Method for manufacturing a display device

Abstract

To provide a display device in which LEDs are disposed, and a method for manufacturing the same.SOLUTION: This manufacturing method includes: transposing at least one inorganic light-emitting diode formed on a substrate onto a first carrier substrate; disposing a plurality of spacers composed so as to elastically deform on a substrate where pixels including a plurality of subpixels are arranged; and transposing at least one inorganic light-emitting diode on the first carrier substrate onto the substrate. This manufacturing method may further include removing the plurality of spacers.SELECTED DRAWING: Figure 7C

Description

[Technical Field]

[0001] One embodiment of the present invention relates to a display device and a method for manufacturing the same. For example, one embodiment of the present invention relates to a display device using an inorganic light-emitting diode as a light-emitting element and a method for manufacturing the same. [Background technology]

[0002] In recent years, development has progressed on display devices that arrange inorganic light-emitting diodes (LEDs) within a matrix of pixels. Because LEDs use inorganic compounds containing group 12, 13, and 15 elements such as gallium, indium, arsenic, zinc, and selenium as light-emitting elements, they exhibit higher reliability compared to organic light-emitting diodes (organic electroluminescent devices), and are capable of high brightness and high efficiency. For these reasons, LED displays are expected to be highly reliable displays capable of providing high-brightness, high-contrast images (see Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-163945 [Patent Document 2] Japanese Patent Publication No. 2021-5632 [Overview of the project] [Problems that the invention aims to solve]

[0004] One embodiment of the present invention aims to provide a display device having a novel structure and a method for manufacturing the same. Alternatively, one embodiment of the present invention aims to provide a display device in which LEDs are arranged and a method for manufacturing the same. Alternatively, one embodiment of the present invention aims to provide a method for manufacturing a display device in which LEDs are arranged at low cost. [Means for solving the problem]

[0005] One embodiment of the present invention is a method for manufacturing a display device. This manufacturing method includes transposing at least one inorganic light-emitting diode formed on a substrate onto a first carrier substrate, arranging a plurality of spacers configured to be elastically deformable on a substrate on which pixels including a plurality of subpixels are arranged, and transposing at least one inorganic light-emitting diode on the first carrier substrate onto a substrate.

[0006] One embodiment of the present invention is a method for manufacturing a display device. This manufacturing method includes transposing at least one inorganic light-emitting diode formed on a substrate onto a first carrier substrate, transposing at least one inorganic light-emitting diode on the first carrier substrate onto a second carrier substrate, arranging a plurality of spacers configured to be elastically deformable on a substrate on which pixels including a plurality of subpixels are arranged, and transposing at least one inorganic light-emitting diode on the second carrier substrate onto a substrate.

[0007] One embodiment of the present invention is a display device. This display device comprises a substrate on which pixels including a plurality of subpixels are arranged, and a plurality of spacers arranged on the substrate and configured to be elastically deformable. Each of the plurality of subpixels has a pixel electrode, a protective insulating film covering the edge of the pixel electrode, and an inorganic light-emitting diode located on the pixel electrode and electrically connected to the pixel electrode.

[0008] One embodiment of the present invention is a display device. This display device comprises a substrate on which pixels including a plurality of subpixels are arranged. Each of the plurality of subpixels has a pixel electrode, a protective insulating film covering the edges of the pixel electrode, and an inorganic light-emitting diode located on the pixel electrode and electrically connected to the pixel electrode. The protective insulating film has a recess on its upper surface. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic top view of a display device according to an embodiment of the present invention. [Figure 2A]Schematic top view of a pixel of a display device according to an embodiment of the present invention. [Figure 2B] Schematic top view of a pixel of a display device according to an embodiment of the present invention. [Figure 2C] Schematic top view of a pixel of a display device according to an embodiment of the present invention. [Figure 3A] Schematic end view of a sub-pixel of a display device according to an embodiment of the present invention. [Figure 3B] Schematic end view of a sub-pixel of a display device according to an embodiment of the present invention. [Figure 4A] Schematic end view showing a method of manufacturing a display device according to an embodiment of the present invention. [Figure 4B] Schematic end view showing a method of manufacturing a display device according to an embodiment of the present invention. [Figure 4C] Schematic end view showing a method of manufacturing a display device according to an embodiment of the present invention. [Figure 5A] Schematic end view showing a method of manufacturing a display device according to an embodiment of the present invention. [Figure 5B] Schematic end view showing a method of manufacturing a display device according to an embodiment of the present invention. [Figure 6A] Schematic end view showing a method of manufacturing a display device according to an embodiment of the present invention. [Figure 6B] Schematic end view showing a method of manufacturing a display device according to an embodiment of the present invention. [Figure 7A] Schematic end view showing a method of manufacturing a display device according to an embodiment of the present invention. [Figure 7B] Schematic end view showing a method of manufacturing a display device according to an embodiment of the present invention. [Figure 7C] Schematic end view showing a method of manufacturing a display device according to an embodiment of the present invention. [Figure 8] Schematic top view showing a method of manufacturing a display device according to an embodiment of the present invention. [Figure 9A] Schematic perspective view of a spacer used in a method of manufacturing a display device according to an embodiment of the present invention. [Figure 9B] Schematic perspective view of a spacer used in a method of manufacturing a display device according to an embodiment of the present invention. [Figure 9C] Schematic perspective view of a spacer used in a method for manufacturing a display device according to an embodiment of the present invention. [Figure 10A] Schematic top view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 10B] Schematic top view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 11] Schematic top view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 12A] Schematic end view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 12B] Schematic end view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 12C] Schematic end view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 13A] Schematic end view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 13B] Schematic end view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 14A] Schematic end view of a part of a pixel of a display device according to an embodiment of the present invention. [Figure 14B] Schematic top view of a part of a pixel of a display device according to an embodiment of the present invention. [Figure 15A] Schematic end view showing a method for manufacturing a conventional display device. [Figure 15B] Schematic end view showing a method for manufacturing a conventional display device. [Figure 15C] Schematic end view showing a method for manufacturing a conventional display device. [Figure 16A] Schematic end view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 16B] Schematic end view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 16C] Schematic end view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 17A] Schematic end view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 17B]A schematic end view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 17C] A schematic end view showing a method for manufacturing a display device according to an embodiment of the present invention. [Figure 18] A schematic end view showing a method for manufacturing a display device according to an embodiment of the present invention. [Modes for carrying out the invention]

[0010] The embodiments of the present invention will be described below with reference to the drawings and other materials. However, the present invention can be implemented in various forms without departing from its spirit, and is not to be interpreted as being limited to the embodiments described below.

[0011] While drawings may schematically represent the width, thickness, shape, etc., of each part compared to the actual embodiment in order to clarify the explanation, these are merely examples and do not limit the interpretation of the present invention. In this specification and each figure, elements having the same function as those described in previously shown figures may be denoted by the same reference numeral to omit redundant explanations. This reference numeral is used to represent multiple identical or similar structures collectively, and when representing them individually, a hyphen and a natural number are added after the reference numeral. Furthermore, when indicating a part of a single structure, a lowercase alphabet letter may be added after the reference numeral.

[0012] In this specification and claims, when describing a manner in which one structure is placed on top of another structure, unless otherwise specified, the term "on top of" includes both cases: when one structure is placed directly on top of another structure so as to be in contact with it, and when another structure is placed above another structure via yet another structure.

[0013] In this specification and claims, the expression "a structure is exposed from another structure" means a portion of a structure that is not covered by another structure, and this portion that is not covered by another structure may also be covered by yet another structure. Furthermore, the expression also includes a portion of a structure that is not in contact with another structure.

[0014] The following describes a display device and a method for manufacturing the same, which are embodiments of the present invention. This display device is an LED display, and as described below, multiple LEDs are mounted on each pixel.

[0015] 1. Overall structure of the display device Figure 1 shows a schematic top view of the display device 100. The display device 100 includes a substrate 102 on which various patterned insulators, conductors, and semiconductor thin films are laminated, thereby forming multiple pixels 104, drive circuits (scan line drive circuit 106, signal line drive circuit 108), and various wirings (not shown) that electrically connect them. The multiple pixels 104 are arranged in a matrix. A single area surrounding all the pixels 104 is the display area, and the area outside the display area is called the peripheral area or frame area. Multiple wirings extend from the drive circuits to one side of the substrate 102, becoming exposed at the edge of the substrate 102 and forming multiple terminals (not shown). The multiple terminals are electrically connected to a connector 110 such as a flexible printed circuit (FPC) board, thereby supplying power and various signals from an external circuit (not shown) to the drive circuits via the connector 110. Alternatively, instead of the signal line drive circuit 108, or together with the signal line drive circuit 108, a drive IC 112 comprising an integrated circuit formed on a semiconductor substrate may be mounted on the substrate 102 or connector 110.

[0016] Each of the multiple pixels 104 is connected to a scan line drive circuit 106 and a signal line drive circuit 108. The scan line drive circuit 106 and the signal line drive circuit 108 generate signals for displaying an image (video signals, gate signals, initialization signals, etc.) based on signals supplied from an external circuit, and supply these signals along with power to the multiple pixels 104. As a result, the multiple pixels 104 are controlled, and an image can be displayed on the display area.

[0017] 2. Pixel structure A schematic top view of a single pixel 104 is shown in Figure 2A. As shown in Figure 2A, each pixel 104 has multiple subpixels 103. Typically, each pixel 104 is composed of three subpixels 103, each providing the primary colors red, green, and blue, respectively. An LED 120 is placed in each subpixel 103. For example, three LEDs 120-1, 120-2, and 120-3, each emitting red, green, and blue light, can be placed in the three subpixels 103, respectively. In this specification, a subpixel 103 is the smallest unit that contains one LED 120 and provides color information. A pixel 104 includes all the subpixels 103 that emit different colors and represents a rectangular region surrounding the smallest subpixel 103.

[0018] The arrangement of sub-pixels 103 within each pixel 104 is arbitrary. For example, as shown in Figures 2A and 2C, multiple LEDs 120 may be placed in one row and one LED 120 in another row. Alternatively, all LEDs 120 may be placed in a single row (Figure 2B). The size (area) and height of the multiple LEDs 120 provided in each pixel 104 can also be set arbitrarily. That is, in each pixel 104, all LEDs 120 may have the same size and height, or at least one LED 120 may have a different size or height from at least one other LED. The area of ​​the LED 120 is, for example, 1.0 × 10⁻⁶. 2 μm 2 The above 1.0 × 10 4 μm 2 Below, 2.0 × 10 2 μm 2 The above 5.0 × 10 3 μm 2 The following, or 1.0 × 103 μm 2 2.5×10 or more 3 μm 2 It may be selected from the following. For example, a so-called micro-LED having a size of about 15 μm × 30 μm can be used.

[0019] Each sub-pixel 103 is provided with a pixel circuit for controlling the LED 120 by operating according to a signal supplied from a drive circuit. The configuration of the pixel circuit may be arbitrarily determined, and the pixel circuit is formed by appropriately combining one or more transistors and one or more capacitive elements, etc.

[0020] An example of the sub-pixel 103 is shown in the schematic end view of FIG. 3A. In FIG. 3A, only one transistor 140 is shown, but as described above, each pixel circuit may include a plurality of transistors, and may further include one or more capacitive elements. The pixel circuit including the transistor 140 is provided directly on the substrate 102 or via an undercoat 114 having an arbitrary configuration. The transistor 140 shown in FIG. 3A includes a first gate electrode 142, a first gate insulating film 144 on the first gate electrode 142, a semiconductor film 146 on the first gate insulating film 144, a second gate insulating film 148 on the semiconductor film 146, a second gate electrode 150 on the second gate insulating film 148, an interlayer film 152 covering the second gate electrode 150 and the second gate insulating film 148, a first terminal 154 and a second terminal 156 that are electrically connected to the semiconductor film 146 through an opening provided in the second gate insulating film 148 and the interlayer film 152, etc. The transistor 140 has two gate electrodes sandwiching the semiconductor film 146, but the configuration of the transistor 140 may also be arbitrarily determined, for example, it may be a bottom gate type transistor or a top gate type transistor.

[0021] The sub-pixel 103 may further include a planarization film 158 on the first terminal 154 and the second terminal 156, a pixel electrode 160 electrically connected to the second terminal 156 through an opening in the planarization film 158, a common electrode 162 provided on the planarization film 158 to which a constant potential is supplied, and a protective insulating film 164 covering the ends of the pixel electrode 160 and the common electrode 162.

[0022] These structures can be formed by appropriately applying known materials and film deposition methods. For example, the substrate 102 can be a glass substrate, a quartz substrate, a substrate containing metals such as stainless steel or aluminum, or a substrate containing polymer materials such as polyimide, polycarbonate, or polyester. The substrate 102 may also be flexible. The undercoat 114, the first gate insulating film 144, the second gate insulating film 148, the interlayer film 152, the protective insulating film 164, etc., may each be composed of one or more layers containing silicon-containing inorganic compounds such as silicon oxide or silicon nitride, using chemical vapor deposition (CVD) or sputtering methods, etc. Alternatively, these films may be formed with one or more layers containing inorganic compounds such as aluminum oxide or aluminum nitride. The first gate electrode 142, the second gate electrode 150, the first terminal 154, the second terminal 156, the pixel electrode 160, and the common electrode 162 may be constructed using methods such as CVD or sputtering, and may contain metals such as tantalum, molybdenum, tungsten, chromium, hafnium, titanium, aluminum, and copper. The planarization film 158 may be formed using polymer materials such as polyimide, polyamide, polysiloxane, or acrylic resin. The interlayer film 152 may also be formed using polymer materials. The semiconductor film 146 is also formed by applying CVD or sputtering. The semiconductor film 146 is constructed to contain silicon or an oxide semiconductor such as zinc oxide, indium gallium oxide, or indium gallium oxide. The configuration including the substrate 102 to the protective insulating film 164 is also called an array substrate or a backplane substrate (indicated as BP in the figure). In the following description, the configuration including the substrate 102 to the protective insulating film 164 will be referred to as a backplane substrate.

[0023] An LED 120 is provided on the backplane substrate. The LED 120 may include a laminate comprising, for example, a p-type cladding layer 126, an active layer (light-emitting layer) 128, and an n-type cladding layer 130, with an anode 122 and a cathode 124 electrically connected to the p-type cladding layer 126 and the n-type cladding layer 130, respectively. Bumps 166 are formed on the common electrode 162 and the pixel electrode 160 as a conductive adhesive, and the anode 122 and cathode 124 of the LED 120 are electrically connected to the common electrode 162 and the pixel electrode 160, respectively, via the bumps 166. The bumps 166 are, for example, an alloy containing a metal such as silver or tin. Although not shown, the LED 120 may also have a buffer layer on top of the n-type cladding layer 130 (on the side opposite to the p-type cladding layer 126).

[0024] The p-type cladding layer 126, the active layer 128, and the n-type cladding layer 130 are each composed of one or more functional layers containing an inorganic semiconductor. Examples of inorganic semiconductors include compounds containing group 13 and group 15 elements. More specifically, examples include compound semiconductors containing aluminum, gallium, and / or indium, as well as nitrogen, phosphorus, and / or arsenic. Typically, gallium-based materials are used. Examples include gallium nitride-based materials such as gallium nitride (GaN), aluminum gallium nitride (AlGaN), and indium gallium nitride (InGaN), and gallium phosphide-based materials such as gallium phosphide (GaP) and aluminum indium gallium phosphide (AlGaInP). Each functional layer may further contain dopants. Examples of dopants include elements such as silicon, germanium, magnesium, zinc, cadmium, and beryllium. By adding these elements, it becomes possible to control the valence electrons of each functional layer, not only maintaining intrinsicity (i-type) but also controlling the band gap and imparting p-type or n-type conductivity. The active layer 128 may be a single layer or may have a quantum well structure. A quantum well structure is a structure in which multiple thin films with different band gaps and thicknesses of about 1 to 5 nm are alternately stacked. Examples include alternating stacks of InGaN and GaN, alternating stacks of GaInAsP and InP, and alternating stacks of AlInAs and InGaAs.

[0025] The LED 120 shown in Figure 3A has an anode 122 and a cathode 124 on one side, but the LED 120 does not necessarily have to have such a structure. For example, as shown in Figure 3B, an LED 120 may be used that has a structure in which a p-type cladding layer 126, an active layer 128, and an n-type cladding layer 130 are sandwiched between the anode 122 and the cathode 124. In this case, a constant potential is supplied to the anode 122 by wiring (not shown).

[0026] 3. Method for manufacturing a display device The display device 100 is manufactured by arranging LEDs 120 on a backplane substrate and electrically connecting the LEDs 120 to the pixel electrodes 160 and the common electrode 162. A detailed explanation will be given below using Figures 4A to 13B. These figures may not show the detailed configuration of the LEDs 120 or the backplane substrate. Note that the backplane substrate, including the substrate 102 on which the pixel circuit is provided, can be formed using known materials and methods, so a detailed explanation will be omitted.

[0027] (1) Making an LED Although a detailed explanation is omitted as LED120 can be fabricated by known methods, for example, as shown in Figure 4A, a compound semiconductor film is epitaxially grown on a substrate 170 such as a single-crystal silicon substrate or a sapphire substrate to form an n-type cladding layer 130, an active layer 128, and a p-type cladding layer 126. Subsequently, by forming a cathode 124 and an anode 122 on the n-type cladding layer 130 and the p-type cladding layer 126, respectively, multiple LEDs 120 can be formed on a single substrate 170.

[0028] (2) Transfer of LEDs to carrier substrate A. First transposition After the LED 120 is fabricated, the LED 120 on the substrate 170 is transferred to the backplane substrate. Specifically, first, a first carrier substrate 172 is bonded to the substrate 170 (Figure 4B). The first carrier substrate 172 is also called a dicing film or dicing sheet and may include a base layer 176 and an adhesive layer 174. The base layer 176 may be a substrate with low flexibility, such as a quartz substrate, a glass substrate, or a metal substrate such as a stainless steel substrate, or it may be a flexible substrate (film) containing polyester such as polyethylene terephthalate or polyethylene naphthalate, nylon, polycarbonate, polyolefin such as polyethylene, polypropylene, or polystyrene, cycloolefin polymers containing polynorbornene as a basic skeleton, or ring-opening metathesis polymers of norbornene. On the other hand, the adhesive layer 174 may include polyolefin elastomers, polystyrene elastomers, vinyl chloride elastomers, polyurethane elastomers, polyester elastomers, polyacrylonitrile elastomers, polyamide elastomers, and the like. More specifically, the adhesive layer 174 may include styrene-butadiene rubber, isobutylene-isoprene rubber, ethylene-propylene-diene rubber, nitrile rubber, butadiene rubber, isoprene rubber, as well as silicone rubber and natural rubber. The adhesive layer 174 may also be a water-soluble adhesive.

[0029] Subsequently, light having a wavelength that penetrates the substrate 170 and is absorbed by the n-type cladding layer 130 is irradiated from the substrate 170 side (Figure 4B). For example, a laser with a wavelength selected from the range of 200 nm to 370 nm is irradiated. As the laser, a pulsed high-density KrF excimer laser, a YAG laser doped with Nd ions, etc., can be used. When the n-type cladding layer 130 absorbs light and generates heat, a portion of it decomposes and vaporizes, and as a result, the adhesion between the n-type cladding layer 130 and the substrate 170 decreases. Therefore, the substrate 170 can be removed while the LED 120 remains on the first carrier substrate 172 (Figure 4C).

[0030] When the LEDs 120 are transferred from the substrate 170 to the first carrier substrate 172, the arrangement of the LEDs 120 on the substrate 170 is reproduced directly on the first carrier substrate 172. This arrangement may differ from the arrangement of the LEDs 120 on the backplane substrate. More specifically, the distance between adjacent LEDs 120 (or the pitch of the LEDs 120) on the backplane substrate may differ from that on the substrate 170. Therefore, the first carrier substrate 172 may be stretched as appropriate to adjust the distance between adjacent LEDs 120 to accommodate the required arrangement of LEDs 120 on the backplane substrate.

[0031] (i) Second transposition If the anode 122 and cathode 124 of the LED 120 are located on the same side (see Figure 3A), when the LED 120 is transferred from the base material 170 to the first carrier substrate 172, the anode 122 and cathode 124 will be located on the first carrier substrate 172 side. Therefore, if the LED 120 transferred to the first carrier substrate 172 is directly transferred to the backplane substrate, the LED 120 cannot be electrically connected to the backplane substrate.

[0032] Therefore, in this case, a second transposition is performed. Specifically, as shown in Figure 5A, a second carrier substrate 178, which has a base layer 180 and an adhesive layer 182, is attached to the first carrier substrate 172 such that the adhesive layer 182 and the LED 120 are sandwiched between the first carrier substrate 172 and the second carrier substrate 178. Then, the first carrier substrate 172 is removed so that the LED 120 remains on the second carrier substrate 178, thereby transposing the LED 120 onto the second carrier substrate 178 (Figure 5B).

[0033] The base layer 180 may include a material usable in the base layer 176 of the first carrier substrate 172. The adhesive layer 182 may also include a material usable in the adhesive layer 174 of the first carrier substrate 172, but it is preferable to select the material of the adhesive layer 182 to adhere more strongly to the LED 120 than the adhesive layer 174 in order to selectively leave the LED 120 on the second carrier substrate 178. Alternatively, the adhesive strength of the adhesive layer 174 may be reduced by heating the anode 122 and cathode 124 by irradiating them with light (for example, light or laser having a wavelength in the range of 400 nm to 3000 nm) from the first carrier substrate 172 or the second carrier substrate 178 side, thereby decomposing a portion of the adhesive layer 174 in contact with them. Alternatively, the transposition may be performed by using a water-soluble adhesive for the adhesive layer 174 and reducing its adhesive strength with water. The distance between the LEDs 120 may also be adjusted by extending the second carrier board 178.

[0034] Typically, multiple LEDs 120 with the same structure are formed on a single substrate 170. That is, LEDs 120 that emit light of the same color are formed on a single substrate 170. Therefore, the LEDs 120 are transferred from three substrates 170, each having red, green, and blue LEDs 120-1 to 120-3, to three first carrier substrates 172 (Figure 6A). After that, the LEDs 120 on the three first carrier substrates 172 may be transferred to a single second carrier substrate 178, and the red, green, and blue LEDs 120-1 to 120-3 may be transferred onto the second carrier substrate 178 (Figure 6B).

[0035] (3) Arrangement of spacers Next, bumps 166 are formed on the pixel electrode 160 and the common electrode 162. The bumps 166 are formed on the portions of the pixel electrode 160 and the common electrode 162 that are exposed from the protective insulating film 164. After that, the LED 120 that has been moved onto the second carrier substrate 178 is moved onto the backplane substrate. At this time, in order to ensure that the LED 120 is moved more reliably, a plurality of spacers 184 are placed on the backplane substrate (Figure 7A). That is, a plurality of spacers 184 that are in contact with the protective insulating film 164 are placed on the protective insulating film 164 (see Figure 3A). The spacers 184 are configured to be elastically deformable. Therefore, the spacers 184 include elastic materials such as styrene-butadiene rubber, isobutylene-isoprene rubber, ethylene-propylene-diene rubber, nitrile rubber, butadiene rubber, isoprene rubber, silicone rubber, and natural rubber.

[0036] The spacer 184 should be configured to transmit or absorb visible light so as to reflect as little of the light emitted from the LED 120 as possible. In the latter case, the surface of the spacer 184 containing the material described above should be coated with a black resin or a low-reflectivity metal film such as chromium.

[0037] One preferred shape for the spacer 184 is spherical. In this case, the shape of the spacer 184 may be adjusted so that the average circularity is 80 or higher. By forming the spacer 184 to have a spherical shape, the spacer 184 can have a nearly constant height on the backplane substrate, regardless of its rotation. Here, circularity is the value obtained by analyzing images obtained by microscopic observation of the spacer 184, determining the circularity for multiple spacers 184, and averaging them. As for circularity, for example, the value obtained by dividing the perimeter of the projection surface of each spacer 184 in the microscopic image by the perimeter of a circle with an area equal to the area of ​​the projection surface can be used. The diameter of the spacer 184 is greater than the sum of the heights of the transposed LED 120 and the heights of the bumps 166, and the difference is preferably between 0.5 μm and 5 μm. Specifically, the diameter of the spacer 184 should be adjusted within the range of 3 μm to 20 μm.

[0038] The spherical spacers 184 may be directly scattered as powdered spacers 184, or a dispersion of spacers 184 in a liquid such as water or an alcohol-based solvent such as ethanol or isopropyl alcohol may be dropped, scattered, or coated onto the backplane substrate. The spacers 184 may be randomly arranged on the backplane substrate as schematically shown in Figure 8. Alternatively, they may be scattered so that a portion of them is located within the display area or pixel 104. The spacers 184 should be arranged so as not to overlap with the pixel electrodes 160 or the common electrode 162. If the spacers 184 overlap with the pixel electrodes 160 or the common electrode 162, the backplane substrate may be vibrated, for example, to move the spacers 184 to a position away from the pixel electrodes 160 or the common electrode 162.

[0039] Another preferred shape for the spacer 184 is a columnar shape. For example, as shown in Figures 9A to 9C, the spacer 184 may have a cylindrical or polygonal prism shape, and may be configured so that its cross-sectional area (area on the parallel surface of the substrate 102) increases as it approaches the substrate 102. Although not shown, the spacer 184 may have an elliptical columnar shape. For a columnar spacer 184, it is preferable that its height is greater than the sum of the heights of the LED 120 and the bump 166, and that the difference is between 0.5 μm and 5 μm. Specifically, the height of the spacer 184 should be adjusted within the range of 3 μm to 20 μm.

[0040] When providing columnar spacers 184, one preferred method for manufacturing the spacers 184 is photolithography. This is because, unlike spherical spacers 184, the height of columnar spacers 184 varies depending on the angle at which they are stretched on the backplane substrate (or protective insulating film 164). By forming the spacers 184 using photolithography, it is possible to form spacers 184 with a constant height. Specifically, columnar spacers 184 can be formed by forming a photoresist on the protective insulating film 164, and then performing exposure and development through a photomask. Therefore, by appropriately designing the photoresist, the spacers 184 can be accurately positioned and fixed on the protective insulating film 164. Furthermore, the spacers 184 can be arranged at a constant pitch. For example, as shown in Figure 10A, spacers 184 may be selectively provided outside the display area so as to surround all pixels 104. Alternatively, multiple spacers 184 may be arranged so as to surround each pixel 104 (Figure 10B). Alternatively, as shown in Figure 11, one or more spacers 184 may be selectively placed in each pixel 104.

[0041] Another preferred method for fabricating columnar spacers 184 is the transfer method. In this method, a spacer transfer substrate 186, in which a base layer 192, a photothermal conversion layer 190, and a transfer layer 188 are laminated, is first placed on a backplane substrate (Figure 12A). The base layer 192 includes, for example, glass or quartz. The photothermal conversion layer 190 is a layer that generates heat when irradiated with light, and can be, for example, a film in which carbon black is dispersed in a polymer material such as polyester or polycarbonate. The transfer layer 188 is composed of the materials included in the spacer 184 as described above. Then, light, such as a YAG laser, Nd laser, or CO2 laser, is irradiated onto the region where the spacer 184 will be formed (Figure 12B). This selectively heats the photothermal conversion layer 190 in the region irradiated with the laser. This heat melts the transfer layer 188 and transfers it onto the backplane substrate, providing the spacer 184. By using the transfer method, it is also possible to arrange the spacers 184 at a constant pitch.

[0042] (4) Transfer of LEDs to the backplane substrate After positioning the spacer 184, the backplane substrate and the second carrier substrate 178 are bonded together (Figures 7B and 7C). Specifically, the substrate 102 and the second carrier substrate 178 are pressed together so that the pixels on the substrate 102 and the LEDs 120 on the second carrier substrate 178 are sandwiched between the substrate 102 and the second carrier substrate 178. At this time, the substrate 102 and the second carrier substrate 178 are sandwiched between a pair of stages (not shown) and pressure is applied. If the base layer 180 of the substrate 102 and / or the second carrier substrate 178 is flexible, an auxiliary substrate (not shown) with sufficient rigidity may be placed under the substrate 102 and / or on the second carrier substrate 178, respectively, before bonding. During bonding, the backplane substrate and the second carrier substrate 178 are aligned so that the anode 122 and cathode 124 of the LED 120 are electrically connected to the common electrode 162 and the pixel electrode 160, respectively.

[0043] Furthermore, during bonding, pressure is applied to the substrate 102 and the second carrier substrate 178 so that the elastically deformable spacer 184 deforms (Figure 7C). Therefore, for example, if a spherical spacer 184 is used, the spacer 184 deforms into an ellipsoid shape during bonding. In addition, to ensure that the anode 122 and cathode 124 are reliably electrically connected to the common electrode 162 and pixel electrode 160, respectively, light (for example, light or laser with a wavelength in the range of 400 nm to 3000 nm) is irradiated from the second carrier substrate 178 side to heat the anode 122 and cathode 124, and this heat may melt part or all of the bump 166. As the bump 166 solidifies again, the anode 122 and common electrode 162, and the cathode 124 and pixel electrode 160 are firmly fixed.

[0044] Subsequently, the display device 100 can be manufactured by removing the second carrier substrate 178 and selectively leaving the LED 120 on the backplane substrate (Figure 13A). The spacer 184 may also be left on the backplane substrate. In this case, the display device 100 includes a spacer 184 on the protective insulating film 164 that is in contact with the protective insulating film 164.

[0045] When spherical spacers 184 are scattered and arranged on a backplane substrate, the spacers 184 may be removed by a cleaning process using water or an alcohol-based organic solvent (Figure 13B). In this case, the protective insulating film 164 may deform due to the pressure applied to the spacers 184 during bonding. Therefore, as shown in the schematic end view of the region enclosed by the dotted circle in Figure 3 (Figure 14A) and the corresponding schematic top view (Figure 14B), the protective insulating film 164 may have a recess 164a caused by the spacers 184. The planar shape of the recess 164a is, for example, a circle.

[0046] When transposing the LED 120, it is necessary to reliably electrically connect the anode 122 to the common electrode 162, and the cathode 124 to the pixel electrode 160. However, there may be in-plane variations in the thickness of the substrate 102 included in the backplane substrate, and it is not always easy to form the bump 166 at a constant height. Furthermore, there may be in-plane variations in the thickness of the adhesive layer 182, and the amount of sinking of the LED 120 into the adhesive layer 182 is not constant. Also, the LED 120 may tilt during the first and / or second transposition. Furthermore, as mentioned above, when placing LEDs 120 with different emission colors on the second carrier substrate 178, the height of the LED 120 may differ depending on the emission color (see Figure 6B). In addition, the stages used to apply pressure during bonding may not always have high flatness, and it is not easy to apply pressure to the second carrier substrate 178 and the backplane substrate while the pair of stages are perfectly parallel.

[0047] Therefore, for example, if the heights of the LEDs 120 differ as shown in Figure 15A, some of the LEDs 120 may not be able to make contact with the bumps 166 during bonding, and may not be able to electrically connect with the pixel electrodes 160 or the common electrode 162 (Figure 15B). Conversely, the distance between some of the LEDs 120 and the pixel electrodes 160 or the common electrode 162 may become too small, and as a result, the conductive bumps 166 may flow between the anode 122 and the cathode 124, causing a short circuit between the anode 122 and the cathode 124 (Figure 15C).

[0048] To avoid the problems described above, it is necessary to maintain an appropriate distance between the backplane substrate and the second carrier substrate 178 while applying sufficient pressure during bonding. In the method for manufacturing a display device according to one embodiment of the present invention, as described above, an elastically deformable spacer 184 is provided between the backplane substrate and the second carrier substrate 178 during bonding. Therefore, even if the backplane substrate and the second carrier substrate 178 are pressed together with great pressure to ensure that all LEDs 120 are electrically connected to the pixel electrode 160 and the common electrode 162, the distance between the backplane substrate and the second carrier substrate 178 can be maintained appropriately. Because great pressure can be used, even if the substrate 102, the first carrier substrate 172, and / or the second carrier substrate 178 are warped, the warping can be corrected. Furthermore, even if the parallelism and flatness of the stage are low, bonding is possible while absorbing the low parallelism and flatness. Furthermore, even when using a large-area first carrier substrate 172 or second carrier substrate 178, a large amount of pressure can be applied across the entire substrate, making it possible to transfer a large number of LEDs 120 in a single transfer. The above-mentioned features contribute to improved manufacturing yield and reduced manufacturing costs, and by applying embodiments of the present invention, it becomes possible to provide LED displays at a low cost.

[0049] 4. Modified Examples of Methods for Manufacturing Display Devices (1) Variation 1 As mentioned above, the height (thickness) of the LED 120 may vary depending on the color of light emitted (see Figure 6B). Therefore, when mounting multiple LEDs 120 of different heights on the display device 100, spacers 184 of different sizes should be used in the repositioning process according to the height of the LEDs 120.

[0050] Specifically, when the height increases in the order of LED120-1, LED120-2, and LED120-3, as shown in Figures 16A and 16B, a backplane substrate with spacer 184-1 placed on it and a second carrier substrate 178-1 on which the LED with the smallest height, LED120-1, is placed are prepared, and LED120-1 and spacer 184-1 are bonded together so that they are sandwiched between the second carrier substrate 178-1 and the backplane substrate. Because spacer 184-1 deforms due to the pressure applied to the second carrier substrate 178-1 and the backplane substrate during bonding, a large pressure can be applied while appropriately maintaining the distance between the second carrier substrate 178-1 and the backplane substrate. As a result, LED120-1 can be securely fixed to the pixel electrode 160 and the common electrode 162. After that, the second carrier substrate 178-1 and spacer 184-1 are removed while leaving LED120-1 on the backplane substrate.

[0051] Next, the second carrier substrate 178-2, on which LED120-2 is placed, is bonded to the backplane substrate (Figures 16C and 17A). At this time, a spacer 184-2 larger than spacer 184-1 is used. Since LED120-1 is shorter in height than LED120-2, even when pressure is applied during bonding, the second carrier substrate 178-2 and LED120-1 do not interfere with each other, and spacer 184-2 deforms instead. As a result, LED120-2 is securely fixed to the pixel electrode 160 and the common electrode 162.

[0052] Next, the second carrier substrate 178-3, on which LED 120-3 has been transposed, is similarly bonded to the backplane substrate (Figures 17B and 17C). At this time, since spacer 184-3 is larger than spacer 184-2, the second carrier substrate 178-2 and LEDs 120-1 and 102-2 do not interfere with each other, and spacer 184-3 deforms due to the pressure during bonding. As a result, LED 120-3 is securely fixed to the pixel electrode 160 and the common electrode 162. After that, spacer 184-3 and the second carrier substrate 178-3 are removed (Figure 18).

[0053] In this way, by performing the transposition process multiple times in order of increasing height of the LEDs, and increasing the size of the spacer 184 each time the transposition process progresses, multiple LEDs 120 with different heights can be arranged on a single backplane substrate. The preferred size of the spacer 184 is as described above. Therefore, this process makes it possible to arrange four or more types of LEDs 120 with different heights on the backplane substrate.

[0054] (2) Modification example 2 As described above, the LED 120 may have a structure in which the cathode 124 and anode 122 are sandwiched between a p-type cladding layer 126, an active layer 128, and an n-type cladding layer 130 (see Figure 3B). In this case, even after the first transposition, one electrode is located on the opposite side from the first carrier substrate 172, so a second transposition is not necessary. Therefore, the LED 120 that has been transposed onto the first carrier substrate 172 can be transposed onto the backplane substrate without going through the second carrier substrate 178. A detailed explanation is omitted, but similar to the manufacturing method described above, a plurality of spacers 184 are placed on the backplane substrate, and the first carrier substrate 172 on which the LED 120 has been transposed is bonded on top of them. The bonding process is carried out so that the pixel 104 and LED 120 are sandwiched between the backplane substrate and the first carrier substrate 172, the multiple spacers 184 are deformed, and the cathode 124 and anode 122 of the LED 120 are electrically connected to the common electrode 162 of the pixel electrode 160, respectively. Subsequently, pressure is applied to the first carrier substrate 172 and substrate 102, pressing them together. If the base layer 176 of the first carrier substrate 172 does not have sufficient rigidity, an auxiliary substrate (not shown) may be provided on the first carrier substrate 172. The subsequent steps are the same as the manufacturing method described above, so the explanation is omitted.

[0055] In this modified example, since the LED 120 is transposed after the multiple spacers 184 are placed, it is possible to apply a sufficiently large pressure between the first carrier substrate 172 and the substrate 102 while appropriately maintaining the distance between the backplane substrate and the first carrier substrate 172. Therefore, the same effects as the manufacturing method described above can be achieved.

[0056] The embodiments described above as embodiments of the present invention can be combined and implemented as appropriate, insofar as they do not contradict each other. Furthermore, devices based on the display devices of each embodiment, in which a person skilled in the art has added, deleted, or modified components, or added, omitted, or modified processes, are also included within the scope of the present invention, as long as they retain the essence of the present invention.

[0057] Any effects or benefits other than those brought about by the embodiments described above, if they are clear from the description herein or easily predictable to a person skilled in the art, are naturally considered to be brought about by the present invention. [Explanation of symbols]

[0058] 100: Display device, 102: Substrate, 103: Sub-pixel, 104: Pixel, 106: Scan line driving circuit, 108: Signal line driving circuit, 110: Connector, 112: Driving IC, 114: Undercoat, 122: Anode, 124: Cathode, 126: p-type cladding layer, 128: Active layer, 130: n-type cladding layer, 140: Transistor, 142: First gate electrode, 144: First gate insulating film, 146: Semiconductor film, 148: Second gate insulating film, 150: Second gate electrode, 152: Interlayer film, 154: First terminal, 156: Second terminal, 158: Planarization film, 160: Pixel electrode, 162: Common electrode, 164: Protective insulating film, 164a: Recess, 166: Bump, 170: Substrate, 172: First carrier substrate, 174: Adhesive layer, 176: Base layer, 178: Second carrier substrate, 178-1: Second carrier substrate, 178-2: Second carrier substrate, 178-3: Second carrier substrate, 180: Base layer, 182: Adhesive layer, 184: Spacer, 184-1: Spacer, 184-2: Spacer, 184-3: Spacer, 186: Spacer transfer substrate, 188: Transfer layer, 190: Photothermal conversion layer, 192: Base layer

Claims

1. Transferring at least one inorganic light-emitting diode formed on a substrate onto a first carrier substrate, Placing multiple spacers configured to be elastically deformable on a substrate on which pixels including multiple subpixels are arranged, A method for manufacturing a display device, comprising transposing the at least one inorganic light-emitting diode on the first carrier substrate onto the substrate.

2. Transferring at least one inorganic light-emitting diode formed on a substrate onto a first carrier substrate, Transposing the at least one inorganic light-emitting diode on the first carrier substrate onto the second carrier substrate, Placing multiple spacers configured to be elastically deformable on a substrate on which pixels including multiple subpixels are arranged, A method for manufacturing a display device, comprising transposing the at least one inorganic light-emitting diode on the second carrier substrate onto the substrate.

3. The transposition of the at least one inorganic light-emitting diode on the first carrier substrate onto the substrate is The first carrier substrate and the substrate are pressed together such that the pixel and the at least one inorganic light-emitting diode are sandwiched between the first carrier substrate and the substrate, at least one of the plurality of spacers is deformed, and the at least one inorganic light-emitting diode is electrically connected to one of the plurality of sub-pixels, and The manufacturing method according to claim 1, which is carried out by removing the first carrier substrate and leaving the at least one inorganic light-emitting diode on the substrate.

4. The transposition of the at least one inorganic light-emitting diode on the second carrier substrate onto the substrate is The second carrier substrate and the substrate are pressed together such that the pixel and the at least one inorganic light-emitting diode are sandwiched between the second carrier substrate and the substrate, at least one of the plurality of spacers is deformed, and the at least one inorganic light-emitting diode is electrically connected to one of the plurality of subpixels, and The manufacturing method according to claim 2, comprising removing the second carrier substrate and leaving the at least one inorganic light-emitting diode on the substrate.

5. The manufacturing method according to claim 1 or 2, further comprising removing the plurality of spacers.

6. The manufacturing method according to claim 1 or 2, wherein the arrangement of the plurality of spacers is performed by scattering the plurality of spacers on the substrate.

7. The manufacturing method according to claim 1 or 2, wherein the plurality of spacers are formed by photolithography or a transfer method.

8. The manufacturing method according to claim 1 or 2, wherein each of the plurality of spacers has a spherical shape.

9. The manufacturing method according to claim 1 or 2, wherein each of the plurality of spacers has a columnar shape.

10. The at least one inorganic light-emitting diode includes a plurality of inorganic light-emitting diodes arranged within a display area partitioned on the substrate, The manufacturing method according to claim 1 or 2, wherein the plurality of spacers are arranged outside the display area.

11. The manufacturing method according to claim 1 or 2, wherein the plurality of spacers are arranged at a constant pitch.

12. The manufacturing method according to claim 1 or 2, wherein at least one of the plurality of spacers is arranged within the pixel.

13. The at least one inorganic light-emitting diode includes a plurality of inorganic light-emitting diodes, The manufacturing method according to claim 1 or 2, wherein at least one of the plurality of inorganic light-emitting diodes has a different height from at least one of the other plurality of inorganic light-emitting diodes.

14. The manufacturing method according to claim 1 or 2, wherein each of the plurality of spacers has a spherical shape.

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