Lights for displays such as advertising, signage, signals or emergency signaling are typically of three types: incandescent, fluorescent and light emitting diodes (LED). Each of these types of lights has drawbacks that make them undesirable in certain applications. For example, although incandescent lights are readily available in various colors, and are able to emit bright light viewable from substantially any angle, incandescent lights also produce a substantial amount of heat in comparison to quantity of light emitted. Thus, the heat generation of incandescent lights wastes electrical power. Fluorescent lights also produce substantial amounts of heat, but brightness and shapes of fluorescent lights are limited.
Alternatively, LEDs produce a relatively low amount of heat in comparison to the light emitted, and thus use substantially less electrical power as compared to incandescent lights. However, there are numerous restrictions on LEDs. For example, LEDs are typically circular or cylindrical; and it is not cost-effective for LEDs to be manufactured in an alternative shape that is better suited to a particular lighting application. Additionally, white light or multiple-color LEDs are not yet cost-effectively manufactured. LEDs also have relatively slow blink rates (e.g., 5 kHz) which causes a video display of sixty-four or higher levels of brightness to be distorted, for example, making it difficult or impossible to create animated displays with arrays of LEDs. Further, LEDs have a relatively narrow emission angle within which emitted light is effectively viewed—typically a maximum of 120 to 130 degrees.
In one embodiment, a light emitting device includes an enclosure with a face portion, a cold cathode within the enclosure, a phosphor layer disposed on an interior surface of the face portion, a tubulator between the cold cathode and the phosphor layer, the tubulator having a conductive insert, a first electrical conductor extending through the enclosure to provide electrical connectivity to the cold cathode, a second electrical conductor extending through the enclosure to provide electrical connectivity to the conductive insert and a third electrical conductor extending through the enclosure to provide electrical connectivity to the phosphor layer. Electrons from the cold cathode are defocused by the conductive insert and impact the phosphor layer when an electric field is created between the cold cathode and the phosphor layer due to applied voltages at the cold cathode, conductive insert and phosphor layer. The phosphor layer emits light through the face portion in response to electrons incident thereon.
In another embodiment, a light emitting device includes an enclosure with a face portion, a cold cathode within the enclosure, a phosphor layer disposed on an interior surface of the face portion, a conductive ring between the cold cathode and the phosphor layer, a first electrical conductor extending through the enclosure to provide electrical connectivity to the cold cathode, a second electrical conductor extending through the enclosure to provide electrical connectivity to the conductive ring, and a third electrical conductor extending through the enclosure to provide electrical connectivity to the phosphor layer. Electrons from the cold cathode impact the phosphor layer when an electric field is created between the cold cathode and the phosphor layer due to applied voltages at the cold cathode, conductive ring and phosphor layer. The phosphor layer emits light through the face portion in response to electrons incident thereon.
In another embodiment, a light emitting device includes an enclosure with a face portion, a transparent conductive coating on the interior surface of the face portion, a phosphor layer disposed on an interior surface of the enclosure opposite to the face portion, a cold cathode within the enclosure, a conductive ring between the cold cathode and the face portion, a first electrical conductor extending through the enclosure to provide electrical connectivity to the cold cathode, a second electrical conductor extending through the enclosure to provide electrical connectivity to the conductive ring, a third electrical conductor extending through the enclosure to provide electrical connectivity to the transparent conductive coating, and a fourth electrical conductor extending through the enclosure to provide electrical connectivity to the phosphor layer. Electrons from the cold cathode are defocused by the conductive ring and impact the phosphor layer when an electric field is created between the cold cathode and the phosphor layer due to applied voltages at the cold cathode, conductive insert, transparent conductive coating and phosphor layer. The phosphor layer emits light through the transparent conductive coating and face portion in response to electrons incident thereon.
Light emitting device 2510 has an enclosure 2514 with a face portion 2522. The interior surface 2523 of face portion 2522 is coated with a phosphor 2518 and a mirror layer 2526. A base section 2504 provides three electrical connection points 2516(P), 2516(T) and 2516(C) that connect phosphor 2518 (via mirror layer 2526) to conductive insert 2504 and to cathode 2530, respectively. An insulator 2506 electrically insulates connection points 2516(P) and 2516(T) from each other; and an insulator 2508 electrically insulates connection points 2516(T) and 2516(C) from each other. In the embodiment of
In an example of operation, connection point 2516(T) is connected to ground (zero volts), connection point 2516(C) is connected to a negative voltage supply (e.g., −250V) and connection point 2516(P) is connected to a positive voltage supply (e.g., +10,000V). The electric field produced between cathode 2530 and conductive insert 2504 accelerates electrons from cathode 2530, through tubulator 2502, towards phosphor 2518. The shape, length and electrical potential of conductive insert 2504 defocuses electron beam 2509, emitted by cathode 2530, to produce a uniform electron distribution over phosphor 2518, and hence a uniform light distribution across face portion 2522. The voltage differential between cathode 2530 and conductive insert 2504 may be varied (e.g., by varying the voltage applied to connection point 2516(C) and/or connection point 2516(T)) to modify the light intensity output from light emitting device 2510.
In an alternate embodiment, tubulator 2502 is conductive and is shaped to include conductive insert 2404, which is then omitted. Thus, in this alternate embodiment, tubulator 2502 operates to extract and accelerate electrons from cathode 2530 towards phosphor 2518, defocus and multiply these electrons such that a uniform light distribution from face portion 2522 is achieved.
Separator 3002 may be made of glass and formed together with enclosure 3014. Alternatively, separator 3002 may be a non-conductive material positioned and fixed within enclosure 3014. A base section 3004 of device 3010 provides three electrical connection points 3016(P), 3016(R) and 3016(C) that connect phosphor 3018 (via mirror layer 3026) to conductive ring 3006 and to cathode 3030, respectively. An insulator 3052 electrically insulates connection points 3016(P) and 3016(R) from each other; and an insulator 3054 electrically insulates connection points 3016(R) and 3016(C) from each other. In the embodiment of
In an example of operation, connection point 3016(R) is connected to ground (zero volts), connection point 3016(C) is connected to a negative voltage supply (e.g., −250V) and connection point 3016(P) is connected to a positive voltage supply (e.g., +10,000V). A strong electric field is generated between cathode 3030 and conductive ring 3006; it extends through hole 3007 in separator 3002 towards cathode 3030, causing electrons (shown as electron beam 3001) to be extracted from cathode 3030 and accelerated through hole 3007 towards phosphor 3018. The shape of conductive ring 3006 and the electric field created by conductive ring 3006 defocuses electron beam 3001 to produce a uniform electron distribution over phosphor 3018, and hence a uniform light distribution across face portion 3022.
In another example of operation, connection point 3016(R) is connected to a positive voltage supply (e.g., +500V), connection point 3016(C) is connected to ground (zero volts) and connection point 3016(P) is connected to a positive voltage supply (e.g., +10,000V).
The intensity of light produced by light emitting device 3010 may be adjusted by either varying the voltage applied to connection point 3016(P), and hence phosphor 3018, and/or by varying the voltage applied to connection point 3016(R), and hence conductive ring 3006.
In another embodiment, conductive ring 3006 is replaced by two conductive rings, an extraction ring and a defocusing ring. The voltage applied to each conductive ring may be varied to improve emission of light from device 3010. Further, the defocusing ring may be replaced by a defocusing grid with similar operation.
In an alternate embodiment, conductive ring 3006 may be replaced by a defocusing grid such that electron beam 3001 is distributed uniformly over phosphor 3018.
In an example of operation, an electric field generated by a potential difference between cold cathode 3130 and extraction grid 3134 extracts electrons (indicated by exemplary electron paths 3140) from cold cathode 3130 and accelerates these electrons towards phosphor 3118. Defocusing grid 3138 changes the trajectory of these electrons to form an even distribution over phosphor 3118. Phosphor 3118, when impacted by the electrons, generates light as shown by light rays 3142. As light rays 3142 pass through lens 3115, they are focused (or defocused), as shown. Specifically, lens 3115 may be selected to focus or defocus light emitted by light emitting device 3110 as desired.
Glass screen 3117 may have a shaped surface to provide a desired light distribution to lens 3115. For example, glass screen 3117, phosphor 3118 and mirror layer 3126 may be formed with a convex or a concave surface.
Lens 3115 may also be added to other embodiments of light emitting device described herein. For example, lens 3115, and optionally mirror layer 3226, may be added to light emitting devices 3010, 3310 and 3410 of
In an example of operation, a voltage differential is applied between cold cathode 3330 and conductive ring 3334 (via pins 3316(C) and 3316(R), respectively) such that electrons are extracted from cold cathode 3330 and accelerated, as a beam of electrons, towards surface 3346. Conductive ring 3334 is shaped such that the beam of electrons is also defocused. Transparent layer 3344 may be held at a negative or neutral potential and therefore acts as an electron mirror, repelling the electrons. A positive potential (e.g., 10 kV) is applied via pin 3316(P) to mirror layer 3326 (and phosphor 3318) thereby attracting electrons to phosphor 3318, as shown by exemplary electron paths 3314. Light, emitted from phosphor 3318 when excited by the electrons, passes through transparent layer 3344 and face portion 3322, as shown by arrows 3342.
Operation of device 3410 is similar to operation of device 3310 with performance enhanced by shaped surfaces 3422, 3446 and/or 3448.
Techniques for producing cathode 30 are disclosed in the following patents and patent applications, each of which is fully incorporated herein by reference:
Although carbon nano-tubes may work as an electron emitting material of cold cathode 2530, 3030, 3130, 3330, 3430, their structure is fragile and may break down under strong electrical fields, causing electrical shorting within, and thus failure of, the light emitting device. Carbon nano-tubes may nonetheless be encapsulated within a conductive polymer material to reduce failure of the nano-tubes under strong electrical fields.
But the electron-emitting material may be formed of carbon crystal (e.g., diamond) that is deposited onto a substrate by CVD. Strict control of the CVD process may be used to prevent formation of nano-tubes and/or hair-like formations upon the substrate, since these nano-tubes and/or hair-like formations may cause shorting between the electron-emitting material of the cold cathode and tubulator 2502 and/or conductive insert 2504.
In an example of operation, a voltage differential is applied between cold cathode 4130 and conductive ring 4134 (via pins 4116(C) and 4116(R), respectively) such that electrons are extracted from cold cathode 4130 and accelerated, as a beam of electrons, towards surface 4146. Conductive ring 4134 is shaped such that the beam of electrons is also defocused. Transparent layer 4144 may be held at a negative or neutral potential and therefore acts as an electron mirror, repelling the electrons. A positive potential (e.g., 10 kV) is applied via pin 4116(P) to mirror layer 4126 (and phosphor 4118) thereby attracting electrons to phosphor 4118, as shown by exemplary electron paths 4114. Light, emitted from phosphor 4118 when excited by the electrons, passes through transparent layer 4144 and face portion 4122, as shown by arrows 4142.
In an example of operation, a voltage differential is applied between cold cathode 4230 and conductive ring 4234 (via pins 4216(C) and 4216(R), respectively) such that electrons are extracted from cold cathode 4230 and accelerated, as a beam of electrons, towards surface 4246. Conductive ring 4234 is shaped such that the beam of electrons is also defocused. Transparent layer 4244 may be held at a negative or neutral potential and therefore acts as an electron mirror, repelling the electrons. A positive potential (e.g., 10 kV) is applied via pin 4216(P) to mirror layer 4226 (and phosphor 4218) thereby attracting electrons to phosphor 4218, as shown by exemplary electron paths 4214. Light, emitted from phosphor 4218 when excited by the electrons, passes through transparent layer 4244 and face portion 4222, as shown by arrows 4242.
Each light emitting device 2510, 3010, 3110, 3210, 3310, 3410, 4110 and 4210 may also include an ion trapping system to prevent cold cathode damage. The ion removing system removes existing (e.g., ion already existing within the enclosure) and new (e.g., ions created by the electron emission process of the cold cathode) ions from within the enclosure (particularly proximate to the cold cathode). If these ions are not removed, they are attracted towards the cold cathode (since they are positively charged) and may cause damage to the cold cathode and reduce electron emission. By utilizing a positively charged ring or plated area around the cold cathode, ions are attracted to, and impact, this ring instead of the cold cathode, thus avoiding damage to the cold cathode.
The foregoing discussion has been presented for purposes of illustration and description. Further, the description is not intended to be limited to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, within the skill and knowledge of the relevant art, are within the scope of the features disclosed herein. The embodiments described hereinabove are further intended to explain the best mode presently known of practicing the light emitting device and to enable others skilled in the art to utilize the features disclosed herein as such, or in other embodiments, and with the various modifications required by their particular application or use. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.
Changes may be made in the above methods and systems without departing from the scope hereof. For example, cold cathodes 2530, 3030, 3130, 3330, 3430, 3530, 4130 and 4230 may be replaced by thermionic (hot) cathodes, requiring an additional conductor to power a heating element and resulting in the light emitting device operating at a slightly higher temperature and higher energy. It should thus be noted that the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall there between.
This application is a continuation-in-part of commonly-owned and copending Patent Cooperative Treaty Application No. PCT/US2005/045713, filed 16 Dec. 2005 and incorporated herein by reference. This application also claims priority to commonly-owned U.S. Provisional Patent Application No. 60/780,930, filed 9 Mar. 2006 and incorporated herein by reference.
Number | Date | Country | |
---|---|---|---|
60780930 | Mar 2006 | US |
Number | Date | Country | |
---|---|---|---|
Parent | PCT/US05/45713 | Dec 2005 | US |
Child | 11684303 | Mar 2007 | US |