Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
1999-04-16
2001-06-05
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C428S480000
Reexamination Certificate
active
06242081
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an oriented laminated polyester film for pasting on car windows. More particularly, it relates to an oriented laminated polyester film for pasting on car windows, which polyester film has a dye-incorporated intermediate layer(s).
BACKGROUND OF ART
Recently, attention is focused on the laminated polyester films having a dye-incorporated intermediate layer(s), for pasting on car windows. In such laminated films, there is a problem that the casting rolls, longitudinal stretching rolls and tenters during manufacture of the films are contaminated due to the sublimation property of the dye even if a dye with high heat resistance is selected.
In Japanese Patent Application Laid-Open (KOKAI) No. 8-230126, in order to solve the above problem, the present inventor has proposed an oriented laminated polyester film for pasting on car window, which polyester film comprises at least three layers comprising two outermost layers containing no dye and an intermediate layer containing a dye, the film satisfying the following three formulae {circle around (1)} to {circle around (3)} simultaneously.
0.02 ≦ IB-IA ≦ 0.10
{circle around (1)}
0.05 ≦ dA/dB ≦ 0.45
{circle around (2)}
0.05 ≦ TA/TB ≦ 0.60
{circle around (3)}
In the above formulae, IA represents a viscosity of the polyester composition forming the intermediate layer, IB represents a viscosity of the polyester composition forming both outermost layers, dA a represents thickness (&mgr;m) of the intermediate layer, dB a represents thickness (&mgr;m) of the outermost layers, TA represents a visible light transmittance (%) of the intermediate layer, and TB represents a visible light transmittance (%) of the outermost layers.)
As seen from a film thickness of 10.5 &mgr;m/4 &mgr;m/10.5 &mgr;m shown in the Examples of the above Japanese patent application, the thickness of the intermediate layer of the said laminated film is smaller than the thickness of the outermost layers in due to the definition of the above formula {circle around (2)}. This thickness relation is based on the reason that sublimation of the dye can be prevented by sandwiching the dye-containing intermediate layer between the relatively thick outermost layers.
However, the laminated film based on the above conception, that is, the intermediate layer being smaller in thickness than the outermost layers, involves the following problem. Namely, the dye concentration necessary for obtaining a film of high light screening effect is increased, and consequently, the film haze is elevated because of clouding caused by precipitation of the undissolved dye.
As for the method of pasting (sticking) the said laminated film on curved car window glass, the conventional method comprising pasting several strips of laminated film is being superseded by the one-piece pasting method which is advantageous in cost and appearance. In this case, it is required to prevent wrinkling of the film when it is pasted on a car window. Also, the laminated film is required to have excellent transparency.
However, the laminated film proposed in the said Japanese patent application is not improved in wrinkle resistance and transparency.
DISCLOSURE OF THE INVENTION
The present invention has been made in view of the above circumstances, and the object of the present invention is to provide an oriented laminated polyester film for pasting on car window, which film is free from the problem of sublimation of the dye in the film manufacturing process and is also excellent in workability on application to curved car window glass and excellent in transparency.
As a result of the present inventor's earnest studies, the present it has been found that by forming a film having a specific layer structure, it is possible to prevent sublimation of the dye in the film manufacturing process and imparts the specific properties to the film, so that workability and transparency can be improved. The present invention has been attained on the basis of the above finding.
In an aspect of the present invention, there is provided an oriented laminated polyester film for pasting on car window, comprising at least three layers including intermediate layer(s) being incorporated with a dye, which laminated polyester film satisfies the following formulae {circle around (1)} to {circle around (6)} simultaneously:
CA/CB ≦ 0.5
{circle around (1)}
0.02 ≦ DA/DZ ≦ 0.8
{circle around (2)}
1.0 ≦ SMD ≦ 5.0
{circle around (3)}
STD ≦ 2.0
{circle around (4)}
0.005 ≦ Ra ≦ 0.05
{circle around (5)}
H ≦ 5
{circle around (6)}
wherein CA represents a dye concentration (%) in the outermost layers on both sides, in case where the dye concentrations in the outermost layers are different, CA represents a dye concentration the outermost layer with a higher dye concentration; CB represents a dye concentration (%) in the intermediate layer, in case where there exist plural intermediate layers, CB represents an average of the dye concentrations in the layers excluding the outermost layers on both sides; DA represents a sum of the thicknesses (&mgr;m) of the outermost layers; DZ represents an overall thickness (&mgr;m) of the whole layers; SMD represents a heat shrinkage (%) in the machine direction of the film when heat-treated at 180° C. for 5 minutes; STD represents a heat shrinkage (%) in the transverse direction of the film when heat-treated at 180° C. for 5 minutes; Ra represents a center line average roughness (&mgr;m) of the film surface; and H represents a film haze (%).
The present invention is described in detail, hereinafter.
The laminated polyester film according to the present invention is produced by stretching the sheet obtained by co-extrusion method and heat-setting it as required. Hereinafter, the present invention is described by showing an embodiment where the film is constituted in a three-layer structure.
The polyester used in the present invention is the one obtained by reacting an aromatic dicarboxylic acid or an ester thereof with a glycol as principal starting materials. Especially, polyesters in which not less than 80% of the repeating structural units are constituted by the ethylene terephthalate units or ethylene-2,6-naphthalate units, are preferred. Such polyesters may contain a third component.
As the aromatic dicarboxylic acid, there can be used, beside terephthalic acid and 2,6-naphthalene dicarboxylic acid, for instance, isophthalic acid, phthalic acid, adipic acid, sebacic acid and oxycarboxylic acids (such as p-oxyethoxybenzoic acid). As the glycol, there can be used, beside ethylene glycol, for instance, one or more of diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like.
In the present invention, the “outermost layers” are the layers which constitute the two exposed sides of the film. The other layers are all called “intermediate layers”. The intrinsic viscosity (IV) of the polyester of the respective layers is usually 0.52 to 0.75, preferably 0.55 to 0.70, more preferably 0.58 to 0.67. If the IV is less than 0.52, it may be difficult to obtain a film having excellent heat resistance and mechanical strength, while if the IV exceeds 0.75, the extrusion step in the film producing process may be overloaded, causing a drop of productivity.
The overall thickness of the laminated film of the present invention is usually 10 to 50 &mgr;m, preferably around 25 &mgr;m.
In the laminated film of the present invention, the ratio of dye concentration (CA) of the outermost layers to dye concentration (CB) of the intermediate layer(s) (CA/CB) is not more than 0.5, preferably not more than 0.3, more preferably not more than 0.1, even more preferably not more than 0.05. When the CA/CB ratio exceeds 0.5, the dye may tend to sublime in the film manufacturing process, causing contamination of the film production line.
Also, in the laminated film of the present invention, the ratio of the sum of the thicknesses (DA) of the outermost layers to the overall thickness (DZ) of the film (DA/DZ) is 0.02 to 0
Conlin David G.
Dike Bronstein, Roberts & Cushman LLP
Hazzard Lisa Swiszcz
Hess Bruce H.
Mitsubishi Polyester Film Corporation
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