Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
2001-08-06
2004-03-09
Jackson, Monique R. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C428S458000, C428S480000, C264S173160, C264S173170, C264S210700, C427S457000
Reexamination Certificate
active
06703119
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a transparent, biaxially oriented polyester film with a base layer B which comprises at least 80% by weight of thermoplastic polyester, and with at least one outer layer A and with a metallic or ceramic layer arranged on the outer layer A. The invention further relates to the use of the film and to a process for its production.
Prior art
EP-A-0 878 298 describes a biaxially oriented polyester film with a base layer B, at least 80% by weight of which is composed of a thermoplastic polyester, and with an outer layer A and with a metallic or ceramic layer arranged on the outer layer A. The outer layer A of this film is composed of a mixture of polymers which contains at least 60% by weight of ethylene 2,6-naphthalate units (PEN), up to 40% by weight of ethylene terephthalate units (PET) and optionally up to 10% of units derived from cycloaliphatic or aromatic diols and/or dicarboxylic acids.
If the metallized or ceramic-coated outer layer A of the film of EP-A-0 878 298 contains high concentrations of ethylene 2,6-naphthalate units, the film has a tendency for delamination between the outer layer A and the base layer B. If, on the other hand, the outer layer A contains low concentrations of ethylene 2,6-naphthalate units, the thickness of this layer has to be raised in order to achieve the desired low oxygen permeation of not more than 0.3 cm
3
/(m
2
·bar·d).
In a film in Example 8 of EP-A-0 878 298 the metallized outer layer A uses pure polyethylene 2,6-naphthalate (corresponding to 100% by weight of ethylene 2,6-naphthalate units). In this case there is no significant adhesion between the outer layer A and the base layer B. The film is unsuitable for industrial use (e.g. as a composite film), since the bond releases even when subjected to a low level of mechanical stress, due to the low adhesion between the outer layer A and the base layer B of the polyester film.
In a film in Example 11 of EP-A-0 878 298, the metallized outer layer A contains 60% by weight of ethylene 2,6-naphthalate units. In order to achieve the low oxygen permeation demanded, below 0.3 cm
3
/(m
2
·bar·d), the thickness of the outer layer A has to be raised to 2.5 &mgr;m, and this is economically disadvantageous (high capital expenditure and high material costs).
U.S. Pat. No. 5,795,528 describes a coextruded film laminate which has alternating layers of PEN and PET. Like the film of EP-A-0 878 298, this film has a tendency toward delamination between the individual layers of PEN and PET. There is no significant adhesion between these layers. A laminate of this type is therefore again unsuitable for industrial use.
It was an object of the present invention, therefore, to provide a metallized or ceramic-coated, biaxially oriented polyester film which overcomes the disadvantage of the prior art films and in particular has improved adhesion between the individual layers. It should be simple and cost-effective to produce, have very good barrier properties, and pose no problems of disposal.
SUMMARY OF THE INVENTION
The object is achieved by means of a biaxially oriented polyester film with a base layer B which comprises at least 80% by weight of thermoplastic polyester, with at least one outer layer A and with a metallic or ceramic layer arranged on the outer layer A, the characterizing features of which are regarded as being that
the outer layer A is composed of a copolymer or of a mixture of polymers/copolymers, which contains from 90 to 98% by weight of ethylene 2,6-naphthalate units and up to 10% by weight of ethylene terephthalate units, and/or units derived from cycloaliphatic or aromatic diols and/or dicarboxylic acids;
the thickness of the outer layer A is more than 0.7 &mgr;m and this makes up less than 25% by weight of the entire film, and the T
g
2 value of the polyester film is above the T
g
2 value of the base layer but below the T
g
2 value of the outer layer.
The metallized or ceramic-coated film of the invention has an oxygen permeation below 0.3 cm
3
/(m
2
·bar·d), and minimum adhesion between the individual layers of the film of greater than or equal to 0.5 N/25 mm.
DETAILED DESCRIPTION OF THE INVENTION
The structure of the film of the invention has at least two layers, and is then composed of the metallized or ceramic-coated outer layer A, and of a base layer B.
Preference is given to a polyester film in which the copolymer or the mixture of polymers of the outer layer A contain from 91% to 97% by weight of ethylene 2,6-naphthalate units and up to 9% by weight of ethylene terephthalate units and/or units derived from cycloaliphatic or aromatic diols and/or dicarboxylic acids. Among these, particular preference is in turn given to a polyester film in which the copolymer or mixture of polymers of the outer layer A contain from 92 to 96% by weight of ethylene 2,6-naphthalate units and up to 8% by weight of ethylene terephthalate units and/or units derived from cycloaliphatic or aromatic diols and/or dicarboxylic acids.
Preference is also given to a polyester film whose metallized or ceramic-coated outer layer A has a thickness of more than 0.8 &mgr;m, where this makes up less than 22% by weight of the entire film, and particular preference is given to a polyester film whose metallized or ceramic-coated outer layer A has a thickness of more than 0.9 &mgr;m, where this makes up less than 20% by weight of the entire film.
Examples of suitable aliphatic diols are diethylene glycol, triethylene glycol, aliphatic glycols of the formula HO—(CH
2
)
n
—OH, where n is an integer from 3 to 6 (in particular 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol), or branched aliphatic glycols having up to 6 carbon atoms, and cycloaliphatic diols having one or more rings and if desired containing heteroatoms. Among the cycloaliphatic diols, mention may be made of cyclohexanediols (in particular 1,4-cyclohexanediol). Examples of other suitable aromatic diols are those of the formula HO—C
6
H
4
—X—C
6
H
4
—OH where X is —CH
2
—, —C(CH
3
)
2
—, —C(CF
3
)
2
—, —O—, —S— or —SO
2
—. Besides these, bisphenols of the formula HO—C
6
H
4
—C
6
H
4
—OH are also very suitable.
Preferred aromatic dicarboxylic acids are benzenedicarboxylic acids, naphthalenedicarboxylic acids (for example naphthalene-1,4- or -1,6-dicarboxylic acid), biphenyl-x,x′-dicarboxylic acids (in particular biphenyl-4,4′-dicarboxylic acid), diphenylacetylene-x,x′-dicarboxylic acids (in particular diphenylacetylene-4,4′-dicarboxylic acid) or stilbene-x,x′-dicarboxylic acids. Among the cycloaliphatic dicarboxylic acids, mention may be made of cyclohexanedicarboxylic acids (in particular cyclohexane-1,4-dicarboxylic acid). Among the aliphatic dicarboxylic acids, the C
3
-C
19
-alkanedioic acids are particularly suitable, where the alkane moiety may be straight-chain or branched.
The base layer of the film is preferably composed of at least 90% by weight of the thermoplastic polyester. Polyesters suitable for this are those made from ethylene glycol and terephthalic acid (=polyethylene terephthalate, PET), from ethylene glycol and naphthalene-2,6-dicarboxylic acid (=polyethylene 2,6-naphthalate, PEN), from 1,4-bishydroxymethylcyclohexane and terephthalic acid (=poly-1,4-cyclohexanedimethylene terephthalate, PCDT), and also from ethylene glycol, naphthalene-2,6-dicarboxylic acid and biphenyl-4,4′-dicarboxylic acid (=polyethylene 2,6-naphthalate bibenzoate, PENBB). Particular preference is given to polyesters which are composed of at least 90 mol %, preferably at least 95 mol %, of ethylene glycol units and terephthalic acid units or of ethylene glycol units and naphthalene-2,6-dicarboxylic acid units. The remaining monomer units are derived from other diols and/or dicarboxylic acids. Examples of suitable diol comonomers are diethylene glycol, triethylene glycol, aliphatic glycols of the formula HO—(CH
2
)
n
—OH, where n is an integer from 3 to 6, branched aliphatic glycols having up to 6 carbon atoms, aromatic diols of the formu
Davis Richard Lee
Hilkert Gottfried
Peiffer Herbert
Jackson Monique R.
Mitsubishi Polyester Film GmbH
ProPat L.L.C.
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