuration Fig. 4 is a circuit diagram showing a schematic diagram of a driving circuit CC1 of the LED display D1 of the first embodiment. As shown in Fig. 4, the driving circuit CC1 has a scanning line circuit 210, a PWM circuit 220, a scanning line 230, a data line 240, and transistors TrR1, TrG1, and TrB1.

The scanning line circuit 210 and the PWM circuit 220 are realized as LSI elements and mounted on the drive circuit board 200.

The scanning line circuit 210 is a circuit that sequentially selects and turns on each of the scanning lines 230 provided for each row of the LED display D1. The scanning line circuit 210 sequentially selects and scans the rows to be illuminated among the subpixel light emitting portions R1, G1, and B1 one by one.

The PWM circuit 220 is provided for each column of the LED display D1. The PWM circuit 220 is connected to the data line 240. The PWM circuit 220 is a circuit that pulse modulates the current flowing through the partial light-emitting unit (RC1, etc.), and is a circuit that controls the brightness of the partial light-emitting unit by the duty ratio. By using PWM control, it is possible to control the brightness without causing a deviation in the emission wavelength of the partial light-emitting unit. In this way, the PWM circuit 220 is provided for each column of the sub-pixel light-emitting units R1, G1, and B1, and controls the duty ratio by pulse modulating the current flowing through the sub-pixel light-emitting units R1, G1, and B1.

A scanning line 230 is provided for each row of the LED display D1. The scanning line 230 is connected in parallel to the gates of the transistors TrR1, TrG1, and TrB1 of the corresponding row.

Data lines 240 are provided for each column of LED display D1. Data lines 240 are connected in parallel to the drains of transistors TrR1, TrG1, and TrB1 in the corresponding column.

Transistors TrR1, TrG1, and TrB1 are provided for each subpixel. The gates of transistors TrR1, TrG1, and TrB1 are connected to the scanning line 230, the drains are connected to the data line 240, and the sources are connected to the anode (p-electrode P1) of the partial light-emitting section (RC1, etc.). The on/off of transistors TrR1, TrG1, and TrB1 is controlled by applying a voltage to the gates; when they are on, the line is conductive and current can flow to the partial light-emitting section (RC1, etc.), and when they are off, the line is cut off and no current flows to the partial light-emitting section (RC1, etc.).

The subpixel light-emitting unit R1 has a first partial light-emitting unit RC1, a second partial light-emitting unit RC2, and a transistor TrR1. The subpixel light-emitting unit G1 has a first partial light-emitting unit GC1, a second partial light-emitting unit GC2, and a transistor TrG1. The subpixel light-emitting unit B1 has a first partial light-emitting unit BC1, a second partial light-emitting unit BC2, and a transistor TrB1.

The transistors TrR1, TrG1, and TrB1 of the row selected by the scanning line circuit 210 are turned on, allowing current to flow to the subpixel light-emitting portions R1, G1, and B1. The transistors TrR1, TrG1, and TrB1 of the row not selected by the scanning line circuit 210 are turned off, allowing no current to flow to the subpixel light-emitting portions R1, G1, and B1.

4-2. Transistor Arrangement The drive circuit CC1 has one transistor for each subpixel light-emitting portion. One electrode of the transistor TrR1 is electrically connected to the first partial light-emitting portion RC1 via a p-electrode P1a and to the second partial light-emitting portion RC2 via a p-electrode P1b. The other transistors TrG1 and TrB1 are arranged similarly.

As shown in FIG. 1, the transistors TrR1, TrG1, and TrB1 each have an electrode P2. The electrode P2 is a source electrode that is electrically connected to the p-electrode P1 of the partial light-emitting portion. Since two p-electrodes P1 are electrically connected to one electrode P2, the micro LED element 100 is easy to mount on the drive circuit board 200. In other words, even if the positional accuracy is not very high, poor bonding is unlikely to occur.

4-3. Circuit operation First, the scanning line circuit 210 selects one of the scanning lines 230. At this time, a voltage is applied to the gate of the transistor connected to the selected scanning line 230. At this stage, the partial light emitting portion connected to the source of the transistor does not emit light yet.

When the scanning line circuit 210 is selected, the PWM circuit 220 generates a pulse-modulated current on the data line 240. This current is input to the drain of the transistor. This causes a current to flow through the two partial light-emitting sections connected to the source of the transistor, causing these partial light-emitting sections to emit light.

5. Effects of the First Embodiment In the LED display D1 of the first embodiment, the subpixel light-emitting unit R1 has a first partial light-emitting unit RC1 and a second partial light-emitting unit RC2. One transistor TrR1 is provided in one subpixel light-emitting unit R1. One transistor TrR1 drives the first partial light-emitting unit RC1 and the second partial light-emitting unit RC2. The first partial light-emitting unit RC1 and the second partial light-emitting unit RC2 are connected in parallel. Therefore, even if one of the first partial light-emitting unit RC1 and the second partial light-emitting unit RC2 has a light emission defect, the other partial light-emitting unit emits light. Therefore, the LED display D1 hardly produces image defects.

In this way, one transistor TrR1 is arranged for one subpixel light-emitting portion R1. This simplifies the drive circuit CC1 and allows the LED display D1 to be made smaller.

In addition, since the PWM circuit 220 is provided for each column, the number of circuits can be reduced compared to when a PWM circuit 220 is provided for each partial light-emitting section. In other words, the LED display D1 can be miniaturized.

The driver circuit CC1 is simplified, which reduces the occurrence of defective products due to poor connections. In other words, the yield is improved.

6. Modification 6-1. Number of driving circuits The LED display D1 of the first embodiment has one driving circuit CC1. However, the area of the LED display D1 may be divided into a plurality of areas, and a driving circuit CC1 may be arranged corresponding to each area.

(Additional Note)
The LED display in a first aspect has a monolithic light-emitting element and a drive circuit board having a drive circuit for driving the light-emitting element. The light-emitting element has a pixel light-emitting portion corresponding to one pixel. The pixel light-emitting portion has one or more sub-pixel light-emitting portions. The sub-pixel light-emitting portion has a first partial light-emitting portion and a second partial light-emitting portion connected in parallel. The first partial light-emitting portion has a first p-electrode. The second partial light-emitting portion has a second p-electrode. The drive circuit has one transistor for each sub-pixel light-emitting portion. One electrode of the transistor is electrically connected to the first partial light-emitting portion via the first p-electrode and is electrically connected to the second partial light-emitting portion via the second p-electrode.

In the LED display of the second aspect, the pixel light-emitting units are arranged in a matrix. The drive circuit has a scanning line circuit that sequentially selects and scans the rows of the subpixel light-emitting units to be illuminated one by one, and a PWM circuit that is provided for each column of the subpixel light-emitting units and pulse-modulates the current flowing through the subpixel light-emitting units to control the duty ratio.

In the LED display of the third embodiment, the transistors in the row selected by the scanning line circuit are turned on, causing current to flow to the subpixel light-emitting portion. The transistors in the row not selected by the scanning line circuit are turned off, causing no current to flow to the subpixel light-emitting portion.

The LED display in the fourth aspect has a first subpixel light-emitting portion, a second subpixel light-emitting portion, and a third subpixel light-emitting portion. The first subpixel light-emitting portion has a first light-emitting layer. The second subpixel light-emitting portion has a first light-emitting layer and a second light-emitting layer. The third subpixel light-emitting portion has a first light-emitting layer, a second light-emitting layer, and a third light-emitting layer.

In the LED display of the fifth aspect, the light-emitting element has an n-electrode. The n-electrode is shared by the first partial light-emitting section and the second partial light-emitting section.

D1...LED display 100...micro LED element 120...n-type contact layer 130...first light-emitting layer 140...first intermediate layer 150...second light-emitting layer 160...second intermediate layer 170...third light-emitting layer 180...cap layer 190...p-type contact layers P1a, P1b, P1c, P1d, P1e, P1f...p-electrode N1...n-electrode

Claims (5)

A monolithic light emitting device;
a drive circuit board having a drive circuit for driving the light emitting element;
having
The light-emitting element is
A pixel light emitting portion corresponding to one pixel is provided,
The pixel light emitting unit includes:
having one or more subpixel emitting portions;
The sub-pixel light emitting portion is
a first partial light-emitting unit and a second partial light-emitting unit connected in parallel;
The first partial light-emitting unit is
A first p-electrode is provided.
The second partial light-emitting portion is
A second p-electrode is provided.
The drive circuit includes:
a transistor for each of the subpixel light emitting portions;
One electrode of the transistor is
electrically connected to the first partial light emitting portion via the first p-electrode;
the second p-electrode being electrically connected to the second light-emitting portion. 2. The LED display according to claim 1,
The pixel light emitting unit includes:
They are arranged in a matrix,
The drive circuit includes:
a scanning line circuit for sequentially selecting and scanning rows of the sub-pixel light emitting units to be illuminated one by one;
a PWM circuit provided for each column of the subpixel light emitting units, the PWM circuit controlling a duty ratio by pulse modulating a current flowing in the subpixel light emitting units;
An LED display including: 3. The LED display according to claim 2,
The transistors in the row selected by the scan line circuit are turned on, causing a current to flow through the subpixel light emitting section.
The transistors in rows not selected by the scan line circuit are turned off so that no current flows through the sub-pixel light emitting portions. 4. The LED display according to claim 1,
a first sub-pixel light-emitting portion, a second sub-pixel light-emitting portion, and a third sub-pixel light-emitting portion;
The first sub-pixel light emitting portion is
A first light-emitting layer is provided.
The second sub-pixel light-emitting portion is
The first light-emitting layer and the second light-emitting layer are included,
The third sub-pixel light-emitting portion is
an LED display comprising the first light-emitting layer, the second light-emitting layer, and a third light-emitting layer; 5. The LED display according to claim 1,
The light-emitting element is
An n-electrode is provided.
The n-electrode is
The LED display includes a common first light-emitting portion and a common second light-emitting portion.

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