Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
1999-09-29
2001-01-30
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S213000, C428S323000, C428S327000, C428S328000, C428S330000, C428S337000, C428S339000, C428S480000, C428S690000, C428S690000, C428S910000
Reexamination Certificate
active
06180209
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a biaxially oriented polyester film. More particularly, it relates to a biaxially oriented polyester film which, when used as a base film for high-quality magnetic recording media, can highly satisfy the running property and electromagnetic transducing performance required of the magnetic recording media, and is also excellent in chipping resistance, prevention of dropout, handling property and winding property in the film-forming and magnetic recording medium production processes.
Biaxially oriented polyester films are widely used as an industrial material because they have various advantageous properties in a well-balanced manner and high cost performance.
Recently, in use of polyester films for magnetic tapes in particular, it is noted that the property requirement for the base film is becoming more and more strict for realizing higher quality of magnetic tapes. Specifically, in order to improve electromagnetic transducing performance, it is strongly desired that the film surface be flat, and particularly it is an essential condition that there exist in the film surface no coarse projections which might become a cause of dropout. On the other hand, it is also necessary to roughen the film surface to a pertinent degree to reduce the friction coefficient of the film so as to enhance the running property of the magnetic recording medium.
On the other hand, in the film working steps, for example in the steps of magnetic layer coating, calendering and take-up of the film in the manufacture of magnetic recording media, the problem exists that the film surface could be chipped off through contact with the rolls or guides, and the resulting flaw deteriorates the electromagnetic transducing performance or the chipping dust causes dropout.
Also, with prevalence of video software in recent years, high-speed dubbing devices have come to be used for enhancing soft video tape productivity, and in use of such high-speed dubbing devices, high quality of the magnetic tape, and of the base film for such magnetic tape, has become an essential requirement. Since the magnetic tape running speed at dubbing is faster than the tape run in normal video replay, there is required a design different from that required for improvement of running property of the conventional magnetic tapes. For example, it is required that the magnetic tape has high running stability and won't move zigzag in high-speed run, and that the tape remains safe from being chipped off during running so that there will be no risk of dropout being caused by chipping dust. That is, the magnetic tape is required to have high-degree chipping resistance. Further, in addition to such chipping resistance in high-speed run, it is also required for the magnetic tape to show high durability, namely extraordinarily high degree of wear resistance, in repeated use of the magnetic recording medium.
Beside these strict quality requirements, request for cost reduction is also intense, and it is essential that the base film productivity is high.
As a result of the present inventors' earnest studies to solve the above problems, it has been found that by containing the inorganic particles having a specific average diameter as well as the crosslinked polymer particles having a specific average diameter in a biaxially oriented polyester film, the above problems can be solved.
The present invention has been attained on the basis of the above finding.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a biaxially oriented polyester film which, when for instance used as a base film for magnetic recording media, can highly satisfy the winding property, running property and electromagnetic transducing performance required of a magnetic recording medium, and is excellent in slitting performance in production of films and magnetic recording media, preventive of occurrence of dropout, minimized in the risk of suffering scratches and generating abrasion dust, high in productivity and low in production cost.
To attain the above object, in the first aspect of the present invention, there is provided a biaxially oriented polyester film containing 0.01 to 3.0% by weight of inorganic particles X and 0.001 to 1.5% by weight of crosslinked polymer particles Y, the particles diameters of said particles X and Y satisfying the following relationships (1) to (3) at the same time:
0.1≦dX50≦1.5 (1)
dX50<dY50≦dX10 (2)
1.0
dY
25/
dY
75≦1.5 (3)
wherein dX50 represents the average diameter (&mgr;m) of the inorganic particles X; dX10 represents the particle diameter at the point of 10% of the total volume when the volume has been integrated from the large particle diameter in the particle size distribution of the inorganic particles X; dY50 represents the average diameter (&mgr;m) of the crosslinked polymer particles Y; and dY25 and dY75 represent the particle diameters (&mgr;m) at the points of 25% and 75%, respectively, of the total volume when the volume has been integrated from the large particle side in the particle size distribution of the crosslinked polymer particles Y.
In the second aspect of the present invention, there is provided a biaxially oriented laminated polyester film comprising:
a layer B comprising a polyester and
at least one layer A comprising a polyester and containing 0.01 to 3.0% by weight of inorganic particles X and 0.001 to 1.5% by weight of crosslinked polymer particles Y,
the particles diameters of said particles X and Y satisfying the following relationships (1) to (3) at the same time:
0.1≦dX50≦1.5 (1)
dX50<dY50≦dX10 (2)
1.0
dY
25/
dY
75≦1.5 (3)
wherein dX50 represents the average diameter (&mgr;m) of the inorganic particles X; dX10 represents the particle diameter at the point of 10% of the total volume when the volume was integrated from the large particle diameter in the particle size distribution of the inorganic particles X; dY50 represents the average diameter (&mgr;m) of the crosslinked polymer particles Y; and dY25 and dY75 represent the particle diameters (&mgr;m) at the points of 25% and 75%, respectively, of the total volume when the volume was integrated from the large particle side in the particle size distribution of the crosslinked polymer particles Y.
In the third aspect of the present invention, there is provided a biaxially oriented laminated polyester film comprising:
a layer B comprising a polyester,
a layer A comprising a polyester and laminated on one side of the layer B and
a layer C comprising the same polyester composition as the layer A and laminated on the opposite side of the layer B,
the layer C thickness tc being 0.1 to 0.7 times the layer A thickness, and
the difference in root mean square roughness between the layer A surface and the layer C surface, as determined by a noncontact type surface roughness tester, being within the range of 2 to 15 nm.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is explained in detail below.
The polyester constituting the film of the present invention is a polyester obtained by using an aromatic dicarboxylic acid or an ester thereof and a glycol as starting materials, in which not less than 80% of the repeating structural units comprise ethylene terephthalate units or ethylene-2,6-naphthalate units. A third material may be contained as far as the above condition is maintained.
The aromatic dicarboxylic acids usable as starting material include, for example, terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, phthalic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid and oxycarboxylic acids (such as p-oxyethoxybenzoic acid). The glycols usable as another starting material include, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol and neopentyl glycol. These glycols may be used either singly or as a mixture of two or more of them.
The “laminated film” referred to
Meguro Yoshio
Sato Yoshinori
Chen Vivian
Conlin David G.
Dike Bronstein, Roberts & Cushman LLP
Mitsubishi Polyester Film Corporation
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