U.S. patent number RE33,517 [Application Number 07/169,846] was granted by the patent office on 1991-01-08 for thermosensitive recording label.
This patent grant is currently assigned to Ricoh Electronics, Inc.. Invention is credited to Wissam J. Jurdi, Tomoo Shibata.
United States Patent |
RE33,517 |
Shibata , et al. |
January 8, 1991 |
Thermosensitive recording label
Abstract
A thermosensitive recording label includes a substrate, a
thermosensitive color-forming layer disposed on one side of the
substrate, a protective layer disposed on the thermosensitive
color-forming layer, a pressure-sensitive hot melt adhesive layer
disposed on another side of the substrate and a releasable backing
sheet disposed on the pressure-sensitive adhesive layer. The use of
a hot melt adhesive layer enables the thermosensitive label to be
placed on plastic films without migration of plasticizers in the
film from migrating into the color-sensitive layer. The hot melt
adhesive not only prevents such plasticizers migration, but enables
the labels to be placed on beef products without discoloration of
the beef beneath the label.
Inventors: |
Shibata; Tomoo (Irvine, CA),
Jurdi; Wissam J. (Tustin, CA) |
Assignee: |
Ricoh Electronics, Inc. (Santa
Ana, CA)
|
Family
ID: |
26865440 |
Appl.
No.: |
07/169,846 |
Filed: |
March 18, 1988 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
614287 |
May 25, 1984 |
04577204 |
Mar 18, 1986 |
|
|
Current U.S.
Class: |
84/605 |
Current CPC
Class: |
B41M
5/30 (20130101); B41M 5/44 (20130101); G09F
3/0291 (20130101) |
Current International
Class: |
B41M
5/40 (20060101); B41M 5/44 (20060101); B41M
5/30 (20060101); G09F 3/02 (20060101); B41M
005/18 () |
Field of
Search: |
;427/150,151,152
;428/40,201-204,206,207,352,354,355,913,914
;503/200,201,204,226 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hess; Bruce H.
Attorney, Agent or Firm: Cooper & Dunham
Claims
What is claimed is:
1. A thermosensitive recording label comprising:
a substrate;
a thermosensitive color-forming layer disposed on one side of said
substrate, said thermosensitive color-forming layer comprising a
colorless or light-colored leuco dye and acidic substance capable
of causing said leuco dye to undergo color formation upon heating
of the thermosensitive recording label;
a protective layer disposed on said thermosensitive color-forming
layer;
a pressure-sensitive hot melt adhesive layer disposed on another
side of said substrate said pressure-sensitive hot melt adhesive
layer comprising at least one adhesive agent selected from the
group consisting of a styrene-butadiene rubber hot melt adhesive
and an acrylic hot melt adhesive, and,
a releasable backing sheet disposed on said pressure-sensitive
adhesive layer.
2. The thermosensitive recording label according to claim 1 wherein
the pressure-sensitive hot melt adhesive layer has a transition
glass temperature of at most about 50.degree. C.
3. The thermosensitive recording label according to claim 2 wherein
the pressure-sensitive hot melt adhesive layer comprises one of the
groups of thermoplastic rubber adhesive and thermoplastic acrylic
adhesive.
4. The thermosensitive recording label according to claim 3 wherein
the pressure-sensitive hot melt adhesive layer has a thickness from
about 15 .mu.m (0.6 mil) to about 23 .mu.m (0.9 mil).
5. The thermosensitive recording label according to claim 1 wherein
the adhesive agent selected enables the use of the thermosensitive
recording label on refrigerated beef products wrapped with plastic
wrapping film without subsequent discoloration of the beef beneath
the thermosensitive recording label.
6. The thermosensitive recording label according to claim 1 wherein
the adhesive agent selected enables the use of the thermosensitive
recording label on refrigerated beef products wrapped with a
plastic stretch film wrap selected from the group consisting of
polyvinylchloride, polyethylene and polyolefin without subsequent
discoloration of the beef beneath the thermosensitive recording
label.
7. The thermosensitive recording label according to claims 5 or 6
wherein the pressure-sensitive hot melt adhesive layer has a
transition glass temperature of at most about 50.degree. C.
8. The thermosensitive recording label according to claim 7 wherein
the pressure-sensitive hot melt adhesive layer has a thickness
sufficient to prevent migration of plasticizers within the plastic
wrapping film from migrating to the thermosensitive color-forming
layer when the thermosensitive recording label is disposed on said
plastic wrapping film.
9. The thermosensitive recording label according to claim 7 wherein
the pressure-sensitive hot melt adhesive layer has a thickness from
about 15 .mu.m (0.6 mil) to about 23 .mu.m (0.9 mil).
10. A thermosensitive recording label comprising:
a substrate;
a thermosensitive color-forming layer disposed on one side of said
substrate, said thermosensitive color-forming layer comprising a
colorless or light-colored leuco dye and an acidic substance
capable of causing said leuco dye to undergo color formation upon
heating of the thermosensitive recording label;
a second protective layer disposed on another side of said
substrate;
a pressure-sensitive hot melt adhesive layer disposed on said
second protective layer, said pressure-sensitive hot melt adhesive
layer comprising at least one adhesive agent selected from the
group consisting of a styrene-butadiene rubber hot melt adhesive
and an acrylic hot melt adhesive, said selected adhesive agent
enabling the use of the thermosensitive recording label on
refrigerated products wrapped with a stretch wrapping film selected
from the group consisting of polyvinylchloride, polyethylene and
polyolefin and polyethylene; and,
a releasable backing sheet disposed on said pressure-sensitive
adhesive layer.
11. The thermosensitive recording label according to claim 10
wherein the pressure-sensitive hot melt adhesive layer has a
transition glass temperature of at most about 50.degree. C.
12. The thermosensitive recording label according to claim 11
wherein the pressure-sensitive hot melt adhesive layer has a
thickness from about 15 .mu.m (0.6 mil) to about 23 .mu.m (0.9
mil). .Iadd.
13. A thermosensitive recording label comprising:
a substrate;
a thermosensitive color-forming layer disposed on one side of said
substrate, said thermosensitive color-forming layer comprising a
colorless or light-colored leuco dye and acidic substance capable
of causing said leuco dye to undergo color formation upon heating
of the thermosensitive recording label;
a pressure-sensitive hot melt adhesive layer disposed on another
side of said substrate, said pressure-sensitive hot melt adhesive
layer comprising at least one adhesive agent selected from the
group consisting of a styrene-butadiene rubber hot melt adhesive
and an acrylic hot melt adhesive, and,
a releasable backing sheet disposed on said pressure-sensitive
adhesive layer. .Iaddend. .Iadd.14. The thermosensitive recording
label according to claim 13 wherein the pressure-sensitive hot melt
adhesive layer has a transition glass temperature of at most about
50.degree. C. .Iaddend. .Iadd.15. The thermosensitive recording
label according to claim 14 wherein the pressure-sensitive hot melt
adhesive layer comprises one of the groups of thermoplastic rubber
adhesive and thermoplastic acrylic adhesive. .Iaddend. .Iadd.16.
The thermosensitive recording label according to claim 15 wherein
the pressure-sensitive hot melt adhesive layer has a thickness from
about 15 microns (0.6 mil) to about 23 microns
(0.9 mil). .Iaddend. .Iadd.17. The thermosensitive recording label
according to claim 13 wherein the adhesive agent selected enables
the use of the thermosensitive recording label on refrigerated beef
products wrapped with plastic wrapping film without subsequent
discoloration of the beef beneath the thermosensitive recording
label. .Iaddend. .Iadd.18. The thermosensitive recording label
according to claim 13 wherein the adhesive agent selected enables
the use of the thermosensitive recording label on refrigerated beef
products wrapped with a plastic stretch film wrap selected from the
group consisting of polyvinylchloride, polyethylene and polyolefin
without subsequent discoloration of the beef beneath the
thermosensitive recording label. .Iaddend. .Iadd.19. The
thermosensitive recording label according to claims 17 or 18
wherein the pressure-sensitive hot melt adhesive layer has a
transition glass temperature of at most about 50.degree. C.
.Iaddend. .Iadd.20. The thermosensitive recording label according
to claim 19 wherein the pressure-sensitive hot melt adhesive layer
has a thickness sufficient to prevent migration of plasticizers
within the plastic wrapping film from migrating to the
thermosensitive color-forming layer when the thermosensitive
recording label is disposed on said plastic wrapping film.
.Iaddend. .Iadd.21. The thermosensitive recording label according
to claim 19 wherein the pressure-sensitive hot melt adhesive layer
has a thickness from about 15 microns (0.6 mil) to about 23 microns
(0.9 mil). .Iaddend.
Description
The present invention relates generally to thermosensitive
recording labels and more particularly relates to thermosensitive
recording labels suitable for use on polyvinylchloride and
polyethylene stretch wrapping films.
Thermosensitive recording labels such as described in U.S. Pat. No.
4,370,370 have been developed to overcome many of the drawbacks of
conventional printing with oily or water base inks. Problems
associated with conventional printing utilizing oily or water based
inks, include the smearing tendency of the ink due to insufficient
drying time before utilization of the label, the high maintenance
of printing equipment, and the continued replenishment of printing
inks, or ribbons if ink impregnated ribbon is used in the printing
process. In addition, it is well known that conventional printing
with wet ink can be a very messy operation.
Hence, thermosensitive recording labels have been developed which
utilize a thermosensitive coloring material comprising a colorless
or light-colored leuco dye and acidic substance capable of causing
the leuco dye to undergo color formation upon heating of the
thermosensitive recording label.
As is well known in the art, a layer of thermosensitive coloring
material is disposed on a substrate and a thermal head printer is
thereafter used to contact and heat specific areas of the layer to
cause color-formation in the areas heated, while the remainder of
the layer stays colorless, or light-colored, thereby producing
visible alphanumeric characters in the layer.
While these labels may be used on many products without fading of
the color formations over long periods of time, it is also well
known that when such labels are placed on plastic wrapped products,
contact with the plastic wrap from co-mingled products or packages
is inevitable. When this occurs, degradation of the heat-formed
printing begins as evidenced by fading of the color formed by the
leuco dye and the acidic substance.
It is believed that this degradation occurs because migration of
the plasticizers used in the plastic wrap occurs. The migration of
the plasticizer into the thermosensitive color-forming layer and
subsequent reaction therein is believed to cause the fading
phenomenon.
As disclosed in U.S. Pat. No. 4,370,370, an attempt to produce a
non-fading thermosensitive recording label has included the
addition of protective, or barrier, layers on both sides of the
thermosensitive color forming layer in order to prevent such
migration.
Specifically, after the color-forming layer is applied to a
substrate, a barrier layer comprising a water soluble polymeric
material is placed over the thermosensitive color forming area, and
a second barrier comprising a water soluble polymeric material is
placed on the other side of the substrate.
The barrier layer on the substrate is provided to prevent migration
of plasticizers from the plastic film on which the label is placed
from migrating through the substrate and into the color-forming
layer, and the barrier layer placed on the thermosensitive
color-forming layer is intended to prevent migration of
plasticizers from co-mingled plastic wrapped goods which may come
in contact with the label, for migrating thereinto.
While this combination of layers is satisfactory for use as a
thermosensitive recording label in many applications, manufacture
of the label is made more costly and additional steps must be taken
in the production of the label in order to incorporate the barrier
label on the substrate.
In addition, it has been found that when such label is placed on
plastic stretch wrap film containing beef products, that a dark
discoloring of the beef products occurs beneath the label a few
hours after application of the label to the packaged beef.
While it is not believed that any deterioration or spoilage of the
beef products occurs because of this darkened area, it nonetheless
is unattractive to the consumer after removal of the plastic wrap
and renders the beef product unacceptable for use by the
consumer.
It is not known at the present time exactly why this discoloration
occurs only on beef products, but it is suspected to be related to
the lack of oxygen penetration beneath the label.
Prior art sensitive recording labels have typically used an acrylic
adhesive agent, a styrene-butadiene rubber (SBR) latex adhesive
agent, a vinyl acetate adhesive agent or a rubber adhesive agent
for securing the label, via the substrate, to goods.
While these adhesives are satisfactory for use on warm, relatively
dry goods, they are not suitable as adhesives in holding the
thermosensitive recording label to moist, damp, refrigerated or
frozen plastic wrap goods such as packaged meats and vegetables or
the like.
The present invention overcomes many of the disadvantages of the
hereinbefore produced thermosensitive recording labels. It has been
found that the use of a hot melt adhesive layer applied to a
thermosensitive recording label substrate enables a label, in
accordance with the present invention, to be applied to moist and
refrigerated goods with sufficient adhesion thereto to ensure
contact between the label and the goods even though they may rub up
against and come in contact with associated goods during handling
of the product.
Further, a label, in accordance with the present invention,
utilizing a hot melt type adhesive layer enables the production of
a thermosensitive recording label without a barrier layer
protecting the substrate. This reduces both the cost of the label
and the complexity of manufacture because less steps are required.
It appears that the hot melt adhesive prevents migration of the
plasticizers from plastic film and the like, onto which the label
is placed, from migrating through the hot melt adhesive and into
the thermosensitive color forming layer.
In addition, and importantly, it has been discovered that the use
of a hot melt adhesive layer, in combination with the substrate and
thermosensitive color forming layer, results in a thermosensitive
recording label that can be used on refrigerated beef products
without discoloration of the beef beneath the labels as occurs with
hereinbefore manufactured thermosensitive recording labels.
SUMMARY OF THE INVENTION
A thermosensitive recording label, in accordance with the present
invention, includes a substrate, a thermosensitive color-forming
layer disposed on one side of the substrate, a protective layer
disposed on the thermosensitive color-forming layer, a
pressure-sensitive hot melt adhesive layer disposed on another side
of said substrate, and a releasable backing sheet disposed on said
pressure-sensitive adhesive layer.
The thermosensitive color-forming layer comprises a colorless, or
light colored leuco dye and an acidic substance capable of causing
the leuco dye to undergo color formation upon heating of the
thermosensitive recording label.
More particularly, the thermosensitive recording label according to
the present invention includes a pressure-sensitive hot melt
adhesive layer comprising at least one adhesive agent selected from
the group consisting of thermoplastic styrene-butadiene rubber hot
melt adhesive, and acrylic hot melt adhesive.
In a preferred embodiment of the present invention, the
thermosensitive recording label includes a pressure-sensitive hot
melt adhesive layer having a transition glass temperature of at
most about 50.degree. C.
The adhesive agent selected enables the use of the thermosensitive
recording label on refrigerated beef products wrapped with a
plastic stretch film wrap selected from the group consisting of
polyvinylchloride, polyethylene and polyolefin without subsequent
discoloration of the beef beneath the thermosensitive recording
label. The pressure-sensitive hot melt adhesive layer on the
present thermosensitive recording label invention has a thickness
from about 15 .mu.m (0.6 mil) to about 23 .mu.m (0.9 mil).
BRIEF DESCRIPTION OF THE DRAWINGS
A better understanding of the present invention may be had from the
consideration of the following detailed description, taken in
conjunction with the accompanying drawings in which:
FIG. 1 is a cross-sectional view of the thermosensitive recording
label in accordance with the present invention generally showing
each of the layers included in the label;
FIG. 2 is a diagram showing the production of a thermosensitive
recording label in accordance with the present invention showing
specifically the application of hot melt adhesives to a backing
sheet and subsequent combination of the backing sheet with the
remainder of the label with chilled rollers;
FIG. 3 is a perspective view of a roll of thermosensitive recording
labels according to the present invention; and,
FIG. 4 is a perspective drawing of the thermosensitive recording
label in accordance with the present invention as applied to a
plastic wrapped refrigerated product.
DETAILED DESCRIPTION OF THE DRAWINGS
Turning now to FIG. 1, the thermosensitive recording label 10 in
accordance with the present invention includes a substrate 12, a
thermosensitive color-forming layer 14 disposed on one side 16 of
the substrate 12, a protective layer 18 disposed on the
thermosensitive color-forming layer 14, a pressure-sensitive hot
melt adhesive layer 20 disposed on another side 22 of the substrate
12 and a releasable backing sheet 26 disposed on the
pressure-sensitive adhesive layer 20.
In general, the substrate 12 may be a high quality paper and the
thermosensitive recording color-forming layer 14 is typical of that
known in the art as shown in U.S. Pat. Nos. 4,370,370 and
4,388,362, and examples of the colorless or light colored leuco dye
and the acidic substances are given therein.
Additionally, as pointed out in U.S. Pat. No. 4,388,362 enhancers
may be included in the thermosensitive color-forming layer in order
to enhance the distinctiveness of the color images. Such enhancers
may include fine powders of calcium carbonate, magnesium carbonate,
alumina, silica, talc, barium sulfate, aluminum sterate, styrene
resin, urea-formalin resin, or the like. Binder agents also may be
utilized in thermosensitive color-forming layers as is well known
in the art.
A water soluble resin solution coated on the thermosensitive
color-forming layer 14 and thereafter dried forms the protective
layer 18. A number of water soluble resins may be utilized in the
thickness of the protective layer 18 control as is well known in
the art, to prevent subsequent deterioration of the thermosensitive
color-forming layer by plasticizers contained in plastic sheet
which may be placed on, or in contact with the thermosensitive
recording label 10.
Also, in accordance with the prior art, the function of the
protective, or barrier label, may be enhanced by adding
water-resisting property improvement agents such as formaldehyde,
glyoxal, chromium alum, melamine, melamine-formaldehyde resin,
polyamide resin.
As generally shown in FIG. 2, the pressure-sensitive hot melt
adhesive layer 20, such as thermoplastic rubber copolymer or
acrylic thermoplastic hot melt adhesive is disposed on the
substrate 26 by heating the hot melt adhesive to a temperature of
about 350.degree. F. (177.degree. C.) and thereafter forming a film
on the substrate.
It should be appreciated that the hot melt rubber adhesives
utilized in the present invention may be classified as
thermoplastic rubber block copolymers having, for example,
connected blocks of styrene and butadiene which are solid at room
temperature but liquid when heated above about 50 to about 100
degrees centigrade.
Thereafter, the substrate 26 with the hot melt adhesive thereon is
contacted with the other side 22 of the substrate 12 by passing the
backing sheet 26 along with the substrate 12 through a set 28 of
chilled rollers thereby disposing the hot melt adhesive 20 onto the
substrate 12 without significant heating of the thermosensitive
color-forming layer 14.
This is diagramatically shown in FIG. 2 where a roll 30 of backing
sheet 26 material which may be high quality paper or densified
silicone coated craft paper coated with a film of molten hot melt
adhesive 20 by an extruder 34 in a conventional manner and
thereafter passed through the chilled rollers 28 along with the
substrate 12 already coated with the thermosensitive color-forming
layer 14 and barrier 18, pulled from a roll 42.
The resulting labels may be formed into a roll 44 (see FIG. 3) for
ease in subsequent use.
It should also be appreciated that the releasable backing sheet 26
may be silicone coated and/or the substrate surface 22 treated in a
manner such that the pressure-sensitive hot melt adhesive layer 20
remains on the substrate surface 22 when the releasable backing
sheet 26 is removed or peeled therefrom to enable the
thermosensitive recording label 10 to be fixed to goods 50 (see
FIG. 4).
The pressure-sensitive hot melt adhesives that may be used with the
present invention are cold and freezer graded commercially
available adhesive products.
The following example is presented by way of illustration only, and
is not to be considered limiting to the present invention.
EXAMPLE 1
A solution of leuco dye and acid substance was prepared as
follows:
______________________________________ Parts by Weight
______________________________________ Dispersant A
3-diethyl-C-methyl-7-anilino 1.5 fluoran Polyvinyl alcohol (20%
aqueous solution) 5.0 Water 43.5 Dispersant B Bisphenol A 6.0
Stearic acid amide 1.0 Polyvinyl alcohol (20% aqueous solution)
10.0 Water 33.0 ______________________________________
The prepared Dispersant A and Dispersant B were mixed to form a
thermosensitive coloring liquid which was applied to a substrate
consisting of high quality paper and weighing about 58 gr./m.sup.2,
and thereafter dried at room temperature up to 120.degree. C. to
form a thermosensitive color-forming layer in which the solids
therein amounted to about 4.0 to about 10 gr./m.sup.2. Thereafter,
a water soluble resin solution comprising 5 parts of polyvinyl
alcohol in 95 parts of water was applied to the heat sensitive
color-forming layer and dried at about 25.degree. to 120.degree. C.
to thereby form a protective layer over the thermosensitive
color-forming layer, said protective layer having a quantity of
solids of about 2 gr./m.sup.2.
A backing sheet consisting of high quality paper and weighing about
70 grs./m.sup.2 was silicone treated by either solvent-base or 100%
solid release paper coating and thereafter cold or freezer type hot
melt adhesive was heated to 350.degree. F. (177.degree. C.) and
applied to the substrate, such application amounting to a layer
having a quantity of solids of about 23 gr./m.sup.2. Thereafter,
the backing sheet with the hot melt adhesive applied thereto was
passed through chilled rollers to contact the substrate material
and form a roll of thermosensitive recording labels.
Subsequently, a label prepared in accordance with this example was
applied to a beef filet mignon wrapped with polyethylene or
polyolefin stretch plastic film, which had been refrigerated. The
label adhered to and was not easily removed from the plastic film
and after 24 hours at a refrigerated temperature of about
37.degree. F. (2.degree. C.), the plastic film, along with the
thermosensitive label, was removed from the filet mignon. On
subsequent examination, the filet mignon showed no discoloration
under the label disposed on the plastic wrap over the filet
mignon.
By comparison, a label made in accordance with U.S. Pat. No.
4,370,370 did not adhere well to the refrigerated plastic film
material covering the filet mignon. In addition, it was observed
that after a lapse of approximately 4 hours, a discoloration of the
filet mignon was observed underneath the prior art label.
EXAMPLE 2
A label prepared as in Example 1 was applied to a beef sirloin
steak wrapped with polyethylene or polyolefin stretch plastic film
which had been refrigerated. The label adhered to and was not
easily removed from the plastic sheet and after 24 hours at a
refrigerated temperature of about 37.degree. F. (2.degree. C.), the
plastic film, along with the thermosensitive label, was removed
from the sirloin steak. On subsequent examination, the sirloin
steak showed no discoloration under the label disposed on the
plastic film over the sirloin steak.
By comparison, a label made in accordance with U.S. Pat. No.
4,370,370 did not adhere well to the refrigerated plastic sheet
material covering the sirloin steak. In addition, it was observed
that after a lapse of approximately 6 to 8 hours a discoloration of
the sirloin steak was observed underneath the prior art label.
EXAMPLE 3
A label prepared as in Example 1 was applied to a New York steak
wrapped with polyethylene or polyolefin stretch plastic film which
had been refrigerated. The label adhered to and was not easily
removed from the plastic sheet and after 24 hours at a refrigerated
temperature of about 37.degree. F. (2.degree. C.), the plastic
sheet, along with the thermosensitive label, was removed from the
New York steak. On subsequent examination, the New York steak
showed no discoloration under the label disposed on the plastic
film over the New York steak.
By comparison, a label made in accordance with U.S. Pat. No.
4,370,370 did not adhere well to the refrigerated plastic film
material covering the New York steak. In addition, it was observed
that after a lapse of approximately 6 to 8 hours a discoloration of
the New York steak was observed underneath the prior art label.
Although there has been described hereinabove a specific
thermosensitive recording label in accordance with the present
invention for the purposes of illustrating the manner in which the
invention may be used to advantage, it will be appreciated that the
invention is not limited thereto. Accordingly, any and all
modifications, variations, or equivalent arrangements which may
occur to those skilled in the art should be considered to be within
the scope of the invention as defined in the appended claims.
* * * * *