Quantum dot composition, quantum dot film, and display device

Abstract

The present invention is for achieving the technical objective of providing a quantum dot composition for providing: a quantum dot film having a uniform film thickness and low thickness variation; and a quantum dot film in which the coffee ring effect is reduced. Provided, in order to achieve said technical objective, are a quantum dot composition, a quantum dot film, and a display device, the quantum dot composition comprising: quantum dots; carboxylic acid having a melting point of 25°C or lower, and having a branched aliphatic hydrocarbon group; and a solvent.

Description

Quantum dot composition, quantum dot film and display device

[0001] The present invention relates to a quantum dot composition, a quantum dot film, and a display device.

[0002]

[0003] Quantum dot compositions containing quantum dots exhibit high color purity and a variety of color-emitting properties, making them suitable for use as materials in high-resolution display devices. Quantum dot compositions can be incorporated into display devices by patterning. Inkjet printing can be considered as one of the patterning methods.

[0004] Among quantum dot compositions, there are solvent-free compositions, but solvent-based compositions in which quantum dots are dispersed in a solvent are also being used. Applying and drying a composition containing quantum dots dispersed in a solvent using inkjet printing can form a pattern containing quantum dots. It is preferable for the pattern to have a uniform film thickness and low thickness variation. A more uniform film thickness and low thickness variation can improve screen quality by ensuring more uniform light emission.

[0005]

[0006] The present invention provides a quantum dot composition capable of providing a quantum dot film having a uniform film thickness and low thickness variation.

[0007] The present invention provides a quantum dot composition capable of providing a quantum dot film with a mitigated coffee ring effect.

[0008]

[0009] According to one embodiment, a quantum dot composition is provided.

[0010] The quantum dot composition comprises a quantum dot, a carboxylic acid having a melting point of 25°C or lower and a branched aliphatic hydrocarbon group, and a solvent.

[0011] According to another embodiment, a quantum dot film is provided.

[0012] The quantum dot film includes a lower surface and an upper surface opposite to the lower surface, the upper surface is a concave surface or a convex surface from the lower surface, and the concave surface has a ratio of a minimum height to a maximum height of 0.2 or more.

[0013] In another embodiment, a display device is provided.

[0014] The display device includes the quantum dot film or a cured product of the quantum dot film.

[0015]

[0016] A quantum dot composition according to an embodiment can improve screen quality by providing a quantum dot film with a uniform film thickness and low thickness variation by alleviating the coffee ring effect, thereby making light emission uniform when applied to a display device.

[0017]

[0018] Figure 1 is a conceptual diagram of a quantum dot film according to an embodiment.

[0019] Figure 2 is a conceptual diagram of a quantum dot film according to another embodiment.

[0020] Figure 3 shows the results of a quantum dot film manufactured in Example 1.

[0021] Figure 4 shows the results of a quantum dot film manufactured in Example 2.

[0022] Figure 5 shows the results of a quantum dot film manufactured in Example 3.

[0023] Figure 6 shows the results of a quantum dot film manufactured in Example 4.

[0024] Figure 7 shows the results of a quantum dot film manufactured in Comparative Example 1.

[0025]

[0026] Hereinafter, embodiments of the present application will be described in more detail with reference to the attached drawings. However, the technology disclosed in the present application is not limited to the embodiments described herein and may be embodied in other forms. However, the embodiments introduced herein are provided so that the disclosed content can be thorough and complete and so that the spirit of the present application can be sufficiently conveyed to those skilled in the art. In order to clearly express the components of each device in the drawings, the sizes of the components, such as width and thickness, are somewhat enlarged. However, the sizes of the components, such as width and thickness, in the present invention do not limit the scope of the present invention. The same reference numerals in multiple drawings indicate substantially the same components.

[0027] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0028] In this specification, "upper" and "lower" are defined based on the drawing, and depending on the perspective, "upper" may be changed to "lower" and "lower" may be changed to "upper", and reference to "on" or "on" may include not only directly on but also cases where another structure is interposed in between. On the other hand, reference to "directly on" or "directly above" or "directly formed" indicates cases where there is no intervening other structure such as an intermediate body.

[0029] When describing a numerical range in this specification, “X to Y” means X or more and Y or less (X≤ and ≤Y).

[0030] A quantum dot composition according to one embodiment is a solvent-based quantum dot composition comprising a solvent. The quantum dot composition can be applied to a substrate by inkjet printing or the like, and then the solvent can be dried to form a quantum dot film. The quantum dot film can be applied to a display device as is or can be cured and applied to the display device.

[0031] In one specific example, the quantum dot film can form a color filter or color conversion layer in a display device.

[0032] The above quantum dot composition can improve screen quality by providing a quantum dot film with a uniform film thickness and low thickness variation by alleviating the coffee ring effect, thereby making light emission uniform when applied to a display device.

[0033] The above coffee ring effect refers to a phenomenon in which, when a quantum dot composition is printed and dried, the solvent evaporates, resulting in a difference in thickness between the inner and outer surfaces of the film when viewed from the cross-section. As shown in Fig. 7, the coffee ring effect refers to a film in which the outer surface is thick and the inner surface is relatively thin. Therefore, the coffee ring effect cannot provide uniform light emission and can degrade screen quality.

[0034] According to one embodiment, the quantum dot composition comprises a quantum dot, a carboxylic acid having a melting point of 25°C or lower and a branched aliphatic hydrocarbon group, and a solvent. The carboxylic acid having a melting point of 25°C or lower and a branched aliphatic hydrocarbon group can alleviate the coffee ring effect, thereby providing a quantum dot film having a uniform film thickness and low thickness variation. The carboxylic acid having a melting point of 25°C or lower may not remain within the film during the manufacturing process of the quantum dot film or subsequent processes thereof, and thus may not affect the luminescence characteristics.

[0035] Hereinafter, a quantum dot composition according to an embodiment is described in detail.

[0036] quantum dots

[0037] The quantum dot can absorb light in a wavelength range of 300 nm to 780 nm, for example, a wavelength range of 350 nm to 780 nm, and emit fluorescence in a wavelength range of 400 nm to 700 nm, for example, 400 nm to 500 nm, or 480 nm to 580 nm or 580 nm to 680 nm. The quantum dot can have a maximum fluorescence emission wavelength (fluorescence λ) in a wavelength range of 400 nm to 680 nm. em ) can have.

[0038] The above quantum dots may each independently have a full width at half maximum (FWHM) of 20 nm to 100 nm, for example, 20 nm to 50 nm. When the quantum dots have a full width at half maximum (FWHM) within the above range, the color purity is high, resulting in an effect of increasing color reproducibility when used as a color material in a color filter.

[0039] The above quantum dots may each independently be organic, inorganic, or a hybrid (hybrid) of organic and inorganic materials.

[0040] The above quantum dots can each independently be composed of a core and a shell surrounding the core, and the core and shell can each independently have a structure such as a core, core / shell, core / first shell / second shell, alloy, alloy / shell, etc., made of group II-IV, group III-V, etc., but are not limited thereto.

[0041] For example, the core may include at least one material selected from the group consisting of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, GaN, GaP, GaAs, InP, InAs, AgInGaS (AIGS), CuInGaS (CIGS), and alloys thereof, but is not necessarily limited thereto. The shell surrounding the core may include at least one material selected from the group consisting of CdSe, ZnSe, ZnS, ZnTe, CdTe, PbS, TiO, SrSe, HgSe, and alloys thereof, but is not necessarily limited thereto.

[0042] In one implementation example, since interest in the environment has recently increased significantly worldwide and regulations on toxic substances have been strengthened, an environmentally friendly non-cadmium-based luminescent material (InP / ZnS, InP / ZnSe / ZnS, etc.) was used instead of a luminescent material having a cadmium-based core, but the present invention is not necessarily limited thereto.

[0043] In one embodiment, the core of the quantum dot comprises a core comprising Ag, In, Ga, and S; and a shell comprising at least two selected from the group consisting of Ag, Ga, and S, and is surface-modified with a ligand having a pKa of less than 10.4. That is, the shell is passivated by ligand substitution with a functional group having a pKa of less than 10.4, but is not necessarily limited thereto.

[0044] In the case of the quantum dot of the above core / shell structure, the size (average particle diameter) of each quantum dot including the shell may be 1 nm to 15 nm, for example, 5 nm to 15 nm.

[0045] For example, the quantum dots may each independently include a red quantum dot, a green quantum dot, a blue quantum dot, or a combination thereof. The red quantum dots may each independently have an average particle diameter of 5 nm to 15 nm. The green quantum dots may each independently have an average particle diameter of 5 nm to 15 nm. The blue quantum dots may each independently have an average particle diameter of 5 nm to 15 nm.

[0046] Meanwhile, in order to ensure dispersion stability of the quantum dots, the quantum dot composition according to one embodiment may further include a dispersant. The dispersant helps to uniformly disperse the photoconversion material, such as quantum dots, within the quantum dot composition, and any nonionic, anionic, or cationic dispersant may be used. Specifically, polyalkylene glycol or its esters, polyoxyalkylene, polyhydric alcohol ester alkylene oxide adducts, alcohol alkylene oxide adducts, sulfonic acid esters, sulfonic acid salts, carboxylic acids, carboxylic acid esters, carboxylic acid salts, alkyl amide alkylene oxide adducts, alkyl amines, etc. may be used, and these may be used alone or in combination of two or more. The dispersant may be used in an amount of 0.1 wt% to 100 wt%, for example, 1 wt% to 30 wt%, relative to the solid content of the photoconversion material, such as quantum dots.

[0047] According to one embodiment, the quantum dot may or may not be surface-modified with a surface-modifying material. For example, the surface-modifying material may include one or more of a material having a thiol group, a material having a carboxylic acid group, and a material having an amine group.

[0048] The quantum dot may be included in the quantum dot composition in an amount of 1 to 30 wt%, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 wt%, for example, 1 to 20 wt%, 2 to 10 wt%.

[0049] Carboxylic acid having a melting point of 25°C or lower and a branched aliphatic hydrocarbon group

[0050] The above carboxylic acid has a melting point of 25°C or lower. For example, the above carboxylic acid may have a melting point of -100 to 25°C or -50 to 25°C.

[0051] The above carboxylic acid has a branched aliphatic hydrocarbon group. The branched aliphatic hydrocarbon group can alleviate the coffee ring effect when a composition including the quantum dots and a solvent is applied by a method such as inkjet printing, thereby providing a quantum dot film with a uniform film thickness and low thickness variation.

[0052] According to one embodiment, the carboxylic acid may include one or more compounds represented by the following chemical formula 1:

[0053] [Chemical Formula 1]

[0054]

[0055] (In the above chemical formula 1,

[0056] L 11 Inland L 15 are each independently hydrogen, deuterium, a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms,

[0057] L 11 , L 12 , L 13 , L 14 At least one of them is a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms, or L 15is a branched chain alkyl group having 1 to 10 carbon atoms).

[0058] For example, the carboxylic acid may include at least one of 2-ethylhexanoic acid, 4-methylnonanoic acid, 2-butyloctanoic acid, and 2-hexyldecanoic acid.

[0059] In one specific example, the carboxylic acid may have a weight average molecular weight of 100 g / mol or more, for example, 100 to 300 g / mol. Within this range, the production of a quantum dot film may be facilitated. The weight average molecular weight may be determined in polystyrene equivalents by gel permeation chromatography.

[0060] In one specific example, the carboxylic acid may have a viscosity of 1 to 50 cps at 25°C.

[0061] The carboxylic acid may be included in an amount of 0.1 to 100 parts by weight, for example, 0.1, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 parts by weight, for example, 1 to 30 parts by weight, 5 to 30 parts by weight, 10 to 30 parts by weight, or 20 to 30 parts by weight, based on 100 parts by weight of the quantum dot. In the above range, the effect of the above-described quantum dot composition may be excellent.

[0062] The carboxylic acid may be included in the quantum dot composition in an amount of 0.1 to 10 wt%, for example, 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 wt%, for example, 0.1 to 5 wt%, 0.5 to 3 wt%, 0.5 to 2 wt%, or 1 to 2 wt%. In the above range, the coffee ring effect can be alleviated to provide a quantum dot film having a uniform film thickness and low thickness variation, and may not remain in the quantum dot film.

[0063] The carboxylic acid may be included in an amount of 0.1 to 10 parts by weight, for example, 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts by weight, for example, 0.1 to 5 parts by weight, or 0.5 to 3 parts by weight, based on 100 parts by weight of the solvent described below. In the above range, a quantum dot film having a uniform film thickness and low thickness variation without a coffee ring effect can be provided.

[0064] menstruum

[0065] The above solvent may be at least one of an aliphatic organic solvent and an aromatic organic solvent.

[0066] Non-limiting examples of usable solvents include hexane, octane, decane, dodecane, styrene, cyclohexylbenzene, chlorobenzene, dichlorobenzene, cyclohexanone, hexadecane, etc. The above-mentioned components may be used alone or in combination of two or more. Preferably, the solvent used may be cyclohexylbenzene.

[0067] The content of the solvent is not particularly limited and can be appropriately adjusted within a range known in the art. For example, it may be a residual amount satisfying 100 parts by weight of the quantum dot composition, and specifically, may be 70 to 95 parts by weight.

[0068] The above quantum dot composition may further include at least one additive known in the art within a range that does not impair the above-described effect.

[0069] The above quantum dot composition can be prepared by mixing and stirring the quantum dot; the carboxylic acid; and a solvent, and other additives added as needed, according to a conventional method known in the art.

[0070] At this time, the mixing method is not particularly limited, and for example, a mixer known in the art such as a homodisper, homomixer, universal mixer, planetary mixer, kneader, or 3-bone roll can be used.

[0071] The quantum dot composition manufactured as described above may include 1 to 30 parts by weight of the quantum dot; 0.1 to 10 parts by weight of the carboxylic acid; and the remainder of the solvent, based on the total weight of the composition. More specifically, the quantum dot composition may include 2 to 15 parts by weight of the quantum dot; 0.1 to 4 parts by weight of the carboxylic acid; and the remainder of the solvent. However, the present invention is not limited thereto.

[0072] The above quantum dot composition can be applied onto a substrate and then dried to form a quantum dot film.

[0073] quantum dot film

[0074] Another view is a quantum dot film. The quantum dot film includes a lower surface and an upper surface opposite the lower surface, the upper surface being a concave or convex surface relative to the lower surface, and the concave surface has a ratio of a minimum height to a maximum height of 0.2 or more.

[0075] According to one embodiment, the upper surface of the quantum dot film is convex. This indicates that the quantum dot film does not exhibit any coffee ring effect.

[0076] In another embodiment, the upper surface of the quantum dot film is a concave surface, and the ratio of the minimum height to the maximum height of the concave surface is 0.2 or more. This means that even if a coffee ring effect occurs in the quantum dot film, the coffee ring effect occurs at a significantly low level. For example, the ratio may be 0.2 to 0.5, for example, 0.2 to 0.3.

[0077] In one specific embodiment, the concave surface is a curved surface. In one specific embodiment, the quantum dot film may have a film thickness that gradually increases from the center to both ends in the cross-section of the quantum dot film, and then gradually decreases after reaching a maximum film thickness.

[0078] Figure 1 is a conceptual diagram of a quantum dot film according to an embodiment.

[0079] Referring to Fig. 1, a quantum dot film CL is formed on a substrate SUB, and the quantum dot film CL has a convex upper surface and a maximum film thickness Hmax.

[0080] Figure 2 is a conceptual diagram of a quantum dot film according to another embodiment.

[0081] Referring to FIG. 2, a quantum dot film CL is formed on the substrate SUB, and the quantum dot film CL has a concave upper surface and a maximum film thickness Hmax and a minimum film thickness Hmin.

[0082] In one specific example, the substrate may be a glass plate.

[0083]

[0084] Hereinafter, the structure and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, these are presented as preferred examples of the present invention and should not be construed as limiting the present invention in any way.

[0085]

[0086] (Manufacturing of quantum dot composition)

[0087] (A) Quantum dot: Green quantum dot dispersion solution (InP / ZnSe / ZnS, Hansol Chemical; quantum dot solid content 23 wt%)

[0088] (B) Carboxylic acids: 2-ethylhexanoic acid (EHA), 4-methylnonanoic acid (MNA), 2-butyloctanoic acid (BOA), 2-hexyldecanoic acid (HDA)

[0089] (C) Solvent: Cyclohexylbenzene

[0090]

[0091] Example 1

[0092] A quantum dot composition was prepared by mixing 5 wt% of quantum dots, 1.2 wt% of 2-ethylhexanoic acid, and the remainder of cyclohexylbenzene and stirring at room temperature for 12 hours.

[0093]

[0094] Examples 2 to 4

[0095] A quantum dot composition was prepared in the same manner as in Example 1, except that the carboxylic acid shown in Table 1 below was used instead of 2-ethylhexanoic acid.

[0096]

[0097] Comparative Example 1

[0098] A quantum dot composition was prepared in the same manner as in Example 1, except that 2-ethylhexanoic acid was not used.

[0099]

[0100] The quantum dot compositions manufactured in the Examples and Comparative Examples were applied under the conditions described below and dried under the conditions described below to form a quantum dot film. The formed quantum dot film was evaluated against the specifications in Table 1 below. The results are shown in Table 1 below and FIGS. 3 to 7.

[0101] Volume of quantum dot composition: 10 μL

[0102] Drying: Dry at 20~25℃ and 0.1 Torr for 60 minutes.

[0103] Example Comparative Example 12341 Compound EHAMNABOAHDA-quantum dot film diameter (mm) 8.2 8.3 8.4 7.6 9.8 Shape Concave Concave Concave Convex Concave Convex Shape 3 degrees 4 degrees 5 degrees 6 degrees 7 Coffee ring effect Negligible Negligible Negative Occurrence Occurrence Hmin / Hmax 0.2 1 0.3 0 0.24-0.16

[0104]

[0105] As shown in Table 1 above, when a specific carboxylic acid of the example is applied, it can be confirmed that the Coffee ring effect is alleviated and the Hmin / Hmax value increases or the Coffee ring effect does not occur at all.

[0106] On the other hand, it can be confirmed that the quantum dot film manufactured with the quantum dot composition of the comparative example that does not contain the specific carboxylic acid of the embodiment exhibited a coffee ring effect.

[0107] The results of the examples and comparative examples can also be confirmed through FIGS. 3 to 7. Referring to FIG. 6, the composition of Example 4 provided a quantum dot film in which the coffee ring effect did not occur at all. Referring to FIGS. 3 to 5, the composition of the examples provided a quantum dot film in which the coffee ring effect was alleviated and slightly formed. Referring to FIG. 7, the composition of the comparative example provided a quantum dot film in which the coffee ring effect occurred severely, which prevented uniform light emission and caused problems with screen quality.

[0108]

[0109] Simple modifications or changes of the present invention can be easily implemented by a person having ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims

1. A quantum dot composition comprising a quantum dot, a carboxylic acid having a melting point of 25°C or higher and a branched aliphatic hydrocarbon group, and a solvent.

2. In the first paragraph, the quantum dot composition comprises at least one compound represented by the following chemical formula 1: [Chemical Formula 1] (In the above chemical formula 1, L 11 Inland L 15 are each independently hydrogen, deuterium, a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms, L 11 , L 12 , L 13 , L 14 At least one of them is a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms, or L 15 is a branched chain alkyl group having 1 to 10 carbon atoms).

3. A quantum dot composition according to claim 1, wherein the carboxylic acid comprises at least one of 2-ethylhexanoic acid, 4-methylnonanoic acid, 2-butyloctanoic acid, and 2-hexyldecanoic acid.

4. A quantum dot composition according to claim 1, wherein the carboxylic acid is included in an amount of 0.1 to 10 wt% of the composition.

5. A quantum dot composition according to claim 1, wherein the carboxylic acid is contained in an amount of 0.1 to 100 parts by weight based on 100 parts by weight of the quantum dot.

6. A quantum dot composition according to claim 1, wherein the solvent is at least one of an aliphatic organic solvent and an aromatic organic solvent.

7. A quantum dot composition in claim 6, wherein the solvent comprises at least one of hexane, octane, decane, dodecane, styrene, cyclohexylbenzene, chlorobenzene, dichlorobenzene, cyclohexanone, and hexadecane.

8. A quantum dot composition in the first paragraph, wherein the quantum dot is surface-modified with a surface-modifying material or is not surface-modified.

9. A quantum dot composition in the first paragraph, wherein the carboxylic acid is contained in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the solvent.

10. As a quantum dot film, The quantum dot film includes a lower surface and an upper surface opposite to the lower surface, A quantum dot film, wherein the upper surface is a concave or convex surface from the lower surface, and the concave surface has a ratio of a minimum height to a maximum height of 0.2 or more.

11. A quantum dot film in claim 10, wherein the concave surface and the convex surface are each curved.

12. A quantum dot film in claim 10, wherein the quantum dot film comprises a dried product of any one of claims 1 to 11.

13. A display device comprising the quantum dot film of claim 10 or a cured product of the quantum dot film of claim 10.

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