Display device and manufacturing method for same

Abstract

The purpose of the present invention is to provide: a display device, which comprises a partition wall excellent in light shielding properties and alignment accuracy; and a method for manufacturing such display device. This display device is characterized in that: the display device includes a light-emitting element provided on a substrate, a partition wall formed around the light-emitting element, and a color conversion layer disposed on the light-emitting element and filling the internal space of the partition wall; and the partition wall includes a material that blocks visible light and transmits infrared light. In the present invention, a light-shielding characteristic value (OD × t), which is indicated by the product of an optical density (OD) and the height dimension (t) of the partition wall, is preferably 4 to 20.

Description

Display device and manufacturing method thereof

[0001] The present invention relates to a display device and a manufacturing method thereof.

[0002] Patent Document 1 discloses an invention related to an LED display device. The LED display device is configured with an LED array substrate and a light-shielding member. The light-shielding member is configured with a transparent resin and a light-shielding film made of aluminum or the like formed on the side surface of the transparent resin. In Patent Document 1, the light-shielding member is formed on a substrate separate from the LED array substrate, and the light-shielding member is transferred to the LED array substrate by a lift-off method.

[0003] Japanese Patent Application Laid-Open No. 2021-56386

[0004] The light blocking member is required to have not only light blocking properties but also high alignment accuracy with respect to the LED array substrate.

[0005] However, with the configuration of the light blocking member of Patent Document 1, as pixel sizes become finer, it becomes difficult to form the partition walls with high alignment precision, resulting in a decrease in yield.

[0006] The present invention has been made in view of the above points, and an object of the present invention is to provide a display device including partition walls that are excellent in light blocking properties and alignment accuracy, and a method for manufacturing the same.

[0007] One embodiment of the display device of the present invention is characterized in that it comprises a light-emitting element provided on a substrate, a partition formed around the light-emitting element, and a color conversion layer on the light-emitting element and filling an internal space of the partition, wherein the partition is configured to block visible light and transmit infrared light.

[0008] According to the display device and the manufacturing method thereof of the present invention, partition walls having high light-blocking properties can be formed with high alignment accuracy, and can appropriately accommodate the trend toward higher pixel size resolution.

[0009] FIG. 1 is a cross-sectional schematic diagram of a micro LED display as a display device in the present embodiment. FIG. 2 is a plan view showing one step in the manufacturing process of a micro LED display. FIG. 3 is a cross-sectional view taken along the line A-A in FIG. 2. FIG. 4 is a partially enlarged cross-sectional view showing one step in the manufacturing process of a micro LED display. FIG. 5 is a partially enlarged cross-sectional view showing one step in the manufacturing process of a micro LED display. FIG. 6 is a SEM photograph showing partition walls of an example. FIG. 7A is a schematic diagram of FIG. 7A. FIG. 7B is a graph showing the relationship between wavelength and transmittance for each film thickness of a partition wall. FIG. 7C is a graph showing the relationship between wavelength and refractive index of a partition wall.

[0010] The following describes in detail an embodiment of the present invention, but the following description is merely an example (typical example) of the embodiment of the present description, and the present invention is not limited to these details as long as it does not deviate from the gist of the present invention. In addition, the notation "to" used below includes both the lower limit and the upper limit within the range.

[0011] <Background to the Invention of the Display Device of the Present Embodiment> Liquid crystal on silicon (LCOS), laser beam scanning (LBS), or organic light emitting diode (OLED) microdisplays are becoming mainstream for applications such as head-mounted displays for AR (Augmented Reality) / MR (Mixed Reality).

[0012] However, these methods do not provide sufficient brightness in outdoor light, and are therefore primarily used indoors.

[0013] In contrast, the micro LED method is considered to be more advantageous than the above methods in terms of brightness, and is expected to see expanded application in the future.

[0014] As a method for displaying full color using a micro LED display, a technology has been proposed in which blue light-emitting elements are used as light-emitting elements (LEDs), and color conversion (wavelength conversion) is performed using a color conversion layer using quantum dots to enable RGB display.

[0015] At this time, the outer periphery of each light-emitting element is surrounded by a partition wall to prevent light emitted by the micro LEDs and light color-converted from the quantum dots from penetrating into adjacent pixels. Therefore, the partition wall needs to have light-blocking properties.

[0016] For example, in Patent Document 1, a partition wall is provided in which the side surface of a transparent resin is coated with a metal element. In Patent Document 1, the partition wall is formed on a substrate separate from a substrate having light-emitting elements, and the partition wall is transferred to the substrate on which the light-emitting elements are arranged by a lift-off method, so that the outer periphery of the light-emitting element is surrounded by the partition wall.

[0017] However, the lift-off method is not suitable for high-resolution pixel sizes (for example, about 2 μm to 5 μm per side). That is, the lift-off method does not have sufficient alignment precision, so that when the partition wall is transferred to the substrate side on which the light-emitting element is provided, misalignment becomes large, resulting in a decrease in yield.

[0018] Therefore, the present inventors have conducted extensive research into forming partition walls directly on a substrate having light-emitting elements, rather than by the lift-off method.

[0019] To directly form the partition walls, a partition wall material layer is applied to the entire surface of a substrate provided with light-emitting elements, and the partition wall material layer is patterned by exposure and development to obtain the partition walls. Therefore, the surface of the alignment mark provided on the substrate is covered with the partition wall material layer, but the alignment mark needs to be read during exposure.

[0020] To take advantage of the high-brightness light-emitting characteristics of micro-LEDs, it is necessary to improve the wavelength conversion characteristics of the color conversion layer formed on the light-emitting element. To achieve this, it is necessary to increase the fluorescent content of quantum dots or the like contained in the color conversion layer and to increase the film thickness of the color conversion layer. While not limited to this, the film thickness of the color conversion layer is, for example, approximately 2 μm to 10 μm. Accordingly, the height of the partition walls surrounding the color conversion layer must also be increased.

[0021] However, when carbon black or titanium black, which are known as light-shielding materials, are used as the partition wall material, the coating thickness becomes large (specifically, 2 μm or more), completely blocking light from the alignment marks provided on the substrate surface, which makes it impossible to read the alignment marks through the partition wall material layer during exposure, and thus makes it impossible to form the partition walls.

[0022] Therefore, as a result of extensive research, the inventors have developed a display device that has high light-blocking properties and is equipped with partitions that are formed with high alignment precision, by using a material for the partitions that blocks visible light and transmits infrared light.

[0023] <Description of Display Device of the Present Embodiment> The display device of the present embodiment is configured as a micro LED (Light Emitting Diode) display 1 shown in Fig. 1. Fig. 1 is a schematic cross-sectional view of the micro LED display 1.

[0024] As shown in Fig. 1, the micro LED display 1 includes a plurality of display pixels 2a, 2b, and 2c. For example, the display pixel 2a shown in Fig. 1 is a red display pixel, the display pixel 2b is a green display pixel, and the display pixel 2c is a blue display pixel.

[0025] 1, a plurality of light-emitting elements 4 are arranged on a substrate 3. For example, the light-emitting elements 4 are arranged in a matrix on the substrate 3. For example, each light-emitting element 4 is a blue-emitting micro LED.

[0026] As shown in Fig. 1, partition walls 5 are formed on the substrate 3 to separate the light-emitting elements 4 from one another. The partition walls 5 are formed so as to surround the outer periphery of each light-emitting element 4 in a plan view. The partition walls 5 are formed containing a material that blocks visible light and transmits infrared light. The configuration of the partition walls 5 will be described in detail later.

[0027] Alignment marks M are provided at the edge of the substrate 3. The alignment marks M are marks for aligning a mask when exposing the partition material layer. The alignment marks M may be removed from the substrate 3 by dicing. In other words, the alignment marks M may not be provided in the micro LED display 1.

[0028] 1, the internal spaces of the partition walls 5 of the red display pixels 2a and the green display pixels 2b are filled with color conversion layers 6a and 6b. As shown in FIG. 1, the color conversion layers of the red display pixels 2a and the green display pixels 2b have red quantum dots 7 and green quantum dots 8 dispersed therein, respectively.

[0029] The quantum dots 7 and 8 are dispersed in a resin 9. The resin 9 is preferably a transparent resin. There are no limitations on the material of the resin 9, but examples thereof include acrylic resins, polyurethane resins, polyester resins, polyolefin resins, polycarbonate resins, polyethyleneimine resins, epoxy resins, and thioether resins.

[0030] The red quantum dots 7 preferably have a fluorescence peak wavelength of 600 nm to 680 nm, and the green quantum dots 8 preferably have a fluorescence peak wavelength of 520 nm to 560 nm. These quantum dots 7 and 8 absorb blue light as excitation light irradiated from the light-emitting element 4, and emit red or green light after color conversion.

[0031] Although the materials are not limited, because cadmium (Cd) is toxic and its use is restricted in various countries, it is preferable that the quantum dots 7 and 8 be cadmium-free. Furthermore, the quantum dots 7 and 8 preferably have a core-shell structure consisting of a core and a shell covering the core, such as ZnSe / ZnS, ZnSe / ZnSeS, ZnTe / ZnS, ZnSeTe / ZnS, or InP / ZnS. However, the quantum dots 7 and 8 may be composed of only a core. Furthermore, to improve dispersibility, it is preferable that the quantum dots 7 and 8 have a ligand (organic ligand) on their surfaces.

[0032] The particle size of the quantum dots 7 and 8 is several nanometers to several tens of nanometers. The fluorescence peak wavelength can be controlled by adjusting the particle size and composition. Note that the color conversion layers 6 a and 6 b may contain phosphors other than the quantum dots 7 and 8.

[0033] On the other hand, as shown in Figure 1, the internal space of the partition wall 5 of the blue display pixel 2c is filled with resin 9, but does not contain quantum dots. The resin 9 is preferably a transparent resin. "Transparent" means that the visible light transmittance is 50% or more, preferably 70% or more, and most preferably 90% or more. The visible light transmittance can be measured in accordance with JIS K 7375:2008.

[0034] As another example, white light may be used for the light emitting element 4 used in the blue display pixel 2 c , and blue quantum dots may be mixed into the resin 9 .

[0035] The color conversion layers 6a and 6b may contain fluorescent particles different from the quantum dots in addition to or instead of the quantum dots.

[0036] 1, the surfaces of the color conversion layers 6a, 6b and resin 9 may be formed at substantially the same height as the partition walls 5, or may be slightly lower than the partition walls 5. The thickness of the color conversion layers 6a, 6b is about 2 to 10 μm.

[0037] 1, a color filter 11 is provided on the surfaces of the color conversion layers 6a, 6b and the resin 9 via a barrier layer 10. The color filter 11 includes a red filter 11a, a green filter 11b, and a blue filter 11c. The thickness of the color filter 11 is not limited, but is, for example, about 0.5 μm to 2.0 μm.

[0038] Although the barrier layer 10 is not an essential layer, providing the barrier layer 10 can reduce the thermal influence on the quantum dots 7 and 8 in the color conversion layers 6a and 6b when the color filter 11 is formed. Furthermore, if there are irregularities between the surfaces of the partition wall 5 and the color conversion layers 6a and 6b and the resin 9, the barrier layer 10 can smooth out the irregularities. This allows the color filter 11 to be formed on a flat surface. There are no restrictions on the material of the barrier layer 10, but it is preferably an oxide film or a nitride film, for example, SiO ２ The thickness of the barrier layer 10 is not limited, but is about 50 nm to 1 μm.

[0039] The color filters 11 are arranged such that a red filter 11a is located at the position of the red display pixel 2a, a green filter 11b is located at the position of the green display pixel 2b, and a blue filter 11c is located at the position of the blue display pixel 2c.

[0040] The red filter 11a absorbs short wavelength blue light and transmits red light, the green filter 11b absorbs short wavelength blue light and transmits red light, and the blue filter 11c transmits blue light.

[0041] 1, microlenses 12a to 12c can be provided on the surface of the color filter 11. The microlenses 12a to 12c are optically transparent. Although not limited thereto, the microlenses 12a to 12c can be made of organic materials such as acrylic resin, epoxy resin, and silicon resin, or SiN, SiO ２ 1, the microlenses 12a to 12c are convex lenses, but they can also be concave lenses or metalenses. The surface shapes of the microlenses 12a to 12c can be changed in various ways depending on the relationship between the refractive index and the layer located on the surface of the microlenses 12a to 12c.

[0042] 1 shows a configuration in which color filters 11 are provided on the surfaces of the color conversion layers 6a, 6b and resin 9 via barrier layers 10, but the configuration is not limited to this. For example, a resin layer may be formed on the surfaces of the color conversion layers 6a, 6b and resin 9, and then the barrier layer 10 may be formed thereon. Because the barrier layer 10 is usually formed as a thin film, if it is formed directly on the surfaces of the color conversion layers 6a, 6b and resin 9, the barrier properties may be reduced due to the influence of the unevenness of the color conversion layers 6a, 6b and resin 9. By forming a resin layer in this case, it is possible to improve the flatness of the color conversion layers 6a, 6b and resin 9, and the barrier properties also improve.

[0043] <Characteristic Configuration of the Micro LED Display 1 of the Present Embodiment> The micro LED display 1 of the present embodiment has the following characteristics: The partition wall 5 provided around the light emitting element 4 is configured to block visible light and transmit infrared light.

[0044] The wavelength of visible light is 400 nm to 780 nm, preferably 400 nm to 730 nm, and the wavelength of infrared light is 800 nm or more, preferably 830 nm or more.

[0045] In this embodiment, "shielding visible light" refers to a state in which the alignment mark M provided on the substrate 3 cannot be read even when irradiated with visible light in the exposure step of the partition wall material layer. Note that a state in which the alignment mark M cannot be read or is difficult to read even when some visible light is transmitted corresponds to "shielding visible light." Alternatively, "shielding visible light" can also be expressed by the optical density or spectral transmittance shown below.

[0046] That is, the light blocking property for visible light can be expressed by optical density (OD: Optical solid density), and the intensity I of incident light that is perpendicularly incident can be expressed by the optical density (OD: Optical solid density). ｉｎ and the intensity of the transmitted light I ｏｕｔ Using "log １０ (I ｉｎ / I ｏｕｔ))." For example, the optical density is calculated as the optical density per 1 μm of film thickness by measuring the spectral transmittance using a Solid Spec-3700 manufactured by Shimadzu Corporation. As will be described later, a preferred range of the optical density can be determined based on the light-shielding characteristic value (OD×t) expressed as the product of the height dimension t of the partition walls 5. Although not limited, the optical density is preferably in the range of 1 to 3. The optical density is more preferably 2 to 3. The spectral transmittance of visible light is 20% or less, preferably 15% or less, more preferably 13% or less, even more preferably 10% or less, even more preferably 5% or less, and most preferably 3% or less.

[0047] "Transmitting infrared rays" refers to a state in which the alignment mark M provided on the substrate 3 can be read when irradiated with infrared rays in the exposure process of the partition wall material layer. Note that even if the infrared rays are blocked to some extent, a state in which the alignment mark M can be read corresponds to "transmitting infrared rays." Alternatively, "transmitting infrared rays" can be expressed by the spectral transmittance shown below. The camera that reads the alignment mark M of the exposure machine is provided with an infrared camera, and has the function of measuring alignment by transmitting infrared rays. Although the exposure machine is not limited, an i-line stepper FPA5510iZ manufactured by Canon Inc. can be used.

[0048] The infrared spectral transmittance is preferably 40% or more, more preferably 50% or more, even more preferably 60% or more, and even more preferably 70% or more.

[0049] The material used for the partition walls 5 is not particularly limited as long as it is an infrared-transmitting material that blocks visible light and transmits infrared light. For example, the black matrix described in JP-A-2020-071433 can be exemplified.

[0050] That is, the infrared-transmitting material contains a colorant (A), a photopolymerizable monomer (B), a photopolymerization initiator (C), and a resin (D). The colorant (A) contains at least a blue pigment, a yellow pigment, and a violet pigment. The photopolymerizable monomer (B) contains a compound represented by the following general formula (1). The resin (D) is a resin obtained by reacting a hydroxyl group of a hydroxyl-containing polymer obtained by polymerizing an ethylenically unsaturated monomer (c) containing a hydroxyl-containing ethylenically unsaturated monomer (b) in the presence of a reaction product between the hydroxyl groups of a compound (a) having two hydroxyl groups and one thiol group in the molecule and the acid anhydride groups of pyromellitic anhydride and / or trimellitic anhydride, with the isocyanate groups of a compound (d) having one isocyanate group and one or more (meth)acryloyl groups. The photosensitive acrylic resin (E) contains a hydroxyl group-containing ethylenically unsaturated monomer (b) in an amount of 35% by mass or more and 80% by mass or less of the total amount of structural units derived from the ethylenically unsaturated monomer (c). ２ =CHC(=O)-(OC ｍ H ２ｍ ) ｎ -OCH ２ ] ３ -CCH ２ CH ３ (In general formula (1), m represents an integer of 1 to 3, n represents an integer of 0 to 2, and multiple m's and multiple n's may be the same or different.)

[0051] Resin (D) is a resin having a transmittance of preferably 80% or more, more preferably 95% or more, over the entire wavelength range of 400 to 700 nm in the visible light region. Resin (D) contains at least the above-mentioned photosensitive acrylic resin (E) and may further contain other resins. Resin (D) can be used as a resin-type dispersant or binder resin. Resin (D) is preferably used as a resin-type dispersant. Resin (D) also contains a photosensitive acrylic resin, and examples of resins include thermoplastic resins, thermosetting resins, and photosensitive resins.

[0052] Alternatively, the cured product of the photosensitive coloring composition contains a colorant (A), a photopolymerizable monomer (B), a photopolymerization initiator (C), and a resin (D), and the cured product has a red spectral transmittance, when the film thickness is 1.5 μm, of which the maximum transmittance of light in the wavelength range of 450 nm to 560 nm is 0.5% or less, and the transmittance of light in the wavelength range of 500 nm to 700 nm is 80% or more but less than 100%; a green spectral transmittance, when the film thickness is 1.5 μm, of which the maximum transmittance of light in the wavelength range of 400 nm to 470 nm is 2% or less, and the maximum transmittance of light in the wavelength range of 525 to 535 nm is 67% or more, and the short wavelength-side 50% half maximum wavelength is 497 to 507 nm and the long wavelength-side 50% half maximum wavelength is 554 to 581 nm; and a blue spectral transmittance, when the film thickness is 1.5 μm, of which the maximum transmittance of light in the wavelength range of 500 nm to 560 nm is less than 20%. The red color is obtained by mixing the colorant (A) with Pigment Red 177 and other colorants, the green color is obtained by mixing the colorant (A) with Pigment Yellow 185 and other colorants, and the content of Pigment Yellow 185 in the green colorant (A) is 49% by weight to 59% by weight, the blue color is obtained by mixing the colorant (A) with Pigment Blue 15:6 and other colorants, and the other colorants include one or more selected from the group consisting of Pigment Red 254, Pigment Yellow 139, Pigment Green 36, Pigment Green 58, Pigment Blue 15:3, Pigment Blue 15:6, Pigment Violet 23, and xanthene dyes. The photopolymerizable monomer (B) contains a compound represented by the following general formula (2), and the photopolymerization initiator (C) contains an oxime ester photopolymerization initiator. General formula (2) [CH ２ =CHC(=O)-(OC ｍ H ２ｍ ) ｎ -OCH ２ ] ３ -CR (in general formula (1), m represents an integer of 1 to 3, n represents an integer of 0 to 2, and plural m's and n's may be the same or different. R represents -CH ２ CH ３ , -CH ２ OH, -CH ２ O(C=O)C=CH ２ represents a substituent selected from

[0053] In this embodiment, the light-blocking characteristic value (OD×t), which is the product of the optical density (OD) of the partition 5 and the height dimension (t) of the partition 5, is preferably 4 or more and 20 or less. This enables the alignment mark M to be read during exposure, allows the partition 5 to be formed with high alignment precision, and improves yield. In addition, the partition 5 can be stably formed to a desired height, and improves light-emitting characteristics.

[0054] In this embodiment, the partition walls 5 are configured to have a film thickness of 1.0 μm, and the transmittance for a predetermined wavelength is specified, thereby enabling stable and accurate transmission and light-blocking characteristics to be obtained. Note that the partition walls 5 actually manufactured may be larger than 1.0 μm, and in that case, they are sampled and measured at a film thickness of 1.0 μm.

[0055] In the present embodiment, when a 1.0 μm-thick portion of the partition wall 5 is extracted and measured, it is preferable that the transmittance at a wavelength of 900 nm is 90% or more and the wavelength at which the transmittance is 50% is 760 nm or more and 810 nm or less. This makes it possible to obtain a transmittance curve that blocks visible light and transmits infrared light, and even when the thickness (height dimension t) of the partition wall 5 is applied to the dimensions shown in FIG. 1 , it is possible to configure the partition wall 5 to block visible light and transmit infrared light.

[0056] The transmittance at a wavelength of 900 nm is more preferably 93% or more, and even more preferably 95% or more. The wavelength at which the transmittance is 50% is more preferably 780 nm or more and 810 nm or less, and even more preferably 780 nm or more and 800 nm or less.

[0057] Furthermore, in this embodiment, when the thickness of the partition wall 5 is 1.0 μm, it is preferable that the transmittance at a wavelength of 450 nm is smaller than the transmittance at a wavelength of 700 nm. The wavelength of 450 nm is blue light, and the wavelength of 700 nm is red light. This allows the blue light emitted by the micro LEDs that cannot be fully wavelength-converted by the color conversion layers 6 a and 6 b to be efficiently removed (absorbed).

[0058] In this embodiment, when the thickness of the partition wall 5 is 1.0 μm, the transmittance of light having a wavelength of 700 nm is preferably 5% or more and 15% or less, so that the transmittance of red light can be kept low.

[0059] In this embodiment, the refractive index of the partition walls 5 at wavelengths of 800 nm and 900 nm is preferably 1.75 or more. Since the refractive index of the partition walls 5 is high at wavelengths of 800 nm and 900 nm, infrared light can be efficiently transmitted through the partition walls 5. As a result, the alignment marks can be detected with high accuracy. Furthermore, since the refractive index of the partition walls 5 is high at a wavelength of 700 nm, part of the red light whose wavelength has been converted by the color conversion layers 6 a and 6 b can be reflected by the partition walls 5.

[0060] The shape stability and light-emitting characteristics of the partition 5 will now be described. As shown in FIG. 1 , the side surface 5 a of the partition 5 is inclined so that the width of the partition 5 gradually narrows upward from the substrate 3 (in the direction away from the substrate 3: in the direction toward the color filter 11). Therefore, the upper end width of the partition 5 narrows as the height dimension t of the partition 5 increases. In particular, as image size becomes increasingly finer, the partition 5 may not be formed depending on the height dimension t of the partition 5. Therefore, it is necessary to stably form the partition 5 in accordance with the increasing fineness of the pixel size. Therefore, as long as the light-blocking characteristic value (OD×t) is within the above-described range, the partition 5 can be stably formed with the desired height dimension t while ensuring an optical density (OD) of 1 or more (preferably 2 or more) and 3 or less.

[0061] Specifically, the height dimension t of the partition walls 5 (which may be rephrased as film thickness) can be adjusted to 2 μm or more and 10 μm or less. This allows the film thickness of the color conversion layers 6 a, 6 b to be formed similarly thick. This allows the content of the quantum dots 7, 8 filled in the color conversion layers 6 a, 6 b to be increased, making it possible to obtain good light-emitting characteristics. To facilitate and stabilize the formation of the partition walls 5, the height dimension t of the partition walls 5 is preferably 6 μm or less. To obtain better optical characteristics, the height dimension t of the partition walls 5 is preferably 3 μm or more. Therefore, the height dimension t of the partition walls 5 is more preferably 3 μm or more and 6 μm or less.

[0062] The light-blocking characteristic value (OD×t) is more preferably 6 or more and 12 or less. This makes it easier to adjust the height dimension of the partition walls 5 to the above-mentioned range of 3 μm or more and 6 μm or less while ensuring an optical density of 2 or more and 3 or less, thereby more effectively promoting stabilization of the formation of the partition walls 5 and obtaining better light-emitting characteristics.

[0063] <Method of forming partition wall 5> In this embodiment, the partition wall 5 is formed directly on the substrate 3 on which the light-emitting element 4 is formed, which is different from the lift-off method described in Patent Document 1.

[0064] In this embodiment, an infrared-transmitting material that blocks visible light and transmits infrared light is used as the material for forming the partition walls 5. Therefore, by transmitting infrared light and reading the alignment marks during exposure, the partition walls 5 can be formed directly on the substrate 3 with high alignment accuracy, thereby improving the yield.

[0065] The manufacturing process of the micro LED display 1 of this embodiment will be described with reference to the drawings.

[0066] As shown in the plan view of Fig. 2, a plurality of chips 21 each including a light-emitting element, a wiring structure, etc. are formed on a wafer 20. Fig. 3 shows a cross-sectional view of the wafer 20 shown in Fig. 2 cut along line A-A. As shown in Fig. 3, a plurality of light-emitting elements 4 and alignment marks M are formed on a substrate 3 constituting each chip 21. The plurality of light-emitting elements 4 form an RGB pixel region.

[0067] The position where the alignment mark M is formed is not particularly limited, and for example, as shown in FIG. 3, it can be formed on the substrate 3 outside the plurality of light-emitting elements 4, and is preferably formed near the edge of the substrate 3. It is also preferable to form a plurality of alignment marks M. For example, the alignment marks M can be formed at the four corners of the substrate 3. Alternatively, the alignment marks M can be formed on the wafer 20 separate from the chips 21, for example, on the wafer 20 between the chips 21.

[0068] The pattern of the alignment mark M is not limited. Examples include a circle, a ring, and a bar shape. The alignment mark M may be made up of a single pattern, or may be made up of a collection of multiple patterns. The method of forming the alignment mark M is also not particularly limited. As long as the alignment mark M can be read by infrared rays, the method of forming the alignment mark M is not particularly limited, and may include a method of forming the alignment mark M by printing, pasting, chemical etching, vapor deposition, or sputtering.

[0069] Next, a partition material layer 22 is formed over the entire surface of the wafer 20. Fig. 4 is a partially enlarged cross-sectional view showing only one chip 21 in the wafer cross section of Fig. 3. As shown in Fig. 4, the partition material layer 22 is formed over the entire areas of the plurality of light-emitting elements 4 and alignment marks M provided on the substrate 3.

[0070] In this embodiment, an infrared-transmitting material that blocks visible light but transmits infrared light is used for the partition material layer 22. The infrared-transmitting material is applied onto the wafer 20 to form the partition material layer 22. For details of the infrared-transmitting material, please refer to the above-mentioned <Characteristic Configuration of the Micro LED Display 1 of this Embodiment>.

[0071] In this embodiment, the optical density and the thickness t of the partition wall material layer 22 are adjusted so that the light-shielding characteristic value (OD×t), which is the product of the optical density (OD) and the height dimension t of the partition wall 5 (corresponding to the thickness t of the partition wall material layer 22 in FIG. 4 ), is 4 or more and 20 or less. The optical density is calculated as the optical density per μm. The optical density is preferably in the range of 1 or more and 3 or less, and more preferably in the range of 2 or more and 3 or less. The thickness t of the partition wall material layer 22 is preferably in the range of 2 μm or more and 10 μm or less. The optical density and the thickness t of the partition wall material layer 22 are adjusted so that the light-shielding characteristic value (OD×t) is in the range of 4 or more and 20 or less. For example, the optical density of the partition wall material layer 22 is set to 2, and the thickness t of the partition wall material layer 22 is adjusted to be in the range of 2 μm or more and 10 μm or less. Preferably, the optical density of the barrier rib material layer 22 is set to 2, and the thickness t of the barrier rib material layer 22 is adjusted to be in the range of 3 μm to 6 μm.

[0072] After the barrier rib material layer 22 is applied, a heat treatment is carried out. The heat treatment temperature is not limited, but is about 70° C. to 150° C. Alternatively, high-temperature baking at 200° C. to 250° C. may be used. The heat treatment time is about several minutes to several tens of minutes.

[0073] Next, as shown in FIG. 4 , a resist layer 23 is applied to the upper surface 22 a of the partition wall material layer 22. A known material can be selected for the resist layer 23, and a material that is transparent to infrared rays is used. As shown in FIG. 4 , a mask 24 is placed above the resist layer 23. The mask 24 has light-transmitting portions 24 a and non-transmitting portions 24 b. If the resist layer 23 is a positive type, the unexposed portions remain, and if the resist layer 23 is a negative type, the exposed portions remain. The patterns of the light-transmitting portions 24 a and non-transmitting portions 24 b of the mask 24 are changed depending on the type of resist layer 23. The mask 24 has a planar pattern of the partition walls 5. The resist layer 23 is exposed through the mask 24 and developed to form a resist pattern 23 a shown in FIG. 5 on the upper surface 22 a of the partition wall material layer 22. At least the light-transmitting portions 24 a of the mask 24 are transparent to infrared rays.

[0074] 4, infrared rays are irradiated, and the alignment marks M are read by an infrared camera provided in the exposure machine. At this time, the infrared rays pass through the mask 24, the resist layer 23, and the partition wall material layer 22, and the alignment marks M are read. This allows the mask 24 to be aligned with high precision. Therefore, by exposure and development, the resist pattern 23a shown in FIG. 5 can be accurately formed at the formation position of the partition wall 5.

[0075] Then, the partition wall material layer 22 not covered with the resist pattern 23a is removed by etching, thereby forming the partition walls 5 directly on the substrate 3 with high alignment accuracy.

[0076] Next, the quantum dots and resin are filled into the internal spaces of the partitions 5 above the light-emitting elements 4 to form a color conversion layer, and then the color filter layer and microlenses shown in Fig. 1 are formed. Finally, the wafer 20 is diced to separate it into individual chips 21, thereby obtaining a plurality of micro LED displays 1. During this dicing, the alignment marks M may be left on the substrate 3 or may be removed.

[0077] <Effects of the Present Embodiment> In the present embodiment, the partition walls 5 are configured to block visible light and transmit infrared light, which allows the partition walls 5 with high light-blocking properties to be formed directly on the substrate 3 on which the light-emitting elements 4 are formed with high alignment precision.

[0078] That is, if the partition walls are formed using conventional carbon black or titanium black, the alignment marks M are blocked during exposure, making it impossible to read the alignment marks M. In particular, if the film thickness of the color conversion layer is increased to improve the light-emitting characteristics, the height of the partition walls must also be increased accordingly, but increasing the height of the partition walls further reduces alignment accuracy, leading to a decrease in yield.

[0079] In contrast to this, in the present embodiment, an infrared-transparent material is used for the partition walls 5, and therefore, during exposure, the alignment marks M can be read by irradiating them with infrared light, and the partition walls 5 can be formed directly on the substrate 3 on which the light-emitting elements 4 are provided with high alignment accuracy. This makes it possible to appropriately accommodate higher pixel size resolution.

[0080] Furthermore, in this embodiment, by adjusting the light-blocking characteristic value (OD×t) of the partition 5, which is the product of the optical density (OD) and the height dimension (t), to 4 or more and 20 or less, the partition can be formed with a desired height dimension t while having excellent light-blocking properties, and therefore the film thickness of the color conversion layers 6 a, 6 b can be increased, thereby realizing a micro LED display 1 with excellent light-emitting characteristics.

[0081] The present invention will be described in detail below with reference to examples carried out to clarify the effects of the present invention, but the present invention is not limited to the following examples.

[0082] The partition walls were formed from an infrared-transmitting material containing a material that shields visible light and transmits infrared light. The optical density (OD) of the infrared-transmitting material per 1 μm of film thickness was 2.

[0083] Specifically, 22.5 parts of a pigment dispersion (containing C.I. Pigment Blue PB15:6, acrylic resin solution 1 (acid value 36, weight average molecular weight 12,000), and acrylic resin solution 2 (weight average molecular weight (Mw) 26,000), pigment:acrylic resin solution 1:acrylic resin solution 2:propylene glycol monomethyl ether acetate = 14.0 parts:11.0 parts, 8.0 parts:67.0 parts), and 22.5 parts of a pigment dispersion (containing C.I. Pigment Yellow PY139, acrylic resin solution 1 (acid value 36, weight average molecular weight 12,000), and acrylic resin solution 2 (weight average molecular weight (Mw) 26,000), pigment Acrylic resin solution 1: Acrylic resin solution 2: Propylene glycol monomethyl ether acetate = 14.0 parts: 11.0 parts, 8.0 parts: 67.0 parts): 24.4 parts, pigment dispersion (containing C.I. Pigment Violet PV23 and acrylic resin solution 1 (acid value 36, weight average molecular weight 12,000) and acrylic resin solution 2 (weight average molecular weight (Mw) 26,000), pigment: Acrylic resin solution 1: Acrylic resin solution 2: Propylene glycol monomethyl ether acetate = 13.3 parts: 11.0 parts, 11.4 parts: 64.3 parts): 18.3 parts, photopolymerization monomer ("Aronix" manufactured by Toagosei Co., Ltd.) M-309"): 4.2 parts, photopolymerization initiator (BASF "Irgacure OXE-02" (ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(0-acetyloxime)): 0.7 parts, leveling agent solution (Dow Corning Toray Co., Ltd. "FZ-2122"): 1.0 parts, and solvent (propylene glycol monomethyl ether acetate): 28.9 parts were stirred and mixed uniformly, and the mixture was filtered through a filter to obtain an infrared-transmitting material.

[0084] Comparative Example: The barrier ribs were formed using a black matrix containing carbon black or titanium black. The optical density (OD) per 1 μm of film thickness of the barrier rib material was 3.

[0085] <Reading of Alignment Marks> Each of the materials in the above Examples and Comparative Examples was coated to a predetermined film thickness on a silicon wafer on which an alignment mark had been formed, and the substrate was passed through an i-line stepper FPA5510iZ manufactured by Canon Inc. to verify whether the alignment mark could be read through a mask.

[0086] <Experimental Results in Examples> Table 1 below shows the experimental results in the examples.

[0087]

[0088] As shown in Table 1, in Experimental Examples 1 to 4, the height dimension t of the partition walls was changed to 2 μm, 3 μm, 6 μm, and 10 μm. In all of the Experimental Examples, it was possible to read the alignment marks. Furthermore, although the partition walls could be stably formed, in Experimental Example 4, in which the height dimension t was 10 μm, the upper end portion was significantly narrower, and it was found that in order to obtain shape stability, the height dimension t should be less than 10 μm, preferably 6 μm or less.

[0089] FIG. 7A is an SEM photograph showing an example of a partition wall of an example. FIG. 7B is a schematic diagram of the SEM photograph. The height of the partition wall was approximately 4.2 μm. The width of the upper surface of the partition wall was approximately 0.7 μm, and the width of the lower surface of the partition wall was approximately 2.0 μm. The inclination of the side surface of the partition wall (the angle between the lower surface and the side surface of the partition wall) was approximately 82°. The spacing between the partition walls near the bottom surface was approximately 3.1 μm, and the spacing between the partition walls near the upper end was approximately 3.8 μm. As shown in FIGS. 7A and 7B, the side surface of the partition wall was inclined, and the width of the partition wall gradually narrowed upward from the substrate side. Since the height of the partition wall in FIGS. 7A and 7B is approximately 4.2 μm, if the height of the partition wall was increased to 10 μm or more, the height would be more than double that of the partition wall in FIGS. 7A and 7B, and the upper end of the partition wall would be significantly narrower. Therefore, from the SEM photograph of FIG. 7A and the schematic diagram of FIG. 7B, it can be said that the height of the partition wall is preferably 10 μm or less in order to obtain shape stability and ease of formation.

[0090] Furthermore, as for the light-emitting characteristics, the content of quantum dots that can be filled into the internal space of the partition walls can be increased by the amount of increase in the height of the partition walls, and as a result, the wavelength conversion efficiency can be increased and the light-emitting characteristics can be improved. However, in order to improve the light-emitting characteristics, a thicker color conversion layer is preferable, and therefore the height of the partition walls is preferably 2 μm or more, and more preferably 3 μm or more.

[0091] From the experimental results shown in Table 1, it was found that the light-blocking characteristic value (OD×t), which is the product of the optical density and the height of the partition wall, is preferably 4 or more and 20 or less. Furthermore, taking into consideration the shape stability and light-emitting characteristics of the partition wall, it was found that the light-blocking characteristic value is more preferably 6 or more and 12 or less.

[0092] <Experimental Results in Comparative Examples> Table 2 below shows the experimental results in the comparative examples.

[0093]

[0094] As shown in Table 2, in all experimental examples using carbon black and titanium black, it was found that the alignment marks could not be read when the height of the partition walls was 2 μm or more. Since the partition walls could not be formed in the first place when the height of the partition walls was 2 μm or more, the "shape stability of the partition walls" was rated as x. Furthermore, it was found that the alignment marks could be read when the height of the partition walls was 1 μm, but the partition walls were too low, so the amount of quantum dots filled in the internal spaces of the partition walls was insufficient, resulting in a thin film thickness of the color conversion layer and a deterioration in the light-emitting characteristics.

[0095] <Measurement of Spectral Transmittance> The partition walls made of the infrared-transmitting material of the above examples were coated on a quartz substrate to a predetermined film thickness under the same conditions to prepare measurement samples. A Solid Spec-3700 manufactured by Shimadzu Corporation was used as the spectral transmittance measuring device. Note that the measurement samples with film thicknesses of 0.8 μm, 1.0 μm, and 1.2 μm are actual measurement results, while the measurement samples with film thicknesses of 2.0 μm, 5.0 μm, and 10.0 μm are simulation results.

[0096] The relationship between wavelength and transmittance is shown in Figure 8. As shown in Figure 8, the transmittance curve shows low transmittance up to a wavelength of about 760 nm, regardless of the film thickness of the partition walls, and the transmittance increases sharply when the wavelength is 780 nm or more, and remains almost constant when the wavelength is about 840 nm. It was also found that the transmittance relative to the wavelength decreases as the film thickness increases, and the transmittance curve shifts to the longer wavelength side in the infrared region.

[0097] 8, when the partition wall thickness was 1.0 μm, the transmittance at a wavelength of 900 nm was 90% or more, and the wavelength at which the transmittance became 50% was 760 nm or more and 810 nm or less. It was found that the transmittance at a wavelength of 900 nm was more preferably 93% or more, and even more preferably 95% or more. It was also found that the wavelength at which the transmittance became 50% was more preferably 780 nm or more and 810 nm or less, and even more preferably 780 nm or more and 800 nm or less.

[0098] The reason for the evaluation of the barrier rib thickness being 1.0 μm is that it is possible to obtain stable and accurate light transmission and light blocking characteristics, that is, it is possible to reduce measurement errors.

[0099] In this way, the transmittance is evaluated assuming that the thickness of the partition wall is 1.0 μm. When the transmittance is within the above-described numerical range, it can be recognized that the partition wall 5 can be configured to block visible light and transmit infrared light even when the thickness (height dimension t) of the partition wall 5 is applied to the dimension shown in FIG. 1 .

[0100] When the simulation results shown in Fig. 8 for partition wall thicknesses of 2.0 µm, 5.0 µm, and 10.0 µm are examined, it can be seen that the partition wall is configured to block visible light and transmit infrared light, as shown in Fig. 8. When the partition wall height is 2.0 µm or more and 10.0 µm or less, it can be determined, or at least estimated, that the transmittance at a wavelength of 900 nm is approximately 60% or more and 95% or more. Furthermore, when the partition wall height is 2.0 µm or more and 10.0 µm or less, it can be determined, or at least estimated, that the wavelength at which the transmittance is 50% is 800 nm or more and 840 nm or less.

[0101] Furthermore, the transmittance at a wavelength of 840 nm exceeds 90% when the thickness of the partition wall is 1.0 μm, and can be specified or at least estimated to be 50% to 90% when the thickness of the partition wall is 2.0 μm to 10.0 μm.

[0102] 8, when the thickness of the partition walls is 1.0 μm, the transmittance at a wavelength of 450 nm is smaller than the transmittance at a wavelength of 700 nm. It can be determined, or at least estimated, that when the thickness of the partition walls is 2.0 μm or more and 10.0 μm or less, the transmittance at a wavelength of 450 nm and the transmittance at a wavelength of 700 nm are both nearly 0%. Thus, in the examples, it was found that the transmittance of blue light can be kept low, and therefore, it was found that the blue light that could not be fully wavelength-converted by the color conversion layers 6 a and 6 b shown in FIG. 1 can be efficiently removed.

[0103] 8, when the thickness of the partition walls is 1.0 μm, the transmittance at a wavelength of 700 nm is found to be 5% or more and 15% or less. It can be determined, or at least estimated, that the transmittance at a wavelength of 700 nm is nearly 0% when the thickness of the partition walls is 2.0 μm or more and 10.0 μm or less. This indicates that the transmittance of red light can be kept low.

[0104] The experimental results shown in FIG. 8 are expressed in specific numerical values: when the wavelength is 400 nm, the transmittance is 3.91% when the film thickness is 0.8 μm, 1.96% when the film thickness is 1.0 μm, 0.77% when the film thickness is 1.2 μm, 0.03% when the film thickness is 2.0 μm, 0.00% when the film thickness is 5.0 μm, and 0.00% when the film thickness is 10.0 μm. Furthermore, at a wavelength of 450 nm, the transmittance was 1.77% when the film thickness was 0.8 μm, 0.76% when the film thickness was 1.0 μm, 0.24% when the film thickness was 1.2 μm, 0.00% when the film thickness was 2.0 μm, 0.00% when the film thickness was 5.0 μm, and 0.00% when the film thickness was 10.0 μm. Furthermore, at a wavelength of 700 nm, the transmittance was 15.66% when the film thickness was 0.8 μm, 10.60% when the film thickness was 1.0 μm, 6.23% when the film thickness was 1.2 μm, 0.98% when the film thickness was 2.0 μm, 0.00% when the film thickness was 5.0 μm, and 0.00% when the film thickness was 10.0 μm. Furthermore, when the wavelength was 850 nm, the transmittance was 92.80% when the film thickness was 0.8 μm, 93.35% when the film thickness was 1.0 μm, 94.25% when the film thickness was 1.2 μm, 90.60% when the film thickness was 2.0 μm, 78.13% when the film thickness was 5.0 μm, and 61.04% when the film thickness was 10.0 μm. Furthermore, when the wavelength was 900 nm, the transmittance was 95.84% when the film thickness was 0.8 μm, 97.65% when the film thickness was 1.0 μm, 95.51% when the film thickness was 1.2 μm, 92.62% when the film thickness was 2.0 μm, 82.57% when the film thickness was 5.0 μm, and 68.18% when the film thickness was 10.0 μm.

[0105] <Measurement of refractive index> A partition wall made of the infrared-transmitting material of the above example was applied to a quartz substrate at a predetermined film thickness to prepare a measurement sample. A J. A. Woollam M-2000V was used as the refractive index measuring device. The refractive index measurement conditions were as follows: Partition wall film thickness: 1.4 μm Measurement wavelength: 400 to 1000 nm Incident angle: 65°, 70°, 75°

[0106] The experimental results are shown in FIG. 9 . As shown in FIG. 9 , it was found that the refractive index of the partition walls at wavelengths of 800 nm and 900 nm was 1.75 or higher. Thus, it was found that a high refractive index of the partition walls at a wavelength of 900 nm allows infrared light to efficiently pass through the partition walls. Furthermore, a high refractive index of the partition walls at a wavelength of 700 nm allows a portion of the red light wavelength-converted by the color conversion layers 6 a and 6 b to be reflected by the partition walls 5. The experimental results shown in FIG. 9 are shown in specific numerical values: the refractive index at a wavelength of 400 nm was 1.647, the refractive index at a wavelength of 700 nm was 1.769, the refractive index at a wavelength of 780 nm was 1.869, the refractive index at a wavelength of 800 nm was 1.845, the refractive index at a wavelength of 850 nm was 1.784, and the refractive index at a wavelength of 900 nm was 1.761.

[0107] From the above, by forming the partition walls from an infrared-transmitting material containing a material that blocks visible light and transmits infrared light, it becomes possible to read the alignment marks during exposure, and partition walls with excellent light-blocking properties can be directly formed on a substrate having light-emitting elements with high alignment accuracy. Furthermore, in forming the partition walls, by adjusting the optical density (OD) and height dimension so that the light-blocking characteristic value calculated by the product of the optical density (OD) and height dimension of the partition walls is 4 to 20, it becomes possible to improve the shape stability and light-emitting characteristics of the partition walls as well as the light-blocking properties of the partition walls.

[0108] This application is based on Japanese Patent Application No. 2024-016765, filed February 7, 2024, the contents of which are incorporated herein in their entirety.

Claims

1. A display device comprising: a light-emitting element provided on a substrate; a partition formed around the light-emitting element; and a color conversion layer on the light-emitting element that fills an internal space of the partition, wherein the partition is configured to block visible light and transmit infrared light.

2. The display device according to claim 1, characterized in that the light-blocking characteristic value (OD x t) expressed as the product of the optical density (OD) and the height dimension (t) of the partition wall is 4 or more and 20 or less.

3. The display device according to claim 1, wherein the height of the partition wall is 2 μm or more and 10 μm or less.

4. The display device according to claim 1, characterized in that, when the thickness of the partition wall is 1.0 μm, the transmittance at a wavelength of 900 nm is 90% or more, and the wavelength at which the transmittance becomes 50% is 760 nm or more and 810 nm or less.

5. The display device according to claim 1, wherein when the thickness of the partition wall is 1.0 μm, the transmittance at a wavelength of 450 nm is smaller than the transmittance at a wavelength of 700 nm.

6. The display device according to claim 1, wherein when the thickness of the partition wall is 1.0 μm, the transmittance at a wavelength of 700 nm is 5% or more and 15% or less.

7. The display device according to claim 1, wherein the refractive index of said partition walls for wavelengths of 800 nm and 900 nm is 1.75 or more.

8. The display device according to claim 1, wherein the color conversion layer contains quantum dots.

9. The display device according to claim 1, wherein the light-emitting element is a micro LED.

10. A method for manufacturing a display device according to claim 1, wherein the partition walls are formed directly on the substrate.

11. The method for manufacturing a display device according to claim 10, further comprising the steps of: forming a barrier rib material layer on the substrate; transmitting infrared light through the barrier rib material layer to read alignment marks; and forming the barrier ribs by exposure and development.

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