1. introduction
A smart card, also known as an IC card, refers to a card in which an integrated circuit chip is packaged. IC card has the characteristics of large storage capacity, high data security, good anti-counterfeiting, low cost of application equipment and mature technology. It has been widely used in various fields such as finance, public security, transportation, communication, service and medical care.
Since the use of IC cards in telephone cards in France in 1984 and has achieved great success, IC cards have achieved tremendous development. China started the gold card project in 1993, and its technology and market are relatively mature.
The plastic sheet for making IC cards is called card base material. The common card base materials are mainly ABS (acrylonitrile butadiene styrene 1, PVC (polyvinyl chloride), PET (polyethylene terephthalate). Alcohol ester), PC (polycarbonate), PETG (modified PET), etc. The most widely used card base material is PVC, but because PVC contains chlorine, such materials are not conducive to environmental protection. With the continuous introduction of new materials and the rapid development of IC card technology, the materials used for card-based materials are also constantly changing. Some new card-based materials that are environmentally friendly and resistant to high temperature and can be preserved for a long time have been introduced, such as PETG, PC, PC/ Each material has different characteristics, such as PBT, and should be selected according to different needs.
2. Card base material introduction
2.1 PVC material
PVC (polyvinyl chloride) granular rubber is a multi-component plastic, and the appearance varies greatly depending on the content of each component. There are transparent materials and opaque materials: some are soft and elastic, and are resistant to folding; they also have hard and rigid mechanical properties. Most PVC is slightly toxic, but there are also food grade PVC gel particles.
PVC can be divided into soft PVC and rigid PVC. The surface hardness, tensile strength, rigidity, etc. of rigid PVC are close to the index of engineering materials. Soft PVC is commonly used on wallpapers, floors, ceilings and leather. Hard PVC becomes brittle at low temperature, which is sensitive to deformation and cannot be completely recovered after deformation: soft PVC is hardened at low temperature, has poor thermal stability, and is thermally degraded (see Table 1).
At the same time as various new card-based materials are gradually being applied, PVC card-based materials still occupy a large proportion of the market share because of its low production cost and superior performance. PVC films can be printed almost without any treatment. It is still hot-pressed, so it is still widely used. PVC material is suitable for IC cards that need to print magnetic strips, signatures or embossed characters and holographic marks on the card surface. However, its environmental protection is poor, and it will release HCL gas at high temperature. The environment has caused harm, and the industry has begun to phase out PVC card-based materials.
With the development of the plastics industry, some PVC composite materials, such as PVC/ABS, PVC/PET, PVC/PE, etc., have improved their performance compared with PVC.
2. 2 PET
PET is a thermoplastic polymer formed by the esterification reaction of terephthalic acid and ethylene glycol. It is a crystalline polyester with a distinct melting point. It melts at 250 ° C. Decomposes at 360 ° C: the general processing temperature is 280 ° C -320 ° C (see Table 1); PET is a colorless transparent high hardness and tough material. Therefore, it is a substrate for producing photo negatives, and can also be used to produce audio tapes and video tapes. PET film material has low specific gravity, no moisture absorption, high insulation and transparency, excellent mechanical properties, small processing deformation, good wear resistance, good chemical resistance, high surface finish and long service life. It is also an environmentally friendly material. South to these
Advantages, PET materials are widely used in the card manufacturing industry.
The PET film material is processed by a biaxial stretching process. After biaxial stretching, the macromolecular chains in the initial amorphous state are oriented in the direction of stretching to produce crystals. The deformation of the molecular chains at different positions of the film is not uniform, and the molecular chain deformation closer to the center line direction is smaller. The orientation direction is also different. The general direction gradually approaches the two sides along the center line, and the magnitude of the deviation angle is proportional to the stretch ratio. Therefore, PET materials should be paired and used during use. If the stress direction of the material is not paid attention to, the deformation direction of the polymer material on both sides of the card body will cause warpage of the card body.
The original state of PET material is not suitable for printing and thermo-compression bonding, and needs to be surface treated. To make the PET surface easy to print and bond, the current research is focused on improving its antistatic properties. Printing adaptability, adhesion, etc. face to face.
The surface modification treatment method is mainly through corona, rubber coating and photografting. Make the surface functional. Achieve the purpose of printing and bonding.
At present, most of the ordinary PET protective film on the market is coated with a layer of hot melt adhesive on the PET surface. For example, EVA, some of them are through the surface photopolymerization grafting technology, a low melting point polyester compound is synthesized on the PET surface to improve the printability and adhesion. DuPont has a molded PET protective film under the trade name MELINEX PETF 3368. The film is made by a special process to change the crystalline state of PET and co-extruded with a conventional PET film. This card-based material supports a variety of printing techniques and quickly bonds to the card body at around 120 °C. The bonding process is irreversible. This material is used in large quantities in Europe and the United States, but because of its high cost, there are only a few important legal documents in use in the country.
Because PET film often needs to print or print patterns, its surface electrostatic treatment is also a hot topic. According to the specific requirements of PET film, antistatic liquid and antistatic particles can be sprayed or sprayed on the surface of PET film material. Or apply an antistatic coating to solve these problems. The First Institute of the Ministry of Public Security has extensive experience in this area. Some anti-static technologies have been used in the large-scale certification process. I got a very good antistatic effect.
2.3 ABS
ABS is synthesized from acrylonitrile, butadiene and styrene. It is a pale yellow opaque particle with a high gloss on the surface. ABS is an amorphous material with a slightly heavier specific gravity than water (see Table 1). ABS material has high rigidity and medium tensile strength: it has good chemical resistance and surface hardness, good toughness and impact resistance, easy processing, strong fluidity, and easy printing and dyeing.
Different types of ABS materials can be made by changing the ratio of the three monomers in the ABS and the molecular structure in the two phases, and the properties of the various types of materials are also very different. In general, all types of ABS materials have a good luster. Hardness. Tough, rigid and moderately mechanical. Because it is easy to surface treatment such as printing and plating and has a stable dimensional stability, it is suitable for card-based materials. One of the disadvantages of ABS used as a card-based material is that it cannot be printed with embossed characters. In addition, ABS has poor weather resistance, and it is easy to age and fade. The mobile phone SIM card uses PVC+ABS mixture. This material can be used in higher temperature environments in mobile phones. If the environment of the card body is required to be heat-resistant and flame-retardant, ABS card-based materials are generally used.
2.4 PC and its alloy materials
1) PC (polycarbonate) is rigid and tough, with high transparency. The surface has a high gloss and the mechanical strength is close to nylon: impact resistance, high temperature resistance, resistance to friction, intolerance
Stress cracking (see Table 1) swells in steam and many organic solvents and causes stress cracking. PC materials have high processing temperatures, and have high requirements for laminated card equipment. Some cards in the United States use more PC materials, and domestic card manufacturers use PCs to produce some high-end cards. Because PC has a high carbon content. And no high temperature release of harmful gases, PC materials can be used for laser etching anti-counterfeiting.
2) PC alloy material, relative to PC. PC alloy material is widely used due to its good processing properties. PC-PBT is a blending material of PC and PBT, which retains the advantages of both: high temperature resistance, stress crack resistance, high surface hardness and high rigidity. And resilience. This material is mainly used to make large or precision instrument casings, such as mobile phone casings or car dashboards. Its film materials can also be used as card-based materials, which have good printing and environmental protection. US GE and Japan's Mitsubishi have film products for this material. This material is used in large quantities on Japanese cards.
There is also a kind of PC/ABS plastic: PC-ABS has the easy addition of ABS and PC. It has good mechanical and thermal stability, high surface hardness, high rigidity and toughness, and high resistance. Stress cracking: Mechanical properties are between ABS and PC. This type of card base material is relatively less used.
2.5 PETG
PETG is a kind of polyester obtained by copolymerization of ethylene glycol (EG) and terephthalic acid (TPA) polycondensation polyester (PET) with south 1,4 cyclohexanedimethanol (CHDM). Amorphous copolyester. High material transparency, high impact resistance, high hardness and good low temperature toughness. Widely used in sheet metal, high-performance shrink film, profile, toys, food, high-grade packaging materials and other fields.
PETG has been used more and more in the card industry because it has a lower heating temperature (about 100%), higher mechanical strength and excellent flexibility, higher transparency than PVC, good gloss and easy Printed and has an environmental advantage.
In Europe, the United States, and El Ben, PETG materials are widely used in electronic payment and identification documents. Visa has recognized PETG as its card base material. Some high-end securities cards and important legal documents have begun to use PETG as the card-based material.
The manufacturers of PETG resin in the world are mainly Eastman and SK. Manufacturers of card-based materials purchase PETG resin and formula by calendering or casting to add T-sheets, sheets, films, etc. There are currently four manufacturers of PETG materials in China, all of which use imported Eastman. The resin produces a card base material.
2.6 paper card base material
Because the IC card contains chips and coils. One of the functions of the card-based material is to protect the chip and the coil from damage when an external force acts. Paper is less used on IC cards due to its low hardness, resistance to bending, tearing, tearing, non-water resistance, oil resistance, and resistance to friction. However, one of the most important advantages of paper is its good printing adaptability and low cost. Some existing anti-counterfeiting printing methods must be realized on paper. Paper-based materials can also be used to make antennas by printing, which can reduce the card making. Cost and improve card making efficiency.
Due to the above characteristics of the paper-based material, the frequency of use of the card is not very high, and the use time is not very long, considering the cost of the paper material and good printing performance. Paper can also be used as a card base material on some travel documents. Due to the need for special anti-counterfeiting methods, it is often made of paper-based materials.
With the continuous development of papermaking technology and materials science, a variety of specialty papers have been created to meet different requirements. Such as the United States TESLIN composite paper: the material is composed of polyolefin and SiO2 composite. Both the performance of the paper and the performance of the plastic, with micro-pores, high filling, high waterproof, high adsorption and other characteristics. The material is soft and strong and can be formed by press molding. American passports and military certificates were made with TESLIN. In some countries in Europe, this material is used as the INLAY for electronic travel documents; YUPO is a synthetic paper based on polypropylene. It has the advantages of paper and plastic film, and has great applications in various fields such as label, packaging and information paper, card in commercial printing film; DURASOFF/P paper. Dutch SMARTRAC products. Synthesized from polyethylene and silica and other additives. SMARTRAC mainly uses it to make INLAY.
The various high performance synthetic papers mentioned above have the following common features:
Beautiful appearance, excellent printing; water, oil and corrosion resistance; excellent durability; wide temperature applicability: good dimensional stability; not easy to tear; easy to combine with ink, toner, adhesive; very good environmental protection.
Since the above materials have the advantages of paper and plastics, they are being used more and more widely in the field of cards.
2.7 other
In a broad sense. The electronic label is also a kind of smart card. The label has a wide range of materials: in addition to the above mentioned materials, there are PU (polyurethane), PP (polypropylene), etc., in some specific operating environments, Materials have high requirements, and some T-process plastics such as PPS, PPO, PSF, PEN, etc. can be used as carrier materials for electronic labels.
3. summary
Smart cards belong to the high-tech industry, which includes various fields such as radio frequency, materials, adhesives, printing, and anti-counterfeiting. Any improvement in technology will bring great development to the card industry. The choice of the card base material should consider the market supply, the cost performance of the material and the functions and applications to be realized by the card. Before selecting a card base material, the easiest way is to perform physical and chemical tests according to the standard. These test methods are specified in ISO7810, IS07816, GB/1116649.1-1996, GB/T17553-1998, and GB/T17554-1998.
As people's functional requirements for smart cards are getting higher and higher. The use of smart cards is becoming more and more extensive, and card-based materials are constantly being developed as a carrier of smart cards. With the continuous improvement of materials and related technologies, there will be better materials to enter the market to meet the growing market demand. In general, high-performance green composite materials that meet environmental requirements are the development direction of card-based materials.
ã€references】
Wang Zhuoren. The structure, function and application of a smart card. Beijing: Electronic Industry Press. 2002
Yang Zhenye. Ic card technology and its applications. Beijing: Science Press, 2006
Ding Hao. Plastic application technology. Beijing: Chemical Industry Press. 2006
Wu Zhangyong, etc., Gold Card and Kaki Materials, Shanghai Plastics, 2001, 114: 9-13
Wen Yaoxian. Functional plastic film. Beijing: Chemical Industry Press, 2005
Chen Changjie. Printing and Composite of Plastic Films Beijing: Chemical Industry Press, 2004
About the author: Wang Cheng (1978-), male, engineer of the Forensic Center of the First Institute of the Ministry of Public Security, mainly engaged in research work on card-making materials.
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