Indication device

Abstract

The present invention provides a display device that drives light-emitting elements such as micro-LEDs using a non-matrix drive method. [Solution] The display device 100 of the present invention comprises a drive circuit 110 and a circuit board 120 on which a plurality of light-emitting elements are mounted on the surface. The plurality of light-emitting elements are arranged on the circuit board 120 to form a two-dimensional shape of fixed display patterns 130, 132, 134, 136, 138, and some or all of the plurality of light-emitting elements are connected in series via wiring. The drive circuit 110 turns on or off selected light-emitting elements via wiring 140.

Description

Technical Field

[0005] , ,

[0001] The present invention relates to a display device in which a plurality of light-emitting elements are arranged on a substrate, and particularly to a display device in which light-emitting elements such as micro light-emitting diodes (LEDs) are mounted on a circuit board.

Background Art

[0002] In recent years, micro LEDs that can directly display images from light-emitting diodes have been developed. As driving methods for micro LED displays that display arbitrary images, there are an active matrix method and a passive matrix method. The active matrix method requires a thin film transistor (TFT) for controlling the on / off of each pixel to control the on / off of each pixel. Since an LED is a current-driven device, the driving circuit is more complex than that of a liquid crystal display. Furthermore, a large capital investment is required to configure a circuit for driving each pixel, similar to a liquid crystal display (for example, Patent Document 1).

[0003] On the other hand, the passive matrix method drives pixels in a time division manner, so it does not require active elements on the panel and can be composed of only wiring patterns. However, as the resolution increases, the lighting time becomes shorter and the brightness decreases. For example, at a resolution of 256×64, the lighting time becomes 1 / 64, and although the resolution is high, the brightness is too dark, resulting in an unrealistic display device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As mentioned above, when it comes to driving microLED displays that display arbitrary images, the active matrix method requires complex driving circuits and enormous capital investment, while the passive matrix method has the problem that brightness degradation becomes critical at high resolutions.

[0006] The present invention aims to solve these conventional problems and provide a display device that drives light-emitting elements such as micro-LEDs using a non-matrix driving method. [Means for solving the problem]

[0007] The display device according to the present invention comprises a plurality of light-emitting elements and a circuit board on which the plurality of light-emitting elements are mounted on the surface, wherein the plurality of light-emitting elements are arranged on the circuit board to constitute a fixed display pattern, and some or all of the plurality of light-emitting elements are connected in series via wiring. [Effects of the Invention]

[0008] According to the present invention, since multiple light-emitting elements are connected in series and driven, the driving circuit is simpler compared to the active matrix method, and the reduction in brightness due to high resolution, as seen in the passive matrix method, can be avoided. Furthermore, by connecting multiple light-emitting elements in series, it becomes possible to use a single-layer substrate, thereby reducing the manufacturing cost of the display device. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1(A) shows the overall configuration of a display device according to an embodiment of the present invention, and Figure 1(B) shows an example of the arrangement of light-emitting elements or pixels that constitute a display pattern. [Figure 2] Figure 2(A) shows an example of the display pattern when it is turned off, and Figure 2(B) shows an example of the display pattern when it is lit. [Figure 3] This figure shows an example of the arrangement of light-emitting elements that make up a display pattern. [Figure 4]Figure 4(A) is a top view of a 4-terminal package LED, Figure 4(B) is a bottom view of a 4-terminal package LED, Figure 4(C) shows the connection of the R, G, and B light-emitting elements in a common cathode configuration, and Figure 4(D) is a comparative example of a display pattern constructed using a 4-terminal package LED. [Figure 5] This figure shows an example of chip LED arrangement according to a preferred embodiment of the present invention. [Figure 6] This figure illustrates improvements to the example of chip LED arrangement shown in Figure 5. [Figure 7] This figure shows an example of chip LED arrangement according to a preferred embodiment of the present invention. [Figure 8] This diagram shows the wiring pattern when the chip LEDs shown in Figure 7 are arranged. [Figure 9] This is a bottom view of a 6-terminal package LED. [Modes for carrying out the invention]

[0010] The present invention relates to a display device (display) that mounts multiple light-emitting elements on a circuit board, and more particularly to a display device that drives the light-emitting elements in a non-matrix manner. The light-emitting elements are, for example, R, G, and B microLEDs, and the R, G, and B microLEDs may each be independent chips or may be housed in a single package. The multiple light-emitting elements are arranged on the circuit board to form a two-dimensional shape of a display pattern, and the multiple light-emitting elements connected in series by wiring are controlled to emit light by a drive circuit. It should be noted that the drawings referenced in the following description include exaggerations to facilitate understanding of the invention and do not directly represent the shape or scale of the actual product. [Examples]

[0011] Figure 1(A) is a block diagram showing the overall configuration of a display device according to an embodiment of the present invention. As shown in the figure, the display device 100 of this embodiment is configured to include a drive circuit 110 and a circuit board 120 on which a plurality of light-emitting elements are mounted.

[0012] The circuit board 120 is not particularly limited, but for example, it has a rectangular plane as shown in the figure. The material of the circuit board 120 is not particularly limited, but for example, it can be made of glass, plastic, acrylic, polyimide, etc., and the circuit board 120 may be a flexible transparent substrate. Wiring for electrically connecting the light-emitting elements is formed on the surface of the circuit board 120, and this wiring is electrically connected to the drive circuit 110 via drive wiring 140. Here, the drive wiring 140 and the drive circuit 110 are shown separately from the circuit board 120, but the drive wiring 140 may be formed on the surface of the circuit board 120 together with the wiring for the light-emitting elements, and the drive circuit 110 may be mounted on the circuit board 120.

[0013] A light-emitting element is, for example, a micro-LED. When displaying a single-color image, one pixel consists of one micro-LED from among R, G, and B. However, when displaying a color image, one pixel consists of three micro-LEDs: an R_LED that emits red light, a G_LED that emits green light, and a B_LED that emits blue light.

[0014] Multiple light-emitting elements are arranged on the circuit board 120 to form a two-dimensional shape of a fixed display pattern. In the example shown in Figure 1(A), the multiple light-emitting elements mounted on the circuit board 120 constitute display patterns 130, 132, 134, 136, and 138. Display pattern 130 represents a power icon shape, display pattern 132 represents a three-digit number, display pattern 134 represents the letters "km", display pattern 136 represents a light icon shape, and display pattern 138 represents a bar-shaped indicator to show the remaining amount of fuel, etc. The type, shape, size, etc. of the display patterns are not limited to those described above and can be determined arbitrarily.

[0015] FIG. 1(B) shows an arrangement example of one digit 132A of the display pattern 132 and the light-emitting elements constituting the display pattern 134. One rectangular box P in the figure represents one light-emitting element or one pixel. The digit 132A is composed of seven segments 132A_1, 132A_2, 132A_3, 132A_4, 132A_5, 132A_6, and 132A_7. The plurality of light-emitting elements are arranged at a resolution of 56 dots in the vertical direction × 30 dots in the horizontal direction so as to represent the two-dimensional shape of each segment. In this example, one segment is composed of 160 light-emitting elements, and when the segment displays a color image, it is composed of 480 light-emitting elements.

[0016] Similarly, the two-dimensional shape of the display pattern 134 is also composed of light-emitting elements arranged at a resolution of 56 dots in the vertical direction × 30 dots in the horizontal direction. Although not shown here, the two-dimensional shapes of the other display patterns 130, 132, 136, and 138 are also composed of light-emitting elements arranged at a resolution of 56 dots in the vertical direction × 30 dots in the horizontal direction.

[0017] FIG. 2(A) shows the state when the display pattern is turned off, and FIG. 2(B) shows an example of the display pattern being lit. The display patterns 130, 134, 136, and 138 are either constantly lit or not. Among the segments constituting the display pattern 132, the segments corresponding to the digits to be displayed are selected by the drive circuit 110, and the light-emitting elements of the selected segments are lit. In the example of the figure, the display pattern 132 displays "111". These display patterns can vary in color when the light-emitting elements include R_LED, G_LED, and B_LED.

[0018] FIG. 3 schematically shows a wiring example of light-emitting elements that constitute the region S1 of the segment 132A. As shown in the figure, a plurality of light-emitting elements P are arranged to represent the two-dimensional shape or contour of the segment 132A in the region S1. The plurality of light-emitting elements P are divided into groups G1 and G2 including a certain number of light-emitting elements connected in series, and the groups G1 and G2 are connected in parallel between the Vdd wiring and the GND wiring from the drive circuit 110. The plurality of light-emitting elements within the groups G1 and G2 are connected in series by wiring. The wiring is routed like a single stroke so as not to cross. The drive circuit 110 supplies current to each light-emitting element P of the groups G1 and G2 via the Vdd wiring, and lights up the light-emitting elements P of the groups G1 and G2 simultaneously. If it is desired to drive the group G1 and the group G2 individually, two sets of Vdd wiring and GND wiring are prepared, with the group G1 connected to one and the group G2 connected to the other.

[0019] In this way, by connecting in series the light-emitting elements that constitute a fixed display pattern and turning on / off the light-emitting elements connected in series collectively, compared with the active matrix method and the passive matrix method, it is possible to realize a simple and low-cost drive circuit, and it is possible to suppress the capital investment for manufacturing the display device.

[0020] Next, a display device according to a more preferred embodiment of the present invention will be described. In manufacturing a micro LED panel (a circuit board on which light-emitting elements are mounted), it is desirable to improve the following points. (1) It is desired to wire the circuit board in a single layer Since fine wiring for high definition is required, if the circuit board is made multi-layer or multi-layered, problems such as open circuits between layers and shorts with other wirings will occur, increasing the production difficulty and reducing the yield. (2) It is desired to reduce the number of I / Fs with the drive circuit It is necessary to drive a large number of micro LEDs mounted on the circuit board, but if the number of wirings for connecting the micro LEDs in series, that is, the number of drive wirings 140, is too large, it will be a design constraint. (3) It is desired to reduce the current When wiring becomes thinner, the wiring resistance increases, and the current flowing through the wiring decreases. On the other hand, micro-LEDs are current-driven devices, and the more micro-LEDs connected in series there are, the greater the current flowing through the wiring. In order to carry a large current, the wiring width must be increased, but this makes it difficult to arrange micro-LEDs at a narrow pitch. Therefore, it is desirable to keep the current flowing through the wiring as low as possible.

[0021] Figure 4 shows a comparative example of a display pattern constructed using a 4-terminal package LED containing three LEDs (R, G, and B). Figure 4(A) is a top view of the 4-terminal package LED, Figure 4(B) is a bottom view of the 4-terminal package LED, Figure 4(C) shows the common cathode electrical connection, and Figure 4(D) shows an example of the 4-terminal package LED arrangement.

[0022] As shown in Figure 4(A), the 4-terminal package LED 200 includes light-emitting sections R, G, and B on its top surface 210, and electrodes R, G, B, and C (common) on its bottom surface 220. Electrode R is connected to the anode of LED R, electrode G is connected to the anode of LED G, electrode B is connected to the anode of LED B, and electrode C is commonly connected to the cathodes of LEDs R, G, and B.

[0023] The 4-terminal package LED 200 is arranged to form a two-dimensional shape of the display pattern, as shown in Figure 4(D). In order to make the circuit board a single layer, the R, G, B, and C wirings WR, WG, WB, and WC on the circuit board must be routed in a single continuous line, in other words, the R, G, B, and C wirings must not cross each other. Therefore, the 4-terminal package LED 200 is arranged so that the orientation is reversed by 180 degrees between odd-numbered rows and even-numbered rows. In this way, the R, G, B, and C wirings WR, WG, WG, and WC from the drive circuit 110 are connected in series to the R, G, B, and C electrodes of the arranged 4-terminal package LED 200 without crossing each other.

[0024] However, in the 4-terminal package LED200, the cathodes of the R, G, and B LEDs are common, so the R, G, and B LEDs within a single package LED are connected in parallel, resulting in a larger current flowing through that single package LED. As a result, the difference in applied voltage between the front and back of the series-connected 4-terminal package LED200 becomes large, which leads to uneven brightness.

[0025] Therefore, in this embodiment, instead of using a 4-terminal package LED, the display pattern is constructed using chip LEDs with R, G, and B each being independent, or a 6-terminal package LED as described later.

[0026] Figure 5 shows an example of the arrangement of chip LEDs that make up a display pattern. Each of the R, G, and B chip LEDs has an anode electrode and a cathode electrode, and all of the R, G, and B chip LEDs are arranged so that the orientation of the anode / cathode electrodes matches the column direction of the display pattern. Wiring WR from the drive circuit 110 is connected to the anode electrode of the R chip LED, and its cathode electrode is electrically connected to the cathode electrode of the adjacent R chip LED via wiring WR. Similarly, wiring WG is connected to the anode electrode of the G chip LED, and its cathode electrode is electrically connected to the cathode electrode of the adjacent G chip LED via wiring WG, and wiring WB is connected to the anode electrode of the B chip LED, and its cathode electrode is electrically connected to the cathode electrode of the adjacent B chip LED via wiring WB, so that each of the R, G, and B chip LEDs that make up the display pattern are connected in series.

[0027] If all chip LEDs are aligned in the row direction, as shown in the diagram, it becomes possible to route the wiring WR, WG, and WB in a single continuous line without crossing them. However, the three wirings WR, WG, and WB must be folded back in the narrow space S2 between adjacent rows. This results in longer wiring lengths and smaller wiring widths, making it extremely difficult to lay out wiring that requires a certain line width to ensure a certain current capacity on a single-layer substrate.

[0028] To improve the arrangement of the light-emitting elements in Figure 5, Figure 6 shows the orientation of the R, G, and B chip LEDs in each row reversed by 180 degrees. The rectangular frame S3 shows the R, G, and B chip LEDs with their orientations reversed. By reversing the orientation of the R, G, and B chip LEDs in each row, the wiring WR, WG, and WB can essentially pass over the R, G, and B chip LEDs, eliminating the need to pass through the narrow space between adjacent rows as in Figure 5. Therefore, the wiring pattern can be easily formed on a single-layer substrate.

[0029] However, in the arrangement of light-emitting elements shown in Figure 6, the R chip LEDs of adjacent rows are adjacent in section Q1, and the G chip LEDs and B chip LEDs of adjacent rows are adjacent in section Q2. As a result, areas where red light emission is uneven and areas where blue light emission is uneven occur, making red and blue stripes noticeable and degrading image quality.

[0030] To further improve the arrangement of the light-emitting elements in Figure 6, Figure 7 shows that the orientation of the R, G, and B chip LEDs is aligned horizontally, i.e., with the row direction of the display pattern, and that the orientation of the R, G, and B chip LEDs is reversed compared to the orientation of adjacent R, G, and B chip LEDs. Frame S4 ​​in the figure shows the R, G, and B chip LEDs with their orientations reversed.

[0031] Figure 8 shows the wiring pattern when the chip LEDs are laid out as in Figure 7. Wires WR, WG, and WB are routed in a single continuous line to connect the R, G, and B chip LEDs in series. Considering the forward voltage Vf of the chip LEDs, it is reasonable for one wire to drive approximately 10 to 15 chip LEDs (the number of chip LEDs connected in series). By arranging the R, G, and B chip LEDs in an alternating orientation in this way, the red and blue stripes caused by color bias are suppressed compared to the arrangement in Figure 6, and the wiring pattern on a single-layer substrate can be formed relatively easily.

[0032] Figures 5, 6, and 7 show examples of arrangements of R, G, and B chip LEDs, but these chip LEDs can be replaced with a 6-terminal package LED that incorporates three R, G, and B LEDs. Figure 9 is a bottom view of the 6-terminal package LED. The bottom surface of the 6-terminal package LED 300 has three anode electrodes 310 and three cathode electrodes 320 for each of the R, G, and B LEDs. The electrode arrangement of the 6-terminal package LED 300 can be matched to the electrode arrangement of the R, G, and B chip LEDs, and the 6-terminal package LED can be placed on the circuit board in place of the R, G, and B chip LEDs.

[0033] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims. [Explanation of symbols]

[0034] 100: Display device 110: Drive circuit 120: Circuit board 130~138: Display pattern 140: Drive wiring; 200, 300: Package LED

Claims

1. Multiple light-emitting elements, The circuit board has the plurality of light-emitting elements mounted on its surface, The plurality of light-emitting elements are arranged on the circuit board to form a fixed display pattern. A display device in which some or all of the aforementioned plurality of light-emitting elements are connected in series via wiring.

2. The plurality of light-emitting elements include a red light-emitting element (R), a green light-emitting element (G), and a blue light-emitting element (B). Multiple R-emitting elements are connected in series via a first wiring, Multiple G-light-emitting elements are connected in series via a second wiring, The display device according to claim 1, wherein a plurality of B light-emitting elements are connected in series via a third wiring.

3. The display device according to claim 2, wherein the plurality of R-emitting elements, plurality of G-emitting elements, and plurality of B-emitting elements are arranged to face the same direction.

4. The display device according to claim 2, wherein each of the light-emitting elements, each consisting of a set of R-emitting elements, B-emitting elements, and G-emitting elements, is arranged so as to have its orientation reversed with respect to a set of light-emitting elements in the adjacent row direction or adjacent column direction.

5. The display device according to claim 2, wherein a set of light-emitting elements consisting of an R-emitting element, a B-emitting element, and a G-emitting element is arranged so as to have its orientation reversed with respect to an adjacent set of light-emitting elements.

6. The display device according to claim 2, wherein the circuit board is a single-layer substrate on which the first wiring, the second wiring, and the third wiring are formed on the same surface.

7. The display device further includes a drive circuit for driving all or some of the plurality of light-emitting elements, the drive circuit for turning on or off selected light-emitting elements, according to claim 1.

8. The display device according to claim 2, wherein the R light-emitting element, G light-emitting element, and B light-emitting element are chip LEDs or 6-terminal packaged LEDs.

Images