JP2024071058A - LED display device - Google Patents

Abstract

[Problem] To provide an LED display device equipped with a partition board in which cracks and pinholes are less likely to occur in the metal film formed thereon. [Solution] The display device includes an LED board 20 on which an array of pixels is formed by an array of LED elements 22, and a partition board 10 on which partition boards 12 are formed in a lattice pattern on a transparent substrate 11, the LED board and the partition board are arranged so that the LED elements and the partition boards face each other, and the partition board has a light reflecting layer 12B made of a thin film including a metal film formed on the surface of a partition board body 12A made of resin, and a cutout portion 14 on the top of the partition board where no light reflecting layer is formed. [Selected Figure] Figure 2

Description

The present invention relates to an LED display device, and in particular to the structure of partitions formed between pixels.

As full-color display devices, liquid crystal display devices, organic EL display devices, and the like have been put to practical use and are commercially available. In the midst of this, a new display device, an LED display device in which multiple light-emitting diode (LED) elements are arranged as the light source, has been proposed and is attracting attention. LED display devices use LEDs as the light source, and because their brightness and on/off control are easy, they are expected to achieve better display performance than liquid crystal display devices and organic EL display devices.

LED display devices are classified into micro LED displays and mini LED displays depending on the method of controlling the lighting of the LED elements. Mini LED displays are display devices that use backlighting, as seen in conventional LCD displays. The backlighting of mini LED displays is characterized by the fact that the screen is divided into multiple areas and the LED elements are turned on and off for each area (micro dimming method). In other respects, there are many similarities to conventional LCD display devices.

On the other hand, micro LED displays are so-called self-luminous displays, characterized by the turning on and off of LED elements that are assigned to each pixel. Because the LED elements are placed at positions equivalent to pixels, they are easy to accommodate larger screens, and because light emission can be controlled on a pixel-by-pixel basis, they are suitable for displaying higher-definition images such as 4K and 8K.

For this LED display, a method using blue LEDs and a color conversion layer has been proposed as a method for emitting RGB colors. In this method, a blue LED is used as the light source element, and first, in the blue pixels, blue light is obtained by passing the light through a layer filled with a scattering material that adjusts the amount of light from the light source. In addition, in the red and green pixels, red and green light are obtained by passing the blue light emitted from the blue LED through a conversion layer filled with phosphors and quantum dots. Full color expression is possible by controlling these three colors of light.

However, because the color-emitting section containing the color-converting phosphor is thick, the light used for display tends to spread out and mix with the light from adjacent pixels, causing problems with light leakage, which reduces contrast and creates color mixing.

In order to prevent light from leaking into adjacent pixels, it is believed that placing light-shielding partitions between pixels to prevent the spread of light is effective, and various proposals have been made (for example, Patent Document 1).

On the other hand, if the partition is made taller, when the light emitted from the LED hits the partition and is reflected, there is a dimming effect based on the reflectivity, and if this is repeated, the amount of light that passes through the partition area, or the so-called light extraction efficiency, decreases. In particular, in high-definition displays such as 4K and 8K, where the pixel size becomes smaller, the pixel area becomes smaller, so there is a problem that the screen appears dark. As a countermeasure to this, the applicant proposed in Patent Document 2, as shown in the schematic diagram of Figure 7, a partition wall in which the main body of the partition wall is made of a transparent resin or the like and the surface is formed with a highly reflective metal film, thereby suppressing light absorption by the partition wall and preventing light from passing through or leaking.

However, after further investigation, the applicant found that when a metal reflective layer is formed on the surface of a resin barrier rib body to form a high barrier rib, there is concern that the following two phenomena may occur.
First, the high bulkhead is made of transparent resin, which increases the volume of the resin. As a result, when the LED is turned on, gas is generated from the resin due to heat, which can cause cracks and pinholes (defects) in the metal film. This is especially likely to occur at corners and bottoms where the metal film tends to become thinner.
Secondly, cracks may occur due to the above-mentioned thermal stress or stress during lamination.

JP 2018-182282 A JP 2021-173926 A

In view of the above problems, the present invention aims to provide an LED display device equipped with a partition substrate that is less likely to develop cracks or pinholes in the metal film formed on the partition.

In order to solve the above problems, the present invention provides
1. An LED display device, comprising:
an LED substrate on which an array of pixels is formed by an array of LED elements;
a partition wall substrate in which partition walls are formed in a lattice pattern on a transparent substrate,
the LED substrate and the partition substrate are arranged such that the LED elements and the partitions face each other, and the partitions separate the LED elements;
The partition wall has a light reflecting layer formed of a thin film including a metal film on a surface of a partition wall body made of a resin,
The LED display device is characterized in that the partition has a top portion having a cutout portion where the light reflecting layer is not formed.

In the above LED display device,
The partition wall may have a transparent protective layer laminated so as to cover the light reflecting layer.

In the above LED display device,
The partition wall may be formed to have a forward tapered shape with respect to the transparent substrate.

In the above LED display device,
The LED element may be a blue LED element.

In the above LED display device,
A light scattering layer may be provided in each of the areas surrounded by the partition wall, the transparent substrate, and the LED element.

In the above LED display device,
A light wavelength conversion layer may be provided in each of the areas surrounded by the partition wall, the transparent substrate, and the LED element.

In the above LED display device,
The thin film may have a three-layer structure in which a conductive oxide thin film, a metal film, and a conductive oxide thin film are laminated in this order.

In the above LED display device,
The metal film may be made of any one of silver, a silver alloy, aluminum, an aluminum alloy, copper, and a copper alloy.

The present invention makes it possible to use LED light-emitting elements with higher brightness, resulting in an LED display device with high contrast and excellent color reproducibility.

1 is a schematic partial cross-sectional view of an embodiment of an LED display device of the present invention; 2 is a partial cross-sectional schematic view of a partition wall substrate of the LED display device of FIG. 1; FIG. 4 is an enlarged view of a partition portion of the LED display device of the present invention. FIG. 2 is a plan view of a partition wall of the LED display device of the present invention. FIG. 4 is a schematic partial cross-sectional view of a second embodiment of a partition wall substrate of an LED display device according to the present invention; FIG. 4 is a partial cross-sectional schematic view of a third embodiment of a partition wall substrate of an LED display device according to the present invention; FIG. 1 is a partial schematic cross-sectional view of an example of a partition wall substrate of a conventional LED display device.

The following describes in detail the embodiments of the present invention with reference to the drawings. Note that the present invention is not limited to the embodiments described below. In addition, the embodiments described below have technically preferable limitations for implementing the invention, but these limitations are not essential requirements for the present invention.

Figure 1 is a partial cross-sectional schematic diagram of one embodiment of the LED display device of the present invention (hereinafter, sometimes referred to as "the device"). The LED display device 1 of the present invention has an LED substrate 20 on which LED light-emitting elements 22 driven by thin film transistors (TFTs) (not shown) are arranged in a two-dimensional matrix at a fixed pitch on a substrate 21, and a partition substrate 10 on which partitions 12 are formed on a transparent substrate 11 so that they form a lattice shape in a plan view seen from the normal direction of the transparent substrate 11, and the LED light-emitting elements 22 and the partitions 12 are combined and abutted against each other in an opposing orientation. The partitions 12 are combined so as to be positioned between the LED light-emitting elements 22, and therefore each LED light-emitting element 22 forms a pixel in a manner that is surrounded by the partitions 12.

Each of the above pixels is formed with a light scattering layer or a light wavelength conversion layer (sometimes collectively referred to as a light adjustment layer) 13R, 13G, 13B. The light scattering layer or light wavelength conversion layer is provided to adjust the light emitted from the LED light emitting element 22 to the three primary colors of light, red, green, and blue. In FIG. 1, the light adjustment layer 13R is illustrated as a light adjustment layer for emitting red light, the light adjustment layer 13G as a light adjustment layer for emitting green light, and the light adjustment layer 13B as a light adjustment layer for emitting blue light, but the colors, number of colors, and combinations of the light adjustment layers are not limited to these.

For example, when the LED light emitting element 22 is composed of three types of LEDs, namely red LEDs, green LEDs, and blue LEDs, and the LED elements themselves emit red, green, and blue light, respectively, the light adjustment layers 13R, 13G, and 13B can be used as scattering layers for the respective lights.
The ED light-emitting element 22 can also be constructed using only blue LEDs, in which case the light adjustment layer 13B can be a light scattering layer, the light adjustment layer 13R can be a light wavelength conversion layer that converts the wavelength of blue light to red light, and the light adjustment layer 13G can be a light wavelength conversion layer that converts the wavelength of blue light to green light.

The light scattering layer can be made of transparent resin particles or metal oxide particles dispersed in a transparent resin. For example, it is preferable to use light scattering particles with an average particle size of 0.03 μm or more and 5.0 μm or less for the light scattering layer.

The light wavelength conversion layer can be appropriately selected from quantum dots and known fluorescent dyes, and these may be used in combination. It is preferable to use an inorganic phosphor with excellent heat resistance as the fluorescent dye. If the particle size of the inorganic phosphor particles used in the wavelength conversion layer is within the range of 1.0 μm to 10.0 μm, the wavelength conversion efficiency and dispersibility in the coating film are good. The thickness of the wavelength conversion layer is required to allow the inorganic phosphor or quantum dot material to sufficiently absorb and convert the excitation light emitted from the light source, and the thickness can be, for example, within the range of 2 μm to 200 μm.

The substrate 21 and the transparent substrate 11 may be, for example, a glass substrate, a quartz substrate, a sapphire substrate, a plastic substrate, etc.

Figure 2 is a diagram showing details of the partition substrate 10 of the LED display device 1 of Figure 1. The partition 12 is formed so that the surface of the partition body 12A made of resin is covered with a light reflecting layer 12B made of a thin film (hereinafter, sometimes simply referred to as "thin film") including a metal film. The light of the LED light-emitting element 22 is reflected by the light reflecting layer 12B, which provides the same effect as light blocking, and there is no decrease in contrast or light leakage to adjacent pixels, so the partition body 12A does not necessarily need to have light blocking properties.

The partition body 12A can be formed, for example, by coating a photosensitive resin onto the transparent substrate 11, patterning it with light, and developing it, but is not limited to this.

At the top of the partition 12, i.e., the portion that abuts against the LED substrate 20, a cutout portion 14 is formed where no thin film is formed.

When the LED element 22 is turned on, the heat generated may cause a small amount of gas to be released from the resin of the partition body 12A. If the cutout portion 14 is not provided, the surface of the partition body 12A is covered with a thin film containing a metal film that is impermeable to gas, and the gas cannot escape. The gas that reaches the interface between the partition body 12A and the thin film may cause blisters, cracks, pinholes, etc. in the thin film. If blisters, cracks, pinholes, etc. occur, the reflection of light may become irregular, which may cause light leakage and may affect the durability of the LED display device. By providing the cutout portion 14, the gas can escape from the cutout portion 14, and the occurrence of such an event can be suppressed.

The cutout 14 is preferably located at the top, since if it is located on the side of the bulkhead body 12A, it may come into contact with the phosphor in the light adjustment layer or the light from the LED element 22 may enter the cutout 14.

To improve reliability, the partition 12 may be further laminated with a transparent resin layer 12C as shown in FIG. 3(a). This will cover the cutout portion 14, but as it is a resin layer, gas can pass through it, so this poses little problem.

The height of the partition walls 12 is required to be equal to or thicker than the thickness of the wavelength converting layer when the wavelength converting layer is filled in the partition walls, and can be, for example, in the range of 2 μm to 200 μm. Note that the height of the partition walls may be 200 μm or more, but when the partition walls are formed using a general coating device such as a curtain coater or a slit coater, it is difficult to form a coating film with a thick thickness after drying, so that it is appropriate to set the upper limit at 200 μm.

The light reflecting layer 12B formed of a thin film including a metal film may be a film of a single metal film, and a thin film of silver, a silver alloy, aluminum, an aluminum alloy, copper, or a copper alloy, which has a high reflectivity, can be suitably applied. However, since a thin silver film or a thin silver alloy film has a weak adhesion to a glass substrate or a resin, the adhesion can be improved by forming a three-layer structure in which a thin silver film or a silver alloy film 121B is sandwiched between thin conductive oxide films 121A, as shown in FIG. 3(b).

Examples of conductive oxides include composite oxides such as indium oxide, zinc oxide, tin oxide, antimony oxide, and gallium oxide. The electrical conductivity and solubility in acid can be adjusted by combining and using these metal oxides. For silver and copper, a three-layer structure sandwiched between these conductive oxides can improve adhesion to glass substrates.

The shape of the cutouts 14 is not particularly limited, but for example, as shown in FIG. 4(a), they can be provided in a continuous groove shape on the top of the lattice-shaped partition 12. Alternatively, as shown in FIG. 4(b), the cutouts 14 may be discontinuous spot-shaped.

The formation of a thin film containing a metal film that will become the light reflecting layer 12B can be achieved, for example, by a process that combines metal layer sputtering and pattern etching, but is not limited to this.

Figure 5 is a partial cross-sectional schematic diagram of a second embodiment of a partition substrate for an LED display device of the present invention. In the partition substrate 10B of this embodiment, the partition 12 is formed in a forward tapered shape with respect to the transparent substrate 11. That is, the inner angle that the side wall portion makes with respect to the transparent substrate is an acute angle that is smaller than 90°. The forward tapered shape makes it easier to form the partition, and the partition is reverse tapered with respect to the LED substrate 20, making it difficult for reflected light from the light reflecting layer 12B to leak through adjacent pixels.

Figure 6 is a partial cross-sectional schematic diagram of a third embodiment of a partition substrate for an LED display device of the present invention. In the partition substrate 10C of this embodiment, a black matrix 15 is provided on the transparent substrate 10 so as to cover the base of the partition 12. By providing the black matrix 15, it is possible to more effectively prevent light from the LED elements from leaking to adjacent pixels on the front side of the device, i.e., the side on which the user views the device.

Electronic devices to which the LED display devices according to the above-described embodiments can be applied include electronic devices such as mobile phones, portable game machines, portable information terminals, personal computers, electronic books, video cameras, digital still cameras, head-mounted displays, navigation systems, audio playback devices (car audio, digital audio players, etc.), copiers, facsimiles, printers, multifunction printers, vending machines, automated teller machines (ATMs), personal authentication devices, optical communication devices, and IC cards. The above-described embodiments can be freely combined for use. Electronic devices equipped with the display devices according to the embodiments of the present invention are preferably further equipped with antennas for communication and contactless power reception and supply.

The LED display device of the present invention can be applied to both mini LED displays and micro LED displays, but is particularly effective when applied to high-definition micro LED displays that are susceptible to defects in the light-reflecting layer. In addition, it is possible to form barrier ribs with excellent light-shielding properties and good pattern shapes, and to suppress the occurrence of cracks in the thin film.
An LED display device having high brightness and contrast and capable of suppressing color mixing between adjacent pixels can be obtained.

1 LED display device 10, 10B, 10C partition wall substrate 11 transparent substrate 12 partition wall 12A partition wall body 12B light reflecting layer 12C transparent resin layer 13R, 13G, 13B light scattering layer or light wavelength conversion layer (light adjustment layer)
14: Cutout portion 15: Black matrix 20: LED substrate 21: Substrate 22: LED element

Claims (8)

1. An LED display device, comprising:
an LED substrate on which an array of pixels is formed by an array of LED elements;
a partition wall substrate in which partition walls are formed in a lattice pattern on a transparent substrate;
the LED substrate and the partition substrate are arranged such that the LED elements and the partitions face each other, and the partitions separate the LED elements;
The partition wall has a light reflecting layer formed of a thin film including a metal film on a surface of a partition wall body made of a resin,
4. An LED display device, comprising: a top portion of said partition wall having a cutout portion where said light reflecting layer is not formed. The LED display device according to claim 1, characterized in that the partition has a transparent protective layer laminated so as to cover the light reflecting layer. The LED display device according to claim 1, characterized in that the partition is formed to have a forward tapered shape with respect to the transparent substrate. The LED display device according to claim 1, characterized in that the LED elements are blue LED elements. The LED display device according to claim 1, characterized in that it has a light scattering layer in each area surrounded by the partition, the transparent substrate, and the LED element. The LED display device according to claim 1, characterized in that each area surrounded by the partition, the transparent substrate, and the LED element has a light wavelength conversion layer. The LED display device according to claim 1, characterized in that the thin film has a three-layer structure in which a conductive oxide thin film, a metal film, and a conductive oxide thin film are laminated in this order. The LED display device according to claim 1, characterized in that the metal film is made of any one of silver, a silver alloy, aluminum, an aluminum alloy, copper, and a copper alloy.

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