KR102604946B1 - Composite sheet of quantum dots and organic nanophosphor, and display device comprising same - Google Patents

Abstract

The composite sheet according to the present invention is a first color conversion layer containing green quantum dots or a combination of green quantum dots and red quantum dots, and a second color conversion layer containing a green organic nano-phosphor is combined to form a display device without deterioration in brightness and reliability. Color reproducibility can be improved .

Description

Composite sheet of quantum dots and organic nanophosphor and display device containing the same {COMPOSITE SHEET OF QUANTUM DOTS AND ORGANIC NANOPHOSPHOR, AND DISPLAY DEVICE COMPRISING SAME}

The present invention relates to a composite sheet used for color conversion, and a display device including the same.

Liquid crystal display (LCD) devices display images using the optical characteristics of liquid crystal. Since the liquid crystal panel that displays the image is a non-emissive device that does not emit light on its own, it is placed on the back of the liquid crystal panel along with the liquid crystal panel. It is equipped with a back-light unit that supplies light. Liquid crystal display devices are attracting attention as display devices used in mobile devices, computer monitors, and high-definition (HD) TVs.

As a light emitting diode (LED) light source for a liquid crystal display device, a structure that implements white light by placing a phosphor on a blue light source is generally used. However, since the phosphor used in this case exhibits a wide range of emission spectrum from green light to red light, there are problems such as low color purity, narrow color reproduction range, and poor image quality.

To solve this problem, alternative technologies include using light-emitting diodes with green and red phosphors separately, increasing color purity by reducing the half width of the phosphors, or adding a sheet containing a pigment that absorbs a specific wavelength range. However, there were limits to the improvement of brightness and color purity along with the increase in manufacturing costs.

Meanwhile, in order to increase the color gamut of liquid crystal display devices, various technologies have been developed that use blue LEDs as light sources and quantum dot sheets containing quantum dots, which are separate light conversion means. Referring to FIG. 2, the conventional quantum dot sheet has a structure in which a color conversion layer 110 containing quantum dots is formed between two barrier films 150 and 160, and for example, light incident from a blue light source passes through. It is configured to emit green and/or red light.

Korean Patent Publication No. 2014-0056490 Korean Patent Publication No. 2013-0123718

Recently, quantum dots that do not contain cadmium (Cd) have been used due to environmental issues, but these quantum dots have a wide half width and there is a large overlapping wavelength region between green quantum dots and red quantum dots, so there is a problem of poor color reproducibility. In addition, in order to increase color reproducibility, green quantum dots with a short wavelength are needed, but this requires reducing the particle size of the quantum dots, which leads to an increase in defects on the surface of the quantum dots, which reduces performance and reliability. In addition, when the content of green quantum dots was increased to improve brightness, there was a problem that color reproducibility deteriorated due to the phenomenon that the green emission peak shifted to a longer wavelength.

To solve this problem, alternative technologies include using light-emitting diodes with green and red phosphors separately, increasing color reproducibility by reducing the half width of the phosphors, or adding a sheet containing a pigment that absorbs a specific wavelength range. However, there were limits to the improvement of luminance and color reproducibility along with the increase in manufacturing costs.

Accordingly, as a result of research by the present inventors, it was discovered that when the color conversion layer of green quantum dots and the color conversion layer of green organic nano-phosphor are combined, color reproducibility is improved while luminance is not reduced.

Therefore, the object of the present invention is to provide a composite sheet that can simultaneously achieve excellent color reproduction and brightness in a display device using 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 containing a green organic nanophosphor, and satisfying the following formulas (a) and (b).

505 nm ≤ EM _MAX [G _PHOS ] ≤ 535 nm ... (a)

EM _MAX [G _PHOS ] < EM _MAX [G _QDOT ] ... (b)

Here, 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 _PHOS ] is the wavelength (nm) of the highest point of the green emission peak of the second color conversion layer. )am.

Also according to the present invention, preparing a first composition comprising green quantum dots, or a combination of green quantum dots and red quantum dots, and a first binder resin; Preparing a second composition comprising a green organic nanophosphor and a second binder resin; and obtaining a laminate including a first color conversion layer formed from the first composition and a second color conversion layer formed from the second composition.

Also according to the present invention, there is provided a light source that emits blue light; a display panel that receives light from the light source and displays an image; and the composite sheet disposed in an optical path from the light source to the display panel.

The composite sheet according to the present invention is a first color conversion layer containing green quantum dots or a combination of green quantum dots and red quantum dots, and a second color conversion layer containing a green organic nano-phosphor is combined to form a display device without deterioration in brightness and reliability. Color reproducibility can be improved .

Specifically, compared to a general quantum dot sheet (i.e., a sheet containing only the first color conversion layer), in the case of a sheet in which the first color conversion layer and the second color conversion layer are combined to satisfy the above equations (a) and (b), The green emission peak may shift toward shorter wavelengths. In particular, by replacing part of the green quantum dots with green organic nanophosphors as a green light-emitting material, the long-wavelength shift of the emission peak that occurs when there is a large amount of green quantum dots can be reduced and color reproducibility can be significantly improved.

Accordingly, a display device including the composite sheet of the present invention may have improved color reproducibility and no decrease in luminance compared to a conventional quantum dot display.

1A and 1B show cross-sectional views of a composite sheet according to one embodiment of the present invention.
Figure 1c shows a cross-sectional view of a composite sheet according to another embodiment of the present invention.
Figure 2 shows a cross-sectional view of a quantum dot sheet according to the prior art.
Figure 3a shows a method of manufacturing a composite sheet according to one embodiment.
Figure 3b shows a method of manufacturing a composite sheet according to another embodiment.
Figure 4a shows a cross-sectional view of the first color conversion layer according to one implementation.
Figure 4b shows a cross-sectional view of the first color conversion layer according to another embodiment.
Figure 5 shows a cross-sectional view of the second color conversion layer according to one embodiment.
Figure 6 shows an example of the emission spectrum of green quantum dots and green organic nanophosphor.
Figure 7 is an emission spectrum obtained through a blue light source for composite sheets according to Examples and Comparative Examples.
Figure 8 shows an example of the emission spectrum of green quantum dots and the emission and absorption spectra of red quantum dots.
Figure 9 shows an example of the emission spectrum of green quantum dots and the emission and absorption spectra of red organic nanophosphors.
Figure 10 shows an exploded perspective view of a display device according to an embodiment of the present invention.

Hereinafter, various implementation examples 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 will be omitted. Additionally, the size of each component in the drawings may be exaggerated or omitted for explanation and may differ from the actual size.

In this specification, the description that one component is formed above/below another component, or is connected or combined with each other, includes all those formed, connected, or combined directly between these components or indirectly through another component. . Additionally, it should be understood that the standards for the top/bottom of each component may vary depending on the direction in which the object is observed.

In this specification, terms referring to each component are used to distinguish them from other components and are not intended to limit the present invention. Additionally, in this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

In this specification, the term "include" is intended to specify specific characteristics, areas, steps, processes, elements and/or components, and unless specifically stated to the contrary, other characteristics, areas, steps, processes, elements and /or does not exclude the presence or addition of ingredients.

In this specification, terms such as first and second 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.

composite sheet

The composite sheet according to one embodiment of the present invention includes a first color conversion layer including green quantum dots or a combination of green quantum dots and red quantum dots; and a second color conversion layer containing a green organic nanophosphor. Accordingly, the composite sheet can improve the color reproducibility of the display device without reducing brightness and reliability . In particular, by replacing part of the green quantum dots with green organic nanophosphors as a green light-emitting material, the long-wavelength shift of the emission peak that occurs when there is a large amount of green quantum dots can be reduced and color reproducibility can be significantly improved.

The composite sheet according to another embodiment of the present invention may further include a third color conversion layer containing a red organic nanophosphor. In the third color conversion layer, the red organic nanophosphor absorbs blue light and part of the green light emitted from the green quantum dots and emits red light, thereby improving color reproducibility of the display device without reducing brightness and reliability. there is.

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

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

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

EM _MAX [G _PHOS ]: Wavelength (nm) of the highest green emission peak of the second color conversion layer containing green organic nanophosphor

AB _MAX [G _PHOS ]: Wavelength (nm) of the highest absorption peak of the second color conversion layer containing green organic nanophosphor

EM _MAX [R _PHOS ]: Wavelength (nm) of the highest red emission peak of the third color conversion layer containing red organic nanophosphor

AB _MAX [R _PHOS ]: Wavelength (nm) of the highest absorption peak of the third color conversion layer containing red organic nanophosphor

EM _FWHM [G _QDOT ]: Half width (nm) of the green emission peak of the first color conversion layer containing green quantum dots

EM _FWHM [G _PHOS ]: Half width (nm) of the green emission peak of the second color conversion layer containing green organic nanophosphor

EM _FWHM [R _PHOS ]: Half width (nm) of the red emission peak of the third color conversion layer containing 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 ]: Wavelength (nm) of the highest point of the red emission peak of the composite sheet

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

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

The emission peak refers to a peak appearing in an emission spectrum, that is, a curve of emission intensity (y-axis) versus wavelength (x-axis). Additionally, the absorption peak refers to a valley that appears in the emission spectrum, or a peak that appears in the absorption spectrum, that is, a curve of absorption intensity (y-axis) with respect to wavelength (x-axis).

The highest point of the emission peak means the point where the emission intensity is maximum in the emission peak, and the highest point of the emission peak means the point where the emission intensity is maximum in the emission peak. As an example, the wavelength of the highest point of the green emission peak means the wavelength (x-axis) of the point where the emission intensity (y-axis) is the highest in the peak (peak-shaped curve) appearing in the green wavelength band in the emission spectrum.

The emission spectrum of the composite sheet can be obtained by passing a blue light source through a composite sheet sample using a spectroradiometer. The blue light source may include a blue LED and/or a blue phosphor, such as a blue GaN (Gallium Nitride) light emitting chip. For example, a backlight unit with a blue light source can be used, and if necessary, the spectrum can be obtained after laminating one or more optical films, such as prism sheets, on the composite sheet sample.

Additionally, the emission spectrum or absorption spectrum of each color conversion layer can be obtained by passing a blue light source through each color conversion layer sample using a spectroradiometer or spectrophotometer. The color conversion layer sample can be obtained by separating it from the composite sheet, or by forming each color conversion layer separately on a transparent film.

Characteristics of Composite Sheet

According to one embodiment, the composite sheet satisfies the following formulas (a) and (b).

505 nm ≤ EM _MAX [G _PHOS ] ≤ 535 nm ... (a)

EM _MAX [G _PHOS ] < EM _MAX [G _QDOT ] ... (b)

When the above equations (a) and (b) are satisfied, the green emission peak combined in the first color conversion layer and the second color conversion layer moves toward a shorter wavelength than the emission peak of the existing green quantum dot alone, Color reproducibility can be improved compared to quantum dot displays.

Referring to FIG. 6, the green organic nanophosphor used in the present invention has high luminous efficiency and may have a maximum peak value in the range between 505 nm and 535 nm. The luminescent properties of this type of green organic nanophosphor shift the green emission peak to a shorter wavelength when combined with general green quantum dots, thereby improving color reproducibility by increasing the purity of green in displays. Additionally, light absorbed by the organic nanophosphor in the blue wavelength range is used to generate green light, thereby minimizing light loss. `

The EM _MAX [G _PHOS ] may be, for example, 505 nm or more, 510 nm or more, 515 nm or more, or 520 nm or more, and may also be 535 nm or less, 530 nm or less, 525 nm or less, or 520 nm or less.

Meanwhile, the AB _MAX [G _PHOS ] may be, for example, 485 nm to 525 nm, and more specifically, 495 nm to 515 nm.

In addition, 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 may also be 560 nm or less, 555 nm or less, 550 nm or less, or 545 nm or less. It may be nm or less.

The difference between the EM _MAX [G _PHOS ] and the EM _MAX [G _QDOT ] may be 1 nm or more, 5 nm or more, 10 nm or more, or 15 nm or more, and as specific examples, 1 nm to 50 nm, or 10 nm to 10 nm. It may be 30 nm.

Figure 7 shows a sheet in which the first color conversion layer and the second color conversion layer are combined to satisfy the above equations (a) and (b), and a general quantum dot sheet (i.e., a sheet containing only the first color conversion layer) as a comparative example. This shows the spectrum measured through a blue LED light source. As shown in Figure 7, it can be seen that the green emission peak of the composite sheet of the Example compared to the Comparative Example is shifted to a shorter wavelength, and thus color reproducibility can be improved.

In this way, the composite sheet according to the above embodiment can satisfy Equation (1) below.

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

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

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

Specifically, the ΔEM _MAX [G] may be 1 nm to 15 nm, 1 nm to 10 nm, or 1 nm to 6 nm. More specifically, the ΔEM _MAX [G] may be 2 nm or more. Additionally, the ΔEM _MAX [G] may be 3 nm or more, 4 nm or more, or 5 nm or more.

The EM _MAX [G _COMP ] may be, for example, 515 nm or more, 520 nm or more, 525 nm or more, or 530 nm or more, and may also be 555 nm or less, 550 nm or less, 545 nm or less, or 540 nm or less. all.

In addition, the composite sheet may have an EM _MAX [R _COMP ] of 600 nm or more, 605 nm or more, 610 nm or more, 615 nm or more, or 620 nm or more, and may also be 650 nm or less, 645 nm or less, 640 nm or less, and 635 nm. It may be less than or equal to 630 nm.

Meanwhile, the half width of the green emission peak of the composite sheet can be maintained at a similar level compared to the half width of the green emission peak of only the quantum dots before being combined with the organic nanophosphor. For example, the composite sheet may have a ΔEM _FWHM [G] defined in the equation below of 5 nm or less.

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

Specifically, the ΔEM _FWHM [G] may be 3 nm or less or 2 nm or less.

The EM _FWHM [G _QDOT ] and the EM _FWHM [G _COMP ] may be 20 nm or more, 25 nm or more, 30 nm or more, or 35 nm or more, respectively, and may also be 60 nm or less, 55 nm or less, 50 nm or less, or It may be 45 nm or less. As a specific example, the EM _FWHM [G _QDOT ] and the EM _FWHM [G _COMP ] may each range from 30 nm to 50 nm.

Third color conversion layer

According to another embodiment, the composite sheet may further include a third color conversion layer containing a red organic nanophosphor and further satisfy 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, part of the luminous energy of the first color conversion layer containing green quantum dots is absorbed by the red organic nanophosphor, and the luminescence peak of the green quantum dots moves toward a short wavelength and the half width narrows. You can. Accordingly, color reproducibility may be improved compared to a conventional quantum dot display, while luminance may not deteriorate.

Referring to Figure 8, the absorption spectrum of a typical red quantum dot has low absorption efficiency and an unclear absorption peak in the range of 540 nm to 600 nm. 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 dots to a shorter wavelength or reducing the half width.

On the other hand, referring to FIG. 9, the red organic nanophosphor used in the present invention has a high absorption efficiency in the range of 540 nm to 600 nm, and the absorption intensity of the peak may have a maximum value. The light absorption characteristics of this type of red organic nanophosphor shift the peak of the green quantum dots to a shorter wavelength and reduce the half width when combined with green quantum dots, thereby improving the color reproducibility of the display by increasing the purity of green. Additionally, the light absorbed by the red organic nanophosphor is used to generate red light between 600 nm and 640 nm, so light loss can be minimized.

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 may also be 600 nm or less, 595 nm or less, 590 nm or less, and 585 nm or less. , or may be 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 may also be 640 nm or less, 635 nm or less, 630 nm or less, or 625 nm or less. You can.

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

The composite sheet according to the above embodiment may further satisfy equation (2) below.

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

When the above equation (2) is satisfied, the half-width of the emission peak of the first color conversion layer containing green quantum dots becomes narrower than before being combined with the third color conversion layer containing red organic nano-phosphors, so that the conventional quantum dot display Compared to this, color reproducibility can be improved.

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

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

Specifically, the △EM _FWHM [G] is 2 nm or more, which can indicate a significant improvement in color reproducibility compared to the prior 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.

Meanwhile, in the composite sheet, the half width of the red emission peak of the third color conversion layer containing a red organic nano-phosphor may be almost the same as before being combined with the first color conversion layer containing green quantum dots. For example, the composite sheet may have a ΔEM _FWHM [R] defined in the formula below of 5 nm or less.

△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.

Additionally, 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 also 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. 4A, 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 with 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 semiconductors, and mixtures thereof. As an example, the green quantum dot may be a multilayer 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. Additionally, 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 specific examples may include ZnSe and ZnS.

The green quantum dots included in the composite sheet of the present invention do not contain cadmium (Cd) and 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 had a problem in that their emission peaks partially overlapped in the red region, but according to the present invention, this problem could be solved by complexing them with a green organic nanophosphor.

Referring to FIG. 4B, the composite sheet according to the present invention may additionally 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 semiconductors, and mixtures thereof. As an example, the red quantum dot may be a multilayer 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. Additionally, 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 specific examples may include ZnSe and ZnS.

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

The content of green quantum dots in the first color conversion layer may be 0.01 weight% or more, 0.05 weight% or more, 0.1 weight% or more, or 0.5 weight% or more, and may also be 10 weight% or less, 5 weight% or less, or 3 weight% or less, Or it may be 1% by weight or less. Specifically, the first color conversion layer may include 0.05 to 3% by weight of the green quantum dots. When within the above range, the color conversion effect is sufficiently exhibited and the shift of the emission peak to a long wavelength due to excessive quantum dots can be prevented.

The first color conversion layer 110 may include a binder resin 105, for example, a thermosetting or UV curing polymer resin. Specifically, the binder resin may be one or more 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, and in this case, 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, and 55 parts by weight or less, specifically 5 parts by weight, based on 100 parts by weight of the green quantum dots. It may be from 99 parts by weight, or from 10 parts by weight to 70 parts by weight.

Referring to FIG. 5, the composite sheet according to the present invention includes a green organic nanophosphor 103 in the second color conversion layer 120. The green organic nanophosphor has a shorter wavelength of emission peak than that of green quantum dots, so color reproducibility can be improved by shifting the green emission peak of the composite sheet to a shorter wavelength. Preferred examples of the green organic nanophosphor include bodipy-based, perylene-based, pyrrole-based, pyrene-based, coumarin-based, xanthene-based, acridine-based, arylmethane-based, polycyclic aromatic hydrocarbon-based, and polycyclic heteroaromatic-based derivatives. In addition, various green organic nanophosphors can be used.

In addition, the average particle diameter of the green organic nanophosphor may be several nm or smaller, for example, 5 nm or less, 3 nm or less, 1 nm or less, or 0.01 nm to 1 nm, respectively, but is not particularly limited thereto. No.

The content of the green organic nanophosphor in the second color conversion layer may be 0.001% by weight or more, 0.005% by weight or more, 0.01% by weight or more, 0.05% by weight or more, 0.1% by weight or more, or 0.5% by weight or more, and may be 10% by weight or more. % or less, 5 weight % or less, 3 weight % or less, or 2 weight % or less.

The second color conversion layer 120 may include a binder resin 105, and the binder resin may be, for example, polyester-based, polyurethane-based, polybutadiene-based, acrylic-based, epoxy-based, polycarbonate-based, silicone-based, It may be one or more types selected from the group consisting of melamine-based resins and copolymers thereof, and the content of the binder resin may be 50 to 95% by weight, or 80 to 95% by weight, based on the weight of the second color conversion layer. there is.

In addition, the green organic nano-phosphor content may be 0.001 to 5.0 parts by weight, specifically 0.005 to 3.0 parts by weight, and more specifically 0.01 to 2.0 parts by weight, based on 100 parts by weight of the binder resin in the second color conversion layer. You can.

Additionally, the composite sheet according to the present invention may include a red organic nanophosphor in the third color conversion layer. The red organic nanophosphor absorbs part of the light emitted by the green quantum dots and emits red light, thereby improving color reproducibility without reducing luminance.

Preferred red organic nano-phosphors include bodifi-based, perylene-based, pyrrole-based, pyrene-based, coumarin-based, xanthene-based, acridine-based, arylmethane-based, polycyclic aromatic hydrocarbon-based, and polycyclic heteroaromatic-based derivatives. In addition, various red organic nanophosphors can 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, 3 nm or less, 1 nm or less, or 0.01 nm to 1 nm, respectively, but is not particularly limited thereto. No.

The third color conversion layer may include a binder resin, and its specific type and content may be applied similarly to the type and content of the binder resin in the second color conversion layer.

Additionally, the red organic nanophosphor content 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 third color conversion layer.

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

At least one of the first color conversion layer and the second color conversion layer may further include a light scattering agent.

The light scattering agent may be amorphous or spherical or hollow particles. The light scattering agent may have an average particle diameter of 0.01 ㎛ or more, or 0.01 to 10 ㎛. The light scattering agent may be one having a large difference in refractive index from the binder resin, for example, one selected from the group consisting of BaSO ₄ , ZnO, TiO ₂ , ZrO ₂ , silica, silicon, melamine, polystyrene, and polybutyl methacrylate. It may contain more than one type of ingredient. 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.

Among the components included in the color conversion layer, the emission peak and absorption peak of the color conversion layer can be determined by quantum dots or organic nano-phosphors, and other binder resins, scattering agents, or other additives are optically transparent and contribute to color conversion. There may be little effect on the emission and absorption peaks of the layer.

Laminated configuration example of composite sheet

1A and 1B, the composite sheet 100 according to one embodiment includes 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 ㎛ to 200 ㎛, specifically 10 ㎛ to 100 ㎛.

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

The first color conversion layer and/or the second color conversion layer may be formed as a coating on a base film. Accordingly, the composite sheet may additionally include a base film coated with these color conversion layers. The base film can be applied without any special restrictions as long as it is a transparent polymer film. For example, it may be a polyethylene terephthalate film with 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 ㎛ to 350 ㎛, specifically 25 ㎛ to 250 ㎛.

Additionally, the composite sheet may additionally include one or more barrier films as an outer layer or inner layer. As an example, the composite sheet may further include a barrier film formed on one or both sides 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 sides 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 100 sequentially includes a first barrier film 150, a first color conversion layer 110, a second barrier film 160, and a second color conversion layer 120. can do. Or, referring to FIG. 1B, the composite sheet 100 sequentially includes a first barrier film 150, a first color conversion layer 110, a second color conversion layer 120, and a second barrier film 160. It can be included.

Referring to FIG. 1C, the composite sheet 100' according to another embodiment may further include the third color conversion layer 125.

The thickness of the third color conversion layer may be, for example, 1 ㎛ to 50 ㎛, specifically 2 ㎛ to 20 ㎛.

The third color conversion layer may be formed as a coating on a base film.

Referring to FIG. 1C, the first color conversion layer 110 may be disposed between the second color conversion layer 120 and the third color conversion layer 125.

In addition, the composite sheet 100' includes a first barrier film 150 disposed between the first color conversion layer 110 and the third color conversion layer 125, and the first color conversion layer 110. It may further include a second barrier film 160 disposed between the second color conversion layer 120.

The barrier film maintains the shape of the color conversion layer and effectively blocks the penetration of oxygen and moisture into the color conversion layer from the outside, thereby ensuring the stability and reliability of 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 and, for example, may have the same composition and thickness as the base film described above.

The inorganic layer serves to effectively block the penetration of moisture and oxygen into the color conversion layer. At this time, 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 oxides, nitrides, and fluorides of metals and non-metals. Specific examples of the inorganic material include one or more selected from the group consisting of aluminum oxide, silicon oxide, silicon nitride, silicon oxynitride, magnesium oxide, indium oxide, and magnesium fluoride. The thickness of the inorganic layer may be 10 nm to 1 ㎛.

In addition, the barrier film further includes an organic layer between the base layer and the inorganic layer, thereby flattening the surface of the base layer and uniformly forming the inorganic layer, thereby further improving the moisture and oxygen blocking performance of the base layer. there is. Additionally, the barrier film can increase adhesion with the color conversion layer by additionally including an organic layer on the surface of the inorganic layer. The organic layer may be made of a typical organic polymer resin. The thickness of the organic layer may be 0.1 ㎛ to 10 ㎛, specifically 0.3 ㎛ to 7 ㎛, more specifically 0.5 ㎛ to 5 ㎛.

The barrier film may be laminated directly on the surface of the color conversion layer or through an adhesive layer. Accordingly, the composite sheet may additionally 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 ㎛ to 100 ㎛, 5 ㎛ to 100 ㎛, or 15 ㎛ to 25 ㎛.

Referring to FIG. 1A, the composite sheet 100 according to one 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. It may have a structure in which the conversion layer 120 and the base film 130 are stacked in that order. Alternatively, referring to FIG. 1B, the composite sheet 100 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. ), and the second barrier film 160 may be stacked in that order. Also, referring to FIG. 1C, the composite sheet 100' according to another embodiment includes a base film 130, a third color conversion layer 125, an adhesive layer 140, a first barrier film 150, and a first color. It may have a structure in which the conversion layer 110, the second barrier film 160, the adhesive layer 140, the second color conversion layer 120, and the base film 130 are stacked in that order.

Additionally, 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.

Manufacturing method of composite sheet

A method of manufacturing a composite sheet according to one embodiment includes preparing a first composition including green quantum dots, or a combination of green quantum dots and red quantum dots, and a first binder resin; Preparing a second composition comprising a green organic nanophosphor and a second binder resin; and obtaining a laminate including a first color conversion layer formed from the first composition and a second color conversion layer formed from the second composition.

A method of manufacturing a composite sheet according to another embodiment includes preparing a first composition including green quantum dots, or a combination of green quantum dots and red quantum dots, and a first binder resin; Preparing a second composition comprising a green organic nanophosphor and a second binder resin; Preparing a third composition comprising a red organic nanophosphor and a third binder resin; and obtaining a laminate including a first color conversion layer formed from the first composition, a second color conversion layer formed from the second composition, and a third color conversion layer formed from the third composition.

In the step of obtaining the first composition, the green quantum dots may be used in an amount of 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 first binder resin. In the step of obtaining the second composition, the green organic nanophosphor may be used in an amount of 0.001 to 5.0 parts by weight, specifically 0.005 to 3.0 parts by weight, and more specifically 0.01 to 2.0 parts by weight, based on 100 parts by weight of the second binder resin. there is. According to one example, in these steps, the green quantum dots may be used in an amount of 0.2 to 2 parts by weight based on 100 parts by weight of the first binder resin, and the green organic nanophosphor may be used in an amount of 0.01 to 2.0 parts by weight compared to 100 parts by weight of the second binder resin. there is.

Additionally, in the step of obtaining the third composition, the red organic nanophosphor may be used in an amount of 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 third binder resin.

The first color conversion layer and the second color conversion layer may be formed to have the thickness range described above. For example, the first color conversion layer may be 5 ㎛ to 200 ㎛, specifically formed to have a thickness of 10 ㎛ to 100 ㎛, and the second color conversion layer may be 1 ㎛ to 50 ㎛, , specifically, may be formed to have a thickness of 2 ㎛ to 20 ㎛. According to one example, the first color conversion layer may be formed to have a thickness of 10 ㎛ to 100 ㎛, and the second color conversion layer may be formed to have a thickness of 2 ㎛ to 20 ㎛. Additionally, the third color conversion layer may have a thickness of 1 ㎛ to 50 ㎛, and specifically may be formed to have a thickness of 2 ㎛ to 20 ㎛.

The step of obtaining the laminate can be performed in various ways.

As a specific example, the step of obtaining the laminate includes obtaining a first sheet including a first color conversion layer formed from the first composition on one surface of the barrier film; Obtaining a second sheet including a second color conversion layer formed from the second composition on one side of the base film; and laminating the first sheet and the second sheet.

Referring to FIG. 3A, the step of obtaining the laminate includes forming a second color conversion layer 120 by coating the second composition on one surface of the base film 130 (S100); Forming an adhesive layer 140 on one side of the second barrier film 160 and laminating it with the second color conversion layer 120 (S200); Forming a first color conversion layer 110 by coating the first composition on one surface of the first barrier film 150 (S300); It includes laminating the first color conversion layer 110 with the second barrier film 150 (S400).

As another specific example, the step of obtaining the laminate includes obtaining a first sheet including a first color conversion layer formed from the first composition on one surface of the barrier film; Obtaining a second sheet including a second color conversion layer formed from the second composition on one side of the base film; Obtaining a third sheet including a third color conversion layer formed from the third composition on one side of the base film; And it may include laminating the first sheet, the second sheet, and the third sheet sequentially or simultaneously.

Referring to FIG. 3B, obtaining the laminate includes forming a second color conversion layer 120 by coating the second composition on one surface of the base film 130 (S100); Forming a third color conversion layer 125 by coating the third composition on one surface of the base film 130 (S200); Forming an adhesive layer 140 on one side of the second barrier film 160 and laminating it with the second color conversion layer 120 (S300); Forming an adhesive layer 140 on one side of the first barrier film 150 and laminating it with the third color conversion layer 125 (S400); Forming a first color conversion layer 110 by coating the first composition on the other side of the first barrier film 160 (S500); It includes laminating the first color conversion layer 110 with the second barrier film 150 (S600).

The first color conversion layer may be formed through UV curing. For example, after obtaining the laminate, the first color conversion layer may be cured by irradiating UV light.

display device

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

Blue light from the light source is combined with green light and red light in the process of passing through the composite sheet, and the characteristics are improved, and the display panel can display an image using the light with the improved characteristics.

Specifically, referring to FIG. 10, the display device 1 includes a backlight unit 10; And it may include a display panel 20 disposed on the backlight unit 10. The backlight unit 10 includes a composite sheet 100; Light guide plate or diffusion plate 700; and a light source 900.

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

Referring to FIG. 10, the light generated from the light source 900 is reflected by the reflector 800 and enters the lower part of the composite sheet 100 through the diffusion plate 700. The incident light passes vertically through the composite sheet 100 and is emitted upward. The light emitted from the top 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 improvement. The optical film 200 may be, for example, a prism film, diffusion film, or dual brightness enhancement film. The prism sheet may have a prism pattern layer formed on one side of the base layer, and may be used in combination with a vertical prism sheet and a horizontal prism sheet. The diffusion film may have a bead coating on one side of the base layer. Additionally, the dual brightness enhancement film may have a multilayer structure of fine thin films with 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, with special limitations. It doesn't work.

The display panel 20 may include a liquid crystal cell and one or more polarizing plates. As a specific example, it 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 formed between these polarizing plates and the liquid crystal cell. This can be formed.

The display device of the present invention can improve color reproducibility of the display device without reducing brightness and reliability by providing the composite sheet of the configuration described above. For example, the display device can exhibit a color gamut of more than 90% in the DCI-P3 color space. Specifically, the display device can exhibit a color gamut of more than 95% in the DCI-P3 color space. DCI-P3 is a color gamut defined by Digital Cinema Initiatives to be used as the color gamut of digital projectors in the American film industry. It can express a 25% wider color gamut than existing sRGB, and its main feature is that it has especially wider coverage in the red area. Therefore, very excellent color reproducibility can be achieved when DCI-P3 is 95% or more.

In particular, when measuring the relative luminance of the display device and the color gamut in the DCI-P3 color space, compared to the control device manufactured by excluding only the second color conversion layer of the composite sheet from the display device, the display device It can exhibit higher relative luminance and color gamut than .

The above will be explained in more detail by the following examples. However, the following examples are only for illustrating the present invention, and the scope of the examples is not limited to these only.

Example 1: Preparation of composite sheet (green quantum dots + red quantum dots + green organic nanophosphor)

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

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

- 4.1 parts by weight of green quantum dot solution (quantum dot content: 10% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 539 nm

- 2.6 parts by weight of red quantum dot solution (quantum dot content: 5% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 628 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 green organic nanophosphor composition was prepared by mixing the following ingredients.

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

- 40 parts by weight of solvent (butyl acetate)

- 0.2 parts by weight of green organic nanophosphor (UBP-G, Wooksung Chemical) - Highest emission peak at 520 nm in the second color conversion layer

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

The nanophosphor composition was coated on one side of a base film (PET) with a thickness of 50 ㎛ and dried at 120°C for 5 minutes to form a second color conversion layer with a thickness of 5 ㎛.

An optically clear adhesive (OCA, SKC HT&M) was coated on one side of a second barrier film (SBL123B, SKC HT&M) with a thickness of 75 ㎛ and dried at 100°C for 2 minutes to form an adhesive layer with a thickness of 15 ㎛. 2 It was laminated with the surface of the color conversion layer.

The quantum dot composition was coated on one side of a first barrier film (SBL123B, SKC HT&M) with a thickness of 75 ㎛ to form a first color conversion layer with a thickness of 50 ㎛, and then laminated with the second barrier film and UV cured. was carried out.

As a result, referring to FIG. 1A, the first barrier film 150/first color conversion layer 110/second barrier film 160/adhesive layer 140/second color conversion layer 120/base film A composite sheet with a layer composition of (130) was obtained.

Example 2: Preparation of composite sheet (green quantum dots + red quantum dots + green organic nanophosphor)

The procedure of Example 1 was repeated, but a composite sheet was manufactured using green quantum dots and red quantum dots in the amounts below.

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

- 2.5 parts by weight of red quantum dot solution (quantum dot content: 5% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 628 nm

Example 3: Preparation of composite sheet (green quantum dots + red quantum dots + green organic nanophosphor)

The procedure of Example 1 was repeated, but a composite sheet was manufactured using green quantum dots and red quantum dots in the amounts below.

- 4.8 parts by weight of green quantum dot solution (Quantum dot content: 10% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 542 nm

- 2.4 parts by weight of red quantum dot solution (quantum dot content: 5% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 627 nm

Example 4: Preparation of composite sheet (green quantum dots + red quantum dots + green organic nanophosphor + red organic nanophosphor)

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

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

- 5.2 parts by weight of green quantum dot solution (quantum dot content: 10% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 542 nm

- 1.0 parts by weight of red quantum dot solution (Quantum dot content: 5% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 628 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 green organic nanophosphor composition was prepared by mixing the following ingredients.

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

- 40 parts by weight of solvent (butyl acetate)

- 0.2 parts by weight of green organic nanophosphor (UBP-G, Wooksung Chemical) - Highest emission peak at 520 nm in the second color conversion layer

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

A red organic nanophosphor composition was prepared by mixing the following ingredients.

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

- 40 parts by weight of solvent (butyl acetate)

- 0.04 parts by weight of red organic nanophosphor (UBP-R, Wooksung Chemical) - highest absorption peak in the third color conversion layer: 574 nm, highest emission peak: 620 nm

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

The green organic nanophosphor composition was coated on one side of a base film (PET) with a thickness of 50 ㎛ and dried at 120°C for 5 minutes to form a second color conversion layer with a thickness of 5 ㎛. An optically clear adhesive (OCA, SKC HT&M) was coated on one side of the second barrier film (SBL123B, SKC HT&M) with a thickness of 75 ㎛ and dried at 100°C for 5 minutes to form an adhesive layer with a thickness of 15 ㎛. 2 It was laminated with the surface of the color conversion layer.

The red organic nanophosphor composition was coated on one side of a base film (PET) with a thickness of 50 ㎛ and dried at 120°C for 5 minutes to form a third color conversion layer with a thickness of 5 ㎛. An optically clear adhesive (OCA, SKC HT&M) was coated on one side of the first barrier film (SBL123B, SKC HT&M) with a thickness of 75 ㎛ and dried at 100°C for 5 minutes to form an adhesive layer with a thickness of 15 ㎛. 3 It was laminated with the surface of the color conversion layer.

The quantum dot composition was coated on one side of the first barrier film (SBL123B, SKC HT&M) to form a first color conversion layer with a thickness of 50 ㎛, and after lamination with the second barrier film, UV curing was performed. .

As a result, referring to FIG. 1C, base film 130/third color conversion layer 125/adhesive layer 140/first barrier film 150/first color conversion layer 110/second barrier film A composite sheet having a layer structure of (160)/adhesive layer (140)/second color conversion layer (120)/base film (130) was obtained.

Comparative Example 1: Preparation of composite sheet (green quantum dot + red quantum dot)

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

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

- 5.2 parts by weight of green quantum dot solution (quantum dot content: 10% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 539 nm

- 2.6 parts by weight of red quantum dot solution (quantum dot content: 5% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 628 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)

The quantum dot composition was coated on one side of a first barrier film (SBL123B, SKC HT&M) with a thickness of 75 ㎛ to form a first color conversion layer with a thickness of 50 ㎛, and after lamination with the second barrier film, UV curing was performed. carried out.

As a result, referring to FIG. 2, a composite sheet having a layer structure of the first barrier film 150/first color conversion layer 110/second barrier film 160 was obtained.

Comparative Example 2: Preparation of composite sheet (green quantum dot + red quantum dot)

The procedure of Comparative Example 1 was repeated, but a composite sheet was manufactured using green quantum dots and red quantum dots in the amounts below.

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

- 2.5 parts by weight of red quantum dot solution (quantum dot content: 5% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 628 nm

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 manufactured using green quantum dots and red quantum dots in the amounts below.

- 6.3 parts by weight of green quantum dot solution (Quantum dot content: 10% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 542 nm

- 2.4 parts by weight of red quantum dot solution (quantum dot content: 5% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 627 nm

Comparative Example 4: Preparation of composite sheet (green quantum dots + red quantum dots + light-absorbing dye)

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

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

- 7.1 parts by weight of green quantum dot solution (quantum dot content: 10% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 543 nm

- 2.5 parts by weight of red quantum dot solution (quantum dot content: 5% by weight, InP type, NANOSYS, US) - Highest emission peak in the first color conversion layer: 629 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 dye composition was prepared by mixing the following ingredients.

- 36 parts by weight binder resin (AOF2914, Aekyungsa)

- 4 parts by weight of hardener (AH2100, Aekyungsa)

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

- 0.01 part by weight of light absorbing dye (PANAX, Wooksung Chemical) - Highest light absorption peak 594 nm

The dye composition was coated on one side of a base film (PET) with a thickness of 50 ㎛ and dried at 120°C for 3 minutes to form a dye coating layer with a thickness of 5 ㎛.

An optically clear adhesive (OCA, SKC HT&M) was coated on one side of the second barrier film (SBL123B) with a thickness of 75 ㎛ and dried at 100°C for 2 minutes to form an adhesive layer with a thickness of 15 ㎛, and the surface of the dye coating layer and It was combined.

The quantum dot composition was coated on one side of a first barrier film (SBL123B, SKC HT&M) with a thickness of 75 ㎛ to form a first color conversion layer with a thickness of 50 ㎛, and then laminated with the second barrier film and UV cured. was carried out.

As a result, a composite sheet having a layer structure of first barrier film/first color conversion layer/second barrier film/adhesive layer/dye coating layer/base film was obtained.

Comparative Example 5: Preparation of composite sheet (green quantum dots + red quantum dots + green organic nanophosphor)

The procedure of Example 1 above was repeated, but a composite sheet was prepared using the green organic nanophosphor in the following ingredients and amounts.

- 0.15 parts by weight of green organic nanophosphor (UBP-G1, Wooksung Chemical) - Highest emission peak in the second color conversion layer: 538 nm

Comparative Example 6: Preparation of composite sheet (green quantum dot + red quantum dot + green organic nanophosphor)

The procedure of Example 1 above was repeated, but a composite sheet was prepared using the green organic nanophosphor in the following ingredients and amounts.

- 0.3 parts by weight of green organic nanophosphor (UBP-G2, Wooksung Chemical) - Highest emission peak in the second color conversion layer: 502 nm

Test example

The following tests were performed on the composite sheets of the above examples and comparative examples.

(1) Absorption peak

The absorption peak of the quantum dots or nano-phosphors described in the Examples and Comparative Examples was determined by forming a specimen by forming each color conversion layer containing it on a transparent PET film, and then using a spectrophotometer (U4100, HITACHI). It was measured.

(2) Luminescence peak

The composite sheet sample was placed on the diffusion plate of a direct backlight unit with a blue light source, and a vertical prism sheet, a horizontal prism sheet, and a double brightness enhancement film (DBEF) were sequentially stacked on top of it, and then a spectroradiometer (SR-3, TOPCON) was placed on the diffusion plate. , Working Distance: 660 mm, Field Spec.: 0.2D), the emission spectrum was measured, and the wavelength (nm) and half width (nm) of the highest point of the emission peak (blue/green/red) were calculated.

In addition, the emission peaks of the quantum dots or nanophosphors described in the examples and comparative examples above were measured according to the above test method after forming each color conversion layer containing them on a transparent PET film.

(3) Relative luminance

The composite sheet sample was placed on the diffusion plate of a direct backlight unit with a blue light source, and a vertical prism sheet, a horizontal prism sheet, and a double brightness enhancement film (DBEF) were sequentially stacked on top of it, and then a spectroradiometer (SR-3, TOPCON) was placed on the diffusion plate. , 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

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

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

division Luminescence 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 447 Quantum dot + organic nano
phosphor 534 39 quantum dot 628 43 Example 2 LED 447 536 39 quantum dot 628 43 Example 3 LED 447 537 39 quantum dot 628 43 Example 4 LED 447 536 38 Quantum dot + organic nano
phosphor 624 41 Comparative Example 1 LED 447 quantum dot 539 38 quantum dot 628 43 Comparative Example 2 LED 447 quantum dot 541 38 quantum dot 628 43 Comparative Example 3 LED 447 quantum dot 542 38 quantum dot 628 43 Comparative Example 4 LED 447 quantum dot 538 37 quantum dot 629 41 Comparative Example 5 LED 447 Quantum dot + organic nano
phosphor 540 42 quantum dot 628 43 Comparative Example 6 LED 447 526 54 quantum dot 628 43

division BLU DCI-P3
(%) Color coordinates
Wx/W relative luminance
(%) Example 1 0.255 / 0.220 100% 96.1% Example 2 0.255 / 0.230 103% 95.7% Example 3 0.255 / 0.240 106% 95.4% Example 4 0.255 / 0.240 105% 95.9% Comparative Example 1 0.255 / 0.220 98% 94.8% Comparative Example 2 0.255 / 0.230 101% 94.4% Comparative Example 3 0.255 / 0.240 104% 94.2% Comparative Example 4 0.255 / 0.240 83% 95.3% Comparative Example 5 0.255 / 0.220 108% 94.6% Comparative Example 6 0.255 / 0.220 98% 93.7%

As shown in Table 1, the composite sheets of Examples 1 to 3 are the result of combining the first color conversion layer (including green and red quantum dots) and the second color conversion layer (green organic nanophosphor), and Comparative Examples 1 to 3 As shown, it can be confirmed that the green emission peak has shifted to a shorter wavelength compared to the conventional quantum dot sheet having only the first color conversion layer (including green and red quantum dots). Accordingly, as shown in Table 2, the composite sheets of Examples 1 to 3 can improve the color reproducibility of the display device without deteriorating brightness and reliability . On the other hand, in the case of Comparative Examples 2 and 3 in which the amount of quantum dots was increased compared to Comparative Example 1, the luminance could be improved, but the green emission peak shifted to a longer wavelength and color reproducibility deteriorated.

In particular, as seen in the evaluation results of Comparative Examples 5 and 6, when equations (a) and (b) for the highest point of the green emission peak are not satisfied, it was found that at least one of luminance and color reproducibility was poor.

In addition, the composite sheet of Example 4 was able to obtain the effect of reducing the half width of the green emission peak as a result of additionally forming a third color conversion layer (red organic nanophosphor).

On the other hand, in Comparative Example 4, as a result of forming a dye coating layer instead of the second color conversion layer, there was a problem in that the luminance was greatly reduced due to light loss due to the light absorption dye.

1: display device, 10: backlight unit,
20: display panel, 30: cover window,
51: upper frame, 52: lower frame,
100, 100': composite sheet, 101: green quantum dot,
102: red quantum dot, 103: green organic nanophosphor,
105: binder resin, 107: light scattering agent,
110: first color conversion layer, 120: second color conversion layer,
125: third color conversion layer,
130: base film, 140: adhesive layer,
150: first barrier film, 160: second barrier film,
500: Quantum dot sheet according to the prior art,
700: diffuser plate, 800: reflector plate,
900: Light source.

Claims (19)

A first color conversion layer including green quantum dots or a combination of green quantum dots and red quantum dots; and
Comprising a second color conversion layer containing a green organic nanophosphor,
A composite sheet that satisfies the following formulas (a), (b), and (1):
505 nm ≤ EM _MAX [G _PHOS ] ≤ 535 nm ... (a)
EM _MAX [G _PHOS ] < EM _MAX [G _QDOT ] ... (b)
EM _MAX [G _QDOT ] > EM _MAX [G _COMP ] ... (1)
Here, 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 _PHOS ] is the wavelength (nm) of the highest point of the green emission peak of the second 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.
delete According to claim 1,
The composite sheet has ΔEM defined in the equation below_MAXComposite sheet with [G] of 2 nm or more:
△EM_MAX[G] = EM_MAX[G_QDOT]-EM_MAX[G_COMP]
EM here_MAX[G_QDOT] is the first color conversion layer green It is the wavelength (nm) of the highest point of the emission peak, and EM_MAX[G_COMP] is the wavelength (nm) of the highest point of the green emission peak of the composite sheet.
According to claim 1,
A composite sheet wherein the green quantum dots do not contain cadmium (Cd).
According to claim 1,
A composite sheet wherein the first color conversion layer includes 0.05 to 3% by weight of the green quantum dots.
According to claim 1,
The first color conversion layer includes a combination of the green quantum dots and the red quantum dots,
A composite sheet wherein the content of the red quantum dots is less than the content of the green quantum dots.
According to claim 1,
A composite sheet, wherein at least one of the first color conversion layer and the second color conversion layer further includes a light scattering agent.
According to claim 1,
The composite sheet further includes a barrier film formed on one or both sides of the first color conversion layer.
According to claim 8,
The composite sheet sequentially includes a first barrier film, the first color conversion layer, the second color conversion layer, and the second barrier film.
According to claim 8,
The composite sheet sequentially includes a first barrier film, the first color conversion layer, a second barrier film, and the second color conversion layer.
According to claim 1,
The composite sheet
It further includes a third color conversion layer containing a red organic nanophosphor,
A composite sheet further satisfying the following formulas (i) and (ii):
540 nm ≤ AB _MAX [R _PHOS ] ≤ 600 nm ... (i)
600 nm ≤ EM _MAX [R _PHOS ] ≤ 640 nm ... (ii)
Here, AB _MAX [R _PHOS ] is the wavelength (nm) of the highest point of the absorption peak of the third color conversion layer, and EM _MAX [R _PHOS ] is the wavelength (nm) of the highest point of the red emission peak of the third color conversion layer. am.
According to claim 11,
A composite sheet where the composite sheet satisfies equation (2) below:
EM _FWHM [G _QDOT ] > EM _FWHM [G _COMP ] ... (2)
Here, EM _FWHM [G _QDOT ] is the green emission peak of the first color conversion layer. is the half width (nm), and EM _FWHM [G _COMP ] is the half width (nm) of the green emission peak of the composite sheet.
According to claim 11,
The first color conversion layer is
A composite sheet disposed between the second color conversion layer and the third color conversion layer.
According to claim 11,
The composite sheet is
A first barrier film disposed between the first color conversion layer and the third color conversion layer, and
The composite sheet further includes a second barrier film disposed between the first color conversion layer and the second color conversion layer.
Preparing a first composition comprising green quantum dots, or a combination of green quantum dots and red quantum dots, and a first binder resin;
Preparing a second composition comprising a green organic nanophosphor and a second binder resin; and
A method for producing the composite sheet of claim 1, comprising obtaining a laminate including a first color conversion layer formed from the first composition and a second color conversion layer formed from the second composition.
According to claim 15,
Using 0.2 to 2 parts by weight of the green quantum dots relative to 100 parts by weight of the first binder resin,
A method of manufacturing a composite sheet, using 0.01 to 2.0 parts by weight of the green organic nanophosphor based on 100 parts by weight of the second binder resin.
According to claim 16,
The first color conversion layer is formed to have a thickness of 10 ㎛ to 100 ㎛,
A method of manufacturing a composite sheet, wherein the second color conversion layer is formed to have a thickness of 2 ㎛ to 20 ㎛.
A light source emitting blue light;
a display panel that receives light from the light source and displays an image; and
A display device comprising the composite sheet of claim 1 disposed in an optical path from the light source to the display panel.
According to claim 18,
When measuring the relative luminance of the display device and the color gamut in the DCI-P3 color space, the display device has a higher brightness compared to a control device manufactured by excluding only the second color conversion layer of the composite sheet from the display device. A display device that exhibits higher relative luminance and color gamut.