Light guide plate with diffusion function

Abstract

The invention discloses a light guide plate with a diffusion function, and relates to the field of display equipment, and the light guide plate comprises the following sequentially stacked structures: a light guide substrate layer: a PMMA substrate with a thickness of 0.5-1.5 mm, the surface of which is provided with a micro-pit array structure, the pit diameter is 10-50 [mu] m, the depth is 5-20 [mu] m, and the distribution density is 500-5000 / cm < 2 >; the first diffusion layer is coated on the surface of the light guide base material layer and comprises inorganic scattering particles: nano barium sulfate or silicon dioxide with the particle size of 20-200nm and the mass ratio of 5-15wt%; according to the light guide plate and the preparation method thereof, the long-term dispersion stability of the quantum dots in an ultraviolet curing adhesive system is realized, the balance between high light transmittance and low haze can be kept, the overall optical efficiency and color consistency of the light guide plate are effectively improved, and the strict requirements on a green display technology at present are met.

Description

Technical Field

[0001] The present invention relates to the technical field of display devices, and in particular to a light guide plate with a diffusion function. Background Art

[0002] With the rapid development of display technology, especially the rise of new display technologies such as liquid crystal displays and organic light-emitting diodes, the demand for high-performance light guide plates is increasing. In particular, in the fields of televisions, mobile phones, tablets and large display screens, there are high requirements for color performance, viewing angle consistency and high brightness. Quantum dot technology has developed rapidly in recent years. Its excellent optoelectronic properties have made it show great potential in display technology, especially perovskite quantum dots, which have a wider luminous range and higher quantum efficiency, and are a highlight of future display technology.

[0003] Traditional diffusion films use a PET substrate coated with silica or organic particles, which makes it difficult to balance haze and transmittance. Existing quantum dot diffusion films mostly rely on cadmium-based materials, such as CdSe, which are subject to environmental restrictions and patent barriers. Perovskite quantum dots, such as CsPbX3, have a high fluorescence quantum yield greater than 90% and a narrow emission spectrum with a Full Width Half Maximum (FWHM) of less than 30nm, but are susceptible to corrosion by water and oxygen, and their service life is less than ideal. Summary of the Invention

[0004] (1) Technical problems solved

[0005] In view of the above-mentioned shortcomings of the prior art, the present invention provides a light guide plate with a diffusion function, which can effectively solve the problems of the prior art.

[0006] (2) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] The present invention discloses a light guide plate with a diffusion function, which includes the following stacked structures:

[0009] Light guide substrate layer: PMMA substrate with a thickness of 0.5–1.5 mm, with a micro-pit array structure on its surface. The pit diameter is 10–50 μm, the depth is 5–20 μm, and the distribution density is 500–5000 / cm 2 ;

[0010] The first diffusion layer is coated on the surface of the light guide substrate layer, including:

[0011] Inorganic scattering particles: nano-barium sulfate or silicon dioxide, particle size 20–200 nm, mass proportion 5–15 wt%;

[0012] UV curing adhesive: composed of polyurethane acrylate prepolymer, tripropylene glycol diacrylate and photoinitiator in a weight ratio of 1:1:0.05;

[0013] Quantum dot light-emitting layer: coated on the surface of the first diffusion layer, including:

[0014] Inorganic perovskite quantum dots: chemical formula CsPbX3, particle size 5–8nm, surface coated with SiO2 passivation layer, mass percentage 1–3wt%;

[0015] Scattering particles: nano-alumina, particle size 50–100 nm, mass percentage 8–12 wt%;

[0016] UV curing adhesive: composed of polyurethane acrylate prepolymer, tripropylene glycol diacrylate and photoinitiator in a weight ratio of 1:1:0.05;

[0017] Second diffusion layer: coated on the surface of the quantum dot light-emitting layer, with the same composition as the first diffusion layer, and the mass proportion of scattering particles is adjusted to 3–10wt%.

[0018] Furthermore, the surface of the perovskite quantum dots is modified with a dual ligand layer, the inner layer is oleylamine, and the outer layer is perfluorooctanoic acid. After the ligand modification, the dispersion stability of the quantum dots in the UV-curing adhesive is greater than 6 months.

[0019] Furthermore, the micro-pit structure of the light-guiding substrate layer is a composite grating microlens, which is composed of circular pits and a tapered prism array, with a prism vertex angle of 90°-120° and a height of 10-30 μm.

[0020] Furthermore, 0.1-0.5 wt% of an oxygen barrier is added to the quantum dot light-emitting layer, the oxygen barrier is an ethylene-vinyl alcohol copolymer, and rare earth-doped phosphor is dispersed therein as a blue light conversion compensation material.

[0021] Furthermore, the method for preparing the light guide plate includes the following steps:

[0022] Step 1: Forming a composite microstructure on the surface of a PMMA substrate by femtosecond laser engraving;

[0023] Step 2: Mix the scattering particles, oxygen barrier agent and UV curing adhesive, and prepare the first diffusion layer slurry by ultrasonic-high shear emulsification;

[0024] Step 3: Apply the first diffusion layer slurry to the substrate using a precision micro-gravure coating process with a wet film thickness of 30–50 μm.

[0025] Step 4: Curing with a 365nm UV-LED light source for 5 seconds under a nitrogen atmosphere;

[0026] Step 5: Mix the passivated perovskite quantum dots, scattering particles and UV glue, and control the quantum dot aggregate size to less than 100 nm through a microfluidic chip;

[0027] Step 6: Apply the quantum dot layer slurry to the first diffusion layer using an electrostatic spray deposition process with a film thickness of 15–25 μm.

[0028] Step 7: In an environment with oxygen concentration less than 10ppm, 395nm UV-LED (250mJ / cm 2 ) gradient solidification;

[0029] Step 8: Prepare the second diffusion layer in the same manner as steps 2-4.

[0030] Furthermore, in step 5, 0.3 wt % of a quantum dot surface anchoring agent (ie, a silane coupling agent containing a phosphonic acid group) is added to the quantum dot slurry to enhance the interfacial bonding strength with the curing adhesive.

[0031] Furthermore, the UV curing adhesive adopts a dual curing system, comprising:

[0032] UV curing components: polyurethane acrylate prepolymer, tripropylene glycol diacrylate and photoinitiator;

[0033] Heat curing component: epoxy resin E51 and latent curing agent dicyandiamide are mixed in a ratio of 10:1 and cured at 80°C.

[0034] Furthermore, the gradient curing process in step 7 includes: first 100mJ / cm 2 Pre-curing, then 150mJ / cm 2 Fully cured.

[0035] (3) Beneficial effects

[0036] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0037] 1. By using inorganic perovskite quantum dots as fluorescent conversion materials, it can provide purer and richer color performance in wide color gamut display applications, while avoiding the environmental risks of cadmium-based materials. By introducing dual ligands and silica passivation coating on the surface of quantum dot particles, it not only achieves long-term dispersion stability of quantum dots in UV-curable adhesive systems, but also maintains a balance between high transmittance and low haze, effectively improving the overall optical efficiency and color consistency of the light guide plate, and meeting the strict requirements of current green display technology.

[0038] 2. Through process innovations such as a multi-layer functional coating architecture and a dual-curing system, efficient encapsulation and stable embedding of the quantum dot layer are achieved. The substrate concave structure and double diffusion layer design of the composite grating microlens not only optimize the light path dispersion and extraction efficiency, but also form a physical barrier between different layers. The introduction of microfluidic dispersion, electrostatic spraying, and nitrogen and low-oxygen curing environments ensures that quantum dot agglomeration is minimized and interfacial bonding is maximized. This not only significantly extends the operating life of the light guide plate to tens of thousands of hours, but also combines the high-yield characteristics of industrialized manufacturing such as roll-to-roll and precision coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0040] Figure 1 It is a structural schematic diagram of the present invention;

[0041] Figure 2 Schematic diagram of the top view of the light-guiding substrate layer of the present invention.

[0042] The numbers in the figure represent: 1. first diffusion layer; 2. quantum dot light-emitting layer; 3. second diffusion layer; 4. light-guiding substrate layer. DETAILED DESCRIPTION

[0043] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] like Figure 1-Figure 2 As shown, the present invention is further described below in conjunction with embodiments.

[0045] Example 1

[0046] A light guide plate with a diffusion function according to this embodiment includes:

[0047] A PMMA transparent substrate with a thickness of 1.2 mm was selected, and a composite grating microlens structure was formed on its surface using femtosecond laser engraving. The circular concave dots had a diameter of 30 μm, a depth of 15 μm, and a distribution density of 2000 / cm 2, a composite conical prism array, a prism vertex angle of 100°, and a height of 20 μm, to obtain a light-guiding substrate layer 4.

[0048] 10 wt% of nano-silica (average particle size 80 nm), 0.3 wt% of ethylene-vinyl alcohol copolymer (EVOH, oxygen barrier) and 89.7 wt% of UV-curable adhesive (mixed by polyurethane acrylate prepolymer, tripropylene glycol diacrylate and photoinitiator in a ratio of 1:1:0.05) were weighed and evenly mixed in an ultrasonic high-shear emulsifier to form a first diffusion layer 1 slurry, which was evenly coated on the surface of the light-guiding substrate layer 4 using a precision micro-gravure coating process with a wet film thickness of 40 μm. Subsequently, the mixture was cured for 5 seconds using a 365 nm UV-LED light source under a nitrogen atmosphere.

[0049] 2 wt% of inorganic perovskite quantum dots with double ligand modification (oleylamine / perfluorooctanoic acid), 9 wt% of nano-alumina with a particle size of 80 nm, 0.5 wt% of rare earth doped blue light compensation phosphor and 0.3 wt% of silane coupling agent containing phosphonic acid group were mixed with 88.2 wt% of UV curable adhesive. The size of quantum dot agglomerates was controlled to be less than 80 nm by microfluidic chip. The agglomerates were coated on the first diffusion layer 1 by electrostatic spray deposition process with a film thickness of 20 μm. In an environment with an oxygen concentration of less than 10 ppm, the agglomerates were first exposed to 395 nm UV-LED 100 mJ / cm 2 Pre-curing, then 150mJ / cm 2 Fully cured.

[0050] 5wt% nano-barium sulfate (particle size 50nm) and 95wt% UV-curing glue were weighed, and the second diffusion layer 3 slurry was prepared by ultrasonic emulsification. It was coated on the surface of the quantum dot light-emitting layer 2 with a wet film thickness of 40μm. It was also cured for 5 seconds under a 365nm UV-LED in a nitrogen atmosphere to obtain a composite light guide plate with diffusion function.

[0051] Performance indicators:

[0052] Haze: 92.3%

[0053] Total Transmittance: 65.2%

[0054] Color gamut coverage (NTSC): 115.0%;

[0055] Thermal aging (85°C × 1000h);

[0056] Light transmittance retention: 64.9% (initial 65.2%);

[0057] Haze retention: 92.1%;

[0058] Appearance: No yellowing, no blistering, no delamination.

[0059] Example 2

[0060] A light guide plate with a diffusion function according to this embodiment includes:

[0061] A PMMA substrate with a thickness of 0.8 mm was selected, and a composite microstructure was formed on the surface using a femtosecond laser. The circular pits had a diameter of 20 μm, a depth of 10 μm, and a distribution density of 3500 / cm 2 , the cone prism array has a vertex angle of 120° and a height of 15 μm, to obtain a light guide substrate layer 4;

[0062] Take 8wt% nano-barium sulfate (particle size 100nm), 0.2wt% EVOH, and 91.8wt% UV curing adhesive (the ratio is the same as above), stir evenly and then ultrasonically disperse to make the first diffusion layer 1 slurry. Use micro-gravure to spread the glue to a wet film thickness of 35μm, and cure it with 365nm UV-LED under nitrogen atmosphere for 5 seconds;

[0063] 1.5wt% (Cl / Br mixed) perovskite quantum dots (5nm, oleylamine / perfluorooctanoic acid double layer modified), 10wt% nano-alumina (particle size 60nm), 0.2wt% rare earth doped phosphor, 0.3wt% phosphonic acid group-containing silane coupling agent, and 88wt% UV curing adhesive were mixed. The quantum dot agglomeration size was controlled to be less than 90nm by microfluidic chip, and the film was coated on the first diffusion layer 1 by electrostatic spraying with a film thickness of 18μm. Under an oxygen concentration of less than 10ppm, a 395nm UV-LED with a 100mJ / cm 2 Pre-curing, after 150mJ / cm 2 Fully cured;

[0064] 4 wt% nano-silica (particle size 120 nm) and 96 wt% UV-curing glue were weighed, ultrasonically dispersed, and the second diffusion layer 3 slurry was coated on the surface of the quantum dot light-emitting layer 2 with a wet film thickness of 35 μm. 365 nm UV-LED was used for curing for 5 seconds to obtain the finished product.

[0065] Performance indicators:

[0066] Haze: 90.8%;

[0067] Light transmittance: 66.0%;

[0068] Color gamut coverage (NTSC): 114.7%;

[0069] Thermal aging (85°C × 1000h);

[0070] Light transmittance retention: 65.5%;

[0071] Haze retention: 90.5%;

[0072] Appearance: No yellowing, no blistering, no delamination.

[0073] Example 3

[0074] A light guide plate with a diffusion function according to this embodiment includes:

[0075] A PMMA substrate with a thickness of 1.5 mm was selected, and the surface was engraved with a composite microstructure by femtosecond laser. The circular pits had a diameter of 50 μm, a depth of 20 μm, and a density of 1000 / cm 2 , the cone prism array has a vertex angle of 95° and a height of 30 μm, to prepare a light guide substrate layer 4;

[0076] Prepare a slurry by ultrasonically dispersing 15 wt% nano-silica (200 nm particle size), 0.5 wt% EVOH, and 84.5 wt% UV-curable adhesive (polyurethane acrylate prepolymer: tripropylene glycol diacrylate: photoinitiator = 1:1:0.05). Micro-gravure coating is performed to a wet film thickness of 50 μm and cured for 5 seconds using a 365 nm UV-LED under a nitrogen atmosphere.

[0077] 3wt% perovskite quantum dots (surface oleylamine / perfluorooctanoic acid modified, particle size 8nm, Cl / I combination type), 8wt% nano-alumina (particle size 100nm), 0.1wt% rare earth doped phosphor, 0.3wt% phosphonic acid group-containing silane coupling agent, mixed with 88.6wt% UV curing glue, microfluidic chip control quantum dot agglomerate size <100nm. Electrostatic spray deposition on the first diffusion layer 1, the film thickness of 25μm. In an environment with an oxygen concentration of <10ppm, 395nm UV-LED is used in two steps of gradient curing (100mJ / cm 2 Pre-curing, 150mJ / cm 2 Fully cured);

[0078] Take 10wt% nano-barium sulfate (particle size 90nm) and 90wt% UV curing glue, ultrasonically disperse them evenly, prepare the second diffusion layer 3 slurry, apply it to the surface of the quantum dot light-emitting layer 2, the wet film thickness is 50μm, and cure it for 5 seconds with 365nm UV-LED to obtain the target product.

[0079] Performance indicators:

[0080] Haze: 93.1%;

[0081] Light transmittance: 64.7%;

[0082] Color gamut coverage (NTSC): 116.2%;

[0083] Thermal aging (85°C × 1000h);

[0084] Light transmittance retention: 64.3%;

[0085] Haze retention: 92.9%;

[0086] Appearance: No yellowing, no blistering, no delamination.

[0087] In summary, the present invention achieves not only a high haze of about 92%, a high transmittance of about 65% and an NTSC wide color gamut coverage of more than 115% by precisely engraving a composite microstructure on a PMMA substrate and superimposing a first diffusion layer 1, a second diffusion layer 2 and a quantum dot light-emitting layer 2, but also no yellowing, blistering or delamination after high-temperature aging, and has both excellent optical properties and thermal aging stability, and can meet the strict requirements of the backlight module for light uniformity and color performance.

[0088] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A light guide plate with a diffusion function, characterized in that: The light guide plate includes the following stacked structures: Light guide substrate layer: PMMA substrate with a thickness of 0.5–1.5 mm, with a micro-pit array structure on its surface. The pit diameter is 10–50 μm, the depth is 5–20 μm, and the distribution density is 500–5000 / cm 2 ; The first diffusion layer is coated on the surface of the light guide substrate layer, including: Inorganic scattering particles: nano-barium sulfate or silicon dioxide, particle size 20–200 nm, mass proportion 5–15 wt%; UV curing adhesive: composed of polyurethane acrylate prepolymer, tripropylene glycol diacrylate and photoinitiator in a weight ratio of 1:1:0.05; Quantum dot light-emitting layer: coated on the surface of the first diffusion layer, including: Inorganic perovskite quantum dots: chemical formula CsPbX3, particle size 5–8nm, surface coated with SiO2 passivation layer, mass percentage 1–3wt%; Scattering particles: nano-alumina, particle size 50–100 nm, mass percentage 8–12 wt%; UV curing adhesive: composed of polyurethane acrylate prepolymer, tripropylene glycol diacrylate and photoinitiator in a weight ratio of 1:1:0.05; Second diffusion layer: coated on the surface of the quantum dot light-emitting layer, with the same composition as the first diffusion layer, and the mass proportion of scattering particles is adjusted to 3–10wt%.

2. The light guide plate with diffusion function according to claim 1, characterized in that: The surface of the perovskite quantum dots is modified with a double ligand layer, the inner layer is oleylamine and the outer layer is perfluorooctanoic acid. After the ligand modification, the dispersion stability of the quantum dots in the UV-curing adhesive is greater than 6 months.

3. The light guide plate with diffusion function according to claim 1, characterized in that: The micro-pitted structure of the light-guiding substrate layer is a composite grating microlens, which is composed of a composite of circular pits and a tapered prism array, with a prism vertex angle of 90°-120° and a height of 10-30 μm.

4. The light guide plate with diffusion function according to claim 1, characterized in that: 0.1-0.5 wt% of an oxygen barrier is added to the quantum dot light-emitting layer, the oxygen barrier is an ethylene-vinyl alcohol copolymer, and rare earth-doped phosphor is dispersed therein as a blue light conversion compensation material.

5. The light guide plate with diffusion function according to claim 1, characterized in that: The method for preparing the light guide plate comprises the following steps: Step 1: Forming a composite microstructure on the surface of a PMMA substrate by femtosecond laser engraving; Step 2: Mix the scattering particles, oxygen barrier agent and UV curing adhesive, and prepare the first diffusion layer slurry by ultrasonic high shear emulsification; Step 3: Apply the first diffusion layer slurry to the substrate using a precision micro-gravure coating process with a wet film thickness of 30–50 μm. Step 4: Curing with a 365nm UV-LED light source for 5 seconds under a nitrogen atmosphere; Step 5: Mix the passivated perovskite quantum dots, scattering particles and UV glue, and control the quantum dot aggregate size to less than 100 nm through a microfluidic chip; Step 6: Apply the quantum dot layer slurry to the first diffusion layer using an electrostatic spray deposition process with a film thickness of 15–25 μm. Step 7: In an environment with oxygen concentration less than 10ppm, 395nm UV-LED (250mJ / cm 2 ) gradient solidification; Step 8: Prepare the second diffusion layer in the same manner as steps 2-4.

6. The light guide plate with diffusion function according to claim 5, characterized in that: In step 5, 0.3 wt% of a quantum dot surface anchoring agent is added to the quantum dot slurry.

7. The light guide plate with diffusion function according to claim 5, characterized in that: The UV curing adhesive adopts a dual curing system, comprising: UV curing components: polyurethane acrylate prepolymer, tripropylene glycol diacrylate and photoinitiator; Heat curing component: epoxy resin E51 and latent curing agent dicyandiamide are mixed in a ratio of 10:1 and cured at 80°C.

8. The light guide plate with diffusion function according to claim 5, characterized in that: The gradient curing process in step 7 includes: first, 100 mJ / cm 2 Pre-curing, then 150mJ / cm 2 Fully cured.

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