KR102287241B1 - Composite sheet of quantum dots and organic nanophosphor, and display device comprising same - Google Patents

Abstract

A composite sheet according to the present invention is formed by combining a combination of a first color conversion layer including green quantum dots or green quantum dots and a second color conversion layer including red organic nano-phosphor. Therefore, the color reproducibility of a display device can be improved without the deterioration of luminance and reliability.

Description

Composite sheet of quantum dots and organic nanophosphor and display device including the same

The present invention relates to a color conversion sheet that has excellent color reproducibility and does not reduce luminance by combining quantum dots and an organic nanophosphor, and a display device including the same.

A liquid crystal display (LCD) device displays an image by using the optical properties of liquid crystal. Since the liquid crystal panel that displays the image is a non-emissive element that does not emit light by itself, it is disposed on the back side of the liquid crystal panel together with the liquid crystal panel. A backlight unit for supplying light is provided. The liquid crystal display device is spotlighted as a display device used in mobile devices, computer monitors, high-definition (HD) TVs, and the like.

As a light emitting diode (LED) light source of a liquid crystal display device, a structure in which a phosphor is placed on a blue light source to realize white light is generally used. However, since the phosphor used in this case exhibits a wide range of emission spectrum from green light to red light, the purity of color is low, the color reproduction range is narrow, and the quality of the image is deteriorated.

In order to solve this problem, alternative techniques include using light emitting diodes having green and red phosphors, respectively, reducing the half width of the phosphor to increase color purity, or adding a sheet containing a dye that absorbs a specific wavelength region. However, there is a limit to the improvement of luminance and color purity along with an increase in manufacturing cost.

Meanwhile, in order to increase the color gamut of the liquid crystal display device, various technologies have been developed using a blue LED as a light source and a quantum dot sheet including a quantum dot as a separate light conversion means (Korea Patent Publication No. 2014). -056490 and 2013-123718).

Recently, quantum dots that do not contain cadmium (Cd) have been used due to environmental problems, but these quantum dots have a wide half maximum width and have many overlapping wavelength regions of green quantum dots and red quantum dots, so there is a problem in color reproducibility. In addition, in order to increase color reproducibility, green quantum dots with short wavelengths are required, but since it is necessary to reduce the particle size of the quantum dots, defects on the surface of the quantum dots increase, resulting in poor performance and reliability.

Korean Patent Publication No. 2014-056490 Korean Patent Publication No. 2013-123718

Referring to FIG. 4 , the absorption spectrum of a typical red quantum dot has low absorption efficiency in the range of 540 nm to 600 nm and the absorption peak is not clear. When this type of light absorption characteristic is combined with green quantum dots, it is difficult to expect the effect of improving color reproducibility by shifting the emission peak of the green quantum dot to a shorter wavelength or reducing the half width. As a result, referring to FIG. 5 , when a spectrum was obtained through a blue LED light source for a film prepared by combining green quantum dots and red quantum dots, a spectrum form having the same peak wavelength and half maximum width as the green quantum dots before combining with red quantum dots. It can be seen that there is no effect of improving color reproducibility.

In order to solve this problem, a dye layer having an absorption peak in the vicinity of 570 to 620 nm has been conventionally disposed on one surface of the quantum dot film. However, in this case, the peak of the green quantum dot is shifted to the shorter wavelength side and the half width may be reduced, but there is a problem in that the luminance is greatly reduced due to light loss due to the absorption dye.

As a result of research conducted by the present inventors, it was found that when green quantum dots were combined with red organic nanophosphors, color reproducibility was improved while luminance was not lowered.

Accordingly, an object of the present invention is to provide a composite sheet capable of simultaneously achieving excellent color reproducibility and luminance in a display device by combining quantum dots and organic nanophosphors.

According to the present invention, a first color conversion layer comprising green quantum dots, or a combination of green quantum dots and red quantum dots; and a second color conversion layer including a red organic nanophosphor, and satisfying the following formulas (i) and (ii), a composite sheet is provided:

540 nm ≤ AB _MAX [R _PHOS ] ≤ 600 nm ... (i)

600 nm ≤ EM _MAX [R _PHOS ] ≤ 640 nm ... (ii)

where AB _MAX [R _PHOS ] is the wavelength (nm) of the highest point of the absorption peak of the second color conversion layer, and EM _MAX [R _PHOS ] is the wavelength (nm) of the highest point of the red emission peak of the second color conversion layer am.

Also according to the present invention, a light source emitting blue light; a display panel receiving the light from the light source to display an image; and the composite sheet disposed in a light path from the light source to the display panel.

In the composite sheet according to the present invention, a second color conversion layer including a red organic nanophosphor is combined with a first color conversion layer including green quantum dots or a combination of green quantum dots and red quantum dots. the color reproducibility can be improved.

In particular, when the above formulas (i) and (ii) are satisfied, the green emission energy of the first color conversion layer is partially absorbed by the red organic nanophosphor, and the green emission peak of the first color conversion layer moves toward a shorter wavelength. The half width may also be narrowed. Accordingly, the display device including the composite sheet of the present invention may have improved color reproducibility as compared to the conventional quantum dot display, but the luminance may not be lowered.

1A shows a cross-sectional view of a composite sheet according to an embodiment of the present invention.
1B shows a cross-sectional view of a composite sheet according to another embodiment of the present invention.
2A is a cross-sectional view of a first color conversion layer according to an exemplary embodiment.
2A is a cross-sectional view of a first color conversion layer according to another embodiment.
3 is a cross-sectional view of a second color conversion layer according to an exemplary embodiment.
4 shows spectra of a typical green quantum dot and a red quantum dot.
5 is a spectrum obtained through a blue light source for a general green quantum dot and a red quantum dot.
6 shows an example of a spectrum of a green quantum dot and a red organic nanophosphor.
7 is a spectrum obtained through a blue light source for composite sheets according to Examples and Comparative Examples.
8 is an exploded perspective view of a display device according to an embodiment of the present invention.

Hereinafter, various embodiments and embodiments of the present invention will be described in detail with reference to the drawings.

In describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, the size of each component in the drawings may be exaggerated or omitted for the sake of explanation, and may be different from the size actually applied.

In the present specification, the description that one component is formed above/under another component or connected or coupled to each other includes both the formation, connection, or coupling between these components directly or indirectly through another component. . In addition, it should be understood that the criteria for the top/bottom of each component may vary depending on the direction in which the object is observed.

In the present specification, terms referring to each component are used to distinguish it from other components, and are not intended to limit the present invention. Also, in this specification, the singular expression includes the plural expression unless the context clearly dictates otherwise.

As used herein, the phrase “comprising” is intended to specify a particular characteristic, region, step, process, element, and/or component, and unless otherwise specifically stated, other characteristics, regions, steps, processes, elements and It does not exclude the presence or addition of/or components.

In this specification, terms such as first, second, etc. are used to describe various components, and the components should not be limited by the terms. The above terms are used for the purpose of distinguishing one component from another component.

composite sheet

The composite sheet according to the present invention includes a first color conversion layer including green quantum dots, or green quantum dots and red quantum dots; and a second color conversion layer including a red organic nano-phosphor.

In the composite sheet, the green quantum dots may absorb blue light to emit green light, and the red organic nanophosphor may absorb blue light and a portion of green light emitted from the green quantum dots to emit red light.

Accordingly, the composite sheet according to the above can improve the color reproducibility of the display device without deterioration of luminance and reliability.

For example, referring to FIG. 6 , the red organic nanophosphor used in the present invention may have a high absorption efficiency and a minimum peak value in the range of 540 nm and 600 nm. The light absorption characteristic of this type of red organic nanophosphor moves the peak of the green quantum dot to a shorter wavelength and reduces the half width when combined with the green quantum dot, so it can increase the purity of green and improve the color reproducibility of the display. In addition, light absorbed by the organic nanophosphor in the range of 480 nm to 630 nm is used to generate red light between 550 nm and 700 nm, so that light loss can be minimized.

7 shows the spectrum measured through a blue LED light source for the composite sheet of green quantum dots and red organic nanophosphor according to an embodiment of the present invention, and the composite sheet of green quantum dots and red quantum dots according to a comparative example. As shown in FIG. 7 , it can be confirmed that the green emission peak of the composite sheet of Examples compared to Comparative Example is shifted to a shorter wavelength and the half width is also narrowed. As described above, the spectrum of the green quantum dot combined with the red organic nanophosphor exhibits a form in which the emission peak is shifted to the shorter wavelength side compared to the original green quantum dot, and the half maximum width is also narrowed, so that the color reproducibility improvement effect can be obtained.

Hereinafter, the characteristics of the composite sheet of the present invention will be described in detail in various aspects.

For this purpose, the following abbreviations are used for various properties in this specification:

EM _MAX [G _QDOT ]: wavelength (nm) of the highest point of the green emission peak of the first color conversion layer including green quantum dots

AB _MAX [R _PHOS ]: the wavelength (nm) of the highest point of the absorption peak of the second color conversion layer including the red organic nanophosphor

EM _MAX [R _PHOS ]: The wavelength (nm) of the highest point of the red emission peak of the second color conversion layer including the red organic nanophosphor

EM _FWHM [G _QDOT ]: Full width at half maximum (nm) of the green emission peak of the first color conversion layer including green quantum dots

EM _FWHM [R _PHOS ]: Full width at half maximum (nm) of the red emission peak of the second color conversion layer including the red organic nanophosphor

EM _MAX [G _COMP ]: wavelength (nm) of the highest point of the green emission peak of the composite sheet

EM _MAX [R _COMP ]: the wavelength of the peak of the red emission peak of the composite sheet (nm)

EM _FWHM [G _COMP ]: Width at half maximum (nm) of the green emission peak of the composite sheet

EM _FWHM [R _COMP ]: Full width at half maximum (nm) of the red emission peak of the composite sheet

The highest point of the emission peak means a point at which the emission intensity is maximum, and the highest point of the absorption peak means a point at which the absorption intensity is maximum.

Characteristics of Composite Sheet

According to one embodiment, in the composite sheet according to the present invention, the red organic nanophosphor satisfies the following formulas (i) and (ii).

540 nm ≤ AB _MAX [R _PHOS ] ≤ 600 nm ... (i)

600 nm ≤ EM _MAX [R _PHOS ] ≤ 640 nm ... (ii)

When the above formulas (i) and (ii) are satisfied, the emission energy of the first color conversion layer including green quantum dots is partially absorbed by the red organic nanophosphor, so that the emission peak of the green quantum dot moves toward a shorter wavelength and the half width becomes narrow. can Accordingly, while color reproducibility is improved compared to a conventional quantum dot display, luminance may not decrease.

The AB _MAX [R _PHOS ] may be, for example, 540 nm or more, 545 nm or more, 550 nm or more, 555 nm or more, or 560 nm or more, and also 600 nm or less, 595 nm or less, 590 nm or less, 585 nm or less , or 580 nm or less.

The EM _MAX [R _PHOS ] may be, for example, 600 nm or more, 605 nm or more, 610 nm or more, 615 nm or more, or 620 nm or more, and also 640 nm or less, 635 nm or less, 630 nm or less, or 625 nm or less. can

As a specific example, the AB _MAX [R _PHOS ] may be within a range of 550 nm to 590 nm, and the EM _MAX [R _PHOS ] may be within a range of 610 nm to 640 nm.

According to another embodiment, the composite sheet according to the present invention satisfies Equation (1) below.

EM _MAX [G _QDOT ] > EM _MAX [G _COMP ] ... (1)

When the above formula (1) is satisfied, the green emission peak of the first color conversion layer including green quantum dots moves toward a shorter wavelength than before being compounded with the second color conversion layer including the red organic nanophosphor, so that the conventional quantum dot display color reproducibility can be improved.

For example, in the composite sheet, ΔEM _MAX [G] defined in the following equation may be 1 nm or more.

△EM _MAX [G] = EM _MAX [G _QDOT ] - EM _MAX [G _COMP ]

Specifically, the ΔEM _MAX [G] is 2 nm or more, which may indicate a significant improvement in color reproducibility compared to the related art. As a specific example, the ΔEM _MAX [G] may be 2 nm to 15 nm, 2 nm to 10 nm, or 2 nm to 6 nm. More specifically, the ΔEM _MAX [G] may be 3 nm or more, 4 nm or more, or 5 nm or more.

The EM _MAX [G _QDOT ] may be, for example, 525 nm or more, 530 nm or more, 535 nm or more, 536 nm or more, or 540 nm or more, and also 560 nm or less, 555 nm or less, 550 nm or less, or 545 nm may be below. As a specific example, the EM _MAX [G _QDOT ] may be in the range of 536 nm to 550 nm.

In addition, the EM _MAX [G _COMP ] may be, for example, 520 nm or more, 525 nm or more, 530 nm or more, or 535 nm or more, and also 555 nm or less, 550 nm or less, 545 nm or less, or 540 nm or less. . As a specific example, the EM _MAX [G _COMP ] may be in the range of 535 nm to 545 nm.

According to another embodiment, the composite sheet according to the present invention satisfies Equation (2) below.

EM _FWHM [G _QDOT ] > EM _FWHM [G _COMP ] ... (2)

When the above formula (2) is satisfied, the half width of the emission peak of the first color conversion layer including green quantum dots is narrower than before being compounded with the second color conversion layer including red organic nano-phosphors, so that in a conventional quantum dot display Compared to that, color reproducibility can be improved.

For example, in the composite sheet, ΔEM _FWHM [G] defined in the following equation may be 1 nm or more.

△EM _FWHM [G] = EM _FWHM [G _QDOT ] - EM _FWHM [G _COMP ]

Specifically, the ΔEM _FWHM [G] is 2 nm or more, which may indicate a significant improvement in color reproducibility compared to the prior art. As a specific example, the ΔEM _FWHM [G] may be 2 nm to 15 nm, 2 nm to 10 nm, or 2 nm to 6 nm. More specifically, the ΔEM _FWHM [G] may be 3 nm or more, 4 nm or more, or 5 nm or more.

The EM _FWHM [G _QDOT ] may be, for example, 30 nm or more, 33 nm or more, 35 nm or more, or 38 nm or more, and may also be 50 nm or less, 47 nm or less, 45 nm or less, or 42 nm or less. Specifically, the EM _FWHM [G _QDOT ] may be in the range of 35 nm to 45 nm.

In addition, the EM _FWHM [G _COMP ] may be 25 nm or more, 33 nm or more, or 35 nm or more, and may be 45 nm or less, 42 nm or less, 40 nm or less, or 37 nm or less. Specifically, the EM _FWHM [G _COMP ] may be 40 nm or less.

In addition, the composite sheet may have an EM _MAX [R _COMP ] of 590 nm or more, 595 nm or more, 600 nm or more, 605 nm or more, or 610 nm or more, and also 640 nm or less, 635 nm or less, 630 nm or less, 625 nm or more. or less, or 620 nm or less. As a specific example, the EM _MAX [R _COMP ] may be within 600 nm to 630 nm.

On the other hand, in the composite sheet, the half width of the red emission peak of the second color conversion layer including the red organic nanophosphor may not be substantially different from that before being compounded with the first color conversion layer including the green quantum dots. For example, the composite sheet may have a ΔEM _FWHM [R] of 5 nm or less as defined in the following equation.

△EM _FWHM [R] = │EM _FWHM [R _PHOS ] - EM _FWHM [R _COMP ]│

Specifically, the ΔEM _FWHM [R] may be 3 nm or less or 1 nm or less.

In addition, the EM _FWHM [R _COMP ] may be 30 nm or more, 33 nm or more, 35 nm or more, or 38 nm or more, and may be 50 nm or less, 47 nm or less, 45 nm or less, or 42 nm or less. Specifically, the EM _FWHM [R _COMP ] may be 40 nm or less.

Composition of color conversion layer

Referring to FIG. 2A , the composite sheet according to the present invention includes green quantum dots 101 in the first color conversion layer 110 . The green quantum dot absorbs light and then emits green light having a wavelength corresponding to the band gap of the quantum dot.

The green quantum dot may include a semiconductor selected from the group consisting of group II-VI, group III-V, group IV-VI, group IV semiconductor, and mixtures thereof. As an example, the green quantum dot may be a multi-layered nanostructure including a core and one or more shells. In the multilayer nanostructure, the core may be selected from the group consisting of ZnS, ZnSe, CdSe, CdS and InP, and may include InP as a specific example. In addition, in the multilayer nanostructure, the shell may be selected from the group consisting of ZnS, ZnSe, ZnTe, GaN, GaP, AlP, CdS, CdSe, CdTe, AlAs and AlSb, and may include ZnSe and ZnS as specific examples.

The green quantum dots included in the composite sheet of the present invention do not contain cadmium (Cd), and thus may not cause environmental problems. Accordingly, the cadmium content in the composite sheet may be less than 100 ppm, less than 10 ppm, less than 1 ppm, or 0 ppm. Green quantum dots that do not contain cadmium have a problem in that the emission peak partially overlaps the red region and the half maximum width is wide.

Referring to FIG. 2B , the composite sheet according to the present invention may further include red quantum dots 102 in the first color conversion layer 110 . The addition of the red quantum dots can increase the distance from the green emission peak by shifting the wavelength of the highest point of the red emission peak of the composite sheet to a longer wavelength.

The red quantum dot may include a semiconductor selected from the group consisting of group II-VI, group III-V, group IV-VI, group IV semiconductor, and mixtures thereof. As an example, the red quantum dots may be a multi-layered nanostructure including a core and one or more shells. In the multilayer nanostructure, the core may be selected from the group consisting of ZnS, ZnSe, CdSe, CdS and InP, and may include InP as a specific example. In addition, in the multilayer nanostructure, the shell may be selected from the group consisting of ZnS, ZnSe, ZnTe, GaN, GaP, AlP, CdS, CdSe, CdTe, AlAs and AlSb, and may include ZnSe and ZnS as specific examples.

The green quantum dots and the red quantum dots are spherical nanoparticles, and may have, for example, an average particle diameter of 2 nm to 10 nm, respectively.

The first color conversion layer 110 may include a binder resin 105, for example, a thermosetting type or UV curing type polymer resin. Specifically, the binder resin may be at least one selected from the group consisting of polyester-based, polyurethane-based, polybutadiene-based, acrylic-based, epoxy-based, polycarbonate-based, silicone-based, melamine-based resins, and copolymers thereof. The content of the binder resin may be 50 to 95% by weight, 80 to 95% by weight, or 85 to 95% by weight based on the weight of the first color conversion layer.

The content of the green quantum dots may be 0.1 to 10 parts by weight, 0.1 to 5 parts by weight, or 0.2 to 2 parts by weight based on 100 parts by weight of the binder resin in the first color conversion layer.

Meanwhile, the first color conversion layer may include a combination of green quantum dots and red quantum dots, wherein the content of the red quantum dots may be less than the content of the green quantum dots. For example, the content of the red quantum dots may be 99 parts by weight or less, 85 parts by weight or less, 70 parts by weight or less, 55 parts by weight or less, and specifically 5 parts by weight or less, based on 100 parts by weight of the green quantum dot. to 99 parts by weight, or 10 parts by weight to 70 parts by weight.

Referring to FIG. 3 , the composite sheet according to the present invention includes a red organic nanophosphor 103 in the second color conversion layer 120 . The red organic nanophosphor absorbs some light emitted by the green quantum dots and emits red light, thereby improving color reproducibility without lowering luminance.

The red organic nanophosphor is preferably a bodipyrene, perylene, pyrrole, pyrene, coumarin, xanthene, acridine, arylmethane, polycyclic aromatic hydrocarbon, polycyclic heteroaromatic derivative, etc. In addition, various organic nanophosphors may be used.

In addition, the average particle diameter of the red organic nanophosphor may be several nm or smaller, for example, 5 nm or less or 1 nm or less, but is not particularly limited thereto.

The second color conversion layer 120 may include the binder resin 105 , and a specific type and content thereof may be similarly applied to the type and content of the binder resin in the first color conversion layer.

In addition, the content of the red organic nanophosphor may be 0.001 to 1.0 parts by weight, specifically 0.005 to 0.5 parts by weight, based on 100 parts by weight of the binder resin in the second color conversion layer.

In addition, the first color conversion layer 110 and the second color conversion layer 120 may further include other additives, for example, a light scattering agent 107, a photoinitiator, and the like.

The light scattering agent may be amorphous or may be spherical or hollow particles. The light scattering agent may have an average particle diameter of 0.01 μm or more, or 0.01 to 10 μm. The light scattering agent may use one having a large refractive index difference from the binder resin, for example, BaSO ₄ , ZnO, TiO ₂ , ZrO ₂ , silica, silicon, melamine, polystyrene, and one selected from the group consisting of polybutyl methacrylate It may contain more than one component. The content of the light scattering agent may be 0.1 to 10 parts by weight, or 0.2 to 5 parts by weight based on 100 parts by weight of the binder resin.

As such, among the components included in the first color conversion layer and the second color conversion layer, the emission peaks and absorption of the first color conversion layer and the second color conversion layer by the green quantum dots, red quantum dots, and red organic nano-phosphors A peak may be determined, and other binder resins, scattering agents, or other additives may be optically transparent and may have little effect on the emission peak and absorption peak of the first color conversion layer and the second color conversion layer.

Example of laminated structure of composite sheet

1A and 1B , the composite sheet 100 according to the present invention has a laminated structure including the first color conversion layer 110 and the second color conversion layer 120 .

The thickness of the first color conversion layer may be, for example, 5 μm to 200 μm, and specifically, 10 μm to 100 μm.

In addition, the thickness of the second color conversion layer may be, for example, 1 μm to 50 μm, specifically, 2 μm to 20 μm.

The first color conversion layer and/or the second color conversion layer may be coated on a base film. Accordingly, the composite sheet may further include a base film coated with the first color conversion layer and/or the second color conversion layer. As the base film, any transparent polymer film can be applied without any special restrictions, and for example, it may be a polyethylene terephthalate film having high transparency and excellent heat resistance. For example, the light transmittance of the base film may be 90% or more, and the thickness may be 12 μm to 350 μm, specifically 25 μm to 250 μm.

In addition, the composite sheet may further include one or more barrier films as an outer layer or an inner layer. As an example, the composite sheet may further include a barrier film formed on one or both surfaces of the first color conversion layer. As another example, the composite sheet may further include a barrier film formed between the first color conversion layer and the second color conversion layer. As another example, the composite sheet may further include a barrier film formed on one or both surfaces of the second color conversion layer.

As an example, the composite sheet may include the first color conversion layer, the second color conversion layer, a first barrier film, and a second barrier film. Referring to FIG. 1A , the composite sheet may sequentially include a first barrier film 150 , a first color conversion layer 110 , a second barrier film 160 , and a second color conversion layer 120 . . Referring to FIG. 1B , the composite sheet may sequentially include a first barrier film 150 , a first color conversion layer 110 , a second color conversion layer 120 , and a second barrier film 160 . there is.

The barrier film serves to secure the stability and reliability of the color conversion layer by maintaining the shape of the color conversion layer and effectively blocking the transmission of oxygen and moisture from the outside to the color conversion layer.

The barrier film may include a base layer and an inorganic layer formed on the base layer.

The base layer may be a transparent polymer film, for example, may have the same composition and thickness as the base film described above.

The inorganic layer serves to effectively block the permeation of moisture and oxygen to the color conversion layer. In this case, the inorganic layer may be in contact with the color conversion layer. The inorganic layer may be formed by depositing an inorganic material on the surface of the base layer, and the inorganic material may be selected from metal and non-metal oxides, nitrides, fluorides, and the like. Specific examples of the inorganic material include at least one selected from the group consisting of aluminum oxide, silicon oxide, silicon nitride, silicon oxynitride, magnesium oxide, indium oxide, and magnesium fluoride. The inorganic layer may have a thickness of 10 nm to 1 μm.

In addition, the barrier film may further improve the moisture and oxygen barrier performance of the base layer by further including an organic layer between the base layer and the inorganic layer, thereby making the surface of the base layer flat to uniformly form the inorganic layer. there is. In addition, the barrier film may increase adhesion with the color conversion layer by further including an organic layer on the surface of the inorganic layer. The organic layer may be made of a conventional organic polymer resin. The thickness of the organic layer may be 0.1 μm to 10 μm, specifically 0.3 μm to 7 μm, and more specifically 0.5 μm to 5 μm.

The barrier film may be directly laminated on the surface of the color conversion layer or may be laminated through an adhesive layer. Accordingly, the composite sheet may further include an adhesive layer between the barrier film and the color conversion layer.

The adhesive layer may include an optically transparent adhesive resin such as an acrylic adhesive, and may have a thickness of 2 μm to 100 μm, 5 μm to 100 μm, or 15 μm to 25 μm.

1A, the composite sheet according to an embodiment includes a first barrier film 150, a first color conversion layer 110, a second barrier film 160, an adhesive layer 140, and a second color conversion layer ( 120) and the base film 130 may have a stacked structure in that order. Referring to FIG. 1B , the composite sheet according to another embodiment includes a first barrier film 150 , a first color conversion layer 110 , a base film 130 , a second color conversion layer 120 , and an adhesive layer 140 . , the second barrier film 160 may have a stacked structure in that order.

In addition, the composite sheet may further include an anti-blocking layer or a diffusion coating layer on at least one surface of the base film or the barrier film.

display device

The display device of the present invention includes a light source emitting blue light; a display panel receiving the light from the light source to display an image; and the composite sheet disposed in a light path from the light source to the display panel.

The blue light from the light source is combined with green light and red light in a process of passing through the composite sheet, and properties are improved, and the display panel may display an image using the light of the improved properties.

Specifically, with reference to FIG. 8 , the display device 1 may include a backlight unit 10 ; and a display panel 20 disposed on the backlight unit 10 . The backlight unit 10 includes a composite sheet 100; a light guide plate or a diffuser plate 700; and a light source 900 .

In addition, the light source 900 may be disposed on a side surface of the light guide plate or under the diffusion plate 700 . The light guide plate or the diffusion plate 700 is disposed under the composite sheet 100 to transmit light generated from the light source 900 to the display panel 20 . The light guide plate is used in the case of an edge type light source, the diffusion plate 700 is used in the case of a direct light source, and an LED surface light source may be used.

Referring to FIG. 8 , the light generated from the light source 900 is reflected by the reflection plate 800 and is incident on the lower portion of the composite sheet 100 through the diffusion plate 700 . The incident light passes through the composite sheet 100 vertically and is emitted upward. The light emitted to the upper portion of the composite sheet 100 is incident on the display panel 20, and as a result, an image may be displayed on the screen of the display panel.

The light source may be a blue light source, for example, a blue LED. Specifically, the light source may include a blue gallium nitride (GaN) light emitting chip.

The backlight unit may further include one or more optical films 200 for functions such as light collection, light diffusion, and brightness enhancement. The optical film 200 may be, for example, a prism film, a diffusion film, a dual brightness enhancement film, or the like. The prism sheet may have a prism pattern layer formed on one surface of the base layer, and a combination of a vertical prism sheet and a horizontal prism sheet may be used. The diffusion film may have a configuration in which beads are coated on one surface of the base layer. In addition, the double brightness enhancement film may have a multilayer structure of fine thin films having different refractive indices. The optical film 200 may be disposed, for example, between the display panel 20 and the composite sheet 100 or between the composite sheet 100 and the light guide plate or diffuser plate 700 , and is particularly limited. doesn't happen

The display panel 20 may include a liquid crystal cell and one or more polarizing plates. As a specific example, the display panel 20 may have a structure in which a first polarizing plate, a liquid crystal cell, and a second polarizing plate are stacked, and an adhesive layer is disposed between the polarizing plate and the liquid crystal cell. can be formed.

Since the display device of the present invention includes the composite sheet having the above-described configuration, color reproducibility of the display device can be improved without deterioration in luminance and reliability. For example, the display device may exhibit a color gamut of 90% or more in the DCI-P3 color space. Specifically, the display device may exhibit a color gamut of 95% or more in the DCI-P3 color space. DCI-P3 is a color gamut defined by the Digital Cinema Initiatives for use in the American film industry as a color gamut for digital projectors. It can express 25% wider color gamut than conventional sRGB, and its main feature is that it has a wider coverage especially in the red part. Therefore, very good color reproducibility can be realized when DCI-P3 is 95% or more.

The above will be described in more detail with reference to the following examples. However, the following examples are only for illustrating the present invention, and the scope of the examples is not limited thereto.

Example 1: Preparation of Composite Sheet (Green Quantum Dot + Red Organic Nanophosphor)

Hereinafter, the manufacturing procedure of the composite sheet was described with reference to FIG. 1A.

First, a quantum dot composition was prepared by mixing the following components.

- 90 parts by weight of binder (UV-curable acrylate resin, SKC HT&M)

- 6.5 parts by weight of green quantum dot solution (quantum dot content: 10% by weight, InP type, NANOSYS, US) - Highest emission peak 541 nm in the first color conversion layer

- 3.0 parts by weight of light scattering agent (TiO ₂ , Ti-Pure R902+) - Refractive index 2.7, average particle diameter 0.4 ㎛

- 2.0 parts by weight of photoinitiator (Irgacure TPO)

After forming the first color conversion layer 110 by coating the quantum dot composition on one surface of the first barrier film 150 (SBL125B, SKC HT&M Corporation), the second barrier film 160 (SBL125B, SKC HT&M Corporation) ) and laminated to prepare a first sheet by performing UV curing.

Next, a nanophosphor composition was prepared by mixing the following components.

- 60 parts by weight of binder (thermoplastic acrylic resin, solid content 20% by weight)

- 40 parts by weight of solvent (butyl acetate)

- 0.05 parts by weight of red organic nanophosphor (UBP-R, manufactured by Uksung Chemical) - Absorption peak at 574 nm, emission peak at 620 nm in the second color conversion layer

- 1 part by weight of light scattering agent (TiO ₂ , Ti-Pure R902+) - Refractive index 2.7, average particle diameter 0.4 ㎛

A second color conversion layer 120 having a thickness of 5 μm is formed by coating the nanophosphor composition on one surface of a polyethylene terephthalate (PET) film having a thickness of 50 μm as the base film 130 and drying at 120° C. for 5 minutes. A second sheet was obtained.

One side of the second barrier film 160 of the first sheet is coated with an optically clear adhesive (OCA, SKC HT&M) and dried at 100° C. for 5 minutes to form an adhesive layer 140 having a thickness of 15 μm. A composite sheet was prepared by laminating two sheets to be in contact with the second color conversion layer 120 .

Example 2: Preparation of Composite Sheet (Green Quantum Dot + Red Organic Nanophosphor)

A composite sheet was prepared by repeating the procedure of Example 1 above, but using the following ingredients as green quantum dots.

- 6.7 parts by weight of green quantum dot solution (quantum dot content: 10% by weight, InP type, NANOSYS, US) - Highest emission peak at 538 nm in the first color conversion layer

Example 3: Preparation of Composite Sheet (Green Quantum Dot + Red Quantum Dot + Red Organic Nanophosphor)

First, a quantum dot composition was prepared by mixing the following components.

- 90 parts by weight of binder (UV-curable acrylate resin, SKC HT&M)

- 6.7 parts by weight of green quantum dot solution (quantum dot content: 10% by weight, InP type, NANOSYS, US) - Highest emission peak at 538 nm in the first color conversion layer

- 1.0 parts by weight of a red quantum dot solution (quantum dot content: 5% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer 630 nm

- 3.0 parts by weight of light scattering agent (TiO ₂ , Ti-Pure R902+) - Refractive index 2.7, average particle diameter 0.4 ㎛

- 2.0 parts by weight of photoinitiator (Irgacure TPO)

Next, a nanophosphor composition was prepared by mixing the following components.

- 60 parts by weight of binder (thermoplastic acrylic resin, solid content 20% by weight)

- 40 parts by weight of solvent (butyl acetate)

- 0.04 parts by weight of red organic nano-phosphor (UBP-R, Uksung Chemicals) - Absorption peak at 574 nm, emission peak at 620 nm in the second color conversion layer

- 1 part by weight of light scattering agent (TiO ₂ , Ti-Pure R902+) - Refractive index 2.7, average particle diameter 0.4 ㎛

The procedure of Example 1 was repeated, but the quantum dot composition was used to prepare the first color conversion layer, and the nanophosphor composition was used to prepare the second color conversion layer, to prepare a composite sheet.

Comparative Example 1: Preparation of Composite Sheet (Green Quantum Dot + Red Quantum Dot)

A quantum dot composition was prepared by mixing the following components.

- 90 parts by weight of binder (UV curable acrylate resin)

- 5.1 parts by weight of green quantum dot solution (quantum dot content: 10% by weight, InP type, NANOSYS, US) - Maximum emission peak 541 nm in the color conversion layer

- 2.6 parts by weight of a red quantum dot solution (quantum dot content: 5% by weight, InP type, NANOSYS, US) - Highest emission peak in the color conversion layer 630 nm

- 3.0 parts by weight of light scattering agent (TiO ₂ , Ti-Pure R902+) - Refractive index 2.7, average particle diameter 0.4 ㎛

- 2.0 parts by weight of photoinitiator (Irgacure TPO)

A color conversion layer is formed by coating the quantum dot composition on one surface of a first barrier film (SBL125B, SKC HT&M), and a second barrier film (SBL125B, SKC HT&M) is laminated thereon, followed by UV curing. A composite sheet was prepared.

Comparative Example 2: Preparation of Composite Sheet (Green Quantum Dot + Red Quantum Dot)

A composite sheet was prepared by repeating the procedure of Comparative Example 1 using the green quantum dots used in Example 2.

- 5.3 parts by weight of green quantum dot solution (quantum dot content: 10% by weight, InP type, NANOSYS, US) - Maximum emission peak 538 nm in the color conversion layer

Comparative Example 3: Preparation of Composite Sheet (Green Quantum Dot + Red Quantum Dot)

The procedure of Comparative Example 1 was repeated, but a composite sheet was prepared using the following ingredients.

- 5.5 parts by weight of a green quantum dot solution (quantum dot content: 10% by weight, InP type, NANOSYS, US) - Maximum emission peak 535 nm in the color conversion layer

Comparative Example 4: Preparation of Composite Sheet (Green Quantum Dot + Red Quantum Dot + Absorption Dye)

A quantum dot composition was prepared by mixing the following components.

- 90 parts by weight of binder (UV curable acrylate resin)

- 6.2 parts by weight of a green quantum dot solution (quantum dot content: 10% by weight, InP type, NANOSYS, US) - Maximum emission peak 541 nm in the color conversion layer

- 2.9 parts by weight of a red quantum dot solution (quantum dot content: 5% by weight, InP type, NANOSYS, US) - Highest emission peak in the color conversion layer 630 nm

- 3.0 parts by weight of light scattering agent (TiO ₂ , Ti-Pure R902+) - Refractive index 2.7, average particle diameter 0.4 ㎛

- 2.0 parts by weight of photoinitiator (Irgacure TPO)

A first barrier film (SBL125B, SKC HT&M) is coated on one side of the film to form a color conversion layer by coating the quantum dot composition, and a second barrier film (SBL125B, SKC HT&M) is laminated thereon, followed by UV curing. was performed to prepare a composite sheet.

Next, a dye composition was prepared by mixing the following components.

- 36 parts by weight of binder (AOF-2914, Aekyung Corporation)

- 4 parts by weight of curing agent (AH-2100, Aekyung Corporation)

- 60 parts by weight of solvent (methylethylketone/toluene=1:1, w/w)

- 0.01 parts by weight of absorption dye (PANAX, Wooksung Chemical) - The highest point of absorption peak 594 nm

As the base film 130, the dye composition was coated on one surface of a polyethylene terephthalate (PET) film having a thickness of 50 μm and dried at 120° C. for 3 minutes to obtain a second sheet having a thickness of 5 μm.

One side of the second barrier film 160 of the first sheet is coated with an optically clear adhesive (OCA, SKC HT&M) and dried at 100° C. for 2 minutes to form an adhesive layer 140 having a thickness of 15 μm. A composite sheet was prepared by laminating the two sheets so as to be in contact with the absorbent dye coating layer.

test example

The following tests were performed on the composite sheets of Examples and Comparative Examples.

(1) absorption peak

For the absorption peaks of quantum dots or nanophosphors described in Examples and Comparative Examples, a spectrophotometer (Spectrophotometer, U4100, HITACHI) is used after preparing a specimen by forming each color conversion layer including the same on a transparent PET film. and measured.

(2) luminescence peak

A composite sheet sample is placed on a diffuser plate of a direct backlight having a blue light source, and a vertical prism sheet, a horizontal prism sheet, and a dual luminance enhancement film (DBEF) are sequentially laminated thereon. Then, a spectroradiometer (SR-3, TOPCON, Working Distance: 660 mm, Field Spec.: 0.2D) was used to measure the emission spectrum, and the peak wavelength (nm) and full width at half maximum (nm) of the emission peaks (blue/green/red) were calculated.

In addition, the emission peaks of quantum dots or nanophosphors described in Examples and Comparative Examples above are measured according to the test method after each color conversion layer including the same is formed on a transparent PET film.

(3) Relative luminance

A composite sheet sample is placed on a diffuser plate of a direct backlight having a blue light source, and a vertical prism sheet, a horizontal prism sheet, and a dual luminance enhancement film (DBEF) are sequentially laminated thereon. Then, a spectroradiometer (SR-3, TOPCON, Working Distance: 660 mm, Field Spec.: 0.2D) was used to measure luminance. The relative luminance was calculated by setting the luminance of the composite sheet of Example 1 to 100%.

(4) DCI-P3

A composite sheet sample was applied to a liquid crystal display device equipped with a direct backlight having a blue light source and CIE 1931 using a spectroradiometer (Spectroradiometer, SR-3, TOPCON, Working Distance: 660 mm, Field Spec.: 0.2D) The chromaticity coordinates xy were measured and the overlap ratio of the DCI-P3 color gamut was calculated using this. It is preferable that DCI-P3 is 95% or more.

(5) Reliability - high temperature

a. Test apparatus: hot air circulation high temperature oven

b. Test procedure/condition: A composite sheet sample was cut to an A4 size, and luminance and chromaticity coordinates xy were measured. Thereafter, the sample was placed in an oven at 85° C., and after 1000 hours had elapsed, the luminance and chromaticity coordinates xy were measured again to calculate the change in luminance retention and chromaticity coordinates xy.

c. Test result

- Good: Luminance retention rate of 90% or more, chromaticity coordinates x and y change amount within 0.01

- Poor: Luminance retention rate less than 90%, chromaticity coordinates x and y change amount greater than 0.01

(6) Reliability - high humidity

a. Test device: hot air circulation high temperature humidification oven

b. Test procedure/condition: A composite sheet sample was cut to an A4 size, and luminance and chromaticity coordinates xy were measured. Thereafter, the sample was placed in an oven at 65° C. and a humidity of 90%, and after 1000 hours had elapsed, the luminance and chromaticity coordinates xy were measured again to calculate the change in luminance retention and chromaticity coordinates xy.

c. Test result

- Good: Luminance retention rate of 90% or more, chromaticity coordinates x and y change amount within 0.01

- Poor: Luminance retention rate less than 90%, chromaticity coordinates x and y change amount more than 0.01

(7) Reliability - light resistance

a. Test apparatus: It was installed in a direct backlight 60 ℃ oven equipped with a high-brightness blue LED, and voltage and current were applied under the conditions of ^{50 mW/cm 2 .}

b. Test procedure/condition: A composite sheet sample was cut to an A4 size, and luminance and chromaticity coordinates xy were measured. After that, the sample is placed on a direct backlight equipped with a high-brightness blue LED driven in an oven at 60°C, and the luminance and chromaticity coordinates xy are calculated after 1000 hours of laminating a horizontal prism sheet, a vertical prism sheet, and a dual brightness enhancement film (DBEF). By measuring again, the amount of change in luminance retention and chromaticity coordinates xy was calculated.

c. Test result

- Good: Luminance retention rate of 90% or more, chromaticity coordinates x and y change amount within 0.01

- Poor: Luminance retention rate less than 90%, chromaticity coordinates x and y change amount more than 0.01

The test results are shown in Tables 1 and 2 below.

division Emission peak of composite sheet blue green Red light source peak
solstice
(nm) radiation
matter peak
solstice
(nm) half width
(nm) radiation
matter peak
solstice
(nm) half width
(nm) Example 1 LED 445 quantum dots 538 35 organic nano
phosphor 620 40 Example 2 LED 445 quantum dots 535 35 organic nano
phosphor 620 40 Example 3 LED 445 quantum dots 536 36 organic nano
Phosphor + Quantum Dot 625 41 Comparative Example 1 LED 445 quantum dots 541 38 quantum dots 630 44 Comparative Example 2 LED 445 quantum dots 538 38 quantum dots 630 44 Comparative Example 3 LED 445 quantum dots 535 38 quantum dots 630 44 Comparative Example 4 LED 445 quantum dots 537 38 quantum dots 630 41

division BLU DCI-P3
(%) reliability color coordinates
Wx / Wy Relative luminance
(%) High temperature high humidity light fastness Example 1 0.250 / 0.225 100% 95.5% Good Good Good Example 2 0.250 / 0.225 97% 96.4% Good Good Good Example 3 0.250 / 0.225 98% 96.2% Good Good Good Comparative Example 1 0.250 / 0.225 101% 93.8% Good Good Good Comparative Example 2 0.250 / 0.225 99% 94.5% Good Good Good Comparative Example 3 0.250 / 0.225 97% 95.4% error error error Comparative Example 4 0.250 / 0.225 86% 95.7% Good Good Good

As shown in Tables 1 and 2, in the composite sheets of Examples 1 to 3, as a result of compounding the green quantum dot with the red organic nanophosphor, the emission peak of the green quantum dot shifted toward the shorter wavelength, and the half width of the emission peaks of green and red was All appeared to be narrow. As such, the composite sheets of Examples 1 to 3 had improved color reproducibility and did not deteriorate in terms of relative luminance. In contrast, the composite sheets of Comparative Examples 1 and 2 used only green quantum dots and red quantum dots, and there was no effect of shifting the emission peak of the green quantum dots or reducing the half width, so the color reproducibility was poor, and the composite sheet of Comparative Example 3 had a short wavelength. Using green quantum dots, color reproducibility was good, but reliability was poor. In addition, the luminance of the composite sheet of Comparative Example 4 decreased by 10% or more due to light loss due to the absorbing dye.

1: display device, 10: backlight unit,
20: display panel, 30: cover window,
51: upper frame, 52: lower frame,
100: composite sheet, 101: green quantum dots;
102: red quantum dots, 103: red organic nanophosphor,
105: binder resin, 107: light scattering agent,
110: a first color conversion layer, 120: a second color conversion layer,
130: base film, 140: adhesive layer,
150: a first barrier film, 160: a second barrier film,
700: diffuser plate, 800: reflector,
900: light source.

Claims (15)

a first color conversion layer including green quantum dots or a combination of green quantum dots and red quantum dots; a second color conversion layer including a red organic nano-phosphor; and a barrier film formed between the first color conversion layer and the second color conversion layer,
The red organic nanophosphor absorbs a portion of the green light emitted from the green quantum dots and emits red light while shifting the green emission peak of the composite sheet to the short wavelength side, and satisfying the following formulas (i), (ii) and (1) Composite sheet for improving color reproducibility of liquid crystal display:
540 nm ≤ AB _MAX [R _PHOS ] ≤ 600 nm ... (i)
600 nm ≤ EM _MAX [R _PHOS ] ≤ 640 nm ... (ii)
EM _MAX [G _QDOT ] > EM _MAX [G _COMP ] ... (1)
here
AB _MAX [R _PHOS ] is the wavelength (nm) of the highest point of the absorption peak of the second color conversion layer, and EM _MAX [R _PHOS ] is the wavelength (nm) of the highest point of the red emission peak of the second color conversion layer, and , EM _MAX [G _QDOT ] is the wavelength (nm) of the highest point of the green emission peak of the first color conversion layer, and EM _{MAX [} G _COMP ] is the wavelength (nm) of the highest point of the green emission peak of the composite sheet.
The method of claim 1,
The AB _MAX [R _PHOS ] is in the range of 550 nm to 590 nm,
The EM _MAX [R _PHOS ] is in the range of 610 nm to 640 nm, a liquid crystal display color reproducibility improvement composite sheet.
The method of claim 1,
The composite sheet for improving color reproducibility of a liquid crystal display, wherein the wavelength of the highest point of the green emission peak belongs to 535 nm to 545 nm.
The method of claim 1,
The composite sheet is a composite sheet for improving color reproducibility of a liquid crystal display, wherein the half width of the green emission peak is 40 nm or less.
The method of claim 1,
The composite sheet is a composite sheet for improving color reproducibility of a liquid crystal display, wherein the wavelength of the highest point of the red emission peak is within 600 nm to 630 nm.
The method of claim 1,
The composite sheet is a composite sheet for improving color reproducibility of a liquid crystal display, wherein the half width of the red emission peak is 40 nm or less.
The method of claim 1,
The first color conversion layer comprises a combination of the green quantum dots and the red quantum dots,
The content of the red quantum dots is less than the content of the green quantum dots, liquid crystal display color reproducibility composite sheet.
The method of claim 1,
The green quantum dots absorb blue light and emit green light,
The red organic nanophosphor absorbs a portion of blue light and green light emitted from the green quantum dots to emit red light, a liquid crystal display color reproducibility composite sheet.
The method of claim 1,
The composite sheet comprises an additional barrier film as an outer layer in addition to the barrier film formed between the first color conversion layer and the second color conversion layer, the liquid crystal display color reproducibility composite sheet.
The method of claim 1,
A composite sheet for improving color reproducibility of a liquid crystal display, wherein the barrier film includes a base layer and an inorganic layer formed on the base layer.
delete delete delete a light source emitting blue light;
a display panel receiving the light from the light source to display an image; and
A display device comprising the composite sheet of claim 1 disposed in a light path from the light source to the display panel.
15. The method of claim 14,
the display device
A display device that exhibits a color gamut of 95% or more in the DCI-P3 color space.

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