A method for preparing a large-area flexible scintillator screen based on doctor-blade forming technology

Abstract

The application relates to the technical field of screens and discloses a preparation method of a large-area flexible scintillator screen based on a doctor-blade forming technology, which comprises the following steps: S1, providing a flexible transparent base material; S2, coating a scintillator slurry on the surface of the base material, wherein the slurry comprises scintillator particles, a polymer matrix and an organic solvent; S3, adopting the doctor-blade forming technology, and scraping the slurry into a wet film with a uniform thickness through a doctor blade with an adjustable gap; S4, gradient drying of the wet film to evaporate the solvent, so as to form a flexible scintillator functional layer; and S5, covering a protective layer on the surface of the functional layer to package into a screen structure. Through the combined use of three synergistic modification technologies of argon plasma treatment on the surface of the base material, modification of the scintillator particles by a silane coupling agent and design of a multimodal particle size distribution, the interface light scattering loss can be reduced, the visible light transmittance and the X-ray conversion efficiency can be improved, and the requirements of high-precision imaging scenes such as medical CT on optical uniformity and resolution can be met.

Description

Technical Field

[0001] This invention relates to the field of screen technology, specifically to a method for preparing a large-area flexible scintillator screen based on a scraping coating technique. Background Technology

[0002] A screen is an electrical device used to display images and colors, also known as a display screen. Its size is measured in inches based on its diagonal length, and common aspect ratios include 4:3, 16:10, and 16:9. Screens include CRT displays, LCD screens, and LED screens, and are widely used in homes, cinemas, advertising, computers, mobile phones, and other scenarios. Among them, flexible scintillator screens are a special type of screen, mainly used in the field of X-ray indirect imaging. They can convert high-energy X-ray radiation into low-energy ultraviolet / visible photons, adapt to non-planar surfaces, solve the distortion and vignetting problems of rigid scintillator screens, and achieve high-quality imaging of non-planar objects. At the same time, they can also alleviate the vignetting problem caused by uneven spatial distribution of X-ray dose on large-area objects.

[0003] Existing flexible scintillator screens contain scintillator particles such as cesium iodide and gadolinium oxysulfide with a metal oxide passivation layer on their surface. This layer has poor compatibility with polymer matrices such as polyvinylidene fluoride and polymethyl methacrylate. When the screen is bent, the particles fall off, generating light scattering points. This limits the imaging resolution to 3-4 line pairs / mm, which cannot meet the requirements for high resolution. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing a large-area flexible scintillator screen based on a scraping coating technique, which solves the problem that the presence of a metal oxide passivation layer on the surface of the scintillator particles in the flexible scintillator screen prevents it from meeting high-resolution requirements.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a large-area flexible scintillator screen based on a coating molding technique, comprising the following steps:

[0006] S1. Provide flexible transparent substrate;

[0007] S2. Coating a scintillator slurry onto the surface of a substrate, wherein the slurry comprises scintillator particles, a polymer matrix and an organic solvent, in a mass ratio of 5:3:2.

[0008] S3. Using scraping coating technology, the slurry is scraped into a wet film of uniform thickness by an adjustable gap scraper.

[0009] S4. Gradient drying of the wet film to evaporate the solvent to form a flexible scintillator functional layer;

[0010] S5. Cover the surface of the functional layer with a protective layer and encapsulate it into a screen structure.

[0011] Through the above technical solution, in the fabrication of the flexible scintillator screen, in step S1, a polyethylene terephthalate or polyethylene naphthalate film with a thickness of 80-200 micrometers and a surface roughness Ra not exceeding 0.1 μm is selected as the flexible transparent substrate. Its high light transmittance and low coefficient of thermal expansion ensure the dimensional stability of subsequent coatings. Furthermore, the substrate surface is subjected to plasma treatment or coated with a silica nanolayer to enhance the wettability of the slurry. In step S2, scintillator particles with a particle size of 1-10 micrometers are mixed with a polymer matrix at a mass ratio of 40%-65%. Mix the ingredients, adding N-methylpyrrolidone or cyclohexanone as a solvent, along with 1%-5% (w / w) of dioctyl phthalate plasticizer and 0.5%-2% of polyethylene glycol dispersant. Use ball milling or high-speed shearing at 2000-4000 rpm for 30-60 minutes to achieve uniform dispersion of the slurry, controlling the viscosity at 500-5000 mPa·s to balance the leveling properties of the coating with the risk of particle settling. In step S3, using a stainless steel scraper with a gap of 0.1-2.0 mm, at a speed of 5-20 cm / min, while preheating to 3... Coating is performed on substrates at 0-60℃. Preheating reduces the viscosity of the slurry, promoting uniform wet film spreading. Simultaneously, ambient humidity is controlled at 30%-60%RH to prevent surface skinning. Step S4 employs a three-stage gradient drying process: first, treatment at 40℃ for 15-20 minutes, followed by treatment at 60℃ for 25-35 minutes, and finally treatment at 80℃ for 40-50 minutes. Gradual temperature increases slow solvent evaporation, preventing stress concentration and cracking of the film. Vacuum assistance or nitrogen protection is also used to reduce solvent residue to below 0.1%. Step S5 involves coating the functional layer... A polydimethylsiloxane protective layer is spin-coated on the surface, and a 100-500 nm silica gradient refractive index antireflective layer is deposited outside the protective layer using the sol-gel method, which increases the visible light transmittance to over 92%. The resulting flexible scintillator screen has a functional layer thickness of 50-500 micrometers, a visible light transmittance of no less than 85%, and exhibits no cracking after 1000 bends at a 5 mm bending radius. The uniformity deviation of light output during X-ray excitation does not exceed 5%, and the performance remains stable after thermal cycling tests from -20℃ to 80℃, demonstrating good mechanical toughness and environmental adaptability.

[0012] Preferably, the polymer matrix in S2 is selected from at least one of polyvinylidene fluoride, polymethyl methacrylate, and polyvinyl butyral, and the organic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, and cyclohexanone. The molecular weight of polyvinylidene fluoride is 500,000-800,000, the molecular weight of polyvinyl butyral is 30,000-50,000, and the boiling point of the solvent is in the range of 150-250°C. The solid content of the slurry is 45%-75%, and the viscosity is controlled at 500-5000 mPa·s at 25°C.

[0013] Preferably, the scintillator particles are at least one of cesium iodide, cadmium tungstate, and gadolinium oxysulfide. The particle size distribution of the particles is unimodal or multimodal, with the main peak particle size being 3-8 micrometers and the particle size dispersion index being ≤0.3. The mass fraction of the scintillator particles in the slurry is 50%-60%, and the particle surface is pretreated with a coupling agent.

[0014] Preferably, in step S3, the blade gap adjustment range is 0.2-1.5 mm, the scraping speed is 8-15 cm / min, the blade material is one of stainless steel and polytetrafluoroethylene, the substrate preheating temperature is controlled at 40-50℃ and temperature is controlled by an infrared heating plate, and the scraping environment humidity is controlled at 30%-60%RH.

[0015] Preferably, the S4 gradient drying includes three stages:

[0016] First stage: Dry at 40℃±2℃ for 15-20 minutes, with a humidity of 50%-70%RH;

[0017] Second stage: Dry at 60℃±2℃ for 25-35 minutes, with a humidity of 30%-50%RH;

[0018] Third stage: Dry at 80℃±2℃ for 40-50 minutes, humidity ≤20%RH;

[0019] During the drying process, a stepped heating rate of ≤5℃ / min is used, and nitrogen gas is introduced for protection.

[0020] Preferably, the protective layer is either a biaxially oriented polyethylene terephthalate film or a polydimethylsiloxane coating, wherein the surface of the biaxially oriented polyethylene terephthalate film is corona-treated, and the polydimethylsiloxane coating is formed by either spin coating or dip coating. The protective layer has a thickness of 20-30 micrometers, a light transmittance of ≥92%, and a surface hardness of ≥3H.

[0021] Preferably, the flexible transparent substrate is either polyethylene terephthalate or polyethylene naphthalate, the glass transition temperature Tg of the flexible transparent substrate is ≥80℃, the substrate thickness is 100-150 micrometers, the surface is plasma treated, the substrate transmittance is ≥88%, the haze is ≤2%, and the coefficient of thermal expansion is ≤20ppm / ℃.

[0022] Preferably, the flexible scintillator functional layer has a thickness of 100-300 micrometers, a visible light transmittance of ≥85%, a refractive index of 1.5-1.6, can withstand repeated bending with a bending radius of ≤3mm, and can maintain stable performance within a temperature range of -20℃ to 80℃.

[0023] Preferably, the slurry further comprises the following additives:

[0024] Plasticizer: Dioctyl phthalate, mass fraction 2%-4%;

[0025] Dispersant: Polyethylene glycol, mass fraction 0.8%-1.5%;

[0026] Defoamer: polydimethylsiloxane or mineral oil, mass fraction 0.1%-0.5%;

[0027] The total mass fraction of the additives is ≤6%.

[0028] Preferably, the screen structure includes an anti-reflective layer disposed on the outer surface of the protective layer, the anti-reflective layer being a silicon dioxide nano-coating with a thickness of 100-500 nm.

[0029] This invention provides a method for fabricating a large-area flexible scintillator screen based on a coating technology. It has the following advantages:

[0030] 1. This invention combines three synergistic modification technologies: argon plasma treatment of the substrate surface, silane coupling agent modification of scintillator particles, and multi-peak particle size distribution design. Among them, plasma treatment increases the surface energy of the substrate from 35-40 mN / m to 50-55 mN / m, reduces the wetting angle to ≤15°, and enhances the spreadability of the slurry. The hydrolysis reaction of the coupling agent forms covalently grafted organic long chains on the particle surface, increasing the shear strength of the particle-matrix interface by 30-50%. The multi-peak particle size distribution optimizes the particle packing structure, achieving a filling density of ≥95% of the theoretical value, reducing defects in the light transmission path, thereby reducing interfacial light scattering loss, improving visible light transmittance and X-ray conversion efficiency, and achieving an imaging resolution of ≥5 line pairs / mm, meeting the requirements of optical uniformity and resolution for high-precision imaging scenarios such as medical CT.

[0031] 2. This invention adds 2-4% dioctyl phthalate plasticizer, whose ester groups form a hydrogen bond network with the polar groups of the polyvinylidene fluoride / polymethyl methacrylate matrix, reducing the glass transition temperature by 10-15℃ and improving the intrinsic flexibility of the film layer. At the same time, a three-stage gradient drying combined with vacuum assistance or nitrogen protection is used to keep the solvent residue ≤0.1%, eliminating the risk of microcracks caused by drying stress. The thermal expansion coefficients of the substrate and the functional layer are synergistically controlled at ≤20ppm / ℃, ensuring uniform distribution of interfacial stress during bending. After 2000 bends, the light transmittance retention rate is ≥95%. Thus, the prepared flexible scintillator functional layer can withstand 5000 repeated bends at a bending radius of 3 mm without cracking, while traditional constant temperature drying and plasticizer-free processes fail after 200 bends, improving mechanical stability by 25 times.

[0032] 3. This invention forms an environmental erosion barrier by using a 20-30 micrometer polydimethylsiloxane coating or corona-treated polyethylene terephthalate film, and uses a vacuum gradient drying process to reduce solvent residue to ≤0.1%, eliminating the risk of thermal stress cracking. At the same time, a 100-500 nanometer silica anti-reflective layer is constructed using the sol-gel method, forming a porous gradient structure with a pore size of 10-50 nanometers, so that the light reflectivity is ≤0.8%, reducing interface light loss. Thus, it can ensure that the light output and transmittance of the flexible screen decrease by ≤2% after 100 thermal cycles from -30℃ to 100℃, and the performance decreases by <3% after immersion in water for 72 hours, ensuring that the flexible scintillator screen can work normally in extreme environments. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating the fabrication process of a large-area flexible scintillator screen based on a scraping coating technique proposed in this invention. Detailed Implementation

[0034] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Please see the appendix Figure 1 This invention provides a method for fabricating a large-area flexible scintillator screen based on a scraping coating technique, comprising the following steps:

[0036] S1. Provide flexible transparent substrate;

[0037] S2. Coat the substrate surface with a scintillator slurry, the slurry containing scintillator particles, a polymer matrix and an organic solvent, in a mass ratio of 5:3:2.

[0038] S3. Using scraping coating technology, the slurry is scraped into a wet film of uniform thickness by an adjustable gap scraper.

[0039] S4. Gradient drying of the wet film to evaporate the solvent to form a flexible scintillator functional layer;

[0040] S5. Cover the surface of the functional layer with a protective layer and encapsulate it into a screen structure.

[0041] Specifically, in S1, a polyethylene terephthalate or polyethylene naphthalate film with a thickness of 80-200 micrometers and a surface roughness Ra≤0.1μm is selected as a flexible transparent substrate. Its high light transmittance (≥88%) and low coefficient of thermal expansion (≤20ppm / ℃) ensure the dimensional stability of subsequent coatings. The substrate surface is plasma-treated or coated with a silica nanolayer to enhance the wettability of the slurry. In S2, scintillator particles with a particle size of 1-10 micrometers are mixed with a polymer matrix at a mass ratio of 40%-65%, and N-methylpyrrolidone or cyclohexanone is added as... Solvents are added, along with 1%-5% by mass of dioctyl phthalate plasticizer and 0.5%-2% by mass of polyethylene glycol dispersant. The mixture is then treated by ball milling or high-speed shearing at 2000-4000 rpm for 30-60 minutes to achieve uniform dispersion of the slurry. Simultaneously, the viscosity is controlled at 500-5000 mPa·s to balance the leveling properties of the coating and the risk of particle settling. In S3, a stainless steel doctor blade with a gap of 0.1-2.0 mm is used to coat the substrate preheated to 30-60℃ at a speed of 5-20 cm / min. The preheating temperature reduces the slurry viscosity and promotes uniform wet film formation. The film is evenly spread while maintaining an ambient humidity of 30%-60%RH to prevent surface skin formation. S4 employs a three-stage gradient drying process: first, treatment at 40℃ for 15-20 minutes, followed by treatment at 60℃ for 25-35 minutes, and finally treatment at 80℃ for 40-50 minutes. This gradual temperature increase reduces the solvent evaporation rate, preventing stress concentration and cracking of the film. Combined with vacuum assistance (pressure -0.08~-0.1MPa) or nitrogen protection, solvent residue is reduced to ≤0.1%. In S5, a 10-50 micrometer thick biaxially stretched film is applied to the functional layer surface. A PET film or spin-coated polydimethylsiloxane protective layer is used, and a 100-500 nm silica gradient refractive index antireflective layer (refractive index 1.2-1.5) is deposited on the outside of the protective layer using the sol-gel method, which increases the visible light transmittance to ≥92%. The resulting flexible scintillator screen has a functional layer thickness of 50-500 micrometers, a visible light transmittance of ≥85%, and exhibits no cracking after 1000 bends at a bending radius of 5 mm. The uniformity deviation of light output under X-ray excitation is ≤5%, and the performance does not degrade after thermal cycling tests from -20℃ to 80℃, indicating that it has high mechanical toughness and environmental stability.

[0042] See appendix Figure 1In S2, the polymer matrix is ​​selected from at least one of polyvinylidene fluoride, polymethyl methacrylate and polyvinyl butyral, and the organic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide and cyclohexanone. The molecular weight of polyvinylidene fluoride is 500,000-800,000, the molecular weight of polyvinyl butyral is 30,000-50,000, and the boiling point of the solvent is in the range of 150-250℃. The solid content of the slurry is 45%-75%, and the viscosity is controlled at 500-5000 mPa·s at 25℃.

[0043] Specifically, in S2, the selection of the polymer matrix is ​​based on its excellent mechanical properties, chemical stability, and compatibility with scintillator particles. Polyvinylidene fluoride (PVDF), due to its high chemical resistance and good mechanical strength, is suitable for forming a stable film layer on a flexible substrate. Polymethyl methacrylate (PMMA) has excellent transparency and easy processing properties, making it suitable as a matrix material. Polyvinyl butyral, due to its good adhesion and toughness, can enhance the adhesion of the film layer while controlling the viscosity at 500-5000 mPa·s, ensuring the fluidity of the slurry and preventing particle sedimentation. The organic solvents are selected from N-methylpyrrolidone, N,N-dimethylformamide, and cyclohexanone. These solvents have a boiling point range of 150-250℃, which can meet the requirements of the gradient drying process and avoid substrate deformation or functional layer cracking at high temperatures. N-methylpyrrolidone and N,N-dimethylformamide have strong dissolving capabilities and can fully dissolve the polymer matrix, while cyclohexanone, due to its low surface tension, helps to improve the wetting properties of the slurry. The process promotes uniform coating of the substrate surface. The solid content of the slurry is controlled within the range of 45%-75%, ensuring sufficient solid components in the slurry to form a dense functional layer without causing poor flowability or uneven coating due to excessive solid content. By optimizing the matching of solid content and viscosity, the slurry can achieve uniform spreading during the coating process, avoiding the accumulation of air bubbles or particles. In addition, 1%-5% by mass of plasticizer (dioctyl phthalate) is added to the slurry to improve the flexibility and bending resistance of the film layer, and 0.5%-2% by mass of dispersant (polyethylene glycol) is added to improve the dispersion of scintillator particles in the slurry and prevent particle agglomeration. Through the above process optimization, the obtained slurry exhibits good leveling and uniformity during the coating process. The final prepared flexible scintillator functional layer has excellent visible light transmittance (≥85%) and mechanical stability (able to withstand repeated bending with a bending radius of ≤5mm). At the same time, it exhibits uniform light output characteristics under X-ray excitation, proving the feasibility and efficiency of the preparation method.

[0044] See appendix Figure 1The scintillator particles are at least one of cesium iodide, cadmium tungstate, and gadolinium oxysulfate. The particle size distribution is unimodal or multimodal, with the main peak particle size being 3-8 micrometers and the particle size dispersion index being ≤0.3. The mass fraction of scintillator particles in the slurry is 50%-60%, and the particle surface is pretreated with a coupling agent.

[0045] Specifically, the scintillator particles are selected from at least one of cesium iodide, cadmium tungstate, or gadolinium oxysulfate. The particle surface pretreatment uses a silane coupling agent (KH-550). In a water-ethanol solution at pH 8-10, a hydrolysis reaction causes the silanol groups of the coupling agent to form covalent bonds with the metal oxides on the particle surface. Simultaneously, long-chain organic amino groups from KH-550 are introduced onto the particle surface, enhancing the interfacial bonding force with the polymer matrix and increasing the particle-matrix interfacial shear strength by 30%-50%. The mass fraction of scintillator particles in the slurry is controlled at 50%-60%, verified through mass fraction gradient experiments (40%, 50%, 60%, 70%), confirming that this range can achieve high scintillation efficiency (light yield ≥ 4). The slurry exhibited a particle size distribution of 0,000 photons / MeV and good flowability (viscosity ≤3000 mPa·s). During implementation, zirconia ball milling was used with a ball-to-particle ratio of 5:1, a rotation speed of 2000 rpm, and a time of 4 hours to achieve uniform particle dispersion. Ultrasonic treatment was then applied to further eliminate agglomeration. After coating, the pretreated slurry showed a light output uniformity deviation of ≤3% (under X-ray excitation), and no particles fell off after 1000 bends (radius 5 mm), indicating significant strengthening of interfacial bonding. The optimized multi-peak particle size distribution resulted in a functional layer density exceeding 95% of the theoretical value, improving X-ray imaging resolution to ≥5 lp / mm, meeting the requirements of high-precision medical imaging and industrial non-destructive testing.

[0046] See appendix Figure 1 In S3, the blade gap adjustment range is 0.2-1.5 mm, the scraping speed is 8-15 cm / min, the blade material is either stainless steel or polytetrafluoroethylene, the substrate preheating temperature is controlled at 40-50℃ and temperature is controlled by infrared heating plate, and the scraping environment humidity is controlled at 30%-60%RH.

[0047] Specifically, in S3, the doctor blade gap adjustment range is 0.2-1.5 mm, preferably 0.5-1.0 mm, to ensure uniform wet film thickness and dense particle distribution; the doctor blade speed is controlled at 8-15 cm / min to balance the uniformity of slurry spreading with the surface tension of the substrate, avoiding discontinuous film layer due to excessive speed or particle settling due to excessive slow speed; the doctor blade material is selected from stainless steel or polytetrafluoroethylene (PTFE). The former has high rigidity and excellent wear resistance, suitable for high-viscosity slurries; the latter, due to its chemical inertness and low coefficient of friction, is suitable for coating highly sensitive materials. The substrate preheating temperature is controlled at 40-50℃, and uniform temperature control is achieved through an infrared heating plate to reduce slurry viscosity and promote coating. The substrate surface is activated, thereby enhancing the wettability and adhesion between the slurry and the substrate. At the same time, the ambient humidity is controlled at 30%-60%RH to avoid skinning or bubble formation on the slurry surface, ensuring the leveling of the slurry and the density of the film during the coating process. By optimizing the doctor blade gap, speed, and temperature and humidity parameters, the resulting wet film thickness deviation is ≤5%, the particle distribution uniformity is ≥95%, and there are no obvious defects such as bubbles or scratches on the film surface. This process can prepare flexible scintillator functional layers with a thickness of 50-500 micrometers, visible light transmittance ≥85%, and no cracking after repeated bending 1000 times at a bending radius of 5mm, indicating that the functional layer has excellent mechanical stability and optical performance.

[0048] See appendix Figure 1 S4 gradient drying consists of three stages:

[0049] First stage: Dry at 40℃±2℃ for 15-20 minutes, with a humidity of 50%-70%RH;

[0050] Second stage: Dry at 60℃±2℃ for 25-35 minutes, with a humidity of 30%-50%RH;

[0051] Third stage: Dry at 80℃±2℃ for 40-50 minutes, humidity ≤20%RH;

[0052] During the drying process, a stepped heating rate of ≤5℃ / min is used, and nitrogen gas is introduced for protection.

[0053] Specifically, in S4, the gradient drying process is divided into three stages. The first stage is set at 40℃±2℃, with a drying time of 15-20 minutes and humidity controlled at 50%-70%RH. This stage aims to gently initiate solvent evaporation, preventing cracking or shrinkage stress on the wet film surface due to rapid drying. Humidity control helps balance the solvent evaporation rate, avoiding particle accumulation or uneven film layer caused by excessively rapid local drying. The second stage increases the temperature to 60℃±2℃, extends the drying time to 25-35 minutes, and reduces the humidity to 30%-50%RH. This stage accelerates solvent evaporation by gradually increasing the temperature while reducing humidity to promote a more efficient drying process and reduce the impact of residual moisture on film performance. The temperature increase ensures sufficient cross-linking of the polymer matrix in the slurry, forming a stable three-dimensional network structure and enhancing the mechanical strength and chemical stability of the film layer. The third stage... The temperature is increased to 80℃±2℃, the drying time is extended to 40-50 minutes, and the humidity is controlled at ≤20%RH. The goal of this stage is to completely remove residual solvent from the wet film, ensuring low solvent residue (≤0.1%) in the final film layer, thereby improving its optical performance and mechanical durability. During the drying process, a stepped heating rate of ≤5℃ / min is used to avoid film cracking or performance degradation caused by sudden temperature changes. At the same time, nitrogen gas is introduced for protection to ensure the inertness of the drying environment, prevent oxygen from oxidizing the polymer or scintillator particles in the slurry, and avoid oxidative degradation under high temperature conditions. Through the above optimized process, the visible light transmittance of the obtained flexible scintillator functional layer is ≥85%, the film thickness deviation is ≤5%, and no cracking occurs after 1000 repeated bends at a bending radius of 5mm. X-ray excitation tests show that its light output uniformity deviation is ≤3%, and the performance of the functional layer is improved.

[0054] See appendix Figure 1 The protective layer is either a biaxially oriented polyethylene terephthalate film or a polydimethylsiloxane coating. The surface of the biaxially oriented polyethylene terephthalate film is treated with corona discharge, and the polydimethylsiloxane coating is formed by either spin coating or dip coating. The thickness of the protective layer is 20-30 micrometers, the light transmittance is ≥92%, and the surface hardness is ≥3H.

[0055] Specifically, the protective layer uses biaxially oriented polyethylene terephthalate (PET) film or polydimethylsiloxane (PDS) coating. The surface of the PET film is corona-treated, introducing polar groups such as hydroxyl and carboxyl groups onto the film surface through high-energy electron bombardment, increasing the surface energy to ≥45 mN / m, compared to 35-40 mN / m before treatment, thus enhancing the adhesion between the protective layer and the scintillator functional layer. The thickness is controlled at 20-30 micrometers to balance light transmittance and scratch resistance, and the heat shrinkage rate is ≤1.5% (150℃ / 30 minutes) to ensure dimensional stability under high-temperature processes. The methylsiloxane coating is applied using spin coating (1000-3000 rpm, 30-60 seconds) or dip coating (5-20 mm / s). The prepolymer and curing agent are mixed at a mass ratio of 10:1 and then heat-cured at 80-100℃ for 30-60 minutes to form a cross-linked network structure with a thickness of 20-30 micrometers. The coating hardness is increased to 3H by adding 1%-3% by mass of nano-silica, while maintaining a light transmittance of ≥92%. Its low surface energy (≤25 mN / m) imparts hydrophobic properties to the surface (water contact angle ≥110°), which can inhibit the adhesion of pollutants.

[0056] See appendix Figure 1 The flexible transparent substrate is either polyethylene terephthalate or polyethylene naphthalate. The glass transition temperature (Tg) of the flexible transparent substrate is ≥80℃, the substrate thickness is 100-150 micrometers, the surface is plasma treated, the light transmittance of the substrate is ≥88%, the haze is ≤2%, and the coefficient of thermal expansion is ≤20ppm / ℃.

[0057] Specifically, the flexible transparent substrate is made of polyethylene terephthalate or polyethylene naphthalate, with a glass transition temperature ≥80℃ to ensure no thermal deformation occurs during subsequent coating, drying, and use. The substrate thickness is controlled at 100-150 micrometers. Three-point bending tests show that a thickness <100 micrometers results in insufficient puncture resistance, while >150 micrometers leads to decreased flexibility. The substrate surface is treated with oxygen or argon plasma at a power of 50-100W for 30-60 seconds and a vacuum of 10-50Pa. High-energy particle bombardment generates polar groups such as hydroxyl and carboxyl groups, increasing the surface energy from 35-40 mN / m to 50-55 mN / m, thus improving the wetting angle of the slurry. ≤15°, enhancing the interfacial adhesion with the scintillator functional layer; the orderly arrangement of molecular chains is achieved through raw material purification and biaxial stretching processes, reducing light scattering, resulting in a substrate transmittance ≥88% and haze ≤2%; the addition of 1%-3% by mass of silica nanoparticles (particle size 50-100nm) ensures thermal expansion matching with the functional layer, with a thermal expansion coefficient ≤20ppm / ℃, and no delamination or warping at the interface after 100 cycles of thermal cycling from -20℃ to 80℃; the substrate retains a transmittance of ≥95% after 2000 bends at a bending radius of 5mm, with no microcracks on the surface, and light output attenuation ≤1.5% under X-ray excitation, meeting the mechanical and environmental stability requirements of high-precision flexible imaging devices.

[0058] See appendix Figure 1 The flexible scintillator has a functional layer thickness of 100-300 micrometers, a visible light transmittance of ≥85%, a refractive index matching of 1.5-1.6, can withstand repeated bending with a bending radius of ≤3mm, and can maintain stable performance in a temperature range of -20℃ to 80℃.

[0059] Specifically, the thickness of the flexible scintillator functional layer is controlled to be 100-300 micrometers through synergistic optimization of the coating process and the slurry solid content, balancing X-ray absorption efficiency and flexibility. The interaction between the polymer matrix and the scintillator particles ensures a visible light transmittance of ≥85%. The particle interface is modified with a surface coupling agent (KH-550) to reduce light scattering, and the multi-peak particle size distribution optimizes the filling density, reducing light transmission path loss. By adjusting the volume ratio of the polymer matrix to the particles to 60:40 to 50:50, the refractive index matching range is controlled to be 1.5-1.6, ensuring a total internal reflection angle of ≥45° at the interface and increasing light yield (≥40,000 photons). The bending resistance (bending radius ≤3mm) depends on the thermal expansion matching between the substrate and the functional layer, as well as the interfacial bonding strength. The bending resistance is improved by plasma treatment of the substrate and coupling agent to enhance the shear strength of the particle-matrix interface. Temperature stability is achieved by eliminating solvent residue and internal stress through gradient drying process. Combined with the wide temperature range stability of the polymer matrix, the transmittance decreases by ≤2% and the light output deviation is ≤3% after 100 thermal cycles. The functional layer shows no cracks after 5000 bends at a bending radius of 3mm (SEM observation), the transmittance retention rate is ≥90%, and the X-ray imaging resolution is ≥5lp / mm, meeting the long-term stability requirements of the device in extreme environments.

[0060] See appendix Figure 1 The slurry also contains the following additives:

[0061] Plasticizer: Dioctyl phthalate, mass fraction 2%-4%;

[0062] Dispersant: Polyethylene glycol, mass fraction 0.8%-1.5%;

[0063] Defoamer: polydimethylsiloxane or mineral oil, mass fraction 0.1%-0.5%;

[0064] The total mass fraction of additives is ≤6%.

[0065] Specifically, the plasticizers, dispersants, and defoamers added to the slurry work synergistically to optimize process performance and functional layer characteristics. Among them, the plasticizer dioctyl phthalate (DOP) has a mass fraction of 2%-4%. Its flexible ester groups form intermolecular hydrogen bonds with the polar groups of the polymer matrix, lowering the glass transition temperature of the matrix and improving the flexibility of the slurry film. However, excessive amounts can lead to plasticizer migration and precipitation; 4% was selected as the critical value through DSC testing. The dispersant polyethylene glycol (PEG) has a mass fraction of 0.8%-1.5%. Its long-chain ether bonds inhibit the agglomeration of scintillator particles through steric hindrance and electrostatic repulsion. Combined with ball milling, it achieves particle dispersion uniformity of D90 / D50 ≤ 1.5. The defoamer has a mass fraction of 0.1%-0.5%. Polydimethylsiloxane reduces the surface tension of the slurry through siloxane segments, rapidly destroying the bubble film (defoaming efficiency ≥90%), while mineral oil achieves defoaming by adsorbing the bubble interface through non-polar alkane chains (efficiency ≥80%). Both require ultrasonic treatment to ensure the slurry porosity is ≤3%. The optimized slurry viscosity is stable at 2000-3000 mPa·s (25℃), the light transmittance after coating is ≥85%, the adhesion test of the cross-cut adhesion test is ≥4B grade, and there are no cracks after 5000 bends at a 3mm bending radius (SEM observation shows good interface bonding), the X-ray excitation light yield is ≥40,000 photons / MeV, and the light output uniformity deviation is ≤3%, meeting the optical and mechanical reliability requirements of high-precision flexible detectors.

[0066] See appendix Figure 1 The screen structure includes an anti-reflective layer on the outer surface of the protective layer. The anti-reflective layer is a silicon dioxide nano-coating with a thickness of 100-500nm.

[0067] Specifically, the anti-reflective layer in the screen structure is a silica nano-coating, prepared on the outer surface of the protective layer using magnetron sputtering or a sol-gel method. The thickness is precisely controlled between 100-500 nm. Through optical interference principles, a wide-band reflectivity of ≤1.5% is achieved, while the reflectivity of the uncoated surface is ≥8%. In the sputtering process, the argon flow rate is controlled at 20-50 sccm, the RF power at 100-300 W, and the substrate temperature at 80-150℃ to regulate the coating density (1.8-2.2 g / cm³) and refractive index (1.45-1.48). The sol-gel method further reduces the refractive index to 1.2-1.3 by forming a nanoporous structure through the hydrolysis and condensation of tetraethyl orthosilicate. The coating exhibits ultra-low reflectance (≤0.8%). Coating thickness is monitored in real-time using an ellipsometry, and gradient deposition eliminates internal stress, ensuring no cracking of the coating when the flexible substrate is bent. The reaction mechanism is based on the destructive phase interference of light waves at the coating-air interface and the coating-protective layer interface. Thickness and structure are optimized through finite-difference time-domain simulation, increasing the average transmittance across the entire wavelength range to ≥93%, while the original substrate transmittance is 88%. Implementation verification shows that the screen exhibits enhanced visibility under strong light conditions after coating, with a surface pencil hardness ≥4H, a haze increase ≤1% after abrasion resistance testing, and no performance degradation after aging at 85℃ / 85%RH for 500 hours, meeting the optical requirements of highly durable flexible displays and imaging devices.

[0068] Example 1:

[0069] Element:

[0070] Substrate: Polyethylene naphthalate film with a light transmittance of ≥90% and surface treated with argon plasma;

[0071] Slurry: The slurry contains 55% scintillation particles, 25% mechanical and 20% solvent, wherein the scintillation particles are cesium iodide (thallium doped), with an average particle size of 5 micrometers, and are surface modified with silane coupling agent (KH-550). The scintillation particles are stirred with 5% KH-550 ethanol solution at 60°C for 2 hours, filtered and dried before use.

[0072] Polymer matrix: polyvinylidene fluoride;

[0073] Organic solvent: N-methylpyrrolidone;

[0074] Additives: dioctyl phthalate (plasticizer, 3% by mass), polyethylene glycol (dispersant, 1.2% by mass), polydimethylsiloxane (defoamer, 0.3% by mass).

[0075] Protective layer: 25-micron thick biaxially oriented polyethylene terephthalate film with corona treatment on the surface.

[0076] Preparation process:

[0077] S1: Substrate pretreatment: A 150-micron thick polyethylene naphthalate film is used as a flexible transparent substrate with a light transmittance ≥90% and a haze ≤1.5%. Argon plasma treatment equipment is used with a power of 80 watts, a treatment time of 45 seconds, and a vacuum degree of 20 Pa to raise the surface energy of the substrate to ≥50 mN / m and the wetting angle to ≤10°. The treated substrate is placed in a clean environment for later use to avoid secondary contamination.

[0078] S2: Slurry preparation and dispersion: Cesium iodide particles were mixed with polyvinylidene fluoride, N-methylpyrrolidone was added as a solvent, and dioctyl phthalate, polyethylene glycol and polydimethylsiloxane were added. The mixture was ball-milled with zirconia balls at a ball-to-particle ratio of 5:1 at a speed of 2500 rpm for 4 hours to ensure uniform dispersion of the slurry. The viscosity of the slurry was controlled at 2500 mPa·s (25℃) to avoid insufficient sedimentation or leveling.

[0079] S3: Scraping and forming: Fix the pretreated substrate on the preheating platform, set the temperature to 45℃, use a stainless steel scraper, adjust the gap to 0.8 mm, scraping speed 10 cm / min, control the ambient humidity at 40% relative humidity to avoid skinning or bubble formation on the slurry surface, after scraping and forming, the wet film thickness uniformity deviation ≤5%, and there are no visible defects on the surface.

[0080] S4: Gradient drying: First stage: constant temperature drying at 40℃ for 20 minutes, relative humidity of 60%, to allow the solvent to evaporate slowly and avoid film cracking;

[0081] Second stage: Heat to 60℃, dry for 30 minutes, reduce humidity to 40% relative humidity to accelerate solvent evaporation;

[0082] Third stage: Heat to 80℃, dry for 45 minutes, maintain relative humidity ≤20%, purge with nitrogen for protection, and ensure solvent residue ≤0.1%;

[0083] After drying, the flexible scintillator functional layer is about 200 micrometers thick and has a smooth surface without cracks.

[0084] Performance testing:

[0085] Light transmittance: ASTM D1003 (Standard Test Method for Light Transmittance and Haze of Transparent Plastics);

[0086] Bending resistance: ISO 7854 (Determination of repeated bending resistance of coated fabrics);

[0087] Optical output: IEEE N42.14 (performance characterization of scintillator detectors).

[0088] application

[0089] Suitable for medical curved X-ray detectors, it can conform to the curved surface of the human body for imaging, improving detection accuracy.

[0090] Control group 1:

[0091] Element:

[0092] Untreated cesium iodide particles, no plasticizer / dispersant, polymethyl methacrylate matrix, solvent: N-methylpyrrolidone, solid content 60%.

[0093] Preparation process;

[0094] S1: Polyethylene naphthalate film is used directly without plasma treatment.

[0095] S2: Simple mechanical mixing of slurry, without ball milling.

[0096] S3: Scraper gap 1.0 mm, speed 10 cm / min, substrate not preheated.

[0097] S4: Directly dry at 80℃ for 60 minutes without nitrogen protection.

[0098] Performance testing:

[0099] Consistent with Example 1.

[0100] Performance Comparison Table 1:

[0101] Test Project Control Group 1 Example 1 in conclusion Light transmittance (%) 76 89 Surface treatment and slurry optimization improved performance by 17%. Bending resistance (times) 500 5000 Plasticizers bond with the interface, increasing lifespan by 10 times. Photovoltaic yield (photons / megaelectronvolts) 35000 42000 Particle dispersion uniformity improved by 20%.

[0102] in conclusion:

[0103] Substrate surface treatment: Plasma treatment improves the wettability of the slurry, increasing light transmittance by 13%;

[0104] Slurry optimization: The ball milling process and additives work synergistically to achieve uniform particle dispersion and enhanced mechanical properties;

[0105] Drying process: Gradient drying combined with nitrogen protection reduces solvent residue and avoids film defects.

[0106] Example 2: Ultra-thin flexible screen

[0107] Element:

[0108] Substrate: 100-micron thick polyethylene terephthalate film with a 50-nanometer silicon dioxide layer spin-coated on the surface;

[0109] Slurry: Scintillator particles: cadmium tungstate, 50% by mass;

[0110] Polymer matrix: Polyvinyl butyral;

[0111] Organic solvent: Cyclohexanone (55% solids);

[0112] Additives: 2.5% dioctyl phthalate, 1.0% polyethylene glycol;

[0113] Protective layer: 20-micron thick polydimethylsiloxane (containing 2% nano-silica).

[0114] Preparation process:

[0115] S1: Substrate pretreatment: A 100-micron polyethylene terephthalate film was ultrasonically cleaned with ethanol for 10 minutes, and a 50-nanometer silica layer was coated using a spin coater at a speed of 3000 rpm. Then, it was heat-treated at 120°C for 30 minutes to cure, and the surface energy was increased to 48 millinewtons.

[0116] S2: Slurry preparation and dispersion: Cadmium tungstate particles and polyvinyl butyral were mixed in a certain proportion, cyclohexanone solvent and additives were added, and the mixture was continuously ground three times using a three-roll mill (roller gap 50 micrometers), followed by ultrasonic treatment at 40 kHz for 30 minutes, resulting in a final viscosity of 1800 mPa·s.

[0117] S3: Microgravure coating: Precision coating is performed using an anilox roller (200 lines / inch), the substrate is preheated to 40°C, the coating speed is 15 cm / min, the ambient humidity is controlled at 45% relative humidity, and the wet film thickness is controlled at 80±4 microns.

[0118] S4: Vacuum gradient drying:

[0119] First stage: 45℃ / -0.09 MPa vacuum, 25 minutes;

[0120] Second stage: 65℃ / -0.095 MPa, 35 minutes;

[0121] Third stage: 85℃ / -0.1 MPa, 40 minutes;

[0122] Nitrogen purging throughout the process results in solvent residue ≤0.08%.

[0123] Performance testing:

[0124] Thickness tolerance: ASTM D7091 (Standard for measuring the thickness of non-magnetic coating dry film).

[0125] Light uniformity deviation: SJ / T11540 (Brightness uniformity test of display devices);

[0126] Underwater stability degradation: ISO2812-2 (Coating stability against liquid media).

[0127] application:

[0128] Wearable radiation monitoring device, suitable for humid environments.

[0129] Control group 2:

[0130] Composition: Unimodal cadmium tungstate (10 microns), silica-free coating, polymethyl methacrylate matrix.

[0131] Preparation process:

[0132] Simple scraping (1.2 mm gap), drying in an 80°C constant temperature oven without vacuum assistance, otherwise consistent with Example 2.

[0133] Performance testing:

[0134] Consistent with Example 2.

[0135] Performance Comparison Table 2:

[0136] Test Project Control Group 2 Example 2 in conclusion Thickness deviation (%) 15 5 Microgravure coating precision increased by 3 times Light uniformity deviation (%) 8 2.1 The optimization effect of bimodal distribution is significant. Underwater stability degradation (%) >10 <3 Vacuum drying improves sealing performance

[0137] in conclusion:

[0138] By employing micro-gravure extrusion coating combined with multi-stage gradient drying, the bending resistance of flexible screens is improved by 5-10 times.

[0139] Example 3: High-resolution screen

[0140] Element:

[0141] Substrate: 200-micron polyethylene naphthalate,

[0142] Slurry: Scintillator particles: Gadolinium oxide: Praseodymium (4 microns, KH-560 treated), 60% by mass.

[0143] Polymer matrix: polymethyl methacrylate / polyvinylidene fluoride (3:1).

[0144] Organic solvent: N,N-dimethylformamide (58% solids content).

[0145] Protective layer: 30-micron polyethylene terephthalate + 200-nanometer silica anti-reflective layer.

[0146] Preparation process:

[0147] S1: Substrate treatment:

[0148] Double-sided argon plasma treatment

[0149] Surface energy increased to 55 millinewtons.

[0150] Apply the coating immediately to prevent surface energy decay.

[0151] S2: Slurry preparation:

[0152] The sample was processed for 1 hour using a high-speed shear disperser (3500 rpm) with simultaneous ice-water bath temperature control (≤25℃) and viscosity controlled at 3200±200 mPa·s.

[0153] S3: Slit extrusion coating:

[0154] The die is 300 mm wide, the slit gap is 0.5 mm, the extrusion pressure is 0.2 MPa, the substrate conveying speed is 8 cm / min, and the online thickness gauge monitors the thickness in real time (accuracy ±2 μm).

[0155] S4: Infrared gradient drying:

[0156] Phase 1: 50℃ (heating rate 3℃ / min), 25 minutes.

[0157] Second stage: 70℃ (2℃ / minute), 35 minutes.

[0158] Phase 3: 90℃ (1℃ / minute), 50 minutes

[0159] The uniformity deviation of infrared radiation throughout the entire process is ≤5%.

[0160] Performance testing;

[0161] Resolution: ISO 12233 (Resolution evaluation of optical imaging systems):

[0162] Thermal cycling stability: JESD22-A104 (Temperature cycling reliability test);

[0163] Refractive index matching: ASTM E1967 (Measurement of refractive index of materials).

[0164] application:

[0165] Flexible sensors for industrial CT inspection, suitable for environments with large temperature differences.

[0166] Control group 3:

[0167] Composition: Unmodified gadolinium oxide granules, single polyvinylidene fluoride resin, direct coating and drying.

[0168] Preparation process:

[0169] Traditional doctor blade coating, rapid drying at 120°C, no gradient temperature control, otherwise the same as in Example 3.

[0170] Performance testing:

[0171] Consistent with Example 3.

[0172] Performance Comparison Table 3:

[0173] Test Project Control Group 3 Example 3 in conclusion Resolution (line pairs / mm) 4 6.5 The mixed matrix improved by 62.5%. Thermal cycling stability Layering intact Gradient drying eliminates internal stress Refractive index matching degree 1.62 1.55 Reduced interface light scattering by 7%

[0174] in conclusion:

[0175] The polymer matrix hybrid design and refractive index control enabled Example 3 to maintain stable performance at extreme temperatures, while the control group suffered from increased light scattering due to material mismatch.

[0176] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for fabricating a large-area flexible scintillator screen based on a scraping coating technique, characterized in that, Includes the following steps: S1. Provide flexible transparent substrate; S2. Coating a scintillator slurry onto the surface of a substrate, wherein the slurry comprises scintillator particles, a polymer matrix and an organic solvent, in a mass ratio of 5:3:

2. S3. Using scraping coating technology, the slurry is scraped into a wet film of uniform thickness by an adjustable gap scraper. S4. Gradient drying of the wet film to evaporate the solvent to form a flexible scintillator functional layer; S5. Cover the surface of the functional layer with a protective layer and encapsulate it into a screen structure.

2. The method for fabricating a large-area flexible scintillator screen based on scraping molding technology according to claim 1, characterized in that, The polymer matrix in S2 is selected from at least one of polyvinylidene fluoride, polymethyl methacrylate, and polyvinyl butyral. The organic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, and cyclohexanone. The molecular weight of polyvinylidene fluoride is 500,000-800,000, the molecular weight of polyvinyl butyral is 30,000-50,000, and the boiling point of the solvent is in the range of 150-250℃. The solid content of the slurry is 50%-80%, and the viscosity is controlled at 500-5000 mPa·s at 25℃.

3. The method for fabricating a large-area flexible scintillator screen based on scraping molding technology according to claim 1, characterized in that, The scintillator particles are at least one of cesium iodide, cadmium tungstate, and gadolinium oxysulfide. The particle size distribution is unimodal or multimodal, with the main peak particle size being 3-8 micrometers and the particle size dispersion index being ≤0.

3. The mass fraction of the scintillator particles in the slurry is 50%-60%, and the particle surface is pretreated with a coupling agent.

4. The method for fabricating a large-area flexible scintillator screen based on scraping coating technology according to claim 1, characterized in that, In S3, the blade gap adjustment range is 0.2-1.5 mm, the scraping speed is 8-15 cm / min, the blade material is either stainless steel or polytetrafluoroethylene, the substrate preheating temperature is controlled at 40-50℃ and temperature is controlled by an infrared heating plate, and the scraping environment humidity is controlled at 30%-60%RH.

5. The method for fabricating a large-area flexible scintillator screen based on scraping coating technology according to claim 1, characterized in that, The S4 gradient drying process includes three stages: First stage: Dry at 40℃±2℃ for 15-20 minutes, with a humidity of 50%-70%RH; Second stage: Dry at 60℃±2℃ for 25-35 minutes, with a humidity of 30%-50%RH; Third stage: Dry at 80℃±2℃ for 40-50 minutes, humidity ≤20%RH; During the drying process, a stepped heating rate of ≤5℃ / min is used, and nitrogen gas is introduced for protection.

6. The method for fabricating a large-area flexible scintillator screen based on scraping molding technology according to claim 1, characterized in that, The protective layer is either a biaxially oriented polyethylene terephthalate film or a polydimethylsiloxane coating. The surface of the biaxially oriented polyethylene terephthalate film is corona-treated, and the polydimethylsiloxane coating is formed by either spin coating or dip coating. The protective layer has a thickness of 20-30 micrometers, a light transmittance of ≥92%, and a surface hardness of ≥3H.

7. The method for fabricating a large-area flexible scintillator screen based on scraping molding technology according to claim 1, characterized in that, The flexible transparent substrate is either polyethylene terephthalate or polyethylene naphthalate. The glass transition temperature (Tg) of the flexible transparent substrate is ≥80℃, the substrate thickness is 100-150 micrometers, the surface is plasma treated, the light transmittance of the substrate is ≥88%, the haze is ≤2%, and the coefficient of thermal expansion is ≤20ppm / ℃.

8. The method for fabricating a large-area flexible scintillator screen based on scraping coating technology according to claim 1, characterized in that, The flexible scintillator functional layer has a thickness of 100-300 micrometers, a visible light transmittance of ≥85%, a refractive index matching of 1.5-1.6, can withstand repeated bending with a bending radius of ≤3mm, and can maintain stable performance within a temperature range of -20℃ to 80℃.

9. The method for fabricating a large-area flexible scintillator screen based on scraping molding technology according to claim 1, characterized in that, The slurry also contains the following additives: Plasticizer: Dioctyl phthalate, mass fraction 2%-4%; Dispersant: Polyethylene glycol, mass fraction 0.8%-1.5%; Defoamer: polydimethylsiloxane or mineral oil, mass fraction 0.1%-0.5%; The total mass fraction of the additives is ≤6%.

10. A method for fabricating a large-area flexible scintillator screen based on a coating molding technology according to claim 1, characterized in that, The screen structure includes an anti-reflective layer disposed on the outer surface of the protective layer. The anti-reflective layer is a silicon dioxide nano-coating with a thickness of 100-500 nm.

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