Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
This invention relates to a temperature indicatiny
device. More particularly it relates to a temperature indi-
cating device used as a disposable thermometer.
Reference is made to my Canadian Patent Application
Serial No. 302,322 filed on May 1, 1978 and entitled "Tempera-
ture Indicating Device Using a Pressure Sensitive Adhesive
Seal".
Temperature indicating devices which utilize ther-
mally responsive mixtures of ortho-chloronitrobenzene and
orthobromonitrobenzene are known and one such device is des-
cribed in U.S. Patent 3,704,9~5. The device described in the
above patent includes a layer having a dye impregnated therein
which is separated from the thermally responsive mixture. It
would be desirable to include a dye in the mixture, however,
it has never been applied in practice because it had not been
possible to find suitable dyestuffs which meet particular re-
quirements. These requirements are: no detrimental effect on
the melting point of the mixture of ortho-chloronitrobenzene
and ortho-bromonitrobenzene, a distinctly perceptible color
change of the indicator layer upon the melting of said mixture
and, particularly, good durability without premature discolora-
tion of the indicator layer.
Owing to the lack of suitable dyestuffs recourse was
made in practice to the use of special constructions in which a
shield was positioned between the meltable solid mixture and the
indicator layer, which shield is removed just prior to use of
the temperature indicating device. Such a construction is des-
cribed in U.S~ Patent 3,674,176. Although such a temperature
indicating device can very well be used, the above described
shield causes production and use thereof to be complicated and
expensive. Particular dyestuffs have now been found which
eliminate the need for making use of a shield.
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: ~
OnJI~CTS ()F 1'11~ VI~ TIOM
..
I It is one object of this invention to provide an
im~roved temperature indicatin~ clevice.
It is another object of the invention to provide~ a
temperature indicating device which is simpler and cheaper to
manufacture than prior art devices.
It is another object of this invention to provide a
temPerature indicating device which utilizes thermally responsive
chemicals mixed with a dye which vields accurate temperature
information. -
'1~ SUMMARV OF TH~ INVEN'rION
_ _ ,
In accordance with one form of this invention, there is i¦provided a temperature indicating device which includes a ,
¦thermally conductive sheet,as a carrier layer provided with one ,
lor more cavities formed by depressions in the sheet material. At
least one of the cavities is illed with a solid mixture which
melts at a predetermined temperature and includes ortho-chloro-
nitrobenzene, ortho-brornonitrobenzene and a dyestuff. An
indicator layer of absorbent material is superimposed on the
~0 ¦solid mixture. A transparent cover layer seals the cavities and
their contents.
The dyestuff applied is selected from the group of
dyestuffs which in accordance with the Colour Index are referred !
to as solvent blue 10, solvent blue 44~ solvent hlue 45 solvent
~blue 49, solvent blue 67, solvent r~d 90, solvent orange 59 and I
solvent green 19.
The temperature indicating device according to the I
invention is of simple construction and has surprisingly good
durabil ty. Morè~ve-, its indlcation of the temperature is
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accurate and reproducible, and distinctly visible. Of the blue
dyestuffs according to the invention solvent blue 49 is pre-
ferred. Under certain circumstances it is preferred that,
because of its red color, solvent red 90 be used.
The indicator layer of absorbent material applied to
the solid mixture is preferably constituted of paper made from
cellulose fibers. Because of its lower sensitivity to the
influence of moisture it is preferred that under certain circum--
stances use should be made of an indicator layer consisting of
paper made from synthetic fibers. In view of the desired high
absorptivity and high porosity of the indicator layer, it is
preferred that this indicator layer should be of a coarse
filter paper~
The temperature indicating device according to the
invention is excellently suitable for clinical use and is
preferably so constructed then that the carrier layer consists
of aluminium sheet provided with a number of cavities which
contain solid mixtures having different melting points, and
the transparent cover layer consists of polyester film. The
polyes-ter film is preferably bonded to the aluminium film by
means of a pressure-sensitive adhesive agent. Preferably,
polyisobutylene is used as the pressure sensitive adhesive agent
According to a broad aspect of the present invention,
there is provided a temperature indicating device which com-
prises a thermally conductive sheet as carrier layer provided
with one or more cavities formed by depressions in -the sheet
material. At least one of the depressions is filled with a
solid mixture which melts at a predetermined temperature and
is composed of ortho-chloronitrobenzene, orthobromonitroben-
zene and a dyestuff. An indicator layer of absorbent materialis superimposed on the solid mixture. A transparent cover
layer seals the cavities and their contents and it is charac-
_ 4 _
P?
77
, terized in that the dyestuff used is selected from the group
consisting of dyestuffs which in accordance with the Colour
Index are referred to as solvent blue 10, solvent blue 44,
solvent blue 45, solvent blue 49, solvent blue 67, soLvent
red 90, solvent orange 59 and solvent green 19.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is further described with reference
to the accompanying drawings.
-~ Figure 1 is a plan view of a temperature indicating
device according to the invention.
Figure 2 is a vertical section along the line A-A'
given in Figure 1.
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'~,":1
~ Q~
D~SCRIPTIOl`~ OF lHl~ PRT~FF,RT~D F,'l~ ODI~ TS
In Figure 1 the temperature indicatiny device has a
portion 1 which serves as a handle and an indicator portion 2
adapted to be inserted into the mouth for oral temperature
measurement. The indicator portion 2 is provided with a number
of suitably spaced cavities 3. ~ach cavity is filled with a
solia mixture 4 (Figure ~) which melts at a known temperature.
In the adjacent cavities the melting temperature may, for
instance, be 0.1C higher or lower, which can be realized by a
¦proper choice of the composition of the solid mixture.
¦ Although in Figure 1 a series of cavities 3 are shown,
there is only need for one cavity if the temperature indicating
device is used to establish whether or not a certain temperature
value has been exceeded. The cavities 3 are formed by depression
lof the thermally conductive sheet material, which serves as '
carrier layer 5. Although the thermally conductive sheet i
material may very well be of aluminium, also other flexible ther- j
mally conductive materials may be used. On the solid mixture
¦and in intimate contact therewith is an irldicator layer 6 of I
labsorbent material, which is usually an absorbent paper having a ¦
high porosity and a high absorptivity, so that when the solid
mixture melts, the indicator layer is immediately wetted by the I
liquid phase formed. A transparent cover layer 7 seals the !
cavities 3 and their contents. The cover layer 7 is of film
material which is sufficiently impervious to the substances
present in the cavities, and to substances, for example moisture,
which may unfavorably influence temperature indication. It is I
preferred that the transparent cover layer should be o !
polyester, more particularly of the polyethylene tere~hthalate !
type. The thickness of the transparent cover layer is preferably !
20-100 microns.
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.
The cover layer 7 is bonded to the carrier layer 5
by an adhesive layer 8. This adhesive layer ~3 consists of an
adhesive agent which can be applied without the melt tem~era-
ture of the solid mixtures being exceeded. For this purpose
use may be made of a pressure-sensitive adhesive or a bonding
agent with which the cover layer 7 and the carrier layer 5 may
be welded together ultrasonically. It is preferred that the
adhesive layer 8 should be of polyisobutylene.
The E'igures 1 and 2 show a special embodiment of the
temperature indicating device according to the invention. It
will be clear that within the scope of the invention it is
possible for a man skilled in the art to realize many other
embodiments and/or modifications. The nature of the thermally
conductive material for the carrier layer, the number, the
dimensions and the arrangement of the cavities provided therein,
the weight ratio of ortho-chloronitrobenzene and ortho-bromo-
nitrobenzene in the solid mixture and the choice of the material
of the transparent cover layer can immediately be derived from
the state of the art by a man skilled in the same art. The
same applies to the amount of -the solid mixture in each of the
cavities and the way of filling the cavities. When use is
made of the temperature indicating device according to the in-
vention, the melt temperature of the solid mixture will be ex-
ceeded in one or more cavities, depending on the level of the
temperature to be measured, so that the respective mixture will
pass from the solid into the liquid state. The liquid formed
is then sucked up by the absorbent material of the indicator
layer. The dyestuff contained in the liquid causes a visually
perceptible discoloration of the indicator layer. From the
position of the border between cavities having a colored and
those not having a colored indicator layer immediately the
value of the temperature to be determined can be read.
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Z~7
The dyestuffs to be used according to the invention
are dissolved in mixtures of ortho-chloronitrobenzene and
ortho-bromonitrobenzene in an amount which is usually about
0.05 - 0.2 percent by weight. Al-though it is possible to use
amounts smaller than 0.05 percent by weight, the color change
in the indicatox layer will be less clearly perceptible then.
On the other hand, if the dyestuff is used in an amount con-
siderably higher than 0.2 percent by weight, an undesirable
change of the melting point of the particular solid mixtures
will take place. In the above-mentioned range of 0.05 - 0.2
percent by weight there will be no detrimental change of the
melt temperature of the solid mixtures used. The dyestuffs
used according to the invention are known in themselves and
are referred to under the names mentioned in the colour Index,
; 3rd Edition (1971), published by the Society of Dyers and
Colourists, Great Britain (five volumes).
Solvent blue 10 is marketed, for instance, by the
firm of Sandoz, Switzerland, under the registered trademark
Savinyl Blue B.
Solvent blue 44 is marketed, fGr instance, by the
firm of Sandoz, under the registered trademark Savinyl Blue GLS.
Solvent blue 45 is marketed, for instance, by the
firm of Sandoz under the registered trademark Savinyl Blue RS.
Solvent blue 49 is marketed by the firm of Ciba-Geigy,
Switzerland, under the registered trademark Orasol Blue BLN.
Solvent blue 67 is marketed by Ciba-Geigy under the
re~gistered trademark Orasol Blue GN.
Solvent red 90 is marketed by the firm of Sandoz
under the registered trademark Savinyl Red BLSN.
Solvent orange 59 is marketed, for instance, by Ciba-
Geigy under the registered trademark orasol Orange RLN.
7 --
Solvent green 19 is marketed, for ins-tance, by the
firm of Sandoz under the registered trademark Savinyl Green B.
The dyestuffs used according to the invention are
remarkable particularly for the speed at which they migrate
from the solid mixture to the indicator layer. This means
that there is no premature discoloration of the indicator
layer, in spite of the fact that the indicator layer and the
dyestuff-containing solid mixture are constantly in contact
with each other also during storage. Because of this resis-
tance to premature discoloration the durability is excellent.
All solid mixtures that are present in the various cavities
of the temperature indicating device may contain one and the
same dyestuff. It is also possible to use different dyes.
For instance, the use of a blue dyestuff may be combined
with that of a red one to clearly indicate that a particular
temperature value is exceeded.
Suitable materials for the indicator layer are
cellulose paper and paper from synthetic starting materials,
for instance polyester. It is preferred that the paper used
should be opaque, have a uniform structure and evenly discolor
upon getting into contact with the melted solid mixture. It
has been found that these requirements are fully met by coarse
filter paper (No~ 589') supplied by~the firm of Schleicher &
Schull and by chromatography paper No. 1 supplied by the firm
of r~hatman. The transparent cover layer consists of a material
which does not change -the melting point of the solid mixture
contained in the cavities, and is not adversely affected by
said mixture and is sufficiently impervious to the various
substances~ It is preferred that the transparent layer should
consist of polyester film, for instance Melinex (registered
trademark) film supplied by I.C.I., Great Britain.
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Bonding the transparent cover layer to the carrier
layer should be carried out at such a low temperature that
the melting temperature of the solid mixtures present in the
cavities is not exceeded. The cavities must then be sealed
off from each o-ther as well as from the ambient air. The ad-
hesive agent used should be properly resistant to the chem-
ical substances present in the cavities, not influence their
melting point, and hardly absorb chemical substance nor allow
the passage thereof. It has been found that polyisobutylene
is a very suitable pressure-sensitive adhesive agent. Alter-
natively, the cover layer and the carrier layer may be bonded
to each other by a short ultrasonic welding treatment, use
being made of an ionomer, for instance, Surlyn (registered
trademark), as adhesive agent.
The temperature indicating device according to the
invention is particularly suitable to be applied as disposable
thermometer for single clinical use. As the temperature indi-
cation is irreversible, it should be taken care that prior to
actual use, for example, during transport and storage, the
temperature indicating device is protected from exposure to
temperatures which are higher than the temperature to be mea-
sured. The invention will be further described in the follow-
ing examples.
EX~MPLE 1
A mixture of equal parts by weigh-t of ortho-chloro-
nitrobenzene and ortho~bromonitrobenzene in which 0.1% by weight
of a dyestuff has been dissolved i5 poured inside a metal ring
which is closed off on one side with polyester film tMelinex,
registered trademark, I.C.I., Great Britain) coated with
polyisobutylene (Oppanol D 3061, registered trademark, BASF,
,~ `.
W-Germany). After the surface of the tablet thus formed
has been smooth, the tablet is placed on coarse, white filter
paper in such a way that the mixture of chemicals and dyestuff
is in contact with the paper. It is determined how long it
will take for the paper to display discoloration at a storage
temperature of 28C. The results are listed in Table I.
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TABI,r I
Num~er o~ days the
, paper remains
nyes--tuff/supplier Color Index uncolored at 28C
. .
savinyl blue GLS solvent blue 44 ~ 28
Sandoz
orasol blue BLN solvent blue 49 ~ 28
Ciba-Geigy
orasol blue GN solvent blue 67 > 28
Ciba-Geigy .
savinyl red BLSN solvent red 90 ~ 28
Sandoz -
¦ savinyl blue RS solvent blue 45 > 28
: ¦ Sandoz
savinyl b].ue B solvent blue 10 ~28
Sandoz
savinyl green B solvent green 19 >28
Sandoz
orasol orange RLM solvent orange 59 > 28
Ciba-Geigy
orasol navy blue 2RB solvent blue 53 7
Ciba-Geigy
D~C green 6 solvent green 3 . 7
blue VIF organol JN solvent blue 63
Ugine ~uhlmann C.I. Mo. 61250
: irgalith violet MNC pigment violet 3
t~- Ciba-Geigy C.I, No. 42535
. fettrot ~S solvent red 24
Sandoz C.I. ~lo. ~6105
~- 30 irgalith ~ink TYNC pigment red 81~
Ciba-Geigy - C.I~ No. 45160:2
irgalith blue TNC pigment blue 1
Ciba-Ge y C.I. Mo. 42595:Z
. I
~ 2~ 7
It appears that the dyestu~fs to be used according to~
the invention, viz. solvent blue 10, solvent blue 44, solvent~
blue ~5, solvent blue ~9, solvent blue 67, solvent red 90, !
solvent orange 59 and solvent green 19 still do not cause any
discoloration of the filter paper after 28 days' storage at 28C.
By contrast, the majority of the other dyestuffs
examined cause discoloration of the paper already after one day.
Also, the solvent green 3 employed in the known single-use
thermometers causes discoloration of the paper already afterl
seven days and is therefore not quite suitable. ~
EXA~IPLE 2
In this example the suitability as absorbent indicator
material ahsorben~ oE various makes of paper is demonstrated.
j The test procedure is as follows. Six cavities formed in an
. I aluminium carrier layer are filled with a mixture of ortho-j
¦ chloronitrobenzene and ortho-bromonitrobenzene having a melting
point of 38.5~C in which 0.1~ by weight of orasol blue BLM
~solvent blue 49) is dissoIved. In three of the cavities thus,
filled the solid mixture is covered by the kind of paper to be
examined, and the other three cavities are covered by a reference
paper. The reference paper is of a type used in known tempera-,
ture indicatin~ devices. Subsequently, the cavities are sealed !
with polyester film (Melinex) coated with a pressure-sensitive
adhesive layer of polyisobutylene (Oppanol D 3061). The test
objects thus rnade are placed in water of 37.5C. The temperaturej
is then increased at a rate of 0.25C/min.
The ternperature at which in the first and in the last~
of the three cavities the paper is fully discolored are written
down both for the paper to be examined and for the reference
paper. Table II gives:
~ 2.~
a. shift in the temperature level at which dis-
coloration occurs with respect to the reference
paper (differences between the avera~e values of
~he paper to be examined and the reference
paper);
b. spread of the measured ternperatures in the three
cavities;
c. rating of discoloration.
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TA~LE I I
Discolor-
ation temp. Spread
Paper relative to of disc. ~iscolor-
reference temp. ation
No. Name/firm type (C) (C) ratinq
1 Schleicher & cellu- -0.20 0.07 good,
! Shcull lose uniform
chromatogra- color
phy pa~er
No. 2040 a
2 ditto cellu- -0.14 0.06 good color
No. 2043 a lose
3 ditto cellu- -0.14 0.07 qood color
No. 2045 a lose
4 Schleicher & cellu- -0.11 0.04 good color
Schull lose
filter paper (coarse)
No. 589'
Tyvek style polypro- +0.08 0.10 poor color
820
6 Pellon* polyester - - very
7450 transp.
paper, no
distinct
color
change
7 Pellon* polyester -0.52 0.06 good color
7600
8 Pellon polyester -0.28 0.14 good color
8650
9 reference cellu- - 0.08 good color
paper lose
*Registered Trademark
,~ `. .
2~t7
From Table II it can be concluded that paper No. 4
(Schleicher & Schull, coarse filter paper, No. 589') is to be
preferred because of its small spread of discoloration tempera-
ture. Unsuitabie for use is paper No. 6 (Pellon 7450,
registered trademark), which because of its transparency does
not display a clearly perceptible color change.
EXAMPLE 3
In this example the reproducibility of the tempera-
ture indication is demonstrated. A number of cavities formed
in an aluminium carrier layer are filled with a series of mix-
tures of ortho-chloronitrobenzene, ortho-bromonitrobenzene and
0.1% by weight of Orasol Blue BLN, registered trademark,
(solvent blue 49), whose melting temperatures progressively
increase by 0.1C. The cavities thus filled are covered with
Whatman chromatographypaper No. 1 and subsequently with poly-
ester film (Melinex, registered trademark), provided with a
pressure-sensitive adhesive coating of polyisobutylene. The
test objects are stored at 28C. and after 3, 7 and 10 weeks,
respectively, placed in a water bath of a particular tempera-
ture to measure the temperature at which discoloration of the
indicator layer takes place. The results obtained as average
values of 4 temperature indicating devices are listed in
Table III.
TABLE III
Temperature at which discoloration occurs (C~
after 0 weeks 36.40
3 weeks 36.45
7 weeks 36.48
10 weeks 36.50
It appears that the temperature indication as a
function of times does not or hardly undergo any change.
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IF~ J~
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From the foregoing description of the em~odiments o~
the invention it ~ill be apparent that many modifications may be
made therein. It will he understood that these embodiments of'
the invention are intended as an exemplification of the invention
only, and the invention is not limited thereto. It is to bej
understood there~ore that it is intended in the appended claims !
to cover all such modifications which fall ~ithin the true scope
and spirit of the invention.
