Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
2000-06-09
2002-11-26
Resan, Stevan A. (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S323000, C428S3550RA, C428S690000, C428S690000, C428S336000, C428S337000, C428S409000, C428S480000, C428S331000, C428S329000, C428S327000, C428S065100
Reexamination Certificate
active
06485810
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a biaxially oriented polyester film and to a flexible disk comprising the same as a base film. More specifically, it relates to a biaxially oriented polyester film which has excellent handling properties and is free from a dimensional change when or after it is processed for use in a flexible disk and to a flexible disk which comprises the same as a base film and has excellent electromagnetic conversion characteristics.
RELATED ART
A biaxially oriented polyester film typified by a biaxially oriented polyethylene terephthalate film and a biaxially oriented polyethylene naphthalene dicarboxylate film is widely used as a base film for magnetic recording media due to its excellent physical and chemical properties. In recent years, an adhesive polyester film prepared by forming an adhesive layer on a biaxially oriented polyester film to improve its adhesion to a magnetic layer and simplify the production process of a magnetic recording medium (improving production efficiency) has been becoming the main stream of the market.
Meanwhile, along with the popularization of personal computers and the like, floppy disk drive units and floppy disks have been widely used as storage devices and the capacity and density of floppy disks have been increasing. Therefore, a base film having a more flat surface and better handling properties is now desired.
Further, due to the recent improvement of the performance of notebook type personal computers, personal computers equipped with a floppy disk drive and the like involve such a problem as high temperature inside the drive. Therefore, dimensional stability is an extremely important factor for a high-density magnetic recording medium.
A base film having a more flat surface is now in demand and the further improvement of blocking resistance is desired. In addition, along with an increase in the flatness of the surface of the base film, coating defects readily exert an influence upon the electromagnetic conversion characteristics of a magnetic tape. Accordingly, an adhesive polyester film free from coating defects and having excellent coatability is desired from the market.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a biaxially oriented polyester film which is flat, excellent in handling properties and free from a dimensional change when and after it is processed for use in a flexible disk.
It is another object of the present invention to provide a biaxially oriented polyester film which is useful as a base film for a flexible disk because its dimensional stability is not deteriorated by tension applied when a magnetic layer is formed.
It is still another object of the present invention to provide a biaxially oriented polyester film which has excellent adhesion, blocking resistance and coatability in addition to the above performance.
It is a further object of the present invention to provide a flexible disk which comprises the above biaxially oriented polyester film of the present invention as a base film and has excellent electromagnetic conversion characteristics.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by a biaxially oriented polyester film which has:
(A) a difference between refractive index on the front side and refractive index on the rear side of the film of 0 to 0.002;
(B) a heat shrinkage factor of 0 to 0.6% when it is heated at 105° C. for 30 minutes under no load;
(C) a Young's modulus of 4,609 MPa (470 kg/mm
2
) or more and a difference between the maximum value and the minimum value of Young's modulus on the film plane of 981 MPa (100 kg/mm
2
) or less;
(D) a center line average roughness on the film plane of 2 to 10 nm; and
(E) a static friction coefficient between the films of 0.55 or less.
According to the present invention, secondly, the above objects and advantages of the present invention are attained by a laminate polyester film consisting of the above biaxially oriented polyester film of the present invention and an adhesive layer which contains colloidal particles having an average particle diameter of 0 to 200 nm and resin components including a water-soluble or water-dispersible copolyester having a sulfonate group as the main component and which is formed on both sides of the above film.
Further, according to the present invention, thirdly, the above objects and advantages of the present invention are attained by a flexible disk comprising the above laminate polyester film of the present invention and magnetic layers formed on the adhesive layers on both side of the laminate polyester film.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The polyester forming the biaxially oriented polyester film of the present invention is a polyester which comprises an aromatic dicarboxylic acid as the main dicarboxylic acid component and an aliphatic glycol as the main glycol component. The polyester is substantially linear and has film formability, particularly film formability by melt molding.
Illustrative examples of the aromatic dicarboxylic acid include terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethanedicarboxylic acid, diphenyldicarboxylic acid, diphenylether dicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenyl ketone dicarboxylic acid, anthracenedicarboxylic acid and the like.
Illustrative examples of the aliphatic glycol include polymethylene glycols having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and decamethylene glycol; and alicyclic diols such as cyclohexane dimethanol.
The polyester used for the production of the biaxially oriented polyester film of the present invention preferably comprises an alkylene terephthalate and/or an alkylene naphthalene dicarboxylate as the main recurring ingredient.
Out of the polyesters, polyethylene terephthalate- and polyethylene-2,6-naphthalene dicarboxylate-based polyesters which are a homopolymer and copolymer comprising terephthalic acid and/or 2,6-naphthalenedicarboxylic acid in an amount of 80 mol % or more based on the total of all the dicarboxylic acid components and ethylene glycol in an amount of 80 mol % or more based on the total of all the glycol components are particularly preferred.
In the case of a copolymer, less than 20 mol % of the total of all the acid components may consist of any one of the above dicarboxylic acids other than terephthalic acid and/or 2,6-naphthalenedicarboxylic acid, for example, an aliphatic dicarboxylic acid such as adipic acid or sebacic acid, or an alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid.
Less than 20 mol % of the total of all the glycol components may consist of any one of the above glycols other than ethylene glycol, for example, an aromatic diol such as hydroquinone, resorcin or 2,2-bis(4-hydroxyphenyl)propane; an aliphatic diol having an aromatic ring such as 1,4-dihydroxydimethylbenzene; or a polyalkylene glycol(polyoxyalkylene glycol) such as polyethylene glycol, polypropylene glycol or polytetramethylene glycol.
The polyester in the present invention comprehends a polyester prepared by copolymerizing an oxycarboxylic acid such as an aromatic oxyacid exemplified by hydroxybenzoic acid or aliphatic oxyacid exemplified by w-hydroxycaproic acid in an amount of 20 mol % or less based on the total of the dicarboxylic acid component and the oxycarboxylic acid component. When the amount of the oxycarboxylic acid is more than 20 mol %, the obtained film can be hardly used as a base film due to deterioration in its physical and chemical properties.
The polyester in the present invention further comprehends a polyester prepared by copolymerizing a polycarboxylic acid component having a functionality of 3 or more or a polyhydroxy compound component such as trimellitic acid or pentaerythritol in such an amount that i
Osawa Toshifumi
Uchida Toshikazu
Bernetz Kevin M.
Resan Stevan A.
Teijin Limited
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