Introduction to basic performance indicators of LCD polarizers
- Jul 12, 2018 -

       

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The basic performance indicators of LCD polarizers are: basic technical specifications for optical performance, durability, bonding properties, appearance properties and other special properties.


The optical properties of the polarizer include: three main performance indicators: polarization, transmittance and hue. Others include UV protection and transmissivity, total reflectance and diffuse reflectance of the semi-transmissive polarizer. . In the use of general LCD products, it is required that the higher the degree of polarization and transmittance performance, 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 power 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 the color tone. Therefore, the general polarized light is generally used. The polarizedness of the film products is between 90% and 99%, and the transmittance is between 41% and 44%. The "Fudi" brand polarizer universal PLN produced by Guangdong Fudi Rihe Polarization Device Co., Ltd. has a partial polarization of 97% or more and a transmittance of 43%, while the medium-durable and high-contrast PMN products have a polarization of 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 color tone deviation of the polarizer product is required to be small to ensure the consistency of the color tone of the final product of the LCD, which is mainly determined by the chromaticity coordinate parameters L, a, b of the polarizer product and Their control tolerance range is used to identify, generally the smaller the range of control tolerances, the better.


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The durability specifications of the polarizer include four indexes of high temperature resistance, heat and humidity resistance, low temperature resistance and cold and heat shock resistance, the most important of which is the level of resistance to heat and humidity. 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 generally divided into general type: working temperature is 70 ° C × 500 HR; medium durable type: working temperature is 80 ° C × 500HR; high durability type: the working temperature is three levels of 90 ° C × 500H. The heat and humidity resistance index refers to the heat and humidity resistance of the polarizer under constant temperature and humidity conditions. It is also generally divided into three technical grades, which are common: wet heat working conditions are 40 ° C × 90% RH × 500 HR; medium durable type : Damp heat working conditions are 60 ° C × 90% RH × 500 HR; high durability type: damp heat working conditions: 70 ° C × 95% RH × 500 HR or more. Since the basic material PVA film constituting the polarizing film and iodine and iodide are extremely easily hydrolyzable materials, and also because the pressure sensitive adhesive used for the polarizing plate is easily deteriorated under high temperature and high humidity conditions, the durability of the polarizer is high. The most important of the technical indicators are the high temperature and humidity resistance indicators. If the high temperature and humidity resistance indicators pass, other durability indicators will usually not cause problems. "Fudi" brand general-purpose PLN products and medium-durable PMN products are able to meet the requirements of the durability specifications specified in their respective technical grades.


The bonding characteristics of the polarizer mainly refer to the characteristics of the polarizer pressure sensitive adhesive, generally including: peeling force between the pressure sensitive adhesive and the glass substrate, peeling force between the pressure sensitive adhesive and the peeling film, and polarizer protection The peeling force between the film and the polarizer and the bonding 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 standard EIAJ-ED-2521A standard, expressed in g/25mm. Generally, the peeling force of the LCD polarizer pressure sensitive adhesive on the glass substrate is specified to be 500g/25mm or more. The upper limit of the actual use is generally 1000g/25mm or less. There are practical examples showing that when the peeling force of the adhesive to the glass substrate is 500 g/25 mm or less, the polarizing film is automatically peeled off and warped after bonding on the surface of the glass screen.


The appearance performance technical specifications of the polarizer mainly refer to the surface flatness and the number of appearance defects of the polarizer product. These technical indicators mainly affect the utilization rate of the polarizer product in the patch. These technical indicators generally have relatively consistent technical regulations in the polarizer industry, generally 15 points below each polarizer product (500 × 1000mm) and less than 150μm. Since the final visual inspection of the polarizer products is performed by manual visual inspection, in the mass production process of the polarizer products, the distribution of the appearance defects will have a certain discrete distribution, and each polarizer production enterprise adopts a certain degree. The difference between the internal control specification and the delivery specification guarantees the delivery quality standard. However, it should be noted that since 150μm is already close to the minimum limit of visual discrimination of the human eye, especially in the industrial mass production process, the inspectors will also experience visual fatigue during long-term operation, so the 150μm under-point inspection standard is more reasonable. Trustworthy.


Main factors affecting the performance of LCD polarizers


The main factors affecting the performance of the polarizer are related to the basic performance indicators of the polarizer.


The main influencing factors affecting the optical performance of polarizers include: choice of polarizing film materials, selection of dyeing materials, dyeing of polarizing films, selection of process conditions for stretching, and limitations of equipment capabilities. These are all related to the core technology of polarizer production. Therefore, the choice of these materials and process conditions is very cautious for the manufacturers of polarizers, and generally will not be easily changed. Once the products of the polarizer production company are approved by the customer, the polarizer production enterprise will adopt strict production quality management measures to ensure the stability of the optical performance of the polarizer.


The durability specifications 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 polarizing film include: selection of basic materials for polarizing film, selection of dyeing materials, dyeing of polarizing film, stretching, and compounding process conditions. In general, the larger the molecular weight of the PVA film selected for the polarizer, the higher the draw ratio, the better the durability of the polarizing film, and vice versa. At the same time, the better the degree of coloration of the polarizing film in the production process, the stronger the anti-solution 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: choice of adhesive formulation, choice of binder solvent, choice of binder blending process conditions, choice of binder drying process conditions, and binder storage conditions. s Choice. It should be noted that the durability index of the adhesive is a comprehensive indicator, its impact is multifaceted, and this is another core technology for the production of polarizers. Generally, the polarizer manufacturer determines the process conditions of the adhesive. After that, it will not be easily changed and has strict process quality management requirements, otherwise it will easily cause bad products in batches.


The main factors affecting the appearance performance of polarizers are also various. Mainly include: environmental purification conditions for polarizer production, material selection for polarizer production, equipment conditions for polarizer production, process flow and process formulation for polarizer production, polarizer packaging, storage, transportation conditions, and polarizer for customer use. Storage environment and processing methods. In short, the polarizer is a very "squeaky" product that must be carefully stored and used, otherwise it will easily cause surface defects such as surface pits, black spots and warpage.


Find a non-delayed polarizer of known angle, superimposed with an unknown angle polarizer, and observe the polarizer by light observation, when the transmittance is the lowest (the darkest background or the bluish-purple Background color, the angle between the known angle polarizer and the unknown angle polarizer is 90 degrees.


If the unknown angle polarizer has a retardation film, the darkest background color (usually green, bright purple, etc.) cannot be observed by rotation. At this time, it is proved that there is a retardation film between the two light sheets, and the unknown polarizer bottom is The surface can be reversed and observed. Refer to the previous method to determine the angle.