LCD polarizer performance and indicators
The optical properties of the polarizer include three main performance indexes: polarization degree, transmittance, and color tone. Others also include ultraviolet ray resistance and transmissivity, total reflectivity, and diffuse reflectance of the semi-transmissive polarizer semipermeable membrane. . In the use of general LCD products, the higher the degree of polarization and transmittance performance indicators, the better. The higher the degree of polarization and transmittance, the higher the display efficiency of the LCD display device and the smaller the relative energy consumption. However, in the case of conventional iodine-dyed polarizer products, the degree of polarization and transmittance are contradictory. The higher the degree of polarization, the lower the transmittance and the more constrained by the color tone. The degree of polarization of the products is between 90% and 99%, and the transmittance is between 41% and 44%. The degree of polarization of general-purpose PLN products produced by Guangdong Fudi Riyang Polarization Device Co., Ltd. is 97% or more, and the transmittance is 43%. The polarization degree of medium-durability, high-contrast PMN products is 99.9%. Above, the transmittance is over 42%. The hue index is mainly to satisfy people's visual habits, and at the same time, the hue deviation of the polarizer products is required to be small to ensure the consistency of the appearance hue of the LCD final product. This is mainly due to the chromaticity coordinate parameters L, a, b values of the polarizer products and Their control range of tolerance to identify, generally the smaller the range of its control tolerance as possible.
The technical specifications of the polarizer include four technical indexes: high temperature resistance, heat and humidity resistance, low temperature resistance, and cold and heat shock resistance. The most important one is the level of the humidity and heat resistance index. High temperature resistance refers to the working condition of the polarizer at a constant baking temperature. At present, according to the technical level of the polarizer, it is generally divided into general types: the working temperature is 70°C×500HR; the medium durable type: the working temperature is 80°C× 500HR; High Durability: The operating temperature is above 90°C×500H. The humidity-heat resistance technical index refers to the humidity-heat-resistance performance of polarizers under constant temperature and humidity conditions. It is also generally divided into three technical levels, both general-purpose type: hot and humid working conditions are 40°C×90%RH×500HR; medium-duty type : Hot and humid working conditions are 60°C×90%RH×500HR; High endurance type: Hot and humid working conditions: 70°C×95%RH×500HR or more. Since the PVA film, the basic material constituting the polarizing film, and iodine and iodide are both highly hydrolyzable materials, the pressure-sensitive adhesive used for the polarizer is also easily deteriorated under high temperature and high humidity conditions. Therefore, the durability of the polarizer is improved. The most important of the technical indicators is the high-temperature resistance and humidity-heat resistance index. If the high-temperature resistance and heat-and-moisture resistance indexes pass, other durability-type indicators usually do not cause problems.
The characteristics of polarizers' adhesive properties mainly refer to the characteristics of polarizers, which generally include: peel force between pressure-sensitive adhesive and glass substrate, peel force between pressure-sensitive adhesive and release film, polarizer protection The peel force between the film and the polarizer and the adhesive durability of the pressure-sensitive adhesive. The peeling force between the pressure-sensitive adhesive and the glass substrate is also called the adhesive strength of the adhesive, which is the most important adhesive property index of the LCD polarizer product. This technical index is usually measured by the Japan Electromechanical Industry Association specification EIAJ-ED-2521A standard, expressed in g/25mm units, usually the LCD polarizer pressure sensitive adhesive peeling force on the glass substrate is specified in 500g/25mm above , but the actual use of the upper limit is generally below 1000g/25mm. There are practical examples showing that when the peeling force of the adhesive to the glass substrate is below 500g/25mm, the phenomenon that the polarizer is peeled off and warped automatically after the glass panel surface is adhered may occur.
The appearance and performance specifications of polarizers mainly refer to the surface flatness and the number of appearance defects of polarizers. These technical indexes mainly affect the utilization of polarizers when they are applied. These technical indicators usually have relatively consistent technical regulations in the polaroid industry. Generally, each polarizer product (500×1000mm) has 15 or less than 150 μm underdraw points. Since the final appearance of the polaroid products is visually inspected manually, the distribution of the appearance of the polarities during the mass production of the polarizer products will have a discrete distribution. For this reason, each polarizer manufacturer must adopt a certain degree of distribution. The difference between the internal control specifications and delivery specifications guarantees the delivery quality standards. However, it should be noted that since 150 μm is already close to the minimum limit of visual discrimination of the human eye, especially in the industrial mass production process, the inspection personnel will also produce visual fatigue during long-term operations, so the 150 μm under-dot check standard is more reasonable Trusted.
Main factors affecting the performance of LCD polarizers
The main factors that affect the performance of polarizers are related to the basic performance indicators of polarizers.
The main influencing factors affecting the optical performance of the polarizer include: selection of polarizing film materials, selection of dyeing materials, dyeing of polarizing films, selection of stretching process conditions, and limitation of equipment capabilities. These involve the core technology of polarizer production, so polarizer manufacturers are very cautious about the selection of these materials and process conditions, and generally will not be easily changed. Once the products of polarizer manufacturers are approved by customers, polarizer manufacturers will adopt strict production quality management measures to ensure the stability of the optical performance of the polarizer products.
The durability specifications of polarizer products actually include two aspects of the durability index: the durability of the polarizing film and the durability of the pressure-sensitive adhesive. The main factors influencing the durability of the polarizing film include the selection of the basic material of the polarizing film, the selection of the dyeing material, the dyeing of the polarizing film, the stretching, and the composite process conditions. In general, the larger the molecular weight of the PVA film selected for the polarizer and the higher the stretching ratio, the better the durability of the polarizing film, and vice versa. At the same time, the better the coloring degree of the polarizing film in the production process, the stronger the anti-degradability of the dye used, the better the durability of the polarizing film, so the durability of the dye-based polarizer is much better than that of the iodine dyeing polarizer. The durability of the product. The main factors affecting the durability of pressure-sensitive adhesives include: choice of adhesive formulation, choice of adhesive solvent, choice of adhesive blending process conditions, choice of adhesive drying process conditions, and adhesive storage conditions s Choice. It should be noted that the durability index of the adhesive is a comprehensive index, its impact is multi-faceted, and this is another core technology of polarizer production. Generally, the polarizer manufacturer determines the process conditions of the adhesive. Afterwards, it will not be easily changed and has strict quality management requirements. Otherwise, it may easily cause bad batches of products.
The main factors affecting the appearance of polarizers are also numerous. Mainly include: environmental purification conditions for polarizer production, material selection for polarizer production, equipment conditions for polarizer production, process flow and process recipes for polarizer production, polarizer packaging, storage, transportation conditions, and polarizers for customer use Storage environment and processing methods. In short, the polarizer is a very “queer” product that must be carefully stored and used, otherwise surface defects such as pits, black spots, and warpage can easily occur.