Stock material or miscellaneous articles – Composite – Of polyester
Reexamination Certificate
2001-06-05
2003-07-22
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyester
C428S423700, C428S304400, C428S306600, C428S308400, C428S315500, C428S319700
Reexamination Certificate
active
06596407
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a coated polyester film superior in ink adhesive property, printability and resistance to falling off of particles from a coating layer, which is particularly preferable as a substrate for labels.
BACKGROUND OF THE INVENTION
Polyester films have been applied to a wide variety of uses because of their high crystallinity and superiority in transparency, gloss, mechanical property and chemical resistance. For imparting functionality, such as printability, blocking resistance, antistatic property and the like, a coating layer is generally formed on the surface of a polyester film. For achieving both the transparency and handling property (blocking resistance, slip property, wear and abrasion resistance and the like), it is a general practice to add particles to a coating layer of a polyester film, thereby to form irregularities on the film surface.
In the seal printing frequently used particularly for label printing and offset printing, however, the roll of a printer slips on the print surface and the like and rubs the film. As a result, the film is scraped and particles of the coating layer fall in a powder from the surface of the coating layer. While the falling off of particles from the coating layer has not been noted heretofore, it leads to the loss of the above-mentioned properties and further to staining of the roll. Moreover, deinking occurs to degrade the product value.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to solve the above-mentioned problems and provide a coated polyester film superior in resistance to falling off of particles from a coating layer and printability, while maintaining the ink adhesive property.
According to the present invention, it has been found that specifying of the specular glossiness of the surface of the coating layer of a polyester film leads to the production of a coated polyester film having satisfactory ink adhesive property, printability and resistance to falling off of particles from a coating layer.
The object of the present invention can be achieved by the following.
1) A coated polyester film comprising a polyester film having opacity as shown by an optical density of not less than 0.3, and a coating layer formed on at least one surface of said polyester film, wherein a surface of the coating layer shows a 60-degree specular glossiness G
1
and a 75-degree specular glossiness G
2
that satisfy the following formulas (1) and (2):
G
1
≦20 (1)
1<G
2
/G
1
≦4 (2)
2) The coated polyester film of the aforementioned 1), wherein the polyester film has voids in the film and an apparent density of 0.3−1.3 g/cm
3
.
3) The coated polyester film of the aforementioned 1), wherein the aforementioned coating layer is made from a composition comprising, as main components, at least one resin selected from polyester, polyurethane, acrylic polymer and copolymers thereof, and one or more kinds of inert particles.
4) The coated polyester film of the aforementioned 1), wherein the aforementioned resin comprises a water-insoluble and water-dispersible polyester resin and a water-soluble polyurethane resin having at least one block isocyanate in a molecule.
5) The coated polyester film of the aforementioned 1), wherein a surface of the aforementioned coating layer has a surface resistivity of not more than 1×10
13
&OHgr;/□.
6) The coated polyester film of the aforementioned 1), wherein the polyester film has voids in the film and wherein a ratio of the number of voids to a film thickness is not less than 0.20 void/&mgr;m.
DETAILED DESCRIPTION OF THE INVENTION
The polyester resin, which is a main component of the polyester film to be used for a substrate in the present invention, comprises a polyester obtained by polycondensation of an aromatic dicarboxylic acid, such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and the like or an ester thereof, and glycol, such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexamethylene glycol, neopentyl glycol and the like.
The polyester resin may contain copolymerizable aromatic, aliphatic or alicyclic dicarboxylic acid and aromatic, aliphatic or alicyclic glycol as components.
Such polyester resin can be produced by polycondensation of aromatic dicarboxylic acid and glycol after esterification, polycondensation of aromatic dicarboxylic acid alkyl ester and glycol after transesterification, polycondensation of aromatic dicarboxylic acid diglycol ester, or by other known method.
Examples of the polyester resin include thermoplastic polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, and the like. The polyester may be a homopolymer, or contain a heterologous polyester resin, or a copolymer comprising a third component. In any case, a polyester comprising ethylene terephthalate, butylene terephthalate, ethylene-2,6-naphthalate unit in a proportion of not less than 70 mol %, preferably not less than 80 mol %, more preferably not less than 90 mol %, is preferable. Of these, polyethylene terephthalate is most preferable.
The polyester film to be used in the present invention is particularly preferably a biaxially oriented film from the practical aspect of strength, stiffness and the like.
The polyester film to be used in the present invention may have a monolayer structure or a multilayer structure. The film preferably contains a layer that is partly or entirely non-transparent. The polyester film has an optical density showing the opacity of not less than 0.3, preferably 0.3-4.0, particularly preferably 0.5-3.0. When the optical density is less than 0.3, any printing on the surface of the coated polyester film obtained from such film becomes unpreferably illegible and unclear. When the optical density is not more than 4.0, more superior legibility can be expected.
The optical density within the above-mentioned range can be achieved without particular limitation by any method. For example, it is achieved by adding, to a polyester resin, inorganic particles or a thermoplastic resin incompatible with the polyester resin, without particular limitation on the content thereof. When inorganic particles are added, the content thereof is preferably 5-35 wt %, particularly preferably 8-25 wt %, of the polyester produced. When an incompatible thermoplastic resin is added, its content is preferably 5-35 wt %, particularly preferably 8-28 wt %, of the polyester. When inorganic particles and a thermoplastic resin incompatible with the polyester resin are used in combination, the total amount thereof is preferably not more than 40 wt % of the polyester film, from the aspects of film strength, stiffness and stability during film forming.
While the inorganic particles to be used are not subject to any particular limitation, those having an average particle size of 0.1-4.0 &mgr;m, particularly preferably 0.3-1.5 &mgr;m, are preferable. The inorganic particles are exemplified by white pigments such as titanium oxide, barium sulfate, calcium carbonate, zinc sulfide and the like, which may be used in combination upon mixing. Furthermore, inorganic particles, such as silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride, calcium sulfate and the like, which are generally used for films, may be concurrently used.
While the thermoplastic resin incompatible with a polyester resin is not subject to any particular limitation, polyolefin resin such as polystyrene resin, polyethylene resin, polypropylene resin, polymethylpentene resin and the like, acrylic resin, phenoxy resin, polyphenylene oxide resin, polycarbonate resin and the like can be mixed with a polyethylene terephthalate resin. These thermoplastic resins may be used in a mixture and may be modified. It is needless to say that they can be used concurrently with the above-mentioned inorganic particles. Where necessary, various brighteners may be added.
The polyester film to b
Morishige Chikao
Nishi Mutsuo
Nishimura Syuichi
Okudaira Tadashi
Tsukamoto Satoshi
Bissett Melanie
Morrison & Foerster / LLP
Seidleck James J.
Toyo Boseki Kabushiki Kaisha
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