Stock material or miscellaneous articles – Composite – Of polyester
Patent
1999-06-28
2000-09-26
Acquah, Samuel A.
Stock material or miscellaneous articles
Composite
Of polyester
528298, 528300, 528301, 528302, 528308, 525437, 525444, 430533, 430627, 428900, 428902, B32B 2706, G03C 176, C08G 6318
Patent
active
061240435
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a biaxially oriented film formed from a polyethylene naphthalate copolymer. More specifically, it relates to a biaxially oriented film useful as a base film for a magnetic recording medium or photo film.
BACKGROUND ART
Polyesters typified by polyethylene terephthalate are now widely used in such application fields as fibers, films and molded articles on account of their excellent physical and chemical properties. Especially, in the field of magnetic recording media which have been making remarkable progress these days, such as audio tapes, video tapes, computer tapes and floppy disks, a biaxially oriented film of polyethylene terephthalate is advantageously used as a base film.
However, along with a recent tendency to reduce the size and weight of electric and electronic equipment and to improve performance thereof, properties required for a base film having been becoming increasingly restricted. For instance, in the field of magnetic recording media, a base film must be thin to realize long-time recording and reductions in size and weight. At the same time, it is important to retain the stiffness of a film by improving elastic modulus. Therefore, it has been found in some cases that an extremely thin base film formed from conventional polyethylene terephthalate is unsatisfactory in terms of elastic modulus.
In contrast to the film formed from polyethylene terephthalate (to be referred to as "PET film" hereinafter), a film formed from polyethylene-2,6-naphthalate (to be referred to as "PEN film" hereinafter) has excellent mechanical properties, heat resistance, chemical properties and high Tg and is preferably used in the above application fields. However, the PEN film has a lower tear strength (lower delamination resistance) than an ordinary PET film. Particularly when it is stretched like a biaxially oriented film, the tear strength of an intermediate or final product in the process of molding is low in many cases. Therefore, the film is broken so frequently that a product cannot be obtained, for example, in the production process of a sequentially biaxially oriented film of polyethylene-2,6-naphthalate, or even if a product is obtained, a film which is readily torn in a specific direction is obtained.
Meanwhile, a triacetate film has been used as a base film for a photo film. This triacetate film involves safety and environmental problems because an organic solvent is used in its production process. In addition, it has limits in mechanical strength and dimensional stability. Therefore, a PET film has started to be used in part of the application fields of this triacetate film as a substitute base film. However, when kept in the form of a roll and unrolled, this PET film remains curled and this curl is difficult to remove. Therefore, the PEN film shows low handling properties after developed, thereby making it difficult to use it for a photo film which is used as a rolled film.
As a technology for improving the anti-curling property of this PET film, JP-A 53-146773 and JP-A 1-244446 propose films which are formed from modified polyethylene terephthalate to improve, for example, steam permeability and moisture content. Although the effect of improving anti-curling property is observed in these films, moisture absorption causes a reduction in dimensional stability and a reduction in glass transition temperature, which in turn increase the deformation of the end portions of the films. Therefore, they are unsatisfactory as a base film for a photo film.
Further, a demand for a photo film of higher quality has recently arisen. For instance, attempts are being made to increase the winding speed of a rolled film at the time of photographing and to reduce the size of a photographing device. The film is demanded to show excellent anti-curling property even when rolled to a very small diameter and excellent mechanical strength and dimensional stability when reduced in thickness. Both the above triacetate film and the modified polyethylene terephthalate film canno
REFERENCES:
patent: 4732799 (1988-03-01), Sakamoto et al.
patent: 4804736 (1989-02-01), Utsumi
patent: 4812360 (1989-03-01), Utsumi
patent: 5556712 (1996-09-01), Kimura et al.
patent: 5703283 (1997-12-01), McClish et al.
patent: 5753172 (1998-05-01), Forrest, Jr. et al.
patent: 5759467 (1998-06-01), Carter et al.
patent: 5885501 (1999-03-01), Gardner et al.
Furuya Koji
Ito Seiji
Kawai Shinichi
Suzuki Kenji
Teramoto Mitsuru
Acquah Samuel A.
Teijin Limited
LandOfFree
Biaxially oriented film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Biaxially oriented film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Biaxially oriented film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2098275