LCD polarizer knowledge
The basic technical indicators of LCD polarizer
The basic performance indicators of LCD polarizer are mainly: optical performance, durability, bonding characteristics, appearance performance and other special performance of several aspects of the basic technical indicators requirements.
The optical properties of the polarizer include: polarization, transmittance and tone three main performance indicators, other including UV protection performance and semi-transmittance, full reflectivity and diffuse reflectance of the semi-transmittance film of the semi-transmittance polarizer. In the use of general LCD products, the higher the polarization and transmittance indicators are required, the better. The higher the polarization and transmittance, the higher the display efficiency of the LCD display device, and the relative energy consumption is small. However, for conventional iodine dyed polarizing products, the polarizing degree and transmittance is a contradiction, the higher the polarizing degree, the lower the transmittance will be, and it is also subject to the color restriction, so the general polarizing degree of the ordinary type of polarizing product is between 90% and 99%, and the transmittance is between 41% and 44%. The general PLN product of “Fudi” brand polarizer produced by Guangdong Fudi Rihe Polarizer Device Co., Ltd. has a polarizability of more than 97% and a transmittance of 43%, while the polarizability of medium-durability and high-contrast PMN products is more than 99.9% and a transmittance of more than 42%. The color index is mainly to meet people’s visual habits, and the hue deviation of the polarizer product is required to be small to ensure the consistency of the appearance of the LCD final product hue, which is mainly identified by the color coordinate parameters of the polarizer product L, a, b values and their control tolerance range, generally the smaller the range of its control tolerance, the better.
The durability technical indicators of the polarizer include four technical indicators: high temperature resistance, humidity and heat resistance, low temperature resistance and cold and heat shock resistance, the most important of which is the level of humidity and heat resistance performance indicators. High temperature resistance refers to the temperature resistance working conditions of the polarizer at a constant baking temperature. At present, according to the technical grade of the polarizer, it is usually divided into general types: the working temperature is 70℃×500HR; Medium durability type: the working temperature is 80℃×500HR; High durability type: the operating temperature is 90℃×500H above these three grades. Humidity and heat resistance technical indicators refer to the humidity and heat resistance performance of the polarizer under constant temperature and humidity conditions, which is usually divided into three technical levels, both general type: humidity and heat working conditions of 40℃×90%RH×500HR; Medium durability type: hot and humid working conditions of 60℃×90%RH×500HR; High durability type: hot and humid working conditions: 70℃×95%RH×500HR or more. Because the basic materials of the polarizing film PVA film and iodine and iodide are easily hydrolyzed materials, but also because the pressure sensitive adhesive used in the polarizing film is also easy to deteriorate under high temperature and high humidity conditions, therefore, the most important technical indicators of the durability of the polarizing film are high temperature and humidity resistance indicators, if the high temperature and humidity resistance indicators pass, Other durability indicators are usually not a problem. “Good Luck” brand general purpose PLN products and medium durability PMN products can well meet the requirements of the durability technical indicators specified in their respective technical levels (see Figure 2).
The bonding characteristics of the polarizer mainly refer to the characteristics of the polarizer pressure-sensitive adhesive, which generally includes: the stripping force between the pressure-sensitive adhesive and the glass substrate, the stripping force between the pressure-sensitive adhesive and the stripping film, the stripping force between the polarizer protective 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 bonding strength of the adhesive, which is the most important bonding characteristic indicator of LCD polarizer products. This technical indicator is usually measured by the Japanese Electronic Machinery Industry Association specification EIAJ-ED-2521A standard, expressed in g/25mm, usually the stripping force of LCD polarizer pressure sensitive adhesive on the glass substrate is stipulated at more than 500g/25mm, and the actual use of the upper limit is generally below 1000g/25mm. There are practical examples that show that when the stripping force of the adhesive on the glass substrate is below 500g/25mm, the phenomenon of automatic stripping and warping of the polarizer after bonding on the glass screen surface will occur.
The appearance performance technical indicators of the polarizer mainly refer to the surface flatness of the polarizer product and the number of appearance points, and these technical indicators mainly affect the utilization rate of the polarizer product in the patch. These technical indicators usually have more consistent technical regulations in the polarizer industry, generally for each polarizer product (500×1000㎜) less than 15 points of less than 150μm. Because the final appearance inspection of the polarizer product is the use of manual visual inspection, so in the mass production process of the polarizer product, the distribution of the appearance of the point will have a certain discrete distribution, in this regard, each polarizer production enterprises are using a certain difference between the internal control specifications and the delivery specifications to ensure the quality of delivery standards. However, it should be noted that since 150μm is close to the minimum limit of human visual resolution, especially in the process of industrial mass production, inspectors will produce visual fatigue during long-term operation, so the underpoint inspection standard of 150μm is more reasonable and credible. The main factors affecting the performance index of LCD polarizer
The main factors affecting the performance of polarizer are related to the basic performance index of polarizer.
The main factors affecting the optical performance of the polarizer include the selection of the material of the polarizing film, the selection of the dyeing material, the selection of the polarizing film dyeing, the selection of the stretching process conditions and the limitation of the equipment capacity. These all involve the core technology of polarizer production, so polarizer manufacturers are very careful about the choice of these materials and process conditions, and generally will not easily change. Once the product of the polarizer manufacturer is recognized 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 durability technical index of polarizing plate products actually includes two aspects of durability index: the durability of polarizing film and the durability of pressure sensitive adhesive. The main factors that affect the durability of polarized film include: the selection of basic materials of polarized film, the selection of dyeing materials, dyeing, stretching, composite process conditions and other factors. In general, the larger the molecular weight of the PVA film selected by the polarizer and the higher the tensile ratio, the better the durability of the polarizing film, and vice versa. At the same time, the better the color of the polarizing film in the production process, the stronger the anti-hydrolysis ability of the dye used, the better the durability of the polarizing film, so the durability of the dye-based polarizing film is far better than the durability of the iodine dyeing polarizing film products. The main factors affecting the durability of pressure-sensitive adhesive include: the choice of adhesive formula, the choice of adhesive solvent, the choice of adhesive mixing process, the choice of adhesive drying process and the choice of adhesive storage conditions. It should be noted that the durability index of the adhesive is a comprehensive indicator, its impact is multifactorial, and this is another core technology of polarizer production, general polarizer production enterprises will not easily change after determining the process conditions of the adhesive and have strict process quality management requirements, otherwise it is easy to cause bad batch products.
The main factors that affect the appearance performance of polarizer are also many. Mainly include: environmental purification conditions for polarizing plate production, material selection for polarizing plate production, equipment conditions for polarizing plate production, process flow and process formula for polarizing plate production, polarizing plate packaging, storage, transportation conditions, and storage environment and processing methods for polarizing plate when used by customers. In short, the polarizer is a very “delicate” product, which must be carefully kept and used, otherwise it is easy to cause surface pits, black spots and warping and other surface defects. Find a polarizer with no delay of a known Angle, and the unknown Angle polarizer superposition, observe through the light, rotate the known polarizer, when the transmittance is lowest (the darkest background color or slightly blue-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 delay film, the blackest background color (generally green, bright purple, etc.) can not be observed by rotating, then it is proved that there is a delay film between the two pieces of light, the unknown polarizer bottom and surface can be reversed to observe, refer to the previous method to determine the Angle.