Magnetic recording medium comprising an oriented polyester substrate, an antistatic coating of a polymer with pyrrolidium rings in the main chain and a magnetic layer

#The present invention relates a stretched antistatic laminate polyester film. More particularly, the present invention relates to a stretched antistatic laminate film prepared by coating a polymer having pyrrolidium rings to at least one surface of a polyester film and then stretching the resultant film, a magnetic recording medium having a magnetic layer on the stretched antistatic laminate film, a film having a silicon resin layer on the stretched antistatic laminate film, recording material for a thermal transfer printing having the stretched antistatic laminate film, as well as a method of manufacturing a film having the stretched antistatic laminate film.

#Biaxially stretched polyester films have generally been used as a film having excellent properties but they have a fault of being easily charged.

#As a method of preventing static charges, there are a method of kneading an anionic compound such as an organic sulfonate and organic phosphate, a method of vacuum-evaporating a metal compound, a method of coating an anionic compound, cationic compound or so-called electroconductive particles, etc. The method of kneading the anionic compound can be conducted at a reduced cost but it involves problems such as the limit for the antistatic effect, as well as deterioration in the adhesion between the film and the laminated layer due to blooming, lacking in water proofness and transferring the compound since the compound usable herein is a low molecular weight compound. The method of vacuum-evaporating the metal compound can provide excellent antistatic effect and the application use for transparent electroconductive films of the resultant films has been increased in recent years. However, since the production cost thereof is high, it is unfavorable to use the method for usual antistatic films although suitable to particular application uses. The method of coating the electroconductive carbon or electroconductive metal particles has relatively satisfactory antistatic effect and a merit capable of producing films at a relatively reduced cost, but it has a fault that the transparency of the films become worse.

#Polyethylene terephthalate having an intrinsic viscosity of 0.65 was melt-extruded at a temperature from 280.degree.-300.degree. C. and cast on a cooling drum while using an electrostatic cooling method thereby obtaining an amorphous film of 820 .mu.m in thickness.

#A coating solution of a Sharoll DC-902P (trade name Daiichi Kogyo Seiyaku Co., Ltd.) which is a polymer comprising a constitution unit represented by the formula (I) was coated on one surface of a polyester film after longitudinally stretching the thus obtained amorphous polyester film by 3.3 times at 90.degree. C. but before transversally stretching. Then, the coated film was stretched transversally by 3.3 times at 110.degree. C. and then subjected to heat-treatment at 210.degree. C. to obtain polyester films having coating layers of various coating thickness (thickness of the polyester film : 75 .mu.m). The relation between the thickness of the coating layer of the film and the antistatic property was as described below.

#TABLE 1 ______________________________________ Coating layer thickness (.mu.m) 0.015 0.030 0.045 0.100 ______________________________________ Charge somewhat satis- extremely extremely attenuation satisfactory factory satisfac- satisfac- tory tory Inherent somewhat satis- extremely extremely surface satisfactory factory satisfac- satisfac- resistivity tory tory ______________________________________