CN114764201B

CN114764201B - Light conversion device and backlight module comprising same

Info

Publication number: CN114764201B
Application number: CN202110057332.3A
Authority: CN
Inventors: 余世荣; 赵飞; 康永印; 罗飞; 白俊; 陶真
Original assignee: Najing Technology Corp Ltd
Current assignee: Najing Technology Corp Ltd
Priority date: 2021-01-15
Filing date: 2021-01-15
Publication date: 2023-08-01
Anticipated expiration: 2041-01-15
Also published as: CN114764201A

Abstract

The invention provides a light conversion device and a backlight module. The light conversion device comprises a first diffusion layer, a quantum dot layer and a second diffusion layer which are sequentially stacked, wherein the light transmittance of the first diffusion layer is larger than that of the second diffusion layer, the haze of the first diffusion layer is smaller than that of the second diffusion layer, the first diffusion layer comprises first diffusion particles, the second diffusion layer comprises second diffusion particles, and the mass fraction of the first diffusion particles in the first diffusion layer is smaller than that of the second diffusion particles in the second diffusion layer.

Description

Light conversion device and backlight module comprising same

Technical Field

The application relates to the technical field of quantum dot photoinduced application, in particular to a light conversion device and a backlight module comprising the same.

Background

The quantum dot light conversion device is used for a backlight assembly in a display field to improve color representation of a display apparatus. The existing mainstream product form is a quantum dot membrane, comprising two barrier layers and one quantum dot layer. However, quantum dot films are still needed for use in conjunction with other optical devices, such as diffusion plates, brightness enhancing films, and the like. The current trend is integration of quantum dot membranes and other optical devices, cost reduction and convenience for use of terminal customers. However, the integrated diffusion photoconversion device still has the technical problems of light shadow phenomenon, low quantum dot stability and low light emitting efficiency.

Disclosure of Invention

An objective of the present application is to provide a light conversion device and a backlight module, so as to solve the technical problem of low light emitting efficiency caused by low stability of quantum dots of the light conversion device in the prior art.

In order to achieve the above object, according to one aspect of the present application, there is provided a light conversion device including a first diffusion layer, a quantum dot layer, and a second diffusion layer stacked in this order, wherein the light transmittance of the first diffusion layer is greater than that of the second diffusion layer, the haze of the first diffusion layer is smaller than that of the second diffusion layer, the first diffusion layer includes first diffusion particles, the second diffusion layer includes second diffusion particles, and the mass fraction of the first diffusion particles in the first diffusion layer is smaller than that of the second diffusion particles in the second diffusion layer.

Further, the light transmittance of the first diffusion layer is 20% -93%; the light transmittance of the second diffusion layer is 5% -90%.

Further, the difference between the light transmittance of the first diffusion layer and the light transmittance of the second diffusion layer is 1% to 50%, preferably 10% to 30%.

Further, the light transmittance of the quantum dot layer is more than 30%, the haze of the quantum dot layer is 0.5% to 99%, and preferably, the haze of the quantum dot layer is 1% to 50%.

Further, the first diffusion particles account for 0.01wt% to 10wt%, preferably 0.01wt% to 2wt% of the first diffusion layer.

Further, the second diffusion particles account for 0.01wt% to 10wt%, preferably 0.05wt% to 5wt% of the second diffusion layer.

Further, the thickness ratio of the first diffusion layer to the second diffusion layer is 0.5:1 to 1:0.5, preferably 1:1.

Further, the thickness ratio of the first diffusion layer to the quantum dot layer is 1:3 to 1:5, preferably 1:4.

Further, the thickness of the quantum dot layer is 0.5-1.8 micrometers.

Further, the first diffusion layer and the second diffusion layer further comprise an anti-aging agent, wherein the anti-aging agent is one or more of hindered phenol main antioxidants, phosphite auxiliary antioxidants and compound antioxidants.

Further, the quantum dot layer has a single-layer structure and includes red quantum dots and green quantum dots, and preferably the ratio of the mass of the red quantum dots to the mass of the green quantum dots is 1:2 to 2:1.

Further, the photoconversion device may further include an inorganic halide, where the inorganic halide is located in one or more of the first diffusion layer, the quantum dot layer, and the second diffusion layer.

Further, the above inorganic halides are selected from one or more of chlorides, or bromides, or iodides of potassium, calcium, sodium, cesium, barium, magnesium, aluminum, zinc, iron, cadmium, copper, titanium, manganese, and indium.

Further, the halogen content in the photoconversion device is less than or equal to 1500ppm, preferably less than 900ppm.

Further, the matrix of at least one of the first diffusion layer, the quantum dot layer, and the second diffusion layer is a polymer that blocks water vapor or a polymer that blocks oxygen.

Further, at least one of the first diffusion layer, the quantum dot layer, and the second diffusion layer includes polymer particles that block water vapor or polymer particles that block oxygen.

Further, the substrate of the first diffusion layer or the second diffusion layer is a polymer for blocking water vapor, and the first diffusion layer or the second diffusion layer further comprises polymer particles for blocking oxygen.

Further, the polymer for blocking water vapor is any one or more of polymethyl methacrylate, polymethyl acrylate, polystyrene, polycarbonate and methyl methacrylate-styrene copolymer, and the polymer for blocking oxygen is any one or more of polyacrylic acid, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyethylene oxide, styrene-acrylonitrile copolymer, polyacrylonitrile and polyimide.

Further, the polymer particles for blocking water vapor are any one or more of polymethyl methacrylate particles, polymethyl acrylate particles, polystyrene particles, polycarbonate particles and methyl methacrylate-styrene copolymer particles, and the polymer particles for blocking oxygen are any one or more of polyacrylic acid particles, polyvinyl alcohol particles, ethylene-vinyl alcohol copolymer particles, polyethylene oxide particles, styrene-acrylonitrile copolymer particles, polyacrylonitrile particles and polyimide particles.

Further, the quantum dots in the quantum dot layer are distributed in an aggregate manner in the quantum dot layer.

In still another aspect of the present application, a backlight module is provided, the backlight module includes an initial light source and any one of the above light conversion devices, where the light conversion device is a quantum dot diffusion plate.

Further, the quantum dot diffusion plate is located above the initial light source, and the first diffusion layer is far away from the initial light source compared with the second diffusion layer.

By the technical scheme, the second diffusion layer is low in light transmittance, the haze is high relative to the first diffusion layer, excitation light of the light conversion device in the use process can be blocked, light intensity is reduced, the phenomenon that the light intensity of quantum dots in the quantum dot layer is too strong due to illumination is reduced, the stability of the quantum dots is improved, and the service life of the light conversion device is prolonged. For the application of the direct type backlight module, the problem of the initial light source lamp shadow can be further solved. In addition, the first diffusion layer has high light transmittance and low mass fraction of diffusion particles, so that the light utilization rate of an initial light source can be improved, scattered light excites quantum dots in the quantum dot layer for multiple times, and the light emitting efficiency of a light conversion device is improved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:

fig. 1 shows a schematic cross-sectional structure of a light conversion device according to an embodiment of the present application.

Fig. 2 shows a schematic cross-sectional structure of a backlight module according to an embodiment of the present application.

Fig. 3 illustrates a partial Transmission Electron Microscope (TEM) image of a quantum dot diffusion plate according to various embodiments of the present application.

Fig. 4 shows a partial TEM image of a quantum dot diffusion plate according to one embodiment of the present application.

Wherein the above figures include the following reference numerals:

1. a first diffusion layer. 2. And a quantum dot layer. 3. And a second diffusion layer. 4. An initial light source.

Detailed Description

It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terms "first," "second," and the like in the description and in the claims of the present application are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate in order to describe the embodiments of the present application described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Exemplary embodiments of the light conversion device or the backlight module provided according to the present application will be described in more detail below. These exemplary embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It should be appreciated that these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of these exemplary embodiments to those skilled in the art.

As described in the background art, the prior art light conversion devices that have a diffusion function have low performance. In a first aspect of the present application, as shown in fig. 1, a light conversion device is provided, including a first diffusion layer 1, a quantum dot layer 2, and a second diffusion layer 3 stacked in sequence, where the light transmittance of the first diffusion layer 1 is greater than that of the second diffusion layer 3, the haze of the first diffusion layer 1 is less than that of the second diffusion layer 3, the first diffusion layer 1 includes first diffusion particles, the second diffusion layer 3 includes second diffusion particles, and the mass fraction of the first diffusion particles in the first diffusion layer 1 is less than that of the second diffusion particles in the second diffusion layer 3. The second diffusion layer 3 has low light transmittance and high haze compared with the first diffusion layer, can block the excitation light of the light conversion device in the use process, is favorable for reducing the light intensity, reduces the excessively strong illumination of the quantum dots in the quantum dot layer 2, improves the stability of the quantum dots, and further improves the service life of the light conversion device. For the application of the direct type backlight module, the problem of the initial light source lamp shadow can be further solved. The first diffusion layer has high light transmittance and low mass fraction of diffusion particles, so that the light utilization rate of an initial light source can be improved, scattered light excites the quantum dots in the quantum dot layer 2 for multiple times, and the light emitting efficiency of a light conversion device is improved.

It should be noted that "layer" in the present application does not represent a word that must be able to distinguish the layer by naked eyes or be peeled off by a physicochemical method, and is used for convenience of description of the structure. It should be understood that "layers" of the light conversion device include those that are able to distinguish between layers and those that have not been able to distinguish "layers", and that factors that affect whether layering is primarily process dependent. The haze can be controlled by adding the diffusion particles, or by producing frosted lines by surface rolling, or by any other combination of one or more of the above ways. The above theory is only speculated and does not therefore limit the scope of protection of the present application.

In some embodiments, the first diffusion layer 1 has a light transmittance of 20% to 93%, or 30% to 80%; the light transmittance of the second diffusion layer 3 is 5% to 90%, or 20% to 60%.

In some embodiments, the difference between the light transmittance of the first diffusion layer 1 and the light transmittance of the second diffusion layer 3 is 1% to 50%, preferably 10% to 30%.

In some embodiments, the light transmittance of the quantum dot layer 2 is greater than 30%, and the haze of the quantum dot layer 2 is 0.5% to 99%, preferably 1% to 50%.

In some embodiments, quantum dots and a polymer matrix are included in the quantum dot layer 2.

In some embodiments, the first diffusion layer 1 and/or the second diffusion layer 3 does not comprise an inorganic water-resistant layer, an inorganic oxygen-resistant layer, or an inorganic water-resistant layer and an inorganic oxygen-resistant layer, and comprises only a diffusion material and a polymer matrix.

In some embodiments, the "light transmittance" is blue (430-470 nm) or white (430-700 nm) light transmittance.

In some embodiments, the photoconversion device no longer comprises other functional layers, i.e. the photoconversion device is composed of the first diffusion layer 1, the quantum dot layer 2 and the second diffusion layer 3.

In some embodiments, the first diffusion particles comprise 0.01wt% to 10wt%, preferably 0.01wt% to 2wt%, more preferably 0.05wt% to 1wt% of the first diffusion layer 1.

In some embodiments, the second diffusion particles comprise 0.01wt% to 10wt%, preferably 0.05wt% to 5wt%, more preferably 0.1wt% to 2wt% of the second diffusion layer 3.

In some embodiments, the first diffusion layer has a high light transmittance, and may be selected from diffusion particles with a low refractive index (e.g. refractive index 1.3-1.5) such as silicon-based or resin microsphere systems, or a small amount of diffusion materials with a high refractive index. The second diffusion layer has low light transmittance, and can be selected from diffusion particles with large refractive index (such as titanium dioxide, etc. (refractive index is 1.5-2.5)) or titanium dioxide and other diffusion particles with large refractive index. The diffusion particles may be polysiloxane polymer micropowder, PS microsphere, PMMA microsphere, silica (SiO) ₂ ) Or titanium dioxide (TiO) ₂ )。

In some embodiments, the first diffusion particles may include a plurality of diffusion particles; the second diffusion particles may include a plurality of diffusion particles. When the diffusion particles have a plurality of types, the mass fraction of the first diffusion particles is the total mass fraction of the plurality of diffusion particles in the first diffusion layer, and likewise, the mass fraction of the second diffusion particles is the total mass fraction of the plurality of diffusion particles in the second diffusion layer.

In some embodiments, the thickness ratio of the first diffusion layer 1 to the second diffusion layer 3 is 0.5:1 to 1:0.5, preferably 1:1.

In some embodiments, the ratio of the thickness of the first diffusion layer 1 to the quantum dot layer 2 is 1:3 to 1:5, preferably 1:4.

In some embodiments, the quantum dot layer 2 has a thickness of 0.5 to 1.8 microns. The thickness is favorable for thinning the light conversion device.

In some embodiments, the first diffusion layer 1 and the second diffusion layer 3 further comprise an anti-aging agent that is one or more of a hindered phenolic primary antioxidant, a phosphite secondary antioxidant, and a compounded antioxidant. The hindered phenol main antioxidants are antioxidant 1010 (trade names, the same applies to the antioxidants described below), antioxidant 1076, antioxidant 1098, antioxidant 1024 and the like, the phosphite ester auxiliary antioxidants are antioxidant 168, antioxidant 626, antioxidant 627A and the like, and the compound antioxidants comprise more than two of antioxidant 215, antioxidant 900 and antioxidant 1171 which are matched for use, so that the quantum dot layer is further protected.

In some embodiments, the quantum dot layer 2 is a single-layer structure and includes red quantum dots and green quantum dots, preferably, the ratio of the mass of the red quantum dots to the mass of the green quantum dots is 1:2 to 2:1, and more preferably, the ratio of the mass of the red quantum dots to the mass of the green quantum dots is 1:1.5 to 1.5:1.

In some embodiments, the quantum dots described above are not perovskite quantum dots or graphene quantum dots or carbon quantum dots or silicon quantum dots or germanium quantum dots.

In some embodiments, the light conversion device is air stable such that the light emission efficiency of the light conversion device decreases by 10% or less or 5% within 1000 hours when exposed to air having a relative humidity of 95% and a temperature of 65 ℃. The photoconversion device is photostable and thermally stable such that when exposed to 500 milliwatts per square centimeter (mW/cm) ² ) When the light conversion device emits light at an acceleration flux of 70 ℃ for 1000 hours, the light emission efficiency of the light conversion device is reduced by 10% or less. The photoconversion device is thermally stable such that the luminous efficiency of the photoconversion device decreases by 10% or less or 5% within 1000 hours when exposed to air at a temperature of 85 ℃.

In some embodiments, the photoconversion device has a cadmium content of 100ppm or less.

In some embodiments, quantum dot layer 2 is a multi-layer structure comprising at least one red quantum dot layer and at least one green quantum dot layer, preferably the green quantum dot layer is sandwiched between the red quantum dot layers. The red quantum dot layer has higher stability than the green quantum dot layer, thereby further protecting the green quantum dot layer. In some embodiments, the quantum dot layer 2 is two layers. In some embodiments, the red quantum dot layer and the first diffusion layer are the same layer, i.e., the red quantum dot and the first diffusion particle are located in the same layer.

In some embodiments, quantum dot layer 2 is a single layer structure comprising green quantum dots; the red quantum dots are positioned on the first diffusion layer. The preparation process and equipment of the three-layer structured light conversion device are simpler.

In some embodiments, the photoconversion device further comprises an inorganic halide, where the inorganic halide is located in any one or more of the first diffusion layer 1, the quantum dot layer 2, and the second diffusion layer 3. Inorganic halides can improve the stability and lifetime of the photoconversion device.

In some embodiments, the inorganic halide is selected from one or more of chlorides, or bromides, or iodides of potassium, calcium, sodium, cesium, barium, magnesium, aluminum, zinc, iron, cadmium, copper, titanium, manganese, and indium. Preferably the inorganic halide is one or more of potassium chloride, sodium chloride, calcium chloride, zinc chloride, magnesium chloride, aluminum chloride, potassium bromide, sodium bromide, calcium bromide, zinc bromide, magnesium bromide, aluminum bromide.

In some embodiments, the halogen content of the photoconversion device is less than or equal to 1500ppm, preferably less than 900ppm.

In some embodiments, the matrix of at least one of the first diffusion layer 1, the quantum dot layer 2, and the second diffusion layer 3 is a polymer that blocks water vapor or a polymer that blocks oxygen. The protection of the quantum dots of the quantum dot layer 2 is improved.

In some embodiments, at least one of the first diffusion layer 1, the quantum dot layer 2, the second diffusion layer 3 comprises polymer particles that are moisture barrier or polymer particles that are oxygen barrier. The protection of the quantum dots of the quantum dot layer 2 is improved.

In some embodiments, the mass fraction of the polymer or polymer particles in the first diffusion layer 1, the quantum dot layer 2, the second diffusion layer 3 is 10wt% to 99wt%, or 80wt% to 95wt%.

In some embodiments, the matrix of the first diffusion layer 1 or the second diffusion layer 3 is a polymer that blocks water vapor, and the first diffusion layer 1 or the second diffusion layer 3 further comprises polymer particles that block oxygen. The protection of the quantum dots of the quantum dot layer 2 is improved.

In some embodiments, the processing temperature of the matrix of the quantum dot layer is less than 150 ℃, which is advantageous for protecting the quantum dots during processing. Processing temperature refers to the temperature at which the matrix is capable of being extruded from the extruder.

In some embodiments, the water vapor barrier polymer is any one or more of polymethyl methacrylate, polymethyl acrylate, polystyrene, polycarbonate, methyl methacrylate-styrene copolymer, and the oxygen barrier polymer is any one or more of polyacrylic acid, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyethylene oxide, styrene-acrylonitrile copolymer, polyacrylonitrile, polyimide. The organic barrier material may reduce the overall cost of the photoconversion device.

In some embodiments, the water vapor barrier polymer particles are any one or more of polymethyl methacrylate particles, polymethyl acrylate particles, polystyrene particles, polycarbonate particles, methyl methacrylate-styrene copolymer particles, and oxygen barrier polymer particles are any one or more of polyacrylic acid particles, polyvinyl alcohol particles, ethylene-vinyl alcohol copolymer particles, polyethylene oxide particles, styrene-acrylonitrile copolymer particles, polyacrylonitrile particles, polyimide particles.

In some embodiments, the quantum dot surface includes an ester ligand. In some embodiments, the quantum dot surface comprises n-octadecyl phosphate ligands. Through the interaction of the ester ligand and the ester polymer in the quantum dot layer matrix, the quantum dots are easier to disperse, so that the uniform distribution of the quantum dots in the quantum dot layer is realized.

In some embodiments, the raw material for preparing the quantum dot layer is a quantum dot solution, and when the ligand of the quantum dot is an ester ligand, the solvent of the quantum dot solution is one or more of ethyl acetate, butyl acetate, amyl acetate, propylene glycol polyether acetate, methyl methacrylate, butyl methacrylate, isobutyl methacrylate, methyl acrylate and butyl acrylate. When the ligand of the quantum dot is oleic acid ligand, the solvent of the quantum dot solution is one or more of toluene, n-hexane, cyclohexane, n-octane, lauryl methacrylate, isobornyl acrylate and 3, 5-trimethylcyclohexyl acrylate. The monomer of the lauryl methacrylate, the isobornyl acrylate and the 3, 5-trimethylcyclohexyl acrylate has small polarity, good solvent property, higher boiling point than common solvents and good compatibility with quantum dots.

In some embodiments, the outer surface of the first diffusion layer 1 and/or the second diffusion layer 3 remote from the quantum dot layer 2 has a microstructure. Further improving the light-emitting efficiency. The microstructure refers to a micron-sized optical structure, the microstructure can be repeated, can be prepared by printing dots and the like, can be a prism layer, and can further solve the problem of lamp shadow.

In some embodiments, the quantum dots in the quantum dot layer 2 are distributed in an aggregate in the quantum dot layer, that is, a plurality of quantum dots are combined into one aggregate, and through research by the applicant, it is found that the aggregate does not affect the luminous efficiency, so that the raw material formulation and the process flexibility of the quantum dot layer can be improved, and the distribution of forming single quantum dots is not limited. The particle size of the agglomerate ranges from 20nm to 1 mu m, and the agglomerate can have the effect of diffusing particles. The quantum dot agglomerates are seen in the TEM image of fig. 3.

In some embodiments, one or more of quantum dot glass powder, inorganic oxide coated quantum dots are included in quantum dot layer 2. The stability of the quantum dots is improved, and the service life of the light conversion device is further prolonged. In some embodiments, the quantum dot surface is coated with a shell of silica, alumina, titania, or a combination thereof. When the surface of the quantum dot is coated with oxide, the particles have the function of diffusing particles.

In other embodiments, one or both of the first diffusion layer 1 and the second diffusion layer 3 further include a phosphor, which may also perform light conversion luminescence.

In some embodiments, the photoconversion device is prepared by a three-layer raw material melt coextrusion process. Realizing integral molding. In some embodiments, the number of layers of the light conversion device is greater than 3, and a coextrusion process may also be selected.

In some embodiments, the method for preparing the photoconversion device includes preparing a first master batch for a first diffusion layer, preparing a second master batch for a second diffusion layer, preparing a quantum dot master batch for a quantum dot layer, placing the first master batch, the second master batch and the quantum dot master batch in an extrusion device, melting and co-extrusion, and cooling to obtain the photoconversion device, wherein the mass fraction of diffusion particles in the first master batch is smaller than the mass fraction of diffusion particles in the second master batch. The quantum dot master batch comprises quantum dots and a matrix, the first master batch comprises first diffusion particles and a matrix, and the first master batch comprises second diffusion particles and a matrix.

In some embodiments, the method of preparing the quantum dot master batch comprises uniformly mixing the quantum dot dispersion liquid with a matrix, removing the dispersing agent in the quantum dot dispersion liquid, and performing high-temperature extrusion granulation by an extrusion granulator to obtain the quantum dot master batch with uniformly distributed quantum dots. In some embodiments, the dispersant of the quantum dot dispersion is ethyl acetate and the ligand of the quantum dot is n-octadecyl phosphate ligand. In some embodiments, the dispersant of the quantum dot dispersion is lauryl methacrylate and the ligand of the quantum dot is oleic acid.

In some embodiments, the processing temperature of the matrix of the quantum dot master batch is less than 150 ℃, which is beneficial to the protection of the quantum dots during processing. In some embodiments, the quantum dot master batch includes red quantum dots and green quantum dots.

In some embodiments, the quantum dots of the photoconversion device are made of quantum dots or quantum dot polymer particles (or quantum dot master batch), the shape of the quantum dot polymer particles is not limited, and the size of the quantum dot polymer particles is nano-scale, micro-scale or millimeter-scale.

In some embodiments, the diffusion particles in the diffusion layer are made of diffusion particle polymer particles (or diffusion master), the shape of the diffusion particle polymer particles is not limited, and the size of the diffusion particle polymer particles is in the micrometer or millimeter scale.

According to a second aspect of the present application, a backlight module is provided, the backlight module includes an initial light source 4 and any of the above light conversion devices, and the light conversion device is a quantum dot diffusion plate. The second diffusion layer 3 has low light transmittance and high haze compared with the first diffusion layer, can block the excitation light of the light conversion device in the use process, is favorable for reducing the light intensity, reduces the phenomenon that the quantum dots in the quantum dot layer 2 are too strong in illumination, improves the stability of the quantum dots, and further improves the service life of the light conversion device. The first diffusion layer has high light transmittance and low mass fraction of diffusion particles, so that the light utilization rate of an initial light source can be improved, scattered light excites the quantum dots in the quantum dot layer 2 for multiple times, and the light emitting efficiency of a light conversion device is improved.

In some preferred embodiments, as shown in fig. 2, the quantum dot diffusion plate is located above the initial light source 4 (the arrow represents the light emitting direction), and the first diffusion layer 1 is far away from the initial light source compared to the second diffusion layer 2. The arrangement mode can solve the problem of lamp shadow on the quantum dot diffusion plate of the initial light source, and improves the luminous uniformity.

In some embodiments, the initial light source 4 may be a blue light source or a violet light source.

The light conversion device and the backlight module according to the present invention will be further described with reference to the following embodiments.

Example 1

Mixing concentrated quantum dot solution with the mass fraction of 10% (the mixing ratio of red quantum dots and green quantum dots is 1:1.2, the initial ligand of the red and green quantum dots is oleic acid, the dispersing agent is lauryl methacrylate) with polymethyl methacrylate matrix white material, vacuumizing to remove the solvent and uniformly stirring to obtain matrix particles with the surfaces covered with the quantum dots, and extruding and granulating at 230 ℃ by an extrusion granulator to obtain quantum dot master batches with the quantum dots embedded with matrix polymer, wherein the master batches are used as raw materials of quantum dot layers. Mixing diffusion particles (titanium dioxide and silicon oxide) with polymethyl methacrylate matrix white material (so that the diffusion particles account for 5 wt%), and carrying out extrusion granulation at 230 ℃ through an extrusion granulator to obtain first diffusion master batch which is used as a raw material of a first diffusion layer; mixing the diffusion particles (titanium dioxide and silicon oxide) with the matrix white material (so that the diffusion particles account for 10 wt%) and carrying out extrusion granulation at 230 ℃ by an extrusion granulator to obtain a second diffusion master batch which is used as a raw material of a second diffusion layer. Adding a first diffusion master batch mixed polymethyl methacrylate matrix white material (the mass ratio is 10:100, and the mass ratio is not particularly shown in brackets below) into a first auxiliary extruder, adding a second diffusion master batch mixed polymethyl methacrylate matrix white material (the mass ratio is 10:100) into a second auxiliary extruder, adding a quantum dot master batch mixed polymethyl methacrylate matrix white material (the mass ratio is 8:100) into a main extruder, controlling and regulating the thickness of each layer to be 1:4:1, extruding at 230 ℃ through a three-layer coextrusion process, and performing pressure cooling and cutting by a roller (a smooth roller) to obtain the photoconversion device. The obtained TEM image of the part of the quantum dot diffusion plate is shown in fig. 3, the black agglomerates are quantum dot agglomerates, the agglomerates are irregular, and the size of the agglomerates is about 50nm to 300nm.

Example 2

The difference from example 1 is that: and (3) mixing titanium dioxide, silicon oxide diffusion particles and zinc bromide with a matrix white material (so that the diffusion particles account for 10wt% and the zinc bromide accounts for 0.3 wt%) and carrying out extrusion granulation by an extrusion granulator at 230 ℃ to obtain a second diffusion master batch, wherein the second diffusion master batch is used as a raw material of a second diffusion layer. Adding a first diffusion master batch mixed polymethyl methacrylate matrix white material (mass ratio of 10:100) into a first auxiliary extruder, adding a second diffusion master batch mixed polymethyl methacrylate matrix white material (mass ratio of 10:100) into a second auxiliary extruder, adding a quantum dot master batch mixed polymethyl methacrylate matrix white material (mass ratio of 8:100) into a main extruder, controlling and regulating the thickness of each layer to be 1:4:2, extruding through a three-layer coextrusion process at 230 ℃, and performing roll (smooth roll) pressure cooling and cutting to obtain a light conversion device. The bromine halogen content was tested to be 800ppm.

Example 3

Mixing a concentrated quantum dot solution with the mass fraction of 10% (the mixing ratio of red quantum dots to green quantum dots is 1:1.2, the initial ligand of the red and green quantum dots is oleic acid, the dispersing agent is lauryl methacrylate) with a polystyrene matrix white material, vacuumizing to remove the solvent and uniformly stirring to obtain matrix particles with the surfaces covered with the quantum dots, and extruding and granulating at 210 ℃ by an extrusion granulator to obtain quantum dot master batches of matrix polymer embedded quantum dots, wherein the raw materials are used for a quantum dot layer. Mixing diffusion particles (titanium dioxide and silicon oxide) with polystyrene matrix white material (so that the diffusion particles account for 5 wt%), and carrying out extrusion granulation at 210 ℃ through an extrusion granulator to obtain first diffusion master batch which is used as a raw material of a first diffusion layer; and mixing the diffusion particles (titanium dioxide and silicon oxide) with polystyrene matrix white material (so that the diffusion particles account for 10 wt%) and carrying out extrusion granulation at 210 ℃ by an extrusion granulator to obtain a second diffusion master batch which is used as a raw material of a second diffusion layer. Adding a first diffusion master batch mixed polystyrene matrix white material (mass ratio of 10:100) into a first auxiliary extruder, adding a second diffusion master batch mixed polystyrene matrix white material (mass ratio of 10:100) into a second auxiliary extruder, adding a quantum dot master batch mixed polystyrene matrix white material (8:100) into a main extruder, controlling and regulating the thickness of each layer to be 1:4:1, extruding at 210 ℃ through a three-layer coextrusion process, and performing roll (smooth roll) pressing, cooling and cutting to obtain the photoconversion device.

Example 4

The difference from example 3 is that: adding a first diffusion master batch mixed polystyrene matrix white material (mass ratio of 10:100) into a first auxiliary extruder, adding a second diffusion master batch mixed polystyrene matrix white material (mass ratio of 10:100) into a second auxiliary extruder, adding a quantum dot master batch mixed polystyrene matrix white material (mass ratio of 8:100) into a main extruder, controlling and regulating each layer thickness to be 1:6:1, extruding at 210 ℃ through a three-layer coextrusion process, and performing roll (smooth roll) pressure cooling and cutting to obtain the photoelectric conversion device.

Example 5

Mixing concentrated quantum dot solution with the mass fraction of 10% (the mixing mass ratio of red quantum dots and green quantum dots is 1:1.2, the initial ligand of the red and green quantum dots is oleic acid, the dispersing agent is lauryl methacrylate), 2% of 2-mercaptobenzimidazole antioxidant, and polymethyl methacrylate matrix white, vacuumizing to remove the solvent and uniformly stirring to obtain matrix particles with the surfaces covered with the quantum dots, mixing, extruding and granulating at 230 ℃ through an extrusion granulator to obtain quantum dot master batches with the quantum dots embedded with matrix polymer, and raw materials for quantum dot layers. Mixing diffusion particles (titanium dioxide and silicon oxide) and a 2-mercaptobenzimidazole anti-aging agent with polymethyl methacrylate matrix white material (so that the diffusion particles account for 5wt% and the anti-aging agent accounts for 2 wt%), and extruding and granulating at 230 ℃ through an extrusion granulator to obtain first diffusion master batches which are used as raw materials of a first diffusion layer; and mixing the diffusion particles (titanium dioxide and silicon oxide) and the 2-mercaptobenzimidazole anti-aging agent with matrix white material (so that the diffusion particles account for 10wt% and the anti-aging agent accounts for 2 wt%) and carrying out extrusion granulation by an extrusion granulator at 230 ℃ to obtain a second diffusion master batch which is used as a raw material of a second diffusion layer. Adding a first diffusion master batch mixed polystyrene matrix white material (mass ratio of 10:100) into a first auxiliary extruder, adding a second diffusion master batch mixed polystyrene matrix white material (mass ratio of 10:100) into a second auxiliary extruder, adding a quantum dot master batch mixed polystyrene matrix white material (mass ratio of 8:100) into a main extruder, controlling and regulating each layer thickness to be 2:4:1, extruding at 210 ℃ through a three-layer coextrusion process, and performing roll (smooth roll) pressure cooling and cutting to obtain the photoelectric conversion device.

Example 6

Mixing concentrated red quantum dot solution (initial ligand of red quantum dot is oleic acid, dispersant is lauryl methacrylate, isobornyl acrylate and 3, 5-trimethyl cyclohexyl acrylate) with polymethyl methacrylate matrix white material, vacuumizing to remove solvent and uniformly stirring to obtain matrix particles with surface covered with quantum dots, and extruding and granulating at 230 ℃ by an extrusion granulator to obtain quantum dot master batches with matrix polymer embedded with red quantum dots, wherein the quantum dot master batches are used as one of raw materials of a first diffusion layer. Mixing a concentrated quantum dot solution (green quantum dots, one or a mixture of toluene, n-hexane, cyclohexane, n-octane, lauryl methacrylate, isobornyl acrylate, 3, 5-trimethylcyclohexyl acrylate and the like) with a mass fraction of 10 percent with polymethyl methacrylate matrix white material, vacuumizing to remove the solvent and uniformly stirring to obtain matrix particles with surfaces covered with the quantum dots, and extruding and granulating at 230 ℃ by an extrusion granulator to obtain quantum dot master batches with matrix polymers embedded with the green quantum dots, wherein the quantum dot master batches are used as raw materials of green quantum dot layers. Mixing diffusion particles (titanium dioxide and silicon oxide) with polymethyl methacrylate matrix white material (so that the diffusion particles account for 5 wt%), and carrying out extrusion granulation at 230 ℃ through an extrusion granulator to obtain first diffusion master batch which is used as a raw material of a first diffusion layer; mixing the diffusion particles (titanium dioxide and silicon oxide) with the matrix white material (so that the diffusion particles account for 10 wt%) and carrying out extrusion granulation at 230 ℃ by an extrusion granulator to obtain a second diffusion master batch which is used as a raw material of a second diffusion layer. Adding a first diffusion master batch and a quantum dot master batch mixed polymethyl methacrylate matrix white material (mass ratio of 10:8:100) of red quantum dots into a first auxiliary extruder, adding a second diffusion master batch mixed polymethyl methacrylate matrix white material (mass ratio of 10:100) into a second auxiliary extruder, adding a green quantum dot master batch mixed polymethyl methacrylate matrix white material (mass ratio of 8:100) into a main extruder, controlling and regulating each layer thickness to be 1:4:1, extruding at 230 ℃ through a three-layer coextrusion process, and performing pressure cooling and cutting by a roller (a smooth roller) to obtain the light conversion device.

Example 7

The difference from example 1 is that the diffusion particles (titanium white powder and silicon oxide), zinc chloride and the white material of the mixed matrix (such that the diffusion particles account for 10wt% and zinc chloride accounts for 0.3 wt%) were extrusion-granulated by an extrusion granulator at 230 ℃ to obtain a second diffusion master batch, which was used as a raw material for the second diffusion layer. Mixing and stirring the particles for the quantum dot layer, the particles for the first diffusion layer and the particles for the second diffusion layer uniformly, adding the mixture into an extruder, extruding at 230 ℃, rolling, cooling and cutting to obtain the quantum dot diffusion plate. The chlorine halogen content was tested to be 500ppm.

Example 8

The difference from example 1 is that: mixing a concentrated quantum dot solution with the mass fraction of 10% (the mixing ratio of red quantum dots to green quantum dots is 1:1.2, the initial ligands of the red quantum dots and the green quantum dots are oleic acid, the ligands of the red quantum dots and the green quantum dots after ligand exchange are n-octadecyl phosphate ligands, and the solvent is ethyl acetate), vacuumizing to remove the solvent, and stirring uniformly to obtain matrix particles with the surfaces covered with the quantum dots, and extruding and granulating at 230 ℃ by an extrusion granulator to obtain quantum dot master batches with uniformly dispersed quantum dots, wherein the quantum dot master batches are used as raw materials of a quantum dot layer. The obtained partial TEM image of the quantum dot diffusion plate is shown in fig. 4, and black dots are quantum dots and are distributed in a non-agglomerated state.

The white light transmittance and haze test method comprises the following steps: and respectively manufacturing a first diffusion layer or a second diffusion layer or a quantum dot layer with a single layer corresponding to the thickness on the PMMA light-transmitting (93%) substrate, and testing the light transmittance and the haze by using a haze meter.

The parameters of the various layers of the photoconversion device (quantum dot diffusion plate) obtained in the various examples are shown in table 1 below:

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comparative example 1

The preparation method is different from example 1 in that the quantum dot master batch is prepared only according to the method of example 1, the quantum dot master batch mixed polymethyl methacrylate matrix white material (8:100) is added into a main extruder, the thickness is controlled and regulated, the extrusion is carried out at 230 ℃ through an extrusion process, and a light conversion device without a first diffusion layer and a second diffusion layer is obtained by roll (smooth roll) pressing, cooling and cutting.

Comparative example 2

The preparation method was the same as in example 1, except that the preparation of the second diffusion layer was modified. The master batch of the first diffusion layer of example 1 was used for the preparation of the second diffusion layer of this comparative example, so that the materials, haze, light transmittance, and layer thickness of the first and second diffusion layers were the same.

Comparative example 5

The preparation method was the same as in example 3, except that the preparation of the second diffusion layer was modified. The master batch of the first diffusion layer of example 3 was used for the preparation of the second diffusion layer of this comparative example, so that the materials, haze, light transmittance, and layer thickness of the first and second diffusion layers were the same.

Example 10

The quantum dot diffusion plate of example 1 (first diffusion layer was away from the initial light source) was placed on a direct-type backlight element, wherein the initial light source was an LED with an emission wavelength of 450nm and an emission intensity of 4mW/cm ² 。

Comparative example 3

The difference from example 10 is that the quantum dot diffusion plate of comparative example 2 was placed on the direct type backlight element.

Comparative example 4

The difference from embodiment 10 is that the quantum dot diffusion plate (first diffusion layer near the initial light source) of embodiment 1 is placed on the direct type backlight element.

And (3) detection: the properties of the quantum dot diffusion plates prepared in the above examples and comparative examples were measured by the following methods, and the measurement results are shown in table 2.

The detection method of the luminous efficiency of the quantum dot diffusion plate comprises the following steps: and using a 450nm blue LED lamp as a backlight light source, wherein the first diffusion layer is far away from the LED light source, and the second diffusion layer is close to the LED light source. And respectively testing a blue backlight spectrum and a spectrum penetrating through the quantum dot diffusion plate by using an integrating sphere, and calculating the luminous efficiency of the quantum dot by using the integral area of the spectrogram.

Luminous efficiency of the diffusion plate = quantum dot emission peak area/(blue backlight peak area-blue peak area not absorbed through quantum dot diffusion plate) × 100%.

The method for detecting the luminous stability of the diffusion plate comprises the following steps: the method for testing luminescence stability mainly comprises high temperature blue light illumination (70deg.C, blue light wavelength 450nm, average light intensity 0.5W/cm) ² ) And detecting the efficiency change of the quantum dot diffusion plate under aging conditions such as high temperature and high humidity (65 ℃/95% relative humidity), high temperature storage (85 ℃). The initial efficiency of each of the examples and comparative examples was set to 100%.

Table 2:

as can be seen from table 2, comparative example 1 without a diffusion layer had the worst effect. Different polymer systems have an influence on the properties. Examples 3 to 6 and comparative example 5 are polystyrene systems, and it can be seen that the effect of example is better than comparative example 5; the remaining examples and comparative example 2 are PMMA systems, and it can be seen that the effect of the examples is better than that of comparative example 2. The same diffusion layer material has a detrimental effect on performance.

The backlight modules of example 10 and comparative examples 3 to 4 were tested for chromaticity uniformity and luminance, and recorded in table 3, with CIE (x, y) being chromaticity coordinate values, and 3 x 3 points were selected at equal intervals, with CIE-x deviation value=cie-x maximum value minus CIE-x minimum value, and CIE-y deviation value=cie-y maximum value minus CIE-y minimum value. The smaller the CIE-x and CIE-y deviation values, the better the chromaticity uniformity of the backlight unit. Luminance uniformity=minimum luminance among 9 points/maximum luminance among 9 points, and a closer luminance uniformity to 1 indicates more uniform luminance, a percentage increase in CIE-x chromaticity uniformity= | (CIE-x deviation value of this example-CIE-x deviation value of the comparative example)/a percentage increase in CIE-y chromaticity uniformity= | (CIE-y deviation value of this example-CIE-y deviation value of the comparative example)/a percentage increase in CIE-y deviation value of the comparative example.

Table 3:

as can be seen from table 3, example 10 has a significant improvement in luminance and chromaticity uniformity over comparative example 3 (no difference in two diffusion layers). Example 10 has a significant improvement in luminance and chromaticity uniformity over comparative example 4, and therefore the position of the first diffusion layer relative to the initial light source also affects luminance and chromaticity uniformity.

The foregoing description is only of the preferred embodiments of the present application and is not intended to limit the same, but rather, various modifications and variations may be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. The light conversion device is characterized by comprising a first diffusion layer, a quantum dot layer and a second diffusion layer which are sequentially stacked, wherein the light transmittance of the first diffusion layer is larger than that of the second diffusion layer, the haze of the first diffusion layer is smaller than that of the second diffusion layer, the first diffusion layer comprises first diffusion particles, the second diffusion layer comprises second diffusion particles, the mass fraction of the first diffusion particles in the first diffusion layer is smaller than that of the second diffusion particles in the second diffusion layer, and the light transmittance of the first diffusion layer is 20% -93%; the light transmittance of the second diffusion layer is 20% -60%, the difference between the light transmittance of the first diffusion layer and the light transmittance of the second diffusion layer is 1% -50%, the light conversion device is used in a backlight module, the backlight module comprises an initial light source, the light conversion device is located above the initial light source, and the first diffusion layer is far away from the initial light source compared with the second diffusion layer.

2. The light conversion device according to claim 1, wherein a difference between the light transmittance of the first diffusion layer and the light transmittance of the second diffusion layer is 10% to 30%.

3. The photoconversion device of claim 1, wherein the light transmittance of the quantum dot layer is greater than 30% and the haze of the quantum dot layer is from 0.5% to 99%.

4. The photoconversion device of claim 3, wherein the quantum dot layer has a haze of 1% to 50%.

5. The light-converting device of claim 1, wherein the first diffusing particles comprise from 0.01wt% to 10wt% of the first diffusing layer.

6. The light-converting device of claim 5, wherein the first diffusing particles comprise from 0.01wt% to 2wt% of the first diffusing layer.

7. The light conversion device of claim 1, wherein the second diffusion particles comprise from 0.01wt% to 10wt% of the second diffusion layer.

8. The light-converting device of claim 7, wherein the second diffusing particles comprise from 0.05wt% to 5wt% of the second diffusing layer.

9. The light conversion device of claim 1, wherein a thickness ratio of the first diffusion layer to the second diffusion layer is 0.5:1 to 1:0.5.

10. The light conversion device of claim 9, wherein the ratio of the thicknesses of the first diffusion layer and the second diffusion layer is 1:1.

11. The photoconversion device of claim 1, wherein a thickness ratio of the first diffusion layer to the quantum dot layer is 1:3 to 1:5.

12. The photoconversion device of claim 11, wherein a thickness ratio of the first diffusion layer to the quantum dot layer is 1:4.

13. The photoconversion device of claim 1, wherein the quantum dot layer has a thickness of 0.5 to 1.8 microns.

14. The light conversion device of claim 1, wherein the first diffusion layer and the second diffusion layer further comprise an anti-aging agent, the anti-aging agent being one or more of a hindered phenol primary antioxidant, a phosphite secondary antioxidant, and a compounded antioxidant.

15. The photoconversion device of claim 1, wherein the quantum dot layer is a single layer structure and comprises red quantum dots and green quantum dots.

16. The photoconversion device of claim 15, wherein a ratio of the mass of the red quantum dots to the mass of the green quantum dots is 1:2-2:1.

17. The light conversion device of claim 1, further comprising an inorganic halide in one or more of the first diffusion layer, the quantum dot layer, and the second diffusion layer.

18. The light conversion device of claim 17, wherein the inorganic halide is selected from one or more of chloride, bromide, or iodide of potassium, calcium, sodium, cesium, barium, magnesium, aluminum, zinc, iron, cadmium, copper, titanium, manganese, and indium.

19. The photoconversion device of claim 17, wherein the halogen content of the photoconversion device is less than or equal to 1500ppm.

20. The light conversion device of claim 1, wherein the matrix of at least one of the first diffusion layer, the quantum dot layer, and the second diffusion layer is a polymer that blocks water vapor or a polymer that blocks oxygen.

21. The light conversion device of claim 1, wherein at least one of the first diffusion layer, the quantum dot layer, and the second diffusion layer comprises polymer particles that are moisture barrier or polymer particles that are oxygen barrier.

22. The light conversion device of claim 1, wherein the matrix of the first diffusion layer or the second diffusion layer is a polymer that blocks water vapor, and wherein the first diffusion layer or the second diffusion layer further comprises polymer particles that block oxygen.

23. The light conversion device of claim 20, wherein the polymer that blocks water vapor is any one or more of polymethyl methacrylate, polymethyl acrylate, polystyrene, polycarbonate, and methyl methacrylate-styrene copolymer, and the polymer that blocks oxygen is any one or more of polyacrylic acid, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyethylene oxide, styrene-acrylonitrile copolymer, polyacrylonitrile, and polyimide.

24. The light conversion device of claim 21, wherein the polymer particles that block water vapor are any one or more of polymethyl methacrylate particles, polymethyl acrylate particles, polystyrene particles, polycarbonate particles, methyl methacrylate-styrene copolymer particles, and the polymer particles that block oxygen are any one or more of polyacrylic acid particles, polyvinyl alcohol particles, ethylene-vinyl alcohol copolymer particles, polyethylene oxide particles, styrene-acrylonitrile copolymer particles, polyacrylonitrile particles, polyimide particles.

25. The photoconversion device of any of claims 1-17, wherein the quantum dots in the quantum dot layer are distributed as agglomerates in the quantum dot layer.

26. A backlight module comprising an initial light source and a light conversion device according to any one of claims 1 to 25, wherein the light conversion device is a quantum dot diffusion plate.