Light emitting element ink and method of manufacturing display device

Abstract

The present application relates to a light emitting element ink, the light emitting element ink including a light emitting element solvent; a light emitting element dispersed in the light emitting element solvent, the light emitting element including a plurality of semiconductor layers and an insulating film surrounding an outer surface of the plurality of semiconductor layers; a thickening agent dispersed in the light emitting element solvent, wherein the thickening agent includes a compound represented by the following Chemical Structural Formula 1 as a polyol-based compound capable of forming an intermolecular hydrogen bond with the light emitting element solvent or another thickening agent, and the thickening agent has a boiling point of about 200°C to about 450°C at atmospheric pressure.[Chemical Structural Formula 1]

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2020-0096767, filed with the Korean Intellectual Property Office on August 3, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to light-emitting element inks and methods for manufacturing display devices. More specifically, the present invention relates to light-emitting element inks containing a thickener whose viscosity can be adjusted according to temperature, and to methods for manufacturing display devices using said light-emitting element inks. Background Technology

[0004] The importance of display devices has increased with the development of multimedia. Therefore, various types of display devices have been developed, such as organic light-emitting diodes (OLEDs) and liquid crystal displays (LCDs).

[0005] Display devices for displaying images include display panels, such as organic light-emitting display panels or liquid crystal display panels. In display panels, organic light-emitting display panels include organic light-emitting elements, such as light-emitting diodes (LEDs). Light-emitting diodes (LEDs) include organic light-emitting diodes (OLEDs) that use organic materials as fluorescent materials and inorganic light-emitting diodes that use inorganic materials as fluorescent materials. Summary of the Invention

[0006] This disclosure provides an ink for light-emitting elements that can be stored for a long time by including a thickener in which the light-emitting elements are dispersed.

[0007] Another aspect of this disclosure provides a method for manufacturing a display device using the light-emitting element ink, wherein foreign matter is completely removed after the printing process to improve product reliability.

[0008] However, the aspects of this disclosure are not limited to those set forth herein. These and other aspects of this disclosure will become more apparent to those skilled in the art upon reference to the following detailed description of this disclosure.

[0009] According to embodiments of the present disclosure, a light emitting element ink can include: a light emitting element solvent; light emitting elements dispersed in the light emitting element solvent, the light emitting elements including a plurality of semiconductor layers and an insulating film surrounding an outer surface of the plurality of semiconductor layers; a thickening agent dispersed in the light emitting element solvent. The thickening agent can include a compound represented by the following Chemical Structural Formula 1 as a polyol-based compound capable of forming an intermolecular hydrogen bond with the light emitting element solvent or another thickening agent, and the thickening agent can have a boiling point of about 200°C to about 450°C at atmospheric pressure,

[0010] [Chemical Structural Formula 1]

[0011]

[0012] wherein, in Chemical Structural Formula 1, R 1 is a linear or branched alkyl group or a linear or branched alkyl ether group each having 1 to 3,000 carbon atoms, the linear or branched alkyl group and the linear or branched alkyl ether group being substituted with a hydroxyl group (-OH) or being unsubstituted, and I is an integer of 1 to 10.

[0013] The thickening agent can include a compound represented by one of the following Chemical Formula 1 to Chemical Formula 8:

[0014] [Chemical Formula 1]

[0015]

[0016] [Chemical Formula 2]

[0017]

[0018] [Chemical Formula 3]

[0019]

[0020] [Chemical Formula 4]

[0021]

[0022] [Chemical Formula 5]

[0023]

[0024] [Chemical Formula 6]

[0025]

[0026] [Chemical Formula 7]

[0027]

[0028] [Chemical Formula 8]

[0029]

[0030] wherein, in Chemical Formula 7 and Chemical Formula 8, n is an integer of 1 to 1000.

[0031] The thickening agent can form intermolecular hydrogen bonds with the light emitting element solvent and another thickening agent to form a network structure at a temperature of about 25°C.

[0032] The light emitting element ink can have a viscosity of about 20 cP to about 300 cP at a temperature of about 25°C.

[0033] The light emitting element ink can have a viscosity of about 5 cP to about 15 cP at a temperature of about 40°C to about 60°C.

[0034] The amount of the light emitting element can be about 0.01 parts by weight to about 1 parts by weight with respect to 100 parts by weight of the light emitting element ink, and the amount of the thickening agent can be about 5 parts by weight to about 50 parts by weight with respect to 100 parts by weight of the light emitting element ink.

[0035] The light emitting element ink can further include a dispersant dispersed in the light emitting element solvent, wherein the amount of the dispersant can be about 10 parts by weight to 100 parts by weight with respect to 100 parts by weight of the light emitting element.

[0036] The plurality of semiconductor layers of the light emitting element can include a first semiconductor layer, a second semiconductor layer, and a light emitting layer between the first semiconductor layer and the second semiconductor layer. The insulating film of the light emitting element can be disposed to surround at least an outer surface of the light emitting layer.

[0037] According to embodiments of the disclosure, a method of manufacturing a display device can include preparing a light emitting element ink including a light emitting element solvent, a plurality of light emitting elements, and a thickening agent, preparing a target substrate provided with a first electrode and a second electrode, jetting the light emitting element ink on the target substrate at a first temperature, forming an electric field on the target substrate to place the plurality of light emitting elements on the first electrode and the second electrode, and heating the light emitting element ink in a low pressure environment to remove the light emitting element solvent and the thickening agent.

[0038] The thickening agent of the light emitting element ink can include a polyol-based compound capable of forming intermolecular hydrogen bonds with the light emitting element solvent or another thickening agent.

[0039] The thickening agent can include a compound represented by one of the above Chemical Formula 1 to Chemical Formula 8.

[0040] The amount of the plurality of light emitting elements can be about 0.01 parts by weight to about 1 part by weight with respect to 100 parts by weight of the light emitting element ink, and the amount of the thickening agent can be about 100 parts by weight to about 500 parts by weight with respect to 100 parts by weight of the plurality of light emitting elements.

[0041] In the preparation of the light emitting element ink, the thickening agent can form an intermolecular hydrogen bond with the light emitting element solvent and another thickening agent to form a network structure.

[0042] In the preparation of the light emitting element ink, the light emitting element ink can have a viscosity of about 20 cP to about 300 cP at a temperature of about 25℃.

[0043] The jetting of the light emitting element ink can be performed through a printing process via an inkjet printing apparatus, and the light emitting element ink can be jetted through a nozzle on the target substrate at the first temperature higher than about 25℃.

[0044] In the jetting of the light emitting element ink, the first temperature can be about 40℃ to about 60℃, and the light emitting element ink can have a viscosity of about 5 cP to about 15 cP at the first temperature.

[0045] In the placing of the plurality of light emitting elements, the target substrate can be heat-treated at the first temperature or higher than the first temperature to form the electric field.

[0046] The removing of the light emitting element solvent and the thickening agent can be performed at a pressure of about 10 -4 tor to about 1 torr, and the first temperature can be about 25℃ to about 150℃.

[0047] In the placing of the plurality of light emitting elements, a first end portion of each of the plurality of light emitting elements can be disposed on the first electrode, and a second end portion of each of the plurality of light emitting elements can be disposed on the second electrode.

[0048] The plurality of light emitting elements can include a first semiconductor layer, a second semiconductor layer, an active layer between the first semiconductor layer and the second semiconductor layer, and an insulating film disposed to surround at least an outer surface of the active layer. BRIEF DESCRIPTION OF DRAWINGS

[0049] Embodiments of the present disclosure will be described in detail with reference to the attached drawings, on the basis of which the above and other aspects and features of the present disclosure will become apparent, in which:

[0050] Figure 1 is a schematic plan view of a display device according to an embodiment;

[0051] Figure 2 is a schematic plan view illustrating a pixel of a display device according to an embodiment;

[0052] Figure 3 is a schematic cross-sectional view taken along Figure 2 line Q1-Q1', line Q2-Q2', and line Q3-Q3' of the light-emitting element of

[0053] Figure 4 is a schematic perspective view of a light-emitting element according to an embodiment;

[0054] Figure 5 and Figure 6 are schematic perspective views of light-emitting elements according to other embodiments;

[0055] Figure 7 is a schematic perspective view of a light-emitting element ink according to an embodiment;

[0056] Figure 8 is a schematic view illustrating intermolecular hydrogen bonds between a thickening agent and a light-emitting element solvent in a light-emitting element ink of Figure 7 at room temperature;

[0057] Figure 9 is a schematic view illustrating intermolecular hydrogen bonds between a thickening agent and a light-emitting element solvent in a light-emitting element ink of Figure 7 at another temperature;

[0058] Figure 10 is a schematic flowchart illustrating a method of manufacturing a display device according to an embodiment;

[0059] Figures 11 to 13 is a schematic cross-sectional view illustrating a step in a process of manufacturing a display device according to an embodiment;

[0060] Figure 14 is a graph illustrating a change in viscosity of a light-emitting element ink according to temperature;

[0061] Figures 15 to 17 is a schematic cross-sectional view illustrating another step in a process of manufacturing a display device according to an embodiment;

[0062] Figure 18 is a schematic cross-sectional view illustrating a step in a process of manufacturing a display device according to another embodiment; and

[0063] Figure 19 is a schematic cross-sectional view illustrating a step in a process of manufacturing a display device according to another embodiment. DETAILED DESCRIPTION

[0064] The present disclosure will now be described more fully with reference to the accompanying drawings, in which some embodiments of the present disclosure are illustrated. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0065] In the specification and claims, the expression "at least one of... " is intended to include the meaning of "at least one selected from the group consisting of... " For example, "at least one of A and B" can be interpreted to mean "A, B, or A and B."

[0066] Unless otherwise defined or implied herein, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It should further be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0067] It will also be understood that when a layer is referred to as being "on" another layer or substrate, it can be directly on the other layer or substrate, or intervening layers can also be present. Same reference numerals refer to same components throughout the specification.

[0068] It will be understood that, although the terms "first", "second", etc. can be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element discussed below could be termed a second element without departing from the teachings of the present disclosure. Similarly, a second element could be termed a first element.

[0069] In the following, embodiments of the present disclosure will be described with reference to the drawings.

[0070] Figure 1 is a schematic plan view of a display device according to an embodiment.

[0071] Reference Figure 1The display device 10 can display a moving image or a still image. The display device 10 can refer to any electronic device that provides a display screen. For example, the display device 10 can be used in a television, a laptop computer, a monitor, a billboard, an Internet of Things device, a mobile phone, a smart phone, a tablet personal computer (PC), an electronic watch, a smart watch, a watch phone, a head-mounted display, a mobile communication terminal, an electronic notebook, an electronic book, a portable multimedia player (PMP), a navigation system, a game console, a digital camera, a camcorder, etc.

[0072] The display device 10 can include a display panel for providing a display screen. Examples of the display panel can include an inorganic light emitting diode display panel, an organic light emitting display panel, a quantum dot light emitting display panel, a plasma display panel, and a field emission display panel. Hereinafter, the inorganic light emitting diode display panel can be used as an example of the display panel, but the present disclosure is not limited thereto. Any display panel can be used as the display panel as long as the same technical idea is applicable.

[0073] The shape of the display device 10 can be variously modified. For example, the display device 10 can have a shape such as a rectangle having a longer horizontal side, a rectangle having a longer vertical side, a square, a rectangle having a rounded corner (apex), another polygon, or a circle. The shape of the display area DPA of the display device 10 can also be similar to the overall shape of the display device 10. Figure 1 The display device 10 and the display area DPA each having a rectangular shape having a longer horizontal side are exemplified.

[0074] The display device 10 can include a display area DPA and a non-display area NDA. The display area DPA can be an area in which an image can be displayed, and the non-display area NDA can be an area in which an image is not displayed. The display area DPA can be referred to as an active area, and the non-display area NDA can be referred to as an inactive area. The display area DPA can generally occupy the center of the display device 10.

[0075] The display area DPA can include pixels PX. The pixels PX can be arranged in a matrix direction. Each of the pixels PX can have a rectangular shape or a square shape in a plan view, but the shape thereof is not limited thereto. Each of the pixels PX can have a diamond shape in which each side is inclined with respect to one direction. The respective pixels PX can be alternately arranged in a stripe type or a mosaic type. Each of the pixels PX can include at least one light emitting element 30 (see Figure 2 ) that emits light of a specific wavelength band to display a specific color.

[0076] A non-display area NDA can be disposed around the display area DPA. The non-display area NDA can completely or partially surround the display area DPA. The display area DPA can have a rectangular shape, and the non-display area NDA can be disposed adjacent to four sides of the display area DPA. The non-display area NDA can form (or constitute) a bezel of the display device 10. Wires or circuit drivers included in the display device 10 can be disposed in the non-display area NDA, or external devices can be mounted in the non-display area NDA.

[0077] Figure 2 is a schematic plan view illustrating a pixel of a display device according to an embodiment.

[0078] Referring to Figure 2 Each of the pixels PX can include a sub-pixel PXn (where n is an integer of 1 to 3). For example, the pixel PX can include a first sub-pixel PX1, a second sub-pixel PX2, and a third sub-pixel PX3. The first sub-pixel PX1 can emit light of a first color, the second sub-pixel PX2 can emit light of a second color, and the third sub-pixel PX3 can emit light of a third color. For example, the first color can be blue, the second color can be green, and the third color can be red. However, the disclosure is not limited thereto, and each of the sub-pixels PXn can emit light of the same color. Although Figure 2 Although the pixel PX is illustrated as including three sub-pixels PXn, the disclosure is not limited thereto, and the pixel PX can include a greater number of sub-pixels PXn.

[0079] Each of the sub-pixels PXn of the display device 10 can include a light emitting area EMA and a non-light emitting area (not shown). The light emitting area EMA can be defined as an area in which the light emitting element 30 is disposed to emit light of a specific wavelength band, and the non-light emitting area can be defined as an area in which the light emitting element 30 is not disposed and light rays emitted from the light emitting element 30 cannot reach, such that no light is emitted therefrom. The light emitting area EMA can include an area in which the light emitting element 30 is disposed, and an area adjacent thereto to emit light emitted from the light emitting element 30.

[0080] However, the disclosure is not limited thereto, and the light emitting area can further include an area in which light emitted from the light emitting element 30 is reflected or refracted by another member and then emitted. The light emitting element 30 can be arranged in each of the sub-pixels PXn, and an area in which the light emitting element 30 is arranged and an area adjacent thereto can form the light emitting area EMA.

[0081] Each of the sub-pixels PXn can include a cutout region CBA disposed in the non-light emitting region. The cutout region CBA can be disposed at one side of the light emitting region EMA in the second direction DR2. The cutout region CBA can be disposed between the light emitting regions EMA of adjacent sub-pixels PXn in the second direction DR2. The plurality of light emitting regions EMA and the plurality of cutout regions CBA can be arranged in the display area DPA of the display device 10. For example, the light emitting regions EMA and the cutout regions CBA can be repeatedly arranged in the first direction DR1, respectively, and can be alternately arranged in the second direction DR2. A distance between the cutout regions CBA spaced apart from each other in the first direction DR1 can be smaller than a distance between the light emitting regions EMA spaced apart from each other in the first direction DR1. The second blocks BNL2 can be disposed between the cutout regions CBA and the light emitting regions EMA, and a distance therebetween can vary depending on a width of the second blocks BNL2. Since the light emitting elements 30 are not disposed in the cutout regions CBA, no light is emitted therefrom, but some of the electrodes (21 and 22) disposed in each of the sub-pixels PXn can be disposed in the cutout regions CBA. The electrodes (21 and 22) disposed for each of the sub-pixels PXn can be disposed separately from each other in the cutout regions CBA.

[0082] Figure 3 is a schematic cross-sectional view taken along Figure 2 lines Q1-Q1', line Q2-Q2', and line Q3-Q3'. Figure 3 illustrates a cross-section of an end portion of the light emitting element 30 disposed in the first sub-pixel PX1 across Figure 2

[0083] Referring to Figure 3 and Figure 2 The display device 10 can include a first substrate 11, and a semiconductor layer, a conductive layer, and an insulating layer disposed on the first substrate 11. The semiconductor layer, the conductive layer, and the insulating layer can form a circuit layer and a light emitting element layer of the display device 10.

[0084] The first substrate 11 can be an insulating substrate. The first substrate 11 can be made of an insulating material such as glass, quartz, or a polymer resin. The first substrate 11 can be a rigid substrate, but can also be a flexible substrate capable of being bent, folded, curled, etc.

[0085] ​A light-blocking layer BML can be provided on the first substrate 11. The light-blocking layer BML is provided so as to overlap the active layer ACT1 of the first transistor T1. The active layer ACT1 can include a first region ACT_a, a second region ACT_b, and a channel region ACT_c. The light-blocking layer BML can include a material that blocks light, thereby preventing light from entering the active layer ACT1 of the first transistor T1. For example, the light-blocking layer BML can be formed of an opaque metal material that blocks transmission of light. However, the present disclosure is not limited thereto. For example, the light-blocking layer BML can be omitted.

[0086] The buffer layer 12 can be provided entirely on the first substrate 11. For example, the buffer layer 12 can be provided so as to cover or overlap the light-blocking layer BML and the upper surface of the first substrate 11. The buffer layer 12 can be formed on the first substrate 11 to protect the first transistor T1 of the pixel PX from moisture permeating through the first substrate 11, which is susceptible to moisture permeation, and can perform a surface planarization function.

[0087] The active layer ACT1 can be provided on the buffer layer 12. The active layer ACT1 can be provided so as to partially overlap the gate electrode G1 or the first conductive layer to be described below.

[0088] In the drawings, only the first transistor T1 included in the transistor in the sub-pixel PXn of the display device 10 is illustrated, but the present disclosure is not limited thereto. The display device 10 can include a larger number of transistors. For example, for each sub-pixel PXn, the display device 10 can include two or three transistors, including one or more transistors in addition to the first transistor T1.

[0089] The active layer ACT1 can include polycrystalline silicon, single-crystal silicon, or an oxide semiconductor. In the case where the active layer ACT1 includes an oxide semiconductor, the active layer ACT1 can include a conductive region and a channel region therebetween. The oxide semiconductor can be an oxide semiconductor containing indium (In). For example, the oxide semiconductor can be indium tin oxide (ITO), indium zinc oxide (IZO), indium gallium oxide (IGO), indium zinc tin oxide (IZTO), indium gallium tin oxide (IGTO), indium gallium zinc oxide (IGZO), or indium gallium zinc tin oxide (IGZTO).

[0090] In another embodiment, the active layer ACT1 can include polycrystalline silicon. The polycrystalline silicon can be formed by crystallizing amorphous silicon, and in this case, the conductive regions of the active layer ACT1 can be regions respectively doped with impurities.

[0091] A first gate insulating layer 13 can be disposed on the active layer ACT1 and the buffer layer 12. For example, the first gate insulating layer 13 can be disposed to completely cover or overlap the active layer ACT1 and the buffer layer 12. The first gate insulating layer 13 can function as a gate insulating film of each transistor.

[0092] A first conductive layer can be disposed on the first gate insulating layer 13. The first conductive layer can include a gate electrode G1 of the first transistor T1 and a first capacitor electrode CSE1 of a storage capacitor. The gate electrode G1 can be disposed to overlap a channel region ACT_c of the active layer ACT1 in a thickness direction. The first capacitor electrode CSE1 can be disposed to overlap a second capacitor electrode CSE2, which will be described below, in the thickness direction. In an embodiment, the first capacitor electrode CSE1 can be integrated with the gate electrode G1. The first capacitor electrode CSE1 can be disposed to overlap the second capacitor electrode CSE2 in the thickness direction, and a storage capacitor can be formed therebetween.

[0093] A first interlayer insulating layer 15 can be disposed on the first conductive layer. The first interlayer insulating layer 15 can function as an insulating film between the first conductive layer and other layers disposed thereon. The first interlayer insulating layer 15 can be disposed to overlap the first conductive layer to perform a function of protecting the first conductive layer.

[0094] A second conductive layer can be disposed on the first interlayer insulating layer 15. The second conductive layer can include a first source electrode S1 and a first drain electrode D1 of the first transistor T1, a data line DTL, and a second capacitor electrode CSE2.

[0095] The first source electrode S1 and the first drain electrode D1 of the first transistor T1 can contact a doped region of the active layer ACT1 through contact holes that penetrate the first interlayer insulating layer 15 and the first gate insulating layer 13, respectively. In addition, the first source electrode S1 of the first transistor T1 can contact the photoresist blocking layer BML through another contact hole.

[0096] The data line DTL can apply a data signal to another transistor (not shown) included in the display device 10. Although not shown in the drawings, the data line DTL can be electrically connected to a source / drain electrode of the other transistor to transmit a signal applied from the data line DTL.

[0097] The second capacitor electrode CSE2 can be disposed to overlap the first capacitor electrode CSE1 in the thickness direction. In an embodiment, the second capacitor electrode CSE2 can be integrated with and / or electrically connected to the first source electrode S1.

[0098] A second interlayer insulating layer 17 can be disposed on the second conductive layer. The second interlayer insulating layer 17 can function as an insulating film between the second conductive layer and other layers disposed thereon. The second interlayer insulating layer 17 can be disposed to overlap the second conductive layer to perform a function of protecting the second conductive layer.

[0099] A third conductive layer can be disposed on the second interlayer insulating layer 17. The third conductive layer can include a first voltage line VL1, a second voltage line VL2, and a first conductive pattern CDP. A high potential voltage (or a first power voltage) supplied to the first transistor T1 can be applied to the first voltage line VL1, and a low potential voltage (or a second power voltage) supplied to the second electrode 22 can be applied to the second voltage line VL2. An alignment signal necessary to align the light emitting element 30 during a process of manufacturing the display device 10 can be applied to the second voltage line VL2.

[0100] The first conductive pattern CDP can be electrically connected to the second capacitor electrode CSE2 through a contact hole formed in the second interlayer insulating layer 17. The second capacitor electrode CSE2 can be integrated with the first source electrode S1 of the first transistor T1, and the first conductive pattern CDP can be electrically connected to the first source electrode S1. The first conductive pattern CDP can contact the first electrode 21, which will be described below, and the first transistor T1 can transmit the first power voltage applied from the first voltage line VL1 to the first electrode 21 through the first conductive pattern CDP. Although it is shown in the drawings that the third conductive layer includes one second voltage line VL2 and one first voltage line VL1, the present disclosure is not limited thereto. The third conductive layer can include a greater number of first voltage lines VL1 and a greater number of second voltage lines VL2.

[0101] Each of the buffer layer 12, the first gate insulating layer 13, the first interlayer insulating layer 15, the second interlayer insulating layer 17, and the third interlayer insulating layer can be formed of inorganic layers alternately stacked. For example, each of the buffer layer 12, the first gate insulating layer 13, the first interlayer insulating layer 15, and the second interlayer insulating layer 17 can be formed as a bilayer in which the inorganic layers each contain at least one of silicon oxide (SiO x ), silicon nitride (SiN x ), and silicon oxynitride (SiO x N y ), or as a plurality of layers in which these inorganic layers are alternately stacked. As another example, each of the above layers can also be formed of inorganic layers.

[0102] A first planarization layer 19 can be disposed on the third conductive layer. The first planarization layer 19 can contain an organic insulating material, for example, an organic material such as polyimide (PI), to perform a surface planarization function.

[0103] The first block BNL1, the electrodes (21 and 22), the light emitting element 30, the contact electrodes (CNE1 and CNE2), and the second block BNL2 can be disposed on the first planarization layer 19. Further, the insulating layers (PAS1, PAS2, PAS3, and PAS4) can be provided on the first planarization layer 19.

[0104] The first block BNL1 can be directly provided on the first planarization layer 19. The first block BNL1 can have a shape having a predetermined width and extending in the second direction DR2 within each sub-pixel PXn but can not extend to another adjacent sub-pixel PXn in the second direction DR2, and can be disposed in the light emitting area EMA. The first blocks BNL1 can be spaced apart from each other in the first direction DR1.

[0105] The first block BNL1 can be provided in the sub-pixel PXn. Although two first blocks BNL1 are shown to be provided for each sub-pixel PXn to form a linear pattern in the display area DPA in the drawings, the disclosure is not limited thereto. A greater number of first blocks BNL1 can be disposed depending on the number of electrodes (21 and 22). The number of first blocks BNL1 can vary depending on the number of electrodes (21 and 22) and the arrangement of the light emitting element 30, or the first blocks BNL1 can have different shapes to form an island pattern.

[0106] The first block BNL1 can have a structure in which at least a portion of the first block BNL1 protrudes from the upper surface of the first planarization layer 19. The protruding portion of the first block BNL1 can have an inclined side surface, and light emitted from the light emitting element 30 can be reflected by the electrodes (21 and 22) provided on the first block BNL1 and emitted in the upward direction of the first planarization layer 19. The first block BNL1 can provide an area in which the light emitting element 30 is disposed, and can function as a reflection barrier that reflects light emitted from the light emitting element 30 in the upward direction. The side surface of the first block BNL1 can be inclined in a linear shape, but is not limited thereto. For example, the first block BNL1 can have a curved semicircular or semi-elliptical shape. The first block BNL1 can contain an organic insulating material such as polyimide (PI), but the material thereof is not limited thereto. The first block BNL1 can be omitted.

[0107] The electrodes (21 and 22) can have a shape extending in one direction, and can be provided for each sub-pixel PXn. The electrodes (21 and 22) can extend in the second direction DR2, and can be provided to be spaced apart from each other in the first direction DR1. For example, the first electrode 21 and the second electrode 22 spaced apart from the first electrode 21 in the first direction DR1 can be provided in the sub-pixel PXn. However, the disclosure is not limited thereto, and the positions of the electrodes (21 and 22) provided in each sub-pixel PXn can vary depending on the number of electrodes provided in each sub-pixel PXn or the number of light emitting elements 30.

[0108] The first electrode 21 and the second electrode 22 can be provided in the light emitting area EMA of each sub-pixel PXn, and a portion thereof can be provided to overlap the second block BNL2 in the thickness direction beyond the light emitting area EMA. The electrodes (21 and 22) can extend in the second direction DR2 within the sub-pixel PXn, and can be spaced apart from the electrodes (21 and 22) of another sub-pixel PXn in the second direction DR2 in the cutting area CBA.

[0109] Each of the first electrode 21 and the second electrode 22 can extend in the second direction DR2 within the sub-pixel PXn, and can be separated from the other electrodes (21 and 22) in the cutting area CBA. For example, the cutting area CBA can be provided between the light emitting areas EMA of the sub-pixels PXn adjacent in the second direction DR2, and the first electrode 21 and the second electrode 22 can be separated from the other first electrode 21 and the second electrode 22 provided in the sub-pixel PXn adjacent in the second direction DR2 in the cutting area CBA. However, the disclosure is not limited thereto. For example, for each sub-pixel PXn, some of the electrodes (21 and 22) can be provided to extend beyond the sub-pixel PXn adjacent in the second direction DR2 without being separated from each other, or only one of the first electrode 21 and the second electrode 22 can be separated.

[0110] In the arrangement of the electrodes (21 and 22), electrode lines extending in the second direction DR2 can be formed, and then separated from each other in a subsequent process after the light emitting elements 30 are arranged. During the process of manufacturing the display device 10, the electrode lines can be used to generate an electric field in the sub-pixel PXn in order to align the light emitting elements 30. For example, in the case where the light emitting elements 30 are sprayed on the electrode lines by an inkjet printing process or the ink containing the light emitting elements 30 is sprayed on the electrode lines, an alignment signal can be applied to the electrode lines to generate an electric field. The light emitting elements 30 dispersed in the ink can be arranged on the electrodes (21 and 22) by receiving a dielectrophoretic force through the generated electric field. After the light emitting elements 30 are arranged, some of the electrode lines can be separated from each other to form the electrodes (21 and 22) separated in each sub-pixel PXn.

[0111] The electrodes (21 and 22) can be electrically connected to the third conductive layer so that a signal allowing the light emitting element 30 to emit light can be applied. The first electrode 21 can electrically contact the first conductive pattern CDP through a first contact hole CT1 that penetrates the first planarization layer 19 under the first electrode 21. The second electrode 22 can electrically contact the second voltage line VL2 through a second contact hole CT2 that penetrates the first planarization layer 19 under the second electrode 22. The first electrode 21 can be electrically connected to the first transistor T1 through the first conductive pattern CDP to apply a first power voltage, and the second electrode 22 can be electrically connected to the second voltage line VL2 to apply a second power voltage.

[0112] The electrodes (21 and 22) can be electrically connected to the light emitting element 30. Each of the electrodes (21 and 22) can be electrically connected to an end portion of the light emitting element 30 through the contact electrodes (CNE1 and CNE2) to be described below, and can transmit an electrical signal applied from the third conductive layer to the light emitting element 30. Since the electrodes (21 and 22) are separately disposed in each sub-pixel PXn, the light emitting elements 30 of different sub-pixels PXn can individually emit light.

[0113] Although the first contact hole CT1 and the second contact hole CT2 are illustrated as being formed at positions overlapping the second blocks BNL2 in the drawings, the disclosure is not limited thereto. For example, each of the contact holes (CT1 and CT2) can be located in the light emitting area EMA surrounded by the second blocks BNL2.

[0114] The electrodes (21 and 22) disposed in each sub-pixel PXn can be disposed on the first blocks BNL1 spaced apart from each other. Each of the electrodes (21 and 22) can be disposed on a side surface of the first blocks BNL1 inclined in the first direction DR1. In an embodiment, a width of the electrodes (21 and 22) measured in the first direction DR1 can be less than a width of the first blocks BNL1 measured in the first direction DR1. Each of the electrodes (21 and 22) can be disposed to overlap at least one side of the first blocks BNL1 to reflect light emitted from the light emitting element 30.

[0115] A distance between the electrodes (21 and 22) spaced apart from each other in the first direction DR1 can be less than a distance between the first blocks BNL1. Each of the electrodes (21 and 22) can have at least some regions disposed directly on the third interlayer insulating layer so that the electrodes (21 and 22) can be disposed on the same plane or layer.

[0116] Each of the electrodes (21 and 22) can include a conductive material having high reflectivity. For example, each of the electrodes (21 and 22) can include a metal such as silver (Ag), copper (Cu), or aluminum (Al) as a conductive material having high reflectivity, or can include an alloy containing aluminum (Al), nickel (Ni), or lanthanum (La). Each of the electrodes (21 and 22) can reflect light emitted from the light emitting element 30 and advancing to a side surface of the first block BNL1 in an upward direction of each sub-pixel PXn.

[0117] However, the disclosure is not limited thereto, and each of the electrodes (21 and 22) can further include a transparent conductive material. For example, each of the electrodes (21 and 22) can include a material such as indium tin oxide (ITO), indium zinc oxide (IZO), or indium tin zinc oxide (ITZO). In some embodiments, each of the electrodes (21 and 22) can have a structure in which one or more layers of a transparent conductive material and one or more layers of a metal having high reflectivity are stacked, or can be formed to include layers thereof. For example, each of the electrodes (21 and 22) can have a stacked structure of ITO / Ag / ITO, ITO / Ag / IZO, or ITO / Ag / ITZO / IZO.

[0118] The first insulating layer PAS1 can be disposed on the electrodes (21 and 22) and the first block BNL1. The first insulating layer PAS1 can be disposed to overlap the first block BNL1 as well as the first electrode 21 and the second electrode 22, and can be disposed to expose a portion of an upper surface of the first electrode 21 and a portion of an upper surface of the second electrode 22. An opening OP can be formed to expose a portion of an upper surface of the electrodes (21 and 22) disposed on the first block BNL1, and contact electrodes (CNE1 and CNE2) can electrically contact the electrodes (21 and 22) through the opening OP.

[0119] In an embodiment, a step or a height difference can be formed in the first insulating layer PAS1 so that a portion of an upper surface of the first insulating layer PAS1 is recessed between the first electrode 21 and the second electrode 22. When the first insulating layer PAS1 is disposed to cover or overlap the first electrode 21 and the second electrode 22, the first insulating layer PAS1 can have a height difference between the first electrode 21 and the second electrode 22. However, the disclosure is not limited thereto. The first insulating layer PAS1 can protect the first electrode 21 and the second electrode 22 and insulate them from each other. In addition, the first insulating layer PAS1 can prevent the light emitting element 30 disposed on the first insulating layer PAS1 from being damaged by direct contact with other members.

[0120] The second blocks BNL2 can be disposed on the first insulating layer PAS1. The second blocks BNL2 can be disposed in a grid pattern on the entire surface of the display area DPA while including portions extending in the first direction DR1 and the second direction DR2 on the plane (or layer). The second blocks BNL2 can be disposed over the boundaries between the respective sub-pixels PXn to distinguish adjacent sub-pixels PXn. Also, the second blocks BNL2 can be disposed to surround the light emitting areas EMA and the cut areas CBA disposed in each sub-pixel PXn to distinguish the light emitting areas EMA and the cut areas CBA. In the portions of the second blocks BNL2 extending in the second direction DR2, the portions disposed between the light emitting areas EMA can have a greater width than the portions disposed between the cut areas CBA. Accordingly, the distance between the cut areas CBA can be less than the distance between the light emitting areas EMA.

[0121] The second blocks BNL2 can be formed to have a greater height than the height of the first blocks BNL1. In an inkjet printing process of a process of manufacturing the display device 10, the second blocks BNL2 can prevent ink from spilling to adjacent sub-pixels PXn so that the ink in which different light emitting elements 30 are dispersed for each sub-pixel PXn can be separated from each other without being mixed with each other. Similar to the first blocks BNL1, the second blocks BNL2 can include polyimide (PI), but the material thereof is not limited thereto.

[0122] The light emitting elements 30 can be disposed on the first insulating layer PAS1. The light emitting elements 30 can be arranged to be spaced apart from each other in the second direction DR2 in which the electrodes (21 and 22) extend, and can be aligned substantially in parallel to each other. The light emitting elements 30 can have a shape extending in one direction. The direction in which each of the electrodes (21 and 22) extends can be substantially perpendicular to the direction in which the light emitting elements 30 extend. However, the disclosure is not limited thereto. For example, the light emitting elements 30 can be disposed obliquely at a predetermined angle so that they do not extend perpendicular to the direction in which each of the electrodes (21 and 22) extends.

[0123] The light emitting elements 30 can include a semiconductor layer doped with a dopant of a different conduction type. The light emitting elements 30 can include a semiconductor layer and can be aligned so that the end portions of the light emitting elements 30 face a certain direction according to the direction of an electric field generated on the electrodes (21 and 22). The light emitting elements 30 can include a light emitting layer 36 (see Figure 4 ) to emit light of a certain wavelength band. The light emitting elements 30 disposed in each sub-pixel PXn can emit light of different wavelength bands according to the material forming the light emitting layer 36. However, the disclosure is not limited thereto. For example, the light emitting elements 30 disposed in each of the sub-pixels PXn can emit light of the same color.

[0124] The light emitting element 30 can be provided with layers in a direction perpendicular to the upper surface of the first substrate 11. The light emitting element 30 of the display device 10 can be disposed such that its extension direction is parallel to the upper surface of the first substrate 11, and the semiconductor layers included in the light emitting element 30 can be arranged in order in a direction parallel to the upper surface of the first substrate 11. However, the present disclosure is not limited thereto. In some cases, in a case where the light emitting element 30 has a different structure, the semiconductor layers can be arranged in a direction perpendicular to the upper surface of the first substrate 11.

[0125] The light emitting element 30 can be disposed on each of the electrodes (21 and 22) between the first blocks BNL1. For example, the light emitting element 30 can be disposed such that one end portion thereof is placed on the first electrode 21 and the other end portion thereof is placed on the second electrode 22. The light emitting element 30 can have an elongated length greater than a distance between the first electrode 21 and the second electrode 22, and both end portions of the light emitting element 30 can be disposed on the first electrode 21 and the second electrode 22.

[0126] Both end portions of the light emitting element 30 can electrically contact the contact electrodes (CNE1 and CNE2), respectively. Since the light emitting element 30 can not be provided with the insulating film 38 (see FIG. 4) on the end surface in one direction, and a portion of the semiconductor layers can be exposed, the exposed semiconductor layers can contact the contact electrodes (CNE1 and CNE2). However, the present disclosure is not limited thereto. In some cases, at least a portion of the insulating film 38 can be removed such that the side surface of the end portion of the semiconductor layers can be partially exposed. The exposed side surface of the semiconductor layers can directly contact the contact electrodes (CNE1 and CNE2). Figure 4

[0127] The second insulating layer PAS2 can be partially disposed on the first insulating layer PAS1 and the light emitting element 30. For example, the second insulating layer PAS2 can be disposed to partially surround the outer surface of the light emitting element 30 without covering or overlapping both end portions of the light emitting element 30. During a process of manufacturing the display device 10, the shape of the second insulating layer PAS2 can be formed by a process of placing the second insulating layer PAS2 completely on the first insulating layer PAS1 and then removing the second insulating layer PAS2 to expose both end portions of the light emitting element 30.

[0128] ​A portion of the second insulating layer PAS2 provided on the light emitting element 30 can be provided to extend on the first insulating layer PAS1 in the second direction DR2 on the plane (or layer), thereby forming a linear or island-like pattern in each sub-pixel PXn. The second insulating layer PAS2 can protect and fix the light emitting element 30 in the process of manufacturing the display device 10. The second insulating layer PAS2 can be provided to fill a space between the light emitting element 30 and the first insulating layer PAS1 under the light emitting element 30.

[0129] The contact electrodes (CNE1 and CNE2) and the third insulating layer PAS3 can be provided on the second insulating layer PAS2. The first contact electrode CNE1 and the second contact electrode CNE2 of the contact electrodes (CNE1 and CNE2) can be provided on a portion of the first electrode 21 and a portion of the second electrode 22, respectively. The first contact electrode CNE1 can be provided on the first electrode 21, the second contact electrode CNE2 can be provided on the second electrode 22, and each of the first contact electrode CNE1 and the second contact electrode CNE2 can have a shape extending in the second direction DR2. The first contact electrode CNE1 and the second contact electrode CNE2 can be spaced apart from each other in the first direction DR1 and can form a linear pattern in the light emitting area EMA of each sub-pixel PXn.

[0130] Each of the contact electrodes (CNE1 and CNE2) can electrically contact the light emitting element 30 and the electrodes (21 and 22). In the light emitting element 30, the semiconductor layer is exposed on both end surfaces in the extension direction, and the first contact electrode CNE1 and the second contact electrode CNE2 can electrically contact the light emitting element 30 on the end surface in which the semiconductor layer is exposed. An end portion of the light emitting element 30 can be electrically connected to the first electrode 21 through the first contact electrode CNE1, and the other end portion thereof can be electrically connected to the second electrode 22 through the second contact electrode CNE2.

[0131] Although the first contact electrode CNE1 and the second contact electrode CNE2 are shown to be provided in the sub-pixel PXn in the drawings, the disclosure is not limited thereto. The number of the first contact electrode CNE1 and the second contact electrode CNE2 can vary depending on the number of the electrodes (21 and 22) provided in each sub-pixel PXn.

[0132] The contact electrodes (CNE1 and CNE2) can include a conductive material. For example, the contact electrodes (CNE1 and CNE2) can include ITO, IZO, ITZO, or aluminum (Al). Light emitted from the light emitting element 30 can pass through the contact electrodes (CNE1 and CNE2) and advance toward the electrodes (21 and 22). However, the disclosure is not limited thereto.

[0133] The third insulating layer PAS3 can be provided between the first contact electrode CNE1 and the second contact electrode CNE2. The third insulating layer PAS3 can also be provided on the first contact electrode CNE1 and the second insulating layer PAS2, except for the area in which the second contact electrode CNE2 is provided. The third insulating layer PAS3 can insulate the first contact electrode CNE1 and the second contact electrode CNE2 from each other, such that they do not directly contact each other. For example, in an embodiment, the first contact electrode CNE1 and the second contact electrode CNE2 can be provided on different layers. The first contact electrode CNE1 can be directly provided on the second insulating layer PAS2, and the second contact electrode CNE2 can be directly provided on the third insulating layer PAS3.

[0134] Although the third insulating layer PAS3 is provided between the first contact electrode CNE1 and the second contact electrode CNE2 to insulate them from each other as described above, the third insulating layer PAS3 can be omitted. In these cases, the first contact electrode CNE1 and the second contact electrode CNE2 can be provided on the same layer.

[0135] The fourth insulating layer PAS4 can be entirely provided on the display area DPA of the first substrate 11. The fourth insulating layer PAS4 can function to protect the members provided on the first substrate 11 from the external environment. However, the fourth insulating layer PAS4 can be omitted.

[0136] Each of the first insulating layer PAS1, the second insulating layer PAS2, the third insulating layer PAS3, and the fourth insulating layer PAS4 described above can include an inorganic insulating material or an organic insulating material. For example, each of the first insulating layer PAS1, the second insulating layer PAS2, the third insulating layer PAS3, and the fourth insulating layer PAS4 can include an inorganic insulating layer, such as silicon oxide (SiO x ), silicon nitride (SiN x ), silicon oxynitride (SiO x N y ), aluminum oxide (Al2O3), or aluminum nitride (AlN x ). As another example, each of the first insulating layer PAS1, the second insulating layer PAS2, the third insulating layer PAS3, and the fourth insulating layer PAS4 can include an organic insulating layer, such as an acrylic resin, an epoxy resin, a phenol resin, a polyamide resin, a polyimide resin, an unsaturated polyester resin, a polyphenylene resin, a polyphenylene sulfide resin, a benzocyclobutene resin, a cardo resin, a siloxane resin, a silsesquioxane resin, a polymethyl methacrylate, a polycarbonate, or a polymethyl methacrylate-polycarbonate synthetic resin. However, the present disclosure is not limited thereto.

[0137] Figure 4is a schematic perspective view of a light emitting element according to an embodiment.

[0138] The light emitting element 30 can be a light emitting diode. Specifically, the light emitting element 30 can be an inorganic light emitting diode having a size of micrometers or nanometers and being made of an inorganic material. In a case where an electric field is formed between two electrodes facing each other in a predetermined direction, an organic light emitting diode can be aligned between the two electrodes having polarity. The light emitting element 30 can be aligned between the two electrodes by an electric field formed on the two electrodes.

[0139] The light emitting element 30 can have a shape extending in one direction. The light emitting element 30 can have a shape of a cylinder, a rod, a wire, or a tube. However, the shape of the light emitting element 30 is not limited thereto, and the light emitting element 30 can have various shapes, such as a cube, a cuboid, or a hexagonal cylinder, or can have a shape extending in one direction and having a partially inclined outer surface. The semiconductor layers included in the light emitting element 30, which will be described below, can be arranged or stacked in one direction in order.

[0140] The light emitting element 30 can include a semiconductor layer doped with an impurity of any conduction type, for example, a p-type or an n-type. The semiconductor layer can receive an electrical signal applied by an external power source and emit light of a specific wavelength band.

[0141] Referring to Figure 4 , the light emitting element 30 can include a first semiconductor layer 31, a second semiconductor layer 32, a light emitting layer 36, an electrode layer 37, and an insulating film 38.

[0142] The first semiconductor layer 31 can be an n-type semiconductor layer. In a case where the light emitting element 30 emits light of a blue wavelength band, the first semiconductor layer 31 can include at least one of AlGaInN, GaN, AlGaN, InGaN, AlN, and InN each doped with an n-type impurity. The first semiconductor layer 31 can be doped with an n-type dopant. The n-type dopant can be Si, Ge, or Sn. For example, the first semiconductor layer 31 can include n-GaN doped with n-type Si. The length of the first semiconductor layer 31 can be about 1.5 µm to about 5 µm, but is not limited thereto. x Ga y In 1-x-y N (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ x + y ≤ 1). For example, the semiconductor material can be at least one of AlGaInN, GaN, AlGaN, InGaN, AlN, and InN each doped with an n-type impurity. The first semiconductor layer 31 can be doped with an n-type dopant. The n-type dopant can be Si, Ge, or Sn. For example, the first semiconductor layer 31 can include n-GaN doped with n-type Si. The length of the first semiconductor layer 31 can be about 1.5 µm to about 5 µm, but is not limited thereto.

[0143] The second semiconductor layer 32 can be disposed on the light emitting layer 36, which will be described below. The second semiconductor layer 32 can be a p-type semiconductor layer. In a case where the light emitting element 30 emits light of a blue wavelength band or a green wavelength band, the second semiconductor layer 32 can include at least one of AlGaInN, GaN, AlGaN, InGaN, AlN, and InN each doped with a p-type impurity. The second semiconductor layer 32 can be doped with a p-type dopant. The p-type dopant can be Mg, Zn, or Cd. For example, the second semiconductor layer 32 can include p-GaN doped with p-type Mg. The length of the second semiconductor layer 32 can be about 1.5 µm to about 5 µm, but is not limited thereto. xGa y In 1-x-y semiconductor material of a chemical formula of Ga x Al y In z N (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ x + y + z ≤ 1). For example, the semiconductor material can be at least one of AlGaInN, GaN, AlGaN, InGaN, AlN, and InN each doped with a p-type impurity. The second semiconductor layer 32 can be doped with a p-type dopant. The p-type dopant can be Mg, Zn, Ca, Se, or Ba. For example, the second semiconductor layer 32 can include p-GaN doped with a p-type Mg. The length of the second semiconductor layer 32 can be about 0.05 µm to about 1.10 µm, but is not limited thereto.

[0144] Although each of the first semiconductor layer 31 and the second semiconductor layer 32 is shown as being formed as one layer in Figure 4 , the present disclosure is not limited thereto. Each of the first semiconductor layer 31 and the second semiconductor layer 32 can further include a greater number of layers, for example, a cladding layer or a tensile-strained barrier reduction (TSBR) layer according to the material of the light emitting layer 36.

[0145] The light emitting layer 36 can be disposed between the first semiconductor layer 31 and the second semiconductor layer 32. The light emitting layer 36 can include a material of a single quantum well structure or a multi-quantum well structure. In the case where the light emitting layer 36 includes a material of a multi-quantum well structure, the light emitting layer 36 can have a structure in which quantum layers and well layers are alternately stacked. The light emitting layer 36 can emit light by recombination of electron-hole pairs according to an electrical signal applied through the first semiconductor layer 31 and the second semiconductor layer 32. In the case where the light emitting layer 36 emits light of a blue wavelength band, the light emitting layer 36 can include a material such as AlGaN or AlGaInN. In particular, in the case where the light emitting layer 36 has a multi-quantum well structure in which quantum layers and well layers are alternately stacked, the quantum layers can include a material such as AlGaN or AlGaInN, and the well layers can include a material such as GaN or AlInN. For example, the light emitting layer 36 can include quantum layers each containing AlGaInN and well layers each containing AlInN, and thus the light emitting layer 36 can emit blue light having a central wavelength band of about 450 nm to about 495 nm, as described above.

[0146] However, the present disclosure is not limited thereto, and the light emitting layer 36 can have a structure in which a semiconductor material having a high band gap energy and a semiconductor material having a low band gap energy are alternately stacked, and can include other Group III to Group V semiconductor materials depending on the wavelength band of light. The light emitted from the light emitting layer 36 is not limited to light of a blue wavelength band, and in some cases, the light emitting layer 36 can emit light of a red wavelength band or a green wavelength band. The length of the light emitting layer 36 can be about 0.05 µm to about 1.10 µm, but is not limited thereto.

[0147] Light emitted from the light emitting layer 36 can be emitted to both end surfaces of the light emitting element 30 and the longitudinal outer surface of the light emitting element 30. The direction of light emitted from the light emitting layer 36 is not limited to one direction.

[0148] The electrode layer 37 can be an ohmic contact electrode. However, the present disclosure is not limited thereto, and the electrode layer 37 can be a Schottky contact electrode. The light emitting element 30 can include at least one electrode layer 37. Although it is shown in Figure 4

[0149] In a case where the light emitting element 30 is electrically connected to an electrode or a contact electrode in the display device 10 according to an embodiment, the electrode layer 37 can reduce the electrical resistance between the light emitting element 30 and the electrode or the contact electrode. The electrode layer 37 can include a conductive metal and / or a metal oxide. For example, the electrode layer 37 can include at least one of aluminum (Al), titanium (Ti), indium (In), gold (Au), silver (Ag), indium tin oxide (ITO), indium zinc oxide (IZO), and indium tin zinc oxide (ITZO). The electrode layer 37 can include a semiconductor material doped with an n-type or p-type impurity. However, the present disclosure is not limited thereto.

[0150] The insulating film 38 can be disposed to surround the outer surfaces of the above-described semiconductor layer and the electrode layer. For example, the insulating film 38 can be disposed to surround at least the outer surface of the light emitting layer 36, and can extend in a direction in which the light emitting element 30 extends. The insulating film 38 can function as a protective member. For example, the insulating film 38 can be formed to surround the side surface of the member, and can be formed so that both ends of the light emitting element 30 in the length direction are exposed.

[0151] Although it is shown in Figure 4

[0152] ​​The thickness of the insulating film 38 can be about 10 nm to about 1.0 μm, but is not limited thereto. The thickness of the insulating film 38 can be about 40 nm.

[0153] The insulating film 38 can include a material having insulating properties, for example, silicon oxide (SiO x ), silicon nitride (SiN x ), silicon oxynitride (SiO x N y ), aluminum nitride (AlN x ), or aluminum oxide (AlO x ). Thus, the insulating film 38 can prevent an electrical short that can occur in the case where the light emitting layer 36 directly contacts an electrode through which an electrical signal is transmitted to the light emitting element 30. In addition, since the insulating film 38 protects the outer surface of the light emitting element 30 as well as the light emitting layer 36, it can prevent degradation of light emission efficiency.

[0154] In addition, the outer surface of the insulating film 38 can be surface-treated. The light emitting element 30 can be aligned by being sprayed on an electrode in a state in which the light emitting element 30 is dispersed in a predetermined ink. Here, the surface of the insulating film 38 can be hydrophobically treated or hydrophilically treated in order to maintain the light emitting element 30 in a dispersed state without being aggregated with other adjacent light emitting elements 30 in the ink. For example, the outer surface of the insulating film 38 can be surface-treated with a material such as stearic acid or 2,3-naphthalene dicarboxylic acid.

[0155] The length h of the light emitting element 30 can be about 1 μm to about 10 μm, about 2 μm to about 6 μm, or about 3 μm to about 5 μm. The diameter of the light emitting element 30 can be about 30 nm to about 700 nm, and the aspect ratio of the light emitting element 30 can be about 1.2 to about 100. However, the present disclosure is not limited thereto, and the light emitting element 30 included in the display device 10 can have a different diameter according to a difference in composition of the light emitting layer 36. For example, the diameter of the light emitting element 30 can be about 500 nm.

[0156] The shape and material of the light emitting element 30 are not limited to those of Figure 4 . In some embodiments, the light emitting element 30 can include a greater number of layers, or can have a different shape.

[0157] Figure 5 and Figure 6 are schematic perspective views of light emitting elements according to other embodiments.

[0158] First, reference is made to Figure 5The light emitting element 30' according to the embodiment can further include a third semiconductor layer 33' disposed between the first semiconductor layer 31' and the light emitting layer 36', a fourth semiconductor layer 34' and a fifth semiconductor layer 35' disposed between the light emitting layer 36' and the second semiconductor layer 32', and an insulating layer 38'. Figure 5 The light emitting element 30' according to the embodiment can further include a third semiconductor layer 33' disposed between the first semiconductor layer 31' and the light emitting layer 36', a fourth semiconductor layer 34' and a fifth semiconductor layer 35' disposed between the light emitting layer 36' and the second semiconductor layer 32', and an insulating layer 38'. Figure 4 The light emitting element 30' according to the embodiment can further include a third semiconductor layer 33' disposed between the first semiconductor layer 31' and the light emitting layer 36', a fourth semiconductor layer 34' and a fifth semiconductor layer 35' disposed between the light emitting layer 36' and the second semiconductor layer 32', and an insulating layer 38'.

[0159] In the light emitting element 30 according to the embodiment, Figure 4 In the light emitting element 30 according to the embodiment, Figure 5 The light emitting element 30' according to the embodiment can further include a third semiconductor layer 33' disposed between the first semiconductor layer 31' and the light emitting layer 36', a fourth semiconductor layer 34' and a fifth semiconductor layer 35' disposed between the light emitting layer 36' and the second semiconductor layer 32', and an insulating layer 38'.

[0160] Specifically, the first semiconductor layer 31' can be an n-type semiconductor layer, and can include a semiconductor material having a chemical formula of In x Al y Ga 1-x-y P (0≤x≤1, 0≤y≤1, 0≤x+y≤1). The first semiconductor layer 31' can include at least one of InAlGaP, GaP, AlGaP, InGaP, AlP, and InP doped with an n-type impurity. For example, the first semiconductor layer 31' can include n-AlGaInP doped with n-type Si.

[0161] The second semiconductor layer 32' can be a p-type semiconductor layer, and can include a semiconductor material having a chemical formula of In x Al y Ga 1-x-y P (0≤x≤1, 0≤y≤1, 0≤x+y≤1). The second semiconductor layer 32' can include at least one of InAlGaP, GaP, AlGaNP, InGaP, AlP, and InP doped with a p-type impurity. For example, the second semiconductor layer 32' can include p-GaP doped with p-type Mg.

[0162] The light emitting layer 36' can be disposed between the first semiconductor layer 31' and the second semiconductor layer 32'. The light emitting layer 36' can include a material having a single quantum well structure or a multiple quantum well structure to emit light of a specific wavelength band. In a case where the light emitting layer 36' has a multiple quantum well structure in which quantum layers and well layers are alternately stacked, the quantum layers can include a material such as AlGaP or AlInGaP, and the well layers can include a material such as GaP or AlInP. For example, the light emitting layer 36' can include quantum layers including AlGaInP and well layers including AlInP to emit red light having a center wavelength band of about 620 nm to about 750 nm.

[0163] Figure 5 The light emitting element 30' of FIG. 1A can include cladding layers disposed adjacent to the light emitting layer 36'. As shown in FIG. 1A, the third semiconductor layer 33' and the fourth semiconductor layer 34' disposed between the first semiconductor layer 31' and the second semiconductor layer 32' and on and under the light emitting layer 36' can be cladding layers. Figure 5

[0164] The third semiconductor layer 33' can be disposed between the first semiconductor layer 31' and the light emitting layer 36'. Similar to the first semiconductor layer 31', the third semiconductor layer 33' can be an n-type semiconductor layer, and can include a semiconductor material having a chemical formula of In x Al y Ga 1-x-y P (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ x + y ≤ 1). For example, the first semiconductor layer 31' can include n-AlGaInP, and the third semiconductor layer 33' can include n-AlInP.

[0165] The fourth semiconductor layer 34' can be disposed between the light emitting layer 36' and the second semiconductor layer 32'. Similar to the second semiconductor layer 32', the fourth semiconductor layer 34' can be a p-type semiconductor layer, and can include a semiconductor material having a chemical formula of In x Al y Ga 1-x-y P (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ x + y ≤ 1). For example, the second semiconductor layer 32' can include p-GaP, and the fourth semiconductor layer 34' can include p-AlInP.

[0166] ​The fifth semiconductor layer 35' can be provided between the fourth semiconductor layer 34' and the second semiconductor layer 32'. Similar to the second semiconductor layer 32' and the fourth semiconductor layer 34', the fifth semiconductor layer 35' can be a p-type semiconductor layer. In some embodiments, the fifth semiconductor layer 35' can function to reduce a difference in lattice constant between the fourth semiconductor layer 34' and the second semiconductor layer 32'. The fifth semiconductor layer 35' can be a tensile-strained barrier-reducing (TSBR) layer. For example, the fifth semiconductor layer 35' can include p-GaInP, p-AlInP, or p-AlGaInP, but its material is not limited thereto. The length of each of the third semiconductor layer 33', the fourth semiconductor layer 34', and the fifth semiconductor layer 35' can be about 0.08 μm to about 0.25 μm, but is not limited thereto.

[0167] The first electrode layer 37a' and the second electrode layer 37b' can be provided on the first semiconductor layer 31' and the second semiconductor layer 32', respectively. The first electrode layer 37a' can be provided on the lower surface of the first semiconductor layer 31', and the second electrode layer 37b' can be provided on the upper surface of the second semiconductor layer 32'. However, the present disclosure is not limited thereto, and at least one of the first electrode layer 37a' and the second electrode layer 37b' can be omitted. For example, in the light emitting element 30', the first electrode layer 37a' can not be provided on the lower surface of the first semiconductor layer 31', and only one second electrode layer 37b' can be provided on the upper surface of the second semiconductor layer 32'.

[0168] Subsequently, referring to Figure 6 , the light emitting element 30" can have a shape extending in one direction, but can have a partially inclined side surface. For example, the light emitting element 30" according to an embodiment can have a partially conical shape.

[0169] The light emitting element 30" can be formed such that the layers are not stacked in one direction and each layer surrounds the outer surface of another layer. The light emitting element 30" can include a semiconductor core having at least some regions extending in one direction and an insulating film 38" formed to surround the semiconductor core. The semiconductor core can include a first semiconductor layer 31", a light emitting layer 36", a second semiconductor layer 32", and an electrode layer 37".

[0170] The first semiconductor layer 31" can extend in one direction, and both end portions thereof can be formed to be inclined toward the center thereof. The first semiconductor layer 31" can include a body portion of a rod shape or a cylindrical shape, and upper and lower end portions each formed on and below the body portion, having an inclined side surface. The upper end portion of the body portion can have a steeper slope than the lower end portion.

[0171] The light emitting layer 36" can be provided to surround the outer surface of the main body portion of the first semiconductor layer 31". The light emitting layer 36" can have a ring shape extending in one direction. The light emitting layer 36" can not be formed on the upper end portion and the lower end portion of the first semiconductor layer 31". However, the present disclosure is not limited thereto. Light emitted from the light emitting layer 36" can be emitted to both side surfaces of the light emitting element 30" in the length direction and to both end portions of the light emitting element 30" in the length direction. Compared to the light emitting element 30 of Figure 4 FIG. 1, Figure 6 The light emitting element 30" can include the light emitting layer 36" having a large area, and thus can emit a larger amount of light.

[0172] The second semiconductor layer 32" can be provided to surround the outer surface of the light emitting layer 36" and the upper end portion of the first semiconductor layer 31". The second semiconductor layer 32" can include a ring-shaped main body portion extending in one direction and an upper end portion having an inclined side surface. For example, the second semiconductor layer 32" can directly contact the parallel side surface of the light emitting layer 36" and the inclined upper end portion of the first semiconductor layer 31". However, the second semiconductor layer 32" is not formed on the lower end portion of the first semiconductor layer 31".

[0173] The electrode layer 37" can be provided to surround the outer surface of the second semiconductor layer 32". The shape of the electrode layer 37" can be substantially the same as that of the second semiconductor layer 32". The electrode layer 37" can completely contact the outer surface of the second semiconductor layer 32".

[0174] The insulating film 38" can be provided to surround the outer surface of the electrode layer 37" and the first semiconductor layer 31". The insulating film 38" can directly contact the lower end portion of the first semiconductor layer 31" and the exposed lower portions of the light emitting layer 36" and the second semiconductor layer 32" and the electrode layer 37".

[0175] The light emitting element 30 can be sprayed on each of the electrodes (21 and 22) through an inkjet printing process. The light emitting element 30 can be dispersed in a solvent to be prepared in an ink state and sprayed on the electrodes (21 and 22), and can be disposed between the electrodes (21 and 22) through a process of applying an alignment signal to the electrodes (21 and 22). In the case where an alignment signal is applied to each of the electrodes (21 and 22), an electric field can be formed thereon, and the light emitting element 30 can receive a dielectrophoretic force through the electric field. The light emitting element 30 that has received the dielectrophoretic force can be disposed on the first electrode 21 and the second electrode 22 while changing the alignment direction and the position of the light emitting element 30.

[0176] ​The light emitting element 30 can include a semiconductor layer, and can generally be made of (or include) a material having a specific gravity greater than that of a solvent. When the light emitting element 30 is dispersed and stored in a solvent, the dispersion can be maintained for a predetermined period of time, and then gradually precipitates due to the difference in specific gravity. When the light emitting element 30 is precipitated in the solvent, the number of light emitting elements 30 per ink droplet is not uniform. Accordingly, when a device including the light emitting element 30 is manufactured using this ink, the number of light emitting elements 30 for each region is not constant, and thus, the quality of the product can be degraded.

[0177] According to an embodiment, the ink including the light emitting element 30 can further include a thickening agent 500 (see Figure 7 ), and thus, the viscosity of the ink can vary depending on the temperature of the solution. The ink including the light emitting element 30 can have a high viscosity in a state in which the ink is stored in a container or at room temperature, and thus, the light emitting element 30 can be stored in a dispersed state for a long time. Further, in the case in which the ink including the light emitting element 30 is discharged through a nozzle in an inkjet printing process, the temperature of the nozzle of the inkjet printing apparatus can be adjusted to reduce the viscosity of the ink, and thus the ink can be easily discharged through the nozzle. Accordingly, according to an embodiment, the ink including the light emitting element 30 can be sprayed by including a uniform number of light emitting elements 30 in a unit area through a printing process, while preventing precipitation of the light emitting element 30. Hereinafter, the ink including the light emitting element 30 will be described.

[0178] Figure 7 is a schematic perspective view of a light emitting element ink according to an embodiment.

[0179] Referring to Figure 7 , the light emitting element ink 1000 according to an embodiment can include a light emitting element solvent 100, a light emitting element 30 dispersed in the light emitting element solvent 100, and a thickening agent 500. The light emitting element 30 can be one of the light emitting elements (30, 30', and 30") described above with reference to Figures 4 to 6 , and the light emitting element 30 is exemplified in the drawings Figure 4 . Since the description of the light emitting element 30 is the same as described above, the light emitting element solvent 100 and the thickening agent 500 will be described in detail below.

[0180] The light emitting element solvent 100 can store the light emitting element 30 including the semiconductor layer in a dispersed state with a high specific gravity, and can be an organic solvent that does not react with the light emitting element 30. The light emitting element solvent 100 can have a viscosity sufficient to be discharged in a liquid state through a nozzle of an inkjet printing apparatus. The solvent molecules of the light emitting element solvent 100 can disperse the light emitting element 30 while surrounding the surface of the light emitting element 30. The light emitting element ink 1000 can include the light emitting element 30 prepared in a solution or a colloidal state. In an embodiment, examples of the light emitting element solvent 100 can include, but are not limited to, acetone, water, alcohol, toluene, propylene glycol (PG), propylene glycol methyl acetate (PGMA), triethylene glycol monobutyl ether (TGBE), diethylene glycol monophenyl ether (DGPE), an amide-based solvent, a dicarbonyl-based solvent, diethylene glycol dibenzoate, a tricarbonyl-based solvent, triethyl citrate, a phthalate-based solvent, butyl benzyl phthalate, bis(2-ethylhexyl) phthalate, bis(2-ethylhexyl) isophthalate, and ethyl phthalyl ethyl glycolate. More various examples of the light emitting element solvent 100 will be described below.

[0181] In the specification, the term "light emitting element solvent 100" refers to a solvent or a medium in which the light emitting element 30 can be dispersed, and the term "solvent molecule 101" refers to a molecule included in the light emitting element solvent 100. For example, it can be understood that the term "light emitting element solvent 100" is a liquid solvent including the solvent molecule 101. However, these terms can not necessarily be used alone, and in some cases, the terms "light emitting element solvent 100" and "solvent molecule 101" can be used interchangeably and can be substantially the same.

[0182] The thickening agent 500 can be dispersed in the light emitting element solvent 100 together with the light emitting element 30. A predetermined amount of the thickening agent 500 can be included in the light emitting element ink 1000 to change the viscosity of the solution according to the temperature of the light emitting element ink 1000. According to an embodiment, the thickening agent 500 can be a polyol-based compound including a functional group capable of forming an intermolecular hydrogen bond. The thickening agent 500 can form an intermolecular hydrogen bond with the solvent molecule 101 of the light emitting element solvent 100 or another thickening agent 500 to form a relatively strong attractive force between different molecules.

[0183] Figure 8 is a schematic diagram illustrating an intermolecular hydrogen bond between a thickening agent and a light emitting element solvent in a light emitting element ink at room temperature. Figure 7 is a schematic diagram illustrating an intermolecular hydrogen bond between a thickening agent and a light emitting element solvent in a light emitting element ink at room temperature. Figure 8 is a schematic diagram illustrating an intermolecular hydrogen bond between a thickening agent and a light emitting element solvent in a light emitting element ink at room temperature. Figure 7An enlarged view of the area A, and illustrates the form of the molecules of the thickening agent 500 dispersed in the light emitting element solvent 100 in a state where the light emitting element ink 1000 is stored at room temperature or 25°C. In the specification, the term "room temperature" generally refers to about 25°C, but can refer to a temperature of about 25°C, including 25°C. For example, the term "room temperature" can include a temperature of about 20°C to about 30°C.

[0184] Referring to Figure 8 The thickening agent 500 can include a hydroxyl group (-OH) as a polyol-based compound capable of forming an intermolecular hydrogen bond. The thickening agent 500 can include a main chain portion CP to which at least one hydroxyl group (-OH) is bonded. The main chain portion CP can be a carbon chain, such as an alkyl group, an alkenyl group, or an alkynyl group, but is not limited thereto, and can further include other functional groups, such as an ether group (-O-). In the thickening agent 500, the hydroxyl group (-OH) can form an intermolecular hydrogen bond HB with an atom having a non-covalent electron pair (for example, oxygen (O) or nitrogen (N)) of a solvent molecule 101 of the light emitting element solvent 100 or a hydroxyl group (-OH) of another thickening agent 500. According to an embodiment, the thickening agent 500 can form an intermolecular hydrogen bond with a molecule of another thickening agent 500 or a solvent molecule 101, and can form a network structure between the main chain portion CP and the solvent molecule 101 and between the main chain portions CP of the other thickening agents 500 at room temperature of about 25°C. Due to the network structure formed by the thickening agent 500, the light emitting element ink 1000 can have a high viscosity, and a precipitation rate of the light emitting elements 30 can be reduced in a state where the light emitting element ink 1000 is stored therein.

[0185] For example, the light emitting element ink 1000 can have a viscosity of about 30 cP to about 300 cP measured at room temperature (about 25°C). To prevent precipitation of the light emitting elements 30, the light emitting element ink 1000 can have a viscosity of at least about 20 cP or greater than 20 cP in a state where no shear stress is applied. In the light emitting element ink 1000, the light emitting elements 30 can be maintained in a dispersed state for a long time until a printing process using an inkjet printing apparatus. However, the present disclosure is not limited thereto. The viscosity of the light emitting element ink 1000 can be adjusted in the range of 20 cP or greater than 20 cP by the molecular structure and molecular weight of the thickening agent 500.

[0186] According to an embodiment, in the thickening agent 500 of the light emitting element ink 1000, the main chain portion CP to which at least one hydroxyl group (-OH) is bonded can be a substituted or unsubstituted alkyl group, an alkylene group, an alkenyl group, or an alkyl ether group having 2 or more carbon atoms.

[0187] In some embodiments, the thickening agent 500 of the light emitting element ink 1000 can include a structure represented by the following Chemical Structure 1.

[0188] [Chemical Structure 1]

[0189]

[0190] In the above Chemical Structure 1, R 1 may be a linear or branched alkyl group or alkyl ether each having 1 to 3,000 carbon atoms, substituted or unsubstituted with a hydroxyl group (-OH), and I can be an integer of 1 to 10. The thickening agent 500, which is a polyhydric alcohol-based compound, can form intermolecular hydrogen bonds with the light emitting element solvent 100, and the light emitting element ink 1000 can have a specific viscosity and boiling point.

[0191] In embodiments, the thickening agent 500 of the light emitting element ink 1000 can be a compound represented by the following Chemical Formula 1 to Chemical Formula 8.

[0192] [Chemical Formula 1]

[0193]

[0194] [Chemical Formula 2]

[0195]

[0196] [Chemical Formula 3]

[0197]

[0198] [Chemical Formula 4]

[0199]

[0200] [Chemical Formula 5]

[0201]

[0202] [Chemical Formula 6]

[0203]

[0204] [Chemical Formula 7]

[0205]

[0206] [Chemical Formula 8]

[0207]

[0208] In the above Chemical Formula 7 and Chemical Formula 8, n can be an integer of 1 to 1,000.

[0209] Each of the compounds of Chemical Formula 1 to Chemical Formula 8 can include a main chain portion CP including a carbon chain or an alkyl ether group, and at least one hydroxyl group (-OH) bonded to the main chain portion CP. The hydroxyl group (-OH) of the thickening agent 500 can form an intermolecular hydrogen bond with oxygen (O) or hydrogen (H) included in another thickening agent 500 or a solvent molecule 101 of the light emitting element solvent 100. In a case where the light emitting element ink 1000 is stored at room temperature, the thickening agent 500 can form a network structure through hydrogen bonds between molecules, and the light emitting element ink 1000 can have a high viscosity. Since the thickening agent 500 is a compound of one of Chemical Formula 1 to Chemical Formula 8, the thickening agent 500 itself can have a high boiling point at room temperature. In an embodiment, the thickening agent 500 can have a boiling point of about 200℃ to about 450℃, for example, can have a boiling point of about 350℃. However, the present disclosure is not limited thereto. The light emitting element ink 1000 according to an embodiment can include a light emitting element 30 and a thickening agent 500 having a relatively high specific gravity to prevent the light emitting element 30 from precipitating even at room temperature.

[0210] As a structure of the thickening agent 500, the above Chemical Formula 1 to Chemical Formula 8 have been discussed, but the present disclosure is not limited thereto. In some embodiments, in a case where the thickening agent 500 is a polyhydric alcohol-based compound including at least one hydroxyl group (-OH), the main chain portion CP of the thickening agent 500 can be further substituted with other substituents. For example, the main chain portion CP of the thickening agent 500 can be further substituted with a functional group including a halogen group, an ethoxy group, a thiol group, or a thioalkanol group.

[0211] Further, according to an embodiment, in order for the light emitting element solvent 100 of the light emitting element ink 1000 to have a high viscosity at room temperature through intermolecular hydrogen bonds with the thickening agent 500, the light emitting element solvent 100 can further include a functional group capable of forming an intermolecular hydrogen bond. For example, similar to the thickening agent 500, the solvent molecule 101 of the light emitting element solvent 100 can include at least one hydroxyl group (-OH) or can include an element capable of forming an intermolecular hydrogen bond with hydrogen (H) of the hydroxyl group (-OH) included in the thickening agent 500, such as oxygen (O), nitrogen (N), or fluorine (F). However, the light emitting element solvent 100 can have a structure sufficient to disperse the light emitting element 30.

[0212] In an embodiment, the solvent molecule 101 of the light emitting element solvent 100 of the light emitting element ink 1000 can have a structure of the following Chemical Structure Formula 2 as a structure including a benzene ring.

[0213] [Chemical Structure Formula 2]

[0214]

[0215] In Chemical Formula 2 above, R 2 may include at least one of a substituted or unsubstituted alcohol group, ether group, and ester group each having 2 to 10 carbon atoms, and m can be an integer of 1 or 2. The solvent molecule 101 of the light emitting element solvent 100 can have a structure in which a benzene ring is substituted with at least one functional group among an alcohol group, ether group, and ester group as a functional group capable of forming an intermolecular hydrogen bond with a hydroxyl group (-OH) of the thickening agent 500. For example, the solvent molecule 101 of the light emitting element solvent 100 can be a compound represented by one of the following Chemical Formula 9 to Chemical Formula 25.

[0216] [Chemical Formula 9]

[0217]

[0218] [Chemical Formula 10]

[0219]

[0220] [Chemical Formula 11]

[0221]

[0222] [Chemical Formula 12]

[0223]

[0224] [Chemical Formula 13]

[0225]

[0226] [Chemical Formula 14]

[0227]

[0228] [Chemical Formula 15]

[0229]

[0230] [Chemical Formula 16]

[0231]

[0232] [Chemical Formula 17]

[0233]

[0234] [Chemical Formula 18]

[0235]

[0236] [Chemical Formula 19]

[0237]

[0238] [Chemical Formula 20]

[0239]

[0240] [Chemical Formula 21]

[0241]

[0242] [Chemical Formula 22]

[0243]

[0244] [Chemical Formula 23]

[0245]

[0246] [Chemical Formula 24]

[0247]

[0248] [Chemical Formula 25]

[0249]

[0250] In the above Chemical Formula 9 to Chemical Formula 25, in Chemical Formula 9 to Chemical Formula 12, each of the solvent molecules 101 of the light emitting element solvent 100 can include at least one hydroxyl group (-OH) to form an intermolecular hydrogen bond with the thickening agent 500. In contrast, in Chemical Formula 13 to Chemical Formula 25, each of the solvent molecules 101 of the light emitting element solvent 100 can include a carbonyl group or an ester group as a functional group capable of forming an intermolecular hydrogen bond, and thus a hydrogen (H) of the thickening agent 500 and an oxygen (O) of the solvent molecule 101 can form an intermolecular hydrogen bond with each other. When the solvent molecule 101 of the light emitting element solvent 100 includes a benzene ring, the reactivity with the light emitting element 30 can be low, and the degree of dispersion thereof can further increase depending on the surface treatment of the light emitting element 30. In the case where the light emitting element solvent 100 of the light emitting element ink 1000 includes a compound represented by one of Chemical Formula 9 to Chemical Formula 25, a greater number of intermolecular hydrogen bonds can be formed between the thickening agent 500 and the solvent molecule 101, and thus the light emitting element ink 1000 can have a higher viscosity. Accordingly, in the case where the light emitting element ink 1000 is stored at room temperature, the precipitation of the light emitting element 30 can be more effectively prevented.

[0251] However, the present disclosure is not limited thereto, and various solvents can be used as the light emitting element solvent 100. For example, in addition to the above-described examples, the light emitting element solvent 100 can be caffeine, triethanolamine, glycerol, L-tyrosine, epinephrine, L-dopa, serotonin, dibenzyl sebacate, di(tridecyl)phthalate, diethanolamine, benzyl butyl phthalate, nonyl phenol, acetaminophen, triphenyl phosphate, 1,3-butanediol, 1,4-butanediol, 1-hexadecanol, oleyl alcohol, N-(2-hydroxyethyl)-2-pyrrolidone, tri-n-butyl citrate, di-(2-ethylhexyl)sebacate, diethylene glycol, thymine, 1,9-nonanediol, benzoin, dipropylene glycol, sebacic acid, thiodiglycol, 5,6-dihydroxyindole, di-(2-ethylhexyl)azelate, dihexyl phthalate, N-cyclohexyl-2-pyrrolidone, oleic acid, norephedrine, 1-naphthol, 2,4,6-trinitrophenol, N-benzylpyrrolidone, hexane-1,6-diol, ε-caprolactam, tridecanol, acridine, and propylene glycol methyl ether acetate. In the case where the light emitting element solvent 100 includes the above-described compounds, it can have a high boiling point, similar to the thickening agent 500. In an embodiment, the light emitting element solvent 100 can have a boiling point of about 200°C to about 350°C. However, the present disclosure is not limited thereto.

[0252] In some embodiments, in the light emitting element ink 1000, the thickening agent 500 can be glycerol having the structure of Chemical Formula 1, and the light emitting element solvent 100 can be a glycol ether-based compound. In the case where the thickening agent 500 and the light emitting element solvent 100 of the light emitting element ink 1000 are a combination of the above-described compounds, the light emitting element ink 1000 can have a viscosity and a boiling point within the ranges described above, and thus the light emitting element ink 1000 can have physical properties that easily discharge the light emitting element 30. However, the present disclosure is not limited thereto, and the kinds of the thickening agent 500 and the light emitting element solvent 100 of the light emitting element ink 1000 can variously change within a range in which the light emitting element ink 1000 can have a viscosity and a boiling point within the ranges described above. Further, the physical properties (e.g., viscosity and boiling point) of the light emitting element ink 1000 can variously change according to a mixing ratio of the thickening agent 500 and the light emitting element solvent 100.

[0253] To discharge the light emitting element ink 1000 through a nozzle, it should have a low viscosity. In the light emitting element ink 1000, in a case where the solvent molecules 101 and the thickening agent 500 receive energy at a predetermined temperature higher than room temperature, molecular motion becomes active. For example, at a temperature where energy stronger than the energy of intermolecular hydrogen bonds between the thickening agent 500 and the solvent molecules 101 or between the thickening agent 500 can be transmitted, the intermolecular hydrogen bonds can be broken. In the light emitting element ink 1000 placed at or above the predetermined temperature, the thickening agent 500 can not form a network structure with the solvent molecules 101 of the light emitting element solvent 100 or other thickening agents 500, and thus the light emitting element ink 1000 can have a low viscosity.

[0254] Figure 9 is a schematic view illustrating intermolecular hydrogen bonds between the thickening agent of the light emitting element ink 1000 and the light emitting element solvent at another temperature. Figure 7 Figure 9 is an enlarged view of the region A of Figure 7 , and illustrates a form of molecules of the thickening agent 500' dispersed in the light emitting element solvent 100 at a predetermined temperature at or above room temperature.

[0255] Referring to Figure 9 , in a printing process of the light emitting element ink 1000, the light emitting element solvent 100 should have a viscosity of a predetermined value or lower in order to make the light emitting element ink 1000 flow in an inkjet head of an inkjet printing apparatus or be discharged through a nozzle of the inkjet printing apparatus.

[0256] In the specification, the term "printing" of the light emitting element 30 can mean discharging or ejecting the light emitting element 30 to a predetermined object by using an inkjet printing apparatus. For example, the term "printing" of the light emitting element 30 can mean that the light emitting element 30 is directly discharged through a nozzle of the inkjet printing apparatus or is discharged in a state in which the light emitting element 30 is dispersed in the light emitting element ink 1000. However, the present disclosure is not limited thereto, and the term "printing" of the light emitting element 30 can mean that the light emitting element 30 or the light emitting element ink 1000 in which the light emitting element 30 is dispersed is ejected on a target substrate SUB (see Figure 11 ) to allow the light emitting element 30 or the light emitting element ink 1000 to be mounted on the target substrate SUB.

[0257] ​In a case where the light emitting element ink 1000 is discharged through a nozzle of an inkjet printing apparatus, when the temperature of the nozzle is adjusted such that the light emitting element ink 1000 is left at room temperature or above, the thickening agent 500' can not form a network structure. At room temperature or above, the hydrogen bonds (HB1 and HB2) between the molecules of the thickening agent 500' of the light emitting element ink 1000 can be broken as the molecular motion becomes active, and the solvent molecules 101 of the thickening agent 500' and the light emitting element solvent 100 can be individually dispersed without forming a network structure.

[0258] According to an embodiment, the light emitting element ink 1000 can have a viscosity of about 5 cP to about 15 cP, about 7 cP to about 13 cP, or about 10 cP, measured at a temperature of about 40°C to about 60°C. In a case where the light emitting element ink 1000 has a viscosity within the above range, the light emitting element ink 1000 can be easily discharged through a nozzle, and the degree of dispersion of the light emitting element 30 can be maintained because the printing process has been previously performed even if the light emitting element 30 gradually precipitates. For example, the number of light emitting elements 30 of the light emitting element ink 1000 per unit drop discharged from the nozzle of the inkjet printing apparatus can be maintained uniform. However, the viscosity of the light emitting element ink 1000 is not limited thereto, and the temperature within the nozzle of the inkjet head and the viscosity of the light emitting element ink 1000 can be variously changed within a range in which the light emitting element ink 1000 can be discharged from the nozzle of the inkjet head.

[0259] The light emitting element ink 1000 can contain a predetermined amount of light emitting elements 30 per unit weight, and can contain the thickening agent 500 at a predetermined content with respect to the weight of the light emitting elements 30. According to an embodiment, the light emitting element ink 1000 can contain about 5 parts by weight to 50 parts by weight of the thickening agent 500 with respect to 100 parts by weight of the light emitting element ink 1000. In a case where the thickening agent 500 is contained in an amount of less than about 5 parts by weight with respect to 100 parts by weight of the light emitting element ink 1000, the effect of preventing the precipitation of the light emitting elements 30 in a storage state can be insufficient, and in a case where the thickening agent 500 is contained in an amount of about 50 parts by weight or more, the viscosity of the light emitting element ink 1000 can be too high, and thus the nozzle inlet can be clogged during the printing process. In a case where the light emitting element ink 1000 contains the thickening agent 500 within the above range, the light emitting element ink 1000 can be smoothly discharged through a nozzle while preventing the precipitation of the light emitting elements 30.

[0260] The content of the light emitting element 30 included in the light emitting element ink 1000 can vary depending on the number of light emitting elements 30 per unit drop of the light emitting element ink 1000 discharged through the nozzle during the printing process. In an embodiment, the light emitting element 30 can be included in an amount of about 0.01 parts by weight to about 1 part by weight with respect to 100 parts by weight of the light emitting element ink 1000. However, this is an example, and the content of the light emitting element 30 can vary depending on the number of light emitting elements 30 per unit drop of the light emitting element ink 1000.

[0261] The light emitting element ink 1000 can further include a dispersant (not shown) that improves the degree of dispersion of the light emitting element 30. The kind of the dispersant is not particularly limited, and the dispersant can be added in an appropriate amount to further disperse the light emitting element 30. For example, the dispersant can be included in an amount of about 10 parts by weight to about 100 parts by weight with respect to 100 parts by weight of the light emitting element 30. However, the content of the dispersant is not limited thereto.

[0262] According to an embodiment, the light emitting element ink 1000 can include a thickener 500, and thus the viscosity of the light emitting element ink 1000 can be changed during the process of manufacturing the display device 10. The light emitting element ink 1000 can have a suitable viscosity for each storage step of the light emitting element ink 1000 and each printing step through the nozzle. In particular, in the storage step of the light emitting element ink 1000, since the light emitting element ink 1000 has a high viscosity, precipitation of the light emitting element 30 can be prevented, and in the printing step through the nozzle, since the light emitting element ink 1000 has a low viscosity, the printing process of the light emitting element 30 can be smoothly performed.

[0263] When a product including the light emitting element 30 using the light emitting element ink 1000 is manufactured according to an embodiment, a uniform number of light emitting elements 30 can be disposed in each unit area, and the light emitting element solvent 100 and the thickener 500, which are foreign matter residues in a subsequent process, can be completely removed. Thus, the reliability of the product including the light emitting element 30 can be improved. According to an embodiment, the light emitting element ink 1000 can be used to manufacture the above-mentioned Figures 1 to 3 The display device 10 described above.

[0264] In the process of manufacturing the display device 10, a process of placing the light emitting element 30 on the electrodes (21 and 22) can be performed, and the process can be performed by a printing process using the light emitting element ink 1000.

[0265] Hereinafter, a process of manufacturing the display device 10 according to an embodiment will be described with reference to other drawings.

[0266] Figure 10 is a flowchart illustrating a method of manufacturing a display device according to an embodiment.

[0267] Referring to Figures 11 to 13 A method of manufacturing the display device 10 according to the embodiment can include the steps of preparing the light emitting element ink 1000 and a target substrate SUB provided with electrodes (21 and 22) (S100); jetting the light emitting element ink 1000 on the target substrate SUB at a first temperature (S200); forming an electric field on the electrodes (21 and 22) to place the light emitting element 30 on the electrodes (21 and 22) (S300); and removing the light emitting element solvent 100 and the thickening agent 500 of the light emitting element ink 1000 at a second temperature (S400).

[0268] The light emitting element ink 1000 can have a high viscosity at room temperature, and can be stored so that the light emitting element 30 is not precipitated. The process of manufacturing the display device 10 can include the steps of printing the light emitting element ink 1000 containing the light emitting element 30 on the target substrate SUB at a first temperature higher than room temperature; and removing the light emitting element solvent 100 and the thickening agent 500 of the light emitting element ink 1000 at a second temperature different from the first temperature. In the light emitting element ink 1000, the viscosity thereof can change depending on the temperature during the storing step and the printing step, and the light emitting element ink 1000 can be easily printed on the target substrate SUB while preventing precipitation of the light emitting element. Hereinafter, the method of manufacturing the display device 10 will be described in detail with reference to other drawings.

[0269] Figure 11 is a schematic cross-sectional view illustrating steps of a process of manufacturing a display device according to an embodiment.

[0270] First, referring to Figure 12 The light emitting element ink 1000 containing the light emitting element 30, the light emitting element solvent 100, and the thickening agent 500 is prepared, and the target substrate SUB provided with the first electrode 21 and the second electrode 22. Although a pair of electrodes is shown to be disposed on the target substrate SUB in the drawings, a larger number of pairs of electrodes can be disposed on the target substrate SUB. The target substrate SUB can include circuit elements disposed on the first substrate 11 of the display device 10, in addition to the first substrate 11. Hereinafter, these circuit elements will be omitted for convenience of description.

[0271] The light emitting element ink 1000 can include a light emitting element solvent 100, a light emitting element 30 dispersed in the light emitting element solvent 100, and a light-degradable thickening agent 500. In some embodiments, the light emitting element ink 1000 can be stored at room temperature or a temperature of about 25℃, and the thickening agent 500 can form hydrogen bonds between molecules to form a three-dimensional network structure in the light emitting element solvent 100. The light emitting element ink 1000 can have a high viscosity, for example, about 20 cp to about 300 cp, even at room temperature, and the light emitting element 30 can be maintained in a dispersed state for a long time.

[0272] The steps of preparing the light emitting element ink 1000 can be performed by a first dispersion process of mixing the light emitting element 30, the light emitting element solvent 100, and the dispersant to prepare a solution, and a second dispersion process of adding the thickening agent 500 to the solution prepared in the first dispersion process. For example, the first dispersion process can be performed by mixing the light emitting element 30 and the dispersant with the light emitting element solvent 100, and then stirring the solution for 5 minutes or more. As described above, the light emitting element 30 can have a diameter of about 1 µm or less than 1 µm or about 500 nm or less than 500 nm, and a length of about 1 µm to 10 µm or about 4 µm or more than 4 µm. The light emitting element 30 can be included in an amount of about 0.01 parts by weight to about 1 part by weight with respect to 100 parts by weight of the light emitting element ink 1000, and the dispersant can be included in an amount of 10 parts by weight to 100 parts by weight with respect to 100 parts by weight of the light emitting element 30. The mixing process can be performed by an ultrasonic process, a stirring process, a grinding process, or the like.

[0273] Subsequently, a second dispersion process in which the thickening agent 500 is further added to and mixed with the solution prepared in the first dispersion process is performed. The thickening agent 500 can be included in an amount of about 5 parts by weight to about 50 parts by weight with respect to 100 parts by weight of the light emitting element ink 1000. The mixing process can be performed by sequentially performing an ultrasonic process and a stirring process, each for 5 minutes or more. In order to easily mix the thickening agent 500, the mixing process can be performed at a temperature higher than room temperature (25℃), for example, at a temperature of about 40℃ or more than 40℃.

[0274] The light emitting element ink 1000 prepared by the first dispersion process and the second dispersion process can be stored at room temperature (25℃). The thickening agent 500 of the light emitting element ink 1000 can form intermolecular hydrogen bonds with the light emitting element solvent 100 and another thickening agent 500, and the light emitting element ink 1000 can have a viscosity of at least about 20 cP or more than 20 cP. The light emitting element 30 can be maintained in a dispersed state with little precipitation.

[0275] Subsequently, with reference to Figure 13 and Figure 14The light emitting element ink 1000 can be sprayed on the first and second electrodes 21 and 22 on the target substrate SUB. In an embodiment, the light emitting element ink 1000 can be sprayed on the electrodes (21 and 22) by a printing process using an inkjet printing apparatus. The light emitting element ink 1000 can be ejected through a nozzle of an inkjet head included in the inkjet printing apparatus. The light emitting element ink 1000 discharged from the nozzle can be attached on the electrodes (21 and 22) disposed on the target substrate SUB. The light emitting elements 30 can have a shape extending in one direction, and can be dispersed in the light emitting element ink 1000 in a state in which the extending direction has a random alignment direction.

[0276] In some embodiments, a third dispersion process of redispersion of the light emitting elements 30 and the thickening agent 500 can be performed before the light emitting element ink 1000 is ejected through the nozzle. For example, the stored light emitting element ink 1000 can be subjected to an ultrasonic process as well as a vortex or stirring process, each for 5 minutes or longer than 5 minutes. Even though the light emitting element ink 1000 has a high viscosity and thus the light emitting elements 30 are hardly precipitated, the third dispersion process of sufficient dispersion of the light emitting elements 30 can be performed before the printing process through the nozzle. Accordingly, the light emitting elements 30 of the light emitting element ink 1000 prepared in the inkjet printing apparatus can have a level of dispersion similar to that of the initial storage state.

[0277] According to an embodiment, in the printing process of the light emitting element ink 1000, the discharge portion JP of the nozzle can be adjusted to a first temperature higher than room temperature, and the light emitting element ink 1000 can have a relatively low viscosity at the first temperature and can be discharged on the target substrate SUB through the discharge portion JP. In some embodiments, the first temperature can be about 40℃ to about 60℃, and at the first temperature, the light emitting element ink 1000 can have a viscosity of about 5cP to about 15cP, or a viscosity of about 10cP. During the printing process of the light emitting element ink 1000, in the case where the temperature of the discharge portion JP of the nozzle is controlled to room temperature or the first temperature higher than room temperature, the light emitting element ink 1000 can have a low viscosity and can be easily discharged from the nozzle to prevent the nozzle from being clogged due to the viscosity of the solution.

[0278] Figure 14 is a graph illustrating a change in viscosity of the light emitting element ink 1000 according to temperature. Figure 14 illustrates a change in viscosity (cP) of the light emitting element ink 1000 containing the thickening agent 500 according to temperature (℃).

[0279] Reference Figure 14The light emitting element ink 1000 can have a high viscosity at room temperature. At a temperature of about 25°C, the light emitting element ink 1000 can have a viscosity of 20 cP or more and 200 cP or less, for example, about 100 cP, due to the formation of a three-dimensional network structure by the thickening agent 500. In a storage state of the light emitting element ink 1000, the light emitting elements 30 are hardly precipitated and can maintain an initial dispersion state.

[0280] In contrast, the light emitting element ink 1000 can have a low viscosity at room temperature or a temperature higher than room temperature. At a temperature of about 40°C to about 60°C, the light emitting element ink 1000 can have a viscosity of about 5 cp to about 17 cp. A solution having a viscosity within the above range (the "ejectable viscosity range") can be easily discharged through a nozzle, and the nozzle is not clogged due to the viscosity of the solution. Figures 15 to 17

[0281] In the case where the light emitting element ink 1000 has a low viscosity at any temperature or even at room temperature, the light emitting elements 30 contained in the light emitting element ink 1000 do not maintain an initial dispersion state over time and can be precipitated. When a printing process is performed using the light emitting element ink 1000 in which the light emitting elements 30 are dispersed, the light emitting elements 30 can be precipitated, so that the number of the light emitting elements 30 contained in a unit drop of the solution can be less than a calculated value or can not be uniform per unit drop. When a process of redispersing the precipitated light emitting elements 30 is performed, the process of manufacturing the display device 10 can become complicated, and in some cases, it can not be easy to redisperse the light emitting elements 30 at a desired dispersion degree. When a printing process is performed by using the light emitting element ink 1000 according to the embodiment, the light emitting elements 30 are dispersed and hardly precipitated, and the number of the light emitting elements 30 contained in a unit drop can be uniform per unit drop. In the method of manufacturing the display device 10, the display device 10 is manufactured by using the light emitting element ink 1000, and the manufactured display device 10 can have a uniform number of the light emitting elements 30 disposed per unit area, so that product reliability can be improved. Meanwhile, during a printing process through a nozzle, the temperature is controlled so that the light emitting element ink 1000 can have a low viscosity, and thus, it is possible to prevent the discharge portion JP of the nozzle from being clogged during the printing process.

[0282] Subsequently, an electric field can be formed in the light emitting element ink 1000 to place the light emitting elements on the electrodes (21 and 22), and the light emitting element solvent 100 and the thickening agent 500 can be removed (S400).

[0283] Figure 15 is a schematic cross-sectional view illustrating other steps in the process of manufacturing a display device according to an embodiment.

[0284] First, reference is made to​Figure 16 When the light emitting element ink 1000 including the light emitting elements 30 is sprayed on the target substrate SUB, an alignment signal can be applied to the electrodes (21 and 22) to generate an electric field EL on the target substrate SUB. The light emitting elements 30 dispersed in the light emitting element solvent 100 can be subjected to dielectrophoretic force by the electric field EL and can be disposed on the electrodes (21 and 22) while changing the alignment direction and position of the light emitting elements 30.

[0285] When the electric field EL is generated on the target substrate SUB, the light emitting elements 30 can be subjected to dielectrophoretic force. In the case where the electric field EL generated on the target substrate SUB is generated in parallel with the upper surface of the target substrate SUB, the extension direction of the light emitting elements 30 is aligned in parallel with the target substrate SUB, so that the light emitting elements 30 can be disposed on the first electrode 21 and the second electrode 22. The light emitting elements 30 can move from the initial dispersed position toward the electrodes (21 and 22) by the dielectrophoretic force. The two end portions of the light emitting elements 30 can be disposed on the first electrode 21 and the second electrode 22 while changing their positions and alignment directions by the electric field EL. The light emitting elements 30 can include a semiconductor layer doped with a dopant of a different conduction type and can have a dipole moment therein. In the case where the light emitting elements 30 having the dipole moment are placed in the electric field EL, the light emitting elements 30 can be subjected to dielectrophoretic force so that the two end portions thereof are disposed on the electrodes (21 and 22), respectively.

[0286] The term "alignment degree" of the light emitting elements 30 can refer to the deviation of the alignment direction and mounting position of the light emitting elements 30 aligned on the target substrate SUB. For example, in the case where the deviation of the alignment direction and mounting position of the light emitting elements 30 is large, it can be understood that the alignment degree of the light emitting elements 30 is low, and in the case where the deviation of the alignment direction and mounting position of the light emitting elements 30 is small, it can be understood that the alignment degree of the light emitting elements 30 is high or improved.

[0287] However, during the manufacturing process of the display device 10, after the light-emitting element 30 is disposed between the electrodes (21 and 22), a process can be performed to remove the light-emitting element solvent 100 and thickener 500 by applying heat or light to the light-emitting element ink 1000. The light-emitting element ink 1000 can have a high viscosity due to the intermolecular hydrogen bonds of the thickener 500, depending on the temperature. Therefore, the light-emitting element solvent 100 and thickener 500 may not be easily removed and may remain as foreign matter on the electrodes (21 and 22) or the light-emitting element 30. Furthermore, due to the high viscosity of the light-emitting element ink 1000, the strength of the dielectric force on the light-emitting element 30 caused by the electric field formed on the electrodes (21 and 22) may be insufficient. In addition, high-temperature heat treatment may be required to remove the high-viscosity light-emitting element solvent 100 and thickener 500, and the initial alignment state of the light-emitting element 30 may be changed by the attraction caused by the flow of fluid or by the attraction between the thickener 500 and the light-emitting element 30, while removing the light-emitting element solvent 100 and thickener 500.

[0288] In the method of manufacturing the display device 10 according to the embodiment, the light-emitting element solvent 100 and thickener 500 can be removed at a second temperature, and for easier removal, they can be completely removed by a heat treatment process under low pressure.

[0289] refer to Figure 17 and Figure 18 The process of removing the light-emitting element solvent 100 and thickener 500 can be performed in a chamber VCD capable of adjusting the internal pressure. In the chamber VCD, the internal pressure of the device can be adjusted, and the target substrate SUB can be heated under this adjusted internal pressure to remove the light-emitting element solvent 100 and thickener 500. With the light-emitting element 30 positioned on electrodes (21 and 22) via an electric field EL, the thickener 500 can form intermolecular hydrogen bonds depending on the temperature. The light-emitting element solvent 100 and thickener 500 can be removed by heat treatment at a second temperature while reducing the viscosity of the light-emitting element solvent 100. However, in addition to the energy required to volatilize their respective molecules, further energy may be needed to remove the intermolecular hydrogen bonds between the molecules of the light-emitting element solvent 100 and the thickener 500. In this case, the heat treatment process should be performed at a temperature higher than the boiling point of each molecule, and the high-temperature heat treatment process may damage the circuit layers of the display device 10.

[0290] In the method of manufacturing the display device 10, the light-emitting element solvent 100 and the thickener 500' can be heat-treated under low pressure to completely remove them, even at temperatures below the boiling point of the thickener 500' at atmospheric pressure. According to an embodiment, the process of removing the light-emitting element solvent 100 and the thickener 500' can be completed in about 10...-4 The heat treatment process is performed at a pressure of about 1 Torr to about 1 Torr and a temperature of about 25°C to about 150°C. In the case of performing the heat treatment process in the above pressure range, the boiling point of the thickening agent 500' and the light emitting element solvent 100 can be lowered, and the intermolecular hydrogen bond therebetween can be more easily removed. For example, in the case where the thickening agent 500' is a polyol-based compound, the boiling point thereof can be about 200°C to about 450°C at atmospheric pressure. However, in the chamber VCD in a low pressure environment as described above, the thickening agent 500' and the light emitting element solvent 100 can be easily removed even at a temperature range of about 150°C or less than 150°C. The heat treatment process in the chamber VCD can be performed for about 1 minute to about 30 minutes. However, it is not limited thereto.

[0291] Since the process of removing the light emitting element solvent 100 and the thickening agent 500' is performed by the heat treatment process in a low pressure environment, the light emitting element solvent 100 and the thickening agent 500' which can remain as foreign substances in a subsequent process can be completely removed. Further, in the process of removing the light emitting element solvent 100 and the thickening agent 500', a change in the initial alignment state of the attractive force of the light emitting element 30 due to the flow of the fluid or the attractive force between the thickening agent 500' and the light emitting element 30 can be prevented. For example, in the display device 10, the degree of alignment of the light emitting element 30 can be improved.

[0292] Subsequently, an insulating layer and a contact electrode can be formed on the light emitting element 30 and the electrodes (21 and 22) to manufacture the display device 10. Through the above process, the display device 10 including the light emitting element 30 can be manufactured. The display device 10 can be manufactured using the light emitting element ink 1000 including the thickening agent 500. In the display device 10, a uniform number of light emitting elements 30 per unit area can be arranged with a high degree of alignment, and product reliability can be improved.

[0293] After the light emitting element ink 1000 is discharged from the discharge portion JP of the nozzle, the viscosity can vary depending on the temperature of the upper portion of the target substrate SUB. In the case where the light emitting element ink 1000 applied on the target substrate SUB has a high viscosity, the process of aligning the light emitting element 30 by the electric field EL can not be easy. According to an embodiment, the process of applying the light emitting element 30 to the electrodes (21 and 22) during the manufacturing process of the display device 10 can be performed at a first temperature similar to the temperature of the discharge portion JP of the nozzle or at a temperature higher than the first temperature. For this purpose, in the process of generating the electric field EL on the electrodes (21 and 22), a process or a device for controlling the temperature of the upper portion of the target substrate SUB can be further included.

[0294] Figure 18is a schematic cross-sectional view illustrating steps in a process of manufacturing a display device according to another embodiment.

[0295] Referring to Figure 18 In the process of manufacturing the display device 10, in the step of forming the electric field EL on the electrodes (21 and 22) and applying the light emitting elements 30 on the electrodes (21 and 22), the process of irradiating light can be further performed while the target substrate SUB is heated (heated). Figure 19 The "heat" in the process of manufacturing the display device 10 can be performed while the target substrate SUB is heated (heated). The process of manufacturing the display device 10 can be a process of manufacturing the display device 10 by applying the light emitting element ink 1000 to the electrodes (21 and 22) and then controlling the temperature of the target substrate SUB to be higher than the first temperature. The light emitting element ink 1000 applied to the electrodes (21 and 22) can be cured by the heat of the target substrate SUB. The light emitting element ink 1000 can be cured by the heat of the target substrate SUB, and the light emitting elements 30 can be arranged on the electrodes (21 and 22) in a high degree of alignment. In the drawings, the process performed by a separate heating device is exemplified as a method of heating the target substrate SUB, but the present disclosure is not limited thereto. In some embodiments, the process of manufacturing the display device 10 can be performed by placing the target substrate SUB on a platform including a heat source or a heat sink and then controlling the temperature of the upper surface of the platform to be higher than the first temperature.

[0296] During the process of manufacturing the display device 10, in order to further improve the degree of alignment of the light emitting elements 30, the process of irradiating light can be further performed.

[0297] Figure 19 is a schematic cross-sectional view illustrating steps in a process of manufacturing a display device according to another embodiment.

[0298] Referring to ​ In the process of manufacturing the display device 10, in the step of forming the electric field EL on the electrodes (21 and 22), ultraviolet light UV can be applied to the light emitting elements 30 sprayed on the target substrate SUB. The light emitting elements 30 can have a dipole moment, and when the ultraviolet light UV is applied to the light emitting elements 30, the light emitting elements 30 can react with the ultraviolet light UV to have a larger dipole moment. The light emitting elements 30 having a large dipole moment can be aligned so that one end portion thereof faces a predetermined direction in response to the electric field EL formed on the electrodes (21 and 22). At the same time, at least one end portion of the light emitting elements 30 can be disposed on the first electrode 21 or the second electrode 22. For example, each of the light emitting elements 30 can have a first end portion disposed on the first electrode 21 and a second end portion disposed on the second electrode 22.

[0299] In the step of placing the light emitting element 30 on the electrodes (21 and 22), when the electric field EL is formed while the ultraviolet light UV is applied, the first end portion of the light emitting element 30 can be aligned in a predetermined direction as electrophoretic reactivity of the light emitting element 30 increases. Accordingly, the light emitting element 30 can be disposed on the electrodes (21 and 22) with a high degree of alignment, and product reliability of the display device 10 can be further improved.

[0300] The light emitting element ink according to the embodiments can include a thickening agent to have different viscosity according to temperature. In a storage state of the light emitting element ink at room temperature, the viscosity of the solution can be high so that precipitation of the light emitting element can be prevented. In a printing state of the light emitting element ink, the viscosity of the solution can be low so that a nozzle is not clogged and thus the ink can be easily discharged.

[0301] In the method of manufacturing a display device according to the embodiments, the display device can be manufactured using the light emitting element ink so that a printing process can be performed in a state in which the light emitting element is dispersed in the ink, a uniform number of light emitting elements can be disposed in each unit area with a high degree of alignment. Further, by heat treatment under a low pressure environment, the light emitting element solvent and the thickening agent, which are foreign matter residues in a subsequent process, can be completely removed. Accordingly, a display device having increased product reliability can be manufactured.

[0302] In summarizing the detailed description, those skilled in the art will understand that many changes and modifications can be made to the embodiments without substantially departing from the principles of the present disclosure. Accordingly, the disclosed preferred embodiments of the present disclosure are used only in a general and descriptive sense and are not for limiting purposes.

Claims

1. Light-emitting element ink, comprising: Solvent for light-emitting elements; A light-emitting element dispersed in the solvent of the light-emitting element, the light-emitting element comprising: Multiple semiconductor layers; and An insulating film surrounding the outer surface of the plurality of semiconductor layers; A thickener dispersed in the solvent of the light-emitting element, wherein The thickener comprises a compound represented by the following chemical structural formula 1, which is a polyol-based compound capable of forming intermolecular hydrogen bonds with the solvent of the light-emitting element or another thickener. The thickener has a boiling point of 200°C to 450°C at atmospheric pressure. [Chemical structural formula 1] In chemical structural formula 1, R 1 They are straight-chain or branched alkyl groups or straight-chain or branched alkyl ether groups, each having 1 to 3000 carbon atoms. The straight-chain or branched alkyl groups and the straight-chain or branched alkyl ether groups are substituted with hydroxyl groups or are not substituted, and I is an integer from 1 to 10. The solvent for the light-emitting element comprises a compound represented by the following chemical structural formula 2: [Chemical structural formula 2] In chemical structural formula 2, R 2 Including at least one of substituted or unsubstituted alcohol groups, ether groups, and ester groups, each having 2 to 10 carbon atoms, and m is an integer of 1 or 2.

2. The light-emitting element ink as described in claim 1, wherein... The thickener comprises a compound represented by one of the following chemical formulas 1 to 8: [Chemical Formula 1] [Chemical Formula 2] [Chemical Formula 3] [Chemical Formula 4] [Chemical Formula 5] [Chemical Formula 6] [Chemical Formula 7] [Chemical Formula 8] in, In chemical formulas 7 and 8, n is an integer from 1 to 1000.

3. The light-emitting element ink of claim 2, wherein the thickener forms intermolecular hydrogen bonds with the light-emitting element solvent and another thickener at a temperature of 25°C to form a network structure.

4. The light-emitting element ink of claim 3, wherein the light-emitting element ink has a viscosity of 20 cP to 300 cP at a temperature of 25°C.

5. The light-emitting element ink of claim 2, wherein the light-emitting element ink has a viscosity of 5 cP to 15 cP at a temperature of 40°C to 60°C.

6. The light-emitting element ink as described in claim 2, wherein... The amount of the light-emitting element is 0.01 parts by weight to 1 part by weight relative to 100 parts by weight of the light-emitting element ink, and The amount of the thickener is from 5 to 50 parts by weight relative to 100 parts by weight of the light-emitting element ink.

7. The light-emitting element ink as described in claim 6, further comprising: Dispersant dispersed in the solvent of the light-emitting element, The amount of the dispersant is from 10 parts by weight to 100 parts by weight relative to 100 parts by weight of the light-emitting element.

8. The light-emitting element ink as claimed in claim 1, wherein... The plurality of semiconductor layers of the light-emitting element include: First semiconductor layer; Second semiconductor layer; as well as The light-emitting layer between the first semiconductor layer and the second semiconductor layer, and The insulating film of the light-emitting element is configured to at least surround the outer surface of the light-emitting layer.

9. A method for manufacturing a display device, comprising: Prepare a light-emitting element ink comprising a solvent for light-emitting elements, multiple light-emitting elements, and a thickener; Prepare a target substrate having a first electrode and a second electrode; The light-emitting element ink is sprayed onto the target substrate at a first temperature; An electric field is formed on the target substrate to place the plurality of light-emitting elements on the first electrode and the second electrode; as well as The ink of the light-emitting element is heated under low pressure to remove the solvent and thickener from the light-emitting element. The thickener comprises a compound represented by the following chemical structural formula 1, which is a polyol-based compound capable of forming intermolecular hydrogen bonds with the solvent of the light-emitting element or another thickener. The thickener has a boiling point of 200°C to 450°C at atmospheric pressure. [Chemical structural formula 1] In chemical structural formula 1, R 1 They are straight-chain or branched alkyl groups or straight-chain or branched alkyl ether groups, each having 1 to 3000 carbon atoms. The straight-chain or branched alkyl groups and the straight-chain or branched alkyl ether groups are substituted with hydroxyl groups or are not substituted, and I is an integer from 1 to 10. The solvent for the light-emitting element comprises a compound represented by the following chemical structural formula 2: [Chemical structural formula 2] In chemical structural formula 2, R 2 Including at least one of substituted or unsubstituted alcohol groups, ether groups, and ester groups, each having 2 to 10 carbon atoms, and m is an integer of 1 or 2.

10. The method of claim 9, wherein The thickener comprises a compound represented by one of the following chemical formulas 1 to 8: [Chemical Formula 1] [Chemical Formula 2] [Chemical Formula 3] [Chemical Formula 4] [Chemical Formula 5] [Chemical Formula 6] [Chemical Formula 7] [Chemical Formula 8] in, In chemical formulas 7 and 8, n is an integer from 1 to 1000.

11. The method of claim 9, wherein Relative to 100 parts by weight of the light-emitting element ink, the amount of the plurality of light-emitting elements is from 0.01 parts by weight to 1 part by weight, and The amount of the thickener is from 100 parts by weight to 500 parts by weight relative to 100 parts by weight of the plurality of light-emitting elements.

12. The method of claim 9, wherein in the preparation of the light-emitting element ink, the thickener forms intermolecular hydrogen bonds with the light-emitting element solvent and another thickener to form a network structure.

13. The method of claim 12, wherein in the preparation of the light-emitting element ink, the light-emitting element ink has a temperature of 25°C. Viscosities ranging from 20 cP to 300 cP at a temperature of C.

14. The method of claim 9, wherein The ink ejection from the light-emitting element is performed via a printing process using an inkjet printing device, and The light-emitting element ink is above 25 At the first temperature of C, the material is sprayed onto the target substrate through a nozzle.

15. The method of claim 14, wherein In the ejection of the ink for the light-emitting element, the first temperature is 40°C to 60°C, and The light-emitting element ink has a viscosity of 5 cP to 15 cP at the first temperature.

16. The method of claim 15, wherein in the placement of the plurality of light-emitting elements, the target substrate is heat-treated at or above the first temperature to form the electric field.

17. The method of claim 9, wherein the removal of the light-emitting element solvent and the thickener is performed in 10... -4 The pressure was increased to 1 Torr, and The first temperature is 25 C to 150 C.

18. The method of claim 9, wherein in the placement of the plurality of light-emitting elements, a first end of each of the plurality of light-emitting elements is disposed on the first electrode, and The second end of each of the plurality of light-emitting elements is disposed on the second electrode.

19. The method of claim 9, wherein the plurality of light-emitting elements comprises: First semiconductor layer; Second semiconductor layer; An active layer between the first semiconductor layer and the second semiconductor layer; as well as An insulating film is configured to at least surround the outer surface of the active layer.

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