CA2004530A1 - Desiccant for el lamps - Google Patents
Desiccant for el lampsInfo
- Publication number
- CA2004530A1 CA2004530A1 CA 2004530 CA2004530A CA2004530A1 CA 2004530 A1 CA2004530 A1 CA 2004530A1 CA 2004530 CA2004530 CA 2004530 CA 2004530 A CA2004530 A CA 2004530A CA 2004530 A1 CA2004530 A1 CA 2004530A1
- Authority
- CA
- Canada
- Prior art keywords
- layer
- improved
- electroluminescent lamp
- desiccant
- lamp
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H13/00—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch
- H01H13/70—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard
- H01H13/702—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard with contacts carried by or formed from layers in a multilayer structure, e.g. membrane switches
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B33/00—Electroluminescent light sources
- H05B33/02—Details
- H05B33/04—Sealing arrangements, e.g. against humidity
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H2219/00—Legends
- H01H2219/002—Legends replaceable; adaptable
- H01H2219/018—Electroluminescent panel
Abstract
IMPROVED DESICCANT FOR EL LAMPS
Abstract of the Disclosure An improved electroluminescent lamp is described comprising a desiccant layer comprising a formed-in-place patternable hygroscopic film layer.
Abstract of the Disclosure An improved electroluminescent lamp is described comprising a desiccant layer comprising a formed-in-place patternable hygroscopic film layer.
Description
2C~0~5~0 4 This invention relates to a method of manufacturing S visible display devices from electroluminescent phosphors 6 and more particularly to a method of making an 7 electroluminescent light source in the form of a thin, 8 flexible, multi-layered assembly, and to a lamp as 9 produced.
An electroluminescent lamp is basically composed of a 11 layer of electroluminescent phosphor material typically of 12 a metal activated zinc sulfide fixed in place by a polymer 13 binder between two conductive layers, one of which is 14 transparent. When an alternating electric field is applied across the conductors, the phosphors are excited 16 and emit photons with almost all of the radiated energy 17 lying within the visible li~ht spectrum. The emission ]8 spectrum and wavelength generated by the phosphors is l~ controlled by the activator element such as copper or manganese.
21 Electroluminescent phosphors and the polymer binders 22 used are inherently hygroscopic and sensitive to moisture.
23 When exposed to high humidity, the luminescent capability 24 of the phosphor particles is diminished, and performance deteriorates. The sensitivity of the phosphor particles 26 to moisture is so strong that exposure even to conditions 27 of low humidity may adversely affect performance and 2C~0~5~0 1 decrease the light output capacity and useful life of the 2 lamp in which the phosphors are incorporated. To 3 effectively reduce the exposure of the electroluminescent 4 phosphors to moisture, an internal desiccant layer may be incorporated in the lamp.
6 One method of fabricating an electroluminescent lamp 7 is currently employed starting with a conductive non-8 transparent substrate of, for example, a sheet of aluminum 9 foil upon which is coated an insulating layer of high dielectric constant material such as barium titanate.
11 Then, an electroluminescent phosphor in a polymer binder 12 is deposited over the dielectric layer and oven dried. A
13 transparent conductive coating formed from, for example, 14 indium oxide and/or indium tin oxide is then deposited over the phosphor layer to form the front electrode.
16 Alternatively, the front electrode may be formed from 17 indium-tin-oxide sputtered Mylar film. A busbar having a 18 conductivity greater than the conductivity of the 19 transparent conductive coating is formed adjacent the pe~iphery of the transparent conductive coatin~, and a 21 thin nylon preformed film is then applied over the busbar 22 and front electrode. The nylon film or other suitable 23 desiccant film acts as an internal desiccant whose purpose 24 is to collect and hold any small traces of moisture left over from the manufacturing process and to scavenge and 26 retain any moisture which may infiltrate the lamp area.
27 Thereafter, the nylon desiccant film is pulled up to ZC0f~530 1 position and attach the front lead, and a second lead is 2 attached to the aluminum foil conductive substrate.
3 Alternatively, the front lead may be positioned before 4 applying the desiccant film, but this may present staining problems since the desiccant film also protects the lamp 6 during processing and handling to prevent staining due, 7 for example, to skin oils from the person handling the 8 lamp. Therefore, the preferable method is to apply the 9 desiccant film and peel it back to position the lead on the busbar.
11 The entire assem~ly excluding a portion of the 12 connecting leads is then sandwiched between two moisture 13 barrier films such as a polychlorotrifluoroethylene 14 (PCTFE) film which is commercially available from Allied Chemical Co. under the trade name ACLARR, or a polyester 16 film, both of which are heat laminated to the assembly and ]7 to each other around the perimeter of the lamp. As will 18 be appreciated, the current manufacturing procedure is l9 labor intensive and time consuming, and has inherent quality control problems resulting in a considerable 21 number of unusable lamps. Moreover, in current 22 manufacture liftinq the ny~on desiccator film in order to 23 position and attach the front lead may break the busbar, 24 andtor permit ingress of moisture and/or contaminants which may result in premature lamp failure in the field.
26 Moreover, the use of nylon desiccant films adds other 27 manufacturing difficulties. These include the necessary 206)~S30 l precutting which is usually done off-line, and static 2 charge build-up which inherently occurs in the handling of 3 nylon film. This static charge attracts dust, often 4 causing unacceptable lamps. Other problems involve hand tacking and lead attachment when using nylon film.
8 The present invention overcomes the aforesaid and 9 other prior art problems by using a patternable formed-in-p]ace desiccant polymer film in place of a preformed ll desiccant film of nylon or other suitable desiccator 12 materials. The patternable formed-in-place desiccant 13 polymer material is applied directly to the assembly 14 following attachment of the busbars, leaving the lead traces exposed, and is cured-in-place by a method 16 appropriate to the particular material selected, for 17 example, thermal curing, air drying, or exposure to ultra-18 violet or other radiation. The resulting cured-in-place 19 pol~meric film material completely protects the underlying layers. Besides applying a layer of the desiccant polymer 21 material to the light-emitting side of the lamp, a similar 22 layer may be applied to the back of the lamp. Thereafter, 23 the resulting assembly can be, and is preferably sealed 24 between two moisture barrier members such as ACLARR PCTFE
film.
27 For a fuller understanding of the invention reference 20~)~530 1 should be made to the following specification taken in 2 connection with the drawings in which:
3 Figure 1 shows an exploded diagrammatic schematic view 4 of an electroluminescent lamp made in accordance with the present invention. This drawing also included a flow 6 sheet of the processing steps involved in a preferxed form 7 of the inventi~n; and 8 Figure 2 shows a membrane switch incorporating an 9 electroluminescent lamp made in accordance with the present invention.
11 Referring now to Figure 1 of the drawings, the 12 construction and process of the present invention involves 13 the following steps: An aluminum 24 oz. foil sheet 10 is 14 first coated with A barium titanate paint layer 12, which is then oven dried. Thereafter, a phosphor paint layer 14 16 is applied over layer 12 and this is oven dried. An 17 indium tin oxide electrode 16 is then silkscreened on, and 18 this is oven dried. Next silver busbars 18 are 19 silkscreened onto electrode 16 and oven dried. The resulting assembly is then coated with a patternable 21 curable desiccant polymer coating 20 which is silkscreened 22 over the busbars 18 (leaving an area for lead attachment 23 exposed) and over the indium tin oxide electrode 16, and 24 the coating is cured-in-place to form a desiccant film coating. The patternable curable desiccant polymer 26 coating may comprise one or a mixture of screenable 27 materials which form on curing a film. The term curing as 20~)~530 1 used herein inclufles, but is not limited to, air drying, 2 oven drying, heat curing, solvent evaporation, 3 photocurin~, and radiation curing. The term patternable 4 as used herein refers to materials which are capable of being applied using any one of a number of techniques, 6 including but not limited to printing, coating, spraying, 7 depositing, painting, silkscreening, or otherwise forming 8 in place. While there are a large number of materials 9 which can be used as the patternable curable desiccant polymer coating material in accordance with the present 11 invention, the preferred materials comprise those which 12 (1) are sufficiently flowable in the uncured state so as 13 to be capable of being patternable, printable, formed-in-14 place, or applied using selective deposition techniques such as silkscreening, in order to cure to films; (2) have 16 good bonding characteristics to the underlying surfaces;
17 (3) are thermally stable at the expected processing and 18 operating temperatures of the lamp; and (4) have a 19 relatively low but sufficient solubility in water to scavenge and retain any moisture left over from the 21 manufacturing process or which may infiltrate the lamp 22 during its design life. Among suitable materials are 23 mentioned so]uble nylon such as ElvamideR (available from 24 E.I. ~uPont de Nemours Co.), cellulose acetate, polyvinyl alcohol (PVA), and polyethyloxazoline (PEOXR, available 26 from Dow Chemical Co.) resins. Additionally, certain 27 thermal setting polymers and resins can be used to achieve 20~)~5~n 1 the advantages of the present invention. Yet another and 2 preferred class of materials useful in the present 3 invention comprise UV or other radiation curable 4 materials. Amongst suitable and preferred UV curable materials are mentioned Lite-TakTM 375 W curing adhesive 6 and Lite-TakTM 376 UV curing adhesive, both available from 7 Loctite Corporation. The manu~acturer describes these 8 materials as comprising a mixture of polyurethane acrylate 9 resins, a cyclic amide, acrylate or ethoxyethocyethyl acrylate, and a photoinitiator.
11 The coated assembly then is subjected to appropriate 12 conditions to cure the polymer material. Thereafter, the 13 leads 19 are attached and the resulting assembly is sealed 14 between two layers (22 and 24) of moisture barrier sheet lS materials such as ACLARR film available from Allied 16 Chemical Co., which may be laminated to the opposite faces 17 of the assembly using an adhesive or hot laminating 18 technique whereby to form an electroluminescent lamp.
19 The features and advantages of the present invention are more fully shown with respect to the following working 21 example which describes a preferred embodiment of the 22 invention.
In a preferred embodiment of the invention the basic 26 lamp structure is fabricated in known manner by applying a 27 suspension of barium titanate in a heat curable resin and 201[)~530 1 drying onto an aluminum foil substrate. A phosphor paint 2 is depcsited over the barium titanate layer, indium tin - 3 oxide electrode is formed over the phosphor paint, and 4 silver busbars are formed all in known manner.
Thereafter, a screenable UV curable desiccant layer 6 comprising a mixture of polyurethane acrylate resins, a 7 cyclic amide, an acrylate ester and a photoinitiator of 8 the type sold by Loctite Corporation under the Trademark 9 "Lite-Tak" type 375 UV Curing Adhesive is applied to the resulting assembly. The manufacturer describes the "Lite-11 Tak" 375 formulation as follows: The polyurethane 12 acrylate resin mixture in the UV curable adhesive is a 13 mixture of resins sold by Celanese Chemical Co. under the 14 designation Interez CMD-8800. The cyclic amide is N-vinyl pyrrolidone sold by GAF Corp. Chemical Products under the 16 designation V-Pyrol. The acrylate ester is ethoxy ethyl-17 ethoxy ethyl acrylate sold by Thiokol Chemical Corp. under 18 the designation RC-20 and the photoinitiator is Irgacure 19 651 sold by Ciba Geigy. This photoinitiator is a substituted acetophenone. The UV curable desiccant layer 21 should be applied to form a cured film of 0.2 to 20 mil;
22 preferably 1 to 2 mil. Curing time is directly 23 proportional to film thickness. For example, for a one 24 mil dried thickness of "Lite-Tak" 375, 5 seconds exposure at 365 nanometers, 150,000 microwatts per square 26 centimeter is adequate. For three mils thickness, 10 27 seconds exposure is desired.
2Q![)~530 1 Electrical characteristics of an electroluminescent 2 lamp made in accordance with the foregoing working example 3 were recorded hefore and after life tests and co~pared 4 with a conventional, prior art electroluminescent lamp made using a 4 mil thick modified Nylon-6 desiccant film.
6 The results are summarized as follows:
7 1. Brightness degradation measured over time in a B 98% relative humidity environment at 40C is similar for 4 9 mil thicK modified Nylon-6 and 3 mil thick "Lite~Tak"
films.
11 2. Power and power factor were similar for "Lite-12 Tak" and modified Nylon-6.
13 3. Initial brightness was about 10% lower with 14 "Lite-Tak".
As can be seen from the foregoing, the present 16 invention offers a number of significant advantages over 17 the prior art. These include:
18 1~ Dirt and contamination are less of a problem than 19 with a preformed film, since dirt can be filtered out prior to silkscreening; also, there is no problem with 21 static dust;
22 2. When the lamp assembly process involves lifting 23 the desiccant to place the leads, busbar liftoff can be 24 eliminated, since the desiccant can be patterned leaving exposed areas for the lead contact;
~Ot)~530 1 3. Lead attachment can be automated since the prior 2 art step of partially hand-liftin~ the nylon desiccant 3 film to attach the front lead is eliminated; and 4 4. The lamp assembly process can be automated much easier because the desiccant layer can be accurately 6 aligned to the lamp, preventing intrusion into the sealed 7 area; also, the placement of the leads is simplified;
8 5. Dyes can be incorporated into the desiccant layer 9 to create varying colors, eliminating the extra layer, filter, or processin~ step which is sometimes needed for 11 colorization;
12 6. The lamp assembly can become an in-line automated 13 process.
14 While the above embodiments are shown to provide a preferred embodiment of the invention, modifications 16 thereof may be made within the spirit and scope of the 17 invention. For example, as shown in Figure 2, the 18 invention also may be advantageously used in the 19 manufacture of thin, highly-flexible lights for use in membrane switch products where it becomes necessary to use 21 other flexible substrates as opposed to the traditionally 22 used rigid aluminum foil. Prior art membrane switch lamps 23 made of soft foil or aluminized polyester typically 24 comprise holes and cut-out areas for the membrane switch.
2~ When used with a sheet desiccant, the phosphor and barium 26 titanate coatings have a tendency to delaminate from the 27 soft foil or aluminized polyester when cut. The use of a 200'1lS~30 1 patternable formea-in-place desiccant polymeric film in 2 place of the traditionally used Nylon desiccant film 3 prevents this from occuring since the cured film coating 4 strengthens the layers. More particularly, as seen in Figure 2, an electroluminescent lamp is produced following 6 the general procedure detailed for Figure 1, however, 7 substitutin~ for the 24 oz. aluminum foil sheet 10 10 oz.
8 soft aluminum foil lOA or aluminized polyester. Barium 9 titanate 12 is deposited as before, and a phosphor paint layer 14 deposited over the barium titanate coating 12.
11 A~ indium tin oxide electrode 16 is screened on as before, 12 and the resulting assembly is coated with a patternable 13 curable desiccant polymer coating 20 in accordance with 14 the teachings of the present invention. The resulting assembly is laminated between ACLAR films 22, 24 and 16 affixed between the switch and graphics layers of the 17 membrane switch. (Further details of the membrane switch 18 panel 26 have been omitted since the switch panel per se 19 forms no part of the present invention.) It should be noted that typical membrane switch lamps inherently have a 21 low life since they use thin materials and no desiccant 22 layer to increase the tactility (in order to minimize 23 actuation force). The membrane switch lamp in this 24 invention uses a desiccant layer which increases the life of the lamp.
26 Still other changes may be made in the invention 27 without departing from the spirit and scope thereof.
An electroluminescent lamp is basically composed of a 11 layer of electroluminescent phosphor material typically of 12 a metal activated zinc sulfide fixed in place by a polymer 13 binder between two conductive layers, one of which is 14 transparent. When an alternating electric field is applied across the conductors, the phosphors are excited 16 and emit photons with almost all of the radiated energy 17 lying within the visible li~ht spectrum. The emission ]8 spectrum and wavelength generated by the phosphors is l~ controlled by the activator element such as copper or manganese.
21 Electroluminescent phosphors and the polymer binders 22 used are inherently hygroscopic and sensitive to moisture.
23 When exposed to high humidity, the luminescent capability 24 of the phosphor particles is diminished, and performance deteriorates. The sensitivity of the phosphor particles 26 to moisture is so strong that exposure even to conditions 27 of low humidity may adversely affect performance and 2C~0~5~0 1 decrease the light output capacity and useful life of the 2 lamp in which the phosphors are incorporated. To 3 effectively reduce the exposure of the electroluminescent 4 phosphors to moisture, an internal desiccant layer may be incorporated in the lamp.
6 One method of fabricating an electroluminescent lamp 7 is currently employed starting with a conductive non-8 transparent substrate of, for example, a sheet of aluminum 9 foil upon which is coated an insulating layer of high dielectric constant material such as barium titanate.
11 Then, an electroluminescent phosphor in a polymer binder 12 is deposited over the dielectric layer and oven dried. A
13 transparent conductive coating formed from, for example, 14 indium oxide and/or indium tin oxide is then deposited over the phosphor layer to form the front electrode.
16 Alternatively, the front electrode may be formed from 17 indium-tin-oxide sputtered Mylar film. A busbar having a 18 conductivity greater than the conductivity of the 19 transparent conductive coating is formed adjacent the pe~iphery of the transparent conductive coatin~, and a 21 thin nylon preformed film is then applied over the busbar 22 and front electrode. The nylon film or other suitable 23 desiccant film acts as an internal desiccant whose purpose 24 is to collect and hold any small traces of moisture left over from the manufacturing process and to scavenge and 26 retain any moisture which may infiltrate the lamp area.
27 Thereafter, the nylon desiccant film is pulled up to ZC0f~530 1 position and attach the front lead, and a second lead is 2 attached to the aluminum foil conductive substrate.
3 Alternatively, the front lead may be positioned before 4 applying the desiccant film, but this may present staining problems since the desiccant film also protects the lamp 6 during processing and handling to prevent staining due, 7 for example, to skin oils from the person handling the 8 lamp. Therefore, the preferable method is to apply the 9 desiccant film and peel it back to position the lead on the busbar.
11 The entire assem~ly excluding a portion of the 12 connecting leads is then sandwiched between two moisture 13 barrier films such as a polychlorotrifluoroethylene 14 (PCTFE) film which is commercially available from Allied Chemical Co. under the trade name ACLARR, or a polyester 16 film, both of which are heat laminated to the assembly and ]7 to each other around the perimeter of the lamp. As will 18 be appreciated, the current manufacturing procedure is l9 labor intensive and time consuming, and has inherent quality control problems resulting in a considerable 21 number of unusable lamps. Moreover, in current 22 manufacture liftinq the ny~on desiccator film in order to 23 position and attach the front lead may break the busbar, 24 andtor permit ingress of moisture and/or contaminants which may result in premature lamp failure in the field.
26 Moreover, the use of nylon desiccant films adds other 27 manufacturing difficulties. These include the necessary 206)~S30 l precutting which is usually done off-line, and static 2 charge build-up which inherently occurs in the handling of 3 nylon film. This static charge attracts dust, often 4 causing unacceptable lamps. Other problems involve hand tacking and lead attachment when using nylon film.
8 The present invention overcomes the aforesaid and 9 other prior art problems by using a patternable formed-in-p]ace desiccant polymer film in place of a preformed ll desiccant film of nylon or other suitable desiccator 12 materials. The patternable formed-in-place desiccant 13 polymer material is applied directly to the assembly 14 following attachment of the busbars, leaving the lead traces exposed, and is cured-in-place by a method 16 appropriate to the particular material selected, for 17 example, thermal curing, air drying, or exposure to ultra-18 violet or other radiation. The resulting cured-in-place 19 pol~meric film material completely protects the underlying layers. Besides applying a layer of the desiccant polymer 21 material to the light-emitting side of the lamp, a similar 22 layer may be applied to the back of the lamp. Thereafter, 23 the resulting assembly can be, and is preferably sealed 24 between two moisture barrier members such as ACLARR PCTFE
film.
27 For a fuller understanding of the invention reference 20~)~530 1 should be made to the following specification taken in 2 connection with the drawings in which:
3 Figure 1 shows an exploded diagrammatic schematic view 4 of an electroluminescent lamp made in accordance with the present invention. This drawing also included a flow 6 sheet of the processing steps involved in a preferxed form 7 of the inventi~n; and 8 Figure 2 shows a membrane switch incorporating an 9 electroluminescent lamp made in accordance with the present invention.
11 Referring now to Figure 1 of the drawings, the 12 construction and process of the present invention involves 13 the following steps: An aluminum 24 oz. foil sheet 10 is 14 first coated with A barium titanate paint layer 12, which is then oven dried. Thereafter, a phosphor paint layer 14 16 is applied over layer 12 and this is oven dried. An 17 indium tin oxide electrode 16 is then silkscreened on, and 18 this is oven dried. Next silver busbars 18 are 19 silkscreened onto electrode 16 and oven dried. The resulting assembly is then coated with a patternable 21 curable desiccant polymer coating 20 which is silkscreened 22 over the busbars 18 (leaving an area for lead attachment 23 exposed) and over the indium tin oxide electrode 16, and 24 the coating is cured-in-place to form a desiccant film coating. The patternable curable desiccant polymer 26 coating may comprise one or a mixture of screenable 27 materials which form on curing a film. The term curing as 20~)~530 1 used herein inclufles, but is not limited to, air drying, 2 oven drying, heat curing, solvent evaporation, 3 photocurin~, and radiation curing. The term patternable 4 as used herein refers to materials which are capable of being applied using any one of a number of techniques, 6 including but not limited to printing, coating, spraying, 7 depositing, painting, silkscreening, or otherwise forming 8 in place. While there are a large number of materials 9 which can be used as the patternable curable desiccant polymer coating material in accordance with the present 11 invention, the preferred materials comprise those which 12 (1) are sufficiently flowable in the uncured state so as 13 to be capable of being patternable, printable, formed-in-14 place, or applied using selective deposition techniques such as silkscreening, in order to cure to films; (2) have 16 good bonding characteristics to the underlying surfaces;
17 (3) are thermally stable at the expected processing and 18 operating temperatures of the lamp; and (4) have a 19 relatively low but sufficient solubility in water to scavenge and retain any moisture left over from the 21 manufacturing process or which may infiltrate the lamp 22 during its design life. Among suitable materials are 23 mentioned so]uble nylon such as ElvamideR (available from 24 E.I. ~uPont de Nemours Co.), cellulose acetate, polyvinyl alcohol (PVA), and polyethyloxazoline (PEOXR, available 26 from Dow Chemical Co.) resins. Additionally, certain 27 thermal setting polymers and resins can be used to achieve 20~)~5~n 1 the advantages of the present invention. Yet another and 2 preferred class of materials useful in the present 3 invention comprise UV or other radiation curable 4 materials. Amongst suitable and preferred UV curable materials are mentioned Lite-TakTM 375 W curing adhesive 6 and Lite-TakTM 376 UV curing adhesive, both available from 7 Loctite Corporation. The manu~acturer describes these 8 materials as comprising a mixture of polyurethane acrylate 9 resins, a cyclic amide, acrylate or ethoxyethocyethyl acrylate, and a photoinitiator.
11 The coated assembly then is subjected to appropriate 12 conditions to cure the polymer material. Thereafter, the 13 leads 19 are attached and the resulting assembly is sealed 14 between two layers (22 and 24) of moisture barrier sheet lS materials such as ACLARR film available from Allied 16 Chemical Co., which may be laminated to the opposite faces 17 of the assembly using an adhesive or hot laminating 18 technique whereby to form an electroluminescent lamp.
19 The features and advantages of the present invention are more fully shown with respect to the following working 21 example which describes a preferred embodiment of the 22 invention.
In a preferred embodiment of the invention the basic 26 lamp structure is fabricated in known manner by applying a 27 suspension of barium titanate in a heat curable resin and 201[)~530 1 drying onto an aluminum foil substrate. A phosphor paint 2 is depcsited over the barium titanate layer, indium tin - 3 oxide electrode is formed over the phosphor paint, and 4 silver busbars are formed all in known manner.
Thereafter, a screenable UV curable desiccant layer 6 comprising a mixture of polyurethane acrylate resins, a 7 cyclic amide, an acrylate ester and a photoinitiator of 8 the type sold by Loctite Corporation under the Trademark 9 "Lite-Tak" type 375 UV Curing Adhesive is applied to the resulting assembly. The manufacturer describes the "Lite-11 Tak" 375 formulation as follows: The polyurethane 12 acrylate resin mixture in the UV curable adhesive is a 13 mixture of resins sold by Celanese Chemical Co. under the 14 designation Interez CMD-8800. The cyclic amide is N-vinyl pyrrolidone sold by GAF Corp. Chemical Products under the 16 designation V-Pyrol. The acrylate ester is ethoxy ethyl-17 ethoxy ethyl acrylate sold by Thiokol Chemical Corp. under 18 the designation RC-20 and the photoinitiator is Irgacure 19 651 sold by Ciba Geigy. This photoinitiator is a substituted acetophenone. The UV curable desiccant layer 21 should be applied to form a cured film of 0.2 to 20 mil;
22 preferably 1 to 2 mil. Curing time is directly 23 proportional to film thickness. For example, for a one 24 mil dried thickness of "Lite-Tak" 375, 5 seconds exposure at 365 nanometers, 150,000 microwatts per square 26 centimeter is adequate. For three mils thickness, 10 27 seconds exposure is desired.
2Q![)~530 1 Electrical characteristics of an electroluminescent 2 lamp made in accordance with the foregoing working example 3 were recorded hefore and after life tests and co~pared 4 with a conventional, prior art electroluminescent lamp made using a 4 mil thick modified Nylon-6 desiccant film.
6 The results are summarized as follows:
7 1. Brightness degradation measured over time in a B 98% relative humidity environment at 40C is similar for 4 9 mil thicK modified Nylon-6 and 3 mil thick "Lite~Tak"
films.
11 2. Power and power factor were similar for "Lite-12 Tak" and modified Nylon-6.
13 3. Initial brightness was about 10% lower with 14 "Lite-Tak".
As can be seen from the foregoing, the present 16 invention offers a number of significant advantages over 17 the prior art. These include:
18 1~ Dirt and contamination are less of a problem than 19 with a preformed film, since dirt can be filtered out prior to silkscreening; also, there is no problem with 21 static dust;
22 2. When the lamp assembly process involves lifting 23 the desiccant to place the leads, busbar liftoff can be 24 eliminated, since the desiccant can be patterned leaving exposed areas for the lead contact;
~Ot)~530 1 3. Lead attachment can be automated since the prior 2 art step of partially hand-liftin~ the nylon desiccant 3 film to attach the front lead is eliminated; and 4 4. The lamp assembly process can be automated much easier because the desiccant layer can be accurately 6 aligned to the lamp, preventing intrusion into the sealed 7 area; also, the placement of the leads is simplified;
8 5. Dyes can be incorporated into the desiccant layer 9 to create varying colors, eliminating the extra layer, filter, or processin~ step which is sometimes needed for 11 colorization;
12 6. The lamp assembly can become an in-line automated 13 process.
14 While the above embodiments are shown to provide a preferred embodiment of the invention, modifications 16 thereof may be made within the spirit and scope of the 17 invention. For example, as shown in Figure 2, the 18 invention also may be advantageously used in the 19 manufacture of thin, highly-flexible lights for use in membrane switch products where it becomes necessary to use 21 other flexible substrates as opposed to the traditionally 22 used rigid aluminum foil. Prior art membrane switch lamps 23 made of soft foil or aluminized polyester typically 24 comprise holes and cut-out areas for the membrane switch.
2~ When used with a sheet desiccant, the phosphor and barium 26 titanate coatings have a tendency to delaminate from the 27 soft foil or aluminized polyester when cut. The use of a 200'1lS~30 1 patternable formea-in-place desiccant polymeric film in 2 place of the traditionally used Nylon desiccant film 3 prevents this from occuring since the cured film coating 4 strengthens the layers. More particularly, as seen in Figure 2, an electroluminescent lamp is produced following 6 the general procedure detailed for Figure 1, however, 7 substitutin~ for the 24 oz. aluminum foil sheet 10 10 oz.
8 soft aluminum foil lOA or aluminized polyester. Barium 9 titanate 12 is deposited as before, and a phosphor paint layer 14 deposited over the barium titanate coating 12.
11 A~ indium tin oxide electrode 16 is screened on as before, 12 and the resulting assembly is coated with a patternable 13 curable desiccant polymer coating 20 in accordance with 14 the teachings of the present invention. The resulting assembly is laminated between ACLAR films 22, 24 and 16 affixed between the switch and graphics layers of the 17 membrane switch. (Further details of the membrane switch 18 panel 26 have been omitted since the switch panel per se 19 forms no part of the present invention.) It should be noted that typical membrane switch lamps inherently have a 21 low life since they use thin materials and no desiccant 22 layer to increase the tactility (in order to minimize 23 actuation force). The membrane switch lamp in this 24 invention uses a desiccant layer which increases the life of the lamp.
26 Still other changes may be made in the invention 27 without departing from the spirit and scope thereof.
Claims (21)
1. An improved electroluminescent lamp wherein the improvement comprises the inclusion, in the construction of said lamp of a desiccant layer comprising a patternable hygroscopic film (20).
2. The improved electroluminescent lamp of claim 1 wherein the lamp comprises, in order, a base electrode layer (10), an electroluminescent phosphor layer (14), and a transparent or translucent electrode layer (16), and adjacent any one or more of the foregoing layers, at least one patternable desiccant layer (20).
3. The improved electroluminescent lamp of claim 1 wherein the desiccant layer (20) is transparent or translucent in its formed state and is patternable in its unformed state.
4. The improved electroluminescent lamp of claim 2 wherein the desiccant layer (20) is transparent or translucent in its formed state and is patternable in its unformed state.
5. The improved electroluminescent lamp of any one of claims 1 to 3, wherein said lamp construction is encased between two moisture barrier film layers (22, 24).
6. The improved electroluminescent lamp of any one of claims 1 to 3, wherein the at least one desiccant layer (20) is adjacent the phosphor layer (14) or the transparent electrode layer (16) or both.
7. The improved electroluminescent lamp of any one of claims 1 to 3, and comprising an insulating layer (12) preferably barium titanate, between said base electrode layer (10) and said electroluminescent phosphor layer (14).
8. The improved electroluminescent lamp of any one of claims 1 to 3, wherein the electroluminescent phosphor layer (14) comprises an insulating material having the phosphor dispersed therein.
9. The improved electroluminescent lamp of any one of claims 1 to 3, wherein said desiccant layer (20), in its unformed state, comprises any one of the following:
(i) a film forming polymer solution, (ii) a film forming polymer emulsion, and (iii) a film forming curable composition;.
(i) a film forming polymer solution, (ii) a film forming polymer emulsion, and (iii) a film forming curable composition;.
10. The improved electroluminescent lamp of any one of claims 1 to 3, wherein the desiccant layer (20) comprises a photocured polyurethane acrylate resin.
11. The improved electroluminescent lamp of any one of claims 1 to 3, and comprising a busbar (18) adjacent said transparent electrode layer (16).
12. The improved electroluminescent lamp of any of claims 1 to 3, characterized in that said desiccant layer (20) further comprises a dye.
13. The improved electroluminescent lamp of claim 4, characterized in that said desiccant layer (20) further comprises a dye.
14. An improved method for manufacturing electroluminescent lamps comprising a base electrode, an electroluminescent phosphor layer and a transparent electrode layer, said improvement comprising applying a patternable film forming hygroscopic material over at least one of the foregoing layers and curing said material in place so as to form a hydroscopic film adhering to said underlying layer prior to continuing with the construction of said electroluminescent lamp.
15. The improved method for manufacturing electroluminescent lamps according to claim 14 wherein said method comprises the steps of (a) forming a base electrode, (b) providing an electroluminescent phosphor layer on said base electrode, (c) curing said phosphor layer, (d) providing a transparent electrode layer over said phosphor layer, and (e) curing said transparent electrode layer wherein the improvement step is inserted following step (a) or following step (d) or following step (e) or any combination thereof.
16. The improved method according to claim 15 further characterized by the step of sealing said resulting electroluminescent lamp between two moisture-proof films by either (i) placing the construction between two layers of moisture-proof film and sealing the same, or (ii) forming the base electrode layer on a first layer of a moisture-proof film and following the last step of claim 16 placing a second moisture-proof film atop the entire assembly opposite said first moisture proof film layer and sealing the entire assembly therein.
17. The method of claim 15 wherein the improvement step is executed following the curing of the transparent electrode layer.
18. The method of any of claims 15 to 17 and further comprising the step of providing a busbar adjacent said transparent electrode layer.
19. The method of any of claims 15 to 17 wherein the patternable curable desiccant material comprises a photocurable polyurethane acrylate resin.
20. The method of any of claims 15 to 17 wherein said film-forming hygroscopic material is cured by any one of solvent evaporation, photocuring, heat curing, air drying, oven drying, and radiation curing as appropriate for the selected film forming material.
21. An improved membrane switch-electroluminescent lamp assembly characterized by comprising a membrane switch panel and an electroluminescent lamp according to any of claims 1 to 3.
24. An improved membrane switch-electroluminescent lamp assembly characterized by comprising a membrane switch panel and an electroluminescent lamp according to claim 4.
24. An improved membrane switch-electroluminescent lamp assembly characterized by comprising a membrane switch panel and an electroluminescent lamp according to claim 4.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US28579688A | 1988-12-16 | 1988-12-16 | |
| US285,796 | 1988-12-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2004530A1 true CA2004530A1 (en) | 1990-06-16 |
Family
ID=23095727
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2004530 Abandoned CA2004530A1 (en) | 1988-12-16 | 1989-12-04 | Desiccant for el lamps |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0374050B1 (en) |
| JP (1) | JPH02257590A (en) |
| CA (1) | CA2004530A1 (en) |
| DE (1) | DE68920981T2 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0329291A (en) * | 1989-06-27 | 1991-02-07 | Sumitomo Bakelite Co Ltd | Water-absorbing film for organic compound dispersed el lamp |
| US5359261A (en) * | 1990-12-28 | 1994-10-25 | Stanley Electric Co., Ltd. | Electroluminescence display |
| KR100392212B1 (en) * | 1995-03-30 | 2003-07-23 | 마쯔시다덴기산교 가부시키가이샤 | El sheet diaphragm and switch using the same |
| JP3244025B2 (en) * | 1996-12-05 | 2002-01-07 | 三菱電機株式会社 | Illumination device for illumination switch and method of manufacturing the same |
| AU2003221876A1 (en) | 2002-04-10 | 2003-10-27 | Flexcon Company, Inc. | Hydro-insensitive electroluminescent devices and methods of manufacture thereof |
| KR100474001B1 (en) * | 2002-08-14 | 2005-03-10 | 엘지.필립스 엘시디 주식회사 | Dual Panel Type Organic Electroluminescent Device and Method for Fabricating the same |
| US20060138946A1 (en) * | 2004-12-29 | 2006-06-29 | Jian Wang | Electrical device with a low reflectivity layer |
| US8673184B2 (en) | 2011-10-13 | 2014-03-18 | Flexcon Company, Inc. | Systems and methods for providing overcharge protection in capacitive coupled biomedical electrodes |
| US9818499B2 (en) | 2011-10-13 | 2017-11-14 | Flexcon Company, Inc. | Electrically conductive materials formed by electrophoresis |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2035454C3 (en) * | 1970-07-17 | 1978-11-30 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | Electroluminescent light cell |
| US4066925A (en) * | 1976-08-03 | 1978-01-03 | Minnesota Mining And Manufacturing Company | Electroluminescent lamp and electrode preform for use therewith |
| US4104555A (en) * | 1977-01-27 | 1978-08-01 | Atkins & Merrill, Inc. | High temperature encapsulated electroluminescent lamp |
| US4357557A (en) * | 1979-03-16 | 1982-11-02 | Sharp Kabushiki Kaisha | Glass sealed thin-film electroluminescent display panel free of moisture and the fabrication method thereof |
| JPS60185394A (en) * | 1984-03-01 | 1985-09-20 | アルプス電気株式会社 | Electric field light emitting device |
| US4687968A (en) * | 1985-08-12 | 1987-08-18 | Rogers Corporation | Encapsulated electroluminescent lamp |
| JPS63213289A (en) * | 1987-02-28 | 1988-09-06 | アルプス電気株式会社 | Thin film el device |
-
1989
- 1989-12-04 CA CA 2004530 patent/CA2004530A1/en not_active Abandoned
- 1989-12-14 DE DE1989620981 patent/DE68920981T2/en not_active Expired - Fee Related
- 1989-12-14 EP EP19890403482 patent/EP0374050B1/en not_active Expired - Lifetime
- 1989-12-15 JP JP1325758A patent/JPH02257590A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE68920981D1 (en) | 1995-03-16 |
| JPH02257590A (en) | 1990-10-18 |
| DE68920981T2 (en) | 1995-08-10 |
| EP0374050B1 (en) | 1995-02-01 |
| EP0374050A1 (en) | 1990-06-20 |
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| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |