CN116410736A - Light-color conversion material and light-color conversion ink - Google Patents

Abstract

The invention provides a light-color conversion material and a light-color conversion ink. Light-color conversion materials include quantum dots and cross-linkable cholesteric liquid crystal materials. A cross-linkable cholesteric liquid crystal material coats the quantum dots. The cross-linkable cholesteric liquid crystal material has Bragg diffraction characteristics after cross-linking, and can simultaneously reflect blue light with a wavelength between 400nm and 480nm and allow the blue light to pass through.

Description

Light-color conversion material and light-color conversion ink

technical field

The invention relates to a light-color conversion material and a light-color conversion ink.

Background technique

Quantum dots (QDs) are semiconductor materials with a nanometer size (typically less than 100 nanometers) and a crystalline structure, and may include hundreds to thousands of atoms. Quantum dots have the characteristics of high fluorescence brightness, high color purity (half-wave width less than 50nm), good photostability and thermal stability, etc., so they have been widely used in display devices. However, how to improve the quantum efficiency and light-color conversion efficiency of quantum dots is still an extremely important issue for this technology.

Contents of the invention

According to an embodiment of the present invention, the light-color conversion material includes quantum dots and a cross-linkable cholesteric liquid crystal material. A cross-linkable cholesteric liquid crystal material coats the quantum dots. The cross-linkable cholesteric liquid crystal material has Bragg diffraction characteristics after cross-linking, and can simultaneously reflect blue light with a wavelength between 400nm and 480nm and allow the blue light to pass through.

According to an embodiment of the present invention, the light-color conversion ink includes a solvent and a light-color conversion material dispersed in the solvent. Light-color conversion materials include quantum dots and cross-linkable cholesteric liquid crystal materials. A cross-linkable cholesteric liquid crystal material coats the quantum dots. The cross-linkable cholesteric liquid crystal material has Bragg diffraction characteristics after cross-linking, and can simultaneously reflect blue light with a wavelength between 400nm and 480nm and allow the blue light to pass through.

In order to make the present invention more comprehensible, the following specific embodiments are described in detail in conjunction with the accompanying drawings.

Description of drawings

FIG. 1 is a graph showing the relationship between light transmittance/reflectance and light wavelength of a cross-linkable cholesteric liquid crystal material in a light-color conversion material according to an embodiment of the present invention.

Detailed ways

In the embodiment of the present invention, after being irradiated by light with a wavelength between 400nm and 480nm (such as blue light), the light-color conversion material can reflect and be transmitted by the incident light at the same time. The incident light will form a diffraction resonance (ie, Bragg diffraction) after multiple reflection coupling (coupling). In this way, the incident light with the wavelength range can break through the energy gap barrier of the quantum dots, thus increasing the absorption of the incident light by the light-color conversion material, thus making the light-color conversion material have a higher optical density (optical density) , OD). As a result, the excitation conversion of the quantum dots is increased, thereby improving the emission fluorescence intensity and light-color conversion efficiency. The photochromic conversion material of the embodiment of the present invention will be described in detail below.

The light-color conversion material of the embodiment of the present invention includes quantum dots and a cross-linkable cholesteric liquid crystal material. The cholesteric liquid crystal material coats the quantum dot, so that the surface of the quantum dot is covered with a layer of cholesteric liquid crystal material. In this embodiment, the cross-linkable cholesteric liquid crystal material has Bragg diffraction characteristics after cross-linking, and can simultaneously reflect blue light with a wavelength between 400 nm and 480 nm and be transmitted by the blue light. In this embodiment, "the cholesteric liquid crystal material can simultaneously reflect light with a wavelength between 400nm and 480nm and be transmitted by said light after crosslinking" means that the cholesteric liquid crystal material has a light with a wavelength between 400nm and 480nm after crosslinking. The light in the space has the characteristic of selective reflection/transmission. Light with a wavelength between 400 nm and 480 nm is, for example, blue light. Referring to Figure 1, when the photochromic conversion material is crosslinked and irradiated with light with a wavelength between 400nm and 480nm, the crosslinkable cholesteric liquid crystal material can reflect the light and be transmitted by the light at the same time after crosslinking. through.

In this embodiment, the cholesteric liquid crystal material includes an optically active substance and a nematic liquid crystal monomer having a photopolymerizable acrylic functional group.

In an embodiment, the optically active substance may be a compound represented by at least one of [Formula 1-1] to [Formula 1-16].

In an embodiment, the nematic liquid crystal monomer having a photopolymerizable acryl functional group may be a compound represented by [Formula 2] to [Formula 7]. The above-mentioned compounds can be used alone or in combination of two or more.

The light-color conversion material of the embodiment of the present invention can be prepared by mixing an optically active compound with a nematic liquid crystal monomer having a photopolymerizable acrylic functional group, but the present invention is not limited thereto.

In addition, the quantum dots can be any well-known quantum dot materials, and the present invention is not limited thereto. For example, the quantum dots can be single-core quantum dots, core-shell quantum dots or alloy quantum dots. The material of the quantum dots can be II-VI compound, III-V compound or IV-VI compound. The group II-VI compound is, for example, CdSe, the group III-V compound is, for example, InP, and the group IV-VI compound is, for example, PbS, but the present invention is not limited thereto. Structurally, quantum dots can have ligands, monomer layers, polymer layers, inorganic layers or combinations thereof, and can be dot-like, rod-like, polygonal or irregular in shape, but the present invention is not limited thereto.

The light-color conversion material of the embodiment of the present invention can be mixed into a solvent to prepare the light-color conversion ink of the embodiment of the invention. The solvent may be toluene, cyclopentanone, cyclohexanone, propylene glycol methyl ether acetate (PGMEA) or methyl ethyl ketone (MEK). For example, the light-color conversion material of the embodiment of the present invention can be mixed into toluene to obtain a light-color conversion ink with a solid content of 30%, but the invention is not limited thereto.

The photochromic conversion ink of the embodiment of the present invention is coated on the substrate and subjected to light treatment, so that the cross-linkable cholesteric liquid crystal material can undergo a cross-linking reaction. After the solvent in the light-color conversion ink evaporates, the light-color conversion layer of the embodiment of the present invention can be formed. The light-color conversion layer formed by the light-color conversion ink of the embodiment of the present invention can have a higher optical density, thus improving the luminous intensity and light-color conversion efficiency, and applying it to the light-emitting component of the display can make the display have Better display effect.

The effect of the light-color conversion layer of the embodiment of the present invention will be described below with experimental examples and comparative examples.

quantum dot

Green core-shell quantum dots and red core-shell quantum dots purchased from Taiwan Nanocrystalline (TWNC) were used, wherein the material of the core is CdSe, and the material of the shell is ZnS. The emission wavelengths of the green core-shell quantum dots and the red core-shell quantum dots are 528nm and 630nm respectively, the half-wave widths are 19nm and 25nm respectively, and the quantum efficiencies of both are greater than 90%.

Cross-linkable cholesteric liquid crystal materials

Mix the optically active substance represented by [Formula 1-1] with the nematic liquid crystal monomer represented by [Formula 6] to prepare a cross-linkable cholesteric liquid crystal material, wherein the added concentration of the optically active substance accounts for approximately the content of the nematic liquid crystal monomer 6%, so that the cross-linkable cholesteric liquid crystal material has the characteristics of being able to reflect light with a wavelength between 400nm and 480nm and be transmitted by the light at the same time after cross-linking.

light color conversion ink

<Experiment example>

Quantum dots are mixed with cross-linkable cholesteric liquid crystal materials to obtain light and color conversion materials. The photochromic conversion material was added into toluene, and ultrasonic wave was used for 2 hours of shaking and dispersion, so that the cross-linkable cholesterol liquid crystal material was cross-linked and coated with quantum dots, so as to prepare photochromic conversion ink.

<Comparative example>

First mix isodecyl acrylate and 1,6-hexanediol diacrylate, then add quantum dots and toluene, and disperse with ultrasonic waves for 2 hours to prepare a solid A photochromic conversion ink with a content of 30wt.%.

light color conversion layer

The light-color conversion inks of the experimental example and the comparative example were respectively coated on a polyethylene terephthalate (PET) film with a thickness of 50 μm at a rotational speed of 200 rpm. After drying at 90° C., exposure was performed with a UV 365 nm light source (500 mJ dose) to form a light-color conversion layer with a thickness of 9 μm to 10 μm.

Luminous Intensity Test and Optical Density Test

Use a blue light-emitting diode (LED) (maximum wavelength at about 447nm) to irradiate the light-color conversion layer of the experimental example and the comparative example, and use a spectrometer (Ocean Optics USB4000 Spectrometer) to measure the position where the sub-point is irradiated and converts the light-emitting wavelength position ( Green light is about 528nm, red light is about 630nm), and the maximum luminous intensity (compared to the same blue light condition), and calculate the extinction degree of the light color conversion layer to the blue light-emitting diode, the so-called optical density (OD), the result As shown in Table 1.

The optical density (OD) is calculated as follows, where intensity 1 is the light intensity of the original blue light, and intensity 2 is the remaining blue light intensity after passing through the light color conversion layer.

OD=-log(intensity2/intensity1)

Table 1

* Experimental Examples 1, 2, 3 and Comparative Examples 1, 2, 3 use green quantum dots, Experimental Examples 4, 5, 6 and Comparative Examples 4, 5, 6 use red quantum dots.

It can be clearly seen from Table 1 that in the light-color conversion layer formed by the light-color conversion material of the embodiment of the present invention, since the light-color conversion material contains a cross-linkable cholesteric liquid crystal material (which has Bragg diffraction characteristics after cross-linking ), which can simultaneously reflect blue light with a wavelength between 400nm and 480nm and be penetrated by the blue light, so that incident light with a wavelength between 400nm and 480nm can break through the energy gap barrier of quantum dots, thereby improving the light color The absorption of incident light by the conversion layer makes the light-color conversion layer have a higher optical density, and thus improves the light emission intensity and light-color conversion efficiency.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (10)

1. A light color conversion material, comprising:

a quantum dot; and

a crosslinkable cholesteric liquid crystal material coating the quantum dots,

wherein the crosslinkable cholesteric liquid crystal material has Bragg diffraction characteristics after crosslinking and can simultaneously reflect blue light with a wavelength between 400nm and 480nm and allow the blue light to penetrate.

2. The photochromic switching material of claim 1 wherein the crosslinkable cholesteric liquid crystal material comprises an optically active substance and a nematic liquid crystal monomer having a photopolymerisable acrylic functional group.

3. The light color conversion material according to claim 2, wherein the optically active substance comprises a compound represented by at least one of [ formula 1-1] to [ formula 1-16],

4. the light color conversion material according to claim 2, wherein the nematic liquid crystal monomer having a photopolymerizable acrylic functional group comprises a compound represented by at least one of [ formula 2] to [ formula 7],

5. the light color conversion material according to claim 1, wherein the quantum dots comprise single-core quantum dots, core-shell quantum dots, or alloy quantum dots.

6. The light color conversion material according to claim 1, wherein the material of the quantum dots comprises a group II-VI compound, a group III-V compound, or a group IV-VI compound.

7. A photochromic conversion ink comprising:

a solvent; and

the light color conversion material of claim 1 dispersed in the solvent.

8. The photochromic switching ink of claim 7 wherein the crosslinkable cholesteric liquid crystal material comprises an optically active substance and a nematic liquid crystal monomer having a photopolymerisable acrylic functional group.

9. The photochromic conversion ink of claim 7 wherein the quantum dots comprise single core quantum dots, core shell quantum dots, or alloy quantum dots.

10. The photochromic switching ink of claim 7 wherein the solvent comprises toluene, cyclopentanone, cyclohexanone, propylene glycol methyl ether acetate or methyl ethyl ketone.

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