Note: Descriptions are shown in the official language in which they were submitted.
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IMAGABLE LINERLESS
PRESSURE SENSITIVE ADHESIVE LABELS
Backqround of the Invention
The present invention relates to a series of linerless
pressure sensitive adhesive labels having imagable coatings
thereon and more particularly, to a series of linerless labels
comprising a web including on selected portions of its surface
a series of coatings of color formers and color developers
which may be activated, when subjected to heat or pressure, to
form colored areas or images.
In the field of product labeling, direct thermal printing
has been a well-known means of non-impact printing. Direct
thermal printers are capable of forming images by the
application of heat to a substrate containing heat-reactive
chemicals thereon. Typically, a substrate such as paper is
coated with a coating of color forming and color developing
reactants which, when heated, combine to form a visible color.
When such a coated substrate passes under the print head of a
thermal printer, selected areas containing the coating are
activated by the heated print elements, forming colored images
on the surface of the substrate.
It is also possible to achieve colored images from the
use of self-contained carbonless coatings which produce
colored images upon the application of pressure such as that
from an impact printer. Such coatings are known, and
typically contain dispersed color developers and initially
colorless leuco dyes contained in solution within
microcapsules.
Pressure sensitive adhesive labels utilizing such heat or
pressure-sensitive imagable coatings generally include a
substrate having the coatings on its surface, and a pressure
sensitive adhesive on the surface of the substrate opposite
that of the imagable coatings. However, typical pressure
sensitive adhesive label products in current use require that
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a release liner overly and cover the pressure sensitive
adhesive so that the labels may be fed through and imaged in
printers. Otherwise, any exposed pressure sensitive adhesive
will interfere with the handling and printing process. Such
liners, however, add to the expense of manufacturing labels,
add thickness and stiffness to the labels, and create disposal
problems for the discarded liner material.
Attempts have been made to coat a release layer on the
surface of the labels which eliminates the need for a liner
ply and enables the labels to be wound upon themselves into a
roll form without transfer of adhesive to the surface of the
label. For example, Fickenscher et al, U.S. Patent No.
4,851,383 teach a thermosensitive pressure sensitive label in
which the thermosensitive layer is covered with a silicone
layer to enable the labels to be rolled without the use of a
release liner. However, the use of a barrier layer is also
required between the thermosensitive layer and sllicone layer
to prevent discoloration or unwanted color formation in the
thermosensitive layer.
In addition, such labels are fully coated with a
thermosensitive layer and thus do not provide a method for
providing different colored areas or images on a series of
labels. For example, it may be desirable to provide
different colored areas or images on selected portions of a
label to delineate or differentiate information, or to
designate how the article to which the label is attached is to
be processed.
Accordingly, there remains a need in this art for
linerless pressure sensitive adhesive labels which may be
provided in roll form. There also remains a need for a series
of such labels having selected portions which may be activated
by heat or pressure to form-colored images or areas.
Summary of the Invention
The present invention meets those needs by providing a
series of linerless pressure sensitive adhesive labels having
on selected portions thereof a series of imagable coatings
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which may be activated to form colored images or areas. The
labels may be provided in the form of a continuous series of
labels wound in a roll. Alternatively, the series of labels
may be stacked atop one another. In either embodiment, the
labels may be dispensed one at a time from the roll or stack.
According to one aspect of the invention, a linerless
series of labels is provided comprising a series of labels
having first and second major surfaces, said first surface of
said labels including on one or more selected portions thereof
a series of imagable coatings of color formers and color
developers which may be activated to form colored images or
areas, a coating of a release material on said first surface
of said labels which overlies said coatings of color formers
and color developers; and a coating of a pressure sensitive
adhesive on the second surface of said labels.
The label is preferably selected from the group
consisting of coated or uncoated paper, liner stock, calendar
liner, thermoplastic polymeric film, and heat-resistant
polymeric film. One heat resistant polymeric film, for
example, is a polyimide film.
The first surface of the label includes on one or more
selected portions thereof a series of imagable coatings of
color formers and color developers which may be activated to
form colored images or areas. A coating of release material
is applied to the first surface of the label and preferably
overlies the coatings of color formers and color developers.
A coating of a pressure sensitive adhesive is positioned on
the second surface of the label. In an alternative
embodiment, the pressure sensitive adhesive may be pattern
coated on the second surface of the label.
In one embodiment of the invention, the series of labels
are in the form of a continuous web which may be wound so that
the coating of pressure sensitive adhesive contacts the
release material to permit individual labels to be unwound and
dispensed from the roll. If wound on a roll, cross
perforations may also be provided between individual ones of
the series of labels to aid in dispensing them, although the
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labels may also be dispensed from a device which includes a
cutting edge for severing individual labels from the roll.
In an alternative embodiment of the invention, the series
of labels are stacked so that the coating of pressure
sensitive adhesive on the second surface of one label contacts
the release material on the first surface of the adjacent
label in the stack.
In a preferred embodiment of the invention, a base
coating is applied to the label surface prior to the
application of the release material. The base coating acts to
fill voids or irregularities in the substrate and provides a
smooth, receptive surface for the release material.
Preferably, the release material and pressure sensitive
adhesive are selected to provide a release value when the
labels are unwound or peeled from a stack at a 90 angle of
from about 60 to 160 gm/5.04 cm
(2 inch) width.
The color formers and color developers on the web combine
to form colored visible areas including images, symbols,
indicia or the like, when exposed to an imaging force which
may take the form of heat or pressure. Preferably, the color
formers comprise initially colorless leuco dyes, while the
color developers comprise acidic phenolic compounds or resins.
The color formers and developers are preferably contained in a
binder matrix as separately dispersed particulate solids.
Exposure of the coatings to heat such as from a thermal
printer causes selected reactants to melt, permitting the
color former and color developer to mix and react. In one
embodiment, such thermally activated coatings may be coated on
the web as a pattern such as stripes, etc.
In an alternative embodiment of the invention, the color
formers and color developers combine upon exposure to pressure
such as an impact printing device. In this embodiment, the
imagable coatings comprise self-contained coatings of
pressure-rupturable microcapsules containing either color
formers or color developers.
The imagable coatings, whether activated by heat or
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pressure, may form a plurality of different colors on the
label. For example, one portion of the label may be activated
to form a first color, while another portion of the label is
activated to form a second color. It is also within the scope
of the invention to activate selected portions of the coated
areas so as to produce only one color. For example, coatings
which produce different colors may be coated in a side-by-side
relationship around the periphery of a label in the series.
By activating selected areas, the periphery can be made to
show a selected color.
While it is possible to coat the labels in a number of
different areas so that multiple colored images are formed
when the labels are passed through a printer, it is also
possible to coat only one selected area of each label. In one
embodiment of the invention, the labels are coated on selected
portions with a series of imagable coatings with the remaining
areas of the labels not containing the imagable coatings. For
example, if a bar code is to be thermally imaged on a label,
the coating may be applied to one section of a label where the
bar code is to be printed. The imagable coatings may be
applied to the labels in a number of different patterns,
depending on the desired end use.
In a preferred embodiment, a series of repetitive images
are printed on at least a portion of one surface of the label,
where each of the repetitive images corresponds to an
individual label in the series of labels. Preferably, the
repetitive images are printed on a portion of the label which
does not include the imagable coatings.
Accordingly, it is a feature of the present invention to
provide a linerless continuous series of labels having
imagable coatings on selected portions which may be activated
to produce colored images or areas. Other features and
advantages of the invention will be apparent from the
following description, the accompanying drawings, and the
appended claims.
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Brief Description of the Drawings
Fig. 1 is a perspective view of a roll of labels in
accordance with the present invention;
Fig. 2 is a perspective view of a stack of labels in
accordance with the present invention;
Fig. 3 is a sectional view of one label in a series
illustrating one embodiment of the invention;
Fig. 4 is a plan view of one label in a series
illustrating one possible pattern of the imagable coatings;
Fig. 5 is a plan view of another label in a series
illustrating an alternative pattern of the imagable coatings;
Fig. 6 is a plan view of a label in a series illustrating
self-contained imagable coatings;
Fig. 7 is a fragmentary sectional view of a label
illustrating the self-contained imagable coatings;
Fig. 8 is a bottom view of a label illustrating one
pattern of the pressure sensitive adhesive; and
Fig. 9 is a bottom view of a label illustrating an
alternative pattern of the pressure sensitive adhesive.
Detailed DescriPtion of the Preferred Embodiments
With reference to the drawings, it must be appreciated
that Patent Office requirements for solid black line drawings
on a white surface make illustration of some of the subtleties
of our invention relating to different colors difficult by the
required Patent Office drawings alone. Reference to the
following detailed description of the illustration will make
full appreciation of the drawings and our invention possible.
Referring now to Fig. 1, one embodiment of the series of
linerless labels is shown in roll form 10 comprising a web 28
having individual labels 12, 14, etc. The individual labels
may be unwound and severed from roll 10 along perforations 16.
Alternatively, if the roll is mounted in a dispenser having a
cutting edge, the perforations may be omitted, and the
individual labels may be unwound and severed as needed.
The first surface of the web 28 includes a selected area
18 containing an imagable coating of initially colorless color
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formers and color developers. As shown, the coated area 18
has been imaged to provide a bar code 24 and numbers 26 on the
labels.
The web also includes an area 20 which does not contain
5 the imagable coating but which contains a repetitive image 22.
By repetitive image, we mean any background, symbol, object,
lettering, or numbering which is common to and repeated for
each of the individual labels. For example, labels 12, 14 may
be tracking labels which are secured to parcels, packages, and
letters to identify the method of transport (i.e., by ground,
air, etc.). When imaged, the coatings in area 18 provide
unique bar code information which may be used to track the
parcel.
This embodiment of the label construction is also
15 illustrated in Fig. 3 where a partial side sectional view of
an individual label in the series is shown. The web 28
includes a first surface 30 and a second surface 32. The web
can be any of a number of suitable materials including coated
or uncoated paper, liner stock, calender liner (not
siliconized), thermoplastic polymeric film, and heat resistant
polymeric film. One example of a heat resistant polymeric
film is a polyimide.
The first surface 30 of the web is coated on one or more
selected portions with an imagable coating 34 of initially
25 colorless color formers and color developers. As shown in
this embodiment, the imagable coating is coated on only one
selected portion of the label where, for example, bar code
information is to be printed, while the remaining area of the
label is uncoated. Alternatively, the imagable coating may be
coated on two or more portions.
Suitable color formers for use in the present invention
include colorless chromogenic dye precursors known in the art
such as triphenyl methanes, diphenyl methanes, leuco dyes,
xanthene compounds, thiazene compounds, and spiropyran
3 5 compounds such as those described in U.S. Patent No.
5,102,856. Many different shades or hues of color may be
produced on a document by combining color formers which form
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blue, yellow, green and red colors. Black images may also be
produced by using a combination of color formers. Preferably,
the color formers comprise from about 5 to 15~ by weight of
the coating formulation.
The color developers may be selected from acidic color
developers known in the art such as zinc salicylate,
acetylated phenolic resins, salicylic acid modified phenolic
resins, zincated phenolic resins, novolac type phenolic
resins, and other monomolecular phenols such as bisphenol A,
4,4'-isopropylidene diphenol, 4,4'-sulfonyl diphenol, p,p'(l-
methyl-n-hexylidene)diphenol, p-tert-butyl phenol, and p-
phenyl phenol. The color developer is preferably present in
the coating formulation from about 15 to 30~ by weight.
In addition, the coating contains from about 40-70~ by
weight water. Thermally activatable coatings preferably
contain from about 5 to 25~ by weight of a sensitizer. Such
sensitizers are low melting point solids which, when subjected
to heat, melt and become solvents for the color forming and
developing reactants. Suitable sensitizers include B-naphthol
benzyl ether, p-benzyl biphenyl, ethylene glycol-m-tolyl
ether, m-Terphenyl, Bis [2(4-methoxy) phenoxy] ether, and
dibenzyl oxalate.
A binder is also preferably included in the coatings to
improve the rheological properties of the coating for better
printability and to promote good adhesion of the coatings to
the sheet surface. Suitable binders include starch, casein,
polyvinyl alcohol, polyvinyl pyrrolidone, acrylamide/acrylate
copolymers, carboxylated styrene butadiene latex, styrene
acrylic latex, and mixtures thereof.
The coating formulation may also include from about 5 to
30~ by weight of a pigment such as calcined clay, calcium
carbonate, or plastic pigments. Other optional ingredients
include from about 5 to 25~ by weight of lubricant and from
about 1 to 10~ by weight of an anti-fading agent. The anti-
fading agent may comprise hindered phenols of the antioxidant
class such as l,1,3-tris(2-methyl-4-hydroxy-5-
cyclohexylphenyl) butane.
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The coatings are generally applied to the web by any
suitable coating or printing process including flexographic or
gravure printing techniques. The coatings may be applied in
selected areas which can form blocks of background color, or
they may be applied so as to form images, symbols, stripes,
borders, and the like when imaged. Coatings which produce
different colors are preferably coated or printed separately
on each desired portion of the web. The coatings are
preferably applied at a dry coating weight of between about
1.9 to 9.5 gm/m2 (0.50 and 2.50 lbs/17"x22"x500 sheet ream),
and may be selectively printed or coated on the surface of
stock papers during the manufacturing process, although it is
preferred that they be applied in register with repetitive
indicia and therefore applied in-line with printing
operations.
As shown in Fig. 3, a base coating 36 preferably overlies
the imagable coatings 34 which acts to fill in any voids or
irregularities in web 11. The base coating also provides a
smooth, receptive coating for the release material 38 which is
applied over base coating 36. However, it should be noted
that the base coating may not be needed on some substrates
such as polymeric films which may already have a smooth
surface.
Base coating 36 may be a water-based, solvent-based, or
ultraviolet light or electron beam curable polymer which may
be applied in liquid form. Examples of suitable base coating
compositions are taught in commonly-assigned published PCT
International Application No. WO 90/13064, published
November 1, 1990.
A coating of a release material 38 overlies base coating
36. The release material may be any suitable ultraviolet
light, electron beam, or heat curable polymer including
silicone based polymers and acrylate-based polymers. Examples
of suitable release materials for use in the present invention
are disclosed in commonly-assigned U.S. Application Serial No.
08/198,353 filed June 5, 1995 and entitled "Variably Imaged
Linerless Pressure Sensitive Adhesive Labels and Method of
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Making". The release coating should be chosen so as to
provide a release value for the labels when dispensed at a 90
angle of from about 60 to 160 gm/5.08 cm (2 inch) width.
Both base coating 36 and release material 38 must be
substantially transparent so that the colored areas or images
may be viewed therethrough. The formulations listed above
meet that requirement.
Also as shown in Fig. 3, a coating of a pressure
sensitive adhesive 40 is applied to the second surface 32 of
web 11. Generally, the pressure sensitive adhesive may be
selected from any of several known classes of compositions
including hot melt or water based pressure sensitive adhesives
and may be either permanent or repositionable. One example of
a suitable pressure sensitive adhesive is a rubber-based hot
melt adhesive, Fuller HM 1547, which is applied at a coating
rate of from about 38 to 57 gm/m2 (10 to 15 lb/17"x 22"x500
sheet ream).
The pressure sensitive adhesive may also be pattern
coated on the second surface 32 of the web as illustrated in
Fig. 8, which shows an individual label in a series. For
example, the label may be divided into two portions as shown,
where one portion includes the pressure sensitive adhesive 40
and the other portion has no adhesive. The two portions may
be separated by perforations 16 such that the portion without
adhesive may be separated and used as a receipt or record,
either before or after the label is adhered to another
surface. The label may also include an adhesive free corner
or edge 42 as illustrated in Fig. 9 to aid in peeling the
label from the roll.
In another embodiment of the invention illustrated in
Fig. 2, the individual labels 12 are stacked on top of one
another to form a stack from which the labels may be peeled
away and dispensed one by one. Again in this embodiment, each
label 12 includes at least one area 18 which has an imagable
coating and an area 20 which includes a repetitive image 22
printed thereon. Preferably, in this embodiment, the pressure
sensitive adhesive on the second surface of the substrate is
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pattern coated such that there remains at least a free-lifting
edge as illustrated in Fig. 9 to aid in peeling each label
from the stack.
Figs. 4 and 5 illustrate varying arrangements of imagable
coatings on individual labels in a series. Such labels may be
in a series on a roll or stacked. Fig. 4 illustrates a label
which is coated in selected areas to create different colored
areas when imaged. If desired, the web may be preprinted with
nonvariable, repetitive information by automated equipment and
then coated in accordance with the present invention so that
variable information may be printed in the color activatable
areas. For example, as shown in Fig. 4, areas 52 contain
preprinted repetitive information, area 54 is coated with a
color former and color developer which forms a first color,
and area 56 is coated with a color former and color developer
which form a second color different from the first color.
As shown in Fig. 5, the coatings may also be applied in
alternating side-by-side relationship about the periphery of a
label. For example, block 46 is coated with a color former
and color developer which form a first color, block 48 is
coated with a color former and color developer which form a
second color, and block 50 is coated with a color former and
color developer which form a third color, with each of the
colors differing from one another. Such an arrangement allows
one color to be selectively activated around the boundary of
the label to provide an indication of how the item to which
the label is affixed is to be processed.
As can be seen in the drawing figures, the color former
and color developer coatings may be printed on selected
portions of a document or label in a number of patterns,
depending on the desired application. It should be
appreciated that many different combinations for placement of
the coatings on a web or substrate are possible and are within
the scope of this invention. While the embodiments
illustrated show selected portions of a label containing the
coatings, it should also be appreciated that the coatings may
be applied as a full coating on a label.
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Figs. 6 and 7 illustrate yet another embodiment of the
invention in which a label 66 in a series is shown having
selected areas which may be activated to produce color upon
the application of pressure. The label has been coated with
self-contained coatings 64 comprising encapsulated color
formers and color developers. The coatings are preferably
applied at a dry coating weight of between about 1.14 to 11.4
gm/m2 (0.30 and 3.00 lbs/17"x22"x500 sheet ream). In this
embodiment, the color former-containing microcapsules may be
produced by any method known in the art; however, a preferred
method of microencapsulation is disclosed in Seitz, U.S.
Patent No. 4,889,877.
As shown in Fig. 7, when an imaging force, indicated by
the arrow, applies pressure to the surface of the web 28
containing the self-contained coating 64, the color former and
color developer combine to form a colored visible image 70 in
the area beneath the imaging force. As shown in Fig. 6, area
68 is coated with a self-contained coating which forms a first
color, area 60 is coated with a self-contained coating which
forms a second color, and area 62 is coated with a self-
contained coating which forms a third color, where the colors
differ from one another.
The invention provides the advantage that a series of
labels may be easily provided with a means of emphasizing or
designating information on the label. As the imagable
coatings are initially colorless, the entire web may be
initially white, and only the information and colors required
for a particular label need be activated. This permits the
end user to print color customized labels or documents as
desired. The invention also has the advantage that the
colored images or areas may be provided by printing in a
single pass through a thermal or impact printer.
Further, the invention allows a series of pressure
sensitive adhesive labels to be wound in a roll or stacked
without the need for a release liner.
While certain representative embodiments and details have
been shown for purposes of illustrating the invention, it will
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be apparent to those skilled in the art that various changes
in the methods and apparatus disclosed herein may be made
without departing from the scope of the invention, which is
defined in the appended claims.
The embodiments in which an exclusive property or
privilege is claimed are defined as follows:
