Performance and index of LCD polarizer
The optical properties of the polarizer include: three main performance indicators of polarization, transmittance, and color tone, and others include the UV protection performance and the transmittance, total reflectance, and diffuse reflectance of the semi-permeable film of the semi-transmissive polarizer. In the use of general LCD products, the higher the performance index of polarization and transmittance required, the better. The higher the degree of polarization and the transmittance, the higher the display efficiency of the LCD display device and the lower the relative energy consumption. However, for conventional iodine-dyed polarizer products, the degree of polarization and the transmittance are a pair of contradictions. The polarization degree of the film products is between 90% and 99%, and the transmittance is between 41% and 44%. The general-purpose PLN product of the "Fudi" brand polarizer produced by Guangdong Fudi Rihe Polarizing Device Co., Ltd. has a polarization degree of more than 97% and a transmittance of 43%, while the polarization degree of the medium-durable and high-contrast PMN product is 99.9%. Above, the transmittance is above 42%. The color tone index is mainly to meet people's visual habits, and at the same time, the color tone deviation of the polarizer product is required to be small to ensure the consistency of the color tone of the final LCD product. This is mainly determined by the chromaticity coordinate parameters L, a, and b value of the polarizer product They are identified by their control tolerance range, and generally the smaller the control tolerance range, the better.
The durability technical indicators of polarizers include four technical indicators: high-temperature resistance, heat and humidity resistance, low-temperature resistance, and thermal shock resistance, the most important of which is the performance index of heat and humidity resistance. High-temperature resistance refers to the temperature-resistant working condition of the polarizer at a constant baking temperature. Currently, according to the technical grade of the polarizer, it is usually divided into general-purpose type: the working temperature is 70℃×500HR; medium durable type: the working temperature is 80℃× 500HR; high durability type: the three grades of working temperature above 90℃×500H. The humidity and heat resistance technical index refers to the humidity and heat resistance performance of the polarizer under constant temperature and humidity conditions. It is also usually divided into three technical grades, which are general-purpose: the humidity and heat working condition is 40°C×90%RH×500HR; the medium durability type: Damp heat working condition: 60℃×90%RH×500HR; high durability type: Damp heat working condition: 70℃×95%RH×500HR or more. Since PVA film, iodine, and iodide, which are the basic materials of the polarizing film, are easily hydrolyzed materials, and the pressure-sensitive adhesive used in the polarizing film also easy to deteriorates under high temperature and high humidity conditions, therefore, in the durability of the polarizing film The most important of the permanent technical indicators are the high temperature and humidity resistance indicators. If the high-temperature resistance and humidity and heat resistance indicators pass, other durability indicators usually will not have problems.
The technical indicators of the bonding characteristics of the polarizer mainly refer to the various characteristics of the polarizer pressure-sensitive adhesive, generally including the peeling force between the pressure-sensitive adhesive and the glass substrate, the peeling force between the pressure-sensitive adhesive and the release film, and the protection of the polarizer. The peel force between the film and the polarizer and the adhesion durability of the pressure-sensitive adhesive. The peeling force between the pressure-sensitive adhesive and the glass substrate is also called the bonding strength of the adhesive, which is the most important bonding characteristic index of LCD polarizer products. This technical indicator is usually measured by the standard EIAJ-ED-2521A of the Japan Electronic Machinery Industry Association, expressed in g/25mm. Usually, the peeling force of the LCD polarizer pressure-sensitive adhesive to the glass substrate is stipulated at 500g/25mm or more. , and the upper limit in actual use is generally below 1000g/25mm. Practical examples have shown that when the peeling force of the adhesive to the glass substrate is below 500g/25mm, the phenomenon of automatic peeling and warping of the polarizer after bonding on the surface of the glass screen will occur.
The technical indicators of the appearance performance of the polarizer mainly refer to the surface flatness of the polarizer product and the number of defects in the appearance. These technical indicators mainly affect the utilization rate of the polarizer product during patching. These technical indicators usually have relatively consistent technical regulations in the polarizer industry, generally, for each polarizer product (500×1000㎜) less than 15 undershoots not larger than 150μm. Since the final appearance inspection of polarizer products is performed by manual visual inspection, in the mass production process of polarizer products, the distribution of appearance defects will have a certain discrete distribution. For this, each polarizer manufacturer adopts a certain difference between the internal control specification and the delivery specification is used to ensure the delivery quality standard. However, it should be noted that since 150 μm is already close to the minimum limit of human visual resolution, especially in the process of industrialized mass production, inspectors will also experience visual fatigue during long-term work, so the 150 μm short-point inspection standard is more reasonable Believable.
Main Factors Affecting LCD Polarizer Performance Index
The main factors affecting the performance of polarizers are related to the basic performance indicators of polarizers.
The main influencing factors affecting the technical indicators of the optical performance of the polarizer include the selection of polarizing film material, the selection of dyeing material, the dyeing of the polarizing film, the selection of stretching process conditions, and the limitation of equipment capacity. These all involve the core technology of polarizer production, so polarizer manufacturers are very cautious in the selection of these materials and process conditions, and generally will not change easily. Once the polarizer manufacturer's products are approved by the customer, the polarizer manufacturer will take strict production quality management measures to ensure the stability of the optical performance of the polarizer product.
The technical indicators of the durability of polarizer products actually include two aspects of durability indicators: the durability of the polarizing film and the durability of the pressure-sensitive adhesive. The main influencing factors affecting the durability of the polarizing film include the selection of basic material for the polarizing film, the selection of dyeing material, the process conditions of dyeing, stretching and compounding of the polarizing film, etc. Generally speaking, the greater the molecular weight and the higher the stretching ratio of the PVA film selected for the polarizer, the better the durability of the polarizer film, and vice versa. At the same time, the better the coloring degree of the polarizing film in the production process and the stronger the anti-decomposition ability of the dye used, the better the durability of the polarizing film. Therefore, the durability of the dye-based polarizer is much better than that of the iodine-dyed polarizer. Product durability. The main factors affecting the durability of pressure-sensitive adhesives include the selection of adhesive formulations, the selection of adhesive solvents, the selection of adhesive mixing process conditions, the selection of adhesive drying process conditions, and the storage conditions of adhesives s Choice. It should be noted that the durability index of the adhesive is a comprehensive index, and its influence is multifaceted, and it is another core technology of polarizer production. Generally, polarizer manufacturers determine the process conditions of the adhesive It will not be changed easily in the future and has strict process quality management requirements, otherwise it will easily cause bad products in batches.
There are also many factors that affect the appearance and performance of polarizers. Mainly include environmental purification conditions for polarizer production, material selection for polarizer production, equipment conditions for polarizer production, process flow and process formula for polarizer production, polarizer packaging, storage, transportation conditions, and polarizer use by customers When the storage environment and processing methods. In short, the polarizer is a very "delicate" product, which must be kept and used carefully, otherwise, it will easily cause surface defects such as surface pits, black spots and warping.
