CA2422539A1 - Dark electrode - Google Patents
Dark electrode Download PDFInfo
- Publication number
- CA2422539A1 CA2422539A1 CA 2422539 CA2422539A CA2422539A1 CA 2422539 A1 CA2422539 A1 CA 2422539A1 CA 2422539 CA2422539 CA 2422539 CA 2422539 A CA2422539 A CA 2422539A CA 2422539 A1 CA2422539 A1 CA 2422539A1
- Authority
- CA
- Canada
- Prior art keywords
- electrically conductive
- reflective layer
- electrode
- layer
- partially
- 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
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Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1343—Electrodes
- G02F1/13439—Electrodes characterised by their electrical, optical, physical properties; materials therefor; method of making
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/133553—Reflecting elements
Landscapes
- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- Mathematical Physics (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Devices For Indicating Variable Information By Combining Individual Elements (AREA)
Abstract
An electrode for use in LCDs or other applications where a dark appearance of the electrode is desired. The electrode consists of a multi-layer structure that has a combination of optical properties which reduce light incident on the electrode. The electrode materials are also chosen to be conductive of electricity.
Description
D.c~lZl~ EL,EOTROE
Field of the Invention [0001] The present invention relates generally to electronics and electronic circuitry and more particularly relates to an electrode for use in providing current to electronics and that appears dark.
Background of the Invention [0002' In many display and other technologies there is a general need for creating areas that are dark in colour. In many cases these areas are also electrically active, in that they are electrodes within the display. For example in both OLEIC and TFEL displays the rear electrodes often need to be rendered black or dark, to improve the display contrast. This can be addressed by using circular polarizing technology - while circular polarizers do not actually make the electrodes black pef° se, they can absorb light entering the device by controlling the polarization state of the incoming light and the reflected light. Another method of approaching this problem is to use electrodes that are transparent (e.g. ITO, ~n0) and subsequently use black paint or black resin or black polyamide (polymer) on the back of the display, physically behind the electrode, generally on the opposite side of the glass where the ITO is located.
[0003] Another method for achieving a dark display is through tile use of optical interference. For example US Patent 5,049,780 to Dobrowolslci and L1S Patent 6,411,019 to Hofstra (both of which are incorporated herein by reference) teach the use of an optical interference member within inorganic and organic thin film electroluminescent devices respectively. While the foregoing circular polarizes and optical interference art can be useful in rendering areas of an electroluminescent display dark, the inventors of the present invention have discovered a need for improved methods of providing an overall dark electrode that can be used in devices and applications other than electroluminescent devices.
Summary of the Invention [0004] It is therefore an object of the present invention to provide a dark electrode that obviates or mitigates at least one of the above-identified disadvantages of the prior art.
The present invention provides various methods and structures for rendering electrodes dark.
In a particular aspect darkness of the electrode is achieved with a partially-reflective material, and a partially absorbing material as a phase shifting layer to provide greater darkness over a wider range of viewing angles.
[0005] In an aspect of the invention there is provided an electrode comprising an electrically conductive thin partially-reflective layer having a first n value ranging from about 0.8 to about 4 and a first k value ranging from about 2.5 to about 8. The electrode also comprises an electrically conductive transparent phase shifting layer disposed behind the partially-reflective layer, the electrically conductive transparent phase shifting layer having a second n value ranging from about 1.65 to about 4 and a second k value ranging from about 0 to about 0.7. 'The electrode also comprises an electrically conductive thick reflective layer disposed behind the electrically conductive transparent phase shifting layer, wherein the first and second n values and the first and second k values cooperate with a reflectivity of the reflective layer to reduce light incident on the thin partially-reflective layer.
brief I)escriution of the I)rawran~s [0006) Embodiments of the invention will now be discussed, by way of example only, with reference to the attached Figure in which ,. CA 02422539 2003-03-18 Figure 1 is a side schematic view of a dark electrode in accordance with an embodiment of the invention.
Detailed Description of the Invention [0007] Referring now to Figure 1, a dark electrode in accordance with an embodiment of the invention is indicated generally at 20. Electrode; 20 comprises an electrically conductive thin partially-reflective layer 24, an electrically conductive transparent phase shifting layer 28, and an electrically conductive thick reflective layer 32.
As will be discussed in greater detail below, the relative thicknesses and materials of electrode 20 are chosen to provide the desired level of electrical conductivity and desired reflectivities so as to reduce reflections off of electrically conductive partially-reflective layer 28. Electrode 20 is shown in Figure 1 as connected to a power supply 40 and a load 36. Load 36 can be any type of electrical load 36 to be used in conjunction with electrode 20, as desired.
Examples of possible load 36 could be certain emissive materials or structures such as plasma. It is also contemplated that electrode 20 can be incorporated into an liquid crystal display ("LCD") pixel, where load 36 is the shuttering mechanism inside the LCD, such that when power supply 40 is "on", the shutter is activated, and when power supply 40 is "ofP', the shutter is deactivated.
[0010] Thin partially-reflective layer 24 is typically made from a conducting and partially reflective material such as Al or Cr. Al or Cr are presently preferred because they have an "n" value ranging from about 0.8 to about 4 and a "k" value ranging from about 2.5 to about 8. (i.e. Vdhere the "n" value is the index of refraction, and where the "k" value is ", CA 02422539 2003-03-18 the absorption constant) A presently preferred "n" value is about 3, and a presently preferred "k" value is about 5.
[0011 ] Electrically conductive transparent phase shifting layer 28 is typically made from conducting and substantially transparent materials such as ITO, Znt~, AlSaO or CrSiO.
The material for layer 28 will typically have an "n" value in the range of from about 1.65 to about 4, while having a "k" value in the range of about 0 to about 0.7. A
presently preferred "n" value is about 2, while a presently preferred "k" value is about 0.25. The k value is chosen to be low enough to provide a desired level of transparency, without unduly impacting the desired effects achievable from the selected "n" value.
[0012] Electrically conductive thick reflective layer 32 is typically thicker than layer 28 and is made from a conducting and mirror-like material. Layer 32 is typically made from Cr or Al, or a number of sub-layers including combinations thereof.
[0013] Electrode 20 can be placed above a pre-fabricated structure incorporating load 36 andlor in conjunction with power supply 40. Alternatively, electrode 20 or can be deposited directly onto a substrate (not shown) with load 36 subsequently fabricated atop thereof. Electrode 20 can also be buried integrally within a larger device, such as a cell phone, PDA, watch or other device where a dark electrode is desired.
[0014] As well, the surface of partially-reflective layer 24 of electrode 20 can be modified with another transparent conducting material if desired and/or necessary to operate with load 36. For example, ITD or Zn~ or LiF may be placed on the surface of partially-reflective layer 24 to modify its work function properties.
[0015] In operation, the n values and the k values of the aforementioned layers 24 and 28 cooperate with a reflectivity of the reflective layer to reduce light incident on the thin partially-reflective layer 32. In particular, incident light L on. layer 24 is partially reflected as per reflection Rl, and partially transmitted through layers 24 and 28. The light traveling through layers 24 and 28 is shifted in phase through layer 28, and reflected off of layer 32 as reflection R2, so that it is out of phase with reflection Rl . The phase mismatch of reflection Rl and reflection R2 at the surface of layer 24 cause a destructive interaction of these two reflections R1 and R2, causing at least some reduction in incident light.
Where the phase shift is about one-hundred-and-eighty degrees between reflection Rl and reflection R2, there can be a substantial reduction of incident light.
[0016] In the present invention electrode 20 can be used as the electrode in TFEL
devices and OLED devices, but also in other display technologies such as LCD, 1'DP and FED technologies. Furthermore this dark electrode 20 can be used in other non-display related technologies where a dark conducting device is desired.
[0017] An example electrode in accordance with the embodiments herein provides a partially-reflective layer 24 having a thickness of about 24 A and made of Cr, an electrically conductive transparent phase shifting layer 28 having a thickness of about 562 A and made from Cr~iO; an electrically conductive thick reflective layer 32 having a thickness of about 1500.A and made from Cr and disposed on a glass substrate, The average photopic reflectance for this structure is about 0.37%, while the conductivity for this structure is substantially similar to that of Cr.
[0018] The above-described embodiments of the invention are intended to be examples of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention which is defined solely by the claims appended hereto.
Field of the Invention [0001] The present invention relates generally to electronics and electronic circuitry and more particularly relates to an electrode for use in providing current to electronics and that appears dark.
Background of the Invention [0002' In many display and other technologies there is a general need for creating areas that are dark in colour. In many cases these areas are also electrically active, in that they are electrodes within the display. For example in both OLEIC and TFEL displays the rear electrodes often need to be rendered black or dark, to improve the display contrast. This can be addressed by using circular polarizing technology - while circular polarizers do not actually make the electrodes black pef° se, they can absorb light entering the device by controlling the polarization state of the incoming light and the reflected light. Another method of approaching this problem is to use electrodes that are transparent (e.g. ITO, ~n0) and subsequently use black paint or black resin or black polyamide (polymer) on the back of the display, physically behind the electrode, generally on the opposite side of the glass where the ITO is located.
[0003] Another method for achieving a dark display is through tile use of optical interference. For example US Patent 5,049,780 to Dobrowolslci and L1S Patent 6,411,019 to Hofstra (both of which are incorporated herein by reference) teach the use of an optical interference member within inorganic and organic thin film electroluminescent devices respectively. While the foregoing circular polarizes and optical interference art can be useful in rendering areas of an electroluminescent display dark, the inventors of the present invention have discovered a need for improved methods of providing an overall dark electrode that can be used in devices and applications other than electroluminescent devices.
Summary of the Invention [0004] It is therefore an object of the present invention to provide a dark electrode that obviates or mitigates at least one of the above-identified disadvantages of the prior art.
The present invention provides various methods and structures for rendering electrodes dark.
In a particular aspect darkness of the electrode is achieved with a partially-reflective material, and a partially absorbing material as a phase shifting layer to provide greater darkness over a wider range of viewing angles.
[0005] In an aspect of the invention there is provided an electrode comprising an electrically conductive thin partially-reflective layer having a first n value ranging from about 0.8 to about 4 and a first k value ranging from about 2.5 to about 8. The electrode also comprises an electrically conductive transparent phase shifting layer disposed behind the partially-reflective layer, the electrically conductive transparent phase shifting layer having a second n value ranging from about 1.65 to about 4 and a second k value ranging from about 0 to about 0.7. 'The electrode also comprises an electrically conductive thick reflective layer disposed behind the electrically conductive transparent phase shifting layer, wherein the first and second n values and the first and second k values cooperate with a reflectivity of the reflective layer to reduce light incident on the thin partially-reflective layer.
brief I)escriution of the I)rawran~s [0006) Embodiments of the invention will now be discussed, by way of example only, with reference to the attached Figure in which ,. CA 02422539 2003-03-18 Figure 1 is a side schematic view of a dark electrode in accordance with an embodiment of the invention.
Detailed Description of the Invention [0007] Referring now to Figure 1, a dark electrode in accordance with an embodiment of the invention is indicated generally at 20. Electrode; 20 comprises an electrically conductive thin partially-reflective layer 24, an electrically conductive transparent phase shifting layer 28, and an electrically conductive thick reflective layer 32.
As will be discussed in greater detail below, the relative thicknesses and materials of electrode 20 are chosen to provide the desired level of electrical conductivity and desired reflectivities so as to reduce reflections off of electrically conductive partially-reflective layer 28. Electrode 20 is shown in Figure 1 as connected to a power supply 40 and a load 36. Load 36 can be any type of electrical load 36 to be used in conjunction with electrode 20, as desired.
Examples of possible load 36 could be certain emissive materials or structures such as plasma. It is also contemplated that electrode 20 can be incorporated into an liquid crystal display ("LCD") pixel, where load 36 is the shuttering mechanism inside the LCD, such that when power supply 40 is "on", the shutter is activated, and when power supply 40 is "ofP', the shutter is deactivated.
[0010] Thin partially-reflective layer 24 is typically made from a conducting and partially reflective material such as Al or Cr. Al or Cr are presently preferred because they have an "n" value ranging from about 0.8 to about 4 and a "k" value ranging from about 2.5 to about 8. (i.e. Vdhere the "n" value is the index of refraction, and where the "k" value is ", CA 02422539 2003-03-18 the absorption constant) A presently preferred "n" value is about 3, and a presently preferred "k" value is about 5.
[0011 ] Electrically conductive transparent phase shifting layer 28 is typically made from conducting and substantially transparent materials such as ITO, Znt~, AlSaO or CrSiO.
The material for layer 28 will typically have an "n" value in the range of from about 1.65 to about 4, while having a "k" value in the range of about 0 to about 0.7. A
presently preferred "n" value is about 2, while a presently preferred "k" value is about 0.25. The k value is chosen to be low enough to provide a desired level of transparency, without unduly impacting the desired effects achievable from the selected "n" value.
[0012] Electrically conductive thick reflective layer 32 is typically thicker than layer 28 and is made from a conducting and mirror-like material. Layer 32 is typically made from Cr or Al, or a number of sub-layers including combinations thereof.
[0013] Electrode 20 can be placed above a pre-fabricated structure incorporating load 36 andlor in conjunction with power supply 40. Alternatively, electrode 20 or can be deposited directly onto a substrate (not shown) with load 36 subsequently fabricated atop thereof. Electrode 20 can also be buried integrally within a larger device, such as a cell phone, PDA, watch or other device where a dark electrode is desired.
[0014] As well, the surface of partially-reflective layer 24 of electrode 20 can be modified with another transparent conducting material if desired and/or necessary to operate with load 36. For example, ITD or Zn~ or LiF may be placed on the surface of partially-reflective layer 24 to modify its work function properties.
[0015] In operation, the n values and the k values of the aforementioned layers 24 and 28 cooperate with a reflectivity of the reflective layer to reduce light incident on the thin partially-reflective layer 32. In particular, incident light L on. layer 24 is partially reflected as per reflection Rl, and partially transmitted through layers 24 and 28. The light traveling through layers 24 and 28 is shifted in phase through layer 28, and reflected off of layer 32 as reflection R2, so that it is out of phase with reflection Rl . The phase mismatch of reflection Rl and reflection R2 at the surface of layer 24 cause a destructive interaction of these two reflections R1 and R2, causing at least some reduction in incident light.
Where the phase shift is about one-hundred-and-eighty degrees between reflection Rl and reflection R2, there can be a substantial reduction of incident light.
[0016] In the present invention electrode 20 can be used as the electrode in TFEL
devices and OLED devices, but also in other display technologies such as LCD, 1'DP and FED technologies. Furthermore this dark electrode 20 can be used in other non-display related technologies where a dark conducting device is desired.
[0017] An example electrode in accordance with the embodiments herein provides a partially-reflective layer 24 having a thickness of about 24 A and made of Cr, an electrically conductive transparent phase shifting layer 28 having a thickness of about 562 A and made from Cr~iO; an electrically conductive thick reflective layer 32 having a thickness of about 1500.A and made from Cr and disposed on a glass substrate, The average photopic reflectance for this structure is about 0.37%, while the conductivity for this structure is substantially similar to that of Cr.
[0018] The above-described embodiments of the invention are intended to be examples of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention which is defined solely by the claims appended hereto.
Claims (7)
1. An electrode comprising an electrically conductive thin partially-reflective layer having a first n value ranging from about 0.8 to about 4 and a first k value ranging from about 2.5 to about 8; an electrically conductive transparent phase shifting layer disposed behind said partially-reflective layer, said electrically conductive transparent phase shifting layer having a second n value ranging from about 1.65 to about 4 and a second k value ranging from about 0 to about 0.7; and an electrically conductive thick reflective layer disposed behind said electrically conductive transparent phase shifting layer, wherein said first and second n values and said first and second k values cooperate with a reflectivity of said reflective layer to reduce light incident on said thin partially-reflective layer.
2. The electrode according to claim 1 wherein said electrically conductive partially-reflective layer is made from a material selected from the group consisting of Al or Cr.
3. The electrode according to claim 1 or 2 wherein said electrically conductive partially-reflective layer has an "n" value of about 3 and a "k" of about 5.
4. The electrode according to claim 1, 2, or 3 wherein said electrically conductive transparent phase shifting layer is made from a material selected from the group consisting of ITf3, ZnO, AlSiO or CrSiO.
5. The electrode according to claim 1, 2, 3 or 4 wherein said electrically conductive transparent phase shifting layer material has an "n" value of about 2 and a "k" value of about 0.25.
6. An electrode comprising an electrically conductive thin partially-reflective layer made from Cr and having a thickness of about 24 angstroms; an electrically conductive transparent phase shifting layer disposed behind said partially-reflective layer, said transparent phase-shifting layer made from CrSiO an having a thickness of about 562 angstroms;
and an electrically conductive thick reflective layer disposed behind said electrically conductive transparent phase shifting layer, said electrically conductive thick reflective layer made from Cr and having a thickness of about 1500 angstroms, wherein said partially-reflective layer and said phase-shifting layer cooperate with a reflectivity of said reflective layer to reduce light incident on said thin partially-reflective layer.
and an electrically conductive thick reflective layer disposed behind said electrically conductive transparent phase shifting layer, said electrically conductive thick reflective layer made from Cr and having a thickness of about 1500 angstroms, wherein said partially-reflective layer and said phase-shifting layer cooperate with a reflectivity of said reflective layer to reduce light incident on said thin partially-reflective layer.
7. The electrode according to claim 6 wherein said electrically conductive thick reflective layer is disposed on a substrate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2422539 CA2422539A1 (en) | 2003-03-18 | 2003-03-18 | Dark electrode |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2422539 CA2422539A1 (en) | 2003-03-18 | 2003-03-18 | Dark electrode |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2422539A1 true CA2422539A1 (en) | 2004-09-18 |
Family
ID=32968246
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2422539 Abandoned CA2422539A1 (en) | 2003-03-18 | 2003-03-18 | Dark electrode |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2422539A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012007879A1 (en) | 2010-07-13 | 2012-01-19 | Commissariat A L'energie Atomique Et Aux Energies Alternatives | Organic light-emitting diode and screen having low reflectivity |
-
2003
- 2003-03-18 CA CA 2422539 patent/CA2422539A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012007879A1 (en) | 2010-07-13 | 2012-01-19 | Commissariat A L'energie Atomique Et Aux Energies Alternatives | Organic light-emitting diode and screen having low reflectivity |
| FR2962853A1 (en) * | 2010-07-13 | 2012-01-20 | Commissariat Energie Atomique | ORGANIC ELECTROLUMINESCENT DIODE AND SCREEN WITH LOW REFLECTIVITY. |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |