Patent Publication Number: US-2005140294-A1

Title: Cold cathode fluorescent lamp and method for forming the same

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a cold cathode fluorescent lamp (CCFL), and in particular to a cold cathode fluorescent lamp that excludes unnecessary gases or impurities therefrom, reduces operational potential thereof and prolongs lifespan thereof.  
      2. Description of the Related Art  
      A cold cathode fluorescent lamp (CCFL) generally has poor illumination and reduced lifespan when unnecessary gases or impurities exist therein. In the process of manufacturing the cold cathode fluorescent lamp, getter is employed to absorb the unnecessary gases or impurities existing in the glass tube thereof. The getter is then removed when the glass tube is sealed.  
      Referring to  FIGS. 1A, 1B  and  1 C, an electrode  108  and a mercury-getter mixture alloy  102  are disposed in a glass tube  100 . The electrode  108  includes a glass ball  106  and a metal wire  104 . The mercury-getter mixture alloy  102  is separated from the metal wire  104  of the electrode  108  by a predetermined distance. The glass tube  100  has an opening  110  behind the mercury-getter mixture alloy  102  to connect an evacuating device. The glass tube  100  is evacuated and is filled with an inert gas. The glass tube  100  is then sealed to become a gastight chamber. The mercury-getter mixture alloy  102  is activated by high-frequency electromagnetic wave to release mercury particles into a light-emitting portion  112  of the glass tube  100 . At this point, the getter material can absorb residual unnecessary gases or impurities. The glass ball  106  and glass tube  100  are then fused and the unnecessary part of the glass tube  100  and mercury-getter mixture alloy  102  behind a fusing portion  114  are removed.  
      Nevertheless, in the process of fusing the glass ball  106  and glass tube  100 , additional unnecessary gases or impurities are generated. The additional unnecessary gases or impurities are remained in the glass tube  100  for increasing the operational potential thereof and reducing the lifespan thereof.  
      To solve the aforementioned problem, the getter is deployed in the glass tube to absorb the unnecessary gases or impurities. JP 8-339778, JP 2002-313277 and U.S. Pat. No. 5,572,088 disclose complicated structures to deploy the getter in the glass tubes thereof. Manufacture of the complicated structures, however, is difficult and the getter may be scattered over the entirety of the glass tubes by bombardment of ions therein.  
      Moreover, operation of the cold cathode fluorescent lamps in JP 2002-313277 and JP 7-45183 is changed to comply with structural design thereof, causing difficulty in lighting the cold cathode fluorescent lamps.  
     SUMMARY OF THE INVENTION  
      Accordingly, an object of the invention is to provide a cold cathode fluorescent lamp. The cold cathode fluorescent lamp comprises a transparent tube and at least one absorptive structure. The transparent tube is filled with a gas comprising a material capable of arousing light by means of an electric potential. The absorptive structure is disposed on one end of the transparent tube and comprises a supporting mechanism having at least one opening, and at least one absorptive layer formed in the opening and not filled with the opening.  
      Another object of the invention is to provide a method of forming a cold cathode fluorescent lamp. The method comprises the steps of deploying at least one absorptive layer in an opening of a supporting mechanism, wherein the supporting mechanism and absorptive layer form a absorptive structure; disposing the absorptive structure in a transparent tube; evacuating the transparent tube; filling the transparent tube with a gas comprising a material capable of arousing light by means of an electric potential; and sealing the transparent tube such that the transparent tube and absorptive structure are tightly bonded.  
      Yet another object of the invention is to provide a absorptive structure. The absorptive structure comprises a supporting mechanism and at least one absorptive layer. The supporting mechanism has at least one opening. The absorptive layer is formed in the opening and is not filled with the opening.  
      The shape of the transparent tube is stripped, annular, curved, polygonal, or plated, and the material of the transparent tube is glass or transparent plastic.  
      The material of the absorptive layer is selected from the group consisting of zirconium, barium, vanadium, titanium, a zirconium-based alloy, a barium-based alloy, a vanadium-based alloy, a titanium-based alloy, and the mixture thereof, and the absorptive layer type is evaporative, non-evaporative or mixed.  
      The cold cathode fluorescent lamp further comprises at least one fusing mechanism disposed between the supporting mechanism and the transparent tube. The material of the fusing mechanism is capable of tightly bonding the supporting mechanism and transparent tube. The transparent tube is sealed by using a fusing mechanism to connect the supporting mechanism and transparent tube.  
      The cross section of the recess is circular, annular, rectangular, polygonal, regular, or irregular.  
      The method further comprises a step of forming at least one recess on the bottom of the opening of the supporting mechanism to receive the absorptive layer.  
      The method further comprises a step of forming at least one separating mechanism on the bottom of the opening of the supporting mechanism to form the recess.  
      The absorptive structure further comprises at least one connecting mechanism connected to the opposite side of the opening of the supporting mechanism. The connecting mechanism is connected to the supporting mechanism by integral forming as a single piece, fusing, welding, or embedding.  
      The supporting mechanism is cylindrical or cuplike, and the material of the supporting mechanism is selected from the group consisting of nickel, molybdenum, niobium, tungsten, a nickel-based alloy, a molybdenum-based alloy, a niobium-based alloy, a tungsten-based alloy, a carbon nanotube, a nickel-iron alloy, conductive plastic, and the mixture thereof.  
      The absorptive structure further comprises at least one recess formed on the bottom of the opening of the supporting mechanism. The material of the absorptive layer in one recess is identical to or different from that in the other recess when two or more recesses are formed.  
      To conclude, since the absorptive structure of the cold cathode fluorescent lamp of the invention is deployed with the absorptive layer, the unnecessary gases or impurities existing in the transparent tube can be absorbed at anytime by the absorptive layer. Thus, the unnecessary gases or impurities existing in the transparent tube are effectively reduced, illumination thereof is enhanced and lifespan thereof is prolonged.  
      A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
       FIGS. 1A, 1B  and  1 C are schematic views of the process of manufacturing a conventional cold cathode fluorescent lamp;  
       FIG. 2  is a schematic partial view of the cold cathode fluorescent lamp of the first embodiment of the invention;  
       FIGS. 3A, 3B  and  3 C are schematic partial views of the absorptive structure of the second embodiment of the invention; and  
       FIGS. 4A and 4B  are schematic partial views of the absorptive structure of the third embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     First Embodiment  
      Referring to  FIG. 2 , the cold cathode fluorescent lamp  200  of this embodiment comprises a transparent tube  212  and an absorptive structure  202 . The absorptive structure  202  further comprises a supporting mechanism  204  and an absorptive layer  206 . The absorptive structure  202  may serve as getter. For example, the shape of the absorptive structure  202  is a cuplike shape.  
      The transparent tube  212  is closed and is filled with a gas capable of arousing light by means of an electric potential. The gas can be an inert gas, an inert gas with mercury particles, gaseous mercury, or a gas capable of arousing fluorescence. The material of the transparent tube  212  allows light therein to penetrate and diffuse and can be glass or transparent plastic. The shape of the transparent tube  212  can be stripped, annular, curved, polygonal, plated, regular, or irregular.  
      The supporting mechanism  204  is disposed on one end of the transparent tube  212  to support the absorptive layer  206  and to connect an external power source. The supporting mechanism  204  is a cylindrical or cuplike conductive mechanism and has an opening  214  whose shape is cylindrical or cuplike. A connecting mechanism  210  is connected to the opposite side of the opening  214  of the supporting mechanism  204  and extends therefrom, such that the external power source can be electrically connected to the supporting mechanism  204  via the connecting mechanism  210 . The connecting mechanism  210  can be connected to the supporting mechanism  204  by integral forming as a single piece, fusing, welding, or embedding. The material of the supporting mechanism  204  and connecting mechanism  210  can be nickel, molybdenum, niobium, tungsten, a nickel-based alloy, a molybdenum-based alloy, a niobium-based alloy, a tungsten-based alloy, carbon nanotubes, a nickel-iron alloy, or conductive plastic. Specifically, the material of the supporting mechanism  204  can be identical to or different from that of the connecting mechanism  210 . The height of the supporting mechanism  204  depends on the space near the end of the transparent tube  212 . Preferably, the height of the supporting mechanism  204  is 2 to 6 mm.  
      The absorptive layer  206  can absorb the unnecessary gases or impurities existing in the transparent tube  212  and is disposed in the opening  214  of the supporting mechanism  204 . The shape of the absorptive layer  206  depends on that of the opening  214 . The absorptive layer  206  is bonded to the supporting mechanism  204  by filling, pressing, embedding, or evaporation deposition. The work function of the absorptive layer  206  is less than that of the supporting mechanism  204  and the material of the absorptive layer  206  can be zirconium, barium, vanadium, titanium, a zirconium-based alloy, a barium-based alloy, a vanadium-based alloy, or a titanium-based alloy. The thickness of the absorptive layer  206  is smaller than the depth of the opening  214 . Preferably, the thickness of the absorptive layer  206  is approximately half the depth of the opening  214 . At this point, the absorptive layer  206  can provide excellent absorption.  
      The absorptive layer  206  type can be evaporative, non-evaporative, or mixed. When the absorptive layer  206  is evaporative, the absorptive layer  206  is attached to the inner surface of the supporting mechanism  204  and an absorptive film with low work function and high activity is thereby formed during operation of the cold cathode fluorescent lamp  200 . Accordingly, since the absorptive film has low work function, electrons can be easily aroused thereby. The operational potential of the cold cathode fluorescent lamp  200  is thus reduced. Additionally, since the absorptive film has high activity, it can easily react with and absorb the unnecessary gases or impurities in the transparent tube  212 .  
      Moreover, since the work function of the compound from the absorptive layer  206  and unnecessary gases or impurities is less than that of the supporting mechanism  204 , operational efficiency of the absorptive structure  202  is not reduced after the absorptive layer  206  absorbs the unnecessary gases or impurities.  
      Additionally, the absorptive structure  202  further comprises a fusing mechanism  208 . The absorptive structure  202  is tightly bonded to the transparent tube  212  by means of the fusing mechanism  208 . The material of the fusing mechanism  208  must be capable of being easily bonded to the absorptive structure  202  and transparent tube  212 . For example, the fusing mechanism  208  is a glass ball. Accordingly, ineffective gastight bonding between the absorptive structure  202  and the transparent tube  212  can thereby be prevented.  
      Furthermore, the supporting mechanism  204  of this embodiment is not limited to being cuplike and the absorptive layer  206  in the opening  214  is not limited to being cylindrical. Namely, the supporting mechanism  204  and opening  214  may have the shapes as shown in  FIGS. 3A, 3B ,  3 C,  4 A and  4 B.  
     Second Embodiment  
      Referring to  FIGS. 3A, 3B  and  3 C, the cold cathode fluorescent lamp  200 ′ of this embodiment comprises a transparent tube  212  and a supporting mechanism  204   a . The difference between this embodiment and the first embodiment is that the supporting mechanism  204   a  has a W shape. The supporting mechanism  204   a  comprises an opening  214   a  and an opening  214   b . The opening  214   a  receives an absorptive layer  206   a  and an absorptive layer  206   b  while the opening  214   b  receives a connecting mechanism  210   a . Specifically, the connecting mechanism  210   a  can be bonded to the opening  214   b  by embedding, engagement, or welding. The bottom of the opening  214   a  can be formed with a groove as shown in  FIG. 3B  or with recesses as shown in  FIG. 3C . The depth of the groove or recesses is smaller than or equal to the maximum depth of the opening  214   a . Preferably, the depth of the groove or recesses is half that of the opening  214   a . The cross section of the groove or recesses on the bottom of the opening  214   a  can be annular, rectangular, polygonal, regular, or irregular. The absorptive layers  206   a  and  206   b  are deployed in the groove or recesses. The shapes of the absorptive layers  206   a  and  206   b  depend on the shape of the groove or recesses. Moreover, when the opening  214   a  has two or more recesses, the material of the absorptive layers  206   a  and  206   b  can be same or different.  
     Third Embodiment  
      Referring to  FIG. 4A  and  FIG. 4B , the cold cathode fluorescent lamp  200 ″ of this embodiment comprises a transparent tube  212  and a supporting mechanism  204   b . The difference between this embodiment and the first embodiment is that a separating mechanism  216  is formed in the supporting mechanism  204   b . Accordingly, multiple recesses are formed on the bottom of an opening  214   c  of the supporting mechanism  204   b  by the separating mechanism  216 . The material of the separating mechanism  216  can be nickel, molybdenum, niobium, tungsten, a nickel based alloy, a molybdenum-based alloy, a niobium-based alloy, a tungsten-based alloy, carbon nanotubes, a nickel-iron alloy, or conductive plastic. The material of the separating mechanism  216  can be identical to or different from that of the supporting mechanism  204   b . The separating mechanism  216  can be bonded to the supporting mechanism  204   b  by integral forming, embedding, engagement, welding, or fusing. The height of the separating mechanism  216  is smaller than or equal to the maximum height of the opening  214   c . Preferably, the height of the separating mechanism  216  is half that of the opening  214   c . The cross section of portions formed by the separating mechanism  216  can be circular, annular, rectangular, polygonal, regular, or irregular. Absorptive layers  206   c  and  206   d  are deployed in the portions. The shapes of the absorptive layers  206   c  and  206   d  depend on those of the portions. Additionally, the material of the absorptive layers  206   a  and  206   b  can be same or different.  
      The following description is directed to the process of manufacturing the cold cathode fluorescent lamp  200  of the first embodiment.  
      As shown in  FIG. 2 , the absorptive layer  206  is deployed in the supporting mechanism  204  to obtain the absorptive structure  202 . The absorptive structure  202  is then disposed in the transparent tube  212 . The transparent tube  212  is evacuated and the light-emitting portion thereof is filled with an inert gas or a gas (such as mercury gas) capable of arousing fluorescence. The transparent tube  212  is then sealed such that the transparent tube  212  and absorptive structure  202  are tightly bonded. At this point, the transparent tube  212  is tightly bonded to the supporting mechanism  204  or connecting mechanism  210  of the absorptive structure  202  and manufacture of the cold cathode fluorescent lamp  200  is complete.  
      To conclude, since the absorptive structure of the cold cathode fluorescent lamp of the invention is deployed with the absorptive layer, the unnecessary gases or impurities existing in the transparent tube can be absorbed at anytime by the absorptive layer. Thus, the unnecessary gases or impurities existing in the transparent tube are effectively reduced, illumination thereof is enhanced and lifespan thereof is prolonged.  
      While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art) Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.