Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
1999-03-03
2001-07-10
Resan, Stevan A. (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S216000, C428S323000, C428S327000, C428S328000, C428S329000, C428S331000, C428S332000, C428S336000, C428S337000, C428S480000, C428S690000, C428S900000
Reexamination Certificate
active
06258442
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a biaxially oriented polyester film for a magnetic recording medium and, more specifically, to a biaxially oriented polyester film for a magnetic recording medium which has an extremely small number of coarse protrusions and excellent winding property, abrasion resistance and traveling durability and can be produced at a low production cost.
BACKGROUND ART
A biaxially oriented polyester film typified by a polyethylene terephthalate film is used for various application purposes, particularly for magnetic recording media, due to its excellent physical and chemical properties.
The slipperiness and abrasion resistance of a biaxially oriented polyester film are important factors that affect the workability in the producing step and processing step of a film and, further, the product quality of the film. If a film lacks these properties, when a biaxially oriented polyester film is used in a magnetic tape by forming a magnetic layer on the surface, friction and abrasion between a coating roll and the film surface are large, and the film is readily wrinkled and scratched on the surface. When the film is used for a VTR or data cartridge, friction between the film and many guide portions, reproduction head and the like occurs at the time of drawing out of the cassette or the like, winding or other operation, whereby the film is scratched or distorted and white powder is formed, for example, by abrasion of the surface of the base film, thereby causing a drop out in many cases.
As a solution to these problems, JP-A 62-172031 proposes a method for adding silicone resin fine particles. This method has a great improving effect and is expected to develop as a future technology.
However, even this method encounters such a new problem as an increase in the amount of white powder generated under severe conditions including high-speed processing for improving productivity such as the formation of a magnetic layer or calendering in the recent production process of a video tape, high-speed dubbing of a soft tape, repetitions of traveling and rewinding and the like.
Further, conventional silicone resin fine particles contain a large number of coarse particles or agglomerate particles. For instance, when they are used in a base film which is required to have high electromagnetic conversion characteristics, there is such a problem that coarse protrusions called fly speck are frequently formed.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a biaxially oriented polyester film for a magnetic recording medium.
It is another object of the present invention to provide a biaxially oriented polyester film for a magnetic recording medium, which has an extremely small number of coarse protrusions and excellent winding property, slipperiness, abrasion resistance and traveling durability.
It is still another object of the present invention to provide a biaxially oriented polyester film for a magnetic recording medium which can be produced at a low production cost.
It is still another object of the present invention to provide a biaxially oriented polyester film for a magnetic recording medium which contain not only specific silicone resin particles but also other inert particles.
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 (may be referred to as “the first polyester film of the present invention” hereinafter) for a magnetic recording medium, which comprises an aromatic polyester resin composition comprising:
(A) an aromatic polyester;
(B) 0.01 to 0.3 wt % of silicone resin particles
(a) which can be obtained by polymerizing a silane compound containing trialkoxysilane represented by the following formula (1):
R
1
Si(OR
2
)
3
(1)
wherein R
1
is an alkyl group having 1 to 6 carbon atoms or a phenyl group and R
2
is an alkyl group having 1 to 4 carbon atoms,
in the presence of a surfactant and water and contain at least 80 wt % of recurring units represented by the following formula (2):
R
1
SiO
3/2
(2)
wherein R
1
is the same as defined above,
(b) which are substantially spherical, and
(c) which have an average particle diameter of 0.1 to 1.0 &mgr;m; and
(C) 0.05 to 1.0 wt % of other inert fine particles having an average particle diameter, smaller than that of the above silicone resin particles, of 0.01 to 0.5 &mgr;m.
According to the present invention, secondly, the above objects and advantages of the present invention are attained by a biaxially oriented polyester film (may be referred to as “the second polyester film of the present invention” hereinafter) for a magnetic recording medium, which comprises an aromatic polyester resin composition comprising:
(A) an aromatic polyester;
(B) 0.001 to 0.03 wt % of silicone resin particles
(a) which can be obtained by polymerizing a silane compound containing trialkoxysilane represented by the following formula (1):
R
1
Si(OR
2
)
3
(1)
wherein R
1
is an alkyl group having 1 to 6 carbon atoms or a phenyl group and R
2
is an alkyl group having 1 to 4 carbon atoms,
in the presence of a surfactant and water and contain at least 80 wt % of recurring units represented by the following formula (2):
R
1
SiO
3/2
(2)
wherein R
1
is the same as defined above,
(b) which are substantially spherical, and
(c) which have an average particle diameter of 0.8 to 1.6 &mgr;m;
(C) 0.1 to 0.6 wt % of inert fine particles B having an average particle diameter of 0.4 to 0.7 &mgr;m; and
(D) 0.05 to 1.0 wt % of inert fine particles C having an average particle diameter of 0.01 to 0.3 &mgr;m and a Mohs hardness of 7 or more.
A description is first given of the first polyester film of the present invention and then of the second polyester film of the present invention.
The aromatic polyester in the present invention is a polyester comprising an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. The polyester is substantially linear and has film formation properties, particularly film formation properties by melt molding. Illustrative examples of the aromatic dicarboxylic acid include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethanedicarboxylic acid, biphenyldicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic 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; alicyclic diols such as 1,4-cyclohexane dimethanol; and the like.
In the present invention, preferred are polyesters comprising alkylene terephthalate and/or alkylene naphthalene dicarboxylate as the main recurring component(s).
Of the above polyesters, particularly preferred are homopolymers such as polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate, and copolymers comprising terephthalic acid and/or 2,6-naphthalenedicarboxylic acid in an amount of 80 mol % or more of the total of all dicarboxylic acid components and ethylene glycol in an amount of 80 mol % or more of the total of all glycol components. Twenty mole percent or less of the total of all acid components may be the above aromatic dicarboxylic acid other than terephthalic acid and/or 2,6-naphthalenedicarboxylic acid, an aliphatic dicarboxylic acid such as adipic acid or sebacic acid, or an alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid. Twenty mole percent or less of the total of all glycol components may be the above glycol other than ethylene glycol, 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-dihydro
Kimura Manabu
Ogawa Tatsuya
Watanabe Hideaki
Resan Stevan A.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Teijin Limited
LandOfFree
Biaxially oriented polyester film for magnetic recording media 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 polyester film for magnetic recording media, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Biaxially oriented polyester film for magnetic recording media will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2473680