CA1256541A - Electroluminescent display panel - Google Patents
Electroluminescent display panelInfo
- Publication number
- CA1256541A CA1256541A CA000516397A CA516397A CA1256541A CA 1256541 A CA1256541 A CA 1256541A CA 000516397 A CA000516397 A CA 000516397A CA 516397 A CA516397 A CA 516397A CA 1256541 A CA1256541 A CA 1256541A
- Authority
- CA
- Canada
- Prior art keywords
- electrodes
- insulating layer
- electrode
- layer
- transparent
- 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.)
- Expired
Links
Classifications
-
- 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
- H05B33/12—Light sources with substantially two-dimensional radiating surfaces
- H05B33/22—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers
-
- 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
- H05B33/12—Light sources with substantially two-dimensional radiating surfaces
Abstract
ABSTRACT OF THE DISCLOSURE
An electroluminescent (EL) material is sandwiched between parallel strips of electrodes running at right angles to each other.
Pixels are formed where the electrodes cross to provide a thin film, EL
display. The display includes a layer of insulating material which has a hole at each pixel. The backside electrodes extend into the holes, thus providing a high electric field only at the pixel locations. These backside electrodes are broad to assure electrical continuity despite any open-circuit created by burned-out pixels. The insulating material overlaps the edges of the frontside electodes, thus reducing the electric field which concentrates at the electrode edge. The insulating layer and the backside electrode can be made black, or a light-absorbing, semi-insulating layer used in order to reduce light scattering and reflection. Transparent electrodes can be used to allow light to emit from either the front, the back, or both sides of the display.
An electroluminescent (EL) material is sandwiched between parallel strips of electrodes running at right angles to each other.
Pixels are formed where the electrodes cross to provide a thin film, EL
display. The display includes a layer of insulating material which has a hole at each pixel. The backside electrodes extend into the holes, thus providing a high electric field only at the pixel locations. These backside electrodes are broad to assure electrical continuity despite any open-circuit created by burned-out pixels. The insulating material overlaps the edges of the frontside electodes, thus reducing the electric field which concentrates at the electrode edge. The insulating layer and the backside electrode can be made black, or a light-absorbing, semi-insulating layer used in order to reduce light scattering and reflection. Transparent electrodes can be used to allow light to emit from either the front, the back, or both sides of the display.
Description
~L25~i5~3L
AN ELECTROLUMINESCENT DISPLAY PANEL
Rlchard D. Ketchpel BACKGROUND OF THE INVENTION
Thls invention relates to display devlces and particularly to thin film, electroluminescent (TFEL) display devices.
Light emitting display devices have been fabricated utili~ing the electroluminescent effect obtained by exposing special light-emitting materials (sometimes called phosphors) to an electrical field. In order to provide high contrast in TFRL displays, it is known to provide a light absorbing (black) dielectric layer between the active layer of electroluminescent material and the back electrode as described in U.S. Patent 3,560,784 to G. N. Steele, et al. It is also known to provide such a black background behind a transparent backside electrode and to make electrical connection to the transparent backside electrode through openings or border areas in the black background (U.S. Patent -~,488,084 to S. G. Linfors, et al).
In addition to having high contrast, it is important for a TFEL
display to have a long life. Unfortunately the high electric fields required to provide electroluminescense can cause sporadic breakdowns of the EL film in some locations, and these breakdowns can in turn produce a break in the continuity of the overlying electrode at such locations.
To reduce these breakdowns, it is known to provide strips of insulating material under one side of each of the parallel strips of metal, thus reducing the electrical field in a "bus rail" portion of the backside electrodes (U.S. Patent 4,342,945 to the present inventor, Richard D.
Ketchpel).
These prior art techniques have helped increase the contrast and the life of TFEL displays. However, there is a continuing need to ~s~
85SC~7 provide TFEL display structures whlch can be economically fabrlcated to provide high contrast, long life, and reliable quality, SUMMARY OF T~IE INVENTION
It is an object of the invention to provide TFEL displays with high contrast.
It is an object of the invention to provide T~EL displays with increased lifetimes.
It is an object of the invention to provide reliable TFEL
displays which are not susceptible to propagating modes of failure.
It is an ob~ect of the invention to provide TFEL displays having both high contrast and increased lifetimes.
According to the invention, an EL material is sandwiched between parallel strips of electrodes, running at right angles to each other.
The electrodes form pixels between them in the EL material at locations where they cross over each other.
The backside (the side opposite the substrate, generally the non-viewing side) of the EL layer is covered with a layer of insulating material which has holes through it at each pixel~ Broad parallel strips of backside electrodes are formed on this insulating material so that they extend into the holes and therefore into contact with the EL
layer at each pixel. However, the backside electrodes are spaced away from the EL layer by the insulating material outside the hole in the areas between the pixels. This provides a higher electric field where needed in the light-emitting pixel location (the holes) but lower electric fields outside the pixel (between the holes) to prevent breakdown of the EL layer.
The insulating layer overlaps the edge formed by the frontside electrode to reduce the electric field which tends to concentrate at the electrode edge, further helping to prevent breakdown of the EL layer.
In a second embodiment, the insulating layer is black to absorb light and thus reduce light scattering.
~5S54~ 85SC47 In a third embodiment, the backslde electrode is black, to absorb light and thus reduce llght scatterlng.
In a fourth embodiment, the EL layer has a black semi-insulating layer covering it over the dielectric layer and under the backside electrode to reduce light scattering and reflection.
In a fifth embodiment, the insulating layer with the pixel holes is deposited on the substrate and partly over the frontside electrode rather than on the backside.
In a sixth embodiment, the backside electrode is made transparent so that light can shine from the backside of the display panel.
These and other ob~ects and features of the invention will be apparent from the following detailed description taken with reference to the accompanying drawings.
DRA~INGS
Figure 1 is a perspective, cross-sectional view of a thin film electroluminescent (TFEL) display panel according to a first embodiment of the invention;
Figure 2 is a cross-section showing in detail a pixel of a TFEL
display according to a second embodiment of the invention;
Figure 3 is a cross-section showing in detail a pixel of a TFEL
display according to a third embodiment of the invention;
Figure 4 is a top view (backside) of a TFEL pixel;
Figure 5 shows steps a-g in the fabrication of TFEL displays;
and Figures 6 9 7, and 8 show embodiments which correspond to Figures 1, 2, and 3 (respectively) except that the insulating layer is positioned on the substrate rather than on the EL layer; and Figures 9 and 10 show embodiments which correspond to Figures 3 and 6 except that the light shines through a transparent backside electrode.
~2~541 85SC47 DESCRIPTION OF THE PREFERRED EMBODIMENT
In order to provide a bright, thin film, electroluminescent (TFEL) display it is necessary to provlde a high electric field across a thin film of EL material. However, in order to provide a display with a long life, it is necessary to prevent failure of the EL material which can be caused by high electric fields. These two contradictory requirements are resolved in the present invention by spacing the backside electrode away from the EL layer except at the pix21 location where the backside and frontside electrodes cross. In this pixel location, the electric fields are highest and thus provide bright luminescence. In the locations between the pixels the electric field is greatly reduced by the wider space between the electrodes. Breakdown of the EL layer at each pixel can still occur and cause the adjacent backside electrode to vaporize. However, the portion of the electrode which is spaced away from the pixel is protected and serves as an electrical bypass to continue providing electrical contact with the remaining pixels in the row. Thus, an open circuit failure is limited to a particular pixel and the remainder of the addressed line of the EL
layer continues to operate.
Figure 1 shows a partial view of a TFEL display according to the invention. The front (or viewing) side of the display is covered by glass substrate 2. Transparent electrodes 4 are deposited on the glass in parallel strips. As is known in the art, these can be indium oxide, tin oxide or mixtures of these oxides. The active, light emitting layer 6 contains an EL material such as zinc sulfide doped with manganese. In Figure 1, active layer 6 comprises layer 8 of zinc sulfide doped with manganese and two outer layers 10, 12 of a dielectric material such as yttrium oxide or barium titanate.
An important feature of the invention is insulating layer 14 which covers the entire backside of the display except for holes 16 ~ % S ~`S ~ ~ 85SC47 which are positioned above frontside electrodes 4. Insulating layer 14 must be thick enough to resist breakdown at the operatlng voltage of the display, and it must provide sufficient resistance to avoid leakage to adjacent electrodes. Insulating layer 14 ls thlck between holes 16 and tapers inwardly and downwardly into the holes. It overlaps edges 18 of underlying frontside electrode 4.
Broad backside electrodes 20 are deposited on insulat-lng layer 14. The backside electrodes run in parallel strlps at right angle to the underlying frontside electrodes. They extend into each hole 16, and (in the embodiment shown in Flgure 1) are centered on holes 16. Gaps 22 provide electrical separation between the backside electrodes.
To activate the display, a voltage is applied between the frontside and backside electrodes to provide an electric field across EL
layer 6 which causes light 21 to shine out of active layer 6. The resulting electrlc field is proportional to the applied voltage, v, divided by the distance, x, separating the electrodes (assumlng materials having the same dielectric constant~. As shown ln Figure 1, the electric field between pixels is much less than it is at the pixel because xb is much larger than xp. Any increase in the distance Xb as compared to x will provide a reduced electric field and some protection from breakthrough between pixels. Panels have been made using epoxy (which has a relative dielectric constant of about 4.0 and a resistivity of about 1015 ohm-cm) to form insulating layer 14. In these panels, Xb was about 35 microns and Xp about 1 micron.
This provided over a 10 to 1 reduction of the field strength in the active layer 6 between the pixels.
The electric field produced by electrode 4 tends to concentrate at edges or discontinuities in the electrodes. The resulting high electric field can cause early failure of the adjacent EL layer. In the present invention, this problem is overcome by overlapping the edges of frontside electrode 4 with insulating layer 1~. This overlap reduces the electric field in these critical areas. In Figure 1, the overlap is ~ ~2~5~ 85SC47 shown by dimension Y. By "edges" is meant the sAdes, corners, or any other field-concentrating discontinuities in the electrode.
F.gure 2 shows the cross section st the center of a p,xel for a second embodiment. In th~s embodlment, insu]ating ls~er 14 is black snd is backed up by conducting black electrode 15. Black electrode 15 extends across hole 16 and prov des a light absorb,ng surface .n the pixel area which is not covered by black insulating layer 14. Black electrode 15 can be a metallic layer 20 having a thin black surface 19.
For example, black surface 19 can be a semi-insulat~ng coating such as a thin, sub-oxide layer of aluminum as described in U.S. Patent 4,287,449.
Black electrode 15 together with black insulating layer 14 provide a contlnuous l.ght absorbing surface behind dielectric layer 12, and thereby reduces light scatter~ng and reflection.
In the embodiment shown in Figure 3, a continuous, light-absorbing, semi--nsulating layer 11 completely covers dielectric layer 12. By semi-insulating is meant having a resistivity in the range of 10 to 10 ohm cm. Cadmium telluride or other light absorbing material having a resistivity in this range can be used. It has been discovered that if sem,-.nsu~ating layer 11 is thin (less than about 1000 Angstroms), circuit failures caused by blem shes in light em,tting layer 6 can be limited to non-propagating, pin-hole, open circuit type failures that are less than sbout 0.001 inches in diameter.
Such small failures are barely perceptible to the human eye and have only a negligible effect on image quality. Although insulating layer 13 in the Figure 3 embodiment is not blacX, light is absorbed across the entlre back side of the display because semi-insulating layer 11 completely covers the back side of light emitting layer 6.
Figùre 4 is a plan vlew looking down into hole 16 forming a pixel of the display. This view clearly shows how broad, backside electrode 20 runs normal to frontside electrode 4. It also shows how the edge of the insulating layer overlaps edge 18 of underlying frontside electrode ~t, NGte how broad ~he electrodes are with only ~ 5!~ 85SC47 small gaps 22 separating them to provide electrical isolation between them. This broad electrode structure provides protection agalnst open circuiting an entire electrode by providing a more than ample conductlve path in case of complete vaporization of the electrode at hole 16.
Figure 5 illustrates in steps a to g a process for Eabricating the TFEL display utilizing known lithographic and vacuum deposition techniques. Indium oxide, tin oxide, or a mixture of indium and tin oxide are deposited on glass substrate 2 to form frontside, transparent electrodes 4. A dielectric layer 10 such as yttrium oxide is deposited on substrate 2 and on electrode 4. Flectroluminescent layer 8 (for example zinc sulfide doped with manganese) and second dielectric layer 12 are formed over the first dielectric layer. Second dielectric layer 12 can be yttrium oxide like layer 10.
Except for holes 16, the entire backside of the display is then coated with insulating layer 14 which is typically about 10 microns or more thick. The lnsulating layer can be an epoxy which tends to form a tapered edge into hole 16 as shown in Figure 4f, or a photoresist, or a polyimide, or other suitable insulating material. In order to absorb scattering light, layer 14 can be blackO
Finally, backside electrodes 20 are deposited in parallel strips at right angles to frontside electrodes 4O It has been discovered that burn-outs of the backside electrode can be confined to small pin holes if the electrode thickness in the pixel area is less than about 1200 Angstroms. However, this thickness can be increased as desired in locations outside the pixel areaO The backside electrodes can be a metal such as aluminum, and they can cover insulating layer 14 except for gaps (22 in Figures 1 and 4) between them to provide electrical isolation. This provides a reliable, rugged, reproducible structure which has improved lifetime.
The embodiments shown in Figures 2 and 3 can be made in a sequence similar to that shown in Figure 5 except for additional steps to add the additional light~absorbing layers. Thus, thin black surface ~ ~ S ~ 85SC47 19 in Figure 2 is deposited over the top surface shown in Figure 5f prior to deposltion of metal 20. Similarly, semi-insulating layer 11 in Figure 3 ls deposited over the top surface shown in Figure 5e prior to deposition of insulating layer 13 and metal 20 Although lt may be convenient to cover the entire surface with black electrode 15 (Figure
AN ELECTROLUMINESCENT DISPLAY PANEL
Rlchard D. Ketchpel BACKGROUND OF THE INVENTION
Thls invention relates to display devlces and particularly to thin film, electroluminescent (TFEL) display devices.
Light emitting display devices have been fabricated utili~ing the electroluminescent effect obtained by exposing special light-emitting materials (sometimes called phosphors) to an electrical field. In order to provide high contrast in TFRL displays, it is known to provide a light absorbing (black) dielectric layer between the active layer of electroluminescent material and the back electrode as described in U.S. Patent 3,560,784 to G. N. Steele, et al. It is also known to provide such a black background behind a transparent backside electrode and to make electrical connection to the transparent backside electrode through openings or border areas in the black background (U.S. Patent -~,488,084 to S. G. Linfors, et al).
In addition to having high contrast, it is important for a TFEL
display to have a long life. Unfortunately the high electric fields required to provide electroluminescense can cause sporadic breakdowns of the EL film in some locations, and these breakdowns can in turn produce a break in the continuity of the overlying electrode at such locations.
To reduce these breakdowns, it is known to provide strips of insulating material under one side of each of the parallel strips of metal, thus reducing the electrical field in a "bus rail" portion of the backside electrodes (U.S. Patent 4,342,945 to the present inventor, Richard D.
Ketchpel).
These prior art techniques have helped increase the contrast and the life of TFEL displays. However, there is a continuing need to ~s~
85SC~7 provide TFEL display structures whlch can be economically fabrlcated to provide high contrast, long life, and reliable quality, SUMMARY OF T~IE INVENTION
It is an object of the invention to provide TFEL displays with high contrast.
It is an object of the invention to provide T~EL displays with increased lifetimes.
It is an object of the invention to provide reliable TFEL
displays which are not susceptible to propagating modes of failure.
It is an ob~ect of the invention to provide TFEL displays having both high contrast and increased lifetimes.
According to the invention, an EL material is sandwiched between parallel strips of electrodes, running at right angles to each other.
The electrodes form pixels between them in the EL material at locations where they cross over each other.
The backside (the side opposite the substrate, generally the non-viewing side) of the EL layer is covered with a layer of insulating material which has holes through it at each pixel~ Broad parallel strips of backside electrodes are formed on this insulating material so that they extend into the holes and therefore into contact with the EL
layer at each pixel. However, the backside electrodes are spaced away from the EL layer by the insulating material outside the hole in the areas between the pixels. This provides a higher electric field where needed in the light-emitting pixel location (the holes) but lower electric fields outside the pixel (between the holes) to prevent breakdown of the EL layer.
The insulating layer overlaps the edge formed by the frontside electrode to reduce the electric field which tends to concentrate at the electrode edge, further helping to prevent breakdown of the EL layer.
In a second embodiment, the insulating layer is black to absorb light and thus reduce light scattering.
~5S54~ 85SC47 In a third embodiment, the backslde electrode is black, to absorb light and thus reduce llght scatterlng.
In a fourth embodiment, the EL layer has a black semi-insulating layer covering it over the dielectric layer and under the backside electrode to reduce light scattering and reflection.
In a fifth embodiment, the insulating layer with the pixel holes is deposited on the substrate and partly over the frontside electrode rather than on the backside.
In a sixth embodiment, the backside electrode is made transparent so that light can shine from the backside of the display panel.
These and other ob~ects and features of the invention will be apparent from the following detailed description taken with reference to the accompanying drawings.
DRA~INGS
Figure 1 is a perspective, cross-sectional view of a thin film electroluminescent (TFEL) display panel according to a first embodiment of the invention;
Figure 2 is a cross-section showing in detail a pixel of a TFEL
display according to a second embodiment of the invention;
Figure 3 is a cross-section showing in detail a pixel of a TFEL
display according to a third embodiment of the invention;
Figure 4 is a top view (backside) of a TFEL pixel;
Figure 5 shows steps a-g in the fabrication of TFEL displays;
and Figures 6 9 7, and 8 show embodiments which correspond to Figures 1, 2, and 3 (respectively) except that the insulating layer is positioned on the substrate rather than on the EL layer; and Figures 9 and 10 show embodiments which correspond to Figures 3 and 6 except that the light shines through a transparent backside electrode.
~2~541 85SC47 DESCRIPTION OF THE PREFERRED EMBODIMENT
In order to provide a bright, thin film, electroluminescent (TFEL) display it is necessary to provlde a high electric field across a thin film of EL material. However, in order to provide a display with a long life, it is necessary to prevent failure of the EL material which can be caused by high electric fields. These two contradictory requirements are resolved in the present invention by spacing the backside electrode away from the EL layer except at the pix21 location where the backside and frontside electrodes cross. In this pixel location, the electric fields are highest and thus provide bright luminescence. In the locations between the pixels the electric field is greatly reduced by the wider space between the electrodes. Breakdown of the EL layer at each pixel can still occur and cause the adjacent backside electrode to vaporize. However, the portion of the electrode which is spaced away from the pixel is protected and serves as an electrical bypass to continue providing electrical contact with the remaining pixels in the row. Thus, an open circuit failure is limited to a particular pixel and the remainder of the addressed line of the EL
layer continues to operate.
Figure 1 shows a partial view of a TFEL display according to the invention. The front (or viewing) side of the display is covered by glass substrate 2. Transparent electrodes 4 are deposited on the glass in parallel strips. As is known in the art, these can be indium oxide, tin oxide or mixtures of these oxides. The active, light emitting layer 6 contains an EL material such as zinc sulfide doped with manganese. In Figure 1, active layer 6 comprises layer 8 of zinc sulfide doped with manganese and two outer layers 10, 12 of a dielectric material such as yttrium oxide or barium titanate.
An important feature of the invention is insulating layer 14 which covers the entire backside of the display except for holes 16 ~ % S ~`S ~ ~ 85SC47 which are positioned above frontside electrodes 4. Insulating layer 14 must be thick enough to resist breakdown at the operatlng voltage of the display, and it must provide sufficient resistance to avoid leakage to adjacent electrodes. Insulating layer 14 ls thlck between holes 16 and tapers inwardly and downwardly into the holes. It overlaps edges 18 of underlying frontside electrode 4.
Broad backside electrodes 20 are deposited on insulat-lng layer 14. The backside electrodes run in parallel strlps at right angle to the underlying frontside electrodes. They extend into each hole 16, and (in the embodiment shown in Flgure 1) are centered on holes 16. Gaps 22 provide electrical separation between the backside electrodes.
To activate the display, a voltage is applied between the frontside and backside electrodes to provide an electric field across EL
layer 6 which causes light 21 to shine out of active layer 6. The resulting electrlc field is proportional to the applied voltage, v, divided by the distance, x, separating the electrodes (assumlng materials having the same dielectric constant~. As shown ln Figure 1, the electric field between pixels is much less than it is at the pixel because xb is much larger than xp. Any increase in the distance Xb as compared to x will provide a reduced electric field and some protection from breakthrough between pixels. Panels have been made using epoxy (which has a relative dielectric constant of about 4.0 and a resistivity of about 1015 ohm-cm) to form insulating layer 14. In these panels, Xb was about 35 microns and Xp about 1 micron.
This provided over a 10 to 1 reduction of the field strength in the active layer 6 between the pixels.
The electric field produced by electrode 4 tends to concentrate at edges or discontinuities in the electrodes. The resulting high electric field can cause early failure of the adjacent EL layer. In the present invention, this problem is overcome by overlapping the edges of frontside electrode 4 with insulating layer 1~. This overlap reduces the electric field in these critical areas. In Figure 1, the overlap is ~ ~2~5~ 85SC47 shown by dimension Y. By "edges" is meant the sAdes, corners, or any other field-concentrating discontinuities in the electrode.
F.gure 2 shows the cross section st the center of a p,xel for a second embodiment. In th~s embodlment, insu]ating ls~er 14 is black snd is backed up by conducting black electrode 15. Black electrode 15 extends across hole 16 and prov des a light absorb,ng surface .n the pixel area which is not covered by black insulating layer 14. Black electrode 15 can be a metallic layer 20 having a thin black surface 19.
For example, black surface 19 can be a semi-insulat~ng coating such as a thin, sub-oxide layer of aluminum as described in U.S. Patent 4,287,449.
Black electrode 15 together with black insulating layer 14 provide a contlnuous l.ght absorbing surface behind dielectric layer 12, and thereby reduces light scatter~ng and reflection.
In the embodiment shown in Figure 3, a continuous, light-absorbing, semi--nsulating layer 11 completely covers dielectric layer 12. By semi-insulating is meant having a resistivity in the range of 10 to 10 ohm cm. Cadmium telluride or other light absorbing material having a resistivity in this range can be used. It has been discovered that if sem,-.nsu~ating layer 11 is thin (less than about 1000 Angstroms), circuit failures caused by blem shes in light em,tting layer 6 can be limited to non-propagating, pin-hole, open circuit type failures that are less than sbout 0.001 inches in diameter.
Such small failures are barely perceptible to the human eye and have only a negligible effect on image quality. Although insulating layer 13 in the Figure 3 embodiment is not blacX, light is absorbed across the entlre back side of the display because semi-insulating layer 11 completely covers the back side of light emitting layer 6.
Figùre 4 is a plan vlew looking down into hole 16 forming a pixel of the display. This view clearly shows how broad, backside electrode 20 runs normal to frontside electrode 4. It also shows how the edge of the insulating layer overlaps edge 18 of underlying frontside electrode ~t, NGte how broad ~he electrodes are with only ~ 5!~ 85SC47 small gaps 22 separating them to provide electrical isolation between them. This broad electrode structure provides protection agalnst open circuiting an entire electrode by providing a more than ample conductlve path in case of complete vaporization of the electrode at hole 16.
Figure 5 illustrates in steps a to g a process for Eabricating the TFEL display utilizing known lithographic and vacuum deposition techniques. Indium oxide, tin oxide, or a mixture of indium and tin oxide are deposited on glass substrate 2 to form frontside, transparent electrodes 4. A dielectric layer 10 such as yttrium oxide is deposited on substrate 2 and on electrode 4. Flectroluminescent layer 8 (for example zinc sulfide doped with manganese) and second dielectric layer 12 are formed over the first dielectric layer. Second dielectric layer 12 can be yttrium oxide like layer 10.
Except for holes 16, the entire backside of the display is then coated with insulating layer 14 which is typically about 10 microns or more thick. The lnsulating layer can be an epoxy which tends to form a tapered edge into hole 16 as shown in Figure 4f, or a photoresist, or a polyimide, or other suitable insulating material. In order to absorb scattering light, layer 14 can be blackO
Finally, backside electrodes 20 are deposited in parallel strips at right angles to frontside electrodes 4O It has been discovered that burn-outs of the backside electrode can be confined to small pin holes if the electrode thickness in the pixel area is less than about 1200 Angstroms. However, this thickness can be increased as desired in locations outside the pixel areaO The backside electrodes can be a metal such as aluminum, and they can cover insulating layer 14 except for gaps (22 in Figures 1 and 4) between them to provide electrical isolation. This provides a reliable, rugged, reproducible structure which has improved lifetime.
The embodiments shown in Figures 2 and 3 can be made in a sequence similar to that shown in Figure 5 except for additional steps to add the additional light~absorbing layers. Thus, thin black surface ~ ~ S ~ 85SC47 19 in Figure 2 is deposited over the top surface shown in Figure 5f prior to deposltion of metal 20. Similarly, semi-insulating layer 11 in Figure 3 ls deposited over the top surface shown in Figure 5e prior to deposition of insulating layer 13 and metal 20 Although lt may be convenient to cover the entire surface with black electrode 15 (Figure
2~ or semi-insulating layer 11 (Figure 3), the invention also encompasses covering only the pixel area (hole 16) with black, particularly if the insulating layer is bLack (or light absorbing).
Figures 6, 7, and 8 show embodiments in which insulating layer 14 is located on transparent substrate 2 and on a portion of transparent electrode 4 rather than on light emitting layer 6. These embodiments also provide the advantage of a lower electric field between pixels than at the pixel. Depending upon the properties (contact angle, index of refraction, etc.) of the particular materials used, these embodiments may provide advantages such as easier processing and better adhesion of insulating layer 14. Except ~or the location of insulating layer 14, Figure 6 corresponds to the embodiment shown in Figure 1. Similarly, Figure 7 corresponds to the embodiment shown in Figure 2 with a black conducting back electode 15; and Figure 8 corresponds to the embodiment shown in Figure 3 with light absorbing, semi-insulating layer 11.
Figures 9 and 10 show embodiments in which light 21 is emitted from the oppos-lte side (previously called the backside) of the EL
display panel. This is accomplished by providing a transparent electrode on the opposite side. Means can be provlded on the other side to either absorb or reflect light.
For example, Figure 9 shows backside electrode 20 made from a conducting, transparent material such as lndium and tin oxides.
Frontside electrode 4 can then be made of either a transparent material or of an opaque material such as alumlnum. Similarly, substrate 2 can be an insulating opaque material such as a ceramic or it can have an opaque coating. Figure 9 shows an embodiment in which a separate, semiconductlve, light absorbing layer 11 is included to correspond to ~2~ 85SC~7 the embodiment shown in Flgure 3.
The Figure 10 embodiment is representative of the embodiments shown in Figures 6-7 in which insulating layer 14 is positioned on the substra~e, except that the backside electrode 20 is the transparent electrode and light shines from the backside of the EL panel.
The invention also encompasses an embodiment in which llght shines from both the frontside and the backside of the EL panel. Thls is accomplished by combining the glass substrate and transparent frontside electrode of Figures 1 8 with the transparent backside electrode of Flgures 9 or 10.
Numerous variations can be made without departing from the invention. Accordingly, it should be understood that the form of the invention described above is illustrative and is not intended to limit the scope of the invention.
Figures 6, 7, and 8 show embodiments in which insulating layer 14 is located on transparent substrate 2 and on a portion of transparent electrode 4 rather than on light emitting layer 6. These embodiments also provide the advantage of a lower electric field between pixels than at the pixel. Depending upon the properties (contact angle, index of refraction, etc.) of the particular materials used, these embodiments may provide advantages such as easier processing and better adhesion of insulating layer 14. Except ~or the location of insulating layer 14, Figure 6 corresponds to the embodiment shown in Figure 1. Similarly, Figure 7 corresponds to the embodiment shown in Figure 2 with a black conducting back electode 15; and Figure 8 corresponds to the embodiment shown in Figure 3 with light absorbing, semi-insulating layer 11.
Figures 9 and 10 show embodiments in which light 21 is emitted from the oppos-lte side (previously called the backside) of the EL
display panel. This is accomplished by providing a transparent electrode on the opposite side. Means can be provlded on the other side to either absorb or reflect light.
For example, Figure 9 shows backside electrode 20 made from a conducting, transparent material such as lndium and tin oxides.
Frontside electrode 4 can then be made of either a transparent material or of an opaque material such as alumlnum. Similarly, substrate 2 can be an insulating opaque material such as a ceramic or it can have an opaque coating. Figure 9 shows an embodiment in which a separate, semiconductlve, light absorbing layer 11 is included to correspond to ~2~ 85SC~7 the embodiment shown in Flgure 3.
The Figure 10 embodiment is representative of the embodiments shown in Figures 6-7 in which insulating layer 14 is positioned on the substra~e, except that the backside electrode 20 is the transparent electrode and light shines from the backside of the EL panel.
The invention also encompasses an embodiment in which llght shines from both the frontside and the backside of the EL panel. Thls is accomplished by combining the glass substrate and transparent frontside electrode of Figures 1 8 with the transparent backside electrode of Flgures 9 or 10.
Numerous variations can be made without departing from the invention. Accordingly, it should be understood that the form of the invention described above is illustrative and is not intended to limit the scope of the invention.
Claims (28)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electroluminescent display comprising:
a substrate;
a first electrode on said substrate;
a second electrode spaced apart from said first electrode, at least said first or said second electrode being a transparent electrode;
a light emitting layer containing electroluminescent material between said first and second electrodes;
an insulating layer between said first and second electrodes, said insulating layer having a hole positioned where said first and second electrodes cross each other, said second electrode extending into said hole, whereby said first and second electrodes are closest to each other at said hole.
a substrate;
a first electrode on said substrate;
a second electrode spaced apart from said first electrode, at least said first or said second electrode being a transparent electrode;
a light emitting layer containing electroluminescent material between said first and second electrodes;
an insulating layer between said first and second electrodes, said insulating layer having a hole positioned where said first and second electrodes cross each other, said second electrode extending into said hole, whereby said first and second electrodes are closest to each other at said hole.
2. The electrolumlnescent display as claimed in Claim 1, wherein said insulating layer is positioned between said light emitting layer and said second electrode, said second electrode extending out of said hole and onto said insulating layer.
3. The electroluminescent display as claimed in Claim 1, wherein said insulating layer is positioned between said light emitting layer and said substrate and extends over the edges of said first electrode.
4. The electroluminescent display as claimed in Claim 1 wherein said first and second electrodes are both transparent, whereby light from said light emitting layer is emitted from both sides of said display.
5. The electroluminescent display as claimed in Claim 1 wherein said first electrode and said substrate are transparent and said second electrode is opaque, whereby light from said light emitting layer is emitted through said substrate.
6. The electroluminescent display as claimed in Claim 1 wherein said second electrode is transparent, whereby light from said light emitting layer is emitted through said second electrode.
7. The electroluminescent display as claimed in Claim 5 wherein said second electrode comprises a black electrode.
8. The electroluminescent display as claimed in Claim 5 including a light-absorbing semi-insulating layer on said light emitting layer between said light emitting layer and said second electrode.
9. The electroluminescent display as claimed in Claim 8 wherein said light-absorbing semi-insulating layer is less than about 1500 Angstroms thick.
10. The electroluminescent display as claimed in Claim 1 wherein the sides of said hole in said insulating layer slope inwardly and downwardly to the bottom of said hole and extend over the edges of said first electrode.
11. The electroluminescent display as claimed in Claim 1 wherein said insulating layer is a black insulating layer.
12. The electroluminescent display as claimed in Claim 1 wherein the portion of said second electrode which is in said hole has a thickness less than about 1000 Angstroms.
13. The electroluminescent display as claimed in Claim 1 wherein said light emitting layer comprises an electroluminescent layer sandwiched between two dielectric layers.
14. An electroluminescent display panel comprising:
a transparent substrate;
transparent first electrodes parallel to each other on said transparent substrate;
a first dielectric layer on said substrate and said transparent first electrode;
an electroluminescent layer on said first dielectric layer;
a second dielectric layer on said electroluminescent layer;
an insulating layer covering said second dielectric layer except for holes positioned over said transparent first electrodes, the sides of said holes sloping inwardly and downwardly to the bottom of said holes and extending over the edges of said transparent first electrodes; and second electrodes parallel to each other on said second dielectric layer in said holes and extending out of said holes and onto said insulating layer, said second electrodes crossing over said first electrodes whereby pixels are formed at the location of said holes.
a transparent substrate;
transparent first electrodes parallel to each other on said transparent substrate;
a first dielectric layer on said substrate and said transparent first electrode;
an electroluminescent layer on said first dielectric layer;
a second dielectric layer on said electroluminescent layer;
an insulating layer covering said second dielectric layer except for holes positioned over said transparent first electrodes, the sides of said holes sloping inwardly and downwardly to the bottom of said holes and extending over the edges of said transparent first electrodes; and second electrodes parallel to each other on said second dielectric layer in said holes and extending out of said holes and onto said insulating layer, said second electrodes crossing over said first electrodes whereby pixels are formed at the location of said holes.
15. The electroluminescent display panel as claimed in Claim 14 wherein said second electrodes comprise black electrodes.
16. The electroluminescent display panel as claimed in Claim 14 wherein said insulating layer is a black insulating layer.
17. The electroluminescent display panel as claimed in Claim 14 including a light absorbing, semi-insulating layer between said second dielectric and said insulating layer.
18. The electroluminescent display panel as claimed in Claim 17 wherein said light absorbing, semi-insulating layer is less than about 1500 Angstroms thick.
19. An electroluminescent display comprising:
a transparent substrate;
transparent first electrodes parallel to each other on said transparent substrate;
an insulating layer covering said transparent substrate except for holes positioned over said transparent first electrodes, the sides of said holes sloping downward to the bottom of said holes and extending over the edges of said transparent first electrodes;
a first dielectric layer on said insulating layer and on the portion of said first electrodes that are exposed at said holes;
an electroluminescent layer on said first dielectric layer;
a second dielectric layer on said electroluminescent layer; and second electrodes parallel to each other on said second dielectric layer and extending into said holes, said second electrodes crossing over said first electrodes whereby pixels are formed at the location of said holes.
a transparent substrate;
transparent first electrodes parallel to each other on said transparent substrate;
an insulating layer covering said transparent substrate except for holes positioned over said transparent first electrodes, the sides of said holes sloping downward to the bottom of said holes and extending over the edges of said transparent first electrodes;
a first dielectric layer on said insulating layer and on the portion of said first electrodes that are exposed at said holes;
an electroluminescent layer on said first dielectric layer;
a second dielectric layer on said electroluminescent layer; and second electrodes parallel to each other on said second dielectric layer and extending into said holes, said second electrodes crossing over said first electrodes whereby pixels are formed at the location of said holes.
20. The electroluminescent display as claimed in Claim 19 wherein said second electrode comprises a black electrode.
21. The electroluminescent display as claimed in Claim 19 including a light absorbing, semi-insulating layer between said second dielectric and said insulating layer.
22. The electroluminescent display as claimed in Claim 21 wherein said semi-insulating layer is less than about 1500 Angstroms.
23. The electroluminescent display as claimed in Claim 19 wherein said insulating layer is a black insulating layer.
24. An electroluminescent display comprising:
a transparent substrate;
transparent first electrodes parallel to each other on said transparent substrate;
transparent second electrodes parallel to each other, crossing said first electrodes, and spaced apart from said first electrodes;
a light emitting layer containing electroluminescent material between said first and second electrodes;
an insulating layer between said first and second electrodes, said insulating layer having holes located where said first and second electrodes cross each other, said second electrodes extending into said holes, whereby light from said light emitting layer can shine out of both sides of said display.
a transparent substrate;
transparent first electrodes parallel to each other on said transparent substrate;
transparent second electrodes parallel to each other, crossing said first electrodes, and spaced apart from said first electrodes;
a light emitting layer containing electroluminescent material between said first and second electrodes;
an insulating layer between said first and second electrodes, said insulating layer having holes located where said first and second electrodes cross each other, said second electrodes extending into said holes, whereby light from said light emitting layer can shine out of both sides of said display.
25. An electroluminescent display comprising:
a transparent substrate;
transparent first electrodes parallel to each other on said transparent substrate;
opaque second electrodes parallel to each other, crossing said first electrodes, and spaced apart from said first electrodes;
a light emitting layer containing electroluminescent material between said first and second electrodes;
an insulating layer between said first and second electrodes, said insulating layer having holes located where said first and second electrodes cross each other, said second electrodes extending into said holes, whereby light from said light emitting layer can shine out of said display through said transparent substrate.
a transparent substrate;
transparent first electrodes parallel to each other on said transparent substrate;
opaque second electrodes parallel to each other, crossing said first electrodes, and spaced apart from said first electrodes;
a light emitting layer containing electroluminescent material between said first and second electrodes;
an insulating layer between said first and second electrodes, said insulating layer having holes located where said first and second electrodes cross each other, said second electrodes extending into said holes, whereby light from said light emitting layer can shine out of said display through said transparent substrate.
26. An electroluminescent display comprising:
a substrate;
first electrodes parallel to each other on said substrate;
means for preventing light from shining out said substrate side of said display;
transparent second electrodes parallel to each other, crossing said first electrodes, and spaced apart from said first electrodes;
a light emitting layer containing electroluminescent material between said first and second electrodes;
an insulating layer between said first and second electrodes, said insulating layer having holes located where said first and second electrodes cross each other, said second electrodes extending into said holes, whereby light from said light emitting layer can shine out of said display through said second electrodes.
a substrate;
first electrodes parallel to each other on said substrate;
means for preventing light from shining out said substrate side of said display;
transparent second electrodes parallel to each other, crossing said first electrodes, and spaced apart from said first electrodes;
a light emitting layer containing electroluminescent material between said first and second electrodes;
an insulating layer between said first and second electrodes, said insulating layer having holes located where said first and second electrodes cross each other, said second electrodes extending into said holes, whereby light from said light emitting layer can shine out of said display through said second electrodes.
27. The display as claimed in Claim 26 wherein said means for preventing light comprises a means for absorbing light.
28. The display as claimed in Claim 26 wherein said means for preventing light comprises a means for reflecting light.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/790,690 US4670690A (en) | 1985-10-23 | 1985-10-23 | Thin film electrolumenescent display panel |
| US790,690 | 1991-11-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1256541A true CA1256541A (en) | 1989-06-27 |
Family
ID=25151478
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000516397A Expired CA1256541A (en) | 1985-10-23 | 1986-08-20 | Electroluminescent display panel |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4670690A (en) |
| EP (1) | EP0220470A1 (en) |
| JP (1) | JPS6299783A (en) |
| CA (1) | CA1256541A (en) |
| FI (1) | FI863777A (en) |
Families Citing this family (28)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4774435A (en) * | 1987-12-22 | 1988-09-27 | Gte Laboratories Incorporated | Thin film electroluminescent device |
| JPH0750632B2 (en) * | 1988-06-10 | 1995-05-31 | シャープ株式会社 | Thin film EL device |
| US4963788A (en) * | 1988-07-14 | 1990-10-16 | Planar Systems, Inc. | Thin film electroluminescent display with improved contrast |
| GB2230646B (en) * | 1989-04-13 | 1992-09-30 | Marconi Gec Ltd | Electroluminescent display |
| US5485055A (en) * | 1994-07-11 | 1996-01-16 | Alliedsignal Inc. | Active matrix electroluminescent display having increased brightness and method for making the display |
| US6054809A (en) * | 1996-08-14 | 2000-04-25 | Add-Vision, Inc. | Electroluminescent lamp designs |
| CA2264609A1 (en) * | 1996-08-28 | 1998-03-05 | Add-Vision, Inc. | Transportable electroluminescent display system |
| US6011352A (en) * | 1996-11-27 | 2000-01-04 | Add-Vision, Inc. | Flat fluorescent lamp |
| JP2845233B2 (en) * | 1997-01-29 | 1999-01-13 | 双葉電子工業株式会社 | Organic electroluminescence device and method of manufacturing the same |
| US6476551B1 (en) * | 1998-01-30 | 2002-11-05 | Ricoh Company, Ltd. | LED array head and minute reflection optical elements array for use in the LED array head |
| US6287673B1 (en) | 1998-03-03 | 2001-09-11 | Acktar Ltd. | Method for producing high surface area foil electrodes |
| US6097145A (en) * | 1998-04-27 | 2000-08-01 | Copytele, Inc. | Aerogel-based phase transition flat panel display |
| TW478019B (en) * | 1999-10-29 | 2002-03-01 | Semiconductor Energy Lab | Self light-emitting device |
| US6881501B2 (en) * | 2000-03-13 | 2005-04-19 | Seiko Epson Corporation | Organic electro-luminescence element and the manufacturing method thereof |
| JP4472120B2 (en) * | 2000-06-08 | 2010-06-02 | 東北パイオニア株式会社 | Organic electroluminescence device and method for manufacturing the same |
| US6739931B2 (en) * | 2000-09-18 | 2004-05-25 | Semiconductor Energy Laboratory Co., Ltd. | Display device and method of fabricating the display device |
| JP5041703B2 (en) * | 2000-09-18 | 2012-10-03 | 株式会社半導体エネルギー研究所 | Light emitting device and manufacturing method thereof |
| JP2002164181A (en) * | 2000-09-18 | 2002-06-07 | Semiconductor Energy Lab Co Ltd | Display device and its manufacturing method |
| US6652638B2 (en) * | 2001-06-01 | 2003-11-25 | Aervoe Pacific Company, Inc. | UV-sensitive marking composition |
| JP2003282260A (en) * | 2002-03-26 | 2003-10-03 | Dainippon Printing Co Ltd | Electroluminescent (el) display device |
| USRE41914E1 (en) | 2002-05-10 | 2010-11-09 | Ponnusamy Palanisamy | Thermal management in electronic displays |
| US6849935B2 (en) | 2002-05-10 | 2005-02-01 | Sarnoff Corporation | Low-cost circuit board materials and processes for area array electrical interconnections over a large area between a device and the circuit board |
| US6987259B2 (en) * | 2002-05-30 | 2006-01-17 | Dmetrix, Inc. | Imaging system with an integrated source and detector array |
| DE10308515B4 (en) * | 2003-02-26 | 2007-01-25 | Schott Ag | Method for producing organic light-emitting diodes and organic light-emitting diode |
| US20050081907A1 (en) * | 2003-10-20 | 2005-04-21 | Lewis Larry N. | Electro-active device having metal-containing layer |
| US7352554B2 (en) * | 2004-06-30 | 2008-04-01 | Axcelis Technologies, Inc. | Method for fabricating a Johnsen-Rahbek electrostatic wafer clamp |
| WO2006120854A1 (en) * | 2005-05-09 | 2006-11-16 | Matsushita Electric Industrial Co., Ltd. | Light emission element, light emission element array, method of producing the element and array, and exposure apparatus |
| JP6387828B2 (en) * | 2012-06-14 | 2018-09-12 | コニカミノルタ株式会社 | Electroluminescent device and lighting device using the electroluminescent device |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1194516B (en) * | 1956-09-05 | 1965-06-10 | Philips Nv | Solid-state image converter or image amplifier |
| US3207906A (en) * | 1960-04-06 | 1965-09-21 | Hitachi Ltd | Solid state light amplifying device with sintered photoconductor and electro-luminescent input panel |
| US3184635A (en) * | 1961-07-24 | 1965-05-18 | Gen Telephone & Elect | Electroluminescent display device |
| US3560784A (en) * | 1968-07-26 | 1971-02-02 | Sigmatron Inc | Dark field, high contrast light emitting display |
| US4279690A (en) * | 1975-10-28 | 1981-07-21 | Texas Instruments Incorporated | High-radiance emitters with integral microlens |
| US4342945A (en) * | 1980-05-20 | 1982-08-03 | Rockwell International Corporation | Electroluminescent thin film device |
-
1985
- 1985-10-23 US US06/790,690 patent/US4670690A/en not_active Expired - Fee Related
-
1986
- 1986-08-20 CA CA000516397A patent/CA1256541A/en not_active Expired
- 1986-09-18 EP EP86112872A patent/EP0220470A1/en not_active Withdrawn
- 1986-09-18 FI FI863777A patent/FI863777A/en not_active Application Discontinuation
- 1986-10-21 JP JP61251563A patent/JPS6299783A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP0220470A1 (en) | 1987-05-06 |
| FI863777A0 (en) | 1986-09-18 |
| FI863777A (en) | 1987-04-24 |
| US4670690A (en) | 1987-06-02 |
| JPS6299783A (en) | 1987-05-09 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1256541A (en) | Electroluminescent display panel | |
| US6479930B1 (en) | Dispersion-type electroluminescence element | |
| US5239228A (en) | Thin-film electroluminescence device for displaying multiple colors with groove for capturing adhesive | |
| US5786664A (en) | Double-sided electroluminescent device | |
| US7405514B2 (en) | Organic EL display device with plural electrode segments | |
| RU95122469A (en) | COLOR ELECTROLUMINESCENT INDICATOR PANEL | |
| EP0998171B1 (en) | Dispersed multicolor electroluminescent lamp and electroluminescent lamp unit employing thereof | |
| RU2129344C1 (en) | Luminescent indication board which is visible under day light | |
| US2837661A (en) | Radiation amplifier | |
| US5445898A (en) | Sunlight viewable thin film electroluminescent display | |
| US6075317A (en) | Electroluminescent device having increased brightness and resolution and method of fabrication | |
| CA1144265A (en) | High contrast display device having a dark layer | |
| SU1301327A3 (en) | Electric luminiscent device | |
| GB2106317A (en) | Electroluminescent display devices | |
| US4743801A (en) | Light-emitting electroluminescent device | |
| US4672264A (en) | High contrast electroluminescent display panels | |
| GB2063544A (en) | Thin panel display | |
| US4743808A (en) | Multi-layer electroluminescent element | |
| US5235246A (en) | Electroluminescence panel | |
| US2936379A (en) | Radiation-amplifying device | |
| US3531648A (en) | Solid state storage panel for color reproduction | |
| JPH01144595A (en) | Thin film el element | |
| KR900001405B1 (en) | Thin film el display device | |
| JPH04306589A (en) | Thin film type el panel | |
| KR0147547B1 (en) | Electroluminescence element |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |