Patent Grant
7128439
This invention relates to planar photoluminescent lamps, and more particularly, to a two-sided planar photoluminescent lamp having two glass plates forming a chamber which stores a gas to emit light by fluorescent phenomena.
Thin, planar, and relatively large area light sources are needed in many applications. Because of low light transmission in typical active matrix liquid crystal displays (LCD), very thin and powerful backlights are required to preserve a thin profile and readability in high ambient lighting conditions. Incandescent lamps or LEDs create local bright or dim spots because of the nature of point light sources. Additionally, significant heat dissipation in incandescent lamps or LEDs restrict practical use to low output conditions. Electroluminescent lamps suffer from having relatively low brightness, and are therefore only suitable for low light display outputs.
Recent advances in photoluminescent technology have met the demand for a thin, lightweight, planar lamp having a substantially uniform and durable display. One such fluorescent lamp is described in U.S. patent application Ser. No. 09/796,334. The lamp comprises a pair of glass plates connected by a sidewall, thereby creating an open chamber which contains a gas and photoluminescent material. Electrodes are placed on the outside of the glass plates to create an electric field inside the chamber, which ionizes the gas and causes the photoluminescent material to emit visible light.
Current photoluminescent lamps allow transmission of light through only one glass plate. A reflective coating is provided on the interior of the bottom plate, to guide additional light through the top glass plate. The top electrode may be patterned as a grid on the exterior surface of the plate using a silver-based compound. Thus, the existence of the reflective coating on the bottom surface is in part necessary to counteract the light attenuation by the top electrode.
Because the reflective coating restricts the use of such current lamps to one-sided light output, there remains a need for a two-sided, thin, lightweight lamp with substantial and uniform physical integrity across the entire surface.
According to principles of the present invention, a photoluminescent lamp and a method of producing such a photoluminescent lamp is provided. In one embodiment, a gas-filled photoluminescent lamp contains a plurality of glass spacer beads affixed to a first planar glass plate at selected locations in a pre-determined pattern, and a second glass plate in loose contact with the plurality of glass beads. A plurality of adhesive pads are placed onto the first glass plate to affix the glass spacer beads to the plate. The adhesive pads may be composed of an adhesive binder mixed with a glass bearing a lower melting point as compared to the melting point of the first glass plate and the plurality of glass spacer beads. Sidewalls create a hermetic seal with the two glass plates, to form a chamber that is filled with a gas. The lamp contains first and second transparent electrodes on the outside of the glass plates, and transparent electrically insulating layers extending over the electrodes. Finally, a semi-transparent decorative layer is positioned over the surface of one of the insulating layers.
In another embodiment, the lamp may further contain structurally supportive layers over each of the electrically insulating layers to provide rigidity and adaptability of the lamp. Such supportive layers provide the benefit of easily replacing the external decorative layer(s) without stripping the device down to the insulative layers, but rather sliding a decorative layer in or out of a sleeve on the exterior of the lamp.
In one embodiment, the invention may be used as a two-sided advertising display, or alternatively as a one-sided display. In a two-sided embodiment, a second semi-transparent decorative layer is placed over the second insulating layer. The lamp may also be used as a source of general lighting. Due to the thin profile of the lamp and the ability to have any desired surface area size or shape, it is functional for general lighting for counters under a cupboard, for boat galleys, can lights, or other low profile locations, to name a few uses.
The method of creating the multi-use photoluminescent lamp comprises the steps of affixing a plurality of adhesive pads to a first glass plate, placing a plurality of glass beads in contact with the first glass plate, and moving the beads along the surface of the plate such that the glass beads adhere to the adhesive pads. Once the excess glass spacer beads are discarded, the combination of materials is treated to affix the spacer beads to the first glass plate. A second plate is placed into loose contact with the glass spacer beads, and is affixed to the first plate with a hermetic seal. The atmosphere is evacuated from the chamber between the two plates, and the chamber is filled with a selected gas. Finally, first and second electrodes extend over the exterior of the glass plates.
In one embodiment, the step of treating the combination of materials involves heating them to a temperature higher than the melting point of the glass in the adhesive pads to melt out the adhesive binder and thus fuse the beads to the glass plate.
a is a side elevation, partial cross-sectional view of the different layers of the invention.
b is a cross-sectional view of an enlarged portion within
The bottom glass plate 12 and top glass plate 14 are separated by a plurality of glass spacer members 16. In one embodiment, the spacer members 16 are beads that are UV transmissive glass beads and have a diameter selected to match the height of the sidewall spacer 18. Spacer members 16 made of glass allow UV light generated in the chamber 20 to pass through the spacers relatively unimpeded and thus reduce undesirable dim spots in the lamp 10. In one embodiment, the spacer members 16 can be standard glass beads such as those made from Boro-silicate glass. Glass beads of this type are widely available for a very low cost in large bulk. For example, beads of this type are used in paint stripes on the road to increase the reflectivity.
According to the invention, it is preferred to pass the bulk beads through successive screens or mesh filters to remove all beads larger or smaller than 0.5 mm and those beads which are not round. The spacer members 16 are distributed uniformly across the chamber 20 so as to provide support for the faces of the plates 12, 14 at a height equal to the sidewall spacer 18. The chamber is very thin, in the range of 0.3 mm to 2 mm, thus providing light from a very thin lamp. In one embodiment, the height of the sidewall spacer 18 and equivalent diameter of the spacer members 16 is 0.5 mm. It is preferred that the spacer members 16, in the form of beads, are uniform in diameter and precisely spherical in nature, so that the orientation of the beads on the spacers does not matter and so that uniform stress is placed on the glass plates 12, 14 at points in contact with the spacer members 16. The screen or meshes can be selected to have a desired tolerance level to obtain a selection of balls that are uniform with respect to each other within desired parameters.
In an alternative embodiment, other shapes are used for spacer members 16. For example, cylindrical rods running approximately the length of the chamber and being a diameter of 0.5 mm can be used. Also, the spacer members may be columns, cones, pyramids, cubes or the like.
As also shown in
A bottom transparent electrode 22 and top transparent electrode 24 are on exterior surfaces of the plates 12, 14. The electrodes 22, 24 are coupled to opposite sides of an alternating current power supply 38, or alternatively one electrode to an AC power supply and the other to ground, or as a further alternative, pulsed DC could be used. The electrodes 22, 24 are used to create an electric field by capacitive coupling through the dielectric of the plates 12, 14. This produces a stable and uniform plasma from the ultraviolet emissive gas in the chamber 20. The plasma acts as a uniform source of ultraviolet light, which is a condition conducive to uniform visible light generation.
Bottom and top transparent electrodes 22, 24 are designed to permit light to exit the chamber 20 through the glass plates 12, 14. The electrodes 22, 24 may be a transparent coating on the glass plates as to permit light to pass through without causing undesirable gradations in the produced illumination. Such transparent electrodes are known in the art and any of the many commercially known and used electrodes are acceptable. In an alternate embodiment, the electrodes 22, 24 may comprise conductive lines patterned as a grid on the exterior surface of the plates 12, 14 using a laser or ultraviolet (UV) light and an aqueous development process to yield highly conductive lines of a silver-based compound. However, a transparent electrode layer over the exterior of the glass plates 12, 14 is preferred because it allows minimal light gradation.
A transparent insulating layer 26 covers the bottom and top electrodes 22, 24. The insulating layer 26 may be standard commercial grade silicone, and in one embodiment has a thickness of approximately 0.75 mm. In another embodiment, the thickness of silicone layer 26 is less than 0.1 mm, such as 0.05 mm or less. Thickness is the range of 1 mm to 0.01 mm.
The insulating layer 26 may be mixed with a high molecular weight polymer, such as polydimethylsiloxane, and may be applied by any acceptable technique, including, for example, rolling on layers of silicone, spraying, screen printing, dipping the electrodes into the silicone, or the like. As shown in
In one embodiment, structurally supportive layers 30, 32 extend over the insulating layer 26 on both the bottom and top of the device. Such a layer may be comprised of Mylar®. The bottom and top structurally supportive layers 30, 32 provide additional integrity to the device as well as adaptability for convenience of the user. In one embodiment, one or both of the outermost decorative layers (described below) may be easily replaced by the user without stripping the device down to the insulating layer 26, a benefit made possible because of the intermediate structurally supportive layers 30, 32.
Semi-transparent decorative logo layers 34, 36 are provided on the exterior of the lamp. Such layers contain a pattern of a semi-transparent colored material capable of transmitting light through the layer from within the lamp 10. Typically, the decorative logo layers 34, 36 are easily removable, and may be held in place by a retaining rim 60 (see
It will be appreciated that the present invention may be modified for use as a one-sided lamp, whereby a reflective coating such as TiO2 or Al2O3 may be deposited on the exterior surface of the bottom glass plate 12 so that more light is reflected out the top glass plate 14 and none out the bottom glass plate 12. Additionally, white plastic or some other backing may be applied to one side to enhance the light emanating from the other side of the lamp. This would permit the lamp to be used for general lighting purposes, such as for down lighting such as can lighting, under counter lighting, task lighting, kitchen counter lighting or other specialty lighting applications where the thin profile of the lamp would permit its use where other lamps can't be used. It is a low profile, flat lamp that has a total thickness, all coatings included, of about ¼ of an inch or less. In ships, submarines and other small space environments, this flat lamp will be beneficial in overcoming typical limitations on the thickness of lamps due to space concerns.
The ability to maintain the integrity of the sealed chamber 20 provided by the bottom glass plate 12 and top plate 14 is in part a function of the thickness of the plates 12, 14, the arrangement and number of the spacer members 16, and net atmospheric pressures. The net atmospheric pressure is the difference between external and internal pressure of the chamber 20. The glass of the plates 12, 14 must be thick enough to withstand external atmospheric pressure exerted against portions of the plates that are not supported by the spacer members 16 to prevent implosion of the lamp 10. In one embodiment, bottom glass plate 12 and top glass plate 14 have an approximate thickness of 1 mm. In one embodiment, standard architectural glass of the type used in standard glass windows is used for plates 12 and 14. It is preferred to be annealed glass, of a standard type, that is low cost. A soda lime silicate glass, also known as float glass, is preferred. A thickness in the range of 2–3 millimeters is preferred, but other thicknesses are acceptable. A standard glass of low cost is preferred since this will permit the lamp to be produced in high quantities at a low cost. The glass not need to be tempered glass, but can be used if it desired and available in the desired shape and size. Because of the importance of physical integrity, it is beneficial if the spacer members 16 are positioned in a uniform pattern between the bottom and top glass plates 12, 14.
To apply the glass spacer members 16 onto the adhesive pads 56, a plurality of glass spacer members 16 are poured over the glass plate 12 and adhesive pads 56. The number of spacer members 16 may be many more than the number of adhesive pads 56 to ensure that each dot can have at least a single spacer member 16. The adhesive pads 56 bind the glass spacer members 16 in place, and the additional spacer members 16 that do not connect to a pad are discarded from the plate 12.
If the pads 56 contain a glass, the plate 12 and beads are then heated to a temperature just above the melting point of the adhesive pads 56, yet below the melting temperature of the glass plate 12 and the glass bead spacer members 16. This process drives the adhesive binder material out of the adhesive pads 56 and fuses the glass in the pads 56 to both the glass spacer members 16 and corresponding surface of the glass plate 12. This process melts only the adhesive pads 56 because, as described above, the melting point of the pads 56 is lower than the spacer members 16 and glass plate 12. The top glass plate 14 is then placed on top of the beads during manufacture and attached by the sidewall spacer 18, but is not affixed to the glass spacer members 16.
The loose contact between the second glass plate 14 and glass spacer members 16 allows the insertion of gas into the chamber 20 to take place without placing great strain on the glass plates 12, 14. Because top glass plate 14 is left unfused to the glass spacer members 16, the glass plates 12, 14 are allowed to flex and bend during the evacuation and refill process. To fill the chamber 20 with gasses, it is first necessary to evacuate the air from the chamber 20. Once the sidewall spacer 18 creates a hermetic seal between the glass plates 12, 14, steps are taken to evacuate atmospheric gasses from the chamber 20, fill the chamber 20 with an ultra-violet emissive gas, and seal the chamber 20.
The glass spacer members 16 are affixed directly to the bottom glass plate 12 via adhesive pads 56. The bottom phosphor layer 52 has been applied to the bottom glass plate 12, leaving holes in the layer 52 at locations where adhesive pads 56 are to be positioned. The layer 52 may be applied using a mask, which keeps the phosphor layer 52 from covering the glass plate 12 in the positions where the adhesive pads 56 are to be located. A reverse mask of the phosphor layer may be used when applying the adhesive pads 56 to the glass plate 12.
One sequence for manufacturing the decorative lamp according to the present invention is as follows. The bottom glass plate 12 and the top plate 14 both have a phosphor layer 52 placed on the surfaces thereof. The phosphor coating on the top plate 14 is an unbroken coating, done without a mask while the phosphor coating on the bottom glass plate 12 will usually be done with a mask having openings where the spacer beads are to be affixed to the bottom glass plate 12. The phosphor layer is then dried and cured to be stable. The phosphor layer may have a binder therein to assist in sticking to the glass and to the spacer members 16. After the phosphor layer is on the glass plate 12, adhesive pads 56 are placed on the glass using a screen print process. They are positioned within the openings of the phosphor layer. This can be done by using a reverse mask of that used for the phosphor layer or a new mask can be provided having openings slightly smaller than but aligned with the openings provided in the phosphor layer 52. The adhesive pads therefore directly contact the glass plate 12.
A large number of spacer members 16, such as in the form of beads, far in excess of the number of adhesive pads 56, are then placed onto the bottom glass plate 12 and the plate is moved to roll the beads and ensure that one bead adheres to each adhesive pad 56. The plate 12 is then turned sideways or upside down so that those spacer members 16 which did not adhere fall from the plate 12 for later use.
The plate 12 is then placed in an environment to permanently affix the spacer members 16 to the pads 56. This may be an air dry environment, heat treatment step or some other annealing step. In the embodiment in which the adhesive pads 56 is composed of a binder and glass, the treatment step is preferably a heat treatment step of a sufficient temperature to melt the glass in the adhesive pad sufficient that it binds with both the lower glass plate 12 and the spacer members 16 but does not cause substantially melting of either the beads or the plate 12. The temperature is then lowered, making the glass in the adhesive pads 56 rigid and solidly fusing the spacer members 16 to the respective pads 56 on the plate 12. The heating step also serves to drive out the binders from the adhesive pad so that the interior surface is composed generally of glass and the desired light emitting materials such as the phosphors and the other gasses.
In one embodiment, the phosphor is applied first to plate 12 after which the pads 56 and glass beads are affixed to the plate 12 as has been described. In an alternative embodiment, the sequence of steps is changed so that the glass spacer members 16 are affixed to the plate 12 after which the phosphor layer 52 is adhered to the plate 12 and to the spacer members 16.
Coating the plate 12 with the spacer members 16 attached is done without a mask and provides a blanket covering of all exposed surfaces, including the spacer members 16. This sequence has the advantage of using one less mask and the screen printing for the pads 56 does not need to be aligned with the openings in a phosphor layer, since one is not present when they are applied. The phosphor layer is applied with the glass beads present, which is more difficult than with a flat surface on plate 12, so there are advantages to either approach.
The process may be done in either sequence according to principles of the present invention. The upper glass plate 14 on the sidewall spacer 18 is then affixed to the lower glass plate 12 to create a hermetically sealed chamber 20. The atmosphere, which at this stage of the process will normally be ambient air, is removed from the chamber. This is preferably removed using some vacuum nipple or tubing but other methods of removing the atmosphere are acceptable, such as assembling the final lamp inside a vacuum or other acceptable techniques. When the air is being evacuated from the chamber 20, the upper plate 14 will be drawn towards the bottom glass plate 12 so as to be supported by and in contact with the glass spacer members 16. The spacer members 16 serve to support the upper plate 14 and prevent breakage thereof while the vacuum is drawn in the chamber 20. This permits large plates to be used of hundreds of square inches without fear of breakage. After the atmosphere has been withdrawn, the desired gas and vapor mixture is placed into the chamber 20 so that it emits light when an electric voltage is applied between plates 22 and 24 as is previously described herein. When the emissive gas is placed inside the chamber 20 it may cause the plates 14 and 12 to be pushed away from each other and, in the event it exceeds one atmosphere a pressure will be created forcing the plates apart from each other. Since the plate 14 rests on the spacer members 16 but is not affixed to them, the plate 14 is permitted to flex outward during the gas refill process without causing breakage of the lamp.
According to a preferred embodiment, the gas pressure inside the lamp is approximately 75% of atmospheric pressure although in some embodiments, the pressure may exceed atmospheric pressure by several atmospheres or, may remain a partial vacuum of a tenth of an atmosphere or less. Accordingly, the glass spacer beads serve the dual function of preventing implosion of the chamber 20 by keeping glass plates 14 and 12 spaced a distance apart when a vacuum is drawn, while at the same time permitting some flexing of the plates relative to each other as the air pressure changes. Flexing may also be present between the plates during operation of the lamp as may be caused by local heating effects. While the heat output by a florescent lamp is relatively small, there may nevertheless be some differences in the coefficients of expansion between various materials in the lamp and having the glass spacer members 16 rigidly affixed to one plate while not rigidly affixed to the other plate permits the plates to move relative to each other while maintaining integrity of the lamp. If care is taken to ensure matching thermal coefficients of expansion between all materials and a pressure not greater than atmospheric is used, it is permitted in one embodiment to also fuse or adhere the spacer members 16 to both plates, the bottom plate 12 and the top plate 14.
Symmetrically, the top glass plate 14, which is not affixed to glass spacer beads 14, is covered by top electrode 24. Top electrode 24 is in contact with the insulating layer 26. Extending over the surface of the insulating layer 26 is an optional top supportive layer 32. On the exterior of the device is a decorative logo layer 36. As shown, sidewall spacer 18 creates the hermetic seal with bottom glass plate 12 and top glass plate 14 to create the chamber 20.
A retaining rim 60 wraps around all layers of the device, including the outermost logo layers 34, 36. This retaining rim 60 functions to keep the decorative logo layers 34, 36 physically in place. The rim 60 may be designed as a plastic lip or other simple mechanical securing apparatus, such that it may be easily removed and the decorative logo layers 34, 36 may be easily switched with different layers having a different design thereon.
a shows an enlarged section from
The lamp is functional as a two-sided advertising mark. Thus, an advertising sign may act as a display to the outside through a window 72 in a store as well as to the inside of the store. It will be appreciated that different decorative and advertising logos may be placed on either side of the lamp, and may be easily replaced. While a typical lamp may be 15″ in diameter and circular, the size and shape can be selected as desired. Lamps as small as 3–5 inches in diameter and as large as 100 inches in diameter and larger could easily be used. This technology is not limited to the footprint or shape of the lamp and thus is ideal for a myriad of lighting environments. Resolution and uniformity of light output is unaffected by the shape or size of the display, so even large or odd shaped displays can be created.
From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.
All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety.
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| Number | Date | Country | |
|---|---|---|---|
| 20050135080 A1 | Jun 2005 | US |
