Light emitting device, display panel having the same, and method of manufacturing display panel

Abstract

A light-emitting device (100) has a first bank (102) that separates pixel regions, a second bank (103) that is positioned above the first bank (102) and defines a pixel region, and a light-emitting layer (104) that is positioned within a pixel region surrounded by the first bank (102) or the second bank (103). The light-emitting device (100) has a connecting portion (110) that communicates with two or more pixel regions in which a light-emitting layer (104) of the same color is positioned, at least one of the first bank (102) and the second bank (103). By doing so, the light-emitting device (100) and a display panel equipped with the same can improve the wettability of ink at the ends of the first bank (102) and the second bank (103) and suppress short circuits at the anode and cathode.

Description

Technology Field

[0001] The present invention relates to a light-emitting device, a display panel equipped with the same, and a method for manufacturing the same. Background Technology

[0002] In recent years, active research has been conducted on forming various electronic devices using printing methods. Printing methods allow for the application of the required amount of ink only where necessary. Consequently, they are characterized by higher material utilization efficiency compared to conventional vacuum deposition or sputtering methods. However, the materials used in these electronic devices (functional materials such as light-emitting and conductive materials) are generally very expensive. As a result, material loss becomes a significant problem. On the other hand, since printing methods enable film deposition in the atmosphere, they are desirable from the perspective of operating energy efficiency.

[0003] Examples of electronic device formation using printing methods include wiring using conductive ink, transistors using semiconductor ink, and display devices using light-emitting materials. Printing methods include, for example, screen printing, relief printing, and intaglio printing.

[0004] In recent years, inkjet printing methods that can form arbitrary patterns on printing objects non-contactually and on demand have been attracting attention. Specifically, active development is underway to form display devices, such as color filters, organic EL, and quantum dot displays, using inkjet printing methods.

[0005] Furthermore, as a next-generation display, the development of displays utilizing inorganic quantum dot materials as the light-emitting layer is becoming active. Quantum dots are special semiconductors with a diameter of 2 to 10 nanometers (10 to 50 atoms). Materials of such minute size exhibit properties different from those of ordinary materials. For example, the size of the band gap of a quantum dot can be controlled with high precision simply by changing the particle size of the quantum dot. The emission wavelength of a quantum dot depends on the size of the band gap. Consequently, it becomes possible to control the emission wavelength of the quantum dot with great precision by changing the particle size. In other words, the emission wavelength of a quantum dot can be altered simply by changing the particle size. For example, the emission wavelength of a quantum dot shifts toward the blue side as the particle size decreases, and shifts toward the red side as it increases. Additionally, the half-width of the emission wavelength of a quantum dot is very small. Specifically, the emission spectrum of a quantum dot is less than a few tens of nanometers.

[0006] In other words, for example, if the red, blue, and green light-emitting layers are formed using quantum dots, the half-width of each light-emitting wavelength can be reduced. Consequently, by forming the light-emitting layers using quantum dots, a display device exhibiting high color gamut characteristics can be realized. As a result, the performance of the display device can be dramatically improved.

[0007] Representative quantum dot materials include a core composed of inorganic materials such as cadmium-selenium, indium-phosphorus, copper-indium-sulfur, silver-indium-sulfur, and perovskite structures, and a layer called a shell formed around the core using materials such as zinc sulfide. Additionally, ligands are formed around the shell to achieve stability as an ink.

[0008] Furthermore, materials for quantum dots constituting light-emitting devices include photoluminescence materials that emit light when excited by light energy, and electroluminescence materials that emit light when excited by electrical energy. For example, quantum dot displays using photoluminescence materials are used as color filters for micro-LED displays. Additionally, quantum dot displays using electroluminescence materials include quantum dot displays formed by thinning a quantum dot material between an anode and a cathode.

[0009] Compared to organic EL displays, the above quantum dot display has very high brightness and excellent visibility outdoors. As a result, quantum dot displays are expected to be utilized in applications such as mobile phones, automotive displays, and head-mounted displays. These displays are expected to require a pixel resolution of 200 ppi (pixels per inch) or higher in the future.

[0010] However, when forming display devices such as display panels using the inkjet method, it is difficult to increase pixel resolution due to factors such as the size of the inkjet droplets and the precision of their impact positions. Consequently, in the formation of display devices using the inkjet method, there is a demand for improved ink application stability for high-pixel resolution patterns. In other words, as pixel resolution increases, the pixel area to which ink is applied becomes narrower. Consequently, if the precision of the inkjet droplet impact position is low, the ink may spill out of the pixel area. As a result, color mixing occurs between adjacent pixels.

[0011] Therefore, in order to avoid color mixing with adjacent pixels, for example, International Publication No. 2008 / 149498 (hereinafter referred to as “Patent Document 1”) discloses a method for manufacturing an organic EL device using an inkjet process. FIG. 11 shows a plan view of an organic EL device described in Patent Document 1.

[0012] As illustrated in FIG. 11, the organic EL device has a bank (3) formed in a line shape on a substrate (1), a bank (3') formed to divide two or more pixel regions (11) within the region surrounded by the bank (3), and a functional layer such as a hole transport layer (4) formed within the region surrounded by the bank (3). The bank (3) is composed of a material that exhibits liquid repellency with respect to the functional ink such as the hole transport layer (4). Between the banks (3), a red material (10R), a blue material (10B), and a green material (10G) are respectively arranged.

[0013] In addition, the structure of the organic EL device disclosed in Patent Document 1 has low wettability of the ink in the bank. That is, the contact angle for the ink applied within the bank becomes high. When the contact angle is high, it becomes difficult to apply the ink to the sidewalls of the bank. Furthermore, even if the ink can be applied to the ends of the bank, there is a risk that the ink film thickness will be low due to the surface tension of the ink.

[0014] In addition, the organic EL device comprises a functional thin film, such as a light-emitting layer, formed above an anode within a bank, and a cathode formed above the light-emitting layer. Consequently, if the film thickness of the light-emitting layer formed at the end of the bank is low, there is a risk that the anode and cathode may short-circuit.

[0015] The present invention provides a light-emitting device capable of improving the wettability of ink at the end of a bank and suppressing short circuits between an anode and a cathode, a display panel equipped with the same, and a method for manufacturing the same.

[0016] The present invention is a light-emitting device having a first bank for distinguishing pixel regions, a second bank disposed above the first bank and defining a pixel region, and a light-emitting layer disposed within a pixel region surrounded by the first bank or the second bank. Furthermore, the light-emitting device is configured such that at least one of the first bank and the second bank has a communication portion that communicates with two or more ranges of pixel regions in which a light-emitting layer of the same color is disposed.

[0017] In addition, the display panel of the present invention comprises the light-emitting device.

[0018] In addition, the method for manufacturing a display panel of the present invention includes a first step of forming a first bank that distinguishes pixel regions in which a light-emitting layer of the same light-emitting color is formed on a substrate, and a second step of forming a second bank that distinguishes pixel regions in which a light-emitting layer of a different light-emitting color is formed. In addition, the method for manufacturing a display panel includes a third step of forming a light-emitting layer in a region surrounded by the first bank or the second bank.

[0019] By the above, it is possible to provide a light-emitting device capable of improving the wettability of ink at the end of the bank and suppressing short circuits between the anode and cathode, a display panel equipped with the same, and a method for manufacturing the same. Brief explanation of the drawing

[0020] FIG. 1a is a plan view of a light-emitting device described in an embodiment. Figure 1b is a cross-sectional view along line 1B-1B of Figure 1a. FIG. 1c is a cross-sectional view along line 1C-1C of FIG. 1a. FIG. 1d is a cross-sectional view along line 1D-1D of FIG. 1a. FIG. 2a is a plan view of a light-emitting device described in the same embodiment before drying the ink applied by an inkjet. Figure 2b is a cross-sectional view along line 2B-2B of Figure 2a. FIG. 2c is a cross-sectional view along line 2C-2C of FIG. 2a. FIG. 3 is a plan view of a light-emitting device described in the same embodiment. FIG. 4a is a plan view according to Example 1 of the light-emitting device described in the same embodiment. Figure 4b is a cross-sectional view along line 4B-4B of Figure 4a. Figure 4c is a cross-sectional view along line 4C-4C of Figure 4a. FIG. 5a is a plan view according to Example 2 of the light-emitting device described in the same embodiment. Figure 5b is a cross-sectional view along line 5B-5B of Figure 5a. Figure 5c is a cross-sectional view along line 5C-5C of Figure 5a. FIG. 6a is a cross-sectional view along line 5B-5B of FIG. 5a showing the effect of the light-emitting device described in Example 2. FIG. 6b is a cross-sectional view along line 5B-5B of FIG. 5a showing the effect of the light-emitting device described in Example 2. FIG. 6c is a cross-sectional view along line 5C-5C of FIG. 5a showing the effect of the light-emitting device described in Example 2. FIG. 7a is a plan view according to Example 3 of the light-emitting device described in the same embodiment. Figure 7b is a cross-sectional view along line 7B-7B of Figure 7a. FIG. 8a is a plan view according to Example 4 of the light-emitting device described in the same embodiment. Figure 8b is a cross-sectional view along line 8B-8B of Figure 8a. Figure 8c is a cross-sectional view along line 8C-8C of Figure 8a. FIG. 8d is a cross-sectional view along line 8D-8D of FIG. 8a. FIG. 9a is a plan view according to Example 5 of the light-emitting device described in the same embodiment. Figure 9b is a cross-sectional view along line 9B-9B of Figure 9a. Fig. 9c is a cross-sectional view along line 9C-9C of Fig. 9a. FIG. 10a is a plan view according to Example 6 of the light-emitting device described in the same embodiment. FIG. 10b is a cross-sectional view along line 10B-10B of FIG. 10a. FIG. 10c is a cross-sectional view along line 10C-10C of FIG. 10a. FIG. 11 is a plan view illustrating the structure of an organic EL device described in Patent Document 1. Specific details for implementing the invention

[0021] (Embodiment)

[0022] Hereinafter, a light-emitting device (100) of an embodiment of the present invention will be described with reference to FIGS. 1a to 1d.

[0023] FIG. 1a is a plan view of a light-emitting device (100) of an embodiment. FIG. 1b is a cross-sectional view taken along line 1B-1B of FIG. 1a. FIG. 1c is a cross-sectional view taken along line 1C-1C of FIG. 1a. FIG. 1d is a cross-sectional view taken along line 1D-1D of FIG. 1a.

[0024] As illustrated in FIGS. 1a to 1d, the light-emitting device (100) of the present embodiment comprises a substrate (101), a first bank (102), a second bank (103), and a light-emitting layer (104), etc., formed on the substrate (101). The light-emitting layer (104) is composed of a red light-emitting layer (104R) that emits red light, a green light-emitting layer (104G) that emits green light, and a blue light-emitting layer (104B) that emits blue light.

[0025] The first bank (102) distinguishes the same light-emitting color, for example, a blue light-emitting layer (104B), among the light-emitting layers (104), as shown in FIG. 1c. The second bank (103) communicates the pixel areas in which the same light-emitting color, for example, a blue light-emitting layer (104B), is formed among the light-emitting layers (104), as shown in FIG. 1c, to be connected through the communication unit (110) in two or more ranges. Also, the second bank (103) distinguishes the different light-emitting colors of the light-emitting layer (104), for example, a red light-emitting layer (104R), a green light-emitting layer (104G), and a blue light-emitting layer (104B), respectively, as shown in FIG. 1b.

[0026] Also, the film thickness of the light-emitting layer (104), for example, the blue light-emitting layer (104B), is lower (thinner) than the film thickness of the first bank (102), as shown in FIG. 1C. Also, the film thickness of the red light-emitting layer (104R) and the green light-emitting layer (104G) is likewise lower (thinner) than the film thickness of the first bank (102).

[0027] The light-emitting layer (104) is formed by dispersing a quantum dot material of an inorganic compound in an organic solvent, such as tetradecane, which has a relatively high boiling point, in an ink. Specifically, the ink has a concentration of the quantum dot material contained in the ink of the light-emitting layer (104) of about 1 weight percent to 5 weight percent.

[0028] As described above, the light-emitting device (100) of the present embodiment is configured.

[0029] Hereinafter, the formation step of the light-emitting layer (104) of the light-emitting device (100) is described.

[0030] First, an ink in which a quantum dot material is dispersed in an organic solvent is applied to a substrate (101) using an inkjet method, and then the ink is dried. During the drying step, most of the organic solvent contained in the ink evaporates, leaving only the solid quantum dot material, and a light-emitting layer (104) is formed.

[0031] At this time, immediately after applying the ink of the light-emitting layer (104) by the inkjet method to the area surrounded by the first bank (102) or the second bank (103), there may be cases where a liquid amount of ink is applied to each bank up to the point of overflowing. In this case, if the ink that is in a state of overflowing from the bank is depressurized in a vacuum furnace to dry the organic solvent, the liquid amount of ink decreases along the walls of each bank. And finally, a light-emitting layer (104) is formed that is lower than the first bank (102), for example, with a film thickness of several tens of nm.

[0032] In addition, the ink also contains additives such as a dispersant to disperse the nanoparticles of the quantum dots in an organic solvent. As a result, the surface tension of the ink is relatively lowered, for example, to 15 mN / m to 25 mN / m, due to the additives. That is, the ink having low surface tension is applied to the area surrounded by the first bank (102) or the second bank (103). As a result, the applied ink becomes wettable at the contact surface with each bank. Consequently, the thinning of the film thickness of the light-emitting layer (104) on the side wall surface of the first bank (102) due to the low surface tension can be suppressed. That is, the occurrence of a portion on the anode or cathode electrode where ink cannot be applied is eliminated. As a result, the occurrence of a short circuit between the anode and cathode electrodes can be suppressed more reliably. Here, in this embodiment, a highly reflective metal, such as a silver-palladium-copper alloy, is used as the anode. Meanwhile, a highly transparent material, such as indium-tin oxide, is used as the cathode.

[0033] In addition, the light-emitting device (100) of the present embodiment may have, in addition to the light-emitting layer (104) which is not shown in the drawing, a functional thin film (which may be expressed as a functional layer), such as a hole injection layer, a hole transport layer, or an electron injection layer. These functional thin films are designed with a predetermined film thickness appropriately, taking into account the light emission efficiency of the light-emitting device (100) and the light extraction efficiency. For example, in order to efficiently extract the emitted light, the light-emitting device (100) is designed with a microcavity design. In order to perform a microcavity design, it is necessary to accurately adjust the film thickness of the functional thin film.

[0034] The above functional thin film is formed in an area defined as the first bank (102). Additionally, the functional thin film is formed such that its total thickness is lower than the film thickness of the first bank (102). This is because if the film thickness of the functional thin film is higher than the thickness of the first bank (102), the uniformity of the film thickness of the functional thin film deteriorates in the portion exceeding the first bank (102). Consequently, it becomes difficult to design an appropriate microcavity of the light-emitting device (100).

[0035] Additionally, the first bank (102) is composed of a resin that does not contain liquid-repellent components, such as fluorine. As a result, the first bank (102) becomes relatively wettable with respect to the ink forming the functional thin film. This makes it possible to form a uniform film of the functional thin film in the area defined by the first bank (102).

[0036] In addition, the substrate (101) of the light-emitting device (100) may be transparent or opaque as described above, and may be any material having insulating properties. That is, the substrate (101) may be composed of, for example, a flexible resin sheet such as glass or polyimide. Also, the first bank (102) may be any material having insulating properties. That is, the first bank (102) may be composed of, for example, a photosensitive resin such as acrylic, epoxy, or polyimide, or an inorganic compound such as silicon oxide. As a result, the first bank (102) has the property of being very wettable with ink.

[0037] Meanwhile, the second bank (103) can be made of a material having insulating properties, for example, a photosensitive resin such as acrylic, epoxy, or polyimide. And, like the first bank (102), the second bank (103) is formed on a substrate (101) containing the first bank (102) by photolithography of the above material.

[0038] Additionally, the second bank (103) needs to collect ink that forms a light-emitting layer (104), etc., applied by an inkjet method. Accordingly, it is desirable for the second bank (103) to be resistant to wetting with ink and to have liquid-repellent properties. Therefore, the second bank (103) is composed of a resin containing, for example, a functional group containing a fluorine atom. Thus, the second bank (103) is formed to have liquid-repellent properties with respect to ink.

[0039] In addition, the above fluorine resin is not particularly limited and may be a resin having fluorine atoms in at least some of the repeating units of the polymer. Examples of fluorine resins include fluorinated polyolefin resins, fluorinated polyimide resins, fluorinated polyacrylic resins, etc.

[0040] Due to the above material composition, the static contact angle of the first bank (102) with respect to the ink is 5° to 30°. Meanwhile, the static contact angle of the second bank (103) with respect to the ink is 30° to 70°. That is, the first bank (102) is more easily wetted with ink than the second bank (103).

[0041] Also, as described above, the thickness of the first bank (102) is lower (thinner) than the thickness of the second bank (103). Specifically, the thickness of the second bank (103) is generally 0.5 μm to 3.0 μm, and preferably 0.8 μm to 1.5 μm. Meanwhile, the thickness of the first bank (102) is 0.1 μm to 0.5 μm, and preferably 0.2 μm to 0.4 μm.

[0042] In addition, the light-emitting layer (104) of the light-emitting device (100) of the present embodiment includes a quantum dot material as described above. Specifically, the quantum dot material included in the light-emitting layer (104) is composed of, for example, a cadmium-selenium-based, indium-phosphorus-based, copper-indium-sulfur-based, silver-indium-sulfur-based, or perovskite structure material. And, the ink is composed of the above material dispersed in an organic solvent as a dispersion medium. Specifically, the ink is composed of a concentration of the quantum dot material in the dispersion medium of 0.5 weight percent to 10 weight percent.

[0043] In addition, as described above, the quantum dot material emits a different color of light depending on the particle size, and emits red light as the particle size increases. That is, the red light-emitting layer (104R), the green light-emitting layer (104G), and the blue light-emitting layer (104B) are each formed by quantum dot materials with different particle sizes. Furthermore, the electron injection layer described above is formed using, for example, an ink in which nanoparticles such as zinc oxide are dispersed in an organic solvent.

[0044] As described above, the light-emitting layer (104) of the light-emitting device (100) is configured.

[0045] Hereinafter, the configuration of the second bank (103) of the light-emitting device (100) of the present embodiment will be explained with reference to FIGS. 2a to 3.

[0046] Additionally, the second bank (103) is formed by connecting two or more pixel regions, where a light-emitting layer (104) of the same light-emitting color is formed, through a connecting part (110), as described above.

[0047] FIGS. 2a to 2c show the state before drying the ink when applying ink to the light-emitting device (100) using an inkjet method. Specifically, FIG. 2a is a plan view of the light-emitting device (100). FIG. 2b is a cross-sectional view along line 2B-2B shown in FIG. 2a. FIG. 2c is a cross-sectional view along line 2C-2C shown in FIG. 2a. FIG. 3 is a plan view of the light-emitting device (100) after drying the ink.

[0048] Additionally, when applying ink to form a light-emitting layer (104) using an inkjet method, as shown in FIG. 2a, the inkjet head (201) having a plurality of nozzles (202) is used to apply the droplets. At this time, first, an amount of ink exceeding the height of the first bank (102) is applied. The ink applied exceeding the height of the first bank (102) spreads into the pixel area of ​​the same-colored light-emitting layer (104) through the connecting part (110) of the second bank (103). By applying in this manner, the variation in the droplet volume of the droplets discharged from each nozzle (202) is mitigated. As a result, it becomes possible to apply the ink uniformly within adjacent pixel areas of the same color.

[0049] Generally, each nozzle (202) of the inkjet head (201) has an uneven hole diameter, etc., during processing. As a result, the volume of the droplets discharged from each nozzle (202) is uneven. The variation in the discharged droplets is linked to the variation in the film thickness of the light-emitting layer (104). The variation in film thickness affects the light-emitting characteristics of the light-emitting device (100). Therefore, controlling the uniform amount of ink application is very important.

[0050] In addition, in the light-emitting device (100) of the above embodiment, a configuration in which the communication portion (110) is formed only in the second bank (103) has been described as an example, but it is not limited thereto. For example, the communication portion may be formed in either the first bank (102) or the second bank (103), or in both. If formed in both, it is preferable to make the size of the communication portion formed in the second bank (103) larger than the size of the communication portion formed in the first bank (102). Thus, the applied ink flows in the communication direction, with the communication portion (110) formed in the second bank (103) as the main one. The first bank (102) serves to provide electrical insulation between adjacent pixels and to optically shield light emitted between adjacent pixels. Accordingly, it is preferable that the first bank (102) does not have a communication portion.

[0051] Additionally, as shown in FIG. 3, the communication portion (110) of the second bank (103) is formed such that, in the arrangement direction (long axis direction) of the same color light-emitting layer (104), the cross-sectional area of ​​the communication portion (110) connecting the pixel area arranged on the outer side of the substrate (101) is sequentially reduced with respect to the communication portion (110) connecting the pixel area arranged on the outer side of the substrate (101). That is, the communication portion (110) is formed such that, as it moves outward from the center of the substrate (101), the cross-sectional area in the direction perpendicular to the communication direction is sequentially reduced. Typically, when the ink applied to the area surrounded by the second bank (103) dries, solutes such as light-emitting materials contained in the ink move outward by convection. This is because, in the ink applied to the area surrounded by the second bank (103), the ink located on the outer side dries faster. And, as the ink moves outward, the film thickness of the light-emitting layer (104) placed on the outer side of the bank becomes thicker. As a result, there is a risk that the film thickness of the light-emitting layer (104) may become uneven depending on the placement location.

[0052] Therefore, in this embodiment, the cross-sectional area of ​​the connecting portion is sequentially reduced and the flow resistance is increased so that it becomes difficult for ink to move toward the outside of the bank. By doing so, the movement of the solute in the ink toward the outside during drying is suppressed. As a result, the formation of an uneven film thickness of the light-emitting layer is avoided, and a light-emitting layer with a more uniform film thickness can be formed.

[0053] With the above device structure, it is possible to realize a light-emitting device with high uniformity of the film thickness of the light-emitting layer using an inkjet process. As a result, it becomes possible to manufacture a display panel equipped with a light-emitting device having excellent light-emitting characteristics at a low cost.

[0054] <Method for manufacturing a light-emitting device of an embodiment>

[0055] Hereinafter, a method for manufacturing a light-emitting device (100) of the present embodiment will be described with reference to FIGS. 1a to 3.

[0056] The method for manufacturing the light-emitting device (100) of the present embodiment includes at least three steps, as described below.

[0057] The first step is to form a first bank (102) that distinguishes pixel regions where a light-emitting layer of the same light-emitting color is formed on a substrate (101). The second step is to form a second bank (103) that distinguishes pixel regions where a light-emitting layer of a different light-emitting color is formed. The third step is to form a light-emitting layer (104) by applying ink containing a quantum dot material to an area surrounded by the first bank (102) or the second bank (103).

[0058] Below, each step is explained individually.

[0059] (Stage 1)

[0060] Below, the above-mentioned first step will be explained in detail.

[0061] First, a photosensitive resin that is cured by exposure to ultraviolet light is applied to a substrate (101) using an application method such as spin coating or slit coating. At this time, the conditions for applying the photosensitive resin are adjusted according to the required film thickness, such as the number of spins in the spin coating or the scanning speed in the slit coating.

[0062] Next, a pre-baking of the photosensitive resin coating film is performed using a hot plate or the like, thereby evaporating the solvent component in the photosensitive resin and drying the coating film. Then, the dried coating film is exposed to ultraviolet light through a photomask having a desired pattern (corresponding to the first bank (102)). At this time, the photosensitive resin has a negative type material in which the exposed part irradiated with ultraviolet light hardens, and a positive type material in which the unexposed part of the ultraviolet light hardens.

[0063] Therefore, next, depending on the type of photosensitive resin material used, the uncured portion of the photosensitive resin is removed using an appropriate developer.

[0064] Next, the pattern of the photosensitive resin remaining after removal is post-baked in a curing furnace or the like.

[0065] By the above first step, the first bank (102) is formed.

[0066] (Stage 2)

[0067] Next, the above-mentioned second step will be explained in detail.

[0068] The second step is to form a second bank (103) on the outer side (outer periphery) of the first bank (102).

[0069] Specifically, a second bank (103) is formed by a photolithography process using a photosensitive resin, similar to the first bank (102). At this time, the film thickness of the second bank (103) is formed to be thicker than the film thickness of the first bank (102) (including film thickness of the same degree).

[0070] Additionally, the above description describes an example in which the first bank (102) is formed in the first step and the second bank (103) is formed in the second step in separate steps, but this is not limited thereto. The first bank (102) and the second bank (103) may be formed simultaneously, for example, in a single step.

[0071] Specifically, the transmittance of the photomask to ultraviolet light is locally changed, for example, to half-etch the photosensitive resin applied to the substrate (101). By doing so, patterns of the first bank (102) and the second bank (103) with different film thicknesses can be formed simultaneously.

[0072] For example, when using a photosensitive resin of a negative type material, the amount of ultraviolet light transmitted in the area where the film thickness is to be thinned is reduced. As a result, in areas with low exposure, the degree of curing is reduced, so a large amount of photosensitive resin is etched by the developer.

[0073] By the above method, a first bank (102) and a second bank (103) with different film thicknesses can be formed simultaneously in one step. As a result, productivity can be improved.

[0074] (Stage 3)

[0075] Next, the above-mentioned third step will be explained in detail.

[0076] First, an ink in which a quantum dot material is dispersed in a solvent at a predetermined concentration is applied to an area enclosed by the second bank (103) using an inkjet method. At this time, the amount of ink ejected from the nozzle (202) of the inkjet head (201) is determined so that the film thickness after drying of the applied ink becomes a predetermined film thickness.

[0077] Next, the ink applied on the substrate (101) is dried under reduced pressure using a drying oven. Specifically, the pressure inside the drying oven is reduced by a vacuum pump to lower the pressure and dry the ink. This promotes the evaporation of the solvent in the ink and dries it. Typically, the ink ejected by the inkjet head (201) often uses a solvent with a high boiling point to suppress the drying of the solvent while it is maintained inside the nozzle (202). Consequently, the solvent in the ink is difficult to dry. Therefore, reduced pressure drying is used when drying the coating film. This allows the solvent with a high boiling point contained in the ink of the coating film to be efficiently evaporated.

[0078] In addition, the conditions for vacuum drying are, for example, a vacuum level of several Pa and a holding time of several tens of minutes. However, the conditions for the vacuum level and holding time vary depending on the boiling point of the solvent contained in the ink. Accordingly, the above-described conditions for vacuum drying are examples and are not limited to the above conditions.

[0079] In addition, in the case of an ink in which the extruded ink does not contain a solvent and the quantum dot material is dispersed only in a UV-curing resin, solvent drying by reduced pressure may not be performed.

[0080] Next, the substrate (101) on which the pressure-dried ink coating film is formed is placed on, for example, a hot plate. Then, the coating film is pre-baked by the hot plate under conditions of, for example, 100°C for about 5 minutes.

[0081] Next, ultraviolet light with a wavelength of 365 nm is irradiated onto the pre-baked coating film to perform photolithography and curing of the coating film. At this time, the irradiation dose of ultraviolet light is, for example, 200 mJ / cm² 2 ~1000 mJ / cm² 2 am.

[0082] Next, the coating film that has been photo-cured with ultraviolet light is post-baked using a curing furnace, for example, at 150°C for about 20 minutes. By doing so, a light-emitting layer (104) is formed.

[0083] By the above, the light-emitting device (100) of the present embodiment is manufactured.

[0084] (Example 1)

[0085] Hereinafter, a light-emitting device (100a) according to Example 1 of the light-emitting device (100) of the present embodiment will be described with reference to FIGS. 4a to 4c.

[0086] FIG. 4a is a plan view of a light-emitting device (100a) according to Example 1. FIG. 4b is a cross-sectional view along line 4B-4B of FIG. 4a. FIG. 4c is a cross-sectional view along line 4C-4C of FIG. 4a.

[0087] As illustrated in FIGS. 4a to 4c, the light-emitting device (100a) according to Example 1 has a reflective anode (120) formed on a substrate (101) such as glass.

[0088] Hereinafter, a method for manufacturing a light-emitting device (100a) is described.

[0089] First, a reflective anode (120) is formed on a substrate (101). Specifically, a silver-palladium-copper alloy with high reflectivity, for example, is deposited on the substrate (101) by a sputtering method. Then, a reflective anode (120) is formed by patterning it to fit the pixel area using a photolithography method.

[0090] Next, a first bank (102) is formed to distinguish the emitting layers (104) of the same color. Here, the emitting layers (104) of the same color consist of a red emitting layer (104R) that emits red light, a green emitting layer (104G) that emits green light, and a blue emitting layer (104B) that emits blue light. At this time, it is preferable that the first bank (102) be composed of a photosensitive resin, such as acrylic resin, which is easy to wet with the ink forming the film of the emitting layer (104) within the first bank (102) and does not contain liquid-repellent components such as fluorine. That is, the first bank (102) is formed by patterning the above material using a photolithography method.

[0091] Specifically, first, an acrylic resin is applied onto a substrate (101) by a slit coat, and then pre-baked by heating it on a hot plate at 80°C for 30 minutes. After that, the acrylic resin is cured by irradiating it with ultraviolet light having a wavelength of 365 nm. At this time, the exposure amount is 500 mJ / cm² 2 am.

[0092] Next, the acrylic resin cured by ultraviolet light is developed. The development is performed, for example, by spraying for 60 seconds using a developer solution of 1 wt% Na2CO3.

[0093] Next, the developed acrylic resin is post-baked using a heating furnace at 150°C for 60 minutes.

[0094] Next, a second bank (103) is formed to distinguish pixel regions of different light-emitting colors. The second bank (103) is formed in a line shape to include two or more pixel regions in which a light-emitting layer of the same color, separated by the first bank (102), is formed. At this time, the second bank (103) is formed using a fluorine-containing acrylic resin containing fluorine.

[0095] Specifically, the second bank (103) is formed by photolithography, just like the first bank (102). At this time, a material having the characteristic of having fluorine localized on the surface upon exposure to light is used as a fluorine-containing acrylic resin. Thus, the second bank (103) is formed, in which the side surface is hydrophilic and the top surface is hydrophobic. At this time, the stop contact angle of the ink of the second bank (103) is approximately 50°. Additionally, the film thickness of the first bank (102) is formed to be 0.3 μm, and the film thickness of the second bank (103) is formed to be 1.0 μm.

[0096] Next, a hole injection layer (130) is formed on the reflective anode (120) of the pixel area formed by the first bank (102) and the second bank (103). The ink constituting the hole injection layer (130) is composed by dissolving 2.0 weight percent of a solid component, such as polyethylenedioxythiophene / polystyrenesulfonic acid (PEDOT / PSS), in an alcohol-based solvent. The ink composed as described above is applied to the pixel area using an inkjet method. At this time, the ink is applied from a nozzle at an output amount such that the film thickness after drying of the solvent contained in the ink is 50 nm. The drying of the solvent is performed by vacuum drying by depressurizing the furnace with a vacuum pump. Vacuum drying is performed, for example, with a vacuum degree of several Pa and a holding time of 15 minutes.

[0097] Next, a red light-emitting layer (104R), a green light-emitting layer (104G), and a blue light-emitting layer (104B) constituting the light-emitting layer (104) are formed on the hole injection layer (130). Specifically, as the ink constituting the light-emitting layer (104), an ink is used in which a cadmium-selenium-based quantum dot material is dispersed in a straight-chain aliphatic organic solvent at a concentration of 2.5 weight percent. Additionally, a quantum dot material with a particle size of 10 to 30 nm is used. Then, the above ink is applied to the area surrounded by the second bank (103) by an inkjet method. At this time, the application of the ink is performed to cover the first bank (102). As a result, when the ink is wet after application, the ink is applied to the first bank (102) as well. That is, in order to apply ink in the form described above for the formation of the light-emitting layer (104), the first bank (102) is preferably in a state where the contact angle with respect to the ink is as low as possible and wettable, and additionally has hydrophilicity.

[0098] In addition, the printing direction of the ink is perpendicular to the long axis direction of the second bank (103), in which pixels of the red light-emitting layer (104R), green light-emitting layer (104G), and blue light-emitting layer (104B) are arranged, as shown in FIG. 4a. That is, the nozzle (202) of the inkjet head (201) is installed such that pixels in which a light-emitting layer (104) of the same color is formed are arranged in a linear direction. As a result, the position of the ink impact during ejection can be relatively easily impacted at a predetermined position by adjusting the timing of ejection with respect to the printing direction.

[0099] However, regarding the arrangement direction (long axis direction) of the nozzle (202), it is difficult to correct the position of the ink impact, and as described above, it depends on the machining precision of the nozzle (202) (especially the hole diameter). Therefore, regarding the arrangement direction of the nozzle (202), the area where the ink can impact is widened. By doing so, the range of variation of the allowable impact position of the ink can be greatly increased.

[0100] Additionally, a plurality of nozzles (202) are arranged in the ink application area. Thus, even if one nozzle (202) becomes unable to discharge ink due to blockage of foreign matter or the like, it can be compensated for by ink discharged from an adjacent nozzle (202).

[0101] Additionally, a pixel area consisting of two or more emitting layers (104) of the same color is defined by the second bank (103). As a result, ink constituting the emitting layer (104), such as a red emitting layer (104R), can be applied within the second bank (103) using a plurality of nozzles (202). This allows the deviation of the droplet volume of ink discharged from the nozzle (202) of the inkjet head (201) to be averaged.

[0102] Next, the solvent in the ink forming the light-emitting layer (104) is dried by vacuum drying. At this time, vacuum drying was performed under conditions where the vacuum degree was several Pa and the drying time was 20 minutes. As a result, after vacuum drying, the solvent in the ink is dried, and the film thickness of the ink becomes smaller than that of the first bank (102). Consequently, the ink that was covering the first bank (102) immediately after the above-described coating is also removed.

[0103] Next, after forming the light-emitting layer (104), an electron injection layer (140) is formed. For forming the electron injection layer (140), for example, an ink in which zinc oxide nanoparticles are dispersed in an alcohol-based organic solvent is used. The particle size of the nanoparticles dispersed in the organic solvent is 5 nm to 20 nm, and the concentration of nanoparticles in the ink is 3.0 weight percent. Then, the ink of the above composition is applied to the upper portions of the red light-emitting layer (104R), the green light-emitting layer (104G), and the blue light-emitting layer (104B), respectively, using an inkjet method.

[0104] Next, after applying the ink, the ink is vacuum dried, just like the hole injection layer (130) or the light-emitting layer (104), to dry the solvent in the ink.

[0105] And finally, a transparent electrode (150) made of, for example, indium-tin oxide is formed on the entire surface of the substrate (101) on which each functional film (functional layer) is formed, as shown in FIG. 4b and FIG. 4c.

[0106] At this time, it is preferable to form the corners of the second bank (103) in a shape that is smoothly rounded or has a low taper angle. By doing so, the coverage of the transparent electrode (150) to the second bank (103) can be improved.

[0107] In addition, in this embodiment, the light-emitting characteristics of the light-emitting device are improved by utilizing the microcavity effect, which efficiently extracts light emitted from the light-emitting layer (104) to the outside through the microcavity design. Here, the microcavity effect is an effect that strengthens the light-emitting color by adjusting the film thickness of the light-emitting layer (104) or the hole injection layer (130) to resonate and emphasize light of a specific wavelength.

[0108] In addition, since the microcavity design is performed by controlling the film thickness of functional films such as the hole injection layer (130), the light-emitting layer (104), and the electron injection layer (140), the uniformity of these film thicknesses is very important. Accordingly, in the microcavity design, it is desirable that the total thickness of the stacked films of these functional layers be smaller than the thickness of the first bank (102). This is because if these stacked films are formed to exceed the thickness of the first bank (102), the film shape becomes non-uniform in the excess portion. As a result, it becomes difficult to control the film thickness of these stacked films.

[0109] The light-emitting device (100a) and the display panel equipped with it, manufactured with the structure and manufacturing method described above, have high film thickness uniformity. As a result, a display panel with excellent light-emitting characteristics can be realized.

[0110] (Example 2)

[0111] Hereinafter, a light-emitting device (100b) according to Example 2 of the light-emitting device (100) of the present embodiment will be described with reference to FIGS. 5a to 5c.

[0112] FIG. 5a is a plan view of the light-emitting device (100b) of Example 2. FIG. 5b and FIG. 5c are cross-sectional views along lines 5B-5B and 5C-5C of FIG. 5a.

[0113] As illustrated in FIGS. 5a to 5c, the light-emitting device (100b) according to Example 2 is different from the structure of the light-emitting device (100a) of Example 1 in that it has an irregularity (160) including a step difference of either a convex shape or a concave shape installed on a second bank (103) that distinguishes pixel regions of different light-emitting colors.

[0114] At this time, the uneven surface (160) is formed in a step shape and includes a convex step (160a) as shown in FIG. 5b or a concave step (160b) as shown in FIG. 5c. The height of the convex step (160a) or the depth of the concave step (160b) is, for example, about 100 nm to 200 nm.

[0115] The convex step (160a) and the concave step (160b) are formed by photolithography using, for example, a photomask with a different amount of transmittance.

[0116] In addition, as described above, inks in which nanoparticles such as quantum dot materials are dispersed contain dispersants such as surfactants to disperse the nanoparticles, or various additives to improve dispersion stability. Such inks may have high wettability with respect to the bank. Specifically, the ink forming the red light-emitting layer (104R), green light-emitting layer (104G), and blue light-emitting layer (104B) using quantum dot materials has a receding contact angle with respect to the second bank (103) of 5° to 20°. In contrast, the ink in which a polymer is dissolved, for example, the ink forming the light-emitting layer of an organic EL, has a receding contact angle of approximately 25° to 40°. That is, the receding contact angle of the ink in which nanoparticles are dispersed is lower than the receding contact angle of the ink in which a polymer is dissolved. However, if the receding contact angle is low, when ink of, for example, a red light-emitting layer (104R) is applied to the area surrounded by the second bank (103) and then the solvent, which is the dispersion medium, is dried, there may be cases where ink remains on the top of the second bank (103). Also, depending on the type of ink, the dispersion medium may be a photosensitive resin. In the case of this ink, after the ink is photosensitive and cured and shrunk, there may be cases where ink remains on the top of the second bank (103).

[0117] Hereinafter, using FIGS. 6a to 6c, the residue of the ink after applying and drying the ink will be described.

[0118] FIG. 6a is a cross-sectional view showing the state immediately after applying the ink of the red light-emitting layer (104R), the ink of the green light-emitting layer (104G), and the ink of the blue light-emitting layer (104B) to the light-emitting device (100b) of Example 2 in an area surrounded by the second bank (103), and before drying the ink. FIG. 6b is a cross-sectional view showing the state after drying the ink shown in FIG. 6a.

[0119] As shown in FIG. 6a, the applied ink is divided and applied along the boundary of the convex step (160a) placed on the second bank (103).

[0120] Then, when the applied ink is dried by vacuum drying, the state shown in FIG. 6b is obtained. At this time, because the receding contact angle of the ink is low, there is a residue of ink on the second bank (103) as shown in FIG. 6b. Specifically, it is a residue of ink (104R') of the red light-emitting layer (104R), a residue of ink (104G') of the green light-emitting layer (104G), and a residue of ink (104B') of the blue light-emitting layer (104B).

[0121] If ink remains on the top of the second bank (103), when different colored inks are applied, for example, when ink of the green light-emitting layer (104G) is applied to a pixel area adjacent to the red light-emitting layer (104R), there is a possibility of color mixing through the ink remaining on the second bank (103). That is, for example, when green is applied to an adjacent pixel area after red is applied in FIG. 6, if a residue of red ink remains on the second bank (103), wettability increases in the portion of the ink residue. As a result, when green ink is applied, the clumping (liquidity) of the green ink is weakened, and there is a possibility that the green ink will flow into the red pixel area and mix.

[0122] Therefore, in the light-emitting device (100b) of Example 2, a step-shaped protrusion (160) is installed on the second bank (103). By doing so, color mixing by ink of a light-emitting layer of a different color in adjacent pixel areas can be suppressed more effectively.

[0123] Also, as illustrated in FIG. 6c, when a concave step (160b) is installed on the second bank (103), the ink applied on the second bank (103) stops spreading at the edge of the concave step (160b) due to surface tension. As a result, it becomes possible to avoid mixing of ink in adjacent pixel areas.

[0124] As described above, by the structure of the light-emitting device (100b) of Example 2, an ink dispersed with a quantum dot material having high uniformity of film thickness and high wettability can be applied without mixing colors. By doing so, a display panel with excellent light-emitting properties can be provided.

[0125] In addition, in the light-emitting device (100b) of Example 2, although not specifically illustrated to explain the effect, when manufacturing a display panel using the light-emitting device (100b), it goes without saying that a reflective anode, a hole injection layer, an electron injection layer, a transparent electrode, etc. are formed, just as in Example 1.

[0126] (Example 3)

[0127] Hereinafter, a light-emitting device (100c) according to Example 3 of the light-emitting device (100) of the present embodiment will be described with reference to FIG. 7a and FIG. 7b.

[0128] FIG. 7a is a plan view of the light-emitting device (100c) of Example 3. FIG. 7b is a cross-sectional view along line 7B-7B of FIG. 7a.

[0129] As illustrated in FIG. 7a and FIG. 7b, the light-emitting device (100c) according to Example 3 differs from the light-emitting device (100b) of Example 2 in that a fine irregular structure (160c) is installed on the top portion of the second bank (103).

[0130] The uneven structure (160c) is composed of a height on the order of nanometers, specifically a height of several nanometers to several tens of nanometers. By forming the uneven structure (160c) with such a surface shape, a phenomenon called superhydrophobicity is manifested between the liquid and the solid. As a result, the contact angle of the liquid increases.

[0131] That is, in the conventional configuration, the receding contact angle can be increased even in inks with a low receding contact angle on the second bank (103). By doing so, ink residue on the second bank (103) can be suppressed, and mixing of different colors applied to adjacent pixel areas can be suppressed more effectively.

[0132] (Example 4)

[0133] Hereinafter, a light-emitting device (100d) according to Example 4 of the light-emitting device (100) of the present embodiment will be described with reference to FIGS. 8a to 8d.

[0134] FIG. 8a is a plan view of the light-emitting device (100d) of Example 4. FIG. 8b is a cross-sectional view along line 8B-8B of FIG. 8a. FIG. 8c is a cross-sectional view along line 8C-8C of FIG. 8a. FIG. 8d is a cross-sectional view along line 8D-8D of FIG. 8a.

[0135] As illustrated in FIGS. 8a to 8d, the light-emitting device (100d) according to Example 4 differs from the light-emitting device (100a) of Example 1 in that the first bank (102) is connected to the pixel area of ​​the same-colored light-emitting layer and to two or more ranges through the connecting part (110). In addition, it differs from the light-emitting device (100a) of Example 1 in that the second bank (103) is formed to distinguish the pixel area of ​​the same-colored light-emitting layer as well as the pixel area of ​​the different-colored light-emitting layer. That is, the pixel area of ​​the same-colored light-emitting layer and the pixel area of ​​the different-colored light-emitting layer are not connected through the second bank (103).

[0136] With the configuration of the light-emitting device (100d) above, the ink applied by the inkjet method spreads out to the pixel area of ​​the same color light-emitting layer only through the connecting portion (110) of the first bank (102). In this way, the uniformity of the film thickness of the light-emitting layer can be improved, just like in Example 1.

[0137] (Example 5)

[0138] Hereinafter, a light-emitting device (100e) according to Example 5 of the light-emitting device (100) of the present embodiment will be described with reference to FIGS. 9a to 9c.

[0139] FIG. 9a is a plan view of the light-emitting device (100e) of Example 5. FIG. 9b is a cross-sectional view along line 9B-9B of FIG. 9a. FIG. 9c is a cross-sectional view along line 9C-9C of FIG. 9a.

[0140] As illustrated in FIGS. 9a to 9c, the light-emitting device (100e) according to Example 5 is different from the light-emitting device (100a) of Example 1 in that the first bank (102) is arranged not only in the direction in which the pixel regions of the same-colored light-emitting layer are arranged, but also in the direction in which the pixel regions of the two-colored light-emitting layer are arranged.

[0141] By the configuration of the above-described light-emitting device (100e), the entire perimeter of each light-emitting region of the same-colored and different-colored light-emitting layers is surrounded by the first bank (102). In this way, the uniformity of the film thickness of the light-emitting layer can be improved, just like in Example 1.

[0142] (Example 6)

[0143] Hereinafter, a light-emitting device (100f) according to Example 6 of the light-emitting device (100) of the present embodiment will be described with reference to FIGS. 10a to 10c.

[0144] FIG. 10a is a plan view of the light-emitting device (100f) of Example 6. FIG. 10b is a cross-sectional view along line 10B-10B of FIG. 10a. FIG. 10c is a cross-sectional view along line 10C-10C of FIG. 10a.

[0145] As illustrated in FIGS. 10a to 10c, the light-emitting device (100f) according to Example 6 is different from the light-emitting device (100e) of Example 5, which is composed of a light-emitting material that emits light through electric field excitation, in that the red light-emitting layer (104R), the green light-emitting layer (104G), and the blue light-emitting layer (104B) are composed of a material that emits light through photo-excitation.

[0146] In the case of a light-emitting material that emits light through photo-excitation, the film thickness of the light-emitting layer (104) is formed to a thickness of about 5 μm to 10 μm. The reason for this is that in the case of a light-emitting device using a photo-excitation material, a blue LED is sometimes used as a photo-excitation light source. However, the efficiency of converting the blue light emission color to red or green is low. Therefore, the film thickness of the light-emitting layer (104) is made thick to secure light emission efficiency.

[0147] In addition, the composition of the ink forming the light-emitting layer (104) uses a photosensitive acrylic resin or epoxy resin that cures with light, rather than an ink in which quantum dots are dispersed in an organic solvent as in Examples 1 to 4. At this time, the ink contains not only the light-emitting material of the quantum dots but also a scattering agent having a light scattering effect. Specifically, the scattering agent is, for example, titanium oxide particles.

[0148] The light-emitting device (100f) composed of the above material functions as a color conversion device. Accordingly, the light-emitting device (100f) can be used, for example, as a color filter for a micro LED display.

[0149] In this case, the light-emitting device (100f) is used in conjunction with a substrate having blue LEDs arranged thereon. By doing so, the uniformity of the film thickness of the light-emitting layer can be improved, just like in Examples 1 to 5.

Claims

Claim 1 A light-emitting device having a first bank for separating pixel regions, a second bank disposed above the first bank and defining the pixel regions, and a light-emitting layer disposed within the pixel regions surrounded by the first bank or the second bank, wherein at least one of the first bank and the second bank has a communication portion that communicates with the pixel regions in which the same-colored light-emitting layer is disposed in two or more ranges, and the cross-sectional area of ​​the cross-section perpendicular to the communication direction of the communication portion of the first bank and the second bank decreases as it moves from the central pixel region arranged on the substrate toward the outer pixel regions with respect to the arrangement direction of the same-colored light-emitting layer. Claim 2 A light-emitting device according to claim 1, wherein the wettability of the first bank with respect to the ink forming the light-emitting layer is higher than the wettability of the second bank. Claim 3 A light-emitting device according to claim 1, wherein the thickness of the first bank is lower than the thickness of the second bank. Claim 4 A light-emitting device according to claim 1, wherein the size of the connecting portion of the first bank is smaller than the size of the connecting portion of the second bank. Claim 5 delete Claim 6 A light-emitting device according to claim 1, wherein the thickness of the first bank is higher than the total thickness of a plurality of functional layers disposed within the pixel area, including the light-emitting layer. Claim 7 A light-emitting device according to claim 1, wherein the resting contact angle of the top portion of the first bank with respect to the ink of the light-emitting layer is 5° to 30° and the resting contact angle of the second bank is 30° to 70°. Claim 8 A light-emitting device according to claim 1, wherein the light-emitting layer is made of a quantum dot material which is an inorganic material. Claim 9 A light-emitting device according to claim 8, wherein the retraction contact angle of the top portion of the second bank with respect to the ink of the light-emitting layer is 5° to 15°. Claim 10 A light-emitting device according to claim 1, wherein the second bank separating the pixel regions of different light-emitting colors is formed in two or more stepped shapes parallel to the direction in which the pixel regions of the same light-emitting color are arranged. Claim 11 A light-emitting device according to claim 1, wherein the top portion of the second bank has a surface having an uneven shape. Claim 12 A display panel having a light-emitting device as described in any one of claims 1 to 4 and claims 6 to 11. Claim 13 A method for manufacturing a display panel comprising: a first step of forming a first bank that distinguishes pixel regions in which a emitting layer of the same color is formed on a substrate; a second step of forming a second bank that distinguishes pixel regions in which a emitting layer of a different emitting color is formed; and a third step of forming a emitting layer in a region surrounded by the first bank or the second bank, wherein the cross-sectional area of ​​the cross-section perpendicular to the communication direction of the communication portion of the first bank and the second bank decreases with respect to the arrangement direction of the emitting layers of the same color as it moves from the pixel region of the central portion arranged on the substrate to the pixel region of the outer portion.

Images