U.S. patent application number 10/625316 was filed with the patent office on 2004-03-11 for method for forming inherently ink-receptive film substrates.
This patent application is currently assigned to Avery Dennison Corporation. Invention is credited to Heydarpour, Ramin, Mallya, Prakash, Shih, Frank Y., Venkatasanthanam, Sriram.
Application Number | 20040048006 10/625316 |
Document ID | / |
Family ID | 24186774 |
Filed Date | 2004-03-11 |
United States Patent
Application |
20040048006 |
Kind Code |
A1 |
Venkatasanthanam, Sriram ;
et al. |
March 11, 2004 |
Method for forming inherently ink-receptive film substrates
Abstract
Ink-receptive substrates comprise a base layer formed from a
water-insoluble thermoplastic polymer, and an ink-receptive layer
disposed over the base layer. The ink-receptive layer is formed
from a melt-processable blend of a water-soluble polymer and a
substantially water-insoluble polymer, and provides an inherently
ink-receptive surface without further surface treatment. The
ink-receptive blend comprises in the range of from 20 to 80 percent
by weight water-soluble polymer, and in the range of from 20 to 80
percent by weight substantially water-insoluble polymer based on
the total weight of the blend. The blend has a melting temperature
in the range of from about 100 to 600.degree. F. Preferred
water-soluble polymers include polyvinyl alcohols and polyalkyl
oxazolines. Preferred ink-receptive substrates of this invention
comprise a base layer and ink-receptive layer that are formed
simultaneously by coextrusion process. Ink-receptive substrates of
this invention can include the ink-receptive layer on one or both
surfaces of the base layer, and/or can be constructed in the form
of a pressure-sensitive adhesive label, i.e., with a
pressure-sensitive adhesive material disposed on a surface of the
base layer opposite the ink-receptive layer.
Inventors: |
Venkatasanthanam, Sriram;
(Pasadena, CA) ; Heydarpour, Ramin; (Beverly
Hills, CA) ; Shih, Frank Y.; (Arcadia, CA) ;
Mallya, Prakash; (Sierra Madre, CA) |
Correspondence
Address: |
CHRISTIE, PARKER & HALE, LLP
P.O. BOX 7068
PASADENA
CA
91109-7068
US
|
Assignee: |
Avery Dennison Corporation
|
Family ID: |
24186774 |
Appl. No.: |
10/625316 |
Filed: |
July 23, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10625316 |
Jul 23, 2003 |
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09547942 |
Apr 11, 2000 |
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6623841 |
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Current U.S.
Class: |
428/32.1 |
Current CPC
Class: |
Y10T 428/25 20150115;
B41M 5/5281 20130101; Y10T 428/31855 20150401; Y10T 428/31786
20150401; B41M 5/504 20130101; B41M 5/5254 20130101; B41M 5/506
20130101; Y10T 428/24802 20150115; B41M 5/508 20130101; Y10T 428/28
20150115; B41M 5/52 20130101; B41M 5/5236 20130101; B41M 5/5272
20130101 |
Class at
Publication: |
428/032.1 |
International
Class: |
B32B 003/00 |
Claims
1. A method for forming an ink-receptive substrate comprising the
steps of: forming a melt-processable base layer from a
water-insoluble thermoplastic polymer; and simultaneously forming
an ink-receptive layer over the base layer from a blend of a
water-soluble polymer and a substantially water-insoluble polymer,
wherein the ink-receptive layer provides a printable surface that
is inherently ink-receptive without subsequent treatment.
2. The method as recited in claim 1, further comprising the step of
forming a tie layer over the base layer before the step of forming
the ink-receptive layer, the tie layer being formed from a
thermoplastic polymer and being formed simultaneously with the base
layer and ink-receptive layer.
3. The method as recited in claim 1, further comprising the step of
forming an adhesive layer over a surface of the base layer opposite
from the ink-receptive layer to provide a label.
4. The method as recited in claim 1, wherein the base layer and
ink-receptive layer are formed by coextrusion.
5. The method as recited in claim 1 wherein the substantially
water-insoluble polymer is a polyolefin, and the water-soluble
polymer is selected from the group of compounds consisting of
polyvinyl alcohols, polyalkyl oxazolines, polyphenyl oxazolines,
polyvinyl pyrrolidones, polyacrylic-acids, polymethyl
methacrylates, polymethacrylic acids, styrene maleic anhydrides,
alkyl celluloses, carboxyalkyl celluloses, hydroxyalkyl celluloses,
polyethylene oxides, polyethyleneimines, and mixtures thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This divisional application claims priority of U.S. patent
application Ser. No. 09/547,942, filed Apr. 11, 2002.
FIELD OF THE INVENTION
[0002] This invention relates to film substrates that are used as
an ink-receptive print media and, more particularly, to
non-topcoated film substrates having at least one ink-receptive
surface; constructions such as labels and labelstocks incorporating
such film substrates; and methods for preparing the same.
BACKGROUND OF THE INVENTION
[0003] Ink jet printing is a well-known and commonly used means of
providing an image onto a substrate. Ink jet printers typically use
one of two different types of ink: dye-based inks and pigment-based
inks. With dye-based ink, the color of the ink is imparted by a dye
that is soluble in a fluid carrier. A common type of fluid carrier
is one comprising a blend of water and glycol. Such dye-based inks
are relatively inexpensive, easy to process, and are suitable for
use in low cost applications where long term durability is not a
concern. For pigment-based inks, the color is imparted by particles
which are dispersed, rather than dissolved, in a fluid carrier.
Most of the common pigments used are insoluble in organic solvents
and water, and can be chosen for lightfastness.
[0004] A feature common to both types of inks is that the fluid
carrier used with each is generally water soluble. Thus, substrates
useful for performing as an ink jet receiving media preferably
comprise a surface having ink-receptive properties to allow quick
drying of ink droplets generated by an ink jet print head.
Substrates known in the art useful as an ink jet receiving media
include those having a two-layer construction comprising a base
layer and a topcoat layer. In such known substrate embodiments, the
base layer is formed from a polymeric film such as polypropylene,
polyester, or polyvinyl chloride. The topcoat layer is applied to a
surface of the base layer, using a solvent that is subsequently
removed by drying, and is specially formulated to provide
ink-receptive properties.
[0005] However, the use of a topcoat to provide ink-receptive
properties to a substrate is known to introduce certain
manufacturing limitations and adversely affect other substrate
properties that can ultimately limit ink printed substrate use. For
example, topcoated ink jet substrates are known to lack durability
and, because most topcoat formulations contain water-soluble
components, they are also sensitive to moisture, thereby
necessitating the use of a protective overlaminate layer or film
after printing. Additionally, the level of active components in the
topcoat formulation is limited by the viscosity of the topcoat
formulation that can be handled in the coater. As a result, the
efficiency of the topcoat is commonly increased by increasing the
layer thickness, which is known to introduce increased costs and
coat weight inconsistencies, which inconsistencies are undesirable
because they can adversely affect the performance of the final
product, i.e., the ink jet printed substrate.
[0006] In an effort to avoid the above-mentioned adverse
consequences of topcoated substrates, non-topcoated substrates
having varying degrees of ink-receptive properties have been
developed. For example, U.S. Pat. No. 4,438,175 discloses a film
structure comprising a biaxially-oriented polymeric film having an
ink-receptive surface that is formed by delaminating the
biaxially-oriented polymeric film into two separate layers, each of
which being attached to a skin layer. The resulting polymeric film
structure comprises a first layer of a thermoplastic polymer matrix
material comprising a strata of voids. Void-initiating solid
particles are positioned within a substantial number of the voids
and are phase distinct and incompatible with the matrix material.
The first layer has a surface which, due to the presence and
distribution of voids, is a non-even, microcrater, lamellae-like,
random texturized, ink-receptive configuration. The resulting
polymeric film includes a second layer, formed by the placement of
the skin layer onto the matrix, having a void-free surface.
[0007] While this patent discloses a substrate having an
ink-receptive surface that is formed without topcoating, the so
formed substrate requires a two-step manufacturing process of first
forming the combined polymeric film and skin layer construction,
and then delaminating the combined film and skin layer construction
into two resulting ink-receptive film structures. Thus, while the
substrate described in this patent avoids having to use a
topcoating method, it does not avoid the inefficiencies and costs
associated with having to use multiple preparation steps.
[0008] U.S. Pat. No. 4,861,644 describes a substrate having an
ink-receptive surface comprising a matrix of ultrahigh molecular
weight polyolefin, a large proportion of finely-divided
water-insoluble siliceous filler, and interconnecting pores. The
substrate is produced by first forming an extruded sheet from a
mixture of the polyolefin the siliceous filler and other processing
aids, calendaring the extruded sheet, drying the calendared sheet,
and stretching the dried sheet to provide a desired biaxially
stretched orientation. While the so formed substrate also avoids
the need for topcoating to obtain ink-receptive properties, the
substrate is nevertheless formed using the multi-step process of
extruding, calendaring, drying and stretching.
[0009] International Publication No. WO 92/00188 discloses a
writeable and printable, unstretched synthetic paper that is formed
by extruding a film with a continuous olefin resin matrix that
contains an effective amount of particulate filler having inherent
microvoids. The microvoid-containing particulate filler is
dispersed uniformly and randomly throughout the continuous olefin
resin matrix to provide non-mechanically produced microvoids in
communication with the surface pores to provide ink-receptivity
thereto. The synthetic paper of this patent is formed by extruding
a mixture of the olefin resin matrix and particulate filler into a
desired sheet thickness. While the so-formed substrate avoids the
step of topcoating to achieve an ink-receptive surface structure,
it relies on the formation of a porous or voided surface structure
that can be the source of performance limitations.
[0010] International Publication No. WO 92/00188 discloses an ink
jet printable, microporous, ethylene-vinyl alcohol copolymer film
that is formed by melt blending a mixture of ethylene-vinyl alcohol
copolymer and a compatible polymer or compound in which the
copolymer will dissolve to form a solution at its melting
temperature. The solution is formed into a film, which is cooled.
During the cooling step, a phase separation occurs between the
compatible copolymer or compound and the ethylene-vinyl alcohol
polymer, providing a film comprising an aggregate of a first phase
of particles of ethylene-vinyl alcohol copolymer in a second phase
of the compatible polymer or compound. The cooled film is
collected, the compatible polymer or compound is extracted, and the
resulting film is stretched. Micropores are formed in the film
structure by extracting the compatible polymer or compound
therefrom. While the substrate formed according to this publication
avoids the step of topcoating to achieve an ink-receptive surface
structure, like the other above-described non-topcoating methods,
it also relies on the formation of a porous or voided surface
structure that can be the source of performance limitations.
[0011] The common theme of the above described non-topcoated
ink-receptive substrates is that they each depend on use of a
voided or porous substrate surface to provide a surface structure
that is receptive to ink deposited thereon. The use of a substrate
surface having such a voided or porous structure, however, is not
without its limitations. For example, it is known that such
substrates can suffer from poor image quality. Substrates having
such surface structures tend to act like a sponge, absorbing ink
deep into the substrate body, often resulting in poor color
densities and resolutions. These substrates are also prone to
provide poor optical qualities as the surface voids oftentimes
provides a surface that is mostly opaque or translucent, thereby
limiting potential substrate applications. Additionally, substrates
having such voided surface structures oftentimes require a complex
manufacturing process. For example, it is not unusual for such
substrates to have a complex material formulation and/or multiple
process steps, which can add both to the expense and time
associated with making the substrate.
[0012] For these reasons, it is desired that an ink-receptive
substrate be constructed that avoids both the need for topcoating
and reliance on a voided microstructure. That is, the desired
substrate is "inherently" ink-receptive. It is desired that such
inherently ink-receptive substrates provide properties of image
quality and optics that are superior to those provided by
substrates having voided microstructures. It is desired that such
inherently ink-receptive substrates be fabricated in a manner that
avoids the need for multiple time-consuming and costly process
steps. It is further desired that inherently ink-receptive
substrate constructions of this invention be capable of receiving
ink as deposited by ink jet technique, as well as by other methods
of ink transfer.
SUMMARY OF THE INVENTION
[0013] Ink-receptive substrates of this invention comprise a base
layer formed from a water-insoluble thermoplastic polymer, and an
ink-receptive layer disposed over the base layer. The ink-receptive
layer is formed from a melt processable blend of a water-soluble
polymer and a substantially water-insoluble polymer, and provides
an inherently ink-receptive surface without further surface
treatment. A tie layer can optionally be interposed between base
and ink-receptive layer.
[0014] The base layer is selected from the group of thermoplastic
material consisting of polyolefins, polyesters, polyurethanes,
polyvinyl chlorides, polyamides, polystyrene, ethylene vinyl
alcohol, and mixtures thereof. The ink-receptive blend comprises in
the range of from 20 to 80 percent by weight water-soluble polymer,
and in the range of from 20 to 80 percent by. weight substantially
water-insoluble polymer based on the total weight of the blend. The
blend may include an optional compatibilizing agent that is
chemically compatible with both the water-soluble polymer and the
substantially water-insoluble polymer.
[0015] The blend has a melting temperature in the range of from
about 100 to 600.degree. F. The water-soluble polymer component of
the blend is selected from the group of compounds consisting of
polyvinyl alcohols, polyalkyl oxazolines, polyphenyl oxazolines,
polyvinyl pyrrolidones, polyacrylic-acids, polymethyl
methacrylates, polymethacrylic acids, styrene maleic anhydrides,
alkyl celluloses, carboxyalkyl celluloses, hydroxyalkyl celluloses,
polyethylene oxides, polyethylene-imines, and mixtures thereof.
[0016] Preferred water-soluble polymers include polyalkyl oxazoline
and polyvinyl alcohol. The substantially water-insoluble polymer
component of the blend is selected from the group of polyolefins
consisting of modified and unmodified polyesters, polypropylenes,
polyethylenes, polystyrenes, polybutylenes, and copolymers and
mixtures thereof.
[0017] In a preferred embodiment, the base layer and ink-receptive
layer of ink-receptive substrates of this invention are formed
simultaneously by a coextrusion process. Ink-receptive substrates
of this invention can include the ink-receptive layer on one or
both surfaces of the base layer, and/or can be constructed in the
form of a pressure-sensitive adhesive label, i.e., with a
pressure-sensitive adhesive material disposed on a surface of the
base layer opposite the ink-receptive layer.
[0018] Ink-receptive substrates of this invention are inherently
ink-receptive in that they avoid that need for topcoating or
reliance on a voided microstructure to gain ink receptivity.
Ink-receptive substrates of this invention provide properties of
image quality and optics that are superior to those provided by
substrates having voided microstructures. Ink-receptive substrates
of this invention are fabricated in a manner that avoids the need
for multiple time-consuming and costly process steps.
DESCRIPTION OF THE DRAWINGS
[0019] These and other features and advantages of the present
invention will become appreciated as the same becomes better
understood with reference to the specification, claims and
drawings, wherein:
[0020] FIG. 1 is a schematic cross-sectional side view of an
embodiment of an ink-receptive substrate of this invention
comprising a single ink-receptive surface;
[0021] FIG. 2 is a schematic cross-sectional side view of another
embodiment of an ink-receptive substrate of this invention
comprising a tie layer;
[0022] FIG. 3 is a schematic cross-sectional side view of still
another embodiment of an ink-receptive substrate of this invention
comprising two ink-receptive surfaces;
[0023] FIG. 4 is a schematic cross-sectional side view of still
another embodiment of an ink-receptive substrate of this invention
in the form of a labelstock construction;
[0024] FIG. 5 is a schematic side view of a process used for
forming ink-receptive substrates of this invention;
[0025] FIGS. 6 and 7 are schematic cross-sectional views of a
distribution manifold and die as used in the process of FIG. 5,
taken at 90 degrees to one another;
[0026] FIG. 8 is a schematic front view of a distribution block
face taken along section 8-8 of the distribution manifold of FIG.
6;
[0027] FIG. 9 is a schematic front view of a distribution block
face used to form the ink-receptive substrates of FIGS. 1 and
2;
[0028] FIG. 10 is a schematic front view of a distribution block
face used to form the ink-receptive substrates of FIG. 3;
[0029] FIG. 11 is a schematic front view of a combining block taken
along section 11-11 of the distribution manifold of FIG. 6; and
[0030] FIG. 12 is a schematic cross-sectional side view of an
embodiment of an ink-receptive substrate of this invention
comprising a dual layer ink-receptive surface.
DETAILED DESCRIPTION OF THE INVENTION
[0031] Ink printable substrates of this invention are referred to
as being "inherently" ink-receptive, or ink jet printable, because
the substrate surface structure is engineered to be receptive to an
ink medium without subsequent topcoating, treating (e.g., corona
treating or the like), and without depending on a voided or porous
microstructure. Rather, substrates produced according to principles
of this invention have a surface formed from a specially designed
blend of a water-soluble polymer and a substantially
water-insoluble polymer, which blend provides superior
ink-receptive properties when compared to conventional substrates
having topcoated or voided surfaces.
[0032] FIG. 1 illustrates an embodiment of an ink-receptive
substrate 10 of this invention comprising a base layer 12 having
oppositely oriented surfaces, and an ink-receptive layer 14
disposed on one of the base layer surfaces. The base layer 12 can
be formed from a variety of different thermoplastic polymers
depending on the substrate end use application. Suitable base layer
materials for forming substrates of this invention include
meltable, film-forming substances selected from the group of
materials including polyolefins such as polyethylenes,
polypropylenes and polybutylenes, polyvinyl chlorides, polyamides,
polyesters, polystyrenes, polyurethanes, polyacrylates, polyvinyl
acetate, polysulfone, polyvinylidene chloride, polyethylene methyl
acrylates (EMA), polyethylene methacrylic acids (EMAA),
polyethylene ethyl acrylate, nylons, polyvinylpyrrolidone,
polyether esters, polyether amides, polycarbonates, styrene
acrylonitrile polymer, ionomers based on sodium or zinc salts of
ethylene/methacrylic acid, polymethyl methacrylates, cellulosics,
fluoroplastics, acrylonitrile butadiene styrene polymer,
polyethylenevinyl alcohol, and copolymers and mixtures thereof. The
selected base layer material can also include fillers, pigments,
processing, and/or performance aids conventionally used in the
art.
[0033] Preferred thermoplastic polymers useful for forming the base
layer have a processing temperature within the range of from about
150 to 600.degree. F., with those having a processing temperature
of 250 to 550.degree. F. being particularly preferred. Example
preferred materials for the base layer include polypropylene
homopolymers and copolymers available, for example, from Union
Carbide Corporation, under the product name UCC Polypropylene;
polyesters available, for example, from Eastman Chemical Company,
under the product name Eastar.RTM.; and polyethylenes available,
for example, from Dow Chemical Company, under the product name
Dowlex.RTM.. These example materials are preferred because of their
relatively low cost, their extrudable film-forming ability, and
their ability to provide a degree of stiffness and strength
suitable for most uses.
[0034] The ink-receptive layer comprises a blend of a watersoluble
polymer and a substantially water-insoluble polymer. Suitable
water-soluble polymers useful for forming the ink-receptive layer
include polyvinyl alcohol, polyalkyl oxazoline, polyphenyl
oxazoline, polyvinyl pyrrolidone, polyacrylic-acid, polymethyl
methacrylate, polymethacrylic acid, styrene maleic anhydride,
methyl cellulose, ethyl cellulose, carboxymethyl cellulose,
hydroxyethyl cellulose, polyethylene oxide, polyethylene-imine, and
mixtures thereof. The water-insoluble polymer component of the
blend is either chemically compatible with the water-soluble
polymer or is able to be compatible with the water-soluble
component by the use of suitable compatibilizing agents.
[0035] Forming the ink-receptive surface from a blend of these two
polymers is desired because the combination of a water-soluble
polymer and a substantially water-insoluble polymer provides a
desired degree of hydrophilicity that creates an ink-receptive
surface. Materials useful for forming the ink-receptive layer can
further comprise cationic modifiers, wetting agents, colloidal
silica, inherently dissipative polymer, water proofing agents and
anti-static agents.
[0036] A first preferred ink-receptive layer comprises a blend of a
polyalkyl oxazoline and a polyolefin. A preferred blend comprises a
resin blend of polyethyl oxazoline and polyolefin with a
compatibilizing agent. A blend of water-soluble polyethyl oxazoline
and polyolefin is desired because the substantially hydrophobic
polyolefin is useful for providing a desired degree of
hydrophilicity to create an ink-receptive surface that is
substantially water insoluble. Further, the compatibilizing agent
is used in the blend to provide a miscible polymeric resin blend of
polyethyl oxazoline and polyolefin. Consequently, the
compatibilizing agent enables processing of the present blend into
films without defects that may arise due to the incompatibility
between polyethyl oxazoline and polyolefin.
[0037] A desired polyethyl oxazoline for producing this blend has a
molecular weight in the range from about 50,000 to about 1,000,000,
more preferably from about 200,000 to about 500,000, and kinematic
viscosity in the range from about 18 to about 90 centi-stokes.
Polyethyl oxazolines having a molecular weight outside of this
range are not easily processable using common thermoplastic
processing techniques. Example preferred polyethyl oxazolines are
discussed in greater detail below in Examples 1 and 2.
[0038] Polyolefins useful for combining with the polyethyl
oxazoline to form the ink-receptive layer blend can be selected
from the group including modified and unmodified polypropylenes,
polyethylenes, polystyrenes, polybutylenes and copolymers and
mixtures thereof. These types of polyolefins are preferred because
they are capable of forming a miscible blend with the polyalkyl
oxazoline in the presence of suitable compatibilizing agents, and
at reasonable concentrations become the continuous phase. Being the
continuous phase, the substantially hydrophobic polyolefin provides
the ability to control the degree of hydrophilicity of the surface
by altering the polyolefin concentration in the blend.
[0039] Compatibilizing agents useful for forming the ink-receptive
layer can be selected from the group including anhydridemodified
polyolefins such as anhydride-modified polypropylene,
anhydride-modified polyethylene, anhydride-modified ethylene vinyl
acetate, anhydride-modified ethyl methyl acrylate,
anhydride-modified ethylene ethyl acrylate, anhydride-modified
ethyl acrylic acid, anhydride-modified ethyl glycidyl methacrylate,
anhydride-modified ethyl n-butyl acrylate, and copolymers,
terpolymers and mixtures thereof. These types of anhydride-modified
polyolefins are preferred because they possess a polyolefin
backbone selected to make them miscible in the polyolefin blend
component, and the anhydride groups are capable of reacting with
the oxazoline groups of the polyalkyl oxazoline blend
component.
[0040] A particularly preferred polyalkyl oxazoline, polyolefin,
and optional compatiblizer blend is one that comprises in the range
of from about 20 to 80 percent by weight of polyalkyl oxazoline, in
the range of from about 10 to 80 percent by weight of polyolefin
and, up to about 40 percent by weight compatiblizer. Using an
amount of the polyalkyl oxazoline, polyolefin, and compatiblizer
outside of this range is not desirable because the optimal degree
of hydrophilicity for functioning as an ink-receptive layer may not
be achieved outside these ranges.
[0041] Preferred polyalkyl oxazolines for forming the blend include
those available from, for example, Polymer Chemistry Innovations of
Tucson, Ariz., under the product name Aquazol.RTM.. Preferred
polyolefins for forming the blend include polypropylene available
from Union Carbide Corporation under the product name UCC
Polypropylene. Preferred anhydride-modified polyolefins for forming
the blend include anhydride-modified ethylene vinyl acetate
available from E. I. du Pont under the product name Bynel.RTM..
[0042] A second preferred ink-receptive layer comprises a blend of
polyvinyl alcohol and an aliphatic polyester. An example
alcohol/polyester blend is one disclosed in U.S. Pat. No.
5,658,977, which is incorporated herein by reference, comprising a
miscible polymeric resin blend of polyvinyl alcohol and aliphatic
polyester with minor proportions of diluents, processing, and
performance aids. A blend of polyvinyl alcohol and aliphatic
polyester is desired, as opposed to a blend of polyvinyl alcohol
with another water-soluble polymer, or as opposed to using
polyvinyl alcohol alone, because the aliphatic polyester serves to
provide a desired degree of hydrophilicity to create an
ink-receptive surface that is substantially water insoluble.
Further, the liquid ester diluent disclosed in U.S. Pat. No.
5,658,977 is useful for reducing or depressing the melting point of
the polyvinyl alcohol to aid in film processing.
[0043] As discussed in more detail below, the liquid aliphatic
ester ingredient serves to reduce the melting range of the mixture
to 280 to 360.degree. F. Consequently, the liquid aliphatic ester
enables processing of the present blend into films at temperatures
below which the polyvinyl alcohol would otherwise suffer thermal
degradation. Additionally, this melting range is desired for
forming the ink-receptive substrate of this invention by a
multi-layer co-extrusion process because it provides a wider
processing window than that of polyvinyl alcohol alone, and
complements the melt temperature range of the base layer
material.
[0044] A desired polyvinyl alcohol for producing this blend has a
degree of hydrolysis in the range of from about 80 to 98 percent,
and a degree of polymerization in the range of from about 150 to
650. A polyvinyl alcohol ingredient having a degree of hydrolysis
outside of this stated range is not desired because it may result
in poor printing performance, poor drying and coloring properties
that could cause print image feathering and bleeding. A polyvinyl
alcohol ingredient having a degree of polymerization outside of
this stated range is not desired as polyvinyl alcohols having a
degree of polymerization of less than about 150 are known to be
highly water-sensitive, making them extremely difficult or
impossible to co-extrude. Polyvinyl alcohols having a degree of
polymerization greater than about 650 have a relatively high
viscosity that may create difficulties in forming a continuous thin
film.
[0045] The polyvinyl alcohol ingredient can comprise a single-type
of polyvinyl alcohol having the above-desired properties, or a
mixture of two or more polyvinyl alcohols, wherein the resulting
mixture displays the above-desired properties.
[0046] Aliphatic polyesters useful for forming the ink-receptive
layer blend can be selected from the group including
polycaprolactone, polyethylene-adipate, unsaturated polyesters,
cyclo-polyesters, substituted aliphatic polyesters, and
combinations thereof. These types of aliphatic polyesters are
preferred because they are miscible with the polyvinyl alcohol and,
at a reasonable concentration, become a continuous phase of the
blend. As the continuous phase, the substantially hydrophobic
aliphatic polyester provides the ability to control the degree of
hydrophilicity of the surface by altering the aliphatic polyester
concentration in the blend.
[0047] A particularly preferred polyvinyl alcohol/aliphatic
polyester blend is one that comprises in the range of from about 20
to 80 percent by weight polyvinyl alcohol, and in the range of from
about 20 to 80 percent by weight aliphatic polyester. A blend
formed by using less than about 20 percent by weight of the
polyvinyl alcohol may not create a level of hydrophilicity that can
provide a drying time that is meaningful for the application. A
blend formed by using greater than about 80 percent by weight of
the polyvinyl alcohol may create a surface that is highly
hydrophilic, thereby picking up moisture from air and destroying
the surface integrity. A particularly preferred alcohol/polyester
blend comprises approximately 40 percent by weight of the polyvinyl
alcohol.
[0048] A blend formed by using less than about 20 percent by weight
of the aliphatic polyester ingredient may not form the continuous
phase of the blend, and hence may not function to control the
surface hydrophilicity. A blend formed by using greater than about
80 percent by weight of the aliphatic polyester ingredient may
render the surface completely hydrophobic, and thereby cause poor
ink reception. A particularly preferred alcohol/polyester blend
comprises approximately 60 percent by weight of the aliphatic
polyester.
[0049] Preferred polyvinyl alcohols for forming the blend include
those available from, for example, E. I. du Pont under the product
name Elvanol.RTM., and from Air Products and Chemicals of
Allentown, Pa., under the product name Airvol.RTM.. Preferred
aliphatic polyesters for forming the blend include those available
from, for example, Union Carbide under the product name
Tone.RTM..
[0050] FIG. 2 illustrates another embodiment of an ink-receptive
substrate 16 of this invention comprising a base layer 18 having
oppositely oriented surfaces, and an ink-receptive layer 20 forming
one exposed surface of the base layer. Unlike the embodiment
illustrated in FIG. 1, this embodiment further comprises a
compatiblizing tie layer 22 that is interposed between the base
layer 18 and ink-receptive layer 20 surfaces. The base layer 18 and
ink-receptive layer 20 are each formed from the same types of
materials discussed above. The tie layer 22 is formed from
materials that demonstrate compatibility with the materials
selected for forming the base and ink-receptive layers to bond the
base and ink-receptive layers together, thereby facilitating
formation of substrate of this invention via a multi-layer
co-extrusion process, as will be described in greater detail
below.
[0051] It is to be understood that use of the tie layer is optional
between the ink-receptive layer and base layer, and may be
necessary depending on the relative degree of compatibility between
the materials selected for use as the ink-receptive and tie layers.
Suitable materials useful for forming the tie layer include those
set forth above as being useful for forming the base layer, that
have been modified to display a degree of compatibility with the
blend of water-soluble polymer and substantially water-insoluble
polymer used to form the ink-receptive layer. Therefore, it is to
be understood that the tie layer material can be different for each
different base and ink-receptive material that is selected.
[0052] Example preferred tie layer materials include
anhydride-modified polyolefins such as anhydride-modified
polypropylene, anhydride-modified polyethylene, anhydride-modified
ethylene vinyl acetate, anhydride-modified ethyl methyl acrylate,
anhydride-modified ethyl acrylic acid, and copolymers and mixtures
thereof. A particularly preferred material for forming the tie
layer is an anhydride-modified ethylene vinyl acetate that is
available, for example, from E. I. du Pont under the product name
Bynel.RTM.. This particular type of anhydride-modified polyolefin
is preferred because it is functionalized with reactive monomers
that can covalently or ionically bond to various substrates such as
ethylene- and propylene-based polyolefins, ionomers, polyamides,
polyvinyl alcohols, polyethyl oxazolines, polyesters,
polycarbonates, and styrenics.
[0053] FIG. 3 illustrates still another embodiment of an
ink-receptive substrate 24 of this invention comprising two opposed
ink-receptive surfaces. Specifically, this ink-receptive substrate
embodiment comprises a base layer 26 having tie layers 28 disposed
onto each exposed base layer surface, and having an ink-receptive
layer 30 disposed onto each exposed tie layer surface. The
materials selected for forming the base layer, tie layers and
ink-receptive layers are the same as those discussed above. This
embodiment is useful for applications, e.g., ink jet printable
applications, where a dual-sided printed object is desired, and is
preferably formed by multi-layer co-extrusion process as described
below.
[0054] FIG. 4 illustrates yet another embodiment of an
ink-receptive substrate 32 of this invention in the form of a
labelstock. Specifically, the ink-receptive substrate 32 comprises
a base layer 34 having opposed first and second surfaces. A tie
layer 36 is optionally disposed onto the base layer first surface,
and an ink-receptive layer 38 is disposed onto a surface of the tie
layer, much like the embodiment described above and illustrated in
FIG. 2. However, unlike the embodiment of FIG. 2, this
ink-receptive substrate embodiment is in the form of a labelstock
and further comprises an adhesive layer 40 disposed onto the base
layer second surface.
[0055] In the event that the adhesive layer 40 is formed from a
solvent-activated adhesive, the substrate 32 need not include a
further layer to protect the substrate from unintended adhesion
with contiguous surfaces. In the event that the adhesive layer 40
is formed from a pressure-sensitive adhesive, the substrate 32
comprises a release liner 42 disposed onto the surface of the
adhesive layer to protect the substrate against unintended adhesion
with contiguous surfaces. Constructed in this manner, the
ink-receptive substrate 32 can function in the form of a label for
application onto the surface of a particular substrate after it is
printed upon by placing the exposed surface of the adhesive layer
40 into contact with the particular substrate surface.
[0056] The base layer, 34, tie layer 36, and ink-receptive layer 38
are each formed from the same types of materials discussed above
for the same respective layers. The adhesive layer 40 can be formed
from solvent-activated adhesives or from pressure-sensitive
adhesives well known in the art. Suitable pressuresensitive
adhesives (PSAs) include conventional silicone-based PSAS,
rubber-based PSAS, and acrylic-based PSAS, which can be in the form
of a hot melt, an emulsion or aqueous dispersion, as a solvent
solution, or as a film membrane. Commonly available rubber-based
PSAs that are well suited for hot melt application include those
disclosed in U.S. Pat. No. 3,239,478, which is incorporated herein
by reference. A commercial example of such hot melt adhesives is
H2187-01 hot melt PSA sold by Ato Findley, Inc., of Wauwatosa, Wis.
Suitable emulsion and solvent acrylic-based PSAs include those
disclosed in U.S. Pat. Nos. 5,639,811 and 5,164,444, respectively,
both of which are incorporated herein by reference.
[0057] The adhesive material forming the adhesive layer can be
applied to the base layer surface either by process of multi-layer
coextrusion with the base layer, ink-receptive layer, and tie layer
(if needed) in the form of a hot melt, by extrusion coating onto
the preformed base layer on the form of a hot melt, or by coating
onto the preformed base layer in the form of an emulsion or aqueous
dispersion, as a solvent solution, or as a film membrane.
[0058] The ink-receptive layer used to form each of the
above-described ink-receptive substrates is either formed
simultaneously with the underlying base layer, and any optional
interposed tie layer, by a multi-layer coextrusion process, or can
be deposited by itself or with any optional tie layer by an
extrusion process onto a preformed base layer. The following
examples are illustrative of ink-receptive substrates of this
invention:
Example No. 1
[0059] Ink-receptive Substrate Comprising Polyoxazoline/Polyester
Ink-receptive Surface
[0060] An ink-receptive substrate, as discussed above and
illustrated in FIGS. 1 and 2, was prepared in the following manner
using a multi-layer coextrusion process 50 as illustrated in FIG.
5. A first extruder 52, used for delivering an extrusion of
ink-receptive layer forming material, was loaded with a blend of
Aquazol.RTM., poly(2-ethyl-2-oxazoline), produced by Polymer
Chemistry Innovations, Inc., Kodar.RTM.,
poly(ethylene-terephthalate) copolyester designated as PETG,
produced by Eastman Chemical Co., and Selar.RTM., modified
polyester copolymer, produced by du Pont. The blend in the first
extruder had a melt processing range of from about 150 to
600.degree. F., and the extruder was operated within a temperature
range of from about 450 to 550.degree. F.
[0061] A third extruder 56, used for delivering an extrusion of
base layer forming material, was loaded with Kodar.RTM.,
poly(ethylene-terephthalate- ) copolyester designated as PETG,
produced by Eastman Chemical Co., and was operated within a
temperature range of from about 450 to 550.degree. F.
[0062] A second extruder 54, may be optionally used for delivering
an extrusion of a tie layer of polymeric material adherent to the
ink-receptive layer and the base layer and juxtaposed between the
two layers. The need for the adherent layer would depend on the
level of layer adhesion, between the base layer and the
ink-receptive layer, that is desired in the final product. In this
example, a tie layer formed from Selar.RTM. was loaded into the
second extruder 54 and was operated within a temperature range of
from about 450 to 550.degree. F.
[0063] The extruders 52, 54, and 56 were each screw extruders that
were operated at around 20 to 80 rpms, and within a pressure range
of from about 750 to 4000 psi. The extrudate from each of the
extruders 52, 54 and 56 were delivered to a distribution manifold
58 that was configured to combine the three extrusion feed streams
and direct the combined streams into a die 60 that is configured
and operated at a temperature within the range of from 450 to
550.degree. F.
[0064] The die 60 is configured to provide a multi-layer output
stream 62 comprising an ink-receptive layer 64, a tie layer 66, and
a base layer 68, that were each formed simultaneously with one
another. The so-formed ink-receptive substrate sheet was cooled by
passing over a chilled roller (not shown), and was collected on a
collection roll 66.
Example No. 2
[0065] Ink-receptive Substrate Comprising Polyoxazoline/Polyolefin
Ink-receptive Surface
[0066] The process described above for Example No. 1 and
illustrated in FIG. 5 was repeated using the first extruder 52, for
delivering an extrusion of ink-receptive layer forming material,
that was loaded with a blend of Aquazol.RTM.,
poly(2ethyl-2-oxazoline), DS6D81, UCC polypropylene, and
Bynel.RTM., anhydride-modified ethylene vinyl acetate. The blend in
the first extruder had a melt processing range of 250 to
500.degree. F., and the extruder was operated within a temperature
range of from about 350 to 450.degree. F.
[0067] A third extruder 56, used for delivering an extrusion of
base layer forming material, was loaded with DS6D81, UCC
polypropylene, produced by Union Carbide Corp., and was operated
within a temperature range of from about 350 to 450.degree. F.
[0068] A second extruder 54, may be optionally used for delivering
an extrusion of a tie layer of polymeric material adherent to the
ink-receptive layer and the base layer and juxtaposed between the
two layers. A tie layer formed from an adherent polymeric material,
Bynel.RTM., was loaded into the second extruder 54 and was operated
within a temperature range of from about 350 to 450.degree. F. The
extruders 52, 54, and 56 were each screw extruders that were
operated at around 20 to 80 rpms, and within a pressure range of
from about 750 to 4000 psi. The extrudate was then delivered to die
60, as described above in Example No. 1, that was configured and
operated at a temperature within the range of from 350 to
45.degree. F.
[0069] The die 60 provided a multi-layer output stream 62
comprising an ink-receptive layer 64, a tie layer 66, and a base
layer 68, that were each formed simultaneously with one another.
The so-formed ink-receptive substrate sheet was cooled by passing
over a chilled roller (not shown), and was collected on a
collection roll 66.
Example No. 3
[0070] Ink-receptive Substrate Comprising Polyvinyl
Alcohol/Polyester Ink-receptive Surface
[0071] The process described above in Example Nos. 1 and 2, and
illustrated in FIG. 5, was repeated using a first extruder 52
loaded with a blend of Airvol.RTM. polyvinyl alcohol, Tone.RTM.
poly(caprolactone), and minor amounts of Triacetin and Glycerin for
delivering an extrusion blend of ink-receptive layer. The blend in
the first extruder had a melt processing range of 250 to
450.degree. F., and the extruder was operated within a temperature
range of from about 250 to 350.degree. F.
[0072] A third extruder 56, used for delivering an extrusion of
base layer forming material, was loaded with DX5E66, polypropylene,
and was operated within a temperature range of from about 350 to
450.degree. F. A second extruder 54, may optionally be used for
delivering an extrusion of a tie layer of polymeric material
adherent to the ink-receptive layer and the base layer and
juxtaposed between the two layers. A tie layer formed from an
adherent polymeric material, Bynel.RTM. anhydride-modified ethylene
vinyl acetate, was loaded into the second extruder 54 and was
operated within a temperature range of from about 350 to
450.degree. F. The extruders 52, 54, and 56 were each screw
extruders that were operated at around 20 to 80 rpms, and within a
pressure range of from about 750 to 4000 psi. The extrudate was
then delivered to die a 60, as described above in Example Nos. 1
and 2, which was configured and operated at a temperature within
the range of from 350 to 450.degree. F.
[0073] The die 60 provided a multi-layer output stream 62
comprising an ink-receptive layer 64, a tie layer 66, and a base
layer 68, that were each formed simultaneously with one another.
The so-formed ink-receptive substrate sheet was cooled by passing
over a chilled roller (not shown), and was collected on a
collection roll 66.
[0074] FIGS. 6 and 7 schematically depict the sectional views (at
90 degree angles to one another) of the distribution manifold 58
and die 60 used in the multi-layer coextrusion process 50 of FIG.
5. The distribution manifold 58 includes a first extrusion input
port 82 for receiving the ink-receptive layer-forming material
provided by the first extruder 52, a second extrusion input port 84
for receiving the adherent layer-forming material provided by the
second extruder 54, and a third extrusion input port 86 for
receiving the base layer-forming material provided by the third
extruder 56.
[0075] The first, second, and third extrusion input ports 82, 84
and 86 are configured so that the discharge ends of the three feed
streams 70, 72 and 74 terminate on a face 80 (see FIG. 6) of a
distribution block 76 (see FIG. 6). FIG. 8 shows a view of the face
80 taken along the section 8-8 of FIG. 6, illustrating three
discharge ends 70, 72 and 74. Referring to FIG. 6, the distribution
block 76 comprises a first or feed face 88 at one end, and a second
or discharge face 90 at an opposite end. The design and use of such
a distribution block has been the subject of several patents, for
example U.S. Pat. No. 3,924,990, which is incorporated herein by
reference and which describes a coextrusion apparatus for providing
a variety of products by using different distribution block
designs.
[0076] The main purpose of the distribution block is to alter the
flow path of the feed streams within the distribution manifold as
desired. FIG. 9 shows a distribution block 76a that was used to
provide the ink-receptive substrate constructions illustrated in
FIGS. 1 and 2. In this case, the feed streams are rotated by 90
degrees going from face 88 to face 90. FIG. 11 illustrates a view
along section 11-11 of an inlet portion of a combining block 78,
having parallel adjacent slots 92, of FIG. 6. The combining block
is disposed within the distribution manifold adjacent the
distribution block to bring together the layers of material passing
through the distribution block, and to ensure a uniform volumetric
flow to the die. The distribution manifold and respective extruded
material input ports are operated within the temperature ranges
noted above for the respective extruders.
[0077] Referring back to FIGS. 5 and 6, the die 60 is attached to a
dispensing end 94 of the distribution manifold 58, and comprises a
receiving port 96 that is in fluid communication with a feed block
output port 98. The die includes a final delivery port 100
downstream of and in fluid flow communication with the receiving
port 96 that is sized and shaped to provide the desired multi-layer
ink-receptive substrate. The extruders, feed block, and die are
each operated to provide an ink-receptive substrate having both a
desired overall sheet thickness and a desired discrete
ink-receptive layer, adherent layer, and base layer thickness.
[0078] It is to be understood that the overall substrate and
discrete layer thicknesses for a particular substrate construction
will vary depending on many factors, such as the types of materials
that are used to form each layer, whether a tie layer is used at
all, and the particular type of substrate application.
[0079] In an example embodiment, comprising a three-layer
construction of a base layer, a tie layer, and an ink-receptive
layer formed from the materials noted above, the substrate can have
an overall sheet thickness in the range of from about 10 to 750
micrometers (.mu.m), more preferably in the range of 20 to 500
.mu.m; the base layer can have a thickness in the range of from
about 5 to 745 .mu.m, more preferably in the range of 10 to 500
.mu.m; the tie layer can have a thickness in the range of from
about 2 to 745 .mu.m; more preferably in the range of 5 to 500
.mu.m; and the ink-receptive layer can have a thickness in the
range of from about 2 to 745 .mu.m more preferably in the range of
5 to 500 .mu.m.
[0080] In a particular embodiment, where an above-constructed
ink-receptive substrate is used as an ink jet printable overhead
transparency, the substrate has a preferred overall thickness of
approximately 100 .mu.m, a base layer thickness of approximately 80
.mu.m, a tie layer thickness of approximately 10 .mu.m, and an
ink-receptive layer thickness of approximately 10 .mu.m.
Example No. 4
[0081] Ink-receptive Substrate Comprising Dual Ink-receptive
Layers
[0082] An ink-receptive substrate, as discussed above and
illustrated in FIG. 3, was prepared in the following manner using a
multi-layer coextrusion process as illustrated in FIG. 5. The
distribution block design to provide the construction shown in FIG.
3 is illustrated in FIG. 10. In this case, the distribution block
76b, rotates the feed streams by 90 degrees and at the same time
splits the ink-receptive blend feed streams (stream A of FIG. 8) to
form two opposed ink-receptive layers, with two opposed tie layers
(stream C of FIG. 8) interposed between the ink-receptive layers
and the base layer (stream B of FIG. 8).
[0083] In an example embodiment, comprising a dual multi-layer
construction of a base layer having two opposed tie layers and
respective ink-receptive layers from the materials noted above, the
substrate can have an overall sheet thickness in the range of from
about 10 to 750 .mu.m, more preferably in the range of 20 to 500
.mu.m; the base layer can have a thickness in the range of from
about 5 to 740 .mu.m, more preferably in the range of 10 to 500
.mu.m; each tie layer can have a thickness in the range of from
about 2 to 370 .mu.m, more preferably in the range of 5 to 250
.mu.m; and each ink-receptive layer can have a thickness in the
range of from about 2 to 370 .mu.m, more preferably in the range of
5 to 250 .mu.m.
[0084] In a particular embodiment, where an above-constructed
ink-receptive substrate is used as a dual side ink jet printable
graphic media, the substrate has a preferred overall thickness of
approximately 175 .mu.m, a base layer thickness of approximately
125 .mu.m, each adherent layer thickness of approximately 10 .mu.m,
and each ink-receptive layer thickness of approximately 15
.mu.m.
Example No. 5
[0085] Ink-receptive Substrate in the Form of a Labelstock
[0086] An ink-receptive substrate, as discussed above and
illustrated in FIG. 4, was prepared in the manner described above
in any of the Example Nos. 1, 2 and 3. In addition to this, a layer
of pressure sensitive adhesive (PSA) material was deposited onto
the exposed base layer surface by either direct coating with the
PSA 40, or the PSA 40 may be transferred from a liner 42 with which
the ink-receptive substrate face stock is combined.
[0087] In an example embodiment, comprising an ink-receptive
substrate labelstock construction of a base layer, an adherent tie
layer, an ink-receptive layer, a PSA layer, and a release liner
each formed from the materials noted above, the construction can
have an overall sheet thickness in the range of from about 10 to
1500 .mu.m, more preferably in the range of 20 to 1000 .mu.m; the
base layer can have a thickness in the range of from about 5 to 745
.mu.m, more preferably in the range of 10 to 500 .mu.m; the
adherent tie layer can have a thickness in the range of from about
2 to 740 .mu.m, more preferably in the range of 5 to 500 .mu.m; the
ink-receptive layer can have a thickness in the range of from about
2 to 745 .mu.m, more preferably in the range of 10 to 500 .mu.m;
the PSA layer can have a thickness in the range of from about 2 to
500 .mu.m, more preferably in the range of 5 to 250 .mu.m; and the
release liner can have a thickness in the range of from about 10 to
1480 .mu.m, more preferably in the range of 20 to 1000 .mu.m.
[0088] In a particular embodiment, where an above-constructed
ink-receptive substrate is used as an ink jet printable labelstock,
the construction has a preferred overall thickness of approximately
300 .mu.m, a base layer thickness of approximately 80 .mu.m, an
adherent tie layer thickness of approximately 10 .mu.m, an
ink-receptive layer thickness of approximately 10 .mu.m, a PSA
layer thickness of approximately 25 .mu.m, and a release liner
thickness of approximately 175 .mu.m.
[0089] FIG. 12 illustrates an alternative embodiment of an
ink-receptive substrate 100, constructed according to principles of
this invention, comprising a dual layer ink-receptive substrate
construction. Generally, this embodiment is similar to that
disclosed above and illustrated in FIG. 1, comprising a base layer
102 and a dual layer ink-receptive substrate construction 104
comprising a first ink-receptive layer 106 disposed over a surface
of the base layer 102, and a second ink-receptive layer 108
disposed over a surface of the first ink-receptive layer.
[0090] In this dual layer construction, the first ink-receptive
layer 102 is the same as the ink-receptive layer described above
and illustrated in FIGS. 1 to 4. Further, the ink-receptive layer
is made in the manner as described above and illustrated in FIGS. 5
to 11.
[0091] The second ink-receptive layer 106 is formed from a coating
composition that provides further ink-receptive properties, and
provides other desired properties to the substrate construction.
For example, the second ink-receptive layer 106 can be formed from
a coating material that, in addition to providing ink-receptive
properties, provides properties of weatherability and/or UV
resistance to the substrate surface.
[0092] A first example second ink-receptive layer is a coating
composition like that disclosed in U.S. patent application Ser. No.
08/899,562, filed on Jul. 24, 1997, now U.S. Pat. No. 6,153,288,
issued Nov. 28, 2000, which is incorporated herein by reference. In
an example embodiment, the second ink-receptive layer 106 comprises
a composition including an emulsion polymer and at least one
water-soluble cationic polymer. Emulsion polymers useful for
forming the composition include ethylene-vinyl acetate (EVA)
emulsion polymers, acrylic polymers, and polyurethane polymers.
[0093] The composition can optionally include a pigment dispersed
or mixed therein. The cationic polymer fixes acid dye colorants in
water-based inks, and diminishes dye diffusion. Preferably, the
composition includes at least two water-soluble cationic polymers.
Example cationic polymers include a polymerized
diallyldimethylammonium compound and a copolymer of
dimethylaminoethyl acrylate or methacrylate and at least one
hydroxy-lower organic acrylate or methacrylate, with hydroxyethyl
acrylate (HEA) and hydroxyethyl methacrylate (HEMA) being most
preferred.
[0094] In some embodiments, a nonionic or cationic surfactant is
included within the composition to enhance print quality of the
coating. A preferred ink-receptive composition has, on a percent by
weight (dry weight) basis, about 15-70% emulsion polymer, about
5-50% of at least one water-soluble cationic polymer, up to about
60% pigment(s), and up to about 10% of one or more surfactants.
[0095] Suitable EVA emulsion polymers include those available, for
example, from Air Products & Chemicals, Inc., Allentown, Pa.,
under the AIRFLEX trademark. Examples include AIRFLEX 465.TM. (65%
solids) and AIRFLEX 7200.TM. (72-74% solids). Another suitable EVA
emulsion polymer is AIRFLEX 426.TM., a high solids, carboxylated,
EVA polymer partially functionalized with carboxyl groups. This
polymer is thought to improve the water resistance of the resulting
ink-receptive coating, particularly when the coated substrate is
imaged with a dye-based ink. It is believed that the AIRFLEX brand
EVA emulsion polymers are stabilized with up to about 5% by weight
polyvinyl alcohol (PVOH) and/or, in some formulations, a nonionic
surfactant. EVA emulsion polymers used in the present invention
preferably have a solids content of from about 40 to 75%.
[0096] The EVA emulsion polymer preferably comprises from about 15
to 70%, more preferably from about 25 to 65%, by weight of the
ink-receptive composition, on a dry weight basis (meaning that
water is not included in the calculation of the compositional
percentages).
[0097] Water-soluble cationic polymers useful in forming second
ink-receptive layers of this invention embodiment include, but are
not limited to, quaternary ammonium polymers (also known as
polyquaternary ammonium salts, polyquats and quaternary polymers).
Nonlimiting examples of quaternary ammonium polymers include
polydiallyldimethylammonium compounds and copolymers of quaternary
dimethylaminoethyl acrylate or methacrylate and one or more
hydroxy-lower organic acrylate or methacrylate, for example,
hydroxyethyl acrylate (HEA) and hydroxyethyl methacrylate (HEMA).
To maintain charge neutrality, a monovalent or divalent counterion,
Z, is associated with each quaternary ammonium center. Nonlimiting
examples of such counterions include halides, (for example,
chloride) and dimethylsulfate anion.
[0098] In an example embodiment, the composition further includes
one or more cationic or nonionic surfactants, which help to wet any
optional pigment and/or enhance print quality of the resulting
composition. Nonlimiting examples of nonionic surfactants include
alkylphenol ethoxylates, such as nonylphenol ethoxylate, and
Disponil A 3065, an ethoxylated nonionic surfactant available from
Henkel of America Inc. (King of Prussia, Pa.). A nonlimiting
example of a cationic surfactant useful in the practice of the
invention is hexadecyl trimethylammonium chloride (HDTMAC),
available from Akzo Nobel Chemicals Inc. (Chicago, Ill.). Anionic
surfactants should be avoided because of their likely electrostatic
interaction with the cationic, water-soluble polymer(s).
[0099] Preferably, up to about 10% by weight (on a dry weight
basis) of one or more surfactants is employed in the ink-receptive
composition. Too much surfactant can potentially cause the coating
to have air bubbles, which could adversely effect print quality
when coated on film substrates. Other components, such as
thickeners and defoamers, can be added to the formulation to
improve processability.
[0100] Pigments can optionally be mixed with the composition to
increase the opacity and/or modify the porosity of the underlying
coated first ink-receptive layer. Inorganic pigments are especially
preferred; nonlimiting examples include silica (preferably,
amorphous silica gels), silicic acid, clays, zeolites, alumina,
TiO.sub.2, MgO.sub.3 and the like. The pigment increases the ink
absorption and improves the print quality and water resistance of
the dried coating, and enables the coating to be used with
water-based inks containing a dye colorant, as well as with
pigmented, water-based inks. Preferred ink-receptive compositions
prepared in accordance with the present invention can include up to
about 60% by weight pigment, based on the dry weight of the total
composition.
[0101] In a second example, the second ink-receptive layer can also
be formed from an entirely water-soluble polymer composition, i.e.,
one not comprising an emulsion polymer as discussed above. An
example composition of this type can comprise one or more
water-soluble resins selected from the group including
water-soluble vinyl polymer resins, such as polyvinyl alcohol and
polyvinyl pyrrolidone; polyacrylic polymer resins; water-soluble
cellulose polymer resins, such as methyl cellulose, ethyl
cellulose, carboxymethyl cellulose, and hydroxyethyl cellulose; and
synthetic water-soluble polymer resins, such as polyethylene oxide,
and polyethylene-imine.
[0102] Additionally, the water-soluble polymer composition may
include colloidal silica to improve the wettability of the second
ink-receptive layer by virtue of the presence of the SiOH group of
the colloidal silica per se and absorbed water. The presence of
colloidal silica can also impart an anti-static property to the
second ink-receptive layer. The water-soluble composition can also
include a water-soluble cationic polymer as described above. An
example water-soluble composition useful for forming the second
ink-receptive layer is disclosed in U.S. Pat. No. 5,622,997, which
is incorporated herein by reference.
[0103] In a preferred second example, the water-soluble composition
comprises in the range of from about 50 to 90 percent by weight
water-soluble polymer (which can be in the form of a single
ingredient or a combination of two or more of the above-described
water-soluble polymers), up to about 30 percent by weight
water-soluble cationic polymer, and a remaining amount of pigments,
surfactants, and microbiocides.
[0104] In a preferred second example, the second ink-receptive
layer is formed from a water-soluble composition comprising a blend
of N-vinyl pyrrolidone copolymer and polyvinyl alcohol,
diallyldimethylammonium chloride, a defoamer, a surfactant, and a
biocide in the range of proportions presented above.
[0105] The second ink-receptive layer is disposed onto the surface
of the first ink-receptive layer by conventional methods, such as
by spray coating, roll coating, extrustion and the like. In an
example embodiment, the second ink-receptive layer is formed
sequentially after formation of the first ink-receptive layer.
[0106] A feature of the second ink-receptive layer is that it is
compatible with the underlying ink-receptive layer, in that they
are both hydrophilic, thereby avoiding the need to use a
compatiblizing or tie layer in between.
[0107] The second ink-receptive layer works with the underling
first ink-receptive layer to provide a substrate surface that works
particularly well with ink jet printers and that has a high degree
of ink-receptivity toward both pigment-based and dye-based inks,
colored as well as black. As mentioned above, the second
ink-receptive layer can be formulated to provide added beneficial
properties of UV-resistance and/or weatherability as well.
[0108] The second ink-receptive layer functions to improve ink
receptivity by forming an ionic bond with the ink medium dispensed
onto the substrate surface. The underlying first ink-receptive
layer 104 works with the second ink-receptive layer 106 to further
improve ink receptivity by absorbing the ink medium because of its
inherent property hydrophilicity, as described in greater detail
above. Dual ink-receptive layer substrate embodiments of this
invention provide an ink-receptive surface having improved
properties of color density, resolution, color gradation, drying
time, smudgeproofness and water-fastness when compared to
conventional ink-receptive substrates.
[0109] An additional feature of dual ink-receptive layer substrate
embodiments of this invention is that they can be produced as thin
film constructions. Because the first and second ink-receptive
films work together in a complementary/synergistic fashion, the
effective thickness of each layer can be thinner that that
otherwise needed for a single layer ink-receptive substrate
construction. Thus, dual layer ink-receptive substrate embodiments
of this invention can have a combined first and second
ink-receptive layer thickness that is less than that of an
ink-receptive substrate formed from any single ink-receptive
layer.
[0110] In an example embodiment, the first ink-receptive layer has
a coating thickness within the range noted above for the
ink-receptive substrate embodiments illustrated in FIGS. 1 to 4.
The second ink-receptive layer can have a coating thickness in the
same range as that of the first ink-receptive layer.
[0111] Ink-receptive substrates of this invention make use of a
specially designed blend of a water-soluble polymer and a
substantially water-insoluble polymer to provide a superior
ink-receptive surface. When disposed on a suitable base layer, such
ink-receptive surface provided an inherently printable substrate
that, without further treatment or topcoating, and when printed
onto, displays improved properties of optical clarity, print
quality, and surface integrity, when compared with conventional
ink-receptive substrates having a topcoated, voided or porous
surface structure. Specifically, ink-receptive substrates of this
invention provide improved gloss and haze, color density, water
fastness, and scuff resistance.
[0112] While ink-receptive substrates, and method of forming the
same, of this invention have been described and illustrated as
being receptive to an ink media transferred via an ink jet process,
it is to be understood that ink-receptive substrates of this
invention are receptive to dye and pigment-based ink media that are
transferred by other techniques. Thus, ink-receptive substrates of
this invention are intended to be useful for receiving dye and
pigment-based ink media by various ink transfer techniques,
including but not limited to ink jet printing.
[0113] Additionally, ink-receptive substrates of this invention
comprising such ink-receptive layer and base layer construction,
are produced via a multi-layer coextrusion process that is a more
efficient and cost-effective when compared to those conventional
ink-receptive substrates formed by the multi-step processes of
topcoating or other subsequent treatment to obtain a voided or
porous surface structure. Specifically, the use of a multi-layer
coextrusion process enables the ink-receptive layer to be formed
simultaneously with the base layer or any intermediate adherent tie
layer, thereby avoiding the need for multi-step processing.
[0114] Although limited embodiments of ink-receptive substrates and
methods for making the same according to the principles of this
invention have been described herein, many modifications and
variations will be apparent to those skilled in the art.
Accordingly, it is to be understood that, within the scope of the
appended claims, ink-receptive substrates of this invention may be
prepared other than as specifically described herein.
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