Performance and index of LCD polarizer

The optical performance of the polarizer includes three main performance indexes: polarization, transmittance and hue. Others include anti ultraviolet performance and the transmittance, total reflectivity and diffuse reflectivity of the semi permeable film of the semi permeable polarizer. In the use of general LCD products, the higher the polarization and transmittance performance indicators, the better. The higher the polarization and transmittance, the higher the display efficiency of LCD display devices and the lower the relative energy consumption. However, for the conventional iodine dyed polarizer products, the polarizing degree and transmittance are a pair of contradictions. The higher the polarizing degree, the lower the transmittance will be, and it will be constrained by the hue. Therefore, the polarizing degree of ordinary polarizer products is between 90% - 99% and the transmittance is between 41% - 44%. The "Fudi" brand polarizer general-purpose PLN product produced by Guangdong Fudi rihe polarizing device Co., Ltd. has a polarizing degree of more than 97% and a transmittance of 43%, while the medium durable and high contrast PMN product has a polarizing degree of more than 99.9% and a transmittance of more than 42%. The hue index is mainly to meet people's visual habits. At the same time, it is required that the hue deviation of polarizer products should be small to ensure the consistency of the appearance hue of LCD final products. This is mainly identified by the chromaticity coordinate parameters L, a and B of polarizer products and their control tolerance range. Generally, the smaller the control tolerance range, the better.

The durability technical indexes of polarizer include four technical indexes: high temperature resistance, damp heat resistance, low temperature resistance and cold and heat shock resistance, of which the most important is the damp heat resistance performance index. High temperature resistance refers to the temperature resistant working conditions of polarizer under constant baking temperature. At present, according to the technical level of polarizer, it is usually divided into general type: the working temperature is 70 ℃ × 500HR； Medium durable type: the working temperature is 80 ℃ × 500HR； High durability type: working temperature at 90 ℃ × Above 500h. The technical index of damp heat resistance refers to the working performance of the polarizer under the condition of constant temperature and humidity. It is also generally divided into three technical levels, i.e. general type: the working condition of damp heat is 40 ℃ × 90%RH × 500HR； Medium durable type: hot and humid working condition: 60 ℃ × 90%RH × 500HR； High durability type: hot and humid working condition: 70 ℃ × 95%RH × Above 500hr. As the basic material of polarizing film, PVA film, iodine and iodide are materials that are easy to hydrolyze, and the pressure-sensitive adhesive used in polarizer is easy to deteriorate under high temperature and high humidity conditions, the most important technical indicators of polarizer durability are high temperature resistance and damp heat resistance. If the high temperature resistance and damp heat resistance indicators pass, other durability indicators usually will not have problems.

The technical indexes of the bonding characteristics of the polarizer mainly refer to the characteristics of the polarizer pressure-sensitive adhesive, which generally include the peeling force between the pressure-sensitive adhesive and the glass substrate, the peeling force between the pressure-sensitive adhesive and the peeling film, the peeling force between the polarizer protective film and the polarizer, and the bonding durability of the pressure-sensitive adhesive. The peeling force between pressure-sensitive adhesive and glass substrate is also known as the bonding strength of adhesive, which is the most important bonding characteristic index of LCD polarizer products. This technical index is usually measured by the specification eiaj-ed-2521a of Japan Electronic Machinery Industry Association, expressed in g / 25mm. Generally, the peeling force of LCD polarizer pressure-sensitive adhesive on glass substrate is more than 500g / 25mm, while the upper limit in practical use is generally less than 1000g / 25mm. A practical example shows that when the peeling force of the adhesive on the glass substrate is less than 500g / 25mm, the polarizer will peel and warp automatically after bonding on the surface of the glass screen.

The appearance performance technical indexes of polarizer mainly refer to the surface flatness and the number of appearance defects of polarizer products. These technical indexes mainly affect the utilization rate of polarizer products when they are pasted. These technical indicators usually have relatively consistent technical regulations in the polarizer industry, which is generally 500 yuan per polarizer product × 1000 mm) less than 15, not more than 150 μ Under point of M. As the final appearance inspection of polarizer products adopts manual visual inspection, the distribution of appearance defects will have a certain discrete distribution in the batch production process of polarizer products. Therefore, each polarizer manufacturer adopts a certain difference between internal control specifications and delivery specifications to ensure the delivery quality standard. But it should be noted that due to 150 μ M is close to the minimum limit of human visual discrimination, especially in the process of industrial mass production, inspectors will also produce visual fatigue during long-time operation, so 150 μ M is reasonable and credible.

Main factors affecting the performance index of LCD polarizer

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

The main factors affecting the optical performance technical indexes of polarizer include the selection of polarizing film materials, dyeing materials, polarizing film dyeing, the selection of drawing process conditions and the limitation of equipment capacity. These are related to the core technology of polarizer production. Therefore, polarizer manufacturers are very cautious in the selection of these materials and process conditions, which will not be changed easily. Once the products of the polarizer manufacturer are recognized by the customers, the polarizer manufacturer will take strict production quality management measures to ensure the stability of the optical performance of the polarizer products.

The durability technical index of polarizer products actually includes two durability indexes: the durability of polarizing film and the durability of pressure-sensitive adhesive. The main factors affecting the durability of polarizing film include: the selection of basic materials of polarizing film, the selection of dyeing materials, the process conditions of polarizing film dyeing, stretching and compounding. Generally speaking, the greater the molecular weight and the higher the tensile ratio of the PVA film selected by 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 solution ability of the dye used, the better the durability of the polarizing film. Therefore, the durability of the dye polarizer is much better than that of the iodine dye polarizer. The main factors affecting the durability of pressure-sensitive adhesive include the selection of adhesive formula, adhesive solvent, adhesive blending process conditions, adhesive drying process conditions and adhesive storage conditions. It should be noted that the durability index of adhesive is a comprehensive index, and its impact is multifaceted, and this is another core technology of polarizer production. Generally, polarizer production enterprises will not change easily after determining the process conditions of adhesive, and have strict process quality management requirements, otherwise it is very easy to cause batch bad products.

The main factors affecting the appearance and performance of polarizer are also various. It mainly includes: environmental purification conditions of polarizer production, material selection of polarizer production, equipment conditions of polarizer production, process flow and process formula of polarizer production, packaging, storage and transportation conditions of polarizer, as well as storage environment and processing method of polarizer when used by customers. In short, polarizer is a very "delicate" product, which must be carefully kept and used, otherwise it is easy to cause surface defects such as concave spots, black spots and warpage.