Ink composition

Abstract

The present invention relates to an ink composition. According to an embodiment, the ink composition comprises: inorganic nanoparticles; and a first solvent, wherein the value of the hydrogen bonding term (δH) in the Hansen solubility parameter value is 5 or less, thereby improving the dispersion stability of the inorganic nanoparticles and preventing the nozzle clogging phenomenon in the head of the inkjet printing device.

Description

Technical Field

[0001] The present invention relates to an ink composition and a method for manufacturing a light-emitting element including an electron transport region formed using the ink composition. Background Art

[0002] Various display devices are being developed for multimedia devices such as televisions, mobile phones, tablet computers, navigation devices, game consoles, etc. Among these display devices, so-called self-luminous display elements are used that realize display by making a light-emitting material including an organic compound emit light.

[0003] Furthermore, in order to improve the color reproducibility of a display device, research and development on a light-emitting element using quantum dots as a light-emitting material is being conducted, and there is a need to improve the light-emitting efficiency and life of the light-emitting element using quantum dots. Summary of the invention

[0004] An object of the present invention is to provide an ink composition having improved dispersion stability.

[0005] An object of the present invention is to provide a method for producing a light emitting element which can prevent nozzle clogging in a head during an inkjet printing process by using an ink composition having improved dispersion stability.

[0006] An ink composition according to an embodiment of the present invention includes: inorganic nanoparticles; and a first solvent, wherein a hydrogen bonding term (δH) value of the first solvent in a Hansen solubility parameter value is 5 or less.

[0007] The ink composition may further include a second solvent, and the second solvent may include at least one of triethylene glycol monomethyl ether, propylene glycol, and ethyl alcohol.

[0008] The volume ratio of the first solvent to the second solvent may be 0.5:1 to 2:1.

[0009] The content of the inorganic nanoparticles may be 0.1% by mass to 10% by mass relative to the total amount of the ink composition.

[0010] The first solvent may include diisopropyl phthalate.

[0011] The inorganic nanoparticles may include at least one of Cd, Zn, In, Sn, Sb, Ga, Ge, As, Hg, Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, Os, Mn, Mo, and Cr.

[0012] The inorganic nanoparticles may have a diameter of 1 nm to 30 nm.

[0013] The ink composition may further include a third solvent, and a value of a hydrogen bonding term (δH) in a Hansen solubility parameter value of the third solvent may be 5 or less.

[0014] The value of the hydrogen bonding term (δH) in the Hansen solubility parameter value of the solvent formed by mixing the first solvent and the third solvent may be 3 or less.

[0015] According to one embodiment of the present invention, a method for manufacturing a light-emitting element includes the following steps: forming a hole transport region on a first electrode; forming a light-emitting layer on the hole transport region; forming an electron transport region on the light-emitting layer; and forming a second electrode on the electron transport region, wherein the step of forming the electron transport region includes the following steps: preparing an ink composition including inorganic nanoparticles and a first solvent; applying the ink composition on the light-emitting layer to form a preliminary electron transport region; and supplying heat to the preliminary electron transport region, wherein the hydrogen bond term (δH) value in the Hansen solubility parameter value of the first solvent is less than 5.

[0016] The first solvent may include diisopropyl phthalate.

[0017] The step of preparing the ink composition may include the following steps: preparing an inorganic nanoparticle dispersion by dispersing the inorganic nanoparticles in a second solvent; and mixing the inorganic nanoparticle dispersion into the first solvent, wherein the second solvent is characterized in that the hydrogen bonding term (δH) value in the Hansen solubility parameter value is greater than 5.

[0018] The second solvent may include at least one of triethylene glycol monomethyl ether, propylene glycol, and ethyl alcohol.

[0019] A volume ratio of the first solvent to the second solvent may be 0.5:1 to 2:1.

[0020] The content of the inorganic nanoparticles may be 0.1% by mass to 10% by mass based on the entire content of the ink composition.

[0021] The ink composition may further include a third solvent, and a value of a hydrogen bonding term (δH) among Hansen solubility parameter values ​​of the third solvent may be 5 or less.

[0022] The light emitting layer may include quantum dots.

[0023] The quantum dot may include a core and a shell surrounding the core.

[0024] The method of applying the ink composition onto the light-emitting layer may be achieved by inkjet printing.

[0025] The inorganic nanoparticles may have a diameter of 1 nm to 30 nm.

[0026] According to an embodiment of the present invention, the ink composition can improve the dispersion stability of inorganic nanoparticles in a solution by including a low-polarity solvent having a small hydrogen bonding term value in the Hansen solubility parameter value.

[0027] According to a method for manufacturing a light emitting element according to an embodiment of the present invention, it is possible to prevent nozzle clogging in a head during an inkjet printing process by using an ink composition having improved dispersion stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a combined three-dimensional diagram of an electronic device according to an embodiment of the present invention.

[0029] Figure 2 is an exploded perspective view of an electronic device according to an embodiment of the present invention.

[0030] Figure 3 is with Figure 2 The II' line corresponds to a cross-sectional view of a display device according to an embodiment of the present invention.

[0031] Figure 4 is a plan view of a display device according to an embodiment of the present invention.

[0032] Figure 5 is with Figure 4 The cross-sectional view corresponding to the II-II' line.

[0033] Figures 6 to 9 is a cross-sectional view of a light emitting element according to an embodiment of the present invention.

[0034] Fig.10 is a sequence diagram showing a method for manufacturing a light emitting element according to an embodiment.

[0035] Fig.11 is a sequential diagram detailing steps for forming an electron transport region according to an embodiment.

[0036] Figures 12a to 12c is a cross-sectional view showing an ink composition according to an embodiment.

[0037] Fig.13 is a diagram schematically showing a step of forming a preliminary electron transport region according to an embodiment.

[0038] Fig.14 FIG. 1 is a diagram schematically showing a step of forming an electron transport region according to an embodiment.

[0039] Figures 15a to 15d FIG. 1 is a diagram showing nozzles in a head of an inkjet printing device according to an embodiment.

[0040] Fig.16 1 is a diagram showing visual confirmation of ink compositions of an example and a comparative example according to an embodiment.

[0041] [Description of Reference Numerals]

[0042] DD: Display Device

[0043] ED: Light-emitting element EL1: First electrode

[0044] EL2: Second electrode HTR: Hole transport region

[0045] EML: Emitting Layer ETR: Electron Transport Region

[0046] ICP: ink composition INP: inorganic nanoparticles

[0047] SV1: First solvent SV2: Second solvent

[0048] SV3: Third solvent DETAILED DESCRIPTION

[0049] The present invention may be modified in various ways and may have various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but should be understood to include all changes, equivalents and substitutes included in the concept and technical scope of the present invention.

[0050] In this specification, when a certain component (or region, layer, part, etc.) is mentioned as being "on" another component, "connected" or "combined with" another component, it means that it can be directly arranged on another component or directly connected / combined with another component, or a third component may be arranged between them.

[0051] In addition, in the present application, "directly arranged" may mean that there is no additional layer, film, region, plate, etc. between a layer, film, region, plate, etc. and another part. For example, "directly arranged" may mean that an additional part such as an adhesive part is not used between two layers or two parts.

[0052] The same reference numerals refer to the same components. In addition, in the drawings, the thickness, ratio, and size of the components are exaggerated for the purpose of effectively explaining the technical contents.

[0053] “And / or” includes all combinations of more than one that can be defined for the related constituents.

[0054] The terms "first" and "second" can be used to describe a variety of constituent elements, but the constituent elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one constituent element from another constituent element. For example, without departing from the scope of the present invention, the first constituent element can be named as the second constituent element, and similarly, the second constituent element can also be named as the first constituent element. Singular expressions include plural expressions as long as different meanings are not clearly expressed in the context.

[0055] Furthermore, terms such as “below”, “lower side”, “above”, and “upper side” are used to describe the relationship between the components shown in the drawings. These terms are relative concepts and are described based on the directions shown in the drawings.

[0056] Unless otherwise defined, all terms (including technical terms and scientific terms) used in this specification have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. Furthermore, terms that are the same as those defined in commonly used dictionaries should be interpreted as having the same meaning as that in the context of the relevant technology, and herein, unless explicitly defined, should not be interpreted as having an overly ideal or overly formal meaning.

[0057] The terms such as “including” or “having” should be understood as intending to specify the existence of the features, numbers, steps, operations, constituent elements, parts or combinations thereof recorded in the specification, rather than excluding the existence or additional possibility of one or more other features or numbers, steps, operations, constituent elements, parts or combinations thereof in advance.

[0058] Hereinafter, an ink composition, a light emitting element, and a display device including the light emitting element according to an embodiment of the present invention will be described with reference to the drawings.

[0059] Figure 1 is a perspective view showing an embodiment of the electronic device EA. Figure 2 FIG. 4 is an exploded perspective view of an electronic device EA according to an embodiment. Figure 3 is with Figure 2 The II' line corresponds to a cross-sectional view of a display device according to an embodiment of the present invention.

[0060] In one embodiment, the electronic device EA may be a large electronic device such as a television, a display, or an external advertising board. Also, the electronic device EA may be a small or medium-sized electronic device such as a personal computer, a notebook computer, a personal digital terminal, a car navigation unit, a game console, a smart phone, a tablet computer, and a camera. Moreover, these are only shown as embodiments, and other electronic devices may also be used without departing from the concept of the present invention. In this embodiment, the electronic device EA is exemplarily shown as a smart phone.

[0061] The electronic device EA may include a display device DD and a housing HAU. The display device DD may display an image IM through a display surface IS. Figure 1 The case where the display surface IS is parallel to a plane defined by the first direction DR1 and the second direction DR2 crossing the first direction DR1 is shown. However, this is only exemplary, and in other embodiments, the display surface IS of the display device DD may have a curved shape.

[0062] The normal direction of the display surface IS, that is, the direction of the display image IM in the thickness direction of the display device DD is indicated by the third direction DR3. The front surface (or upper surface) and the rear surface (or lower surface) of each component can be distinguished by the third direction DR3.

[0063] The fourth direction DR4 (refer to Figure 4 ) may be a direction between the first direction DR1 and the second direction DR2. The fourth direction DR4 may be located on a plane parallel to a plane defined by the first direction DR1 and the second direction DR2. In addition, the directions indicated by the first to fourth directions DR1, DR2, DR3, and DR4 are relative concepts and may be converted into other directions.

[0064] In the electronic device EA, the display surface IS displaying the image IM may correspond to the front surface (front surface) of the display device DD, and may correspond to the front surface FS of the window WP. Hereinafter, the display surface, the front surface of the electronic device EA, and the front surface of the window WP will use the same reference numerals. The image IM may include not only dynamic images but also static images. In addition, although not shown, the electronic device EA may include a foldable display device including a folding area and a non-folding area or a curved display device including at least one curved portion, etc.

[0065] The housing HAU may house the display device DD. The housing HAU may be arranged to cover the display device DD in a manner that exposes the upper surface of the display device DD as the display surface IS. The housing HAU may cover the side surface and the bottom surface of the display device DD and expose the entire upper surface. However, the embodiment is not limited thereto, and the housing HAU may cover not only the side surface and the bottom surface of the display device DD but also a portion of the upper surface.

[0066] In the electronic device EA of one embodiment, the window WP may include an optically transparent insulating material. The window WP may include a transmissive area TA and a frame area BZA. The front surface FS of the window WP including the transmissive area TA and the frame area BZA is equivalent to the front surface FS of the electronic device EA. The user may recognize the provided image through the transmissive area TA equivalent to the front surface FS of the electronic device EA.

[0067] exist Figure 1 and Figure 2 In FIG. 1 , the transmission area TA is shown as a quadrilateral with arc-shaped vertices. However, this is only an exemplary case, and the transmission area TA may have various shapes and is not limited to a certain embodiment.

[0068] The transmission area TA may be an optically transparent area. The frame area BZA may be an area having a relatively lower light transmittance than the light transmittance of the transmission area TA. The frame area BZA may have a predetermined color. The frame area BZA may be adjacent to the transmission area TA and may surround the transmission area TA. The frame area BZA may define the shape of the transmission area TA. However, the embodiment is not limited thereto, and the frame area BZA may also be arranged to be adjacent to only one side of the transmission area TA, and may also be partially omitted.

[0069] The display device DD may be arranged below the window WP. In this specification, "below" may mean a direction opposite to a direction in which the display device DD provides an image.

[0070] In one embodiment, the display device DD may be a structure that substantially generates an image IM. The image IM generated from the display device DD is displayed on the display surface IS and is recognized by the user externally through the transmission area TA. The display device DD includes a display area DA and a non-display area NDA. The display area DA may be an area activated according to an electrical signal. The non-display area NDA may be an area covered by a frame area BZA. The non-display area NDA is adjacent to the display area DA. The non-display area NDA may surround the display area DA.

[0071] The display device DD may include: a display panel DP; and an optical component PP arranged on the display panel DP. The display panel DP may include a display element layer DP-EL. The display element layer DP-EL includes a light emitting element ED ( Figure 6 ).

[0072] The display device DD may include a plurality of light emitting elements ED-1, ED-2, ED-3 ( Figure 5 ). The optical part PP may be arranged on the display panel DP to control reflected light generated at the display panel DP due to external light. The optical part PP may include, for example, a polarizing layer or a color filter layer.

[0073] In the display device DD of an embodiment, the display panel DP may be a light-emitting display panel. For example, the display panel DP may be a quantum dot light-emitting display panel including quantum dot light-emitting elements. However, the embodiment is not limited thereto, and the display panel DP may be an organic light-emitting display panel including organic electroluminescent elements.

[0074] The display panel DP may include: a base substrate BS; a circuit layer DP-CL disposed on the base substrate BS; and a display element layer DP-EL disposed on the circuit layer DP-CL.

[0075] The base substrate BS may be a component that provides a base surface on which the display element layer DP-EL is arranged. The base substrate BS may be a glass substrate, a metal substrate, a plastic substrate, etc. However, the embodiment is not limited thereto, and the base substrate BS may be an inorganic layer, an organic layer, or a composite material layer. The base substrate BS may be a flexible substrate that can be easily bent or folded.

[0076] In one embodiment, the circuit layer DP-CL is arranged on the base substrate BS, and the circuit layer DP-CL may include a plurality of transistors (not shown). For example, the circuit layer DP-CL may include a switching transistor and a driving transistor for driving the light emitting element of the display element layer DP-EL.

[0077] Figure 4 is a plan view showing a display device according to an embodiment. Figure 5 FIG. 4 is a cross-sectional view of a display device DD according to an embodiment. Figure 5 is with Figure 4 The cross-sectional view corresponding to the II-II' line.

[0078] Reference Figure 4 and Figure 5, a display device DD of an embodiment includes a plurality of light emitting elements ED-1, ED-2, and ED-3. Furthermore, a display device DD of an embodiment may include a display panel DP including a plurality of light emitting elements ED-1, ED-2, and ED-3, and an optical component PP arranged on the display panel DP. In addition, unlike what is shown in the figure, in a display device DD of an embodiment, the optical component PP may be omitted.

[0079] The display panel DP includes a base substrate BS, a circuit layer DP-CL provided on the base substrate BS, and a display element layer DP-EL. The display element layer DP-EL may include: a pixel defining film PDL; light emitting elements ED-1, ED-2, ED-3, arranged between the pixel defining films PDL; and an encapsulation layer TFE, arranged on the light emitting elements ED-1, ED-2, ED-3.

[0080] The display device DD may include a peripheral area NPXA and light-emitting areas PXA-B, PXA-G, and PXA-R. Each of the light-emitting areas PXA-B, PXA-G, and PXA-R may be an area that emits light generated from each of the light-emitting elements ED-1, ED-2, and ED-3. The light-emitting areas PXA-B, PXA-G, and PXA-R may be spaced apart from each other on a plane.

[0081] The light emitting regions PXA-B, PXA-G, and PXA-R may be divided into a plurality of groups according to the colors of the lights generated by the light emitting elements ED-1, ED-2, and ED-3. Figure 4 and Figure 5 In the display device DD of an embodiment shown, three light-emitting regions PXA-B, PXA-G, and PXA-R emitting blue light, green light, and red light are exemplarily shown. For example, the display device DD of an embodiment may include a blue light-emitting region PXA-B, a green light-emitting region PXA-G, and a red light-emitting region PXA-R that are divided from each other.

[0082] The plurality of light emitting elements ED-1, ED-2, and ED-3 may emit light of different wavelength bands. For example, in one embodiment, the display device DD may include: a first light emitting element ED-1 that emits blue light as a first light; a second light emitting element ED-2 that emits green light as a second light; and a third light emitting element ED-3 that emits red light as a third light. However, the embodiment is not limited thereto, and the first to third light emitting elements ED-1, ED-2, and ED-3 may emit light of the same wavelength band, or at least one of them may emit light of a different wavelength band.

[0083] For example, the blue light emitting region PXA-B, the green light emitting region PXA-G, and the red light emitting region PXA-R of the display device DD may correspond to the first light emitting element ED-1, the second light emitting element ED-2, and the third light emitting element ED-3, respectively.

[0084] The display device DD of one embodiment may include a plurality of light emitting elements ED-1, ED-2, and ED-3. The light emitting elements ED-1, ED-2, and ED-3 may include light emitting layers EML-B, EML-G, and EML-R including quantum dots QD1, QD2, and QD3.

[0085] The first light-emitting layer EML-B of the first light-emitting element ED-1 may include a first quantum dot QD1. The first quantum dot QD1 may emit blue light as the first light. The second light-emitting layer EML-G of the second light-emitting element ED-2 and the third light-emitting layer EML-R of the third light-emitting element ED-3 may include a second quantum dot QD2 and a third quantum dot QD3, respectively. The second quantum dot QD2 and the third quantum dot QD3 may emit green light as the second light and red light as the third light, respectively.

[0086] In one embodiment, the first light may be light having a central wavelength in a band of 410 nm to 480 nm, the second light may be light having a central wavelength in a band of 500 nm to 570 nm, and the third light may be light having a central wavelength in a band of 625 nm to 675 nm.

[0087] The quantum dots QD1, QD2, and QD3 included in the light-emitting layers EML-B, EML-G, and EML-R of one embodiment may be semiconductor nanocrystals that can be selected from II-VI group compounds, III-VI group compounds, I-III-VI group compounds, III-V group compounds, III-II-V group compounds, IV-VI group compounds, IV group elements, IV group compounds, and combinations thereof.

[0088] The II-VI compound can be selected from the group consisting of the following compounds: binary compounds selected from the group consisting of CdSe, CdTe, CdS, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS and mixtures thereof; ternary compounds selected from the group consisting of CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe , CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS and mixtures thereof; and a quaternary compound selected from the group consisting of HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe and mixtures thereof.

[0089] III-VI compounds may include: binary compounds such as In 2 S 3 、In 2 Se 3 etc.; ternary compounds such as InGaS 3 、InGaSe 3 etc.; or any combination thereof.

[0090] The I-III-VI group compound can be selected from: a ternary compound selected from AgInS, AgInS 2 、CuInS、CuInS 2 、AgGaS 2 、CuGaS 2 、CuGaO 2 、AgGaO 2 、AgAlO 2 and mixtures thereof; or quaternary compounds, AgInGaS 2 、CuInGaS 2 wait.

[0091] The III-V compound may be selected from the group consisting of: a binary compound selected from the group consisting of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, and mixtures thereof; a ternary compound selected from the group consisting of GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InGaP, InAlP, InNP, InNAs, InNSb, InPAs, InPSb, and mixtures thereof; and a quaternary compound selected from the group consisting of GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, and mixtures thereof. In addition, the III-V compound may also include a Group II metal. For example, InZnP or the like can be selected as the III-II-V group compound.

[0092] The IV-VI compound may be selected from the group consisting of the following compounds: a binary compound selected from the group consisting of SnS, SnSe, SnTe, PbS, PbSe, PbTe and mixtures thereof; a ternary compound selected from the group consisting of SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe and mixtures thereof; and a quaternary compound selected from the group consisting of SnPbSSe, SnPbSeTe, SnPbSTe and mixtures thereof. The IV group element may be selected from the group consisting of Si, Ge and mixtures thereof. The IV group compound may be a binary compound selected from the group consisting of SiC, SiGe and mixtures thereof.

[0093] At this time, the binary compound, ternary compound or quaternary compound may be present in the particle at a uniform concentration, or may be dispersed in the same particle in a state where the concentration distribution is locally different. In addition, there may be a core / shell structure in which one quantum dot surrounds other quantum dots. The interface between the core and the shell may have a concentration gradient in which the concentration of the element present in the shell decreases as it approaches the center.

[0094] In some embodiments, quantum dots QD1, QD2, and QD3 may have a core-shell structure including a core containing the aforementioned nanocrystals and a shell surrounding the core. The shells of the quantum dots QD1, QD2, and QD3 may act as a protective layer for preventing the chemical denaturation of the core and maintaining the semiconductor properties and / or as a charging layer for imparting electrophoretic properties to inorganic nanoparticles. The shell may be a single layer or multiple layers. The interface between the core and the shell may have a concentration gradient in which the concentration of the element present in the shell decreases as it approaches the center. Examples of the shells of the quantum dots QD1, QD2, and QD3 may include metal or non-metal oxides, semiconductor compounds, or combinations thereof.

[0095] For example, the metal or non-metal oxide may be exemplified by binary compounds such as SiO 2 、Al 2 O 3 、TiO 2 、ZnO、MnO、Mn 2 O 3 , Mn 3 O 4 , CuO, FeO, Fe 2 O 3 , Fe 3 O 4 , CoO, Co 3 O 4 , NiO, etc.; or ternary compounds such as MgAl 2 O 4 、CoFe 2 O 4 、NiFe 2 O 4 、CoMn 2 O 4 Etc., but the present invention is not limited thereto.

[0096] Furthermore, examples of the semiconductor compounds include CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnSeS, ZnTeS, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP, InGaP, InSb, AlAs, AlP, AlSb, etc., but the present invention is not limited thereto.

[0097] The quantum dots QD1, QD2, and QD3 may have a full width at half maximum (FWHM: full width of half maximum) of the emission wavelength spectrum of about 45 nm or less, preferably about 40 nm or less, and more preferably about 30 nm or less. Within this range, the color purity or color reproducibility may be improved. Furthermore, the light emitted by the quantum dots QD1, QD2, and QD3 is emitted in all directions, thereby improving the light viewing angle.

[0098] Furthermore, the morphology of quantum dots QD1, QD2, and QD3 is not particularly limited as long as it is a morphology commonly used in the art. More specifically, spherical, pyramidal, multi-arm, or cubic nanoparticles, nanotubes, nanowires, nanofibers, nanoplate-like particles, and the like can be used.

[0099] Quantum dots QD1, QD2, and QD3 can adjust the color of the light emitted according to the particle size. Therefore, quantum dots QD1, QD2, and QD3 can have a variety of luminescent colors such as blue, red, and green. The smaller the particle size of quantum dots QD1, QD2, and QD3, the shorter the wavelength of light that can be emitted. For example, in quantum dots QD1, QD2, and QD3 having the same core, the particle size of quantum dots that emit green light can be smaller than the particle size of quantum dots that emit red light. Moreover, in quantum dots QD1, QD2, and QD3 having the same core, the particle size of quantum dots that emit blue light can be smaller than the particle size of quantum dots that emit green light. However, the embodiment is not limited to this. In quantum dots QD1, QD2, and QD3 having the same core, the particle size can also be adjusted according to the material forming the shell and the thickness of the shell.

[0100] In addition, in the case where the quantum dots QD1, QD2, QD3 have multiple luminescent colors such as blue, red, and green, the materials of the cores of the quantum dots QD1, QD2, QD3 having different luminescent colors may be different from each other.

[0101] In one embodiment, the first to third quantum dots QD1, QD2, QD3 may have different diameters from each other. For example, the average diameter of the first quantum dot QD1 of the first light-emitting element ED-1 for emitting light in a relatively short wavelength band may be relatively smaller than the average diameters of the second quantum dot QD2 of the second light-emitting element ED-2 emitting light in a relatively long wavelength band and the third quantum dot QD3 of the third light-emitting element ED-3.

[0102] In addition, in this specification, the average diameter corresponds to a value obtained by arithmetically averaging the diameters of a plurality of quantum dot particles. In addition, the diameter of a quantum dot particle may be an average value of the width of the quantum dot particle in a cross section.

[0103] The relationship between the average diameters of the first to third quantum dots QD1, QD2, and QD3 is not limited to the above-mentioned limitations. Figure 5 The case where the sizes of the first to third quantum dots QD1, QD2, and QD3 are similar to each other is shown, but unlike the case shown, the sizes of the first to third quantum dots QD1, QD2, and QD3 included in the light-emitting elements ED-1, ED-2, and ED-3 may be different from each other. In addition, the average diameters of two quantum dots selected from the first to third quantum dots QD1, QD2, and QD3 may be similar, and the others may be different.

[0104] In the light-emitting elements ED-1, ED-2, and ED-3 of one embodiment, the light-emitting layers EML-B, EML-G, and EML-R may include a host and a dopant. In one embodiment, the light-emitting layers EML-B, EML-G, and EML-R may include quantum dots QD1, QD2, and QD3 as dopant materials. In addition, in one embodiment, the light-emitting layers EML-B, EML-G, and EML-R may also include a host material. In addition, in the light-emitting elements ED-1, ED-2, and ED-3 of one embodiment, the light-emitting layers EML-B, EML-G, and EML-R may emit fluorescence. For example, quantum dots QD1, QD2, and QD3 may be used as fluorescent dopant materials.

[0105] Although not shown, each of the first to third quantum dots QD1 , QD2 , and QD3 may have a ligand or the like for improving dispersion stability bonded to the surface of the quantum dots.

[0106] exist Figure 4 and Figure 5 In the display device DD of the embodiment shown, the areas of the light emitting regions PXA-B, PXA-G, and PXA-R may be different from each other. In this case, the area may refer to the area when viewed on a plane defined by the first direction DR1 and the second direction DR2.

[0107] The light-emitting regions PXA-B, PXA-G, and PXA-R may have different areas according to the colors of light emitted from the light-emitting layers EML-B, EML-G, and EML-R of the light-emitting elements ED-1, ED-2, and ED-3. Figure 4 and Figure 5In the display device DD of one embodiment, the blue light emitting region PXA-B corresponding to the first light emitting element ED-1 emitting blue light may have the largest area, and the green light emitting region PXA-G corresponding to the second light emitting element ED-2 generating green light may have the smallest area. However, the embodiment is not limited thereto, and the light emitting regions PXA-B, PXA-G, and PXA-R may emit light of other colors in addition to blue light, green light, and red light, or the light emitting regions PXA-B, PXA-G, and PXA-R may have the same area, or may be arranged in the same area as in Figure 4 The light emitting regions PXA-B, PXA-G, PXA-R are provided at different area ratios as shown.

[0108] Each light-emitting area PXA-B, PXA-G, and PXA-R may be an area divided by a pixel-defining film PDL. The surrounding area NPXA is an area between adjacent light-emitting areas PXA-B, PXA-G, and PXA-R, and may be an area corresponding to the pixel-defining film PDL. In addition, in the present specification, each light-emitting area PXA-B, PXA-G, and PXA-R may correspond to a pixel. The pixel-defining film PDL may divide the light-emitting elements ED-1, ED-2, and ED-3. The light-emitting layers EML-B, EML-G, and EML-R of the light-emitting elements ED-1, ED-2, and ED-3 may be divided by being arranged in the openings OH1, OH2, and OH3 defined in the pixel-defining film PDL. In one embodiment, the first light-emitting layer EML-B of the first light-emitting element ED-1 can be arranged in the first opening portion OH1, the second light-emitting layer EML-G of the second light-emitting element ED-2 can be arranged in the second opening portion OH2, and the third light-emitting layer EML-R of the third light-emitting element ED-3 can be arranged in the third opening portion OH3.

[0109] The pixel defining film PDL can be formed using a polymer resin. For example, the pixel defining film PDL may include a polyacrylate resin or a polyimide resin. In addition to the polymer resin, the pixel defining film PDL may also include an inorganic substance. In addition, the pixel defining film PDL may include a light absorbing substance, or may include a black pigment or a black dye. The pixel defining film PDL formed by a black pigment or a black dye can realize a black pixel defining film. When forming the pixel defining film PDL, carbon black or the like can be used as a black pigment or a black dye, but the embodiment is not limited thereto.

[0110] Furthermore, the pixel definition layer PDL may be formed using an inorganic material. For example, the pixel definition layer PDL may include silicon nitride (SiN x ), silicon oxide (SiOx ), silicon oxynitride (SiO x N y ), silicon oxynitride (SiN x O y ) etc. The pixel definition film PDL may define the light emitting regions PXA-B, PXA-G, and PXA-R. The light emitting regions PXA-B, PXA-G, and PXA-R and the peripheral region NPXA may be divided by the pixel definition film PDL.

[0111] Each light-emitting element ED-1, ED-2, and ED-3 may include: a first electrode EL1; hole transport regions HTR-1, HTR-2, and HTR-3, which are arranged on the first electrode EL1; light-emitting layers EML-B, EML-G, and EML-R, which are arranged on the hole transport regions HTR-1, HTR-2, and HTR-3; electron transport regions ETR-1, ETR-2, and ETR-3, which are arranged on the light-emitting layers EML-B, EML-G, and EML-R; and a second electrode EL2, which is arranged on the electron transport regions ETR-1, ETR-2, and ETR-3.

[0112] The hole transport regions HTR-1, HTR-2, HTR-3 and the electron transport regions ETR-1, ETR-2, ETR-3 included in each light emitting element ED-1, ED-2, ED-3 can be respectively arranged in the openings OH1, OH2, OH3 defined in the pixel defining film PDL and divided.

[0113] For example, the first hole transport region HTR-1 and the first electron transport region ETR-1 included in the first light-emitting element ED-1 may be arranged adjacent to the first light-emitting layer EML-B, and may be patterned and arranged in the first opening portion OH1 where the first light-emitting layer EML-B is arranged. The second hole transport region HTR-2 and the second electron transport region ETR-2 included in the second light-emitting element ED-2 may be arranged adjacent to the second light-emitting layer EML-G, and may be patterned and arranged in the second opening portion OH2 where the second light-emitting layer EML-G is arranged. The third hole transport region HTR-3 and the third electron transport region ETR-3 included in the third light-emitting element ED-3 may be arranged adjacent to the third light-emitting layer EML-R, and may be patterned and arranged in the third opening portion OH3 where the third light-emitting layer EML-R is arranged. However, not limited to this, the hole transport regions HTR-1, HTR-2, HTR-3 and the electron transport regions ETR-1, ETR-2, ETR-3 may also be provided as a common layer commonly arranged in the light emitting regions PXA-B, PXA-G, PXA-R and the surrounding region NPXA.

[0114] In one embodiment, each of the hole transport regions HTR-1, HTR-2, HTR-3 and the electron transport regions ETR-1, ETR-2, ETR-3 may be provided in the openings OH1, OH2, OH3 defined in the pixel defining layer PDL through a printing process.

[0115] The encapsulation layer TFE may cover the light emitting elements ED-1, ED-2, and ED-3. The encapsulation layer TFE may seal the display element layer DP-EL. The encapsulation layer TFE may be a thin film encapsulation layer. The encapsulation layer TFE may be a layer or a plurality of layers stacked. The encapsulation layer TFE includes at least one insulating layer. The encapsulation layer TFE according to an embodiment may include at least one inorganic film (hereinafter referred to as an encapsulation inorganic film). Furthermore, the encapsulation layer TFE according to an embodiment may include at least one organic film (hereinafter referred to as an encapsulation organic film) and at least one encapsulation inorganic film.

[0116] The encapsulation inorganic film protects the display element layer DP-EL from moisture / oxygen, and the encapsulation organic film protects the display element layer DP-EL from foreign matter such as dust particles. The encapsulation inorganic film may include silicon nitride, silicon oxynitride, silicon oxide, titanium oxide, or aluminum oxide, etc., but is not particularly limited thereto. The encapsulation organic film may include an acrylic compound, an epoxy compound, etc. The encapsulation organic film may include an organic substance capable of photopolymerization, but is not particularly limited thereto.

[0117] The encapsulation layer TFE may be disposed on the second electrode EL2 , and disposed to fill the openings OH1 , OH2 , and OH3 .

[0118] In addition, although it is shown in Figure 5 In the display device DD of one embodiment shown, the thicknesses of the light-emitting layers EML-B, EML-G, and EML-R of the first to third light-emitting elements ED-1, ED-2, and ED-3 are similar, but the embodiment is not limited thereto. For example, in one embodiment, the thicknesses of the light-emitting layers EML-B, EML-G, and EML-R of the first to third light-emitting elements ED-1, ED-2, and ED-3 may be different from each other. In addition, the thicknesses of the hole transport regions HTR-1, HTR-2, and HTR-3 and the electron transport regions ETR-1, ETR-2, and ETR-3 of the first to third light-emitting elements ED-1, ED-2, and ED-3 may also be different from each other.

[0119] Reference Figure 4 The blue light emitting regions PXA-B and the red light emitting regions PXA-R may be alternately arranged along the first direction DR1 to form a first group PXG1, and the green light emitting regions PXA-G may be arranged along the first direction DR1 to form a second group PXG2.

[0120] The first group PXG1 and the second group PXG2 may be arranged to be spaced apart from each other in the second direction DR2. The first group PXG1 and the second group PXG2 may be provided in plural, respectively. The first group PXG1 and the second group PXG2 may be arranged alternately with each other along the second direction DR2.

[0121] One green light emitting region PXA-G may be arranged to be spaced apart from one blue light emitting region PXA-B or one red light emitting region PXA-R in the fourth direction DR4. The fourth direction DR4 may be a direction between the first direction DR1 and the second direction DR2.

[0122] Figure 4 The arrangement structure of the light emitting regions PXA-B, PXA-G, and PXA-R shown in the figure may be referred to as a PenTile structure. However, the arrangement structure of the light emitting regions PXA-B, PXA-G, and PXA-R in the display device DD according to an embodiment is not limited to the PenTile structure. Figure 4 For example, in one embodiment, the light-emitting regions PXA-B, PXA-G, and PXA-R may also have a stripe structure in which the blue light-emitting region PXA-B, the green light-emitting region PXA-G, and the red light-emitting region PXA-R are sequentially arranged in a cyclic manner along the first direction DR1.

[0123] Reference Figure 3 and Figure 5 The display device DD of an embodiment may further include an optical component PP. The optical component PP may block external light provided from outside the display device DD to the display panel DP. The optical component PP may block a portion of the external light. The optical component PP may play an anti-reflection function of minimizing reflection caused by external light.

[0124] exist Figure 5 In the illustrated embodiment, the optical component PP may include a color filter layer CFL. That is, the display device DD of an embodiment may further include a color filter layer CFL arranged on the light emitting elements ED-1, ED-2, and ED-3 of the display panel DP.

[0125] In the display device DD of an embodiment, the optical part PP may include a base layer BL and a color filter layer CFL.

[0126] The base layer BL may be a member providing a base surface on which the color filter layer CFL, etc. is disposed. The base layer BL may be a glass substrate, a metal substrate, a plastic substrate, etc. However, the embodiment is not limited thereto, and the base layer BL may be an inorganic layer, an organic layer, or a composite material layer.

[0127] The color filter layer CFL may include a light shielding part BM and a color filter part CF. The color filter part CF may include a plurality of filters CF-B, CF-G, and CF-R. That is, the color filter layer CFL may include: a first filter CF-B that transmits the first light; a second filter CF-G that transmits the second light; and a third filter CF-R that transmits the third light. For example, the first filter CF-B may be a blue filter, the second filter CF-G may be a green filter, and the third filter CF-R may be a red filter.

[0128] Each filter CF-B, CF-G, CF-R may include a polymer photosensitive resin and a pigment or dye. The first filter CF-B may include a blue pigment or dye, the second filter CF-G may include a green pigment or dye, and the third filter CF-R may include a red pigment or dye.

[0129] In addition, the embodiment is not limited thereto, and the first filter CF-B may not include a pigment or a dye. The first filter CF-B may include a polymer photosensitive resin and may not include a pigment or a dye. The first filter CF-B may be transparent. The first filter CF-B may be formed using a transparent photosensitive resin.

[0130] The light shielding part BM may be a black matrix. The light shielding part BM may be formed by an organic light shielding material or an inorganic light shielding material including a black pigment or a black dye. The light shielding part BM may prevent light leakage and may define the boundaries between adjacent filters CF-B, CF-G, and CF-R.

[0131] The color filter layer CFL may further include a buffer layer BFL. For example, the buffer layer BFL may be a protective layer for protecting the color filters CF-B, CF-G, and CF-R. The buffer layer BFL may be an inorganic layer including at least one inorganic substance selected from silicon nitride, silicon oxide, and silicon oxynitride. The buffer layer BFL may be composed of a single layer or a plurality of layers.

[0132] Although in Figure 5 The illustrated embodiment shows a situation where the first filter CF-B of the color filter layer CFL overlaps with the second filter CF-G and the third filter CF-R, but the embodiment is not limited thereto. For example, the first to third filters CF-B, CF-G, CF-R may be divided by the light shielding portion BM and do not overlap with each other. In addition, in an embodiment, the first to third filters CF-B, CF-G, CF-R may be arranged to correspond to the blue light emitting area PXA-B, the green light emitting area PXA-G, and the red light emitting area PXA-R, respectively.

[0133] and Figure 5Unlike the cases shown in the figures, the display device DD of an embodiment may include a polarizing layer (not shown) instead of the color filter layer CFL as the optical part PP. The polarizing layer (not shown) may block external light provided from the outside toward the display panel DP. The polarizing layer (not shown) may block a portion of the external light.

[0134] Furthermore, the polarization layer (not shown) can reduce the reflected light generated on the display panel DP due to external light. For example, the polarization layer (not shown) can block the reflected light in the case where the light provided from the outside of the display device DD is incident on the display panel DP and then emitted again. The polarization layer (not shown) can be a circular polarizer with an anti-reflection function, or the polarization layer (not shown) can include a linear polarizer and a λ / 4 phase retarder. In addition, the polarization layer (not shown) can be arranged on the base layer BL to be exposed, or the polarization layer (not shown) can be arranged under the base layer BL.

[0135] Figures 6 to 9 is a cross-sectional view of a light emitting element according to an embodiment of the present invention.

[0136] refer to Figure 6 According to an embodiment, the light emitting element ED may include a first electrode EL1 , a hole transport region HTR, a light emitting layer EML, an electron transport region ETR, and a second electrode EL2 which are sequentially stacked.

[0137] and Figure 6 compared to, Figure 7 FIG. 4 is a cross-sectional view of a light emitting element ED in which the hole transport region HTR includes a hole injection layer HIL and a hole transport layer HTL, and the electron transport region ETR includes an electron injection layer EIL and an electron transport layer ETL. Figure 6 compared to, Figure 8 A cross-sectional view of a light emitting element ED in one embodiment is shown in which the hole transport region HTR includes a hole injection layer HIL, a hole transport layer HTL and an electron blocking layer EBL, and the electron transport region ETR includes an electron injection layer EIL, an electron transport layer ETL and a hole blocking layer HBL. Figure 6 compared to, Fig. 9 A cross-sectional view of a light emitting element ED including an embodiment of a capping layer CPL disposed on the second electrode EL2 is shown.

[0138] In the light emitting element ED according to an embodiment, the first electrode EL1 has conductivity. The first electrode EL1 may be formed of a metal alloy or a conductive compound. The first electrode EL1 may be an anode. The first electrode EL1 may be a pixel electrode.

[0139] In the light emitting element ED according to an embodiment, the first electrode EL1 may be a reflective electrode. However, the embodiment is not limited thereto. For example, the first electrode EL1 may be a transmissive electrode or a semi-transmissive electrode, etc. In the case where the first electrode EL1 is a semi-transmissive electrode or a reflective electrode, the first electrode EL1 may include at least one of Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF, Mo, Ti, compounds thereof, and mixtures thereof (e.g., mixtures of Ag and Mg, LiF / Ca, LiF / Al). Alternatively, it may be a multi-layer structure including a reflective film or a semi-transmissive film formed using the above-mentioned exemplified substances and a transparent conductive film formed using indium tin oxide (ITO: indium tin oxide), indium zinc oxide (IZO: indium zinc oxide), zinc oxide (ZnO: zinc oxide), indium tin zinc oxide (ITZO: indium tin zinc oxide), etc. For example, the first electrode EL1 may be a multilayer metal film, and may be a structure in which a metal film of ITO / Ag / ITO is stacked.

[0140] The hole transport region HTR is provided on the first electrode EL1. The hole transport region HTR may include a hole injection layer HIL and a hole transport layer HTL, etc. In addition, the hole transport region HTR may also include at least one of a hole buffer layer (not shown) and an electron blocking layer EBL in addition to the hole injection layer HIL and the hole transport layer HTL. The hole buffer layer (not shown) can improve the luminous efficiency by compensating for the resonance distance according to the wavelength of the light emitted from the light emitting layer EML. As a substance included in the hole buffer layer (not shown), a substance that can be included in the hole transport region HTR can be used. The electron blocking layer EBL is a layer that plays a role in preventing electron injection from the electron transport region ETR to the hole transport region HTR.

[0141] The hole transport region HTR may have a single layer structure composed of a single substance, a single layer structure composed of a plurality of substances different from each other, or a multilayer structure having a plurality of layers composed of a plurality of substances different from each other. For example, the hole transport region HTR may have a single layer structure composed of a plurality of substances different from each other, or have a structure of a hole injection layer HIL / hole transport layer HTL, a hole injection layer HIL / hole transport layer HTL / hole buffer layer (not shown), a hole injection layer HIL / hole buffer layer (not shown), a hole transport layer HTL / hole buffer layer (not shown), or a hole injection layer HIL / hole transport layer HTL / electron blocking layer EBL stacked in sequence from the first electrode EL1, but the embodiment is not limited thereto.

[0142] The hole transport region HTR can be formed by various methods such as vacuum deposition, spin coating, casting, LB (Langmuir-Blodgett), inkjet printing, laser printing, laser thermal transfer (LITI: Laser Induced Thermal Imaging), etc.

[0143] The hole injection layer HIL may include, for example, a phthalocyanine compound such as copper phthalocyanine, N,N'-diphenyl-N,N'-bis-[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4'-diamine (DNTPD: N,N'-diphenyl-N,N'-bis-[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4'-diamine), 4,4',4"-[tris(3-methylphenyl)phenylamino]triphenylamine (m-MTDATA: 4,4',4"-[tris(3-methylphenyl)phenylamino]triphenylamine), 4,4',4"-tris(N,N-diphenylamino)triphenylamine (TDATA: 4, 4',4"-Tris(N,N-diphenylamino)triphenylamine), 4,4',4"-tris{N-(2-naphthyl)-N-phenylamino}-triphenylamine (2-TNATA: 4,4',4"-tris{N-(2-naphthyl)-N-phenylamino}-triphenylamine), poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate) (PEDOT / PSS: Poly(3,4-ethylenedioxythiophene) / Poly(4-styrenesulfonate)), polyaniline / dodecylbenzenesulfonic acid (PANI / DBSA: Polyaniline / Dodecylbenzenesulfonic acid), polyaniline / camphor sulfonic acid (PANI / CSA), polyaniline / poly(4-styrenesulfonate) (PANI / PSS), N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine (NPD), triphenylamine-containing polyether ketone (TPAPEK), 4-isopropyl-4'-methyldiphenyliodonium[tetrakis(pentafluorophenyl)borate], dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN: dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile) (HAT-CN: dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile), etc. ,

[0144] The hole transport layer HTL may include common materials known in the art. For example, the hole transport layer HTL may also include carbazole derivatives such as N-phenylcarbazole and polyvinylcarbazole, fluorene derivatives, N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD: N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine), 4,4',4"-tris(N-carbazolyl)triphenylamine (TCTA: 4,4',4"-tris(N-carbazolyl)triphenylamine) and triphenylamine derivatives such as N,N'-di(naphthalene-1-yl)-N,N'-diphenylbenzidine (NPD: N,N'-di 4,4'-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (TAPC: 4,4′-Cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine]), 4,4'-bis[N,N'-(3-tolyl)amino]-3,3'-dimethylbiphenyl (HMTPD: 4,4'-Bis[N,N'-(3-tolyl)amino]-3,3'-dimethylbiphenyl), 1,3-bis(N-carbazolyl)benzene (mCP: 1,3-Bis(N-carbazolyl)benzene), etc.

[0145] The thickness of the hole transport region HTR may be about 5 nm to about 1,500 nm, for example, about 10 nm to about 500 nm. The thickness of the hole injection layer HIL may be, for example, about 3 nm to about 100 nm, and the thickness of the hole transport layer HTL may be about 3 nm to about 100 nm. For example, the thickness of the electron blocking layer EBL may be about 1 nm to about 100 nm. When the thicknesses of the hole transport region HTR, the hole injection layer HIL, the hole transport layer HTL, and the electron blocking layer EBL meet the ranges described above, a more satisfactory degree of hole transport characteristics may be obtained without substantially increasing the driving voltage.

[0146] The light emitting layer EML is provided on the hole transport region HTR. The light emitting layer EML may have a thickness of, for example, about 10 nm to about 100 nm or about 10 nm to about 30 nm. The light emitting layer EML may have a single layer structure composed of a single substance, a single layer structure composed of a plurality of substances different from each other, or a multilayer structure having a plurality of layers composed of a plurality of substances different from each other. In the light emitting element ED according to an embodiment, the light emitting layer EML may include quantum dots QD1, QD2, QD3 (see Figure 5 ).

[0147] The light-emitting layer EML can be formed by various methods such as vacuum deposition, spin coating, casting, LB (Langmuir-Blodgett), inkjet printing, laser printing, laser thermal transfer (LITI: Laser Induced Thermal Imaging), etc. In one embodiment, the light-emitting layer EML can be provided by inkjet printing to include quantum dots QD1, QD2, QD3 (refer to Figure 5 ) is formed by a quantum dot composition.

[0148] In the light emitting element ED of an embodiment, an electron transport region ETR is provided on the light emitting layer EML. The electron transport region ETR may include at least one of a hole blocking layer HBL, an electron transport layer ETL, and an electron injection layer EIL, but the embodiment is not limited thereto.

[0149] The electron transport region ETR may be formed of an ink composition according to an embodiment of the present invention as described below. For example, the electron transport region ETR may be formed of an ink composition including inorganic nanoparticles and a first solvent having a Hansen solubility parameter value of 5 or less for hydrogen bonding terms.

[0150] In the case of including quantum dots as the material of the light-emitting layer or using inorganic nanoparticles as the material of the electron transport region ETR, since it is difficult to form a layer by deposition, a solution process such as spin coating or inkjet printing can be used. In addition, depending on the organic solvent used in the solution process, the dispersion stability of the inorganic nanoparticles may differ, resulting in problems such as nozzle clogging due to agglomeration and the formation of an inhomogeneous surface. In the present invention, the dispersion stability of the inorganic nanoparticles can be improved by including a solvent having a hydrogen bonding term value of 5 or less in the Hansen solubility parameter value in the ink composition forming the electron transport region ETR. As a result, not only can the nozzle clogging phenomenon be prevented, but a uniform thin film can also be formed to improve the efficiency and life characteristics of the light-emitting element. The method for forming the electron transport region ETR will be described in detail in detail. Figures 10 to 14 Explain in more detail.

[0151] The electron transport region ETR may have a single layer structure composed of a single substance, a single layer structure composed of a plurality of substances different from each other, or a multilayer structure having a plurality of layers composed of a plurality of substances different from each other.

[0152] For example, the electron transport region ETR may have a single layer structure of an electron injection layer EIL or an electron transport layer ETL, or may have a single layer structure composed of an electron injection material and an electron transport material. In addition, the electron transport region ETR may have a single layer structure composed of a plurality of different materials, or may have an electron transport layer ETL / electron injection layer EIL, a hole blocking layer HBL / electron transport layer ETL / electron injection layer EIL structure stacked in sequence from the light-emitting layer EML, but is not limited thereto. The thickness of the electron transport region ETR may be, for example, about 20 nm to about 150 nm.

[0153] In the case where the electron transport region ETR is a multilayer structure having a plurality of layers, any one of the plurality of layers may be formed by the ink composition according to an embodiment of the present invention. For example, the electron transport region ETR may include an electron transport layer ETL disposed on the light emitting layer EML and an electron injection layer EIL disposed on the electron transport layer ETL, and the electron transport layer ETL may be formed by the ink composition of an embodiment.

[0154] The electron transport region ETR can be formed by various methods such as vacuum deposition, spin coating, casting, Langmuir-Blodgett (LB), inkjet printing, laser printing, laser induced thermal imaging (LITI), etc. In one embodiment, the electron transport region ETR can be formed by inkjet printing.

[0155] The electron transport region ETR may include inorganic nanoparticles. In one embodiment, the inorganic nanoparticles may include at least one of Cd, Zn, In, Sn, Sb, Ga, Ge, As, Hg, Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, Os, Mn, Mo, and Cr, but is not limited thereto.

[0156] In one embodiment, the inorganic nanoparticles may be zinc oxide. Although the type of zinc oxide is not particularly limited, it may be, for example, ZnO, ZnMgO, or a combination thereof, and may be doped with Li and Y in addition to Mg. In addition, TiO may be used in addition to zinc oxide. 2 、SiO 2 SnO 2 , WO 3 、 2 O 3、BaTiO 3 、BaZrO 3 、ZrO 2 , HfO 2 、Al 2 O 3 , Y 2 O 3 、ZrSiO 4 etc. as the inorganic material, but not limited thereto.

[0157] In one embodiment, the electron transport region ETR may include a known inorganic material or a known organic material.

[0158] In the case where the electron transport region ETR includes an electron transport layer ETL, the electron transport layer ETL may include an anthracene compound. However, it is not limited thereto, and the electron transport region ETR may include, for example, tris(8-hydroxyquinoline)aluminum (Alq 3:Tris(8-hydroxyquinolinato)aluminum、1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene、2,4,6-tris(3'-(pyridin-3-yl)biphenyl-3-yl)-1,3,5-triazine、bis[2-(diphenylphosphino)phenyl]ether oxide(DPEPO:bis[2-(diphenylphosphino)phenyl]ether oxide), 2-(4-(N-phenylbenzoimidazolyl-1-ylphenyl))-9,10-dinaphthylanthracene, 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene (TPBi: 1,3,5-Tri(1-phenyl-1H-benzo[d]imidazol- 2-yl)phenyl), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP: 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline), 4,7-diphenyl-1,10-phenanthroline (Bphen: 4,7-Diphenyl-1,10-phenanthroline), 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ: 3-( 4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole), 4-(naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole (NTAZ: 4-(Naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole), 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD: 2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole), Bis(2-methyl-8-quinolinolato-N1,O8)-(1,1'-biphenyl-4-olato)aluminum (BAlq: Bis(2-methyl-8-quinolinolato-N1,O8)-(1,1'-Biphenyl-4-olato)aluminum), Bis(benzoquinolin-10-yl)beryllium (Bebq2 : berylliumbis(benzoquinolin-10-olate)), 9,10-di(naphthalene-2-yl)anthracene (ADN: 9,10-di(naphthalene-2-yl)anthracene) or a mixture thereof. The thickness of the electron transport layer ETL may be about 10 nm to about 100 nm, for example, about 15 nm to about 50 nm. When the thickness of the electron transport layer ETL satisfies the range as described above, a satisfactory degree of electron transport characteristics may be obtained without substantially increasing the driving voltage.

[0159] In the case where the electron transport region ETR includes the electron injection layer EIL, the electron transport region ETR may include: a halogenated metal such as LiF, NaCl, CsF, RbCl, RbI, etc.; a lanthanide metal such as Yb, etc.; a metal oxide such as Li 2 O, BaO, etc., or lithium quinolate (LiQ: Lithium quinolate), etc., but not limited thereto. The electron injection layer EIL can also be composed of a substance mixed with an electron transport substance and an insulating organic metal salt. For example, the organic metal salt may include metal acetate, metal benzoate, metal acetoacetate, metal acetylacetonate, or metal stearate. The thickness of the electron injection layer EIL may be about 0.1nm to about 10nm, about 0.3nm to about 9nm. When the thickness of the electron injection layer EIL satisfies the range as described above, a more satisfactory degree of electron injection characteristics can be obtained without substantially increasing the driving voltage.

[0160] As mentioned above, the electron transport region ETR may include a hole blocking layer HBL. The hole blocking layer HBL may include at least one of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP: 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline) and 4,7-diphenyl-1,10-phenanthroline (Bphen: 4,7-Diphenyl-1,10-phenanthroline), but is not limited thereto.

[0161] The second electrode EL2 is provided on the electron transport region ETR. The second electrode EL2 may be a common electrode or a cathode. The second electrode EL2 may be a transmissive electrode, a semi-transmissive electrode or a reflective electrode. In the case where the second electrode EL2 is a transmissive electrode, the second electrode EL2 may be formed using a transparent metal oxide, for example, indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium tin zinc oxide (ITZO), etc.

[0162] In the case where the second electrode EL2 is a semi-transmissive electrode or a reflective electrode, the second electrode EL2 may include at least one of Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF, Mo, Ti, compounds thereof, and mixtures thereof (e.g., mixtures of Ag and Mg, LiF / Ca, LiF / Al). Alternatively, it may be a multilayer structure including a reflective film or a semi-transmissive film formed of the above substances and a transparent conductive film formed of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium tin zinc oxide (ITZO), and the like.

[0163] Although not shown, the second electrode EL2 may be connected to the auxiliary electrode. If the second electrode EL2 is connected to the auxiliary electrode, the resistance of the second electrode EL2 may be reduced.

[0164] Fig.10 is a sequence diagram showing a method for manufacturing a light emitting element according to an embodiment. Fig.11 is a sequence diagram detailing the step of forming an electron transport region ( S300 ) according to an embodiment.

[0165] Reference Fig.10 According to one embodiment, a method for manufacturing a light-emitting element includes the following steps: forming a hole transport region on a first electrode (S100); forming a light-emitting layer on the hole transport region (S200); forming an electron transport region on the light-emitting layer (S300); and forming a second electrode on the electron transport region (S400).

[0166] Reference Fig.11 According to an embodiment, the step of forming the electron transport region (S300) includes the following steps: preparing an ink composition (S301); providing a preliminary electron transport region (S302); and applying heat to form the electron transport region (S303).

[0167] Figures 12a to 12c The step (S301) of manufacturing an ink composition in a method for manufacturing a light emitting element according to an embodiment is schematically shown. Figures 12a to 12c The ink composition and the steps for producing the ink composition are described in detail.

[0168] The ink composition ICP according to one embodiment of the present invention may be a material forming an electron transport region of a light-emitting element. However, it is not limited thereto, and the ink composition ICP of one embodiment may be a material forming a hole transport region of a light-emitting element or a functional layer included in a light-emitting layer.

[0169] Reference Fig.12a , the ink composition ICP according to an embodiment of the present invention includes inorganic nanoparticles INP and a first solvent SV1.

[0170] In one embodiment, the hydrogen bonding term (δH) value in the Hansen solubility parameter value of the first solvent SV1 may be 5 or less. When the hydrogen bonding term value in the Hansen solubility parameter value of the first solvent SV1 satisfies the range described above, the agglomeration of the inorganic nanoparticles INP caused by water penetration can be suppressed, and the dispersion stability of the inorganic nanoparticles INP can be improved. When the first solvent SV1 satisfies the hydrogen bonding term value in the Hansen solubility parameter value, its type is not particularly limited, and for example, diisopropyl phthalate may be preferably used.

[0171] In the present invention, the Hansen solubility parameter (HSP) is a solubility parameter introduced by Charles M. Hansen and represents a value used in predicting the solubility of a substance (unit: MPa). 0.5 ). Hansen solubility parameters can be composed of three parameters (δD, δP, δH). δD represents the energy caused by the dispersion force between molecules, δP represents the energy caused by the dipole interaction between molecules, and δH represents the energy caused by the hydrogen bond between molecules.

[0172] Hansen solubility parameter values ​​are described in "Hansen Solubility Parameters; A Users Handbook (CRC Press, 2007)" by Charles M. Hansen, and parameter values ​​of substances not described in the literature can be estimated using a Hansen Solubility Parameters in Practice (HSPiP) program or the like.

[0173] Furthermore, in the present invention, the dispersion stability of inorganic nanoparticles refers to the property that the inorganic nanoparticles can be stably dispersed in a solution for a long period of time without agglomeration.

[0174] In the present invention, after dispersing the inorganic nanoparticles INP in the corresponding solvent to produce a dispersion, the particle size of the inorganic nanoparticles INP is confirmed after two weeks or a predetermined time to judge the dispersion stability of the inorganic nanoparticles INP to the solvent. If the size of the inorganic nanoparticles INP increases by less than two times after two weeks or a predetermined time, it can be judged that the dispersion stability is high, and if the size of the inorganic nanoparticles INP increases by more than two times, it can be judged that the dispersion stability is low. In addition, the particle size of the inorganic nanoparticles INP can be measured by a dynamic light scattering method (DLS: Dynamic Light Scattering).

[0175] The first solvent SV1 may be a solvent having high dispersion stability for the inorganic nanoparticles INP while satisfying the above-described range. In this case, the ink composition ICP may be manufactured using only the first solvent SV1 without mixing other solvents in order to improve dispersion stability.

[0176] Reference Figure 12b According to an embodiment of the present invention, the ink composition ICP may further include a second solvent SV2. The second solvent SV2 may be a solvent that can well disperse the inorganic nanoparticles INP. For example, in a case where the dispersion stability of the inorganic nanoparticles INP to the first solvent SV1 is low, the dispersion stability of the inorganic nanoparticles INP may be improved by further including the second solvent SV2. At this time, the second solvent SV2 may be appropriately selected according to the type of the target inorganic nanoparticles INP.

[0177] In one embodiment, the second solvent SV2 may include at least one of triethylene glycol monomethyl ether, propylene glycol, and ethyl alcohol, but is not limited thereto.

[0178] If the second solvent SV2 is selected, the inorganic nanoparticles INP may be dispersed in the second solvent SV2 to prepare an inorganic nanoparticle INP dispersion liquid, and the inorganic nanoparticle INP dispersion liquid may be mixed with the first solvent SV1 to manufacture the ink composition ICP.

[0179] The hydrogen bonding term (δH) value of the Hansen solubility parameter value of the second solvent may be greater than 5. In this case, the second solvent SV2 may substantially disperse the inorganic nanoparticles INP, and the first solvent SV1 may prevent water penetration in the ink by reducing the polarity of the solution. Accordingly, not only can the dispersion stability of the inorganic nanoparticles INP be improved to prevent nozzle clogging in inkjet printing, but also a thin film may be uniformly formed to increase the life of the light-emitting element. In one embodiment, the volume ratio of the first solvent SV1 to the second solvent SV2 may be 0.5:1 to 2:1.

[0180] Reference Fig.12c According to one embodiment of the present invention, the ink composition ICP may further include a third solvent SV3. In one embodiment, the third solvent SV3 may be a material additionally added to reduce the overall polarity of the ink composition ICP. For example, like the first solvent SV1, the hydrogen bonding term (δH) value in the Hansen solubility parameter value of the third solvent SV3 may be 5 or less. Therefore, the overall polarity of the ink composition ICP may be reduced by mixing the first solvent SV1 and the third solvent SV3 that satisfy the aforementioned range, and the dispersion stability of the inorganic nanoparticles INP in the solution may be improved. In one embodiment, the hydrogen bonding term (δH) value in the Hansen solubility parameter value of the mixed solvent formed by mixing the first solvent SV1 and the third solvent SV3 may be 3 or less.

[0181] In addition, although not shown in the figure, in addition to the first to third solvents SV1, SV2, SV3 described above, other solvents may be added to the ink composition ICP according to an embodiment of the present invention. In this case, the added solvent may be a solvent having physical properties similar to those of the first to third solvents SV1, SV2, SV3 and differing only in the value of the physical property to be corrected. For example, it may be a solvent for correcting the surface tension or viscosity of the ink composition ICP.

[0182] In one embodiment, the inorganic nanoparticles INP may be 0.1% to 10% by mass relative to the total amount of the ink composition ICP. When the content of the inorganic nanoparticles INP is less than 0.1% by mass, it is difficult to form a substantial film due to the low concentration of the inorganic nanoparticles INP. When the content of the inorganic nanoparticles INP exceeds 10% by mass, cost problems and printing speed problems may occur due to increased viscosity of the solution and increased loading of the inorganic nanoparticles.

[0183] In one embodiment, the diameter of the inorganic nanoparticles INP may be 1 nm to 30 nm or less. When the size of the inorganic nanoparticles INP satisfies the above range, the nozzle clogging phenomenon in the head caused by the agglomeration of the inorganic nanoparticles INP during the printing process can be prevented while ensuring the dispersion stability of the ink composition ICP, and the film uniformity of the electron transport region can be ensured.

[0184] When the diameter of the inorganic nanoparticles INP is less than 1 nm, the state of the inorganic nanoparticles INP may be unstable due to the increase in the surface energy of the inorganic nanoparticles INP, and accordingly, the dispersion stability of the inorganic nanoparticles INP in the solution may be reduced and agglomeration may occur. In addition, when the diameter of the inorganic nanoparticles INP is greater than 30 nm, the nozzle in the head may be clogged, and the thickness of the film may be unevenly formed to reduce the life of the element.

[0185] In addition, in the present invention, the diameter of the inorganic nanoparticles INP can represent the size of the inorganic nanoparticles INP after the ink composition ICP is manufactured. Generally, the inorganic nanoparticles INP can be manufactured to have a particle size of several nanometers or tens of nanometers, but if they are used to form the ink composition ICP, agglomeration will occur due to the agglomeration phenomenon between the inorganic nanoparticles INP, and the diameter of the inorganic nanoparticles INP can represent the particle size of the inorganic nanoparticles INP at this time. Although in Figures 12a to 12c The inorganic nanoparticles INP are shown as single particles, but this is only exemplary, and the inorganic nanoparticles INP may form particle clusters due to agglomeration between particles.

[0186] Furthermore, the morphology of the inorganic nanoparticles INP is the morphology commonly used in the art and is not particularly limited, but more specifically, spherical, pyramidal, multi-arm or cubic nanoparticles, nanotubes, nanowires, nanofibers, nanoplate-like particles and the like can be used.

[0187] Fig.13 The step of providing a preliminary electron transport region (S302) in the method for manufacturing a light emitting element according to an embodiment is schematically shown. The step of providing a preliminary electron transport region (S302) is a step of coating an ink composition ICP on the light emitting layer EML.

[0188] In one embodiment, the method of coating the ink composition ICP on the light-emitting layer EML may be an inkjet printing method. For example, the electron transport region ETR may be formed by inkjet printing. However, it is not limited thereto, and the electron transport region ETR may be formed by methods such as vacuum deposition, spin coating, casting, LB (Langmuir-Blodgett), laser printing, laser thermal transfer (LITI: Laser Induced Thermal Imaging), etc. Although in Fig.13 A case where the ink composition ICP is applied between the pixel defining films PDL through the nozzles NZ is shown, but it is not limited thereto.

[0189] Fig.14 Schematically illustrates a step (S303) of forming an electron transport region by supplying heat in a method for manufacturing a light-emitting element according to an embodiment. According to an embodiment, the step of supplying heat to the preliminary electron transport region P-ETR may be a step of curing the preliminary electron transport region P-ETR by supplying heat of 120° C. to 180° C. to the preliminary electron transport region P-ETR for more than 20 minutes.

[0190] The ink composition according to an embodiment of the present invention can improve the dispersion stability of inorganic nanoparticles, thereby preventing nozzle clogging in an inkjet printing device.

[0191] When manufacturing an electron transport region having inorganic nanoparticles as electron transport materials, the inorganic nanoparticles can be dispersed in various types of organic solvents for use. At this time, the dispersion stability of the ink composition varies depending on the added solvent. If the inorganic nanoparticles aggregate or / and the solvent denatures during storage due to low dispersion stability, the nozzle in the head may be clogged during the printing process.

[0192] According to an embodiment of the present invention, the ink composition in which inorganic nanoparticles are dispersed can suppress the aggregation of inorganic nanoparticles due to water penetration by including a first solvent having a hydrogen bonding term value of 5 or less in the Hansen solubility parameter value, thereby improving the dispersion stability and preventing the nozzle clogging phenomenon in the head during the inkjet printing process. In addition, when the ink composition is used to form an electron transport region, it can help the inorganic nanoparticles to be evenly coated, thereby improving the efficiency of the light-emitting element.

[0193] The present invention will be described in more detail below through specific examples and comparative examples. The following examples are only examples to help understand the present invention, and the scope of the present invention is not limited thereto.

[0194] 1. Measurement of the Hansen Solubility Parameters of Solvents

[0195] The Hansen solubility parameter values ​​of the solvents used in Examples and Comparative Examples were measured and are shown in the following Table 1. The Hansen solubility parameter values ​​were confirmed using the HSPiP program.

[0196]

Table 1

[0197] HSP δD δP δH Diisopropyl phthalate 18.8 17.2 7.1 2.8 Triethylene glycol monomethyl ether 21.8 16.2 7.6 12.5 Triamyl phosphate 18.1 16.1 6.6 5.1

[0198] 2. Preparation of ink compositions of Examples and Comparative Examples

[0199] Example 1

[0200] Triethylene glycol monomethyl ether was used as a second solvent, and 3 wt% of zinc oxide (ZnO) nanoparticles were dispersed in the second solvent to obtain an inorganic nanoparticle dispersion. Thereafter, diisopropyl phthalate was used as a first solvent and was added to the inorganic nanoparticle dispersion in a manner such that the volume ratio of the first solvent to the second solvent was 0.5:1 to prepare an ink composition.

[0201] Example 2

[0202] In Example 1, an ink composition was produced in the same manner as in Example 1 except that the volume ratio of the first solvent to the second solvent was 1:1.

[0203] Example 3

[0204] In Example 1, an ink composition was produced in the same manner as in Example 1 except that the volume ratio of the first solvent to the second solvent was 2:1.

[0205] Comparative Example 1

[0206] In Example 1, an ink composition was produced in the same manner as in Example 1 except that triethylene glycol monomethyl ether was used as the first solvent.

[0207] Comparative Example 2

[0208] In Example 1, an ink composition was prepared in the same manner as in Example 1 except that triethylene glycol monomethyl ether was used as the first solvent and the volume ratio of the first solvent to the second solvent was 1:1.

[0209] Comparative Example 3

[0210] In Example 1, an ink composition was prepared in the same manner as in Example 1 except that triethylene glycol monomethyl ether was used as the first solvent and the volume ratio of the first solvent to the second solvent was 2:1.

[0211] Comparative Example 4

[0212] In Example 1, an ink composition was prepared in the same manner as in Example 1 except that triamyl phosphate was used as the first solvent.

[0213] Comparative Example 5

[0214] In Example 1, an ink composition was prepared in the same manner as in Example 1 except that tripentyl phosphate was used as the first solvent and the volume ratio of the first solvent to the second solvent was 1:1.

[0215] Comparative Example 6

[0216] In Example 1, an ink composition was prepared in the same manner as in Example 1 except that tripentyl phosphate was used as the first solvent and the volume ratio of the first solvent to the second solvent was 2:1.

[0217] 3. Evaluation of dispersion stability of inorganic nanoparticles

[0218] In order to evaluate the dispersion stability of inorganic nanoparticles, the ink compositions of Examples and Comparative Examples were stored at room temperature for 24 hours and then the particle sizes were measured using dynamic light scattering (DLS), and the results are shown in Table 2. The dynamic light scattering was performed using a ZetasizerNano ZS90 manufactured by Malvern Panalytical.

[0219]

Table 2

[0220]

[0221]

[0222] Referring to Table 1 above, it can be confirmed that the inorganic nanoparticles of Examples 1 to 3 can have excellent dispersion stability in the ink composition, thereby preventing the inorganic nanoparticles from agglomerating. In particular, it can be seen that as the volume ratio of the first solvent to the second solvent increases, the increase in particle size tends to be more suppressed.

[0223] On the contrary, it can be confirmed that since Comparison Examples 1 to 3 use triethylene glycol monomethyl ether as the second solvent as the first solvent, and do not use a first solvent with a hydrogen bond item value of less than 5 in the Hansen solubility parameter value, water becomes easier to penetrate compared to Examples 1 to 3, thereby causing agglomeration of inorganic nanoparticles.

[0224] Furthermore, in Comparative Examples 4 to 6, triethylene glycol monomethyl ether was used as the second solvent, and a solvent having a hydrogen bond term value greater than 5 in the Hansen solubility parameter value was used as the first solvent. It was determined that compared with Examples 1 to 3, moisture easily penetrated into the composition during storage, resulting in a decrease in the dispersion stability of the inorganic nanoparticles.

[0225] Figures 15a to 15d 1 is a diagram showing a plurality of nozzles of an inkjet head provided in an inkjet printing device, and is a diagram showing the state of the nozzles over time after a process is performed using Comparative Example 1. Figures 15a to 15b The status of the nozzle is shown before the process starts, 5 minutes after the process starts, 15 minutes after the process starts, and 30 minutes after the process starts. Fig.15a In the figure, for convenience of explanation, reference numerals 1 to 6 represent nozzle numbers.

[0226] Reference Fig.15a , it can be confirmed that nozzles 1 to 6 are not clogged just before the inkjet process starts. Figures 15b to 15d It can be confirmed that the inorganic nanoparticles aggregated 5 minutes after the start of the process, and nozzles 4 to 6 began to be clogged. After 30 minutes, the entire nozzle was clogged.

[0227] Fig.16 The graphs are obtained by visually observing the ink compositions of Examples and Comparative Examples after they were stored at room temperature for 25 hours. It can be confirmed that Examples 1 to 3 all exhibit higher transparency than Comparative Examples 1 to 6.

[0228] In contrast, it was confirmed that Comparative Examples 1 to 6 showed milky suspensions compared to Examples due to strong aggregation of inorganic nanoparticles. This was judged to be due to the fact that the dispersion stability of inorganic nanoparticles was reduced by using only the second solvent or a solvent having a hydrogen bonding term value of more than 5 in the Hansen solubility parameter value as the first solvent, resulting in aggregation of nanoparticles.

[0229] Although the embodiments of the present invention are described above, it is understood by those with ordinary knowledge in the technical field to which the present invention belongs that the present invention can be implemented in other specific forms without changing its technical ideas or essential features. Therefore, it should be understood that the embodiments described above are exemplary in all aspects and are not restrictive.

Claims

1. An ink composition comprising: Inorganic nanoparticles; a first solvent; as well as The second solvent, The hydrogen bonding term value in the Hansen solubility parameter value of the first solvent is less than 5, and the hydrogen bonding term value in the Hansen solubility parameter value of the second solvent is greater than 5. The second solvent includes at least one of triethylene glycol monomethyl ether and propylene glycol, The volume ratio of the first solvent to the second solvent is 0.5:1 to 2:

1.

2. The ink composition according to claim 1, wherein The second solvent also includes ethanol.

3. The ink composition according to claim 2, wherein The content of the inorganic nanoparticles is 0.1% by mass to 10% by mass relative to the total amount of the ink composition.

4. The ink composition according to claim 1, wherein The first solvent includes diisopropyl phthalate.

5. The ink composition according to claim 1, wherein The inorganic nanoparticles include at least one of Cd, Zn, In, Sn, Sb, Ga, Ge, As, Hg, Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, Os, Mn, Mo and Cr.

6. The ink composition according to claim 1, wherein The inorganic nanoparticles have a diameter of 1 nm to 30 nm.

7. The ink composition according to claim 2, wherein: Also includes a third solvent, The hydrogen bonding term value in the Hansen solubility parameter value of the third solvent is 5 or less.

8. The ink composition according to claim 7, wherein The hydrogen bonding term value of the Hansen solubility parameter of the solvent formed by mixing the first solvent and the third solvent is 3 or less.

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