Stock material or miscellaneous articles – Structurally defined web or sheet – Physical dimension specified
Reexamination Certificate
1999-04-26
2002-11-26
Resan, Stevan A. (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Physical dimension specified
C428S323000, C428S336000, C428S482000, C428S483000, C428S910000
Reexamination Certificate
active
06485818
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a transparent polyester film for the imaging media. More particularly, it relates to a transparent primer-coated polyester film for the imaging media which has a priming layer formed by coating a resin on at least one side of a biaxially oriented polyester film, and which has high-degree transparency and adhesion, particularly high adhesion to the functional layers mainly made of a water-soluble or hydrophilic resin such as polyvinyl alcohol.
Polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are used as support films for a variety of purposes owing to their excellence in many properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance and optical properties, in addition to their high cost performance.
These polyester films, however, have disadvantages in which their cohesive force is strong due to their chemical properties and crystallized film surface, and are therefore low in adhesion to the functional layers in various uses. In order to eliminate such disadvantages, various methods and techniques have been proposed, such as laminating a low-crystallizability polyester layer on the surface of a polyester film by means of coextrusion, or coating a water-dispersible polyester or acrylic resin as a primer on a base polyester film (Japanese Patent Publication (KOKOKU) No. 49-10243, Japanese Patent Application Laid-Open (KOKAI) Nos. 52-19786, 52-19787, 54-43017, etc.).
Thus, although the techniques using a support film comprising a polyester or acrylic resin as a primer have been developed, any of these films has been unsatisfactory in adhesion to the functional layers mainly made of a water-soluble or hydrophilic resin such as polyvinyl alcohol.
As a result of the present inventor's earnest studies to solve the above problem, it has been found that by providing a priming layer (offering satisfactory adhesion to aqueous coating) on a polyester film support by coating its surface with a coating solution of a specific composition, the above problem 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 transparent polyester film for imaging media which has a priming layer (primer coated layer) with particularly high adhesion to the functional layers mainly comprising a water-soluble or hydrophilic resin such as polyvinyl alcohol, for example, the ink image receiving layer in ink jet printing which has become widely used in recent years, and the functional layers mainly comprising a water-soluble or hydrophilic resins such as gelatin, for example, sensitive photographic films, and which is also excellent in transparency and flatness.
To attain the above aim, in an aspect of the present invention, there is provided a primer coated polyester film for imaging media, which has a thickness of 40 to 200 &mgr;m and a haze of not more than 5%, and comprises a biaxially oriented polyester film support and at least one a priming layer laminated on said support and oriented at least monoaxially,
said priming layer being formed from a coating solution containing a water-soluble resin (A) having the vinyl alcohol units as main constituent and a water-soluble or water-dispersible resin (B) having an aromatic polyester unit.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in more detail.
The polyesters usable in the present invention as biaxially oriented polyester film support include, for example, polyethylene terephthalate (PET) in which not less than 80 mol % of the structural units is constituted by ethylene terephthalate, polyethylene-2,6-naphthalate (PEN) in which not less than 80 mol % of the structural units is constituted by ethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate (PCT) in which not less than 80 mol % of the structural units is constituted by 1,4-cyclohexanedimethylene terephthalate, polyethylene isophthalate, and poly-1,4-butyrene terephthalate (PBT).
As the copolymer materials other than the said primary constituent, there can be used diols such as propylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, neopentyl glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polytetramethylene glycol and polyalkylene glycol; isophthalic acid, 2,7-naphthalenedicarboxylic acid, 5-sodiumsulfoisophthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, diphenyl ether dicarboxylic acid, oxymonocarboxylic acid, and their ester-forming derivatives.
The polyesters usable in the present invention include homopolymers, copolymers and their blends with a small proportion of other resins.
The polyester film support used in the present invention is biaxially oriented, and it may contain a projection forming agent such as added particles, precipitated particles, catalyst residue, etc., which, when contained in the film, can impart preferable slip properties to the film. The type, size and amount of the projection forming agent may be properly selected according to the required slipperiness and transparency of the film. For instance, in order to provide a required haze with the restricted film thickness in the present invention, it is suggested to contain at least one type of particles having an average size (diameter) of not more than 5 &mgr;m, preferably not more than 3 &mgr;m, in an amount of not more than 1% by weight, preferably not more than 0.5% by weight, in the case of the added particles.
The polyester film support may also contain, if necessary, other additives such as antistatic agent, stabilizer, lubricant, crosslinking agent, anti-blocking agent, antioxidant, UV absorber, etc.
In the present invention, the polyester film support may have a multilayer structure, in which case part of the layers may comprise a polymer or polymers other than polyesters.
The primer coated polyester film according to the present invention has a priming layer (with excellent adhesion for aqueous coatings and easily adherable) on at least one side of the biaxially oriented polyester film, the said priming layer having been oriented at least monoaxially. Stretching of this resin layer is conducive to the uniformity of layer thickness and the improvement of adhesion and transparency.
The primer coated polyester film of the present invention is preferable for use as a support for the imaging media, and its thickness ranges from 40 to 200 &mgr;m. If the thickness is less than 40 &mgr;m, the film have lack the strength required for the support. A film thickness exceeding 200 &mgr;m is more than necessary in practical use and detrimental to economy.
It is also notable that the primer coated polyester film of the present invention is low in haze. High haze of the primer coated polyester film leads to the problems such as reduced distinction of the projected image on OHP and restricts the scope of use of the film. Specifically, the film haze needs to be not more than 5%, preferably not more than 3%.
Regarding transparency of the film, it is preferable that the overall light transmittance of the laminated film is in a high percent range, specifically not less than 80%, preferably not less than 85%, even more preferably not less than 88%, for the same reason as in the case of film haze mentioned above.
The important feature of the present invention resides in that the priming layer of the said laminate film is formed by using a coating solution containing (A) a water-soluble resin having vinyl alcohol units as main constituent and (B) a water-soluble or water-dispersible resin having aromatic polyester unit. More specifically, it is essential for the laminated film of the present invention to have a priming layer formed by applying the said coating solution on at least one side of the support film and drying it, the thus formed layer being oriented at least monoaxially.
As the water-so
Conlin David G.
Edwards & Angell LLP
Mitsubishi Polyester Film Corporation
Resan Stevan A.
Roos Richard J.
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