Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
2001-05-14
2004-04-06
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S329000, C428S336000, C428S690000, C428S690000, C428S690000, C428S690000
Reexamination Certificate
active
06716521
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polyester film, more specifically a polyester film having few large protuberances and defects and having good oligomer deposition preventing properties and productivity, and also to a magnetic recording medium using the film.
The present invention also relates to a polyester composition which has good heat resistance, which, when used in a film, exhibits good running ability and abrasion resistance, and which is particularly suitable for use in a magnetic recording medium; a film using the composition; and a magnetic recording medium using the film.
BACKGROUND ART
Polyester films, particularly polyethylene terephthalate (PET) films, have been widely used for industrial purposes due to their good mechanical, thermal and electrical properties, and are now in increasing demand. However, the properties and productivity required for polyesters have become increasingly severe in various applications as the range of uses of and the demand for polyesters have grown. Therefore, although polyesters have been produced for various purposes including industrial purposes and for use in magnetic materials, they still have many problems that need to be overcome.
When a polyester film is used in a magnetic recording medium, the formation of large protuberances or defects on the surface of the film must be minimized for achieving a high recording density. However, a polyester film has a serious problem of an oligomer. In the esterification of a polyester, an oligomer may be produced as a by—product. In the case of PET, an oligomer mainly comprising an ethylene terephthalate cyclic trimer is usually contained at a concentration of about 1 to 3% by weight. If such a polyester or PET is formed into a film, an oligomer is likely to be deposited on the surface of the film over time, leading to the formation of large protuberances on the surface. In particular, when the film is used in a magnetic material film, the large protuberances based on the oligomer deposited on the surface of the film may cause the drop out on the magnetic layer. Accordingly, one of the problems in this application is to prevent the deposition of an oligomer on the surface of the film.
For overcoming the problem, it has been proposed to add an ester of an aliphatic monocarboxylic acid to prevent the accumulation of a low molecular weight substance (e.g., an oligomer) on a drum during the manufacture of a film, as disclosed in Japanese Unexamined Patent Application Publication No. 58-145418. In this technique, however, there is a problem of forming large protuberances on the surface which are based on foreign particles contained in the substance added, and the oligomer deposition preventing effect after the formation of the film is unsatisfactory. It is also proposed to add an additive such as an organic sulfonic acid alkali metal salt to prevent the deposition of an oligomer on the'surface of a film, as described in Japanese Unexamined Patent Application Publication No. 11-188825. In this technique, however, dimples (defects) are formed on the surface of the film and the film forming ability is reduced. Therefore, the films manufactured by these techniques are hardly usable in magnetic recording media, from the viewpoint of smoothness of the film surface.
On the other hand, it is generally employed to add particles for the purpose of improving handling properties and quality of an article manufactured from the film, or for forming proper protuberances/dimples on the surface of the film to provide sliding properties and abrasion resistance to the film or an article produced from the film (which are required for providing smooth process passage properties during the manufacture or processing of the film).
The particles that are generally used include inorganic particles, such as particles of silicon oxide, aluminum oxide, titanium oxide, calcium carbonate, barium sulfate, calcium phosphate, talk, kaolin, zeolite, calcium fluoride, lithium fluoride and molybdenum sulfate; organic particles, such as particles of silicone resin, fluororesin, cross-linked polystyrene resin and cross-linked acrylic resin; and particles deposited during the esterification of a polyester.
Among these, spherical silicon oxide particles are frequently used. However, the particles have poor abrasion resistance and, when used in a film, may be taken off from the film, causing troubles.
A polyester composition containing particles of a compound oxide mainly comprising silicon dioxide and aluminum oxide is proposed in WO 96/32443. A biaxially oriented polyester film using aluminum silicate particles to improve abrasion resistance is proposed in Japanese Unexamined Patent Application Publication No. 11-130878.
However, further improvement is required in friction properties and abrasion resistance,as the processing speed is increased. In most case, such a film is used after the repeated running. Therefore, even if the film initially exhibits good friction properties, the film is required not to be degraded with the passage of time.
In the field of magnetic tape, higher qualities of a finished article (e.g., the levels of quality and density of an image) have also been required than in the past. Therefore, higher sliding properties and abrasion resistance than those of polyester films produced by conventional methods have been strongly demanded. In particular, the recording density of a magnetic tape can be dramatically improved by forming a magnetic recording layer on a metal-deposited layer. However, since such a magnetic recording layer is thin and smooth, the film is highly susceptible to friction. In addition, when the film is taken up in a roll, the surface profile of the rear side is readily transferred to the front surface, causing recording defects. In the vacuum evaporation process, on the other hand, enormous amounts of thermal loading are applied to the film and, at the same time, a highly vacuum state is maintained around the film. If the film is poor in heat resistance, there is a concern about coloration of the film or any adverse effect of a decomposition product on the film. Therefore, higher heat resistance is required for the film.
Accordingly, the first object of the present invention is to provide a polyester film having few large protuberances and defects, and having good surface properties, oligomer deposition preventing properties and productivity.
The second object of the present invention is to provide a polyester composition which has dramatically improved friction properties and abrasion resistance and improved dispersibility while maintaining the good properties of the conventional compositions, which is capable of achieving extremely high-definition surface properties when made into a film, and which is particularly useful for production of a high-density magnetic recording medium.
DISCLOSURE OF INVENTION
The first object of the present invention can be achieved by using a polyester film containing a wax compound formed from an aliphatic carboxylic acid and an aliphatic alcohol or a constituent of the wax compound at a concentration of 0.1 to 2.0% by weight, and having thereon large protuberances having maximum diameters of not smaller than 2 &mgr;m at a density of 20 protuberances/mm
2
.
The second object of the present invention can be achieved by using a polyester composition comprising a polyester resin; and inorganic particles which mainly consist of a compound oxide of silicon dioxide and aluminum oxide and additionally contain ions of elements in group Ia of the periodic table, wherein on a molar basis 80 to 100% of the ions are potassium ions; the ratio (on molar basis) of silicon element to aluminum element, and the ratio (on molar basis) of ions of elements in group Ia of the periodic table to aluminum element in the inorganic particles satisfying the following equations, respectively:
0.1≦Al/Si≦0.4; and
0.8≦[ions of elements in group Ia of the periodic table]/Al≦1.2.
BEST MODE FOR CARRYING OUT THE INVENTION
The wax compound according to the p
Morimoto Tsutomu
Sasamoto Tai
Tsuzuki Toshihiro
Kubovcik & Kubovcik
Nakarani D. S.
Toray Industries Inc.
Uhlir Nikolas J
LandOfFree
Polyester composition, film made thereof, and magnetic... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyester composition, film made thereof, and magnetic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyester composition, film made thereof, and magnetic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3192708