Stock material or miscellaneous articles – Composite – Of polyester
Reexamination Certificate
1999-06-04
2001-07-03
Michl, Paul R. (Department: 1714)
Stock material or miscellaneous articles
Composite
Of polyester
Reexamination Certificate
active
06254996
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antistatic polyester film and a process for producing the same. More particularly, the invention relates to an antistatic polyester film having excellent antistatic property under low humidity, thus having antistatic property substantially having no humidity dependency, which is useful in packaging materials, photographic materials, electronic materials, graphic materials, plate-making film, magnetic cards (for example, telephone cards and prepaid cards), OHP films, magnetic recording materials (for example, magnetic tapes such as audio tapes or video tapes, and magnetic disks such as floppy disks), printing materials, and the like, and a process for producing the same.
2. Descriptions of the Related Art
Polyester film are widely used in base films of, for example, packaging materials, photographic materials, magnetic cards, magnetic recording media and printing materials. However, as the common problems in plastic films, the polyester films have the disadvantages that static electricity tends to occur, and various troubles tend to occur in plate-making step, processing step and use of products.
As one of the methods for preventing the problems due to electrification of those films, various methods for forming an antistatic coating film on the surface of a film have been proposed and have been put in practical use. As antistatic agents to be contained in this antistatic coating film, electron-conductive materials represented by ion-conductive type of low- or high-molecular-weight organic materials, conductive metal oxides and conductive organic polymers have hitherto been known. However, those materials have advantages and disadvantages, respectively. Therefore, an appropriate antistatic agent is used depending on its purpose of use in view of the characteristic thereof.
For example, surface active agent type anionic antistatic agents such as long chain alkyl compounds having a sulfonate group (Japanese Patent Application Laid-open No. Hei 4-28728 (Hereinafter simply referred to as “JP-A”)) are known as an antistatic agent of low molecular weight organic material. Further, polymers having Ionized nitrogen atom in the main chain (JP-A-3-255139, 4-288127 and 6-172562) and sulfonate-modited polystyrenes (JP-A-5-820890) are known as an antistatic agent of high molecular weight organic material.
However, antistatic coating layers using an ion-conductive type antistatic agent of low molecular weight organic material have the problems that a part of an antistatic agent moves in the coating layer to concentrate the same on an interface, and transfers to the opposite surface of the film, and the antistatic property deteriorates with the passage of time.
On the other hand, antistatic coating layers using an ion-conductive type antistatic agent of high molecular weight organic material require additions of an antistatic agent in high proportion in order to develop good antistatic property, and also require to form an antistatic coating layer having a large thickness, which are not economical. Further, in the case where the ion-conductive antistatic agent is used, its antistatic property depends on humidity, and the antistatic performance completely deactivates under dry condition.
On the other hand antistatic coating layers using an electron-conductive type antistatic agent represented by conductive metal oxides and conductive organic polymers also require the addition of an antistatic agent in the high Proportion in order to develop good antistatic property, and require to form an antistatic coating layer having a large thickness, which are not economical. Further, in the case where the conductive metal oxide is used alone, if an aromatic polyester film and the antistatic coating layer are subjected to, for example, stretching processing, a distance between mutual conductive oxide particles increases, so that an antistatic property lowers.
SUMMARY OF THE INVENTION
The present invention has been made to overcome the above-described problem in the prior art, and therefore has an object of the present invention to provide a polyester film having excellent antistatic property, particularly antistatic property under low humidity, and substantially having no humidity dependency.
Another object of the present invention is to Provide a process for producing the antistatic polyester film.
An antistatic polyester film of the present invention is characterized by comprising a polyester film having formed on at least one surface thereof an antistatic coating layer obtained by coating a coating liquid containing an organic-inorganic composite conductive sol (A) comprising colloidal particles of conductive oxide, having a primary particle size of 5 to 50 nm and colloidal particles of a conductive polymer.
A process for producing an antistatic polyester film of the present invention is characterized by coating an aqueous coating liquid containing an organic-inorganic composite conductive sol (A) comprising colloidal particles of conductive oxide and colloidal particles of a conductive polymer, on at least one surface of a polyester film, and then drying the coating.
Further, an antistatic polyester film is characterized by comprising a polyester film having formed on at least one surface thereof an organic-inorganic composite conductive coating layer comprising a conductive oxide having a primary particle size of 5 to 50 nm and a conductive polymer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is described in detail below.
A polyester which constitutes the polyester film in the present invention is prepared from a dicarboxylic acid component and a glycol component.
Examples of the dicarboxylic acid component which is used in the present invention include terephthalic acid, isophthalic acid 2,6-naphthalenedicarboxylic acid, hexahydroterephthalic acid, 4,4′-diphenyldicarboxylic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid in particular, terephthalic acid and 2,6-naphthalenedicarboxylic acid are preferably used from the points of mechanical properties of the film.
Examples of the glycol component which is used in the present invention include ethylene glycol, diethylene glycol, propylene glycol, 1,3-propane diol, 1,4-butane diol, neopentyl glycol, 1,6-hexane diol, cyclohexane dimethanol, and polyethylene glycol. Ethylene glycol is particularly preferably used from the point of stiffness of the film.
The polyester my be a copolyester having as a third component the above-described dicarboxylic acid component or glycol component copolymerized therewith, or a polyester having a trifunctional or more polycarboxylic acid component or a polyol component copolymerized therewith in a small amount (for example, 5 mol % or less) such that a polyester obtained is substantially linear.
Such a polyester can be prepared by the conventional method. A polyester having an intrinsic viscosity of 0.45 or more is preferable in that mechanical properties of the film are improved such that the film has a large rigidity.
The polyester film can contain white pigments such as titanium oxide and/or barium sulfate. Further, if required and necessary, the polyester can also contain Inorganic fillers such as silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin and talc, organic fillers comprising heat resistant polymers such as crosslinked silicone resins, crosslinked polystyrene resins, crosslinked acrylic resins, urea resins or melamine resins, other resins such as polyethylene, polypropylene, ethylene/propylene copolymer or olefinic ionomer, stabilizers, antioxidants, ultraviolet absorbers, fluorescent whitening agents, and the like.
The polyester film is preferably a biaxially stretched film, and its thickness is 1 &mgr;m or more, preferably 4 to 500 &mgr;m, and more preferably 10 to 300 &mgr;m.
The antistatic coating layer formed on at least one surface of the polyester film is formed by coating a coating liquid containing an organic-inorganic composite conductive sol
Ema Kiyomi
Fukuda Masayuki
Tanegashima Osamu
Watanabe Hideaki
Michl Paul R.
Oliff & Berridg,e PLC
Teijin Limited
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