Phosphorescent identification device

Identification device for distinctively marking objects, location or sides of symmetrical objects such as audio tape cassettes, so that they can be distinguished in the dark. A carrier lamina has a matt phosphorescent pigment coating exposed on one side so that indelible writing or other marks can be made thereon using a writing instrument. The dark writing or other marks are viewable in the dark in contrast against the glow of the unmarked phosphorescent pigment surface and will not smudge or erase when handled. The opposite side carries a permanently tacky pressure sensitive adhesive coating so that the phosphorescent lamina can be easily adhered on objects or locations to be marked.

While there have been numerous proposals for phosphorescent sheets which 
may be applied to articles to enable the articles to be seen in the dark, 
none of the prior proposals of which the applicant is aware have enabled 
the user conveniently to make and apply instinctively marked 
phosphorescent identification devices. Such devices would allow the user 
to distinguish between differently marked locations or devices in the dark 
and so enable the user to, for example, make and apply markers which 
distinctively identify different locations or objects in the dark or which 
a low the user to distinguish between similarly sized and shaped articles 
in the dark, or between opposite faces of symmetrical articles, such as 
tape cassettes. 
The invention provides an identification device comprising a carrier lamina 
having a matt phosphorescent pigment coating continuously and uniformly 
applied on one exposed side whereby a mark can be made on said exposed 
side with a writing instrument such as a pen, pencil, marker or the like. 
The opposite side of the lamina carries a permanently tacky adhesive 
coating which is protected by a peelable release backing. 
In the dark, the coating provides a continuously extending glowing area. 
When the user writes or makes any other marking on the coating with a 
writing instrument which makes an opaque mark, the writing or other mark 
is viewable or readable in the dark by virtue of its dark contrast with 
the surrounding glowing area. 
In the preferred form, the identification device is an indelibly markable 
identification device and the coating is permanently and indelibly ink 
receptive. That is to say, when an ink writing instrument is used to make 
a mark on the coating, the mark is indelible and permanent and cannot be 
removed by wiping, rubbing or by any means except by destroying the 
coating. Preferably, the coating is indelibly and permanently ink 
receptive even when marked with an ink of dry wipe erasable type such as 
for example a SANFORD EXPO (trade-mark) dry erase marker pen. 
In one highly preferred form, the identification device is used to 
distinguish between the sides of the conventional audio magnetic tape 
cassettes having a plane of symmetry and two opposing major sides, so 
that, for example, road vehicle drivers can distinguish one cassette from 
another and one side of the cassette from the other, allowing selection of 
the recorded material at night or in other low illumination conditions 
without needing to turn on the interior lights which may impair the 
driver's night vision. 
The invention will be described in more detail, by way of example only, 
with reference to the accompanying drawings wherein:

Referring to FIGS. 1 and 2, labelling material 10 comprises in this example 
a rectangular sheet of a preferably flexible carrier lamina 11, for 
example paper, having on its upper side a coating 12 of a phosphorescent 
pigment which forms the upper exposed side of the material. The lower side 
of the lamina 11 carries a permanently tacky pressure sensitive adhesive 
coating 13 protected with a peelable release coated backing lamina 14, 
e.g. silicone treated paper. 
The lamina 11 with its coatings is die cut and kiss cut by conventional die 
cutting and kiss cutting procedures along lines 16 through to the upper 
side of the backing 14, so that the latter remains as a continuous lamina 
from which individual labels 10a defined by the die cuts 16 may be peeled 
for application as identification devices. The permanently tacky coating 
13 which is exposed allows easy application of the phosphorescent material 
to objects or locations to be marked for viewing in the dark. 
Normally, before peeling off the individual label 10a but optionally after 
applying it to an object or location to be distinctively marked, the label 
10 is written on or otherwise marked by the user with a dark marking 
writing instrument such as a pen, pencil or marker. Preferably, the 
writing instrument is a fine metal ball tipped writing instrument such as 
the kind available under the trade-mark PILOT from the Pilot Pen Company, 
Japan or under the trade-mark UNI-BALL from Faber-Castell Canada Inc., 
Toronto, Canada, by reason of their definite dark marking abilities. The 
marking may however, if desired, be made with an ink marker of the dry 
wipe erasable type such as the SANDFORD EXPO (trade-mark) dry erase marker 
pen. On smooth glossy surfaces such as plastic film, such inks can be 
removed by rubbing with a dry eraser such as cloth or paper tissue. On the 
matt permanently ink receptive phosphorescent pigment coating, however, 
the ink forms an indelible marking so that the marking will not be erased 
by handling by the user in the dark or under low light level conditions. 
For example, in the case of labels to be applied to audio cassettes, the 
user will write on the labels the title of the cassette, or the name of 
the artist recorded, so as to distinguish the cassette from others in the 
dark, and may write information on the material recorded on each side of 
the cassette, as an aid to memory in the dark of the material recorded on 
each side, this writing being viewable in the dark by reason of the 
contrast between the dark ink lines and the glowing label background. 
As a guide to the user the labels 10a may be printed with lines as shown, 
and in the case of labels to be applied to an audio cassette 20, with 
designations of A and B sides as shown. 
The phosphorescent pigments which are used in the present invention are in 
themselves well known. The term "phosphorescent" is used in it 
conventional sense as meaning a pigment which when exposed to a stimulus 
such as daylight, or a component thereof such as ultraviolet radiation, 
absorbs such light or component and continues to emit visible light after 
the stimulus is removed. Preferably the phosphorescent pigments used have 
relatively long persistence values. Such persistence values are measured 
in terms of the time in minutes after removal of the stimulus for the 
light intensity measured in mcd/m.sup.2 (milli Candles (Int.) per meter 
squared) to fall below 0.32 mcd/m.sup.2, a value 100 times that of the 
threshold of perception. Preferably, the pigments used exhibit persistence 
(100 .times.threshold of perception 0.32 mcd/m.sup.2 in min.) of from 
about 100 min. to about 800 min., preferably about 240 min. to about 800 
min. Typically, the pigments comprise mixtures of zinc, cadmium, strontium 
and calcium sulphides, optionally with metal activator ions such as 
copper, cobalt and bismuth. Examples of such pigments are those available 
under the trade-mark LUMILUX from Riedel de Haen AG of Seelze, West 
Germany. 
In forming the present identification devices an ink or other coating 
composition comprising the phosphorescent pigments is preferably applied 
on a preassembled lamina comprising the adhesive backed paper or other 
lamina 11 provided with the protective release-coated lamina 14. Such 
pre-assembled laminae are commercially available for example under the 
trade-mark STRIP-TAC PLUS from Brown Bridge division of Kimberly-Clark 
Corporation, P.O. Box 370, Troy, Ohio 45373. 
Such inks or other coating compositions normally comprise the 
phosphorescent pigment dispersed in a liquid medium forming on drying a 
binder matrix which binds the pigment to the surface of the lamina 11. 
As noted above, it is important that the surface of the coating have a matt 
finish so that it will readily and permanently receive written indicia 
indelibly thereon and is conducive to the forming of definite dark writing 
or other marks thereon which are not smudged or erased in the hands of the 
user. Such matt finish is preferably perceptibly rough to the finger tip 
and takes up conventional water or solvent based dark ink to form 
continuous uninterrupted marks on drawing a pen such as the PILOT, 
UNI-BALL and SANDFORD EXPO pens mentioned above thereacross. Such matt 
surfaces may be obtained by appropriate formulation of the phosphorescent 
ink or other phosphorescent coating composition, by selection of 
appropriate coating or printing methods or by a combination of these two 
techniques. 
Preferably, in order to provide a matt finish the ink or other coating 
composition comprises a high proportion of solid particles such that on 
drying the coating comprises about 50% to about 95% by weight, more 
preferably about 60% to about 75% by weight of solid particles based on 
the total dry weight of the coating including the particles and matrix 
binder. Preferably the solid particles are substantially wholly 
phosphorescent pigment particles but it is acceptable to use some inert 
non-phosphorescent diluent particles in the ink or other coating 
composition, for example inert pigment particles such as titanium dioxide 
and silica provided those do not adversely affect the brightness of the 
phosphorescent glow. Preferably the quantity of phosphorescent particles 
comprises about 50 to about 100% by weight of the solid particles in the 
ink or other coating composition, more preferably about 75 to about 100%. 
A matt finish is also favoured by using particles which are of relatively 
large size. Preferably the average particle size is about 15 to about 45 
microns as measured a Fisher Sub-Sieve Sizer, more preferably about 20 to 
about 40. Such Fisher Sub-Sieve Sizer micron particle sizes are measured 
using a conventional instrument obtained from Fisher Scientific Company, 
Unionville, Ontario, Canada, Catalogue Item No. 14-311. 
Preferably, a matt finish is achieved by using a coating technique which 
tends to provide surface roughness. For example the coating may be applied 
by air brushing onto the lamina 11 or, more preferably, by screen 
printing. Moreover where the ink or other coating composition tends to 
form a suitable ink receptive matt finish regardless of the application 
method, other conventional application methods may be employed for example 
brushing on the composition or printing it on using standard rotary 
lithographic procedures, wherein for example the coating composition is 
doctored onto a rotating roller in a thin film using a doctor blade and 
transferred onto continuous stock passed in contact with and under the 
roller. 
Although the above description provides ample information to enable one of 
ordinary skill in the art to carry out the invention, for the avoidance of 
doubt some detailed Examples will be given. 
EXAMPLE 1 
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Phosphorescent coating composition 
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2 parts 10% aqueous solution of sodium 
hexametaphosphate 
5 parts 10% aqueous sodium hydroxide solution 
17 parts distilled water 
0.04 parts Aerosil (fine silica) 
5 parts denatured ethyl alcohol 
2 parts butyl glycol acetate 
68.5 parts MOWILITH DC 02 (trade-mark) (resin 
binder available from Hoechst Canada 
Inc.) 
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100 parts of a mixture of the above composition is blended with 300 parts 
of LUMILUX pigment to obtain a coating composition suitable for 
application on paper stock. 
Further examples of phosphorescent inks or coating compositions which may 
be employed include SPEEDBALL NIGHT GLO TEXTILE INKS (trade-mark) 
available from Hunt Manufacturing Co. of Statesville, N.C. 
EXAMPLE 2 
The structure shown in FIGS. 1 and 2 of the drawings was formed by screen 
printing on STRIP-TAC PLUS (trade-mark) self adhesive release backed 
stock. The ink used for the screen printing was SPEEDBALL NIGHT GLO 
TEXTILE INK. It was applied through a large mesh silk screen, 110 mesh 
size (openings per linear inch). After a first application, the ink was 
allowed to dry at 135.degree. F. for 30 to 45 seconds and a second silk 
screen application was made as before. About 0.02 oz. of ink was deposited 
in each application. After drying of the second coating the lines and A 
and B markings shown in FIG. 1 were silk-screened on using a conventional 
black printing ink and a fine mesh silk screen of 305 mesh (305 openings 
per linear inch). After drying of the ink, the printed sheet was die cut 
and kiss cut. The matt phosphorescent coating formed on the sheet 
permanently and indelibly received a marking of ink when applied thereto. 
Such marking was indelible even when the ink was of a dry wipe marking 
erasable type (for example a SANFORD EXPO dry erase marker).