Electroluminescent lamp with novel edge isolation

An electroluminescent sheet-form lamp with a main portion of a conductive layer isolated from an edge region susceptible to detrimental conductive pathways by isolation provided along at least a portion of the perimeter of the lamp as a result of removal of a preapplied conductive coating such that, at the region of the isolation, the main portion of the one conductive layer which forms the respective electrode commences at a line spaced inwardly from the outer edge of the lamp. The preapplied conductive coating material may be removed to form a line of interruption that leaves in place a narrow margin of conductive coating in the edge region which is electrically isolated from the main portion of the coating forming the first electrode. The lamp may be formed by exposing preselected portions of the preapplied conductive coating to laser radiation sufficient to remove the preselected portions and form the region of isolation. A scribing technique or a mask, which may be a printed functional layer of the lamp, are employed.

BACKGROUND OF THE INVENTION 
Electroluminescent lamps are typically formed as sandwiches of a number of 
layers, including a transparent substrate, a transparent front electrode, 
a phosphor layer, a dielectric layer, and a rear electrode. Other layers 
are often included. When electrical current is applied to the two 
electrodes, the phosphor layer emits light, the color of which is 
selectable depending, e.g., upon choice of the phosphors, use of filters, 
etc. Such lamps are suitable for many uses, one example being backlighting 
of automobile dashboards. Cost of such lamps is often a significant factor 
in their suitability for an application. Many applications also require 
the lamps to withstand high humidity conditions and meet other rigorous 
environmental or safety standards. It is common to form electroluminscent 
lamps by application of a general coating of conductive material on a 
large substrate panel, as by sputter coating, the coating providing the 
material for one of the electrodes, upon which the further layers are 
applied. Multiple EL lamps are then cut from the panel. It is known to 
protect the lamp from deleterious effects of moisture by encapsulating the 
entire cut-out lamp in a plastic film such as Aclar.RTM., or by 
encapsulating the lamp in Aclar and laminating the Aclar to itself using a 
thermoplastic adhesive material applied to the Aclar, both of which are 
steps that add to the expense of the lamp. This protection also serves to 
prevent electrical shorting between the two electrodes or failure at the 
edges of the lamp as well as eliminating shock hazards. It is also known 
to use in such lamps phosphor particles that have been individually 
encapsulated for protection against environmental conditions, but general 
encapsulation of the lamps has still been required or, if not generally 
encapsulated, the lamps have had drawbacks with respect to life 
expectancy, safety, etc. 
SUMMARY OF THE INVENTION 
We have discovered that, when making an electroluminescent lamp using a 
generally coated substrate panel to form an electrode, by providing an 
isolation line in the general conductive coating to isolate the main 
portion of the conductive coating that defines the electrode from the edge 
of the lamp, e.g., by a laser scribed line, structural durability, longer 
life expectancy, and avoidance of short circuiting and shock can all be 
achieved. 
As referred to herein, "laser scribing" includes using numerical control 
machines, e.g., a laser and a movable table, to form the line by moving 
the laser and a panel of lamps on the table or by projecting a laser beam 
through a mask to form the line. Scribing an electrode layer in an EL lamp 
to deactivate one or more of its edges enables the lamp to be employed 
with completely bare edges in harsh environmental conditions. Such a lamp 
is less susceptible to electrical shorting between the two electrodes due 
to moisture making contact with the lamp at its edges, the occurrence of 
dendritic failure, i.e., darkened branching starting at the edges of the 
lamp caused by electro-chemical reactions within the lamp upon contact 
with moisture at the edges, and shock hazards due to an electrically 
energized layer being exposed at the edges of the lamp. A lamp with such 
deactivated and exposed edges is less expensive to produce and more 
flexible because it need not be encapsulated in a plastic film, and can 
have a greater life span than previously known lamps which are not 
encapsulated in film. An isolated margin of conductive coating, if left in 
the edge region, can provide advantages, including adherence properties 
that match those of the main body of the coating, which can assure good 
adherence and structural integrity with the subsequent coatings. 
In a first aspect, the invention features, an electroluminescent sheet-form 
lamp having a transparent insulation layer, a transparent first conductive 
layer below the insulation layer forming a first electrode, a layer of 
phosphor material below the first conductive layer, a layer of dielectric 
material below the phosphor layer, a second conductive layer below the 
dielectric layer forming a second electrode, and electrical connection 
means for applying an electrical potential between the conductive layers 
to cause the phosphor to transmit light through the transparent conductive 
layer and the transparent insulation layer, one of the conductive layers 
having been formed as a general conductive coating preapplied over a panel 
of larger dimension than the lamp, from which the lamp has been cut. An 
edge region of the lamp is susceptible to formation of a detrimental, 
electrically conductive path. The improvement is that a main portion of 
the one conductive layer is isolated from the susceptible edge region by 
isolation provided along at least a portion of the perimeter of the lamp 
as a result of removal of the preapplied conductive coating such that, at 
the region of the isolation, the main portion of the one conductive layer 
which forms the respective electrode commences at a line spaced inwardly 
from the outer edge of the lamp. The lamp is the product of the process of 
exposing preselected portions of the preapplied conductive coating to 
laser radiation sufficient to remove the preselected portions and form the 
isolation, making the electrical connection for the one conductive layer 
to the main portion of the one conductive coating in a manner so that the 
electrical connection is electrically isolated from the susceptible edge 
region, and cutting the lamp from the panel of larger dimension to provide 
a lamp for which the formation of the conductive path in the edge region 
does not cause an adverse effect. 
Embodiments described herein may also have one or more of the following 
features. The electroluminescent lamp is formed by providing the laser 
radiation in the form of a beam of greater dimension than the preselected 
portions of the preapplied conductive layer, and providing a mask between 
a source of the radiation and the preapplied conductive layer, the mask 
having aperture regions for exposing only the preselected portions of the 
preapplied conductive layer. The mask is a printed mask layer printed over 
the preapplied conductive coating to expose only the preselected portions 
to be removed. The electroluminescent lamp is formed by a process that 
includes selecting a laser that removes the preapplied conductive coating 
without removing all of the printed mask layer, the printed mask layer 
adapted to serve as a functional layer of the lamp. The electroluminescent 
lamp is formed by a process that includes selecting a laser that removes 
at least part of the printed mask layer along with the preapplied 
conductive coating. The lamp is formed by a process that includes 
preselecting the thickness of the mask layer relative to the thickness of 
the preapplied conductive coating to remove only some of the thickness of 
the mask layer while forming the region of isolation by removing all of 
the preapplied conductive coating in the preselected regions, the 
remaining portion of the printed mask layer adapted to serve as a 
functional layer of the lamp. The printed mask layer is a phosphor layer 
applied directly to the preapplied conductive coating. The printed mask 
layer includes the phosphor layer and at least a portion of a layer 
forming the electrical connection to the preapplied conductive coating. 
The laser radiation is provided by an excimer laser. The laser radiation 
is provided by a TEA laser. The mask is a separate member positioned above 
the preapplied conductive coating and the laser radiation is provided by 
an excimer or TEA laser. The beam is of fan shape, with a cross-section of 
elongated form, and means are employed to produce relative motion of the 
conductive coating and the beam in the direction transverse to the 
direction of elongation of the profile. The laser radiation is formed by a 
spot beam, wherein relative motion of the preapplied coating removes the 
preselected portions of the preapplied coating and the laser radiation is 
provided by a CO.sub.2, TEA or excimer laser. The preapplied conductive 
coating material has been removed by the exposure to laser radiation to 
form a line of interruption that leaves in place a narrow margin of 
conductive coating in the edge region which is electrically isolated from 
the main portion of the coating forming the first electrode. 
In another particular aspect, the invention features an electroluminescent 
sheet-form lamp having a transparent insulation layer, a transparent first 
conductive layer below the insulation layer forming a first electrode, a 
layer of phosphor material below the first conductive layer, a layer of 
dielectric material below the phosphor layer, a second conductive layer 
below the dielectric layer forming a second electrode, and electrical 
connection means for applying an electrical potential between the 
conductive layers to cause the phosphor to transmit light through the 
transparent conductive layer and the transparent insulation layer, one of 
the conductive layers having been formed as a general conductive coating 
preapplied over a panel of larger dimension than the lamp, from which the 
lamp has been cut. An edge region of the lamp susceptible to formation of 
a detrimental, electrically conductive path. The improvement is that a 
main portion of the one conductive layer is isolated from the susceptible 
edge region by isolation provided along at least a portion of the 
perimeter of the lamp as a result of removal of the preapplied conductive 
coating such that, at the region of the isolation, the main portion of the 
one conductive layer which forms the respective electrode commences at a 
line spaced inwardly from the outer edge of the lamp, the electrical 
connection for the one conductive layer is made to the main portion of the 
one conductive coating while being electrically isolated from the 
susceptible edge region; the lamp is formed by cutting its outline from 
the panel of larger dimension to provide a lamp for which the formation of 
the conductive path in the edge region does not cause an adverse effect; 
and the preapplied conductive coating material is removed in a manner to 
form a line of interruption that leaves in place a narrow margin of 
conductive coating in the edge region which is electrically isolated from 
the main portion of the coating forming the first electrode. 
Embodiments described herein may also include one or more of the following 
features. The one conductive layer is the transparent first conductive 
layer forming the first electrode. There is an insulating substrate below 
the second conductive coating and the one conductive layer is the second 
conductive layer forming the second electrode, preapplied to the 
insulating substrate. The phosphor material includes encapsulated phosphor 
particles and the edge region is provided as a bare edge resulting from 
cutting of the lamp from the larger panel. The lamp is mounted in a manner 
that exposes the bare edge region to contact by a person, the isolation 
preventing a shock hazard to the person. The lamp is mounted in a manner 
that allows moisture to reach the bare edge region of the lamp, the 
isolation preventing electrical current leak through the moisture that 
could lead to degradation of the lamp structure. 
In another aspect, the invention features an electroluminescent sheet-form 
lamp having a transparent substrate layer, and, in successive 
relationship, a transparent first conductive layer forming a first 
electrode, a layer of phosphor material comprising encapsulated phosphor 
particles, a layer of dielectric material, a second conductive layer 
forming a second electrode, and electrical connection means for applying 
an electrical potential between the conductive layers to cause the 
phosphor to transmit light through the transparent conductive layer and 
the transparent substrate, the first transparent conductive layer 
comprising a preapplied continuous transparent coating over the substrate, 
outer edges of the layers defining the lamp being exposed to the ambient 
environment and being susceptible to formation of a detrimental conductive 
path. The improvement is a line of interruption provided along at least a 
portion of the perimeter of the lamp as a result of removal of a line of 
the preapplied transparent conductive coating. The line of interruption is 
spaced inwardly from the outer edges of the first conductive layer and 
electrically isolates a main, inner portion of the first transparent layer 
from a margin portion of the conductive layer adjacent to the edge of the 
lamp. The electrical connection for the transparent conductive layer is 
connected to the main inner portion, the main portion serving as the first 
electrode which is electrically isolated from the margin portion of the 
first conductive layer. The isolation of the main portion provides a lamp 
for which the formation of the conductive path in the edge region does not 
cause an adverse effect. 
Embodiments described herein may also include one or more of the following 
features. The line of interruption is formed by laser scribing the 
preapplied conductive layer. The transparent conductive layer comprises 
indium tin oxide. The phosphor material is doped zinc sulfide. The 
substrate layer is formed of polyester. An insulation layer is provided on 
the back of the second conductive layer. 
In another aspect, the invention is a method of forming an 
electroluminescent sheet-form lamp having a predetermined edge 
configuration that may correspond to a custom order or a complex shape. 
The method incudes providing a sheet-form laminate member larger than the 
lamp, the laminate member comprising a transparent substrate layer, a 
transparent first conductive layer over the substrate layer, a layer of 
phosphor material over the first electrode layer, a layer of dielectric 
material over the phosphor layer, and a second conductive layer over the 
dielectric layer, cutting the lamp from the larger laminate member along 
predetermined lines conforming to the predetermined edge configuration, 
and forming electrical connections for applying electrical potential 
between the conductive layers to cause the phosphor to transmit light 
through the conductive layer and the transparent substrate. The 
improvement is that during formation of the laminate member, the first 
transparent electrode is formed by first providing the first transparent 
conductive layer as a continuous layer on a substrate corresponding to the 
size of the larger laminate member and subsequently forming a line of 
interruption in the layer as a result of removal of a line of the 
conductive coating within the predetermined edge configuration of the 
desired lamp. The line of interruption extends about the area of the lamp 
and spaced inwardly from the location of the predetermined edge 
configuration. The line of interruption electrically separates a main, 
inner portion of the first conductive layer, to serve as a first 
electrode, from an electrically isolated margin portion of the first 
conductive layer adjacent to the predetermined edge configuration. After 
completion of formation of the laminate member, the lamp is cut from the 
laminate member to the predetermined edge configuration, leaving exposed 
cut edges susceptible to formation of a detrimental electrically 
conductive path. Electrical connections are formed including forming an 
electrical connection to the inner portion of the first conductive layer 
that serves as the first electrode, while maintaining electrical isolation 
from the margin portion of the first conductive layer. The isolation of 
the main portion provides a lamp for which the formation of the conductive 
path at the cut edges does not cause an adverse effect. 
Various embodiments may also include the following. The line of 
interruption is formed by exposing preselected portions of the preapplied 
conductive coating to laser radiation sufficient to remove the preselected 
portions and thus form the electrically isolated margin portions. 
The invention also includes further methods for manufacture and use of the 
lamps described below. Still further advantages and features of the 
invention will also become apparent from examination of the drawings and 
the detailed description below.

DETAILED DESCRIPTION 
Referring to FIG. 1, there is shown a top view of an electroluminescent 
lamp 8 after it is cut with other such lamps from a panel (see FIGS. 2 and 
7). The panel comprises a clear substrate carrying a preapplied, general 
coating of a transparent conductor, on which the remaining layers have 
been deposited to comprise the lamp. 
The edges of the lamp, according to the invention, are bare, i.e. 
unencapsulated, but nevertheless prevent various electrical and structural 
failure and shock hazard. 
As shown in the cross-sectional and exploded views of FIGS. 1a, 1b and 2, 
the lamp 8 includes a number of layers beginning with a transparent 
substrate 10, e.g., a sheet of polyester film, having a thickness of 
approximately 0.007 inches. In manufacture, the lamp 8 along with other 
lamps as shown in FIGS. 2 and 7 are formed simultaneously by successive 
formation of the layers upon a panel of this substrate. Each lamp 8 is to 
be cut, as described below, along the dashed and dotted lines 11 in FIG. 2 
(along the solid lines 11' in FIG. 7). 
The substrate 10 has on one side a preapplied, general coating of a 
transparent conductive material, preferably, indium tin oxide (ITO), 
although aluminum oxide, gold, and silver, or other composite coatings may 
also be used. The ITO material is, preferably, vacuum sputtered onto a 48 
inch web which is slit to narrower panel widths to provide a general ITO 
coating that extends over the entire substrate panel, i.e., to the edges 
of the panel, to form a transparent front coating 12 that is approximately 
1000 .ANG. thick. Sputter coating is preferred because it provides high 
conductivity as well as high optical transmission of light through the 
front coating 12. 
For each lamp location on the panel, there is first deposited an optional 
bus bar 14 used to distribute power across the front of the lamp 8 when an 
electrical lead is attached to the bus bar by a connector. The bus bar 14 
is formed by screen printing a conductive ink, e.g., silver flakes 
dispersed in a polymeric resin carrier dissolved in a suitable solvent, 
and printed as a layer approximately 0.0005 inches thick. The bus bar 14 
is deposited within the outline 11 of the lamp 8 and within and spaced 
from a line of interruption 22 to be formed in the front conductive 
coating 12 (as described below). The solvent in the ink is then 
volatilized by placing the panel in an oven to remove the solvent and 
leave behind solid resin and silver which forms the bus bar 14. 
Next, for each lamp, a line of interruption 22 is formed in the conductive 
coating 12 using a laser, e.g., by laser scribing the ITO layer with a 
laser having a focused spot beam, with provisions for relative scan in the 
x and y directions of the panel relative to the laser. In an alternative 
embodiment (not shown), the ITO layer may be removed from the substrate 10 
in the margin of the lamp 8, i.e., the area commencing at the line 22 and 
extending to the edge of the lamp. An advantage of the former technique, 
in which a line of conductive coating is removed, leaving adjacent 
portions of conductive coating isolated from each other, is that 
subsequent layers may be bonded predominantly to the remaining conductive 
material and only the small amount of the subsequent layers bridging the 
line from which the conductive material is removed is bonded directly to 
the substrate 10, which in some cases does not provide as secure a bond. 
(Further, it will be understood that a line of interruption can be formed 
prior to the printing of the bus bar.) 
Laser scribing with a CO.sub.2 laser is a preferred method of forming the 
line of interruption because of its ease of use and low cost. That is, the 
relative scanning of the laser upon the panel can be programmably 
controlled as described below in connection with FIG. 8, and does not 
require retooling screens and dies in order to change the pattern of the 
line 22. CO.sub.2 lasers provide adequate processing capability at low 
capital and operating cost. Other techniques employing lasers are 
discussed below. (In addition, other methods may be used to scribe line 
22, including mechanical abrasion, e.g., using a razor blade or abrasive 
pad to cut the ITO layer, water jet sprays, and chemical etching.) 
In another embodiment of the present invention, an excimer laser is used to 
form the line 22. The excimer laser can operate so as to flood a laser 
beam through a mask positioned above and across the entire area of the 
panel. The flood beam ablates the ITO layer forming the front conductive 
coating 12 in the area of the line 22 to be scribed, but, by proper 
selection of wavelength of the laser, ablates little or none of the 
substrate 10. The mask may be formed by coating a quartz substrate with a 
metal and selectively removing, e.g., by imaging and then etching regions 
of the metal to form apertures in the metal in a desired pattern. 
Alternatively, the excimer laser beam can be directed through a hole in a 
mask to form a spot beam and the line 22 is then formed by moving the 
panel under the beam. One advantage of these approaches is that the 
substrate 10 can be thinner, thereby making the lamp 8 more flexible. In 
addition, a stronger lamp can result because the substrate 10 is not 
weakened in the area of the line 22 and is less likely to crack under 
stress. However, use of the excimer laser can entail a certain amount of 
retooling to create different masks for multiple line patterns. 
In an important aspect of the invention, laser scribing the line 22 cuts a 
groove 13 (FIG. 1a) through the ITO layer of the front conductive coating 
12 down to the substrate 10. The conductive coating 12 is thereby divided 
into a main, inner portion serving as the electrode 12a and a margin 
portion 12b which are electrically isolated from one another. Thus, an 
electrical lead attached to the bus bar 14 delivers power to the inner 
portion 12a of the front conductive coating only. The margin portion 12b 
is isolated, the edges of the conductive coating are deactivated, and the 
susceptibility to formation of a detrimental electrical conductive path is 
reduced. Examples of such a detrimental conductive path include paths 
caused by moisture at the exposed edges of the lamp 8 resulting in 
electrical failure of the lamp, or by a person's hand, for example, coming 
in contact with the edges resulting in electrical shock. 
Because of the above described isolation, there is no need to encapsulate 
the entire lamp 8 in a plastic film (or, depending upon the barrier 
qualities of the preapplied coating, even to encapsulate the phosphor 
particles). As a result, the lamp 8 is less expensive to produce and more 
flexible and adaptable to specific applications than EL lamps encapsulated 
in film. In addition, the lamp 8 is more reliable in harsh environments, 
safer for use in consumer applications, and has a greater life span than 
previous non-encapsulated lamps. 
Referring again to FIG. 1a, the width and depth of the groove 13 depend 
primarily on the selected spot size and power of the laser beam. In 
preferred embodiments, the width of the line 22 is between 0.005 and 0.010 
inches, which is sufficient to prevent electrical arcing from the inner 
portion 12a of the front conductive coating 12 across the line 22 to the 
margin portion 12b under typical lamp operating conditions of 115 volts AC 
and 400 Hz. The line 22 may cut approximately 0.002 inches into the 
substrate 10 to ensure electrical separation between the inner portion 12a 
and the margin portion 12b of the coating. As shown in FIG. 1a, the 
resulting groove 13, if present, is then filled with material from one of 
the subsequent layers of the lamp 8 which are described below. 
As shown in FIGS. 1a and 2, the front conductive coating 12, bus bar 14, 
and isolation line 22 are covered with a phosphor layer 16 formed of 
electroluminescent phosphor particles, e.g., zinc sulfide doped with 
copper or manganese, which are dispersed in a polymeric binder. Suitable 
binders include cyanoethyl cellulose, cyanoethyl pullulan, or 
polyvinylidene fluoride and its copolymers, all of which are commercially 
available. In cases where the barrier qualities of the successive layers 
are insufficient to prevent access of moisture through the thickness of 
the lamp to the phosphor particles, the phosphors employed can be of the 
encapsulated type in which each phosphor particle has its own protected 
outer coating that prevents entry of deleterious moisture. Such coatings 
include 72X, available from Sylvania/GTE, and coatings disclosed in U.S. 
Pat. No. 4,855,189 and in co-pending application Ser. No. 07/514,440, 
filed Apr. 25, 1990, which is incorporated herein by reference. The 
phosphor layer 16 is applied to the front conductive coating 12, e.g., by 
screen printing or other coating methods, and has a thickness of 
approximately 0.001 inches. 
In the embodiment shown in FIG. 1a, the phosphor layer 16 extends over the 
inner electrode portion 12a and margin portion 12b of the front conductive 
coating 12, thereby filling in the groove 13 as shown in FIGS. 1a and 1b. 
But, in alternative embodiments, such as the one shown in FIG. 1c, the 
phosphor layer 16 is applied to the inner portion 12a only and stops short 
of the line 22 so that a subsequent layer of the lamp 8 fills in the 
groove 13. Nonetheless, in either embodiment, the phosphor layer 16 is 
applied so as to leave an exposed window 15 above a portion of the bus bar 
14 to which a front lead connection can be attached. 
The next layer of the lamp 8 is a dielectric layer 18 formed of a high 
dielectric constant material, e.g., barium titanate, dispersed in a 
polymeric binder such as one of those mentioned above. The dielectric 
layer 18 measures approximately 0.001 inches thick and is applied, e.g., 
screen printed, over the phosphor layer 16 so that it extends to the edges 
of the lamp 8 but leaves the area of window 15 uncovered. In the lamp of 
FIG. 1c where the phosphor layer 16 stops short of the line 22, material 
from the dielectric layer 18 fills the groove 13. 
Deposited above the dielectric layer is a rear electrode 20, formed of 
conductive particles, e.g., silver, carbon, or nickel, dispersed in one of 
the polymeric binders mentioned above to form a screen printable ink. The 
ink is applied, e.g., screen printed, over the dielectric layer 16 to form 
the rear electrode 20 in a layer approximately 0.0005 inches thick. The 
rear electrode 20 terminates back from the edges of the lamp 8 between 
0.010 and 0.050 inches, thereby reducing the possibility of shorting 
between the rear electrode and the front electrode. 
Finally, in some applications of the lamp 8, an additional insulating layer 
(not shown) is applied over the rear electrode 20, e.g., to prevent 
possible shock hazards or to provide a moisture barrier to protect the 
phosphor particles. When included, the insulating layer may be screen 
printed over the rear electrode 20, or laminated as a preformed layer to 
the lamp using a pressure sensitive adhesive or similar means, or flood 
coated, etc. When applied as a preformed layer, the insulating layer can 
be a preformed film where an area of the film corresponding to the window 
15 is cut and peeled away to allow an electrical connection to the front 
conductive coating 12. The area of the window 15 can be cut and removed by 
laser scribing after the film is applied over the rear electrode 20 (in 
much the same way as the front conductive coating 12 is laser scribed 
after it is applied to the substrate 10), or the area of the notch can be 
cut from the film before it is applied to the rear electrode. 
Alternatively, piercing connectors such as those shown in FIG. 6 can be 
used to pierce the insulation layer and make connection to the underlying 
conductive layer. 
Electrical connectors are then applied to the bus bar 14 and the rear 
electrode 20 to connect electrical leads to the lamp 8. For example, in 
the embodiment of FIG. 3, eyelets 26 and 27 connect with and carry power 
to the rear and front electrodes 20 and 12. The eyelets 26 and 27 are 
typically brass or tin-plated brass barrels which are rolled over on each 
end. The eyelets 26 and 27 are inserted through holes which may be cut by 
the laser in the lamp 8 and are crimped in place to provide a secure 
electrical connection to the electrodes 12 and 20 of the lamp. FIGS. 4 and 
4a show a conductive pin 29 having a head 29a and a shaft 29b which 
extends in a press fit through the eyelet 26 in the lamp 8 and into a 
socket 31 in a printed circuit board 33 to make a connection between the 
lamp and the board. 
Referring to FIG. 5, copper ribbon leads 33 can be captured between the 
eyelets 26 and 27 of the lamp 8 to provide power to the electrodes 12 and 
20. Alternatively, crimp-on termination connectors 35 (FIG. 6) may be 
used, e.g., pin crimp part #88997-2 distributed by AMP. The connectors 35 
have fingers 37 which pierce the lamp and curl inwardly to clamp the 
connector in place. 
Referring to FIG. 7, there is shown a panel 40 of lamps 8, each of which is 
essentially identical to the lamp 8 described above in connection with 
FIGS. 1, 1a, 1b and 2. Panel 40 measures approximately 12 by 15 inches and 
includes registration targets 44 along its outer edges. The registration 
targets 44 are applied, e.g., screen printed, onto the front conductive 
coating 12 on the panel 40 and may be punched out or cut by the laser or 
other means, to form registration points used subsequently by the laser 
and the screen printing devices to assure proper registration. The laser 
is typically mounted on a gantry that moves in one direction (X), while 
the lamp 8 is mounted on a table that moves in the other direction (Y), 
relative to the laser. Both the gantry and the table are numerical control 
(NC) machines, programmed to move in a coordinated manner and to turn the 
laser on and off at appropriate points to form the line 22. In this way, 
the NC machines, i.e., the laser and moveable table, move the panel 
relative to the laser to form the isolation line in each of the lamps 8 
and upon completion of the sandwich to cut the panel 40, i.e., along lines 
11', into individual lamps. In this way, the present invention permits a 
great degree of flexibility in the manufacture of lamps having complex 
shapes since the NC machines can be programmed to scribe the line at any 
desired offset margin from the shape of the lamp. 
Referring to FIGS. 8, 8a, and 8b, a single lamp 8 of the panel 40 is shown 
in various stages of construction. Substrate 10 which forms the first 
layer of the panel 40 is coated with a transparent conductive coating 12, 
e.g. ITO, as by sputter coating or flood coating. If the conductive 
coating 12 is applied by use of a solvent, the panel 40 is then placed in 
an oven and baked to remove solvents in the ITO material. 
The bus bar 14 is then applied over the front conductive coating 12 of each 
lamp 8. Again, the entire panel 40 is placed in an oven to volatilize and 
remove any solvents used in forming the bus bar. After the bus bar 14 is 
applied, alignment pins on the movable table (not shown) are inserted 
through the registration targets 44, thereby allowing the NC machines to 
move the panel so that selected areas are positioned under the laser beam. 
Referring to FIG. 8a, the front conductive coating 12 is divided into an 
inner portion 12a and a margin portion 12b by laser scribing the line 22 
about the perimeter of each lamp 8 and a coating of phosphor 16 is then 
applied. Referring to FIG. 8b, the remaining layers of dielectric 18 and 
rear electrode 20 are successively applied over the panel, leaving window 
15 open on each lamp so that a lead attachment may be made to the front 
conductive coating 12 via the bus bar 14. Having thus formed each of the 
lamps 8 on the panel 40, the panel is repositioned on the table and the 
laser is used to cut each of the lamps 8 out of the panel 40, i.e., along 
lines 11'. Electrical leads are then attached to the front conductive 
coating 12 in the exposed area of the bus bar 14 and to the rear electrode 
20. 
The finished lamp 8, with bare, unencapsulated edges, has many possible 
applications. Referring to FIG. 9, the EL lamp 8 is used to light a sign 
and is connected via conductive leads 60 and 62 to electronics which 
provide power to the lamp. The electronics are located in a plastic or 
metal housing 64 which can be hung on a wall. The lamp 8 fits within the 
housing 64 and is covered with a transparent sheet 66 which can be tinted 
in some preferred color, e.g., red, to alter the color of the light 
emitted through the sheet. Finally, a cover 68 having stenciled letters 
70, i.e., "ABC", or graphics is fitted over the sheet 66 and the lamp 8 
and connected to the housing 64 with clip members 72. 
Because the edges of the lamp 8 have been deactivated by isolating an 
electrode as described above, the lamp can be mounted in the sign with a 
decreased chance of failure due to electrical shorting, e.g., if the lamp 
comes in contact with the housing of the sign or if the sign is exposed to 
moisture. In addition, the lamp 8 is safer for a person to handle, e.g., 
during assembly or repair of the sign. 
Other embodiments of the lamp 8 are, of course, possible. For example, the 
line of interruption may be formed through multiple layers of the lamp, 
e.g., through the phosphor and ITO layers, rather than through the ITO 
layer alone. Furthermore, additional layers may be included in the lamp 
between the layers described above to accomplish specific effects. For 
example, an unfilled resin layer between the second conductive layer and 
the dielectric layer can be added to provide a better physical bond 
between the two layers. Layers may be included to provide vapor barrier 
effects. 
In another embodiment (not shown), the lamp is formed from the rear 
electrode forward. That is, a first conductive coating, which may be 
transparent or non-transparent, is deposited, preferably by sputter 
coating as described above, over a substrate film and a line of 
interruption is formed in the coating to divide the coating into an inner 
portion forming the rear electrode and a margin portion electrically 
isolated from the main portion. Subsequently, a dielectric layer is 
deposited over the first conductive coating and fills the groove formed by 
the line of interruption. Phosphor material is deposited over the 
dielectric layer, and a transparent, conductive coating forming the front 
electrode is deposited over the phosphor layer so that it terminates back 
from the edges of the lamp between 0.010 and 0.050 inches. Finally, a 
clear, insulation coating may be applied to the front electrode to protect 
the electrode and prevent shock hazards. In an alternative embodiment of 
the lamp formed from the rear electrode forward, the substrate film and 
conductive coating may be separately prepared, laser scribed as described 
above, and laminated onto the remaining layers of phosphor, dielectric and 
front electrode to form the lamp. 
In various embodiments, the lines of interruption through the transparent 
conductive layer may be formed using laser radiation and other layers 
printed onto the lamp structure as a mask so as to expose and remove the 
transparent conductive material only from desired locations. For example, 
referring to FIGS. 10 to 10b, in a preferred embodiment, transparent 
substrate 10 (e.g., 0.007 inch polyester) is provided with transparent 
conductive layer 12 (e.g., 1000 A.sup.0 ITO), bus bar 14 (e.g., 0.0005 
inch silver) and phosphor layer 16 (e.g., 0,001 inch 72X). The phosphor 
layer 16 is printed to form central region 16' and edge regions 16" which 
leave the transparent conductive material exposed at line regions 12' and 
12" and along the margin region 12'" (FIG. 10 and 10a). To form lines of 
interruption, the structure is exposed to laser radiation (FIG. 10a). 
Those portions of the transparent conductive material 12', 12", 12'", 
which are directly exposed to the radiation are removed, forming 
interruption 22' between an inner portion 12a and margin portions 12b of 
the transparent conductive layer, interruption 22" around the bus bar 14 
and an interruption 22'" (e.g. 0.050 inch in width), in which in this 
latter case, the transparent conductive material is removed to the margin 
of the substrate 10 (FIG. 10b). (It will be understood that material may 
be removed to the margin or leave margin portions as desired.) Those 
portions of the transparent conductive layer beneath the phosphor and bus 
bar masking layers, particularly importantly the portions to be energized 
when operating the lamp, are not affected by the radiation. After 
exposure, other layers such as a dielectric layer and a back electrode 
layer may be deposited as described hereinabove to form a desired lamp 
product. Connectors, such as crimp connectors, can be used as described 
above. 
The laser radiation may be provided by an Excimer laser (e.g. wavelength 
193, 308, 351 nm or most preferably 248 nm at 450 millijoules, 39 HZ) with 
an expanded (fan) beam (e.g. 9 inch by 0.25 inch) effectively flooding the 
area of the mask. The coated substrate is translated under the beam (e.g. 
10 to 30 inch/min). In other embodiments, the laser may be a TEA laser 
(CO.sub.2 laser with .lambda.=9.6 .mu.m) producing a suitable fan beam. 
(The TEA laser can also be used with a narrow, focused beam, e.g. about 
0.005 inch, in a scribing mode as discussed above with respect to the use 
of a CO.sub.2 laser.) 
Generally, the laser radiation is selected in combination with the masking 
layers. For example, it may be advantageous to select a laser wavelength 
and/or energy and masking layer such that the radiation does not 
substantially ablate the masking layer, while ablating the transparent 
conductive layer. A laser and masking layer may also be selected to ablate 
the masking and transparent conductive layers by known thicknesses per 
laser shot and the relative and absolute initial thickness of the layers 
selected to produce, after exposure, the desired thicknesses of the 
masking, e.g. phosphor, layer, while simultaneously completely removing 
the exposed portions of the transparent conductive layer. Excimer lasers 
are particularly preferred for the latter embodiments since the thickness 
of material ablated can be carefully controlled. Excimer lasers are also 
particularly preferred for lamps which are dynamically flexed during use, 
since the careful control over material removal allows for less ablation 
of the substrate 10 when removing the transparent conductive material. 
As illustrated above, most preferably, the printed mask layer is a 
functional layer of the lamp, e.g. the phosphor layer. In such 
embodiments, the invention provides the particular advantage of 
eliminating the steps of forming a separate mask and does not require a 
separate coating step. Various functional layers may be applied as masking 
layers, e.g. a dielectric layer or a metal layer. In other embodiments, 
sacrificial layers, those provided only for the purpose of masking may 
also be printed, and after radiation exposure to form the lines of 
interruption, removed, e.g. by laser ablation with a different wavelength 
or further exposure at the same wavelength. 
Still other embodiments are within the following claims.