Display device and method for manufacturing the same

Abstract

To improve the performance of a display device.SOLUTION: A display device includes a first substrate having a first surface, and a plurality of LED elements 20 mounted on a first surface of the first substrate. Each of the plurality of LED elements 20 includes a main body portion having a surface 20Bb facing the first surface of the first substrate and a surface 20Bf on an opposite side to the surface 20Bb, an anode electrode 20EA and a cathode electrode 20EC that are provided on the surface 20Bb of the main body portion, and an organic film 20F that is adhesively bonded to the surface 20Bf of the main body portion. The organic film 20F has a surface 20Fb that faces the surface 20Bf and is adhesively bonded to the surface 20Bf, and a surface 20Ff on an opposite side to the surface 20Fb. The surface 20Ff of the organic film 20F has a plurality of recess portions.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a display device. [Background technology]

[0002] Patent Document 1 (JP 2020-167251 A) describes a method for manufacturing a micro LED display device using a transfer substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-167251 A Summary of the Invention [Problem to be solved by the invention]

[0004] There is a micro LED display device that uses multiple LED elements (inorganic light emitting elements) as light emitting elements. The inventors of the present application are studying a technology for improving the performance of a display device that uses multiple LED elements, such as a micro LED display device.

[0005] An object of the present invention is to provide a technique for improving the performance of a display device. [Means for solving the problem]

[0006] A display device according to one embodiment includes a first substrate having a first surface, and a plurality of inorganic light-emitting diode elements mounted on the first surface of the first substrate. Each of the plurality of inorganic light-emitting diode elements includes a main body portion having a second surface facing the first surface of the first substrate and a third surface opposite the second surface, a first electrode and a second electrode provided on the second surface of the main body portion, and a first organic film bonded to the third surface of the main body portion. The first organic film includes a fourth surface bonded to the third surface, and a fifth surface opposite the fourth surface. The fifth surface of the first organic film includes a plurality of recesses.

[0007] A manufacturing method of a display device according to another embodiment includes (a) a step of preparing a first substrate having a first surface, (b) a step of preparing a plurality of inorganic light-emitting diode elements, and (c) a step of mounting the plurality of inorganic light-emitting diode elements on the first surface of the first substrate. The step (b) includes (b1) a step of forming a main body portion, a first electrode, and a second electrode of each of the plurality of inorganic light-emitting diode elements on an element formation substrate, (b2) a step of transferring the plurality of main bodies formed on the element formation substrate to a first transfer substrate, (b3) a step of bonding the plurality of main bodies to a plurality of first organic films held on an organic film holding substrate, and (b4) a step of peeling off an adhesive interface between the organic film holding substrate and the plurality of first organic films. The main body portion has a second surface facing the first surface of the first substrate in the step (c), and a third surface opposite to the second surface. Each of the first electrode and the second electrode is formed on the second surface of the main body portion in the step (b1). The first organic film has a fourth surface that is bonded to the third surface in the step (b3), and a fifth surface opposite the fourth surface. The fifth surface of the first organic film has a plurality of recesses. [Brief description of the drawings]

[0008] [Figure 1] 1 is a plan view showing a configuration example of a micro LED display device according to an embodiment. [Diagram 2]2 is a circuit diagram showing a configuration example of a circuit in the periphery of the pixel shown in FIG. 1. [Diagram 3] 2 is an enlarged transparent plan view showing an example of a peripheral structure of LED elements arranged in each of a plurality of pixels of the display device shown in FIG. [Figure 4] FIG. 4 is an enlarged cross-sectional view taken along line AA in FIG. [Diagram 5] FIG. 5 is an enlarged cross-sectional view of the LED element shown in FIG. [Figure 6] FIG. 6 is an enlarged perspective view showing an example of the shape of one surface of the organic film shown in FIG. 5. [Figure 7] 6 is an explanatory diagram illustrating a typical direction of travel of light generated by the LED element shown in FIG. 5. [Figure 8] 1A to 1C are explanatory diagrams showing an example of a process flow of a manufacturing method of a display device. [Figure 9] 9A to 9C are cross-sectional views showing the LED forming step shown in FIG. 8. [Figure 10] 9 is a cross-sectional view showing a main body picking step shown in FIG. 8. [Figure 11] 9 is a cross-sectional view showing an organic film bonding step shown in FIG. 8. [Figure 12] 9 is a cross-sectional view showing an organic film-holding substrate separation step shown in FIG. 8. [Figure 13] 9 is a cross-sectional view showing the LED element holding step shown in FIG. 8. [Figure 14] 9 is a cross-sectional view showing the LED element transferring step shown in FIG. 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. Note that the disclosure is merely an example, and those who are skilled in the art can easily come up with appropriate modifications while maintaining the gist of the invention, which are naturally included in the scope of the present invention. In addition, in order to make the explanation clearer, the drawings may show the width, thickness, shape, etc. of each part in a schematic manner compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. In addition, in this specification and each figure, elements similar to those described above with respect to the previous figures may be given the same or related symbols, and detailed explanations may be omitted as appropriate.

[0010] <Display device> First, a configuration example of a micro LED display device, which is a display device of the present embodiment, will be described. Fig. 1 is a plan view showing a configuration example of a micro LED display device, which is an embodiment. In Fig. 1, the boundary between the display area DA and the peripheral area PFA, the control circuit 5, the drive circuit 6, and the multiple pixels PIX are each indicated by a two-dot chain line. Fig. 2 is a circuit diagram showing a configuration example of the circuit around the pixel shown in Fig. 1.

[0011] FIG. 1 shows an X direction and a Y direction. The X direction and the Y direction intersect with each other. In the example described below, the X direction is perpendicular to the Y direction. In the following, the XY plane including the X direction and the Y direction will be described as a plane parallel to the display surface of the display device. In the following description, unless otherwise specified, the term "planar view" means a view of a plane parallel to the XY plane. In addition, as described later, the normal direction to the XY plane will be described as the "Z direction" or thickness direction. The X direction, the Y direction, and the Z direction are directions that intersect with each other, and more specifically, are directions that are perpendicular to each other.

[0012] As shown in Fig. 1, the display device DSP1 of the present embodiment has a display area DA, a peripheral area PFA surrounding the periphery of the display area DA in a frame shape, and a plurality of pixels PIX arranged in a matrix within the display area DA. The display device DSP1 also has a substrate 10, a control circuit 5 formed on the substrate 10, and a drive circuit 6 formed on the substrate 10. The substrate 10 is made of glass or resin. As shown in Fig. 4, the substrate 10 has a surface 10f and a surface 10b opposite to the surface 10f.

[0013] The control circuit 5 is a control circuit that controls the driving of the display function of the display device DSP1. For example, the control circuit 5 is a driver IC (Integrated Circuit) mounted on the substrate 10. In the example shown in FIG. 1, the control circuit 5 is arranged along one of the four short sides of the substrate 10. In the example of the present embodiment, the control circuit 5 includes a signal line driving circuit that drives the wiring (video signal wiring) VL (see FIG. 2) connected to the multiple pixels PIX. However, the position and configuration example of the control circuit 5 are not limited to the example shown in FIG. 1, and there are various modified examples. For example, in FIG. 1, a circuit board such as a flexible board may be connected to the position shown as the control circuit 5, and the above-mentioned driver IC may be mounted on the circuit board. In addition, for example, the signal line driving circuit that drives the wiring VL may be formed separately from the control circuit 5.

[0014] The driving circuit 6 includes a circuit for driving the scanning signal lines GL (see FIG. 2 described later) of the multiple pixels PIX. The driving circuit 6 also includes a circuit for supplying a reference potential to the LED elements mounted on each of the multiple pixels PIX. The driving circuit 6 drives the multiple scanning signal lines GL based on a control signal from the control circuit 5. In the example shown in FIG. 1, the driving circuit 6 is disposed along each of two long sides of the four sides of the substrate 10. However, the position and configuration of the driving circuit 6 are not limited to the example shown in FIG. 1, and there are various modified examples. For example, in FIG. 1, a circuit board such as a flexible board may be connected to the position shown as the control circuit 5, and the above-mentioned driving circuit 6 may be mounted on the circuit board.

[0015] Next, an example of the circuit configuration of the pixel PIX will be described with reference to Fig. 2. Note that Fig. 2 shows four pixels PIX as representatives, but each of the pixels PIX shown in Fig. 1 has a circuit similar to that of the pixel PIX shown in Fig. 2. Hereinafter, the switch and the circuit including the LED element 20 provided in the pixel PIX may be referred to as a pixel circuit. The pixel circuit is a voltage signal type circuit that controls the light emission state of the LED element 20 in response to a video signal Vsg supplied from the control circuit 5 (see Fig. 1).

[0016] As shown in Fig. 2, the pixel PIX includes an LED element 20. The LED element 20 is the above-mentioned micro light-emitting diode. The LED element 20 has an anode electrode 20EA and a cathode electrode 20EC. The cathode electrode 20EC of the LED element 20 is connected to a wiring VSL to which a reference potential (fixed potential) PVS is supplied. The anode electrode 20EA of the LED element 20 is electrically connected to a drain electrode ED of the switching element SW via a wiring 31.

[0017] The pixel PIX includes a switching element SW. The switching element SW is a transistor that controls the connection state (on or off state) between the pixel circuit and the wiring VL in response to a control signal Gs. The switching element SW is, for example, a thin film transistor. When the switching element SW is in the on state, a video signal Vsg is input to the pixel circuit from the wiring VL.

[0018] The driving circuit 6 includes a shift register circuit, an output buffer circuit, etc. (not shown). The driving circuit 6 outputs a pulse based on a horizontal scanning start pulse transmitted from the control circuit 5 (see FIG. 1), and outputs a control signal Gs.

[0019] Each of the multiple scanning signal lines GL extends in the X-direction. The scanning signal lines GL are connected to the gate electrodes of the switching elements SW. When a control signal Gs is supplied to the scanning signal lines GL, the switching elements SW are turned on, and a video signal Vsg is supplied to the LED elements 20.

[0020] <Peripheral Structure of LED Element> Next, the peripheral structure of the LED element disposed in each of the plurality of pixels PIX shown in FIG. 1 will be described. FIG. 3 is a transmission enlarged plan view showing an example of the peripheral structure of the LED element disposed in each of the plurality of pixels of the display device shown in FIG. 1. In FIG. 3, the illustration of the inorganic insulating layer 14 shown in FIG. 4 is omitted. In FIG. 3, the outlines of the semiconductor layer, the electrode, and the scanning signal line are indicated by dotted lines. FIG. 4 is an enlarged cross-sectional view taken along the line A-A of FIG. 3.

[0021] As shown in FIG. 3, the display device DSP1 has a plurality of pixels PIX (pixels PIX1, PIX2, and PIX3 in the example shown in FIG. 3) including the pixel PIX1. Each of the plurality of pixels PIX has a switching element SW, an LED element (light-emitting element) 20, a wiring 31, and a wiring 32.

[0022] Note that in each of the pixels PIX1, PIX2, and PIX3, an LED element 20 that emits visible light of one of, for example, red, green, and blue is mounted, and a switching element SW that drives the LED element 20 is formed. By controlling the output and timing of the visible light emitted from the LED element 20 provided in each of the pixels PIX1, PIX2, and PIX3, color display becomes possible. When combining a plurality of pixels PIX that emit visible light of different colors in this way, the pixel PIX for each color may be called a sub-pixel, and a set of a plurality of pixels PIX may be called a pixel. In the present embodiment, the portion corresponding to the sub-pixel is called a pixel PIX.

[0023] The wiring 31 is electrically connected to the drain electrode ED of the switching element SW and the anode electrode 20EA of the LED element 20, respectively. The wiring 32 is connected to the source electrode ES of the switching element SW. In the example shown in FIG. 3, the wiring 32 has a bent structure, one end is connected to the source electrode ES of the switching element SW, and the other end is connected to the wiring VL. The scanning signal line GL is used as the gate electrode EG of the switching element SW.

[0024] The display device DSP1 further includes a wiring VL that extends across a plurality of pixels PIX (see FIG. 2) along the Y direction and is electrically connected to the wiring 32, and a wiring VSL that extends across a plurality of pixels PIX along the X direction intersecting the Y direction (orthogonal in FIG. 3) and is electrically connected to the cathode electrode 20EC of the LED element 20. Note that the layout shown in FIG. 3 is only an example, and there are various modifications. For example, as one of the modifications to FIG. 3, the switching element SW may have a gate electrode (not shown) and the gate electrode may be connected to the scanning signal line GL. In this modification, the scanning signal line GL may be disposed at a position that does not overlap with the semiconductor layer 50.

[0025] As shown in Fig. 4, the display device DSP1 is an electronic device including a substrate 10 made of glass or resin and a plurality of insulating layers laminated on the substrate 10. The plurality of insulating layers included in the display device DSP1 include inorganic insulating layer 11, inorganic insulating layer 12, inorganic insulating layer 13, and inorganic insulating layer 14 laminated on the substrate 10. The substrate 10 has a surface 10f and a surface 10b opposite to the surface 10f. Each of the inorganic insulating layers 11, 12, 13, and 14 is laminated on the surface 10f of the substrate 10.

[0026] The switching element SW includes an inorganic insulating layer 12 formed on a substrate 10, a semiconductor layer 50 formed on the inorganic insulating layer 12, a drain electrode ED connected to a drain region of the semiconductor layer 50, a source electrode ES connected to a source region of the semiconductor layer 50, and an inorganic insulating layer 13 covering the semiconductor layer 50. Each of the wiring 31 and the wiring 32 is, for example, a laminated film of a conductor layer made of titanium or a titanium alloy and a conductor layer made of aluminum or an aluminum alloy. A laminated film in which an aluminum layer is sandwiched between titanium layers is called a TAT laminated film.

[0027] The example shown in Fig. 4 is a bottom gate type example in which the gate electrode EG is between the semiconductor layer 50 and the substrate 10. In the case of the bottom gate type, a portion of the inorganic insulating layer 12 between the gate electrode EG and the semiconductor layer 50 functions as a gate insulating layer. The inorganic insulating layer 12 also functions as a base layer for forming the semiconductor layer 50. The position of the gate electrode EG is not limited to the example shown in Fig. 4, and may be, for example, a top gate type described later as a modified example.

[0028] There is no particular limitation on the material constituting each of the inorganic insulating layers 11, 12, 13, and 14. Examples include silicon oxide (SiO2) and silicon nitride (SiN). The semiconductor layer 50 is a semiconductor film in which a silicon film made of silicon is doped with impurities of P-type or N-type conductivity.

[0029] Each of the source electrode ES and the drain electrode ED is a contact plug for making electrical contact with either the source region or the drain region of the semiconductor layer 50. Examples of the material of the contact plug include tungsten. As a modification of FIG. 4, contact holes for exposing the source region and the drain region of the semiconductor layer 50 are formed in the inorganic insulating layer 13, and a part of the wiring 31 and a part of the wiring 32 are embedded in the contact holes. In this case, the parts of the wiring 31 and the wiring 32 embedded in the contact holes contact the semiconductor layer 50, and the contact interfaces between the wiring 31 and the wiring 32 and the semiconductor layer 50 can be regarded as the drain electrode ED and the source electrode ES.

[0030] The substrate SUB1 refers to the laminate of the substrate 10 and a plurality of insulating layers (inorganic insulating layers 11, 12, 13, and 14 in the example shown in FIG. 4) laminated on the substrate 10. The substrate SUB1 has a surface SUBf.

[0031] In addition, the display device DSP1 includes a plurality of bump electrodes 33. The bump electrodes 33 are terminals for mounting the LED element 20 on the substrate 10. Therefore, one of the two bump electrodes 33 is connected to the anode electrode 20EA of the LED element 20, and the other is connected to the cathode electrode 20EC of the LED element 20.

[0032] The bump electrode 33 is connected to the wiring 31 at a position overlapping with the opening 14H formed in the inorganic insulating layer 14 and protrudes from the inorganic insulating layer 14. Further, the bump electrode 33 is made of, for example, solder containing tin. Alternatively, the bump electrode 33 may be a laminate of a metal layer made of a metal material having a higher electrical conductivity than solder, such as copper, and a solder layer.

[0033] <LED element> Next, the LED element 20 shown in FIGS. 3 and 4 will be described. FIG. 5 is an enlarged cross-sectional view of the LED element shown in FIG. 4. FIG. 6 is an enlarged perspective view showing an example of the shape of one surface of the organic film shown in FIG. 5. FIG. 7 is an explanatory view schematically showing the traveling direction of light generated by the LED element shown in FIG. 5.

[0034] As shown in FIG. 4, each of the plurality of LED elements 20 shown in FIG. 3 has a main body portion 20B, a transparent (in other words, visible light transmissive) organic film 20F, an anode electrode 20EA, and a cathode electrode 20EC.

[0035] The main body portion 20B of the LED element 20 includes a surface 20Bb facing the surface SUBf of the substrate SUB1 and a surface 20Bf on the opposite side of the surface 20Bb. Each of the anode electrode 20EA and the cathode electrode 20EC is provided on the surface 20Bb of the main body portion 20B. The organic film 20F is adhered to the surface 20Bf of the main body portion 20B. The organic film 20F includes a surface 20Fb facing the surface 20Bf and adhered to the surface 20Bf, and a surface 20Ff on the opposite side of the surface 20Fb.

[0036] A detailed structure of the LED element 20 is illustrated in, for example, Fig. 5. In the example illustrated in Fig. 5, the body 20B of the LED element 20 includes an N-type semiconductor layer 24, an active layer 25 laminated on the N-type semiconductor layer 24, a P-type semiconductor layer 26 laminated on the active layer 25, and a passivation film 28 which is an inorganic insulating film.

[0037] The N-type semiconductor layer 24 is formed as a base layer common to the anode electrode 20EA and the cathode electrode 20EC, and an active layer 25 and a P-type semiconductor layer 26 are laminated on the anode electrode 20EA side. On the anode electrode 20EA side, a transparent electrode layer 27a is formed on the P-type semiconductor layer 26. The transparent electrode layer 27a on the anode electrode 20EA side and the N-type semiconductor layer 24 on the cathode electrode 20EC side are covered with a passivation film 28, which is an inorganic insulating film.

[0038] In the passivation film 28, openings are formed at the locations where the anode electrode 20EA and the cathode electrode 20EC are to be formed. In each opening, a metal electrode layer 27c is laminated via a seed layer 27b. The anode electrode 20EA is a laminate of a transparent electrode layer 27a, a seed layer 27b, and a metal electrode layer 27c. On the other hand, the cathode electrode 20EC is a laminate of a seed layer 27b and a metal electrode layer 27c laminated on the N-type semiconductor layer 24. Between the N-type semiconductor layer 24 and the substrate SS1, a buffer layer 29 made of, for example, gallium nitride is formed.

[0039] 5 illustrates an example in which the buffer layer 29 remains between the organic film 20F and the N-type semiconductor layer 24. However, in the manufacturing process of the LED element 20, the buffer layer 29 may be modified and removed by laser irradiation. In this case, the buffer layer 29 may not remain between the organic film 20F and the N-type semiconductor layer 24, and the surface 20Fb of the organic film 20F may be bonded to the N-type semiconductor layer 24.

[0040] 5 and 6, the surface 20Ff of the organic film 20F has a plurality of recesses 20D. In the example shown in Fig. 6, the plurality of recesses 20D are arranged in a lattice pattern. More specifically, the plurality of recesses 20D are arranged in a staggered pattern.

[0041] 7, the recessed portion 20D of the organic film 20F functions as an optical element that refracts a part of the light 20L1 emitted from the light emitting layer of the LED element 20, thereby increasing the component of the emitted light 20L2 traveling in the Z direction, which is the thickness direction of the LED element 20. The Z direction coincides with the normal direction of the surface 20Bb of the main body 20B of the LED element 20.

[0042] As in this embodiment, if the component of the emitted light 20L2 traveling in the Z direction can be increased among the light emitted from the LED element 20, the amount of light that can be used as light for display can be increased. As a result, the brightness of the display device can be improved. In other words, the power required to obtain the required brightness can be reduced.

[0043] As shown in Fig. 6, each of the plurality of recesses 20D has a conical shape. As shown in Fig. 7, the shape of the recesses 20D is not limited to a conical shape, and various modified shapes can be applied, as long as the recesses 20D can function as an optical element that increases the component of the output light 20L2 traveling in the Z direction by refracting a part of the light 20L1. However, according to the study by the inventors of the present application, it is particularly preferable that the recesses 20D have a conical shape.

[0044] The organic film 20F is easier to process than inorganic films such as metal films, metal oxide films, etc. Therefore, the shapes of the multiple recesses 20D formed in the organic film 20F (for example, the height of the cone shown in FIG. 6, the radius of the bottom surface, or the inclination angle of the side surface, etc.) can be easily processed into an optimal shape taking into account the refraction characteristics.

[0045] In the present embodiment, the organic film 20F is made of polyimide resin. The refractive index of the polyimide resin for visible light can be easily adjusted to a value close to the refractive index of the main body 20B of the LED element 20 for visible light. For example, in the present embodiment, the refractive index of the organic film 20F made of polyimide resin is higher than the refractive index of air and lower than the refractive index of a gallium nitride film (for example, the buffer layer 29 shown in FIG. 5). More specifically, the difference in refractive index between the organic film 20F and the gallium nitride film is smaller than the difference in refractive index between the organic film 20F and the air. For this reason, it is preferable that the organic film 20F is made of polyimide resin for optical reasons. In addition, from the viewpoint of ease of processing, it is particularly preferable that the organic film 20F is made of polyimide resin.

[0046] 5, the surface 20Bf of the main body 20B is not roughened. Therefore, the flatness of the surface 20Ff of the organic film 20F is lower than the flatness of the surface 20Bf on which the plurality of recesses 20D are formed. However, in order to improve the adhesive strength between the surface 20Fb of the organic film 20F and the surface 20Bf of the main body 20B, the surface 20Bf of the main body 20B may be roughened. Even in this case, it is preferable that the flatness of the surface 20Ff of the organic film 20F is equal to or lower than the flatness of the surface 20Bf of the main body 20B.

[0047] As described above, the organic film 20F functions as an optical element. For this reason, from the viewpoint of improving the brightness of the display device DSP1 (see FIG. 4), it is preferable that most of the light 20L1 shown in FIG. 7 passes through the surface 20Ff of the organic film 20F. In the case of the present embodiment, the area of ​​the surface 20Fb of the organic film 20F is equal to or larger than the area of ​​the surface 20Bf. In addition, the entire surface 20Bf of the main body 20B is bonded to the surface 20Fb of the organic film 20F. This allows the amount of light 20L1 that passes through the main body 20B and the organic film 20F in this order to be maximized and emitted from the surface 20Ff.

[0048] However, when the area of ​​surface 20Fb of organic film 20F is larger than the area of ​​surface 20Bf, a part of organic film 20F protrudes from main body 20B in the direction along the XY plane shown in Fig. 3. If the volume of the protruding part becomes large, for example, when an external force is applied to organic film 20F during the manufacturing process, the adhesive interface between surface 20Fb and surface 20Bf may peel off. From the viewpoint of suppressing peeling of the adhesive interface between surface 20Fb and surface 20Bf, it is preferable that the area of ​​surface 20Fb of organic film 20F is approximately the same as the area of ​​surface 20Bf.

[0049] In this embodiment, the area of ​​the surface 20Fb of the organic film 20F is equal to the area of ​​the surface 20Bf. In this case, almost the entire surface 20Bf of the main body portion 20B is bonded to the surface 20Fb of the organic film 20F. Even if the positions of the surface 20Fb and the surface 20Bf are not completely aligned due to the influence of positional accuracy in the manufacturing process, the volume of the portion of the organic film 20F protruding from the main body portion 20B can be effectively made small enough to be negligible.

[0050] <Display Device Manufacturing Method> Next, a method for manufacturing the display device according to the present embodiment will be described by taking as a representative example the method for manufacturing the display device DSP1 shown in Fig. 3. Fig. 8 is an explanatory diagram showing an example of a process flow of the method for manufacturing the display device.

[0051] As shown in Fig. 8, the manufacturing method of the display device of the present embodiment includes a substrate preparation step, an LED element preparation step, an LED element holding step, and an LED element transfer step. The LED element preparation step includes an LED formation step, a main body picking step, an organic film bonding step, and an organic film holding substrate separation step. Each step shown in Fig. 8 will be described below.

[0052] In the substrate preparation step shown in Fig. 8, the substrate SUB1 shown in Fig. 4 is prepared. The structure of the substrate SUB1 has already been described, so a duplicated description will be omitted. The substrate SUB1 prepared in this step is in a state before the LED elements 20 shown in Fig. 4 are mounted. Therefore, the bump electrodes 33 are in a state of protruding above the surface SUBf of the substrate SUB1.

[0053] In the LED forming step included in the LED element preparing step shown in Fig. 8, the main body 20B, the anode electrode 20EA, and the cathode electrode 20EC of the LED element 20 described with reference to Fig. 5 are formed on the surface SS1f of the substrate SS1 as shown in Fig. 9. The substrate SS1 is an element forming substrate for forming the LED element, and is, for example, a sapphire substrate made of sapphire. Fig. 9 is a cross-sectional view showing the LED forming step shown in Fig. 8.

[0054] The main body 20B has a surface 20Bf facing the surface SS1f of the substrate SS1, and a surface 20Bb opposite the surface 20Bf. The anode electrode 20EA and the cathode electrode 20EC are each formed on the surface 20Bb.

[0055] In this step, the buffer layer 29, the N-type semiconductor layer 24, the active layer 25, the P-type semiconductor layer 26, the transparent electrode layer 27a, and the passivation film 28 are laminated in this order as described with reference to Fig. 5. An opening is formed in the passivation film 28, and a seed layer 27b and a metal electrode layer 27c are formed on the opening.

[0056] In this process, a plurality of main body portions 20B are formed on one substrate SS1 at a time. After the anode electrode 20EA and the cathode electrode 20EC are formed, the laminated film on the substrate SS1 is diced into a plurality of parts (called a dicing process or a singulation process). In the case of such a manufacturing method, since a plurality of main body portions 20B can be formed at a time, manufacturing efficiency is improved.

[0057] Next, in a main body picking step included in the LED element preparation step shown in Fig. 8, some or all of the multiple main body parts 20B are transferred to a transfer substrate TS1 as shown in Fig. 10. Fig. 10 is a cross-sectional view showing the main body picking step shown in Fig. 8. The example shown in Fig. 10 shows a state in which some (three) of the five main body parts 20B are transferred.

[0058] The reasons for transferring a portion of the plurality of main body parts 20B in this manner are, for example, as follows: The first reason is that the arrangement pitch of the plurality of main body parts 20B formed on the substrate SS1 is different from the arrangement pitch of the plurality of LED elements 20 mounted on the substrate SUB1 shown in FIG.

[0059] The second reason is as follows. That is, the display device DSP1 is equipped with a plurality of types of LED elements 20, such as blue, red, and green LED elements. On the other hand, it is preferable that the plurality of main body parts 20B formed collectively on the substrate SS1 are of the same type. For this reason, in order to mount the different types of LED elements 20 adjacent to each other, it is preferable to pick up some of the plurality of main body parts 20B in this process.

[0060] However, the number of main body parts 20B transferred to the transfer substrate TS1 in this process is not limited to the number shown in Fig. 10, and there are various modifications. For example, as a modification of the present embodiment, all of the multiple main body parts 20B may be picked up in this process.

[0061] In this step, a laser lift-up method can be used in which the buffer layer 29 shown in FIG. 5 is modified by irradiating it with a laser, and the modified buffer layer is selectively picked up.

[0062] The transfer substrate TS1 shown in FIG. 10 is a glass substrate made of, for example, glass. The transfer substrate TS1 has a surface TS1b. A retention layer HL1 is formed on the surface TS1b of the transfer substrate TS1. The retention layer HL1 is made of, for example, an elastically deformable organic film, and is formed so as to cover the entire surface TS1b of the transfer substrate TS1. The retention layer HL1 has a surface HL1f facing the surface TS1b of the transfer substrate TS1, and a surface HL1b opposite to the surface HL1f. At least the surface HL1b, or the entire retention layer HL1, is made of an adhesive material and is capable of adhesively holding the main body portion 20B.

[0063] In this process, a laser is irradiated to modify some or all of the buffer layers 29 (see FIG. 5) of the multiple main body parts 20B while the surface HL1b of the retention layer HL1 is pressed against the anode electrode 20EA and the cathode electrode 20EC formed on the main body part 20B. Thereafter, the transfer substrate TS1 is spaced apart from the substrate SS1, so that the main body part 20B can be transferred to the transfer substrate TS1 as shown in FIG.

[0064] Next, in an organic film bonding step included in the LED element preparation step shown in Fig. 8, a surface 20Fb of the organic film 20F is bonded to each surface 20Bf of the plurality of main body portions 20B as shown in Fig. 11. Fig. 11 is a cross-sectional view showing the organic film bonding step shown in Fig. 8.

[0065] The organic film holding substrate 60 prepared in this step has a surface 60f and a plurality of organic films 20F formed on the surface 60f. The plurality of organic films 20F are spaced apart from one another. In addition, a plurality of protrusions 60P are formed on the surface 60f of the organic film holding substrate 60. Each of the plurality of protrusions 60P has a shape corresponding to the plurality of recesses 20D shown in FIG. 6. In the case of this embodiment, each of the plurality of protrusions 60P is conical. The plurality of organic films 20F are formed on the surface 60f having the plurality of protrusions 60P. Therefore, the surface 20Ff of the organic film 20F facing the surface 60f has recesses 20D (see FIG. 6) formed following the shape of the protrusions 60P.

[0066] In this process, first, the transfer substrate TS1 and the organic film holding substrate 60 are aligned so that the surface 20Bf of the main body portion 20B and the surface 20Fb of the organic film 20F face each other. Next, the transfer substrate TS1 and the organic film holding substrate 60 are brought closer to each other, and the surface 20Bf of the main body portion 20B and the surface 20Fb of the organic film 20F are bonded to each other as shown in Fig. 11. The organic film 20F is made of, for example, a polyimide resin, and at least the surface 20Fb has adhesiveness.

[0067] Next, in the organic film-holding substrate separation step included in the LED element preparation step shown in Fig. 8, as shown in Fig. 12, a laser beam 61 is irradiated from the organic film-holding substrate 60 side to peel off the adhesive interface between the surface 60f of the organic film-holding substrate 60 and the surface 20Ff of the organic film 20F, thereby separating each of the multiple organic films 20F from the organic film-holding substrate 60. Fig. 12 is a cross-sectional view showing the organic film-holding substrate separation step shown in Fig. 8.

[0068] The laser light 61 is emitted from a laser light source 62. When the organic film 20F is irradiated with the laser light 61, the organic film 20F is rapidly heated and expands, and the interface between the surface 60f of the organic film holding substrate 60 and the surface 20Ff of the organic film 20F is peeled off. As shown by the arrows in FIG. 12, the laser light source 62 is continuously moved while irradiating the laser light 61, so that the temperature of the organic film 20F can be lowered before the thermal expansion of the organic film 20F affects the adhesive interface between the main body 20B and the organic film 20F. When the temperature of the organic film 20F is lowered, the organic film 20F contracts, and the surface 20Ff described with reference to FIG. 6 is exposed.

[0069] In this embodiment, a method is shown in which the interface between the surface 60f of the organic film holding substrate 60 and the surface 20Ff of the organic film 20F is peeled off in a state in which a plurality of main body portions 20B are held on the transfer substrate TS1. However, as a modified example, the holding layer HL1 formed on the transfer substrate TS1 may be separated from the main body portions 20B before this step. In this case, in this step, the main body portions 20B and the organic film 20F are transferred to a transfer substrate other than the transfer substrate TS1 shown in FIG.

[0070] Through the above steps, the LED element preparation step shown in Fig. 8 is completed. That is, as described with reference to Fig. 5, the LED element 20 including the anode electrode 20EA, the cathode electrode 20EC, the main body portion 20B, and the organic film 20F is obtained.

[0071] Next, in the LED element holding step shown in Fig. 8, each of the LED elements 20 held on the transfer substrate TS1 via the holding layer HL1 is transferred to a transfer substrate TS2 as shown in Fig. 13. Fig. 13 is a cross-sectional view showing the LED element holding step shown in Fig. 8.

[0072] The transfer substrate TS2 shown in FIG. 13 is a glass substrate made of, for example, glass. The transfer substrate TS2 has a surface TS2b. A retention layer HL2 is formed on the surface TS2b of the transfer substrate TS2. The retention layer HL2 is made of, for example, an elastically deformable organic film, and is formed so as to cover the entire surface TS2b of the transfer substrate TS2. The retention layer HL2 has a surface HL2f facing the surface TS2b of the transfer substrate TS2, and a surface HL2b opposite to the surface HL2f. At least the surface HL2b, or the entire retention layer HL2, is made of an adhesive material and is capable of adhesively holding the main body portion 20B.

[0073] However, the adhesive holding strength of the surface HL2b is smaller than the adhesive strength of the adhesive interface between the surface 20Bf of the main body 20B and the surface 20Fb of the organic film 20F. This is to prevent peeling of the adhesive interface between the surface 20Bf of the main body 20B and the surface 20Fb of the organic film 20F in the LED element transfer process described later.

[0074] In this step, the contact interface between the surface HL1b of the retention layer HL1 and the LED element 20 (specifically, the anode electrode 20EA and the cathode electrode 20EC) is peeled off. As a method for peeling off the contact interface, FIG. 13 illustrates a method of irradiating a laser beam 61. In this step, the operation of the laser beam source 62 is different from that of the organic film retention substrate separation step described with reference to FIG. 12. That is, in this step, as shown in FIG. 13, the laser beam source 62 is moved intermittently to peel off the contact interface between the surface HL1b of the retention layer HL1 and the LED element 20. Moreover, while the laser beam source 62 is moving, the irradiation of the laser beam 61 is stopped.

[0075] The retention layer HL1 is formed so as to cover the entire surface TS1b of the transfer substrate TS1. Therefore, even if a part of the contact interface between the surface TS1b and the surface HL1f is peeled off due to the irradiation of the laser beam 61 in this step, the other parts are adhered, so that the entire retention layer HL1 can be prevented from peeling off.

[0076] In the example shown in FIG. 13, the method of irradiating the laser light 61 has been described as a method of transferring the LED element 20 from the transfer substrate TS1 to the transfer substrate TS2. However, as a method of transferring the LED element 20 from the transfer substrate TS1 to the transfer substrate TS2, for example, a method of utilizing the difference in adhesive strength between the retaining layer HL2 and the retaining layer HL1 can be applied. That is, in the example shown in FIG. 13, the adhesive strength of the retaining layer HL2 is greater than the adhesive strength of the retaining layer HL1. In this case, if the transfer substrate TS1 and the transfer substrate TS2 are separated without irradiating the laser light 61, the retaining layer HL1, which has a relatively low adhesive strength, is peeled off from the LED element 20. In this case, the adhesive strength between the main body 20B and the organic film 20F needs to be greater than at least the adhesive strength between the retaining layer HL1 and the LED element 20.

[0077] Next, in the LED element transfer step shown in Fig. 8, each of the LED elements 20 held on the transfer substrate TS2 via the retaining layer HL2 is transferred to the substrate SUB1 as shown in Fig. 14. Fig. 14 is a cross-sectional view showing the LED element transfer step shown in Fig. 8.

[0078] In this process, the anode electrode 20EA and the cathode electrode 20EC of each of the LED elements 20 are bonded to the bump electrode 33 formed on the substrate SUB1, and then the adhesive interface between the surface HL2b of the retaining layer HL2 and the surface 20Ff of the organic film 20F is peeled off. The adhesive strength of the adhesive interface between the surface HL2b of the retaining layer HL2 and the surface 20Ff of the organic film 20F is smaller than the adhesive strength between the anode electrode 20EA and the cathode electrode 20EC and the bump electrode 33. As described above, the adhesive holding force (in other words, adhesive strength) of the surface HL2b is smaller than the adhesive strength of the adhesive interface between the surface 20Bf of the main body 20B and the surface 20Fb of the organic film 20F. Therefore, after the bump electrode 33 is bonded to the electrode, the transfer substrate TS2 is pulled away, whereby the adhesive interface between the surface HL2b of the retaining layer HL2 and the surface 20Ff of the organic film 20F can be peeled off.

[0079] Through the above steps, the display device DSP1 shown in FIGS. 1 to 4 is obtained.

[0080] Although the embodiment and the representative modified examples have been described above, the above-described technology can be applied to various modified examples other than the modified examples exemplified. For example, the modified examples described above may be combined with each other.

[0081] Within the scope of the concept of the present invention, a person skilled in the art may conceive of various modifications and alterations, and it is understood that such modifications and alterations also fall within the scope of the present invention. For example, those in which a person skilled in the art appropriately adds, deletes, or modifies the design of the above-mentioned embodiments, or adds, omits, or modifies the conditions of steps, are also included in the scope of the present invention as long as they include the gist of the present invention. [Industrial Applicability]

[0082] The present invention can be used in display devices and electronic devices incorporating display devices. [Explanation of symbols]

[0083] 5 Control circuit 6 Drive circuit 10, SS1, SUB1 board 10b,10f,20Bb,20Bf,20Fb,20Ff,60f,HL1b,HL1f,HL2b,HL2f,SUBfTS1b,TS2b surface 11, 12, 13, 14 Inorganic insulating layer 14H opening 20 LED elements (inorganic light emitting elements) 20B Main body 20D recess 20EA Anode electrode (electrode) 20EC Cathode Electrode (Electrode) 20F organic film 20L1,L1 light 20L2 Output light 24 N-type semiconductor layer 25 Active layer 26 P-type semiconductor layer 27a Transparent electrode layer 27b Seed layer 27c Metal electrode layer 28 Passivation film 29 Buffer Layer 31,32,34,VL,VSL wiring 33 Bump electrode 50 Semiconductor layer 60 Organic film holding substrate DA display area DSP1 display device ED drain electrode EG Gate electrode ES source electrode GL scanning signal line Gs control signal HL1,HL2 Holding layer (LED element holding layer) PFA surrounding area PIX, PIX1, PIX2, PIX3 pixels PVS reference potential (fixed potential) SUB1 board SW Switching element TS1, TS2 Transfer substrate Vsg Video signal

Claims

1. a first substrate having a first surface; a plurality of inorganic light emitting diode elements mounted on the first surface of the first substrate; having Each of the plurality of inorganic light emitting diode elements is a main body portion including a second surface facing the first surface of the first substrate and a third surface opposite the second surface; a first electrode and a second electrode provided on the second surface of the main body; a first organic film bonded to the third surface of the main body; having the first organic film has a fourth surface bonded to the third surface and a fifth surface opposite the fourth surface; The display device, wherein the fifth surface of the first organic film has a plurality of recesses.

2. In claim 1, A display device, wherein each of the plurality of recesses is cone-shaped.

3. In claim 2, The display device, wherein the first organic film is made of a polyimide resin.

4. In claim 3, an area of ​​the fourth surface of the first organic film is equal to or greater than an area of ​​the third surface; a display device, wherein the entirety of the third surface of the main body portion is adhered to the fourth surface of the first organic film.

5. In claim 3, an area of ​​the fourth surface of the first organic film and an area of ​​the third surface of the first organic film are equal to each other.

6. In claim 3, A display device, wherein the fifth surface has a flatness lower than the flatness of the third surface.

7. (a) providing a first substrate having a first surface; (b) providing a plurality of inorganic light emitting diode devices; (c) mounting the plurality of inorganic light emitting diode elements on the first surface of the first substrate; having The step (b) comprises: (b1) forming a body portion, a first electrode, and a second electrode of each of the plurality of inorganic light emitting diode elements on an element formation substrate; (b2) transferring the plurality of body portions formed on the element formation substrate onto a first transfer substrate; (b3) bonding the plurality of main body portions to a plurality of first organic films held on an organic film holding substrate, respectively; (b4) peeling off the adhesive interfaces between the organic film holding substrate and the plurality of first organic films; Including, the main body portion includes a second surface facing the first surface of the first substrate in the step (c) and a third surface opposite to the second surface; each of the first electrode and the second electrode is formed on the second surface of the main body portion in the step (b1); the first organic film has a fourth surface bonded to the third surface in the step (b3) and a fifth surface opposite to the fourth surface; The fifth surface of the first organic film has a plurality of recesses.

8. In claim 7, A method for manufacturing a display device, wherein each of the plurality of recesses has a conical shape.

9. In claim 8, The method for manufacturing a display device, wherein the first organic film is made of a polyimide resin.

Images