The present invention relates to full-color LED display panels including fluorescent layers, and more specifically, relates to full-color LED display panels capable of reliably preventing mixing of colors occurring between adjacent fluorescent layers, and methods for manufacturing the full-color LED display panels.
A conventional full-color LED display panel is provided with: an array of micro LED devices, each emitting blue (e.g., 450 nm to 495 nm) light or deep blue (e.g., 420 nm to 450 nm) light; and an array of wavelength conversion layers (fluorescent layers) disposed over the array of the micro LED devices, each wavelength conversion layer absorbing the blue or deep blue light emitted from a corresponding micro LED device to convert the emission wavelength into the wavelength of red, green, or blue light (see, for example, JP 2016-523450 A).
However, in such a conventional full-color LED display panel, a black matrix is used as a partition wall for separating wavelength conversion layers (fluorescent layers) for red, green and blue colors. Thus, when a photosensitive resin containing a black pigment is used as the black matrix in a case in which the wavelength conversion layers are thick, there is a concern that a deep portion of the resin will be prevented from being exposed to the light due to the light shielding performance of the black matrix, and that an unexposed portion will remain. Therefore, when loading a fluorescent resist solution containing a fluorescent colorant (pigment or dye) of the corresponding color into openings (pixels) for each color surrounded by the partition walls, a part of the partition wall may collapse, and the fluorescent resist solution may leak into an adjacent opening for another color. Thus, there is a concern that this may result in colors being mixed. In particular, these problems become particularly notable when the partition walls have great height-to-width aspect ratios.
Thus, in view of the above problems, an object of the present invention is to provide a full-color LED display panel capable of reliably preventing mixing of colors occurring between adjacent fluorescent layers, and to provide a method for manufacturing the full-color LED display panel.
To achieve the object, a full-color LED display panel according to the present invention includes:
an LED array substrate in which multiple LEDs are arranged in a matrix form on a wiring board, each LED emitting light in an ultraviolet or blue wavelength band;
multiple fluorescent layers configured to perform wavelength conversion by being excited by excitation light emitted from a corresponding LED and by emitting fluorescence of a corresponding color, each fluorescent layer being formed in an island pattern, on at least one corresponding LED for red, green, or blue color, and being made of a fluorescent resist containing a fluorescent colorant uniformly dispersed in a photosensitive resin; and
a light shielding member that reflects or absorbs excitation light and fluorescence, and is deposited on a peripheral face of each fluorescent layer, which is other than a light emitting surface.
A method for manufacturing a full-color LED display panel according to the present invention includes:
a first step of arranging multiple LEDs in a matrix form on a wiring board to form an LED array substrate, each LED emitting light in an ultraviolet or blue wavelength band;
a second step of exposing a fluorescent resist containing a fluorescent colorant uniformly dispersed in a photosensitive resin, and then, developing the fluorescent resist, to form multiple fluorescent layers configured to perform wavelength conversion by being excited by excitation light emitted from an LED and by emitting fluorescence of a corresponding color, each fluorescent layer being formed in an island pattern, on at least one corresponding LED for red, green, or blue color; and
a third step of depositing, on a peripheral face of each fluorescent layer, which is other than a light emitting surface, a light shielding member that reflects or absorbs excitation light and fluorescence.
Since, in the present invention, there is provided the light shielding member deposited on the peripheral face, which is other than the light emitting surface, of the fluorescent layer formed in the island pattern and made of the fluorescent resist, unlike the related art, there is no risk that a part of a partition wall between adjacent fluorescent layers collapses and a fluorescent resist solution leaks into an adjacent pixel for another color, to mix colors. Therefore, it is possible to reliably prevent mixing of colors occurring between adjacent fluorescent layers.
Hereinbelow, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The LED array substrate 1 is provided with multiple LEDs 4 arranged in a matrix form, as shown in
The multiple LEDs 4 are provided on the wiring board 5, as shown in
Specifically, as shown in
More specifically, elastic protrusions 7 may be resin protrusions 10 each having a surface on which a conductive film 9 of superior conductivity, such as gold or aluminum, is deposited, or may be protrusions 10 each made of a conductive photoresist obtained by adding conductive fine particles, such as silver, to a photoresist, or be made of a conductive photoresist containing a conductive polymer. Although
Furthermore, as shown in
On each LED 4 on the LED array substrate 1, a fluorescent layer 2 is provided, as shown in
Specifically, each fluorescent layer 2 contains, in a resist film, a fluorescent colorant having a particle diameter of several micrometers, and an adjustment colorant having a particle diameter of several tens of nanometers and selectively transmitting light in a predetermined wavelength band. The fluorescent colorant and the adjustment colorant are uniformly mixed and dispersed in the resist film.
More specifically, the adjustment colorant transmits excitation light EL emitted from an LED 4, and selectively transmits light in wavelength bands corresponding to the three primary colors, from among fluorescence FL emitted from the excited fluorescent colorant, while absorbing the remaining light of unnecessary wavelengths. For the adjustment colorant, pigments or dyes for color filters may be used. That is, the red fluorescent layer 2R contains a red fluorescent colorant, and a red adjustment colorant that selectively transmits excitation light EL and light in a red wavelength band; the green fluorescent layer 2G contains a green fluorescent colorant, and a green adjustment colorant that selectively transmits excitation light EL and light in a green wavelength band; the blue fluorescent layer 2B contains a blue fluorescent colorant, and a blue adjustment colorant that selectively transmits excitation light EL and light in a blue wavelength band.
As shown in
As shown in
In a case in which a metal film is used to form the light shielding member 3, excitation light EL that travels obliquely in a fluorescent layer 2 toward an adjacent fluorescent layer 2 is reflected on the metal film and travels to the inside of the fluorescent layer 2, so that the reflected excitation light EL can be used for excitation of the fluorescent colorant. Thus, it is possible to improve the luminous efficiency of the fluorescent layers 2. Furthermore, since fluorescence FL traveling obliquely in a fluorescent layer 2 is reflected on the metal film, and is then emitted from the light emitting surface 2a of the fluorescent layer 2, it is also possible to improve the light utilization ratio.
Next, a manufacturing method for the full-color LED display panel according to the first embodiment, having the above structure, will be described.
The manufacturing method for the full-color LED display panel according to the first embodiment of the present invention can be roughly divided into a process for manufacturing an LED array substrate, a process for forming a fluorescent layer, and a process for forming a light shielding member. Hereinbelow, each process will be described in order.
First, as shown in
More specifically, before forming the conductive film 9, a resist layer is formed by photolithography on the periphery of each electrode pad 6 (i.e., except on the electrode pad 6), and after forming the conductive film 9, the resist layer is dissolved with a solution, and thus, the conductive film 9 on the resist layer is lifted off.
The elastic protrusions 7 may be protrusions 10, each made of a conductive photoresist obtained by adding conductive fine particles, such as silver, to a photoresist, or a conductive photoresist containing a conductive polymer. In this case, the elastic protrusions 7 are formed by patterning as the protrusions 10 on the electrode pads 6, by applying a conductive photoresist to the entire upper surface of the wiring board 5 to a predetermined thickness, exposing the photoresist using a photomask, and developing the photoresist.
Since the elastic protrusions 7 are thereby formed by applying a photolithography process, it is possible to secure high precision in position and shape, and it is also possible to easily form the elastic protrusions 7 even when the distance between the electrodes 8 of the LEDs 4 is less than about 10 μm. Therefore, it is possible to manufacture a high-definition, full-color LED display panel.
Furthermore, since the elastic protrusion 7 is configured to contact a corresponding electrode 8 of the LED 4 while being elastically deformed by pressing of the LED 4, it is possible to reliably bring each electrode 8 of multiple LEDs 4 into contact with the elastic protrusions 7 even when the multiple LEDs 4 are simultaneously pressed as described below. Therefore, it is possible to improve the production yield of the full-color LED display panel.
Next, as shown in
Next, as shown in
Subsequently, as shown in
First, as shown in
Next, as shown in
Next, by developing the red fluorescent resist 13 with a predetermined developer, the red fluorescent resist 13 having an island pattern remains on the LEDs 4 for red color, as shown in
Then, in a similar manner, a green fluorescent resist and a blue fluorescent resist are subjected to an application process on the LED array substrate 1 and a photolithography process using a photomask, to form a green fluorescent layer 2G on LEDs 4 for green color and a blue fluorescent layer 2B on LEDs 4 for blue color, as shown in
First, as shown in
Then, as shown in
Then, a transparent protective layer (not shown), which transmits visible light, and an antireflection film for preventing external light from being reflected, are formed on the display surface. Thereby, the full-color LED display panel according to the first embodiment of the present invention is completed. When LEDs 4 emitting blue light are used, the blue fluorescent layer 2B may be omitted.
The second embodiment is different from the first embodiment in that the fluorescent layers 2 and the light shielding member 3 are formed on another transparent substrate 15, which is different from the LED array substrate 1. Hereinbelow, a manufacturing method according to the second embodiment will be described.
The manufacturing method according to the second embodiment can be roughly divided into a process for manufacturing an LED array substrate, a process for manufacturing a fluorescent layer array substrate, and an assembling process.
The process for manufacturing an LED array substrate is the same as that in the manufacturing method according to the first embodiment, and description thereof will be omitted.
First, as shown in
Next, as shown in
Then, by developing the red fluorescent resist 13 with a predetermined developer, the remaining red fluorescent resist 13 that is developed forms an island pattern, as shown in
Then, in a similar manner, a green fluorescent resist 13 is subjected to an application process on the transparent substrate 15 and a photolithography process using a photomask, and a blue fluorescent resist 13 is subjected to an application process on the transparent substrate 15 and a photolithography process using a photomask. This forms green fluorescent layer 2G in the island pattern at the same pitch as the arrangement pitch of LEDs 4 for green color, and blue fluorescent layer 2B in the island pattern at the same pitch as the arrangement pitch of LEDs 4 for blue color, as shown in
Next, as shown in
Then, as shown in
Next, as shown in
In the second embodiment, formation of a protective layer and an antireflection film on the fluorescent layer 2 may be performed after the formation of the fluorescent layer array substrate 16, or alternatively, after the completion of the assembling process.
Although in the above description the LEDs 4 are light emitting diodes manufactured using gallium nitride (GaN) as a main material, the present invention is not limited thereto, and the LEDs 4 may include organic EL (organic electroluminescent) diodes. Therefore, the LEDs 4 of the LED array substrate 1 may be formed of an organic EL layer that emits light in the ultraviolet or blue wavelength band.
It should be noted that the entire contents of Japanese Patent Application No. 2018-018009, filed on Feb. 5, 2018, from which convention priority is claimed, is incorporated herein by reference.
It should also be understood that many modifications and variations of the described embodiments of the invention will be apparent to one of ordinary skill in the art, without departing from the spirit and scope of the present invention as claimed in the appended claims.
Number | Date | Country | Kind |
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2018-018009 | Feb 2018 | JP | national |
This application is a continuation application of PCT/JP2019/001987, filed on Jan. 23, 2019.
Number | Date | Country | |
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Parent | PCT/JP2019/001987 | Jan 2019 | US |
Child | 16930873 | US |