Low-reflectivity surface coating for polaroid and preparation method

Abstract

The invention discloses a low-reflectivity surface coating for a polaroid and a preparation method, and belongs to the field of polaroids for vehicle-mounted display, and the preparation method comprises the following steps: 1) adding an additive into cellulose organic acid ester, stirring for reaction, and then introducing tetraethyl orthosilicate and a surfactant for reaction; 2) adding a silane coupling agent and metacrylic acid ester into the mixture obtained in the step 1) for reaction, and finally adding metacrylic acid ester, methyl ethyl ketone, propylene glycol monomethyl ether, an organic binder and metal ions to form a coating liquid; and 3) coating the polaroid with the coating liquid obtained in the step 2), drying, and then carrying out photopolymerization reaction to form the low-reflectivity surface coating for the polaroid. According to the invention, the binding force between the coating and a base film is enhanced, the physical and chemical properties are improved, and finally, the low-reflectivity surface coating method for the vehicle-mounted display polaroid is realized.

Description

Technical Field

[0001] The present invention relates to the field of polaroids for vehicle-mounted displays, and in particular to a low-reflectivity surface coating for polaroids and a preparation method thereof. Background Art

[0002] With the rapid development of intelligent and digital automotive technology, in-vehicle displays have become an indispensable core component of modern automobiles. These displays are widely used for a variety of functions, including in-vehicle entertainment systems, navigation, driver assistance, and information display. The visual quality of these displays plays a crucial role in driving safety, user experience, and driver comfort. In-vehicle display systems operate in unique environments, often characterized by strong sunlight, frequent temperature and humidity fluctuations, and various pollutants both inside and outside the vehicle. As a core optical component of liquid crystal displays (LCDs) or organic light-emitting diode (OLED) displays, polarizers effectively regulate the propagation of light, enhancing the display's contrast, color saturation, and visual clarity. To improve the performance and visual quality of in-vehicle displays and reduce interference from external reflected light, low reflectivity in polarizers has become a key issue that needs to be addressed in their design and manufacturing.

[0003] The low reflectivity of polarizers used in automotive displays is of great significance in the following aspects: Improving visual clarity: High reflectivity can lead to blurred displays, especially under strong light. The displayed content may be interfered with by reflected light, affecting the driver's ability to read the information on the screen. Therefore, reducing reflected light is the key to improving display clarity and readability. Enhancing driving safety: The low reflectivity of polarizers can not only reduce the visual interference caused by reflected light inside and outside the car, but also reduce the reflected light from sunlight reflected on the windshield, thereby avoiding visual impact on the driver and reducing the risk of traffic accidents. Improving display contrast: Low reflectivity helps enhance the contrast of in-vehicle displays, making the displayed content clearer under strong light conditions and improving the user's visual experience. Extending the life of polarizers: Increased reflected light may cause damage and aging of the polarizer surface coating, thereby affecting its service life. The low reflectivity design helps protect the surface coating of the polarizer and extend the product's service life.

[0004] In the process of achieving low reflectivity in polarizers for automotive displays, traditional coating technologies face numerous technical bottlenecks, primarily in the following areas: Coating uniformity: With currently used coating technologies, coating uniformity is often affected by numerous factors, such as the coating solution formulation, coating method, and the surface condition of the base film. Uneven coatings can easily lead to unstable reflectivity, thus affecting the display quality. Ensuring the uniformity of the polarizer coating is crucial for achieving low reflectivity, especially in large-scale automotive displays. Coating weatherability and aging resistance: Polarizers for automotive displays are subject to long-term exposure to the external environment, including strong sunlight, high temperatures, humidity, and airborne pollutants. The coating's weatherability and aging resistance are directly related to the polarizer's reflectivity and display performance. Existing coating technologies still have many limitations in this regard, and the coating is easily affected by environmental factors, resulting in reflectivity fluctuations. The problem of bonding strength between the coating and the base film: In automotive display applications, polarizers often need to withstand large mechanical stresses and temperature changes. The bonding strength between the coating and the base film needs to be strong enough, otherwise the coating may fall off, peel off or bubble, affecting product quality and service life. How to optimize the coating process and enhance the bonding strength between the coating and the base film is a technical difficulty in solving the problem of low reflectivity. The problem of coating hardness and scratch resistance: The surface of the polarizer needs to have high hardness and scratch resistance, especially in the automotive display environment, where the display may be affected by fingerprints, dust, external physical impact and other factors. The coating hardness of traditional coating methods is not enough, and it is easy to be scratched or worn, which affects its optical properties and reflectivity.

[0005] To overcome the aforementioned technical bottlenecks, it is urgent to develop novel coating-based surface treatment processes, encompassing the following areas: Molecular synthesis and formulation design of coating fluids: By optimizing the molecular structure of the coating fluid, a coating fluid with high optical transparency, low reflectivity, and good adhesion is designed to address issues such as uneven coating and fluctuating reflectivity. Improving the weatherability and aging resistance of the coating: Developing coating materials with excellent weatherability and aging resistance to withstand the effects of long-term UV radiation, high temperature, humidity, and other external factors in the automotive environment, maintaining the coating's low reflectivity and high performance. Enhancing the bonding between the coating and the base film: Optimizing the coating process and coating fluid formulation to improve the adhesion between the coating and the base film, preventing the coating from falling off or peeling, and ensuring the long-term stability of the polarizer. Research and development of high-hardness and scratch-resistant coatings: Developing coating materials with high hardness and excellent scratch resistance for polarizers used in automotive displays to prevent damage to the coating due to external physical friction, thereby maintaining low reflectivity and long-term stable display performance. Through this series of technological innovations, multiple requirements such as ultra-low reflectivity, scratch resistance, haze control and high hardness can be achieved on polarizers for automotive displays, providing strong support for the further development of automotive display technology.

[0006] With the increasing demand for in-vehicle displays, low-reflectivity polarizer technology has become a key factor in improving in-vehicle display performance, enhancing user experience, and ensuring driving safety. This invention, by developing a low-reflectivity surface coating for polarizers and its preparation method, addresses technical bottlenecks in existing coating technologies, such as coating uniformity, weather resistance, aging resistance, and coating-to-base film bonding. This technology effectively achieves multiple performance requirements, including low reflectivity, scratch resistance, haze reduction, and hardness, driving further advancements in in-vehicle display technology. Summary of the Invention

[0007] The purpose of the present invention is to solve the above-mentioned problem in the prior art that the reflection intensity of the polarizer for vehicle display is high when disturbed by external reflected light, and to provide a low-reflectivity surface coating for the polarizer and a preparation method thereof.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for preparing a low-reflectivity surface coating for a polarizer comprises the following steps:

[0010] 1) Add additives to cellulose organic acid ester, stir and react, then introduce tetraethyl orthosilicate and surfactant to react;

[0011] 2) adding a silane coupling agent and methacrylate to the mixture obtained in step 1) to react, and finally adding methacrylate, methyl ethyl ketone, propylene glycol monomethyl ether, an organic binder, and metal ions to form a coating solution;

[0012] 3) The coating liquid of step 2) is coated on the polarizer film and dried, and then photopolymerized to form the low reflectivity surface coating for the polarizer.

[0013] The cellulose organic acid ester includes at least one of cellulose acetate, cellulose nitrate, cellulose acetate, cellulose acetate butyrate, and cellulose xanthate.

[0014] The additive includes at least one of succinic acid, phthalate, phosphate, citrate, polyurethane, and silicone.

[0015] The organic binder includes at least one of polyacrylic acid and polyimide.

[0016] The metal ions include at least one of sodium ions, potassium ions, zinc ions, magnesium ions, and iron ions.

[0017] In parts by mass, 0.1-10 parts of additives, 0.1-5 parts of surfactants, 0.1-1 parts of silane coupling agents, 10-20 parts of tetraethyl orthosilicate, 0.1-5 parts of methacrylate, 0.1-5 parts of methyl ethyl ketone, 0.1-3 parts of propylene glycol monomethyl ether, 1-5 parts of organic binders, and 0.1-0.5 parts of metal ions are introduced into 100 parts of cellulose organic acid ester.

[0018] A low-reflectivity surface coating for polarizers is prepared by adopting the above preparation method.

[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0020] 1. Optimizing coating uniformity and physical properties, and improving production stability: This invention incorporates additives and nanoparticles into the coating process. This not only optimizes the coating's surface structure, creating a multi-layered concave-convex structure, but also improves coating uniformity and stability. Furthermore, the addition of additives to the coating fluid enhances the coating's physical properties, such as hardness and scratch resistance.

[0021] 2. Enhanced coating weather resistance, aging resistance, and adhesion: By optimizing the coating liquid composition and introducing metal ions, this invention enhances the coating's weather resistance, aging resistance, and adhesion to the base film. Specifically, the metal ions complex with the hydroxyl groups in the cellulose acetate molecular chains, increasing the coating's structural stability and effectively improving the coating's resistance to wear, UV radiation, and environmental corrosion over long-term use. This ensures that the polarizer maintains better performance over time, extending its service life.

[0022] 3. Significantly Reduces Reflectivity, Improving In-Vehicle Display Quality: This invention boasts a light transmittance of 92%, successfully achieving a low-reflectivity polarizer surface. Formed through a photopolymerization reaction triggered by ultraviolet light, this low-reflectivity coating effectively reduces reflections from ambient light, enhancing display quality. In particular, in in-vehicle display applications, it reduces interference from sunlight or other in-vehicle light sources, improving visibility and providing clearer images, thereby enhancing the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the thickness of the low reflectivity surface coating.

[0024] Figure 2 SEM image of low reflectivity surface coating.

[0025] Figure 3 Elemental composition analysis of low reflectivity surface coatings.

[0026] Figure 4 Use the pencil method to measure the surface hardness of low reflectivity surface coatings.

[0027] Figure 5 ASTM ratings for low-reflectivity surface coatings.

[0028] Figure 6 Steel wool scratch test of low reflectivity surface coatings.

[0029] Figure 7 Contact angle testing of low reflectivity surface coatings. DETAILED DESCRIPTION

[0030] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0031] The method for preparing the low-reflectivity surface coating for polarizers of the present invention comprises the following steps:

[0032] 1. 1 part of succinic acid was introduced as an additive into 100 parts of cellulose acetate (TAC) and stirred for 10 minutes; then 15 parts of tetraethyl orthosilicate was introduced, and the hydrolysis and condensation reaction with cellulose acetate (TAC) was utilized. By adding 2 parts of surfactant hexadecyltrimethylammonium bromide (CTAB) to control the SiO2 morphology, hollow SiO2 microspheres were obtained. On this basis, 0.5 parts of silane coupling agent and 1.5 parts of methacrylate were added to react and organic coupling grafted modified SiO2 microspheres were obtained; compared with the traditional sol-gel method, the problem of nanoparticle agglomeration was effectively overcome; at the same time, 2 parts of methacrylate, 3 parts of methyl ethyl ketone, 1 part of propylene glycol monomethyl ether, 2 parts of polyimide organic binder and 0.2 parts of Zn were further introduced. 2+ Metal ions constitute the coating liquid.

[0033] 2. Apply the coating liquid on the PVA film and dry it. During the drying process, the acrylic ester shrinks while the hollow SiO2 microspheres do not change, thereby constructing a multi-level concave-convex structure on the surface. The low-reflectivity surface coating is then constructed by further initiating polymerization through ultraviolet light.

[0034] Testing and characterization of the low reflectivity polarizer for vehicle display in the present invention:

[0035] The prepared polarizer coating was characterized by SEM, and its thickness was 42~45μm ( Figure 1 ), the surface is relatively rough and some of them have large areas of inorganic nanoparticles ( Figure 2 ), which may be due to the volatilization of the solvent during the drying process, which brings out some silica nanoparticles. Further element scanning analysis also shows that it contains Si element ( Figure 3), with a content of about 0.82%, indicating that inorganic nano-silica particles were successfully introduced into the low-reflection coating through the TEOS hydrolysis condensation method. According to the national standard GB / T6739-2006, the surface concave-convex structure of the low-reflection coating was clearly visible using the pencil method, and the test hardness was 4H ( Figure 4 Adhesion was tested according to ASTM D3359-09 standard method, and it was found that the low-reflective coating had good adhesion, indicating that the curing and cross-linking greatly strengthened the bonding between the base film and the coating. Only small pieces fell off at the intersection of the cut, and the actual damage in the cross-cut area was less than 5%, which was judged to be 4B grade ( Figure 5 ). Scratch resistance test was carried out according to GB / T24116-2008. The results showed that the low-reflective coating has good scratch resistance ( Figure 6 The contact angle test shows that the low-reflection coating is relatively hydrophobic, with an average contact angle of about 76° ( Figure 7 ), significantly improving the polarizer's weather resistance. Testing of the low-reflection coating's optical properties revealed a transmittance of 92%. These test results demonstrate that the coating, achieved through the newly developed coating formulation, significantly enhances the surface hardness of the cellulose acetate (TAC) protective layer, achieving low reflectivity.

[0036] The specific principles of this invention are as follows: additives are introduced into cellulose acetate (TAC) to enhance hydrogen bonding between TAC molecules, improve crystallinity, and build a cross-linked network with TAC to form a coating layer. This addresses technical bottlenecks such as uneven coating, weather resistance, and aging resistance, as well as the weak bonding between the coating layer and the base film. Secondly, nanoparticles are introduced into the coating liquid to enhance the surface properties of the TAC protective layer. A multi-layered concave-convex surface structure is constructed during the drying process, and then a low-reflectivity coating is constructed through photoinitiated polymerization. Furthermore, a small amount of metal ions can be introduced into the coating liquid to further enhance the weather resistance of the low-reflective coating through complexation with the hydroxyl groups on the TAC molecular chains.

Claims

1. A method for preparing a low-reflectivity surface coating for a polarizer, characterized in that: The following steps are involved: 1) Add additives to cellulose organic acid ester, stir and react, then introduce tetraethyl orthosilicate and surfactant to react; 2) adding a silane coupling agent and methacrylate to the mixture obtained in step 1) to react, and finally adding methacrylate, methyl ethyl ketone, propylene glycol monomethyl ether, an organic binder, and metal ions to form a coating solution; 3) The coating liquid of step 2) is coated on the polarizer film and dried, and then photopolymerized to form the low reflectivity surface coating for the polarizer.

2. The method for preparing a low-reflectivity surface coating for a polarizer according to claim 1, wherein: The cellulose organic acid ester includes at least one of cellulose acetate, cellulose nitrate, cellulose acetate, cellulose acetate butyrate, and cellulose xanthate.

3. The method for preparing a low-reflectivity surface coating for a polarizer according to claim 1, wherein: The additive includes at least one of succinic acid, phthalate, phosphate, citrate, polyurethane, and silicone.

4. The method for preparing a low-reflectivity surface coating for a polarizer according to claim 1, wherein: The organic binder includes at least one of polyacrylic acid and polyimide.

5. The method for preparing a low-reflectivity surface coating for a polarizer according to claim 1, wherein: The metal ions include at least one of sodium ions, potassium ions, zinc ions, magnesium ions, and iron ions.

6. The method for preparing a low-reflectivity surface coating for a polarizer according to claim 1, wherein: In parts by mass, 0.1-10 parts of additives, 10-20 parts of tetraethyl orthosilicate, 0.1-5 parts of methacrylate, 0.1-5 parts of methyl ethyl ketone, 0.1-3 parts of propylene glycol monomethyl ether, 1-5 parts of organic binder, and 0.1-0.5 parts of metal ions are introduced into 100 parts of cellulose organic acid ester.

7. A low-reflectivity surface coating for a polarizer, characterized in that: Prepared by the preparation method according to any one of claims 1 to 6.

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