Composite printing film

Details Composite printing film Composite printing film

1999-03-30

2003-05-20

Watkins, III, William P. (Department: 1772)

Stock material or miscellaneous articles

Structurally defined web or sheet

Continuous and nonuniform or irregular surface on layer or...

C428S141000, C428S147000, C428S148000, C428S149000, C428S338000, C428S220000, C428S480000, C428S423700, C428S424600, C428S483000, C428S518000, C428S340000, C428S341000, C428S520000

Reexamination Certificate

active

06565945

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composite printing film. More particularly, the present invention relates to a composite printing film with an improved printability comprising, as a base film, a synthetic polymer film and especially a polypropylene film, and having an improved printability not only for conventional printing methods, for example, gravure printing, relief printing, and offset printing methods but also for a UV ray-flexographic printing method.
2. Description of the Related Arts
Polypropylene films comprising, as a principal component, a propylene homopolymer, a propylene copolymer and/or a mixture of two or more propylene homopolymers and copolymers, have excellent mechanical strengths and transparency and thus are widely usable as packing or wrapping films. However, since the polypropylene resins per se have a poor adhesive properties, the polypropylene films are disadvantageous in that the film surface exhibits a poor adhesion to printing inks, deposited metal layers and polyvinylidene chloride latices which are located on the film surface to form a barrier to a gas.
To overcome the above-mentioned disadvantages of the polypropylene films, Japanese Examined Patent Publication No. 57-14,983 discloses an adhesion-enhancing method in which an ionomeric polyolefin copolymer having polyethyleneimine moieties is coated on a polypropylene film surface. Also, it is generally known that a printing method suitable for the polypropylene films is a gravure printing method. Currently, however, as disclosed in “Convertech”, Aug., 1997, page 1, polypropylene films may be printed by a recent UV-ray flexographic printing technology which has a high print quality. Namely, conventional flexographic printing methods have been mainly applied to letter printing or solid printing. However, flexographic printing inks may be thickened or concentrated by ultraviolet ray-curing. Also, recently, laser engraving of an anilox roller, at an engraving density of 1000 to 1200 lines/25.4 mm, is possible by forming the anilox roller from a ceramic material, and thus process printing, with a high gradation, becomes possible.
With recent developments in UV-ray flexographic printing technology, the quality of the polymer film to be printed must be further enhanced. Especially, with respect to the adhesion of the polymer films to the ink, the polypropylene films are considered to cause no problems in the conventional flexographic, gravure, relief and offset printings. However, in the new UV-ray flexographic printing in which the UV-ray flexographic printing ink and printing system have been changed, a new problem in that the adhesion of the inks to be polypropylene films is poor, occurs.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a composite printing film with an improved printability and exhibiting a high adhesion to printing inks even in UV ray-flexographic printing.
The above-mentioned object can be attained by the composite printing film of the present invention which comprises a substrate film comprising a synthetic polymeric material, and a top layer formed on a surface of the substrate film and comprising a binder resin, said top layer having a printing surface having an arithmetical mean roughness Ra of 0.2 to 3.5 &mgr;m, determined in accordance with Japanese Industrial Standard B 0601-1994.
In the composite printing film of the present invention, optionally an anchor comprising an adhesive resin layer is formed between the substrate film and the top layer.
In the composite printing film of the present invention, the binder resin of the top layer optionally contains at least one pigment selected from inorganic and organic pigments and dispersed in the binder resin.
Preferably, the pigment for the top layer is in the form of fine particles having an average particle size of 1 to 10 &mgr;m and is present in a content of 0.1 to 2% by weight based on the total weight of the top layer.
The inorganic and organic pigments for the top layer are preferably in the form of true spherical particles.
The binder resin for the top layer preferably contains at least one polymer having ester bonds of the formula:
—CO—O—
The ester bond (—CO—O—)-containing polymer for the top layer is preferably selected from the group consisting of homopolymers of a member and copolymers of at least one member each selected from the group consisting of acrylic acid, methacrylic acid, acrylate esters and methacrylate esters, polyester resins, ethylene-vinyl acetate copolymers, and vinyl chloride-vinyl acetate copolymers.
In the composite printing film of the present invention, the binder resin for the top layer is preferably selected from mixtures of (a) at least one ester bond-containing polymer having a glass-transition temperature of −20 to 20° C. with (b) at least one ester bond-containing polymer having a glass transition temperature of 40 to 80° C.
In the composite printing film of the present invention, the top layer is preferably present in an amount of 0.5 to 5 g/m
2
.
In the composite printing film of the present invention, the adhesive resin for the anchor layer preferably contains an isocyanate component (A) comprising at least one member selected from the group consisting of:
(1) isocyanate compounds represented by the general formula (I)
in which formula (I), at least two members of R
1
to R
4
respectively and independently from each other represent a member selected from the groups of the general formula (II):
and the remaining members of R
1
to R
4
respectively represent a —CH
3
group, in which formula (II), one or more members of a, b, c, d and e respectively and independently from each other represent an —N═C═O group and the remaining members of a, b, c, d and e respectively and independently from each other represent a member selected from the group consisting of a hydrogen atom, a —CH
3
group and a chlorine atom, and
(2) isocyanate compounds represented by the general formula (III):
in which formula (III), at least one member of f, g, h, i and j, at least one member of k, l, m, n and o, and at least one member of p, q, r, s and t represent an —N═C═O group, and the remaining members of f to t respectively and independently from each other represent a member selected from the group consisting of a hydrogen atom, a —CH
3
group and a chlorine atom.
In the composite printing film of the present invention, the isocyanate component (A)-containing adhesive resin for the anchor layer optionally further comprises a copolymer component (B) comprising at least one copolymer of 70% to 95% by weight of vinyl chloride with 1 to 20% by weight of vinyl acetate and 0.1 to 10% by weight of at least one modifying ethylenically unsaturated comonomer, different from vinyl acetate, having at least one functional group selected from the group consisting of hydroxyl and carboxyl groups.
In the composite printing film of the present invention, preferably, the isocyanate component (A) and the copolymer component (B) are mixed in a weight ratio (A)/(B) of from 10/90 to 90/10.
In the above-mentioned formula (I) representing the isocyanate compounds (1) for the anchor layer, preferably three members of R
1
, R
2
, R
3
and R
4
represent the group of the general formula (II).
In the composite printing film of the present invention, the adhesive resin for the anchor layer preferably comprises at least one member selected from the group consisting of oxazoline group-containing polymer resins and ethylimine group-containing polymer resins.
In the composite printing film of the present invention, the ethylimine group-containing resins comprise at least one member selected from the group consisting of polyethyleneimine and amino-ethylated resins.
In the composite printing film of the present invention, the anchor layer is preferably present in an amount of 0.01 to 1 g/m
2
.
In the composite printing film of the present invention, in the adhesive resin for the anchor layer, the isocyanate component (A) is presently pr

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