Performance and index of LCD polarizer
The optical properties of polarizers include three main performance indicators: polarization, transmittance and hue. Others include UV protection performance and the transmittance, total reflectance and diffuse reflectance of semi-transmissive polarizer films. . In the use of general LCD products, the higher the 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 lower the relative energy consumption. However, for conventional iodine-dyed polarizer products, the degree of polarization and transmittance are contradictory. The higher the degree of polarization, the lower the transmittance, and it is also constrained by the hue. The polarization degree of the film products is between 90% and 99%, and the transmittance is between 41% and 44%. 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% for general-purpose PLN products, while the polarization degree of medium-durability and high-contrast PMN products is 99.9%. Above, the transmittance is 42% or more. The hue index is mainly to meet people's visual habits, and at the same time, the hue deviation of polarizer products is required to be small to ensure the consistency of the appearance of the final LCD product. They are identified by their control tolerance range. Generally, the smaller the control tolerance range, the better.
The durability technical indicators of polarizers include four technical indicators of high temperature resistance, humidity and heat resistance, low temperature resistance and cold and thermal shock resistance, the most important of which is the level of humidity and heat resistance. High temperature resistance refers to the temperature-resistant working conditions of polarizers at a constant baking temperature. At present, according to the technical level of polarizers, they are usually divided into general-purpose types: working temperature is 70℃×500HR; medium-durability type: working temperature is 80℃× 500HR; high durability: the working temperature is above 90℃×500H. The technical index of resistance to humidity and heat refers to the working performance of polarizer under constant temperature and humidity conditions. It is also usually divided into three technical grades, which are both general-purpose types: the humidity and heat working conditions are 40℃×90%RH×500HR; the medium-durability type : Damp heat working condition is 60℃×90%RH×500HR; High durability type: Damp heat working condition is above 70℃×95%RH×500HR. Since the basic materials of the polarizer film, PVA film, iodine and iodide, are all easily hydrolyzed materials, and because the pressure-sensitive adhesive used in the polarizer is also easily deteriorated under high temperature and high humidity conditions, the durability of the polarizer is The most important of the performance 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 do not have problems.
The technical indicators of the bonding characteristics of polarizers mainly refer to the characteristics of polarizer pressure-sensitive adhesives, generally including: peeling force between pressure-sensitive adhesive and glass substrate, peeling force between pressure-sensitive adhesive and peeling film, polarizer protection Peel force between film and polarizer and bond durability of 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 index is usually measured by the EIAJ-ED-2521A standard 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 specified above 500g/25mm. , while the upper limit in actual use is generally below 1000g/25mm. There are practical examples that when the peeling force of the adhesive to the glass substrate is below 500g/25mm, the polarizer will automatically peel off and warp after the glass screen surface is bonded.
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 in the patch. These technical indicators usually have relatively consistent technical regulations in the polarizer industry, generally, each polarizer product (500 × 1000 mm) has 15 or less blemish points not greater than 150 μm. Since the final appearance inspection of polarizer products is carried out by manual visual inspection, in the mass production process of polarizer products, the distribution of appearance defects will have a certain discrete distribution. The difference between the internal control specification and the delivery specification is to ensure the delivery quality standard. However, it should be noted that since 150μm is already close to the minimum limit of visual resolution of the human eye, especially in the process of industrialized mass production, inspectors will also experience visual fatigue during long-term operations, so the 150μm under-point inspection standard is more reasonable. believable.
The main factors affecting the performance index of LCD polarizer
The main factors affecting the performance of polarizers are related to the basic performance indicators of polarizers.
The main factors affecting the technical indicators of the optical performance of polarizers include: the choice of polarizing film materials, the choice of dyeing materials, the choice of polarizing film dyeing, the choice of stretching process conditions, and the limitation of equipment capacity. These all involve the core technology of polarizer production. Therefore, polarizer manufacturers are very cautious in the selection of these materials and process conditions, and generally do not change them easily. Once the polarizer manufacturer's product is 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 durability of polarizer products actually include two aspects of durability: the durability of polarizing films and the durability of pressure-sensitive adhesives. The main factors affecting the durability of polarizing film include: the selection of basic materials of polarizing film, the selection of dyeing materials, the dyeing of polarizing film, stretching, composite process conditions and other factors. Generally speaking, 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 polarizer 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-decomposition ability 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-dyed polarizer. product durability. The main factors affecting the durability of pressure-sensitive adhesives include: the choice of adhesive formulation, the choice of adhesive solvent, the choice of adhesive blending process conditions, the choice of adhesive drying process conditions and the adhesive storage conditions s Choice. It should be noted that the durability index of the adhesive is a comprehensive index, and its influence is multi-faceted, and this is another core technology of polarizer production. Generally, polarizer manufacturers determine the process conditions of the adhesive. Afterwards, it will not be easily changed and there are strict process quality management requirements, otherwise it will easily cause batch product defects.
The main factors affecting the appearance performance of polarizers are also many. 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, and transportation conditions, as well as polarizers used by customers storage environment and processing method. In short, polarizer is a very "squeamish" product and must be carefully stored and used, otherwise it will easily cause surface pits, black spots and warping and other surface defects.
