U.S. patent application number 10/846617 was filed with the patent office on 2004-10-28 for receptor medium having a microfibrillated surface.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Emslander, Jeffrey O., Hobbs, Terry R., Kody, Robert S., Perez, Mario A., Sebastian, John M., Taylor, Robert D., Woo, Oh Sang, Ylitalo, Caroline M..
Application Number | 20040213928 10/846617 |
Document ID | / |
Family ID | 27658261 |
Filed Date | 2004-10-28 |
United States Patent
Application |
20040213928 |
Kind Code |
A1 |
Sebastian, John M. ; et
al. |
October 28, 2004 |
Receptor medium having a microfibrillated surface
Abstract
A receptor medium with an oriented film having at least one
microfibrillated surface is described. The receptor medium can
receive jettable materials, which include inks, adhesives,
particulate dispersions, electrically, thermally or magnetically
modifiable materials, biological fluids, chemical reagents and
combinations thereof. The microfibrillated surface provides good
ink receptive properties particularly for solvent based inks.
Inventors: |
Sebastian, John M.;
(Maplewood, MN) ; Emslander, Jeffrey O.; (Afton,
MN) ; Perez, Mario A.; (Burnsville, MN) ;
Hobbs, Terry R.; (Saint Paul, MN) ; Kody, Robert
S.; (Minneapolis, MN) ; Ylitalo, Caroline M.;
(Stillwater, MN) ; Taylor, Robert D.; (Stacy,
MN) ; Woo, Oh Sang; (Woodbury, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
27658261 |
Appl. No.: |
10/846617 |
Filed: |
May 14, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10846617 |
May 14, 2004 |
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10059591 |
Jan 29, 2002 |
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6753080 |
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Current U.S.
Class: |
428/32.17 |
Current CPC
Class: |
B41M 5/0064 20130101;
C08J 2323/10 20130101; D06P 5/30 20130101; B41M 5/5272 20130101;
B41M 5/52 20130101; Y10T 428/2913 20150115; B41M 5/0047 20130101;
B41M 5/508 20130101; B41M 5/529 20130101; Y10T 428/249921 20150401;
C08J 5/18 20130101; B41M 5/504 20130101; B41M 5/5218 20130101; B41M
5/5254 20130101; Y10T 428/2495 20150115; Y10T 428/29 20150115; B41M
5/5227 20130101 |
Class at
Publication: |
428/032.17 |
International
Class: |
B41M 005/00 |
Claims
We claim:
1. A receptor medium comprising an oriented film having at least
one microfibrillated surface with a depth of microfibrillation of
greater than 10 microns wherein said microfibrillated surface
comprises polymeric microflakes.
2. The receptor medium of claim 1, wherein said microfibrillated
surface comprises polymeric microflakes selected from the group
consisting of polyethylene, polypropylene, polyoxymethylene,
poly(vinylidine fluoride), poly(methyl pentene),
poly(ethylene-chlorotrifluoroethylene), poly(vinyl fluoride),
poly(ethylene oxide), poly(ethylene terephthalate), poly(butylene
terephthalate), nylon 6, nylon 66, polybutene, polylactides, and
thermotropic liquid crystal polymers.
3. The receptor medium of claim 1, wherein said microfibrillated
surface comprises polymeric microflakes that comprise of a blend of
two or more polymers.
4. The receptor medium of claim 3, wherein the polymers in the
blend are selected from the group consisting of polypropylene,
polyethylene, poly(ethylene-co-methacrylic acid),
poly(ethylene-co-vinyl acetate), acid modified
poly(ethylene-co-vinyl acetate) acid/acrylate modified
poly(ethylene-co-vinyl acetate), poly(ethylene-co-acrylic acid),
and poly(ethylene-co-vinyl acetate-co-carbon monoxide),
poly(methylpentene), poly(ethylene oxide), polybutene, polyesters,
polylactides, polyvinylpyrrolidone with an ionomer copolymer of
ethylene and (meth)acrylic acid, polystyrene/polyisoprene
copolymers, acid, acrylate, and maleic anhydride modified
poly(ethylene-co-vinyl acetate), polyether-ester elastomers,
poly(isobutyl methacrylate), thermoplastic polyurethanes,
polycarbonates, nylons, acrylate and methacrylate homopolymers and
copolymers, polystyrene, poly(vinylchloride-co-vinyl acetate),
poly(vinyl chloride-co-vinyl acetate-co-vinyl alcohol),
polyethyleneimines, poly(ethylene-co-methyl acrylate),
poly(ethylene-co-octene), polyvinylpyrrolidone with
polyvinylalcohol, copolymers or terpolymer of
N-vinyl-2-pyrrolidinone with acrylic acid, dimethylaminoethyl
acrylate, trimethoxysilylethylmethacrylate, and/or poly(ethylene
oxide) acrylate, poly(cyclic olefins), and rubbers.
5. The receptor medium of claim 3, wherein the polyester is
poly(ethylene terephthalate), sulfonated
poly(ethylene-terephthalate), or poly(butylene terephthalate).
6. The receptor medium of claim 1, further comprising one or more
additives selected from the group consisting of surfactants,
mordants and mixtures thereof.
7. The receptor medium of claim 1, wherein said microfibrillated
surface comprises a melt processed polymer or polymer blend, and a
void initiating component.
8. The receptor medium of claim 7, wherein said void initiating
component is an inorganic solid particulate component, a polymer
component, or a mixture thereof.
9. The receptor medium of claim 8, wherein the inorganic component
is selected from the group consisting of solid or hollow glass,
ceramic or metal particles, microspheres or beads, zeolite
particles, metal particles, metal oxides, alkali- or alkaline earth
metal carbonates or sulfates, silicates, metasilicates, aluminates,
feldspar, kaolin, talc, titanium dioxide, and carbon black.
10. The receptor medium of claim 8, wherein the inorganic component
is calcium metasilicate, or calcium carbonate.
11. The receptor medium of claim 9, wherein said void initiating
polymer component is selected from the group consisting of
polypropylene, polyethylene, poly(propylene-co-ethylene),
polylactide, poly(alpha)olefins, polyoxymethylene, poly(vinylidine
fluoride), poly(methyl pentene),
poly(ethylene-chlorotrifluoroethylene), poly(vinyl fluoride),
polyamides, polybutene, thermoplastic polyurethanes,
polycarbonates, polymethylpentene, a polyester, acrylate and
methacrylate homopolymers and copolymers, cyclic polyolefins,
rubbers, copolymers of ethylene, polystyrene, copolymers of
polystyrene, copolymer of polystyrene and polyisoprene,
polyisobutylene, epoxides, polyvinylpyrrolidone, vinylpyrrolidinone
copolymers, and combinations thereof.
12. The receptor medium of claim 11, wherein the polyester is
poly(ethylene terephthalate), sulfonated poly(ethylene
terephthalate), or poly(butylene terephthalate).
13. The receptor medium of claim 11, wherein the copolymers of
ethylene are selected from the group consisting of
poly(ethylene-co-vinylacetate), acid/acrylate modified ethylene
vinyl acetate resin, terpolymer of ethylene/vinyl acetate/carbon
monoxide/ethylene, and combinations thereof.
14. The receptor medium of claim 6, further comprising one or more
additives selected from the group consisting of surfactants,
mordants and mixtures thereof.
15. The receptor medium of claim 1, wherein the film comprises one
or more layers.
16. The receptor medium of claim 1, further comprising an adhesive
layer on a major surface opposite the microfibrillated surface.
17. The receptor medium of claim 16, further comprising a release
liner protecting the adhesive layer.
18. The receptor medium of claim 1, wherein the film is in roll
form.
19. The receptor medium of claim 1, wherein the film is
translucent.
20. A microfibrillated receptor medium comprising the receptor
medium of claim 1 and a material deposited on the microfibrillated
surface.
21. The receptor medium of claim 20, wherein the material is
jettable.
22. The receptor medium of claim 21, wherein the jettable material
is selected from the group comprising inks, adhesives, particulate
dispersions, electrically, thermally or magnetically modifiable
materials, biological fluids, chemical reagents, and combinations
thereof.
23. The receptor medium of claim 20, wherein the jettable material
is a dye or pigmented ink.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the use of microfibers
and/or microflakes as receptor media for a printable substrate. The
printable substrate includes an oriented film with at least one
microfibrillated, ink receptive surface. Printing on such receptor
media with inkjet printers provides fine-resolution images with
good solid fill. This type of printable substrate can be used with
many types of inkjet inks.
BACKGROUND OF THE INVENTION
[0002] Image graphics are omnipresent in modern life. Images and
data that warn, educate, entertain, advertise, etc. are applied on
a variety of interior and exterior, vertical and horizontal
surfaces. Nonlimiting examples of image graphics range from
advertisements on walls or sides of trucks, to posters that
advertise the arrival of a new movie, warning signs near the edges
of stairways, and the like.
[0003] The use of thermal and piezoelectric inkjet inks has greatly
increased in recent years with accelerated development of
inexpensive and efficient inkjet printers, ink delivery systems,
and the like.
[0004] Inkjet printers have come into general use for wide-format
electronic printing for applications such as engineering and
architectural drawings. Because of the simplicity of operation and
economy of inkjet printers, this image process holds a superior
growth potential promise for the printing industry to produce wide
format, image on demand, presentation quality graphics.
[0005] Therefore, the components of an inkjet system used for
making graphics can be grouped into three major categories:
[0006] 1. Computer; software, printer
[0007] 2. Ink
[0008] 3. Receptor medium
[0009] The computer, software, and printer will control the size,
number and placement of the ink drops and will transport the
receptor medium through the printer. The ink will contain the
colorant which forms the image and carrier for that colorant. The
receptor medium provides the repository which accepts and holds the
ink. The quality of the inkjet image is a function of the total
system. However, the compositions and interaction between the ink
and receptor medium are most important in an inkjet system.
[0010] Image quality is what the viewing public and paying
customers will want and demand to see. From the producer of the
image graphic, many other obscure demands are also placed on the
inkjet media/ink system from the print shop. Also, exposure to the
environment can place additional demands on the media and ink
(depending on the application of the graphic).
[0011] Media for inkjet printers are also undergoing accelerated
development. Because inkjet imaging techniques have become vastly
popular in commercial and consumer applications, the ability to use
a personal computer to print a color image on paper or other
receptor media has extended from dye-based inks to pigment-based
inks. The media must accommodate that change. Pigment-based inks
provide more durable images because of the large size of colorant
as compared to dye molecules , which results in superior fade
resistance and improved water fastness.
[0012] Inkjet printing is emerging as the digital printing method
of choice due to its good resolution, flexibility, high speed, and
affordability. Inkjet printers operate by ejecting, onto a
receiving substrate, controlled patterns of closely spaced ink
droplets. By selectively regulating the pattern of ink droplets,
inkjet printers can produce a wide variety of printed features,
including text, graphics, holograms, and the like. The inks most
commonly used in small inkjet printers, such as those used in the
small office and home office (SOHO) markets, are water based.
Industrial type wide format inkjet printers can use water based
inks such as the Novajet printers from Encad Inc. (San Diego,
Calif.), oil based inks such as piezo print 5000 from Raster
Graphics Inc. (San Jose, Calif.), solvent based inks such as the
PressVu printers from VUTEk, Inc. (Meredith, N.H.), or UV curable
inkjet inks such as the SIAS printer from Siasprint Group (Novara,
Italy). This wide variety of inks typically requires specialized
substrates, where each specific substrate is optimized to work with
a specific type of inkjet ink. For example, water based inks
require porous substrates or substrates with special hydrophilic
coatings that absorb the large quantities of water contained in
these inks. Oil based inks are similar to water based inks in that
they require the use of either porous substrates or substrates
coated with a receptor that is oil absorbing.
[0013] On the other hand, solvent based inks typically contain
about 90% organic solvents. These inks work well on substrates that
have high affinity to the solvents, where the solvents can quickly
penetrate the polymeric film preventing the printed ink layer from
running down the film. In high speed inkjet printing, there is a
need to drive off large quantities of solvent so that the substrate
is dry enough to be rolled without blocking in a relatively short
period of time. Therefore, typical solvent based inkjet inks
consist of aggressive solvents such as cyclohexanone and acetates
that penetrate quickly into typical films such as vinyl giving the
printed graphic a "dry" feel within a short period of time from
printing. As a consequence, the quickly penetrating solvents tend
to remain in the film (as well as in the PSA backing if present)
resulting in deteriorated film properties, reduced PSA performance,
and strong odor when the graphic is unrolled and applied to a flat
surface.
[0014] In particular, most wide format solvent based piezo inkjet
inks require a very low viscosity for jetting, resulting in a very
high ratio of solvent to binder/pigment. Large amounts of ink must
be jetted onto the desired substrate to produce a graphic with
acceptable image density. Polyvinyl chloride (PVC) is typically
used for producing large format durable graphics. The solvents used
in the inks are quickly absorbed into the vinyl film and adhesive
layers, leaving the pigment and binder on the surface of the film
and resulting in acceptable image quality. The piezo ink solvents
are very compatible with the PVC and adhesive layers, and also have
relatively high boiling points so it is difficult to fully dry all
of the solvent from a printed sample, especially with the
constraints typical of a graphic production shop. The presence of
the retained solvent negatively affects product performance in
three ways: 1) the solvents migrate through the PVC and plasticize
the adhesive which results in very poor adhesive performance, 2)
the solvents are retained in the PVC film layer resulting in
decreased film properties, and 3) the retained solvents in the film
and adhesive have an objectionable odor which is very noticeable
especially on large format graphics, and has been noted as
objectionable by a number of customers. Traditional olefin-based
graphic films can work well for screenprint and flexographic
printing, but have problems with solvent based piezo inks because
the large amount of solvents jetted cannot be absorbed into the
film. When large amounts of piezo inkjet inks are printed onto
traditional olefin based graphic films the inks pool on the surface
of the film and readily run, producing a poor quality, distorted
image. There is a need for a substrate that is receptive to solvent
based piezo inkjet inks, does not allow running of the inks,
provides good adhesion of the inks when dry, and dries quickly to
prevent objectionable odors.
[0015] In order to avoid the challenges associated with the
above-described inks, there is a drive in the marketplace to move
towards UV curable inkjet inks. These inks are expected to provide
an "instant dry" feature when exposed to UV radiation. However, the
use of UV curable inkjet inks requires redesigning the printer to
accommodate curing lamps. This increases the cost of the printer.
Additionally, there is an inherent problem with UV curable inkjet
inks: in order to obtain fine line resolution, the inks should be
cured within a relatively short time from printing, which results
in poor ink flow and leveling compromising the quality of the solid
fill areas of the graphic. But to obtain good solid fill, the inks
should be allowed to flow and level before curing, which results in
the loss of fine line resolution.
[0016] Therefore, a need exists for a universal substrate that can
be used with all types of inkjet inks, and that does not require a
special receptor coating or UV curing conditions.
[0017] We have discovered that microfibrillated films provide good
ink receptive properties for various types of inkjet inks.
SUMMARY OF THE INVENTION
[0018] The present invention concerns the finding that certain
polymeric films, which are not good receptors for inkjet inks can
produce good inkjet printed articles when they are
microfibrillated. For example, polypropylene and polylactic acid
films can be microfibrillated using a hydroentangling process
described in U.S. Pat. No. 6,110,588 which patent is incorporated
herein by reference. This process produces a microfibrillated
substrate with very fine microfibers or microflakes having a very
large surface area. When printed with solvent based piezo and water
based inkjet inks much of the ink adsorbs onto the large surface
area of the microfibers or microflakes, eliminating ink puddling
and running. Due to the microscale of the microfibers and
microflakes, the solvent in the ink remains close to the air
interface (e.g., from microfibrillated, oriented polypropylene
films) compared with PVC films, the microfibrillated substrates
feel dry to the touch after printing and do not have a significant
solvent odor, which the PVC films often have. The dried images also
have little residual odor resulting from solvent because the
solvents remain close to the surface of the microfibers resulting
in faster evaporation of the solvents from the receptor media. PVC
films that absorb large amounts of the ink solvents typically have
residual odors because evaporation of the solvents from the film is
very slow. Upon drying, the inks bond very well to the
microfibrillated structures and are difficult to abrade off,
resulting in a durable image. This is surprising because the
microfibers and microflakes are composed of materials that the ink
systems do not bond to as well when printed on the unfibrillated
film form. For example, ink solvents (including water) have a very
low rate of diffusion into films of polypropylene (PP), polyester
(PET) and polylactic acid (PLA), and ink in the printed images
pools and runs severely with solvent based inkjet inks, and beads
up and runs with water based inkjet inks. When dry, the beaded-up
areas of ink have poor adhesion to any of these materials in film
form. When these films are microfibrillated the inks are adsorbed
onto the microfibers and microflakes and do not run or puddle. Upon
drying the image is well bonded to the substrate and extremely
difficult to abrade without abrading the fibers. The dried images
also have little residual odor resulting from solvent because the
solvents are held to the surface of the microfibers resulting in
faster evaporation of the solvents from the receptor media. PVC
films, which absorb large amounts of the ink solvents typically,
have residual odors because evaporation of the solvents from the
film is very slow. The excellent adhesion of the inks to
microfibrillated substrates is believed to occur because the very
small microfibers are coated with ink binder/pigment producing a
physical interlock of the inks to the substrate; this is very
different from the chemical bonding mechanism that occurs when the
inks are printed onto a relatively smooth film.
[0019] Accordingly, the present invention is directed to a receptor
medium including an oriented film having at least one
microfibrillated surface with a depth of microfibrillation of
greater than 10 microns.
[0020] One embodiment of the present invention includes a
uniaxially oriented film with a microfibrillated surface containing
melt-processed polymer microfibers having an average effective
diameter of less than 20 microns and a transverse aspect ratio of
1.5:1 to 20:1.
[0021] Another embodiment of the present invention is directed to a
receptive medium including a biaxially oriented film containing a
mixture of a melt-processed polymer or polymer blend and a void
initiating component.
[0022] The present invention also includes a method of producing an
image which includes the step of printing a jettable material
through an inkjet printing head onto the above defined receptor
medium.
[0023] The present invention further includes an imaged graphics
film including the above defined receptor medium having an
inkjettable material on a surface of the receptor medium.
[0024] Another embodiment of the present invention includes a
multiple component receptor medium containing:
[0025] (a) a biaxially oriented film having at least one
microfibrillated surface;
[0026] (b) an adhesive layer on a major surface opposite the
microfibrillated surface;
[0027] (c) a release liner protecting the adhesive layer; and
[0028] (d) an inkjettable material, such as an ink, deposited on
the microfibrillated surface.
[0029] A particular embodiment of the present invention includes a
receptor medium and an imaged graphics film containing the receptor
medium where the receptor medium contains a biaxially oriented film
having at least one microfibrillated surface, the surface
including:
[0030] (a) polypropylene;
[0031] (b) a void initiating component comprising solid particles
and/or an immiscible polymer.
[0032] "Immiscible" refers to polymer blends with limited mutual
solubility and non-zero interfacial tension, i.e. a blend whose
free energy of mixing is greater than zero:
.DELTA.G.sub.m.congruent..DELTA.H.sub.m>0
[0033] Still another particular embodiment of the present invention
includes a multiple component receptor medium containing
[0034] (a) a biaxially oriented film having at least one
microfibrillated surface, said surface comprising:
[0035] (i) polypropylene; and
[0036] (ii) a void initiating component comprising inorganic solid
particles, copolymers of ethylene selected from the group
consisting of acid/acrylate modified ethylene vinyl acetate resin,
terpolymer of ethylene/vinyl acetate/carbon monoxide/ethylene,
poly(isobutyl)methacryla- te and combinations thereof;
[0037] (b) an adhesive layer on a major surface opposite the
microfibrillated surface;
[0038] (c) a release liner protecting the adhesive layer; and
[0039] (d) an inkjet ink deposited on the microfibrillated
surface.
[0040] Advantageously, the present invention allows printing with
solvent-based, water-based, oil based, or radiation curable inkjet
inks onto receptor media containing microfibers and/or microflakes
to provide fine-resolution images with good solid fill.
[0041] These microfibrillated materials are comprised of
microfibers or microflakes, which are physically unique in their
microscopic dimensionality. The microfibers are ribbon like in
contrast to standard melt blown microfibers, which are generally
cylindrical in shape, and the microflakes are flake-like structures
that are physically bound to the polymer film. The microflakes may
have a thickness from 1 to 20 micrometers depending on the nature
of orientation, preferably from 1 to 10 micrometers and most
preferably from 1 to 5 micrometers. The aspect ratio of the surface
of a microflake may range from 1:1 to 1:20 depending on how
balanced the orientation is. If the orientation is unbalanced
(machine direction orientation does not equal transverse direction
orientation), the microflakes have an increased dimension in the
dominant orientation direction, and when the uniaxial orientation
limit is reached, only microfibers are produced from
microfibrillation. The use of the microfibrillated polymers also
allows for the preparation of materials into fibrous substrates
that are not easily made into microfibers of this size by other
means, e.g. high molecular weight resins, incompatible blends,
highly filled systems, and the like. Due to the surface texture
comprising microfibers and microflakes, the present
microfibrillated polymeric materials allow for printing on poor
inkjet-receptive materials (e.g. low surface energy polyolefins)
without surface treatments (i.e. print receptive coatings, corona
discharge, etc.), preventing the inks from feathering and beading
up as they do on the films that have not been microfibrillated. In
addition, this surface texture helps to control dot gain. Dots
printed on the present microfibrillated materials show an immediate
finite dot gain which does not change significantly with time as is
common with most inkjet receptive materials. Thus,
microfibrillation improves resolution, by better controlling the
bleeding together of print lines.
[0042] Because of the presence of microfibers or microflakes in
their surface, the present microfibrillated materials provide a
number of advantageous properties. For example these materials
prevent the inks from running even with high solvent loading and
also minimize intercolor ink bleed. Inkjet printed inks feel dry to
the touch quickly after printing so that they may be transferred
immediately after printing without smudging and may be rolled up
without causing surface impressions or blocking of the image. They
do not retain solvent for long periods of time as PVC based films
do. Thus, they do not tend to emanate an undesirable solvent odor
when unrolled and displayed. Microfibrillated materials can also
provide a moderate degree of waterfastness to water-based inks. The
microfibrillated surfaces may be embossed after printing to provide
other properties, including special optical effects.
[0043] The degree of surface microfibrillation of an oriented
polymer may be selected, controlled, and used as a way to affect
printing quality. Thus, a printed sheet can be generated from a
single precursor film (no lamination or coating or binders
required) when only partial microfibrillation is employed. The
receptor medium has a microfibrous or microflake surface that has a
high surface area but the film itself may not be permeable or have
low permeability to solvents in the ink. Therefore, the receptor
medium of the present invention may comprise both a receptor layer
(the microfibrillated surface) and a solvent barrier layer (the
unmicrofibrillated base film) preventing the solvent in the inkjet
inks from adversely affecting any adhesives located on the
unmicrofibrillated side. This also eliminates curling problems,
which occur when the coatings dry due to swelling and de-swelling
of solvent sensitive materials. Because significant amounts of the
ink solvents are not absorbed into the material comprising the
microfibers or microflakes and do not penetrate into the base film,
there is no need for a carrier liner as is required for printing on
thin (4 mil) PVC-based graphics films which tend to absorb solvent
and curl up.
[0044] Through this microfibrillated film making process it is
possible to incorporate one or more additives that may improve
printing quality directly into the melt instead of having to
solvent coat the additive(s) onto the surface. This eliminates the
need for an extra coating step and the use of solvents which may be
environmentally unfriendly. These print quality improvement
additives tend to improve the color density of inkjet ink on both
the microfibrillated material and the unfibrillated material, but
they do not substantially enhance the image resolution on the
precursor (unfibrillated) film, which still suffers from ink
bleeding and mottling.
[0045] When microfibrillated materials are prepared from low
surface energy polymers (e.g., polyolefins), color density tends to
be low. This low color density does not appear to be due to the
lack of ink absorption into the microfibrillated materials, but
rather due to insufficient ink spreading on the surfaces of the
microfibrillated material. To improve color density, blends of one
or more polymers with print quality improvement additives selected
from the group consisting of polymers, surfactants, and mordants
may be used. These polymers and surfactants are selected for their
ability to increase surface energy of the microfibrillated material
or for their affinity for the binders in the ink to promote
spreading of the ink on the surface. The mordants are selected for
their ability to shorten drying time by complexing with the
colorant in the ink making make the inkjet printed image
smudge-free and/or water fast.
DETAILED DESCRIPTION
[0046] The present invention provides a receptor medium which
includes an oriented film having at least one microfibrillated
surface with a depth of microfibrillation of greater than 10
microns. The films may be uniaxially oriented to produce a fibrous
surface having polymeric microfibers of average effective diameter
of less than 20 microns, generally from 0.01 to 10 microns, and a
substantially rectangular cross-section, having a transverse aspect
ratio (width to thickness) of from 1.5:1 to 20:1. Such microfiber
uniaxially oriented films and methods of making them, including
microfibrillation, are described in U.S. Pat. No. 6,110,588, which
patent is incorporated herein by reference. Alternatively, the
films may be biaxially oriented to produce a microfibrous surface
of microflakes that are thin in cross-section, in comparison to the
width and lengths, and irregular in shape. Such microflake
biaxially oriented films and methods of making them, including
microfibrillation, are described in U.S. Pat. No. 6,331,433, which
patent is incorporated herein by reference. The microflakes are
flake-like structures that are physically bound to the polymer
film. The microflakes may have a thickness from 1 to 20 micrometers
depending on the nature of orientation, preferably from 1 to 10
micrometers and most preferably from 1 to 5 micrometers. The aspect
ratio of the surface of a microflake may range from 1:1 to 1:20
depending on how balanced the orientation is. If the orientation is
unbalanced (machine direction orientation does not equal transverse
direction orientation), the microflakes have an increased dimension
in the dominant orientation direction, and when the uniaxial
orientation limit is reached, only microfibers are produced from
microfibrillation. Both the microfibers and the microflakes impart
a large surface area to the film, which in combination with a high
density of microfibers or microflakes, can minimize ink wicking or
bleeding and provide high resolution in inkjet images.
[0047] Polymers useful in undergoing the microfibrillation process
are single polymers or blends. A first polymer component or single
polymer component includes any melt-processible crystalline,
semi-crystalline or crystallizable polymer or copolymer, including
block, grafted, and random copolymers. Semi-crystalline polymers
consist of a mixture of amorphous regions and crystalline regions.
The crystalline regions are more ordered, and segments of the
chains actually pack in crystalline lattices. Some crystalline
regions may be more ordered than others. If crystalline regions are
heated above the melting temperature of the polymer, the molecules
become less ordered or more random. If cooled rapidly, this less
ordered feature is "frozen" in place and the resulting polymer is
said to be amorphous. If cooled slowly, these molecules can repack
to form crystalline regions and the polymer is said to be
semicrystalline. Some polymers remain amorphous and show no
tendency to crystallize. Some polymers can be made semicrystalline
by heat treatments, stretching or orienting and by solvent
inducement, and these processes can control the degree of true
crystallinity.
[0048] Semicrystalline polymers useful in the present invention
include, but are not limited to, polyethylene, polypropylene,
copolymers of polypropylene and polyethylene, poly(alpha)olefins,
polyoxymethylene, poly(vinylidine fluoride), poly(methyl pentene),
poly(ethylene-chlorotrif- luoroethylene), poly(vinyl fluoride),
poly(vinyl alcohol), poly(ethylene oxide), poly(ethylene
terephthalate)(PET), poly(butylene terephthalate)(PBT),
polylactide, nylon 6, nylon 66, nylon 610, nylon 612, polybutene,
syndiotactic polystyrene and thermotropic liquid crystal polymers.
Examples of suitable thermotropic liquid crystal polymers include
aromatic polyesters, which exhibit liquid crystal properties when
melted, and which are synthesized from aromatic diols, aromatic
carboxylic acids, hydroxycarboxylic acids, and other like monomers.
Typical examples include a first type consisting of
parahydroxybenzoic acid (PHB), terephthalic acid, and biphenol; a
second type consisting of PHB and 2,6-hydroxynaphthoic acid; and a
third type consisting of PHB, terephthalic acid, and ethylene
glycol. Preferred polymers are polyolefins such as polypropylene
and polyethylene and polyethylene/polypropylene copolymers, that
are readily available at low cost and can provide highly desirable
properties in the fibrillated articles such as high modulus and
high tensile strength.
[0049] The semicrystalline polymer component may further comprise,
as a blend, a second polymer to impart desired properties to the
microfibrillated film of the invention. The second polymer of such
blends may be semicrystalline or amorphous and is generally present
in less than 40 weight percent, based on the weight of the
semicrystalline polymer component. For example, small amounts of
polyethylene may be added to polypropylene, when used as the
semicrystalline polymer component, to improve the softness and
drapability of the microfibrillated film. Other polymers may be
added as print quality improvement additives, for example, to
enhance print color density. Still other polymers may be added to
improve film stiffness, crack resistance, Elmendorff tear strength,
elongation, tensile strength and impact strength, as is known in
the art. Examples of particularly useful polymer blends include
polypropylene with poly(ethylene terephthalate) (PET),
poly(butylene terephthalate) (PBT), polyvinylpyrrolidone and an
ionomer copolymer of ethylene and (meth)acrylic acid, ethylene
vinyl acetate, polystyrene/polyisoprene copolymers, acid modified
ethylene vinyl acetate, acid/acrylate modified ethylene vinyl
acetate, polyether-ester elastomers, terpolymers of ethylene/vinyl
acetate/carbon monoxide/ethylene without and with poly(isobutyl
methacrylate), and thermoplastic polyurethanes. Other secondary
polymers may include, for example, polycarbonates;
polymethylpentene; nylons; acrylate and methacrylate homopolymers
and copolymers; polystyrenes; vinylchloride/vinyl acetate
copolymers; vinyl chloride/vinyl acetate/vinyl alcohol terpolymers;
polyethyleneimines; acrylate and maleic anhydride modified ethylene
vinyl acetate copolymers; copolymers of ethylene and methyl
acrylate; ethylene/octene copolymers; blends of
polyvinylpyrrolidone with polyvinylalcohol: copolymers or
terpolymer of N-vinyl-2-pyrrolidinone with acrylic acid,
dimethylaminoethyl acrylate, trimethoxysilylethylmethacrylate,
and/or poly(ethylene oxide) acrylate; poly(cyclic olefins); and
rubbers. When a secondary polymer is used as a print quality
improvement additive, it may be combined with the microfibrillated
film, not only by melt processing, but also by coating the
microfibrillated film with a solution or dispersion of the
additive.
[0050] The void-initiating component is chosen so as to be
immiscible in the semicrystalline polymer component. It may be an
organic or an inorganic solid particulate component having an
average particle size of from about 0.1 to 10.0 microns and may be
any shape including amorphous, needle-like, spindle, plate,
diamond, cube, and sphere shapes. Inorganic solids useful as void
initiating components include solid or hollow glass, ceramic or
metal particles, microspheres or beads; zeolite particles;
inorganic compounds including, but not limited to metal oxides such
as titanium dioxide, alumina and silicon dioxide; metal, alkali- or
alkaline earth carbonates or silicates, metasilicates, sulfates;
kaolin, talc, carbon black and the like. Typically useful is
calcium carbonate or wollastonite, i.e. calcium metasilicate.
Inorganic void initiating components are chosen so as to have
little surface interaction, due to either chemical nature or
physical shapes, when dispersed in the semicrystalline polymer
component. In general the inorganic void initiating components
should not be chemically reactive with the semicrystalline polymer
component, including Lewis acid/base interactions, and have minimal
van der Waals interactions.
[0051] The void initiating component may be a thermoplastic
polymer, including semicrystalline polymers and amorphous polymers,
to provide a blend immiscible with the semicrystalline polymer
component. An immiscible blend shows multiple amorphous phases as
determined, for example, by the presence of multiple amorphous
glass transition temperatures. As used herein, "immiscibility"
refers to polymer blends with limited solubility and non-zero
interfacial tension, i.e. a blend whose free energy of mixing is
greater than zero:
.DELTA.G.sub.m.congruent.H.sub.m>0
[0052] Miscibility of polymers is determined by both thermodynamic
and kinetic considerations. Common miscibility predictors for
non-polar polymers are differences in solubility parameters or
Flory-Huggins interaction parameters. For polymers with
non-specific interactions, such a polyolefins, the Flory-Huggins
interaction parameter can be calculated by multiplying the square
of the solubility parameter difference with the factor (V/RT),
where V is the molar volume of the amorphous phase of the repeated
unit, R is the gas constant, and T is the absolute temperature. As
a result, the Flory-Huggins interaction parameter between two
non-polar polymers is always a positive number indicating that the
two polymers do not mix spontaneousely and the blend is considered
"immiscible".
[0053] Polymers useful as the void-initiating component include the
above described semicrystalline polymers, as well as amorphous
polymers, selected so as to form discrete phases upon cooling from
the melt. Useful void-initiating polymers include, but are not
limited to, polyesters, vinyl resins, copolymers of ethylene,
polystyrene resins and copolymers thereof, polycarbonates,
polyisobutylene, acrylates and methacrylate homopolymers and
copolymers thereof, cyclic polyolefins, maleated polypropylene
block copolymers, rubbers, sulfonated poly(ethylene terephthalate),
polyvinylpyrrolidone and vinylpyrrolidinone copolymers, epoxies,
thermoplastic polyurethanes, and combinations thereof. Examples of
polystyrene copolymers include poly(styrene-co-acrylonitrile),
poly(styrene-co-maleic anhydride), and
poly(acrylonitrile-butadiene-styre- ne). Examples of useful
acrylates and methacrylates include polymers of butyl acrylate,
ethyl acrylate, isopropyl acrylate, methylacrylate, benzyl
methacrylate, butyl methacrylate, cyclohexyl methacrylate, ethyl
methacrylate, hexyl methacrylate, isobutyl methacrylate, isopropyl
methacrylate, methyl methacrylate, phenyl methacrylate and propyl
methacrylate. Examples of useful methacrylate copolymers include
copolymers of methyl methacrylate with butyl methacrylate, ethyl
methacrylate, isobutyl methacrylate, isobornyl methacrylate, and
lauryl methacrylate, and butyl methacrylate with isobutyl
methacrylate. Examples of cyclic polyolefins include polynorbornene
and copolymers thereof. Examples of vinyl resins include poly(vinyl
chloride), poly(vinyl acetate), and poly(vinyl alcohol). Examples
of ethylene copolymers include acid modified ethylene vinyl
acetate, metal ion neutralized copolymers of ethylene and
methacrylic or acrylic acid, maleic anhydride grafted polyethylene,
acid modified ethylene/acrylate/carbon monoxide terpolymers,
ethylene/n-butyl acrylate/carbon monoxide terpolymer,
ethylene/glycidyl methacrylate/carbon monoxide terpolymer, ethylene
acrylic elastomers, ethylene/vinyl acetate/carbon monoxide
terpolymer, and copolymers of ethylene and butyl-, ethyl-, and
methyl acrylate. Typically useful are poly(ethylene terephthalate)
or poly(butylene terephthalate), copolymers of methyl methacrylate
with butyl acrylate, butyl methacrylate, isobutyl methacrylate or
isobornyl methacrylate, copolymers of isobutylmethacrylate and
butyl methacrylate; butyl methacrylate resins, or copolymers of
ethylene, such as acid/acrylate modified ethylene vinyl acetate
resin, terpolymer of ethylene/vinyl acetate/carbon
monoxide/ethylene, and combinations thereof. Preferred void
initiating components include a mixture of an inorganic solid
particulate component and a polymer component as defined above.
[0054] When using an immiscible polymer blend, the relative amounts
of the semicrystalline polymer component and void initiating
polymer component can be chosen so the first polymer forms a
continuous phase and the second polymer forms a discontinuous
phase, or that the second polymer forms a continuous phase and the
first polymer forms a discontinuous phase, or each polymer forms a
continuous phase; as in an interpenetrating polymer network. The
relative amounts of each polymer can vary widely, from 99:1 to 1:99
weight ratio. Preferably, the semicrystalline polymer component
forms the continuous phase while the void initiating component
forms a discontinuous, or discrete phase, dispersed within the
continuous phase of the first polymer. In such constructions, the
amount of void initiating component will affect final film
properties. In general, as the amount of the void initiating
component increases, the amount of voiding in the final film also
increases. As a result, properties that are affected by the amount
of voiding in the film, such as mechanical properties, density,
light transmission, etc., will depend upon the amount of added void
initiating component. When the void initiating component is a
polymer, as the amount of void initiating polymer in the blend is
increased, a composition range will be reached at which the void
initiating polymer can no longer be easily identified as the
dispersed, or discrete, phase. Further increase in the amount of
void initiating polymer in the blend will result in a phase
inversion wherein the void initiating polymer becomes the
continuous phase.
[0055] Preferably, whether the void initiating component is
organic, inorganic or both, the amount of the void initiating
component in the composition is from 1% by weight to 65% by weight,
more preferably from 20% by weight to 50% by weight, most
preferably from 30% by weight to 45% by weight. In these
composition ranges, the first semicrystalline polymer forms a
continuous phase, while the void initiating component forms the
discrete, discontinuous phase.
[0056] Additionally, the selected void initiating component must be
immiscible with the semicrystalline polymer component selected. In
this context, immiscibility means that the discrete phase does not
dissolve into the continuous phase in a substantial fashion, i.e.,
the discrete phase must form separate, identifiable domains within
the matrix provided by the continuous phase.
[0057] The molecular weight of each polymer should be chosen so
that the polymer is melt processible under the processing
conditions. For polypropylene and polyethylene, for example, the
molecular weight may be from about 5000 to 500,000 and is
preferably from about 100,000 to 300,000.
[0058] In order to obtain the maximum physical properties and
render the polymer film amenable to microfibrillation, the polymer
chains need to be oriented along at least one major axis (uniaxial)
in one or more stages, and may further be oriented along two major
axes (biaxial) either simultaneously or sequentially. The degree of
molecular orientation is generally defined by the draw ratio, that
is, the ratio of the final length or width to the original length
or width, respectively. This orientation may be effected by a
combination of techniques in the present invention, including the
steps of calendering, length orienting, and tentering.
[0059] Processes for uniaxially orienting a film and
microfibrillating the film are described in U.S. Pat. No.
6,110,588, which patent is incorporated herein by reference.
Processes for biaxially orienting films and microfibrillating the
films to prepare microfibers and microfibrous flakes (microflakes)
are described in U.S. Pat. No. 6,331,433, which patent is also
incorporated herein by reference.
[0060] Generally, greater void initiating content enhances the
subsequent microfibrillation, and subsequently for uniaxially
oriented films, the greater the yield of microfibers and for
biaxially oriented films, the greater the yield of microflakes.
Preferably, when preparing an article having at least one
microfibrillated surface, the polymer film should have a void
content in excess of 5%, more preferably in excess of 10%, most
preferably in excess of 30%, as measured by density, i.e., the
ratio of the density of the voided film with that of the starting
film. The degree of voiding or void content in the oriented films
is strongly dependent on the temperature and degree of orientation
achieved during processing. To achieve higher void contents, it is
preferred to keep the temperature just high enough to allow flow of
the polymer(s) and to orient the film to the greatest extent
possible without breaking the film.
[0061] In practice, the films first may be subjected to one or more
processing steps to impart the desired degree of crystallinity to
the semicrystalline polymer component, and further processed to
impart the voids, or the voids may be imparted coincident with the
process step(s), which impart crystallinity. Thus the same
calendering or stretching steps that orient the polymer film and
enhance the crystallinity (and orientation) of the polymer may
concurrently impart voids.
[0062] In the present process the degree of microfibrillation can
be controlled to provide a low degree to a high degree of
microfibrillation, whether from a uni- or biaxially oriented film.
In either microfibrillation process most of the microfibers or
microflakes stay attached to the web due to incomplete release from
the polymer matrix. Advantageously the microfibrillated article,
having microfibers or microflakes secured to a web, provides a
convenient and safe means of handling, storing and transporting the
microfibrillated article without contamination due to nonbonded
microfibers or microflakes. For many printing applications it is
desirable to retain the microfibers or microflakes secured to the
web.
[0063] The receptor medium of the present invention may also have
an adhesive layer on the major surface of the sheet opposite the
microfibrillated surface that is also optionally but preferably
protected by a release liner. After imaging, the receptor medium
can be adhered to a horizontal or vertical, interior or exterior
surface to warn, educate, entertain, advertise, etc.
[0064] The choice of adhesive and release liner depends on usage
desired for the image graphic.
[0065] Pressure-sensitive adhesives can be any conventional
pressure-sensitive adhesive that adheres to both the polymer sheet
and to the surface of the item upon which the inkjet receptor
medium having the permanent, precise image is destined to be
placed. Pressure-sensitive adhesives are generally described in
Satas, Ed., Handbook of Pressure Sensitive Adhesives, 2nd Ed. (Von
Nostrand Reinhold 1989). Pressure-sensitive adhesives are
commercially available from a number of sources. Particularly
preferred are acrylate pressure-sensitive adhesives commercially
available from Minnesota Mining and Manufacturing Company and
generally described in U.S. Pat. Nos. 5,141,790; 4,605,592;
5,045,386; and 5,229,207; and EPO Patent Publication No. EP 0 570
515 B1 (Steelman et al.).
[0066] Release liners are also well known and commercially
available from a number of sources. Nonlimiting examples of release
liners include silicone coated craft paper, silicone coated
polyethylene coated paper, silicone coated or non-coated polymeric
materials such as polyethylene or polypropylene, as well as the
aforementioned base materials coated with polymeric release agents
such as silicone urea, urethanes, and long chain alkyl acrylates,
such as defined in U.S. Pat. Nos. 5,957,724; 4,567,073; 4,313,988;
3,997,702; 4,614,667; 5,202,190; and 5,290,615; and those liners
commercially available as Polysilk brand liners from Rexam Release
of Oakbrook, Ill., and EXHERE brand liners from P. H. Glatfelter
Company of Spring Grove, Pa.
[0067] The receptor media of the present invention have utility for
the production of image graphics using inkjet printers. The present
receptor media unexpectedly solve common inkjet image quality
problems as feathering, banding and mud cracking (mud cracking
where pigmented, binderless water based inks are used) in inkjet
printing systems and also provide an adsorptive surface for the
inks to prevent running and help bind the inks to the substrate.
Because of the high surface area of the microfibrillated
structures, the solvents of the ink are able to evaporate quickly,
are not absorbed into the bulk of the fibers, and there is no
residual odor from retained solvents during use as is common with
current PVC-based products. Another advantage of the receptor media
of the present invention is the usefulness of the microfibrillated
surface with organic solvent-based, oil-based, water-based, or
radiation polymerizable inks. The inks used on the receptor medium
can further include either dye- or pigment-based colorants.
[0068] Inkjet receptor media of the present invention can be
employed in any environment where inkjet images are desired to be
precise, stable, rapid drying, handled immediately after printing,
and abrasion resistant.
[0069] Inkjet receptor media of the present invention can accept a
variety of inkjet ink formulations to produce rapid drying and
precise inkjet images. The topography of the microfibrillated
surface of the inkjet receptor medium can be varied for optimum
results, depending on several factors, such as: ink droplet volume;
ink liquid carrier composition; ink type (pigment or blend of
pigment and aqueous or non-aqueous dye); and manufacturing
technique (machine speed, resolution, roller configuration);
etc.
[0070] The formation of precise inkjet images is provided by a
variety of commercially available printers. Nonlimiting examples
include thermal inkjet printers such as Deskjet brand, Paintjet
brand, Deskwriter brand, DesignJet brand, and other printers
commercially available from Hewlett-Packard Corporation of Palo
Alto, Calif. Also included are piezo type inkjet printers such as
those from Seiko-Epson, Raster Graphics, VUTEk, Scitex, Idanit, and
Xerox, spray jet printers and continuous inkjet printers. Any of
these commercially available printers introduces the ink in a jet
spray of a specific image into the medium of the present invention.
Apparent drying time is much more rapid under the present invention
than if the imaging layer were to be applied to a similar
non-microfibrillated media.
[0071] The media of the present invention can be used with a
variety of inkjet inks obtainable from a variety of commercial
sources. It should be understood that each of these inks has a
different formulation, even for different colors within the same
ink family. Nonlimiting sources include Minnesota Mining and
Manufacturing Company, Encad Corporation, Hewlett-Packard
Corporation, DuPont, Inkware, Prizm, NuKote, and the like. These
inks are preferably designed to work with the inkjet printers
described immediately above and in the background section above,
although the specifications of the printers and the inks will have
to be reviewed for appropriate drop volumes and resolution in order
to further refine the usefulness of the present invention.
[0072] Media of the present invention can also be employed with
other jettable materials; that is, those materials capable of
passing through an inkjet printing head. Nonlimiting examples of
jettable materials include adhesives, particulate dispersions,
waxes, electrically, thermally, or magnetically modifiable
materials, biological fluids, chemical reagents, and combinations
thereof.
[0073] The media of the present invention may contain, as desired,
other print quality improvement additive materials, including
mordants and surfactants, to improve printing or other additives to
protect the media. These materials may be blended with the above
defined polymers and processed to form microfibrillated materials
as described above, or coated as a solution or dispersion onto the
microfibrillated materials.
[0074] Thus, for example, an inkjet receptor medium of the present
invention may contain mordants which can act as drying agents for
dye-containing inks and pigment management agents for pigmented
inks. Drying agents include an aromatic or aliphatic acid having
sulfonic, carboxylic, phenolic, hydroxyl functional groups or a
mixture of these functional groups. The drying agent, when combined
with a multivalent inorganic salt and a surfactant, is capable of
drying the medium to obtain a smudge-free rapidly dried image onto
and in the medium when the image is printed.
[0075] Typical salts are alkali metal salts of aromatic acids such
as, for example, sulfosalicylic acid, disulfosalicylic acid,
sulfophthalic acid, sulfoisophthalic acid, sulfoterephthalic acid,
disulfophenyldicarboxylic acid, sulfophenolic acid, hydroquinone
sulfonic acid, hydroquinone disulfonic acid, sulfocarboxyphenolic
acid, hydroxy-phthalic acid and combinations thereof.
[0076] Pigment management agents may also include multivalent metal
salts which destabilize dispersants surrounding pigment particles
and are not soluble in water after complexing with the dispersing
aid that surrounds the pigment particles to provide a water fast
image. Typical multivalent cations employed are those of Group IIA
of the periodic table with counter ions such as sulfate, nitrate,
bisulfate, chloride, aromatic carboxylates, and sulfocarboxylates.
Particularly useful are aluminum sulfate and aluminum
sulfophthalate.
[0077] A further additive for the receptor medium of the present
invention is an organometallic salt of a multivalent metal cation
and an organic acid anion. The metallic salt simultaneously
releases the multivalent metal cation and the organic acid anion
for both pigment management and ink drying. The metallic salt
includes a multivalent metal derivative of an aromatic carboxylic,
sulfocarboxylic, sulfophenolic acid, or combination thereof. The
aromatic moiety can be a simple aromatic, a condensed aromatic, a
heterocyclic aromatic or a combination thereof. The multivalent
metal ion can be derived from Group IIA to VIA and Group IB to
VIIIB of the periodic table. Typical metal ions include, but are
not limited to, Al, Mg, Zn, Fe, Bi, Ga, Sr, Ca, Ti and Zr.
[0078] Surfactants can also be used as a print quality improvement
additive, alone or in combination with one or more polymer or
mordant additives. For example, the above salts may be combined as
mentioned above with a surfactant. Surfactants may also, for
example, be used to improve inkjet ink wetting on the
microfibrillated material, and include non-ionic, anionic,
cationic, zwitterionic or combinations thereof. Non-ionic
surfactants may be fluorocarbon, hydrocarbon, or silicone based.
Preferred surfactants increase the hydrophilicity of the
microfibrillated materials and are particularly useful when
water-based inkjet inks are employed. Examples of useful
surfactants are described in U.S. Ser. No. 09/314,034, filed on May
18, 1999, and entitled "Ink-Jet Printable Macroporous
Material".
[0079] In addition to the above, the receptor medium of the present
invention may also contain free-radical scavengers, heat
stabilizers, ultraviolet light stabilizers and inorganic
fillers.
[0080] Free-radical scavengers can be present in an amount from
about 0.05 to about 1.0 weight percent of the total
microfibrillated material composition. Typically, scavengers
include hindered amine light stabilizers (HALS), hydroxylamines,
sterically hindered phenols, and the like. HALS compounds are
commercially available from Ciba Specialty Chemicals under the
trade designation "Tinuvin 292" and Cytec Industries under the
trade designation "Cyasorb UV3581".
[0081] Heat stabilizers may be used to protect the resulting image
graphic against the effects of heat. These are commercially
available from Witco Corp., Greenwich, Conn. under the trade
designation "Mark V 1923" and Ferro Corp., Polymer Additives Div.,
Walton Hills, Ohio under the trade designation "Synpron 1163",
"Ferro 1237" and "Ferro 1720".
[0082] Ultraviolet light stabilizers may be present in small
amounts ranging from about 0.1 to about 5 weight percent of the
total microfibrillated material. Benzophenone type UV-absorbers are
commercially available from BASF Corp., Parsippany, N.J. under the
trade designation "Uvinol 400"; Cytec Industries, West Patterson,
N.J. under the trade designation "Cyasorb UV1164" and Ciba
Specialty Chemicals, Tarrytown, N.Y. under the trade designations
"Tinuvin 900", "Tinuvin 123" and "Tinuvin 1130".
[0083] Inorganic fillers may be used in the microfibrillated
material as a preferred additive to impart one or more of desirable
properties such as improved solvent absorption, improved dot gain
and color density, and improved abrasion resistance. Typical
fillers include silicates, e.g. amorphous silica, clay particles,
aluminates, e.g. aluminum silicate, feldspar, talc, calcium
carbonate, titanium dioxide, and the like. The particle size of
these fillers is preferably less than one micron and may typically
range from 0.5 to 0.2 microns.
[0084] The following examples further disclose embodiments of the
invention:
EXAMPLES
[0085] Printing Methods
[0086] Two different methods for inkjet printing were employed for
printing evaluations: piezoelectric inkjet printing using
solvent-based inks and thermal inkjet printing using water-based
inks.
[0087] A. Piezoelectric inkjet printing: Unless specified
otherwise, a Xaar Jet XJ128-100 piezoelectric printhead (available
from Xaar Ltd., Cambridge, England) on an x-y translational stage
at 317 by 295 dpi was employed to print test patterns consisting of
filled squares and circles as well as lines printed at 100%-400%
coverage which were used to evaluate image quality. The inks used
were "Scotchcal.TM. 3700" series solvent-based inks (available from
3M, St. Paul, Minn.), specifically 3791 magenta, 3792 yellow, 3795
black, 3796 cyan.
[0088] B. Thermal inkjet printing: Unless specified otherwise, a
Deskjet 950C printer (available from Hewlett-Packard Company, Palo
Alto, Calif.) at 300.times.600 dpi was used to print test patterns
consisting of filled characters of various sizes printed at 100%
coverage which were used to evaluate image quality. A c6578a color
ink cartridge and a 51645A black ink cartridge (both available from
Hewlett-Packard Company, Palo Alto, Calif.) were used.
Test Methods
Test Method 1
Draw Ratio Measurements
[0089] 1-A: Uniaxially-oriented films: The draw ratios of
calendered and length oriented films were calculated by dividing
the roll output speed of the calender/length orienter by the input
speed of the cast web.
[0090] 1-B: Biaxially-oriented films: The machine direction (MD)
and transverse direction (TD) draw ratios of biaxially oriented
films were determined by inscribing equally spaced lines
perpendicularly to both of the stretching directions and by
calculating the corresponding ratio of the final line spacing to
the initial spacing.
Test Method 2
Density Measurement and Void Content Determination
[0091] Densities of cast films and films after calendering and
orienting were measure at 23.degree. C. in deionized water
according to the method of ASTM D792-86. Each film sample was
weighed on a Mettler AG245 high precision balance (Mettler-Toledo,
Inc., Highstown, N.J.) and placed underwater. The mass of the water
displaced was measured using the density measurement fixture. The
volume of water displaced by the sample was thereby determined and,
in combination with the sample weight, used to calculate the sample
density. The void content was then calculated as follows:
Calculated Void content={1-(final density/initial
density)}.times.100
[0092] where the initial density is the density of the cast film
before orientation, and the final density is the density of the
oriented film.
Test Method 3
Image Quality Evaluation
[0093] Image quality was evaluated using the printing test patterns
described above by observing resolution, ink feathering,
inter-color bleed, color uniformity, edge sharpness, and overall
appearance of the test pattern. Solid block color density (CD) was
measured using a Gretag SPM-55 densitometer, available from
Gretag-MacBeth AG, Regensdorf, Switzerland, where D.sub.K, D.sub.M,
D.sub.C, D.sub.Y are the solid block color densities of black,
magenta, cyan, and yellow. No background subtraction was used, and
the reported values were the average of three measurements. An
increase in CD correlated to an increase or improvement in solid
ink fill.
EXAMPLES
Comparative Example C1
[0094] This comparative example is a demonstration of solvent-based
inkjet printing on a uniaxially oriented polypropylene film.
[0095] Sample Preparation:
[0096] A polypropylene film was prepared by extruding polypropylene
homopolymer (Fina 3376X, available from Atofina Inc., Houston,
Tex.) in a single screw extruder with a temperature of 260.degree.
C. at the end of the extruder, in the neck tube and die. The
extruder was equipped with a 152 cm wide, single layer die having
an orifice gapped to a nominal 2.54 mm. A film having a thickness
of 1.78 mm was prepared using a three-roll stack casting station.
In the three-roll stack, the chrome-coated stainless steel rolls
were set to 88.degree. C. The polymer melt exiting the extruder die
entered the three-roll stack between the bottom and middle rolls,
and after passing between the bottom and middle rolls, traveled
over the middle roll into the nip formed by the middle and top
rolls. After passing over the top roll, the resulting cast film
exited the three-roll stack and was slit into two 61 cm wide films.
The cast film had a density of 0.9 g/cm.sup.3 as determined by Test
Method 2.
[0097] The cast film was calendered and length oriented as follows.
The cast film was fed from an unwind station at a rate of 1.22
m/min, through two 145.degree. C. preheat rolls and into the
compressive nip of an "S-wrap" calender (rolls 1 and 2). Rolls 1
and 2 each had surface speeds of 1.31 m/min and 8.69 m/min,
respectively, a temperature of 130.degree. C. and 120.degree. C.,
respectively, and a gap between the rolls of approximately 1 mm.
The film exiting rolls 1 and 2 was further oriented as it passed
over heated roll 3 and then heated roll 4 in an "S" configuration.
Roll 3 had a surface speed of 17.89 m/min and a temperature of
140.degree. C. Roll 4 had a surface speed of 17.95 m/min and a
temperature of 140.degree. C. The resulting film passed around a
portion of roll 5, which was unheated and simply used to cool the
film. The resulting calendered/length oriented film was wound onto
a core under tension. The film was oriented to a draw ratio of
14.7:1 as determined by Test Method 1-A. The oriented film had a
thickness of 165 micrometers and a width of 333 mm.
[0098] Print Image Quality:
[0099] The oriented film sample was printed upon using the Xaar
piezoelectric inkjet printer as described above. Evaluation of the
test pattern indicated that a series of thin lines printed at 100%
and having widths of 0.25 mm and spaced 0.25 mm apart were capable
of being resolved when printed upon the film. However, the low
affinity of the ink with the smooth polypropylene surface caused
the ink to coalesce and run when printing solid squares and
circles, and there was also a high degree of intercolor bleed,
resulting in very poor image quality. Although the ink coverage was
non-uniform, it was possible to measure CDs in certain regions:
D.sub.K=1.37, D.sub.M=0.94, D.sub.C=0.95, D.sub.Y=0.95 as described
in Test Method 3. The surface remained extremely wet after
printing, and when it eventually dried the ink could be easily
scratched off the surface, especially in regions where the ink had
coalesced to form a thicker layer.
Example 1
[0100] This example is a demonstration of solvent-based inkjet
printing on a fully microfibrillated, uniaxially oriented
polypropylene substrate.
[0101] Sample Preparation:
[0102] A polypropylene film was prepared by extruding polypropylene
homopolymer (Fina 3374X, available from Atofina Inc., Houston,
Tex.) in a single screw extruder with a temperature of 232.degree.
C. at the end of the extruder, in the neck tube, and die. The
extruder was equipped with a 25.4 cm wide, single layer die having
an orifice gapped to a nominal 1.27 mm. A film having a thickness
of 1.45 mm and a width of 231 mm was extruded onto a chrome-coated
stainless steel roll that was set to 118.degree. C. The resulting
cast film had a density of 0.9 gram/cm.sup.3 as determined by Test
Method 2.
[0103] The cast film was calendered and length oriented as follows.
The cast film was fed from an unwind station through a series of
idler rolls and into the compressive nip of a calender (rolls 1 and
2). Rolls 1 and 2 had temperatures of 100.degree. C. and
140.degree. C., respectively. The film exiting rolls 1 and 2 was
oriented as it passed over heated roll 3 and then heated roll 4 in
an "S" configuration. Rolls 3 and 4 both had a temperature of
140.degree. C. The resulting film passed around a portion of roll
5, which was unheated and simply used to cool the film. The
resulting calendered/length oriented film was wound onto a core
under tension. The film was oriented to a draw ratio of 17.8:1 as
determined by Test Method 1-A.
[0104] The oriented film was then microfibrillated on both major
surfaces using a hydroentangler (Hydrolace 350 System.TM.,
available from CEL International LTD., Coventry, England) operated
at a system water pressure of 20 MPa and equipped with 7 waterjet
heads. The first jet head was configured with a jet strip having
16.5 orifices/cm, with each orifice dimensioned at 110 .mu.m. The
second through forth jet heads were configured with jet strips
having 11 orifices/cm, with each orifice dimensioned at 150 .mu.m.
The fifth jet head was configured with a jet strip having 16.5
orifices/cm, with each orifice dimensioned at 110 .mu.m. The sixth
and seventh jet heads were configured with jet strips having 14
orifices/cm, with each orifice dimensioned at 130 .mu.m. The
oriented film was conveyed perpendicularly to the jet heads (4
above the film and 3 below) at a speed of 2 m/min.
[0105] Image Quality:
[0106] The resulting microfibrillated material was printed upon
using the Xaar piezoelectric inkjet printer as described above.
Evaluation of the test pattern indicated that a series of lines
printed at 100% and having widths of 0.35 mm and spaced 0.35 mm
apart were resolved on this substrate. The microfibrillated surface
kept the amount of feathering and intercolor bleed to a minimum;
for only at ink lay down of 300% or more was there a small but
detectible indication of ink feathering. The ink coverage on the
surface was quite uniform with no mottling or coalescing. The CDs
were measured to be D.sub.K=0.61, D.sub.M=0.54, D.sub.C=0.48,
D.sub.Y=0.54 as described in Test Method 3. It was observed that
the surface of the substrate felt dry to the touch immediately
after printing, and the colors are held fast to the surface. Thus,
although this specimen had somewhat lower thin line resolution and
CD than C1, the overall imaging quality was far superior because
there was no bleeding or mottling and the ink dried quickly and
uniformly and held fast to the polypropylene surface. These
observations indicate how microfibrillation of the oriented
polypropylene film significantly improved the inkjet printing
performance.
Comparative Example C2
[0107] This comparative example is a demonstration of water-based
inkjet printing on a uniaxially oriented polypropylene film.
[0108] Sample Preparation:
[0109] Polypropylene film was prepared by extruding polypropylene
homopolymer (Fina 3374X, available from Fina Inc., Dallas, Tex.)
with 0.01% of a gamma-quinacridone (Hostaperm Red E3B pigment,
available from Clariant GmbH, Frankfurt, Germany) beta-nucleating
agent in a single screw extruder with a temperature of 232.degree.
C. at the end of the extruder, in the neck tube and die. The
extruder was equipped with a barrier screw having a mixing tip and
with a 12.7 cm wide, single layer die having an orifice gapped to a
nominal 1.27 mm. A film having a thickness of 1.68 mm and a width
of 124 mm was prepared using a three-roll stack casting station. In
the three-roll stack, the bottom chrome-coated stainless steel roll
was set to 99.degree. C., the middle chrome-coated stainless steel
roll was set to 99.degree. C., and the top silicon rubber roll was
cooled with 7.degree. C. water. The polymer melt exiting the
extruder die entered the three-roll stack between the bottom and
middle rolls, and after passing between the bottom and middle
rolls, traveled over the middle roll into the nip formed by the
middle and top rolls. After passing over the top roll, the
resulting cast film exited the three-roll stack. During film
preparation, the silicon rubber roll heated up to near the
temperature of the middle roll. The cast film had a density of 0.9
gram/cm.sup.3 as determined by Test Method 2.
[0110] The cast film was calendered and length oriented as follows.
The cast film was fed from an unwind station into the compressive
nip of a calender (rolls 1 and 2). Rolls 1 and 2 each had a surface
speed of 1.2 m/min, a temperature of 149.degree. C., and a gap
between the rolls set to approximately 0.15 mm. The film exiting
rolls 1 and 2 was further oriented as it passed through a nipped
set of unheated rolls (rolls 3 and 4). Rolls 3 and 4 had a surface
speed of 5.03 m/min. The resulting calendered/length oriented film
was wound onto a core under tension. The film was oriented to a
draw ratio of 22:1 as determined by Test Method 1-A. The oriented
film had a thickness of 142 micrometers, a width of 81 mm, and a
density of 0.73 gram/cm.sup.3. The film was calculated to contain
18.5% voids as determined by Test Method 2.
[0111] Image Quality:
[0112] The oriented film was printed upon using the HP Deskjet 950C
inkjet printer as described above. The colored inks tended to be
very mottled due to poor spreading of the water on the
polypropylene surface. The spreading of the black ink was even
worse, causing it to coalesce into small droplets on the
polypropylene surface. In addition, there was significant
feathering and inter-color bleed. The ink remained wet to the touch
even after 1 hour of printing, and was easily smeared even when
completely dry.
Example 2
[0113] This example is a demonstration of water-based inkjet
printing on the microfibrillated surface of a uniaxially oriented
polypropylene film.
[0114] Sample Preparation:
[0115] A film was cast and oriented in a manner identical to
Comparative Example C2 but microfibrillated on only one major
surface (i.e. not completely through) using the hydroentangler
described in Example 1 operated at a system water pressure of 10
MPa and using only 3 of the 7 water jet heads. The second and third
jet heads were configured with jet strips having 20 orifices/cm,
with each orifice dimensioned at 90 .mu.m. The fourth jet head was
configured with a jet strip having 20 orifices/cm, with each
orifice dimensioned at 110 .mu.m. The oriented film was conveyed
perpendicularly to the jet heads (3 above the film) at a speed of
1.5 m/min. This process was repeated 4 times.
[0116] Image Quality:
[0117] The resulting microfibrillated material was printed upon
using the HP Deskjet 950C inkjet printer as described above. In
contrast to the non-fibrillated film of Comparative Example C2,
both the colored and black inks uniformly covered the surface with
minimal inter-color bleed and sharp edges with little feathering.
Furthermore, the colored inks were dry to the touch after 15
minutes, and the black ink was dry within 1 hour after printing. In
addition, the inks did not smear after drying. Thus, an improvement
in the inkjet printing quality of oriented polypropylene was
achieved even when only the surface of the film was
microfibrillated.
Example 3
[0118] This example is a demonstration of piezoelectric inkjet
printing on a microfibrillated surface of a uniaxially oriented
polypropylene film using UV curable ink.
[0119] Sample Preparation:
[0120] A film was cast and oriented in a manner identical to C1 but
microfibrillated on only one major surface using the hydroentangler
described in Example 1 operated at a system water pressure of 20
MPa and using only 3 of the 7 waterjet heads. These jet heads were
each configured with a jet strip having 20 orifices/cm, with each
orifice dimensioned at 60 .mu.m. The oriented film was conveyed
perpendicularly to the jet heads (3 above the film) at a speed of
1.5 m/min. This process was repeated 4 times.
[0121] Image Quality:
[0122] The resulting microfibrillated surface of the film was
printed upon using the Xaar Jet piezoelectric inkjet printhead
described above with a UV curable ink. The ink containing the
components listed in Table 1 was prepared according to the
following general procedure. A dispersion was first prepared by
pre-dissolving the dispersant in the liquid components and then
adding the pigment powder. Initial wetting of pigment was
accomplished with high shear mixing. Next, the dispersion was
subjected to high energy milling in order to reduce the particle
size to less than 0.5 .mu.m. The dispersion and all remaining
components of the ink composition were then placed together in a
jar and thoroughly mixed until all soluble ingredients were
completely dissolved. Immediately after the resulting ink was
printed on the microfibrillated surface, the printed ink was cured
using a Fusion Systems UV processor (available from Fusion Systems
Inc., Gaithersburg, Md.) at 100% power, equipped with an H bulb at
a total dosage of 480 mJ/cm.sup.2 in two passes. After curing, it
was observed that there was no feathering and the ink spread
uniformly on the polypropylene surface with no mottling or
coalescence.
1TABLE 1 UV Curable Ink Composition Component.sup.1 Weight %
Benzophenone 2 IPTX 1 Irgacure 369 2 Irgacure 651 2 Irgacure 819 5
T-4 Morpholine Adduct 4 Stabaxol I 0.9 Tinuvin 292 2 NVC 5 HDDA 5
IOA 25.1 IBOA 5 EEEA 6 THFFA 3 Ebecryl 80 5 Ebecryl 284 7 Magenta
dispersion.sup.2 20 .sup.1See component descriptions in Table 2.
.sup.2Magenta dispersion: 33.3 wt % Monastral Red RT-343-D pigment,
11.55 wt % Solsperse 32000, 55.45 wt % THFFA.
[0123]
2TABLE 2 Description of Components in UV Curable Ink "Trade
Designation" Chemical Name/Description or Abbreviation Source
Location Monomers 2-(2-Ethoxyethoxy)ethyl EEEA Sartomer Co. Exton,
PA acrylate Isobornyl acrylate IBOA Sartomer Co. Exton, PA
1,6-Hexanediol diacrylate HDDA Sartomer Co. Exton, PA
Tetrahydrofurfuryl acrylate THFFA Sartomer Co. Exton, PA N-vinyl
caprolactam NVC BASF Ludwigshafen, Germany Isooctyl acrylate IOA
Sartomer Co. Exton, PA Oligomers Aliphatic urethane diacrylate
"Ebecryl .TM. 284" UCB Smyrna, GA diluted with 12% HDDA Chemicals
Modified polyester acrylate "Ebecryl .TM. 80" UCB Smyrna, GA
Chemicals Photoinitiators/Synergists Bis(2,4,6-trimethylbenzoyl)
"Irgacure .TM. 819" Ciba Specialty Tarrytown, phenylphosphine oxide
Chemicals NY 2,2-Dimethoxy-1,2- "Irgacure .TM. 651" Ciba Specialty
Tarrytown, diphenylethan-1-one Chemicals NY
2-Benzyl-2-dimethylamino-1-(4- "Irgacure .TM. 369" Ciba Specialty
Tarrytown, morpholinophenyl)butan-1-one Chemicals NY Benzophenone
Benzophenone Sartomer Co Exton, PA Isopropylthioxanthone "IPTX"
Aceto Corp. New Hyde Park, NY Tetraethyleneglycol bis(3- T-4
Morpholine -- -- morpholinopropionate) Adduct.dagger. Stabilizers A
mixture of bis(1,2,2,6,6- "Tinuvin .TM. 292" Ciba Specialty
Tarrytown, pentamethyl-4-piperidinyl)- Chemicals NY sebecate and
1-(Methyl)-8- (1,2,2,6,6-pentamethyl-4- piperidinyl)-sebecate
2,2',6,6'-Tetraisopropyldiphenyl "Stabaxol .TM. I" Rhein Chemie
Trenton, NJ carbodiimide Corp Pigment Magenta pigment "Monastral
Red Ciba-Geigy Tarrytown, RT-343-D" Corp. NY Dispersant High
molecular weight "Solsperse .TM. Zeneca Inc. Wilmington,
polyurethane 32000" DE .dagger.T-4 Morpholine Adduct was prepared
as follows: A partial vacuum (approximately 63 cm water vacuum) was
pulled on a clean 1-Liter flask having an addition buret and
stirring rod attached. The flask was preheated to 37.8.degree. C.
Tetraethylene glycol diacrylate (256 g) #was added to the flask
with mixing at a moderate rate (approximately 70 rpm). The liquid
was allowed to come up to temperature. Morpholine (155 g) was added
to the flask at such a rate that the temperature did not exceed
46.1.degree. C. The temperature control bath was set for
43.3.degree. C. and the flask contents were mixed for 30 minutes.
#The vacuum on the flask was broken and the fluid reaction product
(T-4 morpholine) was decanted through a 25 micron filter into a
container.
Comparative Example C3
[0124] This example is a demonstration of water-based inkjet
printing on a biaxially oriented coextruded (bilayer)
substrate.
[0125] Sample Preparation:
[0126] A two-layer film was cast by coextrusion and oriented using
conventional film orientation techniques. The first layer was a
blend of about 28% by weight of Fina 3230 polypropylene (Fina Inc.,
Dallas, Tex.) having a melt flow index of 1.6 (determined according
to ASTM D-1238, Condition "L") and about 72% by weight dried,
extrusion grade polyethylene terephthalate (PET, available from 3M
Company, St. Paul, Minn.), with an intrinsic viscosity (I.V.) of
about 0.58 dL/g. This blend was fed to the input of a 20 cm
extruder using a volumetric feeder to control the rate of addition
of the polypropylene. The total feed rate of the first (blend)
layer was about 585 kg/hr. The second layer was dried, extrusion
grade polyethylene terephthalate (PET), with an intrinsic viscosity
(I.V.) of about 0.58 dL/g, fed to the input of a 9 cm extruder. The
total feed rate of the second (PET) layer was about 166 kg/hr. A
filter for particulate control and a gear pump for flow rate
control were installed after the extruder gate for both of the
extruders. The first and second layers were combined using a
2-layer feedblock attached to a 94 cm wide sheeting die with a die
gap of about 0.14 cm. The sheet formed by the die was cast onto a
temperature-controlled casting wheel maintained at a temperature of
about 16.degree. C. The sheet was cast such that the second (PET)
layer was against the casting wheel. The cast sheet was held in
place by electrostatic pinning.
[0127] A biaxially oriented film was then made using conventional
polyester biaxial orientation equipment to stretch the resulting
cast sheet in the machine direction (MD) about 3.2 times at a
temperature of about 83.degree. C. and then to stretch the film in
the transverse direction (TD) about 3.7 times at a temperature of
about 103.degree. C. The stretched film was then subjected to a
heat set temperature of about 252.degree. C. while the film was
restrained. The thickness of the resulting finished oriented film
was about 0.13 mm.
[0128] Electron microscopy of the cast web revealed that the
polypropylene in the first (blend) layer formed discrete domains in
a continuous PET matrix in the first (blend) layer. Under the
described processing conditions, voids formed at the interface
between the discrete polypropylene domains and the continuous PET
matrix in the first (blend) layer during film orientation. The
finished film density was an indicator of the amount of voiding
present in the first (blend) layer. The density of the finished
(oriented) film was about 0.83 g/cm.sup.3 by Test Method 2.
[0129] Image Quality:
[0130] The oriented film was printed upon using the HP Deskjet 950C
inkjet printer as described above. The colors on the film were very
mottled due to the poor spreading of the water-based ink on the
PET/PP surface. In addition, there was a large amount of
inter-color bleed and poorly resolved edges due to feathering.
Furthermore, the surface was wet to the touch for more than after 3
hours after printing, and the ink was easily smeared even when
dried.
Example 4
[0131] This example is a demonstration of water-based inkjet
printing on a microfibrillated surface of a biaxially oriented
coextruded (bilayer) substrate.
[0132] Sample Preparation:
[0133] A film was cast and oriented in a manner identical to
Comparative Example C3 but microfibrillated on only one major
surface using the hydroentangler described in Example 1 operated at
a system water pressure of 8 MPa and using only 1 of the 7 water
jet heads with the polymer blend side toward the water-jets. The
jet head was configured with a jet strip having 20 orifices/cm,
with each orifice dimensioned at 110 .mu.m. The oriented film was
conveyed perpendicularly to the jet heads (1 above the film) at a
speed of 2.5 m/min.
[0134] Image Quality:
[0135] The resulting microfibrillated surface of the film was
printed upon using the HP Deskjet 950C inkjet printer as described
above. In contrast to the non-fibrillated material of Comparative
Example C3, the substrate was covered uniformly by the ink with no
mottling and only a small amount of inter-color bleed and
feathering, most noticeable with the black ink. In addition, the
surface was dry to touch after 4 minutes and did not smear after
drying. Thus, surface microfibrillation of a biaxially oriented
PET/Polypropylene blend significantly improved the inkjet printing
quality.
Comparative Example 4
[0136] This example is a demonstration of solvent-based inkjet
printing on a biaxially oriented film comprised of polypropylene,
an inorganic filler, and a styrenic thermoplastic elastomer.
[0137] Sample Preparation:
[0138] A 75 g batch of 40 weight % polypropylene homopolymer (Fina
3376 available from Atofina Inc., Houston, Tex.) with 40 weight %
calcium metasilicate (wollastonite grade 520H available from
Fibertec Inc., Bridgewater, Mass.) and 20 weight % styrenic block
copolymer (Vector.RTM. 4114 available from Dexco Polymers,
Plaquemine, La.) was compounded at 200.degree. C. in a
Plasti-Corder Laboratory batch mixer (type DR-2051, manufactured by
C. W. Brabender Instruments, Inc., South Hackensack, N.J.) until
melted (roughly three to five minutes at 50 to 100 RPM). The
resulting mixture was then pressed into a sheet between metal
platens, using a 0.091 cm spacer shim, in a hot press (model
G-30H-1S-LP manufactured by Wabash MPI, Wabash, Ind.) at
200.degree. C. under a load of 454 kg for 3 min, followed by
pressing under a load of 18,160 kg for an additional 30 seconds,
and finally quenched between cold clamps cooled with running tap
water for 3 minutes. The density of the resulting pressed sheet was
1.23 g/cm.sup.3 as determined by Test Method 2.
[0139] From the pressed sheet, 85 mm.times.85 mm square specimens
were cut out and biaxially oriented in a Karo IV Laboratory
Stretcher (manufactured by Bruckner Maschinenbau GmbH, Siegsdorf,
Germany) at 150.degree. C. A simultaneous balanced stretch at 3.1
m/min in both the machine direction (MD) and the transverse
direction (TD) was employed, resulting in a final biaxial draw
ratio of 3.5.times.3.5 (MD.times.TD) as determined by Test Method
1-B. The resulting oriented film had a thickness of approximately
0.20 mm and a density of 0.30 g/cm.sup.3, indicating a void content
of 75.6% as per Test Method 2.
[0140] Image Quality:
[0141] The oriented film was printed upon using a Xaar
piezoelectric inkjet printhead described above. The ink coverage on
the surface was uniform with no significant mottling, but some
feathering was evident which made the edges of the squares and
circles lose definition and appear blurry. Evaluation of the test
pattern indicated that a series of thin lines printed at 100% and
having widths of 0.68 mm and spaced 0.68 mm apart are capable of
being resolved when printed upon the substrate. The value of
D.sub.K was measured to be 1.07 using Test Method 3.
Example 5
[0142] This example shows solvent-based inkjet printing on the
microfibrillated surface of a biaxially oriented film comprised of
polypropylene, and inorganic filler, and a thermoplastic
elastomer.
[0143] Sample Preparation:
[0144] A film was prepared in a manner identical to C4 but
microfibrillated on only one major surface using the hydroentangler
described in Example 1 and using only 1 of the 7 water jet heads.
The jet head was configured with a jet strip having 20 orifices/cm,
with each orifice dimensioned at 60 .mu.m. The oriented film was
conveyed perpendicularly to the jet heads (1 above the film) at a
speed of 1.5 m/min. This process was followed 1 time while
operating at a system water pressure of 10 MPa and repeated 2
additional times while operating at a system water pressure of 15
MPa and 2 further times while operating at a system water pressure
of 20 MPa.
[0145] Image Quality:
[0146] The resulting microfibrillated surface of the film was
printed upon using a Xaar piezoelectric inkjet printhead as
described above. The ink coverage on the surface was uniform with
no significant mottling, and there was significantly less
feathering than that found on the non-fibrillated material of
Comparative Example C4, making the edges of the squares and circles
look sharper. Evaluation of the test pattern indicated that a
series of thin lines printed at 100% and having widths of 0.35 mm
and spaced 0.35 mm apart were resolved, a distinct improvement over
the non-fibrillated surface of Comparative Example C4. However, a
D.sub.K of 0.84 was measured by Test Method 3, which was markedly
lower than the non-fibrillated surface.
Examples 6-12
Solvent-Based Printing Image Quality Improvement
[0147] As described in Example 1 and Comparative Example C1, as
well as Example 5 and Comparative Example C4, the CD of the
polypropylene-based oriented materials tended to be low when
printed with solvent-based inks and decreased further when
microfibrillated. It was found that by blending certain additives
into the cast film or by applying surface coatings it was possible
to improve the color density of the microfibrillated surface when
printed with solvent-based inks.
[0148] Unless specified otherwise, the following microfibrillated
films prepared as described below were printed upon using a Xaar
Jet piezoelectric inkjet printhead as described above. The ink used
was a mixture of two "Scotchcal 3700" series solvent-based
piezoelectric ink jet inks (available from 3M, St. Paul, Minn.),
specifically a 1:1 ratio of magenta (Scotchcal.TM. 3791) and yellow
(Scotchcal.TM. 3792) to form a red colored ink. The test pattern
used to evaluate color density consisted of a solid filled octagon
and characters printed at 100%. The CD values were measured as
described in Test Method 3 and are reported in TABLE 3. An increase
in CD correlates to an improvement in solid ink fill.
[0149] Sample Preparation:
Example 6
[0150] A surface microfibrillated, uniaxially oriented
polypropylene film was prepared in a manner identical to Example
3.
Example 7
[0151] A surface microfibrillated, uniaxially oriented substrate
derived from a microlayer blend of polypropylene and a
maleated-polypropylene was prepared as follows.
[0152] A microlayer cast web was made using three commercially
available single screw extruders connected to a feedblock and
skinblock. No gear pumps, melt filtration, or static mixers were
used. The feedblock was a 61 layer unit. It has two input ports
designated A and B and generated a 61 layer A-B-A-B . . . -B-A
non-graded stack. That is, all A layers had the same thickness, and
all B layers had the same thickness, but A and B layer thicknesses
were not necessarily equal. The skin block divided the input skin
stream into two nominally equal flows and applied a skin layer to
the top and bottom of the multi-layer stack. The composite stream
then flowed through a die adapter to generate the stream required
for input to the die, a 12" wide, single layer die with orifice
gapped to a nominal 0.050". All melt stream components were heated
to 244.degree. C. The die was set 0.254 cm directly above a cast
wheel cooled to 24.degree. C. The skins were polypropylene
homopolymer (Fina 3376 available from Atofina Inc., Houston, Tex.).
For the alternating A-B layers, the A layers were the same
polypropylene homopolymer. The B layers were composed of a blend of
97 weight % polypropylene homopolymer (Fina 3376) and 3 weight %
maleated polypropylene (Epolene.RTM. G3003, available from Eastman
Chemical Company, Kingsport, Tenn.).
[0153] The resulting cast film was calendered and length oriented
as follows. The cast film was fed from an unwind station, through a
series of idler rolls and into the compressive nip of a calender
(rolls 1 and 2). Rolls 1 and 2 were both set to a temperature of
100.degree. C., and a calender nip force of 22 kN. The film exiting
rolls 1 and 2 was further oriented as it passed over heated roll 3
and then heated roll 4 in an "S" configuration, both held at
130.degree. C. The resulting film passed around a portion of roll
5, which was unheated and simply used to cool the film. The
resulting calendered/length oriented film was wound onto a core
under tension. The film was oriented to a draw ratio of 12:1 as
determined by Test Method 1-A
[0154] The oriented film was then microfibrillated on both major
surfaces using a the Hydrolace hydroentangler operated at a system
water pressure of 15 MPa and equipped with 7 waterjet heads. The
first jet head was configured with a jet strip having 16.5
orifices/cm, with each orifice dimensioned at 110 .mu.m. The second
through forth jet heads were configured with jet strips having 11
orifices/cm, with each orifice dimensioned at 150 .mu.m. The fifth
jet head was configured with a jet strip having 16.5 orifices/cm,
with each orifice dimensioned at 110 .mu.m. The sixth and seventh
jet heads were configured with jet strips having 14 orifices/cm,
with each orifice dimensioned at 130 .mu.m. The oriented film was
conveyed perpendicularly to the jet heads (4 above the film and 3
below) at a speed of 5 m/min.
Example 8
[0155] A surface microfibrillated, biaxially oriented substrate
comprised of a blend of polypropylene with an inorganic filler and
an acid/acrylate modified olefin resin was prepared as follows.
[0156] In the same manner as described in Comparative Example C4, a
film containing 40 weight % polypropylene homopolymer (Fina 3376
available from Atofina Inc., Houston, Tex.) with 40 weight %
calcium metasilicate (wollastonite grade 800H available from
Fibertec Inc., Bridgewater, Mass.) and 20 weight % of an
acid-acrylate modified ethylene vinyl acetate copolymer (Bynel.TM.
3101 available from DuPont Packaging and Industrial Polymers,
Wilmington, Del.) was compounded and melt pressed.
[0157] The resulting pressed sheet was biaxially oriented in the
Karo IV lab stretcher at 155.degree. C. with draw ratios of
3.5.times.3.5 (MD.times.TD) in a similar manner to that described
in Comparative Example C4.
[0158] The resulting biaxially oriented film was exposed to an
array of high pressure water jets using a lab scale hydroentangler
(70 cm wide, S/N 101, Project# 2303: manufactured by Honeycomb
Systems Inc., Biddeford, Me.) operating at approximately 10 MPa
water pressure. The water jet orifices were 110 micrometers in
diameter, with 15.75 orifices/cm. The oriented film was taped onto
a solid plastic sheet that was transported by a conveyor belt
moving 3 m/min perpendicularly beneath the array of water jets. The
oriented film was passed two times beneath the water jets and
exposed on one side only.
Example 9
[0159] A surface microfibrillated, biaxially oriented substrate
comprised of a blend of polypropylene with an inorganic filler and
a thermoplastic polyester elastomer was prepared as follows.
[0160] In the same manner as described in Comparative Example C4, a
film containing 40 weight % polypropylene homopolymer (Fina 3376
available from Atofina Inc., Houston, Tex.) with 40 weight %
calcium metasilicate (wollastonite grade 800H available from
Fibertec Inc., Bridgewater, Mass.) and 20 weight % of a
thermoplastic elastomer copolyester having crystalline polybutylene
terephthalate hard segment with amorphous glycol soft segments
(Hytrel.TM. G3548W available from E. I. duPont de Nemours &
Co., Wilmington, Del.) was compounded and melt pressed. The
resulting pressed sheet was biaxially oriented as in Comparative
Example C4. The resulting biaxially oriented film was
microfibrillated as in Example 8.
Example 10
[0161] A surface microfibrillated, biaxially oriented substrate
comprised of a blend of polypropylene with an inorganic filler and
a terpolymer of ethylene/vinyl acetate/carbon monoxide was prepared
as follows.
[0162] In the same manner as described in Comparative Example C4, a
film containing 40 weight % polypropylene homopolymer (Fina 3376
available from Atofina Inc., Houston, Tex.) with 40 weight %
calcium metasilicate (wollastonite grade 800H available from
Fibertec Inc., Bridgewater, Mass.) and 20 weight % of a terpolymer
of ethylene/vinyl acetate/carbon monoxide (Elvaloy.RTM. 741
available from DuPont Packaging and Industrial Polymers,
Wilmington, Del.) was compounded and melt pressed. The resulting
pressed sheet was biaxially oriented as in Comparative Example C4.
The resulting biaxially oriented film was microfibrillated as in
Example 8.
3TABLE 3 Solid Block Color Densities of Various Solvent-Based
Inkjet Printed Samples Example D.sub.K D.sub.M D.sub.C D.sub.Y 6
0.30 0.48 0.02 0.50 7 0.314 0.535 0.106 0.542 8 0.418 0.773 0.146
0.855 9 0.42 0.75 0.158 0.759 10 0.422 0.782 0.148 0.786
[0163] The results in Table 3 show that the addition of certain
polymers to the polypropylene base material (Examples 7-10)
significantly improved the image quality of the microfibrillated
substrates, especially with respect to color density, compared with
that found for the pure polypropylene microfibrillated, oriented
film of Example 6.
Example 11
[0164] Solvent-based inkjet printing was performed on a fully
microfibrillated, uniaxially oriented polypropylene material that
was hydroentangled with a polypropylene non-microfiber nonwoven
fabric backing.
[0165] Sample Preparation:
[0166] A polypropylene film was prepared by extruding polypropylene
homopolymer (Fina 3371, available from Atofina Inc., Houston, Tex.)
as described in Comparative Example C1. The resulting cast film was
calendered and length oriented in a manner similar to as described
in Comparative Example C1 to a draw ratio of approximately 20:1.
The resulting oriented film was microfibrillated in a manner
similar to as described in Example 1, but during the process, the
oriented film was placed on top of a spunbond polypropylene
nonwoven fabric (AVGOL.TM., 15 g/m.sup.2, available from Avgol
Ltd., Holon, Israel), and the two were hydroentangled together to
form a single hybrid nonowoven.
[0167] Image Quality:
[0168] The microfibrillated hybrid material was printed upon using
the Xaar piezoelectric inkjet printer as described above. Similarly
to Example 1, evaluation of the test pattern indicated that a
series of lines printed at 100% and having widths of 0.35 mm and
spaced 0.35 mm apart were resolved. Likewise, there was only a
minimal amount of edge roughness, and the ink coverage on the
surface was quite uniform with no mottling or coalescing. The color
density of the black ink was measured to be 0.79 as described in
Test Method 3.
Example 12
[0169] Solvent-based inkjet printing was performed on a fully
microfibrillated, uniaxially oriented polypropylene material
hydroentangled with a polypropylene non-woven fabric and coated
with an acrylic primer.
[0170] Sample Preparation:
[0171] The identical microfibrillated hybrid nonwoven of Example 11
was prepared and coated with a 15 weight % solution of an acrylic
resin composed of poly(methyl methacrylate) and poly(butyl
methacrylate) (Paraloid.RTM. B-66 available from Rohm and Haas,
Co., Philadelphia, Pa.) in 2-butoxyethyl acetate (Scotchcal.TM.
Thinner CGS50, available from 3M, St. Paul, Minn.) using a #6 wire
wound rod and dried in a convection oven at 60.degree. C.
[0172] Image Quality:
[0173] The coated substrate was printed in the same manner as
Example 11. The acrylic coating improved the image quality by
increasing the color density from 0.79 to 1.16. In addition, the
coated surface appeared to provide sharper edges than Example 11.
It was also observed that the acrylic coating tended to make the
material feel significantly stiffer.
Comparative Examples C5-C10 and Example 13
[0174] The following example and comparative examples provide a
comparison of solvent-based piezoelectric inkjet printing on a
microfibrillated substrate with other substrates.
Comparative Example C5
Piezoelectric Inkjet Printing on a PVC Film
[0175] A vinyl film (VCC-9929 available from 3M Company, St. Paul,
Minn.) was cleaned with isopropyl alcohol to remove any
contaminants and then printed upon using the Xaar piezoelectric
inkjet printer as described above. The ink coverage on the surface
was uniform with no significant mottling, but feathering and
inter-color bleed was evident, especially at high ink lay down
(>300%) which made the edges of these squares and circles lose
some definition and appear blurry. Evaluation of the test pattern
indicated that a series of thin lines printed at 100% and having
widths of 0.35 mm and spaced 0.35 mm apart were resolved. It was
observed that the ink was still very wet after printing.
Comparative Example C6
Piezoelectric Inkjet Printing on a Polypropylene Meltblown Nonwoven
Fabric
[0176] A polypropylene microfiber was meltblown to form a nonwoven
fabric web having a basis weight of 40 g/m.sup.2. The average
Effective Fiber Diameter (EFD) of the fibers in the web was
calculated, using an air flow rate of 32 L/min according to the
method described in Davies, C. N., "The Separation of Airborne Dust
and Particles," Institution of Mechanical Engineers, London,
Proceedings 1B, 1952, to be 3.9 .mu.m. The nonwoven fabric was
printed upon using the Xaar piezoelectric inkjet printer as
described above. The ink coverage on the surface was uniform with
no significant mottling, but a high degree of feathering and
inter-color bleed was evident due to the wicking of ink along fiber
strands. Evaluation of the test pattern indicated that a series of
thin lines printed at 100% and having widths of 0.50 mm and spaced
0.50 mm apart were resolved. It was observed that the ink was dry
to the touch after printing.
[0177] Vertical Hang Test: To evaluate the solvent-based ink's
uptake on the nonwoven fabric surface, a portion of the sample was
printed with Scotchcal.TM. 3795 black at 1,000% ink fill in a 2.54
cm.times.2.54 cm square and hung vertically immediately after
printing. It was observed that the edges of the square showed a
substantial amount of wicking after printing, but after hanging for
30 minutes, there was no additional bleeding and the image retained
its original shape.
Comparative Example C7
Piezoelectric Inkjet Printing on a Woven Cotton Cloth
[0178] A commercially available woven cotton cloth (TexWipe.RTM.
TX309 available from Texwipe Company Upper Saddle River, N.J.)
having a basis weight of 180 g/m.sup.2 was printed upon using the
Xaar piezoelectric inkjet printer as described above. As with
Comparative Example C6, the ink coverage on the surface was uniform
with no significant mottling, but a high degree of feathering and
inter-color bleed was evident due to the wicking of ink along fiber
strands, especially at high ink lay down (>300%). Evaluation of
the test pattern indicated that a series of thin lines printed at
100% and having widths of 0.35 mm and spaced 0.35 mm apart were
resolved. It was observed that the ink was dry to the touch after
printing.
Comparative Example C8
Piezoelectric Inkjet Printing on Standard Paper
[0179] Commercially available paper (Hammermill.RTM. CopyPlus
Standard White, available from International Paper, Stamford,
Conn.) having a basis weight of 36.3 kg was printed upon using the
Xaar piezoelectric inkjet printer as described above. The ink
coverage on the surface was uniform with no significant mottling.
At high ink lay down (>300%) it was observed that there was
feathering. Evaluation of the test pattern indicated that a series
of thin lines printed at 100% and having widths of 0.35 mm and
spaced 0.35 mm apart were resolved. It was observed that the ink
was dry to the touch after printing.
Comparative Example 9
Piezoelctric Inkjet Printing on PVC Film
[0180] A vinyl film (C3555 available from 3M Company, St. Paul
Minn.) was surface was cleaned with isopropyl alcohol to remove any
contaminants and then printed upon using the Xaar piezoelectric
inkjet printer as described.
[0181] Vertical Hang Test: To evaluate the solvent-based ink's
uptake on the PVC surface, a portion of the sample was printed
using Scotchcal.TM. 3795 black at 1,000% ink fill in a 6.5
cm.times.6.5 cm square and hung vertically immediately after
printing. It was observed that after hanging for 30 minutes there
was a large quantity of ink running down the film.
[0182] Ink Drying Test: To evaluate the solvent-based ink's drying
time on the PVC film, portions of the sample were printed using
black at 100% ink fill in a 2.54 cm.times.2.54 cm square and tested
for dryness at various time intervals by pressing lightly on the
printed surface with a white piece of paper. It was observed that 3
minutes after printing, there was a significant amount of ink
transferred to the paper. The amount of ink transferred was even
greater than the amount transferred from the microfibrillated
surface of Example 13 (see below) immediately after it was printed,
indicating that the PVC surface dried at lower rate than the
microfibrillated surface.
Comparative Example C10
[0183] In this example injet printing was performed on a biaxially
oriented film comprised of a blend of polypropylene with inorganic
filler, a terpolymer of ethylene/vinyl acetate/carbon monoxide, and
a styrenic thermoplastic elastomer.
[0184] Sample Preparation:
[0185] A film having a composition of 30 weight % polypropylene
homopolymer (Fina 3376 available from Atofina Inc., Houston, Tex.)
with 40 weight % calcium metasilicate (wollastonite grade 800H
available from Fibertec Inc., Bridgewater, Mass.), 20 weight % of a
terpolymer of ethylene/vinyl acetate/carbon monoxide (Elvaloy.RTM.
741 available from DuPont Packaging and Industrial Polymers,
Wilmington, Del.) and 10 weight % polystyrene/polyisoprene (Vector
4114, available from Dexco Polymers, Plaquemine, La.) was cast
using a twin screw extruder with a temperature of 175.degree. C. at
the end of the extruder, 185.degree. C. in the neck tube and
195.degree. C. at the die. The extruder was equipped with a 30.5 cm
wide die having an orifice gapped to a nominal 1 mm. The polymer
melt exiting the extruder die entered a three-roll stack between
the bottom and middle rolls, and after passing between the bottom
and middle rolls, traveled over the middle roll into the nip formed
by the middle and top rolls. In the three-roll stack, the bottom
and middle rolls were chrome-coated stainless steel set to
82.degree. C. The resulting film had a thickness of 1 mm and a
density of 1.23 g/cm.sup.3 as determined by Test Method 2.
[0186] This cast film was oriented sequentially using a length
orienter (LO) (available from Killian, a division of Davis-Standard
Corp., Cedar Grove, N.J.) and tenter (available from Bruckner,
France) at a draw ratio of 3.0 in the machine direction (MD) and
2.0 in the transverse direction (TD) as determined by Test Method
1-B. The temperature of the LO rolls was 130.degree. C. and the
tenter zones were all 163.degree. C. The density of the resulting
318 .mu.m thick biaxially oriented film was 0.77 g/cm.sup.3
indicating a void content of 37.4% as determined by Test Method
2.
[0187] Image Quality:
[0188] The biaxially oriented film was printed upon using the Xaar
piezoelectric inkjet printer as described above. The ink coverage
on the surfaces was uniform with no mottling, but some feathering
was evident at higher ink lay down (>300%) that made edges lose
definition and appear blurry. Evaluation of the test pattern
indicated that a series of lines printed at 100% and having widths
of 0.35 mm and spaced 0.35 mm apart were resolved.
Example 13
[0189] In the example a surface microfibrillated, biaxially
oriented substrate comprised of a blend of PP with an inorganic
filler, a terpolymer of ethylene/vinyl acetate/carbon monoxide, and
a styrenic thermoplastic elastomer was inkjet printed. A film was
cast and oriented the same manner as described in Comparative
Example C10 and microfibrillated on a single major surface (i.e.
not the whole way through) using the Hydrolace system described
above, operating at a water pressure of 15 MPa. The sample was
conveyed at 2 m/min below the first jet head having 60 micron in
diameter jet orifices with 7.9 orifices per cm. This was done three
times.
[0190] The resulting microfibrillated material was printed upon
using the Xaar piezoelectric inkjet printer as described above. The
ink coverage on the surfaces was uniform with no mottling.
Evaluation of the test pattern indicated that a series of lines
printed at 100% and having widths of 0.35 mm and spaced 0.35 mm
apart were, which was equal to or better than the comparative
materials examined here. In addition, only at high ink lay down
(400%) was there a small but detectible indication of ink
feathering. However, it was less than any of the substrates of
Comparative Examples C5 through C10, emphasizing that
microfibrillation of the oriented surface appears to keep the
amount of feathering and inter-color bleed to a minimum. Although
this material's surface had a fibrous texture, its microscopic
nature was not as disposed to wicking as the fiber surfaces of
Comparative Examples C6, C7 and C8 and it did surprisingly improve
over the performance of its non-fibrillated oriented counterpart
(Comparative Example C10) as well as the smooth PVC films
(Comparative Examples C5 and C9). It was also observed that the
surface of the substrate felt dry to the touch immediately after
printing and the inks were held fast to the surface after
drying.
[0191] Vertical Hang Test: To evaluate the solvent-based ink's
uptake on the microfibrillated surface, a portion of the sample was
printed with Scotchcal.TM. black 3795 at 1,000% ink fill in a 6.5
cm.times.6.5 cm square and hung vertically immediately after
printing. It was observed that the edges of the square showed a
small amount of roughness after printing. However, even after
hanging for 30 minutes, there was no bleeding and the square
retained its original shape. Thus, the overall high ink lay down
performance of this sample was superior to both the nonwoven of
Comparative Example C6 and the PVC film of Comparative Example
C9.
[0192] Ink Drying Time Test: To evaluate the solvent-based ink's
drying time, a portion of the sample was printed using black at
100% ink fill in a 6.5 cm.times.6.5 cm square and tested for
dryness at various time intervals by pressing lightly on the
printed surface with a white piece of paper. It was observed that
immediately after printing, there was a small but detectable amount
of ink transferred to the paper surface indicating that the ink was
not completely dry. However, after 3 minutes, there was no
detectable amount of ink transferred to the paper surface,
indicating that the ink was dry for handling purposes. This is
substantially better drying speed than the PVC film of Comparative
Example C9.
Example 14
[0193] This example shows solvent-based piezoelectric inkjet
printing on a surface microfibrillated, biaxially oriented
substrate comprised of a blend of polypropylene with inorganic
filler, a terpolymer of ethylene/vinyl acetate/carbon monoxide, and
an acrylic resin laminated to an adhesive liner.
[0194] Sample Preparation:
[0195] In the same manner as described in Comparative Example C4, a
film containing 40 weight % polypropylene homopolymer (Fina 3376
available from Atofina Inc., Houston, Tex.) with 40 weight %
calcium metasilicate (wollastonite grade 800H available from
Fibertec Inc., Bridgewater, Mass.), 10 weight % of a terpolymer of
ethylene/vinyl acetate/carbon monoxide (Elvaloy(.RTM. 741 available
from DuPont Packaging and Industrial Polymers, Wilmington, Del.)
and 10 weight % of polyisobutyl methacrylate (Paraloid.RTM. B-67
available from Rohm and Haas, Co., Philadelphia, Pa.) was
compounded and melt pressed. In a similar manner as described in
Comparative Example C4, the resulting film was stretched in a Karo
IV lab stretcher at 155.degree. C. with draw ratios of
3.5.times.3.5 (MD.times.TD) at 4.2 m/min. The resulting biaxially
oriented film was microfibrillated on a single major surface (i.e.
not the whole way through) using the Hydrolace system described
above, operating at a water pressure of 15 MPa. The sample was
conveyed at 2 m/min below the first jet head having 60 micron in
diameter jet orifices with 7.9 orifices per cm. This was done three
times. The resulting microfibrillated film was laminated on the
non-fibrillated side with an acrylic-based adhesive coated at 25
gsm onto a polyethylene coated paper liner treated with a cured
silicone release system.
[0196] Printing Procedure:
[0197] A graphic image was printed upon the microfibrillated
surface using an Arizona Sign Printer (Model SP-62 available from
Gretag Imaging Inc., Holyoke, Mass.) using the Scotchcal.TM. 3700
series inks described above in addition to light magenta (3781) and
light cyan (3786). The graphic was observed to have very good image
quality including high resolution and good color densities.
Examples 15-19
Water-Based Inkjet Printer Image Quality Improvement
[0198] As with the solvent-based inks, the CD of the
polypropylene-based oriented films printed with water-based inks
tended to be low and decreased further when microfibrillated. As
with the solvent-based inks, it was also found that blending
certain additives into the cast film or applying surface coatings
could improve the color density of the microfibrillated surface
when printed with water-based inks, without losing their very good
image resolution.
[0199] Printing Procedure:
[0200] The following microfibrillated films were printed upon using
the Deskjet 950C inkjet printer described above. The ink used was
the HP 51645A black cartridge, and the test pattern used to
evaluate image quality consisted of filled characters of various
sizes printed at 100% coverage. The CD values were measured as
described in Test Method 3 and are reported in Table 4. An increase
in CD correlates to an improvement in solid ink fill.
Example 15
[0201] This example shows water-based inkjet printing on a surface
microfibrillated, uniaxially oriented polypropylene substrate.
[0202] A film was cast and oriented in a manner identical to C1 but
microfibrillated on a single major surface (i.e. not the whole way
through) using the Hydrolace system described above, operating at a
water pressure of 15 MPa. The sample was conveyed at 2 m/min below
the first jet head having 110 micron in diameter jet orifices with
20 orifices/cm. The second, third, and fourth jet heads were
configured with jet strips having 16.5 orifices/cm, with each
orifice dimensioned at 120 .mu.m. The oriented film was conveyed
perpendicularly to the jet heads (4 above the film) at a speed of
1.5 m/min.
Example 16
[0203] This example shows water-based inkjet printing on a surface
microfibrillated, uniaxially oriented specimen comprised of
polypropylene and a hydrophilic polymer.
[0204] A film was prepared by extruding a blend containing 90
weight % polypropylene homopolymer (Fina 3374X, available from
Atofina Inc., Houston, Tex.) and 10 weight % of an extrudable,
water swellable blend in a single screw extruder with an extruder
temperature profile of 210.degree. C., 226.degree. C., 238.degree.
C., and 246.degree. C. from the feed throat to the end of the
extruder. The neck tube and die were maintained at 246.degree. C.
The extruder was equipped with a barrier screw having a mixing tip
and with a 12.7 cm wide, single layer die having an orifice gapped
to a nominal 1.27 mm. A film having a thickness of 1.36 mm and a
width of 127 mm was prepared using a three-roll stack casting
station. In the three-roll stack, the bottom chrome-coated
stainless steel roll was set to 88.degree. C., the middle
chrome-coated stainless steel roll was set to 99.degree. C., and
the top silicon rubber roll was cooled with 38.degree. C. water.
The polymer melt exiting the extruder die entered the three-roll
stack between the bottom and middle rolls, and after passing
between the bottom and middle rolls, traveled over the middle roll
into the nip formed by the middle and top rolls. After passing over
the top roll, the resulting cast film exited the three-roll stack.
The extrudable, water swellable blend consisted of the following in
weight percent: 57% polyvinylpyrrolidone (PVP K90, available from
International Specialty Products, Wayne, N.J.), 24% ionomer
(ethylene/acrylic acid copolymer, Surlyn.RTM. 1705 available from
Dupont Chemical Co., Wilmington, Del.), 14% polyoxyethylene aryl
ether (Pycal 94 available Uniqema, Wilmington, Del.), 3% glass
beads (MBX-50 available from Sekisui Plastics, Tokyo, Japan), and
2% Irganox 1010 (available from Ciba Specialty Chemicals,
Tarrytown, N.Y.). The resulting cast film had a thickness of 1.27
mm, a width of 124 mm, a density of 0.91 g/cm.sup.3 as determined
by Test Method 2.
[0205] The cast film was fed from an unwind station into the
compressive nip of a first calender (two rolls) at a surface speed
of 1.22 m/min, a temperature of 154.degree. C., and a pressure of
2.76 MPa. The film exiting the first calender was fed into a second
and third pulling calender set (two rolls in each set) operating at
as high a surface speed as possible without breaking the film. The
resulting oriented and voided film was wound onto a core under
tension. The film was oriented to a draw ratio of 14.6:1 as
determined by Test Method 1-A, had a thickness of 119 micrometers,
a width of 99 mm, and contained 5.5% voids as determined by Test
Method 2. As described in Example 8, the oriented film was
microfibrillated on a single major surface using the Honeycomb
hydroentangler, operating at 10 MPa at a belt speed of 3 m/min. The
sample was conveyed on under the water jets eight times.
Example 17
[0206] This example shows water-based inkjet printing on a surface
microfibrillated, uniaxially oriented specimen comprised of
polypropylene, an inorganic filler and a thermoplastic
polyurethane.
[0207] A film having a composition of 35 weight % polypropylene
homopolymer (Fina 3276 available from Atofina Inc., Houston, Tex.)
with 30 weight % calcium carbonate (HiPflex.RTM.100 available from
Specialty Minerals, Adams, Mass.), and 35 weight % of thermoplastic
polyurethane (Eastane.RTM. 58237 available from Noveon Inc.,
Cleveland, Ohio) was cast using a twin screw extruder with a
temperature of 193.degree. C. at the end of the extruder,
211.degree. C. in the neck tube and 195.degree. C. at the die. The
extruder was equipped with a 30.5 cm wide die having an orifice
gapped to a nominal 0.76 mm. The polymer melt exiting the extruder
die entered a three-roll stack between the bottom and middle rolls,
and after passing between the bottom and middle rolls, traveled
over the middle roll into the nip formed by the middle and top
rolls. In the three-roll stack, the bottom and middle rolls were
chrome-coated stainless steel set to 38.degree. C. The resulting
cast film had a thickness of 0.7 mm and a density of 1.26
g/cm.sup.3 as determined by Test Method 2.
[0208] The cast film was calendered and length oriented as follows.
The cast film was fed from an unwind station through a series of
idler rolls and into the compressive nip of a calender (rolls 1 and
2). Rolls 1 and 2 each had a surface temperature of 120.degree. C.
The film exiting rolls 1 and 2 was further oriented as it passed
over heated roll 3 and then heated roll 4 in an "S" configuration.
Rolls 3 and 4 also had surface temperatures of 120.degree. C., and
roll 4 had a surface speed of 10.9 m/min. The resulting film passed
around a portion of roll 5, which was unheated and simply used to
cool the film. The resulting calendered/length oriented film was
wound onto a core under tension. The film was oriented to a draw
ratio of 5:1 as determined by Test Method 1-A.
[0209] The resulting oriented film was microfibrillated on only one
major surface using the hydroentangler described in Example 1
operated at a system water pressure of 15 MPa and using only 1 of
the 7 water jet heads. The jet head was configured with a jet strip
having 20 orifices/cm, with each orifice dimensioned at 110 .mu.m.
The oriented film was conveyed perpendicularly to the jet heads (1
above the film) at a speed of 6 m/min.
Example 18
[0210] This example shows water-based inkjet printing on a surface
microfibrillated, uniaxially oriented specimen comprised of
polypropylene and a surfactant.
[0211] A film was prepared as in Example 17 by extruding a blend
containing 96 weight % polypropylene homopolymer (Fina 3374X,
available from Atofina Inc., Houston, Tex.), 1.2 weight % sorbitan
monolaurate, and 2.8 weight % glycerol monolaurate in a single
screw extruder. The extruder temperature profile was set to
210.degree. C., 226.degree. C., 238.degree. C., and 249.degree. C.,
and the neck tube and die were maintained at 249.degree. C. In the
three-roll stack, the bottom roll was set to 100.degree. C., the
middle roll was set to 100.degree. C., and the top silicon rubber
roll was cooled with 38.degree. C. water. The resulting cast film
had a thickness of 1.18 mm, a width of 112 mm, a density of 0.91
grams/cm.sup.3 as determined by Test Method 2.
[0212] The cast film was fed from an unwind station into the
compressive nip of a first calender (two rolls) with roll surface
speeds of 1.22 m/min, a temperature of 121.degree. C., and a
pressure of 3.45 MPa. The film exiting the first calender was fed
into a second and third pulling calender set (two rolls in each
set) operating at as high a surface speed as possible without
breaking the film. The resulting oriented and voided film was wound
onto a core under tension. The films were oriented to a draw ratio
of 13.5:1 as determined by Test Method 1-A, had a thickness of 138
micrometers, a width of 140 mm, and contained 10.8% voids as
determined by Test Method 2. As described in Example 8, the
oriented film was microfibrillated on a single major surface using
the Honeycomb hydroentangler, operating at 14 MPa at a belt speed
of 3 m/min. The sample was conveyed on a solid plate under the
water jets eight times.
Example 19
[0213] This example shows water-based inkjet printing on a surface
microfibrillated, uniaxially oriented polypropylene film coated
with a surfactant.
[0214] A polypropylene film was prepared by extruding polypropylene
homopolymer (Novolen.RTM. PP1104K available BASF Corporation, Mount
Olive, N.J.) in a single screw extruder with a 30.5 cm wide, single
layer die having an orifice gapped to a nominal 2.54 mm. A film
having a thickness of 1.75 mm and a width of 320 mm was prepared
using a three-roll stack casting station. The resulting cast film
had a density of 0.9 gram/cm.sup.3 as determined by Test Method
2.
[0215] The cast film was calendered and length oriented as follows.
The cast film was fed from an unwind station at a rate of 0.27
m/min, through a series of idler rolls and into the compressive nip
of a calender (rolls 1 and 2). Rolls 1 and 2 each had a surface
speed of 0.29 m/min and 3.17 m/min, respectively, a temperature of
130.degree. C., and a calender nip force of 44.5 kN. The film
exiting rolls 1 and 2 was further oriented as it passed over heated
roll 3 and then heated roll 4 in an "S" configuration. Roll 3 had a
surface speed of 4.75 m/min and a temperature of 130.degree. C.
Roll 4 had a surface speed of 10.9 m/min and a temperature of
120.degree. C. The resulting film passed around a portion of roll
5, which was unheated and simply used to cool the film. The
resulting calendered/length oriented film was wound onto a core
under tension. The film was oriented to a draw ratio of 14.9:1 as
determined by Test Method 1-A. The oriented film had a thickness of
203 micrometers, a width of 203 mm, and a density of 0.82
gram/cm.sup.3. The film was calculated to contain 9% voids as
determined by Test Method 2.
[0216] The oriented film was microfibrillated on a single major
surface (i.e. not the whole way through) using the Hydrolace system
described in Example 1, operating at a water pressure of 15 MPa.
The sample was conveyed at 1.5 m/min below the first through fourth
jet head having 120 .mu.m in diameter jet orifices with 20
orifices/cm.
[0217] The resulting microfibrillated film was immersed in a 3:1
water/isopropyl alcohol solution containing 5 weight % dioctyl
sulfosuccinate, sodium salt (DOS) for 30 min and allowed to dry
prior to inkjet printing.
4TABLE 4 Solid Block Color Densities of Various Solvent-Based
Inkjet Printed Samples Example D.sub.K 15 0.86 16 1.14 17 1.11 18
1.08 19 1.1
[0218] The results in Table 4 show that, by comparison with
polypropylene alone (Example 15), the addition of hydrophilic
polymers (Examples 16 and 17) or hydrophilic surfactants (Example
18) to the microfibrillated films through the polymer melt process,
or the application of a hydrophilic surfactant via surface coating
to the microfibrillated surface significantly improved the image
quality of the microfibrillated films when printed with water-based
inks, especially with respect to color density.
* * * * *