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FIELD OF THE INVENTION
The invention relates generally to a photoluminescent retroreflective sheet
material for use as a guide marker and which has particular utility in
buildings when a power outage occurs. Specifically, the present invention
relates to a photoluminescent retroreflective sheeting combining both
photoluminescent and retroreflective properties in a single product to be
used to form a marker system to help indicate exits, doorways, hazards,
OSHA markings, pipe markings, high voltage areas, fire hoses and
extinguishers and the like, when it is dark in the building, perhaps when
caused by a power outage.
BACKGROUND OF THE INVENTION
The term "building" as used throughout this application is intended to
include any structure such as an aircraft, boat or other moveable and
non-moveable conventional structures.
It is well known that within buildings at night or especially when the
power has been lost, it is difficult to find ones way along the necessary
corridors to the building exits. Similarly, in some emergencies, the
location of important fixtures such as fire alarms, extinguishers,
shut-off valves and the like are difficult to find.
In the prior art, a photoluminescent material is utilized as a guide for
such purposes. The luminous material is attached to doorways, hallways,
and the like, so that in the event of a power outage, the photoluminescent
material will glow in the dark and guide a person to an exit or along a
prescribed path. Of course, it is only useful to those individuals in the
building that have adjusted their eyes to the darkness. Further; the
luminescence produced is significantly lost within the first 20 minutes of
an "outage." This makes it virtually useless to anyone entering the
building after a short period of time.
The present invention overcomes the disadvantages of the prior art by
providing a single sheeting material having both photoluminescent and
retroreflective properties. The sheeting should exhibit the same
photoluminescent properties as the current product being used, and it has
significant retroreflective properties.
Thus it is an important object of the present invention to provide a
photoluminescent retroreflective sheet material that is designed to
provide both photoluminescence and retroreflection of light.
It is also an object of the present invention to provide a photoluminescent
retroreflective sheeting in which a phosphorescent pigment is added to the
retroreflective layer.
It is a further object of the present invention to provide a
photoluminescent retroreflective sheet in which the retroreflective layer
has cube corner retroreflectors embossed on the backside thereof and
covered by a predetermined pattern of hydrophobic silica. A backcoating
contains the phosphorescent pigment and is in contact with the
retroreflective layer in areas of the pattern not covered by the
hydrophobic silica.
It is yet another object of the present invention to provide a
photoluminescent reflective sheet which has a transparent flexible film
with retroreflective cube corners formed on the reverse surface thereof
and a clear adhesive with phosphorescent pigment screen-printed in a
pattern and cured on the cube corners.
It is believed that the present invention may be utilized with
retroreflector sheeting produced in a variety of ways but will be
particularly useful with that retroreflective sheeting described and
claimed in U.S. Pat. No. 4,618,518, issued Oct. 21, 1986, to Robert M.
Pricone, et al. and assigned to applicants' assignee, the disclosure of
which is incorporated by reference. Other forms and methods of producing
retroreflective sheeting include those of "casting" cube corner elements,
such as disclosed in Rowland U.S. Pat. Nos. 3,810,804, issued May 14,
1974; 3,684,348, issued Aug. 15, 1972; and 3,689,346, issued Sep. 15,
1972.
Useful apparatus for embossing a film to provide cube corner
retroreflective elements is disclosed in Pricone, et al. U.S. Pat. No.
4,601,861, issued Jul. 22, 1986, commonly assigned. Other techniques for
compression or sequential embossing are disclosed in Rowland U.S. Pat. No.
4,244,683, dated Jan. 13, 1981.
Efforts have been made in the past to utilize fluorescent pigmented
materials in conjunction with retroreflective sheet materials of the cube
corner type. However, such use of fluorescent materials was intended to
provide a combination of day/night visibility in highway signs. One
example is that found in Rowland U.S. Pat. No. 3,830,682, issued Aug. 20,
1974. However, in such uses, unlike phosphors, the flourescent material
would not continue to glow or provide light under "darkened" conditions
but instead is illuminated by the light of certain wave lengths, so as to
provide some "daylight" visibility to highway signs.
The present invention utilizes a phosphorescent pigmentation in conjunction
with retroreflective sheet material in a manner which does not materially
impede the retroreflective capability of the sign when illuminated either
under normal lighting conditions, such as in a building and under hallway
lighting lights, nor does it impede the "dark" or night light
retroreflective capability when illuminated by a flashlight or other
temporary light source.
SUMMARY OF THE INVENTION
The present invention relates to a photoluminescent retroreflective
sheeting material, which, in one embodiment, comprises a first layer of
transparent retroreflective film having a front face and a plurality of
cube corner retroreflective elements formed on at least a portion of the
reverse or rear face to retroreflect light impinging upon the front face;
a second layer of clear adhesive is screen-printed in a pattern and cured
on the formed cube corner elements; a third layer of opaque film is
adhered to the second layer to form air cells; an adhesive fourth layer is
applied to the third layer for attaching the sheet material to a substrate
surface; and a release liner is normally secured to the adhesive layer to
prevent inadvertent contact of the adhesive layer with a surface. A
phosphorescent pigment is contained in at least one of the first, second,
third or fourth layers to cause the sheet to glow in the dark.
In a second embodiment the second layer is comprised of hydrophobic silica
which eliminates the "air cell".
In a third embodiment, a thermoplastic film is attached to the reverse side
of the transparent retroreflective film by heat sealing or sonic welding.
This second film can be photoluminescent film which has secured to it a
separate white adhesive layer, or can be comprised of two layers, a
photoluminescent layer and an opaque white layer, followed by an adhesive
layer. Other embodiments are disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects of the present invention will be more fully
understood when taken in conjunction with the following detailed
description and the attached drawings in which like numerals represent
like elements and in which:
FIG. 1 is a first embodiment that illustrates a cross sectional view of
photoluminescent retroreflective sheeting of the present invention in
which clear adhesive with a phosphorescent pigment is screen printed in a
pattern on the retroreflective cube corners formed on the rear surface of
a transparent film;
FIG. 2 is a cross-sectional view of a second embodiment of the present
invention in which the retroreflective layer of film has the cube corners
embossed on the rear surface thereof and a hydrophobic silica pattern is
applied on the embossed surfaces; a backcoating with phosphorescent
pigment is applied over the hydrophobic silica and is in contact with the
otherwise exposed retroreflective cube corner elements;
FIG. 3 is a cross-sectional view of a third embodiment of the present
invention in which the retroreflective layer has the cube corner
reflectors on one side thereof and which layer also contains the
phosphorescent pigment for enabling the sheet to be seen when not
illuminated by an external source. An adhesive layer is applied over the
hydrophobic silica layer and exposed cube corner elements, and a release
liner is added to prevent accidental contact of the adhesive with a
substrate surface;
FIG. 4 is a cross-sectional view of yet another embodiment of the present
invention, in which the retroreflective layer contains the phosphorescent
pigment; the hydrophobic silica is screened in a pattern over the embossed
cube corner retroreflectors on the retroreflective layer; a white
backcoating is applied to the silica layer and to the exposed cube corner
elements, an adhesive layer is added and a release liner is applied to
prevent the adhesive from accidentally touching a surface;
FIG. 5 is a schematic drawing of a process for making one embodiment of the
present invention;
FIG. 6 is a schematic drawing of the process for making the invention
illustrated in FIG. 2 of the present invention;
FIG. 7 is a schematic drawing of the process for making the embodiment of
FIG. 3 of the drawings;
FIG. 8 is a schematic drawing of the process for making the
photoluminescent retroreflective sheeting of the FIG. 4 embodiment;
FIG. 9 is a cross-sectional view of another embodiment of the invention in
which the phosphorescent pigment is utilized with "beaded sheeting"
containing microspheres to provide retroreflectivity;
FIG. 10 is a cross-sectional view of yet another embodiment of the
invention in which a phosphorescent film is attached to the reverse side
of the transparent film.
FIG. 11 is a cross-sectional view of a variation of the embodiment of the
invention shown in FIG. 10, with second film having a top photoluminescent
layer and lower opaque white layer.
FIG. 12 is a schematic drawing of the process of making the
photoluminescent retroreflective sheeting embodiments shown in FIG. 10 and
FIG. 11.
DETAILED DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the present photoluminescent retroreflective
sheeting is illustrated in cross-section in FIG. 1. The sheet comprises a
first layer of transparent retroreflective film 12 that is formed
generally in accordance with the method and apparatus disclosed in the
aforesaid Pricone U.S. Pat. No. 4,486,363. However, as noted, other
methods of forming a film with cube corner retroreflector elements (or
spherical retroreflectors) may be used.
In the preferred form, the film 12 is approximately 0.006-0.008 inches
thick and has a plurality of retroreflective corner cube elements 13
embossed on the rear side thereof.
It also has a layer of clear adhesive 14 containing a phosphorescent
pigment screened in a pre-selected pattern over certain of the cube corner
elements 13 so as to leave spaces or cells 22. One such adhesive 14 may be
that known as Flexcryl 1625, sold by Air Products, Inc., and applied by
screen printing. This is a water based acryclic.
The adhesive 14 contains a phosphorescent pigment which may be of a type
known as P-1000, sold by Hanovia, a division of Conrad, Inc. of Newark,
N.J. and which is commercially available. Other phosphorescent pigments
may be used. The pigment may be batch mixed with the adhesive so as to
constitute about 30% by weight thereof.
Other adhesives that may prove satisfactory would be drawn from unpigmented
acrylics; urethanes; UV curable 100% solids; the criteria being that the
adhesive bond between the resin layer and back layer be flexible and be
readily applied.
The transparent retroreflective film 12 with the clear adhesive 14 and
containing the phosphorescent pigment therein is then cured by heating or,
if appropriate, and if UV curable, then curing can be accelerated.
After curing, an opaque layer of material 16, (such as polyester, PVC, or
Mylar), is then applied over the transparent clear adhesive 14 with the
phosphorescent pigment, to complete the "air" cells 22. The air cells
permit retroreflectivity to be achieved, as is known in the art.
Preferably, this layer 16 will be of a white color to enhance the
brightness of the phosphorescent effect, but other colors or metallized
films may be used.
An adhesive fourth layer 18 then may be applied to the white layer 16,
enabling the sheeting material to be attached to a surface. A release
liner 20 is applied to the adhesive layer 18 to prevent inadvertent
contact of the adhesive with a surface until the user is ready to install
the sheeting.
In the embodiment of FIG. 1, the retroreflective cells 22 allow the
transparent film 12 to be retroreflective and reflect light impinging upon
the front surface. The clear adhesive 14 with the phosphorescent pigment
allows the strip to glow in the dark so that it can be followed by an
individual. Thus, such sheeting can be used to form guidance systems that
mark exits, doorways, hazards and the like in the case of a power outage.
When the photoluminescent property of the sheets fail then the
retroreflective cube corner elements will continue to retroreflect
incident light, such as from a flashlight or the like carried by service
individuals such as police, fire or utility department officials.
In FIG. 2, the sheeting 24 could be formed of a retroreflective layer of
transparent flexible film 26 with cube corner retroreflective elements 27
formed on the reverse side thereof by embossing, to reflect incident light
thereon. A hydrophobic silica layer 28 is screen printed in a pattern over
the cube corner retroreflective cells 27. A clear water-based backcoating
30 is then placed over the hydrophobic silica 28. The backcoating contains
the phosphorescent pigment. A white pigment adhesive 32 is laminated to
the backcoating 30 for attaching the sheet to a surface. White pigment is
used to enhance reflectivity as well as brightness of the phosphorescent
material. A release liner 34 is laminated to the adhesive to prevent the
adhesive 32 from inadvertently contacting a surface until the user is
ready.
In the embodiment illustrated in FIG. 3, the retroreflective layer 38 also
includes the phosphorescent pigment therein. The hydrophobic silica 42 is
then screened on the cube corners 40 in a predetermined pattern and a
white pigmented adhesive 44 is coated over the hydrophobic silica pattern.
Again, a release liner 46 is laminated to the adhesive 44 to prevent the
sheet from inadvertently sticking to a surface until the user is ready for
it.
Other advantageous uses of the present invention with respect to
retroreflective sheeting of other kinds, such as metallizing over some or
all of the reflector elements, also will be recognized. Thus, for example,
retroreflective sheeting material is disclosed and Martin U.S. Pat. No.
4,801,193 may be provided with the phosphorescent pigmentation
advantageously employed in the present invention.
In the embodiment illustrated in FIG. 4, the sheet 48 is again formed of a
transparent flexible film 50 that has retroreflective cube corner elements
52 formed on the reverse side thereof and which contains the
phosphorescent pigment described earlier. Again, a hydrophobic silica 54
is screened on the cube corners of the translucent reflective flexible
film 50 in a predetermined pattern. A white backcoating 56 as described
earlier is coated over the hydrophobic silica 54. An adhesive layer 58 is
laminated to the white backcoating 56 and a release liner 60 is laminated
to the adhesive 58 to prevent the adhesive from inadvertently contacting a
surface before the user desires.
The method of application and composition of the hydrophobic silica,
backcoating and adhesive as discussed herein may be as disclosed in the
aforesaid Pricone et al, U.S. Pat. No. 4,618,518.
A process for forming the photoluminescent retroreflective sheeting shown
in FIG. 1 is illustrated in FIG. 5. The transparent flexible film may be
extruded and have retroreflective cube corner elements embossed or cast on
the reverse side thereof at step 64. At step 68, a clear adhesive
containing a phosphorescent pigment is screen printed in a predetermined
pattern on the cube corner elements on the reverse or rear side of the
flexible film. At step 70, the adhesive is cured and at step 72 an opaque
film, preferably white, is adhered to the adhesive to form air cells. At
step 74, an adhesive layer is added to the film and at step 76 a release
layer is laminated to the adhesive layer to prevent the adhesive from
adhering to a surface prior to the time it is needed.
FIG. 6 illustrates the process steps for forming the invention of FIG. 2.
Again, in step 1, the transparent flexible film is extruded. At step 80
retroreflective cube corners are formed on the reverse side by casting or
embossing. At step 82, hydrophobic silica is screen printed in a pattern
over the cube corner elements. At step 84, the silica is coated with a
clear water-based backcoating containing the phosphorescent pigment. A
white (or other color) pigmented adhesive is applied to the silica coating
at step 86 and a release layer is laminated to the pigmented adhesive at
step 88 to prevent the adhesive from inadvertently sticking to a surface.
FIG. 7 is a flow chart of the process for forming the photoluminescent
retroreflective sheeting illustrated in FIG. 3. As can be seen in FIG. 7,
the flexible film is extruded and contains the phosphorescent pigment
which glows in the dark. The retroreflective cube corner elements are then
embossed on the reverse side of the extruded flexible film at step 92.
Hydrophobic silica is then screen printed on the cube corners in a
predetermined pattern at step 94. A water-based backcoating adhesive is
applied to the hydrophobic silica at step 96. Finally, a release liner is
laminated to the adhesive at step 98 to prevent the product from sticking
to a surface inadvertently.
The flow chart of FIG. 8 discloses the method of making the sheeting sample
illustrated in FIG. 4. Again, at step 100, the flexible film containing
the phosphorescent pigment is extruded. In step 102 the reverse side of
the sheet is embossed with the cube corner elements. In step 104, the
hydrophobic silica is coated with a pigmented water-based backcoating,
preferably white. At step 108 the layer of adhesive is applied to the
backcoating and in step 110 a release liner is laminated to the adhesive.
Again, such liner is used to prevent the adhesive from inadvertently
sticking to a surface before it is intended to be used.
Since the present film is primarily to be used indoors, additional overlays
or other ultraviolet inhibitors which help prevent deterioration of
outdoor retroreflective sheeting may not be necessary, further reducing
the processing cost.
FIG. 9 discloses a sample microsphere beaded type sheet material 130
employing the present invention. The beaded sheeting 130 may be of the
type produced by 3M Corporation and sold under the trademark
Scotchlite.RTM.. It is believed such material is made in accordance with
various 3M patents such as U.S. Pat. Nos. 2,407,680 and 4,511,210. In this
embodiment the sheeting comprises a layer of monosphere beads 135 and a
transparent layer of resin below which may be a specially reflecting
surface 136. The phosphorescent pigment 134 may be employed in an overlay
over the beads, or in the binder layer 137 in which the beads are
embedded. In the case of so-called high intensity beaded sheets, the
phosphorescent pigment may be incorporated into the cell walls. A layer of
adhesive 138 and-a release liner 139 also may be used.
In the alternative embodiment illustrated in FIG. 10, the sheet 140 is
again formed of a transparent flexible film 142 of thickness ranging from
about 0.006 inches to about 0.008 inches that has retroreflective cube
corner elements 144 formed on the reverse side thereof. This embodiment,
however, contains a second, photoluminescent film 146 having thickness in
the range of from about 0.010 to about 0.020 inches, which is attached to
the reverse side of the transparent retroreflective sheet by heat sealing,
sonic welding or other process known in the art. Preferably, the
photoluminescent film 146 contains the photoluminescent pigment described
above.
The attachment of the photoluminescent film to the transparent film is
according to a pre-selected pattern. Preferably, the pattern is created in
the photoluminescent film at the time of heat sealing or sonic welding as
shown in FIG. 10. Alternatively, the pattern can be created in the
transparent film before attachment to the photoluminescent film by
creation of a pattern in the embossing tool which forms the cube corner
micro-prisms.
At least part of the photoluminescent film is spaced from the cube corner
micro-prisms on the reverse side of the retroreflective sheet to form air
cells 148 therebetween, thereby maintaining the retroreflective quality.
There is no air between the retroreflective film and photoluminescent film
at the points where the heat sealing or sonic welding 150 attachment has
been made to the reverse side of the retroreflective layer. Moreover, the
cube corners will be deformed or destroyed by the heat sealing and sonic
welding processes.
The second, photoluminescent film has attached to its backside a white
adhesive layer 152 which can be either laminated to or coated directly on
the film. A release liner 153 covers the adhesive to prevent contact of
the adhesive with any surface until the sheeting is to be applied. The
release liner can be removed from the sheeting without removing the white
adhesive, as is known in the art.
FIG. 11 shows yet another alternative embodiment 154 of the inventive
photoluminescent retroreflective sheeting. Again, this embodiment contains
a transparent flexible film 156 of about 0.006 inches to about 0.008
inches in thickness, and has embossed on its reverse side a series of cube
corner micro-prisms 158 producing the retroreflective characteristics
discussed above.
The reverse side of the retroreflective film has attached to it a flexible
thermoplastic film 160 composed of two distinct layers. The first layer
162 contains photoluminescent pigment and the second layer 164 is an
opaque white layer. The thickness of this two layer film is in the range
of from about 0.015 inches to about 0.030 inches. Such films are
commercially available as "photoluminescent vinyl tape" sold by Hanovia of
Newark, N.J. (as part of its Escape Route System), and as Lumilux.RTM.
sold by the Fine Chemicals Division of Hoechst Celanese, Charlotte, N.C.
This two layered second thermoplastic film is attached preferably in a
pre-selected pattern to the cube corner containing reverse side of the
retroreflective sheet by heat sealing, sonic welding or similar process
known in the art 166. Alternatively, the pattern can be created in the
transparent retroreflective sheet before heat sealing or sonic welding to
the second film. The second film is spaced from the retroreflective
micro-prisms where it is not heat sealed, sonic welded or otherwise
attached, to form air cells 168 therebetween. The retroreflective quality
of the top sheet is preserved where the air cells have been created.
An adhesive layer 170 is either laminated to or coated directly on the
second two-layer film. The adhesive has a release liner 172 reversibly
attached to its reverse side. The release liner prevents inadvertent
contact of the adhesive with any surface until the sheeting is to be
applied. The release liner 172 may be removed from the sheet without
removing or otherwise staying attached to the adhesive of the adhesive
layer 170.
FIG. 12 shows a schematic drawing of the process of making the embodiments
shown in FIGS. 10 and 11. The initial step, shown at the top of FIG. 12,
is the extrusion of a flexible transparent film 174 having thickness of
approximately 0.006 inches to about 0.008 inches. After this film is
extruded, cube corner prisms or micro-prisms are formed 176 on its reverse
side, preferably by embossing. The formation of the cube corner prisms or
micro-prisms transforms the transparent material into a retroreflective
sheet capable of reflecting incident light.
The extrusion of the flexible film and the formation of the cube corners on
its reverse side is followed by application of the second film 178 which
contains the photoluminescent pigment. This film is attached in a
pre-selected pattern to the reverse side of the first, retroreflective
sheet through heat sealing, sonic welding or other similar means. The
photoluminescent film is spaced from the cube corner micro-prisms on the
reverse side of the retroreflective sheet, except where it is attached by
heat sealing or sonic welding. This photoluminescent film is about 0.010
inches to about 0.020 inches in thickness and has attached to its reverse
side in the next process step 180 a white adhesive layer. This adhesive
layer is capable of attaching the sheeting to a desired surface.
A release liner is applied to the adhesive layer in the following step 182
to prevent contact of the adhesive with any surface until the sheeting is
desired to be applied. The release liner may be removed from the adhesive
layer without removing the adhesive layer, leaving the adhesive intact so
that it will be present when the sheeting comes into contact with the
desired application surface.
The above-described process will result in the sheet illustrated in FIG.
10. A variation of this process will result in the embodiment shown in
FIG. 11. This variation is made by the process described above except for
steps 178 and 180. For step 178 a second, thermoplastic film which has a
thickness of approximately 0.015 inches to about 0.030 inches is applied
instead of the photoluminescent film described for step 178 above. This
second film contains a top photoluminescent first layer containing a
photoluminescent pigment, followed by a second, white opaque layer.
Because of the presence of the opaque white layer in the second film
applied in step 178, the adhesive layer applied in step 180 need not be
white. All the remaining details of the process steps to produce the
embodiment of FIG. 11 are the same as described above to produce the
embodiment in FIG. 10.
It will be appreciated from the foregoing that the present invention
provides significant advantages for safety purposes in that dual functions
can be obtained while utilizing sheeting having a high degree of
retroreflectivity and photoluminescence while minimizing the amount of
material required for each such purpose.
While the invention has been described in connection with a preferred
embodiment, it is not intended to limit the scope of the invention to the
particular form set forth, but, on the contrary, it is intended to cover
such alternatives, modifications, and equivalents as may be included
within the spirit and scope of the invention as defined by the appended
claims.
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