Note: Descriptions are shown in the official language in which they were submitted.
wo ssl34263 r~ C~
~ ' 21 92850=
--1--
LAsER-NAR~ABLE PLASTIC LABELS
~3ACKCi~OU~D OF ~E TNVENTION
The present invention relates to flexible, plastic labels for
~use on flexible plastic bottles, which labels are both ink printa_le
nd laser-markable.
Many ~ ';t;P~ are supplied today in s~loP7~hl0~ flexible
s plastic bottles. Examples of such materials are hml~Phnl~ cleaning
products such as sink and bathtub cleaners, liquid soaps and ~otPr~Pnt~
and the like as well as personal care products such as shampoos,
rnn~it;nnPr~, lotiong, suntan oils and the like.
Traditionally, flexible labels for s~Po7~hlo, flexible plastic
bottles have been made from paper coated with pressure sensitive
~ adhesives. More recently, plastics have replaced paper to a large
extent for this purpose. Plastic labels tend to exhibit a higher
degrce of flPYih;lity~ s~P~hility and a greater resistance to water
and other chemicals than paper. Accordingly, plastic labels are
becoming increasingly popular for use on flexible plastic bottles.
Attaching flexible plastic labels to flexible plastic bottles is
normally A, 1; ~ho~ in one of two ways. In one way, a pressure
sensitive adhesive is applied to the label and the label attached to a
previously formed bottle by pressure. In the other way, known as IMFL
(In Mold Film Label), the labcl is placed into the mold used to form
the bottle by blow molding and the label incorporated physically into
the pla9tic bottle itself as part of the blow molding operation. In
this procedure, a heat-activatable adhesive is normally applied to the
label for firmly bondiny the label to the bottle body.
In actual industrial practice, flexible plastic la_els are
attached to flexible plastic bottles at high rates of speed. For
example, typical industrial ~prl;r~t;nn~ using pressure sensitive
la_els can process as many as 200 bottles per minute and even up to 600
bottles per minute. In typical industrial ~rplin~tin~ for IMF~, S to
--~ 30 150 bottles per minute can be made with lahels attached.
An important property of flexible plastic labels is that they
are ink-printable. Ink printability depends both on the physical as
well as chemical nature of the label surface to be printed.
~nr~ingly, it is important in producing such labels that the
materials and processes used to form the labels give label products
having the appropriate 3urface properties.
SUBSTITUTE SHEET (RULE 26)
... . , , ~
W095134263 P~ll~ S '~
21 92.~50
--2--
In addition to surface properties, however, it i8 also important
that label9 exhibit appropriate gross ' ;r~l properties. In order
that the labels can flex with the bottles to which they are attached,
they obviously must exhibit suitable fl~;h;l;ty, at least in one
s direction (usually the L~L~LL~V~e direction). Moreover, in order that
they can be effectively used in the modern, high-speed industrial
processes described above, the labela muat also exhibit R5~;t;n"~l
properties such as die cutability, matrix stripability, ~;npenq~h;l;ry
* (i.e., with enough stiffness to be dispensed at high speed from a peel
plate or handled for inaertion in a mold) and the like. Also, pressure
sensitive labels further need to be r~pn~it;nn~h1r, i.e., when
m; r~Lprl;r~ they can be easily peeled off the bottle in a single piece
with all the adhesive remaining on the label.
In order to meet these requirements, much technology has been
developed for the -- ~F~ of flexible plastic labels. In
CLL~LL~ CC with one such development, the label body is made by
coextruding a number of different plastic materials together to form a
multilayer ~ l product. A real advantage of this approach i8
that the main body of the film can be ' lAt~ to maximize the
desired gross m rh~n;r~l properties of the label, while the skin layers
of the product can be tailored for accepting printing ink, for
receiving adhesives or both.
A good description of how flexible plastic label6 can be
tailored to meet a variety of different physical requirements while
still retaining ink-printability, both in the caae of presaure
sensitive adhesive labels and heat sensitive adhesive labels, can be
found ln ~.5. 4,713,273; ~.5. 4,888,075; U.S. 4,945,532i
.5. 5,143,570; U.S. 5,156,782 and U.S. 5,242,650, the disclosures of
which are incorporated herein by reference.
30one type of product that is often sold in flexible plastic
bottles is rhArr~ t;r~1q such as contact lena solutions and various
other health care products. In order to conform to various labeling
laws and other legal rerS,uirements relating to such products, it is
often necessary for the ~ lfnrt~lrer to mark the product cnnt~;n~rn
with the date of ~-n~lf~rtl~re as well as the lot number of the material
being sold. In the past, this has normally been done by marking a
pr~rr;"t~5 label, i.e. a label which has previously been printed with
all of the deaired information thereon other than the lot number and
date, with the lot number and date i ~ ~tr1y before or after the
bottle ia filled. ~ypically, this is done either by a thermal transfer
process or other conventional ink-printing process. Unfortunately,
such printing np~r~t;nn~ are very time consuming and hence represent a
real bottleneck in mass producing individually marked flexible bottles
rapidly and rff;r;~nt1y
SUBSTITUTE SHEET (RULE 26)
_ _ _ _ _ _ _ _ ... ... . . . . ~ .. ~ _, . . . . . . . '
~ W 095134263 2 ~ 9 2 8 5 0 ~ R
In order to overcome this drawback, it has been proposed to
employ laser-marking technology to mark the date and lot number on
individual bottles. In accordance with one such proposal, the date _nd
lot number are marked directly on the bottle body. Most plastics,
s however, are LL~aLq~L to laser light, and accordingly, it i5
necessary if adopting this proposal to incorporate a material which is
opague to laser light into the plastic forming the bottle body. Such
materials are well known and , ,~;f;~, for example, in
U.S. 4,595,647; U.S. 4,654,290; U.S. 4,753,863; U.S. 4,816,374 and
U.S. 4,861,620. See also European Patent 0 190 997 as well as Rilp,
~aser Markinq of Plasticc, Ortech International, M;qqic~AIlg~ Ontario,
Canada, copyright A~TEC 1991, pp. 1901-1903. Each of these disclosures
is also in~L~L~Led herein hy reference.
Another material also known to impart laser markability to
various types of plastics is titanium dioxide-coated mica particles.
Such materials are sold, for example, under the name AFFLAIR~ by E.
Merk Company of Raway, New ~ersey and MEARLIN~ Lustre Pigments sold by
the Mearl ~nrpnrAt;nn of New York, New York.
Unfortunately, such materials are comparatively expensive.
Accordingly, il..~L~L~Ling such materials into the plastic materials
used to form the bodies of the flexible bottles is not cost effective.
In order to deal with this problem, it has also been proposed to
laser imprint the labels used on the bottles rather than the bottles
themselves. In a,.~L.l-~,ce with one method of applying this technique,
2s a preprinted label is provided with an ink-printed black field and the
lot number and date laser imprinted on the black field by burning off
the black ink with the laser. ~3ecause registration of the laser image
with the black field becomes difficult at the high speeds involved in
in~nctr;~1 op~rAtinnq, this techni~ue requires a black field of
relatively large size to be effective. This, in turn, is regarded by
many as being aesthetically llnrloAc;ng and is therefore not desired.
Another techni~ue proposed for laser marking flexible plastic
labels is to make the labels from a vinyl plastic such as polyvinyl
chloride. Carbon dioxide lasers produce high ~uality, good contrast
marks ranging in color from gold to deep orange on polyvinyl chloride
films. unfortunately, many ~-mlfArtnrers also regard this -n1nrAt;nn
as being A~qther;rA~ly lm~-r~rtAhl~, AlLo, polyvinyl chloride contains
chlorine as well as r1~qtir;7~rc and therefore often produces noxious
by-products upon laser I ' ,' . Accordingly, laser marking of
vinyl labels is not attractive.
Accordingly, it is an object of the present invention to provide
a mcthod for producing laser-markable labels whose L~L~L~dS are
transparent or light in color and which can be easily imprinted with
SU8STITUTE SHEET (RULE 26)
WO95/34263 2 1 92~0 ~ 7~Q
--4--
easily-readable, high intensity indicia by conventional laser marking
technology.
In addition, it i9 a further object of the present invention to
provide a method for producing laser-markable labels as described above
S which does not adversely affect the various other properties of the
label such as ink-printability, die cutability, matrix stripability,
~;arrnqAh;l;ty, rprrc; t; nnAh;l; ty and the like.
It is a still further object of the present invention to provide
~ method for producing ink-printable, laser-markable, flexible, plastic
labels which employs a minimum amount of additives and thus is
inexpensive to carry out.
It is a still further object of the present invention to provide
new flexible, plastic labels for use on flexible plastic bottles which
meet all of the foregoing objects as well as to further provide web or
sheet stock that can be processed by normal label --nllfArtnring
terhniqu~c and equipment to provide these labels.
S~MM~RY 0~ THE INVENTION
These and other objects are Al l; ch~ by the present
invention which i9 based on the discovery that flexible plastic labels
which exhibit excellent ink-rr;ntAh;l;ty, excellent laser-markability
and excellent ' rAl properties can be produced by in~L~L~ing a
suitable laser-opaque material into the core layer of a multilayer
~ L.u~te of the type previously used for labeling flexible plastic
bottles.
Surprisingly, it has been found that by burying the laser-opaque
materials in the core rather than in the surface layers of these
multilayer coextrudates, neither the surface properties of the product,
which control its ink-printability, nor the gross, -hAn;rAl properties
of the product, which control the ability of the product to be
m~n;r~-lAtA~ properly in modern high speed equipment, are compromised.
At the same time, it has also been found that intense, highly visible
contrasting marks can be produced in light-colored or tr~ncrAr~nt
.~e~LLuù~Les made in this manner using conventional laser marking
technology even though the laser opaque materials are restricted to the
core layer and not present in the product surface where the laser lisht
first i.-.pinges on the product.
Accordingly, it is possible in ~rrnr~Anre with the present
invention to produce flexible, plastic labels for affixing to flexible
plastic bottles, as well as webs or sheets of flexible plastic
coextrudates useful in -~mlfArt~rlnrJ such labels, which exhibit the
same excellent ~ nAr;nn of ink-printability and other mArhAn;rAl
properties as prior labels and which at the same time are readily
laser-markable with conve~tional laser marking technology.
SUBSTITUTE SHEET (RULE 26)
.
~ W 09~/34263 2l 92850 I~ln -7~
_S_
n~TD TT.T~'
The present invention utilizes known laser marking technology to
,~ impart laser imprinted images to the unique, flexible, plastic label9
made in A~rnr5~n~ with the present invention.
s These unique plastic labels are multilayer .~AL.~tes which
are produced by rn~Yfrllc; nn of at least two di~ferent polymer materials
to ~orm a product with at least two and preferably at least three
distinct polymer layers bonded together.
In general, such products are composed of an inner core layer
and at least one outer skin layer. Usually, the product will have two
outer skin layers, one on each side. One of these outer skin layers is
typically intended to be ink printable ~hereinafter ~printing skin"),
and accordingly the material used to form this layer and the manner of
its extrusion are selected to maximize its ability to accept and retain
printing ink. Usually, the other outer skin (hereinafter "bonding
skin") is intended ~or bonding or f~ tAt;ng bonding of the label to
a bottle. Depending on the chemical nature of the core material, the
method of bonding and the chemical nature of the bottle, this means
that the bonding skin layer can either be adapted to receive a
~ , ~ly applied adhesive or, in fact, may rnnctitll~e the a & esive
itself.
For example, where a label having a highly olefinic core layer
is intended to be bonded to a bottle with an acrylic latex-b_sed
pressure sensitive adhesive, the bonding skin is preferably a material
which promotes adhesion of the acrylic adhesive to the olefin core, for
example, an olefin copolymer ~nn~Ain;ng polymerized vinyl acetate.
Where, however, a label having a highly olefinic core layer is intended
to be attached by IMFL to a highly olefinic bottle made, for example,
from HDPE ~high density polyethylene), the bonding skin layer can
itself comprise the heat-activatable adhesive normally used for this
purpose. A homopolymer or copolymer of ethylene or propylene is a good
example of an appropriate material for this purpose.
The thickness of the inventive labels can vary widely.
Typically, they range between 0.5 and 15 mils, more preferably 1 to 10
mils, even more preferably between about 2 and 5 mils, thick. of this
amount, the printing and bonding skins each occupy about 5 to 25
percent of the thickness of the label, more typically about lo to 15
percent of the thickness of the label, while the core layer occupies
the rest.
In most ~pl;~Atinnc, --n~fA~tnre of the inventive label~
involves production of a ~nntin-lnl-c sheet or web of the .~ d~Le,
nr;~n~A~;nn of the web or sheet usually in a single direction (machine
direction) only, and finally cutting or otherwise subdividing the web
or sheet into individual, discrete labels.
SUBSTITUTE SHEET (RULE 26)
.
W095134263 2 1 9 2 8 5 0 ~ .c8
In the case of pressure sensitive adhesive labels, the
~OCAL~ l web or sheet after nri~nrAt;nn is usually laminated to a
release liner , _ -q;ng the pressure sensitive adhesive, a release
agent such as a silicone resin and a paper or fllm backing layer. The
S laminate so formed is then typically slit lnng;tl~;nAlly into strips
and the strips wound up on spools, which are stored and/or sold, as
desired.
When it is desired to make and use labels, the laminate strip
after unwinding from the spool is fed to a printer/die cutter. This
machine ink prints the desired graphics on the coextrudate layer and
itmediately cuts this layer plus attached adhesive into individual
labels. In this cutting operation, a small strip o~ the coextrudate
layer is typically left between adjacent labels so that the ~ 5_lP
layer a}ter cutting i9 composed of a plurality of individual, discrete
labels plus an intergral matrix of coextrudate material surrounding the
individual labels. This matrix is then removed leaving a strip
comprising ~a ~nnt;n~-nllq paper backing layer carrying discrete,
physically separated labels thereon, each label comprising an ink-
printed ~o~ with attached pressure sensitive adhesive mounted
on the backing layer via a silicone release agent. This strip is then
fed to an automatic label applying machine which ~-n;~nlAt~q the strip,
for example, by sliding or rolling the strip around a peel plate at
high speed, to oause the individual labels to ~ lly detach from
the back,ing strip and be projected onto suitably placed bottles.
In the case of IMFL, the procedure is similar, except that the
~c~L~dcd web or sheet is not laminated to a release layer. Rather,
the web or sheet, after optional winding up into bulk rolls for
storage, is slit and subjected to printing/die cutting with the
individual labels produced thereby being bundled together in a stack.
The blow-molder then loads individual labels from the stack into the
label magazine of his blow-molding machine for automatic ;nrnrpnrAt;nn
into the blow molded bottles as part of the bottle forming operation.
In both I~FL and pressure sensitive adhesive labels, it is
conventional to employ coextrudates which have been oriented in the
lnng;tl1~nAl~ or machine, direction only. Typically, orientation is
done by stretching the ~c~L~d~Le while still hot in the machine
direction at a stretch ratio of about 2:1 to about 9:1, with stretch
ratios of 4:1 to 6:1 being typical. This results in a qign;f;~Ant
decrease in overall film thickness as well as aiju~L..._.lL of the
1 ' ;cAl properties of the ~ L~d~Le in a known manner. For
example, using a S:l stretch ratio will reduce the overall extrudate
thickness from 16 mils at the extrusion nozzle to approximately 3.2
mils after stretching and will orient the polymer chains in the machine
direction to thereby impart rnnR;~rAhl~ stiffness in this direction
SUESTITUTE SHEET (RULE 26)
. . , . = = = ~
_, _
~ W 095l34263 2~92850 r "~
but not in the L~u~ direction. Other known methods for orienting
polymer films, for example compression nr;~ntAr;nn or nblowing" a film
produced by extru5ion through an annular ori_ice, can be used.
The hot-otretched ~e~L~d~Les produced as described above can
also be annealed or "heat set" in accordance with known t~rhn;rpl~q
Typically, this i8 done after extrusion and initial chilling of the
extrudate by reheating the extrudate to an elevated t, ~ e, for
example, 300~F.
After coextrusion, nr;ont=t;nn heat setting, etc., the
~t~L~d-Les can oe directly processed into labels. More typically,
however, the u~c~L~u~hLes are taken up (i.e. wound around) suitable
cores to form rolls of material typically rnntA;n;ng 500 to 15,000,
preferably 2,000 to 10,000, linear meters of material in the form of
rnnt;m1n1lc sheets or webs. Such rolls, which can be suodivided
lS radially ~i.e., cut in planes perp~n~;r--lar to their axes to form rolls
of smaller axial width) or left as is, can be stored, shipped and sold
for use as needed.
Processes for forming~n~ t~q in the manner described above
for use as flexi_le labels for flexible bottles are well known in the
art and shown, for example, in the above-i~ntif;~ patents. Any such
procedure can be used in Arrnr~Anre with the present invention.
The ,~e~L~hLes of the present invention can be formed from any
materials commonly employed for making ~ le flexible plastic
labels. For example, a suitable material for making the core layer for
2s many Aprl;rAt;nnA in Arrnr~Anr~ with the present invention is
polyethylene of low, medium or high density between 0.915 and 0.965
specific gravity. This is a relatively low cost, extrudable film-
forming material whose stiffness is dependent, among other things, on
the density selected and whose body and strength are 5llff;r;rnt for
most uses. Polyethylene of lower densities, down to a specific gravity
of 0.890, may be employed for greater flr~;h;l;ty,
A preferred material for the core layer i9 polypropylene (or a
propylene copolymer) having a flex modulus ranging between about
130,000 and 300,000 psi at 73~F., depending on the stiffness desired.
3S Still other preferred materials for forming the core layer comprise
copolymers of olefin monomers with ethylenically.-nqAt..rAt~ carboxylic
acid ester ~ , such as ethylene-vinyl acetate copolymer, as
well as blends of such copolymers with any and all of the other
polymers and copolymers described above. Still other preferred
materials comprise physical blends of (1) polypropylene or copolymers
of polypropylene and polyethylene and (2) ethylene-vinyl acetate (EVA)
in weight ratios ranging from 50/50 to 80/20, preferably 55/45 to
65/35.
SUBSTITUTE SHEET ~RULE 26)
WO 9~134163 2 ~ 9 2 8 5 ~ 8
-B-
Por clear label Arrl;rAtinn~, a physical blend of (1) a
copolymer of polypropylene and polyethylene and (2) ethylene-vinyl
acetate (~VA) i3 also preferred. For opaque film label9 ~rrl;rAt;nrc,
a preferred core layer is a physical blend of polypropylene and EVA.
S Polystyrene is also a candidate material for the core layer
particularly where a sti~fer label i9 desired.
In order to make core layers opaque, various inorganic fillers
may be i.~ L~L-d into the polymer forming the layer. Useful fillers
include calcium carbonate, titanium dioxide and blends thereof.
Pigments and dyes can also be added for imparting color thereto.
Examples of materials found suitable for the skin layers of the
inventive labels are materials which are formed ~L~' lnAntly from
polyolefins. By being formed "pro8nm;"A"tly from polyolefin~ is meant
that the layer is formed from a homopolymer or copolymer of a
polyolefin or blends of such homopolymers and/or copolymers, with the
proviso that at least SO~ of the polymerized monomers in the layer are
polyolefins. Examples o~ such materials are homopolymers and
copolymers of ethylene and propylene such as polyethylene,
polypropylene and ethylene/propylene copolymer, copolymers of olefin
monomers with ethylenically ~ t~ratod carboxylic acid or ethyleni-
cally ~I~AAt~rAt~ carboxylic acid ester ~ such as ethylene-
vinyl acetate copolymer (EVA) and blends of such homopolymers and
copolymers. In m~ny Arrl;rAt;n"q, the polymers, copoiymers and blends
describe,d above in rnnnort; nn with the core layer can be used.
Other materials useful for maklng the outer skin layers of the
inventive labels include meltable film-forming s~lhctAnroc used alone or
in ~ nAt;nn such as polyethylene methyl acrylic acid, polyethylene
ethyl acrylate, polyethylene methyl acrylate, acrylonitrile butadiene
styrene polymer, polyethylene vinyl alcohol, nylon, polybutylene,
polystyrene, polyurethane, polysulfone, polyvinylidene chloride, poly-
propylene, polycarbonate, polymethyl pentene, styrene maleic anhydride
polymer, styrene acrylonitrile polymer, ionomers based on sodium,
potassium, calcium or zinc salts of ethylene/ methacrylic acid,
polymethyl methacrylates, r~ ncirc, fluoroplaEtics, polyacryloni-
3s triles, and thPrmnpl~ctic polyesters.
The preferred materials to use in forming both the core and the
skin layers of the inventive ~ S-toc are basically matters of
choice and depend on the particular Arp1;rAt;nnc involved. The
foregoing patents and pl-hl;rAt;nnc incorporated herein by reference go
into great detail in oYrlA;n;ng how to pick particular materials for
p~rticular uses and these torh";ql-oc can also be used in accordance
with the present invention to design a particular coextrudate for a
particular utility.
SUBSTITUTE SHEET (RULE 26)
WO 95l34263 ~ C8
~ 21 9285()
g
In accordance with the present invention, flexible plastic
labels as described above are made laser-markable hy including in the
., core layer of the label a laser-opaque material. By laser-opaque
material is meant any material which will ahsorb or reflect laser light
50 as to cause marking of the polymer layer in which the laser-opaque
material is contained. Surprisinyly, it has been found that the
intensity of the marks made as a result of laser marking will not be
_ ~ ce~, and in fact may be improved, by restricting the laser-
opaque materials to the core of the extrudate rather than in its skins.
Moreover, keeping the laser-opaque material out of the skins also ha5
the hon~f;r;a~ effect of not ~lot~r;r~ly affecting the physical
properties, particularly the smoothness of the skins or their chemical
nature either. Furthermore, by keeping the laser-opaque material in
the core only, the coextrudates can be made without adversely affecting
the variou5 ~o~hAnir~l properties such as ~; ;mnAl stability,
stiffness, high speed ~;Qpo"QAh;l;ty, die cuta~ility, matrix
str;rAh;l;ty, reposit;~nAh;l;ty and the like of the label product.
Any type of laser-opaque material can be employed in a~Ld~n~G
with the present invention. In this rnnnor~;rn, there are many
materials known for their ability to absor_ and/or reflect laser light
of different wave lengths and energy densities and, as a result,
"interact" with a polymer materlal in which they are contained to cause
a visible mark to form. The type of ~;ntor~rt;~n,~ e,g., thermal
~ogra~At;rn of the polymer, simple chemical reaction, .~ n of gas
2s bubbles, etc., varies depending on the type and operation of the laser
employed as well as the type of polymer material employed, and
accordingly there must be a "match~ of the laser-opa~ue material with
the polymer employed as well as the type and operation of the laser
employed. In a~L.k~l~G with the present invention, any known laser-
opaque material can be employed, so long as it "matches" both thepolymer as well as the type and operation of the laser employed.
The preferred laser-opaque materials used in Q~LdCUICG with the
present invention are solid, particulate materials. Solid particulate
materials having a high aspect ratio, particularly those which have a
platelet structure, are especially preferred When particulate
materials are used, it is preferable that they have an average particle
size from 0.2 to 400, preferably 0.5 to 60, most preferably 1 to 2s
microns.
Examples of this type of laser-opaque materials for use in the
present invention, particularly with respect to C02 TEA lasers as
~;arl.cao~ oelow, are kaolin, mica, mixtures o_ mica and titanium
dioxide and woll~atnn;to. Also useful are the various types of laser
markable materials shown in the following patents, the disclosures of
which are ;nrrrprrArod herein by reference: European Patent 0 190 997;
SUBSTITUTE SHEET (RULE 26)
W 095l34263 2 1 9 2 8 5 0 r~
-10 -
U.S. 4,595,647; U.S. 4,654,290; U.S. 4,753,863; U.S. 4,816,374 and ~.S.
4,861,620.
Especially preferred laser-opaque materials are titanium
dioxide-coated mica particles. These materials are commercially
s available from E. Merck ~nrpArat;An of ~awthorne, New York under the
~ n~r;An AFFLAI~ and The Mearl Corporation of New York, New York
under the A~;gnAt;nn of MEARBINX luster pigments. These materials
typically have particle sizes of 1 to 200, preferably 1 to 60, more
preferably 1 to 25 microns.
The amount of laser-opaque material to be incorporated into the
core layer of the inventive c~e~Lud~te products can vary widely.
Basically, the minimum amount is that amount which is sufficient to
form a visible marking of the desired intensity. The maximum amount,
in turn, is usually dictated by economics, amounts over that necessary
to produce a mark of a desired intensity being ""., r ~y. Typically,
the amount will be on the order of 0.1 to 10 percent by weight, based
on the weight of the material forming the core layer (including any
other filler or pigment such as titanium dioxide, calcium carbonate and
the like). More typically, the amount of laser-opague material will be
on the order of about 0.5 to 5 percent by weight,
In this regard, it is convenient to refer to the amount of laser
opaque material in the core layer of the inventive labels in terms of
effective thickness. By "effective thickness" is meant the number
obtained by multiplying the thickness of the core layer, measured in
2s mils, times the rnnr~ntrat;nn of the laser-opaque material in the core
layer, measured in weight percent expressed as a decimal. Measured in
this way, it is preferable that the amount of laser opaque material in
the oore layer be enough so that the effective thickness thereof is
0.005 to 0.15, more preferably 0.01 to 0.10, even more preferably 0.02
30 to 0.06.
In order to laser imprint the desired image or ;nfnrm~t;An onto
labels made in accordance with the present invention, the labels are
;rr~a;ntr~5 with laser light rnnrr1n;nrJ or embodying the desired
; - ;An or image therein.
As a practical matter, only three basic types of marking lasers
are now available commercially. These are eximer lasers based on rare
earth gas halides, Nd/YAG systems and pulsed carbon dioxide lasers. Of
these, the Nd/YAG systems and carbon dioxide lasers are typically used
for plastics. ~owever, eximer lasers have also been used for this
purpose. In ~ Ld~l.ce wlth the invention, each of these types of
lasers can be used, although pulsed carbon dioxide TEA (LL~U1r~eLr~=
excited ~L...~ Le~ lasers are preferred from the point of view of cost
and reliability.
SUBSTITUTE SHEET (RULE 26)
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~ W0 95/34263 -ll- 2 1 9 2 8 5 0 ~ ,~C-~R
The conditions of laser marking vary widely and are dependent on
a number of factors such as the identity and amounts of laser-opaque
materials in the films, film thickness and the like.
In the case of the preferred TEA carbon dioxide laser (wave
S length 10.6 m;~ 'nrc -- infrared range), energy densities on the
order of 0.8 to 36, preferably 1.8 to 28.8, Joules per square
~nt; '~r per pulse at pulse durationg of 50 to l,000, preferably 100
to 300, "~,..-~c., 1~ are appropriate.
The particular operating variables of the lager to employ in a
.0 particular : ~ ' of the invention can be easily ~torm;n~d by
roUtine ~Yp~r; ';nn. As well appreciated by those skilled in the
art, the rate in whioh energy is supplied by the laser should not be so
great that the film is destroyed or otherwise~n~r~pt~hly degraded but
yet needs to be enough 80 that indicia of suitable intensity will be
lS produced.
In order to imprint a label by the laser marking technique of
the present invention, the laser beam generated by the laser is passed
through a suitable stencil ~nnt~;nin~ the desired ;nfnrm~t;nn to
generate an information-rnntA;n;ng laser beam. This beam is then
focused onto the label to be marked and the label ;rr~ t~ with the
laser light for the ;~r;nt;ng process. Exactly how this is done is
well known to those skilled in the art of laser marking, and any
conventional procedure for this purpose can be employed in accordance
with the present invention.
25WOR~ING ~MPT.~.C
In order to more thoroughly ;ll~ctr~t~ the present invention,
the following working examples are presented.
In these examples, a hot ~ LL~te was produced in accordance
with the process described in U.S. 5,242,650 with a total thickness of
17.5 mils. The ~oe~L~da-e was then hot stretched to make a film of
3.s mils. In each example, the .~c~L~ te was made with two identical
skins, each 6kin layer making up 10~ of the total thickness of the
coextrudate and the remainder comprising the core.
After m~nl-f~t--re, each film was them imprinted with a simulated
date and lot code by means of a Blazer 6000 Pulsed Carbon Dioxide Laser
made by Lasertechnics Corporation of Albuquerque, New Mexico. The
laser beam produced was passed through a mask having a 6imulated date
and lot code about one inch wide and then focused to a reduced size
onto the target film to imprint the image thereon. Tmrr;nt;ng was done
at different energy level9 (3 and 4 Joules per pulse) and different
reduction ratios (ratio of mask size to image size).
In these experiments, the laser beam as produced by the laser
has an energy density of 0.8 Joules/cm', at a maximum energy of 5
SUBSTITUTE SHEET (RULE 26~
W 095/34263 21 928~0 P "~J"~f
-12-
Joules. The energy density of the beam as it strikes the target can be
reduced from this value by reducing the energy of the laser or
increased by reducing (nArro~;ng) the beam size between the mask and
the surface of the target. In the following working examples, the
approximate energy densities of the laser beam striking the targets
were as follows:
p~-lc~ Enerqv P~ tion Ratio Enerqv Densitv
4 ~oules 2.75:1 5 Joules/cm'
4 ~oules 2.0:1 3 Joules/Cm'
3 Joules 2.75:1 4 ~oules/cm
3 Joules 2.0:1 2 ~oules/cm'
Two mask~ were used to optimize the width of the image to give
four 0.95" charzcter for the 2:1 size reductio~ ~reduction ratio), and
two rowc of O.9C~ rhAr~t~rc for the 2.75:1 size reduction. The larger
characters apparently ;nfl--~nr~ the visual impact oi the mark, as the
mark contrast seems to be higher for the larger mark than the energy
density would predict, as more fully illustrated below."
The laser produces silvery-gray laser imprinted marks. The images
so produced were visually observed and rated using an arbitrary scale
of irom 0 (no mark) to 10 Iblack and very distinct).
The following examples were r~nS--~te~-
r 1~ 1
A ~e~L~ud~Le having the following ;t;~n was produced:
Table 1
Weiqht
2s Printing Polypropylene homopolymer IHPP) so
Skin Ethylene-vinyl acetate copolymer ~EVA-18% VA) 50
Core Layer Calcium particulate carbonate ~ 40
(40~ part.culate CaC0, in HPP)
Ethylene-viny_ acetate copolymer (EVA-13% VA) 35
Titanium diox.de ~ e 15
(so~ Ruti_e TiO2 in HPP)
AFFLAIR 110 ~ 10
(20~ TiO2 coated mica in HPP)
Eonding Polypropylene homopolymer (HPP) 50
Skin Ethylene-vinyl acetate copolymer IEVA-l3~ VA) 50
The results are obtained by laser-imprinting their
coextrudate in the manner described above.
SUBSTITUTE SHEET (RULE 26)
~ W 095~42C3 -13- 21 928~0 r~ s.: ~8
Table 2
Concentra-
tion of AFFLAIR Visual Intengity of Image at
AFFLAIR 110 Effective different energy intensities
ExamDlein core Thirkn~QQ An~ P~ct;nn Ratios
3 ~oules 4 ~ouleg
M M M M
2:1 2 75 1 2 1 2 75 1
1 2~ 0 056~ 6 7 7 7
~ (3 5 mils) x (80~ x (20~) x (10~) = 0 056
S Table 2 shows that the lager marking techni~ue ag described above
produced images having a fairly high degree of contrast or inten3ity
under ~cn~nt;Ally all the rnn~;tinnQ tried in the r~yr1 , This
shows that images of good intensity can be produced in AornrAAnr~ with
the present invention, even though the laser-opague material is buried
in the core and not preser,t in the skin layers
r 1~ ~-6
Example 1 was repeated except that initial film thickness was 15
mils before stretrhinrJ and final fill thickLess was 3 mils after
stretchir,g In addition, the amount of laser-opaoue material in the
~5 core wag varied from 0 to 3 3 weight percent, based on the weight of
the core, to ;ll~1ctrAte the effect of varying ," ~ ~l ;nn of this
material The specific compositions of the different layers used in
these examples is set forth in the following Table 3 Unless otherwise
indicated, the polymers and copolymers used have the same ~ , t;nnQ
as in Example 1
~able 3
Printing Polypropylene homopolymer 40
Skin Ethylene-vinyl acetate copolymer (EVA) 50
Polypropylene-maleic anhydride graft copolymer 10
(0 25 weight % maleic anhydride)
Core Layer Propylene-ethylene random copolymer 40
(3 2 weight ~ ethylene) 35-X
Ethylene-vinyl acetate copolymer (EVA) 20
Titanium dioxide nnnr~ntrAtr 5
(so~ Ti~/S0~ polypropylene) X
Polypropyl~ lrir anhydride graft copolymer
AFFLAIR 110 ~ ~L~Le (40~ in EVA)
2S Bonding Polypropylene homopolymer 40
Skin Ethylene-vinyl acetate copolymer 50
Polypropyl~.e ~~l~;r anhydride graft polymer 10
SU9STITUTE SHEET (RULE 26)
W O95/34263 2 1 9 2 8 5 0 ~ r ~ ~
-14-
The following results were o~taiDed:
Table 4
rnn_ nr~ r~
i ellO in core ~iwu~l Intenr}cy of lF~ge ~t
E~imlL~ AFFLAIR llO~ (Wx )) Thlc~nerr 2eduction R~tios
~ ~ ~oule~
M M RR M
~i~L2.75:1 2 1~_}
.i ~ o o O O O O O
3 1 5 0 6 01i4 2 ~ I 3
~ i 0 96 .0~3 3 3 i' 4
s ~ 75 1 9 0~56il 5 5 51
6 9 5 3.~ 091~5~ 6 6~ 7
~ Equrln Y/O i rince AFFLAIR ir iOI of the AFFLAIR 110/EVA o7ncentr te
lO The foregoing result~3 show that the contrast of the vi3ual images
produced in ~rrrr~n~ with the present invention increases
proportionally with the effective thickness of the laser-opaque
material in the core layer. In addition, these example3 show that the
image3 produced appear to be more intense at higher reduction ratios
and also at higher laser impulse energy levels.
r l~A 7-9
Example 1 was repeated except that the ~ L~ tes in Examples 7
and 8 had the composition set forth in the following Tables 5 and 6:
~ ble S
20 Printing Polypropylene homopolymer (HPP) 40
Skin Ethylene-vinyl acetate copolymer (EVA) 50
Polypropylene-maleic anhydride graft copolymer 10
Core Layer Propylene-ethylene copolymer 35
Ethylene-vinyl acetate copolymer (EVA) 35
Titanium dioxide l.,.. r. m.~lr 20
Polypropyl~ r-l ; r aDhydride graft copolymer 5
AFFLAI~ 110 ~... ,l .~t~ (20~ in EVA) 5
i3Onding Polypropylene homopolymer 40
9kin Ethylene-vinyl acetate copolymer 50
Polypropylene-maleic anhydride graft polymer 10
2s Table 6
Printing AFFLAIE 110 r~nr~ntr~t~ ~20~ in HPP) 40
Skin Ethylene-vinyl acetate copolymer (EVA) 50
Polypropylene-maleic anhydride graft copolymer 10
Core Layer Propylene-ethylene copolymer 40
Ethylene-vinyl acetate copolymer (EVA) 35
Titanium dioxide rrn r n t r~ t 20
Polypropylene-maleic anhydride graft copolymer 5
SUBSTITUTE SHEET (RULE 26)
... _ . _ . . = . . . , .. . . ,,, _ , .. .. . .
~ W095~342C3 21 92850 r~". 't''~R
--15-
Printing AFFLAIR 110 ~ e (20~ in HPP) 40
fikin Ethylene-vinyl acetate copolymer (EVA~ 50
Polypropylcnc r-lr; r anhydride graft copolymer 10
Bonding AFFLAIR 110 cv~.. ~LL~Le (20~ in ~PP) 40
Skin Ethylene-vinyl acetate copolymer 50
Polypropylene-maleic anhydride graft polymer 10
In addition, in Example 9, a single layer extrudate was used, this
single layer having the same composition as the core layer of Example 7
and the same overall thicknesa as the total extrudate thickness of
Example 7.
The following results were obtained:
~a~le 7
Rel~lve
1hloknerw of
Cont inlng o~ A~L~IR Vleunl Ineensiey of Im-g- ue
AffL LeAcrlY- Lnyer ARYL~IR EffcelYc Differlng Energy Intenslcles nd
E~=~le~3 ~ilJ rnrAII (wc ~)T~ ~w~.................. Reduo~ion R~io5
3 70ule~ 4 ~oul~s
RR ~R l~R RR
11~ikl~sa ~ ,7e 1
7 801 l 0 024 3 3 ~ 4
8 lO~ 3,0 ,02~ ole~ ol-~
9 lO0~ l,0 030 3 3
Examples 7 and 8 compare the effect of placing the laser-opaque
material in the core rather than in the skin. In this regard, note
that the cAlrl~lAt;rn~ of effective thickness in Example 8 assume that
only the outer skin layer is effected by the laser impregnation. In
other words, in asDessing the visual impact of a laser ; , ~d~ion,
any effect on the lower skin layer is disregarded.
Example 7, illustrating the present invention, shows that when the
laser-opaque material is present in the core layer at an effective
thiokness of 0.024, visual images having A;Jrn;firAnt contraat are
produced at all operating rnnA;t;nnc, On the other hand, when the same
amount of laser-opaque material as used in the core of Example 7 is
placed in the printing skin of the Example 8 composite, images with
25 little if any contrast are produced at reduction ratios of 2:1r while
holes are produced in the printing skin at the higher reduction ratio
of 2.75:1 This shows that the images produced by laser marking are
not simply a result of the amount of laser opaque material in the
system but also depend on where it is located. In addition, this also
shows that locating the laser opaque material in the core, rather than
in the skin layer which first receives the laser light impinging on the
article provides a R;rJn;f;rAntly, and llnryrer-t~Aly~ superior result.
To show the effect of not having any skins at all, Example 9 was
rnnAllrt~A In this example, a single layer extrudate having the same
SUBSTITUTE SHEET ~RULE 26)
, . . .
w 095/34263 2 1 9 2 8 5 0
-16-
thickness as the .~ r~. of Examples 7 and 8 was filled with the
same ,,, ~ irn of laser opaque material as in the core of the
Example 7 ~uc~L~ulate. This means that the Example 9 extrudate
contained a rir;n;f;r~ntly greater overall amount of laser-opaque
S material than the ~ e of Bxample 7. ~otwith~tA~ , t_is
greater amount of active ingredient, the images produced in the Example
9 .~c~LL~daLe have r~ t;Ally the same visual impact as those of the
Example 7 ~c~Li~te.
This shows that burying the laser-opaque material in the core and
thereby keeping the laser-opaoue material out of the skins does not
adversely impact the contrast or intensity of the images produced.
This, in turn, shows that images of Arc~ptAhlr contrast can be produced
with less overall laser-opaque material and further that this
adval.La~ 9 result can be obtained while the outer and inner skin
lS layers are ~A;nt~;n ~ free of this material so that they can retain
their _ hn~~ and ink-printability properties. T_is also means that
it is possible to adopt the use of laser marking with opague materials
in such a way that the laser opaque material is kept away from the
' rAl equipment involved in processing, such as the die lips of
the extrusion die, or the calender rolls used in s"h~rrlllrnt processing.
This prevent9 die lines from appearing in the product as well as
excessive wear on the die lips and other equipment which would
otherwise occur.
T~r,;~rntAlly, note that the results obtained in Example 7 are
almost identical to those obtained in Example 4 in which the
coextrudate had an effective t_ickness of laser-opaque material of
0.023. This, in turn, shows that l'effective thickness'~ is a meaningful
number.
~ lr.~ 10-14
Examples 2 to 6 were repeated except that the Afflair additive was
Afflair 100, rather than Afflair 110. Afflalr 100 i8 slightly larger
in particle size, and as can be seen below appears to be slightly less
effective.
Also, in some of Examples 10-14, a single layer extrudate was
produced rather than a multi-layer extrudate, while in one of these
examples, Example 14, the extrudate was not oriented after extrusion
but was simply produced as cast.
SUESTITUTE SHEET (RULE 26)
~ W0 ~5l34263 2 1 9 2 8 ~ ~
-17-
The results obtained are set forth in the following Table 8:
Table 8
Concentro
AF~LAI}
Mulcl Tot 1 aOtiye MoDrO EffecC nt Different Energy Intenei-
Ex mvle Layer? mlls Laver Da~t Thiok t1.. dnd ~.A~ tloo
3 .Toule~
M M M M
1 ~ 75 1 2 1 ~ 75 1
9v 2 8 0 9 MD0 02s2 2 l 3 3 3vl~o
11 Ye- 3 5 0 9 MD0 0252 lt 3 3
11 do 3 O O 9 MD0 027 i I 3 3 4
13 Y A 3 f 2 1 MD0 0586 4 4 ~ 5
14 I!lv 3 0 2 1 Cd~t OSaE 4 4 4 4
~ orienced in the m ohine direction only
Comparison of Examples 10 and 11 in the above Table 8 shows that
providing an extrudate with protective skins as ~ 1; cho~ in
accordance with the present invention, does not hurt and also may even
prevent burn through at more intense ~nn~; t; nnR ~ Note in particular
that the composite of Example 11 is PRR~nt;~lly the same as Example 10
15 in terms of the active thickness and active ingredient .,..... .~ i nn,
the only difference between that in Example 11, protective skins having
no laser-opaque material therein are provided. This is R;gn;fi~nt in
that it shows the .u~ALL~Led skins can be fine tuned to meet
u. . r~ - . .,. ~ criteria without reducing laser r-rk~h;l;ty at the same
additive cost.
Comparison of Example 12, in which a single layer extrudate
thicker than that of Example 10 and hence having more overall laser-
opaoue material than in Examples 10 or 11 (0.027 effective thickness
r~ther than 0.0252) shows that the visual impact of this extrudate i5
no better than that of the ~u~L~d~Le of Bxample 11 even though the
extrudate of Example 12 has more laser-opaque material.
Examples 13 and 14 are r,3hl 0 in that both have the same
effective thicknes3 of laser-opaque material. ~owever, the Example 14
product, which is a single layer extrudate not subjected to
nr;~nt~t;~n, provides a visual impact which is noticeably less intense
than that provided by the Example 13 product which i5 composed of
multiple layers having been oriented in the machine direction. ~his
shows that the ~~n~t;nn of burying the la9er-opaque material in the
core and orienting in at lea3t the machine direction f~; 1; t~to~
reduction in the amount of expensive laser-opaque material necessary to
produce a visually acceptable image.
SUESTITUTE SHEET (RULE 26)
WO 95/34263 2 1 9 2 8 5 0 P~l/L_ 5 ~ -~C8
-18-
.~mnl ~ 15
The procedure of Examples 2 to 7 was repeated except that the
thickne3s of the .~LLu~Le passing out of the extrusion die was 12.5
mils and the ~ L~u~Le so made was stretched to a iinal product
S thickness of 2.5 mils. A7so, the composition of the individual layers
of the ~e~LIud~te was changed so that the .~e~L~u.l~Le product was a
slightly hazy, ~ca~nt;Rlly LL~Ia~L~L film The ~ t;nnq of the
individual layers of the ~e~LLud~te are set forth in the following
Table 9:
Table 9
Printing Polypropylene homopolymer 40
Skin Ethylene-vinyl acetate copolymer ~EVA) S0
Polypropylene-maleic anhydride yraft copolymer 10
Core Layer Propylene-ethylene copolymer 60
Ethylene-vinyl acetate copolymer (EVA) 32.5
Polypropylene-maleic anhydride graft copolymer S
AFFLAIR 110 ~ Ir (40~ in ~A) 2.5
Ponding Polypropylene homopolymer 40
lS Skin Ethylene-vinyl acetate copolymer (EVA) S0
Polypropylene-maleic anhydride graft copolymer 10
The results obtained are set forth in the iollowing Table 10:
Table 10
r__~._r~.r~_
ol ~b2~UR
~ llo inAot~e ~ffeotlve ~tDtffrertb~er~y Inten~lti~ ~d
.~ckn~s ~ed~tton ~tio,
3 Soule~ 4 ~rlle~
Rl M lEI BR
~:1 Z.75:1 2:1 Z.
1 0 0 . 020 b B b b
From Table 10, it can be seen that under all operating rnn~;t;rn~
a very high visual impact image was produced even though the effective
thickness of the laser-opaque material in the active layer was
relatively low. This ;11l1ctr~t~q that the present invention is
particularly efiective in providing laser-markable images on
L~ LellL labels.
r 1~ 16
The following example d~ llaLlrLes the present invention is
readily ~rr~; r~hl ~ to making in-mold, machine direction oriented
labels.
The recipe for an opaque white flexible film with a print layer,
and an adhesive layer, is as follows:
SULSTITUTE SHEET (RULE 26)
~ W 095/34263 -19- 2 1 928 50
T~hle 11
Top Polypropylene homopolymer 50
Ethylene-vinyl acetate copolymer (~VA) 50
Central Propylene-ethylene copolymer 70
Ethylene-vinyl acetate copolymer (EVA~ lO
~ Titanium dioxide rnnr~nrr~ 15
AFF1PIR llO .. ,.. _.t._l~ (16~ in EVA) S
Bottom Low-density polyethylene (LDPE) 24
Ethylene-vinyl acetate copolymer (EVA) 40
~ Anti-block rnnr~n~rAt~ (20i in polyethylene) 36
S The above film was ~ LLu~lud as in previous Examples 2 through 7, but
the coextrudate thickne3s was 20 mils, and stretching was done to
produce a film of 4.0 mils. As in the previous examples, the thickness
of the top and bottom layers were each 10~ of the total, the certral
layer making up the remaining 80~.
Table 12
Or AFPL~R
110 ir. Accive i3flcctlve DLli rene Ener9ytIyntor ltiU~ie t
~~I-~t ~) ~Ç~ p.,~ tio~
~ ~ .Jo~le~
Rl~ M RR Lll
~ a.~.L 2: 1 2 . 75:
l~0.8 0.0202~
Although only a few. ' ' ~ q Of the preser,t irvention have been
described above, it should be appreciated that many modifications can
lS be made without departing from the spirit and scope of the present
irvention. Por example, although the multi-layer ~ aLes of the
present invention have been described above in terms of three layers,
it should be appreciated that any number of plural layers can be
employed. For example, where necessary, suitable tie layers for
bonding ~;qq;m;l~r skin and core layers can be employed. In addition,
a bonding skin layer may be ll.~.Fc. .y in some instances, particularly
wherein a heat sersitive adhesive ~yhih;t;nt7 good adhesion to the core
layer is or will be employed. All such m~S;f;r~;nnq are ir,tended to
be included in within the scope of the present invention, which is to
be limited only by the following claims.
SUBSTITUTE SHEET (RULE26)
